BACKGROUND: 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. METHODS: 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 Ca 2+ -related pathway by Western blotting. Tumor-bearing models were also established to validate the causal role of Cx43 in reversing IM resistance. RESULTS: 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 Ca 2+ 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. CONCLUSIONS 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.
Animals ; Humans ; Mice ; Apoptosis ; Bone Marrow Cells ; Cell Communication ; Connexin 43/genetics* ; Gap Junctions/metabolism* ; Imatinib Mesylate/therapeutic use* ; K562 Cells ; Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology* ; Mesenchymal Stem Cells/metabolism* ; Tumor Microenvironment ; Calcium/metabolism*

Homoeostasis depends on the close connection and intimate molecular exchange between extracellular, intracellular and intercellular networks. Intercellular communication is largely mediated by gap junctions (GJs), a type of specialized membrane contact composed of variable number of channels that enable direct communication between cells by allowing small molecules to pass directly into the cytoplasm of neighbouring cells. Although considerable evidence indicates that gap junctions contribute to the functions of many organs, such as the bone, intestine, kidney, heart, brain and nerve, less is known about their role in oral development and disease. In this review, the current progress in understanding the background of connexins and the functions of gap junctions in oral development and diseases is discussed. The homoeostasis of tooth and periodontal tissues, normal tooth and maxillofacial development, saliva secretion and the integrity of the oral mucosa depend on the proper function of gap junctions. Knowledge of this pattern of cell-cell communication is required for a better understanding of oral diseases. With the ever-increasing understanding of connexins in oral diseases, therapeutic strategies could be developed to target these membrane channels in various oral diseases and maxillofacial dysplasia.
Bone and Bones ; Cell Communication ; Connexins ; metabolism ; physiology ; Gap Junctions ; metabolism ; pathology ; Homeostasis ; physiology ; Humans ; Mouth Diseases ; Phosphorylation

Gap junctions (GJ), as a special membrane structure between adjacent cells, are composed of connexins (Cx) and regulate the proliferation and differentiation of cells. Studies show that gap junctional intercellular communication is weakened or lost in most tumor cells and this abnormality is often accompanied by changed expression of Cxs. Cx43 is a major connexin in the testis tissue. This review focuses on the latest progress in the studies of Cx43 in testicular tumors.
Animals ; Cell Communication ; Cell Differentiation ; Connexin 43 ; metabolism ; Gap Junctions ; metabolism ; Male ; Testicular Neoplasms ; metabolism

Gap junctions mediate direct communication between cells; however, toxicological cascade triggered by nonessential metals can abrogate cellular signaling mediated by gap junctions. Although cadmium (Cd) is known to induce apoptosis in organs and tissues, the mechanisms that underlie gap junction activity in Cd-induced apoptosis in BRL 3A rat liver cells has yet to be established. In this study, we showed that Cd treatment decreased the cell index (a measure of cellular electrical impedance) in BRL 3A cells. Mechanistically, we found that Cd exposure decreased expression of connexin 43 (Cx43), increased expression of p-Cx43 and elevated intracellular free Ca2+ concentration, corresponding to a decrease in gap junctional intercellular communication. Gap junction blockage pretreatment with 18β-glycyrrhizic acid (GA) promoted Cd-induced apoptosis, involving changes in expression of Bax, Bcl-2, caspase-3 and the mitochondrial transmembrane electrical potential (Δψm). Additionally, GA was found to enhance ERK and p38 activation during Cd-induced activation of mitogen-activated protein kinases, but had no significant effect on JNK activation. Our results indicated the apoptosis-related proteins and the ERK and p38 signaling pathways may participate in gap junction blockage promoting Cd-induced apoptosis in BRL 3A cells.
Animals ; Apoptosis/*drug effects ; Cadmium/*toxicity ; Calcium/metabolism ; Cell Communication/drug effects ; Connexin 43/genetics ; Enzyme Activation/drug effects ; Gap Junctions/*drug effects ; Gene Expression Regulation/drug effects ; Hepatocytes/cytology/*drug effects ; Rats ; Signal Transduction/drug effects

OBJECTIVETo investigate the effects of the quinoline derivative PQ1 combined with cisplatin on the proliferation and gap junction communication of prostate cancer PC3 cells.

METHODSWe cultured in vitro prostate cancer PC3 cells and divided them into DMSO blank control, cisplatin control, and cisplatin (10 mg/ml) plus PQ1 (1, 2, 5, 10, and 15 μmol/L) groups. We measured the proliferation of the prostate cancer PC3 cells, determined the expressions of the connexin 43 (Cx43) mRNA and protein by RT-PCR and Western blot, and compared the indexes among different groups.

