STING: Stay near to STIM(1) neuroprotection.

In a recent publication in Cell, Woo et al.1 report that stimulator of interferon genes (STING) links inflammation with glutamate-driven excitotoxicity to induce ferroptosis, identifying a mechanism of inflammation-induced neurodegeneration and also a novel candidate therapeutic target for multiple sclerosis.

Disease-associated astrocyte epigenetic memory promotes CNS pathology.

Disease-associated astrocyte subsets contribute to the pathology of neurologic diseases, including multiple sclerosis and experimental autoimmune encephalomyelitis1-8 (EAE), an experimental model for multiple sclerosis. However, little is known about the stability of these astrocyte subsets and their ability to integrate past stimulation events. Here we report the identification of an epigenetically controlled memory astrocyte subset that exhibits exacerbated pro-inflammatory responses upon rechallenge. Specifically, using a combination of single-cell RNA sequencing, assay for transposase-accessible chromatin with sequencing, chromatin immunoprecipitation with sequencing, focused interrogation of cells by nucleic acid detection and sequencing, and cell-specific in vivo CRISPR-Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP-citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) that is used by histone acetyltransferase p300 to control chromatin accessibility. The number of ACLY+p300+ memory astrocytes is increased in acute and chronic EAE models, and their genetic inactivation ameliorated EAE. We also detected the pro-inflammatory memory phenotype in human astrocytes in vitro; single-cell RNA sequencing and immunohistochemistry studies detected increased numbers of ACLY+p300+ astrocytes in chronic multiple sclerosis lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, multiple sclerosis. These findings may guide novel therapeutic approaches for multiple sclerosis and other neurologic diseases.

Identification of astrocyte regulators by nucleic acid cytometry.

Multiple sclerosis is a chronic inflammatory disease of the central nervous system1. Astrocytes are heterogeneous glial cells that are resident in the central nervous system and participate in the pathogenesis of multiple sclerosis and its model experimental autoimmune encephalomyelitis2,3. However, few unique surface markers are available for the isolation of astrocyte subsets, preventing their analysis and the identification of candidate therapeutic targets; these limitations are further amplified by the rarity of pathogenic astrocytes. Here, to address these challenges, we developed focused interrogation of cells by nucleic acid detection and sequencing (FIND-seq), a high-throughput microfluidic cytometry method that combines encapsulation of cells in droplets, PCR-based detection of target nucleic acids and droplet sorting to enable in-depth transcriptomic analyses of cells of interest at single-cell resolution. We applied FIND-seq to study the regulation of astrocytes characterized by the splicing-driven activation of the transcription factor XBP1, which promotes disease pathology in multiple sclerosis and experimental autoimmune encephalomyelitis4. Using FIND-seq in combination with conditional-knockout mice, in vivo CRISPR-Cas9-driven genetic perturbation studies and bulk and single-cell RNA sequencing analyses of samples from mouse experimental autoimmune encephalomyelitis and humans with multiple sclerosis, we identified a new role for the nuclear receptor NR3C2 and its corepressor NCOR2 in limiting XBP1-driven pathogenic astrocyte responses. In summary, we used FIND-seq to identify a therapeutically targetable mechanism that limits XBP1-driven pathogenic astrocyte responses. FIND-seq enables the investigation of previously inaccessible cells, including rare cell subsets defined by unique gene expression signatures or other nucleic acid markers.

Lactate limits CNS autoimmunity by stabilizing HIF-1α in dendritic cells.

