HIF-1: a key mediator in hypoxia

Effects of Histone Deacetylase Inhibitor (Valproic Acid) on the Expression of Hypoxia-inducible Factor-1 Alpha in Human Retinal Müller Cells

Purpose

To evaluate the effects of valproic acid (VPA), a histone deacetylase inhibitor (HDACI), on the expression of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in human retinal Müller cells under hypoxic conditions.

Methods

Chemical hypoxia was induced in human retinal Müller cells (MIO-M1) by treatment with increasing concentrations of cobalt(II) chloride (CoCl₂). Müller cells were also treated with a set concentration of CoCl₂, along with various concentrations of VPA. The expression of HIF-1α and VEGF in the treated Müller cells was determined by enzyme-linked immunosorbent assay.

Results

Exposure of human retinal Müller cells to increasing concentrations of CoCl₂ produced a dose-dependent increase in HIF-1α expression. The addition of increasing concentrations of VPA lead to a dose-dependent decrease in expression of HIF-1α and VEGF in Müller cells exposed to a set concentration of CoCl₂.

Conclusions

HDACI VPA downregulated the expressions of HIF-1α and VEGF in human retinal Müller cells under hypoxic conditions. Using HDACI to target HIF-1α expression in Müller cells could be a new therapeutic strategy for the treatment of retinal vascular diseases.

HIF-1α may provide only short-term protection against ischemia-reperfusion injury in Sprague-Dawley myocardial cultures

Hypoxia-inducible factor-1 (HIF-1α) exerts an important role in protecting against cardiac tissue damage, for example, following ischemia-reperfusion (I/R), although the time frame during which it acts has yet to be fully elucidated. In the present study, a culture model of myocardial cells from Sprague-Dawley rats was used to examine the expression levels of HIF-1α and various downstream effectors at different times following I/R. The levels of HIF-1α were manipulated by overexpressing HIF-1α prior to I/R. HIF-1α levels peaked at 6 h following I/R, subsequently decreasing to low levels. The levels of downstream effectors peaked at 48 h, and decreased almost to pre-I/R levels by 72 h. These results suggest that HIF-1α and its downstream targets offer only short-term protection following I/R. These results may have implications for the treatment of I/R-associated injury in a variety of clinical contexts.

Induction of cellular prion protein (PrPc) under hypoxia inhibits apoptosis caused by TRAIL treatment

Hypoxia decreases cytotoxic responses to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein. Cellular prion protein (PrPc) is regulated by HIF-1α in neurons. We hypothesized that PrPc is involved in hypoxia-mediated resistance to TRAIL-induced apoptosis. We found that hypoxia induced PrPc protein and inhibited TRAIL-induced apoptosis. Thus silencing of PrPc increased TRAIL-induced apoptosis under hypoxia. Overexpression of PrPc protein using an adenoviral vector inhibited TRAIL-induced apoptosis. In xenograft model in vivo, shPrPc transfected cells were more sensitive to TRAIL-induced apoptosis than in shMock transfected cells. Molecular chemo-therapy approaches based on the regulation of PrPc expression need to address anti-tumor function of TRAIL under hypoxia. Molecular chemo-therapy approaches based on the regulation of PrPc expression need to address anti-tumor function of TRAIL under hypoxia.

Autophagy, a double-edged sword in anti-angiogenesis therapy

Autophagy is a highly conservative cell behavior to keep the intracellular homeostasis and is frequently activated when cells encounter disgusting conditions, such as nutrition or growth factor deprive, hypoxia and cytotoxic agents. However, the precise role of autophagy under various conditions may be opposite, differ from protect cells survival to promote cells death, and the mechanism of this conditional-dependent role is still unclear. Anti-angiogenesis agents, such as bevacizumab, sorafenib and sunitinib, could reduce tumor microvascular density and increase tumor hypoxia, thus up-regulating autophagy activation of tumor cells, but the function of autophagy induced by anti-angiogenesis agents is still divergent and is considered to play a cytoprotective role in most cases. In this review, we mainly discuss the relationship between anti-angiogenesis therapy-induced hypoxia and autophagy, and pay special attention on the exact role of anti-angiogenesis agents induced autophagy in the process of anti-angiogenesis treatment.

Overexpression of Carbonic Anhydrase IX is a Dismal Prognostic Marker in Breast Carcinoma in Egyptian Patients

Carbonic anhydrase IX (CAIX) is an enzyme whose expression is very limited in normal tissues and it is highly expressed in various cancers. Therefore, inhibition of CAIX is considered as a promising therapeutic target for the treatment of solid tumors where hypoxic environment has developed. The aim of the current work is to evaluate the immunohistochemical (IHC) expression of CAIX in breast cancer (BC) of Egyptian patients and to investigate the associations of CAIX expression with the standard clinicopathologic features, IHC subtypes of BC, and overall survival. This retrospective study was conducted on 56 archival cases of Egyptian BC patients. Fifty-one of 56 cases (91.1%) showed positive expression of CAIX with cytoplasmic localization, whereas 5 cases (8.9%) showed negative expression. CAIX IHC overexpression is significantly associated with advanced stage and presence of coagulative tumor cell necrosis (P=0.03 and 0.02, respectively). Multivariate analysis revealed Ki67 labeling index and CAIX H-score grouping (P=0.03 and 0.02, respectively) as independent prognostic factors affecting BC patients' overall survival. We concluded that CAIX could play a role in the progression of the studied BC cases. CAIX is a good candidate for target therapy.

Increased expression of surface CD44 in hypoxia-DCs skews helper T cells toward a Th2 polarization

A low partial oxygen pressure (hypoxia) occurs in many pathological environments, such as solid tumors and inflammatory lesions. Understanding the cellular response to hypoxic stress has broad implications for human diseases. As we previously reported, hypoxia significantly altered dendritic cells (DCs) to a DC2 phenotype and promoted a Th2 polarization of naïve T cells with increased IL-4 production. However, the underlying mechanisms still remain largely unknown. In this study, we found the over-expression of surface CD44 in DCs was involved in this process via ligand binding. Further investigation showed hypoxia could reduce the surface expression of membrane type 1 metalloprotease (MT1-MMP) via down-regulating the kinesin-like protein KIF2A, which subsequently alleviated the shedding of CD44 from DCs. Moreover, KIF2A expression was found negatively regulated by HIF-1α in hypoxic microenvironment. These results suggest a previously uncharacterized mechanism by which hypoxia regulates the function of DCs via KIF2A/MT1-MMP/CD44 axis, providing critical information to understand the immune response under hypoxia.

