Mitochondrial Oxidative Stress Enhances Vasoconstriction by Altering Calcium Homeostasis in Cerebrovascular Smooth Muscle Cells under Simulated Microgravity / 生物医学与环境科学（英文）

Objective@#Exposure to microgravity results in postflight cardiovascular deconditioning in astronauts. Vascular oxidative stress injury and mitochondrial dysfunction have been reported during this process. To elucidate the mechanism for this condition, we investigated whether mitochondrial oxidative stress regulates calcium homeostasis and vasoconstriction in hindlimb unweighted (HU) rat cerebral arteries.@*Methods@#Three-week HU was used to simulate microgravity in rats. The contractile responses to vasoconstrictors, mitochondrial fission/fusion, Ca @*Results@#An increase of cytoplasmic Ca @*Conclusion@#The present results suggest that mitochondrial oxidative stress enhances cerebral vasoconstriction by regulating calcium homeostasis during simulated microgravity.

El lado oculto de la hipoxemia / The dark side of hypoxemia

Acute respiratory distress syndrome (ARDS) is characterized by an increase in the intrapulmonary shunt (measured by the PaO2/FiO2 ratio) caused by bilateral alveolar-interstitial infiltrates which are not fully explained by fluid overload. However, there are some ARDS cases which present severe hypoxemia without clear lung infiltrates. An example of this, which has generated great controver- sy, is the infection caused by SARS-CoV-2. Understanding the pathophysiology of hypoxemia is absolutely crucial in order to establish the most appropriate therapeutic strategy for each patient. In the case of a severe hypoxemia (PaO/ FiO2 < 200 which represents a shunt greater than 30%) with a chest X-ray (or CT) without clear and extensive bilateral infiltrates, it is important to consider that the shunt can be caused due to vascular involvement. This shunt could be explained two ways: an increase in pulmonary vascular resistance (PVR), which generates a right-to-left shunt through the patent foramen ovale (PFO), or an alteration of the hypoxic pulmonary vasoconstriction reflex (HPV). The HPV reflex is activated in an attempt to redistribute the vascular flow to better ventilated areas. However, there are some situations (such as viral infections) that can alter this reflex and worsen the hypoxemia. The concomitant use of vasoactive drugs (such as inhaled nitric oxide) and vasopressors (such as dopa- mine or norepinephrine) has been proposed with the aim of reducing PVR and the flow through the PFO; or to redistribute the flow to better ventilated areas if an alteration of the RVP is suspected.

Un síndrome de distrés respiratorio agudo (SDRA) se caracteriza por un incremento del intrapulmonar (medido por el cociente PaO2/FiO2) causado por una afectación alveolo-intersticial bilateral no explicada por sobrecarga hídrica. Sin embargo, hay casos de SDRA que presentan una marcada hipoxemia sin claros infiltrados pulmonares. Un ejemplo de este caso, que ha generado gran controversia, es la infección por SARS-CoV-2. El entendimiento de la fisiopato- logía de la hipoxemia es absolutamente clave para establecer la estrategia terapéutica más adecuada en cada paciente. Ante una hipoxemia grave (PaO2/FiO2 < 200 que representa un superior al 30%) y con una radiografía de tórax (o con TAC) sin claros y extensos infiltrados bilaterales, el podría deberse a una afectación vascular. Esto podría explicarse por dos causas: un aumento de las resistencias vasculares pulmonares (RVP), que genera un derecha- izquierda a través del foramen oval permeable (FOP) o una alteración del reflejo de vasoconstricción pulmonar hipóxico (VPH). El reflejo de VPH se activa en un intento por redistribuir el flujo vascular hacia las zonas mejor ventiladas. Sin embargo, existen situaciones (como infecciones víricas) que pueden alterar dicho reflejo y agravar la hipoxemia. Se ha propuesto el uso concomitante de fármacos vasoactivos (como el óxido nítrico inhalado) y vasopresores (como do- pamina o noradrenalina) con el objetivo de disminuir las RVP y el flujo a través del FOP; o para redistribuir el flujo a zonas mejor ventiladas si se sospecha una alteración del RVP.

Mecanismos regulatorios del tono vascular pulmonar neonatal: una perspectiva molecular / Regulatory mechanisms of neonatal pulmonary vascular tone: a molecular perspective

La adaptación al medio extrauterino incluye un aumento considerable de la PaO2, que induce especialmente cambios estructurales y vasoactivos en la circulación pulmonar, que llevarán a una circulación previamente pobremente irrigada, a recibir ∼100% del gasto cardíaco del recién nacido, permitiendo el normal intercambio gaseoso. La regulación local de la circulación arterial pulmonar neonatal basal, es mantenida por un delicado equilibrio entre agentes vasoconstrictores y vasodilatadores. Este equilibrio, permite mantener la circulación pulmonar como un territorio de gran flujo sanguíneo y baja resistencia. La acción de los vasoconstrictores permite la formación de las interacciones entre actina y la cadena liviana de la miosina, esta es inducida en la célula muscular lisa principalmente por dos vías: a) dependiente de calcio, que consiste en aumentar el calcio intracelular, facilitando finalmente la unión de actina y miosina, y b) independiente de calcio, la cual a través de consecutivas fosforilaciones logra sensibilizar a las proteínas involucradas promoviendo la unión de actina y miosina. Estas acciones son mediadas por agonistas generados principalmente en el endotelio pulmonar, como endotelina-1 y tromboxano, o por agonistas provenientes de otros tipos celulares como la serotonina. Los agentes vasodilatadores regulan la respuesta vasoconstrictora, principalmente inhibiendo la señalización que induce la vasocontricción independiente de calcio, a través de la activación de proteínas quinasas que inhibirán la función de la ROCK quinasa, uno de los últimos efectores de la vasocontricción antes de la formación de la unión de actina y miosina. Esta revisión describe estos mecanismos de primordial importancia en las primeras horas de nuestra vida como individuos independientes.

