| Cadmium (Cd) is an inorganic toxicant of great occupational and environmental concern, which has been classified as a category I carcinogen (human carcinogen) by the International Agency for Research on Cancer in 1993. After entering into the organism through food, cigarette smoke, and alcoholic. Cd accumulates primarily in the kidney and is eliminated very slowly with a half-life of 15~20 years. Cd binds to albumins and erythrocytes in the blood and can cause severeal tissuses damange, including liver and kidney, testis, placenta and brain. Cd has led to an increased interest in its toxicity and biological effects. The most important sources of Cd in humans are food, cigarette smoke, and alcoholic beverages. As tobacco leaves naturally accumulate high amounts of cadmium, cigarette smoking constitutes a major source of inhaled cadimium. Unfortunately, human contact with cadmium is an inescapable consequence of human life, with exposures occurring from both occupational and environmental sources. Cigarette smoke is by far the largest source of Cd exposure in the general human populationIt. has been estimated that the amount of cadmium inhaled from smoking one cigarette containing about 1.7μg Cd was estimated to be 0.14 to 0.19μg, corresponding to about 10% of the total cadmium content in the cigarette. Epidemiological studies have shown that blood plasma Cd concentrations from heavy smokers (20 or more cigarettes per day ) were 1.0μg/L ~4.5μg/L. In our preliminary studies, we treated rats with Cd at 25 nmol/kg every other day for four weeks, resulting in an accumulation of blood plasma Cd to 1.011±0.002μg/L and 3.27±0.67μg/L respectively, which cover the concentration range of blood plasma Cd found in both light and heavy smokers. Though some of the studies implicated the liver as a target organ where the toxic effects of Cd are expressed, however, there have been no experiments on animals exposed to Cd to this dose range equivalent to CSR-Cd levels using proteomics technology.Our proteomics analysis combined 2-DE with MS to study changes in protein expression, modification and degradation, between treated and untreated samples at the 20th and 52nd wk. This approach is useful to elucidate mechanisms of toxicity and to find novel biomarkers of toxicity. In this study, we gave CSR-Cd as a hepatotoxin to male Wistar rats in order to induce chronic liver damage. The objective of this investigation was to explore the proteins that are involved in liver damage induced by CSR-Cd.Recently, proteomics analysis technology has been used most in biological innovative reserches and has been one of the most important technologies in functional genomics.The proteomics is the study of most protein properties (expression level, post-translation modification, et al) at the whole cell level to obtain a global, integrated view of disease process, physiogical and biochemical processes of cells and regulatory networks at the protein level.Proteomics technolohy has been applied in studing cell growth and regulation, stimulus response, protein function, et al. By using proteomics technology, it has become possible to analyze stimultaneously hundreds or even thousands of protein. These technologies should allow the investigation of the molecular aspects of toxicological responses as well as normal cellular functions and biological processes by simultaneous such as genes and proteins. Safety biomarkers might also be developed with toxicopanomic analyses. The objective of this investigation was to explore the proteins that are involved in CSR-Cd induced liver injury.We studied the dynamic changes in protein expression in the CSR-Cd exposed mouse livers using two-dimensional electrophoresis/mass spectra (2DE/MS) approaches.Comparative proteomics has provided new insights into the mechanisms and processes of several diseases. Mapping of liver proteome content is expected to facilitate the understanding of hepaticbiological processes and their dysregulation in disease.Objective To investigate the molecular mechanisms of the late effects of cadmium (Cd) at CS-relevant levels (CSR-Cd) in rat liver.Methods 20 Male Wistar rats were given with 20 nmol/kg i.p injections of Cd in form of CdCl2 every other day for 4 weeks (Cd group), while control animals were given with 20 nmol/kg i.p injections of physiological saline for the same periods as the Cd group. At the 20th and 52nd week after treatment, rats were killed and the livers were removed. Proteins extracted from the liver were analysed with two-dimensional electrophoresis (2-DE) and mass spectrometry. Using HE staining to observe the pathological change in liver in 20th and 52nd. Using the immunohistochemical staining to detect the PHB and Apo A-I protein expression of liver of control and Cd at cigarette smoking-relevant levels in 20th and 52nd. The expression levels of prohibitin (PHB), d-dopachrome tautomerase (DDT) and apolipoprotein A-I(Apo A-I) in the liver tissues were validated with western blot analyses.Results HE dyeing showed remarkable pathologic change in liver after the accumulation of Cadmium: compared with control, the volume of hepatocyte and nucleus increased, and nucleus in different size, chromatin offered coarse grain form, hepatocyte generated extensive granular degeneration, some cell nucleus enlarged and became round or ellipse, which were 1~3 fold than the normal nucleus. Coarse granular chromatin situated at the rim of nuclear membrane, lymphocyte infiltration was observed at central veins and interlobar veins, Kupffer's cells swelling and became more, fibroplasia, showed focal necrosis. And, along with the accumulation of Cadmium (52w), showed grave tendency. Six protein spots with significant difference were found in 20th wk .Four of six spots were successfully identified. These proteins included prohibitin, pyrophosphatase 1 quinolinate, phosphoribos- yltransferase, 3-mercaptopyruvate sulfurtransferase.Nineteen protein spots with significant difference were found in 20th wk .Ten of nineteen spots were successfully identified. These proteins included Chain A, Rat Transthyretin, D-dopachrome tautomerase, biliverdin reductase B, Delta(3, 5)-Delta(2, 4)-dienoyl-CoA isomerase, electron-transfer-flavoprotein, alpha polypeptide, apolipoprotein A-I, rCG50422, isoform CRA_d, prohibitin, Chain A, Crystal Structure Of The H141c Arginase Variant Complexed With Products Ornithine And Urea and Chain A, Crystal Structure Of Rat Short Chain Acyl-Coa Dehydrogenase Complexed With Acetoacetyl-Coa. DDT and Apo A-I are down-rugulation the 52nd wk , the change of prohibitin (PHB) occurred at the 20th wk and 52nd wk. The expression of prohibitin (PHB), d-dopachrome tautomerase (DDT) and apolipoprotein A-I(Apo A-I) protein by Immunohistochemistry and Western Blot assay demonstrated. The expression of PHB protein showed positive in Cd group compared with control in weak positive 20w and 52 w.Western blot show that no obviously difference observed PHB in 20w and 52w Cd-group. The expression of Apo A-I protein showed positive in Cd group compared with control in weak positive 20w and 52 w.Western blot show that no obviously difference observed PHB in 20w and 52w Cd-group. Western blot show that no obviously difference observed DDT in 20w and 52w Cd-group.Conclusions The animal model of smoking-dosage cadmium was built,Cd at CS-relevant levels (CSR-Cd) exerted some effects on liver, and its damage to the livers lasted for a long time. These proteins may provide new clues to investigate the molecular events involved in liver injury. These result imply that Cd at cigarette smoking-relevant levels may lead to liver disorders in anti-oxidative system and cholesterol metabolism, and as well provide mew clue for the research on toxicity mechanism of Cd at cigarette smoking-relevant levels. The target is to achieve a totally acceptable exposure situation without adverse health effects from Cd. Thus, the research provides scientific theory and experiment foundation in advising people to give up smoking or to avoid Cadmium intake in the smoking population. |
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