Annexin 1 peptides protect against experimental myocardial ischemia-reperfusion: analysis of their mechanism of action

Myocardial reperfusion injury is associated with the infiltration of blood-borne polymorphonuclear leukocytes. We have previous described the protection afforded by annexin 1 (ANXA1) in an experimental model of rat myocardial ischemia-reperfusion (IR) injury. We examined the 1) amino acid region of ANXA1 that retained the protective effect in a model of rat heart IR; 2) changes in endogenous ANXA1 in relation to the IR induced damage and after pharmacological modulation; and 3) potential involvement of the formyl peptide receptor (FPR) in the protective action displayed by ANXA1 peptides. Administration of peptide Ac2-26 at 0, 30, and 60 min postreperfusion produced a significant protection against IR injury, and this was associated with reduced myeloperoxidase activity and IL-1 beta levels in the infarcted heart. Western blotting and electron microscopy analyses showed that IR heart had increased ANXA1 expression in the injured tissue, associated mainly with the infiltrated leukocytes. Finally, an antagonist to the FPR receptor selectively inhibited the protective action of peptide ANXA1 and its derived peptides against IR injury. Altogether, these data provide further insight into the protective effect of ANXA1 and its mimetics and a rationale for a clinical use for drugs developed from this line of research.

Annexin 1 mimetic peptide protects against renal ischemia/reperfusion injury in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Experimental ischemia and reperfusion in equine small colon

Sob anestesia geral, com constante controle sobre a pressão arterial e a saturação de oxigênio da hemoglobina arterial, realizou-se celiotomia em 12 eqüinos. No cólon menor exposto foram demarcados três segmentos de 25cm, separados entre si por igual distância. Dois desses segmentos foram submetidos à isquemia arteriovenosa completa por 90 (grupo A) ou 180 minutos (grupo B). O terceiro segmento foi o grupo-controle. Amostras para histopatologia foram colhidas ao final dos períodos de isquemia e após 90 e 180 minutos de reperfusão no grupo A e após 90 minutos de reperfusão no grupo B. No controle, colheram-se amostras no início e final do procedimento. Avaliaram-se as lesões produzidas na mucosa e na submucosa pelos métodos semiquantitativos-escores para desprendimento de epitélio, edema, hemorragia e infiltrado de neutrófilos, e pelos quantitativos-porcentagem de perda de mucosa (PM) e razão cripta:interstício (C:I). As lesões isquêmicas foram mais intensas no grupo B do que no A para PM, C:I, desprendimento de epitélio e edema de mucosa. As amostras obtidas após a reperfusão revelaram que houve agravamento na PM, C:I, desprendimento de epitélio e edema de submucosa em ambos os grupos. Concluiu-se que a reperfusão agravou as lesões isquêmicas no cólon menor e que o modelo proposto é viável para produção dessas lesões.

Ischemia and reperfusion in skin flaps: effects of mannitol and vitamin C in reducing necrosis area in a rat experimental model

OBJETIVO: Neste trabalho foi padronizado modelo experimental de isquemia e reperfusão em retalho cutâneo em ratos no qual estudou-se possibilidade de uma solução antioxidante, composta por Ringer lactato, vitamina C e manitol de reduzir a área de necrose. MÉTODOS: O modelo consistiu de levantamento de retalho cutâneo axial de 6,0 x 3,0cm, submetido à isquemia de 8 horas e reperfusão de 7 dias. Os animais foram divididos em quatro grupos: grupos S1, S2 (10 animais cada), C e T (14 animais cada). Nos grupos S1 e S2 todos os procedimentos dos demais grupos foram efetuados, exceto a isquemia e reperfusão: S1 recebeu apenas Ringer lactato e S2 a solução antioxidante. Os grupos C e T foram submetidos à isquemia. O grupo C recebeu somente Ringer lactato e o grupo T a solução antioxidante. No 7(0) dia de pós-operatório as áreas de necrose e pele viável do retalho foram delineadas em decalque de acetato, os quais foram por sua vez analisados em sistema computadorizado KS-300 (Carl Zeiss). RESULTADOS: A análise estatística mostrou que não houve diferenças significativas entre o grupo tratado e controle quanto à área de necrose. CONCLUSÃO: Concluiu-se que o modelo experimental é consistente, determinando área de necrose limitada e uniforme nos animais não tratados e que as drogas usadas, nessa posologia e modo de aplicação, não foram efetivas em diminuir a área de necrose no modelo experimental em questão.

