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

Abstract

PGE(2), produced in the lung during infection with microbes such as Klebsiella pneumoniae, inhibits alveolar macrophage (AM) antimicrobial functions by preventing H(2)O(2) production by NADPH oxidase (NADPHox). Activation of the NADPHox complex is poorly understood in AMs, although in neutrophils it is known to be mediated by kinases including PI3K/Akt, protein kinase C (PKC) δ, p21-activated protein kinase (PAK), casein kinase 2 (CK2), and MAPKs. The p40phox cytosolic subunit of NADPHox has been recently recognized to function as a carrier protein for other subunits and a positive regulator of oxidase activation, a role previously considered unique to another subunit, p47phox. The regulation of p40phox remains poorly understood, and the effect of PGE(2) on its activation is completely undefined. We addressed these issues in rat AMs activated with IgG-opsonized K. pneumoniae. The kinetics of kinase activation and the consequences of kinase inhibition and silencing revealed a critical role for a PKCδ-PAK-class I PI3K/Akt1 cascade in the regulation of p40phox activation upon bacterial challenge in AMs; PKCα, ERK, and CK2 were not involved. PGE(2) inhibited the activation of p40phox, and its effects were mediated by protein kinase A type II, were independent of interactions with anchoring proteins, and were directed at the distal class I PI3K/Akt1 activation step. Defining the kinases that control AM p40phox activation and that are the targets for inhibition by PGE(2) provides new insights into immunoregulation in the infected lung.

Leukotriene B 4 –mediated sterile inflammation promotes susceptibility to sepsis in a mouse model of type 1 diabetes

“…In another set of experiments, peritoneal cells were cultured in serum-free media (macrophage-SFM Invitrogen) with or without 10 U/mL insulin or DMEM plus 10% serum (which contains ~ 10 U/mL of insulin) for 24h. Macrophages cultured in the serum-free media were incubated with ERK 1/2 inhibitor (U0126 10 µM), PI3K inhibitor (wortmannin 10 nM) and NFκB inhibitor (BAY117082, 10 µM), with doses previously tested (78, 79). Alternatively, C57BL/6 mice were injected i.p.…”

Transcellular delivery of vesicular SOCS proteins from macrophages to epithelial cells blunts inflammatory signaling

“…These data show that abundant intracellular expression of SOCS proteins is necessary but not sufficient molecules. The lipid mediator PGE 2 down-regulates many features of AM activation (Aronoff et al, 2004;Bourdonnay et al, 2012), and the cytokine IL-10 is well known for its antiinflammatory and immunosuppressive actions (Sabat et al, 2010); these are of particular interest because both are known to be secreted by AECs (Chauncey et al, 1988;Jose et al, 2009) and thus could potentially mediate communication from AECs to AMs. Both rapidly potentiated basal secretion of SOCS3 when added during the post-adherence phase (Fig.…”

SHIP-1 Couples to the Dectin-1 hemITAM and Selectively Modulates Reactive Oxygen Species Production in Dendritic Cells in Response to Candida albicans

“…At the same time, PDK1 activity depends on binding to PIP 3 through its PH domain, facilitating not only Akt activation but also some other targets such as p70 ribosomal protein S6 or PKC (68). Although PDK1 does not directly phosphorylate the p40 NADPH subunit (69), the PDK1 target PKC promotes activation of the NADPH oxidase complex (43, 70). Gp91phox and p40phox components of the NADPH oxidase are implicated in Dectin-1-mediated ROS production (71, 72) and in accordance with our results, enhanced ROS production in response to Saccharomyces cerevisiae is accompanied by increased p40phox and Syk phosphorylation (42).…”