Extracellular matrix abnormalities in the hippocampus of subjects with substance use disorder

Contextual triggers are significant factors contributing to relapse in substance use disorders (SUD). Emerging evidence points to a critical role of extracellular matrix (ECM) molecules as mediators of reward memories. Chondroitin sulfate proteoglycans (CSPGs) are a subset of ECM molecules that form perineuronal nets (PNN) around inhibitory neurons. PNNs restrict synaptic connections and help maintain synapses. Rodent models suggest that modulation of PNNs may strengthen contextual reward memories in SUD. However, there is currently a lack of information regarding PNNs in the hippocampus of people with SUD as well as how comorbidity with major depressive disorder (MDD) may affect PNNs. We used postmortem hippocampal tissues from cohorts of human and nonhuman primates with or without chronic alcohol use to test the hypothesis that PNNs are increased in subjects with SUD. We used histochemical labeling and quantitative microscopy to examine PNNs, and qRT-PCR to examine gene expression for ECM molecules, synaptic markers and related markers. We identified increased densities of PNNs and CSPG-labeled glial cells in SUD, coinciding with decreased expression of the ECM protease matrix metalloproteinase 9 (Mmp9), and increased expression for the excitatory synaptic marker vesicle associated membrane protein 2 (Vamp2). Similar increases in PNNs were observed in monkeys with chronic alcohol self-administration. Subjects with MDD displayed changes opposite to SUD, and subjects with SUD and comorbid MDD had minimal changes in any of the outcome measures examined. Our findings demonstrate that PNNs are increased in SUD, possibly contributing to stabilizing contextual reward memories as suggested by preclinical studies. Our results also point to a previously unsuspected role for CSPG expression in glial cells in SUD. Evidence for increased hippocampal PNNs in SUD suggests that targeting PNNs to weaken contextual reward memories is a promising therapeutic approach for SUD, however comorbidity with MDD is a significant consideration.

Extracellular Matrix Abnormalities in the Hippocampus of Subjects with Substance Use Disorder

Contextual triggers are significant factors contributing to relapse in substance use disorders (SUD). Emerging evidence points to a critical role of extracellular matrix (ECM) molecules as mediators of reward memories. Chondroitin sulfate proteoglycans (CSPGs) are a subset of ECM molecules that form perineuronal nets (PNN) around inhibitory neurons. PNNs restrict synaptic connections and help maintain synapses. Rodent models suggest that modulation of PNNs may strengthen contextual reward memories in SUD. However, there is currently a lack of information regarding PNNs in the hippocampus of people with SUD as well as how comorbidity with major depressive disorder (MDD) may affect PNNs. We used postmortem hippocampal tissues from cohorts of human and nonhuman primates with or without chronic alcohol use to test the hypothesis that PNNs are increased in subjects with SUD. We used histochemical labeling and quantitative microscopy to examine PNNs, and qRT-PCR to examine gene expression for ECM molecules, synaptic markers and related markers. We identified increased densities of PNNs and CSPG-labeled glial cells in SUD, coinciding with decreased expression of the ECM protease matrix metalloproteinase 9 (Mmp9), and increased expression for the excitatory synaptic marker vesicle associated membrane protein 2 (Vamp2). Similar increases in PNNs were observed in monkeys with chronic alcohol self-administration. Subjects with MDD displayed changes opposite to SUD, and subjects with SUD and comorbid MDD had minimal changes in any of the outcome measures examined. Our findings demonstrate that PNNs are increased in SUD, possibly contributing to stabilizing contextual reward memories as suggested by preclinical studies. Our results also point to a previously unsuspected role for CSPG expression in glial cells in SUD. Evidence for increased hippocampal PNNs in SUD suggests that targeting PNNs to weaken contextual reward memories is a promising therapeutic approach for SUD, however comorbidity with MDD is a significant consideration.

The role of premeditation in suicide: Identifying factors associated with increased planning among suicide decedents

INTRODUCTION

Suicide premeditation is a critical factor to consider when assessing suicide risk. Understanding which individuals are more or less likely to plan their suicidal behavior can shed light on how suicidal thoughts turn into actions.

METHOD

The present study used psychological autopsy data to identify factors associated with level of premeditation among 131 adults who died by suicide.

RESULTS

Logistic regression analyses indicated that suicide decedents with higher premeditation scores had higher odds of being diagnosed with a depressive disorder and choosing a violent suicide method, specifically a firearm. Individuals with lower premeditation scores had higher odds of being diagnosed with a polysubstance use disorder.

CONCLUSION

Suicide decedents exhibiting greater premeditation before their deaths were different in several ways from suicide decedents exhibiting less premeditation. A better understanding of suicide premeditation can ultimately aid in the development of improved risk assessments and targeted safety interventions for those struggling with suicidal thoughts.

Markers of elevated oxidative stress in oligodendrocytes captured from the brainstem and occipital cortex in major depressive disorder and suicide

Major depressive disorder (MDD) and suicide have been associated with elevated indices of oxidative damage in the brain, as well as white matter pathology including reduced myelination by oligodendrocytes. Oligodendrocytes highly populate white matter and are inherently susceptible to oxidative damage. Pathology of white matter oligodendrocytes has been reported to occur in brain regions that process behaviors that are disrupted in MDD and that may contribute to suicidal behavior. The present study was designed to determine whether oligodendrocyte pathology related to oxidative damage extends to brain areas outside of those that are traditionally considered to contribute to the psychopathology of MDD and suicide. Relative telomere lengths and the gene expression of five antioxidant-related genes, SOD1, SOD2, GPX1, CAT, and AGPS were measured in oligodendrocytes laser captured from two non-limbic brain areas: occipital cortical white matter and the brainstem locus coeruleus. Postmortem brain tissues were obtained from brain donors that died by suicide and had an active MDD at the time of death, and from psychiatrically normal control donors. Relative telomere lengths were significantly reduced in oligodendrocytes of both brain regions in MDD donors as compared to control donors. Three antioxidant-related genes (SOD1, SOD2, GPX1) were significantly reduced and one was significantly elevated (AGPS) in oligodendrocytes from both brain regions in MDD as compared to control donors. These findings suggest that oligodendrocyte pathology in MDD and suicide is widespread in the brain and not restricted to brain areas commonly associated with depression psychopathology.

Suicide among older adults: Interactions among key risk factors

OBJECTIVE

The present study aimed to understand how key risk factors of older adult suicide interact to ultimately lead to death by suicide using data collected post-mortem.

METHOD

A psychological autopsy was used to gather detailed information about psychiatric diagnosis, medical problems, social isolation, and negative attitudes expressed by the individual during the six months prior to their death. Interviews with next-of-kin, medical and psychiatric records, and the Cumulative Illness Rating Scale for Geriatrics were used. Subjects included 32 older adults who died by suicide and 45 older adults who died by natural causes.

RESULTS

Hopelessness, depression, and negative health attitudes were strongly correlated with suicide. Older age was associated with social isolation, suggesting an indirect relationship with suicide via hopelessness, depression, and negative health attitudes. Physical illness did not increase risk. Multivariate analyses suggested that hopelessness fully mediated the effects of social isolation, negative health attitudes, and depression on suicide.

CONCLUSIONS

Psychological factors played the largest role in suicide deaths compared to social isolation and physical illness. Suicide interventions aimed at older adults should ensure hopelessness, depression, and negative health attitudes are primary targets.

The path not taken: Distinguishing individuals who die by suicide from those who die by natural causes despite a shared history of suicide attempt

OBJECTIVES

This study aimed to identify variables that distinguish suicide risk among individuals with previous suicide attempts.

METHOD

Using psychological autopsy procedures, we evaluated 86 decedents who had at least one lifetime suicide attempt before eventual death by suicide (n = 65) or natural causes (n = 21).

RESULTS

The Suicide Death group was more likely to be male, to have alcohol in the toxicology report at time of death, and to have a depression diagnosis, while the Natural Cause Death group was more likely to have personality disorder traits, a polysubstance use disorder, higher reported health stress, and an antidepressant in the toxicology report at time of death. Hopelessness and ambivalence were found to distinguish between groups during the 6 months before death.

CONCLUSIONS

These findings suggest important differences between individuals with a shared history of a suicide attempt who die by suicide versus natural causes.

Exploring autoantibody signatures in brain tissue from patients with severe mental illness

In recent years, studies have shown higher prevalence of autoantibodies in patients with schizophrenia compared to healthy individuals. This study applies an untargeted and a targeted affinity proteomics approach to explore and characterize the autoantibody repertoire in brain tissues from 73 subjects diagnosed with schizophrenia and 52 control subjects with no psychiatric or neurological disorders. Selected brain tissue lysates were first explored for IgG reactivity on planar microarrays composed of 11,520 protein fragments representing 10,820 unique proteins. Based on these results of ours and other previous studies of autoantibodies related to psychosis, we selected 226 fragments with an average length of 80 amino acids, representing 127 unique proteins. Tissue-based analysis of IgG reactivities using antigen suspension bead arrays was performed in a multiplex and parallel fashion for all 125 subjects. Among the detected autoantigens, higher IgG reactivity in subjects with schizophrenia, as compared to psychiatrically healthy subjects, was found against the glutamate ionotropic receptor NMDA type subunit 2D (anti-GluN2D). In a separate cohort with serum samples from 395 young adults with a wider spectrum of psychiatric disorders, higher levels of serum autoantibodies targeting GluN2D were found when compared to 102 control individuals. By further validating GluN2D and additional potential autoantigens, we will seek insights into how these are associated with severe mental illnesses.

