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。     

复方藤梨根制剂对裸鼠荷人肺巨细胞癌细胞E-钙黏附素影响的研究

目的研究复方藤梨根制剂对荷人肺巨细胞癌(PG)裸鼠移植瘤的抗癌效应,并初步探讨其对瘤体细胞E-钙黏附素(E-cad)表达水平的影响。方法建立PG裸鼠移植瘤模型;复方藤梨根制剂灌胃21d,称瘤重;采用免疫组化ABC法检测E-cad的表达。结果复方藤梨根制剂三个剂量组与对照组对比,均能明显抑制肿瘤生长,并提高E-cad表达。结论复方藤梨根制剂对PG裸鼠移植瘤具有的抑瘤效果,明显上调PG细胞E-cad的表达。     

复方藤梨根制剂对裸鼠荷人肺巨细胞癌细胞E-钙黏附素影响的研究

目的研究复方藤梨根制剂对荷人肺巨细胞癌（PG）裸鼠移植瘤的抗癌效应，并初步探讨其对瘤体细胞E-钙黏附素（E—cad）表达水平的影响。方法建立PG裸鼠移植瘤模型；复方藤梨根制剂灌胃21d，称瘤重；采用免疫组化ABC法检测E-cad的表达。结果复方藤梨根制剂三个剂量组与对照组对比，均能明显抑制肿瘤生长，并提高E-cad表达。结论复方藤梨根制剂对PG裸鼠移植瘤具有的抑瘤效果，明显上调PG细胞E-cad的表达。     

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。     

两种藤梨根制剂促凋亡作用的实验研究

目的研究两种藤梨根制剂促进人食管癌Eca-109细胞凋亡的机制及差异。方法采用MTT比色法检测藤梨根正丁醇药液及乙酸乙酯药液在不同浓度(1μg/mL、10μg/mL、100μg/mL等)及不同时间(24h、48h、72h等)对Eca-109细胞生长的抑制作用;采用TUNEL法检测其对癌细胞生长的诱导凋亡效应;采用免疫组化SP法检测凋亡相关蛋白Bax、Bcl-2及caspase的表达。结果藤梨根正丁醇药液对人食管癌Eca-109细胞的生长抑制作用,随着药物浓度的升高和作用时间的延长而增强,其生长抑制率可达87.2%。两种藤梨根制剂对瘤细胞有明显的凋亡效应,而在对照组未见有明显凋亡现象。瘤细胞作用24h、48h、72h后分别与对照组比较,用药组Bax蛋白表达明显增强(P<0.01);同时伴有Bcl-2表达减弱,72h后最明显,差异有显著意义(P<0.01)。藤梨根正丁醇药液促进caspase-3、caspase-9表达明显增强,而对caspase-8表达影响较小。藤梨根乙酸乙酯药液作用于肿瘤细胞时也可观察到类似的效应,且正丁醇药液对肿瘤细胞生长的抑制率高于乙酸乙酯药液。结论藤梨根可通过下调Bcl-2表达,激活caspase-9、caspase-3诱导Eca-109细胞凋亡。     

胃癌中间隙连接蛋白Cx32、Cx43表达与细胞增殖的关系

目的探讨间隙连接蛋白Cx32、Cx43在不典型增生和胃癌的表达及其与胃癌发生发展的关系。方法运用免疫组织化学方法检测Cx32、Cx43和增殖细胞核抗原(PCNA)在70例原发性胃癌、62例不典型增生和16例正常胃黏膜中表达。结果在正常胃黏膜、不典型增生和胃癌中,Cx32、Cx43的表达逐步下降;PCNA标记指数分别为0.75±1.52,13.06±16.09和38.09±21.89。Cx32、Cx43的表达与PCNALI呈负相关(P<0.01)。Cx32、Cx43的表达与胃癌分化有关(P<0.01)。结论Cx32、Cx43表达降低促进胃癌细胞增殖,且与胃癌分化有关,间隙连接蛋白在胃癌发生发展过程中起着重要作用。     

