Blockade of endothelial adenosine receptor 2 A suppresses atherosclerosis in vivo through inhibiting CREB-ALK5-mediated endothelial to mesenchymal transition

Cardiovascular diseases (CVDs) are the leading cause of death worldwide, and morbidity and mortality rates continue to rise. Atherosclerosis constitutes the principal etiology of CVDs. Endothelial injury, inflammation, and dysfunction are the initiating factors of atherosclerosis. Recently, we reported that endothelial adenosine receptor 2 A (ADORA2A), a G protein-coupled receptor (GPCR), plays critical roles in neovascularization disease and cerebrovascular disease. However, the precise role of endothelial ADORA2A in atherosclerosis is still not fully understood. Here, we showed that ADORA2A expression was markedly increased in the aortic endothelium of humans with atherosclerosis or Apoe-/- mice fed a high-cholesterol diet. In vivo studies unraveled that endothelial-specific Adora2a deficiency alleviated endothelial-to-mesenchymal transition (EndMT) and prevented the formation and instability of atherosclerotic plaque in Apoe-/- mice. Moreover, pharmacologic inhibition of ADORA2A with KW6002 recapitulated the anti-atherogenic phenotypes observed in genetically Adora2a-deficient mice. In cultured human aortic endothelial cells (HAECs), siRNA knockdown of ADORA2A or KW6002 inhibition of ADORA2A decreased EndMT, whereas adenoviral overexpression of ADORA2A induced EndMT. Mechanistically, ADORA2A upregulated ALK5 expression via a cAMP/PKA/CREB axis, leading to TGFβ-Smad2/3 signaling activation, thereby promoting EndMT. In conclusion, these findings, for the first time, demonstrate that blockade of ADORA2A attenuated atherosclerosis via inhibition of EndMT induced by the CREB1-ALK5 axis. This study discloses a new link between endothelial ADORA2A and EndMT and indicates that inhibiting endothelial ADORA2A could be an effective novel strategy for the prevention and treatment of atherosclerotic CVDs.

Endothelin-1 acutely increases nitric oxide production via the calcineurin mediated dephosphorylation of Caveolin-1

Endothelin (ET)-1 is an endothelial-derived peptide that exerts biphasic effects on nitric oxide (NO) levels in endothelial cells such that acute exposure stimulates-while sustained exposure attenuates-NO production. Although the mechanism involved in the decrease in NO generation has been identified but the signaling involved in the acute increase in NO is still unresolved. This was the focus of this study. Our data indicate that exposing pulmonary arterial endothelial cells (PAEC) to ET-1 led to an increase in NO for up to 30min after which levels declined. These effects were attenuated by ET receptor antagonists. The increase in NO correlated with significant increases in pp60Src activity and increases in eNOS phosphorylation at Tyr83 and Ser1177. The ET-1 mediated increase in phosphorylation and NO generation were attenuated by the over-expression of a pp60Src dominant negative mutant. The increase in pp60Src activity correlated with a reduction in the interaction of Caveolin-1 with pp60Src and the calcineurin-mediated dephosphorylation of caveolin-1 at three previously unidentified sites: Thr91, Thr93, and Thr95. The calcineurin inhibitor, Tacrolimus, attenuated the acute increase in pp60Src activity induced by ET-1 and a calcineurin siRNA attenuated the ET-1 mediated increase in eNOS phosphorylation at Tyr83 and Ser1177 as well as the increase in NO. By using a Caveolin-1 celluSpot peptide array, we identified a peptide targeting a sequence located between aa 41-56 as the pp60Src binding region. This peptide fused to the TAT sequence was found to decrease caveolin-pp60Src interaction, increased pp60Src activity, increased eNOS pSer1177 and NO levels in PAEC and induce vasodilation in isolated aortic rings in wildtype but not eNOS knockout mice. Together, our data identify a novel mechanism by which ET-1 acutely increases NO via a calcineurin-mediated dephosphorylation of caveolin-1 and the subsequent stimulation of pp60Src activity, leading to increases in phosphorylation of eNOS at Tyr83 and Ser1177.

Direct endothelial ENaC activation mitigates vasculopathy induced by SARS-CoV2 spike protein

Introduction

Although both COVID-19 and non-COVID-19 ARDS can be accompanied by significantly increased levels of circulating cytokines, the former significantly differs from the latter by its higher vasculopathy, characterized by increased oxidative stress and coagulopathy in lung capillaries. This points towards the existence of SARS-CoV2-specific factors and mechanisms that can sensitize the endothelium towards becoming dysfunctional. Although the virus is rarely detected within endothelial cells or in the circulation, the S1 subunit of its spike protein, which contains the receptor binding domain (RBD) for human ACE2 (hACE2), can be detected in plasma from COVID-19 patients and its levels correlate with disease severity. It remains obscure how the SARS-CoV2 RBD exerts its deleterious actions in lung endothelium and whether there are mechanisms to mitigate this.

Methods

In this study, we use a combination of in vitro studies in RBD-treated human lung microvascular endothelial cells (HL-MVEC), including electrophysiology, barrier function, oxidative stress and human ACE2 (hACE2) surface protein expression measurements with in vivo studies in transgenic mice globally expressing human ACE2 and injected with RBD.

Results

We show that SARS-CoV2 RBD impairs endothelial ENaC activity, reduces surface hACE2 expression and increases reactive oxygen species (ROS) and tissue factor (TF) generation in monolayers of HL-MVEC, as such promoting barrier dysfunction and coagulopathy. The TNF-derived TIP peptide (a.k.a. solnatide, AP301) -which directly activates ENaC upon binding to its a subunit- can override RBD-induced impairment of ENaC function and hACE2 expression, mitigates ROS and TF generation and restores barrier function in HL-MVEC monolayers. In correlation with the increased mortality observed in COVID-19 patients co-infected with S. pneumoniae, compared to subjects solely infected with SARS-CoV2, we observe that prior intraperitoneal RBD treatment in transgenic mice globally expressing hACE2 significantly increases fibrin deposition and capillary leak upon intratracheal instillation of S. pneumoniae and that this is mitigated by TIP peptide treatment.

Ythdf2 promotes pulmonary hypertension by suppressing Hmox1-dependent anti-inflammatory and antioxidant function in alveolar macrophages

Pulmonary hypertension (PH) is a devastating disease characterized by irreversible pulmonary vascular remodeling (PVR) that causes right ventricular failure and death. The early alternative activation of macrophages is a critical event in the development of PVR and PH, but the underlying mechanisms remain elusive. Previously we have shown that N⁶-methyladenosine (m⁶A) modifications of RNA contribute to phenotypic switching of pulmonary artery smooth muscle cells and PH. In the current study, we identify Ythdf2, an m⁶A reader, as an important regulator of pulmonary inflammation and redox regulation in PH. In a mouse model of PH, the protein expression of Ythdf2 was increased in alveolar macrophages (AMs) during the early stages of hypoxia. Mice with a myeloid specific knockout of Ythdf2 (Ythdf2^{Lyz2 Cre}) were protected from PH with attenuated right ventricular hypertrophy and PVR compared to control mice and this was accompanied by decreased macrophage polarization and oxidative stress. In the absence of Ythdf2, heme oxygenase 1 (Hmox1) mRNA and protein expression were significantly elevated in hypoxic AMs. Mechanistically, Ythdf2 promoted the degradation of Hmox1 mRNA in a m⁶A dependent manner. Furthermore, an inhibitor of Hmox1 promoted macrophage alternative activation, and reversed the protection from PH seen in Ythdf2^{Lyz2 Cre} mice under hypoxic exposure. Together, our data reveal a novel mechanism linking m⁶A RNA modification with changes in macrophage phenotype, inflammation and oxidative stress in PH, and identify Hmox1 as a downstream target of Ythdf2, suggesting that Ythdf2 may be a therapeutic target in PH.

