Gap Junctional Intercellular Communication Function Research Articles

The Cytotoxic Effects of Human Mesenchymal Stem Cells Induced by Uranium.

Bone is a major tissue for uranium deposition in human body. Considering mesenchymal stem cells (MSCs) play a vital role in bone formation and injury recovery, studying the mechanism of MSCs responding to uranium poisoning can benefit the understanding of bone damage and repair after uranium exposure. Cellular structural alterations were analyzed via transmission electron microscopy (TEM). Changes in cellular behaviors were assessed through cellular viability, apoptosis, and the production of DNA double-strand breaks (DSBs). In addition, the influence of gap junctional intercellular communication (GJIC) on uranium toxicity was assessed. The disruption of MSCs was elevated with the increase in uranyl nitrate concentration, as shown by TEM micrograph. This was verified by the results of cellular viability and DSB production. Interestingly, the results of apoptosis assay indicated significant apoptosis occurred, which was accompanied with an obvious disruption of cellular membranes. Furthermore, closely contacted cell confluence groups exhibited resistant to uranium poisoning in contrast to sparse growth groups, which can be eliminated with the pretreatment of a GJIC inhibitor in the close connection group. To verify the association between GJIC and cytotoxic effects of uranyl nitrate, GJIC function was evaluated by wound healing and cellular migration. The results showed an inhibition of the healing ratio and migration ability induced by the exposure of uranyl nitrate. The low transfer efficiency of the dye coupling experiment and depressed expression of gap functional protein connexins confirmed the impairment of GJIC function. These results suggest that uranium toxicity is involved with GJIC dysfunction.

Interactive mechanism between connexin43 and Cd-induced autophagic flux blockage and gap junctional intercellular communication dysfunction in rat hepatocytes

Cadmium (Cd) is a significant environmental contaminant known for its potential hepatotoxic effects. However, the precise mechanisms underlying Cd-induced hepatotoxicity have yet to be fully understood. Therefore, the purpose of this study was to investigate the dynamic role of connexin 43 (Cx43) in response to Cd exposure, particularly its impact on gap junctional intercellular communication (GJIC) and autophagy in hepatocytes. To establish an in vitro model of Cd-induced hepatocyte injury, the Buffalo rat liver 3A cell line (BRL3A) was utilized.In order to elucidate the mechanism by which Cx43 influences Cd-induced hepatocyte toxic injury, inhibitors of Cx43 (Dynasore) and P-Cx43 (Ro318220) were employed in the model. The findings revealed that inhibiting Cx43 and its phosphorylation further compromised GJIC function, exacerbating the impairment, while also intensifying the blockage of autophagic flux. To gain further insight into the role of Cx43, siRNA was utilized to knock down Cx43 expression, yielding similar results. The down-regulation of Cx43 expression was found to worsen the morphological damage induced by cadmium exposure, diminish the cell proliferation capacity of BRL3A cells, and exacerbate the disruption of GJIC and autophagic flow caused by Cd.These findings suggest that Cx43 may serve as a potential therapeutic target for the treatment of liver damage resulting from Cd exposure. By targeting Cx43, it may be possible to mitigate the adverse effects of Cd on hepatocytes.

Novel antidepressant mechanism of hypericin: Role of connexin 43-based gap junctions

Hypericin is widely utilized for its precise antidepressant properties, but its exact antidepressant mechanism remains unclear. Gap junctions, which were predominantly expressed in astrocytes in the central nervous system, are concerned with the pathogenesis of depression. However, the role of hypericin in gap junctional dysfunction in depression has rarely been investigated. Here, we found that gap junctions were ultra-structurally broadened in the chronic unpredictable stress (CUS) rat model of depression, while hypericin repaired the dysfunction of gap junctions. Suppression of gap junctions by bilateral injection of carbenoxolone (CBX) in the prefrontal cortex of rats significantly inhibited the restoration of gap junctional dysfunction in depression by hypericin. Meanwhile, hypericin failed to show antidepressant benefits. Furthermore, in corticosterone (CORT)-stimulated primary astrocytes derived from neonatal rats, hypericin dramatically reversed the phosphorylation of connexin 43 (Cx43), normalizing the expression of Cx43 and thereby ameliorating gap junctional dysfunction. Comparatively, CBX inhibited the remission of hypericin on gap junctional intercellular communication function. Gap junctional function might be a novel therapeutic target for hypericin in the treatment of depression and provide potential novel insights into the antidepressant mechanism of other herbal ingredients.

