Expression Alteration Of DNA Repair-re1ated Gene In Rats Exposed Subchronica11y To Cadmium

1. Objective:Cadmium (Cd), one of non-essentia1heavy meta1s in the human body, iswide1y app1ied in industria1manufacture. However, it is toxic and affects humanhea1th through occupationa1and environmenta1exposure The avai1ab1eexperimenta1and epidemio1ogica1data have shown that Cd and its compounds caninduce mu1ti-system toxico1ogica1responses of humans and anima1s, even1ead tothe occurrence of a variety of tumors, such as1ung cancer,1iver cancer, kidneycancer, prostate cancer, pancreatic cancer, b1adder cancer and breast cancer. In1993,Cd was c1assified as the first category of carcinogens by the Internationa1Agency forResearch on Cancer (IARC,1993), but its mo1ecu1ar toxic mechanisms were sti11unc1ear. In recent years, different researches were tried to clarily cadmium toxicity onthe body and its mechanism, from the whole, organ, cell and molecular level. Somestudies suggest that the function of DNA repair inhibition may be plays an important rolein the toxic mechanism of metal molecular. Therefor, Cd exposure and its hea1th damage,especia11y toxic effects of1ong-term1ow1eve1exposure to Cd has become a hotspotin toxico1ogica1study. However, the a1ternative expression of DNA repair gene in thetarget organs attacked by cadmium toxicity is poor1y understood. In this study, weinvestigate the a1ternative expression of DNA repair gene in the target organs of rats1ike the heart,1iver, kidney and1ung exposed subchronica11y to cadmium to providea new experimenta1data for sub-chronic toxicity of cadmium compounds in rats. 2. Methods:2.1According to mRNA sequence of XRCC1and hOGG1gene, upstream anddownstream primers of XRCC1and hOGG1were designed by Primer Express5.0.Using TRIzo1reagent. The tota1RNAs from1iver, kidney，heart and1ung wereiso1ated and the XRCC1and hOGG1mRNA expressions were ana1ysed with reversetranscrispion (RT) and f1uorescent quantitative-po1ymerase chain reaction.2.2The tota1protein was extracted with Tissue Protein Extraction(Thermo). Tota1protein content of samp1es was measured by BCA Protein Assay Kit (Thermo), andthe XRCC1and hOGG1protein expressions were ana1ysed with western-b1ot.Futhermore, the statistically corre1ations between XRCC1and hOGG1expression1eve1s and Cd concentration in heart,1iver, kidney and1ung were ana1ysed, and withpathological damage.2.3All experiments were repted three times, datas were expressed as mean±standard deviation (x±s). If the original data were skew distribution, usedlogarithmic(log) to convert in order to achieve the normalization, and statistic11yana1ysed with variance ana1ysis, Games-Howe11test, Student-Newman-Keu1sa testand corre1ation ana1ysis and so on. The1eve1of significance was set at p<0.05.3. Resu1ts:3.1After RT-PCR(Taqman) ana1ysis, under the inner standard of TBP, showedprimari1y that the1eve1s of XRCC1expression were44%,31%and13%downregu1ation in1iver, and were62%,29%and15%down regu1ation in the kidney,were42%,30%and15%down regu1ation in1iver, and were47%,28%and19%down regu1ation in the kidney of rats treated with CdC12in high-dose, med-dose, and1ow-dose, respective1y (P<0.01). when compared with contro1s. The data abovedisplayed a obvious1y dose-response re1ationship since the down regu1ations werea1ong with Cd-exposure1eve1s (P<0.01).3.2After FQ-PCR(SYBR Green) ana1ysis, under the inner standard of β-actin,showed primari1y that the1eve1s of hOGG1expression were40%,21%and12%down regu1ation in1iver, and were67%,50%and16%down regu1ation in the kidney,were72%,59%and27%down regu1ation in1iver, and were75%,52%and29%down regu1ation in the kidney of rats treated with CdC12in high-dose, med-dose, and1ow-dose, respective1y (P<0.01). when compared with contro1s. The data abovedisp1ayed a obvious1y dose-response re1ationship since the down regu1ations were a1ong with Cd-exposure1eve1s (P<0.01).3.3After Western-b1ot ana1ysis, under the inner standard of GADPH, showedprimari1y that the XRCC1and hOGG1protein were1ower expression in the1iver,kidney of rats treated with CdC12,in high-dose, med-dose, and1ow-dose. Furtherconfirmed XRCC1and hOGG1gene lower-expression in the target organs of ratsexposed subchronically to cadmium. However, after the statistica1corre1ationana1ysis, in the heart,1iver, kidney and1ung of rats treated with CdC12,there were thenegeative corre1ation between XRCC1and hOGG1expression1eve1s and Cdcumu1ation, also with pathological damage.4. Conc1usions:4.1Long time1ow1evel cadmium exposure can cause XRCC1and hOGG1geneexpression1eve1s change significant1yin rat interna1organs. There was a goodnegative dose-response re1ationship between the XRCC1and hOGG1expression1eve1s and Cd exposure in rats’ heart,1iver, kidney and1ung, respective1y.4.2Indution of DNA repair gene XRCC1and hOGG1was observed in rat interna1targnt organs on the basis of the subchronic Cd-exposed model, revea1ing that there wasa statiscial correlationl re1ationship between the XRCC1and hOGG1expression1eve1sand Cd cumulation, also with pathological damaga, respective1y. These findingsindicate that expression damages of XRCC1and hOGG1factor seem to be a significantbiomarker of exposure or effect to Cd subchronic toxicity.