RESULTSCisplatin combined with PQl at 1 - 10 μmol/L significantly inhibited the proliferation of the PC3 cells and the inhibition rate rose in a concentration- and time-dependent manner, from (48.72 ± 0.98)% vs (50.33 ± 0.62)% at 0 μmol/L to (77.38 ± 1.12)% vs (83.50 ± 1.05)% at 15 μmol/L at 24 and 48 hours (P < 0.05). Compared with the cisplatin control, cisplatin combined with PQ1 at 1, 2, 5, 10, and 15 μmol/L increased the expression of Cx43 mRNA from 0.379 ± 0.113 to 0.669 ± 0.031, 0.831 ± 0. 127, 0.769 ± 0.100, 0.532 ± 0.086, and 0.475 ± 0.134, respectively (P < 0.05), and cisplatin combined with PQ1 at 1, 2, 5, and 10 μmol/L elevated that of Cx43 protein from 0.138 ± 0.146 to 0.263 ± 0.111, 0.306 ± 0.152, 0.415 ± 0.280, and 0.643 ± 0.310, respectively (P < 0.05).

CONCLUSIONThe quinoline derivative PQ1 can promote the gap junction communication of prostate cancer PC3 cells and enhance the killing effect of cisplatin on PC3 cells by upregulating the expressions of Cx43 mRNA and protein.

Aminoquinolines ; pharmacology ; Antineoplastic Combined Chemotherapy Protocols ; pharmacology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Cisplatin ; pharmacology ; Connexin 43 ; genetics ; metabolism ; Dose-Response Relationship, Drug ; Gap Junctions ; drug effects ; physiology ; Humans ; Male ; Prostatic Neoplasms ; metabolism ; pathology ; physiopathology ; RNA, Messenger ; metabolism ; Time Factors

OBJECTIVETo investigate the effect of sodium valproate, a histone deacetylase inhibitor, on the cytotoxicity of doxorubicin in breast cancer cells.

METHODSWestern blotting was used to assess Cx43 protein expression in breast cancer Hs578T cells exposed to doxorubicin and sodium valproate. MTT assay was used to determine the cytotoxicity of doxorubicin; annexin V/PI double staining and Hochest 33258 fluorescence staining were employed to detect doxorubicin-induced early and late apoptosis, respectively.

RESULTSWestern blotting showed that sodium valproate significantly increased Cx43 protein expression in Hs578T cells (P/0.01). The cells exposed to both sodium valproate and doxorubicin showed significantly lowered cell viability compared with the cells exposed to doxorubicin alone (P/0.01). Exposure to both sodium valproate and doxorubicin resulted in significantly increased early and late cell apoptosis rate compared with doxorubicin treatment alone (P/0.01).

CONCLUSIONsodium valproate can significantly enhance the cytotoxicity of doxorubicin and increase doxorubicin-induced apoptosis in breast cancer cells in vitro possibly by enhancing the gap junction function.

Apoptosis ; drug effects ; Breast Neoplasms ; pathology ; Cell Line, Tumor ; drug effects ; Cell Survival ; drug effects ; Connexin 43 ; metabolism ; Doxorubicin ; pharmacology ; Drug Synergism ; Gap Junctions ; Histone Deacetylase Inhibitors ; pharmacology ; Humans ; Valproic Acid ; pharmacology

Gap junctions play a critical role in electrical synchronization and exchange of small molecules between neighboring cells; connexins are a family of structurally related transmembrane proteins that assemble to form vertebrate gap junctions. Hyperglycemia changes the structure gap junction proteins and their expression, resulting in obstruction of neural regeneration, vascular function and wound healing, and also promoting vascular atherosclerosis. These pathogenic factors would cause diabetic foot ulcers. This article reviews the involvement of connexins in pathogenesis of diabetic foot.
Atherosclerosis ; Connexins ; metabolism ; Diabetic Foot ; pathology ; Gap Junctions ; metabolism ; Humans ; Hyperglycemia ; physiopathology ; Regeneration ; Wound Healing

OBJECTIVETo investigate the protective effect of propofol against focal cerebral ischemia/reperfusion (I/R) injury in rats and its relation with gap junction.

METHODSSeventy adult male SD rats were randomly divided into sham-operated group, I/R group, low-, moderate-, and high-dose propofol groups (25, 50, 100 mg/kg; P25, P50, P100 groups, respectively), I/R+CBX group and P100+CBX group. Thread occlusion was used to induce middle cerebral artery occlusion (MCAO) in the mice for 2 h followed by reperfusion for 24 h. Longa's scores were used to evaluate the neurological behavior of the rats. TTC staining was used to measure the cerebral infarction volume and Western blotting was performed to detect the expressions of Cx43, PKC, Bax, and Bcl-2 in the brain of the rats.

