Background and Objective. Exosomes secreted from mesenchymal stem cells (MSC) have demonstrated cardioprotective effects. This study examined the role of exosomes derived from MSC overexpressing CXCR4 for recovery of cardiac functions after myocardial infarction (MI). Methods. In vitro, exosomes from MSC transduced with lentiviral CXCR4 (ExoCR4) encoding a silencing sequence or null vector were isolated and characterized by transmission electron microscopy and dynamic light scattering. Gene expression was then analyzed by qPCR and Western blotting. Cytoprotective effects on cardiomyocytes were evaluated and effects of exosomes on angiogenesis analyzed. In vivo, an exosome-pretreated MSC-sheet was implanted into a region of scarred myocardium in a rat MI model. Angiogenesis, infarct size, and cardiac functions were then analyzed. Results. In vitro, ExoCR4 significantly upregulated IGF-1α and pAkt levels and downregulated active caspase 3 level in cardiomyocytes. ExoCR4 also enhanced VEGF expression and vessel formation. However, effects of ExoCR4 were abolished by an Akt inhibitor or CXCR4 knockdown. In vivo, ExoCR4 treated MSC-sheet implantation promoted cardiac functional restoration by increasing angiogenesis, reducing infarct size, and improving cardiac remodeling. Conclusions. This study reveals a novel role of exosomes derived from MSCCR4 and highlights a new mechanism of intercellular mediation of stem cells for MI treatment.

Hydrogen sulfide (H 2 S) displays anti-inflammatory and cytoprotective activities as evidenced by the inhibition of myocardial ischemia-reperfusion injury and production of lipid peroxidation. H 2 S also exerts many physiological or pathological effects on livers. Therefore, we designed the present study to investigate the roles of H 2 S in hepatic ischemia-reperfusion (HIR)-induced injury in rats by measuring H 2 S levels, H 2 S synthesizing activity, and cystathionine ␥-lyase (CSE) messenger RNA (mRNA) expression. We also applied DL-propargyl glycine (PAG) and sodium hydrosulfide (NaHS) to investigate their effects on the severity of liver injury induced by HIR. The levels of H 2 S, H 2 S production activity, and CSE mRNA expression in livers were increased by HIR. Administration of NaHS significantly attenuated the severity of liver injury and inhibited the production of lipid peroxidation, serum inflammatory factors [including nitric oxide, tumor necrosis factor ␣ (TNF-␣), interleukin 10, and intercellular cell adhesion molecule 1], cell apoptosis, and apoptosis-related proteins (including caspase-3, Fas, Fas ligand, and TNF-␣), which were caused or elevated by HIR, whereas PAG aggravated them. However, NaHS or PAG did not show significant effects on the activation of caspase-9, which was also increased by HIR. Although further investigation is required, this study may indicate that H 2 S plays a protective role in HIR-induced injury. Hydrogen sulfide (H 2 S), a "toxic gas" in environmental pollution leading to intoxication of the nervous system and inhibition of the respiratory system, 1 has recently been found to exert many physiological effects and is regarded as the third gaseous mediator after its 2 counterparts, nitric oxide (NO) and carbon monoxide.2 H 2 S is endogenously produced from L-cysteine by cystathionine ␤-synthase and/or cystathionine ␥-lyase (CSE). 2The initial study on H 2 S focused on its vasodilative activity.3 Later, it was demonstrated that H 2 S plays a role in neuronal excitation, 4 enhances N-methyl-D-aspartate receptor-mediated responses, 5 modifies longterm potentiation, 6 and modulates hypothalamic-pituitary-adrenal axis function.7 H 2 S is also involved in hypoxia pulmonary hypertension, 8,9 septic and endotoxin shock, 10 and diseases of the gastrointestinal tract and liver. 11,12 Recent studies have shown that H 2 S displays antiinflammatory and cytoprotective activities. In a mouse model of myocardial ischemia-reperfusion injury, deliv-

