Whole genome expression profile in neuroblastoma cells exposed to 1-methyl-4-phenylpyridine

Abstract

Mitochondrial dysfunction and subsequent energy failure is a contributing factor to degeneration of the substantia nigra pars compacta associated with Parkinson’s disease (PD). In this study, we investigate molecular events trigger by 1-methyl-4-phenylpyridine (MPP+) using whole genome-expression microarray, western blot and HPLC quantification of metabolites. The data show that MPP+ (500μM) evokes obstruction of mitochondrial respiration/oxidative phosphorylation (OXPHOS) in mouse neuroblastoma Neuro-2a cells, juxtapose to accelerated glucose consumption and production of lactic acid. While additional glucose concentrations restored viability at MPP+ (500μM), loss of OXPHOS was sustained suggesting that compensatory anaerobic metabolic systems were fulfilling required energy needs. Under these conditions, MPP+ initiated significant changes to the transcription of 799 genes (596 up-regulated and 203 down-regulated) of which 612 David IDS were applied and 136 functional annotation clusters were identified. Prominent changes were as follows; MPP+ initiated loss of mRNA for mitochondrial encoded NADH dehydrogenase 4, 5 genes, cytochrome b and NADH dehydrogenase (ubiquinone) flavoprotein 3, concomitant to rise in a mitochondrial fission gene; ganglioside-induced differentiation-associated-protein 1 (GDAP1). These negative changes to OXPHOS components were accompanied by a number of protective forces to the mitochondria including elevated ratio of mitochondrial anti/pro-apoptotic processes including a loss of apoptotic Bcl-2/adenovirus E1B 19-kDa-interacting protein (BNIP3) and family with sequence similarity 162, member A (FAM162a) and rise of heat shock protein 1 and Lon peptidase 1. There were no changes indicative of free radical damage (e.g. SOD, GSH-Px), rather MPP+ initiated a large number of significant G protein signaling components (which trigger catabolic processes) and anaerobic metabolic systems involving carboxylic acid/ transamination reactions (e.g. glutamate oxaloacetate transaminase 1 (GOT1), glutamic pyruvate-alanine transaminase 2 (GPT2), cystathionase and redox proteins such as cytochrome b5 reductase 1 and ferredoxin reductase. Counter-intuitively, the data show reduction of mRNA in glycolytic processes [DAVID enrichment score 9.96 p value 1.90E-19], some corroborated by western blot, bringing in to question the sources of lactate observed in the presence of MPP+. Examining this aspect, the data show that diverse carboxylic acids (succinate, oxaloacetate and a-ketoglutarate) are capable of contributing to the lactate pool in addition to phosph(enolpyruvate) or pyruvate in the absence of glucose by this cell line. In conclusion, these findings show that MPP+ negatively affects the transcriptome involved with complex I, but evoked elevation in G protein signaling and anaerobic metabolic systems involved with nitrogen/carboxylic acid metabolism and redox reactions. Anaerobic survival systems appear to be far more complex than previously believed, and future research will be required to elucidate th...

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