PSVIII-1 Up-regulation of genes involved in oxidative stress and a potential antioxidant response in aging canines.

Abstract Aging is associated with increased oxidative stress (OS), characterized by elevated levels of reactive oxygen species/reactive nitrogen species (ROS/RNS). One consequence of OS is the damage to proteins, lipids, and DNA leading to impaired cell function and pathologies in aging. A response to increased levels of OS is an increase in antioxidant systems, but this mechanism appears to decline with age. We characterized the OS changes in leukocytes in aging canines from whole blood collected in PAXgene RNA tubes from healthy dogs that were divided into two groups: young (n = 12, 2-3 yr) and old (n = 12, 10-13 yr). Following RNA isolation, gene expression was measured using the RT2 ProfilerTM PCR Array Dog Oxidative Stress panel of 84 genes. Analysis for ΔΔCT was performed using Qiagen’s GeneGlobe portal and normalized to RPLP1. There was a significant increase in CCL5 (3.69 fold, p < 0.05), a chemokine secreted by T cells and also expressed in macrophages, in older dogs when compared to young. CCL5 acts on CCR5 which leads to activation of signaling pathways that promote ROS. In addition, there was also a significant increase in the levels of OS-related genes in older dogs when compared to young, including CYBB (Nox-2), that can promote ROS formation (1.31 fold), and NCF-1, a neutrophil cytosolic factor, that together with Nox-2 can increase ROS production (1.42 fold, both p< 0.05). Heme oxygenase-1 (HMOX1), an enzyme upregulated during OS, was increased in aging dogs (1.58 fold, p< 0.05). A decrease in superoxide dismutase 1 (SOD1), a cytosolic enzyme that converts superoxide to hydrogen peroxide, was seen in older dogs compared to young (-1.13, p< 0.05). However, there was also an increase in levels of genes involved in an antioxidant response in aging dogs when compared to young including glutathione transferases (GSTP1, GSTZ1), selenoproteins (SEPP1, VIMP), thioredoxin (TXNRD3) and peroxiredoxin (PRDX5), oxidative resistance -1 (OXR1), oxidative stress response -1 (OXSR-1) and SOD-2 (all p< 0.05). Our results indicate an increased level of oxidative stress in leukocytes of aging canines but this increase may also initiate an innate antioxidant response to help leukocyte integrity. Whether the increase in genes involved in combating OS is sufficient to neutralize the harmful effects of oxidative damage on leukocyte function is not clear. Downregulation of OS related genes may be an attractive therapeutic strategy to mitigate damage to leukocytes in order for them to function effectively in aging canines.