Wouter Beumer

The mononuclear phagocyte system and its cytokine inflammatory networks in schizophrenia and bipolar disorder

This review describes patients with schizophrenia and bipolar disorder. In such patients, a high inflammatory set point of circulating monocytes at the transcriptome level is observed, involving various inflammatory transcripts forming distinct fingerprints (the transcriptomic monocyte fingerprint in schizophrenia overlaps with that in bipolar disorder, but also differs with it at points). There are increased levels of compounds of the IL-1, IL-6 and TNF system in the serum (be it modest and inconsistent). There is also evidence that the IL-2 system is activated in patients with schizophrenia (and perhaps those with mania), although independently of the activation of the IL-1, IL-6 and TNF systems, suggesting separate inducing mechanisms for monocyte and T-cell activation. It is not yet known whether such T cell activation involves the Th1/Th2/Th17 or Treg systems.

The immune theory of psychiatric diseases : a key role for activated microglia and circulating monocytes

This review describes a key role for mononuclear phagocytes in the pathogenesis of major psychiatric disorders. There is accumulating evidence for activation of microglia (histopathology and PET scans) and circulating monocytes (enhanced gene expression of immune genes, an overproduction of monocyte/macrophage‐related cytokines) in patients with bipolar disorder, major depressive disorder, and schizophrenia. These data are strengthened by observations in animal models, such as the MIA models, the chronic stress models, and the NOD mouse model. In these animal models of depressive‐, anxiety‐, and schizophrenia‐like behavior, similar activations of microglia and circulating monocytes can be found. These animal models also make in‐depth pathogenic studies possible and show that microglia activation impacts neuronal development and function in brain areas congruent with the altered depressive and schizophrenia‐like behaviors.

Prevalence of interferon type I signature in CD14 monocytes of patients with Sjögren's syndrome and association with disease activity and BAFF gene expression

Objective To determine the prevalence of upregulation of interferon (IFN) type I inducible genes, the so called ‘IFN type I signature’, in CD14 monocytes in 69 patients with primary Sjögrens syndrome (pSS) and 44 healthy controls (HC) and correlate it with disease manifestations and expression of B cell activating factor (BAFF). Methods Expression of IFI44L, IFI44, IFIT3, LY6E and MX1 was measured using real time quantitative PCR in monocytes. Expression values were used to calculate IFN type I scores for each subject. pSS patients positive for the IFN type I signature (IFN score≥10) and patients negative for the signature (IFN score<10) were then compared for clinical disease manifestations and BAFF expression. A bioassay using a monocytic cell line was performed to study whether BAFF mRNA expression was inducible by IFN type I activity in serum of patients with pSS. Results An IFN type I signature was present in 55% of patients with pSS compared with 4.5% of HC. Patients with the IFN type I signature showed: (a) higher EULAR Sjögrens Syndrome Disease Activity Index scores; higher anti-Ro52, anti-Ro60 and anti-La autoantibodies; higher rheumatoid factor; higher serum IgG; lower C3, lower absolute lymphocyte and neutrophil counts; (b)higher BAFF gene expression in monocytes. In addition, serum of signature-positive patients induced BAFF gene expression in monocytes. Conclusions The monocyte IFN type I signature identifies a subgroup of patients with pSS with a higher clinical disease activity together with higher BAFF mRNA expression. Such patients might benefit from treatment blocking IFN type I production or activity.

Increased level of serum cytokines, chemokines and adipokines in patients with schizophrenia is associated with disease and metabolic syndrome

