大腸桿菌感染影響膀胱功能機制之探討

泌尿道感染為婦女常見的傳染病。據統計婦女終其一生約有百分之六十的機會至少曾經罹患過一次泌尿道感染。而在急診常見的感染急症中，泌尿道感染亦是最常見引起敗血症的原因。大腸桿菌是常引起人類感染的致病菌，而其也是最常引起泌尿道感染的致病菌。即使在抗生素使用十分普遍的現在，泌尿道感染仍是常見且重要的感染症。近來有許多關於泌尿道感染的分子生物相關研究，其重點多在於細菌的致病因素(virulence factors)和宿主膀胱表皮細胞(uroepithelium)上的接受器(receptors)之間的關係。而動物實驗則對於細菌進入動物膀胱後所引起的免疫反應，細胞凋亡，和恢復方式，提供強而有力的證據。而無論是細胞或動物實驗對於幫助我們了解細菌如何導致泌尿道感染的致病機轉，以及其如何上升感染(ascending infection)至腎臟，皆有莫大的幫助。過去的研究已知當細菌入侵時，膀胱表皮細胞(uroepitheliumm) 所組成的屏障 (barrier)遭受破壞，使細菌足以入侵膀胱之內層組織。當膀胱表皮細胞被破壞後，將改變膀胱表面的滲透力(permeability)，此時膀胱表皮細胞將啟動免疫反應，分泌細胞激素(cytokines)，例如: IL-8，IL-6等，更進一步吸引嗜中性細胞(neutrophils)，巨噬細胞(macrophages)的活化，分泌更多的細胞激素(cytokines，chemokines等)，而這些反應也將造成神經傳導的改變，此對於泌尿道感染所引起的生理反應和症狀，應佔有非常重要的角色，但相關的研究並不多。目前關於細菌所導致泌尿道感染的研究，有許多研究是取細菌本身的部分致病因子來從事相關研究。關於大腸桿菌則以取其內毒素(lipopolysaccharides)， N-formylmethionyl oligopeptides和lipoteichoic acid以上這些和細菌所引起泌尿道感染致病力有密切相關的成分進行研究。但對於細菌感染或使用細菌的致病因子所導致膀胱的感染染所造成的生理病理變化，二者的現象和機制是否完全相同，目前則不十分清楚。故在我們的研究中，將探索泌尿道感染後其對膀胱detrusor muscle收縮力所造成的影響。我們的假說是膀胱在細菌感染後，其detrusor muscle在感染早期和晚期可能有不同的變化，並探討其相關機制。在泌尿系統中，一氧化氮一直被認為和泌尿道感染後細胞所受到的傷害和生理病理變化息息相關。在各種細菌所引起的泌尿道感染中，我們也都可以短時間內其會藉由eNOS活化導致一氧化氮產生大量增加，而長時間後則觀察到inducible NO synthase (iNOS)的mRNA大量表現和蛋白質的活化，而藉由iNOS所產生的一氧化氮將持續相當長的時間，且其產出量十分可觀。雖然在正常生理情況下所產生的一氧化氮對膀胱detrusor muscle的收縮影響甚小，但是在感染後如此高濃度一氧化氮的刺激下，其對於膀胱detrusor muscle的收縮是否有所影響呢? 在我們的研究中將探討在泌尿道感染的不同時期中，一氧化氮產生的來源，以及其對detrusor muscle生理病理變化的影響。此外，過去的研究中也已知PKC的活化和膀胱得收縮息息相關，而在泌尿道感染時，PKC所扮演的角色則不十分清楚，故在本研究中亦將觀察PKC在此情況下所扮演的角色。而在過去的研究中已知pERK具有調控PKC所影響平滑肌收縮的能力，故本研究亦將觀察ERK在此情況下對膀胱收縮的影響。我們的發現為無論是內毒素或細菌對膀胱所造成的感染，早期和晚期對膀胱收縮的影響有所不同。在膀胱注射細菌或內毒素一小時後，二者皆透過eNOS的活性表現增加來增加膀胱detrusor muscle的收縮力，但是內毒素乃藉由PKC活化的增加進而增加detrusor muscle的收縮力，但是細菌可能藉由eNOS的活性增加導致一氧化氮產量改變而導致膀胱收縮的增加。而在內毒素所導致泌尿道感染二十四小時後，則藉由iNOS的表現增加，進而減少PKC的活性，導致detrusor muscle收縮減少。然而在細菌所導致泌尿道感染長時間的作用下，iNOS則藉由調控ERK1/2使得detrusor muscle收縮力下降，反而與PKC的活化無關。由此推論細菌和內毒素所導致detrusor muscle收縮改變的機轉不同。本研究的臨床意義為可以解釋病人在泌尿道感染初期時，膀胱收縮增加所導致病人頻尿的現象，而在細菌長時間感染後，可能藉由膀胱收縮力之下降，而導致細菌更容易吸附在泌尿系統表皮細胞上造成上升感染，進而造成急性腎盂腎炎。本研究未來的目標希望能利用活體實驗，進一步了解泌尿道感染後對膀胱收縮功能的影響，並探討糖尿病大鼠罹患泌尿道感染後，對膀胱收縮功能的影響並探討其機制。

