A 771726, the active metabolite of leflunomide, inhibits TNF-alpha and IL-1 from Kupffer cells.

This study was conducted to investigate the importance of direct contact between Kupffer cells (KCs) and hepatocytes (HCs) during the hepatic inflammatory responses, and the effect of leflunomide's active metabolite, A771726, on cytokines in KCs and HCs (DC cocultures) and KC cultures using an in vitro approach. Lipopolysaccharide (LPS)-induced inflammatory response in monocultures of rats HCs and KCs were compared with DC cocultures. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) concentrations of different culture supernatants were measured with ELISA. TNF-alpha and IL-1 mRNA in KCs of inflammatory liver injury was analyzed with reverse transcription polymerase chain reaction (RT-PCR). Our data showed that DC cocultures exhibited the highest production of TNF-alpha and IL-1 compared with other cultures, and these cytokines were mainly produced by KCs, in particular activated KCs. Time course studies revealed an increased production of TNF-a preceding the IL-1 production, suggesting that increased TNF-alpha levels could be involved in the increased IL-1 production. Leflunomide's active metabolite, A771726, has significantly inhibitory effect on TNF-a and IL-1 at protein and transcription levels, and reduced production of IL-1 by A771726 was associated with inhibitory action of A771726 on TNF-alpha. These results provided evidence that leflunomide significantly inhibited TNF-alpha and IL-1 from KCs.