[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stem cells (MSCs) are pleiotropic cells with potential therapeutic benefits for a wide range of diseases. Because of their immunomodulatory properties they have been utilized to treat autoimmune diseases such as multiple sclerosis (MS), which is characterized by demyelination. The microenvironment surrounding MSCs is thought to affect their differentiation and phenotype, which could in turn affect the efficacy. We thus sought to dissect the potential for differential impact of MSCs on central nervous system (CNS) disease in T cell mediated and non-T cell mediated settings using the MOG35–55 experimental autoimmune encephalomyelitis (EAE) and cuprizone-mediated demyelination models, respectively. As the pathogeneses of MS and EAE are thought to be mediated by IFNγ-producing (TH1) and IL-17A-producing (TH17) effector CD4+ T cells, we investigated the effect of MSCs on the development of these two key pathogenic cell groups. Although MSCs suppressed the activation and effector function of TH17 cells, they did not affect TH1 activation, but enhanced TH1 effector function and ultimately produced no effect on EAE. In the non- T cell mediated cuprizone model of demyelination, MSC administration had a positive effect, with an overall increase in myelin abundance in the brain of MSC-treated mice compared to controls. These results highlight the potential variability of MSCs as a biologic therapeutic tool in the treatment of autoimmune disease and the need for further investigation into the multifaceted functions of MSCs in diverse microenvironments and the mechanisms behind the diversity.
[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stem cells (MSCs) are a pleiotropic population of cells that are self-renewing and capable of differentiating into canonical cells of the mesenchyme, including adipocytes, chondrocytes, and osteocytes. They employ multi-faceted approaches to maintain bone marrow niche homeostasis and promote wound healing during injury. Biomedical research has long sought to exploit their pleiotropic properties as a basis for cell therapy for a variety of diseases and to facilitate hematopoietic stem cell establishment and stromal reconstruction in bone marrow transplantation. Early results demonstrated their usage as safe, and there was little host response to these cells. The discovery of their immunosuppressive functions ushered in a new interest in MSCs as a promising therapeutic tool to suppress inflammation and down-regulate pathogenic immune responses in graft-versus-host and autoimmune diseases such as multiple sclerosis, autoimmune diabetes, and rheumatoid arthritis. MSCs produce a large number of soluble and membrane-bound factors, some of which inhibit immune responses. However, the full range of MSC-mediated immune-modulation remains incompletely understood, as emerging reports also reveal that MSCs can adopt an immunogenic phenotype, stimulate immune cells, and yield seemingly contradictory results in experimental animal models of inflammatory disease. The present review describes the large body of literature that has been accumulated on the fascinating biology of MSCs and their complex effects on immune responses.
[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stem cells (MSC) have emerged as a promising candidate for inflammatory suppression and disease amelioration, especially of neuro‐inflammatory diseases such as multiple sclerosis (MS). Auto‐reactive CD4+ and CD8+ T cells acquire pathogenic IFNγ‐producing‐ (Type I) and IL‐17A‐producing‐ (Type 17) effector phenotypes in MS and its animal model experimental autoimmune encephalomyelitis (EAE). Although MSC have been extensively demonstrated to suppress pathogenic effector CD4+ T cells and CD4+ T cell‐mediated EAE, surprisingly few studies have addressed their modulation of effector CD8+ T cells represented in MS or their impact on CD8+ T cell‐mediated EAE. We find that MSC differentially modulate CD8+ T cell development depending on effector T cell subtype. MSC drive activated low‐IFNγ producers toward an enhanced high‐IFNγ Tc1‐like phenotype but strongly inhibit the production of IL‐17A and Tc17 polarization in vitro. These observations are underscored by differential MSC modulation of T cell activation, proliferation, and signature transcription factor up‐regulation. In addition, effector CD8+ T cells co‐cultured with MSC exhibited increased production of IL‐2, a molecule known to enhance IFNγ, yet suppress IL‐17A, production. Based on these in vitro effects on CD8+ T cells, we next evaluated their impact on the severity of EAE. To better evaluate CD8+ T cells, we immunized mice with MOG37‐50, which is a CD8‐targeted epitope. Our results revealed a worsening of disease, consistent with their in vitro stimulation of Tc1 cells. These findings highlight the emerging duality of MSC in immune modulation and provide implications for their future use in immune‐related diseases. Stem Cells 2014;32:2744–2755