Key role of the 5-HT1A receptor addressing protein Yif1B in serotonin neurotransmission and SSRI treatment

BACKGROUND

Altered function of serotonin receptor 1A (5-HT1AR) has been consistently implicated in anxiety, major depressive disorder and resistance to antidepressants. Mechanisms by which the function of 5-HT1AR (expressed as an autoreceptor in serotonergic raphe neurons and as a heteroreceptor in serotonin [5-HT] projection areas) is altered include regulation of its expression, but 5-HT1AR trafficking may also be involved.

METHODS

We investigated the consequences of the lack of Yif1B (the 5-HT1AR trafficking protein) on 5-HT neurotransmission in mice, and whether Yif1B expression might be affected under conditions known to alter 5-HT neurotransmission, such as anxious or depressive states or following treatment with fluoxetine (a selective serotonin reuptake inhibitor) in humans, monkeys and mice.

RESULTS

Compared with wild-type mice, Yif1B-knockout mice showed a significant decrease in the forebrain density of 5-HT projection fibres and a hypofunctionality of 5-HT1A autoreceptors expressed on raphe 5-HT neurons. In addition, social interaction was less in Yif1B-knockout mice, which did not respond to the antidepressant-like effect of acute fluoxetine injection. In wild-type mice, social defeat was associated with downregulated Yif1B mRNA in the prefrontal cortex, and chronic fluoxetine treatment increased Yif1B expression. The expression of Yif1B was also downregulated in the postmortem prefrontal cortex of people with major depressive disorder and upregulated after chronic treatment with a selective serotonin reuptake inhibitor in monkeys.

LIMITATIONS

We found sex differences in Yif1B expression in humans and monkeys, but not in mice under the tested conditions.

CONCLUSION

These data support the concept that Yif1B plays a critical role in 5-HT1AR functioning and brain 5-HT homeostasis. The opposite changes in its expression observed in anxious or depressive states and after therapeutic fluoxetine treatment suggest that Yif1B might be involved in vulnerability to anxiety and depression, and fluoxetine efficacy.

Label-free proteomics differences in the dorsolateral prefrontal cortex between bipolar disorder patients with and without psychosis

BACKGROUND

Psychosis is common in bipolar disorder (BD) and is related to more severe cognitive impairments. Since the molecular mechanism of BD psychosis is elusive, we conducted this study to explore the proteomic differences associated with BD psychosis in the dorsolateral prefrontal cortex (DLPFC; BA9).

METHODS

Postmortem DLPFC gray matter tissues from five pairs of age-matched male BD subjects with and without psychosis history were used. Tissue proteomes were identified and quantified by label-free liquid chromatography tandem mass spectrometry and then compared between groups. Statistical significance was set at q < 0.40 and Log₂ fold change (Log₂FC) ≥ |1|. Protein groups with differential expression between groups at p < 0.05 were subjected to pathway analysis.

RESULTS

Eleven protein groups differed significantly between groups, including the reduction of tenascin C (q = 0.005, Log₂FC = -1.78), the elevations of synaptoporin (q = 0.235, Log₂FC = 1.17) and brain-specific angiogenesis inhibitor 1-associated protein 3 (q = 0.241, Log₂FC = 2.10) in BD with psychosis. The between-group differences of these proteins were confirmed by Western blots. The top enriched pathways (p < 0.05 with ≥ 3 hits) were the outgrowth of neurons, neuronal cell proliferation, growth of neurites, and outgrowth of neurites, which were all predicted to be upregulated in BD with psychosis.

LIMITATIONS

Small sample size and uncertain relationships of the observed proteomic differences with illness stage and acute psychosis.

CONCLUSIONS

These results suggested BD with psychosis history may be associated with abnormalities in neurodevelopment, neuroplasticity, neurotransmission, and neuromodulation in the DLPFC.

Acute stressors and clinical characteristics differentiate death by suicide, accident, or natural causes among illicit and prescription opiate users

BACKGROUND

Opiate misuse has reached epidemic levels. Prevention efforts depend on distinguishing opiate users from abusers. The current study compared opioid users who died by natural cases, accidents, and suicide using psychological autopsy methods. Groups were compared on substance use characteristics, treatment history, experiences of negative life events, and circumstances at the time of death.

METHODS

Substance use and suicide risk were evaluated using psychological autopsy methods in 63 decedents with positive toxicology for opiates at death divided into three groups: adults dying by suicide (n = 19), accident (n = 19), and natural causes (n = 25). Groups were compared on several dependent measures, using chi-square analyses to examine categorical variables and one-way analyses of variance (ANOVA) to examine continuous variables.

RESULTS

Individuals who died by suicide were similar in many ways to adults who died by an accidental overdose. However, suicide completers were more likely to have struggled with severe depression, and previously attempted suicide, whereas the accidental overdose sample was more likely to display a chronic pattern of severe drug abuse.

CONCLUSIONS

The current study helps to distinguish between opiate users who are at risk for death by an accidental or intentional overdose. In the ongoing opiate crisis, clinicians must understand the risk of overdose and the nuances of accidental behaviors compared to purposeful ones. Signs of suicidal planning, relevant psychopathology, and ongoing life stress may be useful points of intervention for stopping the increasing number of deaths among opiate users.

Differential Dorsolateral Prefrontal Cortex Proteomic Profiles of Suicide Victims with Mood Disorders

Suicide is a major public health concern; nevertheless, its neurobiology remains unknown. An area of interest in suicide research is the dorsolateral prefrontal cortex (DLPFC). We aimed to identify altered proteins and potential biological pathways in the DLPFC of individuals who died by suicide employing mass spectrometry-based untargeted proteomics. Postmortem DLPFC from age-matched male suicide mood disorder cases (n = 5) and non-suicide mood disorder cases (n = 5) were compared. The proteins that differed between groups at false discovery rate (FDR) adjusted p-values (Benjamini-Hochberg-Yekutieli) <0.3 and Log2 fold change (FC) >|0.4| were considered statistically significant and were subjected to pathway analysis by Qiagen Ingenuity software. Thirty-three of the 5162 detected proteins showed significantly altered expression levels in the suicide cases and two of them after adjustment for body mass index. The top differentially expressed protein was potassium voltage-gated channel subfamily Q member 3 (KCNQ3) (Log2FC = -0.481, p = 2.10 × 10-09, FDR = 5.93 × 10-06), which also showed a trend to downregulation in Western blot (p = 0.045, Bonferroni adjusted p = 0.090). The most notably enriched pathway was the GABA receptor signaling pathway (p < 0.001). Here, we report a reduction trend of KCNQ3 levels in the DLPFC of male suicide victims with mood disorders. Further studies with a larger sample size and equal sex representation are needed.

BACK TO BASICS: HOPELESSNESS AS THE MEDIATING FACTOR FOR COMPLETED SUICIDE AMONG OLDER ADULTS

Individuals 65 years and older are at high risk for completing suicide. Though risk factors have been established in the literature, the dominant atheoretical approach has left the field at an impasse. The present study aimed to integrate core risk factors of hopelessness, depression, physical illness, and social isolation by proposing a biopsychosocial framework of older adult suicide. A psychological autopsy was used to compare individuals 65 years and older who died either by suicide (n = 32) or natural causes (n = 45). Structural equation modeling results suggested that hopelessness was the only factor directly associated with suicide (B = .01, β = 0.84, SE = 13.31, p ≤ .001), fully mediating the relationships between suicide and social isolation, negative attitudes about physical health, and depression. The proposed model adequately fit the data, explaining 71% of the variance in cause of death. Advanced age (75+ years) moderately increased social isolation, which weakly increased hopelessness, contributing to suicide in a smaller magnitude than expected. Though individuals in the advanced age group had a wider range of physical illnesses, this did not increase risk. Rather, negative perceptions of health increased risk for all individuals 65 years and older via depression and hopelessness, irrespective of the presence of impairing physical illness. Findings support the claim that hopelessness plays a pivotal role in the progression from suicidal ideation to completion among older adults. Directly targeting hopelessness could help prevent at-risk older adults from acting on their thoughts of suicide.

Genome-wide DNA methylomic differences between dorsolateral prefrontal and temporal pole cortices of bipolar disorder

Dorsolateral prefrontal cortex (DLPFC) and temporal pole (TP) are brain regions that display abnormalities in bipolar disorder (BD) patients. DNA methylation - an epigenetic mechanism both heritable and sensitive to the environment - may be involved in the pathophysiology of BD. To study BD-associated DNA methylomic differences in these brain regions, we extracted genomic DNA from the postmortem tissues of Brodmann Area (BA) 9 (DLPFC) and BA38 (TP) gray matter from 20 BD, ten major depression (MDD), and ten control age-and-sex-matched subjects. Genome-wide methylation levels were measured using the 850 K Illumina MethylationEPIC BeadChip. We detected striking differences between cortical regions, with greater numbers of between-brain-region differentially methylated positions (DMPs; i.e., CpG sites) in all groups, most pronounced in the BD group, and with substantial overlap across groups. The genes of DMPs common to both BD and MDD (hypothetically associated with their common features such as depression) and those distinct to BD (hypothetically associated with BD-specific features such as mania) were enriched in pathways involved in neurodevelopment including axon guidance. Pathways enriched only in the BD-MDD shared list pointed to GABAergic dysregulation, while those enriched in the BD-only list suggested glutamatergic dysregulation and greater impact on synaptogenesis and synaptic plasticity. We further detected group-specific between-brain-region gene expression differences in ODC1, CALY, GALNT2, and GABRD, which contained significant between-brain-region DMPs. In each brain region, no significant DMPs or differentially methylated regions (DMRs) were found between diagnostic groups. In summary, the methylation differences between DLPFC and TP may provide molecular targets for further investigations of genetic and environmental vulnerabilities associated with both unique and common features of various mood disorders and suggest directions of future development of individualized treatment strategies.

