Effect Of Hypoxia-inducible Factor-1 Research Articles

Hypoxia-inducible factor 1α activates the NLRP3 inflammasome to regulate epithelial differentiation in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is an upper airway inflammation disease associated with hypoxia-mediated inflammation. The effect of hypoxia-inducible factor 1α (HIF-1α) on NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation in the pathogenesis of sinonasal mucosa is unclear. We investigated the effect and mechanism of HIF-1α on NLRP3 inflammasome activation in the primary human nasal epithelial cells (hNECs). We measured the expression levels of HIF-1α and the NLRP3 inflammasome in nasal biopsy samples and hNECs derived from negative controls (healthy) and patients with CRS with and without nasal polyps, then further analyzed the specific mechanism of HIF-1α regulation of the NLRP3 inflammasome and its effect on hNEC differentiation. Increased mRNA and protein expression levels of HIF-1α and the NLRP3 inflammasome were found in all CRS biopsy samples. HIF-1α enhanced expression of phosphorylated NLRP3 (S295) in both HEK293T cells and hNECs; it also promoted recruitment of caspase-1 and apoptotic speck-like protein containing caspase recruitment domain (aka ASC) by NLRP3. HIF-1α also improved NLRP3's stability by preventing NLRP3 degradation caused by hypoxia-mediated inflammation. In addition, HIF-1α could also increase expression of Mucin5AC and decrease expression of α-tubulin by promoting activation of the NLRP3 inflammasome in hNECs. In addition, HIF-1α could also directly promote P63 expression in hNECs. HIF-1α could potentially induce cilia loss and enhance the proliferation of goblet cells, possibly mediated by the regulation of NLRP3 phosphorylation in CRS inflammation.

The Potential Role of Hypoxia-Inducible Factor-1 in the Progression and Therapy of Central Nervous System Diseases.

Hypoxia-inducible factor-1 (HIF-1) is a heterodimer protein composed of an oxygenregulated functional subunit, HIF-1α, and a structural subunit, HIF-1β, belonging to the basic helixloop- helix family. Strict regulation of HIF-1 protein stability and subsequent transcriptional activity involves various molecular interactions and is primarily controlled by post-transcriptional modifications. Hypoxia, owing to impaired cerebral blood flow, has been implicated in a range of central nervous system (CNS) diseases by exerting a deleterious effect on brain function. As a master oxygen- sensitive transcription regulator, HIF-1 is responsible for upregulating a wide spectrum of target genes involved in glucose metabolism, angiogenesis, and erythropoiesis to generate the adaptive response to avoid, or at least minimize, hypoxic brain injury. However, prolonged, severe oxygen deprivation may directly contribute to the role-conversion of HIF-1, namely, from neuroprotection to the promotion of cell death. Currently, an increasing number of studies support the fact HIF-1 is involved in a variety of CNS-related diseases, such as intracranial atherosclerosis, stroke, and neurodegenerative diseases. This review article chiefly focuses on the effect of HIF-1 on the pathogenesis and mechanism of progression of numerous CNS-related disorders by mediating the expression of various downstream genes and extensive biological functional events and presents robust evidence that HIF-1 may represent a potential therapeutic target for CNS-related diseases.

Inhibition of hypoxia inducible factor 1 by YC-1 attenuates tissue plasminogen activator induced hemorrhagic transformation by suppressing HMGB1/TLR4/NF-κB mediated neutrophil infiltration in thromboembolic stroke rats

Hemorrhagic transformation (HT) is a frequent complication of ischemic stroke after thrombolytic therapy and seriously affects the prognosis of stroke. Due to the limited therapeutic window and hemorrhagic complications, tissue plasminogen activator (t-PA) is underutilized in acute ischemic stroke. Currently, there are no clinically effective drugs to decrease the incidence of t-PA-induced HT. Hypoxia-inducible factor 1 (HIF-1) is an important transcription factor that maintains oxygen homeostasis and mediates neuroinflammation under hypoxia. However, the effect of HIF-1 on t-PA-induced HT is not clear. The aim of this study was to investigate the role of HIF-1 in t-PA-induced HT by applying YC-1, an inhibitor of HIF-1. In the present study, we found that HIF-1 expression was significantly increased in ischemic brain tissue after delayed t-PA treatment and was mainly localized in neurons and endothelial cells. Inhibition of HIF-1 by YC-1 improved infarct volume and neurological deficits. YC-1 inhibited matrix metalloproteinase protein expression, increased tight junction protein expression, and ameliorated BBB disruption and the occurrence of HT. Furthermore, YC-1 suppressed the release of inflammatory factors, neutrophil infiltration and the activation of the HMGB1/TLR4/NF-κB signaling pathway. These results demonstrated that inhibition of HIF-1 could protect BBB integrity by suppressing HMGB1/TLR4/NF-κB-mediated neutrophil infiltration, thereby reducing the risk of t-PA-induced HT. Thus, HIF-1 may be a potential therapeutic target for t-PA-induced HT.

