Mouse Pulmonary Endothelial Cells Research Articles

Investigation into the role of H2-Ab1 in vascular remodeling in pulmonary arterial hypertension via Bioinformatics

BackgroundPulmonary arterial hypertension (PAH) is a progressive disease of vascular remodeling characterized by persistent pulmonary arterial pressure elevation, which can lead to right heart failure and premature death. Given the complex pathogenesis and poor prognosis of PAH, the identification and investigation of biomarkers become increasingly critical for advancing further understanding of the disease.MethodsPAH-related datasets, GSE49114, GSE180169 and GSE154959, were downloaded from the publicly available GEO database. By performing WGCNA on the GSE49114 dataset, a total of 906 PAH-related key module genes were screened out. By carrying out differential analysis on the GSE180169 dataset, a total of 576 differentially expressed genes were identified. Additionally, the GSE154959 single-cell sequencing dataset was also subjected to differential analysis, leading to the identification of 34 DEGs within endothelial cells. By taking intersection of the above three groups of DEGs, five PAH-related hub genes were screened out, namely Plvap, Cyp4b1, Foxf1, H2-Ab1, and H2-Eb1, among which H2-Ab1 was selected for subsequent experiments.ResultsA SuHx mouse model was prepared using the SU5416/hypoxia method, and the successful construction of the model was evaluated through Hematoxylin-Eosin staining, hemodynamic detection, fulton index, and Western Blot (WB). The results of WB and qRT-PCR demonstrated a significant upregulation of H2-Ab1 expression in SuHx mice. Consistent with the results of bioinformatics analysis, a time-dependent increase was observed in H2-Ab1 expression in hypoxia-treated mouse pulmonary artery endothelial cells (PAECs). To investigate whether H2-Ab1 affects the development and progression of PAH, we knocked down H2-Ab1 expression in PAECs, and found that its knockdown inhibited the viability, adhesion, migration, and angiogenesis, while concurrently promoted the apoptosis of PAECs.ConclusionH2-Ab1 could regulate the proliferation, apoptosis, adhesion, migration, and angiogenesis of PAECs.

Dexmedetomidine alleviates pulmonary ischemia-reperfusion injury through modulating the miR-21-5p/Nr4a1 signaling pathway.

This study aims to investigate the protection of dexmedetomidine (Dex) against pulmonary ischemia-reperfusion injury (PIRI) in the mouse model and reveal the mechanism in hypoxia reoxygenation (H/R)-induced mouse pulmonary vascular endothelial cells (MPVECs). The lung wet-to-dry weight ratio, histopathological features, and malondialdehyde (MDA) concentrations were measured. The H/R-induced MPVECs were exposed to Dex, and the cell viability, cell apoptosis and protein expressions were assessed by the Cell Counting Kit-8 (CCK8) assay, flow cytometry and western blot, respectively. In addition, the regulatory relationship between miR-21-5p and orphan nuclear receptor 4A1 (Nr4a1) was revealed by several assays, including the dual-luciferase reporter assay, real-time quantitative polymerase chain reaction (RT-qPCR) and western blot. We found that the Dex treatment significantly alleviated pulmonary injury and decreased the level of MDA and wet/dry weight ratio in PIRI mice. Dex treatment also increased cell viability, reduced apoptotic ratio and downregulated expression levels of Cleaved Caspase-3 and Cleaved Caspase-9 in H/R induced MPVECs. Furthermore, the expression of miR-21-5p was upregulated, while Nr4a1 was downregulated by Dex in a concentration-dependent manner in H/R induced MPVECs. Moreover, Nr4a1 was verified as a target of miR-497-5p. Overexpression of Nr4a1 could reverse the protective effects of Dex on alleviating H/R-induced injury in MPVECs. Taken together, Dex treatment attenuated ischemia-reperfusion induced pulmonary injury through modulating the miR-21-5p/Nr4a1 signaling pathway.

Chronic Hypoxia Decreases Endothelial Connexin 40, Attenuates Endothelium-Dependent Hyperpolarization-Mediated Relaxation in Small Distal Pulmonary Arteries, and Leads to Pulmonary Hypertension.

