CD200R1 Expression Research Articles

The regulation of NFKB1 on CD200R1 expression and their potential roles in Parkinson’s disease

BackgroundOveractivated microglia are a key contributor to Parkinson’s disease (PD) by inducing neuroinflammation. CD200R1, a membrane glycoprotein mainly found on microglia, is crucial for maintaining quiescence with its dysregulation linked to microglia’s abnormal activation. We and other groups have reported a decline in CD200R1 levels in several neurological disorders including PD. However, the mechanism regulating CD200R1 expression and the specific reasons for its reduction in PD remain largely unexplored. Given the pivotal role of transcription factors in gene expression, this study aimed to elucidate the transcriptional regulation of CD200R1 and its implications in PD.MethodsThe CD200R1 promoter core region was identified via luciferase assays. Potential transcription factors were predicted using the UCSC ChIP-seq database and JASPAR. NFKB1 binding to the CD200R1 core promoter was substantiated through electrophoretic mobility shift and chromatin immunoprecipitation assays. Knocking-down or overexpressing NFKB1 validated its regulatory effect on CD200R1. Correlation between decreased CD200R1 and deficient NFKB1 was studied using Genotype-Tissue Expression database. The clinical samples of the peripheral blood mononuclear cells were acquired from 44 PD patients (mean age 64.13 ± 9.78, 43.2% male, median Hoehn-Yahr stage 1.77) and 45 controls (mean age 64.70 ± 9.41, 52.1% male). NFKB1 knockout mice were utilized to study the impact of NFKB1 on CD200R1 expression and to assess their roles in PD pathophysiology.ResultsThe study identified the CD200R1 core promoter region, located 482 to 146 bp upstream of its translation initiation site, was directly regulated by NFKB1. Significant correlation between NFKB1 and CD200R1 expression was observed in human PMBCs. Both NFKB1 and CD200R1 were significantly decreased in PD patient samples. Furthermore, NFKB1-/- mice exhibited exacerbated microglia activation and dopaminergic neuron loss after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment.ConclusionOur study identified that NFKB1 served as a direct regulator of CD200R1. Reduced NFKB1 played a critical role in CD200R1 dysregulation and subsequent microglia overactivation in PD. These findings provide evidence that targeting the NFKB1-CD200R1 axis would be a novel therapeutic strategy for PD.

Abstract 2359: New insights into targeting the CD200R1 pathway in T and NK cells using 23ME-00610 as a single agent or in combination

Abstract 23ME-00610 is a monoclonal antibody that is being evaluated as a single agent in a Phase 1/2a clinical trial for advanced solid malignancies (NCT05199272). It binds with high affinity (KD < 0.1 nM) to CD200R1, a promising immune-oncology (IO) target identified by surveying the 23andMe genetic and health survey database. CD200R1 is an inhibitory receptor that when bound to its ligand CD200, reduces pro-inflammatory cytokine production, and leads to an immunosuppressive tumor environment. To gain further insight into the mechanism of action of 23ME-00610 and its potential for combination therapy, we profiled CD200R1 and other immune inhibitory receptors in human dissociated solid tumor samples using spectral flow cytometry. CD200R1 was broadly expressed across tumor-infiltrating immune cells, including T cells and NK cells, cytotoxic cell types with known antitumor functions. Notably, CD200R1 expression pattern was differentiated from PD-1, which is mostly restricted to T cells, indicating differences in patient populations that could potentially benefit from anti-CD200R1 and anti-PD-1 treatments. The ligand, CD200 was broadly expressed, including on tumor cells and endothelial cells. The differential expression profiles of CD200R1 and PD-1 on immune cells, along with CD200 expression on endothelial cells, suggest that combining 23ME-00610 with other clinically validated immunomodulatory agents could enhance antitumor responses. Follow-up experiments were conducted to validate and extend these findings. In an in vitro assay with cancer patient-derived PBMCs, 23ME-00610 promoted higher production of IFNγ, a key functional antitumor cytokine, compared to anti-PD-1 in 9 of 10 donors. Subsequent attempts were made to pinpoint immune cells responsible for 23ME-00610's anti-tumor activity. 23ME-00610 reversed CD200-mediated suppression of chronically stimulated primary T cells and CD200-mediated inhibition of NK cell degranulation, suggesting that 23ME-00610 can mediate tumor cell killing through at least two different cell types. To test the potential of 23ME-00610 to combine with anti-PD-1 to enhance T cell function, an artificial antigen-presenting cell (aAPC) line overexpressing PD-L1 and CD200 was co-cultured with chronically stimulated primary human T cells. Anti-PD-1 and 23ME-00610 each independently enhanced IFNy secretion levels compared to isotype control, yet their combination resulted in a more than additive effect. Taken together, these data demonstrate that 23ME-00610 can enhance both NK and T cell antitumor effector functions, and 23ME-00610 could synergize with anti-PD-1 to further increase the activity of T cells against cancer cells. The results of this study provide evidence that 23ME-00610 could expand IO treatment options for patients with advanced solid malignancies as a single agent or in combination with other anti-tumor therapeutics. Citation Format: Mithra R. Kumar, Shiteng Duan, Shruti Yadav, Abigail Jarret, Zhonghao Yan, Jill Fenaux, Martin Kinisu, Zuoan Yi, Mauro Poggio, Patrick Collins, Antony Symons, Lorena Riol Blanco, Maike Schmidt, Sophia Majeed, Anh Diep, Clarissa Lee. New insights into targeting the CD200R1 pathway in T and NK cells using 23ME-00610 as a single agent or in combination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2359.

