Losartan prevents portal hypertension-induced, redox-mediated endothelial dysfunction in the mesenteric artery in rats

Effects of Resveratrol on Vascular Function in Retinal Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) events are involved in the development of various ocular pathologies, e.g., retinal artery or vein occlusion. We tested the hypothesis that resveratrol is protective against I/R injury in the murine retina. Intraocular pressure (IOP) was elevated in anaesthetized mice to 110 mm Hg for 45 min via a micropipette placed in the anterior chamber to induce ocular ischemia. In the fellow eye, which served as control, IOP was kept at a physiological level. One group received resveratrol (30 mg/kg/day p.o. once daily) starting one day before the I/R event, whereas the other group of mice received vehicle solution only. On day eight after the I/R event, mice were sacrificed and retinal wholemounts were prepared and immuno-stained using a Brn3a antibody to quantify retinal ganglion cells. Reactivity of retinal arterioles was measured in retinal vascular preparations using video microscopy. Reactive oxygen species (ROS) and nitrogen species (RNS) were quantified in ocular cryosections by dihydroethidium and anti-3-nitrotyrosine staining, respectively. Moreover, hypoxic, redox and nitric oxide synthase gene expression was quantified in retinal explants by PCR. I/R significantly diminished retinal ganglion cell number in vehicle-treated mice. Conversely, only a negligible reduction in retinal ganglion cell number was observed in resveratrol-treated mice following I/R. Endothelial function and autoregulation were markedly reduced, which was accompanied by increased ROS and RNS in retinal blood vessels of vehicle-exposed mice following I/R, whereas resveratrol preserved vascular endothelial function and autoregulation and blunted ROS and RNS formation. Moreover, resveratrol reduced I/R-induced mRNA expression for the prooxidant enzyme, nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2). Our data provide evidence that resveratrol protects from I/R-induced retinal ganglion cell loss and endothelial dysfunction in the murine retina by reducing nitro-oxidative stress possibly via suppression of NOX2 upregulation.

Role of the posterior mucosal defense barrier in portal hypertensive gastropathy

Portal hypertensive gastropathy (PHG) is a complication of cirrhotic or noncirrhotic portal hypertension. PHG is very important in the clinic because it can cause acute or even massive blood loss, and its treatment efficacy and prognosis are poor. Currently, the incidence of PHG in patients with cirrhosis is 20-80%, but its pathogenesis is complicated and poorly understood. Studies have shown that portal hypertension can cause changes in gastric mucosal microcirculation hemodynamics, leading to changes in gastric mucosal histology and function and thereby weakening the mucosal defense barrier. However, no specific drug treatment plans are currently available. This article reviews the current literature to further our understanding of the mechanism underlying PHG and the relationship between PHG and the posterior mucosal defense barrier and to explore new therapeutic targets.

DPP4 inhibitor reduces portal hypertension in cirrhotic rats by normalizing arterial hypocontractility

AIMS

Dipeptidyl peptidase-4 inhibitor (DPP4i), a new antidiabetic agent, is reported to affect the progression of chronic liver diseases. The study aims to investigate the effects of DPP4i on contractile response, splanchnic hemodynamics, and portal pressure in cirrhotic rats.

MATERIALS AND METHODS

A rat model of carbon tetrachloride-induced cirrhosis was used in this study. Sixteen rats with cirrhosis were treated with DDP4i sitagliptin for 5 consecutive days. Portal and systemic pressures and portal blood flow were measured. Mesenteric arterioles were isolated, and concentration-response curves to norepinephrine (NE) were evaluated. The expression of NADPH oxidase (Nox)1, Nox2, Nox4, and soluble epoxide hydrolase (sEH) were detected. Reactive oxygen species (ROS) and epoxyeicosatrienoic acid (EET) levels in mesenteric arteries were also measured.

KEY FINDINGS

In cirrhotic rats, sitagliptin significantly reduced portal blood flow and portal pressure without effects on systemic pressure and reversed the decreased response of mesenteric arterioles to NE in an endothelium-dependent manner. Sitagliptin suppressed the increased Nox4 expression and ROS production. In vitro studies showed that Nox4 inhibitor enhanced arteriolar response to NE and reduced hydrogen peroxide (H2O2) level in cirrhotic rats. Sitagliptin also reduced EET levels and increased sEH expression of mesenteric vessels. Pre-incubation with sEH inhibitor in vitro reversed sitagliptin-induced augmentation of response to NE in cirrhotic rats.

SIGNIFICANCE

DPP4 inhibition by sitagliptin in vivo has beneficial effects on portal hypertension in cirrhotic rats through normalizing arterial hypocontractility. DDP4 inhibitor may be a novel strategy in the treatment of patients with cirrhosis and portal hypertension.

Metformin Regulates the Expression of SK2 and SK3 in the Atria of Rats With Type 2 Diabetes Mellitus Through the NOX4/p38MAPK Signaling Pathway

We previously found that metformin regulates the ion current conducted by the small conductance calcium-activated potassium channels (SK channels) in the atria of rats with type 2 diabetes mellitus (T2DM) as well as the mRNA and protein expression of the SK2 and SK3 subtypes of SK channels. In this study, we hypothesized that the nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4)/p38 mitogen-activated protein kinase (p38MAPK) signaling pathway was involved in the metformin-mediated regulation of SK2 and SK3 expression in the atria of rats with T2DM. We randomly divided Wistar rats into the control group, the untreated T2DM group, the metformin-treated group, the group receiving subcutaneous injections of the nicotinamide adenine dinucleotide phosphate oxidase (NOX) inhibitor diphenyleneiodonium (DPI), and the group receiving tail vein injections of the p38MAPK agonist anisomycin. Real-time polymerase chain reaction, Western blot, and immunohistochemistry were applied to examine the expression levels of SK2, SK3, NOX4, and phospho-p38MAPK (p-p38MAPK) mRNAs and proteins in the atrial tissue of relevant groups. We observed that the expression levels of NOX4 mRNA and protein and p-p38MAPK protein were significantly elevated in the atria of rats with T2DM compared with the control group. In addition, SK2 protein expression was reduced, whereas SK3 protein expression was increased. The 8-week treatment with metformin markedly reduced the expression levels of NOX4 mRNA and protein and p-p38MAPK protein, upregulated the SK2 expression, and downregulated the SK3 expression. Tail vein injection with anisomycin significantly increased the p-p38MAPK expression while further inhibiting the expression of SK2 and enhancing the expression of SK3. Subcutaneous injection with DPI considerably inhibited the expression of NOX4, further enhanced the expression of SK2 and suppressed the expression of SK3. In addition, subcutaneous injection with DPI significantly suppressed the phosphorylation of p38MAPK. In conclusion, the NOX4/p38MAPK signaling pathway mediates the downregulation of SK2 and the upregulation of SK3 in the atria of rats with T2DM. Long-term metformin treatment upregulates SK2 protein expression and downregulates SK3 protein expression by inhibiting the NOX4/p38MAPK signaling pathway.

NADPH oxidase 1/4 inhibition attenuates the portal hypertensive syndrome via modulation of mesenteric angiogenesis and arterial hyporeactivity in rats

AIM

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) plays key roles in the development of portal hypertension (PHT) and represents a potential therapeutic method. The objective of this study was to investigate whether pharmacological inhibition of NADPH oxidase activity could ameliorate PHT in rats.

