Prostanoid signaling in retinal cells elicits inflammatory responses relevant to early-stage diabetic retinopathy

Inflammation is a critical driver of the early stages of diabetic retinopathy (DR) and offers an opportunity for therapeutic intervention before irreversible damage and vision loss associated with later stages of DR ensue. Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown mixed efficacy in slowing early DR progression, notably including severe adverse side effects likely due to their nonselective inhibition of all downstream signaling intermediates. In this study, we investigated the role of prostanoids, the downstream signaling lipids whose production is inhibited by NSAIDs, in promoting inflammation relevant to early-stage DR in two human retinal cell types: M & uuml;ller glia and retinal microvascular endothelial cells. When cultured in multiple conditions modeling distinct aspects of systemic diabetes, M & uuml;ller glia significantly increased production of prostaglandin E2 (PGE2), whereas retinal endothelial cells significantly increased production of prostaglandin F2 alpha (PGF2 alpha). M & uuml;ller glia stimulated with PGE2 or PGF2 alpha increased proinflammatory cytokine levels dose-dependently. These effects were blocked by selective antagonists to the EP2 receptor of PGE2 or the FP receptor of PGF2 alpha, respectively. In contrast, only PGF2 alpha stimulated adhesion molecule expression in retinal endothelial cells and leukocyte adhesion to cultured endothelial monolayers, effects that were fully prevented by FP receptor antagonist treatment. Together these results identify PGE2-EP2 and PGF2 alpha-FP signaling as novel, selective targets for future studies and therapeutic development to mitigate or prevent retinal inflammation characteristic of early-stage DR.