Hypoxia inducible factor-1: regulation by nitric oxide in posthypoxic microvascular endothelium

Hypoxia-induced signaling in the cardiovascular system: pathogenesis and therapeutic targets

Hypoxia, characterized by reduced oxygen concentration, is a significant stressor that affects the survival of aerobic species and plays a prominent role in cardiovascular diseases. From the research history and milestone events related to hypoxia in cardiovascular development and diseases, The "hypoxia-inducible factors (HIFs) switch" can be observed from both temporal and spatial perspectives, encompassing the occurrence and progression of hypoxia (gradual decline in oxygen concentration), the acute and chronic manifestations of hypoxia, and the geographical characteristics of hypoxia (natural selection at high altitudes). Furthermore, hypoxia signaling pathways are associated with natural rhythms, such as diurnal and hibernation processes. In addition to innate factors and natural selection, it has been found that epigenetics, as a postnatal factor, profoundly influences the hypoxic response and progression within the cardiovascular system. Within this intricate process, interactions between different tissues and organs within the cardiovascular system and other systems in the context of hypoxia signaling pathways have been established. Thus, it is the time to summarize and to construct a multi-level regulatory framework of hypoxia signaling and mechanisms in cardiovascular diseases for developing more therapeutic targets and make reasonable advancements in clinical research, including FDA-approved drugs and ongoing clinical trials, to guide future clinical practice in the field of hypoxia signaling in cardiovascular diseases.

Nitric oxide promotes cerebral ischemia/reperfusion injury through upregulating hypoxia-inducible factor1-α-associated inflammation and apoptosis in rats

Nitric oxide (NO) was one of the key factors to sustain hypoxia-inducible factor-1- α (HIF-1α) activation during hypoxia. However, the mechanism by which NO production promotes upregulation of HIF-1α to cause cerebral ischemia/reperfusion (I/R) injury remains unclear. The present study investigated whether eliminating NO would decrease HIF-1α level, and then reduce the subsequent inflammatory actions as well as neuronal apoptotic death in middle cerebral artery occlusion (MCAO) rats. Our results revealed that HIF-1α was correlated with 3-NT, a marker for nitrosative/oxidative stress, in the brain of MCAO rats. Treatment with NOS inhibitor L-NAME suppressed HIF-1α/3-NT double-positive cells, suggesting that HIF-1α was correlated with NO overproduction during cerebral I/R. Furthermore, pro-inflammatory cytokines TNF-α, IL-1β and NF-κB p65 were significantly increased and colocalized with HIF-1α in the brain of MCAO rats, all of which could be attenuated by NO inhibition, suggesting that eliminating NO reduced MCAO-induced HIF-1α upregulation, which in turn exerted anti-inflammatory actions. Accordingly, cleaved caspase-3, as well as HIF-1α and TUNEL double-positive cells in ischemic brain were also decreased by L-NAME treatment. These results suggest that NO accumulation after cerebral ischemia leads to HIF-1α upregulation, which may activate pro-inflammatory cytokines, resulting in neuronal apoptotic death. These findings demonstrate a novel mechanism of NO-induced cerebral I/R injury.

Mutual Antagonism of Hypoxia-Inducible Factor Isoforms in Cardiac, Vascular, and Renal Disorders

Hypoxia-inducible factor (HIF)-1α and HIF-2α promote cellular adaptation to acute hypoxia, but during prolonged activation, these isoforms exert mutually antagonistic effects on the redox state and on proinflammatory pathways. Sustained HIF-1α signaling can increase oxidative stress, inflammation, and fibrosis, actions that are opposed by HIF-2α. Imbalances in the interplay between HIF-1α and HIF-2α may contribute to the progression of chronic heart failure, atherosclerotic and hypertensive vascular disorders, and chronic kidney disease. These disorders are characterized by activation of HIF-1α and suppression of HIF-2α, which are potentially related to mitochondrial and peroxisomal dysfunction and suppression of the redox sensor, sirtuin-1. Hypoxia mimetics can potentiate HIF-1α and/or HIF-2α; ideally, such agents should act preferentially to promote HIF-2α while exerting little effect on or acting to suppress HIF-1α. Selective activation of HIF-2α can be achieved with drugs that: 1) inhibit isoform-selective prolyl hydroxylases (e.g., cobalt chloride and roxadustat); or 2) promote the actions of the redox sensor, sirtuin-1 (e.g., sodium-glucose cotransporter 2 inhibitors). Selective HIF-2α signaling through sirtuin-1 activation may explain the effect of sodium-glucose cotransporter 2 inhibitors to simultaneously promote erythrocytosis and ameliorate the development of cardiomyopathy and nephropathy.

