Impaired Endothelium-dependent Dilation Research Articles

Downregulated calmodulin expression contributes to endothelial cell impairment in diabetes.

Endothelial dysfunction, a central hallmark of cardiovascular pathogenesis in diabetes mellitus, is characterized by impaired endothelial nitric oxide synthase (eNOS) and NO bioavailability. However, the underlying mechanisms remain unclear. Here in this study, we aimed to identify the role of calmodulin (CaM) in diabetic eNOS dysfunction. Human umbilical vein endothelial cells and murine endothelial progenitor cells (EPCs) treated with high glucose (HG) exhibited downregulated CaM mRNA/protein and vascular endothelial growth factor (VEGF) expression with impeded eNOS phosphorylation and cell migration/tube formation. These perturbations were reduplicated in CALM1-knockdown cells but prevented in CALM1-overexpressing cells. EPCs from type 2 diabetes animals behaved similarly to HG-treated normal EPCs, which could be rescued by CALM1-gene transduction. Consistently, diabetic animals displayed impaired eNOS phosphorylation, endothelium-dependent dilation, and CaM expression in the aorta, as well as deficient physical interaction of CaM and eNOS in the gastrocnemius. Local CALM1 gene delivery into a diabetic mouse ischemic hindlimb improved the blunted limb blood perfusion and gastrocnemius angiogenesis, and foot injuries. Diabetic patients showed insufficient foot microvascular autoregulation, eNOS phosphorylation, and NO production with downregulated CaM expression in the arterial endothelium, and abnormal CALM1 transcription in genome-wide sequencing analysis. Therefore, our findings demonstrated that downregulated CaM expression is responsible for endothelium dysfunction and angiogenesis impairment in diabetes, and provided a novel mechanism and target to protect againstdiabetic endothelial injury.

Early life thymectomy induces arterial dysfunction in mice.

Aging of the arteries is characterized by increased large artery stiffness and impaired endothelium-dependent dilation. We have previously shown that in old (22-24month) mice T cells accumulate within aorta and mesentery. We have also shown that pharmacologic and genetic deletion of these T cells ameliorates age-related arterial dysfunction. These data indicate that T cells contribute to arterial aging; however, it is unknown if aged T cells alone can induce arterial dysfunction in otherwise young mice. To produce an aged-like T cell phenotype, mice were thymectomized at three-weeks of age or were left with their thymus intact. At 9months of age, thymectomized mice exhibited greater proportions of both CD4 + and CD8 + memory T cells compared to controls in the blood. Similar changes were observed in the T cells accumulating in the aorta and mesentery. We also observed greater numbers of proinflammatory cytokine producing T cells in the aorta and mesentery. The phenotypic T cell changes in the blood, aorta and mesentery of thymectomized mice were similar to those observed when we compared young (4-6month) to old thymus intact mice. Along with these alterations, compared to controls, thymectomized mice exhibited augmented large artery stiffness and greater aortic collagen deposition as well as impaired mesenteric artery endothelium dependent dilation due to blunted nitric oxide bioavailability. These results indicate that early life thymectomy results in arterial dysfunction and suggest that an aged-like T cell phenotype alone is sufficient to induce arterial dysfunction in otherwise young mice.

Abstract 424: Arachidonic Acid Synergizes With Aspirin In Cardioprotection Following Acute Myocardial Infarction

Introduction: Membrane-released arachidonic acid (AA) is metabolized via cyclooxygenase pathway to form prostanoids, including thromboxane, prostacyclin and prostaglandin E2. Aspirin suppresses platelet synthesis of thromboxane, rendering its first-line use for anti-thrombosis in patients with acute myocardial ischemia. We report that endogenous PGE2 protects against myocardial ischemia-reperfusion (MI/R) injury (Nat Commun. 2019;10(1):1888). The impact of AA administration while suppressing thromboxane on MI/R injury is unknown. Methods and Results: C57BL/6J mice were treated intravenously with vehicle, AA, aspirin, or their combination and then subjected to 30min coronary artery ligation and 24hr reperfusion. Cardiac function was assessed by ultrasonography and infraction size quantified by TTC staining. Cardiac microcirculation was assessed by laser doppler flow and vasomotor reactivity determined with isolated coronary arteries. Single treatment with AA at an optimized dose of 0.1mg/Kg, or combined with aspirin at a dose of 10mg/Kg that allowed sufficient suppressing of platelet activation over 24hr, decreased infarct size and improved heart function. Impressively, combination of AA with aspirin provided additional cardioprotection compared with either single treatment. While aspirin, not AA, ameliorated microvascular obstruction following MI/R injury, co-administration of AA and aspirin further increased coronary microcirculatory blood perfusion with improved vascular permeability compared with aspirin alone. MI/R impaired endothelium-dependent dilatation of coronary arteries, and the dual treatment, not AA or ASA alone, increased coronary artery relaxation. Cardiac infiltrated neutrophils and platelet-neutrophil aggregates were also reduced by the combination treatment, consistent with a suppressed leukocyte-ECs adhesion as assessed in vitro. Conclusions: AA and aspirin synergistically protect against MI/R injury and this is attributable to suppressed neutrophil inflammation and improved microvascular obstruction. AA might be used as an adjunct therapy to aspirin in patients with acute myocardial infarction.

