Chronic treatment with the cannabinoid 1 antagonist rimonabant altered vasoactive cyclo-oxygenase-derived products on arteries from obese Zucker rats.

To investigate the effect of chronic cannabinoid 1 antagonism on vascular prostanoid production, obese Zucker rats were treated with rimonabant (10 mg/kg per day) during 20 weeks and then vascular and endothelial reactivity were assessed in aortic rings by analyzing response to phenylephrine and acetylcholine. The presence of cyclo-oxygenase-1 and cyclo-oxygenase-2 selective inhibitors (SC-560 and NS-398, respectively) and the enzyme immunoassay revealed lower PGI2 production by aortic rings from obese rats with rimonabant able to restore such response toward levels found in the lean animals. The treatment also reduced TXB2 but did not alter its participation on acetylcholine-induced relaxation as the TP receptor antagonist ICI-192,605 revealed. Those effects were associated with an enhancement of cyclo-oxygenase-2 expression without affecting p38MAPK phosphorylation. Obese rats also exhibited higher nitric oxide plasma concentrations and greater inducible nitric oxide synthase participation on vascular phenylephrine-induced response without changes in inducible nitric oxide synthase protein expression. Although rimonabant reduced such alteration, the values were still higher than those found in lean rats. Finally, rimonabant was also able to reduce tumor necrosis factor-α produced by adipose tissue of obese Zucker rats. These results highlight a crosstalk among cannabinoids and cyclo-oxygenase-derived products in the vasculature of obese animals.

Effects of chronic treatment with the CB1 antagonist, rimonabant on the blood pressure, and vascular reactivity of obese Zucker rats.

Rimonabant (RM) is a cannabinoid CB1 receptor antagonist useful in the treatment of obesity associated cardiovascular risk factors. Since cannabinoids are vasoactive compounds, the aim of this study is to evaluate the effect of chronic treatment with RM on systolic blood pressure (SBP), and endothelial and vascular reactivity. Obese Zucker rats (OZRs) and their lean counterparts were orally treated during 20 weeks with either RM (10 mg/kg/day). Endothelial and vascular function was assessed in aorta and small mesenteric arteries (SMAs) by concentration response curves to acetylcholine (ACh) and phenylephrine (Phe), respectively. Participation of nitric oxide (NO) was evaluated by incubation with the NO synthase (NOS) inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME) and cyclooxygenase (COX)-derived products involvement was analyzed by incubation with indomethacin (INDO). Plasma lipid profile, insulin and adiponectin were also analyzed. Sympathetic activity was evaluated by urinary excretion of noradrenaline. As expected, RM decreased body weight gain and enhanced adiponectin concentration. Insulin resistance and sympathetic activity were also decreased. The increase in SBP observed in OZRs was reduced by treatment with RM. Aortae and SMAs from OZRs exhibited lower contractile response to Phe, being this effect prevented by RM administration. Although ACh-induced response and NO participation remained unaltered with obesity, enhanced COX-derived constrictor products were found in OZRs. RM treatment neither altered endothelium-dependent relaxation nor L-NAME-sensitive component of the response. Nevertheless, it was able to regulate COX-derived vasoactive products participation. Those effects may contribute to explain some of the cardiovascular protective actions elicited by this drug.

Effects of HMG-CoA reductase inhibition by simvastatin on vascular dysfunction induced by lipopolysaccharide in rats.

AIMS: Statins have been identified as a potentially interesting treatment against sepsis. Here, we study the vascular reactivity of aortae from rats treated with lipopolysaccharide (LPS), 4 mg . kg(-1), following chronic administration of simvastatin (SV) 10 mg . kg(-1). METHODS: The rats were treated with either vehicle or SV for 4 weeks before administration of LPS. After 18 h, the systolic blood pressure (SBP) was measured using a tail cuff and vascular and endothelial responses of aortic rings to several agonists were studied in an organ bath. RESULTS: LPS injection decreased the SBP by 38 mm Hg and vascular response to phenylephrine (Phe) by 60%. Plasma nitrates and nitrites (NO(x)) were 3-fold higher after LPS. This attenuated response to Phe was prevented by incubation with either the inducible-nitric-oxide-synthase (iNOS)-selective inhibitor 1400W or the endothelial nitric oxide synthase (eNOS)/iNOS nonselective blocker L-NAME. The presence of endothelium did not alter these findings. Administering LPS to SV-treated rats also decreased the SBP and increased the NO(x) concentration. The impaired response to Phe was restored by blocking NO synthesis in endothelium-denuded but not in intact aortic rings. The response to acetylcholine demonstrated an enhanced reduction in arteries from the SV + LPS group compared with the LPS group. The inhibition of iNOS prevented acetylcholine-induced relaxation in rings from LPS-treated rats but not in those from the SV + LPS group. CONCLUSION: These results suggest that statins may reduce iNOS-mediated NO production in endothelial but not in vascular smooth-muscle cells.

