Evidence of microglial activation following exposure to serum from first-onset drug-naïve schizophrenia patients.

Abnormal activation of brain microglial cells is widely implicated in the pathogenesis of schizophrenia. Previously the pathophysiology of microglial activation was considered to be intrinsic to the central nervous system. We hypothesised that due to their perivascular localization, microglia can also be activated by factors present in circulating blood. Through application of high-content functional screening, we show that peripheral blood serum from first-onset drug-naïve schizophrenia patients is sufficient to provoke microglial cell signalling network responses in vitro which are indicative of proinflammatory activation. We further explore the composition of the serum for the presence of analytes, with the potential to activate microglia, and the utility of the resultant microglial cellular phenotype for novel drug discovery.

Study on inflammation-related genes and microRNAs, with special emphasis on the vascular repair factor HGF and miR-574-3p, in monocytes and serum of patients with T2D.

BACKGROUND: Recently, we reported signs of inflammation (raised IL-8, reduced miR-146a) and signs of vascular repair (raised HGF) in the serum of Ecuadorian patients with type 2 diabetes (T2D). In contrast, we found that the circulating monocytes lacked up-regulation of classical inflammatory genes (IL-1B, IL-6, and TNF) and there was even significant down-regulation of PTGS2. Notably, genes and a microRNA involved in adhesion, cell differentiation and morphology (CD9, DHRS3, PTPN7 and miR-34c-5p) were up-regulated in the T2D monocytes, suggesting a role of the anti-inflammatory cells in adhesion, vascular repair and invasion. AIM: To determine the gene expression of the vascular repair factor HGF in the circulating monocytes of patients with T2D and to investigate the relationship between HGF and the expression of the other previously tested monocyte genes and the contribution to the raised serum level of HGF. In addition, we tested the level of 6 microRNAs, which were previously found abnormal in the circulating monocytes, in the serum of the patients. METHODS: A gene and microRNA expression study in monocytes and serum of 64 Ecuadorian patients with T2D (37-85 years) and 44 non-diabetic controls (32-87 years). RESULTS: The gene expression of HGF was significantly raised in the monocytes of the patients with T2D and associated with the expression of genes involved in adhesion, cell differentiation and morphology. HGF gene expression did not correlate with the serum level of HGF. The monocyte expression of pro-inflammatory cytokine genes was also not associated with the serum levels of these cytokines. The level of miR-574-3p was significantly decreased in the serum of the patients with T2D, and correlated in expression with the decreased well-established inflammation-regulating miR-146a. The level of the microRNAs in serum did not correlate with their expression level in monocytes. CONCLUSION: In circulating monocytes of Ecuadorian T2D patients, the microRNA and gene expression of important inflammatory/chemotactic/motility/vascular repair factors differs from the expression in serum. While monocytes show a gene expression profile compatible with an anti-inflammatory state, serum shows a molecular profile compatible with an inflammatory state. Both compartments show molecular signs of vascular repair support, i.e. up-regulated HGF levels.

Type 2 Diabetes Monocyte MicroRNA and mRNA Expression: Dyslipidemia Associates with Increased Differentiation-Related Genes but Not Inflammatory Activation.

OBJECTIVE: To study the expression pattern of microRNAs and mRNAs related to inflammation in T2D monocytes. DESIGN: A microRNA finding study on monocytes of T2D patients and controls using array profiling was followed by a quantitative Real Time PCR (qPCR) study on monocytes of an Ecuadorian validation cohort testing the top over/under-expressed microRNAs. In addition, monocytes of the validation cohort were tested for 24 inflammation-related mRNAs and 2 microRNAs previously found deregulated in (auto)-inflammatory monocytes. RESULTS: In the finding study, 142 significantly differentially expressed microRNAs were identified, 15 having the strongest power to discriminate T2D patients from controls (sensitivity 66%, specificity 90%). However, differences in expression of these microRNAs between patients and controls were small. On the basis of >1.4 or <0.6-fold change expression 5 microRNAs were selected for further validation. One microRNA (miR-34c-5p) was validated as significantly over-expressed in T2D monocytes. In addition, we found over expression of 3 mRNAs (CD9, DHRS3 and PTPN7) in the validation cohort. These mRNAs are important for cell morphology, adhesion, shape change, and cell differentiation. Classical inflammatory genes (e.g. TNFAIP3) were only over-expressed in monocytes of patients with normal serum lipids. Remarkably, in dyslipidemia, there was a reduction in the expression of inflammatory genes (e.g. ATF3, DUSP2 and PTGS2). CONCLUSIONS: The expression profile of microRNAs/mRNAs in monocytes of T2D patients indicates an altered adhesion, differentiation, and shape change potential. Monocyte inflammatory activation was only found in patients with normal serum lipids. Abnormal lipid values coincided with a reduced monocyte inflammatory state.

