Neural markers of symptomatic improvement during antidepressant therapy in severe depression: subgenual cingulate and visual cortical responses to sad, but not happy, facial stimuli are correlated with changes in symptom score

Resting state activity in the ventral cingulate may be an important neural marker of symptomatic improvement in depression. The number of task related functional magnetic resonance imaging (fMRI) studies correlating blood oxygenation level dependent (BOLD) response with symptomatic improvement is limited and methodologies are still evolving. We measured BOLD responses to sad and happy facial stimuli in 12 severely depressed individuals in the early stages of antidepressant treatment (Time 1) and 12 weeks later (Time 2) using event-related fMRI. We calculated correlations between temporal changes in BOLD response and changes in symptom scores. Most subjects improved markedly by Time 2. At Time 1, depression severity correlated positively with responses to sad stimuli in the right visual cortex, subgenual cingulate, anterior temporal pole and hippocampus and correlated negatively with responses to happy stimuli in left visual cortex and right caudate. Decreases in individual effect sizes of right subgenual cingulate and right visual cortical responses to sad, but not happy, facial stimuli were correlated with decreases in symptom scores. There are contrasting cortical and subcortical responses to sad and happy stimuli in severe depression. Responses to sad stimuli show the strongest correlates of clinical improvement, particularly in the subgenual cingulate.     

抑郁症信号转导通路研究

长期给予抗抑郁剂可以增加脑内cAMP依赖性PKA的表达水平,继而激活cAMP反应元件结合蛋白。CREB可以调节脑源性神经生长因子的表达。大量的研究表明cAMP和BDNF是多种抗抑郁剂的共同通路,现就此进行综述,探讨其与抗抑郁剂之间的关系,为精神药理和新药研发提供依据。     

Antidepressant effect on connectivity of the mood-regulating circuit: an FMRI study.

The mechanisms by which antidepressant-induced neurochemical changes lead to physiological changes in brain circuitry and ultimately an antidepressant response remain unclear. This study investigated the effects of sertraline, a selective serotonin reuptake inhibitor antidepressant, on corticolimbic connectivity, using functional magnetic resonance imaging (fMRI). In all, 12 unmedicated unipolar depressed patients and 11 closely matched healthy control subjects completed two fMRI scanning sessions at baseline and after 6 weeks. Depressed patients received treatment with sertraline between the two sessions. During each fMRI session, subjects first completed a conventional block-design experiment. Next, connectivity between cortical and limbic regions was measured using correlations of low-frequency blood oxygen level-dependent (BOLD) fluctuations (LFBF) during continuous exposure to neutral, positive, and negative pictures. At baseline, depressed patients had decreased corticolimbic LFBF correlations compared to healthy subjects during the resting state and on exposure to emotionally valenced pictures. At rest and on exposure to neutral and positive pictures, LFBF correlation between the anterior cingulate cortex and limbic regions was significantly increased in patients after treatment. However, on exposure to negative pictures, corticolimbic LFBF correlations remained decreased in depressed patients. The results of this study are consistent with the hypothesis that antidepressant treatment may increase corticolimbic connectivity, thereby possibly increasing the regulatory influence of cortical mood-regulating regions over limbic regions.     

High baseline BDNF serum levels and early psychopathological improvement are predictive of treatment outcome in major depression

Rationale

Major depressive disorder has been associated with low serum levels of brain-derived neurotrophic factor (sBDNF), which is functionally involved in neuroplasticity. Although sBDNF levels tend to normalize following psychopathological improvement with antidepressant treatment, it is unclear how closely sBDNF changes are associated with treatment outcome.

Objectives

To examine whether baseline sBDNF or early changes in sBDNF are predictive of response to therapy.

Methods

Twenty-five patients with major depressive disorder underwent standardized treatment with duloxetine. Severity of depression, measured by the Hamilton Depression Rating Scale, and sBDNF were assessed at baseline, and after 1, 2, and 6 weeks of treatment. Therapy outcome after 6 weeks was defined as response (≥50 % reduction in baseline Hamilton Depression Rating score) and remission (Hamilton Depression Rating score <8). The predictive values for treatment outcome of baseline sBDNF, and early (i.e., ≤2 weeks) changes in sBDNF and Hamilton Depression Rating score were also assessed.

