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Background: Accumulating evidence underscores the pivotal role of heightened inflammation in the pathophysiology of stress-related diseases, but the underlying mechanisms remain elusive. The complement system, a key effector of the innate immune system, produces the C5–cleaved activation product C5a upon activation, initiating inflammatory responses through the canonical C5a receptor 1 (C5aR1). While C5aR1 is expressed in stress-responsive brain regions, its role in stress responsiveness remains unknown. Methods: To investigate C5a-C5aR1 signaling in stress responses, mice underwent acute and chronic stress paradigms. Circulating C5a levels and messenger RNA expression of C5aR1 in the hippocampus and adrenal gland were measured. C5aR1-deficient mice were used to elucidate the effects of disrupted C5a-C5aR1 signaling across behavioral, hormonal, metabolic, and inflammation parameters. Results: Chronic restraint stress elevated circulating C5a levels while reducing C5aR1 messenger RNA expression in the hippocampus and adrenal gland. Notably, the absence of C5aR1 signaling enhanced adrenal sensitivity to adrenocorticotropic hormone, concurrently reducing pituitary adrenocorticotropic hormone production and enhancing the response to acute stress. C5aR1-deficient mice exhibited attenuated reductions in locomotor activity and body weight under chronic stress. Additionally, these mice displayed increased glucocorticoid receptor sensitivity and disrupted glucose and insulin homeostasis. Chronic stress induced an increase in C5aR1-expressing microglia in the hippocampus, a response mitigated in C5aR1-deficient mice. Conclusions: C5a-C5aR1 signaling emerges as a key metabolic regulator during stress, suggesting that complement activation and dysfunctional C5aR1 signaling may contribute to neuroinflammatory phenotypes in stress-related disorders. The results advocate for further exploration of complement C5aR1 as a potential therapeutic target for stress-related conditions.

Inflammation is a complex host response to harmful infection or injury, and it seems to play a crucial role in tissue regeneration both positively and negatively. We have previously demonstrated that the activation of the complement C5a pathway affects dentin-pulp regeneration. However, limited information is available to understand the role of the complement C5a system related to inflammation-mediated dentinogenesis. The aim of this study was to determine the role of complement C5a receptor (C5aR) in regulating lipopolysaccharide (LPS)-induced odontogenic differentiation of dental pulp stem cells (DPSCs). Human DPSCs were subjected to LPS-stimulated odontogenic differentiation in dentinogenic media treated with the C5aR agonist and antagonist. A putative downstream pathway of the C5aR was examined using a p38 mitogen-activated protein kinase (p38) inhibitor (SB203580). Our data demonstrated that inflammation induced by the LPS treatment potentiated DPSC odontogenic differentiation and that this is C5aR dependent. C5aR signaling controlled the LPS-stimulated dentinogenesis by regulating the expression of odontogenic lineage markers like dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP-1). Moreover, the LPS treatment increased the total p38, and the active form of p38 expression, and treatment with SB203580 abolished the LPS-induced DSPP and DMP-1 increase. These data suggest a significant role of C5aR and its putative downstream molecule p38 in the LPS-induced odontogenic DPSCs differentiation. This study highlights the regulatory pathway of complement C5aR/p38 and a possible therapeutic approach for improving the efficiency of dentin regeneration during inflammation. [ABSTRACT FROM AUTHOR]

BackgroundPharmacologic inhibition of C5aR1, a receptor for the complement activation proinflammatory fragment, C5a, suppressed pathology and cognitive deficits in Alzheimer's disease (AD) mouse models. To validate that the effect of the antagonist was specifically via C5aR1 inhibition, mice lacking C5aR1 were generated and compared in behavior and pathology. In addition, since C5aR1 is primarily expressed on cells of the myeloid lineage, and only to a lesser extent on endothelial cells and neurons in brain, gene expression in microglia isolated from adult brain at multiple ages was compared across all genotypes.MethodsC5aR1 knock out mice were crossed to the Arctic AD mouse model, and characterized for pathology and for behavior performance in a hippocampal dependent memory task. CX3CR1GFP and CCR2RFP reporter mice were bred to C5aR1 sufficient and knockout wild type and Arctic mice to enable sorting of microglia (GFP-positive, RFP-negative) isolated from adult brain at 2, 5, 7 and 10 months of age followed by RNA-seq analysis.ResultsA lack of C5aR1 prevented behavior deficits at 10 months, although amyloid plaque load was not altered. Immunohistochemical analysis showed no CCR2+ monocytes/macrophages near the plaques in the Arctic brain with or without C5aR1. Microglia were sorted from infiltrating monocytes (GFP and RFP-positive) for transcriptome analysis. RNA-seq analysis identified inflammation related genes as differentially expressed, with increased expression in the Arctic mice relative to wild type and decreased expression in the Arctic/C5aR1KO relative to Arctic. In addition, phagosomal-lysosomal gene expression was increased in the Arctic mice relative to wild type but further increased in the Arctic/C5aR1KO mice. A decrease in neuronal complexity was seen in hippocampus of 10 month old Arctic mice at the time that correlates with the behavior deficit, both of which were rescued in the Arctic/C5aR1KO.ConclusionsThese data are consistent with microglial polarization in the absence of C5aR1 signaling reflecting decreased induction of inflammatory genes and enhancement of degradation/clearance pathways, which is accompanied by preservation of CA1 neuronal complexity and hippocampal dependent cognitive function. These results provide links between microglial responses and loss of cognitive performance and, combined with the previous pharmacological approach to inhibit C5aR1 signaling, support the potential of this receptor as a novel therapeutic target for AD in humans.

Complement component fragment 5a (C5a) is one of the potent proinflammatory modulators of the complement system. C5a recruits two genomically related G protein-coupled receptors (GPCRs), like C5aR1 and C5aR2, constituting a binary complex. The C5a-C5aR1/C5aR2 binary complexes involve other transducer proteins like heterotrimeric G-proteins and β-arrestins to generate the fully active ternary complexes that trigger intracellular signaling through downstream effector molecules in tissues. In the absence of structural data, we had recently developed highly refined model structures of C5aR2 in its inactive (free), meta-active (complexed to the CT-peptide of C5a), and active (complexed to C5a) state embedded to a model palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer. Compared to C5aR1, C5aR2 is established as a noncanonical GPCR, as it recruits and signals through β-arrestins rather than G-proteins. Notably, structural understanding of the ternary complex involving C5a-C5aR2-β-arrestin is currently unknown. The current study has attempted to fill the gap by generating a highly refined, fully active ternary model structural complex of the C5a-C5aR2-β-arrestin1 embedded in a model POPC bilayer. The computational modeling, 500 ns molecular dynamics (MD) studies, and the principal component analysis (PCA), including the molecular mechanics Poisson-Boltzmann surface area (MM PBSA) based data presented in this study, provide an experimentally testable hypothesis about C5a-C5aR2-β-arrestin1 extendable to other such ternary systems. The model ternary complex of C5a-C5aR2-β-arrestin1 will further enrich the current structural understanding related to the interaction of β-arrestins with the C5a-C5aR2 system.Communicated by Ramaswamy H. Sarma.

