25-Hydroxycholesterol in health and diseases.

Cholesterol is an essential structural component of all membranes of mammalian cells where it plays a fundamental role not only in cellular architecture, but also, for example, in signaling pathway transduction, endocytosis process, receptor functioning and recycling, or cytoskeleton remodeling. Consequently, intracellular cholesterol concentrations are tightly regulated by complex processes, including cholesterol synthesis, uptake from circulating lipoproteins, lipid transfer to these lipoproteins, esterification, and metabolization into oxysterols that are intermediates for bile acids. Oxysterols have been considered for long time as sterol waste products, but a large body of evidence has clearly demonstrated that they play key roles in central nervous system functioning, immune cell response, cell death, or migration and are involved in age-related diseases, cancers, autoimmunity, or neurological disorders. Among all the existing oxysterols, this review summarizes basic as well as recent knowledge on 25-hydroxycholesterol which is mainly produced during inflammatory or infectious situations and that in turn contributes to immune response, central nervous system disorders, atherosclerosis, macular degeneration, or cancer development. Effects of its metabolite 7α,25-dihydroxycholesterol are also presented and discussed.

Ocrelizumab Impairs the Phenotype and Function of Memory CD8+ T Cells: A 1-Year Longitudinal Study in Patients With Multiple Sclerosis.

BACKGROUND AND OBJECTIVE: Depleting CD20+ B cells is the primary mechanism by which ocrelizumab (OCRE) is efficient in persons with multiple sclerosis (pwMS). However, the exact role of OCRE on other immune cell subsets directly or indirectly remains elusive. The purpose of this study is to characterize the dynamics of peripheral immune cells of pwMS on OCRE. METHODS: We collected blood samples from 38 pwMS before OCRE onset (T0) and at 6 and 12 months (T6, T12) after initiation. To cover the immune cell diversity, using mass cytometry time of flight, we designed a 38-parameter panel to analyze B, T, and innate immune cell markers and CNS migratory markers. In parallel, viral-specific CD8+ T-cell responses were assessed by the quantification of interferon-γ secretion using the enzyme-linked immunospot assay on cytomegalovirus, Epstein-Barr virus, and influenza stimulations. RESULTS: Beside B-cell depletion, we observed a loss in memory CD8+CD20+ and central memory CD8+ T cells but not in CD4+CD20+ T cells already at T6 and T12 (p < 0.001). The loss of memory CD8+ T cells correlated with a lower CXCR3 expression (p < 0.001) and CNS-related LFA-1 integrin expression (p < 0.001) as well as a reduced antiviral cellular immune response observed at both time points (p < 0.001). Of note, we did not observe major changes in the phenotype of the other cell types studied. Seven of 38 (18.4%) patients in our cohort presented with infections while on OCRE; 4 of which were switched from dimethyl fumarate. Finally, using a mixed linear model on mass cytometry data, we demonstrated that the immunomodulation induced by previous disease-modifying therapies (DMTs) was prolonged over the period of the study. DISCUSSION: In addition to its well-known role on B cells, our data suggest that OCRE also acts on CD8+ T cells by depleting the memory compartment. These changes in CD8+ T cells may be an asset in the action of OCRE on MS course but might also contribute to explain the increased occurrence of infections in these patients. Finally, although more data are needed to confirm this observation, it suggests that clinicians should pay a special attention to an increased infection risk in pwMS switched from other DMTs to OCRE.

Association of age and disease duration with comorbidities and disability: A study of the Swiss Multiple Sclerosis Registry.

