蛋白激酶C ε亚型在AVP调节休克血管MLC20磷酸化水平及MLCK/MLCP活性中的作用

目的研究蛋白激酶C（PKC）ε亚型在精氨酸血管加压素（AVP）调节休克血管肌球蛋白轻链（MLC20）磷酸化及缺氧血管平滑肌细胞（VSMC）肌球蛋白轻链激酶（MLCK）和肌球蛋白轻链磷酸酶（MLCP）活性中的作用。方法采用大鼠失血性休克模型和缺氧培养VSMC,观察PKCε亚型在AVP调节失血性休克大鼠肠系膜上动脉（SMA）血管平滑肌MLC20磷酸化水平中的作用,同时检测缺氧VSMC中MLCK和MLCP活性的变化。结果失血性休克后SMA血管平滑肌MLC20磷酸化水平降低,同时缺氧VSMC的MLCP活性明显升高,MLCK活性明显降低;AVP处理可显著升高MLC20磷酸化水平和抑制缺氧VSMC的MLCP活性升高,特异性的PKCε抑制肽可明显拮抗AVP升高MLC20磷酸化、降低MLCP的作用;而AVP和PKCε抑制肽对MLCK活性的变化无明显影响。结论AVP可通过PKCε亚型来发挥改善休克血管反应性的作用,其机制可能是通过抑制MLCP活性、升高MLC20磷酸化水平,进而增强血管平滑肌细胞钙敏感性升高血管反应性。     

蛋白激酶C ε亚型在AVP调节休克血管MLC20磷酸化水平及MLCK/MLCP活性中的作用

目的 研究蛋白激酶C(PKC) ε亚型在精氨酸血管加压素(AVP)调节休克血管肌球蛋白轻链(MLC₂₀)磷酸化及缺氧血管平滑肌细胞(VSMC)肌球蛋白轻链激酶(MLCK)和肌球蛋白轻链磷酸酶(MLCP)活性中的作用。方法 采用大鼠失血性休克模型和缺氧培养VSMC,观察PKC ε亚型在AVP调节失血性休克大鼠肠系膜上动脉(SMA)血管平滑肌MLC20磷酸化水平中的作用,同时检测缺氧VSMC中MLCK和MLCP活性的变化。结果 失血性休克后SMA血管平滑肌MLC₂₀磷酸化水平降低,同时缺氧VSMC的MLCP活性明显升高,MLCK活性明显降低;AVP处理可显著升高MLC₂₀磷酸化水平和抑制缺氧VSMC的MLCP活性升高,特异性的PKC ε抑制肽可明显拮抗AVP升高MLC₂₀磷酸化、降低MLCP的作用;而AVP和PKC ε抑制肽对MLCK活性的变化无明显影响。结论 AVP可通过PKC ε亚型来发挥改善休克血管反应性的作用,其机制可能是通过抑制MLCP活性、升高MLC₂₀磷酸化水平,进而增强血管平滑肌细胞钙敏感性升高血管反应性。     

Rac对失血性休克大鼠血管反应性的调节作用

目的探讨Rac在失血性休克大鼠血管反应性调节中的作用。方法采用SD大鼠复制休克模型,取离体血管环,观察休克早期和晚期血管反应性的变化以及Rac激动剂和特异性抑制剂对休克早期和晚期血管反应性的影响;通过酶消化法培养原代血管平滑肌细胞（vascular smoot hmuscle cell,VSMC）,采用双室培养方式分别观察VSMC缺氧10min和90min后VSMC对去甲肾上腺素（norepinephrine,NE）的收缩反应性变化,同时观察Rac活性调节剂对缺氧后VSMC收缩反应性的影响。结果在休克早期和短暂缺氧后,离体血管环和VSMC对NE收缩反应性均有所升高,Rac的激动剂血小板衍生生长因子（platelet derived growth factor,PDGF）可部分降低休克早期或短暂缺氧后血管反应性,Rac特异性抑制剂NSC23766可拮抗由PDGF所引起的血管反应性的变化,而在休克晚期或长时间缺氧后,离体血管环和VSMC对NE收缩反应性明显降低,NSC23766对休克晚期或长时间缺氧所致血管反应性降低有升高作用。结论休克后血管反应性呈双相变化,休克早期升高,休克晚期降低,Rac参与了休克血管反应性的调节。     