METHOD

PHT model was established by partial portal vein ligation (PPVL). Rats were treated with 30 mg/kg GKT137831 (the most specific Nox1/4 inhibitor) or vehicle daily by gavage for 14 days beginning at the day of PPVL or sham operation (SO). Hemodynamics, severity of portal-systemic shunting, vascular contractility, vascular endothelial growth factor (VEGF), VEGFR-2, CD31, AKT, phospho-AKT (p-AKT, at Ser473), endothelial nitric oxide synthase (eNOS), and phospho-eNOS (p-eNOS, at Ser1177) expressions were evaluated. Nitric oxide (NO) production and oxidative stress in mesenteric arteries, and hydrogen peroxide (H2O2) in both mesenteric tissues and arteries were measured.

RESULT

Inhibition of NOX1/4 with GKT137831 significantly decreased cardiac index, increased portal flow resistance, reduced portal pressure (PP), portal blood flow, mesenteric angiogenesis and portal-systemic shunting (PSS) in PPVL rats. GKT137831 reduced the production of H2O2, down regulated mesenteric angiogenesis markers (CD31, vascular endothelial growth factor (VEGF) and VEGFR-2 expression. Compared with controls), the mesenteric artery contraction to norepinephrine (NE) was impaired in PPVL rats, which was reversed by exposure to GKT137831. In addition, GKT137831 markedly decrease NADPH oxidase activity and ROS production in mesenteric arteries, and reduced NO production by decreasing the level of phosphor-AKT and eNOS.

CONCLUSION

Inhibition of NOX1/4 decreased PP, ameliorated hyperdynamic circulation, mesenteric angiogenesis and arterial hyporesonse in portal hypertensive rats. Pharmacological inhibition of NOX1/4 activity may be a potential treatment for PHT-related complications.

Acute-on-chronic liver disease enhances phenylephrine-induced endothelial nitric oxide release in rat mesenteric resistance arteries through enhanced PKA, PI3K/AKT and cGMP signalling pathways

Acute-on-chronic liver disease is a clinical syndrome characterized by decompensated liver fibrosis, portal hypertension and splanchnic hyperdynamic circulation. We aimed to determine whether the alpha-1 agonist phenylephrine (Phe) facilitates endothelial nitric oxide (NO) release by mesenteric resistance arteries (MRA) in rats subjected to an experimental microsurgical obstructive liver cholestasis model (LC). Sham-operated (SO) and LC rats were maintained for eight postoperative weeks. Phe-induced vasoconstriction (in the presence/absence of the NO synthase –NOS- inhibitor L-NAME) and vasodilator response to NO donor DEA-NO were analysed. Phe-induced NO release was determined in the presence/absence of either H89 (protein kinase –PK- A inhibitor) or LY 294002 (PI3K inhibitor). PKA and PKG activities, alpha-1 adrenoceptor, endothelial NOS (eNOS), PI3K, AKT and soluble guanylate cyclase (sGC) subunit expressions, as well as eNOS and AKT phosphorylation, were determined. The results show that LC blunted Phe-induced vasoconstriction, and enhanced DEA-NO-induced vasodilation. L-NAME increased the Phe-induced contraction largely in LC animals. The Phe-induced NO release was greater in MRA from LC animals. Both H89 and LY 294002 reduced NO release in LC. Alpha-1 adrenoceptor, eNOS, PI3K and AKT expressions were unchanged, but sGC subunit expression, eNOS and AKT phosphorylation and the activities of PKA and PKG were higher in MRA from LC animals. In summary, these mechanisms may help maintaining splanchnic vasodilation and hypotension observed in decompensated LC.

Treatment of NASH with Antioxidant Therapy: Beneficial Effect of Red Cabbage on Type 2 Diabetic Rats

Aims

Oxidative stress (OS) plays a major role in type 2 diabetes and its vascular and hepatic complications, and novel therapeutic approaches include natural antioxidants. Our previous chemical and biological studies demonstrated the antioxidant activities of red cabbage (RC), and here, we aimed to determine the in vivo effects of 2-month long RC consumption using a high-fat/high-fructose model of diabetic rats.

Results

This vegetable, associated with lifestyle measurement, was shown to decrease OS and increase vascular endothelial NO synthase expression, ensuring vascular homeostasis. In the liver, RC consumption decreased OS by inhibiting p22phox expression and Nrf2 degradation and increasing catalase activity. It inhibited the activation of SREBP (1c, 2), ChREBP, NF-κB, ERK1/2, PPARγ, and GS and SIRT1 decrease, as observed in diabetic rats.

Conclusion/innovation

RC consumption led to metabolic profile improvement, together with hepatic function improvements. Although lifestyle changes are not sufficient to prevent diabetic complications, enrichment with RC avoids progression hepatic complications. This antioxidant strategy using RC does not only able to increase antioxidant defense, such as classical antioxidant, but also able to assure a metabolic and energetic balance to reverse complications. Whereas traditional medical therapy failed to reverse NASH in diabetic patients, consumption of RC should be a natural therapy to treat it.

Beneficial effects of cherry consumption as a dietary intervention for metabolic, hepatic and vascular complications in type 2 diabetic rats

Background

Oxidative stress (OS) plays an important role in type 2 diabetes (T2D) pathogenesis and its complications. New therapies target natural antioxidants as an alternative and/or supplemental strategy to prevent and control them. Our previous chemical and biological studies highlighted the important antioxidant activities of cherries, among other fruits and vegetables, thus we aimed to determine in vivo effects of 2-month long cherry consumption using a high-fat/high-fructose (HFHF) model of diabetic-rats (Lozano et al. in Nutr Metab 13:15, 2016).

Methods

After 2 months of HFHF, male Wistar rats were divided into: HFHF and HFHF enriched in cherry (nutritional approach) or standard diet ND (lifestyle measures) and ND plus cherry during 2 months. Metabolic, lipidic, oxidative parameters were quantified. Tissues (liver, pancreas and vessels) OS were assessed and hepatic (steatosis, fibrosis, inflammation) and vascular (endothelial dysfunction) complications were characterized.

Results

T2D was induced after 2 months of HFHF diet, characterized by systemic hyperglycaemia, hyperinsulinemia, glucose intolerance, dyslipidaemia, hyperleptinemia, and oxidative stress associated with endothelial dysfunction and hepatic complications. Cherry consumption for 2 months, in addition to lifestyle measures, in T2D-rats decreased and normalized the systemic disturbances, including oxidative stress complications. Moreover, in the vessel, cherry consumption decreased oxidative stress and increased endothelial nitric oxide (NO) synthase levels, thus increasing NO bioavailability, ensuring vascular homeostasis. In the liver, cherry consumption decreased oxidative stress by inhibiting NADPH oxidase subunit p22phox expression, nuclear factor erythroid-2 related factor 2 (Nrf2) degradation and the formation of reactive oxygen species. It inhibited the activation of sterol regulatory element-binding proteins (1c and 2) and carbohydrate-responsive element-binding protein, and thus decreased steatosis as observed in T2D rats. This led to the improvement of metabolic profiles, together with endothelial and hepatic function improvements.

