Changes in Cognitive Function and Relationship Between CDK5 and Phosphorylated Tau Protein in Plasma in Workers Exposed to Aluminum

Objective To observe the changes in cognitive function and the relationship between cyclin-dependent kinase 5(CDK5) and phosphorylated tau protein in plasma in workers exposed to aluminum.

Methods A cross-sectional study with cluster sampling was designed to collect 418 male workers from an aluminum plant. Mini mental state examination(MMSE), digit span(DS), fuld object memory evaluation(FOM), and simple reaction time test(SRTT) were used to assess their cognitive function. Fasting venous blood samples of the workers were collected and analyzed by graphite furnace atomic absorption spectrometry to test blood aluminum content. ELISA was used to determine the expression levels of phosphorylated tau 181(P-tau181), phosphorylated tau 231(P-tau231), and CDK5 in plasma.

Results The subjects were divided into three groups according to the P₂₅ and P₇₅ values of blood aluminum levels: low (64.00±17.78) μg/L, middle (132.59±27.45) μg/L, and high (244.45±69.86) μg/L blood aluminum groups. The cognitive function tests showed that the result differences of MMSE, DS, FOM, and SRTT among the three groups were statistically significant(all Ps < 0.05). The protein determination showed that, compared with the low blood aluminum group, the P-tau181 and P-tau231 levels were significantly higher in the high blood aluminum group, and the levels of CDK5 were significantly increased in the high blood aluminum group and the middle blood aluminum group(P < 0.05). It was found that P-tau181 was negatively correlated with MMSE, DS, and FOM(r=-0.308, -0.285, -0.252; all Ps < 0.05), P-tau231 was negatively correlated with MMSE and DS(r=-0.326, -0.291; both Ps < 0.05) and positively correlated with SRTT(r=0.257, P=0.050); P-tau181 and P-tau231 were positively correlated with CDK5(r=0.327, 0.253; both Ps < 0.05).

Conclusion The changes of cognitive function induced by occupational aluminum exposure are associated with phosphorylated tau. The expression of CDK5 in workers is related to the phosphorylation of tau, and CDK5 may be involved in aluminum-induced tau protein phosphorylation.