bims-hypoxi 2021-06-20 papers

bims-hypoxi

Biomed News

on Hypoxia and HIF1-alpha

Issue of 2021‒06‒20
sixteen papers selected by
Ashish Kaul
University of Tsukuba

Leptin attenuates hypoxia-induced apoptosis in human periodontal ligament cells via the reactive oxygen species/hypoxia-inducible factor-1α pathway.
Curcumin relieves the arecoline-induced fibrosis of oral mucosal fibroblasts via inhibiting HIF-1α/TGF-β/CTGF signaling pathway: an in vitro study.
MiR-194-5p enhances the sensitivity of nonsmall-cell lung cancer to doxorubicin through targeted inhibition of hypoxia-inducible factor-1.
Hypoxia Induced by Cobalt Chloride Triggers Autophagic Apoptosis of Human and Mouse Drug-Resistant Glioblastoma Cells through Targeting the PI3K-AKT-mTOR Signaling Pathway.
Canagliflozin attenuates lipotoxicity in cardiomyocytes and protects diabetic mouse hearts by inhibiting the mTOR/HIF-1α pathway.
Polysulfide inhibits hypoxia-elicited hypoxia-inducible factor activation in a mitochondria-dependent manner.
Thrombomodulin promotes placental function by up-regulating placental growth factor via inhibition of high-mobility-group box 1 and hypoxia-inducible factor 1α.
LncRNA JPX regulates proliferation and apoptosis of nucleus pulposus cells by targeting the miR-18a-5p/HIF-1α/Hippo-YAP pathway.
The relationship between expression of PD-L1 and HIF-1α in glioma cells under hypoxia.
HIF-1α-activated TM4SF1-AS1 promotes the proliferation, migration, and invasion of hepatocellular carcinoma cells by enhancing TM4SF1 expression.
Reduction in mitochondrial oxidative stress mediates hypoxia-induced resistance to cisplatin in human transitional cell carcinoma cells.
HIF-1α and HIF-2α redundantly promote retinal neovascularization in patients with ischemic retinal disease.
Combination of Metformin, Sodium Oxamate and Doxorubicin Induces Apoptosis and Autophagy in Colorectal Cancer Cells via Downregulation HIF-1α.
Hypoxia-inducible factor prolyl hydroxylase domain inhibitor may maintain hemoglobin synthesis at lower serum ferritin and transferrin saturation levels than darbepoetin alfa.
Oxygen-dependent regulation of ion channels: acute responses, post-translational modification, and response to chronic hypoxia.
Modeling hypoxia facilitates cancer cell survival through downregulation of p53 expression.

Exp Physiol. 2021 Jun 18.

Leptin attenuates hypoxia-induced apoptosis in human periodontal ligament cells via the reactive oxygen species/hypoxia-inducible factor-1α pathway.

Jing Gao, Junfei Zhu, Yuwei Zhao, Xueqi Gan, Haiyang Yu.

  NEW FINDINGS: What is the central question of this study? Whether leptin takes an effect on hypoxia-induced apoptosis in hPDLCs, and what's the potential underlying mechanism? What is the main finding and its importance? Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of HIF-1α and ROS accumulation. Leptin shows feedback inhibition on hypoxia-induced ROS-mediated apoptosis in hPDLCs, suggesting a novel application of leptin for hypoxic damage in periodontal diseases.ABSTRACT: Hypoxia-induced apoptosis of human periodontal ligament cells (hPDLCs) is an important contributor to the progression of various periodontal diseases. While leptin has been shown to protect connective tissue cells against hypoxia-induced injury, whether it might do so by attenuating hypoxia-induced apoptosis in hPDLCs remains unclear. Here, using cobalt chloride (CoCl2 ) treatment, we simulated the hypoxia condition in hPDLCs and explored whether apoptosis and reactive oxygen species (ROS) levels were related to hypoxia. After siRNA inhibition of leptin and hypoxia-inducible factor-1α (HIF-1α), the levels of apoptosis, ROS and leptin expression were further measured. First, we showed that in CoCl2 -treated hPDLCs, significantly higher cell apoptosis rates and reactive oxygen species (ROS) accumulation were observed. CoCl2 also increased leptin and HIF-1α expression in hPDLCs. Further investigation of the pathway demonstrated that ROS inhibition attenuated hypoxia-induced cell apoptosis and leptin expression, while siRNA inhibition of leptin aggravated hypoxia-induced cell apoptosis and ROS accumulation. Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of ROS and HIF-1α pathways, leptin shows feedback inhibition on ROS-mediated apoptosis in hPDLCs. These findings suggest a novel application of leptin for hypoxic damage in periodontal diseases. This article is protected by copyright. All rights reserved.

