Altered maturation of circulating dendritic cells in primary progressive MS patients

Berberine: A natural modulator of immune cells in multiple sclerosis

Berberine is a benzylisoquinoline alkaloid found in such plants as Berberis vulgaris, Berberis aristata, and others, revealing a variety of pharmacological properties as a result of interacting with different cellular and molecular targets. Recent studies have shown the immunomodulatory effects of Berberine which result from its impacts on immune cells and immune response mediators such as diverse T lymphocyte subsets, dendritic cells (DCs), and different inflammatory cytokines. Multiple sclerosis (MS) is a chronic disabling and neurodegenerative disease of the central nervous system (CNS) characterized by the recruitment of autoreactive T cells into the CNS causing demyelination, axonal damage, and oligodendrocyte loss. There have been considerable changes discovered in MS regards to the function and frequency of T cell subsets such as Th1 cells, Th17 cells, Th2 cells, Treg cells, and DCs. In the current research, we reviewed the outcomes of in vitro, experimental, and clinical investigations concerning the modulatory effects that Berberine provides on the function and numbers of T cell subsets and DCs, as well as important cytokines that are involved in MS.

Crosstalk between dendritic cells and regulatory T cells: Protective effect and therapeutic potential in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system related to autoimmunity and is characterized by demyelination, neuroinflammation, and neurodegeneration. Cell therapies mediated by dendritic cells (DCs) and regulatory T cells (Tregs) have gradually become accumulating focusing in MS, and the protective crosstalk mechanisms between DCs and Tregs provide the basis for the efficacy of treatment regimens. In MS and its animal model experimental autoimmune encephalomyelitis, DCs communicate with Tregs to form immune synapses and complete a variety of complex interactions to counteract the unbalanced immune tolerance. Through different co-stimulatory/inhibitory molecules, cytokines, and metabolic enzymes, DCs regulate the proliferation, differentiation and function of Tregs. On the other hand, Tregs inhibit the mature state and antigen presentation ability of DCs, ultimately improving immune tolerance. In this review, we summarized the pivotal immune targets in the interaction between DCs and Tregs, and elucidated the protective mechanisms of DC-Treg cell crosstalk in MS, finally interpreted the complex cell interplay in the manner of inhibitory feedback loops to explore novel therapeutic directions for MS.

STING Agonist Mitigates Experimental Autoimmune Encephalomyelitis by Stimulating Type I IFN-Dependent and -Independent Immune-Regulatory Pathways

The cGAS-cyclic GMP-AMP (cGAMP)-stimulator of IFN genes (STING) pathway induces a powerful type I IFN (IFN-I) response and is a prime candidate for augmenting immunity in cancer immunotherapy and vaccines. IFN-I also has immune-regulatory functions manifested in several autoimmune diseases and is a first-line therapy for relapsing-remitting multiple sclerosis. However, it is only moderately effective and can induce adverse effects and neutralizing Abs in recipients. Targeting cGAMP in autoimmunity is unexplored and represents a challenge because of the intracellular location of its receptor, STING. We used microparticle (MP)-encapsulated cGAMP to increase cellular delivery, achieve dose sparing, and reduce potential toxicity. In the C57BL/6 experimental allergic encephalomyelitis (EAE) model, cGAMP encapsulated in MPs (cGAMP MPs) administered therapeutically protected mice from EAE in a STING-dependent fashion, whereas soluble cGAMP was ineffective. Protection was also observed in a relapsing-remitting model. Importantly, cGAMP MPs protected against EAE at the peak of disease and were more effective than rIFN-β. Mechanistically, cGAMP MPs showed both IFN-I-dependent and -independent immunosuppressive effects. Furthermore, it induced the immunosuppressive cytokine IL-27 without requiring IFN-I. This augmented IL-10 expression through activated ERK and CREB. IL-27 and subsequent IL-10 were the most important cytokines to mitigate autoreactivity. Critically, cGAMP MPs promoted IFN-I as well as the immunoregulatory cytokines IL-27 and IL-10 in PBMCs from relapsing-remitting multiple sclerosis patients. Collectively, this study reveals a previously unappreciated immune-regulatory effect of cGAMP that can be harnessed to restrain T cell autoreactivity.

[Dendritic cells in multiple sclerosis]

Main functions, structure and stages of development of dendritic cells (DCs) are reviewed. A role of DCs in the development of immune tolerance and autoimmune diseases as well as involvement of DCs in the immunopathogenesis of multiple sclerosis (MS and their therapeutic potential in the treatment of MS are discussed.

