Effects of Sex Hormones on Vascular Reactivity in Boys With Hypospadias.

BACKGROUND: Arteries from boys with hypospadias demonstrate hypercontractility and impaired vasorelaxation. The role of sex hormones in these responses in unclear. AIMS: We compared effects of sex steroids on vascular reactivity in healthy boys and boys with hypospadias. METHODS: Excess foreskin tissue was obtained from 11 boys undergoing hypospadias repair (cases) and 12 undergoing routine circumcision (controls) (median age [range], 1.5 [1.2-2.7] years) and small resistance arteries were isolated. Vessels were mounted on wire myographs and vascular reactivity was assessed in the absence/presence of 17ß-estradiol, dihydrotestosterone (DHT), and testosterone. RESULTS: In controls, testosterone and 17ß-estradiol increased contraction (percent of maximum contraction [Emax]: 83.74 basal vs 125.4 after testosterone, P < .0002; and 83.74 vs 110.2 after estradiol, P = .02). 17ß-estradiol reduced vasorelaxation in arteries from controls (Emax: 10.6 vs 15.6 to acetylcholine, P < .0001; and Emax: 14.6 vs 20.5 to sodium nitroprusside, P < .0001). In hypospadias, testosterone (Emax: 137.9 vs 107.2, P = .01) and 17ß-estradiol (Emax: 156.9 vs 23.6, P < .0001) reduced contraction. Androgens, but not 17ß-estradiol, increased endothelium-dependent and endothelium-independent vasorelaxation in cases (Emax: 77.3 vs 51.7 with testosterone, P = .02; and vs 48.2 with DHT to acetylcholine, P = .0001; Emax: 43.0 vs 39.5 with testosterone, P = .02; and 39.6 vs 37.5 with DHT to sodium nitroprusside, P = .04). CONCLUSION: In healthy boys, testosterone and 17ß-estradiol promote a vasoconstrictor phenotype, whereas in boys with hypospadias, these sex hormones reduce vasoconstriction, with androgens promoting vasorelaxation. Differences in baseline artery function may therefore be sex hormone-independent and the impact of early-life variations in androgen exposure on vascular function needs further study.

Vasoprotective effects of NOX4 are mediated via polymerase and transient receptor potential melastatin 2 cation channels in endothelial cells.

BACKGROUND: NOX4 activation has been implicated to have vasoprotective and blood pressure (BP)-lowering effects. Molecular mechanisms underlying this are unclear, but NOX4-induced regulation of the redox-sensitive Ca 2+ channel TRPM2 and effects on endothelial nitric oxide synthase (eNOS)-nitric oxide signalling may be important. METHOD: Wild-type and LinA3, renin-expressing hypertensive mice, were crossed with NOX4 knockout mice. Vascular function was measured by myography. Generation of superoxide (O 2- ) and hydrogen peroxide (H 2 O 2 ) were assessed by lucigenin and amplex red, respectively, and Ca 2+ influx by Cal-520 fluorescence in rat aortic endothelial cells (RAEC). RESULTS: BP was increased in NOX4KO, LinA3 and LinA3/NOX4KO mice. This was associated with endothelial dysfunction and vascular remodelling, with exaggerated effects in NOX4KO groups. The TRPM2 activator, ADPR, improved vascular relaxation in LinA3/NOX4KO mice, an effect recapitulated by H 2 O 2 . Inhibition of PARP and TRPM2 with olaparib and 2-APB, respectively, recapitulated endothelial dysfunction in NOX4KO. In endothelial cells, Ang II increased H 2 O 2 generation and Ca 2+ influx, effects reduced by TRPM2 siRNA, TRPM2 inhibitors (8-br-cADPR, 2-APB), olaparib and GKT137831 (NOX4 inhibitor). Ang II-induced eNOS activation was blocked by NOX4 and TRPM2 siRNA, GKT137831, PEG-catalase and 8-br-cADPR. CONCLUSION: Our findings indicate that NOX4-induced H 2 O 2 production activates PARP/TRPM2, Ca 2+ influx, eNOS activation and nitric oxide release in endothelial cells. NOX4 deficiency impairs Ca 2+ homeostasis leading to endothelial dysfunction, an effect exacerbated in hypertension. We define a novel pathway linking endothelial NOX4/H 2 O 2 to eNOS/nitric oxide through PARP/TRPM2/Ca 2+ . This vasoprotective pathway is perturbed when NOX4 is downregulated and may have significance in conditions associated with endothelial dysfunction, including hypertension.

