Nephrectomy and high-salt diet inducing pulmonary hypertension and kidney damage by increasing Ang II concentration in rats.

BACKGROUND: Chronic kidney disease (CKD) is a significant risk factor for pulmonary hypertension (PH), a complication that adversely affects patient prognosis. However, the mechanisms underlying this association remain poorly understood. A major obstacle to progress in this field is the lack of a reliable animal model replicating CKD-PH. METHODS: This study aimed to establish a stable rat model of CKD-PH. We employed a combined approach, inducing CKD through a 5/6 nephrectomy and concurrently exposing the rats to a high-salt diet. The model's hemodynamics were evaluated dynamically, alongside a comprehensive assessment of pathological changes in multiple organs. Lung tissues and serum samples were collected from the CKD-PH rats to analyze the expression of angiotensin-converting enzyme 2 (ACE2), evaluate the activity of key vascular components within the renin-angiotensin-aldosterone system (RAAS), and characterize alterations in the serum metabolic profile. RESULTS: At 14 weeks post-surgery, the CKD-PH rats displayed significant changes in hemodynamic parameters indicative of pulmonary arterial hypertension. Additionally, right ventricular hypertrophy was observed. Notably, no evidence of pulmonary vascular remodeling was found. Further analysis revealed RAAS dysregulation and downregulated ACE2 expression within the pulmonary vascular endothelium of CKD-PH rats. Moreover, the serum metabolic profile of these animals differed markedly from the sham surgery group. CONCLUSIONS: Our findings suggest that the development of pulmonary arterial hypertension in CKD-PH rats is likely a consequence of a combined effect: RAAS dysregulation, decreased ACE2 expression in pulmonary vascular endothelial cells, and metabolic disturbances.

Deficiency of the Deubiquitinase UCHL1 Attenuates Pulmonary Arterial Hypertension.

BACKGROUND: The ubiquitin-proteasome system regulates protein degradation and the development of pulmonary arterial hypertension (PAH), but knowledge about the role of deubiquitinating enzymes in this process is limited. UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), a deubiquitinase, has been shown to reduce AKT1 (AKT serine/threonine kinase 1) degradation, resulting in higher levels. Given that AKT1 is pathological in pulmonary hypertension, we hypothesized that UCHL1 deficiency attenuates PAH development by means of reductions in AKT1. METHODS: Tissues from animal pulmonary hypertension models as well as human pulmonary artery endothelial cells from patients with PAH exhibited increased vascular UCHL1 staining and protein expression. Exposure to LDN57444, a UCHL1-specific inhibitor, reduced human pulmonary artery endothelial cell and smooth muscle cell proliferation. Across 3 preclinical PAH models, LDN57444-exposed animals, Uchl1 knockout rats (Uchl1-/-), and conditional Uchl1 knockout mice (Tie2Cre-Uchl1fl/fl) demonstrated reduced right ventricular hypertrophy, right ventricular systolic pressures, and obliterative vascular remodeling. Lungs and pulmonary artery endothelial cells isolated from Uchl1-/- animals exhibited reduced total and activated Akt with increased ubiquitinated Akt levels. UCHL1-silenced human pulmonary artery endothelial cells displayed reduced lysine(K)63-linked and increased K48-linked AKT1 levels. RESULTS: Supporting experimental data, we found that rs9321, a variant in a GC-enriched region of the UCHL1 gene, is associated with reduced methylation (n=5133), increased UCHL1 gene expression in lungs (n=815), and reduced cardiac index in patients (n=796). In addition, Gadd45α (an established demethylating gene) knockout mice (Gadd45α-/-) exhibited reduced lung vascular UCHL1 and AKT1 expression along with attenuated hypoxic pulmonary hypertension. CONCLUSIONS: Our findings suggest that UCHL1 deficiency results in PAH attenuation by means of reduced AKT1, highlighting a novel therapeutic pathway in PAH.

The relationship between colon polyps and colonic diverticulosis: a retrospective review.

Background: Colonic diverticulosis and colon polyps are common findings on colonoscopy. There is currently no consensus regarding a possible connection between the development of polyps and diverticulosis. Multiple research studies have sought to analyze whether the presence of both conditions is associated with the development of colorectal cancer. Our study aims to add to this body of data and to better assess the relationship between diverticulosis and colon polyps. Methods: A retrospective chart review was performed of all patients who underwent screening and diagnostic colonoscopies between January 2011 and December 2020. Data collection included patient demographics; number, pathology, and location of colon polyps; incidence of colon cancer; and presence and location of colonic diverticulosis. Results: Our study demonstrated that the overall presence of diverticulosis in any location increases the likelihood of having nearby colon polyps, regardless of subtype. The presence of left colonic diverticulosis was particularly associated with adjacent adenomatous and non-adenomatous colon polyps. Conclusions: Colonic diverticulosis in any location may lead to an increased incidence of adenomatous colon polyps. It is important to perform careful examination of the mucosa surrounding colon diverticulosis to avoid missing colon polyps.

