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VEGFR2 signaling in endothelial cells (ECs) is regulated by reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria, which plays an important role in postnatal angiogenesis. However, it remains unclear how highly diffusible ROS signal enhances VEGFR2 signaling and reparative angiogenesis. Protein disulfide isomerase A1 (PDIA1) functions as an oxidoreductase depending on the redox environment. We hypothesized that PDIA1 functions as a redox sensor to enhance angiogenesis. Here we showed that PDIA1 co-immunoprecipitated with VEGFR2 or colocalized with either VEGFR2 or an early endosome marker Rab5 at the perinuclear region upon stimulation of human ECs with VEGF. PDIA1 silencing significantly reduced VEGF-induced EC migration, proliferation and spheroid sprouting via inhibiting VEGFR2 signaling. Mechanistically, VEGF stimulation rapidly increased Cys-OH formation of PDIA1 via the NOX4–mitochondrial ROS axis. Overexpression of “redox-dead” mutant PDIA1 with replacement of the active four Cys residues with Ser significantly inhibited VEGF-induced PDIA1–CysOH formation and angiogenic responses via reducing VEGFR2 phosphorylation. Pdia1(+/−) mice showed impaired angiogenesis in developmental retina and Matrigel plug models as well as ex vivo aortic ring sprouting model. Study using hindlimb ischemia model revealed that PDIA1 expression was markedly increased in angiogenic ECs of ischemic muscles, and that ischemia-induced limb perfusion recovery and neovascularization were impaired in EC-specific Pdia1 conditional knockout mice. These results suggest that PDIA1 can sense VEGF-induced H(2)O(2) signal via CysOH formation to promote VEGFR2 signaling and angiogenesis in ECs, thereby enhancing postnatal angiogenesis. The oxidized PDIA1 is a potential therapeutic target for treatment of ischemic vascular diseases.

Type 1 diabetes (T1D), which prevalence is currently on the rise, is a major risk factor for cardiovascular disease (CVD). Although T1D induces endothelial dysfunction, a precursor and contributor to CVD, its etiology remains ill-defined. Aberrant increases in endothelial cell (EC) glycolysis mainly via increased expression/ activity of its regulatory enzyme, 6-phosphofructo-2- kinase/fructose-2, 6-bisphosphatase 3 (PFKFB3) contribute to several vascular disorders. Nevertheless, whether alterations in EC glycolysis impairs endothelium dependent relaxation (EDR) is unknown. Using Akita mice, a genetic model of T1D, and a newly developed assay to measure EC glycolytic capacity in aortic explants via Seahorse analyzer, we tested the hypothesis that T1D impairs endothelial function via increasing EC glycolysis. Aortic explants from Akita mice exhibited a 1.7-fold increase in glycolysis to WT (P R01s (1R01HL147639-01A1 and 1R01HL155265-01) and 19EIA34760167 to E.J. Belin de Chantemèle. APS APHYS00010 and 2020AHA000POST000204982 to R.T.Atawia This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Neddylation is a reversible post-translational modification that covalently attaches ubiquitin-like protein NEDD8 to target proteins via NEDD8-specific E1-E2-E3 enzymes. Through regulating the function of various cellular proteins, neddylation impacts diverse cellular processes and disease states. We have previously identified an indispensable role for neddylation in cardiac chamber maturation through sustaining YAP signaling in the developing heart. However, the importance of neddylation in post-mitotic hearts remains unclear. Here we report neddylation as a novel post-translation mechanism regulating mitochondrial homeostasis in adult heart. Inducible deletion of NAE1, a regulatory subunit of NEDD8 E1 enzyme, in adult mouse heart resulted in dilated cardiomyopathy, heart failure, and eventually premature lethality. The severe cardiac phenotype was preceded by accumulation of mitophagic vesicles and mitochondrial elongation, accompanied by pronounced upregulation of mitophagic markers and alterations in mitochondrial dynamics proteins. Moreover, we found that neddylation is required for mitochondrial ubiquitination and turnover. Consequently, pharmacological and genetic inhibition of neddylation accumulated damaged mitochondria, impaired mitochondrial membrane potential, inhibited mitochondrial respiration, and increased cardiomyocyte cell death in both neonatal and adult cardiomyocytes. Mechanistically, neddylation of Cullins is essential for the assembly of a functional multi-subunit Cullin-RING ubiquitin ligase, which appears to mediate mitochondrial ubiquitination following mitochondrial damage. Taken together, our findings suggest that neddylation serves as a novel mechanism surveilling mitochondrial quality and is essential for the function of normal adult heart.

