Proinflammatory cytokines trigger biochemical and neurochemical changes in mouse retinal explants exposed to hyperglycemic conditions

PURPOSE: Diabetic retinopathy (DR) is one of the most frequent complications of diabetes affecting the retina and eventually causing vision impairment. Emerging evidence suggests that inflammation plays a vital role in DR progression. In this study, we evaluated the early biochemical and neurochemical changes in mouse retinal explants to understand the contribution of proinflammatory cytokines to disease progression. METHODS: DR was modeled in vitro by incubating mouse retinal explants in a physiological buffer supplemented with high glucose and the proinflammatory cytokines TNF-α and IL-1β. Key metabolites of retinal energy metabolism, including glucose, lactate, ATP, glutamate, glutamine, and enzymes supporting retinal ATP levels were assessed 40 min after the application of high glucose and proinflammatory cytokines. As retinal energy metabolism is tightly coupled to retinal neurochemistry, we also determined the short-term effect on the amino acid distribution of glutamate, gamma aminobutyric acid (GABA), glutamine, and glycine. RESULTS: The results indicated that the combined application of high glucose and proinflammatory cytokines increased retinal glucose, lactate, and ATP levels, and decreased retinal glutamate, without affecting glutamine levels or the enzymes supporting ATP levels. Moreover, we observed a statistically significant increase in ATP and glutamate release. Correspondingly, statistically significant alterations in amino acid distribution were observed in retinal explants coexposed to high glucose and proinflammatory cytokines. CONCLUSIONS: These data suggest that short-term exposure to proinflammatory cytokines contributes to the early biochemical and neurochemical changes caused by hyperglycemia, by affecting retinal energy metabolism and amino acid distribution. These data are consistent with the idea that early intervention to prevent inflammation-triggered loss of metabolic homeostasis in patients with diabetes is necessary to prevent DR progression.