Activity-based protein profiling of the human failing ischemic heart reveals alterations in hydrolase activities involving the endocannabinoid system

Acute myocardial infarction and subsequent post-infarction heart failure are among the leading causes of mortality worldwide. The endocannabinoid system has emerged as an important modulator of cardiovascular disease, however the role of endocannabinoid metabolic enzymes in heart failure is still elusive. Herein, we investigated the endocannabinoids and their metabolic enzymes in ischemic end-stage failing human hearts and non-failing controls.Quantitative real-time PCR, targeted lipidomics, and activity-based protein profiling (ABPP) enabled assessment of the endocannabinoids and their metabolic enzymes in ischemic end-stage failing human hearts and non-failing controls. Based on lipidomic analysis, two subgroups were identified within the ischemic heart failure group; the first similar to control hearts and the second with decreased levels of the endocannabinoid 2-arachidonoyl-glycerol (2-AG) and drastically increased levels of the endocannabinoid anandamide (AEA), other N-acylethanolamines (NAEs) and free fatty acids. The altered lipid profile was accompanied by strong reductions in the activity of 13 hydrolases, including the 2-AG hydrolytic enzyme monoacylglycerol lipase (MGLL).Our findings suggest the presence of different biological states within the ischemic heart failure group, based on alterations in the lipid and hydrolase activity profiles. In addition, this study demonstrates that ABPP is a valuable tool to rapidly analyze enzyme activity in clinical samples with potential for novel drug and biomarker discovery.