OBJECTIVETo examine serum concentration of interleukin-18 (IL-18) and IL-18 mRNA expression in peripheral blood mononuclear cells (PBMCs) in children with primary nephrotic syndrome (PNS) and explore the possible role of IL-18 in steroid-resistant nephrotic syndrome (SRNS).

METHODSSixty-six children with newly diagnosed PNS, including 39 cases of steroid sensitive nephrotic syndrome (SSNS) and 27 cases of SRNS, were enrolled. Forty healthy children were used as a normal control group. Blood samples were collected before and 8 weeks after glucocorticoid treatment. Serum concentration of IL-18 was measured using ELISA. IL-18 mRNA expression in PBMCs was detected by the RT-PCR method. The amount of 24-hr urine protein was measured by the biuret method. Serum contents of total cholesterol (T-Ch), triglyceride (TG), low density lipoprotein (LDL), total protein (TP), and albumin (Alb) were measured by the automatic biochemistry analyzer.

RESULTSSerum concentration of IL-18 and IL-18 mRNA expression in PBMCs in the SSNS and the SRNS groups were significantly higher than those in the normal control group before treatment (P< 0.05). The SRNS group had increased serum protein concentration of IL-18 and IL-18 mRNA expression in PBMCs compared with the SSNS group before treatment (P< 0.05). Serum LDL content in the SRNS group was also significantly higher than that in the SSNS group before treatment (P< 0.05). After treatment, serum concentration of IL-18 and IL-18 mRNA expression in PBMCs in the SRNS group were significantly higher than those in the SSNS and the normal control groups (P< 0.05). Serum concentration of IL-18 and IL-18 mRNA expression in PBMCs in the SSNS group were significantly reduced after treatment, but the alterations of IL-18 were not observed in the SRNS group after treatment.

CONCLUSIONSSRNS was associated with increased serum IL-18 concentration and IL-18 mRNA expression in PBMCs. Over-production of IL-18 may play a role in the development of SRNS.