The　deposition　of　beta-amyloid　protein(A　beta)　and　loss　of　neurons　within　the　brain　are　the　pathologic　hallmarks　of　Alzheimer＇s　disease　(AD).　Apoptosis　is　a　crucial　pathway　in　neuronal　loss　in　AD.　Tanshinone　IIA(tanIIA)　is　one　of　ingredients　of　tanshinone　which　is　the　major　component　of　the　traditional　Chinese　herb　Danshen.　The　present　study　explores　the　effects　of　tanlIA　on　A　beta(1-42)-induced　cytotoxicity.　Cultured　cortical　neurons　that　were　treated　with　4　mu　M　A　beta(1-42)　showed　shrunken　perikaryon　with　loss　of　neurite　processes;　the　survival　rate　of　neurons　decreased　almost　to　57%　and　the　apoptotic　rate　of　neurons　increased　to　47%.　In　addition,　the　level　of　gene　bcl-xl　mRNA　and　Bcl-xL　protein　decreased　significantly.　These　changes,　however,　were　prevented　by　pretreatment　of　neurons　with　tanlIA　for　24　h　before　A　beta(1-42),　which　markedly　increased　neuron　survival　rate　compared　to　neurons　treated　with　A　beta(1-42)　alone;　the　apoptotic　rate　of　neurons　decreased　to　15%,　and　the　decrease　in　level　of　gene　bcl-xl　mRNA　and　Bcl-xL　protein　in　A　beta-treated　neurons,　were　prevented.　Thus,　we　conclude　that　tanIIA　might　serve　as　an　obvious　neuroprotection.　TanIIA　protected　neurons　against　the　A　beta-induced　cytotoxicity　most　likely　via　activation　of　the　Bcl-xL　pathway.　(C)　2012　Elsevier　Inc.　All　rights　reserved.