Reactive oxygen species (ROS; e.g., superoxide [O(2)(•−)] and hydrogen peroxide [H(2)O(2)]) and reactive nitrogen species (RNS; e.g., nitric oxide [NO(•)]) at the physiological level function as signaling molecules that mediate many biological responses, including cell proliferation, migration, differentiation, and gene expression. By contrast, excess ROS/RNS, a consequence of dysregulated redox homeostasis, is a hallmark of cardiovascular disease. Accumulating evidence suggests that both ROS and RNS regulate various metabolic pathways and enzymes. Recent studies indicate that cells have mechanisms that fine-tune ROS/RNS levels by tight regulation of metabolic pathways, such as glycolysis and oxidative phosphorylation. The ROS/RNS-mediated inhibition of glycolytic pathways promotes metabolic reprogramming away from glycolytic flux toward the oxidative pentose phosphate pathway to generate nicotinamide adenine dinucleotide phosphate (NADPH) for antioxidant defense. This review summarizes our current knowledge of the mechanisms by which ROS/RNS regulate metabolic enzymes and cellular metabolism and how cellular metabolism influences redox homeostasis and the pathogenesis of disease. A full understanding of these mechanisms will be important for the development of new therapeutic strategies to treat diseases associated with dysregulated redox homeostasis and metabolism. Antioxid. Redox Signal. 34, 1319–1354.

Supplemental Digital Content is available in the text., Objective: Despite the importance of reactive oxygen species (ROS) and NOX (nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) 2 in platelet activation and in vivo thrombosis, it is unclear how ROS and NOX2 play a role in platelet activation and why NOX2 deficiencies in humans and mice do not affect hemostasis. Outside-in signaling of integrin αIIbβ3 mediates platelet response to shear stress, secondary platelet activation, and thrombus expansion and is critical to thrombosis but dispensable for hemostasis. We studied the mechanisms of platelet ROS generation, ROS-mediated platelet response, and the role of ROS in integrin αIIbβ3 outside-in signaling. Approach and Results: ROS generation in activated platelets was low and slow without shear but was robust under shear. Shear-enhanced ROS generation and activation of p47phox, an important regulatory subunit of NOX2, were diminished by the integrin antagonist integrilin or β3 knockout, and by Gα13 knockout or blocking the Gα13-β3 interaction. Resting platelets spreading on integrin ligand fibrinogen also Gα13-dependently stimulated ROS generation and p47phox activation. Hence, Gα13-mediated outside-in signaling induces NOX2 activation and ROS generation which is greatly enhanced by shear. Outside-in NOX2 activation requires Src, phosphoinositide 3-kinase and Akt downstream of Gα13. Importantly, NOX2-knockout platelets showed defective ROS generation, reduced platelet spreading without shear, and reduced platelet adhesion and thrombus volume on collagen and VWF (von Willibrand factor) under shear, whereas ROS inhibition diminished activation of tyrosine kinase Syk. Conclusions: Outside-in signaling activates the mainly NOX2-mediated ROS generation, which mediates Syk-dependent secondary platelet activation, adhesion, and thrombosis with minimal effect on hemostasis.

Exosomes, key mediators of cell-cell communication, derived from Type 2 diabetes mellitus (T2DM) exhibit detrimental effects. Exercise improves endothelial function in part via secretion of exosomes into circulation. Extracellular superoxide dismutase (SOD3) is a major secretory copper (Cu) antioxidant enzyme that catalyzes the dismutation of O(2)(•-) to H(2)O(2) whose activity requires the Cu transporter ATP7A. However, 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 volunteer wheel exercise. A single bout of exercise in human 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 model, which was associated with 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 H(2)O(2) 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.

Prostaglandin D2 (PGD2) released from immune cells or other cell types activates its receptors, D prostanoid receptor (DP)1 and 2 (DP1 and DP2), to promote inflammatory responses in allergic and lung diseases. Prostaglandin-mediated inflammation may also contribute to vascular diseases such as abdominal aortic aneurysm (AAA). However, the role of DP receptors in the pathogenesis of AAA has not been systematically investigated. In the present study, DP1-deficient mice and pharmacological inhibitors of either DP1 or DP2 were tested in two distinct mouse models of AAA formation: angiotensin II (AngII) infusion and calcium chloride (CaCl2) application. DP1-deficient mice [both heterozygous (DP1+/−) and homozygous (DP1−/−)] were protected against CaCl2-induced AAA formation, in conjunction with decreased matrix metallopeptidase (MMP) activity and adventitial inflammatory cell infiltration. In the AngII infusion model, DP1+/− mice, but not DP1−/− mice, exhibited reduced AAA formation. Interestingly, compensatory up-regulation of the DP2 receptor was detected in DP1−/− mice in response to AngII infusion, suggesting a potential role for DP2 receptors in AAA. Treatment with selective antagonists of DP1 (laropiprant) or DP2 (fevipiprant) protected against AAA formation, in conjunction with reduced elastin degradation and aortic inflammatory responses. In conclusion, PGD2 signaling contributes to AAA formation in mice, suggesting that antagonists of DP receptors, which have been extensively tested in allergic and lung diseases, may be promising candidates to ameliorate AAA.

