| Introduction: As an important industrial material, cadmium has polluted environment more and more seriously with the quickly development of industrial production. Further more, it is difficult to decompose in environment and organism. Cadmium is toxic to kidney, and in 1993, International Agency For Research on Cancer named cadmium as the first carcinogen. In recent years, it has attained a great development on the study of nephrotoxicity and mechanism of cadmium. Rencent studies have suggested that it relate to the oxidative stress. N-acetylcysteine(NAC) is a thiol-containing compound. It has been known that cysteine in the NAC molecule, as a scavenger of reactive oxygen species (ROS) and provider of reductive glutathione, is very important during the antioxidant reactions. Including directly reducing the level of reactive oxygen species, preventing DNA damage, affecting the gene regulation, and so on. In this study, we will investigate the possible mechanism of DNA damage of kidney by cadmium, and we will also study the preventive effect of NAC on cadmium-induced nephrotoxicity and provide scientific evidence against cadmium-induced genotoxicity in kidney cells. Method:LLC-PK1 cells were used as in vitro experimental system. Cytotoxicity was determined by MTT color assay. DNA damage was determined by single cell gel electrophresis assay (SCGE), and ROS were measured by fluorescence method. With the help of the method described above, NAC as an intervenor was added into cultures together with CdCl2 to explore its preventive effects on oxidative damage and DNA damage induced by CdCl2. Male Sprague-Dawley rats were randomly divided into 4 groups according to their weights (six rats in each). Each group was treated as follows: (1) the control, (2) high dose of CdCl2 (5.00mg/kg) group, (2) middle dose of CdCl2 (2.50mg/kg) group, (3) low dose of CdCl2 (1.25mg/kg) group. Rats were treated intraperitoneally by injection (ip) Once a day for 3 consecutive days, and killed on day 4. Nephrotoxicity was assessed by the measurement of body weight, kidney index, contents of blood urea nitrogen (BUN), changes in malondialdehyde (MDA) formation, the kidney cortex and histological changes. And 8-hydroxydeoxyguanosine (8-OhdG) was investigated by immunohistochemical method. Result: After LLC-PK1 cells were treated by different concentrations of CdCl2 for 24 h, growth of the cells was significantly inhibited and inhibitory concentration 50%(IC50 ) was 7.79±0.6mg/L, the cytotoxocity was significantly decreased by NAC and IC50 was 28±5.56mg/L. Single cell gel electrophresis assay showed that CdCl2 at concentrations of above 3μg/ml induced DNA strand-breaks, and the length of the tail of DNA was significantly decreased by 1mM NAC. The production of ROS was significantly increased after LLC-PK1 cells were treated by CdCl2 for 1 h, and 1mM NAC can decrease the production of ROS. In vivo studies, on day 3 after administration of CdCl2 , significantly nephrotoxicity appeared in rats, including the decrease of body weight, increase of kidney index, and contents of BUN. The formation of MDA in kidney cortex were significantly higher than that of the control (P<0.05). Histologically, acute renal damages in structure were observed. The 8-OHdG were positive in the kidney specimens of rats treated with CdCl2, and the percentage of adduct labeling cell (PALC%) at doses of 5.00, 2.50,and 1.25 mg/kg were 79±7.59 %, 69±10.69%, and 47±10.81%, respectively. Whereas the normal kidney tissues were weak positive with 8-OHdG, and PALC% in this group was 6±2.08%. PALC% of rats in groups treated with CdCl2 was significantly higher than that of the control (P<0.01). Conclusion: CdCl2 significantly inhibited the growth of LLC-PK1 cells, induced DNA strand-breaks, and increased production of ROS. NAC can attenuated the cytotoxicity produced by CdCl2. CdCl2 (1.25mg/kg, 2.5 mg/kg, 5 mg/kg) once a day, for 3 days can result in noticeable kidney damage in rats. The 8-OHdG was positive in the kidney specimens of rats treated with CdCl2, which may due... |
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