Mechanisms of Vascular Inflammation and Potential Therapeutic Targets: A Position Paper From the ESH Working Group on Small Arteries

Inflammatory responses in small vessels play an important role in the development of cardiovascular diseases, including hypertension, stroke, and small vessel disease. This involves various complex molecular processes including oxidative stress, inflammasome activation, immune-mediated responses, and protein misfolding, which together contribute to microvascular damage. In addition, epigenetic factors, including DNA methylation, histone modifications, and microRNAs influence vascular inflammation and injury. These phenomena may be acquired during the aging process or due to environmental factors. Activation of proinflammatory signaling pathways and molecular events induce low-grade and chronic inflammation with consequent cardiovascular damage. Identifying mechanism-specific targets might provide opportunities in the development of novel therapeutic approaches. Monoclonal antibodies targeting inflammatory cytokines and epigenetic drugs, show promise in reducing microvascular inflammation and associated cardiovascular diseases. In this article, we provide a comprehensive discussion of the complex mechanisms underlying microvascular inflammation and offer insights into innovative therapeutic strategies that may ameliorate vascular injury in cardiovascular disease.

Oxidative Stress and Endoplasmic Reticular Stress Interplay in the Vasculopathy of Hypertension

Under physiologic conditions, reactive oxygen species (ROS) function as signalling molecules that control cell function. However, in pathologic conditions, increased generation of ROS triggers oxidative stress, which plays a role in vascular changes associated with hypertension, including endothelial dysfunction, vascular reactivity, and arterial remodelling (termed the vasculopathy of hypertension). The major source of ROS in the vascular system is NADPH oxidase (NOX). Increased NOX activity drives vascular oxidative stress in hypertension. Molecular mechanisms underlying vascular damage in hypertension include activation of redox-sensitive signalling pathways, post-translational modification of proteins, and oxidative damage of DNA and cytoplasmic proteins. In addition, oxidative stress leads to accumulation of proteins in the endoplasmic reticulum (ER) (termed ER stress), with consequent activation of the unfolded protein response (UPR). ER stress is emerging as a potential player in hypertension as abnormal protein folding in the ER leads to oxidative stress and dysregulated activation of the UPR promotes inflammation and injury in vascular and cardiac cells. In addition, the ER engages in crosstalk with exogenous sources of ROS, such as mitochondria and NOX, which can amplify redox processes. Here we provide an update of the role of ROS and NOX in hypertension and discuss novel concepts on the interplay between oxidative stress and ER stress.

Recent Advances in Understanding the Mechanistic Role of Transient Receptor Potential Ion Channels in Patients With Hypertension

The transient receptor potential (TRP) channel superfamily is a group of nonselective cation channels that function as cellular sensors for a wide range of physical, chemical, and environmental stimuli. According to sequence homology, TRP channels are categorized into 6 subfamilies: TRP canonical, TRP vanilloid, TRP melastatin, TRP ankyrin, TRP mucolipin, and TRP polycystin. They are widely expressed in different cell types and tissues and have essential roles in various physiological and pathological processes by regulating the concentration of ions (Ca2+, Mg2+, Na+, and K+) and influencing intracellular signalling pathways. Human data and experimental models indicate the importance of TRP channels in vascular homeostasis and hypertension. Furthermore, TRP channels have emerged as key players in oxidative stress and inflammation, important in the pathophysiology of cardiovascular diseases, including hypertension. In this review, we present an overview of the TRP channels with a focus on their role in hypertension. In particular, we highlight mechanisms activated by TRP channels in vascular smooth muscle and endothelial cells and discuss their contribution to processes underlying vascular dysfunction in hypertension.

The importance of microvascular inflammation in ageing and age-related diseases: a position paper from the ESH working group on small arteries, section of microvascular inflammation

Microcirculation is pervasive and orchestrates a profound regulatory cross-talk with the surrounding tissue and organs. Similarly, it is one of the earliest biological systems targeted by environmental stressors and consequently involved in the development and progression of ageing and age-related disease. Microvascular dysfunction, if not targeted, leads to a steady derangement of the phenotype, which cumulates comorbidities and eventually results in a nonrescuable, very high-cardiovascular risk. Along the broad spectrum of pathologies, both shared and distinct molecular pathways and pathophysiological alteration are involved in the disruption of microvascular homeostasis, all pointing to microvascular inflammation as the putative primary culprit. This position paper explores the presence and the detrimental contribution of microvascular inflammation across the whole spectrum of chronic age-related diseases, which characterise the 21st-century healthcare landscape. The manuscript aims to strongly affirm the centrality of microvascular inflammation by recapitulating the current evidence and providing a clear synoptic view of the whole cardiometabolic derangement. Indeed, there is an urgent need for further mechanistic exploration to identify clear, very early or disease-specific molecular targets to provide an effective therapeutic strategy against the otherwise unstoppable rising prevalence of age-related diseases.

Impact of Environmental Factors on Hypertension and Associated Cardiovascular Disease

Hypertension is the primary cause of cardiovascular diseases and is responsible for nearly 9 million deaths worldwide annually. Increasing evidence indicates that in addition to pathophysiologic processes, numerous environmental factors, such as geographic location, lifestyle choices, socioeconomic status, and cultural practices, influence the risk, progression, and severity of hypertension, even in the absence of genetic risk factors. In this review, we discuss the impact of some environmental determinants on hypertension. We focus on clinical data from large population studies and discuss some potential molecular and cellular mechanisms. We highlight how these environmental determinants are interconnected, as small changes in one factor might affect others, and further affect cardiovascular health. In addition, we discuss the crucial impact of socioeconomic factors and how these determinants influence diverse communities with economic disparities. Finally, we address opportunities and challenges for new research to address gaps in knowledge on understanding molecular mechanisms whereby environmental factors influence development of hypertension and associated cardiovascular disease.

SARS-CoV-2 spike protein induces endothelial inflammation via ACE2 independently of viral replication

COVID-19, caused by SARS-CoV-2, is a respiratory disease associated with inflammation and endotheliitis. Mechanisms underling inflammatory processes are unclear, but angiotensin converting enzyme 2 (ACE2), the receptor which binds the spike protein of SARS-CoV-2 may be important. Here we investigated whether spike protein binding to ACE2 induces inflammation in endothelial cells and determined the role of ACE2 in this process. Human endothelial cells were exposed to SARS-CoV-2 spike protein, S1 subunit (rS1p) and pro-inflammatory signaling and inflammatory mediators assessed. ACE2 was modulated pharmacologically and by siRNA. Endothelial cells were also exposed to SARS-CoV-2. rSP1 increased production of IL-6, MCP-1, ICAM-1 and PAI-1, and induced NFkB activation via ACE2 in endothelial cells. rS1p increased microparticle formation, a functional marker of endothelial injury. ACE2 interacting proteins involved in inflammation and RNA biology were identified in rS1p-treated cells. Neither ACE2 expression nor ACE2 enzymatic function were affected by rSP1. Endothelial cells exposed to SARS-CoV-2 virus did not exhibit viral replication. We demonstrate that rSP1 induces endothelial inflammation via ACE2 through processes that are independent of ACE2 enzymatic activity and viral replication. We define a novel role for ACE2 in COVID-19- associated endotheliitis.

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.

Abstract 56: Proteome Profile Of Vascular Smooth Muscle Cells During Phenotypic Switching In Human Hypertension

Vascular smooth muscle cells (VSMCs) are key players in vascular dysfunction associated with hypertension, where phenotypic switch is a fundamental process. While various transcription factors have been implicated in this process, the proteomic signature associated with phenotypic switching in human hypertension is unknown. Using high fidelity proteomic analysis, we characterized the proteome profile of VSMC in human hypertension. VSMC derived from resistance arteries from normotensive (NT) and hypertensive (HT) subjects were studied. Protein expression and cell migration were assessed by immunoblotting and wound healing assay. VSMC proteins were labelled with isobaric tandem mass tags and identified by liquid chromatography tandem mass spectrometry. The oxidative proteome was assessed using stable isotope-labelled iodoacetamide to target free reduced cysteine thiols. VSMCs from HT subjects exhibit reduced expression of α-SMA (0.05±0.01 vs NT:0.20±0.03, p<0.05), increased expression of the proliferation marker, PCNA (0.162±0.3 vs NT:0.51±0.004, p<0.05), and increased migration (54.68±2.86 vs NT:23.37±8.36, p<0.05). The proteomic analysis identified 207 proteins upregulated in HT subjects (fold change>1.5, p<0.05). There were no changes in protein expression of pathways related to the contractile phenotype (MYH11, CNN1, TAGLN, TPM, CALD1). However, extracellular matrix (ECM) proteins such as COL1A1, COL9A1, COL10A1, FBN1, FBLN1 were increased in cells from HT (fold change>1.5, p<0.05), suggesting a switch to a fibroblast-like phenotype in hypertension. Expression of proteins related to the interferon and IL-1β pathways (IFIT1, IFIT2, IFIT3, MX1, MX2, ABCA1, ABCA2, IL1RAP, CD36, ICAM1) were also increased in cells from HT subjects (fold change>1.5, p<0.05). Considering the importance of oxidative stress in hypertension, we assessed the VSMC oxidative proteome. Results demonstrate that ECM proteins, such as COL11A1 and COL16A1, were highly oxidized in cells from HT (fold change>1.5, p<0.05). Our study provides new insights into the proteomic changes that define the vascular phenotype in hypertension and highlights candidate targets that may drive phenotypic switching associated with vascular injury in hypertension.