Keywords:  Leptin; human periodontal ligament cells; hypoxia-induced apoptosis; hypoxia-inducible factor-1α; reactive oxygen specie

DOI:  https://doi.org/10.1113/EP089324
Toxicol Res (Camb). 2021 May;10(3): 631-638

Curcumin relieves the arecoline-induced fibrosis of oral mucosal fibroblasts via inhibiting HIF-1α/TGF-β/CTGF signaling pathway: an in vitro study.

Lin Zhang, Jin Tan, Yi-Ping Liu, Xun Liu, Mang Luo.

  Oral submacosal fibrosis (OSF) has been recognized as one of the oral potentially malignant disorders. Areca nut chewing is implicated in this pathological fibrosis. The current treatments for OSF have failed to achieve the desired curative effect. Here, we propose that curcumin has excellent therapeutic effect on OSF and explore its specific mechanism. Transwell assay was performed to detected cell migration. Flow cytometry was used to measured apoptosis. And MTT assay was performed to test cell viability. Gene and protein levels were detected by quantitative real-time polymerase chain reaction (qPCR) and western blotting. Our results displayed that curcumin treatment reduced fibrosis-related molecules (collagen type I alpha 1, collagen type III alpha 1, tissue inhibitor of metalloprotease 2) in arecoline-treated oral mucosal fibroblasts and elevated matrix metalloproteinase 2 expression. Additionally, curcumin could suppress cell proliferation and migration, and enhance the apoptosis of arecoline-treated normal oral mucosal fibroblasts. Most importantly, the hypoxia-inducible factor-1α (HIF-1α), transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) expressions in arecoline-treated normal oral mucosal fibroblasts were reduced after exposure to curcumin, whereas the activation of HIF-1α/TGF-β/CTGF axis reversed curcumin's effect on improving fibrosis of arecoline-treated normal oral mucosal fibroblasts. Therefore, curcumin alleviated oral submucosal fibrosis via inhibiting HIF-1α/TGF-β/CTGF axis. In summary, curcumin effectively inhibited the migration and proliferation and promoted apoptosis in arecoline-induced normal oral mucosal fibroblasts by inactivating HIF-1α/TGF-β/CTGF pathway. And curcumin might be a potential therapeutic drug for OSF treatment.

Keywords:  HIF-1α/TGF-β/CTGF signaling pathway; curcumin; oral submucosal fibrosis

DOI:  https://doi.org/10.1093/toxres/tfab046
World J Surg Oncol. 2021 Jun 14. 19(1): 174

MiR-194-5p enhances the sensitivity of nonsmall-cell lung cancer to doxorubicin through targeted inhibition of hypoxia-inducible factor-1.

Mengning Xia, Lili Sheng, Wei Qu, Xue Xue, Hucheng Chen, Guoyan Zheng, Weigang Chen.

  BACKGROUND: Despite chemotherapy being a common treatment, an increase in chemoresistance over time is unavoidable. We therefore investigated the role of miR-194-5p in regulating chordoma cell behavior and examined the downstream effectors of miR-194-5p.METHODS: In this study, NSCLC cell lines A549 and H460 were cultured under hypoxic conditions for 1 week to induce drug resistance to doxorubicin (DOX). The connection between miR-194-5p and HIF-1 was revealed by reverse transcription and real-time polymerase chain reaction (RT-qPCR), western blot, and dual-luciferase assays. We used TUNEL staining and the CCK-8 test to assess the sensitivity of NSCLC cells to DOX.
RESULTS: We found that hypoxia-induced NSCLC cells enhanced resistance to DOX. MiR-194-5p was substantially reduced, and HIF-1 was increased in hypoxia-induced drug-resistant NSCLC cells. Moreover, miR-194-5p successfully induced NSCLC cell apoptosis by directly inhibiting HIF-1, thereby enhancing DOX sensitivity.
CONCLUSIONS: MiR-194-5p enhanced the sensitivity of NSCLC cells to DOX by directly inhibiting HIF-1. This work provides insights into underlying treatments for drug-resistant NSCLC.

Keywords:  Doxorubicin resistance; HIF-1; NSCLC; miR-194-5p

DOI:  https://doi.org/10.1186/s12957-021-02278-3
Oxid Med Cell Longev. 2021 ;2021 5558618

Hypoxia Induced by Cobalt Chloride Triggers Autophagic Apoptosis of Human and Mouse Drug-Resistant Glioblastoma Cells through Targeting the PI3K-AKT-mTOR Signaling Pathway.

