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Articles by S Izumo
Total Records ( 1 ) for S Izumo
  D Guo , Z Kassiri , R Basu , F. L Chow , V Kandalam , F Damilano , W Liang , S Izumo , E Hirsch , J. M Penninger , P. H Backx and G. Y. Oudit
  Rationale:

Mechanotransduction and the response to biomechanical stress is a fundamental response in heart disease. Loss of phosphoinositide 3-kinase (PI3K), the isoform linked to G protein–coupled receptor signaling, results in increased myocardial contractility, but the response to pressure overload is controversial.

Objective:

To characterize molecular and cellular responses of the PI3K knockout (KO) mice to biomechanical stress.

Methods and Results:

In response to pressure overload, PI3KKO mice deteriorated at an accelerated rate compared with wild-type mice despite increased basal myocardial contractility. These functional responses were associated with compromised phosphorylation of Akt and GSK-3. In contrast, isolated single cardiomyocytes from banded PI3KKO mice maintained their hypercontractility, suggesting compromised interaction with the extracellular matrix as the primary defect in the banded PI3KKO mice. β-Adrenergic stimulation increased cAMP levels with increased phosphorylation of CREB, leading to increased expression of cAMP-responsive matrix metalloproteinases (MMPs), MMP2, MT1-MMP, and MMP13 in cardiomyocytes and cardiofibroblasts. Loss of PI3K resulted in increased cAMP levels with increased expression of MMP2, MT1-MMP, and MMP13 and increased MMP2 activation and collagenase activity in response to biomechanical stress. Selective loss of N-cadherin from the adhesion complexes in the PI3KKO mice resulted in reduced cell adhesion. The β-blocker propranolol prevented the upregulation of MMPs, whereas MMP inhibition prevented the adverse remodeling with both therapies, preventing the functional deterioration in banded PI3KKO mice. In banded wild-type mice, long-term propranolol prevented the adverse remodeling and systolic dysfunction with preservation of the N-cadherin levels.

Conclusions:

The enhanced propensity to develop heart failure in the PI3KKO mice is attributable to a cAMP-dependent upregulation of MMP expression and activity and disorganization of the N-cadherin/β-catenin cell adhesion complex. β-Blocker therapy prevents these changes thereby providing a novel mechanism of action for these drugs.

 
 
 
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