Keshavarzian A, Fusunyan R D, Jacyno M, Winship D, MacDermott R P, Sanderson I R
Department of Medicine, Loyola University Medical School, Maywood, Illinois, USA.
Am J Gastroenterol. 1999 Mar;94(3):704-12. doi: 10.1111/j.1572-0241.1999.00940.x.
Infiltration of neutrophils and their release of toxic reactive oxygen species (ROS) in the colonic mucosa are associated with tissue damage in ulcerative colitis (UC). This neutrophil migration may be induced by chemoattractants, such as cytokines, in the colonic milieu. One such chemoattractant is interleukin-8 (IL-8), a neutrophil chemokine that is present at high concentrations in inflamed mucosa. However, the functional significance of IL-8 in neutrophil attraction and activation in UC has not been established. We hypothesized that IL-8 in the colonic lumen of patients with UC primes neutrophils, leading to their attraction and activation.
The colonic milieu was sampled by rectal dialysis. Using a semi-permeable membrane with a molecular weight cut-off of 12 kDa, dialysis solution was placed in the rectum and allowed to equilibrate over a 4-h period with the colonic milieu of controls or of patients with UC. IL-8 concentrations were measured by ELISA. Two functions of healthy neutrophils (PMN) were measured: expression of CD11-b surface adhesion molecules (by flow cytometry), and production of ROS (by both chemiluminescence and cytochrome C reduction assays). Neutrophil functions after exposure to rectal dialysates or n-formyl-methionyl-leucyl-phenylalanine (fMLP) were assessed before and after adding anti-IL-8 antibody or the fMLP blocker BMLP.
IL-8 concentrations in dialysates from patients with active UC were significantly higher than in controls and correlated with disease activity. UC dialysates significantly increased ROS production and CD11-b expression by neutrophils and anti-IL-8 antibody partially (50%) inhibited these stimulatory effects of UC dialysates. Preincubation of neutrophils with UC dialysates significantly potentiated the fMLP-induced rise in ROS and anti-IL-8 antibody completely abolished this priming effect.
The colonic milieu, sampled by rectal dialysis, from patients with active UC can both activate and prime neutrophils in vitro. High concentrations of IL-8 in the colonic lumen of UC patients are partially responsible for the activating effects of rectal dialysates, and account for all of its priming effects. These findings provide direct evidence for a role for IL-8 in inflammatory bowel disease.
中性粒细胞浸润及其在结肠黏膜中释放有毒活性氧（ROS）与溃疡性结肠炎（UC）的组织损伤有关。这种中性粒细胞迁移可能由结肠环境中的化学引诱剂（如细胞因子）诱导。其中一种化学引诱剂是白细胞介素-8（IL-8），一种在炎症黏膜中高浓度存在的中性粒细胞趋化因子。然而，IL-8在UC中对中性粒细胞吸引和激活的功能意义尚未明确。我们假设UC患者结肠腔中的IL-8使中性粒细胞致敏，导致其吸引和激活。
通过直肠透析采集结肠环境样本。使用截留分子量为12 kDa的半透膜，将透析液置于直肠中，并使其与对照组或UC患者的结肠环境在4小时内达到平衡。通过酶联免疫吸附测定（ELISA）测量IL-8浓度。检测健康中性粒细胞（PMN）的两种功能：CD11-b表面粘附分子的表达（通过流式细胞术）和ROS的产生（通过化学发光和细胞色素C还原试验）。在添加抗IL-8抗体或fMLP阻断剂BMLP之前和之后，评估中性粒细胞暴露于直肠透析液或N-甲酰甲硫氨酰亮氨酰苯丙氨酸（fMLP）后的功能。
活动性UC患者透析液中的IL-8浓度显著高于对照组，且与疾病活动度相关。UC透析液显著增加中性粒细胞的ROS产生和CD11-b表达，抗IL-8抗体部分（50%）抑制了UC透析液的这些刺激作用。用UC透析液预孵育中性粒细胞显著增强了fMLP诱导的ROS升高，抗IL-8抗体完全消除了这种致敏作用。
通过直肠透析采集的活动性UC患者的结肠环境在体外既能激活又能使中性粒细胞致敏。UC患者结肠腔中高浓度的IL-8部分导致了直肠透析液的激活作用，并解释了其所有的致敏作用。这些发现为IL-8在炎症性肠病中的作用提供了直接证据。
