Representative Chrysotile Asbestos In Different Regions—induced Oxidative Damage In Wistar Rats

Objective To investigate the effect of representative chrysotile asbestos in four different regions on pulmonary oxidative damage in Wistar rats,and to compare the oxidative damage of those.Methods Representative chrysotile were collected from four mining areas,then processed into particles with a particle size less than 10μm.The phase,main chemical composition of the sample and structures were analyzed by X ray diffraction（XRD）,X ray fluorescence（XRF）and scanning electron microscop（SEM）,the particle size was measured by laser particle size analyzer.There were 90 newborn cleaning Wistar male rats,which were randomly divided into 5 groups,each group of 18.Wistar rats in every group were administered by intratracheal instillation for2.0mg/ml of chrysotile（Gansu Akesai,Sichuan Kang,Shaanxi,Qinghai mangnai,China）dissolved in saline,and the negative control group was treated with physiological saline as the same way,repeated once a month for 6 month with 0.5ml.Weighted rat and lung weight,observed the pathological change of rats by Hematoxylin and eosin（HE）staining;Collected the alveolar lavage fluid（BALF）of rats and counte the total number of leukocytes and their classification,The content of lactate dehydrogenase（LDH）,alkaline phosphatase（AKP）and total protein（TP）were monitored.The total content of reactive oxygen species（ROS）,malondialdehyde（MDA）and activity of superoxide dismutase（SOD）in serum and lung tissue of Wistar rats were determined with 1,3,6 months.The expression levels of HO-1 and HSP70genes in lung tissues were detected by Real-Time PCR.Result The particle size of the mineral powder samples in Shaanxi,Qinghai mangnai and Gansu Akesai groups is mainly concentrated in 2～10μm,while Sichuan Kang group is mainly concentrated in 0～2μm.Si O₂and Mg O is the main chemical composition of four representative chrysotile asbestos and containing a small amount of Fe₂O_3,Al₂O₃,etc.as a result of chrysotile producing area is different,there is a certain difference in the content of each oxide.The results of XRD analysis showed that the four kinds of chrysotile asbestos had representative chrysotile characteristic peaks,and the peaks of magnesium-silicon were clear and disused the amphibole mineral fibers were not detected.The samples of four chrysotile asbestos were stiff and straight fibrous or needlelike,with obvious brittleness characteristics,among which chrysotile asbestos in Sichuan Kang has agglomeration phenomenon.In Sichuan Kang and Qinghai mangnai group,chrysotile exposed lead to body weight grow slowly and the lung weight were highter than negative control group.Inflammatory cell aggregation,destruction of alveolar structureand fibrosis were observed by HE staining.Compared with the negative control group,the leukocytes,neutrophils and lymphocytes in BALF were increased by four chrysotile groups at different time points,and increased with the exposure time（P<0.05）;The percentage of macrophages decreased from 1 month and decreased with the exposure time（P<0.05）;In Sichuan Kang,Qinghai mangnaiai and Gansu Akesai groups,the concentration of LDH in BALF increased significantly from 1 month after exposure（P<0.05）;In the four kinds of chrysotile group,the concentrations of AKP and TP in BALF were statistically different from 1 month after exposure,and the changes of the three indexes increased with the exposure time（P<0.05）.The content of ROS,MDA between Sichuan Kang,Qinghai mangnai and negative control group is significantin statistics,meanwhile the SOD activity were increased firstly and then decreased in both lung tissue and serum.With the increasing of exposure time,the content of MDA increased（P<0.05）and the activity of SOD showed a decreasing trend in lung tissue and serum（P<0.05）.From 1 month,anti-oxidative damage gene HO-1 and HSP70 in Shaanxi and Gansu Akesai groups express significantly more than the negative control group（P<0.05）;Compared with the negative control group,The expression of HO-1and HSP70 genes in lung tissue of the exposed groups of Qinghai mangnai and Sichuan Kang were increased in 1 months and 3 months,but decreased significantly in 6 months（P<0.05）.Conclusion Sichuan Kang and Gansu mangnai chrysotile can produce excessive ROS and MDA,resulting in lipid peroxidation and SOD activity decreased in vivo.This process may break down the balance between oxidative and antioxidant,finally caused by lung oxidative damage in rats.The results suggest that there may be differences in oxidative damage between representative chrysotile asbestos in different regions.