Abstract 216: Macrophage Efferocytosis Is Controlled By Epigenetic Modifications Mediated By RBPJ

Abstract

Efferocytosis, phagocytic clearance of apoptotic cells, is essential for inflammation resolution and tissue homeostasis. A defect in efferocytosis is associated with advanced atherogenesis leading to the necrotic formation which can result in plaque rupture and abrupt thrombotic cardiovascular diseases. We observed that the recombination signal binding protein for immunoglobulin kappa J region (RBPJ), a transcription factor that normally involves in the canonical Notch signaling, was highly expressed by inflammatory macrophages. Our subsequent experiments revealed that although RBPJ did not affect inflammation, the transcription factor promoted apoptotic cell clearance by atherosclerotic plaque, alveolar, peritoneal, and bone marrow-derived macrophages. Inhibition of γ-secretase, which facilitates Notch intracellular domain release and RBPJ-mediated gene expression, significantly reduced efferocytosis. RNA sequencing analysis of RBPJ-deficient macrophages revealed Stard13 and Arsg as possible mediators of RBPJ-mediated efferocytosis. CUT&RUN and ChIP-qPCR experiments revealed that RBPJ diminished H3K9me3, a heterochromatin marking suppressing gene activity, on the Stard13 and Arsg promoters. Stard13 inhibited and activated Rho and RAC GTPases, respectively, promoting actin polymerization and efferocytosis. In sum, our findings indicate that RBPJ controls epigenetic modification of the Stard13 and Arsg promoters, encouraging apoptotic cell clearance.