title: Enhancement of chondrocyte autophagy is an early response in the degenerative cartilage of the temporomandibular joint to biomechanical dental stimulation.
abstract: Autophagy is a cell protective mechanism for maintaining cellular homeostasis. The present study aimed to investigate whether autophagy is enhanced in the biomechanically induced degenerative cartilage of the temporomandibular joint (TMJ) and the potential role of mitogen-activated protein kinase kinase kinase kinase 3 (MAP4K3) and mammalian Target of rapamycin (mTOR) in this observation. To induce degenerative changes in the TMJs, rats were subjected to biomechanical dental stimulation by moving 4 molars away from their original position as we previously reported. The ultrastructure of autophagosome was observed by transmission electron microscopy. The number of lysosomes was analyzed by flow cytometry. The expression levels of Beclin1 and LC3 and the involvement of MAP4K3 activity were detected by immunohistochemistry, real-time PCR and western blot. The activity of the mTOR pathway indicated by p-mTOR and p-p70S6 K was assayed by western blot. TMJ degeneration, characterized by irregular cell arrangement and cell-free area, was induced in the experimental groups. Under transmission electron microscopy, we observed the presence of autophagosomes, small patches of condensed chromatin, abundant rough endoplasmic reticulum and Golgi apparatus. The number of lysosomes and the expression levels of Beclin1 and LC3 increased, while the activity of mTOR and the expression level of MAP4K3 decreased in the experimental groups. Cartilage in TMJ which was induced to be degenerative biomechanically exhibited autophagy accompanied by reduced mTOR and MAP4K3 activity.
authors: Department of Oral Anatomy and Physiology and TMD, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an 710032, China.
authors: Mian
authors: M
authors: Zhang
authors: Jing
authors: J
authors: Zhang
authors: Lei
authors: L
authors: Lu
authors: Zhong-Ying
authors: ZY
authors: Qiu
authors: Xu
authors: X
authors: Zhang
authors: Shi-Bin
authors: SB
authors: Yu
authors: Yao-Ping
authors: YP
authors: Wu
authors: Mei-Qing
authors: MQ
authors: Wang
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis; D001343:Autophagy; D000071186:Beclin-1; D002356:Cartilage / Q000502:physiology*; D002470:Cell Survival; D019902:Chondrocytes / Q000502:physiology*; D005260:Female; D008247:Lysosomes; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction; D013314:Stress, Mechanical; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D013704:Temporomandibular Joint / Q000502:physiology*; D014087:Tooth Movement Techniques
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D008869:Microtubule-Associated Proteins; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C512829:Becn1 protein, rat; C526109:Anxa3 protein, rat; C546845:mTOR protein, rat; C485755:Map4k3 protein, rat