Glycocalyx-targeted therapy ameliorates age-related arterial dysfunction.

Advanced age is accompanied by arterial dysfunction, as well as a diminished glycocalyx, which may be linked to reduced high molecular weight-hyaluronan (HMW-HA) synthesis. However, the impact of glycocalyx deterioration in age-related arterial dysfunction is unknown. We sought to determine if manipulations in glycocalyx properties would alter arterial function. Tamoxifen-induced hyaluronan synthase 2 (Has2) reduction was used to decrease glycocalyx properties. Three weeks post-tamoxifen treatment, glycocalyx thickness was lower in Has2 knockout compared to wild-type mice (P<0.05). Has2 reduction induced arterial dysfunction, demonstrated by impaired endothelium-dependent dilation (EDD) and elevated aortic stiffness (P<0.05). To augment glycocalyx properties, old mice received 10 weeks of a glycocalyx-targeted therapy via Endocalyx™ (old+ECX), which contains HMW-HA and other glycocalyx components. Compared to old control mice, glycocalyx properties and EDD were augmented, and aortic stiffness decreased in old+ECX mice (P<0.05). Old+ECX mice had a more youthful aortic phenotype, demonstrated by lower collagen content and higher elastin content than old control mice (P<0.05). Functional outcomes were repeated in old mice that underwent a diet supplemented solely with HMW-HA (old+HA). Compared to old controls, glycocalyx properties and EDD were augmented, and aortic stiffness was lower in old+HA mice (P<0.05). We did not observe any differences between old+HA and old+ECX mice (P>0.05). Has2 reduction phenocopies age-related arterial dysfunction, while 10 weeks of glycocalyx-targeted therapy that restores the glycocalyx also ameliorates age-related arterial dysfunction. These findings suggest that the glycocalyx may be a viable therapeutic target to ameliorate age-related arterial dysfunction.

High pulse pressure impairs cerebral artery endothelial function in young, but not old, mice

One of the hallmarks of vascular aging is increased pulse pressure. This elevated pulse pressure is associated with deleterious effects on cerebral vascular function; however, it is unknown if age modulates the susceptibility to high pulse pressure. To examine the effects of age on the cerebral artery response to pulse pressure, we studied isolated cerebral arteries collected from young (6.1 ± 0.2 mo) and old (26.7 ± 0.5 mo) male C57BL/6 mice. Isolated cerebral arteries were exposed ex vivo to static pressure, low pulse pressure (25 mmHg), and high pulse pressure (50 mmHg). In cerebral arteries from young mice, endothelium-dependent dilation was similar between the static and low pulse pressure conditions. Exposure to high pulse pressure impaired endothelium-dependent dilation in cerebral arteries from young mice, mediated by less nitric oxide bioavailability and greater oxidative stress. Cerebral arteries from old mice had impaired cerebral artery endothelium-dependent dilation at static pressure compared with young cerebral arteries. However, exposure to low or high pulse pressure did not cause any further impairments to endothelium-dependent dilation in old cerebral arteries compared with static pressure. The old cerebral arteries had less distension during exposure to high pulse pressure and greater stiffness compared with young cerebral arteries. These results indicate that acute exposure to high pulse pressure impairs endothelium-dependent dilation in young, but not old, cerebral arteries. The greater stiffness of cerebral arteries from old mice potentially protects against the negative consequences of high pulse pressure.

Maybe angiotensin II is getting on our nerves, and the role of exercise.

Maybe angiotensin II is getting on our nerves, and the role of exercise.

T cells mediate cell non-autonomous arterial ageing in mice.

