EP1 Receptor Antagonism as a Therapeutic Intervention Strategy in Renal Fibrosis

Abstract

Renal fibrosis is a hallmark of Chronic Kidney Disease (CKD), which affects 10–16% of the world’s adult population. It has previously been shown that the cyclooxygenase/prostaglandin (COX/PG) system affects the progression of renal fibrosis. The downstream elements of this system, the eicosanoid prostaglandin (EP) receptors, EP1–4, have various physiological roles in health and disease. We therefore evaluated the effect of antagonizing one of these downstream receptors for prostaglandin, the EP1 receptor, on renal fibrosis.This was accomplished with a translational approach by utilizing three models of renal fibrosis; Transforming growth factor β (TGF‐β) treated Madin‐Darby Canine Kidney (MDCK) cells, mice that underwent seven days of unilateral ureteral obstruction (UUO), as well as TGF‐β treated Human Precision Cut Kidney Slices (HPCKS). We evaluated the extent of fibrosis in these models on the gene and protein level using QPCR as well as Western blotting and immunohistochemical analysis. Moreover, we determined the corresponding effects of the EP1 agonist 17‐phenyl trinor prostaglandin E2 (17‐phenyl PGE2) and the EP1 antagonist SC‐19220 on the intracellular Ca2+ concentration in MDCK cells measured by Flou‐4‐AM.We found, that as a whole, treatment with the EP1 receptor antagonist SC‐19220 successfully ameliorated renal fibrosis in all three models. Treatment with the EP1 receptor antagonist SC‐19220 (25mg/kg per day) diminished fibrosis in mice that underwent seven days of UUO. UUO‐induced protein expression of the fibrosis markers fibronectin (FN), α Smooth Muscle Actin (αSMA) and collagen measured by western blot, qPCR and immunohistochemical staining, was lowered by SC‐19220 treatment when compared to SHAM operated mice. Adding to this, treatment of HPCKS with SC‐19220 reduced TGF‐β‐mediated fibrosis as shown by decreased collagen 1A1, FN and αSMA gene expression as well as reduced staining intensity of Sirius Red and Masson’s Trichrome stains. In MDCK cells, fibrosis induced by TGF‐β was significantly reduced when treated with SC‐19220. This was evident by lower FN protein levels and possibly mediated by hampering of TGF‐β signalling. The specificity of SC‐19220 as an antagonist of the 17‐phenyl PGE2‐induced [Ca2+]i response was determined with standard concentration response experiments.Thus, this study shows that the EP1 receptor is a promising target for the treatment of renal fibrosis. However, further investigations into the mechanism underlying the anti‐fibrotic effect of EP1 receptor antagonism are necessary. It seems though, that intracellular calcium regulation is profoundly altered by the EP1 receptor and that this may alter fibrosis dynamics.Support or Funding InformationFunding for the project was provided by the Danish Research Council.