Choroid Plexus-Infiltrating T Cells as Drivers of Murine Neuropsychiatric Lupus

Characterisation of choroid plexus-infiltrating T cells reveals novel therapeutic targets in murine neuropsychiatric lupus

OBJECTIVE

Diffuse central nervous system manifestations, referred to as neuropsychiatric lupus (NPSLE), are observed in 20-40% of lupus patients and involve complex mechanisms that have not yet been adequately elucidated. In murine NPSLE models, choroid plexus (ChP)-infiltrating T cells have not been fully evaluated as drivers of neuropsychiatric disease.

METHOD

Droplet-based single-cell transcriptomic analysis (single-cell RNA sequencing) and immune T-cell receptor profiling were performed on ChP tissue from MRL/lpr mice, an NPSLE mouse model, at an 'early' and 'late' disease state, to investigate the infiltrating immune cells that accumulate with NPSLE disease progression.

RESULTS

We found 19 unique clusters of stromal and infiltrating cells present in the ChP of NPSLE mice. Higher resolution of the T-cell clusters uncovered multiple T-cell subsets, with increased exhaustion and hypoxia expression profiles. Clonal analysis revealed that the clonal CD8+T cell CDR3 sequence, ASGDALGGYEQY, matched that of a published T-cell receptor sequence with specificity for myelin basic protein. Stromal fibroblasts are likely drivers of T-cell recruitment by upregulating the VCAM signalling pathway. Systemic blockade of VLA-4, the cognate ligand of VCAM, resulted in significant resolution of the ChP immune cell infiltration and attenuation of the depressive phenotype.

CONCLUSION

Our analysis details the dynamic transcriptomic changes associated with murine NPSLE disease progression, and highlights its potential use in identifying prospective lupus brain therapeutic targets.

Ectopic CD4+ T cells in choroid plexus mediate neuropsychiatric lupus symptoms in mice via interferon-γ induced microglia activation

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a disabling and potentially life-threatening complication of SLE. This study aims to investigate whether ectopic CD4+ T cells in the choroid plexus mediate NPSLE in mice. Intracerebroventricular (ICV) injection of anti-CD4 antibody effectively depleted CP-resident CD4+ T cells and alleviated NPSLE-like symptoms in MRL/lpr mice. Following ICV injection, the majority of isolated lupus CD4+ T cells from donor MRL/lpr mice predominantly stayed in the CP for at least 28 days in recipient C57BL/6 mice, while nearly all isolated CD4+ T cells from MRL/MpJ mice disappeared within 7 days. ICV injection of lupus CD4+ T cells resulted in NPSLE-like symptoms, including impaired behavioral performances, increased microglial activation, and abnormal microstructure changes. Flow cytometry analysis revealed that the majority of isolated lupus CD4+ T cells were positive for IFN-γ. Neutralizing intracerebral IFN-γ alleviated NPSLE-like symptoms in MRL/lpr mice. Moreover, ICV injection of anti-IFN-γ antibody or microglial depletion by PLX3397 benefited most NPSLE-like symptoms in lupus CD4+ T-treated mice, while ICV injection of IFN-γ mimicked most NPSLE-like symptoms. In conclusion, CP-resident lupus CD4+ T cells contribute to NPSLE-like symptoms in mice via Interferon-γ induced microglia activation. Depleting CP-resident lupus CD4+ T cells, interferon-γ, or activated microglia may be potential therapeutic targets for NPSLE.

Constitutive knockout of interleukin-6 ameliorates memory deficits and entorhinal astrocytosis in the MRL/lpr mouse model of neuropsychiatric lupus

BACKGROUND

Neuropsychiatric lupus (NPSLE) describes the cognitive, memory, and affective emotional burdens faced by many lupus patients. While NPSLE's pathogenesis has not been fully elucidated, clinical imaging studies and cerebrospinal fluid (CSF) findings, namely elevated interleukin-6 (IL-6) levels, point to ongoing neuroinflammation in affected patients. Not only linked to systemic autoimmunity, IL-6 can also activate neurotoxic glial cells the brain. A prior pre-clinical study demonstrated that IL-6 can acutely induce a loss of sucrose preference; the present study sought to assess the necessity of chronic IL-6 exposure in the NPSLE-like disease of MRL/lpr lupus mice.

METHODS

We quantified 1308 proteins in individual serum or pooled CSF samples from MRL/lpr and control MRL/mpj mice using protein microarrays. Serum IL-6 levels were plotted against characteristic NPSLE neurobehavioral deficits. Next, IL-6 knockout MRL/lpr (IL-6 KO; n = 15) and IL-6 wildtype MRL/lpr mice (IL-6 WT; n = 15) underwent behavioral testing, focusing on murine correlates of learning and memory deficits, depression, and anxiety. Using qPCR, we quantified the expression of inflammatory genes in the cortex and hippocampus of MRL/lpr IL-6 KO and WT mice. Immunofluorescent staining was performed to quantify numbers of microglia (Iba1 +) and astrocytes (GFAP +) in multiple cortical regions, the hippocampus, and the amygdala.

