Regulation of endothelin-1 production in cultured rat vascular smooth muscle cells

Endothelin-1 (ET-1) is secreted from all rat vascular smooth muscle cells (VSMCs) examined, in addition to endothelial cells (ECs). An average secretion rate of ET-1 from rat VSMCs was determined to be 10% that excreted from ECs. We examined the effects of 22 substances on ET-1 secretion from VSMCs and compared them with those from ECs. Transforming growth factor-beta1 (TGF-beta), acidic and basic fibroblast growth factors, epidermal growth factor, angiotensin II, and adrenaline stimulated ET-1 secretion from VSMCs, whereas forskolin, thrombin, and platelet-derived growth factor-BB reduced it. Only TGF-beta and phorbol ester elicited consistent effects on ET-1 secretion from VSMCs and ECs. Regulation of ET-1 and adrenomedullin secretion from VSMCs was distinctly different. These data suggest that ET- 1 production in VSMCs is regulated by a mechanism separate from that in ECs and from adrenomedullin production in VSMCs. Chromatographic analysis showed immunoreactive ET-1 secreted from VSMCs was mainly composed of big ET- 1, whereas approximately 90% of that from ECs was ET-1. By TGF-beta stimulation of VSMCs, the ratio of big ET-1 to ET-1 was further increased. Because big ET-1 is converted into ET-1 only on the surface of the ECs in the culture system, big ET-1 secreted from the VSMCs may function as a mediator transmitting a signal from VSMCs to ECs in vivo.     

高糖增强兔血管平滑肌细胞对内皮素—1的增殖反应性

目的;观察高糖对内皮素－１促兔主动脉血管平滑肌细胞增殖的影响。方法：ＶＳＭＣ分别培养于含正常葡萄糖,高糖或高渗的培养基中,「＾３Ｈ」胸腺嘧啶掺入法检测ＤＮＡ合成速率,蛋白质印迹法检测磷酸化ｐ４４／４２ ＭＡＰＫ的表达。结果：在１０＾－１２至１０＾－８ｍｏｌ．Ｌ＾－１浓度范围内,ＥＴ－１浓度依赖方式增加ＶＳＭＣ的「＾３Ｈ」胸腺嘧啶掺入及磷酸化ｐ４４／ｐ４２ＭＡＰＫ的表达。     

Cl~-通道在内皮素-1引起的血管平滑肌细胞增殖中的作用

目的　研究Cl-通道在内皮素 1(endothelin 1,ET 1)引起的血管平滑肌细胞增殖中的作用 ,并探讨其可能的作用机制。方法　通过细胞计数和3H TdR参入实验 ,并结合fura 2 /AM荧光测定胞浆游离Ca2 + 浓度 ([Ca2 + ]i)等技术 ,观察了Cl-通道阻断剂对ET 1引起的 [Ca2 + ]i 变化及血管平滑肌细胞增殖的影响。结果　Cl-通道阻断剂DIDS可呈浓度依赖性地抑制 10nmol·L-1ET 1引起的血管平滑肌细胞增殖 ,其它Cl-通道阻断剂如IAA 94、NPPB、SITS、DPC和速尿均无此作用 ,DIDS也能抑制 10nmol·L-1ET 1引起的内流相 [Ca2 + ]i 升高 ,而对ET 1引起的Ca2 + 释放无影响 ;预先将细胞与 1μmol·L-1nifedipine作用后 ,3μmol·L-1DIDS对 10nmol·L-1ET 1引起的内流相 [Ca2 + ]i 升高及血管平滑肌细胞增殖不再有效 ,将细胞与 10 μmol·L-1SK&F96 36 5预孵后 ,DIDS却能进一步抑制ET 1的上述作用 ;3μmol·L-1DIDS对 30mmol·L-1KCl引起的胞浆[Ca2 + ]i升高无影响。结论　DIDS可通过阻断Cl-通道来抑制ET 1因促发Cl-通道开放经电压依赖性钙通道的Ca2 +内流及细胞增殖 ,DIDS敏感的Cl-通道可能在ET 1促发的Ca2 + 内流及血管平滑肌细胞增殖的调控上都起着重要的作用     

高糖增强兔血管平滑肌细胞对内皮素-1的增殖反应性(英文)

