TNF/iNOS/NO pathway mediates host susceptibility to endothelial-dependent circulatory failure and death induced by betacoronavirus infection.

Poor disease outcomes and lethality are directly related to endothelial dysfunction in betacoronavirus infections. Here, we investigated the mechanisms underlying the vascular dysfunction caused by the betacoronaviruses MHV-3 and SARS-CoV-2. Wild-type C57BL/6 (WT) and knockout mice for inducible nitric oxide synthase (iNOS-/-) or TNF receptor 1 (TNFR1-/-) were infected with MHV-3, and K18-hACE2 transgenic mice expressing human ACE2 were infected with SARS-CoV-2. Isometric tension was used to evaluate vascular function. Protein expression was determined by immunofluorescence. Tail-cuff plethysmography and Doppler were used to assess blood pressure and flow, respectively. Nitric oxide (NO) was quantified with the DAF probe. ELISA was used to assess cytokine production. Survival curves were estimated using Kaplan-Meier. MHV-3 infection reduced aortic and vena cava contractility, arterial blood pressure, and blood flow, resulting in death. Resistance mesenteric arteries showed increased contractility. The contractility of the aorta was normalized by removing the endothelium, inhibiting iNOS, genetically deleting iNOS, or scavenging NO. In the aorta, iNOS and phospho-NF-kB p65 subunit expression was enhanced, along with basal NO production. TNF production was increased in plasma and vascular tissue. Genetic deletion of TNFR1 prevented vascular changes triggered by MHV-3, and death. Basal NO production and iNOS expression were also increased by SARS-CoV-2. In conclusion, betacoronavirus induces an endothelium-dependent decrease in contractility in macro-arteries and veins, leading to circulatory failure and death via TNF/iNOS/NO. These data highlight the key role of the vascular endothelium and TNF in the pathogenesis and lethality of coronaviruses.

The synthetic peptide PnPP-19 potentiates erectile function via nNOS and iNOS.

PnPP-19 peptide has a primary sequence design based on molecular modeling studies of PnTx2-6 toxin. It comprises the amino acid residues that are potentially significant for the pharmacological action of PnTx2-6. Ex vivo and in vivo experiments in normotensive, hypertensive, or diabetic murine models have shown a significant improvement in penile erection after administration of PnPP-19. Given the potential use of PnPP-19 in pharmaceutical formulations to treat erectile dysfunction and the lack of information concerning its mode of action, the present work investigates its activities on the nitrergic system. PnPP-19 induced a significant increase in nitric oxide (NO) and cGMP levels in corpus cavernosum (cc). These effects were inhibited by l-NAME, a non-selective inhibitor of nitric oxide synthase (NOS); were partially inhibited by 7- Nitroindazole, a selective inhibitor of neuronal NOS (nNOS); and were abolished by L-NIL, a selective inhibitor of inducible NOS (iNOS). This potentiating effect was not affected by atropine. PnPP-19 also led to changes in mRNA levels, protein expression and phosphorylation at specific sites of NOS, in cc. Assays using cavernous tissue from knockout mice to endothelial NOS (eNOS), nNOS or iNOS showed that PnPP-19 potentiates relaxation only in eNOS-knockout mice, which suggests an essential role for nNOS. Surprisingly, iNOS enhanced the potentiation of erectile function evoked by PnPP-19. Our results demonstrate that this new synthetic peptide potentiates erectile function via nitric oxide activation and reinforce its role as a new pharmacological tool for the treatment of erectile dysfunction.

Decreased expression of neuronal nitric oxide synthase contributes to the endothelial dysfunction associated with cigarette smoking in human.

Endothelial nitric oxide synthase (eNOS) malfunctioning has been proposed to contribute to the endothelial damage produced by cigarette. Besides eNOS, neuronal NOS (nNOS) is also expressed in most vascular tissues and plays an important role in the endothelium-dependent vascular relaxation. We hypothesize that nNOS may contribute to the endothelium dysfunction produced by cigarette in smokers. Vascular function was assessed in human resistance mesenteric arteries using a wire myograph, the level of protein expression by Western blot, eNOS and nNOS localization by immunofluorescence. Measurement of NO was assessed by fluorescence microscopy. Arteries of smokers showed impaired endothelium-dependent vascular relaxation in response to acetylcholine. Pharmacological nonselective blockade of NOS with l-NAME and selective nNOS blockade with inhibitor 1 reduced the relaxation of the mesenteric artery of both smokers and nonsmokers. Interestingly, the inhibitory effect of NOS inhibitors was greater in nonsmokers than in smokers. The expression of total nNOS and eNOS and the level of phosphorylation at eNOS-pSer1177 were reduced in arteries of smokers as compared with nonsmokers. No differences between groups were observed in the expression of total COX-1, COX-2, catalase and SOD-1. Immunofluorescence analysis showed the presence of nNOS in the vascular endothelium in both groups. Acetylcholine-induced NO production was impaired in arteries from smokers as compared to nonsmokers. Selective inhibition of nNOS caused a decreased in NO production, which was greater in nonsmokers than in smokers. Our data show that a decrease in nNOS expression contributes to the endothelial dysfunction caused by cigarette smoking in human.

