Hypoxia inducible factor -1 regulates WSSV-induced glycolytic genes in the white shrimp Litopenaeus vannamei

Hypoxia-inducible factor -1 (HIF-1) is a transcriptional factor that regulates the expression of several glycolytic genes. The white spot syndrome virus (WSSV) induces a shift in glycolysis that favors viral replication in white shrimp Litopenaeus vannamei. HIF-1 is related to the pathogenesis of the WSSV infection through the induction of metabolic changes in infected white shrimp. Although the WSSV infection is associated with metabolic changes, the role of HIF-1 on key glycolytic genes during the WSSV infection has not been examined. In this work, we evaluated the effect of HIF-1α silencing on expression and activity of glycolytic enzymes (Hexokinase-HK, phosphofructokinase-PFK and pyruvate kinase-PK) along with the glucose transporter 1 (Glut1), regulatory enzymes (glucose-6-phosphate dehydrogenase-G6PDH and pyruvate dehydrogenase-PDH), and metabolic intermediates of glycolysis (glucose-6-phosphate-G6P and pyruvate). The expression of Glut1 increased in each tissue evaluated after WSSV infection, while HK, PFK and PK gene expression and enzyme activities increased in a tissue-specific manner. G6PDH activity increased during WSSV infection, and its substrate G6P decreased, while PDH activity decreased and its substrate pyruvate increased. Silencing of HIF-1α blocked the WSSV-induced Glut1 and glycolytic genes upregulation and enzyme activity in a tissue-specific manner. We conclude that HIF-1 regulates the WSSV-induced glycolysis through induction of glycolytic genes contributing to glucose metabolism in tissues of infected shrimp. Also, the inhibition, and activation of regulatory genes are likely to decrease the availability of the raw materials essential for WSSV replication and increase oxidative metabolism.

[Activation of HIF-1α/β-catenin signal pathway leads to radioresistance of prostate cancer cells]

Objective: To investigate the role of hypoxia-inducible factor-1α (HIF-1α) and β-catenin in radioresistance of prostate cancer (PCa) cells. Method: Two PCa cell lines, LNCaP and C4-2B, were grouped as: negative control (no treatment), HIF-1α overexpression group (transfected with HIF-1α plasmids), and β-catenin silencing group (transfected with HIF-1α plasmids and β-catenin-shRNA). Cell proliferation, cycle, invasion, and radiosensitivity were measured under normal or hypoxic condition. Radiosensitivity was tested in two mice PCa models (the LNCaP orthotopic BALB/c-nu mice model and the C4-2B subcutaneous SCID mice model). Results: In both LNCaP and C4-2B cells, HIF-1α transfection led to an enhanced β-catenin nuclear translocation, while β-catenin silencing inhibited the β-catenin nuclear translocation. Enhanced β-catenin nuclear translocation caused by HIF-1α overexpression resulted in enhanced cell proliferation and invasion, altered cell cycle distribution, reduced apoptosis, and improved non-homologous-end-joining (NHEJ) repair under irradiation condition. In vivo imaging of orthotopic models showed that HIF-1α overexpression LNCaP cells produced tumors with 3-fold volume (P=0.003 1) and 2-fold wet weight (P=0.039 4) than those by negative control cells at day 21, and β-catenin silencing cells aberrantly reduced both tumor volume (P=0.000 3) and wet weight (P=0.017 5) than HIF-1α overexpression cells. In addition, C4-2B subcutaneous models showed similar tumor promotion effects induced by HIF-1α overexpression (tumor volume: P=0.000 1 and wet weight: P=0.047 3) and suppressive effects by β-catenin silencing (tumor volume: P<0.000 1 and wet weight: P=0.022 1) as LNCaP orthotopic xenograft with regard to tumor volume and wet weight. Conclusions: HIF-1α overexpression enhanced β-catenin nuclear translocation, which led to the activation of the β-catenin/NHEJ signaling pathway and increased cell proliferation, invasion, and DNA repair. These results suggest that HIF-1α overexpression led to radioresistance of PCa cells.

Regulation of lactate dehydrogenase in response to WSSV infection in the shrimp Litopenaeus vannamei

Lactate dehydrogenase (LDH) is key for anaerobic glycolysis. LDH is induced by the hypoxia inducible factor -1 (HIF-1). HIF-1 induces genes involved in glucose metabolism and regulates cellular oxygen homeostasis. HIF-1 is formed by a regulatory α-subunit (HIF-1α) and a constitutive β-subunit (HIF-1β). The white spot syndrome virus (WSSV) induces anaerobic glycolysis in shrimp hemocytes, associated with lactate accumulation. Although infection and lactate production are associated, the LDH role in WSSV-infected shrimp has not been examined. In this work, the effects of HIF-1 silencing on the expression of two LDH subunits (LDHvan-1 and LDHvan-2) in shrimp infected with the WSSV were studied. HIF-1α transcripts increased in gills, hepatopancreas, and muscle after WSSV infection, while HIF-1β remained constitutively expressed. The expression for both LDH subunits increased in each tissue evaluated during the WSSV infection, translating into increased enzyme activity. Glucose concentration increased in each tissue evaluated, while lactate increased in gills and hepatopancreas, but not in muscle. Silencing of HIF-1α blocked the increase of LDH expression and enzyme activity, along with glucose (all tissues) and lactate (gills and hepatopancreas) concentrations produced by WSSV infection. These results demonstrate that HIF-1 up regulates the expression of LDH subunits during WSSV infection, and that this induction contributes to substrate metabolism in energetically active tissues of infected shrimp.