BackgroundAbnormal endothelial function in the lungs is implicated in the development of pulmonary hypertension; however, there is little information about the difference of endothelial function between small distal pulmonary artery (PA) and large proximal PA and their contribution to the development of pulmonary hypertension. Herein, we investigate endothelium‐dependent relaxation in different orders of PAs and examine the molecular mechanisms by which chronic hypoxia attenuates endothelium‐dependent pulmonary vasodilation, leading to pulmonary hypertension.Methods and ResultsEndothelium‐dependent relaxation in large proximal PAs (second order) was primarily caused by releasing NO from the endothelium, whereas endothelium‐dependent hyperpolarization (EDH)–mediated vasodilation was prominent in small distal PAs (fourth–fifth order). Chronic hypoxia abolished EDH‐mediated relaxation in small distal PAs without affecting smooth muscle–dependent relaxation. RNA‐sequencing data revealed that, among genes related to EDH, the levels of Cx37, Cx40, Cx43, and IK were altered in mouse pulmonary endothelial cells isolated from chronically hypoxic mice in comparison to mouse pulmonary endothelial cells from normoxic control mice. The protein levels were significantly lower for connexin 40 (Cx40) and higher for connexin 37 in mouse pulmonary endothelial cells from hypoxic mice than normoxic mice. Cx40 knockout mice exhibited significant attenuation of EDH‐mediated relaxation and marked increase in right ventricular systolic pressure. Interestingly, chronic hypoxia led to a further increase in right ventricular systolic pressure in Cx40 knockout mice without altering EDH‐mediated relaxation. Furthermore, overexpression of Cx40 significantly decreased right ventricular systolic pressure in chronically hypoxic mice.ConclusionsThese data suggest that chronic hypoxia‐induced downregulation of endothelial Cx40 results in impaired EDH‐mediated relaxation in small distal PAs and contributes to the development of pulmonary hypertension.

Endothelial BMPR2 Loss Drives a Proliferative Response to BMP (Bone Morphogenetic Protein) 9 via Prolonged Canonical Signaling.

Pulmonary arterial hypertension is a disease of proliferative vascular occlusion that is strongly linked to mutations in BMPR2-the gene encoding the BMPR-II (BMP [bone morphogenetic protein] type II receptor). The endothelial-selective BMPR-II ligand, BMP9, reverses disease in animal models of pulmonary arterial hypertension and suppresses the proliferation of healthy endothelial cells. However, the impact of BMPR2 loss on the antiproliferative actions of BMP9 has yet to be assessed. Approach and Results: BMP9 suppressed proliferation in blood outgrowth endothelial cells from healthy control subjects but increased proliferation in blood outgrowth endothelial cells from pulmonary arterial hypertension patients with BMPR2 mutations. This shift from growth suppression to enhanced proliferation was recapitulated in control human pulmonary artery endothelial cells following siRNA-mediated BMPR2 silencing, as well as in mouse pulmonary endothelial cells isolated from endothelial-conditional Bmpr2 knockout mice (Bmpr2EC-/-). BMP9-induced proliferation was not attributable to altered metabolic activity or elevated TGFβ (transforming growth factor beta) signaling but was linked to the prolonged induction of the canonical BMP target ID1 in the context of BMPR2 loss. In vivo, daily BMP9 administration to neonatal mice impaired both retinal and lung vascular patterning in control mice (Bmpr2EC+/+) but had no measurable effect on mice bearing a heterozygous endothelial Bmpr2 deletion (Bmpr2EC+/-) and caused excessive angiogenesis in both vascular beds for Bmpr2EC-/- mice. BMPR2 loss reverses the endothelial response to BMP9, causing enhanced proliferation. This finding has potential implications for the proposed translation of BMP9 as a treatment for pulmonary arterial hypertension and suggests the need for focused patient selection in clinical trials.