Abstract P262: Spike Protein 1 Of Sars-cov-2 Increases Interferon Stimulated Genes And Induces An Immune/inflammatory Responses In Human Endothelial Cells

Introduction: Interferon (IFN) alpha (IFNα) and lambda3 (IFNL3) constitute the first line of immunity against SARS-CoV-2 infection by increasing interferon-stimulated genes (ISGs). IFNs influence the expression of angiotensin-converting enzyme 2 (ACE2), the receptor for S-protein (S1P) of SARS-CoV-2. Here we hypothesized that in human microvascular endothelial cells (EC) IFNL3 and IFNα influence ACE2 and immune/inflammatory responses mediated by S1P.

Methods: EC were stimulated with S1P of SARS-CoV-2 (1 μg/10^6 cells), IFNα (100 ng/mL) or IFNL3 (100 IU/mL). Because ACE2, metalloproteinase domain 17 (ADAM17) and type II transmembrane serine protease (TMPRSS2) are important for SARS-CoV-2 infection, cells were treated with inhibitors of ADAM17 (marimastat, 3.8nM and TAPI-1, 100nM), ACE2 (MLN4760, 440pM), and TMPRSS2 (camostat, 50μM). Expression of ISGs (ISG15, IFIT1, and MX1) was investigated by real-time PCR (5h) and protein expression by immunoblotting (24h).

Results: EC stimulated with S1P increased expression of ISGs: ISG15 (2 fold), IFIT1 (6 fold), MX1 (6 fold) (n=12, p<0.05). EC exhibited higher responses to IFNα (ISG15: 16 fold, IFIT1: 21 fold, MX1: 31 fold) than to IFNL3 (ISG15: 1.7 fold, IFIT1: 1.9 fold, MX1: 1.7 fold) (p<0.05). S1P increased gene expression of IL-6 (1.3 fold), TNFα (6.2 fold) and IL-1β (3.3 fold), effects that were maximized 100% by IFNα. Only marimastat inhibited S1P effects. IL-6 was increased by IFNα (1230 pg/mL) and IFNL3 (1124 pg/mL) vs control (591pg/mL). IFNα increased expression of ACE2 (75 kDa) (63%), ADAM17 (36%), and TMPRSS2 (65%). This was associated with increased phosphorylation of Stat1 (134%), Stat2 (102%), ERK1/2 (42%). Nitric oxide production and eNOS phosphorylation (Ser1177) were reduced by IFNα and (40%) and IFNL3 (40%).

Conclusions: In human microvascular endothelial cells, S1P, IFNα and IFNL3 induced an immune response characterized by increased expression of interferon-stimulated genes and IL-6 production, processes that involve ADAM17. Inflammation induced by S1P was amplified by IFNα. Our novel findings demonstrate that S1P induces an endothelial immune/inflammatory response that may be important in endotheliitis associated with COVID-19.

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.

The potential anti-inflammatory and anti-nociceptive effects of rat hemopressin (PVNFKFLSH) in experimental arthritis

Inflammatory arthritis, such as rheumatoid arthritis (RA), stands out as one of the main sources of pain and impairment to the quality of life. The use of hemopressin (PVNFKFLSH; Hp), an inverse agonist of type 1 cannabinoid receptor, has proven to be effective in producing analgesia in pain models, but its effect on neuro-inflammatory aspects of RA is limited. In this study, antigen-induced arthritis (AIA) was evoked by the intraarticular (i.art.) injection of methylated bovine serum albumin (mBSA) in male Sprague Dawley rats. Phosphate buffered saline (PBS)-injected ipsilateral knee joints or AIA contralateral were used as control. Nociceptive and inflammatory parameters such as knee joint oedema and leukocyte influx and histopathological changes were carried out in addition to the local measurement of interleukins (IL) IL-6, IL-1β, tumor necrosis factor-α and the immunoreactivity of the neuropeptides substance P (SP) and calcitonin gene related peptide (CGRP) in the spinal cord (lumbar L3-5 segments) of AIA rats. For 4 days, AIA rats were treated daily with a single administration of saline, Hp injected (10 or 20 μg/day, i.art.), Hp given orally (20 μg/Kg, p.o.) or indomethacin (Indo; 5 mg/Kg, i.p.). In comparison to the PBS control group, the induction of AIA produced a significant and progressive mono-arthritis condition. The degree of AIA severity progressively compromised the normal walking pattern and impaired mobility over the next four days in relation to PBS-injected rats or contralateral knee joints. In AIA rats, the reduction of the distance between footprints and disturbances of gait evidenced signs of nociception. This response worsened at day 4, and a loss of footprint from the ipsilateral hind paw was evident. Daily treatment of the animals with Hp either i.art. (10 and 20 μg/knee) or p.o. (20 μg/Kg) as well as Indo (5 mg/Kg, i.p.) ameliorated the impaired mobility in a time-dependent manner (P < 0.05). In parallel, the AIA-injected ipsilateral knee joints reach a peak of swelling 24 h after AIA induction, which persisted over the next four days in relation to PBS-injected rats or contralateral knee joints. There was a significant but not dose-dependent inhibitory effect produced by all dosages and routes of Hp treatments on AIA-induced knee joint swelling (P < 0.05). In addition, the increased synovial levels of MPO activity, total leukocytes number and IL-6, but not IL-1β, were significantly reduced by the lower i.art. dose of Hp. In conclusion, these results successfully demonstrate that Hp may represent a novel therapeutic strategy to treat RA, an effect which is unrelated to the proinflammatory actions of the neuropeptides CGRP and SP.

Importance of cholesterol-rich microdomains in the regulation of Nox isoforms and redox signaling in human vascular smooth muscle cells

Vascular smooth muscle cell (VSMC) function is regulated by Nox-derived reactive oxygen species (ROS) and redox-dependent signaling in discrete cellular compartments. Whether cholesterol-rich microdomains (lipid rafts/caveolae) are involved in these processes is unclear. Here we examined the sub-cellular compartmentalization of Nox isoforms in lipid rafts/caveolae and assessed the role of these microdomains in VSMC ROS production and pro-contractile and growth signaling. Intact small arteries and primary VSMCs from humans were studied. Vessels from Cav-1^-/- mice were used to test proof of concept. Human VSMCs express Nox1, Nox4, Nox5 and Cav-1. Cell fractionation studies showed that Nox1 and Nox5 but not Nox4, localize in cholesterol-rich fractions in VSMCs. Angiotensin II (Ang II) stimulation induced trafficking into and out of lipid rafts/caveolae for Nox1 and Nox5 respectively. Co-immunoprecipitation studies showed interactions between Cav-1/Nox1 but not Cav-1/Nox5. Lipid raft/caveolae disruptors (methyl-β-cyclodextrin (MCD) and Nystatin) and Ang II stimulation variably increased O₂^- generation and phosphorylation of MLC20, Ezrin-Radixin-Moesin (ERM) and p53 but not ERK1/2, effects recapitulated in Cav-1 silenced (siRNA) VSMCs. Nox inhibition prevented Ang II-induced phosphorylation of signaling molecules, specifically, ERK1/2 phosphorylation was attenuated by mellitin (Nox5 inhibitor) and Nox5 siRNA, while p53 phosphorylation was inhibited by NoxA1ds (Nox1 inhibitor). Ang II increased oxidation of DJ1, dual anti-oxidant and signaling molecule, through lipid raft/caveolae-dependent processes. Vessels from Cav-1^-/- mice exhibited increased O₂^- generation and phosphorylation of ERM. We identify an important role for lipid rafts/caveolae that act as signaling platforms for Nox1 and Nox5 but not Nox4, in human VSMCs. Disruption of these microdomains promotes oxidative stress and Nox isoform-specific redox signalling important in vascular dysfunction associated with cardiovascular diseases.