Yuan-Wen Lee, Yih-Giun Cherng, Shun-Tai Yang, Shing-Hwa Liu, Ta-Liang Chen, Ruei-Ming Chen.

Glioblastoma multiforme (GBM) is the most aggressive brain tumor. Drug resistance mainly drives GBM patients to poor prognoses because drug-resistant glioblastoma cells highly defend against apoptotic insults. This study was designed to evaluate the effects of cobalt chloride (CoCl2) on hypoxic stress, autophagy, and resulting apoptosis of human and mouse drug-resistant glioblastoma cells. Treatment of drug-resistant glioblastoma cells with CoCl2 increased levels of hypoxia-inducible factor- (HIF-) 1α and triggered hypoxic stress. In parallel, the CoCl2-induced hypoxia decreased mitochondrial ATP synthesis, cell proliferation, and survival in chemoresistant glioblastoma cells. Interestingly, CoCl2 elevated the ratio of light chain (LC)3-II over LC3-I in TMZ-resistant glioblastoma cells and subsequently induced cell autophagy. Analyses by loss- and gain-of-function strategies further confirmed the effects of the CoCl2-induced hypoxia on autophagy of drug-resistant glioblastoma cells. Furthermore, knocking down HIF-1α concurrently lessened CoCl2-induced cell autophagy. As to the mechanisms, the CoCl2-induced hypoxia decreased levels of phosphoinositide 3-kinase (PI3K) and successive phosphorylations of AKT and mammalian target of rapamycin (mTOR) in TMZ-resistant glioblastoma cells. Interestingly, long-term exposure of human chemoresistant glioblastoma cells to CoCl2 sequentially triggered activation of caspases-3 and -6, DNA fragmentation, and cell apoptosis. However, pretreatment with 3-methyladenine, an inhibitor of autophagy, significantly attenuated the CoCl2-induced autophagy and subsequent apoptotic insults. Taken together, this study showed that long-term treatment with CoCl2 can induce hypoxia and subsequent autophagic apoptosis of drug-resistant glioblastoma cells via targeting the PI3K-AKT-mTOR pathway. Thus, combined with traditional prescriptions, CoCl2-induced autophagic apoptosis can be clinically applied as a de novo strategy for therapy of drug-resistant GBM patients.

DOI: https://doi.org/10.1155/2021/5558618
iScience. 2021 Jun 25. 24(6): 102521

Canagliflozin attenuates lipotoxicity in cardiomyocytes and protects diabetic mouse hearts by inhibiting the mTOR/HIF-1α pathway.

Pengbo Sun, Yangyang Wang, Yipei Ding, Jingyi Luo, Jin Zhong, Naihan Xu, Yaou Zhang, Weidong Xie.

  Lipotoxicity plays an important role in the development of diabetic heart failure (HF). Canagliflozin (CAN), a marketed sodium-glucose co-transporter 2 inhibitor, has significantly beneficial effects on HF. In this study, we evaluated the protective effects and mechanism of CAN in the hearts of C57BL/6J mice induced by high-fat diet/streptozotocin (HFD/STZ) for 12 weeks in vivo and in HL-1 cells (a type of mouse cardiomyocyte line) induced by palmitic acid (PA) in vitro. The results showed that CAN significantly ameliorated heart functions and inflammatory responses in the hearts of the HFD/STZ-induced diabetic mice. CAN significantly attenuated the inflammatory injury induced by PA in the HL-1 cells. Furthermore, CAN seemed to bind to the mammalian target of rapamycin (mTOR) and then inhibit mTOR phosphorylation and hypoxia-inducible factor-1α (HIF-1α) expression. These results indicated that CAN might attenuate lipotoxicity in cardiomyocytes by inhibiting the mTOR/HIF-1α pathway and then show protective effects on diabetic hearts.

Keywords:  Human metabolism; Molecular biology

DOI:  https://doi.org/10.1016/j.isci.2021.102521
Mitochondrion. 2021 Jun 13. pii: S1567-7249(21)00080-5. [Epub ahead of print]

Polysulfide inhibits hypoxia-elicited hypoxia-inducible factor activation in a mitochondria-dependent manner.

Takeo Uba, Yoshiyuki Matsuo, Chisato Sumi, Tomohiro Shoji, Kenichiro Nishi, Munenori Kusunoki, Hiroshi Harada, Hideo Kimura, Hidemasa Bono, Kiichi Hirota.