Common-variant associations with fragile X syndrome

Fragile X syndrome is rare but a prominent cause of intellectual disability. It is usually caused by a de novo mutation that occurs on multiple haplotypes and thus would not be expected to be detectible using genome-wide association (GWA). We conducted GWA in 89 male FXS cases and 266 male controls, and detected multiple genome-wide significant signals near FMR1 (odds ratio = 8.10, P = 2.5 × 10^-10). These findings withstood robust attempts at falsification. Fine-mapping yielded a minimum P = 1.13 × 10^-14, but did not narrow the interval. Comprehensive functional genomic integration did not provide a mechanistic hypothesis. Controls carrying a risk haplotype had significantly longer FMR1 CGG repeats than controls with the protective haplotype (P = 4.75 × 10^-5), which may predispose toward increases in CGG number to the premutation range over many generations. This is a salutary reminder of the complexity of even "simple" monogenetic disorders.

Risk-taking behaviors and stressors differentially predict suicidal preparation, non-fatal suicide attempts, and suicide deaths

Negative life events are elevated in suicidal populations. Diathesis-stress and kindling effects models suggest different mechanisms by which negative life events increase suicide risk. Different forms of negative life events - risk-taking behaviors and stressors - may have different effects on non-fatal suicide attempts and suicide. We assessed the effects of risk-taking behaviors and stressors on suicide, history of non-fatal suicide attempts, and active preparation for suicide in a sample of adults who died by suicide or other causes (N = 377). Psychological autopsy procedures using family member interviews and collateral record review were used to complete a risk-taking behaviors composite measure from the Structured Interview for DSM-IV Personality Disorders, the Modified Life Experiences Scale, and the planning subscale of the Suicide Intent Scale. Stressors were significantly associated with death by suicide, even when accounting for demographic and diagnostic characteristics. Risk-taking behaviors were significantly associated with non-fatal suicide attempts, even when accounting for demographic and diagnostic characteristics. Suicide decedents who did not actively prepare for suicide showed significantly higher risk-taking scores than suicide decedents who actively planned for suicide. Our results suggest that risk-taking behaviors and stressors impact suicide risk through separate mechanisms. Risk-taking behaviors may represent a longstanding vulnerability to act impulsively on suicidal thoughts. Stressors may impact risk for fatal suicidal behaviors in mood disordered populations.

Altered Expression of Phox2 Transcription Factors in the Locus Coeruleus in Major Depressive Disorder Mimicked by Chronic Stress and Corticosterone Treatment In Vivo and In Vitro

Phox2a and Phox2b are two homeodomain transcription factors playing a pivotal role in the development of noradrenergic neurons during the embryonic period. However, their expression and function in adulthood remain to be elucidated. Using human postmortem brain tissues, rat stress models and cultured cells, this study aimed to examine the alteration of Phox2a and Phox2b expression. The results show that Phox2a and Phox2b are normally expressed in the human locus coeruleus (LC) in adulthood. Furthermore, the levels of Phox2a protein and mRNA and protein levels of Phox2b were significantly elevated in the LC of brain donors that suffered from the major depressive disorder, as compared to age-matched and psychiatrically normal control donors. Fischer 344 rats subjected to chronic social defeat showed higher mRNA and protein levels of Phox2a and Phox2b in the LC, as compared to non-stressed control rats. In rats chronically administered oral corticosterone, mRNA and protein levels of Phox2b, but not Phox2a, in the LC were significantly increased. In addition, the corticosterone-induced increase in Phox2b protein was reversed by simultaneous treatment with either mifepristone or spironolactone. Exposing SH-SY5Y cells to corticosterone significantly increased expression of Phox2a and Phox2b, which was blocked by corticosteroid receptor antagonists. Taken together, these experiments reveal that Phox2 genes are expressed throughout the lifetime in the LC of humans and Fischer 344 rats. Alterations in their expression may play a role in major depressive disorder and possibly other stress-related disorders through their modulatory effects on the noradrenergic phenotype.

Evaluation of chromatin accessibility in prefrontal cortex of individuals with schizophrenia

Schizophrenia genome-wide association studies have identified >150 regions of the genome associated with disease risk, yet there is little evidence that coding mutations contribute to this disorder. To explore the mechanism of non-coding regulatory elements in schizophrenia, we performed ATAC-seq on adult prefrontal cortex brain samples from 135 individuals with schizophrenia and 137 controls, and identified 118,152 ATAC-seq peaks. These accessible chromatin regions in the brain are highly enriched for schizophrenia SNP heritability. Accessible chromatin regions that overlap evolutionarily conserved regions exhibit an even higher heritability enrichment, indicating that sequence conservation can further refine functional risk variants. We identify few differences in chromatin accessibility between cases and controls, in contrast to thousands of age-related differential accessible chromatin regions. Altogether, we characterize chromatin accessibility in the human prefrontal cortex, the effect of schizophrenia and age on chromatin accessibility, and provide evidence that our dataset will allow for fine mapping of risk variants.

Genome-wide association analyses identify 44 risk variants and refine the genetic architecture of major depression

Major depressive disorder (MDD) is a common illness accompanied by considerable morbidity, mortality, costs, and heightened risk of suicide. We conducted a genome-wide association meta-analysis based in 135,458 cases and 344,901 controls and identified 44 independent and significant loci. The genetic findings were associated with clinical features of major depression and implicated brain regions exhibiting anatomical differences in cases. Targets of antidepressant medications and genes involved in gene splicing were enriched for smaller association signal. We found important relationships of genetic risk for major depression with educational attainment, body mass, and schizophrenia: lower educational attainment and higher body mass were putatively causal, whereas major depression and schizophrenia reflected a partly shared biological etiology. All humans carry lesser or greater numbers of genetic risk factors for major depression. These findings help refine the basis of major depression and imply that a continuous measure of risk underlies the clinical phenotype.

Altered neuro-inflammatory gene expression in hippocampus in major depressive disorder

Major Depressive Disorder (MDD) is a common psychiatric disorder for which available medications are often not effective. The high prevalence of MDD and modest response to existing therapies compels efforts to better understand and treat the disorder. Decreased hippocampal volume with increasing duration of depression suggests altered gene expression or even a decrease in neurogenesis. Tissue punches from the dentate gyrus were collected postmortem from 23 subjects with MDD and 23 psychiatrically-normal control subjects. Total RNA was isolated and whole transcriptome paired-end RNA-sequencing was performed using an Illumina NextSeq 500. For each sample, raw RNA-seq reads were aligned to the Ensembl GRCh38 human reference genome. Analysis revealed 30 genes differentially expressed in MDD compared to controls (FDR<0.05). Down-regulated genes included several with inflammatory function (ISG15, IFI44L, IFI6, NR4A1/Nur-77) and GABBR1 while up-regulated genes included several with cytokine function (CCL2/MCP-1), inhibitors of angiogenesis (ADM, ADAMTS9), and the KANSL1 gene, a histone acetyltransferase. Similar analyses of specific subsets of MDD subjects (suicide vs. non-suicide, single vs. multiple episodes) yielded similar, though not identical, results. Enrichment analysis identified an over-representation of inflammatory and neurogenesis-related (ERK/MAPK) signaling pathways significantly altered in the hippocampal dentate gyrus in MDD. Together, these data implicate neuro-inflammation as playing a crucial role in MDD. These findings support continued efforts to identify adjunctive approaches towards the treatment of MDD with drugs including anti-inflammatory and neuroprotective properties.

MicroRNA-21: Expression in oligodendrocytes and correlation with low myelin mRNAs in depression and alcoholism

MiR-21 is a microRNA implicated in cancer, development, and cardiovascular diseases and expressed in the central nervous system (CNS), especially after injury. However, the cellular expression of miR-21 in the adult CNS has not been clearly established either in mice or human subjects, while its alteration in psychiatric disorders is unknown. MiR-21 expression was characterized in reporter mice expressing β-galactosidase (LacZ) under the endogenous miR-21 promoter (miR-21/LacZ). Brain co-localization of miR-21/LacZ with specific neural markers was examined by double immunofluorescence in reporter mice, while extent of immunostaining for myelin basic protein and PDGFRα was determined in miR-21 knockout and wild-type mice. Levels of miR-21, and mRNAs of selected miR-21 targets, miR-21 regulator STAT3 and myelin-related proteins were measured by qRT-PCR in the white matter (WM) adjacent to the left postmortem orbitofrontal cortex (OFC) of human subjects with major depressive disorder (MDD), alcoholism, comorbid MDD plus alcoholism (MDA) and non-psychiatric control subjects. MiR-21/LacZ was highly expressed in cell bodies of WM and myelinated portions of gray matter (GM). Labeled cell bodies were identified as oligodendrocytes, while miR-21/LacZ was barely detectable in other cell types. MiR-21, as well as the mRNAs of several myelin-related proteins, were reduced in the WM of subjects with MDD and alcoholism. MiR-21 positively correlated with mRNA of myelin-related proteins and astrocytic GFAP. High expression of miR-21 in adult oligodendrocytes and the correlation of miR-21 decrease with mRNA of some myelin proteins, regulator STAT3, and oligodendrocyte-related transcription factors suggest an involvement of miR-21 in WM alterations in depression and alcoholism.

