title: Leptin protects rat articular chondrocytes from cytotoxicity induced by TNF-α in the presence of cyclohexamide.
abstract: OBJECTIVE
  Although leptin appears to be an important local and systemic factor influencing cartilage homeostasis, the role of leptin in chondrocyte death is largely unknown. Tumor necrosis factor α (TNF-α) is a pro-inflammatory cytokine that plays a central role in the pathogenesis of articular diseases. This study examines whether leptin modulates TNF-α-induced articular chondrocyte death.
  
  
  METHODS
  Primary rat articular chondrocytes were isolated from knee joint cartilage slices. To induce cell death, the chondrocytes were treated with TNF-α. To examine whether leptin modulates the extent of TNF-α-mediated chondrocyte death, the cells were pretreated with leptin for 3 h before TNF-α treatment followed by viability analysis. To examine the mechanism by which leptin modulates the extent of TNF-α-mediated chondrocyte death, we utilized mitochondrial membrane potential (MMP) measurements, flow cytometry, nuclear morphology observation, co-immunoprecipitation, western blot analysis and confocal microscopy.
  
  
  RESULTS
  We demonstrated that leptin suppresses TNF-α induced chondrocyte death. We further found that apoptosis partially contributes to TNF-α induced chondrocyte death while necroptosis primarily contributes to TNF-α induced chondrocyte death. In addition, we observed that leptin exerts anti-TNF-α toxicity via c-jun N-terminal kinase (JNK) in rat articular chondrocytes.
  
  
  CONCLUSIONS
  Based on our findings, we suggest that the leptin present in the articular joint fluid protects articular chondrocytes against cumulative mechanical load and detrimental stresses throughout a lifetime, delaying the onset of degenerative changes in chondrocytes. We can further hypothesize that leptin protects articular chondrocytes against destructive stimuli even in the joints of osteoarthritis (OA) patients.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Dong-A University College of Medicine, Busan, South Korea. Electronic address: leesw@dau.ac.kr.
authors.forename: S W
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Dong-A University College of Medicine, Busan, South Korea; Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, Dong-A University College of Medicine, Busan, South Korea. Electronic address: rogiken@hanmail.net.
authors.forename: J H
authors.initials: JH
authors.lastname: Rho
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Dong-A University College of Medicine, Busan, South Korea. Electronic address: leesy@dau.ac.kr.
authors.forename: S Y
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, Dong-A University College of Medicine, Busan, South Korea; BK21 Plus Research Group, Longevity and Marine Biotechnology, College of Natural Sciences, Pusan National University, Busan, South Korea. Electronic address: freemj0629@naver.com.
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.affiliation: BK21 Plus Research Group, Longevity and Marine Biotechnology, College of Natural Sciences, Pusan National University, Busan, South Korea. Electronic address: molecule85@pusan.ac.kr.
authors.forename: J-H
authors.initials: JH
authors.lastname: Cheong
authors.affiliation: Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, Dong-A University College of Medicine, Busan, South Korea. Electronic address: dolph02@dau.ac.kr.
authors.forename: H Y
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, Dong-A University College of Medicine, Busan, South Korea. Electronic address: jnyjjy@dau.ac.kr.
authors.forename: N Y
authors.initials: NY
authors.lastname: Jeong
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Dong-A University College of Medicine, Busan, South Korea. Electronic address: wtchung@dau.ac.kr.
authors.forename: W T
authors.initials: WT
authors.lastname: Chung
authors.affiliation: Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, Dong-A University College of Medicine, Busan, South Korea. Electronic address: yhyoo@dau.ac.kr.
authors.forename: Y H
authors.initials: YH
authors.lastname: Yoo
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000166:cytology; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D003513:Cycloheximide / Q000494:pharmacology*; D005434:Flow Cytometry; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007719:Knee Joint; D020738:Leptin / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D018613:Microscopy, Confocal; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D020738:Leptin; D011500:Protein Synthesis Inhibitors; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D048031:JNK Mitogen-Activated Protein Kinases
keywords: Apoptosis; JNK; Leptin; Necroptosis; TNF-α