The extrauterine-milieu adaptation includes a considerable increase in PaO2, that specifically induces structural and vasoactive changes at pulmonary circulation. Such changes transform a poor irrigated circulation into a circulation that receive ∼100% of neonatal cardiac output, supporting the normal alveolar-capillary gas exchange. Local regulation of basal neonatal pulmonary circulation is maintaining by a delicate equilibrium between vasoconstrictor and vasodilator agents. This equilibrium, allows to maintain the pulmonary circulation as an hemodynamic system with a high blood flow and a low vascular resistance. Vasocontrictors action allows actin and light-chain myosin interaction. Two main pathways induced this effect in smooth muscle cell: a) a calcium dependent pathway, that increases intracellular calcium, facilitating actin - myosin binding, and b) the independent calcium pathway, which achieves through consecutive phosphorylation reactions sensitize the proteins involved, promoting the binding of actin and light-chain myosin. These actions are mediated by agonists produced mainly in the pulmonary endothelium, such as endothelin-1 and thromboxane, or by agonists from other cell types such as serotonin. Vasodilator agents regulate the vasoconstrictor response, mainly by inhibiting signals that induce calcium-independent vasoconstriction, through activation of protein kinases, which in turn will inhibit the function of ROCK kinase, one of the last effectors of vasoconstriction before formation of the actin and light-chain myosin binding. This review will focus on describing these mechanisms of primal importance in the first hours of our lives as independent individuals.

A Single Resistance Exercise Session Improves Aortic Endothelial Function in Hypertensive Rats / Uma Única Sessão de Exercício Resistido Melhora a Função Endotelial Aórtica em Ratos Hipertensos

Abstract Background: Physical exercise is an important tool for the improvement of endothelial function. Objective: To assess the effects of acute dynamic resistance exercise on the endothelial function of spontaneously hypertensive rats (SHR). Methods: Ten minutes after exercise, the aorta was removed to evaluate the expression of endothelial nitric oxide synthase (eNOS), phosphorylated endothelial nitric oxide synthase (p-eNOS1177) and inducible nitric oxide synthase (iNOS) and to generate concentration-response curves to acetylcholine (ACh) and to phenylephrine (PHE). The PHE protocol was also performed with damaged endothelium and before and after NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin administration. The maximal response (Emax) and the sensitivity (EC50) to these drugs were evaluated. Results: ACh-induced relaxation increased in the aortic rings of exercised (Ex) rats (Emax= -80 ± 4.6%, p < 0.05) when compared to those of controls (Ct) (Emax = -50 ± 6.8%). The Emax to PHE was decreased following exercise conditions (95 ± 7.9%, p < 0.05) when compared to control conditions (120 ± 4.2%). This response was abolished after L-NAME administration or endothelial damage. In the presence of indomethacin, the aortic rings' reactivity to PHE was decreased in both groups (EC50= Ex -5.9 ± 0.14 vs. Ct -6.6 ± 0.33 log µM, p < 0.05 / Emax = Ex 9.5 ± 2.9 vs. Ct 17 ± 6.2%, p < 0.05). Exercise did not alter the expression of eNOS and iNOS, but increased the level of p-eNOS. Conclusion: A single resistance exercise session improves endothelial function in hypertensive rats. This response seems to be mediated by increased NO production through eNOS activation.

Resumo Fundamento: O exercício físico é uma importante ferramenta para o aprimoramento da função endotelial. Objetivo: Avaliar os efeitos do exercício dinâmico resistido agudo na função endotelial de ratos espontaneamente hipertensos (SHR). Métodos: Após 10 minutos de exercício, a aorta foi removida para avaliação da expressão de óxido nítrico sintase endotelial (eNOS), óxido nítrico sintase endotelial fosforilada (p-eNOS1177) e óxido nítrico sintase endotelial induzível (iNOS), e para a construção de curvas concentração-resposta de acetilcolina (ACT) e fenilefrina (FEN). O protocolo FEN foi também realizado com lesão endotelial e antes e depois da administração de N-nitro-L-arginina metil éster (L-NAME) e indometacina. A resposta máxima (Emax) e a sensibilidade (EC50) a esses fármacos foram avaliadas. Resultados: Houve aumento do relaxamento induzido por ACT nos anéis aórticos dos ratos exercitados (Ex) (Emax = -80 ± 4,6%; p < 0,05) quando comparado àquele dos controles (Ct) (Emax = -50 ± 6,8%). A Emax à FEN diminuiu após exercício (95 ± 7,9%; p < 0,05) quando comparada àquela dos controles (120 ± 4,2%). Tal resposta foi abolida após administração de L-NAME ou lesão endotelial. Na presença de indometacina, a reatividade dos anéis aórticos à FEN diminuiu nos dois grupos (EC50= Ex -5,9 ± 0,14 vs. Ct -6,6 ± 0,33 log µM; p < 0,05/ Emax = Ex 9,5 ± 2,9 vs. Ct 17 ± 6,2%; p < 0,05). O exercício não alterou a expressão de eNOS e de iNOS, mas aumentou o nível de p-eNOS. Conclusão: Uma única sessão de exercício resistido melhora a função endotelial em ratos hipertensos. Essa resposta parece ser mediada por elevação da produção de NO através de ativação de eNOS.

