Regulation of alveolar macrophage p40phox: hierarchy of activating kinases and their inhibition by PGE2

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141717/1/jlb0219.pd

EP4 and EP2 Receptor Activation of Protein Kinase A by Prostaglandin E 2 Impairs Macrophage Phagocytosis of Clostridium sordellii

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102186/1/aji12153.pd

Games of Incomplete Information and Myopic Equilibria

A new concept of an equilibrium in games is introduced that solves an open question posed by A. Neyman

Modulation de l'expression génique par l'arsenic inorganique dans le monocyte/macrophage humain

L arsenic (PM = 74,92 g/mol) est un contaminant environnemental majeur dans le monde présent au niveau de la croûte terrestre. Sa concentration dans le sol est d environ 2 ppm. L arsenic peut être redistribué vers les compartiments aquatiques et atmosphériques. Par ailleurs, les diverses utilisations industrielles et agricoles de l arsenic sont également responsables de son accumulation dans l environnement. La consommation d eau au niveau de nappes phréatiques contaminées conduit à un empoisonnement chronique à l arsenic dans de nombreuses régions du monde, et les troubles développés par ces individus sont multiples. Toutefois, les bases moléculaires restent encore mal connues. Des études récentes suggèrent que l immunotoxicité de l arsenic pourrait expliquer certains effets chez l homme. Au laboratoire il a été montré que l arsenic est capable d induire des modifications phénotypiques importantes au niveau du macrophage pouvant être assimilées à une dé-différenciation macrophagique. La différenciation macrophagique est un ensemble de mécanismes moléculaires complexes, modulant l expression de nombreux gènes, et permettant l induction de caractéristiques phénotypiques spécifiques du macrophage. Elle peut être induite par des facteurs de croissance de type GM-CSF et G-CSF et implique l intervention de facteurs de transcription, tel que PU.1. Dans un premier projet, nous avons précisé l impact de l arsenic sur les processus de différenciation macrophagique induits par le GM-CSF, et notamment ses effets sur l expression de gènes associés au processus de différenciation, à l aide d une étude transcriptomique. Nous avons montré que l arsenic est capable de moduler l expression d un grand nombre de gènes dans le macrophage exposé à ce toxique. Ce sont, d une part, des gènes de stress mais aussi des gènes associés au processus de différenciation. Par ailleurs, ces régulations géniques impliquent des voies de signalisation sensibles au statut rédox indépendantes de la synthèse d Espèces Activées de l Oxygène (EAO). L arsenic est également capable de sensibiliser le macrophage à une exposition au LPS. De plus, une exposition chronique d individus à l arsenic puis au LPS/IFN? ex-vivo sensibilise les PBMC à la réponse cytokinique au LPS. C est donc qu il existe un mécanisme opérant in vivo. Le second projet a eu pour but d identifier les voies de signalisation impliquées dans la potentialisation par l arsenic de la réponse cytokinique induite par le LPS dans le monocyte humain; ceci met en jeu la voie de signalisation SRC-pMKK3/6-p38-kinase et la synthèse d EAO.Au total, ces travaux ont permis de préciser les mécanismes de toxicité de l arsenic vis-à-vis des cellules immunitaires humaines.RENNES1-BU Santé (352382103) / SudocSudocFranceF

Transcriptional Regulation of Inflammasomes

Inflammasomes are multimolecular complexes with potent inflammatory activity. As such, their activity is tightly regulated at the transcriptional and post-transcriptional levels. In this review, we present the transcriptional regulation of inflammasome genes from sensors (e.g., NLRP3) to substrates (e.g., IL-1β). Lineage-determining transcription factors shape inflammasome responses in different cell types with profound consequences on the responsiveness to inflammasome-activating stimuli. Pro-inflammatory signals (sterile or microbial) have a key transcriptional impact on inflammasome genes, which is largely mediated by NF-κB and that translates into higher antimicrobial immune responses. Furthermore, diverse intrinsic (e.g., circadian clock, metabolites) or extrinsic (e.g., xenobiotics) signals are integrated by signal-dependent transcription factors and chromatin structure changes to modulate transcriptionally inflammasome responses. Finally, anti-inflammatory signals (e.g., IL-10) counterbalance inflammasome genes induction to limit deleterious inflammation. Transcriptional regulations thus appear as the first line of inflammasome regulation to raise the defense level in front of stress and infections but also to limit excessive or chronic inflammation

Arsenic increases lipopolysaccharide-dependent expression of interleukin-8 gene by stimulating a redox-sensitive pathway that strengthens p38-kinase activation.

