The Study Of MnSOD MRNA Expression Change In Crowd Of Occupational Chronic Manganism And PC12Cells Induced By Manganese

【Background】Manganese is an essentia1trace element and a kind of important environmental andindustrial pollutants also. Because the contact of professional, iatrogenic andenvironment,Mn is mainly absorpted through the respiratory and the content increased inbody. Mn can into the brain tissue through the blood brain barrier and damage the centralnervous system. The content of manganese accumulation in the brain with chronic contact,especially in the striatum is the highest. It mainly affect the globus pallidus and substantianigra reticularzone and cause dopamine neurons in the basal ganglia degenerative diseases.Due to the higher morbidity, much more attention has been paid to the occupationalchronic manganism. The typical symptom of manganism are muscle tremor and increasedmuscle tension, which is similar to Parkinson’s disease (PD). Manganism also can appearthe obvious obstacle in learning and memorial function, cognitive function and spatialsense of direction,or mood modification as easy to cry, be agitated, timidity hearken,loneliness and so on.The neurotoxic mechanism of Mn is not completely understood at present,and itmainly involves the oxidative stress, mitochondrial damage, the neurotransmittermetabolism and cell apoptosis, etc. In the mechanism of oxidative stress and mitochondrialdamage, the manganese superoxide dismutase (MnSOD) which is the main antioxidantplays a very important role. Previous studies have found that MnSOD polymorphisms may berelated with the susceptibility to occupational chronic manganism,and it may be susceptibility genes.In the process of manganese exposure, the research of MnSOD gene expression changesand the happening of the disease has the very vital significance.【Objectives】 To observe the mRNA expression level of MnSOD gene between occupational chronicmanganism cases and controls. To observe inhibition of cells proliferation and MnSODmRNA expression level,using the PC12cells which were in the role of different doses ofmanganese and different time.To explore the effect of MnSOD in the neurotoxicitymechanism by manganese.【Methods】131clinically diagnosed patients of occupational chronic manganism were screenedas the case group.We choosed people who did not have the manganism as contrl, furthermore,they worked in the same period and had the same type of word,same workshop,samegender and age with the case. History of personal life and family inheritance was alsosimilar. Whole blood RNA was extracted, and half quantitative RT-polymerase chainreaction (PCR) was used to detect the expression of MnSOD mRNA.Then we made astatistical analysis of the differences between case and control group,and studied therelationship of MnSOD gene expression with the management of occupational chronicmanganism.2It adopted pheochromocytoma cell (PC12) of rats adrenal for cell model, and thelogarithmic growth period PC12cells were cultured for1,2,3,4days by the chlorinatedmanganese (MnCl2) of0,100,200,400,600,800,1000μmol/L concentration. We observedcell proliferation and morphological change by optical microscope in this process. The cellviability Was examed by MTT and RT-PCR was used to test the expression of MnSODmRNA.【Results】1There was no statistically significant in the difference of gender, age, and workingage between the control group and the case group.Significantly discrepancy of MnSODmRNA expression level was appeared between case group and control group(t=-4.589,p＜0.05),and the95%confidence interval is [0.277,0.107]. The expression of MnSODmRNA in case group was less than the control group.2According to MTT,manganese inhibited the proliferation of PC12cellstime,concentration dependently.The inhibitory effect of manganese on PC12cellproliferation enhanced with the increment of the concentration of manganese and theprolongation of exposure.At the same concentration of MnCl2(400μmol/L), the cellsgrowth inhibition rate exceeded50%. Related analysis found that the correlationcoefficient of MnCl2concentration to cell inhibition rate was0.975, p <0.05, and MnCl2effect time to cell inhibition rate was0.116, p>0.05. According to expression of MnSOD mRNA, there was significant difference of gene expression in each concentration of theMnCl2under the same time (p＜0.05). With increasing MnCl2concentration, expressionof MnSOD mRNA gradually reduced. The correlation coefficient of MnCl2concentrationto expression of MnSOD mRNA was-0.958, p <0.05, and MnCl2effect time to expressionof MnSOD mRNA was-0.14, p>0.05.【Conclusion】1The expression level of MnSOD mRNA may be in relation to the occupationalchronic manganism,and the MnSOD lower expression may contribute to the occurrence ofmanganism.2MnCl2may have toxic effects to PC12cells,and the higher the MnCl2concentration,the stronger the toxic effects, the less expression of MnSOD mRNA. It shows that theMnSOD expression may be involved in the nerve cells’ damage process which caused bymanganese. It may be speculated that high expression of MnSOD mRNA may play ainhibiting effect in the process of manganese neurotoxic.