OBJECTIVEPrimary nephrotic syndrome (PNS) is one of the common renal diseases in children, the pathogenesis of which is unclear. Evidences suggested that the proteinuria of NS is associated with the increased expression of the interleukin-8 (IL-8) genes. The purpose of the study was to evaluate the serum concentration and mRNA expression of IL-8 before and after the methylprednisolone pulse therapy (MPT) in PNS.

METHODThirty children with PNS diagnosed from December 2000 to October 2001 were enrolled in this study (patients group). They were not treated with glucocorticoid at least within the recent 3 months. The children aged from 1.5 to 14 years (mean 8.5 years), and included 24 boys and 6 girls. Eighteen healthy children were selected as control group after physical examination. The children in control group aged from 2 to 14 years (mean 8 years) and included 13 boys and 5 girls. All patients were treated with MPT intravenously (30 mg/kg) for successive 3 days followed by oral prednisone. The serum protein level of IL-8 was measured by ELISA according to the manufacturer's instructions. Human IL-8 ELISA kit was purchased from Jingmei corporation Shenzhen, China. And the concentration was obtained after drawing the standard curve. The expression of IL-8 gene was detected with RT-PCR method. The important reverse transcription reagent kit and Trizol reagent were all bought from GIBCO BRL, USA. Statistical analysis of rank sum test was adopted for data processing.

RESULTSComparison of the serum IL-8 level in the same patient before and after the therapy showed significant difference [29.59 (7.14-352.08) ng/L vs. 10.80 (4.27-77.86) ng/L, u = 4.26, P < 0.01]. The serum level in patient group before the therapy increased obviously in comparison to the level of the control group [10.37 (5.46-33.31) ng/L, u = 4.53 P < 0.01]. The serum level of IL-8 in patient group after the therapy also showed significant difference compared to the control group (u = 2.73 P < 0.01). The mRNA expression of IL-8 in the same patient before and after therapy showed significant difference [0.862 (0.776-0.95) vs. 0 (0-0.754), u = 3.902 P < 0.01].

CONCLUSIONIL-8 may be involved in the pathogenesis of PNS because of the significant increase of the serum IL-8 level and PBMC IL-8 mRNA expression in nephrotic syndrome children. Methylprednisolone pulse therapy in PNS was able to inhibit the protein production and PBMC mRNA expression of IL-8, so the therapeutic mechanism of MPT in PNS might be associated with the inhibition of IL-8 expression.