Acetylcholine-mediated Relaxation Research Articles

Effect of prepubertal caffeine consumption and recovery on adult erectile tissue functions in Wistar rats

The study examines the impact of caffeine consumption during prepubertal development and recovery on the contractile function of the adult corpus cavernosum in Wistar rats. Prepubertal male rats consumed distilled water (vehicle) and caffeine (5 mg/kg). A third group consumed caffeine and was allowed a period of recovery. Cavernosa tissues were excised at adulthood, and their contractile functions in the presence of Ca2+, K+, indomethacin, glibenclamide, methyl blue, L-NAME, and sodium nitroprusside were assessed. K+-induced increase in contraction in the caffeine-treated group was similar to that in the recovery group. Ca2+ ions, however, increased contraction significantly in the caffeine group compared to the recovery group. Acetylcholine-mediated relaxation (%) was significantly higher in the recovery compared to the caffeine treated after incubation with indomethacin and methyl blue. Acetylcholine-mediated relaxation, however, was higher in caffeine as compared to the recovery group after incubation with glibenclamide and L-NAME. Relaxation in the presence of sodium nitroprusside was significantly reduced in recovery than in the caffeine-treated group. Prepubertal caffeine intake had an erectogenic effect on the cavernous tissues in the presence of glibenclamide, nifedipine, and L-NAME. Inhibitors of prostacyclin (indomethacin) and cGMP (methyl blue) militate caffeine-induced relaxation. Effects were reversed after recovery.

Abstract P303: Contribution Of Adrenal Leptin Receptor To The Control Of Aldosterone Synthase Expression And Endothelial Function In Female Mice

While premenopausal women are severally affected by the current obesity epidemic, the mechanisms whereby obesity promotes vascular dysfunction in this population remain ill-defined. We previously demonstrated that the adipokine leptin acts on the adrenal gland to promote aldosterone production and that leptin-mediated aldosterone production impairs endothelial function in female mice only. Herein, we investigated whether these mechanisms are dependent on the presence of leptin receptors (lepR) in adrenal glands. We generated lean female mice exhibiting a selective deficiency in LepR in adrenals (AdKO), and obese mice expressing LepR in adrenal glands (db/ad + ) only. Under baseline conditions, AdKO exhibited no alteration in adrenal CYP11B2, renal renin level, aortic endothelial function (measured by acetylcholine-mediated relaxation), arterial stiffness (pulse wave velocity test, PWV), or metabolic parameters including heart and visceral adipose tissue (VAT) weights, fluid amount, glycemia, and HbA1c. Chronic leptin infusion for a week induced trends towards increases in adrenal CYP11B2 (ΔΔCt 1.10±0.12 vs 2.01±0.51, P=0.077), aldosterone (557±95 vs 918±526 pg/ml, P=0.859), and renin levels in WT. AdKO conferred no protection against any of these changes. Leptin infusion impaired endothelial function in WT (Emax 73.3±3.9 vs 52.8±3.1%, P=0.019), which was exacerbated in AdKO (52.8±3.1 vs 34.3±4.1%, P=0.052). However, leptin infusion did not change PWV in WT (3.93±0.22 vs 4.17±0.32 m/s, P=0.999), but induced a trend towards a decrease in AdKO (4.17±0.32 vs 3.11±0.44 m/s, P=0.228). Restoration of adrenal LepR in db/db mice did not alter CYP11B2 nor aldosterone levels but increased renin (ΔΔCt 1.04±0.11 vs 1.48±0.12, P=0.029), heart weight, VAT weight (5.14±0.29 vs 6.52±0.62 g/g, P=0.052), and HbA1c (5.7±0.2 vs 6.9±0.4 %, P=0.035). Although PWV was worsened in db/ad + (5.40±0.27 vs 6.39±0.49 m/s, P=0.035), db/ad + presented improved relaxation compared to db/db (58.5±5.6 vs 73.0±2.2%, P=0.067), inconsistent with our hypothesis. Collectively these data indicate that adrenal LepR might not directly control adrenal CYP11B2 levels expression but latently contributes to changes in endothelial function and arterial stiffness.

Vascular nitrosative stress in hypertension induced by fetal undernutrition in rats

Fetal undernutrition predisposes to hypertension development. Since nitric oxide (NO) is a key factor in blood pressure control, we aimed to investigate the role of NO alterations in hypertension induced by fetal undernutrition in rats. Male and female offspring from dams exposed to undernutrition during the second half of gestation (MUN) were studied at 21 days (normotensive) and 6 months of age (hypertension developed only in males). In aorta, we analyzed total and phosphorylated endothelial NO synthase (eNOS, p-eNOS), 3-nitrotyrosine (3-NT), and Nrf2 (Western blot). In plasma we assessed l-arginine, asymmetric and symmetric dimethylarginine (ADMA, SDMA; LC–MS/MS), nitrates (NOx, Griess reaction), carbonyl groups, and lipid peroxidation (spectrophotometry). In iliac arteries, we studied superoxide anion production (DHE staining, confocal microscopy) and vasodilatation to acetylcholine (isometric tension). Twenty-one-day-old MUN offspring did not show alterations in vascular e-NOS or 3NT expression, plasma l-Arg/ADMA ratio, or NOx. Compared to control group, 6-month-old MUN rats showed increased aortic expression of p-eNOS/eNOS and 3-NT, being Nrf2 expression lower, elevated plasma l-arginine/ADMA, NOx and carbonyl levels, increased iliac artery DHE staining and reduced acetylcholine-mediated relaxations. These alterations in MUN rats were sex-dependent, affecting males. However, females showed some signs of endothelial dysfunction. We conclude that increased NO production in the context of a pro-oxidative environment, leads to vascular nitrosative damage and dysfunction, which can participate in hypertension development in MUN males. Females show a better adaptation, but signs of endothelial dysfunction, which can explain hypertension in ageing.

