The Mincle ligand trehalose dibehenate differentially modulates M1‐like and M2‐like macrophage phenotype and function via Syk signaling

Abstract

IntroductionMacrophages play a significant role in the progression of diseases, such as cancer, making them a target for immune‐modulating agents. Trehalose dibehenate (TDB) is known to activate M1‐like macrophages via Mincle, however, the effect of TDB on M2‐like macrophages, which are found in the tumor microenvironment, has not been studied.MethodsqRT‐PCR, flow cytometry, cytokine ELISA, and Western Blotting were used to study the effect of TDB on GM‐CSF and M‐CSF/IL‐4 derived bone marrow macrophages (BMMs) from C57BL/6 and Mincle−/− mice.ResultsTDB treatment up‐regulated M1 markers over M2 markers by GM‐CSF BMMs, whereas M‐CSF/IL‐4 BMMs down‐regulated marker gene expression overall. TDB treatment resulted in Mincle‐independent down‐regulation of CD11b, CD115, and CD206 expression by GM‐CSF macrophages and CD115 in M‐CSF/IL‐4 macrophages. GM‐CSF BMMs produced of significant levels of proinflammatory cytokines (IL‐1β, IL‐6, TNF‐α), which was Mincle‐dependent and further enhanced by LPS priming. M‐CSF BMMs produced little or no cytokines in response to TDB regardless of LPS priming. Western blot analysis confirmed that the absence of cytokine production was associated with a lack of activation of the Syk kinase pathway.ConclusionThis study illustrates that TDB has the potential to differentially regulate M1‐ and M2‐like macrophages in the tumor environment.

The coadministration of trehalose dibehenate and monosodium urate crystals promotes an antitumor phenotype in human‐derived myeloid cells

“…In addition to being a marker of “M2‐like” macrophages, CD115 has been negatively correlated with the prognosis of cancer patients, with CD115 inhibition or deletion proving to be promising anticancer therapies 43 . Herein, our findings support those of our murine assays 20 with CD115 on all three human myeloid cells being downregulated upon treatment with TDB. The coadministration of MSU + TDB further augmented this response in the monocyte population.…”

“…Accordingly, the trend toward the downregulation of Mincle upon the stimulation of human Mo‐M and Mo‐DCs with TDB may favor an antitumorigenic phenotype, although further studies into the role of Mincle and cancer need to be undertaken. Herein, it is important to note that in murine studies, the treatment of macrophages with TDB led to an increase in Mincle expression 14,20,29 . Thus, our findings further illustrate species‐specific differences that may exist with regard to Mincle expression 17,46 .…”

“…Upon binding of TDM or TDB to Mincle, the Syk and Card9–Bcl10–MALT1 inflammasome pathways are activated, which ultimately leads to the cellular production of cytokines and chemokines and a type 1 helper immune response 14,16,18,19 . We demonstrated that TDB alters the phenotype of murine macrophages to one that favors tumor regression 20 . MSU, a damage‐associated molecular pattern, is an innate adjuvant that boosts immune responses through the activation of the NLRP3 inflammasome and the release of active interleukin (IL)‐1β, 21 and has been found to enhance tumor rejection, potentially though the stimulation of APCs 12,13 .…”

The Role of Macrophage-Inducible C-Type Lectin in Different Stages of Chronic Liver Disease

“…The downstream signaling of the complex proceeds inter alia via spleen associated tyrosine kinase (SYK) and the nuclear factor kappa-light-chain-enhancer (NF-κB) to induce the gene expression of pro-inflammatory cytokines, chemokines, and enzymes (4,5). On the cellular level, mincle stimulation promotes the inflammatory phenotype of mainly M1 macrophages (6,7).…”

Mycobacterial Trehalose 6,6′-Dimycolate–Induced M1-Type Inflammation

“…A related Mincle ligand, the shorter chain TDM analog trehalose dibehenate, was also shown to differentially modulate M1like (and M2-like) macrophage phenotypes through Syk signaling processes. 56 Both Syk and CARD9 pathway interactions have shown to then further engage development of directed hypersensitive responses, 57,58 as well as inflammatory signaling pathways. 59 Perhaps additional experiments comparing trehalose 6-monomycolate (TMM) or galactose-galactose 6,6 0 dimycolate (GDM) may shed light on the inflammatory response leading to the presence of M1-like phenotype found in this study.…”