Inflammatory cytokine gene expression in the urinary sediment of patients with lupus nephritis

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Abstract
Objective Lupus nephritis is characterized by intrarenal inflammation and lymphocyte activation. In the present study, the expression of cytokine genes in the urinary sediment of patients with systemic lupus erythematosus (SLE) was examined. Methods We studied 3 SLE patient groups (25 with active lupus nephritis [active group], 25 with inactive SLE and previous renal involvement [remission group], 20 with inactive SLE and no history of renal involvement [nonrenal SLE group]) and 2 control groups (10 patients with noninflammatory renal diseases [non-SLE group] and 10 healthy volunteers [healthy group]). Cytokine gene expression in the urinary sediment was studied by real-time quantitative polymerase chain reaction. Results Expression of interferon-γ (IFNγ) in urinary sediment was significantly higher in the active group than in all other groups (P < 0.001 by Kruskal-Wallis test). Among the SLE patient groups, there was a close correlation between IFNγ expression and the overall SLE Disease Activity Index (SLEDAI) score (Spearman's r = 0.590, P < 0.001) and the SLEDAI renal score (r = 0.642, P < 0.001). Urinary expression of interleukin-2 (IL-2) in the active group was significantly higher than that in the healthy group (P = 0.046) but not in the remission or nonrenal SLE groups. There was no difference in the levels of IL-4 expression among the SLE groups. Conclusion We found a predominance of Th1 cytokine in the urinary sediment of patients with active lupus nephritis. Measurement of cytokine gene expression in urinary sediment may be a useful noninvasive tool for assessing the severity of renal involvement in SLE.