Cyclic stretch affects pulmonary endothelial cell control of pulmonary smooth muscle cell growth

Endothelial cells are subjected to mechanical forces in the form of cyclic stretch resulting from blood pulsatility. Pulmonary artery endothelial cells (PAECs) produce factors that stimulate and inhibit pulmonary artery smooth muscle cell (PASMC) growth. We hypothesized that PAECs exposed to cyclic stretch secrete proteins that inhibit PASMC growth. Media from PAECs exposed to cyclic stretch significantly inhibited PASMC growth in a time-dependent manner. Lyophilized material isolated from stretched PAEC-conditioned media significantly inhibited PASMC growth in a dose-dependent manner. This inhibition was reversed by trypsin inactivation, which is consistent with the relevant factor being a protein(s). To identify proteins that inhibited cell growth in conditioned media from stretched PAECs, we used proteomic techniques and found that thrombospondin (TSP)-1, a natural antiangiogenic factor, was up-regulated by stretch. In vitro, exogenous TSP-1 inhibited PASMC growth. TSP-1-blocking antibodies reversed conditioned media-induced inhibition of PASMC growth. Cyclic stretched PAECs secrete protein(s) that inhibit PASMC proliferation. TSP-1 may be, at least in part, responsible for this inhibition. The complete identification and understanding of the secreted proteome of stretched PAECs may lead to new insights into the pathophysiology of pulmonary vascular remodeling.     

The effects of monocrotaline pyrrole on cultured bovine pulmonary artery endothelial and smooth muscle cells.

Monocrotaline pyrrole (MCTP), a reactive electrophile, induces delayed and progressive pulmonary edema, vascular remodeling, and pulmonary hypertension after a single intravenous administration to rats. The effects of a single exposure of cultured bovine pulmonary artery endothelial cells (BEC) and bovine pulmonary artery smooth muscle cells (BSMC) to MCTP were examined. Monocrotaline pyrrole caused a dose-dependent, delayed, and progressive cell detachment and release of lactate dehydrogenase activity from monolayers of BECs but not BSMCs. Monolayers of BECs also released increased concentrations of 6-keto-prostaglandin F1 degrees, the stable metabolite of prostacyclin, as the post-treatment interval increased. Progressive and marked endothelial cell hypertrophy occurred after exposure to a nominal concentration of 5 or 50 micrograms/ml of MCTP but not after 0.5 micrograms/ml. Morphologic changes in monolayers of BSMCs were minimal, even up to 2 weeks after exposure. Ultrastructurally the hypertrophic, MCTP-treated BECs had enlarged cell profiles with enlarged nuclei. The nucleoli were prominent, occasionally multiple, and had separation of granular and fibrillar components. Cytoplasmic microtubules and perinuclear intermediate filaments were prominent in some cells, as were the golgi apparatus and endoplasmic reticulum. Degenerative changes were not prominent in cells that remained in the monolayer. Monocrotaline pyrrole inhibited proliferation of both cell types at concentrations (0.5 micrograms/ml) that were not cytotoxic. These findings indicate that MCTP induces direct, dose-dependent injury to cells in culture that is delayed and progressive, and the expression of this injury depends, in part, on the cell type.     

Smooth muscle cell conditioned medium elevates angiotensin-converting enzyme of bovine pulmonary artery endothelial cells

Conditioned medium obtained from bovine pulmonary artery smooth muscle cells (SMC) in culture was found to elevate angiotensin-I-converting enzyme (ACE) of bovine pulmonary artery endothelial cells (EC) by 2- to 3-fold upon incubation for 24 to 48 h. The elevation in ACE was time dependent and inhibited by 10(-6) M cycloheximide, making it likely that the elevation was related to new protein synthesis by EC. Conditioned medium from EC failed to produce the same effect. The stimulatory effect of SMC conditioned medium on EC ACE was uninfluenced by exposures to anoxia as compared with room air, either during conditioning of medium or while assaying the effect of conditioned medium on EC ACE. Inhibitors of prostaglandin metabolism and calcium transport failed to influence the stimulatory effect of SMC conditioned medium on EC ACE. The stimulatory effect on EC ACE by conditioned medium was additive to that produced by Ca2+ ionophore A23187 and 3-isobutyl-1-methylxanthine and, similar to baseline ACE, was inhibited by 3 x 10(-8) M ouabain. Thus, SMC produce a factor that regulates the level of EC ACE.     

