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。     

Increased connexin43 gap junction protein in hamster cardiomyocytes during cold acclimatization and hibernation

OBJECTIVE: The physiology of hibernation is characterized by dramatic reductions of heart rate, respiration, metabolism, blood pressure and body temperature and by resistance to ventricular fibrillation. Gap junctions in the heart provide low resistance pathways, facilitating electrical and metabolic coupling between cardiac muscle cells for coordinated action of the heart and tissue homeostasis. The conductance of these junctions, and therefore their function, is likely to be affected by the physiological changes that take place during hibernation. Our objective was to quantitate gap junction protein levels in cold acclimatization, hibernation and arousal. METHODS: We have used specific antibodies to connexins 43 and 40, in combination with confocal microscopy, to quantitatively analyze the expression of connexin protein in hamster (Mesocricetus auratus) left ventricles in four animal groups: normal controls at euthermy, cold controls (cold-exposed animals that did not undergo hibernation), hibernating animals and animals aroused from hibernation for 2 h. RESULTS: Connexin40 immunostaining was not detected in ventricular cardiomyocytes in any animal group but connexin43 was found in all groups. Connexin43 expression was significantly enhanced in hibernation and cold control ventricular cardiomyocytes. Total plaque area, numerical density and plaque size were higher in the cold controls and hibernating hamsters compared to normal controls and animals aroused from hibernation. CONCLUSION: It is possible that the increased size and number of connexin43 gap junction plaques in the cold controls may represent a compensatory response in order to maintain sufficient gap junction communication during physiological conditions that would reduce conductance. These changes may represent a mechanism by which the hamster avoids ventricular fibrillation during hibernation and arousal.     

Spatial distribution of connexin43, the major cardiac gap junction protein, in the developing and adult rat heart.

The developmental appearance and spatial distribution pattern of gap junctions were studied in prenatal and adult rat hearts. Gap junctions were visualized immunohistochemically with an antibody raised against a unique cytoplasmic epitope of connexin43, and the spatial distribution pattern was determined by three-dimensional reconstruction. The results demonstrate that from embryonic day 13 onward, connexin43 becomes detectable immunohistochemically in the myocardium of atria and ventricles. No expression is initially detectable in the myocardium of the sinus venosus, the sinoatrial node, the posterior wall of the atrium and pulmonary veins, the interatrial septum, the atrioventricular canal, including atrioventricular node and bundle, the interventricular septum, and the outflow tract. The developmental increase in the density of gap junctions in atria and ventricles of prenatal hearts correlates well with the reported developmental increase in conduction velocity. Whereas connexin43 becomes expressed in the derivatives of the sinus venosus (except for the sinoatrial node) and in the subepicardial layer of the ventricular free wall shortly before birth, it remains undetectable in the atrioventricular node and bundle and the proximal part of the ventricular conduction tissue, even in the adult heart. The apparent absence of an abundant expression of connexin43 at a location with a supposedly high conduction velocity (i.e., the atrioventricular bundle and bundle branches) is unexpected. These observations were confirmed in studies of the adult mouse heart, which showed, in addition, that connexin32 is not expressed in any part of the heart.     

β2受体对心肌缝隙连接蛋白Cx43的调节

目的探讨β-肾上腺素受体（β-AR）亚型对心肌缝隙连接蛋白connexin43（Cx43）表达及功能的调节。方法采用免疫印迹技术和划痕标记示踪技术（SLDT）观察心肌细胞Cx43的表达和功能变化。结果给予异丙基肾上腺素（ISO）刺激5min，即可明显增加心肌细胞非磷酸化Cx43的表达，同时促进荧光染料在细胞间的扩散；选择性β2-AR拮抗剂ICI 118551，可完全拮抗异丙基肾上腺素所诱导的该作用。结论异丙基肾上腺素主要通过刺激BrAR参与调控Cx43，这可能是β2-AR诱导心律失常的一个重要机制。     

Effects of angiotensin II on expression of the gap junction channel protein connexin43 in neonatal rat ventricular myocytes

