Importance of selected ABCB1 SNPs for the level of severity of depressive symptoms and effectiveness of recurrent depressive disorder therapy

Abstract

The expression level of mRNA and also the function of P-gp are strictly connected with the polymorphic nature of the ABCB1 gene. In this study, we evaluated the association between promoter SNP, i.e. T-129C, three other SNPs investigated earlier and ABCB1 expression in the depression group. To assess the additive significance of these SNPs on clinicopathological features a mathematical model was also built.102 patients suffering from recurrent depressive disorder (rDD) and 94 healthy individuals from a local blood bank were enrolled in this study. ABCB1 gene polymorphism was identified by the RFLP method. The relative level of ABCB1 expression was measured by real-time PCR.For SNP T-129C no statistically significant differences in allele and genotype frequencies between depression and control groups were found (p = 0.3176). There was no statistically significant association between the expression value and 4 studied SNPs in ABCB1 (T-129C, C1236T, G2677T/A and C3435T) or the investigated clinicopathological features. Furthermore, a correlation between the initial HDRS score (lower than 23) and presence of at least 1236 T allele was observed, in particular in combination with 3435 T or 2677 T/A. Mutated allele of each SNP was also significantly associated with declined response to antidepressant therapy, both individually and in combination with others.Results of this study suggest that T-129C does not play an important role in the rDD development. The influence of the studied SNPs on ABCB1 gene expression is still unknown. However, the additive impact of 3 most frequently studied SNPs of ABCB1 on the course of depression and effectiveness of its treatment was confirmed.