  In cellular signaling, the diverse physiological actions of biological gases, including O2, CO, NO, and H2S, have attracted much interest. Hypoxia-inducible factors (HIFs), including HIF-1 and HIF-2, are transcription factors that respond to reduced intracellular O2 availability. Polysulfides are substances containing varying numbers of sulfur atoms (H2Sn) that are generated endogenously from H2S by 3-mercaptopyruvate sulfurtransferase in the presence of O2, and regulate ion channels, specific tumor suppressors, and protein kinases. However, the effect of polysulfides on HIF activation in hypoxic mammalian cells is largely unknown. Here, we have investigated the effect of polysulfide on cells in vitro. In established cell lines, polysulfide donors reversibly reduced cellular O2 consumption and inhibited hypoxia-induced HIF-1α protein accumulation and the expression of genes downstream of HIFs; however, these effects were not observed in anoxia. In Von Hippel-Lindau tumor suppressor (VHL)- and mitochondria-deficient cells, polysulfides did not affect HIF-1α protein synthesis but destabilized it in a VHL- and mitochondria-dependent manner. For the first time, we show that polysulfides modulate intracellular O2 homeostasis and regulate HIF activation and subsequent hypoxia-induced gene expression in a VHL- and mitochondria-dependent manner.

Keywords:  Electron Transport Chain; RNA-Seq; VHL; hydrogen sulfide; hypoxia-inducible factor; mitochondria; oxygen consumption; polysulfide; sulfane sulfur; ρ0 cell

DOI:  https://doi.org/10.1016/j.mito.2021.06.007
Placenta. 2021 Jun 11. pii: S0143-4004(21)00167-3. [Epub ahead of print]111 1-9

Thrombomodulin promotes placental function by up-regulating placental growth factor via inhibition of high-mobility-group box 1 and hypoxia-inducible factor 1α.

Hiroko Oda, Takeshi Nagamatsu, Horacio Cabral, Takuya Miyazaki, Takayuki Iriyama, Kei Kawana, Tomoyuki Fujii, Yutaka Osuga.

  INTRODUCTION: Pregnancy is a state of maternal systemic stress due to inflammation and hypoxic reactions originating from the utero-placental unit. Maternal tolerance to these stresses is a key for successful outcomes. Thrombomodulin (TM), a glycoprotein expressed on cell surface, regulates local inflammatory pathways by inhibiting proinflammatory factor, High-mobility-group box1(HMGB1). Although TM is highly expressed on placental trophoblast cells, biological activities of TM during pregnancy remains unclear. Here, we hypothesized that TM may contribute to the maternal stress coping mechanisms.METHODS: By administering recombinant-TM (rTM) to the pregnant mice, we investigated the influence of TM functions on the placenta and fetal growth. We further examined its effect on trophoblast cells, focusing on HMGB1-regulated inflammatory signalings and hypoxia-inducible factor 1α (HIF1α)-dependent regulation of placental angiogenic factors.
RESULTS: Administration of rTM increased fetal weight and fetal/placental-weight ratios, which implies the improvement of placental function. These features were accompanied by maternal serum HMGB1 reduction and suppressed placental proinflammatory cytokine, IL-6 and TNF-α, expressions. In addition, rTM reduced HIF1α protein accumulation and enhanced placental growth factor (PlGF) expression in the placenta, that explains the improvement of maternal features.
DISCUSSION: Our study revealed the supportive effect of TM on the placental function in mice. By inhibiting HMGB1, rTM suppresses proinflammatory cytokines, downregulates HIF1α and induces PlFG expression in the placental tissue. Our results have elucidated the novel aspects of TM; the regulation of placental inflammatory cytokines and angiogenic factors, during pregnancy. These findings may reveal potential therapeutic opportunities for the management of maternal complications.

Keywords:  Angiogenesis; HIF1α; HMGB1; PlGF; Placenta; Thrombomodulin

DOI:  https://doi.org/10.1016/j.placenta.2021.06.002
Biochem Biophys Res Commun. 2021 Jun 07. pii: S0006-291X(21)00860-3. [Epub ahead of print]566 16-23

LncRNA JPX regulates proliferation and apoptosis of nucleus pulposus cells by targeting the miR-18a-5p/HIF-1α/Hippo-YAP pathway.

Helin Yang, Guangji Wang, Jian Liu, Mingxia Lin, Jian Chen, Yehan Fang, Yibo Li, Wentao Cai, Daolu Zhan.