Decreased serum level of miR-146a as sign of chronic inflammation in type 2 diabetic patients.

BACKGROUND: There is increasing evidence that chronic inflammation is an important determinant in insulin resistance and in the pathogenesis of type 2 diabetes (T2D). MicroRNAs constitute a newly discovered system of cell regulation and in particular two microRNAs (miR-146a and miR-155) have been described as regulators and biomarkers of inflammation. AIM: To determine a putative association between the levels of miR-146a and miR-155 in serum of T2D patients, clinical parameters and serological indicators of inflammation. METHODS: We performed quantitative Real Time PCR (qPCR) of microRNAs from serum (56 Ecuadorian T2D ambulatory patients and 40 non-diabetic controls). In addition, we evaluated T2D-related serum cytokines.chemokines and growth factors using a commercially available multi-analyte cytometric bead array system. We correlated outcomes to clinical parameters, including BMI, HbA1c and lipid state. RESULTS: The Ecuadorian non-diabetic controls appeared as overweight (BMI>25: patients 85%, controls 82.5%) and as dyslipidemic (hypercholesterolemia: patients 60.7%, controls 67.5%) as the patients. The serum levels of miR-146a were significantly reduced in T2D patients as compared to these non-diabetic, but obese/dyslipidemic control group (mean patients 0.61, mean controls set at 1; p = 0.042), those of miR-155 were normal.The serum levels of both microRNAs correlated to each other (r = 0.478; p<0.001) and to leptin levels. The microRNAs did not correlate to BMI, glycemia and dyslipidemia.From the tested cytokines, chemokines and growth factors, we found IL-8 and HGF significantly raised in T2D patients versus non-diabetic controls (p = 0.011 and 0.023 respectively). CONCLUSIONS: This study shows decreased serum anti-inflammatory miR-146a, increased pro-inflammatory IL-8 and increased HGF (a vascular/insular repair factor) as discriminating markers of failure of glucose control occurring on the background of obesity and dyslipidemia.

Down-regulation of inflammation-protective microRNAs 146a and 212 in monocytes of patients with postpartum psychosis.

BACKGROUND: Postpartum psychosis (PP) is thought to belong to the bipolar spectrum. Recently we described an immune activation signature in monocytes of patients with PP using gene expression profiling. Immune activation genes are regulated by microRNAs (miRNAs). We therefore profiled miRNA expression in monocytes of PP patients to identify differentially expressed miRNAs between PP and the healthy state. METHODS: In a profiling study we carried out miRNA profiling using TaqMan array human microRNA A cards v2.0 and monocytes of 8 PP patients. Data were analyzed against monocytes of healthy postpartum women (CP). Nine miRNAs were selected and tested using individual Q-PCR in a larger validation study on monocytes of 20 PP patients, 20 CP and 20 healthy non-postpartum women (HC). RESULTS: In the validation study miR-146a expression was significantly down-regulated in the monocytes of first onset PP patients as compared to CP and HC; miR-212 expression was significantly down-regulated in PP patients with prior bipolar disorder. In silico miR-146a targeted 4 genes of the previously described monocyte activation signature in bipolar disorder; miR-212 targeted 2 of such genes. In a correlation study decreased expression of miR-146a in monocytes was related to decreased natural T regulator cells in PP patients; decreased miR-212 was correlated to increased Adrenomedulin and decreased IL-6 expression in monocytes and to higher Th2 cell levels. CONCLUSIONS: This study identified changes in miR-146a and -212 expression in PP. Since these miRNAs are linked to inflammation, the study strengthens the view that PP is an inflammation-like condition.

Immune system dysregulation in first-onset postpartum psychosis.