Vasodilatación mediada por flujo en niños con sobrepeso / Flow mediated vasodilation in overweight children

Introducción: El conocimiento actual sugiere que la enfermedad cardiovascular se origina y progresa desde la infancia y la adolescencia. La disfunción endotelial es un evento temprano y crucial en la aterosclerosis. Pacientes y Método: Estudio prospectivo que comparó la vasodilatación mediada por flujo (VMF) en niños con sobrepeso y niños de peso normal. Para medir la VMF se utilizó transductor adecuado de ultrasonido y el método estándar. Resultados: Ochenta y dos niños fueron incluidos; 49 eran casos (sobrepeso) y 33 controles. Los valores de VMF oscilaron entre -6 y 56% (promedio 11,1%) en niños con sobrepeso y de 0 a 29,6% (promedio 16,6%) en niños control (p < 0,05). Se presentó vasoconstricción paradójica en el 34,7% de los niños con sobrepeso y en ninguno de los controles (p < 0,05). Se encontró una asociación significativa entre vasoconstricción paradójica con obesidad central e hipertensión. Conclusión: Los resultados de este estudio muestran que la VMF es menor en niños con sobrepeso en comparación con los niños eutróficos, por lo que es más probable que exista disfunción endotelial en ellos.

Introduction: Present knowledge suggests that cardiovascular disease originates and progresses from childhood and adolescence. Endothelial dysfunction is an early and crucial event in atherosclerosis. Patients and Method: Prospective study that compares Flow Mediated Vasodilation (FMV) in children with overweight (OWC) and normal weight children. An ultrasound transducer a standard method were used to measure FMD. Results: The study included 82 children, of whom 49 were cases (OWC) and 33 controls. FMV values ranged from -6 to 56% (x = 11.1%) in OW, and from 0 to 29.6% (x = 16.6%) in control children (P<.005). Paradoxical vasoconstriction was found in 34.7% in OWC as compared to nil in controls (P<.005). A significant association was found between vasoconstriction and central obesity and hypertension. Conclusion: The results of this study show that FMV is lower in obese compared to normal children; thus they are more likely to have endothelial dysfunction.

Vascular O-GlcNAcylation augments reactivity to constrictor stimuli by prolonging phosphorylated levels of the myosin light chain

O-GlcNAcylation is a modification that alters the function of numerous proteins. We hypothesized that augmented O-GlcNAcylation levels enhance myosin light chain kinase (MLCK) and reduce myosin light chain phosphatase (MLCP) activity, leading to increased vascular contractile responsiveness. The vascular responses were measured by isometric force displacement. Thoracic aorta and vascular smooth muscle cells (VSMCs) from rats were incubated with vehicle or with PugNAc, which increases O-GlcNAcylation. In addition, we determined whether proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation. PugNAc enhanced phenylephrine (PE) responses in rat aortas (maximal effect, 14.2±2 vs 7.9±1 mN for vehicle, n=7). Treatment with an MLCP inhibitor (calyculin A) augmented vascular responses to PE (13.4±2 mN) and abolished the differences in PE-response between the groups. The effect of PugNAc was not observed when vessels were preincubated with ML-9, an MLCK inhibitor (7.3±2 vs 7.5±2 mN for vehicle, n=5). Furthermore, our data showed that differences in the PE-induced contractile response between the groups were abolished by the activator of AMP-activated protein kinase (AICAR; 6.1±2 vs 7.4±2 mN for vehicle, n=5). PugNAc increased phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and protein kinase C-potentiated inhibitor protein of 17 kDa (CPI-17), which are involved in RhoA/Rho-kinase-mediated inhibition of myosin phosphatase activity. PugNAc incubation produced a time-dependent increase in vascular phosphorylation of myosin light chain and decreased phosphorylation levels of AMP-activated protein kinase, which decreased the affinity of MLCK for Ca2+/calmodulin. Our data suggest that proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation, favoring vascular contraction.

Inhibition of PKC-dependent extracellular Ca2+ entry contributes to the depression of contractile activity in long-term pressure-overloaded endothelium-denuded rat aortas

We examined the contractile responsiveness of rat thoracic aortas under pressure overload after long-term suprarenal abdominal aortic coarctation (lt-Srac). Endothelium-dependent angiotensin II (ANG II) type 2 receptor (AT2R)-mediated depression of contractions to ANG II has been reported in short-term (1 week) pressure-overloaded rat aortas. Contractility was evaluated in the aortic rings of rats subjected to lt-Srac or sham surgery (Sham) for 8 weeks. ANG I and II levels and AT2R protein expression in the aortas of lt-Srac and Sham rats were also evaluated. lt-Srac attenuated the contractions of ANG II and phenylephrine in the aortas in an endothelium-independent manner. However, lt-Srac did not influence the transient contractions induced in endothelium-denuded aortic rings by ANG II, phenylephrine, or caffeine in Ca2+-free medium or the subsequent tonic constrictions induced by the addition of Ca2+ in the absence of agonists. Thus, the contractions induced by Ca2+ release from intracellular stores and Ca2+ influx through stored-operated channels were not inhibited in the aortas of lt-Srac rats. Potassium-elicited contractions in endothelium-denuded aortic rings of lt-Srac rats remained unaltered compared with control tissues. Consequently, the contractile depression observed in aortic tissues of lt-Srac rats cannot be explained by direct inhibition of voltage-operated Ca2+ channels. Interestingly, 12-O-tetradecanoylphorbol-13-acetate-induced contractions in endothelium-denuded aortic rings of lt-Srac rats were depressed in the presence but not in the absence of extracellular Ca2+. Neither levels of angiotensins nor of AT2R were modified in the aortas after lt-Srac. The results suggest that, in rat thoracic aortas, lt-Srac selectively inhibited protein kinase C-mediated activation of contraction that is dependent on extracellular Ca2+ entry.