Hypoxia-induced autophagy contributes to the invasion of salivary adenoid cystic carcinoma through the HIF-1α/BNIP3 signaling pathway

Adenoid cystic carcinoma (ACC) is one of the most common types of salivary gland malignancy in the head and neck, and its aggressive ability to invade and metastasize is an important reason for its poor survival rates. Our previous investigations confirmed that autophagy-associated gene expression is closely associated with the occurrence and development of ACC. On this basis, the present study further investigated hypoxia-induced autophagy and its role in tumor invasion. Cobalt chloride (CoCl₂) was used to mimic hypoxia. The results of the present study indicated that autophagosome formation and upregulation of autophagy-associated microtubule-associated protein 1 light chain 3 and Beclin 1 were observed in ACC-M cells in response to CoCl₂. The hypoxia-inducible factor 1α/B cell lymphoma 2/adenovirus E1B 19K-interacting protein 3 signaling pathway was involved in hypoxia-induced autophagy in ACC. Furthermore, inhibition of autophagy by chloroquine markedly attenuated the tumor invasion induced by mimetic hypoxia in ACC. These results suggested that hypoxia-induced autophagy may serve as a potential target for the future treatment of ACC.

microRNA-18a regulates gastric carcinoma cell apoptosis and invasion by suppressing hypoxia-inducible factor-1α expression

Hypoxia is associated with various pathophysiological events, including cancer, lung and cardiovascular diseases. A number of studies have indicated that alterations in microRNA (miRNA) expression may be involved in the regulation of the cellular response to hypoxia. In the present study, miR-18a expression was revealed to be markedly downregulated under hypoxic conditions in MGC-803 and HGC-27 gastric carcinoma cell lines. Furthermore, miR-18a was demonstrated to affect the rate of cell apoptosis and the cell invasion ability in MGC-803 and HGC-27 cells under hypoxic conditions. Cell apoptosis was were analyzed using flow cytometry and cell invasiveness was evaluated using a Transwell-matrigel assay. The results showed that miR-18a overexpression was able to promote cell apoptosis and inhibit cell invasion. Using bioinformatic analysis, hypoxia-inducible factor (HIF)-1α was identified as one of the target genes of miR-18a, and based on the function of HIF-1α in hypoxia, miR-18a was predicted to regulate HIF-1α expression. This hypothesis was confirmed by a further luciferase assay and the detection of the mRNA and protein expression levels of HIF-1α following the induction of miR-18a overexpression. In addition, the expression levels of mitochondrial apoptosis-associated genes were detected following the induction of miR-18a overexpression. In the cells overexpressing miR-18a, the Bcl-2 protein expression level was downregulated, while the protein expression levels of Bax, caspase 3 and caspase 9 were upregulated in the MGC-803 and HGC-27 cell lines. Therefore, miR-18a was hypothesized to induce apoptosis through the HIF-1α/mitochondrial apoptosis pathway.

Clinical implications of serum hypoxia inducible factor-1α and vascular endothelial growth factor in lung cancer

AIMS AND BACKGROUND

Hypoxia inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) have been deemed as key in angiogenesis of lung cancer. The aim of this study was to investigate diagnostic and prognostic values of HIF-1α and VEGF in patients with lung cancer.

METHODS

From May 1, 2011, to April 20, 2014, blood samples and/or pleural effusions were collected from 100 patients with lung cancer, 18 patients with tuberculosis, 47 patients with community-acquired pneumonia, and 29 healthy controls. The pretreatment levels of HIF-1α and VEGF were measured by enzyme-linked immunoassays. Patients with lung cancer were followed up during the period of this study and survival times were recorded for analysis.

RESULTS

We detected that the levels of serum and pleural HIF-1α in lung cancer were significantly higher than those in the tuberculosis population, and that the VEGF expressions were not significantly different between malignancy and benign diseases. An area under the curve of pleural HIF-1α (0.877 ± 0.053) showed a high ability to differentiate lung cancer from benign diseases. The significant negative predictors of survival in the univariate analysis were performance status (gt;1), no anticancer therapy, low serum albumin, advanced stage, and serum high level of VEGF (gt;324.17 pg/mL), while in the multivariate Cox regression analysis, only the pretreatment serum level of VEGF, stage, and anticancer therapy were identified as independent prognostic factors.

CONCLUSIONS

The overexpression of HIF-1α especially in pleural effusion may be an angiogenic factor for distinguishing malignancy from tuberculosis, and the pretreatment level of serum VEGF may be an independent predictor of survival.

Nijmegen breakage syndrome protein 1 (NBS1) modulates hypoxia inducible factor-1α (HIF-1α) stability and promotes in vitro migration and invasion under ionizing radiation

Hypoxia-inducible factor (HIF) is a heterodimer transcription factor complex that monitors the cellular response to the oxygen levels in cells. Hypoxia-inducible factor-1α (HIF-1α) has been shown to be stabilized by ionizing radiation (IR) and its stabilization promotes tumor progression and metastasis. Nijmegen breakage syndrome protein 1 (NBS1), a component of the MRE11-RAD50-NBS1 complex, plays an important role in the cellular response to DNA damage but its overexpression contributes to transformation and has been found to correlate with metastasis. However, whether NBS1 participates in IR-induced metastasis needs to be further determined. The aim of this study is to investigate whether radiation-induced HIF-1α stabilization is regulated by NBS1 and thereby promotes tumor cell migration/invasion. Here, we show that both NBS1 and HIF-1α expression are up-regulated after exposure to IR, and NBS1 increases HIF-1α expression at the protein level. In addition, IR treatment promotes the epithelial-mesenchymal transition (EMT) and in vitro cell migration and invasion activity, which could be abolished by suppression of NBS1. Furthermore, NBS1 directly interacts with HIF-1α and reduces the ubiquitination of HIF-1α⋅ Co-expression of HIF-1α and NBS1 in primary tumors of patients with lung adenocarcinoma correlates with a worse prognosis. These results provide a new function of NBS1 in stabilizing HIF-1α under IR, which leads to enhanced cancer cell migration and invasion.

Hypoxia-inducible factor 1α mediates neuroprotection of hypoxic postconditioning against global cerebral ischemia

Hypoxia administered after transient global cerebral ischemia (tGCI) has been shown to induce neuroprotection in adult rats, but the underlying mechanisms for this protection are unclear. Here, we tested the hypothesis that hypoxic postconditioning (HPC) induces neuroprotection through upregulation of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF), and that this involves phosphatidylinositol-3-kinase (PI3K), p38 mitogen-activated protein kinase (p38 MAPK), and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) pathways. The expression of HIF-1α, VEGF, and cleaved caspase-9 were determined by immunohistochemistry and Western blot. As pharmacologic interventions, the HIF-1α inhibitor 2-methoxyestradiol (2ME2), PI3K inhibitor LY294002, p38 MAPK inhibitor SB203580, and MEK inhibitor U0126 were administered before HPC or after tGCI. We found that HPC maintained the higher expression of HIF-1α and VEGF and decreased cleaved caspase-9 levels in CA1 after tGCI. These effects were reversed by 2ME2 administered before HPC, and the neuroprotection of HPC was abolished. LY294002 and SB203580 decreased the expression of HIF-1α and VEGF after HPC, whereas U0126 increased HIF-1α and VEGF after tGCI. These findings suggested that HIF-1α exerts neuroprotection induced by HPC against tGCI through VEGF upregulation and cleaved caspase-9 downregulation, and that the PI3K, p38 MAPK, and MEK pathways are involved in the regulation of HIF-1α and VEGF.