LncRNA Gm16410 regulates PM2.5-induced lung Endothelial-Mesenchymal Transition via the TGF-β1/Smad3/p-Smad3 pathway

Exposure to PM2.5 can cause serious harm to the respiratory system. Until now, although many toxicological studies have shown that pulmonary fibrosis can be caused by long-term PM2.5 exposure, there is no evidence that Endothelial–Mesenchymal Transition (EndMT) can trigger the process of pulmonary fibrosis after exposure. LncRNAs are a class of non-coding RNAs detected in mammalian cells. Nevertheless, researchers have not found whether lncRNAs participate in PM2.5 induced EndMT during pathophysiological duration. The Balb/c mouse model was exposed to PM2.5 for 4 months by dynamic intoxication. The levels of specific endothelial and mesenchymal markers were evaluated by molecular biology experiments to elucidate the mechanisms of EndMT induced by PM2.5 in lung tissues. LncRNA microarray analysis of the established mouse model of PM2.5 exposure was performed. Based on a bioinformatics analysis and RT-qPCR analysis, lncRNA Gm16410 attracted our attention. The change of lncRNA Gm16410 in mouse pulmonary vascular endothelial cells (MHCs) exposed to PM2.5 was verified, and the mechanism of lncRNA Gm16410 in EndMT was discussed. The changes of cell function were evaluated by cell migration and proliferation experiments. The molecular biology experiments proved that PM2.5 induced EndMT by activating the TGF-β1/Smad3/p-Smad3 pathway in vitro. The relationship of EndMT and lncRNA Gm16410 was verified in mouse lung tissues and MHC cells by PM2.5 exposure. The involvement of lncRNA Gm16410 in PM2.5-induced EndMT highlights the potential of lncRNA to promote pulmonary fibrosis under environmental pollution.

Chronic Hypoxia Attenuates Endothelium‐dependent Hyperpolarization‐induced Vascular Relaxation in Pulmonary Artery and Leads to Pulmonary Hypertension

Endothelial cell dysfunction is implicated in the development and progression of many cardiovascular diseases including pulmonary hypertension (PH). It has been well documented that endothelium‐dependent relaxation (EDR) is attenuated due to decreased NO bioavailability in pulmonary artery (PA) of PH model animals; however there is few report investigating the role of endothelium‐dependent hyperpolarization (EDH)‐mediated vascular relaxation in PH. In this study, we examined the role of chronic hypoxia on EDH‐induced pulmonary arterial relaxation with a special focus on connexin 40 (Cx40). Connexins are a group of membrane proteins that form gap junctions between the cells and serve as a tunnel during electrical propagation (e.g., hyperpolarization). Cx40 is predominantly expressed in vascular endothelial cells (ECs). We first examined vasorelaxant properties in the different size of PAs dissected from wild type (Wt) and Cx40 knockout (KO) mice. There was no difference of acetylcholine (ACh)‐induced relaxation (i.e., EDR) in second order of PAs between Wt mice and Cx40 KO mice, while EDR was significantly attenuated in the fourth order of PAs of Cx40 KO mice compared to the Wt mice. In the second order of PAs, we did not observe EDH‐dependent vascular relaxation in both Wt and Cx40 KO mice. In the fourth order of PAs, strong EDH‐dependent relaxation was observed in Wt mice and it was significantly reduced in Cx40 KO mice. Cx40 KO mice exhibited a significant increase in right ventricle systolic pressure (RVSP) compared to Wt mice. Chronic hypoxia (10% O2, 4 weeks) increased RVSP in both Wt and Cx40 KO mice and Cx40 KO mice exposed to hypoxia exhibited significantly higher RVSP than Wt mice exposed to hypoxia. Furthermore, chronic hypoxia attenuated EDR and EDH‐dependent relaxation in the fourth order of PAs from Wt mice; however, there was no difference of EDR and EDH‐dependent relaxation in the fourth order of PAs in Cx40 KO mice. Mouse pulmonary endothelial cells isolated from hypoxia‐exposed Wt mice exhibited significant decrease in Cx40 protein level compared to Wt mice exposed to normoxia. These data suggest that chronic hypoxia decreases Cx40 protein expression and attenuates EDH in small PAs that subsequently leads to increase in pulmonary arterial resistance and develops pulmonary hypertension.Support or Funding InformationNIH R01HL115578This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hypoxia-induced pulmonary hypertension in type 2 diabetic mice.

