Elevated Concentrations of Human Neutrophil Peptides in Plasma, Blood, and Body Fluids from Patients with Infections

Abstract

Neutrophil peptides, also called defensins, are antimicrobial molecules localized in the azurophil granules of neutrophils. We used a sensitive radioimmunoassay to measure the concentrations of human neutrophil peptides (HNPs) 1-3 in the plasma and blood of 86 healthy volunteers who served as controls and 54 patients with various infections. The respective mean plasma concentrations of HNPs 1-3 in the patients at the onset of bacterial infection, nonbacterial infection, and pulmonary tuberculosis were 4.2, 3.2, and 1.8 times the mean value (+/- SE) for the controls (254.8 +/- 7.1 pg/microL). Plasma concentrations of HNPs 1-3 for the patients were correlated with the peripheral blood neutrophil counts (correlation coefficient = 0.629; P = .0001). The mean concentration (+/- SE) of blood HNPs 1-3 in patients with bacterial infections was higher than the mean value (+/- SE) for controls (10.4 +/- 0.6 ng/microL), whereas the mean concentration (+/- SE) in patients with nonbacterial infections or tuberculosis did not differ from that for controls. Reverse-phase high performance liquid chromatography of plasma samples from patients with bacterial infections showed high concentrations of two precursors of HNPs 1-3, indicating that the biosynthesis of HNPs in neutrophil precursor cells is stimulated in response to infection and/or that the release of pro-HNPs is enhanced. HNPs 1-3 concentrations in the pleural fluid, bronchoalveolar lavage fluid, urine, and cerebrospinal fluid were also elevated in patients with infections. Our results suggest that HNPs have physiological significance in infection and that this family of peptides may be useful in assessing neutrophil function during infection.

Human neutrophil peptides induce interleukin-8 production through the P2Y6 signaling pathway

“…Transfection of SAECs and A549 cells with the sense or antisense oligonucleotides (final concentration, 2.5 M) corresponding to the translation initiation sites of human P2Y 2 , P2Y 4 , and P2Y 6 were performed with the use of Lipofectamine reagent (Gibco). Sequences included P2Y 2 sense, 5Ј-GCGATGGCAGCAGACCTGG-3Ј; P2Y 2 antisense, 5Ј-CCAGGTCT-GCTGCCAT-CGC-3Ј; P2Y 4 sense, 5Ј-GCCATGGCCAGTACAGAGT-3Ј; P2Y 4 antisense, 5Ј-ACTCTGT-ACTGGCCATGC-3Ј; P2Y 6 sense, 5Ј-GCCATGGAATGGGACAATG-3Ј; and P2Y 6 antisense, 5Ј-CATTGTC-CCATTCCATGGC-3Ј.…”

“…In patients experiencing the onset of bacterial infection, those with nonbacterial infection, and those with pulmonary tuberculosis, mean HNP levels were 2-to 4-fold greater than they were in healthy volunteers. 6 In patients with sepsis, HNP levels might be elevated to concentrations measured in milligrams per milliliter. 3 In lung lavage fluid, HNP concentrations were 50-fold higher in patients with ARDS than in healthy controls, 7 5 orders of magnitude greater in patients with bacterial pneumonia than in healthy volunteers, 6 and 31-fold higher in patients with diffuse panbronchiolitis than in controls.…”

“…6 In patients with sepsis, HNP levels might be elevated to concentrations measured in milligrams per milliliter. 3 In lung lavage fluid, HNP concentrations were 50-fold higher in patients with ARDS than in healthy controls, 7 5 orders of magnitude greater in patients with bacterial pneumonia than in healthy volunteers, 6 and 31-fold higher in patients with diffuse panbronchiolitis than in controls. 8 In sputum, we have shown an HNP concentration of 240 Ϯ 40 g/mL in patients with cystic fibrosis compared with undetectable levels in healthy controls.…”

“…9 These and other studies showing increased levels of HNP in the circulation and in the airways of patients with inflammatory lung diseases suggest that HNPs may contribute to the pathogenesis of inflammatory lung disorders. [6][7][8][9][10][11][12] Indeed, in addition to their microbicidal role, extracellular HNPs can modulate immunologic responses. For example, HNPs are chemotactic to human CD4 ϩ /CD45RA ϩ naive T cells, CD8 ϩ T cells, immature human dendritic cells, 13 and monocytes.…”

“…21 The P2Y family members are pertussis toxin-sensitive, G i -protein-coupled receptors. At least 8 subtypes of P2Y receptors (P2Y 1 , P2Y 2 , P2Y 4 , P2Y 6 , P2Y 11 , P2Y 12 , P2Y 13 , and P2Y 14 ) expressed by mammalian cells have been identified, and each has different nucleotidebinding affinity. [22][23][24] 25,26 Recent studies have demonstrated UDP (ligand of P2Y 6 )-dependent IL-8 production from THP-1 monocytes, 27 human eosinophils, 26 and human mature dendritic cells.…”