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Updated: Jul 13, 2026
In Vivo Alkaline Comet Assay and Enzyme-modified Alkaline Comet Assay for Measuring DNA Strand Breaks and Oxidative DNA Damage in Rat Liver
Published on: May 4, 2016
Effects of cadmium on hepatocellular DNA damage, proto-oncogene expression and apoptosis in rats
Ri-An Yu1, Ling-Fei He, Xue-Min Chen
1Department of Occupational and Environmental Health, Shool of Public Health, Guangdong Pharmaceutical University, Guangzhou 510310, Guangdong, China. yurian.tj@163.com
Objective:
To study the effects of cadmium on hepatocellular DNA damage, expression of proto-oncogenes c-myc, c-fos, and c-jun as well as apoptosis in rats.
Methods:
Cadmium chloride at the doses of 5, 10, and 20 micromol/kg was given to rats by i.p. and there were 5 male SD rats in each group. Hepatocellular DNA damage was measured by single cell gel electrophoresis (or comet assay), while expression of proto-oncogenes c-myc, c-fos, and c-jun in rat hepatocytes were measured by Northern dot hybridization. C-Myc, c-Fos, and c-Jun were detected with immuno-histochemical method. Hepatocellular apoptosis was determined by TUNEL (TdT-mediated dUTP Nick End Labelling) and flow cytometry.
Results:
At the doses of 5, 10, and 20 micromol/kg, cadmium chloride induced DNA damage in rat hepatocytes and the rates of comet cells were 50.20%, 88.40%, and 93.80%, respectively. Results also showed an obvious dose-response relationship between the rates of comet cells and the dose of cadmium chloride (r = 0.9172, P < 0.01). Cadmium chloride at the doses of 5, 10, and 20 micromol/kg induced expression of proto-oncogenes c-myc, c-fos, and c-jun. The positive brown-yellow signal for c-myc, c-fos, and c-jun was mainly located in the cytoplasm of hepatocytes with immunohistochemical method. TUNEL-positive cells were detected in cadmium-treated rat livers. Apoptotic rates (%) of cadmium-treated liver cells at the doses of 5, 10, and 20 micromol/kg were (17.24 +/- 2.98), (20.58 +/- 1.35), and (24.06 +/- 1.77) respectively, being significantly higher than those in the control. The results also displayed an obvious dose-response relationship between apoptotic rates and the dose of cadmium chloride (r = 0.8619, P < 0.05).
Conclusion:
Cadmium at 5-20 micromol/kg can induce hepatocellular DNA damage, expression of proto-oncogenes c-myc, c-fos, and c-jun as well as apoptosis in rats.
Insights
Cadmium exposure causes DNA damage and apoptosis in rat liver cells. It also increases the expression of proto-oncogenes c-myc, c-fos, and c-jun, indicating potential carcinogenic effects.
Area of Science:
- Toxicology
- Molecular Biology
- Hepatology
Background:
- Cadmium is a toxic heavy metal with known adverse health effects.
- Hepatocellular damage and oncogene activation are critical steps in carcinogenesis.
Purpose of the Study:
- To investigate the impact of cadmium chloride on DNA damage, proto-oncogene expression (c-myc, c-fos, c-jun), and apoptosis in rat hepatocytes.
Main Methods:
- Rats were administered varying doses of cadmium chloride (5, 10, 20 micromol/kg).
- Hepatocellular DNA damage was assessed using the comet assay.
- Proto-oncogene expression was analyzed via Northern dot hybridization and immunohistochemistry.
- Apoptosis was quantified using TUNEL assay and flow cytometry.
Main Results:
- Cadmium chloride induced significant hepatocellular DNA damage in a dose-dependent manner (50.20% to 93.80% comet cells).
- Expression of c-myc, c-fos, and c-jun proto-oncogenes was elevated in cadmium-treated hepatocytes.
- Apoptotic rates in liver cells increased significantly with cadmium exposure, showing a dose-response relationship (17.24% to 24.06%).
Conclusions:
- Cadmium exposure at doses of 5-20 micromol/kg induces hepatocellular DNA damage, proto-oncogene expression, and apoptosis in rats.
- These findings suggest a potential role for cadmium in hepatocarcinogenesis.
