Angiotensin-Converting Enzyme Inhibitor (ACEI)-Mediated Amelioration in Renal Fibrosis Involves Suppression of Mast Cell Degranulation

Abstract

Background/Aims: The mechanism by which angiotensin-converting enzyme inhibitors (ACEIs) attenuate renal fibrosis has not been fully uncovered. Methods: Renal fibrosis in rats was triggered by unilateral ureteral obstruction (UUO) and treated with Enalapril. Results: Enalapril attenuated renal fibrosis, as evidenced by the fibrosis scores (1.07±0.73 versus 2.18±0.75 for 200 mg/ml Enalapril versus control, p<0.01) of Enalapril-treated UUO rats compared to mock-treated UUO rats. The amelioration was mast cell dependent, as Enalapril exhibited no effects on mast cell-deficient Kitwsh/wsh mice developing renal fibrosis. We detected lower levels of transforming growth factor β (TGF-β) and alpha-smooth muscle actin (α-SMA, a fibroblast activation marker) in the kidney tissue of Enalapril-treated UUO rats relative to the control UUO rats. Enalapril-treated UUO rats exhibited far fewer mast cells infiltrating per area in the kidney tissue than the control UUO rats (8.00±0.65 versus 29.00±0.57, p<0.01). Electron microscopy images revealed that mast cell degranulation was inhibited by Enalapril treatment. Further, IgE-mediated passive cutaneous anaphylaxis demonstrated that Enalapril blocked mast cell degranulation in vivo. Conclusion: Enalapril attenuated renal fibrosis in UUO rats, possibly by a mechanism involving the suppression of mast cell degranulation.