Interactions
of oxidant
stress and vascular
reactivity
GAIL H. GURTNER AND THERESA BURKE-WOLIN Departments of Medicine and Physiology, New York Medical College, Valhalla, New York 10595
GURTNER,GAIL H., AND THERESA BURKE-W• LIN.ILQ~MZtions of oxidant stress and vascular reactivity. Am. J. Physiol. 260 (Lung Cell. Mol. Physiol. 4): L207-L211, 1991.-Oxidants have complex effects on pulmonary vascular reactivity. They can stimulate production of vasoconstrictor arachidonate mediators and can also cause vasodilation through activation of guanylate cyclase. Oxidants can also inactivate vasomotor phenomenon by interfering with mechanisms of signal transduction or smooth muscle contraction. The final physiological response depends on the balance of these complex actions. pulmonary circulation; arachidonic nylate cyclase; hydroge n peroxide;
acid; cyclooxyge nase; guaorgani .c peroxide
IMPORTANCE of oxidants is becoming increasingly clear. Exogenous oxidants as well as endogenously formed partial oxygen reduction products of cellular respiration appear to be involved in mechanisms of tissue injury and physiological regulation of vasomotor tone. These effects are complex because oxidants can alter cellular function in a number of ways including direct effects, (23, 28, 29), actions mediated through production of arachidonate mediators (13, 15, 22, 23), or by reactions involving hydrogen peroxide-induced activation of guanylate cyclase (2, 4). The indirect effects appear to mediate stimulatory actions of oxidants in causing pulmonary hypertension or in modulating hypoxic vasoconstriction. Direct oxidant effects appear to primarily involve inhibition of agonist-induced or hypoxic vasoconstriction (23).
THE BIOLOGICAL
Oxidant-Induced
Pulmonary Vasoconstriction
Our initial observation was that administration of the oxidant tertiary butyl hydroperoxide (t-bu-OOH) to the perfusate of an isolated rabbit lung caused a dose-related pulmonary vasoconstriction, which was rapid in onset and partially reversible on cessation of the stimulus. This phenomenon can be caused by other strong oxidants such as hydrogen peroxide (37), superoxide (40), or oxygen at hyperbaric pressures (28). Oxidant-induced pulmonary vasoconstriction can be completely blocked by indomethacin and is closely correlated with the concentration of thromboxane (TxB~) in the effluent perfusate (13, 15, 22). It is not clear whether this phenomenon is unique in the pulmonary circulation or occurs generally. 1040-0605/91 $1.50 Copyright
6
It may, however, require the presence of arterial endothelium. We have carried out experiments using reversed pulmonary flow and did not observe a pressor response. In addition, we did not observe vasoconstriction in isolated rat livers perfused via the portal vein. These results suggest that thromboxane production may occur in arterial endothelium, upstream of reactive smooth muscle elements. Bovine pulmonary artery cells produce thromboxane, when challenged with t-bu-OOH (7), which supports this idea. We also found that thromboxane was not produced during pulmonary vasoconstriction caused by angiotensin II, indicating thromboxane production was not the result of elevated vascular pressure or shear stress (22) The phenomenon of oxidant-induced pulmonary vasoconstriction is highly reproducible with repeated oxidant challenge (15). This property lends itself to the use of inhibitors to investigate the mechanism of thromboxaneinduced vasoconstriction. We found that t-bu-OOH-induced pulmonary vasoconstriction and thromboxane production could be blocked by cyclooxygenase or thromboxane synthetase inhibitors, (13, 15, 22), which further supports a causal role for thromboxane in the vasoconstriction. Vasoconstriction, but not thromboxane production, could be inhibited by calcium entry blockers or by calcium free perfusate suggesting that thromboxane causes pulmonary vasoconstriction by increasing cytosol calcium. Similar observations were made using hydrogen peroxide or superoxide (37, 40). Oxidants also cause production of peptide leukotrienes that are associated with increased vascular permeability (13, 14). Administration of exogenous leukotriene Dq (LTD4) causes edema formation, vasoconstriction, and bronchoconstriction (14). LTD*-induced vasoconstriction and bronchoconstriction are blocked by cyclooxygenase inhibition, indicating a secondary stimulation of cyclooxygenase activity. LTD4-induced edema formation is not affected by cyclooxygenase inhibition, suggesting a direct effect on vascular permeability. The mechanism by which oxidants stimulate arachidonic acid (AA) metabolism is not well understood. Administration of t-bu-OOH to bovine pulmonary endothelial cells causes a dose-related release of AA and increases phospholipase A, (PLAz) activity (7). t-bu-OOH-induced AA release can be inhibited by dexamethasone pretreatment, which also supports an action of oxidants on PLA,.
1991 the American
Physiological
Society
L207
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
1,208
COMMENTARY
We investigated the effect of mepacrine, a putative PLAz inhibitor on t-bu-OOH-induced vasoconstriction and found that 100 PM mepacrine completely blocked t-buOOH-induced vasoconstriction (38). Mepacrine also blocked vasoconstriction caused by AA; however, AAinduced thromboxane production was not inhibited. To further investigate this unexpected result, we measured the effect of mepacrine on vasoconstriction caused by KC1 or angiotensin II. Mepacrine blocked vasoconstriction caused by both agonists. These observations cannot be explained by inhibition of phospholipase and are more consistent with an inhibitory action of mepacrine on calmodulin as had previously been demonstrated (43). In other systems, protease inhibitors can block PLAY activity (25). Because of this, we investigated the effect of the competitive protease inhibitor tosyl-argininemethyl-ester (TAME) on t-bu-OOH-induced pulmonary vasoconstriction (11). TAME inhibited thromboxane production and pulmonary vasoconstriction in a doserelated manner, consistent with inhibition of PLA+ These findings suggest involvement of a protease in the oxidant-induced activation of PLAZ (11). TAME also blocked pulmonary vasoconstriction due to U46619 and angiotensin II, which act through receptors. TAME did not block vasoconstriction caused by KCl, which directly activates voltage-operated calcium channels. These observations taken together suggest TAME interferes with receptor-mediated signal transduction. Because neutrophils produce superoxide anion (0, neutrophil-induced lung injury may involve a component of oxidant-induced vasoconstriction. Administration of endotoxin causes leukocyte sequestration, thromboxanemediated vasoconstriction, and lung injury in several species. A logical way to investigate possible oxidant contribution to endotoxin injury is to determine whether administration of antioxidant enzymes or antioxidants can modify the pathophysiological events. Administration of Ficoll-conjugated catalase failed to modify the pathophysiological events in endotoxin injury, and the authors concluded that leukocyte oxidants do not contribute to endotoxin-induced events (24). Although the results warrant the author’s conclusion, it might be useful to determine the action of lipid-soluble antioxidants as well as macromolecule-conjugated enzymes. Since leukocytes must adhere to membrane surfaces to effectively cause lung injury, the adherent region might not be permeable to the large molecule bearing the active enzyme. A different test of the hypothesis could involve pretreatment with lipid-soluble antioxidants like butylated hydroxyanisole (BHA) or vitamin E that do protect against the direct oxidant effects of normobaric hyperoxia (23, 29). Although little thromboxane is produced under basal conditions by the lung, there is substantial basal production of prostacyclin (15, 22, 23). In contrast to the observation that thromboxane production does not increase with vascular pressures, pressure or shear stress, prostacyclin or other vasodilator prostaglandins appear to be produced in response to these stimuli and may provide a mechanism for maintenance of the normally low pulmonary artery pressure. Several investigators have demonstrated that cyclooxygenase inhibition can l
),
