Effects of insulin-like growth factor-1 on okadaic acid-induced apoptosis in SH-SY5Y cells

The effects of insulin-like growth factor-1 (IGF-1) on the cytotoxicity and apoptosis induced by okadaic acid (OA) in SH-SY5Y cells were investigated. Cell viability was measured using the MTT (3-(4,5-dimethylthiazolyl-2)-2,-5-diphenyltetrazolium bromide) assay. Early and late apoptosis/necrosis were analyzed by flow cytometry using Annexin V and propidium iodide (PI) double-staining. Caspase-3 activation was detected by Western blot analysis. Preincubation with IGF-1 for 24 h prevented cytotoxicity induced by 40 nM OA given for 24 h, and the MTT value significantly increased. Incubation with 20 nM OA for 24 h caused a marked increase in the percentage of early apoptotic and late apoptotic/necrotic cells, which was not dependent on the activation of caspase-3. OA-induced apoptosis was significantly decreased by pretreatment with 10 ng/ml of IGF-1 for 24 h. The results supported the hypothesis that IGF-1 may be useful in the treatment of Alzheimer's disease.