Abstract MP13: TRPM7 Downregulation Contributes To Cardiovascular Injury And Hypertension Induced By Aldosterone And Salt

TRPM7 has cation channel and kinase properties, is permeable to Mg 2+ , Ca 2+ , and Zn 2+ and is protective in the cardiovascular system. Hyperaldosteronism, which induces hypertension and cardiovascular fibrosis, is associated with Mg 2+ wasting. Here we questioned whether TRPM7 plays a role in aldosterone- induced hypertension and fibrosis and whether it influences cation regulation. Wild-type (WT) and TRPM7-deficient (M7+/Δ) mice were treated with aldosterone (600μg/Kg/day) and/or 1% NaCl (drinking water) (aldo, salt or aldo-salt) for 4 weeks. Blood pressure (BP) was evaluated by tail-cuff. Vessel structure was assessed by pressure myography. Molecular mechanisms were investigated in cardiac fibroblasts (CF) from WT and M7+/Δ mice. Protein expression was assessed by western-blot and histology. M7+/Δ mice exhibited reduced TRPM7 expression (30%) and phosphorylation (62%), levels that were recapitulated in WT aldo-salt mice. M7+/Δ exhibited increased BP by aldo, salt and aldo-salt (135-140mmHg) vs M7+/Δ-veh (117mmHg) (p<0.05), whereas in WT, BP was increased only by aldo-salt (134mmHg). Mesenteric resistance arteries from WT aldo-salt exhibited increased wall/lumen ratio (80%) and reduced internal diameter (15%) whereas vessels from M7+/Δ exhibited thinner walls by reducing cross-sectional area (35%) and increased internal diameter (23%) after aldo-salt. Aldo-salt induced greater collagen deposition in hearts (68%), kidneys (126%) and aortas (45%) from M7+/Δ vs WT. Hearts from M7+/Δ veh exhibited increased TGFβ, IL-11 and IL-6 (1.9-fold), p-Smad3 and p-Stat1 (1.5-fold) whereas in WT these effects were only found after aldo-salt. Cardiac expression of protein phosphatase magnesium-dependent 1A (PPM1A), a Mg 2+ -dependent phosphatase, was reduced (3-fold) only in M7+/Δ mice. M7+/Δ CF showed reduced proliferation (30%) and PPM1A (4-fold) and increased expression of TGFβ, IL-11 and IL-6 (2-3-fold), activation of Stat1 (2-fold), Smad3 (9-fold) and ERK1/2 (8-fold) compared with WT. Mg 2+ supplementation normalized cell proliferation and reduced protein phosphorylation in M7+/Δ CF (p<0.05). Our findings indicate a protective role of TRPM7 in aldosterone-salt induced cardiovascular injury through Mg 2+ -dependent mechanisms.

Abstract MP48: EGF Regulates VSMC Migration And Proliferation Through Crosstalk Between TRPM7 And EGFR

Epidermal growth factor (EGF), signals throught the EGF receptor (EGFR) and plays an important role in the pathogenesis of vascular remodeling. Transient receptor potential melastatin 7 (TRPM7) is a channel bound to a kinase domain important for Mg 2+ , Zn 2+ and Ca 2+ homeostasis. Cancer patients treated with EGFR inhibitors develop hypomagnesemia, suggesting a relationship between EGFR and TRPM7. Here we investigated the role of TRPM7 in EGF signaling in vascular smooth muscle cell (VSMC) from humans (hVSMC) and rats (rVSMC). VSMCs were stimulated with EGF (50ng/ml) for 5min and 24h with/without pretreatment of gefitinib (1μM), PP2 (10μM), 2APB (30μM) and NS8593 (40μM), inhibitors of EGFR, c-Src kinase and TRPM7 respectively. Aortas were isolated from wild type (WT), TRPM7-deficient (TRPM7 +/Δkinase ) and kinase-dead (TRPM7 R/R ) mice. Protein expression was assessed by immunoblotting. Ca 2+ and Mg 2+ were assessed using Cal-520 and Mg-green probes respectively. EGFR/TRPM7 interaction was investigated by proximity ligation assay (PLA), immunoprecipitation and confocal microscopy. VSMC migration and proliferation were examined by wound healing and CFSE proliferation assays. In hVSMC and rVSMC, EGF increased TRPM7 expression (47%) and phosphorylation (21%), (p<0.05); effects abolished by gefitinib and PP2. EGF-induced Mg 2+ and Ca 2+ influx was attenuated by gefitinib (4% and 8% respectively), NS8593 (5% for Mg 2+ ) and 2-APB (6% and 13% respectively). EGF enhanced ERK1/2 phosphorylation (3-fold) through c-Src, EGFR and TRPM7, p<0.05. Cell migration (26%) and proliferation (17%) were enhanced by EGF, and reduced by inhibitors of EGFR, TRPM7 and ERK1/2, p<0.05. EGF induced TRPM7-EGFR interaction (51%), which was reduced by gefitinib (34%) and PP2 (25%). VSMC from TRPM7 +/Δkinase showed reduced EGFR expression (73%), phospho-c-Src (22%), and phospho-ERK1/2 (90%). Aortas from TRPM7 R/R exhibited reduced phospho-EGFR (63%) and phospho-ERK1/2 (36%). Vessels from TRPM7 +/Δkinase showed reduced wall thickness (35%). Our findings demonstrate that interaction between EGFR/TRPM7 is a key process underlying EGF-induced VSMC migration and growth. This novel EGF-c-Src-EGFR-TRPM7 pathway may play an important role in vascular remodeling.

Abstract P090: Nox5 Induces Vascular Damage Through C-src Activation In Human Hypertension

Nox5 is the major ROS-generating Nox isoform in human vascular smooth muscle cells (VSMC). The role of Nox5 in oxidative stress and redox signaling underlying vascular dysfunction in hypertension is unclear. We examined molecular processes that regulate VSMC Nox5-induced ROS generation, focusing on c-Src. VSMC isolated from small arteries from normotensive (NT) and hypertensive (HT) subjects were studied. Nox5 expression and phosphorylation (immunoblotting, immunoprecipitation); ROS generation (chemiluminescence); activation of contractile signaling pathways (immunoblotting), Ca 2+ influx (Cal-520AM fluorescence), reversible protein oxidation (cysteine sulfenic acid probe BCN-E-BCN), actin polymerization (phalloidin staining) and migration (wound healing assay) were assessed in absence/presence of Nox5 (melittin) and Src (PP2) inhibitors. To study Nox5-specific effects, we used p22phox-silenced VSMCs (siRNA). Vascular function in VSMC-specific Nox5 transgenic mice was studied by wire myography. In HT, ROS levels (139±27%), Nox5 expression (103±23%) and phosphorylation were increased (77±17.93%) (p<0.05, vs NT). Activation of c-Src (101±26%), PKC (96±33%), MLC 20 (416±71%) and Ang II-induced Ca 2+ influx (574±44 vs NT:451±26) were also increased in HT (p<0.05, vs NT). Melittin reduced Ang II-induced ROS generation in both groups (p<0.05 vs Ctl). In contrast, p22phox silencing increased ROS in both groups, an effect blocked by melittin (p<0.05 vs Ctl). Nox5 inhibition reduced Ang II-induced c-Src phosphorylation and oxidation. In HT, p22phox silencing was associated with sustained Ang II-induced PKC (83±21% vs Ctl) and MLC 20 (89±22% vs Ctl) phosphorylation, effects blocked by melittin and PP2 (p<0.05 vs Ctl). Nox5 and c-Src inhibition reduced Ca 2+ influx, actin polymerization and migration in HT. Hypercontractility observed in Nox5 mice was abolished by melittin and PP2. Our findings demonstrate that Nox5 is upregulated in human hypertension. This is associated with activation of c-Src, increased redox signaling and VSMC cytoskeletal reorganization, migration and vascular contraction. We define a novel Nox5-ROS-c-Src signaling pathway that may play a role in vascular remodeling/dysfunction in hypertension.

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.

