4.6 Article

Glutamine protects articular chondrocytes from heat stress and NO-induced apoptosis with HSP70 expression

Journal

OSTEOARTHRITIS AND CARTILAGE
Volume 14, Issue 6, Pages 545-553

Publisher

ELSEVIER SCI LTD
DOI: 10.1016/j.joca.2005.12.008

Keywords

glutamine; articular cartilage; chondrocyte; stress; heat shock protein 70; chondroprotective effect

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Objective: To investigate the effect of L-glutamine (Gin) on stress responses of chondrocytes exposed to heat stress or nitric oxide (NO). Methods: Cultures of articular chondrocytes were established from rabbit joints, and treated for 12 h with various concentrations of Gin (0-20 mM). In some experiments, cells were also treated with quercetin (Que), a heat shock protein 70 (HSP70) inhibitor. Heat stress (43 degrees C) was applied to the cells for 0-120 min. Apoptosis was induced by 0.5 mM sodium nitroprusside (SNP) dihydrate that produces NO. After stress loading, HSP70 expression was detected by Western blot analysis. Cell viability was assessed by lactate dehydrogenase (LDH) release and tetrazolium salt-based assays, while apoptosis was evaluated by Hoechst 33342 staining, TUNEL methods and active caspase-3 determination. Results: Gin demonstrated dose-dependent enhancing effect on stress-mediated induction of HSP70, while in the absence of any stress HSP70 was not induced by Gin alone. After heating or SNP loading, chondrocytes showed severe reduction in viability, while the cytotoxic outcome was almost completely abrogated by conditioning with Gin. The protective effect of Gin was significantly blocked by Que that effectively suppressed stress-induced HSP70 expression in chondrocytes. The Gin also rendered chondrocytes unsusceptible to NO-induced apoptosis that was frequently seen in SNP-treated culture. Conclusion: This study demonstrated that the treatment of chondrocytes with Gin protected the cells from heat stress and NO-induced apoptosis. These chondroprotective effects of Gin may be mediated by HSP70. (c) 2005 OsteoArthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

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