L-carnitine Inhibits H 2 O 2 Induced SH-SY5Y Cell Injury By Mitochondrial Pathway

OBJECTIVE: To copy hydrogen peroxide（H₂O₂）-induced oxidative damage Alzheimer’s disease model in SH-SY5 Y cells, screen and determine the effective concentration of L-carnitine（LC） to decrease the oxidative damage, and explore the protective effect of LC in SH-SY5 Y cells via modulating mitochondrial apoptotic pathway. METHODS: The cells were divided into groups randomly as below: control group, H₂O₂（400μmol?L-1） model group and L-carnitine pretreatment group（50、100、200 μmol?L-1 3h pretreatment followed by H₂O₂ treatment）. The cell viability was detected by MTT assay. The activity caspase-3 was determined by enzyme activity detection. Mitochondrial membrane potential was determined by JC-1 staining. The GRP75 m RNA was analyzed by RT-PCR. The expression of GRP75, cyto C, and Bax were analyzed by western-blot. RESULTS: The cells were incubated with 400μmol?L-1H₂O₂ for 20 min to establish the oxidative damage model. The cell viability was decreased sharply in the H₂O₂ treated group and L-carnitine pretreatment retrieved the cell viability effectively. The result of caspase-3 activity analyses indicated that caspase-3activity was increased in H₂O₂ treated group and decreased after the L-carnitine pretreatment. JC-1 stain showed that the mitochondrial membrane potential was destroled by H₂O₂ and L-carnitine pretreatment could restore the mitochondrial membrane potential damaged by H₂O₂. The result of RT-PCR indicated that GRP75 m RNA was stimulated by H₂O₂ treatment and suppressed by L-carnitine pretreatment. The result of western-blot showed that the expression of GRP78, cyto C and bax were enhanced obviously in H₂O₂ treated group. Meanwhile in the L-carnitine-pretreated groups, the expression of GRP78,cyto C and bax were dropped to yield an inhibitory effect to the mitochondrial apoptotic pathway in the cells. After GRP sh RNA silence, Bax was inhibited greatly which suggested that Bax was the downstreamed factor of GRP75. CONCLUSION:L-carnitine could inhibit the oxidative damage and the mitochondria-mediated apoptosis induced by H₂O₂ in SH-SY5 Y cells. The protective effect of L-carnitine was through the suppression of GRP75 and the inhibition of the pro-apoptotic bax protein.