Peripheral Ischemia Imprints Epigenetic Changes in Hematopoietic Stem Cells to Propagate Inflammation and Atherosclerosis.

BACKGROUND: Peripheral ischemia caused by peripheral artery disease is associated with systemic inflammation, which may aggravate underlying comorbidities such as atherosclerosis and heart failure. However, the mechanisms of increased inflammation and inflammatory cell production in patients with peripheral artery disease remain poorly understood. METHODS: We used peripheral blood collected from patients with peripheral artery disease and performed hind limb ischemia (HI) in Apoe-/- mice fed a Western diet and C57BL/6J mice with a standard laboratory diet. Bulk and single-cell RNA sequencing analysis, whole-mount microscopy, and flow cytometry were performed to analyze hematopoietic stem and progenitor cell (HSPC) proliferation, differentiation, and relocation. RESULTS: We observed augmented numbers of leukocytes in the blood of patients with peripheral artery disease and Apoe-/- mice with HI. RNA sequencing and whole-mount imaging of the bone marrow revealed HSPC migration into the vascular niche from the osteoblastic niche and their exaggerated proliferation and differentiation. Single-cell RNA sequencing demonstrated alterations in the genes responsible for inflammation, myeloid cell mobilization, and HSPC differentiation after HI. Heightened inflammation in Apoe-/- mice after HI aggravated atherosclerosis. Surprisingly, bone marrow HSPCs expressed higher amounts of the receptors for IL (interleukin)-1 and IL-3 after HI. Concomitantly, the promoters of Il1r1 and Il3rb had augmented H3K4me3 and H3K27ac marks after HI. Genetic and pharmacological inhibition of these receptors resulted in suppressed HSPC proliferation, reduced leukocyte production, and ameliorated atherosclerosis. CONCLUSIONS: Our findings demonstrate increased inflammation, HSPC abundance in the vascular niches of the bone marrow, and elevated IL-3Rb and IL-1R1 (IL-1 receptor 1) expression in HSPC following HI. Furthermore, the IL-3Rb and IL-1R1 signaling plays a pivotal role in HSPC proliferation, leukocyte abundance, and atherosclerosis aggravation after HI.

Forestalling age-impaired angiogenesis and blood flow by targeting NOX: Interplay of NOX1, IL-6, and SASP in propagating cell senescence.

In an aging population, intense interest has shifted toward prolonging health span. Mounting evidence suggests that cellular reactive species are propagators of cell damage, inflammation, and cellular senescence. Thus, such species have emerged as putative provocateurs and targets for senolysis, and a clearer understanding of their molecular origin and regulation is of paramount importance. In an inquiry into signaling triggered by aging and proxy instigator, hyperglycemia, we show that NADPH Oxidase (NOX) drives cell DNA damage and alters nuclear envelope integrity, inflammation, tissue dysfunction, and cellular senescence in mice and humans with similar causality. Most notably, selective NOX1 inhibition rescues age-impaired blood flow and angiogenesis, vasodilation, and the endothelial cell wound response. Indeed, NOX1i delivery in vivo completely reversed age-impaired hind-limb blood flow and angiogenesis while disrupting a NOX1-IL-6 senescence-associated secretory phenotype (SASP) proinflammatory signaling loop. Relevant to its comorbidity with age, clinical samples from diabetic versus nondiabetic subjects reveal as operant this NOX1-mediated vascular senescence and inflammation in humans. On a mechanistic level, our findings support a previously unidentified role for IL-6 in this feedforward inflammatory loop and peroxisome proliferator-activated receptor gamma (PPARγ) down-regulation as inversely modulating p65-mediated NOX1 transcription. Targeting this previously unidentified NOX1-SASP signaling axis in aging is predicted to be an effective strategy for mitigating senescence in the vasculature and other organ systems.

NADPH oxidase 2 activity in Parkinson's disease.