Conclusion

Cherry consumption normalized vascular function and controlled hepatic complications, thus reduced the risk of diabetic metabolic disorders. These results demonstrate that a nutritional intervention with a focus on OS could prevent and/or delay the onset of vascular and hepatic complications related to T2D.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0744-6) contains supplementary material, which is available to authorized users.

Characterization of pressure-mediated vascular tone in resistance arteries from bile duct-ligated rats

In cirrhosis, changes in pressure-mediated vascular tone, a key determinant of systemic vascular resistance (SVR), are unknown. To address this gap in knowledge, we assessed ex vivo dynamics of pressurized mesenteric resistance arteries (diameter ~ 260 μm) from bile duct-ligated (BDL) and sham-operated (SHAM) rats and determined the underlying mechanisms. At isobaric intraluminal pressure (70 mmHg) as well as with step-wise increase in pressure (10-110 mmHg), arteries from SHAM-rats constricted more than BDL-rats, and had reduced luminal area. In both groups, incubation with LNAME (a NOS inhibitor) had no effect on pressure-mediated tone, and expression of NOS isoforms were similar. TEA, which enhances Ca²⁺ influx, augmented arterial tone only in SHAM-rats, with minimal effect in those from BDL-rats that was associated with reduced expression of Ca²⁺ channel TRPC6. In permeabilized arteries, high-dose Ca²⁺ and γGTP enhanced the vascular tone, which remained lower in BDL-rats that was associated with reduced ROCK2 and pMLC expression. Further, compared to SHAM-rats, in BDL-rats, arteries had reduced collagen expression which was associated with increased expression and activity of MMP-9. BDL-rats also had increased plasma reactive oxygen species (ROS). In vascular smooth muscle cells in vitro, peroxynitrite enhanced MMP-9 activity and reduced ROCK2 expression. These data provide evidence that in cirrhosis, pressure-mediated tone is reduced in resistance arteries, and suggest that circulating ROS play a role in reducing Ca²⁺ sensitivity and enhancing elasticity to induce arterial adaptations. These findings provide insights into mechanisms underlying attenuated SVR in cirrhosis.

Hyperhomocysteinemia potentiates diabetes-impaired EDHF-induced vascular relaxation: Role of insufficient hydrogen sulfide

Insufficient hydrogen sulfide (H₂S) has been implicated in Type 2 diabetic mellitus (T2DM) and hyperhomocysteinemia (HHcy)-related cardiovascular complications. We investigated the role of H₂S in T2DM and HHcy-induced endothelial dysfunction in small mesenteric artery (SMA) of db/db mice fed a high methionine (HM) diet. HM diet (8 weeks) induced HHcy in both T2DM db/db mice and non-diabetic db/+ mice (total plasma Hcy: 48.4 and 31.3 µM, respectively), and aggravated the impaired endothelium-derived hyperpolarization factor (EDHF)-induced endothelium-dependent relaxation to acetylcholine (ACh), determined by the presence of eNOS inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) and prostacyclin (PGI₂) inhibitor indomethacin (INDO), in SMA from db/db mice but not that from db/+ mice. A non-selective Ca²⁺-active potassium channel (K_Ca) opener NS309 rescued T2DM/HHcy-impaired EDHF-mediated vascular relaxation to ACh. EDHF-induced relaxation to ACh was inhibited by a non-selective K_Ca blocker TEA and intermediate-conductance K_Ca blocker (IK_Ca) Tram-34, but not by small-conductance K_Ca (SK_Ca) blocker Apamin. HHcy potentiated the reduction of free sulfide, H₂S and cystathionine γ-lyase protein, which converts L-cysteine to H₂S, in SMA of db/db mice. Importantly, a stable H₂S donor DATS diminished the enhanced O₂^- production in SMAs and lung endothelial cells of T2DM/HHcy mice. Antioxidant PEG-SOD and DATS improved T2DM/HHcy impaired relaxation to ACh. Moreover, HHcy increased hyperglycemia-induced IK_Ca tyrosine nitration in human micro-vascular endothelial cells. EDHF-induced vascular relaxation to L-cysteine was not altered, whereas such relaxation to NaHS was potentiated by HHcy in SMA of db/db mice which was abolished by ATP-sensitive potassium channel blocker Glycolamide but not by K_Ca blockers.

Conclusions

Intermediate HHcy potentiated H₂S reduction via CSE-downregulation in microvasculature of T2DM mice. H₂S is justified as an EDHF. Insufficient H₂S impaired EDHF-induced vascular relaxation via oxidative stress and IK_Ca inactivation in T2DM/HHcy mice. H₂S therapy may be beneficial for prevention and treatment of micro-vascular complications in patients with T2DM and HHcy.

The Ketone Metabolite β-Hydroxybutyrate Attenuates Oxidative Stress in Spinal Cord Injury by Suppression of Class I Histone Deacetylases

The ketone metabolite β-hydroxybutyrate (βOHB), is reported to be neuroprotective after spinal cord injury (SCI) in rats, but the underlying mechanism remains unknown. The present study aims to investigate effects of βOHB on suppression of oxidative stress and inhibition of class I histone deacetylases (HDACs) in in vivo and in vitro models. Rats were fed with ketogenic diet (KD) or standard diet (SD) for 3 weeks. A C5 hemi-contusion injury was applied to these animals on the 14th day of experiment, and spinal cord samples were harvested on the 1st, 3rd and 7th days after SCI, respectively. The blood ketone levels were significantly higher in the KD groups. KD reduced oxidative stress markers and reactive oxygen species (ROS) products, downregulated the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX)2 and NOX4, and upregulated the expression of forkhead box group O (FOXO)3a, mitochondrial superoxide dismutase (MnSOD), and catalase after SCI. The in vitro study, performed on PC12 cells, indicated that βOHB inhibited H₂O₂-induced ROS production, decreased NOX2 and NOX4 protein levels, and upregulated FOXO3a, MnSOD, and catalase levels in a dose-dependent manner, which was consistent with the in vivo results. The ketone metabolite βOHB inhibited HDAC1, HDAC2, and HDAC3 activity, but not HDAC8 in SCI rats and PC12 cells. Depletion of HDAC1 or HDAC2 with small interfering RNA (siRNA) attenuated H₂O₂-induced ROS production and protein carbonylation and elevated FOXO3a protein levels, meanwhile reducing NOX2 and NOX4 protein expression in PC12 cells. Our results indicate that the ketone metabolite βOHB attenuates oxidative stress in SCI by inhibition of class I HDACs, and selected suppression of HDAC1 or HDAC2 regulates FOXO3a, NOX2, and NOX4 expression. Therefore, the ketone metabolite βOHB may be a novel promising therapeutic agent for SCI.