肌内皮缝隙连接在失血性休克大鼠内皮依赖和非内皮依赖的血管舒/缩功能调节中的作用

目的 研究肌内皮缝隙连接(myo-endothelial gap junction,MEGJ)通道在失血性休克大鼠肠系膜上动脉血管(SMA)的内皮依赖和非内皮依赖的血管收缩/舒张功能调节中的作用.方法 利用在体血管管径测定技术,观察MEGJ的阻断剂18α-甘草次酸(18α-GA)对非内皮依赖的血管收缩剂去甲肾上腺素(N...     

细胞缝隙连接对miR-124抗肿瘤作用的影响和机制研究

目的探讨不同连接蛋白(connexin,Cx)组成的缝隙连接(gap junction,GJ)对miR-124抗肿瘤作用的影响及机制。方法在稳定转染表达Cx26或Cx32的Hela细胞(Hela26、Hela32),以及稳定转染shRNA-Cx43的人胶质瘤U87细胞(U87~(shRNA-Cx43))中,应用Western blot和荧光示踪实验分别测定Cx表达和GJ功能;集落形成实验检测miR-124对细胞增殖影响;膜片钳检测Cy3荧光标记的miR-124在细胞间的传递。结果多西环素可诱导Hela26和Hela32细胞上Cx表达和GJ形成;miR-124抑制Hela细胞增殖,但在有GJ(Dox诱导)和无GJ形成(无Dox诱导)条件下统计学上无明显差异。相较于U87~(shRNA-NC),U87~(shRNA-Cx43)细胞中Cx43表达、GJ功能及miR-124的增殖抑制作用均明显降低;显微镜下可见导入到"供体细胞"中的荧光miRNA逐渐布满整个细胞并传递到相邻非"导入"细胞内。结论 GJ可影响miR-124的抗肿瘤作用,但具有Cx异质性。相较Cx26或Cx32,Cx43组成的GJ可调控miR-124的抗肿瘤作用,这可能与该GJ通道对miR-124的传递作用较强有关。     

缝隙连接蛋白Connexin43参与神经精神疾病发病机制的研究进展

缝隙连接(gap junction,GJ)是细胞间的一种连接形式,主要由缝隙连接蛋白(connexin,Cx)构成。细胞间的物质能量交换通过GJ完成。Cx43蛋白是星形胶质细胞中构成GJ的Cx家族主要成员之一。近些年的研究越来越清晰地阐述了Cx43蛋白的特性及其在神经、肿瘤、心血管等系统疾病发病过程中的重要作用。该文就GJ的结构与功能,Cx43蛋白的编码基因、结构解析、合成、细胞膜定位、调节和在人体中发挥的生理功能,及其在相关神经系统疾病发病进程中的作用等方面的研究成果展开综述。     

赖氨匹林增强Cx32/Cx26组成的Hela细胞缝隙连接功能

目的 体外观察赖氨匹林对转染并稳定表达连接蛋白32/26 （Cx32/Cx26）的Hela细胞缝隙连接通讯（GJIC）功能和Cx32/Cx26蛋白表达水平的影响.方法 不同浓度（0、1、5、10 mmol·L^-1）赖氨匹林作用于人宫颈癌Hela细胞24 h后,以划痕标记/染料示踪技术（SL/DT）检测赖氨匹林作用Hela细胞48 h后荧光黄在细胞之间传递的距离来评价其对缝隙连接（GJ）功能的影响;Western blot方法检测赖氨匹林对Cx32/Cx26蛋白表达的影响.结果 SL/DT检测显示赖氨匹林具有上调GJ功能的作用;Western blot显示赖氨匹林增加Cx32/Cx26蛋白表达水平.结论 赖氨匹林抑制转染并稳定表达Cx32/Cx26的Hela细胞的增殖、上调GJ功能且这种作用可能与其增加Cx32/Cx26蛋白表达水平有关.     

