RESUMEN

Impaired redox balance contributes to the cardiovascular alterations of hypertension and activation of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway may counteract these alterations. While nitrite recycles back to NO and exerts antioxidant and antihypertensive effects, the mechanisms involved in these responses are not fully understood. We hypothesized that nitrite treatment of two-kidney, one-clip (2K1C) hypertensive rats activates the Nrf2 pathway, promotes the transcription of antioxidant genes, and improves the vascular redox imbalance and dysfunction in this model. Two doses of oral nitrite were studied: 15 mg/kg and the sub-antihypertensive dose of 1 mg/kg. Nitrite 15 mg/kg (but not 1 mg/kg) decreased blood pressure and increased circulating plasma nitrite and nitrate. Both doses blunted hypertension-induced increases in mesenteric artery reactive oxygen species concentrations assessed by DHE technique and restored the impaired mesenteric artery responses to acetylcholine. While 2K1C hypertension decreased nuclear Nrf2 accumulation, both doses of nitrite increased nuclear Nrf2 accumulation and mRNA expression of Nrf2-regulated genes including superoxide dismutase-1 (SOD1), catalase (CAT), glutathione peroxidase (GPX), thioredoxin-1(TRDX-1) and -2 (TRDX-2). To further confirm nitrite-mediated antioxidant effects, we measured vascular SOD and GPX activity and we found that nitrite at 1 or 15 mg/kg increased the activity of both enzymes (P < 0.05). These results suggest that activation of the Nrf2 pathway promotes antioxidant effects of nitrite, which may improve the vascular dysfunction in hypertension, even when nitrite is given at a sub-antihypertensive dose. These findings may have many clinical implications, particularly in the therapy of hypertension and other cardiovascular diseases.

Asunto(s)

Antioxidantes/metabolismo , Hipertensión Renovascular/tratamiento farmacológico , Factor 2 Relacionado con NF-E2/genética , Nitritos/farmacología , Animales , Antihipertensivos/farmacología , Presión Sanguínea/efectos de los fármacos , Catalasa/genética , Modelos Animales de Enfermedad , Glutatión Peroxidasa/genética , Humanos , Hipertensión Renovascular/genética , Hipertensión Renovascular/metabolismo , Hipertensión Renovascular/patología , Masculino , Oxidación-Reducción/efectos de los fármacos , Ratas , Especies Reactivas de Oxígeno , Transducción de Señal/efectos de los fármacos , Superóxido Dismutasa-1/genética , Tiorredoxinas/genética

RESUMEN

Hypertension is associated with cardiovascular remodeling. Given that impaired redox state activates matrix metalloproteinase (MMP)- 2 and promotes vascular remodeling, we hypothesized that nitrite treatment at a non-antihypertensive dose exerts antioxidant effects and attenuates both MMP-2 activation and vascular remodeling of hypertension. We examined the effects of oral sodium nitrite at antihypertensive (15 mg/kg) or non-antihypertensive (1 mg/kg) daily dose in hypertensive rats (two kidney, one clip; 2K1C model). Sham-operated and 2K1C hypertensive rats received vehicle or nitrite by gavage for four weeks. Systolic blood pressure decreased only in hypertensive rats treated with nitrite 15 mg/Kg/day. Both low and high nitrite doses decreased 2K1C-induced vascular remodeling assessed by measuring aortic cross-sectional area, media/lumen ratio, and number of vascular smooth muscle cells/aortic length. Both low and high nitrite doses decreased 2K1C-induced vascular oxidative stress assessed in situ with the fluorescent dye DHE and with the lucigenin chemiluminescence assay. Vascular MMP-2 expression and activity were assessed by gel zymography, Western blot, and in situ zymography increased with hypertension. While MMP-2 levels did not change in response to both doses of nitrite, both doses completely prevented hypertension-induced increases in vascular MMP activity. Moreover, incubation of aortas from hypertensive rats with nitrite at 1-20 µmol/L reduced gelatinolytic activity by 20-30%. This effect was fully inhibited by the xanthine oxidase (XOR) inhibitor febuxostat, suggesting XOR-mediated generation of nitric oxide (NO) from nitrite as a mechanism explaining the responses to nitrite. In vitro incubation of aortic extracts with nitrite 20 µmol/L did not affect MMP-2 activity. These results show that nitrite reverses the vascular structural alterations of hypertension, independently of anti-hypertensive effects. This response is mediated, at least in part, by XOR and is attributable to antioxidant effects of nitrite blunting vascular MMP-2 activation. Our findings suggest nitrite therapy to reverse structural alterations of hypertension.

