Neutrophil signaling pathways activated by bacterial DNA stimulation

ALVAREZ ME, FUXMAN BASS JI, GEFFNER JR, CALOTTI PX, COSTAS M, COSO OA, GAMBERALE R, VERMEULEN ME, SALAMONE G, MARTINEZ D, TANOS T, TREVANI AS.

JOURNAL OF IMMUNOLOGY

HighWire Press Portal

Lugar: New York; Año: 2006 vol. 177 p. 4037 - 4046

0022-1767

We have previously shown that bacterial DNA activates human neutrophils in a CpG-independent manner. In this study, we have characterized the signaling pathways involved in the activation mechanism. We found that p38 MAPK, ERK1/2, and JNK pathways, as well as the PI3K/Akt pathway, are activated by bacterial DNA. We also determined that bacterial DNA induces NF-kappaB and AP-1 activation. When analyzing the role of these pathways on neutrophil functions, we observed that up-regulation of CD11b triggered by bacterial DNA was decreased by pharmacological inhibitors of the p38 MAPK, ERK1/2, and JNK, whereas stimulation of IL-8 release was dependent on p38, ERK1/2, and NF-kappaB. Moreover, we found that IL-8 production was markedly enhanced by inhibition of JNK, suggesting that this pathway negatively modulates NF-kappaB-dependent transcription. We also observed that bacterial DNA stimulated IL-1R-associated kinase-1 kinase activity and its partial degradation. Finally, we determined that bacterial DNA stimulated CD11b up-regulation in TLR9(-/-) but not in MyD88(-/-) mouse neutrophils, supporting that bacterial DNA induces neutrophil activation through a TLR9-independent and MyD88-dependent pathway.