The impact of DNase I and LMW heparin on systemic lupus erythematosus: Assessing renal inflammation, immune complex deposition, and tubular epithelial responses in IMQ-treated NZB/W-F1 and RPTEC/hTERT1 models

Abstract

Systemic lupus erythematosus (SLE) is an autoimmune disease marked by production of anti-dsDNA autoantibodies, and immune complex (IC) deposition, particularly in the kidneys, leading to lupus nephritis (LN). DNase I degrades extracellular DNA and low molecular weight (LMW) heparin is suggested to support DNase I function and reduce IC formation. The main aim of this project was to investigate whether treatment with DNase I and/or LMW heparin could influence on extracellular DNA availability, IC deposition, and renal inflammation in SLE, impacting both systemic and kidney-specific disease processes. Human renal proximal tubule epithelial cells (RPTEC) are central to kidney immunity and serve as a relevant in vitro model for studying renal tubular inflammation. This was studied using a lupus-prone NZB/W F1 mouse model with IMQ-induced LN, by hematological analysis, enzyme-linked immunosorbent assay, immunohistochemistry, quantitative polymerase chain reaction, immune-electron microscopy, and radial diffusion assay. Parallel in vitro experiments using 3D RPTEC/hTERT1 to model kidney tubular epithelial cells to investigate tubular involvement in LN progression.

IMQ treatment induced lupus-like symptoms in NZB/W mice, including enlargement of the spleen, anemia, and thrombocytopenia. IMQ, DNase I, LMW heparin, and DNase I + LMW heparin all caused autoantibody formation. IgG deposition was observed in glomerular and mesangial ultrastructure across all groups, with reduced tubular interstitial IgG deposition in DNase I and DNase I + LMW heparin-treated mice. Urinary DNase I activity was increased in all treated groups, while serum activity showed the opposite trend. Expression of genes such as FcγRIIb and TGF-β1 was reduced in DNase I, LMW heparin, and DNase I + LMW heparin-treated mice, suggesting ongoing immune dysregulation. In vitro, RPTEC responded to inflammatory and IMQ stimuli, inducing differential gene expression patterns in 2D and 3D cultures. 3D cultures showed successful polarization and a more physiologically relevant inflammatory profile.

Although DNase I and LMW heparin reduced tubular interstitial IgG deposition, they did not prevent overall disease progression or anti-dsDNA antibody production. The findings suggest a potential synergistic effect but highlight the complexity of LN pathogenesis and the need for improved therapeutic strategies. The RPTEC models confirmed their value for studying renal inflammation, with 3D cultures being a more relevant system for future investigations.