The innate immune system and neurogenesis as modulating mechanisms of electroconvulsive therapy in pre-clinical studies.

BACKGROUND: Electroconvulsive therapy (ECT) is a powerful and fast-acting anti-depressant strategy, often used in treatment-resistant patients. In turn, patients with treatment-resistant depression often present an increased inflammatory response. The impact of ECT on several pathophysiological mechanisms of depression has been investigated, with a focus which has largely been on cellular and synaptic plasticity. Although changes in the immune system are known to influence neurogenesis, these processes have principally been explored independently from each other in the context of ECT. OBJECTIVE: The aim of this review was to compare the time-dependent consequences of acute and chronic ECT on concomitant innate immune system and neurogenesis-related outcomes measured in the central nervous system in pre-clinical studies. RESULTS: During the few hours following acute electroconvulsive shock (ECS), the expression of the astrocytic reactivity marker glial fibrillary acidic protein (GFAP) and inflammatory genes, such as cyclooxygenase-2 (COX2), were significantly increased together with the neurogenic brain-derived neurotrophic factor (BDNF) and cell proliferation. Similarly, chronic ECS caused an initial upregulation of the same astrocytic marker, immune genes, and neurogenic factors. Interestingly, over time, inflammation appeared to be dampened, while glial activation and neurogenesis were maintained, after either acute or chronic ECS. CONCLUSION: Regardless of treatment duration ECS would seemingly trigger a rapid increase in inflammatory molecules, dampened over time, as well as a long-lasting activation of astrocytes and production of growth and neurotrophic factors, leading to cell proliferation. This suggests that both innate immune system response and neurogenesis might contribute to the efficacy of ECT.

The immunomodulatory effect of ketamine in depression.

Major depression is one of the most frequent psychiatric conditions. Despite many available treatment methods, more than 30% of patients do not achieve remission, even after trying several antidepressants and augmentation strategies. S-enantiomer of ketamine, well-known anesthetic and analgesic, has been recently approved by Food and Drug Administration in the intranasal form as a new generation antidepressant. However, the mechanism in which ketamine reduces depressive symptoms in treatment-resistant depression patients is still not completely understood. There are several theories explaining how ketamine might reduce depressive symptoms, which have been described in detail; one of them is immunomodulatory effect of ketamine, according to the inflammatory theory of depression. In the review authors present and summarize studies showing ketamine effect on human immune system ex vivo and in vitro, including changes in cytokine levels, number, ratio and activity of various immune cell population and the correlation with clinical improvement in depressive symptoms. Most of the results confirm the anti-inflammatory effect of ketamine. There are only a few studies in the population of patients suffering from depression receiving ketamine, focused on correlation between immunological changes and clinical outcome of the therapy; further studies of that area are neccesary for understanding the immunomodulatory effect of ketamine in depression.

Antidepressant treatment resistance is associated with increased inflammatory markers in patients with major depressive disorder.

BACKGROUND: One third of patients with major depressive disorder (MDD) fail to respond to currently available antidepressant medications. Inflammation may contribute to treatment non-response through effects on neurotransmitter systems relevant to antidepressant efficacy. In post-hoc analyses, increased concentrations of inflammatory markers prior to treatment predict poor antidepressant response. However, limited data exists on whether depressed patients with multiple failed treatment trials in their current episode of depression exhibit increased inflammation. METHODS: Plasma concentrations of inflammatory markers were measured in unmedicated, medically stable patients with MDD (n = 98) and varying numbers of adequate antidepressant treatment trials in the current depressive episode as measured by the Massachusetts General Hospital Antidepressant Treatment Response Questionnaire. Covariates including age, sex, race, education, body mass index (BMI) and severity of depression were included in statistical models where indicated. RESULTS: A significant relationship was found between number of failed treatment trials and tumor necrosis factor (TNF), soluble TNF receptor 2 (sTNF-R2) and interleukin (IL)-6 (all p < 0.05 in multivariate analyses). Post hoc pairwise comparisons with correction for multiple testing revealed that patients with 3 or more failed trials in the current episode had significantly higher plasma TNF, sTNF-R2 and IL-6 compared to individuals with 0 or 1 trial (all p < 0.05). High sensitivity c-reactive protein was also associated with a greater number of treatment failures, but only in models with BMI excluded. CONCLUSIONS: Measuring inflammatory markers and targeting inflammation or its downstream mediators may be relevant for depressed patients with multiple failed antidepressant treatment trials in their current depressive episode.

Antidepressant efficacy of electroconvulsive therapy is associated with a reduction of the innate cellular immune activity in the cerebrospinal fluid in patients with depression.