The new organic nitrate 2-nitrate-1,3-diocthanoxypropan (NDOP) induces nitric oxide production and vasorelaxation via activation of inward-rectifier potassium channels (KIR).

INTRODUCTION: Cardiovascular diseases are coupled to decreased nitric oxide (NO) bioavailability, and there is a constant search for novel and better NO-donors. Here we synthesized and characterized the cardiovascular effects of the new organic nitrate 2-nitrate-1,3-dioctanoxypropan (NDOP). METHODS: A combination of in vitro and in vivo experiments was performed in C57BL/6 mice and Wistar rats. Thus, the ability of NDOP in donating NO in a cell-free system and in vascular smooth muscles cells (VSMC) and its ability to induce vasorelaxation in aortic rings from mice were evaluated. In addition, changes in blood pressure and heart rate to different doses of NDOP were evaluated in conscious rats. Finally, acute pre-clinical toxicity to oral administration of NDOP was assessed in mice. RESULTS: In cell-free system, NDOP increased NO levels, which was dependent on xanthine oxidoreductase (XOR). NDOP also increased NO levels in VSMC, which was not influenced by endothelial NO synthase. Furthermore, incubation with the XOR inhibitor febuxostat blunted the vasorelaxation in aortic ring preparations. In conscious rats, NDOP elicited dose-dependent reduction in blood pressure accompanied with increased heart rate. In vessel preparations, NDOP (10-8-10-3 mol/L) induced endothelium-independent vasorelaxation, which was inhibited by the NO scavengers 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and hydroxocobalamin or by inhibition of soluble guanylyl cyclase using H- [1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one. To investigate if NDOP acts through potassium channels, selective blockers were used. Inhibition of BKCa, Kv or KATP subtypes of potassium channels had no effect, but inhibition of inward-rectifier potassium channels (KIR) significantly reduced NDOP-mediated vasorelaxation. Lastly, NDOP showed low toxicity (LD50 ~5000 mg/kg). CONCLUSION: Bioactivation of NDOP involves functional XOR, and this new organic nitrate elicits vasorelaxation via NO-cGMP-PKG signaling and activation of KIR channels. Future studies should further characterize the underlying mechanism and evaluate the therapeutic benefits of chronic NDOP treatment in relevant cardiovascular disease models.

The Cyclitol L-(+)-Bornesitol as an Active Marker for the Cardiovascular Activity of the Brazilian Medicinal Plant Hancornia speciosa.

The cyclitol bornesitol is the main constituent of the leaves from the antihypertensive medicinal plant Hancornia speciosa. This study aimed to investigate the ability of bornesitol to reduce blood pressure and its mechanism of action. Normotensive Wistar rats were divided into control group and bornesitol groups treated intravenously with bornesitol (0.1, 1.0 and 3.0 mg/kg). Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded in non-anesthetized awake animals. Nitric oxide (NO) and angiotensin-converting enzyme (ACE) were measured in plasma by using colorimetric methods. Vascular reactivity study was performed in rat aorta rings and the involvement of nitric oxide synthase (NOS), calcium-calmodulin complex and phosphatidylinositol-3-kinase (PI3K)/Akt pathway in the vasodilator effect was investigated. Administration of bornesitol significantly reduced the SBP, increased the plasmatic level of nitrite, and decreased ACE activity in normotensive rats. In the rat aorta, bornesitol induced endothelium-dependent vasodilatation, which was abolished by NOS blockade. While calcium-calmodulin complex inhibition decreased the vasodilator effect of bornesitol, the inhibition of PI3K/Akt pathway did not alter it. Bornesitol reduced the blood pressure by a mechanism involving an increased production or bioavailability of NO, inhibition of ACE, and by an endothelium- and NO-dependent vasodilator effect. The present results support the use of bornesitol as an active marker for the cardiovascular activity of Hancornia speciosa.

Neuronal nitric oxide synthase contributes to the normalization of blood pressure in medicated hypertensive patients.

