Winter-dormant shoot apical meristem in poplar trees shows environmental epigenetic memory.

Trees have a long lifespan and must continually adapt to environmental pressures, notably in the context of climate change. Epigenetic mechanisms are doubtless involved in phenotypic plasticity and in stress memory; however, little evidence of the role of epigenetic processes is available for trees growing in fields. Here, we analyzed the possible involvement of epigenetic mechanisms in the winter-dormant shoot apical meristem of Populus × euramericana clones in memory of the growing conditions faced during the vegetative period. We aimed to estimate the range of genetic and environmentally induced variations in global DNA methylation and to evaluate their correlation with changes in biomass production, identify differentially methylated regions (DMRs), and characterize common DMRs between experiments. We showed that the variations in global DNA methylation between conditions were genotype dependent and correlated with biomass production capacity. Microarray chip analysis allowed detection of DMRs 6 months after the stressful summer period. The 161 DMRs identified as common to three independent experiments most notably targeted abiotic stress and developmental response genes. Results are consistent with a winter-dormant shoot apical meristem epigenetic memory of stressful environmental conditions that occurred during the preceding summer period. This memory may facilitate tree acclimation.

Magnesium deficiency affects HNF1ß expression in rat liver in vivo and in vitro.

Hepatocyte nuclear factor 1ß (HNF1ß) is a transcription factor that is involved in embryonic development and tissue-specific gene expression in several organs, including the kidney and the liver. HNF1ß mutations are associated with hypomagnesemia and renal magnesium wasting; however, to date, the exact molecular mechanism involved in this regulation is unclear. Furthermore, it is not known whether the Mg concentration could per se participate to this regulation by modifying HNF1ß expression. We have studied in rats the effects of a 6-week diet with deficient or supplemented Mg concentrations compared to a diet with a standard Mg concentration on HNF1ß protein expression. HNF1ß expression was increased in the Mg-deficient group as compared to the other groups in the liver but not in the kidney. No changes in tissue Mg level were obtained in both organs. By contrast, a significant correlation between plasma Mg concentration and HNF1ß level in the rat liver was evidenced. In rat hepatocyte cultures exposed for 72h to various extracellular Mg concentrations, HNF1ß expression was modified after 72h of treatment of the hepatocytes with the lowest Mg concentrations as compared to the other Mg conditions. Moreover, these changes were correlated with extracellular but not intracellular Mg concentrations. In conclusion, HNF1ß expression is modified by the extracellular Mg concentration in the liver, both in vivo and in vitro, suggesting regulations with membrane events in hepatocytes.

Running Exercise and Angiotensin II Type I Receptor Blocker Telmisartan Are Equally Effective in Preventing Angiotensin II-Mediated Vulnerable Atherosclerotic Lesions.

INTRODUCTION: The present study was conducted to directly compare the efficacy of running exercise and telmisartan treatment on angiotensin (Ang) II-mediated atherosclerosis and plaque vulnerability. MATERIALS AND METHODS: Apolipoprotein E-deficient (ApoE-/-) mice with Ang II-mediated atherosclerosis (2-kidney, 1-clip [2K1C] renovascular hypertension model) were randomized into 3 groups: treadmill running exercise (RUN), telmisartan treatment (TEL), and sedentary untreated controls (SED) for 5 weeks. Atherosclerosis was assessed using histological and immunohistochemical analyses. Gene expression was determined by real-time reverse transcription polymerase chain reaction. RESULTS: TEL but not RUN mice significantly decreased (50%) atherosclerotic lesion size compared to SED. RUN and TEL promoted plaque stabilization to a similar degree in ApoE-/- 2K1C mice. However, plaque composition and vascular inflammatory markers were differently affected: RUN decreased plaque macrophage infiltration (35%), whereas TEL reduced lipid core size (88%); RUN significantly increased aortic peroxisome proliferator-activated receptor (PPAR)-α, -δ, and -γ expression, whereas TEL significantly modulated T-helper 1/T-helper 2 (Th1/Th2) aortic response toward an anti-inflammatory state (decreased aortic interleukin [IL] 2 to IL-10 and IL-2 to IL-13 expression ratios). Plaque smooth muscle cell content was similarly increased (128% and 141%, respectively). Aortic AT1 and AT2 receptor expression as well as aortic CD11c/CD206 and IL-1ß/IL-1ra expression ratios were not significantly modulated by either RUN or TEL. CONCLUSION: Running exercise and telmisartan treatment are equally effective in preventing Ang II-mediated plaque vulnerability but through distinct cellular and molecular mechanisms. Our findings further support the use of exercise training and selective AT1 receptor blocker therapies for atherosclerotic cardiovascular disease prevention.

