Calcineurin inhibitors, cyclosporin A and tacrolimus inhibit expression of inducible nitric oxide synthase in colon epithelial and macrophage cell lines.

Nitric oxide (NO) production is increased in inflammatory bowel disease and selective inducible nitric oxide synthase (iNOS) inhibitors have proved to be anti-inflammatory in experimentally induced colitis. The aim of the present study was to test if drugs used in the treatment of inflammatory bowel disease effect on NO production in colon epithelial and macrophage cell lines. We tested the effects of cyclosporin A, tacrolimus (FK-506), methotrexate, sulfasalazine, 5-aminosalicylic acid and two novel TNF-alpha antagonists etanercept and infliximab on endotoxin-induced NO production in human T84 colon epithelial cells and in murine J774 macrophages. Cyclosporin A and FK-506 inhibited iNOS expression, and subsequent NO production, in a dose-dependent manner at therapeutically achievable drug concentrations in both cell lines. The effect was most pronounced when cyclosporin A was given 1 h prior to 4 h after endotoxin, and declined thereafter, indicating that cyclosporin A does not inhibit iNOS activity. Neither cyclosporin A nor FK-506 altered the activation of nuclear factor-kappaB (NF-kappaB) that is a critical transcription factor for iNOS. Sulfasalazine inhibited NO production slightly only when given at high (100 microM) drug concentrations. Methotrexate, 5-aminosalicylic acid and TNF-alpha antagonists infliximab and etanercept were practically ineffective. Two inhibitors of phosphatase calcineurin, cyclosporin A and FK-506, inhibited iNOS expression and NO production in human T84 colon epithelial cells and in murine J774 macrophages by an NF-kappaB independent manner. These findings are implicated in the anti-inflammatory action of these compounds. Copyright 2002 Elsevier Science B.V.