Mesenteric Microcirculatory Dysfunctions and Translocation of Indigenous Bacteria in a Rat Model of Strangulated Small Bowel Obstruction

PRUPOSE: Bacterial translocation has been shown to occur in critically ill patients after extensive trauma, shock, sepsis, or thermal injury. The present study investigates mesenteric microcirculatory dysfunctions, the bacterial translocation phenomenon, and hemodynamic/metabolic disturbances in a rat model of intestinal obstruction and ischemia. METHODS: Anesthetized (pentobarbital 50 mg/kg, i.p.) male Wistar rats (250-350 g) were submitted to intestinal obstruction or laparotomy without intestinal obstruction (Sham) and were evaluated 24 hours later. Bacterial translocation was assessed by bacterial culture of the mesenteric lymph nodes (MLN), liver, spleen, and blood. Leukocyte-endothelial interactions in the mesenteric microcirculation were assessed by intravital microscopy, and P-selectin and intercellular adhesion molecule (ICAM)-1 expressions were quantified by immunohistochemistry. Hematocrit, blood gases, lactate, glucose, white blood cells, serum urea, creatinine, bilirubin, and hepatic enzymes were measured. RESULTS: About 86% of intestinal obstruction rats presented positive cultures for E. coli in samples of the mesenteric lymph nodes, liver, and spleen, and 57% had positive hemocultures. In comparison to the Sham rats, intestinal obstruction induced neutrophilia and increased the number of rolling (~2-fold), adherent (~5-fold), and migrated leukocytes (~11-fold); this increase was accompanied by an increased expression of P-selectin (~2-fold) and intercellular adhesion molecule-1 (~2-fold) in the mesenteric microcirculation. Intestinal obstruction rats exhibited decreased PaCO2, alkalosis, hyperlactatemia, and hyperglycemia, and increased blood potassium, hepatic enzyme activity, serum urea, creatinine, and bilirubin. A high mortality rate was observed after intestinal obstruction (83% at 72 h vs. 0% in Sham rats). CONCLUSION: Intestinal obstruction and ischemia in rats is a relevant model for the in vivo study of mesenteric microcirculatory dysfunction and the occurrence of bacterial translocation. This model parallels the events implicated in multiple organ dysfunction (MOD) and death

Mechanisms of endothelial dysfunction in obesity-associated hypertension

Obesity is strongly associated with high blood pressure, dyslipidemia, and type 2 diabetes. These conditions synergistically increase the risk of cardiovascular events. A number of central and peripheral abnormalities can explain the development or maintenance of high blood pressure in obesity. Of great interest is endothelial dysfunction, considered to be a primary risk factor in the development of hypertension. Additional mechanisms also related to endothelial dysfunction have been proposed to mediate the development of hypertension in obese individuals. These include: increase in both peripheral vasoconstriction and renal tubular sodium reabsorption, increased sympathetic activity and overactivation of both the renin-angiotensin system and the endocannabinoid system and insulin resistance. The discovery of new mechanisms regulating metabolic and vascular function and a better understanding of how vascular function can be influenced by these systems would facilitate the development of new therapies for treatment of obesity-associated hypertension

Reduced endothelium-dependent relaxation to anandamide in mesenteric arteries from young obese Zucker rats

Impaired vascular function, manifested by an altered ability of the endothelium to release endothelium-derived relaxing factors and endothelium-derived contracting factors, is consistently reported in obesity. Considering that the endothelium plays a major role in the relaxant response to the cannabinoid agonist anandamide, the present study tested the hypothesis that vascular relaxation to anandamide is decreased in obese rats. Mechanisms contributing to decreased anandamide-induced vasodilation were determined. Resistance mesenteric arteries from young obese Zucker rats (OZRs) and their lean counterparts (LZRs) were used. Vascular reactivity was evaluated in a myograph for isometric tension recording. Protein expression and localization were analyzed by Western blotting and immunofluorescence, respectively. Vasorelaxation to anandamide, acetylcholine, and sodium nitroprusside, as well as to CB1, CB2, and TRPV1 agonists was decreased in endothelium-intact mesenteric arteries from OZRs. Incubation with an AMP-dependent protein kinase (AMPK) activator or a fatty acid amide hydrolase inhibitor restored anandamide-induced vascular relaxation in OZRs. CB1 and CB2 receptors protein expression was decreased in arteries from OZRs. Incubation of mesenteric arteries with anandamide evoked endothelial nitric oxide synthase (eNOS), AMPK and acetyl CoA carboxylase phosphorylation in LZRs, whereas it decreased phosphorylation of these proteins in OZRs. In conclusion, obesity decreases anandamide-induced relaxation in resistance arteries. Decreased cannabinoid receptors expression, increased anandamide degradation, decreased AMPK/eNOS activity as well as impairment of the response mediated by TRPV1 activation seem to contribute to reduce responses to cannabinoid agonists in obesity.National Institutes of Health (HL71138, HL74167)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)INCT Obesity and DiabetesConselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq

