Chronic Hypoxia Increases TRPC6 Expression and Basal Intracellular Ca(2+) Concentration in Rat Distal Pulmonary Venous Smooth Muscle

BACKGROUND: Hypoxia causes remodeling and contractile responses in both pulmonary artery (PA) and pulmonary vein (PV). Here we explore the effect of hypoxia on PV and pulmonary venous smooth muscle cells (PVSMCs). METHODS: Chronic hypoxic pulmonary hypertension (CHPH) model was established by exposing rats to 10% O(2) for 21 days. Rat distal PVSMCs were isolated and cultured for in vitro experiments. The fura-2 based fluorescence calcium imaging was used to measure the basal intracellular Ca(2+) concentration ([Ca(2+)](i)) and store-operated Ca(2+) entry (SOCE). Quantitative RT-PCR and western blotting were performed to measure the expression of mRNA and levels of canonical transient receptor potential (TRPC) protein respectively. RESULTS: Hypoxia increased the basal [Ca(2+)](i) and SOCE in both freshly dissociated and serum cultured distal PVSMCs. Moreover, hypoxia increased TRPC6 expression at mRNA and protein levels in both cultured PVSMCs exposed to prolonged hypoxia (4% O(2), 60 h) and distal PV isolated from CHPH rats. Hypoxia also enhanced proliferation and migration of rat distal PVSMCs. CONCLUSIONS: Hypoxia induces elevation of SOCE in distal PVSMCs, leading to enhancement of basal [Ca(2+)](i) in PVSMCs. This enhancement is potentially correlated with the increased expression of TRPC6. Hypoxia triggered intracellular calcium contributes to promoted proliferation and migration of PVSMCs.