Is there a link between TNF gene expression and cognitive deficits in depression?

Neuroinflammation is a known factor in the pathogenesis of recurrent depressive disorders. Depression is accompanied by activated immune-inflammatory pathways including increased levels of TNF alpha, sTNFR1and sTNFR2. The purpose of this study was to analyse the TNF-alpha, TNFRSF1A and TNFRSF1B genes on both mRNA and protein levels in patients with rDD, and to investigate the relationship between TNF-alpha, TNFRSF1A and TNFRSF1B gene expression and cognitive performance. The study comprised 158 subjects: patients with recurrent depressive disorder (n=89) and healthy subjects (n=69). Cognitive function assessment was based on: Trail Making Test, The Stroop Test, Verbal Fluency Test and Auditory Verbal Learning Test. Both mRNA and protein expression levels of all genes were significantly higher in rDD subjects when compared to healthy controls. No statistically significant correlations were observed between the analysed variables in both the rDD group and the HS test group. The only exception was noticed in the HS test group, where increased expression of TNFRSF1A and TNFRSF1B gene negatively affected the performance of the AVLT test. However, statistically significant correlations between TNF, TNFRSF1A, TNFRSF1B mRNA gene expression levels and all the neuropsychological tests used in the survey for the entire group were observed. Conclusions: 1.The results of our study show increased expression of the TNF, TNFRSF1A and TNFRSF1B genes on both mRNA and protein levels in depression. 2. Elevated expression of TNF-alpha, TNFRSF1A and TNFRSF1B negatively correlates with cognitive efficiency: working memory, executive functions, attention, auditory-verbal memory, effectiveness of learning processes and verbal fluency.