Hsp70 prevents nitric oxide–induced apoptosis in articular chondrocytes

Abstract

Objective. To deliver and overexpress the hsp70 gene in cultured chondrocytes to investigate its effect on nitric oxide (NO)-induced apoptosis of chondrocytes.Methods. Primary chondrocyte cultures were established from rabbit joints. The cells were transduced with an empty adenovirus vector (Ax1w) or an adenovirus vector harboring the hsp70 E-tag fusion gene (AxSHEwt Degradation of articular cartilage, the major component of a joint, causes serious dysfunction of joints. Osteoarthritis (OA) is associated with degeneration of articular cartilage, but its pathogenesis has not yet been fully elucidated. Various biologic and chemical stress factors are thought to be involved in the occurrence and progression of OA, including mechanical stress, inflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor ␣, and reactive oxygen species (ROS) such as nitric oxide (NO). Chondrocytes are responsible for the maintenance of articular cartilage. Reduced cartilage cellularity has been postulated to play a role in the pathogenesis of OA (1,2), and the reduction in cellularity in human OA cartilage is partly attributable to apoptosis, i.e., programmed cell death. Recent studies have shown apoptosis of articular chondrocytes in OA in humans and in experimental animals (3,4), which implies the importance of apoptosis in the progression of the pathology of OA. Thus, apoptosis has attracted the attention of researchers as a potential etiologic factor in OA progression (5). If apoptosis of OA chondrocytes could be controlled, the implications of apoptosis in OA pathogenesis would become clearer, and the suppression method would suggest a novel therapeutic intervention against OA.One of the major cellular responses to stress involves synthesis of a set of highly conserved proteins, called heat-shock proteins (HSPs), during a process referred to as the stress response. In mammalian systems, HSPs include proteins with molecular weights of 110, 90, 70, 60, 40, and 27 kd. Some HSP members are constitutively expressed, and the expression levels increase in response to stress, while others are induced after exposure to stress. HSPs not only protect cells from stress-induced damage, but also facilitate the recovery of cells from the damage by binding to degraded or misfolded polypeptides (6-8). The inducible Hsp70 is a major HSP, and its expression is augmented in OA

Suppression of heat shock protein 70 by siRNA enhances the antitumor effects of cisplatin in cultured human osteosarcoma cells

“…In cells that express Hsp70, however, Hsp70 expression has been shown to exert a strongly anti-apoptotic effect (Terauchi et al 2003;Saleh et al 2000). In this study, we used three different types of assessments to show that apoptosis is significantly increased: the changes in mitochondrial membrane potential that occur at an early stage of apoptosis; activity of caspase-3, an enzyme in the caspase family that is activated downstream; and DNA fragmentation, the final stage of cell death.…”

Saponin-rich fraction from Clematis chinensis Osbeck roots protects rabbit chondrocytes against nitric oxide-induced apoptosis via preventing mitochondria impairment and caspase-3 activation

“…The chondrocytes, isolated from the knee joints of rabbits, were seeded to the 96-well plates at 2 9 10 4 cells per well and stabilized for 24 h. After incubation with SFC (30, 100, 300 and 1,000 lg/ml) plus SNP (2 mM), the cells were fixed with methanol acetic acid for 10 min followed by staining with Hoechst 33258 1 mg/ml for 5 min at room temperature. The cells were then washed twice with PBS, observed and immediately photographed under a fluorescence microscope with excitation at 355 nm and emission at 465 nm (Terauchi et al 2003). …”

Effects of heat stimulation via microwave applicator on cartilage matrix gene and HSP70 expression in the rabbit knee joint

“…It has been reported that HSP70 expression levels in chondrocytes are correlated with histological severity in OA, 8,9 and that the overexpression of HSP70 results in promotion of metabolic activity of chondrocytes 10 and protection of chondrocytes from various stresses. 11,12 In chondrocytes of OA patients, however, the expression level of HSP70 may not be high enough to eliminate stress-induced damages of the cartilage or accelerate metabolic activity in the damaged cartilage; this may cause the progression of the disorder. Control of HSP70 expression in the articular cartilage by thermotherapy may provide a novel therapeutic strategy for OA.…”