Hypoxia decreases expression of soluble guanylate cyclase in cultured rat pulmonary artery smooth muscle cells

Nitric oxide (NO) has an important role in modulating the pulmonary vascular tone. NO acts, in part, by stimulating soluble guanylate cyclase (sGC) to synthesize the intracellular second messenger cyclic GMP. In vascular smooth muscle cells, sGC is a heterodimer composed of alpha1 and beta1 subunits. The objective of this study was to test whether oxygen concentration regulates sGC expression in cultured rat pulmonary artery smooth muscle cells (rPaSMC). rPaSMC were exposed to 0, 3, and 20% oxygen for 1-48 h, and sGC subunit mRNA levels were measured. Compared with rPaSMC exposed to 20% oxygen, sGC alpha1 and beta1 subunit mRNA levels were markedly decreased in rPaSMC exposed to 0% and 3% oxygen. The decrease in sGC subunit mRNA levels in hypoxic rPaSMC was detected as early as 6 h of exposure. Compared with rPaSMC exposed to 20% oxygen, exposure of rPaSMC to 3% oxygen progressively decreased sGC subunit protein levels at 24 and 48 h. There was also a 30% and 50% decrease in sGC enzyme activity in cells exposed to hypoxia for 24 and 48 h (P < 0.05 and P < 0.001, respectively, as compared with cells maintained in normoxia). These results demonstrate that hypoxia decreases sGC expression in cultured pulmonary artery smooth muscle cells and suggest that, in hypoxic vascular smooth muscle, decreased cyclic GMP synthesis may limit the vasodilator response to NO.     

缺氧内皮细胞介导肺动脉平滑肌细胞血小板源性生长因子mRNA表达

目的探讨缺氧时肺动脉内皮细胞对肺动脉平滑肌细胞ＰＤＧＦ自分泌的影响。方法实验分３组：无血清培养组、常氧性内皮细胞条件培养液组及缺氧性内皮细胞条件培养液组。应用原位杂交和图像分析技术检测猪肺动脉平滑肌细胞ＰＤＧＦＡ和ＰＤＧＦＢ链ｍＲＮＡ表达。结果无血清培养的肺动脉平滑肌细胞有ＰＤＧＦＡ和ＰＤＧＦＢ链ｍＲＮＡ弱表达;内皮细胞条件培养液明显增加肺动脉平滑肌细胞ＰＤＧＦＡ和ＰＤＧＦＢ链ｍＲＮＡ表达,两者分别为无血清培养组的１．８倍和１．７倍（Ｐ＜０．０１）,为常氧内皮细胞条件培养液培养组的１．４倍和１．５倍（Ｐ＜０．０１）。结论缺氧时肺动脉内皮细胞可以介导肺动脉平滑肌细胞ＰＤＧＦ的自分泌,可能在缺氧性肺动脉高压血管构形改建中具有重要作用     

Hypoxia stimulates release of the soluble form of fas ligand that inhibits endothelial cell apoptosis

Fas ligand (FasL), an apoptosis-inducing cytokine, is constitutively expressed on endothelial cells (EC). Here, we report that the soluble form of FasL (sFasL) is released from EC and inhibits hypoxia-induced EC apoptosis. For hypoxia experiments, human EC were exposed to low oxygen tension in airtight chambers flushed with preanalyzed gas mixtures (1% oxygen, 5% CO2, 94% N2) at 37 degrees C. Exposure of cultured EC to hypoxia transiently increased FasL mRNA and protein levels. The maximum increase was observed at 3 and 6 hours after exposure to hypoxia, respectively. Although sFasL protein was not detected in the supernatant from EC without hypoxia, sFasL protein level in the supernatant was transiently increased from 6 hours and disappeared again at 24 hours after the exposure to hypoxia. Interestingly, the supernatant from hypoxia-exposed EC inhibited EC apoptosis induced by hypoxia, which was abolished by a neutralizing antibody against FasL. In addition, incubation with KB8301, an inhibitor of metalloproteinase, suppressed the release of sFasL from EC and enhanced hypoxia-induced apoptosis in EC. Furthermore, exogenously added recombinant sFasL inhibited hypoxia-induced apoptosis. These findings indicate that sFasL released from EC may inhibit hypoxia-induced EC apoptosis. Therefore, the shedding of FasL could be a new therapeutic target in regulating hypoxia-induced EC injury.     

