RGS10 inhibits proliferation and migration of pulmonary arterial smooth muscle cell in pulmonary hypertension via AKT/mTORC1 signaling

Objective: Excessive proliferation and migration of pulmonary arterial smooth muscle cell (PASMC) is a core event of pulmonary hypertension (PH). Regulators of G protein signaling 10 (RGS10) can regulate cellular proliferation and cardiopulmonary diseases. We demonstrate whether RGS10 also serves as a regulator of PH.Methods: PASMC was challenged by hypoxia to induce proliferation and migration. Adenovirus carrying Rgs10 gene (Ad-Rgs10) was used for external expression of Rgs10. Hypoxia/SU5416 or MCT was used to induce PH. Right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) were used to validate the establishment of PH model.Results: RGS10 was downregulated in hypoxia-challenged PASMC. Ad-Rgs10 significantly suppressed proliferation and migration of PASMC after hypoxia stimulus, while silencing RGS10 showed contrary effect. Mechanistically, we observed that phosphorylation of S6 and 4E-Binding Protein 1 (4EBP1), the main downstream effectors of mammalian target of rapamycin complex 1 (mTORC1) as well as phosphorylation of AKT, the canonical upstream of mTORC1 in hypoxia-induced PASMC were negatively modulated by RGS10. Both recovering mTORC1 activity and restoring AKT activity abolished these effects of RGS10 on PASMC. More importantly, AKT activation also abolished the inhibitory role of RGS10 in mTORC1 activity in hypoxia-challenged PASMC. Finally, we also observed that overexpression of RGS10 in vivo ameliorated pulmonary vascular wall thickening and reducing RVSP and RVHI in mouse PH model.Conclusion: Our findings reveal the modulatory role of RGS10 in PASMC and PH via AKT/mTORC1 axis. Therefore, targeting RGS10 may serve as a novel potent method for the prevention against PH."

Naked cuticle homolog 1 prevents mouse pulmonary arterial hypertension via inhibition of Wnt/β-catenin and oxidative stress

Pulmonary arterial hypertension (PAH) is a poorly prognostic cardiopulmonary disease characterized by abnormal contraction and remodeling of pulmonary artery (PA). Excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) are considered as the major etiology of PA remodeling. As a negative regulator of Wnt/β-catenin pathway, naked cuticle homolog 1 (NKD1) is originally involved in the tumor growth and metastasis via affecting the proliferation and migration of different types of cancer cells. However, the effect of NKD1 on PAH development has not been investigated. In the current study, downregulated NKD1 was identified in hypoxia-challenged PASMCs. NKD1 overexpression by adenovirus carrying vector encoding Nkd1 (Ad-Nkd1) repressed hypoxia-induced proliferation and migration of PASMCs. Mechanistically, upregulating NKD1 inhibited excessive reactive oxygen species (ROS) generation and β-catenin expression in PASMCs after hypoxia stimulus. Both inducing ROS and recovering β-catenin expression abolished NKD1-mediated suppression of proliferation and migration in PASMCs. In vivo, we also observed decreased expression of NKD1 in dissected PAs of monocrotaline (MCT)-induced PAH model. Upregulating NKD1 by Ad-Nkd1 transfection attenuated the increase in right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), pulmonary vascular wall thickening, and vascular β-catenin expression after MCT treatment. After recovering β-catenin expression by SKL2001, the vascular protection of external expression of NKD1 was also abolished. Taken together, our data suggest that NKD1 inhibits the proliferation, migration of PASMC, and PAH via inhibition of β-catenin and oxidative stress. Thus, targeting NKD1 may provide novel insights into the prevention and treatment of PAH.

Aloperine protects pulmonary hypertension via triggering PPARγ signaling and inhibiting calcium regulatory pathway in pulmonary arterial smooth muscle cells

