Expression Patterns Of HIF-1α Research Articles

SUMOylation indirectly suppresses activity of the HIF-1α pathway in intestinal epithelial cells

The hypoxia-inducible factor (HIF) is a master regulator of the cellular transcriptional response to hypoxia. While the oxygen-sensitive regulation of HIF-1α subunit stability via the ubiquitin-proteasome pathway has been well described, less is known about how other oxygen-independent post-translational modifications impact the HIF pathway. SUMOylation, the attachment of SUMO (small ubiquitin-like modifier) proteins to a target protein, regulates the HIF pathway, although the impact of SUMO on HIF activity remains controversial. Here, we examined the effects of SUMOylation on the expression pattern of HIF-1α in response to pan-hydroxylase inhibitor dimethyloxalylglycine (DMOG) in intestinal epithelial cells. We evaluated the effects of SUMO-1, SUMO-2, and SUMO-3 overexpression and inhibition of SUMOylation using a novel selective inhibitor of the SUMO pathway, TAK-981, on the sensitivity of HIF-1α in Caco-2 intestinal epithelial cells. Our findings demonstrate that treatment with TAK-981 decreases global SUMO-1 and SUMO-2/3 modification and enhances HIF-1α protein levels, whereas SUMO-1 and SUMO-2/3 overexpression results in decreased HIF-1α protein levels in response to DMOG. Reporter assay analysis demonstrates reduced HIF-1α transcriptional activity in cells overexpressing SUMO-1 and SUMO-2/3, whereas pretreatment with TAK-981 increased HIF-1α transcriptional activity in response to DMOG. In addition, HIF-1α nuclear accumulation was decreased in cells overexpressing SUMO-1. Importantly, we showed that HIF-1α is not directly SUMOylated, but that SUMOylation affects HIF-1α stability and activity indirectly. Taken together, our results indicate that SUMOylation indirectly suppresses HIF-1α protein stability, transcriptional activity, and nuclear accumulation in intestinal epithelial cells.

Hypoxia‑inducible factor‑1α: A critical target for inhibiting the metastasis of hepatocellular carcinoma (Review)

Metastasis is one of the major reasons for patient mortality in hepatocellular carcinoma (HCC), and the progression of HCC to a metastatic state depends on the local microenvironment. Hypoxia is a key condition affecting the microenvironment of HCC. Currently, various studies have shown that the expression of hypoxia-ainducible factor-1α (HIF-1α) is associated with the invasion and metastasis of HCC. High expression of HIF-1α often leads to poor prognosis in patients with HCC. In this review, the molecular structure of HIF-1α is described, and the expression pattern of HIF-1α in HCC under hypoxia, which is associated with metastasis and poor prognosis in HCC, is explained. The molecular mechanisms of HIF-1α function and the metastasis of HCC are further discussed. The modulation of HIF-1α can reduce sorafenib resistance and improve the prognosis of patients after TACE. Therefore, HIF-1α may be a critical target for inhibiting HCC metastasis in the future.

The correlation between hypoxia-inducible factor-1α, matrix metalloproteinase-9 and functional recovery following chronic spinal cord compression

The molecular mechanisms underlying cervical spondylotic myelopathy (CSM) are poorly understood. To assess the correlation between HIF-1α, MMP-9 and functional recovery following chronic cervical spinal cord compression (CSCI). Rats in the sham group underwent C5 semi-laminectomy, while a water-absorbable polyurethane polymer was implanted into the C6 epidural space in the chronic CSCI group. Basso, Beattie and Bresnahan score and somatosensory evoked potentials were used to evaluate neurological function. Hematoxylin and eosin staining was performed to assess pathological changes in the spinal cord, while immunohistochemical analysis was used to examine HIF-1α and MMP-9 expression on days 7, 28, 42 and 70 post-surgery. Normal rats were only used for HE staining. The BBB score was significantly reduced on day 28 following CSCI, while SEPs exhibited decreased amplitude and increased latency. In chronic CSCI group, the BBB score and SEPs significantly improved on day 70 compared with day 28. HE staining revealed different level of spinal cord edema after chronic CSCI. Compared with the sham group, immunohistochemical analyses revealed that HIF-1α- and MMP-9-positive cells were increased on day 7 and peaked on day 28. HIF-1α and MMP-9 expression were demonstrated to be significantly positively correlated, whereas HIF-1α expression and BBB score were significantly negatively correlated, as well MMP-9 expression and BBB score. HIF-1α and MMP-9 expression are increased following chronic spinal cord compression and are positively correlated with one another. Decreased expression of HIF-1α and MMP-9 may contribute to functional recovery following CSCI. This expression pattern of HIF-1α and MMP-9 may give a new perspective on the molecular mechanisms of CSM.