Influence of castration on the leukocyte behavior and adhesion molecule expression in mesenteric microcirculation of rats.

A inflamação pode representar papel importante em doenças cardiovasculares. A testosterona exerce importantes efeitos sobre a função vascular, que se encontra alterada na hipertensão arterial, podendo contribuir assim, para possíveis alterações na resposta inflamatória. Neste estudo, avaliamos a influência da hipertensão e da castração sobre o comportamento leucocitário em vênulas pós-capilares do leito mesentérico de ratos espontaneamente hipertensos, investigando a participação das moléculas de adesão nesse processo. Nossos resultados demonstraram que a hipertensão interfere no comportamento leucocitário e que os andrógenos podem ter participação neste processo. O número de leucócitos circulantes e os parâmetros hemodinâmicos não estão envolvidos nessas alterações. Nos ratos hipertensos, o aumento da expressão das moléculas de adesão P-selectina, ICAM-1, VCAM-1 e PECAM-1 contribuem para o aumento do rolamento e da adesão leucocitária e a castração corrige as alterações do comportamento leucocitário interferindo na expressão dessas moléculas.Inflammation can have an important role in the cardiovascular diseases. Testosterone exerts important effects on the vascular function, which is altered in arterial hypertension, contributing for the possible alterations in inflammatory response. In this study we evaluated the influence of hypertension and the castration on the leucocytes behavior in post-capillaries venules of the mesenteric bed of spontaneously hypertensive rats, investigating the participation of the adhesion molecules. We have shown that the hypertension interfere in leukocyte behavior and androgens can participate in this process. In addition, circulating leukocyte and hemodynamics parameters are not involved in those alterations. The higher expression of adhesion molecules such as P-selectin, ICAM-1, VCAM-1 and PECAM-1 present in hypertensive rats, compared to the normotensive ones, contribute for the higher leukocyte rolling and adhesion. Furthermore, castration correct those alterations of the leukocyte behavior by modulating the expression of the adhesion molecule

Influence of castration on the leukocyte behavior and adhesion molecule expression in mesenteric microcirculation of rats.

A inflamação pode representar papel importante em doenças cardiovasculares. A testosterona exerce importantes efeitos sobre a função vascular, que se encontra alterada na hipertensão arterial, podendo contribuir assim, para possíveis alterações na resposta inflamatória. Neste estudo, avaliamos a influência da hipertensão e da castração sobre o comportamento leucocitário em vênulas pós-capilares do leito mesentérico de ratos espontaneamente hipertensos, investigando a participação das moléculas de adesão nesse processo. Nossos resultados demonstraram que a hipertensão interfere no comportamento leucocitário e que os andrógenos podem ter participação neste processo. O número de leucócitos circulantes e os parâmetros hemodinâmicos não estão envolvidos nessas alterações. Nos ratos hipertensos, o aumento da expressão das moléculas de adesão P-selectina, ICAM-1, VCAM-1 e PECAM-1 contribuem para o aumento do rolamento e da adesão leucocitária e a castração corrige as alterações do comportamento leucocitário interferindo na expressão dessas moléculas.Inflammation can have an important role in the cardiovascular diseases. Testosterone exerts important effects on the vascular function, which is altered in arterial hypertension, contributing for the possible alterations in inflammatory response. In this study we evaluated the influence of hypertension and the castration on the leucocytes behavior in post-capillaries venules of the mesenteric bed of spontaneously hypertensive rats, investigating the participation of the adhesion molecules. We have shown that the hypertension interfere in leukocyte behavior and androgens can participate in this process. In addition, circulating leukocyte and hemodynamics parameters are not involved in those alterations. The higher expression of adhesion molecules such as P-selectin, ICAM-1, VCAM-1 and PECAM-1 present in hypertensive rats, compared to the normotensive ones, contribute for the higher leukocyte rolling and adhesion. Furthermore, castration correct those alterations of the leukocyte behavior by modulating the expression of the adhesion molecule

Characterization of vasorelaxant response to equilin in mesenteric arteries from spontaneously hypertensive rats.