Chanzyme TRPM7 protects against cardiovascular inflammation and fibrosis

AIMS

Transient Receptor Potential Melastatin 7 (TRPM7) cation channel is a chanzyme (channel + kinase) that influences cellular Mg2+ homeostasis and vascular signalling. However, the pathophysiological significance of TRPM7 in the cardiovascular system is unclear. The aim of this study was to investigate the role of this chanzyme in the cardiovascular system focusing on inflammation and fibrosis.

METHODS AND RESULTS

TRPM7-deficient mice with deletion of the kinase domain (TRPM7+/Δkinase) were studied and molecular mechanisms investigated in TRPM7+/Δkinase bone marrow-derived macrophages (BMDM) and co-culture systems with cardiac fibroblasts. TRPM7-deficient mice had significant cardiac hypertrophy, fibrosis, and inflammation. Cardiac collagen and fibronectin content, expression of pro-inflammatory mediators (SMAD3, TGFβ) and cytokines [interleukin (IL)-6, IL-10, IL-12, tumour necrosis factor-α] and phosphorylation of the pro-inflammatory signalling molecule Stat1, were increased in TRPM7+/Δkinase mice. These processes were associated with infiltration of inflammatory cells (F4/80+CD206+ cardiac macrophages) and increased galectin-3 expression. Cardiac [Mg2+]i, but not [Ca2+]i, was reduced in TRPM7+/Δkinase mice. Calpain, a downstream TRPM7 target, was upregulated (increased expression and activation) in TRPM7+/Δkinase hearts. Vascular functional and inflammatory responses, assessed in vivo by intra-vital microscopy, demonstrated impaired neutrophil rolling, increased neutrophil: endothelial attachment and transmigration of leucocytes in TRPM7+/Δkinase mice. TRPM7+/Δkinase BMDMs had increased levels of galectin-3, IL-10, and IL-6. In co-culture systems, TRPM7+/Δkinase macrophages increased expression of fibronectin, proliferating cell nuclear antigen, and TGFβ in cardiac fibroblasts from wild-type mice, effects ameliorated by MgCl2 treatment.

CONCLUSIONS

We identify a novel anti-inflammatory and anti-fibrotic role for TRPM7 and suggest that its protective effects are mediated, in part, through Mg2+-sensitive processes.

Abstract 011: TRPM7 is Cardiovascular Protective in Aldosterone-Induced Hypertension

TRPM7 is a chanzyme that influences cellular Mg 2+ homeostasis and vascular signaling. We demonstrated that aldosterone mediates cellular effects through TRPM7-dependent signaling pathways. Since hyperaldosteronism causes hypertension and Mg 2+ wasting, we questioned whether TRPM7 plays a role in aldosterone-induced hypertension. Wild-type (WT) and TRPM7-deficient (M7+/Δ) mice were treated with aldosterone (600μg/Kg/day) and/or 1% NaCl (drinking water) (aldo, salt or aldo/salt) for 4 weeks. Blood pressure (BP) was evaluated by tail-cuff. Vessel function was investigated in mesenteric arteries by wire and pressure myography. Protein expression was assessed by western-blot and histology. Cardiac fibroblasts (CF) were isolated from WT and M7+/Δ. M7+/Δ exhibited increased BP by aldo (140mmHg), salt (135mmHg) and aldo/salt (137mmHg) vs M7+/Δ-veh (117mmHg) (p<0.05), whereas in WT, BP was increased only by aldo/salt (134mmHg). All treatments induced endothelial dysfunction in M7+/Δ as observed in acetylcholine-relaxation curves [Emax % M7+/Δ: aldo (81±4), salt (69±4) and aldo/salt (75±3.0), p<0.05], whereas in WT, Emax % was reduced after aldo (68±4) and aldo/salt (80±3). Phenylephrine-contraction and SNP-relaxation curves were similar among groups. Pressure myography showed that in WT, aldo/salt increased wall/lumen ratio (83%) inducing eutrophic inward remodeling, whereas M7+/Δ-veh presented 62% reduction in cross-sectional area vs WT, which was increased by salt and aldo/salt, resulting in hypertrophic outward remodeling. Collagen was increased in aortas from M7+/Δ by aldo (31%) and aldo/salt (45%) and no changes in WT. Aldo/salt induced higher collagen deposition in hearts (68%) and kidneys (126%) from M7+/Δ vs WT. Hearts and kidneys from M7+/Δ veh exhibited increased α-SMA (2-fold) and p-Stat1 (1.5-fold), whereas tissues from WT exhibited 3-fold increase only after treatments. CF from M7+/Δ stimulated with aldosterone (100nM) showed increased activation of Stat1 (177%), Smad3 (300%) and reduced pStat3 (70%) vs WT, p<0.05. We define a novel protective role of TRPM7 in the cardiovascular system, which when downregulated, promotes increased blood pressure, vascular remodeling and cardiac fibrosis mediated by aldosterone and salt.

Abstract P3002: Endoplasmic Reticulum Stress Plays a Role in Nox5 Mediated Vascular Contraction

We previously reported that Nox5 regulates contraction through mechanisms involving ROS and Ca 2+ channels in the endoplasmic reticulum (ER). In young mice expressing human Nox5 in VSMCs (Nox5+SM22+), we observed hypercontractility, without changes in blood pressure. Here we tested the hypothesis that Nox5 influences ER Ca 2+ homeostasis and vascular function and that Nox5 amplifies aging-associated vascular dysfunction through processes involving ER stress. Female WT and Nox5+SM22+ mice aged 20 and 35weeks were studied. Blood pressure (BP) was assessed by tail-cuff and vascular function/structure by myography. BP was similar in all groups. Vascular contraction to U46619, a TXA2 analogue, was increased in aged Nox5+SM22+ (EMax - %KCl: 114±2.8 vs WT 95±2.4, p<0.05). Hypercontractility was reversed by NAC (antioxidant - 0.01 mM, EMax: 92±5%), melittin (Nox5 inhibitor - 0.1 μM, EMax 92±3.2%) and dantrolene (RyR Ca 2+ channel blocker - 0.01 mM, EMax: 67±4.2%) (p<0.05). VSMCs isolated from 20 and 35 wk WT and Nox5+SM22+ mice were used to study molecular mechanisms whereby Nox5 influences the contractile machinery, focusing on the ER. Expression of BIP, a marker of ER stress, was increased only in VSMCs from aged Nox5+SM22+ mice (AU: 0.13±0.01 vs WT 0.05±0.002, p<0.05). 4-PBA, an inhibitor of ER stress (1 mM), reversed the hypercontractile responses in 35 wk Nox5+SM22+ mice (EMax: 87±3%, p<0.05). We identified calreticulin, important in ER Ca 2+ homeostasis and channel function, as a molecular target of Nox5. As Nox regulates signalling by oxidation, we assessed calreticulin oxidation by pulldown using dimedone based probe (DCP-Bio). Calreticulin oxidation was increased in mesenteric arteries, aorta and VSMCs from 35 week Nox5+SM22+. Moreover, expression of calreticulin (23.5±2%) and BIP (27.6±9%) was increased by U46619 in VSMCs from Nox5+SM22+ (p<0.05); an effect inhibited by melittin and 4-PBA. Our study highlights molecular mechanisms whereby Nox5 regulates contraction, through oxidation of calcium regulatory proteins, such as calreticulin, and ER stress in aged Nox5 mice. These age related changes may predispose Nox5 mice to cardiovascular damage when challenged with factors associated with hypertension.

