TLR9 activation induces normal neutrophil responses in a child with IRAK-4 deficiency: involvement of the direct PI3K pathway.

International audiencePolymorphonuclear neutrophils (PMN) play a key role in innate immunity. Their activation and survival are tightly regulated by microbial products via pattern recognition receptors such as TLRs, which mediate recruitment of the IL-1R-associated kinase (IRAK) complex. We describe a new inherited IRAK-4 deficiency in a child with recurrent pyogenic bacterial infections. Analysis of the IRAK4 gene showed compound heterozygosity with two mutations: a missense mutation in the death domain of the protein (pArg12Cys) associated in cis-with a predicted benign variant (pArg391His); and a splice site mutation in intron 7 that led to the skipping of exon 7. A nontruncated IRAK-4 protein was detected by Western blotting. The patient's functional deficiency of IRAK-4 protein was confirmed by the absence of IRAK-1 phosphorylation after stimulation with all TLR agonists tested. The patient's PMNs showed strongly impaired responses (L-selectin and CD11b expression, oxidative burst, cytokine production, cell survival) to TLR agonists which engage TLR1/2, TLR2/6, TLR4, and TLR7/8; in contrast, the patient's PMN responses to CpG-DNA (TLR9) were normal, except for cytokine production. The surprisingly normal effect of CpG-DNA on PMN functions and apoptosis disappeared after pretreatment with PI3K inhibitors. Together, these results suggest the existence of an IRAK-4-independent TLR9-induced transduction pathway leading to PI3K activation. This alternative pathway may play a key role in PMN control of infections by microorganisms other than pyogenic bacteria in inherited IRAK-4 deficiency

Punicic Acid a Conjugated Linolenic Acid Inhibits TNFα-Induced Neutrophil Hyperactivation and Protects from Experimental Colon Inflammation in Rats

BACKGROUND:Neutrophils play a major role in inflammation by releasing large amounts of ROS produced by NADPH-oxidase and myeloperoxidase (MPO). The proinflammatory cytokine TNFalpha primes ROS production through phosphorylation of the NADPH-oxidase subunit p47phox on Ser345. Conventional anti-inflammatory therapies remain partially successful and may have side effects. Therefore, regulation of neutrophil activation by natural dietary components represents an alternative therapeutic strategy in inflammatory diseases such as inflammatory bowel diseases. The aim of this study was to assess the effect of punicic acid, a conjugated linolenic fatty acid from pomegranate seed oil on TNFalpha-induced neutrophil hyperactivation in vitro and on colon inflammation in vivo. METHODOLOGY AND PRINCIPAL FINDINGS:We analyzed the effect of punicic acid on TNFalpha-induced neutrophil upregulation of ROS production in vitro and on TNBS-induced rat colon inflammation. Results show that punicic acid inhibited TNFalpha-induced priming of ROS production in vitro while preserving formyl-methionyl-leucyl-phenylalanine (fMLP)-induced response. This effect was mediated by the inhibition of Ser345-p47phox phosphorylation and upstream kinase p38MAPK. Punicic acid also inhibited fMLP- and TNFalpha+fMLP-induced MPO extracellular release from neutrophils. In vivo experiments showed that punicic acid and pomegranate seed oil intake decreased neutrophil-activation and ROS/MPO-mediated tissue damage as measured by F2-isoprostane release and protected rats from TNBS-induced colon inflammation. CONCLUSIONS/SIGNIFICANCE:These data show that punicic acid exerts a potent anti-inflammatory effect through inhibition of TNFalpha-induced priming of NADPH oxidase by targeting the p38MAPKinase/Ser345-p47phox-axis and MPO release. This natural dietary compound may provide a novel alternative therapeutic strategy in inflammatory diseases such as inflammatory bowel diseases

Processus oxydants et reponses immunitaires : mecanismes biochimiques et cellulaires

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Régulation de la production des formes réactives de l'oxygène par le polynucléaire neutrophile humain (rôle de la phosphorylation de la protéine p47phox dans l'activation et le priming de la NADPH oxydase)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Effets de l'interleukine 18 sur l'expression des molécules d'adhérence et l'explosion oxydative des polynucléaires neutrophiles humains

PARIS-BIUP (751062107) / SudocSudocFranceF

Regulation de la nadph oxydase phagocytaire par la pat1 protein interacting with app tail 1

Ce travail montre qu une protéine non encore décrite dans les phagocytes, la PAT1 Protein interacting with APP Tail 1 , interagit avec la partie cytosolique de la p22phox (composant du cytochrome b558 membranaire de la NADPH oxydase). Nous avons utilisé différentes approches pour montrer cette interaction : le système double hybride, la technique de GST-pull down, la microscopie confocale et la technique de co-immunoprécipitation. De plus, nous avons montré que la PAT1a recombinante augmente l activité de la NADPH oxydase, in vitro dans un système acellulaire reconstitué, et dans les cellules intactes (monocytes et cellules COS-phox). Cette nouvelle interaction régule donc l activation de la NADPH oxydase et la production des FRO. Par ailleurs, la liaison de PAT1 aux microtubules pourrait favoriser l assemblage du complexe NADPH oxydase pendant son activation. Ceci pourrait conduire à l identification de nouvelles cibles thérapeutiques qui préviennent la survenue des lésions tissulaires dans les maladies inflammatoires.Reactive oxygen species (ROS) production by the phagocyte NADPH oxidase plays a crucial role in host defenses. NADPH oxidase is composed of the membrane flavocytochrome b558 components (p22phox and gp91phox/NOX2), and cytosolic components (p40phox, p47phox, p67phox and a small GTPase Rac1 or Rac2). In this work we identified PAT1 by double hybrid system as a potential partner of p22phox. The interaction between p22phox and PAT1a was further confirmed by in vitro GST pull-down assay, confocal microscopy and co-immunoprecipitation. Addition of recombinant PAT1a to the cell free-system enhanced NADPH oxidase activation and it s over-expression in human monocytes and in COSphox cells increased ROS production in resting and fMLP-stimulated cells.These data clearly identify PAT1 as a novel regulator of NADPH oxidase activation in phagocytes.Inhibition of p22phox/PAT1 interaction could be used as new approach to limit ROS production by phagocytes at inflammatory sites.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Effects of venoms on neutrophil respiratory burst: a major inflammatory function

International audienc