miR-369-3p ameliorates diabetes-associated atherosclerosis by regulating macrophage succinate-GPR91 signaling

AIMS

Diabetes leads to dysregulated macrophage immunometabolism, contributing to accelerated atherosclerosis progression. Identifying critical factors to restore metabolic alterations and promote resolution of inflammation remains an unmet goal. MicroRNAs (miRs) orchestrate multiple signaling events in macrophages, yet their therapeutic potential in diabetes-associated atherosclerosis remains unclear.

METHODS AND RESULTS

MiRNA profiling revealed significantly lower miR-369-3p expression in aortic intimal lesions from Ldlr-/- mice on a high-fat sucrose containing (HFSC) diet for 12 weeks. miR-369-3p was also reduced in peripheral blood mononuclear cells (PBMCs) from diabetic patients with coronary artery disease (CAD). Cell-type expression profiling showed miR-369-3p enrichment in aortic macrophages. In vitro, oxLDL treatment reduced miR-369-3p expression in mouse bone marrow-derived macrophages (BMDMs). Metabolic profiling in BMDMs revealed that miR-369-3p overexpression blocked the oxLDL-mediated increase in the cellular metabolite succinate and reduced mitochondrial respiration (OXPHOS) and inflammation (lL-1β, TNF-a, IL-6). Mechanistically, miR-369-3p targeted the succinate receptor (GPR91) and alleviated the oxLDL-induced activation of inflammasome signaling pathways. Therapeutic administration of miR-369-3p mimics in HFSC-fed Ldlr-/- mice reduced GPR91 expression in lesional macrophages and diabetes-accelerated atherosclerosis, evident by a decrease in plaque size and pro-inflammatory Ly6Chi monocytes. RNA-seq analyses showed more pro-resolving pathways in plaque macrophages from miR-369-3p treated mice, consistent with an increase in macrophage efferocytosis in lesions. Finally, a GPR91 antagonist attenuated oxLDL-induced inflammation in primary monocytes from human subjects with diabetes.

CONCLUSION

These findings establish a therapeutic role for miR-369-3p in halting diabetes-associated atherosclerosis by regulating GPR91 and macrophage succinate metabolism.

Coronary Microvascular Function Following Severe Preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-specific hypertensive disorder associated with an imbalance in circulating proangiogenic and antiangiogenic proteins. Preclinical evidence implicates microvascular dysfunction as a potential mediator of preeclampsia-associated cardiovascular risk.

METHODS

Women with singleton pregnancies complicated by severe antepartum-onset preeclampsia and a comparator group with normotensive deliveries underwent cardiac positron emission tomography within 4 weeks of delivery. A control group of premenopausal, nonpostpartum women was also included. Myocardial flow reserve, myocardial blood flow, and coronary vascular resistance were compared across groups. sFlt-1 (soluble fms-like tyrosine kinase receptor-1) and PlGF (placental growth factor) were measured at imaging.

RESULTS

The primary cohort included 19 women with severe preeclampsia (imaged at a mean of 15.3 days postpartum), 5 with normotensive pregnancy (mean, 14.4 days postpartum), and 13 nonpostpartum female controls. Preeclampsia was associated with lower myocardial flow reserve (β, -0.67 [95% CI, -1.21 to -0.13]; P=0.016), lower stress myocardial blood flow (β, -0.68 [95% CI, -1.07 to -0.29] mL/min per g; P=0.001), and higher stress coronary vascular resistance (β, +12.4 [95% CI, 6.0 to 18.7] mm Hg/mL per min/g; P=0.001) versus nonpostpartum controls. Myocardial flow reserve and coronary vascular resistance after normotensive pregnancy were intermediate between preeclamptic and nonpostpartum groups. Following preeclampsia, myocardial flow reserve was positively associated with time following delivery (P=0.008). The sFlt-1/PlGF ratio strongly correlated with rest myocardial blood flow (r=0.71; P<0.001), independent of hemodynamics.

CONCLUSIONS

In this exploratory cross-sectional study, we observed reduced coronary microvascular function in the early postpartum period following preeclampsia, suggesting that systemic microvascular dysfunction in preeclampsia involves coronary microcirculation. Further research is needed to establish interventions to mitigate the risk of preeclampsia-associated cardiovascular disease.

Coronary Microvascular Function Following Severe Preeclampsia

Background

Preeclampsia is a pregnancy-specific hypertensive disorder associated with an imbalance in circulating pro- and anti-angiogenic proteins. Preclinical evidence implicates microvascular dysfunction as a potential mediator of preeclampsia-associated cardiovascular risk.

Methods

Women with singleton pregnancies complicated by severe antepartum-onset preeclampsia and a comparator group with normotensive deliveries underwent cardiac positron emission tomography (PET) within 4 weeks of delivery. A control group of pre-menopausal, non-postpartum women was also included. Myocardial flow reserve (MFR), myocardial blood flow (MBF), and coronary vascular resistance (CVR) were compared across groups. Soluble fms-like tyrosine kinase receptor-1 (sFlt-1) and placental growth factor (PlGF) were measured at imaging.

Results

The primary cohort included 19 women with severe preeclampsia (imaged at a mean 16.0 days postpartum), 5 with normotensive pregnancy (mean 14.4 days postpartum), and 13 non-postpartum female controls. Preeclampsia was associated with lower MFR (β=-0.67 [95% CI -1.21 to -0.13]; P=0.016), lower stress MBF (β=-0.68 [95% CI, -1.07 to -0.29] mL/min/g; P=0.001), and higher stress CVR (β=+12.4 [95% CI 6.0 to 18.7] mmHg/mL/min/g; P=0.001) vs. non-postpartum controls. MFR and CVR after normotensive pregnancy were intermediate between preeclamptic and non-postpartum groups. Following preeclampsia, MFR was positively associated with time following delivery (P=0.008). The sFlt-1/PlGF ratio strongly correlated with rest MBF (r=0.71; P<0.001), independent of hemodynamics.

Conclusions

In this exploratory study, we observed reduced coronary microvascular function in the early postpartum period following severe preeclampsia, suggesting that systemic microvascular dysfunction in preeclampsia involves the coronary microcirculation. Further research is needed to establish interventions to mitigate risk of preeclampsia-associated cardiovascular disease.

Association of electronic cigarette use with circulating angiogenic cell levels in healthy young adults: Evidence for chronic systemic injury

BACKGROUND

Circulating angiogenic cells (CACs) are indicative of vascular health and repair capacity; however, their relationship with chronic e-cigarette use is unclear. This study aims to assess the association between e-cigarette use and CAC levels.

METHODS

We analyzed CAC levels in 324 healthy participants aged 21-45 years from the cross-sectional Cardiovascular Injury due to Tobacco Use study in four groups: never tobacco users (n = 65), sole e-cigarette users (n = 19), sole combustible cigarette users (n = 212), and dual users (n = 28). A total of 15 CAC subpopulations with four cell surface markers were measured using flow cytometry: CD146 (endothelial), CD34 (stem), CD45 (leukocyte), and AC133 (early progenitor/stem). Generalized linear models with gamma distribution and log-link were generated to assess association between CACs and smoking status. Benjamini-Hochberg were used to adjust p-values for multiple comparisons.

RESULTS

The cohort was 47% female, 51% Black/African American, with a mean (± SD) age of 31 ± 7 years. Sole cigarette use was significantly associated with higher levels of two endothelial marker CACs (Q ⩽ 0.05). Dual users had higher levels of four endothelial marker CACs and one early progenitor/stem marker CAC (Q ⩽ 0.05). Sole e-cigarette users had higher levels of one endothelial and one leukocyte marker CAC (Q ⩽ 0.05).

CONCLUSION

Dual use of e-cigarettes and combustible cigarettes was associated with higher levels of endothelial origin CACs, indicative of vascular injury. Sole use of e-cigarettes was associated with higher endothelial and inflammatory CACs, suggesting ongoing systemic injury. Distinct patterns of changes in CAC subpopulations suggest that CACs may be informative biomarkers of changes in vascular health due to tobacco product use.

Pod-based e-liquids impair human vascular endothelial cell function

Pod-based electronic (e-) cigarettes more efficiently deliver nicotine using a protonated formulation. The cardiovascular effects associated with these devices are poorly understood. We evaluated whether pod-based e-liquids and their individual components impair endothelial cell function. We isolated endothelial cells from people who are pod users (n = 10), tobacco never users (n = 7), and combustible cigarette users (n = 6). After a structured use, pod users had lower acetylcholine-mediated endothelial nitric oxide synthase (eNOS) activation compared with never users and was similar to levels from combustible cigarette users (overall P = 0.008, P = 0.01 pod vs never; P = 0.96 pod vs combustible cigarette). The effects of pod-based e-cigarettes and their constituents on vascular cell function were further studied in commercially available human aortic endothelial cells (HAECs) incubated with flavored JUUL e-liquids or propylene glycol (PG):vegetable glycerol (VG) at 30:70 ratio with or without 60 mg/mL nicotine salt for 90 min. A progressive increase in cell death with JUUL e-liquid exposure was observed across 0.0001-1% dilutions; PG:VG vehicle with and without nicotine salt induced cell death. A23187-stimulated nitric oxide production was decreased with all JUUL e-liquid flavors, PG:VG and nicotine salt exposures. Aerosols generated by JUUL e-liquid heating similarly decreased stimulated nitric oxide production. Only mint flavored e-liquids increased inflammation and menthol flavored e-liquids enhanced oxidative stress in HAECs. In conclusion, pod e-liquids and their individual components appear to impair endothelial cell function. These findings indicate the potential harm of pod-based devices on endothelial cell function and thus may be relevant to cardiovascular injury in pod type e-cigarette users.

