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.

SEC31A may be associated with pituitary hormone deficiency and gonadal dysgenesis

PURPOSE

Disorders/differences of sex development (DSD) result from variants in many different human genes but, frequently, have no detectable molecular cause.

METHODS

Detailed clinical and genetic phenotyping was conducted on a family with three children. A Sec31a animal model and functional studies were used to investigate the significance of the findings.

RESULTS

By trio whole-exome DNA sequencing we detected a heterozygous de novo nonsense SEC31A variant, in three children of healthy non-consanguineous parents. The children had different combinations of disorders that included complete gonadal dysgenesis and multiple pituitary hormone deficiency. SEC31A encodes a component of the COPII coat protein complex, necessary for intracellular anterograde vesicle-mediated transport between the endoplasmic reticulum (ER) and Golgi. CRISPR-Cas9 targeted knockout of the orthologous Sec31a gene region resulted in early embryonic lethality in homozygous mice. mRNA expression of ER-stress genes ATF4 and CHOP was increased in the children, suggesting defective protein transport. The pLI score of the gene, from gnomAD data, is 0.02.

CONCLUSIONS

SEC31A might underlie a previously unrecognised clinical syndrome comprising gonadal dysgenesis, multiple pituitary hormone deficiencies, dysmorphic features and developmental delay. However, a variant that remains undetected, in a different gene, may alternatively be causal in this family.

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.

Exosomes and the cardiovascular system: role in cardiovascular health and disease

Exosomes, which are membrane-bound extracellular vesicles (EVs), are generated in the endosomal compartment of almost all eukaryotic cells. They are formed upon the fusion of multivesicular bodies and the plasma membrane and carry proteins, nucleic acids, lipids and other cellular constituents from their parent cells. Multiple factors influence their production including cell stress and injury, humoral factors, circulating toxins, and oxidative stress. They play an important role in intercellular communication, through their ability to transfer their cargo (proteins, lipids, RNAs) from one cell to another. Exosomes have been implicated in the pathophysiology of various diseases including cardiovascular disease (CVD), cancer, kidney disease, and inflammatory conditions. In addition, circulating exosomes may act as biomarkers for diagnostic and prognostic strategies for several pathological processes. In particular exosome-containing miRNAs have been suggested as biomarkers for the diagnosis and prognosis of myocardial injury, stroke and endothelial dysfunction. They may also have therapeutic potential, acting as vectors to deliver therapies in a targeted manner, such as the delivery of protective miRNAs. Transfection techniques are in development to load exosomes with desired cargo, such as proteins or miRNAs, to achieve up-regulation in the host cell or tissue. These advances in the field have the potential to assist in the detection and monitoring progress of a disease in patients during its early clinical stages, as well as targeted drug delivery.

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.

Expanding the Phenotypic Spectrum of Kenny-Caffey Syndrome

CONTEXT

Kenny-Caffey syndrome (KCS) is a rare hereditary disorder characterized by short stature, hypoparathyroidism, and electrolyte disturbances. KCS1 and KCS2 are caused by pathogenic variants in TBCE and FAM111A, respectively. Clinically the phenotypes are difficult to distinguish.

OBJECTIVE

The objective was to determine and expand the phenotypic spectrum of KCS1 and KCS2 in order to anticipate complications that may arise in these disorders.

METHODS

We clinically and genetically analyzed 10 KCS2 patients from 7 families. Because we found unusual phenotypes in our cohort, we performed a systematic review of genetically confirmed KCS cases using PubMed and Scopus. Evaluation by 3 researchers led to the inclusion of 26 papers for KCS1 and 16 for KCS2, totaling 205 patients. Data were extracted following the Cochrane guidelines and assessed by 2 independent researchers.

RESULTS

Several patients in our KCS2 cohort presented with intellectual disability (3/10) and chronic kidney disease (6/10), which are not considered common findings in KCS2. Systematic review of all reported KCS cases showed that the phenotypes of KCS1 and KCS2 overlap for postnatal growth retardation (KCS1: 52/52, KCS2: 23/23), low parathyroid hormone levels (121/121, 16/20), electrolyte disturbances (139/139, 24/27), dental abnormalities (47/50, 15/16), ocular abnormalities (57/60, 22/23), and seizures/spasms (103/115, 13/16). Symptoms more prevalent in KCS1 included intellectual disability (74/80, 5/24), whereas in KCS2 bone cortical thickening (1/18, 16/20) and medullary stenosis (7/46, 27/28) were more common.

CONCLUSION

Our case series established chronic kidney disease as a new feature of KCS2. In the literature, we found substantial overlap in the phenotypic spectra of KCS1 and KCS2, but identified intellectual disability and the abnormal bone phenotype as the most distinguishing features.

Withdrawn as duplicate: Expanding the phenotypic spectrum of Kenny-Caffey syndrome: a case series and systematic literature review

This article has been withdrawn due to a publisher error that caused it to be duplicated. The definitive version of this article is published under https://doi.org/10.1210/clinem/dgad147.

