Fig. 8. Activation of autophagy as specific mechanism of rapamycin-dependent neuroprotection from PrP90-231 A1 toxicity.

a Cells were treated with rapamycin (10 nM), 3-methyladenine (3-MA, 1 mM) and PrP90-231 (1 μM); cell viability was measured by MTT assay after 48 h of treatment. The presence of 3-MA fully prevented rapamycin protection of PrP90-231-induced neurotoxicity. **P < 0.01 vs. control; °°P < 0.01 vs. PrP90-231. All the data are reported as mean + /− SEM of three independent experiments each performed in quadruplicate. b Differential cytoprotection induced by rapamycin and reduced glutathione (GSH) against PrP90-231 and hydrogen peroxide (H₂O₂) neurotoxicity. Cells were treated with rapamycin (10 nM) or GSH (1 mM), in the presence of PrP90-231 (1 μM) or H₂O₂ (200 μM), for 48 h. GSH was added 1 h before PrP90-231 or H₂O₂, since it was reported that is slowly incorporated within the cells⁶². Cell viability was determined by MTT assay, and reported as percent on vehicle-treated samples (Control). PrP90-231 toxicity was strongly reverted by rapamycin, but slightly, although significantly, by GSH; conversely cell death induced by H₂O₂ was unmodified by rapamycin and completely abolished by GSH. The data are reported as mean + /− SEM of three independent experiments each performed in quadruplicate. **P < 0.01 vs. control; °P < 0.05, and °°P < 0.01 vs. PrP90-231; ^XXP < 0.01 vs. H₂O₂