University of Calgary, Department of Biological Sciences, Calgary, Alberta, Canada.
Antimicrob Agents Chemother. 2011 Jan;55(1):338-48. doi: 10.1128/AAC.01052-10. Epub 2010 Oct 18.
Clearance of apoptotic neutrophils is a central feature of the resolution of inflammation. Findings indicate that immuno-modulation and induction of neutrophil apoptosis by macrolide antibiotics generate anti-inflammatory benefits via mechanisms that remain obscure. Tulathromycin (TUL), a new antimicrobial agent for bovine respiratory disease, offers superior clinical efficacy for reasons not fully understood. The aim of this study was to identify the immuno-modulating effects of tulathromycin and, in this process, to establish tulathromycin as a new model for characterizing the novel anti-inflammatory properties of antibiotics. Bronchoalveolar lavage specimens were collected from Holstein calves 3 and 24 h postinfection, challenged intratracheally with live Mannheimia haemolytica (2 × 10(7) CFU), and treated with vehicle or tulathromycin (2.5 mg/kg body weight). Terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining and enzyme-linked immunosorbent assay (ELISA) revealed that tulathromycin treatment significantly increased leukocyte apoptosis and reduced levels of proinflammatory leukotriene B(4) in M. haemolytica-challenged calves. In vitro, tulathromycin concentration dependently induced apoptosis in freshly isolated bovine neutrophils from healthy steers in a capase-3-dependent manner but failed to induce apoptosis in bovine fibroblasts, epithelial cells, and endothelial cells, as well as freshly isolated bovine blood monocytes and monocyte-derived macrophages. The proapoptotic effects of TUL were also, in part, drug specific; equimolar concentrations of penicillin G, oxytetracycline, and ceftiofur failed to cause apoptosis in bovine neutrophils. In addition, tulathromycin significantly reduced levels of phosphorylated IκBα, nuclear translocation of NF-κB p65, and mRNA levels of proinflammatory interleukin-8 in lipopolysaccharide (LPS)-stimulated bovine neutrophils. The findings illustrate novel mechanisms through which tulathromycin confers anti-inflammatory benefits.
凋亡中性粒细胞的清除是炎症消退的一个核心特征。研究结果表明，通过大环内酯类抗生素的免疫调节和诱导中性粒细胞凋亡，产生抗炎作用的机制尚不清楚。替米考星（TUL）是一种新型的牛呼吸道疾病抗菌药物，其卓越的临床疗效的原因尚不完全清楚。本研究旨在确定替米考星的免疫调节作用，并在此过程中，将替米考星确立为一种新的模型，用于描述抗生素的新型抗炎特性。将荷斯坦小牛在感染后 3 小时和 24 小时收集支气管肺泡灌洗液标本，经气管内滴注活的溶血曼海姆菌（2×10(7)CFU），并用载体或替米考星（2.5mg/kg 体重）处理。末端脱氧核苷酸转移酶介导的 dUTP-生物素缺口末端标记（TUNEL）染色和酶联免疫吸附试验（ELISA）显示，替米考星治疗可显著增加白细胞凋亡，并降低溶血曼海姆菌感染小牛的促炎白三烯 B(4)水平。在体外，替米考星浓度依赖性地诱导来自健康牛的新鲜分离中性粒细胞凋亡，这是一种依赖半胱天冬酶-3 的方式，但不能诱导牛成纤维细胞、上皮细胞和内皮细胞以及新鲜分离的牛血单核细胞和单核细胞衍生的巨噬细胞凋亡。TUL 的促凋亡作用也部分是药物特异性的；青霉素 G、土霉素和头孢噻呋的等摩尔浓度不能引起牛中性粒细胞凋亡。此外，替米考星还显著降低了脂多糖（LPS）刺激的牛中性粒细胞中磷酸化 IκBα、NF-κB p65 核易位和促炎白细胞介素-8 的 mRNA 水平。这些发现说明了替米考星发挥抗炎作用的新机制。