At present there are strong indications of a shared vulnerability factor for schizophrenia (SZ), diabetes and the metabolic syndrome (metS). In this study we focus on an aberrantly activated monocyte/macrophage system as the shared factor. We measured in SZ patients (n=144), the serum levels of monocyte/macrophage cytokines/chemokines/adipokines CCL2, CCL4, IL-1β, TNF-α, IL-6, PTX3, leptin, adiponectin, PAI-1, OPG and ICAM-1 and compared these levels to healthy controls (HC) (n=138). Using multivariate analysis, we studied the effect of the presence of the disease SZ, the components of the metS including BMI, the levels of lipids (HDL cholesterol and triglycerides (TG)), diabetes (hyperglycemia) and the use of antipsychotic medication, on the serum levels of these immune compounds. We found all measured immune compounds with the exception of PAI-1 and OPG to be elevated in the SZ patient population. Multivariate analysis showed that elevations were linked to gender (ICAM-1, leptin, TNF-α and adiponectin), an increased BMI (leptin, adiponectin), hyperglycemia/diabetes (CCL4, and OPG), reduced HDL-cholesterol or increased levels of TG (adiponectin and PTX3) or the metS (CCL2, leptin and adiponectin). IL-1β and IL-6 were the only immune compounds raised in the serum of patients not affected by any of the included factors. Although many of the immune compounds were found linked to (components of) the metS, the most dominant linkage was found with the disease schizophrenia, confirming earlier reports on increased monocyte/macrophage activation as a key component for understanding the pathogenesis of schizophrenia.

Microglia shape corpus callosum axon tract fasciculation: functional impact of prenatal inflammation.

Microglia colonise the brain parenchyma at early stages of development and accumulate in specific regions where they participate in cell death, angiogenesis, neurogenesis and synapse elimination. A recurring feature of embryonic microglial is their association with developing axon tracts, which, together with in vitro data, supports the idea of a physiological role for microglia in neurite development. Yet the demonstration of this role of microglia is lacking. Here, we have studied the consequences of microglial dysfunction on the formation of the corpus callosum, the largest commissure of the mammalian brain, which shows consistent microglial accumulation during development. We studied two models of microglial dysfunction: the loss‐of‐function of DAP12, a key microglial‐specific signalling molecule, and a model of maternal inflammation by peritoneal injection of lipopolysaccharide at embryonic day (E)15.5. We also took advantage of the Pu.1−/− mouse line, which is devoid of microglia. We performed transcriptional profiling of maternally inflamed and Dap12‐mutant microglia at E17.5. The two treatments principally down‐regulated genes involved in nervous system development and function, particularly in neurite formation. We then analysed the developmental consequences of these microglial dysfunctions on the formation of the corpus callosum. We show that all three models of altered microglial activity resulted in the defasciculation of dorsal callosal axons. Our study demonstrates that microglia display a neurite‐development‐promoting function and are genuine actors of corpus callosum development. It further shows that microglial activation impinges on this function, thereby revealing that prenatal inflammation impairs neuronal development through a loss of trophic support.

Contrasting expression pattern of RNA-sensing receptors TLR7, RIG-I and MDA5 in interferon-positive and interferon-negative patients with primary Sjögren's syndrome.

Objective The interferon (IFN) type I signature is present in over half of patients with primary Sjögrens syndrome (pSS) and associated with higher disease-activity and autoantibody presence. Plasmacytoid dendritic cells (pDCs) are considered as the main source of enhanced IFN type I expression. The objective of this study was to unravel the molecular pathways underlying IFN type I bioactivity in pDCs of patients with pSS. Methods Blood samples from 42 healthy controls (HC) and 115 patients with pSS were stratified according to their IFN type I signature. CD123+BDCA4+ pDCs and CD14+ monocytes were isolated from peripheral blood mononuclear cells (PBMCs). Genome-wide microarray analysis was conducted on sorted pDCs in a small sample set, followed by validation of differentially expressed genes of interest in pDCs and monocytes. Results We found an upregulation of endosomal toll-like receptor (TLR) 7, but not TLR9, in IFN-positive (IFNpos) pDCs (p<0.05) and monocytes (p=0.024). Additionally, the downstream signalling molecules MyD88, RSAD2 and IRF7 were upregulated, as were the cytoplasmic RNA-sensing receptors DDX58/retinoic acid inducible gene-I (RIG-I) and IFIH1/melanoma differentiation associated gene-5 (MDA5). In vitro triggering of the TLR7-pathway in HC PBMCs induced upregulation of DDX58/RIG-I and IFIH1/MDA5, and downregulated TLR9. The upregulation of TLR7, its downstream signalling pathway, DDX58/RIG-I and IFIH1/MDA5 were confined to patients with IFN-positive pSS. IFN-negative patients had a contrasting expression pattern—TLR7 normal, and decreased TLR9, RIG-I and MDA5. Conclusions Here we conclude a contrasting expression pattern of the RNA-sensing receptors TLR7, RIG-I and MDA5 in pDCs and monocytes of patients with IFNpos pSS. This profile could explain the pathogenic IFN production and might reveal novel therapeutic targets in these patients.

