前列腺癌细胞连接蛋白43表达和细胞间隙连接交流状况

目的　观察前列腺癌 (PCa)细胞连接蛋白 (Connexin ,Cx)表达和细胞间隙连接交流(GJIC)状况 ,探讨胸苷激酶 (TK)自杀基因治疗前列腺癌时旁观者效应不够强大的原因以及GJIC与前列腺癌发生的关系。　方法　分别采用逆转录 聚合酶链式反应 (RT PCR)、链霉亲和素免疫组化法 (SABC法 )和划痕标记染料示踪技术 (SLDT)检测前列腺癌细胞系PC 3m的连接蛋白 4 3(Cx4 3)mRNA、蛋白表达和GJIC功能状况 ,并观察Cx4 3蛋白在正常前列腺和前列腺癌组织中的表达。　结果　PC 3m有Cx4 3mRNA和蛋白表达 ,但其表达较弱 ,且Cx4 3蛋白大多异常定位于细胞浆中而非细胞膜上 ;组织切片显示前列腺癌组织Cx4 3蛋白异常定位且表达水平较正常前列腺组织明显减弱 ,与病理分级呈负相关关系 (χ2 =4 0 2 5 ,P <0 0 5 ) ,高分化和中等分化、低分化腺癌的表达率分别为5 2 9%及 7 1%。此外 ,PC 3m细胞GJIC功能低下 ,半定量为 ( )或 (- )。　结论　前列腺癌细胞GJIC功能低下 ,Cx4 3基因下调表达和蛋白异常定位均可能为导致这一现象的原因。GJIC功能缺陷可能是引起单纯疱疹病毒 胸苷激酶 /更昔洛韦系统杀伤前列腺癌细胞时旁观者效应不够强大的原因 ,亦可能是前列腺癌发生、发展中的分子事件。     

Signal transduction of gap junctional genes,connexin32, connexin43 in human hepatocarcinogenesis

AIM: To investigate gap junctional intercellular communication (GJIC) in hepatocellular carcinoma cell lines, and signal transduction mechanism of gap junction genes connexin32(cx32),connexin43(cx43) in human hepatocarcinogenesis. METHODS: Scarped loading and dye transfer (SLDT) was employed with Lucifer Yellow (LY) to detect GJIC function in hepatocellular carcinoma cell lines HHCC, SMMC-7721 and normal control liver cell line QZG. After Fluo-3AM loading, laser scanning confocal microscope (LSCM) was used to measure concentrations of intracellular calcium (Ca(2+))i in the cells. The phosphorylation on tyrosine of connexin proteins was examined by immunoblot. RESULTS: SLDT showed that ability of GJIC function was higher in QZG cell than that in HHCC and SMMC-7721 cell lines. By laser scanning confocal microscopy, concentrations of intracellular free calcium (Ca(2+))i was much higher in QZG cell line (108.37 nmol/L) than those in HHCC (35.13 nmol/L) and SMMC-7721 (47.08 nmol/L) cells. Western blot suggested that only QZG cells had unphosphorylated tyrosine in Cx32 protein of 32 ku and Cx43 protein of 43 ku; SMMC-7721 cells showed phosphorylated tyrosine Cx43 protein. CONCLUSION: The results indicated that carcinogenesis and development of human hepatocellular carcinoma related with the abnormal expression of cx genes and disorder of its signal transduction pathway, such as decrease of (Ca(2+))i, post-translation phosphorylation on tyrosine of Cx proteins which led to a dramatic disruption of GJIC.     

大蒜素对胃上皮细胞Cx37、Cx43 mRNA表达及细胞间隙连接通讯功能的影响

目的观察体外实验中大蒜素对胃上皮细胞系MGC-803Cx37 mRNA、Cx43 mRNA表达及细胞间隙连接通讯功能的影响。方法终浓度为3μg／ml、6μg／ml、9μg／ml、12μg／ml大蒜素分别加入胃上皮细胞MGC-803培养24h、48h、72h，同时设立不加药物的阴性对照，用RT，PCR法检测细胞cx37mRNA、Cx43 mRNA表达，LY染料传输方法检测细胞间隙连接通讯功能。结果MGC-803细胞cx37mRNA有表达，cx43mRNA无表达，GJIC功能弱，加入不同浓度大蒜素后，cx37mRNA表达和细胞间隙连接通讯功能增强，cx37mRNA表达随大蒜素浓度和培养时间的增加而增强（均P〈0．05），Cx43 mRNA仍无表达。结论大蒜素在转录水平上调胃上皮细胞MGC-803 Cx37基因的表达，改善细胞间隙连接通讯功能。     

