Evaluation of a novel phytochemical Nrf2 activator on cytoprotective gene expression and proteostasis in vivo

2017 Summer.Includes bibliographical references.Aging is associated with increases in oxidative stress. Redox imbalance occurs when chronic production of reactive oxygen species (ROS) exceeds the capacity of antioxidant enzymes to eliminate ROS. Chronic levels of intracellular ROS can compromise proteostasis by causing irreversible damage to proteins. The transcription factor nuclear factor erythroid-derived 2-like 2 (Nrf2) mediates the cellular endogenous antioxidant defense system by regulating antioxidant enzymes that are cytoprotective against ROS. The phytochemical dietary supplement Protandim activates Nrf2. Previous work from our lab has demonstrated that Protandim treatment can improve proteostasis in skeletal muscle in vivo. Recently, we have begun to characterize a second-generation Nrf2 activator dietary supplement (PB125) that can inhibit components of the Nrf2 shutdown pathway, potentially allowing Nrf2 to stay transcriptionally active for longer. Therefore, we speculated that PB125 might have additional benefits on proteostatic processes. The purpose of the present study was to examine in vivo the effects of three doses (low, medium, high) of PB125 supplementation on Nrf2 activation and proteostasis. We assigned sixty male CB6F1 mice aged 10-11 months to diets containing low, medium, or high doses of PB125 in a 5 week feeding study. Mice were isotopically labeled with 8% deuterium oxide (D2O) administered in the drinking water to simultaneously measure protein and DNA fractional synthesis rates in liver, heart, and skeletal muscle. We assessed Nrf2 activation through analysis of gene expression profiles via Affymetrix GeneChip microarray. Proteostatic mechanisms increased in the liver mitochondrial fraction in the low treatment group. There were no differences in proteostatic mechanisms in heart. In the skeletal muscle mixed fraction, there was a reduction in proteostatic mechanisms in the medium treatment group. In the medium treatment group, there was also upregulation of Nrf2-dependent cytoprotective genes (Akr1c19, Akr1d1, Gpx2, Gclm, Fthl17b) as detected by microarray analysis. From our data we were able to conclude that all three doses were safe, and that 100 ppm was effective at activating Nrf2. In addition, there was an indication of increased proteostatic processes in the liver, but not heart or skeletal muscle, perhaps due to the healthy status of the mice