Prefrontal alterations in GABAergic and glutamatergic gene expression in relation to depression and suicide

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Abstract

People that committed suicide were reported to have enhanced levels of gene transcripts for synaptic proteins in their prefrontal cortex (PFC). Given the close association of suicide with major depressive disorder (MDD), we here assessed whether these changes are related to suicide or rather to depression per se.

We used quantitative PCR to determine mRNA levels of 32 genes encoding for proteins directly involved in glutamatergic or GABAergic synaptic transmission in postmortem samples of the anterior cingulate cortex (ACC) and the dorsolateral PFC (DLPFC). Seventy-two brain samples from 3 groups of subjects were derived from the Stanley Medical Research Institute (SMRI): i) patients with MDD who committed suicide (MDD-S), ii) MDD patients who died of non-suicidal causes (MDD-NS) and iii) age-matched, non-psychiatric control subjects.

In the ACC, a significantly enhanced expression of genes related to glutamatergic or GABAergic synaptic transmission was found only in MDD-S patients, whereas in MDD-NS patients, decreased levels for these transcripts were found. Moreover, in the DLPFC, expression of these genes was decreased in MDD-S, relative to MDD-NS patients, whereas both groups showed increased expression compared to control subjects.

In conclusion, our findings indicate that MDD is associated with increases in GABA and glutamate related genes in the DLPFC (irrespective of suicide), while in the ACC, the increase in GABA and glutamate related genes may relate to suicide, rather than to MDD per se.

Introduction

Major depressive disorder (MDD) is a serious and disabling psychiatric illness that affects 121 million individuals worldwide, and is predicted to be the second most common cause of disability, after heart disease, by 2020 (Baune et al., 2007). MDD is also the most common psychiatric diagnosis associated with suicide. Up to 15% of those who are clinically depressed eventually commit suicide, and more than half of all people who commit suicide meet the criteria for depressive disorder (Alsalman and Alansari, 2016; Cavanagh et al., 2003). Several studies on a relationship between monoaminergic neurotransmission, depression and suicide have emerged in the past decades. However, both the limited efficacy and the delayed onset of the therapeutic effects of selective serotonin reuptake inhibitors (SSRIs), the most commonly prescribed antidepressant drugs, raise doubts as to whether the monoaminergic system is indeed in general a primary affected system in depression (Lawrence et al., 2017; Thase et al., 2005; Trivedi et al., 2006).

In recent years, increasing evidence suggests that, in addition to hypothalamic neuroendocrine changes (Bao et al., 2008; Qi et al., 2013a; Swaab et al., 2005), an impaired balance between inhibition and excitation within the prefrontal cortex (PFC) and related limbic brain circuitry is involved in MDD, probably mediated by altered gamma-aminobutyric acid (GABA) and glutamate neurotransmission (Gao and Bao, 2011; Ghosal et al., 2017). Large-scale gene array studies in post-mortem tissue have provided strong support for alterations in GABAergic and glutamatergic neurotransmission in depression. For instance, Choudary and colleagues demonstrated significant down-regulation of SLC1A2 and SLC1A3, and up-regulation of several glutamate and GABA-A receptor subunits by using microarray analysis from MDD patients (Choudary et al., 2005).

Later, altered glutamate related genes, SLC1A2, SLC1A3 and GLUL were also found in the MDD patients by microarray and confirmed by quantitative real-time PCR (Q-PCR) and in situ hybridization (Bernard et al., 2011). Another study also demonstrates significant dysregulation of glutamate receptor subunit genes GRIA1 and GRIA3 in the subjects diagnosed with MDD by microarrays and a subgroup of identified genes was confirmed by Q-PCR (Duric et al., 2013). Moreover, morphometric studies have reported a reduced density and size of cortical neurons (Bernstein et al., 2016; Chana et al., 2003; Rajkowska et al., 1999), an effect that has been attributed to alterations in interneurons in some (Maciag et al., 2010; Rajkowska et al., 2007) but not all studies (Cotter et al., 2002; Lucassen et al., 2014). In particular the PFC has received considerable attention in recent years given its role in inhibitory control, emotions and mood, and prominent changes in depression and suicide (Fuster, 2008; Kekesi et al., 2012; Qi et al., 2013a, 2013b; Zhang et al., 2013).

As post-mortem studies have often been inconsistent, the exact molecular mechanisms underlying the aetiology and pathophysiology of depression and suicide, and factors that distinguish these, have so far remained obscure. One critical issue, however, for interpreting discrepancies between existing studies is the different case-control matching strategies. For instance, many studies that claimed to determine molecular alterations in relation to depression had selected depressed patient groups in which most patients had committed suicide, and compared these to non-psychiatric controls (Bernard et al., 2011; Deschwanden et al., 2011; Kimoto et al., 2015; Kunii et al., 2015; Martins-de-Souza et al., 2012; Matosin et al., 2014; Shelton et al., 2011). Without an adequate comparison to a disease control group, consisting of depressed patients who did not commit suicide, it is impossible to determine whether the reported alterations are due to depression or to suicide. On the other hand, studies that claimed to show changes in relation to suicide per se, often compared suicide cases to matched controls without any psychiatric disorder (Du et al., 2014; Kekesi et al., 2012; Lopez et al., 2014; Pandey et al., 2013; Poulter et al., 2008; Schiavone et al., 2016; Sequeira et al., 2012; Valdizan et al., 2010), thus disregarding the fact that the majority of suicide cases suffer from psychiatric disorders, including depression, anxiety, substance abuse, schizophrenia or personality disorders (Hawton and van Heeringen, 2009).

