Cilostazol is specific inhibition of cyclic nucleotide phosphodiesterase 3 (PDE3) with IC50 value of 200 nM.[1]
PDE3 is one of phosphodiesterase. PDE3 plays an important role in regulating vascular smooth muscle, heart muscle and platelet aggregation, so, it is clinically significant. The PDE3 family consists of two members including PDE3A and PDE3B. PDE3A is mainly related cardiovascular function and PDE3B is mainly related to lipolysis. The activity of PDE3 is regulated by phosphorylation pathways. PDE 3 is activited via phosphorylation at different phosphorylation sites by protein kinase A and protein kinase B. PDE3 enzymes also are involved in regulation of vascular and  cardiac smooth muscle contractility.
Cilostazol prevents platelet aggregation by specifically and selectively inhibiting PDE3 in platelets with IC50 value of 200 nM. Cilostazol also cause intracellular cAMP levels increasing by inhibiting adenosine uptake leading to increased adenosine levels in cells. Cilostazol also inhibits the expression of platelet surface P-selectin, platelet factor 4 (PF4), thromboxane B2 production release. Cilostazol also cause decrease in triglyceride levels and an increase in high-density lipoprotein. [1]
Cilostazol may has effective function in dementia. Cilostazol has beneficial effects on learning impairment induced by Aβ25-35 in mice. Cilostazol attenuated the impairment induced by Aβ25-35 at 100 mg/kg.[2]
References:
[1].    Rondina MT, Weyrich AS: Targeting phosphodiesterases in anti-platelet therapy. Handb Exp Pharmacol 2012(210):225-238.
[2].    Hiramatsu M, Takiguchi O, Nishiyama A, Mori H: Cilostazol prevents amyloid beta peptide(25-35)-induced memory impairment and oxidative stress in mice. Br J Pharmacol 2010, 161(8):1899-1912.