Hyperbaric oxygen therapy in acute ischemic stroke: a review

Stroke, also known as cerebrovascular disease, is a common and serious neurological disease, which is also the fourth leading cause of death in the United States so far. Hyperbaric medicine, as an emerging interdisciplinary subject, has been applied in the treatment of cerebral vascular diseases since the 1960s. Now it is widely used to treat a variety of clinical disorders, especially hypoxia-induced disorders. However, owing to the complex mechanisms of hyperbaric oxygen (HBO) treatment, the therapeutic time window and the undefined dose as well as some common clinical side effects (such as middle ear barotrauma), the widespread promotion and application of HBO was hindered, slowing down the hyperbaric medicine development. In August 2013, the US Food and Drug Administration declared artery occlusion as one of the 13 specific indications for HBO therapy. This provides opportunities, to some extent, for the further development of hyperbaric medicine. Currently, the mechanisms of HBO therapy for ischemic stroke are still not very clear. This review focuses on the potential mechanisms of HBO therapy in acute ischemic stroke as well as the time window.

Silencing HIF-1α reduces the adhesion and secretion functions of acute leukemia hBMSCs

Hypoxia inducible factor-1α (HIF-1α) is an important transcription factor, which plays a critical role in the formation of solid tumor and its microenvironment. The objective of the present study was to evaluate the expression and function of HIF-1α in human leukemia bone marrow stromal cells (BMSCs) and to identify the downstream targets of HIF-1α. HIF-1α expression was detected at both the RNA and protein levels using real-time PCR and immunohistochemistry, respectively. Vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1α (SDF-1α) were detected in stromal cells by enzyme-linked immunosorbent assay. HIF-1α was blocked by constructing the lentiviral RNAi vector system and infecting the BMSCs. The Jurkat cell/BMSC co-cultured system was constructed by putting the two cells into the same suitable cultured media and conditions. Cell adhesion and secretion functions of stromal cells were evaluated after transfection with the lentiviral RNAi vector of HIF-1α. Increased HIF-1α mRNA and protein was detected in the nucleus of the acute myeloblastic and acute lymphoblastic leukemia compared with normal BMSCs. The lentiviral RANi vector for HIF-1α was successfully constructed and was applied to block the expression of HIF-1α. When HIF-1α of BMSCs was blocked, the expression of VEGF and SDF-1 secreted by stromal cells were decreased. When HIF-1α was blocked, the co-cultured Jurkat cell's adhesion and migration functions were also decreased. Taken together, these results suggest that HIF-1α acts as an important transcription factor and can significantly affect the secretion and adhesion functions of leukemia BMSCs.

Overcoming hypoxic-resistance of tumor cells to TRAIL-induced apoptosis through melatonin

A solid tumor is often exposed to hypoxic or anoxic conditions; thus, tumor cell responses to hypoxia are important for tumor progression as well as tumor therapy. Our previous studies indicated that tumor cells are resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell apoptosis under hypoxic conditions. Melatonin inhibits cell proliferation in many cancer types and induces apoptosis in some particular cancer types. Here, we examined the effects of melatonin on hypoxic resistant cells against TRAIL-induced apoptosis and the possible mechanisms of melatonin in the hypoxic response. Melatonin treatment increased TRAIL-induced A549 cell death under hypoxic conditions, although hypoxia inhibited TRAIL-mediated cell apoptosis. In a mechanistic study, hypoxia inducible factor-1α and prolyl-hydroxylase 2 proteins, which increase following exposure to hypoxia, were dose-dependently down-regulated by melatonin treatment. Melatonin also blocked the hypoxic responses that reduced pro-apoptotic proteins and increased anti-apoptotic proteins including Bcl-2 and Bcl-xL. Furthermore, melatonin treatment reduced TRAIL resistance by regulating the mitochondrial transmembrane potential and Bax translocation. Our results first demonstrated that melatonin treatment induces apoptosis in TRAIL-resistant hypoxic tumor cells by diminishing the anti-apoptotic signals mediated by hypoxia and also suggest that melatonin could be a tumor therapeutic tool by combining with other apoptotic ligands including TRAIL, particularly in solid tumor cells exposed to hypoxia.

The Role of Hypoxia-Inducible Factor in Wound Healing

Significance: Poor wound healing remains a significant health issue for a large number of patients in the United States. The physiologic response to local wound hypoxia plays a critical role in determining the success of the normal healing process. Hypoxia-inducible factor-1 (HIF-1), as the master regulator of oxygen homeostasis, is an important determinant of healing outcomes. HIF-1 contributes to all stages of wound healing through its role in cell migration, cell survival under hypoxic conditions, cell division, growth factor release, and matrix synthesis throughout the healing process. Recent Advances: Positive regulators of HIF-1, such as prolyl-4-hydroxylase inhibitors, have been shown to be beneficial in enhancing diabetic ischemic wound closure and are currently undergoing clinical trials for treatment of several human-ischemia-based conditions. Critical Issues: HIF-1 deficiency and subsequent failure to respond to hypoxic stimuli leads to chronic hypoxia, which has been shown to contribute to the formation of nonhealing ulcers. In contrast, overexpression of HIF-1 has been implicated in fibrotic disease through its role in increasing myofibroblast differentiation leading to excessive matrix production and deposition. Both positive and negative regulators of HIF-1 therefore provide important therapeutic targets that can be used to manipulate HIF-1 expression where an excess or deficiency in HIF-1 is known to correlate with pathogenesis. Future Directions: Targeting HIF-1 during wound healing has many important clinical implications for tissue repair. Counteracting the detrimental effects of excessive or deficient HIF-1 signaling by modulating HIF-1 expression may improve future management of poorly healing wounds.

Expression of monocyte chemotactic protein-1/CCL2 in gastric cancer and its relationship with tumor hypoxia

AIM: To investigate the expression and prognostic value of CCL2 in gastric cancer, as well as its relationship with tumor hypoxia.

METHODS: Tumor tissues from 68 gastric cancer patients (GC) were analyzed, and the expression of CCL2 and hypoxia-inducible factor 1 alpha (HIF-1α) in tumor tissues was detected by immunohistochemistry. Statistical evaluations that were used included univariate log-rank tests of Kaplan-Meier curves and multivariate Cox regression model analysis.

RESULTS: CCL2 was highly expressed in 66.2% (45/68) of gastric cancer specimens. The distribution of CCL2 expression in tumor tissue was consistent with that of HIF-1α. Patients with high CCL2 expression in GC had a lower overall survival rate [50.6 mo (95%CI: 44.44-56.93) vs 64.6 mo (95%CI: 60.27-68.94), P = 0.013].

CONCLUSION: CCL2 expression correlates closely with HIF-1α expression in gastric cancer. CCL2 may be an independent prognostic marker for GC.

Anthrax lethal toxin inhibits translation of hypoxia-inducible factor 1α and causes decreased tolerance to hypoxic stress

Hypoxia is considered to be a contributor to the pathology associated with administration of anthrax lethal toxin (LT). However, we report here that serum lactate levels in LT-treated mice are reduced, a finding inconsistent with the anaerobic metabolism expected to occur during hypoxia. Reduced lactate levels are also observed in the culture supernatants of LT-treated cells. LT inhibits the accumulation of hypoxia-inducible factor (HIF)-1α, a subunit of HIF-1, the master regulator directing cellular responses to hypoxia. The toxin has no effect on the transcription or protein turnover of HIF-1α, but instead it acts to inhibit HIF-1α translation. LT treatment diminishes phosphorylation of eIF4B, eIF4E, and rpS6, critical components of the intracellular machinery required for HIF-1α translation. Moreover, blockade of MKK1/2-ERK1/2, but not p38 or JNK signaling, lowers HIF-1α protein levels in both normoxic and hypoxic conditions, consistent with a role for MKK1 and MKK2 as the major targets of LT responsible for the inhibition of HIF-1α translation. The physiological importance of the LT-induced translation blockade is demonstrated by the finding that LT treatment decreases the survival of hepatocyte cell lines grown in hypoxic conditions, an effect that is overcome by preinduction of HIF-1α. Taken together, these data support a role for LT in dysregulating HIF-1α and thereby disrupting homeostatic responses to hypoxia, an environmental characteristic of certain tissues at baseline and/or during disseminated infection with Bacillus anthracis.

