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Ischemic preconditioning reduces neutrophil accumulation and myocardial apoptosis
N P Wang1, B L Bufkin, M Nakamura
1Department of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia 30365-2225, USA.
Insights
Ischemic preconditioning (IP) significantly reduces myocardial apoptosis and neutrophil accumulation after ischemia and reperfusion injury. This protective effect was observed in a canine model, highlighting IP
Area of Science:
- Cardiovascular Research
- Cellular Biology
- Ischemia-Reperfusion Injury
Background:
- Ischemic preconditioning (IP) is a phenomenon where brief periods of ischemia protect against subsequent longer ischemic insults.
- Myocardial apoptosis, or programmed cell death, is a significant contributor to heart damage following ischemia and reperfusion.
- Understanding the mechanisms of IP is crucial for developing therapeutic strategies to limit myocardial injury.
Purpose of the Study:
- To test the hypothesis that ischemic preconditioning (IP) inhibits myocardial apoptosis.
- To investigate the effect of IP on neutrophil accumulation in the myocardium after ischemia and reperfusion.
- To evaluate the efficacy of IP in a nonlethal acute ischemia and reperfusion model.
Main Methods:
- Anesthetized dogs underwent either 30 minutes of left anterior descending (LAD) coronary artery occlusion followed by 3 hours of reperfusion (control) or IP (5 minutes occlusion/5 minutes reperfusion) before the 30-minute occlusion.
- Myocardial tissue samples were analyzed for apoptosis using DNA agarose gel electrophoresis (DNA laddering) and terminal transferase UTP nick end-labeling (TUNEL) assay.
- Neutrophil accumulation was quantified by measuring cardiac myeloperoxidase activity.
Main Results:
- Ischemia and reperfusion significantly reduced blood flow, with comparable reductions between control and IP groups.
- DNA laddering, indicative of apoptosis, was observed in the area at risk (AAR) in 6 of 9 control dogs but in none of the IP dogs.
- The percentage of apoptotic cells in the AAR was significantly lower in the IP group (1.2% +/- 0.2%) compared to the control group (6.7% +/- 0.9%).
- Cardiac myeloperoxidase activity, a marker of neutrophil accumulation, was significantly reduced in the IP group (0.04 U/g) compared to the control group (0.07 U/g).
Conclusions:
- Ischemic preconditioning effectively attenuates myocardial apoptosis in the area at risk following acute ischemia and reperfusion.
- IP also significantly reduces neutrophil accumulation in the myocardium during ischemia-reperfusion injury.
- These findings demonstrate the protective role of ischemic preconditioning in a nonlethal model of acute myocardial ischemia and reperfusion.
Background:
This study tested the hypothesis that ischemic preconditioning (IP) inhibits myocardial apoptosis after a short period of ischemia and reperfusion.
Methods:
In 9 anesthetized dogs, the left anterior descending (LAD) coronary artery was occluded for 30 min and reperfused for 3 h (control), while in 9 others, LAD occlusion was preceded by 5 min of occlusion and 5 min of reperfusion (IP). DNA from frozen myocardial tissue samples was extracted, and apoptosis were identified as "ladders" by agarose gel electrophoresis or confirmed histologically using the terminal transferase UTP nick end-labeling (TUNEL) assay. Neutrophil accumulation was detected by measuring cardiac myeloperoxidase activity.
Results:
Thirty minutes of LAD occlusion caused a significant decrease in blood flow (colored microspheres), which was comparable between groups. In the control group, DNA ladders occurred in the area at risk (AAR) in six out nine experiments. In contrast, DNA laddering in the AAR was not observed in any of the IP group. AAR in the control group showed a greater percentage of apoptotic cells than IP (6.7 +/- 0.9% vs 1.2 +/- 0.2%; p < 0.01). Cardiac myeloperoxidase activity (U/g tissue) was significantly reduced from 0.07 +/- 0.004 in control to 0.04 +/- 0.01 in IP group (p < 0.05).
Conclusions:
We conclude that ischemic preconditioning attenuates apoptosis and neutrophil accumulation in the AAR in a model of nonlethal acute ischemia and reperfusion.