ATIC-Associated De Novo Purine Synthesis Is Critically Involved in Proliferative Arterial Disease

BACKGROUND

Proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of arterial diseases, especially in arterial restenosis after angioplasty or stent placement. VSMCs reprogram their metabolism to meet the increased requirements of lipids, proteins, and nucleotides for their proliferation. De novo purine synthesis is one of critical pathways for nucleotide synthesis. However, its role in proliferation of VSMCs in these arterial diseases has not been defined.

METHODS

De novo purine synthesis in proliferative VSMCs was evaluated by liquid chromatography-tandem mass spectrometry. The expression of ATIC (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase), the critical bifunctional enzyme in the last 2 steps of the de novo purine synthesis pathway, was assessed in VSMCs of proliferative arterial neointima. Global and VSMC-specific knockout of Atic mice were generated and used for examining the role of ATIC-associated purine metabolism in the formation of arterial neointima and atherosclerotic lesions.

RESULTS

In this study, we found that de novo purine synthesis was increased in proliferative VSMCs. Upregulated purine synthesis genes, including ATIC, were observed in the neointima of the injured vessels and atherosclerotic lesions both in mice and humans. Global or specific knockout of Atic in VSMCs inhibited cell proliferation, attenuating the arterial neointima in models of mouse atherosclerosis and arterial restenosis.

CONCLUSIONS

These results reveal that de novo purine synthesis plays an important role in VSMC proliferation in arterial disease. These findings suggest that targeting ATIC is a promising therapeutic approach to combat arterial diseases.

Receptor-independent fluid-phase macropinocytosis promotes arterial foam cell formation and atherosclerosis

Accumulation of lipid-laden foam cells in the arterial wall plays a central role in atherosclerotic lesion development, plaque progression, and late-stage complications of atherosclerosis. However, there are still fundamental gaps in our knowledge of the underlying mechanisms leading to foam cell formation in atherosclerotic arteries. Here, we investigated the role of receptor-independent macropinocytosis in arterial lipid accumulation and pathogenesis of atherosclerosis. Genetic inhibition of fluid-phase macropinocytosis in myeloid cells (LysMCre+ Nhe1fl/fl) and repurposing of a Food and Drug Administration (FDA)-approved drug that inhibits macrophage macropinocytosis substantially decreased atherosclerotic lesion development in low-density lipoprotein (LDL) receptor-deficient and Apoe-/- mice. Stimulation of macropinocytosis using genetic (H-RASG12V) and physiologically relevant approaches promoted internalization of unmodified native (nLDL) and modified [e.g., acetylated (ac) and oxidized (ox) LDL] lipoproteins in both wild-type and scavenger receptor (SR) knockout (Cd36-/-/Sra-/-) macrophages. Pharmacological inhibition of macropinocytosis in hypercholesterolemic wild-type and Cd36-/-/Sra-/- mice identified an important role of macropinocytosis in LDL uptake by lesional macrophages and development of atherosclerosis. Furthermore, serial section high-resolution imaging, LDL immunolabeling, and three-dimensional (3D) reconstruction of subendothelial foam cells provide visual evidence of lipid macropinocytosis in both human and murine atherosclerotic arteries. Our findings complement the SR paradigm of atherosclerosis and identify a therapeutic strategy to counter the development of atherosclerosis and cardiovascular disease.

Mesenchymal Stem Cell-Derived Nanovesicles as a Credible Agent for Therapy of Pulmonary Hypertension

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have been evaluated in many studies as promising therapeutic agents for pulmonary hypertension (PH). However, low yields and heterogeneity are a major barrier in the translational utility of EVs for clinical studies. To address these limitations, we fabricated MSCs derived nanovesicles (MSC-NVs) by serial extrusion through filters resulting in MSC-NVs with characteristics similar to conventional EVs but with much higher production yields. Herein, we examined the therapeutic efficacy of MSC-NVs in preclinical models of PH in vitro and in vivo. Intervention with MSC-NVs improved the core pathologies of monocrotaline (MCT) induced PH in rat. Intravenous administration of MSC-NVs resulted in significant uptake within hypertensive lungs, pulmonary artery lesions and especially in pulmonary artery smooth muscle cells (PASMCs). In vitro, MSC-NVs inhibited PDGF-induced proliferation, migration, and phenotype switch of PASMCs. miRNA sequencing analysis of the genetic cargo of MSC-NVs revealed that miR-125b-5p and miR-100-5p are highly abundant, suggesting they might account for the therapeutic effects of MSC-NVs in PH. Depletion of miR-125b-5p and miR-100-5p in MSCs almost completely abolished the beneficial effects of MSC-NVs in protecting PASMCs from PDGF stimulated changes in vitro, and also diminished the protective effects of MSC-NVs in MCT induced PH in vivo. These data highlight the efficacy and advantages of MSC-NVs over MSC-EVs as a promising therapeutic strategy against PH.

Abstract 209: ATIC-associated De Novo Purine Biosynthesis Is Critically Involved In Proliferative Arterial Disease

Background: Proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of arterial diseases, especially in arterial restenosis following angioplasty or stent placement. VSMCs reprogram their metabolisms to meet increased requirement of lipid, protein and nucleotide for their proliferation. D e novo purine biosynthesis is one of critical pathways for nucleotide synthesis. However, its role in proliferation of VSMCs in these arterial diseases has not been defined.

Methods: De novo purine synthesis in proliferative VSMCs was evaluated by LC-MS/MS. The expression of ATIC/Atic (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase), the critical bifunctional enzyme in the last two steps of de novo purine biosynthesis pathway, was assessed in VMSCs of proliferative arterial neointima. Global and VSMC-specific knockout of Atic mice were generated and used for examining the role of Atic-associated purine metabolism in the formation of arterial neointima and atherosclerotic lesion.

Results: In this study, we found that de novo purine synthesis was increased in proliferative VSMCs. Upregulated purine synthesis genes including ATIC/Atic were observed in the neointima of the injured vessels and atherosclerotic lesions both in mouse and human. Global or specific knockout of Atic in VSMCs inhibited cell proliferation, attenuating the arterial neointima in models of mouse atherosclerosis and arterial restenosis.

Conclusions: These results reveal that de novo purine biosynthesis plays an important role in VSMC proliferation in arterial disease. These findings suggest that targeting ATIC is a promising therapeutic approach to combat arterial diseases.

