9 1992 by The Humana Press, Inc. All rights of any nature, whatsoever, reserved. 0163-4984/92/3201-3-43355 $02.00

Effects of Acute Prednisolone Administration on Plasma and Liver Copper in Rats with Adjuvant Arthritis JEANINE FONTAINE, "'1 J E A N NEVE, 2 ANNE PERETZ, 3

JEAN-PIERRE FAMAEY3 1Department of Pharmacology,, Institute of Pharmacy, University of Brussels, Campus Plaine 205- Z B- 1050 Brussels, Belgium; 2Department of Pharmaceutical Organic Chemistoz, Institute of Pharmacy, University of Brussels, Campus Plaine 205-5, B-1050 Brussels, Belgium; and 3Departrnent of Rheumatology and Physical Medicine, Saint-Pierre Hospital, rue Haute, 322, B- 1000 Brussels, Belgium AND

Received January 31, 1991; Accepted March 21, 1991

ABSTRACT Several studies in animals and humans have shown that copper metabolism could be affected by inflammation or by corticosteroids. The relative importance of these two factors, often imbedded in clinical practice, was assessed by investigating the effects of acute prednisolone administration (30 mg/kg, ip) on healthy and adjuvant arthritis rats. Plasma copper levels were significantly higher in arthritic rats compared to healthy animals, whereas there was a slight, but nonsignificant increase in liver copper. Acute prednisolone administration in healthy rats resulted in a significant increase in plasma copper (10-15%) as early as 4 h after corticosteroid administration, which was maintained for 12 h. In arthritic rats, the response was much higher (25-40%), but somewhat delayed and shorter. Liver copper was not clearly modified by prednisolone treatment in both groups. This time-controlled study showed that acute prednisolone administration increased plasma copper in both healthy and arthritic rats, but in different ways, indicating that inflammation and corticosteroids may act synergistically. *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research

355

Vol. 32, 1992

356

Fontaine et

aL

Index Entries: Adjuvant arthritis; inflammation; copper; corticosteroid; liver; plasma; rats.

INTRODUCTION Copper status is known to be modified in inflammatory diseases in humans (1) or in laboratory animals (2), with significant increases in the plasma copper and ceruloplasmin concentrations. A previous study by us documented the modifications with time of adjuvant-induced arthritis in the rat, causing an early increase in plasma copper remaining at the same high level during the observation period (26 d), and a late, but considerable increase in liver copper (3). These modifications were interpreted as a physiological response of the organism against inflammation. In this context, the exogenous administration of copper salts has been proven beneficial in the treatment of experimental inflammation and of various clinical inflammatory diseases, including rheumatoid arthritis (4,5). It has also been observed that copper metabolism can be affected by short-term corticosteroid administration in humans (6) and by short(7) or long-term (8) administration in healthy rats. The effects of corticosteroids are probably owing to their property of enhancing the hepatic synthesis of specific proteins, such as: (i) metallothionein, a powerful ligand of metals including copper, and (ii) ceruloplasmin as well as other acute-phase reactants, which are released in the blood circulation (9). These changes are thought to account for the antiinflammatory activity of these drugs (1). The present study was designed to assess the relative importance of the inflammatory process and of acute glucocorticoid administration in modifying plasma and liver copper levels. To this purpose, the effects of acute prednisolone administration (30 mg/kg, ip) were investigated in a group of healthy rats and in a group of adjuvant arthritis rats.

MATERIAL AND METHODS The methodology of this experiment was described in a previous study devoted to the effects of corticosteroids on zinc status (10). In a first experiment, a group of 90 healthy Wistar rats (200 + 5 g) were injected with prednisolone 30 mg/kg, ip (homemade suspension). In the second experiment, a group of 60 Wistar rats with adjuvant arthritis (229 -+ 8 g) received the same prednisolone treatment 2 wk after injection of the Freund's adjuvant (experimental induction of arthritis). In both experiments, an identical number of control rats were injected with the vehicle only. Subgroups of 10 rats were sacrificed at various times after injection (between 2-72 h). In addition to these animals, two groups of 20 healthy or arthritic animals, which did not receive any treatment, were sacrificed to determine initial values (time 0). The animals' diet Biological Trace Element Research

VoL 32, 1992

Prednisolone Administration

357

was withdrawn 16 h before sacrifice. Plasma and liver copper were determined by flame atomic absorption spectroscopy as previously described (3).