Abstract 540: Impaired Microvascular Angiogenesis And Altered Tissue MicroRNA In Patients With Peripheral Artery Disease

Microvascular dysfunction contributes to adverse clinical outcomes in patients with peripheral artery disease (PAD). Compromised angiogenesis is an important mechanism of limb ischemia that may be a treatment target but is challenging to assess in patients. Selected circulating microRNA (miRNAs) have been implicated in the pathogenesis of PAD. Thus, we sought to characterize angiogenesis potential and identify altered miRNA in patients with PAD. We collected adipose tissue from ischemic limbs of patients with PAD (n=15, age=64±11, 33% women, 66% T2DM, 61% current smoking) at the time of revascularization surgery. Control adipose tissue was procured patients without PAD undergoing joint replacement surgery (n=6, age=58±6, 50% women, 17% T2DM, 33% current smoking). Using matrigel sprouting assay, we observed a significantly lower angiogenesis response over 8 days in adipose tissue samples from PAD patients compared to controls (p=0.008). We performed miRNA profiling using NextSeq (Illumina Inc.) sequencer. miRNA NGS libraries were prepared using QIAseq miRNA Library Kit. Quality controlled NGS libraries were sequenced according to the manufacturer protocol. Our results demonstrated 40 upregulated and 11 downregulated miRNAs (FDR q<0.01, log2 fold change>2). Using bioinformatics approaches to prioritize differentially expressed miRNA predicted to impact pathways relevant to cardiovascular disease, we identified miR205-5p and miR182-5p as top candidate. There were higher levels of miR205-5p (4.8-fold, FDRq=1.5e-10) and miR182-5p (4.1-fold, FDRq=5.4e-16) in adipose tissue from PAD patients compared to controls. We confirmed the differentially expressed levels using qPCR in selected samples. Ingenuity pathway analysis indicates that miR205-5p inhibits VEGF-A, a key regulator of angiogenesis. We observed a trend toward an association of miR205-5p (r=-0.58, p=0.1) and miR182-5p (r=-0.67, p=0.06) and lower angiogenesis response. Taken together our findings demonstrate impaired microvascular angiogenesis response in patients with PAD along with upregulation of selected miRNA predicted to impair angiogenesis pathways. Further work is needed to confirm a functional role of miRNA in the impaired angiogenesis in patients with PAD.

Oxidized GAPDH transfers S-glutathionylation to a nuclear protein Sirtuin-1 leading to apoptosis

AIMS

S-glutathionylation is a reversible oxidative modification of protein cysteines that plays a critical role in redox signaling. Glutaredoxin-1 (Glrx), a glutathione-specific thioltransferase, removes protein S-glutathionylation. Glrx, though a cytosolic protein, can activate a nuclear protein Sirtuin-1 (SirT1) by removing its S-glutathionylation. Glrx ablation causes metabolic abnormalities and promotes controlled cell death and fibrosis in mice. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme of glycolysis, is sensitive to oxidative modifications and involved in apoptotic signaling via the SirT1/p53 pathway in the nucleus. We aimed to elucidate the extent to which S-glutathionylation of GAPDH and glutaredoxin-1 contribute to GAPDH/SirT1/p53 apoptosis pathway.

RESULTS

Exposure of HEK 293T cells to hydrogen peroxide (H₂O₂) caused rapid S-glutathionylation and nuclear translocation of GAPDH. Nuclear GAPDH peaked 10-15 min after the addition of H₂O₂. Overexpression of Glrx or redox dead mutant GAPDH inhibited S-glutathionylation and nuclear translocation. Nuclear GAPDH formed a protein complex with SirT1 and exchanged S-glutathionylation to SirT1 and inhibited its deacetylase activity. Inactivated SirT1 remained stably bound to acetylated-p53 and initiated apoptotic signaling resulting in cleavage of caspase-3. We observed similar effects in human primary aortic endothelial cells suggesting the GAPDH/SirT1/p53 pathway as a common apoptotic mechanism.

CONCLUSIONS

Abundant GAPDH with its highly reactive-cysteine thiolate may function as a cytoplasmic rheostat to sense oxidative stress. S-glutathionylation of GAPDH may relay the signal to the nucleus where GAPDH trans-glutathionylates nuclear proteins such as SirT1 to initiate apoptosis. Glrx reverses GAPDH S-glutathionylation and prevents its nuclear translocation and cytoplasmic-nuclear redox signaling leading to apoptosis. Our data suggest that trans-glutathionylation is a critical step in apoptotic signaling and a potential mechanism that cytosolic Glrx controls nuclear transcription factors.

Lipid profiles in users of combustible and electronic cigarettes

Electronic cigarette use has especially risen among adolescents and young adults. The aim of this study was to investigate fasting blood glucose and lipid profiles in chronic combustible cigarette and electronic cigarette users. We evaluated participants aged 21 to 45 (n = 525, mean age 31 ± 7 years, 45% women) without established cardiovascular disease or risk factors who were combustible cigarette users (n = 290), electronic cigarette users (n = 131; 65 sole users and 66 dual users), or never users (n = 104). In the first wave of enrollment (2014-2017), electronic cigarette users reported their products as first, second and third generation devices (e-cig users) and were all largely current (i.e., dual) or former (sole) combustible cigarette users, whereas in the second wave of enrollment (2019-2020), electronic cigarette users all reported pod-based device use (pod users) and included more sole users who were never smokers. In multivariable-adjusted analyses comparing to never users, both sole e-cig users and combustible cigarette users had higher glucose and triglycerides and lower high-density lipoprotein (HDL) cholesterol levels. Dual e-cig users showed higher triglycerides and very-low-density lipoprotein cholesterol, and lower HDL cholesterol compared to never users. In contrast, pod users (both sole and dual) had lipid profiles and glucose levels similar to never users. Overall, users of early generation electronic cigarettes display adverse metabolic profiles. In contrast, pod-based electronic cigarette users have similar lipid profiles to never users. Future studies are needed to understand the cumulative effects of electronic cigarette use on cardiometabolic health.

O-GlcNAcylation Mediates Glucose-Induced Alterations in Endothelial Cell Phenotype in Human Diabetes Mellitus

Background Posttranslational protein modification with O-linked N-acetylglucosamine (O-GlcNAc) is linked to high glucose levels in type 2 diabetes mellitus (T2DM) and may alter cellular function. We sought to elucidate the involvement of O-GlcNAc modification in endothelial dysfunction in patients with T2DM. Methods and Results Freshly isolated endothelial cells obtained by J-wire biopsy from a forearm vein of patients with T2DM (n=18) was compared with controls (n=10). Endothelial O-GlcNAc levels were 1.8-ford higher in T2DM patients than in nondiabetic controls (P=0.003). Higher endothelial O-GlcNAc levels correlated with serum fasting blood glucose level (r=0.433, P=0.024) and hemoglobin A1c (r=0.418, P=0.042). In endothelial cells from patients with T2DM, normal glucose conditions (24 hours at 5 mmol/L) lowered O-GlcNAc levels and restored insulin-mediated activation of endothelial nitric oxide synthase, whereas high glucose conditions (30 mmol/L) maintained both O-GlcNAc levels and impaired insulin action. Treatment of endothelial cells with Thiamet G, an O-GlcNAcase inhibitor, increased O-GlcNAc levels and blunted the improvement of insulin-mediated endothelial nitric oxide synthase phosphorylation by glucose normalization. Conclusions Taken together, our findings indicate a role for O-GlcNAc modification in the dynamic, glucose-induced impairment of endothelial nitric oxide synthase activation in endothelial cells from patients with T2DM. O-GlcNAc protein modification may be a treatment target for vascular dysfunction in T2DM.

Alterations in Vascular Function Associated With the Use of Combustible and Electronic Cigarettes

Background Electronic cigarettes (e-cigarettes) have been proposed as a potential harm reduction tool for combustible cigarette smokers. The majority of adult e-cigarette users continue to smoke combustible cigarettes and are considered dual users. The vascular impact of e-cigarettes remains incompletely defined. Methods and Results We examined the association of e-cigarette use with measures of vascular function and tonometry, preclinical measures of cardiovascular injury. As part of the CITU (Cardiovascular Injury due to Tobacco Use) study, we performed noninvasive vascular function testing in individuals without known cardiovascular disease or cardiovascular disease risk factors who were nonsmokers (n=94), users of combustible cigarettes (n=285), users of e-cigarettes (n=36), or dual users (n=52). In unadjusted analyses, measures of arterial stiffness including carotid-femoral pulse wave velocity, augmentation index, carotid-radial pulse wave velocity, and central blood pressures differed across the use groups. In multivariable models adjusted for age, sex, race, and study site, combustible cigarette smokers had higher augmentation index compared with nonusers (129.8±1.5 versus 118.8±2.7, P=0.003). The augmentation index was similar between combustible cigarette smokers compared with sole e-cigarette users (129.8±1.5 versus 126.2±5.9, P=1.0) and dual users (129.8±1.5 versus 134.9±4.0, P=1.0). Endothelial cells from combustible cigarette smokers and sole e-cigarette users produced less nitric oxide in response to A23187 stimulation compared with nonsmokers, suggestive of impaired endothelial nitric oxide synthase signaling. Conclusions Our findings suggest that e-cigarette use is not associated with a more favorable vascular profile. Future longitudinal studies are needed to evaluate the long-term risks of sustained e-cigarette use.

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Background Prior studies have shown that nutrient excess induces endoplasmic reticulum ( ER ) stress in nonvascular tissues from patients with diabetes mellitus ( DM ). ER stress and the subsequent unfolded protein response may be protective, but sustained activation may drive vascular injury. Whether ER stress contributes to endothelial dysfunction in patients with DM remains unknown. Methods and Results To characterize vascular ER stress, we isolated endothelial cells from 42 patients with DM and 37 subjects without DM. Endothelial cells from patients with DM displayed higher levels of ER stress markers compared with controls without DM. Both the early adaptive response, evidenced by higher phosphorylated protein kinase-like ER eukaryotic initiation factor-2a kinase and inositol-requiring ER-to-nucleus signaling protein 1 ( P=0.02, P=0.007, respectively), and the chronic ER stress response evidenced by higher C/ EBP α-homologous protein ( P=0.02), were activated in patients with DM . Higher inositol-requiring ER-to-nucleus signaling protein 1 activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction ( r=0.53, P=0.02). Acute treatment with liraglutide, a glucagon-like peptide 1 receptor agonist, reduced p-inositol-requiring ER-to-nucleus signaling protein 1 ( P=0.01), and the activation of its downstream target c-jun N-terminal kinase ( P=0.025) in endothelial cells from patients with DM . Furthermore, liraglutide restored insulin-stimulated endothelial nitric oxide synthase activation in patients with DM ( P=0.019). Conclusions In summary, our data suggest that ER stress contributes to vascular insulin resistance and endothelial dysfunction in patients with DM . Further, we have demonstrated that liraglutide ameliorates ER stress, decreases c-jun N-terminal kinase activation and restores insulin-mediated endothelial nitric oxide synthase activation in endothelial cells from patients with DM .

Flavorings in Tobacco Products Induce Endothelial Cell Dysfunction

Supplemental Digital Content is available in the text.

Objective—

Use of alternative tobacco products including electronic cigarettes is rapidly rising. The wide variety of flavored tobacco products available is of great appeal to smokers and youth. The flavorings added to tobacco products have been deemed safe for ingestion, but the cardiovascular health effects are unknown. The purpose of this study was to examine the effect of 9 flavors on vascular endothelial cell function.