Vascular mechanisms of post-COVID-19 conditions: Rho-kinase is a novel target for therapy.

BACKGROUND: In post-coronavirus disease-19 (post-COVID-19) conditions (long COVID), systemic vascular dysfunction is implicated, but the mechanisms are uncertain, and the treatment is imprecise. METHODS AND RESULTS: Patients convalescing after hospitalization for COVID-19 and risk factor matched controls underwent multisystem phenotyping using blood biomarkers, cardiorenal and pulmonary imaging, and gluteal subcutaneous biopsy (NCT04403607). Small resistance arteries were isolated and examined using wire myography, histopathology, immunohistochemistry, and spatial transcriptomics. Endothelium-independent (sodium nitroprusside) and -dependent (acetylcholine) vasorelaxation and vasoconstriction to the thromboxane A2 receptor agonist, U46619, and endothelin-1 (ET-1) in the presence or absence of a RhoA/Rho-kinase inhibitor (fasudil), were investigated. Thirty-seven patients, including 27 (mean age 57 years, 48% women, 41% cardiovascular disease) 3 months post-COVID-19 and 10 controls (mean age 57 years, 20% women, 30% cardiovascular disease), were included. Compared with control responses, U46619-induced constriction was increased (P = 0.002) and endothelium-independent vasorelaxation was reduced in arteries from COVID-19 patients (P < 0.001). This difference was abolished by fasudil. Histopathology revealed greater collagen abundance in COVID-19 arteries {Masson's trichrome (MT) 69.7% [95% confidence interval (CI): 67.8-71.7]; picrosirius red 68.6% [95% CI: 64.4-72.8]} vs. controls [MT 64.9% (95% CI: 59.4-70.3) (P = 0.028); picrosirius red 60.1% (95% CI: 55.4-64.8), (P = 0.029)]. Greater phosphorylated myosin light chain antibody-positive staining in vascular smooth muscle cells was observed in COVID-19 arteries (40.1%; 95% CI: 30.9-49.3) vs. controls (10.0%; 95% CI: 4.4-15.6) (P < 0.001). In proof-of-concept studies, gene pathways associated with extracellular matrix alteration, proteoglycan synthesis, and viral mRNA replication appeared to be upregulated. CONCLUSION: Patients with post-COVID-19 conditions have enhanced vascular fibrosis and myosin light change phosphorylation. Rho-kinase activation represents a novel therapeutic target for clinical trials.

Role of PARP and TRPM2 in VEGF Inhibitor-Induced Vascular Dysfunction.

Background Hypertension and vascular toxicity are major unwanted side effects of antiangiogenic drugs, such as vascular endothelial growth factor inhibitors (VEGFis), which are effective anticancer drugs but have unwanted side effects, including vascular toxicity and hypertension. Poly (ADP-ribose) polymerase (PARP) inhibitors, used to treat ovarian and other cancers, have also been associated with elevated blood pressure. However, when patients with cancer receive both olaparib, a PARP inhibitor, and VEGFi, the risk of blood pressure elevation is reduced. Underlying molecular mechanisms are unclear, but PARP-regulated transient receptor potential cation channel, subfamily M, member 2 (TRPM2), a redox-sensitive calcium channel, may be important. We investigated whether PARP/TRPM2 plays a role in VEGFi-induced vascular dysfunction and whether PARP inhibition ameliorates the vasculopathy associated with VEGF inhibition. Methods and Results Human vascular smooth muscle cells (VSMCs), human aortic endothelial cells, and wild-type mouse mesenteric arteries were studied. Cells/arteries were exposed to axitinib (VEGFi) alone and in combination with olaparib. Reactive oxygen species production, Ca2+ influx, protein/gene analysis, PARP activity, and TRPM2 signaling were assessed in VSMCs, and nitric oxide levels were determined in endothelial cells. Vascular function was assessed by myography. Axitinib increased PARP activity in VSMCs in a reactive oxygen species-dependent manner. Endothelial dysfunction and hypercontractile responses were ameliorated by olaparib and a TRPM2 blocker (8-Br-cADPR). VSMC reactive oxygen species production, Ca2+ influx, and phosphorylation of myosin light chain 20 and endothelial nitric oxide synthase (Thr495) were augmented by axitinib and attenuated by olaparib and TRPM2 inhibition. Proinflammatory markers were upregulated in axitinib-stimulated VSMCs, which was reduced by reactive oxygen species scavengers and PARP-TRPM2 inhibition. Human aortic endothelial cells exposed to combined olaparib and axitinib showed nitric oxide levels similar to VEGF-stimulated cells. Conclusions Axitinib-mediated vascular dysfunction involves PARP and TRPM2, which, when inhibited, ameliorate the injurious effects of VEGFi. Our findings define a potential mechanism whereby PARP inhibitor may attenuate vascular toxicity in VEGFi-treated patients with cancer.