Exercise improves angiogenic function of circulating exosomes in type 2 diabetes: Role of exosomal SOD3

Exosomes, key mediators of cell-cell communication, derived from type 2 diabetes mellitus (T2DM) exhibit detrimental effects. Exercise improves endothelial function in part via the secretion of exosomes into circulation. Extracellular superoxide dismutase (SOD3) is a major secretory copper (Cu) antioxidant enzyme that catalyzes the dismutation of O₂^•- to H₂ O₂ whose activity requires the Cu transporter ATP7A. However, the role of SOD3 in exercise-induced angiogenic effects of circulating plasma exosomes on endothelial cells (ECs) in T2DM remains unknown. Here, we show that both SOD3 and ATP7A proteins were present in plasma exosomes in mice, which was significantly increased after two weeks of volunteer wheel exercise. A single bout of exercise in humans also showed a significant increase in SOD3 and ATP7A protein expression in plasma exosomes. Plasma exosomes from T2DM mice significantly reduced angiogenic responses in human ECs or mouse skin wound healing models, which was associated with a decrease in ATP7A, but not SOD3 expression in exosomes. Exercise training in T2DM mice restored the angiogenic effects of T2DM exosomes in ECs by increasing ATP7A in exosomes, which was not observed in exercised T2DM/SOD3^-/- mice. Furthermore, exosomes overexpressing SOD3 significantly enhanced angiogenesis in ECs by increasing local H₂ O₂  levels in a heparin-binding domain-dependent manner as well as restored defective wound healing and angiogenesis in T2DM or SOD3^-/- mice. In conclusion, exercise improves the angiogenic potential of circulating exosomes in T2DM in a SOD3-dependent manner. Exosomal SOD3 may provide an exercise mimetic therapy that supports neovascularization and wound repair in cardiometabolic disease.

Abstract P275: Deletion Of Endothelial Leptin Receptor Elevates Blood Pressure And Impairs Endothelial-dependent Relaxation Via Upregulation Of Endothelial Glycolytic Enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3)

The adipokine leptin plays a crucial role in blood pressure (BP) regulation notably by exerting pressor effects centrally via sympatho-activation and depressor effects via direct activation of its receptor (LepR) peripherally resulting in nitric oxide (NO)-mediated vasodilation. However, the predominant effects and cell type responsible for leptin-mediated NO production is not clearly understood. Herein, we examined the effect of selective deletion of LepR in endothelial cells (LepR EC-/- , KO) on BP and vascular function. BP recording via radiotelemetry in male KO and WT (LepR EC+/+ ) mice revealed significant increases in diastolic and mean arterial pressure in KO mice (DBP, WT: 90.2±2.1 vs. KO: 100.1±3.6; MAP, WT: 105.7±2.1 vs. KO: 113.7±2.6 mmHg, n=5, p<0.05). There was no difference in Systolic blood pressure or heart rate between KO and WT. Leptin infusion (0.9mg/kg/day,7 days) elicits a significant increase in BP of WT but not KO mice (DBP, WT: 89.2± 2.6 vs WT+Leptin 95.7±3.3; MAP, WT: 104 ±2.8 vs WT+Leptin: 110 ±2.7, n=5, p<0.05). We quantified sympathetic contribution to BP elevation by measuring BP response to glanglionic blockade (Hexamethonium). At baseline, KO mice exhibited a lower BP response than WT supporting a reduced neurogenic control of BP regulation in KO mice. Vascular contribution to high BP was investigated using wire myography in thoracic aorta. LepR deficiency impaired endothelial-dependent relaxation (EDR) to acetylcholine (n=7, p<0.05). L-NAME completely abolished EDR in KO and WT indicating that EC LepR deficiency reduced NO bioavailability. Recent evidence presents PFKFB3-mediated EC glycolysis as a new regulator of endothelial homeostasis. We found that aortic EC from KO exhibited increased PFKFB3 mRNA expression (p=0.065) and PFKFB3 inhibition restored EDR in KO. Remarkably, overexpression of PFKFB3 increased EC glycolysis in vitro and impaired EDR in WT aortic rings ex vivo . Collectively, our data suggest that impaired endothelial leptin receptor signaling induces a PFKFB3-dependent hyper-glycolytic phenotype resulting in NO deficiency and endothelial dysfunction that predisposes to higher BP regardless the reduced sympatho-activation which might prevent the increase in BP induced by exogenous leptin.

Endothelial arginase 2 mediates retinal ischemia/reperfusion injury by inducing mitochondrial dysfunction

Objective

Retinal ischemic disease is a major cause of vision loss. Current treatment options are limited to late-stage diseases, and the molecular mechanisms of the initial insult are not fully understood. We have previously shown that the deletion of the mitochondrial arginase isoform, arginase 2 (A2), limits neurovascular injury in models of ischemic retinopathy. Here, we investigated the involvement of A2-mediated alterations in mitochondrial dynamics and function in the pathology.

Methods

We used wild-type (WT), global A2 knockout (A2KO-) mice, cell-specific A2 knockout mice subjected to retinal ischemia/reperfusion (I/R), and bovine retinal endothelial cells (BRECs) subjected to an oxygen-glucose deprivation/reperfusion (OGD/R) insult. We used western blotting to measure levels of cell stress and death markers and the mitochondrial fragmentation protein, dynamin related protein 1 (Drp1). We also used live cell mitochondrial labeling and Seahorse XF analysis to evaluate mitochondrial fragmentation and function, respectively.

Results

We found that the global deletion of A2 limited the I/R-induced disruption of retinal layers, fundus abnormalities, and albumin extravasation. The specific deletion of A2 in endothelial cells was protective against I/R-induced neurodegeneration. The OGD/R insult in BRECs increased A2 expression and induced cell stress and cell death, along with decreased mitochondrial respiration, increased Drp1 expression, and mitochondrial fragmentation. The overexpression of A2 in BREC also decreased mitochondrial respiration, promoted increases in the expression of Drp1, mitochondrial fragmentation, and cell stress and resulted in decreased cell survival. In contrast, the overexpression of the cytosolic isoform, arginase 1 (A1), did not affect these parameters.

Conclusions

This study is the first to show that A2 in endothelial cells mediates retinal ischemic injury through a mechanism involving alterations in mitochondrial dynamics and function.

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Ischemic retinopathy is a common feature of blinding eye disease.

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Arginase 2 overexpression in endothelial cells induces mitochondrial dysfunction.

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Endothelial-specific arginase 2 deletion improves neuronal survival after ischemia.

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Endothelial cell arginase 2 plays a crucial role in ischemic retinal injury.

Dual Role of Hydrogen Peroxide as an Oxidant in Pneumococcal Pneumonia

Significance:Streptococcus pneumoniae (Spn), a facultative anaerobic Gram-positive human pathogen with increasing rates of penicillin and macrolide resistance, is a major cause of lower respiratory tract infections worldwide. Pneumococci are a primary agent of severe pneumonia in children younger than 5 years and of community-acquired pneumonia in adults. A major defense mechanism toward Spn is the generation of reactive oxygen species, including hydrogen peroxide (H₂O₂), during the oxidative burst of neutrophils and macrophages. Paradoxically, Spn produces high endogenous levels of H₂O₂ as a strategy to promote colonization. Recent Advances: Pneumococci, which express neither catalase nor common regulators of peroxide stress resistance, have developed unique mechanisms to protect themselves from H₂O₂. Spn generates high levels of H₂O₂ as a strategy to promote colonization. Production of H₂O₂ moreover constitutes an important virulence phenotype and its cellular activities overlap and complement those of other virulence factors, such as pneumolysin, in modulating host immune responses and promoting organ injury. Critical Issues: This review examines the dual role of H₂O₂ in pneumococcal pneumonia, from the viewpoint of both the pathogen (defense mechanisms, lytic activity toward competing pathogens, and virulence) and the resulting host-response (inflammasome activation, endoplasmic reticulum stress, and damage to the alveolar-capillary barrier in the lungs). Future Directions: An understanding of the complexity of H₂O₂-mediated host-pathogen interactions is necessary to develop novel strategies that target these processes to enhance lung function during severe pneumonia.

Bmi-1 alleviates adventitial fibroblast senescence by eliminating ROS in pulmonary hypertension

Objectives

Pulmonary hypertension (PH) is a life-threatening progressive disease with high mortality in the elderly. However, the pathogenesis of PH has not been fully understood and there is no effective therapy to reverse the disease process. This study aims to determine whether cellular senescence is involved in the development of PH.

