Glia-dependent TGF-beta signaling, acting independently of the TH17 pathway, is critical for initiation of murine autoimmune encephalomyelitis

Myelin oligodendrocyte glycoprotein reactive Th17 cells drive Janus Kinase 1 dependent transcriptional reprogramming in astrocytes and alter cell surface cytokine receptor profiles during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune demyelinating disease affecting the central nervous system (CNS). T helper (Th) 17 cells are involved in the pathogenesis of MS and its animal model of experimental autoimmune encephalomyelitis (EAE) by infiltrating the CNS and producing effector molecules that engage resident glial cells. Among these glial cells, astrocytes have a central role in coordinating inflammatory processes by responding to cytokines and chemokines released by Th17 cells. In this study, we examined the impact of pathogenic Th17 cells on astrocytes in vitro and in vivo. We identified that Th17 cells reprogram astrocytes by driving transcriptomic changes partly through a Janus Kinase (JAK)1-dependent mechanism, which included increased chemokines, interferon-inducible genes, and cytokine receptors. In vivo, we observed a region-specific heterogeneity in the expression of cell surface cytokine receptors on astrocytes, including those for IFN-γ, IL-1, TNF-α, IL-17, TGFβ, and IL-10. Additionally, these receptors were dynamically regulated during EAE induced by adoptive transfer of myelin-reactive Th17 cells. This study overall provides evidence of Th17 cell reprogramming of astrocytes, which may drive changes in the astrocytic responsiveness to cytokines during autoimmune neuroinflammation.

Nicorandil and carvedilol mitigates motor deficits in experimental autoimmune encephalomyelitis-induced multiple sclerosis: Role of TLR4/TRAF6/MAPK/NF-κB signalling cascade

Multiple sclerosis (MS) is an inflammatory demyelinating neurodegenerative disease that negatively affects neurotransmission. It can be pathologically mimicked by experimental autoimmune encephalomyelitis (EAE) animal model. ATP-sensitive potassium channels (KATP) plays a crucial role in the control of neuronal damage, however their role in MS are still obscure. Additionally, Carvedilol showed a promising neuroprotective activity against several neurological disorders. Therefore, the present study aimed to investigate the potential neuroprotective effect of KATP channel opener (nicorandil) as well as α and β adrenoceptor antagonist (Carvedilol) against EAE induced neurodegeneration in mice. Mice was treated with nicorandil (6 mg/kg/day; p.o.) and carvedilol (10 mg/kg/day; p.o.) for 14 days. Nicorandil and carvedilol showed improvement in clinical scoring, behaviour and motor coordination as established by histopathological investigation and immunohistochemical detection of MBP. Furthermore, both treatments downregulated the protein expression of TLR4/ MYD88/TRAF6 signalling cascade with downstream inhibition of (pT183/Y185)-JNK/p38 (pT180/Y182)-MAPK axis leading to reduction of neuroinflammatory status, as witnessed by reduction of NF-κB, TNF-α, IL-1β and IL-6 contents. Moreover, nicorandil and carvedilol attenuated oxidative damage by increasing Nrf2 content and SOD activity together with reduction of MDA content. In addition, an immunomodulating effect via inhibiting the gene expression of CD4, TGF-β, and IL-17 as well as TGF-β, IL-17, and IL-23 contents along with anti-apoptotic effect by decreasing Bax protein expression and Caspase-3 content and increasing Bcl-2 protein expression was observed with nicorandil and carvedilol treatments. In conclusion, nicorandil and carvedilol exerted a neuroprotective activity against EAE induced neuronal loss via inhibition of TLR4/MYD88/TRAF6/JNK/p38-MAPK axis besides antioxidant and anti-apoptotic effects.

Transforming growth factor β (TGF-β) pathway in the immunopathogenesis of multiple sclerosis (MS); molecular approaches

INTRODUCTION

Multiple sclerosis (MS) is an acute demyelinating disease with an autoimmune nature, followed by gradual neurodegeneration and enervating scar formation. Dysregulated immune response is a crucial dilemma contributing to the pathogenesis of MS. The role of chemokines and cytokines, such as transforming growth factor-β (TGF-β), have been recently highlighted regarding their altered expressions in MS. TGF-β has three isoforms, TGF-β1, TGF-β2, and TGF-β3, that are structurally similar; however, they can show different functions.

RESULTS

All three isoforms are known to induce immune tolerance by modifying Foxp3⁺ regulatory T cells. Nevertheless, there are controversial reports concerning the role of TGF-β1 and 2 in the progression of scar formation in MS. At the same time, these proteins also improve oligodendrocyte differentiation and have shown neuroprotective behavior, two cellular processes that suppress the pathogenesis of MS. TGF-β3 shares the same properties but is less likely contributes to scar formation, and its direct role in MS remains elusive.

DISCUSSION

To develop novel neuroimmunological treatment strategies for MS, the optimal strategy could be the one that causes immune modulation, induces neurogenesis, stimulates remyelination, and prevents excessive scar formation. Therefore, regarding its immunological properties, TGF-β could be an appropriate candidate; however, contradictory results of previous studies have questioned its role and therapeutic potential in MS. In this review article, we provide an overview of the role of TGF-β in immunopathogenesis of MS, related clinical and animal studies, and the treatment potential of TGF-β in MS, emphasizing the role of different TGF-β isoforms.

The role of sphingosine 1-phosphate metabolism in brain health and disease

Lipids are essential structural and functional components of the central nervous system (CNS). Sphingolipids are ubiquitous membrane components which were discovered in the brain in the late 19^th century. In mammals, the brain contains the highest concentration of sphingolipids in the body. Sphingosine 1-phosphate (S1P) derived from membrane sphingolipids evokes multiple cellular responses which, depending on its concentration and localization, make S1P a double-edged sword in the brain. In the present review we highlight the role of S1P in brain development and focus on the often contrasting findings regarding its contributions to the initiation, progression and potential recovery of different brain pathologies, including neurodegeneration, multiple sclerosis (MS), brain cancers, and psychiatric illnesses. A detailed understanding of the critical implications of S1P in brain health and disease may open the door for new therapeutic options. Thus, targeting S1P-metabolizing enzymes and/or signaling pathways might help overcome, or at least ameliorate, several brain illnesses.

The Role of Decorin in Autoimmune and Inflammatory Diseases

Decorin is an extracellular matrix protein that belongs to the family of small leucine-rich proteoglycans. As a matrix protein, the first discovered role of decorin is participating in collagen fibril formation. Many other functions of decorin in various biological processes have been subsequently identified. Decorin is involved in an extensive signaling network and can interact with other extracellular matrix components, growth factors, receptor tyrosine kinases, and various proteases. Decorin has been shown to be involved in wound repair, cell cycle, angiogenesis, tumor metastasis, and autophagy. Recent evidence indicates that it also plays a role in immune regulation and inflammatory diseases. This review summarizes the characteristics of decorin in immune and inflammatory diseases, including inflammatory bowel disease (IBD), Sjögren's syndrome (SS), chronic obstructive pulmonary disease (COPD), IgA nephropathy, rheumatoid arthritis (RA), spondyloarthritis (SpA), osteoarthritis, multiple sclerosis (MS), idiopathic inflammatory myopathies (IIM), and systemic sclerosis (SSc) and discusses the potential role in these disorders.

Neuronal activity induces glucosylceramide that is secreted via exosomes for lysosomal degradation in glia

Recessive variants in GBA1 cause Gaucher disease, a prevalent form of lysosome storage disease. GBA1 encodes a lysosomal enzyme that hydrolyzes glucosylceramide (GlcCer) into glucose and ceramide. Its loss causes lysosomal dysfunction and increased levels of GlcCer. We generated a null allele of the Drosophila ortholog Gba1b by inserting the Gal4 using CRISPR-Cas9. Here, we show that Gba1b is expressed in glia but not in neurons. Glial-specific knockdown recapitulates the defects found in Gba1b mutants, and these can be rescued by glial expression of human GBA1. We show that GlcCer is synthesized upon neuronal activity, and it is transported from neurons to glia through exosomes. Furthermore, we found that glial TGF-β/BMP induces the transfer of GlcCer from neurons to glia and that the White protein, an ABCG transporter, promotes GlcCer trafficking to glial lysosomes for degradation.