Results

At baseline, sBDNF correlated with Hamilton Depression Rating scores. Treatment response was associated with a higher baseline sBDNF concentration, and a greater Hamilton Depression Rating score reduction after 1 and 2 weeks. A greater early rise in sBDNF correlated with a decreased early Hamilton Depression Rating score reduction.

Conclusions

Even though higher baseline sBDNF levels are associated with more severe depression, they may reflect an increased capacity to respond to treatment. In contrast, changes in sBDNF over the full course of treatment are not associated with psychopathological improvement.     

Can we increase the speed and efficacy of antidepressant treatments? Part II. Glutamatergic and RNA interference strategies

In the second part we focus on two treatment strategies that may overcome the main limitations of current antidepressant drugs. First, we review the experimental and clinical evidence supporting the use of glutamatergic drugs as fast-acting antidepressants. Secondly, we review the involvement of microRNAs (miRNAs) in the pathophysiology of major depressive disorder (MDD) and the use of small RNAs (e.g.., small interfering RNAs or siRNAs) to knockdown genes in monoaminergic and non-monoaminergic neurons and induce antidepressant-like responses in experimental animals.The development of glutamatergic agents is a promising venue for antidepressant drug development, given the antidepressant properties of the non-competitive NMDA receptor antagonist ketamine. Its unique properties appear to result from the activation of AMPA receptors by a metabolite [(2 S,6 S;2 R,6 R)-hydroxynorketamine (HNK)] and mTOR signaling. These effects increase synaptogenesis in prefrontal cortical pyramidal neurons and enhance serotonergic neurotransmission via descending inputs to the raphe nuclei. This view is supported by the cancellation of ketamine's antidepressant-like effects by inhibition of serotonin synthesis.We also review existing evidence supporting the involvement of miRNAs in MDD and the preclinical use of RNA interference (RNAi) strategies to target genes involved in antidepressant response. Many miRNAs have been associated to MDD, some of which e.g., miR-135 targets genes involved in antidepressant actions. Likewise, SSRI-conjugated siRNA evokes faster and/or more effective antidepressant-like responses. Intranasal application of sertraline-conjugated siRNAs directed to 5-HT_1A receptors and SERT evoked much faster changes of pre- and postsynaptic antidepressant markers than those produced by fluoxetine.     

The role of neurotrophic factors in adult hippocampal neurogenesis, antidepressant treatments and animal models of depressive-like behavior

Major depressive disorder (MDD) is characterized by structural and neurochemical changes in limbic structures, including the hippocampus, that regulate mood and cognitive functions. Hippocampal atrophy is observed in patients with depression and this effect is blocked or reversed by antidepressant treatments. Brain-derived neurotrophic factor and other neurotrophic/growth factors are decreased in postmortem hippocampal tissue from suicide victims, which suggests that altered trophic support could contribute to the pathophysiology of MDD. Preclinical studies demonstrate that exposure to stress leads to atrophy and cell loss in the hippocampus as well as decreased expression of neurotrophic/growth factors, and that antidepressant administration reverses or blocks the effects of stress. Accumulating evidence suggests that altered neurogenesis in the adult hippocampus mediates the action of antidepressants. Chronic antidepressant administration upregulates neurogenesis in the adult hippocampus and this cellular response is required for the effects of antidepressants in certain animal models of depression. Here, we review cellular (e.g. adult neurogenesis) and behavioral studies that support the neurotrophic/neurogenic hypothesis of depression and antidepressant action. Aberrant regulation of neuronal plasticity, including neurogenesis, in the hippocampus and other limbic nuclei may result in maladaptive changes in neural networks that underlie the pathophysiology of MDD.     

Serial vagus nerve stimulation functional MRI in treatment-resistant depression.

