Aggarwal B B, Totpal K, LaPushin R, Chaturvedi M M, Pereira-Smith O M, Smith J R
Department of Clinical Immunology and Biological Therapy, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Exp Cell Res. 1995 May;218(1):381-8. doi: 10.1006/excr.1995.1169.
The limited life span in culture of normal human diploid fibroblasts (HDF) has provided a model of cellular senescence. The short-term growth of these cells in culture is regulated by a number of different cytokines, including tumor necrosis factor (TNF), interleukin-1 (IL-1), and fibroblast growth factor (FGF). However, the effect of senescence on the responsiveness of HDF to these cytokines is not known. In the present report, we examined the effects of TNF on foreskin-derived HDF at different passage levels. We compared the response of HDF cells at population doubling (PD) 23 (young) with that of cells at PD 70 (senescent). Young cells proliferated in response to TNF in a dose-dependent manner. Under these conditions TNF had no effect on senescent HDF. The decrease in TNF responsiveness was found to be dependent on PD. The lack of response of senescent HDF was not unique to TNF, since FGF and IL-1 were also ineffective. In contrast to senescent HDF, TNF-dependent proliferation of young HDF could be further potentiated by IL-1 and FGF, suggesting an independent signaling mechanism. On exposure to TNF, senescent HDF produced IL-6 and IL-8, but to a much lower degree than that produced by young HDF. The diminished responsiveness of senescent HDF to TNF does not appear to be due to the difference in either receptor number or affinity, since senescent cells had two- to threefold higher number of TNF receptors than young HDF but the same affinity. TNF induced the activation of a nuclear transcriptional factor, NF-kappa B, equally in both young and senescent cells, which indicates the lack of a defect in the early events of TNF signal transduction in senescent fibroblasts. Overall, our results indicate that there is an age-dependent decline in TNF-induced proliferation and in the production of interleukins by fibroblasts; this unresponsiveness appears not to be due to TNF receptors or NF-kappa B activation. These results may have importance in understanding the diminished immune response, inflammation, and wound healing associated with aging.
正常人二倍体成纤维细胞（HDF）在培养中的有限寿命为细胞衰老提供了一个模型。这些细胞在培养中的短期生长受多种不同细胞因子调节，包括肿瘤坏死因子（TNF）、白细胞介素-1（IL-1）和成纤维细胞生长因子（FGF）。然而，衰老对HDF对这些细胞因子反应性的影响尚不清楚。在本报告中，我们研究了TNF对不同传代水平的包皮来源HDF的影响。我们比较了群体倍增（PD）23（年轻）时HDF细胞与PD 70（衰老）时细胞的反应。年轻细胞对TNF的反应呈剂量依赖性增殖。在这些条件下，TNF对衰老的HDF没有影响。发现TNF反应性的降低取决于传代次数。衰老的HDF缺乏反应并非TNF所特有，因为FGF和IL-1也无效。与衰老的HDF相反，IL-1和FGF可进一步增强年轻HDF依赖TNF的增殖，提示存在独立的信号传导机制。衰老的HDF在暴露于TNF时会产生IL-6和IL-8，但程度远低于年轻HDF产生的水平。衰老的HDF对TNF反应性降低似乎不是由于受体数量或亲和力的差异，因为衰老细胞的TNF受体数量比年轻HDF高两到三倍，但亲和力相同。TNF在年轻和衰老细胞中均能同等程度地诱导核转录因子NF-κB的激活，这表明衰老成纤维细胞中TNF信号转导的早期事件不存在缺陷。总体而言，我们的结果表明，成纤维细胞中TNF诱导的增殖以及白细胞介素的产生存在年龄依赖性下降；这种无反应性似乎不是由于TNF受体或NF-κB激活所致。这些结果对于理解与衰老相关的免疫反应减弱、炎症和伤口愈合可能具有重要意义。