Modulatory effect of silymarin on pulmonary vascular dysfunction through HIF-1α-iNOS following rat lung ischemia-reperfusion injury

Silymarin is a traditional therapeutic used to protect the liver, acting to oppose lipid peroxidation, to enhance liver regeneration and functioning as an antioxidant. However, the effects of silymarin on pulmonary vascular dysfunction have not been investigated. In the present study, the modulatory effects of silymarin on pulmonary vascular dysfunction and the underlying mechanisms behind this were investigated in a lung ischemia-reperfusion (I/R) injury rat model. Male Sprague Dawley rats were randomly divided into 3 groups, including: i) A control group (n=10); ii) an I/R group (n=10); and iii) a silymarin-treated group (n=10). All experimental rats received 250 mg/kg/day of silymarin for 8 days. Silymarin was demonstrated to markedly improve lung I/R-induced pulmonary vascular dysfunction and lung moisture. Following silymarin treatment, inflammation and oxidative stress in the lung I/R-injury rats were demonstrably suppressed. Treatment with silymarin also inhibited the activation of caspase-3 and -9, and hypoxia inducible factor-1α (HIF-1α) and inducible nitric oxide synthase (iNOS) protein expression in the lung I/R-injury rats. Silymarin was concluded to impact upon pulmonary vascular dysfunction through the HIF-1α-iNOS pathway in the lung I/R injury rat model.

Hypoxia inducible factor 1-alpha (HIF-1 alpha) is induced during reperfusion after renal ischemia and is critical for proximal tubule cell survival

Acute tubular necrosis (ATN) caused by ischemia/reperfusion (I/R) during renal transplantation delays allograft function. Identification of factors that mediate protection and/or epithelium recovery could help to improve graft outcome. We studied the expression, regulation and role of hypoxia inducible factor 1-alpha (HIF-1 α), using in vitro and in vivo experimental models of I/R as well as human post-transplant renal biopsies. We found that HIF-1 α is stabilized in proximal tubule cells during ischemia and unexpectedly in late reperfusion, when oxygen tension is normal. Both inductions lead to gene expression in vitro and in vivo. In vitro interference of HIF-1 α promoted cell death and in vivo interference exacerbated tissue damage and renal dysfunction. In pos-transplant human biopsies, HIF-1 α was expressed only in proximal tubules which exhibited normal renal structure with a significant negative correlation with ATN grade. In summary, using experimental models and human biopsies, we identified a novel HIF-1 α induction during reperfusion with a potential critical role in renal transplant.

Sumoylation of hypoxia-inducible factor-1α ameliorates failure of brain stem cardiovascular regulation in experimental brain death

BACKGROUND

One aspect of brain death is cardiovascular deregulation because asystole invariably occurs shortly after its diagnosis. A suitable neural substrate for mechanistic delineation of this aspect of brain death resides in the rostral ventrolateral medulla (RVLM). RVLM is the origin of a life-and-death signal that our laboratory detected from blood pressure of comatose patients that disappears before brain death ensues. At the same time, transcriptional upregulation of heme oxygenase-1 in RVLM by hypoxia-inducible factor-1α (HIF-1α) plays a pro-life role in experimental brain death, and HIF-1α is subject to sumoylation activated by transient cerebral ischemia. It follows that sumoylation of HIF-1α in RVLM in response to hypoxia may play a modulatory role on brain stem cardiovascular regulation during experimental brain death.

