Previous studies have demonstrated that copper up-regulates hypoxia-inducible factor 1 (HIF-1). The present study was undertaken to test the hypothesis that copper is required for HIF-1 activation. Treatment of HepG2 cells with a copper chelator tetraethylenepentamine (TEPA) or short interfering RNA targeting copper chaperone for superoxide dismutase 1 (CCS) suppressed hypoxia-induced activation of HIF-1. Addition of excess copper relieved the suppression by TEPA, but not that by CCS gene silencing, indicating the requirement of copper for activation of HIF-1, which is CCS-dependent. Copper deprivation did not affect production or stability of HIF-1α but reduced HIF-1α binding to the hypoxia-responsive element (HRE) of target genes and to p300, a component of HIF-1 transcriptional complex. Copper probably inhibits the factor inhibiting HIF-1 to ensure the formation of HIF-1 transcriptional complex. This study thus defines that copper is required for HIF-1 activation through the regulation of HIF-1α binding to the HRE and the formation of the HIF-1 transcriptional complex.

The biologic function of metallothionein (MT) has been a perplexing topic ever since the discovery of this protein. Many studies have suggested that MT plays a role in the homeostasis of essential metals such as zinc and copper, detoxification of toxic metals such as cadmium, and protection against oxidative stress. However, mechanistic insights into the actions of MT have not been adequately achieved. MT contains high levels of sulfur. The mutual affinity of sulfur and transition metals makes the binding of these metals to MT thermodynamically stable. Under physiologic conditions, zinc-MT is the predominant form of the metal-binding protein. The recognition of the redox regulation of zinc release from or binding to MT provides an alternate perspective on biologic function of MT. Oxidation of the thiolate cluster by a number of mild cellular oxidants causes zinc release and formation of MT-disulfide (or thionin if all metals are released from MT, but this is unlikely to occur In vivo), which have been demonstrated in vivo. Therefore, the thermodynamic stability of zinc binding makes MT an ideal zinc reservoir in vivo, and the redox regulation of zinc mobilization enables MT function in zinc homeostasis. MT-disulfide can be reduced by glutathione in the presence of selenium catalyst, restoring the capacity of the protein to bind zinc. This MT redox cycle may play a crucial role in MT biologic function. It may link to the homeostasis of essential metals, detoxification of toxic metals and protection against oxidative stress.

Sustained pressure overload causes cardiac hypertrophy and the transition to heart failure. We show here that dietary supplementation with physiologically relevant levels of copper (Cu) reverses preestablished hypertrophic cardiomyopathy caused by pressure overload induced by ascending aortic constriction in a mouse model. The reversal occurs in the continued presence of pressure overload. Sustained pressure overload leads to decreases in cardiac Cu and vascular endothelial growth factor (VEGF) levels along with suppression of myocardial angiogenesis. Cu supplementation replenishes cardiac Cu, increases VEGF, and promotes angiogenesis. Systemic administration of anti-VEGF antibody blunts Cu regression of hypertrophic cardiomyopathy. In cultured human cardiomyocytes, Cu chelation blocks insulin-like growth factor (IGF)-1– or Cu-stimulated VEGF expression, which is relieved by addition of excess Cu. Both IGF-1 and Cu activate hypoxia-inducible factor (HIF)-1α and HIF-1α gene silencing blocks IGF-1– or Cu-stimulated VEGF expression. HIF-1α coimmunoprecipitates with a Cu chaperone for superoxide dismutase-1 (CCS), and gene silencing of CCS, but not superoxide dismutase-1, prevents IGF-1– or Cu-induced HIF-1α activation and VEGF expression. Therefore, dietary Cu supplementation improves the condition of hypertrophic cardiomyopathy at least in part through CCS-mediated HIF-1α activation of VEGF expression and angiogenesis.

Alcoholic steatosis is a fundamental metabolic disorder in the progression of alcoholic liver disease. Zinc deficiency is one of the most consistently observed biochemical/nutritional manifestations of alcoholic liver disease. The purpose of this study is to determine whether dietary zinc supplementation to mice previously exposed to alcohol could reverse alcoholic steatosis. Male 129S mice were pair-fed an alcohol or isocaloric maltose dextrin liquid diet for 16 weeks with or without dietary zinc supplementation for the last 4 weeks. Zinc supplementation significantly attenuated alcohol-mediated increases in hepatic triglyceride, cholesterol, and free fatty acids in association with accelerated hepatic fatty acid oxidation and very low density lipoproteins (VLDL) secretion. Hepatic genes related to fatty acid oxidation and VLDL secretion were up-regulated by zinc supplementation, which was accompanied by restoring activity of hepatocyte nuclear factor-4α (HNF-4α) and peroxisome proliferators activated receptor-α (PPAR-α). Zinc supplementation enhanced alcohol metabolism and attenuated oxidative stress and liver injury. Zinc supplementation also normalized alcohol-mediated increases in plasma triglycerides and partially reversed decrease in gonadal adipose depot mass. Studies in HepG2 cells showed that zinc deprivation significantly suppressed the DNA-binding activities of HNF-4α and PPAR-α, and reduced HNF-4α and PPAR-α target proteins. Consequently, zinc deprivation caused cellular accumulation of lipid droplets, triglycerides and free fatty acids in the HepG2 cells. Conclusion: Zinc supplementation reverses alcoholic steatosis, and reactivation of HNF-4α and PPAR-α by increasing zinc availability and inhibiting oxidative stress are potential mechanisms underlying these beneficial effects of zinc on hepatic lipid homeostasis. (Hepatology 2009.)

Being the second leading cause of death globally, cancer has been a long-standing and rapidly evolving focus of biomedical research and practice in the world. A tremendous effort has been made to understand the origin of cancer cells, the formation of cancerous tissues, and the mechanism by which they spread and relapse, but the disease still remains mysterious. Here, we made an attempt to scrutinize evidences that indicate the role of stem cells in tumorigenesis and metastasis, and cancer relapse. We also looked into the influence of cancers on stem cells, which in turn represent a major constituent of tumor microenvironment. Based on current understandings of the properties of (cancer) stem cells and their relation to cancers, we can foresee that novel therapeutic approaches would become the next wave of cancer treatment.