BACKGROUND: Accumulating evidence suggests that dysregulation of the immune system represents an important vulnerability factor for mood disorders. Postpartum psychosis (PP) is a severe mood disorder occurring within 4 weeks after delivery, a period of heightened immune responsiveness and an altered endocrine set point. Therefore, the aim of this study was to examine immune activation in patients with first-onset PP at the level of monocytes, T cells, and serum cytokines/chemokines. METHODS: We included 63 women admitted with first-onset PP. Control groups included healthy postpartum (n = 56) and nonpostpartum (n = 136) women. A quantitative-polymerase chain reaction monocyte gene expression analysis was performed with 43 genes previously identified as abnormally regulated in nonpostpartum mood disorder patients including the isoforms of the glucocorticoid receptor. Peripheral blood mononuclear cells percentages were measured by fluorescence-activated cell sorter analysis, whereas serum cytokines/chemokines were determined with a cytometric bead array. RESULTS: In healthy women, postpartum T cell levels were significantly elevated compared with nonpostpartum. Patients with PP failed to show the normal postpartum T cell elevation. In contrast, these patients showed a significant elevation of monocyte levels and a significant upregulation of several immune-related monocyte genes compared with control subjects postpartum and nonpostpartum. Furthermore, the glucocorticoid receptor α/ß gene expression ratio was decreased in monocytes of PP patients, strongly correlating with their immune activation. CONCLUSIONS: This study demonstrates a robust dysregulation of the immuno-neuro-endocrine set point in PP, with a notable over-activation of the monocyte/macrophage arm of the immune system.

Immune and neuroimmune alterations in mood disorders and schizophrenia.

A large number of publications over the past 20 years have indicated that immune system function is altered in schizophrenia and mood disorder patients. This chapter reviews the evidence, which suggests that a proinflammatory state of the cytokine network induces psychopathologic symptoms and may be involved in the pathogenesis and pathophysiology of these major mental illnesses. The authors also present recent data, which relates immune activation to present theories on the influence of activated immune cells in altering brain function. They also focus on the role of the environment in immune activation and on the role of the microbiome and gut flora. Increased understanding of such factors could help in the development of novel treatment strategies and improved clinical management of mental disorders.

TREM-1 and DAP12 expression in monocytes of patients with severe psychiatric disorders. EGR3, ATF3 and PU.1 as important transcription factors.

INTRODUCTION: Immune activation is a characteristic of schizophrenia (SCZ), bipolar disorder (BD) and unipolar major depressive disorder (MDD). The triggering receptor expressed on myeloid cells 1 (TREM-1), its' adaptor molecule DAP12 and their transcription factor (TF) PU.1 are important key genes in inflammation and expressed in activated monocytes and microglia. AIM: To test: (1) if the expressions of TREM-1, DAP12 and PU.1 are increased in monocytes of patients with severe psychiatric disorders and (2) if PU.1 and the TFs ATF3 and EGR3 (which have been found as prominent increased monocyte genes in previous studies) are involved in the regulation of TREM-1 and DAP12 expression. METHODS: Using Q-PCR, we studied the gene expression of TREM-1, DAP12, PU.1, ATF3 and EGR3 in the monocytes of 73 patients with severe psychiatric disorders (27 recent onset SCZ patients, 22 BD patients and 24 MDD patients) and of 79 healthy controls (HC). Using in silico TF binding site prediction and in vivo chromatin immunoprecipitation (ChIP), we studied the actual binding of EGR3, ATF3 and PU.1 to the promoter regions of TREM-1 and DAP12. RESULTS: 1. TREM-1 gene expression was increased in the monocytes of SCZ and BD patients and tended to be increased in the monocytes of MDD patients. 2. DAP12 gene levels were neither increased in the monocytes of SCZ, BD, nor MDD patients. 3. PU.1 expression levels were increased in the monocytes of MDD patients, but not in those of SCZ and BD patients. 4. TREM-1 expression levels correlated in particular to ATF3 and EGR3 expression levels, DAP12 expression levels correlated in particular to PU.1 expression levels. 5. We found using binding site prediction and ChIP assays that the TFs EGR3 and ATF3 indeed bound to the TREM-1 promoter, PU.1 bound to both the TREM-1 and DAP12 promoter. CONCLUSION: In this study, we provide evidence that TREM-1 gene expression is significantly increased in monocytes of SCZ and BD patients and that the TREM-1 gene is a target gene of the TFs ATF3 and EGR3. In MDD patients, PU.1 gene expression was increased with a tendency for TREM-1 gene over expression. Our observations support the concept that monocytes are in a pro-inflammatory state in severe psychiatric conditions and suggest differences in monocyte inflammatory set points between SCZ, BD and MDD.