Hypoxia-induced pulmonary hypertension (HPH) is a progressive disease that is mainly caused by chronic exposure to high altitude, chronic obstructive lung disease, and obstructive sleep apnea. The increased pulmonary vascular resistance and increased pulmonary arterial pressure result in increased right ventricular afterload, leading to right heart failure and increased morbidity. There are several clinical reports suggesting a link between PH and diabetes, insulin resistance, or obesity; however, it is unclear whether HPH is associated with diabetes as a progressive complication in diabetes. The major goal of this study is to examine the effect of diabetic “preconditioning” or priming effect on the progression of HPH and define the molecular mechanisms that explain the link between diabetes and HPH. Our data show that HPH is significantly enhanced in diabetic mice, while endothelium-dependent relaxation in pulmonary arteries is significantly attenuated in chronically hypoxic diabetic mice (DH). In addition, we demonstrate that mouse pulmonary endothelial cells (MPECs) isolated from DH mice exhibit a significant increase in mitochondrial reactive oxygen species (ROS) concentration and decreased SOD2 protein expression. Finally, scavenging mitochondrial ROS by mitoTempol restores endothelium-dependent relaxation in pulmonary arteries that is attenuated in DH mice. These data suggest that excessive mitochondrial ROS production in diabetic MPECs leads to the development of severe HPH in diabetic mice exposed to hypoxia.

Mesenchymal Stem Cells Alleviate LPS-Induced Acute Lung Injury in Mice by MiR-142a-5p-Controlled Pulmonary Endothelial Cell Autophagy

Background/Aims: Damages of pulmonary endothelial cells (PECs) represent a critical pathological process during acute lung injury (ALI), and precede pulmonary epithelial cell injury, and long-term lung dysfunction. Transplantation of mesenchymal stem cells (MSCs) has proven therapeutic effects on ALI, whereas the underlying mechanisms remain ill-defined. Method: We transplanted MSCs in mice and then induced ALI using Lipopolysaccharides (LPS). We analyzed the changes in permeability index and lung histology. Mouse PECs were isolated by flow cytometry based on CD31 expression and then analyzed for autophagy-associated factors LC3 and Beclin-1 by Western blot. Beclin-1 mRNA was determined by RT-qPCR. In vitro, we performed bioinformatics analyses to identify the MSCs-regulated miRNAs that target Beclin-1, and confirmed that the binding was functional by 3'-UTR luciferase reporter assay. Results: We found that MSCs transplantation significantly reduced the severity of LPS-induced ALI in mice. MSCs increased autophagy of PECs to promote PEC survival. MSCs increased Beclin-1 protein but not mRNA. MiR-142a-5p was found to target the 3'-UTR of Beclin-1 mRNA to inhibit its protein translation in PECs. MSCs reduced the levels of miR-142a-5p in PECs from LPS-treated mice. Conclusion: MSCs may alleviate LPS-ALI through downregulation of miR-142a-5p, which allows PECs to increase Beclin-1-mediated cell autophagy.

Expression of mutant bone morphogenetic protein receptor II worsens pulmonary hypertension secondary to pulmonary fibrosis.