The Novel Lysosomal Autophagy Inhibitor (ROC-325) Ameliorates Experimental Pulmonary Hypertension.

BACKGROUND: Autophagy plays an important role in the pathogenesis of pulmonary hypertension (PH). ROC-325 is a novel small molecule lysosomal autophagy inhibitor that has more potent anticancer activity than the antimalarial drug hydroxychloroquine, the latter has been prevalently used to inhibit autophagy. Here, we sought to determine the therapeutic benefit and mechanism of action of ROC-325 in experimental PH models. METHODS AND RESULTS: Hemodynamics, echocardiography, and histology measurement showed that ROC-325 treatment prevented the development of PH, right ventricular hypertrophy, fibrosis, dysfunction, and vascular remodeling after monocrotaline and Sugen5416/hypoxia administration. ROC-325 attenuated high K+ or alveolar hypoxia-induced pulmonary vasoconstriction and enhanced endothelial-dependent relaxation in isolated pulmonary artery rings. ROC-325 treatment inhibited autophagy and enhanced endothelial nitric oxide synthase activity in lung tissues of monocrotaline-PH rats. In cultured human and rat pulmonary arterial smooth muscle cell and pulmonary arterial endothelial cell under hypoxia exposure, ROC-325 increased LC3B (light chain 3 beta) and p62 accumulation, endothelial cell nitric oxide production via phosphorylation of endothelial nitric oxide synthase (Ser1177) and dephosphorylation of endothelial nitric oxide synthase (Thr495) as well as decreased HIF (hypoxia-inducible factor)-1α and HIF-2α stabilization. CONCLUSIONS: These data indicate that ROC-325 is a promising novel agent for the treatment of PH that inhibits autophagy, downregulates HIF levels, and increases nitric oxide production.

Flavored and Nicotine-Containing E-Cigarettes Induce Impaired Angiogenesis and Diabetic Wound Healing via Increased Endothelial Oxidative Stress and Reduced NO Bioavailability.

The prevalent use of electronic cigarettes (e-cigarettes) has increased exponentially in recent years, especially in youth who are attracted to flavored e-cigarettes. Indeed, e-cigarette or vaping product use-associated lung injury (EVALI) cases started to emerge in the United States in August 2019, resulting in 2807 hospitalized cases and 68 deaths as of 18 February 2020. In the present study, we investigated, for the first time, whether flavored and nicotine containing e-cigarettes induce endothelial dysfunction to result in impaired angiogenesis and wound healing particularly under diabetic condition. Nicotine containing e-cigarettes with various contents of nicotine (0, 1.2%, 2.4%), and flavored e-cigarettes of classic tobacco, mint, menthol, and vanilla or fruit from BLU (nicotine 2.4%) or JUUL (nicotine 3%), were used to treat endothelial cells in vitro and streptozotocin-induced diabetic mice in vivo. Endothelial cell superoxide production, determined by dihydroethidium (DHE) fluorescent imaging and electron spin resonance (ESR), was markedly increased by exposure to e-cigarette extract (e-CSE) in a nicotine-content dependent manner, while nitric oxide (NO) bioavailability detected by DAF-FM fluorescent imaging was substantially decreased. All of the different flavored e-cigarettes examined also showed significant effects in increasing superoxide production while diminishing NO bioavailability. Endothelial cell apoptosis evaluated by caspase 3 activity was markedly increased by exposure to e-CSE prepared from flavored and nicotine containing e-cigarettes. Endothelial monolayer wound assays revealed that nicotine-containing and flavored e-cigarettes induced impaired angiogenic wound repair of endothelial cell monolayers. Furthermore, vascular endothelial growth factor (VEGF) stimulated wound healing in diabetic mice was impaired by exposure to e-CSEs prepared from nicotine-containing and flavored e-cigarettes. Taken together, our data demonstrate for the first time that flavored and nicotine-containing e-cigarettes induce endothelial dysfunction through excessive ROS production, resulting in decreased NO bioavailability, increased endothelial cell apoptosis, and impairment in angiogenesis and wound healing, especially under diabetic condition. These responses of endothelial dysfunction likely underlie harmful effects of e-cigarettes in endothelial-rich organs, such as heart and lungs. These data also indicate that rigorous regulation on e-cigarette use should be enforced in diabetic and/or surgical patients to avoid severe consequences from impaired angiogenesis/wound healing.

Excess neuropeptides in lung signal through endothelial cells to impair gas exchange.

