Peptidoglycan of staphylococcus aureus induces atypical cell death of microglial cells by a caspase-3 independent pathway

ARROYO, DS; GAVIGLIO, EA; SORIA, JA; RODRIGUEZ-GALAN, MC; IRIBARREN, P

Mar del Plata, Argentina

Congreso; REUNIÓN ANUAL SOCIEDAD ARGENTINA DE INMUNOLOGÍA; 2009

Microglial cells (MC) are involved in central nervous system diseases. Our preliminary studies have shown that after stimulation of MC with peptidoglycan of Staphylococcus aureus (PGN, TLR2 agonist) several neurotoxic factors and MC death were induced. Our goal was to study the mechanisms responsible of the cell death induced by PGN. Kinetic studies of MC (BV2) treated with PGN showed the presence of AnnexinV/7AAD double positive cell staining and low levels of early apoptotic cells (AnnexinV+), suggesting the presence of necrosis. In addition, BV2 cells stimulated with PGN showed, by electronic microscopy, the presence of double membrane vesicles (compatible with the ultrastructure of autophagic vesicles) and strong vacuolization in the cell cytoplasm. These findings correlated with both a particulated pattern of cytoplasmic staining with Monodansylcadaverine (MDC) and with detection by western blot of clivated LC3B (LC3B II). These effects were inhibited by the autophagy specific inhibitor, 3-Methyladenine (3 MA). Furthermore, we found a decrease of BCL-2 protein (apoptosis and autophagy negative regulator) expression. Moreover the effects of PGN were caspase 3 independent. These preliminary results suggest that PGN is able to induce atypical MC death, probably by induction of exacerbated autophagy in a caspase 3- independent manner.Staphylococcus aureus (PGN, TLR2 agonist) several neurotoxic factors and MC death were induced. Our goal was to study the mechanisms responsible of the cell death induced by PGN. Kinetic studies of MC (BV2) treated with PGN showed the presence of AnnexinV/7AAD double positive cell staining and low levels of early apoptotic cells (AnnexinV+), suggesting the presence of necrosis. In addition, BV2 cells stimulated with PGN showed, by electronic microscopy, the presence of double membrane vesicles (compatible with the ultrastructure of autophagic vesicles) and strong vacuolization in the cell cytoplasm. These findings correlated with both a particulated pattern of cytoplasmic staining with Monodansylcadaverine (MDC) and with detection by western blot of clivated LC3B (LC3B II). These effects were inhibited by the autophagy specific inhibitor, 3-Methyladenine (3 MA). Furthermore, we found a decrease of BCL-2 protein (apoptosis and autophagy negative regulator) expression. Moreover the effects of PGN were caspase 3 independent. These preliminary results suggest that PGN is able to induce atypical MC death, probably by induction of exacerbated autophagy in a caspase 3- independent manner.