Study On Determination Technology, Monitoring Technology And Molecular Mechanism Of Cadmium-Induced Renal Injury

Kidney is one of the important target organs of chronic cadmium exposure. It has been shown that long term and low dose exposure to cadmium can cause damage to the proximal tubular epithelium which contributed to the reduction of the reabsorption ability with the increase of the low-molecular weight proteins in the urine, and the final developing of osteoporosis and/or osteomalacia in that the metabolism dysfunction of calcium can be disturbed by cadmium.With the rapid development of economy, the health hazard caused by the cadmium pollution in the environment becomes increasingly prominent. The early detecting of the chronic damage due to the cadmium pollutions and taking some measurements in medical preventions and health compensations are of significance for the health protection of the inhabitants. However, the lack of diagnosis standards for the chronic cadmium poisoning syndrome resulting from environmental cadmium pollution combining with lower specificity about the corresponding biochemical detection index are ofproblems at present. Besides that, the accurate pathogenesis of the kidney damage caused by cadmium are still under discussion. In this case, studying the determination and detection technique and pathogenesis about the health hazards caused by environmental cadmium pollution has become the focus in this field.In present study we selected the cadmium pollution area in Hezhang Region of Guizhou province as the research location and 85 residents with the value of bone density one standard deviation less than the average among the local residents exposing to cadmium in the environment as the subjects to analyze the diagnostic value of urinary cadmium for chronic cadmium toxicity after exposing to the environment pollutions. The research showed that for 85 subjects the levels of cadmium, NAG and 0 2-MG in the urine were 14.46 u g/g.a\ 14.53U/g.a\ 402.21 u g/g.cr respectively;and once the level of urinary cadmium the was above 15 u g/g.cr, the levels of NAG and P 2 -MG would significantly increase to more than reference standards of general population. At the same time for those nineteen patients with the osteoporosis or osteomalacia the levels of cadmium, NAG and P 2-MG in the urine were 21.39 ji g/g.a\ 20.15U/g.a\ 3409.50 u g/g.cr respectively. Our research results proved that the level of the cadmium in the urine above than 15 p g/g.cr as one diagnostic index for chronic cadmium toxicity caused by the environmental cadmium pollution is practicable.On the basis of the research and some diagnosis standards' reviewing,including the diagnosis standard of the occupational cadmium poisoning, the determination standard of the health damage area by environmental cadmium pollution and the Japanese diagnosis standard of itai-itai disease, the author put forward the diagnosis standard of the chronic cadmium poisoning caused by environmental pollution which can be used for the determination of individuals. The standard consists of the diagnosis criteria, the diagnosis evidence, the diagnosis method and the supplement.Daye environmental cadmium pollution area in Hubei province was selected as the research location and morning urine from 90 residents were collected to analyze the correlativity among the levels of Cd-MT,NAG and 3 2-MG in the urine. The results showed that the levels of cadmium, Cd-MT, NAG and P 2-MG as geometric mean and standard deviation are 5.17+2.40 u g/g.cr, 6.42 ± 2.53 u g/g.cr, 12.74 + 2.14U/g.cr, 266.11±3.71 u g/g.cr respectively;when the levels of urinary cadmium were enhanced 1.96 fold and 5.49 fold, the levels of Cd-MT were increased 1.12 fold and 2.24 fold respectively and the levels of NAG with 0.58 fold and 0.66 fold respectively while ￡ 2-MG were increased only 0.05 fold and 0. 90 fold respectively;the levels of Cd-MT closely correlated with the levels of cadmium and NAG in the urine. Therefore Cd-MT could be regarded as a sensitive and specific biological index to reflect cadmium-induced renal injury.In the following experiment NRK cells were chosen as the experimental subjects and a series of assay methods such as MTT, DNA gel electrophoresis,How cytometry, Reverse transcription-polymerase chain reaction and immuno-histochemistry were taken to study the apoptosis of the NRK cells and the expressions of corresponding regulating-genes induced by various concentrations of cadmium chloride in different poisoning times, thereby in the terms of molecular levels the toxicity mechanism of cadmium-induced renal injury were also investigated. The result showed that Cadmium prohibited the growth of NRK cells and dose-effect relationship were between the levels of cadmium and the prohibition rate of NRK cells in certain time scopes (10min~6h))and certain concentration scopes (5~20}iM). Cadmium could induce the apoptosis of NRK cells, whose early apoptosis rate were time-effect correlative and dose-effect correlative, at the same time the mid-late period and overall apoptosis rate shared the similar trends with the early apoptosis rate. Further studies showed that when NRK cells were treated with 20nM cadmium chloride for 12hours, a typical "ladder" strip could be seen from DNA gel electrophoresis with the size gradually increasing every 180-200bp. During cadmium induced the apoptosis of NRK cells, the expression contents of c-fos> c-jun mRNA had been increased obviously accompanied by the decrease of bcl-2 protein and the increase of bax protein and also the ratio altering of bcl-2/bax, which proved that the apoptosis of NRK cells induced by cadmium chloride are closely relative with the expressions of c-fos, c-jun genes and the ratio altering of Bcl-2/Bax expressions.In summary, the diagnostic value of urinary cadmium for the kidney damage caused by the cadmium pollution in the environment are investigated in the present study in order to provide references and evidences for establishing the diagnostic standards of chronic cadmium toxicity caused by the cadmium pollution in the environment. Besides, it is the first time at home to probe into the correlation among Cadmium-Metallothionein and other kidney damages caused by cadmium which would establish the foundation for further finding more sensitive and specific biomarker of cadmium-induced renal injury. Finally the corresponding molecular mechanism of cadmium-induced renal injury and the expression status of relevant genes studied with NRK cells as the experiment model and corresponding research results would be more promising either academically or practically. And the diagnosis standard of chronic cadmium poisoning caused by environmental pollution would provide a guideline for the determination of inhabitants' health damage by cadmium pollution.