Circulating CD200 is increased in the secretory phase of women with endometriosis as is endometrial mRNA, and endometrial stromal cell CD200R1 is increased in spite of reduced mRNA.

Estrogen-dependent extrauterine implantation and growth of menstrual endometrial tissue affects roughly 10% of reproductive age women and depends on suppression of local innate immune defenses to prevent ectopic tissue rejection. Immunohistochemistry has shown the immune check-point inhibitor CD200 which can suppress rejection is expressed in eutopic endometrium and in ectopic deposits. Soluble CD200 accumulated in venules draining eutopic and ectopic endometrium of endometriosis cases in the secretory phase but not proliferative phase of the menstrual cycle, and should be increased in the circulation. Sera from endometriosis and non-endometriosis controls were tested by ELISA for CD200. Endometrial CD200, CD200R1 and CD200R2 mRNA in eutopic was quantified by RT-PCR and localized by in situ hybridization. CD200R1 protein was quantified by immunohistochemistry. Secretory phase serum CD200 was elevated in women with endometriosis compared to controls. Serum CD200 correlated with matched endometrial CD200 mRNA levels. Expression of mRNA for CD200R1 which signals immune suppression was decreased whereas mRNA for the CD200R2 activating receptor was increased. In situ staining of CD200R1 and CD200R2 mRNA showed both receptors were expressed and the fraction of CD200R that is CD200R1 was reduced in secretory and menstrual phase endometriosis endometrium consistent with the RT-PCR result. By contrast, CD200R1 protein and CD200R1 fraction of total CD200R protein were increased in endometriosis. Failure to suppress circulating CD200 levels in the secretory phase had an 87% specificity and 90% sensitivity for endometriosis. CD200 and increased CD200R1 expression may facilitate development of ectopic deposits by suppressing rejection mechanisms.

Altered expression of the immunoregulatory ligand-receptor pair CD200-CD200R1 in the brain of Parkinson\u2019s disease patients

Neuroinflammation, in which activated microglia are involved, appears to contribute to the development of Parkinson’s disease (PD). However, the role of microglial activation and the mechanisms governing this process remain uncertain. We focused on one inhibitory mechanism involved in the control of microglial activation, the microglia inhibitory receptor CD200R1, and its ligand CD200, mainly expressed by neurons. The human CD200R1 gene encodes two membrane-associated and two soluble protein isoforms and the human CD200 gene encodes full-length proteins (CD200full) but also truncated (CD200tr) proteins which act as CD200R1 antagonists. Little is known about their expression in the human brain under pathological conditions. We used human peripheral blood monocytes and monocyte-derived microglia-like cells from control subjects to characterize the expression of the CD200R1 mRNA variants, which showed stimulus-specific responses. We provide evidence of increased CD200R1 (mRNA variants and protein isoforms) and CD200 expression (CD200tr mRNA) in brain tissue of PD patients, mainly in the hippocampus, as well as increased CD200 expression (CD200full and CD200tr mRNAs) in iPSCs-derived dopaminergic neurons generated from skin fibroblasts of PD patients. Our results suggest that CD200-CD200R1 signalling is altered in PD, which may affect the microglial function and constitute a potential target in therapeutic strategies for PD.

