防治血管再狭窄的新靶点——缝隙连接蛋白43

缝隙连接是介导相邻细胞间离子和小分子信号物质直接交换的跨膜通道,血管平滑肌细胞中主要表达连接蛋白43(connexin43,CX43)。研究表明,CX43表达上调与平滑肌细胞的增殖、迁移及细胞外基质生成密切相关,促使血管损伤后新内膜生成,引起血管再狭窄,提示CX43可能成为血管性疾病治疗的新靶点。本文综述CX43与血管再狭窄之间关系及以CX43为靶点的药物和基因治疗的研究进展。     

间隙连接蛋白43在肿瘤领域的研究进展

间隙连接又叫缝隙连接、通讯连接,是细胞间连接方式的一种,为相邻细胞间信息和物质交换的膜通道结构。其基本功能和结构是间隙连接蛋白（connexin,Cx）,每6个连接蛋白单体聚合形成1个连接子,每个连接子中央有1个六棱形小孔道,两侧膜上连接子端端相连,形成缝隙连接通道（gap junction channel,GJC）,     

血浆纤维连接蛋白测定在急性白血病中的初步应用

纤维连接蛋白(Fibronectin,Fn) 为主要由肝脏合成的糖蛋白类,在多种疾病时各有其变化,已引起临床工作者的重视,但目前对急性白血病时的研究较少。本文对52例急性白血病及60例健康对照进行血浆Fn测定,并对急性白血病未经化疗、化疗后未缓解、缓解及并发感染等情况进行分析,以探讨其临床价值。 1 对象和方法:急性白血病52例,其中男34例,女18例,平均年龄34.8岁(16～     

肿瘤坏死因子α对人肝癌细胞株SMMC-7721体外侵袭能力的影响

目的 探讨肿瘤坏死因子α(tumor necrosis factor-α,TNF-α)对人肝癌细胞株SMMC-7721体外侵袭能力的影响及其相关机制. 方法不同浓度TNF-α作用于人肝癌细胞株SMMC-7721后,采用Transwell试验检测细胞侵袭能力的改变,采用划痕标记荧光传输试验显示缝隙连接细胞通讯功能的变化,采用Western blot法检测连接蛋白32(Cx32)在细胞膜的表达. 结果 不同浓度TNF-α作用于人肝癌细胞株SMMC-7721后,Transwell试验显示细胞侵袭能力较对照组提高,且随TNF-α浓度增加而升高. 同时,缝隙连接细胞通讯功能减弱,细胞膜上Cx32的表达减少. 结论 TNF-α可能通过影响Cx32在细胞膜的表达及细胞通讯促进人肝癌细胞株SMMC-7721的侵袭能力.     

连接蛋白32及细胞缝隙连接对卵巢癌细胞顺铂耐药性的影响

目的研究连接蛋白32及细胞缝隙连接对卵巢癌细胞顺铂耐药性的影响。方法以A2780为亲代细胞,采用药物浓度递增法构建对顺铂耐药的卵巢癌细胞系(A2780-CDDP),CCK8法测定顺铂对肿瘤细胞的IC50,计算耐药指数(resistance index,RI)。"细胞接种荧光示踪法"检测卵巢癌细胞耐药行程过程中细胞的缝隙连接功能及Cx32的表达情况;调节A2780-CDDP细胞Cx32的表达,观察耐药性的变化;提细胞膜及胞浆蛋白,用Western印迹分别检测Cx32在A2780和A2780-CDDP的表达分布情况。结果本研究建立了顺铂耐药人卵巢癌细胞株A2780-CDDP,亲代细胞IC50为4.7 mg·L~(-1),A2780-CDDP的IC50为33.8 mg·L~(-1),耐药指数为7.2。同时,随着耐药性的增强,Cx32表达量逐渐增加,增强A2780-CDDP细胞中的GJ功能可提高顺铂的细胞毒性。此外,尽管Cx32在A2780-CDDP细胞中表达增加,但它更多地定位于细胞质而不是细胞膜,并且在A2780-CDDP细胞中下调Cx32的表达可以使其对顺铂治疗敏感。结论 Cx32参与顺铂耐药,Cx32在胞质中的定位对卵巢癌顺铂耐药有重要意义。     

