大鼠心室肌M3受体与间隙连接蛋白43作为抗心律失常药物靶点的综合研究

目的在蛋白质分子水平研究心律失常相关蛋白质M₃受体与间隙连接蛋白43之间的结构相互作用，并为其作为筛选药物靶点提供依据。方法通过免疫组化结合激光共聚焦显微镜，及免疫沉淀与免疫印迹技术，研究M受体与间隙连接蛋白43的结构性共定位关系。结果证实了大鼠心室肌细胞膜蛋白中M₁～M₅等5个亚型的存在；观察到大鼠单个心肌细胞膜上M₃受体与间隙连接蛋白43的结构性共定位；发现M受体各亚型与间隙连接蛋白43均存在结构整合，且一定浓度离子型去垢剂可破坏M₃受体与间隙连接蛋白43的结构整合关系，并进一步发现参与M₃受体结构整合的是间隙连接蛋白43的磷酸化形式。结论大鼠心室肌M受体亚型与间隙连接蛋白43的磷酸化形式存在结构性共定位关系，且可被一定浓度离子型去垢剂破坏。     

双环醇拮抗DDT引起的细胞间隙连接通讯功能抑制研究

目的研究治肝炎药物双环醇对促癌剂滴滴涕(DDT)引起细胞间隙连接通讯(GJIC)功能抑制的拮抗作用及作用机制。方法划痕标记染料示踪技术直接观察DDT引起的大鼠肝上皮WB-F344细胞GJIC功能抑制并分析双环醇的作用。利用Western blot方法检测间隙连接蛋白43(Cx43)、磷酸化Cx43、E-cadherin及β-Catenin的表达和活性。细胞免疫荧光技术考察WB-F344细胞Cx43蛋白亚细胞定位、间隙连接的形成及E-cadherin和β-Catenin在细胞内的表达。结果 DDT能剂量依赖性的抑制WB-F344细胞GJIC功能,20μM浓度时小分子荧光染料Luciferyellow CH仅能从伤沿细胞向后传递1-2列细胞。双环醇能部分恢复DDT引起的GJIC功能抑制,且具有一定剂量依赖关系,其作用机制与抑制DDT引起的磷酸化Cx43蛋白表达量升高,进而恢复DDT损伤的间隙连接形成有关。DDT和双环醇对与Cx43蛋白功能密切相关的E-cadherin及β-Catenin的表达、活性及细胞内定位均无明显影响。结论双环醇能通过影响Cx43蛋白的磷酸化水平,部分恢复环境促癌剂DDT引起的WB-F344细胞间隙连接的形成,改善GJIC功能。对GJIC的功能抑制是多种促癌剂诱发肿瘤发生的重要原因,前期研究显示双环醇具预防二甲基亚硝胺/苯巴比妥诱发肝癌发生的作用,本文研究结果进一步提示,双环醇在预防杀虫剂DDT(一种主要的环境致癌物)诱发的肿瘤方面亦具有一定潜能。     