Objectives. To elucidate signal transduction pathways regulating expression of myocardial gap junction channel proteins (connexins) and to determine whether mediators of cardiac hypertrophy might promote remodeling of gap junctions, we characterized the effects of angiotensin II on expression of the major cardiac gap junction protein connexin43 (Cx43) in cultured neonatal rat ventricular myocytes.Background. Remodeling of the distribution of myocardial gap junctions appears to be an important feature of anatomic substrates of ventricular arrhythmias in patients with heart disease. Remodeling of intercellular connections may be initiated by changes in connexin expression caused by chemical mediators of the hypertrophic response.Methods. Cultures were exposed to 0.1 μmol/liter angiotensin II for 6 or 24 h, and Cx43 expression was characterized by immunoblotting, confocal microscopy and electron microscopy.Results. Immunoblot analysis revealed a twofold increase in Cx43 content in cells treated for 24 h with angiotensin II (n = 4, p < 0.05). This response was inhibited by the presence of 1.0 μmol/liter losartan, an AT1-receptor blocker. Confocal and electron microscopy demonstrated enhanced Cx43 immunoreactivity and increases in the number and size of gap junction profiles in cells exposed to angiotensin II for 24 h. These effects were also blocked by losartan. Immunoprecipitation of Cx43 from cells metabolically labeled with [³⁵S]methionine demonstrated 2.4- and 2.9-fold increases in Cx43 radioactivity after 6 and 24 h exposure to angiotensin II, respectively (p < 0.03 at each time point).Conclusions. Angiotensin II up-regulates gap junctions in cultured neonatal rat ventricular myocytes by increasing Cx43 synthesis. Signal transduction pathways activated by angiotensin II under pathophysiologic conditions could initiate remodeling of conduction pathways, leading to the development of anatomic substrates of arrhythmias.     

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.     

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.     

Lindane, a gap junction blocker, suppresses FSH and transforming growth factor beta1-induced connexin43 gap junction formation and steroidogenesis in rat granulosa cells

The present study was designed to explore the role of gap junctions in follicle-stimulating hormone (FSH) and transforming growth factor beta1 (TGF beta1)-stimulated steroidogenesis in ovarian granulosa cells of gonadotropin-primed immature rats. There were three specific aims. First, we investigated the effect of FSH and TGF beta1 as well as lindane (a general gap junction blocker) on the level of connexin43 (Cx43), the major gap junction constituent in granulosa cells, and on gap junction function. The second aim was to determine the effect of lindane on FSH and TGF beta1-stimulated progesterone production and the levels of two critical players, cytochrome P450 side-chain cleavage (P450scc) enzyme and steroidogenic acute regulatory (StAR) protein. The third aim was to further investigate the specific involvement of Cx43 gap junctions in FSH and TGF beta1-stimulated steroidogenesis using a Cx43 mimetic peptide blocker. Immunoblotting analysis showed that FSH plus TGF beta1 dramatically increased the levels of phosphorylated Cx43 without significantly influencing the level of nonphosphorylated Cx43, and this stimulatory effect was completely suppressed by lindane. Also, immunofluorescence analysis showed that Cx43 immuno-reactivity increased in the FSH plus TGF beta1-treated group and predominantly appeared in a punctate pattern at cell-cell contact sites, and lindane reduced such cell periphery immunostaining. Furthermore, TGF beta1 enhanced the FSH-induced gap junction intercellular communication and lindane completely suppressed this effect. In addition, lindane suppressed the FSH and TGF beta1-stimulated increases in progesterone production and the levels of P450scc enzyme and StAR protein. This study demonstrates a clear temporal association between the Cx43 protein level/gap junction communication and progesterone production in rat ovarian granulosa cells in response to FSH and TGF beta1 as well as lindane. Furthermore, a specific Cx43 gap junction blocker suppressed FSH plus TGF beta1-stimulated progesterone production. In conclusion, this study suggests that Cx43 gap junctions may play a critical role in FSH plus TGF beta1-stimulated progesterone production in rat ovarian granulosa cells.     

Clustering of connexin 43-enhanced green fluorescent protein gap junction channels and functional coupling in living cells

Communication-incompetent cell lines were transfected with connexin (Cx) 43 fused with enhanced green fluorescent protein (EGFP) to examine the relation between Cx distribution determined by fluorescence microscopy and electrical coupling measured at single-channel resolution in living cell pairs. Cx43-EGFP channel properties were like those of wild-type Cx43 except for reduced sensitivity to transjunctional voltage. Cx43-EGFP clustered into plaques at locations of cell-cell contact. Coupling was always absent in the absence of plaques and even in the presence of small plaques. Plaques exceeding several hundred channels always conferred coupling, but only a small fraction of channels were functional. These data indicate that clustering may be a requirement for opening of gap junction channels.     