以siRNA表达载体稳定抑制缝隙连接蛋白43表达的睾丸间质细胞和睾丸支持细胞系的建立

目的构建Cx43-siRNA真核表达载体,获得连接蛋白43(connexin43,Cx43)被长期稳定抑制的睾丸间质细胞(TM3细胞)系和睾丸支持细胞(TM4细胞)系,为研究Cx43及其形成的细胞缝隙连接(gap junction,GJ)在睾丸组织中的作用提供有用模型。方法设计合成3对针对Cx43的短发夹样siRNA的DNA模板序列,定向连接到siRNA真核表达载体pSilencerTM2.1-U6neo上,通过测序鉴定后以脂质体法瞬时转染睾丸支持细胞,以Western blot方法检测Cx43蛋白表达水平,筛选出最有效的干扰序列,再将之分别转染睾丸间质细胞和睾丸支持细胞,G418筛选出能稳定表达siRNA的细胞系,以"Parachute"荧光传递示踪法检测细胞缝隙连接功能。结果 Western blot结果显示,第3对干扰序列对Cx43表达抑制效果最佳,以表达该序列的质粒稳定转染的TM3细胞和TM4细胞上Cx43蛋白表达水平均明显降低;荧光传递示踪法检测表明,两种细胞系的GJ功能均被明显抑制。结论以Cx43-siRNA真核表达载体稳定转染的方法能长期干扰TM3和TM4细胞上Cx43的表达,并抑制由其形成的GJ功能。     

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.     

薯蓣皂苷对人肾癌786-0细胞缝隙连接功能的影响

目的探讨薯蓣皂苷(Dioscin,Dio)对人肾癌786-0细胞缝隙连接(Gap junction,GJ)功能的影响及其作用机制。方法 MTT法测Dio对786-0细胞生长的影响,荧光显微镜观察及流式细胞术结合荧光示踪法分析GJ功能变化,RT-PCR和Western blot分析连接蛋白基因表达。结果 0～2.5μmol.L-1 Dio处理786-0细胞48h不影响其存活率;用0、0.1、0.5、1和2μmol.L-1 Dio处理细胞48 h后,荧光显微镜下观察,Dio能明显提高786-0细胞Calcein传递,流式细胞术分析对照组和实验组的绿色荧光细胞(G4)与双阴性受体细胞(G3)比值(G4/G3)分别是0.13±0.01、0.23±0.01、0.30±0.01、0.56±0.02和1.15±0.02,各实验组G4/G3值明显高于对照组(P<0.01);RT-PCR和Western blot分析结果显示,用0、0.1、0.5、1和2μmol.L-1 Dio处理细胞48 h对其Cx43、Cx32和Cx26表达无明显影响。结论体外较低浓度Dio能够有效促进786-0细胞GJ功能,且具有明显的剂量效应关系。但Dio促进GJ机制并不是通过上调Cx43、Cx32和Cx26蛋白表达途径。     

缝隙连接阻断剂heptanol对内皮素收缩大鼠肠系膜动脉的抑制作用

缝隙连接(Gap junction,GJ )为相邻细胞间特化的胞膜结构,其基本构成元素是缝隙连接蛋白(Connexin,Cxs).目前至少已克隆或测序出16种不同的连接蛋白[1].GJ广泛分布于各脏器组织,在平滑肌细胞的协调性收缩、细胞生长调控等发挥重要作用,是目前国际上研究最热门的课题之一[2].1-庚醇(1-heptanol,heptanol)是较公认的GJ特异性阻断剂.我们在前期研究中发现,GJ参与了苯肾上腺素的缩血管作用[3].     

一种快速可靠筛选作用于细胞缝隙连接药物的方法建立

目的建立一种可以快速有效地筛选能影响细胞缝隙连接(gap junction,GJ)功能药物的方法;为研制以GJ为靶点的新型药物提供技术手段。方法构建能同时双向表达两种不同连接蛋白(connexins,Cxs)的质粒;用能表达Cx26/Cx32的质粒转染HeLa细胞,建立可以稳定表达Cx26/Cx32并形成异质性GJ的HeLa细胞模型。用荧光传递示踪法测定荧光示踪剂在细胞之间的传递,以此反映GJ的功能。观察公认的GJ激活剂——维甲酸(retinoid acid,RA)和GJ抑制剂——油酸酰胺(oleamide)对GJ功能的影响,检验该方法是否能够准确地检测出GJ功能。结果 Western blot和荧光传递示踪法的结果表明,转染含有Cx26/Cx32 cDNA质粒的HeLa细胞,可以稳定表达Cx26/Cx32;并能够形成可以传递荧光示踪剂在相邻细胞间的GJ。RA和油酸酰胺能分别增强和抑制荧光示踪剂的传递。结论在转染Cx26/Cx32质粒并稳定表达Cxs的HeLa细胞上,用荧光传递示踪法测定GJ功能,可以快速准确地检测出药物对GJ的作用。该方法的建立为筛选作用于GJ的药物提供了一种有用的技术手段。     