Pulmonary fibrosis is often complicated by pulmonary hypertension (PH), and previous studies have shown a potential link between bone morphogenetic protein receptor II (BMPR2) and PH secondary to pulmonary fibrosis. We exposed transgenic mice expressing mutant BMPR2 and control mice to repetitive intraperitoneal injections of bleomycin for 4 weeks. The duration of transgene activation was too short for mutant BMPR2 mice to develop spontaneous PH. Mutant BMPR2 mice had increased right ventricular systolic pressure compared to control mice, without differences in pulmonary fibrosis. We found increased hypoxia-inducible factor (HIF)1-α stabilization in lungs of mutant-BMPR2-expressing mice compared to controls following bleomycin treatment. In addition, expression of the hypoxia response element protein connective tissue growth factor was increased in transgenic mice as well as in a human pulmonary microvascular endothelial cell line expressing mutant BMPR2. In mouse pulmonary vascular endothelial cells, mutant BMPR2 expression resulted in increased HIF1-α and reactive oxygen species production following exposure to hypoxia, both of which were attenuated with the antioxidant TEMPOL. These data suggest that expression of mutant BMPR2 worsens secondary PH through increased HIF activity in vascular endothelium. This pathway could be therapeutically targeted in patients with PH secondary to pulmonary fibrosis.

Lipopolysaccharide induces inflammation and facilitates lung metastasis in a breast cancer model via the prostaglandin E2-EP2 pathway

Inflammation is a potent promoter of tumor metastasis. The aim of the present study was to explore the function of systemic inflammation in the formation of lung metastasis of breast cancer cells in a mouse model. BALB/c mice were injected intraperitoneally with lipopolysaccharide (LPS) in order to establish an inflammatory animal model and 4T1 murine breast cancer cells were injected through the tail vein to induce lung metastasis. The levels of proinflammatory cytokines were evaluated by ELISA. Metastases on the surface of the lungs were counted and histologically analyzed by hematoxylin and eosin staining. Angiogenesis in the lungs was examined by CD31 immunofluorescence. Mouse pulmonary endothelial cells (MPVECs) were isolated and used to assay endothelial tube formation and determine the protein expression levels of vascular endothelial growth factor (VEGF) invitro. Serum levels of VEGF and prostaglandinE2 (PGE2), the number and size of metastatic lesions, and the expression levels of cyclooxygenase‑2 were significantly greater in the lungs of LPS‑treated mice, as compared with those in control mice threated with phosphate‑buffered saline. Blood vessel density was also markedly increased in the LPS‑treated mice. These increases were reversed by treatment with celecoxib. Invitro, the protein expression levels of VEGF produced by the PGE2‑treated cells were significantly increased in a concentration‑dependent manner. In addition, the production of VEGF was increased in response to treatment with the PGE2 receptor (EP2) agonist ONO‑AE1‑259‑01; however, this increase was abrogated by treatment with AH6809, an EP2 receptor antagonist. Treatment with PGE2 or VEGF alone promoted the tube formation of MPVECs and this effect was reversed by treatment with celecoxib. These results demonstrated that PGE2 may regulate the release of VEGF by MPVECs through the EP2 receptor pathway and thereby promoted pulmonary angiogenesis and breast cancer metastasis in a mouse model.

Podocalyxin regulates murine lung vascular permeability by altering endothelial cell adhesion.

Despite the widespread use of CD34-family sialomucins (CD34, podocalyxin and endoglycan) as vascular endothelial cell markers, there is remarkably little known of their vascular function. Podocalyxin (gene name Podxl), in particular, has been difficult to study in adult vasculature as germ-line deletion of podocalyxin in mice leads to kidney malformations and perinatal death. We generated mice that conditionally delete podocalyxin in vascular endothelial cells (Podxl ΔEC mice) to study the homeostatic role of podocalyxin in adult mouse vessels. Although Podxl ΔEC adult mice are viable, their lungs display increased lung volume and changes to the matrix composition. Intriguingly, this was associated with increased basal and inflammation-induced pulmonary vascular permeability. To further investigate the etiology of these defects, we isolated mouse pulmonary endothelial cells. Podxl ΔEC endothelial cells display mildly enhanced static adhesion to fibronectin but spread normally when plated on fibronectin-coated transwells. In contrast, Podxl ΔEC endothelial cells exhibit a severely impaired ability to spread on laminin and, to a lesser extent, collagen I coated transwells. The data suggest that, in endothelial cells, podocalyxin plays a previously unrecognized role in maintaining vascular integrity, likely through orchestrating interactions with extracellular matrix components and basement membranes, and that this influences downstream epithelial architecture.

