Neuroprotection by the synthetic neurosteroid enantiomers ent-PREGS and ent-DHEAS against Aβ25-35 peptide-induced toxicity in vitro and in vivo in mice

Pregnenolone sulfate (PREGS) and dehydroepiandrosterone sulphate (DHEAS) are pro-amnesic, anti-amnesic and neuroprotective steroids in rodents. In Alzheimer's disease (AD) patient's brains, their low concentrations are correlated with high levels of A beta and tau proteins. The unnatural enantiomer ent-PREGS enhanced memory in rodents. We investigated here whether ent-PREGS and ent-DHEAS could be neuroprotective in AD models. The effects of PREGS, ent-PREGS, DHEAS and ent-DHEAS against A beta(25-35) peptide-induced toxicity were examined in vitro on B104 neuroblastoma cells and in vivo in mice. B104 cells pretreated with the steroids before A beta(25-35) were analysed by flow cytometry measuring cell viability and death processes. Mice injected intracerebroventricularly with A beta(25-35) and the steroids were analysed for their memory abilities. Additionally, lipid peroxidation levels in the hippocampus were measured. ent-PREGS and PREGS significantly attenuated the A beta(25-35)-induced decrease in cell viability. Both steroids prevented the A beta(25-35)-induced increase in late apoptotic cells. PREGS further attenuated the ratio of necrotic cells. ent-DHEAS and DHEAS significantly reduced the A beta(25-35)-induced toxicity and prevented the cells from entering late apoptosis and necrosis. All steroids stimulated neurite outgrowth per se and prevented the A beta(25-35)-induced decrease. In vivo, ent-PREGS and ent-DHEAS significantly attenuated the A beta(25-35)-induced decrease in memory (spontaneous alternation and passive avoidance) and an increase in lipid peroxidation levels. In contrast to the natural steroids, both enantiomers prevented amnesia when injected 6 h before A beta(25-35) in contrast to the natural steroids. The unnatural steroids ent-PREGS and ent-DHEAS are potent neuroprotective agents and could be effective therapeutical tools in AD.