Influence of Hypoxia Inducible Factor-1α of Endothelial Progenitor Cells on Left Ventricular Function in Experimental Myocardial Infarction

Based on the promotion of myocardial activity via endothelial progenitor cells (EPCs) subsequent to acute myocardial infarction (AMI), our research was designed to explore the influence of excessive HIF-1α expression in expanded EPCs (eEPCs) on promotion of the activity of left ventricle subsequent to MI. Isolation of EPCs from cord blood was performed before transduction with the help of retroviral vector with or without HIF-1α expression. Transplantation was performed subsequent to ligation of the left anterior descending coronary artery in mice. Ejection fraction (EF) of left ventricle was promoted via transplantation after 2 weeks. Excessive HIF-1α expression enhanced EF of left ventricle and decreased the extent of MI. It was revealed via functional studies that excessive HIF-1α expression enhanced proliferation of EPCs triggered by low oxygen concentration and suppressed cell death in the region of infarction. Moreover, markers of endothelium CD31, VEGF, and eNOS were upregulated. Transplantation of eEPCs with excessive HIF-1α expression in AMI can promote myocardial activities by increasing differentiation, generation of vessels, proliferation of eEPCs, and suppressing cell death. The above findings propose that regulation of EPCs via HIF-1α enhances the activity as well as mobilization of EPCs, indicating that reinforcement of expression of HIF-1α is beneficial for coronary heart disease.

Comparative study on the distribution and expression of Neuroglobin and Hypoxia-inducible factor-1α in the telencephalon of yak and cattle

The telencephalon refers to the most highly developed and anterior part of the forebrain, consisting mainly of the cerebral hemispheres. The study determined Neuroglobin (Ngb) and Hypoxia-inducible factor (HIF-1α) expression in the telencephalon of yak and cattle, and compare the expression and distribution pattern of Ngb and HIF-1α in the two animals. Immunohistochemistry (IHC), quantitative real-time Polymerase Chain Reaction (qRT-PCR), and Western blot (WB) were employed to investigate Ngb and Hif-1α expression in the telencephalon of yak and cattle. mRNA and protein expressions of Ngb and HIF-1α showed positive in different tissues of the yak and cattle telencephalon. Ngb expression in tissues of the yak recorded higher as compare to cattle while HIF-1α expression was found higher in cattle than yak. The HIF-1α expression in some tissues of yak telencephalon was consistent with the cattle. The results documented that HIF-1α may have a direct or indirect synergistic effect on Ngb expression in the yak telencephalon to improve hypoxia adaptation. It is suggested that yak may need more Ngb expression for adaptation, but the expression of HIF-1α seems to be down-regulated during long-term adaptation, and the specific causes of this phenomenon needs to be further verified.

E74-Like Factor 3 Promotes Endometrial Cancer Cell Proliferation, Migration and Invasion via Regulating Mucin 1/Hypoxia-Inducible Factor 1α Pathway

High expression of E74-like factor 3 (ELF3) has been reported in type 1 endometrial cancer (EC). Bioinformatics analysis predicted a positive correlation with ELF3 and mucin 1 (MUC1)/hypoxiainducible factor 1α (HIF-1α), a previously identified cancer-promoting pathway. This study focused on the MUC1/HIF-1α-involved action mechanism of ELF3 in EC. ELF3 expression in EC cell lines was measured by RT-qPCR and western blot analysis. Following the expression of ELF3 was silent, cell proliferation was examined using CCK-8 and colony formation assay, cell migration and invasion were observed using wound healing and transwell assays. The effect of ELF1 silencing on MUC1/HIF-1α expression was detected by western blot. Rescue experiments incorporating pcDNA3.1(+)/MUC1 explored the interaction between ELF3 and MUC1/HIF-1α in EC cell proliferation, migration and invasion. ELF3 was found to be expressed at a high level in EC cell lines, and the silencing of it effectively inhibited EC cell proliferation. Moreover, ELF silencing also inhibited the migration and invasion of EC cells. Consistent with the database prediction, a positive correlation between ELF3 and MUC1/HIF-1α was observed. More importantly, MUC1 overexpression abated the promotive effect of ELF3 silencing on EC cell proliferation, migration and invasion. ELF3 promotes EC cell proliferation, migration and invasion by regulating MUC1/HIF-1α pathway. Thus, ELF3 as well as MUC1/HIF-1α pathway may be particle targets in the treatment of EC.