Although increased neuropeptides are often detected in lungs that exhibit respiratory distress, whether they contribute to the condition is unknown. Here, we show in a mouse model of neuroendocrine cell hyperplasia of infancy, a pediatric disease with increased pulmonary neuroendocrine cells (PNECs), excess PNEC-derived neuropeptides are responsible for pulmonary manifestations including hypoxemia. In mouse postnatal lung, prolonged signaling from elevated neuropeptides such as calcitonin gene-related peptide (CGRP) activate receptors enriched on endothelial cells, leading to reduced cellular junction gene expression, increased endothelium permeability, excess lung fluid, and hypoxemia. Excess fluid and hypoxemia were effectively attenuated by either prevention of PNEC formation, inactivation of CGRP gene, endothelium-specific inactivation of CGRP receptor gene, or treatment with CGRP receptor antagonist. Neuropeptides were increased in human lung diseases with excess fluid such as acute respiratory distress syndrome. Our findings suggest that restricting neuropeptide function may limit fluid and improve gas exchange in these conditions.

Established pulmonary hypertension in rats was reversed by a combination of a HIF-2α antagonist and a p53 agonist.

BACKGROUND AND PURPOSE: Recent studies reported therapeutic effects of monotherapy with either tumour suppressor p53 (p53) agonist or hypoxia-inducible factor 2α (HIF-2α) antagonist for pulmonary hypertension (PH). This study investigated whether a combined treatment of p53 agonist, Nutlin3a, and HIF-2α antagonist, PT2385, would be more effective than monotherapy, based on the cell type-divergent regulation of p53 in pulmonary arterial smooth muscle cells (PASMC) and endothelial cells (PAEC) in patients and animals with PH. EXPERIMENTAL APPROACH: The SU5416/hypoxia-induced PH (SuHx-PH) rat model was used, along with cultured human PASMC and PAEC. Western blot, RT-PCR, siRNA and immunohistochemical methods were used along with echocardiography and studies with isolated pulmonary arteries. KEY RESULTS: Hypoxia-induced proliferation of PASMC is associated with decreased p53, whereas hypoxia-induced PAEC apoptosis is associated with increased p53, via a HIF-2α-dependent mechanism. Combined treatment with Nutlin3a and PT2385 is more effective by simultaneously inhibiting the hypoxia-induced PASMC proliferation and PAEC apoptosis, overcoming the side-effects of monotherapy. These are (i) Nutlin3a exacerbates hypoxia-induced PAEC apoptosis by inducing p53 in PAEC and (ii) PT2385 inhibits PAEC apoptosis because HIF-2α is predominantly expressed in PAEC but lacks direct effects on the hypoxia-induced PASMC proliferation. In rats, combination treatment is more effective than monotherapy in reversing established SuHx-PH, especially in protecting pulmonary arterial vasculature, by normalizing smooth muscle thickening, protecting against endothelial damage and improving function. CONCLUSION AND IMPLICATIONS: Combination treatment confers greater therapeutic efficacy against PH through a selective modulation of p53 and HIF-2α in PASMC and PAEC.

Efficacy and safety of elexacaftor plus tezacaftor plus ivacaftor versus tezacaftor plus ivacaftor in people with cystic fibrosis homozygous for F508del-CFTR: a 24-week, multicentre, randomised, double-blind, active-controlled, phase 3b trial.

