Longitudinal alterations in mRNA expression of the BDNF neurotrophin signaling cascade in blood correlate with changes in depression scores in patients undergoing electroconvulsive therapy.

Electroconvulsive therapy (ECT) appears to be the most effective treatment for severe depression. However, its mechanisms of action are incompletely understood. Evidence suggests ECT enhances neuroplasticity and neurogenesis. While studies on ECT-induced neuroplasticity focused on brain-derived neurotrophic factor (BDNF), other factors of the BDNF/TrkB signaling cascade remain underinvestigated. We assessed longitudinal changes in depression scores, serum BDNF protein levels, and mRNA expression of BDNF/TrkB related genes (BDNF, AKT1, ERK1, CREB), NR3C1 and IGF1 in peripheral blood in 19 treatment-resistant depressed patients undergoing ECT. We also analysed DNA methylation patterns at various timepoints to explore possible epigenetic regulation of mRNA expression. Using multilevel regression, we found a negative association between depression scores and blood-based mRNA expression of BDNF/TrkB related genes and NR3C1. Expression of BDNF, ERK1 and NR3C1 increased significantly over time (BDNF: β = 0.0295, p = 0.003; ERK1: β = 0.0170, p = 0.034; NR3C1: β = 0.0035, p = 0.050). For these three genes changes in mRNA expression were highly correlated (R = 0.59 - 0.88) with changes in DNA methylation for multiple CpG sites in the respective genes. Also, serum BDNF protein levels increased across the study period (β = 0.11, p = 0.001). Our findings show that the antidepressant effects of ECT are associated with changes in expression of BDNF and its signaling molecules and that these molecular markers can be detected in peripheral blood. Alterations in DNA methylation could be a key mechanism whereby ECT influences gene expression.