Up-regulation of HIF-1α and VEGF Expression by Elevated Glucose Concentration and Hypoxia in Cultured Human Retinal Pigment Epithelial Cells

Summary： In order to explore the effect of high glucose concentration and high glucose concentration with hypoxia on the production of hypoxia-inducible factor-1α （HIF-1α） and vascular endothelial growth factor （VEGF）, human RPE cells were cultured in 5,56 mmol/L glucose （control group）, 5.56 mmol/L glucose with 150 !a mol/L COCl2 （hypoxic group）, 25 mmol/L glucose （high glucose group） and 25 mmol/L glucose with 150 μmol/L COCl2 （combination group）. RT-PCR was used to detect the expression of HIF-1α and VEGF mRNAs. Western blot analysis was used to measure the levels of HIF-1α and VEGF proteins. Although the small amount of HIF-1α protein was able to be detected in high glucose group but not in control group, there was no significant difference between the expression of HIF-1α mRNA of RPE cells in high glucose group and that of RPE cells in control group. As compared with RPE cells in control group, the mRNA expression and the protein synthesis of VEGF in high glucose group were up-regulated. As compared with RPE cells in hypoxic group, the expression of HIF-1α mRNA of RPE cells in combination group was not different, but the protein synthesis of HIF-1α, the mRNA expression and the protein synthesis of VEGF were more obviously up-regulated. In conclusion, high concentration glucose mainly influence the protein synthesis of HIF-1α of RPE cell, and HIF-1α protein is able to be accumulated in high concentration glucose. Under hypoxia, the HIF-1α protein induced by high concentration glucose is more stable, and the expression of VEGF is obviously increased. It is suggested that high concentration glucose may play a role in retinal neovascularization, especially at ischemia stage of diabetic retinopathy.     

Regulation of Hypoxic Response Elements on the Expression of Vascular Endothelial Growth Factor Gene Transfected to Rat Skeletal Myoblasts under Hypoxic Environment

The regulation of hypoxic response elements on the expression of vascular endothelial growth factor （VEGF） gene transfected to primary cultured rat skeletal myoblasts under hypoxic environment was investigated. pEGFP-C3-9HRE-CMV-VEGF vector was constructed with molecular biology technique and transfected to primary cultured rat skeletal myoblasts by lipofectamine in vitro. Gene expression of transfected myoblasts was detected by RT-PCR, Western blot and fluorescence microscope under different oxygen concentrations and different hypoxia time. The results showed that in hypoxia group, the VEGF gene bands were seen and with the decrease of oxygen concentrations and prolongation of hypoxia time, the expression of VEGF mRNA was obviously increased. Under hypoxic environment, the expression of VEGF protein in the transfected myoblasts was significantly increased. EGFP was expressed only under hypoxic environment but not under normoxic environment. It was concluded that hypoxia promoter could be constructed with HRE and regulate the expression of VEGF gene under hypoxic and normoxic environment, which could enhance the re- liability of gene therapy.     

Over-expression of hypoxia-inducible factor 1 alpha increases angiogenesis of LNCaP cells

Objective:To evaluate the effect of HIF-1 α over-expression on angiogenesis in human prostate cancer cells. Methods:LNCaP cells(a human prostate cancer cell line) were transfected with the recombinant plasmid pcDNA3.1(-)-HIF-1α with Lipofectamine 2000 system. The positive clones were selected by G418 being further confirmed by Western blot and immunofluorescence. The expression levels of VEGF, iNOS and Ang- Ⅱ were determined. Results:The expression of HIF-1α in the LNCaP/HIF1α cells was significantly increased in transfected cells, which induced the up-regulation of VEGF, iNOS, whereas Ang- Ⅱ expression remained un- changed. Conclusion :Over-expression of HIF-1α can induce angiogenesis proteins and may improve the angiogenesis potency of prostate cancer.     

