Anti-dsDNA antibodies induce epithelial-to-mesenchymal transition and fibrotic processes in human proximal renal tubular epithelial cells

Abstract

BACKGROUND: Tubulo-interstitial pathology predicts renal prognosis. We investigated the role of anti-dsDNA antibodies in the pathogenesis of tubulo-interstitial pathology in lupus nephritis, focusing on proximal renal tubular epithelial cells (PTEC) and epithelial-to-mesenchymal transition (EMT). METHODS: Female NZBWF1/J mice at different stages of nephritis were sacrificed and kidneys harvested to assess the tubulo-interstitial changes over time. Growth-arrested primary human PTEC were cultured with human polyclonal anti-dsDNA antibodies or control IgG (10μg/ml for both) for periods up to 48h, and investigated for the synthesis of mediators of fibrosis and EMT. RESULTS: NZBWF1/J mice showed progressive tubular damage over time, as denoted by tubular atrophy, protein cast deposition, mononuclear cell infiltration and increasing tubulo-interstitial expression of fibronectin, collagen type I and fibroblast specific protein-1 (FSP-1). Anti-dsDNA antibodies significantly induced the synthesis of soluble and insoluble fibronectin in PTEC after 24h incubation (P<0.01 for both). Anti-dsDNA antibodies induced FSP-1 and β-catenin synthesis (P<0.001 for both), which was accompanied by increased ERK and PKC-α phosphorylation. Inhibition of ERK and PKC-α activation using specific inhibitors reduced anti-dsDNA antibody induced EMT markers and fibronectin synthesis, and preserved normal PTEC phenotype. CONCLUSIONS: Our data demonstrate that anti-dsDNA antibodies contribute to tubulo-interstitial pathology in lupus nephritis via direct effects on PTEC which are mediated through ERK and PKC-α activation.