雷帕霉素对低氧下人HL-60细胞增殖和凋亡的影响

本研究拟通过小分子化合物氯化钴（CoCl2）模拟的低氧环境,探讨雷帕霉素（RPM）对该低氧下人急性髓细胞白血病HL-60细胞的生物学行为的影响。低氧模拟组、低氧雷帕霉素处理组、常氧雷帕霉素处理组HL-60细胞分别采用CoCl2、CoCl2／RPM、RPM进行处理,对照组为常氧下常规培养的HL-60细胞,处理及培养24h、48h、72h后收集细胞,采用倒置相差显微镜观察细胞生长状况,常规瑞氏染色后光学显微镜下观察细胞形态;MTT比色法检测各组细胞的活性和增殖能力;AnnexinV—FITC／PI双染法流式细胞术检测细胞凋亡。结果表明,与对照组细胞形态规则,胞核呈圆形或椭圆形相比,低氧模拟组和低氧雷帕霉素处理组细胞密度降低,生长明显受抑,细胞胞核呈不规则形或杆状,染色质粗糙,伴扭曲折叠等变化。各组间不同时问细胞增殖抑制率差异显著（P〈0．05）,低氧模拟组和低氧雷帕霉素处理组增殖抑制率随着处理时间延长而增大,且低氧雷帕霉素处理组的增殖抑制率大于低氧模拟组。与常氧下的对照组及雷帕霉素处理组比较,低氧的模拟组和雷帕霉素处理组诱导细胞发生较明显的凋亡,且后期72h低氧雷帕霉素处理组凋亡率显著高于模拟低氧处理组。以上结果表明,模拟低氧环境下,HL-60细胞生长明显受抑制,且诱导细胞凋亡;雷帕霉素可增强对低氧对细胞的生长抑制和诱导凋亡作用。     

雷帕霉素对内皮细胞迁移和血管内皮生长因子表达的影响

目的：研究不同浓度的雷帕霉素对体外培养的人血管内皮细胞（rE）4移及血管内皮生长因子（VEGF）表达的影响。方法：用含10％胎牛血清的细胞培养基（DMEM）培养正常VE细胞,用10nM,50nM,100nM和200nM的雷帕霉素孵育vE细胞24h,Westernbloting测定雷帕霉素对VE中mTOR和VEGF表达的影响,Transwell迁移模型观察不同浓度的雷帕霉素对内皮细胞迁移影响。结果：①雷帕霉素可显著抑制VE的迁移,除了在100riM之外,基本呈浓度依赖性的。100nM雷帕霉素对VE迁移的抑制作用显著减弱（P〈0．01）。②雷帕霉素对mTOR和VEGF165的表达呈浓度依赖性的抑制;而VEGF121的表达则是先升高后降低,在100nM雷帕霉素时表达最高,远远高于该浓度雷帕霉素时VEGF165的表达,可以解释100nM雷帕霉素时VE迁移抑制显著减轻的现象。结论：雷帕霉素抑制了VEGF165的表达,并且其对VE迁移抑制的效应主要由VEGF165表达减少所介导。VEGF121的表达在一定雷帕霉素浓度范围内可显著上调,从而显著改善了雷帕霉素诱导的VEGF165表达减少所致的内皮细胞迁移抑制。     

