Hyperthermia induced NFκB mediated apoptosis in normal human monocytes

Conceptual approaches of heat-induced cytotoxic effects against tumor cells must address factors affecting therapeutic index, i.e., the relative toxicity for neoplastic versus normal tissues. Accordingly, we investigated the effect of hyperthermia treatment (HT) on the induction of DNA fragmentation, apoptosis, cell-cycle distribution, NF kappa B mRNA expression, DNA-binding activity, and phosphorylation of I kappa B alpha in the normal human Mono Mac 6 (MM6) cells. For HT, cells were exposed to 43A degrees C. FACS analysis showed a 48.5% increase in apoptosis, increased S-phase fraction, and reduced G2 phase fraction after 43A degrees C treatments. EMSA analysis showed a dose-dependent inhibition of NF kappa B DNA-binding activity after HT. This HT-mediated inhibition of NF kappa B was persistent even after 48 h. Immunoblotting analysis revealed dose-dependent inhibition of I kappa B alpha phosphorylation. Similarly, RPA analysis showed that HT persistently inhibits NF kappa B mRNA. These results demonstrate that apoptosis upon HT exposure of MM6 cells is regulated by I kappa B alpha phosphorylation mediated suppression of NF kappa B.