Differential effects of interleukin-4 and interleukin-10 on nitric oxide production by murine macrophages

Objective. To study the effect of interleukin (IL)-4 and IL-10 on nitric ox ide (NO) production by macrophages. Materials and Methods: Elicited or resident peritoneal macrophages (PMO) an d a macrophage cell line Raw264.7 were primed by IL-4 or IL-10 for 6 hours, and were further incubated in the presence of interferon (IFN)-gamma and/o r lipopolysaccharide (LPS) for 48 hours. NO2- accumulation in the supernata nt of cultured cells was used as an indicator of NO production and was dete rmined by the standard Griess reaction adapted for microplates. The amount of tumor necrosis factor (TNF)-alpha in the culture supernatants was determ ined with a commercially available ELISA kit. The absorbance was measured a t 350 nm with a microplate photometer. Results: IL-4 inhibited NO production by murine macrophages of different so urces and the macrophage cell line Raw264.7. In contrast, different macroph age populations showed differential responses to IL-IO. After stimulation w ith LPS or IFN-gamma IL-10 suppressed NO production by elicited PMO but enh anced NO production by resident PMO or by Raw264.7. Both IL-4 and IL-10 inh ibited the production of TNF-alpha, which has been shown to play a crucial role in NO production. In the presence or the absence of blocking antibody to TNF-alpha, IL-10 always enhanced NO production by resident PMO. This res ult suggests that the inhibition of TNF-alpha production and the enhancemen t of NO production by resident PMO stimulated with IL-10 are independent, c oexisting events. Conclusions: Factors other than TNF-alpha have been suspected to influence NO production by macrophages, and this study indicates that IL-10 may be a candidate cytokine for resident PMO.