雷帕霉素对糖尿病肾病大鼠足细胞生物学行为及mTOR信号通路的影响

为了探究雷帕霉素对糖尿病肾病大鼠足细胞生物学行为及哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin,mTOR）信号通路的影响,采用链脲霉素腹腔注射构建糖尿病肾病大鼠模型,将正常大鼠体内取出的足细胞设为对照组,模型大鼠体内取出的足细胞设为糖尿病肾病模型组（DN组）,取2 mg·kg^-1雷帕霉素干预DN组足细胞,并将其设为雷帕霉素组（RAPA组）。采用3-（4,5-二甲基噻唑-2）-2,5-二苯基四氮唑溴盐[3-（4,5-dimethylthiahiazo-z-y1）-2,5-diphenytetrazoliumromide,MTT]法检测足细胞增殖水平,Transwell检测细胞迁移和侵袭能力,流式细胞术检测细胞凋亡水平,Western blot法检测上皮-间充质转化标志物[E-钙黏蛋白（E-cadherin）、N-钙黏蛋白（N-cadherin）、波形纤维蛋白（vimentin）]、mTOR和核糖体S6激酶1（S6K1）蛋白表达水平。结果显示,与对照组相比,DN组细胞增殖水平显著被抑制,细胞迁移、侵袭水平显著升高,细胞凋亡率显著增加,上皮-间充转标志物E-cadherin表达显著下调,N-cadherin和Vimentin表达显著上调,mTOR/S6K1信号通路被显著活化（P<0.05）。与DN组相比,RAPA组细胞增殖水平显著升高,细胞迁移、侵袭水平显著降低,细胞凋亡率显著降低,E-cadherin表达显著上调,N-cadherin和Vimentin表达显著下调,mTOR和S6K1的蛋白表达显著被抑制（P<0.05）。结果表明,雷帕霉素通过抑制mTOR信号通路,促进足细胞体外增殖,抑制细胞迁移、侵袭、凋亡和上皮-间充质转化,发挥对糖尿病肾病大鼠足细胞的保护作用。     

低氧条件下大鼠肺动脉平滑肌细胞中活性氧与低氧诱导因子-1α和细胞增殖的关系

在低氧条件下,观察大鼠肺动脉平滑肌细胞（pulmonary arterial smooth muscle cells,PASMCs）中活性氧（reactive oxygen species,ROS）的变化,探讨ROS的变化是否通过调控低氧诱导因子-4α（hypoxia-inducible factor 1α, HIF-1α）的表达影响PASMCs的增殖。采用组织块法原代培养大鼠PASMCs,分成3组：常氧组（21％O2,24h）,低氧组（5％O2,24h）,低氧＋Mn-TBAP组（5％O2,24h,Mn-TBAP是一种ROS清除剂）。用激光共聚焦显微镜荧光染色法检测细胞内ROS的变化;用RT-PCR和免疫组织化学方法分别测定HIF-1α mRNA和蛋白的表达;用MTT法检测细胞增殖程度。结果显示：（1）低氧组PASMCs内ROS水平明显高于常氧组（P〈0．05）,低氧＋Mn-TBAP组ROS水平明显低于低氧组（P〈0．05）,但仍高于常氧组（P〈0．05）;（2）低氧组及低氧＋Mn-TBAP组的HIF-1α mRNA和蛋白表达均高于常氧组（P〈0．05）,且低氧组表达高于低氧＋Mn-TBAP组（P〈0．05）;（3）低氧组细胞增殖明显高于常氧组和低氧＋Mn-TBAP组（P〈0．05）,低氧＋Mn-TBAP组细胞增殖高于常氧组（P〈0．05）。结果表明：在低氧条件下大鼠PASMCs中ROS水平明显升高,RROS的变化能够调节HIF-1α的表达,进而影响平滑肌细胞的增殖,提示ROS可能在肺动脉高压的发病机制和低氧信号转导中具有重要作用。     

雷帕霉素对内皮细胞迁移和血管内皮生长因子表达的影响

目的:研究不同浓度的雷帕霉素对体外培养的人血管内皮细胞(VE)迁移及血管内皮生长因子(VEGF)表达的影响。方法:用含10%胎牛血清的细胞培养基(DMEM)培养正常VE细胞,用10nM,50nM,100nM和200nM的雷帕霉素孵育VE细胞24 h,Western bloting测定雷帕霉素对VE中mTOR和VEGF表达的影响,Transwell迁移模型观察不同浓度的雷帕霉素对内皮细胞迁移影响。结果:①雷帕霉素可显著抑制VE的迁移,除了在100nM之外,基本呈浓度依赖性的。100nM雷帕霉素对VE迁移的抑制作用显著减弱(P<0.01)。②雷帕霉素对mTOR和VEGF165的表达呈浓度依赖性的抑制;而VEGF121的表达则是先升高后降低,在100nM雷帕霉素时表达最高,远远高于该浓度雷帕霉素时VEGF165的表达,可以解释100nM雷帕霉素时VE迁移抑制显著减轻的现象。结论:雷帕霉素抑制了VEGF165的表达,并且其对VE迁移抑制的效应主要由VEGF165表达减少所介导。VEGF121的表达在一定雷帕霉素浓度范围内可显著上调,从而显著改善了雷帕霉素诱导的VEGF165表达减少所致的内皮细胞迁移抑制。     

