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.

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.

Polyphenol-rich extract and fractions of Terminalia phaeocarpa Eichler possess hypoglycemic effect, reduce the release of cytokines, and inhibit lipase, α-glucosidase, and α-amilase enzymes.

ETHNOPHARMACOLOGICAL RELEVANCE: species of Terminalia (Combretaceae) are used to treat diabetes and metabolic disorders in Asia, Africa, and America. Terminalia phaeocarpa Eichler is an endemic tree from Brazil, popularly known as capitão. This species is closely related to Terminalia argentea Mart., also vulgarly known as capitão, a native but not endemic tree. Due to their phenotype similarity, these species might eventually prove inseparable and they are indistinctly used by locals to treat diabetes, among other diseases. The potential antidiabetic effect of T. argentea has been previously reported, whereas the biological effects and chemical composition of T. phaeocarpa have never been addressed so far. AIM OF THE STUDY: investigate the hypoglycaemic effect of an ethanol extract (EE) of T. phaeocarpa leaves and its ethyl acetate (FrEtOAc) and hydromethanolic (FrMEOH) fractions, in addition to their activity on the release of pro-inflammatory mediators and inhibition of lipase, α-amylase, and α-glucosidase enzymes. Additionally, it aimed to characterize the chemical composition of the extract and fractions, seeking to identify the compounds related to the biological activities. MATERIALS AND METHODS: The effect on the release of TNF-α, IL-1ß, and CCL-2 was evaluated in LPS-stimulated THP-1 cells (ATCC TIB-202). The inhibition of lipase, α-amylase, and α-glucosidase was tested in vitro, whereas the hypoglycemic effect was assayed in the oral starch tolerance test. The chemical composition was investigated by extensive UHPLC-DAD-ESI-MS/MS analyses. RESULTS: The extract and derived fractions reduced TNF-α (EE pIC50 = 4.58 ± 0.01; FrEtOAc pIC50 = 4.69 ± 0.01; FrMeOH pIC50 = 4.54 ± 0.02) and IL-1ß (EE pIC50 = 4.86 ± 0.02; FrEtOAc pIC50 = 4.86 ± 0.02; FrMeOH pIC50 = 4.75 ± 0.01) release by LPS-stimulated THP-1 cells in a concentration-dependent manner, whereas the inhibitory effect on CCL-2 release did not reach a clear linear relationship for the tested concentrations. The extract and fractions also inhibited in vitro the activity of lipase (EE pIC50 = 3.97 ± 0.12; FrEtOAc pIC50 = 3.87 ± 0.04; FrMeOH pIC50 = 3.67 ± 0.14), α-amylase (EE pIC50 = 4.46 ± 0.27; FrEtOAc pIC50 = 5.47 ± 0.27; FrMeOH pIC50 = 4.26 ± 0.22), and α-glucosidase (EE pIC50 = 5.46 ± 0.05; FrEtOAc pIC50 = 5.79 ± 0.11; FrMeOH pIC50 = 5.74 ± 0.05). The pIC50 values of the test samples were lower than those obtained with orlistat (7.59 ± 0.08) and acarbose (6.04 ± 0.37 and 7.63 ± 0.04) employed as the positive controls respectively in the lipase, α-amylase, and α-glucosidase assays. When assayed in the oral starch tolerance test, the extract and fractions also reduced animal glycaemia. UHPLC-DAD-ESI-MS/MS analyses of the extract and fractions led to the identification of 38 phenolic compounds, mainly phenolic acids, ellagitannins and flavonoids, among others, all of them first-time described for the species. CONCLUSION: Based on our findings, T. phaeocarpa has hypoglycaemic activity and polyphenols are the probable bioactive compounds, which support the ethnomedical use of the species.

Bioguided chemical characterization of pequi (Caryocar brasiliense) fruit peels towards an anti-diabetic activity.

