Allopregnanolone attenuates N-methyl-D-aspartate-induced excitotoxicity and apoptosis in the human NT2 cell line in culture

Progesterone modulates γ-aminobutyric acid and excitatory amino acid neurotransmitter systems and has neuroprotective properties in models of hypoxia-ischemia. This study examined the in vitro effects of allopregnanolone, the active progesterone metabolite, in models of N-methyl-D-aspartate (NMDA)-induced necrosis and apoptosis. Cultured NT2 neurons were exposed to 1 mM NMDA. Lactate dehydrogenase (LDH) release was measured 24 h later. NMDA at a concentration of 1 mM produced a 39±19% release of total LDH. Exposure to 10 μM allopregnanolone prior to NMDA exposure reduced LDH release by 51% (P=0.0028). NMDA stimulated apoptotic cell changes defined by terminal dUTP nick-end labeling (TUNEL) and 5,5′, 6,6′-tetrachloro-1,1,3,3′-tetra ethlybenzimidazolycarbocyanide iodide staining were reduced to baseline values by both 10 μM allopregnanolone and 100 μM MK-801. Pretreatment with allopregnanolone (0-10 μM) reduced the percentage of TUNEL-positive cells in a dose-dependent manner (EC₅₀=2.7±0.1 nM). Physiologic concentrations of allopregnanolone provided protection against both necrotic and apoptotic injury induced by NMDA excitotoxicity.