Role Of Hypoxia-inducible Factor 1alpha Research Articles

The Role of Hypoxia-Inducible Factor-1 Alpha in Renal Disease.

Partial pressure of oxygen (pO2) in the kidney is maintained at a relatively stable level by a unique and complex functional interplay between renal blood flow, glomerular filtration rate (GFR), oxygen consumption, and arteriovenous oxygen shunting. The vulnerability of this interaction renders the kidney vulnerable to hypoxic injury, leading to different renal diseases. Hypoxia has long been recognized as an important factor in the pathogenesis of acute kidney injury (AKI), especially renal ischemia/reperfusion injury. Accumulating evidence suggests that hypoxia also plays an important role in the pathogenesis and progression of chronic kidney disease (CKD) and CKD-related complications, such as anemia, cardiovascular events, and sarcopenia. In addition, renal cancer is linked to the deregulation of hypoxia pathways. Renal cancer utilizes various molecular pathways to respond and adapt to changes in renal oxygenation. Particularly, hypoxia-inducible factor (HIF) (including HIF-1, 2, 3) has been shown to be activated in renal disease and plays a major role in the protective response to hypoxia. HIF-1 is a heterodimer that is composed of an oxygen-regulated HIF-1α subunit and a constitutively expressed HIF-1β subunit. In renal diseases, the critical characteristic of HIF-1α is protective, but it also has a negative effect, such as in sarcopenia. This review summarizes the mechanisms of HIF-1α regulation in renal disease.

Possible Role of Hypoxia-Inducible Factor-1Alpha and Vascular Endothelial Growth Factor During Periovulation and Corpus Luteum Formation in Cows

Possible Role of Hypoxia-Inducible Factor-1Alpha and Vascular Endothelial Growth Factor During Periovulation and Corpus Luteum Formation in Cows

The role of hypoxia-inducible factor-1 alpha in multidrug-resistant breast cancer

Breast cancer is the most common cancer in women worldwide with increasing incidence. Significant therapeutics advances in the field of breast cancer have resulted in a growing number of treatment options, whereas de novo or acquired resistance is still a persistent clinical challenge. Drug resistance involves a variety of mechanisms, and hypoxia is one of the many causes. Hypoxia-inducible Factor-1 Alpha (HIF-1α) is a key transcription factor which can regulate the response of cells to hypoxia. HIF-1α can trigger anaerobic glycolysis of tumor cells, induce angiogenesis, promote the proliferation, invasion, and migration of tumor cells, and lead to multidrug resistance. This review mainly discusses the role of HIF-1α in the drug-resistant breast cancer and highlighted the potential of HIF-1α -targeted therapy.

Knockdown of hypoxia-inducible factor 1-alpha (HIF1α) interferes with angiopoietin-like protein 2 (ANGPTL2) to attenuate high glucose-triggered hypoxia/reoxygenation injury in cardiomyocytes

ABSTRACT To investigate the role of hypoxia-inducible factor 1-alpha (HIF1A) in hypoxia/reoxygenation (H/R) injury of cardiomyocytes induced by high glucose (HG). The in vitro model of coronary heart disease with diabetes was that H9c2 cells were stimulated by H/R and HG. Quantitative reverse transcription PCR (RT-qPCR) and Western blot analysis were used to detect the expression of HIF1A and angiopoietin-like protein 2 (ANGPTL2) in H9c2 cells. Cell viability and apoptosis were, respectively, estimated by Cell Counting Kit 8 (CCK-8) and TUNEL assays. Lactate dehydrogenase (LDH) activity, inflammation and oxidative stress were in turn detected by their commercial assay kits. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were used to confirm the association between HIF1A and ANGPTL2 promoter. The expression of nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway-related proteins and apoptosis-related proteins were also detected by Western blot analysis. As a result, ANGPTL2 expression was upregulated in H9c2 cells induced by HG or/and H/R. ANGPTL2 positively modulated HIF1A expression in H9c2 cells. HG or/and H/R suppressed the cell viability and promoted apoptosis, inflammatory response and oxidative stress levels in H9c2 cells. However, the knockdown of ANGPTL2 could reverse the above phenomena in H/R-stimulated-H9c2 cells through activation of Nrf2/HO-1 pathway. HIF1A transcriptionally activated ANGPTL2 expression. The effect of knockdown of ANGPTL2 on H/R triggered-H9c2 cells was weakened by HIF1A overexpression. In conclusion, knockdown of HIF1A downregulated ANGPTL2 to alleviate H/R injury in HG-induced H9c2 cells by activating the Nrf2/HO-1 pathway.

Regeneration in Spinal Disease: Therapeutic Role of Hypoxia-Inducible Factor-1 Alpha in Regeneration of Degenerative Intervertebral Disc.

The intervertebral disc (IVD) is a complex joint structure comprising three primary components—namely, nucleus pulposus (NP), annulus fibrosus (AF), and cartilaginous endplate (CEP). The IVD retrieves oxygen from the surrounding vertebral body through CEP by diffusion and likely generates ATP via anaerobic glycolysis. IVD degeneration is characterized by a cascade of cellular, compositional, structural changes. With advanced age, pronounced changes occur in the composition of the disc extracellular matrix (ECM). NP and AF cells in the IVD possess poor regenerative capacity compared with that of other tissues. Hypoxia-inducible factor (HIF) is a master transcription factor that initiates a coordinated cellular cascade in response to a low oxygen tension environment, including the regulation of numerous enzymes in response to hypoxia. HIF-1α is essential for NP development and homeostasis and is involved in various processes of IVD degeneration process, promotes ECM in NP, maintains the metabolic activities of NP, and regulates dystrophic mineralization of NP, as well as angiogenesis, autophagy, and apoptosis during IVD degeneration. HIF-1α may, therefore, represent a diagnostic tool for early IVD degeneration and a therapeutic target for inhibiting IVD degeneration

Роль индуцируемого гипоксией фактора – 1α и трансформирующего ростового фактора – β1 в развитии оксидативного и иммунного дисбаланса при эндометриозе

Роль индуцируемого гипоксией фактора – 1α и трансформирующего ростового фактора – β1 в развитии оксидативного и иммунного дисбаланса при эндометриозе

370 Hypoxic Conditions and Hypoxia-Inducible Factor 1-Alpha are Critical in the Radioresistance of Meningioma

Abstract INTRODUCTION Meningiomas are common benign intracranial neoplasms treated with a combination of surgical resection, radiotherapy, and chemotherapy. Hypoxia-inducible factor 1 alpha (HIF1A) can predict disease aggressiveness, response to oxygen tension and regulate meningioma pathogenesis. The role of HIF1A and hypoxia was explored in the radiation resistance of meningioma, hypothesizing that HIF1A confers resistance to radiotherapy in meningiomas and that oxygen tension is key to radiation responsiveness. METHODS Various primary meningioma cell lines were studied (IOMM-LE, JEN, GAR, SAM). GAR primary cell lines were utilized in addition to a shRNA-HIF1A knockdown (GAR1589). Cell proliferation, viability, and apoptosis were evaluated in response to radiation in both normoxia (21% O2) and hypoxia (1% O2). RESULTS >Doubling times of the various meningioma cell lines ranged from 19.5 to 213.2 hours. Cell density impacted responsiveness to radiation, with confluent cells showing greater dose tolerance before reduced proliferation. In normoxic environments, HIF1A knockout resulted in increased susceptibility to single radiation fractions of 2 Gy (P = 0.05) and 10 Gy (P = 0.02); however, both cells had strong susceptibility at 20 Gy. Hypoxic environments reduced the viability differences between GAR and GAR1589 cells and slightly increased GAR cell viability at 2 Gy (P < 0.05). Fractionated radiotherapy (2 Gy) daily showed reduced GAR and GAR1589 cell viability in normoxia and hypoxia. Cell viability for GAR1589 at 3 fractions of 2-Gy radiation was reduced, but this effect was eliminated in hypoxic environments. Apoptosis was increased in GAR1589 cells at baseline and with increased fractions of radiation; however, this effect was reduced in hypoxic conditions. CONCLUSION These results support important findings for meningioma response to radiation, including 1) importance of cell density, 2) dependence on HIF1A mutation, and 3) a critical role for oxygen tension. These results may be helpful in understanding the mechanisms of meningioma resistance to radiation and serve as a model to trial novel adjuvant therapies and treatment types.