Hypoxia-inducible factor-1 alpha regulates the role of vascular endothelial growth factor on pulmonary arteries of rats with hypoxia-induced pulmonary hypertension

Background Hypoxia-inducible factor-1α (HIF-1α) is one of the pivotal mediators in the response of lungs to decreased oxygen availability, and increasingly has been implicated in the pathogenesis of pulmonary hypertension. Vascular endothelial growth factor (VEGF), a downstream target gene of HIF-1α, plays an important role in the pathogenesis of hypoxic pulmonary hypertension and hypoxic pulmonary artery remodelling. In this study, we investigated the dynamic expression of HIF-1α and VEGF in pulmonary artery of rats with hypoxia-induced pulmonary hypertension. Methods Forty male Wistar rats were exposed to hypoxia for 0, 3, 7, 14 or 21 days. Mean pulmonary arterial pressure (mPAP), vessel morphometry and right ventricle hypertrophy index (RVHI) were estimated. Lungs were inflated and fixed for in situ hybridisation and immunohistochemistry. Results mPAP values were significantly higher than the control values after 7days of hypoxia ［(18.4±0.4) mmHg, P<0.05］. RVHI developed significantly after 14 days of hypoxia. Expression of HIF-1α protein increased in pulmonary arterial tunica intima of all hypoxic rats. In pulmonary arterial tunica media, HIF-1α protein was markedly increased by day 3 (0.20±0.02, P<0.05), reached the peak by day 7, then declined after day 14 of hypoxia. HIF-1α mRNA increased significantly after day 14 of hypoxia （0.20±0.02, P<0.05）. VEGF protein began to increase markedly after day 7 of hypoxia, reaching its peak around day 14 of hypoxia (0.15±0.02, P<0.05). VEGF mRNA began to increase after day 7 of hypoxia, then remained more or less stable from day 7 onwards. VEGF mRNA is located mainly in tunica intima and tunica media, whereas VEGF protein is located predominantly in tunica intima. Linear analysis showed that HIF-1α mRNA, VEGF and mPAP were correlated with hypoxic pulmonary artery remodelling. HIF-1α mRNA was positively correlated with VEGF mRNA and protein (P<0.01). Conclusion HIF-1α and VEGF are both involved in the pathogenesis of hypoxia-induced pulmonary hypertension in rats.     

Advances on hypoxia inducible factor-1

Hypoxia inducible factor-1 (HIF-1) was first discovered by Semenza et al1 in 1991 as a protein which could specifically bind to the oligonucleotide sequence of the erythropoietin gene enhancer.The dimmers of HIF-1 were isolated in the following year.As its subunits were found to be induced by hypoxic conditions,it was subsequently named as hypoxia inducible factor.2 HIF-1,commonly found in human and mammalian cells,also expressed in normoxic conditions.     

Effect of Yifei Huoxue Granule (益肺活血颗粒) on the proliferation of rat pulmonary artery smooth muscle cells upon exposure to chronic hypoxic conditions in vitro

Objective:To investigate the inhibitory effect of Yifei Huoxue Granule （益肺活血颗粒,YFHXG） on the hypoxia-induced proliferation of rat pulmonary artery smooth muscle cells（PASMCs） and its mechanism of decreasing pulmonary arterial pressure.Methods:Twenty male Sprague-Dawley（SD） rats were randomly divided into four groups:saline,and 0.66,3.30 and 16.50 g/kg of YFHXG groups,the saline and different concentrations of YFHXG were given twice daily for 7 days,respectively.Serum-pharmacology method was used in the preparation of YFHXG serum.Tissue block anchorage was employed in the primary culture of rat PASMCs.The PASMCs were randomly divided into normoxia group,hypoxia group,and hypoxia+YFHXG group （0.66,3.30 and 16.50 g/kg doses of YFHXG-treated serum groups,exposed to hypoxic condition）.PASMCs in normoxia and hypoxia group were cultured with saline serum,hypoxia+YFHXG groups were cultured with different concentrations of YFHXG serum.Cell viability was assessed with 3-（4,5-dimethylthiazol-2-yl）-2,5- diphenyltetrazolium bromide（MTT） assay.Cell cycle was analyzed using flow cytometry.In addition,hypoxia inducible factor-1-alpha（HIF-1α） protein expression was evaluated by immunocytochemistry analysis,the concentration of intracellular reactive oxygen species（ROS） and Ca²⁺ were determined by laser scanning confocal microscopy（LSCM）.Results:MTT assay and flow cytometry showed that hypoxia could directly activate the proliferation of PASMCs,while YFHXG dose-dependently inhibited hypoxia-induced proliferation of rat PASMCs.Immunocytochemistry showed that hypoxia enhanced HIF-1αprotein expression,and LSCM showed that hypoxia significantly increased intracellular ROS and Ca²⁺,while YFHXG decreased the expression of HIF- 1αand attenuated the hypoxia-induced increase in intracellular concentration of ROS and Ca²⁺.Conclusions: YFHXG could inhibit hypoxia-induced proliferation of rat PASMCs,which may decrease pulmonary arterial pressure and vascular remodeling.The anti-hypoxia effect of YFHXG may be explained by its regulation of HIF-1α expression and of the levels of intracellular ROS and Ca²⁺.     