Rac对失血性休克大鼠血管反应性的调节作用

目的 探讨Rac在失血性休克大鼠血管反应性调节中的作用。方法 采用SD大鼠复制休克模型,取离体血管环,观察休克早期和晚期血管反应性的变化以及Rac激动剂和特异性抑制剂对休克早期和晚期血管反应性的影响;通过酶消化法培养原代血管平滑肌细胞(vascular smooth muscle cell, VSMC),采用双室培养方式分别观察VSMC缺氧10 min和90 min后VSMC对去甲肾上腺素(norepinephrine, NE)的收缩反应性变化,同时观察Rac活性调节剂对缺氧后VSMC收缩反应性的影响。结果 在休克早期和短暂缺氧后,离体血管环和VSMC对NE收缩反应性均有所升高,Rac的激动剂血小板衍生生长因子(platelet derived growth factor, PDGF)可部分降低休克早期或短暂缺氧后血管反应性,Rac特异性抑制剂NSC 23766可拮抗由PDGF所引起的血管反应性的变化,而在休克晚期或长时间缺氧后,离体血管环和VSMC对NE收缩反应性明显降低,NSC 23766对休克晚期或长时间缺氧所致血管反应性降低有升高作用。结论 休克后血管反应性呈双相变化,休克早期升高,休克晚期降低,Rac参与了休克血管反应性的调节。     

缝隙连接在缺血后处理保护大鼠脑缺血再灌注损伤中的作用及可能机制

目的：探讨缝隙连接在缺血后处理保护大鼠脑缺血再灌注损伤中的作用及其可能的机制。方法：60只雄性SD大鼠随机分为假手术（sham）组、缺血再灌注（ischmia／reperfusion,I／R）组、缺血后处理（ischemicpost—conditioning,IP0）组、甘珀酸（carbenox010ne,CBX）干预缺血再灌注（I／R＋CBX）组和甘珀酸干预缺血后处理（IPO＋CBX）组。采用线栓法建立大鼠大脑中动脉栓塞模型;Longgs法进行神经功能评分;TTC染色法和HE染色法分别检测大鼠脑梗死体积和脑组织形态学变化;WesternBlot法检测脑组织中缝隙连接蛋白43（Cx43）、蛋白激酶C（PKC）蛋白的表达。结果：与sham组相比,I／R组神经功能评分显著增高,脑梗死体积增大,细胞排列紊乱、胞核固缩等组织形态学改变显著;IP0可使I／R组损伤减轻;CBX可以进一步增强IPO对I／R损伤的保护作用。WesternBlot结果显示,I／R组较sham组Cx43表达增多,PKC表达降低;IPO组较I／R组Cx43表达降低（P〈0．01）,PKC表达增高（P〈O．01）,同时,IPO＋CBX组较IPO组也有类似的改变。结论：IPO可通过抑制缝隙连接而减轻I／R损伤,其机制可能与影响PKC蛋白的表达有关。     

血管加压素1a与血管加压素2受体在精氨加压素调节缺氧血管平滑肌细胞蛋白激酶C表达中的作用

目的观察血管加压素1a(V1a)受体与V2受体拮抗剂对精氨加压素(AVP)调节缺氧血管平滑肌细胞(VSMC)蛋白激酶C(PKC)α,δ和ε亚型表达的影响,以及磷脂酶C(PLC)、磷脂酶D(PLD)和磷脂酶A2(PLA2)活性的变化。方法缺氧培养大鼠肠系膜上动脉VSMC,采用Western蛋白印迹法检测PKCα,δ和ε亚型蛋白表达;采用酶偶联荧光分析法测定PLC和PLD的活性,酸碱滴定法检测PLA2的活性。结果缺氧处理1.5h,VSMC胞膜PKC-α和ε亚型蛋白表达量明显升高,AVP进一步升高胞膜PKC-α和ε的表达。V1a受体拮抗剂d(CH2)5[Tyr2(Me)]AVP预处理可明显拮抗AVP诱导的胞膜PKCα和ε亚型蛋白表达升高,同时也明显拮抗AVP诱导的缺氧VSMC中PLC和PLD活性升高。而V2受体拮抗剂d(CH2)[d-Ile2Abu4]AVP对缺氧诱导的胞膜PKC-α和ε表达增加和VSMC中PLC和PLD活性升高无明显作用。结论AVP诱导PKC激活的机制可能与V1a受体介导的PLC/PLD途径有关,而V2受体在这一信号传导途径中可能并不起主要作用。     

