The gut microbial metabolite trimethylamine N-oxide aggravates GVHD by inducing M1 macrophage polarization in mice

Abstract

The diversity of human microbiome heralds the difference of impact that gut microbial metabolites exert on allogenic graft-versus-host disease (GVHD), even though short-chain fatty acids and indole were demonstrated to reduce its severity. In this study, we dissected the role of choline-metabolized trimethylamine N-oxide (TMAO) in GVHD process. Either TMAO or high choline diet enhanced allogenic GVH reaction, while the analog of choline, 3,3-dimethyl-1-butanol reversed TMAO-induced GVHD severity. Interestingly, TMAO-induced alloreactive T cell proliferation and differentiation into T helper (Th) subtypes was seen in GVHD mice but not in in vitro cultures. We thus investigated the role of macrophage polarization which was absent from in vitro culture system. F4/80+CD11b+CD16/32+ M1 macrophage and signature genes, IL-1β, IL-6, TNF-α, CXCL9 and CXCL10 were increased in TMAO-induced GVHD tissues and in TMAO-cultured bone marrow derived macrophages (BMDMs). Inhibition of NLRP3 inflammosome reversed TMAO-stimulated M1 features, indicating that NLRP3 is the key proteolytic activator involved in macrophage's response to TMAO stimulation. Consistently, mitochondrial reactive oxygen species and enhanced NF-κB nuclear re-localization were investigated in TMAO-stimulated BMDMs. In vivo depletion of NLRP3 in GVHD recipients not only blocked M1 polarization but also reversed GVHD severity in the presence of TMAO treatment. In conclusion, our data revealed that TMAO-induced GVHD progression is resulted from Th1 and Th17 differentiation, which is mediated by polarized M1 macrophage requiring NLRP3 inflammasome activation. It provides the link among the host choline diet, microbial metabolites and GVH reaction, shedding light on alleviating GVHD by controlling choline diet.

Interaction between microbiota and immunity in health and disease

“…88 Recently, it has been demonstrated that a soluble microbiome-derived metabolite, trimethylamine N-oxide (TMAO), can drive murine macrophage polarization in an NLRP3 inflammasome-dependent manner. 89 Innate lymphoid cells (ILCs) are a more recently discovered heterogenous innate immune cell population specialized in the rapid secretion of polarized cytokines and chemokines to combat infection and promote mucosal tissue repair. 90 ILCs have been categorized into three distinct types based on transcription factors and cytokine signatures.…”

Inflammasomes and the Maintenance of Hematopoietic Homeostasis: New Perspectives and Opportunities

“…Recently, a study from China reported that the gut microbial metabolite choline-metabolized trimethylamine N-oxide exacerbates GvHD by inducing M1 macrophage polarization, and the underlying mechanism also involves NLRP3 inflammasome activation [ 145 ]. Therefore, further understanding the activation mechanism of the inflammasome in different types of cells and their roles in GvHD will help to effectively prevent and treat GvHD in the clinic.…”

Microbiome-Derived Metabolites in Allogeneic Hematopoietic Stem Cell Transplantation

“…Wu et al recently reported the role of choline-derived trimethylamine N-oxide (TMAO) in the HSCT context [ 16 ]. This metabolite is already well known to play an important role in vascular inflammation and endothelial dysfunction, contributing to the genesis of atherosclerosis and thrombosis [ 60 ].…”

“…The main involved bacterial strains are Anaerococcus hydrogenalis , Clostridium asparagiforme , Clostridium hathewayi , Clostridium sporogenes , Edwardsiella tarda , Escherichia fergusonii , Proteus penneri and Providencia rettgeri [ 62 ]. Both TMAO and choline were found to be associated in mouse model with an enhanced allogeneic GvHD reaction [ 16 ]. Furthermore, the authors demonstrate that TMAO induces the expression of M1 macrophages and M1-like cytokines both in tissues and in bone marrow in an NLRP3-dependent fashion [ 16 , 63 ].…”