Vascular dysfunction as a target for adjuvant therapy in cerebral malaria

Cerebral malaria (CM) is a life-threatening complication of Plasmodium falciparum malaria that continues to be a major global health problem. Brain vascular dysfunction is a main factor underlying the pathogenesis of CM and can be a target for the development of adjuvant therapies for the disease. Vascular occlusion by parasitised red blood cells and vasoconstriction/vascular dysfunction results in impaired cerebral blood flow, ischaemia, hypoxia, acidosis and death. In this review, we discuss the mechanisms of vascular dysfunction in CM and the roles of low nitric oxide bioavailability, high levels of endothelin-1 and dysfunction of the angiopoietin-Tie2 axis. We also discuss the usefulness and relevance of the murine experimental model of CM by Plasmodium berghei ANKA to identify mechanisms of disease and to screen potential therapeutic interventions.

Lipoic acid, but not tempol, preserves vascular compliance and decreases medial calcification in a model of elastocalcinosis

Vascular calcification decreases compliance and increases morbidity. Mechanisms of this process are unclear. The role of oxidative stress and effects of antioxidants have been poorly explored. We investigated effects of the antioxidants lipoic acid (LA) and tempol in a model of atherosclerosis associated with elastocalcinosis. Male New Zealand white rabbits (2.5-3.0 kg) were fed regular chow (controls) or a 0.5% cholesterol (chol) diet+104 IU/day vitamin D2 (vitD) for 12 weeks, and assigned to treatment with water (vehicle, n=20), 0.12 mmol·kg-1·day-1 LA (n=11) or 0.1 mmol·kg-1·day-1 tempol (n=15). Chol+vitD-fed rabbits developed atherosclerotic plaques associated with expansive remodeling, elastic fiber disruption, medial calcification, and increased aortic stiffness. Histologically, LA prevented medial calcification by ∼60% and aortic stiffening by ∼60%. LA also preserved responsiveness to constrictor agents, while intima-media thickening was increased. In contrast to LA, tempol was associated with increased plaque collagen content, medial calcification and aortic stiffness, and produced differential changes in vasoactive responses in the chol+vitD group. Both LA and tempol prevented superoxide signals with chol+vitD. However, only LA prevented hydrogen peroxide-related signals with chol+vitD, while tempol enhanced them. These data suggest that LA, opposite to tempol, can minimize calcification and compliance loss in elastocalcionosis by inhibition of hydrogen peroxide generation.

Treinamento resistido controla a pressão arterial de ratos hipertensos induzidos por l-NAME / Resistance training controls arterial blood pressure in rats with L-NAME- induced hypertension

FUNDAMENTO: A hipertensão arterial é uma síndrome multifatorial, crônica, causada tanto por fatores congênitos ou adquiridos. OBJETIVO: Avaliar os efeitos do treinamento físico resistido (TR) sobre pressão arterial, reatividade e morfologia vascular de ratos hipertensos induzidos por L-NAME. MÉTODOS: Ratos Wistar machos (200-250 g) foram divididos em 3 grupos: normotenso sedentário (NS), hipertenso sedentário (HS) e hipertenso treinado (HT). A hipertensão foi induzida pela administração de L-NAME (40 mg/kg) na água de beber por 4 semanas. A pressão arterial foi avaliada antes e após o TR. O TR foi realizado utilizando 50% de 1RM, em 3 séries de 10 repetições, 3 vezes por semana, durante quatro semanas. A reatividade vascular foi mensurada em artéria mesentérica superior por curvas concentração resposta ao nitroprussiato de sódio (NPS) e fenilefrina (FEN). Além disso, foram realizadas análises histológicas e estereológicas. RESULTADOS: O TR inibiu o aumento das pressões arteriais média e diastólica. Foi observada uma redução significativa na resposta máxima e na potência da FEN entre os grupos HS e HT. A análise histológica evidenciou aspecto normal para as túnicas íntima, média e adventícia em todos os grupos. Não houve diferença significativa nas áreas do lúmen, da túnica média e total das artérias dos grupos HS e HT em relação ao NS. A razão parede/lúmen arterial do grupo HS apresentou diferença significativa em relação ao NS (p < 0,05), mas esta não foi diferente do HT. CONCLUSÕES: O TR foi capaz de prevenir a elevação da pressão arterial sob as condições deste estudo. Este controle parece envolver a regulação de mecanismo vasoconstritor e a manutenção do diâmetro luminal de ratos hipertensos induzidos por L-NAME.

BACKGROUND: Arterial hypertension is a multifactorial chronic condition caused by either congenital or acquired factors. OBJECTIVE: To evaluate the effects of Resistance Training (RT) on arterial pressure, and on vascular reactivity and morphology, of L-NAME-treated hypertensive rats. METHODS: Male Wistar rats (200 - 250 g) were allocated into Sedentary Normotensive (SN), Sedentary Hypertensive (SH) and Trained Hypertensive (TH) groups. Hypertension was induced by adding L-NAME (40 mg/Kg) to the drinking water for four weeks. Arterial pressure was evaluated before and after RT. RT was performed using 50% of 1RM, 3 sets of 10 repetitions, 3 times per week for four weeks. Vascular reactivity was measured in rat mesenteric artery rings by concentration-response curves to sodium nitroprusside (SNP); phenylephrine (PHE) was also used for histological and stereological analysis. RESULTS: Resistance training inhibited the increase in mean and diastolic arterial pressures. Significant reduction was observed in Rmax (maximal response) and pD2 (potency) of PHE between SH and TH groups. Arteries demonstrated normal intima, media and adventitia layers in all groups. Stereological analysis demonstrated no significant difference in luminal, tunica media, and total areas of arteries in the SH and TH groups when compared to the SN group. Wall-to-lumen ratio of SH arteries was significantly different compared to SN arteries (p<0.05) but there was no difference when compared to TH arteries. CONCLUSIONS: RT was able to prevent an increase in blood pressure under the conditions in this study. This appears to involve a vasoconstrictor regulation mechanism and maintenance of luminal diameter in L-NAME induced hypertensive rats.

