Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypoxia-inducible factor-1 (HIF-1) is a key mediator of oxygen homeostasis that was first identified as a transcription factor that is induced and activated by decreased oxygen tension. Upon activation, HIF-1 upregulates the transcription of genes that promote adaptation and survival under hypoxic conditions. HIF-1 is a heterodimer composed of an oxygen-regulated subunit known as HIF-1alpha and a constitutively expressed HIF-1beta subunit. In general, the availability and activity of the HIF-1alpha subunit determines the activity of HIF-1. Subsequent studies have revealed that HIF-1 is also activated by environmental and physiological stimuli that range from iron chelators to hormones. Preclinical studies suggest that HIF-1 activation may be a valuable therapeutic approach to treat tissue ischemia and other ischemia/hypoxia-related disorders. The focus of this review is natural product-derived small molecule HIF-1 activators. Natural products, relatively low molecular weight organic compounds produced by plants, animals, and microbes, have been and continue to be a major source of new drugs and molecular probes. The majority of known natural product-derived HIF-1 activators were discovered through the pharmacological evaluation of specifically selected individual compounds. On the other hand, the combination of natural products chemistry with appropriate high-throughput screening bioassays may yield novel natural product-derived HIF-1 activators. Potent natural product-derived HIF-1 activators that exhibit a low level of toxicity and side effects hold promise as new treatment options for diseases such as myocardial and peripheral ischemia, and as chemopreventative agents that could be used to reduce the level of ischemia/reperfusion injury following heart attack and stroke.
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PMID:Natural product-derived small molecule activators of hypoxia-inducible factor-1 (HIF-1). 1684 66

In the ischemic or hypoxic brain, astrocytes appear to be one of the main sources of erythropoietin (EPO). In this study, we investigated the differential contribution of hypoxia inducible factor (HIF) isoforms to the regulation of hypoxic EPO expression in cultured astrocytes. In addition, using an in vitro model of oxygen-glucose deprivation (OGD), we studied the role of HIF-1alpha and HIF-2alpha in the generation of paracrine protective signals by astrocytes that modulate the survival of neurons exposed to OGD. Expression of HIF-1alpha or HIF-2alpha was abrogated by infecting astrocytes with lentiviral particles encoding small interference RNA specific for HIF-1alpha or HIF-2alpha (siHIF-1alpha or siHIF-2alpha). Astrocytes infected with siHIF-1alpha showed abrogated hypoxic induction of vascular endothelial growth factor (VEGF) and lactate dehydrogenase (LDH) but normal EPO induction. In contrast, reduction of HIF-2alpha expression by siHIF-2alpha led to a drastic decrease of EPO hypoxic expression, but it did not affect LDH or VEGF upregulation. To further test whether HIF-2 is sufficient to drive EPO upregulation, we expressed oxygen-insensitive mutant forms of HIF-1alpha (mtHIF-1alpha) (P402A/P577A) and HIF-2alpha (mtHIF-2alpha) (P405A/P530A). Expression of mtHIF-2alpha but not mtHIF-1alpha in normoxic astrocytes resulted in a significant upregulation of EPO mRNA and protein. Accordingly, HIF-2alpha but not HIF-1alpha was found to be associated with the EPO hypoxia-response element by a chromatin immunoprecipitation assay. Interestingly, conditioned medium from astrocytes challenged by sublethal OGD improved neuronal survival to OGD; however, this effect was abolished during the downregulation of astrocytic HIF-2alpha using siHIF-2alpha. These results indicate that HIF-2alpha mediates the transcriptional activation of EPO expression in astrocytes, and this pathway may promote astrocytic paracrine-dependent neuronal survival during ischemia.
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PMID:The transcriptional activator hypoxia inducible factor 2 (HIF-2/EPAS-1) regulates the oxygen-dependent expression of erythropoietin in cortical astrocytes. 1697 31

