Abstract P047: Epigenetic Mechanisms of Sodium Butyrate- and Retinoic Acid-dependent Attenuation of Renal Fibrosis and Inflammation in Npr1 Gene-targeted Mice

Abstract

The objective of the present study was to determine the combined effect of sodium butyrate (NaBu), a histone deacetylase (HDAC) inhibitor and all-trans retinoic acid (ATRA) on attenuation of renal fibrosis and inflammation in Npr1 (coding for natriuretic peptide receptor-A) gene-disrupted mutant mice. Adult (18-20 week old) male Npr1 gene-disrupted heterozygous (1-copy; Npr1+/-) wild-type (2-copy; Npr1+/+), and gene-duplicated (3-copy; Npr1++/+) mice were treated by injecting ATRA-NaBu hybrid drug (1.0 mg/kg/day) intraperitoneally for 2-weeks. A marked attenuation in tubulo-interstitial fibrosis was observed in Npr1+/- mice after treatment with ATRA-NaBu (50%, p < 0.001). Western blot analyses exhibited the reduction in renal expression of collagen type I alpha 2 and transforming growth factor-beta (55%, p < 0.001, 67%, p < 0.001, respectively) in ATRA-NaBu-treated Npr1+/- mice compared with vehicle-treated mice. A significant decrease in systolic blood pressure was observed in ATRA-NaBu-treated Npr1+/- mice (treated 110.3 ± 2.6 vs. Npr1 +/- control mice, 126.3 ± 2.7, p < 0.01). The ATRA-NaBu also enhanced plasma cGMP levels (pmol/ml) in Npr1+/- (treated, 22.7 ± 3.3 vs. control, 6.2 ± 1.6; p < 0.05), Npr1+/+ (treated, 50.9 ± 3.5 vs. control, 20.8 ± 3.6; p < 0.05), and Npr1++/+ (treated, 71.4 ± 6.4 vs. control, 34.5 ± 2.9; p < 0.05) mice. Treatment with ATRA-NaBu significantly lowered renal levels (pg/mg protein) of monocyte chemoattractant protein-1 (MCP-1) (treated, 109.5 ± 9.9 vs. control, 24.3 ± 1.7; p < 0.01) in Npr1+/- mice compared with vehicle-treated mice. Western blot analyses confirmed the reduction in renal expression of MCP-1 (72%, p < 0.001) in ATRA-NaBu-treated Npr1+/- mice compared with control mice. Moreover, the increased HDAC activity in Npr1+/- mice was significantly reduced by ATRA-NaBu treatment compared with untreated Npr1+/- control mice. The present results provide direct evidence that ATRA-NaBu acts as a potent antifibrotic agent and repairs the renal pathology in Npr1+/- mice, which will have important implications in prevention of hypertension-related renal pathophysiological conditions.