Acute Physical Stress Preconditions the Heart Against Ischemia/Reperfusion Injury Through Activation of Sympathetic Nervous System / Estresse Físico Agudo Precondiciona o Coração Contra a Injúria por Isquemia/Reperfusão Através da Ativação do Sistema Nervoso Simpático

Abstract Background: Stress is defined as a complicated state that related to homeostasis disturbances, over-activity of the sympathetic nervous system and hypothalamus-pituitary-adrenal axis responses. Cardiac preconditioning reduces myocardial damages. Objective: This study was designed to assess the cardioprotective effects of acute physical stress against ischemia/reperfusion (I/R) injury through the activation of the sympathetic nervous system. Methods: Thirty-two male Wistar rats were divided into four groups; (1) IR (n = 8): rats underwent I/R, (2) Acute stress (St+IR) (n = 8): physical stress induced 1-hour before I/R, (3) Sympathectomy (Symp+IR) (n = 8): chemical sympathectomy was done 24-hours before I/R and (4) Sympathectomy- physical stress (Symp+St+IR) (n = 8): chemical sympathectomy induced before physical stress and I/R. Chemical sympathectomy was performed using 6-hydroxydopamine (100 mg/kg, sc). Then, the hearts isolated and located in the Langendorff apparatus to induce 30 minutes ischemia followed by 120 minutes reperfusion. The coronary flows, hemodynamic parameters, infarct size, corticosterone level in serum were investigated. P < 0.05 demonstrated significance. Results: Physical stress prior to I/R could improve left ventricular developed pressure (LVDP) and rate product pressure (RPP) of the heart respectively, (63 ± 2 versus 42 ± 1.2, p < 0.05, 70 ± 2 versus 43 ± 2.6, p < 0.05) and reduces infarct size (22.16 ± 1.3 versus 32 ± 1.4, p < 0.05) when compared with the I/R alone. Chemical sympathectomy before physical stress eliminated the protective effect of physical stress on I/R-induced cardiac damages (RPP: 21 ± 6.6 versus 63 ± 2, p < 0.01) (LVDP: 38 ± 4.5 versus 43 ± 2.6, p < 0.01) (infarct size: 35 ± 3.1 versus 22.16 ± 1.3, p < 0.01). Conclusion: Findings indicate that acute physical stress can act as a preconditional stimulator and probably, the presence of sympathetic nervous system is necessary.

Resumo Fundamento: O estresse é definido como um estado complicado de distúrbios da homeostase, hiperatividade do sistema nervoso simpático e das respostas do eixo hipotálamo-hipófise-adrenal. O pré-condicionamento cardíaco diminui os danos do miocárdio. Objetivo: Esse estudo avaliou os efeitos cardioprotetores do estresse físico agudo contra a lesão por isquemia-reperfusão (I/R) através da ativação do sistema nervoso simpático. Métodos: Trinta e dois ratos machos Wistar foram divididos em quatro grupos; (1) IR (n = 8): ratos submetidos a I/R, (2) Estresse agudo (St+IR) (n = 8): estresse físico induzido 1 hora antes da I/R, (3) Simpatectomia (Symp+IR) (n = 8): a simpatectomia química foi realizada 24 horas antes da I/R e (4) Simpatectomia-estresse físico (Symp+St+IR) (n = 8): simpatectomia induzida antes do estresse físico e da I/R. A simpatectomia química foi realizada com 6-hidroxidopamina (100 mg/kg, SC). Em seguida, os corações foram isolados e colocados em aparato de Lagendorff por 30 minutos para induzir isquemia, seguida de reperfusão por 120 minutos. Os fluxos coronarianos, os parâmetros hemodinâmicos, o tamanho do infarto e os níveis de corticosterona plasmática foram investigados. Valores de p < 0,05 foram considerados significativos. Resultados: O estresse físico anterior à I/R pode melhorar a pressão desenvolvida no ventrículo esquerdo (PDVE) e duplo produto (DP), respectivamente, (63 ± 2 versus 42 ± 1,2, p < 0,05, 70 ± 2 versus 43 ± 2,6, p < 0,05) e reduzir o tamanho do infarto (22,16 ± 1,3 versus 32±1,4, p < 0,05) quando comparado com a I/R isoladamente. A simpatectomia química antes do estresse físico eliminou o efeito protetor do estresse físico sobre os danos cardíacos induzidos pela I/R (DP: 21 ± 6,6 versus 63 ± 2, p < 0,01) (PDVE: 38 ± 4,5 versus 43 ± 2,6, p < 0,01) (tamanho do infarto: 35 ± 3,1 versus 22,16 ± 1,3, p < 0,01). Conclusão: Os achados indicam que o estresse físico agudo pode funcionar como um estimulador pré-condicional e, provavelmente, a presença do sistema nervoso simpático é necessária.

Cardioprotective effect of preconditioning is more efficient than postconditioning in rats submitted to cardiac ischemia and reperfusion

Abstract Purpose: To investigate the cardioprotective effects of ischemic preconditioning (preIC) and postconditioning (postIC) in animal model of cardiac ischemia/reperfusion. Methods: Adult rats were submitted to protocol of cardiac ischemia/reperfusion (I/R) and randomized into three experimental groups: cardiac I/R (n=33), preCI + cardiac I/R (n=7) and postCI + cardiac I/R (n=8). After this I/R protocol, the incidence of ventricular arrhythmia (VA), atrioventricular block (AVB) and lethality (LET) was evaluated using the electrocardiogram (ECG) analysis. Results: After reestablishment of coronary blood flow, we observed variations of the ECG trace with increased incidence of ventricular arrhythmia (VA) (85%), atrioventricular block (AVB) (79%), and increase of lethality (70%) in cardiac I/R group. The comparison between I/R + preIC group with I/R group demonstrated significant reduction in VA incidence to 28%, AVB to 0% and lethality to 14%. The comparison of I/R + postIC group with I/R group was observed significance reduction in AVB incidence to 25% and lethality to 25%. Conclusion: The preconditioning strategies produce cardioprotection more efficient that postconditioning against myocardial dysfunctions and lethality by cardiac ischemia and reperfusion.

Is Local Nitric Oxide Availability Responsible for Myocardial Salvage after Remote Preconditioning? / A Disponibilidade de Óxido Nítrico Local é Responsável por Resgate Miocárdio após Pré-Condicionamento Remoto?