CD200R family receptors are expressed on porcine monocytes and modulate the production of IL-8 and TNF-α triggered by TLR4 or TLR7 in these cells

The inhibitory receptor CD200R1 and its paired activating receptor CD200R1L are involved in the regulation of myeloid cell immune responses. The aim of this study was to analyze their distribution, regulation by cytokines, and function in porcine monocyte subsets. We had previously observed that CD200R1 and CD200R1L genes can generate different protein isoforms through alternative mRNA splicing, therefore in this study, we explored the diversity of transcripts in monocyte subsets, and described several new splicing variants of both CD200R1 and CD200R1L, some of which could be expressed on the porcine monocyte surface. A substantial proportion of CD163-SLAII+ and most CD163+SLAII+ monocytes expressed CD200R1 and CD200R1L receptors, while CD163-SLAII- monocytes did not. CD200R1 and CD200R1L expression was down-regulated in monocytes polarized by IFN-ɣ, a cytokine that induces classical activation of macrophages, while IL-10 which gives rise to regulatory macrophages, increased the expression of CD200R1. Finally, treatment of monocyte subsets with a monoclonal antibody specific for the inhibitory CD200R1 receptor and its splicing variants enhanced TNFα and IL-8 production, induced by TLR4 or TLR7 stimulation, suggesting a modulatory role for these receptors on porcine monocyte functions.

MicroRNA-129-5p-regulated microglial expression of the surface receptor CD200R1 controls neuroinflammation

CD200R1 is an inhibitory surface receptor expressed in microglia and blood macrophages. Microglial CD200R1 is known to control neuroinflammation by keeping the microglia in resting state, and therefore, tight regulation of its expression is important. CCAAT/enhancer-binding protein β (CEBPβ) is the known regulator of CD200R1 transcription. In the present study, our specific intention was to find a possible posttranscriptional regulatory mechanism of CD200R1 expression. Here we investigated a novel regulatory mechanism of CD200R1 expression following exposure to an environmental stressor, arsenic, combining in silico analysis, in vitro, and in vivo experiments, as well as validation in human samples. The in silico analysis and in vitro studies with primary neonatal microglia and BV2 microglia revealed that arsenic demethylates the promoter of a microRNA, miR-129-5p, thereby increasing its expression, which subsequently represses CD200R1 by binding to its 3′-untranslated region and shuttling the CD200R1 mRNA to the cytoplasmic-processing body in mouse microglia. The role of miR-129-5p was further validated in BALB/c mouse by stereotaxically injecting anti-miR-129. We found that anti-miR-129 reversed the expression of CD200R1, as well as levels of inflammatory molecules IL-6 and TNF-α. Experiments with a CD200R1 siRNA-induced loss-of-function mouse model confirmed an miR-129-5p→CD200R1→IL-6/TNF-α signaling axis. These main findings were replicated in a human cell line and validated in human samples. Taken together, our study revealed miR-129-5p as a novel posttranscriptional regulator of CD200R1 expression with potential implications in neuroinflammation and related complications.

CD200R1 and CD200R1L expression is regulated during B cell development in swine and modulates the Ig production in response to the TLR7 ligand imiquimoid.

The CD200R family comprises a group of paired receptors that can modulate the activation of immune cells. They are expressed both on myeloid cells and lymphocyte subsets. Here we report that the expression of these receptors on porcine B cells is tightly regulated, being mainly expressed on mature cells. The expression of the inhibitory receptors CD200R1 and/or its splicing variant CD200R1X2, either in combination or not with the activating receptor CD200R1L, is upregulated in sIgM+ effector/memory cells, and tends to decline thereafter as these cells progress to plasmablasts or switch the Ig isotype. sIgM+ naïve and primed cells only express, by contrast, the CD200R1X2 receptor. B-1 like cells also express CD200R1 isoforms, either alone or in combination with CD200R1L. Treatment of peripheral blood mononuclear cells with a monoclonal antibody specific for inhibitory receptors, enhances the IgM and IgG production induced by TLR7 stimulation suggesting a modulatory role of B cell functions of these receptors.

