Annexin 5 overexpression increased articular chondrocyte apoptosis induced by basic calcium phosphate crystals.

Abstract

OBJECTIVES:

Basic calcium phosphate (BCP) crystals (octacalcium phosphate (OCP), carbapatite (CA) and hydroxyapatite (HA)) are associated with severe forms of osteoarthritis. In advanced osteoarthritis, cartilage shows chondrocyte apoptosis, overexpression of annexin 5 (A5) and BCP crystal deposition within matrix vesicles. We assessed in vitro whether BCP crystals and overexpression of A5 increased chondrocyte apoptosis.

METHODS:

Apoptosis was induced by BCP crystals, tumour necrosis factor (TNF)-alpha (20 ng/ml) and Fas ligand (20 ng/ml) in normal articular chondrocytes (control) and in A5 overexpressed chondrocytes, performed by adenovirus infection. Apoptosis was assessed by caspase 3 (Cas3) activity, and DNA fragmentation.

RESULTS:

All BCP crystals, TNF-alpha and Fas ligand induced chondrocyte apoptosis as demonstrated by decreased cell viability and increased Cas3 activity and DNA fragmentation. TUNEL (terminal deoxyribonucleotide transferase-mediated dUTP nick end-labelling)-positive staining chondrocytes were increased by OCP (12.4 (5.2)%), CA (9.6 (2.6)%) and HA (9.2 (3.0)%) crystals and TNF-alpha (9.6 (2.4)%) stimulation compared with control (3.1 (1.9)%). BCP crystals increased Cas3 activity in a dose-dependent fashion. BCP-crystal-induced chondrocyte apoptosis was independent from TNF-alpha and interleukin-1beta pathways but required cell-crystal contact and intralysosomal crystal dissolution. Indeed, preincubation with ammonium chloride, a lysosomal inhibitor of BCP crystal dissolution, significantly decreased BCP-crystal-induced Cas3 activity. Finally, overexpression of A5 enhanced BCP crystal- and TNF-alpha-induced chondrocyte apoptosis.

CONCLUSIONS:

Overexpression of A5 and the presence of BCP crystals observed in advanced osteoarthritis contributed to chondrocyte apoptosis. Our results suggest a new pathophysiological mechanism for calcium-containing crystal arthropathies.

• Authors: H K Ea, V Monceau, E Camors, M Cohen-Solal, D Charlemagne, F Lioté
• Journal: Annals of the rheumatic diseases (Ann Rheum Dis) Vol. 67 Issue 11 Pg. 1617-25 (Nov 2008) ISSN: 1468-2060 [Electronic] England
• PMID: 18218665 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Annexin A5
• Calcium Phosphates
• Tumor Necrosis Factor-alpha
• Uric Acid
• Caspase 3

Topics

• Animals
• Annexin A5 (metabolism, physiology)
• Apoptosis (drug effects, physiology)
• Calcium Phosphates (metabolism, pharmacology)
• Cartilage, Articular (cytology, drug effects, metabolism)
• Caspase 3 (metabolism)
• Cattle
• Cells, Cultured
• Chondrocytes (drug effects, metabolism)
• Crystallization
• DNA Fragmentation
• Tumor Necrosis Factor-alpha (physiology)
• Uric Acid (metabolism)