C5a Receptor Research Articles

Complement System and Adhesion Molecule Skirmishes in Fabry Disease: Insights into Pathogenesis and Disease Mechanisms

Fabry disease is a rare X-linked lysosomal storage disorder caused by mutations in the galactosidase alpha (GLA) gene, resulting in the accumulation of globotriaosylceramide (Gb3) and its deacetylated form, globotriaosylsphingosine (Lyso-Gb3) in various tissues and fluids throughout the body. This pathological accumulation triggers a cascade of processes involving immune dysregulation and complement system activation. Elevated levels of complement 3a (C3a), C5a, and their precursor C3 are observed in the plasma, serum, and tissues of patients with Fabry disease, correlating with significant endothelial cell abnormalities and vascular dysfunction. This review elucidates how the complement system, particularly through the activation of C3a and C5a, exacerbates disease pathology. The activation of these pathways leads to the upregulation of adhesion molecules, including vascular cell adhesion molecule 1 (VCAM1), intercellular adhesion molecule 1 (ICAM1), platelet and endothelial cell adhesion molecule 1 (PECAM1), and complement receptor 3 (CR3) on leukocytes and endothelial cells. This upregulation promotes the excessive recruitment of leukocytes, which in turn exacerbates disease pathology. Targeting complement components C3a, C5a, or their respective receptors, C3aR (C3a receptor) and C5aR1 (C5a receptor 1), could potentially reduce inflammation, mitigate tissue damage, and improve clinical outcomes for individuals with Fabry disease.

CAF-macrophage crosstalk in tumour microenvironments governs the response to immune checkpoint blockade in gastric cancer peritoneal metastases

BackgroundPeritoneal metastasis is the most common metastasis pattern of gastric cancer. Patients with gastric cancer peritoneal metastasis (GCPM) have a poor prognosis and respond poorly to conventional treatments. Recently, immune...

Avacopan in the treatment of refractory scleritis secondary to granulomatosis with polyangiitis: A case report.

Avacopan is a novel C5a receptor inhibitor which was recently licensed for treatment of severe granulomatosis with polyangiitis (GPA) in the European Union and the United Kingdom. To the best of our knowledge, this is the first described case on initial ophthalmic outcomes in a patient with severe GPA and concurrent refractory scleritis treated with avacopan. We present a case of de novo scleritis in a 77-year-old male with a background of retinitis pigmentosa with Argus II implant in situ. Severe scleral inflammation occurred following a suture removal from the implant site. Remission was not maintained despite orbital floor injections and high dose oral prednisolone. The diagnostic work-up revealed GPA which quickly progressed to involve vital organs. In view of his systemic deterioration, he was started on avacopan alongside rituximab, cyclophosphamide and high dose oral prednisolone. Sustained remission of scleritis was noted after 7 months of treatment with avacopan and low dose oral prednisolone with no other maintenance immunosuppression. We observed a sustained benefit of avacopan in allowing for successful taper of systemic steroids. We report that avacopan used alongside other immunosuppressants may be a viable option in patients with GPA and concurrent refractory scleritis. Further studies are needed to establish the longer term impact of this agent on the control of scleral inflammation.

Cardiac Repair after Myocardial Infarction is Controlled by a Complement C5a Receptor 1-Driven Signaling Cascade.

Cardiac repair following myocardial infarction is important in regenerating functionally viable myocardium to prevent cardiac death. Previous studies have linked C5aR1 to cardiac regeneration and inflammation. However, C5a receptor-driven responses during the late phases, up to 4 weeks of the infarction insult - a time window that specifically reflects the outcome of the repair process - and the underlying mechanisms are poorly defined. Here, we show that C5ar1, but not C5ar2, deficiency attenuates infarct size following coronary artery ligation-induced myocardial infarction (MI). C5ar1 deficiency limited the deposition of collagen and mitigated cell death in infarcted areas leading to overall improved cardiac function four weeks after MI. While infiltration of neutrophils was reduced in both C5ar1-/- and C5ar2-/- infarcted myocardium 24 h after MI, influx of monocytes after 1 week of MI was reduced only upon C5ar1 deficiency. Subsequent analysis revealed reduced accumulation of myofibroblast, elevated expression of transforming growth factor-beta1 (Tgf-β1) and vascular endothelial growth factor-A (Vegf-A) in C5ar1-/- infarcted hearts. In vitro, exogenous TGF-β1 triggered conversion of fibroblasts into myofibroblasts, which expressed Vegf-A mRNA - an effect that was enhanced upon C5ar1 deficiency. Incubation of C5ar1+/+ or C5ar1-/- endothelial cells (ECs) with supernatants from C5ar1+/+ or C5ar1-/- myofibroblasts respectively, mimicking the in vivo microenvironment in our model, led to significant increase in matrigel tube formation in C5ar1-/- ECs. This was consistent with enhanced neoangiogenesis in C5ar1-/- infarcted hearts. Collectively, our study demonstrates that inhibition of C5aR1 has the potential to improve cardiac function after myocardial infarction.