Dendritic cells as therapeutic targets in neuroinflammation

Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disorder of the central nervous system characterized by infiltration of immune cells and progressive damage to myelin sheaths and neurons. There is still no cure for the disease, but drug regimens can reduce the frequency of relapses and slightly delay progression. Myeloid cells or antigen-presenting cells (APCs) such as dendritic cells (DC), macrophages, and resident microglia, are key players in both mediating immune responses and inducing immune tolerance. Mounting evidence indicates a contribution of these myeloid cells to the pathogenesis of multiple sclerosis and to the effects of treatment, the understanding of which might provide strategies for more potent novel therapeutic interventions. Here, we review recent insights into the role of APCs, with specific focus on DCs in the modulation of neuroinflammation in MS.

IFN-β Therapy Regulates TLR7-Mediated Response in Plasmacytoid Dendritic Cells of Multiple Sclerosis Patients Influencing an Anti-Inflammatory Status

Plasmacytoid dendritic cells (pDCs) display altered immune-phenotype in multiple sclerosis (MS) patients and are found actively recruited in postmortem MS brain lesions, implying that their immune regulation may represent an important aspect of MS pathogenesis. Because of the reported Toll-like receptor 7 (TLR7) implication in autoimmunity, in this study we characterized how IFN-β therapy impacts on pDC activation to TLR7 triggering in MS patients, aspect only poorly investigated so far. In vivo IFN-β administration regulates pDC functions in TLR7-treated peripheral blood mononuclear cell (PBMC) cultures differently from what is observed in isolated cells, suggesting that IFN-β may activate inhibitory mechanisms in MS peripheral blood involved in turning off pDC response to dampen the ongoing inflammation. Indeed, IL-10, a key regulatory cytokine found increased upon TLR7 stimulation in in vivo IFN-β-exposed PBMCs, directly reduced pDC-mediated IFN-α production. IFN-β therapy also shaped T-cell responses by decreasing TLR7-induced pDC maturation and inducing T-cell inhibitory molecules. Accordingly, raised pDC-induced IL-27 and decreased IL-23 expression, together with high IL-10 level, contribute to inhibit Th17 cell differentiation. Our study uncovered a role for IFN-β in the regulation of TLR7-mediated pDC responses in MS toward an anti-inflammatory phenotype opening new opportunities to better understand mechanisms of action of this drug in controlling MS immunopathogenesis.

Role of the immunogenic and tolerogenic subsets of dendritic cells in multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disorder in the central nervous system (CNS) characterized by inflammation and demyelination as well as axonal and neuronal degeneration. So far effective therapies to reverse the disease are still lacking; most therapeutic drugs can only ameliorate the symptoms or reduce the frequency of relapse. Dendritic cells (DCs) are professional antigen presenting cells (APCs) that are key players in both mediating immune responses and inducing immune tolerance. Increasing evidence indicates that DCs contribute to the pathogenesis of MS and might provide an avenue for therapeutic intervention. Here, we summarize the immunogenic and tolerogenic roles of DCs in MS and review medicinal drugs that may affect functions of DCs and have been applied in clinic for MS treatment. We also describe potential therapeutic molecules that can target DCs by inducing anti-inflammatory cytokines and inhibiting proinflammatory cytokines in MS.

IFN-β and multiple sclerosis: cross-talking of immune cells and integration of immunoregulatory networks

Multiple sclerosis (MS) is characterized by autoimmune inflammation affecting the central nervous system and subsequent neurodegeneration. Historically, damage was thought to be mediated exclusively by auto-antigen-activated pro-inflammatory T cells. However, more recently, we are gaining increasing knowledge on the pathogenic role played in MS by B cells, dendritic cells and monocytes. IFN-β therapy was one the first approved therapy for MS for its ability to reduce relapse rate and MRI lesion activity and to significantly decrease risk of disability progression. IFN-β-mediated mechanisms of action, even if not completely understood, mainly rely on its multifaceted pleiotropic effects resulting in sustained anti-inflammatory properties directed toward almost every immune cell type. Here, we will discuss in detail literature data characterizing the pathogenic activity of the different immune cell subsets involved in MS pathogenesis and how IFN-β therapy regulates their function by modulating bystander responses. We believe that the effectiveness of this drug in MS treatment, even if in use for a long time, can unveil new insights on this disease and still teach a lesson to researchers in the MS field.

Accumulation and therapeutic modulation of 6-sulfo LacNAc(+) dendritic cells in multiple sclerosis

Objective:

To examine the potential role of 6-sulfo LacNAc⁺ (slan) dendritic cells (DCs) displaying pronounced proinflammatory properties in the pathogenesis of multiple sclerosis (MS).