Increased large artery stiffness and impaired endothelium-dependent dilatation occur with advanced age. We sought to determine whether T cells mechanistically contribute to age-related arterial dysfunction. We found that old mice exhibited greater proinflammatory T cell accumulation around both the aorta and mesenteric arteries. Pharmacologic depletion or genetic deletion of T cells in old mice resulted in ameliorated large artery stiffness and greater endothelium-dependent dilatation compared with mice with T cells intact. Ageing of the arteries is characterized by increased large artery stiffness and impaired endothelium-dependent dilatation. T cells contribute to hypertension in acute rodent models but whether they contribute to chronic age-related arterial dysfunction is unknown. To determine whether T cells directly mediate age-related arterial dysfunction, we examined large elastic artery and resistance artery function in young (4-6months) and old (22-24months) wild-type mice treated with anti-CD3 F(ab'2) fragments to deplete T cells (150μg, i.p. every 7days for 28days) or isotype control fragments. Old mice exhibited greater numbers of T cells in both aorta and mesenteric vasculature when compared with young mice. Old mice treated with anti-CD3 fragments exhibited depletion of T cells in blood, spleen, aorta and mesenteric vasculature. Old mice also exhibited greater numbers of aortic and mesenteric IFN-γ and TNF-α-producing T cells when compared with young mice. Old control mice exhibited greater large artery stiffness and impaired resistance artery endothelium-dependent dilatation in comparison with young mice. In old mice, large artery stiffness was ameliorated with anti-CD3 treatment. Anti-CD3-treated old mice also exhibited greater endothelium-dependent dilatation than age-matched controls. We also examined arterial function in young and old Rag-1-/- mice, which lack lymphocytes. Rag-1-/- mice exhibited blunted increases in large artery stiffness with age compared with wild-type mice. Old Rag-1-/- mice also exhibited greater endothelium-dependent dilatation compared with old wild-type mice. Collectively, these results demonstrate that T cells play an important role in age-related arterial dysfunction.

Chronic stress induced perivascular adipose tissue impairment of aortic function and the therapeutic effect of exercise.

What is the central question of this study? Thoracic perivascular adipose tissue (tPVAT) is known to, in part, regulate aortic function: what are the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and what is the role of exercise training in alleviating the potential negative actions of UCMS on tPVAT? What is the main finding and its importance? UCMS causes tPVAT to disrupt endothelium-dependent dilatation, increases inflammatory cytokine production and diminishes tPVAT-adiponectin. Exercise training proved efficacious in preventing tPVAT-mediated disruption of aortic function. The data support a tPVAT mechanism through which chronic stress negatively impacts vascular health, which adds to our knowledge of how psychological disorders might increase the risk of cardiovascular disease. Chronic stress is a major risk for cardiovascular disease. Perivascular adipose tissue (PVAT) has been shown to regulate vascular function; however, the impact of chronic stress and the comorbidity of metabolic syndrome (MetS) on thoracic (t)PVAT is unknown. Additionally, aerobic exercise training (AET) is known to combat the pathology of MetS and chronic stress, but the role of tPVAT in these actions is also unknown. Therefore, the purpose of this study was to examine the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and the preventative effect of AET. Lean (LZR) and obese (OZR) Zucker rats (16-17weeks old) were exposed to 8weeks of UCMS with and without treadmill exercise (AET). In LZR, UCMS impaired aortic endothelium-dependent dilatation (EDD) (assessed ex vivo by wire myography) and aortic stiffness (assessed by elastic modulus) with no change in OZR subject to UCMS. However, both LZR and OZR UCMS tPVAT impaired EDD compared to respective controls. LZR and OZR subject to UCMS had higher oxidative stress production, diminished adiponectin and impaired aortic nitric oxide levels. Divergently, UCMS induced greater inflammatory cytokine production in LZR UCMS tPVAT, but not in OZR UCMS tPVAT. AET prevented the tPVAT impairment of aortic relaxation with UCMS in LZR and OZR. Additionally, AET reduced aortic stiffness in both LZR and OZR. These beneficial effects on tPVAT regulation of the aorta are likely due to AET preservation of adiponectin, reduced oxidative stress and inflammation, and enhanced nitric oxide. UCMS impaired tPVAT-regulated aortic function in LZR, and augmented MetS-induced EDD in OZR. Conversely, AET in combination with UCMS largely preserved aortic function and the tPVAT environment, in both groups.

Inorganic Nitrite Supplementation Improves Endothelial Function With Aging: Translational Evidence for Suppression of Mitochondria-Derived Oxidative Stress.

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Soluble epoxide hydrolase inhibition improves cognitive function and parenchymal artery dilation in a hypertensive model of chronic cerebral hypoperfusion

Parenchymal arterioles (PAs) regulate perfusion of the cerebral microcirculation, and impaired PA endothelium-dependent dilation occurs in dementia models mimicking chronic cerebral hypoperfusion (CCH). Epoxyeicosatrienoic acids (EETs) are vasodilators; their actions are potentiated by soluble epoxide hydrolase (sEH) inhibition. We hypothesized that chronic sEH inhibition with trifluoromethoxyphenyl-3 (1-propionylpiperidin-4-yl) urea (TPPU) would prevent cognitive dysfunction and improve PA dilation in a hypertensive CCH model. Bilateral carotid artery stenosis (BCAS) was used to induce CCH in twenty-week-old male stroke-prone spontaneously hypertensive rats (SHSRP) that were treated with vehicle or TPPU for 8weeks. Cognitive function was assessed by novel object recognition. PA dilation and structure were assessed by pressure myography, and mRNA expression in brain tissue was assessed by qRT-PCR. TPPU did not enhance resting cerebral perfusion, but prevented CCH-induced memory deficits. TPPU improved PA endothelium-dependent dilation but reduced the sensitivity of PAs to a nitric oxide donor. TPPU treatment had no effect on PA structure or biomechanical properties. TPPU treatment increased brain mRNA expression of brain derived neurotrophic factor, doublecortin, tumor necrosis factor-alpha, sEH, and superoxide dismutase 3, CONCLUSIONS: These data suggest that sEH inhibitors may be viable treatments for cognitive impairments associated with hypertension and CCH.

