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Blockade of C5aR1 resets M1 via gut microbiota-mediated PFKM stabilization in a TLR5-dependent manner

ABSTRACT: Increased researches show that complement, the codominant central mediator of humoral immunity, is a critical factor in tumor initiation, development, and chemotherapy resistance. C5a/C5aR1 signaling has been shown to promote tumor progression by recruiting MDSCs in breast malignancies And blockade of C5aR1 resets M1 via gut microbiota-mediated PFKM stabilization in a TLR5-dependent manner. We here report that TLR5 as a key regulator of tumor associated macrophages M1 polarization. Flagellin, the protein subunit of the bacterial flagellum, stimulates the innate immune receptor Toll-like receptor 5 (TLR5) after pattern recognition. Receptor activity was turned by a TLR5-flagellin interaction distal to the site of pattern recognition. Thus, activation of downstream signaling pathway is promoted.

ORGANISM(S): Mus musculus

PROVIDER: GSE252048 | GEO | 2024/01/20

REPOSITORIES: GEO

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Project description:The healthy gut microbiota is composed of three different functional subgroups, symbionts, commensals and pathobionts. Additionally, infection with pathogenic bacteria can occur. Microbe Associated Molecular Patterns (MAMPs) are expressed by most members of both, microbiota and pathogens and interact with Pattern Recognition Receptors (PRRs), resulting in activation of the innate immune system. It is still unclear whether the interaction of PRRs with MAMPs of different origin, leads to a differential activation of innate immunity and whether thereby, distinction can be made between symbionts, commensals, pathobionts and pathogens. Here we addressed the question whether the interaction of flagellin with Toll-like receptor 5 (TLR5) might be a possible mechanism of the innate immune system to distinguish between the different microbial subgroups and initiate the respective immune response. To characterize distinct cellular immune responses to symbiont or pathogen derived flagellin we run transcriptomics, phosphoproteomics and proteomics of TLR5 overexpressing cells. Responses to different flagellins were characterized by differential kinetics and regulation of protein phosphorylation as well as variant protein expression patterns. In vivo experiments revealed that commensal derived flagellin mediated an inert TLR5 signal, thus not affecting Dextran-Sodium-Sulfate (DSS) induced intestinal inflammation. In vitro pathogenic derived flagellin induced a strong pro-inflammatory TLR5 response and did not ameliorate intestinal inflammation. In contrast, symbiont derived flagellin revealed an intermediate TLR5 activation and clearly ameliorated DSS induced intestinal inflammation thus shifting the host immune response in favor of mucosal immune balance. Bone marrow chimeric mice proofed that CD11c+TLR5+ intestinal lamina propria cells mediate the anti-inflammatory symbiotic effect of flagellin. We suggest that the quality of flagellin-induced TL signal might determine the balance between homeostasis and intestinal inflammation and may help the innate immune system to distinguish between symbionts, commensals, pathobionts and pathogenic microbes. We used microarrays to analyze differential expression of genes between treatments with flagellins of E. coli Nissle (EcN) and Salmonella Typhimurium SL1344 (ST).

Project description:The complement system is part of the innate immune system that works to clear pathogens and cellular debris. In the central nervous system (CNS) complement activation can promote synaptic pruning clearance of neuronal blebs recruitment of phagocytes and protection from pathogens. However in a neuropathologic environment complement activation may contribute to inflammatory pathways neuronal dysfunction and in the Alzheimer’s disease (AD) brain cognitive decline. If complement activation proceeds to the cleavage of C5 and thus generation of C5a engagement of C5a with the receptor C5aR1 can instigate a feed-forward loop of inflammation injury and neuronal death thus making this molecule a potential target for modulation in AD therapeutics. The Arctic (Arc) AD mouse model known to rapidly accumulate fibrillar amyloid plaques was crossed to a model that lacks the receptor for C5a (ArcC5aR1KO) or to a transgenic mouse that generates C5a under the GFAP promoter (ArcC5a+). ArcticC5a+ mice showed accelerated loss of spatial memory compared to Arc mice. While eliminating C5aR1 did not alter amyloid plaque accumulation in this AD model C5aR1KO delayed or prevented the expression of important AD-associated genes in the hippocampus indicating a separation between those genes induced by amyloid plaques and those influenced by C5a-C5aR1 signaling. C5ar1 deletion also reduced/delayed the expression of select pan-reactive and A1 reactive astrocyte genes. ArcC5aR1KO showed delayed expression of genes enriched for biological processes that are significant in the AD context such as regulation of inflammatory signaling microglial cell activation astrocyte migration and lysosome pathway. Interestingly overexpression of C5a also delayed the increase of some AD- complement and astrocyte-associated genes perhaps mediated by C5aR2 and emphasizing the importance of selectively suppressing C5aR1. Immunohistochemical investigation further confirmed that modulation of C5a-C5aR1 either delayed or reduced some reactive microglial markers in the Arc hippocampus including CD11b and CD11c. These results suggest that C5a-C5aR1 signaling in the context of AD largely exerts its effects by suppressing those microglial activation pathways that accelerate disease enhancing pathways. Given the highly focused modulation of a common driver of neurotoxicity pharmacological inhibition of this C5aR1 signaling pathway is a promising therapeutic strategy to treat AD.

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Blockade of C5aR1 resets M1 via gut microbiota-mediated PFKM stabilization in a TLR5-dependent manner

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