Methods:

We determined the presence of slanDCs in demyelinated brain lesions and CSF samples of patients with MS. In addition, we explored the impact of methylprednisolone, interferon-β, glatiramer acetate, or natalizumab on the frequency of blood-circulating slanDCs in patients with MS. We also evaluated whether interferon-β modulates important proinflammatory capabilities of slanDCs.

Results:

SlanDCs accumulate in highly inflammatory brain lesions and are present in the majority of CSF samples of patients with MS. Short-term methylprednisolone administration reduces the percentage of slanDCs in blood of patients with MS and the proportion of tumor necrosis factor-α– or CD150-expressing slanDCs. Long-term interferon-β treatment decreases the percentage of blood-circulating slanDCs in contrast to glatiramer acetate or natalizumab. Furthermore, interferon-β inhibits the secretion of proinflammatory cytokines by slanDCs and their capacity to promote proliferation and differentiation of T cells.

Conclusion:

Accumulation of slanDCs in highly inflammatory brain lesions and their presence in CSF indicate that slanDCs may play an important role in the immunopathogenesis of MS. The reduction of blood-circulating slanDCs and the inhibition of their proinflammatory properties by methylprednisolone and interferon-β may contribute to the therapeutic efficiency of these drugs in patients with MS.

The Lymphotoxin Network: orchestrating a type I interferon response to optimize adaptive immunity

The Lymphotoxin (LT) pathway is best known for its role in orchestrating the development and homeostasis of lymph nodes and Peyer's patches through the regulation of homeostatic chemokines. More recently an appreciation of the LTβR pathway in the production of Type I interferons (IFN-I) during homeostasis and infection has emerged. LTβR signaling is essential in differentiating stromal cells and macrophages in lymphoid organs to rapidly produce IFN-I in response to virus infections independently of the conventional TLR signaling systems. In addition, LTβR signaling is required to produce homeostatic levels of IFN-I from dendritic cells in order to effectively cross-prime a CD8+ T cell response to protein antigen. Importantly, pharmacological inhibition of LTβR signaling in mice has a profound positive impact on a number of autoimmune disease models, although it remains unclear if this efficacy is linked to IFN-I production during chronic inflammation. In this review, we will provide a brief overview of how the "Lymphotoxin Network" is linked to the IFN-I response and its impact on the immune system.

Circulating dendritic cells of multiple sclerosis patients are proinflammatory and their frequency is correlated with MS-associated genetic risk factors

BACKGROUND

The role of the adaptive immune system and more specifically T cells in the pathogenesis of multiple sclerosis (MS) has been studied extensively. Emerging evidence suggests that dendritic cells (DCs), which are innate immune cells, also contribute to MS.

OBJECTIVES

This study aimed to characterize circulating DC populations in MS and to investigate the contribution of MS-associated genetic risk factors to DCs.

METHODS

Ex vivo analysis of conventional (cDCs) and plasmacytoid DCs (pDCs) was carried out on peripheral blood of MS patients (n = 110) and age- and gender-matched healthy controls (n = 112).

RESULTS

Circulating pDCs were significantly decreased in patients with chronic progressive MS compared to relapsing-remitting MS and healthy controls. While no differences in cDCs frequency were found between the different study groups, HLA-DRB1*1501(+) MS patients and patients not carrying the protective IL-7Rα haplotype 2 have reduced frequencies of circulating cDCs and pDCs, respectively. MS-derived DCs showed enhanced IL-12p70 production upon TLR ligation and had an increased expression of the migratory molecules CCR5 and CCR7 as well as an enhanced in vitro chemotaxis.

CONCLUSION

DCs in MS are in a pro-inflammatory state, have a migratory phenotype and are affected by genetic risk factors, thereby contributing to pathogenic responses.

Plasmacytoid dendritic cells and immunotherapy in multiple sclerosis

Plasmacytoid dendritic cells (pDCs) are specialized APCs implicated in the pathogenesis of many human diseases. Compared with other peripheral blood mononuclear cells, pDCs express a high level of TLR9, which recognizes viral DNA at the initial phase of viral infection. Upon stimulation, these cells produce large amounts of type I interferon and other proinflammatory cytokines and are able to prime T lymphocytes. Thus, pDCs regulate innate and adaptive immune responses. This article reviews select aspects of pDC biology relevant to the disease pathogenesis and immunotherapy in multiple sclerosis. Many unresolved questions remain in this area, promising important future discoveries in pDC research.

Dendritic cells in multiple sclerosis: key players in the immunopathogenesis, key players for new cellular immunotherapies?