A costimulatory signal from the tumor necrosis factor receptor (TNFR) family molecule OX40 (CD134), which is induced on activated T cells, is important for T-cell immunity. Aberrant OX40 cosignaling has been implicated in autoimmune and inflammatory disorders. However, the molecular mechanism by which the OX40 cosignaling regulates the T-cell response remains obscure. We found that OX40 associated with a scaffold protein, IQ motif-containing GTPase-activating protein 1 (IQGAP1) after ligation by its ligand OX40L. Naive CD4+ T cells from Iqgap1-/- mice displayed enhanced proliferation and cytokine secretion upon receiving OX40 cosignaling. A C-terminal IQGAP1 region was responsible for its association with OX40, and TNFR-associated factor 2 (TRAF2) bridged these two proteins. The enhanced cytokine response in Iqgap1-/- T cells was restored by the expression of the C-terminal IQGAP1. Thus, the IQGAP1 binding limits the OX40 cosignaling. Disease severity of experimental autoimmune encephalomyelitis (EAE) was significantly exacerbated in Iqgap1-/- mice as compared to wild-type mice. Additionally, recipient mice with Iqgap1-/- donor CD4+ T cells exhibited significantly higher EAE scores than those with their wild-type counterparts, and OX40 blockade led to a significant reduction in the EAE severity. Thus, our study defines an important component of the OX40 cosignaling that restricts inflammation driven by antigen-activated T cells.

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.

Reactive oxygen species (ROS) derived from both nicotinamide adenine dinucleotide phosphate oxidase (NOX) and mitochondria play a critical role in many physiological and pathological processes. However, how highly diffusible ROS produced from different sources can coordinate to drive angiogenesis and other responses is poorly understood. Recently, the cross-talk between NOX and mitochondria, termed “ROS-induced ROS release (RIRR)” has been proposed as a mechanism for ROS amplification and localized ROS production. NOX-derived ROS increase mitochondrial ROS while mitochondrial ROS stimulate NOX activation. This RIRR mechanism may represent a feed-forward vicious cycle of ROS production, which can be targeted under conditions of oxidative stress or enhanced in physiological condition. In this chapter, we will summarize the recent knowledge regarding the RIRR involved in vascular signaling and disease especially focusing on angiogenesis.

Background: VEGFR2 (KDR/Flk1) signaling in endothelial cells (ECs) plays a central role in angiogenesis. Copper (Cu) is essential micronutrient and has been implicated in angiogenesis. The P-type ATPase transporter ATP7A is key regulator of Cu homeostasis but its role in VEGFR2 signaling in ECs and post-ischemic neovascularization is entirely unknown. Results: Here we show that ATP7A expression was dramatically increased in the angiogenic ECs in mice hindlimb ischemia model. EC-specific ATP7A deficient mice or Cu transporter-dysfunctional ATP7A mut mice showed significant decrease in blood flow recovery and CD31+ capillary density (angiogenesis) in ischemic tissues compared to their control mice. In cultured human ECs, ATP7A knockdown with siRNA significantly inhibited VEGF-induced migration (67%), capillary network formation on Matrigel (46%). Immunofluorescence, co-immunoprecipitation, and proximity ligation assays showed that VEGF stimulated ATP7A translocation from the trans-Golgi network to the plasma membrane where it bound to VEGFR2. Surprisingly, loss of ATP7A promoted VEGF-induced VEGFR2 protein degradation (56%) and inhibited VEGFR2 signaling via enhancing VEGFR2 ubiquitination (2.0-fold) in a Cu-independent manner. This was associated with reduced cell surface VEGFR2 expression, increased VEGFR2 binding to selective autophagic cargo/adaptor p62/SQSTM1 (60%) and LC3-GFP+autophagic puncta (34%) and autolysosome formation (transmission electron microscopy). Inhibition of autophagy by bafilomycin A1 or chloroquine prevented enhanced VEGFR2 degradation in ATP7A-depleted ECs. Furthermore, overexpression of p62, but not p62 lacking ubiquitin binding domain, or autophagy inducer rapamycin treatment increased VEGFR2 degradation (26% and 87%, respectively) and p62 overexpression inhibited ECs migration (29%). Enhanced autophagy flux due to ATP7A dysfunction in vivo was confirmed by employing autophagy reporter CAG-ATP7A mut -RFP-EGFP-LC3 transgenic mice. Conclusion: Our study uncovers the unexpected and novel function of ATP7A to limit autophagic degradation of VEGFR2, thereby promoting VEGFR2 signaling and angiogenesis, which restores neovascularization in ischemic disease.

