Complement component C3 - The "Swiss Army Knife" of innate immunity and host defense

Improved immunocompatibility of active targeting liposomes by attenuating nucleophilic attack of cyclic RGD peptides on complement 3

One of the challenges for the clinical translation of active targeting nanomedicines is the adverse interactions between targeting ligands and blood components. Herein, a novel regularity, which reveals the interactions between cyclic RGD (Arg-Gly-Asp) peptide-modified liposomes and complement components in blood, is reported. As the nucleophilicity of arginine guanidine group within the cyclic RGD-like peptide increases, targeting liposomes potentiate complement cascade via the amplification loop of complement 3 (C3), ultimately leading to accelerated blood clearance, increased deposition in the reticuloendothelial system (RES) organs, enhanced immune responses, and potential side effects. By appropriately reducing the nucleophilicity of guanidine group, cyclic R2 peptide is designed for modification of liposomes to target integrin αvβ3. Compared to the widely used targeting molecule c(RGDyK), R2 eliminates the negative effects of C3 opsonization and specific antibody production, significantly improves the in vivo immunocompatibility of targeting liposomes, and demonstrates superior anti-tumor efficacy in mouse models of orthotopic breast cancer and glioma. Thus, the proposed regularity of interactions between guanidine nucleophilicity and C3, along with the successful application of the low complement activation capacity targeting ligand R2, provides new insights for addressing challenges related to complement activation in the clinical translation of active targeting nanomedicines.

[Diagnostic approach and treatment paradigm in atrophic age related macular degeneration: Recommendations of the France Macula Federation]

Atrophic age-related macular degeneration (AMD) represents a detrimental progression of age-related maculopathy, characterized by advanced retinal lesions associated with drusen and pseudodrusen as well as alterations in the outer retinal layers and RPE. It is characterized by a thinning of the neuroretinal tissue linked to the disappearance of the outer layers of the retina and the RPE. Our goal is to offer to ophthalmologists recommendations in the diagnosis and management of atrophic AMD with a standardized approach, in order to facilitate and optimize the management of this disease. The diagnosis of atrophic AMD is based on multimodal imaging; color fundus photography, autofluorescence images of the fundus (AFF) and structural optical coherence tomography (OCT) are the first-line examinations to assess lesion size and foveolar sparing. OCT-angiography (OCT-A) is useful in diagnosing associated choroidal neovascularization. At times, the differential diagnosis will require other complementary examinations, such as fluorescein and/or indocyanine green angiography. The assessment of visual function is essentially based on the measurement of visual acuity; other functional tests such as reading speed, measurement of visual acuity in low luminance (LLVA), contrast sensitivity or microperimetry are of definite interest, but are not yet used in routine clinical practice. The therapeutic solutions for this pathology are multidisciplinary; they combine regular clinical monitoring, medical treatment, psychological support, orthoptic rehabilitation and optical visual aids. Support groups are of significant benefit.

Association of Complement Proteins with C Reactive Protein in Non-Obese Women with and Without Polycystic Ovary Syndrome

Complement proteins are increased in polycystic ovary syndrome (PCOS), as are markers of inflammation, such as the C-reactive protein (CRP); however, both may be increased in obesity. We hypothesised that body mass index (BMI)-driven CRP would comparably associate with an increase in complement proteins when obesity was accounted for in non-obese women with and without PCOS. In a non-obese, non-insulin-resistant population without inflammation (24 with PCOS and 24 control women), plasma CRP was measured by immunoassay. Slow Off-rate Modified Aptamer (SOMA)-scan plasma proteomic analysis of the classical, lectin, and alternative pathway complement proteins was undertaken. BMI, insulin resistance, and CRP did not differ (p < 0.05) between the cohorts. The alternative pathway of the complement protein system was overexpressed in PCOS (p < 0.05). CRP correlated positively (p < 0.05) with alternate pathway parameters in women with and without PCOS for C3a, iC3b, Factor B, Factor H, and Factor I; in PCOS alone for C3, C3adesArg, and C3d; and in women without PCOS, for properdin. CRP did not correlate with lectin pathway C2 or MBL (p > 0.05). CRP correlated positively (p < 0.05) with C4 of the classical pathways in women with PCOS alone. Hyperandrogenemia did not correlate with CRP or complement in non-obese PCOS. BMI correlated positively with C3, C3adesArg, C3a, iC3b, Factor B, Factor H, and properdin: classical pathway proteins; C1q, C4, C5 and C5a in PCOS women; BMI only correlated negatively with C1q in non-PCOS women. Upregulation of complement proteins occur in non-obese PCOS, and CRP is positively associated with complement protein changes in both women with and without PCOS. This indicates that BMI induces changes in CRP that lead to changes in the complement pathways, particularly the alternate pathway, with increases in CRP (though still within the reference laboratory normal range) leading to upregulation of complement proteins in PCOS. This suggests an enhanced set point for CRP-induced complement protein dysregulation in PCOS.