观察高糖对内皮素－１（ＥＴ－１）促兔主动脉血管平滑肌细胞（ＶＳＭＣ）增殖的影响．方法： ＶＳＭＣ分别培养于含正常葡萄糖、高糖或高渗（５．５，２５，葡萄糖 ５．５＋甘露醇 １９．５ ｍｍｏｌ·Ｌ－１）的培养基中［３Ｈ］胸腺嘧啶掺入法检测ＤＮＡ合成速率，蛋白质印迹法检测磷酸化 ｐ４４／４２ ＭＡＰＫ的表达．结果：在 １０至 １０－８ｍｏｌ·Ｌ－１浓度范围内， ＥＴ－１以浓度依赖方式增加 ＶＳＭＣ的［３Ｈ］胸腺嘧啶掺入及磷酸化ｐ４４／４２ ＭＡＰＫ的表达，从 １０－１１到 １０－８ｍｏｌ·Ｌ－１，培养于高糖的 ＶＳＭＣ对相同浓度 ＥＴ－１的增殖反应性高于正常糖或高渗培养条件下的ＶＳＭＣ（Ｐ＜ ０．０５，或 Ｐ＜ ０．０１），而在后两种条件下，ＶＳＭＣ对ＥＴ－１的增殖反应无显著差别．同样，在高糖条件下，ＥＴ－１诱导的ＶＳＭＣ磷酸化ｐ４４／４２ＭＡＰＫ的表达较正常糖和高渗ＶＳＭＣ增加 ６０％－６５％结论：高糖增强ＶＳＭＣ对ＥＴ－１的增殖反应性，可能与磷酸化的 ｐ４４／４２ ＭＡＰＫ高表达有关     

Desensitization of angiotensin-stimulated inositol phosphate accumulation in human vascular smooth muscle cells

The effect of angiotensin II treatment on desensitization of phospholipase C (PLC)-mediated inositol phosphate accumulation has not been quantitated in human aortic vascular smooth muscle (HVSM) cells. We determined the angiotensin II pretreatment dose dependency and time course for desensitization of PLC activation in HVSM cells and the effect of protein kinase C (PKC) activators on angiotensin II-mediated inositol phosphate accumulation. Our results with PKC activators and direct G protein stimulators suggest that PKC activation may play a negative feedback role in desensitization of angiotensin II-activated signaling in HVSM cells by modifying the Gq transducer, PLC-beta effector, or related proteins in the signaling pathway. However, neither angiotensin II nor PKC activator affected basal phosphorylation levels of PLC-beta1 or PLC-beta3 in HVSM cells; PLC-beta isoenzymes were shown to be phosphorylated in unstimulated cells independent of PKC inhibition. We suggest that desensitization of G protein-stimulated inositol phosphate accumulation in HVSM differs from other cell types in which phosphorylation of PLC-beta isoenzymes accompanies desensitization.     

Pentoxifylline potentiates nitric oxide production in interleukin-1beta-stimulated vascular smooth muscle cells through cyclic AMP-dependent protein kinase A pathway

In the present study, we observed that pentoxifylline (PTX) significantly augmented the nitric oxide (NO) production and the iNOS gene expression by interleukin-1beta (IL-1beta)-stimulated vascular smooth muscle cells (VSMCs). The enhancing effects of PTX on the IL-1beta-induced NO production was associated with an increased intracellular cyclic AMP (cAMP) levels, and the synergistic effects of PTX on the IL-1beta-induced NO production was blocked by cAMP-dependent protein kinase A (PKA) inhibitors. PKA inhibitors, KT5720 and H89, markedly decreased the augmented expression of iNOS gene whereas ODQ, a soluble guanylate cyclase inhibitor, did not affect the enhancing effect. In addition, the pretreatment with KT5720 or H89 abolished the increased translocation of the p65 subunit of NF-kappaB into the nucleus by PTX in the IL-1beta-stimulated VSMCs. These results suggest that enhancing effects of PTX on the iNOS gene expression in the IL-1beta-stimulated VSMCs is mediated predominantly through the activation of NF-kappaB via cAMP-dependent PKA pathway.     

Characterization of Ca(2+) channels involved in endothelin-1-induced mitogenic responses in vascular smooth muscle cells.

