GRK2-YAP signaling is implicated in pulmonary arterial hypertension development.

BACKGROUND: Pulmonary arterial hypertension (PAH) is characterized by excessive proliferation of small pulmonary arterial vascular smooth muscle cells (PASMCs), endothelial dysfunction, and extracellular matrix remodeling. G protein-coupled receptor kinase 2 (GRK2) plays an important role in the maintenance of vascular tone and blood flow. However, the role of GRK2 in the pathogenesis of PAH is unknown. METHODS: GRK2 levels were detected in lung tissues from healthy people and PAH patients. C57BL/6 mice, vascular smooth muscle cell-specific Grk2 -knockout mice ( Grk2ΔSM22 ), and littermate controls ( Grk2flox/flox ) were grouped into control and hypoxia mice ( n  = 8). Pulmonary hypertension (PH) was induced by exposure to chronic hypoxia (10%) combined with injection of the SU5416 (cHx/SU). The expression levels of GRK2 and Yes-associated protein (YAP) in pulmonary arteries and PASMCs were detected by Western blotting and immunofluorescence staining. The mRNA expression levels of Grk2 and Yes-associated protein ( YAP ) in PASMCs were quantified with real-time polymerase chain reaction (RT-PCR). Wound-healing assay, 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay, and 5-Ethynyl-2'-deoxyuridine (EdU) staining were performed to evaluate the proliferation and migration of PASMCs. Meanwhile, the interaction among proteins was detected by immunoprecipitation assays. RESULTS: The expression levels of GRK2 were upregulated in the pulmonary arteries of patients with PAH and the lungs of PH mice. Moreover, cHx/SU-induced PH was attenuated in Grk2ΔSM22 mice compared with littermate controls. The amelioration of PH in Grk2ΔSM22 mice was accompanied by reduced pulmonary vascular remodeling. In vitro study further confirmed that GRK2 knock-down significantly altered hypoxia-induced PASMCs proliferation and migration, whereas this effect was severely intensified by overexpression of GRK2 . We also identified that GRK2 promoted YAP expression and nuclear translocation in PASMCs, resulting in excessive PASMCs proliferation and migration. Furthermore, GRK2 is stabilized by inhibiting phosphorylating GRK2 on Tyr86 and subsequently activating ubiquitylation under hypoxic conditions. CONCLUSION: Our findings suggest that GRK2 plays a critical role in the pathogenesis of PAH, via regulating YAP expression and nuclear translocation. Therefore, GRK2 serves as a novel therapeutic target for PAH treatment.

Salt-inducible kinase 1 deficiency promotes vascular remodeling in pulmonary arterial hypertension via enhancement of yes-associated protein-mediated proliferation.

Pulmonary arterial remodeling at an early stage, including excessive proliferation and migration of smooth muscle cells, is a hallmark of pulmonary arterial hypertension (PAH). Salt-inducible kinases (SIKs) have been increasingly reported to play a key role in smooth muscle cell proliferation and phenotype switching, which may be associated with arterial remodeling. However, the potential effects of SIK1 in PAH and the underlying mechanisms have not been explored. The aim of this study was to determine whether reduced expression or inactivation of SIK1 is associated with pulmonary arterial remodeling in PAH and to elucidate whether it is related to the Hippo/Yes-associated protein (YAP) pathway. Using mouse models of PAH and hypoxia-stimulated hPASMCs, we observed that SIK1 expression was robustly reduced in lung tissues of PAH mice and hPASMCs cultured under hypoxia. In hypoxia-induced PAH mice, pharmacological SIK inhibition or AAV9-mediated specific smooth muscle SIK1 knockdown strongly aggravated pathological changes caused by hypoxia, including right ventricular hypertrophy and small pulmonary arterial remodeling. Meanwhile, in hypoxia-stimulated hPASMCs, SIK1 knockdown or inhibition promoted proliferation and migration under hypoxia, accompanied by decreased phosphorylation and increased nuclear accumulation of YAP, while SIK1 overexpression inhibited hypoxia-induced proliferation, migration and nuclear translocation of YAP in hPASMCs. YAP knockdown attenuated the increase in cell proliferation induced by HG-9-91-01 treatment or SIK1 siRNA transfection under hypoxia in hPASMCs. Here, we identified SIK1 as an antiproliferative factor in hypoxia-induced pulmonary arterial remodeling via YAP-mediated mechanisms. These results show that targeting SIK1 may be a promising therapeutic strategy for the treatment of PAH.

Oscillating flow promotes inflammation through the TLR2-TAK1-IKK2 signalling pathway in human umbilical vein endothelial cell (HUVECs).