Asunto(s)

Hipertensión Renovascular/tratamiento farmacológico , Metaloproteinasa 2 de la Matriz/genética , Nitritos/farmacología , Estrés Oxidativo/efectos de los fármacos , Animales , Antihipertensivos/farmacología , Antioxidantes , Aorta/efectos de los fármacos , Aorta/patología , Presión Sanguínea/efectos de los fármacos , Modelos Animales de Enfermedad , Febuxostat/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Hipertensión Renovascular/genética , Hipertensión Renovascular/patología , Músculo Liso Vascular/efectos de los fármacos , Óxido Nítrico/metabolismo , Ratas , Especies Reactivas de Oxígeno , Remodelación Vascular/efectos de los fármacos , Xantina Oxidasa/antagonistas & inhibidores , Xantina Oxidasa/genética

RESUMEN

Cardiac hypertrophy is a common consequence of chronic hypertension and leads to heart failure and premature death. The anion nitrite is now considered as a bioactive molecule able to exert beneficial cardiovascular effects. Previous results showed that nitrite attenuates hypertension-induced increases in reactive oxygen species (ROS) production in the vasculature. Whether antioxidant effects induced by nitrite block critical signaling pathways involved in cardiac hypertrophy induced by hypertension has not been determined yet. The Akt/mTOR signaling pathway is responsible to activate protein synthesis during cardiac remodeling and is activated by increased ROS production, which is commonly found in hypertension. Here, we investigated the effects of nitrite treatment on cardiac remodeling and activation of this hypertrophic signaling pathway in 2 kidney-1 clip (2K1C) hypertension. Sham and 2K1C rats were treated with oral nitrite at 1 or 15 mg/kg for four weeks. Nitrite treatment (15 mg/kg) reduced systolic blood pressure and decreased ROS production in the heart tissue from hypertensive rats. This nitrite dose also blunted hypertension-induced activation of mTOR pathway and cardiac hypertrophy. While the lower nitrite dose (1 mg/kg) did not affect blood pressure, it exerted antioxidant effects and tended to attenuate mTOR pathway activation and cardiac hypertrophy induced by hypertension. Our findings provide strong evidence that nitrite treatment decreases cardiac remodeling induced by hypertension as a result of its antioxidant effects and downregulation of mTOR signaling pathway. This study may help to establish nitrite as an effective therapy in hypertension-induced cardiac hypertrophic remodeling.

Asunto(s)

Antioxidantes/farmacología , Cardiomegalia/metabolismo , Hipertensión/metabolismo , Nitritos/farmacología , Serina-Treonina Quinasas TOR/metabolismo , Animales , Cardiomegalia/etiología , Hipertensión/complicaciones , Masculino , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Transducción de Señal/efectos de los fármacos , Serina-Treonina Quinasas TOR/efectos de los fármacos

RESUMEN

Senescent cells withdraw from the cell cycle and do not proliferate. The prevalence of senescent compared to normally functioning parenchymal cells increases with age, impairing tissue and organ homeostasis. A contentious principle governing this process has been the redox theory of aging. We linked matricellular protein thrombospondin 1 (TSP1) and its receptor CD47 to the activation of NADPH oxidase 1 (Nox1), but not of the other closely related Nox isoforms, and associated oxidative stress, and to senescence in human cells and aged tissue. In human endothelial cells, TSP1 promoted senescence and attenuated cell cycle progression and proliferation. At the molecular level, TSP1 increased Nox1-dependent generation of reactive oxygen species (ROS), leading to the increased abundance of the transcription factor p53. p53 mediated a DNA damage response that led to senescence through Rb and p21cip, both of which inhibit cell cycle progression. Nox1 inhibition blocked the ability of TSP1 to increase p53 nuclear localization and p21cip abundance and its ability to promote senescence. Mice lacking TSP1 showed decreases in ROS production, p21cip expression, p53 activity, and aging-induced senescence. Conversely, lung tissue from aging humans displayed increases in the abundance of vascular TSP1, Nox1, p53, and p21cip Finally, genetic ablation or pharmacological blockade of Nox1 in human endothelial cells attenuated TSP1-mediated ROS generation, restored cell cycle progression, and protected against senescence. Together, our results provide insights into the functional interplay between TSP1 and Nox1 in the regulation of endothelial senescence and suggest potential targets for controlling the aging process at the molecular level.

Asunto(s)

Antígeno CD47/genética , Senescencia Celular/genética , Células Endoteliales/metabolismo , NADPH Oxidasa 1/genética , Trombospondina 1/genética , Adulto , Anciano , Envejecimiento/genética , Animales , Antígeno CD47/metabolismo , Línea Celular , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Femenino , Regulación de la Expresión Génica , Humanos , Pulmón/irrigación sanguínea , Pulmón/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , NADPH Oxidasa 1/metabolismo , Interferencia de ARN , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal/genética , Trombospondina 1/metabolismo , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo

RESUMEN

Pulmonary arterial hypertension (PAH) is a rapidly degenerating and devastating disease of increased pulmonary vessel resistance leading to right heart failure. Palliative modalities remain limited despite recent endeavors to investigate the mechanisms underlying increased pulmonary vascular resistance (PVR), i.e. aberrant vascular remodeling and occlusion. However, little is known of the molecular mechanisms responsible for endothelial proliferation, a root cause of PAH-associated vascular remodeling. Lung tissue specimens from PAH and non-PAH patients and hypoxia-exposed human pulmonary artery endothelial cells (ECs) (HPAEC) were assessed for mRNA and protein expression. Reactive oxygen species (ROS) were measured using cytochrome c and Amplex Red assays. Findings demonstrate for the first time an up-regulation of NADPH oxidase 1 (Nox1) at the transcript and protein level in resistance vessels from PAH compared with non-PAH patients. This coincided with an increase in ROS production and expression of bone morphogenetic protein (BMP) antagonist Gremlin1 (Grem1). In HPAEC, hypoxia induced Nox1 subunit expression, assembly, and oxidase activity leading to elevation in sonic hedgehog (SHH) and Grem1 expression. Nox1 gene silencing abrogated this cascade. Moreover, loss of either Nox1, SHH or Grem1 attenuated hypoxia-induced EC proliferation. Together, these data support a Nox1-SHH-Grem1 signaling axis in pulmonary vascular endothelium that is likely to contribute to pathophysiological endothelial proliferation and the progression of PAH. These findings also support targeting of Nox1 as a viable therapeutic option to combat PAH.