Neuronal nitric oxide synthase (nNOS) is expressed in the cardiovascular system and besides NO, generates H2O2. nNOS has been proposed to contribute to the control of blood pressure in healthy humans. The aim of this study was to verify the hypothesis that nNOS can contribute to the control of vascular relaxation and blood pressure in hypertensive patients undergoing drug treatment. The study was conducted in resistance mesenteric arteries from 63 individuals, as follows: 1) normotensive patients; 2) controlled hypertensive patients (patients on antihypertensive treatment with blood pressure normalized); 3) uncontrolled hypertensive patients (patients on antihypertensive treatment that remained hypertensive). Only mesenteric arteries from uncontrolled hypertensive patients showed impaired endothelium-dependent vasorelaxation in response to acetylcholine (ACh). Selective nNOS blockade with inhibitor 1 and catalase, which decomposes H2O2, decreased vasorelaxation in the three groups. However, the inhibitory effect was greater in controlled hypertensive patients. Decreased eNOS expression was detected in both uncontrolled and controlled hypertensive groups. Interestingly nNOS expression and ACh-stimulated H2O2 production were greater in controlled hypertensive patients, than in the other groups. ACh-stimulated NO production was lower in controlled hypertensive when compared to normotensive patients, while uncontrolled hypertensive patients showed the lowest levels. Catalase and nNOS blockade inhibited ACh-induced H2O2 production. In conclusion, nNOS-derived H2O2 contributes to the endothelium-dependent vascular relaxation in human resistance mesenteric arteries. The endothelial dysfunction observed in uncontrolled hypertensive patients involves decreased eNOS expression and NO production. The normalization of vascular relaxation and blood pressure in controlled hypertensive patients involves increased nNOS-derived H2O2 and NO production.

Endothelial dysfunction in DOCA-salt-hypertensive mice: role of neuronal nitric oxide synthase-derived hydrogen peroxide.

Endothelial dysfunction is a common problem associated with hypertension and is considered a precursor to the development of micro- and macro-vascular complications. The present study investigated the involvement of nNOS (neuronal nitric oxide synthase) and H2O2 (hydrogen peroxide) in the impaired endothelium-dependent vasodilation of the mesenteric arteries of DOCA (deoxycorticosterone acetate)-salt-hypertensive mice. Myograph studies were used to investigate the endothelium-dependent vasodilator effect of ACh (acetylcholine). The expression and phosphorylation of nNOS and eNOS (endothelial nitric oxide synthase) were studied by Western blot analysis. Immunofluorescence was used to examine the localization of nNOS and eNOS in the endothelial layer of the mesenteric artery. The vasodilator effect of ACh is strongly impaired in mesenteric arteries of DOCA-salt-hypertensive mice. Non-selective inhibition of NOS sharply reduced the effect of ACh in both DOCA-salt-hypertensive and sham mice. Selective inhibition of nNOS and catalase led to a higher reduction in the effect of ACh in sham than in DOCA-salt-hypertensive mice. Production of H2O2 induced by ACh was significantly reduced in vessels from DOCA-salt-hypertensive mice, and it was blunted after nNOS inhibition. The expression of both eNOS and nNOS was considerably lower in DOCA-salt-hypertensive mice, whereas phosphorylation of their inhibitory sites was increased. The presence of nNOS was confirmed in the endothelial layer of mesenteric arteries from both sham and DOCA-salt-hypertensive mice. These results demonstrate that endothelial dysfunction in the mesenteric arteries of DOCA-salt-hypertensive mice is associated with reduced expression and functioning of nNOS and impaired production of nNOS-derived H2O2 Such findings offer a new perspective for the understanding of endothelial dysfunction in hypertension.

Dihydrogoniothalamin, an Endothelium and NO-Dependent Vasodilator Drug Isolated from Aniba panurensis.

Dihydrogoniothalamin is a styrylpyrone isolated from the leaves of Aniba panurensis. The present work aimed at investigating the vasorelaxant activity of dihydrogoniothalamin and its underlying mechanism of action in the rat aorta. Dihydrogoniothalamin (0.01-100 µM) induced a concentration-dependent vasodilatation of aortas precontracted with phenylephrine. Endothelium removal or pretreatment of the preparation with NG nitro-L-arginine-methyl-ester abolished the vasodilator response for dihydrogoniothalamin. Pretreatment with calmidazolium did not affect the vasodilator response of dihydrogoniothalamin. On the other hand, wortmannin, a nonselective inhibitor of phosphatidylinositol 3-kinases, and protein kinase B inhibitor IV significantly shifted the concentration-response curve of dihydrogoniothalamin to the right and reduced its maximal effect. A nonselective antagonist of estrogen receptors, ICI 182,780, and a selective antagonist of estrogen receptor α, methyl-piperidino-pyrazole, were able to reduce the relaxation induced by dihydrogoniothalamin, but no effect was observed in the presence of the selective antagonists of estrogen receptor ß and G protein-coupled receptor 30, 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP), and G-15, respectively. Dihydrogoniothalamin also increased the phosphorylation of the activation sites of endothelial nitric oxide synthase and protein kinase B. The present results led us to conclude that dihydrogoniothalamin is a vasodilator drug acting in an endothelium- and nitric oxide-dependent manner through a mechanism involving the activation of nitric oxide synthase via the phosphatidylinositol 3-kinase/protein kinase B pathway, partially by stimulation of estrogen receptor α.