Dietary magnesium intake alters age-related changes in rat adipose tissue cellularity.

Obesity and related metabolic diseases are associated with increased risk of cardiovascular disease. We have previously shown the beneficial effects of dietary magnesium (Mg) supplementation on cardiovascular disease in rats. Therefore, we aimed to examine the effect of an Mg-deficient or supplemented diet on adipose tissue cellularity changes during aging, and on blood pressure (BP), in rats. Male rats received for one (young adult) or 22 months (old), an Mg-deficient (Def) (150 mg/kg), standard (Std) (800 mg/kg) or Mg-supplemented (Sup) (3200 mg/kg) diet. Adipose tissue development and cellularity, BP and leptinemia were evaluated. In rats fed a standard diet, the large increase in adipose tissue weight observed during aging was related to an increase in both size and number of adipocytes. In young adult rats, although adiposity was unchanged, Mg supplementation resulted in a shift of the frequency distribution of adipocytes toward greater sizes, adipose cell weight increasing by 62%. Mg deficiency did not modify adipocyte size, but increased their number (30% more than for the standard or Sup-diet). In old rats, the Def-diet led to relative adipocyte hypotrophy, which was counterbalanced by an increase in the number of adipocyte. Conversely, adipocyte size and number were similar in the Sup-diet and standard diet-fed rats. BP was modified in old rats according to dietary Mg, whereas it remained unchanged young adult rats regardless of the diet received. This study suggests that Mg intake may affect age-related changes in rat adipose tissue lipid storage capacity.

Treatment with an extract of Terminalia superba Engler & Diels decreases blood pressure and improves endothelial function in spontaneously hypertensive rats.

ETHNOPHARMACOLOGICAL RELEVANCE: The stem bark of Terminalia superba (TS) is widely used as a decoction by Cameroonian folk medicine for the treatment of hypertension. The aim of the present study was to evaluate the effect of a chronic treatment with a TS extract on spontaneously hypertensive rats (SHR) with respect to efficacy, biochemical mechanisms and safety. MATERIALS AND METHODS: Eleven-week-old SHR and normotensive Wistar Kyoto rats (WKY) were daily treated by gavage with a methylene chloride extract of stem bark of Terminalia superba (TMSE, 150mg/kg) or with the vehicle for 5 weeks. Systolic blood pressure (SBP) was measured weekly using the tail-cuff method. At the end of the treatment period, vascular function was assessed on isolated thoracic rings, urinary 8-iso-PGF2α levels were measured and cytochrome P-450 3A (CYP 3A) activity was evaluated in liver microsomes. RESULTS: TMSE reduced SBP (P<0.001) in SHR but not in WKY rats. In SHR, the vasorelaxant response to acetylcholine was significantly improved by TMSE as a result of increased nitric oxide synthase (NO) activity and decreased superoxide anion production. In addition, TMSE reduced the vasoconstrictive effect of phenylephrine and improved the sensitivity of smooth muscle cells to NO. TMSE dramatically decreased 8-iso-PGF2α levels in SHR. By contrast, TMSE did not affect all these parameters in WKY rats. Neither diuresis nor the hepatic CYP 3A activity was modified in both animal groups. CONCLUSIONS: This study demonstrated that Terminalia superba has a potent antihypertensive activity in SHR which is partly due to endothelium-dependent and endothelium-independent effects as well as decreased oxidative stress. The data also provide evidence for the lack of herb-drug interaction through hepatic CYP 3A.