Background: Exosomes, key mediators of cell-cell communication, derived from type 2 diabetes mellitus (T2DM) have detrimental effects. Exercise not only improves endothelial dysfunction and angiogenesis in T2DM but also induces secretion of exosomes into circulation. Extracellular superoxide dismutase (ecSOD) is a major secretory Cu containing antioxidant enzyme that catalyzes dismutation of O 2 •- to H 2 O 2 and its full activity requires Cu transporter ATP7A. We reported that ecSOD-derived H 2 O 2 in endothelial cells (ECs) enhances angiogenesis while impaired ATP7A-ecSOD axis in diabetes induces endothelial dysfunction. Here we examined whether exercise-derived exosomes (Exe-Exo) may have pro-angiogenic effects via regulating ATP7A-ecSOD axis in T2DM. Results: Two weeks of voluntary wheel exercise of control C57Bl6 mice increased plasma exosome levels (6.2-fold) characterized by Nanosight, TEM and exosome markers (CD63, CD81, Tsg101). Treatment of HUVECs with equal number of exosomes revealed that angiogenic responses such as EC migration (1.8-fold) and tube formation (1.7-fold) were significantly enhanced by Exe-Exo compared to sedentary-derived exosomes (Sed-Exo). This was associated with increased ATP7A (2.9-fold) and ecSOD (1.4-fold) expression in Exe-Exo. Sed-Exo from high fat-induced T2DM mice significantly decreased EC migration (40%) and tube formation (10%) as well as ATP7A expression (28%) compared to Sed-Exo from control mice, which were restored by T2DM Exe-Exo, but not by T2DM/ecSOD KO Exe-Exo. Furthermore, exosomes overexpressing ecSOD (ecSOD-Exo) which mimic exercise increased angiogenesis and H2O2 levels in ECs, which were inhibited by overexpression of catalase. In vivo, skin wound healing model showed that direct application of T2DM Sed-Exo delayed while T2DM Exe-Exo enhanced wound healing of control mice. Furthermore, defective wound healing in T2DM mice or ecSOD KO mice were rescued by ecSOD-Exo application. Conclusion: Exercise training improves pro-angiogenic function of circulating exosomes in T2DM via increasing ATP7A-ecSOD axis, which may provide an effective therapy for promoting angiogenesis and wound repair in metabolic and cardiovascular diseases.

Introduction: Neovascularization in response to ischemia depends on inflammation, angiogenesis and reactive oxygen species (ROS). Copper (Cu) is implicated in inflammation and angiogenesis. We reported that cytosolic Cu chaperone Atox1 activates secretory Cu enzymes lysyl oxidase (LOX), while nuclear Atox1 functions as a Cu-dependent transcription factor to promote ROS/NFkB-dependent inflammation in endothelial cells (ECs). However, mechanism of Atox1 nuclear translocation as well as role of endothelial Atox1 in inflammatory angiogenesis in vivo remain unknown. SUMOylation and its deSUMOylation by SENPs regulates transcription factor function. Silica analysis identified a conserved putative SUMOylation motif at Lys(K3) of Atox1. Results: Atox1 expression was dramatically increased in angiogenic ECs in mice hindlimb ischemia model. EC-specific Atox1-deficient mice significantly reduced angiogenesis (CD31+, 67%) and Mac+ inflammatory cells in ischemic tissues. In cultured ECs, inflammatory cytokine TNFα or hypoxia promoted Atox1 nuclear translocation and Atox1 SUMOylation (3.6-fold), which were inhibited by antioxidant NAC or overexpression of “SUMO-dead” Atox1K3R. Mechanistically, TNFα induced Cys603 oxidation/inactivation of SENP1 in cytosol, which in turn increased Atox1 SUMOylation and nuclear translocation. Functionally, siAtox1or Atox1K3R inhibited TNFα-induced inflammatory/angiogenic genes VCAM/ICAM, IL-15 and RANTES. In nucleus with reduced state, ChIP assay using SUMO-Atox1 revealed that Atox1 deSUMOylation by nuclear SENP1 increases Atox1 transcriptional activity for inflammatory genes. In parallel, Atox1K3R which maintains Cu chaperone function inhibited TNFα-induced EC permeability by activating LOX. In vivo, Atox1 SUMOylation was increased after hindlimb ischemia while CRISPR/Cas9-generated SUMO-dead Atox1K3R knock-in mice showed impaired angiogenesis in hindlimb ischemia model. Conclusion: Atox1 SUMOylation via oxidative/inactivation of SENP1 in cytosol promotes: 1) its translocation to nucleus where deSUMOylated Atox1 can function as Cu-dependent transcription factor to drive inflammatory angiogenesis and 2) EC barrier dysfunction in inflamed/hypoxic ECs after ischemic injury.