Exercise Training Reduces Inflammation and Fibrosis and Preserves Myocardial Function and Perfusion in a Model of Chronic Chagas Cardiomyopathy. / Treinamento Físico Reduz a Inflamação e a Fibrose e Preserva a Função e a Perfusão Miocárdica em um Modelo de Cardiomiopatia Chagásica Crônica.

BACKGROUND: Chronic Chagas cardiomyopathy (CCC) is caused by an inflammatory process induced by Trypanosoma cruzi, which leads to myocarditis with reactive and reparative fibrosis. CCC progresses with myocardial perfusion abnormalities and histopathological events that affect cardiorespiratory fitness (CRF). OBJECTIVES: We evaluated the effects of aerobic physical training (APT) on myocardial perfusion and on morphological and functional impairments related with inflammation and fibrosis in Syrian hamsters with CCC. As a secondary objective, we analyzed the cross-sectional areas of the skeletal muscle. METHODS: Hamsters with CCC and their respective controls were divided into four groups: CCC sedentary, CCC-APT, sedentary control and APT control. Seven months after infection, the animals underwent echocardiography, myocardial perfusion scintigraphy and cardiopulmonary exercise testing. Moderate-intensity APT was performed for fifty minutes, five times a week, for eight weeks. Subsequently, the animals were reassessed. Histopathological analysis was conducted after the above-mentioned procedures. The level of significance was set at 5% in all analyses (p<0.05). RESULTS: CCC sedentary animals presented worse myocardial perfusion defects (MPD) over time, reduced left ventricle ejection fraction (LVEF) and showed more inflammation and fibrosis when compared to other groups (mixed ANOVA analysis). Conversely, APT was able to mitigate the progression of MPD, ameliorate inflammation and fibrosis and improve CRF efficiency in CCC-APT animals. CONCLUSIONS: Our study demonstrated that APT ameliorated cardiac dysfunction, MPD, and reduced inflammation and fibrosis in CCC hamster models. Additionally, CCC-SED animals presented skeletal muscle atrophy while CCC-APT animals showed preserved skeletal muscle CSA. Understanding APT's effects on CCC's pathophysiological dimensions is crucial for future research and therapeutic interventions.

FUNDAMENTO: A Cardiomiopatia Chagásica Crônica (CCC) é causada por um processo inflamatório induzido pelo Trypanosoma cruzi, que leva à miocardite com fibrose reativa e reparativa. A CCC progride com alterações de perfusão miocárdica e eventos histopatológicos que afetam a Aptidão Cardiorrespiratória (ACR). OBJETIVOS: Avaliamos os efeitos do Treinamento Físico Aeróbico (TFA) na perfusão miocárdica e nos comprometimentos morfológicos e funcionais relacionados à inflamação e fibrose em hamsters sírios com CCC. Como objetivo secundário, analisamos as áreas de secção transversa do músculo esquelético. MÉTODOS: Hamsters com CCC e seus respectivos controles foram divididos em quatro grupos: CCC sedentário, CCC-TFA, controle sedentário e controle TFA. Sete meses após a infecção, os animais foram submetidos à ecocardiografia, à cintilografia de perfusão miocárdica e ao teste de esforço cardiopulmonar. TFA de intensidade moderada foi realizado durante cinquenta minutos, cinco vezes por semana, por oito semanas. Posteriormente, os animais foram reavaliados. A análise histopatológica foi realizada após os procedimentos acima mencionados. O nível de significância foi estabelecido em 5% em todas as análises (p<0,05). RESULTADOS: Animais com CCC sedentários apresentaram piores Defeitos de Perfusão Miocárdica (DPM) ao longo do tempo, Fração de Ejeção do Ventrículo Esquerdo (FEVE) reduzida, e apresentaram mais inflamação e fibrose quando comparados aos demais grupos (análise ANOVA mista). Por outro lado, o TFA foi capaz de mitigar a progressão do DPM, atenuar a inflamação e a fibrose e melhorar a eficiência da ACR em animais CCC-TFA. CONCLUSÃO: Nosso estudo demonstrou que o TFA melhorou a disfunção cardíaca, DPM e reduziu a inflamação e a fibrose em modelos de hamster com CCC. Além disso, os animais CCC-SED apresentaram atrofia do músculo esquelético, enquanto os animais CCC-TFA apresentaram a AST do músculo esquelético preservada. Compreender os efeitos da TFA nas dimensões fisiopatológicas da CCC é crucial para futuras pesquisas e intervenções terapêuticas.

