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Updated: Jul 3, 2026
A Rat Methyl-Seq Platform to Identify Epigenetic Changes Associated with Stress Exposure
Published on: October 24, 2018
Cytotoxicity and stress gene microarray analysis in cadmium-exposed CRL-1439 normal rat liver cells
Veera L D Badisa1, Lekan M Latinwo, Caroline O Odewumi
1Department of Biology, College of Arts and Sciences, Florida A & M University, Tallahassee, FL 32307, USA.
Abstract:
Cadmium is a biologically non-essential divalent hazardous metal. Previous studies demonstrated that cadmium toxic effect was caused by reactive oxygen species. Since gene expression is influenced by the presence of these reactive oxygen species, the association between metal intoxication and gene expression has recently become a major focus of research. We examined the effect of cadmium chloride on cell viability at 4, 8 and 24 h. Our results indicate that cadmium chloride did not alter cell viability at 4 or 8 h, but decreased the viability in a dose-dependent manner (p>0.01) at 24 h. Using DNA microarray, we studied the profile of stress gene expression in rat primary hepatocytes treated with cadmium for different time periods using a 100 microM cadmium chloride concentration. Microarray analysis indicated that cadmium treatment caused different patterns of gene expression profiles at each time point of incubation. Of the 207 stress genes on the microarray, only 32 genes were regulated. Since microarrays were hybridized by radioactive cDNA which was less sensitive than fluorescent-labeled cDNA, an experimental/control ratio >1.3 or <0.7 (30% increase or decrease) was taken as significant up- or down-regulation. Exposure of cells to cadmium for 4 h resulted in the expression of three up-regulated genes and six down-regulated genes. Longer exposure to cadmium for 8 h resulted in an increase in up-regulated genes to six and down-regulated genes to 14. After 24 h of cadmium exposure, 15 genes were down-regulated and six genes were up-regulated. Our findings suggest that the cells maintained complete viability up to 8 h with cadmium due to expression of various heat shock proteins and stress response proteins like heme oxygenase. Longer exposure periods, due to the down-regulation of the basic cell function proteins and cell-cycle regulating proteins, led to toxicity in cells and eventually to cell death.
Insights
Cadmium exposure initially triggers stress responses in rat hepatocytes, maintaining cell viability. Prolonged exposure, however, leads to toxicity and cell death by altering critical gene expression.
Area of Science:
- Toxicology
- Molecular Biology
- Cell Biology
Background:
- Cadmium is a hazardous metal whose toxic effects are linked to reactive oxygen species.
- Gene expression changes are increasingly studied in relation to metal intoxication.
- Understanding cadmium's impact on gene expression is crucial for assessing its toxicity.
Purpose of the Study:
- To investigate the effects of cadmium chloride on rat primary hepatocyte viability.
- To analyze the gene expression profile of stress-related genes following cadmium exposure at different time points.
- To elucidate the relationship between cadmium exposure duration, gene expression patterns, and cellular toxicity.
Main Methods:
- Cell viability assays were performed at 4, 8, and 24 hours post-cadmium chloride treatment.
- DNA microarray analysis was employed to profile stress gene expression in rat primary hepatocytes.
- A concentration of 100 microM cadmium chloride was used for treatment, with significant gene regulation defined as a >1.3 or <0.7 experimental/control ratio.
Main Results:
- Cadmium chloride did not affect cell viability at 4 or 8 hours but decreased it dose-dependently at 24 hours.
- Microarray analysis revealed distinct gene expression profiles at each time point, with 32 out of 207 stress genes regulated.
- Gene expression changes varied over time: 4h (3 up, 6 down), 8h (6 up, 14 down), and 24h (6 up, 15 down).
Conclusions:
- Hepatocytes maintain viability up to 8 hours of cadmium exposure due to the upregulation of heat shock and stress response proteins.
- Extended cadmium exposure (24 hours) results in cell toxicity and death, associated with the downregulation of essential cellular function and cell-cycle regulating proteins.
- The study highlights a time-dependent modulation of gene expression by cadmium, linking specific expression patterns to cellular viability and toxicity.