Genome-independent hypoxic repression of estrogen receptor alpha in breast cancer cells

BackgroundAbout 75–80% of breast tumors express the estrogen receptor alpha (ER-α) and are treated with endocrine-target therapeutics, making this the premier therapeutic modality in the breast cancer clinic. However, acquired resistance is common and about 20% of resistant tumors loose ER-α expression via unknown mechanisms. Inhibition of ER-α loss could improve endocrine therapeutic efficacy, benefiting a significant number of patients. Here we test whether tumor hypoxia might commonly produce ER-α loss.MethodsUsing standard molecular and cellular biological assays and a work station/incubator with controllable oxygen levels, we analyze the effects of hypoxia on ER-α protein, mRNA, and transcriptional activity in a panel of independently-derived ER-α positive cell lines. These lines were chosen to represent the diverse genetic backgrounds and mutations commonly present in ER-α positive tumors. Using shRNA-mediated knockdown and overexpression studies we also elucidate the role of hypoxia-inducible factor 1-alpha (HIF-1α) in the hypoxia-induced decrease in ER-α abundance.ResultsWe present the first comprehensive overview of the effects of bona fide low environmental oxygen (hypoxia) and HIF-1α activity on ER-α abundance and transcriptional activity. We find that stabilized HIF-1α induces rapid loss of ER-α protein in all members of our diverse panel of breast cancer cell lines, which involves proteolysis rather than transcriptional repression. Reduced ER-α severely attenuates ER-α directed transcription, and inhibits cell proliferation without overt signs of cell death in the cell lines tested, despite their varying genomic backgrounds.ConclusionsThese studies reveal a common hypoxia response that produces reduced ER-α expression and cell cycle stalling, and demonstrate a common role for HIF-1α in ER-α loss. We hypothesize that inhibitors of HIF-1α or the proteasome might stabilize ER-α expression in breast tumors in vivo, and work in combination with endocrine therapies to reduce resistance. Our data also suggests that disease re-occurrence in patients with ER-α positive tumors may arise from tumor cells chronically resident in hypoxic environments. We hypothesize that these non-proliferating cells may survive undetected until conditions change to oxygenate the environment, or cells eventually switch to proliferation via other signaling pathways.

Abstract B22: Invitro and invivo proof of concept for an effective antineoplastic combination of novel anti HIF therapy in pancreatic cancer

Abstract New therapeutic approaches for pancreatic cancer are needed owing to the extremely poor prognosis, in large part as a consequence of high rates of metastasis. Hypoxia plays a crucial role in carcinogenesis, and metastasis. We also know that HIF plays a significant role in tumor resistance to cytotoxic therapies, and further explains the pancreatic cancer lack of response in clinic. Unfortunately to our knowledge there has been no effective therapy to this date to overcome such cellular pathology. To address this shortcoming, we used both in vitro and in vivo approaches to evaluate the overall effects of anti HIF-1alpha protocol in pancreatic cancer. Here we used a novel combination of two epigenetic modifiers that were investigated in 2 and 3 dimentional cell cultures to synergistically inhibit HIF, migration and invasion of pancreatic cancer cell lines, and further were able to show significant clinical application of such therapy in a series of metastatic or refractory disease in human. Background: Hypoxia-inducible factor-1alpha (HIF-1alpha) is essential for the pancreatic cancer progression and metastasis, and has been suggested to be a target for cancer therapy, as the result, there has been tremendous efforts in recent years to target HIF, as a dominant factor driving the metastatic progression of pancreatic cancer, a meaningful therapeutic approach, both independently as well as in combination with current standard of care. Both in vitro and in vivo analysis has suggested that hypoxia significantly promotes cell proliferation and migration, resulting in metastasis. Pancreatic cancer cells in which HIF-1alpha expression was inhibited were less invasive, with reduced resistance to hypoxia, impaired migration, and reduced capacity to cause metastasis. It is also suggested by our colleagues as well as our own published data, that epigenetic modifiers are able to improve the degradation of HIF through VHL. We were convinced that such approach we would be able to reduce the activity of HIF or hypoxia response elements ( HRE). We tested this hypothesis by application of a combination of epigenetic modifiers in laboratory and further in human, successfully. Methods: To illustrate the role of hypoxia-inducible factor-1alpha in pancreatic cancer metastasis and the value of the molecule as a target for pancreatic cancer therapy, we tested the pancreatic cell lines ( Panc 1) in the experimental therapeutic laboratory using a 3 dimentional cell culture model, and were able to show the significant spheroid production by these cells as a result on intratumoral hypoxia and HIF. Further we were able to test the HIF activity/Hypoxia response element ( HRE), after exposure to two synergistic compounds. It was shown that HIF activity significantly reduces by such combination, as a result of sensitization of cells to the subsequent exposure. Clinical application of such method showed significant clinical superiority to the standard of care alone. We will review a case series of patients with advanced disease, and their clinical outcome in summary. Conclusions: HIF-1alpha is a dominant factor driving the metastatic progression of pancreatic cancer is a potent therapeutic target for the disease. Here we were able to show synergism in combining epigenetic modifiers to inhibit HIF both invitro and in human, with relevant and significant outcome. We conclude that a multitargeted epigenetic therapy ( MTET) using combination of drugs modifying the HIF activity is clinically relevant and we further suggest large clinical trials to optimize the response in clinic. Citation Format: M. A. Nezami, Steve Hager.{Authors}. Invitro and invivo proof of concept for an effective antineoplastic combination of novel anti HIF therapy in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B22.

