Incubation Of Aorta Research Articles

Deacetylation mimetic of mitochondrial cyclophilin D CypD‐K166R mutant mice are protected from inflammation, oxidative stress, endothelial dysfunction and hypertension

Despite treatment with multiple drugs, a third of hypertensive patients remain hypertensive, therefore, new treatments may improve treatment of hypertension. Hypertension is a multifactorial disorder associated with inflammation, mitochondrial oxidative stress and vascular dysfunction. We have previously reported that depletion or inhibition of Cyclophilin D (CypD), a regulatory subunit of mitochondrial permeability transition pore, improves vascular function and attenuates hypertension. Analysis of human arterioles showed 3-fold increase in CypD acetylation in hypertensive subjects. We hypothesized that hyperacetylation of CypD promotes vascular oxidative stress and hypertension, and deacetylation mimetic CypD-K166R mutation prevents vascular oxidative stress and attenuates hypertension. To test this hypothesis, we used CypD-K166R mutant mice developed in our lab, angiotensin II model of hypertension and ex vivo treatment of aortic tissue with inflammatory cytokines. It was found that angiotensin II-induced hypertension was substantially attenuated in CypD-K166R mice (144 mmHg) compared with wild-type C57B/6J mice (161 mmHg). Furthermore, MitoSOX/HPLC analysis of mitochondrial superoxide in aortas isolated from angiotensin II-infused mice showed 2-fold increase in wild-type mice which was abrogated in CypD-K166R mice. Angiotensin II infusion in wild-type mice significantly impaired endothelial dependent relaxation and reduced the level of endothelial nitric oxide measured by electron spin resonance and NO spin trap. Meanwhile, endothelial dependent relaxation and vascular nitric oxide production were preserved in angiotensin II-infused CypD-K166R mice. Hypertension is linked to inflammation, increased levels of TNFα and IL-17A which promote vascular oxidative stress and end-organ damage. We have tested if CypD-K166R mice are protected from cytokine-induced oxidative stress. Indeed, ex vivo incubation of aorta with the mixture of angiotensin II, TNFα and IL-17A (24 hours) increased mitochondrial superoxide by 2-fold in wild-type tissue which was abolished in CypD-K166R mice. To define molecular mechanisms of mitochondrial protection in CypD-K166R mice we have investigated respiration and calcium-induced swelling in isolated kidney mitochondria. It was found that mitochondria isolated from deacetylation mimetic CypD-K166R mice have improved respiration and diminished swelling with pyruvate and palmitoyl-carnitine as a substrates which promote CypD acetylation in wild-type animals. These data support the pathophysiological role of CypD acetylation in inflammation, oxidative stress and hypertensive end-organ damage. We conclude that targeting CypD acetylation may have therapeutic potential in treatment of vascular dysfunction and hypertension.

P716Role of EDRFs in aortic and mesenteric arterial function of the UC Davis Type 2 Diabetic Mellitus (UCD-T2DM) male rats

Abstract Several studies have shown vascular dysfunction in diabetic rats, however, there is no data on the vascular function of UC Davis type 2 diabetes Mellitus (UCD-T2DM) rats. UCD-T2DM is a novel but validated model of type 2 diabetes (T2D) which more closely resembles the pathophysiology of diabetes in humans. The aim of this study was to determine whether aortic or mesenteric arterial function were altered in UCD-T2DM male rats. Specifically, we determined the responses to endothelium-dependent vasodilator and vasoconstrictor in this model. We also studied the relative contribution of endothelium-derived relaxing factors (EDRFs) in modulating vascular reactivity of aorta or mesenteric artery (MA) in UCD-T2DM male rats. Endothelium-dependent vasodilation (EDV) to acetylcholine (ACh) was measured in rat aorta or MA pre-contracted with phenylephrine (PE). Particularly, EDV to ACh were measured before and after pretreatment with indomethacin (indo, cyclooxygenase inhibitor), ODQ (soluble guanylate cyclase inhibitor), L-NNA (nitric oxide synthase (NOS) inhibitor), TRAM-34 (IKca blocker), or Apamin (SKca blocker). Constrictor response curves to PE were also generated in both aorta and MA. Furthermore, the protein expression of IK channels were determined using Western blotting. We demonstrated that EDV to ACh was impaired in MA, while potentiated in the aortic rings of UCD-T2DM rats. In diabetic MA, the importance of endothelium-derived hyperpolarizing factor (EDHF) in ACh-induced relaxation was decreased, while the contribution of nitric oxide (NO) was enhanced. On the other hand, in diabetic aorta, the relative contribution of EDHF in relaxation responses to ACh was significantly enhanced (as measured by ACh response which was insensitive to indo, ODQ and L-NNA). The incubation of aorta or MA with TRAM-34 blunted the relaxation responses to ACh in both control and diabetic groups. However, the inhibitory effects of TRAM 34 on ACh responses were more prominent in arteries taken from UCD-T2DM groups compared to those in controls. By contrast, ACh responses were not affected following incubation of aorta or MA with Apamin in either control or diabetic groups suggesting that SKca channels plays no role in EDHF-mediated relaxation in either vascular beds. Accordingly, the IKca expression level was significantly higher in aortic rings of diabetic group than in the controls. The responsiveness to PE was significantly enhanced in the aortic rings of diabetic group, whereas in MA, diabetes did not alter the contractile responses to PE. These data suggest that in MA of UCD-T2DM rats, the predisposition to vascular injury may be due to a shift away from EDHF, initially the major vasodilatory factor, toward a greater reliance on NO. However, in aorta, despite elevated contractile responses, ACh responses were enhanced. Increased contribution of NO-independent factors specifically IKca channel plays a role in potentiated responses to ACh in this model. Acknowledgement/Funding NIHLBI

