P2Y₂ 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 P2Y₂ in the PAT by using P2Y₂-null mice. We observed that P2Y₂-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 P2Y₂ receptor in pericardial preadipocytes decreased their adipogenic differentiation and maturation abilities in vitro. Gene profiling identified P2Y₂ 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 P2Y₂-null pericardial fat. In addition, follicular helper T cells, which contribute to B cell expansion in germinal centers, were dramatically decreased. The effect of P2Y₂ loss was also investigated after ischemia-mediated expansion of FALCs in a model of myocardial infarct. Loss of P2Y₂ 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 P2Y₂ nucleotide receptor as a regulator of the formation and inflammatory status of pericardial fat. The P2Y₂ receptor could represent a therapeutic target in the regulation of PAT function before and during cardiac ischemia.

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