Endothelial cell-derived oxysterol ablation attenuates experimental autoimmune encephalomyelitis.

The vasculature is a key regulator of leukocyte trafficking into the central nervous system (CNS) during inflammatory diseases including multiple sclerosis (MS). However, the impact of endothelial-derived factors on CNS immune responses remains unknown. Bioactive lipids, in particular oxysterols downstream of Cholesterol-25-hydroxylase (Ch25h), promote neuroinflammation but their functions in the CNS are not well-understood. Using floxed-reporter Ch25h knock-in mice, we trace Ch25h expression to CNS endothelial cells (ECs) and myeloid cells and demonstrate that Ch25h ablation specifically from ECs attenuates experimental autoimmune encephalomyelitis (EAE). Mechanistically, inflamed Ch25h-deficient CNS ECs display altered lipid metabolism favoring polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) expansion, which suppresses encephalitogenic T lymphocyte proliferation. Additionally, endothelial Ch25h-deficiency combined with immature neutrophil mobilization into the blood circulation nearly completely protects mice from EAE. Our findings reveal a central role for CNS endothelial Ch25h in promoting neuroinflammation by inhibiting the expansion of immunosuppressive myeloid cell populations.

Perivascular B cells link intestinal angiogenesis to immunity and to the gut-brain axis during neuroinflammation.

Disruption of gut barrier function and intestinal immune cell homeostasis are increasingly considered critical players in pathogenesis of extra-intestinal inflammatory diseases, including multiple sclerosis (MS) and its prototypical animal model, the experimental autoimmune encephalomyelitis (EAE). Breakdown of epithelial barriers increases intestinal permeability and systemic dissemination of microbiota-derived molecules. However, whether the gut-vascular barrier (GVB) is altered during EAE has not been reported. Here, we demonstrate that endothelial cell proliferation and vessel permeability increase before EAE clinical onset, leading to vascular remodeling and expansion of intestinal villi capillary bed during disease symptomatic phase in an antigen-independent manner. Concomitant to onset of angiogenesis observed prior to neurological symptoms, we identify an increase of intestinal perivascular immune cells characterized by the surface marker lymphatic vessel endothelial hyaluronic acid receptor 1 (LYVE-1). LYVE-1+ is expressed more frequently on B cells that show high levels of CD73 and have proangiogenic properties. B cell depletion was sufficient to mitigate enteric blood endothelial cell proliferation following immunization for EAE. In conclusion, we propose that altered intestinal vasculature driven by a specialized LYVE-1+ B cell subset promotes angiogenesis and that loss of GVB function is implicated in EAE development and autoimmunity.

Lowering blood cholesterol does not affect neuroinflammation in experimental autoimmune encephalomyelitis.

BACKGROUND: Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system (CNS) commonly affecting young adults. There is increasing evidence that environmental factors are important in the development and course of MS. The metabolic syndrome (MetS) which comprises dyslipidemia has been associated with a worse outcome in MS disease. Furthermore, the lipid-lowering drug class of statins has been proposed to improve MS disease course. However, cholesterol is also rate-limiting for myelin biogenesis and promotes remyelination in MS animal models. Thus, the impact of circulating blood cholesterol levels during the disease remains debated and controversial. METHODS: We assessed the role of circulating cholesterol on the murine model of MS, the experimental autoimmune encephalomyelitis (EAE) disease using two different approaches: (1) the mouse model of familial hypercholesterolemia induced by low-density lipoprotein receptor (LDLr) deficiency, and (2) the use of the monoclonal anti-PCSK9 neutralizing antibody alirocumab, which reduces LDLr degradation and consequently lowers blood levels of cholesterol. RESULTS: Elevated blood cholesterol levels induced by LDLr deficiency did not worsen clinical symptoms of mice during EAE. In addition, we observed that the anti-PCSK9 antibody alirocumab did not influence EAE disease course, nor modulate the immune response in EAE. CONCLUSIONS: These findings suggest that blood cholesterol level has no direct role in neuro-inflammatory diseases and that the previously shown protective effects of statins in MS are not related to circulating cholesterol.

How Microbiota-Derived Metabolites Link the Gut to the Brain during Neuroinflammation.

Microbiota-derived metabolites are important molecules connecting the gut to the brain. Over the last decade, several studies have highlighted the importance of gut-derived metabolites in the development of multiple sclerosis (MS). Indeed, microbiota-derived metabolites modulate the immune system and affect demyelination. Here, we discuss the current knowledge about microbiota-derived metabolites implications in MS and in different mouse models of neuroinflammation. We focus on the main families of microbial metabolites that play a role during neuroinflammation. A better understanding of the role of those metabolites may lead to new therapeutical avenues to treat neuroinflammatory diseases targeting the gut-brain axis.

Increased central obesity correlates with physical activity and food processing in recently diagnosed multiple sclerosis.

BACKGROUND: Environmental and lifestyle factors are associated with an increased risk of Multiple Sclerosis (MS). Metabolic syndrome (MetS) contributes to systemic inflammation, which is associated with poorer MS disease evolution. We compared persons with MS (PwMS) and controls to assess metabolic and lifestyle parameters associated with MS. METHODS: We pooled data from two prospective observational studies with the same eligibility criteria, matching PwMS and controls (1:2 ratio) by sex, age, and body mass index (BMI). We compared anthropometric, biological and lifestyle parameters, including sleep and physical activity. RESULTS: We included 53 PwMS and 106 controls with a median age of 35 years and 79% of women. PwMS had low Expanded Disability Status Scale (median 1.5). Compared to controls, PwMS had increased waist-to-hip (p<0.001) and waist-to-height (p=0.007) ratios, and practiced less physical activity (p=0.03). In regression models, lifestyle factors with the strongest factor loadings to predict central obesity were processed food consumption, and vigorous physical activity. DISCUSSION: Although both groups were matched by age, sex, and BMI, we found increased central obesity in PwMS. Even with minimal neurological impairment, PwMS practiced less physical activity. This suggests that improvement of lifestyle and metabolic parameters should be targeted in MS.