Methods

The rat PH model was established by intraperitoneal injection of monocrotaline and evaluated by pulmonary arteriole wall thickness and right ventricular hypertrophy index. Human lung fibroblasts (HLFs) were treated with CoCl₂ or hypoxia to induce cellular senescence in vitro. SA-β-gal staining and the changes of senescent markers were used to examine cellular senescence. The molecular mechanism of cellular senescence was further explored by detecting reactive oxygen species (ROS) levels and culturing cells with a conditioned medium.

Results

We revealed the cellular senescence of pulmonary adventitial fibroblasts in vivo in the rat PH model. The expression of Bmi-1, an important regulator of senescence, was decreased in the lungs of PH rats and localized in adventitial fibroblasts. The in vitro experiments showed that p16 expression was increased while Bmi-1 expression was decreased after CoCl₂ treatment in HLFs. Mechanistically, Bmi-1 could alleviate CoCl₂-induced HLFs senescence by eliminating ROS which further promoted the proliferation of pulmonary artery smooth muscle cells by paracrine mode of action of HLFs.

Conclusion

Bmi-1 alleviates the cellular senescence of pulmonary fibroblasts in PH, which expands the pathogenesis of PH and provides a theoretical basis for targeting senescent cells in the treatment of PH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01439-0.

Adenosine kinase is critical for neointima formation after vascular injury by inducing aberrant DNA hypermethylation

AIMS

Adenosine receptors and extracellular adenosine have been demonstrated to modulate vascular smooth muscle cell (VSMC) proliferation and neointima formation. Adenosine kinase (ADK) is a major enzyme regulating intracellular adenosine levels but is function in VSMC remains unclear. Here, we investigated the role of ADK in vascular injury-induced smooth muscle proliferation and delineated the mechanisms underlying its action.

METHODS AND RESULTS

We found that ADK expression was higher in the neointima of injured vessels and in platelet-derived growth factor-treated VSMCs. Genetic and pharmacological inhibition of ADK was enough to attenuate arterial injury-induced neointima formation due to inhibition of VSMC proliferation. Mechanistically, using infinium methylation assays and bisulfite sequencing, we showed that ADK metabolized the intracellular adenosine and potentiated the transmethylation pathway, then induced the aberrant DNA hypermethylation. Pharmacological inhibition of aberrant DNA hypermethylation increased KLF4 expression and suppressed VSMC proliferation as well as the neointima formation. Importantly, in human femoral arteries, we observed increased ADK expression and DNA hypermethylation as well as decreased KLF4 expression in neointimal VSMCs of stenotic vessels suggesting that our findings in mice are relevant for human disease and may hold translational significance.

CONCLUSION

Our study unravels a novel mechanism by which ADK promotes VSMC proliferation via inducing aberrant DNA hypermethylation, thereby down-regulating KLF4 expression and promoting neointima formation. These findings advance the possibility of targeting ADK as an epigenetic modulator to combat vascular injury.

The changing sociocultural context of wildlife conservation

We introduced a multilevel model of value shift to describe the changing social context of wildlife conservation. Our model depicts how cultural-level processes driven by modernization (e.g., increased wealth, education, and urbanization) affect changes in individual-level cognition that prompt a shift from domination to mutualism wildlife values. Domination values promote beliefs that wildlife should be used primarily to benefit humans, whereas mutualism values adopt a view that wildlife are part of one's social network and worthy of care and compassion. Such shifts create emergent effects (e.g., new interest groups) and challenges to wildlife management organizations (e.g., increased conflict) and dramatically alter the sociopolitical context of conservation decisions. Although this model is likely applicable to many modernized countries, we tested it with data from a 2017-2018 nationwide survey (mail and email panel) of 43,949 residents in the United States. We conducted hierarchical linear modeling and correlational analysis to examine relationships. Modernization variables had strong state-level effects on domination and mutualism. Higher levels of education, income, and urbanization were associated with higher percentages of mutualists and lower percentages of traditionalists, who have strong domination values. Values affected attitudes toward wildlife management challenges; for example, states with higher proportions of mutualists were less supportive of lethal control of wolves (Canis lupus) and had lower percentages of active hunters, who represent the traditional clientele of state wildlife agencies in the United States. We contend that agencies will need to embrace new strategies to engage and represent a growing segment of the public with mutualism values. Our model merits testing for application in other countries.

Caveolin-1 stabilizes ATP7A, a copper transporter for extracellular SOD, in vascular tissue to maintain endothelial function

Caveolin-1 (Cav-1) is a scaffolding protein and a major component of caveolae/lipid rafts. Previous reports have shown that endothelial dysfunction in Cav-1-deficient (Cav-1-/-) mice is mediated by elevated oxidative stress through endothelial nitric oxide synthase (eNOS) uncoupling and increased NADPH oxidase. Oxidant stress is the net balance of oxidant generation and scavenging, and the role of Cav-1 as a regulator of antioxidant enzymes in vascular tissue is poorly understood. Extracellular SOD (SOD3) is a copper (Cu)-containing enzyme that is secreted from vascular smooth muscle cells/fibroblasts and subsequently binds to the endothelial cells surface, where it scavenges extracellular [Formula: see text] and preserves endothelial function. SOD3 activity is dependent on Cu, supplied by the Cu transporter ATP7A, but whether Cav-1 regulates the ATP7A-SOD3 axis and its role in oxidative stress-mediated vascular dysfunction has not been studied. Here we show that the activity of SOD3, but not SOD1, was significantly decreased in Cav-1-/- vessels, which was rescued by re-expression of Cav-1 or Cu supplementation. Loss of Cav-1 reduced ATP7A protein, but not mRNA, and this was mediated by ubiquitination of ATP7A and proteasomal degradation. ATP7A bound to Cav-1 and was colocalized with SOD3 in caveolae/lipid rafts or perinucleus in vascular tissues or cells. Impaired endothelium-dependent vasorelaxation in Cav-1-/- mice was rescued by gene transfer of SOD3 or by ATP7A-overexpressing transgenic mice. These data reveal an unexpected role of Cav-1 in stabilizing ATP7A protein expression by preventing its ubiquitination and proteasomal degradation, thereby increasing SOD3 activity, which in turn protects against vascular oxidative stress-mediated endothelial dysfunction.

Abstract P242: Perivascular Adipose Tissue Regulates Endothelial Function And Glucose Disposal Via Leptin Control Of The 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 / NADPH Oxidase 1 Pathways

Our group has previously reported that lack of adipose tissue (lipodystrophy) leads to glucose intolerance and impaired endothelial-dependent vasorelaxation (EDR) via reduced signaling of the adipokine, leptin in the endothelium. However, the identity of the adipose depot responsible for endothelial leptin signaling activation and the underlying mechanism remains ill-defined. Our new data indicate that the perivascular adipose tissue (PVAT) is an important source of leptin. Thus, we hypothesized that leptin specifically derived from PVAT restores EDR and glucose tolerance in a mouse model with global deficiency in adipose tissue (lipodystrophic, BSCL2 -/- ). Restoration of PVAT in BSCL2 -/- mice corrected systemic glycemic status (GTT AUC, BSCL2 -/- + PVAT 635.3 ± 31.28 vs sham 741.6 ± 45.87, p<0.05). Moreover, PVAT transplantation restored EDR locally (abdominal aorta EDR AUC, BSCL2 -/- + PVAT 224.9 ± 23.97 vs 109 ± 19, P<0.05) but not systemically (thoracic aorta EDR AUC, BSCL2 -/- + PVAT 143.8 ± 22.29 vs sham 131.3 ± 11.54, P<0.05), indicating a distinctive paracrine role for PVAT-derived leptin in the vasculature. Concomitantly, we reported that inhibition of endothelial glycolysis, the main bioenergetic pathway of endothelial cells, via inhibition of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a major regulator of the glycolytic pathway, significantly improved endothelial function in both lipodystrophic mice and endothelial leptin receptor (LepR) deficient mice, as leptin does. Also, endothelial cells extracted from aortas of BSCL2 -/- mice showed a trend towards an increase in PFKFB3 mRNA expression compared to WT mice. Moreover, we found that overexpression of PFKFB3 in aortic rings and endothelial cells impaired EDR and increased the ROS generating enzyme, Nox1 expression, respectively. Collectively, our results showed the critical role of PVAT-driven leptin and endothelial leptin receptor signaling in regulating systemic glucose disposal as well as endothelial function via a mechanism that potentially regulates endothelial glycolysis and oxidative stress-mediated via PFKFB3/NOX1.

