Anti-dsDNA antibodies induce cell activation and fibronectin synthesis in human renal proximal tubular epithelial cells

Abstract

INTRODUCTION AND AIMS: Tubulo-interstitial inflammation and fibrosis correlate with renal prognosis. We investigated the role of anti-dsDNA antibodies in the pathogenesis of tubulo-interstitial pathology in lupus nephritis, focusing on their effect on epithelial-to-mesenchymal transition (EMT) and fibrogenesis in renal proximal tubular epithelial cells (PTEC). METHODS: Polyclonal anti-dsDNA antibodies were isolated from the sera of 10 patients with lupus nephritis using affinity chromatography. Confluent, growth-arrested human PTEC were cultured with human polyclonal anti-dsDNA antibodies or control IgG (10 μg/ml for both) for periods up to 48h and synthesis of mediators of cell activation, EMT and fibrosis investigated. RESULTS: Anti-dsDNA antibodies significantly induced synthesis of soluble and insoluble fibronectin in PTEC after 24h incubation (P<0.01 for both). Anti-dsDNA antibodies induced fibroblast specific protein-1 and β-catenin synthesis (P<0.001 for both), which was accompanied by increased ERK, p38 MAPK and PKC-α phosphorylation. Inhibition of ERK, p38 MAPK and PKC-α activation using PD98059, SB203580 and Go6976 respectively preserved normal PTEC phenotype and reduced anti-dsDNA antibody-induced EMT markers and fibronectin synthesis. CONCLUSIONS: Our data demonstrate that human polyclonal anti-dsDNA antibodies can induce the EMT cascade and fibronectin synthesis in PTEC through activation of MAPK and PKC pathways, thereby contributing to amplification of matrix protein deposition within the tubulo-interstitium during pathogenesis of lupus nephritis.