Pequi fruit peels are an underexploited source of polyphenols. The anti-diabetic potential of an extract and fractions from the peels were evaluated in a panel of assays. The extract and fractions thereof inhibited the release of cytokines involved in insulin resistance - TNF, IL-1ß, and CCL2 - by lipopolysaccharide-stimulated THP-1 cells. The ethyl acetate fraction inhibited in vitro α-glucosidase (pIC50 = 4.8 ± 0.1), an enzyme involved in the metabolization of starch and disaccharides to glucose, whereas a fraction enriched in tannins (16C) induced a more potent α-glucosidase inhibition (pIC50 = 5.3 ± 0.1). In the starch tolerance test in mice, fraction 16C reduced blood glucose level (181 ± 10 mg/dL) in comparison to the vehicle-treated group (238 ± 11 mg/dL). UPLC-DAD-ESI-MS/MS analyses disclosed phenolic acids and tannins as constituents, including corilagin and geraniin. These results highlight the potential of pequi fruit peels for developing functional foods to manage type-2 diabetes.

Determination of l-(+)-bornesitol, the hypotensive constituent of Hancornia speciosa, in rat plasma by LC-MS/MS and its application on a pharmacokinetic study.

Hancornia speciosa is a medicinal plant with proven antihypertensive activity. The cyclitol l-(+)-bornesitol is the main constituent of its leaves and is a potent inhibitor of the angiotensin-converting enzyme. We herein investigated the pharmacokinetic properties of bornesitol administered orally to Wistar rats, as well as bornesitol permeation in Caco-2 cells. Bornesitol was isolated and purified from an ethanol extract of H. speciosa leaves. An ultra-high performance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC-ESI-MS/MS) method was developed and validated to quantify bornesitol in rat plasma based on Multiple Reaction Monitoring, using pentaerythritol as an internal standard. Pharmacokinetics was evaluated by the administration of single doses via intravenous in bolus (3 mg/kg) and gavage (3, 15 and 25 mg/kg). Bornesitol permeation was assayed in a transwell Caco-2 cells model, tested alone, or combined with rutin, or as a constituent of H. speciosa extract, using a developed and validated UPLC-ESI-MS/MS method. All assayed validation parameters (selectivity, residual effect, matrix effect, linearity, precision, accuracy and stability of analyte in plasma and solution) for the bioanalytical method met the acceptance criteria established by regulatory guidelines. Bornestiol reached peak plasma concentration within approximately 60 min after oral administration with a half-life ranging from 72.15 min to 123.69 min. The peak concentration and area under the concentration-time curve of bornesitol did not rise proportionally with the increasing doses, suggesting a non-linear pharmacokinetics in rats and the oral bioavailability ranged from 28.5%-59.3%. Bornesitol showed low permeability in Caco-2 cells, but the permeability apparently increased when it was administered either combined with rutin or as a constituent of H. speciosa extract. In conclusion, bornesitol was rapidly absorbed after a single oral administration to rats and followed a non-linear pharmacokinetics. The obtained data will be useful to guide further pre-clinical development of bornesitol-containing herbal preparations of H. speciosa as an antihypertensive agent.

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.

Role of the α7 Nicotinic Acetylcholine Receptor in the Pathophysiology of Atherosclerosis.

Atherosclerosis constitutes a major risk factor for cardiovascular diseases, the leading cause of morbidity and mortality worldwide. This slowly progressing, chronic inflammatory disorder of large- and medium-sized arteries involves complex recruitment of immune cells, lipid accumulation, and vascular structural remodeling. The α7 nicotinic acetylcholine receptor (α7nAChR) is expressed in several cell types involved in the genesis and progression of atherosclerosis, including macrophages, dendritic cells, T and B cells, vascular endothelial and smooth muscle cells (VSMCs). Recently, the α7nAChR has been described as an essential regulator of inflammation as this receptor mediates the inhibition of cytokine synthesis through the cholinergic anti-inflammatory pathway, a mechanism involved in the attenuation of atherosclerotic disease. Aside from the neuronal cholinergic control of inflammation, the non-neuronal cholinergic system similarly regulates the immune function. Acetylcholine released from T cells acts in an autocrine/paracrine fashion at the α7nAChR of various immune cells to modulate immune function. This mechanism additionally has potential implications in reducing atherosclerotic plaque formation. In contrast, the activation of α7nAChR is linked to the induction of angiogenesis and VSMC proliferation, which may contribute to the progression of atherosclerosis. Therefore, both atheroprotective and pro-atherogenic roles are attributed to the stimulation of α7nAChRs, and their role in the genesis and progression of atheromatous plaque is still under debate. This minireview highlights the current knowledge on the involvement of the α7nAChR in the pathophysiology of atherosclerosis.

