Carnosinylation of Cardiac Antigens Attenuates Immunogenic Responses and Improves Function in Failing Hearts.

Objective: To investigate the effects of carnosine on heart failure and to examine whether this is associated with reduced immunogenicity of oxidatively-generated aldehyde modified proteins.

Background: Heart failure is associated with the accumulation of lipid derived aldehydes that form immunogenic protein adducts. However, the pathological impact of these aldehydes and aldehyde-modified proteins in heart failure has not been assessed. Histidyl dipeptides, such as carnosine found in the heart, bind to aldehydes, and their protein adducts. However, the effects of carnosine on heart failure or the antigenicity of aldehyde modified proteins have not been studied.

Methods: Male, wild type C57BL/6J mice were subjected to either sham or transverse aortic constriction (TAC) surgery. To increase carnosine levels, they were placed on drinking water with or without β-alanine prior to surgery, and for the remainder of the study. Cardiac function was evaluated by echocardiography, and the levels of histidyl dipeptides, immune cell populations, and CD4 T cell activation were assessed via LC-MS/MS and flow cytometry, respectively.

Results: Myocardial levels of histidyl dipeptides decreased at both 3-and 8-weeks post-TAC. Supplementation with β-alanine increased myocardial histidyl dipeptide levels, attenuated adverse cardiac remodeling, and reduced aldehyde stress. Carnosine formed covalent bond with protein-bound aldehydes in the failing heart, reducing their antigenic potential and decreasing activation of dendritic cells and CD4 T cells . β-alanine supplementation decreased the population of CD11b CD64 Ly6G neutrophils and CD4 CD44 effector T cells in the failing heart.

Conclusions: Increasing myocardial carnosine levels reduces aldehyde stress, dampens maladaptive immune responses, and preserves cardiac function during heart failure.

Highlights: Levels of endogenous dipeptide carnosine are depleted in failing hearts, while supplementation of the carnosine precurson β-alanine increases myocardial carnosine and preserves cardiac function during heart failure. Heart failure is associated with increased activation and infiltration of CD4 T cells and generation of aldehyde modified protein adducts in failing hearts. The free aldehyde moiety of aldehyde modified protein adducts activates CD4 T cells through dendritic cell presentation and capping this moiety with carnosine diminishes their antigencity. Increasing myocardial carnosine levels diminishes aldehyde stress and activation of CD4 T cells during heart failure.