Purchase this article with an account.
D.M. Linn, C.L. Linn; Neuroprotective Effect of Tropisetron in Pig RGCs: Role of the AKT Signaling Cascade . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1324.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Tropisetron is best known as a selective 5–HT3 antagonist used to treat nausea and emesis in cancer patients undergoing chemotherapy and radiation. However, some studies have suggested that tropisetron acts as an α7 nAChR agonist in the brain (Cortes–Burgos et al., 2001). Methods: To explore this possibility, we examined the neuroprotective effect of tropisetron on glutamate–induced excitotoxicity in cultured isolated adult pig retinal ganglion cells (RGCs). In this model system, glutamate–induced excitotoxicity is eliminated in the presence of 5 µM ACh through α7 nAChRs (Wehrwein et al., 2004). To determine if tropisetron mimicked the neuroprotective effect of ACh, various concentrations of tropisetron were applied to panned adult pig RGCs two hours before application of 500 µM L–glutamate. After 3 days of chronic exposure, surviving cells were counted and compared to control conditions. Results: We found that 100 nM tropisetron had a maximal effect and inhibited the excitotoxic effect of glutamate by 82% (+/– 4.2) compared to 98% (+/– 4.3) associated with 5 µM ACh. The effects of tropisetron were significantly reduced in the presence of the α7 antagonists, α–bungarotoxin and MLA, but not in the presence of the 5–HT3 selective antagonist, tropine, supporting the hypothesis that tropisetron activates α7 nAChRs on pig RGCs to induce neuroprotection. The ACh neuroprotection in isolated cultured pig RGCs is partially mediated through up–regulation of enzymes in the AKT cell survival pathway (Linn & Asomugha, 2005). ELISA studies were performed to determine if tropisetron neuroprotection also involved up–regulation of phosphorylated AKT protein content. Total and phosphorylated protein content was collected under each of the following conditions: 1) control untreated cells, 2) RGCs treated with 100 nM tropisetron 3) RGCs treated with 100 nM tropisetron before 500 µM glutamate. Conclusions: Results demonstrated that tropisetron had no effect on the regulation of phosphorylated AKT under any condition, suggesting that the neuroprotective role of tropisetron is mediated through a mechanism other than the one mediating the ACh neuroprotective effect.
This PDF is available to Subscribers Only