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Objective:To investigate the effect and mechanism of histone methyltransferase enhancer of zeste homolog 2 (EZH2) on sepsis-induced T cell dysfunction.Methods:Twenty-four male C57BL/6 mice were divided into three groups randomly: sham operated group, sepsis model group [cecum ligation and puncture (CLP)+dimethyl sulfoxide (DMSO) group] and EZH2 selective inhibitor treated group (CLP+GSK126 group), with 8 mice in each group. Sepsis murine model was reproduced by CLP. CLP+DMSO group and CLP+GSK126 group were treated with DMSO or GSK126 (10 mg/kg) respectively right after surgery through intraperitoneal injection. The mice were sacrificed 24 hours after operation, and the mesenteric lymph nodes were collected. The expression of EZH2, apoptosis rates, cell proliferation marker ki-67 antigen positive T lymphocytes (ki-67 + cell), interferon-γ positive T lymphocytes (IFN-γ + cell), programmed death receptor-1 positive T lymphocytes (PD-1 + cell) and programmed death-ligand 1 positive T lymphocytes (PD-L1 + cell) were determined by flow cytometry. Results:Compared with sham operated group, the expression of EZH2 in T lymphocytes was up-regulated on mesenteric lymph nodes of CLP+DMSO group. Compared with CLP+DMSO group, the ratio of CD3 + T lymphocytes in CLP+GSK126 group was up-regulated (0.70±0.02 vs. 0.50±0.07, P < 0.01), indicating that the EZH2 inhibitor could increase the number of T lymphocytes in lymph nodes of septic mice; the ratio of ki-67 + cells in CD4 + and CD8 + T lymphocytes in CLP+GSK126 group was increased (CD4 +: 0.74±0.05 vs. 0.63±0.04, CD8 +: 0.82±0.06 vs. 0.70±0.04, both P < 0.05), indicating that the EZH2 inhibitor could increase the ratio of T lymphocytes with high proliferative activity in lymph nodes of septic mice. However, no significant difference was found on both CD4 + and CD8 + T lymphocytes apoptosis rates in the mesenteric lymph nodes of mice between CLP+GSK126 group and CLP+DMSO group [CD4 +: (21.53±2.87)% vs. (20.48±3.21)%, CD8 +: (8.34±1.02)% vs. (7.71±1.38)%, both P > 0.05], indicating that no extra T lymphocytes apoptosis was induced by EZH2 inhibitor. Compared with CLP+DMSO group, the ratios of IFN-γ + CD4 + and IFN-γ + CD8 + T lymphocytes were increased in CLP+GSK126 group (IFN-γ +CD4 +: 0.31±0.11 vs. 0.14±0.06, IFN-γ +CD8 +: 0.30±0.10 vs. 0.13±0.06, both P < 0.05), suggesting that secretion of IFN-γ in lymph nodes by sepsis T lymphocytes was augmented after EZH2 inhibitor administration. Furthermore, compared with CLP+DMSO group, the ratio of PD-1 + cell in CD8 + T lymphocyte was down-regulated in CLP+GSK126 group (0.092±0.006 vs. 0.135±0.004, P < 0.01), suggesting that EZH2 inhibitor restrained the PD-1 expression on sepsis lymphoid node CD8 + T lymphocytes, however, it had no significant effect on PD-L1 + cells. Conclusion:EZH2, regulates sepsis-induced T lymphocyte dysfunction, possibly through modulating the expression of PD-1.
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Objective To investigate the effects of a novel enhancer of Zeste homolog 2 (EZH2) inhibitor GSK126 in vitro on the cell proliferation and apoptosis in acute leukemia and lymphoma cells. Methods CCKˉ8 assay was used to measure the effects of GSK126 with different concentrations and time on the cell proliferation in human Tˉcell acute lymphoblastic leukemia (TˉALL) CEM cell line, acute monocytic leukemia U937 cell line and Burkitt lymphoma Raji cell line. Annexin V/PI double staining method was used to determine the effects of GSK126 on the cell apoptosis. The effect of GSK126 on the mRNA levels of EZH2, bclˉ2 and bclˉxL were measured by using quantitative polymerase chain reaction (qPCR). Results After the function for 24 h, 48 h and 72 h, compared to the negative control group (0 μmol/L), 5, 10, 15, 20, 25 μmol/L GSK126 treatment showed a significant doseˉand timeˉdependent cell proliferation suppression in CEM cells; 5, 10, 15, 20 μmol/L GSK126 treatment showed a significant doseˉand timeˉdependent cell proliferation suppression in U937 cells; 5, 10, 15, 20, 25, 30 μmol/L GSK126 treatment showed a significant timeˉdependent suppression in Raji cells (all P< 0.05). The 48 h 50% inhibitory concentration ( IC 50) of GSK126 on CEM, U937, Raji cells was (13.46 ±0.83), (11.65 ±1.02), (15.00 ±0.19) μmol/L, respectively. GSK126 treatment with the doses of 8, 12 and 16 μmol/L promoted the apoptosis of CEM and U937 cells compared with the negative control group (0 μmol/L), and there were statistical differences in the apoptosis rate (F＝ 167.995, P< 0.01; F＝ 158.400, P< 0.01). In Raji cells, only 16 μmol/L GSK126 treatment had a higher cell apoptosis rate compared with the control group (t＝ 47.998, P< 0.05). Furthermore, 8, 12 and 16 μmol/L GSK126 treatment suppressed the expressions of EZH2 mRNA in CEM, U937 and Raji cells compared with the control group (F＝82.035, P<0.01; F＝ 252.712, P< 0.01; F＝ 690.536, P< 0.01), and the expressions of bclˉ2 and bclˉxL mRNA (bclˉ2: F＝ 1 900.525, P< 0.01; F＝ 431.324, P< 0.01; F＝216.184, P<0.01; bclˉxL: F＝256.751, P<0.01; F＝147.019, P<0.01; F＝209.325, P<0.01). Conclusion EZH2 plays an important role in the occurrence and development of acute leukemia and lymphoma. GSK126 as a high selective inhibitor of EZH2 might be a potential new drug in treatment of hematological malignancies.