Smith Lane M, Wells Jonathan D, Vachharajani Vidula T, Yoza Barbara K, McCall Charles E, Hoth J Jason
From the Departments of Emergency Medicine (L.M.S.), General Surgery (J.J.H., J.D.W., B.K.Y.), and Anesthesiology/Critical Care (V.T.V.), and Section on Molecular Medicine (C.E.M.), Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina.
J Trauma Acute Care Surg. 2015 May;78(5):1034-8. doi: 10.1097/TA.0000000000000598.
Pulmonary contusion (PC) is a common, potentially lethal injury that results in priming for exaggerated inflammatory responses to subsequent immune challenge like infection (second hit). The molecular mechanism of priming and the second hit phenomenon after PC remain obscure. With the use of a mouse model of PC, this study explores the role of sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, in priming for a second hit after injury.
With the use of a mouse model of PC, injury-primed second-hit host responses were tested at 24 hours after PC by (1) in vivo infectious challenge of injured mice or (2) ex vivo inflammatory challenge of isolated immune cells from injured mice. SIRT activators or repressors were used to test for SIRT1 participation in these second-hit responses.
PC-injured mice given an in vivo infectious challenge by cecal ligation and puncture (CLP) had significantly increased mortality compared with injury or infectious challenge alone. Isolated bronchoalveolar lavage (BAL) cells from injured mice given an ex vivo inflammatory challenge with bacterial lipopolysaccharide (LPS) had increased levels of tumor necrosis factor α messenger RNA compared with uninjured mice. We found that PC reduced SIRT1 protein, messenger RNA, and SIRT1 enzymatic activity in injured lung tissue. We also found decreased SIRT1 protein levels in BAL cells from injured mice. We further found that injured mice treated with a SIRT1 activator, resveratrol, showed significantly decreased polymorphonuclear leukocytes (PMN) in the BAL in response to intratracheal LPS and increased survival from CLP.
These results showed that PC decreased SIRT1 levels in the lung correlated with enhanced responses to infectious or inflammatory stimuli in injured mice. Treatment of injured mice with a SIRT1 activator, resveratrol, decreased LPS inflammatory response and increased survival after CLP. Our results suggest that SIRT1 participates in the second-hit response after injury.
肺挫伤（PC）是一种常见的、具有潜在致命性的损伤，会引发对后续免疫挑战（如感染，即“二次打击”）的过度炎症反应。PC后引发炎症及二次打击现象的分子机制仍不清楚。本研究利用PC小鼠模型，探讨烟酰胺腺嘌呤二核苷酸（NAD⁺）依赖性脱乙酰酶沉默调节蛋白1（SIRT1）在损伤后引发二次打击中的作用。
利用PC小鼠模型，在PC后24小时通过以下方式测试损伤引发的二次打击宿主反应：（1）对受伤小鼠进行体内感染攻击；（2）对从受伤小鼠分离出的免疫细胞进行体外炎症刺激。使用SIRT激活剂或抑制剂来测试SIRT1是否参与这些二次打击反应。
与单独的损伤或感染攻击相比，经盲肠结扎穿孔术（CLP）进行体内感染攻击的PC损伤小鼠死亡率显著增加。与未受伤小鼠相比，用细菌脂多糖（LPS）进行体外炎症刺激的受伤小鼠分离出的支气管肺泡灌洗（BAL）细胞中，肿瘤坏死因子α信使核糖核酸水平升高。我们发现，PC降低了受伤肺组织中SIRT1蛋白、信使核糖核酸及SIRT1酶活性。我们还发现受伤小鼠BAL细胞中SIRT1蛋白水平降低。我们进一步发现，用SIRT1激活剂白藜芦醇治疗的受伤小鼠，气管内注射LPS后BAL中的多形核白细胞（PMN）显著减少，且CLP后的存活率提高。
这些结果表明，PC导致肺中SIRT1水平降低，这与受伤小鼠对感染或炎症刺激的反应增强相关。用SIRT1激活剂白藜芦醇治疗受伤小鼠，可降低LPS炎症反应，并提高CLP后的存活率。我们的结果表明，SIRT1参与损伤后的二次打击反应。