Over-expression of microRNA-494 up-regulates hypoxia-inducible factor-1 alpha expression via PI3K/Akt pathway and protects against hypoxia-induced apoptosis

BACKGROUND

Hypoxia-inducible factor-1 alpha (HIF-1α) is one of the key regulators of hypoxia/ischemia. MicroRNA-494 (miR-494) had cardioprotective effects against ischemia/reperfusion (I/R)-induced injury, but its functional relationship with HIF-1α was unknown. This study was undertaken to determine if miR-494 was involved in the induction of HIF-1α.

RESULTS

Quantitative RT-PCR showed that miR-494 was up-regulated to peak after 4 hours of hypoxia in human liver cell line L02. To investigate the role of miR-494, cells were transfected with miR-494 mimic or miR-negative control, followed by incubation under normoxia or hypoxia. Our results indicated that overexpression of miR-494 significantly induced the expression of p-Akt, HIF-1α and HO-1 determined by qRT-PCR and western blot under normoxia and hypoxia, compared to negative control (p < 0.05). While LY294002 treatment markedly abolished miR-494-inducing Akt activation, HIF-1α and HO-1 increase under both normoxic and hypoxic conditions (p < 0.05). Moreover, apoptosis detection using Annexin V indicated that overexpression of miR-494 significantly decreased hypoxia-induced apoptosis in L02 cells, compared to control (p < 0.05). MiR-494 overexpression also decreased caspase-3/7 activity by 1.27-fold under hypoxia in L02 cells.

CONCLUSIONS

Overexpression of miR-494 upregulated HIF-1α expression through activating PI3K/Akt pathway under both normoxia and hypoxia, and had protective effects against hypoxia-induced apoptosis in L02 cells. Thus, these findings suggested that miR-494 might be a target of therapy for hepatic hypoxia/ischemia injury.

Hypoxia-inducible factor-1α polymorphisms link to coronary artery collateral development and clinical presentation of coronary artery disease

AIMS

This study aimed to investigate the association of Hypoxia-inducible factor-1α (HIF-1α) C1772T and G1790A single nucleotide polymorphisms (SNPs) with: incidence, clinical type, severity of coronary atherosclerosis and coronary collaterals of coronary artery disease (CAD).

METHODS

The clinical data and genomic DNA were gathered in 958 subjects, including 560 controls and 398 patients with CAD. CAD was confirmed with coronary angiography (CAG). The genotypes for two SNPs were determined by high resolution melting after PCR amplification.

RESULTS

Neither the HIF-1α C1772T nor the G1790A genotype was significantly associated with CAD and, no gene-gene or gene-environmental interactions were identified. However, both HIF-1α C1772T and G1790A (P<0.05) alleles were associated with clinical type and formation of coronary collaterals (P<0.05). Patients carrying genotype CT (P=0.019, OR=4.905,91, 95% CI: 1.355-17.761) and GA (P=0.026, OR=3.052, 95% CI: 1.180-7.892) had significantly higher stable angina pectoris (SAP) than unstable angina pectoris (UAP) and acute myocardial infarction (AMI). The presence of HIF-1 genotype CT (P=0.016, OR=13.373, 95% CI: 15.468-32.709) and GA (P=0.001, OR=19.741, 95% CI: 8.125-47.966) predicted lower collateral formation and severity of CAD secondary to the absence of collaterals (r=0.242, P<0.001).

CONCLUSIONS

We conclude that functional polymorphisms in the HIF-1α gene do not modify CAD risk but they are associated with the formation of coronary collaterals and clinical presentation of CAD.

Over expression of HIF-1α in human mesenchymal stem cells increases their supportive functions for hematopoietic stem cells in an experimental co-culture model

INTRODUCTION

Bone marrow transplantation is a critical approach for the treatment of many hematological disorders. Success of this approach is dependent on many factors the most important of which is the number of hematopoietic stem cells along with an efficient stroma. Co-transplantation of efficient mesenchymal stem cells can greatly improve the outcome of transplantations. Current researches assign a critical role for hypoxia inducible factor (HIF)-1α in protection of various cells and tissues probably through induction of cytokines. To make this feature applicable to human bone marrow-derived mesenchymal stem cells, we manipulated these cells to over express HIF-1α gene.

MATERIALS AND METHODS

Full-length cDNA of human HIF-1α was inserted into human bone marrow mesenchymal stem cells by pcDNA.3.1 non-viral plasmid vector, and the effect of this over expression on production of some hematopoietic growth factors was explored. Moreover, using a co-culture system, the interactive impact of HIF-1α-overexpressed mesenchymal stem cells on hematopoietic stem cells was evaluated. Results Over expression of HIF-1α in mesenchymal stem cells in normoxia increased production of one of the most important hematopoietic growth factors, Stem cell factor (also known as Steel factor or c-kit ligand). HIF-1α overexpression had no effect on production of other hematopoietic growth factors. In co-culture of mesenchymal stem cells-HIF-1α with hematopoietic stem cells, enhancement of colony formation and reduced differentiation of hematopoietic stem cells were observed. Conclusion Over expression of HIF-1α in human bone marrow-derived mesenchymal stem cells can augment the production of some hematopoietic growth factors, and we suggest this response of mesenchymal stem cells could help to improve the outcome of bone marrow transplantation.

Hypoxia-induced overexpression of DEC1 is regulated by HIF-1α in hepatocellular carcinoma

Hypoxia-inducible factor-1α (HIF-1α) and differentiated embryo-chondrocyte expressed gene 1 (DEC1) are two key factors that protect hepatocellular carcinoma (HCC) cells from a hypoxic microenvironment. However, little is known concerning the effects of hypoxia on the expression of HIF-1α and DEC1 in HCC. In the present study, RT-PCR and western blotting were conducted to assay the mRNA and protein levels of HIF-1α and DEC1 under normoxia and hypoxia induced by exposure to CoCl2 for different time periods (0, 2, 4, 6, 24 and 48 h). In addition, the HIF-1α protein inhibitor, YC-1, was used to analyze the interaction between DEC1 and HIF-1α expression and the related mechanism. Results showed that expression of DEC1 in HCC was significantly upregulated at both the mRNA and protein levels, when compared with that in normal liver cells (P<0.05). Hypoxia induced the upregulation of HIF-1α in a time-dependent manner, which was also observed at the DEC1 mRNA and protein levels (P<0.05). However, hypoxia did not affect the transcription of HIF-1α (P>0.05). A positive correlation was found between HIF-1α and DEC1 expression in both BEL-7402 (r=0.885, P<0.05) and SMMC-7721 cells (r=0.826, P<0.05). Furthermore, inhibition of HIF-1α by YC-1 led to a significant decrease in DEC1 induced by hypoxia (P<0.05). We suggest that hypoxia induced the overexpression of DEC1, the mechanism of which may be related to the upregulation of HIF-1α in HCC. The efficacy of inhibiting HIF-1α and DEC1 expression as a possible treatment for HCC should be assessed in clinical trials.

