Maria Alvarez de Sotomayor

Endothelial dysfunction and aging: An update

Aging is an important risk factor for the development of many cardiovascular diseases as atherosclerosis and hypertension with a common underlying circumstance: the progressive decline of endothelial function. Vascular endothelial dysfunction occurs during the human aging process and is accompanied by deterioration in the balance between vasodilator and vasoconstriction substances produced by the endothelium. This imbalance is mainly characterized by a progressive reduction of the bioavailability of nitric oxide (NO) and an increase in the production of cyclooxygenase (COX)-derived vasoconstrictor factors. Both circumstances are in turn related to an increased production of reactive oxygen and nitrogen species. The aim of this review is to describe the pathophysiological mechanisms involved in the endothelial function declination that accompanies the multifactorial aging process, including alterations related to oxidative stress and pro-inflammatory cytokines, senescence of endothelial cells and genetic factors.

Vascular bed heterogeneity in age-related endothelial dysfunction with respect to NO and eicosanoids

Endothelial dysfunction has been described with ageing but the mechanisms responsible have not been clearly elucidated and might be different from one vessel to the other. This study assesses the relative contribution of endothelial nitric oxide (NO) and cyclo‐oxygenase (COX) metabolites in relaxation to acetylcholine with ageing in the aorta and the small mesenteric artery of the rat. In the aorta and branch II or III of superior mesenteric artery (SMA), endothelium‐dependent relaxation to acetylcholine was not different between 12–14 (adult) and 32‐week‐old rats whereas it was reduced at 70–100 (old) weeks of age. Despite an increased endothelial NO‐synthase protein expression, the NO‐synthase inhibitor, NG‐nitro‐L‐arginine‐sensitive component of relaxation decreased with ageing. In old rats, exposure to the COX inhibitor, indomethacin, but not the selective COX‐2 inhibitor, NS‐398, potentiated response to acetylcholine. The thromboxane A2/prostaglandin H2 receptor antagonist, GR 32191B enhanced relaxation to acetylcholine in aorta but it had no effect in SMA. Furthermore, acetylcholine increased thromboxane B2 production (enzymeimmunoassay) in aorta but not in SMA. Finally, Western blot analysis showed enhanced expression of COX‐1 and 2 in the two arteries with ageing. These results suggest that the decrease in acetylcholine‐induced relaxation with ageing involves reduced NO‐mediated dilatation and increased generation of vasoconstrictor prostanoids most likely from COX‐1. They also point out vascular bed heterogeneity related to the nature of prostanoids involved between the aorta (i.e., thromboxane A2) and the SMA (unidentified) arteries even though increased expression of COX occurs in both vessels.

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.

A pharmacological study of Cecropia obtusifolia Bertol aqueous extract

Cecropia obtusifolia (Cecropiaceae) is a species from tropical America and its leaves are used in traditional medicine for the treatment of diabetes and as an anti-inflammatory agent. In the present study, the analgesic, anti-inflammatory and central nervous system depressant effects of the aqueous extract from the leaves of C. obtusifolia were investigated in different experimental models, with the purpose of validating its ethnomedical uses. The results obtained with the extract from the leaves of C. obtusifolia reflect a low toxicity, a substantial central depressor effect and analgesic activity and significant motor incoordination and muscle relaxant activity. Concerning the analgesic activity, using the hot plate test, the extract did not produce any effect, however it showed a significant effect on the pain induced by chemical stimuli (acetic and formalin test); this suggests the peripheral analgesic effect of the extract. The extract also showed a topical and systemic anti-inflammatory effect. Thus this work could justify the popular use of C. obtusifolia in rheumatic and kidney inflammation pathologies and reveals that this plant is an interesting species.

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.