Mitochondrial dysfunction and oxidative stress are strongly implicated in Parkinson's disease (PD) pathogenesis and there is evidence that mitochondrially-generated superoxide can activate NADPH oxidase 2 (NOX2). Although NOX2 has been examined in the context of PD, most attention has focused on glial NOX2, and the role of neuronal NOX2 in PD remains to be defined. Additionally, pharmacological NOX2 inhibitors have typically lacked specificity. Here we devised and validated a proximity ligation assay for NOX2 activity and demonstrated that in human PD and two animal models thereof, both neuronal and microglial NOX2 are highly active in substantia nigra under chronic conditions. However, in acute and sub-acute PD models, we observed neuronal, but not microglial NOX2 activation, suggesting that neuronal NOX2 may play a primary role in the early stages of the disease. Aberrant NOX2 activity is responsible for the formation of oxidative stress-related post-translational modifications of α-synuclein, and impaired mitochondrial protein import in vitro in primary ventral midbrain neuronal cultures and in vivo in nigrostriatal neurons in rats. In a rat model, administration of a brain-penetrant, highly specific NOX2 inhibitor prevented NOX2 activation in nigrostriatal neurons and its downstream effects in vivo, such as activation of leucine-rich repeat kinase 2 (LRRK2). We conclude that NOX2 is an important enzyme that contributes to progressive oxidative damage which in turn can lead to α-synuclein accumulation, mitochondrial protein import impairment, and LRRK2 activation. In this context, NOX2 inhibitors hold potential as a disease-modifying therapy in PD.

Endothelial-Derived miR-17∼92 Promotes Angiogenesis to Protect against Renal Ischemia-Reperfusion Injury.

BACKGROUND: Damage to the renal microvasculature is a hallmark of renal ischemia-reperfusion injury (IRI)-mediated AKI. The miR-17∼92 miRNA cluster (encoding miR-17, -18a, -19a, -20a, -19b-1, and -92a-1) regulates angiogenesis in multiple settings, but no definitive role in renal endothelium during AKI pathogenesis has been established. METHODS: Antibodies bound to magnetic beads were utilized to selectively enrich for renal endothelial cells from mice. Endothelial-specific miR-17∼92 knockout (miR-17∼92endo-/- ) mice were generated and given renal IRI. Mice were monitored for the development of AKI using serum chemistries and histology and for renal blood flow using magnetic resonance imaging (MRI) and laser Doppler imaging. Mice were treated with miRNA mimics during renal IRI, and therapeutic efficacies were evaluated. RESULTS: miR-17, -18a, -20a, -19b, and pri-miR-17∼92 are dynamically regulated in renal endothelial cells after renal IRI. miR-17∼92endo-/- exacerbates renal IRI in male and female mice. Specifically, miR-17∼92endo-/- promotes renal tubular injury, reduces renal blood flow, promotes microvascular rarefaction, increases renal oxidative stress, and promotes macrophage infiltration to injured kidneys. The potent antiangiogenic factor thrombospondin 1 (TSP1) is highly expressed in renal endothelium in miR-17∼92endo-/- after renal IRI and is a target of miR-18a and miR-19a/b. miR-17∼92 is critical in the angiogenic response after renal IRI, which treatment with miR-18a and miR-19b mimics can mitigate. CONCLUSIONS: These data suggest that endothelial-derived miR-17∼92 stimulates a reparative response in damaged renal vasculature during renal IRI by regulating angiogenic pathways.

Notch2 suppression mimicking changes in human pulmonary hypertension modulates Notch1 and promotes endothelial cell proliferation.

Pulmonary arterial hypertension (PAH) is a fatal cardiopulmonary disease characterized by increased vascular cell proliferation with apoptosis resistance and occlusive remodeling of the small pulmonary arteries. The Notch family of proteins subserves proximal signaling of an evolutionarily conserved pathway that effects cell proliferation, fate determination, and development. In endothelial cells (ECs), Notch receptor 2 (Notch2) was shown to promote endothelial apoptosis. However, a pro- or antiproliferative role for Notch2 in pulmonary endothelial proliferation and ensuing PAH is unknown. We postulated that suppressed Notch2 signaling drives pulmonary endothelial proliferation in the context of PAH. We observed that levels of Notch2 are ablated in lungs from PAH subjects compared with non-PAH controls. Notch2 expression was attenuated in human pulmonary artery endothelial cells (hPAECs) exposed to vasoactive stimuli including hypoxia, TGF-ß, ET-1, and IGF-1. Notch2-deficient hPAECs activated Akt, Erk1/2, and antiapoptotic protein Bcl-2 and reduced levels of p21cip and Bax associated with increased EC proliferation and reduced apoptosis. In addition, Notch2 suppression elicited a paradoxical activation of Notch1 and canonical Notch target gene Hes1, Hey1, and Hey2 transcription. Furthermore, reduction in Rb and increased E2F1 binding to the Notch1 promoter appear to explain the Notch1 upregulation. Yet, when Notch1 was decreased in Notch2-suppressed cells, the wound injury response was augmented. In aggregate, our results demonstrate that loss of Notch2 in hPAECs derepresses Notch1 and elicits EC hallmarks of PAH. Augmented EC proliferation upon Notch1 knockdown points to a context-dependent role for Notch1 and 2 in endothelial cell homeostasis.NEW & NOTEWORTHY This study demonstrates a previously unidentified role for Notch2 in the maintenance of lung vascular endothelial cell quiescence and pulmonary artery hypertension (PAH). A key novel finding is that Notch2 suppression activates Notch1 via Rb-E2F1-mediated signaling and induces proliferation and apoptosis resistance in human pulmonary artery endothelial cells. Notably, PAH patients show reduced levels of endothelial Notch2 in their pulmonary arteries, supporting Notch2 as a fundamental driver of PAH pathogenesis.

