Identification of Cardiac Myosin-binding Protein C as a Candidate Biomarker of

Acute myocardial infarction (AMI) is a common cause of death for which effective treatments are available pro-vided that diagnosis is rapid. The current diagnostic gold standards are circulating cardiac troponins I and T. However, their slow release delays diagnosis, and their persistence limits their utility in the identification of re-infarction. The aim was to identify candidate biomarkers of AMI. Isolated mouse hearts were perfused with oxy-genated protein-free buffer, and coronary effluent was collected after ischemia or during matched normoxic perfusion. Effluents were analyzed using proteomics ap-proaches based on one- or two-dimensional initial sep-aration. Of the 459 proteins identified after ischemia with one-dimensional separation, 320 were not detected in the control coronary effluent. Among these were all classic existing biomarkers of AMI. We also identified the cardiac isoform of myosin-binding protein C in its full-length form and as a 40-kDa degradation product. This protein was not detected in the other murine or-gans examined, increased markedly with even trivial myocardial infarction, and could be detected in the plasma after myocardial infarction in vivo, a profile com-patible with a biomarker of AMI. Two-dimensional fluo-rescence DIGE of ischemic and control coronary efflu-ents identified more than 200 asymmetric spots verified by swapping dyes. Once again existing biomarkers of injury were confirmed as well as posttranslational mod-ifications of antioxidant proteins such as peroxiredox-ins. Perfusing hearts with protein-free buffers pro-vides a platform of graded ischemic injury that allows detailed analysis of protein release and identification of candidate cardiac biomarkers like myosin-binding pro