Nitrite treatment downregulates vascular MMP-2 activity and inhibits vascular remodeling in hypertension independently of its antihypertensive effects

Hypertension is associated with cardiovascular remodeling. Given that impaired redox state activates matrix metalloproteinase (MMP)− 2 and promotes vascular remodeling, we hypothesized that nitrite treatment at a non-antihypertensive dose exerts antioxidant effects and attenuates both MMP-2 activation and vascular remodeling of hypertension. We examined the effects of oral sodium nitrite at antihypertensive (15 mg/kg) or non-antihypertensive (1 mg/kg) daily dose in hypertensive rats (two kidney, one clip; 2K1C model). Sham-operated and 2K1C hypertensive rats received vehicle or nitrite by gavage for four weeks. Systolic blood pressure decreased only in hypertensive rats treated with nitrite 15 mg/Kg/day. Both low and high nitrite doses decreased 2K1C-induced vascular remodeling assessed by measuring aortic cross-sectional area, media/lumen ratio, and number of vascular smooth muscle cells/aortic length. Both low and high nitrite doses decreased 2K1C-induced vascular oxidative stress assessed in situ with the fluorescent dye DHE and with the lucigenin chemiluminescence assay. Vascular MMP-2 expression and activity were assessed by gel zymography, Western blot, and in situ zymography increased with hypertension. While MMP-2 levels did not change in response to both doses of nitrite, both doses completely prevented hypertension-induced increases in vascular MMP activity. Moreover, incubation of aortas from hypertensive rats with nitrite at 1–20 μmol/L reduced gelatinolytic activity by 20–30%. This effect was fully inhibited by the xanthine oxidase (XOR) inhibitor febuxostat, suggesting XOR-mediated generation of nitric oxide (NO) from nitrite as a mechanism explaining the responses to nitrite. In vitro incubation of aortic extracts with nitrite 20 μmol/L did not affect MMP-2 activity. These results show that nitrite reverses the vascular structural alterations of hypertension, independently of anti-hypertensive effects. This response is mediated, at least in part, by XOR and is attributable to antioxidant effects of nitrite blunting vascular MMP-2 activation. Our findings suggest nitrite therapy to reverse structural alterations of hypertension.

Irisin improves perivascular adipose tissue dysfunction via regulation of the heme oxygenase-1/adiponectin axis in diet-induced obese mice

AimsTo determine whether irisin could improve perivascular adipose tissue (PVAT) dysfunction via regulation of the heme oxygenase-1 (HO-1)/adiponectin axis in obesity. Materials and methodsC57BL/6 mice were given chow or a high-fat diet (HFD) with or without treatment with irisin. The concentration-dependent responses of the thoracic aorta with or without PVAT (PVAT+ or PVAT−) to phenylephrine were studied in an organ bath. Protein levels of HO-1 and adiponectin were determined by western blot. UCP-1, Cidea, and TNF-α gene expression in PVAT were analyzed by real-time PCR. ResultsTreatment of obese mice with irisin improved glucose and lipid metabolism, reduced plasma levels of TNF-α and malondialdehyde, and increased plasma adiponectin levels (P<0.01). The anti-contractile effects of PVAT were attenuated in HFD mice and this attenuation was restored in HFD mice treated with irisin (P<0.05). Incubation of aortas (PVAT+) with the HO-1 inhibitor and adiponectin receptor blocking peptide in irisin-treated HFD mice abolished the beneficial effects of irisin on PVAT function. The same results were also observed in HFD mice treated with irisin ex vivo. Treatment of HFD mice with irisin significantly enhanced protein levels of HO-1 and adiponectin, and reduced superoxide production and TNF-α expression in PVAT. Irisin treatment enhanced brown adipocyte markers UCP-1 and Cidea expression in PVAT from HFD mice. ConclusionIrisin improved the anti-contractile properties of PVAT from the thoracic aorta in diet-induced obese mice. The mechanism for protective effects of irisin appeared to be related to upregulation of the HO-1/adiponectin axis in PVAT and browning of PVAT.