Genotoxic carcinogen 7,12-dimethylbenz[a]anthracene inhibits gap junction intercellular communication through post-transcriptional and post-translational processing involved in connexin 43 stability.

Gap junctional intercellular communication (GJIC) is composed of connexin (Cx) and plays an important role in maintaining intracellular homeostasis. Loss of GJIC is involved in the early stages of cancer pathways of non-genotoxic carcinogens; however, the effect of genotoxic carcinogens, including polycyclic aromatic hydrocarbons (PAHs), on GJIC function remains unclear. Therefore, we determined whether and how a representative PAH 7,12-dimethylbenz[a]anthracene (DMBA) suppresses GJIC in WB-F344cells. First, DMBA significantly inhibited GJIC and dose-dependently reduced Cx43 protein and mRNA expression. In contrast, Cx43 promoter activity was upregulated after DMBA treatment via the induction of specificity protein 1 and hepatocyte nuclear factor 3β, indicating that the promoter-independent loss of Cx43 mRNA can be associated with the inhibition of mRNA stability, which was verified by actinomycin D assay. In addition to a decrease in mRNA stability involved in human antigen R, we also observed DMBA-induced acceleration of Cx43 protein degradation, which was closely related to the loss of GJIC through Cx43 phosphorylation via MAPK activation. In conclusion, the genotoxic carcinogen DMBA suppresses GJIC by inhibiting post-transcriptional and post-translational processing of Cx43. Our findings suggest that the GJIC assay is an efficient short-term screening test for predicting the carcinogenic potential of genotoxic carcinogens.

Connexin 43-modified bone marrow stromal cells reverse the imatinib resistance of K562 cells via Ca2+-dependent gap junction intercellular communication.

Imatinib mesylate (IM) resistance is an emerging problem for chronic myeloid leukemia (CML). Previous studies found that connexin 43 (Cx43) deficiency in the hematopoietic microenvironment (HM) protects minimal residual disease (MRD), but the mechanism remains unknown. Immunohistochemistry assays were employed to compare the expression of Cx43 and hypoxia-inducible factor 1α (HIF-1α) in bone marrow (BM) biopsies of CML patients and healthy donors. A coculture system of K562 cells and several Cx43-modified bone marrow stromal cells (BMSCs) was established under IM treatment. Proliferation, cell cycle, apoptosis, and other indicators of K562 cells in different groups were detected to investigate the function and possible mechanism of Cx43. We assessed the Ca2+-related pathway by Western blotting. Tumor-bearing models were also established to validate the causal role of Cx43 in reversing IM resistance. Low levels of Cx43 in BMs were observed in CML patients, and Cx43 expression was negatively correlated with HIF-1α. We also observed that K562 cells cocultured with BMSCs transfected with adenovirus-short hairpin RNA of Cx43 (BMSCs-shCx43) had a lower apoptosis rate and that their cell cycle was blocked in G0/G1 phase, while the result was the opposite in the Cx43-overexpression setting. Cx43 mediates gap junction intercellular communication (GJIC) through direct contact, and Ca2+ is the key factor mediating the downstream apoptotic pathway. In animal experiments, mice bearing K562, and BMSCs-Cx43 had the smallest tumor volume and spleen, which was consistent with the in vitro experiments. Cx43 deficiency exists in CML patients, promoting the generation of MRD and inducing drug resistance. Enhancing Cx43 expression and GJIC function in the HM may be a novel strategy to reverse drug resistance and promote IM efficacy.

