The Study On The Relationship Between TNFR1-RIP1/RIP3 Expression And Cognitive Function In Occupationally Aluminum Exposed Workers

Objective:This research carried out occupational epidemiological research investigation to explore change of cognitive function and the relationship between peripheral blood Tumor Necrosis Factor Receptor 1(TNFR1),Receptor interacting Protein 1(RIP1),Receptor interacting Protein 3(RIP3)expression levels and cognitive function in occupational aluminum exposed workers.The effects of TNFR1,RIP1 and RIP3 on cognitive function of long-term aluminum exposed workers and the possibility that the above mentioned indicators act as biomarkers of aluminum neurotoxicity in peripheral blood level of aluminum neurotoxicity were discussed.Methods:(1)A cluster sampling method was used to collect 306 male workers from an aluminum factory in Shanxi Province.Among them,160 electrolytic aluminum workshop workers were selected as exposed group,146 thermo electric workshops and logistics workers were selected as control group.The method of face to face interview and a questionnaire designed by us were used to the epidemiological study.The research content includes: general demographic situation,Mini Mental State Exam(MMSE),Digit Span Test(DST,Digit Span Forward Test(DSFT)and Digit Span Backward Test(DSBT)],Clock-Drawing Test(CDT),Flud Object Memory Evaluation(FOME)and Simple Reaction Time Test(SRTT).(2)Fasting venous blood of the research object were collected and then separated to gain whole blood,plasma and lymphocyte.Whole blood was stored at 4? plasmalymphocyte were stored at-80 ?.Total mRNA was extracted in whole blood and reversely transcripted into cDNA which was stored at-80 ?.Aluminum concentration in plasma was determined by graphite furnace atomic absorption spectrometry.TNFR1,RIP1 and RIP3 mRNA expression in peripheral blood were evaluated by RT-PCR method.Using enzyme-linked immunosorbent method to determine TNFR1,RIP1 and RIP3 protein expression levels in lymphocytes.Result:(1)The statistical analysis of aluminum concentration inplasma of workers and general demographic situation: The difference between the age of control group workers [40(34,46)years old] and that of the exposed group workers [43(37,47)years old] was not statistically significant(Z=1.807,P=1.807).The differences between the exposed group and the control group in per capita income(?~2=3.390,P=0.184),level of education(?~2=2.081,P=0.353),smoking(?~2=2.447,P=0.118),alcohol consumption(?~2=2.895,P=0.089)were compared.There was no statistically significant difference between them(P>0.05).The plasma aluminum concentration was higher in the AL-exposed group [77.45(54.65,89.26)?g/L] than that in the control group [59.15(40.49,76.49)?g/L],and the difference between them was statistically significant(z=-5.997,P=0.000).(2)Comparison of cognitive function between two groups: The score of ATIME in the exposed group was higher than that in the controls(z=-4.189,P=0.000).So,the subjects were divided into the lowplasma aluminum concentration group [34.88(22.55,41.23)?g/L],the middle plasma aluminum concentration group [67.07(57.47,74.65)?g/L] and the high theplasma aluminum concentration group[102.38(93.52,117.16)?g/L] based on the plasma aluminum concentration and the higher and lower percentile of it.(3)The comparison of cognitive ability in differen tplasma aluminum concentration groups:The differences of MMSE,CDT,DST and ATIME in the three plasma aluminum concentration groups were statistically significant(?~2=61.572,189.235,241.471,251.567,P<0.05).Compared with the low plasma aluminum concentration group,thescores of CDT,DST in the middle and high plasma aluminum concentration groups were decreased,ATIME score was increased.The difference among them was statistically significant(P<0.05).The scores of MMSE,CDT and DST were significantly decreased and the score of ATIME was significantly increased in the high plasma aluminum concentration group than those in the middle plasma aluminum group.The difference among them was statistically significant(P<0.05).(4)The multiple regressive analysis of cognitive function influencing factors: The plasma aluminum concentration and age were the main influencing factors of cognitive function(P<0.05).