Reactive Oxygen Species-Dependent Calpain Activation Contributes to Airway and Pulmonary Vascular Remodeling in Chronic Obstructive Pulmonary Disease

Aims: Airway and pulmonary vascular remodeling is an important pathological feature in the pathogenesis of chronic obstructive pulmonary disease (COPD). Tobacco smoke (TS) induces the production of large amounts of reactive oxygen species (ROS) in COPD lungs. We investigated how ROS lead to airway and pulmonary vascular remodeling in COPD. Results: We used in vitro bronchial and pulmonary artery smooth muscle cells (BSMCs and PASMCs), in vivo TS-induced COPD rodent models, and lung tissues of COPD patients. We found that H2O2 and TS extract (TSE) induced calpain activation in BSMCs and PASMCs. Calpain activation was elevated in smooth muscle of bronchi and pulmonary arterioles in COPD patients and TS-induced COPD rodent models. Calpain inhibition attenuated H2O2- and TSE-induced collagen synthesis and proliferation of BSMCs and PASMCs. Exposure to TS causes increases in airway resistance, right ventricular systolic pressure (RVSP), and thickening of bronchi and pulmonary arteries. Calpain inhibition by smooth muscle-specific knockout of calpain and the calpain inhibitor MDL28170 attenuated increases in airway resistance, RVSP, and thickening of bronchi and pulmonary arteries. Moreover, smooth muscle-specific knockout of calpain did not reduce TS-induced emphysema in the mouse model, but MDL28170 did reduce TS-induced emphysema in the rat model. Innovation: This study provides the first evidence that ROS-induced calpain activation contributes to airway and pulmonary vascular remodeling in TS-induced COPD. Calpain might be a novel therapeutic target for the treatment of COPD. Conclusion: These results indicate that ROS-induced calpain activation contributes to airway and pulmonary vascular remodeling and pulmonary hypertension in COPD.

Copper Transporter ATP7A (Copper-Transporting P-Type ATPase/Menkes ATPase) Limits Vascular Inflammation and Aortic Aneurysm Development: Role of MicroRNA-125b

OBJECTIVE

Copper (Cu) is essential micronutrient, and its dysregulation is implicated in aortic aneurysm (AA) development. The Cu exporter ATP7A (copper-transporting P-type ATPase/Menkes ATPase) delivers Cu via the Cu chaperone Atox1 (antioxidant 1) to secretory Cu enzymes, such as lysyl oxidase, and excludes excess Cu. Lysyl oxidase is shown to protect against AA formation. However, the role and mechanism of ATP7A in AA pathogenesis remain unknown. Approach and Results: Here, we show that Cu chelator markedly inhibited Ang II (angiotensin II)-induced abdominal AA (AAA) in which ATP7A expression was markedly downregulated. Transgenic ATP7A overexpression prevented Ang II-induced AAA formation. Conversely, Cu transport dysfunctional ATP7A^mut/+/ApoE^-/- mice exhibited robust AAA formation and dissection, excess aortic Cu accumulation as assessed by X-ray fluorescence microscopy, and reduced lysyl oxidase activity. In contrast, AAA formation was not observed in Atox1^-/-/ApoE^-/- mice, suggesting that decreased lysyl oxidase activity, which depends on both ATP7A and Atox1, was not sufficient to develop AAA. Bone marrow transplantation suggested importance of ATP7A in vascular cells, not bone marrow cells, in AAA development. MicroRNA (miR) array identified miR-125b as a highly upregulated miR in AAA from ATP7A^mut/+/ApoE^-/- mice. Furthermore, miR-125b target genes (histone methyltransferase Suv39h1 and the NF-κB negative regulator TNFAIP3 [tumor necrosis factor alpha induced protein 3]) were downregulated, which resulted in increased proinflammatory cytokine expression, aortic macrophage recruitment, MMP (matrix metalloproteinase)-2/9 activity, elastin fragmentation, and vascular smooth muscle cell loss in ATP7A^mut/+/ApoE^-/- mice and reversed by locked nucleic acid-anti-miR-125b infusion.

CONCLUSIONS

ATP7A downregulation/dysfunction promotes AAA formation via upregulating miR-125b, which augments proinflammatory signaling in a Cu-dependent manner. Thus, ATP7A is a potential therapeutic target for inflammatory vascular disease.

Engineering molecularly imprinted polymers (MIPs) for the selective extraction and quantification of the novel psychoactive substance (NPS) methoxphenidine and its regioisomers

In this communication, we present the first developed Molecularly Imprinted Polymers (MIPs) for the specific detection of a New Psychoactive Substance (NPS); namely, methoxphenidine (MXP) and its regioisomers. Selectivity of the MIP towards MXP is studied by analysing mixtures and an acquired street sample with High Performance Liquid Chromatography coupled to UV detection. The study demonstrates that the engineered polymers selectively extract MXP from heterogeneous samples, which makes for a very powerful diagnostic tool that can detect traces of MXP in complicated NPS samples.

Histone deacetylases in vascular permeability and remodeling associated with acute lung injury

Acute lung injury (ALI) is a severe progressive disorder that arises from a wide range of causes such as toxins or inflammation, resulting in significant morbidity and mortality. There are no effective therapeutic options apart from mechanical ventilation strategies. While the mechanisms that govern the clinically relevant process of increased EC permeability and remodeling associated with ALI are under intense investigation, our knowledge of the processes that determine barrier enhancement or preservation are far from completion. Recently, epigenetic mechanisms have emerged as a major regulator of enduring changes in cell behavior and the therapeutic potential of inhibiting histone deacetylases (HDACs) for the treatment of cardiovascular and inflammatory diseases has gained remarkable attention. Although HDACs have been shown to play an important role in regulating EC barrier function, the involved HDAC subtypes and mechanisms remain undefined. Further investigation of the HDAC signaling may provide therapeutic approaches for the prevention and treatment of ALI.

