A panel of urinary proteins predicts active lupus nephritis and response to rituximab treatment

Abstract

Objectives: ∼30% of patients with SLE develop LN. Presence and/or severity of LN are currently assessed by renal biopsy, but biomarkers in serum or urine samples may provide an avenue for non-invasive routine testing. We aimed to validate a urinary protein panel for its ability to predict active renal involvement in SLE.

Methods: A total of 197 SLE patients and 48 healthy controls were recruited, and urine samples collected. Seventy-five of the SLE patients had active LN and 104 had no or inactive renal disease. Concentrations of lipocalin-like prostaglandin D synthase (LPGDS), transferrin, alpha-1-acid glycoprotein (AGP-1), ceruloplasmin, monocyte chemoattractant protein 1 (MCP-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were quantified by MILLIPLEX® Assays using the MAGPIX Luminex platform. Binary logistic regression was conducted to examine whether proteins levels associate with active renal involvement and/or response to rituximab treatment.

Results: Urine levels of transferrin (P <0.005), AGP-1 (P <0.0001), MCP-1 (P <0.001) and sVCAM-1 (P <0.005) were significantly higher in SLE patients when compared with healthy controls. Furthermore, levels of transferrin, AGP-1, ceruloplasmin, MCP-1 and sVCAM-1 (all P <0.0001) were higher in SLE patients with active LN when compared with patients without active LN. A combination of five urine proteins, namely LPGDS, transferrin, ceruloplasmin, MCP-1 and sVCAM-1 was a good predictor of active LN (AUC 0.898). A combined model of LPGDS, transferrin, AGP-1, ceruloplasmin, MCP-1 and sVCAM-1 predicted response to rituximab treatment at 12 months (AUC 0.818).

Conclusions: Findings support the use of a urinary protein panel to identify active LN and potentially predict response to treatment with rituximab in adult SLE patients. Prospective studies are required to confirm findings.

Keywords: SLE; biomarker; inflammation; lupus nephritis; renal; rituximab; stratification; treatment.

© The Author(s) 2020. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Figures

Fig. 1

Comparison of protein levels in the urine of SLE patients and healthy controls Analysis of concentrations of LPGDS (A), transferrin (B), AGP-1 (C), ceruloplasmin (D), MCP-1 (E) and sVCAM-1 (F) in SLE patients and healthy controls. Boxplots show median, IQR and extremes in grey with individual results as black dots. Mann–Whitney U tests with Bonferroni adjustment to account for multiple testing were performed to compare differences in urinary protein levels between groups. Corrected P-values (Pc) are reported. AGP-1: alpha-1-acid glycoprotein; HC: healthy controls; LPGDS: lipocalin-like prostaglandin D synthase; MCP-1: monocyte chemoattractant protein 1; ns: not significant; sVCAM-1: soluble vascular cell adhesion molecule-1.

Fig. 2

Comparison of protein levels in the urine of SLE patients grouped by disease severity Analysis of concentrations of LPGDS (A), transferrin (B), AGP-1 (C), ceruloplasmin (D), MCP-1 (E), sVCAM-1 (F) and proteinuria (G) in SLE patients grouped by disease severity according to SLEDAI score. No–mild was defined as a score of 0–4, Moderate as a score of 5–14, and High–very high as a score of 15 and above. Boxplots show median, IQR and extremes in grey with individual results as black dots. Kruskal–Wallis test with Dunn’s multiple comparison post hoc test was used to compare differences in urinary protein levels between groups. Corrected P-values (Pc) are reported. AGP-1: alpha-1-acid glycoprotein; LPGDS: lipocalin-like prostaglandin D synthase; MCP-1: monocyte chemoattractant protein 1; sVCAM-1: soluble vascular cell adhesion molecule-1.

Fig. 3

Protein levels in the urine of SLE patients with active renal disease Analysis of concentrations of LPGDS (A), transferrin (B), AGP-1 (C), ceruloplasmin (D), MCP-1 (E) and sVCAM-1 (F) in SLE patients based on presence of active renal disease. Boxplots show median, IQR and extremes in grey with individual results as black dots. Mann–Whitney U tests with Bonferroni adjustment to account for multiple testing were performed to compare differences in urinary protein levels between groups. Corrected P-values (Pc) are reported. AGP-1: alpha-1-acid glycoprotein; LPGDS: lipocalin-like prostaglandin D synthase; MCP-1: monocyte chemoattractant protein 1; ns: not significant; sVCAM-1: soluble vascular cell adhesion molecule-1.