Shawcross Debbie L, Wright Gavin A K, Stadlbauer Vanessa, Hodges Stephen J, Davies Nathan A, Wheeler-Jones Caroline, Pitsillides Andrew A, Jalan Rajiv
Liver Failure Group, The University College London (UCL) Institute of Hepatology, Division of Medicine, University College London, London, UK.
Hepatology. 2008 Oct;48(4):1202-12. doi: 10.1002/hep.22474.
Hyperammonemia is a feature of liver failure, which is associated with increased risk of infection. The aims of the present study were to determine in vitro, in rats fed an ammoniagenic diet and in patients with cirrhosis, whether induction of hyperammonemia results in neutrophil dysfunction. As hyperammonemia produces cell swelling, we explored the role of the osmoregulating, p38 mitogen-activated protein kinase (p38(MAPK)) pathway in mediating this neutrophil dysfunction. Neutrophils were isolated from blood of healthy volunteers and incubated with either 75 microM ammonia or phosphate-buffered saline. Both groups were studied under hyponatremic conditions and/or with the addition of p38(MAPK) modulators. Neutrophil phagocytosis was measured in naive rats and rats fed an ammoniagenic diet and in patients with stable cirrhosis given placebo (n = 8) or an amino acid solution inducing hyperammonemia (n = 8). Cell volume and phagocytosis was analyzed by fluorescent-activated cell sorting using fluorescein isothiocyanate-labeled E. coli. p38(MAPK) phosphorylation was measured by western blotting. In healthy neutrophils incubated with ammonia and in rats fed an ammoniagenic diet, neutrophils showed evidence of swelling, impaired phagocytosis, and increased spontaneous oxidative burst compared to controls. Phagocytosis was significantly impaired in patients with induced hyperammonemia compared to placebo. The effects of hyperammonemia and hyponatremia were synergistic. The p38(MAPK) intracellular signaling pathways were activated in healthy neutrophils exposed to ammonia in association with increased burst activity. Neutrophil phagocytic dysfunction was abrogated by the addition of a p38(MAPK) agonist.
Ammonia produces neutrophil swelling and impairs neutrophil phagocytosis. The p38(MAPK) intracellular signaling pathway has been shown to be important in mediating the ammonia-induced neutrophil dysfunction.
高氨血症是肝衰竭的一个特征，与感染风险增加相关。本研究的目的是在体外、给大鼠喂食产氨饮食以及在肝硬化患者中，确定高氨血症的诱导是否会导致中性粒细胞功能障碍。由于高氨血症会导致细胞肿胀，我们探讨了渗透调节的p38丝裂原活化蛋白激酶（p38(MAPK)）途径在介导这种中性粒细胞功能障碍中的作用。从健康志愿者的血液中分离出中性粒细胞，并与75微摩尔的氨或磷酸盐缓冲盐水一起孵育。两组均在低钠血症条件下和/或添加p38(MAPK)调节剂的情况下进行研究。在未处理的大鼠、喂食产氨饮食的大鼠以及给予安慰剂（n = 8）或诱导高氨血症的氨基酸溶液（n = 8）的稳定肝硬化患者中测量中性粒细胞吞噬作用。使用异硫氰酸荧光素标记的大肠杆菌通过荧光激活细胞分选分析细胞体积和吞噬作用。通过蛋白质印迹法测量p38(MAPK)磷酸化。与对照组相比，在与氨孵育的健康中性粒细胞和喂食产氨饮食的大鼠中，中性粒细胞表现出肿胀、吞噬作用受损和自发氧化爆发增加的迹象。与安慰剂相比，诱导高氨血症的患者吞噬作用明显受损。高氨血症和低钠血症的影响是协同的。在暴露于氨的健康中性粒细胞中，p38(MAPK)细胞内信号通路被激活，同时爆发活性增加。添加p38(MAPK)激动剂可消除中性粒细胞吞噬功能障碍。
氨会导致中性粒细胞肿胀并损害中性粒细胞吞噬作用。已证明p38(MAPK)细胞内信号通路在介导氨诱导的中性粒细胞功能障碍中很重要。