Historical and current perspectives on blood endothelial cell heterogeneity in the brain

Dynamic brain activity requires timely communications between the brain parenchyma and circulating blood. Brain-blood communication is facilitated by intricate networks of brain vasculature, which display striking heterogeneity in structure and function. This vascular cell heterogeneity in the brain is fundamental to mediating diverse brain functions and has long been recognized. However, the molecular basis of this biological phenomenon has only recently begun to be elucidated. Over the past century, various animal species and in vitro systems have contributed to the accumulation of our fundamental and phylogenetic knowledge about brain vasculature, collectively advancing this research field. Historically, dye tracer and microscopic observations have provided valuable insights into the anatomical and functional properties of vasculature across the brain, and these techniques remain an important approach. Additionally, recent advances in molecular genetics and omics technologies have revealed significant molecular heterogeneity within brain endothelial and perivascular cell types. The combination of these conventional and modern approaches has enabled us to identify phenotypic differences between healthy and abnormal conditions at the single-cell level. Accordingly, our understanding of brain vascular cell states during physiological, pathological, and aging processes has rapidly expanded. In this review, we summarize major historical advances and current knowledge on blood endothelial cell heterogeneity in the brain, and discuss important unsolved questions in the field.

TGF-β as a Key Modulator of Astrocyte Reactivity: Disease Relevance and Therapeutic Implications

Astrocytes are essential for normal brain development and functioning. They respond to brain injury and disease through a process referred to as reactive astrogliosis, where the reactivity is highly heterogenous and context-dependent. Reactive astrocytes are active contributors to brain pathology and can exert beneficial, detrimental, or mixed effects following brain insults. Transforming growth factor-β (TGF-β) has been identified as one of the key factors regulating astrocyte reactivity. The genetic and pharmacological manipulation of the TGF-β signaling pathway in animal models of central nervous system (CNS) injury and disease alters pathological and functional outcomes. This review aims to provide recent understanding regarding astrocyte reactivity and TGF-β signaling in brain injury, aging, and neurodegeneration. Further, it explores how TGF-β signaling modulates astrocyte reactivity and function in the context of CNS disease and injury.

Astrocytic YAP protects the optic nerve and retina in an experimental autoimmune encephalomyelitis model through TGF-β signaling

Rationale: Optic neuritis is one of main symptoms in multiple sclerosis (MS) that causes visual disability. Astrocytes are pivotal regulators of neuroinflammation in MS, and astrocytic yes-associated protein (YAP) plays a critical role in neuroinflammation. Meanwhile, YAP signaling is involved in visual impairment, including glaucoma, retinal choroidal atrophy and retinal detachment. However, the roles and underlying mechanisms of astrocytic YAP in neuroinflammation and demyelination of MS-related optic neuritis (MS-ON) remains unclear. Methods: To assess the functions of YAP in MS-ON, experimental autoimmune encephalomyelitis (EAE, a common model of MS) was established, and mice that conditional knockout (CKO) of YAP in astrocytes, YAP^GFAP-CKO mice, were successfully generated. Behavior tests, immunostaining, Nissl staining, Hematoxylin-Eosin (HE) staining, TUNEL staining, Luxol Fast Blue (LFB) staining, electron microscopy (EM), quantitative real-time PCR (qPCR), gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) by RNA sequencing were used to examine the function and mechanism of YAP signaling based on these YAP^GFAP-CKO mice and EAE model mice. To further explore the potential treatment of YAP signaling in EAE, EAE mice were treated with various drugs, including SRI-011381 that is an agonist of transforming growth factor-β (TGF-β) pathway, and XMU-MP-1 which inhibits Hippo kinase MST1/2 to activate YAP. Results: We found that YAP was significantly upregulated and activated in the astrocytes of optic nerve in EAE mice. Conditional knockout of YAP in astrocytes caused more severe inflammatory infiltration and demyelination in optic nerve, and damage of retinal ganglion cells (RGCs) in EAE mice. Moreover, YAP deletion in astrocytes promoted the activation of astrocytes and microglia, but inhibited the proliferation of astrocytes of optic nerve in EAE mice. Mechanically, TGF-β signaling pathway was significantly down-regulated after YAP deletion in astrocytes. Additionally, both qPCR and immunofluorescence assays confirmed the reduction of TGF-β signaling pathway in YAP^GFAP-CKO EAE mice. Interestingly, SRI-011381 partially rescued the deficits in optic nerve and retina of YAP^GFAP-CKO EAE mice. Finally, activation of YAP signaling by XMU-MP-1 relieved the neuroinflammation and demyelination in optic nerve of EAE mice. Conclusions: These results suggest astrocytic YAP may prevent the neuroinflammatory infiltration and demyelination through upregulation of TGF-β signaling and provide targets for the development of therapeutic strategies tailored for MS-ON.

M-CSF, IL-6, and TGF-β promote generation of a new subset of tissue repair macrophage for traumatic brain injury recovery

Traumatic brain injury (TBI) leads to high mortality rate. We aimed to identify the key cytokines favoring TBI repair and found that patients with TBI with a better outcome robustly increased concentrations of macrophage colony-stimulating factor, interleukin-6, and transforming growth factor-β (termed M6T) in cerebrospinal fluid or plasma. Using TBI mice, we identified that M2-like macrophage, microglia, and endothelial cell were major sources to produce M6T. Together with the in vivo tracking of mCherry+ macrophages in zebrafish models, we confirmed that M6T treatment accelerated blood-borne macrophage infiltration and polarization toward a subset of tissue repair macrophages that expressed similar genes as microglia for neuroprotection, angiogenesis and cell migration. M6T therapy in TBI mice and zebrafish improved neurological function while blocking M6T-exacerbated brain injury. Considering low concentrations of M6T in some patients with poor prognostic, M6T treatment might repair TBI via generating a previously unidentified subset of tissue repair macrophages.

Acute and late administration of colony stimulating factor 1 attenuates chronic cognitive impairment following mild traumatic brain injury in mice

Traumatic brain injury (TBI) is a leading cause of long-term neurological disability. Currently there is no effective pharmacological treatment for patients suffering from the long-lasting symptoms of TBI. We recently discovered that colony stimulating factor 1 (CSF1), an essential regulator of macrophage homeostasis, is neuroprotective and reduces neuroinflammation in two models of neurological disease in mice. Here we used a mouse model of repetitive mild TBI (mTBI) to examine whether CSF1 would attenuate cognitive deficits and improve pathological outcomes in two paradigms. In the acute paradigm, a single bolus treatment of CSF1 administered 24 h after injury significantly reduces memory impairment and astrocyte reactivity assessed 3 months later. In the chronic paradigm, the mice were tested 3 months after mTBI when they showed cognitive deficits. The mice were then randomly assigned to receive CSF1 or PBS (as control) treatment. After one month of treatment, the PBS-treated mice remained cognitively impaired, but the CSF1-treated showed significant improvements in cognitive function. RNA-seq and Ingenuity Pathway Analysis reveals CSF1 treatment alters cognition- and memory-related transcriptomic changes and pathways. The results of this study show that acute as well as delayed CSF1 treatment attenuate chronically impaired cognitive functions and improve pathological outcomes long after mTBI. The wide therapeutic time window of CSF1, together with the fact that CSF1 is approved for human use in clinical trials, strongly supports the potential clinical usefulness of this treatment in patients with mTBI.

IL-38 Ablation Reduces Local Inflammation and Disease Severity in Experimental Autoimmune Encephalomyelitis

IL-38 is an IL-1 family receptor antagonist that restricts IL-17-driven inflammation by limiting cytokine production from macrophages and T cells. In the current study, we aimed to explore its role in experimental autoimmune encephalomyelitis in mice, which is, among others, driven by IL-17. Unexpectedly, IL-38-deficient mice showed strongly reduced clinical scores and histological markers of experimental autoimmune encephalomyelitis. This was accompanied by reduced inflammatory cell infiltrates, including macrophages and T cells, as well as reduced expression of inflammatory markers in the spinal cord. IL-38 was highly expressed by infiltrating macrophages in the spinal cord, and in vitro activated IL-38-deficient bone marrow-derived macrophages showed reduced expression of inflammatory markers, accompanied by altered cellular metabolism. These data suggest an alternative cell-intrinsic role of IL-38 to promote inflammation in the CNS.