Abstract Background: Remote ischemic preconditioning (RIPC) represents an attractive therapy for myocardial protection, particularly when ischemic events can be anticipated. Although several hypothetic mechanisms have been proposed, no definite molecular pathways have been elucidated. Objective: We evaluated the effect of brachial circulation cuff occlusion on myocardial ischemic tolerance, necrosis, and nitric oxide (NO) in patients with ischemic heart disease undergoing elective percutaneous coronary interventions (PCI). Methods: 46 patients were randomly allocated into two groups: control and RIPC before PCI procedures. Electrocardiographic analysis, serum concentrations of troponin I (cTn-I) were measured at baseline and 24 hours after PCI. A blood sample from the atherosclerotic plaque was drawn to determine nitrate and nitrites. Results: RIPC increased the availability of NO in the stented coronary artery. Control patients presented a small but significant increase in cTn-I, whilst it remained unchanged in preconditioned group. The preconditioning maneuver not only preserved but also enhanced the sum of R waves. Conclusions: RIPC induced an intracoronary increase of NO levels associated with a decrease in myocardial damage (measured as no increase in cTn-I) with electrocardiographic increases in the sum of R waves, suggesting an improved myocardium after elective PCI.

Resumo Fundamento: Pré-condicionamento isquêmico remoto (PCIR) é uma terapia para proteção miocárdica, em particular quando é possível prever eventos isquêmicos. Embora vários mecanismos hipotéticos tenham sido propostos, nenhuma via molecular definitiva foi elucidada. Objetivo: Avaliar o efeito da oclusão da circulação braquial com manguito sobre a tolerância à isquemia miocárdica, a necrose miocárdica e a biodisponibilidade de óxido nítrico (NO) em pacientes com cardiopatia isquêmica submetidos a intervenção coronariana percutânea (ICP) eletiva. Métodos: 46 pacientes foram alocados aleatoriamente em dois grupos: controle e PCIR antes da ICP. Análise eletrocardiográfica e medidas da concentração sérica de troponina I (cTn-I) foram realizadas na condição basal e 24 horas após ICP. Coletou-se amostra de sangue da placa aterosclerótica para determinar os níveis de nitratos e nitritos. Resultados: O PCIR aumentou a disponibilidade de NO na artéria coronária que recebeu o stent. O grupo controle apresentou um aumento pequeno, mas significativo, da cTn-I, que permaneceu inalterada no grupo pré-condicionado. O pré-condicionamento não só preservou, como melhorou o somatório de ondas R no eletrocardiograma. Conclusões: O PCIR induziu aumento intracoronariano dos níveis de NO associado com redução do dano miocárdico (medido como aumento da cTn-I) e com aumento do somatório de ondas R, sugerindo melhora miocárdica após ICP eletiva.

Sevoflurane preconditioning during myocardial ischemia-reperfusion reduces infarct size and preserves autonomic control of circulation in rats

ABSTRACT PURPOSE: To investigate the myocardial ischemia-reperfusion with sevoflurane anesthetic preconditioning (APC) would present beneficial effects on autonomic and cardiac function indexes after the acute phase of a myocardial ischemia-reperfusion. METHODS: Twenty Wistar rats were allocated in three groups: control (CON, n=10), myocardial infarction with sevoflurane (SEV, n=5) and infarcted without sevoflurane (INF, n=5). Myocardial ischemia (60 min) and reperfusion were performed by temporary coronary occlusion. Twenty-one days later, the systolic and diastolic function were evaluated by echocardiography; spectral analysis of the systolic arterial pressure (SAPV) and heart rate variability (HRV) were assessed. After the recording period, the infarct size (IS) was evaluated. RESULTS: The INF group presented greater cardiac dysfunction and increased sympathetic modulation of the SAPV, as well as decreased alpha index and worse vagal modulation of the HRV. The SEV group exhibited attenuation of the systolic and diastolic dysfunction and preserved vagal modulation (square root of the mean squared differences of successive R-R intervals and high frequency) of HRV, as well as a smaller IS. CONCLUSION: Sevoflurane preconditioning better preserved the cardiac function and autonomic modulation of the heart in post-acute myocardial infarction period.

Dexmedetomidina genera óxido nítrico mediante un mecanismo independiente de la óxido nítrico sintasa inducible / Dexmedetomidine protects the heart against ischemia-reperfusion injury by an endothelial eNOS/NO dependent mechanism

El infarto del miocardio es una de las principales causas de muerte a nivel mundial y se produce a consecuencia de procesos de isquemia-reperfusión (IR). El daño miocárdico generado por IR puede ser atenuado a través del pre-condicionamiento isquémico (PI) temprano, mediado por la vía RISK o PI tardío, que se asocia a una respuesta genómica en la que se activan proteínas como óxido nítrico sintasa inducible (iNOS). Las vías de señalización que median el PI también pueden ser activadas farmacológicamente. Dexmedetomi-dina (Dex) es un agonista alfa2-adrenérgico, que se ha descrito como un potente agente cardioprotector frente a IR. Recientemente, nuestro grupo describió que Dex requiere el endotelio y la activación de la vía óxido nítrico sintasa endotelial (eNOS)-óxido nítrico (NO) para pre-condicionar el miocardio. Sin embargo, no existen estudios que muestren la posible participación de iNOS en la protección conferida por Dex. La presente adenda tiene por objetivo evaluar si Dex activa iNOS en el corazón y en cardiomiocitos. Para esto, corazones de rata adulta fueron estimulados con Dex 10 nM y se observó que el fármaco aumentó la producción de NO medida por cuantificación de nitritos, mas no estimuló la activación de iNOS medida por Western blot. Además, Dex tampoco indujo el aumento de mRNA de iNOS en cardiomiocitos adultos. Por lo tanto, Dex genera NO independiente a iNOS durante su efecto pre-condicionante agudo. Sin embargo, se requieren más estudios que clarifiquen su papel en una posible protección a largo plazo frente a IR generada por Dex.

Myocardial infarction is one of the leading causes of death worldwide and is generated as a consequence of ischemia-reperfusion (IR). Myocardial damage inflicted by IR can be attenuate by early ische-mic pre-conditioning (IP), which is mediated by the RISK pathway or late IP, which is associated to a genomic response involving the activation of proteins such as inducible nitric oxide synthase (iNOS). The signaling pathways mediating IP can also be pharmacologically activated. Dexmedetomidine (Dex) is an alpha2-adrenergic receptor agonist, which has been described as a strong cardio protective agent against IR. Recently, our group reported that Dex requires the endothelium and the activation of the endothelial nitric oxide synthase (eNOS)-ni-tric oxide (NO) pathway to precondition the myocardium. However, there are no studies showing the involvement of iNOS in the protection elicited by Dex. The aim of this Addendum is to evaluate if Dex activates iNOS in the heart and cardiomyocytes. To test this, adult rat hearts were stimulated with Dex 10 nM and we observed that NO production measured by quantification of nitrites was increased, but Dex did not activate iNOS measured by Western blot. Moreover, Dex did not induce an increase in the mRNA levels of iNOS in adult cardiomyocytes. Therefore, Dex generates NO independent of iNOS during its early pre-conditioning effect. Nevertheless, more studies are required to clarify its role in a possible long term protection against IR generated by Dex.