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.

Activation of Cav1.2 and BKCa is involved in the downregulation of caffeine-induced contraction in mice mesenteric arteries.

AIMS: Caffeine is a methylxanthine with multiple actions in vascular smooth muscle cells (VSMCs), including the increase in the intracellular Ca2+ (iCa2+) concentration by the activation of ryanodine receptors (RyRs). The present study aimed at investigating the participation of Ca2+-influx through different Ca2+-channels on the transient contraction (TC) induced by caffeine in mice mesenteric arteries. MAIN METHODS: Second-order of mesenteric arteries was isolated from male Swiss mice. Vessels without functional endothelium were stimulated with caffeine (10 mM). The caffeine-induced TC was evaluated after the incubation of artery rings for 30 min with the following drugs: nifedipine (10 µM), a Cav1.2 blocker; 2-aminoethoxydiphenyl borate (2-APB; 10 µM) and ruthenium red (RuR; 10 µM), transient receptor potential (TRPs) channels blockers; capsazepine (10 µM) and HC067047 (10 µM), TRPV1 and TRPV4 antagonists, respectively; paxilline (1 µM), a selective BKCa blocker; and SKF-96365 (30 µM), an Orai blocker. Ca2+-fluorescence measurements were also performed on the investigated arteries. KEY FINDINGS: The TC induced by caffeine was partially dependent on Ca2+-influx. However, the blockage of Cav1.2 increased the TC while reduced the iCa2+ signal. Similar results were observed after the blockage of TRPs or BKCa. Therefore, caffeine promoted Ca2+-influx via TRPs and Cav1.2, and hyperpolarization through the activation of BKCa, inducing negative feedback of TC. SIGNIFICANCE: Our results indicate an alternative mechanism for the control of VSMCs contraction in resistance arteries. The evidence of the negative feedback of contraction via TRP-Cav1.2-BKCa provides a new perspective for understanding the mechanism involved in the vascular responses triggered by caffeine.

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.

Forced degradation of l-(+)-bornesitol, a bioactive marker of Hancornia speciosa: Development and validation of stability indicating UHPLC-MS method and effect of degraded products on ACE inhibition.

The antihypertensive activity of the medicinal plant Hancornia speciosa has been previously demonstrated by us, being the activity ascribed to polyphenols and cyclitols like l-(+)-bornesitol. We herein evaluated the stability of the bioactive marker bornesitol submitted to forced degradation conditions. Bornesitol employed in the study was isolated from H. speciosa leaves. An UHPLC-ESI-MS/MS method was developed to investigate bornesitol stability based on MRM (Multiple Reaction Monitoring) acquisition mode and negative ionization mode, employing both specific (m/z 193 → 161 Da) and confirmatory (m/z 193 → 175 Da) transitions. A gradient elution of 0.1% formic acid in water and acetonitrile was performed on a HILIC column. The method was validated and showed adequate linearity (r2 > 0.99), selectivity, specificity, accuracy, and precision (RSD < 2.9%). The method was robust for deliberate variations on dessolvation temperature, but not for changes in the flow rate and dessolvation gas. The results from the stability studies allowed us to classify bornesitol as labile for acidic and alkaline hydrolysis, but as very stable for oxidative and neutral hydrolysis exposure. Bornesitol was categorized as practically stable under photolysis degradation, whereas a considerable reduction on its contents was induced by metal ions and thermolysis exposure. Degraded samples from neutral hydrolysis and thermolysis were assayed in vitro for ACE inhibition and showed a substantial decrease in biological activity as compared to intact bornesitol. myo-Inositol was identified as the major degradation products in both matrices. This is the first report on bornesitol stability under different stress conditions and the obtained data are relevant for the development and quality control of standardized products from H. speciosa leaves.

Activation of eNOS by D-pinitol Induces an Endothelium-Dependent Vasodilatation in Mouse Mesenteric Artery.

