miR-34a/SIRT1/p53 is suppressed by ursodeoxycholic acid in the rat liver and activated by disease severity in human non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) comprises a spectrum of stages from simple steatosis to non-alcoholic steatohepatitis (NASH). However, disease pathogenesis remains largely unknown. microRNA (miRNA or miR) expression has recently been reported to be altered in human NASH, and modulated by ursodeoxycholic acid (UDCA) in the rat liver. Here, we aimed at evaluating the miR-34a/Sirtuin 1(SIRT1)/p53 pro-apoptotic pathway in human NAFLD, and to elucidate its function and modulation by UDCA in the rat liver and primary rat hepatocytes. Liver biopsies were obtained from NAFLD morbid obese patients undergoing bariatric surgery. Rat livers were collected from animals fed a 0.4% UDCA diets. Primary rat hepatocytes were incubated with bile acids or free fatty acids (FFAs) and transfected with a specific miRNA-34a precursor and/or with a p53 overexpression plasmid. p53 transcriptional activity was assessed by ELISA and target reporter constructs. miR-34a, apoptosis and acetylated p53 increased with disease severity, while SIRT1 diminished in the NAFLD liver. UDCA inhibited the miR-34a/SIRT1/p53 pathway in the rat liver in vivo and in primary rat hepatocytes. miR-34a overexpression confirmed its targeting by UDCA, which prevented miR-34a-dependent repression of SIRT1, p53 acetylation, and apoptosis. Augmented apoptosis by FFAs in miR-34a overexpressing cells was also inhibited by UDCA. Finally, p53 overexpression activated miR-34a/SIRT1/p53, which in turn was inhibited by UDCA, via decreased p53 transcriptional activity. Our results support a link between liver cell apoptosis and miR-34a/SIRT1/p53 signaling, specifically modulated by UDCA, and NAFLD severity. Potential endogenous modulators of NAFLD pathogenesis may ultimately provide new tools for therapeutic intervention.

Castro RE ，Ferreira DM ，Afonso MB ，Borralho PM ，Machado MV ，Cortez-Pinto H ，Rodrigues CM ... -  《-》

c-Jun N-terminal kinase 1/c-Jun activation of the p53/microRNA 34a/sirtuin 1 pathway contributes to apoptosis induced by deoxycholic acid in rat liver.

Ferreira DM ，Afonso MB ，Rodrigues PM ，Simão AL ，Pereira DM ，Borralho PM ，Rodrigues CM ，Castro RE ... -  《-》

Activation of the miR-34a/SIRT1/p53 Signaling Pathway Contributes to the Progress of Liver Fibrosis via Inducing Apoptosis in Hepatocytes but Not in HSCs.

Tian XF ，Ji FJ ，Zang HL ，Cao H ... -  《PLoS One》

Activation of the SIRT1/p66shc antiapoptosis pathway via carnosic acid-induced inhibition of miR-34a protects rats against nonalcoholic fatty liver disease.

Shan W ，Gao L ，Zeng W ，Hu Y ，Wang G ，Li M ，Zhou J ，Ma X ，Tian X ，Yao J ... -  《Cell Death & Disease》

MicroRNA-34a: a novel tumor suppressor in p53-mutant glioma cell line U251.

Previous studies showed that microRNA-34 (miR-34a) family was found to be a direct target of p53, functioning downstream of the p53 pathway as tumor suppressors. MiR-34a was identified to represent the status of p53 and participate in initiation and progress of cancers. We undertook this study to investigate the role of miR-34a in glioma cells. Expression levels of miR-34a in glioma cell lines and normal brains were detected using qRT-PCR. Human U251 glioma cells were transfected with miR-34a mimics, and the effects of miR-34a restoration were assessed by MTT assays, cell cycle analysis, caspase-3 activation, and in vitro migration and invasion assays. A computational search revealed a conserved target site of miR-34a within the 3'-untranslated region of SIRT1. Luciferase reporter assay was performed to examine the effects of miR-34a on expression of potential target gene SIRT1, and mRNA and protein expression of SIRT1 after miR-34a transfection were detected by qRT-PCR and Western blot analysis. MiR-34a expression was markedly reduced in p53-mutant cells U251 compared with A172 and SHG-44 cells expressing wild-type p53 and normal brains. Overexpression of miR-34a in U251 cells resulted in inhibition of cell growth and arrest in G0-G1 phase and induced apoptosis. Also, restoration of miR-34a significantly reduced in vitro migration and invasion capabilities. Reporter assays indicated that SIRT1 was a direct target of miR-34a. In U251 cells, overexpression of miR-34a decreased SIRT1 protein levels but not mRNA expressions, which demonstrated miR-34a-induced SIRT1 inhibition occurred at the posttranscriptional level. Our results demonstrate that miR-34a acts as a tumor suppressor in p53-mutant glioma cells U251, partially through regulating SIRT1.

Luan S ，Sun L ，Huang F 《-》