Changes in Serum Adhesion Molecules, Chemokines, Cytokines, and Tissue Remodeling Factors in Euthyroid Women Without Thyroid Antibodies Who Are at Risk for Autoimmune Thyroid Disease: A Hypothesis on the Early Phases of the Endocrine Autoimmune Reaction

BACKGROUND The target glands in spontaneous animal models of endocrine autoimmune disease show, prior to the autoimmune reaction, growth and connective tissue abnormalities, whereas the autoimmune reaction is initiated by an early accumulation of macrophages and dendritic cells in the target glands. AIM The aim of the study was to test the hypothesis that serum factors related to these growth and connective tissue abnormalities and the early accumulation of immune cells, ie, tissue growth/remodeling factors, adhesion molecules, chemokines, and pro- and anti-inflammatory cytokines, are related to thyroid peroxidase autoantibodies (TPO-Abs) seroconversion in subjects at risk to develop autoimmune thyroid disease (AITD). DESIGN A controlled study on 64 TPO-Ab-negative euthyroid female relatives with at least 1 first- or second-degree relative with documented autoimmune hyper- or hypothyroidism, 32 of whom did and 32 who did not seroconvert to TPO-Ab positivity in 5-year follow-up. The relatives were compared with 32 healthy controls. In all subjects we measured serum levels of chemokine (C-C motif) ligand (CCL)-2, CCL3, CCL4, soluble vascular cell adhesion molecule, soluble intercellular adhesion molecule-1, thrombospondin-1, vascular endothelial growth factor-A, angiopoietin 1 receptor-2, metalloproteinase-13, platelet-derived growth factor-BB, fibronectin, IL-1β, IL-6, TNF-α, IL-10, and growth differentiation factor-15 by multiplex (cytometric bead array) or a single commercial ELISA. RESULTS Both seroconverting and nonseroconverting family members showed an up-regulation of fibronectin and a down-regulation of platelet-derived growth factor-BB and the adhesion and migration factors CCL2, CCL4, soluble vascular cell adhesion molecule-1, angiopoietin 1 receptor-2, and metalloproteinase-13. The seroconverters differed from the nonseroconverters by an up-regulation of the proinflammatory compounds Il-1β, IL-6, and CCL3. CONCLUSION This study shows that euthyroid females within AITD families show a characteristic pattern of abnormalities in serum levels of tissue remodeling factors, growth factors, chemokines, (vascular) adhesion molecules, and cytokines prior to the occurrence of TPO-Abs in serum. The results provide proof of principle that preseroconversion stages and seroconversion to AITD might be predicted using serum analytes related to growth/connective tissue abnormalities and migration/accumulation abnormalities of macrophages and dendritic cells.

The gene expression profile of CD11c + CD8α - dendritic cells in the pre-diabetic pancreas of the NOD mouse

Two major dendritic cell (DC) subsets have been described in the pancreas of mice: The CD11c+CD8α− DCs (strong CD4+ T cell proliferation inducers) and the CD8α+CD103+ DCs (T cell apoptosis inducers). Here we analyzed the larger subset of CD11c+CD8α− DCs isolated from the pancreas of pre-diabetic NOD mice for genome-wide gene expression (validated by Q-PCR) to elucidate abnormalities in underlying gene expression networks. CD11c+CD8α− DCs were isolated from 5 week old NOD and control C57BL/6 pancreas. The steady state pancreatic NOD CD11c+CD8α− DCs showed a reduced expression of several gene networks important for the prime functions of these cells, i.e. for cell renewal, immune tolerance induction, migration and for the provision of growth factors including those for beta cell regeneration. A functional in vivo BrdU incorporation test showed the reduced proliferation of steady state pancreatic DC. The reduced expression of tolerance induction genes (CD200R, CCR5 and CD24) was supported on the protein level by flow cytometry. Also previously published functional tests on maturation, immune stimulation and migration confirm the molecular deficits of NOD steady state DC. Despite these deficiencies NOD pancreas CD11c+CD8α− DCs showed a hyperreactivity to LPS, which resulted in an enhanced pro-inflammatory state characterized by a gene profile of an enhanced expression of a number of classical inflammatory cytokines. The enhanced up-regulation of inflammatory genes was supported by the in vitro cytokine production profile of the DCs. In conclusion, our data show that NOD pancreatic CD11c+CD8α− DCs show various deficiencies in steady state, while hyperreactive when encountering a danger signal such as LPS.