Many studies have demonstrated the role of the adaptive immune system in the pathogenesis of multiple sclerosis (MS). Recent data suggest that dendritic cells (DCs), which are innate immune cells, also contribute to the pathogenesis of MS. In patients with MS, DCs are abundantly present in brain lesions, and display an altered phenotype and/or function as compared with this in healthy controls. DCs are thus in the position to pathologically influence the effector function of (auto-reactive) T and B cells. Interestingly, current first-line immunomodulating therapies for MS have been shown to restore DC phenotype and function, albeit in a non-specific manner. To date, clinical trials using agents specifically targeting DC function are ongoing. Moreover, several studies worldwide are currently investigating possible strategies to develop tolerogenic DCs. This review focuses on the phenotypic and functional alterations of conventional DCs and plasmacytoid DCs in patients with MS. Furthermore, we discuss how existing immunomodulating therapies for MS patients affect DC function and address future perspectives in the development of immunotherapies specifically targeting DCs.

Pathogen-triggered activation of plasmacytoid dendritic cells induces IL-10-producing B cells in response to Staphylococcus aureus

Induction of polyclonal B cell activation is a phenomenon observed in many types of infection, but its immunological relevance is unclear. In this study we show that staphylococcal protein A induces T cell-independent human B cell proliferation by enabling uptake of TLR-stimulating nucleic acids via the V(H)3(+) BCR. We further demonstrate that Staphylococcus aureus strains with high surface protein A expression concomitantly trigger activation of human plasmacytoid dendritic cells (pDC). Sensitivity to chloroquine, cathepsin B inhibition, and a G-rich inhibitory oligodeoxynucleotide supports the involvement of TLR9 in this context. We then identify pDC as essential cellular mediators of B cell proliferation and Ig production in response to surface protein A-bearing S. aureus. The in vivo relevancy of these findings is confirmed in a human PBMC Nod/scid(Prkdc)/γc(-/-) mouse model. Finally, we demonstrate that co-operation of pDC and B cells enhances B cell-derived IL-10 production, a cytokine associated with immunosuppression and induction of IgG4, an isotype frequently dominating the IgG response to S. aureus. IL-10 release is partially dependent on TLR2-active lipoproteins, a hallmark of the Staphylococcus species. Collectively, our data suggest that S. aureus exploits pDC and TLR to establish B cell-mediated immune tolerance.

Long-term decrease in VLA-4 expression and functional impairment of dendritic cells during natalizumab therapy in patients with multiple sclerosis

Myeloid and plasmacytoid dendritic cells (mDCs, pDCs) are central to the initiation and the regulation of immune processes in multiple sclerosis (MS). Natalizumab (NTZ) is a humanized monoclonal antibody approved for the treatment of MS that acts by blocking expression of VLA-4 integrins on the surface of leukocytes. We determined the proportions of circulating DC subsets and analyzed expression of VLA-4 expression in 6 relapsing-remitting MS patients treated with NTZ for 1 year. VLA-4 expression levels on pDCs and mDCs decreased significantly during follow-up. In vitro coculture of peripheral blood mononuclear cells and pDCs, with different doses of NTZ in healthy controls (HC) and MS patients showed dose-dependent down-regulation of VLA-4 expression levels in both MS patients and HC, and reduced functional ability to stimulate antigen-specific T-lymphocyte responses. The biological impact of NTZ may in part be attributable to inhibition of transmigration of circulating DCs into the central nervous system, but also to functional impairment of interactions between T cells and DC.

Innate-adaptive crosstalk: how dendritic cells shape immune responses in the CNS

Dendritic cells (DCs) are a heterogeneous group of professional antigen presenting cells that lie in a nexus between innate and adaptive immunity because they recognize and respond to danger signals and subsequently initiate and regulate effector T-cell responses. Initially thought to be absent from the CNS, both plasmacytoid and conventional DCs as well as DC precursors have recently been detected in several CNS compartments where they are seemingly poised for responding to injury and pathogens. Additionally, monocyte-derived DCs rapidly accumulate in the inflamed CNS where they, along with other DC subsets, may function to locally regulate effector T-cells and/or carry antigens to CNS-draining cervical lymph nodes. In this review we highlight recent research showing that (a) distinct inflammatory stimuli differentially recruit DC subsets to the CNS; (b) DC recruitment across the blood-brain barrier (BBB) is regulated by adhesion molecules, growth factors, and chemokines; and (c) DCs positively or negatively regulate immune responses in the CNS.