Vascular TSP1-CD47 signaling promotes sickle cell-associated arterial vasculopathy and pulmonary hypertension in mice.

Pulmonary hypertension (PH) is a leading cause of death in sickle cell disease (SCD) patients. Hemolysis and oxidative stress contribute to SCD-associated PH. We have reported that the protein thrombospondin-1 (TSP1) is elevated in the plasma of patients with SCD and, by interacting with its receptor CD47, limits vasodilation of distal pulmonary arteries ex vivo. We hypothesized that the TSP1-CD47 interaction may promote PH in SCD. We found that TSP1 and CD47 are upregulated in the lungs of Berkeley (BERK) sickling (Sickle) mice and patients with SCD-associated PH. We then generated chimeric animals by transplanting BERK bone marrow into C57BL/6J (n = 24) and CD47 knockout (CD47KO, n = 27) mice. Right ventricular (RV) pressure was lower in fully engrafted Sickle-to-CD47KO than Sickle-to-C57BL/6J chimeras, as shown by the reduced maximum RV pressure (P = 0.013) and mean pulmonary artery pressure (P = 0.020). The afterload of the sickle-to-CD47KO chimeras was also lower, as shown by the diminished pulmonary vascular resistance (P = 0.024) and RV effective arterial elastance (P = 0.052). On myography, aortic segments from Sickle-to-CD47KO chimeras showed improved relaxation to acetylcholine. We hypothesized that, in SCD, TSP1-CD47 signaling promotes PH, in part, by increasing reactive oxygen species (ROS) generation. In human pulmonary artery endothelial cells, treatment with TSP1 stimulated ROS generation, which was abrogated by CD47 blockade. Explanted lungs of CD47KO chimeras had less vascular congestion and a smaller oxidative footprint. Our results show that genetic absence of CD47 ameliorates SCD-associated PH, which may be due to decreased ROS levels. Modulation of TSP1-CD47 may provide a new molecular approach to the treatment of SCD-associated PH.

A novel combinatorial technique for simultaneous quantification of oxygen radicals and aggregation reveals unexpected redox patterns in the activation of platelets by different physiopathological stimuli.

The regulation of platelets by oxidants is critical for vascular health and may explain thrombotic complications in diseases such as diabetes and dementia, but remains poorly understood. Here, we describe a novel technique combining electron paramagnetic resonance spectroscopy and turbidimetry, which has been utilized to monitor simultaneously platelet activation and oxygen radical generation. This technique has been used to investigate the redox-dependence of human and mouse platelets. Using selective peptide inhibitors of NADPH oxidases (NOXs) on human platelets and genetically modified mouse platelets (NOX1-/- or NOX2-/-), we discovered that: 1) intracellular but not extracellular superoxide anion generated by NOX is critical for platelet activation by collagen; 2) superoxide dismutation to hydrogen peroxide is required for thrombin-dependent activation; 3) NOX1 is the main source of oxygen radicals in response to collagen, while NOX2 is critical for activation by thrombin; 4) two platelet modulators, namely oxidized low density lipoproteins (oxLDL) and amyloid peptide ß (Aß), require activation of both NOX1 and NOX2 to pre-activate platelets. This study provides new insights into the redox dependence of platelet activation. It suggests the possibility of selectively inhibiting platelet agonists by targeting either NOX1 (for collagen) or NOX2 (for thrombin). Selective inhibition of either NOX1 or NOX2 impairs the potentiatory effect of tested platelet modulators (oxLDL and Aß), but does not completely abolish platelet hemostatic function. This information offers new opportunities for the development of disease-specific antiplatelet drugs with limited bleeding side effects by selectively targeting one NOX isoenzyme.

