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Abstract: FR-PO312

SLC26A6 Plays a Major Role in Release of Soluble Oxalate from Macrophages Following Internalization of Calcium Oxalate Crystals

Session Information

Category: Bone and Mineral Metabolism

  • 501 Bone and Mineral Metabolism: Basic

Authors

  • Najenson, Ana Clara, Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
  • Wagner, Teresa Raphaela, NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
  • Bachmann, Sebastian, Institute of Functional Anatomy, Charité - Universitätsmedizin Berlin, Berlin, Germany
  • Thomson, Robert Brent, Department of Internal Medicine, Section of Nephrology, Yale University School of Medicine, New Haven, Connecticut, United States
  • Knauf, Felix, Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
  • Aronson, Peter S., Department of Internal Medicine, Section of Nephrology, Yale University School of Medicine, New Haven, Connecticut, United States
Background

Accumulating evidence indicates that macrophages play an important role in recovery from oxalate-induced nephropathy. In vitro studies showed that macrophages can engulf and dissolve calcium oxalate crystals. In vivo models demonstrated that decreased renal macrophage infiltration is accompanied by increased crystal deposition, suggesting involvement of macrophages in removing oxalate crystals. Despite these findings, the mechanisms mediating crystal clearance by macrophages remain unknown. We previously showed that macrophages express transporter SLC26A6. SLC26A6 functions as a Cl-oxalate exchanger in macrophages. Our studies indicated that under steady-state conditions, SLC26A6 mediates net oxalate efflux and prevents intracellular oxalate accumulation in macrophages. In the present work, we analyzed the role of SLC26A6 in mediating the release of soluble oxalate from macrophages following internalization of calcium oxalate crystals.

Methods

Primary murine wild-type (WT) and Slc26a6-deficient (Slc26a6-/-) macrophages were exposed to calcium oxalate crystals for up to 48 hours. Internalization of oxalate crystals by macrophages was analyzed by transmission electron microscopy (TEM). After crystal uptake, macrophages were washed and re-incubated in an oxalate-free medium. Release of soluble oxalate after crystal internalization was measured as appearance of oxalate in the supernatant by use of an enzymatic assay.

Results

We found that WT and Slc26a6-/- macrophages are equally capable of oxalate crystal internalization. The presence of soluble oxalate increases with time in the supernatant of both WT and Slc26a6-/- macrophages after preloading with oxalate crystals. When compared with WT macrophages, macrophages from Slc26a6-/- mice showed greatly reduced release of soluble oxalate after 48 hours.

Conclusion

Our findings indicated that soluble oxalate is released from macrophages following internalization of calcium oxalate crystals. Slc26a6-/-macrophages demonstrated greatly reduced soluble oxalate release compared to WT macrophages. We therefore concluded that Slc26a6 plays a major role in the release of soluble oxalate from macrophages following internalization of calcium oxalate crystals.

Funding

  • Government Support – Non-U.S.