Ligation of α-Dystroglycan on Podocytes Induces Intracellular Signaling: A New Mechanism for Podocyte Effacement?

Contains fulltext : 79974.pdf (publisher's version ) (Open Access)BACKGROUND: Alpha-dystroglycan is a negatively charged glycoprotein that covers the apical and basolateral membrane of the podocyte. Its transmembrane binding to the cytoskeleton is regulated via tyrosine phosphorylation (pY892) of beta-dystroglycan. At the basolateral side alpha-dystroglycan binds the glomerular basement membrane. At the apical membrane, it plays a role in the maintenance of the filtration slit. In this study, we evaluated whether ligation of alpha-dystroglycan with specific antibodies or natural ligands induces intracellular signaling, and whether there is an effect on podocyte architecture. METHODOLOGY/PRINCIPAL FINDINGS: Conditionally immortalized podocytes were exposed in vitro to antibodies to alpha-dystroglycan, and to fibronectin, biglycan, laminin and agrin. Intracellular calcium fluxes, phosphorylation of beta-dystroglycan and podocyte architecture were studied. Antibodies to alpha-dystroglycan could specifically induce calcium signaling. Fibronectin also induced calcium signaling, and led to dephosphorylation of pY892 in beta-dystroglycan. Ligation of alpha-dystroglycan resulted in an altered actin architecture, a decreased number of podocyte pedicles and a more flattened appearance of the podocyte. CONCLUSIONS/SIGNIFICANCE: We conclude that ligation of alpha-dystroglycan on podocytes induces intracellular calcium signaling, which leads to an altered cytoskeleton architecture akin to the situation of foot process effacement. In particular the ability of fibronectin to induce intracellular signaling events is of interest, since the expression and excretion of this protein is upregulated in several proteinuric diseases. Therefore, fibronectin-induced signaling via dystroglycan may be a novel mechanism for foot process effacement in proteinuric diseases

Characterization of anticoagulant heparinoids by immunoprofiling

Heparinoids are used in the clinic as anticoagulants. A specific pentasaccharide in heparinoids activates antithrombin III, resulting in inactivation of factor Xa and–when additional saccharides are present–inactivation of factor IIa. Structural and functional analysis of the heterogeneous heparinoids generally requires advanced equipment, is time consuming, and needs (extensive) sample preparation. In this study, a novel and fast method for the characterization of heparinoids is introduced based on reactivity with nine unique anti-heparin antibodies. Eight heparinoids were biochemically analyzed by electrophoresis and their reactivity with domain-specific anti-heparin antibodies was established by ELISA. Each heparinoid displayed a distinct immunoprofile matching its structural characteristics. The immunoprofile could also be linked to biological characteristics, such as the anti-Xa/anti-IIa ratio, which was reflected by reactivity of the heparinoids with antibodies HS4C3 (indicative for 3-O-sulfates) and HS4E4 (indicative for domains allowing anti-factor IIa activity). In addition, the immunoprofile could be indicative for heparinoid-induced side-effects, such as heparin-induced thrombocytopenia, as illustrated by reactivity with antibody NS4F5, which defines a very high sulfated domain. In conclusion, immunoprofiling provides a novel, fast, and simple methodology for the characterization of heparinoids, and allows high-throughput screening of (new) heparinoids for defined structural and biological characteristics

Health-related quality of life and treatment burden in patients with proliferative lupus nephritis treated with cyclophosphamide or azathioprine/methylprednisolone in a randomized controlled trial

Objective. To study prospectively the effect of treatment with cyclophosphamide pulses (CYC) or azathioprine with methylprednisolone (AZA), both for 24-month periods, on health-related quality of life (HRQOL) in patients with proliferative lupus nephritis (LN) in a randomized controlled trial. We expected better HRQOL during AZA treatment. Methods. HRQOL and disease activity were measured at start and after 12 and 24 months. Generic questionnaires [patient's visual analog scale (VAS), Medical Outcomes Study Short Form-36 Health Survey (SF-36), Profile of Mood States] and a disease-specific measure [Systemic Lupus Erythernatosus (SLE) Symptom Checklist] were used. Treatment burden was assessed at 24 months. Disease activity was measured with the SLE Disease Activity Index (SLEDAI) and physician's VAS. Results. Complete questionnaire data were available from 47 of the 87 patients included in the trial. These patients were representative of the whole group, except that completers were more often Caucasian. HRQOL scores improved significantly during treatment, particularly during the first year, on both generic and disease-specific outcomes. No statistically significant differences were found in HRQOL between the CYC and AZA groups, except for the SF-36 mental component summary scale, which showed more favorable scores in the AZA group. The mean reported treatment burden at 24 months was significantly higher in the CYC group. HRQOL scores did not correlate with the SLEDAI and physician's VAS. The disease activity measures correlated positively with each other. Conclusion. Treatment of patients with proliferative LN with immunosuppressive drugs and corticosteroids improves HRQOL, particularly in the first year. Due to the small groups studied, the absence of differences between AZA and CYC for most HRQOL scales should be interpreted cautiously: our data suggest that there may be no significant differences. Differences were a higher perceived treatment burden and worse mental HRQOL in the CYC group

A prospective study of anti‐chromatin and anti‐C1q autoantibodies in patients with proliferative lupus nephritis treated with cyclophosphamide pulses or azathioprine/methylprednisolone

Contains fulltext : 52040.pdf (publisher's version ) (Closed access)OBJECTIVE: To study the prevalence and course of anti-chromatin (anti-nucleosome, anti-double-stranded (ds) DNA and anti-histone) and anti-C1q autoantibodies in patients with proliferative lupus nephritis (LN), treated in a randomised controlled trial with either cyclophosphamide or azathioprine plus methylprednisolone. METHODS: Autoantibody levels were measured and analysed in 52 patients with proliferative LN, during their first year of treatment. Levels in both treatment arms were compared and associations with clinical, serological and outcome parameters were studied. RESULTS: At study entry, prevalences for anti-nucleosome, anti-dsDNA, anti-histone and anti-C1q autoantibodies were 81%, 96%, 23% and 65%, respectively. Anti-chromatin autoantibodies correlated with each other, but not with anti-C1q levels. If patients were divided for their autoantibody titre at the start of treatment above or below the median, the only significant differences were higher SLE disease activity index with higher anti-nucleosome, and higher creatinine with higher anti-C1q autoantibodies. During the first year, a comparable rapid decline in the levels of anti-nucleosome, anti-dsDNA and anti-C1q autoantibodies was seen in both treatment arms. Anti-histone autoantibody levels were low and did not change. Renal flares were not preceded by rises in autoantibody titres. CONCLUSIONS: These results indicate that measurement of anti-chromatin and anti-C1q autoantibodies is useful for diagnosing LN, but not for monitoring disease course