Binding of EBP50 to Nox organizing subunit p47phox is pivotal to cellular reactive species generation and altered vascular phenotype

Despite numerous reports implicating NADPH oxidases (Nox) in the pathogenesis of many diseases, precise regulation of this family of professional reactive oxygen species (ROS) producers remains unclear. A unique member of this family, Nox1 oxidase, functions as either a canonical or hybrid system using Nox organizing subunit 1 (NoxO1) or p47(phox), respectively, the latter of which is functional in vascular smooth muscle cells (VSMC). In this manuscript, we identify critical requirement of ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50; aka NHERF1) for Nox1 activation and downstream responses. Superoxide (O2 (•-)) production induced by angiotensin II (AngII) was absent in mouse EBP50 KO VSMC vs. WT. Moreover, ex vivo incubation of aortas with AngII showed a significant increase in O2 (•-) in WT but not EBP50 or Nox1 nulls. Similarly, lipopolysaccharide (LPS)-induced oxidative stress was attenuated in femoral arteries from EBP50 KO vs. WT. In silico analyses confirmed by confocal microscopy, immunoprecipitation, proximity ligation assay, FRET, and gain-/loss-of-function mutagenesis revealed binding of EBP50, via its PDZ domains, to a specific motif in p47(phox) Functional studies revealed AngII-induced hypertrophy was absent in EBP50 KOs, and in VSMC overexpressing EBP50, Nox1 gene silencing abolished VSMC hypertrophy. Finally, ex vivo measurement of lumen diameter in mouse resistance arteries exhibited attenuated AngII-induced vasoconstriction in EBP50 KO vs. WT. Taken together, our data identify EBP50 as a previously unidentified regulator of Nox1 and support that it promotes Nox1 activity by binding p47(phox) This interaction is pivotal for agonist-induced smooth muscle ROS, hypertrophy, and vasoconstriction and has implications for ROS-mediated physiological and pathophysiological processes.

Acute and Chronic Biological Effects of Copeptin on Vascular Function in Mice and Humans

BackgroundCopeptin, the 39 amino acid C‐terminal segment of the precursor protein of arginine vasopressin (AVP), is secreted from the posterior pituitary in a 1:1 ratio with AVP in response to osmotic and hemodynamic stimuli. Copeptin is significantly elevated in pregnant women with preeclampsia, and predicts the development of preeclampsia as early as the 6th week of gestation. Preliminary data in a recent prospective study demonstrated that higher copeptin was associated with lower endothelial function (brachial artery flow‐mediated dilation, FMD) during the 2nd trimester in pregnant women at high risk of preeclampsia. However, whether copeptin itself has any independent biological effects on the vasculature is completely unknown.Methods and ResultsChronic incubation of mouse aortic rings with copeptin (n=4 male mice, 1nM, 24 hours) had no effect on endothelium‐ dependent (acetylcholine) or ‐independent (sodium nitroprusside) vasodilatory responses, indicating the lack of effect on endothelial or vascular smooth muscle function. Similarly, circulating copeptin was not associated with brachial artery FMD in non‐pregnant young women (n=11, r= −0.08, P=0.81), postmenopausal women (n=15, r=0.06, P=0.82) or men (n=24, r=0.10, P=0.62). In contrast, acute incubation of aortic rings (n=6 male mice) with copeptin demonstrated a dose response vasodilation beginning at 1nM up to a maximum relaxation at 100nM (43.6 ± 15.5%, p&lt;0.05, n=6). Co‐incubation with the nitric oxide (NO) inhibitor of L‐NG‐Nitroarginine methyl ester (L‐NAME) significantly attenuated the max vasodilatory response to 12.5 ± 0.6%, indicating that the acute vascular response to copeptin is largely NO‐mediated. Incubation of aorta with copeptin (60 min, 0.5nM) caused a significant increase in protein kinase B (AktSer473) phosphorylation (Western blot) vs. control tissue (0.63 ± 0.19 vs 1.27 ± 0.6, p&lt;0.04, n=5) and a trend towards increased phosphorylation of eNOSSer1177 (0.69 ± 0.02 vs 0.91 ± 0.21, p&lt;0.3, n=2).ConclusionsThese data indicate that acute exposure of aorta of mice to high copeptin results in marked NO‐mediated vasodilation. However, chronic exposure to high copeptin does not alter vascular endothelial or smooth muscle function in mice nor is circulating copeptin associated with endothelial function in males or non‐pregnant females. This suggests that adverse vascular effects associated with chronically elevated copeptin concentrations in preeclampsia are more likely a result of the pathophysiological consequences of high AVP rather than copeptin.Support or Funding InformationAPS STRIDE Undergraduate Summer Research Fellowship;AHA 15SFRN23730000;University of Iowa Center for Research by Undergraduates (ICRU); University of Iowa Center for Hypertension Research.

