Nathalie Muls

Amyloid precursor protein controls cholesterol turnover needed for neuronal activity.

Perturbation of lipid metabolism favours progression of Alzheimer disease, in which processing of Amyloid Precursor Protein (APP) has important implications. APP cleavage is tightly regulated by cholesterol and APP fragments regulate lipid homeostasis. Here, we investigated whether up or down regulation of full‐length APP expression affected neuronal lipid metabolism. Expression of APP decreased HMG‐CoA reductase (HMGCR)‐mediated cholesterol biosynthesis and SREBP mRNA levels, while its down regulation had opposite effects. APP and SREBP1 co‐immunoprecipitated and co‐localized in the Golgi. This interaction prevented Site‐2 protease‐mediated processing of SREBP1, leading to inhibition of transcription of its target genes. A GXXXG motif in APP sequence was critical for regulation of HMGCR expression. In astrocytes, APP and SREBP1 did not interact nor did APP affect cholesterol biosynthesis. Neuronal expression of APP decreased both HMGCR and cholesterol 24‐hydroxylase mRNA levels and consequently cholesterol turnover, leading to inhibition of neuronal activity, which was rescued by geranylgeraniol, generated in the mevalonate pathway, in both APP expressing and mevastatin treated neurons. We conclude that APP controls cholesterol turnover needed for neuronal activity.

Upregulation of IL-17, but not of IL-9, in circulating cells of CIS and relapsing MS patients. Impact of corticosteroid therapy on the cytokine network.

The concomitant production of IL-17A and IL-9, both Th17 cytokines, has not been compared in MS patients. We show that IL-17A but not IL-9 expression by CD3(+) cells was increased during a MS relapse. Co-expression of IL-17A and IL-9 was marginal. In addition to Th1 and Th2 cytokines, IL-17A, IL-6 and IL-23p19 were down-regulated by ivMP, but Foxp3 was not, while an increase in IL-10, TGF-β1 and IL-27p28 mRNA was observed. This change in the Th17, Treg and IL-10 balance could be an additional mechanism by which corticosteroids shorten the duration of a MS relapse and promote recovery.

Fingolimod increases CD39-expressing regulatory T cells in multiple sclerosis patients.

Background Multiple sclerosis (MS) likely results from an imbalance between regulatory and inflammatory immune processes. CD39 is an ectoenzyme that cleaves ATP to AMP and has been suggested as a novel regulatory T cells (Treg) marker. As ATP has numerous proinflammatory effects, its degradation by CD39 has anti-inflammatory influence. The purpose of this study was to explore regulatory and inflammatory mechanisms activated in fingolimod treated MS patients. Methods and Findings Peripheral blood mononuclear cells (PBMCs) were isolated from relapsing-remitting MS patients before starting fingolimod and three months after therapy start. mRNA expression was assessed in ex vivo PBMCs. The proportions of CD8, B cells, CD4 and CD39-expressing cells were analysed by flow cytometry. Treg proportion was quantified by flow cytometry and methylation-specific qPCR. Fingolimod treatment increased mRNA levels of CD39, AHR and CYP1B1 but decreased mRNA expression of IL-17, IL-22 and FOXP3 mRNA in PBMCs. B cells, CD4+ cells and Treg proportions were significantly reduced by this treatment, but remaining CD4+ T cells were enriched in FOXP3+ cells and in CD39-expressing Tregs. Conclusions In addition to the decrease in circulating CD4+ T cells and CD19+ B cells, our findings highlight additional immunoregulatory mechanisms induced by fingolimod.

IL-22, GM-CSF and IL-17 in peripheral CD4+ T cell subpopulations during multiple sclerosis relapses and remission. Impact of corticosteroid therapy.

Multiple sclerosis (MS) is thought to be a Th17-mediated dysimmune disease of the central nervous system. However, recent publications have questioned the pathogenicity of IL-17 per se and rather suggest the implication of other Th17-related inflammatory mediators. Therefore, we studied the expression of GM-CSF, IL-22, IL-24, IL-26 and CD39 in peripheral blood mononuclear cells (PBMCs) from MS patients during relapses, remission and following corticosteroid treatment. We performed qPCR to measure mRNA levels from ex vivo or in vitro-stimulated PBMCs. Cytokine levels were determined by ELISA. We used flow cytometry to assess GM-CSF+, IL-22+ and CD39+ cells in relationship to IL-17+ CD4+ T cells. Our results showed that IL-22 mRNA and IL-22+CD4+ lymphocytes are increased in circulating cells of relapsing MS patients compared to remitting patients while GM-CSF was unchanged. We have further shown that 12.9, 39 and 12.4% of Th17 cells from MS patients during relapses expressed IL-22, GM-CSF and CD39 respectively. No changes in these proportions were found in stable MS patients. However, the majority of GM-CSF+ or IL-22+ T cells did not co-express IL-17. GM-CSF mRNA, but not IL-22 mRNA, was dramatically decreased ex vivo by ivMP. Our results contribute to a better characterisation of Th17, Th22 and ThGM-CSF cells in the setting of MS and according to disease activity.

Regulation of Treg-associated CD39 in multiple sclerosis and effects of corticotherapy during relapse.

Background: Accumulating data highlight proinflammatory processes leading to MS relapses. Whether anti-inflammatory mechanisms are concomitantly activated is unclear. The ectonucleotidase CD39 has been described as a novel T regulatory cell (Treg) marker. The purpose of this study was to explore whether regulatory mechanisms are activated during MS relapses and reinforced by intravenous methylprednisolone (ivMP). Methods: Blood samples were collected from stable and relapsing MS patients and healthy controls. We used FOXP3 methylation-specific qPCR and CD4+CD25highFOXP3+ analysis to quantify Tregs. Cytokine mRNA expression levels were measured in peripheral blood mononuclear cells (PBMCs) and in CD4+ T cells. CD39 expression was determined by flow cytometry in monocytes, NK, T and B cells. CD39 enzymatic activity was assessed by ATP luminometry. Results: The proportion of Tregs was similar in relapsing MS patients and healthy controls. CD39 mRNA level was higher in PBMCs of relapsing MS patients than in controls. The proportion of CD39-expressing Tregs was higher in MS patients. IvMP decreased the overall proportion of Tregs while it increased CD39 mRNA levels, the proportions of CD39-expressing Tregs and monocytes as well as CD39 ectonucleotidase activity. Conclusions: Our data suggest that immunoregulatory mechanisms are ongoing in MS patients, particularly during relapses, and strengthened by ivMP.

Free Kappa light chains in neuroinflammatory disorders: Complement rather than substitute?

The detection of cerebrospinal fluid (CSF)‐specific IgG oligoclonal bands (OCB) by isoelectric focusing (IEF) is widely used to help diagnose inflammatory neurological disorders (IND), including multiple sclerosis. However, the quantification of free light chains (FLC) is increasingly evaluated as a surrogate method to determine the presence of an intrathecal inflammatory process. The objective of this study was to evaluate the diagnostic performance of kappa (κ) FLC measurement in comparison with OCB detection by IEF.