[Show abstract][Hide abstract] ABSTRACT: The initiation and maintenance of the immune response require a coordinated regulation of signal transduction pathways. Identifying
the mechanisms by which these pathways are controlled and modulated is a significant goal of immunology. In the present report,
we show a novel role for the zinc finger transcription factor Kruppel-like factor 4 (KLF4) in the modulation of the inflammatory
immune response via its regulation of IL-6. We analyzed the role of KLF4 in the production of IL-6 by dendritic cells. Our
data indicate that KLF4 can act in a dual function manner. It acts as a transcription factor in that it can bind to and activate
the IL-6 promoter at specific binding sites. KLF4 also has a role in the chromatin remodeling of the IL-6 promoter in that
cells deficient in KLF4 exhibited a relative hypoacetylation. These results indicate a molecular role for KLF4 in modulating
the intensity of the inflammatory response and help to explain its pleiotropic role in different settings.
[Show abstract][Hide abstract] ABSTRACT: Increased expression of the voltage-gated potassium channel Kν1.3 on activated effector memory T cells (T(EM)) is associated with pathology in multiple sclerosis (MS). To date, most studies of Kν1.3 channels in MS have focused on CD4+ T(EM) cells. Much less is known about the functional relevance of Kv1.3 on CD8+ T(EM) cells. Herein, we examined the effects of Kν1.3 blockade on CD8+ T cell proliferation, differentiation into cytotoxic effector cells, and release of granzyme B (GrB), a key effector of CD8+ T cell-mediated cytotoxicity. We confirmed the expression of Kv1.3 channels on activated human CD8+ T lymphocytes by immunofluorescent staining. To test the functional relevance of the Kv1.3 channel in CD8+ T cells, we inhibited this channel via pharmacological blockers or a lentiviral-dominant negative (Kv1.xDN) approach and determined the effects of the blockade on critical pathogenic parameters of CD8+ T cells. We found that blockade of Kv1.3 with both lentivirus and pharmacologic agents effectively inhibited cytotoxic effector memory cells' proliferation, secretion of GrB, and their ability to kill neural progenitor cells. Intriguingly, the KvDN transduced T cells exhibited arrested differentiation from central memory (T(CM)) to effector memory (T(EM)) states. Transduction of cells that had already differentiated into T(EM) with KvDN led to their conversion into T(CM). CD8+ T(EM) have a critical role in MS and other autoimmune diseases. Our present results indicate a critical role for Kv1.3 in the conversion of CD8+ T cells into potential pathogenic effector cells with cytotoxic function.
[Show abstract][Hide abstract] ABSTRACT: Increasing evidence suggests ion channels have critical functions in the differentiation and plasticity of T cells. Kv1.3, a voltage-gated K(+) channel, is a functional marker and a pharmacological target for activated effector memory T cells. Selective Kv1.3 blockers have been shown to inhibit proliferation and cytokine production by human and rat effector memory T cells. We used Kv1.3 knockout (KO) mice to investigate the mechanism by which Kv1.3 blockade affects CD4(+) T cell differentiation during an inflammatory immune-mediated disease. Kv1.3 KO animals displayed significantly lower incidence and severity of myelin oligodendrocyte glycoprotein (MOG) peptide-induced experimental autoimmune encephalomyelitis. Kv1.3 was the only K(V) channel expressed in MOG 35-55-specific CD4(+) T cell blasts, and no K(V) current was present in MOG-specific CD4(+) T cell-blasts from Kv1.3 KO mice. Fewer CD4(+) T cells migrated to the CNS in Kv1.3 KO mice following disease induction, and Ag-specific proliferation of CD4(+) T cells from these mice was impaired with a corresponding cell-cycle delay. Kv1.3 was required for optimal expression of IFN-γ and IL-17, whereas its absence led to increased IL-10 production. Dendritic cells from Kv1.3 KO mice fully activated wild-type CD4(+) T cells, indicating a T cell-intrinsic defect in Kv1.3 KO mice. The loss of Kv1.3 led to a suppressive phenotype, which may contribute to the mechanism by which deletion of Kv1.3 produces an immunotherapeutic effect. Skewing of CD4(+) T cell differentiation toward Ag-specific regulatory T cells by pharmacological blockade or genetic suppression of Kv1.3 might be beneficial for therapy of immune-mediated diseases such as multiple sclerosis.
