In this study we investigated the mechanisms of neuronal cell death induced by lipoteichoic acid (LTA) and muramyl dipeptide (MDP) from Gram-positive bacterial cell walls using primary cultures of rat cerebellum granule cells (CGCs) and rat cortical glial cells (astrocytes and microglia). LTA (± MDP) from Staphylococcus aureus induced a strong inflammatory response of both types of glial cells (release of interleukin-1 β, tumour necrosis factor-α and nitric oxide). The death of CGCs was caused by activated glia because in the absence of glia (treatment with 7.5 μM cytosine-D-arabinoside to inhibit non-neuronal cell proliferation) LTA + MDP did not cause significant cell death (less than 20%). In addition, staining with rhodamine-labelled LTA confirmed that LTA was bound only to microglia and astrocytes (not neurones). Neuronal cell death induced by LTA (± MDP)-activated glia was partially blocked by an inducible nitric oxide synthase inhibitor (1400 W; 100 μM), and completely blocked by a superoxide dismutase mimetic [manganese (III) tetrakis (4-benzoic acid)porphyrin chloride; 50 μM] and a peroxynitrite scavenger [5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron (III); 100 μM] suggesting that nitric oxide and peroxynitrite contributed to LTA-induced cell death. Moreover, neuronal cell death was inhibited by selective inhibitors of caspase-3 (z-DEVD-fmk; 50 μM) and caspase-8 (z-lle-Glu(O-Me)-Thr-Asp(O-Me) fluoromethyl ketone; 50 μM) indicating that they were involved in LTA-induced neuronal cell death.
- Gram-positive bacteria
- Reactive oxygen and nitrogen species
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience