Exocytosis of macrophage lysosomes leads to digestion of apoptotic adipocytes and foam cell formation

Abigail S. Haka, Valéria C. Barbosa-Lorenzi, Hyuek Jong Lee, Domenick J. Falcone, Clifford A. Hudis, Andrew J. Dannenberg, Frederick R. Maxfield

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

Many types of apoptotic cells are phagocytosed and digested by macrophages. Adipocytes can be hundreds of times larger than macrophages, so they are too large to be digested by conventional phagocytic processes. The nature of the interaction between macrophages and apoptotic adipocytes has not been studied in detail. We describe a cellular process, termed exophagy, that is important for macrophage clearance of dead adipocytes and adipose tissue homeostasis. Using mouse models of obesity, human tissue, and a cell culture model, we show that macrophages form hydrolytic extracellular compartments at points of contact with dead adipocytes using local actin polymerization. These compartments are acidic and contain lysosomal enzymes delivered by exocytosis. Uptake and complete degradation of adipocyte fragments, which are released by extracellular hydrolysis, leads to macrophage foam cell formation. Exophagy-mediated foam cell formation is a highly efficient means by which macrophages internalize large amounts of lipid, which may ultimately overwhelm the metabolic capacity of the macrophage. This process provides a mechanism for degradation of objects, such as dead adipocytes, that are too large to be phagocytosed by macrophages.-Haka, A. S., V. C. Barbosa-Lorenzi, H. J. Lee, D. J. Falcone, C. A. Hudis, A. J. Dannenberg, and F. R. Maxfield. Exocytosis of macrophage lysosomes leads to digestion of apoptotic adipocytes and foam cell formation.

Original languageEnglish (US)
Pages (from-to)980-992
Number of pages13
JournalJournal of lipid research
Volume57
Issue number6
DOIs
StatePublished - Jun 2016

Keywords

  • Adipose tissue
  • Crown-like structure
  • Extracellular catabolism
  • Lipolysis and fatty acid metabolism
  • Obesity

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Cell Biology

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