Dioscin potentiates the antitumor effect of suicide gene therapy in melanoma by gap junction intercellular communication-mediated antigen cross-presentation.

Dioscin (Dio), steroid saponin, exists in several medicinal herbs with potent anticancer efficacy. This study aimed to explore the effect of Dio on the immune-related modulation and synergistic therapeutic effects of the herpes simplex virus thymidine kinase/ganciclovir (HSV-Tk/GCV) suicide gene therapy system in murine melanoma, thereby providing a research basis to improve the potential immunomodulatory mechanism underlying combination therapy. Using both in vitro and in vivo experiments, we confirmed the immunocidal effect of Dio-potentiated suicide gene therapy on melanoma. The results showed that Dio upregulated connexin 43 (Cx43) expression and improved gap junction intercellular communication (GJIC) in B16 cells while increasing the cross-presentation of antigens by dendritic cells (DCs), eventually promoting the activation and antitumor immune killing effects of CD8+ T lymphocytes. In contrast, inhibition or blockade of the GJIC function (overexpression of mutant Cx43 tumor cells/Gap26) partially reversed the potentiating effect. The significant synergistic effect of Dio on HSV-Tk/GCV suicide gene therapy was further investigated in a B16 xenograft mouse model. The increased number and activation ratio of CD8+ T lymphocytes and the levels of Gzms-B, IFN-γ, and TNF-α in mice reconfirmed the potential modulatory effects of Dio on the immune system. Taken together, Dio targets Cx43 to enhance GJIC function, improve the antigens cross-presentation of DCs, and activate the antitumor immune effect of CD8+ T lymphocytes, thereby providing insights into the potential immunomodulatory mechanism underlying combination therapy.

3D Microtissues Mimic the Architecture, Estradiol Synthesis, and Gap Junction Intercellular Communication of the Avascular Granulosa.

Humans are consistently exposed to thousands of untested chemicals that have been detected in the follicular fluid of the ovaries, and can disrupt reproductive health. Human granulosa cells (GCs) are the functional unit of the ovarian follicle with steroidogenic and signaling activities, and play a pivotal role in oocyte development. During follicle progression, GCs multiply to form a 3D avascular structure, and establish gap junction intercellular communication (GJIC) that is critical to maintaining optimal viability and function. We developed a high-throughput in vitro platform of human GCs for the screening of chemicals that can impact GJIC and estradiol (E2) production of human granulosa. Our granulosa 3D microtissues fabricated with human ovarian granulosa-like tumor KGN cells are multicell-layered structures that mimic the avascular granulosa layers surrounding the oocyte. These microtissues robustly expressed the steroidogenic CYP19 aromatase enzyme and GJIC intercellular membrane channel, connexin 43. Granulosa microtissues produced E2 at rates comparable to primary human GCs as previously reported. E2 production was suppressed by the CYP19 inhibitor, letrozole, and induced by CYP19 activators, bisphenol A at 100 µM, and genistein at 100 µM. Granulosa microtissues displayed active GJIC function, as demonstrated by the connexin 43-dependent diffusion of calcein fluorescent dye from microtissue surface to the core using high-throughput confocal microscopy in conjunction with our open-sourced automated image analysis tool. Overall, our 3D human granulosa screening platform is highly promising for predictive and efficient in vitro toxicity testing to screen for chemicals that contaminate follicular fluid and may affect fertility.

Guiding mechanism of platycodin D in treatment of mouse lung cancer with doxorubicin

