RNA interference for HIF-1alpha inhibits foam cells formation in vitro

Macrophage-derived foam cells in atherosclerotic lesions are generally thought to play a major role in the pathology of the disease. Hypoxia-inducible factor-1alpha (HIF-1alpha) was recently found to play an important role in atherosclerosis. Here we applied RNA interference to study the role of HIF-1alpha in foam cell formation in vitro. Transfection of HIF-1alpha-siRNA reduced HIF-1alpha synthesis as measured on mRNA and protein level by real-time RT-PCR, Western blot. It was found that RNA interference for HIF-1alpha with small interfering RNAs (HIF-1alpha-siRNA) inhibits foam cell formation by the human monoblastic cell line (U937) which was treated with oxidized low-density lipoprotein (ox-LDL) while the majority of atherosclerosis-related genes, such as cyclooxygenase-2 (COX-2), vascular cell adhesion molecule-1 (VCAM-1), interleukin-1beta (IL-1beta), and so on, were down-regulated, through large scale gene expression analysis using DNA microarrays. These data demonstrate that induction of HIF-1alpha by atherogenic factors may be a key step in coordinating the cellular events that result in atherosclerotic lesions.     

Neovastat (AE-941) inhibits the airway inflammation via VEGF and HIF-2 alpha suppression

Vascular endothelial growth factor (VEGF) contributes to airway inflammation and angiogenesis in asthma. Hypoxia inducible factor (HIF), the most potent regulator of VEGF, is a heterodimer of a constitutively expressed beta subunit and an oxygen-regulated alpha subunit (HIF-alpha). Three HIF-alpha isoforms have been described, of which HIF-2 alpha are abundantly expressed in lung tissue. Neovastat is a naturally occurring inhibitor of angiogenesis derived from marine cartilage. We previously reported that Neovastat can inhibit the airway inflammation in asthma. In this study, we hypothesized that the anti-inflammatory effect of Neovastat is mediated with inhibition of VEGF and HIF-2 alpha. BALB/c mice were immunized subcutaneously and challenged with inhaled ovalbumin (OVA). Neovastat was administrated by gavage three times with 12-h interval, beginning at 30 min before OVA inhalation. VEGF concentration in bronchoalveolar lavage fluid was measured by ELISA. We evaluate the expression of VEGF and HIF-2 alpha in lung tissue by immunohistochemistry. Mice treated with Neovastat had significantly reduced inflammatory cell count in BAL fluid compared with untreated asthmatic mice. Furthermore, Mice treated with Neovastat showed significantly reduced VEGF and HIF-2 alpha expression on lung tissue. These results suggest that anti-inflammatory effects of Neovastat could be linked to inhibition of VEGF and HIF-2 alpha.     

ATP6V0C competes with von Hippel-Lindau protein in hypoxia-inducible factor 1alpha (HIF-1alpha) binding and mediates HIF-1alpha expression by bafilomycin A1

HIF-1alpha not only enables cells to survive under hypoxic conditions but also promotes cell cycle arrest and apoptosis. Therefore, its expression should be controlled at optimal levels in growing tumors. We recently reported that bafilomycin A1 exorbitantly expressed HIF-1alpha and induced the p21(WAF1/Cip1)-mediated growth arrest of tumors (Mol Pharmacol 70:1856-1865, 2006). In the present study, we addressed the mechanism underlying bafilomycin-induced HIF-1alpha expression. Bafilomycin stabilized HIF-1alpha under normoxic conditions without changes in intracellular pH. However, when ATP6V0C, the target protein of bafilomycin, was knocked down, this bafilomycin effect was significantly attenuated. Inversely, ATP6V0C expression increased HIF-1alpha levels in a gene dose-dependent manner. ATP6V0C competed with Von Hippel-Lindau protein in HIF-1alpha binding by directly interacting with HIF-1alpha, which was stimulated by bafilomycin. In confocal images, ATP6V0C was normally present in the cytoplasm but was translocated in company with HIF-1alpha to the nucleus by bafilomycin. The N-terminal end (amino acids 1-16) of HIF-1alpha was identified as the ATP6V0C-interacting motif. These results suggest that ATP6V0C, a novel regulator of HIF-1alpha, mediates HIF-1alpha expression by bafilomycin.     

