Mitochondrial morphology is dynamically remodeled by fusion and fission in cells, and dysregulation of this process is closely implicated in tumorigenesis. However, the mechanism by which mitochondrial dynamics influence cancer cell survival is considerably less clear, especially in hepatocellular carcinoma (HCC). In this study, we systematically investigated the alteration of mitochondrial dynamics and its functional role in the regulation of autophagy and HCC cell survival. Furthermore, the underlying molecular mechanisms and therapeutic application were explored in depth. Mitochondrial fission was frequently upregulated in HCC tissues mainly due to an elevated expression ratio of DNM1L to MFN1, which significantly contributed to poor prognosis of HCC patients. Increased mitochondrial fission by forced expression of DNM1L or knockdown of MFN1 promoted the survival of HCC cells both in vitro and in vivo mainly by facilitating autophagy and inhibiting mitochondria-dependent apoptosis. We further demonstrated that the survival-promoting role of increased mitochondrial fission was mediated via elevated ROS production and subsequent activation of AKT, which facilitated MDM2-mediated TP53 degradation, and NFKBIA- and IKK-mediated transcriptional activity of NFKB in HCC cells. Also, a crosstalk between TP53 and NFKB pathways was involved in the regulation of mitochondrial fission-mediated cell survival. Moreover, treatment with mitochondrial division inhibitor-1 significantly suppressed tumor growth in an in vivo xenograft nude mice model. Our findings demonstrate that increased mitochondrial fission plays a critical role in regulation of HCC cell survival, which provides a strong evidence for this process as drug target in HCC treatment.

Mitochondrial Ca signaling, which is strongly dependent on the mitochondrial Ca uniporter (MCU) complex, has a series of key roles in physiopathological processes, including energy metabolism, reactive oxygen species (ROS) production and cell apoptosis. However, a mechanistic understanding of how the mitochondrial Ca signaling is remodeled and its functional roles remains greatly limited in cancers, especially in hepatocellular carcinoma. Here we demonstrated that the MCU complex was dysregulated in hepatocellular carcinoma (HCC) cells and significantly correlated with metastasis and poor prognosis of HCC patients. Upregulation of MCU clearly enhanced the Ca uptake into mitochondria, which significantly promoted ROS production by downregulating nicotinamide adenine dinucleotide (NAD)/reduced form of nicotinamide adenine dinucleotid (NADH) ratio and the NAD-dependent deacetylase activity of sirtuin 3 to inhibit superoxide dismutase 2 (SOD2) activity. Moreover, our data indicated that the MCU-dependent mitochondrial Ca uptake promotes matrix metalloproteinase-2 activity and cell motility by ROS-activated c-Jun N-terminal kinase pathway, and thus contributed to the increased ability of invasion and migration in vitro and intrahepatic and distal lung metastasis in vivo of HCC cells. In addition, treatment with the mitochondrial Ca-buffering protein parvalbumin significantly suppressed ROS production and the ability of HCC metastasis. Our study uncovers a mechanism that links the remodeling of mitochondrial Ca homeostasis to ROS production, and provides evidence supporting a metastasis-promoting role for the MCU-dependent mitochondrial Ca uptake in HCC. Our findings suggest that the mitochondrial Ca uptake machinery may potentially be a novel therapeutic target for HCC metastasis.

