Elucidating the Role of the α7 Nicotinic Receptor in the Etiology of Schizophrenia.

The α7 subunit of the nicotinic receptor, a ligand gated ion channel with an affinity for nicotine, has long been implicated in the pathophysiology of schizophrenia due to the extremely high rate of smoking within the patient population. However, the exact role of the receptor has never fully been determined. In the following studies, various functions the receptor may assume in disease state are evaluated. There is a strong relationship between the immune system and schizophrenia, with the α7 subunit possibly serving as the link between the two. One of the following studies looks at the possibility of the receptor functioning as antigen in an autoimmune response. Blood sera of schizophrenic patients, as well as controls, were analyzed for the presence of antibodies to the α7 subunit of the nicotinic receptor. A sensitive ligand-based assay revealed schizophrenic patients could possess a pathogenic level of antibody that may exacerbate the degenerative nature of the disease, allowing for the possibility that receptor antibodies may serve as a contributing factor in the etiology of the disorder in at least a subset of patients. In other studies, the expression of the α7 receptor was investigated. Recombinant α7 receptor production has eluded researchers in non-mammalian species and this was the focus of our initial studies. In general, the lack of sufficient molecular recombinant techniques utilizing the receptor makes characterization of the α7 receptor and it\u27s specific protein interactions difficult to evaluate. The regulatory mechanisms of the nicotinic receptor α7 subunit production and receptor formation have yet to be completely elucidated. Results in this investigation found a relationship between a functional CRE-element in the promoter region

Microbiome Diversity and Differential Abundances Associated with BMI, Immune Markers, and Fecal Short Chain Fatty Acids Before and After Synbiotic Supplementation

The gut microbiota and its metabolites – namely short chain fatty acids (SCFAs) – interact with the digestive, immune, and nervous systems. Microbiota with disrupted composition are highly associated with obesity, gastrointestinal symptoms, and chronic inflammation. Levels of SCFAs in the feces can represent dynamics of the microbiota, and they represent one mechanism by which the microbiota interacts with its host. This study aimed to further our understanding of associations between microbiota bacterial diversity and SCFAs, immune markers, BMI, and GI symptoms and to identify bacteria that are differentially abundant in different BMI groups and with synbiotic supplementation. Data (SCFAs, immunoglobulins, body mass index, fecal fiber, fecal protein, measures of GI symptoms, and 16s RNA sequences, n=11) was extracted from a randomized control trial investigating the effects of synbiotic supplementation in non-celiac gluten-sensitive participants. QIIME2 was used to process 16s RNA data, analyze quantitative, qualitative, phylogenetic quantitative, and phylogenetic qualitative measures of alpha and beta diversity and to perform an analysis of composition of microbiomes (ANCOM) for identification of differential abundances. Multiple metrics of alpha diversity were found to significantly correlate with IgG4, IgM, IL-2, acetate, propionate, isobutyrate, valerate, isovalerate, caproate, heartburn, urgent need to defecate, and feelings of incomplete evacuation. Multiple metrics of beta diversity were significantly different between normal and overweight, normal and obese, and overweight and obese BMI classification groups. Beta diversity was also found to significantly correlate with IgG1, IgG3, IgG4, IgA, IL-6, IL-8, fecal fiber, propionate, butyrate, heartburn, acid regurgitation, nausea and vomiting, bloating, abdominal distension, increased gas, and eructation. The synbiotic intervention did not significantly alter alpha or beta diversity. An ANCOM identified bacterial taxa differentially abundant with BMI shifts and synbiotic supplementation, though these taxa were not those included in the synbiotic. Findings demonstrate alpha and beta diversity associations with various SCFAs, GI symptoms, immune markers, and BMI, and the results of the placebo-controlled intervention suggest careful consideration of placebo contents moving forward. This research supports plans to apply analysis to larger sample sizes to elucidate changes microbial profiles that are associated with clinically relevant biomarkers and symptoms

Reserpine-Induced Reduction in Norepinephrine Transporter Function Requires Catecholamine Storage Vesicles

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 5min decreased [ H]NE uptake capacity, an effect characterized by a robust decrease in the V of the transport of [ H]NE. As expected, reserpine did not displace the binding of [ H]nisoxetine from the NET in membrane homogenates. The potency of reserpine for reducing [ H]NE uptake was dramatically lower in SK-N-SH cells that have reduced storage capacity for catecholamines. Reserpine had no effect on [ 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 /Ca -calmodulin dependent kinase and protein kinases A, C and G, did not affect the ability of reserpine to reduce [ H]NE uptake. Treatment of PC12 cells with the catecholamine depleting agent, α-methyl-p-tyrosine, increased [ H]NE uptake and eliminated the inhibitory effects of reserpine on [ H]NE uptake. Reserpine non-competitively inhibits NET activity through a Ca -independent process that requires catecholamine storage vesicles, revealing a novel pharmacological method to modify NET function. Further characterization of the molecular nature of reserpine\u27s action could lead to the development of alternative therapeutic strategies for treating disorders known to be benefitted by treatment with traditional competitive NET inhibitors

Shortened Telomere Length in White Matter Oligodendrocytes in Major Depression: Potential Role of Oxidative Stress

