IntroductionMajor depressive disorder (MDD) has a lifetime prevalence of 16% in the United States.1 Antidepressant drugs are the most used intervention for those with a diagnosis of depressive disorders, but the road to remission is long and uncertain, with 40% of patients never reaching full remission and at least 15% not experiencing any symptomatic improvements.2 Elucidating the biological bases of MDD is likely to provide novel targets for the development of more effective drugs, or at the very least, adjunctive treatments for existing antidepressants that increase the chance of remission.Speculation that norepinephrine plays a role in depressive disorders dates back to the early 1950s, and research since then increasingly supports this. The locus coeruleus (LC) in the pontine brainstem contains the cell bodies of the major source of norepinephrine in the brain and has been the subject of numerous investigations regarding the neuropathology of MDD.3 The human LC is an area with very high densities of radioligand binding of antidepressant drugs to monoamine oxidase, 4 the norepinephrine transporter 5 and the serotonin transporter.6 Numerous postmortem studies demonstrate abnormal neurochemistry of the noradrenergic LC in people with MDD and in people who died by suicide. A role of 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 a...

Telomere shortening is observed in peripheral mononuclear cells from patients with major depressive disorder (MDD). Whether this finding and its biological causes impact the health of the brain in MDD is unknown. Brain cells have differing vulnerabilities to biological mechanisms known to play a role in accelerating telomere shortening. Here, two glia cell populations (oligodendrocytes and astrocytes) known to have different vulnerabilities to a key mediator of telomere shortening, oxidative stress, were studied. The two cell populations were separately collected by laser capture micro-dissection of two white matter regions shown previously to demonstrate pathology in MDD patients. Cells were collected from brain donors with MDD at the time of death and age-matched psychiatrically normal control donors (N = 12 donor pairs). Relative telomere lengths in white matter oligodendrocytes, but not astrocytes, from both brain regions were significantly shorter for MDD donors as compared to matched control donors. Gene expression levels of telomerase reverse transcriptase were significantly lower in white matter oligodendrocytes from MDD as compared to control donors. Likewise, the gene expression of oxidative defence enzymes superoxide dismutases (SOD1 and SOD2), catalase (CAT) and glutathione peroxidase (GPX1) were significantly lower in oligodendrocytes from MDD as compared to control donors. No such gene expression changes were observed in astrocytes from MDD donors. These findings suggest that attenuated oxidative stress defence and deficient telomerase contribute to telomere shortening in oligodendrocytes in MDD, and suggest an aetiological link between telomere shortening and white matter abnormalities previously described in MDD.

Glutamate receptors are promising drug targets for the treatment of urgent suicide ideation and chronic major depressive disorder (MDD) that may lead to suicide completion. Antagonists of glutamatergic NMDA receptors reduce depressive symptoms faster than traditional antidepressants, with beneficial effects occurring within hours. Glutamate is the prominent excitatory input to the noradrenergic locus coeruleus (LC). The LC is activated by stress in part through this glutamatergic input. Evidence has accrued demonstrating that the LC may be overactive in MDD, while treatment with traditional antidepressants reduces LC activity. Pathological alterations of both glutamatergic and noradrenergic systems have been observed in depressive disorders, raising the prospect that disrupted glutamate-norepinephrine interactions may be a central component to depression and suicide pathobiology. This study examined the gene expression levels of glutamate receptors in post-mortem noradrenergic LC neurons from subjects with MDD (most died by suicide) and matched psychiatrically normal controls. Gene expression levels of glutamate receptors or receptor subunits were measured in LC neurons collected by laser capture microdissection. MDD subjects exhibited significantly higher expression levels of the NMDA receptor subunit genes, GRIN2B and GRIN2C, and the metabotropic receptor genes, GRM4 and GRM5, in LC neurons. Gene expression levels of these receptors in pyramidal neurons from prefrontal cortex (BA10) did not reveal abnormalities in MDD. These findings implicate disrupted glutamatergic-noradrenergic interactions at the level of the stress-sensitive LC in MDD and suicide, and provide a theoretical mechanism by which glutamate antagonists may exert rapid antidepressant effects.

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.