Este estudo investigou a ação do equilin em artérias mesentéricas de resistência de ratas espontaneamente hipertensas, bem como o mecanismo envolvido, comparando com o 17b-estradiol. O equilin promoveu vasodilatação equivalente à do 17b-estradiol, não demonstrando diferença nas respostas observadas em ratas intactas e ovariectomizadas. A resposta ao equilin não foi alterada pelo antagonista de receptores de estrógeno. De modo similar, a remoção do endotélio ou a inibição da adenilato ciclase, da PKA, da óxido nítrico sintase, da guanilato ciclase e da PKG não afetou o relaxamento ao equilin. Além disso, a incubação com diferentes bloqueadores de canais de K+ não alterou o relaxamento ao equilin. O equilin diminuiu a contração ao CaCl2 e ao BAYK 8644 (ativador de canais de Ca2+ do tipo-L), porém, não modificou a contração à cafeína (que promove liberação de Ca2+ do retículo sarcoplasmático), demonstrando que o efeito relaxante do equilin em artérias mesentéricas de ratas espontaneamente hipertensas se deve predominantemente ao bloqueio de canais de Ca2+ do tipo L.The present study investigated the action of equilin in mesenteric resistance arteries from female hypertensive rats. Mechanisms contributing to equilin-induced effects were determined, comparing with 17b-estradiol. Equilin evoked vasodilatation equivalent to that of 17b-estradiol, with no difference between intact and ovariectomized rats. Equilin-induced response was not altered by the estrogen receptor antagonist. Similarly, endothelium removal or inhibition of adenylyl cyclase, PKA, NOS, guanylate cyclase or PKG did not affect the relaxation to equilin. Furthermore, the relaxation to this hormone was not altered after incubation with K+ channel blockers. Equilin reduced contraction induced by both CaCl2 and Bay K 8644 (an L-type Ca2+ channel activator), however, it was unable to alter caffeine-induced contraction (via Ca2+ release from the intracellular stores), demonstrating that equilin vasorelaxant effect in mesenteric arteries from female spontaneously hypertensive rats occurs predominantly due to blockade of L-type Ca2+ channels

Improvement of metabolic parameters and vascular function by metformin in obese non-diabetic rats

Aims: Metformin is an insulin sensitizing agent with beneficial effects in diabetic patients on glycemic levels and in the cardiovascular system. We examined whether the metabolic changes and the vascular dysfunction in monosodium glutamate-induced obese non-diabetic (MSG) rats might be improved by metformin. Main methods: 16 week-old MSG rats were treated with metformin for 15 days and compared with age-matched untreated MSG and non-obese non-diabetic rats (control). Blood pressure, insulin sensitivity, vascular reactivity and prostanoid release in the perfused mesenteric arteriolar bed as well as nitric oxide production and reactive oxygen species generation in isolated mesenteric arteries were analyzed. Key findings: 18-week-old MSG rats displayed higher Lee index, fat accumulation, dyslipidemia, insulin resistance and hyperinsulinemia. Metformin treatment improved these alterations. The norepinephrine-induced response, increased in the mesenteric arteriolar bed from MSG rats, was corrected by metformin. Indomethacin corrected the enhanced contractile response in MSG rats but did not affect metformin effects. The sensitivity to acetylcholine, reduced in MSG rats, was also corrected by metformin. Indomethacin corrected the reduced sensitivity to acetylcholine in MSG rats but did not affect metformin effects. The sensitivity to sodium nitroprusside was increased in preparations from metformin-treated rats. Metformin treatment restored both the reduced PGI2/TXA2 ratio and the increased reactive oxygen species generation in preparations from MSG rats. Significance: Metformin improved the vascular function in MSG rats through reduction in reactive oxygen species generation, modulation of membrane hyperpolarization. correction of the unbalanced prostanoids release and increase in the sensitivity of the smooth muscle to nitric oxide. (c) 2011 Elsevier Inc. All rights reserved.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa doEstado de Sao Paulo (FAPESP)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)INCT Obesity and Diabetes/CNPq, BrazilINCT Obesity and Diabetes/CNPq, Brazi