Selenization of S. cerevisiae increases its protective potential in experimental autoimmune encephalomyelitis by triggering an intestinal immunomodulatory loop

Multiple sclerosis is an autoimmune disease that affects the myelinated central nervous system (CNS) neurons and triggers physical and cognitive disabilities. Conventional therapy is based on disease-modifying drugs that control disease severity but can also be deleterious. Complementary medicines have been adopted and evidence indicates that yeast supplements can improve symptoms mainly by modulating the immune response. In this investigation, we evaluated the therapeutic potential of Saccharomyces cerevisiae and its selenized derivative (Selemax) in experimental autoimmune encephalomyelitis (EAE). Female C57BL/6 mice submitted to EAE induction were orally supplemented with these yeasts by gavage from day 0 to day 14 after EAE induction. Both supplements determined significant reduction in clinical signs concomitantly with diminished Th1 immune response in CNS, increased proportion of Foxp3⁺ lymphocytes in inguinal and mesenteric lymph nodes and increased microbiota diversity. However, Selemax was more effective clinically and immunologically; it reduced disease prevalence more sharply, increased the proportion of CD103⁺ dendritic cells expressing high levels of PD-L1 in mesenteric lymph nodes and reduced the intestinal inflammatory process more strongly than S. cerevisiae. These results suggest a clear gut-brain axis modulation by selenized S. cerevisiae and suggest their inclusion in clinical trials.

Altered astrocytic function in experimental neuroinflammation and multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that affects about 2.5 million people worldwide. In MS, the patients' immune system starts to attack the myelin sheath, leading to demyelination, neurodegeneration, and, ultimately, loss of vital neurological functions such as walking. There is currently no cure for MS and the available treatments only slow the initial phases of the disease. The later-disease mechanisms are poorly understood and do not directly correlate with the activity of immune system cells, the main target of the available treatments. Instead, evidence suggests that disease progression and disability are better correlated with the maintenance of a persistent low-grade inflammation inside the CNS, driven by local glial cells, like astrocytes and microglia. Depending on the context, astrocytes can (a) exacerbate inflammation or (b) promote immunosuppression and tissue repair. In this review, we will address the present knowledge that exists regarding the role of astrocytes in MS and experimental animal models of the disease.

Opposing and potentially antagonistic effects of BMP and TGF-β in multiple sclerosis: The "Yin and Yang" of neuro-immune Signaling

Bone Morphogenetic Proteins (BMP) and Transforming Growth Factor-beta (TGF-β) are cytokines with similar receptors and messengers. They are important for immune cell function, with BMPs exerting mainly proinflammatory but also anti-inflammatory effects, and TGF-β suppressing inflammation. Patients with Multiple Sclerosis exhibit BMP overactivity and suppressed TGF-β signaling. This dysregulated signaling participates in the crosstalk between infiltrating immune cells and glia, where BMP inhibits remyelination. Reciprocal antagonism between the two pathways takes place via a variety of mechanisms. Although this antagonism has not been studied in the setting of Multiple Sclerosis, it could inform further research and treatment discovery.

Cell Signaling Pathway Reporters in Adult Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) develop at several anatomical locations and are thought to undergo different niche regulatory cues originating from highly conserved cell signaling pathways, such as Wnt, Notch, TGF-β family, and Hedgehog signaling. Most insight into these pathways has been obtained by reporter models and loss- or gain of function experiments, yet results differ in many cases according to the approach. In this review, we discuss existing murine reporter models regarding these pathways, considering the genetic constructs and reporter proteins in the context of HSC studies; yet these models are relevant for all other stem cell systems. Lastly, we describe a multi-reporter model to properly study and understand the cross-pathway interaction and how reporter models are highly valuable tools to understand complex signaling dynamics in stem cells.

TGFβRI antagonist inhibits HIV-1 Nef-induced CC chemokine family ligand 2 (CCL2) in the brain and prevents spatial learning impairment

BACKGROUND

HIV-1-associated neurocognitive disorders (HAND) progression is related to continued inflammation despite undetectable viral loads and may be caused by early viral proteins expressed by latently infected cells. Astrocytes represent an HIV reservoir in the brain where the early viral neurotoxin negative factor (Nef) is produced. We previously demonstrated that astrocytic expression of Nef in the hippocampus of rats causes inflammation, macrophage infiltration, and memory impairment. Since these processes are affected by TGFβ signaling pathways, and TGFβ-1 is found at higher levels in the central nervous system of HIV-1+ individuals and is released by astrocytes, we hypothesized a role for TGFβ-1 in our model of Nef neurotoxicity.

METHODS

To test this hypothesis, we compared cytokine gene expression by cultured astrocytes expressing Nef or green fluorescent protein. To determine the role of Nef and a TGFβRI inhibitor on memory and learning, we infused astrocytes expressing Nef into the hippocampus of rats and then treated them daily with an oral dose of SD208 (10 mg/kg) or placebo for 7 days. During this time, locomotor activity was recorded in an open field and spatial learning tested in the novel location recognition paradigm. Postmortem tissue analyses of inflammatory and signaling molecules were conducted using immunohistochemistry and immunofluorescence.

RESULTS

TGFβ-1 was induced in cultures expressing Nef at 24 h followed by CCL2 induction which was prevented by blocking TGFβRI with SD208 (competitive inhibitor). Interestingly, Nef seems to change the TGFβRI localization as suggested by the distribution of the immunoreactivity. Nef caused a deficit in spatial learning that was recovered upon co-administration of SD208. Brain tissue from Nef-treated rats given SD208 showed reduced CCL2, phospho-SMAD2, cluster of differentiation 163 (CD163), and GFAP immunoreactivity compared to the placebo group.

CONCLUSIONS

Consistent with our previous findings, rats treated with Nef showed deficits in spatial learning and memory in the novel location recognition task. In contrast, rats treated with Nef + SD208 showed better spatial learning suggesting that Nef disrupts memory formation in a TGFβ-1-dependent manner. The TGFβRI inhibitor further reduced the induction of inflammation by Nef which was concomitant with decreased TGFβ signaling. Our findings suggest that TGFβ-1 signaling is an intriguing target to reduce neuroHIV.

Molecular signature of different lesion types in the brain white matter of patients with progressive multiple sclerosis

To identify pathogenetic markers and potential drivers of different lesion types in the white matter (WM) of patients with progressive multiple sclerosis (PMS), we sequenced RNA from 73 different WM areas. Compared to 25 WM controls, 6713 out of 18,609 genes were significantly differentially expressed in MS tissues (FDR < 0.05). A computational systems medicine analysis was performed to describe the MS lesion endophenotypes. The cellular source of specific molecules was examined by RNAscope, immunohistochemistry, and immunofluorescence. To examine common lesion specific mechanisms, we performed de novo network enrichment based on shared differentially expressed genes (DEGs), and found TGFβ-R2 as a central hub. RNAscope revealed astrocytes as the cellular source of TGFβ-R2 in remyelinating lesions. Since lesion-specific unique DEGs were more common than shared signatures, we examined lesion-specific pathways and de novo networks enriched with unique DEGs. Such network analysis indicated classic inflammatory responses in active lesions; catabolic and heat shock protein responses in inactive lesions; neuronal/axonal specific processes in chronic active lesions. In remyelinating lesions, de novo analyses identified axonal transport responses and adaptive immune markers, which was also supported by the most heterogeneous immunoglobulin gene expression. The signature of the normal-appearing white matter (NAWM) was more similar to control WM than to lesions: only 465 DEGs differentiated NAWM from controls, and 16 were unique. The upregulated marker CD26/DPP4 was expressed by microglia in the NAWM but by mononuclear cells in active lesions, which may indicate a special subset of microglia before the lesion develops, but also emphasizes that omics related to MS lesions should be interpreted in the context of different lesions types. While chronic active lesions were the most distinct from control WM based on the highest number of unique DEGs (n = 2213), remyelinating lesions had the highest gene expression levels, and the most different molecular map from chronic active lesions. This may suggest that these two lesion types represent two ends of the spectrum of lesion evolution in PMS. The profound changes in chronic active lesions, the predominance of synaptic/neural/axonal signatures coupled with minor inflammation may indicate end-stage irreversible molecular events responsible for this less treatable phase.

