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  • Title: Effect of melatonin on calyculin A-induced tau hyperphosphorylation.
    Author: Li XC, Wang ZF, Zhang JX, Wang Q, Wang JZ.
    Journal: Eur J Pharmacol; 2005 Mar 07; 510(1-2):25-30. PubMed ID: 15740721.
    Abstract:
    We have found in the present study that incubation of neuroblastma N2a with calyculin A, an inhibitor of protein phosphatase-2A (PP-2A) and protein phosphatase-1 (PP-1), reduces cell viability in a dose-dependent manner, and leads to tau hyperphosphorylation at tau-1 (Ser198/199/202) and PHF-1 (Ser396/404) epitopes. In addition to inhibit PP-2A, calyculin A treatment also results in significant activation of glycogen synthase kinase-3 (GSK-3). Calyculin A induces oxidative stress manifested by elevated level of malondialdehyde and decreased activity of superoxide dismutase. When the cells were incubated simultaneously with calyculin A and melatonin (25 microM or 50 microM), the calyculin A-induced decrease in cell viability, tau hyperphosphorylation, PP-2A/GSK-3 imbalance and oxidative stress were attenuated accordingly. These results suggest (i) that calyculin A induces tau hyperphosphorylation not only by inhibition of PP-2A, but also by activation of GSK-3 in N2a cells; (ii) that melatonin efficiently attenuates the calyculin A-induced damages through not only its antioxidant effect but also its modulation to the phosphorylation system.
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