Epithelial exposure to hypoxia modulates neutrophil transepithelial migration

Polymorphonuclear leukocytes (PMN) are central to the pathogenesis of a number of intestinal diseases. PMN-induced damage to the protective epithelium occurs in hemorrhagic shock, necrotizing enterocolitis and conditions resulting in intestinal reperfusion injury. In such diseases, tissue hypoxia has been implicated as a pathophysiologic mediator. Thus, we hypothesized that exposure of intestinal epithelia to hypoxia may modulate PMN-epithelial interactions. In this study, T84 cell monolayers, a human intestinal crypt cell line, and isolated human PMN were used to examine the influence of hypoxia/reoxygenation (H/R) on PMN transepithelial migration. Confluent T84 cell monolayers were exposed to hypoxia (range 2-21% O2 for 0-72 h) and reoxygenated with buffer containing PMN. Transmigration of PMN (basolateral to apical orientation) was driven by a transepithelial gradient of the chemotactic peptide tMLP. In response to hypoxia/reoxygenation (H/R), transmigration into, and across epithelial monolayer was increased in a dose- (EC50 approximately 7% O2) and time-dependent fashion (3.5 +/- 0.3-fold increase at 2% O2 for 48 h, P < 0.001). Such conditions of H/R were not toxic to epithelia and did not influence epithelial barrier function. The influence of H/R on PMN transmigration was protein synthesis-dependent (> 80% decreased in the presence of cycloheximide) and could be inhibited by addition of functionally inhibitory antibodies to the PMN beta 2 integrin CD11b/18 (> 80% attenuated) and to CD47 (> 90% decreased compared to control). Hypoxia induced epithelial production and basolateral release of the PMN activating chemokine interleukin-8 (IL-8, nearly sixfold increase over normoxic control) which remained avidly associated with the epithelial matrix. Treatment of epithelial cells with IL-8 antisense oligonucleotides resulted in decreased monolayer-associated PMN but did not influence PMN transmigration, suggesting that epithelial IL-8 production may serve as a recruitment signal for PMN to the basal surface of polarized epithelia. The present observations indicate that H/R provides a relevant stimulus for novel biochemical crosstalk between epithelia and PMN.     

Response of the left ventricular connective tissue to hypoxia

The collagen content (measured as myocardial concentration of hydroxyproline) and dry weight (expressed as ventricle weight to body weight ratio) were determined in the left ventricle of male Sprague-Dawley rats (200--220 g b.wt.) exposed to a simulated altitude of 7,000 m for 18 h a day for 10 days in a hypobaric chamber. Hypoxia resulted in a significant increase (P less than 0.001) in the mass of the left ventricle with a concomitant significantly increased collagen concentration (P less than 0.001). The data indicate that hypoxia effects the synthesis of a significant amount of connective tissue in the left ventricle, which is the ventricle not exposed to pressure load. These results may be related to clinical, hemodynamic, and pathologic observations showing the left ventricular dysfunction in patients with chronic respiratory insufficiency. Since the amount of collagen in the left ventricle might interfere with contractile function, it is suggested that the hypoxia in these patients could affect the left ventricular myocardium via a direct action on the connective metabolism.     

大豆异黄酮耐缺氧的作用

目的:探讨大豆异黄酮对小鼠耐缺氧作用的影响及其机制。方法:①小鼠(n=40)随机分为4组,分别腹腔注射大豆异黄酮(0.4mg/g,0.8mg/g),15min后,将小鼠分别放入250mL的磨口广口瓶内密封,以最后一次呼吸为指标,观察小鼠存活时间。②小鼠(n=30)随机分为3组,分别腹腔注射大豆异黄酮(0.4mg/g,0.8mg/g),15min后,不需麻醉,用剪刀在耳下部快速断头,记录喘气时间。③小鼠(n=30)随机分为3组,对照组按0.03mL/g剂量给小鼠皮下注射生理盐水溶液,5min后按0.02mL/g剂量给小鼠腹腔注射生理盐水;模型组按0.015mg/g的剂量给小鼠皮下注射异丙肾上腺素,5min后按0.02mL/g剂量给小鼠腹腔注射生理盐水溶液。给药组按0.015mg/g剂量给小鼠皮下注射异丙肾上腺素,5min后腹腔注射大豆异黄酮(0.4mg/g)。给药后10min,分别放入广口瓶内密封,记录小鼠存活时间。结果:大豆异黄酮(0.4mg/g,0.8mg/g)能非常显著延长常压耐缺氧条件下小鼠的存活时间[(55.1±8.6)和(61.7±8.8)min],与对照组比较(42.1±6.3)min,差异均有显著性意义(t=2.778,3.462;P<0.05～0.01);大豆异黄酮(0.4mg/g,0.8mg/g)能显著延长断头小鼠的呼吸时间[(21.9±1.7)和(27.6±3.6)s],与对照组比较(18.1±1.0)s,差异有显著性意义(t=2.638,3.361;P<0.05～0.01);大豆异黄酮(0.1mg/g)能     

