Hydrogen peroxide induces apoptosis of chondrocytes; involvement of calcium ion and extracellular signal-regulated protein kinase

Objective: Recent observations demonstrated that reactive oxygen species facilitate cartilage degradation. We demonstrated that hydrogen peroxide (H₂O₂) caused inhibition of proteoglycan synthesis, induction of apoptosis and stimulation of extracellular signal-regulated protein kinase (ERK) of the chondrocytes (Inflamm Res 48: 399-403, 1999). To determine whether activation of ERK is involved in the induction of chondrocyte apoptosis, we examined the signal transduction pathways in this hydrogen peroxide induced apoptosis.¶Design: Bovine articular chondrocytes were cultured. To determine the induction of apoptosis, Annexin V staining and terminal deoxynucleotidyl transferase were used. The activity of caspase-3 was measured using an apopain assay kit. Intracellular Ca²⁺ imaging was observed after fura2-AM loading.¶Results: Hydrogen peroxide enhanced annexin V positive apoptotic cells and caspase-3 activity, which is an executor of apoptosis. Hydrogen peroxide also enhanced intracellular Ca²⁺ and preincubation with the intracellular Ca²⁺ chelator protected chondrocytes against hydrogen peroxide-induced cell apoptosis, indicating that an increase in the cytosolic Ca²⁺ plays a decisive role in this action. When ERK activity was blocked with geldanamycin and PD098059, increased apoptosis was evident.¶Conclusion: Hydrogen peroxide induces chondrocyte apoptosis via Ca²⁺ signaling, and ERK is involved in these signal transduction pathways.¶

Authors and Affiliations

1. Department of Orthopaedic Surgery, Kinki University School of Medicine. Ohno-higashi 377-2, Osaka-sayama, Osaka 589-8511, Japan, Fax: 723660206, e-mail: k-fukuda@med.kindai.ac.jp , , , , , , JP

   S. Asada, K. Fukuda, F. Nishisaka, M. Matsukawa & C. Hamanisi

Received 9 March 2000; returned for revision 1 May 2000; accepted by W.B. van den Berg 24 August 2000

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