Abstract 11644: The Role of Neutrophil Extracellular Traps in Models of Diabetic Vascular Dysfunction

Aim: NETosis is a type of neutrophil cell death that results in the release of pro-inflammatory neutrophil extracellular traps (NETs). While NETs contribute to some diabetes-associated complications such as dysfunctional wound healing, their potential role in diabetic vascular dysfunction has not been studied. To investigate this possibility, we utilized knockout mice ( Elane -/- and Pad4 -/- ) deficient in NETosis through loss of neutrophil elastase and peptidylarginine deiminase 4, respectively. Methods and Results: Akita mice develop hypoinsulinemia and hyperglycemia by 4 weeks of age. Akita mice were crossed separately with Elane -/- and Pad4 -/- mice to generate NETosis-deficient diabetic mice. Endothelium-dependent vasodilation was assessed in the aortae of the following strains by wire myography (n=10-15/group): wild-type (WT), Akita, Akita- Elane -/- , and Akita- Pad4 -/- . By 24 weeks of age, Akita mice demonstrated consistent impairment of acetylcholine-mediated relaxation (Akita E max =54.1% ± 1.8 and WT=80.6% ± 1.8; p<0.0001). As compared with Akita mice, both Akita- Elane -/- mice (E max =75.1% ± 1.7; p<0.0001) and Akita- Pad4 -/- mice (E max =70.2% ± 1.5; p<0.0001) demonstrated superior relaxation. Furthermore, transfer of neutrophils from aged Akita mice into young WT mice rapidly triggered impaired acetylcholine-mediated relaxation (p<0.0001). Prostanoid metabolites were measured in aortae of 24-week-old mice. TXB 2 (a surrogate for TXA 2 ) was 5-fold higher in both intact and denuded aortae of Akita mice as compared with WT mice (p<0.01); Akita- Elane -/- and Akita- Pad4 -/- mice had TXB 2 levels near WT. Interestingly, 15-deoxy-Δ12,14-PGJ 2 (a dehydration product of PGD 2 and potent PPARγ agonist) was upregulated 10-fold (p<0.001) in Akita endothelium, suggesting an attempted compensatory mechanism. Conclusion: Inhibition of NETosis largely prevented the development of vascular dysfunction in diabetic mice. Thromboxane was strongly upregulated in the vessel walls of NETosis-competent diabetic mice suggesting a role for neutrophils in driving the production of this vasoconstrictive and atherogenic prostanoid. NETosis may represent a novel target for prevention of diabetic complications including vascular dysfunction.

Inhibition of Endoplasmic Reticulum Stress Improves Acetylcholine-Mediated Relaxation in the Aorta of Type-2 Diabetic Rats

Endoplasmic reticulum (ER) stress contributes to insulin resistance and macro- and microvascular complications associated with diabetes. This study aimed to evaluate the effect of ER stress inhibition on endothelial function in the aorta of type-2 diabetic rats. Type-2 diabetes was developed in male Sprague–Dawley rats using a high-fat diet and low-dose streptozotocin. Rat aortic tissues were harvested to study endothelial-dependent relaxation. The mechanisms for acetylcholine-mediated relaxation were investigated using pharmacological blockers, Western blotting, oxidative stress, and inflammatory markers. Acetylcholine-mediated relaxation was diminished in the aorta of diabetic rats compared to control rats; supplementation with TUDCA improved relaxation. In the aortas of control and diabetic rats receiving TUDCA, the relaxation was mediated via eNOS/PI3K/Akt, NAD(P)H, and the KATP channel. In diabetic rats, acetylcholine-mediated relaxation involved eNOS/PI3K/Akt and NAD(P)H, but not the KATP channel. The expression of ER stress markers was upregulated in the aorta of diabetic rats and reduced with TUDCA supplementation. The expression of eNOS and Akt were lower in diabetic rats but were upregulated after supplementation with TUDCA. The levels of MDA, IL-6, and SOD activity were higher in the aorta of the diabetic rats compared to control rats. This study demonstrated that endothelial function was impaired in diabetes, however, supplementation with TUDCA improved the function via eNOS/Akt/PI3K, NAD(P)H, and the KATP channel. The improvement of endothelial function was associated with increased expressions of eNOS and Akt. Thus, ER stress plays a crucial role in the impairment of endothelial-dependent relaxation. Mitigating ER stress could be a potential strategy for improving endothelial dysfunction in type-2 diabetes.

