First Prize (Tie): Oxidative Renal Cell Injury Induced by Calcium Oxalate Crystal and Renoprotection with Antioxidants: A Possible Role of Oxidative Stress in Nephrolithiasis

Abstract

Calcium oxalate (CaOx) is one of the key elements for kidney stone formation, but the exact mechanism needs to be defined. CaOx has been shown to cause renal cell injury through oxidative stress, leading to potential crystal deposition in the kidneys. We thus investigated if CaOx crystal would induce such renal cell injury in vitro and also explored how it would be carried out. Renal tubular epithelial LLC-PK(1) cells were employed, and CaOx monohydrate (COM) was used as CaOx crystal in this study. Cytotoxic effects of COM were assessed on cell viability and biochemical parameters, while protective effect of antioxidants against COM was also examined. COM demonstrated its cytotoxicity on LLC-PK(1) cells, exhibiting a approximately 35% cell viability reduction with 500 microg/mL COM in 6 hours. This was presumably attributed to oxidative stress, indicated by lipid peroxidation assay, and N-acetylcysteine (NAC), a potent antioxidant, indeed neutralized such COM cytotoxicity. Although COM also induced inactivation of glutathione-dependent enzymes and partial degradation of heat shock protein 90, these adverse effects were completely prevented with NAC. Moreover, such reduced cell viability with COM was rather associated with apoptosis, evidenced by DNA analysis. COM is cytotoxic to LLC-PK(1) cells through oxidative stress, leading to the cell viability reduction, adverse effects on biochemical parameters, and, consequently, apoptosis. However, NAC effectively averted such severe cytotoxic effects, sustaining the renal cell integrity. Thus, NAC may provide full renoprotection against COM assault, preventing renal cell injury and ultimate stone formation.