CRX ChIP-seq reveals the cis-regulatory architecture of mouse photoreceptors.

Approximately 98% of mammalian DNA is noncoding, yet we understand relatively little about the function of this enigmatic portion of the genome. The cis-regulatory elements that control gene expression reside in noncoding regions and can be identified by mapping the binding sites of tissue-specific transcription factors. Cone-rod homeobox (CRX) is a key transcription factor in photoreceptor differentiation and survival, but its in vivo targets are largely unknown. Here, we used chromatin immunoprecipitation with massively parallel sequencing (ChIP-seq) on CRX to identify thousands of cis-regulatory regions around photoreceptor genes in adult mouse retina. CRX directly regulates downstream photoreceptor transcription factors and their target genes via a network of spatially distributed regulatory elements around each locus. CRX-bound regions act in a synergistic fashion to activate transcription and contain multiple CRX binding sites which interact in a spacing- and orientation-dependent manner to fine-tune transcript levels. CRX ChIP-seq was also performed on Nrl(-/-) retinas, which represent an enriched source of cone photoreceptors. Comparison with the wild-type ChIP-seq data set identified numerous rod- and cone-specific CRX-bound regions as well as many shared elements. Thus, CRX combinatorially orchestrates the transcriptional networks of both rods and cones by coordinating the expression of photoreceptor genes including most retinal disease genes. In addition, this study pinpoints thousands of noncoding regions of relevance to both Mendelian and complex retinal disease.

The novel activated microglia/macrophage WAP domain protein, AMWAP, acts as a counter-regulator of proinflammatory response.

Microgliosis is a common phenomenon in neurodegenerative disorders, including retinal dystrophies. To identify candidate genes involved in microglial activation, we used DNA-microarray analysis of retinal microglia from wild-type and retinoschisin-deficient (Rs1h(-/Y)) mice, a prototypic model for inherited retinal degeneration. Thereby, we cloned a novel 76 aa protein encoding a microglia/macrophage-restricted whey acidic protein (WAP) termed activated microglia/macrophage WAP domain protein (AMWAP). The gene consists of three exons and is located on mouse chromosome 11 in proximity to a chemokine gene cluster. mRNA expression of AMWAP was detected in microglia from Rs1h(-/Y) retinas, brain microglia, and other tissue macrophages. AMWAP transcription was rapidly induced in BV-2 microglia upon stimulation with multiple TLR ligands and IFN-gamma. The TLR-dependent expression of AMWAP was dependent on NF-kappaB, whereas its microglia/macrophage-specific transcription was regulated by PU.1. Functional characterization showed that AMWAP overexpression reduced the proinflammatory cytokines IL-6 and IL-1beta and concomitantly increased expression of the alternative activation markers arginase 1 and Cd206. Conversely, small interfering RNA knockdown of AMWAP lead to higher IL-6, IL-1beta, and Ccl2 transcript levels, whereas diminishing arginase 1 and Cd206 expression. Moreover, AMWAP expressing cells had less migratory capacity and showed increased adhesion in a trypsin-protection assay indicating antiserine protease activity. In agreement with findings from other WAP proteins, micromolar concentrations of recombinant AMWAP exhibited significant growth inhibitory activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis. Taken together, we propose that AMWAP is a counter-regulator of proinflammatory microglia/macrophage activation and a potential modulator of innate immunity in neurodegeneration.

Docosahexaenoic acid attenuates microglial activation and delays early retinal degeneration.