METHODOLOGY/PRINCIPAL FINDINGS

A clinically relevant animal model that employed mevinphos as the experimental insult in Sprague-Dawley rat was used. Biochemical changes in RVLM during distinct phenotypes in systemic arterial pressure spectrum that reflect maintained or defunct brain stem cardiovascular regulation were studied. Western blot analysis, EMSA, ELISA, confocal microscopy and immunoprecipitation demonstrated that drastic tissue hypoxia, elevated levels of proteins conjugated by small ubiquitin-related modifier-1 (SUMO-1), Ubc9 (the only known conjugating enzyme for the sumoylation pathway) or HIF-1α, augmented sumoylation of HIF-1α, nucleus-bound translocation and enhanced transcriptional activity of HIF-1α in RVLM neurons took place preferentially during the pro-life phase of experimental brain death. Furthermore, loss-of-function manipulations by immunoneutralization of SUMO-1, Ubc9 or HIF-1α in RVLM blunted the upregulated nitric oxide synthase I/protein kinase G signaling cascade, which sustains the brain stem cardiovascular regulatory machinery during the pro-life phase.

CONCLUSIONS/SIGNIFICANCE

We conclude that sumoylation of HIF-1α in RVLM ameliorates brain stem cardiovascular regulatory failure during experimental brain death via upregulation of nitric oxide synthase I/protein kinase G signaling. This information should offer new therapeutic initiatives against this fatal eventuality.

Heme oxygenase-1 plays a pro-life role in experimental brain stem death via nitric oxide synthase I/protein kinase G signaling at rostral ventrolateral medulla

Background

Despite its clinical importance, a dearth of information exists on the cellular and molecular mechanisms that underpin brain stem death. A suitable neural substrate for mechanistic delineation on brain stem death resides in the rostral ventrolateral medulla (RVLM) because it is the origin of a life-and-death signal that sequentially increases (pro-life) and decreases (pro-death) to reflect the advancing central cardiovascular regulatory dysfunction during the progression towards brain stem death in critically ill patients. The present study evaluated the hypothesis that heme oxygnase-1 (HO-1) may play a pro-life role as an interposing signal between hypoxia-inducible factor-1 (HIF-1) and nitric oxide synthase I (NOS I)/protein kinase G (PKG) cascade in RVLM, which sustains central cardiovascular regulatory functions during brain stem death.

Methods

We performed cardiovascular, pharmacological, biochemical and confocal microscopy experiments in conjunction with an experimental model of brain stem death that employed microinjection of the organophosphate insecticide mevinphos (Mev; 10 nmol) bilaterally into RVLM of adult male Sprague-Dawley rats.

Results

Western blot analysis coupled with laser scanning confocal microscopy revealed that augmented HO-1 expression that was confined to the cytoplasm of RVLM neurons occurred preferentially during the pro-life phase of experimental brain stem death and was antagonized by immunoneutralization of HIF-1α or HIF-1β in RVLM. On the other hand, the cytoplasmic presence of HO-2 in RVLM neurons manifested insignificant changes during both phases. Furthermore, immunoneutralization of HO-1 or knockdown of ho-1 gene in RVLM blunted the augmented life-and-death signals exhibited during the pro-life phase. Those pretreatments also blocked the upregulated pro-life NOS I/PKG signaling without affecting the pro-death NOS II/peroxynitrite cascade in RVLM.

Conclusions

We conclude that transcriptional upregulation of HO-1 on activation by HIF-1 in RVLM plays a preferential pro-life role by sustaining central cardiovascular regulatory functions during brain stem death via upregulation of NOS I/PKG signaling pathway. Our results further showed that the pro-dead NOS II/peroxynitrite cascade in RVLM is not included in this repertoire of cellular events.