BACKGROUND: Elexacaftor plus tezacaftor plus ivacaftor is a triple-combination cystic fibrosis transmembrane conductance regulator (CFTR) modulator regimen shown to be generally safe and efficacious in people with cystic fibrosis aged 12 years or older with at least one F508del-CFTR allele. We aimed to assess the magnitude and durability of the clinical effects of this triple combination regimen in people with cystic fibrosis homozygous for the F508del-CFTR mutation. METHODS: We conducted a multicentre, randomised, double-blind, active-controlled, phase 3b trial of elexacaftor plus tezacaftor plus ivacaftor at 35 medical centres in Australia, Belgium, Germany, and the UK. Eligible participants were those with cystic fibrosis homozygous for the F508del-CFTR mutation, aged 12 years or older with stable disease, and with a percent predicted FEV1 of 40-90% inclusive. After a 4-week run-in period, in which participants received tezacaftor 100 mg orally once daily and ivacaftor 150 mg orally every 12 h, participants were randomly assigned (1:1) to receive 24 weeks of either elexacaftor 200 mg orally once daily plus tezacaftor 100 mg orally once daily plus ivacaftor 150 mg orally every 12 h (elexacaftor plus tezacaftor plus ivacaftor group) or tezacaftor 100 mg orally once daily plus ivacaftor 150 mg orally every 12 h (tezacaftor plus ivacaftor group). Randomisation was stratified by percent predicted FEV1, age at screening visit, and whether the participant was receiving CFTR modulators at the time of the screening visit. Patients, investigators, and sponsor's study execution team were masked to treatment assignment. The primary endpoint was the absolute change in Cystic Fibrosis Questionnaire-Revised (CFQ-R) respiratory domain score from baseline (ie, at the end of the tezacaftor plus ivacaftor run-in period) up to and including week 24. The key secondary endpoint was the absolute change from baseline in percent predicted FEV1 up to and including week 24; other secondary endpoints were the absolute change from baseline in sweat chloride concentrations up to and including week 24, and safety and tolerability. All endpoints were assessed in all randomised patients who had received at least one dose of their assigned regimen. This study is registered with ClinicalTrials.gov, NCT04105972. FINDINGS: Between Oct 3, 2019, and July 24, 2020, 176 participants were enrolled. Following the 4-week tezacaftor plus ivacaftor run-in period, 175 participants were randomly assigned (87 to the elexacaftor plus tezacaftor plus ivacaftor group and 88 to the tezacaftor plus ivacaftor group) and dosed in the treatment period. From baseline up to and including week 24, the mean CFQ-R respiratory domain score increased by 17·1 points (95% CI 14·1 to 20·1) in the elexacaftor plus tezacaftor plus ivacaftor group and by 1·2 points (-1·7 to 4·2) in the tezacaftor plus ivacaftor group (least squares mean treatment difference 15·9 points [95% CI 11·7 to 20·1], p<0·0001), the mean percent predicted FEV1 increased by 11·2 percentage points (95% CI 9·8 to 12·6) in the elexacaftor plus tezacaftor plus ivacaftor group and by 1·0 percentage points (-0·4 to 2·4) in the tezacaftor plus ivacaftor group (least squares mean treatment difference 10·2 percentage points [8·2 to 12·1], p<0·0001), and the mean sweat chloride concentration decreased by 46·2 mmol/L (95% CI 43·7 to 48·7) in the elexacaftor plus tezacaftor plus ivacaftor group and by 3·4 mmol/L (1·0 to 5·8) in the tezacaftor plus ivacaftor group (least squares mean treatment difference -42·8 mmol/L [-46·2 to -39·3], nominal p<0·0001). Most participants (70 [80%] in the elexacaftor plus tezacaftor plus ivacaftor group and 74 [84%] in the tezacaftor plus ivacaftor group) had adverse events that were mild or moderate in severity; serious adverse events occurred in five (6%) of 87 participants in the elexacaftor plus tezacaftor plus ivacaftor group and 14 (16%) of 88 participants in the tezacaftor plus ivacaftor group. One (1%) participant in the elexacaftor plus tezacaftor plus ivacaftor group discontinued treatment due to an adverse event of anxiety and depression. Two (2%) participants in the tezacaftor plus ivacaftor group discontinued treatment due to adverse events of psychotic disorder (n=1) and obsessive-compulsive disorder (n=1). INTERPRETATION: The elexacaftor plus tezacaftor plus ivacaftor regimen was safe and well tolerated, and led to significant and clinically meaningful improvements in respiratory-related quality of life and lung function, as well as improved CFTR function, changes that were durable over 24 weeks and superior to those seen with tezacaftor plus ivacaftor in this patient population. FUNDING: Vertex Pharmaceuticals.

Real-world safety and effectiveness of ledipasvir/sofosbuvir for the treatment of chronic hepatitis C virus genotype 1 in Japan.

As patients with chronic hepatitis C virus (HCV) tend to be older and/or have advanced liver disease in Japan, real-world data are needed to evaluate safe and effective treatment options. The study aim was to assess safety and effectiveness of ledipasvir/sofosbuvir (LDV/SOF) in a real-world cohort of Japanese patients with HCV genotype (GT) 1 infection overall and by patient subgroups: elderly, compensated cirrhotic, advanced fibrotic and those with hepatocellular carcinoma (HCC). A large prospective observational study was conducted, enrolling adult patients treated for HCV GT1 infection with LDV/SOF at clinical sites across Japan. Patients were observed for safety outcomes during and 4 weeks after treatment, and for sustained virologic response at 12-weeks post-treatment (SVR12). Incidence rates (IRs) of adverse drug reactions (ADRs) and serious ADRs (SADRs) and SVR12 rates were assessed overall and by subgroups. ADR and SADR IRs were low (2.26 and 0.17 per 100 person-months, respectively) and did not significantly differ in elderly patients or those with presence of compensated cirrhosis, worsening fibrosis or HCC. SVR12 rates were high overall (98.5%) and across subgroups investigated (≥94%), including patients who were elderly (98.2%), treatment-experienced (97.6%), advanced fibrotic (≥95.8%), had existing NS5A resistance-associated substitutions reported pre-treatment (95.0%), compensated cirrhosis (95.7%), HCC (94.0%) and other chronic liver diseases (96.1%). In this large, real-world observational study of Japanese patients with HCV GT1 infection, LDV/SOF treatment resulted in low incidence of adverse events, with high real-world effectiveness, even among patients with potentially higher risks of adverse safety outcomes and treatment failure.

Revisiting the mechanism of hypoxic pulmonary vasoconstriction using isolated perfused/ventilated mouse lung.