GW27-e0564 The role of Hypoxia-Inducible Factor 1-Alpha (HIF1-α) in maintaining the balance between survival and cell death during the course of myocardial infraction.

GW27-e0564 The role of Hypoxia-Inducible Factor 1-Alpha (HIF1-α) in maintaining the balance between survival and cell death during the course of myocardial infraction.

HIF-1α and Resistance to Ionizing Radiation in Rectal Cancer

Introduction: There is a wide range of responses to pre-operative chemoradiation (CRT) in patients with rectal cancer. Factors that dictate tumors response have not been identified. The objective of this study was to determine the role of hypoxia-inducible factor 1-alpha (HIF-1α) in in vitro and ex vivo models of rectal cancer. Methods: Levels of HIF-1α were assessed in radiosensitive (HCT-116) and a radioresistant (HT-29) cells. Radioresistant HT-29 cells were exposed to a potent radiosensitizing agent (a nitric oxide donor: DETANONOate [1 mM]) and IR followed by Western blot analysis with anti- HIF-1α antibodies. Patients with rectal cancer that were treated with CRT were separated based on good responders (≥ 50% reduction in tumor by comparing tumor size pre-operatively and postoperatively) compared to those that did not respond (<50% reduction in tumor). Blocks were stained for HIF-1α. Tissues collected from normal colonic epithelium from all these patients were subjected to the same treatments. Results: In vitro, radiosensitive HCT-116 colorectal cancer cells demonstrated low levels of HIF-1α following treatment IR. Western blot analysis showed high protein levels of HIF-1α in radioresistant HT-29 cells subjected to IR with induction at 2.0 and 4.0 Gy. Protein levels of HIF-1α were attenuated by treatment of cells HT-29 with the radiosensitizing agent DETANONOate following exposure to IR. Ex vivo, tissue microarrays demonstrated no difference in HIF-1α expression between patients with a poor response to CRT (418.1 ± 32.6) vs. good responders (371.1 ± 31.5; p=0.3). However, examination tumor tissue compared to normal epithelium showed an increase in HIF-1α (1.5 fold; p<0.001) in patients who responded poorly to IR. This effect was not observed in the cohort of patients who responded well to IR. Conclusions: The results of this study further support the potential role of HIF-1α in resistance to IR. This study implicates it a potential role of HIF-1α in rectal cancers.

Lipopolysaccharide-induced cross-tolerance against renal ischemia–reperfusion injury is mediated by hypoxia-inducible factor-2α-regulated nitric oxide production

Although the protective effect of lipopolysaccharide (LPS) pretreatment on renal ischemia/reperfusion injury is known, a link to hypoxia-inducible factors (HIFs) has not been established. Here we show that LPS treatment led to HIF-2α accumulation in mouse kidneys and endothelial cells, a result of nuclear factor-κB activation. Inactivation of HIF-2α, rather than HIF-1α, completely negated LPS-mediated protection against renal ischemia/reperfusion injury. LPS-stimulated renoprotection was related to inducible/endothelial nitric oxide synthase (iNOS/eNOS) expression, increased production of nitric oxide, and enhanced postischemic microcirculatory recovery. All these effects were lost in HIF-2α knockout mice. Preischemic administration of a nitric oxide donor, rather than erythropoietin, restored the lost preconditioning effect of LPS in HIF-2α knockout mice. In vitro and in vivo studies demonstrated that HIF-2α in endothelial cells, rather than myeloid cells or hepatocytes, was responsible for the LPS-mediated effects. Thus, our results demonstrated that LPS preconditioning protected against renal ischemia/reperfusion injury by HIF-2α activation in endothelial cells that subsequently improved renal microvascular perfusion and reduced ischemic tubular damage.