Pathologies of senescence, in particular those of neurosensory organs represent an important health problem. The improvement of the life expectation entails the fast increase of the frequency of the age-related hearing loss (ARHL) in the population. There are numerous factors that contribute to this process, which include altered vascular characteristics, hypoxia/ischemia, genetic mutations and production of reactive oxygen species. We were interested in understanding the mechanisms involved in the cochlear degeneration in a mouse model of ARHL, the cd/1 mice. Since in human, hypoxia/ischemia is an important pathogenetic factor for inner ear disease, the regulation of HIF-1 activity in the cochlea, the presence of radical oxygen species in the cochlea and its subsequent disturbances of cellular signaling cascades were investigated. In this study, we explored auditory function of cd/1 mice at the age of 4, 12 and 24 weeks and correlated it with the presence of oxidative damage in the cochlea, and cochlear HIF-1 responsive target genes regulation, involved in pathways promoting inflammation such as tumor necrosis factor (TNF-alpha), or cell death with the p53 protein, Bax protein and surviving factors with insulin-like growth factor-1 (IGF-1). After implantation of electrodes for auditory nerve acoustic thresholds measurements, we analyzed every cochlea. First, we confirmed that the cd/1 mice presented a characteristic profile of ARHL starting at 12 weeks of age. Then, according to our previous report [Riva, C., Longuet, M., Lucciano, M., Magnan, J., Lavieille, J.P., 2005. Implication of mitochondrial apoptosis in neural degeneration in a murin model for presbyacusis. Rev. Laryngol. Otol. Rhinol. 126 (2), 67-74], we noticed many alterations in the cochlea. Histologically, at 4 weeks, intensive HIF-1alpha expression was detected in the cochlea followed by ROS formation at 12 weeks, which may lead to cochlear degeneration and induction the onset of ARHL in the cd/1 mice model. In the cochlea, while the inner and the outer hair cells remained intact at 4 and 12 weeks, the spiral ganglion was more altered. Moreover, the Schwann cells of the spiral ganglion seemed to be more vulnerable to free radical damage than the neurons and degenerated more rapidly. The mechanisms of degeneration in the spiral ganglion involved a caspase-3 and Bax mediated-apoptosis via p53 protein accumulation. Since oxygen radicals are required for the post-translational stabilization of HIF-1alpha during hypoxia, the tandem " HIF-ROS " induced multiple reactions within the cochlea, like a strong inflammatory response with increased expression of TNF-alpha, and inhibition of neuronal protection mechanisms with repression of IGF-1.
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PMID:Age-related hearing loss in CD/1 mice is associated to ROS formation and HIF target proteins up-regulation in the cochlea. 1714 99

In the Western world, peripheral vascular disease (PVD) has a high prevalence and is associated with high morbidity and mortality. More patients are presenting with critical limb ischemia (CLI), the end stage of PVD, because of an increased life expectancy owing to improved medical care. In a large percentage of these patients, lower limb amputation is still required, despite current advances in surgery and interventional radiology. Studies of ischemic skeletal muscles disclosed evidence of endogenous angiogenesis and adaptive skeletal muscle metabolic changes in response to hypoxia. Many of the genes responsible for these responses are regulated by hypoxia-inducible factor (HIF)-1. HIF-1, consisting of HIF-1alpha and HIF-1beta subunits, is a major transcription factor that functions as a master regulator of oxygen homeostasis that plays essential roles in cellular and systemic pathophysiology. HIF-1alpha expression and HIF-1 transcriptional activity increase exponentially as cellular oxygen concentration is decreased. More than 60 target genes that are transactivated by HIF-1 have been identified. Many of the target genes, such as vascular endothelial growth factor, have been studied extensively, especially in tumors. However, only recently that interest in HIF-1 is growing in relation to ischemic diseases. Most of the studies concentrated mainly on the angiogenic property of HIF-1. In contrast, there is a lack of information on the role of HIF-1 in skeletal muscle metabolic adaptive changes as the end-organ in PVD. This review aims to summarize our current understanding of HIF-1 roles and the therapeutic potential in PVD.
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PMID:Hypoxia-inducible factor 1 in lower limb ischemia. 1715 Jan 52