Hypoxic Pulmonary Vasoconstriction (HPV) is an important physiological mechanism of the lungs that matches perfusion to ventilation thus maximizing O2 saturation of the venous blood within the lungs. This study emphasizes on principal pathways in the initiation and modulation of hypoxic pulmonary vasoconstriction with a primary focus on the role of Ca2+ signaling and Ca2+ influx pathways in hypoxic pulmonary vasoconstriction. We used an ex vivo model, isolated perfused/ventilated mouse lung to evaluate hypoxic pulmonary vasoconstriction. Alveolar hypoxia (utilizing a mini ventilator) rapidly and reversibly increased pulmonary arterial pressure due to hypoxic pulmonary vasoconstriction in the isolated perfused/ventilated lung. By applying specific inhibitors for different membrane receptors and ion channels through intrapulmonary perfusion solution in isolated lung, we were able to define the targeted receptors and channels that regulate hypoxic pulmonary vasoconstriction. We show that extracellular Ca2+ or Ca2+ influx through various Ca2+-permeable channels in the plasma membrane is required for hypoxic pulmonary vasoconstriction. Removal of extracellular Ca2+ abolished hypoxic pulmonary vasoconstriction, while blockade of L-type voltage-dependent Ca2+ channels (with nifedipine), non-selective cation channels (with 30 µM SKF-96365), and TRPC6/TRPV1 channels (with 1 µM SAR-7334 and 30 µM capsazepine, respectively) significantly and reversibly inhibited hypoxic pulmonary vasoconstriction. Furthermore, blockers of Ca2+-sensing receptors (by 30 µM NPS2143, an allosteric Ca2+-sensing receptors inhibitor) and Notch (by 30 µM DAPT, a γ-secretase inhibitor) also attenuated hypoxic pulmonary vasoconstriction. These data indicate that Ca2+ influx in pulmonary arterial smooth muscle cells through voltage-dependent, receptor-operated, and store-operated Ca2+ entry pathways all contribute to initiation of hypoxic pulmonary vasoconstriction. The extracellular Ca2+-mediated activation of Ca2+-sensing receptors and the cell-cell interaction via Notch ligands and receptors contribute to the regulation of hypoxic pulmonary vasoconstriction.

MDM2-Mediated Ubiquitination of Angiotensin-Converting Enzyme 2 Contributes to the Development of Pulmonary Arterial Hypertension.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) converts angiotensin II, a potent vasoconstrictor, to angiotensin-(1-7) and is also a membrane protein that enables coronavirus disease 2019 (COVID-19) infectivity. AMP-activated protein kinase (AMPK) phosphorylation of ACE2 enhances ACE2 stability. This mode of posttranslational modification of ACE2 in vascular endothelial cells is causative of a pulmonary hypertension (PH)-protective phenotype. The oncoprotein MDM2 (murine double minute 2) is an E3 ligase that ubiquitinates its substrates to cause their degradation. In this study, we investigated whether MDM2 is involved in the posttranslational modification of ACE2 through its ubiquitination of ACE2, and whether an AMPK and MDM2 crosstalk regulates the pathogenesis of PH. METHODS: Bioinformatic analyses were used to explore E3 ligase that ubiquitinates ACE2. Cultured endothelial cells, mouse models, and specimens from patients with idiopathic pulmonary arterial hypertension were used to investigate the crosstalk between AMPK and MDM2 in regulating ACE2 phosphorylation and ubiquitination in the context of PH. RESULTS: Levels of MDM2 were increased and those of ACE2 decreased in lung tissues or pulmonary arterial endothelial cells from patients with idiopathic pulmonary arterial hypertension and rodent models of experimental PH. MDM2 inhibition by JNJ-165 reversed the SU5416/hypoxia-induced PH in C57BL/6 mice. ACE2-S680L mice (dephosphorylation at S680) showed PH susceptibility, and ectopic expression of ACE2-S680L/K788R (deubiquitination at K788) reduced experimental PH. Moreover, ACE2-K788R overexpression in mice with endothelial cell-specific AMPKα2 knockout mitigated PH. CONCLUSIONS: Maladapted posttranslational modification (phosphorylation and ubiquitination) of ACE2 at Ser-680 and Lys-788 is involved in the pathogenesis of pulmonary arterial hypertension and experimental PH. Thus, a combined intervention of AMPK and MDM2 in the pulmonary endothelium might be therapeutically effective in PH treatment.

Overexpression of p53 due to excess protein O-GlcNAcylation is associated with coronary microvascular disease in type 2 diabetes.

