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Atrial natriuretic peptide (ANP) protects against acute lung injury (ALI), but the receptor that mediates this effect is not known. Transgenic mice with 0 (knockout), 1 (heterozygote), or 2 (wild-type) functional copies of Npr3, the gene that encodes for natriuretic peptide receptor-C (NPR-C), were treated with intravenous infusion of ANP or saline vehicle before oropharyngeal aspiration of Pseudomonas aeruginosa (PA103) or saline vehicle. Lung injury was assessed 4 h following aspiration by measurement of lung wet/dry (W/D) weight, whole lung leukocyte and cytokine levels, and protein, leukocyte, and cytokine concentration in bronchoalveolar lavage fluid (BALF). PA103 induced acute lung injury as evidenced by increases in lung W/D ratio and protein concentration in BALF. The severity of PA103-induced lung injury did not differ between NPR-C genotypes. Treatment with intravenous ANP infusion reduced PA103-induced increases in lung W/D and BALF protein concentration in all three NPRC genotypes. PA103 increased the percentage of leukocytes that were neutrophils and cytokine levels in whole lung and BALF in NPR-C wild-type and knockout mice. This effect was blunted by ANP in wild-type mice but not in the NPR-C knockout mice. NPR-C does not mediate the protective effect of ANP on endothelial cell permeability in settings of PA103-induced injury but may mediate the effect of ANP on inhibition of the recruitment of neutrophils to the lung and thereby attenuate the release of inflammatory cytokines.

It is unknown whether biological sex influences phenotypes of commercially available human pulmonary artery endothelial cells (HPAECs). Ten lots of commercial HPAECs were used (Lonza Biologics; PromoCell). Five (50%) were confirmed to be genotypically male (

One distinguishing characteristic of acute respiratory distress syndrome (ARDS) or its lesser form, acute lung injury (ALI), is dysfunction of the lung endothelium. This dysfunction leads to increased permeability and eventual pulmonary edema. Despite the globally climbing rates of ARDS, the mechanisms of endothelial dysfunction are poorly understood. Recently, extracellular vesicles (EVs) have been shown to induce various microvascular disease states, as they contain various endothelial-targeting cargo in the form of mRNA, proteins, lipids, and miRNAs. Therefore, we hypothesized that EVs play a role in the endothelial dysfunction observed in ARDS/ALI. EVs were isolated from the plasma of male Sprague Dawley rats which were given saline or P. aeruginosa (PA103) via intratracheal (IT) injection for 48h. ALI was confirmed by determining the wet to dry weights of the rodent lungs. We then tested the effect of the EVs isolated from saline- and ALI treated animals (sEVs and ALI-EVs, respectively) on endothelial barrier function and modifications in gene expression. We found that treatment with ALI-EVs, but not sEVs, increased rat lung microvascular endothelial cell (RLMVEC) permeability in the presence of lipopolysaccharide (LPS). Interestingly, ALI-EVs did not induce endothelial dysfunction on their own, rather exacerbated the damage induced by LPS. We further noted ALI-EVs, but not sEVs, increased gene expression of toll-like receptor 4 (TLR4), which is the main pattern recognition receptor (PRR) for LPS and its downstream signaling molecule, MyD88 in the presence of LPS in RLMVEC. Further, we found that ALI-EVs, together with LPS, increased gene expression of intracellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), and interleukin 6 (IL-6), which are all involved in inflammatory signaling. Thus, it is likely that through the modulation of inflammatory signaling mediators, ALI-EVs contain select cargo that worsen the endothelial barrier in settings where LPS is present, such as bacterial-ARDS.

Chitinase 3 like 1 (CHI3L1) is the prototypic chitinase-like protein mediating inflammation, cell proliferation, and tissue remodeling. Limited data suggest CHI3L1 is elevated in human pulmonary arterial hypertension (PAH) and is associated with disease severity. Despite its importance as a regulator of injury/repair responses, the relationship between CHI3L1 and pulmonary vascular remodeling is not well understood. We hypothesize that CHI3L1 and its signaling pathways contribute to the vascular remodeling responses that occur in pulmonary hypertension (PH). We examined the relationship of plasma CHI3L1 levels and severity of PH in patients with various forms of PH, including group 1 PAH and group 3 PH, and found that circulating levels of serum CHI3L1 were associated with worse hemodynamics and correlated directly with mean pulmonary artery pressure and pulmonary vascular resistance. We also used transgenic mice with constitutive knockout and inducible overexpression of CHI3L1 to examine its role in hypoxia-, monocrotaline-, and bleomycin-induced models of pulmonary vascular disease. In all 3 mouse models of pulmonary vascular disease, pulmonary hypertensive responses were mitigated in CHI3L1-null mice and accentuated in transgenic mice that overexpress CHI3L1. Finally, CHI3L1 alone was sufficient to induce pulmonary arterial smooth muscle cell proliferation, inhibit pulmonary vascular endothelial cell apoptosis, induce the loss of endothelial barrier function, and induce endothelial-mesenchymal transition. These findings demonstrate that CHI3L1 and its receptors play an integral role in pulmonary vascular disease pathobiology and may offer a target for the treatment of PAH and PH associated with fibrotic lung disease.