RESULTS

MRL/lpr CSF analyses revealed increases in IL-17, MCP-1, TNF-α, and IL-6 (a priori p-value < 0.1). Serum levels of IL-6 correlated with learning and memory performance (R2 = 0.58; p = 0.03), but not motivated behavior, in MRL/lpr mice. Compared to MRL/lpr IL-6 WT, IL-6 KO mice exhibited improved novelty preference on object placement (45.4% vs 60.2%, p < 0.0001) and object recognition (48.9% vs 67.9%, p = 0.002) but equivalent performance in tests for anxiety-like disease and depression-like behavior. IL-6 KO mice displayed decreased cortical expression of aif1 (microglia; p = 0.049) and gfap (astrocytes; p = 0.044). Correspondingly, IL-6 KO mice exhibited decreased density of GFAP + cells compared to IL-6 WT in the entorhinal cortex (89 vs 148 cells/mm2, p = 0.037), an area vital to memory.

CONCLUSIONS

The inflammatory composition of MRL/lpr CSF resembles that of human NPSLE patients. Increased in the CNS, IL-6 is necessary to the development of learning and memory deficits in the MRL/lpr model of NPSLE. Furthermore, the stimulation of entorhinal astrocytosis appears to be a key mechanism by which IL-6 promotes these behavioral deficits.

Autoimmune and neuropsychiatric phenotypes in a Mecp2 transgenic mouse model on C57BL/6 background

Introduction

Systemic Lupus Erythematosus (SLE) impacts the central nervous system (CNS), leading to severe neurological and psychiatric manifestations known as neuropsychiatric lupus (NPSLE). The complexity and heterogeneity of clinical presentations of NPSLE impede direct investigation of disease etiology in patients. The limitations of existing mouse models developed for NPSLE obstruct a comprehensive understanding of this disease. Hence, the identification of a robust mouse model of NPSLE is desirable.

Methods

C57BL/6 mice transgenic for human MeCP2 (B6.Mecp2Tg1) were phenotyped, including autoantibody profiling through antigen array, analysis of cellularity and activation of splenic immune cells through flow cytometry, and measurement of proteinuria. Behavioral tests were conducted to explore their neuropsychiatric functions. Immunofluorescence analyses were used to reveal altered neurogenesis and brain inflammation. Various signaling molecules implicated in lupus pathogenesis were examined using western blotting.

Results

B6.Mecp2Tg1 exhibits elevated proteinuria and an overall increase in autoantibodies, particularly in female B6.Mecp2Tg1 mice. An increase in CD3+CD4+ T cells in the transgenic mice was observed, along with activated germinal center cells and activated CD11b+F4/80+ macrophages. Moreover, the transgenic mice displayed reduced locomotor activity, heightened anxiety and depression, and impaired short-term memory. Immunofluorescence analysis revealed IgG deposition and immune cell infiltration in the kidneys and brains of transgenic mice, as well as altered neurogenesis, activated microglia, and compromised blood-brain barrier (BBB). Additionally, protein levels of various key signaling molecules were found to be differentially modulated upon MeCP2 overexpression, including GFAP, BDNF, Albumin, NCoR1, mTOR, and NLRP3.

Discussion

Collectively, this work demonstrates that B6.Mecp2Tg1 mice exhibit lupus-like phenotypes as well as robust CNS dysfunctions, suggesting its utility as a new animal model for NPSLE.

Choroid plexus and perivascular space enlargement in neuropsychiatric systemic lupus erythematosus

Choroid plexus (CP) enlargement is proposed as a marker of neuroinflammation in immune-mediated conditions. CP involvement has also been hypothesized in the immunopathology of systemic lupus erythematosus (SLE). We investigated whether CP enlargement occurs in SLE patients and its association with neuropsychiatric involvement. Additionally, we explored abnormalities along the glymphatic system in SLE patients through enlarged perivascular space (PVS) quantification. Clinical assessment and 3 Tesla brain dual-echo and T1-weighted MRI scans were obtained from 32 SLE patients and 32 sex and age-matched healthy controls (HC). CPs were manually segmented on 3D T1-weighted sequence and enlarged PVS (ePVS) were assessed through Potter's score. Compared to HC, SLE patients showed higher normalized CP volume (nCPV) (p = 0.023), with higher CP enlargement in neuropsychiatric SLE (NPSLE) (n = 12) vs. non-NPSLE (p = 0.027) patients. SLE patients with antiphospholipid antibodies (APA) positivity (n = 18) had higher nCPV compared to HC (p = 0.012), while APA negative ones did not. SLE patients also had higher Potter's score than HC (p < 0.001), with a tendency towards a higher number of basal ganglia ePVS in NPSLE vs. non-NPSLE patients. Using a random forest analysis, nCPV emerged as a significant predictor of NPSLE, together with T2-hyperintense white matter (WM) lesion volume (LV) and APA positivity (out-of-bag AUC 0.81). Our findings support the hypothesis of a role exerted by the CP in SLE physiopathology, especially in patients with neuropsychiatric involvement. The higher prevalence of ePVS in SLE patients, compared to HC, suggests the presence of glymphatic system impairment in this population.