M1胆碱受体通过AMPA受体GluA1亚基改善β-淀粉样肽导致的学习记忆功能障碍

目的碱型乙酰胆碱受体(M受体)亚型M1受体在脑内的分布量最大,并且在大脑皮质和海马中大量表达,发挥着重要的促进学习和记忆的功能。M1受体是治疗以胆碱神经元丢失、淀粉样斑块沉积等为病理特征的神经退行性疾病阿尔茨海默病(AD)的潜在治疗靶标。我们前期研究发现,选择性激活M1受体可促进AMPA受体GluA1亚基向神经元表面和突触后膜运输,并且在激动M1受体促进学习记忆中起着重要作用。本研究进一步探讨AMPA受体GluA1亚基在M1受体改善β-淀粉样肽(Aβ)所致学习记忆障碍中的作用。方法选用野生型和AMPA受体GluA1亚基Ser845位点突变小鼠(S845A小鼠),以3次脑室内注射Aβ纤丝以破坏学习记忆功能,通过Morris水迷宫实验研究给予M1受体选择性激动剂77-LH-28-1对野生小鼠和突变小鼠的学习记忆的改善作用。实验结束后收集海马组织进行Western蛋白印迹法和免疫荧光检测,研究77-LH-28-1对海马组织内GluA1亚基表达及其向突触转运的影响。结果 Morris水迷宫实验表明,S845A小鼠的空间学习记忆能力与野生型小鼠相同,表明S845A小鼠学习记忆功能未受损。给予3次脑室内Aβ纤丝注射使野生型和S845A小鼠的空间记忆能力受损,给予M1受体选择性激动剂77-LH-28-1可明显缩短野生型小鼠寻找平台的潜伏期和游泳路程,但对S845A小鼠无明显作用。Morris水迷宫训练期24 h后进行目标象限探索实验,结果表明,77-LH-28-1可使注射Aβ纤丝的野生型小鼠在目标象限的时间和路程百分百显著提高,与正常野生小鼠无区别,而这些作用在注射Aβ纤丝的S845A小鼠都缺失。并且各组小鼠的游泳速度不存在显著性差异,说明M1受体激动通过GluA1亚基显著改善了Aβ所致的空间学习和记忆障碍。Western蛋白印迹法检测表明,77-LH-28-1提高野生型小鼠海马内GluA1亚基的表达及其Ser845位点的磷酸化。免疫荧光检测表明,77-LH-28-1提高野生型小鼠海马内GluA1亚基与突触后蛋白PSD95的共定位,而这些作用在S845A小鼠中缺失。结论选择性激动M1受体显著改善Aβ所致的学习记忆障碍,该作用与其调控对AMPA受体GluA1亚基的调控有关。激动M1受体可使GluA1亚基Ser845位点的磷酸化程度增加,并由此增加GluA1的表达和向突触后的转运。Ser845位点突变可阻断M1受体对GluA1亚基的调控作用从而不能改善Aβ所致的学习记忆障碍。本研究揭示了M1受体改善学习记忆的分子机制。     

复方藤梨根制剂调节PG细胞间隙连接蛋白Cx43基因表达水平的研究

目的探讨复方藤梨根制剂对高转移性人肺癌细胞(PG)的生长及细胞间隙连接蛋白Cx43表达水平的影响。方法采用MTT法体外观察不同浓度复方藤梨根制剂对PG细胞的杀伤作用;应用流式细胞仪检测用药后PG细胞Cx43的表达水平。结果4个浓度的复方藤梨根制剂对PG细胞均有杀伤作用,呈剂量依赖关系。与对照组相比,Cx43表达水平逐渐上升。结论复方藤梨根制剂对PG细胞具有生长抑制作用,其机制可能与上调间隙连接蛋白Cx43表达水平有关。     

复方藤梨根制剂调节PG细胞间隙连接蛋白Cx43基因表达水平的研究

目的探讨复方藤梨根制剂对高转移性人肺癌细胞(PG)的生长及细胞间隙连接蛋白Cx43表达水平的影响。方法采用MTT法体外观察不同浓度复方藤梨根制剂对PG细胞的杀伤作用;应用流式细胞仪检测用药后PG细胞Cx43的表达水平。结果4个浓度的复方藤梨根制剂对PG细胞均有杀伤作用,呈剂量依赖关系。与对照组相比,Cx43表达水平逐渐上升。结论复方藤梨根制剂对PG细胞具有生长抑制作用,其机制可能与上调间隙连接蛋白Cx43表达水平有关。     

