Protective effect of transforming growth factor beta 1 on experimental autoimmune diseases in mice

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

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.

Anti-cancer therapeutic strategies based on HGF/MET, EpCAM, and tumor-stromal cross talk

As an intelligent disease, tumors apply several pathways to evade the immune system. It can use alternative routes to bypass intracellular signaling pathways, such as nuclear factor-κB (NF-κB), Wnt, and mitogen-activated protein (MAP)/phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR). Therefore, these mechanisms lead to therapeutic resistance in cancer. Also, these pathways play important roles in the proliferation, survival, migration, and invasion of cells. In most cancers, these signaling pathways are overactivated, caused by mutation, overexpression, etc. Since numerous molecules share these signaling pathways, the identification of key molecules is crucial to achieve favorable consequences in cancer therapy. One of the key molecules is the mesenchymal-epithelial transition factor (MET; c-Met) and its ligand hepatocyte growth factor (HGF). Another molecule is the epithelial cell adhesion molecule (EpCAM), which its binding is hemophilic. Although both of them are involved in many physiologic processes (especially in embryonic stages), in some cancers, they are overexpressed on epithelial cells. Since they share intracellular pathways, targeting them simultaneously may inhibit substitute pathways that tumor uses to evade the immune system and resistant to therapeutic agents.

Transforming growth factor-β1 protects against LPC-induced cognitive deficit by attenuating pyroptosis of microglia via NF-κB/ERK1/2 pathways

Background

Demyelinating diseases in central nervous system (CNS) are a group of diseases characterized by myelin damage or myelin loss. Transforming growth factor beta1 (TGF-β1) is widely recognized as an anti-inflammatory cytokine, which can be produced by both glial and neuronal cells in CNS. However, the effects of TGF-β1 on demyelinating diseases and its underlying mechanisms have not been well investigated.

Methods

A demyelinating mouse model using two-point injection of lysophosphatidylcholine (LPC) to the corpus callosum in vivo was established. Exogenous TGF-β1 was delivered to the lesion via brain stereotactic injection. LFB staining, immunofluorescence, and Western blot were applied to examine the severity of demyelination and pyroptosis process in microglia. Morris water maze test was used to assess the cognitive abilities of experimental mice. Furthermore, lipopolysaccharide (LPS) was applied to induce pyroptosis in primary cultured microglia in vitro, to explore potential molecular mechanism.

Results

The degree of demyelination in LPC-modeling mice was found improved with supplement of TGF-β1. Besides, TGF-β1 treatment evidently ameliorated the activated proinflammatory pyroptosis of microglia, with downregulated levels of the key pyroptosis effector Gasdermin D (GSDMD), inflammasomes, and cleaved-IL-1β, which effectively attenuated neuroinflammation in vivo. Evaluated by behavioral tests, the cognitive deficit in LPC-modeling mice was found mitigated with application of TGF-β1. Mechanistically, TGF-β1 could reverse pyroptosis-like morphology in LPS-stimulated primary cultured microglia observed by scanning electron microscopy, as well as decrease the protein levels of cleaved-GSDMD, inflammasomes, and cleaved-IL-1β. Activation of ERK1/2 and NF-κB pathways largely abolished the protective effects of TGF-β1, which indicated that TGF-β1 alleviated the pyroptosis possibly via regulating NF-κB/ERK1/2 signal pathways.

Conclusions

Our studies demonstrated TGF-β1 notably relieved the demyelinating injury and cognitive disorder in LPC-modeling mice, by attenuating the inflammatory pyroptosis of microglia via ERK1/2 and NF-κB pathways. Targeting TGF-β1 activity might serve as a promising therapeutic strategy in demyelinating diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02557-0.

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.

Immune Inhibitory Properties and Therapeutic Prospects of Transforming Growth Factor-Beta and Interleukin 10 in Autoimmune Hepatitis

Transforming growth factor-beta and interleukin 10 have diverse immune inhibitory properties that have restored homeostatic defense mechanisms in experimental models of autoimmune disease. The goals of this review are to describe the actions of each cytokine, review their investigational use in animal models and patients, and indicate their prospects as interventions in autoimmune hepatitis. English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed. Transforming growth factor-beta expands the natural and inducible populations of regulatory T cells, limits the proliferation of natural killer cells, suppresses the activation of naïve CD8⁺ T cells, decreases the production of interferon-gamma, and stimulates fibrotic repair. Interleukin 10 selectively inhibits the CD28 co-stimulatory signal for antigen recognition and impairs antigen-specific activation of uncommitted CD4⁺ and CD8⁺ T cells. It also inhibits maturation of dendritic cells, suppresses Th17 cells, supports regulatory T cells, and limits production of diverse pro-inflammatory cytokines. Contradictory immune stimulatory effects have been associated with each cytokine and may relate to the dose and accompanying cytokine milieu. Experimental findings have not translated into successful early clinical trials. The recombinant preparation of each agent in low dosage has been safe in human studies. In conclusion, transforming growth factor-beta and interleukin 10 have powerful immune inhibitory actions of potential therapeutic value in autoimmune hepatitis. The keys to their therapeutic application will be to match their predominant non-redundant function with the pivotal pathogenic mechanism or cytokine deficiency and to avoid contradictory immune stimulatory actions.

