TRAIL-related neurotoxicity implies interaction with the Wnt pathway in human neuronal cells in vitro.

Tumor necrosis factor related apoptosis inducing ligand (TRAIL) is involved in amyloid beta dependent neurotoxicity via the extrinsic pathway. Recently, several genes modulating TRAIL cytotoxicity have been characterized, providing evidence for a role of wingless-type mouse mammary tumor virus integration site family (Wnt), Jun-N-terminal kinase and other pathways in increased cell susceptibility to the cytokine. We investigated whether neurotoxic effects of TRAIL could be due to modulation of the Wnt signaling pathway. Western blot analysis of Wnt in SH-SY5Y human neuroblastoma cells showed significantly decreased Wnt expression in cultures treated with TRAIL. Correspondingly, both phosphorylation of glycogen synthase kinase 3 beta and degradation of cytoplasmic beta-catenin were increased, as well as phosphorylation of the tau protein, bringing about the picture of neuronal damage. As a counterproof of the interaction of TRAIL with the Wnt pathway, the addition of the specific glycogen synthase kinase 3 beta inhibitor SB216763 resulted in rescue of a significant percent of cells from TRAIL-induced apoptosis. The rescue was total when the caspase 8 inhibitor z-IETD-FMK was added in combination with SB216763. Results show that, probably, in addition to triggering caspase signaling, TRAIL also interferes with the Wnt pathway, additionally concurring to neuronal damage. These data suggest that the Wnt pathway substantially contributes to the TRAIL-related neurotoxicity and indicate the TRAIL system as a candidate target for pharmacological treatment of Alzheimer's disease and related disorders.

Trail interacts redundantly with nitric oxide in rat astrocytes: potential contribution to neurodegenerative processes.

The proapoptotic cytokine TRAIL has been shown to enhance amyloid-beta-dependent neurotoxicity. Here are reported interactions between TRAIL and nitric oxide (NO) in cultured rat astrocytes in vitro. Rat astrocytes expressed all TRAIL receptor mRNAs and proteins. However, TRAIL failed in inducing apoptosis of astrocytes, whereas these cells released substantial amounts of nitrites. A TRAIL-neutralizing antibody was able to prevent LPS-induced iNOS expression in astrocytes. Interestingly, TRAIL induced its own expression in astrocytes. These data suggest that redundancy between TRAIL and NO in astrocytes could be fueling neuronal damage/death processes, potentially uncovering novel molecular targets for the treatment of neurodegenerative disorders.

Levels of matrix metalloproteinases 1 and 2 in human gingival crevicular fluid during initial tooth movement.

INTRODUCTION: During orthodontic treatment, the early response of periodontal tissues to mechanical stress involves several metabolic changes that allow tooth movement. Many studies have evaluated these modifications through the analysis of various metabolites released into gingival crevicular fluid (GCF). The purpose of this investigation was to evaluate matrix metalloproteinase (MMP)-1 and MMP-2 in the GCF of human teeth exposed to orthodontic force on both the tension and compression sides in the initial phase of orthodontic tooth movement. METHODS: GCF samples were obtained from 11 healthy orthodontic patients (8 girls, 3 boys; age, 13-15 years; mean, 13.9 years) who needed their 4 first premolars extracted for orthodontic reasons. In each patient, the left maxillary canine having the fixed orthodontic appliance was used as the test tooth, and its antagonist, with no appliance, was the control tooth. Orthodontic force was applied by using a Sentalloy coil-spring (GAC International, Bohemia, NY) of 150 g. The GCF sampling on the mesiobuccal and distobuccal aspects of each experimental and control tooth was performed at specific times up to 8 hours with paper strips. Processing was carried out with western blot analysis to detect MMP-1 and MMP-2 levels on the compression and tension sides. RESULTS: Compression force induced a significant increase of MMP-1 protein after 1 hour; the increase lasted until the third hour of force application and disappeared thereafter. The tension force induced significantly increased levels of the MMP-1 protein after just 1 hour of force application. MMP-2 protein was induced by compression and increased significantly in a time-dependent fashion, reaching a peak after 8 hours of force application. On the tension side, MMP-2 was significantly increased after 1 hour but gradually returned to basal levels within 8 hours. CONCLUSIONS: Orthodontic forces affect both MMP-1 and MMP-2 protein levels on the compression and the tension sides, although to different extents, whereas MMP-1 and MMP-2 protein levels change in a time-dependent fashion.