线粒体ATP敏感钾通道对大鼠肺动脉平滑肌细胞低氧诱导因子-1α表达及细胞增殖的作用

本文旨在探讨线粒体ATP敏感钾（mitochondrial ATP-sensitive K＋,MitoKATP）通道对大鼠肺动脉平滑肌细胞低氧诱导因子-1α（hypoxia inducible factor-1α,HIF-1α）表达和细胞增殖的影响。原代培养大鼠肺动脉平滑肌细胞,分为常氧对照组、常氧＋diazoxide（MitoKATP通道的选择性开放剂）组、常氧＋5-hydroxydecanoate（5-HD,MitoKATP通道的选择性阻断剂）组、低氧对照组、低氧＋diazoxide组、低氧＋5-HD组,共6组,分别应用罗丹明123荧光技术检测各组大鼠肺动脉平滑肌细胞的线粒体膜电位,免疫组化检测HIF-1α的表达及酶联免疫检测仪检测细胞增殖的变化。结果显示,常氧＋ diazoxide组与常氧对照组比较,罗丹明123荧光、HIF-1α表达及细胞增殖明显增强（P〈0．05）;低氧＋diazoxide组与低氧对照组比较,罗丹明123荧光、HIF-1α表达及细胞增殖明显增强（P〈0.05）：常氧＋5-HD组与常氧对照组比较,罗丹明123荧光、HIF-1α表达、细胞增殖没有明显变化（P〉0．05）;但低氧＋5-HD组与低氧对照组比较,罗丹明123荧光明显减弱、HIF-1α表达及细胞增殖有所减弱（P〈0．05）。结果提示：MitoKATP通道的开放能引起大鼠肺动脉平滑肌细胞线粒体膜去极化,并可以促进HIF-1α的表达及细胞增殖。     

低氧促进大鼠肺动脉平滑肌细胞Periostin表达及其信号转导机制

观察低氧对大鼠肺动脉平滑肌细胞（pulmonary artery smooth muscle cells,PASMCs）Periostin表达的影响及其相关信号转导机制。胶原酶I法原代培养PASMCs,经低氧（5％O2）分别处理PASMCs2,6,12,24h后,RT-PCR和Western blot法检测Periostin mRNA和蛋白表达。加入PI3K/Akt通路特异性抑制剂LY294002（10μmol／L）进行干预,Western blot分析比较不同条件下低氧处理24h后大鼠PASMCs中Periostin和Akt／P-Akt的蛋白表达。结果表日月,与常氧组比较,低氧处理6h组、12h组和24h纽Periostin mRNA和蛋白的表达均显著上升（P〈0．05,P〈0．01）,低氧处理后的PASMCs中Periostin mRNA和蛋白的表达逐渐升高：低氧处理2h组无显著差异（P〉0．05）。用LY294002对PASMCs处理,并低氧24h后,Periostin的表达被显著抑制（P〈0．01）,细胞P-Akt的表达下调（P〈0．05）,总Akt的蛋白表达没有明显差异（P〉0．05）。推测低氧可诱导大鼠PASMCs中Periostin mRNA和蛋白的表达上调。低氧可能通过激活P13K/Akt通路促进Akt的磷酸化,进而使Periostin在PASMCs中过表达,提示Periostin在低氧性PASMCs增殖过程中可能起着重要作用。     

