| In Vitro | In vitro activity: Tropisetron is a high affinity ligand for both th α7 nAChR and 5HT3R. Tropisetron has very low affinity for the other nicotinic subtypes tested. Tropisetron is a potent and selective serotonin 3 (5-hydroxytryptamine3; 5-HT3) receptor antagonist with antiemetic properties, probably mediated via antagonism of receptors both at peripheral sites and in the central nervous system. Tropisetron is a potent inhibitor of early and late events in TCR-mediated T cell activation. Tropisetron specifically inhibits both IL-2 gene transcription and IL-2 synthesis in stimulated T cells. Ttropisetron inhibits both the binding to DNA and the transcriptional activity of NFAT and AP-1. Tropisetron is a potent inhibitor of PMA plus ionomycin-induced NF-(kappa)B activation but in contrast TNF(alpha)-mediated NF-(kappa)B activation is not affected by this antagonist. Tropisetron acts on α7 nAChRs on isolated pig retinal ganglion cells (RGCs) to provide neuroprotection against glutamate-induced excitotoxicity. Tropisetron acts to decrease p38MAP kinase levels to inhibit apoptosis. Tropisetron is able to protect retinal ganglion cells (RGCs) from a glutamate assault in a dose-dependent manner when applied to cultures 1 hour prior to glutamate application.
Cell Assay: Retinal ganglion cells(RGCs) pretreated with 100 nM tropisetron before glutamate increased cell survival to an average of 105% compared to controls. Inhibition studies using the alpha7 nAChR antagonist, MLA (10 nM), support the hypothesis that tropisetron is an effective neuroprotective agent against glutamate-induced excitotoxicity; mediated by α7 nAChR activation. Tropisetron had no discernible effects on pAkt levels but significantly decreased p38 MAPK levels associated with excitotoxicity from an average of 15 ng/ml to 6 ng/ml. Tropisetron, but not granisetron, significantly inhibits the phosphatase activity of calcineurin, over-expresses the CB(1) receptors at both transcriptional and protein levels, and reduces cAMP content in cerebellar granule neurons (CGNs). |
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