MSC therapy attenuates obliterative bronchiolitis after murine bone marrow transplant.

RationaleObliterative bronchiolitis (OB) is a significant cause of morbidity and mortality after lung transplant and hematopoietic cell transplant. Mesenchymal stromal cells (MSCs) have been shown to possess immunomodulatory properties in chronic inflammatory disease.ObjectiveAdministration of MSCs was evaluated for the ability to ameliorate OB in mice using our established allogeneic bone marrow transplant (BMT) model.MethodsMice were lethally conditioned and received allogeneic bone marrow without (BM) or with spleen cells (BMS), as a source of OB-causing T-cells. Cell therapy was started at 2 weeks post-transplant, or delayed to 4 weeks when mice developed airway injury, defined as increased airway resistance measured by pulmonary function test (PFT). BM-derived MSC or control cells [mouse pulmonary vein endothelial cells (PVECs) or lung fibroblasts (LFs)] were administered. Route of administration [intratracheally (IT) and IV] and frequency (every 1, 2 or 3 weeks) were compared. Mice were evaluated at 3 months post-BMT.Measurements and Main ResultsNo ectopic tissue formation was identified in any mice. When compared to BMS mice receiving control cells or no cells, those receiving MSCs showed improved resistance, compliance and inspiratory capacity. Interim PFT analysis showed no difference in route of administration. Improvements in PFTs were found regardless of dose frequency; but once per week worked best even when administration began late. Mice given MSC also had decreased peribronchiolar inflammation, lower levels of hydroxyproline (collagen) and higher frequencies of macrophages staining for the alternatively activated macrophage (AAM) marker CD206.ConclusionsThese results warrant study of MSCs as a potential management option for OB in lung transplant and BMT recipients.

Bidirectional cross-regulation between the endothelial nitric oxide synthase and β-catenin signalling pathways.

Aimsβ-catenin has been shown to be regulated by inducible nitric oxide synthase (NOS) in endothelial cells. We investigated here whether β-catenin interacts with and regulates endothelial NOS (eNOS) and whether eNOS activation promotes β-catenin signalling.Methods and resultsWe identified β-catenin as a novel eNOS binding protein in human umbilical vein endothelial cells (HUVECs) by mass spectroscopy and western blot analyses of β-catenin and eNOS immunoprecipitates. This was confirmed by in situ proximity ligation assay. eNOS activity, assessed by cGMP production and eNOS phosphorylation (Ser1177), was enhanced in β-catenin−/− mouse pulmonary endothelial cells (MPECs) relative to wild-type MPECs. eNOS activation (using adenosine, salbutamol, thrombin, or histamine), or application of an NO donor (spermine NONOate) or cGMP-analogue (8-bromo-cGMP) caused nuclear translocation of β-catenin in HUVEC as shown by western blotting of nuclear extracts. Exposure to spermine NONOate, 8-bromo-cGMP, or sildenafil (a phosphodiesterase type 5 inhibitor) also increased the expression of β-catenin-dependent transcripts, IL-8, and cyclin D1. Stimulation of wild-type MPECs with basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), spermine NONOate, 8-bromo-cGMP, or sildenafil increased tube length relative to controls in an angiogenesis assay. These responses were abrogated in β-catenin−/− MPECs, with the exception of that to bFGF which is NO-independent. In C57BL/6 mice, subcutaneous VEGF-supplemented Matrigel plugs containing β-catenin−/− MPECs exhibited reduced angiogenesis compared with plugs containing wild-type MPECs. Angiogenesis was not altered in bFGF-supplemented Matrigel.ConclusionThese data reveal bidirectional cross-talk and regulation between the NO-cGMP and β-catenin signalling pathways.

209 Beta-catenin Functions as an Endogenous Negative Regulator of Endothelial Nitric Oxide Synthase Function

IntroductionNitric oxide (NO) derived from endothelial NO synthase (eNOS) has multiple anti-atherogenic actions in the vasculature. eNOS activity is controlled by association with a number of regulatory proteins. We here...

