OBJECTIVETo investigate the effect and potential mechanism of lysophosphatidic acid (LPA) and antiarrhythmic peptide (AAP10) on rabbit ventricular arrhythmia.

METHODSTwenty-four rabbits were randomly divided into three groups (n = 8 each): control group, LPA group and AAP10 + LPA group. Using arterially perfused rabbit ventricular wedge preparations, transmural ECG and action potentials from both endocardium and epicardium were simultaneously recorded in the whole process of all experiments with two separate floating microeletrodes. The incidence of ventricular arrhythmia post S1S2 stimulation was recorded. Protein levels of nonphosphorylated Cx43 and total Cx43 were evaluated by Western blot. The distribution of nonphosphorylated Cx43 was observed by confocal immunofluorescence microscopy.

RESULTSCompared with the control group, the QT interval, endocardial action potential duration, transmural repolarization dispersion (TDR) and incidence of ventricular arrhythmia were significantly increased and nonphosphorylated Cx43 expression was significantly upregulated in the LPA group. Compared with the LPA group, cotreatment with AAP10 can reduce the QT interval, endocardial action potential duration, TDR and incidence of ventricular arrhythmia (25.0% vs 62.5%, P < 0.01) and downregulate nonphosphorylated Cx43.

CONCLUSIONSLPA could promote the arrhythmia possibly by upregulating nonphosphorylated Cx43 and subsequent gap junction transmission inhibition. Gap junction enhancer AAP10 could attenuate the pro-arrhythmic effect of LPA probably by downregulating myocardial nonphosphorylated Cx43 expression.

Animals ; Anti-Arrhythmia Agents ; pharmacology ; Arrhythmias, Cardiac ; chemically induced ; metabolism ; physiopathology ; Connexin 43 ; metabolism ; Lysophospholipids ; adverse effects ; Oligopeptides ; pharmacology ; Rabbits

Animals ; Cardiomyopathy, Dilated ; metabolism ; Connexin 43 ; metabolism ; Disease Models, Animal ; Hypericum ; Male ; Plant Extracts ; pharmacology ; Rats ; Rats, Wistar

OBJECTIVE: To explore whether the using of mimetic peptide Gap27, a selective inhibitor of connexin 43 (Cx43), could block the death of dopamine neurons and influence the expression of Cx43 in 6-hydroxydopamine (6-OHDA)-induced Parkinson's disease mouse models. METHODS: Eighteen C57BL/6 mice were randomly divided into control group, 6-OHDA group and 6-OHDA+Gap27 group, with 6 mice in each group. Bilateral substantia nigra stereotactic injection was performed. The control group was injected with ascorbate solution, 6-OHDA group was injected with 6-OHDA solution, and 6-OHDA+Gap27 group was injected with 6-OHDA and Gap27 mixed solution. Immuno-histochemical staining was used to detect the number of dopamine neurons, quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of Cx43 messenger ribonucleic acid (mRNA), immuno-fluorescence staining was used to detect the distribution of Cx43 protein, the contents of Cx43 protein and Cx43 phosphorylation at serine 368 (Cx43-ps368) in mouse midbrain were detected by Western blot. RESULTS: After injection of 6-OHDA, numerous dopamine neurons in substantia nigra died as Cx43 content increased, Cx43-ps368 content decreased. Mixing Gap27 while injecting 6-OHDA could reduce the number of death dopamine neurons and weaken the changes of Cx43 and Cx43-ps368 content caused by 6-OHDA. The number of tyrosine hydroxylase (TH) immunoreactive positive neurons in 6-OHDA group decreased to 27.7% ± 0.02% of the control group (P < 0.01); The number of TH immunoreactive positive neurons in 6-OHDA+Gap27 group was (1.64±0.16) times higher than that in 6-OHDA group (P < 0.05); The content of total Cx43 protein in 6-OHDA group was (1.44±0.07) times higher than that in 6-OHDA+Gap27 group (P < 0.05) while (1.68±0.07) times higher than that in control group (P < 0.01). In 6-OHDA group, the content of Cx43-ps368 protein and its proportion in total Cx43 protein were significantly lower than that in 6-OHDA+Gap27 group (P < 0.05). CONCLUSION In 6-OHDA mouse models, mimetic peptide Gap27 played a protective role in reducing the damage to substantia nigra dopamine neurons, which was induced by 6-OHDA. The overexpression of Cx43 protein might have neurotoxicity to dopamine neuron. Meanwhile, decreasing Cx43 protein level and keeping Cx43-ps368 protein level may be the protective mechanisms of Gap27.
Animals ; Connexin 43/pharmacology* ; Disease Models, Animal ; Dopaminergic Neurons/metabolism* ; Mice ; Mice, Inbred C57BL ; Oxidopamine/metabolism* ; Parkinson Disease/metabolism* ; Peptides/pharmacology* ; Tyrosine 3-Monooxygenase/pharmacology*

OBJECTIVETo determine the expression of connexin 43 (Cx43) protein and explore the functional modulation of gap junction intercellular communication in astrocytes.