Regulation of connexin43 gap junctional conductance by ventricular action potentials

Transjunctional voltage regulates cardiac gap junctional conductance, but the kinetics of inactivation were considered too slow to affect cardiac action potential propagation. Connexin43 (Cx43) is abundantly expressed in the atrial and ventricular myocardium and the rapid ventricular conduction tissues (ie, His-Purkinje system) of the mammalian heart and is important to conduction through these cardiac tissues. The kinetics of Cx43 voltage gating were examined at peak action potential voltages using simulated ventricular myocardial action potential waveforms or pulse protocols exceeding 100-mV transjunctional potentials. Junctional current responses approximate the action potential morphology but conductance calculations reveal a 50% to 60% decline from peak to near constant plateau values. Junctional conductance recovers during phase 3 repolarization and early diastole to initial values. The bases for these transient changes in junctional conductance are the rapid decay kinetics in tens of milliseconds at peak transjunctional voltages (Vj) of 130 mV and the gradual increase in junctional conductance as Vj returns toward 0 mV. The decay time constants change e-fold per 22.1 mV above the half-inactivation voltage for Cx43 gap junctions of +/-58 mV. A realistic dynamic model for changes in junctional resistance between excitable and nonexcitable cells during cardiac action potential propagation was developed based on these findings. This dynamic model of cardiac gap junctions will further our understanding of the role gap junctions play in the genesis and propagation of cardiac arrhythmias. The full text of this article is available online at http://www.circresaha.org.     

Role of connexin 43 in ischemic preconditioning does not involve intercellular communication through gap junctions

Connexin 43 (Cx 43) has recently been implicated in protection of ischemic preconditioning. Cx 43 colocalization with protein kinase C and p38 mitogen-activated protein kinase is increased in preconditioned myocardium, Cx 43 phosphorylation is preserved in preconditioned myocardium, and hearts from Cx 43-deficient mice cannot be preconditioned. It is, however, unclear whether the important role of Cx 43 relates to intercellular communication through gap junctions or its function in volume homeostasis. To address this issue, we used isolated cardiomyocytes, which no longer-form gap junctions, from wild-type (n = 5) and heterozygous Cx 43-deficient mice (n = 8) and subjected them to 2 h simulated ischemia (hypoxia, acidosis) and an additional challenge by extracellular hypo-osmolarity (from 310 to 250 mOsm/l). Viability (trypan blue exclusion) was well maintained in normoxic wild-type cardiomyocytes (54 +/- 5% at baseline vs. 46 +/- 4 (mean +/- S.D.) % at 2 h). With simulated ischemia, viability was reduced to 17 +/- 5%. Preconditioning by a preceding exposure to 10 min simulated ischemia and 15 min reoxygenation preserved viability after 2 h simulated ischemia (36 +/- 1%, P < 0.001 vs. simulated ischemia). In Cx 43-deficient cardiomyocytes, viability was also well maintained in normoxia (56 +/- 10% vs. 44 +/- 10%). Viability was also reduced to 17 +/- 6% with 2 h simulated ischemia. In contrast to wild-type cells, preconditioning did not prevent the reduction in viability (18 +/- 8%). In conclusion, Cx 43 is essential for preconditioning in the absence of gap junctions, supporting its function through improved volume regulation.     

细胞间隙连接通讯及其通路蛋白与大肠癌发生关系的研究进展

细胞间隙连接通讯(gap junctional intercellular communication,GJIC)是多细胞生物体内普遍存在的一种通讯方式,他参与离子和其他小分子信号物质的转运.GJIC对细胞的生长、增殖和分化起重要的调控作用,他的改变与肿瘤的发生密切相关.大肠癌是人类常见的恶性肿瘤之一,目前研究表明,大肠癌的发生是一个多步骤、多基因、多阶段的过程,包括癌基因激活、抑癌基因失活、DNA转录表达失控、DNA损伤等.不论何种原因的细胞转化,其最终表现为细胞周期失控、细胞无限增殖.本文就GJIC及其通路蛋白、细胞因子与大肠癌的发生的研究进展作一综述.     