Abstract P197: TRPM7 is Involved in the Effects of VEGF and EGF in Vascular Cells

TRPM6 and 7 are channels important in Mg 2+ and Ca 2+ homeostasis. We demonstrated that TRPM7 is influenced by angiotensin II. TRPM6 is influenced by EGF and cancer patients treated with EGFR inhibitors exhibit hypomagnesemia and hypertension by unclear mechanisms. Whether growth factors influence vascular TRPM7 is unknown. Here we questioned if VEGF/EGF mediate vascular effects through TRPM7. Studies were performed in human VSMC, wild type (WT) and TRPM7-deficient (M7+/Δ) mice. VSMC were stimulated with VEGF or EGF (50ng/ml) in the absence/presence of vatalanib, gefitinib (1μM), 2APB (30μM) and NS8593 (40μM), inhibitors of VEGFR, EGFR and TRPM7 respectively. Ca 2+ and Mg 2+ levels were assessed by Cal-520 and Mg-green. VEGF/EGF signaling was assessed by immunoblotting and vascular function by myography in mesenteric arteries from WT and M7+/Δ mice and treated with EGF or VEGF (50ng/ml). TRPM7 expression in aortas and kidneys from WT treated with vatalanib or gefitinib (100mg/Kg/day, 2 weeks) was assessed by immunoblotting. VEGF and EGF increased TRPM7 expression (50% and 67% respectively) and phosphorylation (2-fold), promoted influx of Ca 2+ (8% and 10%) and Mg 2+ (8%), effects that were reduced by vatalanib, gefitinib, NS8593, and 2-APB. EGF but not VEGF increased phosphorylation of PKC (43%), p38MAPK (47%), and ERK1/2 (120%). These responses were reduced by gefitinib, however only ERK1/2 phosphorylation was inhibited by NS8593, and 2-APB. Mice treated with vatalanib or gefitinib showed reduced expression of TRPM7 in aortas (50% and 74% respectively) and kidneys (36% and 66% respectively). Vessels exposed to EGF were less responsive to acetylcholine (ACh)-induced relaxation, [Emax %: WT (veh 97±3 vs EGF 63±10, p<0.05), M7+/Δ (veh 89%±5% vs EGF 69%±5%, p<0.05)]. Vessels from M7+/Δ treated with VEGF were less sensitive to sodium nitroprusside (SNP)-induced relaxation [pD2: WT (veh 7±0.12 vs VEGF 7.4±0.12, p<0.05), M7+/Δ (veh 6.7±0.15 vs VEGF 6.9±0.09)]. EGF and VEGF regulate VSMCs through TRPM7-dependent pathways. These processes involve MAP kinases and influence vascular function. Our findings identify novel mechanisms whereby growth factors influence vascular contraction/relaxation and suggest that TRPM7-regulated Mg 2+ and Ca 2+ are important.

Abstract 089: Role of Nox5 in Systemic Vascular Dysfunction in Ischemic Heart Disease

Patients with coronary microvascular dysfunction (CMD), a potential cause of heart ischemia, have systemic vascular dysfunction, characterized by increased vascular contraction to ET-1 and a thromboxane A2 analogue (U46619). Nox5 regulates vascular contraction and is involved in cardiovascular diseases. In our study, we questioned whether Nox5 plays a role in systemic vascular dysfunction in heart ischemia. As Nox5 expression has been described in the cardiovascular system of rabbits, a model of ischaemic cardiomyopathy (IC) was used. Coronary artery ligation was performed in Male New Zealand White rabbits. After 8 weeks, skin and mesenteric arteries were isolated and vascular function assessed by wire myography. Vascular contraction to NA (EMax %KCl: 122±4 vs sham 97±3.7) and U46619 (EMax %KCl: 82±3 vs sham 67±4) were exacerbated in skin arteries from IC (p<0.05); an effect blocked by tiron (antioxidant, 10 μM) and melittin (nox5 inhibitor, 0.1 μM). In mesenteric arteries from IC animals, NA (EMax %KCl: 108±3 vs sham 98±7) and ET-1 (EMax %KCl: 103±3 vs sham 81±4) induced contraction were increased in a Nox5-ROS-dependent manner (p<0.05). No differences were observed in mRNA levels of Cav1.2 and IP3R Ca 2+ channels, but an increase in RyR was observed (2^-ddCT: 1.67±0.15 vs sham 0.98±0.08) in VSMCs isolated from IC animals. Peroxiredoxin (Prdx), antioxidant, mRNA was increased in IC (2^-ddCT: 1.95±0.4 vs sham 0.88±0.1, p<0.05). Conoidin A, an inhibitor of Prdx oxidation, reduced vascular contraction to NA in arteries from IC animals (EMax %KCl: 95±4, p<0.05). In subjects with CMD, we assessed total number of microparticles (MP) as biomarkers of vascular dysfunction. MPs were increased in CMD subjects (x10 11 /mL: 4.8±0.6 vs control 1.75±0.2), where Nox5 expression was also increased (AU: 0.11±0.02 vs control MP 0.03±0.006) (p<0.05). In separate studies, we exposed WT control arteries to MPs from WT and Nox5-expressing mice before assessing contraction. MPs from Nox5 mice increased contraction to a higher level of that observed with MPs from WT mice (EMax %KCl: 106±2 vs WT 96±2, p<0.05). In our study, we identify Nox5 as a regulator of systemic vascular dysfunction in ischemic heart diseases, through mechanisms that may involve ROS, Prdx oxidation and MPs.

Abstract 068: Interplay Between Nox5 and Endoplasmic Reticulum Stress Regulates Vascular Signalling in Human Hypertension

Nox5, a major ROS-generating oxidase in human vessels, regulates vascular contraction. We demonstrated an ER-perinuclear Nox5 localization and questioned the role of ER stress in Nox5 regulation. Vascular smooth muscle cells (VSMC) were isolated from small arteries from subcutaneous fat from normotensive (NT) and hypertensive (HT) subjects. Nox5 compartmentalization (cell fractionation); ROS generation (chemiluminescence); peroxiredoxin/DJ-1 oxidation, activation of ER stress and contractile signalling (IRE1α, Src, PKC, MLC phosphorylation; immunoblotting) and actin cytoskeleton organization (phalloidin staining) were assessed. In hypertension, ROS levels (139±27% vs NT, p<0.05), oxidation of peroxiredoxin (870.4±188.7% vs NT, p<0.05) and DJ-1 (125±34% vs NT, p<0.05) were increased. IRE1α phosphorylation was increased in the HT group (58±21% vs NT, p<0.05). ER stress inhibition (4-PBA, 1mM) reduced ROS levels in HT subjects (20±6% vs NT, p<0.05), suggesting association between ER and oxidative stress. Nox5 expression was increased in the HT group (103±23% vs NT, p<0.05) in a compartment specific manner: Nox5 levels were reduced in plasma membrane (45±7% vs NT, p<0.05), but increased in the ER/nuclear fraction (46±13% vs NT, p<0.05). IRE1 inhibition (STF083010, 60μM) decreased Nox5 expression in the HT group (65±5% vs Ctl, p<0.05), while induction of ER stress (tunicamycin, 5μg/ml, 24h) increased Nox5 expression in cells from both groups (p<0.05). To investigate the role of Nox5 on contractile signalling, cells were treated with mellitin (100nM), a Nox5 inhibitor. ROS generation and phosphorylation of c-Src, PKC and MLC 20 induced by Ang II were reduced by mellitin in both groups (p<0.05 vs Ctl). In contrast, silencing of p22phox increased ROS and activation of c-Src, PKC and MLC 20 in both groups, an effect blocked by mellitin (p<0.05 vs Ctl). VSMC from hypertensive subjects had increased number of stress fibres, an effect attenuated by mellitin. Our findings demonstrate that Nox5 is upregulated in a compartment specific manner and is regulated by ER stress in hypertension. Nox5 upregulation influences pro-contractile signalling and cytoskeleton reorganization in VSMC, processes that contribute to vascular dysfunction in hypertension.

Vascular smooth muscle contraction in hypertension

Hypertension is a major risk factor for many common chronic diseases, such as heart failure, myocardial infarction, stroke, vascular dementia, and chronic kidney disease. Pathophysiological mechanisms contributing to the development of hypertension include increased vascular resistance, determined in large part by reduced vascular diameter due to increased vascular contraction and arterial remodelling. These processes are regulated by complex-interacting systems such as the renin-angiotensin-aldosterone system, sympathetic nervous system, immune activation, and oxidative stress, which influence vascular smooth muscle function. Vascular smooth muscle cells are highly plastic and in pathological conditions undergo phenotypic changes from a contractile to a proliferative state. Vascular smooth muscle contraction is triggered by an increase in intracellular free calcium concentration ([Ca²⁺]_i), promoting actin–myosin cross-bridge formation. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase, protein Kinase C and mitogen-activated protein kinase signalling, reactive oxygen species, and reorganization of the actin cytoskeleton. Activation of immune/inflammatory pathways and non-coding RNAs are also emerging as important regulators of vascular function. Vascular smooth muscle cell [Ca²⁺]_i not only determines the contractile state but also influences activity of many calcium-dependent transcription factors and proteins thereby impacting the cellular phenotype and function. Perturbations in vascular smooth muscle cell signalling and altered function influence vascular reactivity and tone, important determinants of vascular resistance and blood pressure. Here, we discuss mechanisms regulating vascular reactivity and contraction in physiological and pathophysiological conditions and highlight some new advances in the field, focusing specifically on hypertension.

