Identification of miRNAs involved in liver injury induced by chronic exposure to cadmium

To elaborate the molecular mechanism underlying the hepatotoxicity induced by chronic exposure to cadmium (Cd), a mouse model with hepatocyte-specific deletion of Ppp2r1a (encoding protein phosphatase 2 A Aα subunit, PP2A Aα) gene was used to investigate the effect of cadmium exposure on liver injury. The wild type littermates (WT) and PP2A Aα-/- mice (KO) were treated with cadmium chloride (CdCl2) at concentrations of 0 mg/L, 10 mg/L, 100 mg/L in drinking water for 3, 6 and 9 months (KO mice only for 9 months), respectively. The pathological findings were characterized by progressive inflammation, steatosis, and liver fibrosis upon treatment of CdCl2 in a dose-response and time-dependent manner. Notably, PP2A Aα depletion leads to a more profound liver injury induced by CdCl2 treatment. The transcriptome analysis in livers of KO mice revealed 20 differentially expressed microRNAs (miRNAs) appeared in both 3- and 9-month. Particularly, the alterations of miR-34a-5p, miR-345-5p, and miR-30e-5p expressions were implicated in the development of liver disease and correlated with the degree of liver injury induced by cadmium treatment. Further analysis indicated that miR-34a-5p, miR-345-5p, and miR-30e-5p might be involved in CdCl2-induced liver injury, in part by dysregulation of lipid metabolism and inflammation. The in vitro studies showed that miR-34a-5p was involved in regulation of CdCl2-induced cytotoxicity through directly targeted adiponectin receptor 2 (AdipoR2) mRNA. Taken together, we identified that specific miRNAs were implicated in hepatotoxicity induced by chronic exposure to CdCl2. These findings also provide new insight into the role of PP2A in regulation of miRNAs-mediated liver injury.