Impaired hepatocellular regeneration in murine sepsis is dependent on regulatory protein levels.

Sepsis is a poorly understood syndrome. Therefore we examined the mechanisms underlying failed regeneration in sham operated (SO), mildly septic (CLP) and severely septic (2CLP) C57Bl6 mice. Relative to no operation (T0) or SO, CLP, but not 2CLP, increased the number of cells staining for proliferating cell nuclear antigen (PCNA), a marker for cell division. Levels of the retinoblastoma protein (pRb) was detected at T0 and after SO. CLP increased while 2CLP decreased pRb abundance. Changes in phosphorylated pRB (P-pRb) were similar but more profound. The abundance of the transcription factor E2F was unaltered by SO, CLP or 2CLP. However, E2F DNA binding activity, while unchanged after SO, increased after CLP and decreased after 2CLP. The abundance of cyclinD1 in nuclear fractions increased following CLP but decreased after 2CLP. Neither SO or 2CLP altered the abundance of the cyclin-dependant kinase cdk-4. However, cdk-4 abundance increased after CLP. Finally, CLP increased the steady-state abundance of the mRNAs encoding Thymadine Kinase (TK), DNA Polymerase α (DNAPolα and dihydrofolate reductase (DHFR), all required for DNA replication. No changes was noted after 2CLP. We conclude that 2CLP impaired hepatocyte proliferation following 2CLP in part via impaired CyclinD1/cdk-4 induced phosphorylation of pRb, maintaining the association between pRB and E2F and inhibited E2F transcriptional activity.