Molecular mechanisms involved in IL-1beta release by human neutrophils

GABELLONI ML,; FUXMAN BASS JI; GEFFNER JR; SALAMONE G; CATALANO M; TREVANI AS

Viña del Mar

Congreso; Immunochile 2009. 9th Latin American Congress of Immunology; 2009

Asociacion Latinoamericana de Inmunologia

IL-1beta is released by proteolytic processing of its precursor, pro-IL-1beta. Stimulation of NOD cytosolic receptors by microbial products or endogen stress signals leads to the formation of an inflammasome, which recruits and activates caspase-1, the enzyme responsible for processing pro-IL-1 beta. Alternatively, pro-IL-1 beta might be clived by a not yet characterized caspase-1-independent mechanism. We have evaluated the capacity of human neutrophils to produce IL-1 beta and the underlying molecular mechanisms. LPS-pretreated neutrophils released IL-1b in response to ATP, PMA or Pseudomonas aeruginosa culture supernatant (PaCS) stimulation and also in response to co-culture with the whole bacteria (pg/ml IL-1 beta detected by ELISA: 15± 6; 85± 25; 521± 85; 361± 43; 231± 49; 218± 55; for media, LPS -200 ng/ml-, LPS+PMA 20 ng/ml; LPS+ATP 2mM; LPS+5% PaCS o 107 bacteria/ml, respectively; n=6, p<0.05). IL-1 beta  release induced by all agonists except PMA was significantly reduced by caspase-1 inhibitor II (% inh. 19± 4; 59± 13; 76± 6; for PMA, ATP and PaCS, respectively; n= 8, p<0.05).  Pretreatment of neutrophils with DPI, a NADPH oxidase inhibitor, markedly reduced PMA and PaCS-induced IL-1 release, while pretreatment with catalase, a H2O2 scavenger, increased ATP, PMA and PaCS-induced IL-1 beta release. Altogether, our results suggest that a mechanism involving caspase-1 takes place in neutrophils for IL-1 beta release, even though they do not rule out that a caspase-1- independent mechanism could also be operating. At least in response to PMA and PaCS, IL-1b release seems to require NADPH oxidase activation. However, reactive oxygen species could also negatively regulate IL-1 beta release.