Interleukin 1alpha and interleukin 6 protect human neuronal SH-SY5Y cells from oxidative damage

Interleukin (IL)-1alpha and IL-6 are powerful inflammatory cytokines produced in brain primarily by microglia and astrocytes. Here we demonstrate, using an in vitro assay system, that they can have a direct neuroprotective action against oxidative attack. Exposure of retinoic acid-differentiated human SH-SY5Y neuroblastoma cells to 270 microM hydrogen peroxide caused activation of caspase 3 and significant neuronal death. Treatment with IL-1alpha or IL-6 caused a dose-dependent increase in survival as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. An antibody against single-strand DNA demonstrated many apoptotic neuroblastoma cells following exposure to hydrogen peroxide, with a decrease following cytokine treatment. These data indicate that IL-1alpha and IL-6 can, under appropriate circumstances, protect neurons from oxidative damage in addition to their well-known action of stimulating inflammation.