Ellagic Acid Inhibits TGFβ1/Smad-Induced Renal Fibrosis in Diabetic Kidney Injury

Abstract

Aim: Free radical formation increases due to hyperglycemia occurring in the pathogenesis of diabetes mellitus (DM), and as a result, oxidative stress occurs. Hyperglycemia-mediated oxidative stress plays an important role in the pathogenesis of diabetic nephropathy. The antihyperglycemic, antioxidative, anti-apoptotic, and anti-inflammatory effects of ellagic acid (EA) have been demonstrated by many studies. In this study, it was aimed to demonstrate the antifibrotic effect of EA on TGFβ1/Smad signaling in rats with streptozotocin induced diabetic nephropathy. Material and Methods: A total of 24 male Sprague Dawley rats, weighing 200-250 g, were used in this study. The animals were divided into four groups as control, EA, DM, and DM+EA. The kidney tissues were used for histological and immunohistochemical procedures. While the collagen density in kidney tissues was revealed by Masson's trichrome staining, the expression levels of fibrotic markers TGFβ1, p-Smad3, and αSMA were determined by the immunocytochemical method. Results: It was shown that the collagen density in the renal tissue of the DM group increased significantly in the intertubular area, while the collagen density in the EA-treated DM group was statistically significantly decreased. When TGFβ1, p-Smad3, and αSMA immunopositivity in kidney tissue sections of all groups were evaluated, the highest staining intensity was in the DM group, while the intensity of staining was close to the control group in the treatment group. It was observed that αSMA, TGFβ1, and p-Smad3 protein expression were down-regulated with EA treatment. Conclusion: EA reduced fibrosis in diabetic nephropathy by returning profibrotic parameters to normal levels.