15-keto-Prostaglandin E2 exhibits bioactive role by modulating glomerular cytoarchitecture through EP2/EP4 receptors

Aims: Prostaglandins are important signaling lipids with prostaglandin E2 (PGE2) known to be the most abundant prostaglandin across tissues. In kidney, PGE2 plays an important role in the regulation of kidney homeostasis through its EP receptor signaling. Catabolism of PGE2 yields the metabolic products that are widely considered biologically inactive. Although recent in vitro evidence suggested the ability of 15-keto-PGE2 (a downstream metabolite of PGE2) to activate EP receptors, the question whether 15-keto-PGE2 exhibits physiological roles remains unresolved.Materials and methods: Pharmacological treatment was performed in transgenic zebrafish embryos using 500 mu M 15-keto-PGE2 and 20 mu M EP receptors antagonists' solutions during zebrafish embryonic development. After the exposure period, the embryos were fixed for confocal microscopy imaging and glomerular morphology analysis.Key findings: Here, we show that 15-keto-PGE2 can bind and stabilize EP2 and EP4 receptors on the plasma membrane in the yeast model. Using lipidomic analysis, we demonstrate both PGE2 and 15-keto-PGE2 are present at considerable levels in zebrafish embryos. Our high-resolution image analysis reveals the exogenous treatment with 15-keto-PGE2 perturbs glomerular vascularization during zebrafish development. Specifically, we show that the increased levels of 15-keto-PGE2 cause intercalation defects between podocytes and endothelial cells of glomerular capillaries effectively reducing the surface area of glomerular filtration barrier. Importantly, 15-keto-PGE2-dependent defects can be fully reversed by combined blockade of the EP2 and EP4 receptors.Significance: Altogether, our results reveal 15-keto-PGE2 to be a biologically active metabolite that modulates the EP receptor signaling in vivo, thus playing a potential role in kidney biology.