Length of axons expressing the serotonin transporter in orbitofrontal cortex is lower with age in depression

Studies of major depressive disorder (MDD) in postmortem brain tissue report enhanced binding to inhibitory serotonin-1A autoreceptors in midbrain dorsal raphe and reductions in length of axons expressing the serotonin transporter (SERT) in dorsolateral prefrontal cortex. The length density of axons expressing SERT in the orbitofrontal cortex (OFC) was determined in 18 subjects with MDD and 17 age-matched control subjects. A monoclonal antibody was used to immunohistochemically label the SERT in fixed sections of OFC. The 3-dimensional length density of SERT-immunoreactive (ir) axons in layer VI of OFC was estimated. The age of subjects with MDD was negatively correlated with SERT axon length (r=-0.77, p<0.0005). The significant effect of age persisted when removing four depressed subjects with an antidepressant medication present at the time of death, or when removing nine depressed subjects that had a recent prescription for an antidepressant medication. Neither gender, tissue pH, postmortem interval, 5-HTTLPR genotype, time in fixative, nor death by suicide had a significant effect on axon length. The age-related decrease in SERT-ir axon length in MDD may reflect pathology of ascending axons passing through deep white matter hyperintensities. Greater length of axons expressing SERT in younger subjects with MDD may result in a significant deficit in serotonin availability in OFC.

Elevated DNA Oxidation and DNA Repair Enzyme Expression in Brain White Matter in Major Depressive Disorder

BACKGROUND

Pathology of white matter in brains of patients with major depressive disorder (MDD) is well-documented, but the cellular and molecular basis of this pathology are poorly understood.

METHODS

Levels of DNA oxidation and gene expression of DNA damage repair enzymes were measured in Brodmann area 10 (BA10) and/or amygdala (uncinate fasciculus) white matter tissue from brains of MDD (n=10) and psychiatrically normal control donors (n=13). DNA oxidation was also measured in BA10 white matter of schizophrenia donors (n=10) and in prefrontal cortical white matter from control rats (n=8) and rats with repeated stress-induced anhedonia (n=8).

RESULTS

DNA oxidation in BA10 white matter was robustly elevated in MDD as compared to control donors, with a smaller elevation occurring in schizophrenia donors. DNA oxidation levels in psychiatrically affected donors that died by suicide did not significantly differ from DNA oxidation levels in psychiatrically affected donors dying by other causes (non-suicide). Gene expression levels of two base excision repair enzymes, PARP1 and OGG1, were robustly elevated in oligodendrocytes laser captured from BA10 and amygdala white matter of MDD donors, with smaller but significant elevations of these gene expressions in astrocytes. In rats, repeated stress-induced anhedonia, as measured by a reduction in sucrose preference, was associated with increased DNA oxidation in white, but not gray, matter.

CONCLUSIONS

Cellular residents of brain white matter demonstrate markers of oxidative damage in MDD. Medications that interfere with oxidative damage or pathways activated by oxidative damage have potential to improve treatment for MDD.

Zinc transporters protein level in postmortem brain of depressed subjects and suicide victims

BACKGROUND

Major depressive disorder (MDD) is a serious psychiatric illness, associated with an increasing rate of suicide. The pathogenesis of depression may be associated with the disruption of zinc (Zn) homeostasis. In the brain, several proteins that regulate Zn homeostasis are present, including Zn transporters (ZnTs) which remove Zn from the cytosol. The present study was designed to investigate whether depression and suicide are associated with alterations in the expression of the ZnTs protein.

METHODS

Protein levels of ZnT1, ZnT3, ZnT4, ZnT5 and ZnT6 were measured in postmortem brain tissue from two different cohorts. Cohort A contained 10 subjects diagnosed with MDD (7 were suicide victims) and 10 psychiatrically-normal control subjects and cohort B contained 11 non-diagnosed suicide victims and 8 sudden-death control subjects. Moreover, in cohort A we measured protein level of NMDA (GluN2A subunit), AMPA (GluA1 subunit) and 5-HT1A receptors and PSD-95. Proteins were measured in the prefrontal cortex (PFC) using Western blotting. In addition, Zn concentration was measured using a voltammetric method.

RESULTS

There was a significant increase in protein levels of ZnT1, ZnT4, ZnT5 in the PFC in MDD, relative to control subjects, while ZnT3 protein level was decreased in MDD. There was no significant difference in the Zn concentration in the PFC between control and MDD subjects. Similarly, in the PFC of suicide victims (non-diagnosed), an increase in protein levels of ZnT1, ZnT4, ZnT5 and ZnT6 was observed. Conversely, protein levels of ZnT3 were decreased in both suicide victims and subjects with MDD, in comparison with control subjects. There was also a significant decrease in the protein level of GluA1, GluN2A, PSD-95 and 5-HT1A in MDD.

CONCLUSIONS

Our studies suggest that alterations in Zn transport proteins are associated with the pathophysiology of MDD and suicide.

Opioid precursor protein isoform is targeted to the cell nuclei in the human brain

BACKGROUND

Neuropeptide precursors are traditionally viewed as proteins giving rise to small neuropeptide molecules. Prodynorphin (PDYN) is the precursor protein to dynorphins, endogenous ligands for the κ-opioid receptor. Alternative mRNA splicing of neuropeptide genes may regulate cell- and tissue-specific neuropeptide expression and produce novel protein isoforms. We here searched for novel PDYN mRNA and their protein product in the human brain.

METHODS

Novel PDYN transcripts were identified using nested PCR amplification of oligo(dT) selected full-length capped mRNA. Gene expression was analyzed by qRT-PCR, PDYN protein by western blotting and confocal imaging, dynorphin peptides by radioimmunoassay. Neuronal nuclei were isolated using fluorescence-activated nuclei sorting (FANS) from postmortem human striatal tissue. Immunofluorescence staining and confocal microscopy was performed for human caudate nucleus.

RESULTS

Two novel human PDYN mRNA splicing variants were identified. Expression of one of them was confined to the striatum where its levels constituted up to 30% of total PDYN mRNA. This transcript may be translated into ∆SP-PDYN protein lacking 13 N-terminal amino acids, a fragment of signal peptide (SP). ∆SP-PDYN was not processed to mature dynorphins and surprisingly, was targeted to the cell nuclei in a model cellular system. The endogenous PDYN protein was identified in the cell nuclei in human striatum by western blotting of isolated neuronal nuclei, and by confocal imaging.

CONCLUSIONS AND GENERAL SIGNIFICANCE

High levels of alternatively spliced ∆SP-PDYN mRNA and nuclear localization of PDYN protein suggests a nuclear function for this isoform of the opioid peptide precursor in human striatum.

Up-Regulation of PKR Signaling Pathway by Ethanol Displays an Age of Onset-Dependent Relationship

BACKGROUND

Ethanol (EtOH) neurotoxicity can result in devastating effects on brain and behavior by disrupting homeostatic signaling cascades and inducing cell death. One such mechanism involves double-stranded RNA activated protein kinase (PKR), a primary regulator of protein translation and cell viability in the presence of a virus or other external stimuli. EtOH-mediated up-regulation of interferon-gamma (IFN-γ; the oxidative stress-inducible regulator of PKR), PKR, and its target, p53, are still being fully elucidated.

METHODS

Using Western blot analysis, immunofluorescence, and linear regression analyses, changes in the IFN-γ-PKR-p53 pathway following chronic EtOH treatment in the frontal cortex of rodents were examined. The role of PKR on cell viability was also assessed in EtOH-treated cells using PKR overexpression vector and PKR inhibitor (PKRI).

RESULTS

In rats chronically fed EtOH, PKR, phosphorylated PKR (p-PKR), IFN-γ, and p53 were significantly increased following chronic EtOH exposure. Linear regression revealed a significant correlation between IFN-γ and p-PKR protein levels, as well as p-PKR expression and age of EtOH exposure. Overexpression of PKR resulted in greater cell death, while use of PKRI enhanced cell viability in EtOH-treated cells.

CONCLUSIONS

Chronic EtOH exposure activates the IFN-γ-PKR-p53 pathway in the frontal cortex of rodents. p-PKR expression is greater in brains of rodents exposed to EtOH at earlier ages compared to later life, suggesting a mechanism by which young brains could be more susceptible to EtOH-related brain injury. PKR and p-PKR were also colocalized in neurons and astrocytes of rats. This study provides additional insight into biochemical mechanisms underlying alcohol use disorder related neuropathology and warrants further investigation of PKR as a potential pharmacotherapeutic target to combat EtOH-related neurotoxicity, loss of protein translation and brain injury.

Binge ethanol exposure increases the Krüppel-like factor 11-monoamine oxidase (MAO) pathway in rats: Examining the use of MAO inhibitors to prevent ethanol-induced brain injury

Binge drinking induces several neurotoxic consequences including oxidative stress and neurodegeneration. Because of these effects, drugs which prevent ethanol-induced damage to the brain may be clinically beneficial. In this study, we investigated the ethanol-mediated KLF11-MAO cell death cascade in the frontal cortex of Sprague-Dawley rats exposed to a modified Majchowicz 4-day binge ethanol model and control rats. Moreover, MAO inhibitors (MAOIs) were investigated for neuroprotective activity against binge ethanol. Binge ethanol-treated rats demonstrated a significant increase in KLF11, both MAO isoforms, protein oxidation and caspase-3, as well as a reduction in BDNF expression in the frontal cortex compared to control rats. MAOIs prevented these binge ethanol-induced changes, suggesting a neuroprotective benefit. Neither binge ethanol nor MAOI treatment significantly affected protein expression levels of the oxidative stress enzymes, SOD2 or catalase. Furthermore, ethanol-induced antinociception was enhanced following exposure to the 4-day ethanol binge. These results demonstrate that the KLF11-MAO pathway is activated by binge ethanol exposure and MAOIs are neuroprotective by preventing the binge ethanol-induced changes associated with this cell death cascade. This study supports KLF11-MAO as a mechanism of ethanol-induced neurotoxicity and cell death that could be targeted with MAOI drug therapy to alleviate alcohol-related brain injury. Further examination of MAOIs to reduce alcohol use disorder-related brain injury could provide pivotal insight to future pharmacotherapeutic opportunities.