No preview · Article · May 2012 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: The maintenance of T cell memory is critical for the development of rapid recall responses to pathogens, but may also have the undesired side effect of clonal expansion of T effector memory (T(EM)) cells in chronic autoimmune diseases. The mechanisms by which lineage differentiation of T cells is controlled have been investigated, but are not completely understood. Our previous work demonstrated a role of the voltage-gated potassium channel Kv1.3 in effector T cell function in autoimmune disease. In the present study, we have identified a mechanism by which Kv1.3 regulates the conversion of T central memory cells (T(CM)) into T(EM). Using a lentiviral-dominant negative approach, we show that loss of function of Kv1.3 mediates reversion of T(EM) into T(CM), via a delay in cell cycle progression at the G2/M stage. The inhibition of Kv1.3 signaling caused an up-regulation of SMAD3 phosphorylation and induction of nuclear p21(cip1) with resulting suppression of Cdk1 and cyclin B1. These data highlight a novel role for Kv1.3 in T cell differentiation and memory responses, and provide further support for the therapeutic potential of Kv1.3 specific channel blockers in T(EM)-mediated autoimmune diseases.
No preview · Article · Nov 2011 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: The goal of this study was to investigate the effects of natalizumab therapy on the immune cell composition and phenotype in the blood of relapsing MS patients treated over the course of 12 months. We collected peripheral blood from 26 RRMS patients before treatment onset, and then 6 and 12 months after therapy. PBMC was isolated and then analyzed for phenotypic characteristics by FACS and for cytokine production by ELISA. The results of our studies showed changes in both numbers and activation states of immune cells following therapy. These changes were observed at the 6 month timepoint and generally persisted through the 12 month timepoint. The proportions of NK cells (CD3⁻CD56+) and hematopoetic stem cells (CD34+lin⁻) were increased after natalizumab treatment. Decreases were noted in numbers of CD14+ monocytes, and possibly their migratory potential, since their expression levels of α4β1 were decreased. Relative numbers of CD20+ B cells were increased, but the proportion of CD20+ cells expressing high levels of α4β1 integrin was decreased. While proportions of CD4+ and CD8+ T cells did not change, the percentage of cells expressing α4β1 integrin was significantly decreased for both subsets. Natalizumab therapy produces a number of phenotypic changes in the immune composition of peripheral blood. These changes may help to explain both the mechanisms of action of natalizumab and also shed light on the potential for the observed increase in PML in these patients.
No preview · Article · Jun 2011 · Journal of neuroimmunology
[Show abstract][Hide abstract] ABSTRACT: Th17 cells play a significant role in inflammatory and autoimmune responses. Although a number of molecular pathways that contribute to the lineage differentiation of T cells have been discovered, the mechanisms by which lineage commitment occurs are not fully understood. Transcription factors play a key role in driving T cells toward specific lineages. We have identified a role for the transcription factor Kruppel-like factor (KLF) 4 in the development of IL-17-producing CD4(+) T cells. KLF4 was required for the production of IL-17, and further, chromatin immunoprecipitation analysis demonstrated binding of KLF4 to the IL-17 promoter, indicating a direct effect on the regulation of IL-17. Further, KLF4-deficient T cells upregulated expression of retinoic acid-related orphan receptor γt similar to wild-type during the polarization process toward Th17, suggesting that these two transcription factors are regulated independently.
