Free radical scavengers, catalase and superoxide dismutase provide protection from oxalate-associated injury to LLC-PK1 and MDCK cells.
OBJECTIVE
Current studies have provided evidence that exposure of renal epithelial cells to oxalate and calcium oxalate crystals induces lipid peroxidation and injures the cells. Since oxidant/antioxidant balance is likely to play a critical role, we determined the effect of antioxidant scavengers on production of free radicals and injury to LLC-PK1 and MDCK cells from exposure to oxalate (Ox) or Ox + calcium oxalate monohydrate (COM) crystals.


METHODS
LLC-PK1 and MDCK cells were grown in monolayers and exposed to 1.0 mmol. Ox or 1.0 mmol. Ox + 500 microg. /ml. COM crystals for 120 or 240 minutes. We measured the release of lactate dehydrogenase (LDH) as a marker for cell injury and malondialdehyde (MDA) as a marker of lipid peroxidation. Superoxide and hydroxyl radicals were measured in the presence or absence of 400 U/ml. catalase, or superoxide dismutase (SOD).


RESULTS
Exposure of LLC-PK1 cells to Ox resulted in a significant increase in MDA and release of LDH, which was further elevated when COM crystals were added. MDCK cells responded similarly to both challenges, but showed significantly less impact when compared with LLC-PK1 cells. Both treatments were associated with significant increase in the generation of hydroxyl and superoxide radicals by both cell types. In both cell lines, the addition of catalase or SOD significantly reduced the increase of MDA and release of LDH.


CONCLUSIONS
Results of the present study indicate that both Ox and COM crystals are injurious to renal epithelial cells and the injury is associated with generation of free radicals. Cells of proximal tubular origin are more susceptible than those of distal tubules and collecting ducts. Free radical scavengers, catalase and SOD provide significant protection.
Thamilselvan
S
S
Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida 32610, USA.
Byer
K J
KJ
Hackett
R L
RL
Khan
S R
SR
D000818:Animals; D002374:Catalase / Q000494:pharmacology*; D002478:Cells, Cultured; D004285:Dogs; D016166:Free Radical Scavengers / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000096:biosynthesis; D018374:LLC-PK1 Cells / Q000187:drug effects*; D015227:Lipid Peroxidation; D008315:Malondialdehyde / Q000378:metabolism; D010070:Oxalates / Q000633:toxicity*; D013482:Superoxide Dismutase / Q000494:pharmacology*; D013552:Swine
D016166:Free Radical Scavengers; D010070:Oxalates; D008315:Malondialdehyde; D007770:L-Lactate Dehydrogenase; D002374:Catalase; D013482:Superoxide Dismutase