Decreased Dicer expression is linked to increased expression of co-stimulatory molecule CD80 on B cells in multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the central nervous system. B cells have been strongly implicated in disease pathogenesis based on clinical trials with B-cell ablation. There is a growing body of evidence linking microRNAs with regulation of the immune system. Dicer, a key enzyme involved in microRNA biogenesis, is necessary for normal B-cell function. OBJECTIVE: We aimed to determine whether Dicer expression is impaired in B cells and is linked to increased expression co-stimulatory molecules in patients with MS. METHODS: B cells were separated from blood samples of MS patients and healthy subjects. Expression of Dicer and co-stimulatory molecules CD80 and CD86 was tested. The effect of Dicer modulation on CD80 and CD86 expression in B cells was studied. RESULTS: Dicer expression was decreased in B cells but not in monocytes of patients with MS compared with healthy subjects. CD80 and CD86 expression was increased on B cells of MS patients compared with healthy subjects. Inhibition of Dicer expression in B cells by small interfering RNA led to increased expression of CD80. CONCLUSION: Dicer expression is decreased and is mechanistically linked to increased expression of co-stimulatory molecule CD80 in B cells of patients with MS. This may contribute to activation of immune responses in MS.

Acute demyelinating lesions with restricted diffusion in multiple sclerosis.

BACKGROUND AND OBJECTIVES: It is widely accepted that typical acute demyelinating lesions in relapsing-remitting multiple sclerosis (RRMS) exhibit vasogenic edema with increased diffusion, as demonstrated by an increased apparent diffusion coefficient on MRI. In contrast, acute ischemic lesions demonstrate cytotoxic edema with restricted diffusion. Recent reports have documented selected cases of acute demyelinating lesions exhibiting restricted diffusion (ADLRD) in MS. We aimed to assess the morphologies, distributions, signal characteristics and changes over time of nine ADLRD. An additional goal was to obtain clinical correlations and relate our findings to all previously published case reports describing ADLRD. METHODS: A retrospective case series study was performed at two academic centers. MRI characteristics of nine ADLRD found in six RRMS patients were compared with typical active symptomatic contrast-enhancing lesions with increased or normal diffusion in control RRMS patients. RESULTS: The average size of ADLRD was not significantly different from typical lesions. A periventricular location and faint signal on T2-weighted images were significantly more common for ADLRD compared with typical lesions. Two patients with ADLRD on initial MRI exhibited new ADLRD on their follow up scans. CONCLUSION: Our results and review of prior published cases suggest that ADLRD represent a new variant of MS lesion. The restricted diffusion that is a characteristic of ADLRD on MRI is a new challenge in the differential diagnosis of stroke in young adults. The pathogenesis of ADLRD remains to be understood.

Fecal Lcn-2 level is a sensitive biological indicator for gut dysbiosis and intestinal inflammation in multiple sclerosis.

Multiple Sclerosis (MS) has been reported to be associated with intestinal inflammation and gut dysbiosis. To elucidate the underlying biology of MS-linked gut inflammation, we investigated gut infiltration of immune cells during the development of spontaneous experimental autoimmune encephalomyelitis (EAE) in humanized transgenic (Tg) mice expressing HLA-DR2a and human T cell receptor (TCR) specific for myelin basic protein peptide (MBP87-99)/HLA-DR2a complexes. Strikingly, we noted the simultaneous development of EAE and colitis, suggesting a link between autoimmune diseases of the central nervous system (CNS) and intestinal inflammation. Examination of the colon in these mice revealed the infiltration of MBP-specific Th17 cells as well as recruitment of neutrophils. Furthermore, we observed that fecal Lipocalin-2 (Lcn-2), a biomarker of intestinal inflammation, was significantly elevated and predominantly produced by the gut-infiltrating neutrophils. We then extended our findings to MS patients and demonstrate that their fecal Lcn-2 levels are significantly elevated compared to healthy donors (HDs). The elevation of fecal Lcn-2 levels correlated with reduced bacterial diversity and increased levels of other intestinal inflammation markers including neutrophil elastase and calprotectin. Of interest, bacteria thought to be beneficial for inflammatory bowel disease (IBD) such as Anaerobutyricum, Blautia, and Roseburia, were reduced in fecal Lcn-2-high MS patients. We also observed a decreasing trend in serum acetate (a short-chain fatty acid) levels in MS Lcn-2-high patients compared to HDs. Furthermore, a decrease in the relative abundance of Blautia massiliensis was significantly associated with a reduction of acetate in the serum of MS patients. This study suggests that gut infiltration of Th17 cells and recruitment of neutrophils are associated with the development of gut dysbiosis and intestinal inflammation, and that fecal Lcn-2 level is a sensitive biological indicator for gut dysbiosis in multiple sclerosis.

Plasmacytoid dendritic cells are increased in cerebrospinal fluid of untreated patients during multiple sclerosis relapse.

The plasmacytoid dendritic cells (pDCs) express a high level of Toll-like receptor 9 (TLR-9), which recognizes viral DNA. Activated via TLR-9, pDCs also secrete large amounts of type I interferon which are involved either in stimulation or down regulation of immune response in multiple sclerosis (MS). In the present study, we determinate pDCs levels by flow cytometry in Cerebrospinal Fluid (CSF) and Peripheral Blood from MS patients in relapsing and in remitting phases of the disease, comparing with other non-inflammatory diseases (OND). We provide evidence that MS patients in relapse without any treatment have a significantly (p < 0.01) higher percentage of pDCs in CSF than do patients in remission or those with OND. No change in the percentage of pDCs was observed in the peripheral blood of any of these patients. The increase of pDCs in central nervous system during relapse may be explained either by a virus infection or a down regulatory process.

