[Role of ash2 (absent, small, or homeotic)-like and Jumonji domain-containing protein 3 on histone methylation of interferon-gamma gene and their associations with vascular damage of Kawasaki disease]

Objective: To investigate the impacts of ash2 (absent, small, or homeotic)-like (Ash2L) and Jumonji domain-containing protein 3 (Jmjd3) on histone methylation of interferon-gamma(IFN-γ) gene and association with vascular damage of Kawasaki disease (KD) in acute phase. Methods: This study was performed among 36 children with KD in acute phase (KD group) and 28 age-matched health children (control group), who were treated or underwent physical examination in our hospital between February 2015 and June 2016. Patients were further divided into KD groups with or without coronary artery lesions (KD-CAL(+) , 16 cases; KD-CAL(-), 20 cases). All KD patients were treated with intravenous immunoglobulin. The proportion of type 1 helper T(Th1) cells and protein levels of IFN-γ, T-box expressed in T cells(T-bet), phosphorylated signal transducer and activator of transcription 1(pSTAT1) and phosphorylated signal transducer and activator of transcription 4(pSTAT4) were analyzed by flow cytometry.Chromatin immunoprecipitation was performed to determine histone methylation (histone H3 tri-methyl K4(H3K4me3), histone H3 tri-methyl K27(H3K27me3)) and binding levels of Ash2L, Jmjd3 and Ezh2 associated with IFN-γ in CD4(+) T cells. Quantitative real-time PCR was used to determine mRNA levels of IFN-γ, interferon γ receptor 1(IFN-γR1), interferon γ receptor 2(IFN-γR2), interleukin 12 receptor subunit beta 1(IL-12Rβ1), interleukin 12 receptor subunit beta 2(IL-12Rβ2), interleukin 18 receptor subunit beta α(IL-18Rα), interleukin 18 receptor subunit beta β(IL-18Rβ), tumor necrosis factor receptor 1(TNFR1), toll-like receptor 4(TLR4), receptor interacting serine/threonine kinase 1(RIP-1) and myeloid differentiation primary response gene 88(MyD88) in CD4(+) T cells. Plasma concentrations of IFN-γ, interleukin 12(IL-12), interleukin 18(IL-18) and tumor necrosis factor α(TNF-α) were measured by enzyme-linked Immunosorbent assay. Results: (1)The proportion of Th1 and its protein level of IFN-γ were significantly higher in KD group than those in control group and higher in KD-CAL(+) group than in KD-CAL(-) group (all P<0.05), and lower after treatment than before treatment (all P<0.05). (2)Compared with control group, mRNA level of IFN-γ and IFN-γ-associating H3K4me3 was increased, while level of IFN-γ associating H3K27me3 in CD4(+) T cells was reduced in KD group (all P<0.05), which resulted in a higher rate of H3K4me3/H3K27me3 (P<0.05) in KD group, which was positively correlated with IFN-γ mRNA in KD group(r=0.55, P<0.05). Similar results were found between KD-CAL(+) group and KD-CAL(-) group (all P<0.05). Level of IFN-γ associating H3K27me3 was increased, and mRNA level of IFN-γ and IFN-γ associating H3K4me3 was decreased after treatment than before treatment (all P<0.05). (3)Expression of T-bet protein and binding levels of Ash2L and Jmjd3 with IFN-γ gene were significantly higher in KD group than those in control group(all P<0.05), higher in KD-CAL(+) group than those in KD-CAL(-) group (all P<0.05). These parameters were significantly lower after treatment than before treatment (all P<0.05). Binding level of Ezh2 with IFN-γ gene was similar among various groups (all P>0.05). (4)In comparison with control or after treatment, surface receptors(IFN-γR1/2, IL-12Rβ1/2, IL-18Rα/β, TNFR1 and TLR4) and its downstream molecules(pSTAT1, pSTAT4, RIP(1) and MyD88) in CD4(+) T cells, and plasma concentrations of inflammatory cytokines(IFN-γ, IL-12, IL-18 and TNF-α) were found to be higher in KD group(all P<0.05). These parameters were also higher in KD-CAL(+) group than in KD-CAL(-) group (all P<0.05). Conclusion: Aberrant histone methylation of IFN-γ associating H3K4me3 and H3K27me3 caused by over-binding of Ash2L and Jmjd3 might be involved in immune dysfunction and vascular damage in KD in the acute phase.