Pathogenic role of calcium-sensing receptors in the development and progression of pulmonary hypertension

Abstract

An increase in cytosolic free Ca(2+) concentration ([Ca(2+)]cyt) in pulmonary arterial smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction and a critical stimulation for PASMC proliferation and migration. Previously, we demonstrated that expression and function of calcium sensing receptors (CaSR) in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH) and animals with experimental pulmonary hypertension (PH) were greater than in PASMC from normal subjects and control animals. However, the mechanisms by which CaSR triggers Ca(2+) influx in PASMC and the implication of CaSR in the development of PH remain elusive. Here, we report that CaSR functionally interacts with TRPC6 to regulate [Ca(2+)]cyt in PASMC. Downregulation of CaSR or TRPC6 with siRNA inhibited Ca(2+)-induced [Ca(2+)]cyt increase in IPAH-PASMC (in which CaSR is upregulated), whereas overexpression of CaSR or TRPC6 enhanced Ca(2+)-induced [Ca(2+)]cyt increase in normal PASMC (in which CaSR expression level is low). The upregulated CaSR in IPAH-PASMC was also associated with enhanced Akt phosphorylation, whereas blockade of CaSR in IPAH-PASMC attenuated cell proliferation. In in vivo experiments, deletion of the CaSR gene in mice (casr(-/-)) significantly inhibited the development and progression of experimental PH and markedly attenuated acute hypoxia-induced pulmonary vasoconstriction. These data indicate that functional interaction of upregulated CaSR and upregulated TRPC6 in PASMC from IPAH patients and animals with experimental PH may play an important role in the development and progression of sustained pulmonary vasoconstriction and pulmonary vascular remodeling. Blockade or downregulation of CaSR and/or TRPC6 with siRNA or miRNA may be a novel therapeutic strategy to develop new drugs for patients with pulmonary arterial hypertension.

Calcium-Sensing Receptor Stimulation in Cultured Glomerular Podocytes Induces TRPC6-Dependent Calcium Entry and RhoA Activation

“…Our study also observed that the PLC inhibitor almost completely abolished the R-568-induced [Ca 2+ ] i increase. Compelling evidence has revealed that in colonic epithelial cells, CaSR stimulation by 5 mM [Ca 2+ ] o triggers DAG production [29], and in vascular smooth muscle cells, the upregulated TRPC6 mediated by CaSR is functionally sensitive to DAG [12]. DAG can directly increase TRPC6 activity and does not seem to affect the plasma membrane expression of TRPC6 [27, 28].…”

“…Relatively little is known about the Ca 2+ influx mechanism upon CaSR activation. Canonical transient receptor potential (TRPC) channels, nonselective cation channels, seem to be responsible for Ca 2+ entry induced by CaSR activation in some cell types, such as salivary ductal cells [11], vascular smooth muscle cells [12, 13], keratinocytes [14], MCF-7 breast cancer cells [15] and glomerular mesangial cells [6]. …”

Calcium-Sensing Receptor Regulates Cytosolic [Ca2+] and Plays a Major Role in the Development of Pulmonary Hypertension

“…Transient receptor potential conical (TRPC) channels have been shown to function as both ROC and SOC in PASMC (Yu et al, 2003, 2004). We recently discovered that CaSR functionally interacts with TRPC6 channels in PASMC from IPAH patients and animals with experimental PH and may play important role in the development and progression of sustained pulmonary vasoconstriction and pulmonary vascular remodeling (Tang et al, 2016). As discussed earlier, extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt is enhanced in IPAH-PASMC due to increased expression of CaSR (Yamamura et al, 2012).…”

“…As discussed earlier, extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt is enhanced in IPAH-PASMC due to increased expression of CaSR (Yamamura et al, 2012). Blockade of TRPC6 channels significantly inhibits extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt in IPAH-PASMC (Tang et al, 2016). Overexpression of CaSR or TPRC6 in normal PASMC results in enhanced extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt , however, overexpression of both CaSR and TRPC6 dramatically increases extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt compared to either alone (Tang et al, 2016).…”

“…Blockade of TRPC6 channels significantly inhibits extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt in IPAH-PASMC (Tang et al, 2016). Overexpression of CaSR or TPRC6 in normal PASMC results in enhanced extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt , however, overexpression of both CaSR and TRPC6 dramatically increases extracellular Ca 2+ -induced increase in [Ca 2+ ] cyt compared to either alone (Tang et al, 2016). These data strongly suggest that CaSR is functionally coupled to TRPC6 channels in IPAH-PASMC and that receptor—and store-operated Ca 2+ entry via CaSR-mediated activation of TRPC6 is an important signaling cascade which leads to PASMC contraction, proliferation, and migration in patients with IPAH.…”