Species differences in opsonization and phagocyte recognition of preclinical poly-2-alkyl-2-oxazoline-coated nanoparticles

Poly(ethylene glycol) (PEG) is widely used in nanomedicine design, but emerging PEG immunogenicity in the general population is of therapeutic concern. As alternative, polyoxazolines are gaining popularity, since "polyoxazolinated" nanoparticles show long-circulating properties comparable to PEGylated nanoparticles in mice. Here, we show species differences in opsonization and differential uptake by monocytes and macrophages of nanoparticles coated with either poly-2-methyl-2-oxazoline or poly-2-ethyl-2-oxazoline. These nanoparticles evade murine opsonization process and phagocytic uptake but porcine ficolin 2 (FCN2), through its S2 binding site, recognizes polyoxazolines, and mediates nanoparticle uptake exclusively by porcine monocytes. In human sera, FCN opsonization is isoform-dependent showing inter-individual variability but both FCN2 and complement opsonization promote nanoparticle uptake by human monocytes. However, nanoparticle uptake by human and porcine macrophages is complement-dependent. These findings advance mechanistic understanding of species differences in innate immune recognition of nanomaterials' molecular patterns, and applicable to the selection and chemical design of polymers for engineering of the next generation of stealth nanoparticles.

Integrated multi-omics analysis reveals complement component 3 as a central driver of immune dysregulation in polycystic ovary syndrome

Background

Polycystic Ovary Syndrome (PCOS) is a prevalent endocrine disorder with a complex pathophysiology, affecting various aspects of women's health. Despite its widespread impact, the molecular basis and immunological aspects of PCOS remain insufficiently understood, limiting effective diagnosis and treatment strategies.

Objective

This study aims to elucidate the molecular and immunological landscape of PCOS by integrating gene expression profiles from healthy and PCOS-affected ovaries using both bulk and single-cell omics data, with the goal of constructing a comprehensive bioinformatics network that identifies potential biomarkers and therapeutic targets.

Methods

Leveraging publicly available omics datasets, we compared gene expression between healthy ovaries and those affected by PCOS through both bulk and single-cell analyses. Our approach focused on differential gene expression analysis, identification of distinct cell types and gene signatures in PCOS, construction of disease-specific gene expression modules, and mapping of cellular differentiation trajectories. Additionally, we examined the alterations in the immune microenvironment within PCOS to identify immune-related changes.

Results

Our analyses uncovered unique molecular signatures and immune modules in PCOS, characterized by differential gene expression, the presence of unique cell types, and altered pathways compared to healthy controls. Notably, we identified a significant role for Complement Component 3 (C3) in mediating these changes. Through gene intervention targeting C3 in granulosa cells and functional studies examining the effects of secreted C3 protein on H295R cells, Low level C3 mitigated inflammatory responses, while excess C3 proved detrimental to cell growth.

Conclusion

Our integrative omics analysis provides new insights into the molecular and immunological underpinnings of PCOS, highlighting the role of C3 in the disease's pathogenesis. The identification of key molecular signatures and immune modules, including the involvement of C3, opens promising avenues for the development of novel diagnostic and therapeutic strategies for PCOS. These observations suggest that modulating C3 levels could have therapeutic implications for managing PCOS.