Cardiovascular toxicity of tyrosine kinase inhibitors during cancer treatment: Potential involvement of TRPM7

Receptor tyrosine kinases (RTKs) are a class of membrane spanning cell-surface receptors that transmit extracellular signals through the membrane to trigger diverse intracellular signaling through tyrosine kinases (TKs), and play important role in cancer development. Therapeutic approaches targeting RTKs such as vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR), and platelet-derived growth factor receptor (PDGFR), and TKs, such as c-Src, ABL, JAK, are widely used to treat human cancers. Despite favorable benefits in cancer treatment that prolong survival, these tyrosine kinase inhibitors (TKIs) and monoclonal antibodies targeting RTKs are also accompanied by adverse effects, including cardiovascular toxicity. Mechanisms underlying TKI-induced cardiovascular toxicity remain unclear. The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a ubiquitously expressed chanzyme consisting of a membrane-based ion channel and intracellular α-kinase. TRPM7 is a cation channel that regulates transmembrane Mg²⁺ and Ca²⁺ and is involved in a variety of (patho)physiological processes in the cardiovascular system, contributing to hypertension, cardiac fibrosis, inflammation, and atrial arrhythmias. Of importance, we and others demonstrated significant cross-talk between TRPM7, RTKs, and TK signaling in different cell types including vascular smooth muscle cells (VSMCs), which might be a link between TKIs and their cardiovascular effects. In this review, we summarize the implications of RTK inhibitors (RTKIs) and TKIs in cardiovascular toxicities during anti-cancer treatment, with a focus on the potential role of TRPM7/Mg²⁺ as a mediator of RTKI/TKI-induced cardiovascular toxicity. We also describe the important role of TRPM7 in cancer development and cardiovascular diseases, and the interaction between TRPM7 and RTKs, providing insights for possible mechanisms underlying cardiovascular disease in cancer patients treated with RTKI/TKIs.

PMON312 A De Novo Heterozygous Nonsense Variant In The SEC31A Gene Associated With Pituitary Hormone Deficiency And Disorders Of Sex Development

Introduction

XYdisorders of sex development (DSD) result from variants in many different human genes but frequently have no detectable molecular cause. In approximately 25% of cases of XY DSD, the index case may have associated malformations. Genetic disorders of endoplasmic reticulum (ER) function are increasingly being recognised but have not been associated with DSD or pituitary disorders.

Clinical case

Three siblings (with unaffected non-consanguineous parents) were reviewed at the tertiary endocrine clinic. Child I was noted at birth to have cliteromegaly. Imaging and examination under anaesthetic revealed a normal vagina and uterus but gonads of indeterminate origin. She was 46,XY and basal endocrine investigations at the age of 4 years showed a low AMH for male but otherwise normal gonadal and thyroid function and normal IGF-1. She had a laparoscopic bilateral gonadectomy aged 5 years. Pathology demonstrated bilateral testicular tissue, with substantial fibrotic atrophic change and occasional placental alkaline phosphatase (PLAP) positive cells, suggestive of germ cell tumours. Aged 8 years she developed obesity and later hypertension. Child II was reviewed due to short stature and diagnosed with GH deficiency aged 2 years. She has normal adrenal and thyroid function and gonadotrophins. MRI demonstrated an ectopic posterior pituitary. Child III presented with perineal hypospadias, a small phallus, bilateral undescended testes and craniofacial abnormalities. Endocrine investigations revealed hypogonadotrophic hypogonadism, with no testosterone response to hCG stimulation, a low normal AMH and no response of LH or FSH on LHRH stimulation. He has panhypopituitarism with an ectopic posterior pituitary gland on MRI and is currently on treatment with GH, hydrocortisone and levothyroxine. His BP is on the 98th centile for age and height. Child I and Child III have mild developmental delay but are in mainstream school with additional educational support. High-throughput DNA sequencing revealed, in all three siblings, a heterozygous truncating variant in the SEC31A gene that encodes a component of the COPII-complex that coats the vesicles mediating ER to Golgi transport. CRISPR-Cas9 targeted knockout of the corresponding Sec31a region resulted in embryonic lethality in homozygous mice. mRNA phenotyping of ER-related genes demonstrated increased mRNA expression of ATF4 and CHOP in the affected children, genes encoding key ER stress-related proteins, associated with defective protein transport.

Conclusions

Dysregulation ofanterograde and retrograde COPII-coated-vesicle ER-Golgi transport is increasingly recognised to underlie human developmental disorders, including Craniolenticulosutural dysplasia (OMIM 607812) and Saul-Wilson syndrome (OMIM 618150). The de novo SEC31A nonsense variant in all three affected siblings, the ER stress response, plus reported developmental syndromes with dysfunction of this transport mechanism and evidence from the preclinical mouse model suggest that SEC31A might underlie a previously unrecognised clinical syndrome comprising DSD, endocrine abnormalities, dysmorphic features and developmental delay.

Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Abstract 020: Nox5 Regulates Vascular Smooth Muscle Cell De-differentiation In Human Hypertension

Nox5 is an important source of reactive oxygen species and aberrant redox-sensitive signalling in vascular smooth muscle cells (VSMC) in human hypertension. We aimed to characterize the VSMC proteomic profile and investigate the effects of Nox5-derived ROS on VSMC phenotype in human hypertension. VSMC from resistance arteries from normotensive (NT) and hypertensive (HT) subjects were studied. 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 cysteine thiols. Nox5 silencing was performed by siRNA. Protein expression was detected by western blotting. Pro-inflammatory cytokines (IL-6, IL-8) and pro-collagen I was measured by ELISA in the culture media. Proteomic analysis identified 207 proteins upregulated in HT subjects (fold change>1.5, p<0.05). Gene ontology enrichment analysis showed proteins upregulated in HT were involved in extracellular matrix (ECM) organization, immune response and cell proliferation. ECM proteins (COL1A1, COL9A1, COL10A1, FBN1, FBLN1) and proteins related to interferon and IL-1β pathways (IFIT1, IFIT2, IFIT3, MX1, MX2, ABCA1, ABCA2, IL1RAP, CD36, ICAM1) were increased in cells from HT subjects. The VSMC oxidative proteome analysis identified 88 cysteine-containing peptides highly oxidized in HT (fold change>1.5, p<0.05), including COL11A1, COL16A1, FBLN1 and FBLN2. VSMCs from HT exhibit increased expression of the proliferation marker, PCNA (0.162±0.3 vs NT:0.051±0.04RFU, p<0.05) and pro-collagen I (23.6±2 vs NT:13.2±0.3ng/ml, p<0.05). Production of pro-inflammatory cytokines IL-6 (501.8±23.6 vs NT:121.7±6.4pg/mL) and IL-8 (373.6±34.1 vs NT:262.5±24.6pg/mL, p<0.05) were increased in HT. Nox5 silencing in VSMC from HT subjects reduced PCNA expression(43%), pro-collagen I release (8%), baseline and LPS-induced IL-6 (30% baseline, 43% LPS-induced) and IL-8 (21% baseline, 23% LPS-induced) release (p<0.05). We provide new insights into the proteomic changes related to vascular phenotype in hypertension and demonstrated that Nox5 plays an important role in VSMC phenotypic switching associated with vascular dysfunction in hypertension.

Abstract 127: Nox5 Expression In A Vascular Smooth Muscle Cell-specific Manner Induces Fibroblast To Myofibroblast Differentiation

Mice expressing human Nox5 (hNox5) in VSMC exhibit cardfiovascular fibrosis, where mechanisms are unknown. We postulated that VSMC-Nox5 promotes fibroblast to myofibroblast differentiation that contributes to fibrosis. Fibroblasts were cultured from wildtype (WT) and hNOX5 mice. Mice (20 weeks old) were infused with Ang II (600 ng/Kg/day) for 28 days and renal fibrosis/inflammation studied. Markers of myofibroblasts (αSMA), and pro-fibrotic and inflammatory signaling molecules were assessed by qPCR and immunoblotting. Inflammatory infiltrate was assessed by FACS. Fibroblasts from Nox5 mice exhibited increased mRNA of markers of myofibroblast αSMA (2 -ddC :1.54±0.05 vs. WT 0.78±0.17) and Myocd (2 -ddC :1.36±0.17 vs. WT 0.39±0.22), as well as, pro-fibrotic markers, Col1A1 (2 -ddC :1.74±0.16 vs. WT 0.67±0.11), Col3A1 (2 -ddC :1.74±0.18 vs. WT 0.96±0.24) and TIMP3 (2 -ddC :2.65±0.25 vs. WT 0.38±0.07), p<0.05. mRNA expression of CD36 (2 -ddC :1.37±0.07 vs. WT 86±0.24), TNFα (2 -ddC :1.32±0.2 vs. WT 0.71±0.17) and TNFR1 (2 -ddC :1.26±0.04 vs. WT 1.02±0.10) were increased, while CD68 expression was decreased (2 -ddC :0.82±0.11 vs. WT 1.36±0.18) in fibroblasts from Nox5 mice (p<0.05). In Nox5 mice fibroblasts, ROS production and TGFβ protein expression (AU:1.8±0.05 vs. WT 1.4±0.06), as well as TGFβR2 gene expression (2 -ddC :2.04±0.17 vs. WT 0.57±0.12), were increased (p<0.05). mRNA of DNMT3a and TET2, DNA methylation regulatory enzymes, were also increased in fibroblasts from Nox5 mice, p<0.05. Kidneys from Ang II-infused Nox5 mice exhibited significant perivascular fibrosis and inflammatory cell infiltration compared to WT, as well as increased protein expression of TGFβ (AU: 3.59±0.8 vs. WT 1.54±0.2) and IL-11 (AU: 0.64±0.08 vs. WT 0.39±0.04), p<0.05; where levels of macrophage F4/80+ cells (%:24±2 vs WT 18±1, p<0.05) and levels of cytotoxic CD8+ T cells were increased, p<0.05. Kidney expression of vimentin (AU:1.01±0.05 vs WT 0.85±0.03) and αSMA (AU:0.44±0.03 vs WT 0.33±0.01), were increased in Nox5 mice (p<0.05). Nox5 regulates fibrosis by inducing fibroblast-to-myofibroblast differentiation, possibly through increased ROS. These processes may be important in Nox5-assocated cardiovascular-renal fibrosis.

