Role of IL-1 beta and TNF-alpha in the regulation of NGF in experimentally induced arthritis in mice

The aim of this study was to investigate the effects of IL-1 beta and TNF-alpha on NGF levels in the knee joint in experimentally induced arthritis in adult mice. Out data showed that IL-1 beta, but not TNF-alpha, induces an increase in NGF levels, while concomitant injection of both cytokines enhances the effect of IL-1 beta on NGF presence. Analysis of NGF levels in the knee joint of carrageenan- and IL-1 beta-induced inflammation after administration of antibodies against TNF-alpha supports this hypothesis. Our studies also showed that exogenous administration of NGF antibody reduces the enhanced level of TNF-alpha occurring in arthritic mice. This latter observation indirectly suggests that NGF is implicated in the upregulation of TNF-alpha in these animal models of joint inflammation. The functional significance of NGF or NGF antibody in inflammatory arthritis is discussed.