TRPM7 deficiency exacerbates cardiovascular and renal damage induced by aldosterone-salt.

Hyperaldosteronism causes cardiovascular disease as well as hypomagnesemia. Mechanisms are ill-defined but dysregulation of TRPM7, a Mg2+-permeable channel/α-kinase, may be important. We examined the role of TRPM7 in aldosterone-dependent cardiovascular and renal injury by studying aldosterone-salt treated TRPM7-deficient (TRPM7+/Δkinase) mice. Plasma/tissue [Mg2+] and TRPM7 phosphorylation were reduced in vehicle-treated TRPM7+/Δkinase mice, effects recapitulated in aldosterone-salt-treated wild-type mice. Aldosterone-salt treatment exaggerated vascular dysfunction and amplified cardiovascular and renal fibrosis, with associated increased blood pressure in TRPM7+/Δkinase mice. Tissue expression of Mg2+-regulated phosphatases (PPM1A, PTEN) was downregulated and phosphorylation of Smad3, ERK1/2, and Stat1 was upregulated in aldosterone-salt TRPM7-deficient mice. Aldosterone-induced phosphorylation of pro-fibrotic signaling was increased in TRPM7+/Δkinase fibroblasts, effects ameliorated by Mg2+ supplementation. TRPM7 deficiency amplifies aldosterone-salt-induced cardiovascular remodeling and damage. We identify TRPM7 downregulation and associated hypomagnesemia as putative molecular mechanisms underlying deleterious cardiovascular and renal effects of hyperaldosteronism.

Vascular dysfunction and increased cardiovascular risk in hypospadias.

AIMS: Hypogonadism is associated with cardiovascular disease. However, the cardiovascular impact of hypogonadism during development is unknown. Using hypospadias as a surrogate of hypogonadism, we investigated whether hypospadias is associated with vascular dysfunction and is a risk factor for cardiovascular disease. METHODS AND RESULTS: Our human study spanned molecular mechanistic to epidemiological investigations. Clinical vascular phenotyping was performed in adolescents with hypospadias and controls. Small subcutaneous arteries from penile skin from boys undergoing hypospadias repair and controls were isolated and functional studies were assessed by myography. Vascular smooth muscle cells were used to assess: Rho kinase, reactive oxygen species (ROS), nitric oxide synthase/nitric oxide, and DNA damage. Systemic oxidative stress was assessed in plasma and urine. Hospital episode data compared men with a history of hypospadias vs. controls. In adolescents with hypospadias, systolic blood pressure (P = 0.005), pulse pressure (P = 0.03), and carotid intima-media thickness standard deviation scores (P = 0.01) were increased. Arteries from boys with hypospadias demonstrated increased U46619-induced vasoconstriction (P = 0.009) and reduced acetylcholine-induced endothelium-dependent (P < 0.0001) and sodium nitroprusside-induced endothelium-independent vasorelaxation (P < 0.0001). Men born with hypospadias were at increased risk of arrhythmia [odds ratio (OR) 2.8, 95% confidence interval (CI) 1.4-5.6, P = 0.003]; hypertension (OR 4.2, 95% CI 1.5-11.9, P = 0.04); and heart failure (OR 1.9, 95% CI 1.7-114.3, P = 0.02). CONCLUSION: Hypospadias is associated with vascular dysfunction and predisposes to hypertension and cardiovascular disease in adulthood. Underlying mechanisms involve perturbed Rho kinase- and Nox5/ROS-dependent signalling. Our novel findings delineate molecular mechanisms of vascular injury in hypogonadism, and identify hypospadias as a cardiovascular risk factor in males.

Testosterone Contributes to Vascular Dysfunction in Young Mice Fed a High Fat Diet by Promoting Nuclear Factor E2-Related Factor 2 Downregulation and Oxidative Stress.

