Macrophages engulf apoptotic and primary necrotic thymocytes through similar phosphatidylserine-dependent mechanisms.
One of the major roles of professional phagocytes is the removal of dead cells in the body. We know less about the clearance of necrotic cells than apoptotic cell phagocytosis, despite the fact that both types of dead cells need to be cleared together and necrotic cells appear often in pathological settings. In the present study, we examined phagocytosis of heat- or H2O2-killed necrotic and apoptotic thymocytes by mouse bone marrow-derived macrophages (BMDMs) in vitro and found that the two cell types are engulfed at equal efficiency and compete with each other when added together to BMDMs. Phagocytosis of both apoptotic and necrotic thymocytes was decreased by (a) blocking phosphatidylserine on the surface of dying cells; (b) inhibition of Mer tyrosine kinase, Tim-4, integrin β3 receptor signaling, or Ras-related C3 botulinum toxin substrate 1 activity; or (c) using BMDMs deficient for transglutaminase 2. Stimulation of liver X, retinoid X, retinoic acid or glucocorticoid nuclear receptors in BMDMs enhanced not only apoptotic, but also necrotic cell uptake. Electron microscopic analysis of the engulfment process revealed that the morphology of phagosomes and the phagocytic cup formed during the uptake of dying thymocytes is similar for apoptotic and necrotic cells. Our data indicate that apoptotic and necrotic cells are cleared via the same mechanisms, and removal of necrotic cells in vivo can be facilitated by molecules known to enhance the uptake of apoptotic cells.
['Budai|Zsófia|Z|', 'Ujlaky-Nagy|László|L|', 'Kis|Gréta Nikoletta|GN|', 'Antal|Miklós|M|', 'Bankó|Csaba|C|', 'Bacsó|Zsolt|Z|', 'Szondy|Zsuzsa|Z|', 'Sarang|Zsolt|Z|']
D000818:Animals D017209:Apoptosis D002478:Cells, Cultured D006358:Hot Temperature D006861:Hydrogen Peroxide D008264:Macrophages D051379:Mice D008810:Mice, Inbred C57BL D018345:Mice, Knockout D009336:Necrosis D010718:Phosphatidylserines D060168:Thymocytes
macrophages phagocytosis phosphatidylserine apoptosis primary necrosis