Cross-sectional Study On Biomarkers In Workers Exposed To Manganese

Manganese (Mn) is a critical microelement for human normal metabolism, but it also is a poison accumulated in vivo easily which could be found in work site and surrounding. Exposure to excessive level of manganese for a long time would result in a toxic effect on nervous system, which is characterized by the damage of extractor- ticospinal tract and symptom of paralysis agitans. The clinical symptoms of neurological disorder caused by manganese were similar to Parkinson's disease (PD). The severe and inconvertible nervous system damage caused by manganese would be a worrisome burden for patients, family and society, for once it happened, there is no effective approach to control or cure it. So it is significant to achievement the prevention and cure of nervous system damage caused by occupational manganese poisoning asearly as possible.Mechanism of manganese neurotoxicity is not elucidate clearly. It was found the basal nucleus was damaged and dopaminergic neuron was injuried by manganese. The mechanism could be related with interfering the energy metabolism of central nerve, changing neurotransmitters, activating oxidation system and so on. Some biochemical indicators in tissue of nervous system influnced by manganese and some synthetases or catabolic enzymes such as malondialdehyde(MDA), superoxide dismutase(SOD), glutathione peroxidase(GSH-Px), acetylcholinesterase(AChE) could be chosed as biomarkers of effect for the study of manganese.There were only a part of people to be poisoned by manganese in aequales condition which suggested that there was individual variation to the susceptibility of manganese. There would be some sensitive genes in people exposed to manganese with damaged nervous system. Genetic factors could play a significant role in the neurotoxic effect cause by manganese. Some researches had showed that dopamine-β-hydroxylase(DBH), Heat shock proteins 70 (HSP70), manganese superoxide dismutase (MnSOD), monoamine oxidase (MAO) were related with lipid peroxidation and dopaminergic neuron damage, which indicated that the genetic polymorphism of these four enzymes could influence the sensitivity of nerve injury caused by manganese. There were few reports about the relationship between gene polymorphism of DBH, HSP70, MnSOD, MAO and nerve injury cause by manganese. Furtheremore, The results were different among differert countries and races. So it was essential to determine whether they were sensitive genes or not. At the same time the expressions of mRNA and SNP of DBH, HSP70, MnSOD, MAO were investigated for sggregate analysis.Heat shock proteins (HSPs) comprised of a group of highly conserved and stress related proteins with many important physiological and pathological roles such as cellular homeostasis, molecular chaperone tumor markers, molecular adjuvant and so on. HSP70 could strengthen the cytoendurance to damage, maintain the normal metabolism and enhance the viability, it also could protect the damage of central nerve system, cardiacmuscle, liver and lung. HSP70 was proved to be a valuable biomarker to reflect physical stress. So the relationship between HSP70 and stress effect of manganese was investigated.Objective1 The indicators including urine manganese, blood manganese, MDA, SOD, GSH-Px, AChE were investigated to find the relationship with the air concentration of manganese at the work-place. The objective was to find biomarkers of effect for the study of manganese neurotoxicity.2 To detect single nucleotide polymorphism by microfluidic and investigate the relationship between genetic polymorphism of DBH, HSP70, MnSOD, MAO and manganese-induced nerve injury.3 To analysis the expression levels of mRNA and proteins in different exposure to manganese by quantitative real-time reverse transcription-PCR. To find suitable biomarkers for manganese-induced occupational hazard.Methods1 To monitor the 8-hour time weighted average concentration of vocational contact manganese by personal sampler to obtain precise exposure dose. The concentration of MDA, SOD, GSH-Px, AChE in serum were determined, and concentration of blood manganese, urine manganese and air manganese were determined by GFAAS.2 Occupational contact workers of styrene were included in the study. PCR-RFLP was applied to determine the SNPs of DBH, MAO, HSP70, MnSOD and statistically analysed the influence of gene polymorphisms on the metabolism of manganese.3 The mRNA expressions of four different metabolic enzyme were detected by SYBR Green I quantitative real-time polymerase chain reaction The protein level of HSP70 was detected by western-blotting.Results1 The groups were divided into high exposure group and low exposure group by 8-hour time weighted average concentration(8h-TWA). There was significant difference between two groups of MDA concentration and the activities of SOD, GSH-Px, AchE(P<0.05). But there was no obvious correlation with 8h-TWA. There was no significant difference between two groups of urine manganese and no obvious correlation with 8h-TWA.2 Detecting the genotype of DBH, MnSOD, MAO and HSP70 of 402 workers exposed to manganese through collecting peripheral blood. The distribution of A2 A2 genotype and A2 allele of DBH was obviously different. The distribution was wiser in abnormal group than normal group(P<0.05), the VV genotype of MnSOD was obviously different. The distribution was wiser in abnormal group than normal group(P<0.05), the genotype and allele of MAO or HSP70 was with no significant difference(P>0.05).3 The groups were divided by 8h-TWA, and there was significant difference between the two groups on the expressions of HSP70 mRNA and protein, and the HSP70 mRNA level and HSP70 protein level of high exposure group were higher than low exposure group(P<0.05). The expressions of DBH mRNA, MAO mRNA and MnSOD mRNA was found no significant difference between the two groups (P>0.05).Conclusions1 There was significant difference of blood manganese, MDA concentration and the activities of SOD, GSH-Px, AchE between two groups, but these indicators were insensitive to the change of air manganese concentration. So these indicators could not be chosed as biomarkers of effect for the study of manganese. They could be used as reference indicators coupled with others to analyze the exposure dosage and indeced neurotoxicity.2 TaqI polymorphism of DBH and Val-16-Ala polymorphism of MnSOD could play great roles in hereditary susceptibility of occupational hazard cause by manganese. The polymorphism of MAO and HSP70 gene may not related to the occupational hazard cause by manganese.3 The increase of HSP70 protein and mRNA could be concerned with lipid peroxidation which was induced to preotcet nerve cell. The mechanism of manganese-induced neurotoxicity could be related with HSP70 and HSP70 mRNA.