RESULTSCompared with the I/R group, the rats pretreated with moderate and high doses of propofol showed significantly reduced neurological behavior scores and cerebral infarction volume percentage, and the effect was more obvious in high-dose propofol pretreatment group. CBX obviously enhanced the protective effect of propofol against I/R injury. Compared with those in the sham-operated group, the protein expression of Cx43 and the Bax/Bcl-2 ratio were increased and the protein expression of PKC was reduced in I/R group, and these changes were significantly reversed by high-dose propofol pretreatment; the effects of propofol were further enhanced by CBX.

CONCLUSIONThe protective effect of propofol against cerebral I/R injury may involve the inhibition of the gap junction via PKC signaling and by reducing the Bax/Bcl-2 ratio.

Animals ; Brain ; metabolism ; Brain Ischemia ; prevention & control ; Connexin 43 ; metabolism ; Gap Junctions ; Infarction, Middle Cerebral Artery ; Male ; Propofol ; pharmacology ; Protein Kinase C ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Rats ; Rats, Sprague-Dawley ; Reperfusion Injury ; prevention & control ; Signal Transduction ; bcl-2-Associated X Protein ; metabolism

OBJECTIVETo investigate the expression of gap junction protein connexin 26(Cx26) in hepatocellular carcinoma(HCC) and its significance.

METHODSThe expression of Cx26 in liver tissue was examined by immunohistochemistry staining in 159 paraffin-embeded liver sections, including 20 samples of normal liver tissue, 30 samples of chronic hepatitis, 33 samples of liver cirrhosis, and 76 samples of HCC. Normal hepatic cell line LO2 and HCC cell line SMMC-7721 were used in vitro to verify the characteristics of gap junction and Cx26 expression pattern. The expression and localization of Cx26 were measured by Western blotting and immunofluorescence assay, respectively. The function of gap junction between adjacent cells was detected by dye transfer assay.

RESULTSCompared to normal liver samples, the positive rate of Cx26 was markedly decreased in hepatitis, cirrhosis and HCC tissues(all P<0.05). The intensity of Cx26 staining was significantly increased in HCC tissues compared with those in non-carcinomatous liver(NCL) tissues(all P<0.05). In NCL tissues, there was a mild to moderated staining of Cx26 which located mainly on the membranes of hepatocytes at intercellular contacts. The positive staining of Cx26 in HCC tissues was observed mainly in cytoplasm. Positive Cx26 expression was positively associated with tumor size(P=0.036), but not with age, gender, histologic grade, clinical stage, underlying hepatitis and cirhosis, lymph node metastasis and intrahepatic vascular embolism(all P>0.05). Compared with LO2 cells, an aberrant expression and distribution of Cx26 in SMMC-7721 cells was confirmed, which may lead to a decreased function of gap junctions.

CONCLUSIONSThe aberrant expression and distribution of Cx26 protein may be associated with hepatocarcinogenesis, and the residual gap junction in HCC may provide a new target for treatment of HCC.

Carcinogenesis ; Carcinoma, Hepatocellular ; metabolism ; Cell Line, Tumor ; Connexin 26 ; Connexins ; metabolism ; Gap Junctions ; metabolism ; Hepatocytes ; metabolism ; Humans ; Immunohistochemistry ; Liver Cirrhosis ; metabolism ; Liver Neoplasms ; metabolism ; Lymphatic Metastasis

OBJECTIVETo investigate the effect of baicalein on the gap junction intercellular communication (GJIC) in the TM4 Sertoli cells of the mouse testis and its related mechanism.

METHODSWe measured the cytotoxicity of different concentrations of baicalein on the TM4 Sertoli cells in the mouse testis by MTT, detected the fluorescence transfer of the TM4 Sertoli cells by parachute assay, and determined the expression of the protein connexin 43 ( Cx43) in the baicalein-treated cells by Western blot and immunofluorescence assay.

RESULTSBaicalein produced no obvious cytotoxicity on the TM4 Sertoli cells at the concentration below 60 µmol/L but significantly increased their GJIC at 0-20 µmol/L (P < 0.01). Western blot and immunofluorescence assay showed that 0-20 µmol/L baicalein remarkably elevated the expression of Cx43 in the TM4 cells (P < 0.01) and on the membrane of the TM4 cells.

CONCLUSIONBaicalein at the concentration of 0-20 µmol/L can significantly enhance GJIC in mouse TM4 Sertoli cells by increasing the expression of the Cx43 protein.

Animals ; Cell Communication ; drug effects ; Connexin 43 ; metabolism ; Flavanones ; administration & dosage ; pharmacology ; Gap Junctions ; drug effects ; Male ; Mice ; Sertoli Cells ; drug effects ; metabolism ; ultrastructure