The Protective Effect of Antioxidants Consumption on Diabetes and Vascular Complications

Obesity and diabetes is generally accompanied by a chronic state of oxidative stress, disequilibrium in the redox balance, implicated in the development and progression of complications such as micro- and macro-angiopathies. Disorders in the inner layer of blood vessels, the endothelium, play an early and critical role in the development of these complications. Blunted endothelium-dependent relaxation and/or contractions are quietly associated to oxidative stress. Thus, preserving endothelial function and oxidative stress seems to be an optimization strategy in the prevention of vascular complications associated with diabetes. Diet is a major lifestyle factor that can greatly influence the incidence and the progression of type 2 diabetes and cardiovascular complications. The notion that foods not only provide basic nutrition but can also prevent diseases and ensure good health and longevity is now attained greater prominence. Some dietary and lifestyle modifications associated to antioxidative supply could be an effective prophylactic means to fight against oxidative stress in diabesity and complications. A significant benefit of phytochemicals (polyphenols in wine, grape, teas), vitamins (ascorbate, tocopherol), minerals (selenium, magnesium), and fruits and vegetables in foods is thought to be capable of scavenging free radicals, lowering the incidence of chronic diseases. In this review, we discuss the role of oxidative stress in diabetes and complications, highlight the endothelial dysfunction, and examine the impact of antioxidant foods, plants, fruits, and vegetables, currently used medication with antioxidant properties, in relation to the development and progression of diabetes and cardiovascular complications.

Nitric oxide metabolites, nitrative stress, and paraoxonase activity in hepatopulmonary syndrome

AIM

To investigate possible abnormalities of vasoactive compounds, nitrative stress, and antioxidant activity of paraoxonase (PONa) in human hepatopulmonary syndrome (HPS), we determined endothelin-1 (ET), nitric oxide (NOx) metabolites, PONa alongside crude plasma nitrotyrosine (NT) as surrogate marker of nitrative stress.

MATERIAL AND METHODS

Liver cirrhosis (LC) patients with HPS (n = 12) were matched by age, sex, and Child-Pugh score to LC patients without HPS (n = 15) and to healthy controls (CTR) (n = 15); plasma NO2(-) (nitrite) (vascular metabolite), NO3(-) (nitrate) (inflammatory metabolite), and PONa were determined by a colorimetric assay, ET, and NT by immunoassays.

RESULTS

HPS patients showed higher level of ET (p = 0.0002), NO2(-) (p = 0.002), NO3(-) (p = 0.0001), NT (p < 0.0001), and lower PONa (p = 0.0004) than CTR; post-hoc analysis revealed greater ET (p < 0.05) and NO3(-) (p < 0.005) in LC patients with HPS than in LC patients without HPS. NT correlated to Child-Pugh score within HPS (p = 0.04) and LC (p = 0.02).

CONCLUSION

Our HPS patients are characterized by elevated plasma levels of ET and NOx metabolites and lower PONa. Reduced PONa alongside elevated NO3(-) and NT suggests that defective antioxidation may favor nitrative stress and both may be implicated in the pathogenesis of HPS.

Impact of the Type of Continuous Insulin Administration on Metabolism in a Diabetic Rat Model

Exogenous insulin is the only treatment available for type 1 diabetic patients and is mostly administered by subcutaneous (SC) injection in a basal and bolus scheme using insulin pens (injection) or pumps (preimplanted SC catheter). Some divergence exists between these two modes of administration, since pumps provide better glycaemic control compared to injections in humans. The aim of this study was to compare the impacts of two modes of insulin administration (single injections of long-acting insulin or pump delivery of rapid-acting insulin) at the same dosage (4 IU/200 g/day) on rat metabolism and tissues. The rat weight and blood glucose levels were measured periodically after treatment. Immunostaining for signs of oxidative stress and for macrophages was performed on the liver and omental tissues. The continuous insulin delivery by pumps restored normoglycaemia, which induced the reduction of both reactive oxygen species and macrophage infiltration into the liver and omentum. Injections controlled the glucose levels for only a short period of time and therefore tissue stress and inflammation were elevated. In conclusion, the insulin administration mode has a crucial impact on rat metabolic parameters, which has to be taken into account when studies are designed.

Portal or subcutaneous insulin infusion: efficacy and impact on liver inflammation

Intraperitoneal insulin allows physiological portal insulin administration and first-pass hepatic insulin extraction, but the impact on liver metabolism and inflammation is unknown. Our objective was to compare the impact, on metabolic control and liver function, of the same dose of insulin administered either intraperitoneally or subcutaneously during continuous infusion in diabetic rats. Wistar rats were randomly divided into 4 groups: control (C), untreated diabetic (streptozotocin, 100 mg/kg) and diabetic rats treated by continual subcutaneous Insuplant® infusion (CSII) and continual intraperitoneal Insuplant(®) infusion (CPII) of 2 UI/200 g/day (via an osmotic mini-pump for 1-4 weeks). Insulin signalling pathways were analysed through hepatic expression of growth hormone receptor and phosphorylated insulin receptor substrate 1. Metabolic control was determined by measurement of body weight, blood glucose and fructosamine. Liver function was assessed by measuring insulin-like growth factor-1 (IGF-1), with global inflammation assessed by levels of alpha-2-macroglobulin (α2M) and lipid peroxidation in plasma. Liver inflammation was evaluated by quantification of hepatic macrophage infiltration and reactive oxygen species production. CPII induced a better improvement in metabolic control and liver function than CSII, producing a significant decrease in blood glucose and fructosamine, coupled with increased IGF-1 and hepatic glycogen storage. Moreover, liver oxidative stress and liver inflammation were reduced. Such observations indicate that the same insulin level in CPII improves glucose control and hepatic glucose metabolism and function, attenuating the hepatic inflammatory response to diabetes. These data demonstrate the importance of focusing on therapeutics to allow first-pass hepatic insulin extraction or prevent diabetic complications.

Featured Article: Oxidative stress status and liver tissue defenses in diabetic rats during intensive subcutaneous insulin therapy

Long-term insulin delivery can reduce blood glucose variability in diabetic patients. In this study, its impact on oxidative stress status, inflammation, and liver injury was investigated. Diabetes was induced in Wistar rats with a single dose of streptozotocin (100 mg/kg). Untreated rats and rats administered Insuplant® (2 UI/200 g/day) through a subcutaneous osmotic pump for one or four weeks were compared with non-diabetic controls. Body weight, fructosamine level, total cholesterol, Insulin Growth Factor-1 (IGF-1) level, lipid peroxidation, and total antioxidant capacity were measured. Hepatic injury was determined through the measurement of glycogen content, reactive oxygen species (ROS) production, and macrophage infiltration. Liver oxidative stress status was evaluated through the measurement of superoxide dismutase (SOD), catalase (CAT), and nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) expression, and p38 mitogen-activated protein kinase (p38MAPK) activation. Induction of diabetes led to increased plasma oxidative stress and inflammation. Moreover, ROS production and macrophage infiltration increased in addition to SOD, CAT, and NADPH oxidase expression. Intensive insulin therapy improved metabolic control in diabetic animals as seen by a restoration of hepatic glycogen, plasma IGF-1 levels, and a decrease in plasma oxidative stress. However, insulin treatment did not result in a decrease in acute inflammation in diabetic rats as seen by continued ROS production and macrophage infiltration in the liver, and a decrease of p38MAPK activation. These results suggest that the onset of diabetes induces liver oxidative stress and inflammation, and that subcutaneous insulin administration cannot completely reverse these changes. Targeting oxidative stress and/or inflammation in diabetic patients could be an interesting strategy to improve therapeutic options.