D-pinitol is a cyclitol present in several edible plant species and extensively investigated for the treatment of metabolic diseases in humans, as food supplement, and demonstrated protective effects in the cardiovascular system. For these reasons, the present work aimed at investigating the mechanisms involved in the vascular effects of D-pinitol in mouse mesenteric artery. Mesenteric arteries from male C57BL/6 mice were mounted in a wire myograph. Nitrite was measured by the 2,3-diaminonaphthalene (DAN) method. Protein expression and phosphorylation were measured by Western blot. The systolic blood pressure (SBP) was measured by tail-cuff plethysmography. D-pinitol induced a concentration-dependent vasodilatation in endothelium-intact, but not in endothelium-denuded arteries. Nω-Nitro-L-arginine methyl ester (300 µM) abolished the effect of D-pinitol, while 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 µM) shifted the concentration-response curve to the right. KN-93 (1 µM) blunted the vasodilator effect of D-pinitol, but H-89 (0.1 µM) did not change it. 1-[2-(Trifluoromethyl) phenyl]imidazole (300 µM), indomethacin (10 µM), celecoxib (5 µM), wortmannin (1 µM), ruthenium red (10 µM), tiron (10 µM), MnTMPyP (30 µM), MPP (0.1 µM), PHTPP (0.1 µM), and atropine (1 µM) did not change the effect of D-pinitol. D-pinitol increased the concentration of nitrite, which was inhibited by L-NAME and calmidazolium (10 µM). D-pinitol increased the phosphorylation level of eNOS activation site at Ser1177 and reduced the phosphorylation level of its inactivation site at Thr495. In normotensive mice, the intraperitoneal administration of D-pinitol (10 mg/kg) induced a significant reduction of the SBP after 30 min. The present results led us to conclude that D-pinitol has an endothelium- and NO-dependent vasodilator effect in mouse mesenteric artery through a mechanism dependent on the activation of eNOS by the calcium-calmodulin complex, which can explain its hypotensive effect in mice.

Replicative senescence promotes prothrombotic responses in endothelial cells: Role of NADPH oxidase- and cyclooxygenase-derived oxidative stress.

Endothelial senescence has been suggested to promote endothelial dysfunction in age-related vascular disorders. This study evaluated the prothrombotic properties of senescent endothelial cells (ECs) and the underlying mechanism. Serial passaging from passage (P)1 to P4 (replicative senescence) of porcine coronary artery ECs, or treatment of P1 ECs with the endothelial nitric oxide synthase (eNOS) inhibitor L-NAME (premature senescence) induced acquisition of markers of senescence including increased senescence-associated-ß-galactosidase (SA-ß-gal) activity and p53, p21, p16 expression. Approximately 55% of P3 cells were senescent with a high level oxidative stress, and decreased eNOS-derived nitric oxide (NO) formation associated with increased expression of NADPH oxidase subunits (gp91phox, p47phox), cyclooxygenase (COX)-2 but not COX-1, and a decreased eNOS expression leading to a reduced ability of ECs to inhibit platelet aggregation. P3 cells also presented increased expression and activity of tissue factor (TF), a key initiator of the coagulation cascade. Treatment of senesecent cells with a NADPH oxidase inhibitor (VAS-2870) or by a COX inhibitor (indomethacin) reduced oxidative stress, decreased TF activity and expression, and reduced the expression of gp91phox, p47phox and COX-2 and restored the ability of ECs to inhibit effectively platelet aggregation. Thus, replicative endothelial senescence promotes a prothrombotic response involving the down-regulation of the protective NO pathway and the upregulation of the NADPH oxidase- and COXs-dependent oxidative stress pathway promoting TF expression and activity.

Neuronal nitric oxide synthase-derived hydrogen peroxide effect in grafts used in human coronary bypass surgery.

Recently, H2O2 has been identified as the endothelium-dependent hyperpolarizing factor (EDHF), which mediates flow-induced dilation in human coronary arteries. Neuronal nitric oxide synthase (nNOS) is expressed in the cardiovascular system and, besides NO, generates H2O2 The role of nNOS-derived H2O2 in human vessels is so far unknown. The present study was aimed at investigating the relevance of nNOS/H2O2 signaling in the human internal mammary artery (IMA) and saphenous vein (SV), the major conduits used in coronary artery bypass grafting. In the IMA, but not in the SV, ACh (acetylcholine)-induced vasodilatation was decreased by selective nNOS inhibition with TRIM or Inhibitor 1, and by catalase, which specifically decomposes H2O2 Superoxide dismutase (SOD), which generates H2O2 from superoxide, decreased the vasodilator effect of ACh on SV. In the IMA, SOD diminished phenylephrine-induced contraction in endothelium-containing, but not in endothelium-denuded vessels. Importantly, while exogenous H2O2 produced vasodilatation in IMA, it constricted SV. ACh increased H2O2 production in both sets of vessels. In the IMA, the increase in H2O2 was inhibited by catalase and nNOS blockade. In SV, H2O2 production was abolished by catalase and reduced by nNOS inhibition. Immunofluorescence experiments showed the presence of nNOS in the vascular endothelium and smooth muscle cells of both the IMA and SV. Together, our results clearly show that H2O2 induced endothelium-dependent vascular relaxation in the IMA, whereas, in the SV, H2O2 was a vasoconstrictor. Thus, H2O2 produced in the coronary circulation may contribute to the susceptibility to accelerated atherosclerosis and progressive failure of the SV used as autogenous graft in coronary bypass surgery.

