Abstract 084: Sodium Butyrate and Retinoic Acid Attenuate Renal Inflammation and Fibrosis in Npr1 Gene-targeted Haplotype Mice: Role of NF-κB Signaling

Abstract

The objective of the present study was to determine the effect of a hybrid drug of sodium butyrate (NaBu), a histone deacetylase (HDAC) inhibitor and all-trans retinoic acid (ATRA) on the attenuation of renal inflammation and fibrosis in Npr1 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 with ATRA-NaBu hybrid drug (1.0 mg/kg/day) by intraperitoneal injections for 2-weeks. A significant decrease in systolic blood pressure was observed in ATRA-NaBu-treated haplotype Npr1 +/- mice compared with untreated controls (treated, 113.3 ± 1.5 vs. control, 130.4 ± 1.9; p < 0.01). After treatment with ATRA-NaBu, a marked reduction in tubulo-interstitial fibrosis (50%, p < 0.001) and decreased renal collagen type I alpha 2 expression by 55% (treated, 25.9 ± 1.2 vs. control, 57.2 ± 2.9, p < 0.001) was observed in Npr1 +/- mice. Treatment with ATRA-NaBu also increased creatinine clearance (ml/24 h) in Npr1 +/- mice (245.7 ± 24.3 vs. control, 83.8 ± 3.9). Similarly, higher urinary albumin to creatinine ratio was detected in Npr1 +/- mice (0.84 ± 0.03) vs. control (0.35 ± 0.03; p < 0.01) and a complete reversal was observed in drug-treated Npr1 +/- mice (0.39 ± 0.05). Significant decreases were observed in renal (pg/mg protein) tumor necrosis factor-alpha (TNF-α) (4.1 ± 0.7 vs. control, 27.2 ± 2.6; p < 0.01) and interleukin (IL)-6 (11.8 ± 0.8 vs. control, 59.9 ± 3.6; p < 0.01) in ATRA-NaBu-treated Npr1 +/- mice. Western blot analyses showed significant reduction in renal TNF-α and IL-6 protein expression by 54%, (p < 0.001) and 61%, (p < 0.01), respectively, in ATRA-NaBu-treated Npr1 +/- mice. There was 49% increase in renal NF-κB (p65) DNA binding activity in Npr1 +/- mice and 51% lower activity in Npr1 +/++ mice compared with wild-type mice. Western blot analysis revealed distinctly higher levels of renal NF-κB (p65) protein expression in Npr1 +/- mice and reduced levels in Npr1 +/++ mice compared with wild-type controls. The present results provide direct evidence that ATRA-NaBu hybrid drug acts as a potent anti-inflammatory agent, which will have important implications in the pathophysiology of renal injury and hypertension.