Peroxidative block of glucose utilization and survival in CNS neuronal cultures

The search for neuronotrophic factors addressing CNS neurons requires CNS neuronal cell cultures to quantitate putative effects on neuronal survival. Investigation of neurons dissociated from several embryonic CNS tissues have shown that their short-term survival requires supplementation of the culture medium with either pyruvate or the enzyme catalase. Pyruvate can be replaced with alpha-ketoglutarate or oxaloacetate, or with amino acids capable to transaminate to these three metabolites in the presence of exogenous alpha-ketoacid acceptors. Experiments were designed to evaluate the ability of cultured CNS neurons to utilize glucose as their primary source. We show that: (1) catalase requires the availability of glucose in the medium in order to exert its neuronal maintenance effect, (2) in the absence of catalase, the cells are unable to metabolize glucose through the tricarboxylic acid cycle, (3) catalase restores the neuronal ability to utilize glucose for oxydative metabolism, and renders redundant the use of other sources such as glutamate conversion to alpha-ketoglutarate, (4) graded concentrations of glucose in the medium affect in parallel these metabolic activities and the viability of the cultured neurons, and (5) anti-oxidant agents other than catalase mimic the catalase effects. We conclude that dissociated embryonic CNS neurons suffer from a block in glucose utilization which results from an imbalance between free radical attack and cellular defenses to it and speculate on a more general involvement of peroxidation damage in the trophic requirements for neuronal survival.