The novel role of complement 3 in Wnt5a-mediated vascular smooth muscle cell calcification

Abstract Background Although vascular calcification (VC) is a risk factor for cardiovascular and all-cause mortality, a therapy is not yet available. VC involves the transdifferentiation of vascular smooth muscle cells (VSMC) towards an osteochondrogenic lineage that results in calcium phosphate salts deposition in the arterial wall. We have previously shown an association between plasma WNT5A levels and new onset and progression of coronary artery calcification. Purpose We aimed to study the poorly understood role of Wnt5a in VSMC calcification. Methods Study 1 included 18 patients with coronary artery disease (CAD) undergoing cardiac surgery; VSMC were isolated from their saphenous veins to perform in vitro assays and microarrays. Study 2 included 11 patients with CAD; IMA were treated ex vivo with Wnt5a recombinant protein (rWnt5a) to perform western blot (WB) analyses. Study 3 included 647 patients with CAD; RNA sequencing was performed on samples from their internal mammary arteries (IMA), IMA perivascular adipose (PVAT), and thoracic adipose tissue (ThAT). VSMC and human aortic smooth muscle cells (HASMC) from healthy donors were grown in osteogenic medium in the presence or absence of rWnt5a with or without specific protein inhibitors. Calcium deposition and expression of VC markers (i.e. RUNX2, BMP2, and MSX2) were assessed with a colorimetric assay and by RT-qPCR, respectively. Phosphorylation/activation of non-canonical Wnt pathway effectors was evaluated by WB analyses. Results rWnt5a treatment significantly increased calcium deposition in both VSMC and HASMC at a concentration that activates both JNK and CaMKII, that are effectors of the non-canonical planar cell polarity pathway and the calcium-dependent pathway, respectively. Inhibition of either JNK or CaMKII could not counteract rWnt5a-mediated increase in VSMC calcium deposition; whereas, inhibition of both non-canonical pathway effectors (JNK-i and CaMKII-i) prevented rWnt5a-mediated increase in calcium deposition by VSMC (A) and HASMC. Inhibition of JNK and CaMKII also prevented rWnt5a-induced gene expression of VC markers, such as RUNX2 (B). rWnt5a treatment in IMA increased the activation of JNK and CaMKII. Patients with higher WNT5A levels in IMA had significantly higher RUNX2 levels. By intersecting RNA sequencing and microarray data complement 3 (C3) resulted as the most upregulated gene in rWnt5a-treated VSMC among those genes whose levels positively correlated in IMA with both WNT5A and RUNX2 expression (C). Patients with higher WNT5A levels in IMA, their PVAT, and ThAT had significantly higher C3 levels (D), and patients with higher levels of C3AR1, that is the gene coding for the C3a receptor, had higher VC markers expression. C3 inhibition (C3-i) with a C3AR1 antagonist counteracted Wnt5a-induced VSMC calcium deposition (E). Conclusions Non-canonical Wnt signalling promotes VSMC calcification through C3. Wnt5a may be a therapeutic target in VC.Abstract Figure

C3a Mediates Endothelial Barrier Disruption in Brain-Derived, but Not Retinal, Human Endothelial Cells.