Ca(2+) channels involved in the endothelin-1-induced mitogenic response of cultured rat thoracic aorta smooth muscle cells, A7r5 cells, were characterized using the Ca(2+) channel blockers, LOE 908 and SK&F 96365. Stimulation of A7r5 cells with endothelin-1 induced a mitogenic response as well as a biphasic increase in the intracellular-free Ca(2+) concentration. Based on the sensitivity to nifedipine, a specific blocker of L-type voltage-operated Ca(2+) channel (VOCC), Ca(2+) influx through VOCC has a minor role in endothelin-1-induced mitogenic responses. On the other hand, Ca(2+) influx through voltage-independent Ca(2+) channels (VICCs) plays an important part in endothelin-1-induced mitogenesis. Moreover, based on their sensitivity to SK&F 96365 and LOE 908, VICCs consist of two types of Ca(2+)-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and a store-operated Ca(2+) channel (SOCC). Ca(2+) influx through NSCC-1, NSCC-2 and SOCC contributes to 35%, 30% and 35%, respectively, to the nifedipine-resistant component of the endothelin-1 mitogenic response.     

Carbon monoxide inhibits endothelin-1 release by human pulmonary artery smooth muscle cells

Endothelin-1 is a potent vasoconstrictor with mitogenic properties. This 21-amino-acid protein, released in the vasculature by endothelial and smooth muscle cells, has been implicated in pulmonary hypertension. More recently, evidence has accumulated for a role of the heme oxygenase system in pulmonary hypertension. Heme oxygenase catalyses the breakdown of heme to produce carbon monoxide, biliverdin and free iron. Here we show that a carbon monoxide-releasing molecule, but not biliverdin, inhibits endothelin-1 release from serum-stimulated human pulmonary artery smooth muscle cells. Under certain conditions, carbon monoxide appears to act as an endogenous break on endothelin-1 release.     

Mechanism of rat uterine smooth muscle contraction induced by endothelin-1.

1. Endothelin (ET)-1 has been demonstrated to cause contraction of uterine smooth muscle. We investigated the role of ET receptor subtypes (ETA and ETB receptors) in ET-1-induced contraction of rat uterine smooth muscle by using the ETA receptor antagonist BQ-123 and the ETB receptor agonist BQ-3020. 2. ET-1 caused a contraction with superimposed oscillations of the rat isolated uterus suspended in Krebs-Ringer solution; both the amplitude of contraction as well as the oscillation frequency increased in a dose-dependent manner (10(-11)-10(-7)M). 3. BQ-123 (10(-6)M) markedly shifted the dose-response curve of ET-1 for both contractile effects and oscillation frequency to the right. 4. BQ-3020 (10(-11)-3 x 10(-7) M) did not cause uterine contraction; neither did it affect the dose-response curve of ET-1 for either the contractile effect or the increase in oscillation frequency. Thus, stimulation of ETB receptors is not involved in these responses. 5. The present findings suggest that ET-1-induced contractile responses and the increase in oscillation frequency in rat uterine smooth muscle is mediated through ETA receptors, and that ETB receptors play no role in these responses.     

Oxidative stress increases endothelin-1 synthesis in human coronary artery smooth muscle cells.

Endothelins, nitric oxide, and oxygen-derived free radicals decisively regulate vascular tone. An imbalance in the biosynthesis of these substances in pathophysiologic conditions may trigger vasospasm and promote the development of atherosclerosis. Previous studies have shown that oxygen-derived free radicals can increase the synthesis of endothelin-1 in cultured endothelial cells. Interestingly, conditions of increased oxidative stress within smooth muscle cells as induced by angiotensin II infusion or hypercholesterolemia have been shown to be associated with increased autocrine synthesis of endothelin-1. Because endothelin-1 formed in smooth muscle cells can trigger hypersensitivity to vasoconstrictors, we tested whether oxidative stress per se may affect endothelin expression in vascular smooth muscle cells. Cultured human coronary artery smooth muscle cells were exposed to oxidative stress generated by the xanthine/xanthine oxidase reaction or by hydrogen peroxide. Preproendothelin-1 mRNA content was quantitated by means of quantitative polymerase chain reaction and endothelin-1 protein was measured by radioimmunoassay. Incubation with xanthine/xanthine oxidase significantly increased preproendothelin-1 mRNA synthesis, whereas GAPDH remained unchanged. Likewise, xanthine/xanthine oxidase also led to a dose-dependent increase of intracellular endothelin-1. The increase in ET-1 expression induced by xanthine/xanthine oxidase was significantly inhibited by superoxide dismutase but not by catalase. We conclude that oxygen-derived free radicals can stimulate the synthesis of endothelin-1 in endothelial and vascular smooth muscle cells by increasing preproendothelin-1 mRNA content and that this effect is mediated predominantly by superoxide anions. We therefore have identified a new mechanism in the interaction of oxidative stress and endothelin-1 expression in smooth muscle cells that may have important implications in diseases such as atherosclerosis and hypertension.     