Women and heart disease--physiologic regulation of gene delivery and expression: bioreducible polymers and ischemia-inducible gene therapies for the treatment of ischemic heart disease

Ischemic heart disease (IHD) is the leading cause of death in the United States today. This year over 750,000 women will have a new or recurrent myocardial infarction. Currently, the mainstay of therapy for IHD is revascularization. Increasing evidence, however, suggests that revascularization alone is insufficient for the longer-term management of many patients with IHD. To address these issues, innovative therapies that extend beyond revascularization to protection of the myocyte and preservation of ventricular function are required. The emergence of gene therapy and proteomics offers the potential for innovative prophylactic and treatment strategies for IHD. The goal of our research is to develop therapeutic gene constructs for the treatment of myocardial ischemia that are clinically safe and effective. Toward this end, we describe the development of physiologic regulation of gene delivery and expression using bioreducible polymers and ischemia-inducible gene therapies for the potential treatment of ischemic heart disease in women.

Chronic hypoxia increases inducible NOS-derived nitric oxide in fetal guinea pig hearts

Intrauterine hypoxia impacts fetal growth and organ function. Inducible nitric oxide synthase (iNOS) and neuronal NOS (nNOS) expression was measured to assess the response of fetal hearts to hypoxic (HPX) stress. Pregnant guinea pigs were housed in a hypoxic chamber (10.5% O2 for 14 d, n = 17) or room air [normoxic (NMX), n = 17]. Hearts of anesthetized near-term fetuses were removed. mRNA [hypoxia-inducible factor, (HIF)-1alpha, 1beta, 2alpha, 3alpha, iNOS, and nNOS] and protein levels (HIF-1alpha, iNOS, and nNOS) of fetal cardiac left ventricles were quantified by real time polymerase chain reaction (PCR) and Western analysis, respectively. Cardiac nitrite/nitrate levels were measured in the presence/absence of L-N6-(1-iminoethyl)-lysine (L-NIL), an iNOS inhibitor, administered to pregnant sows. Hypoxia significantly increased fetal cardiac HIF-1alpha and -2alpha mRNA, HIF-1alpha protein but not HIF-3alpha or -1beta mRNA levels. Hypoxia increased both iNOS mRNA (by 5x) and protein (by 23%) levels but had no effect on nNOS levels. Nitrite/nitrate levels were increased in HPX hearts by 2.5x and decreased with L-NIL by 67 +/- 14%. Thus, up-regulation of iNOS-derived nitric oxide (NO) generation is an important mechanism by which fetal hearts respond to chronic hypoxic stress.

Selective inhibition of iNOS attenuates trauma-hemorrhage/resuscitation-induced hepatic injury

Although trauma-hemorrhage produces tissue hypoxia, systemic inflammatory response and organ dysfunction, the mechanisms responsible for these alterations are not clear. Using a potent selective inducible nitric oxide (NO) synthase inhibitor, N-[3-(aminomethyl) benzyl]acetamidine (1400W), and a nonselective NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), we investigated whether inducible NO synthase plays any role in producing hepatic injury, inflammation, and changes of protein expression following trauma-hemorrhage. To investigate this, male Sprague-Dawley rats were subjected to midline laparotomy and hemorrhagic shock (mean blood pressure 35-40 mmHg for approximately 90 min) followed by fluid resuscitation. Animals were treated with either vehicle (DMSO) or 1400W (10 mg/kg body wt ip), or L-NAME (30 mg/kg iv), 30 min before resuscitation and killed 2 h after resuscitation. Trauma-hemorrhage/resuscitation induced a marked hypotension and increase in markers of hepatic injury (i.e., plasma alpha-glutathione S-transferase, tissue myeloperoxidase activity, and nitrotyrosine formation). Hepatic expression of iNOS, hypoxia-inducible factor-1alpha, ICAM-1, IL-6, TNF-alpha, and neutrophil chemoattractant (cytokine-induced neutrophil chemoattractant-1 and macrophage inflammatory protein-2) protein levels were also markedly increased following trauma-hemorrhage/resuscitation. Administration of the iNOS inhibitor 1400W significantly attenuated hypotension and expression of these mediators of hepatic injury induced by trauma-hemorrhage/resuscitation. However, administration of L-NAME could not attenuate hepatic dysfunction and tissue injury mediated by trauma-hemorrhage, although it improved mean blood pressure as did 1400W. These results indicate that increased expression of iNOS following trauma-hemorrhage plays an important role in the induction of hepatic damage under such conditions.