RESULTS Healthy Rats As shown in Table 1, acute prednisolone administration caused a significant increase in plasma copper (10-15%), which appeared 4 h after treatment and persisted until 16 h (with 2 nonsignificant values after 9 and 12 h). No fluctuation related to physiological circadian variations in plasma copper was observed in the controls. Figure 1 represents the data in percentages of modification obtained in prednisolone-treated rats vs their respective controls: A clear plateau of higher plasma values was observed during 12 h. This phenomenon was followed by a slow return of copper levels to the values observed in control animals after about 24 h. No unequivocal modification was observed in liver copper levels of prednisolone-treated rats in comparison with controls (data not shown).

Arthritic Rats Food intake and growth of arthritic rats were similar to those of a group of healthy control rats when examined 2 wk after adjuvant injection. However, clinical signs of inflammation were present with an increase in the articular index and a parallel increase in the paw volume. Plasma fibrinogen was also higher in the arthritic animals (data not shown, but can be found in ref. 9). As expected, plasma copper concentrations before any treatment (time 0) were higher in arthritic rats than in healthy animals (Table 1). They did not fluctuate according to the time of blood collection. When compared to time-matched arthritic controls, statistically significant increases in serum copper values were observed in prednisolone-treated animals between 6-9 h after injection. As shown in Fig. 1, these modifications reached approx 25-40% of the control values. Following the peak value observed 9 h after treatment, there was a rapid drop in plasma copper reaching the control values 16-18 h after treatment. As far as liver copper values are concerned, no difference was observed between prednisolone-treated and untreated animals (data not shown).

DISCUSSION We previously documented the effects of acute corticosteroid administration either on copper and zinc levels in humans (5) or on the zinc status of rats (10). In patients with rheumatoid arthritis treated by pulse therapy (1 g/d iv prednisolone during 3 d) as in healthy and adjuvant arthritic rats, a rapid decrease in plasma zinc was observed as a result of Biological Trace Element Research

Vol. 32, 1992

358

Fontaine et al.

Table 1 Plasma Copper in a Group of Healthy Rats and in a Group of Rats with Adjuvant Arthritis (15 d) Treated with Prednisolone ip 30 mg/kg or with Its Vehicle (Controls) and Sacrificed at Various Times After Treatment~ Time after injection, h 0 2 4 6 7 9 12 16 19 24 72

Healthy rats Controls Prednisolone

Arthritic rats Controls Prednisolone

108 +_ 10 ---13 106 _+ 6 + 6 122 --- 11c ---5 115 _+ 6c _+ 17 116 + 10c +-11 117 +-10 -+ 10 123 +_ 10 + 12 124 + 15b 119 +- 11 115 +- 20 115 + 12 120 -+ 21

300 + 45 + 85 306 _+ 70 _+ 70 374 _+ 64b _+ 80 358 +_ 69b _+ 52 400 +__ 45c +_ 79 330 + 99 +_ 66 284 _ 74 -

110 105 105 103 109 115 112

302 302 282 290 298 300

aResults are e x p r e s s e d in ~ g / d L as m e a n s _+ SD, n = 10 (except for t = 0: n = 20). ~p < 0.05. Cp < 0.001. S t u d e n t ' s t-test b e t w e e n treated a n d n o n t r e a t e d animals (healthy or arthritic) at the s a m e time.

drug administration. However, plasma copper levels did not significantly change in h u m a n subjects (5). At variance with these last results, the present s t u d y shows an increase in plasma copper of both healthy and arthritic rats caused by acute prednisolone administration. Such an effect has been partly reported by others (7) at some time intervals after treatment, but to our knowledge, this is the first time that the modification has been so carefully described according to time. In adjuvant arthritic rats, the modification in plasma copper was shorter and delayed, but more intense w h e n c o m p a r e d to healthy animals in which only a moderate but long-lasting increase developed. The observation therefore suggests that the effect of prednisolone is somewhat p r o m o t e d by inflammation. The delay in the appearance of the increase in arthritic animals might be o w i n g to the higher baseline level in these rats in comparison to healthy controls. The mechanisms responsible for the more important increase in plasma copper of arthritic rats are complex and probably related to synergistic effects of both the inflammatory process and corticosteroid administration (7). These conditions are i n d e e d liable to induce an accelerated uptake of copper by the liver, which increases the available copper pool, partly b o u n d to metallothionein (7). Quite simultaneously, the synthesis of ceruloplasmin is markedly stimulated, allowing the incorporation of increased a m o u n t s of the element into this newly synthesized protein, which is finally secreted in blood. Cytokines, such as Interleukin I and lnterleukin 6, which are prod u c e d d u r i n g inflammation, are k n o w n to be promoters of these events Biological Trace Element Research

Vol. 32., 1992

Prednisolone Administration

+/.0

359

~ Modification ~lasma copper

1/11(~

+30

9,~

~

iI

~-20

~

+10 0 -10 9

i

2 /.

i

i

v

i

i

i

i

i

i

i

6 8 10 12 14 16 18 20 22 2/.