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BackgroundHydrogen sulfide (H2S) displays vasodilative, anti-oxidative, anti-inflammatory and cytoprotective activities. Impaired production of H2S contributes to the increased intrahepatic resistance in cirrhotic livers. The study aimed to investigate the roles of H2S in carbon tetrachloride (CCl4)-induced hepatotoxicity, cirrhosis and portal hypertension.Methods and FindingsSodium hydrosulfide (NaHS), a donor of H2S, and DL-propargylglycine (PAG), an irreversible inhibitor of cystathionine γ-lyase (CSE), were applied to the rats to investigate the effects of H2S on CCl4-induced acute hepatotoxicity, cirrhosis and portal hypertension by measuring serum levels of H2S, hepatic H2S producing activity and CSE expression, liver function, activity of cytochrome P450 (CYP) 2E1, oxidative and inflammatory parameters, liver fibrosis and portal pressure. CCl4 significantly reduced serum levels of H2S, hepatic H2S production and CSE expression. NaHS attenuated CCl4-induced acute hepatotoxicity by supplementing exogenous H2S, which displayed anti-oxidative activities and inhibited the CYP2E1 activity. NaHS protected liver function, attenuated liver fibrosis, inhibited inflammation, and reduced the portal pressure, evidenced by the alterations of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), albumin, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and soluble intercellular adhesion molecule (ICAM)-1, liver histology, hepatic hydroxyproline content and α-smooth muscle actin (SMA) expression. PAG showed opposing effects to NaHS on most of the above parameters.ConclusionsExogenous H2S attenuates CCl4-induced hepatotoxicity, liver cirrhosis and portal hypertension by its multiple functions including anti-oxidation, anti-inflammation, cytoprotection and anti-fibrosis, indicating that targeting H2S may present a promising approach, particularly for its prophylactic effects, against liver cirrhosis and portal hypertension.

(2012) The role of AKT1 and autophagy in the protective effect of hydrogen sulphide against hepatic ischemia/reperfusion injury in mice, Autophagy, 8:6, 954-962, DOI: 10.4161/auto.19927 To link to this article: https://doi.org/10.4161/auto.19927 Do not distribute.The role of AKT1 and autophagy in the protective effect of hydrogen sulphide against hepatic ischemia/reperfusion injury in mice Keywords: hydrogen sulphide, liver, ischemia-reperfusion injury, autophagy, mouseAbbreviations: I/R, ischemia-reperfusion; H 2 S, hydrogen sulphide; A/R, anoxia/reoxygenation; NaHS, sodium hydrosulfide; GPT, glutamic-pyruvate transaminase/alanine aminotransferase; GOT1, glutamic-oxaloacetic transaminase 1, soluble/aspartate aminotransferase; TNF, tumor necrosis factor(-a); IL6, interleukin 6; PtdIns3K, phosphatidylinositol 3-kinase; LC3, microtubule-associated protein 1 light chain 3; 3MA, 3-methyladenine; TUNEL, TdT-mediated dUTP nick-end labeling;ELISA, enzyme-linked immunosorbent assayHydrogen sulphide (H 2 S) exerts a protective effect in hepatic ischemia-reperfusion (I/R) injury. However, the exact mechanism of H 2 S action remains largely unknown. This study was designed to investigate the role of the PtdIns3K-AKT1 pathways and autophagy in the protective effect of H 2 S against hepatic I/R injury. Primary cultured mouse hepatocytes and livers with or without NaHS (a donor of H 2 S) preconditioning were exposed to anoxia/reoxygenation (A/R) and I/R, respectively. In certain groups, they were also pretreated with LY294002 (AKT1-specific inhibitor), 3-methyladenine (3MA, autophagy inhibitor) or rapamycin (autophagy enhancer), alone or simultaneously. Cell viability, expression of P-AKT1, T-AKT1, LC3 and BECN1 were examined. The severity of liver injury was measured by the levels of serum aminotransferase and inflammatory cytokine, apoptosis and histological examination. GFP-LC3 redistribution and transmission electron microscopy were used to test the activity of autophagy. H 2 S preconditioning activated PtdIns3K-AKT1 signaling in hepatocytes. LY294002 could abolish the AKT1 activation and attenuate the protective effect of H 2 S on hepatocytes A/R and hepatic I/R injuries. H 2 S suppressed hepatic autophagy in vitro and in vivo. Further reducing autophagy by 3MA also diminished the protective effect of H 2 S, while rapamycin could reverse the autophagy inhibitory effect and enhance the protective effect of H 2 S against hepatocytes A/R and hepatic I/R injuries, consequently. Taken together, H 2 S protects against hepatocytic A/R and hepatic I/R injuries, at least in part, through AKT1 activation but not autophagy. An autophagy agonist could be applied to potentiate this hepatoprotective effect by reversing the autophagy inhibition of H 2 S.