Regulation by interleukin-10 and interleukin-4 of cyclooxygenase-2 expression in human neutrophils

Neutrophils are important effector cells of acute inflammation because of their potential capacity to synthesize various proinflammatory mediators, and inhibition of their production is expected to result in anti-inflammatory effects. In this study, we investigate the effects of the anti-inflammatory cytokines, interleukin-10 (IL-10) and IL-4, on prostanoid synthesis in human neutrophils. Neutrophils isolated from healthy donors constitutively produced a small amount of prostaglandin E₂ (PGE₂) without any stimulations, whereas they produced a large amount of PGE₂ after lipopolysaccharide (LPS) stimulation. IL-10 and IL-4 selectively inhibited their LPS-induced PGE₂' production. Inhibition by both cytokines occurred at an early stage of LPS stimulation. Anti IL-10 treatment of LPS-stimulated neutrophils resulted in enhanced PGE₂ production. LPS-induced PGE₂ and thromboxane B₂ (TXB₂) production in aspirin-treated neutrophils was significantly inhibited by IL- 10, IL-4, and NS-398. Moreover, IL-1O and IL-4 inhibited LPS-induced cyclooxygenase (COX) activity in neutrophils. Western blot and immunocytochemical analysis showed that COX^-2 protein was clearly induced in LPS-stimulated neutrophils and that its induction was inhibited by both IL-10 and IL-4. Moreover, both of these cytokines inhibited COX-2 mRNA expression in LPS-stimulated neutrophils. These results raise the possibility that these two cytokines may both offer potent clinical utility as anti- inflammatory agents in the future.