Alzheimer's disease (AD) is a progressive neurodegenerative disease of the brain causing either familial or sporadic dementia. We have previously administered the modified C5a receptor agonist (EP67) for a short period to a transgenic mouse model of AD (5XFAD) and have observed not only reduction in β-amyloid deposition and gliosis but also improvement in cognitive impairment. Inquiring, however, on the effects of EP67 in an already heavily burdened animal, thus representing a more realistic scenario, we treated 6-month-old 5XFAD mice for a period of 14 weeks. We recorded a significant decrease in both fibrillar and pre-fibrillar β-amyloid as well as remarkable amelioration of cognitive impairment. Following proteomic analysis and pathway association, we postulate that these events are triggered through the upregulation of β-adrenergic and GABAergic signaling. In summary, our results reveal how inflammatory responses can be employed in inducing tangible phenotype improvements even in advanced stages of AD. [ABSTRACT FROM AUTHOR]

Alterations in the microenvironment change the phenotypes of dental pulp stem cells (DPSCs). The role of complement component C5a in the differentiation of DPSCs is unknown, especially under oxygen-deprived conditions. The aim of this study was to determine the effect of C5a on the odontogenic differentiation of DPSCs under normoxia and hypoxia. Human DPSCs were subjected to odontogenic differentiation in osteogenic media and treated with the C5a receptor antagonist-W54011 under normal and hypoxic conditions (2% oxygen). Immunochemistry, western blot, and PCR analysis for the various odontogenic differentiation genes/proteins were performed. Our results demonstrated that C5a plays a positive role in the odontogenic differentiation of DPSCs. C5a receptor inhibition resulted in a significant decrease in odontogenic differentiation genes, such as DMP1, ON, RUNX2, DSPP compared with the control. This observation was further supported by the Western blot data for DSPP and DMP1 and immunohistochemical analysis. The hypoxic condition reversed this effect. Our results demonstrate that C5a regulates the odontogenic DPSC differentiation under normoxia. Under hypoxia, C5a exerts a reversed function for DPSC differentiation. Taken together, we identified that C5a and oxygen levels are key initial signals during pulp inflammation to control the odontogenic differentiation of DPSCs, thereby, providing a mechanism for potential therapeutic interventions for dentin repair and vital tooth preservation. [ABSTRACT FROM AUTHOR]

Background C5a promotes alloreactivity via the C5a receptor 1 (C5aR1) on immune cells, but this has not been confirmed in the case of small intestine transplantation immunity. In the present study, we examined the effect of C5aR1 antagonist (PMX53) on macrophage function in small intestinal transplantation. Methods The model was created by heterotopic intestinal transplantation using donor Dark Agouti and recipient Lewis rats. PMX53 was administered starting on the day of operation until postoperative day 7. The graft survivals were compared, and HE staining of grafts, lymphocyte mixed reaction test (MLR, mixed culture of T cells from lymph nodes and spleen cells from donors), and changes in macrophage and T cell accumulation in grafts on day 6 after transplantation were evaluated. In addition, the effect of PMX53 on macrophage differentiation and activation was assessed using macrophages derived from bone marrow (BMDM). Results Graft survival was significantly prolonged in the therapeutic group compared to the untreated group. Histological evaluation showed that PMX53 inhibited the shortening of the graft villus, and the stimulation index of MLR was significantly lower in the therapeutic group compared to the untreated group. In the therapeutic group, the accumulation of macrophages in intestinal graft and monocyte in blood were reduced, compared with the untreated group. PMX53 decreased the differentiation in BMDM and the mRNA expression of IL-1β and TNF-α in activated BMDM. Conclusion Inhibition of C5a/C5aR1 signaling appears to regulate macrophage differentiation and suppress rejection in small intestine transplantation immunity. [ABSTRACT FROM AUTHOR]

Alzheimer’s disease (AD) is a progressive neurodegenerative disease of the brain causing either familial or sporadic dementia. We have previously administered the modified C5a receptor agonist (EP67) for a short period to a transgenic mouse model of AD (5XFAD) and have observed not only reduction in β-amyloid deposition and gliosis but also improvement in cognitive impairment. Inquiring, however, on the effects of EP67 in an already heavily burdened animal, thus representing a more realistic scenario, we treated 6-month-old 5XFAD mice for a period of 14 weeks. We recorded a significant decrease in both fibrillar and pre-fibrillar β-amyloid as well as remarkable amelioration of cognitive impairment. Following proteomic analysis and pathway association, we postulate that these events are triggered through the upregulation of β-adrenergic and GABAergic signaling. In summary, our results reveal how inflammatory responses can be employed in inducing tangible phenotype improvements even in advanced stages of AD.

Background Improvement of proteinuria as a marker for disease activity is associated with a better renal outcome in immunoglobulin A nephropathy (IgAN). Complement is an effector pathway in IgA-mediated kidney injury. Avacopan, a selective C5a receptor inhibitor, has previously shown efficacy in anti-neutrophil cytoplasmic antibody–associated vasculitis. The aim of this study was to evaluate the safety and efficacy of avacopan in patients with IgAN with persistent proteinuria despite a maximally tolerated dose of renin–angiotensin–aldosterone system blockade. The efficacy evaluation was based on the change in proteinuria. Methods This open-label pilot trial enrolled adult patients with biopsy-proven IgAN, urinary protein:creatinine ratio (UPCR) >1 g/g creatinine and an estimated glomerular filtration rate (eGFR) >60 mL/min/1.73 m2 or >45 mL/min/1.73 m2 if eGFR has not declined >10 mL/min/1.73 m2 over the previous 24 weeks. If the UPCR remained at >1 g/g creatinine after an 8-week run-in period, patients started avacopan 30 mg twice daily. The primary efficacy endpoint was the change in the slope of the UPCR from the 8-week run-in period to the slope in the 12-week avacopan dosing period. Results A total of 10 of 15 screened patients entered the run-in period. Seven patients with a UPCR >1 g/g creatinine received avacopan. Six of seven patients had numerical improvement in the UPCR during the avacopan treatment period, three of whom had a numerical improvement of ∼50% at week 12. At week 24, five of seven patients still showed numerical improvement in the UPCR compared with baseline. The urinary monocyte chemoattractant protein-1:creatinine ratio decreased numerically 30% by week 8, possibly reflecting the anti-inflammatory activity of avacopan. Avacopan was well tolerated. There was one serious adverse event of unstable angina, which was deemed to be unrelated to avacopan. Conclusions This short-term pilot study showed an improvement in the slope of the UPCR, with ∼50% improvement in three of seven patients with IgAN. Longer avacopan treatment duration may be indicated for maximal benefit. [ABSTRACT FROM AUTHOR]