Approach and Results—

Freshly isolated endothelial cells from participants who use nonmenthol- or menthol-flavored tobacco cigarettes showed impaired A23187-stimulated nitric oxide production compared with endothelial cells from nonsmoking participants. Treatment of endothelial cells isolated from nonsmoking participants with either menthol (0.01 mmol/L) or eugenol (0.01 mmol/L) decreased A23187-stimulated nitric oxide production. To further evaluate the effects of flavoring compounds on endothelial cell phenotype, commercially available human aortic endothelial cells were incubated with vanillin, menthol, cinnamaldehyde, eugenol, dimethylpyrazine, diacetyl, isoamyl acetate, eucalyptol, and acetylpyrazine (0.1–100 mmol/L) for 90 minutes. Cell death, reactive oxygen species production, expression of the proinflammatory marker IL-6 (interleukin-6), and nitric oxide production were measured. Cell death and reactive oxygen species production were induced only at high concentrations unlikely to be achieved in vivo. Lower concentrations of selected flavors (vanillin, menthol, cinnamaldehyde, eugenol, and acetylpyridine) induced both inflammation and impaired A23187-stimulated nitric oxide production consistent with endothelial dysfunction.

Conclusions—

Our data suggest that short-term exposure of endothelial cells to flavoring compounds used in tobacco products have adverse effects on endothelial cell phenotype that may have relevance to cardiovascular toxicity.

Abstract 164: The Effects of Resveratrol Treatment on Vascular Function in Type 2 Diabetes Mellitus

Patients with diabetes mellitus (DM) have abnormal vascular function characterized by premature aging and aortic stiffness. In animal models of metabolic disease, the plant-derived polyphenol, resveratrol, decreases arterial stiffness through SirT1 activation. Therefore, we hypothesized that resveratrol would improve vascular function and activate SirT1 in patients with DM. We performed a randomized, double-blind, placebo-controlled crossover study of resveratrol supplementation in 57 patients with DM (age 56±8 years, female 52%, African-American 67%, BMI 31.7±4.4 kg/m 2 ). Patients consumed resveratrol 100 mg/d for 2 weeks followed by 300 mg/d for 2 weeks or a matched placebo containing no polyphenols with a two-week wash-out period between treatments. In the overall study group, there was a trend toward lower carotid-femoral pulse wave velocity (CFPWV) with resveratrol treatment (P=0.18). In a subset of patients with high arterial stiffness at baseline, resveratrol treatment lowered CFPWV without a change in systemic blood pressure consistent with reduced central aortic stiffness (Figure). Brachial artery flow-mediated dilation, reactive hyperemia, and pulse amplitude tonometry did not change. In a subset of 7 patients, we collected venous endothelial cells by J-wire biopsy and observed a trend toward increased SirT1 activity with resveratrol treatment. Our findings suggest that resveratrol supplementation may reverse arterial stiffening in patients with DM potentially through activation of endothelial SirT1 activity.

Endothelial Nox4-based NADPH oxidase regulates atherosclerosis via soluble epoxide hydrolase

Nox4-based NADPH oxidase is a major reactive oxygen species-generating enzyme in the vasculature, but its role in atherosclerosis remains controversial.

OBJECTIVE

Our goal was to investigate the mechanisms of endothelial Nox4 in regulating atherosclerosis.

APPROACH AND RESULTS

Atherosclerosis-prone conditions (disturbed blood flow, type I diabetes, and Western diet) downregulated endothelial Nox4 mRNA in arteries. To address whether the downregulated endothelial Nox4 was directly involved in the development of atherosclerosis, we generated mice carrying a human Nox4 P437H dominant negative mutation (Nox4DN), driven by the endothelial specific promoter Tie-2, on atherosclerosis-prone genetic background (ApoE deficient mice) to mimic the effect of decreased endothelial Nox4. Nox4DN significantly increased type I diabetes-induced aortic stiffness and atherosclerotic lesions. Gene analysis indicated that soluble epoxide hydrolase 2 (sEH) was significantly upregulated in Nox4DN endothelial cells (EC). Inhibition of sEH activity in Nox4DN EC suppressed inflammation and macrophage adhesion to EC. On the contrary, overexpression of endothelial wild type Nox4 suppressed sEH, ameliorated Western diet-induced atherosclerosis and decreased aortic stiffness.

CONCLUSIONS

Atherosclerosis-prone conditions downregulated endothelial Nox4 to accelerate the progress of atherosclerosis, at least in part, by upregulating sEH to enhance inflammation.

The redox mechanism for vascular barrier dysfunction associated with metabolic disorders: Glutathionylation of Rac1 in endothelial cells

Background

Oxidative stress is implicated in increased vascular permeability associated with metabolic disorders, but the underlying redox mechanism is poorly defined. S-glutathionylation, a stable adduct of glutathione with protein sulfhydryl, is a reversible oxidative modification of protein and is emerging as an important redox signaling paradigm in cardiovascular physiopathology. The present study determines the role of protein S-glutathionylation in metabolic stress-induced endothelial cell permeability.

Methods and results

In endothelial cells isolated from patients with type-2 diabetes mellitus, protein S-glutathionylation level was increased. This change was also observed in aortic endothelium in ApoE deficient (ApoE^-/-) mice fed on Western diet. Metabolic stress-induced protein S-glutathionylation in human aortic endothelial cells (HAEC) was positively correlated with elevated endothelial cell permeability, as reflected by disassembly of cell-cell adherens junctions and cortical actin structures. These impairments were reversed by adenoviral overexpression of a specific de-glutathionylation enzyme, glutaredoxin-1 in cultured HAECs. Consistently, transgenic overexpression of human Glrx-1 in ApoE^-/- mice fed the Western diet attenuated endothelial protein S-glutathionylation, actin cytoskeletal disorganization, and vascular permeability in the aorta. Mechanistically, glutathionylation and inactivation of Rac1, a small RhoGPase, were associated with endothelial hyperpermeability caused by metabolic stress. Glutathionylation of Rac1 on cysteine 81 and 157 located adjacent to guanine nucleotide binding site was required for the metabolic stress to inhibit Rac1 activity and promote endothelial hyperpermeability.

Conclusions

Glutathionylation and inactivation of Rac1 in endothelial cells represent a novel redox mechanism of vascular barrier dysfunction associated with metabolic disorders.

•

In metabolically stressed endothelial cells, protein S-glutathionylation is elevated.

•

glutaredoxin-1 diminishes protein S-glutathionylation and preserves aortic barrier function.

•

Pharmacological inhibition of Rac1 abrogates Glrx1-mediated barrier protection.

•

Glutathionylation of Rac1 is associated with a defect in Rac1 activation status.

Vascular Smooth Muscle Sirtuin-1 Protects Against Diet-Induced Aortic Stiffness

Arterial stiffness, a major cardiovascular risk factor, develops within 2 months in mice fed a high-fat, high-sucrose (HFHS) diet, serving as a model of human metabolic syndrome, and it is associated with activation of proinflammatory and oxidant pathways in vascular smooth muscle (VSM) cells. Sirtuin-1 (SirT1) is an NAD(+)-dependent deacetylase regulated by the cellular metabolic status. Our goal was to study the effects of VSM SirT1 on arterial stiffness in the context of diet-induced metabolic syndrome. Overnight fasting acutely decreased arterial stiffness, measured in vivo by pulse wave velocity, in mice fed HFHS for 2 or 8 months, but not in mice lacking SirT1 in VSM (SMKO). Similarly, VSM-specific genetic SirT1 overexpression (SMTG) prevented pulse wave velocity increases induced by HFHS feeding, during 8 months. Administration of resveratrol or S17834, 2 polyphenolic compounds known to activate SirT1, prevented HFHS-induced arterial stiffness and were mimicked by global SirT1 overexpression (SirT1 bacterial artificial chromosome overexpressor), without evident metabolic improvements. In addition, HFHS-induced pulse wave velocity increases were reversed by 1-week treatment with a specific, small molecule SirT1 activator (SRT1720). These beneficial effects of pharmacological or genetic SirT1 activation, against HFHS-induced arterial stiffness, were associated with a decrease in nuclear factor kappa light chain enhancer of activated B cells (NFκB) activation and vascular cell adhesion molecule (VCAM-1) and p47phox protein expressions, in aorta and VSM cells. In conclusion, VSM SirT1 activation decreases arterial stiffness in the setting of obesity by stimulating anti-inflammatory and antioxidant pathways in the aorta. SirT1 activators may represent a novel therapeutic approach to prevent arterial stiffness and associated cardiovascular complications in overweight/obese individuals with metabolic syndrome.

Abstract 554: Mitochondrial Biomarkers for Assessing Early Tobacco Product Induced Cardiovascular Injury in Human Participants

Smoking is a major cause of preventable cardiovascular deaths worldwide. A number of new and emerging tobacco-related products including electronic(e)-cigarettes have become readily available as tobacco cigarette alternatives and are often marketed as being less harmful despite growing evidence that toxic aldehydes are absorbed into the circulation following use. However, there is insufficient scientific data to develop policy to regulate and evaluate the claims and toxicity of new tobacco-related products. Prior studies suggest that tobacco cigarette smoking induces cardiovascular oxidative stress which may be linked to mitochondrial abnormalities. Mitochondria are key cellular organelles that are sensitive to environmental toxins and are essential for maintaining cardiovascular health. Upon exposure to environmental stressors, mitochondria become damaged characterized by elevated oxidant production which drives further damage and oxidative stress. Hence, measures of mitochondrial function and damage may serve as novel biomarkers of tobacco product induced injury. We measured mitochondrial biomarkers as a detector of early toxicity of tobacco product-induced injury in peripheral blood mononuclear cells (PBMCs) from non-smoking controls, tobacco cigarette smokers, and e-cigarette users. Following antimycin A stimulation, mitochondrial oxidant production was elevated in PBMCs from both tobacco cigarette smokers and e-cigarette users compared to cells from non-smokers (8.5±0.6, 9.8±0.9 vs 7.0±0.4, p=0.03). Additionally, we assessed the mitochondrial oxidant production in vascular tissue from people utilizing novel techniques developed within our laboratory that allow us to study freshly isolated endothelial cells. Early preliminary data in freshly isolated venous endothelial cells from tobacco cigarette smokers suggests that mitochondrial oxidant production is elevated compared to cells from non-smokers (1.47±0.38 vs 0.96±0.1). This further suggests that mitochondrial biomarkers may have enhanced early sensitivity to tobacco product toxicity prior to overt clinical disease. Whether mitochondrial biomarkers relate to measures of vascular function will be the subject of future studies.