Beneficial effect of arginine vasopressin on hemorrhagic shock through improving the vascular reactivity

The vascular reactivity and calcium sensitivity were decreased following hemorrhagic shock. Arginine vasopressin (AVP) was beneficial to endotoxic, infectious/spetic and hemorrhagic shock. Our previous studies found that Rho kinase played an important role in the occurrence of calcium desensitization following shock. It was reported that AVP was with stimulation effect of Rho kinase. So we hypothesized that AVP might have beneficial effect on shock via activation of Rho kinase to regulate the calcium sensitivity and vascular reactivity. Hemorrhagic shock (40 mmHg for 2 h) Wistar rats in vivo were adopted to observe the effects of small dose of AVP on hemodynamics, 24-h survival rate, the pressor effect of norepinephrine (NE) and the contractility of superior mesenteric artery (SMA). Isolated SMAs from hemorrhagic shock rats were adopted to observe the effects of AVP on vascular reactivity and calcium sensitivity and its relationship to Rho kinase with an isolated organ perfusion system. The results show that AVP at the concentration of 0.1 U/kg and 0.4 U/kg significantly improved the hemodynamic parameters and the 24-h survival rate of hemorrhagic shock rats. Meanwhile, these dosages of AVP significantly increased the pressor effect of NE and the contractile response of SMA to NE. Y-27632 (3 μg/kg), a Rho kinase specific inhibitor, abolished the beneficial effects of AVP. In vitro, the calcium sensitivity and vascular reactivity of SMA to calcium and NE were significantly decreased following hemorrhagic shock. AVP at the concentration of 0.5 nmol/L and 5 nmol/L significantly increased the calcium sensitivity and vascular reactivity. These effects of AVP were abolished by Y-27632 (10 μmol/L). Taken together, the results suggest that AVP at 0.1 U/kg and 0.4 U/kg is beneficial to hemorrhagic shock by improving the vascular reactivity, which involves activation of Rho kinase.     

Regulatory effect of Rac1 on vascular reactivity after hemorrhagic shock in rats

We used isolated superior mesenteric arteries (SMAs) from hemorrhagic-shock rats and hypoxia-treated vascular smooth muscle cells (VSMCs; mimicking the shock state) to observe the effects of platelet-derived growth factor (PDGF; Rac1 stimulator) and NSC23766 (Rac1 antagonist) on vascular reactivity and the relationship with the Rho kinase-myosin light-chain phosphatase (MLCP) and p21-activated kinase (PAK)-myosin light-chain kinase (MLCK) signal pathway. The results indicated that the contractile responses of the SMAs and VSMCs were significantly increased at early shock or after transient hypoxia. NSC23766 (Rac1 antagonist) further increased, whereas PDGF (Rac1 stimulator) decreased the contractile responses of SMAs and VSMCs. In the late period of shock or prolonged hypoxia, the contractile responses of SMAs and VSMCs were significantly decreased; NSC23766 increased (whereas PDGF further decreased) the contractile response of the SMAs and VSMCs. Activation of Rac1 with PDGF significantly increased the activity of PAK and MLCP, and decreased Rho kinase and MLCK activity and 20-kDa myosin light-chain phosphorylation in VSMCs. The PAK inhibitor PAK-18 significantly antagonized the PDGF-induced decrease in MLCK activity, whereas the Rho kinase antagonist Y-27632 further enforced the PDGF-induced increase in MLCP activity. Simple fluid resuscitation did not improve but in combination with NSC23766 significantly improved vascular reactivity and animal survival at 24 hours. This suggested that Rac1 has an inhibitory effect on vasoreactivity after shock. Rac1-mediated regulation of vascular reactivity is mainly through activation of PAK, inhibition of MLCK and inhibition of Rho kinase, unpack the inhibition of Rho kinase to MLCP. Rac1 may be a potential target to treat vascular hyporeactivity in many critical conditions.     