Mechanisms of Diabetes-Induced Endothelial Cell Senescence: Role of Arginase 1

We have recently found that diabetes-induced premature senescence of retinal endothelial cells is accompanied by NOX2-NADPH oxidase-induced increases in the ureohydrolase enzyme arginase 1 (A1). Here, we used genetic strategies to determine the specific involvement of A1 in diabetes-induced endothelial cell senescence. We used A1 knockout mice and wild type mice that were rendered diabetic with streptozotocin and retinal endothelial cells (ECs) exposed to high glucose or transduced with adenovirus to overexpress A1 for these experiments. ABH [2(S)-Amino-6-boronohexanoic acid] was used to inhibit arginase activity. We used Western blotting, immunolabeling, quantitative PCR, and senescence associated β-galactosidase (SA β-Gal) activity to evaluate senescence. Analyses of retinal tissue extracts from diabetic mice showed significant increases in mRNA expression of the senescence-related proteins p16^INK4a, p21, and p53 when compared with non-diabetic mice. SA β-Gal activity and p16^INK4a immunoreactivity were also increased in retinal vessels from diabetic mice. A1 gene deletion or pharmacological inhibition protected against the induction of premature senescence. A1 overexpression or high glucose treatment increased SA β-Gal activity in cultured ECs. These results demonstrate that A1 is critically involved in diabetes-induced senescence of retinal ECs. Inhibition of arginase activity may therefore be an effective therapeutic strategy to alleviate diabetic retinopathy by preventing premature senescence.

Why social values cannot be changed for the sake of conservation

The hope for creating widespread change in social values has endured among conservation professionals since early calls by Aldo Leopold for a "land ethic." However, there has been little serious attention in conservation to the fields of investigation that address values, how they are formed, and how they change. We introduce a social-ecological systems conceptual approach in which values are seen not only as motivational goals people hold but also as ideas that are deeply embedded in society's material culture, collective behaviors, traditions, and institutions. Values define and bind groups, organizations, and societies; serve an adaptive role; and are typically stable across generations. When abrupt value changes occur, they are in response to substantial alterations in the social-ecological context. Such changes build on prior value structures and do not result in complete replacement. Given this understanding of values, we conclude that deliberate efforts to orchestrate value shifts for conservation are unlikely to be effective. Instead, there is an urgent need for research on values with a multilevel and dynamic view that can inform innovative conservation strategies for working within existing value structures. New directions facilitated by a systems approach will enhance understanding of the role values play in shaping conservation challenges and improve management of the human component of conservation.

Epithelial Sodium Channel-α Mediates the Protective Effect of the TNF-Derived TIP Peptide in Pneumolysin-Induced Endothelial Barrier Dysfunction

BACKGROUND

Streptococcus pneumoniae is a major etiologic agent of bacterial pneumonia. Autolysis and antibiotic-mediated lysis of pneumococci induce release of the pore-forming toxin, pneumolysin (PLY), their major virulence factor, which is a prominent cause of acute lung injury. PLY inhibits alveolar liquid clearance and severely compromises alveolar-capillary barrier function, leading to permeability edema associated with pneumonia. As a consequence, alveolar flooding occurs, which can precipitate lethal hypoxemia by impairing gas exchange. The α subunit of the epithelial sodium channel (ENaC) is crucial for promoting Na⁺ reabsorption across Na⁺-transporting epithelia. However, it is not known if human lung microvascular endothelial cells (HL-MVEC) also express ENaC-α and whether this subunit is involved in the regulation of their barrier function.

METHODS

The presence of α, β, and γ subunits of ENaC and protein phosphorylation status in HL-MVEC were assessed in western blotting. The role of ENaC-α in monolayer resistance of HL-MVEC was examined by depletion of this subunit by specific siRNA and by employing the TNF-derived TIP peptide, a specific activator that directly binds to ENaC-α.

RESULTS

HL-MVEC express all three subunits of ENaC, as well as acid-sensing ion channel 1a (ASIC1a), which has the capacity to form hybrid non-selective cation channels with ENaC-α. Both TIP peptide, which specifically binds to ENaC-α, and the specific ASIC1a activator MitTx significantly strengthened barrier function in PLY-treated HL-MVEC. ENaC-α depletion significantly increased sensitivity to PLY-induced hyperpermeability and in addition, blunted the protective effect of both the TIP peptide and MitTx, indicating an important role for ENaC-α and for hybrid NSC channels in barrier function of HL-MVEC. TIP peptide blunted PLY-induced phosphorylation of both calmodulin-dependent kinase II (CaMKII) and of its substrate, the actin-binding protein filamin A (FLN-A), requiring the expression of both ENaC-α and ASIC1a. Since non-phosphorylated FLN-A promotes ENaC channel open probability and blunts stress fiber formation, modulation of this activity represents an attractive target for the protective actions of ENaC-α in both barrier function and liquid clearance.

CONCLUSION

Our results in cultured endothelial cells demonstrate a previously unrecognized role for ENaC-α in strengthening capillary barrier function that may apply to the human lung. Strategies aiming to activate endothelial NSC channels that contain ENaC-α should be further investigated as a novel approach to improve barrier function in the capillary endothelium during pneumonia.

NOX2-Induced Activation of Arginase and Diabetes-Induced Retinal Endothelial Cell Senescence

Increases in reactive oxygen species (ROS) and decreases in nitric oxide (NO) have been linked to vascular dysfunction during diabetic retinopathy (DR). Diabetes can reduce NO by increasing ROS and by increasing activity of arginase, which competes with nitric oxide synthase (NOS) for their commons substrate l-arginine. Increased ROS and decreased NO can cause premature endothelial cell (EC) senescence leading to defective vascular repair. We have previously demonstrated the involvement of NADPH oxidase 2 (NOX2)-derived ROS, decreased NO and overactive arginase in DR. Here, we investigated their impact on diabetes-induced EC senescence. Studies using diabetic mice and retinal ECs treated with high glucose or H₂O₂ showed that increases in ROS formation, elevated arginase expression and activity, and decreased NO formation led to premature EC senescence. NOX2 blockade or arginase inhibition prevented these effects. EC senescence was also increased by inhibition of NOS activity and this was prevented by treatment with a NO donor. These results indicate that diabetes/high glucose-induced activation of arginase and decreases in NO bioavailability accelerate EC senescence. NOX2-generated ROS contribute importantly to this process. Blockade of NOX2 or arginase represents a strategy to prevent diabetes-induced premature EC senescence by preserving NO bioavailability.

Nox2-Mediated PI3K and Cofilin Activation Confers Alternate Redox Control of Macrophage Pinocytosis

AIMS

Internalization of extracellular fluid and its solute by macropinocytosis requires dynamic reorganization of actin cytoskeleton, membrane ruffling, and formation of large endocytic vacuolar compartments, called macropinosomes, inside the cell. Although instigators of macropinocytosis, such as growth factors and phorbol esters, stimulate NADPH oxidase (Nox) activation and signal transduction mediators upstream of Nox assembly, including Rac1 and protein kinase C (PKC), are involved in macropinocytosis, the role of Nox enzymes in macropinocytosis has never been investigated. This study was designed to examine the role of Nox2 and the potential downstream redox signaling involved in macropinocytosis.

RESULTS

Phorbol myristate acetate activation of human and murine macrophages stimulated membrane ruffling, macropinosome formation, and subsequent uptake of macromolecules by macropinocytosis. Mechanistically, we found that pharmacological blockade of PKC, transcriptional knockdown of Nox2, and scavenging of intracellular superoxide anion abolished phorbol ester-induced macropinocytosis. We observed that Nox2-derived reactive oxygen species via inhibition of phosphatase and tensin homolog and activation of the phosphoinositide-3-kinase (PI3K)/Akt pathway lead to activation of actin-binding protein cofilin, membrane ruffling, and macropinocytosis. Similarly, activation of macropinocytosis by macrophage colony-stimulating factor involves Nox2-mediated cofilin activation. Furthermore, peritoneal chimera experiments indicate that macropinocytotic uptake of lipids in hypercholesterolemic ApoE^-/- mice was attenuated in Nox2^y/- macrophages compared with wild-type controls. Innovation and Conclusion: In summary, these findings demonstrate a novel Nox2-mediated mechanism of solute uptake via macropinocytosis, with broad implications for both general cellular physiology and pathological processes. The redox mechanism described here may also identify new targets in atherosclerosis and other disease conditions involving macropinocytosis. Antioxid. Redox Signal. 26, 902-916.