Antiinflammatory adaptation to hypoxia through adenosine-mediated cullin-1 deneddylation

A major adaptive pathway for hypoxia is hypoxic preconditioning (HPC), a form of endogenous protection that renders cells tolerant to severe challenges of hypoxia. We sought to define the antiinflammatory properties of HPC. cDNA microarray analysis of lung tissue from mice subjected to hypoxia or HPC identified a cluster of NF-κB–regulated genes whose expression is attenuated by HPC. Studies using an NF-κB luciferase reporter assay confirmed a significant suppression of NF-κB activation during HPC. HPC-elicited activity was conferrable, as a soluble supernatant from HPC-treated cells, and the active fraction was purified and identified as adenosine (Ado). Guided by recent studies demonstrating bacterial inhibition of NF-κB through cullin-1 (Cul-1) deneddylation, we found a dose-dependent deneddylation of Cul-1 by Ado receptor stimulation predominantly mediated by the Ado A2B receptor subtype. Further, siRNA-mediated repression of CSN5, a subunit of the COP9 signalosome responsible for deneddylation of Cul-1, partially reversed HPC-mediated inhibition of NF-κB. Cul-1 deneddylation was evident in a murine model of HPC and lost in animals lacking extracellular Ado (Cd73^–/– mice). Taken together, these results demonstrate that HPC induces extracellular accumulation of Ado and suppresses NF-κB activity through deneddylation of Cul-1. These results define a molecular regulatory pathway by which Ado provides potent antiinflammatory properties.     

Overcoming hypoxia to improve tissue‐engineering approaches to regenerative medicine

The current clinical successes of tissue engineering are limited primarily to low‐metabolism, acellular, pre‐vascularized or thin tissues. Mass transport has been identified as the primary culprit, limiting the delivery of nutrients (such as oxygen and glucose) and removal of wastes, from tissues deep within a cellular scaffold. While strategies to develop sufficient vasculature to overcome hypoxia in vitro are promising, inconsistencies between the in vitro and the in vivo environments may still negate the effectiveness of large‐volume tissue‐engineered scaffolds. While a common theme in tissue engineering is to maximize oxygen supply, studies suggest that moderate oxygenation of cellular scaffolds during in vitro conditioning is preferable to high oxygen levels. Aiming for moderate oxygen values to prevent hypoxia while still promoting angiogenesis may be obtained by tailoring in vitro culture conditions to the oxygen environment the scaffold will experience upon implantation. This review discusses the causes and effects of tissue‐engineering hypoxia and the optimization of oxygenation for the minimization of in vivo hypoxia. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel chimeric gene promoters responsive to hypoxia and ionizing radiation

Despite being an adverse prognostic factor in radiotherapy, hypoxia represents a physiological difference that can be exploited for selective cancer gene therapy. In this study gene therapy vectors responsive to both hypoxia and ionizing radiation (IR) were developed. Gene expression was regulated by novel, synthetic promoters containing hypoxia responsive elements (HREs) from the erythropoietin (Epo), the phosphoglycerate kinase 1 (PGK1) and the vascular endothelial growth factor (VEGF) genes, and IR-responsive CArG elements from the early growth response (Egr) 1 gene. All chimeric promoters could be activated by hypoxia and/or IR-treatment, and selectively control marker gene expression in human T24 bladder carcinoma and MCF-7 mammary carcinoma cells. Importantly, enhancers containing combinations of HREs and CArG elements were able to respond to both triggering treatments, with the Epo HRE/CArG combination proving to be the most responsive and robust. The Epo HRE/CArG enhancer could effectively control a suicide gene therapy strategy by selectively sensitizing hypoxic and/or irradiated cells expressing the enzyme horseradish peroxidase (HRP) to the prodrug indole-3-acetic acid (IAA). These data indicate that the use of such chimeric promoters may effectively regulate therapeutic gene expression within the tumor microenvironment in gene therapy strategies aimed at addressing the problem of hypoxia in radiotherapy.     