Obesity, Inflammation, and Exercise Training: Relative Contribution of iNOS and eNOS in the Modulation of Vascular Function in the Mouse Aorta.

BACKGROUND: The understanding of obsesity-related vascular dysfunction remains controversial mainly because of the diseases associated with vascular injury. Exercise training is known to prevent vascular dysfunction. Using an obesity model without comorbidities, we aimed at investigating the underlying mechanism of vascular dysfunction and how exercise interferes with this process. METHODS: High-sugar diet was used to induce obesity in mice. Exercise training was performed 5 days/week. Body weight, energy intake, and adipose tissues were assessed; blood metabolic and hormonal parameters were determined; and serum TNFα was measured. Blood pressure and heart rate were assessed by plethysmography. Changes in aortic isometric tension were recorded on myograph. Western blot was used to analyze protein expression. Nitric oxide (NO) was evaluated using fluorescence microscopy. Antisense oligodeoxynucleotides were used for inducible nitric oxide synthase isoform (iNOS) knockdown. RESULTS: Body weight, fat mass, total cholesterol, low-density lipoprotein cholesterol fraction, insulin, and leptin were higher in the sedentary obese group (SD) than in the sedentary control animals (SS). Exercise training prevented these changes. No difference in glucose tolerance, insulin sensitivity, blood pressure, and heart rate was found. Decreased vascular relaxation and reduced endothelial nitric oxide synthase (eNOS) functioning in the SD group were prevented by exercise. Contractile response to phenylephrine was decreased in the aortas of the wild SD mice, compared with that of the SS group; however, no alteration was noted in the SD iNOS(-/-) animals. The decreased contractility was endothelium-dependent, and was reverted by iNOS inhibition or iNOS silencing. The aortas from the SD group showed increased basal NO production, serum TNFα, TNF receptor-1, and phospho-IκB. Exercise training attenuated iNOS-dependent reduction in contractile response in high-sugar diet-fed animals, decreased iNOS expression, and increased eNOS expression. CONCLUSION: Obesity caused endothelium dysfunction, TNFα, and iNOS pathway up-regulation, decreasing vascular contractility in the obese animals. Exercise training was an effective therapy to control iNOS-dependent NO production and to preserve endothelial function in obese individuals.

Neuronal Nitric Oxide Synthase in Vascular Physiology and Diseases.

The family of nitric oxide synthases (NOS) has significant importance in various physiological mechanisms and is also involved in many pathological processes. Three NOS isoforms have been identified: neuronal NOS (nNOS or NOS 1), endothelial NOS (eNOS or NOS 3), and an inducible NOS (iNOS or NOS 2). Both nNOS and eNOS are constitutively expressed. Classically, eNOS is considered the main isoform involved in the control of the vascular function. However, more recent studies have shown that nNOS is present in the vascular endothelium and importantly contributes to the maintenance of the homeostasis of the cardiovascular system. In physiological conditions, besides nitric oxide (NO), nNOS also produces hydrogen peroxide (H2O2) and superoxide ([Formula: see text]) considered as key mediators in non-neuronal cells signaling. This mini-review highlights recent scientific releases on the role of nNOS in vascular homeostasis and cardiovascular disorders such as hypertension and atherosclerosis.

Structure-related blockage of calcium channels by vasodilator alkamides in mice mesenteric artery.