低氧抑制猪肺动脉平滑肌细胞MMP-2和MMP-9的表达

目的探讨低氧对猪肺动脉平滑肌细胞（PASMC）分泌基质金属蛋白酶（MMPs）的影响。方法采用酶谱法测定PASMC培养基中MMP-2和MMP-9的酶活性，免疫印迹法检测培养基中MMP-2和MMP-9的蛋白表达，免疫组化法测定细胞原位MMP-2和MMP-9的蛋白表达，RT-PCR法检测mRNA的表达。结果低氧后PASMC分泌的MMP-2酶活性、细胞内外蛋白表达量、mRNA表达量均下降；MMP-9酶活性、细胞外蛋白表达量下降，而细胞内蛋白表达无变化。结论低氧可抑制PASMC分泌MMP-2和MMP-9的酶活性，其机制可能是低氧影响PASMC中MMP-2基因的转录、影响MMP-9蛋白表达后的分泌与活化，导致MMP-2和MMP-9酶活性的改变。     

血小板源生长因子可促进低氧的牛肺动脉平滑肌细胞核内NF-κB表达

目的:为探讨血小板源生长因子(platelet-derived growth factor,PDGF)受体信号转导途径的介质分子之一过氧化氢( H₂O₂ )在低氧的肺动脉平滑肌细胞(pulmonary artery smooth muscle cell,PASMC )增殖中是否起作用。方法:应用共聚焦显微镜、细胞免疫组织化学及Western印迹杂交等方法,检测了低氧的PASMC PDGF受体途径中的H₂O₂的变化及PDGF和H₂O₂对细胞核内与增殖作用相关的核转录因子NF-κB表达量的影响。 结果:PDGF可使常氧的PASMC中H₂O₂浓度增高,但明显降低低氧的PASMC中H₂O₂的量;同一浓度的H₂O₂,作用于常氧的PASMC,则引起核NF-κB的表达量增加,但对低氧的PASMC核NF-κB有明显的抑制作用;同时加入PDGF和H₂O₂的低氧的PASMC较仅以H₂O₂作用的低氧的PASMC,核NF-κB的量显著增加。结论:PDGF受体的信号转导途径在低氧的PASMC同常氧的PASMC相反,H₂O₂为抑制因子,对细胞可能产生损伤作用,PDGF可抑制低氧的PASMC产生H₂O₂并达到促进NF-κB表达增强的目的,从而使胞内与增殖相关的基因表达增强,最终达到低氧条件下表达增强的PDGF对低氧性PASMC过度增殖的正反馈调节作用。     

Regulation of glutathione by oxidative stress in bovine pulmonary artery endothelial cells

Glutathione plays important roles as an intracellular antioxidant and in the maintenance of cellular thiol-disulfide balance. In addition, glutathione may regulate cell growth signaling induced by oxidative stress. We previously reported that cellular glutathione is up-regulated by bleomycin in bovine pulmonary artery endothelial cells. The present study examined effects of hydrogen peroxide (H(2)O(2)) on cell growth and glutathione levels. Exogenous addition of H(2)O(2) induced biphasic effects on cell growth; 1 micro M was stimulatory and >10 micro M was inhibitory. However, both growth-promoting and inhibitory levels of H(2)O(2) increased cellular glutathione levels. Whereas 1 micro M H(2)O(2) moderately but significantly increased glutathione, 30 micro M caused a more substantial increase. Like bleomycin, both concentrations of H(2)O(2) activated DNA binding of antioxidant response element (ARE), a regulatory element in the promoter of the gamma-glutamylcysteine synthetase heavy chain subunit, a key regulator of glutathione synthesis. However, only high concentrations of H(2)O(2) activated p44/42 mitogen-activated protein (MAP) kinase. Thus, cellular glutathione is up-regulated by H(2)O(2), perhaps via activating ARE-binding factors in a mechanism independent of MAP kinase. H(2)O(2)-mediated increase in glutathione and activation of ARE binding may play important roles in growth and death of pulmonary artery endothelial cells.     