Vasorelaxant effects and mechanisms of action of Heracleum sphondylium L. (Apiaceae) in rat thoracic aorta.

ETHNOPHARMACOLOGICAL RELEVANCE: Aerial parts of Heracleum sphondylium L. (HS) are used in traditional medicine to treat hypertension. To provide pharmacological basis for this use, we investigated the vasorelaxant effects of a dichloromethane extract of HS (HSDE) and the mechanisms involved. MATERIALS AND METHODS: Activity of HSDE was evaluated on rat isolated thoracic aortic rings. RESULTS: HSDE induced vasorelaxation in phenylephrine (PE, 10(-6)mol/L) and high KCl-(6×10(-2)mol/L) pre-contracted aortic rings that was independent on the presence of endothelium. HSDE markedly decreased extracellular Ca(2+)-induced contraction in high-KCl and PE pre-challenged rings. It also inhibited the intracellular Ca(2+) release sensitive to PE (10(-6)M). The relaxant effect of HSDE were blunted by 4-amino-pyridine (4-AP, 10(-3)mol/L), an inhibitor of voltage-dependent K(+) channels. CONCLUSION: Our results provide the first evidence that a dichloromethane extract of Heracleum sphondylium L. exhibits vasorelaxant properties through endothelium-independent mechanisms involving the inhibition of Ca(2+) mobilization and changes in Kv channel conductances. These data argue for its use as antihypertensive therapy in traditional medicine.

Arginase inhibition prevents the low shear stress-induced development of vulnerable atherosclerotic plaques in ApoE-/- mice.

AIMS: Wall shear stress differentially regulates the arginase pathway in carotid arteries perfused ex vivo. Specific patterns of wall shear stress can locally determine atherosclerotic plaque size and composition in vivo. The present work investigates the effects of arginase inhibition on shear stress induced plaque composition. METHODS AND RESULTS: Carotid arteries of apolipoprotein E deficient mice were exposed to high (HSS), low (LSS) and oscillatory (OSS) shear stress conditions by the placement of a local shear stress modifier device for 9 weeks with or without the administration of the arginase inhibitor N-ω-Hydroxy-nor-L-arginine (nor-Noha) (10 mg/kg, i.p., 5 days/week). Carotid arginase activity was measured by colorimetric determination of urea. Atherosclerotic plaque size and composition, arginase expression and cellular localization were assessed by immunohistochemistry. Arginase activity was significantly increased in both LSS and OSS regions as compared to HSS. In the lesions, arginase II isoform co-localized preferentially with EC. Inhibition of arginase by nor-Noha decreased arginase activity and reduced plaque size in both LSS and OSS regions. Arginase inhibition affected mainly the composition of plaques developed in LSS regions by decreasing the total vascular ROS, the number of macrophages, apoptosis rate, lipid and collagen contents. CONCLUSIONS: Arginase activity is modulated by patterns of wall shear stress in vivo. Chronic inhibition of vascular arginase decreased the size of atherosclerotic lesions in both OSS and LSS regions, whereas changes on plaque composition were more pronounced in plaques induced by LSS. We identified wall shear stress as a key biomechanical regulator of arginase during plaque formation and stability.

New insights into the mechanisms of the vasorelaxant effects of apocynin in rat thoracic aorta.

Apocynin is a naturally occurring acetophenone widely used as an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Recent data suggested that apocynin might exert NADPH oxidase-independent pharmacological properties. Among them, vasorelaxant properties have been described, but the mechanisms still give rise to debates. The present study investigated the mechanisms involved in the vasorelaxant effect of apocynin on the in vitro model of rat isolated thoracic aortic rings. Apocynin (30 µM to 10 mM) induced a dose-dependent relaxation in both endothelium-intact and endothelium-denuded aortic rings with respective EC50 values of 0.78 ± 0.08 and 1.91 ± 0.21 mM. Endothelium removal or inhibition of nitric oxide (NO) synthase with N(ω)-nitro-L-arginine-methyl ester (L-NAME) significantly decreased but did not abolish the effect of apocynin. By contrast, apocynin-induced relaxation was unchanged after incubation with indomethacin or charybdotoxin plus apamin. In endothelium-denuded aortas, the vasorelaxant effect of apocynin was significantly reduced by glibenclamide but not by 4-aminopyridine nor by iberiotoxin. Apocynin significantly decreased Ca(2+)-induced contraction and inhibited intracellular Ca(2+) mobilization after contraction with phenylephrine. Finally, the acute intravenous injection of apocynin led to an immediate and transient hypotensive effect in spontaneously hypertensive rats (SHR). In conclusion, our data demonstrated that apocynin induces both endothelium-independent relaxant effects involving inhibition of Ca(2+) mobilization and activation of KATP channels in vascular smooth muscle cells and endothelium-dependent effects mediated by NO. These results should provide a basis for caution when interpreting results on the vascular effects of apocynin.

