Linevsky J K, Pothoulakis C, Keates S, Warny M, Keates A C, Lamont J T, Kelly C P
Section of Gastroenterology, Department of Veterans Affairs Medical Center, Boston 02130, USA.
Am J Physiol. 1997 Dec;273(6):G1333-40. doi: 10.1152/ajpgi.1997.273.6.G1333.
Neutrophil infiltration is central to the pathogenesis of Clostridium difficile toxin A-induced enterocolitis. This study examines whether monocyte activation by C. difficile toxins is instrumental in initiating neutrophil activation and recruitment. Human monocytes were exposed to low concentrations of highly purified C. difficile toxins, and the conditioned media were harvested for cytokine and functional assays. Monocytes exposed to C. difficile toxin A (10(-10) M) or toxin B (10(-12) M) released 100 and 20 times basal levels, respectively, of the neutrophil chemoattractant interleukin-8 (IL-8). Reverse transcriptase-polymerase chain reaction demonstrated a marked increase in IL-8 mRNA expression by monocytes 3 h after toxin exposure. Conditioned media from toxin A- and toxin B-treated monocytes stimulated neutrophil migration (324 and 245% of control, respectively). This effect was completely blocked by IL-8 antiserum. These media also upregulated neutrophil CD11b/CD18 and endothelial cell intercellular adhesion molecule-1 expression. C. difficile toxins, at low concentrations, potently activate monocytes to release factors, including IL-8, that facilitate neutrophil extravasation and tissue infiltration. Our findings indicate a major role for toxin-mediated monocyte and macrophage activation in C. difficile colitis.
中性粒细胞浸润是艰难梭菌毒素A诱导的小肠结肠炎发病机制的核心。本研究探讨艰难梭菌毒素激活单核细胞是否有助于启动中性粒细胞的激活和募集。将人单核细胞暴露于低浓度的高度纯化的艰难梭菌毒素，收集条件培养基用于细胞因子和功能测定。暴露于艰难梭菌毒素A（10^(-10) M）或毒素B（10^(-12) M）的单核细胞分别释放出中性粒细胞趋化因子白细胞介素-8（IL-8）基础水平的100倍和20倍。逆转录聚合酶链反应显示毒素暴露3小时后单核细胞中IL-8 mRNA表达显著增加。来自毒素A和毒素B处理的单核细胞的条件培养基刺激中性粒细胞迁移（分别为对照的324%和245%）。这种效应被IL-8抗血清完全阻断。这些培养基还上调了中性粒细胞CD11b/CD18和内皮细胞细胞间黏附分子-1的表达。低浓度的艰难梭菌毒素可有效激活单核细胞以释放包括IL-8在内的因子，这些因子有助于中性粒细胞渗出和组织浸润。我们的研究结果表明毒素介导的单核细胞和巨噬细胞激活在艰难梭菌结肠炎中起主要作用。