This study is to observe whether platycodin D has the guiding role in treatment of mouse lung cancer with doxorubicin and explore its guiding mechanism. In vitro, platycodin D and doxorubicin(alone or in combination) were added into Lewis lung cancer(LLC) cells to detect the cell proliferation and doxorubicin uptake. Cell morphological changes were analyzed by cell holographic analysis system; cell gap junctional intercellular communication(GJIC) was tested by fluorescent yellow tracer; lyso-tracker red was used to examine lysosomal function; LC-3 B(Light chain 3 beta)and P62(heat shock 90-like protein)staining were used to test auto-phagy and autophagic degradation respectively; and P-glycoprotein(P-gp) expression was examined by Western blot. In vivo, lung solid tumor was formed in mouse LLC cells via intravenous injection. Platycodin D and doxorubicin(alone or in combination) were used to treat tumor-bearing mice for four weeks, and then the tumor size was examined, mouse survival time was recorded, doxorubicin uptake in lung tissues was tested, and lung tissues were stained for observation by HE(hematoxylin-eosin) and immunohistochemistry. The results showed that platycodin D at the experimental concentration had no effect on LLC cell proliferation but decreased LLC cell volume, promoted the cells to uptake doxorubicin and enhanced the inhibitory action of doxorubicin on cell proliferation. Platycodin D could promote GJIC and lysosomal function, increase autophagy and autophagic degradation and suppress P-gp expression. Platycodin D at the experimental dose in this study had no effect on LLC lung solid tumors in mice, increased doxorubicin uptake in lung tissues and enhanced the therapeutic efficacy of doxorubicin on lung solid tumors. Platycodin D could improve the extracellular matrix deposition in lung solid tumors, decreased the lung mucin 5 AC secretion and pulmonary vessel permeability. In summary, platycodin D had the guiding role in treating mouse lung cancer with doxorubicin, and its guiding mechanism may be associated with the promotion of cell communication, lysosomal function, and improvement of extracellular environment.

Expression and functional regulation of gap junction protein connexin 43 in dermal mesenchymal stem cells from psoriasis patients

BackgroundPsoriasis is a chronic recurrent inflammatory disease. Mesenchymal stem cells (MSCs) can regulate the inflammatory microenvironment, thereby controlling the proliferation, differentiation, and migration of immune cells. Connexin 43(Cx43), a key gap junction protein, has been shown to form gap junctions for communication between neighboring cells. ObjectiveWe investigated the expression of Cx43 in dermal mesenchymal stem cells (DMSCs) derived from psoriasis patients and explored the relationship between the Cx43-mediated gap junction intercellular communication (GJIC) and DMSCs. MethodsHuman DMSCs were isolated and propagated in adherent culture. Quantitative real-time reverse transcription PCR and western blot and immunofluorescence were used to detect the expression and localization of Cx43 in DMSCs. Fluorescence redistribution after photobleaching was performed to assess adjacent DMSCs GJIC. CCK8 was used to detect the proliferation of DMSCs before and after gap junction blocker (18α-glycyrrhetinic acid; AGA) treatment. Cell energy metabolism was analyzed with an energy metabolism analyzer. ResultsCx43 was located in the cytoplasm and cytomembrane, as well as partially in the nucleus of DMSCs. The expression of Cx43 in psoriasis DMSCs was higher than that in control samples and the gap junction function was enhanced. In addition, the glycolysis and mitochondrial respiration of psoriasis DMSCs were also enhanced. However, AGA inhibited the expression of Cx43, attenuated GJIC function, and inhibited the proliferation of DMSCs. ConclusionsOur results indicated that the expression of Cx43 in DMSCs from psoriasis lesions is increased and that the inhibition of Cx43 leads to the inhibition of both GJIC and DMSCs proliferation.

Gadolinium Chloride Restores the Function of the Gap Junctional Intercellular Communication between Hepatocytes in a Liver Injury.