關鍵字

大腸桿菌；膀胱感染

並列摘要

Urinary tract infections (UTIs) are among the most common infectious diseases acquired women. It is estimated that as many as 60% of all women report having had a UTI at least once in their lifetime. Escherichia coli are one of the major causes of human infectious diseases and are also the most common cause of urinary tract infection. Recent advances at the molecular level include the elucidation of the structural basis for contacts between primary bacterial virulence factors and key host epithelial receptors. At the microscopic level, the animal model offers a powerful system to examine the temporal and spatial expression of virulence determinants during cystitis. Synergy between such approaches will lead to the development of novel strategies for the pathogenesis of Otis and related ascending infections. The pathophysiology of cystitis is incompletely understood, although altered epithelial permeability, mast cell activation and sensory afferent nerve reaction have critical roles. These factors probably participate in the symptoms of cystitis. Current evidence supports a role for products of uropathogenic bacteria, such as lipopolysaccharides, N-formylmethionyl oligopeptides and lipoteichoic acids, as major factors in the morbidity of infectious cystitis. However, the exact mechanisms by which bacteria and bacterial products cause the symptoms of cystitis are poorly understood. In the present study, we investigated the effects of infection on myogenic tone in the detrusor muscle from rat. We hypothesized that myogenic tone was changed in the contractility of detrusor muscle during early and late infection. . In urinary system, NO has been implicated in the mechanisms of cell injury and long-term physiological changes in the infectious stimulation. In various forms of urinary tract infection, there is increased expression and activation of endothelial NO synthase (eNOS) initially, and inducible NO synthase (iNOS) latter. The production of NO from iNOS is sustained and is of high output. The specific functions of iNOS in UTIs remain elusive. We examined the possible mechanisms by which NO may influence the function of the lower urinary tract, emphasizing the source and synthesis of NO, its mechanisms of action and its evolving role in the pathophysiology of urinary tract infection. The functional importance of PKC in the regulation of detrusor muscle tone during urinary tract infection is also still unclear. We considered the mechanisms of experimentally manipulated PKC activity and attempt to assess them in a physiological context. Extracellular signal-regulated kinase (ERK) has been shown to play an important role in the regulation of PKC-mediated smooth muscle contractility. We also investigated the role of ERK in the regulation of detrusor muscle myogenic tone and its adaptation to infection. These results indicate that there are different mechanisms involved in the alteration of urinary bladder contractions after short-term and long-term treatment of LPS or UPEC. Short-term intravesical instillation of LPS and UPEC enhances detrusor contractions through an eNOS-related pathway. An iNOS-regulated PKC signaling may participate in causing the inhibition of muscle contractions in urinary bladder induced by long-term LPS treatment. However, iNOS-regulated ERK1/2 signaling may be involved in long-term UPEC treatment–induced responses. These data suggest bacterial activation of the resident macrophage and urinary bladder network could participate in causing the frequency symptoms of bacterial cystitis initially. The long term stimulation of UPEC or LPS causes the contractility to decrease, allowing adherence of the bacteria to the urinary bladder. It may cause the ascending infection to the kidney. Our further aims will be to ascertain the causes of the different mechanisms in bladder responses induced by UPEC and LPS in diabetic rats.

並列關鍵字

Uropathogenic Escherichia coli ； lipopolysaccharide ； bladder ； contraction ； inducible nitric oxide synthase ； protein kinase C ； extracellular signal-regulated kinase (ERK)

參考文獻

Abrams, P., Cardozo, L., Fall, M., Griffiths, D., Rosier, P., Ulmsten, U., van Kerrebroeck, P., Victor, A., and Wein, A. (2002). The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn 21, 167-178.

Abrutyn, E., Mossey, J., Berlin, J. A., Boscia, J., Levison, M., Pitsakis, P., and Kaye, D. (1994). Does asymptomatic bacteriuria predict mortality and does antimicrobial treatment reduce mortality in elderly ambulatory women? Ann Intern Med 120, 827-833.

Adam, L. P., Franklin, M. T., Raff, G. J., and Hathaway, D. R. (1995). Activation of mitogen-activated protein kinase in porcine carotid arteries. Circ Res 76, 183-190.

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大腸桿菌感染影響膀胱功能機制之探討

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