Background: Exercise training promotes vascular adaptation (restoration of endothelial function and angiogenesis) in type2 diabetes (T2D). Since eNOS uncoupling/O 2 - are increased in T2D, exercise may promote vascular adaptation via mechanism other than eNOS-NO axis. Extracellular superoxide dismutase (ecSOD) is a secreted copper (Cu) containing SOD that catalyzes the dismutation of O 2 - to H 2 O 2 and its full activity requires Cu transporter ATP7A. We reported that ATP7A-ecSOD pathway is reduced in T2D and that ecSOD-derived H 2 O 2 promotes VEGFR2 signaling and angiogenesis in endothelial cells. However, role of ATP7A-ecSOD axis and H 2 O 2 signaling in vascular adaptation to exercise in T2D have not been reported. Oxidation of Cysteine residues of targets proteins to generate cysteine sulfenic acid (Cys-OH) is a key initial event in H 2 O 2 -mediated signaling. Results: Here we show that ATP7A protein (49%), ecSOD activity (51%) and extracellular H 2 O 2 levels in blood vessels and skeletal muscles were significantly decreased in high fat diet-induced T2D mice compared to control C57Bl6 mice, which were rescued by volunteer wheel exercise (2 weeks) or in T2D/ATP7A overexpressing mice. In parallel, exercise training restored impaired endothelium-dependent relaxation (EDR) of resistant arteries and angiogenesis (CD31+ capillary, 2.4-fold) in skeletal muscle of T2D mice, which were inhibited by exogenous catalase or in T2D/ecSOD KO mice, but not by L-NAME, suggesting that ecSOD-derived H 2 O 2 , but not eNOS/NO, mediates exercise-induced beneficial effects. Mechanistically, exercise significantly increased Cys-OH formation of PKG1α (2.3-fold), which was shown to induce EDR in H 2 O 2 -, but not NO/cGMP-, dependent manner, in T2D vascular tissues as well as Cys-OH formation of AMPK (3.6-fold) and AMPK downstream angiogenic PGC1α and VEGF protein expression in T2D skeletal muscles. Of note, these exercise-induced Cys oxidation of PKG1α and AMPK were not observed in control or T2D/ecSOD KO mice. Conclusion: Exercise-induced ATP7A-ecSOD axis-mediated out-side in H 2 O 2 signaling plays an important role in promoting vascular adaptation in T2D via Cys oxidation of redox-sensitive kinases required for endothelial function and angiogenesis in skeletal muscles.

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.

Angiogenesis, a new vessel formation from the pre-existing ones, is essential for embryonic development, wound repair and treatment of ischemic heart and limb diseases. However, dysregulated angiogenesis contributes to various pathologies such as diabetic retinopathy, atherosclerosis and cancer. Reactive oxygen species (ROS) derived from NADPH oxidase (NOX) as well as mitochondria play an important role in promoting the angiogenic switch from quiescent endothelial cells (ECs). However, how highly diffusible ROS produced from different sources and location can communicate with each other to regulate angiogenesis remains unclear. To detect a localized ROS signal in distinct subcellular compartments in real time in situ, compartment-specific genetically encoded redox-sensitive fluorescence biosensors have been developed. Recently, the intercellular communication, “cross-talk”, between ROS derived from NOX and mitochondria, termed “ROS-induced ROS release”, has been proposed as a mechanism for ROS amplification at distinct subcellular compartments, which are essential for activation of redox signaling. This “ROS-induced ROS release” may represent a feed-forward mechanism of localized ROS production to maintain sustained signaling, which can be targeted under pathological conditions with oxidative stress or enhanced to promote therapeutic angiogenesis. In this review, we summarize the recent knowledge regarding the role of the cross-talk between NOX and mitochondria organizing the sustained ROS signaling involved in VEGF signaling, neovascularization and tissue repair.