Role of mitochondrial ATP-sensitive potassium channel-mediated PKC-ε in delayed protection against myocardial ischemia/reperfusion injury in isolated hearts of sevoflurane-preconditioned rats

This study aimed to determine the role of mitochondrial adenosine triphosphate-sensitive potassium (mitoKATP) channels and protein kinase C (PKC)-ε in the delayed protective effects of sevoflurane preconditioning using Langendorff isolated heart perfusion models. Fifty-four isolated perfused rat hearts were randomly divided into 6 groups (n=9). The rats were exposed for 60 min to 2.5% sevoflurane (the second window of protection group, SWOP group) or 33% oxygen inhalation (I/R group) 24 h before coronary occlusion. The control group (CON) and the sevoflurane group (SEVO) group were exposed to 33% oxygen and 2.5% sevoflurane for 60 min, respectively, without coronary occlusion. The mitoKATP channel inhibitor 5-hydroxydecanoate (5-HD) was given 30 min before sevoflurane preconditioning (5-HD+SWOP group). Cardiac function indices, infarct sizes, serum cardiac troponin I (cTnI) concentrations, and the expression levels of phosphorylated PKC-ε (p-PKC-ε) and caspase-8 were measured. Cardiac function was unchanged, p-PKC-ε expression was upregulated, caspase-8 expression was downregulated, cTnI concentrations were decreased, and the infarcts were significantly smaller (P<0.05) in the SWOP group compared with the I/R group. Cardiac function was worse, p-PKC-ε expression was downregulated, caspase-8 expression was upregulated, cTnI concentration was increased and infarcts were larger in the 5-HD+SWOP group (P<0.05) compared with the SWOP group. The results suggest that mitoKATP channels are involved in the myocardial protective effects of sevoflurane in preconditioning against I/R injury, by regulating PKC-ε phosphorylation before ischemia, and by downregulating caspase-8 during reperfusion.

Long-term, regular remote ischemic preconditioning improves endothelial function in patients with coronary heart disease

Remote ischemic preconditioning (RIPre) can prevent myocardial injury. The purpose of this study was to assess the beneficial effects of long-term regular RIPre on human arteries. Forty patients scheduled for coronary artery bypass graft (CABG) surgery were assigned randomly to a RIPre group (n=20) or coronary heart disease (CHD) group (n=20). Twenty patients scheduled for mastectomy were enrolled as a control group. RIPre was achieved by occluding arterial blood flow 5 min with a mercury sphygmomanometer followed by a 5-min reperfusion period, and this was repeated 4 times. The RIPre procedure was repeated 3 times a day for 20 days. In all patients, arterial fragments discarded during surgery were collected to evaluate endothelial function by flow-mediated dilation (FMD), CD34+ monocyte count, and endothelial nitric oxide synthase (eNOS expression). Phosphorylation levels of STAT-3 and Akt were also assayed to explore the underlying mechanisms. Compared with the CHD group, long-term regular RIPre significantly improved FMD after 20 days (8.5±2.4 vs 4.9±4.2%, P<0.05) and significantly reduced troponin after CABG surgery (0.72±0.31 and 1.64±0.19, P<0.05). RIPre activated STAT-3 and increased CD34+ endothelial progenitor cell counts found in arteries. Long-term, regular RIPre improved endothelial function in patients with CHD, possibly due to STAT-3 activation, and this may have led to an increase in endothelial progenitor cells.

Effects of ischemia and omeprazole preconditioning on functional recovery of isolated rat heart / Efeitos da isquemia e pré-condicionamento com omeprazol na recuperação funcional do coração isolado de rato

Abstract Objective: The aim of this study was to compare protective effects of ischemic and potential protective effects of pharmacological preconditioning with omeprazole on isolated rat heart subjected to ischemia/reperfusion. Methods: The hearts of male Wistar albino rats were excised and perfused on a Langendorff apparatus. In control group (CG) after stabilization period, hearts were subjected to global ischemia (perfusion was totally stopped) for 20 minutes and 30 minutes of reperfusion. Hearts of group II (IPC) were submitted to ischemic preconditioning lasting 5 minutes before 20 minutes of ischemia and 30 minutes of reperfusion. In third group (OPC) hearts first underwent preconditioning lasting 5 minutes with 100μM omeprazole, and then submitted 20 minutes of ischemia and 30 minutes of reperfusion. Results: Administration of omeprazole before ischemia induction had protective effect on myocardium function recovery especially regarding to values of systolic left ventricular pressure and dp/dt max. Also our findings are that values of coronary flow did not change between OPC and IPC groups in last point of reperfusion. Conclusion: Based on our results it seems that ischemic preconditioning could be used as first window of protection after ischemic injury especially because all investigated parameters showed continuous trend of recovery of myocardial function. On the other hand, preconditioning with omeprazole induced sudden trend of recovery with positive myocardium protection, although less effective than results obtained with ischemic preconditioning not withstand, we must consider that omeprazole may be used in many clinical circumstances where direct coronary clamping for ischemic preconditioning is not possible. .

Resumo Objetivo: O objetivo deste estudo foi comparar os efeitos protetores de efeitos protetores isquêmicos e potenciais de précondicionamento farmacológico com omeprazol no coração isolado de rato submetido à isquemia/reperfusão. Métodos: Os corações de ratos albinos Wistar machos foram excisados e perfundidos em um aparelho de Langendorff. No grupo controle (grupo I), após o período de estabilização, os corações foram submetidos à isquemia global (a perfusão foi totalmente interrompida) por 20 minutos e 30 minutos de reperfusão. Corações do grupo II (IPC) foram submetidos a précondicionamento isquêmico com duração de 5 minutos antes de 20 minutos de isquemia e 30 minutos de reperfusão. No terceiro grupo (OPC), corações foram submetidos a pré-condicionamento com duração de 5 minutos com 100 μM de omeprazol, e, então, submetidos a 20 minutos de isquemia e 30 minutos de reperfusão. Resultados: A administração de omeprazol antes da indução da isquemia teve efeito protetor sobre a recuperação funcional do miocárdio especialmente em relação aos valores de pressão sistólica ventricular esquerda e dp/dt max. Também os nossos achados são de que os valores de fluxo coronário não se alteraram entre os grupos OPC e IPC no último ponto de reperfusão. Conclusão: Com base nos nossos resultados, o pré-condicionamento isquêmico poderia ser usado como primeira janela de proteção após a lesão isquêmica, especialmente porque todos os parâmetros analisados apresentam tendência contínua de recuperação da função do miocárdio. Por outro lado, o pré-condicionamento induzido com omeprazol apresenta tendência repentina de recuperação com proteção miocárdio positiva, embora menos efetiva da obtida com o pré-condicionamento isquêmico. Devemos considerar que o omeprazol pode ser usado em muitas circunstâncias clínicas em que o pinçamento coronariano direto para pré-condicionamento isquêmico não é possível. .