Density of GFAP-immunoreactive astrocytes is decreased in left hippocampi in major depressive disorder

Neuroimaging and postmortem studies of subjects with major depressive disorder (MDD) reveal smaller hippocampal volume with lengthening duration of illness. Pathology in astrocytes may contribute significantly to this reduced volume and to the involvement of the hippocampus in MDD. Postmortem hippocampal tissues were collected from 17 subjects with MDD and 17 psychiatrically-normal control subjects. Sections from the body of the hippocampus were immunostained for glial fibrillary acidic protein (GFAP), a marker of intermediate filament protein expressed in astrocytes. The density of GFAP-immunoreactive astrocytes was measured in the hippocampus using 3-dimensional cell counting. Hippocampal subfields were also assessed for GFAP-immunoreactive area fraction. In CA1, there was a significant positive correlation between age and either density or area fraction in MDD. The density of astrocytes in the hilus, but not CA1 or CA2/3, was significantly decreased only in depressed subjects not taking an antidepressant drug, but not for depressed subjects taking an antidepressant drug. The area fraction of GFAP-immunoreactivity was significantly decreased in the dentate gyrus in women but not men with depression. In CA2/3, the area fraction of GFAP-immunoreactivity was inversely correlated with the duration of depression in suicide victims. Astrocyte contributions to neuronal function in the hilus may be compromised in depressed subjects not taking antidepressant medication. Due to the cross-sectional nature of the present study of postmortem brain tissue, it remains to be determined whether antidepressant drug treatment prevented a decrease in GFAP-immunoreactive astrocyte density or restored cell density to normal levels.

Attenuation of social interaction-associated ultrasonic vocalizations and spatial working memory performance in rats exposed to chronic unpredictable stress

Exposure to unpredictable chronic mild stress (CUS) is a commonly used protocol in rats that is reported to evoke antidepressant-reversible behaviors such as loss of preference for a sweetened water solution which is taken as an analog of the anhedonia seen in major depression. However, the induction of anhedonic-like behavior by chronic mild stress, gauged by an animal's preference for sucrose solution, is not fully reproducible and consistent across laboratories. In this study, we compared a widely used behavioral marker of anhedonia - the sucrose preference test, with another phenotypic marker of emotional valence, social interaction-associated ultrasonic vocalizations as well as a marker of an anxiety-like phenotype, novelty-suppressed feeding, and cognitive performance in the eight arm radial maze task in adult male Sprague-Dawley rats. Chronic four-week exposure to unpredictable mild stressors resulted in 1) attenuation of social interaction-associated ultrasonic vocalizations 2) attenuation of spatial memory performance on the radial arm maze 3) attenuation of body weight gain and 4) increased latency to feed in a novelty-suppressed feeding task. However, chronic exposure to CUS did not result in any significant change in sucrose preference at one-week and three-week intervals. Our results argue for the utility of ultrasonic vocalizations in a social interaction context as a comparable alternative or adjunct to the sucrose preference test in determining the efficacy of CUS to generate an anhedonic-like phenotypic state.

Markers of apoptosis induction and proliferation in the orbitofrontal cortex in alcohol dependence

BACKGROUND

Alcohol-dependent (ALC) subjects exhibit glial and neuronal pathology in the prefrontal cortex (PFC). However, in many patients, neurophysiological disturbances are not associated with catastrophic cell depletion despite prolonged alcohol abuse. It is still unclear how some relevant markers of a cell's propensity to degenerate or proliferate are changed in the PFC of ALC subjects without major neurological disorders.

METHODS

Levels of pro-apoptotic caspase 8 (C8), X-linked inhibitor of apoptosis protein (XIAP), direct IAP binding protein with low pI (DIABLO), proliferating cell nuclear antigen (PCNA), and density of cells immunoreactive for proliferation marker Ki-67 (Ki-67-IR) were measured postmortem in the left orbitofrontal cortex (OFC) of 29 subjects with alcohol dependence and 23 nonpsychiatric comparison subjects.

RESULTS

Alcohol subjects had significantly higher levels of the 14 kDa C8 fragment (C8-14), an indicator of C8 activation. However, there was no change in the levels of DIABLO, XIAP, or in the DIABLO/XIAP ratio. PCNA protein level and density of Ki-67-IR cells were not significantly changed in alcoholics, although PCNA levels were increased in older ALC subjects as compared to controls.

CONCLUSIONS

Significant increase of a C8 activation indicator was found in alcoholism, but without significant changes in XIAP level, DIABLO/XIAP ratio, or Ki-67 labeling. These results would help to explain the absence of catastrophic cell loss in the PFC of many Brigman subjects, while still being consistent with an alcoholism-related vulnerability to slow decline in glial cells and neurons in the OFC of alcoholics.

AT-1001 Is a Partial Agonist with High Affinity and Selectivity at Human and Rat α3β4 Nicotinic Cholinergic Receptors

AT-1001 [N-(2-bromophenyl)-9-methyl-9-azabicyclo[3.3.1] nonan-3-amine] is a high-affinity and highly selective ligand at α3β4 nicotinic cholinergic receptors (nAChRs) that was reported to decrease nicotine self-administration in rats. It was initially reported to be an antagonist at rat α3β4 nAChRs heterologously expressed in HEK293 cells. Here we compared AT-1001 actions at rat and human α3β4 and α4β2 nAChRs similarly expressed in HEK 293 cells. We found that, as originally reported, AT-1001 is highly selective for α3β4 receptors over α4β2 receptors, but its binding selectivity is much greater at human than at rat receptors, because of a higher affinity at human than at rat α3β4 nAChRs. Binding studies in human and rat brain and pineal gland confirmed the selectivity of AT-1001 for α3β4 nAChRs and its higher affinity for human compared with rat receptors. In patch-clamp electrophysiology studies, AT-1001 was a potent partial agonist with 65-70% efficacy at both human and rat α3β4 nAChRs. It was also a less potent and weaker (18%) partial agonist at α4β2 nAChRs. Both α3β4 and α4β2 nAChRs are upregulated by exposure of cells to AT-1001 for 3 days. Similarly, AT-1001 desensitized both receptor subtypes in a concentration-dependent manner, but it was 10 and 30 times more potent to desensitize human α3β4 receptors than rat α3β4 and human α4β2 receptors, respectively. After exposure to AT-1001, the time to recovery from desensitization was longest for the human α3β4 nAChR and shortest for the human α4β2 receptor, suggesting that recovery from desensitization is primarily related to the dissociation of the ligand from the receptor.

Oligodendrocyte morphometry and expression of myelin - Related mRNA in ventral prefrontal white matter in major depressive disorder

White matter disturbance in the ventral prefrontal cortex (vPFC) in major depressive disorder (MDD) has been noted with diffusion tensor imaging (DTI). However, the cellular and molecular pathology of prefrontal white matter in MDD and potential influence of antidepressant medications is not fully understood. Oligodendrocyte morphometry and myelin-related mRNA and protein expression was examined in the white matter of the vPFC in MDD. Sections of deep and gyral white matter from the vPFC were collected from 20 subjects with MDD and 16 control subjects. Density and size of CNPase-immunoreactive (-IR) oligodendrocytes were estimated using 3-dimensional cell counting. While neither density nor soma size of oligodendrocytes was significantly affected in deep white matter, soma size was significantly decreased in the gyral white matter in MDD. In rhesus monkeys treated chronically with fluoxetine there was no significant effect on oligodendrocyte morphometry. Using quantitative RT-PCR to measure oligodendrocyte-related mRNA for CNPase, PLP1, MBP, MOG, MOBP, Olig1 and Olig2, in MDD there was a significantly reduced expression of PLP1 mRNA (which positively correlated with smaller sizes) and increased expression of mRNA for CNPase, OLIG1 and MOG. The expression of CNPase protein was significantly decreased in MDD. Altered expression of four myelin genes and CNPase protein suggests a mechanism for the degeneration of cortical axons and dysfunctional maturation of oligodendrocytes in MDD. The change in oligodendrocyte morphology in gyral white matter may parallel altered axonal integrity as revealed by DTI.

