Cellular and molecular mechanism underlying neuroprotective effects of wogonin against brain injury induced by ischemia/reperfusion

• Main Authors: Wang, Cyong-Ling, 王瓊玲
• Other Authors: Wang, Jia-Yi
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/49146605934610470406

碩士 === 國防醫學院 === 生理學研究所 === 95 === Focal cerebral ischemia-reperfusion (I/R) results in characteristic histopathological changes that manifest as a “necrotic core” in which cells die rapidly, and a surrounding “penumbra” region of variable size in which neurons die over an extended time period of days to weeks. In this thesis, I used a rat model of focal cerebral I/R by microinjection of endothelin-1 (400 pmol in 20 μl saline) to middle cerebral artery and unilateral ligation of common carotid artery. Cerebral ischemia, as evidenced by the decrease of the regional cerebral blood flow to 20~25% of the control, followed by 24 hr reperfusion (I/R24) produced stable and reproducible infarcts. Using this animal model we examined the effect of wogonin, which is an active component isolated from Scutellaria baicalensis, on I/R-induced tissue injury and behavioral deficit. Our results indicated that wogonin at the dose of 15 mg/kg (administered 20 min after I/R, i.p.), but not 10 mg/kg, significantly reduced the infarct volume following I/R 24 as well as the number of Fluoro-Jade B positive degenerating neurons in penumbra. Levels of mRNA encoding for Bax, a pro-apoptotic protein (Bax) in penumbra tissue increased gradually following I/R but was attenuated by wogonin treatment. Motor asymmetry, evaluated by swing test and modified neurological severity score (mNSS), resulted from I/R24 was also significantly improved by wogonin. The potential mechanism underlying this neuroprotective effect of wogonin was further studied. Animals were subjected to I/R for various time intervals, and sacrificed after functional evaluations. Wogonin attenuated the increase of cytokine levels in cerebrospinal fluid including TNF-a, IL-1b and IL-6 at I/R 6. Time course of mRNA expression for TNF-a , IL-1b,IL-6 and IL-18 indicated that the maximal levels of cytokine mRNA expression were after I/R 6. Wogonin reduced levels of mRNA encoding for pro-inflammatory cytokines (TNF-, IL-1, IL-6 and IL-18) after I/R 6 . Wogonin also dose-dependenly supressed I/R-induced elevation on levels of mRNA encoding enzyme synthesizing inflammatory mediators (iNOS,COX-2). Wogonin also significantly reduced in vivo superoxide production as early as I/R30min to I/R60min. Taken together, post-treatment of wogonin improved functional deficit and reduced extent of brain damage, with a concomitant reduced mRNA expression of pro-inflammatory proteins and pro-apoptotic protein in ischemic penumbra and reduced levels of pro-inflammatory cytokines in CSF. Wogonin also significantly reduced superoxide production in vivo. These data suggest the neuroprotective effects of wogonin in ischemic injury might be attributed to its anti-inflammatory, antioxidant, and anti-apoptotic mechanisms.