Mechanosignaling with ischemia‐reperfusion: restart of flow triggers a signaling cascade (1180.11)

We concluded earlier that endothelial mechanotransduction with ischemia in the lung activates a signaling cascade comprised of KATP channel closure that leads to NOX2 activation and reactive oxygen species (ROS) production. We studied the mechanosignaling with reperfusion. Isolated perfused mouse lungs and pulmonary endothelial cells showed a 2 fold increase in ROS production with ischemia that increased by 3‐3.5 fold upon reperfusion. This response is not due to hypoxia or reoxygenation since alveolar pO2 is unchanged in these ventilated lungs. ROS production was not observed in lungs and cells from NOX2 null, KATP channel null mice or lungs pre‐treated with KATP agonist (cromakalim) or a NOX2 activation inhibitor (MJ33). Wild type mice (WT) showed ~1.8 fold increase in oxidative lung damage (as assessed by 8‐isoprostanes, TBARS, alveolar permeability) with pulmonary ischemia and a ~2.5 fold increase with reperfusion; no significant change was observed in NOX2 null mice. Calcium influx, observed with ischemia in WT cells increased further with reperfusion; this was not observed in KATP and NOX2 null cells. Reperfusion thus amplifies the effects of the mechanosignaling cascade that is associated with ischemia. Prevention of the cascade with inhibitors such as MJ33 or cromakalim has potential application in lung transplantation which requires reperfusion of a previously ischemic lung.Grant Funding Source: NIHRO1HL‐075587

25 Nitric Oxide-cGMP Signalling Promotes B-Catenin Nuclear Translocation and Transcriptional Activity in Endothelial Cells

Nitric oxide (NO) derived from endothelial NO synthase (eNOS) exerts cardioprotective effects. eNOS binds to a number of proteins that regulate its function. Using mass spectroscopy to study eNOS immunoprecipitated...

Platelet Activating Factor-Induced Ceramide Micro-Domains Drive Endothelial NOS Activation and Contribute to Barrier Dysfunction

The spatial and functional relationship between platelet activating factor-receptor (PAF-R) and nitric oxide synthase (eNOS) in the lateral plane of the endothelial plasma membrane is poorly characterized. In this study, we used intact mouse pulmonary endothelial cells (ECs) as well as endothelial plasma membrane patches and subcellular fractions to define a new microdomain of plasmalemma proper where the two proteins colocalize and to demonstrate how PAF-mediated nitric oxide (NO) production fine-tunes ECs function as gatekeepers of vascular permeability. Using fluorescence microscopy and immunogold labeling electron microscopy (EM) on membrane patches we demonstrate that PAF-R is organized as clusters and colocalizes with a subcellular pool of eNOS, outside recognizable vesicular profiles. Moreover, PAF-induced acid sphingomyelinase activation generates a ceramide-based microdomain on the external leaflet of plasma membrane, inside of which a signalosome containing eNOS shapes PAF-stimulated NO production. Real-time measurements of NO after PAF-R ligation indicated a rapid (5 to 15 min) increase in NO production followed by a > 45 min period of reduction to basal levels. Moreover, at the level of this new microdomain, PAF induces a dynamic phosphorylation/dephosphorylation of Ser, Thr and Tyr residues of eNOS that correlates with NO production. Altogether, our findings establish the existence of a functional partnership PAF-R/eNOS on EC plasma membrane, at the level of PAF-induced ceramide plasma membrane microdomains, outside recognized vesicular profiles.

