| 摘要: | 黃芩是傳統中藥常用的藥物，可清熱燥濕、瀉火解毒、止血、安胎。Baicalein (黃芩素) 及 wogonin (漢黃芩素) 是黃芩的二種主要黃酮素 (flavones)，被證實具有抗氧化及抗發炎作用。本論文的研究目的：於急性發炎動物模式下，探討 wogonin 及 baicalein 是否可產生活體心臟的保護作用；(1) 大鼠麻醉後進行開胸手術，將冠狀動脈結紮四十五分鐘，再循環二小時期，觀察 wogonin (5, 10, 20 mg/kg, ip) 是否可以降低心臟損傷，並探討可能機轉；(2) 將清醒動物靜脈注射 lipopolysaccharide (LPS) 10 mg/kg以誘發敗血症，注射 LPS 半小時後再給 baicalein 10 mg/kg，於 LPS 注射六小時後，觀察 baicalein 是否可以改善敗血症引起的心臟功能不良，並探討可能機轉。於心肌缺血-再循環模式下，預先給予 wogonin 10 mg/kg 可以明顯延後心肌缺血造成的心室早期收縮 (ventricular premature contractions; VPC) 及心室性心搏過速 (ventricular tachycardia; VT) 發生，可明顯抑制 VT 及心室性纖維顫動 (ventricular fibrillation; VF) 之發生率，可明顯降低心肌缺血造成的死亡率，亦可明顯降低心律不整分數 (Arrhythmia Scores)。但是低劑量及高劑量 wogonin (5 & 20 mg/kg) 未能明顯改善心律不整。再循環期間，wogonin (10 mg/kg) 可以明顯降低心肌組織釋放超氧游離基 (superoxide anion)，及血漿中組織壞死因子 (tissue necrosis factor-α) 含量，再循環二小時後，缺血區內心肌組織內單核球趨化蛋白-1 (monocyte chemoattractant protein-1; MCP-1)、磷酸化 p38 mitogen-activated protein kinase (p38 MAPK)、磷酸化 p65、磷酸化 IκBα 以及活化態 caspase-3 蛋白質表現量明顯增加，而 wogonin (10 mg/kg) 可以明顯降低上述蛋白質表現量。另外，於敗血症模式下，LPS 投予六小時後血壓心跳明顯下降，離體心臟收縮功能明顯降低，給予 baicalein 可以維持血壓免於休克，心跳明顯增加，心臟收縮功能亦明顯改善；LPS 投予六小時後心室肌內血基質氧化酶-1 (heme oxygenase-1; HO-1) 蛋白明顯低於 sham 組，baicalein 可以明顯增加 HO-1 表現量，並且降低心室組織超氧游離基含量；LPS 投予六小時後心室組織內 inducible nitric oxide synthase、MCP-1、磷酸化 p65、磷酸化 IκBα 蛋白質表現量及 caspase-3 活性明顯增加，給予 baicalein 後可以明顯降低上述蛋白表現量以及caspase-3 活性。結論：wogonin 於心肌缺血時具有抗心律不整作用，可降低死亡率，並且改善缺血-再循環引起之發炎反應及心肌傷害 (壞死及凋亡)，wogonin 可能藉由其抗氧化作用及抑制細胞內 NF-κB 及 p38 MAPK 訊息傳遞路徑之活化而達到此保護作用； baicalein 改善敗血症引起之心臟收縮功能不良，此與 baicalein 可降低氧化壓力、抗發炎作用及減少細胞凋亡有關。由此活體實驗結果可知： wogonin 及 baicalein 可以保護心臟免於急性發炎的傷害。
Wogonin and baicalein are flavonoids isolated from Scutellaria baicalensis Georgi, a traditional Chinese medicine, and possesses antioxidant and anti-inflammatory effects. The aims of this study are (1) to investigate the in vivo effect of wogonin on myocardial ischemia/reperfusion injury in an open-chest anesthetized rat model, which was induced by 45-min left coronary artery occlusion and 2-h reperfusion; (2) to evaluate the protective effect of baicalein on myocardial dysfunction caused by endotoxemia in rats and to explore the possible mechanisms. Rats were treated with wogonin (5, 10, and 20 mg/kg, i.p.) 40 min prior to ischemia or treatment with wogonin 10 mg/kg 15 min after occlusion. Pretreatment with wogonin 10 mg/kg significantly delayed the occurrence of ventricular premature contractions and tachycardia, and suppressed the incidence of ventricular tachycardia and ventricular fibrillation, and mortality elicited by ischemia when compared with the control group, accompanied with reducing the arrhythmia scores. After 2-h reperfusion, pre- and post-treatment with wogonin 10 mg/kg significantly reduced the infarct size, and plasma levels of creatine kinase-muscle-brain fraction and lactate dehydrogenase. Wogonin also significantly reduced the elevation of plasma tissue necrosis factor-?? and superoxide anion production in myocardium with ischemia/reperfusion. The expression of monocyte chemoattractant protein-1 (MCP-1), phosphorylated p38 mitogen-activated protein kinase (MAPK), p65 and IκBα, and active caspase-3 in ischemic myocardium pronouncedly increased in the control group, those were significantly attenuated by treatment with wogonin. On the other hand, baicalein (10 mg/kg, i.v.) was administered to conscious Wistar rats 30 min after lipopolysaccharide (LPS; 10 mg/kg, intravenous) challenge. Six hours after LPS administration, the contractile function of the isolated heart was examined using the Langendorff technique. Post-treatment with baicalein significantly attenuated the LPS-induced hypotension with accompanying tachycardia. The contractile function of isolated heart was significantly preserved 6 h after LPS administration, following treatment with baicalein. Furthermore, baicalein induced the expression of heme oxygenase-1 protein and reduced superoxide anion formation in the myocardium of LPS-treated rats. Cardiac levels of inducible nitric oxide synthase, monocyte chemoattractant protein-1, phospho-I?羠?? and phospho-p65 protein and caspase-3 activity significantly increased 6 h after LPS challenge but baicalein significantly attenuated these LPS-induced changes. In conclusion, wogonin demonstrated in vivo cardioprotective effects by attenuation of the severity of ischemia-induced arrhythmias and irreversible ischemia/reperfusion injury, which is associated with its antioxidant capacity, and anti-inflammatory effects. Suppression of nuclear factor-?羠 and p38 MAPK activation, and inhibition of monocyte chemoattractant protein-1 expression contribute to the beneficial effects of wogonin. Baicalein improves myocardial contractility in LPS-induced sepsis, which may be related to reductions in oxidative stress, myocardial inflammatory responses and apoptosis. |
