Clearance of dying autophagic cells of different origin by professional and non-professional phagocytes

Abstract

MCF-7 cells undergo autophagic death upon tamoxifen treatment. Plated on non-adhesive substratum these cells died by anoikis while inducing autophagy as revealed by monodansylcadaverine staining, elevated light-chain-3 expression and electron microscopy. Both de novo and anoikis-derived autophagic dying cells were engulfed by human macrophages and MCF-7 cells. Inhibition of autophagy by 3-methyladenine abolished engulfment of cells dying through de novo autophagy, but not those dying through anoikis. Blocking exposure of phosphatidylserine (PS) on both dying cell types inhibited phagocytosis by MCF-7 but not by macrophages. Gene expression profiling showed that though both types of phagocytes expressed full repertoire of the PS recognition and signaling pathway, macrophages could evolve during engulfment of de novo autophagic cells the potential of calreticulin-mediated processes as well. Our data suggest that cells dying through autophagy and those committing anoikis with autophagy may engage in overlapping but distinct sets of clearance mechanisms in professional and non-professional phagocytes.

Cell death and autophagy: Cytokines, drugs, and nutritional factors

“…MDC was used to visualize AVs in MCF-7/7.0.3 cells and to compare the kinetics of AV formation with those of nuclear condensation at the light (fluorescence) microscopy level: AV formation preceded nuclear collapse which is considered to reflect the irreversible stage of cell death . Petrovski et al (2007) confirmed the kinetics of the occurrence of autophagic vacuoles by light chain-3 (LC3) expression, along with quantification of nuclear collapse. Furthermore, by fluorescence microscopy more than 95% of the dying cells were found to be MDC positive (day 4 after TAM); inhibition of autophagy at day 4 by 3-methyladenine almost completely abolished the MDCpositive staining and, as demonstrated by FACS-analysis, led to a significant drop in the number of annexin-V-positive and annexin-V-positive/PI-positive cells (Petrovski et al, 2007).…”

“…Autophagy 4(4), [435][436][437][438][439][440][441]. Furthermore, the self-destruction of MCF-7 cells was found to be completed by phagocytosis of cell residues [Petrovski, G., Zahuczky, G., Katona, K., Vereb, G., Martinet, W., Nemes, Z., Bursch, W., Fésüs, L., 2007. Clearance of dying autophagic cells of different origin by professional and non-professional phagocytes.…”

From regulation of dying cell engulfment to development of anti-cancer therapy

“…We showed that apoptotic cells are engulfed by a zipper-like mechanism of phagocytosis ( Figure 1), whereas necrotic cells are internalized by a macropinocytotic mechanism, such that parts of the cell are co-ingested together with extracellular fluid. 8,31,32 In contrast with the initial paradigm, PS exposure mediates recognition and engulfment not only of apoptotic cells, but also of necrotic cells 33,34 and of cells dying from autophagic cell death, 35 indicating that PS-mediated clearance may be a general mechanism irrespective of the way a cell dies. Accordingly, several macrophage receptor systems known to be involved in the engulfment of apoptotic cells also contribute to the uptake of necrotic cells.…”

Extracellular matrix regulation of autophagy

“…Follow-up work corroborates that the lack of integrin engagement directly induces autophagy. Autophagy is rapidly induced in a variety of nontransformed epithelial cell types grown in low attachment conditions, and has been observed during the detachment of a breast cancer cell line [23,24]. Furthermore, the incubation of attached cells with function blocking antibodies against β1 integrin is sufficient to induce autophagy, whereas exogenous addition of a laminin-rich basement membrane to suspended cells inhibits autophagy.…”