Disialogangliosides and TNFα alter gene expression for cytokines and chemokines in primary brain cell cultures

Gangliosides have long been implicated in multiple pathologies affecting the central nervous system. Empirical studies have suggested the possibility that gangliosides, particularly GD3, work in tandem with pro-inflammatory cytokines, especially tumor necrosis factor alpha (TNFα), to initiate or facilitate cell death in the CNS. As a step toward unraveling the metabolic pathways activated in the pathogenesis of brain cell death, we have surveyed gene expression for a host of cytokines and chemokines in primary brain cell cultures exposed to GD3, GD1b, and TNFα for 24 h. An initial screen of 98 genes on a focused mini-array revealed the expression of at least 28 genes related to cell growth, death, or inflammation in our system of mixed cells cultured from neonatal rat brains. Clear evidence of a differential response to the gangliosides or TNFα was seen in 12 genes. Quantitative PCR was used to validate the response of six of these genes. We found that both GD3 and GD1b, but not TNFα, up-regulated expression of macrophage inflammatory protein 3 (MIP3A) and interleukin-1 receptor 1 (IL1R1), but down-regulated fibroblast growth factor 13 (FGF13). The expression of FGF receptor activating protein 1 (FRAG1) and interleukin-3 receptor alpha (IL3RA) was down-regulated by GD3. Exposure to TNFα resulted in a dramatic up-regulation of IL3RA and chemokine ligand 2 (CCL2), both of which have been implicated in multiple sclerosis. Our results provide strong evidence that the expression of these genes might be critical links in the metabolic cascades leading to cell degeneration and death in the brain.

Interferon-β inhibits toll-like receptor 9 processing in multiple sclerosis

OBJECTIVE

Viral infections have been implicated in the pathogenesis of multiple sclerosis (MS). Plasmacytoid dendritic cells (pDCs) are present in peripheral blood, cerebrospinal fluid, and brain lesions of MS patients. pDCs sense viral DNA via Toll-like receptor 9 (TLR9), which has to be cleaved from the N-terminal to become functional (TLR9 processing). pDCs activated with TLR9 agonists promote T-helper type 1 (Th1)/T-helper type 17 (Th17) responses. In the animal model of MS, TLR9 agonists can induce disease. We hypothesized that pDCs are inhibited by disease-modifying therapy such as interferon (IFN)-β, consequently decreasing the frequency of MS attacks.

METHODS

We separated pDCs from healthy subjects and patients diagnosed with relapsing-remitting MS and clinically isolated syndrome. Cytokine secretion by pDCs activated with TLR9 agonists was measured by enzyme-linked immunosorbent assay and multianalyte profiling. TLR9 gene and protein expression was studied by DNA microarrays and western blot.

RESULTS

In untreated patients, pDCs activated with TLR9 agonists produced increased levels of IFN-α, a Th1-promoting cytokine, as compared to healthy subjects. In IFN-β-treated patients, activated pDCs had decreased ability to produce both IFN-α and the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor α as compared to untreated patients. pDCs separated from IFN-β-treated patients had significantly reduced levels of the processed TLR9 protein but normal levels of the full-length TLR9 protein and TLR9 gene expression as compared to untreated patients.

INTERPRETATION

This finding represents a novel immunomodulatory mechanism of IFN-β: inhibition of TLR9 processing. This results in decreased activation of pDCs by viral pathogens and, thus, may affect the frequency of MS exacerbations.

Plasmacytoid dendritic cells in multiple sclerosis: chemokine and chemokine receptor modulation by interferon-beta

Plasmacytoid dendritic cells (pDCs) are present in peripheral blood, leptomeninges and demyelinating lesions in patients with multiple sclerosis (MS). The ability of pDCs to produce chemokines and express the chemokine receptor CCR7 in MS is not known. We studied pDCs in MS patients and healthy subjects. The ability of pDCs to up-regulate CCR7 was significantly increased in untreated MS patients as compared to healthy subjects. IFN-beta treatment significantly inhibited TLR9 agonist-specific secretion of chemokines, which are ligands for CCR5-positive Th1 cells (CCL3, CCL4, and CCL5), and impaired TLR9 agonist-induced up-regulation of CCR7 and IFN-alpha in MS patients. This finding represents a new immunomodulatory effect of IFN-beta in patients with multiple sclerosis.