Mitochondrial DNA damage and vascular function in patients with diabetes mellitus and atherosclerotic cardiovascular disease

OBJECTIVE

Prior studies demonstrate mitochondrial dysfunction with increased reactive oxygen species generation in peripheral blood mononuclear cells in diabetes mellitus. Oxidative stress-mediated damage to mitochondrial DNA promotes atherosclerosis in animal models. Thus, we evaluated the relation of mitochondrial DNA damage in peripheral blood mononuclear cells s with vascular function in patients with diabetes mellitus and with atherosclerotic cardiovascular disease.

APPROACH AND RESULTS

We assessed non-invasive vascular function and mitochondrial DNA damage in 275 patients (age 57 ± 9 years, 60 % women) with atherosclerotic cardiovascular disease alone (N = 55), diabetes mellitus alone (N = 74), combined atherosclerotic cardiovascular disease and diabetes mellitus (N = 48), and controls age >45 without diabetes mellitus or atherosclerotic cardiovascular disease (N = 98). Mitochondrial DNA damage measured by quantitative PCR in peripheral blood mononuclear cells was higher with clinical atherosclerosis alone (0.55 ± 0.65), diabetes mellitus alone (0.65 ± 1.0), and combined clinical atherosclerosis and diabetes mellitus (0.89 ± 1.32) as compared to control subjects (0.23 ± 0.64, P < 0.0001). In multivariable models adjusting for age, sex, and relevant cardiovascular risk factors, clinical atherosclerosis and diabetes mellitus remained associated with higher mitochondrial DNA damage levels (β = 0.14 ± 0.13, P = 0.04 and β = 0.21 ± 0.13, P = 0.002, respectively). Higher mitochondrial DNA damage was associated with higher baseline pulse amplitude, a measure of arterial pulsatility, but not with flow-mediated dilation or hyperemic response, measures of vasodilator function.

CONCLUSIONS

We found greater mitochondrial DNA damage in patients with diabetes mellitus and clinical atherosclerosis. The association of mitochondrial DNA damage and baseline pulse amplitude may suggest a link between mitochondrial dysfunction and excessive small artery pulsatility with potentially adverse microvascular impact.

Pro-atherogenic role of smooth muscle Nox4-based NADPH oxidase

Nox4-based NADPH oxidase is a major reactive oxygen species-generating enzyme in the vasculature, but its role in atherosclerosis remains controversial.

OBJECTIVE

Our goal was to investigate the role of smooth muscle Nox4 in atherosclerosis.

APPROACH AND RESULTS

Atherosclerosis-prone conditions (disturbed blood flow and Western diet) increased Nox4 mRNA level in smooth muscle of arteries. To address whether upregulated smooth muscle Nox4 under atherosclerosis-prone conditions was directly involved in the development of atherosclerosis, mice carrying a human Nox4 P437H dominant negative mutation (Nox4DN), specifically in smooth muscle, were generated on a FVB/N ApoE deficient genetic background to counter the effect of increased smooth muscle Nox4. Nox4DN significantly decreased aortic stiffness and atherosclerotic lesions, with no effect on blood pressure. Gene analysis indicated that soluble epoxide hydrolase 2 (sEH) was significantly downregulated in Nox4DN smooth muscle cells (SMC), at both mRNA and protein levels. Downregulation of sEH by siRNA decreased SMC proliferation and migration, and suppressed inflammation and macrophage adhesion to SMC.

CONCLUSIONS

Downregulation of smooth muscle Nox4 inhibits atherosclerosis by suppressing sEH, which, at least in part, accounts for inhibition of SMC proliferation, migration and inflammation.

Endothelial Dysfunction in Human Diabetes Is Mediated by Wnt5a-JNK Signaling

OBJECTIVE

Endothelial dysfunction is linked to insulin resistance, inflammatory activation, and increased cardiovascular risk in diabetes mellitus; however, the mechanisms remain incompletely understood. Recent studies have identified proinflammatory signaling of wingless-type family member (Wnt) 5a through c-jun N-terminal kinase (JNK) as a regulator of metabolic dysfunction with potential relevance to vascular function. We sought to gain evidence that increased activation of Wnt5a-JNK signaling contributes to impaired endothelial function in patients with diabetes mellitus.

APPROACH AND RESULTS

We measured flow-mediated dilation of the brachial artery and characterized freshly isolated endothelial cells by protein expression, eNOS activation, and nitric oxide production in 85 subjects with type 2 diabetes mellitus (n=42) and age- and sex-matched nondiabetic controls (n=43) and in human aortic endothelial cells treated with Wnt5a. Endothelial cells from patients with diabetes mellitus displayed 1.3-fold higher Wnt5a levels (P=0.01) along with 1.4-fold higher JNK activation (P<0.01) without a difference in total JNK levels. Higher JNK activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction (r=0.53, P=0.02). Inhibition of Wnt5a and JNK signaling restored insulin and A23187-mediated eNOS activation and improved nitric oxide production in endothelial cells from patients with diabetes mellitus. In endothelial cells from nondiabetic controls, rWnt5a treatment inhibited eNOS activation replicating the diabetic endothelial phenotype. In human aortic endothelial cells, Wnt5a-induced impairment of eNOS activation and nitric oxide production was reversed by Wnt5a and JNK inhibition.

CONCLUSIONS

Our findings demonstrate that noncanonical Wnt5a signaling and JNK activity contribute to vascular insulin resistance and endothelial dysfunction and may represent a novel therapeutic opportunity to protect the vasculature in patients with diabetes mellitus.

Glutathione adducts on sarcoplasmic/endoplasmic reticulum Ca2+ ATPase Cys-674 regulate endothelial cell calcium stores and angiogenic function as well as promote ischemic blood flow recovery

The sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) is key to Ca(2+) homeostasis and is redox-regulated by reversible glutathione (GSH) adducts on the cysteine (C) 674 thiol that stimulate Ca(2+) uptake activity and endothelial cell angiogenic responses in vitro. We found that mouse hind limb muscle ischemia induced S-glutathione adducts on SERCA in both whole muscle tissue and endothelial cells. To determine the role of S-glutathiolation, we used a SERCA 2 C674S heterozygote knock-in (SKI) mouse lacking half the key thiol. Following hind limb ischemia, SKI animals had decreased SERCA S-glutathione adducts and impaired blood flow recovery. We studied SKI microvascular endothelial cells in which total SERCA 2 expression was unchanged. Cultured SKI microvascular endothelial cells showed impaired migration and network formation compared with wild type (WT). Ca(2+) studies showed decreased nitric oxide (·NO)-induced (45)Ca(2+) uptake into the endoplasmic reticulum (ER) of SKI cells, while Fura-2 studies revealed lower Ca(2+) stores and decreased vascular endothelial growth factor (VEGF)- and ·NO-induced Ca(2+) influx. Adenoviral overexpression of calreticulin, an ER Ca(2+) binding protein, increased ionomycin-releasable stores, VEGF-induced Ca(2+) influx and endothelial cell migration. Taken together, these data indicate that the redox-sensitive Cys-674 thiol on SERCA 2 is required for normal endothelial cell Ca(2+) homeostasis and ischemia-induced angiogenic responses, revealing a novel redox control of angiogenesis via Ca(2+) stores.

Nox2 mediates high fat high sucrose diet-induced nitric oxide dysfunction and inflammation in aortic smooth muscle cells

Diet-induced obesity and metabolic syndrome are important contributors to cardiovascular diseases. The decreased nitric oxide (NO) bioactivity in endothelium and the impaired response of smooth muscle cell (SMC) to NO significantly contribute to vascular pathologies, including atherosclerosis and arterial restenosis after angioplasty. Sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) is an important mediator of NO function in both endothelial cells and SMCs, and its irreversible oxidation impairs its stimulation by NO. We used C57BL/6J mice fed a high fat high sucrose diet (HFHSD) to study the role of SMC SERCA in diet-induced obesity and metabolic syndrome. We found that HFHSD upregulated Nox2 based NADPH oxidase, induced inflammation, increased irreversible SERCA oxidation, and suppressed the response of aortic SERCA to NO. Cultured aortic SMCs from mice fed HFHSD showed increased reactive oxygen species production, Nox2 upregulation, irreversible SERCA oxidation, inflammation, and a decreased ability of NO to inhibit SMC migration. Overexpression of wild type SERCA2b or downregulation of Nox2 restored NO-mediated inhibition of migration in SMCs isolated from HFHSD-fed mice. In addition, tumor necrosis factor alpha (TNFα) increased Nox2 which induced SERCA oxidation and inflammation. Taken together, Nox2 induced by HFHSD plays significant roles in controlling SMC responses to NO and TNFα-mediated inflammation, which may contribute to the development of cardiovascular diseases in diet-induced obesity and metabolic syndrome.

Oxidative inhibition of the vascular Na+-K+ pump via NADPH oxidase-dependent β1-subunit glutathionylation: implications for angiotensin II-induced vascular dysfunction

Glutathionylation of the Na(+)-K(+) pump's β1-subunit is a key molecular mechanism of physiological and pathophysiological pump inhibition in cardiac myocytes. Its contribution to Na(+)-K(+) pump regulation in other tissues is unknown, and cannot be assumed given the dependence on specific β-subunit isoform expression and receptor-coupled pathways. As Na(+)-K(+) pump activity is an important determinant of vascular tone through effects on [Ca(2+)]i, we have examined the role of oxidative regulation of the Na(+)-K(+) pump in mediating angiotensin II (Ang II)-induced increases in vascular reactivity. β1-subunit glutathione adducts were present at baseline and increased by exposure to Ang II in rabbit aortic rings, primary rabbit aortic vascular smooth muscle cells (VSMCs), and human arterial segments. In VSMCs, Ang II-induced glutathionylation was associated with marked reduction in Na(+)-K(+)ATPase activity, an effect that was abolished by the NADPH oxidase inhibitory peptide, tat-gp91ds. In aortic segments, Ang II-induced glutathionylation was associated with decreased K(+)-induced vasorelaxation, a validated index of pump activity. Ang II-induced oxidative inhibition of Na(+)-K(+) ATPase and decrease in K(+)-induced relaxation were reversed by preincubation of VSMCs and rings with recombinant FXYD3 protein that is known to facilitate deglutathionylation of β1-subunit. Knock-out of FXYD1 dramatically decreased K(+)-induced relaxation in a mouse model. Attenuation of Ang II signaling in vivo by captopril (8 mg/kg/day for 7 days) decreased superoxide-sensitive DHE levels in the media of rabbit aorta, decreased β1-subunit glutathionylation, and enhanced K(+)-induced vasorelaxation. Ang II inhibits the Na(+)-K(+) pump in VSMCs via NADPH oxidase-dependent glutathionylation of the pump's β1-subunit, and this newly identified signaling pathway may contribute to altered vascular tone. FXYD proteins reduce oxidative inhibition of the Na(+)-K(+) pump and may have an important protective role in the vasculature under conditions of oxidative stress.