Effect of hypoxia-inducible factor-1/vascular endothelial growth factor signaling pathway on spinal cord injury in rats.

The aim of the present study was to evaluate the expression of vascular endothelial growth factor (VEGF) and hypoxia inducible factor-1 (HIF-1), and to investigate the role of the HIF-1/VEGF signaling pathway following spinal cord injury (SCI). A total of 90 12-week-old Sprague Dawley rats were randomly divided into the following three groups: Sham group (operation without SCI); control group (SCI without ML228 treatment); and treatment group (SCI receiving ML228 treatment). ML228 was administered as it is an activator of HIF-1α. The control and treatment groups were subjected to spinal cord hemisection and motor activity was evaluated using the Basso, Beattie and Bresnahan (BBB) scoring system. Expression of HIF-1α and VEGF in each injured spinal cord section was assessed using immunohistochemistry. Prior to SCI, there were no significant differences in the BBB score among the three groups (P>0.05). However, one day after the operation, the BBB score of the sham group was significantly higher than that of the other two groups (P<0.05) and the BBB scores of the control and treatment groups did not differ significantly (P>0.05). BBB scores 3 and 7 days following surgery were significantly higher in the sham group than the other two groups (P<0.05) and the BBB scores of the treatment group were significantly higher than those of the control group (P<0.05). The expression of HIF-1α and VEGF proteins in all groups were measured 1, 3 and 7 days after the operation, and it was observed that their expression was higher in the treatment group than in the control group (P<0.05). Therefore, the results of the current study suggest that ML228 may effectively activate the HIF-1α/VEGF signaling pathway to promote the expression of HIF-1α and VEGF proteins within the injured segment of the spinal cord, which promotes neural functional recovery following SCI in rats. Therefore, treatment with ML228 may be developed as a novel therapeutic strategy to treat SCI.

Effect of hypoxia-inducible factor-1.ALPHA. on inflammatory response and angiogenic factor expression in rats with traumatic brain injury

Objective To investigate the protective effect of hypoxia-inducible factor-1α(HIF-1α) on the neurovascular unit in rats with traumatic brain injury (TBI). Methods The fluid percussion model was applied to induce TBI in rats. A total of 600 rats were divided into sham operation group, TBI group, TBI+ HIF-1α silence group and TBI+ control virus group according to the random number table, with 150 rats in each. Virus-mediated HIF-1α silence gene and control virus were delivered 24 h before the fluid percussion injury. After 3, 7 and 14 d, brain injury area and morphological changes in injured region were detected by HE staining, expressions of vascular endothelial cell markers (vWF) and HIF-1α were detected by Western blot method, and expressions of vascular endothelial growth factor (VEGF), matrix metalloproteinase-9 (MMP-9), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6) and nuclear factor-κB (NF -κB) in peripheral blood and brain tissue were detected by ELISA method. Rat neural function was dynamically assessed using the modified neurological severity score (mNSS). Results (1) Brain injury area and edema area in TBI+ HIF-1α silence group were higher than those in TBI group at all time points (P<0. 05). (2) Compared with sham operation group and TBI+ control virus group, expression of HIF-1α in TBI group gradually increased and remained high at 7 and 14 d postinjury (P<0. 05). Compared with TBI group, expression of vWF in TBI+ HIF-1αsilence group decreased at all time points (P<0. 05) and inhibited angiogenesis. (3) TBI+ HIF-1α silence group versus TBI group showed remarkably decreased VEGF at all time points, increased expressions of TNF-α, IL-6 and NF -κB at all time point, and increased expression of MMP-9 at 7 and 14 d postinjury ( all P<0. 05). (4) TBI+ HIF-1α silence group versus TBI group showed significant difference in mNSS at 7 and 14 d postinjury ( all P<0. 05). Conclusions After TBI, high expression of HIF-1αcan facilitate vascular formation and inhibit inflammatory reaction related factor expression, inducing the mitigation of brain edema and brain injury. Therefore, promoting HIF-1α expression may become a new means to improvement of neurovascular function after TBI. Key words: Brain injuries; Hypoxia-inducible factor 1, alpha subunit; Inflammation; Angiogenesis

