SP408THE AMELIORATION OF GUT ENVIRONMENT BY AST-120 PROTECTS AGAINST THE PROGRESSION OF RENAL IMPAIRMENT THROUGH THE ACTIVATION OF TLR2 IN CKD RATS

Abstract

Introduction and Aims: Oral activated charcoal adsorbent AST‐120 (AST) has been reported to ameliorate renal dysfunction by inhibiting absorption of toxic substances from the gut, although the detailed mechanisms have not been explored. Recent studies revealed that gut microbiota has been shown to have some role in the pathogenesis of various diseases including chronic kidney disease (CKD). However, the effects of AST on the gut environment and microbiota have not been explored thus far. In this study, we elucidated the mechanism how AST improves the renal dysfunction through the gut environment by rat model and human colon cell line. Methods: Six‐week‐old spontaneously hypertensive rats (SHR) were rendered CKD by 5/6th nephrectomy (Nx). The SHRs were divided into three groups; sham‐operated SHR (SHR, n=10), SHR with Nx (Nx, n=10), Nx given AST (Nx+AST, n=10). AST was orally given at a dose of 4g/kg/day. After 12 weeks, rats were sacrificed and biochemical parameters, cytokine marker (IL‐6), histological changes in the kidney and colon were explored. Gut molecular changes in tight junctions, Toll‐like receptor (TLR)2 and acetylcholine receptor (Ach‐R) expression were examined. Furthermore, concentrations of cecal uremic toxins were measured and the gut flora population was analyzed by T‐RFLP and RT‐PCR. The gut permeability was evaluated by the serum Diamine oxidase (DAO) levels. Human colon cell line, Caco‐2 cell were treated with uremic toxin precursor, indole in the presence or absence of Lact or OxPAPC, an inhibitor of toll‐like receptor, putative receptor recognizing Lact. Results: The gut flora analysis revealed that the decrease in Lact in Nx, which was restored in Nx+AST. Cecal uremic toxins of indole, p‐cresol, and phenol did not show significant changes between SHR and Nx, although they elevated in Nx+AST. Increase in serum indoxylsulfate, serum IL‐6 and urinary protein excretion in Nx was ameliorated in Nx+AST. The downregulation in the tight junction proteins Occludin, Zo‐1 and Claudin‐1 in Nx were mitigated by AST. DAO levels increased in Nx, which was reversed by The decrease in the expression of TLR2 was restored in Nx+AST group. The expression of Ach‐R significantly elevated in Nx+AST group compared to SHR and Nx. In Caco‐2 cells, the downregulations of Occludin and Zo‐1 by indole were also ameliorated by Lact. OxPAPC inhibited the Lact‐induced restoration of these tight junction proteins. Conclusions: As Lact improves the expressions of tight junction through TLR2, AST improved tight junction protein expression through the reversal in number of Lact .This mechanism provide the novel antiinflammtory mechanism for AST to protect against renal impairment through the maintaining the amount of Lact in gut environment.