Alzheimer’s disease (AD) is a neurodegenerative disorder with no efficacious treatment. Among pathogenetic factors contributing to AD, amyloid-β (AB) has been regarded as a pivotal molecule, organized in amyloid plaques and neurofibrillary tangles. It has recently been demonstrated that AB increases the expression of both the apoptotic cytokine TRAIL and its receptor DR5 in neurons. Glucocorticoid-induced TNF related protein (GITR) is a receptor belonging to the TNF receptor superfamily (TNF-R), selectively activated by its endogenous ligand, GITRL. The GITR/GITRL system is able to transduce either pro- or antiapoptotic signals. The aim of this work was to characterize possible interactions between TRAIL and the GITR/GITRL system in neurodegenerative processes. Thus, human neuronal cells HCN-2 were treated with the AB fragment 25-35 and then cell viability, as well as the expression of TRAIL and its DR4 and DR5 receptors were evaluated. Cell viability was reduced significantly after 72 hours incubation with AB. Western blot analysis showed that expression of TRAIL was significantly increased by AB in HCN-2 cells. Similar results were obtained in western blot experiments for DR4 and DR5 expression. To assess possible influence of TRAIL upon the GITR/GITRL system, HCN-2 cells were then treated with AB fragment 25-35 or TRAIL at different times. Real-time PCR analysis showed that HCN-2 cells do not express GITR mRNA, neither its expression is induced after treatment with either AB or TRAIL. In addition, following treatment with TRAIL, the expression of GITRL mRNA was increased. All mRNA data were confirmed by western blot at the level of protein expression. Finally, to assess the role of the GITR/GITRL system, neuronal cells were treated with either combinations of both GITRL and AB or GITRL and TRAIL. Results showed that, when associated to AB, GITRL was unable to exert additive toxic effect, which was, on the other hand, elicited by treatment with the combination GITRL-TRAIL. A counterproof to the latter data was provided in experiments performed using the GITR-Fc fusion protein that significantly reduced TRAIL-mediated toxicity. Results show that TRAIL mediates neurotoxic effects of AB in HCN-2 cells. GITRL acted as an apoptotic molecule, and redundantly with TRAIL. Finally, both the TRAIL and the GITR/GITRL systems may represent novel molecular targets for characterization of novel treatment of AD.
|Titolo:||The role of GITR/TRAIL interactions in neurodegenerative processes|
|Data di pubblicazione:||2011|
|Appare nelle tipologie:||4.3 Poster|