Pharmacological effects and clinical applications of propionyl-L-carnitine

Propionyl-L-carnitine (PLC) is a naturally occurring derivative of carnitine that plays an important role in the metabolism of both carbohydrates and lipids, leading to an increase of ATP generation. PLC, however, is not only a metabolic drug; it is also a potent antiradical agent and thus may protect tissues from oxidative damage. PLC has been demonstrated to exert a protective effect in different models of both cardiac and endothelial dysfunction, to prevent the progression of atherosclerosis, and, more recently, to improve some of the cardiometabolic alterations that frequently accompany insulin resistance. As a result, most of the clinical trials conducted in humans highlight PLC as a potential treatment option in cardiovascular diseases such as peripheral arterial disease, chronic heart failure, or stable angina, especially when type 2 diabetes mellitus or hyperglycemia (i.e., patients on hemodialysis) are also present. The aim of this review is to summarize the pharmacological effects and possible therapeutic applications of PLC, including the most recent findings to date.

Rice bran enzymatic extract restores endothelial function and vascular contractility in obese rats by reducing vascular inflammation and oxidative stress.

BACKGROUND Rice bran enzymatic extract (RBEE) used in this study has shown beneficial activities against dyslipidemia, hyperinsulinemia and hypertension. Our aim was to investigate the effects of a diet supplemented with RBEE in vascular impairment developed in obese Zucker rats and to evaluate the main mechanisms mediating this action. METHODS AND RESULTS Obese Zucker rats were fed a 1% and 5% RBEE-supplemented diet (O1% and O5%). Obese and their lean littermates fed a standard diet were used as controls (OC and LC, respectively). Vascular function was evaluated in aortic rings in organ baths. The role of nitric oxide (NO) was investigated by using NO synthase (NOS) inhibitors. Aortic expression of endothelial NOS (eNOS), inducible NOS (iNOS), tumor necrosis factor (TNF)-α and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits and superoxide production in arterial wall were determined. Endothelial dysfunction and vascular hyperreactivity to phenylephrine in obese rats were ameliorated by RBEE treatment, particularly with 1% RBEE. Up-regulation of eNOS protein expression in RBEE-treated aortas should contribute to this activity. RBEE attenuated vascular inflammation by reducing aortic iNOS and TNF-α expression. Aortas from RBEE-treated groups showed a significant decrease of superoxide production and down-regulation of NADPH oxidase subunits. CONCLUSION RBEE treatment restored endothelial function and vascular contractility in obese Zucker rats through a reduction of vascular inflammation and oxidative stress. These results show the nutraceutical potential of RBEE to prevent obesity-related vascular complications.

Time-dependent protective efficacy of Trolox (vitamin E analog) against microcystin-induced toxicity in tilapia (Oreochromis niloticus).

Microcystins (MCs), hepatotoxins from cyanobacteria, induce oxidative stress and pathological changes in fish that can be ameliorated with chemoprotectants such as vitamin E (vit E). This study investigated the time period after MCs exposure in which Trolox, a vitamin E analog, is effective against oxidative and histological damage in different organs of tilapia (Oreochromis niloticus). Fish were fed Trolox supplement (700 mg/kg diet) for 7 days, or received only commercial fish food, and then were exposed to a single oral dose of 120 μg/fish microcystin‐LR, and sacrificed in 24, 48, or 72 h. The Trolox protective efficacy was evaluated based on lipid peroxidation (LPO), protein oxidation, enzymatic and non‐enzymatic antioxidants, and a morphologic study. Regarding the oxidative stress biomarkers altered by MCs, the higher protective action of Trolox was observed 24 h post toxin exposure, although it extends also until 48 h in gills (superoxide dismutase (SOD), catalase (CAT)), and liver, where glutathione reductase (GR) backed to control values 48 and 72 h after the toxin application. Glutathione‐S‐ transferase (GST) activity in the liver was ameliorated by the chemoprotectant after 24 and 48 h, although control values were not recovered. Trolox modulation of these biomarkers and its ability to quench free radicals explain the recovery of LPO values in all organs at 24 h and also in gills at 48 h. Histopathologically, Trolox efficacy was more evident after 72 h.