Impacto dos stents e do sirolimus por via oral na vasomotilidade coronariana dependente e independente do endotelio / Impact of stenting and oral sirolimus on endothelium-dependent and independent coronary vasomotion

FUNDAMENTO: Não há consenso sobre o impacto do implante de stent sobre a função endotelial no longo prazo. Há relatos de disfunção endotelial aumentada com stent com sirolimus quando comparado com o stent metálico convencional (BMS). OBJETIVO: Este estudo visa a avaliar o impacto do BMS e o efeito do sirolimus por via oral sobre a função endotelial. MÉTODOS: Quarenta e cinco pacientes foram randomizados em três grupos: BMS + altas doses de sirolimus oral (dose inicial de 15 mg, seguida de 6 mg/dia durante quatro semanas); BMS + baixa dose de sirolimus (6 mg, seguida de 2 mg por dia durante quatro semanas) e BMS sem sirolimus. Mudanças na vasoconstrição ou vasodilatação, em um segmento de 15 milímetros começando pelo extremo distal do stent em resposta a acetilcolina e nitroglicerina, foram avaliadas por angiografia quantitativa. RESULTADOS: Os grupos apresentaram características angiográficas semelhantes. A variação percentual de diâmetro em resposta a acetilcolina foi semelhante em todos os grupos, nos dois momentos (p = 0,469). Quatro horas após o implante de stent, o segmento alvo apresentou uma disfunção endotelial que se manteve após oito meses em todos os grupos. Em todos os grupos, a vasomotricidade independente de endotélio em resposta a nitroglicerina foi semelhante, às quatro horas e aos oito meses, com diâmetro do segmento alvo aumentado após a infusão de nitroglicerina (p = 0,001). CONCLUSÃO: A disfunção endotelial esteve igualmente presente no segmento distal de 15 milímetros do segmento tratado, às 4 horas e aos 8 meses após implante do stent. O sirolimus administrado por via oral durante quatro semanas para evitar a reestenose não afetou o estado de vasomotricidade endotélio dependente e independente.

BACKGROUND: There is no consensus regarding the impact of stenting on long-term endothelial function. There have been reports of increased endothelial dysfunction with sirolimus-eluting stents as compared to bare metal stenting (BMS). OBJECTIVE: This study aims to assess the impact of BMS and the effect of oral sirolimus on endothelial function. METHODS: Forty-five patients were randomized into three groups: BMS + high-dose oral sirolimus (initial dose of 15 mg, followed by 6 mg/day for four weeks); BMS + low-dose sirolimus (6 mg followed by 2 mg daily for four weeks); and BMS without sirolimus. Changes in vasoconstriction or vasodilation in a 15 mm segment starting at the distal stent end in response to acetylcholine and nitroglycerin were assessed by quantitative angiography. RESULTS: The groups had similar angiographic characteristics. The percent variation in diameter in response to acetylcholine was similar in all groups at the two time points (p = 0.469). Four hours after stenting, the target segment presented an endothelial dysfunction that was maintained after eight months in all groups. In all groups, endothelium-independent vasomotion in response to nitroglycerin was similar at four hours and eight months, with increased target segment diameter after nitroglycerin infusion (p = 0.001). CONCLUSION: The endothelial dysfunction was similarly present at the 15 mm segment distal to the treated segment, at 4 hours and 8 months after stenting. Sirolimus administered orally during 4 weeks to prevent restenosis did not affect the status of endothelium-dependent and independent vasomotion.

Gadolinium increases the vascular reactivity of rat aortic rings

Gadolinium (Gd) blocks intra- and extracellular ATP hydrolysis. We determined whether Gd affects vascular reactivity to contractile responses to phenylephrine (PHE) by blocking aortic ectonucleoside triphosphate diphosphohydrolase (E-NTPDase). Wistar rats of both sexes (260-300 g, 23 females, 7 males) were used. Experiments were performed before and after incubation of aortic rings with 3 µM Gd. Concentration-response curves to PHE (0.1 nM to 0.1 mM) were obtained in the presence and absence of endothelium, after incubation with 100 µM L-NAME, 10 µM losartan, or 10 µM enalaprilat. Gd significantly increased the maximum response (control: 72.3 ± 3.5; Gd: 101.3 ± 6.4 percent) and sensitivity (control: 6.6 ± 0.1; Gd: 10.5 ± 2.8 percent) to PHE. To investigate the blockade of E-NTDase activity by Gd, we added 1 mM ATP to the bath. ATP reduced smooth muscle tension and Gd increased its relaxing effect (control: -33.5 ± 4.1; Gd: -47.4 ± 4.1 percent). Endothelial damage abolished the effect of Gd on the contractile responses to PHE (control: 132.6 ± 8.6; Gd: 122.4 ± 7.1 percent). L-NAME + Gd in the presence of endothelium reduced PHE contractile responses (control/L-NAME: 151.1 ± 28.8; L-NAME + Gd: 67.9 ± 19 percent AUC). ATP hydrolysis was reduced after Gd administration, which led to ATP accumulation in the nutrient solution and reduced ADP concentration, while adenosine levels remained the same. Incubation with Gd plus losartan and enalaprilat eliminated the pressor effects of Gd. Gd increased vascular reactivity to PHE regardless of the reduction of E-NTPDase activity and adenosine production. Moreover, the increased reactivity to PHE promoted by Gd was endothelium-dependent, reducing NO bioavailability and involving an increased stimulation of angiotensin-converting enzyme and angiotensin II AT1 receptors.