The role of dendritic cells in CNS autoimmunity

Multiple sclerosis (MS) is a chronic immune-mediated, central nervous system (CNS) demyelinating disease. Clinical and histopathological features suggest an inflammatory etiology involving resident CNS innate cells as well as invading adaptive immune cells. Encephalitogenic myelin-reactive T cells have been implicated in the initiation of an inflammatory cascade, eventually resulting in demyelination and axonal damage (the histological hallmarks of MS). Dendritic cells (DC) have recently emerged as key modulators of this immunopathological cascade, as supported by studies in humans and experimental disease models. In one such model, experimental autoimmune encephalomyelitis (EAE), CNS microvessel-associated DC have been shown to be essential for local antigen recognition by myelin-reactive T cells. Moreover, the functional state and compartmental distribution of DC derived from CNS and associated lymphatics seem to be limiting factors in both the induction and effector phases of EAE. Moreover, DC modulate and balance the recruitment of encephalitogenic and regulatory T cells into CNS tissue. This capacity is critically influenced by DC surface expression of co-stimulatory or co-inhibitory molecules. The fact that DC accumulate in the CNS before T cells and can direct T-cell responses suggests that they are key determinants of CNS autoimmune outcomes. Here we provide a comprehensive review of recent advances in our understanding of CNS-derived DC and their relevance to neuroinflammation.

Clinical response to interferon-beta-1a may be linked to low baseline circulating BDCA1 myeloid dendritic cells Differential role of circulating dendritic cells and CD4+ regulatory T-cells in relapsing-remitting multiple sclerosis: a 1-year longitudinal study

Many variables with association with better response to interferon-beta-1a (IFNbeta-1a) have been described, but none has yet been shown to be predictive of clinical response. In this real-life observational 1-year longitudinal study of 23 relapsing-remitting multiple sclerosis (RRMS) patients treated with subcutaneous IFNbeta-1a, we have shown a lower proportion of circulating myeloid dendritic cells (mDCs) than in healthy controls at baseline. Both univariate (Kaplan-Meier) and multivariate (Cox regression) analyses were conducted to determine which variables (age, sex, baseline EDSS, MS relapse rates 1 year and 2 years before initiating IFNbeta-1a, mDCs and plasmacytoid (pDCs) subsets, activated and regulatory CD4(+) T-cells (T(Reg))) were associated with clinical response to IFNbeta-1a. During 1 year of treatment, we observed a shift towards lower proportions of CD123(+) pDCs expression and higher numbers and function of the T(Reg). Univariate analysis disclosed that MS activity was significantly associated with baseline BDCA1(+) mDCs below < or = 0.4% (p<0.0025). Cox model analysis revealed that baseline BDCA1(+) mDCs was the most closely associated factor with MS activity on IFN treatment during the 1-year follow-up (p<0.01). A better understanding of the rules that govern the T(Reg)-DC relationship will enable scientists to better manage the immune response in MS patients.

Trends in the molecular pathogenesis and clinical therapeutics of common neurodegenerative disorders

The term neurodegenerative disorders, encompasses a variety of underlying conditions, sporadic and/or familial and are characterized by the persistent loss of neuronal subtypes. These disorders can disrupt molecular pathways, synapses, neuronal subpopulations and local circuits in specific brain regions, as well as higher-order neural networks. Abnormal network activities may result in a vicious cycle, further impairing the integrity and functions of neurons and synapses, for example, through aberrant excitation or inhibition. The most common neurodegenerative disorders are Alzheimer’s disease, Parkinson’s disease, Amyotrophic Lateral Sclerosis and Huntington’s disease. The molecular features of these disorders have been extensively researched and various unique neurotherapeutic interventions have been developed. However, there is an enormous coercion to integrate the existing knowledge in order to intensify the reliability with which neurodegenerative disorders can be diagnosed and treated. The objective of this review article is therefore to assimilate these disorders’ in terms of their neuropathology, neurogenetics, etiology, trends in pharmacological treatment, clinical management, and the use of innovative neurotherapeutic interventions.

Novel therapeutic strategies for multiple sclerosis--a multifaceted adversary

Therapeutic strategies for multiple sclerosis have radically changed in the past 15 years. Five regulatory-approved immunomodulatory agents are reasonably effective in the treatment of relapsing-remitting multiple sclerosis, and appear to delay the time to progression to disabling stages. Inhibiting disease progression remains the central challenge for the development of improved therapies. As understanding of the immunopathogenesis of multiple sclerosis has advanced, a number of novel potential therapeutics have been identified, and are discussed here. It has also become apparent that traditional views of multiple sclerosis simply as a CD4+ T-cell-mediated disease of the central nervous system are incomplete. The pathogenic role of other immune components such as the innate immune system, regulatory T cells, T helper 17 cells and B cells is reaching centre stage, opening up exciting avenues and novel potential targets to affect the natural course of multiple sclerosis.