Palmitoylation regulates cellular distribution of and transmembrane Ca flux through TrpM7

The bifunctional cation channel/kinase TrpM7 is ubiquitously expressed and regulates embryonic development and pathogenesis of several common diseases. The TrpM7 integral membrane ion channel domain regulates transmembrane movement of divalent cations, and its kinase domain controls gene expression via histone phosphorylation. Mechanisms regulating TrpM7 are elusive. It exists in two populations in the cell: at the cell surface where it controls divalent cation fluxes, and in intracellular vesicles where it controls zinc uptake and release. Here we report that TrpM7 is palmitoylated at a cluster of cysteines at the C terminal end of its Trp domain. Palmitoylation controls the exit of TrpM7 from the endoplasmic reticulum and the distribution of TrpM7 between cell surface and intracellular pools. Using the Retention Using Selective Hooks (RUSH) system, we demonstrate that palmitoylated TrpM7 traffics from the Golgi to the surface membrane whereas non-palmitoylated TrpM7 is sequestered in intracellular vesicles. We identify the Golgi-resident enzyme zDHHC17 and surface membrane-resident enzyme zDHHC5 as responsible for palmitoylating TrpM7 and find that TrpM7-mediated transmembrane calcium uptake is significantly reduced when TrpM7 is not palmitoylated. The closely related channel/kinase TrpM6 is also palmitoylated on the C terminal side of its Trp domain. Our findings demonstrate that palmitoylation controls ion channel activity of TrpM7 and that TrpM7 trafficking is dependant on its palmitoylation. We define a new mechanism for post translational modification and regulation of TrpM7 and other Trps.

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.

Interferon-stimulated gene 15 pathway is a novel mediator of endothelial dysfunction and aneurysms development in angiotensin II infused mice through increased oxidative stress

AIMS

Interferon-stimulated gene 15 (ISG15) encodes a ubiquitin-like protein that induces a reversible post-translational modification (ISGylation) and can also be secreted as a free form. ISG15 plays an essential role as host-defence response to microbial infection; however, its contribution to vascular damage associated with hypertension is unknown.

METHODS AND RESULTS

Bioinformatics identified ISG15 as a mediator of hypertension-associated vascular damage. ISG15 expression positively correlated with systolic and diastolic blood pressure and carotid intima-media thickness in human peripheral blood mononuclear cells. Consistently, Isg15 expression was enhanced in aorta from hypertension models and in angiotensin II (AngII)-treated vascular cells and macrophages. Proteomics revealed differential expression of proteins implicated in cardiovascular function, extracellular matrix and remodelling, and vascular redox state in aorta from AngII-infused ISG15-/- mice. Moreover, ISG15-/- mice were protected against AngII-induced hypertension, vascular stiffness, elastin remodelling, endothelial dysfunction, and expression of inflammatory and oxidative stress markers. Conversely, mice with excessive ISGylation (USP18C61A) show enhanced AngII-induced hypertension, vascular fibrosis, inflammation and reactive oxygen species (ROS) generation along with elastin breaks, aortic dilation, and rupture. Accordingly, human and murine abdominal aortic aneurysms showed augmented ISG15 expression. Mechanistically, ISG15 induces vascular ROS production, while antioxidant treatment prevented ISG15-induced endothelial dysfunction and vascular remodelling.

CONCLUSION

ISG15 is a novel mediator of vascular damage in hypertension through oxidative stress and inflammation.

Abstract P265: Hypertension, Vascular Dysfunction And Downregulation Of The Renin Angiotensin System Sequelae Of COVID-19

Hypertension, vascular dysfunction and downregulation of the renin angiotensin system as sequelae of COVID-19