Cell membrane-related toxic responses and disruption of intercellular communication in PCB mechanisms of toxicity: A review

An understanding of polychlorinated biphenyl (PCB) congener-specific effects on cell membrane and intercellular communication is important within the studies of PCB absorption, organ-related PCB accumulation and exertion of toxic responses. Toxic potential of PCBs is linked to various deleterious effects on human health, including neurotoxicity, immunotoxicity, reproductive toxicity and genotoxicity and, recently in 2016 International Agency for Research on Cancer (IARC) has upgraded the classification of PCBs to Group 1 “Carcinogenic to humans.” Proposed mechanisms of aforementioned PCBs adverse effects at cellular membrane level are: (i) downregulation of gap junction intercellular communication and/or connexins; (ii) compromised membrane integrity; and (iii) altered tight junction barrier function. This study, based on an extensive literature survey, shows the progress in scientific research of each of these three levels with the aim of pointing out the earliest toxic events of PCBs, which can result in serious cell/tissue/organ damage.     

Disruption of gap junctions attenuates aminoglycoside-elicited renal tubular cell injury

BACKGROUND AND PURPOSE

Gap junctions play important roles in the regulation of cell phenotype and in determining cell survival after various insults. Here, we investigated the role of gap junctions in aminoglycoside-induced injury to renal tubular cells.

EXPERIMENTAL APPROACH

Two tubular epithelial cell lines NRK-E52 and LLC-PK1 were compared for gap junction protein expression and function by immunofluorescent staining, Western blot and dye transfer assay. Cell viability after exposure to aminoglycosides was evaluated by WST assay. Gap junctions were modulated by transfection of the gap junction protein, connexin 43 (Cx43), use of Cx43 siRNA and gap junction inhibitors.

KEY RESULTS

NRK-E52 cells expressed abundant Cx43 and were functionally coupled by gap junctional intercellular communication (GJIC). Exposure of NRK-E52 cells to aminoglycosides, G418 and hygromycin, increased Cx43 phosphorylation and GJIC. The aminoglycosides also decreased cell viability that was prevented by gap junction inhibitors and Cx43 siRNA. LLC-PK1 cells were gap junction-deficient and resistant to aminoglycoside-induced cytotoxicity. Over-expression of a wild-type Cx43 converted LLC-PK1 cells to a drug-sensitive phenotype. The gap junction inhibitor α-glycyrrhetinic acid (α-GA) activated Akt in NRK-E52 cells. Inhibition of the Akt pathway enhanced cell toxicity to G418 and abolished the protective effects of α-GA. In addition, gentamycin-elicited cytotoxicity in NRK-E52 cells was also significantly attenuated by α-GA.

CONCLUSION AND IMPLICATIONS

Gap junctions contributed to the cytotoxic effects of aminoglycosides. Modulation of gap junctions could be a promising approach for prevention and treatment of aminoglycoside-induced renal tubular cell injury.     

DOMINANT INHIBITION OF INTERCELLULAR COMMUNICATION BY TWO CHIMERIC CONNEXINS

1. The physiological significance of communication through gap junction channels has been difficult to assess because channel activity cannot be experimentally modulated in a specific manner. To address this problem we have constructed chimeric connexins that function as dominant-negative inhibitors of intercellular channel activity.     

Different mechanisms of modulation of gap junction communication by non-genotoxic carcinogens in rat liver in vivo

This is a comparative study of the mechanisms by which three different rodent non-genotoxic carcinogens modulate connexin-mediated gap junction intercellular communication in male rat liver in vivo. In the case of the peroxisome proliferating agent Wy-14,643, a non-hepatotoxic dose of 50mg/kg led to a marked loss of inter-hepatocyte dye transfer associated with a loss of both Cx32 and Cx26 protein expression. In contrast, p,p'-dichlorodiphenyltrichloroethane (DDT) at a non-hepatotoxic dose (25mg/kg) was not found to alter Cx32 or Cx26 expression or to produce a measurable Cx32 serine phosphorylation but did give a small, significant reduction of cell communication. Carbon tetrachloride (CCl(4)) did not affect cell communication (despite a small significant reduction of Cx32 content) at a non-hepatotoxic dose. Both loss of communication and Cx32 expression was observed only at a dose that caused hepatocyte toxicity as evidenced by increased serum alanine aminotransferase activity. Overall, the findings emphasise that loss of gap junctional communication in vivo can contribute to carcinogenesis by non-genotoxic carcinogens through different primary mechanism. In contrast to Wy-14,643 and DDT, the results with CCl(4) are consistent with a requirement for hepatotoxicity in its carcinogenic action.     