Background: Role of blood-based factors in development and progression of heart failure (HF) is poorly characterized. Blood contains myriads of factors released during pathophysiological states that may impact cellular function and provide mechanistic insights to HF management. In this study, we tested effects of blood from two distinct HF models on cardiac metabolism and identified possible cellular targets of the effects. Methods: Blood plasma was obtained from daunorubicin- and myocardial infarction-induced HF rabbits (Dauno-HF and MI-HF) and their controls (Dauno-Control and MI-Control). Effects of plasma on bioenergetics of myocardial tissue from healthy mice and cellular cardiac components; myoblasts, fibroblasts, macrophages, and endothelial cells were assessed using high-resolution respirometry and Seahorse flux analyzer. Since endothelial cell respiration was profoundly affected by HF plasma, effects of plasma on endothelial cell barrier function and death were further evaluated. Western-blot analysis and electron microscopic assessment were performed to detect alterations in mitochondrial proteins and morphology. Results: Brief exposure to HF plasma significantly decreased cardiac tissue respiration. Endothelial cell respiration was most impacted by exposure to HF plasma. Endothelial cell monolayer integrity was significantly decreased by incubation with Dauno-HF plasma. Apoptosis and necrosis were significantly increased in cells incubated with Dauno-HF plasma for 24 h. Significant down-regulation of VDAC-1, Tom20, and MFF in cells exposed to Dauno-HF plasma and mitochondrial Stat3 and MFF in cells exposed to MI-HF plasma were observed. Mitochondrial structure was disrupted in cells exposed to HF plasma.Conclusions: These findings indicate that endothelial cells and mitochondrial structure and function may be a primary target where HF pathology manifests and accelerates. High-throughput blood-based screening of HF may provide innovative ways to advance disease diagnosis and management.

Bronchopulmonary dysplasia (BPD), a chronic lung disease in premature infants, results from mechanical ventilation and hyperoxia, amongst other factors. Although most BPD survivors can be weaned from supplemental oxygen, many show evidence of cardiovascular sequelae in adulthood, including pulmonary hypertension and pulmonary vascular remodeling. Endothelial-mesenchymal transition (EndoMT) plays an important role in mediating vascular remodeling in idiopathic pulmonary arterial hypertension. Whether hyperoxic exposure, a known mediator of BPD in rodent models, causes EndoMT resulting in vascular remodeling and pulmonary hypertension remains unclear. We hypothesized that neonatal hyperoxic exposure causes EndoMT, leading to the development of pulmonary hypertension in adulthood. To test this hypothesis, newborn mice were exposed to hyperoxia and then allowed to recover in room air until adulthood. Neonatal hyperoxic exposure gradually caused pulmonary vascular and right ventricle remodeling as well as pulmonary hypertension. Male mice were more susceptible to developing pulmonary hypertension compared to female mice, when exposed to hyperoxia as newborns. Hyperoxic exposure induced EndoMT in mouse lungs as well as in cultured lung microvascular endothelial cells (LMVECs) isolated from neonatal mice and human fetal donors. This was augmented in cultured LMVECs from male donors compared to those from female donors. Using primary mouse LMVECs, hyperoxic exposure increased phosphorylation of both Smad2 and Smad3, but reduced Smad7 protein levels. Treatment with a selective TGF-β inhibitor SB431542 blocked hyperoxia-induced EndoMT in vitro. Altogether, we show that neonatal hyperoxic exposure caused vascular remodeling and pulmonary hypertension in adulthood. This was associated with increased EndoMT. These novel observations provide mechanisms underlying hyperoxia-induced vascular remodeling and potential approaches to prevent BPD-associated pulmonary hypertension by targeting EndoMT. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A hallmark of acute respiratory distress syndrome (ARDS) is pulmonary vascular permeability. In these settings, loss of barrier integrity is mediated by cell-contact disassembly and actin remodeling. Studies into molecular mechanisms responsible for improving microvascular barrier function are therefore vital in the development of therapeutic targets for reducing vascular permeability in ARDS. The sweet taste receptor T1R3 is a G protein-coupled receptor, activated following exposure to sweet molecules, to trigger a gustducin-dependent signal cascade. In recent years, extraoral locations for T1R3 have been identified; however, no studies have focused on T1R3 within the vasculature. We hypothesize that activation of T1R3, in the pulmonary vasculature, plays a role in regulating endothelial barrier function in settings of ARDS. Our study demonstrated expression of T1R3 within the pulmonary vasculature, with a drop in expression levels following exposure to barrier-disruptive agents. Exposure of lung microvascular endothelial cells to the intensely sweet molecule sucralose attenuated LPS- and thrombin-induced endothelial barrier dysfunction. Likewise, sucralose exposure attenuated bacteria-induced lung edema formation in vivo. Inhibition of sweet taste signaling, through zinc sulfate, T1R3, or G-protein siRNA, blunted the protective effects of sucralose on the endothelium. Sucralose significantly reduced LPS-induced increased expression or phosphorylation of the key signaling molecules Src, p21-activated kinase (PAK), myosin light chain-2 (MLC2), heat shock protein 27 (HSP27), and p110α phosphatidylinositol 3-kinase (p110αPI3K). Activation of T1R3 by sucralose protects the pulmonary endothelium from edemagenic agent-induced barrier disruption, potentially through abrogation of Src/PAK/p110αPI3K-mediated cell-contact disassembly and Src/MLC2/HSP27-mediated actin remodeling. Identification of sweet taste sensing in the pulmonary vasculature may represent a novel therapeutic target to protect the endothelium in settings of ARDS.

