Spinal cord injury (SCI) is a major cause of disability, its clinical outcome depending mostly on the extent of damage in which proapoptotic
cytokines have a crucial function. In particular, the inducers of apoptosis belonging to
TNF receptor superfamily and their respective
ligands are upregulated after SCI. In this study, the function of the proapoptotic
cytokine tumor necrosis factor-related apoptosis-inducing
ligand (TRAIL) in SCI-induced damage was investigated in the mouse. SCI resulted in severe
trauma, characterized by prominent
inflammation-related damage and apoptosis. Immunostaining for TRAIL and its
receptor DR5 was found in the white and gray matter of the perilesional area, as also confirmed by western blotting experiments. Immunoneutralization of TRAIL resulted in improved functional recovery, reduced apoptotic cell number, modulation of molecules involved in the inflammatory response (FasL,
TNF-alpha, IL-1beta, and MPO), and the corresponding signaling (
caspase-8 and -3 activation, JNK phosphorylation, Bax, and Bcl-2 expression). As
glucocorticoid-induced
TNF receptor superfamily-related
protein (GITR) activated by its
ligand (GITRL) contributes to SCI-related
inflammation, interactions between TRAIL and GITRL were investigated. SCI was associated with upregulated GITR and GITRL expression, a phenomenon prevented by anti-TRAIL treatment. Moreover, the expression of both TRAIL and DR5 was reduced in tissues from mice lacking the GITR gene (GITR(-/-)) in comparison with wild-type mice suggesting that TRAIL- and GITRL-activated pathways synergise in the development of SCI-related inflammatory damage. Characterization of new targets within such molecular systems may constitute a platform for innovative treatment of SCI.