Protective effect of zingerone on increased vascular contractility in diabetic rat aorta

The aim of the present study was to investigate the effect and possible mechanism of action of zingerone, the main constituent of ginger, on vascular reactivity in isolated aorta from diabetic rats. The results show that incubation of aortae with zingerone alleviates the exaggerated vasoconstriction of diabetic aortae to phenylephrine, as well as the impaired relaxatory response to acetylcholine in a concentration-dependent manner. Furthermore, Zingerone directly relax phenylephrine-precontracted aortae. The vasorelaxatory response is significantly attenuated by the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester hydrochloride and the guanylate cyclase inhibitor methylene blue but no effect of either the potassium channels blocker tetraethylammonium chloride, or the cyclooxygenase inhibitor indomethacin was observed. Zingerone had no effect on advanced glycation end product formation as well. In conclusion, zingerone ameliorates enhanced vascular contraction in diabetic aortae which may be mediated by its vasodilator effect through NO– and guanylate cyclase stimulation.

Nucleotide Catabolism on the Surface of Aortic Valve Xenografts; Effects of Different Decellularization Strategies

Extracellular nucleotide metabolism controls thrombosis and inflammation and may affect degeneration and calcification of aortic valve prostheses. We evaluated the effect of different decellularization strategies on enzyme activities involved in extracellular nucleotide metabolism. Porcine valves were tested intact or decellularized either by detergent treatment or hypotonic lysis and nuclease digestion. The rates of ATP hydrolysis, AMP hydrolysis, and adenosine deamination were estimated by incubation of aorta or valve leaflet sections with substrates followed by HPLC analysis. We demonstrated relatively high activities of ecto-enzymes on porcine valve as compared to the aortic wall. Hypotonic lysis/nuclease digestion preserved >80 % of ATP and AMP hydrolytic activity but reduced adenosine deamination to <10 %. Detergent decellularization completely removed (<5 %) all these activities. These results demonstrate high intensity of extracellular nucleotide metabolism on valve surface and indicate that various valve decellularization techniques differently affect ecto-enzyme activities that could be important in the development of improved valve prostheses.

6-Gingerol alleviates exaggerated vasoconstriction in diabetic rat aorta through direct vasodilation and nitric oxide generation.

The aim of the present study is to investigate the effect and potential mechanism of action of 6-gingerol on alterations of vascular reactivity in the isolated aorta from diabetic rats. Male Wistar rats were divided into two experimental groups, control and diabetics. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg kg−1), and the rats were left for 10 weeks to develop vascular complications. The effect of in vitro incubation with 6-gingerol (0.3–3 μM) on the vasoconstrictor response of the isolated diabetic aortae to phenylephrine and the vasodilator response to acetylcholine was examined. Effect of 6-gingerol was also examined on aortae incubated with methylglyoxal as an advanced glycation end product (AGE). To investigate the mechanism of action of 6-gingerol, the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester hydrochloride (100 μM), guanylate cyclase inhibitor methylene blue (5 μM), calcium-activated potassium channel blocker tetraethylammonium chloride (10 mM), and cyclooxygenase inhibitor indomethacin (5 μM) were added 30 minutes before assessing the direct vasorelaxant effect of 6-gingerol. Moreover, in vitro effects of 6-gingerol on NO release and the effect of 6-gingerol on AGE production were examined. Results showed that incubation of aortae with 6-gingerol (0.3–10 μM) alleviated the exaggerated vasoconstriction of diabetic aortae to phenylephrine in a concentration-dependent manner with no significant effect on the impaired relaxatory response to acetylcholine. Similar results were seen in the aortae exposed to methylglyoxal. In addition, 6-gingerol induced a direct vasodilation effect that was significantly inhibited by Nω-nitro-l-arginine methyl ester hydrochloride and methylene blue. Furthermore, 6-gingerol stimulated aortic NO generation but had no effect on AGE formation. In conclusion, 6-gingerol ameliorates enhanced vascular contraction in diabetic aortae, which may be partially attributed to its ability to increase the production of NO and stimulation of cyclic guanosine monophosphate.

