Tranilast ameliorates renal tubular damage in unilateral ureteral obstruction

Purpose: We determined whether tranilast, the anti-allergic agent N-(3, 4-dimethoxyciannamoyl)-anthranilic acid, would diminish renal transforming growth factor-β (TGF-β) levels in unilateral ureteral obstruction and concomitantly affect renal tubular apoptosis and proliferation in that condition. Materials and Methods: Tranilast (150 mg./kg.) was administered to rats 1 day before unilateral ureteral obstruction and each day thereafter. Kidneys were harvested day 14 after unilateral ureteral obstruction. Tissue TGF-β was measured by bioassay using mink lung epithelial cells. Renal tubular proliferation and apoptosis were detected by immunostaining proliferating cell nuclear antigen and the terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling assay, respectively. Fibrosis was assessed by measuring collagen deposition with trichrome stained slides. Results: TGF-β bioassay showed that obstructed kidneys in controls contained significantly higher mean TGF-β plus or minus standard deviation than unobstructed kidneys in controls (73.7 ± 13.6 versus 14.1 ± 5.5 pg./mg. tissue) and tranilast significantly decreased tissue TGF-β in obstructed kidneys (15.9 ± 4.8 pg./mg. tissue). The terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling assay demonstrated that obstructed kidneys in controls had significantly more mean tubular apoptosis than the unobstructed counterparts (36.6 ± 6.7 versus 5.8 ± 5.5 nuclei per high power field) and tranilast significantly decreased mean renal tubular apoptosis in obstructed kidneys (16.2 ± 1.7 nuclei per high power field). In addition, immunostaining proliferating cell nuclear antigen showed that obstructed kidneys in controls had significantly more mean renal tubular proliferation than unobstructed kidneys (20.7 ± 3.4 versus 6.2 ± 2.1 per high power field) and tranilast significantly increased proliferating renal tubules in obstructed and unobstructed kidneys (26.5 ± 8.3 and 14.5 ± 3.4 per high power field, respectively). Control obstructed kidneys exhibited significantly more fibrosis, which was also blunted by tranilast. Conclusions: Tranilast significantly decreases tissue TGF-β, resulting in a reduction in tubular apoptosis and an increase in tubular proliferation. This finding suggests that tranilast is a promising agent for preventing renal tubular damage in unilateral ureteral obstruction.