低氧处理不同时间对人肺腺癌A549细胞增殖的影响 及相应缺氧模型探讨*

目的:观察低氧处理不同时间对人肺腺癌A549细胞增殖的影响,探讨合理的人肺腺癌细胞株A549体外模拟缺氧时间。方法:将人肺腺癌细胞A549细胞株在低氧环境下分别培养12 h、24 h、48 h、72 h,设置常氧对照组,通过CCK8法测定A549细胞存活率,RT-PCR和免疫印迹分别检测细胞缺氧诱导因子-1α(hypoxia-inducible factor-1α, HIF-1α)和血管内皮生长因子(vascularendothelial growth factor, VEGF)mRNA及蛋白的表达。结果:低氧24 h组A549细胞存活率最高,低氧48 h、72 h组A549细胞存活率呈时间依赖性明显下降(P0.001)。自低氧12 h起,A549细胞HIF-1αmRNA和VEGFmRNA的表达开始随低氧时间延长而显著增加(P均0.001);HIF-1α和VEGF蛋白表达自24 h开始随低氧时间延长而显著增加(P均0.001)。结论:低氧诱导的A549细胞存活率呈时间依赖性降低,而HIF-1α、VEGF表达呈时间依赖性增高,人肺癌细胞株A549缺氧模型最适时间为24 h。     

急性低氧和间断低氧习服对HepG2细胞内血管内皮细胞生长因子基因表达的影响

目的:观察急性低氧和间断低氧习服对人HepG2细胞内血管内皮细胞生长因子(VEGF)及转录因子低氧诱导因子-1α(HIF-1α)的mRNA和蛋白含量的影响及其可能的生物学意义.方法:HepG2细胞随机分为常氧对照组,急性低氧组和间断低氧习服组.采用Northern blot和Western blot分别检测不同组别HepG2细胞内VEGF和HIF-1α mRNA表达和蛋白含量的变化.结果:急性低氧诱导HepG2细胞内VEGF和HIF-1α基因的转录,增加两种蛋白在细胞内的含量.间断低氧习服组的细胞内VEGF和HIF-1α的mRNA含量分别为常氧对照组细胞的(108.6±17.7)%和(116.74±19.8)%,与常氧对照组相比无显著差异(P＞0.05);而其蛋白表达的含量分别为对照组细胞的1.4和2.7倍,都明显低于急性低氧组细胞内两种蛋白的含量(P＜0.05).结论:HepG2细胞达到低氧习服状态后,抑制急性低氧对HepG2细胞内VEGF基因表达的促进作用,其中HIF-1α可能起着重要的调节作用.     

低氧对少突胶质前体细胞增殖的影响

目的：观察低氧／复氧和间歇性低氧时少突胶质前体细胞（O2A）增殖的影响。方法：取混合培养4d的胶质细胞。按实验分为低氧／复氧、间歇性低氧和常氧3组,低氧／复氧组细胞置低氧环境（3％O2）中分别培养1h、2h、3h、4h、8h、12h、24h、48h和72h后取出,恢复常氧培养至9d。间歇性低氧组每天上午定时将细胞置于低氧环境中分别培养1h、2h、3h、4h后取出。恢复常氧培养。每天一次,分别重复1～4次后。常氧培养至9d。然后同时取出各组细胞,进行O2A细胞的分离纯化和细胞计数。结果：低氧／复氧1h、2h、3h组和间歇性低氧1h、2h、3h组,O2A细胞数均较常氧组明显增多。结论：低氧／复氧和间歇性低氧都可促进体外培养的O2A细胞明显增殖。其机制尚有待于进一步研究。     

Myocardial Hypertrophy Overrides the Angiogenic Response to Hypoxia

Background

Cyanosis and myocardial hypertrophy frequently occur in combination. Hypoxia or cyanosis can be potent inducers of angiogenesis, regulating the expression of hypoxia-inducible factors (HIF), vascular endothelial growth factors (VEGF), and VEGF receptors (VEGFR-1 and 2); in contrast, pressure overload hypertrophy is often associated with impaired pro-angiogenic signaling and decreased myocardial capillary density. We hypothesized that the physiological pro-angiogenic response to cyanosis in the hypertrophied myocardium is blunted through differential HIF and VEGF-associated signaling.