Previous studies have reported the beneficial role of Aloperine (ALO), an active vasodilator purified from the seeds and leaves of the herbal plant Sophora alopecuroides L., on experimental pulmonary hypertension (PH); however, detailed mechanisms remain unclear. In this study, monocrotaline-induced PH (MCT-PH) rat model and primarily cultured rat distal pulmonary arterial smooth muscle cells (PASMCs) were used to investigate the mechanisms of ALO on experimental PH, pulmonary vascular remodeling, and excessive proliferation of PASMCs. Results showed that first, ALO significantly prevented the disease development of MCT-PH by inhibiting right ventricular systolic pressure (RVSP) and right ventricular hypertrophy indexed by the Fulton Index, normalizing the pulmonary arterials (PAs) remodeling and improving the right ventricular function indexed by transthoracic echocardiography. ALO inhibited the excessive proliferation of both PAs and PASMCs. Then, isometric tension measurements showed vasodilation of ALO on precontracted PAs isolated from both control and MCT-PH rats via activating the KCNQ channel, which was blocked by specific KCNQ potassium channel inhibitor linopirdine. Moreover, by using immunofluorescence staining and nuclear/cytosol fractionation, we further observed that ALO significantly enhanced the PPARγ nuclear translocation and activation in PASMCs. Transcriptome analyses also revealed activated PPARγ signaling and suppressed calcium regulatory pathway in lungs from MCT-PH rats treated with ALO. In summary, ALO could attenuate MCT-PH through both transient vasodilation of PAs and chronic activation of PPARγ signaling pathway, which exerted antiproliferative roles on PASMCs and remodeled PAs.NEW & NOTEWORTHY Aloperine attenuates monocrotaline-induced pulmonary hypertension (MCT-PH) in rats by inhibiting the pulmonary vascular remodeling and proliferation of pulmonary arterial smooth muscle cells (PASMCs). In mechanism, Aloperine not only exerts a transient KCNQ-dependent vasodilation in precontracted pulmonary arteries (PAs) from both control and MCT-PH rats but also activates PPARγ nuclear translocation and signaling transduction in PASMCs, which chronically inhibits the calcium regulatory pathway and proliferation of PASMCs.

The protective role of EP300 in monocrotaline-induced pulmonary hypertension

Background

Pulmonary hypertension (PH) is a lethal disease characterized by pulmonary vascular remodeling, which is mediated by the abnormal proliferation/migration of pulmonary arterial smooth muscle cells (PASMCs). Recent reports suggest the involvement of histone acetylation in PAH development and that histone deacetylase (HDAC) inhibitors have therapeutic potential for the treatment of PAH. EP300 is an acetyltransferase that plays diverse roles in cell proliferation, differentiation, and apoptosis. However, the functions of EP3000 in PH are rarely studied.

Results

In this work, we found that the expression of EP300 was increased in the pulmonary arteries of monocrotaline (MCT)-induced PH rats. Knockdown of EP300 by AAV-mediated shRNA exacerbated the PH, with a higher right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), and wall thickness in the pulmonary artery of MCT-induced PH rat. On the cellular level, the proliferation of PASMCs was promoted by EP300 knockdown. In addition, the expression of EP300 was increased in PASMCs by the overexpression of EGR1, while the deletion of EGR1 binding sites in the EP300 promoter region decreased the activity of EP300 promoter. Moreover, deleting the EP300 promoter region containing EGR1 binding sites using CRISPR/Cas9 abolished the upregulation of EP300 in MCT-induced rats and exacerbated MCT-induced PH. To summarize, our data indicate that EP300 upregulation mediated by EGR1 has a protective effect on MCT-induced PH.

Conclusion

These findings showed EP300 expression was increased in the MCT-induced PH model in rats, which could be mediated by EGR1; the EP300 also displayed the potential to provide protection from PH.

Mechanosensitivity in Pulmonary Circulation: Pathophysiological Relevance of Stretch-Activated Channels in Pulmonary Hypertension

A variety of cell types in pulmonary arteries (endothelial cells, fibroblasts, and smooth muscle cells) are continuously exposed to mechanical stimulations such as shear stress and pulsatile blood pressure, which are altered under conditions of pulmonary hypertension (PH). Most functions of such vascular cells (e.g., contraction, migration, proliferation, production of extracellular matrix proteins, etc.) depend on a key event, i.e., the increase in intracellular calcium concentration ([Ca²⁺]_i) which results from an influx of extracellular Ca²⁺ and/or a release of intracellular stored Ca²⁺. Calcium entry from the extracellular space is a major step in the elevation of [Ca²⁺]_i, involving a variety of plasmalemmal Ca²⁺ channels including the superfamily of stretch-activated channels (SAC). A common characteristic of SAC is that their gating depends on membrane stretch. In general, SAC are non-selective Ca²⁺-permeable cation channels, including proteins of the TRP (Transient Receptor Potential) and Piezo channel superfamily. As membrane mechano-transducers, SAC convert physical forces into biological signals and hence into a cell response. Consequently, SAC play a major role in pulmonary arterial calcium homeostasis and, thus, appear as potential novel drug targets for a better management of PH.

