Vitronectin- and fibronectin-containing immune complexes in primary systemic vasculitis

Proteomic and lipidomic landscape of the infrapatellar fat pad and its clinical significance in knee osteoarthritis

Osteoarthritis (OA) is a prevalent joint disease that can be exacerbated by lipid metabolism disorders. The intra-articular fat pad (IFP) has emerged as an active participant in the pathological changes of knee OA (KOA). However, the proteomic and lipidomic differences between IFP tissues from KOA and control individuals remain unclear. Samples of IFP were collected from individuals with and without OA (n = 6, n = 6). Subsequently, these samples underwent liquid chromatography/mass spectrometry-based label-free quantitative proteomic and lipidomic analysis to identify differentially expressed proteins (DEPs) and lipid metabolites (DELMs). The DEPs were further subjected to enrichment analysis, and hub DEPs were identified using multiple algorithms. Additionally, an OA diagnostic model was constructed based on the identified hub DEPs or DELMs. Furthermore, CIBERSORT was utilized to investigate the correlation between hub protein expression and immune-related modules in IFP of OA. Our results revealed the presence of 315 DEPs and eight DELMs in IFP of OA patients compared to the control group. Enrichment analysis of DEPs highlighted potential alterations in pathways related to coagulation, complement, fatty acid metabolism, and adipogenesis. The diagnostic model incorporating four hub DEPs (AUC = 0.861) or eight DELMs (AUC = 0.917) exhibited excellent clinical validity for diagnosing OA. Furthermore, the hub DEPs were found to be associated with immune dysfunction in IFP of OA. This study presents a distinct proteomic and lipidomic landscape of IFP between individuals with OA and those without. These findings provide valuable insights into the molecular changes associated with potential mechanisms underlying OA.

Vascular wall extracellular matrix proteins and vascular diseases

Extracellular matrix proteins form the basic structure of blood vessels. Along with providing basic structural support to blood vessels, matrix proteins interact with different sets of vascular cells via cell surface integrin or non-integrin receptors. Such interactions induce vascular cell de novo synthesis of new matrix proteins during blood vessel development or remodeling. Under pathological conditions, vascular matrix proteins undergo proteolytic processing, yielding bioactive fragments to influence vascular wall matrix remodeling. Vascular cells also produce alternatively spliced variants that induce vascular cell production of different matrix proteins to interrupt matrix homeostasis, leading to increased blood vessel stiffness; vascular cell migration, proliferation, or death; or vascular wall leakage and rupture. Destruction of vascular matrix proteins leads to vascular cell or blood-borne leukocyte accumulation, proliferation, and neointima formation within the vascular wall; blood vessels prone to uncontrolled enlargement during blood flow diastole; tortuous vein development; and neovascularization from existing pathological tissue microvessels. Here we summarize discoveries related to blood vessel matrix proteins within the past decade from basic and clinical studies in humans and animals - from expression to cross-linking, assembly, and degradation under physiological and vascular pathological conditions, including atherosclerosis, aortic aneurysms, varicose veins, and hypertension.

Discoidin domain receptor 1 contributes to eosinophil survival in an NF-kappaB-dependent manner in Churg-Strauss syndrome

Churg-Strauss syndrome (CSS) is a systemic disease that shows marked eosinophilia along with eosinophil infiltration in the tissue. Prolonged eosinophil survival plays an important role in the pathogenesis of CSS; however, its detailed molecular mechanism remains unclear. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase, and its ligand is collagen. DDR1 was expressed in human leukocytes and fibroblasts, and it plays an important role in leukocyte cytokine production and fibroblast survival in an NF-kappaB-dependent manner. In this study, we examined in vitro and in vivo eosinophil DDR1 expression and its function in CSS patients. The expression level of DDR1 was significantly higher in the eosinophils of CSS patients, and the predominant isoform was DDR1b. Immunohistochemical findings revealed that the tissue-infiltrating eosinophils expressed endogenous DDR1. In CSS patients, DDR1 activation inhibited Fas agonistic antibody-induced apoptosis and up-regulated Fas agonistic antibody-induced cytokine production of eosinophils in an NF-kappaB-dependent manner. Suppression of DDR1 expression in the eosinophils by using RNA interference and addition of the DDR1-blocking protein abolished these effects. We propose that DDR1 contributes to the eosinophil survival in the tissue microenvironment of CSS and that it might be involved in the development of CSS.