Microgliosis is a common phenomenon in neurodegenerative disorders including retinal dystrophies. We performed a detailed characterization of activated microglia in the retinoschisin (Rs1h)-deficient (Rs1h(-/Y)) mouse model of inherited retinal degeneration. To visualize and isolate microglia, we crossed Rs1h(-/Y) animals with transgenic MacGreen mice, which express green fluorescent protein under the control of the macrophage-specific csf1r promoter. Activated microglia were detected in retinal sections and whole-mounts of early postnatal MacGreen/Rs1h(-/Y) mice before the onset of overt neuronal cell death. These activated microglia contained prominent lipid droplets and analysis of the retinal lipid composition showed decreased docosahexaenoic acid (DHA) levels in Rs1h(-/Y) retinas. To establish a link between microglia activation, reduced DHA levels, and neurodegeneration, a dietary intervention study was performed. Female Rs1h(-/-) mice and their Rs1h(-/Y) litter were either subjected to a diet enriched with DHA, or a control chow lacking DHA. Supplementation with DHA enhanced photoreceptor survival and converted activated microglia to a quiescent phenotype. Furthermore, DHA, but not docosapentaenoic acid or adrenic acid reduced pro-inflammatory gene expression, migration, and lipid accumulation of cultured BV-2 microglia. We conclude that retinal DHA levels control the activity of microglia and thereby may affect the progression and extent of retinal degeneration.

Induction of early growth response-1 mediates microglia activation in vitro but is dispensable in vivo.

We have previously identified activation of microglia and induction of the early growth response gene 1 (Egr1) in the retina of retinoschisin-deficient (Rs1h(-/Y)) mice. We hypothesized that microglial expression of Egr1 might support retinal microgliosis. To test this, Egr1 transcript levels were determined in RNAs isolated from early postnatal retinas and primary microglia from Rs1h(-/Y) mice and wild-type controls. Egr1 mRNA expression was strongly induced in retinoschisin-deficient retinas as well as in ex vivo isolated microglia. Increased microglial Egr1 protein expression was concordantly detected in retinal sections of Rs1h(-/Y) mice using immunohistochemistry. Prominent activation-dependent Egr1 mRNA and protein expression was also confirmed in murine BV-2 microglia. Using binding site prediction and chromatin immunoprecipitation, we identified that the Egr1 promoter itself and the microglial marker genes Clec7a and Caspase11 are direct transcriptional targets of Egr1. Over-expression of Egr1 in BV-2 cells by adenoviral infection promoted Clec7a and Caspase11 mRNA synthesis, whereas expression of the Egr1 repressor NAB2 blocked the transcription of these genes. To analyze whether Egr1 was absolutely required for microglial marker expression in vivo, transcript levels were quantified in Rs1h(-/Y)/Egr1(-/-) retinas. No significant differences in activation marker expression could be measured in retinal tissue from Rs1h(-/Y)/Egr1(-/-) mice compared to Rs1h(-/Y) mice, suggesting that lack of Egr1 does not impair transcription of microglia genes in vivo. Taken together, our findings suggest that increased Egr1 expression is present in activated retinal microglia and contributes to their activation. However, up-regulation of Egr1 is not absolutely required for retinal microglia activation in vivo.

Transcriptomic profiling identifies a PU.1 regulatory network in macrophages.

PU.1 is a key transcription factor for hematopoiesis and macrophage differentiation. Using chromatin immunoprecipitation we have previously identified several PU.1 target genes in macrophages and microglia. With the aim to complement these studies, we performed a transcriptomic analysis of PU.1(-/-) progenitors after restoration of PU.1 activity. PUER cells committed to macrophage differentiation were analyzed with novel Affymetrix exon 1.0 ST arrays and Affymetrix 430 2.0 genome arrays for crosswise validation. We combined these genome-wide expression data with a publicly-available microarray dataset of PU.1-knockdown hematopoietic stem cells for an integrated analysis. Bibliographic gene connections, binding site prediction and ChIP-Chip data were used to define a multi-level PU.1 regulatory network in macrophages. Moreover, an alternative transcript of the novel PU.1 target gene Ptpro was identified by exon arrays and PU.1 binding to an intronic promoter was demonstrated. In conclusion, we present a PU.1 transcriptional network with novel validated PU.1 target genes.

Induction of STAP-1 promotes neurotoxic activation of microglia.