Asunto(s)

Proliferación Celular , Hipertensión Pulmonar/enzimología , Péptidos y Proteínas de Señalización Intercelular/metabolismo , NADPH Oxidasas/metabolismo , Adulto , Anciano , Células Endoteliales/citología , Células Endoteliales/metabolismo , Femenino , Proteínas Hedgehog/genética , Proteínas Hedgehog/metabolismo , Humanos , Hipertensión Pulmonar/genética , Hipertensión Pulmonar/metabolismo , Hipertensión Pulmonar/fisiopatología , Péptidos y Proteínas de Señalización Intercelular/genética , Masculino , Persona de Mediana Edad , NADPH Oxidasa 1 , NADPH Oxidasas/genética , Arteria Pulmonar/enzimología , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal

RESUMEN

The nitric oxide (NO•) metabolites nitrite and nitrate exert antihypertensive effects by mechanisms that involve gastric formation of S-nitrosothiols. However, while the use of antiseptic mouthwash (AM) is known to attenuate the responses to nitrate by disrupting its enterosalivary cycle, there is little information about whether AM attenuates the effects of orally administered nitrite. We hypothesized that the antihypertensive effects of orally administered nitrite would not be prevented by AM because, in contrast to oral nitrate, oral nitrite could promote S-nitrosothiols formation in the stomach without intereference by AM. Chronic effects of oral nitrite or nitrate were studied in two-kidney, one-clip (2K1C) hypertensive rats (and normotensive controls) treated with AM (or vehicle) once/day. We found that orally administered nitrite exerts antihypertensive effects that were not affected by AM. This finding contrasts with lack of antihypertensive responses to oral nitrate in 2K1C hypertensive rats treated with AM. Nitrite and nitrate treatments increased plasma nitrites, nitrates, and S-nitrosothiols concentrations. However, while treatment with AM attenuated the increases in plasma nitrite concentrations after both nitrite and nitrate treatments, AM attenuated the increases in S-nitrosothiols in nitrate-treated rats, but not in nitrite-treated rats. Moreover, AM attenuated vascular S-nitrosylation (detected by the SNO-RAC method) after nitrate, but not after nitrite treatment. Significant correlations were found between the hypotensive responses and S-nitrosothiols, and vascular S-nitrosylation levels. These results show for the first time that oral nitrite exerts antihypertensive effects notwithstanding the fact that antiseptic mouthwash disrupts the enterosalivary circulation of nitrate. Our results support a major role for S-nitrosothiols formation resulting in vascular S-nitrosylation as a key mechanism for the antihypertensive effects of both oral nitrite and nitrate.

Asunto(s)

Antihipertensivos/farmacología , Hipertensión/tratamiento farmacológico , Antisépticos Bucales/farmacología , Nitratos/farmacología , Nitritos/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Modelos Animales de Enfermedad , Hipertensión/metabolismo , Hipertensión/fisiopatología , Masculino , Nitrosación , Ratas , Ratas Wistar , Arteria Renal/cirugía , Obstrucción de la Arteria Renal/cirugía , S-Nitrosotioles/metabolismo

Asunto(s)

Enfermedades Cardiovasculares/prevención & control , Dieta Vegetariana , Antioxidantes/farmacología , Enfermedades Cardiovasculares/sangre , Enfermedades Cardiovasculares/enzimología , Humanos , Metaloproteinasas de la Matriz/sangre , Metaloproteinasas de la Matriz/metabolismo , Estrés Oxidativo/efectos de los fármacos

RESUMEN

Many effects of nitrite and nitrate are attributed to increased circulating concentrations of nitrite, ultimately converted into nitric oxide (NO(•)) in the circulation or in tissues by mechanisms associated with nitrite reductase activity. However, nitrite generates NO(•) , nitrous anhydride, and other nitrosating species at low pH, and these reactions promote S-nitrosothiol formation when nitrites are in the stomach. We hypothesized that the antihypertensive effects of orally administered nitrite or nitrate involve the formation of S-nitrosothiols, and that those effects depend on gastric pH. The chronic effects of oral nitrite or nitrate were studied in two-kidney, one-clip (2K1C) hypertensive rats treated with omeprazole (or vehicle). Oral nitrite lowered blood pressure and increased plasma S-nitrosothiol concentrations independently of circulating nitrite levels. Increasing gastric pH with omeprazole did not affect the increases in plasma nitrite and nitrate levels found after treatment with nitrite. However, treatment with omeprazole severely attenuated the increases in plasma S-nitrosothiol concentrations and completely blunted the antihypertensive effects of nitrite. Confirming these findings, very similar results were found with oral nitrate. To further confirm the role of gastric S-nitrosothiol formation, we studied the effects of oral nitrite in hypertensive rats treated with the glutathione synthase inhibitor buthionine sulfoximine (BSO) to induce partial thiol depletion. BSO treatment attenuated the increases in S-nitrosothiol concentrations and antihypertensive effects of oral nitrite. These data show that gastric S-nitrosothiol formation drives the antihypertensive effects of oral nitrite or nitrate and has major implications, particularly to patients taking proton pump inhibitors.