Vascular endothelial growth factor receptor type 2 (VEGFR2, also known as KDR and FLK1) signalling in endothelial cells (ECs) is essential for developmental and reparative angiogenesis. Reactive oxygen species and copper (Cu) are also involved in these processes. However, their inter-relationship is poorly understood. Evidence of the role of the endothelial Cu importer CTR1 (also known as SLC31A1) in VEGFR2 signalling and angiogenesis in vivo is lacking. Here, we show that CTR1 functions as a redox sensor to promote angiogenesis in ECs. CTR1-depleted ECs showed reduced VEGF-induced VEGFR2 signalling and angiogenic responses. Mechanistically, CTR1 was rapidly sulfenylated at Cys189 at its cytosolic C terminus after stimulation with VEGF, which induced CTR1-VEGFR2 disulfide bond formation and their co-internalization to early endosomes, driving sustained VEGFR2 signalling. In vivo, EC-specific Ctr1-deficient mice or CRISPR-Cas9-generated redox-dead Ctr1(C187A)-knockin mutant mice had impaired developmental and reparative angiogenesis. Thus, oxidation of CTR1 at Cys189 promotes VEGFR2 internalization and signalling to enhance angiogenesis. Our study uncovers an important mechanism for sensing reactive oxygen species through CTR1 to drive neovascularization.

VEGFR2 (KDR/Flk1) signaling in endothelial cells (ECs) plays a central role in angiogenesis. The P-type ATPase transporter ATP7A regulates copper homeostasis, and its role in VEGFR2 signaling and angiogenesis is entirely unknown. Here, we describe the unexpected crosstalk between the Copper transporter ATP7A, autophagy, and VEGFR2 degradation. The functional significance of this Copper transporter was demonstrated by the finding that inducible EC-specific ATP7A deficient mice or ATP7A-dysfunctional ATP7Amut mice showed impaired post-ischemic neovascularization. In ECs, loss of ATP7A inhibited VEGF-induced VEGFR2 signaling and angiogenic responses, in part by promoting ligand-induced VEGFR2 protein degradation. Mechanistically, VEGF stimulated ATP7A translocation from the trans-Golgi network to the plasma membrane where it bound to VEGFR2, which prevented autophagy-mediated lysosomal VEGFR2 degradation by inhibiting autophagic cargo/adapter p62/SQSTM1 binding to ubiquitinated VEGFR2. Enhanced autophagy flux due to ATP7A dysfunction in vivo was confirmed by autophagy reporter CAG-ATP7Amut -RFP-EGFP-LC3 transgenic mice. In summary, our study uncovers a novel function of ATP7A to limit autophagy-mediated degradation of VEGFR2, thereby promoting VEGFR2 signaling and angiogenesis, which restores perfusion recovery and neovascularization. Thus, endothelial ATP7A is identified as a potential therapeutic target for treatment of ischemic cardiovascular diseases., The role of endothelial copper transporter ATP7A in vascular function and angiogenesis remains largely unexplored. Here the authors show that ATP7A promotes VEGFR2 signaling and angiogenesis by limiting autophagy-mediated degradation of VEGFR2, which enhances reparative neovascularization.

BackgroundColorectal cancer remains a deadly cancer due to metastatic disease. To understand the molecular mechanisms of metastasis in colon cancer, we investigated whether the copper chaperone antioxidant-1 (Atox1) protein plays a role in this process. Recent findings indicate that Atox1 protein has transcription factor activities and plays a vital role in cell proliferation in cancer cells. However, the role of Atox1 in metastasis has not been examined.MethodsAtox1 expression was determined by immunofluorescence in a tissue microarray generated from a spectrum of CRC patients. Subcellular fractionation of colon cancer cell lines SW480 and SW620 cells was used to examine the cellular location of Atox1 in the face of activin A, a cytokine that stimulates colon cancer metastasis. Atox1 expression was genetically manipulated and cellular migration measured through trans-well assay and proliferation measured by colony formation assays.ResultsHere we demonstrate that in patients with metastatic colon cancer, there is a significant increase in the expression of nuclear Atox1. Interestingly, the metastatic CRC cell line SW620 has increased nuclear localization of Atox1 compared to its related non-metastatic cell line SW480. Further, inhibition of endogenous Atox1 by siRNA in SW620 decreased colony formation and reactive oxygen species generation via decreased expression of Atox1 targets cyclin D1 and NADPH oxidase subunit p47 phox, respectively. Additionally, overexpression of nuclear-targeted but not copper binding domain-mutated Atox1 in SW480 cells increased colony formation and cell migration that was further augmented by activin A stimulation, a known enhancer of colon cancer metastasis.ConclusionsOur findings suggest that nuclear Atox1 might be a new therapeutic target as well as a new biomarker for metastatic colorectal cancer.

