Extracellular DNA: A Major Proinflammatory Component of P. aeruginosa Biofilms

JUAN I FUXMAN BASS, DANIELA M RUSSO, MARIA L GABELLONI, JORGE R GEFFNER, MIRTA GIORDANO, MARIANA CATALANO, ÁNGELES ZORREGUIETA, ANALÍA S TREVANI

JOURNAL OF IMMUNOLOGY

AMER ASSOC IMMUNOLOGISTS

Lugar: Bethesda, Maryland; Año: 2010 vol. 184

0022-1767

We previously demonstrated that extracellular bacterial DNA activates neutrophils through a CpG- and TLR9-independent mechanism. Biofilms are microbial communities enclosed in a polymeric matrix that play a critical role in the pathogenesis of many infectious diseases. Because extracellular DNA is a key component of biofilms of different bacterial species, the aim of this study was to determine whether it plays a role in the ability of biofilms to induce human neutrophil activation. We found that degradation of matrix extracellular DNA with DNase I markedly reduced the capacity of Pseudomonas aeruginosa biofilms to induce the release of the neutrophil proinflammatory cytokines IL-8 and -1b (>75%); reduced the upregulation of neutrophil activation markers CD18, CD11b, and CD66b (p , 0.001); reduced the number of bacteria phagocytosed per neutrophil contacting the biofilm; and reduced the production of neutrophil extracellular traps. Consistent with these findings, we found that biofilms formed by the lasIlrhll P. aeruginosa mutant strain, exhibiting a very low content of matrix extracellular DNA, displayed a lower capacity to stimulate the release of proinflammatory cytokines by neutrophils, which was not decreased further by DNase I treatment. Together, our findings support that matrix extracellular DNA is a major proinflammatory component of P. aeruginosa biofilms.