外膜蛋白OmpA在大腸桿菌侵入及活化星狀細胞扮演角色之探討

Study on the OmpA-Mediated Escherichia coli Invasion and Activation of Astrocyte

吳雪霞(Hsueh-Hsia Wu)

指導教授 ： 陳美如

國立臺灣大學/醫學院/微生物學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.10625

摘要

大腸桿菌為引起新生兒腦膜炎主要的革蘭氏陰性細菌，外膜蛋白OmpA是大腸桿菌外膜的主要蛋白質成分之ㄧ，在大腸桿菌與宿主細胞間相互作用上扮演重要的角色。為研究外膜蛋白OmpA在大腸桿菌侵入星狀細胞時的重要性，我們發現OmpA+大腸桿菌菌株E44，E105以及E109相對於OmpA-菌株E91和E111具有高約10至15倍的附著和侵入C6神經膠瘤細胞的能力。細胞內肌動蛋白（actin）的重组，酪氨酸蛋白激酶（protein tyrosine kinase）和磷脂醯肌醇-3激酶（phosphoinositide 3-kinase）的活化都參與在此侵入的過程中。在試管內E44感染C6細胞株的實驗或C57BL/6小鼠經由顱內注射E44的感染，都會刺激星狀細胞過度表現其活化指標膠質纖維酸性蛋白（glial fibrillary acidic protein），同時也會刺激細胞表現發炎性介質，如環氧酵素2（cyclooxygenase 2）以及誘導型一氧化氮合成酶（nitric oxide synthase 2）等。C57BL/6小鼠經由顱內注射E44感染後36小時內會死亡，相對地，如果細菌注射時同時給予純化的重組OmpA蛋白，則能使小鼠有80%的存活率。染色觀察小鼠腦部組織切片，發現重組OmpA蛋白可以抑制細菌感染後所引起的星狀細胞被激活以及嗜中性白血球的浸潤。總言之，本研究的結果顯示大腸桿菌藉由外膜蛋白OmpA附著進而侵入星狀細胞，在細菌感染初期所引起的腦部傷害扮演著重要的角色，同時也暗示其在大腸桿菌腦膜炎治療與預防上可能的應用。

關鍵字

大腸桿菌 ； 外膜蛋白A ； 星狀細胞 ； 膠質纖維酸性蛋白 ； 環氧酵素2 ； 誘導型一氧化氮合成酶

並列摘要

Escherichia coli is the major Gram-negative bacteria pathogen in neonatal meningitis. Outer membrane protein A (OmpA) is a conserved major protein in the E. coli outer membrane and is involved in several host-cell interactions. To characterize the role of OmpA in the invasion of astrocytes by E. coli, we investigated OmpA-positive and OmpA-negative E. coli strains. Outer membrane protein A + E44, E105, and E109 strains adhered to and invaded C6 glioma cells 10- to 15-fold more efficiently than OmpA-negative strains. Actin rearrangement, protein tyrosine kinase, and phosphoinositide 3-kinase activation were required for OmpA-mediated invasion by E. coli. In vitro infection of C6 cells and intracerebral injection into mice of the E44 strain induced expression of the astrocyte differentiation marker glial fibrillary acidic protein and the inflammatory mediators cyclooxygenase 2 and nitric oxide synthase 2. After intracerebral infection with E44, all C57BL/6 mice died within 36 hours, whereas 80% of mice injected with E44 premixed with recombinant OmpA protein survived. Astrocyte activation and neutrophil infiltration were reduced in brain tissue sections in the mice given OmpA. Taken together, these data suggest that OmpA-mediated invasion plays an important role in the early stage of E. coli-induced brain damage, and that it may have therapeutic use in E. coli meningitis.

並列關鍵字

Astrocyte ； Cyclooxygenase 2 ； Escherichia coli ； Glial fibrillary acidic protein ； Nitric oxide synthase 2 ； Outer membrane protein A

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