Apoptosis In Pulmonary Artery Endothelial Cells Research Articles

TRPC4 aggravates hypoxic pulmonary hypertension by promoting pulmonary endothelial cell apoptosis

Pulmonary hypertension (PH) is a devastating disease that lacks effective treatment options and is characterized by severe pulmonary vascular remodeling. Pulmonary arterial endothelial cell (PAEC) dysfunction drives the initiation and pathogenesis of pulmonary arterial hypertension. Canonical transient receptor potential (TRPC) channels, a family of Ca2+-permeable channels, play an important role in various diseases. However, the effect and mechanism of TRPCs on PH development have not been fully elucidated. Among the TRPC family members, TRPC4 expression was markedly upregulated in PAECs from hypoxia combined with SU5416 (HySu)-induced PH mice and monocrotaline (MCT)-treated PH rats, as well as in hypoxia-exposed PAECs, suggesting that TRPC4 in PAECs may participate in the occurrence and development of PH. In this study, we aimed to investigate whether TRPC4 in PAECs has an aggravating effect on PH and elucidate the molecular mechanisms. We observed that hypoxia treatment promoted PAEC apoptosis through a caspase-12/endoplasmic reticulum stress (ERS)-dependent pathway. Knockdown of TRPC4 attenuated hypoxia-induced apoptosis and caspase-3/caspase-12 activity in PAECs. Accordingly, adeno-associated virus (AAV) serotype 6-mediated pulmonary endothelial TRPC4 silencing (AAV6-Tie-shRNA-TRPC4) or TRPC4 antagonist suppressed PH progression as evidenced by reduced right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, PAEC apoptosis and reactive oxygen species (ROS) production. Mechanistically, unbiased RNA sequencing (RNA-seq) suggested that TRPC4 deficiency suppressed the expression of the proapoptotic protein sushi domain containing 2 (Susd2) in hypoxia-exposed mouse PAECs. Moreover, TRPC4 activated hypoxia-induced PAEC apoptosis by promoting Susd2 expression. Therefore, inhibiting TRPC4 ameliorated PAEC apoptosis and hypoxic PH in animals by repressing Susd2 signaling, which may serve as a therapeutic target for the management of PH.

Spermidine attenuates monocrotaline-induced pulmonary arterial hypertension in rats by inhibiting purine metabolism and polyamine synthesis-associated vascular remodeling

Ensuring the homeostatic integrity of pulmonary artery endothelial cells (PAECs) is essential for combatting pulmonary arterial hypertension (PAH), as it equips the cells to withstand microenvironmental challenges. Spermidine (SPD), a potent facilitator of autophagy, has been identified as a significant contributor to PAECs function and survival. Despite SPD's observed benefits, a comprehensive understanding of its protective mechanisms has remained elusive. Through an integrated approach combining metabolomics and molecular biology, this study uncovers the molecular pathways employed by SPD in mitigating PAH induced by monocrotaline (MCT) in a Sprague-Dawley rat model. The study demonstrates that SPD administration (5 mg/kg/day) significantly corrects right ventricular impairment and pathological changes in pulmonary tissues following MCT exposure (60 mg/kg). Metabolomic profiling identified a purine metabolism disorder in MCT-treated rats, which SPD effectively normalized, conferring a protective effect against PAH progression. Subsequent in vitro analysis showed that SPD (0.8 mM) reduces oxidative stress and apoptosis in PAECs challenged with Dehydromonocrotaline (MCTP, 50 μM), likely by downregulating purine nucleoside phosphorylase (PNP) and modulating polyamine biosynthesis through alterations in S-adenosylmethionine decarboxylase (AMD1) expression and the subsequent production of decarboxylated S-adenosylmethionine (dcSAM). These findings advocate SPD's dual inhibitory effect on PNP and AMD1 as a novel strategy to conserve cellular ATP and alleviate oxidative injuries, thus providing a foundation for SPD's potential therapeutic application in PAH treatment.

Salidroside protects pulmonary artery endothelial cells against hypoxia-induced apoptosis via the AhR/NF-κB and Nrf2/HO-1 pathways

