Role of Fuzhisan in reducing Tau protein hyperphosphorylation in cortical neurons through a cyclin-dependent kinase 5 pathway / 中国药理学通报

ABSTRACT

Aim Fuzhisan ( FZS ) , a Chinese herbal complex prescription that has been used for the treat-ment of AD for over 15 years, is known to enhance the cognitive ability in AD patients. In this study, to in-vestigate whether FZS reduces Aβ25-35-induced Tau protein hyperphosphorylation in neonatal rat cortical neurons by suppressing the cyclin-dependent kinase 5 ( CDK5 ) pathway. Methods Neonatal Wistar rats born within 24 h were selected to separate and purify their cortical neurons for culture in vitro. After 7-day culture of cortical neurons in vitro, 20 μmol · L-1 Aβ25-35 was used to act on them for 24 h. Medication groups were pretreated with FZS ( 20 mg · L-1 ) , CDK5 inhibitor roscovitine ( 15 μmol · L-1 ) and cal-pain preparation calpeptin (20 μmol·L-1 ) for 24 h, followed by reaction with 20 μmol·L-1 Aβ25-35 for 24 h. Tau protein phosphorylation levels at Ser396, Ser202 and Thr231 and the protein level of CDK5 acti-vator proteins p25/p35 were assayed by Western blot. Fluorescence intensity was measured with a fluores-cence microplate reader to reflect calpain activity. CDK5 kinase activity was assayed by immunoprecipita-tion. Results After 20 μmol·L-1 Aβ25-35 acting on cortical neurons for 24h, there were increments in the following Tau protein phosphorylation levels at Ser396, Ser202 and Thr231, CDK5 kinase activity, CDK5 activator protein p25 level, and calpain activity. In the 20 mg·L-1 FZS treatment group, Aβ25-35 was suppressed markedly, resulting in increments in Tau protein phosphorylation levels at Ser396 , Ser202 and Thr231 , suppression of CDK5 kinase activity and p25 protein level, and elevation in calpain activity. Both CDK5 inhibitor roscovitine and calpain preparation cal-peptin, as positive control drugs, also played a role in suppressing Tau protein hyperphosphorylation. Con-clusion FZS can suppress Aβ25-35-induced Tau pro-tein hyperphosphorylation in cortical neurons through the calpain/CDK5 pathway.