2,2,5,7,8-Pentamethyl-6-hydroxychromane (PMC) is the most potent analogue of alpha-tocopherol for anti-oxidation. It is more hydrophilic than other alpha-tocopherol derivatives and has potent free radical-scavenging activity. In the present study, PMC significantly attenuated middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia in rats. Administration of PMC at 20mg/kg, showed marked reductions in infarct size compared with that of control rats. MCAO-induced focal cerebral ischemia was associated with increases in HIF-1alpha, active caspase-3, iNOS, and nitrotyrosine expressions in ischemic regions. These expressions were markedly inhibited by treatment with PMC (20mg/kg). In addition, PMC (4-12 microM) inhibited respiratory bursts in human neutrophils stimulated by fMLP (800 nM) and PMA (320 nM). Furthermore, PMC (6, 12, and 60 microM) also significantly inhibited neutrophil migration stimulated by leukotriene B(4) (160 nM). An electron spin resonance (ESR) method was conducted on the scavenging activity of PMC on the free radicals formed. PMC (12 microM) greatly reduced the ESR signal intensities of superoxide anion, hydroxyl radical, and methyl radical formation. In conclusion, we demonstrate a potent neuroprotective effect of PMC on MCAO-induced focal cerebral ischemia in vivo. This effect may be mediated, at least in part, by inhibition of free radical formation, followed by inhibition of HIF-1alpha activation, apoptosis formation (active caspase-3), neutrophil activation, and inflammatory responses (i.e., iNOS and nitrotyrosine expressions), resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury. Thus, PMC treatment may represent a novel approach to lowering the risk or improving function in ischemia-reperfusion brain injury-related disorders.
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PMID:Neuroprotective effects of PMC, a potent alpha-tocopherol derivative, in brain ischemia-reperfusion: reduced neutrophil activation and anti-oxidant actions. 1715 67

PR-39, a proline-arginine-rich angiogenic response peptide, has been implicated in myocardial ischemic reperfusion injury. The present study examined the cardioprotective abilities of PR39 gene therapy. Male C57Bl/J6 mice were randomized to intramyocardial injecton of 10(9) p.f.u. adenovirus encoding PR39 (PR39), FGFR1 dominant negative signaling construct (FGFR1-dn), empty vector (EV), or PR39 adenovirus plus 4 microg of plasmid endcoding a HIF1alpha dominant negative construct (PR39 + HIF1alpha-dn). Seven days later, hearts were subjected to 20 min of ischemia (I) and 2 h. reperfusion (R) ex vivo and aortic and coronary flow, left ventricular developed pressure (LVDP), and LVdp/dt were measured. Myocardial infarct (MI) size and cardiomyocyte apoptosis were measured by TTC staining and TUNEL, respectively. PR39 expression was robust up to 14 days after gene transfer and was absent after EV and FGFR1-dn. Hemodynamics showed no differences at baseline, and heart rate remained unchanged in all groups throughout the experiment. After I-R, hemodynamics remained unchanged in PR39 hearts, but deteriorated significantly in the other groups, except for aortic flow, which remained significantly higher in FGFR1-dn than in EV and PR39 + HIF1alpha-dn (p < 0.05), although it was lower than in PR39 (p < 0.05). MI was 8.7 +/- 0.9 % in PR39, 23.8 +/- 1.1% in FGFR1-dn, 29.9 +/- 2.2% in EV, and 30.8 +/- 2.7 % in PR39 + HIF1alpha-dn (PR39 vs. other groups: p < 0.05; FGFR1-dn vs. EV and PR39 + HIF1alpha-dn: p < 0.05). In PR39, HIF-1alpha protein was higher than in FGFR1-dn and EV. Importantly, cotransfection of HIF1alpha-dn with PR39 completely abolished cardioprotection by PR39. Cardioprotection by PR39 is likely conveyed by protective metabolic and survival responses through HIF1-alpha stabilization and not by angiogenesis, because baseline coronary flow was the same in all groups. Abrogation of FGFR1 signaling conveyed an intermediate degree of cardioprotection.
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PMID:Protection against myocardial ischemia-reperfusion injury by the angiogenic Masterswitch protein PR 39 gene therapy: the roles of HIF1alpha stabilization and FGFR1 signaling. 2223 45

