Valproic Acid Promotes Mitochondria! Dysfunction In Primary Human Hepatocytes In Vitro; Impact Of C/Ebp Alpha-Controlled Gene Expression

Valproic acid (VPA) is a frequently prescribed anti-epileptic drug which is known to cause liver toxicity and steatosis through mitochondrial dysfunction. Nevertheless the mechanisms underlying these adverse effects are incompletely understood. In this study, we determined the effect of relatively short (3 h) or prolonged (72 h) exposure to VPA on mitochondrial function in primary human hepatocytes (PHHs). While 3 h VPA exposure did not affect oxygen consumption rates (OCRs) in PHHs, prolonged exposure (24-72 h) significantly reduced basal and maximal OCRs. Given that in particular prolonged VPA exposure is required to cause mitochondrial dysfunction, we investigated gene expression data after VPA exposure for 24, 48, 72 h and 72 h VPA followed by a 72 h washout period. We were able to reduce the comprehensive gene expression changes into a more comprehensible set of 18 TFs that were predicted to be persistently activated after 72 h of VPA exposure. Lentiviral knock-down of one of the candidate TFs, C/EBP alpha, partly rescued VPA-induced mitochondrial dysfunction. Furthermore, RNA-Seq analysis of shC/EBP alpha and shGFP control PHHs identified 24 genuine C/EBP alpha target genes that are regulated in response to prolonged VPA exposure in PHHs. Altogether this provides new insights on the involvement of C/EBP alpha in driving VPA-induced mitochondrial dysfunction in human liver cells. This hub gene, with its downstream regulators involved in this deregulation, thus represent potential new biomarkers for VPA-induced mitochondrial dysfunction.