Pharmacology and Anesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Perth, Australia.
J Pharmacol Exp Ther. 2012 Feb;340(2):377-85. doi: 10.1124/jpet.111.187872. Epub 2011 Nov 7.
The principal aim of the study was to determine the influence of influenza A virus infection on capsaicin-induced relaxation responses in mouse isolated tracheal segments and clarify the underlying mechanisms. Anesthetized mice were intranasally inoculated with influenza A/PR-8/34 virus (VIRUS) or vehicle (SHAM), and 4 days later tracheal segments were harvested for isometric tension recording and biochemical and histologic analyses. Capsaicin induced dose-dependent relaxation responses in carbachol-contracted SHAM trachea (e.g., 10 μM capsaicin produced 66 ± 4% relaxation; n = 11), which were significantly inhibited by capsazepine [transient receptor potential vanilloid type 1 (TRPV1) antagonist], (2S,3S)-3-{[3,5-bis(trifluoromethyl)phenyl]methoxy}-2-phenylpiperidine hydrochloride (L-733,060) [neurokinin 1 (NK₁) receptor antagonist], indomethacin [cyclooxygenase (COX) inhibitor], and the combination of 6-isopropoxy-9-oxoxanthene-2-carboxylic acid (AH6809) and 7-[5α-([1S,1α(Z)-biphenyl]-4-ylmethoxy)-2β-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid, calcium salt, hydrate (AH23848) [E-prostanoid (EP)₂ and EP₄ receptor antagonists, respectively], indicating that capsaicin-induced relaxation involved the TRPV1-mediated release of substance P (SP), activation of epithelial NK₁ receptors, and production of COX products capable of activating relaxant EP₂/EP₄ receptors. Consistent with this postulate, capsaicin-induced relaxation was associated with the significant release of SP and prostaglandin E₂ (PGE₂) from mouse tracheal segments. As expected, influenza A virus infection was associated with widespread disruption of the tracheal epithelium. Tracheal segments from VIRUS mice responded weakly to capsaicin (7 ± 3% relaxation) and were 25-fold less responsive to SP than tracheas from SHAM mice. In contrast, relaxation responses to exogenous PGE₂ and the β-adrenoceptor agonist isoprenaline were not inhibited in VIRUS trachea. Virus infection was associated with impaired capsaicin-induced release of PGE₂, but the release of SP was not affected. In summary, influenza A virus infection profoundly inhibits capsaicin- and SP-induced relaxation responses, most likely by inhibiting the production of PGE₂.
本研究的主要目的是确定甲型流感病毒感染对小鼠离体气管段中辣椒素诱导松弛反应的影响，并阐明其潜在机制。用甲型流感病毒 A/PR-8/34（VIRUS）或载体（SHAM）滴鼻感染麻醉小鼠，4 天后收获气管段进行等长张力记录和生化及组织学分析。在乙酰胆碱收缩的 SHAM 气管中，辣椒素诱导出剂量依赖性的松弛反应（例如，10 μM 辣椒素产生 66±4%的松弛；n=11），这种反应被辣椒素敏感瞬时受体电位香草酸亚型 1（TRPV1）拮抗剂（capsazepine）、（2S,3S）-3-{[3,5-双（三氟甲基）苯基]甲氧基}-2-苯基哌啶盐酸盐（L-733,060）（神经激肽 1（NK₁）受体拮抗剂）、吲哚美辛（环氧化酶（COX）抑制剂）以及 6-异丙氧基-9-氧杂-9H-芴-2-羧酸和 7-[5α-([1S,1α（Z）-联苯]-4-基甲氧基）-2β-（4-吗啉基）-3-氧代环戊基]-4-庚烯酸钙盐，水合物（AH23848）（分别为前列腺素 E₂（EP₂）和 EP₄ 受体拮抗剂）联合抑制，表明辣椒素诱导的松弛反应涉及 TRPV1 介导的 P 物质（SP）释放、上皮 NK₁ 受体的激活以及能够激活松弛性 EP₂/EP₄ 受体的 COX 产物的产生。与这一假设一致，辣椒素诱导的松弛反应与从小鼠气管段中明显释放 SP 和前列腺素 E₂（PGE₂）有关。正如预期的那样，甲型流感病毒感染与气管上皮的广泛破坏有关。与 SHAM 小鼠的气管相比，来自 VIRUS 小鼠的气管对辣椒素的反应较弱（7±3%的松弛），对 SP 的反应低 25 倍。相比之下，在 VIRUS 气管中，对外源性 PGE₂和β-肾上腺素能激动剂异丙肾上腺素的松弛反应没有被抑制。病毒感染与辣椒素诱导的 PGE₂释放受损有关，但 SP 的释放不受影响。总之，甲型流感病毒感染可显著抑制辣椒素和 SP 诱导的松弛反应，这很可能是通过抑制 PGE₂的产生来实现的。