Pericyte, but not astrocyte, hypoxia inducible factor-1 (HIF-1) drives hypoxia-induced vascular permeability in vivo

Background Ways to prevent disease-induced vascular modifications that accelerate brain damage remain largely elusive. Improved understanding of perivascular cell signalling could provide unparalleled insight as these cells impact vascular stability and functionality of the neurovascular unit as a whole. Identifying key drivers of astrocyte and pericyte responses that modify cell–cell interactions and crosstalk during injury is key. At the cellular level, injury-induced outcomes are closely entwined with activation of the hypoxia-inducible factor-1 (HIF-1) pathway. Studies clearly suggest that endothelial HIF-1 signalling increases blood–brain barrier permeability but the influence of perivascular HIF-1 induction on outcome is unknown. Using novel mouse lines with astrocyte and pericyte targeted HIF-1 loss of function, we herein show that vascular stability in vivo is differentially impacted by perivascular hypoxia-induced HIF-1 stabilization. Methods To facilitate HIF-1 deletion in adult mice without developmental complications, novel Cre-inducible astrocyte-targeted (GFAP-CreERT2; HIF-1αfl/fl and GLAST-CreERT2; HIF-1αfl/fl) and pericyte-targeted (SMMHC-CreERT2; HIF-1αfl/fl) transgenic animals were generated. Mice in their home cages were exposed to either normoxia (21% O2) or hypoxia (8% O2) for 96 h in an oxygen-controlled humidified glove box. All lines were similarly responsive to hypoxic challenge and post-Cre activation showed significantly reduced HIF-1 target gene levels in the individual cells as predicted. Results Unexpectedly, hypoxia-induced vascular remodelling was unaffected by HIF-1 loss of function in the two astrocyte lines but effectively blocked in the pericyte line. In correlation, hypoxia-induced barrier permeability and water accumulation were abrogated only in pericyte targeted HIF-1 loss of function mice. In contrast to expectation, brain and serum levels of hypoxia-induced VEGF, TGF-β and MMPs (genes known to mediate vascular remodelling) were unaffected by HIF-1 deletion in all lines. However, in agreement with the permeability data, immunofluorescence and electron microscopy showed clear prevention of hypoxia-induced tight junction disruption in the pericyte loss of function line. Conclusion This study shows that pericyte but not astrocyte HIF-1 stabilization modulates endothelial tight junction functionality and thereby plays a pivotal role in hypoxia-induced vascular dysfunction. Whether the cells respond similarly or differentially to other injury stimuli will be of significant relevance.

Circulating levels of hypoxia-inducible factor-1α and miR-210 are associated with photosensitivity in systemic lupus erythematosus patients

Background: miR-210, a key HypoxamiR, regulates the hypoxia and inflammation-linked hypoxia. Systemic lupus erythematosus (SLE), a chronic autoimmune disease, responsible for many pathological disorders, including photosensitivity. Objective: Finding the correlation between the circulating miR-210/HIF-1α levels and photosensitivity in SLE patients and other SLE-associated pathological complications, in a single-center case control study. Methods: Study population of 104 SLE Egyptian patients with photosensitivity, 32 SLE patients without photosensitivity, and 32 healthy subjects. SLE activity was assessed for all patients by SLE Disease Activity Index (SLEDAI). The clinical complications/manifestations and the hematological/serological analyses were recorded. HIF-α concentration was investigated by ELISA and miR-210 expression was analyzed by qRT-PCR. Results: The results revealed that circulating miR-210 was significantly increased in SLE/photosensitivity than SLE and controls. The additional occurrence of malar rash, oral ulcers, renal disorders or hypertension resulted in a higher expression of miR-210. SLEDAI activity status showed no effect on miR-210. Erythrocyte sedimentation rate, white blood cells, hemoglobin, platelets, the patients age and the disease duration were positively correlated with circulatory miR-210. HIF-α concentration was significantly induced in SLE/photosensitivity than SLE and controls. In SLE/photosensitivity, presence of renal disorders and hypertension resulted in highest HIF-α concentrations. A strong positive correlation was recorded between HIF-α concentration and circulatory miR-210 in SLE/photosensitivity patients (r = 0.886). Conclusion:: The dysregulation of circulating miR-210/ HIF-1α levels in SLE/photosensitivity‎ patients is controlled by the presence of additional pathological complications and supposed that hypoxia pathway might interact positively with the pathogenesis and illness progress of SLE.

HIF-1 Interacts with TRIM28 and DNA-PK to release paused RNA polymerase II and activate target gene transcription in response to hypoxia

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that acts as a regulator of oxygen (O2) homeostasis in metazoan species by binding to hypoxia response elements (HREs) and activating the transcription of hundreds of genes in response to reduced O2 availability. RNA polymerase II (Pol II) initiates transcription of many HIF target genes under non-hypoxic conditions but pauses after approximately 30–60 nucleotides and requires HIF-1 binding for release. Here we report that in hypoxic breast cancer cells, HIF-1 recruits TRIM28 and DNA-dependent protein kinase (DNA-PK) to HREs to release paused Pol II. We show that HIF-1α and TRIM28 assemble the catalytically-active DNA-PK heterotrimer, which phosphorylates TRIM28 at serine-824, enabling recruitment of CDK9, which phosphorylates serine-2 of the Pol II large subunit C-terminal domain as well as the negative elongation factor to release paused Pol II, thereby stimulating productive transcriptional elongation. Our studies reveal a molecular mechanism by which HIF-1 stimulates gene transcription and reveal that the anticancer effects of drugs targeting DNA-PK in breast cancer may be due in part to their inhibition of HIF-dependent transcription.