Objectives: Avacopan, a selective C5aR1 inhibitor, recently emerged as a glucocorticoid (GCs) sparing agent in ANCA-associated vasculitis (AAV). We aim to evaluate the tolerance and efficacy of avacopan given outside randomized clinical trials or with severe kidney involvement., Methods: In this multicentre retrospective study, we reviewed the clinical charts of patients with AAV and contraindication to high dose of GCs who received avacopan 30 mg b.i.d plus standard-of-care regimen owing to the French early access program between 2020 and 2023. Efficacy and safety data were recorded using a standardized case report form., Results: Among the 31 patients (median age 72 years), 10 had a relapsing AAV, twenty had anti-myeloperoxidase antibodies, and thirty had kidney vasculitis. Induction regimen included rituximab (n = 27), cyclophosphamide (n = 2), or both (n = 2). Five patients did not receive GCs. Despite rapid GCs tapering (which were withdrawn in 23 patients before month 3), 25 patients (81%) had a favorable outcome and no severe adverse event. The estimated glomerular filtration rate increased from 19 [15; 34] to 35 mL/min/1.73m2 [23; 45] at month 12 (p< 0.05), independently of kidney biopsies findings. One patient developed refractory AAV and two had a relapse while receiving avacopan. At month 12, ANCA remained positive in 10/18 patients (55.5%). Two patients developed severe adverse events leading to a withdrawal of avacopan (hepatitis and age-related macular degeneration)., Conclusions: The GCs' sparing effect of avacopan was confirmed, even in patients with severe kidney vasculitis, but further studies are required to identify the optimal dosing of GCs when avacopan is used., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Complement C5a receptor (C5aR) signaling in immune cells has various functions, inducing inflammatory or anti-inflammatory responses based on the type of ligand present. The Co1 peptide (SFHQLPARSRPLP) has been reported to activate C5aR signaling in dendritic cells. We investigated the effect of C5aR signaling via the Co1 peptide on macrophages. In peritoneal macrophages, the interaction between C5aR and the Co1 peptide activated the mTOR pathway, resulting in the production of pro-inflammatory cytokines. Considering the close associations of mTOR signaling with IL-6 and TNF-α in macrophage training, our findings indicate that the Co1 peptide amplifies β-glucan-induced trained immunity. Overall, this research highlights a previously underappreciated aspect of C5aR signaling in trained immunity, and posits that the Co1 peptide is a potentially effective immunomodulator for enhancing trained immunity., Competing Interests: Conflict of Interest: The authors declare no potential conflicts of interest., (Copyright © 2024. The Korean Association of Immunologists.)

Acute kidney injury (AKI) is a critical condition often associated with systemic inflammation and dysregulated gut microbiota. This study aimed to investigate the effects of the C5a receptor antagonist W54011 on lipopolysaccharide (LPS)-induced AKI, focusing on the colon's C5a/C5a receptor pathway, intestinal barrier integrity, and gut microbiota. Our findings demonstrate that W54011 effectively ameliorated kidney injury in the LPS-induced AKI model by selectively inhibiting the colon's C5a/C5a receptor signalling pathway. Additionally, C5a receptor blockade resulted in the inhibition of colonic inflammation and the reconstruction of the intestinal mucosal barrier. Furthermore, W54011 administration significantly impacted the composition and stability of the gut microbiota, restoring the abundance of dominant bacteria to levels observed in the normal state of the intestinal flora and reducing the abundance of potentially harmful bacterial groups. In conclusion, W54011 alleviates LPS-induced AKI by modulating the interplay between the colon, gut microbiota, and kidneys. It preserves the integrity of the intestinal barrier and reinstates gut microbiota, thereby mitigating AKI symptoms. These findings suggest that targeting the colon and gut microbiota could be a promising therapeutic strategy for AKI treatment. [ABSTRACT FROM AUTHOR]

Abstract LukS‐PV is one of the two components of Panton‐Valentine leucocidin (PVL). Our previous study showed that LukS‐PV can induce apoptosis in human acute myeloid leukemia (AML) THP‐1 and HL‐60 cells. C5aR (C5a receptor) is the receptor for PVL, but whether C5aR plays a key role in LukS‐PV induced apoptosis is unclear. The aim of this study was to establish whether C5aR plays a physiological role in apoptosis of leukemia cells induced by LukS‐PV. We investigated the role of C5aR in leukemia cell apoptosis induced by LukS‐PV by pretreatment of THP‐1 and HL‐60 cells with C5aR antagonist and transfection to knockdown C5aR in THP‐1 cells or overexpress C5aR in Jurkat cells before treatment with LukS‐PV. Cell apoptosis was analyzed by staining with Annexin V/propidium iodide or Annexin V‐PE/7‐AAD. Mitochondrial membrane potential (MMP) was determined using JC‐1 dye. The expression of apoptosis‐associated genes and proteins was identified by qRT‐polymerase chain reaction and Western blotting analysis, respectively. As the C5aR antagonist concentration increased, the rate of apoptosis induced by LukS‐PV decreased, the MMP increased, and expression of pro‐apoptotic Bax and Bak genes and proteins was downregulated while that of anti‐apoptotic Bcl‐2 and Bcl‐x genes and proteins was upregulated. Knockdown of C5aR also decreased LukS‐PV–induced THP‐1 cell apoptosis. LukS‐PV did not induce apoptosis of Jurkat cells, which have no endogenous C5aR expression; however, LukS‐PV did induce apoptosis in Jurkat cells after overexpression of C5aR. Correspondingly, the MMP decreased and Bax and Bak were upregulated while Bcl‐2 and Bcl‐x were downregulated. LukS‐PV can induce apoptosis in AML cells by targeting C5aR. C5aR may be a potential therapeutic target for AML and LukS‐PV is a candidate targeted drug for the treatment of AML.

Summary: The complement fragment C5a is closely associated with adaptive immune induction in the mucosa. However, the mechanisms that control CD8+ T cell responses by C5a have not been extensively explored. This study reveals that C5/C5a in the Peyer’s patch (PP) subepithelial dome increases upon oral Listeria infection. We hypothesize that C5aR+ PP cells play an important role in the induction of antigen-specific T cell immunity. Using single-cell RNA sequencing, we identify C5aR- and lysozyme-expressing dendritic cells (C5aR+ LysoDCs) in PP and examine their role in CD8+ T cell immune induction. Stimulation of C5aR+ LysoDCs by C5a increases reactive oxygen species levels, leading to efficient antigen cross-presentation, which elicits an antigen-specific CD8+ T cell response. In C5-deficient mice, oral co-administration of C5a and Listeria enhances Listeria-specific cytotoxic T cell levels. Collectively, these findings suggest a role of the complement system in intestinal T cell immunity.

Background: Accumulating evidence underscores the pivotal role of heightened inflammation in the pathophysiology of stress-related diseases, but the underlying mechanisms remain elusive. The complement system, a key effector of the innate immune system, produces the C5-cleaved activation product C5a upon activation, initiating inflammatory responses through the canonical C5a receptor 1 (C5aR1). While C5aR1 is expressed in stress-responsive brain regions, its role in stress responsiveness remains unknown., Methods: To investigate C5a-C5aR1 signaling in stress responses, mice underwent acute and chronic stress paradigms. Circulating C5a levels and messenger RNA expression of C5aR1 in the hippocampus and adrenal gland were measured. C5aR1-deficient mice were used to elucidate the effects of disrupted C5a-C5aR1 signaling across behavioral, hormonal, metabolic, and inflammation parameters., Results: Chronic restraint stress elevated circulating C5a levels while reducing C5aR1 messenger RNA expression in the hippocampus and adrenal gland. Notably, the absence of C5aR1 signaling enhanced adrenal sensitivity to adrenocorticotropic hormone, concurrently reducing pituitary adrenocorticotropic hormone production and enhancing the response to acute stress. C5aR1-deficient mice exhibited attenuated reductions in locomotor activity and body weight under chronic stress. Additionally, these mice displayed increased glucocorticoid receptor sensitivity and disrupted glucose and insulin homeostasis. Chronic stress induced an increase in C5aR1-expressing microglia in the hippocampus, a response mitigated in C5aR1-deficient mice., Conclusions: C5a-C5aR1 signaling emerges as a key metabolic regulator during stress, suggesting that complement activation and dysfunctional C5aR1 signaling may contribute to neuroinflammatory phenotypes in stress-related disorders. The results advocate for further exploration of complement C5aR1 as a potential therapeutic target for stress-related conditions., (© 2024 The Authors.)