Aperfeiçoamento em técnica de perfusão cardioplégica no pinçamento único de aorta - resultados iniciais / Improvement in cardioplegic perfusion technique in single aortic clamping - initial results

INTRODUÇÃO: O método mais comumente utilizado para a proteção miocárdica é o de administrar-se solução cardioplégica na circulação coronária. Entretanto, a proteção pode ser alcançada através da perfusão intermitente do sistema coronariano com sangue do próprio paciente, que é realizada por meio de múltiplas sequências de pinçamento e abertura do clamp aórtico ou por meio do pinçamento único e canulação acessória da raiz aórtica. Objetivo: Avaliar o desfecho clínico e a ocorrência de eventos neurológicos no período intra-hospitalar dos pacientes submetidos à cirurgia de revascularização do miocárdio com a técnica proposta aqui neste estudo. Métodos: Descreve-se uma técnica de proteção miocárdica no uso do pinçamento único de aorta que consiste na canulação acessória da raiz aórtica com sistema aperfeiçoado para perfusão coronária intermitente, foi realizado estudo observacional transversal prospectivo onde foram estudados 50 pacientes (idade média 58,5±7.19 anos) submetidos à cirurgia de revascularização do miocárdio sob a técnica proposta. Foram avaliadas variáveis clínicas e laboratoriais pré e pós-operatórias. Resultados: O nível médio de pico da CKMB pós-operatória foi de 51,64±27,10 U/L no segundo pós-operatório e da troponina I foi de 3,35±4,39 ng/ml no quarto pós-operatório, e estiveram dentro do limite da normalidade. Não foi observado nenhum óbito e um paciente evoluiu com alteração neurológica leve. A monitorização hemodinâmica não revelou alterações. Conclusão: A cirurgia de rev...

Introduction: The most common method used for myocardial protection is administering cardioplegic solution in the coronary circulation. Nevertheless, protection may be achieved by intermittent perfusion of the coronary system with patient's own blood. The intermittent perfusion may be performed by multiple sequences of clamping and opening of the aortic clamp or due single clamping and accessory cannulation of the aortic root as in the improved technique proposed in this study, reperfusion without the need for multiple clamping of the aorta. Objective: To evaluate the clinical outcome and the occurrence of neurological events in in-hospital patients submitted to myocardial revascularization surgery with the "improved technique" of intermittent perfusion of the aortic root with single clamping. Methods: This is a prospective, cross-sectional, observational study that describes a myocardial management technique that consists of intermittent perfusion of the aortic root with single clamping in which 50 patients (mean age 58.5±7.19 years old) have been submitted to the myocardial revasculrization surgery under the proposed technique. Clinical and laboratory variables, pre- and post-surgery, have been assessed. Results: The mean peak level of post-surgery CKMB was 51.64±27.10 U/L in the second post-surgery and of troponin I was 3.35±4.39 ng/ml in the fourth post-surgery, within normal limits. No deaths have occurred and one patient presented mild neurological disorder. Hemodynamic monitoring has not indicated any changes. Conclusion: The myocardial revascularization surgery by perfusion with the improved technique with intermittent aortic root with single clamping proved to be safe, enabling satisfactory clinical results. .

Remote preconditioning, perconditioning, and postconditioning: a comparative study of their cardio-protective properties in rat models

OBJECTIVE: Ischemia reperfusion injury is partly responsible for the high mortality associated with induced myocardial injury and the reduction in the full benefit of myocardial reperfusion. Remote ischemic preconditioning, perconditioning, and postconditioning have all been shown to be cardioprotective. However, it is still unknown which one is the most beneficial. To examine this issue, we used adult male Wistar rat ischemia reperfusion models to compare the cardioprotective effect of these three approaches applied on double-sided hind limbs. METHODS: The rats were randomly distributed to the following five groups: sham, ischemia reperfusion, remote preconditioning, remote perconditioning, and remote post-conditioning. The ischemia/reperfusion model was established by sternotomy followed by a 30-min ligation of the left coronary artery and a subsequent 3-h reperfusion. Remote conditioning was induced with three 5-min ischemia/5-min reperfusion cycles of the double-sided hind limbs using a tourniquet. RESULTS: A lower early reperfusion arrhythmia score (1.50 + 0.97) was found in the rats treated with remote perconditioning compared to those in the ischemia reperfusion group (2.33 + 0.71). Meanwhile, reduced infarct size was also observed (15.27 + 5.19% in remote perconditioning, 14.53 + 3.45% in remote preconditioning, and 19.84+5.85% in remote post-conditioning vs. 34.47 + 7.13% in ischemia reperfusion, p<0.05), as well as higher expression levels of the apoptosis-relevant protein Bcl-2/Bax following global (ischemia/reperfusion) injury in in vivo rat heart models (1.255 + 0.053 in remote perconditioning, 1.463 + 0.290 in remote preconditioning, and 1.461 +0.541 in remote post-conditioning vs. 1.003 + 0.159 in ischemia reperfusion, p<0.05). CONCLUSION: Three remote conditioning strategies implemented with episodes of double-sided hind limb ischemia/reperfusion have similar therapeutic potential for cardiac ischemia/reperfusion injury, and remote perconditioning has a greater ability to prevent reperfusion arrhythmia.

Pantoprazole provides myocardial protection similar to ischemic preconditioning: experimental study of isolated hearts of rats / Pantoprazol oferece proteção miocárdica semelhante ao pré-condicionamento isquêmico: estudo em corações isolados de ratos

OBJECTIVE: To evaluate pantoprazole effect in the functional recovery of isolated hearts of rats, submitted to ischemia and reperfusion with and without ischemic preconditioning. METHODS: In four groups of eight Wistar breed rats, the hearts were removed after anesthesia and perfused with Krebs-Henseleit solution (95% O2, 5% CO2, 37ºC). GI, GII, GIII and GIV hearts were submitted to ischemia (20 min) and reperfusion (30 min). In GII and GIV, preconditioning was performed with 5 min of ischemia and 5 min of reperfusion before 20 min of the ischemia period induction. In GIII and GIV pantoprazole 100 mg was done before a 20 min-period of ischemia induction. Heart Rate (HR), Coronary Flow (CoF), Systolic Pressure (SP), +dP/dt and -dP/dt were registered before (t0) and after reperfusion (t30). Kruskal-Wallis (P<0.05) test was used. RESULTS: There were no differences (P>0.05) between groups among HR and CoF values. Differences occurred between groups, I and II, III and IV at t30 with SP reduced for 32% mean value in GI, 65% GII, 65% GIII, and 73% GIV; The t30 + dP/dtmax were 34% in GI, 61% GII, 63% GIII and 72% GIV. The t30 -dP/dtmax were GI 28%, GII 63%, GIII 75 % and GIV 75%; (P<0.05). There were no significant differences in the SP, +dP/dtmax, and -dP/dtmax between Groups II, III and IV results. CONCLUSIONS: The administration of pantoprazole before induction of ischemia significantly protected the myocardial functional recovery with the results of SP, + dP / dtmax and dP/dtmax similar to the ischemic preconditioning against ischemia-reperfusion.