Hypoxia directly increases serotonin transport by porcine pulmonary artery endothelial cell plasma membrane vesicles

To determine whether hypoxia has a direct effect on the plasma membrane transport of serotonin (5-HT), we measured 5-HT transport activity: (1) in plasma membrane vesicles isolated from normoxic and hypoxic endothelial cells, (2) in endothelial cell plasma membrane vesicles that were exposed directly to normoxia or hypoxia, and (3) in endothelial cell monolayers incubated in the presence of 1 x 10(-7) M cycloheximide and exposed to normoxia or hypoxia. A 24-h exposure of endothelial cells to hypoxia resulted in a 40% increase (P less than 0.005) in specific 5-HT transport by plasma membrane vesicles derived from these cells. When plasma membrane vesicles were isolated and then directly exposed to normoxia or hypoxia for 1 h at 37 degrees C, a 31% increase (P less than 0.005) in specific 5-HT transport was observed in hypoxic vesicles. Hypoxia did not alter the Km of 5-HT transport (normoxia = 3.47 microM versus hypoxia = 3.76 microM) but markedly increased the maximal rate of transport (Vmax) (normoxia = 202.4 pmol/min/mg protein versus hypoxia = 317.9 pmol/min/mg protein). Cycloheximide alone had no effect on 5-HT transport by normoxic endothelial cells but did block hypoxia-induced increases in 5-HT uptake in endothelial cell monolayers exposed to 24-h hypoxia. These results indicate that hypoxia increases 5-HT transport in pulmonary artery endothelial cells by a direct effect on the plasma membrane, leading to an increase in the effective number of transporter molecules without alteration in transporter affinity for 5-HT, and possibly by an indirect effect involving de novo protein synthesis.     

Inhibition of pulmonary artery smooth muscle cell growth by hypoxanthine, xanthine, and uric acid.

We have previously reported that medium conditioned by hypoxic pulmonary artery endothelial cells (ECCM) contains a factor of small molecular weight that inhibits the growth of pulmonary artery smooth muscle cells (SMC). We postulated that this factor might be a breakdown product of ATP and, therefore, measured the levels of hypoxanthine/xanthine (HX/X) and uric acid (UA) in ECCM and cell lysates from endothelial cells (EC) exposed to hypoxia and normoxia. Although hypoxic and normoxic cell lysates contained no UA and an equal amount of HX/X (2.9 +/- 0.3 and 2.9 +/- 0.5 microM, respectively), there was a 5-fold increase in the amount of HX/X present in hypoxic compared with normoxic ECCM (3.4 +/- 0.3 versus 0.6 +/- 0.4 microM, respectively; P less than 0.001) but no difference in UA levels (5 +/- 2 versus 5 +/- 1 microM, respectively). In separate experiments, we examined the effects of exogenous HX, X, and UA (doses ranging from 0.1 to 100 microM) on the proliferation of pulmonary and aortic SMC and pulmonary artery EC. Our results indicate that HX, X, and UA inhibit the proliferation of SMC in a dose-dependent manner without causing injury to the cells. The proliferation of EC, on the other hand, was not affected by UA and was significantly inhibited by HX and X only at doses of 100 microM. In conclusion, we have found that significant amounts of HX/X accumulate in hypoxic ECCM and that HX, X, and UA inhibit the proliferation of SMC. The relevance of these findings to conditions where hypoxia prevails is discussed.     

Adrenomedullin expression and growth inhibitory effects in distinct pulmonary artery smooth muscle cell subpopulations

The vasodilator peptide adrenomedullin is elevated in patients with pulmonary hypertension and has been implicated in the inhibition of vascular remodeling. We questioned whether adrenomedullin is released by human pulmonary artery smooth muscle cells (PASMCs) and inhibits PASMC growth and release of endothelin, a known smooth muscle cell mitogen. The majority of PASMCs isolated from proximal pulmonary arteries and all PASMCs from distal pulmonary arteries released adrenomedullin, although at differing rates (mean, 177 +/- 28 and 62 +/- 11 fmol/10(5) cells/24 h, respectively). These cells were designated ADM+. However, some proximal PASMC isolates did not release adrenomedullin, designated ADM-. Northern blot analysis confirmed adrenomedullin expression in proximal ADM+ but not ADM- isolates. ADM- and distal ADM+ PASMCs proliferated faster in serum than did proximal ADM+ cells. Adrenomedullin potently and dose-dependently (mean EC(50) = 2.2 +/- 0.5 nM) increased intracellular cyclic adenosine monophosphate (cAMP) in ADM- isolates via specific adrenomedullin receptors. In contrast, both adrenomedullin and calcitonin gene-related peptide modestly elevated cAMP in 50% of ADM+ isolates. Adrenomedullin dose-dependently inhibited platelet-derived growth factor-stimulated [3H]thymidine incorporation and endothelin release in ADM- cells but did not affect [3H]thymidine uptake in ADM+ isolates. We conclude that distinct subpopulations of human PASMCs release and respond to adrenomedullin. The heterogeneity of adrenomedullin release and the inhibition of PASMC DNA synthesis and endothelin release suggest that adrenomedullin may function as a paracrine mediator in the inhibition of pulmonary vascular remodeling.     