Negative regulation of exogeneous polyl-4-hydroxylase domain proteins on hypoxia-inducible factor pathway in human RPE cells

Background Anti-VEGF drugs are generally applied in the treatment of ocular neovascular diseases.However, the therapy effect is unsatisfactory in some patients.Studing the effect of hypoxia-inducible factor-1 (HIF-1), a upstream regulatory gene of VEGF, and its limiting enzyme prolyl-4-hydroxylase domain proteins (PHDs) is of important clinical significance. Objective This study was to investigate the negtive regulation of exogeneous PHDs on HIF-1 pathway in human RPE cells. Methods pFLAG-PHD1, pFLAG-PHD2 and pFLAG-PHD3 plasmids were constructed by extracting RNA from Hela cell line and coloning PHD1, PHD2 and PHD3 using reverse transcription PCR with restriction enzyme.The plasmids were identified by gene sequencing.ARPE-19 cells were cultured at 21% O2 (normoxia group), 1% O2 (hypoxia group), or in hypoxia-mimicking agents (CoCl2, anoxia group), respectively, and then were transfected with plasmids encoding FLAG-tagged PHD1, PHD2, PHD3 and pFLAG-CMV2 transfected cells served as blank control.The expressional intensities of PHD1, PHD2 and PHD3 in the cells were detected and compared among different groups by using Western blot assay.The transcriptional activity of HIF-1 in the cells was evaluated with dual luciferase reporter assay. Results Western blot assay showed that PHD1, PHD2 and PHD3 all were expressed in ARPE-19 cells in the normoxia group, hypoxia group and anoxia group.The expression was strong in PHD2 protein and was weak in PHD3 protein, a statistically significant difference was found between PHD2 protein expression and PHD1 or PHD3 expressions (all at P<0.05). Endogenous HIF-1 activity was elevated in pFLAG-CMX transfected cells in the hypoxia group and anoxia group than that in the normoxia group.Compared with pFLAG-CMX transfected cells, no obvious change was seen in the endogenous HIF-1 activity in the normoxia group, however, HIF-1 activity was declined in the hypoxia group and anoxia group after pFLAG-PHD1, pFLAG-PHD2 or pFLAG-PHD3 transfection.Under the same oxygen environment, HIF-1 activity was lower in the pFLAG-PHD2 transfected cells than that in the pFLAG-PHD1 or pFLAG-PHD3 transfected cells (both at P<0.05). Conclusions PHDs play a negative regulation to HIF-1 activating pathway in human RPE cells, especially in hypoxia and anoxia cells.Among PHDs proteins, PHD2 presents the strongest inhibition on HIF-1 activating pathway. Key words: Cell hypoxia; Vascular endothelial growth factors; Gene expression regulation; Hypoxia-inducible factor-1; Procollagen-proline dioxygenase/metabolism; Humans; Transcription factors; Epithelial cells, retinal

Hypoxia-Inducible Factor 1 Protects Hypoxic Astrocytes against Glutamate Toxicity