BackgroundThe apoptosis of pulmonary artery endothelial cells (PAECs) is an important factor contributing to the development of pulmonary hypertension (PH), a serious cardio-pulmonary vascular disorder. Salidroside (SAL) is a bioactive compound derived from an herb Rhodiola, but the potential protective effects of SAL on PAECs and the underlying mechanisms remain elusive. PurposeThe objective of this study was to determine the role of SAL in the hypoxia-induced apoptosis of PAECs and to dissect the underlying mechanisms. Study designMale Sprague-Dawley (SD) rats were subjected to hypoxia (10% O2) for 4 weeks to establish a model of PH. Rats were intraperitoneally injected daily with SAL (2, 8, and 32 mg/kg/d) or vehicle. To define the molecular mechanisms of SAL in PAECs, an in vitro model of hypoxic cell injury was also generated by exposed PAECs to 1% O2 for 48 h. MethodsVarious techniques including hematoxylin and eosin (HE) staining, immunofluorescence, flow cytometry, CCK-8, Western blot, qPCR, molecular docking, and surface plasmon resonance (SPR) were used to determine the role of SAL in rats and in PAECs in vitro. ResultsHypoxia stimulation increases AhR nuclear translocation and activates the NF-κB signaling pathway, as evidenced by upregulated expression of CYP1A1, CYP1B1, IL-1β, and IL-6, resulting in oxidative stress and inflammatory response and ultimately apoptosis of PAECs. SAL inhibited the activation of AhR and NF-κB, while promoted the nuclear translocation of Nrf2 and increased the expression of its downstream antioxidant proteins HO-1 and NQO1 in PAECs, ameliorating the hypoxia-induced oxidative stress in PAECs. Furthermore, SAL lowered right ventricular systolic pressure, and decreased pulmonary vascular remodeling and right ventricular hypertrophy in hypoxia-exposed rats. ConclusionsSAL may attenuate the apoptosis of PAECs by suppressing NF-κB and activating Nrf2/HO-1 pathways, thereby delaying the progressive pathology of PH.

Effect of RNA interference with HIF-1α on the growth of pulmonary artery endothelial cells in broiler chickens

Pulmonary artery remodeling is a characteristic feature of broiler ascites syndrome (BAS). Pulmonary artery endothelial cells (PAECs) regulated by HIF-1α play a critical role in pulmonary artery remodeling, but the underlying mechanisms of HIF-1α in BAS remain unclear. In this experiment, primary PAECs were cultured in vitro and were identified by coagulation factor VIII. After hypoxia and RNA interference, the mRNA and protein expression levels of HIF-1α and VEGF were determined by qPCR and Western blotting. The transcriptome profiles of PAECs were obtained by RNA sequencing. Our results showed that the positive rate of PAECs was more than 90%, hypoxia-induced promoted the proliferation and apoptosis of PAECs, and RNA interference significantly downregulated the expression of HIF-1α, inhibited the proliferation of PAECs, and promoted the apoptosis of PAECs. In addition, transcriptome sequencing analysis indicated that HIF-1α may regulate broiler ascites syndrome by mediating COL4A, vitronectin, vWF, ITGα8, and MKP-5 in the ECM, CAMs and MAPK pathways in PAECs. These studies lay the foundation for further exploration of the mechanisms of pulmonary artery remodeling, and HIF-1α may be a potentially effective gene for the prevention and treatment of BAS.

Abstract 17047: Contribution of MDA-5/IL-10RA to Pulmonary Artery Homeostasis and Pulmonary Arterial Hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive and lethal disease. The current treatment options do not target pulmonary artery endothelial cell (PAEC) dysfunction. We have previously shown a role for the endosomal double stranded (ds) RNA receptor toll-like receptor 3 (TLR3) and its regulation via interleukin-10 (IL-10) in promoting PAEC dysfunction and experimental pulmonary hypertension (PH). Yet the role of the cytosolic dsRNA receptor melanoma differentiation factor 5 (MDA-5) in endothelial dysfunction is not known. Hypothesis: We hypothesized that a deficient MDA-5/IL-10 receptor A (IL-10RA) signaling axis expression exists in PAH PAECs as a potential cause of endothelial dysfunction. Goals: Our goal is to test the role of a potential new axis of MDA-5 and IL10RA in EC homeostasis and pulmonary hypertension. Methods: Western blot analysis of control and PAH PAECs and PA smooth muscle cells (SMCs) was conducted. Gene silencing was done using siRNA targeting MDA-5 and IL-10RA, followed by bulk RNA sequencing. Apoptosis was tested using Annexin V binding. IL-10 whole body knockout (IL-10 -/- ) and endothelial-specific IL-10RA haploinsufficient mice (IL-10RA fl/wt Cdh5-Cre + ) and appropriate controls were exposed to chronic hypoxia and SU5416 (Hx/Su), followed by hemodynamics. Results: Our data show a reduction of MDA-5 in PAECs, but not in PASMCs. PAH PAECs further had reduced IL-10RA expression and application of dsRNA elevated IL-10RA expression in PAH PAECs. Knockdown of MDA-5 and IL-10RA caused differential expression of 2533 and 2638 genes, respectively. Comparative analysis revealed an overlap of differentially expressed genes (DEGs) in canonical pathways including reduced nitric oxide, VEGF, Apelin and Integrin signaling. Comparison also yielded overlapping DEGs for reduced cell survival, impaired cytoskeleton organization and migration. Gene silencing of MDA-5 resulted in increased PAEC apoptosis. IL-10 -/- and IL-10RA fl/wt Cdh5-Cre + mice showed exaggerated PH. Conclusions: Our data indicate an impaired cytosolic dsRNA receptor MDA-5 and IL-10RA axis in PAH PAECs which contributes to endothelial dysfunction and PH. Experiments are underway to identify the detailed mechanisms underlying our findings.