Asunto(s)

Radicales Libres/metabolismo , Hipertensión Renovascular/tratamiento farmacológico , Nitritos/metabolismo , S-Nitrosotioles/metabolismo , Animales , Antihipertensivos/administración & dosificación , Antioxidantes/administración & dosificación , Antioxidantes/metabolismo , Modelos Animales de Enfermedad , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/metabolismo , Humanos , Hipertensión Renovascular/metabolismo , Hipertensión Renovascular/patología , Ratas , Nitrito de Sodio/administración & dosificación

RESUMEN

Hypertension is a common disease that includes oxidative stress as a major feature, and oxidative stress impairs physiological nitric oxide (NO) activity promoting cardiovascular pathophysiological mechanisms. While inorganic nitrite and nitrate are now recognized as relevant sources of NO after their bioactivation by enzymatic and non-enzymatic pathways, thus lowering blood pressure, mounting evidence suggests that sodium nitrite also exerts antioxidant effects. Here we show for the first time that sodium nitrite exerts consistent systemic and vascular antioxidant and antihypertensive effects in the deoxycorticosterone-salt (DOCA-salt) hypertension model. This is particularly important because increased oxidative stress plays a major role in the DOCA-salt hypertension model, which is less dependent on activation of the renin-angiotensin system than other hypertension models. Indeed, antihypertensive effects of oral nitrite were associated with increased plasma nitrite and nitrate concentrations, and completely blunted hypertension-induced increases in plasma 8-isoprostane and lipid peroxide levels, in vascular reactive oxygen species, in vascular NADPH oxidase activity, and in vascular xanthine oxidoreductase activity. Together, these findings provide evidence that the oral administration of sodium nitrite consistently decreases the blood pressure in association with major antioxidant effects in experimental hypertension.

Asunto(s)

Antihipertensivos/uso terapéutico , Antioxidantes/uso terapéutico , Hipertensión/tratamiento farmacológico , Nitrito de Sodio/uso terapéutico , Animales , Antihipertensivos/farmacología , Antioxidantes/farmacología , Presión Sanguínea/efectos de los fármacos , Desoxicorticosterona/toxicidad , Dinoprost/análogos & derivados , Dinoprost/sangre , Modelos Animales de Enfermedad , Hipertensión/inducido químicamente , Hipertensión/patología , Peróxidos Lipídicos/sangre , Masculino , NADPH Oxidasas/metabolismo , Nitritos/sangre , Óxidos de Nitrógeno/sangre , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Especies Reactivas de Oxígeno/metabolismo , Nitrito de Sodio/farmacología , Xantina Oxidasa/metabolismo

RESUMEN

Nitrite-derived nitric oxide (NO) formation exerts antihypertensive effects. Because NO inhibits angiotensin converting enzyme (ACE) activity, we carried a comprehensive series of experiments in rats to test the hypothesis that sodium nitrite exerts antihypertensive effects by inhibiting ACE. We examined whether sodium nitrite (15 mg/kg; or vehicle; by gavage): (I) attenuates the pressor responses to angiotensin I at doses of 0.03, 0.1, 0.3, 1, 3, and 10 µg/kg intravenously; (II) attenuates the acute hypertension induced by L-NAME (100 mg/kg; or vehicle; by gavage); (III) attenuates the chronic hypertension induced by L-NAME (1 g/L in drinking water; or vehicle) administered for 6 weeks; (IV) attenuates the hypertension in the 2 kidney-1 clip (2K1C) chronic hypertension model. Blood samples were collected at the end of each study and plasma angiotensin converting enzyme (ACE) activity was measured with a fluorimetric assay using Hippuryl-His-Leu as substrate. ACE inhibitors were used as positive controls. Plasma nitrite concentrations were measured by ozone-based reductive chemiluminescence. The in vitro effects of sodium nitrite (0, 1, 3, 10, 30, 100 µmol/L) on plasma ACE activity were also determined. We found that sodium nitrite did not affect the pressor responses to angiotensin I. Moreover, while sodium nitrite exerted significant antihypertensive effects in acute and chronic hypertension models, no significant effects on plasma ACE activity were found. In vitro experiments showed no effects of sodium nitrite on plasma ACE activity. This is the first study to demonstrate that the acute and chronic antihypertensive effects of sodium nitrite are not associated with significant inhibition of circulating ACE activity.