Binding of EBP50 to Nox organizing subunit p47phox is pivotal to cellular reactive species generation and altered vascular phenotype.

Despite numerous reports implicating NADPH oxidases (Nox) in the pathogenesis of many diseases, precise regulation of this family of professional reactive oxygen species (ROS) producers remains unclear. A unique member of this family, Nox1 oxidase, functions as either a canonical or hybrid system using Nox organizing subunit 1 (NoxO1) or p47(phox), respectively, the latter of which is functional in vascular smooth muscle cells (VSMC). In this manuscript, we identify critical requirement of ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50; aka NHERF1) for Nox1 activation and downstream responses. Superoxide (O2 (•-)) production induced by angiotensin II (AngII) was absent in mouse EBP50 KO VSMC vs. WT. Moreover, ex vivo incubation of aortas with AngII showed a significant increase in O2 (•-) in WT but not EBP50 or Nox1 nulls. Similarly, lipopolysaccharide (LPS)-induced oxidative stress was attenuated in femoral arteries from EBP50 KO vs. WT. In silico analyses confirmed by confocal microscopy, immunoprecipitation, proximity ligation assay, FRET, and gain-/loss-of-function mutagenesis revealed binding of EBP50, via its PDZ domains, to a specific motif in p47(phox) Functional studies revealed AngII-induced hypertrophy was absent in EBP50 KOs, and in VSMC overexpressing EBP50, Nox1 gene silencing abolished VSMC hypertrophy. Finally, ex vivo measurement of lumen diameter in mouse resistance arteries exhibited attenuated AngII-induced vasoconstriction in EBP50 KO vs. WT. Taken together, our data identify EBP50 as a previously unidentified regulator of Nox1 and support that it promotes Nox1 activity by binding p47(phox) This interaction is pivotal for agonist-induced smooth muscle ROS, hypertrophy, and vasoconstriction and has implications for ROS-mediated physiological and pathophysiological processes.

Endothelial Nox1 oxidase assembly in human pulmonary arterial hypertension; driver of Gremlin1-mediated proliferation.

Pulmonary arterial hypertension (PAH) is a rapidly degenerating and devastating disease of increased pulmonary vessel resistance leading to right heart failure. Palliative modalities remain limited despite recent endeavors to investigate the mechanisms underlying increased pulmonary vascular resistance (PVR), i.e. aberrant vascular remodeling and occlusion. However, little is known of the molecular mechanisms responsible for endothelial proliferation, a root cause of PAH-associated vascular remodeling. Lung tissue specimens from PAH and non-PAH patients and hypoxia-exposed human pulmonary artery endothelial cells (ECs) (HPAEC) were assessed for mRNA and protein expression. Reactive oxygen species (ROS) were measured using cytochrome c and Amplex Red assays. Findings demonstrate for the first time an up-regulation of NADPH oxidase 1 (Nox1) at the transcript and protein level in resistance vessels from PAH compared with non-PAH patients. This coincided with an increase in ROS production and expression of bone morphogenetic protein (BMP) antagonist Gremlin1 (Grem1). In HPAEC, hypoxia induced Nox1 subunit expression, assembly, and oxidase activity leading to elevation in sonic hedgehog (SHH) and Grem1 expression. Nox1 gene silencing abrogated this cascade. Moreover, loss of either Nox1, SHH or Grem1 attenuated hypoxia-induced EC proliferation. Together, these data support a Nox1-SHH-Grem1 signaling axis in pulmonary vascular endothelium that is likely to contribute to pathophysiological endothelial proliferation and the progression of PAH. These findings also support targeting of Nox1 as a viable therapeutic option to combat PAH.

NADPH oxidases: key modulators in aging and age-related cardiovascular diseases?