Abstract 636: Regulation of Galectin-3 Expression in Pulmonary Vascular Smooth Muscle by Dna Methylation

Pulmonary Arterial Hypertension (PAH) is characterized by excessive vascular cell proliferation, inward remodeling and increased stiffness and inflammation of the pulmonary blood vessels. We found that galectin-3 (Gal-3) is upregulated in PA from multiple models of PAH including monocrotaline (MCT), MCT + pneumonectomy, and SUGEN/hypoxia rats as well as in human PAH and correlated with severity of disease. Gal-3 is a β-galactoside binding lectin implicated in signaling pathways regulating cell proliferation, inflammation and fibrosis, but its role in PAH is poorly defined. Confocal analysis revealed the majority of Gal-3 expression in the media of PA of both rodent models and humans. Selective inhibitors of Gal-3 attenuated PAH in MCT-treated rats and reduced indices of proliferation, fibrosis and increased apoptosis in PA. Overexpression of Gal-3 in PASMC increased proliferation, migration and expression of profibrotic molecules and protected from apoptosis. Acute exposure of cultured HPASMC with various mitogens and factors important in the development of PAH, failed to increase Gal-3 expression. In contrast, PASMC isolated from rats with PAH exhibited an enduring capacity for increased proliferation and expressed higher levels of Gal-3 suggesting an epigenetic mechanism regulating Gal-3 expression. We found that treatment of PASMC with inhibitors of DNA methylation robustly increased Gal-3 expression in control human and rat PASMC but not in MCT-derived PASMC. Methylation analysis of DNA isolated from PA using MeDIP-qPCR and pyrosequencing revealed hypomethylation of Gal-3 proximal promoter. Analysis of DNA methyltransferase expression in PA revealed a significant loss of only Dnmt3A expression in hypertensive PA. To assess the role of local methylation in the regulation of Gal-3 expression we used CRISPR-dCas9. Targeted Gal-3 promoter methylation using multiple RNA guides and dCas9-Dnmt3A-Dnmt3L effectively reduced Gal-3 expression in SMC isolated from MCT rat PA and reversed the excessive proliferation. These results advance an important role of methylation-dependent mechanisms in Gal-3 signaling and provide a mechanism for the enduring changes in vascular cell behavior observed in PAH.

Abstract 3: Cellular Contributions of the Circadian Clock in Atherogenesis

Atherosclerosis is a leading cause of death despite the improvements in lipid and blood pressure control. The circadian clock, a molecular network of genes and proteins that controls 24-hour timing, has emerged to have a surprising role in the control of metabolic and vascular function. Herein we examined the impact of circadian rhythm dysfunction in atherogenesis by implementation of vascular transplant and PCSK9 based approaches to induce accelerated lesion development in mice. We find that atherogenesis is exacerbated in Bmal1-KO aortic grafts immersed in the hypercholesterolemic milieu of ApoE -/- mice. To assess if atherosclerosis was ‘circadian rhythm dependent’ we subjected wild-type mice to a shortened light cycle (4L/4D) and induced atherosclerosis by intravenous injection of a human PCSK-9 adeno associated virus. Atherosclerosis in the jet-lagged PCSK-9 mice was robustly increased relative to the atherosclerosis observed in WT mice on a normal light cycle (12L/12D), providing further evidence that circadian rhythm and the circadian clock contribute to atherosclerosis. However, atherosclerosis is a complex disease that is the net result of interplay between intrinsic (vascular cells) and extrinsic mechanisms (metabolism, blood pressure, and hormones) and the importance of clock function in individual cell types is poorly understood. We found that deletion or silencing of key circadian transcription factors resulted in an enhanced inflammatory and pro-oxidant phenotype with diminished NO production and greater lipid uptake in both macrophages and endothelial cells. Loss of circadian function in smooth muscle cells similarly resulted in enhanced production of reactive oxygen species and greater cell proliferation. Surprising, the silencing of Bmal2 in endothelial cells resulted in greater lipid uptake in oxLDL treated HAEC as well as increased expression of markers of autophagy, suggesting that Bmal2 may orchestrate numerous output functions in different cell types. In conclusion, we find that the circadian clock and circadian rhythm have a profound impact on atherosclerosis, to influence vascular cell inflammatory and lipid uptake responses, and identify an unexpectedly prominent role for the side-partner of Bmal1, Bmal2.

Adventitial Fibroblast Nox4 Expression and ROS Signaling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease arising from remodeling and narrowing of pulmonary arteries (PA) resulting in high pulmonary arterial blood pressure and ultimately right ventricular failure. Elevated production of reactive oxygen species (ROS) by NADPH oxidase 4 (Nox4), a constitutively active enzyme, has been associated with oxygen sensing, vasomotor control, cellular proliferation, differentiation, migration, apoptosis, senescence, fibrosis, and angiogenesis. Further, elevated expression of Nox4 has been reported in a number of cardiovascular diseases, including atherosclerosis, hypertension, cardiac failure, ischemic stroke, and PAH. However, the cellular location of Nox4 and its contribution to aberrant vascular remodeling in PAH remains poorly understood. The goal of this review is to summarize the recent literature on the enzymatic regulation of Nox4 in the production of ROS in PAH. In the vascular wall, Nox4 is present in fibroblasts, a primary cell of the adventitia, and matches the adventitial location of ROS production in PAH. Further, in adventitial fibroblasts, Nox4 overexpression stimulates migration and proliferation as well as matrix gene expression. Collectively, reports indicate that Nox4 contributes to altered fibroblast behavior, ROS production leading to hypertensive vascular remodeling and the development of PAH. Finally, we address the functional significance of Nox4 in fibroblasts, and also suggest an "outside in" (adventitial) process of vascular remodeling that is mediated by Nox4, which although has physiological roles in the intimal layer (i.e., endothelium), may also have pathologic importance in the adventitial layer of the vascular wall through signaling in fibroblasts.

Abstract 646: Redox Control of Macropinocytosis; An Unexplored Target in Atherosclerosis

Aims: Early studies established the paradigm that oxidation of low density lipoprotein (LDL) is necessary for scavenger receptor-mediated LDL uptake and lipid accumulation in macrophages. In addition to this “classical” mode of lipid internalization, scavenger receptor-independent uptake of native, non-oxidized LDL (nLDL) via macropinocytosis has been demonstrated to contribute to lipid uptake by macrophages. Despite this previous information the precise signaling mechanisms regulating macropinocytosis of nLDL and the relative contribution of lipid macropinocytosis to atherosclerosis remain unknown. This study was designed to examine the role of phagocyte NADPH oxidase (a.k.a. Nox2) in macropinocytosis and to investigate macropinocytotic uptake of lipids in hypercholesterolemic ApoE -/- mice in vivo .