Asunto(s)

Inhibidores de la Enzima Convertidora de Angiotensina , Antihipertensivos/farmacología , Peptidil-Dipeptidasa A/metabolismo , Nitrito de Sodio/farmacología , Inhibidores de la Enzima Convertidora de Angiotensina/química , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Animales , Antihipertensivos/química , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Hipertensión/sangre , Hipertensión/inducido químicamente , Hipertensión/enzimología , Masculino , NG-Nitroarginina Metil Éster , Peptidil-Dipeptidasa A/sangre , Ratas , Ratas Wistar , Nitrito de Sodio/química , Relación Estructura-Actividad

Asunto(s)

Arginina/análogos & derivados , Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/metabolismo , Reflujo Gastroesofágico/tratamiento farmacológico , Inhibidores de la Bomba de Protones/efectos adversos , Inhibidores de la Bomba de Protones/uso terapéutico , Animales , Humanos , Masculino

RESUMEN

Nitrate and nitrite have emerged as an important novel source of nitric oxide (NO). We have previously demonstrated that sodium nitrite is an antihypertensive compound that exerts antioxidant effects in experimental hypertension. These unpredicted antioxidant effects of nitrite raised the question whether the beneficial effects found were caused by its conversion to NO or simply due to reversal of endothelial dysfunction as a consequence of its antioxidant effects. Here, we evaluated the antihypertensive effects of a daily dose of sodium nitrite for 4 weeks in L-NAME-induced hypertension in rats. We studied the effects of nitrite on markers of NO bioavailability, vascular oxidative stress, and expression of xanthine oxidoreductase. Moreover, we tested if xanthine oxidoreductase inhibition could attenuate the acute hypotensive effects of sodium nitrite in L-NAME hypertensive rats. We found that a single pharmacological dose of sodium nitrite exerts antihypertensive effects in L-NAME-induced hypertension. While the beneficial antihypertensive properties of nitrite were associated with increased levels of NO metabolites, hypertension increased vascular xanthine oxidoreductase expression by approximately 40%, with minor increases in vascular superoxide production. The inhibition of xanthine oxidoreductase by oxypurinol attenuated the acute hypotensive effects of nitrite. Taken together, our results show that nitrite exerts antihypertensive effects in L-NAME hypertensive rats and provide evidence that xanthine oxidoreductase plays an important role in this antihypertensive effect.

Asunto(s)

Antihipertensivos/uso terapéutico , Hipertensión/inducido químicamente , Hipertensión/enzimología , NG-Nitroarginina Metil Éster/toxicidad , Nitrito de Sodio/uso terapéutico , Xantina Deshidrogenasa/biosíntesis , Animales , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/enzimología , Hipertensión/tratamiento farmacológico , Masculino , Distribución Aleatoria , Ratas , Ratas Wistar

RESUMEN

Endothelium-derived factors play an important role in vascular tone control. This study aimed to evaluate how endothelium and reactive oxygen species (ROS) contribute to phenylephrine (PE)-induced contraction in renovascular hypertensive (2K-1C) and normotensive (2K) rats aortas. The effects of the superoxide scavenger Tiron (0.1mM and 1mM) or catalase (30 U/ml, 90 U/ml, 150 U/ml and 300 U/ml) on the PE-induced contraction were evaluated in both intact endothelium (E+) and denuded (E-) aortas. Endothelium removal increased the PE-induced contractions. The maximum contractile response decreased only in 2K-1C rat E+ aorta, and catalase (30 U/ml, 90 U/ml, 150 U/ml) partially reversed this effect. Endothelium increased the basal hydrogen peroxide (H2O2) production in 2K and 2K-1C rats aortas. PE-stimulated H2O2 production was higher in 2K-1C (E+/E-) than in 2K (E+/E-). Inhibition of the enzymes cyclooxygenase, NADPH-oxidase, xanthine-oxidase, and superoxide dismutase reduced the PE-stimulated H2O2 production in 2K-1C rat aorta. The decreased contraction to PE in 2K-1C rat aorta is partially due to endothelial H2O2 production; however, in denuded aorta, it contributes to maintaining the contractile response. Superoxide plays an important role on the PE-induced contraction in 2K rat denuded aorta, whereas in 2K-1C rat aorta, it is H2O2 that plays an important role in this effect.

Asunto(s)

Aorta/efectos de los fármacos , Aorta/fisiopatología , Peróxido de Hidrógeno/metabolismo , Hipertensión Renal/fisiopatología , Fenilefrina/farmacología , Vasoconstricción/efectos de los fármacos , Animales , Catalasa/farmacología , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Inhibidores Enzimáticos/farmacología , Depuradores de Radicales Libres/farmacología , Hipertensión Renal/metabolismo , Técnicas In Vitro , Masculino , Estrés Oxidativo/efectos de los fármacos , Polietilenglicoles/farmacología , Ratas , Receptores Adrenérgicos alfa 1/metabolismo , Superóxidos/metabolismo