Reactive oxygen species (ROS) and oxidative stress have long been linked to aging and diseases prominent in the elderly such as hypertension, atherosclerosis, diabetes and atrial fibrillation (AF). NADPH oxidases (Nox) are a major source of ROS in the vasculature and are key players in mediating redox signalling under physiological and pathophysiological conditions. In this review, we focus on the Nox-mediated ROS signalling pathways involved in the regulation of 'longevity genes' and recapitulate their role in age-associated vascular changes and in the development of age-related cardiovascular diseases (CVDs). This review is predicated on burgeoning knowledge that Nox-derived ROS propagate tightly regulated yet varied signalling pathways, which, at the cellular level, may lead to diminished repair, the aging process and predisposition to CVDs. In addition, we briefly describe emerging Nox therapies and their potential in improving the health of the elderly population.

MEF2B-Nox1 signaling is critical for stretch-induced phenotypic modulation of vascular smooth muscle cells.

OBJECTIVE: Blood vessel hemodynamics have profound influences on function and structure of vascular cells. One of the main mechanical forces influencing vascular smooth muscle cells (VSMC) is cyclic stretch (CS). Increased CS stimulates reactive oxygen species (ROS) production in VSMC, leading to their dedifferentiation, yet the mechanisms involved are poorly understood. This study was designed to test the hypothesis that pathological CS stimulates NADPH oxidase isoform 1 (Nox1)-derived ROS via MEF2B, leading to VSMC dysfunction via a switch from a contractile to a synthetic phenotype. APPROACH AND RESULTS: Using a newly developed isoform-specific Nox1 inhibitor and gene silencing technology, we demonstrate that a novel pathway, including MEF2B-Nox1-ROS, is upregulated under pathological stretch conditions, and this pathway promotes a VSMC phenotypic switch from a contractile to a synthetic phenotype. We observed that CS (10% at 1 Hz) mimicking systemic hypertension in humans increased Nox1 mRNA, protein levels, and enzymatic activity in a time-dependent manner, and this upregulation was mediated by MEF2B. Furthermore, we show that stretch-induced Nox1-derived ROS upregulated a specific marker for synthetic phenotype (osteopontin), whereas it downregulated classical markers for contractile phenotype (calponin1 and smoothelin B). In addition, our data demonstrated that stretch-induced Nox1 activation decreases actin fiber density and augments matrix metalloproteinase 9 activity, VSMC migration, and vectorial alignment. CONCLUSIONS: These results suggest that CS initiates a signal through MEF2B that potentiates Nox1-mediated ROS production and causes VSMC to switch to a synthetic phenotype. The data also characterize a new Nox1 inhibitor as a potential therapy for treatment of vascular dysfunction in hypertension.

Thrombospondin-1 activation of signal-regulatory protein-α stimulates reactive oxygen species production and promotes renal ischemia reperfusion injury.

Ischemia reperfusion injury (IRI) causes tissue and organ injury, in part, through alterations in tissue blood flow and the production of reactive oxygen species. The cell surface receptor signal-regulatory protein-α (SIRP-α) is expressed on inflammatory cells and suppresses phagocytosis, but the function of SIRP-α in IRI has not been determined. We reported previously that the matricellular protein thrombospondin-1 is upregulated in IRI. Here, we report a novel interaction between thrombospondin-1 and SIRP-α on nonphagocytic cells. In cell-free experiments, thrombospondin-1 bound SIRP-α. In vascular smooth muscle cells and renal tubular epithelial cells, treatment with thrombospondin-1 led to phosphorylation of SIRP-α and downstream activation of Src homology domain 2-containing phosphatase-1. Thrombospondin-1 also stimulated phosphorylation of p47(phox) (an organizer subunit for nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 1/2) and increased production of superoxide, both of which were abrogated by knockdown or antibody blockade of SIRP-α. In rodent aortic rings, treatment with thrombospondin-1 increased the production of superoxide and inhibited nitric oxide-mediated vasodilation in a SIRP-α-dependent manner. Renal IRI upregulated the thrombospondin-1-SIRP-α signaling axis and was associated with increased superoxide production and cell death. A SIRP-α antibody that blocks thrombospondin-1 activation of SIRP-α mitigated the effects of renal IRI, increasing blood flow, suppressing production of reactive oxygen species, and preserving cellular architecture. A role for CD47 in SIRP-α activation in these pathways is also described. Overall, these results suggest that thrombospondin-1 binding to SIRP-α on nonphagocytic cells activates NADPH oxidase, limits vasodilation, and promotes renal IRI.

