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, NFκB mRNA expression, DNA-binding activity, and phosphorylation of IκBα in the normal human Mono Mac 6 (MM6) cells. For HT, cells were exposed to 43°C. FACS analysis showed a 48.5% increase in apoptosis, increased S-phase fraction, and reduced G2 phase fraction after 43°C treatments. EMSA analysis showed a dose-dependent inhibition of NFκB DNA-binding activity after HT. This HT-mediated inhibition of NFκB was persistent even after 48 h. Immunoblotting analysis revealed dose-dependent inhibition of IκBα phosphorylation. Similarly, RPA analysis showed that HT persistently inhibits NFκB mRNA. These results demonstrate that apoptosis upon HT exposure of MM6 cells is regulated by IκBα phosphorylation mediated suppression of NFκB.