Genetic Reduction of DNA Damage Repair Protein ATM Kinase Attenuates Endothelium‐Dependent Dilation and NO Bioavailability via Enhanced Superoxide in Old but not Young Mice

Advanced age is associated with accumulated DNA damage and disruption of selective DNA damage repair pathways which together can accelerate the aging phenotype. In the vasculature, aging is characterized by impaired endothelium‐dependent dilation (EDD) and reduced nitric oxide (NO) bioavailability. Activation of ataxia telangiectasia mutated (ATM) kinase, a key mediator of the response to double‐stranded DNA (dsDNA) breaks, leads to upregulation of its effectors p53 and p21. Importantly, expression of these proteins is negatively correlated to EDD and has been demonstrated to be increased in the endothelium with aging. While these findings suggest that dsDNA breaks impair EDD, it is unknown if alterations in ATM per se modulate EDD. We hypothesized that genetic deletion of ATM would impair endothelial function in young mice (4–6 mo, n=7–9/group) leading to a vascular phenotype that phenocopies aging. In young mice, EDD in response to acetylcholine (Ach) in isolated mesenteric arteries was similar between young ATM +/+ and ATM −/− mice in the absence or presence of the NO synthase inhibitor, L‐NAME (both p&gt;0.05) (Fig 1). Endothelium‐independent dilation (EID) to sodium nitroprusside (SNP) was also not different between young ATM +/+ and ATM −/− mice (p&gt;0.05). Thus, contrary to our hypothesis, EDD and NO were preserved despite ATM deletion, suggesting that an insufficient accumulation of DNA damage may have occurred in young mice to impair endothelial function. We next hypothesized that an additional genomic stressor, such as aging, may be necessary to uncover the effects of ATM deficiency on endothelial function. However, ATM −/− mice die at ~6 mo due to malignant thymic lymphomas, therefore, to explore the effects of an age‐related accumulation of DNA damage on endothelial function, we assessed Ach‐mediated EDD in mesenteric arteries of aged (18–19 mo) ATM +/+ and ATM +/− mice (n=5–13). While aging alone (4–6 vs. 18–19 mo, ATM +/+) only tended to reduce EDD (p=0.1), EDD was significantly blunted in old ATM +/− compared to age‐matched ATM +/+ (p&lt;0.01) (Fig 2A). This impairment in EDD resulted from decreased NO bioavailability, evidenced by a ~35% reduction in NO‐dependent vasodilation in aged ATM +/− compared to ATM +/+ mice (p&lt;0.01) (Fig 2B). EID to SNP did not differ between groups (p&gt;0.05). To determine if increases in reactive oxygen species may underlie blunted EDD/NO in aged ATM +/− mice, EDD was assessed in the presence of the superoxide scavenger, TEMPOL. TEMPOL restored EDD in aged ATM +/− mice (p&lt;0.05) to levels not different from young mice (p&gt;0.05). Here, we provide novel evidence that although ATM deficiency alone is insufficient to impair EDD in young mice, in the face of a known genomic stressor like aging, ATM deficiency leads to impaired EDD and reduced NO via increased superoxide. These findings support the concept that accumulation of DNA damage and genomic instability with advanced age impairs endothelial function.Support or Funding InformationFunding Information: Funded in part by awards from the NIH, R01 AG048366, R01 AG050238, R01 AG060395, K99 AT010017, T32 5T32HL139451‐02, and by US Department of Veterans Affairs I01BX004492ATM kinase deletion does not impair endothelium dependent dilation (EDD) or nitric oxide (NO) bioavailability in mesenteric arteries of young mice.EDD was assessed in response to increasing concentrations of acetylcholine (Ach) in isolated mesenteric arteries from young (4–6 mo) mice lacking ATM (ATM −/−) or wildtype (ATM +/+) littermate controls. To determine the contribution of NO to dilation, Ach responses were repeated in the presence of the NO synthase inhibitor, L‐NAME. †, difference after L‐NAME. p&lt;0.05. Data are means ± SEM.Figure 1ATM kinase deficiency impairs endothelium dependent dilation (EDD) and nitric oxide (NO) bioavailability in mesenteric arteries of aged mice.(A) EDD was assessed in response to increasing concentrations of acetylcholine (Ach) in isolated mesenteric arteries from aged (18–19 mo) mice heterozygous for ATM (ATM +/−) and wildtype (ATM +/+) controls. Ach dose‐responses were repeated in the presence of the NO synthase inhibitor, L‐NAME. (B) NO‐dependent vasodilation, i.e. the difference in maximal dilation to Ach in the absence or presence of L‐NAME, was calculated. *, difference from ATM+/+. †, difference after L‐NAME. p&lt;0.05. Data are means ± SEM.Figure 2

