Mitochondrial complex I inhibitor
rotenone induces apoptosis through enhancing mitochondrial
reactive oxygen species production. Recently, it has been shown that
fraxetin (
coumarin) and
myricetin (
flavonoid) have significant
neuroprotective effects against apoptosis induced by
rotenone, increase the total
glutathione levels in vitro, and inhibit lipid peroxidation. Thus, these considerations prompted us to investigate the way in which
fraxetin and
myricetin affect the
endogenous antioxidant defense system, such as Mn and CuZn
superoxide dismutase (MnSOD, CuZnSOD),
catalase,
glutathione reductase (GR), and
glutathione peroxidase (GPx) on
rotenone neurotoxicity in
neuroblastoma cells.
N-acetylcysteine (NAC), a potent
antioxidant, was employed as a comparative agent. Also, the expression and
protein levels of HSP70 by Northern and Western blot analysis were assayed in SH-SY5Y cells. After incubation for 16 h,
rotenone significantly increased the expression and activity of MnSOD, GPx, and
catalase. When cells were preincubated with
fraxetin, there was a decrease in the
protein levels and activity of both MnSOD and
catalase, in comparison with the
rotenone treatment. The
myricetin effect was less pronounced. Activity and expression of GPx were increased by
rotenone and pre-treatment with
fraxetin did not modify significantly these levels. The significant enhancement in HSP70 expression at
mRNA and
protein levels induced by
fraxetin was observed by pre-treatment of cells 0.5 h before
rotenone insult. These data suggest that major features of
rotenone-induced neurotoxicity are partially mediated by
free radical formation and oxidative stress, and that
fraxetin partially protects against
rotenone toxicity affecting the main protection system of the cells against oxidative injury.