17β-estradiol potentiates endothelium-dependent nitric oxide- and hyperpolarization-mediated relaxations in blood vessels of male but not female apolipoprotein-E deficient mice

The present study investigated the influence of gender on the changes underlying endothelial dysfunction in hyperlipidemia during aging. Isometric tension in rings (with endothelium) of the aortae and superior mesenteric arteries from apolipoprotein-E deficient mice was determined in wire myographs. Nitric oxide (NO)- and endothelium-dependent hyperpolarization (EDH)-mediated relaxations were smaller in the aortae and mesenteric arteries of 32weeks old males than eight weeks old males. In females, NO- and EDH-mediated relaxations were impaired only at 84weeks of age. The levels of reactive oxygen species were elevated in the blood vessels of 32weeks old males, but not females. Acute in vitro treatment with 17β-estradiol and apocynin improved NO- and EDH-mediated relaxations in 32weeks old males but not in 84weeks old males. Relaxations to SKA-31, activator of intermediate (IKCa) and small (SKCa) conductance calcium-activated potassium channels, were attenuated in the mesenteric arteries of 32weeks old males. Such impairment was restored by acute treatment with apocynin. These findings suggest that male hyperlipidemic mice develop endothelial dysfunction at an earlier age than females. This endothelial dysfunction is associated with impaired NO bioavailability and reduced IKCa and SKCa activity. Apocynin and 17β-estradiol restore the endothelial function only in younger male animals but not in older male or female animals.

Effect of the oestrogen receptor antagonist fulvestrant on the cirrhotic rat lung

It has been postulated that cirrhosis-related lung vasodilatation and the subsequent hepatopulmonary syndrome are partly explained by an increased estradiol level through an enhanced endothelial formation of nitric oxide (NO). In this study, we assessed whether the oestrogen receptor antagonist fulvestrant (F) improves cirrhosis-related lung abnormalities. Cirrhosis was induced in rats by chronic bile duct ligation (CBDL). Four groups were studied: CBDL, CBDL+F, sham, and sham+F. Histological, immunohistochemical, and Western blot analyses were performed on lung samples. In the lung, the endothelial NO synthase and the nitrotyrosine protein expressions were increased in CBDL as compared to sham rats. Both parameters were significantly reduced by fulvestrant in the CBDL rats. Surprisingly, the level of pVASP (an indirect marker of NO formation and action) was decreased in CBDL rats, and fulvestrant had no effect on this parameter. The level of the vascular endothelial growth factor, the diameter of small lung vessels, and the number of macrophages were increased in CBDL lungs in comparison with sham lungs, and these parameters were unaffected by fulvestrant treatment. In conclusion, fulvestrant may not be relevant to improve lung abnormalities in cirrhosis because NO may not be biologically active and because key events contributing to the lung abnormalities are not affected by fulvestrant.

Up-regulation of intrarenal renin-agiotensin system contributes to renal damage in high-salt induced hypertension rats

BACKGROUND/AIMS

To investigate the change of intrarenal renin-agiotensin system (RAS) and its role in high-salt induced hypertension.

METHODS

Wistar rats were divided into normal-salt (NS), high-salt diet (HS) and high-salt diet with Losartan group (HS+L), for 6 weeks. Systolic blood pressure (SBP) was monitored. Blood and urine samples were collected every 2 weeks. Angiotensinogen (AGT) was measured by ELISA. AGT mRNA and protein were measured by real-time PCR and immunohistochemistry. Renin activity and angiotensin II (Ang II) were measured by radioimmunoassay.

RESULTS

HS versus NS group, SBP increased from 2(nd) week (P<0.05), urinary protein increased at 6(th) week (P<0.05). Although plasma renin, AGT and Ang II had no significant changes (P>0.05), renal cortex renin, AGT, and Ang II increased significantly in HS (P<0.05). In HS+L, Losartan failed to reduce SBP (P>0.05) but abolished the increase of proteinuria (P<0.01), renal cortex renin, AGT, Ang II and urinary AGT reduced (P<0.05) while plasma renin, AGT and Ang II enhanced (P<0.05) when compared with HS. Urinary AGT was positively correlated with renal AGT (r=0.592, P <0.01) and Ang II (r=0.726, P <0.01).

CONCLUSION

Inappropriate response of the renal RAS to a high salt diet may contribute to hypertension and renal damage, and urinary AGT could reflect intrarenal RAS activity.

Pro-inflammatory and pro-oxidant status of pancreatic islet in vitro is controlled by TLR-4 and HO-1 pathways

Since their isolation until implantation, pancreatic islets suffer a major stress leading to the activation of inflammatory reactions. The maintenance of controlled inflammation is essential to preserve survival and function of the graft. Identification and targeting of pathway(s) implicated in post-transplant detrimental inflammatory events, is mandatory to improve islet transplantation success. We sought to characterize the expression of the pro-inflammatory and pro-oxidant mediators during islet culture with a focus on Heme oxygenase (HO-1) and Toll-like receptors-4 signaling pathways. Rat pancreatic islets were isolated and pro-inflammatory and pro-oxidant status were evaluated after 0, 12, 24 and 48 hours of culture through TLR-4, HO-1 and cyclooxygenase-2 (COX-2) expression, CCL-2 and IL-6 secretion, ROS (Reactive Oxygen Species) production (Dihydroethidine staining, DHE) and macrophages migration. To identify the therapeutic target, TLR4 inhibition (CLI-095) and HO-1 activation (cobalt protoporphyrin,CoPP) was performed. Activation of NFκB signaling pathway was also investigated. After isolation and during culture, pancreatic islet exhibited a proinflammatory and prooxidant status (increase levels of TLR-4, COX-2, CCL-2, IL-6, and ROS). Activation of HO-1 or inhibition of TLR-4 decreased inflammatory status and oxidative stress of islets. Moreover, the overexpression of HO-1 induced NFκB phosphorylation while the inhibition of TLR-4 had no effect NFκB activation. Finally, inhibition of pro-inflammatory pathway induced a reduction of macrophages migration. These data demonstrated that the TLR-4 signaling pathway is implicated in early inflammatory events leading to a pro-inflammatory and pro-oxidant status of islets in vitro. Moreover, these results provide the mechanism whereby the benefits of HO-1 target in TLR-4 signaling pathway. HO-1 could be then an interesting target to protect islets before transplantation.

Probiotics (VSL#3) prevent endothelial dysfunction in rats with portal hypertension: role of the angiotensin system

AIMS

Portal hypertension characterized by generalized vasodilatation with endothelial dysfunction affecting nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) has been suggested to involve bacterial translocation and/or the angiotensin system. The possibility that ingestion of probiotics prevents endothelial dysfunction in rats following common bile duct ligation (CBDL) was evaluated.

METHODS

Rats received either control drinking water or the probiotic VSL#3 solution (50 billion bacteria.kg body wt⁻¹.day⁻¹) for 7 weeks. After 3 weeks, rats underwent surgery with either resection of the common bile duct or sham surgery. The reactivity of mesenteric artery rings was assessed in organ chambers, expression of proteins by immunofluorescence and Western blot analysis, oxidative stress using dihydroethidium, and plasma pro-inflammatory cytokine levels by flow cytometry.