Local inhibition of TGF-β1 signaling improves Th17/Treg balance but not joint pathology during experimental arthritis

TGF-β1 is an important growth factor to promote the differentiation of T helper 17 (Th17) and regulatory T cells (Treg). The potential of TGF-β1 as therapeutic target in T cell-mediated diseases like rheumatoid arthritis (RA) is unclear. We investigated the effect of TGF-β1 inhibition on murine Th17 differentiation in vitro, on human RA synovial explants ex vivo, and on the development of experimental arthritis in vivo. Murine splenocytes were differentiated into Th17 cells, and the effect of the TGF-βRI inhibitor SB-505124 was studied. Synovial biopsies were cultured in the presence or absence of SB-505124. Experimental arthritis was induced in C57Bl6 mice and treated daily with SB-505124. Flow cytometry analysis was performed to measure different T cell subsets. Histological sections were analysed to determine joint inflammation and destruction. SB-505124 potently reduced murine Th17 differentiation by decreasing Il17a and Rorc gene expression and IL-17 protein production. SB-505124 significantly suppressed IL-6 production by synovial explants. In vivo, SB-505124 reduced Th17 numbers, while increased numbers of Tregs were observed. Despite this skewed Th17/Treg balance, SB-505124 treatment did not result in suppression of joint inflammation and destruction. Blocking TGF-β1 signalling suppresses Th17 differentiation and improves the Th17/Treg balance. However, local SB-505124 treatment does not suppress experimental arthritis.

Nobiletin attenuates inflammation via modulating proinflammatory and antiinflammatory cytokine expressions in an autoimmune encephalomyelitis mouse model

The aim of this study is to investigate the potential preventive and therapeutic effects of nobiletin by evaluating the expression of cytokines associated with inflammatory reactions in an autoimmune encephalomyelitis mouse model. A total of 60 male C57BL/6 mice aged between 8 and 10 weeks were used. Mice were divided into six groups (n = 10 mice per group): control, EAE, low-prophylaxis, high-prophylaxis, low-treatment and high-treatment. Experimental autoimmune encephalomyelitis (EAE) was induced by myelin oligodendrocyte glycoprotein (MOG) and pertussis toxin. Nobiletin was administered in low (25 mg/kg) and high (50 mg/kg) doses, intraperitoneally. The prophylactic and therapeutic effects of nobiletin on brain tissue and spinal cord were evaluated by expression of interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), interferon gamma (IFNγ), IL-6, IL-10 and transforming growth factor-beta (TGF-β) using immunohistochemistry and real-time polymerase chain reaction (RT-PCR). Prophylactic and therapeutic use of nobiletin inhibited EAE-induced increase of TNF-α, IL-1β and IL-6 activities to alleviate inflammatory response in brain and spinal cord. Moreover, nobiletin supplement dramatically increased the IL-10, TGF-β and IFNγ expressions in prophylaxis and treatment groups compared with the EAE group in the brain and spinal cord. The results obtained from this study show that prophylactic and therapeutic nobiletin modulates expressions of proinflammatory and antiinflammatory cytokines in brain and spinal cord dose-dependent manner in EAE model. These data demonstrates that nobiletin has a potential to attenuate inflammation in EAE mouse model. These experimental findings need to be supported by clinical studies.

Organ Fibrosis and Autoimmunity: The Role of Inflammation in TGFβ-Dependent EMT

Recent advances in our understanding of the molecular pathways that control the link of inflammation with organ fibrosis and autoimmune diseases point to the epithelial to mesenchymal transition (EMT) as the common association in the progression of these diseases characterized by an intense inflammatory response. EMT, a process in which epithelial cells are gradually transformed to mesenchymal cells, is a major contributor to the pathogenesis of fibrosis. Importantly, the chronic inflammatory microenvironment has emerged as a decisive factor in the induction of pathological EMT. Transforming growth factor-β (TGF-β), a multifunctional cytokine, plays a crucial role in the induction of fibrosis, often associated with chronic phases of inflammatory diseases, contributing to marked fibrotic changes that severely impair normal tissue architecture and function. The understanding of molecular mechanisms underlying EMT-dependent fibrosis has both a basic and a translational relevance, since it may be useful to design therapies aimed at counteracting organ deterioration and failure. To this end, we reviewed the recent literature to better elucidate the molecular response to inflammatory/fibrogenic signals in autoimmune diseases in order to further the specific regulation of EMT-dependent fibrosis in more targeted therapies.

Secreted KIAA1199 promotes the progression of rheumatoid arthritis by mediating hyaluronic acid degradation in an ANXA1-dependent manner

In inflamed joints, enhanced hyaluronic acid (HA) degradation is closely related to the pathogenesis of rheumatoid arthritis (RA). KIAA1199 has been identified as a hyaladherin that mediates the intracellular degradation of HA, but its extracellular function remains unclear. In this study, we found that the serum and synovial levels of secreted KIAA1199 (sKIAA1199) and low-molecular-weight HA (LMW-HA, MW < 100 kDa) in RA patients were significantly increased, and the positive correlation between them was shown for the first time. Of note, treatment with anti-KIAA1199 mAb effectively alleviated the severity of arthritis and reduced serum LMW-HA levels and cytokine secretion in collagen-induced arthritis (CIA) mice. In vitro, sKIAA1199 was shown to mediate exogenous HA degradation by attaching to the cell membrane of RA fibroblast-like synoviosytes (RA FLS). Furthermore, the HA-degrading activity of sKIAA1199 depended largely on its adhesion to the membrane, which was achieved by its G8 domain binding to ANXA1. In vivo, kiaa1199-KO mice exhibited greater resistance to collagen-induced arthritis. Interestingly, this resistance could be partially reversed by intra-articular injection of vectors encoding full-length KIAA1199 instead of G8-deleted KIAA119 mutant, which further confirmed the indispensable role of G8 domain in KIAA1199 involvement in RA pathological processes. Mechanically, the activation of NF-κB by interleukin-6 (IL-6) through PI3K/Akt signaling is suggested to be the main pathway to induce KIAA1199 expression in RA FLS. In conclusion, our study supported the contribution of sKIAA1199 to RA pathogenesis, providing a new therapeutic target for RA by blocking sKIAA1199-mediated HA degradation.

