Is the hypoxia-inducible factor-1 alpha mRNA expression activated by ethanol-induced injury, the mechanism underlying alcoholic liver disease?
ABSTRACT Excessive alcohol consumption can result in multiple organ injury, of which alcoholic liver disease (ALD) is the most common. With economic development and improvement of living standards, the incidence of diseases caused by alcohol abuse has been increasing in China, although its pathogenesis remains obscure. The aim of this study was to investigate the role of hypoxia in chronic ALD.
Twenty-eight male Sprague-Dawley rats were randomized into a control group (n=12) with a normal history and an experimental group (n=16) fed with 10 ml/kg of 56% (vol/vol) ethanol once per day by gastric lavage for 24 weeks. At 24 weeks, blood samples were collected and then the rats were killed. Liver samples were frozen at -80 degrees C and used for RT-PCR; other liver samples were obtained for immunohistochemical staining.
When the period of alcohol consumption increased, the positive rate of expression of hypoxia-inducible factor-1 alpha (HIF-1alpha) mRNA was more significantly elevated in the liver of the alcohol group than in the control group (P < or = 0.05). The HIF-1alpha protein located in the cytoplasm was seldom expressed in the control group, but significantly in the alcohol group (P < or = 0.01).
HIF-1alpha mRNA expression was activated by ethanol-induced injury in this study, suggesting that hypoxia is involved in the underlying mechanism of ALD.
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ABSTRACT: Oral squamous cell carcinomas (OSCCs) have the potential for rapid and unlimited growth. Therefore, hypoxic tissue areas are common in these malignant tumours and contribute to cancer progression, resistance to therapy and poor outcome. Out of all proteins induced by hypoxia, hypoxia-inducible factors (HIFs) and their target genes have been most extensively studied. HIF1 is a heterodimeric transcriptional complex that functions as the main regulator of systemic and cellular oxygen homeostasis; it is composed of HIF1α and HF1β subunits. At physiological concentrations of oxygen, prolyl hydroxylases (PHDs) modify HIF1α and prepare it for proteasomal degradation. In hypoxia, PHDs are inhibited and HIF1α dimerises with HIF1β to form HIF1, which is responsible for the activation of several genes involved in multiple aspects of tumor biology. Among these genes, vascular endothelial growth factor (VEGF) is essential as a regulatory gene of angiogenesis in the adaptation to a hypoxic microenvironment. Previous studies have shown the correlation between HIF1α and VEGF in OSCC and high levels of HIF1α expression appear to predict a poor prognosis. The purpose of the present article is to review the hypoxic condition in OSCC and its correlation with prognosis.Anticancer research 02/2014; 34(2):605-12. · 1.87 Impact Factor
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ABSTRACT: Ethanol induces hypoxia and elevates HIF-1α in the liver. CYP2E1 plays a role in the mechanisms by which ethanol generates oxidative stress, fatty liver, and liver injury. This study evaluated whether CYP2E1 contributes to ethanol-induced hypoxia and activation of HIF-1α in vivo and whether HIF-1α protects against or promotes CYP2E1-dependent toxicity in vitro. Wild-type (WT), CYP2E1-knock-in (KI), and CYP2E1 knockout (KO) mice were fed ethanol chronically; pair-fed controls received isocaloric dextrose. Ethanol produced liver injury in the KI mice to a much greater extent than in the WT and KO mice. Protein levels of HIF-1α and downstream targets of HIF-1α activation were elevated in the ethanol-fed KI mice compared to the WT and KO mice. Levels of HIF prolyl hydroxylase 2, which promotes HIF-1α degradation, were decreased in the ethanol-fed KI mice in association with the increases in HIF-1α. Hypoxia occurred in the ethanol-fed CYP2E1 KI mice as shown by an increased area of staining using the hypoxia-specific marker pimonidazole. Hypoxia was lower in the ethanol-fed WT mice and lowest in the ethanol-fed KO mice and all the dextrose-fed mice. In situ double staining showed that pimonidazole and CYP2E1 were colocalized to the same area of injury in the hepatic centrilobule. Increased protein levels of HIF-1α were also found after acute ethanol treatment of KI mice. Treatment of HepG2 E47 cells, which express CYP2E1, with ethanol plus arachidonic acid (AA) or ethanol plus buthionine sulfoximine (BSO), which depletes glutathione, caused loss of cell viability to a greater extent than in HepG2 C34 cells, which do not express CYP2E1. These treatments elevated protein levels of HIF-1α to a greater extent in E47 cells than in C34 cells. 2-Methoxyestradiol, an inhibitor of HIF-1α, blunted the toxic effects of ethanol plus AA and ethanol plus BSO in the E47 cells in association with inhibition of HIF-1α. The HIF-1α inhibitor also blocked the elevated oxidative stress produced by ethanol/AA or ethanol/BSO in the E47 cells. These results suggest that CYP2E1 plays a role in ethanol-induced hypoxia, oxidative stress, and activation of HIF-1α and that HIF-1α contributes to CYP2E1-dependent ethanol-induced toxicity. Blocking HIF-1α activation and actions may have therapeutic implications for protection against ethanol/CYP2E1-induced oxidative stress, steatosis, and liver injury.Free Radical Biology and Medicine 05/2013; 63:175–186. · 5.27 Impact Factor
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ABSTRACT: Alcohol abuse is involved in the pathogenesis of multiple organ disorders; the underlying mechanism is incompletely understood. The ubiquitin editing enzyme A20 is involved in regulating activities in the cell. Suppression of A20 is suggested as one factor in the initiation of inflammation. This study investigates the mechanism by which chronic alcohol consumption modulates the levels of ubiquitin editing enzyme A20 in macrophages and further contributes to induce endothelial barrier dysfunction in the lung. Mice were gavage-fed with 40% alcohol daily for 0-3 weeks. Airway macrophages were collected by lung lavage. Expression of ubiquitin editing enzyme A20 in isolated macrophages was assessed at both mRNA and protein levels. The endothelial barrier function of the lung was evaluated by the Evans blue method. Mice treated with alcohol for 3 weeks showed an increase in cell infiltration in the lung in response to exposure to peptidoglycan; over 80% of the infiltrated cells were macrophages. Furthermore, we observed that A20 level was suppressed in macrophages of mice treated with alcohol; the levels of tumor necrosis factor, interleukin-6 and nuclear factor kappa B in macrophage were increased. In addition, the endothelial barrier function of the lung was compromised, showing excessive infiltration of Evans blue in the lung indicating lung edema. Pretreatment with synthesized A20 inhibited alcohol-induced lung endothelial barrier dysfunction. We conclude that chronic alcohol ingestion disturbs the endothelial barrier function in the lung by modulating macrophage properties. Increase in A20 in the cell may have potential for the treatment of inflammatory disorders.Multidisciplinary respiratory medicine. 01/2011; 6(6):364-70.