Results: Phorbol myristate acetate (4β-PMA) activation of human and murine macrophages stimulated membrane ruffling, macropinosome formation, and subsequent uptake of nLDL by macropinocytosis. FACS data indicated that 4β-PMA stimulates lipid accumulation following nLDL treatment in macrophages lacking scavenger receptor CD36. Mechanistically, we found that pharmacological blockade of protein kinase C (PKC), inhibition of flavoenzymes by diphenyleneiodonium, and scavenging intracellular superoxide anion abolished phorbol ester-induced macropinocytosis. Transcriptional knockdown of Nox2 using siRNA inhibited 4β-PMA-induced macropinocytosis in THP-1 macrophages. Delving further into the mechanism, we found that Nox2 via redox inactivation of PTEN and activation of the PI3K/Akt pathway dephosphorylates the actin-binding protein cofilin, stimulates membrane ruffling, and induces macropinocytosis. Finally, peritoneal chimera experiments indicate that macropinocytotic uptake of lipids in hypercholesterolemic ApoE -/- mice was attenuated in Nox2 y/- macrophages compared to wild type controls.

Innovation and Conclusion: These findings suggest a previously undescribed redox-sensitive signaling pathway leading to internalization of nLDL by macropinocytosis. The signaling mechanism described herein may identify new targets in atherosclerosis and other disease conditions involving macropinocytosis.

TNFα reduces eNOS activity in endothelial cells through serine 116 phosphorylation and Pin1 binding: Confirmation of a direct, inhibitory interaction of Pin1 with eNOS

Production of NO by the endothelial nitric oxide synthase (eNOS) has a major role in blood pressure control and suppression of atherosclerosis. In a previous study, we presented evidence implicating the Pin1 prolyl isomerase in negative modulation of eNOS activity in bovine aortic endothelial cells (BAECs). Pin1 recognizes phosphoserine/phosphothreonine-proline motifs in target proteins and catalyzes prolyl isomerization at the peptide bond. In the present study, we show, first, with purified proteins, that Pin1 binds to eNOS directly via the Pin1 WW domain. Binding is enhanced by mimicking phosphorylation of eNOS at S116. Interaction of Pin1 with eNOS markedly reduces eNOS enzymatic activity. Second, in BAECs, we show that TNFα induces ERK 1/2-mediated S116 phosphorylation of eNOS, accompanied by Pin1 binding. TNFα treatment of BAECs results in a reduction in NO release from the cells in a manner that depends on the activities of both Pin1 and ERK 1/2. Evidence is also presented that this mechanism of eNOS regulation cannot occur in rat and mouse cells because there is no proline residue in the mouse and rat amino acid sequences adjacent to the putative phosphorylation site. Moreover, we find that phosphorylation of this site is not detectable in mouse eNOS.

Hsp90 inhibition suppresses NF-κB transcriptional activation via Sirt-2 in human lung microvascular endothelial cells

The ability of anti-heat shock protein 90 (Hsp90) drugs to attenuate NF-κB-mediated transcription is the major basis for their anti-inflammatory properties. While the molecular mechanisms underlying this effect are not clear, they appear to be distinct in human endothelial cells. We now show for the first time that type 2 sirtuin (Sirt-2) histone deacetylase binds human NF-κB target gene promoter and prevents the recruitment of NF-κB proteins and subsequent assembly of RNA polymerase II complex in human lung microvascular endothelial cells. Hsp90 inhibitors stabilize the Sirt-2/promoter interaction and impose a "transcriptional block," which is reversed by either inhibition or downregulation of Sirt-2 protein expression. Furthermore, this process is independent of NF-κB (p65) Lysine 310 deacetylation, suggesting that it is distinct from known Sirt-2-dependent mechanisms. We demonstrate that Sirt-2 is recruited to NF-κB target gene promoter via interaction with core histones. Upon inflammatory challenge, chromatin remodeling and core histone H3 displacement from the promoter region removes Sirt-2 and allows NF-κB/coactivator recruitment essential for RNA Pol II-dependent mRNA induction. This novel mechanism may have important implications in pulmonary inflammation.

Low-Dose IL-17 Therapy Prevents and Reverses Diabetic Nephropathy, Metabolic Syndrome, and Associated Organ Fibrosis

Diabetes is the leading cause of kidney failure, accounting for >45% of new cases of dialysis. Diabetic nephropathy is characterized by inflammation, fibrosis, and oxidant stress, pathologic features that are shared by many other chronic inflammatory diseases. The cytokine IL-17A was initially implicated as a mediator of chronic inflammatory diseases, but recent studies dispute these findings and suggest that IL-17A can favorably modulate inflammation. Here, we examined the role of IL-17A in diabetic nephropathy. We observed that IL-17A levels in plasma and urine were reduced in patients with advanced diabetic nephropathy. Type 1 diabetic mice that are genetically deficient in IL-17A developed more severe nephropathy, whereas administration of low-dose IL-17A prevented diabetic nephropathy in models of type 1 and type 2 diabetes. Moreover, IL-17A administration effectively treated, prevented, and reversed established nephropathy in genetic models of diabetes. Protective effects were also observed after administration of IL-17F but not IL-17C or IL-17E. Notably, tubular epithelial cell-specific overexpression of IL-17A was sufficient to suppress diabetic nephropathy. Mechanistically, IL-17A administration suppressed phosphorylation of signal transducer and activator of transcription 3, a central mediator of fibrosis, upregulated anti-inflammatory microglia/macrophage WAP domain protein in an AMP-activated protein kinase-dependent manner and favorably modulated renal oxidative stress and AMP-activated protein kinase activation. Administration of recombinant microglia/macrophage WAP domain protein suppressed diabetes-induced albuminuria and enhanced M2 marker expression. These observations suggest that the beneficial effects of IL-17 are isoform-specific and identify low-dose IL-17A administration as a promising therapeutic approach in diabetic kidney disease.

Heat Shock Protein 70 Prevents Hyperoxia-Induced Disruption of Lung Endothelial Barrier via Caspase-Dependent and AIF-Dependent Pathways

Exposure of pulmonary artery endothelial cells (PAECs) to hyperoxia results in a compromise in endothelial monolayer integrity, an increase in caspase-3 activity, and nuclear translocation of apoptosis-inducing factor (AIF), a marker of caspase-independent apoptosis. In an endeavor to identify proteins involved in hyperoxic endothelial injury, we found that the protein expression of heat-shock protein 70 (Hsp70) was increased in hyperoxic PAECs. The hyperoxia-induced Hsp70 protein expression is from hspA1B gene. Neither inhibition nor overexpression of Hsp70 affected the first phase barrier disruption of endothelial monolayer. Nevertheless, inhibition of Hsp70 by using the Hsp70 inhibitor KNK437 or knock down Hsp70 using siRNA exaggerated and overexpression of Hsp70 prevented the second phase disruption of lung endothelial integrity. Moreover, inhibition of Hsp70 exacerbated and overexpression of Hsp70 prevented hyperoxia-induced apoptosis, caspase-3 activation, and increase in nuclear AIF protein level in PAECs. Furthermore, we found that Hsp70 interacted with AIF in the cytosol in hyperoxic PAECs. Inhibition of Hsp70/AIF association by KNK437 correlated with increased nuclear AIF level and apoptosis in KNK437-treated PAECs. Finally, the ROS scavenger NAC prevented the hyperoxia-induced increase in Hsp70 expression and reduced the interaction of Hsp70 with AIF in hyperoxic PAECs. Together, these data indicate that increased expression of Hsp70 plays a protective role against hyperoxia-induced lung endothelial barrier disruption through caspase-dependent and AIF-dependent apoptotic pathways. Association of Hsp70 with AIF prevents AIF nuclear translocation, contributing to the protective effect of Hsp70 on hyperoxia-induced endothelial apoptosis. The hyperoxia-induced increase in Hsp70 expression and Hsp70/AIF interaction is contributed to ROS formation.