of work: Heat shock proteins (HSPs) are induced in response to a variety of cellular stresses, and appear to be critical for maintaining cellular homeostasis. We and others have provided evidence that there is a general decline in stress-induced HSP expression during aging. Studies in this project are focused on examining HSP expression in a variety of physiologically relevant stress models, many of which involve complex regulatory mechanisms. Efforts are directed at defining critical events involved in controlling HSP expression in response to specific stresses, and determining the cause and significance of the age-related decline in the ability of animals to mount the response. Areas of investigation during the past year included: 1. Potentiation of heat-induced HSP70 induction in the presence of aspirin. Recent studies in cultured cells have provided evidence that nonsteroidal antiinflammatory agents (NSAIDs) can potentiate the cellular response to heat stress by enhancing the DNA binding activity of HSF1. We have obtained evidence indicating that we can imply this strategy to boost heat-induced HSP70 expression in primary hepatocytes derived from aged rats. However, the potentiating effects of the NSAIDs are greater for young cells compared to old cells. We have also shown that aspirin treatment enhances HSP70 expression in vivo during systemic heat stress. This occurs, largely, through metabolic effects leading to elevations in body temperature. 2. Interrelationship between HSP induction and other stress-response pathways. Independent studies have implicated both HSPs and stress activated protein kinases (SAPK) in influencing cell survival following heat stress. The goal of this project is to examine the interrelationships between these two pathways during the acquisition of thermotolerance (the situation in which a prior modest heat stress leads to enhanced tolerance of cells subjected to a second lethal treatment). We have found that thermotolerance is associated with increased levels of HSPs, and decreased JNK and p38 SAPK activation during heat stress. Future studies will address the inter-dependence of these changes and their role in determining cell fate.