Treatment with the arginase inhibitor Nw-hydroxy-nor-L-arginine restores endothelial function in rat adjuvant-induced arthritis.

INTRODUCTION: Endothelial dysfunction (ED) participates to atherogenesis associated to rheumatoid arthritis. We recently reported increased arginase activity/expression in vessels from adjuvant-induced arthritis (AIA) rats. In the present study, we investigated the effects of a curative treatment with the arginase inhibitor Nw-hydroxy-nor-L-arginine (nor-NOHA) on vascular dysfunction in AIA rats. METHODS: AIA rats were treated with nor-NOHA (40 mg/kg/d, ip) for 21 days after the onset of arthritis. A group of untreated AIA rats and a group of healthy rats served as controls. ED was assessed by the vasodilatory effect of acetylcholine (Ach) on aortic rings. The role of superoxide anions, prostanoids, endothelium-derived hyperpolarizing factor (EDHF) and nitric oxide synthase (NOS) pathway was studied. Plasma levels of IL-6 and vascular endothelial growth factor (VEGF) were determined by ELISA kits. Arthritis severity was estimated by a clinical, radiological and histological analysis. RESULTS: Nor-NOHA treatment fully restored the aortic response to Ach to that of healthy controls. The results showed that this beneficial effect is mediated by an increase in NOS activity and EDHF and reduced superoxide anion production as well as a decrease in the activity of cyclooxygenase (COX)-2, thromboxane and prostacyclins synthases. In addition, nor-NOHA decreased IL-6 and VEGF plasma levels in AIA rats. By contrast, the treatment did not modify arthritis severity in AIA rats. CONCLUSIONS: The treatment with an arginase inhibitor has a potent effect on ED in AIA independently of the severity of the disease. Our results suggest that this new pharmacological approach has the potential as a novel add-on therapy in the treatment of RA.

Vasorelaxant and hypotensive effects of a hydroalcoholic extract from the fruits of Nitraria sibirica Pall. (Nitrariaceae).

ETHNOPHARMACOLOGICAL RELEVANCE: Fruits of Nitraria sibirica Pall. are traditionally used in Uighur medicine to treat hypertension. This study aimed to support that folk use by defining their vasoactive and hypotensive properties. MATERIALS AND METHODS: The vasorelaxant activity and the underlying mechanisms of a hydroalcoholic extract from the fruits of Nitraria sibirica Pall. (NSHE) were evaluated on thoracic aortic rings isolated from Wistar rats. In addition, the acute hypotensive effect of NSHE was assessed in anesthetized spontaneously hypertensive rats (SHR) and in their normotensive control Wistar Kyoto (WKY) rats. RESULTS: NSHE (0.1-10 g/l) was clearly more effective to induce vasodilation of phenylephrine- (PE, 1 µM) than high KCl- (60mM) pre-contracted aortic rings with respective E(max) values of 82.9±2.2% and 34.8±3.6%. The removal of endothelium almost abolished the relaxant effect of the extract. In addition, pre-treatment with N(w)-nitro-L-arginine-methyl ester (L-NAME, 100 µM), atropine (1 µM) or charybdotoxin (30 nM) plus apamin (30 nM), respective blockers of nitric oxide (NO) synthase, muscarinic receptors and endothelium-derived hyperpolarizing factor (EDHF), significantly reduced the observed effect of NSHE. By contrast, the cyclooxygenase (COX) inhibitor indomethacin (10 µM) or the K(+) channels blockers glibenclamide (10 µM), iberiotoxin (30 nM) and 4-amino-pyridine (4-AP, 1 mM) failed to modify the vasodilation. Finally, the acute intravenous injection of NSHE (1, 5, 10, 20 mg/kg) induced an immediate and transient hypotensive effect in anesthetized SHR and in WKY rats. CONCLUSIONS: This experimental animal study suggests that hydroalcoholic extract from the fruits of Nitraria sibirica Pall. induces vasorelaxation through an endothelium-dependent pathway involving NO synthase (NOS) activation, EDHF production and muscarinic receptor stimulation. Additionally, our results determine that this vasorelaxant effect is translated by a significant hypotensive effect.

