Apoptotic insults to human chondrocytes induced by sodium nitroprusside are involved in sequential events, including cytoskeletal remodeling, phosphorylation of mitogen-activated protein kinase kinase kinase-1/c-Jun N-terminal kinase, and Bax-mitochondria-mediated caspase activation.
Nitric oxide (NO) can regulate chondrocyte activities. This study was aimed to evaluate the molecular mechanisms of NO donor sodium nitroprusside (SNP)-induced insults to human chondrocytes. Exposure of human chondrocytes to SNP increased cellular NO levels but decreased cell viability in concentration- and time-dependent manners. SNP time dependently induced DNA fragmentation and cell apoptosis. Treatment with 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide, an NO scavenger, significantly lowered SNP-induced cell injuries. Administration of SNP interrupted F-actin and microtubule cytoskeletons and stimulated phosphorylation of mitogen-activated protein kinase kinase kinase-1 (MEKK1) and c-Jun N-terminal kinase (JNK). Similar to SNP, cytochalasin D, an inhibitor of F-actin formation, disturbed F-actin polymerization and increased MEKK1 and JNK activations. Overexpression of a dominant negative mutant of MEKK1 (dnMEK1) in human chondrocytes significantly ameliorated SNP-induced cell apoptosis. Exposure to SNP promoted Bax translocation from the cytoplasm to mitochondria, but application of dnMEKK1 lowered the translocation. SNP time dependently decreased the mitochondrial membrane potential, complex I NADH dehydrogenase activity, and cellular ATP levels, but increased the release of cytochrome c from mitochondria to the cytoplasm. Activities of caspase-9, -3, and -6 were sequentially increased by SNP administration. This study shows that SNP can induce apoptosis of human chondrocytes through sequential events, including cytoskeletal remodeling, activation of MEKK1/JNK, Bax translocation, mitochondrial dysfunction, cytochrome c release, caspase activation, and DNA fragmentation.
Cherng
Yih-Giun
YG
Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250 Wu-Hsing St., Taipei 110, Taiwan, Republic of China.
Chang
Hua-Chia
HC
Lin
Yi-Ling
YL
Kuo
Ming-Liang
ML
Chiu
Wen-Ta
WT
Chen
Ruei-Ming
RM
D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048728:MAP Kinase Kinase Kinase 1 / Q000378:metabolism; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology*; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D051028:bcl-2-Associated X Protein; D009599:Nitroprusside; D009569:Nitric Oxide; D045304:Cytochromes c; D048031:JNK Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D020169:Caspases