Expression of gap junction genes connexin32 and connexin43 mRNAs and proteins, and their role in hepatocarcinogenesis

AIM: To investigate the relationship between hepatocarcinogenesis and the expression of connexin32 (cx32), connexin43 (cx43) mRNAs and proteins in vitro.METHODS: Gap junction genes cx32 and cx43 mRNA in hepatocellular carcinoma cell lines HHCC, SMMC-7721 and normal liver cell line QZG were detected by in situ hybridization (ISH) with digoxin-labeled cx32, and cx43 cDNA probes. Expression of Cx32 and Cx43 proteins in the cell lines was revealed by indirect immuno-fluorescence and flow cytometry (FCM).RESULTS: Blue positive hybridization signals of cx32 and cx43 mRNAs detected by ISH with cx32 and cx43 cDNA probes respectively were located in cytoplasm of cells of HHCC, SMMC-7721 and QZG. No significant difference of either cx32 mRNA or cx43 mRNA was tested among HHCC, SMMC-7721 and QZG (P=2.673, HHCC vs QZG; P=1.375, SMMC-7721 vs QZG). FCM assay showed that the positive rates of Cx32 protein in HHCC, SMMC-7721 and QZG were 0.7%, 1.7% and 99.0%, and the positive rates of Cx43 protein in HHCC, SMMC-7721 and QZG were 7.3%, 26.5% and 99.1% respectively. Significant differences of both Cx32 and Cx43 protein expression existed between hepatocellular carcinoma cell lines and normal liver cell line (P=0.0069, HHCC vs QZG; P=0.0087, SMMC-7721 vs QZG). Moreover, the fluorescent intensities of Cx32 and Cx43 proteins in HHCC, SMMC-7721 were lower than that in QZG.CONCLUSIONS: Hepatocellular carcinoma cell lines HHCC and SMMC-7721 exhibited lower positive rates and fluorescent intensities of Cx32, Cx43 proteins compared with that of normal liver cell line QZG. It is suggested that lower expression of both Cx32 and Cx43 proteins in hepatocellular carcinoma cells could play pivotal roles in the hepatocarcinogenesis. Besides, genetic defects of cx32 and cx43 in post-translational processing should be considered.     

Absence of mutations in the regulatory domain of the gap junction protein connexin 43 in patients with visceroatrial heterotaxy.

OBJECTIVE: To determine the frequency of mutations in the regulatory domain of the gap junction protein connexin 43 in patients with visceroatrial heterotaxy. DESIGN: Mutation screening of the terminal 200 base pairs of connexin43 gene coding sequence in a series of patients from tertiary care centres. PATIENTS: 48 patients with visceroatrial heterotaxy attending UK Regional Paediatric Cardiology Centres. RESULTS: No changes from the published connexin43 consensus sequence were found in any of the 48 patients studied. CONCLUSIONS: Germline mutations of the phosphorylation sites in teh regulatory domain of the connexin43 gene are rare in patients with visceroatrial heterotaxy.     

Expression of gap junction genes connexin 32, connexin 43 and their proteins in hepatocellular carcinoma and normal liver tissues

AIM To investigate the significance and mechanism of cx32 mRNA, cx43 mRNA and their proteins in hepatocarcinogenesis.METHODS Sixty-one cases of HCC and 14 cases of normal liver tissues were detected by immunohistochemical and in situ hybridization (ISH) methods.RESULTS In HCC grades Ⅰ,Ⅱ,Ⅲ and normal liver tissues, the positive rates of Cx32 protein were 55.6%, 42.1%, 18.2% and 92.9%,respectively. The detection rates of Cx43 protein were 44.4%, 26.3%, 12.1% and 78.6%,respectively. There was significant difference in Cx32 and Cx43 protein between HCC and normal liver tissues (P＜0.01). ISH the positive rates of cx32 mRNA shown by ISH in HCC grades Ⅰ,Ⅱ,Ⅲ and normal liver tissues were 88.9%, 84.2%,87.9% and 92.9%, respectively. Those of cx43 mRNA were 77.8%, 78.6%, 78.8% and 85.7%,respectively. There was no statistical difference in the positive rates of cx32 mRNA and cx43 mRNA between HCC and normal liver tissue (P＞0.05).CONCLUSION The aberrant location of Cx32 and Cx43 proteins could be responsible for progression of hepatocarcinogenesis, and the defect of cx genes in post-translational processing might be the possible mechanism.     

