INDUCTION OF HEAT-SHOCK PROTEINS AND THEIR POSSIBLE ROLES IN MACROPHAGES DURING ACTIVATION BY MACROPHAGE-COLONY-STIMULATING FACTOR

(1) Treatment of resident peritoneal macrophages for 8 h with macropha ge colony-stimulating factor (M-CSF) increased release of superoxide a nion (O-2(-)) stimulated by phorbol 12-myristate 13-acetate. Gel elect rophoresis of pulse-labelled proteins with L-[S-35]methionine showed t hat a number of proteins were induced during activation by M-CSF. Immu noblot analysis with antibody against heat shock protein (HSP) 90, HSP 70, or HSP60 demonstrated that M-CSF induced these stress-inducible HS Ps; the timing of induction and level of each HSP correlated with the increase in O-2(-) production. The activated macrophages acquired resi stance to H2O2-induced damage. M-CSF also stimulated the synthesis of a heat shock cognate protein (HSC70); however, the induction occurred at 1h, when O-2(-) production was not yet augmented, but at which time L-[S-35]methionine incorporation into cell proteins was already enhan ced. (2) Gel mobility shift assay with oligonucleotide coding for the heat shock element showed that M-CSF activated the heat shock factor w ithin 15 min, and the activation continued for at least 8 h. Northern- blot analysis with a cDNA probe for human HSP70 or HSC70 showed that. accumulations of HSP70 and HSC70 mRNAs coincided with the inductions o f the respective proteins. (3) These results suggest that M-CSF may in duce the transcriptional activation of heat shock genes, and that the stress-inducible HSPs as well as HSC70 may play an important role in t he activation of macrophages by functioning as molecular chaperones an d by protecting the macrophage against the autooxidative damage associ ated with the respiratory burst.