Obesity, an important risk factor for cardiovascular disease, promotes vascular oxidative stress. Considering that free testosterone levels remain within the reference range, especially in obese young men and that testosterone stimulates reactive oxygen species (ROS) generation, we sought to investigate whether testosterone interferes with obesity-associated oxidative stress and vascular dysfunction in male mice. We hypothesized that testosterone favors ROS accumulation and vascular dysfunction in high fat diet (HFD)-fed obese mice. We also questioned whether testosterone downregulates the nuclear factor E2-related factor 2 (Nrf2), one of the major cellular defense mechanisms against oxidative stimuli. Male C57Bl/6J mice were submitted to orchiectomy or sham-operation. Mice received either a control diet (CD) or HFD for 18 weeks. Vascular function was assessed in thoracic aortic rings and molecular mechanisms by which testosterone contributes to vascular dysfunction were determined. HFD reduced acetylcholine-induced vasodilation and increased vascular ROS generation in sham mice. Castration prevented these effects. Treatment of castrated mice fed either the CD or HFD with testosterone propionate decreased acetylcholine vasodilation. HFD decreased Nrf2 nuclear accumulation, events linked to decreased mRNA expression and activity of Nrf2-regulated enzymes (catalase, heme oxygenase-1, peroxiredoxin, and thioredoxin). These events were prevented in HFD-fed castrated mice. Bardoxolone, a Nrf2 activator, increased nuclear accumulation of Nrf2, decreased ROS generation and improved acetylcholine vasodilation in HFD-fed sham mice. In vitro, testosterone increased ROS generation and decreased Nrf2 nuclear accumulation. These effects were prevented in the presence of an androgen receptor antagonist, an inhibitor of gene transcription and an inhibitor of the pro-oxidant enzyme NOX-1. These results indicate that testosterone downregulates Nrf2, leading to oxidative stress and vascular dysfunction in HFD-fed obese young mice.

Central role of c-Src in NOX5- mediated redox signalling in vascular smooth muscle cells in human hypertension.

AIMS: NOX-derived reactive oxygen species (ROS) are mediators of signalling pathways implicated in vascular smooth muscle cell (VSMC) dysfunction in hypertension. Among the numerous redox-sensitive kinases important in VSMC regulation is c-Src. However, mechanisms linking NOX/ROS to c-Src are unclear, especially in the context of oxidative stress in hypertension. Here, we investigated the role of NOX-induced oxidative stress in VSMCs in human hypertension focusing on NOX5, and explored c-Src, as a putative intermediate connecting NOX5-ROS to downstream effector targets underlying VSMC dysfunction. METHODS AND RESULTS: VSMC from arteries from normotensive (NT) and hypertensive (HT) subjects were studied. NOX1,2,4,5 expression, ROS generation, oxidation/phosphorylation of signalling molecules, and actin polymerization and migration were assessed in the absence and presence of NOX5 (melittin) and Src (PP2) inhibitors. NOX5 and p22phox-dependent NOXs (NOX1-4) were down-regulated using NOX5 siRNA and p22phox-siRNA approaches. As proof of concept in intact vessels, vascular function was assessed by myography in transgenic mice expressing human NOX5 in a VSMC-specific manner. In HT VSMCs, NOX5 was up-regulated, with associated oxidative stress, hyperoxidation (c-Src, peroxiredoxin, DJ-1), and hyperphosphorylation (c-Src, PKC, ERK1/2, MLC20) of signalling molecules. NOX5 siRNA reduced ROS generation in NT and HT subjects. NOX5 siRNA, but not p22phox-siRNA, blunted c-Src phosphorylation in HT VSMCs. NOX5 siRNA reduced phosphorylation of MLC20 and FAK in NT and HT. In p22phox- silenced HT VSMCs, Ang II-induced phosphorylation of MLC20 was increased, effects blocked by melittin and PP2. NOX5 and c-Src inhibition attenuated actin polymerization and migration in HT VSMCs. In NOX5 transgenic mice, vascular hypercontractilty was decreased by melittin and PP2. CONCLUSION: We define NOX5/ROS/c-Src as a novel feedforward signalling network in human VSMCs. Amplification of this system in hypertension contributes to VSMC dysfunction. Dampening the NOX5/ROS/c-Src pathway may ameliorate hypertension-associated vascular injury.

Osteoprotegerin regulates vascular function through syndecan-1 and NADPH oxidase-derived reactive oxygen species.