Dendritic cells (DCs) have a role in the development and activation of self-reactive pathogenic T cells1,2. Genetic variants that are associated with the function of DCs have been linked to autoimmune disorders3,4, and DCs are therefore attractive therapeutic targets for such diseases. However, developing DC-targeted therapies for autoimmunity requires identification of the mechanisms that regulate DC function. Here, using single-cell and bulk transcriptional and metabolic analyses in combination with cell-specific gene perturbation studies, we identify a regulatory loop of negative feedback that operates in DCs to limit immunopathology. Specifically, we find that lactate, produced by activated DCs and other immune cells, boosts the expression of NDUFA4L2 through a mechanism mediated by hypoxia-inducible factor 1α (HIF-1α). NDUFA4L2 limits the production of mitochondrial reactive oxygen species that activate XBP1-driven transcriptional modules in DCs that are involved in the control of pathogenic autoimmune T cells. We also engineer a probiotic that produces lactate and suppresses T cell autoimmunity through the activation of HIF-1α-NDUFA4L2 signalling in DCs. In summary, we identify an immunometabolic pathway that regulates DC function, and develop a synthetic probiotic for its therapeutic activation.

Identification of environmental factors that promote intestinal inflammation.

Genome-wide association studies have identified risk loci linked to inflammatory bowel disease (IBD)1-a complex chronic inflammatory disorder of the gastrointestinal tract. The increasing prevalence of IBD in industrialized countries and the augmented disease risk observed in migrants who move into areas of higher disease prevalence suggest that environmental factors are also important determinants of IBD susceptibility and severity2. However, the identification of environmental factors relevant to IBD and the mechanisms by which they influence disease has been hampered by the lack of platforms for their systematic investigation. Here we describe an integrated systems approach, combining publicly available databases, zebrafish chemical screens, machine learning and mouse preclinical models to identify environmental factors that control intestinal inflammation. This approach established that the herbicide propyzamide increases inflammation in the small and large intestine. Moreover, we show that an AHR-NF-κB-C/EBPß signalling axis operates in T cells and dendritic cells to promote intestinal inflammation, and is targeted by propyzamide. In conclusion, we developed a pipeline for the identification of environmental factors and mechanisms of pathogenesis in IBD and, potentially, other inflammatory diseases.

Protein tyrosine phosphatase conjugated with a novel transdermal delivery peptide, astrotactin 1-derived peptide recombinant protein tyrosine phosphatase (AP-rPTP), alleviates both atopic dermatitis-like and psoriasis-like dermatitis.

BACKGROUND: Atopic dermatitis (AD) and psoriasis are the 2 most common chronic inflammatory skin diseases. There is an unmet medical need to overcome limitations for transcutaneous drug development posed by the skin barrier. OBJECTIVE: We aimed to identify a novel transdermal delivery peptide and to develop a transcutaneously applicable immunomodulatory protein for treating AD and psoriasis. METHODS: We identified and generated reporter proteins conjugated to astrotactin 1-derived peptide (AP), a novel transdermal delivery peptide of human origin, and analyzed the intracellular delivery efficiency of these proteins in mouse and human skin cells and tissues using multiphoton confocal microscopy. We also generated a recombinant therapeutic protein, AP-recombinant protein tyrosine phosphatase (rPTP), consisting of the phosphatase domain of the T-cell protein tyrosine phosphatase conjugated to AP. The immunomodulatory function of AP-rPTP was confirmed in splenocytes on cytokine stimulation and T-cell receptor stimulation. Finally, we confirmed the in vivo efficacy of AP-rPTP transdermal delivery in patients with oxazolone-induced contact hypersensitivity, ovalbumin-induced AD-like, and imiquimod-induced psoriasis-like skin inflammation models. RESULTS: AP-conjugated reporter proteins exhibited significant intracellular transduction efficacy in keratinocytes, fibroblasts, and immune cells. In addition, transcutaneous administration of AP-dTomato resulted in significant localization into the dermis and epidermis in both mouse and human skin. AP-rPTP inhibited phosphorylated signal transducer and activator of transcription (STAT) 1, STAT3, and STAT6 in splenocytes and also regulated T-cell activation and proliferation. Transcutaneous administration of AP-rPTP through the paper-patch technique significantly ameliorated skin tissue thickening, inflammation, and cytokine expression in both AD-like and psoriasis-like dermatitis models. CONCLUSION: We identified a 9-amino-acid novel transdermal delivery peptide, AP, and demonstrated its feasibility for transcutaneous biologic drug development. Moreover, AP-rPTP is a novel immunomodulatory drug candidate for human dermatitis.