Background: The complement system has been suggested to affect injury or disease of the central nervous system (CNS) by regulating numerous physiological events and pathways. The activation of complement following traumatic CNS injury can also result in the formation and deposition of C5b-9 membrane attack complex (C5b-9/MAC), causing cell lysis or sublytic effects on vital CNS cells. Although complement proteins derived from serum/blood-brain barrier breakdown can contribute to injury or disease, infiltrating immune cells may represent an important local source of complement after injury. As the first immune cells to infiltrate the CNS within hours post-injury, polymorphonuclear leukocytes (PMNs) may affect injury through mechanisms associated with complement-mediated events. However, the expression/association of both early and terminal complement proteins by PMNs has not been fully characterized in vitro, and has not observed previously in vivo after traumatic spinal cord injury (SCI). Method: We investigated the expression of complement mRNAs using rt-PCR and the presence of complement proteins associated with PMNs using immunofluroescence and quantitative flow cytometry. Results: Stimulated or unstimulated PMNs expressed mRNAs encoding for C1q, C3, and C4, but not C5, C6, C7 or C9 in culture. Complement protein C1q or C3 was also detected in less than 30% of cultured PMNs. In contrast, over 70% of PMNs that infiltrated the injured spinal cord were associated with C1q, C3, C7 and C5b-9/MAC 3 days post-SCI. The localization/association of C7 or C5b-9/MAC with infiltrating PMNs in the injured spinal cord suggests the incorporation or internalization of C7 or C5b-9/MAC bound cellular debris by infiltrating PMNs because C7 and C5b-9/MAC were mostly localized to granular vesicles within PMNs at the spinal cord epicenter region. Furthermore, PMN presence in the injured spinal cord was observed for many weeks post-SCI, suggesting that this infiltrating cell population could chronically affect complement-mediated events and SCI pathogenesis after trauma. Conclusion: Data presented here provide the first characterization of early and terminal complement proteins associated with PMNs in vitro and in vivo after SCI. Data also suggest a role for PMNs in the local internalization or deliverance of complement and complement activation in the post-SCI environment.

To clarify the role of the C5a/C5aR (C5a receptor) and C5b-9 pathways in macrovascular thrombosis (MAT) and renal microthrombosis (MIT), 73 renal biopsy-proven complement-mediated thrombotic microangiopathy (C-TMA) patients were enrolled; 9 patients with pure MAT and 13 patients with pure MIT were selected for further study. Twenty-five external C-TMA patients were selected as the validation cohort. Plasma C5a and sC5b-9 (soluble C5b-9) levels were significantly higher in patients with MAT than in those with MIT (P = 0.008, P = 0.041, respectively). The mean optical density of C5aR1 in the kidney was significantly higher in MAT patients than in those with MIT (P < 0.001). Both urinary sC5b-9 levels (MIT: P < 0.001, MAT: P = 0.004) and renal deposition of C5b-9 (MIT: P < 0.001, MAT: P = 0.001) were significantly higher in C-TMA patients compared to normal control, but were similar between MAT and MIT groups. In the correlation analysis within 22C-TMA patients, urinary sC5b-9 levels and renal deposition of C5b-9 were positively correlated to renal MIT formation (P = 0.009 and P = 0.031, respectively). Furthermore, the renal citrullinated histone H3 (CitH3)- and neutrophil elastase (NE)-positive area ratios were both significantly higher in the MAT group than in the MIT group (P = 0.006 and P = 0.020, respectively). Therefore, the local C5b-9 and C5a/C5aR1 pathways might have differential contributions to MIT and MAT formation in the disease. • Macrovascular thrombosis was not rare in C-TMA patients. • The local C5b-9 and C5a/C5aR1 pathways have differential contributions to renal microthrombosis and macrovascular thrombosis formations in C-TMA patients. [ABSTRACT FROM AUTHOR]

Abstract Background Pharmacologic inhibition of C5aR1, a receptor for the complement activation proinflammatory fragment, C5a, suppressed pathology and cognitive deficits in Alzheimer's disease (AD) mouse models. To validate that the effect of the antagonist was specifically via C5aR1 inhibition, mice lacking C5aR1 were generated and compared in behavior and pathology. In addition, since C5aR1 is primarily expressed on cells of the myeloid lineage, and only to a lesser extent on endothelial cells and neurons in brain, gene expression in microglia isolated from adult brain at multiple ages was compared across all genotypes. Methods C5aR1 knock out mice were crossed to the Arctic AD mouse model, and characterized for pathology and for behavior performance in a hippocampal dependent memory task. CX3CR1GFP and CCR2RFP reporter mice were bred to C5aR1 sufficient and knockout wild type and Arctic mice to enable sorting of microglia (GFP-positive, RFP-negative) isolated from adult brain at 2, 5, 7 and 10 months of age followed by RNA-seq analysis. Results A lack of C5aR1 prevented behavior deficits at 10 months, although amyloid plaque load was not altered. Immunohistochemical analysis showed no CCR2+ monocytes/macrophages near the plaques in the Arctic brain with or without C5aR1. Microglia were sorted from infiltrating monocytes (GFP and RFP-positive) for transcriptome analysis. RNA-seq analysis identified inflammation related genes as differentially expressed, with increased expression in the Arctic mice relative to wild type and decreased expression in the Arctic/C5aR1KO relative to Arctic. In addition, phagosomal-lysosomal gene expression was increased in the Arctic mice relative to wild type but further increased in the Arctic/C5aR1KO mice. A decrease in neuronal complexity was seen in hippocampus of 10 month old Arctic mice at the time that correlates with the behavior deficit, both of which were rescued in the Arctic/C5aR1KO. Conclusions These data are consistent with microglial polarization in the absence of C5aR1 signaling reflecting decreased induction of inflammatory genes and enhancement of degradation/clearance pathways, which is accompanied by preservation of CA1 neuronal complexity and hippocampal dependent cognitive function. These results provide links between microglial responses and loss of cognitive performance and, combined with the previous pharmacological approach to inhibit C5aR1 signaling, support the potential of this receptor as a novel therapeutic target for AD in humans.

The complement system, a cornerstone of the innate immune defense, typically confers protection against pathogens. However, in various clinical scenarios the complement's defensive actions can harm host cells, exacerbating immune and inflammatory responses. The central components C3 and C5 undergo proteolytic cleavage during complement activation, yielding small active fragments C3a and C5a anaphylatoxins. Traditionally, these fragments were associated with inflammation via the specific receptors C3a receptor (R), C5aR1 and C5aR2. Recent insights, however, spotlight the excessive C3a/C3aR and C5a/C5aR1 signaling as culprits in diverse disorders of inflammatory and autoimmune etiology. This is particularly true for several kidney diseases, where the potential involvement of anaphylatoxins in renal damage is supported by the enhanced renal expression of their receptors and the high levels of C3a and C5a in both plasma and urine. Furthermore, the production of complement proteins in the kidney, with different renal cells synthesizing C3 and C5, significantly contributes to local tissue injury. In the present review, we discuss the different aspects of C3a/C3aR and C5a/C5aR signaling in acute and chronic kidney diseases and explore the therapeutic potential of emerging targeted drugs for future clinical applications., (© 2024 S. Karger AG, Basel.)