STIM 1/Orai 1 contributes to sex differences in vascular responses to calcium in spontaneously hypertensive rats

Sex differences in Ca2+-dependent signalling and homoeostasis in the vasculature of hypertensive rats are well characterized. However, sex-related differences in SOCE (store-operated Ca2+ entry) have been minimally investigated. We hypothesized that vascular protection in females, compared with males, reflects decreased Ca2+ mobilization due to diminished activation of Orai 1/STIM 1 (stromal interaction molecule I). In addition, we investigated whether ovariectomy in females affects the activation of the Orai 1/STIM 1 pathway. Endothelium-denuded aortic rings from male and female SHRSP (stroke-prone spontaneously hypertensive rats) and WKY (Wistar Kyoto) rats and from OVX (ovariectomized) or sham female SHRSP and WKY rats were used to functionally evaluate Ca2+ influx-induced contractions. Compared with females, aorta from male SHRSP displayed: (i) increased contraction during the Ca2+-loading period; (ii) similar transient contraction during Ca2+ release from the intracellular stores; (iii) increased activation of STIM 1 and Orai1, as shown by the blockade of STIM 1 and Orai1 with neutralizing antibodies, which reversed the sex differences in contraction during the Ca2+-loading period; and (iv) increased expression of STIM I and Orai I. Additionally, we found that aortas from OVX-SHRSP showed increased contraction during the Ca2+-loading period and increased Orai1 expression, but no changes in the SR (sarcoplasmic reticulum)-buffering capacity or STIM I expression. These findings suggest that augmented activation of STIM 1/Orai 1 in aortas from male SHRSP represents a mechanism that contributes to sex-related impaired control of intracellular Ca2+ levels. Furthermore, female sex hormones may negatively modulate the STIM/Orai 1 pathway, contributing to vascular protection observed in female rats.American Heart Association [AHA 09GRNT2250383]American Heart AssociationNational Institutes of Health [NIH HL71138, DK83685]National Institutes of HealthSociety for Womens Health ResearchSociety for Women's Health ResearchFundacaode Amparo a Pesquisa do Estado de Sao Paulo [FAPESP 2009/08095-5]Fundacao de Amparo a Pesquisa do Estado de Sao PauloConselho Nacional de Pesquisa e Desenvolviments (CNPq)Conselho Nacional de Pesquisa e Desenvolviments (CNPq

Endothelium-Dependent Vasorelaxant Effect of Butanolic Fraction from Caryocar brasiliense Camb. Leaves in Rat Thoracic Aorta

Caryocar brasiliense Camb. “pequi” is a native plant from the Cerrado region of Brazil that contains bioactive components reported to be antioxidant agents. Previous work has demonstrated that dietary supplementation with pequi decreased the arterial pressure of volunteer athletes. We found that the crude hydroalcoholic extract (CHE) of C. brasiliense leaves relaxed, in a concentration-dependent manner, rat aortic rings precontracted with phenylephrine, and that the butanolic fraction (BF) produced an effect similar to that of the CHE. Aortic relaxation induced by BF was abolished by endothelium removal, by incubation of the nitric oxide synthase inhibitor L-NAME, or the soluble guanylatecyclase inhibitor ODQ. However, incubation with atropine and pyrilamine had no effect on the BF-induced vasorelaxation. Moreover, this effect was not inhibited by indomethacin and tetraethylammonium. The concentration-response curve to calcium in denuded-endothelium rings was not modified after incubation with BF, and the vasorelaxation by BF in endothelium-intact rings precontracted with KCl was abolished after incubation with L-NAME. In addition, administration of BF in anesthetized rats resulted in a reversible hypotension. The results reveal that C. brasiliense possesses both in vivo and in vitro activities and that the vascular effect of BF involves stimulation of the nitric oxide/cyclic GMP pathway