[Effects of benzo(a)pyrene on expressions of insulin-degrading enzyme and neprilysin in neuroglia cells].

ABSTRACT

OBJECTIVE: To investigate effects of benzo(a)pyrene (BaP) on expressions of insulin-degrading enzyme (IDE) and neprilysin (NEP) which have the ability to degrade ß-amyloid (Aß) in neuroglia cells. METHODS: Primary mix-neuroglia cells were cultured from newborn SD rats. After exposure to BaP, Aß1-42 oligomer or Aß1-42 fiber individually or jointly for 24 h, the cell survival rate was measured by cell counting kit-8 (CCK-8). Afterwards, the primary mix-neuroglia cells were divided randomly into six groups Control group, BaP group (2.00 µmol/L), Aß1-42 oligomer group (20.00 mg/L), BaP plus Aß1-42 oligomer group, Aß1-42 fiber group (20.00 mg/L) and BaP plus Aß1-42 fiber group, of which BaP was pretreated for 12 h followed by cotreatment with different aggregated Aß1-42. The expressions of IDE and NEP were measured by quantitative real-time polymerase chain reaction (qRT-PCR) for mRNA level and Western blotting for protein level. RESULTS: The cell survival rate showed no significant differences after treatment with BaP (≤20.00 µmol/L), Aß1-42 oligomer (20.00, 40.00 mg/L), Aß1-42 fiber (20.00, 40.00 mg/L) or cotreatment with BaP and Aß1-42 oligomer or BaP and Aß1-42 fiber. Compared with the control group, expressions of IDE and NEP in BaP-treated alone group had no obvious change; however, exposure to Aß1-42 oligomer alone significantly increased the mRNA and protein level of IDE (P<0.05), and the BaP pretreatment could significantly inhibit the up-regulated expressions of IDE by Aß1-42 oligomer (P<0.05); on the other hand, exposure either to Aß1-42 fiber alone or under the BaP pretreatment did not change the mRNA and protein level of IDE and NEP obviously. CONCLUSION: On the premise of no significant change of cell survival rate, BaP pretreatment inhibited the up-regulated expressions of IDE in primary mixed neuroglia cells under cotreatment with Aß oligomer, indicating that BaP may disturb degradation of Aß oligomer and cause deposition of ß-amyloid and further induce cognitive decline and acceleration of Alzheimer.