Connexin-mimetic peptides dissociate electrotonic EDHF-type signalling via myoendothelial and smooth muscle gap junctions in the rabbit iliac artery

Synthetic peptides corresponding to the Gap 26 and Gap 27 domains of the first and second extracellular loops of the major vascular connexins (Cx37, Cx40 and Cx43), designated as (43)Gap 26, (40)Gap 27, (37,40)Gap 26 and (37,43)Gap 27 according to Cx homology, were used to investigate the role of gap junctions in the spread of endothelial hyperpolarizations evoked by cyclopiazonic acid (CPA) through the wall of the rabbit iliac artery. Immunostaining and confocal microscopy demonstrated that gap junction plaques constructed from Cx37 and Cx40 were abundant in the endothelium, whereas Cx43 was the dominant Cx visualized in the media. None of the Cx-mimetic peptides affected endothelial hyperpolarizations evoked by CPA directly. When administered individually, (40)Gap 27, (37,40)Gap 26 and (37,43)Gap 27, but not (43)Gap 26, attenuated endothelium-dependent subintimal smooth muscle hyperpolarization. By contrast, only (43)Gap 26 and (37,43)Gap 27 reduced the spread of subintimal hyperpolarization through the media of the rabbit iliac artery. The site of action of the peptides therefore correlated closely with the expression of their target Cxs in detectable gap junction plaques. The findings provide further evidence that the EDHF phenomenon is electrotonic in nature, and highlight the contribution of myoendothelial and homocellular smooth muscle communication via gap junctions to arterial function.     

Vascular gap junctions and implications for hypertension

Four connexin (Cx) molecules, namely Cx37, Cx40, Cx43 and Cx45, are expressed in the gap junctions that exist within and between the cellular layers of arteries. Endothelial cells are well coupled by large gap junctions expressing Cx37, Cx40 and, to a lesser extent, Cx43, whose expression may be more subject to regulation by physical factors. Smooth muscle cells are more heterogeneously coupled by gap junctions that are small and rare. The identity of the Cx expressed in the media may vary among different arteries. Myoendothelial gap junctions are small and more common in resistance arteries with fewer layers of smooth muscle cells. Given the small size of these gap junctions and the rapid turnover rate of Cxs, homocellular coupling in the media and heterocellular coupling between the cell layers may be subject to more dynamic control than coupling in the endothelium. Vascular gap junctions have been implicated in a number of vasomotor responses that may regulate vascular tone and blood pressure. These include the mechanism of action of the vasodilator, endothelium-derived hyperpolarizing factor (EDHF), the myogenic constriction to intramural pressure increase, the spontaneous or agonist-induced vasomotion of arteries and arterioles and the spreading vasodilation and constriction observed in microcirculatory networks. Few data are available on Cx expression in the media of resistance arteries during hypertension. Changes in the expression of Cx43 described in the media of the aorta of hypertensive rats vary with the hypertensive model studied and are likely to represent adaptations to structural changes in the vascular wall. In contrast, in the endothelium of the caudal and mesenteric arteries of spontaneously hypertensive rats, expression of Cxs is significantly decreased compared with arteries from normotensive rats and this decrease is reversed by inhibitors of the renin-angiotensin system. During hypertension, the activity of EDHF is decreased in the mesenteric artery, but this occurs much later than the initial increase in blood pressure and the decrease in endothelial Cxs, suggesting that changes in EDHF may not be causally related to hypertension or to the changes in endothelial Cxs. Upregulation of the myogenic response and the incidence of vasomotion has been reported in hypertension. Little is currently known of the effects of hypertension on spreading vasomotor responses. Deletion of specific Cxs in genetically modified mice is complicated by neonatal lethality or coordinate regulation and compensatory changes in the remaining Cxs. Nevertheless, mice in which Cx40 has been deleted are hypertensive and spreading vasodilatory responses are significantly impaired. Determination of a role for specific Cxs in the control of blood pressure must await the development of animals in which Cx expression can be modulated in a more complex temporal and tissue-specific manner.     