M1胆碱受体激动剂治疗阿尔茨海默病的研究进展

阿尔茨海默病(Alzheimer disease，AD)是一种以胆碱能神经元进行性退变、老年斑和神经元缠结为病理特征的神经退行性疾病。尽管AD发病机制尚未阐明，但β淀粉样肽沉积和tau蛋白磷酸化与胆碱能神经退变的恶性循环(vicious cycle)无疑是造成AD的重要病理机制之一。大量研究表明胆碱能神经突触后膜的M1受体的数目在整个病程中变化不大，M1受体选择性激动剂不但可以直接补偿胆碱能的功能，而且可以调节β淀粉样前体蛋白代谢和降低tau蛋白的过度磷酸化，有助于打破这一恶性循环，改善AD的学习记忆功能并延缓病情的发展。因此M1胆碱受体激动剂被认为是最有前途的治疗AD药物之一。目前Xanomeline、Sabcomeline等具有相对选择性M1受体激动剂业已进入新药临床试验阶段。     

左旋丁苯酞对肌萎缩性侧索硬化症细胞损伤的保护作用及其机制

目的肌萎缩性侧索硬化(ALS)是一种复杂的多因素疾病,其特征在于运动神经元的丢失,是引起慢性运动神经元病的最常见类型,其发病机制尚不明确。由于ALS致死率高,目前上市药物只有利鲁唑和依达拉奉,因此寻找针对ALS的有效治疗药物迫在眉睫。左旋丁苯酞(L-NBP)是从芹菜籽中得到的,后合成消旋体丁苯酞,广泛用于急性缺血性脑卒中的治疗。研究发现,L-NBP具有多种神经保护功能,可以明显抑制氧化应激,减轻神经炎症,改善线粒体功能并减少神经细胞凋亡。鉴于突变TAR DNA结合蛋白43 ku(TDP-43)在ALS病理发展中的重要作用,本研究初步探讨L-NBP对于突变TDP-43所致的ALS相关损伤是否有保护作用及其机制。因而,在体外建立了稳定转染TDP-43 M337V的NSC-34细胞模型,旨在从细胞和分子水平揭示L-NBP对稳定转染TDP-43 M337V的NSC-34细胞内损伤状态的调节作用。方法对L-NBP减轻稳转TDP-43 M337V细胞的损伤机制进行研究,分别测定细胞乳酸脱氢酶(LDH)、活性氧(ROS)和丙二醛(MDA)含量;采用彗星实验、免疫荧光、ELISA和Western蛋白印迹法观察L-NBP对细胞损伤的保护作用。结果在建立稳转TDP-43 M337V细胞模型后,分别加入不同浓度的L-NBP。培养24 h后,用CCK-8法检测吸光度值,发现2.5～60μmol·L-1的L-NBP可显著提升细胞的存活率。根据结果选择1,2.5,5和20μmol·L-1浓度的L-NBP进行后续实验。与空载体组相比,稳转TDP-43 M337V造成了细胞内的氧化应激、DNA损伤和蛋白质损伤,L-NBP 20μmol·L-1可显著降低稳转TDP-43 M337V细胞的LDH,ROS和MDA的含量,改善氧化引起的DNA损伤和蛋白质损伤,提升核内NF-E2相关因子2(Nrf2)水平,增加细胞内血红素氧合酶1(HO-1)的含量,但是不能引起稳转TDP-43 M337V细胞的TDP-43和醌氧化还原酶1(NQO1)蛋白水平的显著性改变,且对于泛素-蛋白酶体通路和自噬-溶酶体通路也没有明显影响。结论 L-NBP可浓度依赖性促进稳转TDP-43 M337V细胞的增殖,可能通过激活Nrf2抗氧化通路抑制细胞内氧化应激、降低ROS含量、抑制细胞内脂质和蛋白质过氧化、改善DNA损伤效应,进而发挥其抗ALS的作用。L-NBP在稳转TDP-43 M337V细胞中具有一定的抑制氧化应激的作用,可作为潜在的抗氧化药物用于抗ALS药物的研发中,从而增加L-NBP的新适应症。     