AIMS: We previously reported that increased protein O-GlcNAcylation in diabetic mice led to vascular rarefaction in the heart. In this study, we aimed to investigate whether and how coronary endothelial cell (EC) apoptosis is enhanced by protein O-GlcNAcylation and thus induces coronary microvascular disease (CMD) and subsequent cardiac dysfunction in diabetes. We hypothesize that excessive protein O-GlcNAcylation increases p53 that leads to CMD and reduced cardiac contractility. METHODS AND RESULTS: We conducted in vivo functional experiments in control mice, TALLYHO/Jng (TH) mice, a polygenic type 2 diabetic (T2D) model, and EC-specific O-GlcNAcase (OGA, an enzyme that catalyzes the removal of O-GlcNAc from proteins)-overexpressing TH mice, as well as in vitro experiments in isolated ECs from these mice. TH mice exhibited a significant increase in coronary EC apoptosis and reduction of coronary flow velocity reserve (CFVR), an assessment of coronary microvascular function, in comparison to wild-type mice. The decreased CFVR, due at least partially to EC apoptosis, was associated with decreased cardiac contractility in TH mice. Western blot experiments showed that p53 protein level was significantly higher in coronary ECs from TH mice and T2D patients than in control ECs. High glucose treatment also increased p53 protein level in control ECs. Furthermore, overexpression of OGA decreased protein O-GlcNAcylation and down-regulated p53 in coronary ECs, and conferred a protective effect on cardiac function in TH mice. Inhibition of p53 with pifithrin-α attenuated coronary EC apoptosis and restored CFVR and cardiac contractility in TH mice. CONCLUSIONS: The data from this study indicate that inhibition of p53 or down-regulation of p53 by OGA overexpression attenuates coronary EC apoptosis and improves CFVR and cardiac function in diabetes. Lowering coronary endothelial p53 levels via OGA overexpression could be a potential therapeutic approach for CMD in diabetes.

Transplantation of Mesenchymal Stem Cells Attenuates Pulmonary Hypertension by Normalizing the Endothelial-to-Mesenchymal Transition.

For decades, stem cell therapies for pulmonary hypertension (PH) have progressed from laboratory hypothesis to clinical practice. Promising preclinical investigations have laid both a theoretical and practical foundation for clinical application of mesenchymal stem cells (MSCs) for PH therapy. However, the underlying mechanisms are still poorly understood. We sought to study the effects and mechanisms of MSCs on the treatment of PH. For in vivo experiments, the transplanted GFP+ MSCs were traced at different time points in the lung tissue of a chronic hypoxia-induced PH (CHPH) rat model. The effects of MSCs on PH pathogenesis were evaluated in both CHPH and sugen hypoxia-induced PH models. For in vitro experiments, primary pulmonary microvascular endothelial cells were cultured and treated with the MSC conditioned medium. The specific markers of endothelial-to-mesenchymal transition (EndMT) and cell migration properties were measured. MSCs decreased pulmonary arterial pressure and ameliorated the collagen deposition, and reduced the thickening and muscularization in both CHPH and sugen hypoxia-induced PH rat models. Then, MSCs significantly attenuated the hypoxia-induced EndMT in both the lungs of PH models and primary cultured rat pulmonary microvascular endothelial cells, as reflected by increased mesenchymal cell markers (fibronectin 1 and vimentin) and decreased endothelial cell markers (vascular endothelial cadherin and platelet endothelial cell adhesion molecule-1). Moreover, MSCs also markedly inhibited the protein expression and degradation of hypoxia-inducible factor-2α, which is known to trigger EndMT progression. Our data suggest that MSCs successfully prevent PH by ameliorating pulmonary vascular remodeling, inflammation, and EndMT. Transplantation of MSCs could potentially be a powerful therapeutic approach against PH.

Divergent changes of p53 in pulmonary arterial endothelial and smooth muscle cells involved in the development of pulmonary hypertension.

The tumor-suppressive role of p53, a transcription factor that regulates the expression of many genes, has been linked to cell cycle arrest, apoptosis, and senescence. The noncanonical function or the pathogenic role of p53 has more recently been implicated in pulmonary vascular disease. We previously reported that rapid nuclear accumulation of hypoxia-inducible factor (HIF)-1α in pulmonary arterial smooth muscle cells (PASMCs) upregulates transient receptor potential channels and enhances Ca2+ entry to increase cytosolic Ca2+ concentration ([Ca2+]cyt). Also, we observed differences in HIF-1α/2α expression in PASMCs and pulmonary arterial endothelial cells (PAECs). Here we report that p53 is increased in PAECs, but decreased in PASMCs, isolated from mice with hypoxia-induced pulmonary hypertension (PH) and rats with monocrotaline (MCT)-induced PH (MCT-PH). The increased p53 in PAECs from rats with MCT-PH is associated with an increased ratio of Bax/Bcl-2, while the decreased p53 in PASMCs is associated with an increased HIF-1α. Furthermore, p53 is downregulated in PASMCs isolated from patients with idiopathic pulmonary arterial hypertension compared with PASMCs from normal subjects. Overexpression of p53 in normal PASMCs inhibits store-operated Ca2+ entry (SOCE) induced by passive depletion of intracellularly stored Ca2+ in the sarcoplasmic reticulum, while downregulation of p53 enhances SOCE. These data indicate that differentially regulated expression of p53 and HIF-1α/2α in PASMCs and PAECs and the cross talk between p53 and HIF-1α/2α in PASMCs and PAECs may play an important role in the development of PH via, at least in part, induction of PAEC apoptosis and PASMC proliferation.