The relationship between HIF-1α expression and the early lung fibrosis in rats with acute paraquat poisoning

To explore the role of hypoxia-inducible factor 1alpha (HIF-1α) in early lung fibrosis of rats with acute paraquat (PQ) poisoning. Forty eight healthy SD rats were randomly divided into control group (6 rats) and paraquat poisoning group (42 rats). Control group was exposed to 1 ml normal solution by gastric gavage. The paraquat group was exposed to 1 ml paraquat solution (50 mg/kg) by gastric gavage for 2, 6, 12, 48, 72 and 120 h, respectively. The arterial blood gas analysis (PaO(2)) was detected. The pathological examinations of lung tissues were performed by HE and Mason staining. HIF-1α in lung tissues were measured by immunofluorescence. Western blot assay was used to detect the expression levels of HIF-1α protein in lung tissues. PaO2 of rats exposed to paraquat for 72 h was (62.33 ± 0.22) mm Hg, which was significantly lower than that (96.00 ± 5.20) of control group (P < 0.05). Pathological examination by HE staining indicated that the acute diffuse lesion appeared in the alveolar capillary endothelium, epithelia and interstitial tissues, and there was the inflammatory cell infiltration in the alveolar of rats exposed to paraquat at 2 h after exposure. At 12 h after exposure, the interstitial edema in lung tissues of rats decreased and the alveolar space became narrow. At 120 h after exposure, there were the alveolar structure derangement, abundant cicatrix, more fibroblasts and peripheral inflammation absorption. Pathological examination by Masson staining showed that there was obvious collagen deposition in the alveolar epithelia at 2h after exposure, the increased collagen fibrosis at 24 and 48 h after exposure and the obvious damage of alveolar tissues or much more fibrous connective tissue deposition at 120 h after exposure. The results of western blot and immunofluorescence assays exhibited that the expression levels of HIF-1α in lung tissues at 2, 24 and 48 h after exposure significantly increased, as compared with control group (P < 0.05), but there were no significant differences of HIF-1α expression among sub-groups at different time points after exposure. The results of present study shown that there were the pulmonary fibrosis and increased expression of HIF-1α in acute PQ poisoning rats at the early stage, and HIF-1α may be associated with pulmonary fibrosis.

Effect of hypoxia-inducible factor 1-alpha on hypoxia/reoxygenation-induced apoptosis in primary neonatal rat cardiomyocytes

We studied the role of hypoxia-inducible factor 1-alpha (HIF-1α) in hypoxia/reoxygenation (H/R)-induced apoptosis in primary neonatal rat cardiomyocytes and its possible molecular mechanisms. Isolated neonatal and adult rat cardiac myocytes were cultured for 48h and were submitted to 5h of hypoxia followed by 2, 6, or 12h of reoxygenation. Small interfering RNA was used to target the HIF-1α gene. Cardiac myocyte apoptosis induced by H/R was assessed by Annexin V-FITC apoptosis assay. HIF-1α, Bnip3 and caspase-3 levels were determined by real-time reverse transcription polymerase chain reaction and western blot for mRNA and protein, respectively. H/R resulted in severe injury in cultured rat cardiomyocytes and it upregulated HIF-1α and proapoptotic Bnip3 mRNA and protein expression. HIF-1α activity inhibited by siRNA significantly decreased (P<0.01) the rate of apoptotic cardiomyocytes induced by 5h of hypoxia followed by 6h of reoxygenation compared with cardiomyocytes without siRNA treatment. Additionally, the expression of Bnip3 and caspase-3 was also markedly reduced. We conclude that HIF-1α is a key regulator of apoptosis of cardiomyocytes induced by H/R. H/R enhances primary neonatal rat cardiomyocyte apoptosis through the activation of HIF-1α and the mechanism might involve Bnip3 and caspase-3. HIF-1α may be a possible therapeutic target to limit myocardial injury after myocardial infarction.

P3-03-01: Low Expression of microRNA-210 Is an Independent Good Prognostic Factor in Japanese Triple-Negative Breast Cancer Patients.