The long-term CV consequences of COVID are unknown however the potential for ongoing cardiac and vascular inflammation with RAAS alteration may increase the risk of developing hypertension and CV disease. Non-hypertensive patients hospitalised in April-May 2020 with either confirmed COVID19 (cases) or non-COVID (controls) diagnosis were recruited ≥12 weeks post-discharge. All underwent detailed BP and vascular/immune and RAAS phenotyping. The primary outcome was ABPM 24-hr SBP. Paired t-tests and multivariable regression models used to assess differences. Thirty cases and eighteen controls completed the study. Cases were older (51±7 vs 45±9 years) with lower discharge SBP (121±10 vs 128±15 mmHg; p0.01). ABPM at study visit was higher in the cases compared to controls (24-hour SBP (OR[95%CI]: 8.6[0.9-16.3]; p0.03), day-time SBP (8.6[1.5-17.3]; p0.02), day-time DBP (4.6[0.1-9.1]; p<0.05). Paired analysis of office BP showed a 11 mmHg difference between cases and controls (11.5[3.12];19.8; p=0.008; figure) Cases had lowerRenin and Ang-1-10 levels (-0.4[-0.9-0.1]; p0.08; -0.7[-1.2- -0.1]; p0.02 respectively) and higher TNF-alpha (0.5[0.1-0.9]; p0.01). Confirmed COVID requiring hospitalisation is associated with elevated SBP, reduced renin and Ang-1-10 and elevated TNF-alpha at ≥12 weeks post-discharge.

Abstract 40: SARS-CoV-2/ACE2 Induces Vascular Inflammatory Responses In Human Microvascular Endothelial Cells Independently Of Viral Replication

SARS-CoV-2, the virus responsible for COVID19, binds to ACE2, via its spike protein S1 subunit, leading to viral infection and respiratory disease. COVID-19 is associated with cardiovascular disease and systemic inflammation. Since ACE2 is expressed in vascular cells we questioned whether SARS-CoV-2 induces vascular inflammation and whether this is related to viral infection. Human microvascular endothelial cells (EC) were exposed to recombinant S1p (rS1p) 0.66 μg/mL for 10 min, 5h and 24h. Gene expression was assessed by RT-PCR and levels of IL6 and MCP1, as well as ACE2 activity, were assessed by ELISA. Expression of ICAM1 and PAI1 was assessed by immunoblotting. ACE2 activity was blocked by MLN4760 (ACE2 inhibitor) and siRNA. Viral infection was assessed by exposing Vero E6 (kidney epithelial cells; pos ctl) and EC to 10 5 pfu of SARS-CoV-2 where virus titre was measured by plaque assay. Co-IP coupled mass spectrometry protein identification and label free proteomics were used to investigate ACE2-mediated signalling. rS1p increased IL6 mRNA (14.2±2.1 vs. C:0.61±0.03 2^-ddCT) and levels (1221.2±18.3 vs. C:22.77±3.2 pg/mL); MCP1 mRNA (5.55±0.62 vs. C:0.65±0.04 2^-ddCT) and levels (1110±13.33 vs. C:876.9±33.4 pg/mL); ICAM1 (17.7±3.1 vs. C:3.9±0.4 AU) and PAI1 (5.6±0.7 vs. C: 2.9±0.2), p<0.05. MLN4760, but not rS1p, decreased ACE2 activity (367.4±18 vs. C: 1011±268 RFU, p<0.05) and blocked rS1p effects on ICAM1 and PAI1. ACE2 siRNA blocked rS1p-induced IL6 release, ICAM1, and PAI1 responses as well as rS1p-induced NFκB activation. Proteomics analysis of the global effect of rS1, identified biological process enrichment of proteins from virus transcription and NFκB signalling. ACE2 Co-IP identified 216 interacting proteins (filtered with ≥1 unique peptide, 1% FDR), linked to cytokine production and inflammation. EC were not susceptible to SARS-CoV-2 infection, while the virus replicated well in Vero E6. In conclusion, we demonstrate that rS1p induces an inflammatory response through ACE2 in endothelial cells. These effects seem to be independent of viral infection. Our findings suggest that vascular inflammation in COVID-19 involves activation of ACE2-mediated pro-inflammatory signalling that may be unrelated to viral replication.

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].

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.

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.

Comprehensive Characterization of the Vascular Effects of Cisplatin-Based Chemotherapy in Patients With Testicular Cancer

Background

Cisplatin-based chemotherapy increases the risk of cardiovascular and renal disease.

Objectives

We aimed to define the time course, pathophysiology, and approaches to prevent cardiovascular disease associated with cisplatin-based chemotherapy.

Methods

Two cohorts of patients with a history of testicular cancer (n = 53) were recruited. Cohort 1 consisted of 27 men undergoing treatment with: 1) surveillance; 2) 1 to 2 cycles of bleomycin, etoposide, and cisplatin (BEP) chemotherapy (low-intensity cisplatin); or 3) 3 to 4 cycles of BEP (high-intensity cisplatin). Endothelial function (percentage flow-mediated dilatation) and cardiovascular biomarkers were assessed at 6 visits over 9 months. Cohort 2 consisted of 26 men previously treated 1 to 7 years ago with surveillance or 3 to 4 cycles BEP. Vasomotor and fibrinolytic responses to bradykinin, acetylcholine, and sodium nitroprusside were evaluated using forearm venous occlusion plethysmography.

