The C5a signaling triggers functional intracellular signaling in C5aR+ LysoDCs
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE138972 | GEO | 2021/04/12
REPOSITORIES: GEO
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Project description:The C5a signaling triggers functional intracellular signaling in C5aR+ LysoDCs
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Project description:Macrophages play a crucial role in shaping the immune state within tumor microenvironment (TME) and are often influenced by tumors to hinder antitumor immunity. However, the underlying mechanisms are still elusive. Here, we observed abnormal expression of complement 5a receptor (C5aR) in human ovarian cancer (OC), and identified high levels of C5aR expression on tumor-associated macrophages (TAMs), which led to the polarization of TAMs towards an immunosuppressive phenotype. C5aR knockout or inhibitor treatment restored TAM antitumor response and attenuated tumor progression. Mechanistically, C5aR deficiency reprogrammed macrophages from a protumor state to an antitumor state, associating with the upregulation of immune response and stimulation pathways, which in turn resulted in the enhanced antitumor response of cytotoxic T cells in a manner dependent on chemokine (C-X-C motif) ligand 9 (CXCL9). The pharmacological inhibition of C5aR also improved the efficacy of immune checkpoint blockade therapy. In patients, C5aR expression associated with CXCL9 production and infiltration of CD8+ T cells, and high C5aR level predicted poor clinical outcomes and worse benefits from anti-PD-1 therapy. Thus, our study sheds light on the mechanisms underlying the modulation of TAM antitumor immune response by the C5a-C5aR axis and highlights the potential of targeting C5aR for clinical applications.
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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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Project description:Critical illness is characterised by organ failure, dysregulated immune activation and frequent secondary infections. Unbridled complement activation in these patients exposes immune cells to high levels of the anaphylotoxin, C5a. C5a suppresses antimicrobial functions of key immune cells, in particular the neutrophil, and this suppression is associated with poorer outcomes amongst critically ill adults. The intracellular signalling pathways which mediate C5a-induced neutrophil dysfunction are incompletely understood. Healthy donor peripheral blood neutrophils exposed to purified C5a demonstrated a prolonged defect in phagocytosis of the common nosocomial pathogen Staphylococcus aureus which persisted for 7 hours after exposure. Phosphoproteomic profiling of 2712 unique phosphoproteins identified persistent C5a signalling at 1 hour, and selective impairment of phagosomal protein phosphorylation on exposure to S. aureus. Notable proteins included early endosomal marker ZFYVE16 and V-ATPase proton channel component ATPV1G1. A multi-function assay of bacterial ingestion and phagosomal acidification demonstrated C5a-induced impairment of phagosomal acidification in a whole blood model of Staphylococcal bacteraemia which was recapitulated in neutrophils from critically ill patients. Examination of the C5a-impaired protein phosphorylation indicated a role for the phosphatidylinositol 3-kinase VPS34 in phagosomal maturation. Inhibition of VPS34 impaired neutrophil phagosomal acidification, late bacterial ingestion and killing of S. aureus in whole blood. This study provides a deep phosphoproteomic assessment of human neutrophil signalling in response to S. aureus, and demonstrates how some of these pathways are disrupted by exposure to C5a, identifying a defect in phagosomal maturation and providing new information on mechanisms of immune failure in critical illness.
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Project description:Modulation of C5a-C5aR1 signaling alters the dynamics of AD progression.
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Project description:Epigenetic mechanisms as DNA methylation can affect allograft outcome after kidney transplantation, accelerating renal aging. Complement system is the major player of ischemia reperfusion (I/R) injury and Renal Proximal Tubular Cells (RPTEC) are known to express C5a receptor (C5aR). However, little is known about the downstream effect of C5a-C5aR interaction. We performed a whole-genome DNA methylation analysis on C5a stimulated RPTEC and found several regions regulating genes involved in cell cycle control, DNA damage checkpoints and WNT signaling. These most represented genes were BCL9, CYP1B1 and CDK6. We showed that C5a induced-aberrant gene methylation significantly influences the expression of these genes. Moreover, the stimulation of RTEC by C5a led to senescence by up-regulating SA-β Gal positivity and increasing p53 gene and p21 protein level. IL-6, MCP-1, CTGF gene levels increase indicated the tubular SASP (Senescence associated Secretory Phenotype) acquirement. In accordance, in a swine model of I/R injury, we found that the increase expression of WNT4/βcatenin expression correlated with the augment in SA-β Gal, p21, p16 and IL-6 positivity after 24h from reperfusion. The treatment with C1-INH, a complement inhibitor, efficiently antagonized SASP restoring SA-β Gal, p21, p16, IL-6 expression at basal level and abrogating the WNT4/βcatenin activation. Thus, C5a affects the DNA methylation of genes involved in tubular senescence leading to a persistent, low-grade, inflammatory state called inflammaging. Targeting epigenetic programs may offer novels strategies to protect tubular cells from aging and promote kidney repair and recovery.
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