Background: Gadolinium chloride (GdCl3) has been reported to attenuate liver injury caused by a variety of toxicants. Gap junctional intercellular communication (GJIC) is thought to be essential in controlling liver homeostasis and pathology. Here we evaluate the effects of GdCl3 on functional GJIC and connexin expression in mouse models and primary hepatocytes. Methods: Mice were administered GdCl3 intraperitoneally the day before a carbon tetrachloride (CCl4) injection or bile duct ligation (BDL) operation. Primary hepatocytes were treated with CCl4 or lipopolysaccharides (LPS), with or without GdCl3. A scrape loading/dye transfer assay was performed to assess the GJIC function. The expression of connexins was examined by real-time reverse transcription polymerase chain reaction (RT-PCR), western blot and immunofluorescent staining. Results: CCl4 treatment or the BDL operation led to the dysfunction of GJIC and a down-regulation of Cx32 and Cx26 in injured liver. GdCl3 administration restored GJIC function between hepatocytes by facilitating the transfer of fluorescent dye from one cell into adjacent cells via GJIC, and markedly prevented the decrease of Cx32 and Cx26 in injured liver. In primary hepatocytes, CCl4 or LPS treatment induced an obvious decline of Cx32 and Cx26, whereas GdCl3 pretreatment prevented the down-regulation of connexins. In vivo GdCl3 protected hepatocytes and attenuated the liver inflammation and fibrosis in liver injury mouse models. Conclusion: GdCl3 administration protects functional GJIC between hepatocytes, and prevents the decrease of connexin proteins at mRNA and protein levels during liver injury, leading to the alleviation of chronic liver injury.

Theaflavin 3,3'-digallate reverses the downregulation of connexin 43 and autophagy induced by high glucose via AMPK activation in cardiomyocytes.

Theaflavin 3,3'-digallate (TF3), is reported to protect cardiomyocytes from lipotoxicity and reperfusion injury. However, the role of TF3 in the protection of high-glucose injury is still poorly understood. This study investigated the protective effects of TF3 on gap junctions and autophagy in neonatal cardiomyocytes (NRCMs). NRCMs preincubated with high glucose were coincubated with TF3. The expression of connexins and autophagy-related proteins was determined. The functioning of gap-junctional intercellular communication (GJIC) was measured by a dye transfer assay.Adenosine monophosphate-activated protein kinase (AMPK) activity was determined by western blot. Moreover, AMPK was activated with aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) or inhibited by AMPKα small interfering RNA (siRNA) to explore the role of AMPK in the modulation of connexin 43 (Cx43) and autophagy. Meanwhile, autophagy was activated or blocked to observe the change in Cx43 expression. It was found that the protein expression of Cx43 and autophagy-related proteins was increased in a TF3 dose- and time-dependent manner under high glucose. TF3 also recovered the reduced GJIC function induced by high glucose concentrations. TF3 activated phosphorylated AMPK in a time-dependent way. AMPKα siRNA abrogated the protection of TF3, while AICAR showed similar results compared to the TF3 treatment. Meanwhile, autophagy activation caused decreased Cx43, while cotreatment with baf A1 enhanced Cx43 expression further compared with the TF3 treatment alone under high glucose. We concluded that TF3 partly reversed the inhibition of Cx43 expression and autophagy induced by high glucose in NRCMs, partly by restoring AMPK activity. Inhibition of autophagy might be protective by preserving Cx43 expression in NRCMs stimulated by high glucose.

A novel role of Cx43-composed GJIC in PDT phototoxicity: an implication of Cx43 for the enhancement of PDT efficacy.

In spite of initially promising responses, 5-year recurrence after photodynamic therapy (PDT) sustains high level and an increase in PDT effectiveness is needed. It has been demonstrated that gap junctional intercellular communication (GJIC) formed by Connexin (Cx)43 could improve the transfer of “death signal” between cells, thereby causing the enhancement of cytotoxicity of chemotherapeutics and suicide gene therapy. Nevertheless, whether Cx43-composed GJIC has an effect on PDT phototoxicity remains unknown. This study showed that Cx43-formed GJIC could improve PDT phototoxicity to tumor cells in vitro and in vivo. Specifically, Cx43-formed GJIC under the condition of high cellular density could improve PDT phototoxicity in Cx43-transfected HeLa cells and Cx43-expressing U87 glioma cells. This effect was remarkably inhibited when Cx43 was not expressed or Cx43-formed GJ channels were prohibited. Additionally, the presence of Cx43-mediated GJIC could decrease the mean RTV and tumor weights of xenografts after Photofrin-PDT. The improved PDT efficacy by Cx43-composed GJIC was correlated with stress signaling pathways mediated by ROS, calcium and lipid peroxide. The present study demonstrates the presence of Cx43-composed GJIC improves PDT phototoxicity and suggests that therapeutic strategies designed to upregulate the expression of Cx43 or enhance Cx43-mediated GJIC function may increase the sensitivity of malignant cell to PDT, leading to the increment of PDT efficacy. Oppositely, factors that retard Cx43 expression or prohibit the function of Cx43-mediated GJIC may cause insensitivity of malignant cells to PDT, leading to PDT resistance.

