Changes in airway resistance by simultaneous exposure to TNF-α and IL-1β in perfused rat lungs

Tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta are formed simultaneously under inflammatory conditions such as asthma and acute respiratory distress syndrome. Here we investigated the effects of TNF-alpha (10 ng/ml) and/or IL-1 beta (10 ng/ml) in isolated blood-free perfused rat lungs. In lungs precontracted with methacholine, IL-1 beta alone and IL-1 beta /TNF-alpha decreased airway resistance 10 min after administration, whereas TNF-alpha alone had no effect. In untreated lungs, airway resistance was unaltered by either cytokine alone but started to increase 40 min after treatment with both cytokines together, indicating bronchoconstriction. The bronchoconstriction was accompanied by a steroid-sensitive increase in cyclooxygenase (COX)-2 mRNA expression and thromboxane formation. The cytokine-induced bronchoconstriction was blocked by the thromboxane receptor antagonist SQ-29548, indomethacin, the selective COX-2 inhibitor NS-398, and the steroid dexamethasone. We conclude that IL-1 beta has an early bronchodilatory effect (after 10 min) that is unchanged by TNF-alpha. However, at later time points (after 40 min), IL-1 beta and TNF-alpha in concert cause a COX-2- and thromboxane-dependent bronchoconstriction. Our findings show that TNF-alpha and IL-1 beta exert complex and time-dependent effects on lung functions that cannot be predicted by studying each cytokine alone.