缺氧对培养的猪肺动脉内皮细胞胞浆游离钙的影响

本文应用荧光探针Fura-2/AM测定胞浆游离钙浓度([Ca~(2+)]i)技术,观察培养的猪肺动脉内皮细胞[Ca~(2+)]i在缺氧时变化。实验发现:向细胞悬液中充氮气造成缺氧时,肺动脉内皮细胞[Ca~(2+)]i升高81±21%(P<0.05,n=8)。结果提示肺动脉内皮细胞钙信使系统可能参与缺氧所致血管反应。     

甲基苯丙胺滥用致肺动脉平滑肌细胞氧化性损伤

目的研究甲基苯丙胺(methamphetamine, MA)滥用是否可以诱导肺动脉平滑肌细胞发生氧化应激反应,引起氧化性损伤。方法取7日龄Wistar大鼠肺主动脉段进行肺动脉平滑肌细胞原代培养。将原代细胞(十代以内)给予不同浓度的MA(0.1, 0.5, 1, 3, 5mM)持续刺激36h后,采用流式细胞术检测ROS的含量,并采用western blot检测Nrf2、GCS和SOD2蛋白表达的变化。结果与对照组相比,ROS的产生随给药浓度的增大而增加;而抗氧化因子Nrf2和抗氧化酶GCS蛋白随着给药浓度的增加表达水平明显减弱,而氧化酶SOD2蛋白随着MA浓度的升高表达水平明显增加(P0.05)。结论甲基苯丙胺持续刺激肺动脉平滑肌细胞能抑制抗氧化作用,引起氧化/抗氧化系统失衡,诱导细胞产生氧化应激反应,产生氧化性损伤。     

Role of plasminogen activator inhibitor in the reciprocal regulation of bovine aortic endothelial and smooth muscle cell migration by TGF-beta 1.

Vascular endothelial and smooth muscle cells exhibit reciprocal migratory responses after transforming growth factor (TGF)-beta 1 treatment. Endothelial cells exhibit a decreased migratory rate and smooth muscle cells exhibit an increased migratory rate. Previous studies have demonstrated increases in extracellular matrix and integrin synthesis and expression in response to TGF-beta 1. In this report, we illustrate the roles of plasminogen activator inhibitor in modulating the migratory rates in these two cell types. Endothelial cells appear to require a proteolytic phenotype for rapid migration, whereas vascular smooth muscle cells appear to require an anti-proteolytic phenotype. Modulation of proteinase/anti-proteinase activity ratios was accomplished via TGF-beta 1 induction, addition of exogenous plasminogen activator inhibitor, addition of anti-catalytic antibodies directed against urokinase plasminogen activator, overexpression of plasminogen activator inhibitor utilizing stable transfectants, and the use of vitronectin as a substratum. The reciprocal migratory behaviors exhibited by these two vascular cell types in response to TGF-beta 1 is discussed in the context that these two vascular cell types utilize distinct adhesive and signaling pathways in their interactions with extracellular matrix components and responsiveness to proteolytic activity.     

Elevation of glutathione levels in bovine pulmonary artery endothelial cells by N-acetylcysteine.