. Insulin attenuates myocardial ischemia/reperfusion injury via reducing oxidative/nitrative stress. Am J Physiol Endocrinol Metab 298: E871-E880, 2010. First published February 2, 2010; doi:10.1152/ajpendo.00623.2009.-It is well known that insulin possesses a cardioprotective effect and that insulin resistance is closely related to cardiovascular diseases. Peroxynitrite (ONOO Ϫ ) formation may trigger oxidative/nitrative stress and represent a major cytotoxic effect in heart diseases. This study was designed to investigate whether insulin attenuates ONOO Ϫ generation and oxidative/nitrative stress in acute myocardial ischemia/reperfusion (MI/R). Adult male rats were subjected to 30 min of myocardial ischemia and 3 h of reperfusion. Rats randomly received vehicle, insulin, or insulin plus wortmannin. Arterial blood pressure and left ventricular pressure were monitored throughout the experiment. Insulin significantly improved cardiac functions and reduced myocardial infarction, apoptotic cell death, and blood creatine kinase/lactate dehydrogenase levels following MI/R. Myocardial ONOO Ϫ formation was significantly attenuated after insulin treatment. Moreover, insulin resulted in a significant increase in Akt and endothelial nitric oxide (NO) synthase (eNOS) phosphorylation, NO production, and antioxidant capacity in ischemic/reperfused myocardial tissue. On the other hand, insulin markedly reduced MI/R-induced inducible NOS (iNOS) and gp91 phox expression in cardiac tissue. Inhibition of insulin signaling with wortmannin not only blocked the cardioprotection of insulin but also markedly attenuated insulin-induced antioxidative/antinitrative effect. Furthermore, the suppression on ONOO Ϫ formation by either insulin or an ONOO Ϫ scavenger uric acid reduced myocardial infarct size in rats subjected to MI/R. We concluded that insulin exerts a cardioprotective effect against MI/R injury by blocking ONOO Ϫ formation. Increased physiological NO production (via eNOS phosphorylation) and superoxide anion reduction contribute to the antioxidative/antinitrative effect of insulin, which can be reversed by inhibiting phosphatidylinositol 3=-kinase. These results provide important novel information on the mechanisms of cardiovascular actions of insulin. apoptosis; peroxynitrite; superoxide; nitric oxide EXPERIMENTAL EVIDENCE has revealed that insulin resistance plays a key role in the pathogenesis of cardiovascular diseases, including endothelial dysfunction and myocardial infarction (16,30). In recent years, there have been several landmark studies showing that glucose, insulin, and potassium significantly reduced the mortality of patients with acute myocardial infarction (5,8,27). Our previous studies (10, 25, 43) demonstrated that insulin may play an important role to attenuate both myocardial ischemia and reperfusion injury through the survival signaling, that is, phosphatidylinositol 3=-kinase (PI3-kinase)-Akt-dependent pathway. However, to date, the mechanisms underlying the cardiovascular actions of insulin remain large...

MCUR1 was frequently upregulated in HCC cells to enhance the Ca uptake into mitochondria in an MCU-dependent manner, which significantly facilitated cell survival by inhibiting mitochondria-dependent intrinsic apoptosis and promoting proliferation of HCC cells, and thus led to poor prognosis. In vivo assay confirmed these results, indicating that overexpressed MCUR1 notably decreased the fraction of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells and increased the positive Ki67 staining in xenograft tumors, while reduced MCUR1 expression was associated with impaired growth capacity of HCC cells in nude mice. The survival advantage conferred by MCUR1-mediated mitochondrial Ca uptake was majorly caused by elevated production of mitochondrial reactive oxygen species and subsequent AKT/MDM2- induced P53 degradation, which regulated the expression level of apoptosis-related molecules and cell cycle-related molecules. Treatment of mitochondrial Ca-buffering protein parvalbumin remarkably inhibited the growth of HCC cells. Conclusions and Innovation: Our study provides evidence supporting a possible tumor-promoting role for MCUR1-mediated mitochondrial Ca uptake and uncovers a mechanistic understanding that links change of mitochondrial Ca homeostasis to cancer cell survival, which suggests a potential novel therapeutic target for HCC. Antioxid. Redox Signal. 28, 1120-1136.

Hyperglycaemia during acute myocardial infarction is common and associated with increased mortality. Thioredoxin-interacting protein (Txnip) is a modulator of cellular redox state and contributes to cell apoptosis. This study aimed to investigate whether or not hyperglycaemia enhances Txnip expression in myocardial ischaemia/reperfusion (MI/R) and consequently exacerbates MI/R injury. Rats were subjected to 30 min. of left coronary artery ligation followed by 4 hrs of reperfusion and treated with saline or high glucose (HG, 500 g/l, 4 ml/kg/h intravenously). In vitro study was performed on cultured rat cardiomyocytes subjected to simulated ischaemia/reperfusion (SI/R) and incubated with HG (25 mM) or normal glucose (5.6 mM) medium. In vivo HG infusion during MI/R significantly impaired cardiac function, aggravated myocardial injury and increased cardiac oxidative stress. Meanwhile, Txnip expression was enhanced whereas thioredoxin activity was inhibited following HG treatment in ischaemia/reperfusion (I/R) hearts. In addition, HG activated p38 MAPK and inhibited Akt in I/R hearts. In cultured cardiomyocytes subjected to SI/R, HG incubation stimulated Txnip expression and reduced thioredoxin activity. Overexpression of Txnip enhanced HG-induced superoxide generation and aggravated cardiomyocyte apoptosis, whereas Txnip RNAi significantly blunted the deleterious effects of HG. Moreover, inhibition of p38 MAPK or activation of Akt markedly blocked HG-induced Txnip expression in I/R cardiomyocytes. Most importantly, intramyocardial injection of Txnip siRNA markedly decreased Txnip expression and alleviated MI/R injury in HG-treated rats. Hyperglycaemia enhances myocardial Txnip expression, possibly through reciprocally modulating p38 MAPK and Akt activation, leading to aggravated oxidative stress and subsequently, amplification of cardiac injury following MI/R.