Dual Effects of Bilirubin on the Proliferation of Rat Renal NRK52E Cells and ITS Association with Gap Junctions

Objective:

The effect of bilirubin on renal pathophysiology is controversial. This study aimed to observe the effects of bilirubin on the proliferation of normal rat renal tubular epithelial cell line (NRK52E) and its potential interplay with gap junction function.

Methods:

Cultured NRK52E cells, seeded respectively at high- or low- densities, were treated with varying concentrations of bilirubin for 24 hours. Cell injury was assessed by measuring cell viability and proliferation, and gap junction function was assessed by Parachute dye-coupling assay. Connexin 43 protein was assessed by Western blotting.

Results:

At doses from 17.1 to 513μmol/L, bilirubin dose-dependently enhanced cell viability and colony-formation rates when cells were seeded at either high- or low- densities (all p<0.05 vs. solvent group) accompanied with enhanced intercellular fluorescence transmission and increased Cx43 protein expression in high-density cells. However, the above effects of BR were gradually reversed when its concentration increased from 684 to 1026μmol/L. In high-density cells, gap junction inhibitor 12-O-tetradecanoylphorbol 13-acetate attenuated bilirubin-induced enhancement of colony-formation and fluorescence transmission. However, in the presence of high concentration bilirubin (1026μmol/L), activation of gap junction with retinoid acid decreased colony-formation rates.

Conclusion:

Bilirubin can confer biphasic effects on renal NRK52E cell proliferation potentially by differentially affecting gap junction functions.     

Effects of trichloroethylene and its metabolites on rodent hepatocyte intercellular communication

Chronic exposure to trichloroethylene (TCE) results in hepatocellular cancer in mice but not rats. The induction of hepatic tumors by TCE appears to be mediated through nongenotoxic or tumor promotion mechanisms. One cellular effect exhibited by a number of nongenotoxic carcinogens and tumor promoters is the inhibition of gap junction mediated intercellular communication. In the present study, the effects of trichloroethylene (TCE) and its metabolites, trichloracetic acid (TCA), trichloroethanol (TCEth), and chloral hydrate (CH) on gap junction mediated intercellular communication in cultured B6C3F1 mouse and F344 rat hepatocytes were assessed. TCE and TCA inhibited intercellular communication in mouse hepatocytes but not in rat hepatocytes. TCEth and CH had no effect on hepatocyte intercellular communication in either rat or mouse cells. TCE and TCA inhibited intercellular communication in both 24-hr-old and freshly plated mouse hepatocytes. Both compounds produced greater inhibition of intercellular communication in freshly plated cells when compared to 24-hr-old cultures. TCE appeared to require cytochrome P450 metabolism by the mouse hepatocytes to exhibit its inhibitory effect on dye coupling since treatment with SKF-525A prevented the inhibition of intercellular communication by TCE. The inhibitory effect of TCA on intercellular communication was unaffected by treatment with SKF-525A. While the species dependent effect of TCE on intercellular communication may be correlated with different rates and extent of metabolism of TCE by rat and mouse hepatocytes, the inhibiting effect of TCA only on mouse hepatocytes suggests that other intrinsic factors in the male mouse make this species more susceptible to the effects of TCE and TCA on gap junction mediated intercellular communication. These findings may account, in part, for the observed species difference in susceptibility to TCE induced liver carcinogenesis.     

在Hs578T乳腺癌细胞由Cx43组成的细胞缝隙连接对阿霉素细胞毒性的影响

目的探讨乳腺癌细胞Hs578T中缝隙连接蛋白43(connexin43,Cx43)的表达,以及由其形成的缝隙连接(gapjunction,GJ)对阿霉素(adriamycin,ADM)细胞毒性的影响。方法采用Western blot检测Hs578T细胞中Cx43表达水平;细胞免疫荧光法观察Hs578T细胞膜Cx43蛋白的表达;细胞接种荧光示踪法测定Hs578T细胞荧光传递功能;MTT法检测缝隙连接功能对ADM细胞毒性的影响。结果Hs578T细胞中天然表达Cx43,10μmol·L-1维甲酸(ratinoicacid,RA)处理细胞24 h后,细胞中Cx43蛋白表达水平增高,25μmol·L-1 oleamide和10μmol·L-118-α-GA分别处理细胞24 h后,细胞中Cx43蛋白表达水平降低;Hs578T细胞膜表面有Cx43蛋白表达;10μmol·L-1RA预处理细胞24 h,细胞间荧光传递功能增强(P<0.01),25μmol·L-1oleamide和10μmol·L-118-α-GA预处理细胞1 h,细胞间荧光传递功能降低(P<0.01);在高密度接种细胞(生长融合,有GJ形成),10μmol·L-1RA增强细胞GJ功能,6μmol·L-1ADM对细胞增殖抑制率明显增加(P<0.01),25μmol·L-1 oleamide或10μmol·L-1 18-α-GA抑制细胞GJ功能,6μmol·L-1ADM对细胞增殖抑制率降低(P<0.01),而在低密度接种细胞(生长未融合,无GJ形成)细胞增殖抑制率没有改变(P>0.05)。结论 Hs578T细胞天然表达Cx43蛋白,并且增强细胞间由Cx43形成的GJ功能,ADM的细胞毒性也增加;而抑制细胞GJ功能时,ADM的细胞毒性也相应降低。     