Selective recapitulation of conserved and nonconserved regions of putative NOXA1 protein activation domain confers isoform-specific inhibition of Nox1 oxidase and attenuation of endothelial cell migration.

Excessive vascular and colon epithelial reactive oxygen species production by NADPH oxidase isoform 1 (Nox1) has been implicated in a number of disease states, including hypertension, atherosclerosis, and neoplasia. A peptide that mimics a putative activation domain of the Nox1 activator subunit NOXA1 (NOXA1 docking sequence, also known as NoxA1ds) potently inhibited Nox1-derived superoxide anion (O2·-) production in a reconstituted Nox1 cell-free system, with no effect on Nox2-, Nox4-, Nox5-, or xanthine oxidase-derived reactive oxygen species production as measured by cytochrome c reduction, Amplex Red fluorescence, and electron paramagnetic resonance. The ability of NoxA1ds to cross the plasma membrane was tested by confocal microscopy in a human colon cancer cell line exclusively expressing Nox1 (HT-29) using FITC-labeled NoxA1ds. NoxA1ds significantly inhibited whole HT-29 carcinoma cell-derived O2·- generation. ELISA and fluorescence recovery after photobleaching experiments indicate that NoxA1ds, but not its scrambled control, binds Nox1. FRET experiments conducted using Nox1-YFP and NOXA1-CFP illustrate that NoxA1ds disrupts the binding interaction between Nox1 and NOXA1, whereas a control peptide did not. Moreover, hypoxia-induced human pulmonary artery endothelial cell O2·- production was completely inhibited by NoxA1ds. Human pulmonary artery endothelial cell migration under hypoxic conditions was also reduced by pretreatment with NoxA1ds. Our data indicate that a peptide recapitulating a putative activation subdomain of NOXA1 (NoxA1ds) is a highly efficacious and selective inhibitor of Nox1 activity and establishes a critical interaction site for Nox1-NOXA1 binding required for enzyme activation.

Nox-derived ROS are acutely activated in pressure overload pulmonary hypertension: indications for a seminal role for mitochondrial Nox4.

Pulmonary arterial hypertension is a severe progressive disease with marked morbidity and high mortality in which right ventricular (RV) failure is the major cause of death. Thus knowledge of the mechanisms underlying RV failure is an area of active interest. Previous studies suggest a role of NADPH oxidase in cardiomyocyte dysfunction in the left heart. Here we postulate that acute pressure overload induced by pulmonary artery banding (PAB) leads to a Nox4-initiated increase in reactive oxygen species (ROS) in mouse RV that may lead to feed-forward induction of Nox2. To test our hypothesis, ROS production was measured in RV and left ventricle homogenates. The data show that hydrogen peroxide (H2O2), but not superoxide anion (O2(·-)), was increased in the early phases (within 6 h) of PAB in RV and that this increase was diminished by catalase and diphenyleneiodonium chloride but not by SOD, N(ω)-nitro-l-arginin methyl ester, febuxostat, or indomethacin. H2O2 production in RV was not attenuated in Nox2 null mice subjected to 6 h PAB. Moreover, we observed an upregulation of Nox4 mRNA after 1 h of PAB and an increase in mitochondrial Nox4 protein 6 h post-PAB. In contrast, we observed an increase in Nox2 mRNA 1 day post-PAB. Expression of antioxidant enzymes SOD, catalase, and glutathione peroxidase did not change, but catalase activity increased 6 h post-PAB. Taken together, these findings show a role of mitochondria-localized Nox4 in the early phase of PAB and suggest an involvement of this isozyme in early ROS generation possibly contributing to progression of RV dysfunction and failure.

Development of New Peptidomimetic NADPH Oxidase Inhibitors with Antithrombotic Properties.

The ability of synthetic peptides inhibitors of NOX1 to effectively block the production of ROS by the enzyme was studied with different methodologies. Specifically, taking advantage of our understanding of the active epitope of the regulatory NOX1 subunit NOXA1 as a potent inhibitor of NOX1-derived O2⋅- formation, a panel of peptidomimetic derivatives of this peptide were designed and synthesized with the aim of improving their activity and increasing their stability in plasma. The results highlighted that improved efficacy and potency was found for both the peptide-peptoid hybrid GS2, whereas stapled peptide AC5 and its precursor showed higher stability despite lower biological potency. This study showed that minimal structural modifications of NOXA1 peptides are required to improve both their potency and stability to finally achieve best candidates as new potential anti-thrombotic drugs.

