Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", 153 10, Athens, Greece.
Biogerontology. 2018 Jul;19(3-4):237-249. doi: 10.1007/s10522-018-9753-9. Epub 2018 Mar 26.
Tumor necrosis factor α (TNF-α) is an inflammatory mediator overexpressed in the skin as a response to ultraviolet radiation, as well as in chronic non-healing wounds. On the other hand, senescent fibroblasts have been shown to accumulate in the skin under these stressful conditions. Accordingly, here we assessed the putative implication of TNF-α in the induction of premature senescence of human adult dermal fibroblasts. We showed that TNF-α led to a rapid transient p38 MAPK activation, while elevation of reactive oxygen species (ROS) only occurred after a chronic exposure to TNF-α. Furthermore, in contrast to the majority of previous reports using various cell models and experimental settings, it was a long-term treatment with TNF-α that resulted in the premature senescence of human dermal fibroblasts, as shown by the reduced proliferative potential and the increased senescence associated β-galactosidase staining of the cells. TNF-α-senescent cells displayed a permanent phosphorylation of p38 MAPK and an inflammatory and catabolic phenotype. Increased ROS levels were also observed, possibly attributed to the weakened anti-oxidative response evidenced by the underexpression of the Nrf2-regulated genes encoding HO-1 and NQO1. These traits and the overall senescent phenotype were significantly reversed using the known anti-oxidant N-acetyl-L-cysteine or a specific p38 MAPK inhibitor, suggesting the participation of oxidative stress and of the p38 MAPK pathway in TNF-α-triggered premature senescence. Even more, the observed blockade of ROS accumulation in senescent skin fibroblasts by p38 MAPK inhibition indicates a possible link between these two separate events during the manifestation of TNF-α-induced senescence.
肿瘤坏死因子-α（TNF-α）是一种炎症介质，在皮肤中作为对紫外线辐射的反应过度表达，也存在于慢性非愈合性伤口中。另一方面，已表明衰老的成纤维细胞在这些应激条件下在皮肤中积累。因此，在这里我们评估了 TNF-α在诱导人成体真皮成纤维细胞过早衰老中的可能作用。我们表明，TNF-α导致快速短暂的 p38 MAPK 激活，而活性氧（ROS）的升高仅在慢性暴露于 TNF-α后发生。此外，与使用各种细胞模型和实验条件的大多数先前报道相反，只有长期用 TNF-α处理才能导致人真皮成纤维细胞过早衰老，如细胞增殖潜力降低和衰老相关的β-半乳糖苷酶染色增加所示。TNF-α-衰老细胞显示出 p38 MAPK 的永久磷酸化以及炎症和分解代谢表型。还观察到 ROS 水平增加，这可能归因于抗氧化反应减弱，证据是编码 HO-1 和 NQO1 的 Nrf2 调节基因表达下调。使用已知的抗氧化剂 N-乙酰-L-半胱氨酸或特异性 p38 MAPK 抑制剂可显著逆转这些特征和整体衰老表型，表明氧化应激和 p38 MAPK 途径参与了 TNF-α 触发的过早衰老。甚至，p38 MAPK 抑制作用阻断衰老皮肤成纤维细胞中 ROS 的积累，表明在 TNF-α 诱导的衰老表现过程中这两个独立事件之间可能存在联系。