The CD200R1 microglial inhibitory receptor as a therapeutic target in the MPTP model of Parkinson\u2019s disease

BackgroundIt is suggested that neuroinflammation, in which activated microglial cells play a relevant role, contributes to the development of Parkinson’s disease (PD). Consequently, the modulation of microglial activation is a potential therapeutic target to be taken into account to act against the dopaminergic neurodegeneration occurring in this neurological disorder. Several soluble and membrane-associated inhibitory mechanisms contribute to maintaining microglial cells in a quiescent/surveillant phenotype in physiological conditions. However, the presence of activated microglial cells in the brain in PD patients suggests that these mechanisms have been somehow overloaded. We focused our interest on one of the membrane-associated mechanisms, the CD200-CD200R1 ligand-receptor pair.MethodsThe acute MPTP experimental mouse model of PD was used to study the temporal pattern of mRNA expression of CD200 and CD200R1 in the context of MPTP-induced dopaminergic neurodegeneration and neuroinflammation. Dopaminergic damage was assessed by tyrosine hydroxylase (TH) immunoreactivity, and neuroinflammation was evaluated by the mRNA expression of inflammatory markers and IBA1 and GFAP immunohistochemistry. The effect of the modulation of the CD200-CD200R1 system on MPTP-induced damage was determined by using a CD200R1 agonist or CD200 KO mice.ResultsMPTP administration resulted in a progressive decrease in TH-positive fibres in the striatum and TH-positive neurons in the substantia nigra pars compacta, which were accompanied by transient astrogliosis, microgliosis and expression of pro- and anti-inflammatory markers. CD200 mRNA levels rapidly decreased in the ventral midbrain after MPTP treatment, while a transient decrease of CD200R1 mRNA expression was repeatedly observed in this brain area at earlier and later phases. By contrast, a transient increase in CD200R1 expression was observed in striatum. The administration of a CD200R1 agonist resulted in the inhibition of MPTP-induced dopaminergic neurodegeneration, while microglial cells showed signs of earlier activation in CD200-deficient mice.ConclusionsCollectively, these findings provide evidence for a correlation between CD200-CD200R1 alterations, glial activation and neuronal loss. CD200R1 stimulation reduces MPTP-induced loss of dopaminergic neurons, and CD200 deficiency results in earlier microglial activation, suggesting that the potentiation of CD200R1 signalling is a possible approach to controlling neuroinflammation and neuronal death in PD.

Identification of human cytotoxic ILC3s.

Human ILCs are classically categorized into five subsets; cytotoxic CD127−CD94+ NK cells and non‐cytotoxic CD127+CD94−, ILC1s, ILC2s, ILC3s, and LTi cells. Here, we identify a previously unrecognized subset within the CD127+ ILC population, characterized by the expression of the cytotoxic marker CD94. These CD94+ ILCs resemble conventional ILC3s in terms of phenotype, transcriptome, and cytokine production, but are highly cytotoxic. IL‐15 was unable to induce differentiation of CD94+ ILCs toward mature NK cells. Instead, CD94+ ILCs retained RORγt, CD127 and CD200R1 expression and produced IL‐22 in response to IL‐15. Culturing non‐cytotoxic ILC3s with IL‐12 induced upregulation of CD94 and cytotoxic activity, effects that were not observed with IL‐15 stimulation. Thus, human helper ILCs can acquire a cytotoxic program without differentiating into NK cells.

Identification of an Immunologic Signature of Lung Adenocarcinomas Based on Genome-Wide Immune Expression Profiles.

