Activated neutrophils induce nitric oxide production in Kupffer cells

Neutrophils (PMN) are proposed to contribute to hepatic dysfunction during sepsis. Transmigrating PMN have been demonstrated to adhere to and injure p arenchymal cells (hepatocytes); however, the effect of sepsis-activated PMN on hepatic macrophages or Kupffer cells (KC) is poorly characterized. We h ypothesize that PMN influence KG inflammatory mediator production, includin g nitric oxide. Rodent KC were co-cultured with PMN obtained from controls (Norm-PMN) or endotoxemic rats [lipopolysaccharide (LPS)-PMN] for 18 h. Aft er an 18-h incubation, supernatants and cell lysates of the KC were analyze d for nitric oxide (NO) production. Go-cultures with LPS-PMN/KC demonstrate d significantly increased production of nitrite and up-regulation of induci ble nitric oxide synthase (iNOS) protein compared to KC alone or Norm-PMN/K G co-cultures. Immunohistochemistry revealed preferential iNOS protein stai ning in the cytoplasm of KC cultured with LPS-PMN compared to controls. Nit rite production in co-cultures of KC and LPS-PMN where cell contact was inh ibited by a cell impermeable but diffusable membrane was significantly redu ced. These data provide evidence that KC can be stimulated directly by acti vated PMN for production of NO. Further, they suggest another mechanism by which PMN modulate hepatic function during sepsis.