RESULTS

Both NO- and EDH-mediated relaxations to acetylcholine were reduced in the CBDL group compared to the sham group, and associated with a reduced expression of Cx37, Cx40, Cx43, IKCa and SKCa and an increased expression of endothelial NO synthase (eNOS). In aortic sections, increased expression of NADPH oxidase subunits, angiotensin converting enzyme, AT1 receptors and angiotensin II, and formation of ROS and peroxynitrite were observed. VSL#3 prevented the deleterious effect of CBDL on EDH-mediated relaxations, vascular expression of connexins, IKCa, SKCa and eNOS, oxidative stress, and the angiotensin system. VSL#3 prevented the CBDL-induced increased plasma TNF-α, IL-1α and MCP-1 levels.

CONCLUSIONS

These findings indicate that VSL#3 ingestion prevents endothelial dysfunction in the mesenteric artery of CBDL rats, and this effect is associated with an improved vascular oxidative stress most likely by reducing bacterial translocation and the local angiotensin system.

Reactive oxygen species are involved in regulating hypocontractility of mesenteric artery to norepinephrine in cirrhotic rats with portal hypertension

Background: Oxidative stress is involved in the hypocontractility of visceral artery to vasoconstrictors and formation of hyperdynamic circulation in cirrhosis with portal hypertension. In the present study, we investigated the effect of reactive oxygen species (ROS) on the mesenteric artery contractility in CCl₄-induced cirrhotic rats, and the roles of G protein-coupled receptors (GPCRs) desensitization and RhoA /Rho associated coiled-coil forming protein kinase (ROCK) pathways.

Methods: The mesenteric artery contraction to norepinephrine (NE) was determined by vessel perfusion system following treatments with apocynin, tempol or PEG-catalase. The protein expression of α1 adrenergic receptor, β-arrestin-2, ROCK-1, moesin and p-moesin was measured by western blot. The interaction between α1 adrenergic receptor and β-arrestin-2 was assessed by co-immunoprecipitation.

Results: Pretreatment with apocynin or PEG-catalase in cirrhotic rats, the hydrogen peroxide level in the mesenteric arteriole was significantly decreased, and the dose-response curve of mesenteric arteriole to NE moved to the left with EC₅₀ decreased. There was no significant change for the expression of α1 adrenergic receptor. However, the protein expression of β-arrestin-2 and its affinity with α1 adrenergic receptor were significantly decreased. The ROCK-1 activity and anti- Y-27632 inhibition in cirrhotic rats increased significantly with the protein expression unchanged. Such effects were not observed in tempol-treated group.

Conclusion: The H₂O₂ decrease in mesenteric artery from rats with cirrhosis resulted in down regulation of the β-arrestin-2 expression and its binding ability with α1 adrenergic receptor, thereby affecting the agonist-induced ROCK activation and improving the contractile response in blood vessels.

Estrogen improves the hyperdynamic circulation and hyporeactivity of mesenteric arteries by alleviating oxidative stress in partial portal vein ligated rats

AIM: To evaluate the effects of estrogen (E2) on systemic and splanchnic hyperdynamic circulation in portal hypertensive rats.

METHODS: Fifty castrated female Sprague-Dawley rats were divided into five groups: sham operation (SO), partial portal vein ligation (PPVL) + placebo (PLAC), PPVL + E2, PPVL + ICI and PPVL + E2 + ICI. Hemodynamic measurements were performed using ultrasonography. Mesenteric arteriole contractility in response to norepinephrine was determined using a vessel perfusion system. Oxidative stress in the mesenteric artery was investigated by in situ detection of the superoxide anion (O₂•⁻) and hydrogen peroxide (H₂O₂) concentrations.

RESULTS: Treatment with E2 resulted in a significant decrease of portal pressure (P < 0.01) and portal venous inflow (P < 0.05), and higher systemic vascular resistance (P < 0.05) and splanchnic arteriolar resistance (P < 0.01) in PPVL + E2 rats compared to PPVL + PLAC rats. In the mesenteric arterioles of PPVL + E2 rats, the dose-response curve was shifted left, and the EC₅₀ was decreased (P < 0.01). E2 reduced O₂•⁻ production and H₂O₂ concentration in the mesenteric artery. However, ICI182, 780 reversed the beneficial effects of E2, therefore, the systemic and splanchnic hyperdynamic circulation were more deteriorated in ICI182, 780-treated rats.

CONCLUSION: Treatment with estrogen improved the systemic and splanchnic hyperdynamic circulation in PPVL rats, in part due to the alleviation of oxidative stress.

Grape-Derived Polyphenols Prevent Doxorubicin-Induced Blunted EDH-Mediated Relaxations in the Rat Mesenteric Artery: Role of ROS and Angiotensin II

This study determined whether doxorubicin, an anticancer agent, impairs endothelium-dependent relaxations mediated by nitric oxide (NO) and endothelium-derived hyperpolarization (EDH) in the mesenteric artery and, if so, the mechanism underlying the protective effect of red wine polyphenols (RWPs), a rich natural source of antioxidants. Male Wistar rats were assigned into 4 groups: control, RWPs, doxorubicin, and doxorubicin + RWPs. Vascular reactivity was assessed in organ chambers; the vascular formation of reactive oxygen species (ROS) using dihydroethidine and the expression levels of small and intermediate conductance calcium-activated potassium channels (SKCa, IKCa) and connexin 40 (Cx40), which are involved in EDH-type relaxations, endothelial NO synthase (eNOS), angiotensin II, and AT1 receptors by immunofluorescence. The doxorubicin treatment impaired EDH-mediated relaxations, whereas those mediated by NO were minimally affected. This effect was associated with reduced expression levels of SKCa, IKCa, and Cx40, increased expression levels of eNOS, angiotensin II, and AT1 receptors, and formation of ROS in mesenteric arteries. RWPs prevented both the doxorubicin-induced blunted EDH-type relaxations and the increased vascular oxidative stress, and they improved the expression levels of target proteins. These findings suggest that polyphenol-rich natural products might be of interest in the management of doxorubicin-induced vascular injury possibly by improving the vascular angiotensin system.

Aronia melanocarpa juice, a rich source of polyphenols, induces endothelium-dependent relaxations in porcine coronary arteries via the redox-sensitive activation of endothelial nitric oxide synthase

This study examined the ability of Aronia melanocarpa (chokeberry) juice, a rich source of polyphenols, to cause NO-mediated endothelium-dependent relaxations of isolated coronary arteries and, if so, to determine the underlying mechanism and the active polyphenols. A. melanocarpa juice caused potent endothelium-dependent relaxations in porcine coronary artery rings. Relaxations to A. melanocarpa juice were minimally affected by inhibition of the formation of vasoactive prostanoids and endothelium-derived hyperpolarizing factor-mediated responses, and markedly reduced by N(ω)-nitro-l-arginine (endothelial NO synthase (eNOS) inhibitor), membrane permeant analogs of superoxide dismutase and catalase, PP2 (Src kinase inhibitor), and wortmannin (PI3-kinase inhibitor). In cultured endothelial cells, A. melanocarpa juice increased the formation of NO as assessed by electron paramagnetic resonance spectroscopy using the spin trap iron(II)diethyldithiocarbamate, and reactive oxygen species using dihydroethidium. These responses were associated with the redox-sensitive phosphorylation of Src, Akt and eNOS. A. melanocarpa juice-derived fractions containing conjugated cyanidins and chlorogenic acids induced the phosphorylation of Akt and eNOS. The present findings indicate that A. melanocarpa juice is a potent stimulator of the endothelial formation of NO in coronary arteries; this effect involves the phosphorylation of eNOS via the redox-sensitive activation of the Src/PI3-kinase/Akt pathway mostly by conjugated cyanidins and chlorogenic acids.

