P0668UNILATERAL URETER OBSTRUCTION (UUO)-INDUCED RENAL FIBROSIS IS ATTENUATED BY SUPPRESSION OF INDOXYL SULFATE (IS) ACCUMULATION IN SULFOTRANSFERASE (SULT)1A1-DEFICIENT MICE

Abstract Background and Aims Obstructive nephropathy is the result of functional or anatomic lesions located in the urinary tract, and renal interstitial fibrosis is a common finding associated with long-term nephropathy. Many factors are suggested to be involved in the pathogenesis of renal fibrosis, such as infiltration of macrophages, growth factors, oxidative stress and cytokines. Indoxyl sulfate (IS), a typical sulfate-conjugated uremic solute, accumulates markedly in serum and renal tissue of cisplatin- or ischemia/reperfusion-induced acute kidney injury model animals, thereby inducing generation of oxidative stress. However, the relationship between IS and obstructive nephropathy or renal fibrosis remains unclear. IS is produced in the liver by CYP2A6/2E1-dependent oxidative metabolism of dietary protein-derived indole, followed by sulfotransferase 1a1 (SULT1A1)-mediated sulfate conjugation of indoxyl. IS in the blood circulation is efficiently taken up by renal proximal tubules via basolateral membrane-localized organic anion transporters, OAT1 and OAT3, and excreted into urine via unidentified apical membrane-located transporter. Thus, we established SULT1A1 gene-deficient (SULTKO) mice and developed UUO mice to investigate the pathological role of IS in UUO-induced renal fibrosis. Method The left ureter of C57BL/6J mice (wild type (WT), 8 weeks-old) and SULTKO mice (8 weeks-old) were obstructed last for 2 weeks. IS concentration in serum and kidney was determined by LC-MS/MS. Changes in histology and interstitial fibrosis were examined with PAS staining and Sirius red staining, respectively. Quantitative PCR was applied for determining expression levels of col1a1 encoding the major component of type I collagen, fibronectin, plasminogen activator inhibitor (PAI)-1, the activator of plasminogen and hence fibrinolysis, pro-inflammatory cytokine interleukin 6 (IL-6), Wnt4 encoding one protein of Wnt and Sfrp5, a gene that codes for antagonist of Wnt pathway. Renal fibrosis also evaluated through the expression of alpha smooth muscle actin (SMA) by Western blotting. Results By UUO treatment, the concentration of IS in serum, kidney and liver were elevated, which were suppressed in SULTKO mice. Ureter dilation was obviously observed in the obstructed kidney of WT mice, which was slightly prevented in SULTKO mice with UUO. Sirius red staining revealed that severe collagen deposition was found in the interstitium of WT kidney with UUO, but it was partly