Inhibition of GSK3 differentially modulates NF-κB, CREB, AP-1 and β-catenin signaling in hepatocytes, but fails to promote TNF-α-induced apoptosis

Glycogen synthase kinase-3 (GSK-3) is known to modulate cell survival and apoptosis through multiple intracellular signaling pathways. However, its hepatoprotective function and its role in activation of NF-κB and anti-apoptotic factors are poorly understood and remain controversial. Here we investigated whether inhibition of GSK-3 could induce apoptosis in the presence of TNF-α in primary mouse hepatocytes. We show that pharmacological inhibition of GSK-3 in primary mouse hepatocytes does not lead to TNF-α-induced apoptosis despite reduced NF-κB activity. Enhanced stability of IκB-α appears to be responsible for lower levels of nuclear NF-κB and hence reduced transactivation. Additionally, inhibition of GSK-3 was accompanied by marked upregulation of β-catenin, AP-1, and CREB transcription factors. Stimulation of canonical Wnt signaling and CREB activity led to elevated levels of anti-apoptotic factors. Hence, survival of primary mouse hepatocytes may be caused by the activation and/or upregulation of other key regulators of liver homeostasis and regeneration. These signaling molecules may compensate for the compromised anti-apoptotic function of NF-κB and allow survival of hepatocytes in the presence of TNF-α and GSK-3 inhibition.