l-carnitine and its propionate: improvement of endothelial function in SHR through superoxide dismutase-dependent mechanisms.

To clarify the mechanism underlying the antioxidant properties of l-carnitine (LC) and propionyl-l-carnitine (PLC) on spontaneously hypertensive (SHR) and normotensive WKY, animals were treated with either PLC or LC (200 mg kg(- 1)). Aorta was dissected and contraction to (R)-( - )-phenylephrine (Phe) and relaxation to carbachol (CCh) were assessed in the presence or not of the NO synthase (NOS) inhibitor, l-NAME. [image omitted] production was evaluated by lucigenin-enhanced chemiluminescence and its participation on relaxation was observed after incubation with superoxide dismutase (SOD) plus catalase. Protein expressions of eNOS, Cu/Zn-SOD and Mn-SOD were studied by western blot. Both LC and PLC treatments improved endothelial function of SHR through increasing NO participation and decreasing [image omitted] probably involving higher Cu/Zn-SOD expression. PLC treatment augmented eNOS expression in SHR. Surprisingly, LC increased [image omitted] produced by aorta from WKY and thus diminished NO and damaged endothelial function. Conversely, PLC did not affect CCh-induced relaxation in WKY. These results demonstrate that LC and PLC prevent endothelial dysfunction in SHR through an antioxidant effect.

Vasorelaxant effects of harmine and harmaline extracted from Peganum harmala L. seeds in isolated rat aorta.

The present work describes the mechanisms involved in the vasorelaxant effect of harmine and harmaline. These alkaloids induce in a dose-dependent manner the relaxation in the aorta precontracted with noradrenaline or KCl. However, the removal of endothelium or pre-treatment of intact aortic ring with L-NAME (inhibitor of NOSe synthetase) or with indomethacin (non-specific inhibitor of cyclo-oxygenase), reduces significantly the vasorelaxant response of harmaline but not harmine. According to their IC50 values, prazosin (inhibitor of alpha-adrenorecepteors) reduces the vasorelaxant effect only of harmaline, whereas, pre-treatment with IBMX (non-specific inhibitor of phosphodiesterase) affects both the harmaline and harmine-responses. Inhibitions of L-type voltage-dependent Ca2+ channels (VOCs) in endothelium-intact aortic rings with diltiazem depress the relaxation evoked by harmaline as well as by harmine. Pre-treatment with harmaline or harmine (3, 10 or 30 microM) shifted the phenylephrine-induced dose response curves to the right and the maximum response was attenuated indicating that the antagonist effect of both alkaloids on alpha1-adrenorecepteors was non-competitive. These two alkaloids also exert an antioxidant activity by scavenging the free radical generated by DPPH. Therefore, the present results suggest that the vasorelaxant effect of harmaline but not harmine is related to its action on the prostacyclin pathway and on the endothelial cells to release NO. However, both alkaloids can act as blockers VOCs, as inhibitors of phosphodiesterase resulting in an increase of the second messenger (cAMP and cGMP) levels and finally reduce the levels of free radicals in tissues.

Improvement of age-related endothelial dysfunction by simvastatin: effect on NO and COX pathways.