Background: Lung cancer is one of the most common types of cancer, and it has a poor prognosis. It is urgent to identify prognostic biomarkers to guide therapy.Methods: The immune gene expression profiles for patients with lung adenocarcinomas (LUADs) were obtained from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). The relationships between the expression of 45 immune checkpoint genes (ICGs) and prognosis were analyzed. Additionally, the correlations between the expression of 45 biomarkers and immunotherapy biomarkers, including tumor mutation burden (TMB), mismatch repair defects, neoantigens, and others, were identified. Ultimately, prognostic ICGs were combined to determine immune subgroups, and the prognostic differences between these subgroups were identified in LUAD.Results: A total of 11 and nine ICGs closely related to prognosis were obtained from the GEO and TCGA databases, respectively. CD200R1 expression had a significant negative correlation with TMB and neoantigens. CD200R1 showed a significant positive correlation with CD8A, CD68, and GZMB, indicating that it may cause the disordered expression of adaptive immune resistance pathway genes. Multivariable Cox regression was used to construct a signature composed of four prognostic ICGs (IDO1, CD274, CTLA4, and CD200R1): Risk Score = −0.002*IDO1+0.031*CD274−0.069*CTLA4−0.517*CD200R1. The median Risk Score was used to classify the samples for the high- and low-risk groups. We observed significant differences between groups in the training, testing, and external validation cohorts.Conclusion: Our research provides a method of integrating ICG expression profiles and clinical prognosis information to predict lung cancer prognosis, which will provide a unique reference for gene immunotherapy for LUAD.

CD200-CD200R1 signaling pathway regulates neuroinflammation after stroke.

ObjectiveTo study how the CD200‐CD200R1 signaling pathway modulates poststroke inflammation and advances our knowledge of immune responses to ischemia insults in stroke.MethodsFocal middle cerebral artery occlusion (MCAO) was induced in mice for 90 min, and mice were sacrificed at 1, 3, and 7 days of reperfusion. CD200, CD200R1, iNOS, and Arg‐1 expression in ischemic brains was assessed by Western blotting (WB), and immunohistochemical (IHC) staining was performed to examine the expression of CD200 on neurons and CD200R1 on infiltrating lymphocytes. The severity of neurobehavioral deficits was evaluated by neurological deficit scores (NDS) and infarction volume estimated by TTC staining. To study the relationship between CD200/CD200R1 expression and the diversity of the neuroinflammatory response in stroke, CD200Fc (CD200R1 agonist) was subcutaneously injected at onset, at 1 day and 2 days after MCAO operation, and the brains were collected for detection at 3 days after MCAO/R (reperfusion).ResultsCD200 expression on neurons increased at 1 day and then decreased at 3 days after MCAO/R, and the expression of CD200R1 on lymphocytes showed an opposite temporal pattern as tested by IHC. The WB results showed that CD200/CD200R1 variance exhibited a similar pattern of IHC results, and the level of iNOS peaked at 1 day and then decreased gradually, but Arg‐1 increased with time after MCAO/R in ischemic brains. After CD200Fc injection, CD200R1 expression significantly increased, and CD200Fc promoted Arg‐1 but inhibited iNOS expression. The infarct volume and NDS of the group treated with CD200Fc were significantly smaller than those of the IgG2a‐treated group.ConclusionsThe CD200‐CD200R1 signaling pathway regulates neuroinflammation after stroke. Stimulation of CD200R1 by CD200Fc promotes the anti‐inflammatory response and alleviates ischemic injury.

Early life stress from allergic dermatitis causes depressive-like behaviors in adolescent male mice through neuroinflammatory priming

Allergic dermatitis (AD), associated with pruritus and itchiness, is one of the major stressful conditions early in life. AD also influences the incidence of neuropsychiatric disorders and developmental disorders through neuro-immune interactions. To the best of our knowledge, there is no report that assesses the effects of early childhood dermatitis on psychiatric disorders later in life using an animal model. Here, we developed an oxazolone (Ox)-induced AD model in the early life of male C57BL/6J mice whose ears were challenged by Ox repeatedly from postnatal days (PD) 2 to PD30. On PD30, the Ox-treated ears were remarkably thickened and showed epidermal hyperplasia coupled with increased expression of T helper 2 cytokines, interleukin (IL)-4, and IL-13 in the ear tissue. Additionally, serum immunoglobulin E levels and serum corticosterone levels were higher in the Ox-treated mice than those in the control mice. Although Ox-treated PD40 mice showed neither behavioral abnormalities nor increases in pro-inflammatory cytokine expression in the brain, this study revealed that they experienced downregulation of CD200R1 expression in the amygdala under basal conditions and that additional lipopolysaccharide (LPS) administration induced enhanced neuroinflammatory reaction as the priming effect was accompanied by an increase of Iba-1-positive microglia in the amygdala and hippocampus. Furthermore, the Ox-treated PD40 mice showed depressive-like behaviors 24 h after LPS administration, whereas the control mice did not. Interestingly, the expression of indoleamine 2,3-dioxygenase and kynurenine 3-monooxygenase, key rate-limiting enzymes of the kynurenine metabolism pathway, was upregulated in the hippocampus, prefrontal cortex, and amygdala of the Ox-treated mice 4 h after LPS administration. Based on these results, we suggest that early life stress from AD aggravates susceptibility to systemic inflammation in the adolescent brain, leading to depressive behaviors with abnormal kynurenine metabolism.

