Influence of apolipoprotein E (apoE) on ADAM10 secretase in cerebrospinal fluid of older adults with Alzheimer’s disease

Abstract

AbstractBackgroundThe ε4 allele of APOE is the strongest genetic risk for sporadic late‐onset Alzheimer’s disease (AD), and is associated with an increase in the levels of β‐amyloid (Aβ) deposition. The main α‐secretase that inhibits the Aβ deposition is the ADAM10, which is altered in the blood and cerebrospinal fluid (CSF) of older adults with AD.MethodTo assess whether the levels of ADAM10 forms are altered in CSF of AD and non‐dementia control (NDC) individuals with different APOE genotype, we analysed a total of 13 samples from NDC (mean age = 66.3 ±9.8; T‐tau = 305 ±135 ng/L; Aβ42 = 780 ±253 ng/L) and 41 from AD (mean age 77.0 ±6.2; T‐tau = 845 ±356.1 ng/L; Aβ42 = 456 ± 66 ng/L), subdivided into NDC APOE ε3/ε3 (n = 8), NDC APOE ε3/ε4 (n = 5), AD APOE ε3/ε3 (n = 13), AD APOE ε3/ε4 (n = 14) and AD APOE ε4/ε4 (n = 14). ADAM10 was characterized in human CSF samples by western blotting.ResultAn antibody raised against to the ectodomain region of ADAM10, common to all species, recognized three bands, which might be the proADAM10 (immature form retaining the prodomain), ADAM10f (mature unprocessed full‐length form) and sADAM10 (truncated fragment). Regarding proADAM10, no differences were found among NDC with different APOE genotype. However, the AD APOE ε4/ε4 showed a reduction, which was significantly lower than AD APOE ε3/ε3 (p = 0.0011), NDC APOE ε3/ε3 (p = 0.0460) and NDC APOE ε3/ε3 (p = 0.0012), suggesting the impact of being homozygous for APOE ε4 allele on proADAM10 levels. In the ADAM10f and sADAM10, we observed similar findings. For both species of protein, AD groups carriers of APOE ε4 allele, that is, AD APOE ε3/ε4 and AD APOE ε4/ε4, presented significant lower levels of ADAM10f compared with both non‐carriers subgroups (AD APOE ε3/ε3 and NDC APOE ε3/ε3).ConclusionThe results indicated that being a carrier of the APOE ε4 allele and having developed AD are associated with lower levels of ADAM10f and sADAM10. This study contributes to a better understanding the impact of apoE on the disease.