Immunothrombosis and vascular heterogeneity in cerebral cavernous malformation.

Cerebral cavernous malformation (CCM) is a neurovascular disease that results in various neurological symptoms. Thrombi have been reported in surgically resected CCM patient biopsies, but the molecular signatures of these thrombi remain elusive. Here, we investigated the kinetics of thrombi formation in CCM and how thrombi affect the vasculature and contribute to cerebral hypoxia. We used RNA sequencing to investigate the transcriptome of mouse brain endothelial cells with an inducible endothelial-specific Ccm3 knock-out (Ccm3-iECKO). We found that Ccm3-deficient brain endothelial cells had a higher expression of genes related to the coagulation cascade and hypoxia when compared with wild-type brain endothelial cells. Immunofluorescent assays identified key molecular signatures of thrombi such as fibrin, von Willebrand factor, and activated platelets in Ccm3-iECKO mice and human CCM biopsies. Notably, we identified polyhedrocytes in Ccm3-iECKO mice and human CCM biopsies and report it for the first time. We also found that the parenchyma surrounding CCM lesions is hypoxic and that more thrombi correlate with higher levels of hypoxia. We created an in vitro model to study CCM pathology and found that human brain endothelial cells deficient for CCM3 expressed elevated levels of plasminogen activator inhibitor-1 and had a redistribution of von Willebrand factor. With transcriptomics, comprehensive imaging, and an in vitro CCM preclinical model, this study provides experimental evidence that genes and proteins related to the coagulation cascade affect the brain vasculature and promote neurological side effects such as hypoxia in CCMs. This study supports the concept that antithrombotic therapy may be beneficial for patients with CCM.

Inflammation and neutrophil extracellular traps in cerebral cavernous malformation.

Cerebral Cavernous Malformation (CCM) is a brain vascular disease with various neurological symptoms. In this study, we describe the inflammatory profile in CCM and show for the first time the formation of neutrophil extracellular traps (NETs) in rodents and humans with CCM. Through RNA-seq analysis of cerebellum endothelial cells from wild-type mice and mice with an endothelial cell-specific ablation of the Ccm3 gene (Ccm3iECKO), we show that endothelial cells from Ccm3iECKO mice have an increased expression of inflammation-related genes. These genes encode proinflammatory cytokines and chemokines, as well as adhesion molecules, which promote recruitment of inflammatory and immune cells. Similarly, immunoassays showed elevated levels of these cytokines and chemokines in the cerebellum of the Ccm3iECKO mice. Consistently, both flow cytometry and immunofluorescence analysis showed infiltration of different subsets of leukocytes into the CCM lesions. Neutrophils, which are known to fight against infection through different strategies, including the formation of NETs, represented the leukocyte subset within the most pronounced increase in CCM. Here, we detected elevated levels of NETs in the blood and the deposition of NETs in the cerebral cavernomas of Ccm3iECKO mice. Degradation of NETs by DNase I treatment improved the vascular barrier. The deposition of NETs in the cavernomas  of patients with CCM confirms the clinical relevance of NETs in CCM.

Propranolol Reduces the Development of Lesions and Rescues Barrier Function in Cerebral Cavernous Malformations: A Preclinical Study.

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The involvement of Toll-like receptor 9 in the pathogenesis of erosive autoimmune arthritis.

Endogenous nucleic acids and their receptors may be involved in the initiation of systemic autoimmune diseases including rheumatoid arthritis (RA). As the role of the DNA sensing Toll-like receptor (TLR) 9 in RA is unclear, we aimed to investigate its involvement in the pathogenesis of autoimmune arthritis using three different experimental models of RA. The data obtained revealed involvement of TLR9 in the T cell-dependent phase of inflammatory arthritis. In rats with pristane-induced arthritis (PIA), TLR9 inhibition before disease onset reduced arthritis significantly and almost completely abolished bone erosion. Accordingly, serum levels of IL-6, α-1-acid-glycoprotein and rheumatoid factor were reduced. Moreover, in TLR9-/- mice, streptococcal cell wall (SCW)-induced arthritis was reduced in the T cell-dependent phase, whereas T cell-independent serum-transfer arthritis was not affected. Remarkably, while TLR7 expression did not change during in vitro osteoclastogenesis, TLR9 expression was higher in precursor cells than in mature osteoclasts and partial inhibition of osteoclastogenesis was achieved only by the TLR9 antagonist. These results demonstrate a pivotal role for TLR9 in the T cell-dependent phases of inflammatory arthritis and additionally suggest some role during osteoclastogenesis. Hence, endogenous DNA seems to be crucially involved in the pathophysiology of inflammatory autoimmune arthritis.

Mannan-induced Nos2 in macrophages enhances IL-17-driven psoriatic arthritis by innate lymphocytes.