Effects of TNF-α and curcumin on the expression of VEGF in Raji and U937 cells and on angiogenesis in ECV304 cells

Background To better understand the possibilities of antiangiogenic tumor therapy and to assess possible side effects, we investigated the effect of tumour necrosis factor （TNF）-α and curcumin on the expression of vascular endothelial growth factor （VEGF） in U937 and Raji cell lines and their effect on angiogenesis in a human umbilical vein endothelial cell （HUVECs）-derived cell line （ECV304）, and also the relationship between Notchl and VEGF. The aim of this study was to elucidate potential mechanisms controlling tumor neovascularization. Methods VEGF secreted by U937 and Raji cell lines was determined by ELISA. Angiogenesis was tested by network formation of endothelial cells on Matrigel. Levels of VEGF mRNA in U937 and Raji cells and Notchl mRNA levels in EV304 cells were determined by RT-PCR. Results Secretion of VEGF by U937 and Raji cells was increased by TNF-α treatment and suppressed by curcumin （P 〈 0. 01 ）. The mRNA expression of VEGF165 and VEGF121 （containing 165 and 121 amino acid residues, respectively） were detected in any fractions. TNF-α augmented the expression of VEGF165 and VEGF121 mRNA and curcumin reduced the expression （P 〈0. 01 ）. No networks or cords formed in control and curcumin groups. There was tube formation on matrigel in the supernatants of the Raji culture group and the supernatants groups treated by VEGF group and TNF-α in Raji cell. Notch1 mRNA was detected but there was no significant change in the VEGF group compared with control （P 〉 0. 05）. Conclusions Expressions of VEGF mRNA in U937 and Raji cells were increased by TNF-α and suppressed by curcumin. VEGF and TNF-α can induce angiogenesis, and curcumin can inhibit angiogenesis in ECV304 cells.     

Growth and activation of PI-3K/PKB and Akt by stromal cell-derived factor 1α in endometrial carcinoma cells with expression of suppressor endoprotein PTEN

Background Mutation or deletion in the phosphatase and tensin homologue deleted on chromosome ten （PTEN） gene has been identified as an important cause of endometrial carcinoma; stromal cell derived factor-1α （SDF-1α） exerts growth-promoting effects on endometrial cancer cells through activation of the PI-3 kinase/Akt pathway and downstream effectors such as extracellular-responsive kinase （ERK）. In this study, a plasmid containing the PTEN gene was transfected into Ishikawa cells to investigate the difference in growth and signal transduction between Ishikawa-PTEN and Ishikawa cells after SDF-1α stimulation, and to study mechanisms of the involvement of PTEN protein in endometrial carcinoma development. Methods Ishikawa cells were transfected with a plasmid （pLXSN-PTEN） containing the PTEN gene and a plasmid （pLXSN-EGFP） with enhanced green fluorescent protein （EGFP）. Cells were then screened to obtain Ishikawa-PTEN cells and Ishikawa-neo cells that can both stably express PTEN protein and EGFP. Expression of PTEN protein, phosphorylation levels of AKT and ERK （pAKT and pERK） and growth differences in Ishikawa-PTEN, Ishikawa-neo and Ishikawa cells before and after SDF-1α stimulation were then determined by Western blots and MTT assays. Results Western blot analysis showed that Ishikawa cells produced PTEN after transfection with the PTEN gene. At 15 minutes after SDF-1α stimulation, the pAKT level of Ishikawa-PTEN cells was lower than that of Ishikawa-neo cells and Ishikawa cells. There was no significant difference in pERK levels among the three cell lines. The positive effect of SDF-1α on Ishikawa-PTEN cells growth was markedly less than the effect on Ishikawa-neo and Ishikawa cells. However, in the absence of SDF-1α stimulation （baseline）, the pAKT level in Ishikawa-PTEN cells was less than that in Ishikawa cells. There was a significant difference in growth between the Ishikawa-PTEN cells and the Ishikawa-neo cells. Conclusions PTEN gene transfection can regulate the level of pAKT but not pERK in Ishikawa-PTEN cells. PTEN protein may suppress the growth-promoting effect of SDF-1α on endometrial carcinoma by inhibiting the PI-3K/AKT signal transduction pathway.     

