title: The Interleukin-17 Induced Activation and Increased Survival of Equine Neutrophils Is Insensitive to Glucocorticoids.
abstract: Glucocorticoids (GCs) are the most effective drugs for the treatment of human asthma. However, a subgroup of asthmatic patients with neutrophilic airway inflammation is insensitive to GCs. Interleukin-17 (IL-17), a cytokine upregulated in the airways of a subset of human asthmatic patients, contributes to the recruitment of neutrophils and induces a glucocorticoid resistance in human airway epithelial cells. We hypothesized that IL-17 similarly activates neutrophils and contributes to their persistence in the asthmatic airways in spite of glucocorticoid therapy.
  
  
  
  To determine whether IL-17 directly activates neutrophils and whether this response is attenuated by GCs.
  
  
  
  Neutrophils were isolated from the blood of horses and incubated in the presence of recombinant equine IL-17, LPS and dexamethasone. mRNA and protein expression of IL-17 receptors (IL-17RA/IL-17RC) were assessed by qPCR and immunoblot, respectively. Pro-inflammatory cytokine expression, cell viability and apoptosis were determined by qPCR, Trypan Blue exclusion test, and flow cytometry, respectively.
  
  
  
  Equine neutrophils express both IL-17RA and IL-17RC at the mRNA and protein levels. Neutrophil stimulation with IL-17 increases the mRNA expression of IL-8, which is not attenuated by dexamethasone (p = 0.409). Also, neutrophil viability is significantly increased (p<0.0001) by IL-17 in the presence of LPS when compared to LPS alone. Flow cytometry and light microscopy revealed that LPS-induced apoptosis is decreased by IL-17 (p = 0.02 and p = 0.006 respectively).
  
  
  
  These results indicate that IL-17 directly activates equine neutrophils at 24 hours, and that the expression of IL-8 thus induced is not attenuated by GCs. Additionally, IL-17 increases neutrophil viability and decreases apoptosis. These findings suggest an important role of IL-17 in pulmonary persistence of neutrophils in the asthmatic airways.
authors.affiliation: Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Ruby Yoana
authors.initials: RY
authors.lastname: Murcia
authors.affiliation: Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Amandine
authors.initials: A
authors.lastname: Vargas
authors.affiliation: Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Lavoie
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001249:Asthma / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D006736:Horses; D020381:Interleukin-17 / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects* / Q000276:immunology; D053722:Receptors, Interleukin-17 / Q000378:metabolism
chemical_list: D005938:Glucocorticoids; D020381:Interleukin-17; D053722:Receptors, Interleukin-17; D003907:Dexamethasone