(-)-Deprenyl reduces neuronal apoptosis and facilitates neuronal outgrowth by altering protein synthesis without inhibiting monoamine oxidase.

(-)-Deprenyl stereospecifically reduces neuronal death even after neurons have sustained seemingly lethal damage at concentrations too small to cause monoamine oxidase-B (MAO-B) inhibition. (-)-Deprenyl can also influence the process growth of some glial and neuronal populations and can reduce the concentrations of oxidative radicals in damaged cells at concentrations too small to inhibit MAO. In accord with the earlier work of others, we showed that (-)-deprenyl alters the expression of a number mRNAs or proteins in nerve and glial cells and that the alterations in gene expression/protein synthesis are the result of a selective action on transcription. The alterations in gene expression/protein synthesis are accompanied by a decrease in DNA fragmentation characteristic of apoptosis and the death of responsive cells. The onco-proteins Bcl-2 and Bax and the scavenger proteins Cu/Zn superoxide dismutase (SOD1) and Mn superoxide dismutase (SOD2) are among the 40-50 proteins whose synthesis is altered by (-)-deprenyl. Since mitochondrial ATP production depends on mitochondrial membrane potential (MMP) and mitochondrial failure has been shown to be one of the earliest events in apoptosis, we used confocal laser imaging techniques in living cells to show that the transcriptional changes induced by (-)-deprenyl are accompanied by a maintenance of mitochondrial membrane potential, a decrease in intramitochondrial calcium and a decrease in cytoplasmic oxidative radical levels. We therefore propose that (-)-deprenyl acts on gene expression to maintain mitochondrial function and to decrease cytoplasmic oxidative radical levels and thereby to reduce apoptosis. An understanding of the molecular steps by which (-)-deprenyl selectively alters transcription may contribute to the development of new therapies for neurodegenerative diseases.