Bioassay-guided isolation of vasorelaxant compounds from Ziziphora clinopodioides Lam. (Lamiaceae).

Ziziphora clinopodioides Lam. (Lamiaceae) is traditionally used in Uighur's medicine for the treatment of hypertension. Our study determined and evaluated the bioactive compounds by performing an activity-guided fractionation of a hydroalcoholic extract of the whole plant, using an in vitro model of rat isolated thoracic aortic rings. Seven compounds were identified as active principles: acacetin, apigenin, chrysin, thymonin, acetovanillone, 4-hydroxyacetophenone and ethyl 4-coumarate. Apigenin, chrysin and ethyl 4-coumarate were found to be the most effective. Our results provide the first evidence that the vasodilation induced by Z. clinopodioides Lam. is mediated, at least in part, by phenolic components.

Dietary Mg2+ regulates the epithelial Mg2+ channel TRPM6 in rat mammary tissue.

The epithelial Mg(2+) channel TRPM6 is considered a pivotal component in active Mg(2+)absorption and re-absorption in the intestine and kidney, but its expression and function in other tissues are largely unknown. We have previously demonstrated that extracellular Mg(2+) availability modulates TRPM6, but not the ubiquitous TRPM7, in cultured mammary epithelial cells; in addition, TRPM6 protein expression correlated to Mg(2+) influx capacities. Our results closely remind the modulation of TRPM6 described by others in murine kidney and colon following Mg(2+) dietary restriction. We sought to validate our observations by investigating whether TRPM6 modulation by extracellular Mg(2+)also occurs in vivo. To this aim, we exploited a model consisting of rats fed either with a Mg(2+)-deficient or a Mg(2+)-enriched diet, and studied TRPM6 expression in breast and kidney tissues. Immunohistochemical and western blot analyses confirmed that rat mammary tissues express TRPM6 protein levels similar to those found in the kidney, and that protein expression is modulated by dietary Mg(2+). In particular, Mg(2+) restriction upregulated TRPM6 expression, while Mg(2+) supplementation resulted in a significant decrease in protein levels. This work confirms and extends our previous results on TRPM6 modulation by Mg(2+) availability in mammary tissues. Further studies are required to clarify the functional significance of these findings, and the role of TRPM6 in tissue-specific magnesium homeostasis.

Human recombinant erythropoietin alters the flow-dependent vasodilatation of in vitro perfused rat mesenteric arteries with unbalanced endothelial endothelin-1 / nitric oxide ratio.

Chronic use of human recombinant erythropoietin (r-HuEPO) is accompanied by serious vascular side effects related to the rise in blood viscosity and shear stress. We investigated the direct effects of r-HuEPO on endothelium and nitric oxide (NO)-dependent vasodilatation induced by shear stress of cannulated and pressurized rat mesenteric resistance arteries. Intravascular flow was increased in the presence or absence of the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME; 10(-4) mol/L). In the presence of r-HuEPO, the flow-dependent vasodilatation was attenuated, while L-NAME completely inhibited it. The association of r-HuEPO and L-NAME caused a vasoconstriction in response to the rise in intravascular flow. Bosentan (10(-5) mol/L), an inhibitor of endothelin-1 (ET-1) receptors, corrected the attenuated vasodilatation observed with r-HuEPO and inhibited the vasoconstriction induced by flow in the presence of r-HuEPO and L-NAME. r-HuEPO and L-NAME exacerbated ET-1 vasoconstriction. At shear stress values of 2 and 14 dyn/cm(2) (1 dyn = 10(-5) N), cultured EA.hy926 endothelial cells incubated with r-HuEPO, L-NAME, or both released greater ET-1 than untreated cells. In conclusion, r-HuEPO diminishes flow-induced vasodilatation. This inhibitory effect seems to implicate ET-1 release. NO withdrawal exacerbates the vascular effects of ET-1 in the presence of r-HuEPO. These findings support the importance of a balanced endothelial ET-1:NO ratio to avoid the vasopressor effects of r-HuEPO.

