Restoration of damaged dopamine neurons

Abstract

Several in vitro and in vivo studies demonstrate that some β-carbolines (βC) exert neuroprotective effects. The noncationic 9-methyl-βC enhanced the enzyme activity of triosephosphate isomerase (TPI), whereas the cationic 2-methyl- βC and 2,9-dimethyl-βC inhibited enzyme activity. TPI is a rate-limiting enzyme for glycolysis and its activation improves the energy supply of the cell. In murine primary neurons, exposition to 9-methyl-βC increased the number of dopamine (DA) neurons by up to 50% and of gene transcripts of several genes involved in differentiation while transcripts of proinflammation, proapoptosis, and stress were downregulated. Chronic exposure to rotenone, a toxin which acts by inhibiting complex I of the respiratory chain, decreased the number of DA neurons. After rotenone withdrawal further deterioration was observed as well as ongoing proliferation of microglia. Exposure of cultures to 9-methyl-βC after rotenone withdrawal, resulted in conspicuous regeneration of DA neurons and a reversal of the number of microglia. In an animal model of PD. 9-methyl-βC normalized the decline of DA levels in the striatum. Expression of genes involved in neuronal differentiation, regeneration, and survival were upregulated including brain-derived neurotrophic factor, con¬served DA neurotrophic factor, and nerve growth factor while transcripts of inflam¬mation and apoptosis-inducing factors were downregulated. Further neuroprotective effects are reported in Chaps. 8 and 9.