LRRK2 regulates production of reactive oxygen species in cell and animal models of Parkinson's disease.

Oxidative stress has long been implicated in Parkinson's disease (PD) pathogenesis, although the sources and regulation of reactive oxygen species (ROS) production are poorly defined. Pathogenic mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) are associated with increased kinase activity and a greater risk of PD. The substrates and downstream consequences of elevated LRRK2 kinase activity are still being elucidated, but overexpression of mutant LRRK2 has been associated with oxidative stress, and antioxidants reportedly mitigate LRRK2 toxicity. Here, using CRISPR-Cas9 gene-edited HEK293 cells, RAW264.7 macrophages, rat primary ventral midbrain cultures, and PD patient-derived lymphoblastoid cells, we found that elevated LRRK2 kinase activity was associated with increased ROS production and lipid peroxidation and that this was blocked by inhibitors of either LRRK2 kinase or NADPH oxidase 2 (NOX2). Oxidative stress induced by the pesticide rotenone was ameliorated by LRRK2 kinase inhibition and was absent in cells devoid of LRRK2. In a rat model of PD induced by rotenone, a LRRK2 kinase inhibitor prevented the lipid peroxidation and NOX2 activation normally seen in nigral dopaminergic neurons in this model. Mechanistically, LRRK2 kinase activity was shown to regulate phosphorylation of serine-345 in the p47phox subunit of NOX2. This, in turn, led to translocation of p47phox from the cytosol to the membrane-associated gp91phox (NOX2) subunit, activation of the NOX2 enzyme complex, and production of ROS. Thus, LRRK2 kinase activity may drive cellular ROS production in PD through the regulation of NOX2 activity.

Role of the CCL5 and Its Receptor, CCR5, in the Genesis of Aldosterone-Induced Hypertension, Vascular Dysfunction, and End-Organ Damage.

BACKGROUND: Aldosterone has been described to initiate cardiovascular diseases by triggering exacerbated sterile vascular inflammation. The functions of CCL5 (C-C motif chemokine ligand 5) and its receptor CCR5 (C-C motif chemokine receptor 5) are well known in infectious diseases, their contributions to aldosterone-induced vascular injury and hypertension remain unknown. METHODS: We analyzed the vascular profile, blood pressure, and renal damage in wild-type (CCR5+/+) and CCR5 knockout (CCR5-/-) mice treated with aldosterone (600 µg/kg per day for 14 days) while receiving 1% saline to drink. Vascular function was analyzed in aorta and mesenteric arteries, blood pressure was measured by telemetry and renal injury and inflammation were analyzed via histology and flow cytometry. Endothelial cells were used to study the molecular signaling whereby CCL5 induces endothelial dysfunction. RESULTS: Aldosterone treatment resulted in exaggerated CCL5 circulating levels and vascular CCR5 expression in CCR5+/+ mice accompanied by endothelial dysfunction, hypertension, and renal inflammation and damage. CCR5-/- mice were protected from these aldosterone-induced effects. Mechanistically, we demonstrated that CCL5 increased NOX1 (NADPH oxidase 1) expression, reactive oxygen species formation, NFκB (nuclear factor kappa B) activation, and inflammation and reduced NO production in isolated endothelial cells. These effects were abolished by antagonizing CCR5 with Maraviroc. Finally, aorta incubated with CCL5 displayed severe endothelial dysfunction, which is prevented by blocking NOX1, NFκB, or CCR5. CONCLUSIONS: Our data demonstrate that CCL5/CCR5, through activation of NFκB and NOX1, is critically involved in aldosterone-induced vascular and renal damage and hypertension placing CCL5 and CCR5 as potential therapeutic targets for conditions characterized by aldosterone excess.

Pannexin-3 stabilizes the transcription factor Bcl6 in a channel-independent manner to protect against vascular oxidative stress.