Objective— Copper transporter ATP7A (copper-transporting/ATPase) is required for full activation of SOD3 (extracellular superoxide dismutase), which is secreted from vascular smooth muscle cells (VSMCs) and anchors to endothelial cell surface to preserve endothelial function by scavenging extracellular superoxide. We reported that ATP7A protein expression and SOD3 activity are decreased in insulin-deficient type 1 diabetes mellitus vessels, thereby, inducing superoxide-mediated endothelial dysfunction, which are rescued by insulin treatment. However, it is unknown regarding the mechanism by which insulin increases ATP7A expression in VSMCs and whether ATP7A downregulation is observed in T2DM (type2 diabetes mellitus) mice and human in which insulin–Akt (protein kinase B) pathway is selectively impaired. Approach and Results— Here we show that ATP7A protein is markedly downregulated in vessels isolated from T2DM patients, as well as those from high-fat diet–induced or db/db T2DM mice. Akt2 (protein kinase B beta) activated by insulin promotes ATP7A stabilization via preventing ubiquitination/degradation as well as translocation to plasma membrane in VSMCs, which contributes to activation of SOD3 that protects against T2DM-induced endothelial dysfunction. Downregulation of ATP7A in T2DM vessels is restored by constitutive active Akt or PTP1B −/− (protein-tyrosine phosphatase 1B-deficient) T2DM mice, which enhance insulin–Akt signaling. Immunoprecipitation, in vitro kinase assay, and mass spectrometry analysis reveal that insulin stimulates Akt2 binding to ATP7A to induce phosphorylation at Ser1424/1463/1466. Furthermore, SOD3 activity is reduced in Akt2 −/− vessels or VSMCs, which is rescued by ATP7A overexpression. Conclusion— Akt2 plays a critical role in ATP7A protein stabilization and translocation to plasma membrane in VSMCs, which contributes to full activation of vascular SOD3 that protects against endothelial dysfunction in T2DM.

SUMMARY Mitochondrial dynamics are tightly controlled by fusion and fission, and their dysregulation and excess reactive oxygen species (ROS) contribute to endothelial cell (EC) dysfunction. How redox signals regulate coupling between mitochondrial dynamics and endothelial (dys)function remains unknown. Here, we identify protein disulfide isomerase A1 (PDIA1) as a thiol reductase for the mitochondrial fission protein Drp1. A biotin-labeled Cys-OH trapping probe and rescue experiments reveal that PDIA1 depletion in ECs induces sulfenylation of Drp1 at Cys644, promoting mitochondrial fragmentation and ROS elevation without inducing ER stress, which drives EC senescence. Mechanistically, PDIA1 associates with Drp1 to reduce its redox status and activity. Defective wound healing and angiogenesis in diabetic or PDIA1+/− mice are restored by EC-targeted PDIA1 or the Cys oxidation-defective mutant Drp1. Thus, this study uncovers a molecular link between PDIA1 and Drp1 oxidoreduction, which maintains normal mitochondrial dynamics and limits endothelial senescence with potential translational implications for vascular diseases associated with diabetes or aging., In Brief Kim et al. demonstrate a molecular link between PDIA1 and Drp1 oxidoreduction, which protects against mitochondrial fragmentation and ROS elevation, limiting endothelial senescence. This study provides insights into restoring endothelial PDIA1 function or targeting Drp1 Cys oxidation as potential therapeutic strategies for treating diabetes-associated vascular and metabolic diseases., Graphical Abstract

Reactive oxygen species (ROS) derived from NADPH oxidase (NOX) and mitochondria play a critical role in growth factor-induced switch from a quiescent to an angiogenic phenotype in endothelial cells (ECs). However, how highly diffusible ROS produced from different sources can coordinate to stimulate VEGF signaling and drive the angiogenic process remains unknown. Using the cytosol- and mitochondria-targeted redox-sensitive RoGFP biosensors with real-time imaging, here we show that VEGF stimulation in human ECs rapidly increases cytosolic RoGFP oxidation within 1 min, followed by mitochondrial RoGFP oxidation within 5 min, which continues at least for 60 min. Silencing of Nox4 or Nox2 or overexpression of mitochondria-targeted catalase significantly inhibits VEGF-induced tyrosine phosphorylation of VEGF receptor type 2 (VEGFR2-pY), EC migration and proliferation at the similar extent. Exogenous hydrogen peroxide (H2O2) or overexpression of Nox4, which produces H2O2, increases mitochondrial ROS (mtROS), which is prevented by Nox2 siRNA, suggesting that Nox2 senses Nox4-derived H2O2to promote mtROS production. Mechanistically, H2O2increases S36 phosphorylation of p66Shc, a key mtROS regulator, which is inhibited by siNox2, but not by siNox4. Moreover, Nox2 or Nox4 knockdown or overexpression of S36 phosphorylation-defective mutant p66Shc(S36A) inhibits VEGF-induced mtROS, VEGFR2-pY, EC migration, and proliferation. In summary, Nox4-derived H2O2in part activates Nox2 to increase mtROS via pSer36-p66Shc, thereby enhancing VEGFR2 signaling and angiogenesis in ECs. This may represent a novel feed-forward mechanism of ROS-induced ROS release orchestrated by the Nox4/Nox2/pSer36-p66Shc/mtROS axis, which drives sustained activation of angiogenesis signaling program.

