Keap1 modulates the redox cycle and hepatocyte cell cycle in regenerating liver.

Keap1 negatively controls the activity of transcription factor Nrf2. This Keap1/Nrf2 pathway plays a critical role in combating oxidative stress. We aimed at determining whether and how Keap1 modulates the cell cycle of replicating hepatocytes during liver regeneration. Two-thirds partial hepatectomy (PH) was performed on wild-type mice and Keap1+/- (Keap1 knockdown) mice. We found that, following PH, Keap1 knockdown resulted in a delay in S-phase entry, disruption of S-phase progression, and loss of mitotic rhythm of replicating hepatocytes. These events are associated with dysregulation of c-Met, EGFR, Akt1, p70S6K, Cyclin A2, and Cyclin B1 in regenerating livers. Astonishingly, normal regenerating livers exhibited the redox fluctuation coupled with hepatocyte cell cycle progression, while keeping Nrf2 quiescent. Keap1 knockdown caused severe disruption in both the redox cycle and the cell cycle of replicating hepatocytes. Thus, we demonstrate that Keap1 is a potent regulator of hepatic redox cycle and hepatocyte cell cycle during liver regeneration.