Anti-Inflammatory benefits of antibiotic-induced neutrophil apoptosis: tulathromycin induces caspase-3-dependent neutrophil programmed cell death and inhibits NF-kappaB signaling and CXCL8 transcription.
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.
Fischer
Carrie D
CD
University of Calgary, Department of Biological Sciences, Calgary, Alberta, Canada.
Beatty
Jennifer K
JK
Zvaigzne
Cheryl G
CG
Morck
Douglas W
DW
Lucas
Merlyn J
MJ
Buret
A G
AG
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D004187:Disaccharides / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D006571:Heterocyclic Compounds / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D016209:Interleukin-8 / Q000235:genetics*; D007975:Leukotriene B4 / Q000378:metabolism; D008297:Male; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D018942:Macrolides
D000900:Anti-Bacterial Agents; D000893:Anti-Inflammatory Agents; D053148:Caspase 3; D004187:Disaccharides; D006571:Heterocyclic Compounds; D016209:Interleukin-8; D007975:Leukotriene B4; D016328:NF-kappa B; C485204:tulathromycin; D018942:Macrolides