Analysis of mechanism of activation of kupffer cells in the liver

本研究的目的是确定GdCl3对枯否细胞(KC)功能的影响，并进一步探讨KC产生的细胞因子如肿瘤坏死因子-α和IL-6与内毒素作用后这些细胞因子水平的相关性。给予或不给予GdCl3的大鼠注射脂多糖或生理盐水。于注射脂多糖后各时间点从主动脉取血测定肿瘤坏死因子-α和白介素6。进一步收集肝组织进行病理学评价和免疫组织化学染色。此外，分离的KCs用于检测吞噬功能、超氧化物和炎性细胞因子的产生。所有动物在注射脂多糖后均死亡，但GdCl3完全阻止了这种死亡。两组均可迅速升高肿瘤坏死因子-α水平，但无差异。相比之下，赋形剂组大鼠的IL-6水平逐渐升高，且显著高于GdCl3组。大的KC比小的KC有更强的吞噬功能。LPS可增加小KC细胞产生超氧化物歧化酶和肿瘤坏死因子-α的量，但小KC组明显高于大KC组，小KC组以ED2阳性细胞为主，肝内可见部分ED1阳性细胞。内毒素后EDI阳性细胞数进一步增加，而ED2组则无明显变化。因此，在肝巨噬细胞中观察到了功能异质性。大的KC可能是驻留在肝内的巨噬细胞，小的KC可能是外周单核/巨噬细胞渗入肝脏。活化的大KCs产生的肿瘤坏死因子-α能激活小KCs。随后，这些小KC向肺、肾等其他器官招募，并产生大量IL-6，导致器官损伤和多器官衰竭。因此，肝脏可能是炎症免疫系统的中心器官。

The purpose of this study was to determine how GdCl3 affects Kupffer cell (KC) function and further to investigate a correlation between cytokine productions such as TNF-α or IL-6 by KC and those cytokine levels after LPS administration. Rats with or without GdCl3 were received LPS or saline vehicle. Serum samples were collected from the aorta at each time point after LPS administration for TNF-α and IL-6 measurements. Further, liver tissues were collected for pathological evaluation and immunohistochemistry. Moreover, isolated KCs were used for evaluation of phagocytosis, and production of superoxide and inflammatory cytokines. All animals died after LPS administration but GdCl3 prevented this mortality completely. TNF-α levels were increased rapidly by LPS in both groups without differences. In contrast, IL-6 levels were increased gradually and values were significantly greater in rats treated with vehicle than GdCl3. Large KCs showed greater phagocytosis than small KCs. Superoxide and TNF-α productions by isolated KCs were increased by LPS.These increases were not observed in the small KC.Further, LPS or TNF-α stimulation increased IL-6 production ; however values were significantly greater in the small KC than the large KC.ED2 positive cells were observed predominantly with some ED1 positive cells in the liver. Further EDI positive cells were increased after LPS but not ED2. Thus, functional heterogeneity was observed in the hepatic macrophage. The Large KC may be the resident hepatic macrophage and the small KC may be the peripheral monocyte/macrophage infiltrating into the liver. TNF-α derived from activated large KCs could activate small KCs. Subsequently, these small KCs are recruiting to other organs such as lung and kidney, and produce large amount of IL-6 leading to organ injuries and multiple organ failures. Thus, the liver could be the central organ in the inflammatory immune system.