Óxido nítrico e sistema cardiovascular: ativação celular, reatividade vascular e variante genética / Nitric oxide and the cardiovascular system: cell activation, vascular reactivity and genetic variant / Óxido nítrico y sistema cardiovascular: activación celular, reactividad vascular y variante genética

O óxido nítrico (NO), primariamente identificado como um fator relaxante derivado do endotélio, é um radical livre atuante na sinalização de diferentes processos biológicos. A identificação das isoformas das sintases do NO (NOS) e a subsequente caracterização dos mecanismos de ativação celulares das enzimas possibilitaram tanto a compreensão de parte das interações fisiológicas como a compreensão de parte dos mecanismos de doença, na qual o NO está envolvido. A isoforma endotelial da NOS (eNOS), expressa principalmente no endotélio vascular, desempenha importante papel na regulação da reatividade vascular e no desenvolvimento e na progressão da aterosclerose. Esta revisão tem o propósito de contextualizar o leitor sobre a estrutura da eNOS e seus mecanismos de ativação celular. Tendo em vista os avanços da biologia molecular, trataremos ainda dos conhecidos mecanismos de regulação da expressão gênica e do papel de variantes no código genético da eNOS associados a fenótipos cardiovasculares. Embora se reconheça a importância do NO como molécula ateroprotetora, nossa atenção estará voltada à revisão de literatura envolvendo NO e sua participação na modulação do fenótipo de vasodilatação muscular.

Nitric oxide (NO), primarily identified as an endothelium-derived relaxing factor, is a free radical that signals different biological processes. The identification of NO synthase (NOS) isoforms and the subsequent characterization of the mechanisms of cell activation of the enzymes permitted the partial understanding of both the physiological interactions and of the mechanisms of the diseases in which NO is involved. Mainly expressed in the vascular endothelium, the endothelial NOS isoform (eNOS) plays an important role in the regulation of vascular reactivity and in the development and progression of atherosclerosis. The purpose of this review is to contextualize the reader about the eNOS structure and its mechanisms of cell activation. In view of the advances in molecular biology, we will also address the known mechanisms of gene expression regulation and the role of variants on the genetic code of eNOS associated with cardiovascular phenotypes. Although the importance of NO as an atheroprotective molecule is recognized, our focus will be the review of the literature on NO and its participation in the modulation of the muscle vasodilatation phenotype.

El óxido nítrico (NO), primariamente identificado como un factor relajante derivado del endotelio, es un radical libre actuante en la señalización de diferentes procesos biológicos. La identificación de las isoformas de las sintasas del NO (NOS) y la subsecuente caracterización de los mecanismos de activación celulares de las enzimas posibilitaron tanto la comprensión de parte de las interacciones fisiológicas como la comprensión de parte de los mecanismos de enfermedad, en la cual el NO está envuelto. La isoforma endotelial de la NOS (eNOS), expresada principalmente en el endotelio vascular, desempeña importante papel en la regulación de la reactividad vascular y en el desarrollo y en la progresión de la aterosclerosis. Esta revisión tiene el propósito de contextualizar al lector sobre la estructura de la eNOS y sus mecanismos de activación celular. Teniendo en vista los avances de la biología molecular, trataremos aun de los conocidos mecanismos de regulación de la expresión génica y del papel de variantes en el código genético de la eNOS asociados a fenotipos cardiovasculares. Aunque se reconozca la importancia del NO como molécula ateroprotectora, nuestra atención estará volcada a la revisión de literatura envolviendo NO y su participación en la modulación del fenotipo de vasodilatación muscular.

Rol del riñón en la hipertensión sal-sensible / Role of the kidney in salt sensitive hypertension

An important proportion of patients with essential hypertension are salt sensitive, defined as those who experience signifcant blood pressure changes according to the amount of salt intake. They have a disturbance in the pressure induced natriuresis mechanism and their kidneys have functional and morphological alterations con-sistent with an acquired tubulointerstitial alteration, afferent arteriole damage and alteration of peritubular capillaries. All these alterations lead to disturbances in sodium load excretion under normal pressures. There is also an associated activation of kidney vasoconstrictor/salt retaining systems and a reduction in the vasodilator/ salt eliminating mechanisms. These alterations, that originate early in life, generate a new blood pressure level, that corrects natriuresis at the expense of a sustained hypertension.

Effects of pneumonectomy on nitric oxide synthase expression and perivascular edema in the remaining lung of rats

Pneumonectomy is associated with high mortality and high rates of complications. Postpneumonectomy pulmonary edema is one of the leading causes of mortality. Little is known about its etiologic factors and its association with the inflammatory process. The purpose of the present study was to evaluate the role of pneumonectomy as a cause of pulmonary edema and its association with gas exchange, inflammation, nitric oxide synthase (NOS) expression and vasoconstriction. Forty-two non-specific pathogen-free Wistar rats were included in the study. Eleven animals died during or after the procedure, 21 were submitted to left pneumonectomy and 10 to sham operation. These animals were sacrificed after 48 or 72 h. Perivascular pulmonary edema was more intense in pneumonectomized rats at 72 h (P = 0.0131). Neutrophil density was lower after pneumonectomy in both groups (P = 0.0168). There was higher immunohistochemical expression of eNOS in the pneumonectomy group (P = 0.0208), but no statistically significant difference in the expression of iNOS. The lumen-wall ratio and pO2/FiO2 ratio did not differ between the operated and sham groups after pneumonectomy. Left pneumonectomy caused perivascular pulmonary edema with no elevation of immunohistochemical expression of iNOS or neutrophil density, suggesting the absence of correlation with the inflammatory process or oxidative stress. The increased expression of eNOS may suggest an intrinsic production of NO without signs of vascular reactivity.

