Nuclear factor κB in proliferation, activation, and apoptosis in rat hepatic stellate cells

Abstract

Background/Aims: Activation of the transcription factor NFκB has been demonstrated in activated hepatic stellate cells (HSCs). We investigated the role of NFκB in proliferation, in activation, and in TNFα-induced apoptosis of HSCs. Methods: NFκB activation was inhibited using an adenovirus expressing an IκB dominant negative protein (Ad5IκB) in both quiescent and activated HSCs. Quiescent HSCs were infected with Ad5IκB or an adenovirus expressing β-galactosidase (Ad5LacZ). The cells were cultured for 7 days. HSCs activation was determined by cell morphology, smooth muscle α-actin (α-sma) expression, and steady-state mRNA levels of α1(I) collagen as assessed by Western blot and RNase protection assay, respectively. Proliferation was determined in culture-activated HSCs by 3H-thy-midine incorporation and direct cell counting. Apoptosis was analyzed by infecting quiescent or activated HSCs with Ad5IκB or Ad5LacZ, and then treating with TNFα. Apoptosis was demonstrated by determining cell number, assessing nuclear morphology, TUNEL assay and caspase 3 activity. Results: After 7 days in culture no differences were noted between the Ad5IκB- and the Ad5LacZ-in-fected cells in the morphology, α-sma expression or in α1(I) collagen mRNA levels. Ad5IκB infection did not modify proliferation in activated HSCs. TNFα induced apoptosis only in Ad5IκB-infected activated, but not quiescent HSCs. Apoptosis was initially demonstrated 12 h after exposure to TNFα. Twenty-four h after the TNFα treatment, 60% of the activated HSCs were apoptotic. Conclusion: NFκB activity is not required for proliferation or activation of HSCs; however, NFκB protects activated HSCs against TNFα-induced apoptosis.