The development of new calcium channel blockers is still relevant for the understanding of their physiological role and pharmacological and therapeutic purposes. For this task, natural products represent a relevant source of new drugs. The present work investigated the mechanism and the structural relationship of the vasodilator effect of riparins I, II and III in mouse small mesenteric artery. Riparins I, II and III induced an endothelium-independent and concentration-dependent vasodilator effect in mesenteric arteries. Riparins II and III were more potent than riparin I, suggesting a structural relationship of the effect of these drugs. All riparins inhibited the contractile effect of KCl, similarly to nifedipine. However, the inhibitory profile was different for the contractile responses to phenylephrine and caffeine, passing from similar to nifedipine with riparin I, for similar to SKF-96365 with riparin III. A comparable effect was observed for the increase in the intracellular calcium concentration induced by caffeine and phenylephrine. These results suggest that the higher hydroxylation provides the alkamides the ability to inhibit non-selective cation channels in addition to the inhibition of L-type calcium channels in mouse mesenteric arteries. These observations may give support to the development of new selective inhibitors of non-selective cation channels using alkamides as leading compounds.

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.

Mechanisms of vascular dysfunction in acute phase of Trypanosoma cruzi infection in mice.

Vascular disorders have a direct link to mortality in the acute phase of Trypanosoma cruzi infection. However, the underlying mechanisms of vascular dysfunction in this phase are largely unknown. We hypothesize that T. cruzi invades endothelial cells causing dysfunction in contractility and relaxation of the mouse aorta. Immunodetection of T. cruzi antigen TcRBP28 was observed in endothelial cells. There was a decreased endothelial nitric oxide synthase (eNOS)-derived NO-dependent vascular relaxation, and increased vascular contractility accompanied by augmented superoxide anions production. Endothelial removal, inhibition of cyclooxygenase 2 (COX-2), blockade of thromboxane A2 (TXA2) TP receptors, and scavenger of superoxide normalized the contractile response. COX-2, thromboxane synthase, inducible nitric oxide synthase (iNOS), p65 NFκB subunit and p22(phox) of NAD(P)H oxidase (NOX) subunit expressions were increased in vessels of chagasic animals. Serum TNF-α was augmented. Basal NO production, and nitrotyrosine residue expression were increased. It is concluded that T. cruzi invades mice aorta endothelial cells and increases TXA2/TP receptor/NOX-derived superoxide formation. Alongside, T. cruzi promotes systemic TNF-α increase, which stimulates iNOS expression in vessels and nitrosative stress. In light of the heart failure that develops in the chronic phase of the disease, to understand the mechanism involved in the increased contractility of the aorta is crucial.

Potent antihypertensive effect of Hancornia speciosa leaves extract.

BACKGROUND: Hancornia speciosa Gomes is an herb traditionally used in Brazil for blood pressure control. PURPOSE: The present work investigated the antihypertensive effect of an extract from Hancornia speciosa leaves (SFH) and analyzed its underlying mechanisms of action. METHODS: Hypertension was induced in mice by surgical removal of a kidney and by subcutaneous administration of a pellet with deoxycorticosterone. Vasodilatation was measured in mesenteric arteries with a wire myograph. Nitrites were measured by fluorescence with 2,3-diaminonaphthalene and H2O2 was measured with carbon microsensors. RESULTS: SFH (0.03, 0.1 or 1 mg/kg; po) induced a dose-dependent, long-lasting reduction in the systolic blood pressure in conscious DOCA-salt hypertensive mice (DOCA). Administration of SFH produced a significant increase in the plasmatic level of nitrites. The systemic inhibition of nitric oxide synthase by L-NAME (20 mg/kg) reduced its antihypertensive effect. SFH also induced a concentration-dependent vasodilatation of mesenteric resistance arteries contracted with phenylephrine, which was more potent in arteries from DOCA mice. Removal of the endothelium or pretreatment with L-NAME or catalase reduced the vasodilator response for SFH. The nitrite production induced by SFH was significantly bigger in mesenteric arteries from DOCA than in SHAM mice. However, the production of H2O2 induced by SFH was twice higher in DOCA mice. CONCLUSION: Altogether, our results point to an antihypertensive effect of SFH due to a reduction in peripheral resistance through the production of NO and by a mechanism involving an increased production of H2O2 in the mesenteric arteries from hypertensive mice. These findings are further evidence to support the use of Hancornia speciosa by traditional medicine as an antihypertensive drug.