Store-Operated Ca2+ Entry is involved in Transforming Growth Factor-β1 Facilitated Proliferation of Rat Airway Smooth Muscle Cells

Objective. To investigate the role and underlying mechanisms of store-operated Ca2+ entry (SOCE) in mediating the promoting effect of transforming growth factor (TGF)-beta 1 on the proliferation of airway smooth muscle cells (ASMCs). Methods. Rat bronchial smooth muscle cells were cultured as we described previously. The intracellular Ca2+ concentration ([Ca2+](i)) of ASMCs was measured by laser confocal microscope Ca2+ fluorescence imaging with Fluo-3/AM. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and p27 expression assay were used to determine the proliferation rate of ASMCs. Results. We demonstrated that TGF-beta 1 (10 ng/ml) increased basal (Ca2+](i)) level, [Ca2+](i) rise induced by thapsigargin-induced Ca2+ release and SOCE in rat ASMCs. This effect of TGF-beta 1 on SOCE was not inhibited by glucocorticoid dexamethasone (DXM, 100 nM), antioxidant alpha-tocopherol (100 mu M), and intermediate-conductance Ca2+-activated K+ channels (IKCa) inhibitor charybdotoxin (100 nM), suggesting that reactive oxygen species and IKCa channels might not mediate the effect of TGF-beta 1. TGF-beta 1 slightly increased the expression of Orai1 and STIM1, two important molecules involved in the molecule component and regulation of SOC channels, in the presence of 10% fetal bovine serum (FBS). The proliferation of ASMC stimulated with 2.5% FBS was promoted by TGF-beta 1, and partly inhibited by non-specific Ca2+ channel blocker SKF-96365 (10 mu M) and Ni2+ (100 mu M). DXM, alpha-tocopherol, and charybdotoxin had no effect on the proliferation promoted by TGF-beta 1. Conclusion. TGF-beta 1 promotes ASMC proliferation partly through increasing the expression and activity of SOC channels.