The Effect of Valproic Acid on the Transcriptional Activity of Ngf and Bdnf Genes of in Vitro Cultured Neurons Under Oxidative Stress Conditions

Abstract

Brain-derived neurotrophic factor (BDNF) is a secretory molecule that promotes peripheral neurons synaptic transmission and plasticity by TrkB receptor activation. This is shown in cultured central nervous system (CNS) neurons, including hippocampal and cortical cholinergic, dopaminergic and serotonergic neurons. Hypotheses suggesting that BDNF may play a potential role in the pathophysiology of schizophrenia are based on the key role of BDNF in the synaptic plasticity and, consequently, regulation of cognitive functions. In the schizophrenia treatment valproic acid is used in complex combined therapy regimens. Treatment of schizophrenia patients with valproate increases the BDNF level. Since it is not yet clear whether the BDNF protein levels measured in serum samples and in the brain correlate, we investigated valproate effects on the cultured neurons Bdnf transcription level. The primary neuron-glia culture was obtained from the cerebellum of 8-9-day-old Wistar rats. Valproic acid was added to the neurons (at a concentration of 50 µg/ml), oxidative stress was stimulated by 40 µMof H2O2, and injury was caused by mechanical damage to the neuron culture. It was shown that valproic acid in 3-24 hours increases the transcriptional activity of the Bdnf and Ngf (nerve growth factor) genes 2–2.5-fold (p<0.01) and approximately 1.5-fold (p<0.01), respectively. Mechanical trauma, unlike oxidative stress, activates the transcriptional activity of the Ngf and Bdnf genes (p<0.01). However, under oxidative stress and mechanical damage to neurons, the effect of valproic acid on the Ngf and Bdnf genes expression was insignificant. Fluorescence microscopy analysis using specific antibodies to neurons (anti-Map-2) showed that in the presence of valproic acid, the number of neuronal processes and contacts between them significantly increased. Evidently, valproate addition to antipsychotics can be effective for the overall clinical response. Relatively little research has been done on the signaling pathways in neurons that are activated by the valproic acid. However, we have obtained evidence of activation of the Ngf and Bdnf genes transcription in cultured neurons in vitro. We also found that in the presence of valproic acid, the number of neuronal processes and contacts between them significantly increased. However, we have also found that the oxidative stress accompanying the schizophrenia can significantly reduce the valproic acid effect on the Ngf and Bdnf genes expression. The results of the study may be potentially useful for new schizophrenia therapy strategies development.