Evaluation of Oxidative DNA Damage Using an Alkaline Single Cell Gel Electrophoresis (SCGE) Comet Assay, and the Protective Effects of N-Acetylcysteine Amide on Zearalenone-induced Cytotoxicity in Chang Liver Cells

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin produced by several species of Fusarium that are found in cereals and agricultural products. ZEN has been implicated in mycotoxicosis in farm animals and in humans. The toxic effects of ZEN are well known, but the ability of an alkaline Comet assay to assess ZEN-induced oxidative DNA damage in Chang liver cells has not been established. The first aim of this study was to evaluate the Comet assay for the determination of cytotoxicity and extent of DNA damage induced by ZEN toxin, and the second aim was to investigate the ability of N-acetylcysteine amide (NACA) to protect cells from ZEN-induced toxicity. In the Comet assay, DNA damage was assessed by quantifying the tail extent moment (TEM; arbitrary unit) and tail length (TL; arbitrary unit), which are used as indicators of DNA strand breaks in SCGE. The cytotoxic effects of ZEN in Chang liver cells were mediated by inhibition of cell proliferation and induction of oxidative DNA damage. Increasing the concentration of ZEN increased the extent of DNA damage. The extent of DNA migration, and percentage of cells with tails were significantly increased in a concentration-dependent manner following treatment with ZEN toxin (p < 0.05). Treatment with a low concentration of ZEN toxin (25 microM) induced a relatively low level of DNA damage, compared to treatment of cells with a high concentration of ZEN toxin (250 microM). Oxidative DNA damage appeared to be a key determinant of ZEN-induced toxicity in Chang liver cells. Significant reductions in cytolethality and oxidative DNA damage were observed when cells were pretreated with NACA prior to exposure to any concentration of ZEN. Our data suggest that ZEN induces DNA damage in Chang liver cells, and that the antioxidant activity of NACA may contribute to the reduction of ZEN-induced DNA damage and cytotoxicity via elimination of oxidative stress.

Protective Effects of Houttuynia cordata Thunb. on Gentamicin-induced Oxidative Stress and Nephrotoxicity in Rats

Development of a therapy providing protection from, or reversing gentamicin-sulfate (GS)-induced oxidative stress and nephrotoxicity would be of great clinical significance. The present study was designed to investigate the protective effects of Houttuynia cordata Thunb. (HC) against gentamicin sulfate-induced renal damage in rats. Twenty-eight Sprague-Dawley rats were divided into 4 equal groups as follows: group 1, control; group 2, GS 100 mg/kg/d, intraperitoneal (i.p.) injection; group 3, GS 100 mg/kg/d, i.p. + HC 500 mg/kg/d, oral; and group 4, GS 100 mg/kg/d i.p. + HC 1000 mg/kg/d, oral administration). Treatments were administered once daily for 12 d. After 12 d, biochemical and histopathological analyses were conducted to evaluate oxidative stress and renal nephrotoxicity. Serum levels of creatinine, malondialdehyde (MDA), and blood urea nitrogen (BUN), together with renal levels of MDA, glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) were quantified to evaluate antioxidant activity. Animals treated with GS alone showed a significant increase in serum levels of creatinine, BUN, and MDA, with decreased renal levels of GSH, SOD, and CAT. Treatment of rats with HC showed significant improvement in renal function, presumably as a result of decreased biochemical indices and oxidative stress parameters associated with GS-induced nephrotoxicity. Histopathological examination of the rat kidneys confirmed these observations. Therefore, the novel natural antioxidant HC may protect against GS-induced nephrotoxicity and oxidative stress in rats.