Deregulation of LIMD1-VHL-HIF-1α-VEGF pathway is associated with different stages of cervical cancer.

To understand the mechanism of cellular stress in basal-parabasal layers of normal cervical epithelium and during different stages of cervical carcinoma, we analyzed the alterations (expression/methylation/copy number variation/mutation) of HIF-1α and its associated genes LIMD1, VHL and VEGF in disease-free normal cervix (n = 9), adjacent normal cervix of tumors (n = 70), cervical intraepithelial neoplasia (CIN; n = 32), cancer of uterine cervix (CACX; n = 174) samples and two CACX cell lines. In basal-parabasal layers of normal cervical epithelium, LIMD1 showed high protein expression, while low protein expression of VHL was concordant with high expression of HIF-1α and VEGF irrespective of HPV-16 (human papillomavirus 16) infection. This was in concordance with the low promoter methylation of LIMD1 and high in VHL in the basal-parabasal layers of normal cervix. LIMD1 expression was significantly reduced while VHL expression was unchanged during different stages of cervical carcinoma. This was in concordance with their frequent methylation during different stages of this tumor. In different stages of cervical carcinoma, the expression pattern of HIF-1α and VEGF was high as seen in basal-parabasal layers and inversely correlated with the expression of LIMD1 and VHL. This was validated by demethylation experiments using 5-aza-2'-deoxycytidine in CACX cell lines. Additional deletion of LIMD1 and VHL in CIN/CACX provided an additional growth advantage during cervical carcinogenesis through reduced expression of genes and associated with poor prognosis of patients. Our data showed that overexpression of HIF-1α and its target gene VEGF in the basal-parabasal layers of normal cervix was due to frequent inactivation of VHL by its promoter methylation. This profile was maintained during different stages of cervical carcinoma with additional methylation/deletion of VHL and LIMD1.

Expression Pattern of HIF-1α and VEGF Supports Circumferential Application of Scatter Laser for Proliferative Sickle Retinopathy.

PurposeRetinal vascular occlusions in sickle cell anemia patients cause tissue ischemia and the release of angiogenic mediators that promote the development of retinal neovascularization, initiating proliferative sickle retinopathy (PSR). Laser photocoagulation (LPC) has emerged as the most common treatment for PSR. Nonetheless, only two randomized controlled clinical trials have evaluated the use of LPC for PSR, and both failed to definitively demonstrate efficacy of this approach. This may be due to a lack of knowledge regarding the appropriate location for placement of laser coagulations in PSR eyes. To help address this question, we examined the expression of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) in PSR eyes.MethodsThe expression pattern of HIF-1α and VEGF in PSR (n = 5) and control (n = 3) eyes was examined by immunohistochemistry in different retinal regions defined by the presence or absence of retinal vessels.ResultsHypoxia-inducible factor 1α and VEGF were expressed in the inner retina of 5/5 untreated PSR eyes adjacent to retinal neovascularization; expression of HIF-1α was not detected (and VEGF only lightly detected) in normal retinal and choroidal vasculature of 3/3 control eyes. Hypoxia-inducible factor 1α and VEGF were strongly expressed in retinal cells within avascular (nonperfused) retina, anterior to the boundary between perfused and nonperfused retina, as well as in posterior ischemic retina in the presence or absence of neovascular sea fans.ConclusionsIf the goal of LPC in PSR is to quench the expression of HIF-1–driven angiogenic mediators, our results support broad application of peripheral laser for its treatment.

Expression of Hypoxia-Inducible Factor-1α in the Infiltrative Belt Surrounding Hepatic Alveolar Echinococcosis in Rats.