Results

In cohort 1, the percentage flow-mediated dilatation decreased 24 h after the first cisplatin dose in patients managed with 3 to 4 cycles BEP (10.9 ± 0.9 vs. 16.7 ± 1.6; p < 0.01) but was unchanged from baseline thereafter. Six weeks after starting 3 to 4 cycles BEP, there were increased serum cholesterol levels (7.2 ± 0.5 mmol/l vs. 5.5 ± 0.2 mmol/l; p = 0.01), hemoglobin A1c (41.8 ± 2.0 mmol/l vs. 35.5 ± 1.2 mmol/l; p < 0.001), von Willebrand factor antigen (62.4 ± 5.4 mmol/l vs. 45.2 ± 2.8 mmol/l; p = 0.048) and cystatin C (0.91 ± 0.07 mmol/l vs. 0.65 ± 0.09 mmol/l; p < 0.01). In cohort 2, intra-arterial bradykinin, acetylcholine, and sodium nitroprusside caused dose-dependent vasodilation (p < 0.0001). Vasomotor responses, endogenous fibrinolytic factor release, and cardiovascular biomarkers were not different in patients managed with 3 to 4 cycles of BEP versus surveillance.

Conclusions

Cisplatin-based chemotherapy induces acute and transient endothelial dysfunction, dyslipidemia, hyperglycemia, and nephrotoxicity in the early phases of treatment. Cardiovascular and renal protective strategies should target the early perichemotherapy period. (Clinical Characterisation of the Vascular Effects of Cis-platinum Based Chemotherapy in Patients With Testicular Cancer [VECTOR], NCT03557177; Intermediate and Long Term Vascular Effects of Cisplatin in Patients With Testicular Cancer [INTELLECT], NCT03557164)

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.

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.

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.

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.

TRPM7, Magnesium, and Signaling

The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a ubiquitously expressed chanzyme that possesses an ion channel permeable to the divalent cations Mg2+, Ca2+, and Zn2+, and an α-kinase that phosphorylates downstream substrates. TRPM7 and its homologue TRPM6 have been implicated in a variety of cellular functions and is critically associated with intracellular signaling, including receptor tyrosine kinase (RTK)-mediated pathways. Emerging evidence indicates that growth factors, such as EGF and VEGF, signal through their RTKs, which regulate activity of TRPM6 and TRPM7. TRPM6 is primarily an epithelial-associated channel, while TRPM7 is more ubiquitous. In this review we focus on TRPM7 and its association with growth factors, RTKs, and downstream kinase signaling. We also highlight how interplay between TRPM7, Mg2+ and signaling kinases influences cell function in physiological and pathological conditions, such as cancer and preeclampsia.

Microparticles from vascular endothelial growth factor pathway inhibitor-treated cancer patients mediate endothelial cell injury

Vascular endothelial growth factor pathway inhibitors (VEGFi), used as anti-angiogenic drugs to treat cancer are associated with cardiovascular toxicities through unknown molecular mechanisms. Endothelial cell-derived microparticles (ECMPs) are biomarkers of endothelial injury and are also functionally active since they influence downstream target cell signalling and function. We questioned whether microparticle (MP) status is altered in cancer patients treated with VEGFi and whether they influence endothelial cell function associated with vascular dysfunction. Plasma MPs were isolated from cancer patients before and after treatment with VEGFi (pazopanib, sunitinib, or sorafenib). Human aortic endothelial cells (HAECs) were stimulated with isolated MPs (106 MPs/mL). Microparticle characterization was assessed by flow cytometry. Patients treated with VEGFi had significantly increased levels of plasma ECMP. Endothelial cells exposed to post-VEGFi treatment ECMPs induced an increase in pre-pro-ET-1 mRNA expression, corroborating the increase in endothelin-1 (ET-1) production in HAEC stimulated with vatalanib (VEGFi). Post-VEGFi treatment MPs increased generation of reactive oxygen species in HAEC, effects attenuated by ETA (BQ123) and ETB (BQ788) receptor blockers. VEGFi post-treatment MPs also increased phosphorylation of the inhibitory site of endothelial nitric oxide synthase (eNOS), decreased nitric oxide (NO), and increased ONOO- levels in HAEC, responses inhibited by ETB receptor blockade. Additionally, gene expression of proinflammatory mediators was increased in HAEC exposed to post-treatment MPs, effects inhibited by BQ123 and BQ788. Our findings define novel molecular mechanism involving interplay between microparticles, the ET-1 system and endothelial cell pro-inflammatory and redox signalling, which may be important in cardiovascular toxicity and hypertension associated with VEGFi anti-cancer treatment. New and noteworthy: our novel data identify MPs as biomarkers of VEGFi-induced endothelial injury and important mediators of ET-1-sensitive redox-regulated pro-inflammatory signalling in effector endothelial cells, processes that may contribute to cardiovascular toxicity in VEGFi-treated cancer patients.

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.