Osteogenic factors, such as osteoprotegerin (OPG), are protective against vascular calcification. However, OPG is also positively associated with cardiovascular damage, particularly in pulmonary hypertension, possibly through processes beyond effects on calcification. In the present study, we focused on calcification-independent vascular effects of OPG through activation of syndecan-1 and NADPH oxidases (Noxs) 1 and 4. Isolated resistance arteries from Wistar-Kyoto (WKY) rats, exposed to exogenous OPG, studied by myography exhibited endothelial and smooth muscle dysfunction. OPG decreased nitric oxide (NO) production, eNOS activation and increased reactive oxygen species (ROS) production in endothelial cells. In VSMCs, OPG increased ROS production, H2O2/peroxynitrite levels and activation of Rho kinase and myosin light chain. OPG vascular and redox effects were also inhibited by the syndecan-1 inhibitor synstatin (SSNT). Additionally, heparinase and chondroitinase abolished OPG effects on VSMCs-ROS production, confirming syndecan-1 as OPG molecular partner and suggesting that OPG binds to heparan/chondroitin sulphate chains of syndecan-1. OPG-induced ROS production was abrogated by NoxA1ds (Nox1 inhibitor) and GKT137831 (dual Nox1/Nox4 inhibitor). Tempol (SOD mimetic) inhibited vascular dysfunction induced by OPG. In addition, we studied arteries from Nox1 and Nox4 knockout (KO) mice. Nox1 and Nox4 KO abrogated OPG-induced vascular dysfunction. Vascular dysfunction elicited by OPG is mediated by a complex signalling cascade involving syndecan-1, Nox1 and Nox4. Our data identify novel molecular mechanisms beyond calcification for OPG, which may underlie vascular injurious effects of osteogenic factors in conditions such as hypertension and/or diabetes.

Selective Inhibition of the C-Domain of ACE (Angiotensin-Converting Enzyme) Combined With Inhibition of NEP (Neprilysin): A Potential New Therapy for Hypertension.

[Figure: see text].

Lysophosphatidylcholine induces oxidative stress in human endothelial cells via NOX5 activation - implications in atherosclerosis.

OBJECTIVE: The mechanisms involved in NOX5 activation in atherosclerotic processes are not completely understood. The present study tested the hypothesis that lysophosphatidylcholine (LPC), a proatherogenic component of oxLDL, induces endothelial calcium influx, which drives NOX5-dependent reactive oxygen species (ROS) production, oxidative stress, and endothelial cell dysfunction. APPROACH: Human aortic endothelial cells (HAEC) were stimulated with LPC (10-5 M, for different time points). Pharmacological inhibition of NOX5 (Melittin, 10-7 M) and NOX5 gene silencing (siRNA) was used to determine the role of NOX5-dependent ROS production in endothelial oxidative stress induced by LPC. ROS production was determined by lucigenin assay and electron paramagnetic spectroscopy (EPR), calcium transients by Fluo4 fluorimetry, and NOX5 activity and protein expression by pharmacological assays and immunoblotting, respectively. RESULTS: LPC increased ROS generation in endothelial cells at short (15 min) and long (4 h) stimulation times. LPC-induced ROS was abolished by a selective NOX5 inhibitor and by NOX5 siRNA. NOX1/4 dual inhibition and selective NOX1 inhibition only decreased ROS generation at 4 h. LPC increased HAEC intracellular calcium, important for NOX5 activation, and this was blocked by nifedipine and thapsigargin. Bapta-AM, selective Ca2+ chelator, prevented LPC-induced ROS production. NOX5 knockdown decreased LPC-induced ICAM-1 mRNA expression and monocyte adhesion to endothelial cells. CONCLUSION: These results suggest that NOX5, by mechanisms linked to increased intracellular calcium, is key to early LPC-induced endothelial oxidative stress and pro-inflammatory processes. Since these are essential events in the formation and progression of atherosclerotic lesions, the present study highlights an important role for NOX5 in atherosclerosis.

Angiotensin-II activates vascular inflammasome and induces vascular damage.