• Antibody-mediated complement activation occurs on circulating neutrophils. • Complement activation on neutrophils requires factor B and Fc gamma receptor. • C5a released from complement activation stimulates neutrophil degranulation. • Proteases from neutrophil degranulation modulate endothelial barrier integrity. • C5a receptor antagonism blocks the extracellular release of neutrophil proteases. Neutrophils are essential to the pathogenesis of many inflammatory diseases. In the autoantibody-mediated K/BxN model of inflammatory arthritis, the alternative pathway (AP) of complement and Fc gamma receptors (FcγRs) are required for disease development while the classical pathway is dispensable. The reason for this differential requirement is unknown. We show that within minutes of K/BxN serum injection complement activation (CA) is detected on circulating neutrophils, as evidenced by cell surface C3 fragment deposition. CA requires the AP factor B and FcγRs but not C4, implying that engagement of FcγRs by autoantibody or immune complexes directly triggers AP C3 convertase assembly. The absence of C5 does not prevent CA on neutrophils but diminishes the upregulation of adhesion molecules. In vivo two-photon microscopy reveals that CA on neutrophils is critical for neutrophil extravasation and generation of C5a at the site of inflammation. C5a stimulates the release of neutrophil proteases, which contribute to the degradation of VE-cadherin, an adherens junction protein that regulates endothelial barrier integrity. C5a receptor antagonism blocks the extracellular release of neutrophil proteases, suppressing VE-cadherin degradation and neutrophil transendothelial migration in vivo. These results elucidate the AP-dependent intravascular neutrophil-endothelial interactions that initiate the inflammatory cascade in this disease model but may be generalizable to neutrophil extravasation in other inflammatory processes. [ABSTRACT FROM AUTHOR]

LukS‐PV is one of the two components of Panton‐Valentine leucocidin (PVL). Our previous study showed that LukS‐PV can induce apoptosis in human acute myeloid leukemia (AML) THP‐1 and HL‐60 cells. C5aR (C5a receptor) is the receptor for PVL, but whether C5aR plays a key role in LukS‐PV induced apoptosis is unclear. The aim of this study was to establish whether C5aR plays a physiological role in apoptosis of leukemia cells induced by LukS‐PV. We investigated the role of C5aR in leukemia cell apoptosis induced by LukS‐PV by pretreatment of THP‐1 and HL‐60 cells with C5aR antagonist and transfection to knockdown C5aR in THP‐1 cells or overexpress C5aR in Jurkat cells before treatment with LukS‐PV. Cell apoptosis was analyzed by staining with Annexin V/propidium iodide or Annexin V‐PE/7‐AAD. Mitochondrial membrane potential (MMP) was determined using JC‐1 dye. The expression of apoptosis‐associated genes and proteins was identified by qRT‐polymerase chain reaction and Western blotting analysis, respectively. As the C5aR antagonist concentration increased, the rate of apoptosis induced by LukS‐PV decreased, the MMP increased, and expression of pro‐apoptotic Bax and Bak genes and proteins was downregulated while that of anti‐apoptotic Bcl‐2 and Bcl‐x genes and proteins was upregulated. Knockdown of C5aR also decreased LukS‐PV–induced THP‐1 cell apoptosis. LukS‐PV did not induce apoptosis of Jurkat cells, which have no endogenous C5aR expression; however, LukS‐PV did induce apoptosis in Jurkat cells after overexpression of C5aR. Correspondingly, the MMP decreased and Bax and Bak were upregulated while Bcl‐2 and Bcl‐x were downregulated. LukS‐PV can induce apoptosis in AML cells by targeting C5aR. C5aR may be a potential therapeutic target for AML and LukS‐PV is a candidate targeted drug for the treatment of AML.LukS‐PV can induce apoptosis in acute myeloid leukemia (AML) cells through C5a receptor (C5aR), implicating C5aR as a potential target and LukS‐PV as a targeted drug for the treatment of AML [ABSTRACT FROM AUTHOR]

Activation of the C5/C5a/C5a receptor 1 (C5aR1) axis during allergen sensitization protects from maladaptive T cell activation. To explore the underlying regulatory mechanisms, we analyzed the impact of C5aR1 activation on pulmonary CD11b+ conventional dendritic cells (cDCs) in the context of house-dust-mite (HDM) exposure. BALB/c mice were intratracheally immunized with an HDM/ovalbumin (OVA) mixture. After 24 h, we detected two CD11b+ cDC populations that could be distinguished on the basis of C5aR1 expression. C5aR1− but not C5aR1+ cDCs strongly induced T cell proliferation of OVA-reactive transgenic CD4+ T cells after re-exposure to antigen in vitro. C5aR1− cDCs expressed higher levels of MHC-II and CD40 than their C5aR1+ counterparts, which correlated directly with a higher frequency of interactions with cognate CD4+ T cells. Priming of OVA-specific T cells by C5aR1+ cDCs could be markedly increased by in vitro blockade of C5aR1 and this was associated with increased CD40 expression. Simultaneous blockade of C5aR1 and CD40L on C5aR1+ cDCs decreased T cell proliferation. Finally, pulsing with OVA-induced C5 production and its cleavage into C5a by both populations of CD11b+ cDCs. Thus, we propose a model in which allergen-induced autocrine C5a generation and subsequent C5aR1 activation in pulmonary CD11b+ cDCs promotes tolerance towards aeroallergens through downregulation of CD40.

Introduction We recently reported that caries-associated C5a receptor (C5aR) expression and activation result in up-regulation of brain-derived neurotropic factor secretion by pulp fibroblasts inducing prominent neurite outgrowth toward the carious site. Our data further showed a negative regulation of this brain-derived neurotropic factor secretion by C5L2, another C5aR. C5L2 was considered a nonfunctional receptor and thus has received much less attention than C5aR. The aim of this study was to identify the role of C5L2 in pulp fibroblast–mediated neurite outgrowth. Methods In this study, lipoteichoic acid (LTA) was used to mimic dental caries–like inflammation. To evaluate the role of C5L2 in pulp neurite outgrowth, human pulp fibroblasts were C5L2 small interfering RNA silenced and cocultured with human neurons in a nerve growth assay system. Results C5L2 silencing drastically increased the neurite outgrowth toward the LTA-stimulated pulp fibroblasts. The number of neurites detected was increased in the LTA-treated pulp fibroblasts. Conclusions Our results show that C5L2 constitutes a negative regulator of the neurite outgrowth under LTA stimulation. Of the events occurring during dentin-pulp regeneration, nerve regeneration is the key factor for maintaining tooth viability after infection or injury. Our study provides a foundation for creating therapeutic tools that target pulp fibroblasts during pulp/nerve regeneration. [ABSTRACT FROM AUTHOR]