Background: Sacubitril/valsartan, a first-in-class Angiotensin Receptor-Neprilysin Inhibitor (ARNi), is superior to valsartan in reducing blood pressure in hypertensive patients. However, cardiac effects of sacubitril/valsartan in hypertension treatment and its potential superiority over valsartan are unclear. This study was designed to investigate effects of sacubitril/valsartan on cardiac structural remodeling and oxidative stress using a pressure overload rat model induced by ascending aortic constriction (AAC) and to address whether direct regulation of cardiac myocytes and/or fibroblasts is involved in the cardiac effects independent of afterload changes. Methods and Results: 1 week after AAC surgery, adult male Sprague-Dawley rats were randomized for 10 weeks treatment with vehicle, valsartan, or sacubitril/valsartan. Sacubitril/valsartan was superior to valsartan in inhibiting ventricular fibrosis, while both equally inhibited cardiomyocyte hypertrophy at the cellular level. These findings were supported by in vitro experiments showing that combined LBQ657 (sacubitrilat, active form of sacubitril) and valsartan was superior to valsartan alone in inhibiting angiotensin II (Ang II)-induced adult ventricular fibroblast activation, but not adult cardiomyocyte hypertrophy. In adult cardiomyocytes LBQ657 effectively inhibited Ang II-induced mitochondrial superoxide, and combined LBQ657 and valsartan was superior to valsartan or LBQ657 alone. Importantly, sacubitril/valsartan was also superior to valsartan in reducing mitochondrial superoxide in cardiomyocytes from pressure-overloaded hearts and improved cardiomyocyte mitochondrial maximal and spare respiration capacity. Conclusions: These findings provide direct evidence and novel mechanistic insights on the superior cardioprotective effects of sacubitril/valsartan in the setting of pressure overload: independent of afterload reduction, sacubitril/valsartan is superior to valsartan in attenuating cardiac fibrosis and myocyte oxidative stress and improves myocyte mitochondrial function in rats. Our study thus suggests a greater therapeutic effect of sacubitril/valsartan in the early stage of hypertensive heart disease before heart failure.

Endothelial dysfunction is a hallmark of pulmonary arterial hypertension (PAH) but there are no established methods to study pulmonary artery endothelial cells (PAECs) from living patients. We sought to culture PAECs from pulmonary artery catheter (PAC) balloons used during right-heart catheterisation (RHC) to characterise successful culture attempts and to describe PAEC behaviour.PAECs were grown in primary culture to confluence and endothelial cell phenotype was confirmed. Standard assays for apoptosis, migration and tube formation were performed between passages three to eight. We collected 49 PAC tips from 45 subjects with successful PAEC culture from 19 balloons (39%).There were no differences in subject demographic details or RHC procedural details in successful versus unsuccessful attempts. However, for subjects who met haemodynamic criteria for PAH, there was a higher but nonsignificant (p=0.10) proportion amongst successful attempts (10 out of 19, 53%) versus unsuccessful attempts (nine out of 30, 30%). A successful culture was more likely in subjects with a lower cardiac index (p=0.03) and higher pulmonary vascular resistance (p=0.04). PAECs from a subject with idiopathic PAH were apoptosis resistant compared to commercial PAECs (p=0.04) and had reduced migration compared to PAECs from a subject with portopulmonary hypertension with high cardiac output (p=0.01). PAECs from a subject with HIV-associated PAH formed fewer (p=0.01) and shorter (p=0.02) vessel networks compared to commercial PAECs.Sustained culture and characterisation of PAECs from RHC balloons is feasible, especially in PAH with high haemodynamic burden. This technique may provide insight into endothelial dysfunction during PAH pathogenesis.