Neuromyelitis optica spectrum disorder (NMOSD) is associated with pathological aquaporin-4 immunoglobulin G (AQP4-IgG), which cause brain damage. However, the impact of AQP4-IgG on retinal tissue remains unclear. Additionally, dysregulated complement anaphylatoxins C3a and C5a, known to modulate the endothelial barrier, are implicated in NMOSD. This study evaluates the susceptibility of human brain microvascular endothelial cells (HBMEC) and human retinal endothelial cells (HREC) to C3a- and C5a-mediated stress using real-time cell barrier analysis, immunocytochemical staining, qPCR and IgG transmigration assays. The findings reveal that C3a induced a concentration-dependent paracellular barrier breakdown and increased transcellular permeability in HBMEC, while HREC maintained barrier integrity under the same conditions. C5a attenuated C3a-induced disruption in HBMEC, indicating a protective role. Anaphylatoxin treatment elevated transcript levels of complement component C3 and increased C5 gene and protein expression in HREC, with no changes observed in HBMEC. In HBMEC, C5a treatment led to a transient upregulation of C3a receptor (C3AR) mRNA and an early decrease in C5a receptor 1 (C5AR1) protein detection. Conversely, HREC exhibited a late increase in C5aR1 protein levels. These results indicate that the retinal endothelial barrier is more stable under anaphylatoxin-induced stress compared to the brain, potentially offering better protection against paracellular AQP4-IgG transport.

A novel hollow iron nanoparticle system loading PEG-Fe3O4 with C5a receptor antagonist for breast cancer treatment.

Breast cancer is the most diagnosed malignancy and major cause of cancer death among women population in the worldwide. Ferroptosis is a recently discovered iron-dependent regulated cell death involved in tumor progression and therapeutic response. Moreover, increasing studies have implied that ferroptosis is a promising approach to eliminating cancer cells like developing iron nanoparticles as a therapeutic agent. However, resistance to ferroptosis is a vital distinctive hallmark of cancer. Therefore, further investigation of the mechanism of ferroptosis resistance to enhance its tumor sensitivity is essential for ferroptosis-target breast cancer therapy. Our results revealed that the activation of C5a/C5aR pathway can drive resistance to ferroptosis and reshaping breast cancer immune microenvironment. Accordingly, loading PEG-Fe3O4 with C5aRA significantly improved the anti-tumor effect of PEG- Fe3O4 by inhibiting ferroptosis resistance and increasing macrophage polarization toward M1 phenotype. Our findings presented a novel cancer therapy strategy that combined cancer cell metal metabolism regulation and immunotherapy. The study also provided support for further evaluation of PEG- Fe3O4@C5aRA as a novel therapeutic strategy for breast cancer in clinical trials.

Protective Effects of a Dihydrodiazepine Against Endotoxin Shock Through Suppression of TLR4/NF-κB/IRF3 Signaling Pathways.

Sepsis and septic shock are life-threatening systemic inflammatory conditions and among the most frequent causes of morbidity and mortality globally. Preclinical evidence has identified a number of diazepine-based compounds with therapeutic potential in inflammatory diseases. However, the potential anti-inflammatory properties of diazepines in the overwhelming immune response during sepsis have been rarely examined. Thus, the current study aimed to identify a new diazepine compound with therapeutic potential in sepsis. Assessing the inflammatory response of macrophages to Lipopolysaccharides (LPS) in vitro identified 2-[7-(trifluoromethyl)-2,3-dihydro-1H-1,4-diazepin-5-yl]phenol (2-TDDP) as a potential anti-inflammatory agent. It reduced secretion of Interleukin-1β (IL-1β), IL-6, IL-12p70, IL-18, Tumor necrosis factor-α (TNF-α), Interferon-γ (IFN-γ), IFN-β, and increased the secretion of IL-10. In a mouse model of LPS-induced endotoxin shock, 2-TDDP reduced mortality and attenuated inflammation-induced tissue injury in the spleen, liver, kidney, and lung. This was accompanied by reduced serum levels of IL-1β, IL-6, IL-12p70, TNF-α, IFN-γ, IFN-β, and increased levels of IL-10. Importantly, 2-TDDP suppressed the Toll-like receptor 4 (TLR4)/Nuclear factor-κB (NF-κB) and TLR4/Interferon regulatory factor 3 (IRF3) signaling pathways through a reduction in the expression of TLR4, Myeloid differentiation primary response 88 (MyD88), P65, and TNF receptor-associated factor 3 (Traf3). Moreover, 2-TDDP suppressed the expression of CD86, Programmed death-ligand 1 (PD-L1) and C5a receptor (C5aR), but not Major histocompatibility complex II (MHCII). Analysis of splenic lymphocyte populations revealed a decrease in the number of CD4+, CD8+, and B cells. Collectively, these findings introduced the dihydrodiazepine 2-TDDP as a new anti-inflammatory agent with potent therapeutic potential in endotoxin shock, paving an avenue for future clinical application.

