Whisler R L, Newhouse Y G, Bagenstose S E
Department of Medical Biochemistry, William H. Davis Medical Research Center, Ohio State University, Columbus 43210-1228, USA.
Cell Immunol. 1996 Mar 15;168(2):201-10. doi: 10.1006/cimm.1996.0067.
Age-related changes in the functional properties of human T cells are well described, but less is known about possible changes in T cell signaling pathways. The signaling pathways mediated by mitogen-activated protein kinases (MAPK) are considered essential for normal cellular growth and function. Several stimuli trigger MAPK activation in human T cells and MEK (MAPK or ERK kinases) are immediate upstream inducers of MAPK activation. The current study investigated if aging might influence the activation and expression of MAPK and MEK in human T cells. Exposure of peripheral blood T cells from young subjects to PHA or cross-linked anti-CD3 monoclonal antibodies stimulated rapid increases in MAPK and MEK enzymatic activity. By contrast, significant reductions of MAPK and MEK activation were observed in stimulated T cells from 7 of 13 elderly subjects. Kinetic studies showed that the age-related impairments represented reduction in both the levels and duration of MAPK activation. In addition, Western immunoblot analysis did not reveal significant age-related differences in T cell expression of p42mapk/ERK2, p44mapk/ERK1, or MEK, suggesting impairments in upstream inducers of MEK/MAPK activation. Other experiments determined if agents that directly stimulate upstream Ras or Raf kinase components of the early MAPK cascade might reverse the age-related impairments of MAPK activation. Treatment of elderly T cells with fluoroaluminate (AlF(-)4), phorbol esters/Ca2+ ionophores, or okadaic acid stimulated increased MAPK activation compared to anti-CD3. However, these agents failed to restore MAPK activation in elderly T cells to the levels seen in young T cells. These results suggest that aberrancies in the MAPK activation cascade may underlie the age-related reductions of MAPK activation in human T cells stimulated via the TCR/CD3 complex.
人类T细胞功能特性随年龄的变化已有充分描述，但对T细胞信号通路可能的变化了解较少。丝裂原活化蛋白激酶（MAPK）介导的信号通路被认为对正常细胞生长和功能至关重要。几种刺激可触发人类T细胞中的MAPK激活，而MEK（MAPK或ERK激酶）是MAPK激活的直接上游诱导剂。本研究调查了衰老是否会影响人类T细胞中MAPK和MEK的激活及表达。将年轻受试者的外周血T细胞暴露于PHA或交联的抗CD3单克隆抗体可刺激MAPK和MEK酶活性迅速增加。相比之下，在13名老年受试者中的7名受刺激T细胞中观察到MAPK和MEK激活显著降低。动力学研究表明，与年龄相关的损伤表现为MAPK激活水平和持续时间的降低。此外Western免疫印迹分析未揭示p42mapk/ERK2、p44mapk/ERK1或MEK在T细胞表达方面存在显著的年龄相关差异，提示MEK/MAPK激活的上游诱导剂存在损伤。其他实验确定直接刺激早期MAPK级联反应上游Ras或Raf激酶成分的试剂是否可逆转与年龄相关的MAPK激活损伤。与抗CD3相比，用氟铝酸盐（AlF(-)4）、佛波酯/Ca2+离子载体或冈田酸处理老年T细胞可刺激MAPK激活增加。然而，这些试剂未能将老年T细胞中的MAPK激活恢复到年轻T细胞中的水平。这些结果表明，MAPK激活级联反应异常可能是通过TCR/CD3复合物刺激的人类T细胞中与年龄相关的MAPK激活降低的基础。