Prognostic Value of CD200R1 mRNA Expression in Head and Neck Squamous Cell Carcinoma.

Immune system dysfunction is associated with head and neck squamous cell carcinoma (HNSCC) development and progression and immune checkpoint inhibitors have demonstrated substantial survival benefits in platinum-refractory HNSCC; therefore, we examined the prognostic value of immune-related gene (IRG) expression in HNSCC. We analyzed the expression of 82 IRGs in 71 patients with HNSCC enrolled in a feasibility study for a prospective HNSCC biomarker-driven umbrella trial (Korean Cancer Study Group TRIUMPH study, NCT03292250). CD200R1 was identified as an independent prognostic factor and validated in GEO and TCGA database. CD2000R1 mRNA expression was found to be an independent favorable prognostic factor in patients with HNSCC. Moreover, CD200R1 was found to affect genes and pathways associated with the immune response, while seven differentially expressed genes (CD8A, DOK2, CX3CR1, TYROBP, CXCL9, CD300LF, IFNG) were associated with CD200R1 expression. Samples with higher CD200R1 expression displayed higher tumor-infiltrating immune cell counts both in silico and in histological analysis. These findings will help in the development of more accurate prognostic tools and suggest CD200R1 modulation as a HNSCC immunotherapy.

Parkinsonian neurotoxicants impair the anti-inflammatory response induced by IL4 in glial cells: involvement of the CD200-CD200R1 ligand-receptor pair

Exposure to pesticides such as rotenone is a risk factor for Parkinson’s disease. Dopaminergic neurons are especially sensitive to the toxicity of compounds that inhibit the mitochondrial respiratory chain such as rotenone and 1-methyl-4-phenylpyridinium (MPP+). However, there is scarce information on their effects on glia. To evaluate whether these neurotoxicants affect the immune response of glia, primary mouse mixed glial and microglial cultures were treated with interleukin (IL) 4 in the absence and presence of MPP+ or rotenone. Using qRTPCR or western blot, we determined the expression of anti-inflammatory markers, the CD200R1 microglial receptor and its ligand CD200, and genes regulating glycolysis and oxidative metabolism. ATP and lactate levels were additionally determined as an index of cell metabolism. Microglial phagocytosis was also evaluated. MPP+ and rotenone clearly abrogated the IL4-induced expression of anti-inflammatory markers in mixed glial cultures. CD200 and CD200R1 expression and microglia phagocytosis were also affected by the neurotoxicants. Changes in the mRNA expression of the molecules regulating glycolysis and oxidative metabolism, as well as in ATP levels and lactate release suggested that metabolic reprogramming in response to MPP+ and rotenone differs between microglial and mixed glial cultures. These findings support the hypothesis that parkinsonian neurotoxicants may impair brain immune response altering glial cell metabolism.

Identification of the CD200R1 promoter and the association of its polymorphisms with the risk of Parkinson's disease.

Neuroinflammation is known to be involved in the pathogenesis of Parkinson's disease (PD). Abnormal activation of microglia plays a key role in this pathological process. CD200R1 is a membrane glycoprotein that is expressed primarily on myeloid cells including microglia and is involved in the maintenance of microglia in a stationary state. Our previous study reported that the regulation of CD200R1 expression is altered in PD patients. Such alteration will lead to neuroinflammation and is related to the pathogenesis of PD. The possible role of promoter polymorphisms for abnormal CD200R1 expression in PD was examined in this study. The UCSC database and dual-luciferase assays were used to confirm the promoter region of CD200R1. The promoter of CD200R1 was sequenced in 457 PD patients and 520 matched healthy controls from the Chinese Han population. Dual-luciferase assays were conducted to examine the promoter activity of CD200R1. It was confirmed that the promoter of CD200R1 is located in the region 876-146 bp upstream of the coding DNA sequence. The frequencies of rs144721913 (P=0.001) and rs72952157 (P=0.022) in the promoter were significantly different between the PD group and control group. rs144721913 increases the risk of PD by approximately 14-fold and rs72952157 by 2.6-fold. The dual-luciferase assay indicated that the rs144721913 T allele and the rs72952157 G allele reduced the transcriptional activity of the CD200R1 promoter. For the first time the promoter region of CD200R1 has been defined and two potential risk polymorphisms (rs144721913 and rs72952157) in the region for PD in Chinese Han populations have been reported.