augment hypoxic vasoconstriction (20, 46). This phenomenon could be explained by stimulation of vasodilator prostaglandin synthesis by hypoxia or by shear stress. Elevation of pulmonary venous pressure to levels that cause edema are associated with marked elevation of prostacyclin synthesis (41); however, increased pulmonary blood flow in the absence of pulmonary hypertension, as seen in exercise, does not stimulate increased prostacyclin or thromboxane synthesis (34). Hypoxia appears to inhibit prostacyclin production in bovine pulmonary aortic endothelial cells in culture (32). Simultaneous administration of arachidonic acid and hypoxia abolishes hypoxic vasoconstriction (16). Although there is conflicting evidence as to the stimulus for production of vasodilator prostaglandins, which cannot be addressed here, it seems possible that production of these mediators could represent a regulatory mechanism that contributes to the maintenance of normal pulmonary vascular pressure. Oxidant-Induced
Pulmonary
Vasodilation
The pulmonary circulation is normally dilated so that studies on pulmonary vasodilators usually use a constrictor stimulus in order to demonstrate mechanisms of vasodilation. Peroxide-induced vasodilation of the pulmonary circulation was first shown by Weir and Will in the dog lung. In this study, pulmonary artery pressure was increased with hypoxia and either t-bu-OOH or %butanone peroxide was given intravenously to an anesthetized dog. Both peroxides dilated the pulmonary vascular bed, although 2-butanone peroxide appeared to be more selective for the lung (45). Similar results were seen in studies using isolated perfused rat lung. In these experiments xanthine oxidase-derived oxygen metabolites prevented the increase in pulmonary artery pressure by hypoxia (44). The authors proposed that peroxides may act by oxidizing sulfhydryl groups of a calcium-ATPase, thus reducing the activity of this enzyme resulting in a loss of calcium from the cell (44). This hypothesis has not been tested, and the evidence currently available shows that peroxide administration to aortic endothelial cells or P338D1 cells increases intracellular calcium (12, 26). In isolated bovine pulmonary arteries precontracted with serotonin or other stimuli, H,O, causes a dosedependent relaxation of the smooth muscle. This relaxation is associated in a time- and concentration-dependent manner with an increase in intracellular levels of guanosine 3’,5’-cyclic monophosphate (cGMP) (2). Vascular cGMP levels could also be increased by release of endothelium-derived relaxant factor (EDRF), as has been proposed for substances such as acetylcholine (19). Although relaxation to H,OZ in systemic arteries has an endothelium-dependent component (36), in the pulmonary artery the endothelium does not appear to play a role, since removal of the endothelium does not affect the response (2). Reactive oxygen species have been suggested as possible activators of the soluble form of guanylate cyclase. Hydroxyl radical (33), 0,. (42), and H,O, (47) have all been suggested as stimulators of the enzyme in a variety
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
COMMENTARY
of preparations. By use of a generating system of glucose oxidase/glucose to produce HZ02, this oxygen species does not appear to directly stimulate guanylate cyclase (48). However, if catalase is present within the reaction mixture, guanylate cyclase activity is markedly increased. The activation of the enzyme is dependent on both the peroxide and mammalian catalase as horseradish peroxidase and fungal catalase, which would both remove HgOz, do not activate guanylate cyclase (2). It appears then that changes in guanylate cyclase activity induced by HZ02 are mediated by catalase. Catalase exists in two forms during the steady-state metabolism of physiological concentrations of H,O,. The first molecule of HZOZ reacts with catalase to release water and form the intermediate compound I that is an oxidized form of catalase. The second molecule of H,O, then reacts with compound I, releasing oxygen and returning catalase to its native form (8). It is the formation of compound I that appears to mediate the activation of guanylate cyclase by H,Oz (2). Evidence for this mechanism of guanylate cyclase activation in the relaxation of isolated pulmonary arteries to HZOZ can be found by using probes that react with either catalase or compound I. Ethanol, used classically as a hydroxyl radical scavenger (17), is cometabolized with H,O, by catalase and reduces steady-state levels of compound I (8). Superoxide anion can inhibit catalase directly or react with compound I to form inactive compound II, which also results in a decrease in steady-state compound I levels (31). Aminotriazole forms an irreversible bond with compound I and thus inactivates catalase (50). The mitochondrial inhibitor cyanide has also been found to inhibit pulmonary arterial catalase (3). These agents have all been shown to selectively inhibit guanylate cyclase activation by catalase/H20Z (3) and do not inhibit other stimulators of the enzyme such as nitrovasodilators and protoporphyrin IX (27). Superoxide dismutase used to scavenge 0,. produced by autooxidation of assay components enhances catalase/HzOZ activation of guanylate cyclase (10). These probes have been used in the isolated blood vessel preparation. Ethanol reverses H,O, relaxation in the bovine pulmonary a rtery and inhibits the increase in intracellular cGMP induced by the peroxide (5). Inhibition of H,O, relaxation is also seen with cyanide (6) hydroquinone (Z), which generates superoxide anion, and agents-that increase intracellular levels of 0,. (9). These experiments suggest that the relaxation of the pulmonary artery to H,O, is dependent on its metabolism by catalase. Both lipid and hydrogen peroxides are metabolized by glutathione peroxidase in mammalian cells; however, lipid peroxides cannot be metabolized by catalase; nonetheless, lipid peroxides have been shown to relax pulmonary arteries. As described previously, organic peroxides such as t-bu-OOH dilate the pulmonary circulation and have also been shown to relax isolated pulmonary arteries. Lipid peroxides may form as a result of lipid peroxidation, which can occur during periods of oxidant stress. The lipid peroxide l&hydroperoxyeicosatetraenoic acid (15HPETE) is a lipoxygenase product of arachidonic acid metabolism. This peroxide has been
L209 shown to relax isolated pulmonary arteries and relaxation is antagonized by methylene blue, an inhibitor of the activation of soluble guanylate cyclase (49). However, 15-HPETE failed to activate purified guanylate cyclase even in the presence of added catalase (49). Relaxation of pulmonary arteries to 15-HPETE can also be inhibited by hypoxia. In contrast, the relaxation of isolated pulmonary arteries to H,O, has been found to be enhanced by a decrease in oxygen tension (5). These observations suggest a linkage between the metabolism and action of lipid and hydrogen peroxides. Hydrogen peroxide is produced by lung tissue as a function of oxygen tension, such that at lower oxygen concentrations there is less peroxide production (1). Catalase exists in pulmonary artery smooth muscle at concentrations far less than that of glutathione peroxidase, thus the primary pathway of peroxide metabolism is through the glutathione system (2). During hypoxia, there is a decrease in the production of intracellular HgOa, producing a decrease in the level of HzOz metabolism by catalase (6). When exogenous H,O, is added, relatively more catalase is available to the exogenous peroxide for stimulation of the guanylate cyclase system, and this may explain the increase in relaxation to H,O, under hypoxia. Organic peroxides and lipid peroxides, though not metabolized by catalase, may depend on this mechanism to produce relaxation in the pulmonary artery. Under normoxic or hyperoxic conditions the addition of exogenous 15-HPETE may shunt endogenous H,O, metabolism from glutathione peroxidase to catalase (49). Consequently, H,OZ becomes the mediator of 15-HPETE relaxation. This hypothesis is supported by the observation that 15-HPETE relaxation is reduced under hypoxic conditions (49) where endogenous H,O, formation has been observed to be reduced (6). The observation that depletion of glutathione using diaminde results in vasodilation of preconstricted rat lungs also supports this hypothesis (44). Other agents have been used to inhibit glutathione peroxidase by depletion of glutathione; butathione sulfoxime inhibits glutathione synthesis and prevents pulmonary vasoconstriction to hypoxia in rats (35). The experiments with H,O, and 15-HPETE were carried out using isolated bovine pulmonary arteries. Our initial studies on the effects of H,O, in isolated rabbit lungs, preconstricted with U46619, show that H,O, dilates the pulmonary circulation and this dilation is inhibited by methylene blue (3). Organic peroxides also cause vasodilation in lungs with pulmonary artery tone increased by hypoxia (45). This observation may appear anomalous; however, sufficient oxygen, and thus HYOZ, may be present to stimulate the shunting mechanism. This is supported by the observation that xanthine/ xanthine oxidase-derived oxygen metabolites also produce vasodilation under hypoxia (44). The study of dilator mechanisms of oxygen metabolites in the pulmonary circulation is far from complete. Most studies have concentrated on the effects of exogenous addition of peroxides to determine the vasoactivity of these compounds. At this time it appears that not only is the metabolism of H,O, an important step in assessing the vasoactivity of this oxygen metabolite, but the role