Inhibitory Effects of Saururus chinensis Extract on Receptor for Advanced Glycation End-Products-Dependent Inflammation and Diabetes-Induced Dysregulation of Vasodilation

Advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE) are implicated in inflammatory reactions and vascular complications in diabetes. Signaling pathways downstream of RAGE are involved in NF-κB activation. In this study, we examined whether ethanol extracts of Saururus chinensis (Lour.) Baill. (SE) could affect RAGE signaling and vascular relaxation in streptozotocin (STZ)-induced diabetic rats. Treatment with SE inhibited AGEs-modified bovine serum albumin (AGEs-BSA)-elicited activation of NF-κB and could compete with AGEs-BSA binding to RAGE in a dose-dependent manner. Tumor necrosis factor-α (TNF-α) secretion induced by lipopolysaccharide (LPS)—a RAGE ligand—was also reduced by SE treatment in wild-type Ager+/+ mice as well as in cultured peritoneal macrophages from Ager+/+ mice but not in Ager−/− mice. SE administration significantly ameliorated diabetes-related dysregulation of acetylcholine-mediated vascular relaxation in STZ-induced diabetic rats. These results suggest that SE would inhibit RAGE signaling and would be useful for the improvement of vascular endothelial dysfunction in diabetes.

The Effects of Nitric Oxide Synthase Inhibitors in Acetaminophen-Induced Hepatic Injury in Mice

(1) Aim of the Study: In this study, we aimed to evaluate the vascular damage and the effects of nitric oxide synthase (NOS) enzyme inhibitors in hepatic damage caused by high doses of acetaminophen (APAP). (2) Material and methods: Fifty-three Swiss albino male mice were used for this study. Hepatic and thoracic aorta toxicity caused by 2 or 6 h exposures to APAP (300 mg/kg intraperitoneally (i.p.)) were evaluated. The general NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME: 25 mg/kg and 50 mg/kg, i.p.) and the neuronal NOS inhibitor 7-nitroindazole (7-NI: 15 mg/kg, i.p.) were administered one hour before APAP exposure. (3) Results: Significant morphological deteriorations were observed after 6 h of APAP exposure in histopathological examinations of hepatic sections. Pre-treatment with L-NAME (at 50 mg/kg) or 7-NI before a 6 h APAP exposure significantly decreased hepatic toxicity (p < 0.05). Significant increases in ALT levels in 6 h of APAP exposure were decreased by both L-NAME (with the 25 mg/kg but not at 50 mg/kg) and 7-NI pre-treatments. No significant change was observed in the measured nitrate/nitrite levels and total antioxidant status in either serum or liver homogenates. No significant deteriorations were observed during either hematoxylin-eosin or immunohistochemical staining in thoracic aorta sections. In the thoracic artery sections, no statistical difference was found in acetylcholine-mediated relaxation, which may indicate endothelial dysfunction. (4) Conclusions: This study demonstrated that APAP-induced hepatic toxicity, especially neuronal NOS inhibitors, may decrease hepatic toxicity. It was also shown that APAP-induced hepatic toxicity was not accompanied by vascular dysfunction.

Abstract 03: Ablation Of Endothelial Dysfunction Improves Blood Pressure And Fetal Growth Restriction In A Mouse Model Of Preeclampsia-like Hyperleptinemia

Placental ischemia, an initiating event of preeclampsia (PE), increases plasma leptin levels. We recently developed a model of midgestation (gestation day (GD)11-18) leptin infusion mimicking the midgestation rise in leptin levels of PE patients. Our previous work demonstrates that deletion of endothelial mineralocorticoid receptors (ECMR) improves markers of vascular dysfunction in leptin-infused female mice. We hypothesized vascular function improvement with ECMR deletion ablates hypertension and fetal growth restriction in pregnant leptin-infused mice. Pregnant ECMR +/+ (WT) and ECMR -/- (KO) mice were infused with vehicle or leptin by osmotic pump (lep, 0.9mg/kg/day, s.c.) on GD11-18 while implanted with radiotelemeters for conscious blood pressure (BP) measurement and wire myography of thoracic aorta and 2 nd order mesenteric arteries at GD18 (*=P<0.05). Leptin infusion did not decrease maternal weight in any groups. Leptin decreased pup weight (0.86±0.04g WT vs 0.52±0.11 WT+lep*) and placental efficiency (pup/placenta ratio) (9.7±0.7 WT vs 7.9±0.6 WT+lep*) in WT pregnant mice. ECMR deletion prevented leptin-mediated decreases in pup weight (0.91±0.06g KO vs 1.0±0.07 KO+lep) and placental efficiency (9.6±0.5 KO vs 9.4±1.2 KO+lep). Mean arterial pressure (BP) increased in leptin-infused WT (102±3mmHg WT vs 120±12 WT+lep*), but not KO (107±2 KO vs 106±8 KO+lep), mice from GD11-18. Leptin infusion reduced acetylcholine-mediated relaxation in both aorta and mesenteric arteries of WT* and constriction to KCl in mesenteric arteries in WT*, but not KO, pregnant mice (2-way ANOVA, repeated measures). Leptin increased plasma endothelin-1 (ET-1, 1.1±0.3 pg/ml WT vs 4.4±1.8 WT+lep*), placental mRNA expression of prepro-ET-1 (1.9±0.3-fold change from WT*) and ET-1 converting enzyme-1 (1.6±0.3-fold change from WT*) in pregnant WT mice. Leptin infusion also increased adrenal aldosterone-synthase protein (1.4±0.4 WT ratio/β actin vs 3.2±0.3 WT+lep*) and angiotensin II type 1 receptor b (3.5±0.8-fold change from WT*) mRNA in pregnant mice. Collectively, these data indicate that leptin infusion induces hypertension and fetal growth restriction in pregnant mice due to vascular dysfunction and increased ECMR activation in pregnant mice.