The impact of caffeine on connexin expression in the embryonic chick cardiomyocyte micromass culture system

Cardiomyocytes are electrically coupled by gap junctions, defined as clusters of low‐resistance multisubunit transmembrane channels composed of connexins (Cxs). The expression of Cx40, Cx43 and Cx45, which are present in cardiomyocytes, is known to be developmentally regulated. This study investigates the premise that alterations in gap junction proteins are one of the mechanisms by which teratogens may act. Specifically, those molecules known to be teratogenic in humans could cause their effects via disruption of cell‐to‐cell communication pathways, resulting in an inability to co‐ordinate tissue development. Caffeine significantly inhibited contractile activity at concentrations above and including 1500 μm (P < 0.05), while not affecting cell viability and total protein, in the embryonic chick cardiomyocyte micromass culture system. The effects of caffeine on key cardiac gap junction protein (Cx40, Cx43 and Cx45) expression were analysed using immunocytochemistry and in‐cell Western blotting. The results indicated that caffeine altered the expression pattern of Cx40, Cx43 and Cx45 at non‐cytotoxic concentrations (≥2000 μm ), i.e., at concentrations that did not affect total cell protein and cell viability. In addition the effects of caffeine on cardiomyocyte formation and function (contractile activity score) were correlated with modulation of Cxs (Cx40, Cx43 and Cx45) expression, at above and including 2000 μm caffeine concentrations (P < 0.05). These experiments provide evidence that embryonic chick cardiomyocyte micromass culture may be a useful in vitro method for mechanistic studies of perturbation of embryonic heart development. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of connexin-mimetic peptides on gap junction functionality and connexin expression in cultured vascular cells

1. We have investigated the effects of connexin-mimetic peptides homologous to the Gap 26 and Gap 27 domains of Cxs 37, 40 and 43 against gap junctional communication and connexin expression in rat aortic endothelial cells (RAECs) and A7r5 myocytes. 2. Immunostaining and Western blot analysis confirmed the presence of gap junction plaques containing Cx43, but not Cx40, in RAECs, whereas plaques containing Cxs 40 and 43 were evident in A7r5 cells. Expression of Cx37 was limited in RAECs and absent from A7r5 cells. 3. Under control conditions calcein-loaded RAECs transferred dye to approximately 70% of subjacent A7r5 cells after coculture for 4-5 h. Dye transfer was inhibited by a peptide targeted to Cxs 37 and 43 ((37,43)Gap 27), but minimally affected by peptides targeted to Cxs 37 and 40 ((37,40)Gap 26 and (40)Gap 27). These findings suggest that the myoendothelial gap junctions that couple RAECs and A7r5 cells are constructed principally from Cx43. 4. Inhibition of dye transfer from RAECs to A7r5 cells cocultured in the presence of (37,43)Gap 27 plus (37,40)Gap 26 for 5 h was fully reversible. 5. In A7r5 cells, endogenous expression of Cx40 and Cx43 was unaffected by incubation with (37,43)Gap 27, (37,40)Gap 26, either individually or in combination, and the peptide combination did not impair connexin trafficking or the de novo formation of gap plaques in A7r5 cells transfected to express Cx43-GFP. 6. Treatment of A7r5 cells with (37,43)Gap 27 plus (37,40)Gap 26 abolished synchronized oscillations in intracellular [Ca2+] induced by the alpha1-adrenoceptor agonist phenylephrine. 7. The reversibility and lack of effect of the peptides on plaque formation suggests that they may be considered ideal probes for functional studies of connexin-mediated communication in the vascular wall.     

The effects of 2-aminoethoxydiphenyl borate and diphenylboronic anhydride on gap junctions composed of Connexin43 in TM₄ sertoli cells

2-Aminoethoxydiphenyl borate (2-APB) has recently been demonstrated to inhibit gap junction (GJ) channels, whereas the underlying mechanisms are still unknown. Using mouse TM? Sertoli cell which expresses connexin43 (Cx43), we explored the effects of 2-APB and its analogues on dye-coupling through junctional channels formed by Cx43 and on expression of Cx43. Exposure of the cells to 2-APB (1-50 μM) and one of its analogues diphenylboronic anhydride (DPBA) (1-30 μM) for 4 h leads to a significant decrease in dye coupling of GJ in a concentration-dependent manner. The inhibitory effects of 2-APB and DPBA are reversible since decreased GJ coupling resumes after the two compounds are washed out. The disfunction of GJ induced by 2-APB and DPBA is associated with a decrease in total amount of Cx43 protein and number of GJs on the cell membrane. 2-APB and DPBA do not alter Cx43 phosphorylation state and the level of Cx43 mRNA expression. The loss of Cx43 protein is prevented by either lysosomal or proteasomal inhibitor, suggesting that the decrease in Cx43 results from a 2-APB or DPBA-enhanced degradation of Cx43. The present results indicate that 2-APB and DPBA inhibit GJ communication through decreasing Cx43 expression in TM? cells.     