Disease Progression-Dependent Expression of CD200R1 and CX3CR1 in Mouse Models of Parkinson's Disease.

Microglial activation is an important contributor to the pathogenesis of Parkinson’s disease (PD). Microglia are tightly and efficiently regulated by immune checkpoints, including CD200-CD200R1 and CX3CL1-CX3CR1. Understanding the involvement of these checkpoints in disease progression provides important insights into how microglial activation contributes to PD pathology. However, so far, studies have produced seemingly conflicting results. In this study, we demonstrate that CD200R1 expression is down-regulated at both early and late stage of PD model, and CX3CR1 expression is down-regulated in early stage and recovered in late stage. In primary cultured microglia, CD200R1 and CX3CR1 expressions are both directly regulated by LPS or α-synuclein, and CD200R1 expression is more sensitively regulated than CX3CR1. In addition, CD200 knockout causes an increase in proinflammatory cytokine production and microglial activation in the midbrain. Remarkably, DA neurons in the substantial nigra are degenerated in CD200-/- mice. Finally, activation of the CD200R with CD200Fc alleviates the neuroinflammation in microglia. Together, these results suggest that immune checkpoints play distinct functional roles in different stage of PD pathology, and the CD200-CD200R1 axis plays a significant role in nigrostriatal neuron viability and function.

CD200 and CD200R1 are differentially expressed and have differential prognostic roles in non-small cell lung cancer

ABSTRACT CD200, a member of the immunoglobulin superfamily, interacts with its receptor CD200R1 to modulate cancer immune microenvironments. Here, we explored the clinicopathological and prognostic implications of the CD200/CD200R1 axis in non-small-cell lung cancer (NSCLC) patients. We evaluated CD200/CD200R1 expression in the tumors and stroma of 632 NSCLC patients using immunohistochemistry. Associations between CD200/CD200R1 expression levels and clinicopathological data were analyzed. We also examined their expression in lung cancer cell lines. Changes in endogenous immune-related factors and cell proliferation were evaluated by CD200 and CD200R1 knockdown and CD200Fc fusion protein administration. CD200 expression was observed mainly in the tumor, and also in the stroma among a few cases, whereas CD200R1 expression was observed in both the tumor and stroma. High tumoral CD200 expression was significantly associated with female sex, never-smoking status, adenocarcinoma histology, EGFR mutation, and a low density of tumor-infiltrating lymphocytes. Meanwhile, high CD200R1 expression in the tumor and stroma was associated with ever smoking, non-adenocarcinoma histology, and increased tumor-infiltrating lymphocytes. High CD200R1 expression was associated with worse survival (log-rank, P <.001 for both tumor and stroma), whereas high CD200 expression was associated with better survival outcomes (log-rank, P <.001). The transient knockdown of CD200R1 in lung cancer cell lines impaired cell proliferation, and the in vitro modulation of CD200 and CD200R1 altered endogenous oncogenic and inflammation-related gene expression. CD200R1 expression was associated with poor prognosis, whereas CD200 expression was an independent favorable prognostic factor. Our results suggest the importance of CD200 and CD200R1 in lung cancer biology.

CD200-CD200R1 signalling attenuates imiquimod-induced psoriatic inflammation by inhibiting the activation of skin inflammatory macrophages