Targeted degradation regulates the activity of the transcriptional repressor Bcl6 and its ability to suppress oxidative stress and inflammation. Here, we report that abundance of endothelial Bcl6 is determined by its interaction with Golgi-localized pannexin 3 (Panx3) and that Bcl6 transcriptional activity protects against vascular oxidative stress. Consistent with data from obese, hypertensive humans, mice with an endothelial cell-specific deficiency in Panx3 had spontaneous systemic hypertension without obvious changes in channel function, as assessed by Ca2+ handling, ATP amounts, or Golgi luminal pH. Panx3 bound to Bcl6, and its absence reduced Bcl6 protein abundance, suggesting that the interaction with Panx3 stabilized Bcl6 by preventing its degradation. Panx3 deficiency was associated with increased expression of the gene encoding the H2O2-producing enzyme Nox4, which is normally repressed by Bcl6, resulting in H2O2-induced oxidative damage in the vasculature. Catalase rescued impaired vasodilation in mice lacking endothelial Panx3. Administration of a newly developed peptide to inhibit the Panx3-Bcl6 interaction recapitulated the increase in Nox4 expression and in blood pressure seen in mice with endothelial Panx3 deficiency. Panx3-Bcl6-Nox4 dysregulation occurred in obesity-related hypertension, but not when hypertension was induced in the absence of obesity. Our findings provide insight into a channel-independent role of Panx3 wherein its interaction with Bcl6 determines vascular oxidative state, particularly under the adverse conditions of obesity.

Thrombospondin-1 regulates blood flow via CD47 receptor-mediated activation of NADPH oxidase 1.

OBJECTIVE: Although the matricellular protein thrombospondin-1 (TSP1) is highly expressed in the vessel wall in response to injury, its pathophysiological role in the development of vascular disease is poorly understood. This study was designed to test the hypothesis that TSP1 stimulates reactive oxygen species production in vascular smooth muscle cells and induces vascular dysfunction by promoting oxidative stress. METHODS AND RESULTS: Nanomolar concentrations of TSP1 found in human vascular disease robustly stimulated superoxide (O(2)(•-)) levels in vascular smooth muscle cells at both cellular and tissue level as measured by cytochrome c and electron paramagnetic resonance. A peptide mimicking the C terminus of TSP1 known to specifically bind CD47 recapitulated this response. Transcriptional knockdown of CD47 and a monoclonal inhibitory CD47 antibody abrogated TSP1-triggered O(2)(•-) in vitro and ex vivo. TSP1 treatment of vascular smooth muscle cells activated phospholipase C and protein kinase C, resulting in phosphorylation of the NADPH oxidase organizer subunit p47(phox) and subsequent Nox1 activation, leading to impairment of arterial vasodilatation ex vivo. Further, we observed that blockade of CD47 and NADPH oxidase 1 gene silencing in vivo in rats improves TSP1-induced impairment of tissue blood flow after ischemia reperfusion. CONCLUSIONS: Our data suggest a highly regulated process of reactive oxygen species stimulation and blood flow regulation promoted through a direct TSP1/CD47-mediated activation of Nox1. This is the first report, to our knowledge, of a matricellular protein acting as a ligand for NADPH oxidase activation and through specific engagement of integrin-associated protein CD47.

NADPH oxidase inhibitors: a decade of discovery from Nox2ds to HTS.

NADPH oxidases (Nox) are established as major sources of reactive oxygen species (ROS). Over the past two decades, Nox-derived ROS have emerged as pivotal in the development of myriad diseases involving oxidative stress. In contrast, Nox are also involved in signaling mechanisms necessary for normal cell function. The study of these enzymes in physiological and pathophysiological conditions is made considerably more complex by the discovery of 7 isoforms: Nox1 through 5 as well as Duox1 and 2, each with its own specific cytosolic components, regulatory control mechanisms, subcellular localization and/or tissue distribution. A clear understanding of the role individual isoforms play in a given system is hindered by the lack of isoform-specific inhibitors. In animal models, knockdown or knockout methodologies are providing definitive answers to perplexing questions of the complex interplay of multiple Nox isoforms in cell and tissue signaling. However, the complex structures and interactions of these heteromeric isozymes predict pleiotropic actions of the Nox subunits and thus suppression of these proteins is almost certain to have untoward effects. Thus, as both therapies and pharmacological tools, molecule-based inhibitors continue to prove extremely useful and rational in design. Unfortunately, many of the available inhibitors have proven non-specific, falling into the category of scavengers or inhibitors of more than one source of ROS. Here, we will review some of the efforts that have been undertaken to develop specific inhibitors of NADPH oxidase over the past decade, from the peptidic inhibitor Nox2ds-tat to more recent small molecule inhibitors that have emerged from high-throughput screening campaigns.