Full-text · Article · Nov 2010 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Inflammatory cell infiltration and resident microglial activation within the central nervous system (CNS) are pathological events in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). While MS therapies target the peripheral immune system, no treatment is currently known to also modulate microglia. FMS-like tyrosine-3 (FLT-3) is expressed on hematopoietic and dendritic cells. We reported that FLT-3 inhibition ameliorates early actively induced EAE by predominantly modulating dendritic cell function as compared to microglia. We demonstrate in this report that FLT-3 is expressed in perivascular cuffs, brain parenchyma and in non-lesioned gray and white matter within MS brain but not in these regions within control brain. Furthermore, we demonstrate that FLT-3 is expressed on two populations of cells within MS brain; one which expresses the dendritic cell marker CD209, and the other which does not, suggesting that FLT-3 within MS brain is expressed on infiltrating dendritic cells and a non-dendritic cell such as microglia. Additionally, we report that FLT-3 inhibition in murine microglia blocks, in a dose-dependent manner, IFN-γ-induced expression of MHC class II and CD86, and LPS-induced secretion of IL-6. These data suggest that FLT-3 is involved in microglial cells' capacity to respond to environmental cues to function as antigen presenting cells and mediate CNS inflammation. Furthermore these data suggest that FLT-3 may be a therapeutic target on microglia to mitigate CNS inflammation.
Full-text · Article · Oct 2010 · Experimental and Molecular Pathology
[Show abstract][Hide abstract] ABSTRACT: IL-17- and IFN-gamma-secreting T cells play an important role in autoimmune responses in multiple sclerosis and the model system experimental autoimmune encephalomyelitis (EAE). Dendritic cells (DCs) in the periphery and microglia in the CNS are responsible for cytokine polarization and expansion of this T cell subset. Our results indicate that in vivo administration of a signal transduction inhibitor that targets DCs to mice with EAE led to a decrease in CNS infiltration of pathogenic Ag-specific T cells. Since this approach does not target T cells directly, we assessed the effects on the APCs that are involved in generating the T cell responses. Since in EAE and multiple sclerosis, both microglia and peripheral DCs are likely to contribute to disease, we utilized a bone marrow chimera system to distinguish between these two populations. These studies show that peripheral DCs are the primary target but that microglia are also modestly affected by CEP-701, as numbers and activation states of the cells in the CNS are decreased after therapy. Our results also showed a decrease in secretion of TNF-alpha, IL-6, and IL-23 by DCs as well as a decrease in expression of costimulatory molecules. We further determined that levels of phospho-Stat1, Stat3, Stat5, and NF-kappaB, which are signaling molecules that have been implicated in these pathways, were decreased. Thus, use of this class of signal transduction inhibitors may represent a novel method to treat autoimmunity by dampening the autoreactive polarizing condition driven by DCs.