Methods and Results

Newborn rabbits underwent aortic banding and, together with sham-operated littermates, were transferred into a hypoxic chamber (FiO₂ = 0.12) at 3 weeks of age. Control banded or sham-operated rabbits were housed in normoxia. Systemic cyanosis was confirmed (hematocrit, arterial oxygen saturation, and serum erythropoietin). Myocardial tissue was assayed for low oxygen concentrations using a pimonidazole adduct. At 4 weeks of age, HIF-1α and HIF-2α protein levels, HIF-1α DNA-binding activity, and expression of VEGFR-1, VEGFR-2, and VEGF were determined in hypoxic and normoxic rabbits. At 6 weeks of age, left-ventricular capillary density was assessed by immunohistochemistry. Under normoxia, capillary density was decreased in the banded rabbits compared to non-banded littermates. As expected, non-hypertrophied hearts responded to hypoxia with increased capillary density; however, banded hypoxic rabbits demonstrated no increase in angiogenesis. This blunted pro-angiogenic response to hypoxia in the hypertrophied myocardium was associated with lower HIF-2α and VEGFR-2 levels and increased HIF-1α activity and VEGFR-1 expression. In contrast, non-hypertrophied hearts responded to hypoxia with increased HIF-2α and VEGFR-2 expression with lower VEGFR-1 expression.

Conclusion

The participation of HIF-2α and VEGFR-2 appear to be required for hypoxia-stimulated myocardial angiogenesis. In infant rabbit hearts with pressure overload hypertrophy, this pro-angiogenic response to hypoxia is effectively uncoupled, apparently in part due to altered HIF-mediated signaling and VEGFR subtype expression.     

Expression and role of factor inhibiting hypoxia-inducible factor-1 in pulmonary arteries of rat with hypoxia-induced hypertension

Hypoxia-inducible factor-1alpha subunit (HIF-1alpha) plays a pivotal role during the development of hypoxia-induced pulmonary hypertension (HPH) by transactivating it' target genes. As an oxygen-sensitive attenuator, factor inhibiting HIF-1 (FIH) hydroxylates a conserved asparagine residue within the C-terminal transactivation domain of HIF-1alpha under normoxia and moderate hypoxia. FIH protein is downregulated in response to hypoxia, but its dynamic expression and role during the development of HPH remains unclear. In this study, an HPH rat model was established. The mean pulmonary arterial pressure increased significantly after 7 d of hypoxia. The pulmonary artery remodeling index became evident after 7 d of hypoxia, while the right ventricular hypertrophy index became significant after 14 d of hypoxia. The messenger RNA (mRNA) and protein expression of HIF-1alpha and vascular endothelial growth factor (VEGF), a well-characterized target gene of HIF-1alpha, were markedly upregulated after exposure to hypoxia in pulmonary arteries. FIH protein in lung tissues declined after 7 d of hypoxia and continued to decline through the duration of hypoxia. FIH mRNA had few changes after exposure to hypoxia compared with after exposure to normoxia. In hypoxic rats, FIH protein showed significant negative correlation with VEGF mRNA and VEGF protein. FIH protein was negatively correlated with mean pulmonary arterial pressure, pulmonary artery remodeling index and right ventricular hypertrophy index. Taken together, our results suggest that, in the pulmonary arteries of rat exposed to moderate hypoxia, a time-dependent decrease in FIH protein may contribute to the development of rat HPH by enhancing the transactivation of HIF-1alpha target genes such as VEGF.     

Quercetin suppresses hypoxia-induced accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) through inhibiting protein synthesis

Quercetin, a ubiquitous bioactive plant flavonoid, has been shown to inhibit the proliferation of cancer cells and induce the accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) in normoxia. In this study, under hypoxic conditions (1% O(2)), we examined the effect of quercetin on the intracellular level of HIF-1alpha and extracellular level of vascular endothelial growth factor (VEGF) in a variety of human cancer cell lines. Surprisingly, we observed that quercetin suppressed the HIF-1alpha accumulation during hypoxia in human prostate cancer LNCaP, colon cancer CX-1, and breast cancer SkBr3 cells. Quercetin treatment also significantly reduced hypoxia-induced secretion of VEGF. Suppression of HIF-1alpha accumulation during treatment with quercetin in hypoxia was not prevented by treatment with 26S proteasome inhibitor MG132 or PI3K inhibitor LY294002. Interestingly, hypoxia (1% O(2)) in the presence of 100 microM quercetin inhibited protein synthesis by 94% during incubation for 8 h. Significant quercetin concentration-dependent inhibition of protein synthesis and suppression of HIF-1alpha accumulation were observed under hypoxic conditions. Treatment with 100 microM cycloheximide, a protein synthesis inhibitor, replicated the effect of quercetin by inhibiting HIF-1alpha accumulation during hypoxia. These results suggest that suppression of HIF-1alpha accumulation during treatment with quercetin under hypoxic conditions is due to inhibition of protein synthesis.     