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Treatment of rats with reserpine, an inhibitor of the vesicular monoamine transporter (VMAT), depletes norepinephrine (NE) and regulates NE transporter (NET) expression. The present study examined the molecular mechanisms involved in regulation of the NET by reserpine using cultured cells. Exposure of rat PC12 cells to reserpine for a period as short as 5 min decreased [ 3 H]NE uptake capacity, an effect characterized by a robust decrease in the V max of the transport of [ 3 H]NE. As expected, reserpine did not displace the binding of [ 3 H]nisoxetine from the NET in membrane homogenates. The potency of reserpine for reducing [ 3 H]NE uptake was dramatically lower in SK-N-SH cells that have reduced storage capacity for catecholamines. Reserpine had no effect on [ 3 H]NE uptake in HEK-293 cells transfected with the rat NET (293-hNET), cells that lack catecholamine storage vesicles. NET regulation by reserpine was independent of trafficking of the NET from the cell surface. Pre-exposure of cells to inhibitors of several intracellular signaling cascades known to regulate the NET, including Ca 2+ /Ca 2+ -calmodulin dependent kinase and protein kinases A, C and G, did not affect the ability of reserpine to reduce [ 3 H]NE uptake. Treatment of PC12 cells with the catecholamine depleting agent, α-methyl-p-tyrosine, increased [ 3 H]NE uptake and eliminated the inhibitory effects of reserpine on [ 3 H]NE uptake. Reserpine non-competitively inhibits NET activity through a Ca 2+ -independent process that requires catecholamine storage vesicles, revealing a novel pharmacological method to modify NET function. Further characterization of the molecular nature of reserpine's action could lead to the development of alternative therapeutic strategies for treating disorders known to be benefitted by treatment with traditional competitive NET inhibitors. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The norepinephrine transporter (NET) is a Na + /Cl --dependent transporter responsible for limiting the synaptic action of norepinephrine (NE). The function of the NET is inhibited by several psychotherapeutic drugs that directly bind to the NET, such as desipramine, cocaine, and atomoxetine. Besides acute drug effects on the NET, NET function is up-and downregulated by exposures to several drugs, by activation of specific signaling pathways, and by physiological conditions (Mandela and Ordway, 2006b). Drugs that regulate the NET include compounds that bind directly to the NET such as desipramine, and also drugs and substances such as acetylcholine, that activate receptors and/or intra...

Based on evidence of abnormalities in axon thickness and neuronal disorganization, autism spectrum disorder (ASD) is commonly considered to be a condition resulting from neuronal dysfunction. Yet, recent findings suggest that non-neuronal cell types also contribute to ASD pathology. To investigate the role of glial cells in ASD, a combination of protein and gene expression analyses were used to determine levels of two glial markers, glial fibrillary acidic protein (GFAP) and myelin oligodendrocyte glycoprotein (MOG), in the postmortem brain tissue from control and ASD donors. Levels of GFAP immunoreactivity (ir) were significantly elevated (P = 0.008) in anterior cingulate cortex (Brodmann area 24; BA24) white matter of ASD donors compared to control donors. In contrast, GFAP-ir levels were similar in BA24 gray matter from ASD and control donors. MOG-ir was also similar in both BA24 white and gray matter from ASD and control donors. In anterior prefrontal cortex (BA10), there were no significant differences in GFAP-ir or MOG-ir in either white or gray matter comparing ASD to control donors. Levels of expression of the genes GFAP and MOG also showed no differences between control and ASD donors in BA24 and BA10 white and gray matter. Collectively, these data imply that ASD is associated with an activation of white matter astrocytes in the anterior cingulate cortex as a result of a yet undefined cellular insult. Research is needed to investigate the molecular pathways that underlie this astrocyte reaction and such research may yield important clues regarding the etiology of ASD.

The noradrenergic locus coeruleus (LC) is the principal source of brain norepinephrine, a neurotransmitter thought to play a major role in the pathology of major depressive disorder (MDD) and in the therapeutic action of many antidepressant drugs. The goal of this study was to identify potential mediators of brain noradrenergic dysfunction in MDD. Bone morphogenetic protein 7 (BMP7), a member of the transforming growth factor-β superfamily, is a critical mediator of noradrenergic neuron differentiation during development and has neurotrophic and neuroprotective effects on mature catecholaminergic neurons. Real-time PCR of reversed transcribed RNA isolated from homogenates of LC tissue from 12 matched pairs of MDD subjects and psychiatrically normal control subjects revealed low levels of BMP7 gene expression in MDD. No differences in gene expression levels of other members of the BMP family were observed in the LC, and BMP7 gene expression was normal in the prefrontal cortex and amygdala in MDD subjects. Laser capture microdissection of noradrenergic neurons, astrocytes, and oligodendrocytes from the LC revealed that BMP7 gene expression was highest in LC astrocytes relative to the other cell types, and that the MDD-associated reduction in BMP7 gene expression was limited to astrocytes. Rats exposed to chronic social defeat exhibited a similar reduction in BMP7 gene expression in the LC. BMP7 has unique developmental and trophic actions on catecholamine neurons and these findings suggest that reduced astrocyte support for pontine LC neurons may contribute to pathology of brain noradrenergic neurons in MDD.