This invention relates to methods and compositions for use improving cell viability, particularly neural cell viability, and more particularly to methods and compositions for use improving cell viability by reducing reactive oxygen metabolite-mediated oxidative damage in a cell, regulating redox homeostasis in a cell, or reducing mitochondrial dysfunction in a cell. The invention further relates to the administration of the bile acid tauroursodeoxycholic acid (TUDCA) in combination with phenylbutyric Acid (PBA) to improve cell viability, and treat at least one symptom associated with, prevent the time of onset of, or slow the development of a disease related to oxidative stress.