Abstract 049: Endothelial-Derived Microparticles as Biomarkers and Mediators of Endothelial Cell Injury in VEGF Inhibitor-Treated Cancer Patients: Implications in Hypertension

Vascular endothelial growth factor receptor inhibitors (VEGFRi), used as anti-angiogenic drugs to treat cancer, induce severe hypertension although the underlying molecular mechanisms are still unclear. Endothelial microparticles (MPs) are biomarkers of endothelial injury and are also functionally active since they influence downstream target cell signalling and function. We questioned whether MP status is altered in cancer patients treated with VEGFRi and whether they influence endothelial cell function associated with vascular dysfunction in hypertension. Plasma MPs were isolated from cancer patients before and after treatment with VEGFRi. Human aortic endothelial cells (HAEC) were stimulated with human plasma-isolated MPs (10 6 MPs/mL). MP characterization was assessed by flow cytometry; protein and gene expression by immunoblotting and qPCR; ROS and NO production by lucigenin and immunofluorescence. Patients treated with VEGFRi had significantly increased in endothelial cell-derived MPs (EMP) (0.19±0.02 Pre vs. 0.31±0.04 Post-treatment). HAEC exposed to post-treatment MPs increased pre-pro-ET-1 mRNA (4.10±0.97 vs. 10.57±3.54), corroborating the raise in ET-1 levels (μg/mL: 631.9±46.1 vs. 780.2±37.2) observed in HAEC stimulated with vatalanib (VEGFRi). Post-treatment MPs increased ROS generation in HAEC (100.0 vs. 5 min- 123.4±7.7, 30 min- 162.4±22.5, 60 min- 183.9±44.7), effects that were attenuated by ET A and ET B receptor blockers. VEGFRi post-treatment MPs increased phosphorylation of the inhibitory site of eNOS (Thr 495 ) (100.0 vs. 181.3±18.7) and decreased NO levels in HAEC (100.0 vs. 72.7±9.9) which was inhibited by ET B receptor blockade (eNOS: 109.8±14.9; NO: 142.1±25.9). Gene expression of proinflammatory mediators was increased in HAEC exposed to post-treatment MPs (1.0 vs. TNF-α: 5.4±1.8, MCP-1: 2.1±0.3, iNOS: 3.1±0.8, COX2: 2.4±0.4, ICAM1: 2.7±0.6), effects inhibited by BQ123 and BQ788. In conclusion, our data identify EMPs as biomarkers of VEGFi-induced endothelial injury and important mediators of ET-1-sensitive redox-regulated endothelial cell signalling. These molecular processes may play a role in vascular dysfunction associated with hypertension in VEGFRi-treated cancer patients.

NADPH Oxidase 5 Is a Pro-Contractile Nox Isoform and a Point of Cross-Talk for Calcium and Redox Signaling-Implications in Vascular Function

Background

NADPH Oxidase 5 (Nox5) is a calcium‐sensitive superoxide‐generating Nox. It is present in lower forms and higher mammals, but not in rodents. Nox5 is expressed in vascular cells, but the functional significance remains elusive. Given that contraction is controlled by calcium and reactive oxygen species, both associated with Nox5, we questioned the role of Nox5 in pro‐contractile signaling and vascular function.

Methods and Results

Transgenic mice expressing human Nox5 in a vascular smooth muscle cell–specific manner (Nox5 mice) and Rhodnius prolixus, an arthropod model that expresses Nox5 endogenoulsy, were studied. Reactive oxygen species generation was increased systemically and in the vasculature and heart in Nox5 mice. In Nox5‐expressing mice, agonist‐induced vasoconstriction was exaggerated and endothelium‐dependent vasorelaxation was impaired. Vascular structural and mechanical properties were not influenced by Nox5. Vascular contractile responses in Nox5 mice were normalized by N‐acetylcysteine and inhibitors of calcium channels, calmodulin, and endoplasmic reticulum ryanodine receptors, but not by GKT137831 (Nox1/4 inhibitor). At the cellular level, vascular changes in Nox5 mice were associated with increased vascular smooth muscle cell [Ca²⁺]_i, increased reactive oxygen species and nitrotyrosine levels, and hyperphosphorylation of pro‐contractile signaling molecules MLC20 (myosin light chain 20) and MYPT1 (myosin phosphatase target subunit 1). Blood pressure was similar in wild‐type and Nox5 mice. Nox5 did not amplify angiotensin II effects. In R. prolixus, gastrointestinal smooth muscle contraction was blunted by Nox5 silencing, but not by VAS2870 (Nox1/2/4 inhibitor).

Conclusions

Nox5 is a pro‐contractile Nox isoform important in redox‐sensitive contraction. This involves calcium‐calmodulin and endoplasmic reticulum–regulated mechanisms. Our findings define a novel function for vascular Nox5, linking calcium and reactive oxygen species to the pro‐contractile molecular machinery in vascular smooth muscle cells.

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.