Arterial stiffening precedes systolic hypertension in diet-induced obesity

Stiffening of conduit arteries is a risk factor for cardiovascular morbidity. Aortic wall stiffening increases pulsatile hemodynamic forces that are detrimental to the microcirculation in highly perfused organs, such as the heart, brain, and kidney. Arterial stiffness is associated with hypertension but presumed to be due to an adaptive response to increased hemodynamic load. In contrast, a recent clinical study found that stiffness precedes and may contribute to the development of hypertension although the mechanisms underlying hypertension are unknown. Here, we report that in a diet-induced model of obesity, arterial stiffness, measured in vivo, develops within 1 month of the initiation of the diet and precedes the development of hypertension by 5 months. Diet-induced obese mice recapitulate the metabolic syndrome and are characterized by inflammation in visceral fat and aorta. Normalization of the metabolic state by weight loss resulted in return of arterial stiffness and blood pressure to normal. Our findings support the hypothesis that arterial stiffness is a cause rather than a consequence of hypertension.

Abstract 411: Arterial Stiffening Precedes Systolic Hypertension in Diet-induced Obese Mice and Is Reversed by Weight Loss

BACKGROUND. Aortic stiffness (AS) is an independent predictor of cardiovascular events and is associated with hypertension (HTN) in aging and obesity however it is unclear whether HTN causes AS or AS could develop in advance of HTN. C57Bl/6J mice fed a diet rich in fat and sucrose (HFHS) develop obesity mimicking the metabolic syndrome.

AIMS. We sought to determine: 1) whether AS occurs in HFHS-fed mice; 2) the relation between AS and HTN in such a model and 2) whether weight loss could improve AS and HTN in obese mice.

METHODS. Pulse wave velocity (PWV) was measured by ultrasound as an in vivo index of arterial stiffness and confirmed invasively with high-fidelity pressure catheters. Blood pressure was measured by radiotelemetry in conscious mice. Weight loss was achieved by reversing mice to ND after 5 months of HFHS with bi-weekly assessments of metabolic and cardiovascular parameters.

RESULTS. AS developed in HFHS-fed mice within 2 months (PWV from 2.3 ± 0.2 to 4.1 ± 0.5 m/s, n=6, mean ± SEM, p<0.05) and remained elevated up to 8 months (5.1 ± 0.5 m/s, n=10). Systolic and mean arterial pressures were significantly elevated after 6 months of HFHS (SBP: from 119.2 ± 1.8 to 140.4 ± 2.5 mmHg and MAP: from 106.9 ± 1.9 to 123 ± 1.6 mmHg; n=6). Within two months, when AS was fully developed, aortas from HFHS-fed mice had impaired endothelium-dependent relaxation and increased transglutaminase-2 activity, both in vitro indices of reduced NO bioactivity and ∼3-fold upregulation of pro-inflammatory cytokines TNFα, MCP-1 and MIP1α. Diet reversal induced a return to normal weight within 8 weeks accompanied by a 2-fold reduction in fat mass and hyperinsulinemia. PWV was significantly reduced from 5.3 ± 0.7 to 3.4 ± 0.4 m/s after reversal to ND and SBP and MAP were decreased to normal values (from 138.1 ± 3.7 to 124.2 ± 2.7 mmHg and from 121.2 ± 3.9 to 109.5 ± 3.4 mmHg, respectively). Atomic force measurements on aortic rings, an in vitro indicator of structural stiffness of the intima, was increased after HFHS (52 ± 4.8, n=7 vs 24 ± 2.8 kPa in ND, n=10) and significantly decreased after reversal to ND (30 ± 3.7 kPa, n=8).

CONCLUSIONS. In a model of dietary obesity, arterial stiffness precedes the onset of hypertension and is reversed by normalization of the metabolic state achieved by weight loss.

Redox regulation of SERCA2 is required for vascular endothelial growth factor-induced signaling and endothelial cell migration

AIMS

Vascular endothelial growth factor (VEGF) increases angiogenesis by stimulating endothelial cell (EC) migration. VEGF-induced nitric oxide ((•)NO) release from (•)NO synthase plays a critical role, but the proteins and signaling pathways that may be redox-regulated are poorly understood. The aim of this work was to define the role of (•)NO-mediated redox regulation of the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) in VEGF-induced signaling and EC migration.

RESULTS

VEGF-induced EC migration was prevented by the (•)NO synthase inhibitor, N (G)-nitro-L-arginine methyl ester (LNAME). Either VEGF or (•)NO stimulated endoplasmic reticulum (ER) (45)Ca(2+) uptake, a measure of SERCA activity, and knockdown of SERCA2 prevented VEGF-induced EC migration and (45)Ca(2+) uptake. S-glutathione adducts on SERCA2b, identified immunochemically, were increased by VEGF, and were prevented by LNAME or overexpression of glutaredoxin-1 (Glrx-1). Furthermore, VEGF failed to stimulate migration of ECs overexpressing Glrx-1. VEGF or (•)NO increased SERCA S-glutathiolation and stimulated migration of ECs in which wild-type (WT) SERCA2b was overexpressed with an adenovirus, but did neither in those overexpressing a C674S SERCA2b mutant, in which the reactive cysteine-674 was mutated to a serine. Increased EC Ca(2+) influx caused by VEGF or (•)NO was abrogated by overexpression of Glrx-1 or the C674S SERCA2b mutant. ER store-emptying through the ryanodine receptor (RyR) and Ca(2+) entry through Orai1 were also required for VEGF- and (•)NO-induced EC Ca(2+) influx.

INNOVATION AND CONCLUSIONS

These results demonstrate that (•)NO-mediated activation of SERCA2b via S-glutathiolation of cysteine-674 is required for VEGF-induced EC Ca(2+) influx and migration, and establish redox regulation of SERCA2b as a key component in angiogenic signaling.

The polyphenols resveratrol and S17834 prevent the structural and functional sequelae of diet-induced metabolic heart disease in mice

BACKGROUND

Diet-induced obesity is associated with metabolic heart disease characterized by left ventricular hypertrophy and diastolic dysfunction. Polyphenols such as resveratrol and the synthetic flavonoid derivative S17834 exert beneficial systemic and cardiovascular effects in a variety of settings including diabetes mellitus and chronic hemodynamic overload.

METHODS AND RESULTS

We characterized the structural and functional features of a mouse model of diet-induced metabolic syndrome and used the model to test the hypothesis that the polyphenols prevent myocardial hypertrophy and diastolic dysfunction. Male C57BL/6J mice were fed a normal diet or a diet high in fat and sugar (HFHS) with or without concomitant treatment with S17834 or resveratrol for up to 8 months. HFHS diet-fed mice developed progressive left ventricular hypertrophy and diastolic dysfunction with preservation of systolic function in association with myocyte hypertrophy and interstitial fibrosis. In HFHS diet-fed mice, there was increased myocardial oxidative stress with evidence of oxidant-mediated protein modification via tyrosine nitration and 4-OH-2-nonenol adduction. HFHS diet-fed mice also exhibited increases in plasma fasting glucose, insulin, and homeostasis model assessment of insulin resistance indicative of insulin resistance. Treatment with S17834 or resveratrol prevented left ventricular hypertrophy and diastolic dysfunction. For S17834, these beneficial effects were associated with decreases in oxidant-mediated protein modifications and hyperinsulinemia and increased plasma adiponectin.

CONCLUSIONS

Resveratrol and S17834 administered concurrently with a HFHS diet prevent the development of left ventricular hypertrophy, interstitial fibrosis, and diastolic dysfunction. Multiple mechanisms may contribute to the beneficial effects of the polyphenols, including a reduction in myocardial oxidative stress and related protein modifications, amelioration of insulin resistance, and increased plasma adiponectin. The polyphenols resveratrol and S17834 may be of value in the prevention of diet-induced metabolic heart disease.

Upregulation of Nox4 by TGF{beta}1 oxidizes SERCA and inhibits NO in arterial smooth muscle of the prediabetic Zucker rat

RATIONALE

Vascular smooth muscle cell (SMC) migration is an important pathological process in several vascular occlusive diseases, including atherosclerosis and restenosis, both of which are accelerated by diabetes mellitus.

OBJECTIVE

To determine the mechanisms of abnormal vascular SMC migration in type 2 diabetes, the obese Zucker rat (ZO), a model of obesity and insulin resistance, was studied.

METHODS AND RESULTS

In culture, ZO aortic SMCs showed a significant increase in Nox4 mRNA and protein levels compared with the control lean Zucker rat (ZL). The sarco-/endoplasmic reticulum Ca(2+) ATPase (SERCA) nitrotyrosine-294,295 and cysteine-674 (C674)-SO(3)H were increased in ZO SMCs, indicating oxidant stress. Unlike ZL SMC, nitric oxide (NO) failed to inhibit serum-induced SMC migration in ZO. Transfection of Nox4 small interference RNA or overexpression of SERCA2b wild type, but not C674S mutant SERCA, restored the response to NO. Knockdown of Nox4 also decreased SERCA oxidation in ZO SMCs. In addition, transforming growth factor-β1 via Smad2 was necessary and sufficient to upregulate Nox4, oxidize SERCA, and block the antimigratory action of NO in ZO SMCs. Corresponding to the results in cultured SMCs, immunohistochemistry confirmed that Nox4 and SERCA C674-SO(3)H were significantly increased in ZO aorta. After common carotid artery injury, knockdown of Nox4 by adenoviral Nox4 short hairpin RNA decreased Nox4 and SERCA C674-SO(3)H staining and significantly decreased injury-induced neointima.

CONCLUSION

These studies indicate that the upregulation of Nox4 by transforming growth factor-β1 in ZO SMCs is responsible for the impaired response to NO by a mechanism involving the oxidation of SERCA C674. Knockdown of Nox4 inhibits oxidation of SERCA, as well as neointima formation, after ZO common carotid artery injury.

