IL-18 is upregulated in the kidney and primes neutrophil responsiveness in ANCA-associated vasculitis.
ABSTRACT In antineutrophil cytoplasm autoantibody (ANCA)-associated systemic vasculitis (ASV), autoantibody-induced neutrophil activation is believed to cause organ damage. In vitro, tumor necrosis factor alpha (TNFalpha) primes neutrophils for ANCA stimulation and TNFalpha blockade has been successfully used to treat ASV. Nonetheless, irreversible organ damage can still occur, suggesting that other cytokines may circumvent TNFalpha blockade. We report that interleukin (IL)-18 deposition, as assessed by immunoperoxidase staining, is increased in renal biopsies from ASV patients. Immunofluorescence microscopy demonstrated that podocytes are the predominant glomerular IL-18-positive cell type, whereas in the interstitium, myofibroblasts, distal tubular epithelium, and infiltrating macrophages stained for IL-18. In vitro, IL-18 primed superoxide production by ANCA-activated neutrophils comparably to TNFalpha. IL-18-primed, ANCA-induced superoxide production was unaffected by anti-TNFalpha antibody, which abrogated TNFalpha priming. Furthermore, TNFalpha and IL-18 phosphorylated neutrophil p38 mitogen-activated protein kinase (MAPK), but IL-18-mediated p38 MAPK phosphorylation was unaffected by anti-TNFalpha antibody. The p38 MAPK inhibitor, SB20358, reduced IL-18-primed, ANCA-induced superoxide production in a concentration-dependent manner. ANCA-induced superoxide release was also sensitive to the Leukotriene B4 (LTB4) inhibitor MK-886. IL-18 priming was not associated with increased ANCA antigen expression on isolated neutrophils. We conclude that IL-18 is likely to be important for neutrophil recruitment and priming in ASV. Therapies targeting single priming agents may have limited efficacy in controlling disease.
Article: Higher elastase activity associated with lower IL-18 in GCF from juvenile systemic lupus patients.[show abstract] [hide abstract]
ABSTRACT: Our aim was to evaluate the expression of interleukin-18 (IL-18), interleukin-l-beta (IL-1beta) and the amount of elastase activity in gingival crevicular fluid (GCF) from inflamed gingival sites in patients with juvenile systemic lupus erythematosus (JSLE), and compare these to the expression in GCF from inflamed sites in generally healthy controls. In addition, the local inflammation in periodontal tissues was related to systemic inflammation by the assessment of IL-18 levels in plasma. GCF from 16 patients with JSLE and 14 controls were collected using a washing device. Elastase activity was measured with a specific substrate, and IL-18 and 11-1 were measured by ELISA. The percentage of visible plaque index, gingival bleeding index and attachment level were similar in JSLE and controls, while the percentage of probing depth greater or equal to 3 mm was significantly higher in the controls. The total amount of IL-1beta and IL-18 in GCF were significantly decreased in JSLE, while the total amount and the percentage of free elastase activity were significantly higher in JSLE when compared with the controls. The plasma levels of I1-18 and the erythrocyte sedimentation rate were significantly higher in JSLE patients. We found more active elastase in GCF from inflamed sites in JSLE patients even in the presence of significantly lower levels of IL-18 and IL-13. The increased elastase activity suggests a hyperactivity of neutrophils in JSLE, possibly generated by a priming effect caused by the higher plasma levels of IL-18 found in these JSLE patients.Oral health & preventive dentistry 02/2008; 6(1):75-81. · 0.55 Impact Factor
Article: Serum IL-18 is closely associated with renal tubulointerstitial injury and predicts renal prognosis in IgA nephropathy.[show abstract] [hide abstract]
ABSTRACT: IgA nephropathy (IgAN) was thought to be benign but recently found it slowly progresses and leads to ESRD eventually. The aim of this research is to investigate the value of serum IL-18 level, a sensitive biomarker for proximal tubule injury, for assessing the histopathological severity and disease progression in IgAN. Serum IL-18 levels in 76 IgAN patients and 36 healthy blood donors were measured by ELISA. We evaluated percentage of global and segmental sclerosis (GSS) and extent of tubulointerstitial damage (TID). The correlations between serum IL-18 levels with clinical, histopathological features and renal prognosis were evaluated. The patients were 38.85 ± 10.95 years old, presented with 2.61 (1.43∼4.08) g/day proteinuria. Serum IL-18 levels were significantly elevated in IgAN patients. Baseline serum IL-18 levels were significantly correlated with urinary protein excretion (r = 0.494, P = 0.002), Scr (r = 0.61, P < 0.001), and eGFR (r = -0.598, P < 0.001). TID scores showed a borderline significance with serum IL-18 levels (r = 0.355, P = 0.05). During follow-up, 26 patients (34.21%) had a declined renal function. Kaplan-Meier analysis found those patients with elevated IL-18 had a significant poor renal outcome (P = 0.03), and Cox analysis further confirmed that serum IL-18 levels were an independent predictor of renal prognosis (β = 1.98, P = 0.003).Mediators of Inflammation 01/2012; 2012:728417. · 3.26 Impact Factor