BACKGROUND: Oscillatory shear stress (OSS) occurs in areas where atherosclerosis is prevalent. Toll-like receptor 2 (TLR2) has been associated with mechanical-stress-mediated activation of signalling pathways that may lead to inflammation, apoptosis, and atherosclerosis. Nonetheless, the mechanism underlying the connection between TLR2 and OSS is not fully understood. The purpose of this study was to investigate the link between OSS and TLR2 in human umbilical vein endothelial cell (HUVECs). METHODS: Monolayer endothelial cells were stimulated or not stimulated by OSS. Protein expression was determined by western blotting and immunofluorescent staining. Endothelial function was assessed by using dihydroethidium assay, RT-PCR, immunofluorescent staining and western blotting. The carotid artery of rats was ligated for 1 week, and a section exposed to OSS was excised and analysed. RESULTS: In vitro, the expression of TLR2 in HUVECs was activated by OSS. Additionally, OSS increased apoptosis, inflammatory changes, and oxidative stress in HUVECs, and these effects were reversed by down-regulation the expression of TLR2. We proved that OSS regulates the inflammatory response of endothelial cells through the TLR2-TAK1-IKK2 pathway. In the rats with carotid artery ligation, TLR2, TAK1 and phospho-IKK2 amounts increased at the site of OSS. SIGNIFICANCE: According to our results, the OSS-mediated HUVECs injury may be associated with an increase in TLR2 expression. Accordingly, strategies designed to reduce TLR2 expression or inhibit TLR2 activation may be an effective approach to reduce the incidence of atherosclerosis.

The Role of Angiogenesis in Coronary Artery Disease: A Double-Edged Sword: Intraplaque Angiogenesis in Physiopathology and Therapeutic Angiogenesis for Treatment.

Angiogenesis is described as a sprouting and growth process of new blood vessels from pre-existing vasculature. The relationship between angiogenesis and coronary artery disease (CAD) is double-sided. On one hand, angiogenesis within plaques is responsible for facilitating the growth and vulnerability of plaques by causing intraplaque hemorrhage and inflammatory cell influx, and overabundance of erythrocytes and inflammatory cells within a plaque probably causes plaque rupture, further leading to acute coronary syndrome. Therefore, inhibiting intraplaque angiogenesis has been considered as a potential therapeutic target for CAD. On the other hand, aiming at improving reperfusion to the ischemic myocardium in patients with CAD, angiogenesis promoting has been utilized as a therapeutic approach to expand myocardial microvascular network. Current strategies include direct administration of angiogenic growth factors (protein therapy), promoting angiogenic genes expression in vivo (gene therapy), and delivering stem cells (cell therapy) or exosomes (cell free therapy). This article will start by clarifying the basic concept of angiogenesis, interpret the mechanism of excessive intraplaque angiogenesis in atherosclerosis, and discuss its role in the growth and vulnerability of plaques. Then we will focus on the four distinct strategies of therapeutic angiogenesis. Despite promising animal studies and smallscale clinical trials of therapeutic angiogenesis in patients with ischemic heart disease, investigations have far not shown definite evidence of clinical efficacy. Hence, while acknowledging future work that remains to be done to validate the clinical results, we reviewed the critical challenges in this arena and highlighted the exciting progress that has occurred recently.

Inhibition of angiotension II type 1 receptor reduced human endothelial inflammation induced by low shear stress.

Low shear stress (LSS)-induced endothelial inflammation is the basis for the development of atherosclerosis. However, the mechanism underlying LSS-induced inflammation is not well understood. The angiotensin II type 1 receptor (AT1R), a component of the renin-angiotensin system, participates in atherosclerotic plaque progression. The aim of this study was to investigate the role of AT1R in LSS-induced endothelial activation. Using immunohistochemistry, we noted significant increases in AT1R, vascular endothelial adhesion cell-1 (VCAM1), and intercellular adhesion molecule-1 (ICAM1) expression in the inner curvature of the aortic arch in C57BL/6 mice compared to the descending aorta in these mice. Moreover, western blotting revealed that these LSS-induced increases in AT1R, ICAM1 and VCAM1 expression were time dependent. However, the expression of these proteins was significantly abolished by treatment with the AT1R antagonist Losartan (1µM) or AT1R small interfering RNA (siRNA). AT1R inhibition significantly suppressed extracellular signal-regulated kinase 1/2 (ERK) upregulation, which also resulted in decreases in ICAM1 and VCAM1 protein expression. These findings demonstrate that LSS induces endothelial inflammation via AT1R/ERK signaling and that Losartan has beneficial effects on endothelial inflammation.