The complement system is well appreciated for its role as an important effector of innate immunity that is activated by the classical, lectin or alternative pathway. C5a is one important mediator of the system that is generated in response to canonical and non-canonical C5 cleavage by circulating or cell-derived proteases. In addition to its function as a chemoattractant for neutrophils and other myeloid effectors, C5a and its sister molecule C3a have concerted roles in cell homeostasis and surveillance. Through activation of their cognate G protein coupled receptors, C3a and C5a regulate multiple intracellular pathways within the mitochondria and the lysosomal compartments that harbor multiple enzymes critical for protein, carbohydrate and lipid metabolism. Genetic mutations of such lysosomal enzymes or their receptors can result in the compartmental accumulation of specific classes of substrates in this organelle summarized as lysosomal storage diseases (LSD). A frequent LSD is Gaucher disease (GD), caused by autosomal recessively inherited mutations in GBA1 , resulting in functional defects of the encoded enzyme, acid β-glucosidase (glucocerebrosidase, GCase). Such mutations promote excessive accumulation of β-glucosylceramide (GC or GL1) in innate and adaptive immune cells frequently associated with chronic inflammation. Recently, we uncovered an unexpected link between the C5a and C5a receptor 1 (C5aR1) axis and the accumulation of GL1 in experimental and clinical GD. Here, we will review the pathways of complement activation in GD, its role as a mediator of the inflammatory response, and its impact on glucosphingolipid metabolism. Further, we will discuss the potential role of the C5a/C5aR1 axis in GL1-specific autoantibody formation and as a novel therapeutic target in GD. [ABSTRACT FROM AUTHOR]

Inflammatory cells such as macrophages can play a pro-tumorigenic role in the tumor stroma. Tumor-associated macrophages (TAMs) generally display an M2 phenotype with tumor-promoting activity; however, the mechanisms regulating the TAM phenotype remain unclear. Complement 5a (C5a) is a cytokine-like polypeptide that is generated during complement system activation and is known to promote tumor growth. Herein, we investigated the role of C5a on macrophage polarization in colon cancer metastasis in mice. We found that deficiency of the C5a receptor (C5aR) severely impairs the metastatic ability of implanted colon cancer cells. C5aR was expressed on TAMs, which exhibited an M2-like functional profile in colon cancer liver metastatic lesions. Furthermore, C5a mediated macrophage polarization and this process relied substantially on activation of the nuclear factor-kappa B (NF-κB) pathway. Finally, analysis of human colon carcinoma indicated that C5aR expression is negatively associated with tumor differentiation grade. Our results demonstrate that C5aR has a central role in regulating the M2 phenotype of TAMs, which in turn, contributes to hepatic metastasis of colon cancer through NF-κB signaling. C5a is a potential novel marker for cancer prognosis and drugs targeting complement system activation, specifically the C5aR pathway, may offer new therapeutic opportunities for colon cancer management. [ABSTRACT FROM AUTHOR]

Mucosal vaccination is an ideal strategy to induce protective immunity in both mucosal and parenteral areas. Successful induction of an antigen-specific immune response via mucosal administration essentially requires the effective delivery of antigen into a mucosal immune inductive site, which depends on antigen delivery into M cells. We previously reported that M cells specifically express C5aR, and antigen targeting to C5aR by using specific ligands, including Co1 peptide, promotes the antigen-specific immune response in both mucosal and systemic immune compartments. In this study, we found that application of the Co1 peptide to dengue virus antigen containing CD8 T cell epitopes effectively induced an antigen-specific IFN-γ-producing CD8 + T cell response after oral mucosal administration of antigen. Consequently, we suggest that Co1 peptide-mediated C5aR targeting of antigen into M cells can be used for the induction of an effective antigen-specific CD8 + T cell immune response in oral mucosal vaccine development. [ABSTRACT FROM AUTHOR]

Although C5a receptor (C5aR) interacting with its agonist C5a promotes acute inflammation during the initiation phase, the roles of the recycling C5aR during the resolution phase are still unclear. We found that C5aR interacted with its antagonist/agonist ribosomal protein S19 (RP S19) polymer or a RP S19 polymer functional analogue S‐tagged C5a/RP S19, which connects an RP S19 C‐terminus (IAGQVAAANKKH) to the S‐tagged C5a C‐terminus, promoted acute inflammation at the resolution phase via an activation of the apoptosis‐inducing transcription factor delta lactoferrin (δLf) in neutrophils and the membrane mobilizing factor full‐length annexin A3 (ANXA3) in macrophages. To confirm the antagonistic system of the recycling C5aR, S‐tagged δLf‐coupled BrCN‐activated Sepharose 4B beads were incubated with cytoplasmic proteins and identified a neutrophil‐specific δANXA3 via pull‐down experiments. The S‐tagged C5a/RP S19‐induced agonistic functions in macrophage‐like cells that were differentiated from human promyelocytic leukemia HL‐60 cells by phorbol‐12‐myristate‐13‐acetate were suppressed by δLf and δANXA3 co‐overexpression. δANXA3 seems to participate in the antagonistic system of the neutrophil C5aR involving IAGQVAAANKKH and δLf. Most likely, δANXA3 works as antagonist for the recycling C5aR on neutrophils during the resolution phase of acute inflammation. [ABSTRACT FROM AUTHOR]

Abstract: Pre‐eclampsia (PE) is a life‐threatening multisystem disorder leading to maternal and neonatal mortality and morbidity. Emerging evidence showed that activation of the complement system is implicated in the pathological processes of PE. However, little is known about the detailed cellular and molecular mechanism of complement activation in the development of PE. In this study, we reported that complement 5a (C5a) plays a pivotal role in aberrant placentation, which is essential for the onset of PE. We detected an elevated C5a deposition in macrophages and C5a receptor (C5aR) expression in trophoblasts of pre‐eclamptic placentas. Further study showed that C5a stimulated trophoblasts towards an anti‐angiogenic phenotype by mediating the imbalance of angiogenic factors such as soluble fms‐like tyrosine kinase 1 (sFlt1) and placental growth factor (PIGF). Additionally, C5a inhibited the migration and tube formation of trophoblasts, while, C5aR knockdown with siRNA rescued migration and tube formation abilities. We also found that maternal C5a serum level was increased in women with PE and was positively correlated with maternal blood pressure and arterial stiffness. These results demonstrated that the placental C5a/C5aR pathway contributed to the development of PE by regulating placental trophoblasts dysfunctions, suggesting that C5a may be a novel therapeutic possibility for the disease. [ABSTRACT FROM AUTHOR]

Complement factor C5a has two known receptors, C5aR, which mediates proinflammatory effects, and C5L2, a potential C5a decoy receptor. We previously identified C5a/C5aR signaling as a potent profibrotic pathway in the kidney. Here we tested for the first time the role of C5L2 in renal fibrosis. In unilateral ureteral obstruction (UUO)-induced kidney fibrosis, the expression of C5aR and C5L2 increased similarly and gradually as fibrosis progressed and was particularly prominent in injured dilated tubules. Genetic deficiency of either C5aR or C5L2 significantly reduced UUO-induced tubular injury. Expression of key proinflammatory mediators, however, significantly increased in C5L2- compared with C5aR-deficient mice, but this had no effect on the number of renal infiltrating macrophages or T cells. Moreover, in C5L2-/- mice, the cytokine and matrix metalloproteinase-inhibitor tissue inhibitor of matrix metalloproteinase-1 was specifically enhanced. Consequently, in C5L2-/- mice the degree of renal fibrosis was similar to wild type (WT), albeit with reduced mRNA expression of some fibrosis-related genes. In contrast, C5aR-/- mice had significantly reduced renal fibrosis compared with WT and C5L2-/- mice in UUO. In vitro experiments with primary tubular cells demonstrated that deficiency for either C5aR or C5L2 led to a significantly reduced expression of tubular injury and fibrosis markers. Vice versa, stimulation of WT tubular cells with C5a significantly induced the expression of these markers, whereas the absence of either receptor abolished this induction. In conclusion, in experimental renal fibrosis C5L2 and C5aR both contribute to tubular injury, and, while C5aR acts profibrotic, C5L2 does not play a role in extracellular matrix accumulation, arguing against C5L2 functioning simply as a decoy receptor. [ABSTRACT FROM AUTHOR]