TGFB1-Mediated Gliosis in Multiple Sclerosis Spinal Cords Is Favored by the Regionalized Expression of HOXA5 and the Age-Dependent Decline in Androgen Receptor Ligands

In multiple sclerosis (MS) patients with a progressive form of the disease, spinal cord (SC) functions slowly deteriorate beyond age 40. We previously showed that in the SC of these patients, large areas of incomplete demyelination extend distance away from plaque borders and are characterized by a unique progliotic TGFB1 (Transforming Growth Factor Beta 1) genomic signature. Here, we attempted to determine whether region- and age-specific physiological parameters could promote the progression of SC periplaques in MS patients beyond age 40. An analysis of transcriptomics databases showed that, under physiological conditions, a set of 10 homeobox (HOX) genes are highly significantly overexpressed in the human SC as compared to distinct brain regions. Among these HOX genes, a survey of the human proteome showed that only HOXA5 encodes a protein which interacts with a member of the TGF-beta signaling pathway, namely SMAD1 (SMAD family member 1). Moreover, HOXA5 was previously found to promote the TGF-beta pathway. Interestingly, SMAD1 is also a protein partner of the androgen receptor (AR) and an unsupervised analysis of gene ontology terms indicates that the AR pathway antagonizes the TGF-beta/SMAD pathway. Retrieval of promoter analysis data further confirmed that AR negatively regulates the transcription of several members of the TGF-beta/SMAD pathway. On this basis, we propose that in progressive MS patients, the physiological SC overexpression of HOXA5 combined with the age-dependent decline in AR ligands may favor the slow progression of TGFB1-mediated gliosis. Potential therapeutic implications are discussed.

In vivo Bioluminescence Imaging Used to Monitor Disease Activity and Therapeutic Response in a Mouse Model of Tauopathy

Many studies of tauopathy use transgenic mice that overexpress the P301S mutant form of tau. Neuronal damage in these mice is associated with astrogliosis and induction of glial fibrillary acidic protein (GFAP) expression. GFAP-luc transgenic mice express firefly luciferase under the GFAP promoter, allowing bioluminescence to be measured non-invasively as a surrogate biomarker for astrogliosis. We bred double transgenic mice possessing both P301S and GFAP-luc cassettes and compared them to control mice bearing only the GFAP-luc transgene. We used serial bioluminescent images to define the onset and the time course of astrogliosis in these mice and this was correlated with the development of clinical deficit. Mice containing both GFAP-luc and P301S transgenes showed increased luminescence indicative of astroglial activation in the brain and spinal cord. Starting at 5 months old, the onset of clinical deterioration in these mice corresponded closely to the initial rise in the luminescent signal. Post mortem analysis showed the elevated luminescence was correlated with hyperphosphorylated tau deposition in the hippocampus of double transgenic mice. We used this method to determine the therapeutic effect of JM4 peptide [a small peptide immunomodulatory agent derived from human erythropoietin (EPO)] on double transgenic mice. JM4 treatment significantly decreased the intensity of luminescence, neurological deficit and hyperphosphorylated tau in mice with both the P301S and GFAP-luc transgenes. These findings indicate that bioluminescence imaging (BLI) is a powerful tool for quantifying GFAP expression in living P301S mice and can be used as a noninvasive biomarker of tau-induced neurodegeneration in preclinical therapeutic trials.

Aged blood impairs hippocampal neural precursor activity and activates microglia via brain endothelial cell VCAM1

An aged circulatory environment can activate microglia, reduce neural precursor cell activity, and impair cognition in mice. We hypothesized that brain endothelial cells (BECs) mediate at least some of these effects. We observe BECs in the aged mouse hippocampus express an inflammatory transcriptional profile with focal upregulation of Vascular Cell Adhesion Molecule 1 (VCAM1), a protein that facilitates vascular-immune cell interactions. Concomitantly, the shed, soluble form of VCAM1 is prominently increased in plasma of aged humans and mice, and their plasma is sufficient to increase VCAM1 expression in cultured BECs and young mouse hippocampi. Systemic anti-VCAM1 antibody or genetic ablation of VCAM1 in BECs counteracts the detrimental effects of aged plasma on young brains and reverses aging aspects including microglial reactivity and cognitive deficits in old mouse brains. Together, these findings establish brain endothelial VCAM1 at the blood-brain barrier (BBB) as a possible target to treat age-related neurodegeneration.

Circulating transforming growth factor-β1 facilitates remyelination in the adult central nervous system

Oligodendrocyte maturation is necessary for functional regeneration in the CNS; however, the mechanisms by which the systemic environment regulates oligodendrocyte maturation is unclear. We found that Transforming growth factor (TGF)-β1, which is present in higher levels in the systemic environment, promotes oligodendrocyte maturation. Oligodendrocyte maturation was enhanced by adult mouse serum treatment via TGF-β type I receptor. Decrease in circulating TGF-β1 level prevented remyelination in the spinal cord after toxin-induced demyelination. TGF-β1 administration promoted remyelination and restored neurological function in a multiple sclerosis animal model. Furthermore, TGF-β1 treatment stimulated human oligodendrocyte maturation. These data provide the therapeutic possibility of TGF-β for demyelinating diseases.

The contribution of astrocytes to the neuroinflammatory response in multiple sclerosis and experimental autoimmune encephalomyelitis

Neuroinflammation is the coordinated response of the central nervous system (CNS) to threats to its integrity posed by a variety of conditions, including autoimmunity, pathogens and trauma. Activated astrocytes, in concert with other cellular elements of the CNS and immune system, are important players in the modulation of the neuroinflammatory response. During neurological disease, they produce and respond to cellular signals that often lead to dichotomous processes, which can promote further damage or contribute to repair. This occurs also in multiple sclerosis (MS), where astrocytes are now recognized as key components of its immunopathology. Evidence supporting this role has emerged not only from studies in MS patients, but also from animal models, among which the experimental autoimmune encephalomyelitis (EAE) model has proved especially instrumental. Based on this premise, the purpose of the present review is to summarize the current knowledge of astrocyte behavior in MS and EAE. Following a brief description of the pathological characteristics of the two diseases and the main functional roles of astrocytes in CNS physiology, we will delve into the specific responses of this cell population, analyzing MS and EAE in parallel. We will define the temporal and anatomical profile of astroglial activation, then focus on key processes they participate in. These include: (1) production and response to soluble mediators (e.g., cytokines and chemokines), (2) regulation of oxidative stress, and (3) maintenance of BBB integrity and function. Finally, we will review the state of the art on the available methods to measure astroglial activation in vivo in MS patients, and how this could be exploited to optimize diagnosis, prognosis and treatment decisions. Ultimately, we believe that integrating the knowledge obtained from studies in MS and EAE may help not only better understand the pathophysiology of MS, but also uncover new signals to be targeted for therapeutic intervention.

Unique RNA signature of different lesion types in the brain white matter in progressive multiple sclerosis

The heterogeneity of multiple sclerosis is reflected by dynamic changes of different lesion types in the brain white matter (WM). To identify potential drivers of this process, we RNA-sequenced 73 WM areas from patients with progressive MS (PMS) and 25 control WM. Lesion endophenotypes were described by a computational systems medicine analysis combined with RNAscope, immunohistochemistry, and immunofluorescence. The signature of the normal-appearing WM (NAWM) was more similar to control WM than to lesions: one of the six upregulated genes in NAWM was CD26/DPP4 expressed by microglia. Chronic active lesions that become prominent in PMS had a signature that were different from all other lesion types, and were differentiated from them by two clusters of 62 differentially expressed genes (DEGs). An upcoming MS biomarker, CHI3L1 was among the top ten upregulated genes in chronic active lesions expressed by astrocytes in the rim. TGFβ-R2 was the central hub in a remyelination-related protein interaction network, and was expressed there by astrocytes. We used de novo networks enriched by unique DEGs to determine lesion-specific pathway regulation, i.e. cellular trafficking and activation in active lesions; healing and immune responses in remyelinating lesions characterized by the most heterogeneous immunoglobulin gene expression; coagulation and ion balance in inactive lesions; and metabolic changes in chronic active lesions. Because we found inverse differential regulation of particular genes among different lesion types, our data emphasize that omics related to MS lesions should be interpreted in the context of lesion pathology. Our data indicate that the impact of molecular pathways is substantially changing as different lesions develop. This was also reflected by the high number of unique DEGs that were more common than shared signatures. A special microglia subset characterized by CD26 may play a role in early lesion development, while astrocyte-derived TGFβ-R2 and TGFβ pathways may be drivers of repair in contrast to chronic tissue damage. The highly specific mechanistic signature of chronic active lesions indicates that as these lesions develop in PMS, the molecular changes are substantially skewed: the unique mitochondrial/metabolic changes and specific downregulation of molecules involved in tissue repair may reflect a stage of exhaustion.

