急性ITP患儿外周PPAR-γ mRNA表达变化及与IL-18水平的相关性

Correlation between the expression of PPAR-γ mRNA and plasma IL-18 in children acute ITP

目的检测急性特发性血小板减少性紫癜(idiopathic thrombocytopenic purpura,ITP)患儿外周血浆中IL-18对血淋巴细胞PPAR-γmRNA表达变化影响。方法序贯收集符合试验入选标准的急性ITP患儿53例,同时收集相匹配的同期体检儿童50例作为对照。将血液标本平均分为5份,在取样1、24、48、72 h后,分别采用RT-PCR法检测ITP患儿外周血淋巴细胞PPAR-γ mRNA的表达,蛋白免疫印迹(western blot)检测PPAR-γ蛋白的含量,ELISA法检测血浆中IL-18水平。结果急性ITP组白细胞表达PPAR-γ蛋白在1、24、48、72 h与对照组PPAR-γ蛋白分别相比均明显增强,差异有显著性(t1=7.52,t24=16.38,t48=9.65,t72=12.34,均P<0.05);急性ITP患儿在不同的时间点测定的PPAR-γ mRNA表达水平明显均高于正常对照组(t1=9.25,t24=14.24,t48=8.69,t72=16.14,均P<0.05),同样发现急性ITP患儿血浆IL-18水平均显低于正常对照组(t1=6.38,t24=9.65,t48=8.91,t72=7.19,均P<0.05);血浆IL-18水平与PPAR-γ mRNA表达呈负相关(r=-0.89,P<0.05)。结论血浆中IL-18生成量的减少可能导致了急性ITP患儿外周血淋巴细胞PPAR-γ表达的增加,调控Th1/Th2细胞分化功能出现障碍,使有效的免疫抑制作用降低,导致自身反应性T细胞激活增多、凋亡减少,使得浆细胞产生抗血小板抗体增多,促进了血小板的破坏。

Objective To investigate the influence of serum IL- 18 on the expression of PPAR-γ mRNA in acute ITP children . Methods Fifty - three acute ITP children who met the cviteria of diagnosis in the hospitals affiliated to Guangdong Medical College from September 2007 to July 2008 were enrolled in the study Fifty healthy children were chosen as controls. Expression of PPAR - γ mRNA on peripheral blood lymphocytes was detected by RT - PCR. Plasma IL - 18 was detected by ELISA. Results In acute ITP group, the expression of PPAR - γ protein in leukocyte at 1 h, 24 h, 48 h, 72 h were significantly enhanced in comparison with the control group, with significant differences （t1 = 7. 52, t24 = 16. 38, t48 = 9. 65, t72 = 12.34, P 〈 0. 05 ） ; Levels of IL - 18 has a negative correlation with the expression of PPAR - γ mRNA （ r = - 0. 89, P 〈 0. 05 ）. The expression of PPAR - γ mRNA in acute ITP children were significantly higher than that of the normal control group at different times point （t1 = 9. 25, t24 = 14. 24, t48 = 8.69, t72 = 16. 14, P 〈 0. 05 ）. Plasma IL- 18 from children with acute ITP was significantly lower than that of normal control group （t1 = 6. 38, t24 = 9. 65, t48 = 8.91, t72 = 7. 19, P 〈 0. 05 ） ; Conclusion Reduced plasma IL - 18 may lead to increased expression of PPAR - γ on peripheral blood lymphocytes in acute ITP children and impaired Th1/Th2 cell differentiation, which may result in self - reactive T cells activation, reduced apoptosis, and increased production of anti - platelet antibodies by plasma cells to promote destruction of platelets.