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

衰老的T细胞亚群，其特征在于缺乏CD 28，随着衰老而发展，在慢性炎症中， 炎症性疾病如类风湿性关节炎（RA）和急性冠状动脉综合征。CD4+CD28- 亚群是促炎性和细胞毒性的，并且在发炎的滑膜以及动脉粥样硬化中发现 死于心肌梗死患者的斑块，表明他们参与了自身免疫性疾病 流程. CD 4 + CD 28-亚群异常表达巨噬细胞免疫球蛋白样受体（KIR） 基因和穿孔素，通常在NK细胞上发现，并且过表达IFN-γ、LFA-1和CD 70。的原因 异常基因表达是未知的。在初步研究中，我们发现正常的T细胞具有 KIR、穿孔素、IFN-γ、LFA-1和CD 70表达所必需的转录因子，但这些转录因子的表达 基因被关键调控元件的甲基化所抑制，这些元件的去甲基化是 足以促进转录。此外，我们发现，总T细胞DMA去甲基化与年龄和RA， 部分原因是DNA甲基转移酶（MTase）的减少，以及抑制T细胞ERK和JNK 模拟衰老时信号减少的信号传导降低了DNA MTase表达， 去甲基化DNA最后，我们发现，CD 28提供了共刺激信号，增加DNA MTase， 表情我们推测，DNA低甲基化，由JNK和/或ERK信号转导减少引起， 导致衰老中CD 4 + CD 28-亚群中KIR、穿孔素、IFN-γ、LFA-1和CD 70的过度表达， RA，赋予促炎和细胞毒性功能。这将在3个具体目标中进行测试。我们将：1） 比较CD 4 + CD 28-T细胞中调控元件的甲基化状态和候选基因的表达， 和来自RA患者和老年受试者的CD 4 + CD 28 + T细胞，以及对照中的CD 4 + CD 28+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T细胞亚群中的DNA MTase水平。 正常T细胞，并检查对候选基因甲基化和表达的影响，以及3）比较 ERK和JNK通路信号在相同的T细胞亚群，并检查信号减少的影响， 对DNA甲基转移酶表达和候选基因甲基化、表达和功能的影响。这些研究将 确定在这个病理亚组中改变基因表达的机制，并提出恢复的方法。 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.