Activators of AMP-activated protein kinase (AMPK) increase the expression of the human microsomal fatty acid ω-hydroxylase CYP4F2. A 24-h treatment of either primary human hepatocytes or the human hepatoma cell line HepG2 with 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), which is converted to ZMP, an activator of AMPK, caused an average 2.5- or 7-fold increase, respectively, of CYP4F2 mRNA expression but not of CYP4A11 or CYP4Fs 3, 11 and 12 mRNA. Activation of CYP4F2 expression by AICAR was significantly reduced in HepG2 cells by an AMPK inhibitor, compound C, or by transfection with siRNAs for AMPKα isoforms α1 and α2. A 2.5-fold increase in CYP4F2 mRNA expression was observed upon treatment of HepG2 cells with A-769662, a direct activator for AMPK. Additionally, the indirect activators of AMPK, genistein and resveratrol increased CYP4F2 mRNA expression in HepG2 cells. Pretreatment with compound C or splitomicin, an inhibitor of the NAD+ activated deacetylase SIRT1, only partially blocked activation of CYP4F2 expression by resveratrol suggesting that a SIRT1/AMPK independent pathway also contributes to increased CYP4F2 expression. Compound C greatly diminished genistein activation of CYP4F2 expression. STO-609, a calmodulin kinase kinase (CaMKK) inhibitor, reduced the level of expression of CYP4F2 elicited by genistein, suggesting that CaMKK activation contributed to AMPK activation by genistein. Transient transfection studies in HepG2 cells with reporter constructs containing the CYP4F2 proximal promoter demonstrated that AICAR, genistein, and resveratrol stimulated transcription of the reporter gene. These results suggest that activation of AMPK by cellular stress and by endocrine or pharmacologic stimulation is likely to activate CYP4F2 gene expression.
- Received October 5, 2010.
- Revision received December 26, 2010.
- Accepted December 28, 2010.
- The American Society for Pharmacology and Experimental Therapeutics