氯化钆对PKC的激活可促进成纤维细胞NIH3T3的存活及细胞周期的推进

本研究以氯化钆为代表性含稀土元素的化合物,对其在小鼠胚胎成纤维细胞NIH3T3中对蛋白激酶C家族蛋白的激活进行了研究。利用活细胞成像和共聚焦激光扫描技术可以观察到,在血清饥饿的条件下,50μM的氯化钆可以通过增强细胞粘附和细胞骨架重组促进细胞存活。使用蛋白质印迹技术发现蛋白激酶C家族蛋白在氯化钆作用不同时间后可以发生磷酸化,表明蛋白激酶C被激活。此外,双吲哚马来酰亚胺（bisindolylmaleimide,一种PKCpan的抑制剂）可以有效降低PKCpan磷酸化的水平（βⅡSer660）,同时也可以降低氯化钆引起的ERK的激活。以上结果表明,氯化钆激活的蛋白激酶C可以通过介导MAPK/ERK信号通路的激活,继而推动细胞周期和细胞存活。     

自噬降低异常磷酸化tau蛋白所致的神经细胞毒性

目的观察雷帕霉素和饥饿诱导的自噬对表达异常磷酸化tau蛋白的神经细胞形态、tau蛋白聚集和磷酸化tau降解的影响,探讨这两种经典的诱导自噬方式抑制磷酸化tau的细胞毒性,发挥细胞保护作用的可能机制。方法体外培养小鼠神经瘤母细胞株N2a并转染tau真核表达质粒,蛋白磷酸酯酶抑制剂冈田酸(okadaic acid,OA)诱导tau蛋白异常磷酸化,雷帕霉素(rapamycin,Rapa)或Earle's平衡盐溶液(Earle's balanced salts,EBSS)诱导细胞自噬,巴佛洛霉素A1(Bafilomycin A1,Baf A1)抑制自噬,DAB染色观察表达tau细胞的形态变化;激光共聚焦显微镜观察细胞内tau聚集体;TUNEL染色和caspase-3活性检测细胞凋亡;免疫印迹(immunoblot,IB)检测磷酸化tau和细胞自噬水平。结果过表达tau的细胞胞体变圆,突起减少;OA处理后细胞突起进一步减少甚至消失,胞质出现明显tau聚集体,凋亡细胞增加,剪切型caspase-3水平上调;Rapa和EBSS处理后的细胞形态均有一定程度改善,tau聚集体明显减少,细胞凋亡减少,剪切型caspase-3表达降低;而自噬抑制剂Baf A1处理的细胞变圆,皱缩,胞质大量tau聚集体,凋亡细胞明显增加。IB结果显示Rapa明显降低高分子量的磷酸化tau,而EBSS能明显减少低分子量磷酸化tau的水平。结论 Rapa和EBSS诱导的细胞自噬均能抑制磷酸化tau蛋白的细胞毒作用,但其发挥细胞保护作用的机制不同,Rapa诱导自噬倾向于降解磷酸化tau的寡聚体,而EBSS更易于降解低分子量的磷酸化tau蛋白。     

小檗碱及其主要Ⅰ相代谢产物改善人肝癌Hep G2细胞胰岛素抵抗作用及机制初探

目的探讨小檗碱及其4个主要的Ⅰ相代谢产物改善胰岛素抵抗的作用及相关分子机制。方法首先本研究采用高浓度葡萄糖刺激人肝癌HepG2细胞建立胰岛素抵抗模型。采用葡萄糖氧化酶法和2-NBDG法检测小檗碱及其代谢产物在胰岛素抵抗的HepG2细胞中葡萄糖摄取的情况;分别采用蛋白质免疫印迹法和实时-PCR技术检测小檗碱及其活性代谢产物对于葡萄糖转运及糖异生关键蛋白GLUT1、GLUT2和PEPCK表达的变化;采用蛋白质免疫印迹考察小檗碱及其代谢产物对PI3K/Akt信号通路的影响。结果与空白对照组相比,高浓度葡萄糖刺激HepG2细胞后,葡萄糖摄取显著降低,提示本研究条件可以建立体外胰岛素抵抗模型。小檗碱及其代谢产物M1,M2和M3可以显著增加葡萄糖摄取(P<0.05)。本研究进一步发现,在高糖诱导的胰岛素抵抗的HepG2细胞中,BBR,M1和M2不影响GLUT1的表达,而BBR和M1明显上调GLUT2的膜上蛋白表达(P<0.05);同时,BBR,M1和M2抑制PEPCK的mRNA表达(P<0.05)。此外,BBR和M2上调PI3K和Akt蛋白磷酸化的水平(P<0.05)。结论小檗碱及其代谢产物M1,M2和M3在体外可以明显改善胰岛素抵抗。其中,小檗碱和M1可以通过促进葡萄糖转运缓解胰岛素抵抗,而小檗碱和M2可能通过PI3K/Akt通路调控糖异生进而发挥缓解胰岛素抵抗的作用。     