OBJETIVO: Avaliar o efeito do pantoprazol na recuperação funcional de corações isolados de ratos submetidos à isquemia e reperfusão com e sem pré-condicionamento isquêmico. MÉTODOS: Em quatro grupos de oito ratos Wistar, após anestesia os corações foram removidos e perfundidos com Krebs-Henseleit (95% O2, 5% CO2, 37ºC). Os corações de GI, GII, GIII e GIV foram submetidos a 20' de isquemia e 30'de reperfusão. Em GII e GIV realizou-se pré condicionamento com 5' de isquemia e 5' de reperfusão antes dos 20' de isquemia. Em GIII e GIV, pantoprazol 100mcg foram injetados imediatamente antes dos 20' de isquemia. Frequência cardíaca (FC), Fluxo Coronariano (FCo), Pressão Sistólica (PS), + dP/dt e -dP/dt foram registrados em (T0) e (t30). Estatística: Kruskal-Wallis (P <0,05). RESULTADOS: Não houve diferenças (P> 0,05) entre grupos nos valores de FC e de CFo. Diferenças (P <0,05) ocorreram entre GI e GII, GIII e GIV, com PS t30 reduzida para 32% GI, 65% GII, 65% GIII e 73% GIV. Em t30 + dP/dtmax 34% GI, 61% GII, 63% GIII e 72% GIV. A -dP/dtmax t30 GI 28%, GII 63%, GIII 75% e GIV 75%. Não houve diferença estatística (P< 0,05) nos valores de PS, +dP/dtmax e -dP/dtmax entre os GII, GIII e GIV. CONCLUSÕES: A administração do pantoprazol antes da indução da isquemia protegeu significativamente a recuperação funcional miocárdica com resultados de SP, +dP/ dtmax e -dP/dtmax semelhantes aos do pré-condicionamento isquêmico contra lesão de isquemia-reperfusão.

Ischemic postconditioning protects cardiomyocytes against ischemia/reperfusion injury by inducing MIP2

Cardiomyocytes can resist ischemia/reperfusion (I/R) injury through ischemic postconditioning (IPoC) which is repetitive ischemia induced during the onset of reperfusion. Myocardial ischemic preconditioning up-regulated protein 2 (MIP2) is a member of the WD-40 family proteins, we previously showed that MIP2 was up-regulated during ischemic preconditioning (IPC). As IPC and IPoC engaged similar molecular mechanisms in cardioprotection, this study aimed to elucidate whether MIP2 was up-regulated during IPoC and contributed to IPoC-mediated protection against I/R injury. The experiment was conducted on two models, an in vivo open chest rat coronary artery occlusion model and an in vitro model with H9c2 myogenic cells. In both models, 3 groups were constituted and randomly designated as the sham, I/R and IPoC/hypoxia postconditioning (HPoC) groups. In the IPoC group, after 45 min of ischemia, hearts were allowed three cycles of reperfusion/ischemia phases (each of 30 s duration) followed by reperfusion. In the HPoC group, after 6 h of hypoxia, H9c2 cells were subjected to three cycles of 10 minute reoxygenation and 10 minute hypoxia followed by reoxygenation. IPoC significantly reduced the infarct size, plasma level of Lactate dehydrogenase and creatine kinase MB in rats. 12 h after the reperfusion, MIP2 mRNA levels in the IPoC group were 10 folds that of the sham group and 1.4 folds that of the I/R group. Increased expression of MIP2 mRNA and attenuation of apoptosis were similarly observed in the HPoC group in the in vitro model. These effects were blunted by transfection with MIP2 siRNA in the H9c2 cells. This study demonstrated that IPoC induced protection was associated with increased expression of MIP2. Both MIP2 overexpression and MIP2 suppression can influence the IPoC induced protection.

Nueva estrategia para preacondicionamiento miocárdico en pacientes sometidos a cirugía cardíaca con circulación extracorpórea / Reduction of postoperative atrial fibrillation through antioxidant supplementation

INTRODUCCION: El estrés oxidativo (EO) es importante en la génesis de diversas patologías. Su rol en patología cardiovascular es reconocido, particularmente en isquemia-reperfusión, fenómeno asociado al uso de circulación extracorpórea (CEC) en cardiocirugía. Complicación frecuente es la fibrilación auricular post-operatoria(FAPO), que ha demostrado participación del EO. Estrategias que lo atenúen podrían reducir incidencia de FAPO. Este trabajo busca determinar efectos de un esquema de suplementación para prevenir el EO y FAPO. METODOLOGIA: Ensayo clínico, doble ciego, aleatorizado. A 80 pacientes programados para cardiocirugía con CEC se administró placebo (n=40) o suplementación(n=40), consistiendo desde 7 días antes de la cirugía ácidos grasos poli-insaturados omega-3 (n-3) (2 g/día), y 2 días pre-cirugía se agrega vitamina C (1 g/día) y E (400 UI/día), todo hasta el alta. Se obtuvieron muestras sanguíneas (al ingreso, en suplementación, en cirugía, en postoperatorio y al alta) y auriculares durante cirugía. El estado antioxidante fue medido por la habilidad plasmática para reducir hierro férrico (FRAP) y el índice GSH/GSSG. Se midió actividad de enzimas catalasa, superóxido-dismutasa y glutatión-peroxidasa. Lipoperoxidación fue medida por niveles de malondialdehído. Para variables paramétricas se usó t de student, entre grupos se usó ANOVA-Bonferroni. Significancia fue p<0.05. RESULTADOS: Suplementación con n-3 disminuyó índice GSH/GSSG en 25 por ciento. En postoperatorio hubo 21 por ciento menos de lipoperoxidación y niveles de FRAP 30 por ciento mayores. Actividad de enzimas mostró incremento significativo. Además disminuyó FAPO desde 25 por ciento a 7,5 por ciento. CONCLUSION: Suplementar con n-3 y vitaminas antioxidantes disminuye ocurrencia de FAPO evitando daño miocárdico bioquímico y funcional por EO.

