Upregulated Calcium Sensing Receptor Mediates Pulmonary Venous Remodeling in Pulmonary Hypertension

The mechanism of pulmonary venous remodeling (PVR) remains unclear. We tested the role of the calcium sensing receptor (CaSR) in PVR in pulmonary hypertension (PH).

PVR was investigated in two PH models, monocrotaline (MCT)-induced PH (MCT-PH) and hypoxia-induced PH (HPH). Human pulmonary venous smooth muscle cells (PVSMCs) were subjected to hypoxia. We examined whether CaSR is involved in the enhanced Ca²⁺ influx and proliferation in PVSMCs and whether CaSR mediates PVR.

PVR presented in distal pulmonary veins (PV) in MCT-PH and HPH rats, accompanied by upregulated CaSR expression in PVSMCs from PH rats. Hypoxia promoted human PVSMCs proliferation with increased CaSR and HIF-1α expression in hypoxic cells. Extracellular Ca²⁺ restoration induced a huge increase in [Ca²⁺]_i in MCT-PH PVSMCs and human hypoxic PVSMCs, which was significantly higher than that in normal cells. Both the basal [Ca²⁺]_i and proliferate rate in MCT-PH PVSMCs and human hypoxic PVSMCs were higher than in normal PVSMCs. Spermine or R568 enhanced, whereas both NPS2143 or NPS2390 and siCaSR attenuated the extracellular Ca²⁺-induced [Ca²⁺]_i increase in rat MCT-PH PVSMCs and human hypoxic PVSMCs and hypoxia-induced human PVSMCs proliferation. Blockade of CaSR with NPS2143 attenuated the increases in basal [Ca²⁺]_i in PVSMCs, right ventricular systolic pressure, and Fulton index in PH rats and prevented PVR and PH development in rats injected with MCT or exposed to hypoxia.

Upregulated CaSR mediating excessive PVSMCs proliferation through enhanced CaSR function and increased intracellular Ca²⁺ signaling is an important pathogenic mechanism underlying the development of PVR in PH.