Heat shock-induced necrosis and apoptosis in osteoblasts

Citation
S. Li et al., Heat shock-induced necrosis and apoptosis in osteoblasts, J ORTHOP R, 17(6), 1999, pp. 891-899
Citations number
37
Categorie Soggetti
da verificare
Journal title
JOURNAL OF ORTHOPAEDIC RESEARCH
ISSN journal
07360266 → ACNP
Volume
17
Issue
6
Year of publication
1999
Pages
891 - 899
Database
ISI
SICI code
0736-0266(199911)17:6<891:HSNAAI>2.0.ZU;2-T
Abstract
Damage to bone tissue due to heat shock is one of the main causes of the fa ilure of osseointegration at the bone-implant interface. To investigate the effect of heal shock on regeneration of bone tissue, osteoblasts were expo sed to heat shuck for 10 minutes at 42, 45, or 48 degrees C or kept at 37 d egrees C as a control. After 10 minutes of heat shock, disruption of actin filaments was seen in the cells and the degree of disruption increased with the temperature. The cytoskeleton reassembled after a 12-hour incubation a t 37 degrees C in the cells treated at 42 or 45 degrees C, but this reversi ble recovery did not occur in the cells treated at 48 degrees C. Flow cytom etric analysis showed that heat shock at 48 degrees C increased the number of necrotic cells to 15-20% within minutes (p < 0.05 compared with 37 degre es C). Apoptosis, evidenced by annexin V staining, DNA laddering, and caspa se 3 activation, started after 6-8 hours of incubation, reached a peak at 1 2 hours, and gradually declined (p < 0.05). Pretreatment with the antioxida nt N-acetyl-L-cysteine reduced the necrosis induced at 48 degrees C of heat shock by one-half (p < 0.05) but had no significant effect on caspase 3 ac tivation induced by heat shock, suggesting that reactive oxygen species wer e critical in heat shock-induced necrosis but not in apoptosis. Heat shock at 48 degrees C induced a sustained translocation of p53 into the nucleus a nd a sustained activation of c-jun N-terminal kinase, whereas that at 42 an d 45 degrees C induced only transient p53 translocation and c-jun N-termina l kinase activation. These results suggest that the sustained activation of p53 and c-jun N-terminal kinase pathways may contribute to heat shock-indu ced apoptosis. On the other hand, heat shock protein 70 increased dramatica lly in the cells treated at 45 or 48 degrees C, suggesting that the protect ing mechanism in the cells was also activated. Such protection was able to prevent apoptosis in cells treated at 45 degrees C but not in those treated at 48 degrees C.