Imatinib Triggers Phagolysosome Acidification and Antimicrobial Activity againstMycobacterium bovisBacille Calmette–Guérin in Glucocorticoid-Treated Human Macrophages

Abstract

Glucocorticoids are extensively used to treat inflammatory diseases; however, their chronic intake increases the risk for mycobacterial infections. Meanwhile, the effects of glucocorticoids on innate host responses are incompletely understood. In this study, we investigated the direct effects of glucocorticoids on antimycobacterial host defense in primary human macrophages. We found that glucocorticoids triggered the expression of cathelicidin, an antimicrobial critical for antimycobacterial responses, independent of the intracellular vitamin D metabolism. Despite upregulating cathelicidin, glucocorticoids failed to promote macrophage antimycobacterial activity. Gene expression profiles of human macrophages treated with glucocorticoids and/or IFN-γ, which promotes induction of cathelicidin, as well as antimycobacterial activity, were investigated. Using weighted gene coexpression network analysis, we identified a module of highly connected genes that was strongly inversely correlated with glucocorticoid treatment and associated with IFN-γ stimulation. This module was linked to the biological functions autophagy, phagosome maturation, and lytic vacuole/lysosome, and contained the vacuolar H+-ATPase subunit a3, alias TCIRG1, a known antimycobacterial host defense gene, as a top hub gene. We next found that glucocorticoids, in contrast with IFN-γ, failed to trigger expression and phagolysosome recruitment of TCIRG1, as well as to promote lysosome acidification. Finally, we demonstrated that the tyrosine kinase inhibitor imatinib induces lysosome acidification and antimicrobial activity in glucocorticoid-treated macrophages without reversing the anti-inflammatory effects of glucocorticoids. Taken together, we provide evidence that the induction of cathelicidin by glucocorticoids is not sufficient for macrophage antimicrobial activity, and identify the vacuolar H+-ATPase as a potential target for host-directed therapy in the context of glucocorticoid therapy.

IFN-γ Promotes, but Dexamethasone Dissociates, Toll-Like Receptor 2/1-Induced Host Responses in Human Macrophages

“…Priming with IFN-g alone induced CYP27B1 and cathelicidin expression ( Figure 2b, both P < 0.001). In contrast, dexamethasone priming promoted cathelicidin expression ( Figure 2b, P < 0.05), yet not CYP27B1 expression, consistent with previous findings demonstrating that GCs induce cathelicidin independent of CYP27b1 (Steiger et al, 2016). TLR2/1L induced CYP27B1 mRNA expression, which was further increased by IFN-g (Figure 2b, P < 0.05), but not significantly induced in dexamethasoneprimed MDMs (Figure 2b).…”

“…However, dexamethasone increased TLR2 mRNA expression ( Figure 1a, P < 0.01) as well as surface expression ( Figure 1b, P < 0.05), but had no effect on TLR2 intracellular expression ( Figure 1b). To gain a broader insight into the IFN-ge and dexamethasone-mediated regulation of the TLR pathways, we next analyzed a published whole genome microarray (Steiger et al, 2016) that used MDMs cultured with dexamethasone, IFN-g, or media alone for 20 hours. The dataset was filtered for the Kyoto Encyclopedia of Genes and Genomes TLR signaling pathway and differentially expressed genes (P < 0.05) were identified.…”

“…(b) TLR1 and TLR2 cell surface and intracellular protein expression were quantified by FACS (DMFI, AE SEM, n ¼ 8 and n ¼ 5, respectively). (c) A whole genome array dataset of MDMs cultured with media, dexamethasone, or IFN-g (Steiger et al, 2016) was filtered for the KEGG TLR signaling pathway. Differentially expressed genes (P < 0.05) are shown as fold change compared to media.…”

Adjunct Strategies for Tuberculosis Vaccines: Modulating Key Immune Cell Regulatory Mechanisms to Potentiate Vaccination

“…Regulation of the acidification of intracellular compartments has also shown potential to enhance host defense against pathogens. Imatinib, a tyrosine kinase inhibitor (TKI), promotes lysosome acidification and anti-mycobacterial activity in macrophages in a mouse model, and is being further tested as a potential complementary therapy for TB (47–49). TKI inhibition is a strategy for improving autophagy but may also have other mechanisms of action, including suppression of myeloid-derived suppressor cells (MDSCs) and Tregs.…”

Meta-Analysis of in vitro-Differentiated Macrophages Identifies Transcriptomic Signatures That Classify Disease Macrophages in vivo

“…While there have been attempts to summarize published studies in an effort to attain consensus for in vitro models (5), a proper integrative analysis on multiple published datasets has thus far not been performed. To address this, we integrated 206 microarray and bulk RNA-sequencing (RNA-seq) datasets from 19 different studies (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23) to systematically characterize eight in vitro MDM activation states. Specifically, we investigated unstimulated macrophages (M0) and macrophages activated by: short exposure (2-4 h) to LPS (M-LPS early ) or long exposure (18-24 h) to LPS (M-LPS late ), LPS with IFNγ (M-LPS+IFNγ), IFNγ (M-IFNγ), IL-4 (M-IL4), IL-10 (M-IL10), and dexamethasone (M-dex) ( Table 1).…”