Chronic regulation of the expression of gap junction proteins connexin40, connexin43, and connexin45 in neonatal rat cardiomyocytes

Gap junction channels form the basis of intercellular communication in the heart. In the working myocardium, the connexin43 (Cx43) is most abundantly found, whereas connexin40 (Cx40) is expressed in the atria and in the conduction system [together with low levels of connexin45 (Cx45)]. However, little is known about the differential regulation of the connexins by pathophysiologically stimuli such as tumor necrosis factor alpha (TNFalpha). Inasmuch as TNFalpha may play a contributory role in the concert of factors involved in the pathophysiology of heart failure and because this cardiac disease often leads to ventricular reentrant arrhythmia, the goal of our study was to find out whether TNFalpha may influence the expression of the cardiac connexins connexin43, connexin40, and connexin45. Neonatal rat cardiomyocytes were exposed to TNFalpha (10, 40, 100, 400, and 1000 pg/ml) for 24 h with or without additional treatment with the mitogenic-activated protein kinase (MAP-kinase) inhibitors SB203580 [4-(4-fluorophenyl)-2-(4-methyl-sulfinylphenyl)-5-(4-pyridyl)-1H-imidazole; 10(-5) M, protein38 mitogenic-activated protein kinase (p38 MAP kinase) inhibitor] or the MEK1 (mitogenic-activated protein kinase/extracellular signal-regulated kinase kinase) inhibitor PD98059 [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; 10(-5) M]. Connexin43, connexin40, and connexin45 expressions were analysed using Western blot analysis, immunohistology, and polymerase chain reaction (PCR) studies (connexin43 and connexin40). TNFalpha induced a concentration-dependent increase in connexin43 (by 2.9+/-0.6, P<0.05, n=5) but not in connexin40 or connexin45 expressions. Both connexins (40 and 45) showed a very low expression near the detection limit. The increases in connexin43 expression could be completely suppressed by SB203580 (0.9+/-0.4, P<0.05, n=5) but not by PD98059. In absence of a stimulating drug, these inhibitors (SB203580 or PD98059) did not affect connexin43 content. Additional PCR experiments revealed increases in connexin43 mRNA under the influence of 100 pg/ml TNFalpha (211+/-38%, P<0.05, n=5), which could be completely suppressed by SB203580. In contrast, the connexin40 expression remained unchanged. From these results, we conclude that TNFalpha can differentially regulate cardiac connexin expression via p38 MAP kinase pathway and thus may alter intercellular communication. This may contribute to the changes observed in heart failure with regard to the formation of an arrhythmogenic substrate.     

白藜芦醇能够修复离体缺血再灌注损伤大鼠心脏M3受体与间隙连接蛋白43间结构及功能性整合

为了探讨白藜芦醇是否能通过影响M₃受体和间隙连接蛋白43(Cx43)间结构及功能性整合发挥其抗心肌缺血再灌注损伤作用，应用免疫共沉淀、免疫印迹及免疫荧光技术研究白藜芦醇对M₃受体与Cx43间结构及功能性整合的影响。结合大鼠离体II导联心电图及心肌超氧化物歧化酶(SOD)、丙二醛(MDA)的检测观察白藜芦醇是否能恢复心肌缺血再灌注损伤。白藜芦醇能修复心肌缺血再灌注损伤所致的M₃受体与Cx43间结构及功能性整合的破坏及纠正Cx43表达异常。同时QRS波时限﹑SOD及MDA的改变也得到相应恢复。白藜芦醇能修复M₃受体与Cx43间结构及功能性整合而发挥抗缺血再灌注损伤作用。     

