Tau hyperphosphorylation and P-CREB reduction are involved in acrylamide-induced spatial memory impairment: Suppression by curcumin

Acrylamide (ACR) is an axonal toxicant that produces peripheral neuropathy in laboratory animals and humans. Epidemiological study found that diet ACR exposure was associated with a mild cognitive decline in men. However, limited information is available as regards its potential and underlying mechanism to cause memory alterations. Curcumin is a polyphenol with neuroprotective and cognitive-enhancing properties. In this study, we aimed to investigate the mechanism of ACR-induced spatial memory impairment and the beneficial effect of curcumin. ACR exposure at 10 mg/kg/d for 7 weeks caused slight gait abnormality and spatial memory deficits, which was associated with an activation of glial cells, a reduction of phosphorylated CAMP response elements binding protein (P-CREB) and an aggregation of hyperphosphorylated tau including p-tau (Ser(262)), AT8 (p-tau Ser(202)/Thr(205)) and PHF1 (p-tau Ser(396/404)) in the hippocampus and cortex. ACR markedly regulate the expression of glycogen synthase kinase-3 beta (GSK-3 beta) and cyclin-dependent kinase-5 (cdk5) to accelerate tau hyperphosphorylation. ACR inhibited the protein phosphatase 2A (PP2A) and lysosomal protease cathepsin D to decrease the p-tau dephosphorylation and degradation. The P-CREB and brain derived neurotrophic factor (BDNF) were significantly decreased by ACR. The upstream signalings of P-CREB, extracellular signal-related kinase (ERK) and Akt were markedly inhibited. The protein kinase RNA-like endoplasmic reticulum kinase (PERK) -eukaryotic initiation factor-2 alpha (eIF2 alpha) - activating transcription factor 4 (ATF4) signaling which negatively regulate memory processes by suppressing CREB was activated by ACR. Curcumin alleviated ACR-induced spatial memory impairment through reversing tau abnormalities and P-CREB reduction in the hippocampus. These results offered deeper insight into the mechanisms of and presented a potential new treatment for ACR-induced neurotoxicity.