Ischemia/Reperfusion injury and hemolysis are characterized by erythrocyte lysis and release of free heme into the microcirculation. Following substantial erythrocyte lysis, heme overwhelms circulatory heme-binding protein networks rapidly forming hemin, the oxidized form of iron protoporphyrin IX. Hemin's role in modulating inflammatory responses in microvascular endothelium (MVEC) remains ill-defined. We studied the impact of hemin exposure on human MVEC interleukin-8 (IL-8) expression. Hemin significantly up-regulated MVEC IL-8 secretion and was associated with cellular iron loading. Hemin-induced IL-8 up-regulation was significantly attenuated by increasing environmental serum concentrations. As well, hemin-induced IL-8 secretion was significantly reduced in a concentration-dependent fashion following pyrrolidine dithiocarbamate exposure, suggesting that induction occurred via an oxidant-sensitive mechanism. Interestingly, transfection studies revealed that oxidant-driven transcription factors NF-kappaB and AP-1 played no role in hemin-induced IL-8 transcription. In studies employing actinomycin D, hemin was found to dramatically lengthen IL-8 mRNA half-life. Of major importance in the current report was the finding that hypoxia inducible factor-1 (HIF-1), a powerful transcription factor mediating tissue responses to hypoxia, potently regulated hemin-induced IL-8 secretion in human MVEC. Activation of HIF-1 via the prolyl hydroxylase inhibitor dimethyloxalylglycine attenuated hemin-induced IL-8 secretion. These studies were confirmed via DNA-directed siRNA silencing of HIF-1alpha. In conclusion, hemin induces a serum protein-sensitive pro-inflammatory phenotype in MVEC via an oxidant-sensitive mechanism that is powerfully regulated by HIF-1.
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PMID:Hypoxia inducible factor-1 modulates hemin-induced IL-8 secretion in microvascular endothelium. 1733 40

Apelin and its G-protein-coupled receptor APJ have various beneficial effects on cardiac function and blood pressure. The mechanisms that regulate apelin gene expression are not known. Because apelin gene expression has been shown to increase in cardiac ischemia, we investigated if apelin (Apln) gene expression was sensitive to hypoxia. Here we show that hypoxia increases the apelin expression in rat myocardium and in cultured cardiomyocytes. Pharmacological activation of hypoxia inducible factor by desferrioxamine (DFO) or expression of a constitutively active form of HIF-1alpha increased apelin expression in cardiomyocyte cultures. The induction of apelin by hypoxia was abolished on transient expression of the HIF inhibitory PAS protein in cardiomyocytes. Increased apelin expression induced by hypoxia or DFO was accompanied by the processing of the cellular storage form proapelin into smaller apelin peptides and increased secretion of these biologically active forms of apelin. In a rat in vivo model, acute myocardial infarction (24 h) led to a transient increase in ventricular apelin mRNA levels. Our results indicate that apelin gene is regulated by hypoxia in cardiac myocytes via the HIF pathway, suggesting a role for apelin as a potential marker for acute cardiac hypoxia with a possible compensatory role in myocardial tissue suffering from oxygen deprivation.
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PMID:Hypoxia inducible factor regulates the cardiac expression and secretion of apelin. 1734 85