Vitamin C prevents the endothelial dysfunction induced by acute ethanol intake.

Investigate the effect of ascorbic acid (vitamin C) on the endothelial dysfunction induced by acute ethanol intake. Ethanol (1g/kg; p.o. gavage) effects were assessed within 30min in male Wistar rats. Ethanol intake decreased the endothelium-dependent relaxation induced by acetylcholine in the rat aorta and treatment with vitamin C (250mg/kg; p.o. gavage, 5days) prevented this response. Ethanol increased superoxide anion (O2(-)) generation and decreased aortic nitrate/nitrite levels and these responses were not prevented by vitamin C. Superoxide dismutase (SOD) and catalase (CAT) activities as well as hydrogen peroxide (H2O2) and reduced glutathione (GSH) levels were not affected by ethanol. RhoA translocation as well as the phosphorylation levels of protein kinase B (Akt), eNOS (Ser(1177) or Thr(495) residues), p38MAPK, SAPK/JNK and ERK1/2 was not affected by ethanol intake. Vitamin C increased SOD activity and phosphorylation of Akt, eNOS (Ser(1177) residue) and p38MAPK in aortas from both control and ethanol-treated rats. Incubation of aortas with tempol prevented ethanol-induced decrease in the relaxation induced by acetylcholine. Ethanol (50mM/1min) increased O2(-) generation in cultured aortic vascular smooth muscle cells (VSMC) and vitamin C did not prevent this response. In endothelial cells, vitamin C prevented the increase on ROS generation and the decrease in the cytosolic NO content induced by ethanol. Our study provides novel evidence that vitamin C prevents the endothelial dysfunction induced by acute ethanol intake by a mechanism that involves reduced ROS generation and increased NO availability in endothelial cells.

Effect of high free fatty acids on the anti-contractile response of perivascular adipose tissue in rat aorta

To determine whether high free fatty acids (FFA) could affect the anti-contractile properties of perivascular adipose tissue (PVAT) in rat aortas. Wistar rats were divided into normal, obesity and fenofibrate groups and fed a normal, high-fat, and high-fat plus fenofibrate diet, respectively. Thoracic aortas with or without PVAT (PVAT+ and PVAT−) were prepared with either intact endothelium (E+) or with endothelium removed (E−). Aortas pre-treated with either 500μmol/L of palmitic acid (PA) or physiological salt solution (PSS), as a control, were used for in vitro study. Concentration-dependent responses of aortas to norepinephrine were measured. The anti-contractile effects of PVAT were attenuated in both obese rats with high FFA levels and in the PA group in the presence of endothelium, but not in the absence of endothelium. The attenuation of the anti-contractile effect was restored by reducing FFA levels in the fenofibrate group (P<0.05). Incubation of aortas (PVAT+ E+) with nitric oxide (NO) synthase inhibitor and tumor necrosis factor-alpha (TNF-α) in the normal group caused attenuation of the anti-contractile effect of PVAT (P<0.05). Incubation of aortas (PVAT+ E+) in the obese and PA groups with a NO donor, anti-TNF-α antibodies or free radical scavengers partially restored the anti-contractile effect of PVAT (P<0.05). Under both acute and chronic conditions, high FFA levels could attenuate the anti-contractile properties of PVAT by an endothelium-dependent rather than an endothelium-independent mechanism, in which inflammation and oxidative stress may play important roles.

Aldose reductase inhibitors zopolrestat and ferulic acid alleviate hypertension associated with diabetes: effect on vascular reactivity

This study investigated the effect of aldose reductase (AR) inhibitors on hypertension in diabetes. Diabetes was induced with streptozotocin, while AR inhibitors zopolrestat and ferulic acid were administered at 2 weeks after streptozotocin treatment and for 6 weeks afterwards. Then, blood pressure (BP) and serum level of glucose were determined. Concentration-response curves for phenylephrine (PE), KCl, and acetylcholine (ACh) were obtained in isolated aorta. In addition, ACh-induced NO and reactive oxygen species (ROS) generation in aorta and histopathology were examined. Compared with the control animals, diabetes increased diastolic and systolic BP. AR inhibitors reduced diastolic BP elevation without affecting the developed hyperglycaemia. Diabetes increased the contractile response of aorta to KCl, and decreased the relaxation response to Ach, while administering AR inhibitors prevented an impaired response to ACh. Incubation of aorta isolated from diabetic animals with AR inhibitors did not affect the impaired relaxation response to ACh. In addition, AR inhibitors negated the impaired Ach-stimulated NO generation seen in aorta isolated from diabetic animals. Furthermore, diabetes was accompanied with marked infiltration of leukocytes in aortic adventitia, endothelial cell pyknosis, and increased ROS formation. AR inhibitors reduced leukocyte infiltration and inhibited endothelial pyknosis and ROS formation. In conclusion, AR inhibitors negate diabetes-evoked hypertension via ameliorating impaired endothelial relaxation and NO production.