Vagus nerve stimulation (VNS) therapy has shown antidepressant effects in open acute and long-term studies of treatment-resistant major depression. Mechanisms of action are not fully understood, although clinical data suggest slower onset therapeutic benefit than conventional psychotropic interventions. We set out to map brain systems activated by VNS and to identify serial brain functional correlates of antidepressant treatment and symptomatic response. Nine adults, satisfying DSM-IV criteria for unipolar or bipolar disorder, severe depressed type, were implanted with adjunctive VNS therapy (MRI-compatible technique) and enrolled in a 3-month, double-blind, placebo-controlled, serial-interleaved VNS/functional MRI (fMRI) study and open 20-month follow-up. A multiple regression mixed model with blood oxygenation level dependent (BOLD) signal as the dependent variable revealed that over time, VNS therapy was associated with ventro-medial prefrontal cortex deactivation. Controlling for other variables, acute VNS produced greater right insula activation among the participants with a greater degree of depression. These results suggest that similar to other antidepressant treatments, BOLD deactivation in the ventro-medial prefrontal cortex correlates with the antidepressant response to VNS therapy. The increased acute VNS insula effects among actively depressed participants may also account for the lower dosing observed in VNS clinical trials of depression compared with epilepsy. Future interleaved VNS/fMRI studies to confirm these findings and further clarify the regional neurobiological effects of VNS.     

Antidepressant and anxiolytic effects of the proprietary Chinese medicine Shexiang Baoxin pill in mice with chronic unpredictable mild stress

Depression and anxiety often co-occur with cardiac diseases. The Shexiang Baoxin pill (SBP) is a proprietary Chinese medicine initially used to treat cardiac conditions. This study explored whether SBP has antidepressant and anxiolytic effects in addition to hormonal and psychotropic mechanisms. Mice underwent 6 weeks of chronic unpredictable mild stress (CUMS) to induce depression- and anxiety-like behavior. During the 6-week experiment, mice received SBP at intragastric doses of 20.25 mg/kg or 40.5 mg/kg daily. Animals were then tested for depression in sucrose preference, forced-swimming, and tail suspension paradigms, and for anxiety in open field and elevated plus maze tests. Both SBP doses significantly reduced anhedonic behavior in the sucrose preference test; the high SBP dose also increased the number of entries into the central zone of the open field. SBP-treated mice had markedly lower blood levels of corticotrophin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) than stressed mice treated with vehicle. Either low- or high-dose SBP reversed stress-induced reductions of norepinephrine (NE) and dopamine (DA) metabolites and the expression levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and glial cell-derived neurotrophic factor (GDNF) in related brain regions. These results suggest that SBP could prevent and alleviate prolonged stress-induced anhedonia and anxiety in association with its suppression of the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, modulation of brain monoamine neurotransmitter metabolism and neurotrophins. SBP may be particularly suitable for the management of depressive and anxiety disorders in patients with cardiac conditions.     

Role of neurotrophic factors in depression

Major depression is associated with reduced volumes in the hippocampus and prefrontal cortex, whereas antidepressant treatments promote several forms of neuronal plasticity, including neurogenesis, synaptogenesis and neuronal maturation, in the hippocampus. Several neurotrophic factors are associated with depression or antidepressant action. Stress suppresses brain-derived neurotrophic factor (BDNF) synthesis in the hippocampus, at least partially through a sustained modification of chromatin structure. Essentially all antidepressant treatments increase BDNF synthesis and signaling in the hippocampus and prefrontal cortex. This signaling is required for the behavioral effects of antidepressant drugs in rodents, and increased BDNF levels in the hippocampus mimic the behavioral effects of antidepressants. However, injection of BDNF into the mesolimbic dopamine pathway produces an opposing depression-like response. One hypothesis emerging from these data proposes that mood disorders reflect failed function of critical neuronal networks, whereas a gradual network recovery through activity-dependent neuronal plasticity induces the antidepressant effect. Neurotrophic factors themselves do not control mood, but they act as necessary tools in the activity-dependent modulation of networks, the physiological function of which determines how a plastic change influences mood.     

S100B and response to treatment in major depression: a pilot study.