大黄素对Cx32组成的细胞缝隙连接通讯功能的影响

目的在转染并稳定表达Cx32的Hela细胞上,观察大黄素对Cx32的GJIC以及Cx32蛋白表达水平的影响。方法采用SRB法检测不同浓度大黄素对Hela细胞的毒性;用细胞接种荧光示踪法("parachute"dye-couplinga ssay)观察不同浓度大黄素对GJIC的影响;用western blot法研究大黄素在影响GJIC功能浓度范围内对Cx32蛋白表达的影响。结果大黄素在0~1μmol/L浓度时对Hela细胞无毒性作用;大黄素(24~600nmol/L)预处理4h,能浓度依赖性地增强GJIC及Cx32蛋白表达量。结论大黄素能够增强Cx32的细胞GJIC;此增强作用可能与其增加Cx32蛋白表达水平有关。     

Altered function, localization and phosphorylation of gap junctions in rat liver epithelial, IAR 20, cells after treatment with PCBs or TCDD

Three different PCB-congeners 3,4,5,3′,4′-pentachlorobiphenyl (IUPAC no. 126), 2,4,5,2′,4′,5′-hexachlorobiphenyl (IUPAC no. 153) and 2,4,5,3′,4′-pentachlorobiphenyl (IUPAC no. 118) were investigated for possible structure–activity relationships in altering gap junction intercellular proteins. All tested PCB-congeners and TCDD decreased the gap junctional intercellular communication in IAR 20 cells, but at different treatment periods, suggesting different modes of action. The presence of the Cx43-P₂ band, a phosphorylated isoform of Cx43, was associated with a functional communication. A reduced Cx43 mRNA level was noted after 48 h of exposure with PCB 126, PCB 118 and TCDD. In summary, the non dioxin-like PCB 153 can decrease gap junctional intercellular communication rapidly by reducing the phosphorylated isoform of Cx43, whereas the dioxin-like PCB 126 and TCDD reduce the communication slowly by decreasing the mRNA level of Cx43, resulting in a reduced Cx43 protein level (which includes the P₂-band). The mixed inducing PCB-congener, PCB 118, can act both as the dioxin-like and the non dioxin-like PCBs in gap junction regulation.     

Resveratrol Enhances Chemosensitivity in Mouse Melanoma Model Through Connexin 43 Upregulation

Although current studies indicate that resveratrol exhibits potential antitumor activities, the precise mechanisms of its beneficial effects combined with chemotherapy are not fully understood. This work is warranted to elucidate the underlying mechanism of antitumor effects by the combination therapy of resveratrol and cisplatin. The presence of functional gap junctions is highly relevant for the success of chemotherapy. Gap junctions mediate cell communication by allowing the passage of molecules from one cell to another. Connexin (Cx) 43 is ubiquitous and reduced in a variety of tumor cells. Cx43 may influence the response of tumor cells to treatments by facilitating the passage of antitumor drugs or death signals between neighboring tumor cells. Following resveratrol treatment, dose‐dependent upregulation of Cx43 expressions was observed. In addition, gap junction intercellular communication was increased. To study the mechanism underlying these resveratrol‐induced Cx43 expressions, we found that resveratrol induced a significant increase in mitogen‐activated protein kinases (MAPK) signaling pathways. The MAPK inhibitors significantly reduced the expression of Cx43 protein after resveratrol treatment. Specific knockdown of Cx43 resulted in a reduction of cell death after resveratrol and cisplatin treatment. Our results suggest that treatment of resveratrol in tumor leads to increase Cx43 gap junction communication and enhances the combination of resveratrol and cisplatin therapeutic effects. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 877–886, 2015.