SCOPE: Glutamate excitotoxicity has been observed in association with neurodegenerative disorders. This study aimed to investigate whether a phycoerythrin-derived tryptic peptide of Pyropia yezoensis (PYP) reduces glutamate-induced excitotoxicity and neuronal senescence in primary rat hippocampal neurons. METHODS AND RESULTS: Glutamate exposure (100 μm) decreased cell viability and increased expression of endoplasmic reticulum (ER) stress response protein glucose-regulated protein 78 (GRP78) starting at 60 min following glutamate exposure, which was prevented by pretreating the neurons with PYP (1 μg mL-1 ). The glutamate-induced increase in GRP78 expression was downregulated by blocking N-methyl-d-aspartate (NMDA) receptor with MK801 (10 μm) and inhibiting c-Jun N-terminal kinase (JNK) phosphorylation with SP600125 (10 μm). Moreover, phosphorylation of JNK was decreased by blockade of NMDA receptor. The PYP pretreatment downregulated glutamate-induced increase in GRP78 expression and JNK phosphorylation, and this effect was abolished by inhibiting tropomyosin-related kinase B (TrkB) receptor, phosphatidylinositiol 3-kinase, and extracellular signal-regulated kinase (ERK)1/2 using cyclotraxin B (200 nm), LY294002 (20 μm), and SL327 (10 μm), respectively. In addition, PYP downregulated increase in GRP78 expression, senescence-associated β-galactosidase activity, and neurite degeneration in aging hippocampal neurons. CONCLUSION: These findings indicate that activation of TrkB receptor-mediated ERK1/2 by PYP attenuates glutamate-induced ER stress, which may improve the survival of hippocampal neurons with age.
SCOPE: Glutamate excitotoxicity has been observed in association with neurodegenerative disorders. This study aimed to investigate whether a phycoerythrin-derived tryptic peptide of Pyropia yezoensis (PYP) reduces glutamate-induced excitotoxicity and neuronal senescence in primary rat hippocampal neurons. METHODS AND RESULTS:Glutamate exposure (100 μm) decreased cell viability and increased expression of endoplasmic reticulum (ER) stress response protein glucose-regulated protein 78 (GRP78) starting at 60 min following glutamate exposure, which was prevented by pretreating the neurons with PYP (1 μg mL-1 ). The glutamate-induced increase in GRP78 expression was downregulated by blocking N-methyl-d-aspartate (NMDA) receptor with MK801 (10 μm) and inhibiting c-Jun N-terminal kinase (JNK) phosphorylation with SP600125 (10 μm). Moreover, phosphorylation of JNK was decreased by blockade of NMDA receptor. The PYP pretreatment downregulated glutamate-induced increase in GRP78 expression and JNK phosphorylation, and this effect was abolished by inhibiting tropomyosin-related kinase B (TrkB) receptor, phosphatidylinositiol 3-kinase, and extracellular signal-regulated kinase (ERK)1/2 using cyclotraxin B (200 nm), LY294002 (20 μm), and SL327 (10 μm), respectively. In addition, PYP downregulated increase in GRP78 expression, senescence-associated β-galactosidase activity, and neurite degeneration in aging hippocampal neurons. CONCLUSION: These findings indicate that activation of TrkB receptor-mediated ERK1/2 by PYP attenuates glutamate-induced ER stress, which may improve the survival of hippocampal neurons with age.