Our main aims were to investigate hypoxia inducible factor-1α (HIF-1α) expression in the surrounding invasion range of hepatic alveolar echinococcosis (HAE) lesions and determine the pathological basis of angiogenesis. In total, 23 Wistar rats with hepatic echinococcus multilocularis infection were killed and their livers, which contained 27 HAE lesions, obtained. Specimen segments were generated from 119 paraffin blocks. Comparative analysis of the tissue samples containing HAE nodules and hepatic parenchyma of the surrounding region was performed with the immunohistochemical SP method in this animal experiment. Expression patterns of HIF-1α in the surrounding invasion range and the hepatic parenchyma were compared. The HIF-1α positive expression rate was 97.5% (116/119 samples). Expression of HIF-1α in the actively multiplying infiltrative region of the HAE lesions was significantly higher than that in hepatic parenchyma (P < 0.05). Overexpression of HIF-1α in the actively multiplying infiltrative region of HAE lesions in rats is closely related to angiogenesis and microvasculature. The sensitivity of HIF-1α facilitates its application as a representative maker of HAE. Our data indicate that the invasion range of HAE lesions is based on extrusion and compression, and induces anoxia and ischemia in hepatic tissue. Thus, HIF-1α provides a valuable index for evaluating HAE activity, and induces anoxia and ischemia in hepatic tissue.

Over-expression of thymosin β4 in granulomatous lung tissue with active pulmonary tuberculosis

Recent studies have shown that thymosin β4 (Tβ4) stimulates angiogenesis by inducing vascular endothelial growth factor (VEGF) expression and stabilizing hypoxia inducible factor-1α (HIF-1α) protein. Pulmonary tuberculosis (TB), a type of granulomatous disease, is accompanied by intense angiogenesis and VEGF levels have been reported to be elevated in serum or tissue inflamed by pulmonary tuberculosis. We investigated the expression of Tβ4 in granulomatous lung tissues at various stages of active pulmonary tuberculosis, and we also examined the expression patterns of VEGF and HIF-1α to compare their Tβ4 expression patterns in patients' tissues and in the tissue microarray of TB patients. Tβ4 was highly expressed in both granulomas and surrounding lymphocytes in nascent granulomatous lung tissue, but was expressed only surrounding tissues of necrotic or caseous necrotic regions. The expression pattern of HIF-1α was similar to that of Tβ4. VEGF was expressed in both granulomas and blood vessels surrounding granulomas. The expression pattern of VEGF co-localized with CD31 (platelet endothelial cell adhesion molecule, PECAM-1), a blood endothelial cell marker, and partially co-localized with Tβ4. However, the expression of Tβ4 did not co-localize with alveolar macrophages. Stained alveolar macrophages were present surrounding regions of granuloma highly expressing Tβ4. We also analyzed mRNA expression in the sputum of 10 normal and 19 pulmonary TB patients. Expression of Tβ4 was significantly higher in patients with pulmonary tuberculosis than in normal controls. These data suggest that Tβ4 is highly expressed in granulomatous lung tissue with active pulmonary TB and is associated with HIF-1α- and VEGF-mediated inflammation and angiogenesis. Furthermore, the expression of Tβ4 in the sputum of pulmonary tuberculosis patients can be used as a potential marker for diagnosis.

Regulation of the Hif-system by micro-RNA 17 and 20a – Role during monocyte-to-macrophage differentiation