Immunohistochemical study of the pineal astrocytes in the postnatal development of the cat and dog pineal gland

Abstract: The expression of glial antigens vimentin (VIM) and glial fibrillary acidic protein (GFAP) is described in the pineal gland of cats and dogs from the first postnatal days to adulthood. VIM immunopositive cells were observed from the first postnatal days in both species. GFAP expression starts from the second postnatal week. In adults, a notable population of stellate cells immunopositive for GFAP and VIM was found dispersed throughout the gland. According to their immunocytochemical profile, these cells could be identified as astrocytes.     

Modulation of ganglion cell activity in the pineal gland of the rainbow trout: Effects of cholinergic, catecholaminergic, and GAB Aergic receptor agonists

Abstract: Second order neurons within intact isolated pineal glands of the rainbow trout were explored by extracellular recordings to investigate modulatory effects of putative intrapineal neurotransmitters. Acetylcholine, dopamine, and norepinephrine were found to increase ganglion cell activity in a majority of cells tested. The excitatory effects of acetylcholine, dopamine, and norepinephrine were mimicked by muscarinic, dopamine D2, and β-adrenergic receptor agonists and significantly increased with the applied light intensity, resulting in an attenuation of the ganglion cell response to light. GABA decreased discharge activity in most cells tested. This effect, which could be mimicked with the GABA_A receptor agonist piperidine, was independent from the adaptive status. Acetylcholine and GABA were still active if applied during synaptic blockade with low Ca⁺⁺ high Mg⁺⁺-perfusion medium, whereas dopamine and norepinephrine exhibited no effects if applied during synaptic blockade, suggesting a differential cellular distribution of neurotransmitter receptors in the trout pineal gland. These data demonstrate that ganglion cell activity in the trout pineal gland is under the influence of several neurotransmitters, including acetylcholine, dopamine, norepinephrine, and GABA, which is in contrast to the originally proposed simple bineuronal transduction pathway from photoreceptors onto ganglion cells. Since the above-mentioned neurotransmitters are believed to be released from pineal interneurons, we may conclude that ganglion cell activity in the teleost pineal gland is, similarly to the retina, the product of photoreceptor signals and a modulatory active interneuronal system.     

C-terminal truncation of connexin43 changes number, size, and localization of cardiac gap junction plaques

Haplodeficient mice expressing carboxyl-terminally truncated Cx43 (K258stop/KO), instead of the wild-type Cx43 isoform, reach adulthood and reveal no abnormalities in heart morphology. Here, we have analyzed the expression of K258stop protein and the morphology of gap junctions in adult hearts of these mice. Coimmunofluorescence analysis revealed reduced juxtaposition of K258stop with other junctional proteins at the intercalated disc. Immunoprecipitation studies documented changes in the interaction with previously described Cx43 binding proteins. Quantitative transmission electron and confocal microscopy confirmed the localization of K258stop gap junctions to the periphery of the intercalated disc and further revealed an increase in the size of K258stop gap junction plaques and a reduction in their number. Dual whole cell patch clamp analysis confirmed that K258stop gap junctions were functional, with single channel properties similar to those described in exogenous systems. We conclude that the carboxyl-terminal domain of Cx43 (Cx43CT) is involved in regulating the localization, number and size of Cx43 plaques in vivo. Conversely, protein interactions or posttranslational modifications taking place within the Cx43CT are not required for the assembly of functional gap junctions in the intercalated disc.     

心房肌缝隙连接蛋白40、43表达改变与心房颤动的关系

目的研究心房颤动患者心房肌缝隙连接蛋白(Cx)40、43表达的改变,探讨Cx在房颤发生与维持中的作用.方法39例接受开胸手术者分为房颤组和窦性心律组,手术时取右心耳及左心房各约100mg,采用Western blot与免疫组织化学技术,检测心房肌Cx40、Cx43表达量与分布的改变.结果房颤组Cx40表达量在左心房、右心耳较窦性心律组高,Cx43表达量在左心房较窦性心律组高,在右心耳无差异.免疫组化显示房颤组Cx40、Cx43均分布紊乱,聚集于胞浆或核周.结论房颤患者心房肌Cx40、Cx43表达增高,且分布异常,提示心房肌Cx40、Cx43表达改变与心房颤动的发生与维持有关.