Neuroprotective Effects of 6-Shogaol and Its Metabolite, 6-Paradol, in a Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease characterized by progressive neuronal loss, neuroinflammation, axonal degeneration, and demyelination. Previous studies have reported that 6-shogaol, a major constituent of ginger (Zingiber officinale rhizome), and its biological metabolite, 6-paradol, have anti-inflammatory and anti-oxidative properties in the central nervous system (CNS). In the present study, we investigated whether 6-shogaol and 6-paradol could ameliorate against experimental autoimmune encephalomyelitis (EAE), a mouse model of MS elicited by myelin oligodendrocyte glycoprotein (MOG_35-55) peptide immunization with injection of pertussis toxin. Once-daily administration of 6-shogaol and 6-paradol (5 mg/kg/day, p.o.) to symptomatic EAE mice significantly alleviated clinical signs of the disease along with remyelination and reduced cell accumulation in the white matter of spinal cord. Administration of 6-shogaol and 6-paradol into EAE mice markedly reduced astrogliosis and microglial activation as key features of immune responses inside the CNS. Furthermore, administration of these two molecules significantly suppressed expression level of tumor necrosis factor-α, a major proinflammatory cytokine, in EAE spinal cord. Collectively, these results demonstrate therapeutic efficacy of 6-shogaol or 6-paradol for EAE by reducing neuroinflammatory responses, further indicating the therapeutic potential of these two active ingredients of ginger for MS.

DGAT1 inhibits retinol-dependent regulatory T cell formation and mediates autoimmune encephalomyelitis

The balance of effector versus regulatory T cells (Tregs) controls inflammation in numerous settings, including multiple sclerosis (MS). Here we show that memory phenotype CD4⁺ T cells infiltrating the central nervous system during experimental autoimmune encephalomyelitis (EAE), a widely studied animal model of MS, expressed high levels of mRNA for Dgat1 encoding diacylglycerol-O-acyltransferase-1 (DGAT1), an enzyme that catalyzes triglyceride synthesis and retinyl ester formation. DGAT1 inhibition or deficiency attenuated EAE, with associated enhanced Treg frequency; and encephalitogenic, DGAT1^-/- in vitro-polarized Th17 cells were poor inducers of EAE in adoptive recipients. DGAT1 acyltransferase activity sequesters retinol in ester form, preventing synthesis of retinoic acid, a cofactor for Treg generation. In cultures with T cell-depleted lymphoid tissues, retinol enhanced Treg induction from DGAT1^-/- but not from WT T cells. The WT Treg induction defect was reversed by DGAT1 inhibition. These results demonstrate that DGAT1 suppresses retinol-dependent Treg formation and suggest its potential as a therapeutic target for autoimmune inflammation.

Pioglitazone is superior to quetiapine, clozapine and tamoxifen at alleviating experimental autoimmune encephalomyelitis in mice

Recent evidence suggests that clozapine and quetiapine (atypical antipsychotics), tamoxifen (selective-estrogen receptor modulator) and pioglitazone (PPARγ agonist) may improve functional recovery in multiple sclerosis (MS). We have compared the effectiveness of oral administration of these drugs, beginning at peak disease, at reducing ascending paralysis, motor deficits and demyelination in mice subjected to experimental autoimmune encephalomyelitis (EAE). Mice were immunized with an immunogenic peptide corresponding to amino acids 35-55 of the myelin oligodendrocyte glycoprotein (MOG_35-55) in complete Freund's adjuvant and injected with pertussis toxin to induce EAE. Unlike clozapine, quetiapine and tamoxifen, administration of pioglitazone beginning at peak disease decreased both clinical scores and lumbar white matter loss in EAE mice. Using kinematic gait analysis, we found that pioglitazone also maintained normal movement of the hip, knee and ankle joints for at least 44 days after MOG_35-55 immunization. This long-lasting preservation of hindleg joint movements was accompanied by reduced white matter loss, microglial and macrophage activation and the expression of pro-inflammatory genes in the lumbar spinal cords of EAE mice. These results support clinical findings that suggest pioglitazone may reduce the progressive loss of motor function in MS by decreasing inflammation and myelin damage.

A Unique TGFB1-Driven Genomic Program Links Astrocytosis, Low-Grade Inflammation and Partial Demyelination in Spinal Cord Periplaques from Progressive Multiple Sclerosis Patients

We previously reported that, in multiple sclerosis (MS) patients with a progressive form of the disease, spinal cord periplaques extend distance away from plaque borders and are characterized by the co-occurrence of partial demyelination, astrocytosis and low-grade inflammation. However, transcriptomic analyses did not allow providing a comprehensive view of molecular events in astrocytes vs. oligodendrocytes. Here, we re-assessed our transcriptomic data and performed co-expression analyses to characterize astrocyte vs. oligodendrocyte molecular signatures in periplaques. We identified an astrocytosis-related co-expression module whose central hub was the astrocyte gene Cx43/GJA1 (connexin-43, also named gap junction protein α-1). Such a module comprised GFAP (glial fibrillary acidic protein) and a unique set of transcripts forming a TGFB/SMAD1/SMAD2 (transforming growth factor β/SMAD family member 1/SMAD family member 2) genomic signature. Partial demyelination was characterized by a co-expression network whose central hub was the oligodendrocyte gene NDRG1 (N-myc downstream regulated 1), a gene previously shown to be specifically silenced in the normal-appearing white matter (NAWM) of MS patients. Surprisingly, besides myelin genes, the NDRG1 co-expression module comprised a highly significant number of translation/elongation-related genes. To identify a putative cause of NDRG1 downregulation in periplaques, we then sought to identify the cytokine/chemokine genes whose mRNA levels inversely correlated with those of NDRG1. Following this approach, we found five candidate immune-related genes whose upregulation associated with NDRG1 downregulation: TGFB1(transforming growth factor β 1), PDGFC (platelet derived growth factor C), IL17D (interleukin 17D), IL33 (interleukin 33), and IL12A (interleukin 12A). From these results, we propose that, in the spinal cord periplaques of progressive MS patients, TGFB1 may limit acute inflammation but concurrently induce astrocytosis and an alteration of the translation/elongation of myelin genes in oligodendrocytes.

The Renin-Angiotensin System Regulates Neurodegeneration in a Mouse Model of Optic Neuritis

The major role of the renin-angiotensin system (RAS), including that of angiotensin II (Ang II), the principal effector molecule, in the cardiovascular system is well known. Increasing evidence suggests that the RAS also plays a role in the development of autoimmune diseases. Optic neuritis (ie, inflammation of the optic nerve, with retinal ganglion cell loss) is strongly associated with multiple sclerosis. We investigated the effects of candesartan, an Ang II receptor antagonist, on optic neuritis in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. The Ang II concentration was increased in the early phase of EAE. Oral administration of candesartan markedly attenuated demyelination of the optic nerve and spinal cord and reduced retinal ganglion cell loss and visual impairment in mice with EAE. In vitro analyses revealed that Ang II up-regulated the expression of Toll-like receptor (TLR)-4 in astrocytes via the NF-κB pathway. In addition, Ang II treatment enhanced lipopolysaccharide-induced production of monocyte chemoattractant protein 1 in astrocytes, and pretreatment with candesartan or SN50, an NF-κB inhibitor, suppressed the effects of Ang II. The novel pathway of RAS-NF-κB-TLR4 in glial cells identified in the present study may be a valid therapeutic target for neurodegeneration in neuroinflammatory diseases.

Astrocytic tight junctions control inflammatory CNS lesion pathogenesis

Lesions and neurologic disability in inflammatory CNS diseases such as multiple sclerosis (MS) result from the translocation of leukocytes and humoral factors from the vasculature, first across the endothelial blood-brain barrier (BBB) and then across the astrocytic glia limitans (GL). Factors secreted by reactive astrocytes open the BBB by disrupting endothelial tight junctions (TJs), but the mechanisms that control access across the GL are unknown. Here, we report that in inflammatory lesions, a second barrier composed of reactive astrocyte TJs of claudin 1 (CLDN1), CLDN4, and junctional adhesion molecule A (JAM-A) subunits is induced at the GL. In a human coculture model, CLDN4-deficient astrocytes were unable to control lymphocyte segregation. In models of CNS inflammation and MS, mice with astrocyte-specific Cldn4 deletion displayed exacerbated leukocyte and humoral infiltration, neuropathology, motor disability, and mortality. These findings identify a second inducible barrier to CNS entry at the GL. This barrier may be therapeutically targetable in inflammatory CNS disease.

