Mycophenolic acid ameliorates anti-dsDNA antibody binding to proximal tubular epithelial cells and the subsequent induction of inflammatory and fibrotic processes

Abstract

OBJECTIVES: Severe active proliferative lupus nephritis is associated with inflammation in the renal parenchyma and elevated levels of anti-dsDNA antibodies. Up to 70% of patients with lupus nephritis show immune deposits along the tubular basement membrane, and the severity of tubulo-interstitial inflammation and injury correlate with long-term renal prognosis. We investigated the interaction between polyclonal anti-dsDNA antibodies isolated from patients with lupus nephritis and cultured proximal tubular epithelial cells (PTEC), and the effect of mycophenolic acid (MPA). METHODS: Human polyclonal anti-dsDNA antibodies were isolated from patients with lupus nephritis using affinity chromatography. Their interaction with PTEC in the presence or absence of MPA (5μg/ml) was assessed by flow cytometry, cellular ELISA and immunohistochemistry. Induction of IL-6, IL-8, MCP-1 and fibronectin was assessed by commercial ELISAs, and MAPK activation by Western blot analysis. RESULTS: Anti-dsDNA antibodies bound directly to PTEC surface without the need for bridging chromatin material, and were then internalized, in a time- and temperature-dependent manner, into the cytoplasmic and nuclear compartments. Binding of anti-dsDNA antibodies to PTEC induced cell proliferation, IL-6 secretion through JNK activation, and MCP-1 through p38 MAPK activation. Activation of ERK, p38 MAPK and JNK contributed to the induction of IL-8 and fibronectin secretion by anti-dsDNA antibodies (p<0.05 for all compared to control IgG). MPA inhibited anti-dsDNA antibody binding to PTEC, its induction of cell proliferation, activation of ERK, p38 MAPK and JNK, and IL-6, IL-8, MCP-1 and fibronectin secretion. CONCLUSIONS: Our data demonstrate the significance of anti-dsDNA antibody interaction with PTEC in the pathogenesis of tubulo-interstitial inflammation and fibrosis in lupus nephritis, and the therapeutic effect of MPA in this regard.