Mitochondria‐targeted antioxidant therapy reverses age‐related arterial stiffening

Aging leads to large elastic artery stiffening mediated by increases in superoxide‐dependent oxidative stress and related changes/damage to structural proteins. Mitochondria are a major source of cellular superoxide and may therefore be a therapeutic target for the treatment of arterial stiffening. We studied young (Y: 5 mo, n=5) and old (O: 27–29 mo, n=5) male C57BL6 mice, and O mice treated with the mitochondria targeted antioxidant MitoQ10 (OMQ: 28–29 mo, n=5). Aortic pulse wave velocity (aPWV), an index of arterial stiffness, was higher in O vs. Y mice (485 ± 24 vs. 405 ± 15 cm/s, p&lt;0.05) and was associated with increased aortic superoxide production (electron paramagnetic resonance, O: 7200 ± 1950 vs. Y: 2800 ± 515 AU, p&lt;0.05). O mice also had greater aortic levels of nitrotyrosine (NT), a marker of oxidative stress, and lower levels of manganese (mitochondrial) superoxide dismutase (MnSOD) (western blotting, both p&lt;0.05 vs. Y). MQ treatment (250 μM in water x 3w) normalized aortic stiffening (OMQ: 378 ± 33 cm/s), superoxide production (OMQ: 2835 ± 1131 AU), MnSOD and NT in O mice. MQ also increased expression of complex IV and the mitochondrial biogenesis marker PGC‐1α (both p&lt;0.05 vs. O). Incubation of aortas from Y mice with the mitochondrial superoxide inducer rotenone (0.5 μM, 48h) increased NT by ~300% (p&lt;0.05) and this was inhibited by coincubation with MQ, an effect associated with enhanced MnSOD expression. MQ treatment may be a novel therapy for age‐related stiffening of large elastic arteries by reducing mitochondrial oxidative stress and perhaps increasing mitochondrial biogenesis.NIH AG013038, AG039210

Endothelial nitric oxide synthase enhancer reduces oxidative stress and restores endothelial function in db/db mice

Endothelial dysfunction is caused by reduced nitric oxide (NO) bioavailability and/or over-produced reactive oxygen species (ROS). The present study investigated a vascular benefit of AVE3085, an endothelial nitric oxide synthase (eNOS) enhancer, in preserving endothelial function in diabetic mice and the mechanisms involved. Male db/db and db/m(+) mice were orally administered AVE3085 for 7 days (10 mg kg(-1) day(-1)). Vascular reactivity of arteries was studied via myography under both isometric and isobaric conditions. ROS levels in aortas were determined using dihydroethidium fluorescence dye and electron paramagnetic resonance spin trapping. Chronic treatment with AVE3085 reduced blood pressure, enhanced endothelium-dependent relaxations (EDR) to acetylcholine in aortas, mesenteric, and renal arteries, lowered oxidative stress, and augmented the attenuated flow-dependent dilatation in mesenteric resistance arteries from db/db mice. Incubation of aortas from C57BL/6J mice in high glucose (30 mmol L(-1)) culture medium for 48 h impaired EDR and elevated ROS generation, and these effects were reversed by co-treatment with AVE3085 (1 µmol L(-1)). Benefits of AVE3085 were abolished by the transcription inhibitor actinomycin D, the NOS inhibitor N(G)-nitro-L-arginine methyl ester, and in eNOS(-/-) mice. NO production in primary endothelial cells from mouse aortas was detected with a NO-sensitive fluorescence dye. Protein expression was assayed by western blotting. Treatment with AVE3085 enhanced NO production in endothelial cells and eNOS expression in aortas. AVE3085 ameliorates endothelial dysfunction in db/db mice through increased NO bioavailability, which reduces oxidative stress in the vascular wall. Targeting eNOS and NO production may be a promising approach to combat diabetic vasculopathy.