INTRODUCTION: Oxidative stress is important in the genesis of several diseases. Their role in cardiovascular disease is recognized, particularly in ischemia-reperfusion, a phenomenon associated with the use of cardiopulmonary bypass (CPB) in cardiac surgery. Common complication is postoperative atrial fibrillation (FOAP), which has demonstrated participation of oxidative stress, strategies to mitigate what could reduce the occurrence of FOAP. This paper tries to determine the effect of a supplementation scheme to prevent oxidative stress and its consequences. MATERIALS AND METHODS: Randomized, double-blind, controlled trial. Eighty patients scheduled for CCEC received placebo (n = 40) or supplementation (n = 40). Inclusion criteria: Age 30-80 years, sinus rhythm. Exclusion criteria: previous cardiosurgery, paroxysmal atrial fibrillation, congenital heart disease, chronic diseases. The supplementation consisting of n-3 (2 g / day), vitamins C (1 g /day) and E (400 IU / day) from 7, 2 and 2 days before surgery, respectively, until discharge. In atrial tissue and blood samples the plasma ferric reducing ability (FRAP), index GSH/GSSG, activity of catalase, superoxide dismutase and glutathione-peroxidase, and malondialdehyde levels were measured. Protein carbonylationwas measured in atrial tissue. Parametric variables expressed as mean and standard error were analyzed with student’s t-test, groups were compared using ANOVA-Bonferroni. Significance was p <0.05. RESULTS: The supplementation reduced the incidence of FOAP, lipid peroxidation and protein carbonylation in 73, 21 and 19 percent (p <0.05), respectively, and increased the FRAP (30 percent) and activity of antioxidant enzymes (p <0.05). CONCLUSIONS: Antioxidant supplementation decreases FOAP probably avoiding damage by oxidative stress.

Preconditioning abolishion by midazolam in isolated hearts of rats / Abolição do precondicionamento pelo midazolam em corações isolados de ratos

PURPOSE: To study the effects of benzodiazepine midazolam in the coronary flow (Cflo), cardiac frequency (CF) and myocardial contractility in isolated hearts of rats subjected to ischemic preconditioning (IPC). METHODS: 30 Wistar rats were used, undistinguished by gender. After anesthesia with ethyl ether, the hearts were put into perfusion (Krebs-Henseleit solution, 95 percent O2 and 5 percent CO2, 37°C, 110-120mmHg), in disposable Langendorff type system. Five groups of six animals were constituted: GI- Control; GII- Ischemia; GIII- IPC; GIV- Ischemia + 100mcg of midazolam; GV- IPC + 100mcg of midazolam. After stabilization (t0), and on times t5, t10, t15, t20 and t25, CF, Cflo, systolic pressure (SP) and diastolic pressure (DP) and dP/dt were recorded. DP was maintained at 5 ± 2 mmHg. The statistical method ANOVA and Tukey Test were employed for p < 0.05. RESULTS: No significant variations have occurred between Cflo and CF. On Pd/td, differences have occurred (p<0.05) between groups I and II (respectively 94.7±23.0 and 62.3±12.1 percent). The preconditioning (GIII), improved significantly the results in the group II (respectively 62.3±12.1 and 87.1±12.4 percent). The decrease in dP/dt in group II was not prevented by midazolam (GIV) (62.3±12,1 and 60.5±15.8 percent). In group III, dP/dt was 87.1±12.4 percent, whereas in group V, only 55.5±17.2 percent (p<0.05) CONCLUSION: Midazolam, when administered before the ischemia, was unable to prevent the ischemic deterioration of the myocardium. When administered before the preconditioning, it has abolished its protective effect.

OBJETIVO: Estudar os efeitos do benzodiazepínico midazolam no fluxo coronariano (Fco), freqüência cardíaca (FC) e contratilidade miocárdica de corações isolados de ratos submetidos ao precondicionamento isquêmico (PCI). MÉTODOS: Foram utilizados 30 ratos Wistar sem distinção de sexo. Após anestesia com éter etílico, os corações foram postos em perfusão (solução de Krebs-Henseleit, 95 por cento de O2 e 5 por cento de CO2, 37°C, 110-120mmHg), em sistema tipo Langendorff descartável. Foram constituídos cinco grupos de seis animais: GI- Controle; GII- Isquemia; GIII- PCI; GIV- Isquemia + 100mcg de midazolam ; GV- PCI + 100mcg de midazolam. Após estabilização (t0), e nos tempos t5, t10, t15, t20 e t25, foram registrados a FC, Fco, pressões sistólica (PS) e diastólica (PD) e dP/dt. A PD foi mantida em 5 ± 2 mmHg. Empregou-se método estatístico ANOVA e Teste de Tukey para p < 0,05. RESULTADOS: Não ocorreram variações significantes entre FCo e FC. Na dP/dt, ocorreram diferenças (p<0,05) entre os grupos I e II (respectivamente 94,7±23,0 e 62,3±12,1 por cento). O precondicionamento (GIII), melhorou significantemente os resultados do grupo II (respectivamente 62,3±12,1 e 87,1±12,4 por cento). A queda da dP/dt no grupo II não foi impedida pelo midazolam (GIV) ( 62,3±12,1 e 60,5±15,8 por cento). No grupo III a dP/dT foi 87,1±12,4 por cento, sendo que no grupo V, apenas 55,5±17,2 por cento (p<0,05). CONCLUSÃO: O midazolan quando administrado antes da isquemia não impediu deterioração isquêmica do miocárdio. Quando administrado antes do precondicionamento aboliu seu efeito protetor.

Efeitos da N-acetilcisteína no precondicionamento isquêmico: estudo em corações isolados de ratos / Effects of n-acetylcysteine on ischemic preconditioning: study in isolated rat hearts

OBJETIVO: Avaliar se a N-Acetilcisteína (NAC) altera o Precondicionamento Isquêmico (PC) em corações isolados de ratos usando apenas um ciclo de PC. MÉTODOS: Freqüência Cardíaca (FC), Fluxo Coronariano (FLC) e Contratilidade Miocárdica (dP/dt) foram registradas em 30 corações de ratos Wistar. Após anestesia, os corações foram perfundidos em sistema de Langendorff com solução de Krebs-Hensleit (K-H), equilibrada (95 por cento de O2 e 5 por cento de CO2). GI: Controle (n=6); GII: 20 min. isquemia (n=6); GIII: PC (n=6); GIV 50 µg/ml/min NAC antes do PC (n =6); GV: 100 µg/ml/min NAC antes do PC (n=6). Todos os parâmetros foram mensurados após 15 minutos de estabilização (T0) e T3, T5, T10, T15, T20, T25 e T30 minutos de reperfusão. Significância estatística foi considerada quando P<0,05. RESULTADOS: Foram observadas alterações na FC comparando GI com GII em T20 e T25 e comparando GI com GIII e GIV com GV em T10 e T20 (P<0,05). FLC foi diferente comparando GI com GII em T3 e T5, GI com GIV em T10 e GI com GV em T10 e T25 (P<0,05). dP/dt foi semelhante comparando GIII com GI e GV. GIII apresentou maior dP/dt que GIV, mas sem diferença estatística (P>0,05). dP/dt foi maior no GV comparado com GIV, mas com diferença estatisticamente significativa somente em T30. CONCLUSÃO: Os corações precondicionados tiveram melhor dP/dt, sendo alteradas pelo uso de NAC no GIV e não alteradas no GV.