NOX5: Molecular biology and pathophysiology

NEW FINDINGS

What is the topic of this review? This review provides a comprehensive overview of Nox5 from basic biology to human disease and highlights unique features of this Nox isoform What advances does it highlight? Major advances in Nox5 biology relate to crystallization of the molecule and new insights into the pathophysiological role of Nox5. Recent discoveries have unravelled the crystal structure of Nox5, the first Nox isoform to be crystalized. This provides new opportunities to develop drugs or small molecules targeted to Nox5 in an isoform-specific manner, possibly for therapeutic use. Moreover genome wide association studies (GWAS) identified Nox5 as a new blood pressure-associated gene and studies in mice expressing human Nox5 in a cell-specific manner have provided new information about the (patho) physiological role of Nox5 in the cardiovascular system and kidneys. Nox5 seems to be important in the regulation of vascular contraction and kidney function. In cardiovascular disease and diabetic nephropathy, Nox5 activity is increased and this is associated with increased production of reactive oxygen species and oxidative stress implicated in tissue damage.

ABSTRACT

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox), comprise seven family members (Nox1-Nox5 and dual oxidase 1 and 2) and are major producers of reactive oxygen species in mammalian cells. Reactive oxygen species are crucially involved in cell signalling and function. All Noxs share structural homology comprising six transmembrane domains with two haem-binding regions and an NADPH-binding region on the intracellular C-terminus, whereas their regulatory systems, mechanisms of activation and tissue distribution differ. This explains the diverse function of Noxs. Of the Noxs, NOX5 is unique in that rodents lack the gene, it is regulated by Ca2+ , it does not require NADPH oxidase subunits for its activation, and it is not glycosylated. NOX5 localizes in the perinuclear and endoplasmic reticulum regions of cells and traffics to the cell membrane upon activation. It is tightly regulated through numerous post-translational modifications and is activated by vasoactive agents, growth factors and pro-inflammatory cytokines. The exact pathophysiological significance of NOX5 remains unclear, but it seems to be important in the physiological regulation of sperm motility, vascular contraction and lymphocyte differentiation, and NOX5 hyperactivation has been implicated in cardiovascular disease, kidney injury and cancer. The field of NOX5 biology is still in its infancy, but with new insights into its biochemistry and cellular regulation, discovery of the NOX5 crystal structure and genome-wide association studies implicating NOX5 in disease, the time is now ripe to advance NOX5 research. This review provides a comprehensive overview of our current understanding of NOX5, from basic biology to human disease, and highlights the unique characteristics of this enigmatic Nox isoform.

Vascular Biology of Superoxide-Generating NADPH Oxidase 5-Implications in Hypertension and Cardiovascular Disease

SIGNIFICANCE

NADPH oxidases (Noxs), of which there are seven isoforms (Nox1-5, Duox1/Duox2), are professional oxidases functioning as reactive oxygen species (ROS)-generating enzymes. ROS are signaling molecules important in physiological processes. Increased ROS production and altered redox signaling in the vascular system have been implicated in the pathophysiology of cardiovascular diseases, including hypertension, and have been attributed, in part, to increased Nox activity. Recent Advances: Nox1, Nox2, Nox4, and Nox5 are expressed and functionally active in human vascular cells. While Nox1, Nox2, and Nox4 have been well characterized in models of cardiovascular disease, little is known about Nox5. This may relate to the lack of experimental models because rodents lack NOX5. However, recent studies have advanced the field by (i) elucidating mechanisms of Nox5 regulation, (ii) identifying Nox5 variants, (iii) characterizing Nox5 expression, and (iv) discovering the Nox5 crystal structure. Moreover, studies in human Nox5-expressing mice have highlighted a putative role for Nox5 in cardiovascular disease.

CRITICAL ISSUES

Although growing evidence indicates a role for Nox-derived ROS in cardiovascular (patho)physiology, the exact function of each isoform remains unclear. This is especially true for Nox5.

FUTURE DIRECTIONS

Future directions should focus on clinically relevant studies to discover the functional significance of Noxs, and Nox5 in particular, in human health and disease. Two important recent studies will impact future directions. First, Nox5 is the first Nox to be crystallized. Second, a genome-wide association study identified Nox5 as a novel blood pressure-associated gene. These discoveries, together with advancements in Nox5 biology and biochemistry, will facilitate discovery of drugs that selectively target Noxs to interfere in uncontrolled ROS generation.

Abstract 129: TRPM7 α-kinase Deficiency Causes Cardiovascular Inflammation and Fibrosis

We previously demonstrated that TRPM7, a Mg 2+ /cation channel fused to an α-kinase domain, is regulated by vasoactive mediators and plays a protective role in hypertension. Here we questioned whether TRPM7-kinase influences vascular inflammation and fibrosis. We used Wild-type (WT) and heterozygote mutant mice for TRPM7-kinase (M7+/-). Vascular inflammatory responses were assessed ex vivo by intravital microscopy. Immune cells were investigated by flow cytometry. Fibrosis was investigated by sirius-red staining. Bone-marrow derived macrophages (BMDM) and Cardiac fibroblasts (CF) were obtained from WT and M7+/. [Mg 2+ ]i in cardiac tissue, cardiac macrophages and circulating monocytes was significantly reduced (30-50%) in M7+/- vs WT mice. In small arteries studied by intravital microscopy, leukocytes from M7+/- showed reduced velocity (47%), increased adhesion (222%) and transmigration (480%). Expression of vascular pro-inflammatory markers including VCAM-1(33-fold), iNOS (12-fold), and IL-12 (6.8-fold) was increased in M7+/- vs WT. Cardiac galectin-3 (Gal-3) levels (16.6±3.6 vs WT 9.2±1.2 cells/field), collagen area (6.7% vs WT 2.6%), infiltration of CD45+ cells (6±0.6% vs WT 4±0.4%) and protein expression of fibronectin (280%), TGFβ (125%), and p-Smad3 (66%), were increased in M7+/- mice. BMDM macrophages from M7+/- exhibited increased levels of Gal-3 (2.6±0.05 vs WT 2.1±0.09ng/mL), IL-10 (807±92 vs WT 305±37 pg/mL) and IL-6 (84±8 vs WT 13±5 pg/mL). A similar profile was demonstrated in resident peritoneal macrophages. CF treated with supernatant of macrophages from M7+/- increased fibronectin (43%) and PCNA (36%) vs WT. To evaluate whether these processes are Mg 2+ -sensitive, we examined effects of Mg 2+ treatment and demonstrated that Mg 2+ ameliorated pro-fibrotic and pro-inflammatory signalling evident in TRPM7+/- mice. In conclusion, TRPM7-kinase deficiency is associated with cardiac and vascular inflammation and fibrosis, processes associated with cellular Mg 2+ deficiency. Our findings highlight an important cardiovascular protective role of TRPM7 and Mg 2+ .

Abstract 126: Nox5 Regulation of Vascular Contraction Involves Oxidation of Endoplasmic Reticulum Calcium Channels and Calreticulin

The biological function of calcium-sensitive superoxide-generating Nox5 is unclear, but it may play a role in regulating contraction, as we previously demonstrated. Here we explored molecular mechanisms whereby Nox5 controls contraction. Human arteries and mice expressing human NOX5 in smooth muscle cells (Nox5+SM22+) were studied. In arteries from hypertensive subjects, Nox5 expression, assessed by immunoblotting, was increased (50%, p<0.05 vs control). In human VSMCs, AngII-induced ROS generation (1 fold) and activation of myosin light chain (MLC) (2.5 fold) were exaggerated in VSMCs from hypertensive subjects (p<0.05 vs control); an effect that was attenuated by Nox5 siRNA. In arteries from Nox5+/SM22+ mice, contraction to U46619 was increased in (5.8±0.3 mN vs WT: 4.2±0.2 mN, p<0.05). These hypercontractile responses were inhibited by NAC (ROS scavenger), calmidazolium (calmodulin inhibitor), dantrolene (ryanodine receptor Ca 2+ channel inhibitors) and CDN1163 (SERCA channel activator), but not by a Nox1/Nox4 inhibitor (GKT137831). ONOO - levels were increased in vessels from Nox5+/SM22+ mice (5.8±0.9 vs WT 3.4±0.1 AU/mg, p<0.05). Inactivation of MYPT1 (181±1.8AU vs 164±1.9AU WT) and activation of MLC (207±10.3AU vs 155±2.7AU WT) were increased in VSMCs from Nox5+SM22+ (p<0.05). To assess the oxidative proteome in VSMCs, we immunoprecipitated reversibly oxidized proteins and observed oxidation of Nox5, decreased oxidation of MYPT1 and increased oxidation of SERCA2b in Nox5+/SM22+ mice . Proteome analysis of human VSMCs identified the ER Ca 2+ sensor, calreticulin, as a potential Nox5 binding protein. Calreticulin reversible oxidation was increased in VSMCs from Nox5+SM22+ mice and hypertensive subjects. Our study unravels crosstalk between oxidative stress and Ca 2+ in the vasculature, where Nox5 regulation of contraction involves ROS, Ca 2+ and endoplasmic reticulum localized Ca 2+ channels/proteins. We identify novel mechanisms whereby Nox5 influences pro-contractile signalling through processes involving oxidation of the ER Ca 2+ sensor, calreticulin, and ER Ca 2+ channels.