Protective effects of the Terminalia bellirica tannin-induced Nrf2/HO-1 signaling pathway in rats with high-altitude pulmonary hypertension

BackgroundOxidative stress and endothelial cell dysfunction induced by high-altitude hypoxia have important roles in the pathological process of high-altitude pulmonary hypertension (HAPH). Tannins present in Terminalia bellirica (Gaertn.) Roxb. (TTR) have pharmacological activities that produce oxidation resistance and exert anti-inflammatory effects. Whether TTR exerts a protective effect on HAPH remains unknown.MethodsA rat model of HAPH was established. The mean pulmonary arterial pressure (mPAP) of the animals was measured, the serum levels of SOD, MDA, and GSH-Px were measured using ELISA, and the expression of Bax, Bcl-2, Nrf2, and HO-1 proteins in the lung tissue of each group of rats was measured using Western blotting. Pathological changes in the lung tissue were also observed. A model of damage to H2O2-induced pulmonary artery endothelial cells (PAECs) was generated, and cell proliferation was measured using CCK-8 assays. Flow cytometry was used to measure ROS levels in PAECs. Western blotting was used to detect the expression of Bax, Bcl-2, Nrf2, and HO-1 proteins in PAECs.ResultsThe hemodynamic and pathologic findings showed that the mPAP of HAPH rats increased markedly, and the vascular wall thickness increased (P < 0.05). TTR reduced mPAP, alleviated or slowed pulmonary arterial remodeling, increased GSH-Px and SOD activity, lowered the level of MDA (P < 0.05), and downregulated the expression of Bax in the lung tissues of HAPH rats, while the expression of Bcl-2, Nrf2, and HO-1 was upregulated (P < 0.05). The results of the cell experiments showed that TTR inhibited H2O2-induced PAEC apoptosis and ROS production (P < 0.05), downregulated the expression of Bax in PAECs, and upregulated the expression of Bcl-2, Nrf2, and HO-1 (P < 0.05).ConclusionThe results suggest that TTR reduces pulmonary arterial pressure, decreases oxidative stress during HAPH, and exerts protective effects in rats with HAPH and that its mechanism of action is related to regulation of the Nrf2/HO-1 signaling pathway.

MicroRNA‐144‐3p controls the apoptosis of pulmonary artery endothelial cells in pulmonary arterial hypertension via the BMPR2/Smad4 signaling pathway

AbstractBackgroundThis study was to determine the molecular mechanism of miR‐144‐3p in the treatment of pulmonary arterial hypertension (PAH).MethodsLuciferase assays detected the binding site of miR‐144‐3p. Quantitative reverse transcription‐polymerase chain reaction (PCR) measured the expression of downstream genes of Smad4 in pulmonary artery endothelial cells (PAECs). Cell apoptosis was analysed by fluorescence activated cell sorting (FACS) analysis. In a monocrotaline‐induced rat PAH model, the integrity of PAECs was detected by hematoxylin eosin (H&amp;E) staining, immunohistochemistry, and immunofluorescence. The protein expression of the bone morphogenetic protein receptor 2 (BMPR2)/Smad4 signaling pathway was analysed by Western blotting.ResultsMiR‐144‐3p targeted Smad4 directly and down‐regulated the expression of α‐smooth muscle actin (SMA), Connective tissue growth factor (CTGF) and c‐myelocytomatosis (MYC) in PAECs. There was a significant change in the apoptosis of PAECs transfected with miR‐144‐3p. After transfection, the phosphorylation of Smad4 decreased only at 24 h. The integrity of PAECs was improved by miR‐144‐3p. There was a down‐regulation in BMPR2, Smad1/5 and p‐Smad1/5 in the PAH group. The fold change in Smad4 and p‐Smad4 expression decreased significantly in the PAH‐miR group. Moreover, we observed decreased α‐SMA, CTGF and c‐MYC expression and an up‐regulation of vascular endothelial (VE)‐cadherin.ConclusionsMiR‐144‐3p modulates apoptosis and phenotype switching of PAECs via phosphorylation of the BMPR2/Smad4 signaling pathway.

Endothelial Dec1-PPARγ Axis Impairs Proliferation and Apoptosis Homeostasis Under Hypoxia in Pulmonary Arterial Hypertension.

