| Summary: | 碩士 === 慈濟大學 === 分子生物暨人類遺傳學系碩士班 === 99 === Neurodegenerative diseases such as Alzheimer’s disease (AD) are associated with progressive degeneration and loss of neuronal function in the brain. Patients with neuronal dysfunction in the brain accompanied losses of cognition and learning memory. It has been reported that several dietary flavonoids may transverse the blood-brain-barrier (BBB) and exert beneficial effects on the neurogenesis, neuronal differentiation, neuronal cell survival, and may prevent cognitive losses associated with neurodegeneration.
Luteolin (3',4',5,7-tetrahydroxyflavone), a food-derived flavonoid, has been reported to possess antioxidant, anti-inflammatory, and anticancer activities. In the previous study, we have reported that luteolin induced neurite outgrowth and neuronal differentiation in PC12 cells, however, the detail mechanism is remained unclear. Recently, up-regulation of microRNA 132 (miR-132) has been reported involved in the neurogenesis, neuronal development, and neuronal differentiation. The aim of this study is to investigate the effects of luteolin on the neurotrophic miR-132 and the molecular mechanism underlying the luteolin-mediated neurotrophic action in PC12 cells.
In the present study, we found that luteolin significantly enhanced pre-miR-132 and miR-132 expression in PC12 cells. After transfection of microRNA blocker into PC12 cells, luteolin-mediated neurite outgrowth significantly reduced by the anti-miR-132. This result indicated that miR-132 was up-regulated by luteolin and involved in the neurite outgrowth in PC12 cells. It has been known that cyclic AMP response element binding protein (CREB) is a major transcription factor for miR-132 transcription. Our results showed that luteolin significantly induced the phosphorylation of CREB and activated the cAMP response element (CRE)-mediated reporter gene transcription in PC12 cells. Furthermore, after treatment of CREB activity inhibitor (KG-501) was significantly attenuated CRE-mediated transcription activity and luteolin-induced neurite outgrowth. To identify the molecular signaling pathways involved in the activation of CREB, the pathway selectively specific inhibitors including U0126, bisindolylmaleimide I (BIM)、SQ22536、H-89、KN-62 and LY294002 were used. Our results showed that CREB activation by luteolin via MAPK/ERK, PKA and cAMP signaling pathways. Moreover, we also verified that MAPK/ERK, PKA and cAMP pathways involved in the luteolin-mediated miR-132 expression.
In conclusion, these results indicated that MAPK/ERK, PKA and cAMP signaling pathways activation coupling with CREB-mediated miR-132 expression may be contributed to luteolin-mediated neurite outgrowth in PC12 cells. This study implies that activation of miR-132 expression may be beneficial for prevention and therapeutic use for neurodegenerative disorders.
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