Structure-Function Analysis of the Bifunctional CcsBA Heme Exporter and Cytochrome c Synthetase.

Although intracellular heme trafficking must occur for heme protein assembly, only a few heme transporters have been unequivocally discovered and nothing is known about their structure or mechanisms. Cytochrome c biogenesis in prokaryotes requires the transport of heme from inside to outside for stereospecific attachment to cytochrome c via two thioether bonds (at CXXCH). The CcsBA integral membrane protein was shown to transport and attach heme (and thus is a cytochrome c synthetase), but the structure and mechanisms underlying these two activities are poorly understood. We employed a new cysteine/heme crosslinking tool that traps endogenous heme in heme binding sites. We combined these data with a comprehensive imidazole correction approach (for heme ligand interrogation) to map heme binding sites. Results illuminate the process of heme transfer through the membrane to an external binding site (called the WWD domain). Using meta-genomic data (GREMLIN) and Rosetta modeling programs, a structural model of the transmembrane (TM) regions in CcsBA were determined. The heme mapping data were then incorporated to model the TM heme binding site (with TM-His1 and TM-His2 as ligands) and the external heme binding WWD domain (with P-His1 and P-His2 as ligands). Other periplasmic structure/function studies facilitated modeling of the full CcsBA protein as a framework for understanding the mechanisms. Mechanisms are proposed for heme transport from TM-His to WWD/P-His and subsequent stereospecific attachment of heme. A ligand exchange of the P-His1 for histidine of CXXCH at the synthetase active site is suggested.IMPORTANCE The movement or trafficking of heme is critical for cellular functions (e.g., oxygen transport and energy production); however, intracellular heme is tightly regulated due to its inherent cytotoxicity. These factors, combined with the transient nature of transport, have resulted in a lack of direct knowledge on the mechanisms of heme binding and trafficking. Here, we used the cytochrome c biogenesis system II pathway as a model to study heme trafficking. System II is composed of two integral membrane proteins (CcsBA) which function to transport heme across the membrane and stereospecifically position it for covalent attachment to apocytochrome c We mapped two heme binding domains in CcsBA and suggest a path for heme trafficking. These data, in combination with metagenomic coevolution data, are used to determine a structural model of CcsBA, leading to increased understanding of the mechanisms for heme transport and the cytochrome c synthetase function of CcsBA.

Bone Marrow-Derived Endothelial Progenitor Cells Contribute to Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats via Inhibition of Store-Operated Ca2+ Channels.

PURPOSE: This study aimed to explore whether bone marrow- (BM-) derived endothelial progenitor cells (EPCs) contributing to monocrotaline- (MCT-) induced pulmonary arterial hypertension (PAH) in rats via modulating store-operated Ca2+ channels (SOC). METHODS: Sprague Dawley (SD) rats were assigned into MCT group (n = 30) and control group (n = 20). Rats in MCT group were subcutaneously administered with 60 mg/kg MCT solution, and rats in control group were injected with equal amount of vehicle. After 3 weeks of treatment, right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) of two groups were measured, and BM-derived EPCs were isolated. Immunochemistry identification and vasculogenesis detection of EPCs were then performed. [Ca2+]cyt measurement was performed to detect store-operated calcium entry (SOCE) in two groups, followed by determination of Orai and canonical transient receptor potential (TRPC) channels expression. RESULTS: After 3 weeks of treatment, there were significant increases in RVSP and RVHI in MCT group compared with control group, indicating that MCT successfully induced PAH in rats. Moreover, the SOCE ([Ca2+]cyt rise) in BM-derived EPCs of MCT group was lower than that of control group. Furthermore, the expression levels of Orai3, TRPC1, TRPC3, and TRPC6 in BM-derived EPCs were decreased in MCT group in comparison with control group. CONCLUSIONS: The SOC activities were inhibited in BM-derived EPCs of MCT-treated rats. These results may be associated with the depressed expression of Orai3, TRPC1, TRPC3, and TRPC6, which are major mediators of SOC.

Hypoxia selectively upregulates cation channels and increases cytosolic [Ca2+] in pulmonary, but not coronary, arterial smooth muscle cells.