Using genetics to explore complement C5 as a druggable protein in periodontitis.

An excessively activated or dysregulated complement system has been proven to be a vital contributor to the pathogenesis of periodontitis. It has been previously hypothesized that inhibiting the activity of complement component C5 by targeting the C5a receptor is a powerful candidate for treating periodontitis. Here, we apply the drug target instrumental variable (IV) approach to investigate the therapeutic effect of genetically proxied inhibition of C5 on periodontitis. In our primary analysis, we used 26 independent 'cis' single nucleotide polymorphisms as IVs from the vicinity of the encoding locus of C5 that are associated with plasma C5 levels. In a secondary analysis, we assess the validity of our primary findings, exploring the involvement of alternative downstream biomarkers, interleukin 17 (IL-17), interleukin 1β (IL-1β), and tumor necrosis factor (TNF). Summary statistics of plasma levels (C5, IL-17, IL-1β, and TNF) were obtained from a genome-wide association study (GWAS) of 35,559 European descent individuals. We extracted association statistics from a GWAS of 17,353 clinical periodontitis cases and 28,210 European controls. Wald ratios were combined using inverse-variance weighted meta-analysis. In our primary approach, inhibiting C5 reduced the risk of periodontitis (Odds ratio 0.89 per 1 standard deviation reduction in C5; 95% confidence Interval 0.80-0.98, p value=0.022). Our secondary analysis suggests an involvement of IL-17 within the potential causal pathway, but was inconclusive for other biomarkers. The findings from our study suggest that C5 inhibition may reduce the risk of periodontitis, prioritizing C5 inhibitors as a potential adjunctive therapeutic intervention in this disease.

Intracellular C5aR1 inhibits ferroptosis in glioblastoma through METTL3-dependent m6A methylation of GPX4

Glioblastoma (GBM) is the most common primary intracranial malignant tumor. Recent literature suggests that induction of programmed death has become a mainstream cancer treatment strategy, with ferroptosis being the most widely studied mode. Complement C5a receptor 1 (C5aR1) is associated with both tumorigenesis and tumor-related immunity. However, knowledge regarding the role of C5aR1 in GBM progression is limited. In the present study, we observed significant upregulation of C5aR1 in glioma tissue. In addition, C5aR1 expression was found to be closely associated with patient prognosis and survival. Subsequent experimental verification demonstrated that C5aR1 promoted the progression of GBM mainly by suppressing ferroptosis induction, inhibiting the accumulation of lipid peroxides, and stabilizing the expression of the core antiferroptotic factor glutathione peroxidase 4 (GPX4). Aberrant N6-methyladenosine (m6A) modification of GPX4 mRNA contributes significantly to epigenetic tumorigenesis, and here, we report that selective methyltransferase-like 3 (METTL3)-dependent m6A methylation of GPX4 plays a key role in C5AR1 knockdown-induced ferroptosis induction. Mechanistically, ERK1/2 signaling pathway activation increases the METTL3 protein abundance in GBM cells. This activation then increases the stability of METTL3-mediated m6A modifications on GPX4, enabling it to fulfill its transcriptional function. More importantly, in an intracranial xenograft mouse model, PMX205, a C5aR1 inhibitor, promoted alterations in ferroptosis in GBM cells and inhibited GBM progression. In conclusion, our findings suggest that C5aR1 inhibits ferroptosis in GBM cells and promotes MettL3-dependent GPX4 expression through ERK1/2, thereby promoting glioma progression. Our study reveals a novel mechanism by which the intracellular complement receptor C5aR1 suppresses ferroptosis induction and promotes GBM progression. These findings may facilitate the identification of a potential therapeutic target for glioma.