  With the aggravation of global aging, the rapid rise in the obesity rate, and the increasing number of patients with intervertebral disc degeneration (IDD), the principles and mechanism of this disease remain unclear. This study explored the molecular mechanism of IDD treatment through interactions of the lncRNA-miRNA-mRNA-signaling pathways and the effects on the proliferation and apoptosis of human nucleus pulposus cells (HNPCs) cultured in vitro. Our study revealed that lncRNA JPX is expressed at low levels in HNPCs under normoxic conditions. Luciferase and RNA pull-down assays were used to verify that lncRNA JPX directly bound to miR-18a-5p and influenced HNPC proliferation and apoptosis. Subsequently, a luciferase assay confirmed the direct binding of miR-18a-5p to HIF-1α and demonstrated a negative correlation between miR-18a-5p and HIF-1α. In addition, the HIF-1α antagonist reversed the inhibition of the Hippo-YAP pathway by the miR-18a-5p inhibitor. In conclusion, overexpression of lncRNA JPX upregulated HIF-1α by inhibiting the expression of miR-18a-5p, thereby inhibiting the Hippo-YAP pathway. By inhibiting this pathway, JPX overexpression promoted the proliferation of HNPCs and decreased their apoptosis. Therefore, the lncRNA JPX is a potential new target.

Keywords:  HIF-1α; Hippo-YAP signaling Pathway; Nucleus pulposus cells; lncRNA JPX; microRNA-18a-5p

DOI:  https://doi.org/10.1016/j.bbrc.2021.05.075
J Hematol Oncol. 2021 Jun 12. 14(1): 92

The relationship between expression of PD-L1 and HIF-1α in glioma cells under hypoxia.

Xing-Chen Ding, Liang-Liang Wang, Xue-Dong Zhang, Jun-Long Xu, Pei-Feng Li, Hua Liang, Xian-Bin Zhang, Li Xie, Zi-Han Zhou, Jia Yang, Ralph R Weichselbaum, Jin-Ming Yu, Man Hu.

  Hypoxia inducible factor-1α (HIF-1α) up-regulates the expression of programmed death ligand-1 (PD-L1) in some extracranial malignancies. However, whether it could increase PD-L1 expression in intracranial tumor is still unknown. Here, we explored the relationship between HIF-1α and PD-L1 expression in glioma, and investigated their clinical significance. In glioma patients, HIF-1α and PD-L1 were overexpressed in high grade glioma tissues and were significantly associated with poor survival. In glioma cells, PD-L1 expression was induced under hypoxia condition, and the enhanced PD-L1 expression was abrogated by either HIF-1α knock-down or HIF-1α inhibitor treatment. Furthermore, ChIP-qPCR analysis showed the direct binding of HIF-1α to PD-L1 proximal promoter region, providing evidence that HIF-1α up-regulates PD-L1 in glioma. In glioma murine model, the combination treatment with HIF-1α inhibitor and anti-PD-L1 antibody caused a more pronounced suppressive effect on tumor growth compared to either monotherapy. Immunologically, the combination treatment improved both dendritic cell (DC) and CD8+ T cell activation. Overall, our results demonstrated that positive correlation between PD-L1 and HIF-1α in glioma, and provide an alternative strategy, inhibiting HIF-1α, as combination therapies with immunotherapies to advance glioma treatment.

Keywords:  Glioma; HIF-1 α; Hypoxia; Immunotherapy; PD-L1

DOI:  https://doi.org/10.1186/s13045-021-01102-5
Biochem Biophys Res Commun. 2021 Jun 09. pii: S0006-291X(21)00926-8. [Epub ahead of print]566 80-86

HIF-1α-activated TM4SF1-AS1 promotes the proliferation, migration, and invasion of hepatocellular carcinoma cells by enhancing TM4SF1 expression.

Zhi Zeng, Zhan Shi, Yang Liu, Junjun Zhao, Qiliang Lu, Jinhui Guo, Xin Liu, Dongsheng Huang, Qiuran Xu.

  Long non-coding RNAs (lncRNAs) are essential drivers or suppressors in human hepatocellular carcinoma (HCC) by participating in controlling transcription, translation, mRNA stability, and protein degradation protein-protein interaction. TM4SF1-AS1 is recently identified as a tumor-promoting factor in lung cancer. Nevertheless, its function in HCC and related molecular mechanisms remain unknown. Here, our data indicated that either hypoxia or hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor (DMOG) induced the upregulation of TM4SF1-AS1 in HCC cells. HIF-1α knockdown rather than HIF-2α silencing remarkably abrogated hypoxia-upregulated TM4SF1-AS1 expression. Furthermore, we confirmed the elevated expression of TM4SF1-AS1 in HCC tissue samples and cell lines. The silencing of TM4SF1-AS1 prominently inhibited the proliferative, migratory, and invasive abilities of HCC cells. TM4SF1-AS1 depletion significantly blocked hypoxia-enhanced Hep3B cell proliferation and mobility. Interfering TM4SF1-AS1 remarkably reduced TM4SF1 mRNA and protein levels in HCC cells. But TM4SF1-AS1 knockdown did not impact the stability of TM4SF1 mRNA. Hypoxia enhanced the expression of TM4SF1 mRNA, which was subsequently decreased by TM4SF1-AS1 knockdown in HCC cells. We confirmed the positive correlation between TM4SF1 mRNA and TM4SF1-AS1 expression in HCC specimens. Finally, TM4SF1 prominently reversed the inhibitory role of TM4SF1-AS1 depletion in Hep3B cells. In summary, hypoxia-responsive TM4SF1-AS1 was overexpressed in human HCC and contributed to the malignant behaviors of tumor cells by enhancing TM4SF1-AS1 expression.