OBJECTIVE: The aim of this study is to assess if N-Acetylcysteine (NAC) changes the Ischemic Preconditioning (IP) in isolated rat hearts using only one cycle of IP. METHODS: Heart Rate (HR), Coronary Flow (CF) and Myocardial Contractility (dP/dt) were registered in 30 Wistar rat's hearts. After anesthesia the hearts were removed and perfused with Krebes-Hensleit equilibrated solution with 95 percent of O2 and 5 percent of CO2 according Langendorff's method. GI: Control (n=6); GII: 20 min. ischemia (n=6); GIII: IP (n=6); GIV 50 µg/ml/min NAC before IP (n =6); GV: 100 µg/ ml/min NAC before IP (n=6). Parameters were measured after 15 min. of stabilization (T 0) and T3, T5, T10, T15, T20, T25 and T30 min. after reperfusion. Statistical significance was considered when P<0.05. RESULTS: There were changes on HR comparing GI with GII at T20 and T25 and comparing GI with GIII, GIV with GV at T10 and T20 (P<0.05). CF was different comparing GI with GII at T3 and T5, GI with GIV at T10 and GI with GV at T10 and T25 (P<0.05). Myocardial Contractility was similar comparing GIII with GI and GV. GIII had higher dP/dt than GIV but without statistical difference (P>0.05). dP/dt was higher in GV than GIV but with statistically significant difference only at T30. CONCLUSION: dP/dt was better in preconditioned hearts and was changed if using NAC in GIV. The use of NAC didn't change the effects of preconditioning on myocardial contractility in GV.

Efeitos do pós-condicionamento isquêmico na função ventricular esquerda de corações isolados de ratos / Effects of ischemic postconditioning on left ventricular function of isolated rat hearts

OBJETIVO: Avaliar os efeitos do pós-condicionamento isquêmico na função ventricular esquerda de corações isolados de ratos. MÉTODOS: Corações isolados de 24 ratos Wistar foram submetidos a perfusão pelo método de Langendorff modificado e distribuídos em três grupos: Grupo I - controle (n=8); Grupo II - três ciclos de pós-condicionamento de 10/10s (n=8); Grupo III - três ciclos de pós-condicionamento de 30/30s (n=8). Após estabilização de 15min, os corações foram submetidos a 20min de isquemia e subseqüentes 20min de reperfusão. A freqüência cardíaca (FC), o fluxo coronariano (FCo), a pressão sistólica (PS), a contratilidade (+dP/dt max) e a velocidade de relaxamento (-dP/dt max) miocárdico foram medidas nos tempos 0 (pré-isquemia) e 5, 10, 15 e 20min de reperfusão. Utilizado método estatístico ANOVA com Teste de Tukey para diferenças entre grupos, com significância menor que 0,05 (P< 0,05). RESULTADOS: A FC, em bpm, reduziu em todos os grupos após 20min de reperfusão, sem diferença estatística (GI 232,5 + 36,8; GII 241,8 + 46,7; GIII 249,4 + 40,4; P>0,05). O mesmo ocorreu com a PS, em mmHg, (GI 132,6 + 49,3; GII 140,8 + 43,1; GIII 112,6 + 33,2; P>0,05), FCo, em ml/min, (GI 18,5 + 4,6; GII 21,4 + 4,4; GIII 22,1 + 9,0; P>0,05) e -dP/dt max, em mmHg/s, (GI 1490,6 + 512,0; GII 1770,4 + 406,6; GIII 1399,1 + 327,4, P>0,05). A +dP/dt max, em mmHg/s, reduziu significativamente exceto no Grupo II (GI 1409,0 + 415,2; GII 1917,3 + 403,1; GIII 1344,8 + 355,8), (GII vs. GI, P=0,04) e (GII vs. GIII, P=0,02). CONCLUSÃO: O pós-condicionamento isquêmico com três ciclos de 10/10s de reperfusão/isquemia foi capaz de preservar a contratilidade miocárdica em corações isolados de ratos após 20min de isquemia.

OBJECTIVE: To assess the effects of ischemic postconditioning on left ventricular function in isolated rat hearts. METHODS: Twenty-four Wistar rats were used. These hearts underwent perfusion by modified LANGERDORFF method and distributed into three groups: GI - control (n=8); GII - three cycles of postconditioning of 10/10s (n=8); GIII three cycles of postconditioning of 30/30s (n=8). After a 15min stabilization period, all hearts underwent 20min of global ischemia following 20min of reperfusion. In the times 0 (control), 5, 10, 15 and 20min of reperfusion, the heart rate (HR), the coronary flow (CoF), the systolic pressure, the (+dP/dt max) contractility and (-dP/dt max) velocity of relaxation were measured. Data were analyzed by ANOVA method followed by Tukey's test for differences between groups and P < 0.05 was considered significant. RESULTS: The HR (bpm) decreased in all groups after 20min of reperfusion without statistical differences among them (GI 232.5+36.8; GII 241.8+46.7; GIII 249.4+40.4;P>0.05). The same occurred with the systolic pressure (mmHg) (GI 132.6+49.3; GII 140.8+43.1; GIII 112.6+33.2; P>0.05), coronary blood flow (GI 18.5+4.6; GII 21.4+4.4; GIII 22.1+9.0; P>0.05) and -dP/dt max (mmHg) (GI 1490.6+512.0; GII 1770.4+406.6; GIII 1399.1+327.4; P>0.05). The +dP/dt max (mmHg) decreased significantly in all groups except in group II (GI 1409.0+415.2, GII 1917.3+403.1, GIII 1344.8+355.8) (GII vs GI, P= 0.04; GII vs GIII, P= 0.02). CONCLUSION: The ischemic postconditioning by three cycles of reperfusion/ischemia of 10/10s demonstrated to be effective for preservation of the myocardial contractility in isolated rat hearts which had undergone 20min of ischemia.

Halogenated anaesthetics and cardiac protection in cardiac and non-cardiac anaesthesia.

Volatile anaesthetic agents have direct protective properties against ischemic myocardial damage. The implementation of these properties during clinical anaesthesia can provide an additional tool in the treatment or prevention, or both, of ischemic cardiac dysfunction in the perioperative period. A recent meta-analysis showed that desflurane and sevoflurane reduce postoperative mortality and incidence of myocardial infarction following cardiac surgery, with significant advantages in terms of postoperative cardiac troponin release, need for inotrope support, time on mechanical ventilation, intensive care unit and overall hospital stay. Multicentre, randomised clinical trials had previously demonstrated that the use of desflurane can reduce the postoperative release of cardiac troponin I, the need for inotropic support, and the number of patients requiring prolonged hospitalisation following coronary artery bypass graft surgery either with and without cardiopulmonary bypass. The American College of Cardiology/American Heart Association Guidelines recommend volatile anaesthetic agents during non-cardiac surgery for the maintenance of general anaesthesia in patients at risk for myocardial infarction. Nonetheless, evidence in non-coronary surgical settings is contradictory and will be reviewed in this paper together with the mechanisms of cardiac protection by volatile agents.