VEGFR (Vascular Endothelial Growth Factor Receptor) Inhibition Induces Cardiovascular Damage via Redox-Sensitive Processes

Although VEGF (vascular endothelial growth factor) inhibitors (VEGFIs), are effective anticancer therapies, they cause hypertension through unknown mechanisms. We questioned whether changes in vascular redox state may be important, because VEGF signaling involves nitric oxide (NO) and reactive oxygen species. Molecular mechanisms, including NOS, NADPH oxidase (Nox)–derived reactive oxygen species, antioxidant systems, and vasoconstrictor signaling pathways, were probed in human endothelial cells and vascular smooth muscle exposed to vatalanib, a VEGFI. Vascular functional effects of VEGFI were assessed ex vivo in mouse arteries. Cardiovascular and renal in vivo effects were studied in vatalanib- or gefitinib (EGFI [epidermal growth factor inhibitor])-treated mice. In endothelial cells, vatalanib decreased eNOS (Ser 1177 ) phosphorylation and reduced NO and H 2 O 2 production, responses associated with increased Nox-derived O 2 − and ONOO − formation. Inhibition of Nox1/4 (GKT137831) or Nox1 (NoxA1ds), prevented vatalanib-induced effects. Nrf-2 (nuclear factor erythroid 2–related factor 2) nuclear translocation and expression of Nrf-2–regulated antioxidant enzymes were variably downregulated by vatalanib. In human vascular smooth muscles, VEGFI increased Nox activity and stimulated Ca 2+ influx and MLC 20 phosphorylation. Acetylcholine-induced vasodilatation was impaired and U46619-induced vasoconstriction was enhanced by vatalanib, effects normalized by N-acetyl-cysteine and worsened by L-NAME. In vatalanib-, but not gefitinib-treated mice vasorelaxation was reduced and media:lumen ratio of mesenteric arteries was increased with associated increased cardiovascular and renal oxidative stress, decreased Nrf-2 activity and downregulation of antioxidant genes. We demonstrate that inhibition of VEGF signaling induces vascular dysfunction through redox-sensitive processes. Our findings identify Noxs and antioxidant enzymes as novel targets underling VEGFI-induced vascular dysfunction. These molecular processes may contribute to vascular toxicity and hypertension in VEGFI-treated patients.

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 P510: Nox4 Deficiency Leads to Hypertension and Vascular Damage With Enhanced Effects in Ang II-dependent Hypertension

We previously showed that Nox1 and Nox2 are not involved in chronic Ang II-dependent hypertension, which recapitulates human hypertension. Here we questioned the role of Nox4 by studying transgenic mice expressing human renin (LinA3) crossed with Nox4-/- mice. Four groups were used: wildtype (WT), LinA3, Nox4 KO (Nox4), and LinA3/Nox4 KO (LinA3/Nox4). Blood pressure was measured by tail cuff. Aorta was collected to assess wall thickness, collagen and glycosaminoglycans (GAGs) deposition, and TNFα expression. Mesenteric arteries were used to access vascular function by myography. Blood pressure was increased in LinA3, Nox4 and LinA3/Nox4 mice vs WT (p<0.05). All three experimental groups exhibited vascular remodeling with evidence of increased fibrosis. Although LinA3 had increased aortic wall thickness (+31%), there was no significant change in collagen (10.3±3 vs. 8.5±2% in WT) and GAGs (6.6±3 vs 2.8±2% in WT) deposition (p<0.05). Nox4 mice, which presented a similar increase in wall thickness to LinA3 (+31%), had significant increase in collagen (20.6±6%) and GAGs (22.3±4%) in aorta (p<0.05). In LinA3/Nox4 mice, collagen (24.6±7%) and GAGs (37.1±10%) deposition were increased vs LinA3. TNFα was increased in LinA3 (130.4±6 a.u.) and LinA3/Nox4 mice (129±5 a.u.) vs WT (116.8±9 a.u.) (p<0.05). Mesenteric arteries from LinA3, Nox4 and LinA3/Nox4 mice, exhibit increased Phenylephrine-induced vasoconstriction vs WT (Emax: WT 6.79±0.29 vs LinA3 9.37±0.51; Nox4 9.87±1.59; LinA3/Nox4 9.12±1.63, p<0.05). Endothelium-dependent vasodilation was not reduced in Nox4 but impaired in LinA3 and LinA3/Nox4 (Emax: WT 86.48±0.01 vs LinA3 59.70±0.03; LinA3/Nox4 33.57±0.26, p<0.05). In conclusion, Nox4 deficiency was associated with increased blood pressure, vascular dysfunction and fibrosis, effects that were variably enhanced in LinA3/Nox4 mice. We also observed that the fibrosis in vessels from Nox4 mice was not associated with inflammation. These results suggest that Nox4 may be cardiovascular protective, which when downregulated leads to blood pressure elevation and vascular injury, processes that may be amplified by Ang II-dependent hypertension.