茶多酚对肺癌PG细胞生长的调控研究

目的：探讨茶多酚对人PG细胞生长的影响。方法：采用MTT法体外观察不同浓度茶多酚对PG细胞的杀伤作用；应用激光共聚焦显微镜和流式细胞仪分析，检测用药后PG细胞内Ca^2 浓度，CD44V6表达和细胞增殖周期分布的变化。结果：3个浓度的茶多酚对PG2细胞的有杀伤作用，呈剂量依赖分析。细胞增殖受到明显抑制，使细胞阻滞于G0／G1期，不能进入S期及G2／M期，细胞增殖指数明显下降。细胞内Ca^2 浓度与对照组相比，逐渐上升；CD44V6表达水平则呈逐渐下降。结论：茶多酚对PG细胞的生长具有抑制作用，其作用机制与改变细胞内Ca^2 浓度和CD44V6表达有关。     

茶多酚对肺癌PG细胞生长的调控研究

目的:探讨茶多酚对人PG细胞生长的影响。方法:采用MTT法体外观察不同浓度茶多酚对PG细胞的杀伤作用;应用激光共聚焦显微镜和流式细胞仪分析,检测用药后PG细胞内Ca2 +浓度、CD44 V6表达和细胞增殖周期分布的变化。结果:3个浓度的茶多酚对PG细胞均有杀伤作用,呈剂量依赖关系。细胞增殖受到明显抑制,使细胞阻滞于G0 / G1期,不能进入S期及G2 / M期,细胞增殖指数明显下降。细胞内Ca²⁺浓度与对照组相比,逐渐上升;CD44 V6表达水平则呈逐渐下降。结论:茶多酚对PG细胞的生长具有抑制作用,其作用机制与改变细胞内Ca2 +浓度和CD44 V6表达有关     

Cx43表达与多发性骨髓瘤细胞耐药的相关性

目的探讨骨髓间充质干细胞(BMSCs)连接蛋白43(Cx43)表达对多发性骨髓瘤(MM)RPMI 8226细胞耐药的影响。方法体外分离、培养BMSCs,采用RT-PCR法检测BMSCs、RPMI 8226细胞Cx43的表达,流式细胞术和多重液相蛋白定量技术分别检测BMSCs与RPMI 8226细胞共培养对RPMI 8226细胞凋亡和细胞因子分泌的影响。结果 BMSCs及RPMI 8226细胞均表达Cx43。BMSCs与RPMI 8226细胞共培养后,上清液中IL-6、IL-10和TGF-β水平增加,硼替佐咪诱导的RPMI 8226细胞凋亡作用减弱;而细胞间隙连接通讯(GJIC)特异性阻断剂18α甘草次酸(18α-GA)能明显逆转上述观察指标的改变过程。结论 BMSCs与RPMI 8226细胞间可形成功能性GJIC,是BMSCs促进MM细胞生存及介导其耐药的重要原因之一。     

藤梨根乙醇提取物联合CIK细胞对胃癌细胞SGC-7901杀伤作用的研究

目的观察抗肿瘤中药藤梨根的乙醇提取物与CIK细胞在体外联合对胃癌细胞SGC-7901的杀伤作用。方法运用倒置显微镜观察体外培养的胃癌细胞SGC-7901在分别加入不同浓度的藤梨根醇提物以及不同效靶比的CIK细胞24、48 h后的形态变化;采用MTT法检测藤梨根醇提物、CIK细胞以及两者联合作用后的胃癌细胞SGC-7901的增殖抑制率。结果当1 mg/ml的藤梨根醇提物与效靶比为20：1的CIK细胞相联合24 h,杀伤效率高于单用藤梨根醇提物及CIK细胞（P〈0.05）。结论藤梨根醇提物与CIK细胞在一定条件下联合,具有协同杀伤胃癌细胞的作用。     

Role of connexin 43 in cadmium‐induced proliferation of human prostate epithelial cells

Connexins (Cxs), the subunits of gap junction channels, are involved in many physiological processes. Aberrant control of Cxs and gap junction intercellular communication may contribute to many diseases, including the promotion of cancer. Cd exposure is associated with increased risk of human prostate cancer and benign prostatic hyperplasia. The roles of Cxs in the effects of Cd on the prostate have, however, not been reported previously. In this study, the human prostate epithelial cell line RWPE‐1 was exposed to Cd. A low dose of Cd stimulated cell proliferation along with a lower degree of gap junction intercellular communication and an elevated level of the protein Cx43. Cd exposure increased the levels of intracellular Ca²⁺ and phosphorylated Cx43 at the Ser368 site. Knockdown of Cx43 using siRNA blocked Cd‐induced proliferation and interfered with the Cd‐induced changes in the protein levels of cyclin D1, cyclin B1, p27^Kip1 (p27) and p21^Waf1/Cip1 (p21). The increase in Cx43 expression induced by Cd was presumably mediated by the androgen receptor, because it was abolished upon treatment with the androgen receptor antagonist, flutamide. Thus, a low dose of Cd promotes cell proliferation in RWPE‐1, possibly mediated by Cx43 expression through an effect on cell cycle‐associated proteins. Cx43 might be a target for prostatic diseases associated with Cd exposure. Copyright © 2017 John Wiley & Sons, Ltd.     

