Impaired neutrophil extracellular trap formation: a novel defect in the innate immune system of aged individuals

• Published in: Aging cell Vol. 13; no. 4; pp. 690 - 698
• Main Authors: Hazeldine, Jon, Harris, Phillipa, Chapple, Iain L., Grant, Melissa, Greenwood, Hannah, Livesey, Amy, Sapey, Elizabeth, Lord, Janet M.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.08.2014; BlackWell Publishing Ltd
• Subjects: Acetic acid; Adult; Age; Aged; Aging; Aging - immunology; Aging - pathology; Analysis; Bacteria; Case-Control Studies; Chronic Disease; CXCR2 protein; Defects; Disease susceptibility; Enzyme Activation - drug effects; Enzymes; Extracellular Traps - drug effects; Extracellular Traps - immunology; Female; Gum disease; Health aspects; Humans; Hypochlorous acid; Immune response; Immune system; Immunity, Innate - drug effects; Immunity, Innate - immunology; Infection; Infections; Innate immunity; Interleukin-8 - metabolism; Kinases; Leukocytes (neutrophilic); Lipopolysaccharides; Lipopolysaccharides - pharmacology; Male; MAP kinase; Medical research; Medicine, Experimental; Microscopy; Middle Aged; neutrophil; neutrophil extracellular traps; Neutrophils; Neutrophils - drug effects; Neutrophils - immunology; Older people; Original; p38 Mitogen-Activated Protein Kinases - metabolism; Pathogens; Periodontitis; Periodontitis - immunology; Periodontitis - pathology; Proteins; Reactive oxygen species; Reactive Oxygen Species - metabolism; Receptors, Cell Surface - metabolism; Risk factors; TLR4 protein; Toll-like receptors; Tumor necrosis factor; Tumor Necrosis Factor-alpha - pharmacology; Tumor necrosis factor-TNF; neutrophil extracellular traps; aging; neutrophil; periodontitis
• ISSN: 1474-9718; 1474-9726; 1474-9726
• DOI: 10.1111/acel.12222

Summary 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.