Stroke is a major neurological disorder characterized by an increase in the Glu (glutamate) concentration resulting in excitotoxicity and eventually cellular damage and death in the brain. HIF-1 (hypoxia-inducible factor-1), a transcription factor, plays an important protective role in promoting cellular adaptation to hypoxic conditions. It is known that HIF-1α, the regulatable subunit of HIF-1, is expressed by astrocytes under severe ischaemia. However, the effect of HIF-1 on astrocytes following Glu toxicity during ischaemia has not been well studied. We investigated the role of HIF-1 in protecting ischaemic astrocytes against Glu toxicity. Immunostaining with GFAP (glial fibrillary acidic protein) confirmed the morphological modification of astrocytes in the presence of 1 mM Glu under normoxia. Interestingly, when the astrocytes were exposed to severe hypoxia (0.1% O2), the altered cell morphology was ameliorated with up-regulation of HIF-1α. To ascertain HIF-1's protective role, effects of two HIF-1α inhibitors, YC-1 [3-(50-hydroxymethyl-20-furyl)-1-benzylindazole] and 2Me2 (2-methoxyoestradiol), were tested. Both the inhibitors decreased the recovery in astrocyte morphology and increased cell death. Given that ischaemia increases ROS (reactive oxygen species), we examined the role of GSH (reduced glutathione) in the mechanism for this protection. GSH was increased under hypoxia, and this correlated with an increase in HIF-1α stabilization in the astrocytes. Furthermore, inhibition of GSH with BSO (l-butathione sulfoximine) decreased HIF-1α expression, suggesting its role in the stabilization of HIF-1α. Overall, our results indicate that the expression of HIF-1α under hypoxia has a protective effect on astrocytes in maintaining cell morphology and viability in response to Glu toxicity.

Current Insights into the Role of HIF-1 in Cutaneous Wound Healing

Hypoxia Inducible Factor-1 (HIF-1) is considered the major coordinator of the cellular adaptive response to hypoxia. Over recent years, its activity in the context of wound healing has been the object of increasing investigation. On the molecular level, HIF-1 transcriptional target products have been shown to regulate the process of endothelial cell survival, migration and proliferation (VEGF, ANGPT-1, ANGPT-2, ANGPT-4, FGF-2, PlGF, PDGF-B, RGC-32), vascular smooth muscle cell migration and proliferation (FGF-2, EGF, PDGF, thrombospondin) and mobilization of Circulating Angiogenic Cells to the periphery (SFD-1/CXCR4). Studies on the effect of HIF-1 on the expression and activity of extracellular cell matrix modifying enzymes, such as MMPs and prolidase, have been conducted in the context of tumor angiogenesis and metastasis, and have resulted in controversial findings. A growing body of evidence suggests that HIF-1 also affects reepithelialization of the wound bed, through increasing keratinocyte migration, but decreasing their proliferation. Diminished HIF-1 levels and activity have been documented in conditions of impaired wound healing, such as wound healing in aged and in diabetic mice. The increasing number of studies on the role of HIF-1 in wound healing, apart from answering certain questions, has also raised an equal number, if not more. Clarifying the topics that still remain unclear could introduce a new era of HIF-1 targeted management of a wide range of problematic wounds.

Effect of hypoxia-inducible factor-1 on proliferating retinal disease

缺氧诱导因子-1(HIF-1)是一种在缺氧诱导的细胞核提取物中发现的转录因子,广泛存在于哺乳动物体内,能调节细胞适应低氧状态下的能量代谢和氧运输,是维持细胞内氧供求平衡的主要调控因子,使机体对缺氧产生耐受和适应.HIF-1通过改,变血管内皮生长因子、一氧化氮合酶、内皮素-I和促红细胞生成素等基因的表达,促进视网膜微血管内皮细胞的增生和渗透,最终导致早产儿视网膜病,在增殖性视网膜病的病理生理过程中发挥重要作用。

552. Collateral Circulation under Cerebral Ischemia by Hypoxia Inducible Factor Naked DNA in Rat Indirect-Bypass Model

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that regulates the adaptive response to hypoxia in mammalian cells. It consists of a regulatory subunit HIF-1|[alpha]|, which accumulates under hypoxic conditions, and a constitutively expressed subunit, HIF-1|[beta]|. In this study, we investigated if HIF-1|[alpha]| naked DNA induced angiogenesis in a cerebral ischemic model in vivo. We utilized a rat encephalo-myo-synangiosis (EMS) model and inoculated naked DNA into the brain surface. We analyzed whether DNA induced angiogenic factors and collateral circulation. We measured and compared infarction volumes to investigate the effect of HIF-1|[alpha]| on cerebral infarction induced by permanent middle cerebral artery (MCA) occlusion in rats.