The vasodilatory effect of a synthetic polymer‐based root canal material on thoracic aorta

To test the hypothesis that, Epiphany, either in its mixed form or as separate components, can alter the vascular reactivity of isolated rat thoracic aorta. The possible mechanism of its vascular action was also investigated. The relaxant effect of the base, the catalyst and mixed Epiphany on isolated rat aortic rings pre-contracted with phenylephrine (PE) was tested. The aortic rings were then incubated with either nitric oxide synthase (NOS) inhibitor, cyclooxygenase (COX) inhibitor or K(+) channel inhibitors; after pre-contraction with PE, relaxations to the various compounds of Epiphany were examined. In another set of experiments, to investigate the Ca(2+)channel antagonistic effect of the Epiphany, the effect of these compounds in Ca(2+)-free solution on extracellular Ca(2+)(CaCl(2))-induced contraction in high-K(+) pre-challenged rings (in K(+)-depolarized rings) was examined to determine whether the direct inhibition of [Ca(2+)] influx increase accounted for the vasodilatory effects of these compounds. For comparison, L-type Ca(2+)channel blocker nifedipine (1 micromol L(-1)), instead of Epiphany compounds, was assayed in adjacent rat aortic rings in parallel. The catalyst and the mixture of Epiphany induced concentration-dependent relaxations. However, the base of Epiphany did not cause relaxation in rat aorta. The relaxation responses were not significantly altered by incubation of aorta with NOS, COX and potassium channel inhibitors. Whilst nifedipine, the catalyst and the mixture of Epiphany inhibited CaCl(2)-induced contractions (P < 0.05), the base of Epiphany did not inhibit CaCl(2)-induced contractions significantly (P > 0.05). Epiphany induced relaxation of rat aorta via a calcium antagonistic effect. Provided that the vasodilatory effect elicited by Epiphany can be reversed by the circulation, its haemorrhagic potential by virtue of permanent vascular dilatation can be ignored.

Hydrogen Sulphide Is Involved in Testosterone Vascular Effect

BackgroundTestosterone (T) induces a rapid relaxation in vascular tissues of different species due to a nongenomic effect of this steroid on vessels. Different mechanisms have been proposed to explain T-induced vasodilatation but the effective mechanism(s) and the mediators involved are still a matter of debate. ObjectivesWe have evaluated if H2S pathway is involved in T vascular effects. Design and settingMale Wistar rats were sacrificed and thoracic aorta was rapidly dissected and cleaned from fat and connective tissue. Rings of 2–3mm length were cut and placed in organ baths filled with oxygenated Krebs solution at 37°C and mounted to isometric force transducers. H2S determination was performed on thoracic aortic rings incubated with T or vehicle and in presence of inhibitors. H2S concentration was calculated against a calibration curve of NaHS (3–250μM). Results were expressed as nmoles/mg protein. MeasurementsVascular reactivity was evaluated by using isometric transducers. H2S determination was performed by using a cystathionine β-synthetase (CBS) and cystathionine γ lyase (CSE) activity assay. CSE and CBS protein levels were assessed by Western blot analysis. Statistical analysis was performed by using two-way ANOVA and unpaired Student's t-test where appropriate. ResultsT significantly increased conversion of L-cysteine to H2S. This effect was significantly reduced by PGG and BCA, two specific inhibitors of CSE. T (10nM–10μM) induced a concentration-dependent vasodilatation of rat aortic rings in vitro that was significantly and concentration-dependent inhibited by PGG, BCA, and glybenclamide. Incubation of aorta with T up to 1h did not change CBS/CSE expression, suggesting that T modulates enzymatic activity. ConclusionsHere we demonstrate that T vasodilator effect involves H2S, a novel gaseous mediator. T modulates H2S levels by increasing the enzymatic conversion of L-cysteine to H2S.

Identification of 15-hydroxy-11,12-epoxyeicosatrienoic acid as a vasoactive 15-lipoxygenase metabolite in rabbit aorta