Calvarial defect healing by recruitment of autogenous osteogenic stem cells using locally applied simvastatin

Local statins implant has been shown to promote bone healing, the underlying mechanisms are unclear. The purpose of this study was to test the effect of local simvastatin implant on bone defect healing; to evaluate the mobilization, migration, and homing of bone marrow-derived mesenchymal stem cells (BMSCs) and endothelial progenitor cells (EPCs) induced by simvastatin. We found that local simvastatin implant increased bone formation by 51.8% (week 6) and 64.8% (week 12) compared with polyglycolic acid controls (P < 0.01), as verified by X-ray, CT, and histology. Simvastatin increased migration capacity of BMSCs and EPCs in vitro (P < 0.05). Local simvastatin implant increased mobilization of EPCs to the peripheral blood by 127% revealed by FACS analysis (P < 0.01), and increased osteogenic BMSCs to the peripheral blood dramatically revealed by Alizarin Red-S staining for mineralized nodules formation. Pre-transplanted GFP-transfected BMSCs as a tracing cell and bioluminescence imaging revealed that local simvastatin implant recruited GFP-labeled BMSC. Also, local simvastatin implant induced the HIF-1α and BMP-2 expression. In conclusion, local simvastatin implantation promotes bone defect healing, where the underlying mechanism appears to involve the higher expression of HIF-1α and BMP-2, thus recruit autogenous osteogenic and angiogenetic stem cells to the bone defect area implanted with simvastatin.

The role of hypoxia-induced genes in ovarian angiogenesis

The hypoxic microenvironment that occurs in fast-growing tissue such as the corpus luteum (CL) is a major contributor to its ability to survive via the induction of an intricate vascular network. Cellular responses to hypoxia are mediated by hypoxia-inducible factor-1 (HIF-1), an oxygen-regulated transcriptional activator. HIF-1, a heterodimer consisting of a constitutively-expressed β subunit and an oxygen-regulated α subunit, binds to the hypoxia responsive element (HRE) present in the promoter regions of responsive genes. This review summarises evidence for the involvement of hypoxia and HIF-1α in CL development and function. Special emphasis is given to hypoxia-induced, luteal cell-specific expression of multiple genes (vascular endothelial growth factor A (VEGFA), fibroblast growth factor 2 (FGF-2), prokineticin receptor 2 (PK-R2), stanniocalcin 1 (STC-1) and endothelin 2 (EDN-2) that participate in the angiogenic process during CL formation.

The role of Aurora A in hypoxia-inducible factor 1α-promoting malignant phenotypes of hepatocelluar carcinoma

Overexpression of both hypoxia-inducible factor 1α (HIF-1α) and Aurora A has been found in hepatocellular carcinoma (HCC). However, whether HIF-1α and Aurora A synergistically promote malignant phenotypes of HCC cells is unknown. The purpose of this study was to investigate the roles and functional correlation of HIF-1α and Aurora A in HCC progression. Immunohistochemistry was performed to detect HIF-1α and Aurora A protein expression in 55 primary HCC and corresponding non-tumor tissues and their clinical significance. Gene knockout technology using short hairpin RNA (shRNA) was used to knockdown expression of HIF-1α or Aurora A and analyze their effects on malignant phenotypes of HCC cells. The transcriptional regulation of Aurora A by HIF-1α and the possible downstream molecular signaling pathways were also determined. Results showed that hypoxia could induce the increased expression of HIF-1α and Aurora A in HCC cells. Also, shRNA-mediated HIF-1α downregulation could lead to the decreased Aurora A expression and inhibition of growth or invasion in HCC cells. Moreover, HIF-1α could transcriptionally regulate Aurora A expression by binding to hypoxia-responsive elements in the Aurora A promoter and recruiting the coactivator-p300/CBP. Additionally, shRNA-mediated Aurora A knockdown could mimic the effects of HIF-1α downregulation on phenotypes of HCC cells, and overexpression of Aurora A could partially rescue the phenotypical changes of HCC cells induced by HIF-1α downregulation. Further research indicated that activation of Akt and p38-MAPK signaling pathways mediated the downstream effects of HIF-1α and Aurora A in HCC cells under hypoxic condition. Taken together, our findings indicated that Aurora A might be a key regulator of HIF-1α-promoting malignant phenotypes of HCC by activation of Akt and p38-MAPK signaling pathways.

Identification and comparative analyses of myocardial miRNAs involved in the fetal response to maternal obesity

Human and animal studies show that suboptimal intrauterine environments lead to fetal programming, predisposing offspring to disease in later life. Maternal obesity has been shown to program offspring for cardiovascular disease (CVD), diabetes, and obesity. MicroRNAs (miRNAs) are small, noncoding RNA molecules that act as key regulators of numerous cellular processes. Compelling evidence links miRNAs to the control of cardiac development and etiology of cardiac pathology; however, little is known about their role in the fetal cardiac response to maternal obesity. Our aim was to sequence and profile the cardiac miRNAs that are dysregulated in the hearts of baboon fetuses born to high fat/high fructose-diet (HFD) fed mothers for comparison with fetal hearts from mothers eating a regular diet. Eighty miRNAs were differentially expressed. Of those, 55 miRNAs were upregulated and 25 downregulated with HFD. Twenty-two miRNAs were mapped to human; 14 of these miRNAs were previously reported to be dysregulated in experimental or human CVD. We used an Ingenuity Pathway Analysis to integrate miRNA profiling and bioinformatics predictions to determine miRNA-regulated processes and genes potentially involved in fetal programming. We found a correlation between miRNA expression and putative gene targets involved in developmental disorders and CVD. Cellular death, growth, and proliferation were the most affected cellular functions in response to maternal obesity. Thus, the current study reveals significant alterations in cardiac miRNA expression in the fetus of obese baboons. The epigenetic modifications caused by adverse prenatal environment may represent one of the mechanisms underlying fetal programming of CVD.

The anti-apoptotic effect of fucoxanthin on carbon tetrachloride-induced hepatotoxicity

This study evaluated the anti-apoptotic activity of fucoxanthin in carbon tetrachloride (CCl(4))-induced hepatotoxicity. An in vitro study using the 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay clearly demonstrated an attenuation of CCl(4)-induced hepatotoxicity with fucoxanthin. This effect was dose-dependent; 25 µM was more effective than 10 µM of fucoxanthin for attenuating the hepatotoxicity induced by 5 mM of CCl(4). Acute CCl(4)-hepatotoxicity in rats, with numerous cells positive for the terminal deoxynucleotidyl - transferase (TdT) -mediated deoxyuridine triphosphate-digoxigenin (dUTP) nick-end labeling (TUNEL) stain were seen in the pericentral area of the hepatic lobule. Oral pretreatment of CCl(4)- injected rats with fucoxanthin significantly reduced hepatocyte apoptosis. Fucoxanthin was immunohistochemically shown to increase heme oxygenase-1 expression in the cultured liver cells of Hc cells and TRL1215 cells. By oral pretreatment of CCl(4)-injected rats with fucoxanthin, the hepatic heme oxygenase-1 protein levels were significantly increased compared to those not pretreated with fucoxanthin. Heme oxygenase-1 mRNA expression after CCl(4 )injection was higher in the CCl(4)+fucoxanthin group than in the CCl(4 )group, although the difference was not significant. The findings suggest that fucoxanthin attenuates hepatocyte apoptosis through heme oxygenase-1 induction in CCl(4)-induced acute liver injury.