We recently found that erythroblast-like cells derived from human leukaemia K562 cells express C5a receptor (C5aR) and produce its antagonistic and agonistic ligand ribosomal protein S19 (RP S19) polymer, which is cross-linked between K122 and Q137 by tissue transglutaminases. RP S19 polymer binds to the reciprocal C5aRs on erythroblast-like cells and macrophage-like cells derived from human monocytic THP-1 cells and promotes differentiation into reticulocyte-like cells through enucleation in vitro . To examine the roles of RP S19 polymer in mouse erythropoiesis, we prepared Q137E mutant RP S19 gene knock-in C57BL/6J mice. In contrast to wild-type mice, erythroblast numbers at the preliminary stage (CD71 high /TER119 low ) in spleen based on transferrin receptor (CD71) and glycophorin A (TER119) values and erythrocyte numbers in orbital artery bloods were not largely changed in knock-in mice. Conversely, erythroblast numbers at the early stage (CD71 high /TER119 high ) were significantly decreased in spleen by knock-in mice. The reduction of early erythroblast numbers in spleen was enhanced by the phenylhydrazine-induced pernicious anemia model knock-in mice and was rescued by a functional analogue of RP S19 dimer S-tagged C5a/RP S19. These data indicated that RP S19 polymer plays the roles in the early erythroblast differentiation of C57BL/6J mouse spleen. [ABSTRACT FROM AUTHOR]

Hereditary ATTR V30M amyloidosis is a lethal autosomal dominant sensorimotor and autonomic neuropathy caused by deposition of aberrant transthyretin (TTR). Immunohistochemical examination of sural nerve biopsies in patients with amyloidotic neuropathy show co-aggregation of TTR with several proteins; including apolipoprotein E, serum amyloid P and components of the complement cascade. Complement activation and macrophages are increasingly recognized to play a crucial role in amyloidogenesis at the tissue bed level. In the current study we test the effect of two C5a receptor agonists and a C5a receptor antagonist (PMX53) on disease phenotype in ATTR V30M mice. Our results indicate that amyloid deposition was significantly reduced following treatment with the C5a receptor agonists, while treatment with the antagonist resulted in a significant increase of amyloid load. Administration of the C5a receptor agonists triggered increased recruitment of phagocytic cells resulting in clearance of amyloid deposits.

The complement system is a pivotal driver of innate immunity, coordinating the host response to protect against pathogens. At the heart of the complement response lie the active fragments, C3a and C5a, acting through their specific receptors, C3aR, C5aR1, and C5aR2, to direct the cellular response to inflammation. Their potent function however, places them at risk of damaging the host, with aberrant C3a and C5a signaling activity linked to a wide range of disorders of inflammatory, autoimmune, and neurodegenerative etiologies. As such, the therapeutic control of these receptors represents an attractive drug target, though, the realization of this clinical potential remains limited. With the success of eculizumab, and the progression of a number of novel C5a-C5aR1 targeted drugs to phase II and III clinical trials, there is great promise for complement therapeutics in future clinical practice. In contrast, the toolbox of drugs available to modulate C3aR and C5aR2 signaling remains limited, however, the emergence of new selective ligands and molecular tools, and an increased understanding of the function of these receptors in disease, has highlighted their unique potential for clinical applications. This review provides an update on the growing arsenal of drugs now available to target C5, and C5a and C3a receptor signaling, and discusses their utility in both clinical and pre-clinical development. [ABSTRACT FROM AUTHOR]

Polymicrobial sepsis in mice causes myocardial dysfunction after generation of the complement anaphylatoxin, complement component 5a (C5a). C5a interacts with its receptors on cardiomyocytes (CMs), resulting in redox imbalance and cardiac dysfunction that can be functionally measured and quantitated using Doppler echocardiography. In this report we have evaluated activation of MAPKs and Akt in CMs exposed to C5a in vitro and after cecal ligation and puncture (CLP) in vivo. In both cases, C5a in vitro caused activation (phosphorylation) of MAPKs and Akt in CMs, which required availability of both C5a receptors. Using immunofluorescence technology, activation of MAPKs and Akt occurred in left ventricular (LV) CMs, requiring both C5a receptors, C5aR1 and -2. Use of a water-soluble p38 inhibitor curtailed activation in vivo of MAPKs and Akt in LV CMs as well as the appearance of cytokines and histones in plasma from CLP mice. When mouse macrophages were exposed in vitro to LPS, activation of MAPKs and Akt also occurred. The copresence of the p38 inhibitor blocked these activation responses. Finally, the presence of the p38 inhibitor in CLP mice reduced the development of cardiac dysfunction. These data suggest that polymicrobial sepsis causes cardiac dysfunction that appears to be linked to activation of MAPKs and Akt in heart. [ABSTRACT FROM AUTHOR]

Complement activation has a deep pathogenic influence in immunoglobulin (Ig)A nephropathy (IgAN). C3a and C5a, small cleavage fragments generated by complement activation, are key mediators of inflammation. The fragments exert broad proinflammatory effects by binding to specific receptors (C3aR and C5aR, respectively). However, no studies thus far have investigated the effects of C3a, C5a and their receptors on IgAN. We observed that C3aR and C5aR antagonists repressed IgA-induced cell proliferation and interleukin (IL)-6 and monocyte chemotactic protein 1 (MCP-1) production in cultured human mesangial cells (HMCs). Furthermore, an IgAN mouse model induced by Sendai virus infection was employed to investigate the effects of C3aR and C5aR on IgAN in vivo for the first time. Wild-type (WT) and several knock-out mouse strains (C3aR-/- or C5aR-/-) were immunized intranasally with increasing doses of inactivated virus for 14 weeks and were subjected to two intravenous viral challenges during the time-period indicated. In the Sendai virus-induced IgAN model, C3aR/C5aR-deficient mice had significantly reduced proteinuria, lower renal IgA and C3 deposition, less histological damage and reduced mesangial proliferation compared with WT mice. Both C3aR deficiency and C5aR deficiency, especially C3aR deficiency, inhibited renal tumour necrosis factor (TNF)-α, transforming growth factor (TGF)-β, IL-1β, IL-6 and MCP-1 expression significantly. However, C3aR/C5aR-deficient and WT mice with IgAN did not differ with respect to their blood urea nitrogen (BUN) and serum creatinine levels. Our findings provide further support for the idea that C3aR and C5aR are crucially important in IgAN, and suggest that pharmaceutically targeting C3aR/C5aR may hold promise for the treatment of IgAN. [ABSTRACT FROM AUTHOR]

