Type I interferon-activated microglia are critical for neuromyelitis optica pathology

Neuromyelitis optica (NMO) is an inflammatory disease of the central nervous system (CNS) most frequently mediated by serum autoantibodies against the water channel aquaporin 4, expressed on CNS astrocytes, resulting in primary astrocytopathy. There is no cure for NMO, and treatment with Type I interferon (IFNI)-IFN beta is ineffective or even detrimental. We have previously shown that both NMO lesions and associated microglial activation were reduced in mice lacking the receptor for IFN beta. However, the role of microglia in NMO is not well understood. In this study, we clarify the pathomechanism for IFNI dependence of and the role of microglia in experimental NMO. Transcriptome analysis showed a strong IFNI footprint in affected CNS tissue as well as in microglial subpopulations. Treatment with IFN beta led to exacerbated pathology and further microglial activation as evidenced by expansion of a CD11c(+) subset of microglia. Importantly, depletion of microglia led to suppression of pathology and decrease of IFNI signature genes. Our data show a pro-pathologic role for IFNI-activated microglia in NMO and open new perspectives for microglia-targeted therapies

The Gut Microbiome Contributes to a Substantial Proportion of the Variation in Blood Lipids

Rationale: Evidence suggests that the gut microbiome is involved in the development of cardiovascular disease, with the host–microbe interaction regulating immune and metabolic pathways. However, there was no firm evidence for associations between microbiota and metabolic risk factors for cardiovascular disease from large-scale studies in humans. In particular, there was no strong evidence for association between cardiovascular disease and aberrant blood lipid levels. Objectives: To identify intestinal bacteria taxa, whose proportions correlate with body mass index and lipid levels, and to determine whether lipid variance can be explained by microbiota relative to age, sex, and host genetics. Methods and Results: We studied 893 subjects from the LifeLines-DEEP population cohort. After correcting for age and sex, we identified 34 bacterial taxa associated with body mass index and blood lipids; most are novel associations. Cross-validation analysis revealed that microbiota explain 4.5% of the variance in body mass index, 6% in triglycerides, and 4% in high-density lipoproteins, independent of age, sex, and genetic risk factors. A novel risk model, including the gut microbiome explained ≤25.9% of high-density lipoprotein variance, significantly outperforming the risk model without microbiome. Strikingly, the microbiome had little effect on low-density lipoproteins or total cholesterol. Conclusions: Our studies suggest that the gut microbiome may play an important role in the variation in body mass index and blood lipid levels, independent of age, sex, and host genetics. Our findings support the potential of therapies altering the gut microbiome to control body mass, triglycerides, and high-density lipoproteins

Impact of neuraminidase inhibitors on influenza A(H1N1)pdm09‐related pneumonia: an individual participant data meta‐analysis

BACKGROUND: The impact of neuraminidase inhibitors (NAIs) on influenza‐related pneumonia (IRP) is not established. Our objective was to investigate the association between NAI treatment and IRP incidence and outcomes in patients hospitalised with A(H1N1)pdm09 virus infection. METHODS: A worldwide meta‐analysis of individual participant data from 20 634 hospitalised patients with laboratory‐confirmed A(H1N1)pdm09 (n = 20 021) or clinically diagnosed (n = 613) ‘pandemic influenza’. The primary outcome was radiologically confirmed IRP. Odds ratios (OR) were estimated using generalised linear mixed modelling, adjusting for NAI treatment propensity, antibiotics and corticosteroids. RESULTS: Of 20 634 included participants, 5978 (29·0%) had IRP; conversely, 3349 (16·2%) had confirmed the absence of radiographic pneumonia (the comparator). Early NAI treatment (within 2 days of symptom onset) versus no NAI was not significantly associated with IRP [adj. OR 0·83 (95% CI 0·64–1·06; P = 0·136)]. Among the 5978 patients with IRP, early NAI treatment versus none did not impact on mortality [adj. OR = 0·72 (0·44–1·17; P = 0·180)] or likelihood of requiring ventilatory support [adj. OR = 1·17 (0·71–1·92; P = 0·537)], but early treatment versus later significantly reduced mortality [adj. OR = 0·70 (0·55–0·88; P = 0·003)] and likelihood of requiring ventilatory support [adj. OR = 0·68 (0·54–0·85; P = 0·001)]. CONCLUSIONS: Early NAI treatment of patients hospitalised with A(H1N1)pdm09 virus infection versus no treatment did not reduce the likelihood of IRP. However, in patients who developed IRP, early NAI treatment versus later reduced the likelihood of mortality and needing ventilatory support

The expression and regulation of chemerin in the epidermis.