PDGF/MEK/ERK axis represses Ca2+ clearance via decreasing the abundance of plasma membrane Ca2+ pump PMCA4 in pulmonary arterial smooth muscle cells

Pulmonary arterial hypertension (PAH) is a rare and lethal disease characterized by vascular remodeling and vasoconstriction, which is associated with increased intracellular calcium ion concentration ([Ca2+]i). Platelet-derived growth factor-BB (PDGF-BB) is the most potent mitogen for pulmonary arterial smooth muscle cells (PASMCs) and is involved in vascular remodeling during PAH development. PDGF signaling has been proved to participate in maintaining Ca2+ homeostasis of PASMCs; however, the mechanism needs to be further elucidated. Here, we illuminate that the expression of plasma membrane calcium-transporting ATPase 4 (PMCA4) was downregulated in PASMCs after PDGF-BB stimulation, which could be abolished by restraining the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK). Functionally, suppression of PMCA4 attenuated the [Ca2+]i clearance in PASMCs after Ca2+ entry, promoting cell proliferation and elevating cell locomotion through mediating formation of focal adhesion. Additionally, the expression of PMCA4 was decreased in the pulmonary artery of monocrotaline (MCT)- or hypoxia-induced PAH rats. Moreover, knockdown of PMCA4 could increase the right ventricular systolic pressure (RVSP) and wall thickness (WT) of pulmonary artery in rats raised under normal conditions. Taken together, our findings demonstrate the importance of the PDGF/MEK/ERK/PMCA4 axis in intracellular Ca2+ homeostasis in PASMCs, indicating a functional role of PMCA4 in pulmonary arterial remodeling and PAH development.

Mutual promotion of FGF21 and PPARγ attenuates hypoxia-induced pulmonary hypertension

IMPACT STATEMENT

In this study, we reported for the first time that FGF21 alleviated hypoxia-induced pulmonary hypertension through attenuation of increased pulmonary arterial pressure, pulmonary arterial remodeling and collagen deposition in vivo, and we confirmed the mutual promotion of FGF21 and PPARγ in hypoxia-induced pulmonary hypertension. Additionally, we found that FGF21 and PPARγ mutually promote each other's expression via the AMPK/PGC-1α pathway and KLB protein in vitro and in vivo. Pulmonary hypertension is a progressive and serious pathological phenomenon with a poor prognosis, and current therapies are highly limited. Our results provide novel insight into potential clinical therapies for pulmonary hypertension and establish the possibility of using this drug combination and potential dosage reductions in clinical settings.

Role of miR-223-3p in pulmonary arterial hypertension via targeting ITGB3 in the ECM pathway

Objectives

To investigate the functions of miR‐223‐3p and ITGB3 in pulmonary arterial hypertension (PAH).

Materials and Methods

Microarray analysis was used to detect differentially expressed genes and microRNAs. In in vitro models, the expressions of miR‐223‐3p and ITGB3 were detected by qRT‐PCR and Western blot. α‐SMA expression and cell proliferation were analysed by immunofluorescence and MTT assay, respectively. In in vivo models, PAH progressions were determined by measuring the levels of mPAP and RVSP. Lung and myocardial tissues were subjected to HE staining and Masson and Sirius red‐saturated carbazotic acid staining to investigate the pathological features.

Results

The microarray analysis revealed that ITGB3 was upregulated, while hsa‐miR‐223‐3p was downregulated in PAH. After the induction of hypoxia, miR‐223‐3p was downregulated and ITGB3 was upregulated in PASMCs. Hypoxia induction promoted cell proliferation and inhibited α‐SMA expression in PASMCs. Both the upregulation of miR‐223‐3p and the downregulation of ITGB3 attenuated the aberrant proliferation induced by hypoxia conditions. After approximately 4 weeks, the mPAP and RVSP levels of rats injected with MCT were decreased by the overexpression of miR‐223‐3p or the silencing of ITGB3. The staining results revealed that both miR‐223‐3p overexpression and ITGB3 knockdown alleviated the pulmonary vascular remodelling and improved the PAH pathological features of rats.

Conclusions

MiR‐223‐3p alleviated the progression of PAH by suppressing the expression of ITGB3, a finding which provides novel targets for clinical treatment.

Renin-angiotensin system regulates pulmonary arterial smooth muscle cell migration in chronic thromboembolic pulmonary hypertension