S100B is a protein which exerts both detrimental and neurotrophic effects, depending on its concentration in brain tissue. An increase of S100B in micromolar concentrations is observed in traumatic brain conditions and is associated with poor outcome. Micromolar levels of extracellular S100B in vitro may have deleterious effects. However, in nanomolar concentrations S100B has multiple neurotrophic effects in vitro may in vivo be regarded as a hallmark of neuroprotective efforts. This pilot study addresses the hypothesis that S100B serum concentrations may be of predictive validity for the response to antidepressant treatment in patients with major depression. S100B plasma levels were determined in 25 patients with major depression and 25 matched healthy controls using an immunofluorimetric sandwich assay. S100B plasma levels were significantly higher in major depressive patients than in healthy controls and positively correlated with treatment response after 4 weeks of treatment. In a linear regression model, a significant predictive effect was found only for S100B and severity of depressive symptoms upon admission. These results suggest that neuroprotective functions of S100B counterbalance neurodegenerative mechanisms that are involved in the pathophysiology of major depression and in the response to antidepressant treatment.     

Effects of age on susceptibility to the induction of depressive behavior and imipramine in rats

Effects of age on depression vulnerability and antidepressant efficacy remain an important concern. Here, we show, by using a novel animal model of depressive behavior, that young rats (4 weeks old) are more vulnerable to the induction of depressive behavior than older ones (3, 6, and 14 months old). The induced depressive behavior in different ages of rats, however, was similarly sensitive to imipramine. A direct cerebroventricular administration of brain-derived neurotrophic factor was also sufficient to produce an antidepressant-like effect in the rats of different ages. These results suggest that although different ages of rats exhibit different sensitivity to the induction of depressive behavior, the induced depressive behavior may involve the same type of underlying abnormal neuropathophysiology in the brain and is sensitive to imipramine and brain-derived neurotrophic factor treatment.     

Brain-derived neurotrophic factor gene polymorphisms: influence on treatment response phenotypes of major depressive disorder

Brain-derived neurotrophic factor (BDNF), a member of the nerve growth factor family of neurotrophins, has pivotal roles in neuronal survival, proliferation, and synaptic plasticity in the brain. Both clinical and pharmacological studies have implicated the common single nucleotide polymorphism (SNP) at position 196, Val66Met in the pathophysiology of major depressive disorder (MDD), and antidepressant response. However, inconsistent results were found between Val66Met (rs6265) polymorphism and treatment response phenotypes in genetic association studies. The functional Val66Met polymorphism and seven other tagging SNP markers selected to capture the major allelic variations across BDNF locus were analyzed in depressed patients, treated with antidepressants, and 76 control patients. Two hundred and six patients with Diagnostic and Statistical Manual of Mental Disorders-IV MDD were recruited for this study and genotyped for eight BDNF tagging SNPs (rs11030096, rs925946, rs10501087,rs6265, rs12273363, rs908867, rs1491850, and rs1491851)to investigate the functional impact of genotypes/haplotypes in the susceptibility of depression and on treatment response. None of the eight SNPs, including the rs6265, were significantly associated with MDD after permutation correction. However, we found an association for rs10501087, rs6265 with nonresponse to antidepressant treatment (corrected permutation P:0.03599; 0.0399 and power: 0.1420; 0.1492, respectively).Analysis of each two-marker, three-marker, and four-marker sliding window haplotypes showed significance in haplotype combinations. Especially rs10501087 (C), rs6265 (A), and rs149,1850 (C) together or with the other SNP haplotypes showed a similar pattern in all treatment response phenotypes. Despite the limited power of analysis, our results suggest that these three SNPs may play a role in antidepressant treatment response phenotypes in MDD.     

BDNF plasma levels after antidepressant treatment with sertraline and transcranial direct current stimulation: Results from a factorial,randomized, sham-controlled trial

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation intervention that modifies cortical excitability according to the stimulation parameters. Preclinical and clinical studies in healthy volunteers suggest that tDCS induces neuroplastic alterations of cortical excitability, which might explain its clinical effects in major depressive disorder (MDD). We therefore examined whether tDCS, as compared to the antidepressant sertraline, increases plasma brain-derived neurotrophic factor (BDNF) levels, a neurotrophin associated with neuroplasticity. Patients (n=73) with major depressive disorder were randomized to active/sham tDCS and sertraline/placebo (four groups) in this 6-week, double-blind, placebo-controlled trial. We measured BDNF plasma levels at baseline and endpoint, observing no significant changes of BDNF levels after treatment. In addition, no significant changes were observed in responders and non-responders as well as no relationships between BDNF levels and clinical and psychopathological variables related to depression. Thus, in one of the few placebo-controlled trials evaluating BDNF changes over an antidepressant treatment course, we did not observe BDNF increase regardless of clinical improvement in depressed patients. Regarding tDCS, BDNF plasma levels might not be a good candidate biomarker to evaluate depression improvement or be a predictor of response in patients treated with tDCS, as our results showed that BDNF increase was not necessary to induce clinical response. Finally, our findings do not support a relationship between BDNF and improvement of depression.     