Mechanism of the vasodilator effect of mono-oxygenated xanthones: a structure-activity relationship study.

The present study characterized the mechanisms involved in the vasodilator effect of two mono-oxygenated xanthones, 4-hydroxyxanthone and 4-methoxyxanthone. 9-Xanthenone, the base structure of xanthones, was used for comparison. 4-Hydroxyxanthone and 9-xanthenone induced a concentration-dependent and endothelium-independent vasodilator effect in arteries precontracted with phenylephrine (0.1 µmol ·â€ŠL-1) or KCl (50 mmol ·â€ŠL-1). 4-Methoxyxanthone induced a concentration-dependent vasodilator effect in arteries precontracted with phenylephrine, which was partially endothelium-dependent, and involved production of nitric oxide. In endothelium-denuded arteries precontracted with KCl, the vasodilator effect of 4-methoxyxanthone was abolished. The vasodilator effect of 4-hydroxyxanthone (96.22 ± 2.10 %) and 4-methoxyxanthone (96.57 ± 12.40 %) was significantly higher than observed with 9-xanthenone (53.63 ± 8.31 %). The presence of an oxygenated radical in position 4 made 4-hydroxyxanthone (pIC50 = 4.45 ± 0.07) and 4-methoxyxanthone (pIC50 = 5.04 ± 0.09) more potent as a vasodilator than 9-xanthenone (pIC50 = 3.92 ± 0.16). In addition, 4-methoxyxanthone was more potent than the other two xanthones. Ca2+ transients in vascular smooth muscle cells elicited by high K+ were abolished by 4-hydroxyxanthone and 9-xanthenone. The endothelium-independent effect of 4-methoxyxanthone was abolished by inhibition of K+ channels by tetraethylammonium. The current work shows that an oxygenated group in position 4 is essential to achieve Emax and to increase the potency of xanthones as vasodilators. Substitution of an OH by OCH3 in position 4 increases the potency of the vasodilator effect and changes the underling mechanism of action from the blockade of L-type calcium channels to an increase in NO production and activation of K+ channels.

Mechanism of the antihypertensive and vasorelaxant effects of the flavonoid tiliroside in resistance arteries.

Hypertension is a leading cause of death and disability globally, and its prevalence continues to accelerate. The cardiovascular effects of the flavonoid tiliroside have never been reported. In this work, using complementary in vivo and in vitro approaches, we describe the antihypertensive effect of tiliroside and the underlying mechanisms involved in the reduction of blood pressure. Tiliroside (1, 5 or 10 mg/kg) induced a dose-dependent long-lasting decrease in blood pressure in conscious DOCA-salt hypertensive rats that was accompanied by an increased heart rate. Tiliroside also induced a concentration-dependent vasodilation of mesenteric resistance arteries precontracted with phenylephrine. Removal of the endothelium or pretreatment of the preparation with L-NAME or indomethacin did not modify the vasodilator response for tiliroside. When vessels were precontracted with a high K⁺ (50 mM) solution, tiliroside exhibited a vasodilator effect similar to that observed in vessels precontracted with phenylephrine. Experiments carried out in nominally Ca²âº-free solution showed that tiliroside antagonized CaCl2-induced contractions. Moreover, tiliroside reduced the rise in intracellular Ca²âº concentration induced by membrane depolarization in vascular smooth muscle cells. Finally, tiliroside decreased the voltage-activated peak amplitude of the L-type Ca²âº channel current in freshly dissociated vascular smooth muscle cells from mesenteric arteries. Altogether, our results point to an antihypertensive effect of tiliroside due to a reduction in peripheral resistance through blockage of voltage-activated peak amplitude of the L-type Ca²âº channel in smooth muscle cells.

Oral sub-chronic treatment with Terminalia phaeocarpa Eichler (Combretaceae) reduces liver PTP1B activity in a murine model of diabetes.

