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PREVENTIVE EFFECT OF SPECIFIC ANTIOXIDANT ON OXIDATIVE RENAL CELL INJURY FACILITATING RENAL CRYSTAL FORMATION: IN VITRO AND IN VIVO STUDIES

Login to Access Video or Poster Abstract: 2058
Date & Time: May 18, 2011 08:00 AM
Session Title: Stone Disease: Basic Research
Sources of Funding: Source of Funding: Research Grant from New York Academy of Medicine

INTRODUCTION AND OBJECTIVES:
Calcium oxalate (CaOx), a major element for the most common form of kidney stones, has been shown to induce renal cell injury through oxidative stress, and its crystallization becoming CaOx monohydrate (COM) is a prerequisite for ultimate stone formation. It is yet possible that certain antioxidants may prevent such crystal formation by abolishing oxidative stress. We thus investigated if COM could exert oxidative stress on renal cells (in vitro) and if certain antioxidants might prevent renal crystal formation in the rats (in vivo).

METHODS:
Renal proximal tubular OK cells were employed as our in vitro model, while CaOx crystals were induced in the rats by the established chemical method using ethylene glycol (EG) and vitamin D3 (VD3). Oxidative stress on OK cells was assessed by lipid peroxidation assay and activity of detoxifying enzyme, glyoxalase I (Gly-I), was also determined. Two antioxidants, vitamin C (VC) and N-acetylcysteine (NAC), were examined if they could relieve oxidative stress in vitro and prevent crystal formation in vivo. Wistar rats were divided into 4 groups and received the following agents: Group 1 (Sham); Group 2 received EG/VD3; Group3 received EG/VD3 and NAC; and Group 4 received EG/VD3 and VC. All rats were sacrificed after 2 weeks and kidneys were harvested for histopathological examination and Gly-I activity.

RESULTS:
COM ?500 µg/ml induced a >45% reduction in OK cell viability with a ~1.8-fold greater oxidative stress and a ~55% lower Gly-I activity than controls. However, such adverse events were almost completely prevented with NAC, not with VC. In the rat study, no renal crystals were seen in the Sham Group but numerous crystals, with reduced Gly-I activity, were found in the Groups 2 and 4. Yet, markedly (>70%) less crystals, with full Gly-I activity, were detected in the Group 3, indicating that NAC could effectively prevent crystal formation and Gly-I inactivation in the rats.

CONCLUSIONS:
Although COM indeed exerted oxidative stress on OK cells, inducing the cell viability reduction and Gly-I inactivation, NAC was capable of fully preventing such detrimental outcomes. Similarly, numerous crystal formation with Gly-I inactivation in the rats (Group 2) were significantly prevented with NAC supplement (Group 3). Taken together, oxidative stress appears to be a critical event, which may facilitate CaOx crystal formation, but could be entirely abolished with NAC. Thus, it is plausible that NAC may have clinical implications in preventing oxidative renal cell injury and ultimate kidney stone formation.
Authors
Fishman, Andrew; Green, David; Lynch, Alexandria; Choudhury, Muhammad; Eshghi, Majid; Konno, Sensuke 
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