Neutrophil extracellular traps in bronchial aspirates: a quantitative analysis

Abstract

Neutrophil extracellular traps (NETs) are structures composed of DNA and granular proteins, which rapidly trap and kill pathogens. The formation of NETs has been detected during infection in animal experiments, but their role in humans is unclear. The purposes of this study were to quantitatively evaluate the production of NETs during acute respiratory infection and to study the relationship between the NET length and various inflammatory mediators.We examined bronchial aspirates collected from nine intubated patients in an intensive care unit. Samples were collected at the onset of acute respiratory infection (day 0) and on days 1, 3-5, and 6-8. The NET length was visualised by immunohistochemistry and quantified using computer tracing software.The NET length was measured and compared at each time point. The length differed significantly between time points (p,0.001). NETs were significantly longer on day 1 than on day 0 (p,0.001). Neutrophils released NETs abundantly in response to respiratory infection and regression analysis showed that NET length correlated with six clinical parameters (white blood cells, platelets, lactate, CXC ligand-2, interleukin-8, and procalcitonin) as the explanatory variables.NETs in bronchial aspirates may reflect disease progression of respiratory infections. Quantification of NETs in bronchial aspirates may provide a new indicator of inflammation. @ERSpublications NET length increases with respiratory inflammation which correlates with progression of infections

Serial change of neutrophil extracellular traps in tracheal aspirate of patients with acute respiratory distress syndrome: report of three cases

“…However, the timing of NET formation triggered by stimuli in vivo is unclear. As we reported previously, the maximum amount of NET release was observed on the day following the development of bacterial pneumonia, whereas the level of pro-inflammatory cytokines in the blood was most abundant on the day of onset [13]. The release of NETs via pro-inflammatory stimuli might be delayed in critical situations in humans when compared with that in vitro.…”

“…The amount of NETs appeared to increase after clinical improvement in cases 1 (on day 12) and 2 (on day 17). We previously reported that the length of NETs in tracheal aspirates initially increased and then shortened during acute respiratory infection, and this correlated with the level of pro-inflammatory cytokines (such as interleukin-8 or CXC ligand-2) in the blood [13]. The association between interleukin-8 and NETs was also reported in ventilator-associated pneumonia [9].…”

“…The expression of NETs continued during the ARDS state and decreased along with the recovery from ARDS. We previously reported that NETs were observed during acute respiratory infection in tracheal aspirates of intubated patients [13,15]. NETs in tracheal aspirates might be widely found in acute inflammatory lung diseases.…”

“…We identified NETs by following the method used in a previous study [13]. Extracellular components including DNA and histone H3, which are the major components of NETs, in tracheal aspirate were simultaneously detected using immunostaining in patients with ARDS.…”

Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: I. Light Microscopic Study

“…NETs are also known to be active in such infectious lesions as acute appendicitis and experimental models of shigellosis, necrotizing fasciitis and pneumonia [2, 5, 7, 16]. Hamaguchi et al and Hirose et al demonstrated NETs in the sputum sampled from patients with acute respiratory infection [17, 18]. LF, an iron-containing red protein in milk, has been utilized as a quantitative biomarker for inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease [33].…”