The term necrosis is commonly applied to cells that have died via a non-specific pathway or mechanism but strictly is the description of the degradation processes involved once the plasma membrane of the cell has lost integrity. The signalling pathways potentially involved in accidental cell death (ACD) or oncosis are under-studied. In this study, the flow cytometric analysis of the intracellular antigens involved in regulated cell death (RCD) revealed the phenotypic nature of cells undergoing oncosis or necrosis. Sodium azide induced oncosis but also classic apoptosis, which was blocked by zVAD (z-Vla-Ala-Asp(OMe)-fluoromethylketone). Oncotic cells were found to be viability+ve/caspase-3-ve/RIP3+ve/-ve (Receptor-interacting serine/threonine protein kinase 3). These two cell populations also displayed a DNA damage response (DDR) phenotype pH2AX+ve/PARP-ve, cleaved PARP induced caspase independent apoptosis H2AX-ve/PARP+ve and hyper-activation or parthanatos H2AX+ve/PARP+ve. Oncotic cells with phenotype cell viability+ve/RIP3-ve/caspase-3-ve showed increased DDR and parthanatos. Necrostatin-1 down-regulated DDR in oncotic cells and increased sodium azide induced apoptosis. This flow cytometric approach to cell death research highlights the link between ACD and the RCD processes of programmed apoptosis and necrosis.
Keywords: DDR; accidental cell death; flow cytometry; oncosis; parthanatos.