Role of hypomethylation of suppressor of cytokine signaling in T helper 17 cell/regulatory T cell imbalance in children with Henoch-Schönlein purpura

Abstract:

Objective To investigate the association between suppressor of cytokine signaling (SOCS) hypomethylation and T helper 17 (Th17) cell/regulatory T (Treg) cell imbalance in children with Henoch-Schönlein purpura (HSP) and the immune pathogenesis of HSP. Methods A total of 32 children in the acute stage of HSP who were hospitalized from May 2014 to January 2015 were enrolled as subjects, and 28 children who underwent physical examination were enrolled as normal control group. ELISA was used to measure the plasma level of interleukin-6 (IL-6). Flow cytometry was used to measure the percentages of CD4⁺ IL-17A⁺ T cells (Th17 cells) and CD4⁺CD25⁺ Treg cells (Treg cells) in peripheral blood and mean fluorescence intensity (MFI) for phosphorylated-STAT3 (pSTAT3) protein in CD4⁺ T cells. Quantitative real-time PCR was used to measure the mRNA expression of suppressor of cytokine signaling-1 (SOCS1) and suppressor of cytokine signaling-3 (SOCS3) in CD4⁺ T cells. High-resolution melting (HRM) was used to evaluate the methylation level of the CpG islands in SOCS1 exon 2 and the CpG islands of the potential bind sites for STAT3 in the 5'-untranslated region (5'-UTR) of SOCS3 in peripheral blood mononucleated cells. Results Compared with the normal control group, the HSP group had significant increases in plasma IL-6 concentration and MFI for pSTAT3 in CD4⁺ T cells, as well as a significant increase in the percentage of Th17 cells and a significant reduction in the percentage of Treg cells (P < 0.05). The HSP group had significantly higher mRNA expression of SOCS1 and SOCS3 in peripheral blood mononucleated cells than the normal control group (P < 0.05). In the HSP group, the mRNA expression of SOCS1 and SOCS3 was negatively correlated with Th17/Treg ratio (P < 0.05). The HSP group had hypomethylation of the CpG islands in SOCS1 exon 2 and the potential binding site for STAT3 in SOCS3 5'-UTR, while the normal control group had complete demethylation. Conclusions Low relative expression of SOCS1 and SOCS3 caused by hypomethylation may be a factor for Th17/Treg imbalance in children with HSP.