Background: The hypoxia-induced pro-proliferative and anti-apoptotic characteristics of pulmonary arterial endothelial cells (PAECs) play critical roles in pulmonary vascular remodeling and contribute to hypoxic pulmonary arterial hypertension (PAH) pathogenesis. However, the mechanism underlying this hypoxic disease has not been fully elucidated.Methods: Bioinformatics was adopted to screen out the key hypoxia-related genes in PAH. Gain- and loss-function assays were then performed to test the identified hypoxic pathways in vitro. Human PAECs were cultured under hypoxic (3% O2) or normoxic (21% O2) conditions. Hypoxia-induced changes in apoptosis and proliferation were determined by flow cytometry and Ki-67 immunofluorescence staining, respectively. Survival of the hypoxic cells was estimated by cell counting kit-8 assay. Expression alterations of the target hypoxia-related genes, cell cycle regulators, and apoptosis factors were investigated by Western blot.Results: According to the Gene Expression Omnibus dataset (GSE84538), differentiated embryo chondrocyte expressed gene 1-peroxisome proliferative-activated receptor-γ (Dec1-PPARγ) axis was defined as a key hypoxia-related signaling in PAH. A negative correlation was observed between Dec1 and PPARγ expression in patients with hypoxic PAH. In vitro observations revealed an increased proliferation and a decreased apoptosis in PAECs under hypoxia. Furthermore, hypoxic PAECs exhibited remarkable upregulation of Dec1 and downregulation of PPARγ. Dec1 was confirmed to be crucial for the imbalance of proliferation and apoptosis in hypoxic PAECs. Furthermore, the pro-surviving effect of hypoxic Dec1 was mediated through PPARγ inhibition.Conclusion: For the first time, Dec1-PPARγ axis was identified as a key determinant hypoxia-modifying signaling that is necessary for the imbalance between proliferation and apoptosis of PAECs. These novel endothelial signal transduction events may offer new diagnostic and therapeutic options for patients with hypoxic PAH.

PPARγ-p53-Mediated Vasculoregenerative Program to Reverse Pulmonary Hypertension.

In pulmonary arterial hypertension (PAH), endothelial dysfunction and obliterative vascular disease are associated with DNA damage and impaired signaling of BMPR2 (bone morphogenetic protein type 2 receptor) via two downstream transcription factors, PPARγ (peroxisome proliferator-activated receptor gamma), and p53. We investigated the vasculoprotective and regenerative potential of a newly identified PPARγ-p53 transcription factor complex in the pulmonary endothelium. In this study, we identified a pharmacologically inducible vasculoprotective mechanism in pulmonary arterial and lung MV (microvascular) endothelial cells in response to DNA damage and oxidant stress regulated in part by a BMPR2 dependent transcription factor complex between PPARγ and p53. Chromatin immunoprecipitation sequencing and RNA-sequencing established an inducible PPARγ-p53 mediated regenerative program regulating 19 genes involved in lung endothelial cell survival, angiogenesis and DNA repair including, EPHA2 (ephrin type-A receptor 2), FHL2 (four and a half LIM domains protein 2), JAG1 (jagged 1), SULF2 (extracellular sulfatase Sulf-2), and TIGAR (TP53-inducible glycolysis and apoptosis regulator). Expression of these genes was partially impaired when the PPARγ-p53 complex was pharmacologically disrupted or when BMPR2 was reduced in pulmonary artery endothelial cells (PAECs) subjected to oxidative stress. In endothelial cell-specific Bmpr2-knockout mice unable to stabilize p53 in endothelial cells under oxidative stress, Nutlin-3 rescued endothelial p53 and PPARγ-p53 complex formation and induced target genes, such as APLN (apelin) and JAG1, to regenerate pulmonary microvessels and reverse pulmonary hypertension. In PAECs from BMPR2 mutant PAH patients, pharmacological induction of p53 and PPARγ-p53 genes repaired damaged DNA utilizing genes from the nucleotide excision repair pathway without provoking PAEC apoptosis. We identified a novel therapeutic strategy that activates a vasculoprotective gene regulation program in PAECs downstream of dysfunctional BMPR2 to rehabilitate PAH PAECs, regenerate pulmonary microvessels, and reverse disease. Our studies pave the way for p53-based vasculoregenerative therapies for PAH by extending the therapeutic focus to PAEC dysfunction and to DNA damage associated with PAH progression.

Abstract MP155: Oxidized Lipids Diet Causes Pulmonary Hypertension Through T-cell Dependent Endothelial Cell Apoptosis

Background: Pulmonary hypertension (PH) is a fatal disease characterized by an increased mean pulmonary arterial pressure above 25mmHg. This increased pressure is, at least in part, due to thickening of the distal pulmonary arteries. Recently, numerous studies demonstrated an increased plasma concentration of oxidized lipids in PH and in diseases where secondary PH developed. Furthermore, 15-hydroxyeicosatetraenoic acid (15-HETE) an oxidized lipid and a major metabolite of arachidonic acid in the lung, has been implicated in dysregulation of major biological pathways in PH. However, the mechanisms involved in the causal role of 15-HETE in pulmonary hypertension development are not known. Methods and Results: To study the role of 15-HETE in PH development, we fed C57BL6/J mice a diet supplemented with 15-HETE for 3 weeks with no other insults. After 3 weeks on the diet with added 15-HETE, C57BL6/J mice had increased concentrations of not only 15-HETE but also of other oxidized lipids (5-, 11- and 12-HETE) in plasma and lung, and they developed PH. RNA-seq analysis revealed the activation of pathways involved in antigen processing and presentation, and with evidence of T cell mediated cytotoxicity in lungs of mice fed 15-HETE. Transcriptomic profiling of lung tissues obtained from patients with pulmonary arterial hypertension (PAH) demonstrated activation of pathways similar to those seen mice. In mice fed a 15-HETE diet, there was an increase in the number of CD8/CD69 double positive cells, as well as an increase in pulmonary arterial endothelial cell (PAEC) apoptosis. Furthermore, PAEC exposed to 15-HETE were more prone to apoptosis when exposed to CD8 cells. Adding Tg6F, an apoA-I mimetic peptide to the 15-HETE diet prevented and rescued PH in C57BL6/J mice, in part, by inhibiting PAEC apoptosis. Conclusions: 15-HETE diet induced PH in C57Bl6/J mice by triggering PAEC death in a T-cell dependent mechanism. The apoA-I mimetic peptide Tg6F was able to prevent and rescue PH induced by 15-HETE.

