BDNF PROTECTION OF AUDITORY NEURONS FROM CISPLATIN INVOLVES CHANGES IN INTRACELLULAR LEVELS OF BOTH REACTIVE OXYGEN SPECIES AND GLUTATHIONE

Previous studies have shown that brain derived neurotrophic factor (BD NF) can protect auditory neurons from cisplatin toxicity in vitro. To explore the mechanism of BDNF mediated neuronal protection sequential confocal microscopic sampling of auditory neurons measured intracellul ar levels of reactive oxygen species (ROS) in response to withdrawal o f BDNF supplementation, cisplatin exposure, and BDNF protection from c isplatin damage in normal and oxidative stress states. Additionally, w e examined intraneuronal levels of the free radical scavenger glutathi one (GSH) in response to withdrawal of BDNF. Withdrawal of BDNF result ed in increased production of ROS and decreased survival of auditory n eurons. Levels of GSH within neurons increased after BDNF withdrawal, and this increase was shown to lag behind the production of ROS. Audit ory neurons in cultures supplemented with BDNF and exposed to cisplati n showed significantly lower levels of ROS and increased survival comp ared to neurons in unprotected, cisplatin exposed cultures. Neurons tr eated with buthionine sulfoximine (an inhibitor of GSH synthesis), sup plemented with BDNF, and exposed to cisplatin showed significantly hig her intracellular levels of ROS compared to the neurons in BDNF supple mented cultures exposed to cisplatin. These results suggest that intra cellular levels of ROS play an important role in cisplatin induced cel l death of auditory neurons and that production of ROS can be ameliora ted through supplementation with BDNF. GSH appears to mediate BDNF pro tection of these neurons from cisplatin induced ROS and subsequent dam age. (C) 1997 Elsevier Science B.V.