To determine which factors in cholestatic liver disease may aggravate or protect against bile acid-induced apoptosis, HepG2.rNtcp cells were preconditioned (for 24 h) with sub-apoptotic concentrations of GCDCA (25 μM), superoxide anion donor menadione (10 μM) [23] or pro-inflammatory cytokine TNF-α (10 ng/ml). Here, TNF is linked to Cholestatic liver disease.