Angiotensin II Type 1 receptor blockade protects endothelium-derived hyperpolarising factor-mediated relaxation in a rat model of monoarthritis

AIMS

Rheumatoid arthritis (RA) is associated with high cardiovascular mortality. Impaired endothelial cell (EC) function and elevated angiotensin II levels may be central to the link between vascular dysfunction and RA. Here we investigated the action of angiotensin type 1 receptor (AT1R) blockade on endothelium-dependent relaxation of the isolated saphenous artery in a rat model of monoarthritis.

MAIN METHODS

Adjuvant arthritis was induced in rats with and without prophylactic losartan (AT1R antagonist) treatment. Vehicle-treated rats were used as controls. Wire myography was employed to investigate EC function of isolated rings of saphenous artery.

KEY FINDINGS

EC-dependent relaxation in arteries from non-inflamed control rats was mediated by both nitric oxide (NO) and endothelium-derived hyperpolarising factor (EDHF) with the EDHF response dependent principally on functional myoendothelial gap junctions. While NO-dependent relaxation remained unaffected, the EDHF-mediated response was abolished in arteries from arthritic rats (P<0.001), however, substantial protection (approximately 50%) of the EDHF-relaxation was found in arthritic rats treated with losartan (P<0.01). Thus, the attenuated EDHF response found in the saphenous artery of arthritic rats was significantly reversed by AT1R blockade.

SIGNIFICANCE

These results suggest a key role for the angiotensin system in the EC dysfunction found in chronic joint inflammation and highlights AT1R as a potential therapeutic target to redress the vascular impairment and mortality associated with RA.

Comparison of hepatic venous pressure gradient and two models of end-stage liver disease for predicting the survival in patients with decompensated liver cirrhosis

GOALS

We evaluated the efficacy of initial and follow-up hepatic venous pressure gradient (HVPG), models of end-stage liver disease (MELD), and MELD-Na for predicting the survival of patients with decompensated liver cirrhosis (LC).

BACKGROUND

MELD with/without Na score and HVPG have been important predictors of mortality in patients with LC.

STUDY

Between January 2006 and 2011, a total of 57 patients with decompensated LC, all of whom underwent >2 HVPG measurements for the confirmation of propranolol dosing, were enrolled. MELD and MELD-Na scores were calculated on the day of HVPG measurement. The prognostic accuracy of the initial and follow-up HVPG, MELD, and MELD-Na were analyzed, and independent factors for mortality were evaluated.

RESULTS

Ten patients (17.5%) died from LC. Initial HVPG (0.883), initial MELD-Na (0.877), follow-up HVPG (0.829), and follow-up MELD-Na (0.802) showed good area under the receiver operating characteristic curve scores in predicting 1-year mortality. In predicting 2-year mortality, only follow-up HVPG (0.821, cut-off value 18 mm Hg) showed good score. Overall area under the receiver operating characteristic curves (initial and follow-up) were 0.843 and 0.864 in HVPG, 0.721 and 0.674 in MELD, and 0.762 and 0.715 in MELD-Na, respectively. In the Cox regression analysis, only follow-up HVPG (P=0.02; odds ratio, 1.11) was associated with mortality.

CONCLUSIONS

The efficacy of HVPG for predicting mortality is excellent compared with that of MELD or MELD-Na. Therefore, aside from the confirmation of adequate propranolol dosing, HVPG may be needed for predicting the survival of patients with decompensated LC.

Endothelial calcium-activated potassium channels as therapeutic targets to enhance availability of nitric oxide

The vascular endothelium plays a critical role in vascular health by controlling arterial diameter, regulating local cell growth, and protecting blood vessels from the deleterious consequences of platelet aggregation and activation of inflammatory responses. Circulating chemical mediators and physical forces act directly on the endothelium to release diffusible relaxing factors, such as nitric oxide (NO), and to elicit hyperpolarization of the endothelial cell membrane potential, which can spread to the surrounding smooth muscle cells via gap junctions. Endothelial hyperpolarization, mediated by activation of calcium-activated potassium (K(Ca)) channels, has generally been regarded as a distinct pathway for smooth muscle relaxation. However, recent evidence supports a role for endothelial K(Ca) channels in production of endothelium-derived NO, and indicates that pharmacological activation of these channels can enhance NO-mediated responses. In this review we summarize the current data on the functional role of endothelial K(Ca) channels in regulating NO-mediated changes in arterial diameter and NO production, and explore the tempting possibility that these channels may represent a novel avenue for therapeutic intervention in conditions associated with reduced NO availability such as hypertension, hypercholesterolemia, smoking, and diabetes mellitus.

Thymoquinone improves aging-related endothelial dysfunction in the rat mesenteric artery

Aging-related endothelial dysfunction is characterized by blunted nitric oxide (NO)- and endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in arteries, which may be due, at least in part, to increased oxidative stress. Endothelial dysfunction will promote the initiation and development of major cardiovascular diseases such as atherosclerosis and hypertension. Thymoquinone (TQ) is the most active constituent of the volatile oil of Nigella sativa seeds with well-documented antioxidative properties and vasodilator effects. This study determined whether TQ improves the endothelial function in middle-aged rats. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or TQ (10 mg/kg/day) in the drinking water. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Aging-related blunted NO- and EDHF-mediated responses were associated with downregulation of endothelial NO synthase (eNOS) and calcium-activated potassium channels (SK(Ca) and IK(Ca)) expression. Endothelial dysfunction was also associated with oxidative stress and an upregulation of angiotensin II and AT1 receptor expressions. Intake of TQ for 14 days restored NO- and EDHF-mediated relaxations, normalized oxidative stress, the expression level of eNOS, SK(Ca), IK(Ca), and the components of the angiotensin system in the mesenteric artery of middle-aged rats. Thus, TQ improves endothelial function in aging, at least in part, through inhibition of oxidative stress and normalization of the angiotensin system. TQ may represent a novel therapeutic approach for aging-associated vascular diseases.