Inflammation as a mediator of arterial ageing.

What is the topic of this review? This review summarizes and synthesizes what is known about the contribution of inflammation to age-related arterial dysfunction. What advances does it highlight? This review details observational evidence for the relationship of age-related inflammation and arterial dysfunction, insight from autoimmune inflammatory diseases and their effects on arterial function, interventional evidence linking inflammation and age-related arterial dysfunction, insight into age-related arterial inflammation from preclinical models and interventions to ameliorate age-related inflammation and arterial dysfunction. Advanced age is a primary risk factor for cardiovascular disease, the leading cause of death in the industrialized world. Two major components of arterial ageing are stiffening of the large arteries and impaired endothelium-dependent dilatation in multiple vascular beds. These two alterations are major contributors to the development of overt cardiovascular disease. Increasing inflammation with advanced age is likely to play a role in this arterial dysfunction. The purpose of this review is to synthesize what is known about inflammation and its relationship to age-related arterial dysfunction. This review discusses both the initial observational evidence for the relationship of age-related inflammation and arterial dysfunction and the evidence that inflammatory autoimmune diseases are associated with a premature arterial ageing phenotype. We next discuss interventional and mechanistic evidence linking inflammation and age-related arterial dysfunction in older adults. We also attempt to summarize the relevant evidence from preclinical models. Lastly, we discuss interventions in both humans and animals that have been shown to ameliorate age-related arterial inflammation and dysfunction. The available evidence provides a strong basis for the role of inflammation in both large artery stiffening and impairment of endothelium-dependent dilatation; however, the specific inflammatory mediators, the initiating factors and the relative importance of the endothelium, smooth muscle cells, perivascular adipose tissue and immune cells in arterial inflammation are not well understood. With the expansion of the ageing population, ameliorating age-related arterial inflammation represents an important potential strategy for preserving vascular health in the elderly.

Oxidative Stress Contributes to Microvascular Endothelial Dysfunction in Men and Women With Major Depressive Disorder.

In rodent models of depression, oxidative stress-induced reductions in NO bioavailability contribute to impaired endothelium-dependent dilation. Endothelial dysfunction is evident in major depressive disorder (MDD); however, the molecular mediators remain undefined. We sought to translate preclinical findings to humans by testing the role of oxidative stress in mediating microvascular endothelial dysfunction, including potential modulatory influences of sex, in MDD. Twenty-four treatment-naive, otherwise healthy, young adults with MDD (14 women; 18-23 years) and 20 healthy adults (10 women; 19-30 years) participated. Red blood cell flux (laser Doppler flowmetry) was measured during graded intradermal microdialysis perfusion of the endothelium-dependent agonist acetylcholine, alone and in combination with an NO synthase inhibitor (L-NAME), a superoxide scavenger (Tempol), and an NADPH oxidase inhibitor (apocynin), as well as during perfusion of the endothelium-independent agonist sodium nitroprusside. Tissue oxidative stress markers (eg, nitrotyrosine abundance, superoxide production) were also quantified. Endothelium-dependent dilation was blunted in MDD and mediated by reductions in NO-dependent dilation. Endothelium-independent dilation was likewise attenuated in MDD. In MDD, there were no sex differences in either NO-mediated endothelium-dependent dilation or endothelium-independent dilation. Acute scavenging of superoxide or inhibition of NADPH oxidase improved NO-dependent dilation in MDD. Expression and activity of oxidative stress markers were increased in MDD. In a subset of adults with MDD treated with a selective serotonin reuptake inhibitor for their depressive symptoms and in remission (n=8; 7 women; 19-37 years), NO-mediated endothelium-dependent dilation was preserved, but endothelium-independent dilation was impaired, compared with healthy adults. Oxidative stress-induced reductions in NO-dependent dilation, as well as alterations in vascular smooth muscle function, directly contribute to microvascular dysfunction in MDD. Strategies targeting vascular oxidative stress may be viable therapeutic options for improving NO-mediated endothelial function and reducing cardiovascular risk in MDD.

