CHANGES IN HEAT-SHOCK PROTEIN-70 AND UBIQUITIN MESSENGER-RNA LEVELS IN C1300-N2A MOUSE NEUROBLASTOMA-CELLS FOLLOWING TREATMENT WITH IRON

We have shown that following heat shock (42.5-degrees-C for 30 min). mouse-derived C1300 N2A neuroblastoma cells contain increased levels of mRNA coding for the inducible form of heat shock protein 70 and for ubiquitin. Incubation of C 1 300 cells with iron also induces an elevation in content of mRNAs coding for the same two proteins that can be blocked by alpha-tocopherol and desferrioxamine. Iron was shown to increase mitochondrial and lysosomal activities in differentiated C 1 300 N2A cultures, as shown by the 3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide and neutral red cytotoxicity assays. These responses were not initially associated with any loss of viability, as assessed by the lactate dehydrogenase release assay. These results suggest that there is production of cytoprotective heat shock proteins in response to iron-mediated cell damage, probably involving free radical generation, in neural cells. The apparent stress response of vulnerable neurones in human neurodegenerative diseases, particularly Parkinson's disease, may be induced by iron-mediated free radical production in degenerating neurones, making investigation of the mechanism of free radical-induced responses in neuronal cells of special interest.