Ca2+ signaling, particularly the mechanism via store-operated Ca2+ entry (SOCE) and receptor-operated Ca2+ entry (ROCE), plays a critical role in the development of acute hypoxia-induced pulmonary vasoconstriction and chronic hypoxia-induced pulmonary hypertension. This study aimed to test the hypothesis that chronic hypoxia differentially regulates the expression of proteins that mediate SOCE and ROCE [stromal interacting molecule (STIM), Orai, and canonical transient receptor potential channel TRPC6] in pulmonary (PASMC) and coronary (CASMC) artery smooth muscle cells. The resting cytosolic [Ca2+] ([Ca2+]cyt) and the stored [Ca2+] in the sarcoplasmic reticulum were not different in CASMC and PASMC. Seahorse measurement showed a similar level of mitochondrial bioenergetics (basal respiration and ATP production) between CASMC and PASMC. Glycolysis was significantly higher in PASMC than in CASMC. The amplitudes of cyclopiazonic acid-induced SOCE and OAG-induced ROCE in CASMC are slightly, but significantly, greater than in PASMC. The frequency and the area under the curve of Ca2+ oscillations induced by ATP and histamine were also larger in CASMC than in PASMC. Na+/Ca2+ exchanger-mediated increases in [Ca2+]cyt did not differ significantly between CASMC and PASMC. The basal protein expression levels of STIM1/2, Orai1/2, and TRPC6 were higher in CASMC than in PASMC, but hypoxia (3% O2 for 72 h) significantly upregulated protein expression levels of STIM1/STIM2, Orai1/Orai2, and TRPC6 and increased the resting [Ca2+]cyt only in PASMC, but not in CASMC. The different response of essential components of store-operated and receptor-operated Ca2+ channels to hypoxia is a unique intrinsic property of PASMC, which is likely one of the important explanations why hypoxia causes pulmonary vasoconstriction and induces pulmonary vascular remodeling, but causes coronary vasodilation.

LPS-induced Acute Lung Injury Involves NF-κB-mediated Downregulation of SOX18.

One of the early events in the progression of LPS-mediated acute lung injury in mice is the disruption of the pulmonary endothelial barrier resulting in lung edema. However, the molecular mechanisms by which the endothelial barrier becomes compromised remain unresolved. The SRY (sex-determining region on the Y chromosome)-related high-mobility group box (Sox) group F family member, SOX18, is a barrier-protective protein through its ability to increase the expression of the tight junction protein CLDN5. Thus, the purpose of this study was to determine if downregulation of the SOX18-CLDN5 axis plays a role in the pulmonary endothelial barrier disruption associated with LPS exposure. Our data indicate that both SOX18 and CLDN5 expression is decreased in two models of in vivo LPS exposure (intraperitoneal, intratracheal). A similar downregulation was observed in cultured human lung microvascular endothelial cells (HLMVECs) exposed to LPS. SOX18 overexpression in HLMVECs or in the mouse lung attenuated the LPS-mediated vascular barrier disruption. Conversely, reduced CLDN5 expression (siRNA) reduced the HLMVEC barrier-protective effects of SOX18 overexpression. The mechanism by which LPS decreases SOX18 expression was identified as transcriptional repression through binding of NF-κB (p65) to a SOX18 promoter sequence located between -1,082 and -1,073 bp with peroxynitrite contributing to LPS-mediated NF-κB activation. We conclude that NF-κB-dependent decreases in the SOX18-CLDN5 axis are essentially involved in the disruption of human endothelial cell barrier integrity associated with LPS-mediated acute lung injury.

Hyper-activation of pp60Src limits nitric oxide signaling by increasing asymmetric dimethylarginine levels during acute lung injury.

The molecular mechanisms by which the endothelial barrier becomes compromised during lipopolysaccharide (LPS) mediated acute lung injury (ALI) are still unresolved. We have previously reported that the disruption of the endothelial barrier is due, at least in part, to the uncoupling of endothelial nitric oxide synthase (eNOS) and increased peroxynitrite-mediated nitration of RhoA. The purpose of this study was to elucidate the molecular mechanisms by which LPS induces eNOS uncoupling during ALI. Exposure of pulmonary endothelial cells (PAEC) to LPS increased pp60Src activity and this correlated with an increase in nitric oxide (NO) production, but also an increase in NOS derived superoxide, peroxynitrite formation and 3-nitrotyrosine (3-NT) levels. These effects could be simulated by the over-expression of a constitutively active pp60Src (Y527FSrc) mutant and attenuated by over-expression of dominant negative pp60Src mutant or reducing pp60Src expression. LPS induces both RhoA nitration and endothelial barrier disruption and these events were attenuated when pp60Src expression was reduced. Endothelial NOS uncoupling correlated with an increase in the levels of asymmetric dimethylarginine (ADMA) in both LPS exposed and Y527FSrc over-expressing PAEC. The effects in PAEC were also recapitulated when we transiently over-expressed Y527FSrc in the mouse lung. Finally, we found that the pp60-Src-mediated decrease in DDAH activity was mediated by the phosphorylation of DDAH II at Y207 and that a Y207F mutant DDAH II was resistant to pp60Src-mediated inhibition. We conclude that pp60Src can directly inhibit DDAH II and this is involved in the increased ADMA levels that enhance eNOS uncoupling during the development of ALI.