Guanosine and synthetic organoselenium compounds modulate methylmercury-induced oxidative stress in rat brain cortical slices: Involvement of oxidative stress and glutamatergic system

Excessive formation of reactive oxygen species (ROS) and disruption of glutamate uptake have been pointed as two key mechanisms in methylmercury-toxicity. Thus, here we investigate the involvement of glutamatergic system in methylmercury (MeHg) neurotoxicity and whether diphenyl diselenide, ebselen and guanosine could protect cortical rat brain slices from MeHg-induced ROS generation. MeHg (100 and 200 mu M) increased 2',7'-dichlorodihydrofluorescin (DCFH) oxidation after 2 h of exposure. At 50 mu M, MeHg increased DCFH oxidation only after 5 h of exposure. Guanosine (1 and 5 PM) did not caused any effect per se; however, it blocked the increase in DCFH caused by 200 or 50 mu M MeHg. Ebselen (5 and 10 mu M) decreased significantly the DCFH oxidation after 2 and 5 h of exposure to MeHg. Diphenyl diselenide (5 mu M) did not change the basal DCFH oxidation, but abolished the pro-oxidant effect of MeHg. MK-801 also abolished the pro-oxidant effect of MeHg. These results demonstrate for the first time the potential antioxidant properties of organoseleniun compounds and guanosine against MeHg-induced ROS generation after short-term exposure in a simple in vitro model. In conclusion, endogenous purine (guanosine) and two synthetic organoselenium compounds can modulate the pro-oxidant effect of MeHg in cortical brain slices. (C) 2008 Elsevier Ltd. All rights reserved.