Acute renal failure (ARF) is often the consequence of an ischemia-reperfusion injury (IRI) and associated with high mortality. Warm ischemia (WI) is a crucial factor of tissue damage, and tissue destruction led by ischemia-reperfusion (I/R) can impact the early and long-term functional outcome. Trimetazidine (TMZ) is an anti-ischemic drug. Previously, we already verified its protective effect on a cold-ischemic pig kidney model by directly adding TMZ into the preservation solution (Faure JP, Baumert H, Han Z, Goujon JM, Favreau F, Dutheil D, Petit I, Barriere M, Tallineau C, Tillement JP, Carretier M, Mauco G, Papadopoulos V, Hauet T. Biochem Pharmacol 66: 2241-2250, 2003; Faure JP, Petit I, Zhang K, Dutheil D, Doucet C, Favreau F, Eugene M, Goujon JM, Tillement JP, Mauco G, Vandewalle A, Hauet T. Am J Transplant 4: 495-504, 2004). In this study, we aimed to study the potential effect of TMZ pretreatment (5 mg/kg iv 24 h before WI) on the injury caused by WI for 45, 60, and 90 min and reperfusion in a WI pig kidney model. Compared with sham-operated (control) and uninephrectomized animals (UNX), TMZ pretreatment significantly reduced deleterious effects after 45 min, and particularly 60 and 90 min, of WI by improving the recovery of renal function and minimizing the inflammatory response commonly prevalent in ischemic kidney injury. Compared with controls (control group and UNX group), it was observed that 1) hypoxia-inducible factor-1 (HIF-1alpha) expression occurred earlier and with a higher intensity in the TMZ-treated groups; 2) the reduction of IRI during the first week following reperfusion was correlated with an earlier and greater expression of stathmin, which is involved in the process of tubular repair; and 3) the tubulointerstitial fibrosis was reduced, particularly after 60 and 90 min of WI. In conclusion, TMZ made the warm-ischemic kidneys more resistant to the deleterious impact of a single episode of I/R and reduced early and long-term subsequent damage.
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PMID:Comparison of protective effects of trimetazidine against experimental warm ischemia of different durations: early and long-term effects in a pig kidney model. 1734 18

Central to cellular responses to hypoxic environment is the hypoxia-inducible factor (HIF) transcriptional control system. A role for HIF-2alpha was investigated in a model of renal ischemia-reperfusion injury (IRI) associated with oxidative stress using HIF-2alpha knockdown mice. In these mice, HIF-2alpha expression was approximately one half that of wild-type mice, whereas HIF-1alpha expression was equivalent. HIF-2alpha knockdown mice were more susceptible to renal IRI, as indicated by elevated blood urea nitrogen levels and semiquantitative histologic analysis. Immunostaining with markers of oxidative stress showed enhanced oxidative stress in the kidney of HIF-2alpha knockdown mice, which was associated with peritubular capillary loss. Real-time quantitative PCR analysis showed decreased expression of antioxidative stress genes in the HIF-2alpha knockdown kidneys. Studies that used small interference RNA confirmed regulation of the antioxidative stress genes in cultured endothelial cells. Although HIF-2alpha knockdown mice were anemic, serum erythropoietin levels were not significantly increased, reflecting inappropriate response to anemia as a result of HIF-2alpha knockdown. Experiments that used hemodiluted mice with renal ischemia demonstrated that anemia of this degree did not affect susceptibility to ischemia. Knockdown of HIF-2alpha in inflammatory cells by bone marrow transplantation experiments demonstrated that HIF-2alpha in inflammatory cells did not contribute to susceptibility to renal IRI. Restoration of HIF-2alpha in endothelium by intercrossing with Tie1-Cre mice ameliorated renal injury by IRI, demonstrating a specific role of endothelial HIF-2alpha. These results suggest that HIF-2alpha in the endothelium has a protective role against ischemia of the kidney via amelioration of oxidative stress.
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PMID:Protective role of hypoxia-inducible factor-2alpha against ischemic damage and oxidative stress in the kidney. 1734 27


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