Human monocyte-derived macrophages infected with virulent Shigella flexneri in vitro undergo a rapid cytolytic event similar to oncosis but not apoptosis

Abstract

Infection of human monocyte-derived macrophages in vitro with virulent Shigella flexneri resulted in cell death which involved rupture of the plasma membrane, cell swelling, disintegration of ultrastructure, and generalized karyolysis. These features bore resemblance to oncosis and are in striking contrast to previously described observations of mouse macrophages, where a similar infection by virulent Shigella resulted in cell death by apoptosis. Cell death by oncosis in human macrophages was confirmed by lactate dehydrogenase release, light microscopy, electron microscopy, terminal deoxynucleotidyltransferase end labeling of DNA ends, DNA fragmentation assays, and fluorescence-activated cell sorter analysis of propidium-labeled nuclei. Thus, the phenomena of cell death induced by virulent Shigella in human and mouse macrophages reflect different biochemical pathways. Interleukin-1␤ (IL-1␤) was released in culture supernatants of human macrophages infected with virulent bacteria. Inhibition with IL-1␤-converting enzyme inhibitors indicated, however, that this release occurred as a passive event of cell lysis. The patterns of intracellular survival of Shigella strains within human and mouse macrophages reflect differences that exist not only between Shigella serotypes but also between the two different macrophage cell types.

Inactivation of DsbA alters the behaviour of Shigella flexneri towards murine and human-derived macrophage-like cells

“…The above data are consistent with previous studies [4,5] that indicate that the outcome of the interaction between Shigella and host macrophage cells depends largely on both bacterial virulence and the stage of di¡erentiation of the host cells. In the experiments described here, M90TS is able to escape from J774 phagocytic vacuoles more rapidly than from phagocytic vacuoles of U937 cells, and thus appears to exert a greater cytotoxic e¡ect to J774 cells.…”

“…Virulent Shigella can induce either apoptosis or necrosis in human-derived macrophages depending on the state of di¡erentiation of the host cells [4,5]. A recent study has further con¢rmed this observation with the use of the human monoblastic cell line U937 [15].…”

“…For bacterial infection, the J774 cells were seeded in 24well culture plates and grown overnight in fresh medium without antibiotics at 37³C as previously described [4,5]. Bacterial suspensions were added to each of the wells at a multiplicity of infection (moi) of 10^30 bacteria per cell.…”

Streptococcus pyogenesinduces oncosis in macrophages through the activation of an inflammatory programmed cell death pathway

“…Examples are provided by Pseudomonas aeruginosa, which can cause oncosis of macrophages by secreting type III secretion effectors (Dacheux et al, 2001). Also haemolysin-positive Escherichia coli (Fernandez-Prada et al, 1998), Brucella abortus (Pei et al, 2006) as well as Shigella flexneri (Fernandez-Prada et al, 1997) have been reported to induce cell death of macrophages morphologically consistent with oncosis. In the particular case of S. pyogenes, we have shown that oncosis of macrophages was triggered by the streptococcal cytolysins SLS and SLO.…”

Shigella flexneri YSH6000 induces two types of cell death, apoptosis and oncosis, in the differentiated human monoblastic cell line U937

“…Virulent Shigella-infected and IpaB-injected J774 cells have been reported to show morphological features typical of apoptosis [6,14]. On the other hand, Fernandez-Prada et al reported that human monocyte-derived macrophages infected with S. £exneri in vitro underwent rapid cytolytic cell death di¡erent from apoptosis [15]. Shigella-infected macrophages show rupture of the plasma membrane, cell swelling, disintegration of ultrastructure, and generalized karyolysis, which are characteristics of oncosis, a recently proposed form of cell death [16].…”