Hemodynamic and metabolic changes induced by cocaine in anesthetized rat observed with multimodal functional MRI

Rationale Physiological changes (such as heart rate and respiration rate) associated with strong pharmacological stimuli could change the blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) mapping signals, independent of neural activity.Objectives This study investigates whether the physiological changes per se associated with systemic cocaine administration (1 mg/kg) contaminate the BOLD fMRI signals by measuring BOLD and cerebral blood flow (CBF) fMRI and estimating the cerebral metabolic rate of oxygen (CMRO₂) changes.Materials and methods BOLD and CBF fMRI was performed, and changes in CMRO₂ were estimated using the BOLD biophysical model.Results After systemic cocaine administration, blood pressure, heart rate, and respiration rate increased, fMRI signals remained elevated after physiological parameters had returned to baseline. Cocaine induced changes in the BOLD signal within regions of the reward pathway that were heterogeneous and ranged from −1.2 to 5.4%, and negative changes in BOLD were observed along the cortical surface. Changes in CBF and estimated CMRO₂ were heterogeneous and positive throughout the brain, ranging from 14 to 150% and 10 to 55%, respectively.Conclusions This study demonstrates a valuable tool to investigate the physiological and biophysical basis of drug action on the central nervous system, offering the means to distinguish the physiological from neural sources of the BOLD fMRI signal.     

Prediction of antidepressant treatment response from gray matter volume across diagnostic categories

Dysfunctional limbic, paralimbic and prefrontal brain circuits represent neural substrates of major depression that are targeted by pharmacotherapy. In a high resolution structural magnetic resonance imaging (MRI) study we investigated the potential of variability of the cortex volume to predict the response to antidepressant treatment among patients with major depression. We enrolled 167 patients participating in the Munich Antidepressant Response Signature (MARS) study and employed voxel based morphometry to investigate covariation of gray matter (GM) maps with changes of depression severity over 5 weeks. Larger left hippocampal and bilateral posterior cingulate GM volumes and lower right temporolateral GM volumes were associated with beneficial treatment response. Subcallosal/orbitofrontal GM volumes were associated with treatment response mainly through gender-by-region interactions. A hippocampal/temporolateral composite marker proved robust in both first episode and recurrent unipolar patients and in bipolar patients. Compared with 92 healthy controls, abnormally low volumes were only detected in the left hippocampal area, particularly in recurrent unipolar patients. These findings indicate that variability of the cortex volume of specific brain areas is associated with different response to antidepressants. In addition, hippocampal findings recursively link together unfavorable treatment response and progressive hippocampal structural changes in recurrent depression.     

Brain-derived neurotrophic factor and antidepressant action: another piece of evidence from pharmacogenetics

EVALUATION OF: Gratacòs M, Soria V, Urretavizcaya M et al.: A brain-derived neurotrophic factor (BDNF) haplotype is associated with antidepressant treatment outcome in mood disorders. Pharmacogenomics J. 8, 101-112 (2008). The neurotrophin hypothesis of depression and antidepressant drug action postulates that reduced activity of neurotrophic factors, particularly brain-derived neurotrophic factor (BDNF), plays an important role in the pathogenesis of major depression, and that its restoration may represent a critical mechanism underlying antidepressant therapeutic effect. This hypothesis is supported by numerous animal studies; however, evidence from clinical studies is lacking. This study is the first to use both single-marker as well as haplotype analysis to test the effect of genetic variants of BDNF on the therapeutic effects of antidepressant treatment in mood disorder. Among eight BDNF TagSNPs tested, one allele (rs908867) is associated with antidepressant response, with heterozygote carriers showing a better response than homozygous analog. The authors also identified a haplotype associated with the therapeutic response. This study provides clinical evidence to support the role of BDNF in antidepressant therapeutic mechanisms. However, further work is needed to confirm the findings, for several reasons. First, the study included not only major depression but also bipolar disorder patients; second, various antidepressants were used in this study, which could affect patients' responses; third, the frequency of the haplotype associated with treatment response is rare; and fourth, previous studies of the effects of single BDNF polymorphisms on antidepressant action have reported conflicting findings. Several suggestions for further work are discussed below.     