Deep Vascular Phenotyping in Patients With Renal Multifocal Fibromuscular Dysplasia.

Arterial fibromuscular dysplasia is a nonatherosclerotic, noninflammatory vascular disease, whose pathophysiology is still unknown. We performed deep image-based vascular phenotyping of nonaffected arteries to look for systemic vascular alterations in fibromuscular dysplasia. This single center cross-sectional study included 50 patients with multifocal renal fibromuscular dysplasia, 50 hypertensive patients, and 50 healthy controls, matched for age, sex, and ethnicity; hypertensive patients were matched also for blood pressure. Brachial artery endothelium-dependent and endothelium-independent dilation were studied by echotracking. Aortic stiffness was assessed by carotid-to-femoral pulse wave velocity. We quantified the presence of supernumerary acoustic interfaces within the common carotid wall by the triple signal (TS) score. We plotted the Young incremental elastic modulus/stress curves for common carotid artery, derived from echotracking and tonometry. Patients with fibromuscular dysplasia had impaired endothelium-independent dilation (adjusted P=0.002), smaller brachial artery diameter but comparable endothelium-dependent dilation and aortic stiffness. The prevalence of TS score >6 was 56%, 40%, 24% in patients with fibromuscular dysplasia, hypertensives, and controls, respectively ( P=0.005). Fibromuscular dysplasia remained significantly associated with TS in the multiple regression model ( P=0.022). Impaired endothelium-dependent dilation was present only in patients with fibromuscular dysplasia, TS score >6 ( P=0.047). Incremental elastic modulus was higher for a given wall stress (80 kPa) in the presence of a TS score >6, especially in fibromuscular dysplasia. In conclusion, nonclinically affected large- and medium-sized arteries in patients with multifocal renal fibromuscular dysplasia exhibit a cluster of diffuse alterations in smooth muscle cell function, arterial geometry, wall characteristics, and mechanical properties. Clinical Trial Registration URL: http://www.clinicaltrials.gov . Unique identifier: NCT01935752.

Reversing age-associated arterial dysfunction: insight from preclinical models.

Cardiovascular diseases (CVDs) remain the leading causes of death in the United States, and advancing age is a primary risk factor. Impaired endothelium-dependent dilation and increased stiffening of the arteries with aging are independent predictors of CVD. Increased tissue and systemic oxidative stress and inflammation underlie this age-associated arterial dysfunction. Calorie restriction (CR) is the most powerful intervention known to increase life span and improve age-related phenotypes, including arterial dysfunction. However, the translatability of long-term CR to clinical populations is limited, stimulating interest in the pursuit of pharmacological CR mimetics to reproduce the beneficial effects of CR. The energy-sensing pathways, mammalian target of rapamycin, AMPK, and sirtuin-1 have all been implicated in the beneficial effects of CR on longevity and/or physiological function and, as such, have emerged as potential targets for therapeutic intervention as CR mimetics. Although manipulation of each of these pathways has CR-like benefits on arterial function, the magnitude and/or mechanisms can be disparate from that of CR. Nevertheless, targeting these pathways in older individuals may provide some benefits against arterial dysfunction and CVD. The goal of this review is to provide a brief discussion of the mechanisms and pathways underlying age-associated dysfunction in large arteries, explain how these are impacted by CR, and to present the available evidence, suggesting that targets for energy-sensing pathways may act as vascular CR mimetics.

Suppression of the Gut Microbiome‐Derived Metabolite Trimethylamine N‐oxide Prevents Western Diet‐Induced Arterial Dysfunction