Deficiency in Neuronal TGF-β Signaling Leads to Nigrostriatal Degeneration and Activation of TGF-β Signaling Protects against MPTP Neurotoxicity in Mice

Transforming growth factor-β (TGF-β) plays an important role in the development and maintenance of embryonic dopaminergic (DA) neurons in the midbrain. To study the function of TGF-β signaling in the adult nigrostriatal system, we generated transgenic mice with reduced TGF-β signaling in mature neurons. These mice display age-related motor deficits and degeneration of the nigrostriatal system. Increasing TGF-β signaling in the substantia nigra through adeno-associated virus expressing a constitutively active type I receptor significantly reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced dopaminergic neurodegeneration and motor deficits. These results suggest that TGF-β signaling is critical for adult DA neuron survival and that modulating this signaling pathway has therapeutic potential in Parkinson disease.SIGNIFICANCE STATEMENT We show that reducing Transforming growth factor-β (TGF-β) signaling promotes Parkinson disease-related pathologies and motor deficits, and increasing TGF-β signaling reduces neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a parkinsonism-inducing agent. Our results provide a rationale to pursue a means of increasing TGF-β signaling as a potential therapy for Parkinson's disease.

Delayed ALK5 inhibition improves functional recovery in neonatal brain injury

Neuroinflammation subsequent to developmental brain injury contributes to a wave of secondary neurodegeneration and to reactive astrogliosis that can inhibit oligodendrocyte progenitor differentiation and subsequent myelination. Here we evaluated the therapeutic efficacy of a small molecule antagonist for a TGFß receptor in a model of moderate perinatal hypoxia-ischemia (H-I). Osmotic pumps containing SB505124, an antagonist of the type 1 TGFß1 receptor ALK5, or vehicle, were implanted three days after H-I induced at postnatal day 6. Perinatal H-I induced selective neuronal death, ventriculomegaly, elevated CNS levels of IL-6 and IL-1α, astrogliosis, and fewer proliferating oligodendrocyte progenitors. Myelination was reduced by ∼50%. Anterograde tracing revealed extensive axonal loss in the corticospinal tract. These alterations correlated with functional impairments across a battery of behavioral tests. All of these parameters were brought back towards normal levels with SB505124 treatment. Notably, SB505124 preserved neurons in the hippocampus and thalamus. Our results indicate that inhibiting ALK5 signaling, even as late as three days after injury, creates an environment that is more permissive for oligodendrocyte maturation and myelination producing significant improvements in neurological outcome. This new therapeutic would be especially appropriate for moderately preterm asphyxiated infants, for whom there is presently no FDA approved neuroprotective therapeutic.

Ectonucleotidase activity and immunosuppression in astrocyte-CD4 T cell bidirectional signaling

Astrocytes play a crucial role in neuroinflammation as part of the glia limitans, which regulates infiltration of the brain parenchyma by leukocytes. The signaling pathways and molecular events, which result from the interaction of activated T cells with astrocytes are poorly defined. Here we show that astrocytes promote the expression and enzymatic activity of CD39 and CD73 ectonucleotidases in recently activated CD4 cells by a contact dependent mechanism that is independent of T cell receptor interaction with class II major histocompatibility complex (MHC). Transforming growth factor-β (TGF-β) is robustly upregulated and sufficient to promote ectonucleotidases expression. T cell adhesion to astrocyte results in differentiation to an immunosuppressive phenotype defined by expression of the transcription factor Rorγt, which characterizes the CD4 T helper 17 subset. CD39 activity in T cells in turn inhibits spontaneous calcium oscillations in astrocytes that correlated with enhanced and reduced transcription of CCL2 chemokine and Sonic hedgehog (Shh), respectively. We hypothesize this TCR-independent interaction promote an immunosuppressive program in T cells to control possible brain injury by deregulated T cell activation during neuroinflammation. On the other hand, the increased secretion of CCL2 with concomitant reduction of Shh might promote leukocytes extravasation into the brain parenchyma.

TGF-β1 modulates microglial phenotype and promotes recovery after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating form of stroke that results from the rupture of a blood vessel in the brain, leading to a mass of blood within the brain parenchyma. The injury causes a rapid inflammatory reaction that includes activation of the tissue-resident microglia and recruitment of blood-derived macrophages and other leukocytes. In this work, we investigated the specific responses of microglia following ICH with the aim of identifying pathways that may aid in recovery after brain injury. We used longitudinal transcriptional profiling of microglia in a murine model to determine the phenotype of microglia during the acute and resolution phases of ICH in vivo and found increases in TGF-β1 pathway activation during the resolution phase. We then confirmed that TGF-β1 treatment modulated inflammatory profiles of microglia in vitro. Moreover, TGF-β1 treatment following ICH decreased microglial Il6 gene expression in vivo and improved functional outcomes in the murine model. Finally, we observed that patients with early increases in plasma TGF-β1 concentrations had better outcomes 90 days after ICH, confirming the role of TGF-β1 in functional recovery from ICH. Taken together, our data show that TGF-β1 modulates microglia-mediated neuroinflammation after ICH and promotes functional recovery, suggesting that TGF-β1 may be a therapeutic target for acute brain injury.

TGFβ regulates persistent neuroinflammation by controlling Th1 polarization and ROS production via monocyte-derived dendritic cells

Intracerebral levels of Transforming Growth Factor beta (TGFβ) rise rapidly during the onset of experimental autoimmune encephalomyelitis (EAE), a mouse model of Multiple Sclerosis (MS). We addressed the role of TGFβ responsiveness in EAE by targeting the TGFβ receptor in myeloid cells, determining that Tgfbr2 was specifically targeted in monocyte‐derived dendritic cells (moDCs) but not in CNS resident microglia by using bone‐marrow chimeric mice. TGFβ responsiveness in moDCs was necessary for the remission phase since LysM^CreTgfbr2^fl/fl mice developed a chronic form of EAE characterized by severe demyelination and extensive infiltration of activated moDCs in the CNS. Tgfbr2 deficiency resulted in increased moDC IL‐12 secretion that skewed T cells to produce IFN‐γ, which in turn enhanced the production of moDC‐derived reactive oxygen species that promote oxidative damage and demyelination. We identified SNPs in the human NOX2 (CYBB) gene that associated with the severity of MS, and significantly increased CYBB expression was recorded in PBMCs from both MS patients and from MS severity risk allele rs72619425‐A carrying individuals. We thus identify a novel myeloid cell‐T cell activation loop active in the CNS during chronic disease that could be therapeutically targeted. GLIA 2016;64:1925–1937

Activation of Wnt signaling promotes hippocampal neurogenesis in experimental autoimmune encephalomyelitis

Background

Disease progression in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), as one of its animal models, is characterized by demyelination and neuronal damage in white and gray matter structures, including the hippocampus. It is thought that dysfunction of the hippocampus, a primary locus of learning and memory consolidation, may contribute to cognitive impairment in MS patients. Previously, we reported an increased generation of hippocampal neuronal progenitors in the acute stage of EAE, whereas the microenvironmental signals triggering this process remained uninvestigated.

Results

In the present study, we used the Wnt signaling reporter mouse Axin2^LacZ, to elucidate the molecular mechanisms underlying the activation of the hippocampal neurogenic niche upon autoimmune neuroinflammation. Histological and enzymatic examinations of β-gal during the disease course of EAE, allowed us to survey hippocampal Wnt/β-catenin activity, one of the key signaling pathways of adult neurogenesis. We found that Wnt signaling is transiently upregulated in the acute stage of disease, consistent with a timely induction of canonical Wnt ligands. The enhancement of signaling coincided with hippocampal neuronal damage and local expression of immune cytokines such as TNFα and IFNγ, implicating the role of the inflammatory milieu in activation of the Wnt/β-catenin pathway. Supporting this finding, we show that transient exposure to pro-inflammatory cytokine TNFα triggers Wnt signaling in hippocampal organotypic slice cultures. Importantly, inflammation-mediated activation of the Wnt/β-catenin pathway was associated with enhanced neurogenesis in vitro and in vivo, indicating its potential role in hippocampal tissue regeneration and repair.

Conclusions

This study raises the possibility that enhancement of Wnt signaling may support neurogenic processes to cope with neuronal deficits upon immune-mediated neuroinflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-016-0117-0) contains supplementary material, which is available to authorized users.

