title: Myeloperoxidase delays neutrophil apoptosis through CD11b/CD18 integrins and prolongs inflammation.
abstract: Polymorphonuclear neutrophil granulocytes have a central role in innate immunity and their programmed cell death and removal are critical for efficient resolution of acute inflammation. Myeloperoxidase (MPO), a heme protein abundantly expressed in neutrophils, is generally associated with killing of bacteria and oxidative tissue injury. Because MPO also binds to neutrophils, we investigated whether MPO could affect the lifespan of neutrophils. Here, we report that MPO independent of its catalytic activity through signaling via the adhesion molecule CD11b/CD18 rescued human neutrophils from constitutive apoptosis and prolonged their life span. MPO evoked a transient concurrent activation of extracellular signal-regulated kinase and Akt, leading to phosphorylation of Bad at both Ser112 and Ser136, prevention of mitochondrial dysfunction, and subsequent activation of caspase-3. Consistently, pharmacological inhibition of extracellular signal-regulated kinase, Akt, or caspase-3 reversed the antiapoptosis action of MPO. Acute increases in plasma MPO delayed murine neutrophil apoptosis assayed ex vivo. In a mouse model of self-resolving inflammation, MPO also prolonged the duration of carrageenan-induced acute lung injury, as evidenced by enhanced alveolar permeability and accumulation of neutrophils parallel with suppression of neutrophil apoptosis. Our results indicate that MPO functions as a survival signal for neutrophils and thereby contribute to prolongation of inflammation.
authors.affiliation: Research Center, Maisonneuve-Rosemont Hospital, University of Montreal, 5415 blvd de l'Assomption, Montreal, QC, Canada H1T 2M4.
authors.forename: Driss
authors.initials: D
authors.lastname: El Kebir
authors.forename: Levente
authors.initials: L
authors.lastname: József
authors.forename: Wanling
authors.initials: W
authors.lastname: Pan
authors.forename: János G
authors.initials: JG
authors.lastname: Filep
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D039481:CD11b Antigen / Q000378:metabolism*; D018821:CD18 Antigens / Q000378:metabolism*; D002351:Carrageenan; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008928:Mitochondria / Q000502:physiology; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D009195:Peroxidase / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012128:Respiratory Distress Syndrome / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology
chemical_list: D039481:CD11b Antigen; D018821:CD18 Antigens; D002351:Carrageenan; D009195:Peroxidase; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D053148:Caspase 3