15-HETE mediates sub-acute hypoxia-induced TRPC1 expression and enhanced capacitative calcium entry in rat distal pulmonary arterial myocytes

Sub-acute hypoxia causes pulmonary vasoconstriction (HPV) is associated with increased intracellular Ca2+ concentration ([Ca2+]i) and contraction of pulmonary arterial smooth muscle cells (PASMCs). We previous have demonstrated that 15-hydroxyeicosatetraenoic acid (15-HETE), a metabolite of arachidonic acid by 15-lipoxygenase (15-LO), causes elevated [Ca2+]i in PASMCs partly through Ca2+ entry via other than L-type Ca2+ channels. In this study, we used SKF96365/La3+ (SOCC antagonists) and Nordihydro-guiairetic acid (NDGA, a blockage of 15-LO) to examine the effect of 15-HETE on capacitative Ca2+ entry and activity/expression of store-operated Ca2+ channels (SOCCs) during sub-acute hypoxic procedure and the contribution of SOCCs on the maintenance of vascular tones. The results showed that the 15-HETE induced constriction of PA rings from normoxic and sub-acute hypoxic rats can be abolished by SKF96365 and La3+. Capacitative Ca2+ entry (CCE) was also enhanced in PASMCs cultured with 15-HETE under sub-acute hypoxic condition (3% O2, 48 h) and incubation with NDGA in PASMCs can greatly suppress this enhancement. Moreover, TRPC1, not TRPC4 and TRPC6, mRNA and protein expression were increased in PASMCs during these procedures. Meanwhile, the effect of 15-HETE on CCE and TRPC1 expression under sub-acute hypoxic cultivation were greatly suppressed in 15-LO knockdown PASMCs and PAs. These results suggest that 15-HETE mediated HPV through increased TRPC1 expression, leading to enhanced CCE, contributing to the maintenance of vascular tone.

Research highlights▶ 15-HETE increases the expression of TRPC1 under sub-acute hypoxic condition. ▶ The increased expression of TRPC1 induces enhanced capacitative calcium entry(CCE). ▶ The enhanced CCE contributes to the [Ca2+]i which is associated with HPV.