MicroRNA-206 is involved in hypoxia-induced pulmonary hypertension through targeting of the HIF-1α/Fhl-1 pathway

Hypoxia-induced pulmonary hypertension (PH), which is characterized by vasoconstriction and subsequent structural remodeling of blood vessels, is an important event in chronic obstructive pulmonary disease patients and in people living at high altitudes. Hypoxia-inducible factor-1α (HIF-1α) and its regulator four-and-a-half LIM (Lin-11, Isl-1 and Mec-3) domain 1 (Fhl-1) have important roles in hypoxia-induced PH. MicroRNA-206 (miR-206) is critical for myogenesis and related diseases; however, the role of miR-206 in hypoxia-induced PH is unknown. miR-206 expression was evaluated in a hypoxic rat model and in cultured hypoxic pulmonary artery smooth muscle cells (PASMCs) using real-time quantitative PCR (RT-qPCR). HIF-1α and Fhl-1 expression were evaluated using RT-qPCR, western blotting, immunohistochemistry and immunofluorescence. The function of miR-206 was assessed by transfecting miR-206 mimics and inhibitors. Dual-luciferase reporter gene assays and western blotting were performed to validate the target genes of miR-206. siRNA targeted against Fhl-1 was used to investigate the effect of Fhl-1 on miR-206. Flow cytometry was used to detect the cell cycle phase distribution in each group of PASMCs. Significant downregulation of miR-206 in hypoxic lung tissue and PASMCs was identified, whereas HIF-1α and Fhl-1 were upregulated in these samples. The expression of miR-206 in the serum was different from that in the lung tissue. Transfection of pre-miR miR-206 in hypoxic conditions led to increased expression of HIF-1α and Fhl-1 rather than abolishing hypoxia-induced HIF-1α and Fhl-1, as was expected, and promoted the entry of cells into the S phase and enhanced PASMC proliferation. Fhl-1-targeted siRNA in PASMC prevented cell proliferation and led to an increased proportion of cells in the G1 phase without altering miR-206 expression. Bioinformatic analysis and dual-luciferase reporter gene assays revealed direct evidence for miR-206 targeting of HIF-1α. In conclusion, hypoxia-induced downregulation of miR-206 promotes PH by targeting the HIF-1α/Fhl-1 pathway in PASMCs. miR-206 could be a triggering factor of early stage of hypoxia-induced PH.

A meta-analysis of HIF-1α and esophageal squamous cell carcinoma (ESCC) risk

To investigate the correlation of hypoxia-inducible factor-1α (HIF-1α) expression with clinical prognosis and efficacy of radiochemotherapy in esophageal squamous cell carcinoma (ESCC). Studies assessing the clinical or prognostic significance of HIF-1α expression in ESCC published prior to December 2011 were selected by searching PubMed, EMBASE, Cochrane Library, and (China National Knowledge Infrastructure) CNKI. A meta-analysis was performed to clarify the impact of HIF-1α expression on clinicopathological parameters or survival in ESCC. A total of 16 studies met the inclusion criteria, which included 1261 patients with ESCC. Accordingly, the level of HIF-1α expression in esophageal tissues of patients with ESCC was significantly higher than that in normal patients (odds ratio, OR = 33.111, 95 % confidence interval, CI = 11.912-92.040). The expression of HIF-1α correlated with the depth of invasion (OR = 1.701, 95 % CI = 1.076-4.705), clinical TNM stage (OR = 2.160, 95%CI = 1.516-3.077), as well as lymph node metastasis (OR = 2.393, 95 % CI = 1.319-4.344), regardless of differentiation grading (OR = 1.185, 95 % CI = 0.859-1.635). Furthermore, there was a significant association of increased HIF-1α expression with poorer radiochemotherapy outcomes, 2-year overall survival (OR = 0.219, 95 % CI = 0.104-0.461) and survival (OR = 0.320, 95 % CI = 0.115-0.887, P < 0.05) in patients with ESCC. In addition, HIF-1α expression correlated with VEGF expression in the ESCCs (OR = 4.635, 95%CI = 2.591-8.292). Increased expression of HIF-1α plays an important role in the malignant biology of ESCC resulting in significantly poorer radiochemotherapy outcomes and 2-year overall survival. HIF-1α expression may be a prognostic factor, as well as a potential target for therapy in patients with ESCC.

MicroRNA in the Diseased Pulmonary Vasculature: Implications for the Basic Scientist and Clinician

Since the first descriptions of their active functions more than ten years ago, small non-coding RNA species termed microRNA (miRNA) have emerged as essential regulators in a broad range of adaptive and maladaptive cellular processes. With an exceptionally rapid pace of discovery in this field, the dysregulation of many individual miRNAs has been implicated in the development and progression of various cardiovascular diseases. MiRNA are also expected to play crucial regulatory roles in the progression of pulmonary vascular diseases such as pulmonary hypertension (PH), yet direct insights in this field are only just emerging. This review will provide an overview of pulmonary hypertension and its molecular mechanisms, tailored for both basic scientists studying pulmonary vascular biology and physicians who manage PH in their clinical practice. We will describe the pathobiology of pulmonary hypertension and mechanisms of action of miRNA relevant to this disease. Moreover, we will summarize the potential roles of miRNA as biomarkers and therapeutic targets as well as future strategies for defining the cooperative actions of these powerful effectors in pulmonary vascular disease.

Protein-bound polysaccharide decreases invasiveness and proliferation in pancreatic cancer by inhibition of hedgehog signaling and HIF-1α pathways under hypoxia

To develop an effective therapeutic approach to pancreatic ductal adenocarcinoma (PDAC), we focused on the antitumor mechanism of protein-bound polysaccharide (PSK) under hypoxia. PSK decreased proliferation in PDAC cells under hypoxia but not normoxia. PSK also showed anti-tumor effects in vivo, inhibited invasiveness of PDAC cells, and decreased the expression of HIF-1α and hedgehog (Hh) signaling-related molecules under hypoxia. Inhibition of HIF-1α and Hh signaling reduced proliferation and invasiveness in PDAC cells under hypoxia. In conclusion, we found new PSK-related pathways in invasiveness and proliferation in PDAC under hypoxia. PSK may be a promising therapeutic drug to treat refractory PDAC.

