Myocardial infarction elevates endoplasmic reticulum stress and protein aggregation in heart as well as brain.

ABSTRACT

Cardiovascular diseases, including myocardial infarction (MI), constitute the leading cause of morbidity and mortality worldwide. Protein-aggregate deposition is a hallmark of aging and neurodegeneration. Our previous study reported that aggregation is strikingly elevated in hearts of hypertensive and aged mice; however, no prior study has addressed MI effects on aggregation in heart or brain. Here, we present novel data on heart and brain aggregation in mice following experimental MI, induced by left coronary artery (LCA) ligation. Infarcted and peri-infarcted heart tissue, and whole cerebra, were isolated from mice at sacrifice, 7 days following LCA ligation. Sham-MI mice (identical surgery without ligation) served as controls. We purified detergent-insoluble aggregates from these tissues, and quantified key protein constituents by high-resolution mass spectrometry (LC-MS/MS). Infarct heart tissue had 2.5- to 10-fold more aggregates than non-infarct or sham-MI heart tissue (each P = 0.001). Protein constituents from MI cerebral aggregates overlapped substantially with those from human Alzheimer's disease brain. Prior injection of mice with mesenchymal stem cell (MSC) exosomes, shown to limit infarct size after LCA ligation, reduced cardiac aggregation ~ 60%, and attenuated markers of endoplasmic reticulum (ER) stress in heart and brain (GRP78, ATF6, P-PERK) by 50-75%. MI also elevated aggregate constituents enriched in Alzheimer's disease (AD) aggregates, such as proteasomal subunits, heat-shock proteins, complement C3, clusterin/ApoJ, and other apolipoproteins. These data provide novel evidence that aggregation is elevated in mouse hearts and brains after myocardial ischemia, leading to cognitive impairment resembling AD, but can be attenuated by exosomes or drug (CDN1163) interventions that oppose ER stress.