Hypoxia-inducible factor 1α induces osteo/odontoblast differentiation of human dental pulp stem cells via Wnt/β-catenin transcriptional cofactor BCL9

Accelerated dental pulp mineralization is a common complication in avulsed/luxated teeth, although the mechanisms underlying this remain unclear. We hypothesized that hypoxia due to vascular severance may induce osteo/odontoblast differentiation of dental pulp stem cells (DPSCs). This study examined the role of B-cell CLL/lymphoma 9 (BCL9), which is downstream of hypoxia-inducible factor 1α (HIF1α) and a Wnt/β-catenin transcriptional cofactor, in the osteo/odontoblastic differentiation of human DPSCs (hDPSCs) under hypoxic conditions. hDPSCs were isolated from extracted healthy wisdom teeth. Hypoxic conditions and HIF1α overexpression induced significant upregulation of mRNAs for osteo/odontoblast markers (RUNX2, ALP, OC), BCL9, and Wnt/β-catenin signaling target genes (AXIN2, TCF1) in hDPSCs. Overexpression and suppression of BCL9 in hDPSCs up- and downregulated, respectively, the mRNAs for AXIN2, TCF1, and the osteo/odontoblast markers. Hypoxic-cultured mouse pulp tissue explants showed the promotion of HIF1α, BCL9, and β-catenin expression and BCL9-β-catenin co-localization. In addition, BCL9 formed a complex with β-catenin in hDPSCs in vitro. This study demonstrated that hypoxia/HIF1α-induced osteo/odontoblast differentiation of hDPSCs was partially dependent on Wnt/β-catenin signaling, where BCL9 acted as a key mediator between HIF1α and Wnt/β-catenin signaling. These findings may reveal part of the mechanisms of dental pulp mineralization after traumatic dental injury.

A validated hypoxia-inducible factor (HIF) signature across tissue compartments predicts clinical outcome in human lung fibrosis

We previously reported that oxidative stress drives pseudohypoxic hypoxia-inducible factor (HIF) pathway activation to promote pathogenetic collagen structure-function in human lung fibrosis (Brereton et al., 2022). Here, through bioinformatic studies we investigate HIF pathway activation status in patients with idiopathic pulmonary fibrosis (IPF) and whether this has prognostic significance. Applying a well-established HIF gene expression signature, we classified publicly available datasets into HIF score-high and score-low groups across multiple tissue compartments. TheHIF scores in lung tissue, bronchoalveolar lavage (BAL) and peripheral blood mononuclear cells (PBMC) were increased in IPF patients and significantly correlated with an oxidative stress signature consistent with pseudohypoxic HIF pathway activation. A high HIF score in BAL and in PBMC was a strong independent predictor of mortality in multivariate analysis. Thus, a validated HIF gene signature predicts survival across tissue compartments in IPF and merits prospective study as a non-invasive biomarker of lung fibrosis progression.

Aquatic surface respiration improves survival during hypoxia in zebrafish ( Danio rerio ) lacking hypoxia-inducible factor 1-α

Hypoxia-inducible factor 1-α (Hif-1α), an important transcription factor regulating cellular responses to reductions in O 2 , previously was shown to improve hypoxia tolerance in zebrafish ( Danio rerio ). Here, we examined the contribution of Hif-1α to hypoxic survival, focusing on the benefit of aquatic surface respiration (ASR). Wild-type and Hif-1α knockout lines of adult zebrafish were exposed to two levels (moderate or severe) of intermittent hypoxia. Survival was significantly compromised in Hif-1α knockout zebrafish prevented from accessing the surface during severe (16 mmHg) but not moderate (23 mmHg) hypoxia. When allowed access to the surface in severe hypoxia, survival times did not differ between wild-type and Hif-1α knockouts. Performing ASR mitigated the negative effects of the loss of Hif-1α with the knockouts initiating ASR at a higher P O 2 threshold and performing ASR for longer than wild-types. The loss of Hif-1α had little impact on survival in fish between 1 and 5 days post-fertilization, but as the larvae aged, their reliance on Hif-1α increased. Similar to adult fish, ASR compensated for the loss of Hif-1α on survival. Together, these results demonstrate that age, hypoxia severity and, in particular, the ability to perform ASR significantly modulate the impact of Hif-1α on survival in hypoxic zebrafish.