Portal hypertensive response to kinin

Portal hypertension is the most common complication of chronic liver diseases, such as cirrhosis. The increased intrahepatic vascular resistance seen in hepatic disease is due to changes in cellular architecture and active contraction of stellate cells. In this article, we review the historical aspects of the kallikrein-kinin system, the role of bradykinin in the development of disease, and our main findings regarding the role of this nonapeptide in normal and experimentalmodels of hepatic injury using the isolated rat liver perfusion model (mono and bivascular) and isolated liver cells. We demonstrated that: 1) the increase in intrahepatic vascular resistance induced by bradykinin is mediated by B2 receptors, involving sinusoidal endothelial and stellate cells, and is preserved in the presence of inflammation, fibrosis, and cirrhosis; 2) the hepatic arterial hypertensive response to bradykinin is calcium-independent and mediated by eicosanoids; 3) bradykinin does not have vasodilating effect on the pre-constricted perfused rat liver; and, 4) after exertion of its hypertensive effect, bradykinin is degraded by angiotensin converting enzyme. In conclusion, the hypertensive response to BK is mediated by the B2 receptor in normal and pathological situations. The B1 receptor is expressed more strongly in regenerating and cirrhotic livers, and its role is currently under investigation.

Hipertensão portal é a complicação mais comum das doenças crônicas do fígado, tais como cirrose. A resistência intravascular aumentada observada na doença hepática é devida a alterações na arquitetura celular e contração ativa das células estreladas. Neste trabalho revisamos aspectos históricos do estudo do sistema calicreína-cinina e os resultados de nossos estudos do papel deste nonapeptídeo no controle do tono vascular intra-hepático em condições normais e modelos experimentais de agressão hepática usando a perfusão de fígado isolado de rato (mono e bivascular) e células hepáticas isoladas. Nós demonstramos que: 1) o aumento da resistência vascular intrahepática induzido pela bradicinina é mediado por receptores B2, envolve a participação de células endoteliais sinusoidais e células estreladas e não é alterada pela presença de inflamação, fibrose ou cirrose; 2) a resposta hipertensiva induzida pela bradicinina no sistema arterial hepático é cálcio-independente emediada por eicosanóides; 3) bradicinina não tem efeito dilatador na circulação intra-hepática; 4) após exercer efeito vasoconstritor intra-hepático, a bradicinina é degradada pela enzima conversora de angiotensina. Em conclusão, a resposta hipertensiva à bradicinina é mediada pelo receptor B2 em condições normais e patológicas. Receptor B1 é expresso mais fortemente nos fígados em regeneração e cirróticos e seu papel está sob investigação.

Producción de prostaciclina en arteria radial de diabéticos: comparación con la vena safena y arteria mamaria interna y su relevancia en el pronóstico de estos bypass coronarios / Prostacyclin production in internal mammary ano radial arteries and saphenous veins of diabetic and non diabetic subjects

Background: Myocardial revascularization surgery has used several vessels as coronary grafts including internal mammary and radial arteries which have a better prognosis than saphenous vein. Their long-term patency has been associated with the reléase of endothelium vasodilator and anti-aggregating producís such as prostacyclin. Diabetes induces endothelial dysfunction and a high number of diabetics require revascularization. Aim: To assess the capacity to synthesize prostacyclin of different vessels from diabetics. Material and methods: Internal mammary and radial arteries and saphenous veins obtained from 10 diabetic and 10 non diabetic patients subjected to coronary artery bypass surgery were studied. The capacity to synthesize prostacyclin was assessed in these vessels measuríng its hydrolysis product, the 6-keto-PGFla by radioimmunoassay. Results: Internal mammary arteries and saphenous veins from diabetics synthesized a lower amount of prostacyclin than those from non-diabetics. The radial artery produced similar amounts of prostacyclin in both groups. This response was associated with an increase of the conversión of the precursor arachidonic acid to prostacyclin. The saturating concentrations of this acid required to achieve the maximal stimulation were higher in the radial artery (20 µM) than in the internal mammary artery and saphenous vein (10 µM), suggesting that the enzymatic activity of the radial artery was not affected by diabetes. Conclusions: The radial artery appears as the best replacement vessel for coronary surgery in diabetics. Its favorable biochemical profile and potential lower long-term occlusion rate may be relevant for a better prognosis of myocardial revascularization in these patients.

Diurnal variation of vascular diameter and reactivity in healthy young men

The higher incidence of cardiovascular events in the morning is accompanied by an increased vascular tone. However, there are few published studies designed to evaluate the diurnal variation of vascular and endothelial parameters in healthy subjects. In the present investigation, we evaluated the diurnal variation in brachial artery diameter (BAD), flow-mediated dilation (FMD) and endothelium-independent dilation (NFMD) in a homogeneous sample of healthy non-smoker young men. Fifty subjects aged 20.8 ± 0.3 years (range: 18 to 25 years) were investigated by brachial artery ultrasound. Exclusion criteria were female gender and evidence of clinically significant health problems, including obesity. Volunteers were asked to rest and avoid fat meals as well as alcoholic beverages 48 h before and until completion of the evaluations. BAD, FMD and NFMD were measured at 7 am, 5 pm, and 10 pm and tested by repeated measures ANOVA. BAD was smaller at 7 am (mean ± SEM, 3.8 ± 0.1 mm) in comparison with 5 pm (3.9 ± 0.1) and 10 pm (4.0 ± 0.1 mm; P < 0.001). FMD values did not change significantly during the day, while NFMD increased more at 7 am (18.5 ± 1.1 percent), when compared to 15.5 ± 0.9 percent at 10 pm and 15.5 ± 0.9 percent at 5 pm (P = 0.04). The physiological state of vasoconstriction after awakening, with preserved capability to dilate in the morning, should be considered to be part of the healthy cardiovascular adaptation before considering later life risk factors and endothelial dysfunction.