Consumption of a Western‐style diet (WD; high fat, high sugar) is associated with impaired arterial function and increased risk of cardiovascular diseases (CVD). One possible link between WD and impaired arterial function may be the gut microbiome. WD induces adverse changes to the gut microbiome, and consequently, increased production of the gut‐derived metabolite trimethylamine N‐oxide (TMAO). TMAO is causally atherogenic in mice and predicts incident risk of major CV events in humans, but it is unknown whether TMAO mediates arterial dysfunction that precedes clinical CVD.PURPOSETo determine if inhibition of TMAO with 3,3‐dimethyl‐1‐butanol (DMB; inhibitor of microbial TMA lyase) prevents WD‐induced large elastic artery stiffening and endothelial dysfunction.METHODSTwenty‐four young (3 mo) male C57BL/6 mice were fed WD (40% fat, 25% sugar) for 5 months and were supplemented without (WD‐Control, WD‐C; N=11) or with 1% DMB (N=13) in drinking water for the last 8 weeks. Arterial stiffness was assessed as aortic pulse wave velocity (aPWV) following 3 mo of WD (intervention baseline, BL) and following 4 and 8 weeks on the intervention. Endothelial function and its suppression by oxidative stress were evaluated ex vivo as carotid artery endothelium‐dependent dilation (EDD) to increasing doses of acetylcholine (10−9 to 10−4M) alone and following pre‐incubation with the superoxide dismutase mimetic TEMPOL. Total whole‐cell superoxide production was assessed in aortic rings via electron paramagnetic resonance spectroscopy. The same assessments were made in a reference group of age‐matched C57BL/6 male mice fed standard rodent chow (Normal Chow, NC; N=10). Data are mean±S.E.RESULTSWD induced progressive increases in aPWV (BL: 346±15, 4wks: 363±14, 8wks: 420±23 cm/sec, p=0.01), which were prevented by DMB (BL: 347±10, 4wks: 349±20, 8wks: 355±16cm/sec, p=0.98; DMB vs. WD‐C at 8wks: p=0.02). WD impaired EDD (peak dilation: 83.0±1.1% vs. NC: 92.5±2.0%, p&lt;0.01), which was prevented by DMB (93.4±1.5%, p&lt;0.0001 vs. WD‐C, p=0.71 vs. NC). Group differences in EDD were no longer significant after inhibition of oxidative stress with TEMPOL (peak EDD: p=0.22). Aortic superoxide production tended to be lower in DMB (2.2±0.3 AU) vs. WD‐C mice (3.9±1.1 AU, p=0.12) and was not different from NC (2.5±0.6 AU, p=0.52).CONCLUSIONSDMB supplementation prevented WD‐induced arterial stiffening and endothelial dysfunction, possibly through attenuation of oxidative stress. These data establish a role of the gut microbiome and TMAO in mediating WD‐induced arterial dysfunction and provide initial evidence of a novel strategy for preventing arterial dysfunction and reducing CVD risk.Support or Funding InformationSupported by R01 HL134887 &amp; T32 HL007822This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Carotid artery stenosis in hypertensive rats impairs dilatory pathways in parenchymal arterioles.

Hypertension is a leading risk factor for vascular cognitive impairment and is strongly associated with carotid artery stenosis. In normotensive rats, chronic cerebral hypoperfusion induced by bilateral common carotid artery stenosis (BCAS) leads to cognitive impairment that is associated with impaired endothelium-dependent dilation in parenchymal arterioles (PAs). The aim of this study was to assess the effects of BCAS on PA function and structure in stroke-prone spontaneously hypertensive rats, a model of human essential hypertension. Understanding the effects of hypoperfusion on PAs in a hypertensive model could lead to the identification of therapeutic targets for cognitive decline in a model that reflects the at-risk population. We hypothesized that BCAS would impair endothelium-dependent dilation in PAs and induce artery remodeling compared with sham rats. PAs from BCAS rats had endothelial dysfunction, as assessed using pressure myography. Inhibition of nitric oxide and prostaglandin production had no effect on PA dilation in sham or BCAS rats. Surprisingly, inhibition of epoxyeicosatrienoic acid production increased dilation in PAs from BCAS rats but not from sham rats. Similar results were observed in the presence of inhibitors for all three dilatory pathways, suggesting that epoxygenase inhibition may have restored a nitric oxide/prostaglandin-independent dilatory pathway in PAs from BCAS rats. PAs from BCAS rats underwent remodeling with a reduced wall thickness. These data suggest that marked endothelial dysfunction in PAs from stroke-prone spontaneously hypertensive rats with BCAS may be associated with the development of vascular cognitive impairment. NEW & NOTEWORTHY The present study assessed the structure and function of parenchymal arterioles in a model of chronic cerebral hypoperfusion and hypertension, both of which are risk factors for cognitive impairment. We observed that impaired dilation and artery remodeling in parenchymal arterioles and abolished cerebrovascular reserve capacity may mediate cognitive deficits.

Hyperhomocysteinemia in patients with chronic kidney disease and its relationship with the functional status of the cardiovascular system