Full-text · Article · May 2009 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Activation of dendritic cells (DCs) leads to cell maturation, which is accompanied by a regulated pattern of gene expression changes. Two significant and contradictory consequences of DC activation are that, although activation is necessary for maximal T-cell stimulation, it also leads to the initiation of gene expression that results ultimately in cell death. We have identified a gene, MINOR (mitogen-inducible nuclear orphan receptor), that becomes highly up-regulated on activation and whose expression leads to apoptosis in mature DCs. MINOR is a member of the Nur77 family of nuclear orphan receptors, which includes Nur77 and Nurr1. Although Nur77 and Nurr1 are expressed in macrophages and DCs, their expression levels do not change on DC activation. We thus tested the hypothesis that induction of MINOR would lead to an activation-induced cell death in DCs and that its inhibition would increase the lifespan of DCs and improve their vaccine efficacy. To block natural expression of MINOR by DCs, we generated a lentiviral vector that expresses a small interfering RNA. Our results indicate that blockade of MINOR expression dramatically decreases apoptosis in DCs and suggest that this approach may be a novel means to improve the potency of ex vivo-generated DC vaccines.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Autoimmune diseases encompass a broad range of illnesses with a variety of underlying causes, some of which are known and some of which remain elusive. OBJECTIVE: The focus of this review will be on describing the development of a new type of therapy that could potentially treat T cell-mediated autoimmune diseases. Unlike traditional therapies, which have primarily focused on suppressing T cells directly, targeting the step of antigen presentation may allow a less toxic therapy in which autoimmunity is lessened without compromising the entire immune system. This review will outline the science behind the development of the therapy, the roles of dendritic cells in generating autoimmune disease, and the function of the FLT3 receptor in this process.
No preview · Article · Dec 2008 · Expert Opinion on Investigational Drugs
[Show abstract][Hide abstract] ABSTRACT: T cell receptor (TCR) and costimulatory receptor (CD28) signals cooperate in activating T cells, although understanding of how these pathways are themselves regulated is incomplete. We found that Homer2 and Homer3, members of the Homer family of cytoplasmic scaffolding proteins, are negative regulators of T cell activation. This is achieved through binding of nuclear factor of activated T cells (NFAT) and by competing with calcineurin. Homer-NFAT binding was also antagonized by active serine-threonine kinase AKT, thereby enhancing TCR signaling via calcineurin-dependent dephosphorylation of NFAT. This corresponded with changes in cytokine expression and an increase in effector-memory T cell populations in Homer-deficient mice, which also developed autoimmune-like pathology. These results demonstrate a further means by which costimulatory signals are regulated to control self-reactivity.
[Show abstract][Hide abstract] ABSTRACT: Previous studies have shown that central memory T (T(CM)) cells predominantly use the calcium-dependent potassium channel KCa3.1 during acute activation, whereas effector memory T (T(EM)) cells use the voltage-gated potassium channel Kv1.3. Because Kv1.3-specific pharmacological blockade selectively inhibited anti-CD3-mediated proliferation, whereas naive T cells and T(CM) cells escaped inhibition due to up-regulation of KCa3.1, this difference indicated a potential for selective targeting of the T(EM) population. We examined the effects of pharmacological Kv1.3 blockers and a dominant-negative Kv1.x construct on T cell subsets to assess the specific effects of Kv1.3 blockade. Our studies indicated both T(CM) and T(EM) CD4+ T cells stimulated with anti-CD3 were inhibited by charybdotoxin, which can block both KCa3.1 and Kv1.3, whereas margatoxin and Stichodactyla helianthus toxin, which are more selective Kv1.3 inhibitors, inhibited proliferation and IFN-gamma production only in the T(EM) subset. The addition of anti-CD28 enhanced proliferation of freshly isolated cells and rendered them refractory to S. helianthus, whereas chronically activated T(EM) cell lines appeared to be costimulation independent because Kv1.3 blockers effectively inhibited proliferation and IFN-gamma regardless of second signal. Transduction of CD4+ T cells with dominant-negative Kv1.x led to a higher expression of CCR7+ T(CM) phenotype and a corresponding depletion of T(EM). These data provide further support for Kv1.3 as a selective target of chronically activated T(EM) without compromising naive or T(CM) immune functions. Specific Kv1.3 blockers may be beneficial in autoimmune diseases such as multiple sclerosis in which T(EM) are found in the target organ.