Hypoxia inducible factor-1 upregulates adiponectin in diabetic mouse hearts and attenuates post-ischemic injury

Adiponectin is a circulating cytokine with important cardioprotective effects. Plasma adiponectin levels are significantly reduced in patients with insulin resistance and type II diabetes mellitus and cardiovascular disease. Although adiponectin is primarily synthesized by adipocytes, new studies reveal that adiponectin is secreted by other cell types, including cardiomyocytes. Control of adiponectin gene expression in heart and microvasculature is poorly understood. We investigated the regulation of adiponectin expression by the transcription factor hypoxia inducible factor-1 (HIF-1) and its role in attenuating cardiac reperfusion injury. HIF-1 regulation of adiponectin was examined by isolating and characterizing the murine adiponectin promoter. HIF-1-dependent activation of the murine adiponectin promoter was verified via electrophoretic mobility shift assays, transient transfection assays, and QPCR. We show for the first time that HIF-1 activation via an siRNA-mediated prolyl 4-hydroxylase-2 gene silencing strategy induced adiponectin mRNA expression in murine microvascular endothelium in vitro (17-fold), intact hearts (22-fold, wild type; 5-fold, obese/diabetic) and white adipose tissue (37-fold, wild-type; 9.6-fold, obese/diabetic). HIF-1-induced adiponectin expression was associated with improved myocardial viability in obese/diabetic mice (32% increase) and preservation of left ventricular function (36% increase in rate pressure product). Our studies suggest that local production of adiponectin by cardiomyocytes/microvascular endothelial cells may regulate cardiac function and indicate a novel strategy for protecting diabetic hearts from ischemia/reperfusion injury.

Inducible nitric oxide synthase mediates hypoxia-induced hypoxia-inducible factor-1 alpha activation and vascular endothelial growth factor expression in oxygen-induced retinopathy

OBJECTIVE

Previous studies provided evidence that many factors contribute to retinal angiogenesis, including inducible nitric oxide synthase (iNOS), hypoxia-inducible factor-1 alpha (HIF-1 alpha) and vascular endothelial growth factor (VEGF). But the role of nitric oxide generated by iNOS in the regulation of expression of hypoxia-inducible genes in retinopathy of prematurity remains unclear. So we sought to better define the molecular basis of this iNOS-dependent regulation.

METHODS

In this study, using immunohistochemistry, real-time PCR and Western blotting technologies, we investigated the changes of iNOS, HIF-1 alpha, VEGF and phosphatidylinositol 3-kinase/Akt (PI3K/Akt) expressions.

RESULTS

Hypoxia- induced overexpression of iNOS, HIF-1 alpha, VEGF, PI3K/Akt and phosphorylated PI3K/Akt was observed in the untreated retinopathy of the prematurity group. Administration of the selective iNOS inhibitor aminoguanidine hemisulfate markedly decreased the expression of these genes.

CONCLUSIONS

These results indicate that iNOS mediates HIF-1 alpha activation and VEGF expression in retinal angiogenesis and that the PI3K/Akt signaling pathway may play a role in this process.

Activation of hypoxia-inducible factor-1 via prolyl-4 hydoxylase-2 gene silencing attenuates acute inflammatory responses in postischemic myocardium