(5)The expression analysis of TNFR1,RIP1 and RIP3 in different plasma aluminum concentration groups: TNFR1 mRNA and protein expression levels in the high plasma aluminum concentration groups were significantly increase than in the low plasma aluminum concentration group(P<0.05).Plasma aluminum concentration positively correlated with TNFR1 mRNA,protein expression level and the score of ATIME(r=0.576,0.307,0.144,P<0.05).Plasma aluminum concentration negatively correlated with MMSE,CDT,DST and DSBT(r=-0.398,-0.849,-0.983,-0.977,P<0.05).TNFR1 mRNA expression level positively correlated with TNFR1 protein expression level(r=0.437,P<0.05)and which negatively correlated with CDT and DST scores too(r=-0.857,-0.671,P<0.05).The expression of TNFR1 protein negatively correlated with CDT,DST and DSBT(r=-0.140,-0.150,-0.121,P<0.05).The expression levels of RIP1 mRNA and protein in the middle and high plasma aluminum concentration group were significantly increased than those in the low plasma aluminum concentration group(P<0.05).The expression level of RIP1 mRNA in the high plasma aluminum concentration group was significantly higher than in the middle plasma aluminum concentration group(P<0.05).The expression level of RIP3 mRNA in the high plasma aluminum concentration group was significantly increased than in the low plasma aluminum concentration group(P<0.05).The expression level of RIP3 mRNA in the high plasma aluminum concentration group was significantly higher than that in the middle plasma aluminum concentration group(P<0.05).Theexpression level of RIP3 protein in the middle plasma aluminum concentration group and the high plasma aluminum concentration group were significantly higher than those in the low plasma aluminum concentration group(P<0.05).The expression level of RIP3 protein in the high plasma aluminum concentration group were significantly higher than those in the middle plasma aluminum concentration group(P<0.05).Plasma aluminum concentration positively correlated with RIP1/RIP3 mRNA and protein expression levels(r=0.552,0.429,0.407,0.251,P<0.05).The expression level of RIP1 mRNA positively correlated with the expression level of RIP1 protein(r=0.594,P<0.05)and negatively correlated with the scores of MMSE,CDT,DST and DSBT(r=-0.262,-0.818,-0.706,-0.671,P<0.05).The expression level of RIP1 protein negatively correlated with CDT,DST and DSBT(r=-0.361,-0.354,-0.357,P<0.05).The expression level of RIP3 mRNA negatively correlated with the scores of MMSE,CDT,DST and DSBT(r=-0.183,-0.920,-0.751,-0.736,P<0.05).The expression level of RIP3 protein negatively correlation with the scores of DST and DSBT(r=-0.264,-0.255,P<0.05).The analysis of the intermediary effect of TNFR1,RIP1,RIP3 protein expression levels in the peripheral blood on relation between aluminum and cognitive function change: When the aluminum concentration inplasma as the independent variable X,the Mini Mental State Exam(MMSE)score as the dependent variable Y,TNFR1,RIP1,RIP3 protein expression level in peripheral blood as intermediary variables M,under the 95% confidence interval,the intermediary test results do not contain 0(LLCT = 0.0009,ULCI = 0.0009),(LLCT =0.0004,ULCI = 0.0004),(LLCT = 0.0003,ULCI = 0.0003).TNFR1,RIP1,RIP3 protein showed a significant intermediary effect and the mediation effect of size were0.0015,0.0052,0.0003 respectively.In addition,when TNFR1,RIP1 and RIP3 protein intermediation were controlled,the influence of the independent variable-plasma aluminum concentration on MMSE score was also significant(LLCT=-0.0330,ULCI=-0.0191),(LLCT=-0.0385,ULCI=-0.0213),(LLCT=-0.0323,ULCI=-0.0187).Therefore,TNFR1,RIP1 and RIP3 proteins play a partial intermediary role between plasma aluminum concentration and cognitive function.Conclusions:1.Long-term occupational exposure to aluminum can cause cognitive ability decline and slow response.2.There was a positive correlation between theplasma aluminum concentration in peripheral blood and TNFR1,RIP1,RIP3 mRNA and protein expression levels in occupational Al-exposed workers.There was a negative correlation between TNFR1,RIP1,RIP3 mRNA and protein expression level and cognitive function.TNFR1,RIP1 and RIP3 proteins play a partial intermediary role between plasma aluminum concentration and cognitive function,suggesting that aluminum may affect the expression of TNFR1,RIP1 and RIP3 and thus affect cognitive function.