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Ischemic preconditioning attenuates postischemic leukocyte adhesion and emigration
T Akimitsu1, D C Gute, R J Korthuis
1Department of Physiology and Biophysics, School of Medicine in Shreveport, Louisiana State University 71130, USA.
Abstract:
Intravital microscopy was used to determine whether ischemic preconditioning (IPC; 5 min ischemia and 10 min reperfusion) would attenuate leukocyte adhesion and emigration induced by subsequent prolonged ischemia (60 min) and reperfusion (60 min) (I/R) in murine cremaster muscle and whether adenosine produced during IPC and/or reperfusion contributed to these beneficial effects. I/R elicited a marked increase in the number of adherent and emigrated leukocytes compared with the nonischemic control muscles, an effect that was largely prevented by IPC. Superfusion of the cremaster with adenosine deaminase only during IPC or only during 60-min reperfusion attenuated the inhibitory effect of IPC on postischemic leukocyte adhesion and emigration. However, the beneficial effects of IPC were mimicked in cremaster muscles preconditioned with adenosine (topical application for 10 min beginning 20 min before the onset of prolonged ischemia). Similar results were obtained in experiments in which adenosine was topically applied to the cremaster only during the 60-min reperfusion period. Our findings suggest that the ability of IPC to attenuate postischemic leukocyte adhesion and emigration may be mediated by adenosine released during IPC and during reperfusion after prolonged ischemia.
Insights
Ischemic preconditioning (IPC) significantly reduces leukocyte adhesion and emigration after prolonged ischemia. Adenosine released during IPC and reperfusion mediates these protective effects, offering insights into managing ischemia-reperfusion injury.
Area of Science:
- Cardiovascular Biology
- Inflammation Research
- Microcirculation Studies
Background:
- Ischemia-reperfusion (I/R) injury involves significant leukocyte adhesion and emigration.
- Ischemic preconditioning (IPC) is known to offer protection against I/R injury.
- The precise mechanisms underlying IPC's protective effects, particularly the role of adenosine, require further elucidation.
Purpose of the Study:
- To investigate the efficacy of IPC in attenuating leukocyte adhesion and emigration following prolonged I/R in murine cremaster muscle.
- To determine the contribution of adenosine produced during IPC and/or reperfusion to the protective effects of IPC.
Main Methods:
- Intravital microscopy was employed to visualize and quantify leukocyte adhesion and emigration.
- IPC was induced using a 5-minute ischemia and 10-minute reperfusion protocol.
- Prolonged I/R was induced by 60 minutes of ischemia followed by 60 minutes of reperfusion.
- Adenosine deaminase was used to block adenosine activity during specific periods, and exogenous adenosine was applied to assess its effects.
Main Results:
- Prolonged I/R significantly increased leukocyte adhesion and emigration compared to controls.
- IPC largely prevented the increase in leukocyte adhesion and emigration induced by I/R.
- Blocking adenosine during IPC or reperfusion attenuated the protective effects of IPC.
- Direct application of adenosine mimicked the protective effects of IPC during preconditioning or reperfusion.
Conclusions:
- IPC effectively attenuates post-ischemic leukocyte adhesion and emigration in the cremaster muscle.
- Adenosine released during both ischemic preconditioning and reperfusion plays a crucial role in mediating the protective effects of IPC.
- Targeting adenosine pathways may represent a therapeutic strategy for mitigating ischemia-reperfusion injury.