Tissue Expression of Atrial and Ventricular Myosin Light Chains in the Mechanism of Adaptation to Oxidative Stress.

Ischemia/reperfusion (I/R) injury induces post-translational modifications of myosin light chains (MLCs), increasing their susceptibility to degradation by matrix metalloproteinase 2 (MMP-2). This results in the degradation of ventricular light chains (VLC1) in heart ventricles. The aim of the study was to investigate changes in MLCs content in the mechanism of adaptation to oxidative stress during I/R. Rat hearts, perfused using the Langendorff method, were subjected to I/R. The control group was maintained in oxygen conditions. Lactate dehydrogenase (LDH) activity and reactive oxygen/nitrogen species (ROS/RNS) content were measured in coronary effluents. Atrial light chains (ALC1) and ventricular light chains (VLC1) gene expression were examined using RQ-PCR. ALC1 and VLC1 protein content were measured using ELISA tests. MMP-2 activity was assessed by zymography. LDH activity as well as ROS/RNS content in coronary effluents was higher in the I/R group ( p = 0.01, p = 0.04, respectively), confirming heart injury due to increased oxidative stress. MMP-2 activity in heart homogenates was also higher in the I/R group ( p = 0.04). ALC1 gene expression and protein synthesis were significantly increased in I/R ventricles ( p < 0.01, 0.04, respectively). VLC1 content in coronary effluents was increased in the I/R group ( p = 0.02), confirming the increased degradation of VLC1 by MMP-2 and probably an adaptive production of ALC1 during I/R. This mechanism of adaptation to oxidative stress led to improved heart mechanical function.