Research ReportProtective effects of statins on l-DOPA neurotoxicity due to the activation of phosphatidylinositol 3-kinase and free radical scavenging in PC12 cell culture

Neurotoxic effects have been suggested for l-3,4-dihydroxyphenylalanine (l-DOPA), while neuroprotective effects have been proposed for statins. We investigated whether certain statins (simvastatin or pitavastatin) could inhibit l-DOPA neurotoxicity. Neuronally-differentiated PC12 (nPC12) cells were treated with l-DOPA and/or statins for 24 h, and their viabilities were measured using a cell counting kit, trypan blue staining, and 4′,6-diamidino-2-phenylindole (DAPI) staining. Free radical and specific intracellular signaling protein levels were measured with 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) and Western blotting, respectively. High concentrations of l-DOPA reduced nPC12 cell viability, but combined treatment with statins restored viability. Treatment with 200 μM l-DOPA increased free radical and hydroxyl radical levels, but combined treatment with 5 μM statins decreased these levels. Survival-related signaling proteins were decreased in nPC12 cells treated with 200 μM l-DOPA, but combined treatment with 5 μM statins significantly increased the levels of these proteins. Treatment with 200 μM l-DOPA significantly increased death-related signaling proteins, while combined treatment with 5 μM statins reduced the levels of these proteins. Pretreatment with LY294002, a phosphatidylinositol 3 kinase (PI3K) inhibitor, before combined treatment with statins and l-DOPA almost completely blocked the protective effects of statins. These results indicate that statins reduce l-DOPA neurotoxicity by lowering oxidative stress and by enhancing survival signals and inhibiting death signals via activation of the PI3K pathway.

Research Highlights►L-DOPA produces neurotoxicity at high concentration. ►Statins prevent l-DOPA neurotoxicity. ►Statins' neuroprotective effects are associated with the activation of the PI3K pathway. ►Antioxidant effects of statins are also related to the protective effects against l-DOPA neurotoxicity.