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Molecular mechanisms mediating preconditioning following chronic ischemia differ from those in classical second window.

ABSTRACT: A major difference between experimental ischemic preconditioning (IPC), induced by brief ischemic episodes, and the clinical situation is that patients generally have repetitive episodes of ischemia. We used a swine model to examine differences in genes regulated by classical second-window IPC (SWOP) [two 10-min episodes of coronary artery occlusion (CAO) followed by 24 h reperfusion] compared with repetitive CAO/reperfusion (RCO), i.e., two 10-min CAO 12 h apart, and to repetitive coronary stenosis (RCS), six episodes of 90 min coronary stenosis 12 h apart (n = 5/group). All three models reduced infarct size by 60-85%, which was mediated by nitric oxide in SWOP but not in the other two models. We employed microarray analyses to discover additional molecular pathways intrinsic to models of repetitive ischemia and different from classical SWOP. There was an 85% homology in gene response between the RCO and RCS models, whereas SWOP was qualitatively different. Both RCO and RCS, but not SWOP, showed downregulation of genes encoding proteins involved in oxidative metabolism and upregulation of genes involved in protein synthesis, unfolded protein response, autophagy, heat shock response, protein secretion, and an activation of the NF-kappaB signaling pathway. Therefore, the regulated genes mediating IPC with repetitive ischemia differ radically from SWOP both quantitatively and qualitatively, showing that a repetitive pattern of ischemia, rather than the difference between no-flow vs. low-flow ischemia, dictates the genomic response of the heart. These findings illustrate new cardioprotective mechanisms developed by repetitive IPC, which are potentially more relevant to patients with chronic ischemic heart disease, who are subjected to repetitive episodes of ischemia.

SUBMITTER: Depre C

PROVIDER: S-EPMC2944496 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Molecular mechanisms mediating preconditioning following chronic ischemia differ from those in classical second window.

Depre Christophe C Park Ji Yeon JY Shen You-Tang YT Zhao Xin X Qiu Hongyu H Yan Lin L Tian Bin B Vatner Stephen F SF Vatner Dorothy E DE

American journal of physiology. Heart and circulatory physiology 20100625 3

A major difference between experimental ischemic preconditioning (IPC), induced by brief ischemic episodes, and the clinical situation is that patients generally have repetitive episodes of ischemia. We used a swine model to examine differences in genes regulated by classical second-window IPC (SWOP) [two 10-min episodes of coronary artery occlusion (CAO) followed by 24 h reperfusion] compared with repetitive CAO/reperfusion (RCO), i.e., two 10-min CAO 12 h apart, and to repetitive coronary sten ...[more]

PMID: 20581088

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Project description:Ischemic preconditioning represents the most powerful mechanism of cardioprotection. The mechanisms mediating the second window of preconditioning (SWOP) differ from those mediating first window preconditioning. We hypothesized that chronic ischemia induced by repetitive ischemic stimuli would be mediated by yet different molecular mechanisms. Accordingly, conscious, chronically instrumented pigs (n=5/group) were submitted to a protocol of classical SWOP (two 10-min episodes of coronary artery occlusion followed by 24 hr reperfusion) and compared to pigs submitted to repetitive occlusion/reperfusion (RCO) by repeating 6 episodes of SWOP 12 hrs apart, and to a model of repetitive coronary stenosis (RCS), in which 6 episodes of 90 min coronary stenosis were performed 12 hrs apart. Microarray analysis was performed on the three models. There was an 85% homology in gene response between both models of RCO and RCS, whereas SWOP was qualitatively different. Both models of RCO and RCS but not SWOP showed a down-regulation of genes encoding proteins involved in oxidative metabolism, and an up-regulation of genes involved in protein synthesis and unfolded protein response, autophagy, heat shock response, protein secretion, and a strong activation of the NF-ÎºB signaling pathway. Two thirds of the genes regulated in the three models showed a gradual pattern of up- or down-regulation, in which RCO was quantitatively intermediary between RCS and SWOP. Therefore, the regulated genes in response to chronic, repetitive episodes of ischemia differ radically from classical first or second window preconditioning. Four groups of pigs were used for the study, i.e., control (n=5), SWOP (n=5), RCO (n=5), and RCS (n=5). SWOP was induced by two episodes of 10 min coronary artery occlusion (CAO), each followed by 10 min coronary artery reperfusion (CAR). RCO was induced by the same stimulus as SWOP (two cycles of 10 min CAO and 10 min CAR), but repeated six times every 12 hrs. RCS was induced by 90 min low-flow ischemia repeated six times every 12 hrs.

Project description:There are a limited number of therapies available to prevent heart failure following myocardial infarction. One novel therapy that is currently being pursued is the implantation of cardiac progenitor cells (CPCs); however, their responses to oxidative stress during differentiation have yet to be elucidated. The objective of this study was to determine the effect of hydrogen peroxide (H2O2) treatment on CPC differentiation in vitro, as well as the effect of H2O2 preconditioning before implantation following ischemia-reperfusion (I/R) injury. CPCs were isolated and cloned from adult rat hearts, and then cultured in the absence or presence of H2O2 for 2 or 5 days. CPC survival was assessed with Annexin V, and cellular differentiation was evaluated through mRNA expression for cardiogenic genes. We found that 100??M H2O2 decreased serum withdrawal-induced apoptosis by at least 45% following both 2 and 5 days of treatment. Moreover, 100??M H2O2 treatment for 2 days significantly increased endothelial and smooth muscle markers compared to time-matched untreated CPCs. However, continued H2O2 treatment significantly decreased these markers. Left ventricular cardiac function was assessed 28 days after I/R and I/R with the implantation of Luciferase/GFP(+) CPCs, which were preconditioned with 100??M H2O2 for 2 days. Hearts implanted with Luciferase/GFP(+) CPCs had significant improvement in both positive and negative dP/dT over I/R. Furthermore, cardiac fibrosis was significantly decreased in the preconditioned cells versus both I/R alone and I/R with control cells. We also observed a significant increase in endothelial cell density in the preconditioned CPC hearts compared to untreated CPC hearts, which also coincided with a higher density of Luciferase(+) vessels. These findings suggest that preconditioning of CPCs with H2O2 for 2 days stimulates neoangiogenesis in the peri-infarct area following I/R injury and could be a viable therapeutic option to prevent heart failure.

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Molecular mechanisms mediating preconditioning following chronic ischemia differ from those in classical second window.

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Molecular mechanisms mediating preconditioning following chronic ischemia differ from those in classical second window.

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