Oxygen free radicals as inducers of heat shock protein synthesis in cultured human neuroblastoma cells: relevance to neurodegenerative disease.

We studied heat shock protein (HSP) synthesis by cultured human neuroblastoma cells in response to either hyperthermia or high levels of superoxide anion (oxygen free radical). Both treatment modalities resulted in induced synthesis of the same major HSP species with an additive effect on the latter and on cell growth inhibition upon combined treatments. Exposure to superoxide anion in the presence of the free radical scavenging enzymes, superoxide dismutase and catalase improved cell survival and prevented HSP induction. These findings suggest a common mechanism by which various forms of injury, such as hyperthermia, cause HSP induction, that is, via oxidative stress or increased production of oxygen free radicals. Increased expression of some HSPs has been detected in association with the pathological lesions that characterize some neurodegenerative diseases such as the neurofibrillary tangles of Alzheimer's disease. This, in turn, suggests that chronic oxidative stress may play a role in the pathogenesis of these disorders.