Pulmonary arterial smooth muscle cell (PASMC) migration plays a key role in vascular remodeling, which occurs during development of chronic thromboembolic pulmonary hypertension (CTEPH). Activation of the renin-angiotensin system (RAS) contributes to vascular remodeling observed in many diseases, including idiopathic pulmonary arterial hypertension. However, the role of RAS imbalance in CTEPH has not been characterized. Here, we hypothesize that RAS imbalance regulates vascular remodeling by promoting PASMC migration in CTEPH. Serum renin and angiotensin II levels in patients with CTEPH were quantified by ELISA. The pulmonary endarterectomy tissues were stained and analyzed by immunohistochemistry. PASMCs were isolated and verified by immunofluorescence staining. PASMC migration was determined by Transwell assay. Phosphorylation and protein level were detected by Western blotting. Serum levels of renin and angiotensin II were increased in patients with CTEPH {renin [median (25th percentile, 75th percentile) in pg/ml], 1,199.94 [690.85, 1,656.90] vs. 595.43 [351.48, 936.43], P < 0.001; angiotensin II [in pg/ml], 63.97 [45.97, 345.24] vs. 56.85 [11.20, 90.37], P < 0.05}. The migration of PASMCs isolated from patients with CTEPH was enhanced compared with control. Angiotensin II promoted the migration of PASMCs via activation of angiotensin II receptor 1 and phosphorylation of ERK1/2, whereas angiotensin-(1-7) counteracted this effect through activation of the Mas receptor and ERK1/2. These results demonstrate that the renin-angiotensin system regulates migration of PASMCs from patients with CTEPH via the ERK1/2 pathway. Our findings suggest that angiotensin-(1-7) or reagents targeting the renin-angiotensin system will be beneficial in the development of novel therapies for CTEPH.

Inhibition of CXCL12/CXCR4 suppresses pulmonary arterial smooth muscle cell proliferation and cell cycle progression via PI3K/Akt pathway under hypoxia

Stromal cell-derived factor 1 (CXCL12) and its receptor CXC chemokine receptor 4 (CXCR4) are known to modulate hypoxia-induced pulmonary hypertension (PH) and vascular remodeling by mobilization and recruitment of progenitor cells to the pulmonary vasculature. However, little is known about CXCL12/CXCR4 regulating proliferation and cell cycle progression of pulmonary arterial smooth muscle cells (PASMCs). To determine whether CXCL12/CXCR4 regulates PASMC proliferation and the cell cycle, immunohistochemistry, Western blot, bromodeoxyuridine incorporation and cell cycle analysis were preformed in this study. Our results showed that CXCR4 was induced by hypoxia in pulmonary arteries and PASMCs of rats. Hypoxia-increased cell viability, DNA synthesis and proliferating cell nuclear antigen expression were blocked by administration of CXCR4 antagonist AMD3100, silencing CXCR4 or CXCL12. Furthermore, inhibition of CXCL12/CXCR4 suppressed cell cycle progression, decreased the number of cells in S+G2/M phase and attenuated the expression of proteins that regulate the cell cycle progression at these phases. In addition, PI3K/Akt signaling mediated CXCL12/CXCR4 regulating proliferation and cell cycle progression in PASMCs. Thus, these results indicate that blockade of CXCL12/CXCR4 inhibited PASMC proliferation and cell cycle progression in hypoxia-induced PH via PI3K/Akt signaling pathway.

Id proteins are critical downstream effectors of BMP signaling in human pulmonary arterial smooth muscle cells

Bone morphogenetic protein type II receptor (BMPR-II) mutations are responsible for over 70% of cases of heritable pulmonary arterial hypertension (PAH). Loss of BMP signaling promotes pulmonary vascular remodeling via modulation of pulmonary artery smooth muscle cell (PASMC) proliferation. Id proteins (Id1-4) are major downstream transcriptional targets of BMP signaling. However, the impact of BMPR-II mutation on the expression of the range of Id proteins and the contribution of individual Id proteins to abnormal PASMC function remain unclear. Human PASMCs were used to determine the expression of Id proteins (Id1-4) by real-time PCR and immunoblotting. The BMP responses in control cells were compared with PASMCs harboring BMPR-II mutations and cells in which BMPR-II was knocked down by siRNA transfection. Id3 expression in pulmonary vessels was also investigated in BMPR-II mutant mice and in patients with heritable PAH. BMP4 and BMP6, but not BMP9, induced mRNA expression of Id1, Id2, and Id3. The BMP-stimulated induction of Id1 and Id3 was markedly reduced in BMPR-II mutant PASMCs and in control PASMCs following siRNA silencing of BMPR-II. Pulmonary arteries in BMPR-II mutant mice and patients with heritable PAH demonstrated reduced levels of Id3 compared with control subjects. Lentiviral overexpression of Id3 reduced cell cycle progression and inhibited proliferation of PASMCs. Lipopolysaccharide further reduced Id3 expression in mutant PASMCs. In conclusion, Id proteins, and particularly Id1 and Id3, are critical downstream effectors of BMP signaling in PASMCs. Loss of BMPR-II function reduces the induction of Id genes in PASMCs, Id1, and Id3 regulate the proliferation of PASMCs via cell cycle inhibition, an effect that may be exacerbated by inflammatory stimuli.