72 hours

T i m e a f t c r Inir

Fig. 1. Plasma copper levels at various times after treatment in healthy rats and in arthritic rats injected with prednisolone, 30 mg/kg, ip. The results are expressed in percent as the ratio of values from prednisolone- vs vehicle-treated animals. 9 Healthy rats. 9 Adjuvant arthritis. (11). The similar effects of corticosteroids on these modifications seem, however, to be less pronounced than those of inflammation (7), explaining the difference in the magnitude of the response observed in healthy and arthritic rats. The increase in plasma copper levels here observed is related to the intense inverse change in plasma zinc occurring nearly simultaneously, such as already reported by us in the same experimental model with both arthritic and healthy rats (10) or by others in surrenalectomized animals (12). The modification in zinc status is clearly linked to an accelerated uptake of the element by the liver caused by stimulation of metallothionein synthesis after exogenous corticosteroid administration, by cytokines produced during the inflammatory process, or by both influences (7,9). When considering the physiological consequences of the changes in copper and zinc metabolism, it seems that they are directly relevant to the host defense mechanisms (3,4,6,9).

ACKNOWLEDGMENTS Our thanks are expressed to the "Fonds National de la Recherche Scientifique M~dicale," Belgium, grant no. 3.4510.87, and to Labcatal Laboratories, France, for financial support. We also thank M. Depaix and N. Leclercq for skilled technical assistance. Biological Trace Element Research

Vol. 32, 1992

360

Fontaine et al.

REFERENCES 1. A. J. Lewis, Agents and Actions 15, 513-519 (1984). 2. A. Conforti, L. Franco, R. Milanino, A. Totorizzo, and G. P. Velo, Br. J. Pharmac. 79, 45-52 (1983). 3. J. N6ve, J. Fontaine, A. Peretz, and J. P. Famaey, Agents and Actions 25, 146-155 (1988). 4. A. J. Lewis, W. E. Smith, and D. H. Brown, Trace Elements in the Pathogenesis and Treatment of Inflammation, K. D. Rainsford, K. Brune, and M. W. Whitehouse, eds., Birkh/iuser, Basel, 1981, pp. 327-338. 5. J. R. J. Sorenson, Progress in Medicinal Chemistry, vol. 15, G. P. Ellis and G. B. West, eds., Elsevier, North Holland, 1978, pp. 211-260. 6. A. Peretz, J. N6ve, and J. P. Famaey, J. Trace Elem. Electrolytes Health Dis. 3, 103-108 (1989). 7. A. Yunice, A. Czerwinski, and R. Lindeman, Am. J. Med. Sci. 282, 68-74 (1981). 8. J. P. Famaey, A. Peretz, J. N6ve, and J. Fontaine, Actualit~s en physiologic et pharmacologic articulaires, vol. 2, A. Gaucher, P. Netter, J. Pourel, and D. R6gent, eds., Masson, Paris, 1991, pp. 428-435. 9. R. J. Cousins, Physiol. Rev. 65, 238-309 (1985). 10. J. Fontaine, J. N6ve, A. Peretz, P. Capel, and J. P. Famaey, Agents and Actions, 33, 247-253 (1991). 11. C. A. Dinarello, Inflammation: Basic Principles and Clinical Correlates, J. I. Gallin, I. M. Goldstein, and R. Snyderman, eds., Raven, New York, 1988, pp. 195-208. 12. K. Etzel and R. Cousins, Proc. Soc. Exp. Med. 167, 233-236 (1981).

Biological Trace Element Research

VoL 32, 1992

Effects of acute prednisolone administration on plasma and liver copper in rats with adjuvant arthritis.

Several studies in animals and humans have shown that copper metabolism could be affected by inflammation or by corticosteroids. The relative importan...
323KB Sizes 0 Downloads 0 Views