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 E IRIBARREN, P

Viña del Mar

Congreso; 9th Latin American Congress pf Immunology; 2009

Peptidoglycan from Staphylococcus aureus induces atypical cell death of microglial cells independently of caspase-3 Microglial cell (MC) are involved in responses of the central nervous system (CNS) against infections, aseptic inflammation, injury and neurodegeneration. These cells are accumulated at sites of injury and have the capability of activating when they contact either with endogenous or exogenous signals (pathogens). Our preliminary studies have shown that after prolonged stimulation in MC with peptidoglycan of Staphylococcus aureus (PGN, TLR2 agonist) several neurotoxic factors (IL1beta, TNFalfa, IL6 and nitric oxide (NO)) are produced and death of MC are induced. However, the intracellular mechanism responsible from these effects is unknown Our main aim was to study the mechanisms responsible of the death cell induced by PGN. Kinetic study in CM BV2 treated with PGN shown the presence of double positive cell staining with AnnexinV/7AAD and low levels of early apoptotic cells (AnnexinV+), suggesting the presence of necrosis. In addition, BV2 cells stimulated with PGN shown the presence of double membrane organelles compatibility with the ultraestructure of autophagic vesicles and strongly vacuolization in the cell cytosol by electronic microscopy. These findings correlated with both the particular pattern of cytosol staining with Monodansylcadaverine (MDC) and with the detection of LC3B clivated isoform by western blot assays in BV2 cells treated with PGN. This effect was inhibited by the autophagy specific inhibitor, 3-Methyladenine (3 MA). Furthermore, decrease of BCL-2 expression (apoptosis and autophagy negative regulator) was detected. Moreover the effect of PGN was caspase-3 independent. These preliminary results suggest that PGN is capable of inducing atypical death of microglial cells, probably by exacerbated induction of autophagy and caspase 3 independent manner