E. Marhuenda

Effects of flavonoids on rat aortic smooth muscle contractility: structure-activity relationships.

1. Flavonoids produced a concentration-dependent relaxation of the contractile responses induced by noradrenaline, KCl, or phorbol 12-myristate-13-acetate in rat aortic rings. Only the flavonoid with three contiguous hydroxyls in B rings (myricetin), at low concentrations, potentiates the contractions evoked by these agonists. 2. The relaxant effects of flavanone on the noradrenaline-induced contractions were potentiated by isoprenaline and those of morin, chrysin, flavanone, and naringenin by sodium nitroprusside. 3. Several mechanisms are implicated in the vasodilatory effects of flavonoids: inhibition of protein kinase C; inhibition of cyclic nucleotide phosphodiesterases; and/or decreased Ca2+ uptake.

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.

Characterization of endothelial factors involved in the vasodilatory effect of simvastatin in aorta and small mesenteric artery of the rat.

Vascular effects of the 3‐hydroxy‐3‐methylglutaryl‐coenzyme A (HMG‐CoA) reductase inhibitor, simvastatin, were studied in conductance (aorta) and resistance vessels (branch II or III of superior mesenteric artery, SMA) of the rat (12–14 weeks old). Simvastatin produced relaxation of both aorta and SMA, with and without functional endothelium. These responses were inhibited by the product of HMG‐CoA reductase, mevalonate (1 mmol l−1). In vessels with functional endothelium, the NO‐synthase inhibitor, L‐NG‐nitroarginine (L‐NOARG, 30 μmol l−1), inhibited simvastatin‐induced relaxation. In the presence of L‐NOARG, relaxation to simvastatin was lower in vessels with endothelium than in endothelium‐denuded arteries without L‐NOARG. The cyclo‐oxygenase inhibitor, indomethacin (10 μmol l−1), abolished endothelium‐dependent component of the response to simvastatin in both arteries. The combination of L‐NOARG plus indomethacin did not produce further inhibition. The Tp receptor antagonist, GR 32191B (3 μmol l−1), did not affect relaxation in aorta but it reduced response to low concentrations of simvastatin in SMA. However, the inhibitory effect of L‐NOARG was less marked in the presence of GR 32191B in aorta but not in SMA. The endothelium‐dependent relaxation to simvastatin was inhibited by the superoxide dismutase (SOD, 100 u ml−1) or by the tyrosine kinase inhibitor, genistein (30 μmol l−1) in the two arteries. The present study shows that simvastatin produces relaxation of conductance and small arteries through mevalonate‐sensitive pathway. The endothelium‐dependent relaxation to simvastatin involves both NO and vasodilator eicosanoids by a mechanism sensitive to SOD, and to genistein. Also, the results highlighted participation in the aorta of endothelial vasoconstrictor eicosanoids acting on the Tp receptor after blockage of NO synthase only.

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.

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 dietary oleic-rich oils (virgin olive and high-oleic-acid sunflower) on vascular reactivity in Wistar- Kyoto and spontaneously hypertensive rats

The effects of two monounsaturated fatty acid (MUFA)-rich diets, containing virgin olive oil (OO) and high-oleic-acid sunflower oil (HOSO), on development of vascular response from isolated thoracic rat aorta and lipid composition and fatty acid composition were studied and compared with samples from rats fed on a control diet. Dietary MUFA oils were fed for 6 weeks to spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats from 4 weeks of age. The maximum contraction of aortic ring preparations in response to phenylephrine (10(-6) m) was significantly decreased in SHR rats fed with OO (0.81 (sem 0.05) v. 1.18 (sem 0.09) g, and treatment with HOSO did not alter the phenylephrine-induced contractions. The relaxant responses to acetylcholine (10(-5) m) were significantly enhanced (30.03 (sem 0.70) v. 18.47 (sem 0.28) %, in the rings from SHR rats treated with OO, and were more pronounced than in WKY rats In the same way, OO attenuated the dose-response curves induced by phenylephrine (10(-8)-10(-5) m) from SHR rats, accompanied with a slower contraction. These results suggest that only the chronic feeding of OO diet was able to attenuate the vascular response of rat aorta. In addition, an increase in phospholipid content (186.7 (sd 3.2) v. 159.1 (sd 11.3) g/kg, and changes in the fatty acid composition of aorta (mainly a decrease in arachidonic acid) could contribute to improving endothelial function. Therefore, the effects can not be attributed exclusively to the content of MUFA (mainly oleic acid). Other components of OO, such as polyphenols, not present in HOSO, may help to explain the vascular protective effect of OO consumption.

