Hepatocellular carcinoma (HCC) ranks third in cancer-related mortality due to late diagnosis and poor treatment options. Autophagy is a lysosome-mediated protein and organelle degradation process which is characterized by the formation of double-membrane vesicles, known as autophagosomes. Increasing evidence reveals that autophagy functions as a survival mechanism in liver cancer cells against drug-induced apoptosis. In this study, we found that autophagy was suppressed by miR-101 in the HCC cell line HepG2. miR-101 inhibited autophagy via targets including RAB5A, STMN1 and ATG4D. Moreover, miR-101 enhanced apoptosis induced by cisplatin in the HepG2 cell line. The possible mechanism of this effect may be through inhibition of autophagy. Our results indicate a novel and critical role for miR-101 and autophagy in the chemoresistance of cisplatin in HCC. We propose that gene therapy targeting miR-101/autophagy should be investigated further as a potential alternative therapeutic strategy for HCC.

BackgroundGrowing evidence has linked autophagy to a protective role of preconditioning in liver ischemia/reperfusion (IR). Heme oxygenase-1 (HO-1) is essential in limiting inflammation and preventing the apoptotic response to IR. We previously demonstrated that HO-1 is up-regulated in liver graft after remote ischemic preconditioning (RIPC). The aim of this study was to confirm that RIPC protects against IR via HO-1-mediated autophagy.MethodsRIPC was performed with regional ischemia of limbs before liver ischemia, and HO-1 activity was inhibited pre-operation. Autophagy was assessed by the expression of light chain 3-II (LC3-II). The HO-1/extracellular signal-related kinase (ERK)/p38/mitogen-activated protein kinase (MAPK) pathway was detected in an autophagy model and mineral oil-induced IR in vitro.ResultsIn liver IR, the expression of LC3-II peaked 12–24 h after IR, and the ultrastructure revealed abundant autophagosomes in hepatocytes after IR. Autophagy was inhibited when HO-1 was inactivated, which we believe resulted in the aggravation of liver IR injury (IRI) in vivo. Hemin-induced autophagy also protected rat hepatocytes from IRI in vitro, which was abrogated by HO-1 siRNA. Phosphorylation of p38-MAPK and ERK1/2 was up-regulated in hemin-pretreated liver cells and down-regulated after treatment with HO-1 siRNA.ConclusionsRIPC may protect the liver from IRI by induction of HO-1/p38-MAPK-dependent autophagy.

Glutaredoxins (Grxs) are ubiquitous small heat-stable disulfide oxidoreductases that play a crucial role in plant development and response to oxidative stress. Here, a novel cDNA fragment (SlGRX1) from tomato encoding a protein containing the consensus Grx family domain with a CGFS active site was isolated and characterized. Southern blot analysis indicated that SlGRX1 gene had a single copy in tomato genome. Quantitative real-time RT-PCR analysis revealed that SlGRX1 was expressed ubiquitously in tomato including leaf, root, stem and flower, and its expression could be induced by oxidative, drought, and salt stresses. Virus-induced gene silencing mediated silencing of SlGRX1 in tomato led to increased sensitivity to oxidative and salt stresses with decreased relative chlorophyll content, and reduced tolerance to drought stress with decreased relative water content. In contrast, over-expression of SlGRX1 in Arabidopsis plants significantly increased resistance of plants to oxidative, drought, and salt stresses. Furthermore, expression levels of oxidative, drought and salt stress related genes Apx2, Apx6, and RD22 were up-regulated in SlGRX1-overexpressed Arabidopsis plants when analyzed by quantitative real-time PCR. Our results suggest that the Grx gene SlGRX1 plays an important role in regulating abiotic tolerance against oxidative, drought, and salt stresses.