Oral encapsulated transforming growth factor β1 reduces endogenous levels: Effect on inflammatory bowel disease

BACKGROUND

TreXTAM^® is a combination of the key regulatory cytokine transforming growth factor beta (TGFβ) and all trans retinoic acid (ATRA) microencapsulated for oral delivery to immune structures of the gut. It is in development as a novel treatment for inflammatory bowel disease (IBD).

AIM

To measure TGFβ levels in blood and tissue after oral administration of encapsulated TGFβ.

METHODS

Animals were orally administered encapsulated TGFβ by gavage. Levels of drug substance in blood and in gut tissues at various times after administration were measured by ELISA.

RESULTS

We made the surprising discovery that oral administration of TreXTAM dramatically (approximately 50%) and significantly (P = 0.025) reduced TGFβ levels in colon, but not small intestine or mesenteric lymph nodes. Similarly, levels in rat serum after 25 d of thrice weekly dosing with either TreXTAM, or microencapsulated TGFβ alone (denoted as TPX6001) were significantly (P < 0.01) reduced from baseline levels. When tested in the SCID mouse CD4+CD25- adoptive cell transfer (ACT) model of IBD, oral TPX6001 alone provided only a transient benefit in terms of reduced weight loss.

CONCLUSION

These observations suggest a negative feedback mechanism in the gut whereby local delivery of TGFβ results in reduced local and systemic levels of the active form of TGFβ. Our findings suggest potential clinical implications for use of encapsulated TGFβ, perhaps in the context of IBD and/or other instances of fibrosis and/or pathological TGFβ signaling.

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.

Anti-arthritic activity of ferulic acid in complete Freund's adjuvant (CFA)-induced arthritis in rats: JAK2 inhibition

Ferulic acid (FA), a hydroxycinnamic acid, is an organic compound found in several plant species. Previous studies have shown that FA contains anti-inflammatory and anti-arthritic properties. This study aimed to investigate the anti-arthritic activity and possible mechanism(s) of action of FA in complete Freund's adjuvant (CFA)-induced arthritis. The progression of rheumatoid arthritis (RA) involves the activation of the Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway by proinflammatory cytokines. Molecular docking of FA showed promising Janus kinase 2 (JAK2) inhibition with a docking score of - 6.7, which is comparable with that of ruxolitinib, a standard inhibitor. However, in vitro JAK2 inhibition assay showed a half maximal inhibitory concentration (IC50) of 6.67 ± 0.88 µg/ml. Both doses of FA (25 and 50 mg/kg) significantly attenuated primary (volume of paw edema) and secondary lesions. CFA-induced arthritic rats showed a significant decrease in body weight, A/G ratio, and Hb but showed a greater arthritic index, ESR levels, and percentage of lymphocytes. These alterations were significantly reduced in rats treated with FA and prednisolone. FA also reversed changes to biochemical parameters and inflammatory markers, such as C-reactive protein (CRP) and rhematoid factor (RF). Additionally, we found CFA-induced arthritis triggered the secretion of TNF- α, increased JAK2 levels, and reduced TGF-β levels in tissue homogenates. However, in rats treated with FA, such alterations significantly improved. Thus, our results reveal that FA contains anti-arthritic activity, which is possibly mediated by the inhibition of the JAK/STAT pathway.

Clinical and cytokine profile of adult acute necrotizing encephalopathy

Background

Acute necrotizing encephalopathy (ANE), a fulminant encephalopathy, is often found in childhood. It is still uncertain whether adult patients with ANE display clinical features different from patients with typical pediatric onset. Furthermore, alterations in neuroinflammatory factors in patients with ANE have not been well-characterized. Here, we present an adult patient with ANE, and review all reported adult ANE cases in the literature.

Methods

Serum levels of five cytokines were checked in an adult patient with ANE and compared with gender/age-matched controls. Literature search was performed with PubMed, using the term as “acute necrotizing encephalopathy” with the filter of adult 19 + years.

Results

A total of 13 adult patients were reviewed. Compared with pediatric patients, adult ANE patients had similar clinical symptoms, biochemical data, and neuroimage findings, whereas adult ANE were more female-biased (female:male, 9:4) with a worse prognosis. Elevated cytokine levels in the serum and/or CSF is found in both adult-onset and pediatric-onset ANE. We found significantly elevated serum levels of IL-6 (17.17 pg/mL; healthy control: 1.43 ± 1.22 pg/mL) and VCAM-1 (3033.92 ng/mL; healthy control: 589.71 ± 133.13 ng/mL), and decreased serum TGF-β1 level (14.78 ng/mL, healthy controls: 25.81 ± 6.97 ng/mL) in our patient.

