Acute phase plasma proteins are altered by electroconvulsive stimulation

Peripheral proteomic changes after electroconvulsive seizures in a rodent model of non-response to chronic fluoxetine

Major depressive disorder (MDD) is the psychiatric disorder with the highest prevalence in the world. Pharmacological antidepressant treatment (AD), such as selective serotonin reuptake inhibitors [SSRI, i.e., fluoxetine (Flx)] is the first line of treatment for MDD. Despite its efficacy, lack of AD response occurs in numerous patients characterizing Difficult-to-treat Depression. ElectroConvulsive Therapy (ECT) is a highly effective treatment inducing rapid improvement in depressive symptoms and high remission rates of ∼50–63% in patients with pharmaco-resistant depression. Nevertheless, the need to develop reliable treatment response predictors to guide personalized AD strategies and supplement clinical observation is becoming a pressing clinical objective. Here, we propose to establish a proteomic peripheral biomarkers signature of ECT response in an anxio/depressive animal model of non-response to AD. Using an emotionality score based on the analysis complementary behavioral tests of anxiety/depression (Elevated Plus Maze, Novelty Suppressed Feeding, Splash Test), we showed that a 4-week corticosterone treatment (35 μg/ml, Cort model) in C57BL/6JRj male mice induced an anxiety/depressive-like behavior. A 28-day chronic fluoxetine treatment (Flx, 18 mg/kg/day) reduced corticosterone-induced increase in emotional behavior. A 50% decrease in emotionality score threshold before and after Flx, was used to separate Flx-responding mice (Flx-R, n = 18), or Flx non-responder mice (Flx-NR, n = 7). Then, Flx-NR mice received seven sessions of electroconvulsive seizure (ECS, equivalent to ECT in humans) and blood was collected before and after ECS treatment. Chronic ECS normalized the elevated emotionality observed in Flx-NR mice. Then, proteins were extracted from peripheral blood mononuclear cells (PBMCs) and isolated for proteomic analysis using a high-resolution MS Orbitrap. Data are available via ProteomeXchange with identifier PXD037392. The proteomic analysis revealed a signature of 33 peripheral proteins associated with response to ECS (7 down and 26 upregulated). These proteins were previously associated with mental disorders and involved in regulating pathways which participate to the depressive disorder etiology.

Electroconvulsive therapy, changes in immune cell ratios, and their association with seizure quality and clinical outcome in depressed patients

Major Depressive Disorder (MDD) is a major contributor to the global burden of disease. Approximately 30-50% of depressed patients fail to reach remission with standard treatment approaches. Electroconvulsive therapy (ECT) is one of the most effective options for these patients. Its exact therapeutic mechanism remains elusive, and reliable predictors of response are absent in the routine clinical practice. To characterize its mode of action and to facilitate treatment decision-making, we analyzed ECT's acute and chronic effects on various immune cell subsets. For this purpose, blood was withdrawn from depressed patients (n=21) directly before and 15 min after the first and last ECT session, respectively. After isolating peripheral blood mononuclear cells, we investigated defined populations of immune cells and their proportional changes upon ECT treatment using flow cytometry. By these means, we found ECT remitters (R; n=10) and non-remitters (NR; n=11) to differ in their relative proportion of putative immunoregulatory CD56^highCD16^-/dim and cytotoxic CD56^dimCD16⁺ natural killer (NK) cells (CD56^highCD16^-/dim/CD56^dimCD16⁺: R=0.064(±0.005), NR=0.047(±0.005), p<0.05; linear mixed models) and thus in their NK cell cytotoxicity. NK cell cytotoxicity was further increased after a single ECT session (before=0.066(±0.005), after=0.045(±0.005), p<0.001) and was associated with ECT quality parameters (maximum sustained coherence: r²=0.389, β=-0.656, p<0.001) and long-term BDI-II rating changes (r²=0.459, β=-0.726, p<0.05; both linear regression analysis). To conclude, particular NK cell subsets seem to be involved in ECT's acute effect and its clinical outcome. Due to the limited number of patients participating in our pilot study, future approaches are required to replicate our findings.

Electroconvulsive therapy modulates plasma pigment epithelium-derived factor in depression: a proteomics study

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression, yet its mechanism of action is not fully understood. Peripheral blood proteomic analyses may offer insights into the molecular mechanisms of ECT. Patients with a major depressive episode were recruited as part of the EFFECT-Dep trial (enhancing the effectiveness of electroconvulsive therapy in severe depression; ISRCTN23577151) along with healthy controls. As a discovery-phase study, patient plasma pre-/post-ECT (n=30) was analyzed using 2-dimensional difference in gel electrophoresis and mass spectrometry. Identified proteins were selected for confirmation studies using immunodetection methods. Samples from a separate group of patients (pre-/post-ECT; n=57) and matched healthy controls (n=43) were then used to validate confirmed changes. Target protein mRNA levels were also assessed in rat brain and blood following electroconvulsive stimulation (ECS), the animal model of ECT. We found that ECT significantly altered 121 protein spots with 36 proteins identified by mass spectrometry. Confirmation studies identified a post-ECT increase (P<0.01) in the antiangiogenic and neuroprotective mediator pigment epithelium-derived factor (PEDF). Validation work showed an increase (P<0.001) in plasma PEDF in depressed patients compared with the controls that was further increased post-ECT (P=0.03). PEDF levels were not associated with mood scores. Chronic, but not acute, ECS increased PEDF mRNA in rat hippocampus (P=0.02) and dentate gyrus (P=0.03). This study identified alterations in blood levels of PEDF in depressed patients and further alterations following ECT, as well as in an animal model of ECT. These findings implicate PEDF in the biological response to ECT for depression.