Endothelial dysfunction in rat adjuvant-induced arthritis: up-regulation of the vascular arginase pathway.

OBJECTIVE: To investigate whether arginase pathway abnormalities occur in vessels from rats with adjuvant-induced arthritis (AIA), and to determine whether the up-regulation of arginase, which reciprocally regulates nitric oxide synthase (NOS) by competing for the same substrate, L-arginine, contributes to endothelial dysfunction in AIA. METHODS: We performed vascular reactivity experiments on thoracic aortic rings from AIA rats and control rats, and we investigated the response of rings to norepinephrine (NE), sodium nitroprusside (SNP), and acetylcholine (ACh). ACh-induced relaxation was evaluated in the presence (or not in the presence) of the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), the arginase inhibitor N(ω)-hydroxy-nor-L-arginine (nor-NOHA), or both. Aortic arginase activity was measured using a spectrophotometric method, and the expression of arginase and endothelial NOS (eNOS) was evaluated by Western blotting. RESULTS: ACh-induced vasodilation was significantly impaired in AIA rats, while the responses to NE and to SNP did not differ from those in control rats. L-NAME reduced ACh-induced vasodilation to a lesser extent in AIA rats than in control rats. Incubation of aortic rings with nor-NOHA enhanced the vascular response to ACh in AIA rats and reversed the effects of L-NAME. Compared with control rats, AIA rats exhibited increased vascular expression of arginase II (by 22%) (P < 0.05) as well as increased arginase activity (by 49%) (P < 0.05), whereas eNOS expression was unchanged. Finally, arginase activity and expression correlated positively with arthritis severity. CONCLUSION: Our results are consistent with the notion that arginase up-regulation plays a role in AIA-associated endothelial dysfunction. They suggest that arginase might be an attractive new target for treating endothelial dysfunction in arthritis.

Influence of the consumption pattern of magnesium from magnesium-rich mineral water on magnesium bioavailability.

It is generally considered that the absorption of Mg is inversely related to the ingested dose. The objective of the present study was to determine if the mode of administration (bolus v. consumption throughout the day) could influence Mg bioavailability from Mg-rich natural mineral water comparing the same nutritional Mg amount (126 mg). Using a 2 d cross-over design, twelve healthy men were asked to drink 1·5 litres Mg-rich mineral water either as 2 × 750 ml or 7 × 212 ml throughout the day. Two stable isotopes ((25)Mg and (26)Mg) were used to label the water in order to distinguish both regimens. Fractional apparent Mg absorption was determined by faecal monitoring and Mg retention was determined by measuring urinary excretion of Mg isotopes. Higher Mg absorption (50·7 (SD 12·7) v. 32·4 (SD 8·1) %; P = 0·0007) and retention (47·5 (SD 12·9) v. 29·0 (SD 7·5) %; P = 0·0008) from Mg-rich mineral water were observed when it was consumed in seven servings compared with larger servings. Thus, regular water consumption throughout the day is an effective way to increase Mg bioavailability from Mg-rich mineral water.

Exercise aggravates cardiovascular risks and mortality in rats with disrupted nitric oxide pathway and treated with recombinant human erythropoietin.