Oral 15-Hydroxyeicosatetraenoic Acid Induces Pulmonary Hypertension in Mice by Triggering T Cell–Dependent Endothelial Cell Apoptosis

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by increased mean pulmonary arterial pressure. Elevated plasma and lung concentrations of oxidized lipids, including 15-hydroxyeicosatetraenoic acid (15-HETE), have been demonstrated in patients with PAH and animal models. We previously demonstrated that feeding mice with 15-HETE is sufficient to induce pulmonary hypertension, but the mechanisms remain unknown. RNA sequencing data from the mouse lungs on 15-HETE diet revealed significant activation of pathways involved in both antigen processing and presentation and T cell-mediated cytotoxicity. Analysis of human microarray from patients with PAH also identified activation of identical pathways compared with controls. We show that in both 15-HETE-fed mice and patients with PAH, expression of the immunoproteasome subunit 5 is significantly increased, which was concomitant with an increase in the number of CD8/CD69 (cluster of differentiation 8 / cluster of differentiation 69) double-positive cells, as well as pulmonary arterial endothelial cell apoptosis in mice. Human pulmonary arterial endothelial cells cultured with 15-HETE were more prone to apoptosis when exposed to CD8 cells. Cultured intestinal epithelial cells secreted more oxidized lipids in response to 15-HETE, which is consistent with accumulation of circulating oxidized lipids in 15-HETE-fed mice. Administration of an apoA-I (apolipoprotein A-I) mimetic peptide, Tg6F (transgenic 6F), which is known to prevent accumulation of circulating oxidized lipids, not only inhibited pulmonary arterial endothelial cell apoptosis but also prevented and rescued 15-HETE-induced pulmonary hypertension in mice. In conclusion, our results suggest that (1) 15-HETE diet induces pulmonary hypertension by a mechanism that involves oxidized lipid-mediated T cell-dependent pulmonary arterial endothelial cell apoptosis and (2) Tg6F administration may be a novel therapy for treating PAH.

Adiponectin ameliorates lung injury induced by intermittent hypoxia through inhibition of ROS-associated pulmonary cell apoptosis.

Obstructive sleep apnea hypopnea syndrome has been reported to be associated with pulmonary hypertension (PH). Adiponectin (Ad) has many protective roles in the human body, including its function as an anti-inflammatory and an anti-oxidant, as well as its role in preventing insulin resistance and atherosclerosis. This study aimed to investigate the molecular mechanism of chronic intermittent hypoxia (CIH)-induced pulmonary injury and the protective role of Ad in experimental rats. Thirty male Sprague-Dawley rats were randomly divided into three groups with 10 rats in each group: normal control (NC) group, CIH group, and CIH + Ad group. Rats in the NC group were kept breathing room air for 12weeks. Rats in the CIH group were intermittently exposed to a hypoxic environment for 8h/day for 12weeks. Rats in the CIH + Ad group received 10μg Ad twice weekly via intravenous injection. After 12weeks of CIH exposure, we detected the pulmonary function, pulmonary artery pressure, lung histology, pulmonary cell apoptosis, pulmonary artery endothelial cell apoptosis, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) level. We also analyzed expression proteins involved in the mitochondria-, endoplasmic reticulum (ER) stress-, and Fas receptor-associated pulmonary apoptosis pathways, as well as the SIRT3/SOD2 pathway. CIH exposure for 12weeks did not lead to abnormal pulmonary function, PH, or pulmonary artery endothelial cell apoptosis. However, we observed a significant increase in the rate of pulmonary cell apoptosis, the expression of proteins involved in mitochondria-, ER stress-, and Fas receptor-associated pulmonary apoptosis pathways, and the generation of ROS in the CIH group compared with the NC group. In contrast, the MMP and protein expressions of SIRT3/SOD2 pathway were significantly decreased in the CIH group compared with the NC group. Ad supplementation in the CIH + Ad group partially improved these changes induced by CIH. Even though CIH did not cause abnormal pulmonary function or PH, early lung injury was detected at the molecular level in rats exposed to CIH. Treatment with Ad ameliorated the pulmonary injury by activating the SIRT3/SOD2 pathway, reducing ROS generation, and inhibiting ROS-associated lung cell apoptosis.