Comparison between preconditioning of the myocardium by sevoflurane and propofol in coronary artery surgeries

The brief period of ischemia appear to precondition the myocardium against the reversible and irreversible tissue injury, including stunning, infarction and development of malignant arrhythmias. On the other hand, exposures of myocardium to volatile anesthetics induce similar cardioprotective effect against ischemia activating the same mediators and receptors of ischemic preconditioning [ICP], enhance and augment ICR Anesthetic preconditioning [APC] is a well documented phenomenon with effective cardioprotection against ischemia in experimental studies applied on different animal species, also on isolated human myocardium independent of improvement in oxygen demand -supply ratio. Recurrently, APC was reported with few clinical studies using different parameters to evaluate the preconditioning or the cardioprotective effect. The aim of the work is to evaluate the cardioprotective effect [APC] of sevoflurane against ischemia induced by aortic crossclamping in comparison to propofol in coronary artery bypass graft surgeries. This study was conducted on 38 patients admitted to National Heart Institute undergoing elective coronary artery bypass graft surgeries [CABG]. Patients were randomly equally allocated to one of two groups [19/ group]: Sevoflurane G [G1] and Propofol G [G2]. There was no statistical significant difference between both groups regarding demographic data [age, sex height, BSA], preoperative medications, diseases or echo findings, time of CPB time and aortic crossclamping or number of coronary grafts. There was no statistical significant difference between both groups regarding: HR. MPA, SVRI or CVP. There was no statistical significant difference between both groups regarding ventricular fibrillation or ECG ischemic changes. Post bypass-CI in G1 [2.6 +/- 0.3 L/min/ m[2]] was statistically significantly higher in G2 [2.1 +/- 0.1 L/min /m[2]]. There was high statistical significant difference between both groups, P-Value= [0.0009] < [0.001]. Average of adrenaline support in G1 was [75 +/- 25 ng/kg/min] and in G2 was [150 +/- 50 ng/kg/min] with high statistical significant difference between both groups, P-Value= [0.0001] < [0.001]. Number of patients who received adrenaline in G1 was equal 8 [42%] while in G2 was 13 [68%] with statistical significant difference between both groups, P-Value = [0.0128] < [0.5]. Exposure of the myocardium to sevoflurane [anesthetic preconditioning] before aortic cross clamping induce significant reduction in myocardial damage and dysfunction in comparison to the propofol during coronary artery bypass graft surgeries using the cardiopulmonary bypass. Giving the upper hand of volatile anesthetics in the CABG surgeries and minimizing the use of intravenous anesthetics

The effect of hypercapnic acidosis preconditioning on rabbit myocardium / 华中科技大学学报（医学）（英德文版）

This study observed the protective effect of hypercapnic acidosis preconditioning on rabbit heart suffered from ischemia-reperfusion injury. Hypercapnic acidosis was established in animals with mechanical hypoventilation before ischemia-reperfusion. Thirty-two rabbits were randomly divided into 4 groups, with each having 8 animals in term of the degree of acidification: hypercapnic acidosis group A (group A), hypercapnic acidosis group B (group B), hypercapnic acidosis group C (group C), ischemia and reperfusion group (group IR). Animals in group IR were ventilated normally (tidal volume: 15 mL/kg, breathing rate 35 bpm). The PETCO(2) was maintained at the level of 40-50 mmHg for 30 min. Animals in groups A, B, C received low-frequency, low-volume ventilation to achieve hypercarbonic acidosis and the target levels of PETCO(2) were 75-85,65-75, 55-65 mmHg, respectively, with levels being maintained for 5 min. The animals then were ventilated normally to lower PETCO(2) to 40-50 mmHg. The left anterior branch artery of all the animals was ligated for 30 min and reperfused for 180 min. Then the infarct size was calculated. The cardiomyocytes were morphologically observed and ECG and hemodynamics were monitored on continuous basis. Acid-base balance was measured during procedure. Our results showed that the infarct size was (48.5+/-11.5)% of the risk area in the control group and (42.4+/-7.9)% in group C (P>0.05). Mean infarct size was significantly smaller in group B (34.5%+/-9.4%) (P<0.05 vs control group) and group A (31.0%+/-9.1%) (P<0.01 vs control group). It is concluded that HA-preconditioning can effectively protect the myocardium.

Recombinant human erythropoietin (rhEPO) preconditioning on nuclear factor-kappa B (NF-kB) activation & proinflammatory cytokines induced by myocardial ischaemia-reperfusion.

BACKGROUND & OBJECTIVES: Erythropoietin (EPO), originally identified for its critical hormonal role in promoting erythrocyte survival and differentiation, has shown to a protective effect in myocardial ischaemia-reperfusion (I-R) injury in animal model. However, the precise mechanisms remain unclear. The objective of this study was to determine the roles of nuclear factor-kappa B (NF-kB) and associated cytokines induced by I-R in the cardioprotection by recombinant human erythropoietin (rhEPO). Morphopathological observations were also made on the ultrastructure of myocardial tissue. METHODS: Myocardial I-R rat model was established by 30 min ligation of left descending coronary and 3 h reperfusion. RhEPO or saline solution was intraperitoneally injected 24 h before I-R insult. The infarct sizes were measured by triphenyltetrazolium chloride (TTC)-Evans blue technique and ultrastructural organizations were observed by a transmission electron microscope. Tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10 concentrations were analyzed by enzyme-linked immunosorbance assays and NF-kB by electrophoretic mobility shift assay. TNF-alpha and IL-6 mRNA expression were studied by the reverse-transcription polymerase chain reaction (RT-PCR). RESULTS: A single bolus injection of 5,000 units/kg of rhEPO 24 h before insult remarkably reduced infarct size and improved ultrastructural organization of I-R myocardium. It greatly suppressed TNF-alpha and IL-6 expression, but enhanced IL-10 production. It modestly activated NF-kB before I-R insult and markedly attenuated subsequent NF-kB activation during sustained I-R. INTERPRETATION & CONCLUSION: The suppression of proinflammatory cytokines expression may act by inhibiting NF-kB activation during I-R, but not by induction of IL-10. This might be one of the molecular mechanisms of rhEPO in cardioprotection. In addition, NF-kB was suggested to play a dual role in cardioprotective effects of rhEPO.