Vascular Nox (NADPH Oxidase) Compartmentalization, Protein Hyperoxidation, and Endoplasmic Reticulum Stress Response in Hypertension

Vascular Nox (NADPH oxidase)-derived reactive oxygen species and endoplasmic reticulum (ER) stress have been implicated in hypertension. However, relationships between these processes are unclear. We hypothesized that Nox isoforms localize in a subcellular compartment-specific manner, contributing to oxidative and ER stress, which influence the oxidative proteome and vascular function in hypertension. Nox compartmentalization (cell fractionation), O₂^- (lucigenin), H₂O₂ (amplex red), reversible protein oxidation (sulfenylation), irreversible protein oxidation (protein tyrosine phosphatase, peroxiredoxin oxidation), and ER stress (PERK [protein kinase RNA-like endoplasmic reticulum kinase], IRE1α [inositol-requiring enzyme 1], and phosphorylation/oxidation) were studied in spontaneously hypertensive rat (SHR) vascular smooth muscle cells (VSMCs). VSMC proliferation was measured by fluorescence-activated cell sorting, and vascular reactivity assessed in stroke-prone SHR arteries by myography. Noxs were downregulated by short interfering RNA and pharmacologically. In SHR, Noxs were localized in specific subcellular regions: Nox1 in plasma membrane and Nox4 in ER. In SHR, oxidative stress was associated with increased protein sulfenylation and hyperoxidation of protein tyrosine phosphatases and peroxiredoxins. Inhibition of Nox1 (NoxA1ds), Nox1/4 (GKT137831), and ER stress (4-phenylbutyric acid/tauroursodeoxycholic acid) normalized SHR vascular reactive oxygen species generation. GKT137831 reduced IRE1α sulfenylation and XBP1 (X-box binding protein 1) splicing in SHR. Increased VSMC proliferation in SHR was normalized by GKT137831, 4-phenylbutyric acid, and STF083010 (IRE1-XBP1 disruptor). Hypercontractility in the stroke-prone SHR was attenuated by 4-phenylbutyric acid. We demonstrate that protein hyperoxidation in hypertension is associated with oxidative and ER stress through upregulation of plasmalemmal-Nox1 and ER-Nox4. The IRE1-XBP1 pathway of the ER stress response is regulated by Nox4/reactive oxygen species and plays a role in the hyperproliferative VSMC phenotype in SHR. Our study highlights the importance of Nox subcellular compartmentalization and interplay between cytoplasmic reactive oxygen species and ER stress response, which contribute to the VSMC oxidative proteome and vascular dysfunction in hypertension.

Abstract 029: Nox5 is a Pro-contractile Nox Isoform - Implications in Vascular Contraction and Cardiac Fibrosis

The functional significance of Nox5 is unknown. Considering the fact that Nox5 is closely associated with changes in [Ca 2+ ] and that it generates ROS, both of which are important in contraction, we questioned whether Nox5 plays a role in pro-contractile signaling and whether it influences vascular function. We generated humanised Nox5 mice with Nox5 expressed in a VSMC-specific manner (Nox5+SM22+). Vascular contraction was measured by myography. ROS production was assessed by HPLC, amplex red and ELISA. Protein levels were evaluated by immunoblotting. Fibrosis was assessed by Picro Sirius red staining and polarized microscopy. Contraction to U46619 was increased in Nox5+/SM22+ mice (5.8±0.3 mN vs WT: 4.2±0.2 mN, p<0.05), an effect blocked by a NAC (ROS scavenger), calmidazolium (calmodulin inhibitor), dantrolene (ryanodine receptor Ca 2+ channel inhibitors) and CDN1163 (SERCA channel activator). ONOO - levels were increased in vessels from Nox5+/SM22+ (5.8±0.9 vs WT 3.4±0.1 AU/mg, p<0.05). ZIPK is an important regulator of MYPT1 inactivation. In vessels from Nox5+/SM22+ mice, ZIPK activation was increased (58.6±3.64 vs 27.73±7.64 AU, p<0.05). VSMC-Nox5 exhibited increased cardiac levels of superoxide (WT: 606.3±78.5 vs 1456.0±184.8 nmol/mg of protein), H2O2 (WT: 11.1±1.3 vs 23.88±5.1 μM/μg of protein) lipid peroxidation (WT: 0.70±0.09 vs 1.18±0.18 nmol/ μg of protein), cardiac fibrosis (WT: 3.46±1.71 vs 4.39±0.04 AU), p38 MAPK activation (WT:0.98±0.04 vs 1.61±0.12 AU) and fibronectin expression (WT:1.23±0.07 vs 2.31±0.29 AU) (p<0.05). Moreover, peroxiredoxin oxidation was increased (WT: 1.43±0.4 vs 6.28±2.0 AU, p<0.05). In VSMCs, downregulation of Nox5, but not Nox1,2,4, by siRNA was associated with reduced phosphorylation of MLC20 and MYPT1. In conclusion, our results demonstrate that Nox5 regulates vascular contraction through processes that involve , ROS, calmodulin, ryanodine and ER-Ca 2+ channels. Nox5 may be an important regulator of the contractile machinery in VSMCs. In addition, VSMC-Nox5 induces oxidative stress in the heart, leading to fibrosis. Our study defines a novel role for Nox5 as a pro-contractile Nox isoform that may have important implications in conditions associated with vascular hypercontractility.

Abstract P217: Nox Compartmentalization, Protein Oxidation and ER Stress in Vascular Smooth Muscle Cells in Hypertension

In hypertension, activation of NADPH oxidases (Noxs) is associated with oxidative stress and vascular dysfunction. The exact role of each isoform in hypertension-associated vascular injury is still unclear. We investigated the compartmentalization of Noxs in VSMC from resistance arteries of Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Expression of Nox1 and Nox4 was increased in SHR cells (96.6±28.7% and 48.2±21.2% vs WKY, p<0.05), as well as basal ROS levels measured by chemiluminescence (110.2±26.4% vs WKY, p<0.05) and amplex red (105.2±33.2% vs WKY, p<0.05). Phosphorylation of unfolded protein response activators, PERK and IRE1α, and expression of ER chaperone BiP were elevated in SHR cells (p<0.05 vs WKY), indicating activation of ER stress response. Immunoblotting after organelle fractionation demonstrated that Noxs are expressed in an organelle-specific manner, with Nox1, 2 and 4 present in plasma membrane, ER and nucleus, but not in mitochondria. In SHR cells, NoxA1ds (Nox1 inhibitor, 10μM) and GKT136901 (Nox1/4 inhibitor, 10μM) decreased AngII-induced ROS levels (p<0.001 vs Ctl). Additionally, mito-tempol (mitochondrial-targeted antioxidant, 50nM) and 4-PBA (ER stress inhibitor, 1mM) decreased basal ROS levels in SHR cells (p<0.05 vs Ctl). Furthermore, oxidation of the antioxidant enzymes Peroxiredoxins (Prx) was increased in SHRSP compared to WKY (2.51±0.14 vs 0.56±0.07, p<0.001). One-dimensional isoelectric focusing revealed that cytosolic Prx2 and mitochondrial Prx3 were more oxidized in SHRSP than WKY cells. Using a biotin-tagged dimedone-based probe (DCP-Bio) we identified oxidation of ER stress proteins BiP and IRE1. To investigate the effect of protein oxidation in vascular function, vascular reactivity was evaluated in isolated mesenteric arteries. Inhibition of general oxidation (DTT 1mM; Emax: 111.7±33.1) and peroxiredoxin (Conoidin A 10nM; Emax: 116.0±7.3) reduces vascular contraction in response to noradrenalin in WKY rats (Emax: 166.6±30.2; p<0.05). These findings suggest an important role for Nox1/4 in redox-dependent organelle dysfunction and post-translational modification of proteins, processes that may play an important role in vascular dysfunction in hypertension.