The effects of oral administration of the HMG-CoA reductase inhibitor, simvastatin (SV), on age-related endothelial dysfunction were investigated in the aorta of male Wistar rats. Adult (12-14 weeks) and old (60-80 weeks) rats were treated daily for 12 weeks with either vehicle or SV (1 mg kg(-1)). In old rats, SV treatment did not significantly affect systolic blood pressure and LDL-cholesterol, but it reduced plasma cholesterol, triglycerides and oxidised LDL though it did not affect total antioxidant status. SV improved endothelium-dependent relaxation to acetylcholine and A-23187 in vessels from aged, but not adult, rats. This effect was linked to a greater NO vasodilatation via an increased expression of endothelial NO-synthase. A mechanism sensitive to superoxide dismutase and catalase also accounts for enhanced endothelial vasodilatation. Finally, SV did not affect the release of prostacyclin, but it inhibited the generation of thromboxane (TX) A2 from COX-2 isoform. The effect of the latter was sensitive to the Tp receptor antagonist, ICI-192,605. The present study provides evidence that oral administration of SV improves endothelial dysfunction in the aorta from aged rats by mechanisms associated with enhanced NO vasodilatation, reduced release of TXA2 from cyclo-oxygenase, and increased antioxidant properties of the vessel wall. These data underscore a new therapeutic perspective for SV in age-related endothelial dysfunction.

Regulation of vascular tone from spontaneously hypertensive rats by the HMG-CoA reductase inhibitor, simvastatin.

The acute effect of simvastatin on aortic rings from spontaneously hypertensive rats (SHRs) was identified. Simvastatin-evoked relaxations of both depolarized and phenylephrine-precontracted arteries were independent of the presence of endothelium. This effect was inhibited by diltiazem and mevalonate, but not by the Rho-kinase inhibitor, Y-27632. Simvastatin prevented contraction induced by phenylephrine, calcium ionophore A-23187 and CaCl2 in Ca2+-free medium. Y-27632 decreased the effect of simvastatin. On the contrary, contraction induced by noradrenaline in Ca2+-free medium was not affected. These results suggest that simvastatin elicited an effect on vascular smooth muscle cells from SHRs that may involve blockade of extracellular calcium entry and decrease vascular contraction by affecting Rho-kinase.

Argan (Argania spinosa) oil lowers blood pressure and improves endothelial dysfunction in spontaneously hypertensive rats.

Traditionally hand-pressed argan oil, obtained from Argania spinosa seeds, is eaten raw in south-west Morocco; its rich composition of tocopherols, MUFA and PUFA make a study of its actions on risk factors for CVD, such as hypertension, interesting. The effects of 7 weeks of treatment with argan oil (10 ml/kg) on the blood pressure and endothelial function of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats were investigated. Systolic blood pressure and heart rate were measured every week by the tail-cuff method and endothelial function was assessed by carbachol (10(-8) to 10(-4) M)-induced relaxations of aortic rings and small mesenteric arteries pre-contracted with phenylephrine. Argan-oil administration reduced the mean blood pressure of SHR after the fifth week of treatment (P<0.05) and increased (P<0.01) the endothelial responses of arteries from SHR. The NO synthase inhibitor, L-N-omega-nitroarginine (3 x 10(-5) M) revealed a greater participation of NO in the relaxant effect after the treatment. When cyclooxygenase (COX) was blocked with indomethacin (10(-5) M), an involvement of COX products in the endothelium-dependent response was characterized. Enzyme immunoassay of thromboxane B2 showed a significant decrease (P<0.05) in the release of thromboxane A2 in both aorta and small mesenteric artery after argan-oil treatment of SHR. Experiments in the presence of the thromboxane A2-prostaglandin H2 receptor antagonist ICI 192,605 (10(-5) M) confirmed this result. Results after incubation with the antioxidants superoxide dismutase and catalase suggested that a decreased oxidative stress might contribute to explain the beneficial effects of argan-oil treatment.

Effects of simvastatin on endothelial function after chronic inhibition of nitric oxide synthase by L-NAME.

