Interleukin-13 Inhibits Protein Kinase C-triggered Respiratory Burst in Human Monocytes ROLE OF CALCIUM AND CYCLIC AMP

Abstract Interleukin-13 (IL-13), a novel cytokine produced by activated lymphocytes modulates some monocyte functions, but no data is available concerning the signal transduction pathway. We show here, the inhibitory effect of IL-13 on 12-O-tetradecanoylphorbol-13-acetate (TPA)-triggered reactive oxygen intermediate production in human monocytes and the signals involved in this response. Our results show that IL-13 produces rapid and transient phosphoinositide hydrolysis and intracellular Ca2+ mobilization. Furthermore, IL-13 induces intracellular cAMP accumulation through inositol 1,4,5-trisphosphate-dependent Ca2+ mobilization. Metabolic inhibitors were used to relate the first steps in signaling pathways to the inhibitory effect of IL-13 on TPA-triggered reactive oxygen intermediate production. Indeed, inhibitors of phospholipase C (neomycin), intracellular Ca2+ mobilization (8-[N,N-diethylamino]-octyl 3,4,5-trimethoxybenzoate hydrochloride), adenylate cyclase (Δ9-tetrahydrocannabinol), and protein kinase A (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide) impair the IL-13 inhibitory response. Altogether these observations indicate that modulatory effect of IL-13 on the TPA-induced oxidative burst is the result of the intracellular cAMP accumulation through an inositol 1,4,5-trisphosphate-induced Ca2+ mobilization-dependent pathway.