Angiotensin-II (Ang-II), a major target for treatment of cardiovascular disease, promotes cardiovascular dysfunction by directly modulating structure and function of vascular cells. Inflammasome components are expressed in the vasculature and are activated by specific stimuli. However, whether Ang-II activates the inflammasome in vascular cells or inflammasome activation contributes to Ang-II-induced vascular damage is still not fully elucidated. We tested the hypothesis that Ang-II induces endothelial dysfunction, vascular remodeling, and high blood pressure via inflammasome activation. C57BL6/J wild type (WT) and Caspase-1 knockout (Casp1-/-) mice were infused with vehicle or Ang-II for two weeks (490 ng/Kg/day) to determine whether the inflammasome contributes to vascular damage induced by Ang-II. Rat Aortic Vascular Smooth Muscle cells (RASMC) were used to determine if the interaction between Ang-II and inflammasomes causes migration and proliferation of vascular smooth muscle cells. Ex vivo studies revealed that Ang-II infusion induced vascular oxidative stress, endothelial dysfunction and vascular remodeling in WT mice. Casp1-/- mice were protected against Ang-II-induced vascular injury. In vitro experiments, Ang-II activated the NLRP3 inflammasome in RASMC, i.e. Ang-II increased Caspase-1 (Casp1) activity and cleavage of pro-interleukin (IL)-1ß. MCC950 (NLRP3 receptor antagonist) prevented Ang-II-induced vascular migration and proliferation, but failed to reduce reactive oxygen species production. In conclusion, Ang-II leads to inflammasome activation in the vasculature contributing to endothelial dysfunction and vascular remodeling. Taken together, we place inflammasomes as a possible therapeutic target in conditions associated with increased Ang-II levels.

Oxidative Stress and Hypertension.

A link between oxidative stress and hypertension has been firmly established in multiple animal models of hypertension but remains elusive in humans. While initial studies focused on inactivation of nitric oxide by superoxide, our understanding of relevant reactive oxygen species (superoxide, hydrogen peroxide, and peroxynitrite) and how they modify complex signaling pathways to promote hypertension has expanded significantly. In this review, we summarize recent advances in delineating the primary and secondary sources of reactive oxygen species (nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, endoplasmic reticulum, and mitochondria), the posttranslational oxidative modifications they induce on protein targets important for redox signaling, their interplay with endogenous antioxidant systems, and the role of inflammasome activation and endoplasmic reticular stress in the development of hypertension. We highlight how oxidative stress in different organ systems contributes to hypertension, describe new animal models that have clarified the importance of specific proteins, and discuss clinical studies that shed light on how these processes and pathways are altered in human hypertension. Finally, we focus on the promise of redox proteomics and systems biology to help us fully understand the relationship between ROS and hypertension and their potential for designing and evaluating novel antihypertensive therapies.

Peripheral arteriopathy caused by Notch3 gain-of-function mutation involves ER and oxidative stress and blunting of NO/sGC/cGMP pathway.

Notch3 mutations cause Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), which predisposes to stroke and dementia. CADASIL is characterised by vascular dysfunction and granular osmiophilic material (GOM) accumulation in cerebral small vessels. Systemic vessels may also be impacted by Notch3 mutations. However vascular characteristics and pathophysiological processes remain elusive. We investigated mechanisms underlying the peripheral vasculopathy mediated by CADASIL-causing Notch3 gain-of-function mutation. We studied: (i) small arteries and vascular smooth muscle cells (VSMCs) from TgNotch3R169C mice (CADASIL model), (ii) VSMCs from peripheral arteries from CADASIL patients, and (iii) post-mortem brains from CADASIL individuals. TgNotch3R169C vessels exhibited GOM deposits, increased vasoreactivity and impaired vasorelaxation. Hypercontractile responses were normalised by fasudil (Rho kinase inhibitor) and 4-phenylbutyrate (4-PBA; endoplasmic-reticulum (ER) stress inhibitor). Ca2+ transients and Ca2+ channel expression were increased in CADASIL VSMCs, with increased expression of Rho guanine nucleotide-exchange factors (GEFs) and ER stress proteins. Vasorelaxation mechanisms were impaired in CADASIL, evidenced by decreased endothelial nitric oxide synthase (eNOS) phosphorylation and reduced cyclic guanosine 3',5'-monophosphate (cGMP) levels, with associated increased soluble guanylate cyclase (sGC) oxidation, decreased sGC activity and reduced levels of the vasodilator hydrogen peroxide (H2O2). In VSMCs from CADASIL patients, sGC oxidation was increased and cGMP levels decreased, effects normalised by fasudil and 4-PBA. Cerebral vessels in CADASIL patients exhibited significant oxidative damage. In conclusion, peripheral vascular dysfunction in CADASIL is associated with altered Ca2+ homoeostasis, oxidative stress and blunted eNOS/sGC/cGMP signaling, processes involving Rho kinase and ER stress. We identify novel pathways underlying the peripheral arteriopathy induced by Notch3 gain-of-function mutation, phenomena that may also be important in cerebral vessels.

Epidermal growth factor signaling through transient receptor potential melastatin 7 cation channel regulates vascular smooth muscle cell function.