To investigate whether the aspect of suicide is relevant for the gene expression changes in depression reported before by others, we previously studied a group of well-documented depressed patients who did not commit suicide, and found that surprisingly few GABA and glutamate-related genes had changed in expression in the prefrontal cortex (PFC) (Zhao et al., 2012). This suggested that the alterations reported in this brain area before, may be related to suicide rather than to depression per se. Furthermore, we recently found indications that depressed patients who committed suicide show different expression patterns of genes related to the glutamate-glutamine cycle (Zhao et al., 2016) and of stress related molecules, such as corticotropin-releasing hormone (CRH) and nitric oxide synthase (NOS), than depressed patients who died of causes other than suicide (Zhao et al., 2015).

Here, we follow up on these initial studies in a larger, well-characterized cohort from the Stanley Medical Research Institute (SMRI). We determined the expression patterns of genes involved in different aspects of both the GABA and glutamate pathways, comparing transcript levels from MDD patients who died of suicide, to MDD patients who died of other causes, and to matched controls without a neuropsychiatric disorder. Our results show that changes in the genes involved in glutamatergic and GABAergic neurotransmission may be related either to suicide or to depression per se, depending on the brain area studied.

Section snippets

Material from the Stanley Medical Research Institute (SMRI)

Brain samples were collected from the SMRI (Bethesda, MD, USA). Permission to use the brain material was provided by the next of kin. Diagnoses were made according to the Diagnostic and Statistical Manual of Mental Disorders (DSM) IV (American Psychiatric Association, 1994). All brains were examined microscopically to exclude cases with pathological signs of neurodegeneration or other lesions. Exclusion criteria included anyone over age 70, anyone with a history of seizures or other

Transcription of genes encoding glutamatergic synapse markers

As an indication for changes in excitatory synaptic transmission in the PFC of MDD patients, we analysed Q-PCR values of 16 gene transcripts that encode proteins characteristic for glutamatergic synapses. The glutamatergic markers include genes encoding: AMPA-receptor subunits GRIA1, GRIA2, GRIA3, GRIA4; kainate-receptor subunit GRIK1; NMDA-receptor subunits GRIN1, GRIN2A, GRIN2B; metabotropic glutamate receptors GRM1 (mGluR1), GRM2 (mGluR2), GRM3 (mGluR3); glutaminase (GLS); vesicular

Discussion

Several studies have suggested an increased expression of genes involved in synaptic transmission in the PFC of MDD patients (Choudary et al., 2005; Sequeira et al., 2007, 2009). However, since a large proportion of the MDD patients in these studies were suicide victims, it was unclear whether these gene changes were due to MDD or related to suicide. In brain material of the well-characterized SMRI cohort, we found the expression of both glutamate- and GABA-related genes to be increased in the

Conflict of interest

None to declare.

Acknowledgments

Postmortem brain tissue was donated by The Stanley Medical Research Institute Brain Collection. We are indebted to Dr. Maree Webster for providing us with the brain material and patient information. We thank Unga Unmehopa for her technical help, Wilma Verweij for critical reading of the manuscript. This investigation was supported by project (10CDP037) of the Royal Netherlands Academy of Arts and Sciences. PJL is supported by the Dutch Brain Foundation.

References (90)

  • S. Ghosal et al.

    Prefrontal cortex GABAergic deficits and circuit dysfunction in the pathophysiology and treatment of chronic stress and depression

    Curr. Opin. Behav. Sci.

    (2017)
  • T. Gos et al.

    Suicide and depression in the quantitative analysis of glutamic acid decarboxylase-Immunoreactive neuropil

    J. Affect. Disord.

    (2009)
  • K. Hawton et al.

    Suicide

    Lancet

    (2009)
  • L.C. Houtepen et al.

    Acute stress effects on GABA and glutamate levels in the prefrontal cortex: a 7T 1H magnetic resonance spectroscopy study

    NeuroImage. Clin.

    (2017)
  • R. Lee et al.

    Cerebrospinal fluid GABA concentration: relationship with impulsivity and history of suicidal behavior, but not aggression, in human subjects

    J. Psychiatr. Res.

    (2009)
  • D. Maciag et al.

    Reduced density of calbindin immunoreactive GABAergic neurons in the occipital cortex in major depression: relevance to neuroimaging studies

    Biol. Psychiatr.

    (2010)
  • V.B. Neis et al.

