Abstract 203: Ischemic Preconditioning Enhances Cardiac Tight Junction Formation and Function in Isolated Mouse Heart
Tight junction (TJ) provides barrier function in epithelial and endothelial cells. Coronary endothelial cells contain TJ barrier. However, the TJ formation and function during myocardial ischemia/reperfusion injury (IR) and ischemic preconditioning (IPC) remain unknown. We hypothesize that IR may rupture the structure of TJ in the heart and subsequently impair cardiac function. IPC may protect heart from IR injury through maintenance the integrity of TJ. To this purpose, male C57BL/6J mice were used. Langendorff hearts were prepared with Krebs-Henseleit perfusion. Cardiac contractility was recorded with force transducer. Creatine kinase (CK) release in coronary effluent was measured. Heart edema was calculated from wet/dry heart weight. Cardiac TJ function was evaluated by measuring Evans blue-conjugated albumin (EBA) content in extravascular area of heart. Expression and translocation of zonula occludens (ZO) proteins ZO-1 and ZO-2 were detected by using Western Blotting. Mice were divided into four groups: control, IR, IPC, IPC plus IR. Control hearts were perfused with K-H buffer for 100 min. IR hearts were subjected to 40 min of global ischemia and 40 min of reperfusion. IPC was constituted of 2 min of global ischemia and 5 min of reperfusion. IR significantly decreased cardiac contractile force and increased CK release. EBA content was increased (20.9+/−2.8 μg/ml/g in IR, vs 10.2+/−0.7 in Control, n=3, P<0.05). Heart edema was observed in the IR hearts (6.5+/−0.2 wet/dry heart weight, vs 5.3+/−0.1 in Control, n=3, P<0.05). IPC significantly improved cardiac function (75.2 +/− 5.1 % of preischemia baseline, vs 43.5 +/− 9.7% in IR, n=7, P<0.05) and reduced CK release (Total CK units: 2217 +/− 121 in IPC, n=3, vs 4226 +/− 612 in IR group, n=7, P<0.05). IPC reduced EBA content in the heart (11.6+/−1.0 ug/ml/g, vs IR group, P<0.05) and heart edema formation (5.6+/−0.06, vs IR, P<0.05). ZO-1 and ZO-2 translocation from cytosol to Triton X-100 insoluble fraction was also detected after IPC. In conclusion, myocardial ischemia/reperfusion injury can rupture TJ structure and function. Ischemic preconditioning enhances cardiac tight junction function and ZO-1 or ZO-2 translocation from cytosol to the cytoskeleton fraction.
- © 2010 by American Heart Association, Inc.