Cadmium is an environmental toxicant, which causes cancer in different organs. It was found that it damages DNA in the various tissues and cultured cell lines. To investigate the mechanism of DNA damage, we have studied the effect of cadmium-induced DNA damage in plasmid pBR322 DNA, and the possible ameliorative effects of antioxidative agents under in vitro conditions. It was observed that cadmium alone did not cause DNA damage. However, it caused DNA damage in the presence of hydrogen peroxide, in a dose dependent manner, because of production of hydroxyl radicals. Findings from this study show the conversion of covalently closed circular double-stranded pBR 322 DNA to the open circular and linear forms of DNA when treated with 10 muM cadmium and various concentrations of H(2)O(2). The conversion was due to nicking in DNA strands. The observed rate of DNA strand breakage was dependent on H(2)O(2) concentration, temperature, and time. Metallothionein I failed to prevent cadmium-induced DNA nicking in the presence of H(2)O(2). Of the two antioxidant enzymes (catalase and superoxide dismutase) studied, only catalase conferred significant (50-60%) protection. EDTA and DMSO exhibited protection similar to catalase, while mannitol showed only about 20% protection against DNA damage. Ethyl alcohol failed to ameliorate cadmium-induced DNA strands break. From this study, it is plausible to infer that cadmium in the presence of hydrogen peroxide causes DNA damage probably by the formation of hydroxyl ions. These results may indicate that cadmium in vivo could play a major role in the DNA damage induced by oxidative stress.

Cadmium is non-essential, carcinogenic and multitarget pollutant in the environment. Monoisoamyl 2, 3-dimercaptosuccinate (MiADMS) is an ester of dimercaptosuccinicacid that acts as an antioxidant and chelator. Therefore, the mitigative action of MiADMS on viability, morphology, antioxidative enzymes and cell cycle were studied on rat liver cells treated with cadmium chloride (CdCl2). The cells were treated with 150 μM CdCl2 alone or cotreated with 300 μM MiADMS (concurrently, 2 h or 4 h post CdCl2 treatment) for 24 h. The viability of cells treated with CdCl2 alone was decreased in comparison to the control cells. Cotreatment with MiADMS resulted in an increase in cell viability in comparison to the CdCl2 alone treated cells. The CdCl2 treatment altered the morphological shape of the cells, while cotreatment with MiADMS restored the shape. Antioxidative enzymes activities were decreased in the cells treated with CdCl2 alone, while MiADMS cotreatment resulted in an increase in enzyme activities. The CdCl2 arrested the cells in S phase of the cell cycle. Cotreatment with MiADMS alleviated cell cycle arrest by shifting to G1 phase. These results clearly show the mitigative action of MiADMS on CdCl2 toxicity and may suggest that MiADMS can be used as an antidote against cadmium.

Cadmium affects human health through occupational and environmental exposure. In this report, we present the response of mitochondrial and cytoplasmic antioxidant enzymes of CRL-1439 cells exposed to different concentrations (0-150 μM) of CdCl 2 for 24 h at 37˚C. Exposure of liver cells to 50 μM CdCl 2 increased mitochondrial catalase and glutathione reductase (GR) activities more than the cytoplasmic enzymes. Although the mitochondrial selenium-dependent glutathione peroxidase (Se-GPx) showed less enzymatic activity than the cytoplasmic enzyme, the mitochondrial selenium-independent glutathione peroxidase (non-Se-GPx) showed a slight increase in activity over its cytoplasmic counterpart compared to untreated controls. With 100 μM CdCl 2 , catalase maintained an increase in specific activity in mitochondria over the cytoplasmic enzyme compared to the controls. The level of GR was higher in the cytoplasm than in the mitochondria. However, the activity of Se-GPx and non-Se-GPx decreased slightly in the mitochondria compared to their cytoplasmic counterparts. Exposure of cells to 150 μM CdCl 2 decreased all antioxidant enzyme activities compared to the 100 μM CdCl 2-treated samples due to toxic effect. Each antioxidant enzyme exhibited its own pattern of activation or inhibition upon exposure to different concentrations of cadmium, with more oxidative stress observed in the mitochondria.

No abstract

Cadmium is an environmentally hazardous metal, which causes toxicity in humans. Inhalation of cigarette smoke and industrial fumes containing cadmium are sources of cadmium exposure. It is responsible for the malfunction of various organs, leading to disease particularly in the lungs, liver and kidneys. In the present study, the effect of cadmium chloride (CdCl2) on cell viability, and the expression levels of interleukin (IL)-1α and IL-10 cytokines at various concentrations and incubation durations were assessed in MRC-9 human normal lung and A549 human lung cancer cells to elucidate the mechanism of cadmium toxicity. Cell viability was measured using a crystal violet dye binding assay. The expression levels of the cytokines were measured by cytokine specific enzyme-linked immunosorbent assay kits. The viability assay results revealed higher sensitivity of the A549 lung cancer cells to CdCl2 compared with the normal MRC-9 lung cells. In the normal MRC-9 lung cells, higher expression levels of the cytokines were observed at the lowest CdCl2 concentration at a shorter exposure time compared with the lung cancer cells. Higher levels of the cytokines were observed in the A549 lung cancer cells at all other times and concentrations compared with the MRC-9 cells, indicating higher levels of inflammation. The cytokine levels were reduced at higher CdCl2 concentrations and longer exposure durations, demonstrating the toxic effect of cadmium. The results indicated that CdCl2 affected the expression levels of the cytokines and led to cytotoxicity in human lung cells, and suggested that compounds which reduce inflammation may prevent cadmium toxicity.