Microglia activation in the presence of intact blood-brain barrier and disruption of hippocampal neurogenesis via IL-6 and IL-18 mediate early diffuse neuropsychiatric lupus

INTRODUCTION

Inflammatory mediators are detected in the cerebrospinal fluid of systemic lupus erythematosus patients with central nervous system involvement (NPSLE), yet the underlying cellular and molecular mechanisms leading to neuropsychiatric disease remain elusive.

METHODS

We performed a comprehensive phenotyping of NZB/W-F1 lupus-prone mice including tests for depression, anxiety and cognition. Immunofluorescence, flow cytometry, RNA-sequencing, qPCR, cytokine quantification and blood-brain barrier (BBB) permeability assays were applied in hippocampal tissue obtained in both prenephritic (3-month-old) and nephritic (6-month-old) lupus mice and matched control strains. Healthy adult hippocampal neural stem cells (hiNSCs) were exposed ex vivo to exogenous inflammatory cytokines to assess their effects on proliferation and apoptosis.

RESULTS

At the prenephritic stage, BBB is intact yet mice exhibit hippocampus-related behavioural deficits recapitulating the human diffuse neuropsychiatric disease. This phenotype is accounted by disrupted hippocampal neurogenesis with hiNSCs exhibiting increased proliferation combined with decreased differentiation and increased apoptosis in combination with microglia activation and increased secretion of proinflammatory cytokines and chemokines. Among these cytokines, IL-6 and IL-18 directly induce apoptosis of adult hiNSCs ex vivo. During the nephritic stage, BBB becomes disrupted which facilitates immune components of peripheral blood, particularly B-cells, to penetrate into the hippocampus further augmenting inflammation with locally increased levels of IL-6, IL-12, IL-18 and IL-23. Of note, an interferon gene signature was observed only at nephritic-stage.

CONCLUSION

An intact BBB with microglial activation disrupting the formation of new neurons within the hippocampus represent early events in NPSLE. Disturbances of the BBB and interferon signature are evident later in the course of the disease.

Pediatric Crohn's disease diagnosis aid via genomic analysis and machine learning

Introduction

Determination of pediatric Crohn's disease (CD) remains a major diagnostic challenge. However, the rapidly emerging field of artificial intelligence has demonstrated promise in developing diagnostic models for intractable diseases.

Methods

We propose an artificial neural network model of 8 gene markers identified by 4 classification algorithms based on Gene Expression Omnibus database for diagnostic of pediatric CD.

Results

The model achieved over 85% accuracy and area under ROC curve value in both training set and testing set for diagnosing pediatric CD. Additionally, immune infiltration analysis was performed to address why these markers can be integrated to develop a diagnostic model.

Conclusion

This study supports further clinical facilitation of precise disease diagnosis by integrating genomics and machine learning algorithms in open-access database.

Neuropsychiatric lupus erythematosus: Focusing on autoantibodies

Patients with systemic lupus erythematosus (SLE) frequently suffer from nervous system complications, termed neuropsychiatric lupus erythematosus (NPLE). NPLE accounts for the poor prognosis of SLE. Correct attribution of NP events to SLE is the primary principle in managing NPLE. The vascular injuries and neuroinflammation are the fundamental neuropathologic changes in NPLE. Specific autoantibody-mediated central nerve system (CNS) damages distinguish NPLE from other CNS disorders. Though the central antibodies in NPLE are generally thought to be raised from the periphery immune system, they may be produced in the meninges and choroid plexus. On this basis, abnormal activation of microglia and disease-associated microglia (DAM) should be the common mechanisms of NPLE and other CNS disturbances. Improved understanding of both characteristic and sharing features of NPLE might yield further options for managing this disease.

Neuroimmune signaling at the brain borders

The central nervous system (CNS) has been viewed as an immunologically privileged site, but emerging works are uncovering a large array of neuroimmune interactions primarily occurring at its borders. CNS barriers sites host diverse population of both innate and adaptive immune cells capable of, directly and indirectly, influence the function of the residing cells of the brain parenchyma. These structures are only starting to reveal their role in controlling brain function under normal and pathological conditions and represent an underexplored therapeutic target for the treatment of brain disorders. This review will highlight the development of the CNS barriers to host neuro-immune interactions and emphasize their newly described roles in neurodevelopmental, neurological, and neurodegenerative disorders, particularly for the meninges.