Inhibition of HDAC6 Activity Protects Against Endothelial Dysfunction and Atherogenesis in vivo: A Role for HDAC6 Neddylation.

We previously reported that histone deacetylase 6 (HDAC6) has an important role in endothelial cell (EC) function in vitro. However, whether HDAC6 plays a role in atherogenesis in vivo and the mechanism(s) that control HDAC6 activity/expression in response to atherogenic stimuli are unclear. The goals of this study were to determine whether HDAC6 inhibitor tubacin attenuates atherogenesis and to elucidate specific molecular mechanism(s) that regulate endothelial HDAC6 expression/activity. We evaluated whether administration of tubacin attenuated or reversed the endothelial dysfunction and atherosclerosis induced in mice by a single intraperitoneal injection of adeno-associated viruses encoding liver-target PCSK9 gain-of-function mutant followed by a high fat diet (HFD) for 18 weeks. Tubacin significantly blunted PCSK9-induced increases in pulse wave velocity (index of vascular stiffness and overall vascular health) that are also seen in atherogenic mice. Furthermore, tubacin protected vessels from defective vasorelaxation, as evaluated by acetylcholine-mediated relaxation using wire myograph. Plaque burden defined by Oil Red O staining was also found to be significantly less in mice that received tubacin than in those that received PCSK9 alone. Inhibition of the NEDDylation pathway with MLN4924, an inhibitor of NEDD8-activating enzyme 1 (NAE1), significantly increased HDAC6 activity in HAECs. Interestingly, HDAC6 expression remained unchanged. Further, HAECs exposed to the atherogenic stimulus oxidized low-density lipoprotein (OxLDL) exhibited enhanced HDAC6 activity, which was attenuated by pretreatment with MLN4924. The HDAC6 NEDDylation molecular pathway might regulate genes related to endothelial control of vasomotor tone, reactivity, and atherosclerosis. Tubacin may represent a novel pharmacologic intervention for atherogenesis and other vasculopathies.

Protective effects of wheat germ oil against erectile and endothelial dysfunction in streptozotocin-induced diabetic rats.

Our aim was to investigate the protective effect of wheat germ oil (WGO) at different doses on diabetes mellitus (DM)-induced erectile and endothelial dysfunction. Twenty-four male Wistar rats weighing 250-300 g were divided into four groups as; control group treated with saline, DM group, DM group treated with 3 ml/kg WGO (DM + 3WGO group), DM group treated with 6 ml/kg WGO. Type 1 DM was induced by intraperitoneal injection of 60 mg/kg streptozotocin (STZ). STZ-induced diabetic rats received saline, 3 ml/kg WGO, and 6 ml/kg WGO via oral gavage daily for 5 weeks. The density of WGO used was 0.92 g/ml. The protective effect of WGO was evaluated by (i) in vitro vascular function, (ii) in vivo erectile function, and (iii) oxidative stress parameters in both aorta and penile tissue. Acetylcholine-mediated relaxation in the aorta and erectile functions decreased significantly in the DM group (p = 0.018 and p = 0.005). WGO (3 and 6 ml/kg) improved vascular functions in the DM groups (p = 0.001 and p = 0.014). The beneficial effect of WGO on erectile function appeared at higher doses of WGO. However, a higher dose of WGO substantially increased the oxidative stress parameters in both aorta and penile tissue. These findings suggest that the improvement in vascular or erectile function by WGO was not related to antioxidant effects, and new studies are needed to clarify the mechanism.

Endothelial mineralocorticoid receptor deletion ablates leptin‐induced cardiovascular and fetal growth preeclampsia characteristics in pregnant mice