High blood pressure has been shown to elicit impaired dilation in the vasculature. The purpose of this investigation was to elucidate the mechanisms through which high pressure may elicit vascular dysfunction and determine the mechanisms through which regular aerobic exercise protects arteries against high pressure. Male C57BL/6J mice were subjected to 2 wk of voluntary running (~6 km/day) for comparison with sedentary controls. Hindlimb adipose resistance arteries were dissected from mice for measurements of flow-induced dilation (FID; with or without high intraluminal pressure exposure) or protein expression of NADPH oxidase II (NOX II) and superoxide dismutase (SOD). Microvascular endothelial cells were subjected to high physiological laminar shear stress (20 dyn/cm2) or static condition and treated with ANG II + pharmacological inhibitors. Cells were analyzed for the detection of ROS or collected for Western blot determination of NOX II and SOD. Resistance arteries from exercised mice demonstrated preserved FID after high pressure exposure, whereas FID was impaired in control mouse arteries. Inhibition of ANG II or NOX II restored impaired FID in control mouse arteries. High pressure increased superoxide levels in control mouse arteries but not in exercise mouse arteries, which exhibited greater ability to convert superoxide to H2O2. Arteries from exercised mice exhibited less NOX II protein expression, more SOD isoform expression, and less sensitivity to ANG II. Endothelial cells subjected to laminar shear stress exhibited less NOX II subunit expression. In conclusion, aerobic exercise prevents high pressure-induced vascular dysfunction through an improved redox environment in the adipose microvasculature. NEW & NOTEWORTHY We describe potential mechanisms contributing to aerobic exercise-conferred protection against high intravascular pressure. Subcutaneous adipose microvessels from exercise mice express less NADPH oxidase (NOX) II and more superoxide dismutase (SOD) and demonstrate less sensitivity to ANG II. In microvascular endothelial cells, shear stress reduced NOX II but did not influence SOD expression. Listen to this article’s corresponding podcast at https://ajpheart.podbean.com/e/exercise-averts-high-pressure-induced-vascular-dysfunction/ .

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) and copper (Cu), an essential micronutrient, have been implicated in vascular inflammatory diseases. We reported that in proinflammatory cytokine TNF-α-stimulated endothelial cells (ECs), cytosolic Cu chaperone antioxidant-1 (Atox1) functions as a Cu-dependent transcription factor for the NOX organizer p47phox, thereby increasing ROS-dependent inflammatory gene expression. However, the role and mechanism of Atox1 nuclear translocation in inflamed ECs remain unclear. Using enface staining and nuclear fractionation, here we show that Atox1 was localized in the nucleus in inflamed aortas from ApoE−/− mice with angiotensin II infusion on a high-fat diet, while it was found in cytosol in those from control mice. In cultured human ECs, TNF-α stimulation promoted Atox1 nuclear translocation within 15 min, which was associated with Atox1 binding to TNF-α receptor-associated factor 4 (TRAF4) in a Cu-dependent manner. TRAF4 depletion by siRNA significantly inhibited Atox1 nuclear translocation, p47phox expression, and ROS production as well as its downstream VCAM1/ICAM1 expression and monocyte adhesion to inflamed ECs, which were rescued by overexpression of nuclear targeted Atox1. Furthermore, Atox1 colocalized with TRAF4 at the nucleus in TNF-α-stimulated inflamed ECs and vessels. In summary, Cu-dependent Atox1 binding to TRAF4 plays an important role in Atox1 nuclear translocation and ROS-dependent inflammatory responses in TNF-α-stimulated ECs. Thus the Atox1-TRAF4 axis is a novel therapeutic target for vascular inflammatory disease such as atherosclerosis.