International audienceInorganic arsenic is an immunotoxic metalloid that causes or exacerbates deleterious inflammatory states. Notably, arsenic can increase inflammation-related gene expression induced by lipopolysaccharide (LPS) in monocytes/macrophages. Molecular mechanisms mediating such effects remain however poorly understood. In the present study, we determined molecular basis of arsenic trioxide (ATO) effects on LPS-dependent expression of interleukin-8 (IL-8) gene in human monocytic cells. Pre-treatment with non cytotoxic concentrations of ATO for 48h increase IL-8 gene expression induced by LPS in monocytic U937 cells and in some, but not all, primary cultures of blood monocytes. Actinomycin D blocks induction of IL-8 mRNA levels in LPS-stimulated U937 cells pre-treated or not with ATO, which suggests that the metalloid strengthens LPS-dependent transcriptional regulation of IL-8 expression. ATO increases LPS-dependent expression of IL-8 by enhancing p38-kinase activity induced by LPS in U937 cells. This increment of LPS-dependent p38-kinase activity is caused by the ATO-related production of reactive oxygen species (ROS) and the subsequent activation of the tyrosine kinase Src. The antioxidant N-acetylcysteine almost totally inhibits ROS production and Src kinase activation in ATO-pre-treated cells. In addition, it markedly prevents the increase of both p38-kinase phosphorylation and IL-8 gene expression in LPS-stimulated cells pre-treated with ATO. Finally, as observed with the metalloid, pre-treatment of U937 cells with hydrogen peroxide markedly increases LPS-dependent expression of IL-8 gene. In conclusion, our study demonstrates that ATO increases LPS-dependent expression of the inflammatory IL-8 gene by strengthening the p38 kinase activity induced by LPS through stimulation of a ROS/Src kinase signalling pathway

Human macrophages constitute targets for immunotoxic inorganic arsenic.

International audienceChronic exposure to inorganic arsenic, a widely distributed environmental contaminant, can lead to toxic effects, including immunosuppression. Owing to the established roles of human macrophages in immune defense, we determined, in the present study, whether inorganic arsenic can affect these major immune cells. Our results demonstrate that noncytotoxic concentrations of arsenic trioxide (As2O3), an inorganic trivalent form, markedly impair differentiated features of human blood monocyte-derived macrophages. First, treatment of macrophages with 1 microM As2O3 induced a rapid cell rounding and a subsequent loss of adhesion. These morphologic alterations were associated with a marked reorganization of actin cytoskeleton, which includes retraction of peripheral actin extensions and formation of a cortical actin ring. In addition, As2O3 reduced expression of various macrophagic surface markers, enhanced that of the monocytic marker CD14, and altered both endocytosis and phagocytosis; unexpectedly, exposure of macrophages to the metalloid also strongly potentiated expression of TNFalpha and IL-8 induced by LPS. Finally, like monocytes, As2O3-treated macrophages can be differentiated into dendritic-like cells. Impairment of macrophage function by As2O3 mainly resulted from activation of a RhoA/Rho-associated kinase pathway; indeed, pretreatment of macrophages with the Rho-associated kinase inhibitor Y-27632 prevented metalloid effects on cytoskeleton and phagocytosis. Moreover, As2O3 was found to increase level of the active GTP-bound form of RhoA and that of phosphorylated-Moesin, a major cytoskeleton adaptor protein involved in RhoA regulation. Taken together, our results demonstrated that human macrophages constitute sensitive targets of inorganic arsenic, which may contribute to immunotoxicity of this environmental contaminant

Inorganic arsenic activates reduced NADPH oxidase in human primary macrophages through a Rho kinase/p38 kinase pathway.

International audienceInorganic arsenic is an immunotoxic environmental contaminant to which millions of humans are chronically exposed. We recently demonstrated that human primary macrophages constituted a critical target for arsenic trioxide (As(2)O(3)), an inorganic trivalent form. To specify the effects of arsenic on macrophage phenotype, we investigated in the present study whether As(2)O(3) could regulate the activity of NADPH oxidase, a major superoxide-generating enzymatic system in human phagocytes. Our results show that superoxide levels were significantly increased in a time-dependent manner in blood monocyte-derived macrophages treated with 1 muM As(2)O(3) for 72 h. Concomitantly, As(2)O(3) induced phosphorylation and membrane translocation of the NADPH oxidase subunit p47(phox) and it also increased translocation of Rac1 and p67(phox). Apocynin, a selective inhibitor of NADPH oxidases, prevented both p47(phox) translocation and superoxide production. NADPH oxidase activation was preceded by phosphorylation of p38-kinase in As(2)O(3)-treated macrophages. The p38-kinase inhibitor SB-203580 prevented phosphorylation and translocation of p47(phox) and subsequent superoxide production. Pretreatment of macrophages with the Rho-kinase inhibitor Y-27632 was found to mimic inhibitory effects of SB-203580 and to prevent As(2)O(3)-induced phosphorylation of p38 kinase. Treatment with As(2)O(3) also resulted in an increased secretion of the proinflammatory chemokine CCL18 that was fully inhibited by both apocynin and SB-203580. Taken together, our results demonstrate that As(2)O(3) induced a marked activation of NADPH oxidase in human macrophages, likely through stimulation of a Rho-kinase/p38-kinase pathway, and which may contribute to some of the deleterious effects of inorganic arsenic on macrophage phenotype