Chemerin is a protein ligand for the G protein-coupled receptor CMKLR1 and also binds to two atypical heptahelical receptors, CCRL2 and GPR1. Chemerin is a leukocyte attractant, adipokine, and antimicrobial protein. Although chemerin was initially identified as a highly expressed gene in healthy skin keratinocytes that was downregulated during psoriasis, the regulation of chemerin and its receptors in the skin by specific cytokines and microbial factors remains unexplored. Here we show that chemerin, CMKLR1, CCRL2 and GPR1 are expressed in human and mouse epidermis, suggesting that this tissue may be both a source and target for chemerin mediated effects. In human skin cultures, chemerin is significantly downregulated by IL-17 and IL-22, key cytokines implicated in psoriasis, whereas it is upregulated by acute phase cytokines oncostatin M and IL-1β. Moreover, we show that human keratinocytes in vitro and mouse skin in vivo respond to specific microbial signals to regulate expression levels of chemerin and its receptors. Furthermore, in a cutaneous infection model, chemerin is required for maximal bactericidal effects in vivo. Together, our findings reveal previously uncharacterized regulators of chemerin expression in skin and identify a physiologic role for chemerin in skin barrier defense against microbial pathogens

Bacteria upregulate chemerin expression in epidermis.

<p>Keratinocytes were treated with the indicated factors for 24 (A, B, E) or 48h (C, D). Total RNA was subjected to RT-QPCR. Relative expression of stimulated cells over control is shown as the mean ±SD from five-nine independent experiments (A, C). Levels of secreted chemerin were determined in parallel in conditioned media by ELISA. Data show the mean ±SD from five-nine independent experiments (B, D). Statistical significance between control and the treated cells is shown by asterisk; *p<0.05 by ANOVA followed by a Bonferroni post hoc test. E. c., <i>E. coli</i>; HK, heat-killed; SN, supernatant; S. a., <i>S. aureus</i>; A, ampicillin-treated. Microscope images of keratinocytes stained with hematoxilin and eosin (H&E) and fluorescence microscope images of keratinocytes stained for chemerin (chem) or control rabbit Abs (cAb) (red), with Hoechst counterstain to detect cell nuclei (blue). Scale bar = 10 μm. Data are representative of three different donors. SC, stratum corneum, SG, stratum granulosum, SS, stratum spinosum, SB stratum basale, TM transwell membrane (E).</p

Chemerin is bactericidal <i>in vivo</i>.

<p>Chemerin–deficient (ChemKO) and WT mice were ectopically treated with <i>S. aureus</i>. Bacteria were retrieved from skin 24h later, and presented as a % of input inoculum. Each data point represents one experiment and a horizontal line indicate the mean value in each group. *p<0.05, by <i>t</i> test.</p

Targeting Signaling Pathway Downstream of RIG-I/MAVS in the CNS Stimulates Production of Endogenous Type I IFN and Suppresses EAE

Type I interferons (IFN), including IFN&beta;, play a protective role in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Type I IFNs are induced by the stimulation of innate signaling, including via cytoplasmic RIG-I-like receptors. In the present study, we investigated the potential effect of a chimeric protein containing the key domain of RIG-I signaling in the production of CNS endogenous IFN&beta; and asked whether this would exert a therapeutic effect against EAE. We intrathecally administered an adeno-associated virus vector (AAV) encoding a fusion protein comprising RIG-I 2CARD domains (C) and the first 200 amino acids of mitochondrial antiviral-signaling protein (MAVS) (M) (AAV-CM). In vivo imaging in IFN&beta;/luciferase reporter mice revealed that a single intrathecal injection of AAV-CM resulted in dose-dependent and sustained IFN&beta; expression within the CNS. IFN&beta; expression was significantly increased for 7 days. Immunofluorescent staining in IFN&beta;-YFP reporter mice revealed extraparenchymal CD45+ cells, choroid plexus, and astrocytes as sources of IFN&beta;. Moreover, intrathecal administration of AAV-CM at the onset of EAE induced the suppression of EAE, which was IFN-I-dependent. These findings suggest that accessing the signaling pathway downstream of RIG-I represents a promising therapeutic strategy for inflammatory CNS diseases, such as MS

Bacteria controls the expression of chemerin and its receptors <i>in vivo</i>.

<p>Mice were ectopically treated with <i>S. aureus, E coli</i> or PBS (control) for 24h. The skin exposed to the treatment was then collected for RNA and protein isolation. Chemerin and chemerin receptor message was determined by RT-QPCR. The expression data was normalized to cyclophilin A and presented relative to PBS-treated skin (A, C-E). The amount of chemerin in skin lysates, normalized to total protein was determined by ELISA (B). Data are shown as the mean ±SEM from six mice in each group. Statistically significant differences between PBS-treated and bacteria-treated mice is indicated by an asterisk (*, p<0.05; ANOVA followed by a Bonferroni post hoc test).</p

Chemerin and chemerin receptor expression in mouse skin.

<p>Chemerin mRNA expression (A), chemerin protein expression in tissue lysates (B), chemerin receptor (CMKLR1, CCRL2, GPR1) mRNA expression (C-E), or chemerin protein expression in skin homogenates (F) and chemerin expression in plasma (G) was measured in the indicated tissues isolated from C57BL/6 mice (A-E) or the indicated mice on BalbC backround (F-G) by RT-QPCR and ELISA. The expression data of the indicated genes was normalized to cyclophilin A and RPL13A, and presented relative to liver as the mean ± SEM, n = 4–5 different mice (A, C-E). The amount of chemerin protein in plasma, or skin lysates and homogenates normalized to total protein is shown as the mean ± SEM, n = 4 (B), or n≥6 mice (F-G). Statistical significance is indicated by asterisk(s); *p<0.05, **p<0.01, by ANOVA followed by a Bonferroni post hoc test.</p