Effects of bisphenol A on gap junctions in HaCaT cells as mediated by the estrogen receptor pathway.

Bisphenol A (BPA) is widely used as the raw material for the production of plastics and paper products. People can be exposed to BPA through dermal contact, particularly for cashiers in contact with thermal paper every day. BPA is a known endocrine disruptor that has been shown to be carcinogenic. Many tumors show weak gap junctional intercellular communication (GJIC) function. The aim of this study was to investigate the effects and possible mechanisms of BPA's action on GJIC of human HaCaT skin cells. The results showed that BPA increased cell proliferation rates, prolonged GJIC photobleaching fluorescence recovery times and reduced overall fluorescence recovery rates at 0.01, 0.1 and 1μm. BPA downregulated connexin (Cx)26 mRNA level at 0.1μm. Estrogen receptor (ER) antagonist ICI 182780 at 5nm partially blocked the above effects of BPA indicating involvement of the ER pathway with BPA exposure. However, BPA did not influence Cx43 mRNA and protein levels. Our immunofluorescence data showed that Cx26 was expressed in the cytoplasm and plasma membrane, and was involved in the formation of gap junctions between adjacent cells, while Cx43 was expressed only in the cytoplasm. Therefore, our data indicate that Cx26 gap junctions may be involved in the GJIC inhibition caused by BPA. In conclusion, our results indicate that BPA can promote human skin cell proliferation, inhibit skin cell GJIC function but not formation and downregulate Cx26 mRNA levels partially through the ER pathway. We hypothesize that BPA can exhibit carcinogenicity by inhibiting GJIC.

Erratum: Tanshinone IIA and Astragaloside IV promote the angiogenesis of mesenchymal stem cell-derived endothelial cell-like cells via upregulation of Cx37, Cx40 and Cx43.

[This corrects the article DOI: 10.3892/etm.2017.5636.].

Effects of Helicobacter pylori on the expression levels of GATA-3 and connexin 32 and the GJIC function in gastric epithelial cells and their association by promoter analysis.

The present study aimed to explore the effects of Helicobacter pylori (H. pylori) infection on the expression of transcription factor GATA binding protein 3 (GATA-3) and connexin 32 (Cx32) in cultured gastric mucosa cells, and their association with each other. GES-1 cells were co-cultured with East Asian type cytotoxin-associated gene A+ H. pylori in the H. pylori group, and without H. pylori culture in the control group. Additionally, Mongolian gerbils were gavaged with H. pylori, and later the gastric antrum tissues were collected. The GATA-3 and Cx32 mRNA and protein expression levels were detected by a reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. The scratch labeling fluorescent dye tracer (SLDT) technique was used to detect the gap junctional intercellular communication (GJIC) function. GATA-3 small interfering RNA (siRNA) was transfected into BGC823 cells and its effect on Cx32 expression levels was detected. The impact of GATA-3 on Cx32 promoter transcriptional activity was detected using a dual luciferase reporter assay. The results revealed that H. pylori infection increased GATA-3 expression and decreased Cx32 expression in GES-1 cells and in animal gastric tissues compared with their respective controls, whilst in BGC823 cells, GATA-3 siRNA increased Cx32 expression compared with the control. In the SLDT experiment of GES-1 cells with H. pylori infection, the fluorescent dye was primarily limited to a single cell row close to the scratch, and only a limited amount of dye passing to the second cell row, indicating that the GJIC function was substantially reduced or absent compared with the control group, where the fluorescence dye transferred to the neighboring cells of 3–4 rows, indicating a stronger GJIC function comparatively. GATA-3 inhibited the expression of the luciferase reporter gene, compared with the controls, suggesting that GATA-3 inhibited the expression of Cx32 by binding to Cx32 promoter sites. These results indicated that H. pylori-increased GATA-3 expression, which downregulated Cx32 expression, may serve an important function in gastric carcinogenesis, and GATA-3 siRNA may serve a function in the prevention and treatment of gastric cancer.