Interferon-ß 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)-ß, 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-ß-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-ß-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-ß: inhibition of TLR9 processing. This results in decreased activation of pDCs by viral pathogens and, thus, may affect the frequency of MS exacerbations.

Optic neuritis incidence is increased in spring months in patients with asymptomatic demyelinating lesions.

Optic neuritis (ON) patients can be divided into two groups based on the presence or absence of asymptomatic demyelinating lesions (ADLs) on brain MRI. The presence of ADLs is associated with an increased risk of progression to clinically definite multiple sclerosis (CDMS). The clinical data and brain MRI of 110 patients with acute unilateral ON were analyzed. Patients with ADLs had a significantly higher incidence of ON in spring months as compared with patients with no ADLs (p = 0.0024). Increased incidence of ON in spring months was seen in patients with ADLs whether or not they were diagnosed with CDMS on follow-up.

MMP-9 expression is increased in B lymphocytes during multiple sclerosis exacerbation and is regulated by microRNA-320a.

B cells are necessary to maintain disease activity in relapsing multiple sclerosis (MS) and produce matrix metallopeptidase-9 (MMP-9), which disrupts the blood-brain barrier. MMP-9 protein expression was increased and expression of microRNA-320a (miR-320a), which targets MMP-9 mRNA, was significantly decreased in B lymphocytes of MS patients during a disease relapse compared to remission. Functional significance of these findings was demonstrated by transfecting human B lymphocytes with miR-320a inhibitor, which led to increased MMP-9 expression and secretion. In summary, expression of miR-320a is decreased in B cells of MS patients and may contribute to increased blood-brain barrier permeability and neurological disability.

Comparison of IFN-ß inducible gene expression in primary-progressive and relapsing-remitting multiple sclerosis.

Interferon (IFN)-ß is a type I IFN commonly produced by the innate immune system in response to viral infection. IFN-ß is also used for the treatment of patients with the relapsing-remitting form of multiple sclerosis (RRMS); however, IFN-ß therapy is unable to confer a significant benefit for primary-progressive MS (PPMS) patients. In this study, we assessed the gene profiles of peripheral blood mononuclear cells (PBMCs) isolated from PPMS, RRMS, and healthy donors (HD) in response to IFN-ß treatment in vitro to examine genetic mechanisms underlying the inadequate response of IFN-ß therapy in PPMS patients. Here, we show that HLA-G was significantly less up-regulated in response to IFN-ß in PBMCs from PPMS compared to those from RRMS. This data suggests HLA-G to be a possible candidate gene found impaired in IFN-ß-mediated immune regulation in PPMS patients.

Are Periventricular Lesions Specific for Multiple Sclerosis?

BACKGROUND: The presence of periventricular lesions (PVL) on MRI scans is part of the revised McDonald multiple sclerosis (MS) diagnostic criteria. However, PVL can be found in other neurological diseases including stroke and migraine. Migraine is highly prevalent in patients with MS. OBJECTIVE: To determine if PVL are specific for patients with MS compared to stroke and migraine. METHODS: We studied patients diagnosed with clinically isolated syndrome (CIS), relapsing-remitting MS (RRMS), migraine, and ischemic stroke. The number, location and the volume of PVL were identified on brain MRI scans and analyzed. RESULTS: The number and volume of PVL adjacent to the body and the posterior horn of the lateral ventricles were significantly increased on fluid-attenuated inversion recovery MRI in RRMS compared to migraine. There were no significant differences in the total number and volume of PVL in ischemic stroke patients compared to the age-matched RRMS patients nor in the number and volume of PVL adjacent to the anterior and temporal horns of the lateral ventricles on FLAIR images in migraine compared to CIS or RRMS. CONCLUSION: In contrast to PVL adjacent to the body and the posterior horn of the lateral ventricles, PVL adjacent to the anterior and temporal horns of the lateral ventricles may not be specific for CIS/RRMS when compared to migraine, the disease highly prevalent among patients with MS. PVL are not specific for MS when compared to ischemic stroke.

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.

Multiple sclerosis-linked and interferon-beta-regulated gene expression in plasmacytoid dendritic cells.

The cause of multiple sclerosis (MS) is not known and the mechanism of interferon-beta, a disease-modifying treatment, is not well-understood. We studied gene expression in plasmacytoid dendritic cells (pDCs), antigen-presenting cells implicated in MS pathogenesis. PDCs were separated from healthy donors and MS patients at two time points: before and after initiation of treatment with interferon-beta. Expression of selected MS-linked and interferon-beta-regulated genes was validated with single assays. We have identified 60 genes which were abnormally expressed in MS patients and were corrected after treatment. These genes could be studied as potential MS biomarkers and possible therapeutic targets in MS.

Acute multiple sclerosis lesion: conversion of restricted diffusion due to vasogenic edema.

It is widely accepted that acute demyelinating plaques in patients with multiple sclerosis (MS) demonstrate increased apparent diffusion coefficient (ADC) and increased diffusion weighted imaging (DWI) signals on MRI. These imaging characteristics in acute MS lesions have been postulated to be due to peripheral vasogenic edema that typically increases the ADC. This assumption is commonly used to differentiate stroke from MS lesions since acute and subacute stroke lesions demonstrate increased DWI signal with reduced ADC due to acute cytotoxic edema. We report a case of active relapsing-remitting MS with two new symptomatic contrast-enhancing lesions. The lesions had reduced diffusion on the ADC map in the early acute phase of MS exacerbation. The reduced ADC signal was subsequently "converted" to increased ADC signal that coincided with the development of profound peripheral vasogenic edema seen on T2-weighted images. To our knowledge, this is the first serial MRI study describing decreased ADC signal in the early acute phase of contrast-enhancing MS lesion. The implications of decreased diffusion in the acute phase of MS lesions for the disease pathogenesis are discussed.