Using Drosophila to identify inhibitors of oxalate kidney stone formation

Abstract

BackgroundKidney stones are an expensive and painful health problem with calcium oxalate (CaOx) being 70% of cases. We developed a Drosophila model of CaOx stones [Hirata et al., AJP‐Renal Physiol, 2012]. This work showed that dPrestin (Slc26a5/a6) exchanges Cl− for oxalate (Ox). Thiosulfate (S2O3) and tannic acid (TA) are implicated to inhibit CaOx crystals in supersaturated urine. Here, we report transporter, renal tubule and whole body effects of S2O3 and TA on crystal formation.MethodsS2O3 and TA transport effects were examined by voltage clamping of dPrestin‐expressing Xenopus oocytes. Cis‐inhibition of oxalate transport was also examined in (a) dissected Malpighian tubules (MT) or flies fed ox‐enriched food plus S2O3 or TA. MT CaOx crystals were viewed by DIC, or whole flies by microCT.ResultsdPrestin transports S2O3 but not TA, yet both inhibited Ox transport (Ki(S2O3)~10mM; Ki(TA)~100μM). S2O3 competitively inhibits while TA blocks dPrestin. MT treated with S2O3 or TA ↓ crystal formation compared to MT soaked in Ox only. Flies fed with S2O3 or TA also showed ↓ CaOx in MTs.ConclusionsS2O3 and TA are both inhibitors of CaOx crystallization. These experiments show that these inhibitors have distinct mechanisms of action. Our Results indicate that (a) this Drosophila model can be used as a chemical screening assay for CaOx stone prevention and (b) TA, due to low Ki, might be a reasonable therapy for certain CaOx stones patients.[DK83007, DK92408]