ABSTRACT
Objective@#: Radiation is known to induce autophagy in malignant glioma cells whether it is cytocidal or cytoprotective.Dexamethasone is frequently used to reduce tumor-associated brain edema, especially during radiation therapy. The purpose of the study was to determine whether and how dexamethasone affects autophagy in irradiated malignant glioma cells and to identify possible intervening molecular pathways. @*Methods@#: We prepared p53 mutant U373 and LN229 glioma cell lines, which varied by phosphatase and tensin homolog (PTEN) mutational status and were used to make U373 stable transfected cells expressing GFP-LC3 protein. After performing cell survival assay after irradiation, the IC50 radiation dose was determined. Dexamethasone dose (10 µM) was determined from the literature and added to the glioma cells 24 hours before the irradiation. The effect of adding dexamethasone was evaluated by cell survival assay or clonogenic assay and cell cycle analysis. Measurement of autophagy was visualized by western blot of LC3-I/LC3-II and quantified by the GFP-LC3 punctuated pattern under fluorescence microscopy and acridine orange staining for acidic vesicle organelles by flow cytometry. @*Results@#: Dexamethasone increased cell survival in both U373 and LN229 cells after irradiation. It interfered with autophagy after irradiation differently depending on the PTEN mutational status : the autophagy decreased in U373 (PTEN-mutated) cells but increased in LN229 (PTEN wild-type) cells. Inhibition of protein kinase B (AKT) phosphorylation after irradiation by LY294002 reversed the dexamethasone-induced decrease of autophagy and cell death in U373 cells but provoked no effect on both autophagy and cell survival in LN229 cells. After ATG5 knockdown, radiation-induced autophagy decreased and the effect of dexamethasone also diminished in both cell lines. The diminished autophagy resulted in a partial reversal of dexamethasone protection from cell death after irradiation in U373 cells; however, no significant change was observed in surviving fraction LN229 cells. @*Conclusion@#: Dexamethasone increased cell survival in p53 mutated malignant glioma cells and increased autophagy in PTENmutant malignant glioma cell but not in PTEN-wildtype cell. The difference of autophagy response could be mediated though the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin signaling pathway.
ABSTRACT
BACKGROUND AND PURPOSE: Although plasmapheresis is becoming standard practice as a rescue therapy for neuromyelitis optica (NMO), evidence for the therapeutic efficacy of plasmapheresis is limited, and the effect of plasmapheresis on anti-aquaporin-4 (AQP4) levels in patients with NMO has not been reported. Here, our objective was to evaluate the clinical efficacy of therapeutic plasmapheresis and its effect on anti-AQP4 antibody levels in patients with NMO spectrum disorder (NMOSD). METHODS: We retrospectively reviewed the medical records of 15 patients with NMOSD who had 18 acute attacks and received plasmapheresis because they did not respond to high-dose intravenous methylprednisolone (IVMP) therapy. Anti-AQP4 antibodies were measured before and after plasmapheresis. The primary outcomes were functional improvements immediately and 6 months after plasmapheresis, and the secondary outcome was the change in anti-AQP4 antibody serum levels following plasmapheresis. RESULTS: Plasmapheresis following IVMP therapy led to significant improvement in 50% of the 18 attacks in 15 patients immediately after the procedure was completed, and in 78% (14 attacks) after 6 months. Plasmapheresis was generally well tolerated in all patients. Anti-AQP4 antibody serum levels declined significantly following plasmapheresis, to a mean of 15% of the preplasmapheresis levels. Lower scores on the visual outcome scale recorded before an attack were associated with significant immediate improvement upon the completion of plasmapheresis (p=0.03). CONCLUSIONS: Plasmapheresis following IVMP therapy effectively removed anti-AQP4 antibodies and was accompanied by a substantial improvement in the neurological disability of patients with NMOSD. Lower levels of pre-existing neurological damage may be associated with an improved acute response to plasmapheresis.