Hydrogen sulfide induced neuronal death occurs via glutamate receptor and is associated with calpain activation and lysosomal rupture in mouse primary cortical neurons

Abstract

Hydrogen sulfide (H 2S) is a cytotoxic gas recently proposed as a novel neuromodulator. Endogenous levels of H 2S in the brain range between 50 and 160 μM and perturbed H 2S synthesis has been reported in the brains from stroke, Alzheimer's disease and Down syndrome patients. Recently, in immature non-glutamate receptor expressing mouse cortical neurons H 2S was shown to inhibit cell death exhibited by high concentrations of glutamate whereas H 2S was not cytotoxic. Due to the reported role of H 2S in facilitating LTP through NMDA receptors we examined the effects of H 2S on glutamate receptor functioning using mature cortical neurons expressing functional glutamate receptor subtypes. Addition of 100 μM glutamate exhibited extensive cell death which was exacerbated by co-incubation with ≤200 μM of the H 2S donor sodium hydrosulfide (NaHS). At <200 μM NaHS induced apoptosis whereas >200 μM NaHS induced necrosis. Cell death was inhibited by pharmacological glutamate receptor antagonists MK801 and APV (NMDA receptor antagonists), and CNQX (kainate and AMPA receptor antagonist) but not kynurenate (broad spectrum glutamate receptor antagonist), GYKI52466 (more selective AMPA receptor antagonist) and CYZ (AMPA receptor potentiator). Although markers of apoptosis were observed, we did not detect caspase activation either by Western blotting or fluorescence assays and caspase inhibitors did not prevent cell death. Rather, H 2S induced calpain activation and lysosomal membrane destabilization; processes inhibited by preferential antagonists of NMDA and kainate receptors. These data suggest that H 2S induced neuronal death through ionotropic glutamate receptors, which recruits apoptosis to ensure cellular demise and employs calpains and lysosomal rupture. This study provides novel insights into cell death observed in neurodegenerative diseases involving glutamate receptor activation and perturbed H 2S synthesis.