Sufentanil limits the myocardial infarct size by preservation of the phosphorylated connexin 43

Sufentanil, with a potent analgesia effect, has been wildly used in anesthesia and analgesia, especially for the cardiovascular surgeries. The aim of the study was to evaluate whether sufentanil provides cardioprotection and the effect of connexin 43 on the cardiac infarct size reduction. Sufentanil post-conditioning (bolus injection at 0.1, 0.3, 1, 3, 10 μg/kg) or ischemic post-conditioning (3 cycles of a 10s reperfusion alternating with a 10s ischemia) was induced in an intact rat heart model of ischemia-reperfusion injury. Both ischemic and sufentanil post-conditioning reduced the myocardial infarct size compared with control group. The infarct size limitation of sufentanil was dose-dependent, 1 μg/kg has the optimal effect and increasing dosage could not afford further cardioprotection. Connexin 43 underwent dephosphorylation in response to ischemia-reperfusion measured by Western blot at the anterior myocardium tissues of left ventricle while sufentanil preserved the phosphorylation of connexin 43. The results demonstrated that sufentanil limits myocardial infarct size which is similar with ischemic post-conditioning at the dosage of 1 μg/kg. Preservation of phosphorylation of connexin 43 plays an important role in the cardioprotection of ischemic and sufentanil post-conditioning.     

Sex differences in cardiomyocyte connexin43 expression

Decreases in cardiac connexin43 (Cx43) play a critical role in abnormal cell-to-cell communication and have been linked to the resistance of the female heart to arrhythmias. We therefore hypothesized that Cx43 expression would be greater in female cardiomyocytes than in male cardiomyocytes under pathologic conditions. Adult ventricular myocytes were isolated from male and female rats and treated with phenylephrine (PE), a well-established pathologic stimulus. Cx43 gene and protein expression was determined. The expression of micro-RNA-1 (miR-1), a micro-RNA known to control Cx43 protein expression in cardiomyocytes, was also determined. Cx43 mRNA and protein levels were significantly higher in the female cardiomyocytes than in the male cardiomyocytes (mRNA: 1.4-fold; Protein: 5-fold, both P < 0.05) under both basal and pathologic conditions. PE treatment increased Cx43 expression only in female cardiomyocytes. Cx43 phosphorylation, a marker of preserved Cx43 function, was also higher (P < 0.05), and The expression of miR-1 was lower (P < 0.05) in the female cardiomyocytes after PE treatment. The expression of miR-1 was unchanged by PE treatment in male cardiomyocytes. Thus, a sex difference in miR-1 may be responsible for the sex difference in Cx43 expression in cardiomyocytes under pathologic conditions. Taken together, our results demonstrate a sex difference in Cx43 expression and site-specific phosphorylation that favors cardioprotection in female cardiomyocytes.     

Effect of hypaconitine combined with liquiritin on the expression of calmodulin and connexin43 in rat cardiac muscle in vivo

