Leptin potentiates IFN-γ-induced expression of nitric oxide synthase and cyclo-oxygenase-2 in murine macrophage J774A.1

Abstract

1. Leptin, a pleiotropic hormone believed to regulate body weight, has recently been associated with inflammatory states and immune activity. Here we have studied the effect of leptin on expression of IFN-γ-induced nitric oxide synthase (iNOS) and cyclo-oxygenase-2 (COX-2), both prominent markers of macrophage activation, using the murine macrophage J774A.1 cell line. 2. After 24 h of incubation, leptin (1-10 μg ml -1) potently synergized with IFN-γ (100 U ml -1) in nitric oxide (NO) release, evaluated as nitrite and nitrate (NO x), and prostaglandin E 2 (PGE 2) production in culture medium. 3. The observed increase of NO and PGE 2 was related to enhanced expression of the respective inducible enzyme isoforms, measured in mRNA and protein by RT-PCR and Western blot analysis, respectively. 4. When cells were stimulated only with leptin, a weak induction of NO and PGE 2 release and of the expression of related inducible enzymes was observed. 5. Moreover IFN-γ increased the expression of the functional form of leptin receptor (Ob-Rb) and this effect was potentiated by leptin in a concentration-dependent manner. 6. These data suggest that macrophages, among the peripheral immune cells, represent a target for leptin and confirm the relevance of this hormone in the pathophysiology of inflammation.