METHODSCultured neonatal SD rat astrocytes were divided into normal control group, all-trans retinoic acid (ATRA) group (treated with 10 µmol/L ATRA for 24 h) and oleamide group (treated with 25 µmol/L oleamide for 2 h). Western blotting and immunofluorescence assay were used to detect total cellular Cx43 protein expression and Cx43 expression on the surface of the astrocytes, respectively. Parachute assay was used to evaluate the functional changes of gap junction intercellular communication of the astrocytes.

RESULTSCompared with the normal control cells, ATRA treatment resulted in a significantly increased expression of total Cx43 protein in the astrocytes (P<0.01), and oleamide significantly suppressed its expression (P<0.01). Similarly, ATRA obviously enhanced while oleamide suppressed Cx43 protein expression on the surface of the astrocytes. The gap junction intercellular communication of the astrocytes was enhanced by ATRA (P<0.01) and inhibited by oleamide (P<0.01).

CONCLUSIONATRA and oleamide can modulate gap junction intercellular communication of the astrocytes possibly by regulating the expression of Cx43 protein.

Animals ; Astrocytes ; metabolism ; Cell Communication ; drug effects ; Cells, Cultured ; Connexin 43 ; metabolism ; Gap Junctions ; metabolism ; Oleic Acids ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Tretinoin ; pharmacology

OBJECTIVETo explore the repair of Xiangsha Liujunzi Decoction (XSLJZD) on interstitial cells of Cajal (ICC) and gap junction (GJ) in the gastric muscular layer of rats of Pi-qi deficiency syn- drome (PQDS).

METHODSPQDS was established using purgative method with bitter and cold drugs in 30 healthy Wistar rats. After successful modeling they were randomly divided into the treatment group and the model group, 15 in each group. Another 15 healthy Wistar rats were recruited as the healthy control group. Rats in the treatment group were gastric administered with XSLJZD at 2 mL/100 g body weight, once daily for 14 successive days. Equal volume of normal saline was gastrically administered to those in the healthy control group and the model group. The gastric muscle tissues were taken out before modeling, before intervention, and after intervention, respectively. Ultrastructural changes of ICC and GJ were observed using transmission electron microscope (TEM). The number and distribution of Connexin43 (Cx43) were detected using immunohistochemistry.

RESULTSResults of TEM indicated that compared with the healthy control group, both ICC and GJ in the model group showed obvious injury. ICC and GJ were apparently repaired after intervention in the treatment group. Compared with the same group before modeling, the integrated optical density (IOD) of the Cx43 expression significantly decreased in the model group before and after intervention (P <0.05). Compared with before intervention, the IOD of the Cx43 expression significantly increased in the treatment group (P <0.05). Compared with the healthy control group, the IOD of the Cx43 expression significantly decreased in the model group before and after intervention (P <0.05). Compared with the model group, the IOD of the Cx43 expression significantly increased in the treatment group (P <0.05).

CONCLUSIONSUltrastructures of ICC and GJ in the gastric muscular layer of rats of PQDS were obviously damaged. XSLJZD could repair the structural damage of ICC and GJ in the gastric muscle tissues of rats of PQDS.

Animals ; Connexin 43 ; Drugs, Chinese Herbal ; pharmacology ; Gap Junctions ; Interstitial Cells of Cajal ; drug effects ; Leydig Cells ; Male ; Muscle, Smooth ; Qi ; Rats, Wistar ; Syndrome

OBJECTIVETo investigate whether the cellular gap junctional communication(GJIC) down-regulation in alveolar epithelial cells (CCL-64 cells) induced by silica-stimulated pulmonary alveolar macrophages (PAM) supernatant is related with the phosphorylation states of connexin 43(Cx43) protein.

METHODWestern-blot analysis was used to identify phosphorylated Cx43 species.

RESULTSWestern-blot analyses of SiO2- and phorbol 12-myristate 13-acetate(TPA)-treated CCL-64 cells showed the same phosphorylation states of Cx43 as the control group. There were no Cx43 protein in nucleus of CCL-64 cells.

CONCLUSIONThe inhibition on GJIC induced by SiO2 and TPA in CCL-64 cells may not be brought about by altering the phosphorylation states of Cx43.

Animals ; Cell Communication ; drug effects ; Cell Line ; Connexin 43 ; metabolism ; Gap Junctions ; drug effects ; Lung ; drug effects ; metabolism ; Mink ; Phosphorylation ; Silicon Dioxide ; toxicity ; Tetradecanoylphorbol Acetate ; pharmacology

OBJECTIVETo study the effects of extremely low frequency magnetic fields(ELF MF) on the amount and localization of connexin 43(Cx43) gap-junction protein in the Chinese hamster lung(CHL) cells, and to explore the mechanism of ELF MF suppression on gap-junctional intercellular communication(GJIC).

