树突状细胞的消耗可加重对乙酰氨基酚的肝毒性
背景：APAP的过量使用是在美国引起急性肝衰的最常见原因之一，它主要通过积累在肝脏的毒性代谢产物消耗谷胱甘肽而发挥作用。但是，固有免疫系统的NK、中性粒及枯否细胞等也参与APAP导致肝中央小叶坏死的过程。我们已经证明树突状细胞在慢性肝病的肝内炎症中发挥作用，假定DC也参与APAP引起的肝损伤。方法：老鼠分成四组：盐水对照组、DC耗竭组、APAP处理组及APAP处理DC耗竭组。肝损伤通过病理来判断，并检测血清中的转氨酶、MCP-1、 IL-6、 TNF-a。为了判断DC的耗竭对APAP导致的死亡率的影响，将盐水、APAP及APAP-DC 的老鼠观察两周。测定APAP与APAP-DC两组中DC的免疫分型；通过流式的方法测定盐水对照组与APAP 两组的肝脏DCs总数及CD11c+细胞数；同时，测定APAP与APAP-DC两组老鼠的肝与脾的DC的表面标记及肝DC产生于上清液中IL-6 、TNF-a, MCP-1和 IL-10。将老鼠分为四组处理后，检测肝酶水平及其病理变化。APAP与APAP+DC两组小鼠肝脏白细胞的构成通过流式检测。用APAP处理正常、DC耗竭、DC+中性粒耗竭、DC+NK耗竭的四组老鼠进行相关检测。结果：我们发现肝脏的DC的免疫表型在APAP处理后发生改变。特别是高度表达了MHC-II、协同刺激分子、Toll样受体，并产生了大量的IL-6 、MCP-1, and TNF-a. 而脾脏却没有发生变化。DC的耗竭明显加重了APAP的肝坏死及其死亡率。而通过使用Flt3L扩增DC可减轻肝受APAP的损伤，我们的研究证实，APAP作用后的肝脏DC具有抑制NK活化并诱导中性粒细胞死亡的作用。然而， DC缺乏加重APAP引起老鼠的肝损伤与NK、中性粒、各种免疫调节细胞因子及趋化因子是无关的。结论：总之，肝脏DC可减轻APAP的肝毒性作用，其减少会加重肝毒性。
吉林大学第一医院肝胆胰内科 宋立莎 摘译
本文首次发表于[Hepatology，2011，54:959-968]
Dendritic Cell Depletion Exacerbates Acetaminophen Hepatotoxicity
Background：Acetaminophen (APAP) overdose is one of the most frequent causes of acute liver failure in the United States and is primarily mediated by toxic metabolites that accumulate in the liver upon depletion of glutathione stores. However, cells of the innate immune system, including natural killer (NK) cells, neutrophils, and Kupffer cells, have also been implicated in the centrilobular liver necrosis associated with APAP. We have recently shown that dendritic cells (DCs) regulate intrahepatic inflammation in chronic liver disease and, therefore, postulated that DC may also modulate the hepatotoxic effects of APAP.
Methods：Mice were divided into four groups : saline-treated, DC depleted, APAP, and APAP-DC. The extent of liver injury determined by histopathology．Serum liver enzymes，MCP-1, IL-6 and TNF-a were measured. To determine whether DC depletion resulted in higher APAP mediated mortality, mice were treated with APAP and depleted of DC and then observed for up to 2 weeks．The immune-phenotype of DC in animals challenged with APAP and APAP-DC were interrogated. The total number and fraction of CD11c+ liver NPC per mouse was determined by flow cytometry. Liver or spleen DC expression of surface markers in APAP or saline treated mice were measured．Liver DC production of IL-6, TNF-a, MCP-1, and IL-10 in cell culture supernatant was measured. Mice were treated with saline, APAP, Flt3L, or APAP+Flt3L. Serum liver enzymes as well as histological evidence of liver damage were determined．The cellular composition of hepatic leukocytes was determined by flow cytometry in APAP+DC liver and APAP treatment alone．Mice were depleted of DC and simultaneously depleted of either neutrophils or NK cells before challenge with APAP．
Results：We found that DC immune-phenotype was markedly altered after APAP challenge. In particular, liver DC expressed higher MHC II, costimulatory molecules, and Toll-like receptors, and produced higher IL-6, MCP-1, and TNF-a. Conversely, spleen DC were unaltered. However APAP-induced centrilobular necrosis, and its associated mortality, was markedly exacerbated upon DC depletion. Conversely, endogenous DC expansion using Flt3L protected mice from APAP injury. Our mechanistic studies showed that APAP liver DC had the particular capacity to prevent NK cell activation and induced neutrophil apoptosis. Nevertheless, the exacerbated hepatic injury in DC-depleted mice challenged with APAP was independent of NK cells and neutrophils or numerous immune modulatory cytokines and chemokines.
Conclusions：Taken together, these data indicate that liver DC protect against APAP toxicity, whereas their depletion is associated with exacerbated hepatotoxicity.
