DNA-damaging agents induce the 72-kD heat shock protein in SV40 transformed normal human fibroblasts

DNA damage formation and p53 accumulation in mammalian cells exposed to the space environment

To determine the effects of the space environment on gene instability from the point of view of human health for long-term stays in space, we have studied the formation of DNA strand breaks and the induction of gene expression in mammalian cells. We previously measured DNA damage in human cultured cells and the accumulation of a tumor suppressor gene product, p53, in muscle and skin of rats after space flight, and the relative importance of microgravity and space radiation in causing these effects remains to be clarified. Our results suggest that the p53 pathway may play a role in safeguarding genomic stability against the stressful space environment. We review here the present knowledge on cellular stress signaling and present our space experimental data. The importance of the stress response to the space environment is also discussed.

Suppression of heat-induced HSF activation by CDDP in human glioblastoma cells

PURPOSE

The kinetics of the accumulation of inducible 72-kD heat shock protein (hsp72) and the activation of heat shock transcriptional factor (HSF) after hyperthermia and/or CDDP treatment in two human glioblastoma cell lines, A-172 having the wild-type p53 gene and T98G having the mutated p53 gene were evaluated.

METHODS AND MATERIALS

Western blot analysis of hsp72, gel-mobility shift assay of HSF, cell survival, and development of thermotolerance were examined.

RESULTS

The prominent suppression of heat-induced hsp72 accumulation by CDDP was seen in A-172 cells, but not in T98G cells. This was due to the p53-dependent inhibition of heat-induced HSF activation by CDDP. The interactive hyperthermic enhancement of CDDP cytotoxicity was observed in A-172 cells, but not in T98G cells. In addition, the heat-induced thermotolerance was suppressed by the presence of CDDP in the pretreatment.

CONCLUSION

Suppression of heat-induced hsp72 accumulation by CDDP contributes to an interactive hyperthermic enhancement of CDDP cytotoxicity in the cells bearing the wild-type p53 gene.

Effects of protein kinase inhibitors on heat-induced hsp72 gene expression in a human glioblastoma cell line

We examined the effects of several kinds of protein kinase inhibitors against calcium/phospholipid-dependent protein kinase (PKC) and cAMP-dependent protein kinase (PKA) on heat-induced hsp72 gene expression in a human glioblastoma cell line (T98G) as a source of insight into the type of protein kinase contributing to its gene expression. When the cells were treated with 1-(5-isoquinolinesulphonyl)-2-methylpiperazine [(H7) a potent inhibitor of PKC, PKA, and others], the suppression of heat-induced Hsp72 accumulation was observed. Heat-induced Hsp72 accumulation was also suppressed by staurosporine (a potent inhibitor of PKC and PKA) or calphostin C [(CAL) a potent inhibitor of PKC] at high concentration (10 x IC50) but not at low concentration (1 x IC50). N-(2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulphonamide [(H89) a potent inhibitor of PKA] did not affect heat-induced Hsp72 accumulation at either low (1 x IC50) or high concentrations (10 x IC50). Combination treatment with CAL and H89 suppressed the heat-induced Hsp72 accumulation more strongly than did treatment with either inhibitor alone. Furthermore, the heat-induced DNA-binding activation of heat-shock factor (HSF) was suppressed by CAL at high concentration (10 x IC50), and combination treatment with CAL and H89 showed stronger suppression. In the H7 treatment, the clear suppression of HSF activation was observed even at low concentration (1 x IC50). In addition, the cellular content of Hsp72 increased after the treatment of PKC or PKA activator. These results suggest that not only PKC, but also PKA may play an important role in heat-induced hsp72 gene expression.