Protective effect of L-deprenyl against apoptosis induced by okadaic acid in cultured neuronal cells

L-Deprenyl, an irreversible MAO-B (monoamine oxidase B, EC 1.4.3.4) inhibit or, is used fur the treatment of Parkinson's disease and to delay the progr ession of Alzheimer's disease. L-Deprenyl also exhibits protective effects against neuronal apoptosis which are independent of its ability to inhibit MAQ-B. The purpose of this study was to compare the antiapoptotic efficacy of L-deprenyl against different types of apoptotic inducers in three neuron al cell culture models. The level of apoptosis was quantified by measuring the activation of caspase-3 enzyme, which is the main apoptotic executioner in neuronal cells. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoli um bromide] and LDH (lactate dehydrogenase, EC 1.1.1.27) assays were used t o demonstrate the cytotoxic response of apoptotic treatments. Our results s howed that okadaic acid, an inhibitor of protein phosphatase 1 and 2A, indu ced a prominent increase in caspase-3 activity both in cultured hippocampal and cerebellar granule neurons as well as in Neuro-2 a neuroblastoma cells . Interestingly, L-deprenyl offered a significant protection against the ap optotic response induced by okadaic acid in all three neuronal models. The best protection appeared at the concentration level of 10(-9) M. L-Deprenyl also provided a protection ion against apoptosis after AraC (cytosine beta -D-arabinoside) treatment in hippocampal neurons and Neuro-2a cells and aft er etoposide treatment in Neuro-Za cells. However, L-deprenyl did not offer any protection against apoptosis caused hy serum withdrawal or potassium d eprivation. Okadaic acid treatment in vivo is known to induce an Alzheimer' s type of hyperphosphorylation of tau protein, formation of beta-amyloid pl aques, and a severe memory impairment. Our results show that the okadaic ac id model provides a promising tool to study the molecular basis of Alzheime r's disease and to screen the neuroprotective capacity of L-deprenyl deriva tives. (C) 2000 Elsevier Science Inc.