RESUMEN

Orally administered nitrite exerts antihypertensive effects associated with increased gastric nitric oxide (NO) formation. While reducing agents facilitate NO formation from nitrite, no previous study has examined whether antioxidants with reducing properties improve the antihypertensive responses to orally administered nitrite. We hypothesized that TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) could enhance the hypotensive effects of nitrite in hypertensive rats by exerting antioxidant effects (and enhancing NO bioavailability) and by promoting gastric nitrite-derived NO generation. The hypotensive effects of intravenous and oral sodium nitrite were assessed in unanesthetized freely moving rats with L-NAME (N(ω)-nitro-L-arginine methyl ester; 100mg/kg; po)-induced hypertension treated with TEMPOL (18mg/kg; po) or vehicle. While TEMPOL exerted antioxidant effects in hypertensive rats, as revealed by lower plasma 8-isoprostane and vascular reactive oxygen species levels, this antioxidant did not affect the hypotensive responses to intravenous nitrite. Conversely, TEMPOL enhanced the dose-dependent hypotensive responses to orally administered nitrite, and this effect was associated with higher increases in plasma nitrite and lower increases in plasma nitrate concentrations. In vitro experiments using electrochemical and chemiluminescence NO detection under variable pH conditions showed that TEMPOL enhanced nitrite-derived NO formation, especially at low pH (2.0 to 4.0). TEMPOL signal evaluated by electron paramagnetic resonance decreased when nitrite was reduced to NO under acidic conditions. Consistent with these findings, increasing gastric pH with omeprazole (30mg/kg; po) attenuated the hypotensive responses to nitrite and blunted the enhancement in plasma nitrite concentrations and hypotensive effects induced by TEMPOL. Nitrite-derived NO formation in vivo was confirmed by using the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (C-PTIO), which blunted the responses to oral nitrite. Our results showed that TEMPOL promotes nitrite reduction to NO in the stomach and enhanced plasma nitrite concentrations and the hypotensive effects of oral sodium nitrite through mechanisms critically dependent on gastric pH. Interestingly, the effects of TEMPOL on nitrite-mediated hypotension cannot be explained by increased NO formation in the stomach alone, but rather appear more directly related to increased plasma nitrite levels and reduced nitrate levels during TEMPOL treatment. This may relate to enhanced nitrite uptake or reduced nitrate formation from NO or nitrite.

Asunto(s)

Antioxidantes/farmacología , Presión Sanguínea/efectos de los fármacos , Óxidos N-Cíclicos/farmacología , Óxido Nítrico/biosíntesis , Nitrito de Sodio/farmacología , Animales , Antihipertensivos/farmacología , Espectroscopía de Resonancia por Spin del Electrón , Mucosa Gástrica/metabolismo , Concentración de Iones de Hidrógeno , Luminiscencia , Masculino , Ratas , Ratas Wistar , Marcadores de Spin , Estómago/efectos de los fármacos

RESUMEN

The new pathway nitrate-nitrite-nitric oxide (NO) has emerged as a physiological alternative to the classical enzymatic pathway for NO formation from l-arginine. Nitrate is converted to nitrite by commensal bacteria in the oral cavity and the nitrite formed is then swallowed and reduced to NO under the acidic conditions of the stomach. In this study, we tested the hypothesis that increases in gastric pH caused by omeprazole could decrease the hypotensive effect of oral sodium nitrite. We assessed the effects of omeprazole treatment on the acute hypotensive effects produced by sodium nitrite in normotensive and L-NAME-hypertensive free-moving rats. In addition, we assessed the changes in gastric pH and plasma levels of nitrite, NO(x) (nitrate+nitrite), and S-nitrosothiols caused by treatments. We found that the increases in gastric pH induced by omeprazole significantly reduced the hypotensive effects of sodium nitrite in both normotensive and L-NAME-hypertensive rats. This effect of omeprazole was associated with no significant differences in plasma nitrite, NO(x), or S-nitrosothiol levels. Our results suggest that part of the hypotensive effects of oral sodium nitrite may be due to its conversion to NO in the acidified environment of the stomach. The increase in gastric pH induced by treatment with omeprazole blunts part of the beneficial cardiovascular effects of dietary nitrate and nitrite.

Asunto(s)

Antihipertensivos/administración & dosificación , Jugo Gástrico/química , Nitrito de Sodio/administración & dosificación , Administración Oral , Animales , Antiulcerosos/farmacología , Antihipertensivos/antagonistas & inhibidores , Aorta/efectos de los fármacos , Aorta/fisiopatología , Benzoatos/farmacología , Presión Sanguínea/efectos de los fármacos , Depuradores de Radicales Libres/farmacología , Jugo Gástrico/efectos de los fármacos , Concentración de Iones de Hidrógeno , Hipertensión/inducido químicamente , Hipertensión/tratamiento farmacológico , Imidazoles/farmacología , Técnicas In Vitro , Masculino , NG-Nitroarginina Metil Éster , Óxido Nítrico/sangre , Omeprazol/farmacología , Ratas , Ratas Wistar , S-Nitrosotioles/sangre , Nitrito de Sodio/antagonistas & inhibidores , Vasodilatación/efectos de los fármacos