Inducible expression of hypoxia-inducible factor 1alpha (HIF-1alpha) as a tool for studying HIF-1alpha-dependent gene regulation during normoxia in vitro

The hypoxia-inducible factor 1alpha (HIF-1alpha), a member of the PAS superfamily, is a global regulator of cellular and systemic O(2) homeostasis as well as embryonic development. As the activity of HIF-1alpha is increased by a lowered oxygen tension in vivo and in vitro, we established a cell line producing high amounts of HIF-1alpha under normoxic conditions. As this overexpression was inducible by doxycycline, we can now provide a system to study HIF-1alpha-dependent gene regulation under normoxic as well as hypoxic conditions. We were able to show that the doxycycline-induced induction of the target gene HIF-1alpha--followed by the message of its target genes erythropoietin and vascular endothelial growth factor--is a dose- and time-dependent process. As the inducible overexpression of HIF-1alpha did not increase the rate of apoptosis, it provides a helpful new tool in drug discovery and tumor research to differentiate between hypoxia-dependent and hypoxia-independent pathways during HIF-1alpha-dependent gene regulation and HIF-1alpha-dependent effects on apoptosis.     

Berberine inhibits the interleukin-1 beta-induced inflammatory response via MAPK downregulation in rat articular chondrocytes

Osteoarthritis (OA) is one of the most chronic degenerative arthritic diseases, which gradually results in chondrocyte changes, articular cartilage degeneration, subchondral bone sclerosis, joint pain, swelling, and dysfunction. Berberine (BBR) has various confirmed biological activities, such as anti-inflammatory and antioxidant activities. However, the effect of BBR on the production of inflammation-associated proteins, including inducible nitric oxide synthase (iNOS), cyclooxygenase (Cox)-2, metalloproteinases (MMPs), Collagen II, TNF-α, and IL-6 via the MAPK (mitogen-activated protein kinases) pathway in IL-1β-stimulated rat chondrocytes, has not yet been studied. Thus, the purpose of this study was to evaluate whether BBR would decrease the production of inflammation-associated proteins through the MAPK signal pathway. Rat chondrocytes were cultured and pretreated with BBR at different concentrations (0, 25, 50, and 100 μM) and then stimulated with or without IL-1β (10 ng/mL). The mRNA expression of iNOS, COX-2, MMP-3, MMP-13, TNF-α, and IL-6 was measured by real-time polymerase chain reaction (RT-PCR), and the protein expression of iNOS, COX-2, Collagen II, MMP-3,MMP-13, and MAPKs were measured by Western blotting. The results showed that the expression of iNOS, COX-2, MMP-3, MMP-13, TNF-α, and IL-6 increased in the IL-1β-treated group and BBR showed an ability to inhibit the elevated expression under the pretreatment. Furthermore, the IL-1β-induced downregulation of Collagen II could be ameliorated by BBR. Moreover, the expression of MAPKs was significantly decreased by BBR. These results demonstrated that BBR had the anti-catabolic and anti-inflammation abilities that were through the MAPKs in IL-1β-induced rat chondrocytes. These findings may provide a novel therapeutic choice for treatment of OA using BBR.     

敌百虫经ERK1/2通路影响类固醇激素的合成

目的初步探讨细胞外信号调节激酶(ERK1/2)通路在敌百虫抑制小鼠睾丸间质细胞瘤细胞(MLTC-1)类固醇激素合成中的作用。方法运用放射免疫法检测不同浓度敌百虫及加入ERK1/2通路抑制剂UO126后对MLTC-1细胞孕酮合成的影响;采用蛋白质印迹技术(Western-blot)检测敌百虫对ERK1/2磷酸化表达的影响。结果敌百虫显著抑制MLTC-1细胞孕酮的合成,并且随敌百虫剂量的增加,孕酮合成量呈下降趋势;当同时加入UO126后,随敌百虫染毒剂量的升高孕酮合成量的下降趋势更为明显;敌百虫与UO126一样能明显抑制ERK1/2的磷酸化,而对总ERK1/2表达无明显影响。结论在本试验条件下,敌百虫能明显抑制MLTC-1细胞的孕酮合成,其机制可能是通过ERK1/2通路。     

HIF-1 alpha deficiency perturbs T and B cell functions

The immune system protects organisms from pathogens. The immune cells, in particular T- and B-lymphocytes, develop and acquire effector functions in specialized tissues called the lymphoid organs. The lymphoid organs exhibit lower oxygen tensions than the blood or the atmosphere. Furthermore, inflammatory and tumor environments where lymphocytes execute effector functions also have very low oxygen tensions. These findings led to the hypothesis that lymphocytes may have evolved adaptive mechanisms to function under hypoxic conditions. Cellular responses to hypoxia are triggered by the hypoxia inducible factor-1 alpha (HIF-1 alpha). In this paper we review the development and function of T- and B-lymphocytes in the absence HIF-1 alpha. Our studies suggest that HIF-1 alpha deficiency depresses the function of cytotoxic T-lymphocytes and blocks B-cell development in the bone marrow. B1 lymphocytes of fetal origin, on the other hand, accumulate and may produce auto-antibodies and autoimmunity.     