Activated microglia contribute to neurodegenerative processes in the brain and the retina. Via DNA-microarray analysis, we have previously identified up-regulation of several immune-related genes in the dystrophic retina of retinoschisin-deficient (Rs1h(-/Y)) mice. Here we report a strong overexpression of transcripts for the signal-transducing adaptor protein-1 (STAP-1) in isolated Rs1h(-/Y) microglia. Furthermore, STAP-1 expression was induced in activated bone marrow-derived macrophages as well as LPS-, interferon-gamma-, and CpG-stimulated myeloid cell lines. Ectopic expression of STAP-1 in BV-2 microglia changed the morphology and cytoskeletal organization of the cells and transformed ramified cells to an activated state. STAP-1 overexpression also leads to an interaction with the M-CSF receptor/c-Fms diminishing its ligand-dependent phosphorylation. Finally, STAP-1 expressing cells showed strongly reduced migration with increased cytotoxicity against 661W photoreceptor like cells. Taken together, our study implicates a previously unknown role of STAP-1 in pro-inflammatory microglia activation potentially contributing to neuronal apoptosis and degeneration.

CRX controls retinal expression of the X-linked juvenile retinoschisis (RS1) gene.

X-linked juvenile retinoschisis is a heritable condition of the retina in males caused by mutations in the RS1 gene. Still, the cellular function and retina-specific expression of RS1 are poorly understood. To address the latter issue, we characterized the minimal promoter driving expression of RS1 in the retina. Binding site prediction, site-directed mutagenesis, and reporter assays suggest an essential role of two nearby cone-rod homeobox (CRX)-responsive elements (CRE) in the proximal -177/+32 RS1 promoter. Chromatin immunoprecipitation associates the RS1 promoter in vivo with CRX, the coactivators CBP, P300, GCN5 and acetylated histone H3. Transgenic Xenopus laevis expressing a green fluorescent protein (GFP) reporter under the control of RS1 promoter sequences show that the -177/+32 fragment drives GFP expression in photoreceptors and bipolar cells. Mutating either of the two conserved CRX binding sites results in strongly decreased RS1 expression. Despite the presence of sequence motifs in the promoter, NRL and NR2E3 appear not to be essential for RS1 expression. Together, our in vitro and in vivo results indicate that two CRE sites in the minimal RS1 promoter region control retinal RS1 expression and establish CRX as a key factor driving this expression.

An integrated workflow for analysis of ChIP-chip data.

Although ChIP-chip is a powerful tool for genome-wide discovery of transcription factor target genes, the steps involving raw data analysis, identification of promoters, and correlation with binding sites are still laborious processes. Therefore, we report an integrated workflow for the analysis of promoter tiling arrays with the Genomatix ChipInspector system. We compare this tool with open-source software packages to identify PU.1 regulated genes in mouse macrophages. Our results suggest that ChipInspector data analysis, comparative genomics for binding site prediction, and pathway/network modeling significantly facilitate and enhance whole-genome promoter profiling to reveal in vivo sites of transcription factor-DNA interactions.

Dap12 expression in activated microglia from retinoschisin-deficient retina and its PU.1-dependent promoter regulation.

Several alterations in the expression of immune-related transcripts were identified recently in the degenerating retina of the retinoschisin knockout (Rs1h(-/Y)) mouse, including the strong expression of the adaptor protein Dap12. As Dap12 is found in leukocytes, we hypothesized that its disease-related expression may be confined to activated retinal microglia cells. To test this hypothesis, we established a procedure for isolation and culture of retinal microglia cells and performed genome-wide expression profiling from Rs1h(-/Y) and control microglia. While retaining their activated state in culture, ex vivo microglia expressed high levels of Dap12 and the transcription factor PU.1. The activation-dependent induction of Dap12 was also confirmed in the microglia cell line BV-2 following in vitro stimulation. To examine the transcriptional regulation of Dap12 further, macrophage cell lines were transfected with several Dap12 reporter constructs. Promoter deletion assays and site-directed mutagenesis experiments demonstrated an essential role of evolutionarily conserved PU.1 consensus sites in the proximal -104/+118 Dap12 promoter. In vitro and in vivo binding of PU.1 to this promoter region was demonstrated using EMSA and chromatin immunoprecipitation. Knockdown of PU.1 by RNA interference caused a significant reduction of endogenous Dap12 expression and re-expression, and activation of PU.1 in PU.1(-/-) progenitor cells induced Dap12 transcription. Taken together, our results indicate that activated microglia from degenerating retinae express high levels of Dap12 and PU.1, and PU.1 controls the myeloid-specific regulation of Dap12 directly and may also play a general role in microglia gene expression during retinal degeneration.