卡维地洛对梗死心脏心肌连接蛋白43的影响

目的探讨卡维地洛对梗死心脏心肌组织连接蛋白43的影响。方法结扎大鼠左冠状动脉建立心肌梗死模型。随机将大鼠分为假手术组、手术组和手术加卡维地洛组。术前7d分别用安慰剂、卡维地洛（日剂量2mg／kg,分2次给药）。术后1,3,7d检测左心室游离壁、室间隔、右心室壁连接蛋白43表达,术后7d测心肌梗死病灶大小、室间隔厚度、左心室大小。结果连接蛋白43表达于心肌梗死1～7d呈逐渐增加趋势;左心室游离壁连接蛋白43表达于心肌梗死1～7d时均处于低水平,与对照组差异有统计学意义（P〈0．05）：右心室壁连接蛋白43表达于心肌梗死1～7d与对照组差异无统计学意义（P〉0．05）。卡维地洛能明显地抑制缺血肥厚心肌组织连接蛋白43的上调,抑制左心室扩张和缩小心肌梗死病灶。结论心肌梗死肥厚组织中连接蛋白43上调,卡维地洛能减轻心肌重构与选择性的抑制肥厚心肌组织中的连接蛋白43上调有关。     

Metabolic inhibition induces opening of unapposed connexin 43 gap junction hemichannels and reduces gap junctional communication in cortical astrocytes in culture.

Rat cortical astrocytes in pure culture are functionally coupled to neighboring cells via connexin (Cx) 43 gap junctions under ordinary conditions. Small fluorescent molecules such as Lucifer yellow (LY) pass between cell interiors via gap junctions, but do not enter the cells when externally applied. Subjecting rat and mouse cortical astrocytes to "chemical ischemia" by inhibition of glycolytic and oxidative metabolism induced permeabilization of cells to Lucifer yellow and ethidium bromide before loss of membrane integrity determined by dextran uptake and lactate dehydrogenase release. The gap junction blockers octanol and 18alpha-glycyrrhetinic acid markedly reduced dye uptake, suggesting that uptake was mediated by opening of unapposed hemichannels. Extracellular La(3+) also reduced dye uptake and delayed cell death. The purinergic blocker, oxidized ATP, was ineffective. Astrocytes isolated from mice with targeted deletion of the Cx43 coding DNA exhibited greatly reduced dye coupling and ischemia-induced dye uptake, evidence that dye uptake is mediated by Cx43 hemichannels. Dye coupling was reduced but not blocked by metabolic inhibition. Blockade of lipoxygenases or treatment with free radical scavengers reduced dye uptake by rat astrocytes, suggesting a role for arachidonic acid byproducts in hemichannel opening. Furthermore, permeabilization was accompanied by reduction in ATP levels and dephosphorylation of Cx43. Although hemichannel opening would tend to collapse electrochemical and metabolic gradients across the plasma membrane of dying cells, healthy cells might rescue dying cells by transfer of ions and essential metabolites via Cx43 gap junctions. Alternatively, dying astrocytes might compromise the health of neighboring cells via Cx43 gap junctions, thereby promoting the propagation of cell death.     

人脐动脉内皮细胞和平滑肌细胞体外培养鉴定及缝隙连接通讯功能测定

目的:应用双光子激光扫描共聚焦显微镜鉴定体外培养的脐动脉内皮细胞(ECs)和平滑肌细胞(SMCs),应用荧光光漂白恢复技术(FRAP)测定血管ECs、SMCs之间的缝隙连接通讯(GJIC)功能。方法:人脐动脉ECs、SMCs分离培养,Ⅷ因子和SMα-actin相关抗原鉴定ECs和SMCs,应用FRAP技术测定血管内皮细胞、平滑肌细胞之间的GJIC功能,记录实时成像结果,应用动态比(M)计算漂白区域内标记荧光的分子中动态分子的比例。结果:第一组ECs和SMCs单独培养,选择漂白细胞与周围至少3个同种细胞相连接,SMCs被漂白后平均M值为31.79±5.69;ECs被漂白后平均M值为23.43±2.11;第二组ECs和SMCs混合培养,选择ECs和SMCs独立相连的2个细胞,SMCs被漂白后平均M值为14.47±3.28,ECs被漂白后平均M值为6.41±0.80。结论:FRAP实时动态恢复曲线可直接观察荧光恢复强度及速度,参照FRAP恢复曲线,M值可做为组间GJIC比较相对定量的可靠指标,通过检测证实ECs和SMCs之间存在GJIC,且荧光由ECs向SMCs方向的传递大于由SMCs向ECs方向的传递。     

Quantitative analysis of intercellular connections by immunohistochemistry of the cardiac gap junction protein connexin43