Effects of sling exercise therapy on trunk muscle activation and balance in chronic hemiplegic patients.

Weakening of trunk muscles in stroke patients hinders functional ability, safety and balance. To confirm whether strengthening trunk muscles could facilitate rehabilitation of stroke patients, we investigated the effectiveness of sling exercise therapy (SET) using closed kinetic chain exercises to activate trunk muscles and improve balance in stroke patients. [Subjects and Methods] Twenty stroke patients with chronic hemiplegia were equally divided into 2 groups, a SET group and a control group that performed regular exercises on a mat with the assistance of a table. Patients in both groups exercised for 30 min, three times per week for 4 weeks. Trunk muscle activity was measured using surface electromyography, whereas balance was measured using the Berg Balance Scale, Frailty and Injuries Cooperative Studies of Intervention Technique, Timed Up & Go test, and BioRescue before and after the 4-week experimental period. [Results] Trunk muscle activity and balance before and after intervention in both groups were significantly different. However, no significant differences were observed between the 2 groups. [Conclusion] Although SET was not more effective than regular exercise, significant improvement was observed before and after SET. Therefore, SET can be considered effective in strengthening trunk muscles in stroke patients with chronic hemiplegia.

Effect of Dual-task Rehabilitative Training on Cognitive and Motor Function of Stroke Patients.

[Purpose] To determine the effect of dual-task training with cognitive tasks on cognitive and walking ability after stroke. [Subjects and Methods] Twenty patients diagnosed with stroke participated in this study. All participants were receiving a traditional rehabilitation program 5 days a week. Dual-task and single-task training were additionally performed for 4 weeks, 3 days a week. The Stroop test, Timed Up and Go (TUG) test, 10-Meter Walk Test (10MWT), and Figure-of-8 Walk Test (F8WT) were used to measure cognitive and walking abilities and were evaluated 3 times (before and after training and at the 2-week follow-up). [Results] Dual-task training improved cognitive and walking abilities, and dual-task training subjects' performance was better than single-task training subjects' performance. In addition, these training benefits were maintained for 2 weeks. [Conclusion] Dual-task training improves cognitive and walking abilities of patients with stroke.

Derivation of functional thymic epithelial organoid lines from adult murine thymus.

Thymic epithelial cells (TECs) orchestrate T cell development by imposing positive and negative selection on thymocytes. Current studies on TEC biology are hampered by the absence of long-term ex vivo culture platforms, while the cells driving TEC self-renewal remain to be identified. Here, we generate long-term (>2 years) expandable 3D TEC organoids from the adult mouse thymus. For further analysis, we generated single and double FoxN1-P2A-Clover, Aire-P2A-tdTomato, and Cldn4-P2A-tdTomato reporter lines by CRISPR knockin. Single-cell analyses of expanding clonal organoids reveal cells with bipotent stem/progenitor phenotypes. These clonal organoids can be induced to express Foxn1 and to generate functional cortical- and Aire-expressing medullary-like TECs upon RANK ligand + retinoic acid treatment. TEC organoids support T cell development from immature thymocytes in vitro as well as in vivo upon transplantation into athymic nude mice. This organoid-based platform allows in vitro study of TEC biology and offers a potential strategy for ex vivo T cell development.

Disease-associated astrocyte epigenetic memory promotes CNS pathology.