MiRNAs are a class of endogenous tiny RNAs that act as inhibitors of translation or promote RNA degradation by duplex-formation within the 3′-UTR of target mRNAs. They play an important role during a wide range of cellular processes by fine-tuning of gene expression. The differentiation of monocytes to macrophages plays a pivotal role in physiological as well as pathophysiological processes such as atherosclerosis. Monocytes which can be found in well-oxygenated blood migrate into areas with a high inflammation, such as the atherosclerotic plaque. There, they differentiate into macrophages. Interestingly, macrophages were found mainly at hypoxic sites of the plaque. Key regulators for the adaptation to hypoxia are the hypoxia-inducible factors (Hif). Therefore the aim of the present study was to investigate the regulation of the Hif-system by miRNAs during the process of monocyte differentiation. The present study shows that during the differentiation of monocytes into macrophages a dramatically change in the expression pattern of Hif-1α and Hif-2α took place. This was associated with a downregulation of microRNAs encoded by the miR-17-92 cluster. An in silico analysis of the 3′-UTR of Hif-α subunits for binding sites of miRNAs was performed using different miRNA databases in concert with a secondary structure prediction algorithm. This analysis revealed that both 3′-UTRs contain binding sites for miRNAs of the miR-17-92 cluster. Transfection of HeLa cells with miR-17 and miR-20a led to an inhibition of Hif-1α and -2α mRNA and protein expression and a lowered Hif DNA binding activity. Using a Luciferase-Reporter assay, it could be shown, that both Hif-α subunits are targeted by miR-17 and miR-20a. Furthermore, miR-overexpression in primary human macrophages demonstrates the important role of this microRNA-mediated regulation of the Hif-system for adaption of macrophages to hypoxia.In conclusion, the present study shows that the Hif-system is activated during monocyte-to-macrophage differentiation. This activation is in part mediated by a miRNA-dependent mechanism, which seems to be crucial for the adaption of macrophages to hypoxia.

Expression of hypoxia inducible factor‐1α and vascular endothelia growth factor in vocal polyps

Long-term vocal overuse or sudden vocal-fold microvascular disruption may lead to the formation of a hypoxic zone of injury and the subsequent release of a cascade of cytokines in the vocal fold. To test this hypothesis, we investigated the expression and the role of hypoxia inducible factor-1α (HIF-1α) and vascular endothelia growth factor (VEGF) in the formation of vocal polyps. Expression patterns of HIF-1α and VEGF in surgical specimens of vocal polyps from 36 patients were analyzed using the immunohistochemistry and Western blot method. Normal vocal-fold mucosa from 26 patients who underwent total laryngectomy were collected and used as the control group. The expression of HIF-1α and VEGF were detected both in the vocal polyps group and the control group, while the expression of HIF-1α and VEGF levels were significantly higher when compared to normal vocal-fold mucosa (P < .05). The increased expression of HIF-1α in vocal polyps indicates that vocal fold overvibration induced hypoxia may play an important role in the pathogenetic mechanism of vocal polyps.

Abstract 452: The hypoxic response is differentially regulated in small cell lung carcinoma (SCLC) cells as compared to non-SCLC cells

Abstract Here we study the adaptive capacity of small cell lung carcinoma (SCLC) cells to hypoxia and the importance of activation of hypoxia-inducible factor (HIF) transcription factors in these cells. SCLC is an extremely aggressive tumor form and the 5-year survival rate for these patients is only approximately 9-15%. Regions of hypoxia (∼1% oxygen) often appear in solid tumors and are associated with aggressive tumor behaviour and poor outcome in several tumor forms. Tumor cells adapt to a hypoxic environment by changing the transcription of genes involved in a variety of processes, like angiogenesis, cell survival, and metabolism. This adaptive response is primarily regulated by the transcription factors HIF-1α and HIF-2α, which become stable at low oxygen levels. Studies using among others neuroblastoma, breast carcinoma and lung adenocarcinoma cells have demonstrated that HIF-1α primarily mediates the acute hypoxic response, whereas HIF-2α dominates during the more chronic phase of hypoxia. We investigated cell survival in a panel of SCLC cell lines cultured at different oxygen pressures. In these cells we also studied expression levels of well known hypoxia-driven genes using quantitative real-time PCR. Quantitative real-time PCR, Western blot and immunohistochemistry were used to characterise the expression of HIF transcription factors in SCLC cells as well as in SCLC specimens. In all experiments a panel of non-SCLC cells and neuroblastoma cells were included for comparison. Since tumor hypoxia correlates with poor prognosis it is important to elucidate how tumor cells adapt in response to hypoxia. Our results show that SCLC cells survive well at hypoxia, although the proliferation is somewhat reduced with lower oxygen pressure. Even though the SCLC cells have a high adaptive capacity, only a moderate up-regulation was observed for the investigated hypoxia-regulated genes at 1% oxygen. In addition, the expression patterns of HIF-1α and HIF-2α differ in SCLC as compared to non-SCLC, indicating that a “typical” adaptive response to hypoxia does not occur in SCLC cells. Based on these results a gene expression profile of hypoxic SCLC cells using microarray analyses are performed to further characterise the hypoxic adaptive response. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 452.