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。     

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。     

Silver nanoparticles up-regulate Connexin43 expression and increase gap junctional intercellular communication in human lung adenocarcinoma cell line A549

Abstract

Silver nanoparticles (Ag NPs) are increasingly being used in wound dressings, medical settings, and various household products due to their unique properties and antimicrobial activity. Despite the widespread use of Ag NP products, the molecular mechanisms underlying the biological effects of Ag NPs remain unclear. Gap junctional intercellular communication (GJIC), formed by the connexin protein family, plays a critical role in the maintenance of tissue and organ homeostasis. This study was undertaken to investigate the effects of well characterized, PVP-coated Ag NPs (69 ± 3 nm) and silver nitrate on GJIC and connexin43 (Cx43) expression in human lung adenocarcinoma cell line A549. Our results showed that Ag NPs increased GJIC in A549 cells as assayed by dye transfer method. Western blot analysis showed that incubation of cells with Ag NPs significantly increased the expression of Cx43 protein. In addition, Ag NPs up-regulated expression of Cx43 mRNA in a dose-dependent manner. Silver nitrate failed to increase GJIC and the expression of Cx43 protein. It, however, increased Cx43 mRNA expression in A549 cells. Taken together, our results provide the first evidence that Ag NPs induced the increase of GJIC activity in A549 cells through up-regulation of Cx43 protein, suggesting that Cx43 and GJIC may be one of the targets for Ag NPs biological effects.     

Connexins and apoptotic transformation

We examined the influence of connexin (Cx) expression on the development of apoptosis in HeLa parental cells (coupling deficient cell line) and HeLa cells expressing wild-type Cx43 and Cxs fused with enhanced green fluorescent protein (EGFP). EGFP was attached to the C-terminus of Cx32 and Cx43, Cx32-EGFP and Cx43-EGFP, respectively, and to the N-terminus of Cx32, EGFP-Cx32. All fusion proteins assembled into junctional plaques (JPs) at areas of cell-cell contact, but only the C-terminal fusion proteins formed functional gap junction (GJ) channels as well as hemichannels. In each cell line, apoptosis was induced by treatment with various agents including anisomycin, camptothecin, cis-platinum, colchicine, cycloheximide, etoposide, staurosporin and taxol. Using fluorescence microscopy, time-lapse imaging and dual whole-cell voltage clamp techniques, we correlated the changes in functional properties of GJ channels and Cx distribution with the progression of apoptosis based on cells' labeling with acridine orange and ethidium bromide (EB). The early phase of apoptosis (a viable apoptotic (VA) state) was characterized by shrinkage of the cells and by increased internalization of JPs accompanied by decreased cell-cell coupling. The apoptotic reagents had no direct effect on electrical cell-cell coupling. Transformation from a VA to a nonviable apoptotic (NVA) state was faster in HeLa cells expressing Cx43 or Cx43-EGFP than in HeLa parental cells. The potent GJ uncoupler, octanol, slowed the transition of HelaCx43-EGFP cells into a NVA state. In the absence of apoptotic reagents, the rate of EB uptake was higher in HeLaCx43-EGFP than in HeLa parental cells consistent with the presence of open Cx43-EGFP hemichannels. However, in both cell lines the rate of EB uptake decreased proportionally during the development of apoptosis suggesting that membrane permeability ascribed to Cx hemichannels is reduced. Cells expressing Cx32-EGFP and EGFP-Cx32 demonstrate the same apoptotic patterns as HeLaCx43-EGFP and HeLa parental cells, respectively. Intracellular levels of ATP in HeLaCx43-EGFP cells were substantially lower than in HeLa parental cells, and ATP added to the medium abolished the accelerated transition from a VA to a NVA state in HeLaCx43-EGFP cells. In summary, Cx32 or Cx43 accelerates transformation of cells into a NVA state or secondary necrosis and this depends on the ability of Cxs to form functional GJ channels and hemichannels.     

