Investigating specific genes associated with cytokine signaling in the brains of major depressive disorder patients

Major depressive disorder (MDD) is one of the most common mental illnesses. The results obtainedfrom previous studies conducted in this field show that inflammatory processes increase in MDD patients. However, few studies have addressed the issue of inflammatory markers in the brains of MDD patients. The aim of this study was to investigate the expression of regulatory axis related to cytokine signaling including IL6, TNF, NRG1 and BDNF in prefrontal cortex tissue samples. In the present study, using a bioinformatics approach based on microarray data analysis, the expression of a regulatory axis related to cytokine signaling, including four genes (IL6, TNF, NRG1, and BDNF),in prefrontal cortex tissue (PFC) samples was investigated. Background correction, gene filtering and data normalization were done using different packages in R. Data quality was also evaluated using AgiMicroRna package and PCA plot.The limma package in R was used in order to identify the genes with expression changes. In addition, Pearson's correlation analysis was performed in R to check the correlation between the selected genes. The obtained results showed that the expression of BDNF and NRG1 genes in the PFC tissue of MDD patients was associated with a significant decrease (P= 0.037), and on the other hand, the expression of IL6 and TNF genes was significantly increased (P< 0.001). Also, a strong negative correlation between the IL6 and BDNF (P < 0.001) genes was obtained. In this study, the results show that there is a complex relationship between MDD disease progressionand cytokine signaling. This research provides evidence for a better understanding of the mechanisms of MDD pathogenesis.