Modulation of nitric oxide production in RAW 264.7 cells by transforming growth factor-beta and interleukin-10: differential effects on free and encapsulated immunomodulator.

The mouse macrophage cell line RAW 264.7 can be stimulated to produce nitric oxide (NO) by muramyltripeptide cholesterol included within biodegradable poly(D,L-lactide) nanocapsules (NC MTPChol). The aim of this work was to determine whether one or both of the cytokines transforming growth factor-beta (TGF-beta) and interleukin-10 (IL-10) could be responsible for feedback control seen at high concentrations. Activated RAW 264.7 cells produced TGFbeta1. When exogenous TGF-beta1 was added during stimulation, a dose-dependent inhibition of NO production was observed when NC MTP-Chol was used, whereas activation by the soluble muramyl dipeptide (MDP) was not affected. Furthermore, addition of a blocking antibody to TGF-beta arrested the fall in NO production seen at high concentrations of NC MTP-Chol. Addition of IL-10 during RAW 264.7 cell activation also reduced NO production; however, in this case, both NC MTP-Chol and MDP were equally affected. The presence of anti-IL-10 antibody during activation significantly increased NO production.