Exocytosis of macrophage lysosomes leads to digestion of apoptotic adipocytes and foam cell formation Academic Article uri icon


MeSH Major

  • Adipocytes
  • Exocytosis
  • Macrophages
  • Obesity
  • Phagocytosis


  • 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.

publication date

  • June 2016



  • Academic Article



  • eng

PubMed Central ID

  • PMC4878183

Digital Object Identifier (DOI)

  • 10.1194/jlr.M064089

PubMed ID

  • 27044658

Additional Document Info

start page

  • 980

end page

  • 92


  • 57


  • 6