Astrocytes play important roles in the central nervous system (CNS) physiology and pathology. Indeed, astrocyte subsets defined by specific transcriptional activation states contribute to the pathology of neurologic diseases, including multiple sclerosis (MS) and its pre-clinical model experimental autoimmune encephalomyelitis (EAE) 1-8 . However, little is known about the stability of these disease-associated astrocyte subsets, their regulation, and whether they integrate past stimulation events to respond to subsequent challenges. Here, we describe the identification of an epigenetically controlled memory astrocyte subset which exhibits exacerbated pro-inflammatory responses upon re-challenge. Specifically, using a combination of single-cell RNA sequencing (scRNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), chromatin immunoprecipitation with sequencing (ChIP-seq), focused interrogation of cells by nucleic acid detection and sequencing (FIND-seq), and cell-specific in vivo CRISPR/Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) used by the histone acetyltransferase p300 to control chromatin accessibility. ACLY + p300 + memory astrocytes are increased in acute and chronic EAE models; the genetic targeting of ACLY + p300 + astrocytes using CRISPR/Cas9 ameliorated EAE. We also detected responses consistent with a pro-inflammatory memory phenotype in human astrocytes in vitro ; scRNA-seq and immunohistochemistry studies detected increased ACLY + p300 + astrocytes in chronic MS lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, MS. These findings may guide novel therapeutic approaches for MS and other neurologic diseases.

Effects of Trunk Stabilization Exercises on Different Support Surfaces on the Cross-sectional Area of the Trunk Muscles and Balance Ability.

[Purpose] The purpose of this study was to examine the effects on stroke patients of trunk stabilization exercise on different support surfaces. [Subjects and Methods] Sixteen stroke patients with onset of stroke six months earlier or longer were randomly and equally assigned to group I (exercise performed on a stable support surface) and group II (exercise performed on an unstable support surface). The two groups conducted the trunk stabilization exercises on the respective support surfaces, in addition to existing rehabilitation exercises five times per week for 12 weeks. Changes in the cross-sectional area (CSA) of the muscles were examined using computed tomography (CT), and changes in the balance ability were assessed using a measuring system and the trunk impairment scale (TIS). [Results] In group I, there was a significant increase in the CSA of the mulifidus muscle on the side contralateral to the brain lesion and in the paravertebral and multifidus muscles on the side ipsilateral to the brain lesion. In group II, there was a significant increase in the CSA of the paravertebral and multifidus muscles on the side contralateral to the brain lesion and on the side ipsilateral to the brain lesion. In terms of changes in balance ability, the sway path (SP) and TIS significantly improved in group I, and the SP, sway area (SA), and TIS significantly improved in group II . [Conclusion] Exercise on the unstable support surface enhanced the size of the cross-sectional area of the trunk muscles and balance ability significantly more than exercise on the stable support surface.

Neuroinflammation: An astrocyte perspective.

Astrocytes are abundant glial cells in the central nervous system (CNS) that play active roles in health and disease. Recent technologies have uncovered the functional heterogeneity of astrocytes and their extensive interactions with other cell types in the CNS. In this Review, we highlight the intricate interactions between astrocytes, other CNS-resident cells, and CNS-infiltrating cells as well as their potential therapeutic value in the context of inflammation and neurodegeneration.

Steady-state memory-phenotype conventional CD4+ T cells exacerbate autoimmune neuroinflammation in a bystander manner via the Bhlhe40/GM-CSF axis.

Memory-phenotype (MP) CD4+ T cells are a substantial population of conventional T cells that exist in steady-state mice, yet their immunological roles in autoimmune disease remain unclear. In this work, we unveil a unique phenotype of MP CD4+ T cells determined by analyzing single-cell transcriptomic data and T cell receptor (TCR) repertoires. We found that steady-state MP CD4+ T cells in the spleen were composed of heterogeneous effector subpopulations and existed regardless of germ and food antigen exposure. Distinct subpopulations of MP CD4+ T cells were specifically activated by IL-1 family cytokines and STAT activators, revealing that the cells exerted TCR-independent bystander effector functions similar to innate lymphoid cells. In particular, CCR6high subpopulation of MP CD4+ T cells were major responders to IL-23 and IL-1ß without MOG35-55 antigen reactivity, which gave them pathogenic Th17 characteristics and allowed them to contribute to autoimmune encephalomyelitis. We identified that Bhlhe40 in CCR6high MP CD4+ T cells as a key regulator of GM-CSF expression through IL-23 and IL-1ß signaling, contributing to central nervous system (CNS) pathology in experimental autoimmune encephalomyelitis. Collectively, our findings reveal the clearly distinct effector-like heterogeneity of MP CD4+ T cells in the steady state and indicate that CCR6high MP CD4+ T cells exacerbate autoimmune neuroinflammation via the Bhlhe40/GM-CSF axis in a bystander manner.

