Effect Potassium Dichromate Exposure On HOGG1 And HMTH1 Gene Expression In Human Lung Epithelial Cell

Preface: The malignant carcinoma is one of the serious diseases of endangering the human health,and the incidence and mortality kept on rising in recent years. The number of the patients is nearly up to 1, 700, 000 every year in our country,and the death number of cancer patients is up to 1, 500, 000every year.It has already exceeded the cardiac and cerebrovascular diseases and become the 1st reason to cause death.Lung cancer was one of the most common malignant tumors. Lung cancer was one of reasons to cause death in top ten cancer. It was reported that hexavalent chrome compound is carcinogenic for people.CrVI can enter the lung through respiratory tract and lung is target of CrVI. Epidemiological studies show that there are closely relations between occupational chromium exposure with occupational lung cancer,and International Agency for Research on Cancer(IARC)has confirmed that CrVI is carcinogenic in 1990 year.The mechianism of lung cancer is that carcinogens can induce DNA damage on respiratory tract epithelial cells which change the expression of some correlational genes, and change cellular genetic information, then cells begin to transfer and become carcinogenesis. We do not know the detailed mechianism of chromate cause cancer,but the damage and repair of DNA is of effect in cellular carcinogenesis. Data show that chromium can bring hormesis that cells can give rise to excitability which accelerate the grov/th of celland buildup the recovery ability when factors stimulate cells. The mechianism of hormisis is not a clarity. Some scholar think that low-dose stimulation can increase the repairability and has a closely relation with expression of genes.Investigate show that base excision repair (BER) is the leading way of excise a few damaged nucleotides for mammal and more and more people think much of the human 8-hydroxyguanine glycosylase(hOGG1) gene and human MutT homologue(hMTH1) gene which both belongs to DNA repair genes. Then this study target respiratory tract epithelial cells A549 cell lines to study how potassium dichromate affect the growth of A549 cell lines and the expression of hOGG1 and hMTH1 genes. So this study provide the experimentation foundations for the subsequently study the mechianism of which hexavalent chromium cause cancer.Materials and methods:1. A549 cell lines and potassium dichromate were adopted in this research. The concentrations of potassium dichromate are 0.156μmol/L, 0.312μmol/L, 0.625μmol/L, 1.25μmol/L, 2.5μmol/L, 5μmol/L. The concentration of control group is 0μmol/L.2. Morphological observation. The above-mentioned each concentration group were observed the growth state and morphology of the cell in the board under inverting microscopes and taken pictures before making MTT assay3. MTT assay was used to test suppressing rate of cell growth after above-mentioned potassium dichromate stimulated cell.4. Semi-quantitative reverse transcript polymerase chain reaction (RT-PCR) was employed to measure the hOGG1 and hMTH1 mRNA expressing levels. The point of 24h after above-mentioned potassium dichromate stimulated cell were selected.5. With SAS for windows 9.0 software package,one way ANOVA was used to analyze all experimental data. Size of the test wasα=0.05.Results:1. The effect of cell proliferationPotassium dichromate can accelerate the cellular multiplication with its concentration groups of 0.156μmol/L and 0.312μmol/L and suppress the cellular multiplication with its concentration groups of 0.625μmol/L,1.25μmol/L,2.5μmol/L and 5.000μmol/L. Compared with the control group, the difference of the suppressing rates of else group is significant(P<0.05).2. the expression of hOGG1 and hMTH1 mRNAPotassium dichromate can promote the expression of hOGG1and hMTH1 mRNA with its concentration groups of 0.156μmol/L and 0.312μmol/L, and suppress the expression of hOGG1 and hMTH1 mRNA with its concentration groups of 0.625μmol/L, 1.25μmol/L, 2.5μmol/L and 5.000μmol/L.Conclusions:1. When the concentration of Potassium dichromate is in 0.156μmol/L～5.000μmol/L , it have hormisis phenomena on the A549 cell lines when Potassium dichromate stimulates the A549 cell lines.2. The different expression of hOGG1 and hMTH1 genes with different concentrations maybe have close relation to the hormisis of Potassium dichromate.