The active metabolite of leflunomide, A77 1726, protects rat hepatocytes against bile acid-induced apoptosis.

Leflunomide is used in the treatment of autoimmune diseases as an anti-inflammatory agent. Leflunomide and its active metabolite A77 1726 modulate mitogen-activated protein kinases (MAPK), Src kinases, the phosphoinositide-3 kinase (PI3K)/Akt-pathway and nuclear factor (NF)-kappaB activation. Both cell protective and cytotoxic effects of leflunomide have been described. Since leflunomide affects pathways involved in hepatocyte cell survival, we examined the effects of A77 1726 on hepatocyte cell death. Primary rat hepatocytes were exposed to the bile acid glycochenodeoxycholic acid (GCDCA), the superoxide anion donor menadione, or tumor necrosis factor (TNF) alpha in combination with actinomycin D. Activation of MAP-kinases was determined by Western blot analysis. Apoptosis and necrosis were analyzed by acridine orange staining and caspase activity and Sytox Green staining, respectively. A77 1726 dose-dependently reduces GCDCA-induced apoptosis and necrosis, but not menadione- or TNFalpha/ActD-induced apoptosis. The hepatoprotective effect of A77 1726 does not involve ERK1/2, p38 or PI3K/Akt activation. A77 1726 does not inhibit NF-kappaB activation in hepatocytes. Since A77 1726 inhibits bile acid-induced apoptosis and does not sensitize hepatocytes to TNFalpha, our results suggest that A77 1726 could be considered for the treatment of chronic liver diseases accompanied by elevated bile acid levels and inflammation.