Gelsolin Regulates Cardiac Remodeling After Myocardial Infarction Through DNase I–Mediated Apoptosis

Gelsolin, a calcium-regulated actin severing and capping protein, is highly expressed in murine and human hearts after myocardial infarction and is associated with progression of heart failure in humans. The biological role of gelsolin in cardiac remodeling and heart failure progression after injury is not defined. To elucidate the contribution of gelsolin in these processes, we randomly allocated gelsolin knockout mice (GSN(-/-)) and wild-type littermates (GSN(+/+)) to left anterior descending coronary artery ligation or sham surgery. We found that GSN(-/-) mice have a surprisingly lower mortality, markedly reduced hypertrophy, smaller late infarct size, less interstitial fibrosis, and improved cardiac function when compared with GSN(+/+) mice. Gene expression and protein analysis identified significantly lower levels of deoxyribonuclease (DNase) I and reduced nuclear translocation and biological activity of DNase I in GSN(-/-) mice. Absence of gelsolin markedly reduced DNase I-induced apoptosis. The association of hypoxia-inducible factor (HIF)-1alpha with gelsolin and actin filaments cleaved by gelsolin may contribute to the higher activation of DNase. The expression pattern of HIF-1alpha was similar to that of gelsolin, and HIF-1alpha was detected in the gelsolin complex by coprecipitation and HIF-1alpha bound to the promoter of DNase I in both gel-shift and promoter activity assays. Furthermore, the phosphorylation of Akt at Ser473 and expression of Bcl-2 were significantly increased in GSN(-/-) mice, suggesting that gelsolin downregulates prosurvival factors. Our investigation concludes that gelsolin is an important contributor to heart failure progression through novel mechanisms of HIF-1alpha and DNase I activation and downregulation of antiapoptotic survival factors. Gelsolin inhibition may form a novel target for heart failure therapy.

Expression of Hypoxia Inducible Factor–1α, Macrophage Migration Inhibition Factor, Matrix Metalloproteinase–2 and −9, and Their Inhibitors in Hemodialysis Grafts and Arteriovenous Fistulas

It is well recognized that arteriovenous fistulas (AVFs) used for hemodialysis access have better primary patency rates with less restenosis than polytetrafluoroethylene (PTFE) grafts; however, the mechanism responsible for this is not known. Recent data suggest that hypoxia inducible factor-1 alpha (HIF-1 alpha) is associated with vascular restenosis, possibly through mechanisms that increase the production of macrophage migration inhibition factor (MIF), matrix metalloproteinase-2 (MMP-2) and MMP-9, and their inhibitors (tissue inhibitor of MMPs; TIMP). The present study tested the hypothesis that there are differences in the expression patterns of HIF-1 alpha, MIF, MMP-2, MMP-9, and TIMPs in specimens removed from patients with AVFs and PTFE grafts. Whole-vessel tissue samples were obtained from the vein distal to the vein-to-PTFE graft anastomosis and the proximal outflow vein (within 6 cm of the arteriovenous anastomosis) of AVFs from 17 patients who required a surgical revision for thrombosis and stenosis. Nonstenotic veins of four patients undergoing hemodialysis vascular access placement were used as controls. PTFE grafts (n = 6), AVFs (n = 6), and control samples (n = 3) underwent Western blot analysis and zymography. A separate group of five patients with PTFE hemodialysis grafts and one control subject were used for immunohistochemical analysis. Specimens from patients with PTFE grafts had significantly higher expression of HIF-1 alpha (P = .03), MIF (P = .02), TIMP-1 (P = .0006), pro-MMP-2 (P = .02), and pro-MMP-9 (P = .046) compared with control veins. The expression of only pro-MMP-9 was significantly higher in AVFs compared with control samples (P = .004). There was a significant increase in the expression of MIF (P = .007) and TIMP-1 (P < .0001) in PTFE graft specimens compared with AVFs. MIF and TIMP-1 were localized to the adventitia of the vein distal to the vein-to-PTFE graft anastomosis. There were major differences in the expression patterns of hypoxia (ie, HIF-1 alpha) and proteins regulated by HIF-1?, including MIF, pro-MMP-2, pro-MMP-9, and TIMP-1, in specimens removed from patients with PTFE grafts and AVFs. Understanding the role of HIF-1 alpha and these proteins in hemodialysis access failure can help improve outcomes.

