MTORC1 coordinates the autophagy and apoptosis signaling in articular chondrocytes in osteoarthritic temporomandibular joint
MTORC1 coordinates the autophagy and apoptosis signaling in articular chondrocytes in osteoarthritic temporomandibular joint
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MTORC1 协调骨关节炎颞下颌关节软骨细胞的自噬和凋亡信号传导
DOI：
10.1080/15548627.2019.1606647
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发表时间：
2020-01-01
期刊：
影响因子：
13.3
通讯作者：
Wang, Meiqing
中科院分区：
文献类型：
--
作者：
Yang, Hongxu;Wen, Yi;Wang, Meiqing
摘要骨关节炎（OA）进展过程中软骨细胞从自噬向凋亡的转变，其机制目前尚不清楚。在这项研究中，我们利用了流动流体剪切应力（FFSS）模型在培养的软骨细胞和单侧前牙反（UAC）的动物模型。我们发现FFSS和UAC都能积极诱导颞下颌关节（TMJ）软骨细胞的内质网应激（ERS），表现为HSPA 5、p-EIF 2AK 3、p-ERN 1和ATF 6的表达显著增加。有趣的是，FFSS和UAC不仅激活促死亡p-EIF 2AK 3介导的ERS-凋亡程序，而且还激活促存活p-ERN 1介导的软骨细胞自噬通量。来自FFSS的数据表明，MTORC 1，p-ERN 1的下游，抑制自噬，但促进p-EIF 2AK 3介导的ERS-凋亡。UAC模型的数据表明，在早期阶段，TMJ软骨细胞中的p-ERN 1和p-EIF 2AK 3都被激活，而MTORC 1被抑制。晚期以MTORC 1-p-EIF 2AK 3介导的ERS凋亡为主，而p-ERN 1和自噬通量受到抑制。大鼠TMJ局部注射雷帕霉素抑制MTORC 1或小鼠软骨细胞选择性诱导性切除MTORC 1表达可促进软骨细胞自噬和抑制凋亡，并减少UAC诱导的TMJ软骨丢失。与此相反，MTORC 1激活TMJ局部管理MHY 1485或Tsc 1，上游MTORC 1抑制基因的缺失，导致相反的效果。总的来说，我们的研究结果表明，异常的机械负荷导致软骨退变激活，至少部分，MTORC 1信号调节TMJ软骨细胞的自噬和凋亡程序。因此，抑制MTORC 1为预防和治疗OA提供了一种新的治疗策略。缩略语：ACTB：肌动蛋白β; ATF 6：激活转录因子6; BECN 1：beclin 1; BFL：巴弗洛霉素A1; CASP 12：半胱天冬酶12; CASP 3：半胱天冬酶3; DAPI：4 β，6-二脒基-2-苯基吲哚; DDIT 3：DNA损伤诱导转录物3; EIF 2AK 3/PERK：真核翻译起始因子2 α激酶3; ER：内质网; ERS：内质网应激; ERN 1/IRE 1：内质网至核信号传导1; FFSS：流动流体剪切应力; HSPA 5/GRP 78/BiP：热休克蛋白5; LAMP 2：溶酶体相关膜蛋白2; MAP 1 LC 3B/LC 3B：微管相关蛋白1轻链3 β; MTOR：雷帕霉素激酶的机制靶点; MTORC 1：雷帕霉素复合物1的机制靶点; OA：骨关节炎; PRKAA 1/2/AMPK 1/2：蛋白激酶，AMP活化，α 1/2催化亚基; RPS 6：核糖体蛋白S6; Rapa：雷帕霉素; SQSTM 1/p62：隔离体1; TEM：透射电子显微镜; TG：毒胡萝卜素; TMJ：颞下颌关节; TSC 1/2：结节性硬化症1/2; UAC：单侧前牙反牙合; UPR：未折叠蛋白反应; XBP 1：x盒结合蛋白1。
ABSTRACT A switch from autophagy to apoptosis is implicated in chondrocytes during the osteoarthritis (OA) progression with currently unknown mechanism(s). In this study we utilized a flow fluid shear stress (FFSS) model in cultured chondrocytes and a unilateral anterior crossbite (UAC) animal model. We found that both FFSS and UAC actively induced endoplasmic reticulum stress (ERS) in the temporomandibular joints (TMJ) chondrocytes, as demonstrated by dramatic increases in expression of HSPA5, p-EIF2AK3, p-ERN1 and ATF6. Interestingly, both FFSS and UAC activated not only pro-death p-EIF2AK3-mediated ERS-apoptosis programs but also pro-survival p-ERN1-mediated autophagic flux in chondrocytes. Data from FFSS demonstrated that MTORC1, a downstream of p-ERN1, suppressed autophagy but promoted p-EIF2AK3 mediated ERS-apoptosis. Data from UAC model demonstrated that at early stage both the p-ERN1 and p-EIF2AK3 were activated and MTORC1 was inhibited in TMJ chondrocytes. At late stage, MTORC1-p-EIF2AK3-mediated ERS apoptosis were predominant, while p-ERN1 and autophagic flux were inhibited. Inhibition of MTORC1 by TMJ local injection of rapamycin in rats or inducible ablation of MTORC1 expression selectively in chondrocytes in mice promoted chondrocyte autophagy and suppressed apoptosis, and reduced TMJ cartilage loss induced by UAC. In contrast, MTORC1 activation by TMJ local administration of MHY1485 or genetic deletion of Tsc1, an upstream MTORC1 suppressor, resulted in opposite effects. Collectively, our results establish that aberrant mechanical loading causes cartilage degeneration by activating, at least in part, the MTORC1 signaling which modulates the autophagy and apoptosis programs in TMJ chondrocytes. Thus, inhibition of MTORC1 provides a novel therapeutic strategy for prevention and treatment of OA. Abbreviations : ACTB: actin beta; ATF6: activating transcription factor 6; BECN1: beclin 1; BFL: bafilomycin A1; CASP12: caspase 12; CASP3: caspase 3; DAPI: 4ʹ,6-diamidino-2-phenylindole; DDIT3: DNA-damage inducible transcript 3; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; ER: endoplasmic reticulum; ERS: endoplasmic reticulum stress; ERN1/IRE1: endoplasmic reticulum to nucleus signaling 1; FFSS: flow fluid shear stress; HSPA5/GRP78/BiP: heat shock protein 5; LAMP2: lysosome-associated membrane protein 2; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; OA: osteoarthritis; PRKAA1/2/AMPK1/2: protein kinase, AMP-activated, alpha 1/2 catalytic subunit; RPS6: ribosomal protein S6; Rapa: rapamycin; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TG: thapsigargin; TMJ: temporomandibular joints; TSC1/2: tuberous sclerosis complex 1/2; UAC: unilateral anterior crossbite; UPR: unfolded protein response; XBP1: x-box binding protein 1.