Chronic administration of recombinant human erythropoietin (rHuEPO) can generate serious cardiovascular side effects such as arterial hypertension (HTA) in clinical and sport fields. It is hypothesized that nitric oxide (NO) can protect from noxious cardiovascular effects induced by chronic administration of rHuEPO. On this base, we studied the cardiovascular effects of chronic administration of rHuEPO in exercise-trained rats treated with an inhibitor of NO synthesis (L-NAME). Rats were treated or not with rHuEPO and/or L-NAME during 6 weeks. During the same period, rats were subjected to treadmill exercise. The blood pressure was measured weekly. Endothelial function of isolated aorta and small mesenteric arteries were studied and the morphology of the latter was investigated. L-NAME induced hypertension (197 ± 6 mmHg, at the end of the protocol). Exercise prevented the rise in blood pressure induced by L-NAME (170 ± 5 mmHg). However, exercise-trained rats treated with both rHuEPO and L-NAME developed severe hypertension (228 ± 9 mmHg). Furthermore, in these exercise-trained rats treated with rHuEPO/L-NAME, the acetylcholine-induced relaxation was markedly impaired in isolated aorta (60% of maximal relaxation) and small mesenteric arteries (53%). L-NAME hypertension induced an internal remodeling of small mesenteric arteries that was not modified by exercise, rHuEPO or both. Vascular ET-1 production was not increased in rHuEPO/L-NAME/training hypertensive rats. Furthermore, we observed that rHuEPO/L-NAME/training hypertensive rats died during the exercise or the recovery period (mortality 51%). Our findings suggest that the use of rHuEPO in sport, in order to improve physical performance, represents a high and fatal risk factor, especially with pre-existing cardiovascular risk.

The aqueous extract of Terminalia superba (Combretaceae) prevents glucose-induced hypertension in rats.

AIM OF THE STUDY: The stem bark of Terminalia superba (Combretaceae) (TS) is used in traditional Cameroonian medicine as antihypertensive remedy. The aim of this study was to investigate the hypotensive and the antihypertensive effects of the aqueous extract of the stem bark of Terminalia superba. MATERIALS AND METHODS: Hypertension was obtained in rats by oral administration of 10% D-glucose for 3 weeks. The acute effects of Terminalia superba were studied on blood pressure (BP) and heart rate (HR) after intravenous administration in normotensive rats (NTR) and glucose hypertensive rats (GHR). The antihypertensive effects were studied after oral administration of the extract (50 and 100 mg/kg/day) or nifedipine (10 mg/kg/day) for 3 weeks. At the end of the experiment, BP and HR were measured and reduced glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) activity levels were measured in heart, aorta, liver and kidney. RESULTS: Intravenous administration of the aqueous extract of Terminalia superba induced a significant hypotensive response without any change in HR. The hypotensive effect of the extract was unaffected by atropine or propranolol but decreased by reserpine (5 mg/kg) and yohimbine (0.1 mg/kg). In addition, the oral administration of the extract significantly prevented the rise in BP in glucose-hypertensive rats. Finally, the treatment with plant extract significantly blunted the decrease in GSH and the increase in MDA levels associated with hypertension, and significantly prevents the increase in aortic SOD activity. CONCLUSIONS: The present study demonstrates that the aqueous extract of the stem bark of Terminalia superba exhibits hypotensive and anti-hypertensive properties that are, at least in part, related to a withdrawal of sympathetic tone and to an improvement of the antioxidant status, respectively. Overall data validate the use of Terminalia superba as antihypertensive therapy in traditional medicine.

Long-term swimming exercise does not modulate the Akt-dependent endothelial nitric oxide synthase phosphorylation in healthy mice.

Molecular mechanisms by which exercise exerts cardiovascular benefits are poorly understood. Exercise-induced increase of endothelial NO synthase (eNOS) phosphorylation through the protein kinase Akt has been shown to be a key mechanism underlying the beneficial effect of exercise in coronary artery disease patients. We examined whether this protective pathway might also be activated in long-term-exercised healthy mice. C57BL/6 wild-type mice swam for 24 weeks. A group of sedentary animals were used as controls. Aortic levels of total protein kinase Akt (protein kinase B), phosphorylated Akt at ser473 (p-Akt), total eNOS, phosphorylated eNOS at Ser1177 (p-eNOS), and PECAM-1 (platelet endothelial cell adhesion molecule-1) were assessed by Western blotting. Protein expressions of Akt, p-Akt, eNOS, p-eNOS, and PECAM-1 were not modulated by 24 weeks of exercise. The Akt-dependent eNOS phosphorylation did not seem to be a primary molecular adaptation in response to long-term exercise in healthy mice.