Polyclonal antisera directed against epitopes in the cytoplasmic domain of rat connexin43, the predominant cardiac gap junction protein, were used to delineate immunohistochemically the distribution of gap junctions in sections of canine left ventricle. Antigen-antibody binding and tissue structure were preserved after paraformaldehyde fixation and paraffin embedment of canine myocardium. Specific binding of antibody to the cytoplasmic surfaces of ultrastructurally identified gap junctions was confirmed with electron microscopy. Light microscopic morphometric analysis of immunostained sections in five separate experiments revealed a mean gap junction surface density of 0.0052 micron2/micron3 myocyte volume, which is consistent with previously reported values determined by use of quantitative electron microscopy. This new method permits quantitative determinations of gap junction surface density and distribution in relatively large heterogeneous areas of myocardium in which ultrastructural morphometry would be impractical. This approach should facilitate analysis of the relation between potential alterations in electrical coupling of myocytes and abnormalities of myocardial conduction occurring at the macroscopic scale in regions such as structurally heterogeneous infarct border zones.     

Development of gap junctional channels and intercellular communication in rat liver during ontogenesis

BACKGROUND/AIMS: We investigated the expression of connexin (Cx) 32 and 26 subunit proteins of the gap junction (GJ) in the rat liver during ontogenesis to clarify their roles in control of growth and differentiation, and observed their channels in association with development of gap junctional intercellular communication (GJIC). METHODS: The expression of Cx32 and 26 in prenatal and postnatal livers was examined by Western blot and immunofluorescence. GJ channels were investigated not only by double immunofluorescence study but also by immunogold electron microscopy. The spread of lucifer yellow 5 min after its microinjection was examined in the cultured liver tissues. RESULTS: 1) Western blot showed the expression of both Cx from the late stage of gestation and their peak a week after birth. 2) Cx32- or 26-positive plaques were scattered on hepatocytes of the fetal liver and some of them were colocalized; both were increased just after birth. On day 7 after birth, Cx32-positive plaques were present on all hepatocytes within a lobule, and Cx26-positive plaques were distributed in the periportal area. 3) Double-immunogold electron microscopy just after birth showed that most GJ channels were homotypic type of Cx32 or 26, and that few were heterotypic. On day 7 after birth, most channels had the homotypic type of type of Cx32 in the middle and pericentral areas, and there was a heterotypic type of Cx32 and 26 in the periportal area. 4) The dye transfer of lucifer yellow showed a wider spread in the liver tissues on day 7 after birth than on day 1. CONCLUSION: Increased GJ formation and compatibility or incompatibility of GJ channels are closely associated with development of GJIC, and GJIC may develop at cytodifferentiation during ontogenesis.     

Taurine preserves gap junctional intercellular communication in rat hepatocytes under oxidative stress

Gap junctional intercellular communication (GJIC) between hepatocytes is important for the maintenance of differentiated liver functions. Taurine is known to be cytoprotective, and is used clinically to improve liver functions. We evaluated the effect of taurine on GJIC in hepatocyte doublets under oxidative stress. Hepatocyte doublets were isolated from female Wistar rats, using a collagenase perfusion technique, and cultured in Leibovitz-15 medium containing fetal bovine serum (10%). H₂O₂ (2 mM) and/or taurine (0.1–1 mM) were added 2 h after inoculation, and the culture was incubated for 3 h. Fluorescent dye (Lucifer Yellow CH) coupling between adjacent cells was evaluated by microinjection. The distribution and quantity of connexin 32 (Cx32) in hepatocytes were detected using indirect immunofluorescence analysis and Western blotting. Steady state mRNA levels of Cx32 were detected by Northern blotting. The percentage of dye coupling 5 h after inoculation was 88 ± 6.3% in the control, however, this was decreased to almost half the control value by H₂O₂. Taurine prevented the decrease caused by H₂O₂ in a dose-dependent manner. Immunofluorescence analysis for Cx32 demonstrated numerous punctate fluorescent spots along the intercellular plasma membrane in controls, which were significantly decreased by H₂O₂. Taurine prevented the decrease of Cx32. Western blot analysis also showed the decrease of Cx32 protein levels by H₂O₂ treatment, which decrease was prevented by taurine. Interestingly, H₂O₂ and/or taurine treatments did not affect Cx32 mRNA levels. Our findings indicated that H₂O₂ treatment decreased GJIC between hepatocytes, most likely due to augmenting the degradation of Cx32 proteins, whereas taurine prevented this process. This effect of taurine is beneficial for the preservation of differentiated functions in the liver under oxidative stress. Received: August 12, 1999 / Accepted: November 26, 1999     

EphB signaling inhibits gap junctional intercellular communication and synchronized contraction in cultured cardiomyocytes