Blood pressure, plasma NO(2) and NO(3) level, heart weight index, antioxidant enzyme activity, and vascular reactivity in rat intact aortic rings were assessed to investigate the effects of 8-week treatment with the hydroxy-methyl-glutaryl coenzyme A reductase inhibitor simvastatin (1 mg/kg per day) on endothelial dysfunction induced by chronic Nomega-nitro-l-arginine methyl ester (l-NAME 70 mg/kg per day). Results were compared with those obtained in rats receiving l-NAME, simvastatin or control animals. Coadministration of simvastatin did not restore l-NAME-increased blood pressure but normalized heart weight index (P < 0.05), endothelium-dependent relaxation to acetylcholine (P < 0.001), and plasma NO(2) and NO(3) concentration (P < 0.001) without affecting relaxation to sodium nitroprusside. Endothelium-dependent relaxation in these animals was abolished by acute incubation with l-NAME, unaffected by thromboxane synthetase inhibitor and TXA(2)/PGH(2) receptor antagonist, ridogrel, and decreased by indomethacin. Simvastatin treatment also increased plasma NO(2)+NO(3) without affecting endothelial function, heart weight index, and blood pressure of control rats. The presence of superoxide dismutase (SOD) and catalase improved endothelial relaxation only in l-NAME-treated rats, but O(2)- generated by hypoxanthine and xanthine oxidase inhibited the relaxant effect in both l-NAME and simvastatin plus l-NAME-treated rats. SOD activity was increased in all groups receiving simvastatin. Long-term treatment with simvastatin restored l-NAME-induced endothelial dysfunction, probably by preventing nitric oxide decrease. Other effects of simvastatin, including release of compensating vasodilatory cyclo-oxygenase products and increased SOD activity, could also be involved.

Endothelium-dependent vasorelaxation induced by L-carnitine in isolated aorta from normotensive and hypertensive rats.

The aim of this work was to investigate the mechanism of the vasodilatory effect induced by L-carnitine. Relaxation produced by L-carnitine was studied in rat aortic rings with and without functional endothelium, pre-contracted with phenylephrine by adding cumulative doses of L-carnitine (10(-7) to 10(-3) M). The relaxation evoked by L-carnitine reached higher values in aortic rings from spontaneously hypertensive rats than those obtained in arteries from normotensive rats; no relaxation was produced in de-endothelialized arteries. However, in the presence of N(G)-nitro-L-arginine (3 x 10(-5) M, a nitric oxide synthase inhibitor), Ro 68070 (10(-4) M, a thromboxane synthetase inhibitor-thromboxane A2/prostaglandin H2 receptor antagonist) or ICI 192605 (10(-5) M, a thromboxane A2 receptor antagonist) the relaxant response to L-carnitine was significantly inhibited. These results show that L-carnitine induced endothelium-dependent relaxation in the rat aorta and the mechanism of this relaxation appeared to be mostly mediated by endothelial production of nitric oxide but#10; also could involve prevention of the action of cyclooxygenase endothelial products acting on the thromboxane A2/prostaglandin H2 receptor.

Simvastatin improves endothelial function in spontaneously hypertensive rats through a superoxide dismutase mediated antioxidant effect.

BACKGROUND: Hydroxymethylglutaryl coenzyme A (HMGCoA) reductase inhibitors have beneficial effects beyond their cholesterol-lowering properties. The antioxidant mechanism of HMGCoA reductase inhibitors is not completely understood. OBJECTIVES: To elucidate the antioxidant effect of simvastatin. METHODS: We studied the influence of simvastatin treatment on the development of hypertension, modification of antioxidant systems, and reactivity of aortic rings in Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. RESULTS: Simvastatin had no effect on blood pressure (BP). Simvastatin treatment (either 1 or 2 mg/kg body weight for 12 or 20 weeks) increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in SHR rats compared with untreated control SHR rats. Carbachol-induced relaxation of aortic rings was impaired in control SHR rats and was restored by simvastatin treatment. Addition of SOD improved the response in control SHR rats and did not have any effect in treated SHR rats. Addition of diethyldithiocarbamic acid, a selective inhibitor of SOD, produced a mild non-significant impairment in carbachol-induced relaxation in control SHR rats, suggesting a deficient antioxidant system in these animals. However, in treated SHR and in WKY rats, impairment of the relaxation was marked, implying that SOD activity in these animals was important to maintain endothelial function. In aortic rings without endothelium from SHR rats, contraction induced by free radicals was substantially higher than in WKY rats. This effect was attenuated in 1-mg-treated rats and abolished in 2-mg-treated rats. CONCLUSIONS: Simvastatin promotes intracellular antioxidant systems, fundamentally SOD, restoring endothelial function but not having any effect on blood pressure.