Conclusions

Our findings clearly delineate the clinical features and further indicate the potential change in cytokine levels in adult patients with ANE, advancing our understanding of this rare disease.

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.

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.

HGF/MET and the Immune System: Relevance for Cancer Immunotherapy

An overactivation of hepatocyte growth factor (HGF)/mesenchymal-epithelial transition factor (MET) axis promotes tumorigenesis and tumor progression in various cancer types. Research data recently evidenced that HGF/MET signaling is also involved also in the immune response, mainly modulating dendritic cells functions. In general, the pathway seems to play an immunosuppressive role, thus hypothesizing that it could constitute a mechanism of primary and acquired resistance to cancer immunotherapy. Recently, some approaches are being developed, including drug design and cell therapy to combine MET and programmed cell death receptor-1 (PD-1)/programmed cell death receptor-ligand 1 (PD-L1) inhibition. This approach could represent a new weapon in cancer therapy in the future.

TGFβ1 transduction enhances immunomodulatory capacity of neural stem cells in experimental autoimmune encephalomyelitis

Bone marrow-derived neural stem cells (BM-NSCs) have therapeutic effect on EAE, an animal model of multiple sclerosis. However, the beneficial effect is suboptimal due to the limited immunomodulatory capacity of these cells. In this study, we engineered BM-NSCs with inducible TGFβ1, a potent immunosuppressive cytokine, to enhance their anti-inflammatory capacity. We found that i.v. injected TGFβ1-BM-NSCs more effectively suppressed clinical severity, inflammation and demyelination of the central nervous system of EAE mice. Transduction of TGFβ1 resulted in a higher percentage of Tregs and lower percentage of Th1 and Th17 cells in the periphery, with increased production of IL-10, and reduced production of IFN-γ, IL-17 and GM-CSF. Moreover, myelin-specific splenic proliferation was also inhibited more profoundly by TGFβ1-BM-NSCs. We also found that TGFβ1-BM-NSCs have the capacity to switch microglia from M1 to M2 phenotype. On the other hand, transduction of TGFβ1 did not affect proliferative ability and differentiating potential of BM-NSCs in vitro and in vivo. Together, these findings demonstrate that transduction of TGFβ1 significantly enhanced the immunomodulatory capacity of BM-NSCs for EAE treatment, through inducing Tregs and an M2 phenotype of macrophages/microglia, while retaining their capacity for neural cell differentiation. Thus, our study provides an easily accessible, inducible and effective therapy for CNS inflammatory demyelination.

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.

TGF-β inhibits IL-7-induced proliferation in memory but not naive human CD4+ T cells

TGF-β is a potent suppressor of T cell activation and expansion. Although the antiproliferative effects of TGF-β are well characterized in TCR-activated cells, the effects of TGF-β on T cell proliferation driven by homeostatic cytokines, such as IL-7, are poorly defined. In the current study, we found that TGF-β inhibits IL-7-induced proliferation in memory, but not in naive human CD4⁺ T cells. TGF-β impaired c-myc induction in all CD4⁺ T cell maturation subsets, although the impairment was less sustained in naive CD4⁺ T cells. TGF-β had no discernible effect on IL-7R signaling (p-STAT-5, p-Akt, or p-S6) in memory T cells but selectively enhanced p-S6 signaling in naive T cells. The inhibitory effects of TGF-β on memory T cell proliferation were partially overcome by chemical inhibition of GSK-3, which also led to enhanced c-myc expression. These data suggest that TGF-β could play an important role in limiting homeostatic proliferation of memory T cells. Our observations also point toward a novel strategy to subvert TGF-β-mediated inhibition of memory T cells by targeting GSK-3 for inhibition.

Regulation of the Immune Response by TGF-β: From Conception to Autoimmunity and Infection

Transforming growth factor β (TGF-β) is a pleiotropic cytokine involved in both suppressive and inflammatory immune responses. After 30 years of intense study, we have only begun to elucidate how TGF-β alters immunity under various conditions. Under steady-state conditions, TGF-β regulates thymic T-cell selection and maintains homeostasis of the naïve T-cell pool. TGF-β inhibits cytotoxic T lymphocyte (CTL), Th1-, and Th2-cell differentiation while promoting peripheral (p)Treg-, Th17-, Th9-, and Tfh-cell generation, and T-cell tissue residence in response to immune challenges. Similarly, TGF-β controls the proliferation, survival, activation, and differentiation of B cells, as well as the development and functions of innate cells, including natural killer (NK) cells, macrophages, dendritic cells, and granulocytes. Collectively, TGF-β plays a pivotal role in maintaining peripheral tolerance against self- and innocuous antigens, such as food, commensal bacteria, and fetal alloantigens, and in controlling immune responses to pathogens.