Multiple sclerosis: reduced proportion of circulating plasmacytoid dendritic cells expressing BDCA-2 and BDCA-4 and reduced production of IL-6 and IL-10 in response to herpes simplex virus type 1

OBJECTIVE

We hypothesized that autoaggressive immune responses observed in multiple sclerosis (MS) could be associated with an imbalance in proportion of immune cell subsets and in cytokine production in response to infection, including viruses.

METHODS

We collected blood mononuclear cells (MNC) from 23 patients with MS and 23 sex- and age-matched healthy controls (HC) from the island of Sardinia, Italy, where the prevalence of MS is extraordinarily high. Using flow cytometry, we studied MNC for expression of blood dendritic cell antigens (BDCA)-2 and BDCA-4 surface markers reflecting the proportion of plasmacytoid dendritic cells (pDC) that produce type I interferons (IFNs) after virus challenge and promote Th2/anti-inflammtory cytokine production. In parallel, pro-inflammatory (interleukin [IL]-2, IL-12, IFN-gamma), anti-inflammatory (IL-4, IL-10), and immuno-regulatory/pleiotropic cytokines (type I IFNs including IFN-alpha and beta, IL-6) were measured before and after an in vitro exposure to herpes simplex virus type 1 (HSV-1).

RESULTS

The subset of lineage negative (lin(-)), BDCA-2(+) cells was lower in patients with MS compared with HC (0.08 + or - 0.02% vs 0.24 + or - 0.02%; P < 0.001). A similar pattern was observed for lin(-)BDCA-4(+) cells (0.08 + or - 0.02% vs 0.17% + or - 0.03; P < 0.01). Spontaneous productions of IL-6 (45 + or - 10 pg/mL vs 140 + or - 26 pg/mL; P < 0.01) and IL-10 (17 + or - 0.4 pg/mL vs 21 + or - 1 pg/mL; P < 0.05) by MNC were lower in patients with MS compared with HC. Spontaneous production of IL-6 (6.5 + or - 0.15 pg/mL vs 21 + or - 5 pg/mL; P < 0.01 and IL-10 (11 + or - 1 pg/mL vs 14 + or - 3 pg/mL; P < 0.05) by pDC was also lower in patients with MS compared with HC. Exposure of MNC to HSV-1 showed, in both patients with MS and HC, increased production of IFN-alpha, IL-6, and IL-10 but decreased production of IL-4. In response to HSV-1 exposure, productions of IL-6 (165 +or - 28 pg/mL vs 325 + or - 35 pg/mL; P < 0.01) and IL-10 (27 +or - 3 vs 33 + or - 3 P < 0.05) by MNC as well as by pDC (IL-6: 28 + or - 7 vs 39 + or - 12 P < 0.05; IL-10: 14 + or - 1 vs 16 + or - 3 P < 0.05) were lower in patients with MS compared with HC.

CONCLUSION

The results implicate a new evidence for altered immune cells and reduced immune responses in response to viral challenge in MS.

The role of regulatory T cells in multiple sclerosis

The dysregulation of inflammatory responses and of immune self-tolerance is considered to be a key element in the autoreactive immune response in multiple sclerosis (MS). Regulatory T (T(REG)) cells have emerged as crucial players in the pathogenetic scenario of CNS autoimmune inflammation. Targeted deletion of T(REG) cells causes spontaneous autoimmune disease in mice, whereas augmentation of T(REG)-cell function can prevent the development of or alleviate variants of experimental autoimmune encephalomyelitis, the animal model of MS. Recent findings indicate that MS itself is also accompanied by dysfunction or impaired maturation of T(REG) cells. The development and function of T(REG) cells is closely linked to dendritic cells (DCs), which have a central role in the activation and reactivation of encephalitogenic cells in the CNS. DCs and T(REG) cells have an intimate bidirectional relationship, and, in combination with other factors and cell types, certain types of DCs are capable of inducing T(REG) cells. Consequently, T(REG) cells and DCs have been recognized as potential therapeutic targets in MS. This Review compiles the current knowledge on the role and function of various subsets of T(REG) cells in MS and experimental autoimmune encephalomyelitis. We also highlight the role of tolerogenic DCs and their bidirectional interaction with T(REG) cells during CNS autoimmunity.