Evidence revealing deregulation of the KLF11-MAO A pathway in association with chronic stress and depressive disorders

The biochemical pathways underlying major depressive disorder (MDD) and chronic stress are not well understood. However, it has been reported that monoamine oxidase A (MAO A, a major neurotransmitter-degrading enzyme) is significantly increased in the brains of human subjects affected with MDD and rats exposed to chronic social defeat (CSD) stress, which is used to model depression. In the current study, we compared the protein levels of a MAO A-transcriptional activator, Kruppel-like factor 11 (KLF11 , also recognized as transforming growth factor-beta-inducible early gene 2) between the brains of 18 human subjects with MDD and 18 control subjects. We found that, indeed, the expression of KLF11 is increased by 36% (p<0.02) in the postmortem prefrontal cortex of human subjects with MDD compared with controls. We also observed a positive correlation between KLF11 levels and those of its target gene, MAO A, both in association with MDD. KLF11 protein expression was also increased by 44% (p<0.02) in the frontal cortex of KLF11 wild-type mice (Klf11(+/+)) vs Klf11(-/-) when both exposed to CSD stress. In contrast, locomotor activities, central box duration and sucrose preference were significantly reduced in the stressed Klf11(+/+) mice, suggesting that Klf11(+/+) mice are more severely affected by the stress model compared with Klf11(-/-) mice. These results serve to assign an important role of KLF11 in upregulating MAO A in MDD and chronic social stress, suggesting that inhibition of the pathways regulated by this transcription factor may aid in the therapeutics of neuropsychiatric illnesses. Thus, the new knowledge derived from the current study extends our understanding of transcriptional mechanisms that are operational in the pathophysiology of common human diseases and thus bears significant biomedical relevance.

Chronic Social Stress and Ethanol Increase Expression of KLF11, a Cell Death Mediator, in Rat Brain

Major depressive disorder and alcoholism are significant health burdens that can affect executive functioning, cognitive ability, job responsibilities, and personal relationships. Studies in animal models related to depression or alcoholism reveal that the expression of Krüppel-like factor 11 (KLF11, also called TIEG2) is elevated in frontal cortex, which suggests that KLF11 may play a role in stress- or ethanol-induced psychiatric conditions. KLF11 is a transcriptional activator of monoamine oxidase A and B, but also serves other functions in cell cycle regulation and apoptotic cell death. In the present study, immunohistochemistry was used to quantify intensity of nuclear KLF11, combined with an unbiased stereological approach to assess nuclei in fronto-limbic, limbic, and other brain regions of rats exposed chronically to social defeat or ethanol. KLF11 immunoreactivity was increased significantly in the medial prefrontal cortex, frontal cortex, and hippocampus of both stressed rats and rats fed ethanol. However, expression of KLF11 protein was not significantly affected in the thalamus, hypothalamus, or amygdala in either treatment group compared to respective control rats. Triple-label immunofluorescence revealed that KLF11 protein was localized in nuclei of neurons and astrocytes. KLF11 was also co-localized with the immunoreactivity of cleaved caspase-3. In addition, Western blot analysis revealed a significant reduction in anti-apoptotic protein, Bcl-xL, but an increase of caspase-3 expression in the frontal cortex of ethanol-treated rats compared to ethanol-preferring controls. Thus, KLF11 protein is up-regulated following chronic exposure to stress or ethanol in a region-specific manner and may contribute to pro-apoptotic signaling in ethanol-treated rats. Further investigation into the KLF11 signaling cascade as a mechanism for neurotoxicity and cell death in depression and alcoholism may provide novel pharmacological targets to lessen brain damage and maximize neuroprotection in these disorders.

The IFNγ-PKR pathway in the prefrontal cortex reactions to chronic excessive alcohol use

BACKGROUND

Brain cell death is a major pathological consequence of alcohol neurotoxicity. However, the molecular cascades in alcohol-induced brain tissue injury are unclear.

METHODS

Using Western blot and double immunofluorescence, we examined the expression of interferon (IFN)-induced protein kinase R (PKR), phosphorylated-PKR (p-PKR), and IFN gamma (IFNγ) in the prefrontal cortex (PFC) of postmortem brains from subjects with alcohol use disorders (AUD).

RESULTS

The protein levels of PKR, p-PKR, and IFNγ were significantly increased in subjects with AUD compared with control subjects without AUD, and a younger age of onset of AUD was significantly correlated with higher protein levels of p-PKR. In addition, elevated PKR- and p-PKR-IR were observed in both neurons and astrocytes in the PFC of subjects with AUD compared to subjects without AUD.

CONCLUSIONS

The activation of the IFNγ-PKR pathway in PFC of humans is associated with chronic excessive ethanol use with an age of onset dependent manner, and activation of this pathway may play a pivotal role in AUD-related brain tissue injury. This study provides insight into neurodegenerative key factors related to AUD and identifies potential targets for the treatment of alcohol-induced neurotoxicity.

Basolateral amygdala volume and cell numbers in major depressive disorder: a postmortem stereological study

Functional imaging studies consistently report abnormal amygdala activity in major depressive disorder (MDD). Neuroanatomical correlates are less clear: imaging studies have produced mixed results on amygdala volume, and postmortem neuroanatomic studies have only examined cell densities in portions of the amygdala or its subregions in MDD. Here, we present a stereological analysis of the volume of, and the total number of, neurons, glia, and neurovascular (pericyte and endothelial) cells in the basolateral amygdala in MDD. Postmortem tissues from 13 subjects with MDD and 10 controls were examined. Sections (~15/subject) taken throughout the rostral-caudal extent of the basolateral amygdala (BLA) were stained for Nissl substance and utilized for stereological estimation of volume and cell numbers. Results indicate that depressed subjects had a larger lateral nucleus than controls and a greater number of total BLA neurovascular cells than controls. There were no differences in the number or density of neurons or glia between depressed and control subjects. These findings present a more detailed picture of BLA cellular anatomy in depression than has previously been available. Further studies are needed to determine whether the greater number of neurovascular cells in depressed subjects may be related to increased amygdala activity in depression.

Reduced connexin 43 immunolabeling in the orbitofrontal cortex in alcohol dependence and depression

Reduced density of glial cells and low levels of some astrocyte proteins have been described in the orbitofrontal cortex (OFC) in depression and alcoholism, two disorders often comorbid. These regressive changes may also involve the communication between astrocytes via gap junctions and hemichannels, which play important regulatory roles in neurotransmission. We determined levels and morphological immunostaining parameters of connexin 43 (Cx43), the main protein subunit of astrocyte gap junctions/hemichannels, in the OFC of subjects with depression, alcoholism or comorbid depression/alcoholism as compared to non-psychiatric subjects. Postmortem brain samples from 23 subjects with major depressive disorder (MDD), 16 with alcohol dependence, 13 with comorbid MDD and alcohol dependence, and 20 psychiatrically-normal comparison subjects were processed for western blots to determine Cx43 levels. Area fraction of Cx43 immunoreactivity, and density and average size of immunoreactive puncta were measured in histological sections. There was a significant, larger than 60 percent decrease in Cx43 level in the three psychiatric groups as compared to controls. Area fraction of immunoreactivity and immunoreactive punctum size were reduced in all psychiatric groups, but Cx43-immunoreactive puncta density was reduced only in alcohol-dependent subjects. Among psychiatric subjects, no difference in Cx43 levels or immunostaining was found between suicides and non-suicides. The present data suggest that dysfunction of the OFC is accompanied by reduction in the levels of gap junction protein Cx43 in depression and alcoholism, and reduction in density of Cx43 immunoreactive puncta only in alcoholism, pointing to altered gap junction or hemichannel-based communication in the pathophysiology of those disorders.

REDD1 is essential for stress-induced synaptic loss and depressive behavior

Major depressive disorder (MDD) affects up to 17% of the population, causing profound personal suffering and economic loss (1). Clinical and pre-clinical studies have revealed that prolonged stress and MDD are associated with neuronal atrophy of cortical and limbic brain regions (2-9), but the molecular mechanisms underlying these morphological alterations have not yet been identified. Here, we show that stress increases levels of REDD1 (regulated in development and DNA damage responses 1), an inhibitor of mTORC1 (mammalian/mechanistic target of rapamycin complex 1) (10), in rat prefrontal cortex (PFC). This is concurrent with a decrease in phosphorylation of signaling targets of mTORC1, which is implicated in protein synthesis-dependent synaptic plasticity. We also found that REDD1 levels are increased in the postmortem PFC of human subjects with MDD relative to matched controls. Mutant mice with a deletion of REDD1 are resilient to the behavioral, synaptic, and mTORC1 signaling deficits caused by chronic unpredictable stress (CUS), while viral-mediated over expression of REDD1 in the rat PFC is sufficient to cause anxiety- and depressive-like behaviors and neuronal atrophy. Taken together, these postmortem and pre-clinical findings identify REDD1 as a critical mediator underlying the atrophy of neurons and depressive behavior caused by chronic stress exposure.

Apoptosis-related proteins and proliferation markers in the orbitofrontal cortex in major depressive disorder

BACKGROUND

In major depressive disorder (MDD), lowered neural activity and significant reductions of markers of cell resiliency to degeneration occur in the prefrontal cortex (PFC). It is still unclear whether changes in other relevant markers of cell vulnerability to degeneration and markers of cell proliferation are associated with MDD.

METHODS

Levels of caspase 8 (C8), X-linked inhibitor of apoptosis protein (XIAP), direct IAP binding protein with low pI (DIABLO), proliferating cell nuclear antigen (PCNA) and density of cells immunoreactive (-IR) for proliferation marker Ki-67 were measured in postmortem samples of the left orbitofrontal cortex (OFC) of subjects with MDD, and psychiatrically-normal comparison subjects.

RESULTS

There was significant increase in C8, a higher ratio of DIABLO to XIAP, lower packing density of Ki-67-IR cells, and an unexpected age-dependent increase in PCNA in subjects with MDD vs. controls. PCNA levels were significantly higher in MDD subjects unresponsive to antidepressants or untreated with antidepressants. The DIABLO/XIAP ratio was higher in MDD subjects without antidepressants than in comparison subjects.

