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Hydrostatic pressure induces apoptosis in human chondrocytes from osteoarthritic cartilage through up‐regulation of tumor necrosis factor‐α, inducible nitric oxide synthase, p53, c‐myc, and bax‐α, and suppression of bcl‐2
Author(s) -
Islam Najmul,
Haqqi Tariq M.,
Jepsen Karl J.,
Kraay Matthew,
Welter Jean F.,
Goldberg Victor M.,
Malemud Charles J.
Publication year - 2002
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.10317
Subject(s) - apoptosis , microbiology and biotechnology , chondrocyte , nitric oxide synthase , hydrostatic pressure , nitric oxide , poly adp ribose polymerase , tumor necrosis factor alpha , cartilage , dna fragmentation , chemistry , biology , programmed cell death , immunology , biochemistry , dna , polymerase , endocrinology , anatomy , physics , thermodynamics
Hydrostatic pressure (HP) is thought to increase within cartilage extracellular matrix as a consequence of fluid flow inhibition. The biosynthetic response of human articular chondrocytes to HP in vitro varies with the load magnitude, load frequency, as well as duration of loading. We found that continuous cyclic HP (5 MegaPascals (MPa) for 4 h; 1 Hz frequency) induced apoptosis in human chondrocytes derived from osteoarthritic cartilage in vitro as evidenced by reduced chondrocyte viability which was independent of initial cell densities ranging from 8.1 × 10 4 to 1.3 × 10 6 cells ml −1 . HP resulted in internucleosomal DNA fragmentation, activation of caspase‐3, and cleavage of poly‐ADP‐ribose polymerase (PARP). At the molecular level, induction of apoptosis by HP was characterized by up‐regulation of p53, c‐myc, and bax‐α after 4 h with concomitant down‐regulation of bcl‐2 after 2 h at 5 MPa as measured by RT‐PCR. In contrast, β‐actin expression was unchanged. Real‐time quantitative RT‐PCR confirmed a HP‐induced (5 MPa) 1.3–2.6 log‐fold decrease in bcl‐2 mRNA copy number after 2 and 4 h, respectively, and a significant increase (1.9–2.5 log‐fold) in tumor necrosis factor‐α (TNF‐α) and inducible nitric oxide synthase (iNOS) mRNA copy number after 2 and 4 h, respectively. The up‐regulation of p53 and c‐myc, and the down‐regulation of bcl‐2 caused by HP were confirmed at the protein level by Western blotting. These results indicated that HP is a strong inducer of apoptosis in osteoarthritic human chondrocytes in vitro. J. Cell. Biochem. 87: 266–278, 2002. © 2002 Wiley‐Liss, Inc.