METHODSThe cells were irradiated for 24 h with 50 Hz sinusoidal magnetic field at 0.8 mT without or with 12-O-tetrade-canoylphorbol-3-acetate(TPA), 5 ng/ml for 1 h. The localization of Cx43 proteins were performed by indirect immunofluorescence histochemical analysis and detected by confocal microscopy. The second experiment was conducted to examine the quantity of Cx43 proteins level in nuclei or cytoplasm and detected by Western blotting analysis.

RESULTSThe cells exposed to TPA for 1 h displayed less bright labelled spots in the regions of intercellular junction than the normal cells. Most of Cx43 labelled spots occurred in the cytoplasm and aggregated near the nuclei. At the same time, the amount of Cx43 protein in cytoplasm were increased[(2.03 +/- 0.89) in ELF group, (2.43 +/- 0.82) in TPA group] as compared to normal control(1.04 +/- 0.17) (P < 0.01).

CONCLUSIONInhibition on GJIC function by ELF MF alone or combined with TPA may be related with the shift of Cx43 from the regions of intercellular junction to the cytoplasm.

Animals ; Cell Communication ; radiation effects ; Connexin 43 ; biosynthesis ; Cricetinae ; Cricetulus ; Cytoplasm ; metabolism ; Electromagnetic Fields ; adverse effects ; Gap Junctions ; radiation effects ; Lung ; metabolism ; radiation effects ; Tetradecanoylphorbol Acetate ; pharmacology

OBJECTIVETo investigate the effect of valproate acid sodium (VPA) on gap junction intercellular communication in breast cancer Hs578T cells and explore the mechanism.

METHODSMTT assay was used to detect the cytotoxicity of VPA on Hs578T cells, and parachute assay was used to detect the effect of VPA on dye spread of the cells. Western blotting was employed to detect the expression changes of Cx43 total protein in VPA-treated Hs578T cells. The effect of VPA on the expression of Cx43 on the surface of Hs578T cells was examined with immunofluorescence assay.

RESULTSMTT assay showed no obvious cytotoxicity of VPA on Hs578T cells at the concentrations below 10 mmol/L. VPA below 5 mmol/L obviously increased the gap junction function in Hs578T cells (P<0.01), and significantly enhanced the expression of Cx43 total protein (P<0.01) and Cx43 expression on the surface of Hs578T cells (P<0.01).

CONCLUSIONVPA can obviously increase the gap junction function in Hs578T cells possibly by enhancing Cx43 total protein expression and Cx43 protein expression on the surface of Hs578T cells.

Breast Neoplasms ; metabolism ; Cell Communication ; drug effects ; Cell Line, Tumor ; Connexin 43 ; metabolism ; Female ; Gap Junctions ; drug effects ; Humans ; Valproic Acid ; pharmacology

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine ; analogs & derivatives ; pharmacology ; Animals ; Cardiomyopathy, Hypertrophic ; drug therapy ; metabolism ; Connexin 43 ; metabolism ; Disease Models, Animal ; Male ; Myocardium ; metabolism ; Rats ; Rats, Wistar

OBJECTIVETo observe the effects of TGF-beta on the expression of connexin43 (Cx43) and Cx43-mediated gap junctional intercellular communication (GJIC) in rat Leydig cells, and investigate the association of its effects on Leydig cells with its ability of changing GJIC.

METHODSPrimarily cultured purified Leydig cells were divided into a blank control group, a positive control group (treated with the GJIC inhibitor Carbenoxolone), and four TGF-beta1 groups (treated with TGF-beta1 at the concentration of 1, 2, 5 and 10 ng/ml, respectively, for 20 hours). The localization and expression of Cx43 were detected by immunofluorescence and Western blot, and the changes in GJIC analyzed by FRAP assay.

RESULTSCx43 was expressed as scattered bright spots in the cytoplasm and membrane of Leydig cells. TGF-beta1 significantly elevated the expression of Cx43 in the cytoplasm, but caused no evident change in the membrane. Western blot showed an evident increase in the phosphorylation of Cx43 with the increased concentration of TGF-beta1 as compared with that of the blank control group (P < 0.05). After 20 hours of treatment with TGF-beta1 at 5 ng/ml, the fluorescence intensity of Leydig cells was markedly reduced (P < 0.01), with a mean fluorescence recovery rate of merely (43.58 +/- 1.87)%.

CONCLUSIONTGF-beta1 could significantly down-regulate GJIC between adjacent Leydig cells, and this inhibitory effect may be achieved by promoting the expression of Cx43 in the cytoplasm and elevating the phosphorylation of Cx43.

Animals ; Cell Communication ; drug effects ; Cells, Cultured ; Connexin 43 ; metabolism ; Gap Junctions ; drug effects ; metabolism ; Leydig Cells ; drug effects ; metabolism ; Male ; Phosphorylation ; Rats ; Transforming Growth Factor beta1 ; pharmacology