Targeting NADPH oxidases in vascular pharmacology

Oxidative stress is a molecular dysregulation in reactive oxygen species (ROS) metabolism, which plays a key role in the pathogenesis of atherosclerosis, vascular inflammation and endothelial dysfunction. It is characterized by a loss of nitric oxide (NO) bioavailability. Large clinical trials such as HOPE and HPS have not shown a clinical benefit of antioxidant vitamin C or vitamin E treatment, putting into question the role of oxidative stress in cardiovascular disease. A change in the understanding of the molecular nature of oxidative stress has been driven by the results of these trials. Oxidative stress is no longer perceived as a simple imbalance between the production and scavenging of ROS, but as a dysfunction of enzymes involved in ROS production. NADPH oxidases are at the center of these events, underlying the dysfunction of other oxidases including eNOS uncoupling, xanthine oxidase and mitochondrial dysfunction. Thus NADPH oxidases are important therapeutic targets. Indeed, HMG-CoA reductase inhibitors (statins) as well as drugs interfering with the renin-angiotensin-aldosterone system inhibit NADPH oxidase activation and expression. Angiotensin-converting enzyme (ACE) inhibitors, AT1 receptor antagonists (sartans) and aliskiren, as well as spironolactone or eplerenone, have been discussed. Molecular aspects of NADPH oxidase regulation must be considered, while thinking about novel pharmacological targeting of this family of enzymes consisting of several homologs Nox1, Nox2, Nox3, Nox4 and Nox5 in humans. In order to properly design trials of antioxidant therapies, we must develop reliable techniques for the assessment of local and systemic oxidative stress. Classical antioxidants could be combined with novel oxidase inhibitors. In this review, we discuss NADPH oxidase inhibitors such as VAS2870, VAS3947, GK-136901, S17834 or plumbagin. Therefore, our efforts must focus on generating small molecular weight inhibitors of NADPH oxidases, allowing the selective inhibition of dysfunctional NADPH oxidase homologs. This appears to be the most reasonable approach, potentially much more efficient than non-selective scavenging of all ROS by the administration of antioxidants.

Grape-derived polyphenols improve aging-related endothelial dysfunction in rat mesenteric artery: role of oxidative stress and the angiotensin system

Aging is characterized by the development of an endothelial dysfunction, which affects both the nitric oxide (NO)- and the endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations, associated with vascular oxidative stress and the activation of the angiotensin system. This study investigated whether red wine polyphenols (RWPs), antioxidants and potent stimulators of NO- and EDHF-mediated relaxations improve aging-related endothelial dysfunction, and, if so, examined the underlying mechanism. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or RWPs (100 mg/kg/day) in the drinking water. The acetylcholine-induced endothelium-dependent NO component was slightly reduced whereas the EDHF component was markedly blunted in rings of middle-aged rats compared to young rats. The endothelial dysfunction was associated with oxidative stress, an upregulation of angiotensin II and AT1 receptors and a down-regulation of SK_Ca, IK_Ca, and angiotensin converting enzyme. Intake of RWPs for either one or two weeks improved the NO and the EDHF components of the relaxation, and normalized oxidative stress, the expression of SK_Ca, IK_Ca and the components of the angiotensin system. The protective effect of the 2-week RWPs treatment persisted for one and two weeks following stopping intake of RWPs. Thus, intake of RWPs caused a persistent improvement of the endothelial function, particularly the EDHF component, in middle-aged rats and this effect seems to involve the normalization of the expression of SK_Ca, IK_Ca and the angiotensin system.

Red wine polyphenols improve an established aging-related endothelial dysfunction in the mesenteric artery of middle-aged rats: role of oxidative stress

Aging is associated with blunted endothelium-dependent relaxations and vascular oxidative stress. Our previous study has indicated that daily intake of red wine polyphenols (RWPs) by young rats retards aging-related endothelial dysfunction in middle-aged rats. The aim of the present study is to determine whether intake of RWPs also improves an established endothelial dysfunction in middle-aged rats and, if so, to determine the underlying mechanism. Middle-aged rats (51 weeks) received either solvent (3% ethanol), RWPs extract (100mg/kg/day) or the antioxidant and NADPH oxidase inhibitor apocynin (100mg/kg/day) in the drinking water for 4 weeks. Vascular reactivity of mesenteric artery rings from control young (12 weeks) and middle-aged rats was assessed in organ chambers. The expression level of endothelial NO synthase (eNOS), arginase I, angiotensin II receptors (AT1R and AT2R), NADPH oxidase subunits and nitrotyrosines was assessed by immunohistochemistry, and the vascular formation of reactive oxygen species (ROS) by dihydroethidine. Aging is associated with blunted endothelium-dependent relaxations, an excessive vascular formation of ROS and peroxynitrites, and an up-regulation of eNOS, arginase I, NADPH oxidase subunits (nox-1, p22phox), and AT1R and AT2R expression. RWPs and apocynin treatments improved endothelial dysfunction, normalized oxidative stress and the expression of the different proteins in the mesenteric artery of middle-aged rats. The present findings indicate that aging is associated with blunted endothelium-dependent relaxations involving an increased oxidative stress, and that these responses are improved by the intake of RWPs or apocynin for 4weeks most likely by normalizing the expression of eNOS, arginase I, NADPH oxidase and angiotensin receptors.

Hyperhomocysteinemia impairs endothelium-derived hyperpolarizing factor-mediated vasorelaxation in transgenic cystathionine beta synthase-deficient mice

Hyperhomocysteinemia (HHcy) is associated with endothelial dysfunction (ED), but the mechanism is largely unknown. In this study, we investigated the role and mechanism of HHcy-induced ED in microvasculature in our newly established mouse model of severe HHcy (plasma total homocysteine, 169.5 μM). We found that severe HHcy impaired nitric oxide (NO)- and endothelium-derived hyperpolarizing factor (EDHF)-mediated, endothelium-dependent relaxations of small mesenteric arteries (SMAs). Endothelium-independent and prostacyclin-mediated endothelium-dependent relaxations were not changed. A nonselective Ca(2+)-activated potassium channel (K(Ca)) inhibitor completely blocked EDHF-mediated relaxation. Selective blockers for small-conductance K(Ca) (SK) or intermediate-conductance K(Ca) (IK) failed to inhibit EDHF-mediated relaxation in HHcy mice. HHcy increased the levels of SK3 and IK1 protein, superoxide (O(2)(-)), and 3-nitrotyrosine in the endothelium of SMAs. Preincubation with antioxidants and peroxynitrite (ONOO(-)) inhibitors improved endothelium-dependent and EDHF-mediated relaxations and decreased O(2)(-) production in SMAs from HHcy mice. Further, EDHF-mediated relaxation was inhibited by ONOO(-) and prevented by catalase in the control mice. Finally, L-homocysteine stimulated O(2)(-) production, which was reversed by antioxidants, and increased SK/IK protein levels and tyrosine nitration in cultured human cardiac microvascular endothelial cells. Our results suggest that HHcy impairs EDHF relaxation in SMAs by inhibiting SK/IK activities via oxidation- and tyrosine nitration-related mechanisms.

Polyphenol-induced endothelium-dependent relaxations role of NO and EDHF

The Mediterranean diet has been associated with greater longevity and quality of life in epidemiological studies. Indeed, because of the abundance of fruits and vegetables and a moderate consumption of wine, the Mediterranean diet provides high amounts of polyphenols thought to be essential bioactive compounds that might provide health benefits in terms of cardiovascular diseases and mortality. Several polyphenol-rich sources, such as grape-derived products, cocoa, and tea, have been shown to decrease mean blood pressure in patients with hypertension. The improvement of the endothelial function is likely to be one of the mechanisms by which polyphenols may confer cardiovascular protection. Indeed, polyphenols are able to induce nitric oxide (NO)-mediated endothelium-dependent relaxations in a large number of arteries including the coronary artery; they can also induce endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in some of these arteries. Altogether, these mechanisms might contribute to explain the antihypertensive and cardio-protective effects of polyphenols in vivo. The aim of this review was to provide a nonexhaustive analysis of the effect of several polyphenol-rich sources and isolated compounds on the endothelium in in vitro, ex vivo, and in vivo models as well as in humans.