大鼠延腦鼻端腹外側核區 NADPH 氧化酶衍生之超氧陰離子於內毒素引起心血管功能衰竭角色之探討

The Role of NADPH Oxidase-Derived Superoxide Anion in the Rostral Ventrolateral Medulla on Endotoxin-Induced Cardiovascular Depression in the Rat.

謝尹羚(Yin-Ling Hsieh)

指導教授 ： 許勤

共同指導教授 ： 華瑜(Julie Y. H. Chan)

高雄醫學大學/醫學院/生理及分子醫學研究所/碩士(2006年)

https://doi.org/10.6832/KMU.2006.00143

摘要

敗血症是臨床重症加護病房住院病人常見的死亡原因之一，是台灣地區十大死亡原因的第十二位，其作用機轉非常複雜。研究發現，敗血症的病人當中，約有一半的人會有低血壓的症狀；而血管的功能衰竭，更是導致組織灌流量不足，進而造成器官衰竭的主要因素之一。在延腦鼻端腹外側核區 (rostral ventrolateral medulla, RVLM) 神經細胞，藉由張性調控脊髓交感神經節前神經元活性，維持血壓動態平衡，是延腦調控血壓重要樞紐。實驗室過去研究結果顯示，於內毒素 (lipopolysaccharide, LPS) 引起之實驗性內毒素敗血症，心血管功能衰竭過程中，延腦鼻端腹外側核區的一氧化氮（nitric oxide, NO）與peroxynitrite (ONOO‾) 扮演重要角色；因為NO可與超氧陰離子（superoxide anion, O2‾）反應生成ONOO‾，而NADPH 氧化酶是細胞中超氧陰離子的主要來源之一，因此，我們想進一步研究，實驗性內毒素敗血症引起心血管功能衰竭過程中，延腦鼻端腹外側核區中由 NADPH 氧化酶產生的超氧陰離子所扮演之角色。

研究以成熟雄性的 Sprague-Dawley 大白鼠(體重270~350克) 為實驗動物，在持續靜脈灌流 propofol 麻醉狀況下；利用微量注射方式將lipopolysaccharide LPS (100 ng/50 nl) 投予至雙測延腦鼻端腹外側核區，模擬實驗性內毒素敗血症延腦鼻端腹外側核區參與之角色。實驗結果發現，LPS投予後在延腦鼻端腹外側核區組織中 NADPH 氧化酶不論是蛋白質或活性表現均顯著增加，並伴隨超氧陰離子含量之增高；相反地，以NADPH oxidase 抑制劑diphenyleneiodonium chloride (DPI, 1.25 nmol)，或以過氧化物歧化酶 (superoxide dismutase ) 模擬劑tempol (50 nmol)，預處理至雙側延腦鼻端腹外側核區，發現經 LPS 誘發之心血管功能衰弱情況顯著趨緩，大鼠存活時間亦明顯延長，並且 DPI 處理後可抑制超氧陰離子之產生。根據上述結果推論，在延腦鼻端腹外側核區中由 NADPH 氧化酶衍生而來的超氧陰離子，確實參與內毒素誘發心血管功能衰竭現象。

關鍵字

延腦鼻端腹外側核 ； NADPH 氧化酶超氧陰離子 ； 內毒素

並列摘要

Sepsis is a common cause of death in the patient of intensive care unit and is the 12th major cause of death in Taiwan. Sepsis is the results of complex systemic inflammatory responses to infection. In recent studies, it was found that hypotension develops in approximately half of the patients with sepsis, and cardiovascular depression is a major cause of inadequate tissue perfusion, leading to multiple organ dysfunctions. Our previous results indicate that nitric oxide (NO) and peroxynitrite (ONOO‾) at rostral ventrolateral medulla (RVLM), where sympathetic promotor neurons for the maintenance of arterial pressure are located, play important roles in the elicitation of cardiovascular depression during endotoxemia. Since NO reacts with superoxide anion (O2‾) to form ONOO‾, and NADPH oxidase is one of the major cellular sources of superoxide, we therefore investigated whether NADPH oxidase-derived superoxide in the RVLM participates in the elicitation of cardiovascular depression after LPS treatment. In adult, male Sprague-Dawley rats (body weight, 270~350 g) that were maintained under propofol anesthesia, microinjection bilaterally into the RVLM of E coli lipopolysaccharide (LPS, 100 ng/50 nl) induced progressive hypotension and bradycardia, alongside significant upregulation of protein expression and enzyme activity of gp91-phox or p47-phox subunit of NADPH oxidase, and increase in superoxide production in the RVLM. Microinjection bilaterally into the RVLM of a superoxide dismutase mimetic, Tempol, (50 nmol) or a NADPH oxidase inhibitor, diphenyleneiodonium chloride (DPI, 1.25 nmol), appreciably attenuated the LPS-induced cardiovascular depression and prolonged the survival time. DPI treatment also attenuated the LPS-promoted increase in superoxide production in the RVLM. These results suggest that NADPH oxidase-derived superoxide in the RVLM participates in the elicitation of cardiovascular depression after LPS treatment.

並列關鍵字

Rostral ventrolateral medulla ； NADPH oxidase ； superoxide anion ； endotoxin

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