Abstract Background: microRNAs (miRNAs) have emerged as a new class of non-coding genes involved in regulating cell proliferation, differentiation, and viability. Recent studies have identified miR-210 among a set of hypoxia-regulated miRNAs and demonstrated a direct regulatory role of hypoxia-inducible factor-1 alpha (HIF-1 a) in its transcription. High expression of miR-210 has been reported to be a poor prognostic factor in several types of cancers including breast. Materials and Methods: TaqMan MicroRNA assays for miR-210 expression were performed in 219 breast cancers (58 triple-negative (TNBCs), and 161 ER-positive and HER2−negative). Correlations between miR-210 expression and clinicopathological factors were analyzed. The effects of several variables on survival were tested by Cox proportional hazards regression analysis. Results: miR-210 expression in TNBCs was significantly higher than in ER-positive and HER2−negative breast cancers (p&amp;lt;0.001). Patients whose TNBCs had low miR-210 expression experienced significantly better disease-free and overall survival compared with high miR-210 expressors (p=0.02 and p=0.05, respectively). Notably, among 40 node-negative TNBCs, 5-year disease-free survival was approximately 60% in patients whose tumors had high or intermediate miR-210 expression (n=26), while no patients with low miR-210 expression (n=14) suffered recurrent disease. Cox univariate and multivariate analyses demonstrated that low expression of miR-210 was an independent good prognostic factor in TNBCs. Discussion: Although prognosis of patients with TNBCs is poor, those whose tumors expressed low levels of miR-210 had a more favorable prognosis. Thus, the degree of miR-210 expression might be a clinically useful prognostic factor for decision-making regarding treatment in the adjuvant setting, especially in node-negative TNBC patients. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-03-01.

The role of hypoxia-inducible factor-1 alpha in TEMPI syndrome.

Sir, Two recent reports in The New England Journal of Medicine on a newly described syndrome, namely TEMPI syndrome (telangiectasia, erythrocytosis, monoclonal paraprotein, paranephric fluid collections, intrapulmonary shunting) are fascinating [1, 2], considering the number of cases where the radiological finding of perinephric fluid collections are not investigated further [3] or the concomitant laboratory finding of a paraprotein is dismissed as another case of monoclonal gammopathy of undetermined significance (MGUS). Sykes et al. [2] hypothesize that the IgG paraprotein in TEMPI syndrome may be pathogenic due to the resolution of most clinical features after a trial with the proteasome inhibitor, bortezomib. But, as bortezomib also affects the function of hypoxia-inducible factor-1 alpha (Hif-1α) and down-stream transcription of vascular endothelial growth factor (VEGF) [4], inhibition of Hif-1α would also explain the resolution of the symptoms seen in the patient described by Sykes et al. Expression of Hif-1α and Hif-1α messenger RNA has been detected in all human tissues [5]. Intratumoral hypoxia is known to induce Hif-1α expression that increases VEGF and angiogenesis, but growth factors and loss-of-function mutations in von Hippel Lindau gene and p53 also induce Hif-1α expression (and possibly development of telangiectasias and erythrocytosis) [6]. Zhang et al. [7] showed that even under normoxic conditions, the oncogenic c-Myc/Hif-1α pathway modulates multiple myeloma cell production and mediates production and secretion of VEGF. Bortezomib was also shown to decrease both c-Myc and Hif-1α levels. Specific inhibitors of Hif-1α may therefore reverse most of the pathological manifestations of TEMPI syndrome.

Clopidogrel Exacerbates Aspirin (ASA) Damage and Counteracts the Gastric Adaptation to Repetitive ASA Insult. Role of Hypoxia-Inducible Factor-1alpha, Heme Oxygenase-1 (HO-1) and Proinflammatory Cytokines

Clopidogrel Exacerbates Aspirin (ASA) Damage and Counteracts the Gastric Adaptation to Repetitive ASA Insult. Role of Hypoxia-Inducible Factor-1alpha, Heme Oxygenase-1 (HO-1) and Proinflammatory Cytokines

Acute cobalt-induced lung injury and the role of hypoxia-inducible factor 1alpha in modulating inflammation.

Air pollution is a critical factor in the development and exacerbation of pulmonary diseases. Ozone, automobile exhaust, cigarette smoke, and metallic dust are among the potentially harmful pollution components that are linked to disease progression. Transition metals, such as cobalt, have been identified at significant levels in air pollution. Cobalt exerts numerous biological effects, including mimicking hypoxia. Similar to hypoxia, cobalt exposure results in the stabilization of hypoxia-inducible factors (HIFs), a family of proteins that regulate the cellular response to oxygen deficit. HIFs also play an important role in innate immunity and inflammatory processes. To characterize the role of HIF1alpha, the most ubiquitously expressed HIF, in the early events during cobalt-induced lung inflammation, an inducible lung-specific HIF1alpha deletion model was employed. Control mice showed classical signs of metal-induced injury following cobalt exposure, including neutrophilic infiltration and induction of Th1 cytokines. In contrast, HIF1alpha-deficient mice exhibited pronounced eosinophil counts in bronchoalveolar lavage fluid and lung tissue complemented with Th2 cytokine induction. The timing of these results suggests that the loss of epithelial-derived HIF1alpha alters the lung's innate immune response and biases the tissue toward a Th2-mediated inflammation.