Chemokine production by human vascular smooth muscle cells: modulation by IL-13

1. The production of chemokines by vascular smooth muscle cells (SMC) is implicated in the pathogenesis of atherosclerosis, although the factors regulating chemokine production by these cells are incompletely characterized.
2. We describe the differential stimulation of interleukin-(IL)-8, monocyte chemoattractant protein (MCP)-1 and regulated on activation normal T-cell expressed and secreted (RANTES) synthesis following treatment of human vascular SMC with IL-1α or tumour necrosis factor α (TNFα). Under basal conditions, cultured SMC release very low amounts of IL-8, MCP-1 and RANTES as assessed by specific ELISA. Concentration-response studies with IL-1α or TNFα revealed that each stimulus induced a similar amount of MCP-1. In contrast approximately three fold more IL-8 was induced by IL-1α than by TNFα whereas significant RANTES production was induced only by TNFα. These findings point to a divergence in the regulation of synthesis of the different chemokines in response to IL-1α or TNFα stimulation.
3. The T-cell derived cytokines IL-10 and IL-13 were also found to have differential effects on chemokine production by SMC. IL-13, but not IL-10, significantly enhanced IL-8 and MCP-1 release in response to IL-1α or TNFα. This increase in chemokine release appeared to be accounted for by increased mRNA expression.
4. These findings provide support for the concept that smooth muscle cells can have an active role in a local immune response via the production of chemokines which can be selectively modulated by T-cell derived cytokines.

     

Interaction between monocytes and vascular smooth muscle cells enhances matrix metalloproteinase-1 production

Matrix metalloproteinase-1 (MMP-1) plays an important role in atherosclerotic plaque rupture. The purpose of this study was to investigate the expression of MMP-1 by cell-to-cell interactions between monocytes and vascular smooth muscle cells (VSMCs). Human VSMCs and THP-1 cells (human monocytoid cells) were cocultured. MMP-1 levels were measured by enzyme-linked immunosorbent assay. Collagenolytic activity was determined by fluorescent labeled-collagen digestion. Immunohistochemistry was performed to determine which types of cells produce MMP-1. Adding THP-1 cells to VSMCs markedly increased the MMP-1 levels and activity of the culture media. MMP-1 levels were maximal when the cellular ratio of THP-1 cells/VSMCs was 1.0. Immunohistochemistry revealed that both types of cells in the coculture produced MMP-1. Separated coculture experiments showed that both direct contact and a soluble factor(s) contributed to MMP-1 production. Neutralizing anti-interleukin (IL)-6 and tumor necrosis factor-alpha antibodies inhibited coculture conditioned medium-induced MMP-1 production by VSMCs and THP-1 cells. Protein kinase C inhibitors, tyrosine kinase inhibitors, and a mitogen-activated protein kinase inhibitor significantly inhibited MMP-1 production by cocultures. Direct cell-to-cell interaction between THP-1 cells and VSMCs enhanced MMP-1 synthesis in both types of cells. Increased local MMP-1 production and activity induced by monocyte-VSMC interaction play an important pathogenic role in atherosclerotic plaque rupture.     

Ca2+ entry channels in rat thoracic aortic smooth muscle cells activated by endothelin-1.