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
L210
COMMENTARY
of endogenously formed peroxide sponses must also be considered. Direct
Effects of Oxidant
in mediating
on Pulmonary
these re-
Reactivity
Prolonged exposure to 100% oxygen causes progressive pulmonary failure and death in all mammalian species. Hypoxic pulmonary vasoconstriction is lost late in oxygen toxicity at about the same time as edema formation occurs (25). There is some evidence that this inhibition of hypoxic vasoconstriction may be selective; although the pulmonary vasculature was unreactive to hypoxia the administration of prostaglandin Hz or KC1 caused vasoconstriction. Pretreatment with endotoxin delayed edema formation and loss of hypoxic vasoconstriction. The authors did not measure the effect of endotoxin on KCl- or prostaglandin Hz-induced vasoconstriction. In rabbits 48-60 h of normobaric hyperoxia completely blocks thromboxane-mediated vasoconstriction but did not affect peroxide-induced thromboxane production. This vascular paralysis could be prevented by administration of the antioxidants BHA or vitamin E, suggesting an oxidant mechanism. The same antioxidants also prevent edema formation seen in untreated rabbits exposed to 48 h of normobaric hyperoxia (29). Other oxidants also cause vascular paralysis. Exposure of rabbits to a cumulative dose of 2,000 ppm/min of phosgene, which causes lung injury, inhibits vasoconstriction caused by thromboxane but not arachidonic acid-induced thromboxane production. In these lungs vasoconstriction caused by KC1 or angiotensin was not inhibited, suggesting an oxidant effect on thromboxane receptor or associated signal transduction. The selectivity of oxidants on vasoconstrictor agonists has not been extensively investigated and may provide information on the mechanism of action. The clear association between edema formation and inhibition of vascular reactivity suggests a common mechanism of action. This work was supported by National Heart, Lung, and Blood Institute Grants HL-35483, HL-41728, and a grant from the Chemical Manufacturers’ Association. Address for reprint requests: G. H. Gurtner, Westchester County Medical Center, Pulmonary Lab, Area ZG, Valhalla, NY 10594. REFERENCES 1. ARCHER, S. L., D. P. NELSON, AND E. K. WEIR. Detection of activated 0, species in vitro and in rat lungs by chemiluminescence. J. Appl. Physiol. 67: 19121921, 1989. 2. BURKE, T. M., AND M. S. WOLIN. Hydrogen peroxide elicits pulmonary arterial relaxation and guanylate cyclase activation. Am. J. Physiol. 252 (Heart Circ. Physiol. 21): H721-H732, 1987. 3. BURKE-W• LIN, T., P. D. CHERRY, AND G. H. GURTNER. Tone dependent effects of peroxides in rabbit pulmonary artery and isolated perfused lung (Abstract). FASEB J. 4: A573, 1990. 4. BURKE-W• LIN, T., K. M. MOHAZZAB, AND M. S. WOLIN. Mechanism of antagonism of pulmonary artery relaxation to O2 and Hz02 by cyanide (Abstract). Circulation 78: 11-206, 1988. 5. BURKE-W• LIN, T. M., AND M. S. WOLIN. Inhibition of cGMPassociated pulmonary arterial relaxation to H,02 and 0, by ethanol. Am. J. Physiol. 258 (Heart Circ. Physiol. 26): H1267-H1273, 1990. 6. BURKE-W• LIN, T., AND M. S. WOLIN. H,O, and cGMP may function as an O2 sensor in the pulmonary artery. J. Appl. Physiol. 66: 167-170, 1989. 7. CHAKRABORTI, S., G. H. GURTNER, AND J. R. MICHAEL. Oxidant mediated activation of phospholipase A2 in pulmonary endothe-
lium. Am. 1989.
J. Physiol.
257 (Lung
Cell. Mol.
Physiol.
1): L430-L437,
8. CHANCE, B., H. SEIS, AND A. BOVERIS. Hydroperoxide metabolism in mammalian organs. Physiol. Rev. 59: 527-605, 1979. 9. CHERRY, P. D., H. A. OMAR, K. A. FARRELL, J. S. STUART, AND M. S. WOLIN. Superoxide anion inhibits cGMP-associated bovine pulmonary arterial relaxation. Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H1056-H1062, 1990. 10. CHERRY, P. D., AND M. S. WOLIN. Ascorbate activates soluble guanylate cyclase via H202-metabolism by catalase. Free Rad. Biol. Med. 7: 485-490, 1989. 11. CROWLEY, K., J. R. MICHAEL, AND G. H. GURTNER. A protease inhibitor may block phospholipase A2 and C in rabbit lungs (Abstract). Am. Rev. Respir. Dis. 139: A274, 1989. 12. ELLIOTT, S. J., S. G. ESKIN, AND W. P. SCHILLING. Effect of tButyl-hydroperoxide on bradykinin-stimulated changes in cytosolic calcium in vascular endothelial cells. J. Biol. Chem. 264: 38063810, 1989. 13. FARRUKH, I. S., J. R. MICHAEL, S. P. PETERS, M. SCIUTO, N. F. ADKINSTON, JR., HOWARD S. FREELAND, A. PAKY, E. W. SPANNHAKE, W. R. SUMER, AND G. H. GURTNER. The role of cyclooxygenase and lipoxygenase mediators in oxidant-induced lung injury. Am. Rev. Respir. Dis 137: 1343-1349, 1988. 14. FARRUKH, I. S., E. W. SPANNHAKE, A. M. SCIUTO, J. R. MICHAEL, AND G. H. GURTNER. Leukotriene D4 increases pulmonary vascular permeability and pressure by different mechanisms in the rabbit. Am. Rev. Respir. Dis. 134: 229-232, 1986. 15. FARRUKH, I., W. SUMMER, J. MICHAEL, N. F. ADKINSON, G. H. GURTNER. Thromboxane induced pulmonary vasoconstriction: involvement of calcium. J. Appl. Physiol. 58: 34-44, 1985. 16. FEDDERSEN, C. O., S. CHANG, J. CZARTALOMNA, AND N. F. VOELKEL. Arachidonic acid causes cyclooxygenase dependent and independent pulmonary vasodilation. J. Appl. Physiol. 68: 17991808,199O. 17. FEIERMAN, D. E., G. W. WINSTON, AND A. I. CEDERBAUM. Ethanol oxidation by hydroxyl radicals: role of iron chelates, superoxide and hydrogenperoxide. Alcohol Clin. Exp. Res. 9: 95-102, 1985. 18. FREEMAN, B. A., M. K. TOPOLOSKY, AND J. D. CRAPO. Hyperoxia increases oxygen radical production in rat lung homogenates. Arch. Biochem. Biophys. 216: 477-484, 1982. 19. FURCHGOTT, R. F. The role of the endothelium in the response of vascular smooth muscle to drugs. Annu. Rev. Pharmacol. Toxicol. 24: 175-197, 1984. 20. GORDON, J. B., M. L. TOD, R. C. WETZEL, M. L. MCGEADY, N. F. ADKINSON, JR., AND J. T. SYLVESTER. Age dependent effects of indomethacin on hypoxic vasoconstriction in neonatal lamb lungs. Pediatric Res. 23: 580-584, 1988. 21. Guo, Y. L., T. P. KENNEDY, J. R. MICHAEL, A. M. SCIUTO, A. J. GHIO, N. F. ADKINSON, JR., AND G. H. GURTNER. Mechanism of phosgene-induced lung toxicity: role of arachidonate mediators. J. Appl. Physiol. 69: 1615-1625, 1990. 22. GURTNER, G. H., A. KNOBLAUCH, P. SMITH, H. SIES, AND N. F. ADKINSON. Oxidant and lipid induced pulmonary vasoconstriction mediated by arachidonic acid metabolites. J. Appl. Physiol. 55: 949954, 1983. 23. GURTNER, G. H., J. R. MICHAEL, A. M. SCIUTO, AND N. F. ADKINSON. Mechanism of hyperoxia induced vascular paralysis: effect of antioxidant therapy. J. Appl. Physiol. 59: 953-958, 1985. 24. HAZINSKI, T. A., K. A. KENNEDY, AND M. L. FRANCE. Effect of endotoxin pretreatment on the pulmonary vascular response to hypoxia in 02-exposed lambs. J. Appl. Physiol. 65: 1586-1591,1988. 25. HAZINSKI, T. A., K. A. KENNEDY, M. L. FRANCE, AND T. N. HANSEN. Pulmonary 0, toxicity in lambs: physiological and biochemical effects of endotoxin infusion. J. Appl. Physiol. 65: 15791585, 1988. 26. HYSLOP, P. A., B. HINSHAW, I. U. SCHRAUFSTATTER, L. A. SKLAR, R. C. SPRAGG, AND C. G. COCHRANE. Intracellular calcium homeostasis during hydrogen peroxide injury to cultured P338D cells. J. Cell. Physiol. 129: 356-366, 1986. 27. IGNARRO, L. J., K. S. WOOD, AND M. S. WOLIN. Regulation of purified soluble guanylate cyclase by porphyrins and metalloporphyrins: a unifying concept. Adv. Cyclic Nucleotide Prot. Phosphoryl. Res. 17: 267-274, 1984. 28. JACOBSON, J. M., J. R. MICHAEL, M. B. BRADLEY, AND G. H. GURTNER. Inhibition of thromboxane synthetase prevent h.vper-
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
L211
COMMENTARY
29.