LIMITATIONS

Qualitative nature of responsiveness assessments; definition of resistance to antidepressant treatment is still controversial; and unclear role of PCNA.

CONCLUSIONS

Markers of cell vulnerability to degeneration are increased and density of Ki67-positive cells is low MDD, but accompanied by normal XIAP levels. The results suggest increased vulnerability to cell pathology in depression that is insufficient to cause morphologically conspicuous cell death. Persistent but low-grade vulnerability to cell degeneration coexisting with reduced proliferation readiness may explain age-dependent reductions in neuronal densities in the OFC of depressed subjects.

Astrocyte pathology in major depressive disorder: insights from human postmortem brain tissue

The present paper reviews astrocyte pathology in major depressive disorder (MDD) and proposes that reductions in astrocytes and related markers are key features in the pathology of MDD. Astrocytes are the most numerous and versatile of all types of glial cells. They are crucial to the neuronal microenvironment by regulating glucose metabolism, neurotransmitter uptake (particularly for glutamate), synaptic development and maturation and the blood brain barrier. Pathology of astrocytes has been consistently noted in MDD as well as in rodent models of depressive-like behavior. This review summarizes evidence from human postmortem tissue showing alterations in the expression of protein and mRNA for astrocyte markers such as glial fibrillary acidic protein (GFAP), gap junction proteins (connexin 40 and 43), the water channel aquaporin-4 (AQP4), a calcium-binding protein S100B and glutamatergic markers including the excitatory amino acid transporters 1 and 2 (EAAT1, EAAT2) and glutamine synthetase. Moreover, preclinical studies are presented that demonstrate the involvement of GFAP and astrocytes in animal models of stress and depressive-like behavior and the influence of different classes of antidepressant medications on astrocytes. In light of the various astrocyte deficits noted in MDD, astrocytes may be novel targets for the action of antidepressant medications. Possible functional consequences of altered expression of astrocytic markers in MDD are also discussed. Finally, the unique pattern of cell pathology in MDD, characterized by prominent reductions in the density of astrocytes and in the expression of their markers without obvious neuronal loss, is contrasted with that found in other neuropsychiatric and neurodegenerative disorders.

Morphometric analysis of vascular pathology in the orbitofrontal cortex of older subjects with major depression

OBJECTIVE

Late-life depression has been associated with risk for cerebrovascular pathology, as demonstrated in neuroimaging studies of older depressed patients, as well as mood disorder following cerebrovascular accidents. However, more research is needed on neuroanatomical changes in late-life depression, where there has been no clearly documented link to brain injury. Such studies should examine morphological changes in medium and small sized vessels that supply the cortical gray and white matter.

METHODS

The present study used a non-specific histological Nissl staining and a more vessel-specific immunolabeling with endothelial marker von Willebrand Factor (vWF) to estimate density and size of blood vessel segments in the orbitofrontal cortex of 16 older subjects with major depressive disorder (MDD) and 9 non-psychiatric comparison subjects.

RESULTS

The density of Nissl-stained vessel segments and of segments with perivascular spaces was higher in subjects with MDD than in comparison subjects in gray (GM) and white matter (WM). In GM, the density of vWF-immunoreactive segments with cross-sectional areas greater than 800 µm2 was higher in MDD. In WM, only the density of vWF-immunoreactive segments with patent perivascular spaces and diameters larger than 60 µm was higher in subjects with MDD. Also in the WM, only subjects with late-onset MDD presented a significantly higher density of vWF-positive segments than comparison subjects.

CONCLUSIONS

In older subjects with MDD, there appear to be morphological changes that increase visibility of medium-sized vessel segments with some labeling techniques, and this increased visibility may be related to increased patency of perivascular spaces around arterioles.

The expression of KLF11 (TIEG2), a monoamine oxidase B transcriptional activator in the prefrontal cortex of human alcohol dependence

BACKGROUND

The biochemical pathways underlying alcohol abuse and dependence are not well understood, although brain cell loss and neurotoxicity have been reported in subjects with alcohol dependence. Monoamine oxidase B (MAO B; an enzyme that catabolizes neurotransmitters such as dopamine) is consistently increased in this psychiatric illness. MAO B has been implicated in the pathogenesis of alcohol dependence and alcohol-induced brain neurotoxicity. Recently, the cell growth inhibitor protein, Kruppel-like factor 11 (KLF11), has been reported to be an MAO transcriptional activator. KLF11 is also known as TIEG2 (transforming growth factor-beta-inducible early gene 2) and mediates apoptotic cell death. This study investigates the protein expression of KLF11 and its relationship with MAO B using human postmortem prefrontal cortex from subjects with alcohol dependence.

METHODS

Twelve subjects with alcohol dependence and the respective psychiatrically normal control subjects were investigated. Expression of KLF11 and MAO B proteins in the prefrontal cortex was measured by Western blot analysis. Correlation studies involving KLF11 and MAO B protein expression were performed. Localization of KLF11 in the human prefrontal cortex was also determined by immunohistochemistry.

RESULTS

Levels of KLF11 protein were significantly increased by 44% (p < 0.03) in the postmortem prefrontal cortex of subjects with alcohol dependence as compared to age- and gender-matched, psychiatrically normal control subjects. Furthermore, KLF11 levels were significantly and positively correlated with both the increased MAO B protein levels and blood alcohol content in alcohol-dependent subjects. In addition, KLF11 protein expression was visualized in both neuronal and glial cells.

CONCLUSIONS

This novel study shows the important role of KLF11, an MAO transcriptional activator, in human alcohol dependence. It further supports that the KLF11-MAO B cell death cascade may contribute to chronic alcohol-induced brain damage. This argues a case for KLF11-MAO B inhibition as a novel therapeutic strategy that may impact this highly prevalent illness.

Gene expression deficits in pontine locus coeruleus astrocytes in men with major depressive disorder

BACKGROUND

Norepinephrine and glutamate are among several neurotransmitters implicated in the neuropathology of major depressive disorder (MDD). Glia deficits have also been demonstrated in people with MDD, and glia are critical modulators of central glutamatergic transmission. We studied glia in men with MDD in the region of the brain (locus coeruleus; LC) where noradrenergic neuronal cell bodies reside and receive glutamatergic input.

METHODS

The expression of 3 glutamate-related genes (SLC1A3, SLC1A2, GLUL) concentrated in glia and a glia gene (GFAP) were measured in postmortem tissues from men with MDD and from paired psychiatrically healthy controls. Initial gene expression analysis of RNA isolated from homogenized tissue (n = 9-10 pairs) containing the LC were followed by detailed analysis of gene expressions in astrocytes and oligodendrocytes (n = 6-7 pairs) laser captured from the LC region. We assessed protein changes in GFAP using immunohistochemistry and immunoblotting (n = 7-14 pairs).

RESULTS

Astrocytes, but not oligodendrocytes, demonstrated robust reductions in the expression of SLC1A3 and SLC1A2, whereas GLUL expression was unchanged. GFAP expression was lower in astrocytes, and we confirmed reduced GFAP protein in the LC using immunostaining methods.

LIMITATIONS

Reduced expression of protein products of SLC1A3 and SLC1A2 could not be confirmed because of insufficient amounts of LC tissue for these assays. Whether gene expression abnormalities were associated with only MDD and not with suicide could not be confirmed because most of the decedents who had MDD died by suicide.

CONCLUSION

Major depressive disorder is associated with unhealthy astrocytes in the noradrenergic LC, characterized here by a reduction in astrocyte glutamate transporter expression. These findings suggest that increased glutamatergic activity in the LC occurs in men with MDD.

Gene expression analysis of novel genes in the prefrontal cortex of major depressive disorder subjects

Dysregulation of the glutamatergic system has been implicated not only in the treatment of major depressive disorder (MDD), but also in the excitotoxic effects of stress and anxiety on the prefrontal cortex, which may precede the onset of a depressive episode. Our previous studies demonstrate marked deficits in prominent postsynaptic proteins involved in glutamate neurotransmission in the prefrontal cortex (PFC), Brodmann's area 10 (BA 10) from subjects diagnosed with major depressive disorder (MDD). In the same group of subjects we have identified deficits in expression and phosphorylation level of key components of the mammalian target of rapamycin (mTOR) signaling pathway, known to regulate translation initiation. Based on our previous findings, we have postulated that glutamate-dependent dysregulation of mTOR-initiated protein synthesis in the PFC may underlie the pathology of MDD. The aim of this study was to use the NanoString nCounter System to perform analysis of genes coding for glutamate transporters, glutamate metabolizing enzymes, neurotrophic factors and other intracellular signaling markers involved in glutamate signaling that were not previously investigated by our group in the PFC BA 10 from subjects with MDD. We have analyzed a total of 200 genes from 16 subjects with MDD and 16 healthy controls. These are part of the same cohort used in our previous studies. Setting our cutoff p-value≤0.01, marked upregulation of genes coding for mitochondrial glutamate carrier (GC1; p=0.0015), neuropilin 1 (NRP-1; p=0.0019), glutamate receptor ionotropic N-methyl-d-aspartate-associated protein 1 (GRINA; p=0.0060), and fibroblast growth factor receptor 1 (FGFR-1; p=0.010) was identified. No significant differences in expression of the remaining 196 genes were observed between MDD subjects and controls. While upregulation of FGFR-1 has been previously shown in MDD; abnormalities in GC-1, GRINA, and NRP-1 have not been reported. Therefore, this postmortem study identifies GC1, GRINA, and NRP-1 as novel factors associated with MDD; however, future studies will be needed to address the significance of these genes in the pathophysiology of depression and antidepressant activity.

