Background: Plasma levels of some pro-inflammatory cytokines and soluble adhesion molecules have been suggested to be useful parameters to assess the activity of antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis and lupus nephritis. We hypothesized that the renal activity of these diseases is better reflected by the urinary excretion and fractional excretion of these molecules.
Methods: Plasma levels and urinary excretion of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-8, and the soluble cell adhesion molecules sICAM-1 and sVCAM-1 were measured by enzyme-linked immunosorbent assay (ELISA) in 14 patients with ANCA-positive renal vasculitis (eight active, ANCA-A; six in remission, ANCA-R), six patients with active lupus nephritis (LN), 15 patients with IgA nephropathy (IgAN) and nine healthy subjects. Fractional excretion of selected cytokines and adhesion molecules was also calculated.
Results: Patients with ANCA-A had increased urinary excretion and fractional excretion of TNF-alpha (9.27 +/- 3.19% vs 0.58 +/- 0.02%, P < 0.01), IL-6 (120.79 +/- 65.83% vs 1.89 +/- 0.34%, P < 0.01) and increased fractional excretion of IL-8 (23.34 +/- 6.38% vs 2.56 +/- 1.07%, P < 0.01) and sVCAM-1 (0.81 +/- 0.33% vs 0.03 +/- 0.02%, P < 0.01) compared with controls. Urinary excretion of TNF-alpha and IL-6 and fractional excretion of TNFalpha, IL-6 and IL-8 were higher in ANCA-A than in ANCA-R. Patients with LN had increased plasma TNF-alpha (20.52 +/- 2.01 pg/ml vs 12.33 +/- 0.23 pg/ml, P < 0.05) and sVCAM-1 (1537.88 +/- 276.36 ng/ml vs 692.26 +/- 44.42 ng/ml, P < 0.05) and increased urinary excretion of TNF-alpha (2.81 +/- 0.51 microg/mol creat vs 0.98 +/- 0.05 microg/mol creat, P < 0.01), IL-8 (35.78 +/- 14.03 microg/mol creat vs 12.46 +/- 5.19 microg/mol creat, P < 0.05) and sVCAM-1 (48.98 +/- 20.20 microg/mol creat vs 2.92 +/- 1.35 microg/mol creat, P < 0.01) compared with controls. Patients with IgAN had, in comparison with controls only increased plasma TNF-alpha (18.10 +/- 0.57 pg/ml vs 12.33 +/- 0.23 pg/ml, P < 0.05).
Conclusions: Urinary excretion and fractional excretion, but not plasma levels, of selected pro-inflammatory cytokines (TNF-alpha, IL-6 and IL-8) were increased in patients with active ANCA-positive renal vasculitis, but not in ANCA positive vasculitis in remission. These parameters may be useful to monitor the activity of this disease.