Eph receptors and ephrin ligands are membrane-bound cell–cell communication molecules with important roles not only in development but also in the physiology of many adult organs. However, their cellular localization and functions in the myocardium are virtually unknown and therefore, we have investigated the expression of EphB receptors and ephrin-B ligands in the rodent heart ventricles and their functions in the rodent cardiomyocytes of primary culture. Examinations by RT-PCR, immunohistochemistry and in situ hybridization revealed that the EphB receptors are preferentially expressed in cardiomyocytes and ephrin-B ligands in the vasculature in adult mouse heart ventricles. Interestingly, we found that inducing high levels of EphB receptor activation in primary cultures of rodent cardiomyocytes by stimulation with ephrin-B1-Fc desynchronized the contraction of adjacent clusters of cardiomyocytes that had contracted synchronously before the treatment. Co-immunoprecipitation experiments revealed that EphB4 physically associates with connexin43, a major component of gap junctions in the myocardium, and that EphB activation inhibits gap junctional intracellular communication between cardiomyocytes. The present findings suggest that ephrin-B-EphB signaling can modulate the electrical coupling of cardiomyocytes through effects on gap junctions.     

Alterations of intercellular communication in neonatal cardiac myocytes from connexin43 null mice

Objective: To compare gap junction expression and intercellular coupling in wildtype neonatal cardiac myocytes to those from mice lacking the most abundant cardiac gap junction protein (connexin43, Cx43). Methods: Northern and Western blots compared connexin mRNA and protein levels, immunocytochemistry evaluated connexin distribution in neonatal Cx43 null(-/-), heterozygous(+/-) and wildtype(+/+) mouse hearts. Ca(2+) imaging, dye coupling and electrophysiological methods evaluated intercellular communication. Results: Similar levels of Cx40 and Cx45 were detected in all genotypes, although in adult cardiac tissue from wildtype mice, Cx43 expression was higher than in heterozygotes. After culturing dissociated cells for 3-4 days, cardiocytes beat spontaneously; in Cx43(+/+) and (+/-) cultures, the beating was generally quite synchronous. In Cx43(-/-) mice, interbeat intervals were on average twice as long and more variable than in Cx43(+/+) or Cx43(+/-) cultures. Junctional conductance was lower by about 60% in Cx43(-/-) as compared to Cx43(+/-) and (+/+) littermates; Lucifer Yellow dye coupling was virtually absent in Cx43(-/-) cardiomyocytes but was comparably strong in wildtype and heterozygous siblings. Macroscopic junctional conductance measurements on Cx43(-/-) cardiocytes showed slightly stronger voltage sensitivity in these cells than in Cx43(+/+) cardiocytes. Unitary junctional conductance measurements revealed distinct populations of channels contributing to macroscopic conductance for Cx43(+/+) and Cx43(-/-) genotypes. Conclusions: In Cx43-deficient cardiac myocytes, the expression of other connexins only partially compensates for the functional loss, with dye coupling and spontaneous beating being strongly impaired.     

Melatonin effects on intercellular junctional communication in MCF-7 human breast cancer cells

Melatonin exerts a direct antiproliferative effect on estrogen-responsive MCF-7 cells in culture. Recently, the importance of the anti-invasive actions of melatonin as a part of the oncostatic action of this indolamine has been reported. Gap junctional intercellular communication is known to be involved in controlling cell proliferation and differentiation, and a decrease in intercellular junctional communication has been described in highly invasive mammary cancer cells. Because melatonin at physiological doses (1 nM) shifts MCF-7 cells to a lower invasive status, we postulate that melatonin could modulate the levels of gap junctional intercellular communication in these tumor cells. To test our hypothesis, we studied gap junctional intercellular communication in MCF-7 human breast cancer cells previously (7-8 days) treated, or not, with melatonin (10 microM or 1 nM). Using the scrape-loading assay dye-transfer technique to introduce 0.05% Lucifer yellow into cells, we measured the ability of the tumor cells to transfer dye to adjacent cells. Rhodamine dextran (0.05%) was used as a control dye to verify that dye-transfer occurs through intercellular junctions. The presence of melatonin (10 microM or 1 nM) in the culture medium significantly increased (P < 0.01) the transfer of the dye to adjacent cells through gap junctions. This increase was greater at 10 microM melatonin, and averaged scan profiles of cells treated with melatonin 10 microM showed a statistically significant increase (P < 0.01) in the integrated optical density values, and a broadening of the densitometric scan. These findings suggest that melatonin could exert its antitumor action, at least in part, by increasing regulatory signals that are passed between adjacent epithelial cells through intercellular junctions.