Dexmedetomidine and S(+)-ketamine in ischemia and reperfusion injury in the rat kidney

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Does propofol and isoflurane protect the kidney against ischemia/reperfusion injury during transient hyperglycemia?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of lisinopril on experimental ischemia in rats. Influence of infarct size

OBJECTIVE - Angiotensin-converting enzyme inhibitors (ACEIs) have gained importance in preventing or attenuating the process of ventricular remodeling after myocardial infarction. The significance of infarct size in regard to the response to ACEIs, however, is controversial. This study aimed to analyze the effects of lisinopril on mortality rate, cardiac function, degree of cardiac hypertrophy and fibrosis in rats with different infarct sizes. METHODS - Lisinopril (20 mg/kg/day) dissolved in drinking water was administered to rats immediately after coronary artery occlusion. After being sacrificed, the infarcted animals were divided into two groups: one group of animals with small infarcts (< 40% of the left ventricle) and another group of animals with large infarcts (> 40% of the left ventricle). RESULTS - The mortality rate was 31.7% in treated rats and 47% in the untreated rats. There was no statistical difference between the groups with small and large infarcts in regard to myocardial concentration of hydroxyproline. In small infarcts, the treatment attenuated the heart dysfunction characterized by lower levels of blood pressure and lower values of the first derivative of pressure and of the negative derivative of pressure. The degree of hypertrophy was also attenuated in small infarcts. In regard to large infarcts, no differences between the groups were observed. CONCLUSION - Treatment with the ACEIs had no effect on mortality rate and on the amount of fibrosis. The protective effect of lisinopril on heart function and on the degree of hypertrophy could only be detected in small infarcts

FTY720 prevents renal T-Cell infiltration after ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury, a common early feature in renal transplantation, results from both free radical species generation and local inflammatory responses that attract different types of cells. The interaction with infiltrating leukocytes could promote damage and death of resident renal cells contributing to worsening of renal function. It has been shown that depletion of host T cells protects against kidney damage after I/R injury, although the mechanism is not fully understood. FTY720, a synthetic analog of a natural product extracted from Isaria sincclairii has shown modulatory properties in experimental models of autoimmune disease, transplantation, and I/R injury. FTY720 alters lymphocyte responses to chemokine homing signals, thereby decreasing the number of lymphocytes in inflammatory sites. We evaluated renal function in mice at 3, 5, and 7 days after I/R injury in the presence or absence of FTY720 treatment. FTY720 treatment promoted earlier recovery of renal function associated with a lower number of renal-infiltrating lymphocytes. These findings confirm previous results showing a protective effect of FTY720 in I/R injury models.

Investigations on the new free radical scavenger polynitroxyl-albumin to prevent ischemia and reperfusion injury after orthotopic heart transplantation in the pig model

Objective: Nitroxides have strong antioxidant capacity but their effectiveness is limited by their rapid intracellular inactivation. Poly nitroxyl-Albumin (PNA) is capable of regenerating inactivated nitroxide. We tested the effect of PNA against reperfusion injury in heart transplantation. Methods: Pig hearts were transplanted orthotopically. In the control group (n = 9) reperfusion was performed without reperfusion modifications. In the experimental group (n = 10) 1 ml/kg PNA was given before cross-clamp release. Results: Hemodynamic performance was impaired after transplantation in both groups without significant intergroup differences. Plasma malonedialdehyde levels were significantly diminished in the PNA group as compared to the controls. CK-MB levels in both groups were increased within the first 2 h of reperfusion without significant intergroup differences. In contrast, there were found significant higher values of myocardial specific lactate dehydrogenase (LD1) in the controls versus PNA group. Conclusions: PNA was able to reduce lipid peroxidation and attenuate free radical activity. Contractile dysfunction could no be improved, indicating that (a) the radical scavenging effect was to weak or (b) other mechanisms than free oxygen radicals are responsible for myocardial damage in this experimental model. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Antioxidant Action of Mangrove Polyphenols against Gastric Damage Induced by Absolute Ethanol and Ischemia-Reperfusion in the Rat