Exercise reverses metabolic syndrome in high-fat diet-induced obese rats.

PURPOSE: Chronic consumption of a high-fat diet induces obesity. We investigated whether exercise would reverse the cardiometabolic disorders associated with obesity without it being necessary to change from a high- to normal-fat diet. METHODS: Sprague-Dawley rats were placed on a high-fat (HFD) or control diet (CD) for 12 wk. HFD rats were then divided into four groups: sedentary HFD (HFD-S), exercise trained (motor treadmill for 12 wk) HFD (HFD-Ex), modified diet (HFD to CD; HF/CD-S), and exercise trained with modified diet (HF/CD-Ex). Cardiovascular risk parameters associated with metabolic syndrome were measured, and contents of aortic Akt, phospho-Akt at Ser (473), total endothelial nitric oxide synthase (eNOS), and phospho-eNOS at Ser (1177) were determined by Western blotting. RESULTS: Chronic consumption of HFD induced a metabolic syndrome. Exercise and dietary modifications reduced adiposity, improved glucose and insulin levels and plasma lipid profile, and exerted an antihypertensive effect. Exercise was more effective than dietary modification in improving plasma levels of thiobarbituric acid-reacting substance and in correcting the endothelium-dependent relaxation to acetylcholine and insulin. Furthermore, independent of the diet used, exercise increased Akt and eNOS phosphorylation. CONCLUSIONS: Metabolic syndrome induced by HFD is reversed by exercise and diet modification. It is demonstrated that exercise training induces these beneficial effects without the requirement for dietary modification, and these beneficial effects may be mediated by shear stress-induced Akt/eNOS pathway activation. Thus, exercise may be an effective strategy to reverse almost all the atherosclerotic risk factors linked to obesity, particularly in the vasculature.

Mechanisms of vasorelaxation induced by Ziziphora clinopodioides Lam. (Lamiaceae) extract in rat thoracic aorta.

AIM OF THE STUDY: Ziziphora clinopodioides Lam. (ZC) is widely used in Uyghur folk medicine for the treatment of hypertension diseases in Xinjiang, an autonomous region of China. To provide pharmacological basis for this traditional use, we explored the vasodilating effects of ZC and investigated the underlying mechanisms. MATERIALS AND METHODS: Activity of hexane (ZCHE), dichloromethane (ZCDE) and aqueous (ZCAE) extracts of ZC were evaluated on isolated rat aortic rings pre-contracted with phenylephrine (PE) or high KCl. The mechanisms were evaluated on ZCDE, the most potent extract. RESULTS: ZCDE-induced relaxation in endothelium-intact aortic rings pre-contracted with phenylephrine (PE, 10(-6) M) or high KCl (6×10(-2) M), with respective EC(50) values of 0.27±0.03 and 0.34±0.04 g/l. Mechanic removal of the endothelium did not significantly modify ZCDE-induced relaxation. In endothelium-denuded aorta pre-contracted with PE (10(-6) M), the vasorelaxant effect of ZCDE was significantly decreased by 4-amino-pyridine (10(-3) M), but not by glibenclamide (10(-4) M), iberiotoxin (3×10(-8) M) and thapsigargin (10(-7) M). In Ca(2+) free solution, ZCDE significantly inhibited extracellular Ca(2+)-induced contraction in high KCl and PE pre-contracted rings. Additionally ZDCE inhibited the intracellular Ca(2+) release sensitive to PE (10(-6) M). CONCLUSIONS: The results demonstrate that ZDCE exhibits endothelium-independent vasodilating properties that are mediated by inhibition of extracellular Ca(2+) influx through voltage- and receptor-operated Ca(2+) channels (VDDCs and ROCCs), by inhibition of Ca(2+) release from intracellular stores, and also by the opening of voltage-dependent K(+) channels.