A Newly Identified Protective Role of C5a Receptor 1 in Kidney Tubules against Toxin-Induced Acute Kidney Injury

Acute kidney injury (AKI) remains a major reason for hospitalization with limited therapeutic options. While complement activation is implicated in AKI, the role of C5a receptor 1 (C5aR1) in kidney tubular cells is unclear. We used aristolochic acid nephropathy (AAN) and folic acid nephropathy (FAN) models to establish the role of C5aR1 in kidney tubules during AKI in germline C5ar1-/- mice, myeloid cell-specific, and kidney tubule-specific C5ar1 knockout mice. After aristolochic acid and folic acid injection, C5ar1-/- mice had increased AKI severity and a higher degree of tubular injury. Macrophage depletion in C5ar1-/- mice or myeloid cell-specific C5ar1 deletion did not affect the outcomes of AA-induced AKI. RNA-sequencing data from RTECs showed that C5ar1 deletion was associated with the downregulation of mitochondrial metabolism and ATP production transcriptional pathways. Metabolic studies confirmedreduced mitochondrial membrane potential at baseline and increased mitochondrial oxidative stress after injury in C5ar1-/- RTECs. Moreover, C5ar1-/- RTECs had enhanced glycolysis, glucose uptake, and lactate production upon injury, corroborated by metabolomics analysis of kidneys from AAN mice. Kidney tubule-specific C5ar1 knockout mice recapitulated exacerbated AKI observed in C5ar1-/- mice in AAN and FAN. Our data indicate that C5aR1 signaling in kidney tubules exerts renoprotective effects against toxin-induced AKI by limiting overt glycolysis and maintaining mitochondrial function, revealing a novel link between the complement system and tubular cell metabolism.

Activation of platelets and the complement system in mice with Schistosoma-induced pulmonary hypertension.

Schistosomiasis-induced pulmonary hypertension (PH) presents a significant global health burden, yet the underlying mechanisms remain poorly understood. Here, we investigate the involvement of platelets and the complement system in the initiation events leading to Schistosoma-induced PH. We demonstrate that Schistosoma exposure leads to thrombocytopenia, platelet accumulation in the lung, and platelet activation. In addition, we observed increased plasma complement anaphylatoxins C3a and C5a, indicative of complement system activation, and elevated platelet expression of C1q, C3, decay activating factor (DAF), and complement C3a and C5a receptors. Our findings suggest the active involvement of platelets in responding to complement system signals induced by Schistosoma exposure and form the basis for future mechanistic studies on how complement may regulate platelet activation and promote the development of Schistosoma-induced PH.NEW & NOTEWORTHY Schistosomiasis-induced pulmonary hypertension (PH) is a significant global health burden, yet the underlying mechanisms remain poorly understood. We demonstrate that Schistosoma exposure leads to platelet accumulation in the lung and platelet activation. We observed increased plasma levels of C3a and C5a, indicative of complement system activation, and elevated expression of platelet complement proteins and receptors. These findings underscore the role of platelets and complement in the inflammatory responses associated with Schistosoma-induced PH.

Identification of a genetic region linked to tolerance to MRSA infection using Collaborative Cross mice.

Staphylococcus aureus (S. aureus) colonizes humans asymptomatically but can also cause opportunistic infections, ranging from mild skin infections to severe life-threatening conditions. Resistance and tolerance are two ways a host can survive an infection. Resistance is limiting the pathogen burden, while tolerance is limiting the health impact of a given pathogen burden. In previous work, we established that collaborative cross (CC) mouse line CC061 is highly susceptible to Methicillin-resistant S. aureus infection (MRSA, USA300), while CC024 is tolerant. To identify host genes involved in tolerance after S. aureus infection, we crossed CC061 mice and CC024 mice to generate F1 and F2 populations. Survival after MRSA infection in the F1 and F2 generations was 65% and 55% and followed a complex dominant inheritance pattern for the CC024 increased survival phenotype. Colonization in F2 animals was more extreme than in their parents, suggesting successful segregation of genetic factors. We identified a Quantitative Trait Locus (QTL) peak on chromosome 7 for survival and weight change after infection. In this QTL, the WSB/EiJ (WSB) allele was present in CC024 mice and contributed to their MRSA tolerant phenotype. Two genes, C5ar1 and C5ar2, have high-impact variants in this region. C5ar1 and C5ar2 are receptors for the complement factor C5a, an anaphylatoxin that can trigger a massive immune response by binding to these receptors. We hypothesize that C5a may have altered binding to variant receptors in CC024 mice, reducing damage caused by the cytokine storm and resulting in the ability to tolerate a higher pathogen burden and longer survival.