Exaggerated Increases in Microglia Proliferation, Brain Inflammatory Response and Sickness Behaviour upon Lipopolysaccharide Stimulation in Non-Obese Diabetic Mice

The non-obese diabetic (NOD) mouse, an established model for autoimmune diabetes, shows an exaggerated reaction of pancreas macrophages to inflammatory stimuli. NOD mice also display anxiety when immune-stimulated. Chronic mild brain inflammation and a pro-inflammatory microglial activation is critical in psychiatric behaviour. Objective: To explore brain/microglial activation and behaviour in NOD mice at steady state and after systemic lipopolysaccharide (LPS) injection. Methods: Affymetrix analysis on purified microglia of pre-diabetic NOD mice (8-10 weeks) and control mice (C57BL/6 and CD1 mice, the parental non-autoimmune strain) at steady state and after systemic LPS (100 μg/kg) administration. Quantitative PCR was performed on the hypothalamus for immune activation markers (IL-1β, IFNγ and TNFα) and growth factors (BDNF and PDGF). Behavioural profiling of NOD, CD1, BALB/c and C57BL/6 mice at steady state was conducted and sickness behaviour/anxiety in NOD and CD1 mice was monitored before and after LPS injection. Results: Genome analysis revealed cell cycle/cell death and survival aberrancies of NOD microglia, substantiated as higher proliferation on BrdU staining. Inflammation signs were absent. NOD mice had a hyper-reactive response to novel environments with some signs of anxiety. LPS injection induced a higher expression of microglial activation markers, a higher brain pro-inflammatory set point (IFNγ, IDO) and a reduced expression of BDNF and PDGF after immune stimulation in NOD mice. NOD mice displayed exaggerated and prolonged sickness behaviour after LPS administration. Conclusion: After stimulation with LPS, NOD mice display an increased microglial proliferation and an exaggerated inflammatory brain response with reduced BDNF and PDGF expression and increased sickness behaviour as compared to controls.

Dr. James Matthew Lipton, 1938-2016

Dr. Jim Lipton died on the 10th of July this year. It was a great loss not only to his family and friends but also to the scientific world. The facts and dates of his life are well expressed in the obituary written by his daughter reprinted above, with permission. Many years ago, when Jim and his buddy, S.M. ‘Don’ McCann were both Professors of Physiology in Dallas, they suggested we start a new NIM journal. I was opposed to the idea, because there were already too many journals proliferating at a dizzying pace. The success of the ISNIM journal proved that they were right and I was wrong. One could not imagine two more disparate personalities, but they always managed to work together harmoniously. Both were geniuses, Jim soft-spoken and modest ... and Don, with an amazing photographic memory, boisterous (Don was first my professor at the University of Pennsylvania, and later, my student and honorary lecturer and awardee of the Novera Spector lectureship). A book needs to be written about Don, but most observers agree that he should have shared at least one Nobel Prize. Both remained my good friends all their lives. At one point I went to an international congress organized by Jim, only to find that he had dedicated this meeting to me! I hope that his friends and especially his wife, Luby, will I have been asked to write an obituary-memoriam for the cofounder of Neuroimmunomodulation (NIM) , who died on the 10th of July this year. Below is an obituary written by Jim’s daughter and reprinted with her permission, followed by some informal remembrances from Luby, his widow, and me.