30.
31. 32.
33.
34.
35.
36.
37.
38.
Z39.
baric oxygen induced pulmonary damage (Abstract). Am. Rev. Respir. Ibis. 133: A283, 1986. JACOBSON, J. M., J. R. MICHAEL, AND G. H. GURTNER. Antioxidants and antioxidant enzymes protect against pulmonary oxygen toxicity in the rabbit. J. Appl. Physiol. 68: 1252-1259, 1990. KENNEDY, T. P., J. R. MICHAEL, J. R. HOIDAL, D. HASTY, A. M. SCIUTO, C. HOPKINS, R. LAZAR, G. K. BYSANI, E. TOLLEY, AND G. H. GURTNER. Dibutyryl CAMP, aminophylline, and p-adrenergic agonists protect against pulmonary edema caused by phosgene. J. Appl. Physiol. 67: 2542-2552, 1989. KONO, Y., AND I. FRIDOVICH. Superoxide radical inhibits catalase. J. Biol. Chem. 257: 5751-5754,1982. MADDEN, M. C., R. L. VENDER, AND M. FRIEDMAN. Effect of hypoxia on prostacyclin production in cultured pulmonary artery endothelium. Prostuglandins 31: 1049-1062, 1986. MITTAI,, C. K., AND F. MURAD. Activation of guanylate cyclase by superoxide dismutase and hydroxyl radical: a physiological regulator of guanosine-3’,5’-monophosphate formation. Proc. Nutl. Acad. Sci. USA 74: 4360-4364, 1977. NEWMAN, J. H., B. J. BUTKA, AND K. L. BRIGHAM. Thromboxane A2 and prostacyclin do not modulate pulmonary hemodynamics during exercise in sheep. J. Appl. Physiol. 61: 1706-1711, 1986. PETERS-GOLDEN, M., C. SHELLY, AND M. L. MORGANROTH. Inhibition of rat lung glutathione synthesis attenuates hypoxic pulmonary vasoconstriction and the associated leukotriene C, production. Am. Rev. Respir. Dis. 140: 1210-1215, 1989. RUBANYI, G. M., AND P. M. VANHOUTTE. Oxygen-derived free radicals, endothelium, and responsiveness of vascular smooth muscle. Am. J. Physiol. 251 (Heart Circ. Physiol. 20): H815-H821, 1986. SEEGER, W., N. SUTTORP, F. SCHMIDT, AND H. NEUHOF. The glutathione redox cycle as a defense system against hydrogen peroxide induced prostanoid formation and vasoconstriction in rabbit lungs. Am. Rev. Respir. Dis. 133: 1029-1036, 1986. SHAYEVITZ, ,J. R., R. J. TRAYSTMAN, A. R. MCSHANE, K. CROWLEY, AND G. H. GURTNER. Mepacrine inhibits thromboxane, angiotensin II, and potassium induced vasoconstriction in the rabbit. J. Appl. Physiol. 66: 1921-1926, 1989. SUGATANI, J., M. MIWA, AND D. J. HANAHAN. Platelet-activating factor stimulation of rabbit platelets is blocked by serine protease
40.
41.
42.
43.
44. 45. 46.
47.
48.
49.
50.
inhibitor (chymotryptic protease inhibitor). J. Biol. Chem. 12: 5740-5747, 1987. TATE, P. M., H. G. MORRIS, W. R. SCHROEDER, AND J. E. REPINE. Oxygen metabolites stimulate thromboxane production in isolated saline-perfused lungs. J. Clin. Invest. 74: 608-613, 1984. VANGRONDELLE, A., G. S. WORTHEN, D. ELLIS, M. M. MATHIAS, R. C. MURPHY, R. J. STRIFE, J. T. REEVES, AND N. F. VOELKEL. Altering hydrodynamic variables influences PGI, production by isolated lungs and endothelial cells. J. Appl. Physiol. 57: 388-395, 1984. VESSELY, D. L., B. WATSON, AND G. S. LEVEY. Activation of liver guanylate cyclase by paraquat: possible role of superoxide anion. J. Pharmacol. Exp. Ther. 209: 162-164, 1979. VOLPI, M., R. I. SHAAFI, P. M. EPSTEIN, D. M. ANDRENYAK, AND M. B. FEINSTEIN. Local anesthetics, mepacrine, and propranolol are antagonists of calmodulin. Proc. Natl. Acad. Sci. USA 78: 795799, 1981. WEIR, E. K., J. W. EATON, AND E. CHESLER. Redox status and pulmonary vascular reactivity. Chest 88: 249S-251S, 1985. WEIR, E. K., AND J. A. WILL. Oxidants: a new group of pulmonary vasodilators. Bull. Eur. Physiopathol. Respir. 18: 81-85, 1982. WETZEL, R. C., J. B. GORDON, T. J. GREGORY, F. H. GIOIA, N. F. ADKINSON, JR., AND J. T. SYLVESTER. High-frequency ventilation attenuation of hypoxic pulmonary vasoconstriction. The role of prostacyclin. Am. Rev. Respir. Dis. 132: 99-103, 1985. WHITE, A. A., K. M. CRAWFORD, C. S. PATT, AND P. J. LAD. Activation of soluble guanylate cyclase from rat lung by incubation or by hydrogen peroxide. J. Biol. Chem. 251: 7304-7312, 1976. WOLIN, M. S., AND T. M. BURKE. Hydrogen peroxide elicits activation of bovine pulmonary arterial soluble guanylate cyclase by a mechanism associated with its metabolism by catalase. Biochem. Biophys. Res. Commun. 143: 20-25, 1987. WOLIN, M. S., T. BURKE-W• LIN, L. A. COHN, AND P. D. CHERRY. Potential mechanism of pulmonary arterial relaxation and guanylate cyclase activation by 15-hydroperoxyeicosatetraenoic acid. Adv. Prostaglandin Thromboxane Leukotriene Res. 19: 285-288, 1989. YUSA, T., J. S. BECKMAN, J. D. CRAPO, AND B. A. FREEMAN. Hyperoxia increases H,02 production by brain in vivo. J. Appl. Physiol. 63: 353-358, 1987.