OBJECTIVE: Transient receptor potential (TRP) melastatin 7 (TRPM7) cation channel, a dual-function ion channel/protein kinase, regulates vascular smooth muscle cell (VSMC) Mg2+ homeostasis and mitogenic signaling. Mechanisms regulating vascular growth effects of TRPM7 are unclear, but epidermal growth factor (EGF) may be important because it is a magnesiotropic hormone involved in cellular Mg2+ regulation and VSMC proliferation. Here we sought to determine whether TRPM7 is a downstream target of EGF in VSMCs and if EGF receptor (EGFR) through TRPM7 influences VSMC function. Approach and results: Studies were performed in primary culture VSMCs from rats and humans and vascular tissue from mice deficient in TRPM7 (TRPM7+/Δkinase and TRPM7R/R). EGF increased expression and phosphorylation of TRPM7 and stimulated Mg2+ influx in VSMCs, responses that were attenuated by gefitinib (EGFR inhibitor) and NS8593 (TRPM7 inhibitor). Co-immunoprecipitation (IP) studies, proximity ligation assay (PLA) and live-cell imaging demonstrated interaction of EGFR and TRPM7, which was enhanced by EGF. PP2 (c-Src inhibitor) decreased EGF-induced TRPM7 activation and prevented EGFR-TRPM7 association. EGF-stimulated migration and proliferation of VSMCs were inhibited by gefitinib, PP2, NS8593 and PD98059 (ERK1/2 inhibitor). Phosphorylation of EGFR and ERK1/2 was reduced in VSMCs from TRPM7+/Δkinase mice, which exhibited reduced aortic wall thickness and decreased expression of PCNA and Notch 3, findings recapitulated in TRPM7R/R mice. CONCLUSIONS: We show that EGFR directly interacts with TRPM7 through c-Src-dependent processes. Functionally these phenomena regulate [Mg2+]i homeostasis, ERK1/2 signaling and VSMC function. Our findings define a novel signaling cascade linking EGF/EGFR and TRPM7, important in vascular homeostasis.

Oxidative Stress: A Unifying Paradigm in Hypertension.

The etiology of hypertension involves complex interactions among genetic, environmental, and pathophysiologic factors that influence many regulatory systems. Hypertension is characteristically associated with vascular dysfunction, cardiovascular remodelling, renal dysfunction, and stimulation of the sympathetic nervous system. Emerging evidence indicates that the immune system is also important and that activated immune cells migrate and accumulate in tissues promoting inflammation, fibrosis, and target-organ damage. Common to these processes is oxidative stress, defined as an imbalance between oxidants and antioxidants in favour of the oxidants that leads to a disruption of oxidation-reduction (redox) signalling and control and molecular damage. Physiologically, reactive oxygen species (ROS) act as signalling molecules and influence cell function through highly regulated redox-sensitive signal transduction. In hypertension, oxidative stress promotes posttranslational modification (oxidation and phosphorylation) of proteins and aberrant signalling with consequent cell and tissue damage. Many enzymatic systems generate ROS, but NADPH oxidases (Nox) are the major sources in cells of the heart, vessels, kidneys, and immune system. Expression and activity of Nox are increased in hypertension and are the major systems responsible for oxidative stress in cardiovascular disease. Here we provide a unifying concept where oxidative stress is a common mediator underlying pathophysiologic processes in hypertension. We focus on some novel concepts whereby ROS influence vascular function, aldosterone/mineralocorticoid actions, and immunoinflammation, all important processes contributing to the development of hypertension.

Crosstalk Between Vascular Redox and Calcium Signaling in Hypertension Involves TRPM2 (Transient Receptor Potential Melastatin 2) Cation Channel.

