Abstract
Purpose :
Damage-associated molecular pattern proteins (DAMPs) are endogenous molecules released during cellular stress or tissue injury, leading to the perpetuation of sterile inflammation through the initiation of inflammatory mediators. High-mobility group box 1, heat shock proteins and S100 proteins are examples of well-known DAMPs. We recently described the role of S100A9 in the rodent models of diabetic retinopathy (DR). In this study, we sought to establish the role of S100A9 in the pathogenesis of early-onset DR in a novel Ossabaw pig model of prediabetes.
Methods :
Four-month-old Ossabaw mini pigs were made prediabetic by Western diet (high-fat/high-fructose corn syrup/high-choleric content) for ten weeks. Control pigs were given standard chow for the same duration. At the time of sacrifice, pigs were starved overnight and euthanized for blood and tissue collection. Plasma was analyzed for blood profile and circulating S100A9 content using ELISA. The pig retina tissue was processed for real-time PCR, western blot and immunohistochemistry (IHC).
Results :
Prediabetic Ossabaw pigs showed elevated levels of S100A9 protein in the plasma. Real-time PCR of the S100 protein family in the retina revealed transcript expression of 16 gene members; however only S100A9 showed a significant increase in prediabetic pigs compared to control pigs. This was confirmed using western blot. Inflammatory and chemotactic mediators – IL-1β, IL-6, IL-8, TNFα, and MCP-1 – were also found to be elevated in the retina of pigs fed a Western diet. DAMPs-activated NLRP3 inflammasome was also upregulated in prediabetic pigs at the gene and protein level. IHC of Iba-1 showed increased microglial cells by distribution and morphology in the prediabetic pig retina. Also, double IHC of S100A9 and Iba-1 showed microglia to be the potential source of S100A9 in the prediabetic retina.
Conclusions :
Prediabetic Ossabaw mini pig retina showed elevated levels of S100A9 at gene and protein levels suggesting its role in perpetuating the inflammation milieu involved in the DAMPs-driven initiation of DR pathogenesis.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.