Protection by cilostazol against amyloid-β1-40-induced suppression of viability and neurite elongation through activation of CK2α in HT22 mouse hippocampal cells

Amyloid-beta peptide (A beta) deposits in the brain are critical in the neurotoxicity induced by A beta. This study elucidates the underlying signaling pathway by which cilostazol protects HT22 neuronal cells from A beta 140 (330 mu M)-induced deterioration of cell proliferation, viability, and neurite elongation. Cilostazol rescued HT22 cells from the apoptotic cell death induced by A beta toxicity through the downregulation of phosphorylated p53 (Ser15), Bax, and caspase-3 and the upregulation of Bcl-2 expression, which improved neuronal cell proliferation and viability. Furthermore, A beta 140 suppressed both phosphorylated CK2a protein expression and CK2 activity in the cytosol; these were concentration dependently recovered by cilostazol (330 mu M). Cilostazol significantly increased the levels of GSK-3 beta phosphorylation at Ser9 and beta-catenin phosphorylation at Ser675 in the cytosol and nucleus. Cilostazol effects were reversed by KT5720 (1 mu M, PKA inhibitor) and TBCA (40 mu M, inhibitor of CK2) and CK2a knockdown by siRNA transfection. Likewise, A beta-stimulated GSK-3 beta phosphorylation at Tyr 216 was decreased by cilostazol in the control but not in the CK2a siRNA-transfected cells. Furthermore, the A beta (10 mu M)-induced suppression of neurite elongation was recovered by cilostazol; this recovery was attenuated by inhibitors such as KT5720 and TBCA and blocked by CK2a knockdown. In conclusion, increased cAMP-dependent protein kinase-linked CK2a activation underlies the pharmacological effects of cilostazol in downregulating p53 phosphorylation at Ser15 and upregulating GSK-3 beta phosphorylation at Ser9/beta-catenin phosphorylation at Ser675, thereby suppressing A beta 140-induced neurotoxicity and improving neurite elongation. (c) 2012 Wiley Periodicals, Inc.