Increased generation of reactive oxygen species (ROS) and altered Ca2+ handling cause vascular damage in hypertension. Mechanisms linking these systems are unclear, but TRPM2 (transient receptor potential melastatin 2) could be important because TRPM2 is a ROS sensor and a regulator of Ca2+ and Na+ transport. We hypothesized that TRPM2 is a point of cross-talk between redox and Ca2+ signaling in vascular smooth muscle cells (VSMC) and that in hypertension ROS mediated-TRPM2 activation increases [Ca2+]i through processes involving NCX (Na+/Ca2+ exchanger). VSMCs from hypertensive and normotensive individuals and isolated arteries from wild type and hypertensive mice (LinA3) were studied. Generation of superoxide anion and hydrogen peroxide (H2O2) was increased in hypertensive VSMCs, effects associated with activation of redox-sensitive PARP1 (poly [ADP-ribose] polymerase 1), a TRPM2 regulator. Ang II (angiotensin II) increased Ca2+ and Na+ influx with exaggerated responses in hypertension. These effects were attenuated by catalase-polyethylene glycol -catalase and TRPM2 inhibitors (2-APB, 8-Br-cADPR olaparib). TRPM2 siRNA decreased Ca2+ in hypertensive VSMCs. NCX inhibitors (Benzamil, KB-R7943, YM244769) normalized Ca2+ hyper-responsiveness and MLC20 phosphorylation in hypertensive VSMCs. In arteries from LinA3 mice, exaggerated agonist (U46619, Ang II, phenylephrine)-induced vasoconstriction was decreased by TRPM2 and NCX inhibitors. In conclusion, activation of ROS-dependent PARP1-regulated TRPM2 contributes to vascular Ca2+ and Na+ influx in part through NCX. We identify a novel pathway linking ROS to Ca2+ signaling through TRPM2/NCX in human VSMCs and suggest that oxidative stress-induced upregulation of this pathway may be a new player in hypertension-associated vascular dysfunction.

ER stress and Rho kinase activation underlie the vasculopathy of CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) leads to premature stroke and vascular dementia. Mechanism-specific therapies for this aggressive cerebral small vessel disease are lacking. CADASIL is caused by NOTCH3 mutations that influence vascular smooth muscle cell (VSMC) function through unknown processes. We investigated molecular mechanisms underlying the vasculopathy in CADASIL focusing on endoplasmic reticulum (ER) stress and RhoA/Rho kinase (ROCK). Peripheral small arteries and VSMCs were isolated from gluteal biopsies of CADASIL patients and mesentery of TgNotch3R169C mice (CADASIL model). CADASIL vessels exhibited impaired vasorelaxation, blunted vasoconstriction, and hypertrophic remodeling. Expression of NOTCH3 and ER stress target genes was amplified and ER stress response, Rho kinase activity, superoxide production, and cytoskeleton-associated protein phosphorylation were increased in CADASIL, processes associated with Nox5 upregulation. Aberrant vascular responses and signaling in CADASIL were ameliorated by inhibitors of Notch3 (γ-secretase inhibitor), Nox5 (mellitin), ER stress (4-phenylbutyric acid), and ROCK (fasudil). Observations in human CADASIL were recapitulated in TgNotch3R169C mice. These findings indicate that vascular dysfunction in CADASIL involves ER stress/ROCK interplay driven by Notch3-induced Nox5 activation and that NOTCH3 mutation-associated vascular pathology, typical in cerebral vessels, also manifests peripherally. We define Notch3-Nox5/ER stress/ROCK signaling as a putative mechanism-specific target and suggest that peripheral artery responses may be an accessible biomarker in CADASIL.

Antioxidant and antihypertensive responses to oral nitrite involves activation of the Nrf2 pathway.

Impaired redox balance contributes to the cardiovascular alterations of hypertension and activation of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway may counteract these alterations. While nitrite recycles back to NO and exerts antioxidant and antihypertensive effects, the mechanisms involved in these responses are not fully understood. We hypothesized that nitrite treatment of two-kidney, one-clip (2K1C) hypertensive rats activates the Nrf2 pathway, promotes the transcription of antioxidant genes, and improves the vascular redox imbalance and dysfunction in this model. Two doses of oral nitrite were studied: 15 mg/kg and the sub-antihypertensive dose of 1 mg/kg. Nitrite 15 mg/kg (but not 1 mg/kg) decreased blood pressure and increased circulating plasma nitrite and nitrate. Both doses blunted hypertension-induced increases in mesenteric artery reactive oxygen species concentrations assessed by DHE technique and restored the impaired mesenteric artery responses to acetylcholine. While 2K1C hypertension decreased nuclear Nrf2 accumulation, both doses of nitrite increased nuclear Nrf2 accumulation and mRNA expression of Nrf2-regulated genes including superoxide dismutase-1 (SOD1), catalase (CAT), glutathione peroxidase (GPX), thioredoxin-1(TRDX-1) and -2 (TRDX-2). To further confirm nitrite-mediated antioxidant effects, we measured vascular SOD and GPX activity and we found that nitrite at 1 or 15 mg/kg increased the activity of both enzymes (P < 0.05). These results suggest that activation of the Nrf2 pathway promotes antioxidant effects of nitrite, which may improve the vascular dysfunction in hypertension, even when nitrite is given at a sub-antihypertensive dose. These findings may have many clinical implications, particularly in the therapy of hypertension and other cardiovascular diseases.