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Force patterns of hypoxic myocardium applied to oxygenated muscle preparations: Comparison with effects of regional ischemia on the contraction of non-ischemic myocardium

Objective: To examine the basis for local wall motion abnormalities commonly seen in patients with ischemic heart disease, computer-controlled isolated muscle studies were carried out. Methods: Force patterns of physiologically sequenced contractions (PSCs) from rat left ventricular muscle preparations under well-oxygenated conditions and during periods of hypoxia and reoxygenation were recorded and stored in a computer. Force patterns of hypoxic-reoxygenating and oxygenated myocardium were applied to oxygenated and hypoxic-reoxygenating myocardium, respectively. Results: Observed patterns of shortening and lengthening closely resemble those obtained from ischemic and non-ischemic myocardial segments using ultrasonic crystals in intact dog hearts during coronary occlusion and reperfusion, and are similar to findings reported in angiographic studies of humans with coronary artery disease. Conclusion: The current study, demonstrating motions of oxygenated isolated muscle preparations which are similar to those in perfused segments of intact hearts with regional ischemia, supports the concept that the multiple motions of both ischemic and non-ischemic segments seen in regional myocardial disease can be explained by interactions of strongly and weakly contracting muscle during the physiologic cardiac cycle.

Effect of α-tocopherol, taurine and selenium on the attenuation of ischemia/reperfusion injury of splanchnic organs

Background: Splanchnic artery occlusion shock is caused by increased capillary permeability and cellular injury precipitated by oxygen derived free radicals following ischemia and reperfusion of splanchnic organs. The purpose of this study was to assess the role of several well-known oxygen- derived free radical scavengers in ameliorating or preventing this syndrome. Study design: Anesthetized rats were subjected to periods of occlusion of the visceral arteries and reperfusion. Tocopherol, taurine, selenium or a 'cocktail' of these three agents was injected subcutaneously for 4 consecutive days prior to operation. Mean arterial blood pressure was measured throughout the experimental period. Fluorometry and technetium-99m pyrophosphate counting of the visceral organs were performed as well as a histologic grading system for intestinal viability. Results: Final mean arterial blood pressure associated with the 'cocktail' and selenium groups was 79.1 ± 27.4 mmHg and 83.6 ± 17.8 mmHg, respectively. These values were significantly higher than the control group, 40.8 ± 11.4 mmHg (P < 0.05). Similar patterns of the benefit of selenium in contrast with the other groups were obtained with fluorescein perfusion, radioisotopic activity and histologic analysis. Conclusion: Pretreatment with selenium of splanchnic ischemia and reperfusion in the rat improves mean arterial blood pressure and microcirculatory visceral perfusion. Further analysis of the precise protective mechanism of selenium for reperfusion injury will enable visceral organs to withstand the consequences of increased capillary leakage and oxidant injury.

Pathophysiology of mesenteric ischemia/reperfusion: a review.

During ischemia, the cell structures are progressively damaged, but restoration of the blood flow, paradoxically, intensifies the lesions caused by the ischemia. The mechanisms of ischemia injury and reperfusion (I/R) have not been completely defined and many studies have been realized in an attempt to find an ideal therapy for mesenteric I/R. The occlusion and reperfusion of the splanchnic arteries provokes local and systemic alterations principally derived from the release of cytotoxic substances and the interaction between neutrophils and endothelial cells. Substances involved in the process are discussed in the present review, like oxygen-derived free radicals, nitric oxide, transcription factors, complement system, serotonin and pancreatic proteases. The mechanisms of apoptosis, alterations in other organs, therapeutic and evaluation methods are also discussed.