Mechanosensing with restart of flow drives KATP channel induced NOX2 activation in a model of Lung Ischemia Reperfusion

From our earlier studies in lung ischemia, we concluded that endothelial mechanotransduction with stop of flow in the lung activates the generation of reactive oxygen species (ROS) as a result of KATP closure that leads to NOX2 activation. As the next phase, we evaluated the role of mechanosignaling with reperfusion (I/R). We now propose that the increase in shear with reperfusion triggers a mechanosignaling cascade similar to that associated with ischemia. Isolated perfused mouse lungs and pulmonary endothelial cells showed a 2 fold increase in ROS production (as monitored by ROS sensitive dyes H2DCFDA, H2DFFDA and DHE) with ischemia that is further enhanced by 3–3.5 fold upon reperfusion. This was not observed in lungs from KATP channel null and NOX2 mice. Lungs subjected to ischemia or I/R show ~1.8 fold increase in lung damage (as assessed by 8‐isoprostanes, TBARS, permeability) with ischemia and a ~2.5 fold increase during the reperfusion period. Understanding the initiation of reperfusion signaling has potential application in lung transplantation which requires reperfusion of a previously ischemic lung; thus this model is relevant to design strategies that can reduce NOX2 activation and resultant injury.

Transforming growth factor-β regulates endothelin-1 signaling in the newborn mouse lung during hypoxia exposure

We have previously shown that inhibition of transforming growth factor-β (TGF-β) signaling attenuates hypoxia-induced inhibition of alveolar development and abnormal pulmonary vascular remodeling in the newborn mice and that endothelin-A receptor (ETAR) antagonists prevent and reverse the vascular remodeling. The current study tested the hypothesis that inhibition of TGF-β signaling attenuates endothelin-1 (ET-1) expression and thereby reduces effects of hypoxia on the newborn lung. C57BL/6 mice were exposed from birth to 2 wk of age to either air or hypoxia (12% O(2)) while being given either BQ610 (ETAR antagonist), BQ788 (ETBR antagonist), 1D11 (TGF-β neutralizing antibody), or vehicle. Lung function and development and TGF-β and ET-1 synthesis were assessed. Hypoxia inhibited alveolar development, decreased lung compliance, and increased lung resistance. These effects were associated with increased TGF-β synthesis and signaling and increased ET-1 synthesis. BQ610 (but not BQ788) improved lung function, without altering alveolar development or increased TGF-β signaling in hypoxia-exposed animals. Inhibition of TGF-β signaling reduced ET-1 in vivo, which was confirmed in vitro in mouse pulmonary endothelial, fibroblast, and epithelial cells. ETAR blockade improves function but not development of the hypoxic newborn lung. Reduction of ET-1 via inhibition of TGF-β signaling indicates that TGF-β is upstream of ET-1 during hypoxia-induced signaling in the newborn lung.

Reversal of TNP-470-Induced Endothelial Cell Growth Arrest by Guanine and Guanine Nucleosides

The mechanism of action of TNP-470 [O-(chloroacetyl-carbamoyl) fumagillol], which potently and selectively inhibits the proliferation of endothelial cells, is incompletely understood. Previous studies have established its binding protein and the most distal effector of its growth arrest activity as methionine aminopeptidase 2 (MetAP-2) and p21(WAF1/CIP1), respectively. However, the mechanistic steps between these two effectors have not been identified. We have found that addition of exogenous guanine and guanine-containing nucleosides to culture medium will completely reverse the cytostatic effect of TNP-470 on both cultured bovine aortic and mouse pulmonary endothelial cells. Western blotting showed that supplementation with exogenous guanosine reverses the induction of p21(WAF1/CIP1) by TNP-470. This "rescue" by guanine/guanosine was abolished when the guanine salvage pathway of nucleotide biosynthesis was inhibited with Immucillin H, suggesting that TNP-470 might reduce de novo guanine synthesis in endothelial cells. However, an analysis of inosine 5'-monophosphate dehydrogenase, the rate-limiting enzyme in de novo guanine synthesis and target of the antiangiogenic drug mycophenolic acid, showed no TNP-470-induced changes. Curiously, quantitation of cellular nucleotides confirmed that GTP levels were not reduced after TNP-470 treatment. Addition of guanosine at the start of G(1) phase causes a doubling in GTP levels that persists to the G(1)/S phase transition, where commitment to TNP-470 growth arrest occurs. Thus, guanine rescue involves an augmentation of cellular GTP beyond physiological levels rather than a restoration of a drug-induced GTP deficit. Determining the mechanism whereby this causes restoration of endothelial cell proliferation is an ongoing investigation.