低氧诱导因子-1α在低氧促成肌细胞增殖中的作用

目的:探讨低氧对大鼠骨骼肌成肌细胞(SkMs)增殖的影响及低氧诱导因子(HIF-1α)在低氧促成肌细胞增殖中的相关机制。方法:采用流式细胞仪观察了3、10%O2对SkMs细胞数量和增殖指数的影响;用RT-PCR方法检测了HIF-1αmRNA的表达,用Western blot方法检测了SkMs胞浆、胞核及总HIF-1α蛋白的水平。结果:低氧组较常氧组细胞数量和增殖指数增加(P0.05);HIF-1αmRNA、总蛋白水平在常氧组和低氧组中没有明显差异,常氧下胞浆中HIF-1α蛋白水平高于胞核内,低氧下HIF-1α蛋白水平在胞核内高于胞浆。结论:低氧能够促进SkMs增殖,HIF-1α可能是通过氧浓度调控的核转位的方式参与了低氧促SkMs的增殖。     

Opposite effects of prostaglandin-J2 on VEGF in normoxia and hypoxia: role of HIF-1

The vascular endothelial growth factor (VEGF) is produced in response to hypoxia or inflammatory cytokines. In normoxia VEGF synthesis is upregulated by 15-deoxy-Delta(12,14)-prostaglandin-J(2) (15d-PGJ(2)) via induction of heme oxygenase-1 (HO-1). Here we compared the influence of 15d-PGJ(2) on VEGF expression in human microvascular endothelial cells in normoxia (approximately 20% O(2)) and hypoxia ( approximately 2% O(2)). Regardless of the oxygen concentration, 15d-PGJ(2) inhibited activity of hypoxia inducible factor-1 (HIF-1), the major hypoxic regulator of VEGF. However, in normoxic conditions 15d-PGJ(2) (1-10microM) activated the VEGF promoter and increased synthesis of the VEGF protein. Concomitantly, it strongly induced expression of HO-1. In contrast, in hypoxia, 15d-PGJ(2) decreased VEGF promoter activity and reduced VEGF release by 50%. Inhibition of HO-1 activity additionally attenuated VEGF synthesis in hypoxia. We conclude that induction of HO-1 by 15d-PGJ(2) results in augmentation of VEGF synthesis in normoxia. In hypoxia, however, the stimulatory effect of HO-1 is outweighed by 15d-PGJ(2)-mediated inhibition of the HIF-1 pathway.     

藏红花素抗心肌细胞低氧损伤作用及其机制研究

目的:探讨藏红花素(Crocin)对低氧心肌细胞的保护作用以及低氧诱导因子-1(HIF-1)和脯氨酰羟化酶(PHDs)的调控机制。方法:采用氯化钴(CoCl2)方法建立心肌细胞低氧损伤实验模型。应用Western blot方法检测心肌细胞HIF-1α、血管内皮生长因子(VEGF)、诱导型NO合酶(iNOS)以及PHD1、2、3蛋白表达的变化。结果:与CoCl2低氧组比较,Crocin可显著提高低氧心肌细胞活力。Crocin可进一步促使心肌细胞HIF-1α、及其下游靶基因VEGF、iNOS蛋白表达增强。Crocin可促使心肌细胞PHD2蛋白表达明显增加,PHD3蛋白表达则明显减少。结论:Crocin对低氧心肌细胞具有明显的保护作用,其作用机制与Crocin激活HIF-1介导的低氧反应通路有关,PHDs参与了该反应的病理生理调控过程。