Single cell RNA sequencing of peritoneal cells from macrophage-Cd36-/- and macrophage-Cd36 fl/fl mice at the resolution phase of sterile inflammation.

Monocytes and macrophages as components of innate immunity are critical for both homeostasis and inflammation. The scavenger receptor CD36, highly expressed in macrophages, promotes immunological responses mediated by recognition of molecular patterns on pathogens or endogenous ligands on apoptotic cells. CD36 mediated lipid uptake also allows metabolic adaptations that influence macrophage phenotype and polarization. CD36 binds diverse lipids including fatty acids and various lipoproteins, which could exert differential effects on macrophage conversion. Previous studies reported opposite outcomes due to CD36-mediated lipid uptake; macrophages converted to either an inflammatory or an alternatively activated phenotype. To determine the role of this receptor in vivo in the presence of physiological lipid sources, we created macrophage-specific CD36 knockout mice. Using zymosan-induced peritonitis to activate immune cells, we show through single cell RNA sequencing analysis that a broad variety of resident and infiltrated immune cells are present in the peritoneum 72h after the initial stimulus. CD36 deficiency did not affect the numbers of cells during the infiltration and resolution phases, but CD36 deficiency altered the macrophage transcriptome. Pathways related to innate immunity, antigen presentation and oxidative phosphorylation were upregulated in macrophages with CD36 deficiency, whereas those related to efferocytosis, adaptive immunity and B cell activation were downregulated. Despite these gene changes, neither immunoglobulin production nor peritoneal efferocytosis was altered by macrophage CD36 deficiency, nor were there changes in the numbers of circulating white blood cells. Thus, CD36 deficiency does not reduce the inflammatory phenotype of induced peritoneal macrophages. Overall design: We established the peritonitis model with high dosage of zymosan (1mg/ animal) in macrophage-Cd36-/- and macrophage-Cd36 fl/fl mice. Total peritoneal cells were isolated with 1x PBS and were analyzed using sc-RNAseq.