Reactive oxygen species (ROS) and aberrant growth signaling are important factors in aging and contribute to a variety of age-related pathologies, including neoplastic, cardiovascular and neurodegenerative diseases. At early stages of cancer, aberrant growth signaling increases ROS and causes DNA replication stress (inefficient DNA replication). Both ROS and DNA replication stress lead to DNA damage and oncogene-induced senescence of preneoplastic cells that inappropriately arrest growth in S phase. DNA replication stress also likely occurs in postmitotic neurons downstream of the increased ROS and aberrant growth signaling that is characteristic of many neurodegenerative disorders. In recent years, studies of chronological aging in the model organism S. cerevisiae (budding yeast) have been employed to investigate factors that impact aging of differentiated, postmitotic cells in humans. Our recent studies show that aberrant growth signaling accompanied by increased ROS and DNA replication stress in cells that growth arrest in S phase shortens the chronological lifespan of this organism (defined as the length of time cells survive after undergoing growth arrest in stationary phase). Downregulation of growth signaling pathways by caloric restriction or by caloric restriction mimetics extends chronological lifespan by inhibiting the chronological age-dependent accumulation of ROS and promoting a more efficient stationary phase growth arrest in G1, where cells cannot undergo DNA replication stress. Caloric restriction also extends the lifespans of higher eukaryotes and protects against cancer and neurodegeneration. These effects likely involve similar inhibition of ROS and more efficient G1 arrest of postmitotic, differentiated cells. The primary goal of the proposed research is to implement a high- throughput chemical screen of stationary phase budding yeast cells to identify additional compounds that mimic these conserved effects of caloric restriction. Compounds that exert these effects will be identified by their ability to inhibit the accumulation of age-dependent superoxide anions in concert with a tighter stationary phase growth arrest in G1. These compounds will likely be useful as cancer chemopreventive agents and in the treatment of neurodegenerative and other age-related disorders.
Cancer, cardiovascular, neurodegenerative and other age-related diseases impact the health and finances of millions of Americans and incur enormous costs to society. In organisms as diverse as yeast and mammals, caloric restriction has been shown to prevent or delay the onset of these diseases. The goal of this proposal is to identify compounds that can mimic these beneficial effects. The strategy proposed to achieve this goal is based on recent experimental findings that suggest caloric restriction exerts these effects in part by inhibiting cellular duplication.
