P2Y Nucleotide Receptor Is a Regulator of the Formation of Cardiac Adipose Tissue and Its Fat-Associated Lymphoid Clusters.

The formation of pericardial adipose tissue (PAT) and its regulatory function in cardiac inflammation are not well understood. We investigated the potential role of the ubiquitous ATP/UTP nucleotide receptor P2Y in the PAT by using P2Y-null mice. We observed that P2Y-null mice displayed a lower mass of PAT and a reduced density of its fat-associated lymphoid clusters (FALCs) and, more particularly, B cells. Loss of P2Y receptor in pericardial preadipocytes decreased their adipogenic differentiation and maturation abilities in vitro. Gene profiling identified P2Y target genes in PAT linked to immunomodulation. These data led to the identification of an increase of M2c anti-inflammatory macrophages correlated with increased apoptosis of B lymphocytes in P2Y-null pericardial fat. In addition, follicular helper T cells, which contribute to B cell expansion in germinal centers, were dramatically decreased. The effect of P2Y loss was also investigated after ischemia-mediated expansion of FALCs in a model of myocardial infarct. Loss of P2Y led to reduced expansion of B and neutrophil populations in these clusters, whereas density of M2c anti-inflammatory macrophages was increased. Our study defines the P2Y nucleotide receptor as a regulator of the formation and inflammatory status of pericardial fat. The P2Y receptor could represent a therapeutic target in the regulation of PAT function before and during cardiac ischemia.