Pharmacological Research, Vol . 24, No . 4 . 1991

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INTERLEUKIN-1/3: A POSSIBLE MEDIATOR OF LUNG INFLAMMATION AND AIRWAY HYPERREACTIVITY A . HERNANDEZ, C . OMINI* and L . DAFFONCHIO Institute of Pharmacological Sciences, University of Milan, Italy Received in final form 5 June 199/

SUMMARY Interleukin-1 (IL-1), a peptide released from monocytes/macrophages, plays an important role in the inflammatory and immune responses . Airway hyperreactivity and the underlying airway inflammation are common features in asthma pathology . We investigated and characterized the inflammatory alterations induced within the guinea-pig respiratory system by IL-l/3 . Injection of IL-l f3 (1-6 pg/animal) into the pleural space resulted in a dose-dependent inflammatory response, as shown by the formation of pleural exudate and leucocyte recruitment . A threshold dose of IL-l/3 (1 µg/animal) markedly potentiated the inflammatory reaction triggered by the classical proinflammatory agent croton oil, underlining the amplifying role of IL-1/3 in the inflammatory events . The inflammatory process induced by intrapleural injection of IL-1/3 (6 pg/animal) was associated with the development of a hyperreactive phenomenon which involved both the peripheral and large airways . In fact, increased contractile activity of histamine was evident in the tracheas and parenchymal strips isolated from guinea-pigs exposed to IL-1/3. These results provide evidence for a possible role of IL-1/3 in the genesis of airway inflammation and bronchial hyperreactivity . KEY WORDS :

interleukin-1/3, pulmonary inflammation, airway hyperreactivity, asthma .

INTRODUCTION Cytokines are a novel class of peptides of known amino acid sequence, with a large range of action and the ability to modulate a wide set of biological events [1] . Among cytokines, interleukin-1 (IL-1) was first described in 1972 as a cofactor for lymphocyte proliferation [2] . This peptide is produced mainly by monocytes/macrophages [3] and its role as a proinflammatory mediator has been widely established [4, 5] . In particular, IL-1 is involved in acute-phase inflammatory vascular changes and synthesis of hepatic proteins, in the rise of *Present address : Dompe Farmaceutici, Milan, Italy . Correspondence to : Dr Luisa Daffonchio, Institute of Pharmacological Sciences, via Balzaretti 9, 20133 Milan, Italy . 1043-6618/91/080385-09/$03 .00/0

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1991 The Italian Pharmacological Society

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Pharmacological Research, Vol . 24, No . 4, 1991

temperature and in leucocyte proliferation [6] . In addition, IL-1/3 affects immune responses, being an important accessory signal for T-cell expansion in response to antigen [1, 7] . The importance of the inflammatory reaction within the lung and of airway hyperreactivity has gained increasing relevance to the pathology of asthma [8] . In particular, the underlying bronchial inflammation has a presumptive role in the development of airway hyperresponsiveness, since the association between increased airway reactivity and pulmonary inflammation has been widely reported in several experimental models [9] . In this regard, we have previously demonstrated that also an inflammatory reaction localized to the pleural cavity, such as the one induced by intrapleural injection of croton oil, was paralleled by increased airway reactivity [10] . Therefore, we verified the possible inflammatory role of IL-l/3, using the same model of experimental lung inflammation . In particular, we characterized the inflammatory alterations induced in the guinea-pig lung by intrapleural injection of this cytokine, and investigated the possible link between IL-1/3 induced pleurisy and the development of airway hyperreactivity .

MATERIALS AND METHODS In vivo procedures

Male Dunkin-Hartley guinea-pigs (400-450 g ; Rodentia, Italy) were used for this study . The pleurisy was induced by intrapleural injection of IL-1/3 (1-6 pg/animal, dissolved in 100 pl of 0.9% saline) under light ether anaesthesia, as described previously [10] . At different times after IL-l/3 injection (2-12 h), the animals were sacrificed by excess ether anaesthesia ; a small hole was cut into the diaphragm and the pleural fluid collected for volume and cell count determination . Control animals received 100,ul of 0 .9% saline and were sacrificed 6 h later . In some animals, where inflammatory exudate was found in small amount, the pleural cavity was washed with 1 ml of phosphate buffered saline (pH 7 .4) in order to collect the cells . In another group of animals, 150,ul of 1 % croton oil suspension in 0 .9% saline, or croton oil in combination with IL-1/8 (1 ,ug/animal) were injected into the pleural cavity . These animals were sacrificed 16 h later for collection of the inflammatory exudate .

Cell count determination

Total cell count was determined in the pleural exudate after dilution by Unopette microcollection system (Becton-Dickinson) using an `improved Neubauer' counting chamber and phase contrast microscopy . Differential cell count was evaluated on the same samples of pleural fluid prepared on glass slides and stained with May-GrUnwald-Losung and Giemsa-Losung (Merck), by light microscopy . Two hundred cells were counted in each sample .

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In vitro procedures The development of airway hyperreactivity was assessed comparing the contractile activity of histamine in tissues obtained from control or IL-1/3 exposed guinea-pigs . In particular, 6 h after saline or IL-1/3 (6 pg/animal) injection, the animals were sacrificed by excess ether anaesthesia and the presence of inflammatory exudate was verified . The tracheas and the lungs were isolated . Lung parenchymal strips [11] and zig-zag preparations from the tracheas [121 were placed in 20 ml organ baths containing oxygenated (0 2-CO 2 : 95-5%) Krebs-bicarbonate solution (37 ° C) . A load of 1 g and 1 .2 g was applied to the parenchymal strip and trachea, respectively, and the tissues were allowed to equilibrate for about 60 min . Complete cumulative log-concentration-response curves for histamine (10 -'-3x10-4 M) were performed in each preparation . Changes in the length of the tissues were measured via isotonic transducer (Basile 7006) connected to a Gemini (Basile 7070) pen recorder.

Statistical analysis Data are reported as mean±sE of (n) replications . Regression lines and comparisons between log-concentration-response curves were evaluated using a computer aided program based on the variance analysis for regression lines [13] . As far as the comparison between regression lines is concerned, this procedure allows the calculation of the dose ratio (DR) and its 95% confidence limits . Significance level for a synergistic interaction between croton oil and IL-1/3 was calculated according to the variance analysis for a factorial experimental design [13] . This procedure takes into account at the same time the results obtained after no treatment (control), treatment with each agonist administered alone, and their combination . Comparisons between means were performed with Student's t-test . A probability level of P

Interleukin-1 beta: a possible mediator of lung inflammation and airway hyperreactivity.

Interleukin-1 (IL-1), a peptide released from monocytes/macrophages, plays an important role in the inflammatory and immune responses. Airway hyperrea...
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