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

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.

Tang H ，Yamamura A ，Yamamura H ，Song S ，Fraidenburg DR ，Chen J ，Gu Y ，Pohl NM ，Zhou T ，Jiménez-Pérez L ，Ayon RJ ，Desai AA ，Goltzman D ，Rischard F ，Khalpey Z ，Black SM ，Garcia JG ，Makino A ，Yuan JX ... -  《-》

Enhanced Ca(2+)-sensing receptor function in idiopathic pulmonary arterial hypertension.

Yamamura A ，Guo Q ，Yamamura H ，Zimnicka AM ，Pohl NM ，Smith KA ，Fernandez RA ，Zeifman A ，Makino A ，Dong H ，Yuan JX ... -  《-》

Dihydropyridine Ca(2+) channel blockers increase cytosolic [Ca(2+)] by activating Ca(2+)-sensing receptors in pulmonary arterial smooth muscle cells.

Yamamura A ，Yamamura H ，Guo Q ，Zimnicka AM ，Wan J ，Ko EA ，Smith KA ，Pohl NM ，Song S ，Zeifman A ，Makino A ，Yuan JX ... -  《-》

Flow shear stress enhances intracellular Ca2+ signaling in pulmonary artery smooth muscle cells from patients with pulmonary arterial hypertension.

An increase in cytosolic Ca(2+) concentration ([Ca(2+)]cyt) in pulmonary arterial smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction and an important stimulus for pulmonary arterial medial hypertrophy in patients with idiopathic pulmonary arterial hypertension (IPAH). Vascular smooth muscle cells (SMC) sense the blood flow shear stress through interstitial fluid driven by pressure or direct exposure to blood flow in case of endothelial injury. Mechanical stimulus can increase [Ca(2+)]cyt. Here we report that flow shear stress raised [Ca(2+)]cyt in PASMC, while the shear stress-mediated rise in [Ca(2+)]cyt and the protein expression level of TRPM7 and TRPV4 channels were significantly greater in IPAH-PASMC than in normal PASMC. Blockade of TRPM7 by 2-APB or TRPV4 by Ruthenium red inhibited shear stress-induced rise in [Ca(2+)]cyt in normal and IPAH-PASMC, while activation of TRPM7 by bradykinin or TRPV4 by 4αPDD induced greater increase in [Ca(2+)]cyt in IPAH-PASMC than in normal PASMC. The bradykinin-mediated activation of TRPM7 also led to a greater increase in [Mg(2+)]cyt in IPAH-PASMC than in normal PASMC. Knockdown of TRPM7 and TRPV4 by siRNA significantly attenuated the shear stress-mediated [Ca(2+)]cyt increases in normal and IPAH-PASMC. In conclusion, upregulated mechanosensitive channels (e.g., TRPM7, TRPV4, TRPC6) contribute to the enhanced [Ca(2+)]cyt increase induced by shear stress in PASMC from IPAH patients. Blockade of the mechanosensitive cation channels may represent a novel therapeutic approach for relieving elevated [Ca(2+)]cyt in PASMC and thereby inhibiting sustained pulmonary vasoconstriction and pulmonary vascular remodeling in patients with IPAH.

Song S ，Yamamura A ，Yamamura H ，Ayon RJ ，Smith KA ，Tang H ，Makino A ，Yuan JX ... -  《-》

Calcium-Sensing Receptor Regulates Cytosolic [Ca (2+) ] and Plays a Major Role in the Development of Pulmonary Hypertension.

Smith KA ，Ayon RJ ，Tang H ，Makino A ，Yuan JX ... -  《Frontiers in Physiology》