ETHNOPHARMACOLOGICAL RELEVANCE: The endemic Brazilian medicinal plants of the genus Terminalia (Combretaceae), popularly known as capitão, comprising the similar species Terminalia phaeocarpa Eichler and Terminalia argentea, are traditionally and indistinguishably used in the country to treat diabetes. AIM OF THE STUDY: The present work investigated the effect of 28 days of treatment with the crude ethanolic extract (CEE) and its derived ethyl acetate fraction (EAF) from T. phaeocarpa leaves in a mice model of diabetes. MATERIALS AND METHODS: Streptozotocin-nicotinamide-fructose diabetic model was used to evaluate the antidiabetic activity of 28 days of treatment with the CEE and EAF from the leaves of T. phaeocarpa and metformin as a positive control. Serum levels of total cholesterol, triglycerides, uric acid, ALP, AST, and ALT were measured with specific commercial kits and glucose with a strip glucometer. The thiobarbituric acid method measured the liver MDA level, while a colorimetric assay measured the GSH level and PTP1B activity. A UPLC-DAD profile was obtained to identify the main polyphenolic compound in the EAF. RESULTS: Treatment with CEE and EAF reduced plasma glucose in diabetic mice. At the end of the treatment, the plasma glucose level was significantly lower in EAF-treated (100 mg/kg) diabetic mice (106.1 ± 13.7 mg/dL) than those treated with 100 mg/kg CEE (175.2 ± 20.9 mg/dL), both significantly lower than untreated diabetic mice (350.4 ± 28.1 mg/dL). The serum levels of total cholesterol, triglycerides, uric acid, ALP, AST, and ALT were significantly reduced in diabetic mice treated with CEE and EAF. In the livers of diabetic mice, the treatment with CEE and EAF reduced MDA levels and the activity of the enzyme PTP1B (96.9 ± 3.7%, 113.8 ± 2.8%, and 134.8 ± 4.6% for CEE-, EAF-treated, and untreated diabetic mice, respectively). Galloylpunicalagin was the main polyphenol observed in the EAF of T. phaeocarpa. CONCLUSION: The present results demonstrate the significant antidiabetic effect of CEE and EAF of T. phaeocarpa and their reduction on the markers of liver dysfunction in diabetic mice. Moreover, the antidiabetic activity of T. phaeocarpa might be associated with lowering the augmented activity of the PTP1B enzyme in the liver of diabetic mice.

Swim training attenuates oxidative damage and promotes neuroprotection in cerebral cortical slices submitted to oxygen glucose deprivation.

Although it is well known that regular exercise may promote neuroprotection, the mechanisms underlying this effect are still not fully understood. We investigated if swim training promotes neuroprotection by potentiating antioxidant pathways, thereby decreasing the effects of oxidative stress on glutamate and nitric oxide release. Male Wistar rats (n=36) were evenly randomized into a trained group (TRA) (5 days/week, 8 weeks, 30 min) and a sedentary group (SED). Forty-eight hours after the last session of exercise, animals were killed and brain was collected for in vitro ischemia. Cortical slices were divided into two groups: a group in which oxidative stress was induced by oxygen and glucose deprivation (OGD), and a group of non-deprived controls (nOGD). Interestingly, exercise by itself increased superoxide dismutase activity (nOGD, SED vs. TRA animals) with no effect on pro-oxidative markers. In fact, TRA-OGD slices showed lowered levels of lactate dehydrogenase when compared with SED-OGD controls, reinforcing the idea that exercise affords a neuroprotective effect. We also demonstrated that exercise decreased glutamate and nitrite release as well as lipid membrane damage in the OGD cortical slices. Our data suggest that under conditions of metabolic stress, swim training prevents oxidative damage caused by glutamate and nitric oxide release.

Inhibition of α-glucosidase and hypoglycemic effect of stilbenes from the Amazonian plant Deguelia rufescens var. urucu (Ducke) A. M. G. Azevedo (Leguminosae).

The control of blood glucose levels is critical in the treatment of diabetes mellitus. α-Glucosidase inhibitors are of great importance in reducing hyperglycemia, and plants have provided many of these agents. The present study aimed at investigating the effect of two stilbenes, lonchocarpene and 3,5-dimethoxy-4'-O-prenyl-trans-stilbene (DPS), isolated from the Amazonian plant Deguelia rufescens var. urucu, on α-glucosidase activity and on mice postprandial hyperglycemia. Lonchocarpene and DPS inhibited α-glucosidase in vitro, with pIC(50) values of 5.68 ± 0.12 and 5.73 ± 0.08, respectively. In addition, when given orally, DPS produced a significant reduction of hyperglycemia induced by an oral tolerance test, while lonchocarpene did not. Data suggest that DPS may have a potential use as an antidiabetic drug.

L-NAME treatment enhances exercise-induced content of myocardial heat shock protein 72 (Hsp72) in rats.