RESUMEN

Dietary nitrite and nitrate have been reported as alternative sources of nitric oxide (NO). In this regard, we reported previously that sodium nitrite added to drinking water was able to exert antihypertensive effects in an experimental model of hypertension in a dose-dependent manner. Taking into consideration that nitrite is continuously converted to nitrate in the bloodstream, here we expanded our previous report and evaluate whether a single daily dose of sodium nitrite could exert antihypertensive effects in 2 kidney-1 clip (2K1C) hypertensive rats. Sham-operated and 2K1C rats were treated with vehicle or sodium nitrite (15 mg/kg/day) for 4 weeks. We evaluated the effects induced by sodium nitrite treatment on systolic blood pressure (SBP) and NO markers such as plasma nitrite, nitrite + nitrate (NOx), cGMP, and blood levels of nitrosyl-hemoglobin. In addition, we also evaluated effects of nitrite on oxidative stress and antioxidant enzymes. Dihydroethidium (DHE) was used to evaluate aortic reactive oxygen species (ROS) production by fluorescence microscopy, and plasma levels of thiobarbituric acid-reactive species (TBARS) were measured in plasma samples from all experimental groups. Red blood cell superoxide dismutase (SOD) and catalase activity were evaluated with commercial kits. Sodium nitrite treatment reduced SBP in 2K1C rats (P < 0.05). We found lower plasma nitrite and NOx levels in 2K1C rats compared with normotensive controls (both P < 0.05). Nitrite treatment restored the lower levels of nitrite and NOx. While no change was found in the blood levels of nitrosyl-hemoglobin (P > 0.05), nitrite treatment increased the plasma levels of cGMP in 2K1C rats (P < 0.05). Higher plasma TBARS levels and aortic ROS levels were found in hypertensive rats compared with controls (P < 0.05), and nitrite blunted these alterations. Lower SOD and catalase activities were found in 2K1C hypertensive rats compared with controls (both P < 0.05). Nitrite treatment restored SOD activity (P < 0.05), whereas catalase was not affected. These data suggest that even a single daily oral dose of sodium nitrite is able to lower SBP and exert antioxidant effects in renovascular hypertension.

Asunto(s)

Antihipertensivos/administración & dosificación , Antioxidantes/administración & dosificación , Hipertensión Renovascular/tratamiento farmacológico , Nitrito de Sodio/administración & dosificación , Animales , Presión Sanguínea/efectos de los fármacos , Catalasa/sangre , GMP Cíclico/sangre , Modelos Animales de Enfermedad , Hemoglobinas/metabolismo , Hipertensión Renovascular/sangre , Hipertensión Renovascular/fisiopatología , Masculino , Nitratos/sangre , Nitritos/sangre , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Superóxido Dismutasa/sangre

RESUMEN

Dietary nitrite and nitrate are important sources of nitric oxide (NO). However, the use of nitrite as an antihypertensive drug may be limited by increased oxidative stress associated with hypertension. We evaluated the antihypertensive effects of sodium nitrite given in drinking water for 4 weeks in two-kidney one-clip (2K1C) hypertensive rats and the effects induced by nitrite on NO bioavailability and oxidative stress. We found that, even under the increased oxidative stress conditions present in 2K1C hypertension, nitrite reduced systolic blood pressure in a dose-dependent manner. Whereas treatment with nitrite did not significantly change plasma nitrite concentrations in 2K1C rats, it increased plasma nitrate levels significantly. Surprisingly, nitrite treatment exerted antioxidant effects in both hypertensive and sham-normotensive control rats. A series of in vitro experiments was carried out to show that the antioxidant effects induced by nitrite do not involve direct antioxidant effects or xanthine oxidase activity inhibition. Conversely, nitrite decreased vascular NADPH oxidase activity. Taken together, our results show for the first time that nitrite has antihypertensive effects in 2K1C hypertensive rats, which may be due to its antioxidant properties resulting from vascular NADPH oxidase activity inhibition.

Asunto(s)

Antihipertensivos/farmacología , Antioxidantes/farmacología , Regulación hacia Abajo/efectos de los fármacos , Hipertensión/tratamiento farmacológico , NADPH Oxidasas/antagonistas & inhibidores , Nitrito de Sodio/farmacología , Animales , Antihipertensivos/uso terapéutico , Antioxidantes/uso terapéutico , Presión Sanguínea/efectos de los fármacos , Dinoprost/análogos & derivados , Dinoprost/sangre , Peróxidos Lipídicos/sangre , NADPH Oxidasas/biosíntesis , NADPH Oxidasas/genética , Óxido Nítrico/metabolismo , Nitritos/sangre , Estrés Oxidativo/efectos de los fármacos , Ratas , Especies Reactivas de Oxígeno/sangre , Nitrito de Sodio/uso terapéutico , Xantina Oxidasa/antagonistas & inhibidores