Emerging research suggests that oxidant-driven transcription of key cytokine/chemokine networks within the myocardium plays a crucial role in producing ischemia-reperfusion (I/R) injury. We recently showed that activation of hypoxia-inducible factor-1 (HIF-1) attenuated cardiac I/R injury. Diminished injury in these prior studies was associated with significant reductions in circulating interleukin-8 levels, suggesting that HIF-1 may play an important role in modulating postischemic cardiac inflammation. In the current study, we examined the role of HIF-1 activation in modulating proinflammatory chemokine [macrophage inflammatory protein (MIP)-2, cytokine-induced neutrophil chemoattractant factor (KC), and lipopolysaccharide-induced CXC chemokine (LIX)] and adhesion molecule [intercellular adhesion molecule (ICAM)-1] expression in murine cardiomyocytes in vitro (HL-1 cell line) and in intact murine hearts following in vivo I/R injury. Our results show that HIF-1 activation induced both pharmacologically by the prolyl hydroxylase inhibitor dimethyloxallyl glycine and via small-interfering RNA (siRNA)-mediated prolyl-4 hydroxylase-2 (P4HA2) gene silencing significantly attenuated tumor necrosis factor-α-induced chemokine (KC and LIX) and ICAM-1 expression in cardiomyocytes. In vivo, postischemic hearts obtained from animals receiving the P4HA2 siRNA (HIF-1 activation) exhibited significantly reduced CXC chemokine (MIP-2, KC, and LIX), CC chemokine (monocyte chemoattractant protein-1), and ICAM-1 expression when compared with postischemic hearts from either saline I/R controls or postischemic hearts from animals receiving a nontargeting control siRNA (no HIF-1 activation). Diminished chemokine and adhesion molecule expression in HIF-1-activated postischemic hearts was associated with significantly reduced polymorphonuclear leukocyte infiltration and myocardial infarct size (>60% reduction P4HA2 siRNA I/R vs. saline I/R, P < 0.001, n = 6). In conclusion, these results demonstrate for the first time that HIF-1 activation following infusion of siRNA to P4HA2 plays a key role in modulating I/R-associated cardiac inflammatory responses.

Hypoxia and its downstream targets in DMBA induced mammary carcinoma: Protective role of Semecarpus anacardium nut extract

Tumors are usually exposed to a hypoxic microenvironment due to their irregular growth and abnormal vascular supply. Under hypoxia, gene regulation (selective activation and inactivation of genes) plays an important role in maintenance of tumor. Multiple hypoxic and angiogenic growth factors are expressed for tumor cell survival. In search of novel anticancer drug, Semecarpus anacardium nut extract (SA) was tried against breast cancer. Mammary carcinoma was induced in vivo by 7,12-dimethyl benz(a) anthracene (DMBA) (25mg/kg b.w., p.o.). Tumor development and vascular structures were accelerated by DMBA. Hypoxia inducible factor-1 alpha (HIF-1) was coexpressed with its downstream genes in mammary tissue. Cancer rats were then treated with S. anacardium nut extract (SA) (250mg/kg b.w., p.o.). Delay in the tumor growth was paralleled with a drastic reduction in vascularization by SA treatment. Activities of glycolytic enzymes were normalized with decreased expression of glucose transporter-1 and carbonic anhydrase IX by drug treatment. Inhibition of HIF-1, vascular endothelial growth factor and inducible nitric oxide synthase by SA may in part explain its antiangiogenic action. SA also inhibits endothelial cell proliferation by blocking the overexpressed survival cytokines. In conclusion, our study demonstrates that at least some part of the antitumor activity of SA is due to the suppression of hypoxic and angiogenic factors. The mechanism of this inhibition seems to be through an action of SA on expression of HIF-1 and its downstream targets.

Hypoxia inducible factor-1 modulates hemin-induced IL-8 secretion in microvascular endothelium

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.

Crinamine from Crinum asiaticum var. japonicum inhibits hypoxia inducible factor-1 activity but not activity of hypoxia inducible factor-2

In a search for natural product inhibitors of hypoxia inducible factor-1 (HIF-1) function, crinamine (1), a crinane type alkaloid, showed potent dose dependent inhibition (IC50 = 2.7 microM) of HIF-1alpha in a cell-based reporter gene assay. Crinamine (1) was isolated from the aerial parts of Crinum asiaticum var. japonicum together with lycorine (2), norgalanthamine (3) and epinorgalanthamine (4). The other components (2-4) showed no significant inhibition of HIF-1alpha induced transcriptional activity.

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Obstructive sleep apnea and insulin resistance: a role for microcirculation?