Hypoxia Down-regulates Secretion of MMP-2, MMP-9 in Porcine Pulmonary Artery Endothelial and Smooth Muscle Cells and the Role of HIF-1

Summary： Primary cell culture, techniques of gene transfection, gelatin zymography, and Western blot were used to investigate the effect of hypoxia on the secretion of MMP 2 and MMP-9 in pulmonary artery endothelial cells （PAEC） and smooth muscle cells （PASMC）, and the role of HIF-1. Our results showed that （1） after exposure to hypoxia for 24 h, the protein content and activity of MMP-2 in the PAEC medium as well as these of MMP-2 and MMP-9 in PASMC medium （P〈0. 01 ） decreased significantly in contrast to those in normoxic group （P（0.05） ; （2） after transfection of wild type EPO3＇ enhancer, a HIF-1 decoy, the content and activity of MMP 2 and MMP-9 in hypoxic mediums became higher than those in normoxic group （P〈0. 01）, while transfection of mutant EPO3＇-enhancer didn＇t affect the hypoxia-induced down-regulation. It is concluded that hypoxia could inhibit the secretion and activity of MMP 2 and MMP-9 in PAEC and PASMC, which could he mitigated by the transfection of EPO3 ＇-enhancer and that H1F-1 pathway might contribute to hypoxia-induced down regulation of MMP-2 and MMP-9.     

Neuroprotective effect of exogenous vascular endothelial growth factor on rat spinal cord neurons in vitro hypoxia

Background Vascular endothelial growth factor （VEGF） is well known as a hypoxia-induced protein. That it markedly increased expression of VEGF and improvement of rat motor function after spinal cord injury suggested that VEGF could play a neuroprotective role in ischaemic tolerance. This study investigated whether vascular endothelial growth factor has direct neuroprotective effects on rat spinal cord neurons. Methods We employed primary cultures of embryonic rat spinal cord neurons, then administrated different concentrations of VEGF164 in the culture medium before hypoxia when the number of neurons was counted and the cell viability was detected by MTT. The neuronal apoptosis and expression of VEGF and its receptor genes were evaluated by terminal deoxynucleotidyl transferase mediated dUTP nick-end labelling （TUNEL） and immunohistochemistry. The VEGFR2/FLK-1 inhibitor, SU1498, was used to confirm whether the neuroprotective effect of VEGF was mediated through VEGFR2/Flk-1 receptors. Result In hypoxic conditions,the number and viability of neurons decreased progressively, while the number of TUNEL-positive cells increased along with the prolongation of hypoxic exposure. When the concentration of VEGF in cell culture medium reached 25 ng/ml, the cell viability increased 11% and neuronal apoptosis reduced to half, this effect was dose dependent and led to an approximately 25% increase in cell viability and about threefold decrease in TUNEL-positive cells at a maximally effective concentration of 100 ng/ml. In normal conditions, VEGF/Flk-1 but not VEGF/Flt-1 gene expressed at a low level： after hypoxia, the expression of VEGF/Flk-1, but not VEGF/Flt-1 was significantly increased. The protective effect of VEGF was blocked by the VEGFR2/Flk-1 receptor tyrosine kinase inhibitor, SU1498. Conclusions VEGF has direct neuroprotective effects on rat spinal cord neurons, which may be mediated in vitro through VEGFR2/Flk-1 receptors.     

The Effect of RhoC siRNA on the Invasiveness and Proliferation of Human Cervical Cancer Cell Line SiHa Cells

This study investigated the effect of RhoC GTPase on the proliferation and metastasis of cervical cancer cells, SiHa cells, in vitro. RhoC siRNA was introduced into SiHa cells to silence the RhoC gene. The mRNA and protein expression of RhoC, before and after RhoC siRNA transfection, was examined by RT-PCR and Western blotting, respectively. The proliferation and apoptosis of SiHa cells were examined by MTT assay and flow cytometry （FACS）, respectively. Adhesive rate was evaluated by Matrigel adhesive assay, and the invasive capability and migration capability were assessed by transwell invasive assay and migration assay, respectively. The results showed that after the RhoC siRNA transfection, the mRNA and protein expression of RhoC was down-regulated in SiHa cells. The down-regulation of RhoC GTPase did not affect the cell proliferation and apoptosis （P〉0.05）, but it did suppress SiHa cells＇ adhesion to matrigel （P〈0.01）, the invasive capability （P〈0.01） and the migration capability （P〈0.01）. It was concluded that RhoC obviously promotes the adhesion, invasion and migration of SiHa cells in vitro, but not proliferation and apoptosis, suggesting that RhoC plays an important role in the progression in cervical cancer.