Impaired neutrophil extracellular trap formation: a novel defect in the innate immune system of aged individuals.
Neutrophil extracellular traps (NETs) are a recently discovered addition to the defensive armamentarium of neutrophils, assisting in the immune response against rapidly dividing bacteria. Although older adults are more susceptible to such infections, no study has examined whether aging in humans influences NET formation. We report that TNF-α-primed neutrophils generate significantly more NETs than unprimed neutrophils and that lipopolysaccharide (LPS)- and interleukin-8 (IL-8)-induced NET formation exhibits a significant age-related decline. NET formation requires generation of reactive oxygen species (ROS), and this was also reduced in neutrophils from older donors identifying a mechanism for reduced NET formation. Expression of IL-8 receptors (CXCR1 and CXCR2) and the LPS receptor TLR4 was similar on neutrophils from young and old subjects, and neutrophils challenged with phorbol-12-myristate-13-acetate (PMA) showed no age-associated differences in ROS or NET production. Taken together, these data suggest a defect in proximal signalling underlies the age-related decline in NET and ROS generation. TNF-α priming involves signalling through p38 MAP kinase, but activation kinetics were comparable in neutrophils from young and old donors. In a clinical setting, we assessed the capacity of neutrophils from young and older patients with chronic periodontitis to generate NETs in response to PMA and hypochlorous acid (HOCL). Neutrophil extracellular trap generation to HOCL, but not PMA, was lower in older periodontitis patients but not in comparison with age-matched controls. Impaired NET formation is thus a novel defect of innate immunity in older adults but does not appear to contribute to the increased incidence of periodontitis in older adults.
MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Immunity and Infection, Birmingham University Medical School, Birmingham, B15 2TT, UK.
Jon
J
Hazeldine
Phillipa
P
Harris
Iain L
IL
Chapple
Melissa
M
Grant
Hannah
H
Greenwood
Amy
A
Livesey
Elizabeth
E
Sapey
Janet M
JM
Lord
D000328:Adult; D000368:Aged; D000375:Aging / Q000276:immunology* / Q000473:pathology*; D016022:Case-Control Studies; D002908:Chronic Disease; D004789:Enzyme Activation / Q000187:drug effects; D065206:Extracellular Traps / Q000187:drug effects / Q000276:immunology*; D005260:Female; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000276:immunology*; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology*; D010518:Periodontitis / Q000276:immunology / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016209:Interleukin-8; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D011956:Receptors, Cell Surface; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases
aging; neutrophil; neutrophil extracellular traps; periodontitis