Clinical Research On Cholangiocarcinoma Radiofrequency Catheter Ablation Stent Implantation

ObjectiveArsenic exposure can result in damages of the neurological system. The presentstudy aimed at whether cell proliferation and neurogenesis in the adult mousehippocampus were affected after arsenic exposure and whether they could recover afterexposure cessation. The mechanisms of arsenic induced brain damages were alsoinvestigated at the nucleic acid level.Method90male mice were randomly placed into3groups. The first group received distilledwater alone for4months (control group), the second group received4.0mg/L As2O3through drinking water for4months (arsenic group), the third group received4.0mg/LAs2O3for2months and then changed to distilled water for another2months (recoverygroup). The concentrations of arsenic in serum and cerebrum were detected byinductively coupled plasma mass spectroscopy. Histological changes were observed byhematoxylin and eosin staining (HE). The hippocampus immunoreactive cells werecalculated by confocal microscope in the granule cell layer (GCL) and within two celldiameters below this area in the subgranular zone (SGZ). BrdU-positive cells wereused as marker of cell proliferation, and the BrdU+/NeuN+cells were applied toevaluate neurogenesis. Apoptosis was detected by terminal deoxynucleotidyl transferasedUTP nick end-labeling (TUNEL) assay, and cell death was identified by Fluoro-Jade Cstaining. The hippocampal expression levels of SOD (superoxide dismutase)1、SOD2and Wnt3in different groups were examined by real-time PCR. The spatial learning andmemory ability were evaluated by Morris water maze.In the brain damage researches,32mice were randomly placed into4groups. Theyreceived drinking water containing0,1.0,2.0and4.0mg/L As2O3, respectively, for2months. The histopathological changes were observed, and the8-nitroguanine expressions were detected.Results1. Arsenic concentration in mouse serum and cerebrumAfter two-month exposure to arsenic, the concentrations of arsenic in control mouseserum and cerebrum were28±9.4and31±5.0ng/g, respectively. In the arsenic group,the concentrations of arsenic in serum and cerebrum were42±6.2and60±8.5ng/g,respectively. Cerebrum arsenic level of treated group were significantly higher than thatin control one (p <0.05). After another two-month feeding, the arsenic concentration inthe recovery group decreased significantly as compared with the arsenic group (25±4.4vs.61±3.2ng/g in serum,23±2.8vs.74±6.3ng/g in cerebrum, p <0.01), and showed nodifference with that in the control group (31±3.5ng/g in serum,22±2.4ng/g incerebrum). These results indicated that arsenic was deposited in the brain after exposure,and excreted after it was removed from drinking water.2. Histopathological changes in the hippocampusPathological findings in the mouse hippocampal neurons were observed. Noabnormal histological changes were observed in the control group. After exposure toarsenic for4months, karyopyknosis were apparent. Obvious ameliorations wereobserved in the hippocampus of the recovery group. Relatively slight pathologicalchanges were observed in neurons from2-month arsenic group.3. The inhibition of cell proliferation by arsenic and its reversibilityAfter two-month arsenic administration, the number of BrdU+cells in theSGZ/GCL was104.2±5.4cells/section, which was decreased but with no significantchange as compared with the control group (120.7±12.6cells/section). Afterfour-month administration, the numbers of BrdU+cells in the control, arsenic andrecovery group were111.8±5.6,84.0±2.3and128.5±4.8cells/section, respectively.The arsenic group showed significant decrease in BrdU+cells as compared with thecontrol group (p<0.01), which meant inhibition of cell proliferation by arsenic exposure.However, BrdU+cells in the recovery group increased significantly as compared withthe arsenic group (p<0.01), and showed no differences with the control one, whichindicated that change of arsenic to water in diet gave rise to an increase of cellproliferation in the SGZ/GCL in the recovery groups.4. The inhibition of neurogenesis by arsenic and its reversibilityFormation of new mature hippocampal neurons (hippocampal neurogenesis) ispresented as the BrdU and NeuN double positive cells in the SGZ/GCL. Exposure to arsenic for two months decreased the percentage of BrdU+NeuN+cells as comparedwith the control animals (54±2.7vs.67±2.3%, p<0.01). After four-monthadministration, the percentage of BrdU+NeuN+cells in the recovery group was higheras compared with the arsenic group (71±2.2vs.60±2.8%, p<0.05), and there was nosignificant changes in the recovery and control group (71±2.2vs.73±1.7%, p>0.05).5. There were no significant differences for apoptosis and deathMore than1,000Hoechst-positive cells were counted in the SGZ/GCL for eachanimal. After two-month administration, the percentages of TUNEL positive cells in thecontrol and arsenic group were0.58±0.075and0.65±0.077%, respectively (p>0.05).After change of arsenic to distilled water for two months, the percentages of TUNELpositive cells in the control, arsenic and recovery group were0.67±0.065,0.77±0.063and0.75±0.087%, respectively (p>0.05).There were still no significant differencesamong three groups (p>0.05). Accordingly, arsenic could not induce more apoptosisunder current conditions. There was no Fluoro-Jade C positive cell observed in eachgroup, therefore, arsenic could not lead to cell death under current conditions.6. The relative mRNA expressions of SOD1, SOD2and Wnt3After two-month administration, the SOD1/β-actin mRNA in the arsenic group was0.42±0.0058, which was significantly lower than that of the control（0.65±0.013,p<0.01）. After four-month treatment, the expression level in the arsenic group(0.40±0.0088) was still low (p<0.01) as compared with the control one (0.61±0.017),however, it was significantly increased in the recovery group (0.56±0.0088, p<0.01),while it was not as high as the control one (p<0.05).After two-month administration, the SOD2/β-actin mRNA level in the arsenicgroup was0.29±0.015×10-1, which was significantly lower than that of the control（0.45±0.0033×10-1, p<0.01）. After four-month treatment, the relative expressionlevels in the control, arsenic and recovery group were0.60±0.012×10-1,0.42±0.012×10-1and0.54±0.0088×10-1, respectively. The expression was significantlower in the arsenic group as compared with the control one (p<0.01), and increased inthe recovery group (p<0.01), but not as high as the control one(p<0.05).After four-month treatment, the relative expression level of Wnt3in the arsenicgroup was significant lower as compared with the control one (p<0.01), however, therewas no increase in the recovery group.7. Morris water maze testAfter four-month administration, there were no significant changes of the escape latency and the latency to the target site among the three groups（p>0.05）.8. Detection of8-nitroguanineHigh expressions of8-nitroguanine were detected by immunohistochemistry in thebrain of mice exposed to arsenic subchronically (2months), and histopathologicalchanges were observed, which indicated oxidative and nitrosative damages of nucleicacids.Conclusion1、Chronic arsenic exposure could inhibit hippocampus cell proliferation andneurogenesis.2、The inhibition by arsenic was reversible after its exposure termination.3、High expressions of8-nitroguanine were detected in the brain of mice exposed toarsenic subchronically.