Carbon monoxide protects against hepatic ischemia/reperfusion injury by modulating the miR-34a/SIRT1 pathway.

Hepatic ischemia/reperfusion (I/R) injury can arise as a complication of liver surgery and transplantation. Sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, modulates inflammation and apoptosis in response to oxidative stress. SIRT1, which is regulated by p53 and microRNA-34a (miR-34a), can modulate non-alcoholic fatty liver disease, fibrosis and cirrhosis. Since carbon monoxide (CO) inhalation can protect against hepatic I/R, we hypothesized that CO could ameliorate hepatic I/R injury by regulating the miR-34a/SIRT1 pathway. Livers from mice pretreated with CO, or PFT, a p53 inhibitor, displayed reduced production of pro-inflammatory mediators, including TNF-α, iNOS, interleukin (IL)-6, and IL-1β after hepatic I/R injury. SIRT1 expression was increased by CO or PFT in the liver after I/R, whereas acetylated p65, p53 levels, and miR-34a expression were decreased. CO increased SIRT1 expression by inhibiting miR-34a. Both CO and PFT diminished pro-inflammatory cytokines production in vitro. Knockdown of SIRT1 in LPS-stimulated macrophages increased NF-κB acetylation, and increased pro-inflammatory cytokines. CO treatment reduced miR-34a expression and increased SIRT1 expression in oxidant-challenged hepatocytes; and rescued SIRT1 expression in p53-expressing or miR-34a transfected cells. In response to CO, enhanced SIRT1 expression mediated by miR-34a inhibition protects against liver damage through p65/p53 deacetylation, which may mediate inflammatory responses and hepatocellular apoptosis. The miR-34a/SIRT1 pathway may represent a therapeutic target for hepatic injury.

Kim HJ ，Joe Y ，Yu JK ，Chen Y ，Jeong SO ，Mani N ，Cho GJ ，Pae HO ，Ryter SW ，Chung HT ... -  《-》

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 ... -  《-》

Inhibition of P53/miR-34a improves diabetic endothelial dysfunction via activation of SIRT1.

Endothelial dysfunction contributes to diabetic macrovascular complications, resulting in high mortality. Recent findings demonstrate a pathogenic role of P53 in endothelial dysfunction, encouraging the investigation of the effect of P53 inhibition on diabetic endothelial dysfunction. Thus, high glucose (HG)-treated endothelial cells (ECs) were subjected to pifithrin-α (PFT-α)-a specific inhibitor of P53, or P53-small interfering RNA (siRNA), both of which attenuated the HG-induced endothelial inflammation and oxidative stress. Moreover, inhibition of P53 by PFT-α or P53-siRNA prohibited P53 acetylation, decreased microRNA-34a (miR-34a) level, leading to a dramatic increase in sirtuin 1 (SIRT1) protein level. Interestingly, the miR-34a inhibitor (miR-34a-I) and PFT-α increased SIRT1 protein level and alleviated the HG-induced endothelial inflammation and oxidative stress to a similar extent; however, these effects of PFT-α were completely abrogated by the miR-34a mimic. In addition, SIRT1 inhibition by EX-527 or Sirt1-siRNA completely abolished miR-34a-I's protection against HG-induced endothelial inflammation and oxidative stress. Furthermore, in the aortas of streptozotocin-induced diabetic mice, both PFT-α and miR-34a-I rescued the inflammation, oxidative stress and endothelial dysfunction caused by hyperglycaemia. Hence, the present study has uncovered a P53/miR-34a/SIRT1 pathway that leads to endothelial dysfunction, suggesting that P53/miR-34a inhibition could be a viable strategy in the management of diabetic macrovascular diseases.

Wu J ，Liang W ，Tian Y ，Ma F ，Huang W ，Jia Y ，Jiang Z ，Wu H ... -  《-》

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》

Inhibition of p53/miR-34a/SIRT1 axis ameliorates podocyte injury in diabetic nephropathy.

Liang Y ，Liu H ，Zhu J ，Song N ，Lu Z ，Fang Y ，Teng J ，Dai Y ，Ding X ... -  《-》