Role of Mitochondrial Ca2+‐Activated Cl− Channel anoctamin‐1 and mitochondrial fusion protein OPA1 in pulmonary arterial hypertension

Activation of a Ca2+‐activated chloride channel, anoctamin‐1 (Ano1), is associated with enhanced cell proliferation in multiple cell types, such as endothelial cells (ECs). Recent proteomics studies indicate that Ano1 may interact with mitochondrial proteins in addition to plasma membrane (PM)‐localized proteins. However, the expression levels of Ano1 and its functions in other cellular compartments including mitochondria remain unclear. We previously showed that Ano1 is overexpressed in pulmonary artery ECs isolated from patients with idiopathic pulmonary arterial hypertension (PAH) and that Ano1 activation promotes apoptosis of pulmonary artery ECs from patients with idiopathic PAH, likely via depolarization of mitochondrial membrane potential and increased mitochondrial reactive oxygen species (ROS) generation. Therefore, we hypothesized that Ano1 exists not only at PM, but also in the mitochondria, which may contribute to a hyperproliferative phenotype of ECs under PAH. Here, we determined the mitochondrial expression of Ano1 and further investigated its role in the mitochondria. Subcellular localization of Ano1 was determined by immunostaining of Ano1 in Rat lung microvascular ECs (RLMVECs) and by live cell imaging of HEK293T cells expressing GFP‐tagged Ano1. The mitochondrial and PM localization of Ano1 was also confirmed by biochemical assays using protein fractionation from RLMVECs. Moreover, co‐immunoprecipitation assay showed that Ano1 interacts with a mitochondrial fusion protein OPA1 which is the critical regulator of mitochondrial bioenergetics and cristae formation and possesses a trans‐membrane domain at the inner mitochondrial membrane (IMM). These results indicate that 1) Ano1 expresses at the IMM in addition to the PM and 2) Ano1 and OPA1 interactions may be partly involved in the molecular mechanism underlying the hyperproliferation and apoptosis resistance of pulmonary artery ECs during PAH

Role of Mitochondrial Expression of the Calcium-Activated Chloride Channel Anoctamin-1 in Pulmonary Artery Endothelial Cells

Activation of a Ca2+-activated chloride channel, anoctamin-1 (Ano1), is associated with enhanced cell proliferation in multiple cell types, such as endothelial cells (ECs). Recent proteomics studies indicate that Ano1 may interact with mitochondrial proteins in addition to plasma membrane (PM)-localized proteins. However, the expression levels of Ano1 and its functions in other cellular compartments including mitochondria remain unclear. We previously showed that Ano1 is overexpressed in pulmonary artery ECs isolated from patients with idiopathic pulmonary arterial hypertension (PAH) and that Ano1 activation promotes apoptosis of pulmonary artery ECs from patients with idiopathic PAH, likely via depolarization of mitochondrial membrane potential and increased mitochondrial reactive oxygen species (ROS) generation. Therefore, we hypothesized that Ano1 exists not only at PM, but also in the mitochondria, which may contribute to a hyperproliferative phenotype of ECs under PAH. Here, we determined the mitochondrial expression of Ano1 and further investigated its role in the mitochondria. Subcellular localization of Ano1 was determined by immunostaining of Ano1 in Rat lung microvascular ECs (RLMVECs) and by live cell imaging of HEK293T cells expressing GFP-tagged Ano1. The mitochondrial and PM localization of Ano1 was also confirmed by biochemical assays using protein fractionation from RLMVECs. Moreover, co-immunoprecipitation assay showed that Ano1 interacts with a mitochondrial fusion protein OPA1 which is the critical regulator of mitochondrial bioenergetics and cristae formation and possesses a trans-membrane domain at the inner mitochondrial membrane (IMM). These results indicate that 1) Ano1 expresses at the IMM in addition to the PM and 2) Ano1 and OPA1 interactions may be partly involved in the molecular mechanism underlying the hyperproliferation and apoptosis resistance of pulmonary artery ECs during PAH.

Ovine Models of Congenital Heart Disease and the Consequences of Hemodynamic Alterations for Pulmonary Artery Remodeling.

The natural history of pulmonary vascular disease associated with congenital heart disease (CHD) depends on associated hemodynamics. Patients exposed to increased pulmonary blood flow (PBF) and pulmonary arterial pressure (PAP) develop pulmonary vascular disease more commonly than patients exposed to increased PBF alone. To investigate the effects of these differing mechanical forces on physiologic and molecular responses, we developed two models of CHD using fetal surgical techniques: 1) left pulmonary artery (LPA) ligation primarily resulting in increased PBF and 2) aortopulmonary shunt placement resulting in increased PBF and PAP. Hemodynamic, histologic, and molecular studies were performed on control, LPA, and shunt lambs as well as pulmonary artery endothelial cells (PAECs) derived from each. Physiologically, LPA, and to a greater extent shunt, lambs demonstrated an exaggerated increase in PAP in response to vasoconstricting stimuli compared with controls. These physiologic findings correlated with a pathologic increase in medial thickening in pulmonary arteries in shunt lambs but not in control or LPA lambs. Furthermore, in the setting of acutely increased afterload, the right ventricle of control and LPA but not shunt lambs demonstrates ventricular-vascular uncoupling and adverse ventricular-ventricular interactions. RNA sequencing revealed excellent separation between groups via both principal components analysis and unsupervised hierarchical clustering. In addition, we found hyperproliferation of PAECs from LPA lambs, and to a greater extent shunt lambs, with associated increased angiogenesis and decreased apoptosis in PAECs derived from shunt lambs. A further understanding of mechanical force-specific drivers of pulmonary artery pathology will enable development of precision therapeutics for pulmonary hypertension associated with CHD.