Obesity increases the risk for preeclampsia (PE), a hypertensive syndrome of pregnancy characterized by placental ischemia. Obese PE patients demonstrate increases in plasma leptin levels in midgestation due to increased placental leptin production. We have shown that pregnancy increases endothelial mineralocorticoid receptor (ECMR) expression and that ECMR mediates leptin-induced endothelial dysfunction and hypertension in nonpregnant females. We therefore hypothesized that ECMR deletion protects from the development endothelial dysfunction, hypertension and fetal growth restriction in pregnant leptin-infused mice. Pregnant ECMR+/+ (WT) and ECMR-/- (KO) littermate mice were infused with vehicle or leptin (N=4-6/group) by osmotic minipump (0.9mg/kg/day, s.c.) from GD11-18 and thoracic aortas assessed for vascular function by wire myography. Separate groups (N=1-2/group) were implanted with radiotelemeters for systolic blood pressure (BP) measurement. Leptin decreased pup weight (0.86±0.04g WT vs 0.52±0.11g WT+lep, *P<0.05) and placental efficiency (9.7±0.7 WT vs 7.9±0.6 WT+lep, pup/placenta weight ratio, *P<0.05) indicating fetal growth restriction. ECMRdeletion prevented leptin-mediated decreases in pup weight (0.91±0.06g KO vs 1.0±0.07g KO+lep) and placental efficiency (9.6±0.5 KO vs 9.4±1.2 KO+lep). Preliminary data shows that prior to leptin infusion (GD8-11) all groups demonstrated similar BP and circadian rhythm of BP. Leptin infusion increased BP and ablated circadian rhythm (GD11-18, 114 mmHg WT vs 137 mmHg WT+lep), however, ECMR deletion blunted leptin-induced BP increases (112 KO mmHg vs 120 mmHg KO+lep) and preserved circadian rhythm. Leptin infusion reduced endothelial function (acetylcholine-mediated relaxation) in aortas of WT, but not KO, pregnant mice (2-way ANOVA, repeated measures, *P<0.05). Relaxation to acetylcholine with LNAME showed restoration of endothelial function in KO+lep mice was NO-dependent. In addition, ECMR deletion protected pregnant mice from leptin-induced increases in vascular α1 receptor-mediated constriction (phenylephrine) (*P<0.05). Endothelial-independent relaxation to sodium nitroprusside was similar across all groups. Moreover, ECMR deletion protected from leptin-mediated increases in placental mRNA expression of: sFlt-1 (WT+leptin: 1.2±0.03-fold from WT, *P<0.05, KO+leptin: 1.1±0.1-fold change from KO), HIF1α (WT+leptin: 1.6±0.1-fold, P=0.09, KO+leptin: 1.5±0.2-fold) and galectin 3 (WT+leptin: 3.2±0.5-fold, *P<0.05, KO+leptin: 0.8±0.1-fold). Collectively, these data indicate that ECMR deletion decreases BP, improves vascular function and placental function in association with increased vascular NO bioavailability and fetal growth in an obesity-associated, leptin-infusion model of PE.

Abstract MP40: Hiv Impairs Endothelial Function And Elevates Blood Pressure Via Tnfa Dependent Mechanisms In Male And Female Mice.

HIV is a major health concern with over 37 million individuals worldwide living with HIV. The onset of combination antiretroviral therapy (cART) patients with HIV (PWH) live longer but exhibit accelerated development of cardiovascular disease. Clinical evidence indicates that 35% of PWH exhibit hypertension, however, the etiopathology is still ill-defined. We plan to take advantage of a transgenic mouse model (Tg26) that mimics patients with a repressed virus, to test the hypothesis that viral infection independent of cART induces endothelial dysfunction and hypertension via a TNF-α mediated mechanism. Vascular reactivity was analyzed via wire myography and blood pressure (BP) recorded via radio-telemetry. Results showed that viral infection impaired aorta endothelium-dependent relaxation as reflected by a decrease in acetylcholine-mediated relaxation in both Tg26 mice (P&lt;0.05) which was ameliorated with the NOX 1/4 inhibitor GKT 137831. Smooth muscle cell-dependent relaxation (SNP) and contractility to phenylephrine and KCl remained intact in Tg26 mice. Viral infection increased systolic, diastolic, and mean arterial pressure (MAP: male: WT=112.3±1.3 vs Tg26=121.9±4.0 mmHg/ female: WT=110.6±3.01/ Tg26=120.3±6.9 mmHg) and elevated heart rate (HR) in both sexes (p&lt;0.05). We used atropine, propranolol, and hexamethonium in WT and Tg26 mice to investigate the contribution of the autonomic nervous system to hypertension. HR responses to both atropine (Female: +5.07±2.8% vs. male +4.3±5.4% of baseline) and propranolol (Female: 19.9±6.1% vs. male 12.0±4.3%) revealed no significance or sex differences in WT mice and no effects of viral infection on autonomic control of heart rate in Tg26 mice. BP responses to hexamethonium revealed no effect of sex or viral infection, supporting a limited contribution of the autonomic nervous system to hypertension in Tg26 mice. However, we found that TNFα inhibition with etanercept reduced mean arterial pressure in Tg26 mice to the level of the WT mice (WT=112.3±1.3, Treated=110.1±0.185) and improved endothelial function. These data indicate that HIV infection contributes to cardiovascular disease via inducing endothelial dysfunction and hypertension via NOX and TNFα-dependent mechanisms respectively.

Abstract MP14: Endothelial Mineralocorticoid Receptor Deletion Abrogates Leptin-induced Endothelial Dysfunction And Fetal Growth Restriction In Pregnant Mice