Neovascularization, the formation of new blood vessels, requires multiple processes including vascular leak, migration, and adhesion. Endosomal proteins, such as Rabs, regulate trafficking of key signaling proteins involved in neovascularization. The novel endosome protein, p18, enhances vascular endothelial (VE)-cadherin recycling from early endosome to cell junction to improve pulmonary endothelial barrier function. Since endothelial barrier integrity is vital in neovascularization, we sought to elucidate the role for endosome proteins p18 and Rab4, Rab7, and Rab9 in the process of vessel formation within the pulmonary vasculature. Overexpression of wild-type p18 (p18wt), but not the nonendosomal-binding mutant (p18N39), significantly increased lung microvascular endothelial cell migration, adhesion, and both in vitro and in vivo tube formation. Chemical inhibition of mTOR or p38 attenuated the proneovascularization role of p18wt. Similar to the effect of p18wt, overexpression of prorecycling wild-type (Rab4WT) and endosome-anchored (Rab4Q67L) Rab4 enhanced neovascularization processes, whereas molecular inhibition of Rab4, by using the nonendosomal-binding mutant (Rab4S22N) attenuated VEGF-induced neovascularization. Unlike p18, Rab4-induced neovascularization was independent of mTOR or p38 inhibition but was dependent on p18 expression. This study shows for the first time that neovascularization within the pulmonary vasculature is dependent on the prorecycling endocytic proteins Rab4 and p18.

Enhanced protein tyrosine phosphorylation is associated with changes in vascular permeability through formation and dissolution of adherens junctions and regulation of stress fiber formation. Inhibition of the protein tyrosine phosphorylase SH2 domain-containing protein tyrosine phosphatase 2 (SHP2) increases tyrosine phosphorylation of vascular endothelial cadherin and β-catenin, resulting in disruption of the endothelial monolayer and edema formation in the pulmonary endothelium. Vascular permeability is a hallmark of acute lung injury (ALI); thus, enhanced SHP2 activity offers potential therapeutic value for the pulmonary vasculature in diseases such as ALI, but this has not been characterized. To assess whether SHP2 activity mediates protection against edema in the endothelium, we assessed the effect of molecular activation of SHP2 on lung endothelial barrier function in response to the edemagenic agents LPS and thrombin. Both LPS and thrombin reduced SHP2 activity, correlated with decreased focal adhesion kinase (FAK) phosphorylation (Y(397) and Y(925)) and diminished SHP2 protein-protein associations with FAK. Overexpression of constitutively active SHP2 (SHP2(D61A)) enhanced baseline endothelial monolayer resistance and completely blocked LPS- and thrombin-induced permeability in vitro and significantly blunted pulmonary edema formation induced by either endotoxin (LPS) or Pseudomonas aeruginosa exposure in vivo. Chemical inhibition of FAK decreased SHP2 protein-protein interactions with FAK concomitant with increased permeability; however, overexpression of SHP2(D61A) rescued the endothelium and maintained FAK activity and FAK-SHP2 protein interactions. Our data suggest that SHP2 activation offers the pulmonary endothelium protection against barrier permeability mediators downstream of the FAK signaling pathway. We postulate that further studies into the promotion of SHP2 activation in the pulmonary endothelium may offer a therapeutic approach for patients suffering from ALI.

