Adaptive gene regulation of pyruvate dehydrogenase kinase isoenzyme 4 in hepatotoxic chemical-induced liver injury and its stimulatory potential for DNA repair and cell proliferation

Abstract

The processes involved in the adaptation of animals to environmental factors remain unclear. We examined the mechanisms underlying the adaptive potential of the mouse against hepatotoxic chemical-induced injury. Microarray analysis revealed that ethylbenzene, a hepatotoxic chemical, upregulated PDK4 (encoding pyruvate dehydrogenase kinase isoenzyme 4) in mouse livers and that the upregulation was enhanced by previous exposure to the chemical. Although PDK4 is an energy resource regulator induced by starvation, expression of other fasting-inducible genes was unaffected. PDK4 induced by chemical stress developed hepatic accumulation of sirtuin 1 by regulating pyruvate concentration and activated the Nbn and ATM, which are critical for DNA repair and checkpoint activation. PDK4 overexpression on carbon tetrachloride (CCl₄)-induced liver injury resulted in delayed necrotic tissue recovery with cell cycle arrest and decreased γH2AX foci and micronucleus formation. PDK4 silencing on CCl₄-induced liver injury accelerated necrotic tissue recovery and increased γH2AX foci and micronucleus formation, indicating the essential role of PDK4 in DNA repair and checkpoint activation. PDK4 overexpression induced pancreas-specific transcription factor 1a (Ptf1a) upregulation and transcriptional activation of several pancreatic genes in the liver. Ptf1a overexpression by adenoviral gene delivery resulted in accelerated tissue recovery on CCl₄-induced liver injury. Our data identified PDK4 as a novel pivotal factor in adaptation to chemical stress.

Keywords::

• Adaptation
• PDK4
• SIRT1

Acknowledgments

This work was supported by the Central Research Institute of Electric Power Industry. The authors thank H. Shimizu for technical advice regarding the adenovirus treatments and R. Sasaki for assistance with the experimental preparations.

Declaration of interest

The authors have no potential conflicts of interest.