    Agmatine produces antidepressant-like effects by activating AMPA receptors and mTOR signaling

    Eur. Neuropsychopharmacol

    (2016)
  • T. Nishimura et al.

    Altered expression of GABA(A) and GABA(B) receptor subunit mRNAs in the hippocampus after kindling and electrically induced status epilepticus

    Neuroscience

    (2005)
  • G.N. Pandey et al.

    Region-specific alterations in glucocorticoid receptor expression in the postmortem brain of teenage suicide victims

    Psychoneuroendocrinology

    (2013)
  • M.O. Poulter et al.

    GABAA receptor promoter hypermethylation in suicide brain: implications for the involvement of epigenetic processes

    Biol. Psychiatr.

    (2008)
  • X.R. Qi et al.

    Aberrant stress hormone receptor balance in the human prefrontal cortex and hypothalamic paraventricular nucleus of depressed patients

    Psychoneuroendocrinology

    (2013)
  • G. Rajkowska et al.

    Morphometric evidence for neuronal and glial prefrontal cell pathology in major depression

    Biol. Psychiatr.

    (1999)
  • A.D. Stan et al.

    Human postmortem tissue: what quality markers matter?

    Brain Res.

    (2006)
  • D.F. Swaab et al.

    The stress system in the human brain in depression and neurodegeneration

    Ageing Res. Rev.

    (2005)
  • E.M. Valdizan et al.

    alpha(2)-Adrenoceptor functionality in postmortem frontal cortex of depressed suicide victims

    Biol. Psychiatr.

    (2010)
  • S.D. Vannoy et al.

    The relationship between suicide ideation and late-life depression

    Am. J. Geriatr. Psychiatr.

    (2007)
  • J. Zhao et al.

    Gene expression of GABA and glutamate pathway markers in the prefrontal cortex of non-suicidal elderly depressed patients

    J. Affect. Disord.

    (2012)
  • J. Zhao et al.

    Different stress-related gene expression in depression and suicide

    J. Psychiatr. Res.

    (2015)
  • J. Zhao et al.

    Prefrontal changes in the glutamate-glutamine cycle and neuronal/glial glutamate transporters in depression with and without suicide

    J. Psychiatr. Res.

    (2016)
  • D. Zuo et al.

    Existence of glia mitigated ketamine-induced neurotoxicity in neuron-glia mixed cultures of neonatal rat cortex and the glia-mediated protective effect of 2-PMPA

    Neurotoxicology

    (2014)
  • C. Barbui et al.

    Selective serotonin reuptake inhibitors and risk of suicide: a systematic review of observational studies. CMAJ

    Can. Med. Assoc. J.

    (2009)
  • Y. Benjamini et al.

    Controlling the false discovery rate: a practical and powerful approach to multiple testing

    J. Roy. Stat. Soc.

    (1995)
  • R. Bernard et al.

    Altered expression of glutamate signaling, growth factor, and glia genes in the locus coeruleus of patients with major depression

    Mol. Psychiatr.

    (2011)
  • H.G. Bernstein et al.

    Bilaterally reduced claustral volumes in schizophrenia and major depressive disorder: a morphometric postmortem study

    Eur. Arch. Psychiatr. Clin. Neurosci.

    (2016)
  • K.L. Brunson et al.

    Effect of the noncompetitive NMDA antagonists MK-801 and ketamine on the spastic Han-Wistar mutant: a rat model of excitotoxicity

    Dev. Neurosci.

    (2001)
  • J.T. Cavanagh et al.

    Psychological autopsy studies of suicide: a systematic review

    Psychol. Med.

    (2003)
  • P.V. Choudary et al.

    Altered cortical glutamatergic and GABAergic signal transmission with glial involvement in depression

    Proc. Natl. Acad. Sci. U. S. A.

    (2005)
  • A.C. Davison et al.

    Bootstrap Methods and Their Application

    (1997)
  • A. Deschwanden et al.

    Reduced metabotropic glutamate receptor 5 density in major depression determined by [(11)C]ABP688 PET and postmortem study

    Am. J. Psychiatr.

    (2011)
  • N. DiazGranados et al.

    Rapid resolution of suicidal ideation after a single infusion of an N-methyl-D-aspartate antagonist in patients with treatment-resistant major depressive disorder

    J. Clin. Psychiatr.

    (2010)
  • V. Duric et al.

    Altered expression of synapse and glutamate related genes in post-mortem hippocampus of depressed subjects

    Int. J. Neuropsychopharmacol.

    (2013)
  • J.M. Fuster

    The Prefrontal Cortex

    (2008)
  • S.F. Gao et al.

    Corticotropin-releasing hormone, glutamate, and gamma-aminobutyric acid in depression

    Neuroscientist

    (2011)
  • A.L. Gray et al.

    Sex differences in glutamate receptor gene expression in major depression and suicide

    Mol. Psychiatr.

    (2015)
  • B. Haider et al.

    Neocortical network activity in vivo is generated through a dynamic balance of excitation and inhibition

    J. Neurosci.

    (2006)
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