Renal and hormonal responses to acute hypoxia in normal individuals

We studied, in normal volunteers, the effects of 1 hour of hypoxia on the concentration of angiotensin-converting enzyme and bradykinins, along with previously measured parameters of renal and endocrine function. Ten men, 18 to 42 years of age, undergoing water diuresis, breathed a low-oxygen mixture (five breathed 10.5% O2 and five 12% O2); all breathed 21% O2 on a control day. Measurements included mean blood pressure and heart rate every 2 to 3 minutes; plasma levels of renin activity, aldosterone, arginine vasopressin, norepinephrine, and bradykinin, and angiotensin-converting enzyme activity, before and at the end of gas breathing; and urine volume (UV), creatinine, Na+, and bradykinin concentration. Arterial blood gases and effective renal plasma flow were determined at the end of gas breathing only. Mean values +/- SEM for arterial blood gases with low O2 were pH 7.39 +/- 0.02, PO2 46 +/- 2 torr, PCO2 39 +/- 2 torr (12% O2) and 7.48 +/- 0.01, 35 +/- 1 torr, 33 +/- 1 torr (10.5% O2). Responses were otherwise identical in both groups, and data were combined for analysis. With hypoxia, heart rate and effective renal plasma flow increased significantly, P less than 0.005; no changes occurred in Uv, urine Na+ concentration, glomerular filtration rate, plasma or urine bradykinin concentration, serum angiotensin-converting enzyme activity, plasma renin activity, plasma aldosterone concentration, plasma arginine vasopressin concentration, or plasma norepinephrine concentration.(ABSTRACT TRUNCATED AT 250 WORDS)     

The macrophage - a novel system to deliver gene therapy to pathological hypoxia

The use of activated macrophages in the treatment of cancer has been largely ineffectual. By 'arming' these cells with the ability to express a therapeutic gene we demonstrate significant advances in the efficacy of this approach. We have used a hypoxia-regulated adenoviral vector to transduce human macrophages with either a reporter or a therapeutic gene encoding human cytochrome P4502B6 (CYP2B6). Infiltration of transduced macrophages into a tumour spheroid results in induction of gene expression. We demonstrate significant tumour cell killing only in the presence of cyclophosphamide via activation by P4502B6 and show that this can be further targeted to tumours through hypoxia regulated gene expression. Gene Therapy (2000) 7, 255-262.     

低氧诱导因子在低氧应答及运动时的表达

目的:低氧诱导因子1是细胞在缺氧条件产生的核蛋白,它与靶基因结合,促进靶基因的转录,使机体产生一系列缺氧适应反应。对低氧诱导因子1的结构作用途径以及低氧诱导因子在低氧应答以及在运动时骨骼肌中的表达作一综述,以能够找到提高训练质量乃至运动水平的方法。资料来源:应用计算机检索PubMed1996-01/2003-06的相关文章,同时根据相关的参考文献检索了部分文章,检索词“hypoxiainduciblefactor-1,sport,hypoxia,skeletalmuscle”,限定语言种类为English。同时计算机检索http://www.cnki.net/index.htm1994/2003的相关文章,限定文章种类为中文,检索词“低氧诱导因子,运动,低氧,骨骼肌”。另外参考了2003香山科学会议———低氧与健康研究应受生物学和医学界关注(摘要汇编)。资料选择:对资料进行初审,选取实验包括低氧运动模型中关于低氧诱导因子在骨骼肌中的表达、作用及其含量的变化方面的文献,查找相关文献的全文,判断是否确实是相关研究。纳入条件:①随机对照实验研究。②实验包括对照组与干预组。排除条件:①综述文献。②重复的同一研究。资料提炼:共查找到26篇相关研究文章,18篇符合纳入标准。排除的8篇系为同一研究和综述文献。资料综合:通过18个实验对低氧运动模型中关于低氧诱导因子在骨骼肌中的表达、作用及其含量的变化方面作了相关的研究。结论:低氧诱导因子在低氧应答以及运动的骨骼肌中起着承上启下的作用,通过干预因素诱导/影响低氧因子的合成,乃至加强/减弱其链的作用。