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
of oxidant
stress and vascular
reactivity
GAIL H. GURTNER AND THERESA BURKE-WOLIN Departments of Medicine and Physiology, New York Medical College, Valhalla, New York 10595
GURTNER,GAIL H., AND THERESA BURKE-W• LIN.ILQ~MZtions of oxidant stress and vascular reactivity. Am. J. Physiol. 260 (Lung Cell. Mol. Physiol. 4): L207-L211, 1991.-Oxidants have complex effects on pulmonary vascular reactivity. They can stimulate production of vasoconstrictor arachidonate mediators and can also cause vasodilation through activation of guanylate cyclase. Oxidants can also inactivate vasomotor phenomenon by interfering with mechanisms of signal transduction or smooth muscle contraction. The final physiological response depends on the balance of these complex actions. pulmonary circulation; arachidonic nylate cyclase; hydroge n peroxide;
acid; cyclooxyge nase; guaorgani .c peroxide
IMPORTANCE of oxidants is becoming increasingly clear. Exogenous oxidants as well as endogenously formed partial oxygen reduction products of cellular respiration appear to be involved in mechanisms of tissue injury and physiological regulation of vasomotor tone. These effects are complex because oxidants can alter cellular function in a number of ways including direct effects, (23, 28, 29), actions mediated through production of arachidonate mediators (13, 15, 22, 23), or by reactions involving hydrogen peroxide-induced activation of guanylate cyclase (2, 4). The indirect effects appear to mediate stimulatory actions of oxidants in causing pulmonary hypertension or in modulating hypoxic vasoconstriction. Direct oxidant effects appear to primarily involve inhibition of agonist-induced or hypoxic vasoconstriction (23).
THE BIOLOGICAL
Oxidant-Induced
Pulmonary Vasoconstriction
Our initial observation was that administration of the oxidant tertiary butyl hydroperoxide (t-bu-OOH) to the perfusate of an isolated rabbit lung caused a dose-related pulmonary vasoconstriction, which was rapid in onset and partially reversible on cessation of the stimulus. This phenomenon can be caused by other strong oxidants such as hydrogen peroxide (37), superoxide (40), or oxygen at hyperbaric pressures (28). Oxidant-induced pulmonary vasoconstriction can be completely blocked by indomethacin and is closely correlated with the concentration of thromboxane (TxB~) in the effluent perfusate (13, 15, 22). It is not clear whether this phenomenon is unique in the pulmonary circulation or occurs generally. 1040-0605/91 $1.50 Copyright
6
It may, however, require the presence of arterial endothelium. We have carried out experiments using reversed pulmonary flow and did not observe a pressor response. In addition, we did not observe vasoconstriction in isolated rat livers perfused via the portal vein. These results suggest that thromboxane production may occur in arterial endothelium, upstream of reactive smooth muscle elements. Bovine pulmonary artery cells produce thromboxane, when challenged with t-bu-OOH (7), which supports this idea. We also found that thromboxane was not produced during pulmonary vasoconstriction caused by angiotensin II, indicating thromboxane production was not the result of elevated vascular pressure or shear stress (22) The phenomenon of oxidant-induced pulmonary vasoconstriction is highly reproducible with repeated oxidant challenge (15). This property lends itself to the use of inhibitors to investigate the mechanism of thromboxaneinduced vasoconstriction. We found that t-bu-OOH-induced pulmonary vasoconstriction and thromboxane production could be blocked by cyclooxygenase or thromboxane synthetase inhibitors, (13, 15, 22), which further supports a causal role for thromboxane in the vasoconstriction. Vasoconstriction, but not thromboxane production, could be inhibited by calcium entry blockers or by calcium free perfusate suggesting that thromboxane causes pulmonary vasoconstriction by increasing cytosol calcium. Similar observations were made using hydrogen peroxide or superoxide (37, 40). Oxidants also cause production of peptide leukotrienes that are associated with increased vascular permeability (13, 14). Administration of exogenous leukotriene Dq (LTD4) causes edema formation, vasoconstriction, and bronchoconstriction (14). LTD*-induced vasoconstriction and bronchoconstriction are blocked by cyclooxygenase inhibition, indicating a secondary stimulation of cyclooxygenase activity. LTD4-induced edema formation is not affected by cyclooxygenase inhibition, suggesting a direct effect on vascular permeability. The mechanism by which oxidants stimulate arachidonic acid (AA) metabolism is not well understood. Administration of t-bu-OOH to bovine pulmonary endothelial cells causes a dose-related release of AA and increases phospholipase A, (PLAz) activity (7). t-bu-OOH-induced AA release can be inhibited by dexamethasone pretreatment, which also supports an action of oxidants on PLA,.
1991 the American
Physiological
Society
L207
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
1,208
COMMENTARY
We investigated the effect of mepacrine, a putative PLAz inhibitor on t-bu-OOH-induced vasoconstriction and found that 100 PM mepacrine completely blocked t-buOOH-induced vasoconstriction (38). Mepacrine also blocked vasoconstriction caused by AA; however, AAinduced thromboxane production was not inhibited. To further investigate this unexpected result, we measured the effect of mepacrine on vasoconstriction caused by KC1 or angiotensin II. Mepacrine blocked vasoconstriction caused by both agonists. These observations cannot be explained by inhibition of phospholipase and are more consistent with an inhibitory action of mepacrine on calmodulin as had previously been demonstrated (43). In other systems, protease inhibitors can block PLAY activity (25). Because of this, we investigated the effect of the competitive protease inhibitor tosyl-argininemethyl-ester (TAME) on t-bu-OOH-induced pulmonary vasoconstriction (11). TAME inhibited thromboxane production and pulmonary vasoconstriction in a doserelated manner, consistent with inhibition of PLA+ These findings suggest involvement of a protease in the oxidant-induced activation of PLAZ (11). TAME also blocked pulmonary vasoconstriction due to U46619 and angiotensin II, which act through receptors. TAME did not block vasoconstriction caused by KCl, which directly activates voltage-operated calcium channels. These observations taken together suggest TAME interferes with receptor-mediated signal transduction. Because neutrophils produce superoxide anion (0, neutrophil-induced lung injury may involve a component of oxidant-induced vasoconstriction. Administration of endotoxin causes leukocyte sequestration, thromboxanemediated vasoconstriction, and lung injury in several species. A logical way to investigate possible oxidant contribution to endotoxin injury is to determine whether administration of antioxidant enzymes or antioxidants can modify the pathophysiological events. Administration of Ficoll-conjugated catalase failed to modify the pathophysiological events in endotoxin injury, and the authors concluded that leukocyte oxidants do not contribute to endotoxin-induced events (24). Although the results warrant the author’s conclusion, it might be useful to determine the action of lipid-soluble antioxidants as well as macromolecule-conjugated enzymes. Since leukocytes must adhere to membrane surfaces to effectively cause lung injury, the adherent region might not be permeable to the large molecule bearing the active enzyme. A different test of the hypothesis could involve pretreatment with lipid-soluble antioxidants like butylated hydroxyanisole (BHA) or vitamin E that do protect against the direct oxidant effects of normobaric hyperoxia (23, 29). Although little thromboxane is produced under basal conditions by the lung, there is substantial basal production of prostacyclin (15, 22, 23). In contrast to the observation that thromboxane production does not increase with vascular pressures, pressure or shear stress, prostacyclin or other vasodilator prostaglandins appear to be produced in response to these stimuli and may provide a mechanism for maintenance of the normally low pulmonary artery pressure. Several investigators have demonstrated that cyclooxygenase inhibition can l
),