Obesity increases preeclampsia (PE) risk. Plasma leptin levels increase with body weight in women with PE, and in addition, placental ischemia, an initiating event of PE, also increases plasma leptin. Our lab has shown that hyperleptinemia induces endothelial dysfunction and hypertension in female mice via endothelial mineralocorticoid receptor (ECMR) activation and that high progesterone levels of pregnancy increases ECMR expression. We hypothesized that leptin infusion induces PE-like endothelial dysfunction in pregnant mice, which is abrogated by ECMR deletion. Pregnant mice were infused with leptin by miniosmotic pump (0.9mg/kg/day, s.c.) on gestation day (GD) 11-18. Leptin decreased pup wt (0.86±0.04g ECMR +/+ vs 0.52±0.11 ECMR +/+ +leptin, *P&lt;0.05). and increased fetal resorption (3±39% ECMR +/+ vs 42±32 ECMR +/+ +leptin, P=0.09). ECMR deletion rescued pup weight (0.91±0.06g ECMR -/- vs 1.0±0.07 ECMR -/- +leptin) and protected fetal resorptions (2±2% ECMR -/- vs 0±0 ECMR -/- +leptin) in leptin-infused pregnant mice. In association, placental efficiency (pup/placenta ratio) decreased with leptin in ECMR +/+ (9.7±0.7 ECMR +/+ vs 7.9±0.6 ECMR +/+ +leptin, *P&lt;0.05), but not ECMR -/- (9.6±0.5 ECMR -/- vs 9.4±1.2 ECMR -/- +leptin) mice. Leptin infusion reduced endothelial function (acetylcholine-mediated relaxation) in aortas of ECMR +/+ , but not ECMR -/- , pregnant mice (2-way ANOVA, repeated measures, *P&lt;0.05). Relaxation responses to acetylcholine with LNAME showed restoration of endothelial function in ECMR -/- +leptin mice was due to preserved NO bioavailability. No changes in endothelial-independent sodium nitroprusside or contractile responses to phenylephrine, serotonin or KCl were observed. ECMR deletion reduced aorta IL-1β mRNA (0.5±0.1-fold change ECMR +/+ +leptin vs 0.2±0.1-fold change ECMR -/- +leptin, P=0.06) levels and also placental growth factor mRNA (1.0±0.3-fold change ECMR +/+ +leptin vs 01.3±0.1 ECMR -/- +leptin, P=0.05) in placental tissues. Collectively, these data indicate that ECMR deletion protects pregnant mice from adverse fetal growth and demise in association with increasing NO vascular bioavailability, reducing vascular inflammation and improving placental function in a leptin-infused model of PE.

Endothelial Dysfunction Following Enhanced TMEM16A Activity in Human Pulmonary Arteries

Endothelial dysfunction is one of the hallmarks of different vascular diseases, including pulmonary arterial hypertension (PAH). Ion channelome changes have long been connected to vascular remodeling in PAH, yet only recently has the focus shifted towards Ca2+-activated Cl− channels (CaCC). The most prominent member of the CaCC TMEM16A has been shown to contribute to the pathogenesis of idiopathic PAH (IPAH) in pulmonary arterial smooth muscle cells, however its role in the homeostasis of healthy human pulmonary arterial endothelial cells (PAECs) and in the development of endothelial dysfunction remains underrepresented. Here we report enhanced TMEM16A activity in IPAH PAECs by whole-cell patch-clamp recordings. Using adenoviral-mediated TMEM16A increase in healthy primary human PAECs in vitro and in human pulmonary arteries ex vivo, we demonstrate the functional consequences of the augmented TMEM16A activity: alterations of Ca2+ dynamics and eNOS activity as well as decreased NO production, PAECs proliferation, wound healing, tube formation and acetylcholine-mediated relaxation of human pulmonary arteries. We propose that the ERK1/2 pathway is specifically affected by elevated TMEM16A activity, leading to these pathological changes. With this work we introduce increased TMEM16A activity in the cell membrane of human PAECs for the development of endothelial dysfunction in PAH.

Cadmium exposure activates NADPH oxidase, renin–angiotensin system and cyclooxygenase 2 pathways in arteries, inducing hypertension and vascular damage

Exposure to high concentrations of cadmium (Cd), widely used in many industries and found in air, food and contaminated water, is not uncommon. Cd damages the cardiovascular system, but the vascular mechanisms involved are not fully understood. This study investigated the mechanisms involved in cardiovascular damage after exposure to high Cd concentrations. Three-month-old male Wistar rats were treated intraperitoneally for 14 days with distilled water (Untreated group) or 1 mg/kg cadmium chloride (Cd group). We investigated the systolic blood pressure (SBP) and vascular reactivity of mesenteric resistance arteries (MRA) and the aorta by analysing contractile and relaxation responses in the absence and presence of the endothelium; we also evaluated pathways involved in vascular tone regulation. Superoxide anion production, COX-2 protein expression and in situ detection of COX-2, AT-1, and NOX-1 were evaluated. Oxidative status, creatinine level and angiotensin-converting enzyme (ACE) activity in plasma were also evaluated. Fourteen-day exposure to a high Cd concentration induced hypertension associated with vascular dysfunction in MRA and the aorta. In both vessels, there was increased participation of cyclooxygenase 2 (COX2), angiotensin II type 1 (AT1) receptor and NOX1. MRA also presented endothelial dysfunction, denoted by impaired acetylcholine-mediated relaxation. All vascular changes were accompanied by increased reactive oxygen species production and COX2, NOX1 and AT1 receptor expression in vascular tissue. Overall, high Cd concentrations induced cardiovascular damage: hypertension, endothelial dysfunction and vascular damage in conductance and resistance arteries, NADPH oxidase, renin–angiotensin system and COX2 pathway activation.