RESUMEN

Pregnant women are particularly susceptible to toxic effects associated with lead (Pb) exposure. Pb accumulates in bone tissue and is rapidly mobilized from bones during pregnancy, thus resulting in fetal contamination. While vitamin D receptor (VDR) polymorphisms modify bone mineralization and affect Pb biomarkers including blood (Pb-B) and serum (Pb-S) Pb concentrations, and %Pb-S/Pb-B ratio, the effects of these polymorphisms on Pb levels in pregnant women are unknown. This study aimed at examining the effects of three (FokI, BsmI and ApaI) VDR polymorphisms (and VDR haplotypes) on Pb levels in pregnant women. Pb-B and Pb-S were determined by inductively coupled plasma mass spectrometry in samples from 256 healthy pregnant women and their respective umbilical cords. Genotypes for the VDR polymorphisms were determined by PCR and restriction fragment length digestion. While the three VDR polymorphisms had no significant effects on Pb-B, Pb-S or %Pb-S/Pb-B ratio, the haplotype combining the f, a, and b alleles for the FokI, ApaI and BsmI polymorphisms, respectively, was associated with significantly lower Pb-S and %Pb-S/Pb-B (P<0.05). However, maternal VDR haplotypes had no effects on Pb levels in the umbilical cords. To our knowledge, this is the first study showing that a combination of genetic polymorphisms (haplotype) commonly found in the VDR gene affects Pb-S and %Pb-S/Pb-B ratios in pregnant women. These findings may have major implications for Pb toxicity because they may help to predict the existence of a group of subjects that is genetically less prone to Pb toxicity during pregnancy.

Asunto(s)

Contaminantes Ambientales/sangre , Plomo/sangre , Polimorfismo de Nucleótido Simple , Embarazo/sangre , Receptores de Calcitriol/genética , Adulto , Biomarcadores/sangre , Femenino , Haplotipos , Humanos , Plomo/metabolismo , Exposición Materna , Embarazo/genética , Cordón Umbilical/metabolismo , Adulto Joven

RESUMEN

Foetal exposure to lead (Pb) during pregnancy is a major problem. However, no previous study has examined whether Pb concentrations in blood (Pb-B) and in serum (Pb-S) from pregnant women correlate with Pb-B and Pb-S in the foetuses. This hypothesis was tested in the present study. We measured Pb-B and Pb-S in 120 healthy pregnant women (more than 38 weeks of gestation) and their respective umbilical cord samples. The analyses were carried out with an inductively coupled plasma mass spectrometer. We found higher Pb-B levels in the women compared with their respective umbilical cord samples (1.736 ± 0.090 µg/dL and 1.194 ± 0.062 µg/dL, respectively; p < 0.05). In parallel, we found higher Pb-S levels in the women compared with their respective umbilical cord samples (0.042 ± 0.003 µg/dL and 0.032 ± 0.003 µg/dL, respectively; p < 0.05). However, similar %Pb-S/Pb-B ratios were found in the women compared with their respective umbilical cord samples (2.414 ± 0.210% and 2.740 ± 0.219%, respectively; p > 0.05). Interestingly, we found positive correlations between Pb-B in the umbilical cords and Pb-B in the respective pregnant women (rs = 0.5714; p < 0.0001), and between Pb-S in the umbilical cords and Pb-S in the respective pregnant women (rs = 0.3902; p < 0.0001) as well as between %Pb-B/Pb-S in the umbilical cords and %Pb-B/Pb-S in the respective pregnant women (rs = 0.3767; p < 0.0001). These results indicate that the assessment of Pb-B and Pb-S in pregnant women provides relevant indexes of foetal exposure to Pb. Moreover, the similar %Pb-S/Pb-B in pregnant women and in the umbilical cords shows that the foetuses are directly exposed to the rapidly exchangeable Pb fraction found in their mothers.

Asunto(s)

Plomo/sangre , Intercambio Materno-Fetal , Periodo Periparto , Cordón Umbilical/química , Femenino , Sangre Fetal/química , Feto , Humanos , Embarazo , Suero/química , Adulto Joven

RESUMEN

PROJECT: Serum samples may not be appropriate to assess lead (Pb) concentrations because they may contain artificially higher Pb concentrations compared with those measured in plasma samples. Here, we compared Pb concentrations in serum versus heparin plasma separated from blood collected with or without vacuum. We have also examined the effects of sample standing time on Pb concentrations measured in serum, heparin plasma, and EDTA plasma. PROCEDURE: We studied plasma and serum samples from twelve healthy subjects. Blood samples were collected via venous drainage phlebotomy with and without vacuum into trace metal free tubes containing no anticoagulants (serum), or lithium heparin, or EDTA (to obtain plasma). Variable sample standing times (0, 5, and 30 min) prior to centrifugation were allowed. Plasma and serum Pb and iron concentrations were determined by inductively coupled plasma mass spectrometry. Plasma and serum cell-free hemoglobin concentrations were measured. RESULTS: Pb concentrations in serum and in heparin plasma from blood samples collected with or without vacuum were similar and not associated with significant changes in iron or hemoglobin concentrations. The sample standing time (up to 30 min) did not affect Pb concentrations in serum or in heparin plasma, which were approximately 50% lower than those found in EDTA plasma. CONCLUSIONS: Serum or heparin plasma separated from blood samples collected via venous phlebotomy with or without vacuum are appropriate medium to assess Pb concentrations, independently of the sample standing time.

Asunto(s)

Plomo/sangre , Plasma/química , Suero/química , Espectrofotometría Atómica/métodos , Adulto , Recolección de Muestras de Sangre , Ácido Edético , Humanos , Factores de Tiempo , Adulto Joven