Heterogeneity in the distribution of vascular gap junctions and connexins: implications for function

1. Gap junctions, which are comprised of members of a family of membrane proteins called connexins (Cx), permit the transfer of electrical and chemical information between adjacent cells in a wide variety of tissues. The aim of the present study was to compare the expression of Cx37, 40 and 43 in the smooth muscle and endothelium of a large elastic artery and two smaller muscular arteries of the rat. Serial section electron microscopy was also used to determine the presence of pentalaminar gap junctions in the smooth muscle and the incidence of myoendothelial gap junctions between the smooth muscle and endothelial cells in muscular arteries of different size. 2. Using immunohistochemistry, Cx37, 40 and 43 were found in the endothelium of the aorta, caudal and basilar arteries, with Cx43 being the least abundant. Connexin 43 was readily observed throughout the muscle layers of the aorta, but was not detected in the media of the caudal or basilar arteries. Connexin 40 was not detected in the media of any of the arteries, while very fine punctate staining was observed with Cx37 antibodies in the media of the caudal and basilar arteries, but not in the aorta. 3. Real-time polymerase chain reaction showed that the expression of mRNA for Cx43 was 15-fold greater in the aorta than in the caudal artery of the rat. 4. At the ultrastructural level, small pentalaminar gap junctions (< 100 nm) were found between the fine processes of adjacent smooth muscle cells and also between the smooth muscle and endothelial cells. The incidence of myoendothelial gap junctions in the mesenteric vascular bed and in the caudal artery increased as vessel size decreased. 5. In summary, heterogeneity exists within the vascular system with regard to the distribution of gap junctions and their constituent Cx. Such variation will have important consequences for the coordination and propagation of vascular responses. In muscular arteries, in comparison with elastic arteries, Cx37 may be more important than Cx43 for cell coupling within the smooth muscle layers. The correlation between the incidence of myoendothelial gap junctions and the role of endothelium-derived hyperpolarizing factor, relative to nitric oxide, in vasodilatory responses suggests that myoendothelial gap junctions play an important physiological role in the regulation of vascular tone.     

Chlorpromazine reduces the intercellular communication via gap junctions in mammalian cells

In the work presented herein, we evaluated the effect of chlorpromazine (CPZ) on gap junctions expressed by two mammalian cell types; Gn-11 cells (cell line derived from mouse LHRH neurons) and rat cortical astrocytes maintained in culture. We also attempted to elucidate possible mechanisms of action of CPZ effects on gap junctions. CPZ, in concentrations comparable with doses used to treat human diseases, was found to reduce the intercellular communication via gap junctions as evaluated with measurements of dye coupling (Lucifer yellow). In both cell types, maximal inhibition of functional gap junctions was reached within about 1 h of treatment with CPZ, an recovery was almost complete at about 5 h after CPZ wash out. In both cell types, CPZ treatment increased the phosphorylation state of connexin43 (Cx43), a gap junction protein subunit. Moreover, CPZ reduced the reactivity of Cx43 (immunofluorescence) at cell interfaces and concomitantly increased its reactivity in intracellular vesicles, suggesting an increased retrieval from and/or reduced insertion into the plasma membrane. CPZ also caused cellular retraction reducing cell-cell contacts in a reversible manner. The reduction in contact area might destabilize existing gap junctions and abrogate formation of new ones. Moreover, the CPZ-induced reduction in gap junctional communication may depend on the connexins (Cxs) forming the junctions. If Cx43 were the only connexin expressed, MAPK-dependent phosphorylation of this connexin would induce closure of gap junction channels.