The contraction of the rat aorta induced by endothelin-1 (ET-1) requires entry of extracellular Ca2+, but involvement of voltage-operated Ca2+ channel is minor. Using whole-cell recordings of patch-clamp and monitoring of the intracellular free Ca2+ concentration ([Ca2+]i), we characterized Ca2+ entry channels in A7r5 cells activated by ET-1. ET-1 activates three types of voltage-independent Ca2+ entry channels: two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and a store-operated Ca2+ channel (SOCC). Furthermore, it was found that these channels can be pharmacologically discriminated using Ca2+ channel blockers such as SK&F 96365 and LOE 908. NSCC-1 is resistant to SK&F 96365, but sensitive to LOE 908, whereas NSCC-2 is sensitive to both SK&F 96365 and LOE 908. SOCC is sensitive to SK&F 96365, but resistant to LOE 908. Using these channel blockers, we analyzed Ca2+ entry channels involved in the ET-1-induced contractions of rat thoracic aorta and increases in [Ca2+]i of single smooth muscle cells. The responses to lower concentrations of ET-1 (< or = 0.1 nM) were abolished by either SK&F 96365 or LOE 908 alone. In contrast, the responses to higher concentrations of ET-1 (> or = 1 nM) were suppressed by SK&F 96365 or LOE 908 to about 10% and 35% of controls, respectively, and abolished by combined treatment with SK&F 96365 and LOE 908. These results show that the responses of rat aorta to lower concentrations of ET-1 involve only one Ca2+ channel that is sensitive to SK&F 96365 and LOE 908 (NSCC-2), whereas those to higher concentrations of ET-1 involve NSCC-1, NSCC-2 and SOCC, contributing 10%, 55% and 35%, respectively, to total Ca2+ entry.     

Stimulation by endothelin-1 of mitogen-activated protein kinases and DNA synthesis in bovine tracheal smooth muscle cells.

1. In cultures of bovine tracheal smooth muscle cells, platelet-derived growth factor-BB (PDGF), bradykinin (BK) and endothelin-1 (ET-1) stimulated the tyrosine phosphorylation and activation of both pp42 and pp44 kDa forms of mitogen-activated protein (MAP) kinase. 2. Both ET-1 and PDGF stimulated a sustained activation of MAP kinase whilst the response to BK was transient. 3. Activation of MAP kinase occurred in a concentration-dependent manner (EC50 values: ET-1, 2.3 +/- 1.3 nM; BK, 8.7 +/- 4.1 nM, PDGF, 9.7 +/- 3.2 ng ml-1). 4. Pretreatment with the protein kinase C (PKC) inhibitor Ro-318220, significantly reduced ET-1 activation of MAP kinase at 2 and 5 min but enhanced MAP kinase activation at 60 min. 5. Following chronic phorbol ester pretreatment, BK-stimulated activation of MAP kinase was abolished whilst the responses to PDGF and ET-1 were only partly reduced (80 and 45% inhibition respectively). 6. Pretreatment with pertussis toxin reduced ET-1 stimulated activation of MAP kinase particularly at later times (60 min), but left the responses to both PDGF and BK unaffected. 7. ET-1 also stimulated a 3 fold increase in [3H]-thymidine incorporation which was abolished by pertussis toxin pretreatment. In contrast, PDGF stimulated a 131 fold increase in [3H]-thymidine incorporation which was not affected by pertussis toxin. 8. These results suggest that a pertussis toxin-sensitive activation of MAP kinase may play an important role in ET-1-stimulated DNA synthesis but that activation of MAP kinase alone is not sufficient to induce the magnitude of DNA synthesis observed in response to PDGF.     

Modulation of the beta-adrenergic receptor system of vascular smooth muscle cells in vitro and in vivo by chronically elevated endothelin-1 levels

Endothelin-1 (ET-1) levels are chronically elevated in several cardiovascular diseases and correlate with an increased mortality. However, in contrast to acute biological activities such as vasoconstriction, little is known about long-term effects of ET-1. In this study we determined the effects of ET-1 on the beta(2)-adrenergic receptor (AR) system. Incubation of smooth muscle cells with ET-1 for 72 hr led to increased beta(2)AR density as determined by radioligand binding. Experiments with inhibitors of protein and RNA synthesis as well as RT-PCR revealed that beta(2)AR upregulation required de novo synthesis. In addition, protein kinase C but neither NO nor prostaglandin metabolism were involved in this effect. The enhanced expression of beta(2)AR was associated with an increased expression of its stimulatory G-protein and the receptor's ability to stimulate adenylyl cyclase. To study chronic effects of ET-1 in vivo, rats were infused with ET-1 for 3 weeks. Similarly as in cultured cells, prolonged ET-1 exposure led to increased betaAR expression in vivo. As a consequence, beta(2)AR-induced vasodilatation was increased in aortic rings from ET-1-treated animals. Our results therefore suggest that chronically elevated ET-1 levels in vitro and in vivo induce counterregulatory mechanisms by increasing betaARs that attenuate the vasoconstrictive effects of ET-1.