Engineered probiotics limit CNS autoimmunity by stabilizing HIF-1α in dendritic cells.

Dendritic cells (DCs) control the generation of self-reactive pathogenic T cells. Thus, DCs are considered attractive therapeutic targets for autoimmune diseases. Using single-cell and bulk transcriptional and metabolic analyses in combination with cell-specific gene perturbation studies we identified a negative feedback regulatory pathway that operates in DCs to limit immunopathology. Specifically, we found that lactate, produced by activated DCs and other immune cells, boosts NDUFA4L2 expression through a mechanism mediated by HIF-1α. NDUFA4L2 limits the production of mitochondrial reactive oxygen species that activate XBP1-driven transcriptional modules in DCs involved in the control of pathogenic autoimmune T cells. Moreover, we engineered a probiotic that produces lactate and suppresses T-cell autoimmunity in the central nervous system via the activation of HIF-1α/NDUFA4L2 signaling in DCs. In summary, we identified an immunometabolic pathway that regulates DC function, and developed a synthetic probiotic for its therapeutic activation.

Droplet-based forward genetic screening of astrocyte-microglia cross-talk.

Cell-cell interactions in the central nervous system play important roles in neurologic diseases. However, little is known about the specific molecular pathways involved, and methods for their systematic identification are limited. Here, we developed a forward genetic screening platform that combines CRISPR-Cas9 perturbations, cell coculture in picoliter droplets, and microfluidic-based fluorescence-activated droplet sorting to identify mechanisms of cell-cell communication. We used SPEAC-seq (systematic perturbation of encapsulated associated cells followed by sequencing), in combination with in vivo genetic perturbations, to identify microglia-produced amphiregulin as a suppressor of disease-promoting astrocyte responses in multiple sclerosis preclinical models and clinical samples. Thus, SPEAC-seq enables the high-throughput systematic identification of cell-cell communication mechanisms.

Function and therapeutic value of astrocytes in neurological diseases.

Astrocytes are abundant glial cells in the central nervous system (CNS) that perform diverse functions in health and disease. Astrocyte dysfunction is found in numerous diseases, including multiple sclerosis, Alzheimer disease, Parkinson disease, Huntington disease and neuropsychiatric disorders. Astrocytes regulate glutamate and ion homeostasis, cholesterol and sphingolipid metabolism and respond to environmental factors, all of which have been implicated in neurological diseases. Astrocytes also exhibit significant heterogeneity, driven by developmental programmes and stimulus-specific cellular responses controlled by CNS location, cell-cell interactions and other mechanisms. In this Review, we highlight general mechanisms of astrocyte regulation and their potential as therapeutic targets, including drugs that alter astrocyte metabolism, and therapies that target transporters and receptors on astrocytes. Emerging ideas, such as engineered probiotics and glia-to-neuron conversion therapies, are also discussed. We further propose a concise nomenclature for astrocyte subsets that we use to highlight the roles of astrocytes and specific subsets in neurological diseases.

In Vivo Induction of Regulatory T Cells Via CTLA-4 Signaling Peptide to Control Autoimmune Encephalomyelitis and Prevent Disease Relapse.

