抄録
Introduction
The active ingredient of the commonly abused drug ecstasy, +-3,4-methylenedioximethamphetamine (MDMA), causes euphoria, tirelessness and elevated social interactions acutely. On the long-run, however, selective serotonergic toxicity marked by reduced serotonin transporter (SERT) and tryptophan hydroxylase 2 (TPH2) levels was observed in animals, especially in the hippocampus (HC) that seems to be more vulnerable to the toxic effects of the drug than cortical regions. Such reductions in mRNA and protein levels are often results of altered gene transcription regulations by transcription factors but these remained mostly uninvestigated after MDMA administration.
Methods
In the present study, Dark Agouti rats were administered saline or 15 mg/kg MDMA and sacrificed 3 weeks after. Their HC (from bregma -2.5 mm to -4.5 mm) was dissected and RNA content extracted with the TRIZOL method. After quality control measurements gene expression was assessed by Illumina RatRef-12 v1 whole-genome beadarray microarrays. Raw microarray data were analysed with beadarray, preprocessCore, puma Bioconductor packages and pre-processed data quantile normalized. Default settings in pumaComb, pumaDE, and write.rslts functions were used to obtain a fold change value. Thereafter, gene-set enrichment analysis was performed with MSigDB transcription factor sets to identify the transcription factor with the largest impact for chronic hippocampal gene expression changes after MDMA.
Results
Results showed that MDMA caused the largest downregulation among PAX4 transcription factor regulated genes with highly significant false discovery rate for the set as a whole (FDR q-value = 0.003). This gene set includes genes from insulin-related pathway, like glycogen synthase kinase 3 (GSK3) and insulin-like growth factor 1 receptor (IGF1R).
Conclusions
Insulinergic signaling in the brain was recently discovered as an important mechanism in maintaining neuronal functions. Our results suggest that MDMA may downregulate such processes through PAX4 transcription factor and, thereby, PAX4 may be a subtle, but important contributor to hippocampal impairments after MDMA use.
Acknowledgements
This study was supported by National Hungarian Development Agency (Grant: KTIA-NAP-13-1-2013-0001), Hungarian Brain Research Program (Grant: KTIA-13-NAP-A-II/14), MTA-SE-NAP-B Genetic Brain Imaging Migraine Research Group, Hungarian Academy of Sciences, Semmelweis University (Grant: KTIA_NAP_13-2-2015-0001) and New National Excellence Program of Ministry of Human Capacities (UNKP-16-3, UNKP-17-3-III-SE-2, UNKP-17-4-I-SE-8).