Leukocyte Gene Expression and Plasma Concentration in Multiple Sclerosis: Alteration of Transforming Growth Factor-βs, Claudin-11, and Matrix Metalloproteinase-2

Multiple sclerosis is a neurodegenerative disease characterized by the present of leukocytes in the brain tissue and subsequently the formation of sclerotic plaques. Leukocytes penetration into the blood-brain barrier is related to several factors, such as, the conversion of leukocyte gene expression or plasma characteristics. In this frame, we explore alteration of matrix metalloproteinase-2 (MMP-2), transforming growth factor beta (TGF-β) family, and Claudin-11 (as a main myelin structural protein) in leukocytes and blood plasma of multiple sclerosis patients compared to the normal group. Blood samples were collected from thirteen men affected by MS and fifteen healthy men. Leukocyte gene expression was measured using real-time PCR and plasma parameters were examined by ELISA. The results of this study showed that the gene expression of Claudin-11 was significantly higher in MS group compared with normal. Interestingly, the MMP-2 pattern was similar to Claudin-11 and correlated positively with it. It was observed that, although the expressions of TGF-β1 and TGF-β2 are down-regulated in the leukocytes of subjects with MS, they showed higher levels of these cytokines in blood plasma. The plasma level of TGF-β3 in MS patients was higher than normal and correlated with Claudin-11 concentration. In conclusion, the aberrant pattern of Claudin-11, TGF-βs family, and MMP-2 expression in leukocytes of the MS patients was observed in this study. Moreover, the plasma levels of TGF-βs family increased in the MS group. The findings of this study provide clues for further investigations to assay MS pathogenesis.

Differential TGF-β Signaling in Glial Subsets Underlies IL-6-Mediated Epileptogenesis in Mice

TGF-β1 is a master cytokine in immune regulation, orchestrating both pro- and anti-inflammatory reactions. Recent studies show that whereas TGF-β1 induces a quiescent microglia phenotype, it plays a pathogenic role in the neurovascular unit and triggers neuronal hyperexcitability and epileptogenesis. In this study, we show that, in primary glial cultures, TGF-β signaling induces rapid upregulation of the cytokine IL-6 in astrocytes, but not in microglia, via enhanced expression, phosphorylation, and nuclear translocation of SMAD2/3. Electrophysiological recordings show that administration of IL-6 increases cortical excitability, culminating in epileptiform discharges in vitro and spontaneous seizures in C57BL/6 mice. Intracellular recordings from layer V pyramidal cells in neocortical slices obtained from IL-6 -: treated mice show that during epileptogenesis, the cells respond to repetitive orthodromic activation with prolonged after-depolarization with no apparent changes in intrinsic membrane properties. Notably, TGF-β1 -: induced IL-6 upregulation occurs in brains of FVB/N but not in brains of C57BL/6 mice. Overall, our data suggest that TGF-β signaling in the brain can cause astrocyte activation whereby IL-6 upregulation results in dysregulation of astrocyte -: neuronal interactions and neuronal hyperexcitability. Whereas IL-6 is epileptogenic in C57BL/6 mice, its upregulation by TGF-β1 is more profound in FVB/N mice characterized as a relatively more susceptible strain to seizure-induced cell death.

Nigella sativa amliorates inflammation and demyelination in the experimental autoimmune encephalomyelitis-induced Wistar rats

Multiple sclerosis (MS) is the major, immune-mediated, demyelinating neurodegenerative disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) is a well-established animal model of MS. The aim of the present study was to investigate the protective and ameliorative effects of N. sativa seeds (2.8 g/kg body weight) in EAE-induced Wistar rats. EAE-induced rats were divided into: 1- EAE-induced rats ("EAE" group). 2- "N. sativa + EAE" group received daily oral administration of N. sativa 2 weeks prior EAE induction until the end of the experiment. 3- "EAE + N. sativa" group received daily oral administration of N. sativa after the appearance of first clinical signs until the end of the experiment. All animals were decapitated at the 28th day post EAE-induction. EAE was investigated using histopathological, immunohistochemical and ultrastructural examinations in addition to determination of some oxidative stress parameters in the cerebellum and medulla. N. sativa suppressed inflammation observed in EAE-induced rats. In addition, N. sativa enhanced remyelination in the cerebellum. Moreover, N. sativa reduced the expression of transforming growth factor beta 1 (TGF β1). N. sativa seeds could provide a promising agent effective in both the protection and treatment of EAE.

Analysis of neurogenesis during experimental autoimmune encephalomyelitis reveals pitfalls of bioluminescence imaging

Bioluminescence imaging is a sensitive approach for longitudinal neuroimaging. Transgenic mice expressing luciferase under the promoter of doublecortin (DCX-luc), a specific marker of neuronal progenitor cells (NPC), allow monitoring of neurogenesis in living mice. Since the extent and time course of neurogenesis during autoimmune brain inflammation are controversial, we investigated neurogenesis in MOG-peptide induced experimental allergic encephalomyelitis (EAE) using DCX-luc reporter mice. We observed a marked, 2- to 4-fold increase of the bioluminescence signal intensity 10 days after EAE induction and a gradual decline 1–2 weeks thereafter. In contrast, immunostaining for DCX revealed no differences between EAE and control mice 2 and 4 weeks after immunization in zones of adult murine neurogenesis such as the dentate gyrus. Ex vivo bioluminescence imaging showed similar luciferase expression in brain homogenates of EAE and control animals. Apart from complete immunization including MOG-peptide also incomplete immunization with complete Freund´s adjuvant and pertussis toxin resulted in a rapid increase of the in vivo bioluminescence signal. Blood-brain barrier (BBB) leakage was demonstrated 10 days after both complete and incomplete immunization and might explain the increased bioluminescence signal in vivo. We conclude, that acute autoimmune inflammation in EAE does not alter neurogenesis, at least at the stage of DCX-expressing NPC. Effects of immunization on the BBB integrity must be considered when luciferase is used as a reporter within the CNS during the active stage of EAE. Models with stable CNS-restricted luciferase expression could serve as technically convenient way to evaluate BBB integrity in a longitudinal manner.

Interleukin-10 but not transforming growth factor-β1 gene expression is up-regulated by vitamin D treatment in multiple sclerosis patients

Multiple sclerosis (MS) is an inflammatory and autoimmune disease. Variety of different genetics and environmental factors are involved in MS pathology. The epidemiological studies demonstrated that vitamin D has immune and immunomodulating effects on MS disease. Therefore, this study aims to evaluate the effect of vitamin D treatment on the expression of interleukin-10 (IL-10) and transforming growth factor-β1 (TGF-β1) genes in MS patients. We found that, the expression level of IL-10 gene in treated patients was up-regulated 3.84 times more than before treatment, but the expression level of TGF-β1 was not affected by vitamin D treatment. Also, a significant relationship was observed between vitamin D level and EDSS in MS patients. Our results indicated that the increased level of serum vitamin D and IL-10 gene expression may be associated with the reduction of EDSS scores in MS patients.

Glial metabotropic glutamate receptor-4 increases maturation and survival of oligodendrocytes

Group III metabotropic glutamate (mGlu) receptors mediate important neuroprotective and anti-inflammatory effects. Stimulation of mGlu4 receptor reduces neuroinflammation in a mouse model of experimental autoimmune encephalomyelitis (EAE) whereas mGlu4 knockout mice display exacerbated EAE clinical scores. We now show that mGlu4 receptors are expressed in oligodendrocytes, astrocytes and microglia in culture. Oligodendrocytes express mGlu4 receptors only at early stages of maturation (O4 positive), but not when more differentiated (myelin basic protein, MBP positive). Treatment of immature oligodendrocytes with the mGlu4 receptor agonist L-2-Amino-4-phosphonobutyrate (L-AP4; 50 μM for 48 h) accelerates differentiation with enhanced branching and earlier appearance of MBP staining. Oligodendrocyte death induced by exposure to 1 mM kainic acid for 24 h is significantly reduced by a 30-min pretreatment with L-AP4 (50 μM), an effect observed only in the presence of astrocytes, mimicked by the specific mGlu4 receptor positive allosteric modulator N-Phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC) (30 μM) and prevented by pretreatment with the mGlu4 receptor antagonist, cyclopropyl-4-phosphonophenylglycine (CPPG) (100 μM). In astrocytes, mGlu4 receptor is the most expressed among group III mGlu receptors, as by Quantitative real time PCR (QRT-PCR), and its silencing prevents protective effects. Protection is also observed when conditioned medium (CM) from L-AP4-pretreated astrocytes is transferred to oligodendrocytes challenged with kainic acid. Transforming growth factor β (TGF-β) mediates the increased oligodendrocyte survival as the effect of L-AP4 is mimicked by addition of 10 ng/ml TGF-β and prevented by incubation with a neutralizing anti-TGF-β antibody. In contrast, despite the expression of mGlu4 receptor in resting and activated microglia, CM from L-AP4-stimulated microglia does not modify kainate-induced oligodendrocyte toxicity. Our results suggest that mGlu4 receptors expressed in astrocytes mediate enhanced survival of oligodendrocytes under conditions of excitotoxicity.

