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Dexamethasone induced inhibition of Dectin-1 activation of antigen presenting cells is mediated via STAT-3 and NF-?B signaling pathways.

ABSTRACT: Treatment of patients with glucocorticoids can result in an increased risk of infection with pathogens such as fungi. Dectin-1 is a member of the C-type lectin receptor superfamily and was shown to be one of the major receptors for fungal beta-glucans. Activation of Dectin-1 increases the production of cytokines and chemokines and T-cell stimulatory capacity of DC and mediates resolution of fungal infections. Here we show that antigen-presenting cells generated in the presence of dexamethasone (Dex-DC) have a reduced capacity to stimulate T-cell proliferation and decreased expression of costimulatory molecules, that can not be enhanced upon stimulation with Dectin-1 ligands. Stimulation of Dex-DC with beta-glucans induced a strong upregulation of Syk phosphorylation and increased secretion of IL-10, while the production of IL-12, IL-23 and TNF-alpha was reduced. Downstream of Syk stimulation of Dectin-1 on Dex-DC resulted in phosphorylation of STAT3 and reduced nuclear localization of transcription factors involved in DC activation and function.

SUBMITTER: Kotthoff P

PROVIDER: S-EPMC5495798 | biostudies-other | 2017 Jul

REPOSITORIES: biostudies-other

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Dexamethasone induced inhibition of Dectin-1 activation of antigen presenting cells is mediated via STAT-3 and NF-κB signaling pathways.

Kotthoff Philipp P Heine Annkristin A Held Stefanie Andrea Erika SAE Brossart Peter P

Scientific reports 20170703 1

Treatment of patients with glucocorticoids can result in an increased risk of infection with pathogens such as fungi. Dectin-1 is a member of the C-type lectin receptor superfamily and was shown to be one of the major receptors for fungal beta-glucans. Activation of Dectin-1 increases the production of cytokines and chemokines and T-cell stimulatory capacity of DC and mediates resolution of fungal infections. Here we show that antigen-presenting cells generated in the presence of dexamethasone ( ...[more]

PMID: 28674449

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Project description:Mollusk hemocyanins have biomedical uses as carriers/adjuvants and nonspecific immunostimulants with beneficial clinical outcomes by triggering the production of proinflammatory cytokines in antigen-presenting cells (APCs) and driving immune responses toward type 1 T helper (Th1) polarization. Significant structural features of hemocyanins as a model antigen are their glycosylation patterns. Indeed, hemocyanins have a multivalent nature as highly mannosylated antigens. We have previously shown that hemocyanins are internalized by APCs through receptor-mediated endocytosis with proteins that contain C-type lectin domains, such as mannose receptor (MR). However, the contribution of other innate immune receptors to the proinflammatory signaling pathway triggered by hemocyanins is unknown. Thus, we studied the roles of Dectin-1, Dectin-2, and Toll-like receptor 4 (TLR4) in the hemocyanin activation of murine APCs, both in dendritic cells (DCs) and macrophages, using hemocyanins from Megathura crenulata (KLH), Concholepas concholepas (CCH) and Fissurella latimarginata (FLH). The results showed that these hemocyanins bound to chimeric Dectin-1 and Dectin-2 receptors in vitro; which significantly decreased when the glycoproteins were deglycosylated. However, hemocyanin-induced proinflammatory effects in APCs from Dectin-1 knock-out (KO) and Dectin-2 KO mice were independent of both receptors. Moreover, when wild-type APCs were cultured in the presence of hemocyanins, phosphorylation of Syk kinase was not detected. We further showed that KLH and FLH induced ERK1/2 phosphorylation, a key event involved in the TLR signaling pathway. We confirmed a glycan-dependent binding of hemocyanins to chimeric TLR4 in vitro. Moreover, DCs from mice deficient for MyD88-adapter-like (Mal), a downstream adapter molecule of TLR4, were partially activated by FLH, suggesting a role of the TLR pathway in hemocyanin recognition to activate APCs. The participation of TLR4 was confirmed through a decrease in IL-12p40 and IL-6 secretion induced by FLH when a TLR4 blocking antibody was used; a reduction was also observed in DCs from C3H/HeJ mice, a mouse strain with a nonfunctional mutation for this receptor. Moreover, IL-6 secretion induced by FLH was abolished in macrophages deficient for TLR4. Our data showed the involvement of TLR4 in the hemocyanin-mediated proinflammatory response in APCs, which could cooperate with MR in innate immune recognition of these glycoproteins.

Project description:Anaplasma phagocytophilum subverts neutrophil function permitting intracellular survival, propagation and transmission. Sustained pro-inflammatory response, recruitment of new host cells for population expansion, and delayed apoptosis are associated with prolonged nuclear presence of NF-κB. We investigated NF-κB signaling and transcriptional activity with A. phagocytophilum infection using inhibitors of NF-κB signaling pathways, and through silencing of signaling pathway genes. How inhibitors or silencing affected A. phagocytophilum growth, inflammatory response (transcription of the κB-enhanced genes CXCL8 and MMP9), and NF-κB signaling pathway gene expression were tested. Among A. phagocytophilum-infected HL-60 cells, nuclear NF-κB p50, p65, and p52 were detected by immunoblots or iTRAQ proteomics. A. phagocytophilum growth was affected most by the IKKαβ inhibitor wedelolactone (reductions of 96 to 99%) as compared with SC-514 that selectively inhibits IKKβ, illustrating a role for the non-canonical pathway. Wedelolactone inhibited transcription of both CXCL8 (p = 0.001) and MMP9 (p = 0.002) in infected cells. Compared to uninfected THP-1 cells, A. phagocytophilum infection led to >2-fold down regulation of 64 of 92 NF-κB signaling pathway genes, and >2-fold increased expression in only 4. Wedelolactone and SC-514 reversed downregulation in all 64 and 45, respectively, of the genes down-regulated by infection, but decreased expression in 1 gene with SC-514 only. Silencing of 20 NF-κB signal pathway genes increased bacterial growth in 12 (IRAK1, MAP3K1, NFKB1B, MAP3K7, TICAM2, TLR3, TRADD, TRAF3, CHUK, IRAK2, LTBR, and MALT1). Most findings support canonical pathway activation; however, the presence of NFKB2 in infected cell nuclei, selective non-canonical pathway inhibitors that dampen CXCL8 and MMP9 transcription with infection, upregulation of non-canonical pathway target genes CCL13 and CCL19, enhanced bacterial growth with TRAF3 and LTBR silencing provide evidence for non-canonical pathway signaling. Whether this impacts distinct inflammatory processes that underlie disease, and whether and how A. phagocytophilum subverts NF-κB signaling via these pathways, need to be investigated.

Dataset Information

Dexamethasone induced inhibition of Dectin-1 activation of antigen presenting cells is mediated via STAT-3 and NF-?B signaling pathways.

Publications

Dexamethasone induced inhibition of Dectin-1 activation of antigen presenting cells is mediated via STAT-3 and NF-κB signaling pathways.

Similar Datasets

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