Negative regulation of human growth hormone gene expression by insulin is dependent on hypoxia-inducible factor binding in primary non-tumor pituitary cells

Insulin controls growth hormone (GH) production at multiple levels, including via a direct effect on pituitary somatotrophs. There are no data, however, on the regulation of the intact human (h) GH gene (hGH1) by insulin in non-tumor pituitary cells, but the proximal promoter region (nucleotides -496/+1) responds negatively to insulin in transfected pituitary tumor cells. A DNA-protein interaction was also induced by insulin at nucleotides -308/-235. Here, we confirmed the presence of a hypoxia-inducible factor 1 (HIF-1) binding site within these sequences (-264/-259) and investigated whether HIF-1 is associated with insulin regulation of "endogenous" hGH1. In the absence of primary human pituitary cells, transgenic mice expressing the intact hGH locus in a somatotroph-specific manner were generated. A significant and dose-dependent decrease in hGH and mouse GH RNA levels was detected in primary pituitary cell cultures from these mice with insulin treatment. Increasing HIF-1α availability with a hypoxia mimetic significantly decreased hGH RNA levels and was accompanied by recruitment of HIF-1α to the hGH1 promoter in situ as seen with insulin. Both inhibition of HIF-1 DNA binding by echinomycin and RNA interference of HIF-1α synthesis blunted the negative effect of insulin on hGH1 but not mGH. The insulin response is also sensitive to histone deacetylase inhibition/trichostatin A and associated with a decrease in H3/H4 hyperacetylation in the proximal hGH1 promoter region. These data are consistent with HIF-1-dependent down-regulation of hGH1 by insulin via chromatin remodeling specifically in the proximal promoter region.

Emerging glycolysis targeting and drug discovery from chinese medicine in cancer therapy

Molecular-targeted therapy has been developed for cancer chemoprevention and treatment. Cancer cells have different metabolic properties from normal cells. Normal cells mostly rely upon the process of mitochondrial oxidative phosphorylation to produce energy whereas cancer cells have developed an altered metabolism that allows them to sustain higher proliferation rates. Cancer cells could predominantly produce energy by glycolysis even in the presence of oxygen. This alternative metabolic characteristic is known as the “Warburg Effect.” Although the exact mechanisms underlying the Warburg effect are unclear, recent progress indicates that glycolytic pathway of cancer cells could be a critical target for drug discovery. With a long history in cancer treatment, traditional Chinese medicine (TCM) is recognized as a valuable source for seeking bioactive anticancer compounds. A great progress has been made to identify active compounds from herbal medicine targeting on glycolysis for cancer treatment. Herein, we provide an overall picture of the current understanding of the molecular targets in the cancer glycolytic pathway and reviewed active compounds from Chinese herbal medicine with the potentials to inhibit the metabolic targets for cancer treatment. Combination of TCM with conventional therapies will provide an attractive strategy for improving clinical outcome in cancer treatment.

Significance of combined detection of HIF-1α, TXB2, 6-keto-PGF1α and HA in the diagnosis of hepatic microcirculatory disturbance in patients with chronic hepatitis B

AIM: To evaluate the significance of combined detection of HIF-1α, TXB2, 6-keto-PGF1α and HA in the diagnosis of hepatic microcirculatory disturbance in patients with chronic hepatitis B (CHB).

METHODS: In total, 275 patients with CHB and 15 normal volunteer were included. The ultrastructure of the liver was observed by transmission electron microscopy (TEM). HIF-1α expression in liver biopsies was detected by immunohistochemistry. Plasma levels of TXB2 and 6-keto-PGF1α were determined by chemiluminescence, and serum HA levels was measured by RIA.

RESULTS: As the pathological changes of the liver were aggravated, erythrocyte aggregation, stenosis and blockage of sinus hepaticas, collagen fiber deposition, and basal membrane formation became worsened, the strength and range of expression of HIF-1α was enhanced, the levels of serum HA and plasma TXB2 were raised gradually, and plasma levels of 6-keto-PGF1α slightly declined.

CONCLUSION: Combined detection of HIF-1α, TXB2, 6-keto-PGF1α and HA can help accurately diagnose hepatic microcirculatory disturbance in patients with CHB.

HIF-1α regulation in mammalian hibernators: role of non-coding RNA in HIF-1α control during torpor in ground squirrels and bats

A potential role for non-coding RNAs, miR-106b and antisense hypoxia inducible transcription factor-1 (HIF-1α), in HIF-1α regulation during mammalian hibernation was investigated in two species, the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) and the little brown bat (Myotis lucifugus). Both species showed differential regulation of HIF-1α during hibernation. HIF-1α protein levels increased significantly in skeletal muscle of both species when animals entered torpor, as well as in bat liver. HIF-1α mRNA levels correlated with the protein increase in bat skeletal muscle and liver but not in squirrel skeletal muscle. Antisense HIF-1α transcripts were identified in skeletal muscle of both hibernators. The expression of antisense HIF-1α was reduced in skeletal muscle of torpid bats compared with euthermic controls, suggesting that release of inhibition by the antisense RNA contributes to regulating HIF-1α translation in this tissue during torpor. The expression of miR-106b, a microRNA associated with HIF-1α regulation, also decreased during torpor in both skeletal muscle and liver of bats and in ground squirrel skeletal muscle. These data present the first evidence that non-coding RNA provides novel post-transcriptional mechanisms of HIF-1α regulation when hibernators descend into deep cold torpor, and also demonstrate that these mechanisms are conserved in two divergent mammalian orders (Rodentia and Chiroptera).

Hypoxia-inducible factor-1 α regulates prion protein expression to protect against neuron cell damage

The human prion protein fragment, PrP (106-126), may contain a majority of the pathological features associated with the infectious scrapie isoform of PrP, known as PrP(Sc). Based on our previous findings that hypoxia protects neuronal cells from PrP (106-126)-induced apoptosis and increases cellular prion protein (PrP(C)) expression, we hypothesized that hypoxia-related genes, including hypoxia-inducible factor-1 alpha (HIF-1α), may regulate PrP(C) expression and that these genes may be involved in prion-related neurodegenerative diseases. Hypoxic conditions are known to elicit cellular responses designed to improve cell survival through adaptive processes. Under normoxic conditions, a deferoxamine-mediated elevation of HIF-1α produced the same effect as hypoxia-inhibited neuron cell death. However, under hypoxic conditions, doxorubicin-suppressed HIF-1α attenuated the inhibitory effect on neuron cell death mediated by PrP (106-126). Knock-down of HIF-1α using lentiviral short hairpin (sh) RNA-induced downregulation of PrP(C) mRNA and protein expression under hypoxic conditions, and sensitized neuron cells to prion peptide-mediated cell death even in hypoxic conditions. In PrP(C) knockout hippocampal neuron cells, hypoxia increased the HIF-1α protein but the cells did not display the inhibitory effect of prion peptide-induced neuron cell death. Adenoviruses expressing the full length Prnp gene (Ad-Prnp) were utilized for overexpression of the Prnp gene in PrP(C) knockout hippocampal neuron cells. Adenoviral transfection of PrP(C) knockout cells with Prnp resulted in the inhibition of prion peptide-mediated cell death in these cells. This is the first report demonstrating that expression of normal PrP(C) is regulated by HIF-1α, and PrP(C) overexpression induced by hypoxia plays a pivotal role in hypoxic inhibition of prion peptide-induced neuron cell death. These results suggest that hypoxia-related genes, including HIF-1α, may be involved in the pathogenesis of prion-related diseases and as such may be a therapeutic target for prion-related neurodegenerative diseases.