A Novel Brucine Gel Transdermal Delivery System Designed for Anti-Inflammatory and Analgesic Activities

The seeds of Strychnos nux-vomica L., as a traditional Chinese medicine, have good anti-inflammatory and analgesic activities. However, it usually leads to gastrointestinal irritation and systemic toxicity via oral administration. In the study, it was discovered that a novel gel transdermal delivery system contained brucine, the main effective component extracted from Strychnos nux-vomica. Results showed that the brucine gel system inhibited arthritis symptoms and the proliferation of the synoviocytes in the rat adjuvant arthritis model, which indicated its curative effect for rheumatoid arthritis. Meanwhile, it significantly relieved the xylene-induced ear edema in the mouse ear swelling test, which manifested its anti-inflammatory property. Moreover, the brucine gel eased the pain of paw formalin injection in the formalin test, which demonstrated its analgesic effects. In addition, the brucine significantly inhibited lipopolysaccharide (LPS)-induced Prostaglandin E2 (PGE2) production without affecting the viability of cell in vitro anti-inflammatory test, which proved that its anti-inflammatory and analgesic actions were related to inhibition of prostaglandin synthesis. It is suggested that the brucine gel is a promising vehicle for transdermal delivery on the treatment of inflammatory disease.

Interactions of U24 from Roseolovirus with WW domains: canonical vs noncanonical

U24 is a C-terminal membrane-anchored protein found in both human herpes virus type 6 and 7 (HHV-6 and HHV-7), with an N-terminal segment that is rich in prolines (PPxY motif in both HHV-6A and 7; PxxP motif in HHV-6A). Previous work has shown that U24 interacts strongly with Nedd4 WW domains, in particular, hNedd4L-WW3*. It was also shown that this interaction depends strongly on the nature of the amino acids that are upstream from the PY motif in U24. In this contribution, data was obtained from pull-downs, isothermal titration calorimetry, and NMR to further determine what modulates U24:WW domain interactions. Specifically, 3 non-canonical WW domains from human Smad ubiquitination regulatory factor (Smurf), namely hSmurf2-WW2, hSmurf2-WW3, and a tandem construct hSmurf2-WW2 + 3, were studied. Overall, the interactions between U24 and these Smurf WW domains were found to be weaker than those in U24:Nedd4 WW domain pairs, suggesting that U24 function is tightly linked to specific E3 ubiqitin ligases.

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.

Macrophages and the Recovery from Acute and Chronic Inflammation

In recent years, researchers have devoted much attention to the diverse roles of macrophages and their contributions to tissue development, wound healing, and angiogenesis. What should not be lost in the discussions regarding the diverse biology of these cells is that when perturbed, macrophages are the primary contributors to potentially pathological inflammatory processes. Macrophages stand poised to rapidly produce large amounts of inflammatory cytokines in response to danger signals. The production of these cytokines can initiate a cascade of inflammatory mediator release that can lead to wholesale tissue destruction. The destructive inflammatory capability of macrophages is amplified by exposure to exogenous interferon-γ, which prolongs and heightens inflammatory responses. In simple terms, macrophages can thus be viewed as incendiary devices with hair triggers waiting to detonate. We have begun to ask questions about how these cells can be regulated to mitigate the collateral destruction associated with macrophage activation.

TGF-β regulation of encephalitogenic and regulatory T cells in multiple sclerosis

Transforming growth factor beta (TGF-β) is a pleiotropic cytokine that has been shown to influence the differentiation and function of T cells. The role that TGF-β plays in immune-mediated disease, such as multiple sclerosis (MS), has become a major area of investigation since CD4⁺ T cells appear to be a major mediator of autoimmunity. This review provides an analysis of the literature on the role that TGF-β plays in the generation and regulation of encephalitogenic and regulatory T cells (Treg) in experimental autoimmune encephalomyelitis (EAE), an animal model of MS, as well as in T cells of MS patients. Since TGF-β plays a major role in the development and function of both CD4⁺ effector and Treg, which are defective in MS patients, recent studies have found potential mechanisms to explain the basis for these T-cell defects to establish a foundation for potentially modulating TGF-β signaling to restore normal T-cell function in MS patients.

Ellagic acid alleviates adjuvant induced arthritis by modulation of pro- and anti-inflammatory cytokines

Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown aetiology, but it is now clear that pro-inflammatory cytokines play a central role in its pathogenesis. Ellagic acid (EA) has a variety of biological activities including anti-oxidant, anti-inflammatory, and anti-cancer properties. The aim of the present study was to evaluate the potential effect of ellagic acid on the prevention and/or treatment of adjuvant induced arthritis (AIA) model in mice. Ellagic acid treatment was started one week before AIA induction and continued for three weeks after induction of AIA. Ellagic acid treatment significantly (p < 0.01) inhibited foot paw oedematous swelling and attenuated AIA-associated pathology. Ellagic acid significantly (p < 0.01) reduced serum levels of pro-inflammatory cytokines: interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), and interleukin 17 (IL-17). However, serum levels of IL-10 and interferon γ (IFN-γ) significantly increased (p < 0.01 and p < 0.05, respectively), while serum level of transforming growth factor β (TGF-β) did not significantly alter with EA treatment. In conclusion, these results suggest that EA attenuated AIA-associated pathology in the mouse model by downregulation of pro-inflammatory cytokines and upregulation of anti-inflammatory cytokines.