Hereditary ATTR V30M amyloidosis is a lethal autosomal dominant sensorimotor and autonomic neuropathy caused by deposition of aberrant transthyretin (TTR). Immunohistochemical examination of sural nerve biopsies in patients with amyloidotic neuropathy show co-aggregation of TTR with several proteins; including apolipoprotein E, serum amyloid P and components of the complement cascade. Complement activation and macrophages are increasingly recognized to play a crucial role in amyloidogenesis at the tissue bed level. In the current study we test the effect of two C5a receptor agonists and a C5a receptor antagonist (PMX53) on disease phenotype in ATTR V30M mice. Our results indicate that amyloid deposition was significantly reduced following treatment with the C5a receptor agonists, while treatment with the antagonist resulted in a significant increase of amyloid load. Administration of the C5a receptor agonists triggered increased recruitment of phagocytic cells resulting in clearance of amyloid deposits. [ABSTRACT FROM AUTHOR]

C5-deficient mice usually present moderate neutrophil activation during the initiation phase of acute inflammation. Conversely, C5a receptor (C5aR)-deficient mice show unusually excessive activation of neutrophils. We identified the ribosomal protein S19 (RP S19) polymer, which is cross-linked at Lys122 and Gln137 by transglutaminases in apoptotic neutrophils, as a second C5aR ligand during the resolution phase of acute inflammation. The RP S19 polymer promotes apoptosis via the neutrophil C5aR and phagocytosis via the macrophage C5aR. To confirm the roles of the RP S19 polymer, we employed a carrageenan-induced acute pleurisy mouse model using C57BL/6J mice with a knock-in of the Gln137Glu mutant RP S19 gene and replaced the RP S19 polymer with either an S-tagged C5a/RP S19 recombinant protein or the RP S19 122–145 peptide monomer and dimer (as functional C5aR agonists/antagonists) and the RP S19 122–145 peptide trimer (as a functional C5aR antagonist). Neutrophils and macrophages were still present in the thoracic cavities of the knock-in mice at 24 h and 7 days after carrageenan injection, respectively. Knock-in mice showed structural organization and severe hemorrhaging from the surrounding small vessels of the alveolar walls in the lung parenchyma. In contrast to the RP S19 122–145 peptide monomer and trimer, the simultaneous presence of S-tagged C5a/RP S19 and the RP S19 122–145 peptide dimer completely improved the physiological and pathological acute inflammatory cues. The RP S19 polymer, especially the dimer, appears to play a role at the resolution phase of carrageenan-induced acute pleurisy in C57BL/6J model mice. [ABSTRACT FROM AUTHOR]

Patients with aggressive urothelial cell carcinoma (UCC) that undergo radical cystectomy or nephroureterectomy exhibit markedly high rates of disease recurrence and mortality. To select appropriate adjuvant thxerapies in addition to radical surgery, the identification of predictive prognostic markers for UCC patients is required. The aim of the present study was to identify such markers, by evaluating the association of UCC complement component 5 (C5) fragment a (C5a) receptor (C5aR) expression, detected using immunohistochemistry, with clinicopathological parameters and survival outcomes of UCC patients. The results revealed that C5aR was expressed in cancer cells, particularly at the invasive front, but not in noncancerous urothelial cells or adjacent cells. The UCC C5aR-positive rate of patients treated with radical surgeries was 73% (38/52) and the rate was 83% (20/24) at stages I-II of disease. No correlation between C5aR expression and any of clinicopathological parameters, which included gender, tumor location, World Health Organization grade, T stage, vessel invasion and stage of disease, was identified. However, univariate and multivariate analyses revealed that C5aR-positive UCC patients exhibited significantly lower overall survival rates [hazard ratio (HR), 3.14; 95% confidence interval (CI), 1.03-9.60; P=0.035 and HR, 3.92; 95% CI, 1.15-13.4; P=0.029, respectively] and 5-year survival rates (0.42 vs. 0.83) compared with C5aR-negative UCC patients. Furthermore, 5-year survival and disease-specific survival rates were lower in patients with C5aR-positive UCC (0.51; 95% CI, 0.30-0.71) than patients with C5aR-negative UCC (0.83; 95% CI, 0.62-1.00). These results indicate that UCC C5aR expression is predictive of poor patient outcomes and thus may lead to the appropriate selection of adjuvant therapies at earlier UCC stages, which could improve patient prognosis. [ABSTRACT FROM AUTHOR]

The C5a receptor (C5aR) expressed in various types of cancers is involved in C5a-induced cancer cell invasion. However, its role in gastric cancer has not yet been fully elucidated. Therefore, we studied the clinical significance of C5aR expression in gastric cancer. The association of C5aR expression in gastric cancer, determined by immunostaining using the anti-C5aR antibody, with clinicopathological parameters and outcomes was evaluated in 148 patients. Further, the association of C5aR expression in liver metastatic sites with clinicopathological parameters was investigated in a separate cohort of 58 patients who underwent hepatectomy. High tumoral C5aR expression ( n = 45, 30.4 %) was significantly related to tumor location, cancer invasion depth, vascular and lymphatic invasion, and tumor stage. The 5-year recurrence-free and overall survival rates of patients with high tumoral C5aR expression were significantly lower than those of patients with low tumoral C5aR expression (50.9 vs. 84.2 %, P = 0.002 and 58.8 vs. 86.1 %, P = 0.007, respectively). The incidence of liver metastasis was significantly higher in patients with high tumoral C5aR expression (13.3 %) than in those with low tumoral C5aR expression (3.9 %; P = 0.04). C5aR expression at liver metastatic sites was associated with the C5aR expression status at the primary site ( P = 0.0004), vascular invasion at the primary site ( P = 0.04), and tumor size at the metastatic site ( P = 0.01). C5aR expression in gastric cancer was associated with cancer progression, liver metastasis, and poor prognosis. Therefore, C5aR may represent a prognostic factor and therapeutic target in gastric cancer. [ABSTRACT FROM AUTHOR]

Background: Emerging evidence has shown activation of the complement system in cancer tissues and anaphylatoxin C5a release from C5 by cancer cells, suggesting C5a as a component in the cancer microenvironment. We revealed aberrant expression of C5a receptor (C5aR) in various human cancers and C5a-elicited enhancement of C5aR-expressing cancer cell invasion. Methods: To explore an influence of the C5a-C5aR system in breast cancer (BC), we investigated BC C5aR expression in relation to clinicopathological parameters of the patients and an effect of C5a on BC cell proliferation. Results: BC cell C5aR expression was observed immunohistochemically in 22 of 171 patients (13 %) and related to larger tumor size, higher nuclear grade and Ki-67 labeling index, presence of lymph node metastasis and advanced clinical stages. Interestingly, BC cells were C5aR-negative in all patients with BC in situ and C5aR-positive rate was high (38 %) in patients with hormone receptor-negative, namely triple-negative BC. For BC cells in metastasized lymph nodes, 12 of 22 patients (55 %) were C5aR-positive and included 7 patients with C5aR-negative BC in the primary site. Survival rate of patients with C5aR-positive BC was lower than that of patients with C5aR-negative BC. C5a enhanced proliferation of C5aR-expressing triple-negative BC cells in a C5aR-dependent manner. Conclusion: Relation of BC C5aR expression to tumor development and poor prognosis of the patients and proliferation enhancing effect of C5a on C5aR-expressing BC cells suggest that the C5a-C5aR system is closely associated with BC progression. This system may be a new target to treat BC patients, particularly with triple-negative BC. [ABSTRACT FROM AUTHOR]