Screening of an endothelial cDNA library identifies the C-terminal region of Nedd5 as a novel autoantigen in systemic lupus erythematosus with psychiatric manifestations

Anti-endothelial-cell antibodies are associated with psychiatric manifestations in systemic lupus erythematosus (SLE). Our primary aim in this study was to seek and characterize molecules that behave as endothelial autoantigens in SLE patients with psychiatric manifestations. By screening a cDNA library from human umbilical artery endothelial cells with serum from an SLE patient with psychosis, we identified one positive strongly reactive clone encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. To evaluate anti-Nedd5 serum immunoreactivity, we analyzed by ELISA specific IgG responses in 17 patients with SLE and psychiatric manifestations (group A), 34 patients with SLE without psychiatric manifestations (group B), 20 patients with systemic sclerosis, 20 patients with infectious mononucleosis, and 35 healthy subjects. IgG specific to Nedd5 C-ter was present in 14 (27%) of the 51 SLE patients. The mean optical density value for IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients of group A than in those of group B, those with infectious mononucleosis, or healthy subjects (0.17 ± 0.14 vs, respectively, 0.11 ± 0.07, P = 0.04; 0.11 ± 0.06, P = 0.034; and 0.09 ± 0.045, P = 0.003, on Student's t-test). Moreover, IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients with systemic sclerosis than in patients of group B or healthy subjects (0.18 ± 0.18 vs, respectively, 0.11 ± 0.07, P = 0.046; and 0.09 ± 0.045, P = 0.003). The percentage of patients with anti-Nedd5 C-ter serum IgG was higher in group A than in group B (8 (47%) of 17, vs 6 (17%) of 34, P = 0.045, on Fisher's exact test). In order to clarify a possible mechanism by which Nedd5 might be autoantigenic, we observed that Nedd5 relocated from cytoplasm to the plasma membrane of EAhy926 endothelial cells after apoptotic stimuli. In conclusion, Nedd5 is a novel autoantigen of potential clinical importance that could be successfully used for a more thorough investigation of the pathogenesis of psychiatric manifestations in SLE. Although anti-Nedd5 autoantibodies are not specific to SLE, they are significantly associated with neuropsychiatric SLE and may represent immunological markers of psychiatric manifestations in this pathology.

C1q governs deposition of circulating immune complexes and leukocyte Fcgamma receptors mediate subsequent neutrophil recruitment

Inflammation induced by circulating immunoglobulin G–immune complexes (ICs) characterizes many immune-mediated diseases. In this work, the molecular requirements for the deposition of circulating ICs and subsequent acute leukocyte recruitment in mice were elucidated. We show that after intravenous injection, preformed soluble ICs are rapidly deposited in the postcapillary venules of the cremaster microcirculation, secondary to increased vascular permeability. This deposition is dependent on complement C1q. IC deposition is associated with leukocyte recruitment. Leukocyte rolling, which is mediated by P-selectin in the exteriorized cremaster muscle, is not further increased in response to ICs. In contrast, leukocyte rolling velocity is significantly decreased and leukocyte adhesion is significantly increased in the presence of ICs. The IC-mediated slow leukocyte rolling velocity and subsequent adhesion and emigration are dependent on Fcγ receptors (FcγRs), particularly FcγRIII, with complement C3 and C5 having no detectable role. These studies suggest a regulatory mechanism of IC deposition and leukocyte trafficking in IC-mediated inflammation requiring C1q and FcγRs in sequential, noninteracting roles.

Characterization of a new family of proteins that interact with the C-terminal region of the chromatin-remodeling factor CHD-3

The two human proteins Ki-1/57 and CGI-55 have highly similar amino acid sequences but their functions are unknown. We analyzed them by yeast two-hybrid screens and found that they interact with the C-terminal region of the human chromatin-remodeling factor CHD-3 (chromo-helicase-DNA-binding domain protein-3). The interaction of CGI-55 and CHD-3 could be confirmed in vitro and in vivo by co-immunoprecipitations from Sf9 insect cells. Mapping showed that CGI-55 interacts with CHD-3 via two regions at its N- and C-terminals. The CGI-55 and Ki-1/57 mRNAs show highest expression in muscle, colon and kidney. A CGI55-GFP fusion protein was localized in the cytoplasm, nucleus and perinuclear regions of HeLa cells. These data suggest the possibility that CGI-55 and Ki-1/57 might be involved in nuclear functions like the remodeling of chromatin.