Cysteine-674 of the sarco/endoplasmic reticulum calcium ATPase is required for the inhibition of cell migration by nitric oxide

OBJECTIVES

Nitric oxide inhibits smooth muscle cell migration after arterial injury, but the detailed mechanism is not fully understood. The sarco/endoplasmic reticulum calcium ATPase (SERCA) lowers cell Ca2+ by increasing intracellular Ca2+ uptake and inhibiting extracellular Ca2+ influx. Our previous studies showed that NO causes cyclic GMP-independent arterial relaxation by increasing SERCA activity by inducing reversible S-glutathiolation at cysteine-674. Because Ca2+ is an important second messenger for cell migration, we hypothesized that NO also inhibits cell migration through redox regulation of SERCA activity via cysteine-674.

METHODS AND RESULTS

To test our hypothesis, overexpression of either wild type (WT) or mutant SERCA in which cysteine-674 was mutated to serine was accomplished by stable transfection of HEK 293 or adenoviral expression in rat aortic smooth muscle cells (VSMCs). In the cell models expressing mutant SERCA, biotinylated-iodoacetamide (BIAM) and biotinylated-glutathione labeling of SERCA was decreased, and NO failed to increase SERCA activity or decrease Ca2+ influx, thus validating that the expression of mutant SERCA prevents its redox-dependent activation. In the absence of NO, fetal bovine serum stimulated migration of both cell types expressing WT or C674S SERCA at similar rates. The NO donor S-nitrosopenicillamine inhibited migration of cells with WT SERCA, but had no effect on the migration of either HEK cells or VSMCs with C674S SERCA. The same result was obtained in VSMCs in which endogenous NO was produced by iNOS induced by interleukin (IL)-1beta. Blocking cyclic GMP did not prevent the inhibition of migration by NO.

CONCLUSIONS

In cells overexpressing SERCA, the cyclic GMP-independent, redox regulation of SERCA cysteine-674 is required for the inhibition of cell migration by both exogenous and endogenously generated NO.

The thromboxane A2 receptor antagonist S18886 prevents enhanced atherogenesis caused by diabetes mellitus

BACKGROUND

S18886 is an orally active thromboxane A2 (TXA2) receptor (TP) antagonist in clinical development for use in secondary prevention of thrombotic events in cardiovascular disease. We previously showed that S18886 inhibits atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice by a mechanism independent of platelet-derived TXA2. Atherosclerosis is accelerated by diabetes and is associated with increased TXA(2) and other eicosanoids that stimulate TP. The purpose of this study was to determine whether S18886 lessens the enhanced atherogenesis in diabetic apoE(-/-) mice.

METHODS AND RESULTS

Diabetes mellitus was induced in apoE(-/-) mice with streptozotocin and was treated or not with S18886 (5 mg.kg(-1).d(-1)). After 6 weeks, aortic lesion area was increased >4-fold by diabetes in apoE(-/-) mice, associated with similar increases in serum glucose and cholesterol. S18886 largely prevented the diabetes-related increase in lesion area without affecting the hyperglycemia or hypercholesterolemia. S18886 prevented deterioration of endothelial function and endothelial nitric oxide synthase expression, as well as increases in intimal markers of inflammation associated with diabetes. In human aortic endothelial cells in culture, S18886 also prevented the induction of vascular cell adhesion molecule-1 and prevented the decrease in endothelial nitric oxide synthase expression caused by high glucose.

CONCLUSIONS

The TP antagonist inhibits inflammation and accelerated atherogenesis caused by diabetes, most likely by counteracting effects on endothelial function and adhesion molecule expression of eicosanoids stimulated by the diabetic milieu.

S-Glutathiolation by peroxynitrite activates SERCA during arterial relaxation by nitric oxide

Nitric oxide (NO) physiologically stimulates the sarco/endoplasmic reticulum calcium (Ca(2+)) ATPase (SERCA) to decrease intracellular Ca(2+) concentration and relax cardiac, skeletal and vascular smooth muscle. Here, we show that NO-derived peroxynitrite (ONOO(-)) directly increases SERCA activity by S-glutathiolation and that this modification of SERCA is blocked by irreversible oxidation of the relevant cysteine thiols during atherosclerosis. Purified SERCA was S-glutathiolated by ONOO(-) and the increase in Ca(2+)-uptake activity of SERCA reconstituted in phospholipid vesicles required the presence of glutathione. Mutation of the SERCA-reactive Cys674 to serine abolished these effects. Because superoxide scavengers decreased S-glutathiolation of SERCA and arterial relaxation by NO, ONOO(-) is implicated as the intracellular mediator. NO-dependent relaxation as well as S-glutathiolation and activation of SERCA were decreased by atherosclerosis and Cys674 was found to be oxidized to sulfonic acid. Thus, irreversible oxidation of key thiol(s) in disease impairs NO-induced relaxation by preventing reversible S-glutathiolation and activation of SERCA by NO/ONOO(-).

Reduced sarco/endoplasmic reticulum Ca(2+) uptake activity can account for the reduced response to NO, but not sodium nitroprusside, in hypercholesterolemic rabbit aorta

BACKGROUND

Hypercholesterolemia (HC) impairs acetylcholine-induced relaxation but has little effect on that caused by the NO donor sodium nitroprusside (SNP), suggesting that acetylcholine releases less NO from the endothelium in HC. The relaxation to authentic NO gas, however, is also impaired in HC aortic smooth muscle, indicating an abnormal smooth muscle response. NO relaxes arteries by both cGMP-dependent and -independent mechanisms, and the response involves calcium (Ca(2+)) store refilling via the sarco/endoplasmic reticulum calcium ATPase (SERCA). We studied the involvement of cGMP and SERCA in the smooth muscle response to NO and SNP in HC rabbit aorta.

METHODS AND RESULTS

A selective guanylyl cyclase inhibitor, 1H-[1,2,4]-oxadiazole-[4,3-a]quinoxalin-1-one, eliminated SNP-induced relaxation but only partially blocked NO-induced relaxation in both normal and HC aorta. The residual relaxation to NO was still less in HC and, in both normal and HC aorta, was abolished by concomitant administration of the SERCA inhibitor cyclopiazonic acid (CPA). In contrast, CPA did not affect SNP-induced relaxation in either normal or HC aorta. SERCA activity measured by (45)Ca(2+) uptake was markedly decreased in HC, although SERCA2 protein expression did not change significantly.

CONCLUSIONS

These data suggest that NO-induced relaxation but not that to SNP is partially mediated by cGMP-independent Ca(2+) uptake into sarco/endoplasmic reticulum and that reduced sarco/endoplasmic reticulum Ca(2+) pump function can account for the impaired response to NO in HC.

Properties of a native cation channel activated by Ca2+ store depletion in vascular smooth muscle cells

Depletion of intracellular Ca(2+) stores activates capacitative Ca(2+) influx in smooth muscle cells, but the native store-operated channels that mediate such influx remain unidentified. Recently we demonstrated that calcium influx factor produced by yeast and human platelets with depleted Ca(2+) stores activates small conductance cation channels in excised membrane patches from vascular smooth muscle cells (SMC). Here we characterize these channels in intact cells and present evidence that they belong to the class of store-operated channels, which are activated upon passive depletion of Ca(2+) stores. Application of thapsigargin (TG), an inhibitor of sarco-endoplasmic reticulum Ca(2+) ATPase, to individual SMC activated single 3-pS cation channels in cell-attached membrane patches. Channels remained active when inside-out membrane patches were excised from the cells. Excision of membrane patches from resting SMC did not by itself activate the channels. Loading SMC with BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid), which slowly depletes Ca(2+) stores without a rise in intracellular Ca(2+), activated the same 3-pS channels in cell-attached membrane patches as well as whole cell nonselective cation currents in SMC. TG- and BAPTA-activated 3-pS channels were cation-selective but poorly discriminated among Ca(2+), Sr(2+), Ba(2+), Na(+), K(+), and Cs(+). Open channel probability did not change at negative membrane potentials but increased significantly at high positive potentials. Activation of 3-pS channels did not depend on intracellular Ca(2+) concentration. Neither TG nor a variety of second messengers (including Ca(2+), InsP3, InsP4, GTPgammaS, cyclic AMP, cyclic GMP, ATP, and ADP) activated 3-pS channels in inside-out membrane patches. Thus, 3-pS nonselective cation channels are present and activated by TG or BAPTA-induced depletion of intracellular Ca(2+) stores in intact SMC. These native store-operated cation channels can account for capacitative Ca(2+) influx in SMC and can play an important role in regulation of vascular tone.

Mechanism of nitric oxide-induced vasodilatation: refilling of intracellular stores by sarcoplasmic reticulum Ca2+ ATPase and inhibition of store-operated Ca2+ influx

The precise mechanisms by which nitric oxide (NO) decreases free [Ca2+]i, inhibits Ca2+ influx, and relaxes vascular smooth muscle are poorly understood. In rabbit and mouse aorta, agonist-induced contractions and increases in [Ca2+]i were resistant to nifedipine, suggesting Ca2+ entry through non-L-type Ca2+ channels. Relaxations to NO were inhibited by thapsigargin (TG) or cyclopiazonic acid (CPA) indicating the involvement of sarcoplasmic reticulum ATPase (SERCA). Studies of the effect of NO on [Ca2+]i and the rate of Mn2+ influx with fura-2 fluorometry in rabbit aortic smooth muscle cells in primary culture were designed to test how SERCA is involved in mediating the response to NO. When cells were stimulated with angiotensin II (AII), NO accelerated the removal of Ca2+ from the cytoplasm, decreased [Ca2+]i, and inhibited Ca2+ and Mn2+ influx. Inhibition of SERCA abolished all the effects of NO. In contrast, inhibition of the Na+/Ca2+exchanger or the plasma membrane Ca2+ ATPase had no influence on the ability of NO to decrease [Ca2+]i. NO maximally decreased [Ca2+]i within 5 s, whereas significant inhibition of AII-induced Ca2+ and Mn2+ influx required more than 15 s. The inhibition of cation influx strictly depended on [Ca2+]o and functional SERCA, suggesting that during the delay before NO inhibits Ca2+ influx, the influx of Ca2+ and the uptake into intracellular stores are required. In the absence of [Ca2+]o, NO diminished the AII-induced [Ca2+]i transient by a SERCA-dependent mechanism and increased the amount of Ca2+ in the stores subsequently released by ionomycin. The present study indicates that the initial rapid decrease in [Ca2+]i caused by NO in vascular smooth muscle is accounted for by the uptake of Ca2+ by SERCA into intracellular stores. It is proposed that the refilling of the stores inhibits store-operated Ca2+ influx through non-L-type Ca2+ conducting ion channels and that this maintains the decrease in [Ca2+]i and NO-induced relaxation.