augment hypoxic vasoconstriction (20, 46). This phenomenon could be explained by stimulation of vasodilator prostaglandin synthesis by hypoxia or by shear stress. Elevation of pulmonary venous pressure to levels that cause edema are associated with marked elevation of prostacyclin synthesis (41); however, increased pulmonary blood flow in the absence of pulmonary hypertension, as seen in exercise, does not stimulate increased prostacyclin or thromboxane synthesis (34). Hypoxia appears to inhibit prostacyclin production in bovine pulmonary aortic endothelial cells in culture (32). Simultaneous administration of arachidonic acid and hypoxia abolishes hypoxic vasoconstriction (16). Although there is conflicting evidence as to the stimulus for production of vasodilator prostaglandins, which cannot be addressed here, it seems possible that production of these mediators could represent a regulatory mechanism that contributes to the maintenance of normal pulmonary vascular pressure. Oxidant-Induced
Pulmonary
Vasodilation
The pulmonary circulation is normally dilated so that studies on pulmonary vasodilators usually use a constrictor stimulus in order to demonstrate mechanisms of vasodilation. Peroxide-induced vasodilation of the pulmonary circulation was first shown by Weir and Will in the dog lung. In this study, pulmonary artery pressure was increased with hypoxia and either t-bu-OOH or %butanone peroxide was given intravenously to an anesthetized dog. Both peroxides dilated the pulmonary vascular bed, although 2-butanone peroxide appeared to be more selective for the lung (45). Similar results were seen in studies using isolated perfused rat lung. In these experiments xanthine oxidase-derived oxygen metabolites prevented the increase in pulmonary artery pressure by hypoxia (44). The authors proposed that peroxides may act by oxidizing sulfhydryl groups of a calcium-ATPase, thus reducing the activity of this enzyme resulting in a loss of calcium from the cell (44). This hypothesis has not been tested, and the evidence currently available shows that peroxide administration to aortic endothelial cells or P338D1 cells increases intracellular calcium (12, 26). In isolated bovine pulmonary arteries precontracted with serotonin or other stimuli, H,O, causes a dosedependent relaxation of the smooth muscle. This relaxation is associated in a time- and concentration-dependent manner with an increase in intracellular levels of guanosine 3’,5’-cyclic monophosphate (cGMP) (2). Vascular cGMP levels could also be increased by release of endothelium-derived relaxant factor (EDRF), as has been proposed for substances such as acetylcholine (19). Although relaxation to H,OZ in systemic arteries has an endothelium-dependent component (36), in the pulmonary artery the endothelium does not appear to play a role, since removal of the endothelium does not affect the response (2). Reactive oxygen species have been suggested as possible activators of the soluble form of guanylate cyclase. Hydroxyl radical (33), 0,. (42), and H,O, (47) have all been suggested as stimulators of the enzyme in a variety
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
COMMENTARY
of preparations. By use of a generating system of glucose oxidase/glucose to produce HZ02, this oxygen species does not appear to directly stimulate guanylate cyclase (48). However, if catalase is present within the reaction mixture, guanylate cyclase activity is markedly increased. The activation of the enzyme is dependent on both the peroxide and mammalian catalase as horseradish peroxidase and fungal catalase, which would both remove HgOz, do not activate guanylate cyclase (2). It appears then that changes in guanylate cyclase activity induced by HZ02 are mediated by catalase. Catalase exists in two forms during the steady-state metabolism of physiological concentrations of H,O,. The first molecule of HZOZ reacts with catalase to release water and form the intermediate compound I that is an oxidized form of catalase. The second molecule of H,O, then reacts with compound I, releasing oxygen and returning catalase to its native form (8). It is the formation of compound I that appears to mediate the activation of guanylate cyclase by H,Oz (2). Evidence for this mechanism of guanylate cyclase activation in the relaxation of isolated pulmonary arteries to HZOZ can be found by using probes that react with either catalase or compound I. Ethanol, used classically as a hydroxyl radical scavenger (17), is cometabolized with H,O, by catalase and reduces steady-state levels of compound I (8). Superoxide anion can inhibit catalase directly or react with compound I to form inactive compound II, which also results in a decrease in steady-state compound I levels (31). Aminotriazole forms an irreversible bond with compound I and thus inactivates catalase (50). The mitochondrial inhibitor cyanide has also been found to inhibit pulmonary arterial catalase (3). These agents have all been shown to selectively inhibit guanylate cyclase activation by catalase/H20Z (3) and do not inhibit other stimulators of the enzyme such as nitrovasodilators and protoporphyrin IX (27). Superoxide dismutase used to scavenge 0,. produced by autooxidation of assay components enhances catalase/HzOZ activation of guanylate cyclase (10). These probes have been used in the isolated blood vessel preparation. Ethanol reverses H,O, relaxation in the bovine pulmonary a rtery and inhibits the increase in intracellular cGMP induced by the peroxide (5). Inhibition of H,O, relaxation is also seen with cyanide (6) hydroquinone (Z), which generates superoxide anion, and agents-that increase intracellular levels of 0,. (9). These experiments suggest that the relaxation of the pulmonary artery to H,O, is dependent on its metabolism by catalase. Both lipid and hydrogen peroxides are metabolized by glutathione peroxidase in mammalian cells; however, lipid peroxides cannot be metabolized by catalase; nonetheless, lipid peroxides have been shown to relax pulmonary arteries. As described previously, organic peroxides such as t-bu-OOH dilate the pulmonary circulation and have also been shown to relax isolated pulmonary arteries. Lipid peroxides may form as a result of lipid peroxidation, which can occur during periods of oxidant stress. The lipid peroxide l&hydroperoxyeicosatetraenoic acid (15HPETE) is a lipoxygenase product of arachidonic acid metabolism. This peroxide has been
L209 shown to relax isolated pulmonary arteries and relaxation is antagonized by methylene blue, an inhibitor of the activation of soluble guanylate cyclase (49). However, 15-HPETE failed to activate purified guanylate cyclase even in the presence of added catalase (49). Relaxation of pulmonary arteries to 15-HPETE can also be inhibited by hypoxia. In contrast, the relaxation of isolated pulmonary arteries to H,O, has been found to be enhanced by a decrease in oxygen tension (5). These observations suggest a linkage between the metabolism and action of lipid and hydrogen peroxides. Hydrogen peroxide is produced by lung tissue as a function of oxygen tension, such that at lower oxygen concentrations there is less peroxide production (1). Catalase exists in pulmonary artery smooth muscle at concentrations far less than that of glutathione peroxidase, thus the primary pathway of peroxide metabolism is through the glutathione system (2). During hypoxia, there is a decrease in the production of intracellular HgOa, producing a decrease in the level of HzOz metabolism by catalase (6). When exogenous H,O, is added, relatively more catalase is available to the exogenous peroxide for stimulation of the guanylate cyclase system, and this may explain the increase in relaxation to H,O, under hypoxia. Organic peroxides and lipid peroxides, though not metabolized by catalase, may depend on this mechanism to produce relaxation in the pulmonary artery. Under normoxic or hyperoxic conditions the addition of exogenous 15-HPETE may shunt endogenous H,O, metabolism from glutathione peroxidase to catalase (49). Consequently, H,OZ becomes the mediator of 15-HPETE relaxation. This hypothesis is supported by the observation that 15-HPETE relaxation is reduced under hypoxic conditions (49) where endogenous H,O, formation has been observed to be reduced (6). The observation that depletion of glutathione using diaminde results in vasodilation of preconstricted rat lungs also supports this hypothesis (44). Other agents have been used to inhibit glutathione peroxidase by depletion of glutathione; butathione sulfoxime inhibits glutathione synthesis and prevents pulmonary vasoconstriction to hypoxia in rats (35). The experiments with H,O, and 15-HPETE were carried out using isolated bovine pulmonary arteries. Our initial studies on the effects of H,O, in isolated rabbit lungs, preconstricted with U46619, show that H,O, dilates the pulmonary circulation and this dilation is inhibited by methylene blue (3). Organic peroxides also cause vasodilation in lungs with pulmonary artery tone increased by hypoxia (45). This observation may appear anomalous; however, sufficient oxygen, and thus HYOZ, may be present to stimulate the shunting mechanism. This is supported by the observation that xanthine/ xanthine oxidase-derived oxygen metabolites also produce vasodilation under hypoxia (44). The study of dilator mechanisms of oxygen metabolites in the pulmonary circulation is far from complete. Most studies have concentrated on the effects of exogenous addition of peroxides to determine the vasoactivity of these compounds. At this time it appears that not only is the metabolism of H,O, an important step in assessing the vasoactivity of this oxygen metabolite, but the role