Smad-dependent mechanisms of inflammatory bone destruction

Homeostatic bone remodelling becomes disturbed in a variety of pathologic conditions that affect the skeleton, including inflammatory diseases. Rheumatoid arthritis is the prototype of an inflammatory arthritis characterised by chronic inflammation, progressive cartilage destruction and focal bone erosions and is a prime example for a disease with disturbed bone homeostasis. The inflammatory milieu favours the recruitment and activation of osteoclasts, which have been found to be the cells that are primarily responsible for bone erosions in many animal models of inflammatory arthritis. Among the inflammatory modulators, members of the transforming growth factor (TGF)-β super family are shown to be important regulators in osteoclastogenesis with Smad-mediated signalling being crucial for inducing osteoclast differentiation. These findings have opened a new field for exploring mechanisms of osteoclast differentiation under inflammatory conditions. Recent studies have shown that the TGF-β superfamily members TGF-β1, myostatin and activin A directly regulate osteoclast differentiation through mechanisms that depend on the RANKL–RANK interplay. These growth factors transduce their signals through type I and II receptor serine/threonine kinases, thereby activating the Smad pathway. In this review, we describe the impact of inflammation-induced Smad signalling in osteoclast development and subsequently bone erosion in rheumatoid arthritis.

TGF-β Signal Transduction in Oro-facial Health and Non-malignant Disease (Part I)

The transforming growth factor-beta (TGF-β) family of cytokines consists of multi-functional polypeptides that regulate a variety of cell processes, including proliferation, differentiation, apoptosis, extracellular matrix elaboration, angiogenesis, and immune suppression, among others. In so doing, TGF-β plays a key role in the control of cell behavior in both health and disease. In this report, we review what is known about the mechanisms of activation of the peptide, together with details of TGF-β signal transduction pathways. This review summarizes the evidence implicating TGF-β in normal physiological processes of the craniofacial complex—such as palatogenesis, tooth formation, wound healing, and scarring—and then evaluates its role in non-malignant disease processes such as scleroderma, submucous fibrosis, periodontal disease, and lichen planus.

Inhibition of cytokine response to TLR stimulation and alleviation of collagen-induced arthritis in mice by Schistosoma japonicum peptide SJMHE1

Helminth‐derived products have recently been shown to prevent the development of inflammatory diseases in mouse models. However, most identified immunomodulators from helminthes are mixtures or macromolecules with potentially immunogenic side effects. We previously identified an immunomodulatory peptide called SJMHE1 from the HSP60 protein of Schistosoma japonicum. In this study, we assessed the ability of SJMHE1 to affect murine splenocytes and human peripheral blood mononuclear cells (PBMCs) stimulated by toll‐like receptor (TLR) ligands in vitro and its treatment effect on mice with collagen‐induced arthritis (CIA). We show that SJMHE1 not only modulates the cytokine production of murine macrophage (MΦ) and dendritic cell but also affects cytokine production upon coculturing with allogeneic CD4⁺ T cell. SJMHE1 potently inhibits the cytokine response to TLR ligands lipopolysaccharide (LPS), CpG oligodeoxynucleotides (CpG) or resiquimod (R848) from mouse splenocytes, and human PBMCs stimulated by LPS. Furthermore, SJMHE1 suppressed clinical signs of CIA in mice and blocked joint erosion progression. This effect was mediated by downregulation of key cytokines involved in the pathogenesis of CIA, such as interferon‐γ (IFN‐γ), tumour necrosis factor‐α (TNF‐α), interleukin (IL)‐6, IL‐17, and IL‐22 and up‐regulation of the inhibitory cytokine IL‐10, Tgf‐β1 mRNA, and CD4⁺CD25⁺Foxp3⁺ Tregs. This study provides new evidence that the peptide from S. japonicum, which is the ‘safe’ selective generation of small molecule peptide that has evolved during host–parasite interactions, is of great value in the search for novel anti‐inflammatory agents and therapeutic targets for autoimmune diseases.

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.

Oral Delivery of Particulate Transforming Growth Factor Beta 1 and All-Trans Retinoic Acid Reduces Gut Inflammation in Murine Models of Inflammatory Bowel Disease

BACKGROUND AND AIMS

We investigated oral delivery of transforming growth factor beta 1 [TGFβ]- and all-trans retinoic acid [ATRA]-loaded microspheres as therapy for gut inflammation in murine models of inflammatory bowel disease [IBD].

METHODS

ATRA and TGFβ were separately encapsulated in poly [lactic-co-glycolic] acid or polylactic acid microspheres [respectively]. TGFβ was encapsulated using proprietary phase-inversion nanoencapsulation [PIN] technology.

RESULTS

PIN particles provided sustained release of bioactive protein for at least 4 days and were stable for up to 52 weeks when stored at either 4(0)C or -20(0)C. In the SCID mouse CD4 + CD25- T cell transfer model of IBD, oral treatment starting at disease onset prevented weight loss, significantly reduced average disease score [~ 50%], serum amyloid A levels [~ 5-fold], colon weight-to-length ratio [~ 50%], and histological score [~ 5-fold].

CONCLUSIONS

Both agents given together outperformed either separately. Highest TGFβ doses and most frequent dose schedule were most effective. Activity was associated with a significant increase [45%] in Foxp3 expression by colonic lamina propria CD4+ CD25+ T-cells. Activity was also demonstrated in dextran sulphate sodium-induced colitis. The data support development of the combination product as a novel, targeted immune based therapy for treatment for IBD.

