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Oxalobacter formigenes-Derived Bioactive Factors Stimulate Oxalate Transport by Intestinal Epithelial Cells.

ABSTRACT: Hyperoxaluria is a major risk factor for kidney stones and has no specific therapy, although Oxalobacter formigenes colonization is associated with reduced stone risk. O. formigenes interacts with colonic epithelium and induces colonic oxalate secretion, thereby reducing urinary oxalate excretion, via an unknown secretagogue. The difficulties in sustaining O. formigenes colonization underscore the need to identify the derived factors inducing colonic oxalate secretion. We therefore evaluated the effects of O. formigenes culture conditioned medium (CM) on apical ¹⁴C-oxalate uptake by human intestinal Caco-2-BBE cells. Compared with control medium, O. formigenes CM significantly stimulated oxalate uptake (>2.4-fold), whereas CM from Lactobacillus acidophilus did not. Treating the O. formigenes CM with heat or pepsin completely abolished this bioactivity, and selective ultrafiltration of the CM revealed that the O. formigenes-derived factors have molecular masses of 10-30 kDa. Treatment with the protein kinase A inhibitor H89 or the anion exchange inhibitor 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid completely blocked the CM-induced oxalate transport. Knockdown of the oxalate transporter SLC26A6 also significantly restricted the induction of oxalate transport by CM. In a mouse model of primary hyperoxaluria type 1, rectal administration of O. formigenes CM significantly reduced (>32.5%) urinary oxalate excretion and stimulated (>42%) distal colonic oxalate secretion. We conclude that O. formigenes-derived bioactive factors stimulate oxalate transport in intestinal cells through mechanisms including PKA activation. The reduction in urinary oxalate excretion in hyperoxaluric mice treated with O. formigenes CM reflects the in vivo retention of biologic activity and the therapeutic potential of these factors.

SUBMITTER: Arvans D

PROVIDER: S-EPMC5328155 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Oxalobacter formigenes-Derived Bioactive Factors Stimulate Oxalate Transport by Intestinal Epithelial Cells.

Arvans Donna D Jung Yong-Chul YC Antonopoulos Dionysios D Koval Jason J Granja Ignacio I Bashir Mohamed M Karrar Eltayeb E Roy-Chowdhury Jayanta J Musch Mark M Asplin John J Chang Eugene E Hassan Hatim H

Journal of the American Society of Nephrology : JASN 20161013 3

Hyperoxaluria is a major risk factor for kidney stones and has no specific therapy, although Oxalobacter formigenes colonization is associated with reduced stone risk. O. formigenes interacts with colonic epithelium and induces colonic oxalate secretion, thereby reducing urinary oxalate excretion, via an unknown secretagogue. The difficulties in sustaining O. formigenes colonization underscore the need to identify the derived factors inducing colonic oxalate secretion ...[more]

PMID: 27738124

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Project description:Kidney stones (KS) are very common, excruciating, and are associated with tremendous healthcare cost, chronic kidney disease (CKD), and end stage renal disease (ESRD). Most KS are composed of calcium oxalate and very small increases in urine oxalate concentration increase the risk for stone formation. Besides its critical role in the pathogenesis of KS, emerging data suggest that disturbed oxalate homeostasis (hyperoxaluria and/or hyperoxalemia) contributes to CKD progression, CKD - and ESRD-associated cardiovascular diseases, progression of cyst growth in autosomal dominant polycystic kidney disease (ADPKD), and delayed graft function & poor renal allograft survival. This emphasizes the urgent need for plasma and urinary oxalate lowering therapies, and enhancing the bowel’s ability to secrete oxalate may effectively do so. We previously identified Oxalobacter formigenes (O. formigenes)-derived factors secreted in its culture conditioned medium (CM) which stimulated oxalate transport by human intestinal Caco2-BBE (C2) cells and reduced urinary oxalate excretion in hyperoxaluric mice by enhancing colonic oxalate secretion. Given their remarkable therapeutic potential, we now identified several proteins belonging to Sel1-like family as the major O. formigenes-derived secreted factors, and we determined the crystal structures for six proteins to better understand their function. Importantly, Sel1-14-derived small peptides P8 & P9 were identified as the major factors, with P8+9 closely recapitulate the CM’s effects, including acting through the oxalate transporters SLC26A2 & SLC26A6 and PKA activation. P8+9 also stimulate oxalate transport by human ileal and colonic organoids, confirming that these peptides work in human tissues. Collectively, the identification of these small peptides provide a great opportunity for developing a peptide-based novel therapeutic for hyperoxalemia, hyperoxaluria, and related disorders, impacting the outcomes of patients suffering from KS, primary hyperoxaluria, CKD, ADPKD, ESRD, and renal transplant recipients.

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Oxalobacter formigenes-Derived Bioactive Factors Stimulate Oxalate Transport by Intestinal Epithelial Cells.

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<i>Oxalobacter formigenes-</i>Derived Bioactive Factors Stimulate Oxalate Transport by Intestinal Epithelial Cells.

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