Ionizing Radiation Induces Cellular Senescence of Articular Chondrocytes via Negative Regulation of SIRT1 by p38 Kinase
Ionizing Radiation Induces Cellular Senescence of Articular Chondrocytes via Negative Regulation of SIRT1 by p38 Kinase
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DOI：
10.1074/jbc.m109.058628
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发表时间：
2010-01-08
影响因子：
4.8
通讯作者：
Hwang, Sang-Gu
中科院分区：
文献类型：
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作者：
Hong, Eun-Hee;Lee, Su-Jae;Hwang, Sang-Gu
放射治疗越来越多地用于关节疾病的治疗，但关于放射对软骨的影响的信息有限。在这里，我们描述了导致辐照原代培养关节软骨细胞衰老的分子机制。电离辐射（IR）引起ERK的激活，进而产生细胞内活性氧（ROS），诱导衰老相关的β -半乳糖苷酶（sa - β -gal）活性。ROS激活p38激酶，进一步促进ROS生成，形成一个正反馈回路，维持ROS-p38激酶信号传导。ROS抑制剂，去二氢愈创木酸和GSH，在辐照后抑制p38的磷酸化和sa - β -gal阳性的细胞数量。此外，抑制ERK和p38激酶途径可通过减少ROS生成来阻断ir诱导的sa - β -gal活性。虽然JNK被ROS激活，但该途径与软骨细胞衰老无关。有趣的是，IR触发SIRT1蛋白表达的下调，而不是转录水平的下调，这表明SIRT1蛋白在转录后被切割。IR处理后，SB203589或MG132明显阻断SIRT1的降解，表明其裂解是与p38激酶结合的结果，随后通过26s蛋白酶体降解途径进行加工。SIRT1的过表达或激活可显著降低ir诱导的衰老表型，而SIRT1活性的抑制可诱导衰老。基于这些发现，我们提出IR通过ros依赖的p38激酶激活，通过翻译后SIRT1的负调控诱导关节软骨细胞衰老。
Radiotherapy is increasingly used in the treatment of joint diseases, but limited information is available on the effects of radiation on cartilage. Here, we characterize the molecular mechanisms leading to cellular senescence in irradiated primary cultured articular chondrocytes. Ionizing radiation (IR) causes activation of ERK, in turn generating intracellular reactive oxygen species (ROS) with induction of senescence-associated beta-galactosidase (SA-beta-gal) activity. ROS activate p38 kinase, which further promotes ROS generation, forming a positive feedback loop to sustain ROS-p38 kinase signaling. The ROS inhibitors, nordihydroguaiaretic acid and GSH, suppress phosphorylation of p38 and cell numbers positive for SA-beta-gal following irradiation. Moreover, inhibition of the ERK and p38 kinase pathways leads to blockage of IR-induced SA-beta-gal activity via reduction of ROS generation. Although JNK is activated by ROS, this pathway is not associated with cellular senescence of chondrocytes. Interestingly, IR triggers down-regulation of SIRT1 protein expression but not the transcript level, indicative of post-transcriptional cleavage of the protein. SIRT1 degradation is markedly blocked by SB203589 or MG132 after IR treatment, suggesting that cleavage occurs as a result of binding with p38 kinase, followed by processing via the 26 S proteasomal degradation pathway. Overexpression or activation of SIRT1 significantly reduces the IR-induced senescence phenotype, whereas inhibition of SIRT1 activity induces senescence. Based on these findings, we propose that IR induces cellular senescence of articular chondrocytes by negative post-translational regulation of SIRT1 via ROS-dependent p38 kinase activation.