Impaired Endothelium-Dependent Hyperpolarization Underlies Endothelial Dysfunction during Early Metabolic Challenge: Increased ROS Generation and Possible Interference with NO Function

Endothelial dysfunction is a hallmark of diabetic vasculopathies. Although hyperglycemia is believed to be the culprit causing endothelial damage, the mechanism underlying early endothelial insult in prediabetes remains obscure. We used a nonobese high-calorie (HC)-fed rat model with hyperinsulinemia, hypercholesterolemia, and delayed development of hyperglycemia to unravel this mechanism. Compared with aortic rings from control rats, HC-fed rat rings displayed attenuated acetylcholine-mediated relaxation. While sensitive to nitric oxide synthase (NOS) inhibition, aortic relaxation in HC-rat tissues was not affected by blocking the inward-rectifier potassium (Kir) channels using BaCl2 Although Kir channel expression was reduced in HC-rat aorta, Kir expression, endothelium-dependent relaxation, and the BaCl2-sensitive component improved in HC rats treated with atorvastatin to reduce serum cholesterol. Remarkably, HC tissues demonstrated increased reactive species (ROS) in smooth muscle cells, which was reversed in rats receiving atorvastatin. In vitro ROS reduction, with superoxide dismutase, improved endothelium-dependent relaxation in HC-rat tissues. Significantly, connexin-43 expression increased in HC aortic tissues, possibly allowing ROS movement into the endothelium and reduction of eNOS activity. In this context, gap junction blockade with 18-β-glycyrrhetinic acid reduced vascular tone in HC rat tissues but not in controls. This reduction was sensitive to NOS inhibition and SOD treatment, possibly as an outcome of reduced ROS influence, and emerged in BaCl2-treated control tissues. In conclusion, our results suggest that early metabolic challenge leads to reduced Kir-mediated endothelium-dependent hyperpolarization, increased vascular ROS potentially impairing NO synthesis and highlight these channels as a possible target for early intervention with vascular dysfunction in metabolic disease. SIGNIFICANCE STATEMENT: The present study examines early endothelial dysfunction in metabolic disease. Our results suggest that reduced inward-rectifier potassium channel function underlies a defective endothelium-mediated relaxation possibly through alteration of nitric oxide synthase activity. This study provides a possible mechanism for the augmentation of relatively small changes in one endothelium-mediated relaxation pathway to affect overall endothelial response and highlights the potential role of inward-rectifier potassium channel function as a therapeutic target to treat vascular dysfunction early in the course of metabolic disease.

Abstract 067: Endothelial mTORC1 Signaling Regulates Vascular Function and Mediates Angiotensin II Actions

The mechanistic target of rapamycin complex 1 (mTORC1) serves as an intracellular energy sensor through its downstream signaling components the S6-kinase and the ribosomal S6 protein with recent implications for hypertension. In this study, we tested the hypothesis that endothelial mTORC1 signaling is critical for the regulation of vascular endothelial function. We generated tamoxifen-inducible endothelial-specific Raptor deleted mice (Tek CreERT2 /Raptor F/F ) to disrupt mTORC1 signaling in the endothelium. Tamoxifen-treated wildtype littermates were used as controls. We confirmed endothelial-specific deletion of Raptor by RT-PCR in MACS-sorted endothelial cells. Interestingly, homozygous Raptor deletion cause endothelial dysfunction as indicated by the reduced vasorelaxation of tamoxifen-treated Tek CreERT2 /Raptor F/F mice aortic rings evoked to acetylcholine (Max relax: 34±11 vs 61±7% in controls; p&lt;0.05), but not sodium nitroprusside (Max relax: 82 ±3 vs 84±2%). Restoring mTORC1 signaling in tamoxifen-treated Tek CreERT2 /Raptor F/F aortic rings with an adenoviral S6-kinase constitutively active construct (Ad-S6KCA; 24hrs) rescued the reduction in acetylcholine-mediated relaxation (Max relax: 54±6 vs 31±10% in Ad-GFP; p&lt;0.05), demonstrating that the endothelial dysfunction is Tek CreERT2 /Raptor F/F mice is due to loss of mTORC1 signaling. Notably, aortic rings from heterozygous Tek CreERT2 /Raptor F/+ mice which have intact acetylcholine-induced vasorelaxation responses were protected from angiotensin II (Ang II)-induced endothelial dysfunction. Indeed, incubation of aortic rings from wildtype mice with Ang II (100nM; 24hrs) reduced acetylcholine-mediated vasorelaxation responses (Max relax: 3±8 vs 57±4 % in vehicle group; p&lt;0.05). In contrast, aortic rings of tamoxifen-treated Tek CreERT2 /Raptor F/+ mice were partially protected from the endothelial dysfunction evoked by Ang II (Max relax: 36±9; p&lt;0.05 vs wildtype controls). Our data indicate that endothelial mTORC1 signaling is required for the regulation of endothelial function. Our findings also highlight the importance of mTORC1 signaling in mediating the vascular endothelial effects of Ang II.

Effect of Early and Late Interventions with Dietary Oils on Vascular and Neural Complications in a Type 2 Diabetic Rat Model.