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。     

PKC及缝隙连接蛋白Cx43改变在吗啡和舒芬太尼预处理缺氧复氧损伤心肌中的作用

目的：探讨蛋白激酶C（PKC）信号通路及心肌缝隙连接蛋白Cx43改变在阿片药物预处理中的作用。方法：原代心肌细胞分离培养。将培养5 d的心肌细胞分成8组。正常对照组（C组）不给予任何处理,建立培养乳鼠心肌细胞缺氧/复氧损伤模型（I/R组）,吗啡组（MF组）加入吗啡至终浓度0.3 μmol·L^-1,舒芬太尼组（SF组）加入舒芬太尼至终浓度0.000 3 μmol·L^-1,PKC激动剂PMA+吗啡组（PMA+MF组）加入PMA至终浓度0.02 μmol·L^-1,再进行吗啡预处理;PKC抑制剂Rottlerin+吗啡组（ROT+MF组）加入Rottlerin至终浓度5 μmol·L^-1,再进行吗啡预处理;PKC激动剂PMA+舒芬太尼组（PMA+SF组）加入PMA至终浓度0.02 μmol·L^-1,再进行舒芬太尼预处理;PKC抑制剂Rottlerin+舒芬太尼组（ROT+SF组）加入Rottlerin至终浓度5 μmol·L^-1,再进行舒芬太尼预处理。各组做上述相应处理后取材检测细胞存活率。免疫荧光共聚焦技术检测缝隙连接蛋白Connexin 43（Cx43）的平均光密度（AOD）,用Western-blot检测细胞Cx43总蛋白及其磷酸化水平（P-Cx43）的表达量。结果：与C组比较,其余各组心肌细胞存活率、Cx43 AOD值、心肌细胞Cx43总蛋白表达及P-Cx43表达降低（P<0.05）;与I/R组比较,MF组、SF组、ROT+MF组、ROT+SF组、PMA+MF组、PMA+SF组心肌细胞存活率、Cx43 AOD值、Cx43总蛋白和P-Cx43表达增高（P<0.05）;与MF组比较,ROT+MF组心肌细胞存活率、Cx43 AOD值、Cx43总蛋白及P-Cx43表达降低（P<0.05）,SF组心肌细胞存活率、Cx43 AOD值和Cx43总蛋白降低（P<0.05）,而P-Cx43表达增高（P<0.05）,PMA+MF组心肌细胞存活率、Cx43 AOD值、Cx43总蛋白和P-Cx43表达均增高（P<0.05）;ROT+SF组较SF组心肌细胞Cx43 AOD值、Cx43总蛋白和P-Cx43表达低（P<0.05）,而PMA+SF组较SF组心肌细胞存活率、心肌细胞Cx43 AOD值、Cx43总蛋白和P-Cx43表达高（P<0.05）。结论：吗啡和舒芬太尼预处理可减轻心肌细胞缺氧/复氧损伤,且吗啡对心肌细胞的保护作用较舒芬太尼强,这种心肌细胞保护作用可能与PKC信号通路的激活有关。     

3,4,5,6-Tetrahydroxyxanthone preserves intercellular communication by reduction of the endogenous nitric oxide synthase inhibitor level

To observe the direct effects of 3,4,5,6-tetrahydroxyxanthone on connexin43 (Cx43) expression in cultured endothelial cells, cells were treated with lysophosphatidylcholine (LPC, 10?mg/l) for 24?h in the presence or absence of different concentrations of 3,4,5,6-tetrahydroxyxanthone (1, 3, or 10?μmol?l(-?1)). The reactive oxygen species (ROS) production, cell viability, asymmetric dimethylarginine (ADMA) levels, and Cx43 expression were detected. 3,4,5,6-Tetrahydroxyxanthone significantly inhibited the increase in ROS production and ADMA level, increased cell viability and up-regulated Cx43 mRNA and protein expression induced by LPC. 3,4,5,6-Tetrahydroxyxanthone has protective effect in LPC-induced atherosclerotic lesions, which is at least partly related to the reduction of ADMA level and downregulation of Cx43 expression.     

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.