Obstructive sleep apnea is an increasingly recognized medical problem. The recent attention to its frequency in the general population and its important role in metabolic, vascular, and behavioral aspects have sharply increased the number and nature of investigations, thereby revealing new aspects that open new approaches in research. Whereas obstructive sleep apnea is a well-known phenomenon accompanying obesity and diabetes, new findings strongly suggest that this close relationship may also operate in the opposite direction. Indeed obstructive sleep apnea may be a primary feature inducing or aggravating a series of vascular and metabolic disturbances closely resembling the metabolic syndrome. This review will discuss established and potential mechanisms responsible for these changes. Obstructive sleep apnea indeed appears to gather all the elements necessary to induce insulin resistance, hypertension, and possibly heart failure. After careful analysis of these modifications and considering how they are intertwined, we propose that microcirculation could represent the common denominator mediating the progression of this pathology, as it is eventually the case in the metabolic syndrome and diabetes domain. This plausible hypothesis is discussed in detail and should be verified by appropriate preclinical and clinical protocols, which are now achievable by using noninvasive techniques in humans.

Effects of aspirin on number, activity and inducible nitric oxide synthase of endothelial progenitor cells from peripheral blood

AIM

To investigate whether aspirin has an influence on endothelial progenitor cells (EPC).

METHODS

Total mononuclear cells (MNC) were isolated from peripheral blood by Ficoll density gradient centrifugation, then cells were plated on fibronectin-coated culture dishes. After 7 d of culture, attached cells were stimulated with aspirin (to achieve final concentrations of 1, 2, 5, and 10 mmol/L) for 3, 6, 12, and 24 h. EPC were characterized as adherent cells that were double positive for 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine low density lipoprotein (DiLDL) uptake and lectin binding by direct fluorescent staining. EPC proliferation and migration were assayed using a 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and a modified Boyden chamber assay, respectively. An EPC adhesion assay was performed by replating the EPC on fibronectin-coated dishes, and then adherent cells were counted. In vitro vasculogenesis activity was assayed by using an in vitro vasculogenesis kit. Inducible nitric oxide synthase (iNOS) was assayed by Western blotting.

RESULTS

Incubation of isolated human MNC with aspirin decreased the number of EPC. Aspirin also decreased the proliferative, migratory, adhesive, and in vitro vasculogenesis capacity of EPC, and also their iNOS levels in a concentration- and time-dependent manner.

CONCLUSION

Aspirin decreases (1) the number of EPC; (2) the proliferative, migratory, adhesive and in vitro vasculogenesis capacities of EPC; and (3) iNOS levels in EPC.

Hypoxia regulates cross-talk between Syk and Lck leading to breast cancer progression and angiogenesis

Hypoxia is a key parameter that controls tumor angiogenesis and malignant progression by regulating the expression of several oncogenic molecules. The nonreceptor protein-tyrosine kinases Syk and Lck play crucial roles in the signaling mechanism of various cellular processes. The enhanced expression of Syk in normal breast tissue but not in malignant breast carcinoma has prompted us to investigate its potential role in mammary carcinogenesis. Accordingly, we hypothesized that hypoxia/reoxygenation (H/R) may play an important role in regulating Syk activation, and Lck may be involved in this process. In this study, we have demonstrated that H/R differentially regulates Syk phosphorylation and its subsequent interaction and cross-talk with Lck in MCF-7 cells. Moreover, Syk and Lck play differential roles in regulating Sp1 activation and expressions of melanoma cell adhesion molecule (MelCAM), urokinase-type plasminogen activator (uPA), matrix metalloproteinase-9 (MMP-9), and vascular endothelial growth factor (VEGF) in response to H/R. Overexpression of wild type Syk inhibited the H/R-induced uPA, MMP-9, and VEGF expression but up-regulated MelCAM expression. Our data also indicated that MelCAM acts as a tumor suppressor by negatively regulating H/R-induced uPA secretion and MMP-9 activation. The mice xenograft study showed the cross-talk between Syk and Lck regulated H/R-induced breast tumor progression and further correlated with the expressions of MelCAM, uPA, MMP-9, and VEGF. Human clinical specimen analysis supported the in vitro and in vivo findings. To our knowledge, this is first report that the cross-talk between Syk and Lck regulates H/R-induced breast cancer progression and further suggests that Syk may act as potential therapeutic target for the treatment of breast cancer.