MiR‑371b‑5p inhibits endothelial cell apoptosis in monocrotaline‑induced pulmonary arterial hypertension via PTEN/PI3K/Akt signaling pathways.

Pulmonary arterial hypertension (PAH) is a clinical hemodynamic syndrome. It is characterized by elevated PA pressure and pulmonary vascular resistance. In the present study, the role of microRNA (miRNA/miR)-371b-5p in monocrotaline-induced PAH and the underlying mechanisms were investigated. In a monocrotaline-induced PAH rat model, gene chip and reverse transcription-quantitative polymerase chain reaction were employed to measure miRNA expression levels. The results revealed that miR-371b-5p was downregulated in PAH rats compared with the control group. In addition, in vitro results demonstrated that an miR-371b-5p inhibitor reduced miR-371b-5p expression levels, increased apoptosis and reduced proliferation of pulmonary arterial endothelial cells (PAECs) in rats with monocrotaline-induced PAH. Furthermore, inhibition of miR-371b-5p induced phosphatase and tensin homolog (PTEN) protein expression and suppressed that of phosphoinositide 3-kinase (PI3K) and phosphorylated (p)-Akt in the PAECs. In addition, VO-OHpic, a PTEN inhibitor, reduced the protein expression levels of PTEN in the PAECs and inhibited the effects of anti-miR-371b-5p on cell apoptosis. In addition, LY294002, a PI3K inhibitor, reduced the PI3K and p-Akt protein expression in the PAECs and reversed the effects of miR-371b-5p overexpression on the apoptosis of PAECs in rats with monocrotaline-induced PAH. Collectively, the results of the present study indicate that, in this animal model of PAH, miR-371b-5p inhibits apoptosis of PAECs via PTEN/PI3K/Akt signaling pathways.

Establishment of a model of hydrogen peroxide-induced injury in pulmonary artery endothelium cells and relevant mechanisms of oxidative stress

Objective: To establish a hydrogen peroxide (H(2)O(2)) induced injury model of pulmonary artery endothelial cells (PAECs) and explore the molecular mechanisms of oxidative stress on the structure and function of PAECs in this model. Methods: Human PAECs were treated with H(2)O(2) at different concentrations (25, 50, 100, 200, 400, 800, 1 600, 3 200, 6 400 μmol/L) for 4 and 24 h, respectively. The PAECs survival curve was obtained according to the cell viability measured by CCK-8 assay. The cell apoptosis of PAECs was detected by flow cytometry. The reactive oxygen species (ROS) generation and mitochondrial activity were measured using small molecule fluorescent probes. Proteins were extracted and the phosphorylation levels of signal molecules in PAECs were detected by Western blot assays. Results: (1) The effect of H(2)O(2) at various concentrations on cell viability of PAECs: cell viability of PAECs decreased in proportion to increasing concentration of H(2)O(2) after incubation for 4 h. The half maximal inhibitory concentration (IC(50)) of PAECs exposed to H(2)O(2) for 4 and 24 h were 397.00 and 488.77 μmol/L, respectively. (2) The effect of H(2)O(2) on cell apoptosis of PAECs: After H(2)O(2) incubation for 4 h, proportions of PAECs at late-apoptosis ((22.58±3.69) %) and necrotic stage( (11.86±4.27)%) were significantly higher than those of control PAECs at late-apoptosis stage( (3.41±1.44)%, P<0.01) and at necrotic stage ((1.94±1.15) % , P<0.05). The survival rate of PAECs post H(2)O(2) was dramatically lower than that of control PAECs ((7.98±3.21)% vs. (48.89±8.08)%, P<0.01). However, there is no statistical difference between both groups regarding to the early apoptosis. (3) The effect of H(2)O(2) on mitochondrial activity and ROS production of PAECs: the mitochondrial activity and ROS generation of PAECs treated by H(2)O(2) were significantly increased compared to those in control PAECs (P<0.01). (4) The effect of H(2)O(2) on signaling molecules in PAECs: there was a significant increase in phosphorylation level of Akt in PAECs incubated with H(2)O(2) for 30 minutes compared to that in control PAECs (P<0.01), while there was no significant difference in levels of Akt between H(2)O(2) treated PAECs and control PAECs. Phosphorylation level of JNK as well as p38 were also significantly upregulated in H(2)O(2) treated PAECs (P<0.01). Conclusion: H(2)O(2) at the concentration of 400 μmol/L could induce human PAECs injuries via the regulation of Akt and MAPK signaling pathways.