Objectives To study the effects of hypaconitine used alone and combined with liquiritin on calmodulin (CaM) expression and connexin43 (Cx43) phosphorylation on serine368 (Ser368), as well as to investigate the intervention of liquiritin on these hypaconitine‐induced effects. Methods Adult Wistar rats were orally administered hypaconitine (0.23, 0.69, 2.07 mg/kg per day), liquiritin (20 mg/kg per day), or hypaconitine (2.07 mg/kg per day) plus liquiritin (20 mg/kg per day) for seven consecutive days. The mRNA expression levels of CaM and Cx43 in rat myocardial tissue were determined by real‐time quantitative PCR. The protein contents of CaM and phosphorylated Cx43 (Ser368) were determined by Western blot. Key findings The results indicated that the mRNA and protein expression levels of CaM were significantly decreased by hypaconitine used alone and combined with liquiritin. Although CaM mRNA expression level was inhibited by liquiritin, its protein expression level was upregulated. Meanwhile, although no obvious effect on Cx43 mRNA expression was observed after the drug administration, the phosphorylation level of Cx43 (Ser368) was significantly inhibited. Furthermore, the coadministration of hypaconitine and liquiritin significantly reduced hypaconitine‐induced inhibitory action on Cx43 (Ser368) phosphorylation. Conclusions The study indicated that hypaconitine could inhibit CaM expression and Cx43 (Ser368) phosphorylation, and liquiritin could interfere with this kind of effect by synergistically inhibiting CaM expression and by antagonizing Cx43 (Ser368) dephosphorylation induced by hypaconitine.     

Proteomic and metabolomic responses to connexin43 silencing in primary hepatocyte cultures

Freshly established cultures of primary hepatocytes progressively adopt a foetal-like phenotype and display increased production of connexin43. The latter is a multifaceted cellular entity with variable subcellular locations, including the mitochondrial compartment. Cx43 forms hemichannels and gap junctions that are involved in a plethora of physiological and pathological processes, such as apoptosis. The present study was conducted with the goal of shedding more light onto the role of connexin43 in primary hepatocyte cultures. Connexin43 expression was suppressed by means of RNA interference technology, and the overall outcome of this treatment on the hepatocellular proteome and metabolome was investigated using tandem mass tag-based differential protein profiling and ¹H NMR spectroscopy, respectively. Global protein profiling revealed a number of targets of the connexin43 knock-down procedure, including mitochondrial proteins (heat shock protein 60, glucose-regulated protein 75, thiosulphate sulphurtransferase and adenosine triphosphate synthase) and detoxifying enzymes (glutathione S-transferase μ 2 and cytochrome P450 2C70). At the metabolomic level, connexin43 silencing caused no overt changes, though there was some evidence for a subtle increase in intracellular glycine quantities. Collectively, these data could further substantiate the established existence of a mitochondrial connexin pool and could be reconciled with the previously reported involvement of connexin43 signalling in spontaneously occurring apoptosis in primary hepatocyte cultures.     

Protective Effect of the Natural Product,Chaetoglobosin K,on Lindane- and Dieldrin-induced Changes in Astroglia: Identification of Activated Signaling Pathways

Purpose The purpose of the present study was to identify the biochemical mechanism(s) of the preventative and reversal effects of Chaetoglobosin K (ChK), a bioactive natural product, on inhibition of gap junction-mediated communication and connexin phosphorylation by the tumor promoting organochlorine compounds, lindane, and dieldrin. Materials and methods A fluorescent dye transfer assay was used to quantify gap junction-mediated communication and sensitivity to lindane and dieldrin. Analyses of connexin 43, PKC, ERK, GSK-3β, Raf, and Akt kinase phosphorylation were performed by Western blotting. Results Pre-incubation of astroglial cells with 10 μM ChK prevented inhibition of dye transfer by lindane and dieldrin, which correlates with stabilization of the connexin 43 P2 isoform, and addition of ChK after lindane or dieldrin reversed the inhibitory effect, which correlated with re-appearance of the P2 isoform. Using phosphorylation site-specific antibodies, we demonstrated that lindane, dieldrin, and ChK all activated p44/42 ERK, but only ChK activated Akt kinase. ChK also activated a downstream effector of Akt, GSK-3β, and activation of both kinases was inhibited by Wortmannin. Wortmannin also blocked ChK’s ability to prevent dieldrin-induced inhibition of gap junction-mediated communication between RG-2 cells. Conclusion ChK’s protective effects, both preventative and reversal, on lindane and dieldrin inhibition of gap junction-mediated communication are associated with stabilization and reappearance of the connexin 43 P2 phosphoform and may be mediated by the Akt pathway.