RANKL, OPG and CTR mRNA expression in the temporomandibular joint in rheumatoid arthritis

The calcitonin receptor (CTR) and receptor activator of nuclear factor κB ligand (RANKL) have been found to be involved in the differentiation of osteoclasts. The association between the RANKL:osteoprotegerin (OPG) expression ratio and the pathogenesis of bone-destructive rheumatoid arthritis (RA) has been described in several joints, but the available data for the temporomandibular joint (TMJ) are limited. The aim of the present study was to investigate the involvement of osteoclasts at sites of bone erosion by determining the CTR expression and the RANKL:OPG expression ratio in the TMJ in a collagen-induced arthritis (CIA) model. Forty-eight male Wistar rats were randomly divided into two groups: Control group, injected with saline solution for 6 weeks; and CIA group, injected with emulsion. The RANKL and OPG mRNA expression was significantly increased in immunized rats compared with that in non-immunized rats. The RANKL:OPG expression ratio on the trabecular bone surface was 9.0 and 6.4 in the CIA group at weeks 4 and 6, respectively, while the RANKL:OPG expression ratio in the controls was 1.0:2. CTR mRNA expression was significantly upregulated in immunized rats compared with that in non-immunized rats; the level of CTR mRNA in the CTR-positive osteoclasts on the trabecular bone surface was 10.9- and 7.8-fold higher in the CIA rats than that in the control rats at weeks 4 and 6, respectively. In conclusion, focal bone destruction in an experimental model of arthritis in the TMJ can be attributed to cells expressing CTR, a defining feature of osteoclasts. The expression of RANKL and OPG mRNA within the inflamed synovium provides an insight into the mechanism of osteoclast differentiation and function at the border of bone erosion in arthritis.

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.

Targeted GAS6 delivery to the CNS protects axons from damage during experimental autoimmune encephalomyelitis

Growth arrest-specific protein 6 (GAS6) is a soluble agonist of the TYRO3, AXL, MERTK (TAM) family of receptor tyrosine kinases identified to have anti-inflammatory, neuroprotective, and promyelinating properties. During experimental autoimmune encephalomyelitis (EAE), wild-type (WT) mice demonstrate a significant induction of Gas6, Axl, and Mertk but not Pros1 or Tyro3 mRNA. We tested the hypothesis that intracerebroventricular delivery of GAS6 directly into the CNS of WT mice during myelin oligodendrocyte glycoprotein (MOG)-induced EAE would improve the clinical course of disease relative to artificial CSF (ACSF)-treated mice. GAS6 did not delay disease onset, but significantly reduced the clinical scores during peak and chronic EAE. Mice receiving GAS6 for 28 d had preserved SMI31(+) neurofilament immunoreactivity, significantly fewer SMI32(+) axonal swellings and spheroids and less demyelination relative to ACSF-treated mice. Alternate-day subcutaneous IFNβ injection did not enhance GAS6 treatment effectiveness. Gas6(-/-) mice sensitized with MOG35-55 peptide exhibit higher clinical scores during late peak to early chronic disease, with significantly increased SMI32(+) axonal swellings and Iba1(+) microglia/macrophages, enhanced expression of several proinflammatory mRNA molecules, and decreased expression of early oligodendrocyte maturation markers relative to WT mouse spinal cords with scores for 8 consecutive days. During acute EAE, flow cytometry showed significantly more macrophages but not T-cell infiltrates in Gas6(-/-) spinal cords than WT spinal cords. Our data are consistent with GAS6 being protective during EAE by dampening the inflammatory response, thereby preserving axonal integrity and myelination.

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.

Should losartan be administered following brain injury?

Brain injury is a major health concern and associated with delayed neurological complications, including post-injury epilepsy, cognitive and emotional disabilities. Currently, there is no strategy to prevent post-injury delayed complications. We recently showed that dysfunction of the blood-brain barrier, often reported in brain injuries, can lead to epilepsy and neurodegeneration via activation of inflammatory TGF-β signaling in astrocytes. We further showed that the FDA approved angiotensin II type 1 receptor antagonist, losartan, blocks brain TGF-β signaling and prevents epilepsy in the albumin or blood-brain barrier breakdown models of epileptogenesis. Here we discuss the potential of losartan as an anti-epileptogenic and a neuroprotective drug, the rationale of its use following brain injury and the challenges of designing clinical trials. We highlight the urgent need to develop reliable biomarkers for epileptogenesis (and other complications) after brain injury as a pre-requisite to challenge neuroprotective therapies.

TGF-β1 attenuates spinal neuroinflammation and the excitatory amino acid system in rats with neuropathic pain

Previous studies have reported that the intrathecal (i.t.) administration of transforming growth factor β1 (TGF-β1) prevents and reverses neuropathic pain. However, only limited information is available regarding the possible role and effects of spinal TGF-β1 in neuropathic pain. We aimed to investigate the antinociceptive effects of exogenous TGF-β1 on chronic constriction injury (CCI)-induced neuropathic pain in rats. We demonstrated that sciatic nerve injury caused a downregulation of endogenous TGF-β1 levels on the ipsilateral side of the lumbar spinal dorsal gray matter, and that the i.t. administration of TGF-β1 (.01-10 ng) significantly attenuated CCI-induced thermal hyperalgesia in neuropathic rats. TGF-β1 significantly inhibited CCI-induced spinal neuroinflammation, microglial and astrocytic activation, and upregulation of tumor necrosis factor-α. Moreover, i.t. TGF-β1 significantly attenuated the CCI-induced downregulation of glutamate transporter 1, the glutamate aspartate transporter, and the excitatory amino acid carrier 1 on the ipsilateral side. Furthermore, i.t. TGF-β1 significantly decreased the concentrations of 2 excitatory amino acids, aspartate and glutamate, in the spinal dialysates in CCI rats. In summary, we conclude that the mechanisms of the antinociceptive effects of i.t. TGF-β1 in neuropathy may include attenuation of spinal neuroinflammation, attenuation, or upregulation of glutamate transporter downregulation, and a decrease of spinal extracellular excitatory amino acids.

