Resveratrol Attenuates Formaldehyde Induced Hyperphosphorylation of Tau Protein and Cytotoxicity in N2a Cells

Recent studies have demonstrated that formaldehyde (FA)—induced neurotoxicity is important in the pathogenesis of Alzheimer's disease (AD). Elevated levels of FA have been associated with memory impairments and the main hallmarks of AD pathology, including β-amyloid plaques, tau protein hyperphosphorylation, and neuronal loss. Resveratrol (Res), as a polyphenol anti-oxidant, has been considered to have therapeutic potential for the treatment of AD. However, it has not been elucidated whether Res can exert its neuroprotective effects against FA-induced neuronal damages related to AD pathology. To answer this question, the effects of Res were investigated on Neuro-2a (N2a) cells prior to and after FA exposure. The experiments found that pre-treatment with Res significantly decreased FA-induced cytotoxicity, reduced cell apoptosis rates, and inhibited the hyperphosphorylation of tau protein at Thr181 in a dose-dependent manner. Further tests revealed that this effect was associated with the suppression of glycogen synthase kinase (GSK-3β) and calmodulin-dependent protein kinase II (CaMKII) activities, both of which are important kinases for tau protein hyperphosphorylation. In addition, Res was found to increase the activity of phosphoseryl/phosphothreonyl protein phosphatase-2A (PP2A). In summary, these findings provide evidence that Res protects N2a cells from FA-induced damages and suggests that inhibition of GSK-3β and CaMKII and the activation of PP2A by Res protect against the hyperphosphorylation and/or mediates the dephosphorylation of tau protein, respectively. These possible mechanisms underlying the neuroprotective effects of Res against FA-induced damages provide another perspective on AD treatment via inhibition of tau protein hyperhosphorylation.