Characterization of bacterial DNA binding to human neutrophil surface.

FUXMAN BASS, JI; GABELLONI, ML; ALVAREZ, ME; VERMEULEN, ME; RUSSO, DM; ZORREGUIETA, Á; GEFFNER, JR AND TREVANI AS.; GABELLONI, ML; ALVAREZ, ME; VERMEULEN, ME; RUSSO, DM; ; ZORREGUIETA,A; GEFFNER, JR AND TREVANI AS.

LABORATORY INVESTIGATION

United States and Canadian Academy of Pathology (USCAP)

Año: 2008

0023-6837

Abstract Bacterial DNA activates neutrophils through a CpG- and TLR9-independent mechanism.  Neutrophil activation does not require DNA internalization, suggesting that it results from the interaction of bacterial DNA with a neutrophil surface receptor. The aim of this study was to characterize the interaction of bacterial DNA with neutrophil surface. Bacterial DNA binding showed saturation and was inhibited by unlabeled DNA but not by other poly-anions like yeast tRNA and poly-A. Resembling the conditions under which bacterial DNA triggers neutrophil activation, binding was not modified in the presence or absence of calcium, magnesium or serum. Treatment of neutrophils with proteases not only dramatically reduced bacterial DNA binding but also markedly inhibited neutrophil activation induced by bacterial DNA. Binding assays performed with DNA samples of different lengths obtained after digestion of bacterial DNA with DNase, indicated that only oligomers greater than 170 nucleotides efficiently bind to neutrophil surface. This minimal length coincided with the one able to trigger cell activation. Treatment of neutrophils with chemoattractants or conventional agonists significantly increased bacterial DNA binding. Moreover, neutrophils that underwent transmigration through human endothelial cell monolayers even in the absence of chemoattractants, exhibited higher binding levels of bacterial DNA. Together, our findings provide evidences that binding of bacterial DNA to neutrophils is a receptor-mediated process that conditions the ability of DNA to trigger cell activation. We speculate that neutrophil recognition of bacterial DNA might be modulated by the balance of agonists present at inflammatory foci. This effect might be relevant in bacterial infections with a biofilm aetiology, in which extracellular DNA could function as a potent neutrophil agonist. Abbreviations: biotinylated-E coli DNA, biot-DNA; polyadenilic acid, poly-A; proteinase K, prot K; single stranded DNA, ssDNA; double stranded DNA, dsDNA; pentoxifylline, PTX; double stranded plasmidic DNA, ds pBS. Keywords: bacterial DNA binding, biofilm, CpG, inflammation, neutrophils, TLR9.