BACKGROUND/AIM: Nitric oxide (NO) modulates the expression of the chaperone Hsp72 in the heart, and exercise stimulates both NO production and myocardial Hsp72 expression. The main purpose of the study was to investigate whether NO interferes with an exercise-induced myocardial Hsp72 expression. METHODS: Male Wistar rats (70-100 days) were divided into control (C, n=12), L-NAME-treated (L, n=12), exercise (E, n=13) and exercise plus L-NAME-treated (EL, n=20) groups. L-NAME was given in drinking water (700 mg·L(-1)) and the exercise was performed on a treadmill (15-25 m·min(-1), 40-60 min.day(-1)) for seven days. Left ventricle (LV) protein Hsp content, NOS and phosphorylated-NOS (p-NOS) isoforms were measured using Western blotting. The activity of NOS was assayed in LV homogenates by the conversion of [(3)H]L-arginine to [(3)H]L-citrulline. RESULTS: Hsp72 content was increased significantly (223%; p < 0.05) in the E group compared to the C group, but exercise alone did not alter the NOS content, p-NOS isoforms or NOS activity. Contrary to our expectation, L-NAME enhanced (p < 0.05) the exercise-induced Hsp72 content (EL vs. C, L and E groups = 1019%, 548% and 457%, respectively). Although the EL group had increased stimulatory p-eNOS(Ser1177) (over 200%) and decreased inhibitory p-nNOS(Ser852) (ñ50%) compared to both the E and L groups (p < 0.05), NOS activity was similar in all groups. CONCLUSIONS: Our results suggest that exercise-induced cardiac Hsp72 expression does not depend on NO. Conversely, the in vivo L-NAME treatment enhances exercise-induced Hsp72 production. This effect may be due to an increase in cardiac stress.

Implant-induced intraperitoneal inflammatory angiogenesis is attenuated by fluvastatin.

1. Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) inhibitors, exert anti-inflammatory, anti-oxidant and anti-angiogenic effects. These effects are associated with downregulation of pro-inflammatory/pro-angiogenic molecules and upregulation of endothelial nitric oxide synthase (e-NOS) expression/nitric oxide (NO) production. 2. Using the murine sponge model to induce chronic intraperitoneal inflammatory response, we evaluated the inflammatory components, angiogenic and NO production of the fibrovascular tissue, and their modulation by fluvastatin. 3. Our results showed that fluvastatin (0.6 and 6 mg/kg per day) inhibited haemoglobin (Hb) content 4.9±0.4 (n=15; control) vs 2.2±0.2 (n=6; fluvastatin 0.6) and 1.8±0.2 (n=6; fluvastatin 6.0) and the number of vessels in the treated group when compared with the control group. The inflammatory component, as assessed by myeloperoxidase and N-acetyl-ß-d-glucosaminidase activities and by the pro-inflammatory cytokines, tumour necrosis factor-α (TNF-α) and Monocyte chemotactic protein-1 (MCP-1)/CCL2/JE levels, was also decreased by the compound. In the treated group, inhibition of both enzyme activities was 54% and 57%, respectively. The levels of the cytokines (TNF-α and CCL2/JE) intra-implant were decreased relative to the control. In these implants, fluvastatin was also able to increase NO production, as detected with an NO-sensitive electrode. 4. The inhibitory function of fluvastatin on key components of intraperitoneal inflammatory angiogenesis shown in the present study is clearly associated with the modulatory effects of this statin on vascular endothelial growth factor, TNF-α and NO production.

Phosphoinositide-3 kinase gamma activity contributes to sepsis and organ damage by altering neutrophil recruitment.

RATIONALE: Sepsis is a leading cause of death in the intensive care unit, characterized by a systemic inflammatory response (SIRS) and bacterial infection, which can often induce multiorgan damage and failure. Leukocyte recruitment, required to limit bacterial spread, depends on phosphoinositide-3 kinase γ (PI3Kγ) signaling in vitro; however, the role of this enzyme in polymicrobial sepsis has remained unclear. OBJECTIVES: This study aimed to determine the specific role of the kinase activity of PI3Kγ in the pathogenesis of sepsis and multiorgan damage. METHODS: PI3Kγ wild-type, knockout, and kinase-dead mice were exposed to cecal ligation and perforation-induced sepsis and assessed for survival; pulmonary, hepatic, and cardiovascular damage; coagulation derangements; systemic inflammation; bacterial spread; and neutrophil recruitment. Additionally, wild-type mice were treated either before or after the onset of sepsis with a PI3Kγ inhibitor and assessed for survival, neutrophil recruitment, and bacterial spread. MEASUREMENTS AND MAIN RESULTS: Both genetic and pharmaceutical PI3Kγ kinase inhibition significantly improved survival, reduced multiorgan damage, and limited bacterial decompartmentalization, while modestly affecting SIRS. Protection resulted from both neutrophil-independent mechanisms, involving improved cardiovascular function, and neutrophil-dependent mechanisms, through reduced susceptibility to neutrophil migration failure during severe sepsis by maintaining neutrophil surface expression of the chemokine receptor, CXCR2. Furthermore, PI3Kγ pharmacological inhibition significantly decreased mortality and improved neutrophil migration and bacterial control, even when administered during established septic shock. CONCLUSIONS: This study establishes PI3Kγ as a key molecule in the pathogenesis of septic infection and the transition from SIRS to organ damage and identifies it as a novel possible therapeutic target.

Proteolytic activity of Triatoma infestans saliva associated with PAR-2 activation and vasodilation.