Tanshinone IIA and Astragaloside IV promote the angiogenesis of mesenchymal stem cell-derived endothelial cell-like cells via upregulation of Cx37, Cx40 and Cx43.

Tanshinone IIA (Tan IIA) and Astragaloside IV (AGS-IV) were used as therapeutic treatments for coronary heart diseases (CHDs) in ancient China. However, the underlying mechanisms mediating the effects of Tan IIA and AGS-IV in angiogenesis remain unknown. In the present study, mesenchymal stem cells (MSCs) were induced to differentiate into endothelial cell (EC)-like cells in vitro and the effects of Tan IIA and/or AGS-IV on the functions of these cells, including cell proliferation and tube formation, were assessed. Compared with the single-agent groups (Tan IIA or AGS-IV only), combined-agent (Tan IIA and AGS-IV) treatment significantly enhanced the proliferation and tube formation capacity of EC-like cells. In addition, the expression of connexin 37 (Cx37), Cx40 and Cx43 in the combined-agent group was significantly increased compared with the single-agent groups. Furthermore, enhanced gap junctional intercellular communication (GJIC) was identified in the combined-agent group, as evidenced by increased dye transfer in scrape-loading dye transfer assays. In conclusion, Tan IIA and AGS-IV may promote the angiogenesis of EC-like cells by upregulating the expression of Cx37, Cx40 and Cx43 and enhancing GJIC function. The results of the present study may provide experimental evidence for the clinical application of Tan IIA and AGS-IV as a treatment for CHDs.

Gefitinib enhances oxaliplatin-induced apoptosis mediated by Src and PKC-modulated gap junction function.

Chemotherapeutic drug-induced apoptosis is enhanced by gap junction intercellular communication (GJIC) in a variety of tumor cells. Oxaliplatin and gefitinib are the most widely used chemotherapeutic drugs. However, the synergistic influence remains unknown in testicular cancer chemotherapy. The aim of the present study was to investigate the apoptosis induced by oxaliplatin combined with gefitinib and the potential mechanisms in I-10 testicular cancer cells. The results showed that gefitinib significantly enhanced oxaliplatin-induced apoptosis. Furthermore, the ratio of Bcl-2/Bax and the cleavage of caspase-3and-9 were increased by gefitinib during oxaliplatin-induced apoptosis. The oxaliplatin-induced apoptosis was enhanced through the upregulation of gap junction (GJ) channels composed of connexin43 (Cx43) by gefitinib. The mechanism of GJIC enhancement involved the suppression by gefitinib of the expression levels of Src and PKC, which phosphorylate Cx43 and reduce GJIC. PP2 (Src inhibitor) and GF109203X (PKC inhibitor) also enhanced GJIC function. Our findings demonstrated that gefitinib enhanced oxaliplatin-induced apoptosis in I-10 cells and gefitinib upregulated the GJIC by inhibiting Src and PKC-modulated Cx43 phosphorylation.

