CONTROL OF NITRIC-OXIDE PRODUCTION BY ENDOGENOUS TNF-ALPHA IN MOUSE RETINAL PIGMENTED EPITHELIAL AND MULLER GLIAL-CELLS

Since the induction of nitric oxide synthase (NOS) by lipopolysacchari de (LPS) has been suggested to be partially dependent of the synthesis of tumor necrosis factor alpha (TNF alpha), we have investigated in v itro the production of NO in retinal cells from mice deficient in Lymp hotoxin alpha (LT alpha)/TNF alpha. Treatment of retinal Muller glial (RMG) and retinal pigmented epithelial (RPE) cells from both wild-type and knockout mice with LPS and interferon gamma (IFN gamma) induced N O synthe sis as determined by nitrite release into the media and was c orrelated to an increase in NOS-2 mRNA levels, evaluated by RT-PCR. Ho wever, the level of nitrite and the accumulation of mRNA was always le ss in cells from LT alpha/TNF alpha knockout mice than in wild-type mi ce. Simultaneous addition of TNF alpha restored the level of NO synthe sis by RdMG and RPE cells from LT alpha/TNF alpha knockout mice stimul ated with LPS and IFN gamma to wild type levels. Transforming growth f actor beta (TGF beta) blocked LPS/IFN gamma-induced NO production in R MG and RPE cells from wild-type and LT alpha/TNF alpha knockout mice. Our results demonstrate that induction of NO synthesis in RMG and RPE cells by LPS and lFN gamma is dependent in part on endogenous TNF alph a while inhibition of NO production by TGF beta does not require a mod ulation of TNF alpha synthesis. (C) 1997 Academic Press.