Proliferation of neonatal cardiomyocytes by connexin43 knockdown via synergistic inactivation of p38 MAPK and increased expression of FGF1.
Gap junctions are intercellular channels that connect the cytoplasm of adjacent cell. Gap junctional intercellular communication has long been postulated to contribute to the maintenance of tissue homeostasis. Recent studies, however, have demonstrated that connexins, gap junction proteins, are involved in the regulation of a variety of cellular functions other than intercellular communication. Although, in neonatal rat ventricular myocytes, connexin-40, -43, and -45 are all expressed, connexin43 (Cx43) is the primary subtype. In this study, we examined whether and if so how the knockdown of a gap junction protein Cx43 with siRNA produced changes in the proliferative activity of neonatal cardiomyocytes. Cx43-knockdown resulted in a significant increase in the proliferation of cardiomyocytes. To clarify the mechanisms behind this increase, we investigated whether the activity of mitogen-activated protein kinases (MAPKs) changed on knockdown of Cx43. The knockdown decreased the expression of phosphorylated p38 (p-p38) MAPK. In addition, treatment of cardiomyocytes with a p38 MAPK inhibitor significantly increased the proliferative activity. Cultures were then co-treated with an inhibitor of p38 MAPK and fibroblast growth factor-1 (FGF1), since Cx43-knockdown significantly increased cytosolic FGF1 expression as well. The co-treatment enhanced the proliferation of cardiomyocytes compared with the treatment with the p38 MAPK inhibitor alone. Taken together, the present study demonstrated that Cx43-knockdown produced a significant increase in the proliferation of neonatal cardiomyocytes.
Laboratory of Cellular Cybernetics, Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan.
Daisuke
D
Matsuyama
Koichi
K
Kawahara
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005333:Fetus; D016220:Fibroblast Growth Factor 1 / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering; D051381:Rats; D017208:Rats, Wistar; D048051:p38 Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*
D018031:Connexin 43; D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D016220:Fibroblast Growth Factor 1; D048051:p38 Mitogen-Activated Protein Kinases