OBJECTIVES: A bidirectional link between the antidepressant effects of electroconvulsive therapy (ECT) and the modulation of the immune system has been proposed. To elucidate the interplay between antidepressant treatment and macrophage/microglia activation in humans, we performed a study on the effects of the antidepressant treatment by ECT on markers of macrophage/microglia activation in patients with depression. METHODS: We measured six different markers (IL-6, neopterin, sCD14, sCD163 MIF and MCP1) of macrophage/microglia activation in the cerebrospinal fluid (CSF) and blood of 12 patients with a severe, treatment-resistant depressive episode before and after a course of ECT. RESULTS: Some markers in the CSF of remitters were reduced after the ECT course and differed from non-remitters, but no differences were found before and after ECT independently from the antidepressant efficacy. CSF baseline levels of some markers could predict the reduction of depressive psychopathology during ECT. Higher CSF levels indicating increased macrophage/microglia activation at baseline predicted a better treatment response to ECT. CONCLUSIONS: Although the sample size was small, our data suggest that macrophages/microglia are involved in the pathophysiology of major depression and that antidepressant efficacy by ECT might be partly explained by the modulation of the innate immune system within the brain.

Electroconvulsive therapy, depression, the immune system and inflammation: A systematic review.

BACKGROUND: The management and treatment of major depressive disorder are major public health challenges, the lifetime prevalence of this illness being 4.4%-20% in the general population. Major depressive disorder and treatment resistant depression appear to be, in part, related to a dysfunction of the immune response. Among the treatments for depression ECT occupies an important place. The underlying cerebral mechanisms of ECT remain unclear. OBJECTIVES/HYPOTHESIS: The aim of this review is to survey the potential actions of ECT on the immuno-inflammatory cascade activated during depression. METHODS: A systematic search of the literature was carried out, using the bibliographic search engines PubMed and Embase. The search covered articles published up until october 2017. The following MESH terms were used: Electroconvulsive therapy AND (inflammation OR immune OR immunology). RESULTS: Our review shows that there is an acute immuno-inflammatory response immediately following an ECT session. There is an acute stress reaction. Studies show an increase in the plasma levels of cortisol and of interleukins 1 and 6. However, at the end of the course of treatment, ECT produces, in the long term, a fall in the plasma level of cortisol, a reduction in the levels of TNF alpha and interleukin 6. LIMITATIONS: One of the limitations of this review is that a large number of studies are relatively old, with small sample sizes and methodological bias. CONCLUSION: Advances in knowledge of the immuno-inflammatory component of depression seem to be paving the way towards models to explain the mechanism of action of ECT.

Altered peripheral immune profiles in treatment-resistant depression: response to ketamine and prediction of treatment outcome.

A subset of patients with depression have elevated levels of inflammatory cytokines, and some studies demonstrate interaction between inflammatory factors and treatment outcome. However, most studies focus on only a narrow subset of factors in a patient sample. In the current study, we analyzed broad immune profiles in blood from patients with treatment-resistant depression (TRD) at baseline and following treatment with the glutamate modulator ketamine. Serum was analyzed from 26 healthy control and 33 actively depressed TRD patients free of antidepressant medication, and matched for age, sex and body mass index. All subjects provided baseline blood samples, and TRD subjects had additional blood draw at 4 and 24 h following intravenous infusion of ketamine (0.5 mg kg-1). Samples underwent multiplex analysis of 41 cytokines, chemokines and growth factors using quantitative immunoassay technology. Our a priori hypothesis was that TRD patients would show elevations in canonical pro-inflammatory cytokines; analyses demonstrated significant elevation of the pro-inflammatory cytokine interleukin-6. Further exploratory analyses revealed significant regulation of four additional soluble factors in patients with TRD. Several cytokines showed transient changes in level after ketamine, but none correlated with treatment response. Low pretreatment levels of fibroblast growth factor 2 were associated with ketamine treatment response. In sum, we found that patients with TRD demonstrate a unique pattern of increased inflammatory mediators, chemokines and colony-stimulating factors, providing support for the immune hypothesis of TRD. These patterns suggest novel treatment targets for the subset of patients with TRD who evidence dysregulated immune functioning.

Predicting response to psychopharmacological treatment: survey of recent results.

INTRODUCTION: Treatment with antidepressants and antipsychotics, though effective, is unspecific as agents that differ greatly in their biochemical and pharmacological actions have virtually the same efficacy. Half of the patients with initial improvement show incomplete response, while a large proportion of patients exhibit a refractory clinical picture which is resistant to all treatment modalities. METHODS: Our analyses were based on a reference study of 2,848 depressive inpatients under monotherapeutic treatment with 7 different antidepressants or placebo, along with a naturalistic study of depressive and schizophrenic patients (296 inpatients, 363 outpatients) under today's "standard" polypharmaceutic treatment regimens. RESULTS: The empirical data suggested the following predictors of response: (1) severity at baseline, (2) early onset of improvement, (3) unwanted side-effects, and (4) medical comorbidity. A combination of these predictors with Therapeutic Drug Monitoring (TDM) methods has direct clinical relevance. DISCUSSION: Evidence-based approaches to personalized treatment help improving the unsatisfactory situation patients and clinicians are faced with, given today's incomplete treatments and the fact that the mechanisms by which antidepressants and antipsychotics ultimately exert their therapeutic effects are only marginally understood.