Epizootic haemorrhagic disease virus induced apoptosis in bovine carotid artery endothelium is p53 independent.

Epizootic haemorrhagic disease virus (EHDV) replicates in endothelium and it has been shown that EHDV serotype 2 (Ibaraki) is able to cause cell death by apoptosis in cow pulmonary artery endothelial cells. However, the underlying mechanism has not been established. For some viruses, such as influenza, a p53 dependent mechanism has been demonstrated in viral induced apoptosis. In this study, we investigate the involvement of p53 in the induction of apoptosis in a US isolate of EHDV serotype 2 in cow endothelium. We inoculated cow carotid artery endothelial cell cultures with live and inactivated EHDV‑2 isolated from a white‑tailed deer (Odocoileus virginianus). Using in situ nick end‑labeling (TUNEL), caspase‑3 (cleaved) immunohistochemistry (IHC), flow cytometry and annexin staining we documented the development of apoptosis and its direct relation to viral replication. p53 gene regulation and protein expression were assessed by reverse transcription polymerase chain reaction and IHC, respectively, in infected cells. We show that p53 mRNA was not upregulated and protein expression was not significantly increased. No increase of p53 mRNA or protein expression was observed in cells that stained positive for EHDV antigen. Our results indicate that EHDV induces apoptosis through a p53 independent mechanism.

Hypoxia inhibits pulmonary artery endothelial cell apoptosis via the e-selectin/biliverdin reductase pathway

Hypoxia-induced inhibition of apoptosis in pulmonary artery endothelial cells (PAECs) has an important role in pulmonary arterial remodeling leading to aggravated hypoxic pulmonary arterial hypertension. However, the mechanisms involved in the hypoxia-induced inhibition of PAEC apoptosis have not been elucidated. e-selectin and biliverdin reductase (BVR) have been reported to contribute to the cascade of apoptosis in several cell lines but not in PAECs. In the present study, we show that the expression of e-selectin and BVR was both up-regulated by hypoxia in PAECs. Moreover, hypoxia attenuated the decreased cell survival and apoptotic protein expression, and increased DNA fragmentation induced by serum deprivation in the PAECs, which was mediated by the e-selectin/BVR pathway. In addition, by examining the mitochondrial membrane potential and mitochondrial membrane proteins (Bcl-2 and BAX), we show that the mitochondrial-dependent apoptosis pathway was necessary for the e-selectin/BVR pathway inducing the anti-apoptotic effect of hypoxia in PAECs. Taken all together, our data show that the e-selectin/BVR pathway participates in the inhibitory process of hypoxia in PAEC apoptosis which is mediated by the mitochondrial-dependent apoptosis pathway.

Morphine-induced delayed pre-conditioning against anoxia/reoxygenation injury in pulmonary artery endothelial cells: The role of mitochondrial KATP channels.

Opioids produce delayed pre-conditioning (PC) in vivo and in vitro. Our previous research revealed that opioid‑induced delayed PC has an antiapoptotic effect on pulmonary artery endothelial cells (PAECs) suffering from anoxia/reoxygenation (A/R) injury. The present study hypothesized that activation of endothelial mitochondrial ATP‑sensitive potassium (KATP) channels may result in antiapoptotic effects and against dysfunction in PAECs. Cultured porcine PAECs underwent 16 h anoxia treatment, followed by 1 h reoxygenation, which occurred 24 h following pretreatment with saline (0.9% NaCl; w/v) or morphine (1 µM). To determine the underlying mechanism, a selective mitochondrial KATP inhibitor, 5‑hydroxydecanoic acid (5‑HD; 100 µM), and an opioid receptor antagonist, naloxone (Nal; 10 µM), were administered 30 min prior to the A/R load. The percentage of apoptotic cells was assessed by Annexin V‑fluorescein isothiocyanate staining, using a fluorescence‑activated cell sorter. The mRNA expression of intercellular cell adhesion molecule‑1 (ICAM‑1) was measured by reverse transcription‑quantitative polymerase chain reaction. The endothelin‑1 (ET‑1) content in the supernatant of PAECs cultures was estimated by radioimmunoassay. Compared with the control, A/R caused the apoptosis of PAECs, release of ET‑1 and increased mRNA expression of ICAM‑1. Morphine‑induced delayed PC significantly reduced PAEC apoptosis, increased the release of ET‑1 and reduced the mRNA expression of ICAM‑1 by ~1.7‑times, compared with A/R. The protective effect of morphine was abolished by pretreatment with 5‑HD and Nal, however, the two agents themselves failed to aggravate the A/R injury. These results suggested that morphine-induced delayed PC has a protective effect during A/R injury of PAECs. This effect may be mediated by mitochondrial KATP channels and is opioid receptor-dependent.