腫瘤壞死因子α（TNF-α）是一種促進發炎反應的細胞素，當身體受到致病菌攻擊或其他傷害的刺激時，會引起急性反應導致生理的改變以調節局部或全身性的發炎反應，而Toll-like receptors（TLRs）可辨識多種病原分子，在由微生物引發的先天及後天免疫反應中扮演重要的角色。為研究TNF-α及TLR4在燒傷後因綠膿桿菌感染而引起死亡時所扮演的角色，首先將WT、Tnfrsf1a-/-及TLR4-/-小鼠在燙傷8小時後，於背部注射綠膿桿菌，並在燙傷24小時後取下肺部組織觀察其微血管滲漏及乾溼重比、MPO活性、NF-κB活性及iNOS、IL-1β、p-JNK及TLR4的表現等，結果顯示體表面積燙傷30%後注射綠膿桿菌分別在Tnfrsf1a-/-及WT小鼠上造成30%及60%的存活率。而用Tnfrsf1a-/-及WT小鼠進行60%體表面積燙傷時的存活率分別為100%及10%。進一步研究Tnfrsf1a-/-小鼠死亡率較高的原因時，發現Tnfrsf1a-/-小鼠肺部血管的滲漏、嗜中性白血球的浸潤、血液及肺的含菌量與TLR4、IL-1β、iNOS的表現量均較WT小鼠有明顯的增加，而燙傷後注射綠膿桿菌引發的NF-κB活性上升則只在WT的肺組織表現。當在Tnfrsf1a-/-及WT小鼠燙傷後立即給予iNOS抑制劑SMT時，可減少Tnfrsf1a-/-小鼠的肺水腫及血管滲漏情形，因此TNF-α可降低小鼠燙傷後感染綠膿桿菌造成死亡係經由調控TLR4及iNOS的活性。

Tumor necrosis factor-alpha (TNF-α) is a potent proinflammatory cytokine, inducing the acute-phase response that leads to physiological changes that serve to eliminate the infecting organisms. Toll-like receptors (TLRs) comprise a family of pattern-recognition receptors that detect conserved molecular products of microorganisms. To evaluate the role of TNF-α and TLRs in Pseudomonas aeruginosa infection-induced mortality in thermal injured mice, the wild type (WT), Tnfrsf1a-/-, and TLR4-/- mice were injected the P. aeruginosa in the back at 8 hr after 30% total body surface area burn. At 24 hr after burn, lung tissues of mice were harvested for assays of wet/dry ratio; microvascular dysfunction, myeloperoxidase (MPO) activity, NF-κB DNA binding activity; and expression of IL-1β, iNOS, p-JNK, and TLR4. Injection of P. aeruginosa after burn induced a survival rate in Tnfrsf1a-/- 60% TBSA burn=100%, WT 60% TBSA burn=10%, WT 30% TBSA burn +P.A = 60%, Tnfrsf1a-/- 30% TBSA burn+p.A. = 30%. respectively. The high mortality in Tnfrsf1a-/- mice is related to a significant increase of pulmonary microvascular dysfunction; neutrophil infiltration, bacterial counts of blood and lung; and expression of TLR4, IL-1β, and iNOS as compared with WT mice. On the contrary, significant increase of NF-κB DNA binding activity of lung was observed only in WT mice. When iNOS inhibitor SMT was given immediately after burn to WT and Tnfrsf1a-/- mice, the P. aeruginosa induced increases of pulmonary edema, pulmonary permeability, and lung bacterial counts were decreased significantly in Tnfrsf1a-/- mice, suggesting that TNF-α decreases P. aeruginosa-induced mortality in burned mice is through a negative regulation of TLR4 and iNOS.

Abstract in Chinese…………………………………………………………3
Abstract in English………………………………………………………….4
Introduction…………………………………………………………………5
Materials and Methods……………………………………………………..11
Results……………………………………………………………………...20
Discussion………………………………………………………………….29
Figures……………………………………………………………………...34
References…………………………………………………………………43

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