SOCS3 is epigenetically up-regulated in steroid resistant nephrotic children.

Abstract

The mechanism of steroid resistance in children with the nephrotic syndrome is yet unknown. About 20% of patients demonstrate steroid unresponsiveness and progress to end stage renal disease. Aberrant SOCS3 and SOCS5 expression in steroid resistant and sensitive patients has previously been demonstrated. Here, we investigate genetic and epigenetic mechanisms of regulation of SOCS3 and SOCS5 transcription in nephrotic children. 76 patients with the nephrotic syndrome (40 steroid resistant and 36 steroid sensitive) and 33 matched controls were included in this study. We performed genotyping of a total of 34 single nucleotide polymorphisms for SOCS3 and SOCS5 promoters and evaluated their methylation status using MS-PCR and QMSP methods. Steroid resistant patients had a significantly lower methylation of one region of SOCS3 promoter in comparison with steroid sensitive patients and controls (p < 0.0001). However, the relative methylation level in the steroid sensitive patients and controls differed significantly even before the first steroid dose (p = 0.001758). Other SOCS3 and SOCS5 promoter regions displayed no differences in methylation or were fully methylated/unmethylated in all study groups, showing site-specific methylation. The allele and genotype distribution for SOCS3 and SOCS5 markers did not differ statistically between the groups. We demonstrate an epigenetic mechanism of SOCS3 up-regulation in steroid resistant children with the nephrotic syndrome. The assessment of methylation/unmethylation of SOCS3 promoter might be an early marker for steroid responsiveness in NS patients.