Regulatory T cells play a key role in immune tolerance to self-antigens, thereby preventing autoimmune diseases. However, no drugs targeting Treg cells have been approved for clinical trials yet. Here, a chimeric peptide is generated by conjugation of the cytoplasmic domain of CTLA-4 (ctCTLA-4) with dNP2 for intracellular delivery, dNP2-ctCTLA-4, and evaluated Foxp3 expression during Th0, Th1, Treg, and Th17 differentiation dependent on TGF-ß. The lysine motif of ctCTLA-4, not tyrosine motif, is required for Foxp3 expression for Treg induction and amelioration of experimental autoimmune encephalomyelitis (EAE). Transcriptome analysis reveals that dNP2-ctCTLA-4-treated T cells express Treg transcriptomic patterns with properties of suppressive functions. In addition, the molecular interaction between the lysine motif of ctCTLA-4 and PKC-η is critical for Foxp3 expression. Although both CTLA-4-Ig and dNP2-ctCTLA-4 treatment in vivo ameliorated EAE progression, only dNP2-ctCTLA-4 requires Treg cells for inhibition of disease progression and prevention of relapse. Furthermore, the CTLA-4 signaling peptide is able to induce human Tregs in vitro and in vivo as well as from peripheral blood mononuclear cells (PBMCs) of multiple sclerosis patients. These results collectively suggest that the chimeric CTLA-4 signaling peptide can be used for successful induction of regulatory T cells in vivo to control autoimmune diseases, such as multiple sclerosis.

NFAT-Specific Inhibition by dNP2-VIVITAmeliorates Autoimmune Encephalomyelitisby Regulation of Th1 and Th17.

Nuclear factor of activated T cells (NFATs) is an important transcription factor for T cell activation and proliferation. Recent studies have highlighted the role of NFATs in regulating the differentiation of effector CD4 T helper (Th) subsets including Th1 and Th17 cells. Because controlling the effector T cell function is important for the treatment of autoimmune diseases, regulation of NFAT functions in T cells would be an important strategy to control the pathogenesis of autoimmune diseases. Here, we demonstrated that an NFAT inhibitory peptide, VIVIT conjugated to dNP2 (dNP2-VIVIT), a blood-brain barrier-permeable peptide, ameliorated experimental autoimmune encephalomyelitis (EAE) by inhibiting Th1 and Th17 cells, but not regulatory T (Treg) cells. dNP2-VIVIT negatively regulated spinal cord-infiltrating interleukin-17A (IL-17A) and interferon (IFN)-γ-producing CD4+ T cells without affecting the number of Foxp3+ CD4+ Treg cells, whereas dNP2-VEET or 11R-VIVIT could not significantly inhibit EAE. In comparison with cyclosporin A (CsA), dNP2-VIVIT selectively inhibited Th1 and Th17 differentiation, whereas CsA inhibited the differentiation of all T cell subsets including that of Th2 and Treg cells. Collectively, this study demonstrated the role of dNP2-VIVIT as a novel agent for the treatment of autoimmune diseases such as multiple sclerosis by regulating the functions of Th1 and Th17 cells.

Bystander CD4+ T cells: crossroads between innate and adaptive immunity.

T cells are the central mediators of both humoral and cellular adaptive immune responses. Highly specific receptor-mediated clonal selection and expansion of T cells assure antigen-specific immunity. In addition, encounters with cognate antigens generate immunological memory, the capacity for long-term, antigen-specific immunity against previously encountered pathogens. However, T-cell receptor (TCR)-independent activation, termed "bystander activation", has also been found. Bystander-activated T cells can respond rapidly and secrete effector cytokines even in the absence of antigen stimulation. Recent studies have rehighlighted the importance of antigen-independent bystander activation of CD4+ T cells in infection clearance and autoimmune pathogenesis, suggesting the existence of a distinct innate-like immunological function performed by conventional T cells. In this review, we discuss the inflammatory mediators that activate bystander CD4+ T cells and the potential physiological roles of these cells during infection, autoimmunity, and cancer.