Keywords:  Hepatocellular carcinoma; Hypoxia; Long non-coding RNA; TM4SF1; TM4SF1-AS1; Tumor progression

DOI:  https://doi.org/10.1016/j.bbrc.2021.06.011
Neoplasia. 2021 Jun 13. pii: S1476-5586(21)00035-X. [Epub ahead of print]23(7): 653-662

Reduction in mitochondrial oxidative stress mediates hypoxia-induced resistance to cisplatin in human transitional cell carcinoma cells.

Myung-Chul Kim, Sung-Hyun Hwang, Yeseul Yang, Na-Yon Kim, Yongbaek Kim.

  Tumor hypoxia is known to promote the acquisition of more aggressive phenotypes in human transitional cell carcinoma (TCC), including drug resistance. Accumulating evidence suggests that mitochondria play a central role in the chemoresistance of TCC. However, the role of mitochondria in the hypoxia-induced drug resistance in TCC remains elusive. The present study investigated the function of mitochondria in the drug resistance using a TCC cell line under hypoxic conditions. In vitro hypoxia (0.1% O2, 48 h) was achieved by incubating TCC cells in air chamber. Mitochondrial events involving hypoxia-induced drug resistance were assessed. Hypoxia significantly reduced the cisplatin-induced apoptosis of TCC cells. Additionally, hypoxia substantially decreased the level of mitochondrial reactive oxygen species (ROS) generated by cisplatin treatment. Analogously, elimination of mitochondrial ROS significantly rescued cells from cisplatin-induced apoptosis. Hypoxia enhanced mitochondrial hyperpolarization, which was not related to ATP production or the reversal of ATP synthase activity. The mitochondrial DNA (mtDNA) amplification efficiency data illustrated that hypoxia significantly prevented oxidative damage to the mitogenome. Moreover, transmission electron microscopy revealed that cisplatin-induced disruption of the mitochondrial ultrastructure was abated under hypoxic conditions. Notably, depletion of mtDNA by ethidium bromide abrogated hypoxia-induced resistance to cisplatin. Taken together, the present study demonstrated that TCC cells exposed to hypoxic conditions rendered mitochondria less sensitive to oxidative stress induced by cisplatin treatment, leading to enhanced drug resistance.

Keywords:  Drug resistance; Hypoxia; Mitochondria; Oxidative stress; mtDNA

DOI:  https://doi.org/10.1016/j.neo.2021.05.013
J Clin Invest. 2021 Jun 15. pii: 139202. [Epub ahead of print]131(12):

HIF-1α and HIF-2α redundantly promote retinal neovascularization in patients with ischemic retinal disease.

Jing Zhang, Yaowu Qin, Mireya Martinez, Miguel Flores-Bellver, Murilo Rodrigues, Aumreetam Dinabandhu, Xuan Cao, Monika Deshpande, Yu Qin, Silvia Aparicio-Domingo, Yuan Rui, Stephany Y Tzeng, Shaima Salman, Jin Yuan, Adrienne W Scott, Jordan J Green, M Valeria Canto-Soler, Gregg L Semenza, Silvia Montaner, Akrit Sodhi.