Arachidonic acid (AA) causes endothelium-dependent smooth muscle hyperpolarizations and relaxations that are mediated by a 15-lipoxygenase-I (15-LO-I) metabolite, 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA). We propose that AA is metabolized sequentially by 15-LO-I and hydroperoxide isomerase to an unidentified hydroxyepoxyeicosatrienoic acid (HEETA), which is hydrolyzed by a soluble epoxide hydrolase (sEH) to 11,12,15-THETA. After incubation of aorta with 14C-labeled AA, metabolites were extracted and the HEETAs were resolved by performing HPLC. Mass spectrometric analyses identified 15-Hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA). Incubation of aortic incubates with methanol and acetic acid trapped the acid-sensitive 15-H-11,12-EETA as methoxydihydroxyeicosatrienoic acids (MDHEs) (367 m/z, M-H). Pretreatment of the aortic tissue with the sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA; 10(-6) M) increased the formation of 15-H-11,12-EETA, measured as MDHEs. Thus 15-H-11,12-EETA is an acid- and sEH-sensitive precursor of 11,12,15-THETA. Aortic homogenates and endothelial cells contain a 57-kDa protein corresponding to the rabbit sEH. In preconstricted aortic rings, AA (10(-7)-10(-4) M) and acetylcholine (10(-9)-10(-6) M) caused concentration-related relaxations that were enhanced by pretreatment with AUDA. These enhanced relaxations were inhibited by increasing extracellular [K(+)] from 4.8 to 20 mM. AA (3 x 10(-6) M) induced cell membrane hyperpolarization (from -31.0 +/- 1 to -46.8 +/- 2 mV) in aortic strips with an intact endothelium, which was enhanced by AUDA. These results indicate that 15-H-11,12-EETA is produced by the aorta, hydrolyzed by sEH to 11,12,15-THETA, and mediates relaxations by membrane hyperpolarization. 15-H-11,12-EETA represents an endothelium-derived hyperpolarizing factor.

Increased Induction of Inducible Nitric Oxide Synthase Expression in Aortae of Type 2 Diabetes Rats

The aim of this study was to determine whether the pathway of inducible NO synthase (iNOS) in blood vessels is changed by type 2 diabetes. Lipopolysaccharide (LPS)-induced nitric oxide (NO) production and expression of iNOS and effects of LPS on phenylephrine-induced contractile force were compared in aortae isolated from Goto-Kakizaki (G-K) diabetes rats and aortae isolated from control Wistar rats. Both LPS-stimulated nitrite generation and iNOS expression levels were significantly higher in aortae from G-K rats than in those from control rats. Phenylephrine-induced contractile force in the presence of LPS was significantly lower in aortae from G-K rats than in those from control rats, while contractile force in the absence of LPS was comparable in the diabetic and control groups. On the other hand, incubation of aortae in high glucose-containing medium did not affect the LPS-stimulated nitrite accumulation and iNOS expression and the phenylephrine-induced contractile force, regardless of the presence of LPS. These results suggest that LPS-induced NO production through the iNOS pathway is increased and subsequent attenuation of contractile force by excess NO is enhanced in arteries of rats with type 2 diabetes.

Vascular effect of extract from mulberry leaves and underlying mechanism

To investigate the vascular activity of extract from mulberry leaves (EML) on rat thoracic aorta and the underlying mechanism. Isolated thoracic rings of Sprague-Dawley rats were mounted on the organ bath and the tension of the vessel was recorded. (1) EML produced a concentration-dependent vasorelaxation of aorta preconstricted by high K(+) (60 mmol/L) or 10(-6) mol/L phenylephrine (PE) in endothelium-intact and endothelium-denuded arteries. (2) EML at EC(50) concentration reduced the calcium dose-response curve. (3) After incubation of aorta with verapamil, EML induced vasocontraction of aorta preconstricted by PE, which was abolished by ruthenium red. The vascular effect of EML is biphasic, the vasorelaxation is greater than the vasocontraction. The vasorelaxation induced by EML may be mediated by inhibition of voltage-and receptor-dependent calcium channels in vascular smooth muscle cells, while the vasocontraction is via activation of ryanodine receptor in endoplasmic reticulum.

Ethanol induced relaxation of rat thoracic aorta at different resting tension and its possible mechanism

The aim of this study was to investigate the vascular effect of ethanol on rat aorta at different resting tension and its underlying mechanism. The tension of the isolated Sprague-Dawley rat thoracic aortic rings perfused with different concentrations of ethanol was measured using organ bath technique. At different resting tension (1.0 – 4.0 g), ethanol (0.1 – 7.0 ‰) caused a concentration-dependent relaxation on endothelium-denuded aortic rings precontracted with KCl (6×10−2 mol/L) or phenylephrine (PE, 10−6 mol/L), and the vasodilating effect was the most potent when the aortic rings was at the resting tension of 3 g. Ethanol inhibited the CaCl2 induced contraction and downward shifted concentration-response curve of endothelium-denuded aortic rings precontracted with KCl or PE. Incubation of aorta with ruthenium red (10−5 mol/L) or heparin (50 mg/L) decreased the vasodilating effect of ethanol. The results indicate that endothelium-independent relaxation induced by ethanol is concerned with the resting tension. This effect of ethanol may be mediated by the inhibition of voltage-dependent and receptor-operated Ca2+ channels in the vascular smooth muscle cells as well as the inhibition of the intracellular ryanodine receptor and IP3 pathway. (Supported by the National Natural Science Foundation for Fostering Talents in Basic Science, No. J0530183)