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

Neuroinflammatory Gene Expression Alterations in Anterior Cingulate Cortical White and Gray Matter of Males With Autism Spectrum Disorder

Evidence for putative pathophysiological mechanisms of autism spectrum disorder (ASD), including peripheral inflammation, blood–brain barrier disruption, white matter alterations, and abnormal synaptic overgrowth, indicate a possible involvement of neuroinflammation in the disorder. Neuroinflammation plays a role in the development and maintenance of the dendritic spines involved in glutamatergic and GABAergic neurotransmission, and also influences blood–brain permeability. Cytokines released from microglia can impact the length, location or organization of dendritic spines on excitatory and inhibitory cells as well as recruit and impact glial cell function around the neurons. In this study, gene expression levels of anti- and pro-inflammatory signaling molecules, as well as oligodendrocyte and astrocyte marker proteins, were measured in both gray and white matter tissue in the anterior cingulate cortex from ASD and age-matched typically developing (TD) control brain donors, ranging from ages 4 to 37 years. Expression levels of the pro-inflammatory gene, HLA-DR, were significantly reduced in gray matter and expression levels of the anti-inflammatory gene MRC1 were significantly elevated in white matter from ASD donors as compared to TD donors, but neither retained statistical significance after correction for multiple comparisons. Modest trends toward differences in expression levels were also observed for the pro-inflammatory (CD68, IL1β) and anti-inflammatory genes (IGF1, IGF1R) comparing ASD donors to TD donors. The direction of gene expression changes comparing ASD to TD donors did not reveal consistent findings implicating an elevated pro- or anti-inflammatory state in ASD. However, altered expression of pro- and anti-inflammatory gene expression indicates some involvement of neuroinflammation in ASD. Lay Summary: The anterior cingulate cortex is an integral brain region in modulating social behaviors including nonverbal communication. The study found that inflammatory gene expression levels were altered in this brain region. We hypothesize that the inflammatory changes in this area could impact neuronal function. The finding has future implications in using these molecular markers to identify potential environmental exposures and distinct cell differences in autism

Low Gene Expression of Bone Morphogenetic Protein 7 in Brainstem Astrocytes in Major Depression

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

Elevated Gene Expression of Glutamate Receptors in Noradrenergic Neurons From the Locus Coeruleus in Major Depression

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

Antidepressant-Like Actions of Inhibitors of Poly(ADP-Ribose) Polymerase in Rodent Models

Many patients suffering from depressive disorders are refractory to treatment with currently available antidepressant medications, while many more exhibit only a partial response. These factors drive research to discover new pharmacological approaches to treat depression. Numerous studies demonstrate evidence of inflammation and elevated oxidative stress in major depression. Recently, major depression has been shown to be associated with elevated levels of DNA oxidation in brain cells, accompanied by increased gene expression of the nuclear base excision repair enzyme, poly(ADP-ribose) polymerase-1. Given these findings and evidence that drugs that inhibit poly(ADP-ribose) polymerase-1 activity have antiinflammatory and neuroprotective properties, the present study was undertaken to examine the potential antidepressant properties of poly(ADP-ribose) polymerase inhibitors

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

Neuroinflammation in the C1q/TNF-related over-expression mouse model of chronic ethanol exposure

Alcohol use can negatively impact financial, cognitive, and psychiatric aspects of human life. In the brain, alcohol can have many devastating effects. Alcohol is a well-known cytotoxic agent that can cause specific brain pathology in humans; however, the exact biological mechanisms are not well-elucidated. Animal models are invaluable tools to investigate potential novel treatments in a substance abuse model. Mice studies can be used to screen for negative outcomes prior to human trials. We hypothesize that the C1q tumor necrosis factor-related protein, CTRP3, overexpression in mice reduces neuroinflammation from ethanol consumption that has been coupled with a high fat diet when compared to control mice. The CTRP family of proteins are adipokines and CTRP3 specifically influences cell viability, metabolism, and peripheral inflammation levels. Antibody specific immunoblotting is used to probe protein expression changes in neuroinflammatory markers in mouse cerebellum brain tissue in an overexpression mouse model of CTRP3 when compared to high-fat ethanol exposed mice and baseline control mice. The two proteins examined are MAG and GFAP. Myelin associated glycoprotein, or MAG, is a protein expressed by oligodendrocytes that mediate axonal growth and myelin interactions with neurons in the brain. Oligodendrocytes are extremely sensitive to oxidative stress to which cognitive deficits in ethanol exposure is thought to be attributed. Glial fibrillary acidic protein, or GFAP, is a marker of astrocyte reactivity. Astrocytes are cells in the brain that are responsible for environmental stabilization and actively participate in neurotransmission. Currently, GFAP alterations in ethanol-exposed animals are dose and age dependent. We chose to use young adult mice where GFAP reactiveness is increased during chronic ethanol exposure. The proposed studies are essential in determining CTRP3’s relationship to detrimental neuroinflammatory effects of alcohol and high fat diet in mice. The data obtained from these studies will provide compelling evidence for future clinical trials to investigate CTRP3 as a therapeutic agent in people with a high fat diet that use alcohol chronically