Complement C3a/C3aR inhibition alleviates the formation of aortic aneurysm in Marfan syndrome mice

Mutations in fibrillin 1 (FBN1) is the main cause of Marfan syndrome (MFS) with thoracic aortic aneurysm (TAA) as the main complication. Activation of the complement system plays a key role in the formation of thoracic and abdominal aortic aneurysms. However, the role of the complement system in MFS-associated aortic aneurysms remains unclear. In this study, we observed increased levels of complement C3a and C5a in the plasma of MFS patients and mouse, and the increased deposition of the activated complement system product C3b/iC3b was also observed in the elastic fiber rupture zone of 3-month-old MFS mice. The expression of C3a receptor (C3aR) was increased in MFS aortas, and recombinant C3a promoted the expression of cytokines in macrophages. The administration of a C3aR antagonist (C3aRA) attenuated the development of thoracic aortic aneurysms in MFS mice. The increased inflammation response and matrix metalloproteinases activities were also attenuated by C3aRA treatment in MFS mice. Therefore, these findings indicate that the complement C3a/C3aR inhibition alleviates the formation of aortic aneurysm in Marfan syndrome mice.

The C5AR1/TNFSF13B axis alleviates osteoarthritis by activating the PI3K/Akt/GSK3β/Nrf2/HO-1 pathway to inhibit ferroptosis

Chondrocyte ferroptosis induces the occurrence of osteoarthritis (OA). As a key gene of OA, C5a receptor 1 (C5AR1) is related to ferroptosis. Here, we investigated whether C5AR1 interferes with chondrocyte ferroptosis during OA occurrence. C5AR1 was downregulated in PA-treated chondrocytes. Overexpression of C5AR1 increased the cell viability and decreased ferroptosis in chondrocytes. Moreover, Tumor necrosis factor superfamily member 13B (TNFSF13B) was downregulated in PA-treated chondrocytes, and knockdown of TNFSF13B eliminated the inhibitory effect of C5AR1 on ferroptosis in chondrocytes. More importantly, the PI3K/Akt/GSK3β/Nrf2/HO-1 pathway inhibitor LY294002 reversed the inhibition of C5AR1 or TNFSF13B on ferroptosis in chondrocytes. Finally, we found that C5AR1 alleviated joint tissue lesions and ferroptosis in rats and inhibited the progression of OA in the rat OA model constructed by anterior cruciate ligament transection (ACLT), which was reversed by interfering with TNFSF13B. This study shows that C5AR1 reduces the progression of OA by upregulating TNFSF13B to activate the PI3K/Akt/GSK3β/Nrf2/HO-1 pathway and thereby inhibiting chondrocyte sensitivity to ferroptosis, indicating that C5AR1 may be a potential therapeutic target for ferroptosis-related diseases.

Evaluation of non-invasive biomarkers of kidney allograft rejection in a prospective multicenter unselected cohort study (EU-TRAIN)

Non-invasive biomarkers are promising tools for improving kidney allograft rejection monitoring, but their clinical adoption requires more evidence in specifically designed studies. To address this unmet need, we designed the EU-TRAIN study, a large prospective multicentric unselected cohort funded by the European Commission. Here, we included consecutive adult patients who received a kidney allograft in nine European transplant centers between November 2018 and June 2020. We prospectively assessed gene expression levels of 19 blood messenger RNAs, four antibodies targeting non-human leukocyte antigen (HLA) endothelial antigens, together with circulating anti-HLA donor-specific antibodies (DSA). The primary outcome was allograft rejection (antibody-mediated, T cell-mediated, or mixed) in the first year post-transplantation. Overall, 412 patients were included, with 812 biopsies paired with a blood sample. CD4 gene expression was significantly associated with rejection, while circulating anti-HLA DSA had a significant association with allograft rejection and a strong association with antibody-mediated rejection. All other tested biomarkers, including AKR1C3, CD3E, CD40, CD8A, CD9, CTLA4, ENTPD1, FOXP3, GZMB, ID3, IL7R, MS4A1, MZB1, POU2AF1, POU2F1, TCL1A, TLR4, and TRIB1, as well as antibodies against angiotensin II type 1 receptor, endothelin 1 type A receptor, C3a and C5a receptors, did not show significant associations with allograft rejection. The blood messenger RNAs and non-HLA antibodies did not show an additional value beyond standard of care monitoring parameters and circulating anti-HLA DSA to predict allograft rejection in the first year post-transplantation. Thus, our results open avenues for specifically designed studies to demonstrate the clinical relevance and implementation of other candidate non-invasive biomarkers in kidney transplantation practice.