Vascular permeability is a hallmark of several disease states including acute lung injury (ALI). Endocytosis of VE-cadherin, away from the interendothelial junction (IEJ), causes acute endothelial barrier permeability. A novel protein, p18, anchors to the endosome membrane and plays a role in late endosomal signaling via MAPK and mammalian target of rapamycin. However, the fate of the VE-cadherin-positive endosome has yet to be elucidated. We sought to elucidate a role for p18 in VE-cadherin trafficking and thus endothelial barrier function, in settings of ALI. Endothelial cell (EC) resistance, whole-cell ELISA, and filtration coefficient were studied in mice or lung ECs overexpressing wild-type or nonendosomal-binding mutant p18, using green fluorescent protein as a control. We demonstrate a protective role for the endocytic protein p18 in endothelial barrier function in settings of ALI in vitro and in vivo, through enhanced recycling of VE-cadherin-positive early endosomes to the IEJ. In settings of LPS-induced ALI, we show that Src tethered to the endosome tyrosine phosphorylates p18 concomitantly with VE-cadherin internalization and pulmonary edema formation. We conclude that p18 regulates pulmonary endothelial barrier function in vitro and in vivo, by enhancing recycling of VE-cadherin-positive endosomes to the IEJ.—Chichger, H., Duong, H., Braza, J., Harrington, E. O. p18, a novel adaptor protein, regulates pulmonary endothelial barrier function via enhanced endocytic recycling of VEcadherin.

Pulmonary edema occurs in settings of acute lung injury, in diseases, such as pneumonia, and in acute respiratory distress syndrome. The lung interendothelial junctions are maintained in part by vascular endothelial (VE)-cadherin, an adherens junction protein, and its surface expression is regulated by endocytic trafficking. The Rab family of small GTPases are regulators of endocytic trafficking. The key trafficking pathways are regulated by Rab4, -7, and -9. Rab4 regulates the recycling of endosomes to the cell surface through a rapid-shuttle process, whereas Rab7 and -9 regulate trafficking to the late endosome/lysosome for degradation or from the trans-Golgi network to the late endosome, respectively. We recently demonstrated a role for the endosomal adaptor protein, p18, in regulation of the pulmonary endothelium through enhanced recycling of VE-cadherin to adherens junction. Thus, we hypothesized that Rab4, -7, and -9 regulate pulmonary endothelial barrier function through modulating trafficking of VE-cadherin-positive endosomes. We used Rab mutants with varying activities and associations to the endosome to study endothelial barrier function in vitro and in vivo. Our study demonstrates a key role for Rab4 activation and Rab9 inhibition in regulation of vascular permeability through enhanced VE-cadherin expression at the interendothelial junction. We further showed that endothelial barrier function mediated through Rab4 is dependent on extracellular signal-regulated kinase phosphorylation and activity. Thus, we demonstrate that Rab4 and -9 regulate VE-cadherin levels at the cell surface to modulate the pulmonary endothelium through extracellular signal-regulated kinase-dependent and -independent pathways, respectively. We propose that regulating select Rab GTPases represents novel therapeutic strategies for patients suffering with acute respiratory distress syndrome.

Vasculogenesis and angiogenesis, the formation of new blood vessels, are processes requiring multiple endothelial cell (EC) functions, including proliferation, migration and adhesion. Blood vessel ...

One hallmark of acute lung injury is the disruption of the pulmonary endothelial barrier. Such disruption correlates with increased endothelial permeability, partly through the disruption of cell–cell contacts. Protein tyrosine phosphatases (PTPs) are known to affect the stability of both cell–extracellular matrix adhesions and intercellular adherens junctions (AJs). However, evidence for the role of select PTPs in regulating endothelial permeability is limited. Our investigations noted that the inhibition of PTP1B in cultured pulmonary endothelial cells (ECs), as well as in the vasculature of intact murine lungs via the transient overexpression of a catalytically inactive PTP1B, decreased the baseline resistance of cultured EC monolayers and increased the formation of edema in murine lungs, respectively. In addition, we observed that the overexpression of wild-type PTP1B enhanced basal barrier function in vitro. Immunohistochemical analyses of pulmonary ECs and the coimmunoprecipitation of murine lung homogenates demonstrated the association of PTP1B with the AJ proteins β-catenin, p120-catenin, and VE-cadherin both in vitro and ex vivo. Using LPS in a model of sepsis-induced acute lung injury, we showed that reactive oxygen species were generated in response to LPS, which correlated with enhanced PTP1B oxidation, inhibited phosphatase activity, and attenuation of the interactions between PTP1B and β-catenin, as well as enhanced β-catenin tyrosine phosphorylation. Finally, the overexpression of a cytosolic PTP1B fragment, shown to be resistant to nicotinamide adenine dinucleotide phosphate–reduced oxidase–4 (Nox4)-mediated oxidation, significantly attenuated LPS-induced endothelial barrier dysfunction and the formation of lung edema, and preserved the associations of PTP1B with AJ protein components, independent of PTP1B phosphatase activity. We conclude that PTP1B plays an important role in maintaining the pulmonary endothelial barrier, and PTP1B oxidation appears to contribute to sepsis-induced pulmonary vascular dysfunction, possibly through the disruption of AJs.