BACKGROUND: While comorbidities increase with age, duration of multiple sclerosis (MS) leads to disability accumulation in persons with MS. The influence of ageing vis-a-vis MS duration remains largely unexplored. We studied the independent associations of ageing and MS duration with disability and comorbidities in the Swiss MS Registry participants. METHODS: Self-reported data was cross-sectionally analyzed using confounder-adjusted logistic regression models for 6 outcomes: cancer, type 2 diabetes (T2D), hypertension, cardiac diseases, depression, and having at least moderate or severe gait disability. Using cubic splines, we explored non-linear changes in risk shapes. RESULTS: Among 1615 participants age was associated with cardiac diseases (OR 1.05, 95% CI [1.02, 2.08]), hypertension (OR 1.08, 95% CI [1.06, 2.10]), T2D (OR 1.10, 95%CI [1.05, 1.16]) and cancer (OR 1.04, 95% CI [1.01, 1.07]). MS duration was not associated with comorbidities, except for cardiac diseases (OR 1.03, 95% CI [1.00, 1.06]). MS duration and age were independently associated with having at least moderate gait disability (OR 1.06, 95% CI [1.04, 1.07]; OR 1.04, 95% CI [1.02, 1.05], respectively), and MS duration was associated with severe gait disability (OR 1.05, 95% CI [1.03, 1.08]). The spline analysis suggested a non-linear increase of having at least moderate gait disability with age. CONCLUSIONS: Presence of comorbidities was largely associated with age only. Having at least moderate gait disability was associated with both age and MS duration, while having severe gait disabity was associated with MS duration only.

Discussing Challenges in Diagnosis of Tuberculous Meningitis and Neurosarcoidosis.

Isolated chronic granulomatous meningitis remains a diagnostic challenge for the physician. Symptoms are often nonspecific and ancillary tests have low-sensitivity rates, which may delay targeted treatment and lead to increased morbidity and mortality. Here, we discuss the challenges in diagnosing and treating patients with chronic meningitis by reporting two cases of previously healthy patients who presented with granulomatous meningitis on brain biopsy.

The central vein sign in multiple sclerosis patients with vascular comorbidities.

BACKGROUND: The central vein sign (CVS) is an imaging biomarker able to differentiate multiple sclerosis (MS) from other conditions causing similar appearance lesions on magnetic resonance imaging (MRI), including cerebral small vessel disease (CSVD). However, the impact of vascular risk factors (VRFs) for CSVD on the percentage of CVS positive (CVS+) lesions in MS has never been evaluated. OBJECTIVE: To investigate the association between different VRFs and the percentage of CVS+ lesions in MS. METHODS: In 50 MS patients, 3T brain MRIs (including high-resolution 3-dimensional T2*-weighted images) were analyzed for the presence of the CVS and MRI markers of CSVD. A backward stepwise regression model was used to predict the combined predictive effect of VRF (i.e. age, hypertension, diabetes, obesity, ever-smoking, and hypercholesterolemia) and MRI markers of CSVD on the CVS. RESULTS: The median frequency of CVS+ lesions was 71% (range: 35%-100%). In univariate analysis, age (p < 0.0001), hypertension (p < 0.001), diabetes (p < 0.01), obesity (p < 0.01), smoking (p < 0.05), and the presence of enlarged-perivascular-spaces on MRI (p < 0.005) were all associated with a lower percentage of CVS+ lesions. The stepwise regression model showed that age and arterial hypertension were both associated with the percentage of CVS+ lesions in MS (adjusted R2 = 0.46; p < 0.0001 and p = 0.01, respectively). CONCLUSION: The proportion of CVS+ lesions significantly decreases in older and hypertensive MS patients. Although this study was conducted in patients with an already established MS diagnosis, the diagnostic yield of the previously proposed 35% CVS proportion-based diagnostic threshold appears to be not affected. Overall these results suggest that the presence of VRF for CSVD should be taken into account during the CVS assessment.

IL-27 Induces Th17 Differentiation in the Absence of STAT1 Signaling.