Gli1 activation and protection against hepatic encephalopathy is suppressed by circulating transforming growth factor β1 in mice

BACKGROUND & AIMS

Hepatic encephalopathy (HE) is a neurologic disorder that develops during liver failure. Few studies exist investigating systemic-central signalling during HE outside of inflammatory signalling. The transcription factor Gli1, which can be modulated by hedgehog signalling or transforming growth factor β1 (TGFβ1) signalling, has been shown to be protective in various neuropathies. We measured Gli1 expression in brain tissues from mice and evaluated how circulating TGFβ1 and canonical hedgehog signalling regulate its activation.

METHODS

Mice were injected with azoxymethane (AOM) to induce liver failure and HE in the presence of Gli1 vivo-morpholinos, the hedgehog inhibitor cyclopamine, Smoothened vivo-morpholinos, a Smoothened agonist, or TGFβ-neutralizing antibodies. Molecular analyses were used to assess Gli1, hedgehog signalling, and TGFβ1 signalling in the liver and brain of AOM mice and HE patients.

RESULTS

Gli1 expression was increased in brains of AOM mice and in HE patients. Intra-cortical infusion of Gli1 vivo-morpholinos exacerbated the neurologic deficits of AOM mice. Measures to modulate hedgehog signalling had no effect on HE neurological decline. Levels of TGFβ1 increased in the liver and serum of mice following AOM administration. TGFβ neutralizing antibodies slowed neurologic decline following AOM administration without significantly affecting liver damage. TGFβ1 inhibited Gli1 expression via a SMAD3-dependent mechanism. Conversely, inhibiting TGFβ1 increased Gli1 expression.

CONCLUSIONS

Cortical activation of Gli1 protects mice from induction of HE. TGFβ1 suppresses Gli1 in neurons via SMAD3 and promotes the neurologic decline. Strategies to activate Gli1 or inhibit TGFβ1 signalling might be developed to treat patients with HE.

Obesity- and aging-induced excess of central transforming growth factor-β potentiates diabetic development via an RNA stress response

The brain, in particular the hypothalamus, plays a role in regulating glucose homeostasis; however, it remains unclear whether this organ is causally and etiologically involved in the development of diabetes. Here, we found that hypothalamic transforming growth factor-β (TGF-β) production is excessive under conditions of not only obesity but also aging, which are two general etiological factors of type 2 diabetes. Pharmacological and genetic approaches revealed that central TGF-β excess caused hyperglycemia and glucose intolerance independent of a change in body weight. Further, using cell-specific genetic analyses in vivo, we found that astrocytes and proopiomelanocortin neurons are responsible for the production and prodiabetic effect of central TGF-β, respectively. Mechanistically, TGF-β excess induced a hypothalamic RNA stress response, resulting in accelerated mRNA decay of IκBα, an inhibitor of proinflammatory nuclear factor-κB. These results reveal an atypical, mRNA metabolism-driven hypothalamic nuclear factor-κB activation, a mechanism that links obesity as well as aging to hypothalamic inflammation and ultimately to type 2 diabetes.

TGF-β signaling initiated in dendritic cells instructs suppressive effects on Th17 differentiation at the site of neuroinflammation

While the role of Transforming Growth Factor β (TGF-β) as an intrinsic pathway has been well established in driving de novo differentiation of Th17 cells, no study has directly assessed the capacity of TGF-β signaling initiated within dendritic cells (DCs) to regulate Th17 differentiation. The central finding of this study is the demonstration that Th17 cell fate during autoimmune inflammation is shaped by TGF-β extrinsic pathway via DCs. First, we provide evidence that TGF-β limits at the site of inflammation the differentiation of highly mature DCs as a means of restricting Th17 cell differentiation and controlling autoimmunity. Second, we demonstrate that TGF-β controls DC differentiation in the inflammatory site but not in the priming site. Third, we show that TGF-β controls DC numbers at a precursor level but not at a mature stage. While it is undisputable that TGF-β intrinsic pathway drives Th17 differentiation, our data provide the first evidence that TGF-β can restrict Th17 differentiation via DC suppression but such a control occurs in the site of inflammation, not at the site of priming. Such a demarcation of the role of TGF-β in DC lineage is unprecedented and holds serious implications vis-à-vis future DC-based therapeutic targets.

Discovery of N-((4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-yl)methyl)-2-fluoroaniline (EW-7197): a highly potent, selective, and orally bioavailable inhibitor of TGF-β type I receptor kinase as cancer immunotherapeutic/antifibrotic agent

A series of 2-substituted-4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)imidazoles was synthesized and evaluated to optimize a prototype inhibitor of TGF-β type I receptor kinase (ALK5), 6. Combination of replacement of a quinoxalin-6-yl moiety of 6 with a [1,2,4]triazolo[1,5-a]pyridin-6-yl moiety, insertion of a methyleneamino linker, and a o-F substituent in the phenyl ring markedly increased ALK5 inhibitory activity, kinase selectivity, and oral bioavailability. The 12b (EW-7197) inhibited ALK5 with IC50 value of 0.013 μM in a kinase assay and with IC50 values of 0.0165 and 0.0121 μM in HaCaT (3TP-luc) stable cells and 4T1 (3TP-luc) stable cells, respectively, in a luciferase assay. Selectivity profiling of 12b using a panel of 320 protein kinases revealed that it is a highly selective ALK5/ALK4 inhibitor. Pharmacokinetic study with 12b·HCl in rats showed an oral bioavailability of 51% with high systemic exposure (AUC) of 1426 ng × h/mL and maximum plasma concentration (Cmax) of 1620 ng/mL. Rational optimization of 6 has led to the identification of a highly potent, selective, and orally bioavailable ALK5 inhibitor 12b.

Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice

As human lifespan increases, a greater fraction of the population is suffering from age-related cognitive impairments, making it important to elucidate a means to combat the effects of aging. Here we report that exposure of an aged animal to young blood can counteract and reverse pre-existing effects of brain aging at the molecular, structural, functional and cognitive level. Genome-wide microarray analysis of heterochronic parabionts--in which circulatory systems of young and aged animals are connected--identified synaptic plasticity-related transcriptional changes in the hippocampus of aged mice. Dendritic spine density of mature neurons increased and synaptic plasticity improved in the hippocampus of aged heterochronic parabionts. At the cognitive level, systemic administration of young blood plasma into aged mice improved age-related cognitive impairments in both contextual fear conditioning and spatial learning and memory. Structural and cognitive enhancements elicited by exposure to young blood are mediated, in part, by activation of the cyclic AMP response element binding protein (Creb) in the aged hippocampus. Our data indicate that exposure of aged mice to young blood late in life is capable of rejuvenating synaptic plasticity and improving cognitive function.

Potential neuroprotective role of transforming growth factor β1 (TGFβ1) in the brain

TGFβ1 is a growth factor that is known to be expressed in most neurodegenerative diseases and after vascular accidents in the brain. TGFβ1 downregulates the activity of activated microglia and promotes astrogliosis. It also prevents cell death by a known mechanism dependant on astrocytes and the secretion of the plasminogen activator inhibitor 1 (PAI-1). This mechanism can provide light on what is the mechanism of action of TGFβ1 as a protective factor and it can provide the pharmacological principles in which this pathway could be used with therapeutic purposes. TGFβ1 is upregulated in most neurodegenerative diseases, however, its expression appears dramatically blocked in Huntington's disease, the fastest of those diseases in progress after the onset. This fact suggests that TGFβ1 slows down the neurodegenerative process, preventing tissue damage and neural apoptotic death. However, the exact details of TGFβ1 action are still unknown and the physiological roles on the diseases are still mysterious. Interestingly, all the data regarding the roles of TGFβ1 in health and disease have been also confirmed with the use of transgenic knockouts and TGFβ1 overexpressing mice. What possibly came as a surprise from the study of TGFβ1 overexpressing models is that combining its neuroprotective and antiproliferative effects, this cytokine generates a significant disruption in the hippocampal circuitry with its consequent learning and memory deficit.