Intrarenal Expression of Interleukin-6 and the -174 G/C Polymorphism in IgA Nephropathy

Lim, Chun Soo; Kim, Yon Su; Ahn, Cu Rie; Han, Jin Suk; Kim, Suhng Gwon; Lee, Jung Sang; Chae, Dong Wan

Abstract

BACKGROUND: The proinflammatory cytokine, interleukin-6(IL-6), seems to be involved in the pathogenesis and progression of IgA nephropathy. The aim of this study is to elucidate the relationship between the intrarenal expression of IL-6 and the clinicopathological findings in IgA nephropathy, and to reveal whether allele-frequency differences of -174 G/C polymorphism of IL-6 gene promoter region exist between IgA nephropathy patients and the normal population.
METHODS
The total RNA was extracted from renal tissue of 56 IgA nephropathy patients. Semiquantitative reverse-transcriptase polymerase chain reactions(RT-PCR) using the internal competitors were done for the quantification of IL-6 transcripts. Using PCR-RFLP, we examined the -174 G/C polymorphism in IgA nephropathy patients and in 53 of the normal Korean population.
RESULTS
In RT-PCR, the degree of intrarenal IL-6 expression was not related with any clinicopathological characteristics of IgA nephropathy patients. The degree of IgA deposition in glomeruli was correlated with the expression of IL-6, but the correlation was not statistically significant. Among the 56 IgA nephropathy patients studied, 55 carried the GG wild type and only 1 carried the GC genotype. Among 53 normal controls studied, only 1 carried the GC genotype and the rest carried GG wild type(C allele frequency=0.009).
CONCLUSION
These results suggest that IL-6 is not related with the pathophysiology of IgA nephropathy, and the -174 G to C polymorphism of IL-6 promoter region is very rare in Koreans. And, the IL-6 polymorphism at -174 is unlikely to contribute significantly to susceptibility to or the progression of IgA nephropathy in Koreans.