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Excessive levels of proinflammatory cytokines in the CNS are associated with reduced serotonin (5-HT) synthesis, a neurotransmitter with diverse immune effects. In this study, we evaluated the ability of exogenous 5-HT to modulate the T-cell behavior of patients with MS, a demyelinating autoimmune disease mediated by Th1 and Th17 cytokines. Here, 5-HT attenuated, in vitro, T-cell proliferation and Th1 and Th17 cytokines production in cell cultures from MS patients. Additionally, 5-HT reduced IFN-γ and IL-17 release by CD8 T cells. By contrast, 5-HT increased IL-10 production by CD4 T cells from MS patients. A more accurate analysis of these IL-10-secreting CD4 T cells revealed that 5-HT favors the expansion of FoxP3 CD39 regulatory T cells (Tregs) and type 1 regulatory T cells. Notably, this neurotransmitter also elevated the frequency of Treg17 cells, a novel regulatory T-cell subset. The effect of 5-HT in upregulating CD39 Treg and Treg17 cells was inversely correlated with the number of active brain lesions. Finally, in addition to directly reducing cytokine production by purified Th1 and Th17 cells, 5-HT enhanced in vitro Treg function. In summary, our data suggest that serotonin may play a protective role in the pathogenesis of MS.

SummaryMultiple sclerosis (MS) is thought to be an autoimmune disorder. It is believed that immunological events in the early stages have great impact on the disease course. Therefore, we aimed to evaluate the cytokine profile of myelin basic protein (MBP)-specific T cells from MS patients in the early phase of the disease and correlate it to clinical parameters, as well as to the effect of in vitro corticoid treatment. Peripheral T cells from MS patients were stimulated with MBP with our without hydrocortisone for 5 days. The cytokines level were determined by ELISA. The number of active brain lesions was determined by MRI scans, and the neurological disabilities were assessed by Expanded Disability Status Scale scores. Our results demonstrated that MS-derived T cells responded to MBP by producing high levels of T helper type 1 (Th1) and Th17 cytokines. Although the production of interleukin-6 (IL-6), granulocytemacrophage colony-stimulating factor, IL-17 and IL-22 was less sensitive to hydrocortisone inhibition, only IL-17 and IL-22 levels correlated with active brain lesions. The ability of hydrocortisone to inhibit IL-17 and IL-22 production by MBP-specific CD4 + T cells was inversely related to the number of active brain lesions. Finally, the production of both cytokines was significantly higher in cell cultures from Afrodescendant patients and it was less sensitive to hydrocortisone inhibition. In summary, our data suggest that IL-17-and IL-22-secreting CD4 + T cells resistant to corticoids are associated with radiological activity of the MS in early stages of the disease, mainly among Afrodescendant patients who, normally, have worse prognosis.

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Signalling through Toll-like receptors (TLRs) may play a role in the pathogenesis of autoimmune diseases, such as multiple sclerosis (MS). In the present study, the expression of TLR-2, -4 and -9 was significantly higher on CD4 and CD8 T-cells from MS patients compared to healthy individuals. Following in-vitro activation, the proportion of interleukin (IL)-17 and IL-6 CD4 and CD8 T-cells was higher in the patients. In addition, the proportion of IFN-γ-secreting TLR CD8 T-cells was increased in MS patients. Among different IL-17 T-cell phenotypes, the proportion of IL-17 TLR CD4 and CD8 T-cells producing IFN-γ or IL-6 were positively associated with the number of active brain lesions and neurological disabilities. Interestingly, activation of purified CD4 and CD8 T-cells with ligands for TLR-2 (Pam3Csk4), TLR-4 [lipopolysaccharide (LPS)] and TLR-9 [oligodeoxynucleotide (ODN)] directly induced cytokine production in MS patients. Among the pathogen-associated molecular patterns (PAMPs), Pam3Csk4 was more potent than other TLR ligands in inducing the production of all proinflammatory cytokines. Furthermore, IL-6, IFN-γ, IL-17 and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels produced by Pam3Csk4-activated CD4 cells were directly associated with disease activity. A similar correlation was observed with regard to IL-17 levels released by Pam3Csk4-stimulated CD8 T-cells and clinical parameters. In conclusion, our data suggest that the expansion of different T helper type 17 (Th17) phenotypes expressing TLR-2, -4 and -9 is associated with MS disease activity, and reveals a preferential ability of TLR-2 ligand in directly inducing the production of cytokines related to brains lesions and neurological disabilities.

SummaryInterleukin-6 (IL-6) has been implicated in the induction of pathogenic IL-17-producing T cells in autoimmune diseases, and studies evaluating the role of this cytokine in T-cell function in patients with multiple sclerosis (MS) are lacking. Our objective was to evaluate the role of IL-6 receptor (IL-6R) signalling on in vitro functional status of T cells from patients with relapsing-remitting MS during clinical remission. Our results demonstrated that, even during the remission phase, activated T cells from patients produce higher levels of IL-17, and this cytokine was positively correlated with disease severity, as determined by Expanded Disability Status Scale score. In the MS group, the blockade of IL-6R signalling by anti-IL-6R monoclonal antibody reduced IL-17 production and elevated IL-10 release by activated CD4 + T cells, but it did not alter the production of these cytokines by activated CD8 + T cells. Blockade of IL-6R signalling also reduced the ability of monocytes to up-regulate T helper type 17 phenotype in patients with MS. Finally, both cell proliferation and IL-17 release by CD4 + and, mainly, CD8 + T cells from patients with MS were less sensitive to hydrocortisone inhibition than control group. Interestingly, IL-6R signalling blockade restored the ability of hydrocortisone to inhibit both T-cell proliferation and IL-17 production. Collectively, these results suggest that IL-6 might be involved in MS pathogenesis by enhancing IL-17 production and reducing corticoid inhibitory effects on activated T cells.

BackgroundHigh mobility group box protein 1 (HMGB1) is a transcriptional regulator that is receiving increasing attention in autoimmune disorders including multiple sclerosis (MS). Here, we investigated the role of HMGB1 in the peripheral blood compartment from MS patients.MethodsHMGB1 mRNA expression levels were determined by PCR in peripheral blood mononuclear cells (PBMC) of 29 healthy controls and 57 untreated MS patients (26 with relapsing-remitting MS - RRMS, 13 with secondary progressive MS - SPMS, and 18 with primary progressive MS - PPMS). HMGB1 protein levels were measured by ELISA in serum samples from 18 HC and 37 untreated MS patients (13 with RRMS, 14 with SPMS, and 10 with PPMS).ResultsHMGB1 expression levels were increased in PBMC from the whole MS group compared with controls (P = 0.03). Further stratification of the MS group revealed higher expression levels in PBMC from patients with relapse-onset MS, and differences were statistically significant for RRMS patients compared with PPMS patients and controls (P = 4 × 10−5 and P = 0.005, respectively) and also for SPMS patients compared with PPMS patients (P = 0.001). HMGB1 serum levels were increased in the whole MS group compared with controls (P = 2 × 10−4). In MS clinical forms, the highest HMGB1 serum levels were observed in RRMS patients, and differences were statistically significant compared to PPMS patients (P = 5 × 10−5), SPMS patients (P = 0.001), and controls (P = 0.001).ConclusionsThese results point to a role of HMGB1 mRNA and protein levels as disease activity biomarkers to discriminate the more inflammatory relapse-onset MS forms, particularly RRMS, from the less inflammatory PPMS form of the disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0269-9) contains supplementary material, which is available to authorized users.

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