Full-text · Article · Nov 2007 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Expression of the PD-1 receptor on T cells has been shown to provide an important inhibitory signal that down-modulates peripheral effector responses in normal tissues and tumors. Furthermore, PD-1 up-regulation on chronically activated T cells can maintain them in a partially reversible inactive state. The function of PD-1 in the very early stages of T-cell response to antigen in vivo has not been fully explored. In this study, we evaluate the role of PD-1 and its 2 B7 family ligands, B7-H1 (PD-L1) and B7-DC (PD-L2), in early fate decisions of CD8 T cells. We show that CD8 T cells specific for influenza hemagglutinin (HA) expressed as a self-antigen become functionally tolerized and express high levels of surface PD-1 by the time of their first cell division. Blockade of PD-1 or B7-H1, but not B7-DC, at the time of self-antigen encounter mitigates tolerance induction and results in CD8 T-cell differentiation into functional cytolytic T lymphocytes (CTLs). These findings demonstrate that, in addition to modulating effector functions in the periphery, B7-H1:PD-1 interactions regulate early T-cell-fate decisions.
[Show abstract][Hide abstract] ABSTRACT: Feedback regulation of adaptive immunity is a fundamental mechanism for controlling the overall output of different signal transduction pathways, including that mediated by the T-cell antigen receptor (TCR). Calcineurin and Ras are known to have essential functions during T-cell activation. However, how the calcineurin signalling pathway is terminated in the process is still largely unknown. Although several endogenous inhibitors of calcineurin have been reported, none fulfils the criteria of a feedback inhibitor, as their expression is not responsive to TCR signalling. Here we identify an endogenous inhibitor of calcineurin, named Carabin, which also inhibits the Ras signalling pathway through its intrinsic Ras GTPase-activating protein (GAP) activity. Expression of Carabin is upregulated on TCR signalling in a manner that is sensitive to inhibitors of calcineurin, indicating that Carabin constitutes part of a negative regulatory loop for the intracellular TCR signalling pathway. Knockdown of Carabin by short interfering RNA led to a significant enhancement of interleukin-2 production by antigen-specific T cells in vitro and in vivo. Thus, Carabin is a negative feedback inhibitor of the calcineurin signalling pathway that also mediates crosstalk between calcineurin and Ras.
[Show abstract][Hide abstract] ABSTRACT: Autoimmune diseases often result from inappropriate or unregulated activation of autoreactive T cells. Traditional approaches to treatment of autoimmune diseases through immunosuppression have focused on direct inhibition of T cells. In the present study, we examined the targeted inhibition of antigen-presenting cells as a means to downregulate immune responses and treat autoimmune disease. Dendritic cells (DCs) are the central antigen-presenting cells for the initiation of T cell responses, including autoreactive ones. A large portion of DCs are derived from hematopoietic progenitors that express FLT3 receptor (CD135), and stimulation of the receptor via FLT3 ligand either in vivo or in vitro is known to drive expansion and differentiation of these progenitors toward a DC phenotype. We hypothesized that inhibition of FLT3 signaling would thus produce an inhibition of DC-induced stimulation of T cells, thereby inhibiting autoimmune responses. To this end, we used small-molecule tyrosine kinase inhibitors targeted against FLT3 and examined the effects on DCs and their role in the promulgation of autoimmune disease. Results of our studies show that inhibition of FLT3 signaling induces apoptosis in both mouse and human DCs, and thus is a potential target for immune suppression. Furthermore, targeted inhibition of FLT3 significantly improved the course of established disease in a model for multiple sclerosis, experimental autoimmune encephalomyelitis, suggesting a potential avenue for treating autoimmune disease.
Full-text · Article · Dec 2005 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: A number of signaling pathways are important in the initiation and maintenance of tumor cell survival and growth. Mitogen activated protein kinases are a family of kinases of different lineages that are thought to be important in tumor growth and metastasis. These pathways provide insight into how tumor cells may escape killing by different agents. In addition, since these pathways are involved in tumor cell survival, several strategies to inhibit them are being tested for novel cancer therapies. This review summarizes the evidence for the role of these pathways in cancer and the current status of therapies.
No preview · Article · Jun 2004 · Drug News & Perspectives