Application Of Response Proteins Gene Expression As Biomarkers In Cadmium Exposure

Cadmium (Cd) has been considered as a harmful pollutant of world wide concern. Cadmium exposure with long term and low level has become the focus of toxicological research. It also is of essential importance to develop sensitive and specific biomarkers in order to prevent the adverse health effects of cadmium.Response proteins are produced with cell respond to metabolic perturbations. Induced response protein has been advocated as a sensitive biomarker of compound-induced toxicity. Metallothonein (MT) is a well-known response protein induced by Cd administration and is vital during Cd intoxication and/or detoxification. MT is a special response protein to Cd. So it has been documented with increasing interest about the application of MT as biomarkers in cadmium exposure.Exposure of mammalian cells to various forms of oxidative stress induces haem oxygenase-1 (HO-1), the rate-limiting enzyme in haem degradation. HO-1 mRNA and protein expression, which is a sensitive and reliable indicator of oxidative stress, were also as a biomarker of response to Cd exposure.In order to investigate the validity of MT isoforms and HO-1 gene expression as biomarkers in cadmium exposure, expression of MT isoforms and HO-1 gene and protein were observed in human embryo kidney cells (HEK239T) exposure to cadmium by RT-PCR method and Western blot, respectively. MT isoforms gene expression level was determined in cultured in human peripheral blood lymphocytes (HPBLs) before and after exposure to cadmium. Then MT isoforms and HO-1 gene expression level were measured in HPBLs of populaton exposure to cadmium. In order to develop an applicable population method for routine quantification of gene transcripts of toxicological interest, we utilized to quantitatively assess the levels of gene expression for MT-1A transcripts in HPBLs by real-time PCR quantification methods.Reduced cell relative viability and increased the ratio of apoptosis were observed in HEK239T cells exposed to 5-40 μmol/L of cadmium. The diverse expression patterns of these genes (MT-1A,1F, 1G, 1H, 1X, MT-2A and HO-1) mRNA and protein expression depending on Cd concentration and exposure time was significantly increased after exposure to cadmium(P<0.05).Basal expression of MT-1X. 1A in HPBLs was similar to expression of the housekeeping gene glyceraldehydes 3-phosphate dehydrognase. In contrast, the basal gene expression of MT-1H, IF, IE, 1G was a little transcript in HPBLs. No signal was detected for the MT-1B. The level of gene expression of MT-1 A, IE, IF, 1G, 1H, IX and MT-2A was significantly increased(p<0.05), but not the level of MT-1B after exposure to cadmium.MT-1 A, IE, IF, IX, MT-2A and HO-1 gene expression in HPBLs was observed in occupational populations exposed cadmium. Exposure assessment was composed of questionnaire, measurement of cadmium level in workplace, internal dose (blood cadmium, BCd, urinary cadmium, UCd). Effect biomarkers included in Urinary pVmicroglobulin (UpVMG), N-acetyl-p-glucosaminidase (UNAG), albumin (UALB) and metallothionein (UMT).Basal MT-1 A, IE, IF, IX, MT-2A and HO-1 expression level statistically significant elevated in workers exposed to cadmium as compared with control (P< 0.05). Basal MT-1 A, IE, IF, IX, MT-2A and HO-1 expression level significantly increased with BCd level(P<0.05). There was a good dose-response relationship between basal MT-1 A, IE, IF, IX, MT-2A, HO-1 expression level and BCd. There was a good dose-response relationship between basal MT-1 A expression and UCd. Basal MT-1 A expression level in the 10~u g/gCr UCd group were significantly higher than the 0~ u g/gCr UCd group. Basal MT-2A expression level in the UCd group were significantly higher than the 0~ u g/gCr UCd group.It was showed that basal MT-1 A, IE, IF, IX, MT-2A and HO-1 expression level were significantly correlated with BCd and basal MT-1 A, IF and MT-2A expression level were significantly correlated with UCd. It was also showed that basal MT-1 A expression level were significantly correlated with UP2-MG and UMT and basal MT-1E expression level were significantly correlated with UP2-MG.The BMDL of BCd for a 10% level of risk above the background level of basal MT-1A, F, X, HO-1 expression and UNAG, U(32-MG, UMT were estimated as 3.62, 2.82, 4.99, 5.56, 4.42, 4.28, 4.90 u g/L for population exposed to Cd. The BMDL of UCd for a 10% level of risk above the background level of basal MT-1 A expression and UNAG, Up2-MG, UMT were estimated as 2.89, 4.22, 3.70, 4.38^g/g creatinine for population exposed to Cd.MT isoforms and HO-1 mRNA expression was consistent with protein expression after exposure to Cd in HEK239T cells. It was suggested that MT isoforms and HO-1...