Down-Regulation of Hypoxia-Inducible Factor-1α by Hyperbaric Oxygen Attenuates the Severity of Acute Pancreatitis in Rats

This study investigated the role of hypoxia-inducible factor 1alpha (HIF-1alpha) in acute pancreatitis (AP) and whether HIF-1alpha is involved in the therapeutic effects of hyperbaric oxygen (HBO) on AP. Thirty Wistar rats with taurocholate-induced AP were randomly assigned to 3 groups (each group had 10 rats) receiving oxygen, HBO, or no therapeutic treatment 4 hours after induction. Ten healthy sham-operated rats also served as controls. The arterial oxygen saturation, PaO2, pH, lactate dehydrogenase in the arterial sera, and amylase and tumor necrosis factor alpha in the venous sera were measured 6 hours after induction. Pancreatic tissues were subjected to histopathologic analysis, immunohistochemical and Western-blotted analyses of HIF-1alpha and vascular endothelial growth factor, and measuring of myeloperoxidase activity. The HBO therapy attenuated the severity of acute pancreatitis; reduced histopathologic scores, dry weight-wet weight ratio of pancreatic tissues, and levels of amylase and lactate dehydrogenase; and elevated blood arterial oxygen saturation, PaO2, and pH values. The HBO therapy inhibited AP-induced up-regulation of HIF-1alpha and its downstream effector vascular endothelial growth factor and the production of tumor necrosis factor alpha and myeloperoxidase activity. Hypoxia-inducible factor 1alpha plays a key role in the pathogenesis of AP, and the ability to down-regulate the expression of HIF-1alpha may partially explain the therapeutic effect of HBO on AP.

Role of hypoxia-inducible factor-1 alpha in the regulation of plasminogen activator activity in rat knee joint chondrocytes

To examine the effects of hypoxia-inducible factor-1alpha (HIF-1alpha) on the plasminogen activator's (PA) activity and on the expression of components of PA system in articular chondrocytes of rats. Chondrocytes from rat knee joint cartilage were cultured under normoxic, hypoxic, CoCl(2) simulated hypoxic, and interleukin-1beta (IL-1beta)-stimulated conditions. siRNA targeting HIF-1alpha was transfected into cells cultured under hypoxic, simulated hypoxic, and IL-1beta-stimulated conditions to silence HIF-1alpha. PA activity was determined by the hydrolysis of the chromogenic substrate H-D-Val-Leu-Lys-pNA (S-2251). The mRNA levels were measured by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). The intracellular/matrix-associate protein levels were detected by Western blot and the soluble protein levels were measured by enzyme linked immunosorbent assay (ELISA). Chromatin immunoprecipitation (CHIP) assay was performed to determine whether HIF-1alpha binds to the hypoxia response element (HRE) of target genes. The enhancement of HIF-1alpha by CoCl(2) resulted in a decrease of PA activity, and the silence of HIF-1alpha by siRNA led to an increase of PA activity. The PA inhibitor-1 (PAI-1) mRNA and protein were increased by hypoxia or simulated hypoxia, which was reversed by the siRNA2-mediated silencing of HIF-1alpha. CHIP assay further confirmed that the induction of PAI-1 involved the binding of HIF-1alpha to the PAI-1 promoter, while the enhancement or silencing of HIF-1alpha did not affect the expression of urokinase type PA (uPA), tissue type PA (tPA) or uPA receptor (uPAR). Additionally, IL-1beta stimulated both HIF-1alpha and PAI-1 in articular chondrocytes, and the IL-1beta-mediated induction of PAI-1 was inhibited partly by HIF-1alpha silencing. HIF-1alpha may inhibit the PA activity through stimulating the expression of PAI-1 in normal articular chondrocytes. The inhibition of HIF-1alpha in the PA activity of articular chondrocytes probably plays an important role in the maintenance of articular cartilage matrix.