Plasmacytoid dendritic cells in multiple sclerosis: intracerebral recruitment and impaired maturation in response to interferon-beta

The roles of plasmacytoid dendritic cells (pDCs) and their response to interferon (IFN)-beta therapy in multiple sclerosis (MS) patients are poorly understood. We identified pDC accumulation in white matter lesions and leptomeninges of MS brains and abundant expression of the Type I IFN-induced protein MxA, mainly in perivascular CD3+ lymphocytes in lesions, indicating Type I IFN production by activated pDCs. The pDC chemoattractant chemerin was detected in intralesional cerebrovascular endothelial cells, and the chemerin receptor was expressed on infiltrating leukocytes, including pDCs. The effect of IFN-beta on pDC phenotype and function was evaluated in MS patients before and during IFN-beta treatment. Although IFN-beta did not modify the frequency and immature phenotype of circulating pDC, they showed lower expression of major histocompatibility complex Class II and blood-dendritic cell antigen 2 molecules and upregulation of CD38 and B7H1 costimulatory molecules. On exposure to CpG (a site where cytosine [C] lies next to guanine [G] in the DNA sequence [the p indicates that C and G are connected by a phosphodiester bond]) oligodeoxynucleotides in vitro, pDCs from IFN-beta-treated MS patients showed reduced expression of the pDC maturation markers CD83 and CD86 molecules; in vitro IFN-beta treatment of pDCs from healthy donors resulted in lower secretion of proinflammatory cytokines, including IFN-alpha, and a decreased ability to stimulate allogeneic T cells in response to maturative stimuli. These data indicate that IFN-beta modulates the immunologic functions of pDC, thus identifying pDCs as a novel target of IFN-beta therapy in MS patients.

Diminished myelin-specific T cell activation associated with increase in CTLA4 and Fas molecules in multiple sclerosis patients treated with IFN-beta

Multiple sclerosis (MS) is a chronic inflammatory disease of the white matter of the central nervous system (CNS) characterized by focal areas of demyelination. Interferon-beta (IFN-beta) provides an effective treatment that lessens the frequency and severity of exacerbations in relapsing-remitting multiple sclerosis (RRMS), but the mechanisms by which IFN-beta is efficient remain uncertain. The data presented here demonstrate that IFN-beta impairs the proliferative response to myelin basic protein (MBP) and myelin, as well as increasing the expression of the CTLA4 intracellular molecule. Moreover, this treatment increases the expression of surface Fas molecules and of the soluble form of these molecules. Our hypothesis is that the increase in Fas and CTLA4 molecules in MS patients may lead to lymphocyte apoptosis, which suggests possible mechanisms underlying the therapeutic response to IFN-beta.

The role of dendritic cells in multiple sclerosis

Although multiple sclerosis (MS) is a presumed T-cell- mediated disease, it is unclear what triggers the development of neuroantigen-specific T cells. Autoreactive CD4(+) T cells are activated by antigen presenting cells; dendritic cells (DCs) are the primary antigen presenting cells directing T-cell functions and are, therefore, extremely important in directing the immune pathology characteristic of MS. Three important concepts have emerged regarding DCs in MS. First, DCs are present within the healthy central nervous system (CNS) in association with the cerebrospinal fluid space and microvasculature. Therefore, the potential for sampling of CNS antigens in similar fashion to other tissues and organs exists and likely plays an integral role in CNS immunity. The degree of involvement, as well as the source, of these CNS DCs has been addressed by several studies using the experimental autoimmune encephalomyelitis animal model. Second, DCs are found within MS lesions and have been shown to be functionally abnormal in patients with MS. Lastly, therapeutics directed at DCs could potentially be engineered for treatment in MS and in fact may already be involved in the mechanisms of current immunomodulatory therapies.

CNS myeloid DCs presenting endogenous myelin peptides 'preferentially' polarize CD4+ T(H)-17 cells in relapsing EAE

Peripherally derived CD11b(+) myeloid dendritic cells (mDCs), plasmacytoid DCs, CD8alpha(+) DCs and macrophages accumulate in the central nervous system during relapsing experimental autoimmune encephalomyelitis (EAE). During acute relapsing EAE induced by a proteolipid protein peptide of amino acids 178-191, transgenic T cells (139TCR cells) specific for the relapse epitope consisting of proteolipid protein peptide amino acids 139-151 clustered with mDCs in the central nervous system, were activated and differentiated into T helper cells producing interleukin 17 (T(H)-17 cells). CNS mDCs presented endogenously acquired peptide, driving the proliferation of and production of interleukin 17 by naive 139TCR cells in vitro and in vivo. The mDCs uniquely biased T(H)-17 and not T(H)1 differentiation, correlating with their enhanced expression of transforming growth factor-beta1 and interleukins 6 and 23. Plasmacytoid DCs and CD8alpha(+) DCs were superior to macrophages but were much less efficient than mDCs in presenting endogenous peptide to induce T(H)-17 cells. Our findings indicate a critical function for CNS mDCs in driving relapses in relapsing EAE.