Evidence that additional mechanisms to cyclic GMP mediate the decrease in intracellular calcium and relaxation of rabbit aortic smooth muscle to nitric oxide

1. The role of cyclic GMP in the ability of nitric oxide (NO) to decrease intracellular free calcium concentration [Ca2+]i and divalent cation influx was studied in rabbit aortic smooth muscle cells in primary culture. In cells stimulated with angiotensin II (AII, 10(-1) M), NO (10(-10) - 10(-6) M) increased cyclic GMP levels measured by radioimmunoassay and decreased [Ca2+]i and cation influx as indicated by fura-2 fluorimetry. 2. Zaprinast (10(-4) M), increased NO-stimulated levels of cyclic GMP by 3-20 fold. Although the phosphodiesterase inhibitor lowered the level of [Ca2+]i reached after administration of NO, the initial decreases in [Ca2+]i initiated by NO were not significantly different in magnitude or duration from those that occurred in the absence of zaprinast. 3. The guanylyl cyclase inhibitor, H-(1,2,4) oxadiazolo(4,3-a) quinoxallin-1-one (ODQ, 10(-5) M), blocked cyclic GMP accumulation and activation of protein kinase G, as measured by back phosphorylation of the inositol trisphosphate receptor. ODQ and Rp-8-Br-cyclic GMPS, a protein kinase G inhibitor, decreased the effects of NO, 10(-10) - 10(-8) M, but the decrease in [Ca2+]i or cation influx caused by higher concentrations of NO (10(-7) - 10(-6) M) were unaffected. Relaxation of intact rabbit aorta rings to NO (10(-7) - 10(-5) M) also persisted in the presence of ODQ without a significant increase in cyclic GMP. Rp-8-Br-cyclic GMPS blocked the decreases in cation influx caused by a cell permeable cyclic GMP analog, but ODQ and/or the protein kinase G inhibitor had no significant effect on the decrease caused by NO. 4. Although inhibitors of cyclic GMP, protein kinase G and phosphodiesterase can be shown to affect the decrease in [Ca2+]i and cation influx via protein kinase G, these studies indicate that when these mechanisms are blocked, cyclic GMP-independent mechanisms also contribute significantly to the decrease in [Ca2+]i and smooth muscle relaxation to NO.

Reduced responsiveness of hypercholesterolemic rabbit aortic smooth muscle cells to nitric oxide

The response to nitric oxide of intracellular free Ca2+ levels, measured by fura 2 fluorimetry, and cyclic GMP, measured by RIA, was evaluated on smooth muscle cells of the thoracic aorta in primary culture from normal and cholesterol-fed rabbits. Relaxation to acetylcholine and nitric oxide was also determined in isolated rings of aorta. After 10 weeks of high-cholesterol diet, the intact aorta relaxed less to both acetylcholine and nitric oxide. In cultured cells from hypercholesterolemic rabbits, intracellular Ca2+ oscillated, and the mean Ca2+ levels were approximately twofold greater than in normal aortic cells. Nitric oxide failed to affect basal Ca2+ in either cell type. The peak and sustained rise in intracellular Ca2+ induced by angiotensin II (10(-7) mol/L) were similar in the two cell types. However, nitric oxide (10(-10) to 10(-6) mol/L) decreased the sustained Ca2+ levels to a significantly smaller extent in cells from cholesterol-fed rabbits. In addition, in cells from hypercholesterolemic rabbits, nitric oxide added before angiotensin II inhibited to a smaller degree the transient increase in intracellular free Ca2+ caused by angiotensin II in the nominal absence of extracellular Ca2+, as well as the increase in Ca2+ associated with the addition of extracellular Ca2+. Measurements of fura 2 quenching caused by Mn2+ influx confirmed that nitric oxide inhibited the entry of extracellular divalent cations significantly less in cells from hypercholesterolemic rabbits. Basal levels of cyclic GMP were significantly less than normal, and nitric oxide increased levels of cyclic GMP to a significantly smaller degree in cells from cholesterol-fed rabbits. These data indicate a substantial resistance to nitric oxide action in aortic smooth muscle cells of cholesterol-fed rabbits. This observation is consistent with the notion that resistance of smooth muscle cells to nitric oxide contributes to abnormal endothelium-dependent vasodilation during hypercholesterolemia and can play a role in the pathogenesis of atherosclerosis.

Vasodilatory properties of recombinant maxadilan

Maxadilan is a peptide from the salivary gland of the sand fly Lutzomyia longipalpis, a vector for leishmaniasis. Cutaneous injection of femtomolar quantities of maxadilan produces long-lasting erythema, making it the most potent vasodilator known. Isolated rabbit thoracic and abdominal aorta, carotid artery, and iliac artery demonstrated dose-dependent arterial relaxation in response to maxadilan with a mean effective concentration (EC50) of 2.7 +/- 1.5, 2.1 +/- 0.5, 2.6 +/- 0.4, and 1.9 +/- 0.5 nM, respectively. Maxadilan proved to be at least sevenfold more potent than nitroglycerin in each arterial bed (EC50 = 25 +/- 12, 32 +/- 9, 37 +/- 10, and 22 +/- 13 nM, respectively; P < 0.05 for each vs. maxadilan). Arterial relaxation to maxadilan was independent of endothelium and was equipotent in the thoracic and abdominal aorta, carotid artery, and iliac artery. Arterial relaxation to maxadilan was not inhibited by K(+)-channel antagonists, methylene blue, quinacrine, or ouabain. Maxadilan-mediated arterial relaxation was found to be adenosine 3',5'-cyclic monophosphate (cAMP) dependent, as it was potentiated by the phosphodiesterase inhibitors 3-isobutyl-1-methylxanthine and theophylline, and it was inhibited by the protein kinase A inhibitor H-89. Consistent with this observation, incubation of thoracic aorta with maxadilan (0.1 microM) produced a time-dependent increase in arterial cAMP content coincident with arterial relaxation. Using rabbit aortic smooth muscle cells, we also observed a time-dependent reduction in intracellular calcium in response to maxadilan. Thus these data indicate that maxadilan, a peptide from the sand fly salivary gland, is a potent vasodilator that reduces intracellular calcium through a cAMP-dependent mechanism.

Effect of elevated glucose on cyclic GMP and eicosanoids produced by porcine aortic endothelium

The short-term effects of elevated glucose on cyclic GMP (cGMP) and eicosanoid production in pig aortic endothelial cell monolayers was determined by incubating cells in 5.5 mM or 44 mM glucose for 6 hours. Bradykinin- or A23187-stimulated cGMP production was significantly reduced in cells incubated in 44 mM glucose compared with 5.5 mM glucose. Stimulation of cGMP levels with exogenously added nitric oxide (NO) was also decreased to a similar extent in cells exposed to 44 mM glucose. These data suggest that NO production stimulated by bradykinin or A23187 was unchanged by elevated glucose. Assayed eicosanoids, including 6-ketoprostaglandin (PG) F1 alpha, PGE2 alpha, and 15(S)-hydroxy-(5Z, 8Z, 11Z, 13E)-eicosatetraenoic acid, stimulated by bradykinin or A23187, were increased in cells exposed to 44 mM glucose. These eicosanoid products formed from exogenously added arachidonic acid did not differ between cells incubated in 5.5 mM or 44 mM glucose. Hyperosmolar concentrations of mannose or sucrose had no effect on cGMP levels but did mimic the effect of elevated glucose on eicosanoid production. These data suggest that hyperglycemia in diabetes may interfere with NO-induced guanylate cyclase activation but not NO production in the endothelium and that increased phospholipase activity, secondary to hyperosmolarity, may account for elevated eicosanoid levels.

Aldose reductase inhibition restores endothelial cell function in diabetic rabbit aorta

A possible relationship between increased aldose reductase activity and abnormal endothelium-dependent relaxation was examined in aorta from alloxan-induced diabetic rabbits. Isolated aorta of diabetic rabbits, contracted submaximally with phenylephrine, showed significantly decreased endothelium-dependent relaxations induced by acetylcholine or adenosine diphosphate compared to those from normal rabbits. Basal and acetylcholine-stimulated levels of cyclic GMP and the relaxations in response to an endothelium-independent vasodilator, sodium nitroprusside, were not significantly different between diabetic and normal rabbits, indicating that nitric oxide release and action on the vascular smooth muscle were unchanged. The release of thromboxane A2 from diabetic vessels was increased, as previously demonstrated. Treatment with an aldose reductase inhibitor, zopolrestat, normalized the elevated red blood cell sorbitol levels in diabetic rabbits. Zopolrestat also restored the abnormal acetylcholine- and adenosine diphosphate-induced relaxations of the aorta. The aldose reductase inhibitor had no effect on the levels of cyclic GMP or on the increased release of thromboxane A2 in diabetic aorta. These findings suggest that increased activity of the aldose reductase pathway in hyperglycemia is responsible for the abnormal endothelium-dependent relaxation in diabetic blood vessels. Significant alterations in endothelial production of neither nitric oxide nor vasoconstrictor prostanoids could be directly implicated in the improvement caused by the drug, suggesting another mechanism of action.

Cyclic GMP Modulators on Vascular Adrenergic Neurotransmission

The presence of the endothelium reduced the sensitivity of isolated rabbit carotid artery to endogenous norepinephrine released by electrical stimulation of adrenergic nerves or displaced by tyramine and to exogenously applied norepinephrine, phenylephrine and UK 14304. The maximal contractions induced by the selective alpha 2-agonist UK 14304 were much more profoundly depressed in arteries with endothelium than those induced by the nonselective alpha-adrenoceptor agonist norepinephrine or by the selective alpha 1-agonist. LY 83583, a cyclic-guanosine-monophosphate (GMP)-lowering agent, abolished the endothelium-dependent depression of tone induced by the agonists and converted the sensitivity of arteries with endothelium to that of endothelium-denuded preparations. M & B 22948, a selective cyclic GMP phosphodiesterase inhibitor, significantly inhibited contractions caused by electrical stimulation of adrenergic nerves, tyramine, norepinephrine and UK 14304 in rings with, but not in those without, endothelium. Yohimbine, an alpha 2-adrenoceptor antagonist, increased contractions caused by UK 14304 in rings with endothelium only, but had no significant effect on the contractions caused by exogenously applied norepinephrine or phenylephrine. In the presence of prazosin, an alpha 1-blocker, UK 14304 caused minimal relaxation (about 20%) in rings with endothelium only which were inhibited by yohimbine, suggesting a minor role of direct endothelial cell alpha 2-mediated release of relaxing factors. The over-flow of endogenous norepinephrine caused by electrical stimulation was not affected by treatment with LY 83583 or M & B 22948, suggesting that altering cyclic GMP levels has no major role in prejunctional modulation of norepinephrine release. These findings support the notion that intrinsic levels of cyclic GMP may act as a regulator of adrenergic neurotransmission due primarily to endothelium-derived relaxing factor which is released basally, and to a lesser extent by an activation of endothelial cell alpha 2-adrenoceptors.

