PSIX-15 Elevated level of ATG12, an autophagy–associated gene, in canines with dermatological problems fed a polyphenol-rich food

Autophagy is a controlled intracellular degradation process that removes damaged cellular components through a lysosome-dependent mechanism to maintain cell homeostasis and longevity. Autophagy related proteins (ATGs) require a series of conjugation to other proteins prior to their delivery to lysosomes for degradation. ATGs may also be involved in apoptosis. We assessed the role of ATGs and related genes in circulating leukocytes in dogs with dermatological issues. To investigate if ATG genes are modified with diet we fed 2 test foods (one rich in polyphenols) to canines with dermatological problems (n = 8) and controls (n = 8). Dogs were pre-fed a control food for 28 d and then divided into two groups based on their phenotype (Healthy, Derm) followed by a cross-over design. Dogs were fed for 42 d with test food 1 (TF1) and the second group was fed test food with a higher polyphenol content (TF2) for 42 d followed by a crossover. RNA was extracted from blood collected at the end of the pre-feed period, end of phase 1, and end of phase 2. Gene expression was assessed using NanoString nCounter platform. A mixed model analysis was performed using food as a fixed effect and animal as a random effect. TF2 fed dogs had low pruritus scores and increased the response rate (improvement %) to 30.77% when compared with dogs fed TF1. There was a significant increase in ATG12 in dogs fed TF2 compared with baseline (P < 0.05). But there was no difference in other ATGs including ATG5, ATG7, or ATG10 with TF1 or TF2. Autophagy involves the conjugation of ATG12 to ATG5 which promotes ATG8 to bind to the autophagic membrane which is essential for atuophagosome formation. ATG12 can also exert its action through a non-autophagy pathway by binding to Bcl-2 and inhibiting its activity to promote apoptosis. An increase in Bcl-2 was observed with TF2 and TF1 when compared with baseline (P < 0.05). An increased level of ATG12 and Bcl-2 in our study may have contributed to a decreased expression of selected inflammatory cytokines due to activation of apoptosis in leukocytes. Consistent with this, there was a decline in the expression of IL-5RA, a receptor expressed on eosinophils, TF2 group when compared with baseline (P < 0.05). There was also a decrease in FCRL2, a gene preferentially expressed in memory B-cells and plasma cells and also involved in B-cell receptor signaling, in dogs fed TF2 (P < 0.05). Whether increased ATG12 is directly responsible for an improvement in pruritus in dogs fed TF2 is not clear. However, our results indicate that ATG12 and Bcl-2 together may be involved in promoting apoptosis of pro-inflammatory leukocytes in dogs fed TF2 that may have resulted in a decline in inflammation.