title: Escherichia coli induces bovine neutrophil cell death independent from caspase-3/-7/-1, but with phosphatidylserine exposure prior to membrane rupture.
abstract: Neutrophils are essential for the innate immune response against bacterial pathogens and play a key role during the early phases of infection, including mastitis and endometritis in cows. When directly challenged with bacteria, neutrophils undergo phagocytosis induced cell death (PICD). The molecular mechanisms of this cell death modality are poorly understood, especially for bovine neutrophils. Therefore, this study aimed to determine the mechanisms and hallmarks of PICD in bovine neutrophils after in vitro challenge with Escherichia coli (E. coli). Our data show that various apoptotic hallmarks such as blebbing, chromatin condensation and executioner caspase (C)-3/-7 activity are only observed during constitutive bovine neutrophil apoptosis. In contrast, bovine neutrophil PICD is characterized by production of reactive oxygen species (ROS), pro-inflammatory C-1 activation, nuclear factor (NF)-κB activation, and interleukin (IL)-1β and IL-6 secretion. Nevertheless, under both conditions these phagocytes undergo cell death with the exposure of phosphatidylserine (PS). Although PS exposure is generally attributed to the anti-inflammatory features of executioner caspase-dependent apoptosis, it surprisingly preceded plasma membrane rupture during bovine neutrophil PICD. Moreover, C-1 inhibition strongly affected IL-1β production but not the PICD kinetics. This indicates that the secretion of the latter pro-inflammatory cytokine is a bystander effect rather than a regulator of PICD in bovine neutrophils, in marked contrast to the IL-1β-dependent pyroptosis reported for macrophages.
authors.affiliation: Laboratory of Biochemistry, Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium. Kristel.Demeyere@ugent.be
authors.forename: Kristel
authors.initials: K
authors.lastname: Demeyere
authors.forename: Quinten
authors.initials: Q
authors.lastname: Remijsen
authors.forename: Dieter
authors.initials: D
authors.lastname: Demon
authors.forename: Koen
authors.initials: K
authors.lastname: Breyne
authors.forename: Sofie
authors.initials: S
authors.lastname: Notebaert
authors.forename: Filip
authors.initials: F
authors.lastname: Boyen
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Guérin
authors.forename: Peter
authors.initials: P
authors.lastname: Vandenabeele
authors.forename: Evelyne
authors.initials: E
authors.lastname: Meyer
mesh_terms: D000818:Animals; D017209:Apoptosis; D020170:Caspase 1 / Q000502:physiology; D053148:Caspase 3 / Q000502:physiology; D053179:Caspase 7 / Q000502:physiology; D020169:Caspases / Q000502:physiology*; D002417:Cattle; D004926:Escherichia coli / Q000472:pathogenicity*; D053583:Interleukin-1beta / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D016328:NF-kappa B / Q000378:metabolism; D018375:Neutrophil Activation; D009504:Neutrophils / Q000276:immunology* / Q000502:physiology; D010587:Phagocytosis; D010718:Phosphatidylserines / Q000502:physiology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D015850:Interleukin-6; D016328:NF-kappa B; D010718:Phosphatidylserines; D017382:Reactive Oxygen Species; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; D020170:Caspase 1