It is known that differentiation of Th17 cells is promoted by activation of STAT3 and inhibited by activation of STAT1. Although both transcription factors are activated by several cytokines, including IL-6, IL-21, and IL-27, each of these cytokines has a very different effect on Th17 differentiation, ranging from strong induction (IL-6) to strong inhibition (IL-27). To determine the molecular basis for these differences, we measured STAT3 and STAT1 activation profiles for IL-6, IL-21, and IL-27, as well as for cytokine pairs over time. We found that the ratio of activated STAT3/activated STAT1 is crucial in determining whether cytokines promote or inhibit Th17 differentiation. IL-6 and IL-21 induced p-STAT3/p-STAT1 ratios > 1, leading to the promotion of Th17 differentiation, whereas IL-27 or IL-6+IL-27 induced p-STAT3/p-STAT1 ratios < 1, resulting in inhibition of Th17 differentiation. Consistent with these findings, we show that IL-27 induces sufficient p-STAT3 to promote Th17 differentiation in the absence of STAT1. Furthermore, IL-27-induced STAT1-deficient T cells were indistinguishable from bona fide highly proinflammatory Th17 cells because they induced severe experimental autoimmune encephalomyelitis upon adoptive transfer. Our results suggest that the ratio of p-STAT3/p-STAT1 induced by a cytokine or cytokine pairs can be used to predict whether they induce a competent Th17-differentiation program.

Ag-presenting CpG-activated pDCs prime Th17 cells that induce tumor regression.

Plasmacytoid dendritic cells (pDC) rapidly and massively produce type I IFN and other inflammatory cytokines in response to foreign nucleic acids, thereby indirectly influencing T-cell responses. Moreover, antigen (Ag)-presenting pDCs directly regulate T-cell differentiation. Depending on the immune environment, pDCs exhibit either tolerogenic or immunogenic properties. Here, we show that CpG-activated pDCs promote efficient Th17 differentiation. Indeed, Th17 responses are defective in mice selectively lacking MHCII on pDCs upon antigenic challenge. Importantly, in those mice, the frequency of Th17 cells infiltrating solid tumors is impaired. As a result, the recruitment of infiltrating leukocytes in tumors, including tumor-specific cytotoxic T lymphocytes (CTL), is altered and results in increased tumor growth. Importantly, following immunization with tumor Ag and CpG-B, MHCII-restricted Ag presentation by pDCs promotes the differentiation of antitumor Th17 cells that induce intratumor CTL recruitment and subsequent regression of established tumors. Our results highlight a new role for Ag presenting activated pDCs in promoting the development of Th17 cells and impacting on antitumor immunity.

SOCS3 transactivation by PPARγ prevents IL-17-driven cancer growth.

Activation of the transcription factor PPARγ by the n-3 fatty acid docosahexaenoic acid (DHA) is implicated in controlling proinflammatory cytokine secretion, but the intracellular signaling pathways engaged by PPARγ are incompletely characterized. Here, we identify the adapter-encoding gene SOCS3 as a critical transcriptional target of PPARγ. SOCS3 promoter binding and gene transactivation by PPARγ was associated with a repression in differentiation of proinflammatory T-helper (TH)17 cells. Accordingly, TH17 cells induced in vitro displayed increased SOCS3 expression and diminished capacity to produce interleukin (IL)-17 following activation of PPARγ by DHA. Furthermore, naïve CD4 T cells derived from mice fed a DHA-enriched diet displayed less capability to differentiate into TH17 cells. In two different mouse models of cancer, DHA prevented tumor outgrowth and angiogenesis in an IL-17-dependent manner. Altogether, our results uncover a novel molecular pathway by which PPARγ-induced SOCS3 expression prevents IL-17-mediated cancer growth.

The aryl hydrocarbon receptor interacts with c-Maf to promote the differentiation of type 1 regulatory T cells induced by IL-27.

Type 1 regulatory T cells (Tr1 cells ) that produce interleukin 10 (IL-10) are instrumental in the prevention of tissue inflammation, autoimmunity and graft-versus-host disease. The transcription factor c-Maf is essential for the induction of IL-10 by Tr1 cells, but the molecular mechanisms that lead to the development of these cells remain unclear. Here we show that the ligand-activated transcription factor aryl hydrocarbon receptor (AhR), which was induced by IL-27, acted in synergy with c-Maf to promote the development of Tr1 cells. After T cell activation under Tr1-skewing conditions, the AhR bound to c-Maf and promoted transactivation of the Il10 and Il21 promoters, which resulted in the generation of Tr1 cells and the amelioration of experimental autoimmune encephalomyelitis. Manipulating AhR signaling could therefore be beneficial in the resolution of excessive inflammatory responses.