Complement C5a Receptor Signaling in Macrophages Enhances Trained Immunity Through mTOR Pathway Activation.

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.

Kidney diseases: News from the KDIGO guidelines

The KDIGO Update 2024 was supplemented by new "Clinical Practice Points", which were derived from the current evidence but are not necessarily comprehensively proven by prospective controlled studies. The most significant change in the Update 2024 for Lupus nephritis concerns the recommendations for induction therapy for lupus nephritis classes III and IV. The basis is still high-dose glucocorticoid treatment and the use of hydroxychloroquine. The 2 new developments in the 2024 Update concerning ANCA-associated nephritis are based on the studies on the use of the C5a receptor inhibitor Avacopan and the increasing data on induction protocols with reduced glucocorticoid dosage. Due to the inconsistency and variability of the conditions under which blood pressure measurements are carried out in practice, an international consensus statement was issued which defines 4 steps to achieve sufficient validity of the measurement results. CKD-MBD Controversies Conference 2023: The update for CKD-MBD, which was discussed in the Controversies Conference 2023, is in progress and has not been released yet. However, there were no serious contradictions between the 2023 data and the 2017 guidelines - the risk assessment regarding calcium-containing phosphate binders may have been put into perspective.

Kidney Failure in Pauci-immune Crescentic Glomerulonephritis: Rationale for Immunosuppression to Improve Kidney Outcome.

Pauci-immune crescentic glomerulonephritis is the hallmark finding in ANCA-associated vasculitis (AAV) when the kidneys are affected. The rationale for immunosuppression in AAV is based on the underlying autoimmune nature of the disease. Overall remission rates, kidney outcomes, and the burden of disease have greatly improved since the discovery of various immunosuppressive therapies, but relapses remain common, and a significant proportion of patients continue to progress to end-stage kidney disease. Here, we review the role of immunosuppressive therapies for the treatment of pauci-immune crescentic glomerulonephritis. Besides the recognized role of B and T cells in the pathogenies of AAV, the focus on the contribution of inflammatory cytokines, neutrophil extracellular traps (NETs), and the complement system allowed the discovery of new therapies. Specifically, the C5a receptor blocker (avacopan) has been approved as a glucocorticoid-sparing agent. Additionally, based on observational data, more clinicians are now using combination therapies during the induction phase. There is also an evolving understanding of the role of plasma exchange in removing ANCA antibodies. Furthermore, the recent development of risk score systems provides physicians with valuable prognostic information that can influence decisions on immunosuppression, although future validation from larger cohorts is needed. The over-activation of various immune pathways plays a significant role in the pathogenesis of pauci-immune crescentic glomerulonephritis in AAV. Immunosuppression is, therefore, an important strategy to halt disease progression and improve overall outcomes. Relapse prevention while minimizing adverse events of immunosuppression is a major long-term goal in AAV management.

Structure of Designer Antibody-like Peptides Binding to the Human C5a with Potential to Modulate the C5a Receptor Signaling.

C5a is an integral glycoprotein of the complement system that plays an important role in inflammation and immunity. The physiological concentration of C5a is observed to be elevated under various immunoinflammatory pathophysiological conditions in humans. The pathophysiology of C5a is linked to the "two-site" protein-protein interactions (PPIs) with two genomically related receptors, such as C5aR1 and C5aR2. Therefore, pharmacophores that can potentially block the PPIs between C5a-C5aR1 and C5a-C5aR2 have tremendous potential for development as future therapeutics. Notably, the FDA has already approved antibodies that target the precursors of C5a (Eculizumab, 148 kDa) and C5a (Vilobelimab, 149 kDa) for marketing as complement-targeted therapeutics. In this context, the current study reports the structural characterization of a pair of synthetic designer antibody-like peptides (DePA and DePA1; ≤3.8 kDa) that bind to hotspot regions on C5a and also demonstrates potential traits to neutralize the function of C5a under pathophysiological conditions.