  Therapies targeting VEGF have proven only modestly effective for the treatment of proliferative sickle cell retinopathy (PSR), the leading cause of blindness in patients with sickle cell disease. Here, we shift our attention upstream from the genes that promote retinal neovascularization (NV) to the transcription factors that regulate their expression. We demonstrated increased expression of HIF-1α and HIF-2α in the ischemic inner retina of PSR eyes. Although both HIFs participated in promoting VEGF expression by hypoxic retinal Müller cells, HIF-1 alone was sufficient to promote retinal NV in mice, suggesting that therapies targeting only HIF-2 would not be adequate to prevent PSR. Nonetheless, administration of a HIF-2-specific inhibitor currently in clinical trials (PT2385) inhibited NV in the oxygen-induced retinopathy (OIR) mouse model. To unravel these discordant observations, we examined the expression of HIFs in OIR mice and demonstrated rapid but transient accumulation of HIF-1α but delayed and sustained accumulation of HIF-2α; simultaneous expression of HIF-1α and HIF-2α was not observed. Staggered HIF expression was corroborated in hypoxic adult mouse retinal explants but not in human retinal organoids, suggesting that this phenomenon may be unique to mice. Using pharmacological inhibition or an in vivo nanoparticle-mediated RNAi approach, we demonstrated that inhibiting either HIF was effective for preventing NV in OIR mice. Collectively, these results explain why inhibition of either HIF-1α or HIF-2α is equally effective for preventing retinal NV in mice but suggest that therapies targeting both HIFs will be necessary to prevent NV in patients with PSR.

Keywords:  Angiogenesis; Hypoxia; Mouse models; Ophthalmology; Retinopathy

DOI:  https://doi.org/10.1172/JCI139202
Front Oncol. 2021 ;11 594200

Combination of Metformin, Sodium Oxamate and Doxorubicin Induces Apoptosis and Autophagy in Colorectal Cancer Cells via Downregulation HIF-1α.

Jossimar Coronel-Hernández, Rebeca Salgado-García, David Cantú-De León, Nadia Jacobo-Herrera, Oliver Millan-Catalan, Izamary Delgado-Waldo, Alma D Campos-Parra, Miguel Rodríguez-Morales, Norma L Delgado-Buenrostro, Carlos Pérez-Plasencia.

  Colorectal cancer (CRC) is the third leading cause of cancer-related death worldwide in both sexes. Current therapies include surgery, chemotherapy, and targeted therapy; however, prolonged exposure to chemical agents induces toxicity in patients and drug resistance. So, we implemented a therapeutic strategy based on the combination of doxorubicin, metformin, and sodium oxamate called triple therapy (Tt). We found that Tt significantly reduced proliferation by inhibiting the mTOR/AKT pathway and promoted apoptosis and autophagy in CRC derived cells compared with doxorubicin. Several autophagy genes were assessed by western blot; ULK1, ATG4, and LC3 II were overexpressed by Tt. Interestingly, ULK1 was the only one autophagy-related protein gradually overexpressed during Tt administration. Thus, we assumed that there was a post-transcriptional mechanism mediating by microRNAs that regulate UKL1 expression during autophagy activation. Through bioinformatics approaches, we ascertained that ULK1 could be targeted by mir-26a, which is overexpressed in advanced stages of CRC. In vitro experiments revealed that overexpression of mir-26a decreased significantly ULK1, mRNA, and protein expression. Contrariwise, the Tt recovered ULK1 expression by mir-26a decrease. Due to triple therapy repressed mir-26a expression, we hypothesized this drug combination could be involved in mir-26a transcription regulation. Consequently, we analyzed the mir-26a promoter sequence and found two HIF-1α transcription factor recognition sites. We developed two different HIF-1α stabilization models. Both showed mir-26a overexpression and ULK1 reduction in hypoxic conditions. Immunoprecipitation experiments were performed and HIF-1α enrichment was observed in mir-26a promoter. Surprisingly, Tt diminished HIF-1α detection and restored ULK1 mRNA expression. These results reveal an important regulation mechanism controlled by the signaling that activates HIF-1α and that in turn regulates mir-26a transcription.

Keywords:  AKT; HIF-1α; ULK1; autophagy; mir-26a; proliferation

DOI:  https://doi.org/10.3389/fonc.2021.594200
PLoS One. 2021 ;16(6): e0252439

Hypoxia-inducible factor prolyl hydroxylase domain inhibitor may maintain hemoglobin synthesis at lower serum ferritin and transferrin saturation levels than darbepoetin alfa.

Chie Ogawa, Ken Tsuchiya, Naohisa Tomosugi, Kunimi Maeda.