Gastric anti-ulcer activity of silymarin, a lipoxygenase inhibitor, in rats

Abstract— Oral treatment with silymarin was found to be effective in the prevention of gastric ulceration induced by cold‐restraint stress, in rats. Statistically significant ulcer index values with respect to the control group, were observed. In 6 h pyloric‐ligated animals silymarin showed a significant reduction in the number and severity of the ulcers; however, it did not alter the gastric secretion volume or acidity although histamine concentration was significantly decreased. In absolute ethanol‐induced ulcers, treatment with silymarin 1 or 2 h before the anti‐ulcerogenic agent, did not prevent the formation of gastric lesions. Furthermore, the hexosamine content was decreased significantly, but the total protein output was enhanced, showing similar values to those with the standard drug, carbenoxolone. These results suggest that the anti‐ulcerogenic effect of silymarin could be related to its inhibitory mechanism of enzymatic peroxidation by the lipoxygenase pathway, avoiding leukotriene synthesis.

Effects of chronic treatment with simvastatin on endothelial dysfunction in spontaneously hypertensive rats.

OBJECTIVE To investigate the effects of chronic treatment with simvastatin (SV) on endothelium-dependent relaxation and ouabain-induced contractions in aortic rings from spontaneously hypertensive rats (SHR), comparing with normotensive Wistar-Kyoto rats (WKY). METHODS After a 12-week period of administration of 1 or 2 mg/kg SV to SHR and WKY, systolic blood pressure (SBP) and vascular reactivity in endothelium-intact aortic rings were assessed. RESULTS Relaxation in response to acetylcholine (ACh) in WKY remained unaltered, but in SHR treated with 1 mg/kg SV, enhanced ACh-induced relaxation (P<0.05 versus untreated SHR) reached values observed in untreated WKY. The 2 mg/kg treatment also improved ACh relaxation (P<0.01 and P<0.05 versus untreated SHR and WKY respectively). Inhibiting cyclo-oxygenase (COX) with indomethacin (INDO) improved ACh relaxation in SHR (P<0.05) but not in WKY, independent of treatment with SV. Inhibition of nitric oxide synthase (NOS) with N(G)-nitro-L-arginine (L-NOARG) abolished ACh relaxations in all cases (P<0.001). The result was unaltered when combining INDO plus L-NOARG. SV treatment also decreased ouabain-induced contractions in endothelium-intact aortic rings from SHR, diminishing the percentage effect of contraction from 64.56+/-2.95 (untreated SHR) to 26.98+/-7.06 and 38.10+/-8.21 (1 and 2 mg/kg treated SHR respectively). Response to ouabain in WKY was not significantly affected by SV treatment CONCLUSIONS Chronic treatment of SHR with SV improves endothelium-dependent ACh relaxation of the aortic rings, probably by an NO-involving mechanism more than by inhibiting contractile COX-derived factors. An improvement in endothelial modulation of ouabain-induced contractions was also observed after treatment with SV in SHR, which might be due to an inhibition of a calcium-sodium exchanger.

In vitro scavenger and antioxidant properties of hesperidin and neohesperidin dihydrochalcone

We have assesed the actions as free radical scavengers and inhibitors on peroxidation of hesperidin and neohesperidin dihydrochalcone, two flavonoids, flavanone and dihydrochalcone respectively, as some of the pharmacological properties of flavonoids group have been related with these activities. Hesperidin just at 10(-4) and 5 · 10(-4)M is able to show a low inhibitory activity in the superoxide anion radicals (O(2)(-)) genesis (8.66 ± 1.40 and 11.69 ± 2.36% respectively), and on the non-enzymatic lipid peroxidation at 10(-3)M dose (9.78 ± 0.35%), without affecting the hydroxyl radical (•OH) formation, generated by the ascorbic acid-Fe(3+)-EDTA system. In the other hand, neohesperidin dihydrochalcone is an authentic antioxidant drug as tested at all doses. It showed a great scavenger activity and/or inhibition of formation on O(2)(-) radicals (31.53 - 84.62%) and a significant scavenging effect on OH radicals (6.00 - 23.49%), as well as an important inhibitory action on non-enzymatic lipid peroxidation (15.43-95.33%).

Hesperidin and neohesperidin dihydrochalcone on different experimental models of induced gastric ulcer

Hesperidin and neohesperidin dihydrochalcone show a marked capacity to reduce the ulcer index in cold‐restraint induced ulcer in a clear dose‐related manner. The amount of gastric mucus and total protein were not modified, but there was a significant increase in hexosamine content. When the acute ulcer was induced by absolute ethanol HESP was inactive. These results suggest that mucus is not involved in the antiulcer activity. In both experimental models, HESP and NEOHESP did not produce an increase in total PGE2, suggesting that this mechanism of action is not involved in the antiulcer activity of these compounds.