Transcriptional upregulation of MT2-MMP in response to hypoxia is promoted by HIF-1α in cancer cells

Hypoxia is a critical event in solid tumor development, invasion, and metastasis. Cellular adaptation to hypoxic microenvironment is essential for tumor progression and is largely mediated by hypoxia-inducible factor-1α (HIF-1α) through coordinated regulation of hypoxia-responsive genes. In this study, we found that membrane type-2 matrix metalloproteinase (MT2-MMP), one of the matrix metalloproteinase (MMP) family members, was a novel hypoxia-responsive gene and was upregulated by HIF-1α under hypoxia. When cancer cells were subjected to hypoxia (1% O(2) ) treatment, the mRNA and protein levels of MT2-MMP were significantly increased in a time-dependent manner in all three tested cancer cell lines including pancreatic cancer cells (PANC-1), nonsmall cell lung cancer cells (A-549), and cervix cancer cells (HeLa). Further analyses indicated that there were two hypoxia-responsive elements (HREs) in the MT2-MMP promoter, and HRE1 but not HRE2 was essential for MT2-MMP transcriptional activation under hypoxia. HIF-1α specifically and directly bound to MT2-MMP promoter was analyzed by HIF-1α binding/competition and chromatin immunoprecipitation (ChIP) assays. Furthermore, we found that upregulation of MT2-MMP under hypoxia could confer resistance to hypoxia-induced apoptosis and increase invasiveness of cancer cells. These findings provided a new insight into how cancer cells overcome hypoxic stress and trend to survive and invade, demonstrated a new regulatory mechanism of MT2-MMP expression in caner cells, and also revealed that MT2-MMP was a novel hypoxia-responsive gene and was upregulated by HIF-1α under hypoxia. © 2011 Wiley-Liss, Inc.

Ischaemia-induced retinal neovascularisation and diabetic retinopathy in mice with conditional knockout of hypoxia-inducible factor-1 in retinal Müller cells

AIMS/HYPOTHESIS

Retinal Müller cells are known to produce inflammatory and angiogenic cytokines, which play important roles in diabetic retinopathy. Hypoxia-inducible factor (HIF)-1 has been shown to play a crucial role in retinal inflammation and neovascularisation. We sought to determine the role of Müller cell-derived HIF-1 in oxygen-induced retinopathy (OIR) and diabetic retinopathy using conditional Hif-1α (also known as Hif1a) knockout (KO) mice.

METHODS

Conditional Hif-1α KO mice were generated by crossing mice expressing cyclisation recombinase (cre, also known as P1_gp003) in Müller cells with floxed Hif-1α mice and used for OIR and streptozotocin-induced diabetes to induce retinal neovascularisation and inflammation, respectively. Abundance of HIF-1α and pro-angiogenic and pro-inflammatory factors was measured by immunoblotting and immunohistochemistry. Retinal neovascularisation was visualised by angiography and quantified by counting pre-retinal nuclei. Retinal inflammation was evaluated by leucostasis and vascular leakage.

RESULTS

While the Hif-1α KO mice showed significantly decreased HIF-1α levels in the retina, they exhibited no apparent histological or visual functional abnormalities under normal conditions. Compared with wild-type counterparts, Hif-1α KO mice with OIR demonstrated attenuated overproduction of vascular endothelial growth factor (VEGF) and intercellular adhesion molecule (ICAM)-1, reduced vascular leakage and alleviated neovascularisation in the retina. Under diabetes conditions, disruption of Hif-1α in Müller cells attenuated the increases of retinal vascular leakage and adherent leucocytes, as well as the overproduction of VEGF and ICAM-1.

CONCLUSIONS/INTERPRETATION

Müller cell-derived HIF-1α is a key mediator of retinal neovascularisation, vascular leakage and inflammation, the major pathological changes in diabetic retinopathy. Müller cell-derived HIF-1α is therefore a promising therapeutic target for diabetic retinopathy.

Down-regulation of hypoxia inducible factor-1alpha: a possible explanation for the protective effects of estrogen on genioglossus fatigue resistance

Patients with obstructive sleep apnea/hypopnea syndrome (OSAHS) often exhibit fatigued or inefficient upper airway dilator muscle activity. It has been shown that estrogen may have some impact on upper airway contractility under normoxic conditions. Chronic intermittent hypoxia (CIH) is a frequent feature of OSAHS, and it may alter muscle susceptibility to oxidative stress, a characteristic of a fatigable nature. Hypoxia inducible factor-1 (HIF-1) is a transcription factor that is responsible for the regulation of oxygen homeostasis under hypoxic conditions. We examined the effects of estrogen on the contractility of the genioglossus by exposing rats to alternating cycles of 6-8% O(2) every 15 s for a total duration of 35 d. The results showed that muscle fatigue resistance was significantly decreased after CIH but was partially reversed after estrogen treatment. Compared with the control group, real-time reverse transcription-polymerase chain reaction and western blotting showed higher levels of HIF-1alpha messenger RNA and protein in the CIH group, but estrogen treatment reduced, in a dose-independent manner, the levels of HIF-1alpha messenger RNA and protein in rats exposed to CIH. We conclude that CIH induced the expression of HIF-1alpha in the genioglossus and altered the physical properties towards a more fatigable phenotype, whereas estrogen inhibited the over-expression of HIF-1alpha, and this may account for the improvement of upper airway muscle endurance in CIH rats.

Phosphorylation mechanisms in intensive care medicine

INTRODUCTION

The phosphorylation states of proteins, lipids, carbohydrates, amino acids, and nucleotides control the mechanisms behind nearly all cellular functions. Therefore, not surprisingly, recent findings have shown that alterations in these phosphorylation pathways play a central role in the development and progression of many disease states. This review provides a brief summary of the function and activity of various phosphorylation mechanisms, outlines some of the major phosphorylation signaling cascades, and describes the role of these phosphorylation mechanisms in intensive care medicine.

METHODS

This article will comprise a comprehensive review of the literature in the context of intensive care medicine. Specifically, we will discuss the involvement of phosphorylation in the pathogenesis, diagnosis, and treatment of heart failure, myocardial infarction, stroke, respiratory failure, ventilation-induced lung injury, traumatic brain injury, acute organ failure, systemic sepsis, and shock.

CONCLUSION

Phosphorylation mechanisms clearly play an important role in many pathologies and treatment strategies of intensive care and therefore further understanding of these mechanisms may lead to the development of novel therapies and improved patient care.

Increased expression of hypoxia-inducible factor 1alpha in coeliac disease

Previously, it has been suggested that hypoxia-inducible factor (HIF) 1 signaling may play determinative role in the maintenance of the barrier function of the intestinal epithelium in inflammatory bowel disease. Our aim was to depict the alteration of HIF-1alpha and related genes in celiac disease (CD) where the importance of the barrier function is well known. Duodenal biopsy specimens were collected from 16 children with untreated CD, 9 children with treated CD and 10 controls. HIF-1alpha, trefoil factor 1 (TFF1), ecto-5-prime nucleotidase (CD73), and multi drug resistance gene 1 (MDR1) mRNA and HIF-1alpha protein expression were determined by real-time PCR and Western blot, respectively. Localization of HIF-1alpha was determined by immunofluorescent staining. We found increased HIF-1alpha and TFF1 mRNA and HIF-1alpha protein expression in the duodenal mucosa of children with untreated CD compared with controls or children with treated CD (p < 0.05). In untreated CD children, HIF-1alpha staining was present in cytoplasmic and nuclear region of the villous enterocytes. In treated CD mRNA expression of CD73 and MDR1 were increased compared with controls (p < 0.01 and 0.05, respectively). Our results of increased mucosal HIF-1alpha expression in CD children suggest the contribution of this signaling pathway in the pathomechanism of CD.