Previous identification of the inducible nitric oxide synthase (NOS2) gene as a risk allele for psoriasis (Ps) and psoriatic arthritis (PsA) suggests a possible pathogenic role of nitric oxide (NO). Using a mouse model of mannan-induced Ps and PsA (MIP), where macrophages play a regulatory role by releasing reactive oxygen species (ROS), we found that NO was detectable before disease onset in mice, independent of a functional nicotinamide adenine dinucleotide phosphate oxidase 2 complex. MIP was suppressed by either deletion of Nos2 or inhibition of NO synthases with NG-nitro-l-arginine methyl ester, demonstrating that Nos2-derived NO is pathogenic. NOS2 expression was also up-regulated in lipopolysaccharide- and interferon-γ-stimulated monocyte subsets from patients with PsA compared to healthy controls. Nos2-dependent interleukin-1α (IL-1α) release from skin macrophages was essential for arthritis development by promoting IL-17 production of innate lymphoid cells. We conclude that Nos2-derived NO by tissue macrophages promotes MIP, in contrast to the protective effect by ROS.

Influence of hydrocarbon oil structure on adjuvanticity and autoimmunity.

Mineral oils are extensively used in our daily life, in food, cosmetics, biomedicine, vaccines and in different industrial applications. However, exposure to these mineral oils has been associated with immune adjuvant effects and the development of autoimmune diseases. Here we investigate the structural impacts of the hydrocarbon oil molecules on their adjuvanticity and autoimmunity. First, we showed that hydrocarbon oil molecules with small atomic differences could result in experimental arthritis in DA rats differing in disease severity, incidence, weight change and serum levels of acute phase proteins. Injection of these hydrocarbon oils resulted in the activation, proliferation and elevated expression of Th1 and especially Th17 cytokines by the T cells, which correlate with the arthritogenicity of the T cells. Furthermore, the more arthritogenic hydrocarbon oils resulted in an increased production of autoantibodies against cartilage joint specific, triple-helical type II collagen epitopes. When injected together with ovalbumin, the more arthritogenic hydrocarbon oils resulted in an increased production of αß T cell-dependent anti-ovalbumin antibodies. This study shows the arthritogenicity of hydrocarbon oils is associated with their adjuvant properties with implications to not only arthritis research but also other diseases and medical applications such as vaccines in which oil adjuvants are involved.

Effects of C2ta genetic polymorphisms on MHC class II expression and autoimmune diseases.

Antigen presentation by the MHC-II to CD4+ T cells is important in adaptive immune responses. The class II transactivator (CIITA in human and C2TA in mouse) is the master regulator of MHC-II gene expression. It coordinates the transcription factors necessary for the transcription of MHC-II molecules. In humans, genetic variations in CIITA have been associated with differential expression of MHC-II and susceptibility to autoimmune diseases. Here we made use of a C2ta congenic mouse strain (expressing MHC-II haplotype H-2q ) to investigate the effect of the natural genetic polymorphisms in type I promoter of C2ta on MHC-II expression and function. We demonstrate that an allelic variant in the type I promoter of C2ta resulted in an increased expression of MHC-II on macrophages (72-151% higher mean florescence intensity) and conventional dendritic cells (13-65% higher mean florescence intensity) in both spleen and peripheral blood. The increase in MHC-II expression resulted in an increase in antigen presentation to T cells in vitro and increased T-cell activation. The differential MHC-II expression in B6Q.C2ta, however, did not alter the disease development in models of rheumatoid arthritis (collagen-induced arthritis and human glucose-6-phosphate-isomerase325-339 -peptide-induced arthritis), or multiple sclerosis (MOG1-125 protein-induced and MOG79-96 peptide-induced experimental autoimmune encephalomyelitis). This is the first study to address the role of an allelic variant in type I promoter of C2ta in MHC-II expression and autoimmune diseases; and shows that C2ta polymorphisms regulate MHC-II expression and T-cell responses but do not necessarily have a strong impact on autoimmune diseases.

Conserved 33-kb haplotype in the MHC class III region regulates chronic arthritis.

Genome-wide association studies have revealed many genetic loci associated with complex autoimmune diseases. In rheumatoid arthritis (RA), the MHC gene HLA-DRB1 is the strongest candidate predicting disease development. It has been suggested that other immune-regulating genes in the MHC contribute to the disease risk, but this contribution has been difficult to show because of the strong linkage disequilibrium within the MHC. We isolated genomic regions in the form of congenic fragments in rats to test whether there are additional susceptibility loci in the MHC. By both congenic mapping in inbred strains and SNP typing in wild rats, we identified a conserved, 33-kb large haplotype Ltab-Ncr3 in the MHC-III region, which regulates the onset, severity, and chronicity of arthritis. The Ltab-Ncr3 haplotype consists of five polymorphic immunoregulatory genes: Lta (lymphotoxin-α), Tnf, Ltb (lymphotoxin-ß), Lst1 (leukocyte-specific transcript 1), and Ncr3 (natural cytotoxicity-triggering receptor 3). Significant correlation in the expression of the Ltab-Ncr3 genes suggests that interaction of these genes may be important in keeping these genes clustered together as a conserved haplotype. We studied the arthritis association and the spliceo-transcriptome of four different Ltab-Ncr3 haplotypes and showed that higher Ltb and Ncr3 expression, lower Lst1 expression, and the expression of a shorter splice variant of Lst1 correlate with reduced arthritis severity in rats. Interestingly, patients with mild RA also showed higher NCR3 expression and lower LST1 expression than patients with severe RA. These data demonstrate the importance of a conserved haplotype in the regulation of complex diseases such as arthritis.