小补心汤总黄酮提取物对慢性应激模型大鼠的抗抑郁作用

目的古代文献记载小补心汤(XBXT,由代赭石、旋覆花、竹叶和淡豆豉4味中药组成)有缓解抑郁情绪的作用。应用大鼠慢性应激模型探讨XBXT总黄酮(XBXT-2)的抗抑郁作用及可能机制。方法连续28d给予大鼠一系列慢性不可预测性的刺激建立慢性应激模型,同时给予XBXT-2(25或50mg·kg-1·d-1,ig)或丙米嗪(10mg·kg-1·d-1,ig),采用蔗糖饮水实验、开场活动实验和新奇抑制摄食实验观察抗抑郁行为效应;采用酶联免疫吸附实验检测血清皮质酮含量,Western蛋白印迹法检测海马糖皮质激素受体(GR)α/β、脑源性神经营养因子(BDNF)、磷酸化cAMP反应元件结合蛋白(p-CREB)、细胞外信号调节激酶(ERK1/2)及其磷酸化形式(p-ERK1/2)蛋白表达水平。结果XBXT-2或丙米嗪可逆转慢性应激大鼠蔗糖饮水偏嗜度降低、自发活动减少及新奇抑制摄食潜伏期延长,显著降低应激大鼠血清皮质酮含量,上调海马GRα/β,BDNF,p-CREB和p-ERK1/2蛋白表达。结论XBXT-2对慢性应激大鼠具有抗抑郁作用,其机制可能与抑制下丘脑-垂体-肾上腺轴的过度激活,上调海马BDNF相关的神经营养通路中蛋白表达有关。     

Serum levels of brain‐derived neurotrophic factor in comorbidity of depression and alcohol dependence

Alcohol dependence is often comorbid with depression. The purpose of the present study was to compare serum brain‐derived neurotrophic factor (BDNF) levels between depressive patients with and without alcohol dependence. Our subjects were 16 inpatients (M/F: 13/3, age: 48 ± 8 years) at our university hospital who met the DSM‐IV‐TR criteria for both major depressive disorder and alcohol dependence and whose Hamilton Rating Scale for Depression (HAM‐D) scores were at least 15. Twenty sex‐ and age‐matched depressive patients and 20 healthy subjects were also examined. Serum BDNF levels in the depressive patients with (9.0 ± 4.3 ng/ml) and without (9.8 ± 5.2 ng/ml) alcohol dependence were significantly lower than those in the healthy subjects (21.1 ± 7.0 ng/ml); however, no significant difference was found in the serum BDNF levels of depressive patients with and without alcohol dependence. Eight of the 16 (50%) depressive patients suffering from both depression and alcohol dependence responded to 8 weeks of treatment with antidepressant drugs which significantly increased their serum BDNF levels. These results suggest that the serum BDNF level is a useful biological marker for depression in patients with alcohol dependence. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of MPEP treatment on brain-derived neurotrophic factor gene expression

Treatment with most antidepressants induces expression of the gene coding for brain-derived neurotrophic factor (BDNF) in the hippocampus (and cerebral cortex). Recent data indicate antidepressant-like activity of group I mGlu receptor (mGluR1 and mGluR5) antagonists in animal tests/models. We now report that chronic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective mGlu5 receptor antagonist, increased hippocampal but reduced cortical BDNF mRNA level (Northern blot). Desipramine, a classic antidepressant, increased BDNF mRNA level in both examined brain regions. This is the first demonstration that an antagonist of mGlu5 receptors, like a majority of well-established antidepressants, induces hippocampal BDNF gene expression. A significance of MPEP ability to reduce cortical BDNF needs further study. Nevertheless, this observation further indicates a potential antidepressant activity of the group I mGlu receptor antagonists in human depression.