Inhibition of angiogenesis and HIF-1alpha activity by antimycin A1

We identified antimycin A1 as an inhibitor of the hypoxia-response element (HRE) from screening using a reporter under the control of HRE under hypoxic conditions. Antimycin A1 was effective at 20 pg/ml in inhibiting the reporter activity. The expression of vascular endothelial growth factor (VEGF) mRNA during hypoxia was also inhibited by antimycin A1. Angiogenesis induced by implantation of mouse sarcoma-180 cells was significantly inhibited by non-toxic doses of antimycin A1. Hypoxia inducible factor (HIF)-1alpha protein levels were significantly decreased by antimycin A1, but its mRNA level was not affected. Antimycin A1 is known to be an inhibitor of mitochondrial electron transport system, and depletion of mitochondria abolished antimycin A1-effect, at least in part. Inhibitors of proteasome or protein synthesis did not affect the decrease in HIF-1alpha level induced by antimycin A1. These results indicate that antimycin A1 inhibited angiogenesis through decrease in VEGF production caused by inhibition of HIF-1alpha activation.     

热休克蛋白60对动脉粥样硬化大鼠心肌血管内皮生长因子和缺氧诱导因子-1α表达的影响

目的研究口服热休克蛋白60（HSP60）对动脉粥样硬化（AS）大鼠心肌血管内皮生长因子（VEGF）和缺氧诱导因子-1α（HIF-1α）表达的影响。方法40只4周龄健康雄性SD大鼠,体质量（100±10）g。随机分为4组：健康对照组（C组）,AS未干预组（AS组）,造AS模型前口服HSP60组（HI组）,造模后口服HSP60组（H2组）,以上4组每组10只。本实验采用高脂饲料造AS模型,于大鼠180日龄时采血后处死,并取大鼠心肌作为标本。反转录一聚合酶链反应（RT—PCR）和免疫组织化学检测心肌VEGF和HIF-1α表达情况。结果C组、AS组、H1组、H2组大鼠心肌VEGFmRNA表达分别为：0．37±0．04,0．87±0．05,0．44±0．03,0．58±0．04;HIF-1αmRNA表达分别为：0．46±0．06,0．94±0．03,0．55±0．05,0．62±0．06;VEGF免疫组织化学阳性表达分别为：4．5±0．5,9．2±0．6,5．3±0．4,8．1±0．5;HIF-la免疫组织化学阳性表达分别为：5．8±0．7,13．9±0．4,7．0±0．6,10．4±0．8。结论As大鼠心肌VEGF和HIF-1Q表达较正常对照组增高,口服HSP60能降低VEGF和HIF-1α表达,即减轻心肌缺血缺氧性损伤和血管内皮炎症反应程度,而且越早口服,效果越好。     

Berberine protects against lipopolysaccharide-induced intestinal injury in mice via alpha 2 adrenoceptor-independent mechanisms

Aim:

To investigate the mechanisms responsible for the protective action of berberine (Ber) against gut damage in endotoxemic mice.

Methods:

Male BALB/c mice were administered intragastrically with distilled water (0.1 mL/10 g), Ber (50 mg/kg) alone, yohimbine (2 mg/kg) alone, or Ber (50mg/kg) in combination with yohimbine (2 mg/kg) for 3 d. On the third day, lipopolysaccharide (LPS, 18 mg/kg) or normal saline was intraperitoneally injected one hour after the intragastric administration. Following the treatment, intestinal injury in the ileum was histopathologically accessed; enterocyte apoptosis was examined using TUNEL method; Toll-like receptor 4 (TLR4) mRNA expression was measured using RT-PCR assay; inhibitor protein-κBα (I-κBα) phosphorylation and myeloperoxidase content were examined using Western blloting. The macrophage inflammatory protein-2 (MIP-2) production was measured using ELISA assay.