Molecular pathways in the induction of interleukin-27-driven regulatory type 1 cells.

Type 1 regulatory (Tr1) cells have emerged as key players in the prevention of autoimmunity. They produce high levels of the immunosuppressive cytokine interleukin (IL)-10 and confer protection against a wide panel of autoimmune diseases. However, the molecular pathways leading to their generation have long remained elusive. We have recently identified IL-27, a member of the IL-12 cytokine family, as a novel cytokine that induces Tr1 cells. Further analysis of IL-27-driven Tr1 cells have identified a critical role of the transcription factor avian musculoaponeurotic fibrosarcoma v-maf and of IL-21 in the generation of IL-27-induced Tr1 cells. Importantly, IL-27 also induces Tr1 cells in humans, suggesting that IL-27 administration may dampen tissue inflammation in humans as well. Here, we review the role of IL-27 in the generation of Tr1 cells and discuss its potential to alleviate autoimmune diseases.

Cutting edge: IL-27 induces the transcription factor c-Maf, cytokine IL-21, and the costimulatory receptor ICOS that coordinately act together to promote differentiation of IL-10-producing Tr1 cells.

IL-27 has recently been identified as a differentiation factor for the generation of IL-10-producing regulatory type 1 (Tr1) T cells. However, how IL-27 induces the expansion of Tr1 cells has not been elucidated. In this study we demonstrate that IL-27 drives the expansion and differentiation of IL-10-producing murine Tr1 cells by inducing three key elements: the transcription factor c-Maf, the cytokine IL-21, and the costimulatory receptor ICOS. IL-27-driven c-Maf expression transactivates IL-21 production, which acts as an autocrine growth factor for the expansion and/or maintenance of IL-27-induced Tr1 cells. ICOS further promotes IL-27-driven Tr1 cells. Each of those elements is essential, because loss of c-Maf, IL-21-signaling, or ICOS decreases the frequency of IL-27-induced differentiation of IL-10-producing Tr1 cells.

Combined antiviral-immunosuppressive treatment in human T-lymphotrophic virus 1-Sjögren-associated myelopathy.

BACKGROUND: In several studies, antiretroviral drugs (principally zidovudine) have been used with success in the treatment of myelopathy associated with human T-lymphotrophic virus 1 (HTLV-1) (tropical spastic paraparesis-HTLV-1-associated myelopathy). The retrovirus HTLV-1 has been implicated as a causative agent of Sjögren syndrome (SS) in clinical reports and murine experiments. Moreover, a recognized complication of primary SS is a myelopathy, which has been shown in case reports to respond to immunosuppressive treatment. OBJECTIVE: To describe a patient with a rapidly progressive, extensive myelopathy with evidence of HTLV-1 infection and SS (probably secondary to HTLV-1) in whom we achieved spectacular therapeutic success using combined immunosuppressive and antiviral therapy. DESIGN: Case report. SETTING: University hospital. Patient A young Haitian woman diagnosed with HTLV-1 and SS developed extensive myelopathy leading to severe disability. MAIN OUTCOME MEASURES: Clinical and radiological improvement. RESULTS: Spectacular radiological and clinical recovery as well as stabilization were achieved with combined antiviral and immunosuppressant treatment. Follow-up at 2 years showed no signs of relapse. CONCLUSIONS: Both tropical spastic paraparesis-HTLV-1-associated myelopathy and Sjögren myelopathy are potentially very disabling. Rapidly progressive myelopathy secondary to SS necessitates the introduction of immunosuppressant therapies. The presence of HTLV-1 may confer the necessity to add antiviral therapy.