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
L210
COMMENTARY
of endogenously formed peroxide sponses must also be considered. Direct
Effects of Oxidant
in mediating
on Pulmonary
these re-
Reactivity
Prolonged exposure to 100% oxygen causes progressive pulmonary failure and death in all mammalian species. Hypoxic pulmonary vasoconstriction is lost late in oxygen toxicity at about the same time as edema formation occurs (25). There is some evidence that this inhibition of hypoxic vasoconstriction may be selective; although the pulmonary vasculature was unreactive to hypoxia the administration of prostaglandin Hz or KC1 caused vasoconstriction. Pretreatment with endotoxin delayed edema formation and loss of hypoxic vasoconstriction. The authors did not measure the effect of endotoxin on KCl- or prostaglandin Hz-induced vasoconstriction. In rabbits 48-60 h of normobaric hyperoxia completely blocks thromboxane-mediated vasoconstriction but did not affect peroxide-induced thromboxane production. This vascular paralysis could be prevented by administration of the antioxidants BHA or vitamin E, suggesting an oxidant mechanism. The same antioxidants also prevent edema formation seen in untreated rabbits exposed to 48 h of normobaric hyperoxia (29). Other oxidants also cause vascular paralysis. Exposure of rabbits to a cumulative dose of 2,000 ppm/min of phosgene, which causes lung injury, inhibits vasoconstriction caused by thromboxane but not arachidonic acid-induced thromboxane production. In these lungs vasoconstriction caused by KC1 or angiotensin was not inhibited, suggesting an oxidant effect on thromboxane receptor or associated signal transduction. The selectivity of oxidants on vasoconstrictor agonists has not been extensively investigated and may provide information on the mechanism of action. The clear association between edema formation and inhibition of vascular reactivity suggests a common mechanism of action. This work was supported by National Heart, Lung, and Blood Institute Grants HL-35483, HL-41728, and a grant from the Chemical Manufacturers’ Association. Address for reprint requests: G. H. Gurtner, Westchester County Medical Center, Pulmonary Lab, Area ZG, Valhalla, NY 10594. REFERENCES 1. ARCHER, S. L., D. P. NELSON, AND E. K. WEIR. Detection of activated 0, species in vitro and in rat lungs by chemiluminescence. J. Appl. Physiol. 67: 19121921, 1989. 2. BURKE, T. M., AND M. S. WOLIN. Hydrogen peroxide elicits pulmonary arterial relaxation and guanylate cyclase activation. Am. J. Physiol. 252 (Heart Circ. Physiol. 21): H721-H732, 1987. 3. BURKE-W• LIN, T., P. D. CHERRY, AND G. H. GURTNER. Tone dependent effects of peroxides in rabbit pulmonary artery and isolated perfused lung (Abstract). FASEB J. 4: A573, 1990. 4. BURKE-W• LIN, T., K. M. MOHAZZAB, AND M. S. WOLIN. Mechanism of antagonism of pulmonary artery relaxation to O2 and Hz02 by cyanide (Abstract). Circulation 78: 11-206, 1988. 5. BURKE-W• LIN, T. M., AND M. S. WOLIN. Inhibition of cGMPassociated pulmonary arterial relaxation to H,02 and 0, by ethanol. Am. J. Physiol. 258 (Heart Circ. Physiol. 26): H1267-H1273, 1990. 6. BURKE-W• LIN, T., AND M. S. WOLIN. H,O, and cGMP may function as an O2 sensor in the pulmonary artery. J. Appl. Physiol. 66: 167-170, 1989. 7. CHAKRABORTI, S., G. H. GURTNER, AND J. R. MICHAEL. Oxidant mediated activation of phospholipase A2 in pulmonary endothe-
lium. Am. 1989.
J. Physiol.
257 (Lung
Cell. Mol.
Physiol.
1): L430-L437,
8. CHANCE, B., H. SEIS, AND A. BOVERIS. Hydroperoxide metabolism in mammalian organs. Physiol. Rev. 59: 527-605, 1979. 9. CHERRY, P. D., H. A. OMAR, K. A. FARRELL, J. S. STUART, AND M. S. WOLIN. Superoxide anion inhibits cGMP-associated bovine pulmonary arterial relaxation. Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H1056-H1062, 1990. 10. CHERRY, P. D., AND M. S. WOLIN. Ascorbate activates soluble guanylate cyclase via H202-metabolism by catalase. Free Rad. Biol. Med. 7: 485-490, 1989. 11. CROWLEY, K., J. R. MICHAEL, AND G. H. GURTNER. A protease inhibitor may block phospholipase A2 and C in rabbit lungs (Abstract). Am. Rev. Respir. Dis. 139: A274, 1989. 12. ELLIOTT, S. J., S. G. ESKIN, AND W. P. SCHILLING. Effect of tButyl-hydroperoxide on bradykinin-stimulated changes in cytosolic calcium in vascular endothelial cells. J. Biol. Chem. 264: 38063810, 1989. 13. FARRUKH, I. S., J. R. MICHAEL, S. P. PETERS, M. SCIUTO, N. F. ADKINSTON, JR., HOWARD S. FREELAND, A. PAKY, E. W. SPANNHAKE, W. R. SUMER, AND G. H. GURTNER. The role of cyclooxygenase and lipoxygenase mediators in oxidant-induced lung injury. Am. Rev. Respir. Dis 137: 1343-1349, 1988. 14. FARRUKH, I. S., E. W. SPANNHAKE, A. M. SCIUTO, J. R. MICHAEL, AND G. H. GURTNER. Leukotriene D4 increases pulmonary vascular permeability and pressure by different mechanisms in the rabbit. Am. Rev. Respir. Dis. 134: 229-232, 1986. 15. FARRUKH, I., W. SUMMER, J. MICHAEL, N. F. ADKINSON, G. H. GURTNER. Thromboxane induced pulmonary vasoconstriction: involvement of calcium. J. Appl. Physiol. 58: 34-44, 1985. 16. FEDDERSEN, C. O., S. CHANG, J. CZARTALOMNA, AND N. F. VOELKEL. Arachidonic acid causes cyclooxygenase dependent and independent pulmonary vasodilation. J. Appl. Physiol. 68: 17991808,199O. 17. FEIERMAN, D. E., G. W. WINSTON, AND A. I. CEDERBAUM. Ethanol oxidation by hydroxyl radicals: role of iron chelates, superoxide and hydrogenperoxide. Alcohol Clin. Exp. Res. 9: 95-102, 1985. 18. FREEMAN, B. A., M. K. TOPOLOSKY, AND J. D. CRAPO. Hyperoxia increases oxygen radical production in rat lung homogenates. Arch. Biochem. Biophys. 216: 477-484, 1982. 19. FURCHGOTT, R. F. The role of the endothelium in the response of vascular smooth muscle to drugs. Annu. Rev. Pharmacol. Toxicol. 24: 175-197, 1984. 20. GORDON, J. B., M. L. TOD, R. C. WETZEL, M. L. MCGEADY, N. F. ADKINSON, JR., AND J. T. SYLVESTER. Age dependent effects of indomethacin on hypoxic vasoconstriction in neonatal lamb lungs. Pediatric Res. 23: 580-584, 1988. 21. Guo, Y. L., T. P. KENNEDY, J. R. MICHAEL, A. M. SCIUTO, A. J. GHIO, N. F. ADKINSON, JR., AND G. H. GURTNER. Mechanism of phosgene-induced lung toxicity: role of arachidonate mediators. J. Appl. Physiol. 69: 1615-1625, 1990. 22. GURTNER, G. H., A. KNOBLAUCH, P. SMITH, H. SIES, AND N. F. ADKINSON. Oxidant and lipid induced pulmonary vasoconstriction mediated by arachidonic acid metabolites. J. Appl. Physiol. 55: 949954, 1983. 23. GURTNER, G. H., J. R. MICHAEL, A. M. SCIUTO, AND N. F. ADKINSON. Mechanism of hyperoxia induced vascular paralysis: effect of antioxidant therapy. J. Appl. Physiol. 59: 953-958, 1985. 24. HAZINSKI, T. A., K. A. KENNEDY, AND M. L. FRANCE. Effect of endotoxin pretreatment on the pulmonary vascular response to hypoxia in 02-exposed lambs. J. Appl. Physiol. 65: 1586-1591,1988. 25. HAZINSKI, T. A., K. A. KENNEDY, M. L. FRANCE, AND T. N. HANSEN. Pulmonary 0, toxicity in lambs: physiological and biochemical effects of endotoxin infusion. J. Appl. Physiol. 65: 15791585, 1988. 26. HYSLOP, P. A., B. HINSHAW, I. U. SCHRAUFSTATTER, L. A. SKLAR, R. C. SPRAGG, AND C. G. COCHRANE. Intracellular calcium homeostasis during hydrogen peroxide injury to cultured P338D cells. J. Cell. Physiol. 129: 356-366, 1986. 27. IGNARRO, L. J., K. S. WOOD, AND M. S. WOLIN. Regulation of purified soluble guanylate cyclase by porphyrins and metalloporphyrins: a unifying concept. Adv. Cyclic Nucleotide Prot. Phosphoryl. Res. 17: 267-274, 1984. 28. JACOBSON, J. M., J. R. MICHAEL, M. B. BRADLEY, AND G. H. GURTNER. Inhibition of thromboxane synthetase prevent h.vper-
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
L211
COMMENTARY
29.