Coverage of blood vessels by astrocytic endfeet is reduced in major depressive disorder

BACKGROUND

Depression and cerebrovascular disease influence each other, according to clinical studies. Despite this evidence, no studies have investigated the relationship between major depressive disorder (MDD) and cerebrovascular disease at the cellular level. Astrocytic processes are a crucial interface between blood vessels and neurons, and astrocyte density is reduced in MDD. This study investigated the coverage of vessels by astrocyte endfeet in the prefrontal cortex in MDD.

METHODS

Thirteen pairs of MDD and nonpsychiatric control subjects were used for double immunofluorescent staining and confocal image analysis. Frozen sections of gray matter from orbitofrontal area 47 and white matter from the ventromedial prefrontal cortex were examined. Astrocytic processes (labeled with antibodies for aquaporin-4 (AQP4) or glial fibrillary acidic protein were co-localized with blood vessels (labeled with an antibody to collagen IV) to measure the coverage of vessel walls by astrocyte processes.

RESULTS

The coverage of blood vessels by endfeet of AQP4-immunoreactive (IR) astrocytes was significantly reduced by 50% in subjects with MDD as compared with control subjects [analysis of covariance: F(1,23) = 5.161, p = .033]. This difference was detected in orbitofrontal gray matter but not in white matter. Conversely, the coverage of vessels by glial fibrillary acidic protein-IR processes did not significantly differ between the groups.

CONCLUSIONS

A significant reduction in the coverage of gray matter vessels by AQP4-IR astrocyte processes in MDD suggests alterations in AQP4 functions such as regulation of water homeostasis, blood flow, glucose transport and metabolism, the blood-brain barrier, glutamate turnover, and synaptic plasticity.

Hippocampal volume and total cell numbers in major depressive disorder

Neuroimaging consistently reveals smaller hippocampal volume in recurrent or chronic major depressive disorder (MDD). The underlying cellular correlates of the smaller volume are not clearly known. Postmortem tissues from 17 pairs of depressed and control subjects were obtained at autopsy, and informant-based retrospective psychiatric assessment was performed. Formalin-fixed left temporal lobes were sectioned (40 μm), stained for Nissl substance, and every 60th section selected throughout the entire hippocampus. Total volume of the hippocampal formation was calculated, and total numbers of pyramidal neurons (in hippocampal fields CA1, CA2/3, hilus), dentate gyrus (DG) granule cells, and glial cells were estimated stereologically. While hippocampal volume in all MDD subjects was not significantly smaller versus control subjects, in recurrent/chronic MDD, total volume decreased with duration of depressive illness (r = -0.696, p < 0.026). There was no significant difference between MDD and controls in total number or density of pyramidal neurons/granule cells or glial cells in CA1, CA2/3, hilus, or DG. However, CA1 pyramidal neuron density increased with duration of illness in recurrent/chronic MDD (r = 0.840, p < 0.002). Granule cell (r = 0.971, p < 0.002) and glial cell numbers (r = 0.980, p < 0.001) increased with age in those taking antidepressant medication (n = 6). Increasing DG granule cell and glial cell numbers with age in antidepressant-treated subjects may reflect proliferative effects of antidepressant medications. Decreasing total volume and increasing CA1 pyramidal neuron density with duration of illness in recurrent/chronic MDD lends support to the neuropil hypothesis of MDD.

Decreased expression of synapse-related genes and loss of synapses in major depressive disorder

Previous imaging and postmortem studies have reported a lower brain volume and a smaller size and density of neurons in the dorsolateral prefrontal cortex (dlPFC) of subjects with major depressive disorder (MDD). These findings suggest that synapse number and function are decreased in the dlPFC of patients with MDD. However, there has been no direct evidence reported for synapse loss in MDD, and the gene expression alterations underlying these effects have not been identified. Here we use microarray gene profiling and electron microscopic stereology to reveal lower expression of synaptic-function–related genes (CALM2, SYN1, RAB3A, RAB4B and TUBB4) in the dlPFC of subjects with MDD and a corresponding lower number of synapses. We also identify a transcriptional repressor, GATA1, expression of which is higher in MDD and that, when expressed in PFC neurons, is sufficient to decrease the expression of synapse-related genes, cause loss of dendritic spines and dendrites, and produce depressive behavior in rat models of depression.

Cellular abnormalities in depression: evidence from postmortem brain tissue

During the past two decades, in vivo neuroimaging studies have permitted significant insights into the general location of dysfunctional brain regions in depression. In parallel and often intersecting ways, neuroanatomical, pharmacological, and biochemical studies of postmortem brain tissue are permitting new insights into the pathophysiology of depression. In addition to long-recognized neurochemical abnormalities in depression, novel studies at the microscopic level support the contention that mood disorders are associated with abnormalities in cell morphology and distribution. In the past 6 years, cell-counting studies have identified changes in the density and size of both neurons and glia in a number of frontolimbic brain regions, including dorsolateral prefrontal, orbitofrontal, and anterior cingulate cortex, and the amygdala and hippocampus. Convergence of cellular changes at the microscopic level with neuroimaging changes detected in vivo provides a compelling integration of clinical and basic research for disentangling the pathophysiology of depression. The ultimate integration of these two research approaches will occur with premortem longitudinal clinical studies on well-characterized patients linked to postmortem studies of the same subjects.

Quantitative analysis of focused a-to-I RNA editing sites by ultra-high-throughput sequencing in psychiatric disorders

A-to-I RNA editing is a post-transcriptional modification of single nucleotides in RNA by adenosine deamination, which thereby diversifies the gene products encoded in the genome. Thousands of potential RNA editing sites have been identified by recent studies (e.g. see Li et al, Science 2009); however, only a handful of these sites have been independently confirmed. Here, we systematically and quantitatively examined 109 putative coding region A-to-I RNA editing sites in three sets of normal human brain samples by ultra-high-throughput sequencing (uHTS). Forty of 109 putative sites, including 25 previously confirmed sites, were validated as truly edited in our brain samples, suggesting an overestimation of A-to-I RNA editing in these putative sites by Li et al (2009). To evaluate RNA editing in human disease, we analyzed 29 of the confirmed sites in subjects with major depressive disorder and schizophrenia using uHTS. In striking contrast to many prior studies, we did not find significant alterations in the frequency of RNA editing at any of the editing sites in samples from these patients, including within the 5HT_2C serotonin receptor (HTR2C). Our results indicate that uHTS is a fast, quantitative and high-throughput method to assess RNA editing in human physiology and disease and that many prior studies of RNA editing may overestimate both the extent and disease-related variability of RNA editing at the sites we examined in the human brain.

Mechanistic role for a novel glucocorticoid-KLF11 (TIEG2) protein pathway in stress-induced monoamine oxidase A expression

Chronic stress is a risk factor for psychiatric illnesses, including depressive disorders, and is characterized by increased blood glucocorticoids and brain monoamine oxidase A (MAO A, which degrades monoamine neurotransmitters). This study elucidates the relationship between stress-induced MAO A and the transcription factor Kruppel-like factor 11 (KLF11, also called TIEG2, a member of the Sp/KLF- family), which inhibits cell growth. We report that 1) a glucocorticoid (dexamethasone) increases KLF11 mRNA and protein levels in cultured neuronal cells; 2) overexpressing KLF11 increases levels of MAO A mRNA and enzymatic activity, which is further enhanced by glucocorticoids; in contrast, siRNA-mediated KLF11 knockdown reduces glucocorticoid-induced MAO A expression in cultured neurons; 3) induction of KLF11 and translocation of KLF11 from the cytoplasm to the nucleus are key regulatory mechanisms leading to increased MAO A catalytic activity and mRNA levels because of direct activation of the MAO A promoter via Sp/KLF-binding sites; 4) KLF11 knockout mice show reduced MAO A mRNA and catalytic activity in the brain cortex compared with wild-type mice; and 5) exposure to chronic social defeat stress induces blood glucocorticoids and activates the KLF11 pathway in the rat brain, which results in increased MAO A mRNA and enzymatic activity. Thus, this study reveals for the first time that KLF11 is an MAO A regulator and is produced in response to neuronal stress, which transcriptionally activates MAO A. The novel glucocorticoid-KLF11-MAO A pathway may play a crucial role in modulating distinct pathophysiological steps in stress-related disorders.

A functional alternative splicing mutation in human tryptophan hydroxylase-2

The brain serotonergic system has an essential role in the physiological functions of the central nervous system and dysregulation of serotonin (5-HT) homeostasis has been implicated in many neuropsychiatric disorders. The tryptophan hydroxylase-2 (TPH2) gene is the rate-limiting enzyme in brain 5-HT synthesis, and thus is an ideal candidate gene for understanding the role of dysregulation of brain serotonergic homeostasis. Here, we characterized a common, but functional single-nucleotide polymorphism (SNP rs1386493) in the TPH2 gene, which decreases efficiency of normal RNA splicing, resulting in a truncated TPH2 protein (TPH2-TR) by alternative splicing. TPH2-TR, which lacks TPH2 enzyme activity, dominant-negatively affects full-length TPH2 function, causing reduced 5-HT production. The predicted mRNA for TPH2-TR is present in postmortem brain of rs1386493 carriers. The rs13864923 variant does not appear to be overrepresented in either global or multiplex depression cohorts. However, in combination with other gene variants linked to 5-HT homeostasis, this variant may exhibit important epistatic influences.