Adrenergic denervation in rabbits with diabetes mellitus

The influence of alloxan-induced diabetes mellitus on the sympathetic neuroeffector junction of the rabbit carotid artery denuded of endothelium was studied. Six weeks of diabetes resulted in a neuropathy characterized by a 38% reduction in the arterial content of norepinephrine. Norepinephrine release from the nerves measured from electrically stimulated superfused arterial segments was decreased. The cocaine-sensitive accumulation of [3H]-norepinephrine (NE) was also reduced, reflecting decreased neuronal uptake. The consequences of these prejunctional changes were studied by measuring isometric contractions of arterial rings caused by electrical nerve stimulation or by exogenous norepinephrine. Despite the reduced release of norepinephrine, neurogenic contractions were normal, suggesting an increased sensitivity of the smooth muscle. After neuronal uptake was blocked, the neurogenic contractions of diabetic arteries were less than normal, reflecting the reduction in transmitter release. The sensitivity of diabetic arteries to exogenous norepinephrine was increased under control conditions; maximal contractions were unchanged. Blockade of norepinephrine uptake increased norepinephrine sensitivity more in normal than in diabetic arteries, and there was no longer a significant difference in sensitivity. Thus, under control conditions, neurogenic contractions of the partially denervated diabetic rabbit carotid artery are paradoxically normalized by increased alpha-adrenergic sensitivity of the smooth muscle. The increased sensitivity caused by reduced neuronal uptake can thus preserve neurogenic vasoconstriction and cause supersensitivity to exogenous catecholamines in the sympathetic neuropathy caused by diabetes mellitus.

The endothelium inhibits activation by calcium of vascular neurotransmission

The role of calcium in the inhibition by the endothelium of adrenergic neurotransmission was studied in isolated rabbit carotid artery. Contractions induced by transmural electrical field stimulation (0.5-8 Hz), norepinephrine (10(-8)-3 X 10(-5) M), potassium depolarization (15-30 mM), or by readdition of calcium (0.15-2.4 mM) to a calcium-free medium containing potassium (15 mM) were significantly smaller in rings with compared with rings without endothelium. The voltage-dependent calcium channel activator, BAY K 8644 (10(-6) M), increased contractions to all contractile stimuli in rings with more than in rings without endothelium and thereby abolished the inhibitory influence of the endothelium. The inhibition of neurogenic contractions by the endothelium was also, in part, prejunctional, as indicated by decreased overflow of endogenous norepinephrine from superfused segments with compared with segments without endothelium evoked by electrical stimulation (2 Hz) or by reinfusion of calcium (2.5 mM) to calcium-free medium containing potassium (80 mM). BAY K 8644 (10(-6) M) enhanced the overflow of norepinephrine evoked by electrical stimulation or calcium from segments with more than from segments without endothelium and abolished the difference. Thus the endothelium inhibits activation by extracellular calcium of adrenergic nerves and vascular smooth muscle. The action of the endothelium is overcome by BAY K 8644, suggesting that voltage-dependent calcium channels are important in the inhibitory role of the endothelium in both adrenergic nerves and smooth muscle cells.

Augmented adrenergic contractions of carotid arteries from cholesterol-fed rabbits due to endothelial cell dysfunction

Transmural electrical stimulation was used to elicit frequency-dependent adrenergic neurogenic contractions in isolated carotid arteries from cholesterol-fed and control rabbits. In rings with endothelium, responses to adrenergic nerve stimulation were significantly greater in arteries from cholesterol-fed as compared with those from control rabbits. Responses to adrenergic nerve stimulation of rings without endothelium were not different between the two groups. Methylene blue, a guanylate cyclase inhibitor, increased contractions of rings with endothelium and abolished the difference between the responses of arteries from cholesterol-fed and control rabbits. Methylene blue had no significant effect on arteries without endothelium. The overflow of endogenous norepinephrine (NE) caused by transmural electrical stimulation was not different between segments of arteries from cholesterol-fed and control rabbits. In control rabbits, exogenously applied NE contracted arteries with endothelium less than arteries without endothelium, whereas in cholesterol-fed rabbits the contractions caused by NE were not different between arteries with and without endothelium. Acetylcholine-induced relaxations were not different between rings with endothelium from cholesterol-fed and control rabbits. These results suggest that hypercholesterolemia selectively impairs the inhibitory influence of the endothelium on adrenergic contractions.

Endothelium inhibits norepinephrine release from adrenergic nerves of rabbit carotid artery

The overflow of endogenous norepinephrine caused by transmural electrical stimulation or depolarization with potassium was smaller in superfused segments of the rabbit carotid artery with intact endothelium than in segments denuded of endothelium. In segments preincubated with [3H]norepinephrine, the lesser overflow was found to be partially due to metabolism by the endothelium of the neurotransmitter. Even after treatment to block the disposition of norepinephrine, the endothelium acted as a partial physical barrier to the overflow of norepinephrine into the lumen of arteries superfused and perfused selectively. However, a lesser overflow of norepinephrine to the adventitia of the artery accounted for the majority of the difference in overflow between segments with and without endothelium. The inhibition by the endothelium of the overflow of norepinephrine from adrenergic nerves was unaffected by blocking prejunctional alpha 2-adrenoceptors, prostaglandin synthesis, free radicals, or guanylate cyclase. Vasodilators released from the endothelium of a donor artery inhibited contractions caused by adrenergic nerve stimulation of a bioassay artery but failed to inhibit norepinephrine release. These observations indicate that the endothelium 1) metabolizes norepinephrine, 2) acts as a physical barrier to its overflow into the blood vessel lumen, and 3) inhibits the release of the adrenergic transmitter from adrenergic nerves.

Influence of the endothelium on tone and the response of isolated pig coronary artery to norepinephrine

The influence of the endothelium on smooth muscle tone and the response of the pig right coronary artery to norepinephrine (NE) was studied. Isolated rings of artery with and without endothelium were stretched in the presence of nitroprusside to a tension previously determined to be optimal for contraction. During wash out of the nitroprusside, rings without endothelium spontaneously generated tone representing 24% of the contraction caused by potassium (120 mM); in rings with endothelium no significant spontaneous tone was observed. Relaxations were caused by NE in rings with endothelium contracted with prostaglandin F2 alpha (PGF2 alpha). In rings without endothelium, NE relaxed spontaneously generated tone as well as that produced by PGF2 alpha. Independent of the mode or degree of contraction, rings with endothelium were more sensitive to NE than rings without endothelium. The difference in sensitivity to NE between rings with and without endothelium was likely due to endothelial cell alpha-2 adrenoceptors, inasmuch as the difference was abolished by rauwolscine. In the presence of propranolol and prazosin, endothelium-dependent relaxations were observed which were also inhibited by rauwolscine. Nevertheless, beta adrenoceptors are the predominant mediator of the relaxation to NE of pig coronary smooth muscle, because propranolol caused a greater shift to the right of the relaxation induced by NE compared to that caused by endothelium removal. Accordingly, under resting conditions, NE caused contractions only in the presence of propranolol. These contractions were attenuated by prazosin or rauwolscine, but blocked only by a combination of both alpha adrenoceptor antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Accumulation of 5-hydroxytryptamine leads to dysfunction of adrenergic nerves in canine coronary artery following intimal damage in vivo

Previous in vitro studies have demonstrated that coronary artery adrenergic nerves are a principal site of accumulation of 5-hydroxytryptamine released from aggregating platelets. The purpose of this study was to determine whether 5-hydroxytryptamine is accumulated by adrenergic nerves at sites of endothelial damage and platelet aggregation in vivo. Coronary artery 5-hydroxytryptamine content and response to in vitro adrenergic nerve stimulation were studied in dogs 24 hours following balloon catheter-induced intimal injury. 5-Hydroxytryptamine content was significantly increased in the catheter-damaged arteries, and there was a coincident decrease in the content of norepinephrine. The relaxation caused by acetylcholine was abolished in the catheter-injured arteries, indicating loss of this endothelial cell-mediated function. The normal beta-adrenergic relaxation caused by nerve stimulation was inhibited, and in some cases, contractions resulted; these effects were prevented by serotonergic receptor antagonists. The sensitivity to exogenously added norepinephrine was unchanged, indicating that the changes in the response to nerve stimulation were not due to an altered smooth muscle response to the native neurotransmitter. These observations indicate that following intimal damage, which produces platelet aggregation on the luminal surface of the blood vessel, 5-hydroxytryptamine can assume a transmitter role in coronary artery adrenergic nerves and thereby cause their dysfunction.

Endothelium inhibits responses of rabbit carotid artery to adrenergic nerve stimulation

Transmural electrical stimulation of isolated ring segments of the rabbit carotid artery caused frequency-dependent contractions; these were blocked by tetrodotoxin or prazosin. Mechanical or chemical removal of the endothelium markedly augmented responses to electrical stimulation. Inhibition of norepinephrine uptake and metabolism with cocaine, hydrocortisone, and pargyline increased contractions in rings with endothelium more than those without endothelium, but responses remained greater in rings denuded of endothelium. Methylene blue, an inhibitor of guanylate cyclase, enhanced responses to electrical stimulation of rings with intact endothelium only. Combined inhibition of guanylate cyclase and norepinephrine disposition increased the contractions and abolished the difference between the responses of rings with and without endothelium. In a perfusion-cascade system, the perfusate of donor segments with endothelium relaxed a bioassay ring without endothelium. Electrical stimulation of the segment caused no further relaxation of the bioassay ring. However, contractions caused by electrically stimulating the bioassay ring were depressed during superfusion with the perfusate of segments with, but not without, endothelium, indicating that vasodilators spontaneously released from the endothelium inhibit responses to nerve stimulation. These observations suggest that inhibition by the endothelium of the response to adrenergic nerve stimulation results from 1) spontaneous release of endothelium-derived vasodilators and 2) disposition of norepinephrine by the endothelial cells.