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(Circulation. 2001;104:I-319.)
© 2001 American Heart Association, Inc.

Myocardial Protection and Vascular Biology

Biochemical and Structural Evidence for Pig Myocardium Adherens Junction Disruption by Cardiopulmonary Bypass

Cesario Bianchi, MD, PhD; Eugenio G. Araujo, DVM; Kaori Sato, MD; Frank W. Sellke, MD

Division of Cardiothoracic Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass (C.B., E.G.A., K.S., F.W.S.), and the Department of Cellular Biology (E.G.A.), University of Brasilia, DF, Brazil.

Correspondence to Frank W. Sellke, MD, Beth Israel Deaconess Medical Center/Division of Cardiothoracic Surgery, 110 Francis St, LMOB Suite 2A, Boston, MA 02215. E-mail fsellke{at}caregroup.harvard.edu

Background— Given that cardiopulmonary bypass (CPB) is associated with edema and heart dysfunction and that adherens junctions may regulate vascular permeability barrier integrity and cardiomyocyte function, we investigated adherens junction protein steady-state levels in a pig model of CPB.

Methods and Results— Pigs were subjected to normothermic CPB for 90 minutes, followed by post-CPB perfusion for 90 minutes. Atrial and ventricular myocardium tissue samples were harvested before institution of bypass (basal levels) and at the end of post-CPB perfusion. Adherens junctions were analyzed by either total lysate or cadherin immunoprecipitates that were immunoblotted for pan-cadherin, VE-cadherin, ß-catenin, and -catenin. Adherens junction solubility was addressed with Triton X-100 extraction. Frozen tissue sections were labeled with the same antibodies, and adherens junctions were visualized by confocal microscopy. Immunoblotting of total lysates revealed an increase in smaller-molecular-weight fragments of VE-cadherin, ß-catenin, and -catenin after post-CPB perfusion, indicating partial protein degradation. Smaller-molecular-weight fragments recognized by VE-cadherin and ß-catenin antibodies were also obtained from VE-cadherin immunoprecipitation, indicating degradation of endothelial cell adherens junctions. A prominent increase in adherens junction complex solubility was observed in post-CPB perfusion samples. Confocal microscopy of hearts obtained before CPB showed a continuous, homogeneous pattern of cell-cell labeling that contrasted with an irregular, discontinuous, punctuate, or zigzag pattern observed in post-CPB perfusion samples, corroborating biochemical data.

Conclusions— These results indicate that CPB is associated with signs of degradation of endothelial and cardiomyocytes adherens junctions, pointing to a molecular mechanism leading to increased vascular permeability and cardiomyocyte dysfunction.

Key Words: cardiopulmonary bypass • endothelium • myocardium • intercalated disks • adherens junctions