N-Acetylcysteine (NAC), a cysteine derivative with chemoprotective and radioprotective effects, was found to elevate bovine pulmonary artery endothelial cell (EC) glutathione after in vitro incubation. The elevation in glutathione was associated with enhanced uptake of radioactivity of cystine from the medium. Because cystine in medium was converted rapidly to cysteine and cysteinyl-NAC in the presence of NAC and given that cysteine has a higher affinity for uptake by EC than cystine, we conclude that the enhanced uptake of radioactivity was in the form of cysteine and at least part of the stimulatory effect of NAC on EC glutathione was due to a formation of cysteine by a mixed disulfide reaction of NAC with cystine similar to that previously reported for Chinese hamster ovarian cells (R. D. Issels et al. 1988. Biochem. Pharmacol. 37:881-888). However, NAC was more effective than cysteine in elevating cellular glutathione at equimolar concentrations, and at higher concentrations of NAC an elevation of EC glutathione occurred even in the absence of cystine in the medium through a currently unknown mechanism. Thus, at least two mechanisms are operative in the elevation of endothelial cellular glutathione by NAC. NAC may be a useful compound for elevating glutathione of the pulmonary vasculature for protection against oxidant stress.     

不同方法培养大鼠肺动脉平滑肌细胞的性状

高血压、动脉粥样硬化、肺动脉高压等疾病均以血管平滑肌细胞的异常增生和迁移为特征。为此 ,近几年来 ,血管平滑肌细胞的培养已经成为研究工作的基础。目前 ,仍然多采用贴块片[1 ] 。因其方便经济、技术难度低 ,但贴块片确有不足之处 ,如细胞容易出现“去分化”或“调整”现象。故我们采用单纯胶原酶法 (Ａ)和复合胶原酶法 (Ｂ ,包括胶原酶弹性蛋白酶和胰蛋白酶抑制剂 )培养肺动脉平滑肌细胞 (ｐｕｌｍｏｎａｒｙａｒｔｅｒｉａｌｓｍｏｏｔｈｍｕｓｃｌｅｃｅｌｌ,ＰＡＳＭＣ) ,并初步观察两种方法培养的ＰＡＳＭＣ生长状况。材　料　和　…     

ET-1促进人血管平滑肌细胞的表型变化和增殖

目的：研究ET-1与VSMC表型变化和增殖的关系。方法：用MTT法研究ET—1对平滑肌细胞增殖的影响，^3H-TdR法测定ET-1对平滑肌细胞DNA合成的作用，流式细胞仪法观察对平滑肌细胞增殖周期的影响，逆转录聚合酶链法观察对平滑肌细胞表型变化的影响。结果：与对照组比较，ET-1明显促进平滑肌细胞增殖；促进平滑肌细胞DNA合成；促进平滑肌细胞从G0期向S期的转变，G0／G1期细胞百分比明显降低，而S期细胞百分比增加；促进平滑肌细胞的表型转化，从第2d到第7d随时间延长1-Caldesmon表达逐渐增高。结论：ET-1促进平滑肌细胞表型转化，同时对平滑肌细胞增殖亦有明显的促进作用。     

低氧对肺动脉平滑肌和内皮细胞蛋白激酶C α mRNA表达的影响

目的：探讨低氧对肺动脉平滑肌和内皮细胞蛋白激酶C(PKC)αmRNA表达的影响。方法：应用原位杂交技术了大鼠不同节段肺动脉平滑肌细胞和内皮细胞PKCαmRNA的分布及低氧对在体和离体肺动脉平滑肌细胞及内皮细胞PKCαmRNA表达的影响。结果：正常大鼠各级肺动脉平滑肌细胞和内皮细胞均有PKCαmRNA的表达,腺泡内肺动脉平滑肌细胞中的表达明显高于肌型肺动脉（P＜0．01）,低氧14d和28d肌型动脉和腺泡内肺动脉内皮细胞的表达均明显增高（P＜0．01）,腺泡内腺动脉平滑肌细胞的表达较对照组明显升高（P＜0．01）,低氧14d肌型肺动脉平滑肌细胞表达升高不明显,但低氧28d明显升高（P＜01）,正常条件下离体培养猪肺动脉平滑肌细胞和内皮细胞均有PKCαmRNA的表达,低氧1h对其表达无明显影响,48,72h表达明显升高,以72h升高最显著（P＜0．001）,结论：低氧可促进肺动脉平滑肌细胞和内皮细胞PKC amRNA 的表达,而以腺泡内肺动脉平滑肌细胞的变化最明显,PCKα在低氧性肺动脉高压的形成中可能起一定作用。