Results:

Mice challenged with LPS caused extensive ileum injury, including a significantly increased injury score, decreased intestinal villus height, reduced gut mucosal weight and increased intestinal permeability. Furthermore, LPS significantly induced enterocyte apoptosis, increased TLR4 mRNA expression, I-κBα phosphorylation, MIP-2 production and myeloperoxidase content in the ileum. Pretreatment with Ber significantly alleviated all the alterations in the ileum in the endotoxemic mice. Pretreatment with the α2-adrenoceptor antagonist yohimbine did not block the protective action of Ber against LPS-induced intestinal injury. In addition, treatment with yohimbine alone did not prevent LPS-induced intestinal injury.

Conclusion:

Pretreatment with Ber provides significant protection against LPS-induced intestinal injury in mice, via reducing enterocyte apoptosis, inhibiting the TLR4-nuclear factor κB-MIP-2 pathway and decreasing neutrophil infiltration that are independent of α2-adrenoceptors.     

Dihydrotestosterone inhibits tumor necrosis factor alpha induced interleukin-1alpha mRNA expression in rheumatoid fibroblast-like synovial cells

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects multiple synovial joints. Proinflammatory cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF)alpha play important roles as principle inflammatory and destructive components of the disease. RA is known to be associated with significant gender differences in its prevalence and clinical features. We found that a potent androgen, 5alpha-dihydrotestosterone (DHT) inhibits IL-1alpha mRNA expression induced by TNFalpha and the DHT effect was inhibited by an androgen receptor antagonist, hydroxyflutamide (OHF). DHT inhibited the NF-kappaB activation induced by TNFalpha in a manner dependent on the androgen receptor (AR). These results suggest that DHT inhibits the TNFalpha-induced IL-1alpha mRNA expression by inhibiting NF-kappaB activation, and contributes to the gender differences of the disease.     

Berberine protects HK-2 cells from hypoxia/reoxygenation induced apoptosis via inhibiting SPHK1 expression

Renal ischemia reperfusion injury (RIRI) refers to the irreversible damage for renal function when blood perfusion is recovered after ischemia for an extended period, which is common in clinical surgeries and has been regarded as a major risk for acute renal failures (ARF) that is accompanied with unimaginably high morbidity and mortality. Hypoxia during ischemia followed by reoxygenation via reperfusion serves as a major event contributing to cell apoptosis, which has been widely accepted as the vital pathogenesis in RIRI. Preventing apoptosis in renal tubular epithelial cell has been considered as effective method for blocking RIRI. In this paper, we established a hypoxia/reoxygenation (H/R) injury model in human proximal tubular epithelial HK-2 cells. Here, we found increased SPHK1 levels in H/R injured HK-2 cells, which could be significantly down regulated after berberine treatment. Berberine has been reported to exert a protective effect on H/R-induced apoptosis of HK-2 cells. So, in our present study, we planned to investigate whether SPHK1 participated in the anti-apoptosis process of berberine in H/R injured HK-2 cells. Our study confirmed the protective effect of berberine against H/R-induced apoptosis in HK-2 cells through promoting cells viability, inhibiting cells apoptosis, and down-regulating p-P38, caspase-3, caspase-9 as well as SPHK1, while up regulating the ratio of Bcl-2/Bax. However, SPHK1 overexpression in HK-2 cells induced severe apoptosis, which can be significantly ameliorated with additional berberine treatment. We concluded that berberine could remarkably prevent H/R-induced apoptosis in HK-2 cells through down-regulating SPHK1 expression levels, and the mechanisms included the suppression of p38 MAPK activation and mitochondrial stress pathways.     

Inhibitory effect of 6-formylpterin on HIF-1alpha protein accumulation

Hypoxia-inducible factor-1 (HIF-1) is a main regulator of metabolic adaptation to hypoxia. HIF-1alpha is induced by hypoxia, or by hypoxia-mimicking reagents, such as desferrioxamine (DFX), under a normoxic condition. A xanthine oxidase inhibitor, 6-formylpterin (6FP), is reported to exert its functions on reactive oxygen species (ROS) modulation. In this study, we investigated the effect of 6FP on HIF-1alpha expression under a DFX-treated or hypoxic condition. 6FP decreased HIF-1alpha expression at the protein level, but not at the mRNA level, in a dose-dependent manner, and this suppressive effect was reversed by the antioxidant, N-acetyl-L-cysteine (NAC). Furthermore, the ROS generated by 6FP was reversed with NAC coincubation. These findings suggest that intracellular ROS generated by 6FP decreased the HIF-1alpha protein accumulation under a DFX-treated or hypoxic condition.