Aims Determine the effect of dietary oils enriched in different mono- or polyunsaturated fatty acids, i.e., olive oil (18 : 1, oleic acid), safflower oil (18 : 2 n-6, linoleic acid), flaxseed oil (18 : 3 n-3, alpha linolenic acid), evening primrose oil (18 : 3 n-6, gamma linolenic acid), or menhaden oil (20:5/22 : 6 n-3 eicosapentaenoic/docosahexaenoic acids), on vascular and neural complications in high-fat-fed low-dose streptozotocin-treated Sprague-Dawley rats, an animal model for late-stage type 2 diabetes. Materials and Methods Rats were fed a high-fat diet (45% kcal as fat primarily derived from lard) for 8 weeks and then treated with a low dose of streptozotocin (30 mg/kg) in order to induce hyperglycemia. After an additional 8 (early intervention) or 20 (late intervention) weeks, the different groups of rats were fed diets with 1/2 of the kcal of fat derived from lard replaced by the different dietary oils. In addition, a control group fed a standard diet (4.25% kcal as fat) and a diabetic group maintained on the high-fat diet were maintained. The treatment period was approximately 16 weeks. The endpoints evaluated included vascular reactivity of epineurial arterioles, motor and sensory nerve conduction velocity, thermal and corneal sensitivity, and innervation of sensory nerves in the cornea and skin. Results Our findings show that menhaden and flaxseed oil provided the greatest benefit for correcting peripheral nerve damage caused by diabetes, whereas enriching the high-fat diet with menhaden oil provided the most benefit to acetylcholine-mediated vascular relaxation of epineurial arterioles of the sciatic nerve. Enriching the diets with fatty acids derived from the other oils provided none to partial improvements. Conclusions These studies imply that long-chain n-6 and n-3 polyunsaturated fatty acids could be an effective treatment for diabetic peripheral neuropathy with n-3 polyunsaturated fatty acids derived from fish oil being the most effective.

Putative Nox2 inhibitors worsen homocysteine-induced impaired acetylcholine-mediated relaxation

Background and aimIncreased homocysteine (Hcy) is associated with coronary artery disease (CAD). Hcy increases reactive oxygen species (ROS) via NADPH oxidases (Nox), reducing acetylcholine-mediated vasorelaxation. We aimed to determine if putative Nox2 inhibitors prevent Hcy-impaired acetylcholine-mediated vasorelaxation. Methods and resultsNew Zealand White rabbit and wild-type (C57BL/6) and Nox2−/− (NOX) mice aortic rings were mounted in organ baths. Rabbit rings were incubated with either apocynin (10 μM), gp91ds-tat (GP, 1 μM) or PhoxI2 (1 μM) and mice rings GP (1 μM) only. Some rabbit rings were incubated with 3 mM Hcy, before pre-contraction, followed by dose–response relaxation to acetylcholine (ACh; 0.01μM-10μM). In rabbit rings treated with Hcy and GP, O2‾ donor pyrogallol (1 μM) or Akt activator SC79 (1 μM) was added 5 min before ACh. Mice rings were used to compare Nox2 deletion to normal acetylcholine-mediated relaxation.In rabbits, Hcy reduced acetylcholine-mediated relaxation vs. control (p < 0.0001). Treatment + Hcy reduced relaxation compared with treatment alone (p < 0.0001). Pyrogallol and SC79 reversed the response of GP + Hcy (p = 0.0001). In mice, Nox2 deletion reduced acetylcholine-mediated vasorelaxation. Rabbit tissue analysis revealed that Hcy reduced eNOS phosphorylation at Thr495 and increased eNOS phosphorylation at Ser1177; no further alteration at Thr495 was observed with GP. In contrast, GP prevented increased phosphorylation at Ser1177. ConclusionsApocynin, GP and PhoxI2 worsens acetylcholine-mediated vascular relaxation in rabbit aorta, which is supported by results from mouse Nox2 deletion data. These inhibitors worsen Hcy-induced vascular dysfunction, suggesting that current putative Nox2 inhibitors might not be useful in treating HHcy.

Impaired flow-mediated vasodilatation in mutated estrogen receptor alpha (ERα) mouse reveals a role of unliganted membrane, but not nuclear, ERα in shear stress-dependent mechanotransduction

Flow-mediated dilation (FMD) of resistance arteries (RAs) plays a key role in tissue perfusion. A reduced FMD is the hallmark of the endothelium dysfunction occurring early in cardiovascular and metabolic disorders. Estrogen therapy improves FMD in diseased conditions without major effect in healthy subjects. Nevertheless, estrogen receptor alpha (ERα) mutation in a man was associated with severe and selective FMD reduction. Thus, we evaluated the role of ERα in FMD in healthy young male mice. FMD was determined in vitro in mesenteric RAs isolated from mice lacking ERα (ERα−/−), the ERα nuclear activation function AF2 (AF2-ERα−/−) or the ERα palmitoylation site (C451A-ERα−/−, inactivation of the membrane effects or ERα), compared to littermate wild-type (WT or+/+) mice. We found that FMD was significantly reduced in ERα−/− compared to ERα+/+ male and female (ovariectomized or not) mice. Exogenous ERα stimulation or blockade did not affect FMD. FMD was not affected in AF2-ERα−/− mice whereas it was significantly decreased in C451A-ERα−/− mice. NO-synthesis blockade with L-NNA strongly reduced FMD in WT and AF2-ERα−/− mice without major effect in ERα-/- and C451A-ERα−/− mice. Acetylcholine-mediated relaxation, not affected by the absence of ERα was similarly reduced by L-NNA in all groups. After ROS reduction in vivo, NO-dependent FMD was equivalent in C451A-ERα−/− and C451A-ERα+/+ mice. Thus, membrane ERα is important for FMD through activation of eNOS activity and reduction of ROS production, possibly in a ligand-independent manner.