30.
31. 32.
33.
34.
35.
36.
37.
38.
Z39.
baric oxygen induced pulmonary damage (Abstract). Am. Rev. Respir. Ibis. 133: A283, 1986. JACOBSON, J. M., J. R. MICHAEL, AND G. H. GURTNER. Antioxidants and antioxidant enzymes protect against pulmonary oxygen toxicity in the rabbit. J. Appl. Physiol. 68: 1252-1259, 1990. KENNEDY, T. P., J. R. MICHAEL, J. R. HOIDAL, D. HASTY, A. M. SCIUTO, C. HOPKINS, R. LAZAR, G. K. BYSANI, E. TOLLEY, AND G. H. GURTNER. Dibutyryl CAMP, aminophylline, and p-adrenergic agonists protect against pulmonary edema caused by phosgene. J. Appl. Physiol. 67: 2542-2552, 1989. KONO, Y., AND I. FRIDOVICH. Superoxide radical inhibits catalase. J. Biol. Chem. 257: 5751-5754,1982. MADDEN, M. C., R. L. VENDER, AND M. FRIEDMAN. Effect of hypoxia on prostacyclin production in cultured pulmonary artery endothelium. Prostuglandins 31: 1049-1062, 1986. MITTAI,, C. K., AND F. MURAD. Activation of guanylate cyclase by superoxide dismutase and hydroxyl radical: a physiological regulator of guanosine-3’,5’-monophosphate formation. Proc. Nutl. Acad. Sci. USA 74: 4360-4364, 1977. NEWMAN, J. H., B. J. BUTKA, AND K. L. BRIGHAM. Thromboxane A2 and prostacyclin do not modulate pulmonary hemodynamics during exercise in sheep. J. Appl. Physiol. 61: 1706-1711, 1986. PETERS-GOLDEN, M., C. SHELLY, AND M. L. MORGANROTH. Inhibition of rat lung glutathione synthesis attenuates hypoxic pulmonary vasoconstriction and the associated leukotriene C, production. Am. Rev. Respir. Dis. 140: 1210-1215, 1989. RUBANYI, G. M., AND P. M. VANHOUTTE. Oxygen-derived free radicals, endothelium, and responsiveness of vascular smooth muscle. Am. J. Physiol. 251 (Heart Circ. Physiol. 20): H815-H821, 1986. SEEGER, W., N. SUTTORP, F. SCHMIDT, AND H. NEUHOF. The glutathione redox cycle as a defense system against hydrogen peroxide induced prostanoid formation and vasoconstriction in rabbit lungs. Am. Rev. Respir. Dis. 133: 1029-1036, 1986. SHAYEVITZ, ,J. R., R. J. TRAYSTMAN, A. R. MCSHANE, K. CROWLEY, AND G. H. GURTNER. Mepacrine inhibits thromboxane, angiotensin II, and potassium induced vasoconstriction in the rabbit. J. Appl. Physiol. 66: 1921-1926, 1989. SUGATANI, J., M. MIWA, AND D. J. HANAHAN. Platelet-activating factor stimulation of rabbit platelets is blocked by serine protease
40.
41.
42.
43.
44. 45. 46.
47.
48.
49.
50.
inhibitor (chymotryptic protease inhibitor). J. Biol. Chem. 12: 5740-5747, 1987. TATE, P. M., H. G. MORRIS, W. R. SCHROEDER, AND J. E. REPINE. Oxygen metabolites stimulate thromboxane production in isolated saline-perfused lungs. J. Clin. Invest. 74: 608-613, 1984. VANGRONDELLE, A., G. S. WORTHEN, D. ELLIS, M. M. MATHIAS, R. C. MURPHY, R. J. STRIFE, J. T. REEVES, AND N. F. VOELKEL. Altering hydrodynamic variables influences PGI, production by isolated lungs and endothelial cells. J. Appl. Physiol. 57: 388-395, 1984. VESSELY, D. L., B. WATSON, AND G. S. LEVEY. Activation of liver guanylate cyclase by paraquat: possible role of superoxide anion. J. Pharmacol. Exp. Ther. 209: 162-164, 1979. VOLPI, M., R. I. SHAAFI, P. M. EPSTEIN, D. M. ANDRENYAK, AND M. B. FEINSTEIN. Local anesthetics, mepacrine, and propranolol are antagonists of calmodulin. Proc. Natl. Acad. Sci. USA 78: 795799, 1981. WEIR, E. K., J. W. EATON, AND E. CHESLER. Redox status and pulmonary vascular reactivity. Chest 88: 249S-251S, 1985. WEIR, E. K., AND J. A. WILL. Oxidants: a new group of pulmonary vasodilators. Bull. Eur. Physiopathol. Respir. 18: 81-85, 1982. WETZEL, R. C., J. B. GORDON, T. J. GREGORY, F. H. GIOIA, N. F. ADKINSON, JR., AND J. T. SYLVESTER. High-frequency ventilation attenuation of hypoxic pulmonary vasoconstriction. The role of prostacyclin. Am. Rev. Respir. Dis. 132: 99-103, 1985. WHITE, A. A., K. M. CRAWFORD, C. S. PATT, AND P. J. LAD. Activation of soluble guanylate cyclase from rat lung by incubation or by hydrogen peroxide. J. Biol. Chem. 251: 7304-7312, 1976. WOLIN, M. S., AND T. M. BURKE. Hydrogen peroxide elicits activation of bovine pulmonary arterial soluble guanylate cyclase by a mechanism associated with its metabolism by catalase. Biochem. Biophys. Res. Commun. 143: 20-25, 1987. WOLIN, M. S., T. BURKE-W• LIN, L. A. COHN, AND P. D. CHERRY. Potential mechanism of pulmonary arterial relaxation and guanylate cyclase activation by 15-hydroperoxyeicosatetraenoic acid. Adv. Prostaglandin Thromboxane Leukotriene Res. 19: 285-288, 1989. YUSA, T., J. S. BECKMAN, J. D. CRAPO, AND B. A. FREEMAN. Hyperoxia increases H,02 production by brain in vivo. J. Appl. Physiol. 63: 353-358, 1987.
Downloaded from www.physiology.org/journal/ajplung by ${individualUser.givenNames} ${individualUser.surname} (129.186.138.035) on January 9, 2019.