PERSPECTIVE

Clinically, medical treatment is usually initiated after the onset of intractable pain. Therefore, in the present study, i.t. TGF-β1 was designed to be administered 2 weeks after the establishment of CCI pain. Compared to the continuous TGF-β1 infusion mode, single-dose administration seems more convenient and practical to use.

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.

TGFβ signaling regulates the timing of CNS myelination by modulating oligodendrocyte progenitor cell cycle exit through SMAD3/4/FoxO1/Sp1

Research on myelination has focused on identifying molecules capable of inducing oligodendrocyte (OL) differentiation in an effort to develop strategies that promote functional myelin regeneration in demyelinating disorders. Here, we show that transforming growth factor β (TGFβ) signaling is crucial for allowing oligodendrocyte progenitor (OP) cell cycle withdrawal, and therefore, for oligodendrogenesis and postnatal CNS myelination. Enhanced oligodendrogenesis and subcortical white matter (SCWM) myelination was detected after TGFβ gain of function, while TGFβ receptor II (TGFβ-RII) deletion in OPs prevents their development into mature myelinating OLs, leading to SCWM hypomyelination in mice. TGFβ signaling modulates OP cell cycle withdrawal and differentiation through the transcriptional modulation of c-myc and p21 gene expression, mediated by the interaction of SMAD3/4 with Sp1 and FoxO1 transcription factors. Our study is the first to demonstrate an autonomous and crucial role of TGFβ signaling in OL development and CNS myelination, and may provide new avenues in the treatment of demyelinating diseases.

Flexibilide obtained from cultured soft coral has anti-neuroinflammatory and analgesic effects through the upregulation of spinal transforming growth factor-β1 in neuropathic rats

Chronic neuroinflammation plays an important role in the development and maintenance of neuropathic pain. The compound flexibilide, which can be obtained from cultured soft coral, possesses anti-inflammatory and analgesic effects in the rat carrageenan peripheral inflammation model. In the present study, we investigated the antinociceptive properties of flexibilide in the rat chronic constriction injury (CCI) model of neuropathic pain. First, we found that a single intrathecal (i.t.) administration of flexibilide significantly attenuated CCI-induced thermal hyperalgesia at 14 days after surgery. Second, i.t. administration of 10-μg flexibilide twice daily was able to prevent the development of thermal hyperalgesia and weight-bearing deficits in CCI rats. Third, i.t. flexibilide significantly inhibited CCI-induced activation of microglia and astrocytes, as well as the upregulated proinflammatory enzyme, inducible nitric oxide synthase, in the ipsilateral spinal dorsal horn. Furthermore, flexibilide attenuated the CCI-induced downregulation of spinal transforming growth factor-β1 (TGF-β1) at 14 days after surgery. Finally, i.t. SB431542, a selective inhibitor of TGF-β type I receptor, blocked the analgesic effects of flexibilide in CCI rats. Our results suggest that flexibilide may serve as a therapeutic agent for neuropathic pain. In addition, spinal TGF-β1 may be involved in the anti-neuroinflammatory and analgesic effects of flexibilide.

Oral Escherichia coli colonization factor antigen I fimbriae ameliorate arthritis via IL-35, not IL-27

A Salmonella therapeutic expressing enterotoxigenic Escherichia coli colonization factor Ag I (CFA/I) fimbriae protects against collagen-induced arthritis (CIA) by eliciting two regulatory T cell (Treg) subsets: TGF-β-producing Foxp3(-)CD39(+)CD4(+) T cells and IL-10-producing Foxp3(+)CD39(+)CD4(+) T cells. However, it is unclear whether CFA/I fimbriae alone are protective and whether other regulatory cytokines are involved, especially in the context for the EBI3-sharing cytokines, Treg-derived IL-35 and APC-derived IL-27, both capable of suppressing Th17 cells and regulating autoimmune diseases. Subsequent evaluation revealed that a single oral dose of purified, soluble CFA/I fimbriae protected against CIA as effectively as did Salmonella-CFA/I and found that Foxp3(+)CD39(+)CD4(+) T cells were the source of secreted IL-35, whereas IL-27 production by CD11c(+) cells was inhibited. Inquiring into their relevance, CFA/I fimbriae-treated IL-27R-deficient (WSX-1(-/-)) mice were equally protected against CIA as were wild-type mice, suggesting a limited role for IL-27. In contrast, CFA/I fimbriae-mediated protection was abated in EBI3(-/-) mice, accompanied by the loss of TGF-β- and IL-10-producing Tregs. Adoptive transfer of C57BL/6 CD39(+)CD4(+) T cells to EBI3(-/-) mice with concurrent CFA/I plus IL-35 treatment effectively stimulated Tregs suppressing proinflammatory collagen II-specific Th cells. In contrast, recipients cotransferred with C57BL/6 and EBI3(-/-) CD39(+)CD4(+) T cells and treated with CFA/I plus IL-35 were not protected, implicating the importance of endogenous IL-35 for conferring CFA/I-mediated protection. Thus, CFA/I fimbriae stimulate IL-35 required for the coinduction of TGF-β and IL-10.