Expression pattern of HIF1α mRNA in brain, heart and liver tissues of Tibet chicken embryos in hypoxia revealed with quantitative real-time PCR

The problem of hypoxia adaptation in high altitudes is an unsolved brainteaser in the field of the life sciences. As one of the best chicken breeds with adaptability to highland environment, the Tibet chicken, is genetically different from lowland chicken breeds. It is well known that hypoxia has significant impact on growth by inducing the expression of the alpha subunit of the heterodimeric transcription factor, hypoxia-inducible factor 1 (HIF1α). In the present study, HIF1α expression in brain, heart and liver tissues of the Tibet and Dwarf Recessive White chicken embryos were investigated at the different development stages of days 10, 17 and 20 by real-time PCR, and the expression pattern of HIF1α in chicken embryos of the two chicken breeds incubated under conditions of hypoxia (13% O2) and normoxia (21% O2) was studied. The incubation mortality of the Tibet chicken was lower than the Dwarf Recessive White chicken during the whole incubation in hypoxia, and the mRNA expression of HIF1α had presented the differences in three tissues. The results implied that the hypoxia adaptability of the Tibet chicken embryo was higher than the Dwarf Recessive White chicken, especially in the early stage (day 10) and at a later time (day 20) during the incubation period, but the mechanism of the oxygen transfer of embryos of mountain species is not completely understood, and hypoxia adaptability of the Tibetan chicken remains to be studied further.

Implication of Peritubular Capillary Loss and Altered Expression of Vascular Endothelial Growth Factor in IgA Nephropathy

Background/Aims: To determine the roles of peritubular capillary (PTC) loss and expression of vascular endothelial growth factor (VEGF) and its transcription factor, hypoxia-inducible factor-1 (HIF-1), in the progression of IgA nephropathy (IgAN), we analyzed the expression of VEGF and HIF-1, and the number of PTCs in patients with variable severity of IgAN. Methods: Renal biopsy specimens from patients with IgAN (n = 23) were classified according to interstitial injury score: grade 0 (0%), grade 1 (1–25%), grade 2 (25–50%) and grade 3 (50–100%). We examined the immunohistochemical expression of CD34, VEGF and HIF-1α. Results: VEGF was expressed in the cytoplasm of tubular epithelia, and VEGF-positive area significantly expanded in grades 1 (35.5 ± 5.9%, mean ± SD) and 2 (32.5 ± 5.9%) compared with grade 0 (23.4 ± 4.5%). The numbers of PTCs were significantly lower in grades 2 (559 ± 49/mm²) and 3 (510 ± 56/mm²) than grade 0 (708 ± 49/mm²). HIF-1α was weakly expressed in tubular epithelia in grade 0, increased with progression to grade 2, and markedly decreased in grade 3. It was also increased in pericapsular interstitial area in grade 1. The expression pattern of HIF-1α did not parallel that of VEGF. In renal biopsies of 5 control patients with minor glomerular abnormality, glomerular expression levels of VEGF and HIF-1α were similar to those of IgAN grade 0 kidneys. Conclusion: VEGF production was accelerated in the early stage of IgAN but it did not protect against PTC injury/loss. The lack of correlation between VEGF and HIF-1α expression suggests HIF-independent VEGF production in IgAN.

Early expression of hypoxia-inducible factor 1α in the chicken embryo

Hypoxia is known to regulate angiogenesis and tissue growth by the induction of the alpha subunit of the heterodimeric transcription factor, hypoxia-inducible factor 1. The expression pattern of HIF1α in both epithelial and mesenchymal structures of the chicken embryo through the first 7 days of development is reported here. HIF1α transcript is expressed diffusely throughout the neuroepithelium, limb, mesonephritic and cephalic mesenchyme, progressively becoming restricted to known proliferative zones of the central nervous system. Specific, strong expression is unexpectedly found in the endoderm of Sessel's pouch and in the ectoderm of both Rathke's pouch and the first branchial arch before the disappearance of the buccopharyngeal membrane.