Platelet‐derived growth factor‐BB increases expression of connexin 43 in an extracellular‐regulated protein kinase‐dependent manner in bladder smooth muscle cells

OBJECTIVES: To investigate whether platelet-derived growth factor-BB induces the upregulation of connexin 43 in bladder smooth muscle cells and to examine the involved signaling pathway. METHODS: Bladder smooth muscle cells were exposed to platelet-derived growth factor-BB in the presence or absence of p38 mitogen-activated protein kinase, c-jun amino-terminal kinase or extracellular-regulated protein kinase inhibitors. Transfection of bladder smooth muscle cells with specific small interference ribonucleic acid against platelet-derived growth factor receptor-β gene expression was also carried out to investigate whether platelet-derived growth factor receptor-β was involved in the signaling pathway. Expression of messenger ribonucleic acid and protein for connexin 43 was measured by real time polymerase chain reaction and western blot. RESULTS: The addition of platelet-derived growth factor-BB in cultured bladder smooth muscle cells caused the significant upregulation of connexin 43, and the activation of extracellular-regulated protein kinase, c-jun amino-terminal kinase and p38 mitogen-activated protein kinase compared with the control group. This action of platelet-derived growth factor-BB could be abolished by the pretreatment of bladder smooth muscle cells with the extracellular-regulated protein kinase inhibitor PD98059, whereas p38 mitogen-activated protein kinase and c-jun amino-terminal kinase inhibitors did not have any effect on this. Platelet-derived growth factor-BB could induce the activation of platelet-derived growth factor receptor-β. Transfection of bladder smooth muscle cells with small interference ribonucleic acid specific for platelet-derived growth factor receptor-β gene resulted in the potent suppression of gene expression and inhibition of extracellular-regulated protein kinase activation, as well as upregulation of connexin 43 induced by platelet-derived growth factor-BB. CONCLUSIONS: Platelet-derived growth factor-BB upregulates connexin 43 expression through the activation of extracellular-regulated protein kinase and platelet-derived growth factor receptor-β signaling pathways. This finding suggests that this signaling pathway might provide a potential target to manipulate detrusor overactivity.