Efeitos hemodinâmicos e metabólicos da infusão de vasopressina em crianças com choque: [revisão] / Hemodynamic and metabolic effects of vasopressin infusion in children with shock: [review]

OBJETIVO: A vasopressina é um hormônio neuropeptídico utilizado clinicamente há mais de 50 anos, com papel importante na homeostase circulatória e na regulação da osmolalidade sérica. Seu papel no tratamento do choque vem recebendo ênfase recentemente. Foram revisadas a fisiologia deste neuro-hormônio e as evidências disponíveis para sua utilização no contexto de choque com vasodilatação na criança. FONTES DOS DADOS: MEDLINE, usando os termos vasopressin, vasodilation, shock, septic shock, e sinônimos e termos relacionados, além de publicações clássicas referentes ao tema, sendo escolhidas as mais representativas. SÍNTESE DOS DADOS: A vasopressina é sintetizada na neuro-hipófise e liberada em resposta à diminuição da volemia ou ao aumento da osmolalidade plasmática. A ação da vasopressina dá-se pela ativação de vários receptores acoplados à proteína G, os quais são classificados, de acordo com sua localização e rotas de transmissão intracelular, em receptores V1 (ou V1b), V2 e V3 (ou V1b) e por receptores de ocitocina. A função central da vasopressina é causar vasoconstrição, embora, em determinados órgãos, possa promover vasodilatação seletiva. Diversos estudos clínicos em adultos e crianças apontam efeitos benéficos e seguros da vasopressina no tratamento do choque com vasodilatação por diversas causas. CONCLUSÃO: As evidências são restritas, os estudos na maioria são retrospectivos e com número reduzido de pacientes, mas já há uma experiência bastante significativa no que diz respeito a seu uso em pediatria. A vasopressina possui um efeito clinico benéfico na criança e pode ser indicada no tratamento do choque refratário com vasodilatação, depois de adequada reposição volêmica e quando altas doses de outros vasopressores não foram eficazes.

OBJECTIVE:Vasopressin is a neuropeptide hormone which has been used clinically for more than 50 years and plays a major role in circulatory homeostasis and in the regulation of serum osmolality. Recent work has emphasized its role in the treatment of septic shock. This paper reviews the physiology of this neurohormone and the available evidence in favor of its use as a vasodilator for children in shock. SOURCES: MEDLINE, using the terms vasopressin, vasodilation, shock and septic shock, plus synonyms and related terms. Classic publications on the topic were also reviewed and selected depending on their relevance to the study objectives. SUMMARY OF THE FINDINGS: Vasopressin is synthesized in the neurohypophysis and released in response to a decrease in plasma volume or an increase in serum osmolality. The action of vasopressin is mediated by the activation of oxytocin receptors and of several G protein-coupled receptors, which are classified according to their location and intracellular transmission routes as V1 receptors (or V1b), V2 and V3 receptors (or V1b). The main role of vasopressin is to induce vasoconstriction. However, in certain organs, it can also induce selective vasodilation. Several clinical studies in adults and children have reported that the effects of vasopressin for the treatment of vasodilatory septic shock, due to a variety of causes, are both beneficial and safe. CONCLUSIONS: The evidence is restricted. Most studies are retrospective and include a small number of patients. Nevertheless, there is significant experience concerning the use of vasopressin in Pediatrics. Vasopressin has a beneficial clinical effect in children and can be indicated in the treatment of refractory vasodilatory shock, after adequate volume resuscitation and when high doses of other vasopressors are not effective.

Complicaciones pulmonares de la cirrosis hepática: hipertensión portopulmonar y síndrome hepatopulmonar: la paradoja de la vasoconstricción y vasodilatación pulmonar / Pulmonary complications of hepatic cirrhosis: portopulmonary hypertension and hepatopulmonary syndrome: the paradox of pulmonary vasoconstriction and vasodilation

Las complicaciones pulmonares de las enfermedades crónicas del hígado han sido descritas desde hace más de un siglo. Aunque originadas por una lesión común y vías fisiopatológicas similares, sus manifestaciones clínicas y el diagnóstico son divergentes. Su impacto clínico es importante ya que afectan de forma deletérea el pronóstico de los pacientes. Hasta el momento no existe un tratamiento efectivo para el manejo de estas enfermedades y el trasplante hepático debe ser evaluado de forma muy cuidadosa. En esta revisión se analizan los aspectos más importantes de la hipertensión portopulmonar y del síndrome hepatopulmonar, entidades que bajo el entorno de la hipertensión portal se caracterizan respectivamente por procesos de vasoconstricción y vasodilatación pulmonar.

Cardiopulmonar complications in chronic liver diseases were described 100 years ago. Altough both hepatopulmonary sindrome and portopulmonary hypertension originates from liver damage, clinical findings and diagnosis are very different. These complications are important due to the highly deleterous impact on disease evolution and prognosis. Currently, there is not an ideal treatment for these diseases and liver transplantation should be adequately evaluated. In this review we analyze the most important issues on hepatopulmonary sindrome and portopulmonary hypertension. These complications,under the cornerstone of portal hypertension are characterized by pulmonary constriction and dilatation, respectively.