Aberrant gene expression in CD4+CD28-T cells: mechanisms

一个衰老的T细胞亚群，特征是缺乏CD28，随着年龄的增长而发展，在慢性 炎症性疾病，如类风湿性关节炎(RA)和急性冠脉综合征。CD4+CD28- 亚群是促炎和细胞毒性的，存在于炎症的滑膜和动脉粥样硬化中。 心肌梗死死亡患者的斑块，表明它们参与了自身免疫性疾病 流程。CD4+CD28-亚群异常表达杀伤细胞免疫球蛋白样受体 基因和穿孔素，通常在NK细胞上发现，并过度表达干扰素-γ、LFA-1和CD70。其原因是 基因表达的异常尚不清楚。在初步研究中，我们发现正常T细胞具有 KIR、穿孔素、干扰素-γ、LFA-1和CD70表达所必需的转录因子 基因被关键调控元件的甲基化抑制，而这些元件的去甲基化是 足以促进转录。此外，我们还发现，随着年龄的增长，总T细胞DNA去甲基化，在RA， 部分原因是DNA甲基转移酶(MTase)减少，抑制T细胞ERK和JNK 模拟随着衰老而发生的信号减少的信号会降低DNA MTase的表达和 使DNA去甲基化。最后，我们发现CD28提供了增加DNA MTase的共刺激信号 表情。我们假设，由JNK和/或ERK信号减弱引起的DNA低甲基化， 结果在增龄性T细胞亚群中，KIR、穿孔素、干扰素-γ、LFA-1和CD70过表达 RA，具有促炎和细胞毒作用。这将在3个具体目标中进行测试。我们将：1) CD4+CD28-调控元件甲基化状态与候选基因表达的比较 RA患者和老年患者的CD4+CD28+T细胞和对照组的CD4+CD28+细胞，2) 比较相同T细胞亚群中的DNA MTase水平，然后选择性地降低 并检测对候选基因甲基化和表达的影响，以及3)比较 ERK和JNK通路在相同的T细胞亚群中的信号转导，并检测信号转导减少的影响 DNA MTase表达及候选基因甲基化、表达和功能的研究。这些研究将 确定改变这个病理亚群中基因表达的机制，并提出恢复的方法 在这些细胞中正常的基因表达。

A senescent T cell subset, characterized by the absence of CD28, develops with aging, in chronic inflammatory diseases like rheumatoid arthritis (RA), and in acute coronary syndromes. The CD4+CD28- subset is proinflammatory and cytotoxic, and is found in inflamed synovium as well as atherosclerotic plaques of patients dying from myocardial infarction, suggesting they participate in autoimmune disease processes. The CD4+CD28- subset aberrantly expresses killer-cell immunoglobulin-like receptor (KIR) genes and perforin, normally found on NK cells, and overexpresses IFN-y, LFA-1, and CD70. The reason for the aberrant gene expression is unknown. In preliminary studies we found that normal T cells have the transcription factors necessary for KIR, perforin, IFN-y, LFA-1 and CD70 expression, but expression of these genes is suppressed by methylation of crucial regulatory elements, and demethylation of these elements is sufficient to promote transcription. Further, we found that total T cell DMAdemethylates with age and in RA, due in part to decreases in DNA methyltransferases (Mtase), and that inhibiting T cell ERK and JNK signaling to mimic the decreased signaling that occurs with aging decreases DNA Mtase expression and demethylates DNA. Finally, we found that CD28 provides costimulatory signals increasing DNA Mtase expression. We hypothesize that DNA hypomethylation, caused by decreased JNK and/or ERK signaling, results in the overexpression of KIR, perforin, IFN-y, LFA-1 and CD70 in the CD4+CD28- subset in aging and RA, conferring pro-inflammatory and cytotoxic functions. This will be tested in 3 specific aims. We will: 1) Compare methylation status of regulatory elements and expression of the candidate genes in CD4+CD28- and CD4+CD28+ T cells from RA patients and elderly subjects, and to CD4+CD28+ cells in controls, 2) Compare DNA Mtase levels in the same T cell subsets, then selectively decrease DNA Mtase levels in normal T cells and examine the effects on candidate gene methylation and expression, and 3) Compare ERK and JNK pathway signaling in the same T cell subsets, and examine the effects of decreased signaling on DNA Mtase expression and candidate gene methylation, expression and function. These studies will identify mechanisms modifying gene expression in this pathologic subset, and suggest ways to restore normal gene expression in these cells.