All-trans retinoic acid arrests cell cycle in leukemic bone marrow stromal cells by increasing intercellular communication through connexin 43-mediated gap junction

BackgroundGap junctional intercellular communication (GJIC) is typically decreased in malignant tumors. Gap junction is not presented between hematopoietic cells but occurred in bone marrow stromal cells (BMSCs). Connexin 43 (Cx43) is the major gap junction (GJ) protein; our previous study revealed that Cx43 expression and GJIC were decreased in acute leukemic BMSCs. All-trans retinoic acid (ATRA) increases GJIC in a variety of cancer cells and has been used to treat acute promyelocytic leukemia, but the effects of ATRA on leukemic BMSCs is unknown. In this study, we evaluated the potential effects of ATRA on cell cycle, proliferation, and apoptosis of leukemic BMSCs. Effects of ATRA on Cx43 expression and GJIC were also examined.MethodsHuman BMSCs obtained from 25 patients with primary acute leukemia, and 10 normal healthy donors were cultured. Effects of ATRA on cell cycle, cell proliferation, and apoptosis were examined with or without co-treatment with amphotericin-B. Cx43 expression was examined at both the mRNA and protein expression levels. GJIC was examined by using a dye transfer assay and measuring the rate of fluorescence recovery after photobleaching (FRAP).ResultsATRA arrested the cell cycle progression, inhibited cell growth, and increased apoptosis in leukemic BMSCs. Both Cx43 expression and GJIC function were increased by ATRA treatment. Most of the observed effects mediated by ATRA were abolished by amphotericin-B pretreatment.ConclusionsATRA arrests cell cycle progression in leukemic BMSCs, likely due to upregulating Cx43 expression and enhancing GJIC function.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-015-0212-7) contains supplementary material, which is available to authorized users.

Mechanism of regulating the resistance of prostate cancer PC-3 cells to cisplatin through enhancing cell gap junctions by evodiamine

Objective To evaluate the effect of the combination of cisplatin and evodiamine on the growth of PC-3 cells and gap junction intercellular communication(GJIC). Methods Human prostate cancer PC-3 cells in logarithmic growth phase were cultured in vitro and then treated with various concentrations of cisplatin(5,10,15,20μmol/L)or evodiamine(0. 4μmol/L)combined with various concentrations of cisplatin(5, 10, 15, 20μmol/L).The effects of the proliferation was investigated by cell counting kit-8(CCK-8)assay.Apoptosis rate, and cell cycle distribution were examined by Annexin V-fluoresceine isothiocyanate(FITC)/propidium iodide(PI) double staining flow cytometry.The expression of connexin43(Cx43) protein was detected by Western blotting.The changes in the GJIC function were observed by FRAP. Results Fluorescence recovery rate was(41. 93± 1. 30)%,(36. 32±2. 33)%,(30. 81±1. 43)%, and(22. 54±1. 70)% in cisplatin groups, and (69. 86±2. 16)%,(50. 03±5. 00)%,(45. 38±2. 59)%, and(34. 01±4. 01)% in cisplatin+ evodiamine groups with statistically significant differences within groups respectively(P< 0. 05 for all). Fluorescence recovery rate, apoptosis rate, and the expression of Cx43 protein in cisplatin+ evodiamine groups were significantly increased as compared with cisplatin groups(P< 0. 05 for all). Conclusion Evodiamine could recover the gap junction intercellular communication through increasing the expression of Cx43 protein and enhancing the cytotoxicity of cisplatin to prostate cancer PC-3 cells. Key words: Evodiamine; Cisplatin; Prostate cancer; Gap junctioninter cellular communication

Effects of 50 Hz magnetic fields on gap junctional intercellular communication in NIH3T3 cells.

The present study focused on gap junctional intercellular communication (GJIC) as a target for biological effects of extremely low-frequency (ELF) magnetic field (MF) exposure. Fluorescence recovery after photobleaching microscopy (FRAP) was used to visualize diffusion of a fluorescent dye between NIH3T3 fibroblasts through gap junctions. The direct effect of 24 h exposure to 50 Hz MF at 0.4 or 1 mT on GJIC function was assessed in one series of experiments. The potential synergism of MF with an inhibitor of GJIC, phorbol ester (TPA), was studied in another series by observing FRAP when NIH3T3 cells were incubated with TPA for 1 h following 24 h exposure to MF. In contrast to other reports of ELF-MF effects on GJIC, under our experimental conditions we observed neither direct inhibition of GJIC nor synergism with TPA-induced inhibition from 50 Hz MF exposures.