BACKGROUND: Triatoma infestans (Hemiptera: Reduviidae) is a hematophagous insect and the main vector of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae). In the present study, the authors investigated whether a serine protease activity from the saliva of T. infestans has a role in vasomotor modulation, and in the insect-blood feeding by cleaving and activating protease-activated receptors (PARs). METHODS: T. infestans saliva was chromatographed as previously reported for purification of triapsin, a serine protease. The cleavage activity of triapsin on PAR peptides was investigated based on FRET technology. Mass spectrometry was used to analyze the sites of PAR-2 peptide cleaved by triapsin. NO measurements were performed using the DAN assay (2,3-diaminonapthalene). The vasorelaxant activity of triapsin was measured in vessels with or without functional endothelium pre-contracted with phenylephrine (3 µM). Intravital microscopy was used to assess the effect of triapsin on mouse skin microcirculation. RESULTS: Triapsin was able to induce hydrolysis of PAR peptides and showed a higher preference for cleavage of the PAR-2 peptide. Analysis by mass spectrometry confirmed a single cleavage site, which corresponds to the activation site of the PAR-2 receptor. Triapsin induced dose-dependent NO release in cultured human umbilical vein endothelial cells (HUVECs), reaching a maximum effect at 17.58 nM. Triapsin purified by gel-filtration chromatography (10-16 to 10-9 M) was applied cumulatively to mouse mesenteric artery rings and showed a potent endothelium-dependent vasodilator effect (EC30 = 10-12 M). Nitric oxide seems to be partially responsible for this vasodilator effect because L-NAME (L-NG-nitroarginine methyl ester 300 µM), a nitric oxide synthetase inhibitor, did not abrogate the vasodilation activated by triapsin. Anti-PAR-2 antibody completely inhibited vasodilation observed in the presence of triapsin activity. Triapsin activity also induced an increase in the mouse ear venular diameter. CONCLUSION: Data from this study suggest a plausible association between triapsin activity mediated PAR-2 activation and vasodilation caused by T. infestans saliva.

Exercise capacity is related to calcium transients in ventricular cardiomyocytes.

The aim of the present study was to evaluate the Ca2+ handling and contractility properties of cardiomyocytes isolated from rats with high intrinsic aerobic exercise capacity. Standard-performance (SP) and high-performance (HP) rats were categorized with a treadmill progressive exercise test according to the exercise time to fatigue (TTF). The SP group included rats with TTF between 16.63 and 46.57 min, and the HP group included rats with TTF>46.57 min. Isolated ventricular cardiomyocytes were dissociated from the hearts of SP and HP rats, and intracellular global Ca2+ ([Ca2+]i) transients were measured. The [Ca2+]i transient peak was increased in the HP group relative to the SP group (5.54+/-0.31 vs. 4.18+/-0.12 F/F0; P

Transient receptor potential channel 6-mediated, localized cytosolic [Na+] transients drive Na+/Ca2+ exchanger-mediated Ca2+ entry in purinergically stimulated aorta smooth muscle cells.

The Na+/Ca2+ exchanger (NCX) is increasingly recognized as a physiological mediator of Ca2+ influx and significantly contributes to salt-sensitive hypertension. We recently reported that Ca2+ influx by the NCX (1) is the primary mechanism of Ca2+ entry in purinergically stimulated rat aorta smooth muscle cells and (2) requires functional coupling with transient receptor potential channel 6 nonselective cation channels. Using the Na+ indicator CoroNa Green, we now directly observed and characterized the localized cytosolic [Na+] ([Na+]i) elevations that have long been hypothesized to underlie physiological NCX reversal but that have never been directly shown. Stimulation of rat aorta smooth muscle cells caused both global and monotonic [Na+]i elevations and localized [Na+]i transients (LNats) at the cell periphery. Inhibition of nonselective cation channels with SKF-96365 (50 micromol/L) and 2-amino-4-phosphonobutyrate (75 micromol/L) reduced both global and localized [Na+]i elevations in response to ATP (1 mmol/L). This effect was mimicked by expression of a dominant negative construct of transient receptor potential channel 6. Selective inhibition of NCX-mediated Ca2+ entry with KB-R7943 (10 micromol/L) enhanced the LNats, whereas the global cytosolic [Na+] signal was unaffected. Inhibition of mitochondrial Na+ uptake with CGP-37157 (10 micromol/L) increased both LNats and global cytosolic [Na+] elevations. These findings directly demonstrate NCX regulation by LNats, which are restricted to subsarcolemmal, cytoplasmic microdomains. Analysis of the LNats, which facilitate Ca2+ entry via NCX, suggests that mitochondria limit the cytosolic diffusion of LNats generated by agonist-mediated activation of transient receptor potential channel 6-containing channels.