Tài liệu Báo cáo khoa học: Hypoxic resistance to articular chondrocyte apoptosis – a possible

Hypoxic resistance to articular chondrocyte

apoptosis – a possible mechanism of maintaining

homeostasis of normal articular cartilage

J.-W. Seol1

, H.-B. Lee1

, Y.-J. Lee1

, Y.-H. Lee2

, H.-s. Kang1

, I.-s. Kim1

, N.-S. Kim1 and S.-Y. Park1

1 Center for Healthcare Technology Development, Bio-Safety Research Institute, College of Veterinary Medicine, Chonbuk National

University, Jeonju, Jeonbuk, South Korea

2 Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju, Jeonbuk, South Korea

Keywords

chondrocytes; hypoxia; proteasome; reactive

oxygen species; tumour necrosis

factor-related apoptosis-inducing ligand

(TRAIL)

Correspondence

S.-Y. Park, College of Veterinary Medicine,

Chonbuk National University, Jeonju,

Jeonbuk 561-756, South Korea

Fax: +82 63 270 3780

Tel: +82 63 270 3886

E-mail: [email protected]

(Received 21 August 2009, revised 10

October 2009, accepted 20 October 2009)

doi:10.1111/j.1742-4658.2009.07451.x

Hypoxia and hypoxia-related genes are important factors in articular chon￾drocytes during cartilage homeostasis and osteoarthritis. We have investi￾gated the various apoptotic factors that show significance in synovial fluid

obtained from normal and experimental osteoarthritic animal models and

have evaluated the effect of hypoxia on articular chondrocyte apoptosis

induced by these apoptotic factors. Mature beagle dogs underwent surgical

transections of ligaments and medial meniscectomies to explore the under￾lying mechanisms of osteoarthritis. Cartilage and synovial fluid obtained

from normal animals and those with osteoarthritis were evaluated via pro￾teasome inhibition, tumour necrosis factor-related apoptosis-inducing

ligand (TRAIL) protein expression, mitochondrial transmembrane poten￾tial and levels of reactive oxygen species. Canine chondrocytes were

exposed to the proteasome inhibitor N-acetyl-Leu-Leu-Norleu-al and trea￾ted with recombinant TRAIL protein under normoxic and hypoxic condi￾tions, measuring chondrocyte cell viability, proteasome activity and levels

of apoptotic factors. TRAIL protein expression and ubiquitinated proteins

were increased significantly, but the proteasome activity in the synovial

fluid of osteoarthritic joints relative to that in normal joints was not. Pri￾mary cultured articular chondrocytes cotreated with the proteasome inhibi￾tor and TRAIL progressed to severe apoptosis under normoxic conditions,

but the sensitization caused by the combined treatment was suppressed by

exposure to hypoxia. Caspase-8 activation, c-Jun N-terminal kinase phos￾phorylation, the mitochondrial transmembrane potential and the genera￾tion of reactive oxygen species involved in cell death regulation were

significantly inhibited under hypoxic conditions. These findings suggest that

proteasome inhibition and TRAIL may be possible mechanisms in cartilage

degradation and joint-related diseases. Furthermore, the maintenance

of hypoxic conditions or therapy with hypoxia-related genes in the joint

may be successful for the treatment of joint-related diseases, including

osteoarthritis.

Abbreviations

ALLN, N-acetyl-Leu-Leu-Norleu-al; DCFH2-DA, 2¢,7¢-dichlorodihydrofluorescein diacetate; DR-5, death receptor-5; JC-1, 5,5¢,6,6¢-tetrachloro￾1,1¢3,3¢-tetraethylbenzimidazol-carbocyanine iodide; JNK, c-Jun N-terminal kinase; JNK-SAPK, c-Jun N-terminal kinase-stress-activated protein

kinase; MTP, mitochondrial transmembrane potential; OA, osteoarthritis; ROS, reactive oxygen species; Suc-LLVY-AMC, Suc-Leu-Leu-Val￾Tyr-7-amino-4-methylcoumarin; TRAIL, tumour necrosis factor-related apoptosis-inducing ligand.

FEBS Journal 276 (2009) 7375–7385 ª 2009 The Authors Journal compilation ª 2009 FEBS 7375