TRPV4 channel mediates adventitial fibroblast activation and adventitial remodeling in pulmonary hypertension

Abstract

Pulmonary arterial adventitial fibroblasts (PAF), the most abundant cellular constituent of adventitia, act as a key regulator of pulmonary vascular wall structure and function from the outside-in. Previous studies indicate that transient receptor potential vanilloid 4 (TRPV4) channel plays an important role in the development of pulmonary hypertension (PH), but no attention has been given so far to its role in adventitial remodeling. In this study, we thus investigated TRPV4 implication in PAF activation occurring in PH. First, we isolated and cultured PAF from rat adventitial intrapulmonary artery. RT-PCR, Western blot, immunostaining, and calcium imaging (fluo-4/AM) showed that PAF express functional TRPV4 channels. In extension of these results, using pharmacological and siRNA approaches, we demonstrated TRPV4 involvement in PAF proliferation (BrdU incorporation) and migration (wound-healing assay). Then, Western blot experiments revealed that TRPV4 activation upregulates the expression of extracellular matrix protein synthesis (collagen type I and fibronectin). Finally, we explored the role of TRPV4 in the adventitial remodeling occurring in PH. By means of Western blot, we determined that TRPV4 protein expression was upregulated in adventitia from chronically hypoxic and monocrotaline rats, two animal models of PH. Furthermore, morphometric analysis indicated that adventitial remodeling is attenuated in PH-induced trpv4−/− mice. These data support the concept that PAF play an essential role in hypertensive pulmonary vascular remodeling and point out the participation of TRPV4 channel activity in PAF activation leading to excessive adventitial remodeling.

The mechanism of ions in pulmonary hypertension

“…TRPC mediated the synthesis of extracellular matrix proteins by up-regulating the expression of type I collagen and fibronectin, thus participating in pulmonary adventitia remodelling. 54 TRPC has a direct or indirect effect on the regulation of calcium ions. GPCRs and various angiogenic substances (5-HT, Ang II, ET-1, etc.)…”

TRPC and TRPV Channels’ Role in Vascular Remodeling and Disease

“…Moreover, an increased Ca 2+ entry through TRPV4 contributed to an enhanced PASMCs contraction, migration and proliferation triggered by chronic hypoxia [118]. More recently, TRPV4 was studied in pulmonary arterial adventitial fibroblasts using TRPV4-KO mice, siRNA and the pharmacologic inhibition of TRPV4 [93]. This study revealed that TRPV4 played an important role in the proliferation, migration and synthesis of the extracellular matrix, hallmarks of the pathogenesis of PAH [93].…”

“…TRPV1 and TRPV4 activation evokes Ca 2+ influx, proliferation and contraction of PASMCs [85,89,90,92]. TRPV4 plays a role in fibroblast proliferation and the synthesis of the extracellular matrix in lungs [93].…”

“…Pulmonary arterial hypertension (PAH) is a hemodynamic disorder caused by pulmonary vasculature remodeling, vasoconstriction and thrombosis, responsible for a progressive elevation of the pulmonary arterial pressure that leads to right heart failure, and even death [93,111]. Chronic hypoxia is the main cause of pulmonary artery hypertension and is contributed by pulmonary media hypertrophy caused by the proliferation of pulmonary artery smooth muscle cells (PASMCs), which narrows the intraluminal diameter and increases resistance to blood flow [28,112].…”

“…More recently, TRPV4 was studied in pulmonary arterial adventitial fibroblasts using TRPV4-KO mice, siRNA and the pharmacologic inhibition of TRPV4 [93]. This study revealed that TRPV4 played an important role in the proliferation, migration and synthesis of the extracellular matrix, hallmarks of the pathogenesis of PAH [93]. On the other hand, TRPV3's role in PAH was examined by Zhang et al [91], who showed that TRPV3 was upregulated in the pulmonary vessels of PAH humans when compared to control subjects.…”