Echinacoside inhibits PASMCs calcium overload to prevent hypoxic pulmonary artery remodeling by regulating TRPC1/4/6 and calmodulin.

Abstract: Research indicates that hypoxic pulmonary hypertension (HPH) potentially stimulates the sympathetic nervous system, which may increase norepinephrine (NE) release and cause excessive Ca²⁺ influx into pulmonary artery smooth muscle cells (PASMCs), leading to calcium overload and abnormal PASMC proliferation, factors closely associated with pulmonary vascular remodeling (PVR). This study investigates the potential mechanisms underlying echinacoside (ECH) treatment in HPH.

Method: In the in vitro experiment, NE-induced PASMCs were used to simulate HPH-induced PASMCs' calcium overload and abnormal proliferation. Postincubation with ECH, [Ca²⁺]_cyt changes were detected using Fluo-4 AM. Flow cytometry was employed to ascertain ECH's inhibitory effect on PASMCs proliferation. For in vivo experiments, rats were exposed to a hypoxic and low-pressure oxygen environment to establish the HPH model. Post-ECH treatment, hematoxylin and eosin (HE) staining was conducted to assess PVR, and western blot analysis was used to examine protein expression in the lung tissues of the different groups.

Results: ECH was observed to inhibit [Ca²⁺]_cyt increase in NE-induced PASMCs in a concentration-dependent manner, effectively reducing abnormal cell proliferation. It also reduced the expression of Transient receptor potential channel (TRPC) 1 (TRPC1), TRPC4, TRPC6, and calmodulin in PASMCs. In vivo studies demonstrated that ECH lowered the expression of these proteins in lung tissues of HPH rats, significantly decreased mean pulmonary artery pressure, and mitigated PVR.