Chronic kidney disease (CKD) is an important medical, social and economic problem nowadays. Patients with CKD are known to have an increased risk of development and progression of cardiovascular diseases. However, the causes and pathogenesis of cardiovascular complications are not well understood. One of the recently recognized “non-traditional” risk factors for the increased development of cardiovascular pathology in severe stages of CKD is hyperhomocysteinemia (HHC). The article presents the results of study of HHC frequency in patients with different stages of CKD as well as the relationship between HHC and endothelial dysfunction and structural-functional status of the heart. The study involved 148 persons with different stages of CKD who underwent immunoenzyme determination of total plasma homocysteine (HC), echocardiography, carotid ultrasonograghy, endothelial function was assessed as well. It was found that among the patients with CKD, 26 (21.1%) had normal and 34 (27.7%) had subnormal HC levels, mild HHC was observed in 30 (24.4%) and moderate HHC – in 33 (26.8%) cases, i.e. the total number of patients with elevated HC level was 88.9%. It should be noted that no patients with normal HC level were found among those with stage four CKD as well as in dialysis patients. The increase of blood plasma HC level was actually proportional to the severity of renal failure, which in its turn led to the shift in the number of cases towards higher rank indices of HHC level. In particular, while there were no patients with HHC among those with CKD-I, more than 50% of such patients were found in the group with CKD-V. Reduced myocardial contractility and echocardiographic markers of left ventricular hypertrophy in patients with CKD were found to be closely associated with HC concentrations in blood plasma. The data presented clearly demonstrate strong inverse correlation between endothelial dysfunction indices and HC level. So, the endothelium-dependent brachial artery vasodilation in patients with CKD-IV was lower by 3.8 and 1.5 times compared with control group and CKD-III group, respectively, and endothelium-independent vasodilation of the brachial artery – by 2.4 and 1.9 times, respectively. Correlation analysis also confirmed that impaired endothelium-dependent and endothelium-independent dilation with high statistical significance inversely correlated with the level of HC in blood plasma. Thus, the population of patients with CKD is characterized by high HHC frequency, which is closely associated with cardiovascular disorders (endothelial dysfunction, structural and functional remodelling of the myocardium) and can be an important risk factor for the development of vascular lesions. We believe that adequate correction of HHC, including administration of folic acid preparations could reduce the progression of vascular lesions in patients with CKD.

DOCA-salt hypertension impairs artery function in rat middle cerebral artery and parenchymal arterioles.

Chronic hypertension induces detrimental changes in the structure and function of surface cerebral arteries. Very little is known about PAs, which perfuse distinct neuronal populations in the cortex and may play a role in cerebrovascular disorders. We investigated the effect of DOCA-salt induced hypertension on endothelial function and artery structure in PAs and MCAs. Uninephrectomized male Sprague-Dawley rats were implanted with a subcutaneous pellet containing DOCA (150mg/kg b.w.) and drank salt water (1% NaCl and 0.2% KCl) for 4weeks. Sham rats were uninephrectomized and drank tap water. Vasoreactivity and passive structure in the MCAs and the PAs were assessed by pressure myography. Both MCAs and PAs from DOCA-salt rats exhibited impaired endothelium-dependent dilation (P<.05). In the PAs, addition of NO and COX inhibitors enhanced dilation in DOCA-salt rats (P<.05), suggesting that dysfunctional NO and COX-dependent signaling could contribute to impaired endothelium-mediated dilation. MCAs from DOCA-salt rats exhibited inward remodeling (P<.05). Hypertension-induced MCA remodeling coupled with impaired endothelium-dependent dilation in both the MCAs and PAs may exacerbate the risk of cerebrovascular accidents and the associated morbidity and mortality.

Abstract P242: Microvascular Changes in Brain During Salt-sensitive Hypertension: Molecular Mechanisms and Implications for Small Vessel Disease

Hypertension is a major risk factor for small vessel disease (SVD), a leading contributor to stroke and dementias. Mechanisms that underlie SVD in brain are poorly defined, with no specific therapy at present. Because parenchymal and pial arterioles are targets of the SVD process, we examined microvascular changes in a model using deoxycorticosterone-salt (DOCA) to activate the brain renin-angiotensin system (RAS), with resulting salt-sensitive (sodium- and fluid-dependent) hypertension. Male C57Bl/6 mice were treated with DOCA and given the choice of drinking H 2 O or H 2 O with 0.9% NaCl for 3 wks. Along with a modest elevation in mean arterial pressure (79±2 vs 95±3 mmHg, P&lt;0.05), DOCA impaired endothelium-dependent dilation of both isolated parenchymal (baseline diameter of 15±1 μm) and pial arterioles (37±1 μm) in a pathway specific manner. Endothelium-dependent hyperpolarization was intact while eNOS-mediated vasodilation was markedly impaired along with reductions in phosphorylation in AKT (an upstream activator of eNOS). Local inhibition of angiotensin II type 1 (AT1-R) or mineralocorticoid receptors (MR) or Rho kinase (including ROCK2), restored endothelial function in DOCA-treated mice. Inner diameter of maximally dilated parenchymal arterioles was reduced approximately 20% by DOCA (P&lt;0.05 vs sham). DOCA increased mRNA expression of RAS components (eg, AGT, ACE) in both brain and cerebral vessels. In NZ44 reporter mice that express GFP driven by the AT1A-R promoter, DOCA increased cerebrovascular GFP protein expression about 3-fold (P&lt;0.05). Thus, DOCA activates both the brain and the cerebrovascular RAS, impairs select pathways affecting parenchymal and pial arteriolar function, while producing inward microvascular remodeling. AT1R, MR and ROCK2 are key contributors to cerebral microvascular dysfunction in this clinically relevant model of SVD.