Psoriasis is an autoimmune skin disease caused by interactions between keratinocytes and immune cells, such as macrophages. CD200 is expressed on the surface of various cell types, and its receptor, CD200R1, belongs to a family of immunosuppressive receptors that are mainly expressed on myeloid cells. CD200/CD200R1 signalling is associated with the prevention of autoimmune diseases; however, the role of CD200/CD200R1 signalling in the pathogenesis of psoriasis remains unknown. In this study, we detected in vivo effect of the CD200 protein on psoriasis and in vitro effects of CD200 on macrophages and keratinocytes co-cultured with macrophages were also evaluated. Our data showed that the expression of CD200 and CD200R1 was decreased and the expression of macrophage-related pro-inflammatory factors (IL-6, IL-1β, TNF-α) was increased in IMQ-induced psoriasis-like skin of mice. After subcutaneous injection of CD200, the symptoms were alleviated, local expression of CD200R1 was markedly induced, infiltrated CD68+ cells were significantly reduced and the expression levels of IL-6, IL-1β, and TNF-α were strongly downregulated. In in vitro experiments, CD200 suppressed the migration of macrophages, induced CD200R1 expression on the surface of macrophages, and decreased the levels of pro-inflammatory factors. Western blot (WB) data showed that the CD200-CD200R1 reaction controlled the activation of inflammatory macrophages by inhibiting the NF-κB signalling pathway. These results demonstrate that CD200-CD200R1 signalling can reduce IMQ-induced psoriasis-like skin inflammation by inhibiting the activation of macrophages.

CD200 is up-regulated in R6/1 transgenic mouse model of Huntington's disease.

In Huntington’s disease (HD), striatal medium spiny neurons (MSNs) are particularly sensitive to the presence of a CAG repeat in the huntingtin (HTT) gene. However, there are many evidences that cells from the peripheral immune system and central nervous system (CNS) immune cells, namely microglia, play an important role in the etiology and the progression of HD. However, it remains unclear whether MSNs neurodegeneration is mediated by a non-cell autonomous mechanism. The homeostasis in the healthy CNS is maintained by several mechanisms of interaction between all brain cells. Neurons can control microglia activation through several inhibitory mechanisms, such as the CD200–CD200R1 interaction. Due to the complete lack of knowledge about the CD200–CD200R1 system in HD, we determined the temporal patterns of CD200 and CD200R1 expression in the neocortex, hippocampus and striatum in the HD mouse models R6/1 and HdhQ111/7 from pre-symptomatic to manifest stages. In order to explore any alteration in the peripheral immune system, we also studied the levels of expression of CD200 and CD200R1 in whole blood. Although CD200R1 expression was not altered, we observed and increase in CD200 gene expression and protein levels in the brain parenchyma of all the regions we examined, along with HD pathogenesis in R6/1 mice. Interestingly, the expression of CD200 mRNA was also up-regulated in blood following a similar temporal pattern. These results suggest that canonical neuronal–microglial communication through CD200–CD200R1 interaction is not compromised, and CD200 up-regulation in R6/1 brain parenchyma could represent a neurotrophic signal to sustain or extend neuronal function in the latest stages of HD as pro-survival mechanism.

Glucocorticoids mediate stress induction of the alarmin HMGB1 and reduction of the microglia checkpoint receptor CD200R1 in limbic brain structures

Exposure to stressors primes neuroinflammatory responses to subsequent immune challenges and stress-induced glucocorticoids (GCs) play a mediating role in this phenomenon of neuroinflammatory priming. Recent evidence also suggests that the alarmin high-mobility group box-1 (HMGB1) and the microglial checkpoint receptor CD200R1 serve as proximal mechanisms of stress-induced neuroinflammatory priming.However, it is unclear whether stress-induced GCs play a causal role in these proximal mechanisms of neuroinflammatory priming; this forms the focus of the present investigation. Here, we found that exposure to a severe acute stressor (inescapable tailshock) induced HMGB1 and reduced CD200R1 expression in limbic brain regions and pharmacological blockade of GC signaling (RU486) mitigated these effects of stress. To confirm these effects of RU486, adrenalectomy (ADX) with basal corticosterone (CORT) replacement was used to block the stress-induced increase in GCs as well as effects on HMGB1 and CD200R1. As with RU486, ADX mitigated the effects of stress on HMGB1 and CD200R1. Subsequently, exogenous CORT was administered to determine whether GCs are sufficient to recapitulate the effects of stress. Indeed, exogenous CORT induced expression of HMGB1 and reduced expression of CD200R1. In addition, exposure of primary microglia to CORT also recapitulated the effects of stress on CD200R1 suggesting that CORT acts directly on microglia to reduce expression of CD200R1. Taken together, these findings suggest that GCs mediate the effects of stress on these proximal mechanisms of neuroinflammatory priming.