BACKGROUND: Hypoxia-inducible factor (HIF) prolyl hydroxylase domain inhibitors, which have recently become clinically available for treating renal anemia, are attracting attention for their novel mechanisms of action.METHODS: Relationships of reticulocyte hemoglobin content (CHr), which reflects recent Hb synthesis, with serum ferritin (s-ft) and transferrin saturation (TSAT) were examined in 30 patients on hemodialysis after switching from darbepoetin alfa (DA) to roxadustat (Rox). Iron deficiency was defined as CHr < 32.0 pg. Cutoff values of s-ft and TSAT were determined using receiver operating characteristic curves for the endpoint CHr ≥ 32.0 pg. Logistic analysis was performed with the reference group having s-ft or TSAT below the corresponding cutoff value (low vs high).
RESULTS: With the endpoint CHr ≥ 32.0 pg on Day 0, cutoff values for s-ft and TSAT were respectively 49.7 ng/mL and 21.6% on Day 0 and 35.5 ng/mL and 16.2% on Day 28. With the endpoint CHr ≥ 32.0 pg on Day 28, cutoff values for s-ft and TSAT on Day 0 were 81.6 ng/mL and 23.9%, respectively. According to multivariable logistic analysis, the odds ratios of CHr ≥ 32.0 pg on Day 0 were significantly higher for high TSAT on Day 0 [34.7 (95% CI 2.42-131.0), p<0.003] and Day 28 [24.8 (95% CI 2.75-224.0), p = 0.004]. There were no significant differences by s-ft. Odd ratios of CHr ≥ 32.0 pg on Day 28 were also significantly higher for high s-ft on Day 0 [16.0 (95% CI 1.57-163.0), p = 0.019] and high TSAT on Day 0 [13.5 (95% CI 1.24-147.0), p<0.033].
CONCLUSIONS: Our results suggest Hb synthesis was maintained with lower TSAT and s-ft during Rox therapy compared with DA therapy. To avoid iron deficiency during the 4 weeks after switching DA to Rox, ideal s-ft and TSAT levels before the switch are 81.6 ng/mL and 23.9%, respectively.

DOI: https://doi.org/10.1371/journal.pone.0252439
Pflugers Arch. 2021 Jun 17.

Oxygen-dependent regulation of ion channels: acute responses, post-translational modification, and response to chronic hypoxia.

Hae Young Yoo, Sung Joon Kim.

  Oxygen is a vital element for the survival of cells in multicellular aerobic organisms such as mammals. Lack of O2 availability caused by environmental or pathological conditions leads to hypoxia. Active oxygen distribution systems (pulmonary and circulatory) and their neural control mechanisms ensure that cells and tissues remain oxygenated. However, O2-carrying blood cells as well as immune and various parenchymal cells experience wide variations in partial pressure of oxygen (PO2) in vivo. Hence, the reactive modulation of the functions of the oxygen distribution systems and their ability to sense PO2 are critical. Elucidating the physiological responses of cells to variations in PO2 and determining the PO2-sensing mechanisms at the biomolecular level have attracted considerable research interest in the field of physiology. Herein, we review the current knowledge regarding ion channel-dependent oxygen sensing and associated signalling pathways in mammals. First, we present the recent findings on O2-sensing ion channels in representative chemoreceptor cells as well as in other types of cells such as immune cells. Furthermore, we highlight the transcriptional regulation of ion channels under chronic hypoxia and its physiological implications and summarize the findings of studies on the post-translational modification of ion channels under hypoxic or ischemic conditions.

Keywords:  Carotid body; Hypoxia; Ion channels; Oxygen sensing; Pulmonary artery smooth muscle cells

DOI:  https://doi.org/10.1007/s00424-021-02590-7
Chem Biol Interact. 2021 Jun 11. pii: S0009-2797(21)00189-7. [Epub ahead of print] 109553

Modeling hypoxia facilitates cancer cell survival through downregulation of p53 expression.

Yang Zhang, Maria A Yapryntseva, Alexander Vdovin, Polina Maximchik, Boris Zhivotovsky, Vladimir Gogvadze.

  A hypoxic environment of rapidly growing tumor cells makes them resistant to antitumor drugs. Mimicking hypoxia with iron chelator deferoxamine, suppressed cell death induced by widely used anticancer drugs doxorubicin or cisplatin. Deferoxamine decreased the number of dead (detached) cells, the size of SubG1 population, the release of cytochrome c, and the processing of caspase-3 in HCT116 colon carcinoma cells treated with cisplatin of doxorubicin. Deferoxamine-mediated suppression of apoptosis correlated with the level of pro-apoptotic Bcl-2 family proteins Bax, Bid, and Puma, which stimulate mitochondrial apoptotic pathway through permeabilization of the outer mitochondrial membrane and cytochrome c release. Here we show that one of the reasons for apoptosis suppression is downregulation of p53 expression under hypoxic conditions, and, as a result, attenuation of the expression of pro-apoptotic Bcl-2 family proteins. Indeed, p53 knock-out did not affect the stabilization of hypoxia-inducible factor but made undetectable the expression of pro-apoptotic proteins.

Keywords:  Bcl-2-family proteins; apoptosis; cancer; hypoxia; mitochondria; p53

DOI:  https://doi.org/10.1016/j.cbi.2021.109553