Abstract P228: Protective Role of TRPM7-kinase Against Vascular Dysfunction and Fibrosis Induced by Aldosterone and Salt

TRPM7 is a cationic ion channel and with a serine/threonine kinase important for cellular Mg 2+ homeostasis. We recently showed that TRPM7-kinase plays a role in aldosterone-mediated vascular effects and inflammation. Here we explored the role of TRPM7-kinase in cardiac fibrosis and vascular function in aldosterone-induced hypertension in mice. Wild-type (WT) or heterozygote TRPM7-kinase domain (TRPM7+/-) were treated with infused aldosterone (600 μg/Kg/day) and NaCl 1% in drinking water (aldo/salt) for 4 weeks. Blood pressure (BP) was evaluated by tail-cuff. Vessel function was investigated in mesenteric arteries by wire and pressure myography. Protein expression was assessed in cardiac tissue by western-blot and histology. Aldo/salt increased BP in TRPM7+/- and WT to similar levels (137mmHg vs control 118mmHg). Mesenteric arteries from untreated TRPM7+/- mice were more sensitive to relaxation induced by acetylcholine (LogEC50: 7.6±0.1 vs 7.1±0.2, TRPM7+/- and WT, respectively), effects that were reduced by Aldo/salt treatment (LogEC50: 7.2±0.1). Phenylephrine-contraction and sodium nitroprusside-relaxation curves were similar among groups. Pressure myography showed that in WT, aldo/salt increase the diameter (26%) and cross-sectional area (40%), resulting in hypertrophic outward remodelling, whereas in TRPM7+/-, the treatment decreased the diameter (16%) and increase the wall/lumen ration (82%), resulting in eutrophic inward remodelling. Hearts from TRPM7+/- presented decreased expression of annexin-1, which is a target protein of TRPM7-kinase, that was further decreased by aldo-salt. Hearts from untreated TRPM7+/- mice had increased fibrotic markers: plasma galectin-3 (2.5ng/mL) vs WT (1.4ng/mL) and protein expression for fibronectin (2.4-fold) and TGFβ (2-fold), and the aging marker p-P66Sch (47%) which were similar to WT-aldo/salt. Aldo/salt induced higher collagen expression in TRPM7+/- than in WT animals (15%), as observed by picrosirius red staining. Our findings provide some insights into aldosterone signalling through TRPM7-kinase and suggest that this chanzyme may have protective actions, which when downregulated, promotes vascular remodelling and cardiac fibrosis in aldosterone-induced hypertension.

Abstract 007: TRPM7-kinase Modulates Renal and Splenic Macrophage and T-lymphocyte Infiltration in Aldosterone-salt-induced Hypertension

TRPM7 is a Mg2 + channel linked to a kinase domain important in cell proliferation and survival. We demonstrated that cells deficient in TRPM7-kinase domain are prone to aldosterone (aldo)-induced oxidative stress and inflammation. Here, we investigated whether TRPM7-kinase plays a role in inflammatory responses in aldo-induced hypertension. Wild-type (WT) or heterozygote TRPM7-kinase domain (TRPM7+/-) mice were infused with aldo (600μg/Kg/day - osmotic minipumps) and 1% NaCl in the drinking water (aldo-salt) for 4 weeks. Inflammatory responses were evaluated by examining T cells (CD4+ and CD8+) and macrophages (M1- and M2-phenotype) infiltration in kidneys and spleens, using flow cytometry. Gene and protein expression was assessed by real-time PCR and immunoblot respectively. ROS was evaluated by lucigenin chemiluminescence. Aldo-salt increased kidney mass and urinary levels of albumin, Ca 2+ , Mg 2+ and K + , similarly in WT and TRPM7+/- (p<0.05 vs controls). Kidneys from TRPM7+/- mice presented a higher total number of inflammatory infiltrated cells (0.87x10 6 vs WT 0.22x10 6 cells/g), TCD4+ cells (27% vs WT 19%), and macrophages (47% vs WT 31%) (p<0.05 vs controls). Kidneys from WT aldo-salt showed increased ROS production (1.7-fold) and Nox2 (2-fold) protein expression (p<0.05 vs control) and presented similar cell infiltration to TRPM7+/- mice. Kidneys from TRPM7+/- aldo-salt show increased M2-macrophages CD206+ (4.3% vs WT 2.3%) and mRNA expression for the anti-inflammatory cytokine IL-10 (55% vs WT), whereas decreased the expression of the pro-inflammatory TNFα (30% vs WT) and Nox2 protein (1.8-fold). Spleen mass was increased by 40% only in WT aldo-salt. Spleens from untreated TRPM7+/- showed increased infiltrated inflammatory cells (3.7x10 8 vs WT 2.0x10 8 cells/mg). Splenic macrophages were higher in untreated TRPM7+/- (8.8% vs WT 5.9%) and presented an increase in CD206 M2-marker (16% vs WT 7%), higher TCD4+ (68% vs WT 50%) and TCD8+ (26% vs WT 17%), values that were similar to WT aldo-salt. Our data provide insights into the importance of the TRPM7-kinase domain in the immune system activation, which when down regulated provokes an increase in inflammatory cell infiltration in kidneys and spleens in aldo-salt-induced hypertension.

Peripheral neurokinin-1 receptors contribute to kaolin-induced acute monoarthritis in rats

OBJECTIVE

intra-articular co-injection of kaolin with carrageenan (CGN) in rodents is widely used as an experimental model of arthritis. However, the ability of kaolin to cause arthritis and related immune responses when administered alone is unclear. We evaluated the contribution of prostanoids and sensory C-fibres (and their neuropeptide substance P) to kaolin-induced inflammation in the rat knee.

METHODS

Wistar rats, 8-10 weeks old, received an intra-articular injection of kaolin (1-10 μg/joint) or saline into the knee joint. Knee inflammation, proinflammatory cytokines, pain behaviour and secondary tactile allodynia were assessed over 5 h, when synovial leukocyte counts, histopathological changes and proinflammatory cytokine levels were evaluated.

RESULTS

The intra-articular injection of kaolin caused a dose- and time-dependent knee swelling and impairment of motion that were associated with secondary tactile allodynia, elevated concentrations of IL-1β, IL-6 and TNFα, leukocyte infiltration, and histopathological changes in the ipsilateral hindpaw. The neurokinin-1 (NK1) receptor antagonist SR140333 or neonatal treatment with capsaicin markedly reduced the inflammatory parameters, cytokines and allodynia but failed to significantly inhibit the impaired motion. The cyclo-oxygenase inhibitor indomethacin partially inhibited knee oedema and allodynia but did not affect the leukocyte influx, myeloperoxidase activity or impaired motion in the kaolin-injected rat.

CONCLUSIONS

We show the first evidence that intra-articular injection of kaolin without CGN produced severe acute monoarthritis. This was highly dependent on substance P (released from C-fibres) and NK1 receptor activation, which stimulated local production of proinflammatory cytokines. This model may be of critical importance for mechanistic studies and screening new anti-inflammatory/analgesic drugs.

Endoplasmic reticulum stress and Nox-mediated reactive oxygen species signaling in the peripheral vasculature: potential role in hypertension

SIGNIFICANCE

Reactive oxygen species (ROS) are produced during normal endoplasmic reticulum (ER) metabolism. There is accumulating evidence showing that under stress conditions such as ER stress, ROS production is increased via enzymes of the NADPH oxidase (Nox) family, especially via the Nox2 and Nox4 isoforms, which are involved in the regulation of blood pressure. Hypertension is a major contributor to cardiovascular and renal disease, and it has a complex pathophysiology involving the heart, kidney, brain, vessels, and immune system. ER stress activates the unfolded protein response (UPR) signaling pathway that has prosurvival and proapoptotic components.

RECENT ADVANCES

Here, we summarize the evidence regarding the association of Nox enzymes and ER stress, and its potential contribution in the setting of hypertension, including the role of other conditions that can lead to hypertension (e.g., insulin resistance and diabetes).

CRITICAL ISSUES

A better understanding of this association is currently of great interest, as it will provide further insights into the cellular mechanisms that can drive the ER stress-induced adaptive versus maladaptive pathways linked to hypertension and other cardiovascular conditions. More needs to be learnt about the precise signaling regulation of Nox(es) and ER stress in the cardiovascular system.

FUTURE DIRECTIONS

The development of specific approaches that target individual Nox isoforms and the UPR signaling pathway may be important for the achievement of therapeutic efficacy in hypertension.