Enhancing complement activation by therapeutic anti-tumor antibodies: Mechanisms, strategies, and engineering approaches

The complement system plays an integral role in both innate and adaptive immune responses. Beyond its protective function against infections, complement is also known to influence tumor immunity, where its activation can either promote tumor progression or mediate tumor cell destruction, depending on the context. One such context can be provided by antibodies, with their inherent capacity to activate the classical complement pathway. In recent years, our understanding of the mechanisms governing complement activation by IgG and IgM antibodies has expanded significantly. At the same time, preclinical and clinical studies on antibodies such as rituximab, ofatumumab, and daratumumab have provided evidence for the role of complement in therapeutic success, encouraging strategies to further enhance its activity. In this review we examine the main determinants of antibody-mediated complement activation, highlighting the importance of antibody subclass, affinity, valency, and geometry of antigen engagement. We summarize the evidence for complement involvement in anti-tumor activity and challenges of accurately estimating the extent of its contribution to therapeutic efficacy. Furthermore, we explore several engineering approaches designed to enhance complement activation, including increased Fc oligomerization and C1q affinity, bispecific C1q-recruiting antibodies, IgG subclass chimeras, as well as antibody and paratope combinations. Strategies targeting membrane-bound complement regulatory proteins to overcome tumor-associated complement inhibition are also discussed as a method to boost therapeutic efficacy. Finally, we highlight the potential of complement-dependent cellular cytotoxicity (CDCC) and complement-dependent cellular phagocytosis (CDCP) as effector mechanisms that warrant deeper investigation. By integrating advances in antibody and complement biology with insights from efforts to enhance complement activation in therapeutic antibodies, this review aims to provide a comprehensive framework of antibody design and engineering strategies that optimize complement activity for improved anti-tumor efficacy.

Exosomal-complement system activation in preeclampsia

AIM

Preeclampsia (PE) is a severe pregnancy-related disorder characterized by hypertension and multi-organ failure, primarily affecting the maternal vasculature and placenta. The aim of this review is to explain the molecular mechanisms behind PE by investigating the relationship between exosome release and complement activation, which could provide insight into potential therapeutic targets.

METHODS

This review analyzes existing literature on the role of the complement system and exosomes in the pathophysiology of PE. The focus is on how abnormal complement activation contributes to inflammation and vascular dysfunction, particularly in the placenta, and the role of trophoblast-derived exosomes carrying pathogenic molecules such as soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng).

RESULTS

Findings from recent studies indicate that during PE, abnormal complement activation leads to severe inflammation and vascular dysfunction in the placenta. Additionally, exosomes, particularly those derived from trophoblasts, are present in higher concentrations in maternal circulation during PE and carry molecules that disrupt endothelial function. These factors contribute to the development of hypertension and other maternal complications.

CONCLUSIONS

Understanding the interaction between complement activation and exosome release in PE may open avenues for novel therapeutic approaches. Targeting complement regulation and exosome-mediated signaling could potentially improve maternal and fetal outcomes, offering new strategies for managing this complex condition.

A Narrative Review of Periodontal Vaccines: Hope or Hype?

Globally, periodontal diseases, mainly driven by polymicrobial biofilms, are a widespread concern of social medicine due to their considerable incidence and tie-up to systemic disorders like diabetes, cardiovascular diseases, and complications during pregnancy. Traditional treatments focus on mechanical debridement and antimicrobial therapies, but these approaches have limitations, including recurrence and antibiotic resistance. Periodontal vaccines offer a promising alternative by targeting the immunological mechanisms underlying periodontal disease. This review explores the current state of periodontal vaccine development, highlighting key antigens, vaccine delivery systems, and preclinical and clinical advancements. Special emphasis is placed on antigen selection, host variability, immune tolerance, and future directions to overcome these barriers. This article highlights the advancements and challenges in periodontal vaccine research, offering insights into the capability of immunoprophylaxis as a groundbreaking way to manage periodontal diseases.

Modulating the complement system through epitope-specific inhibition by complement C3 inhibitors

As an integral part of the innate immune system, the complement system is a tightly regulated proteolytic cascade, playing a critical role in microbial defense, inflammation activation, and dying host cell clearance. Complement proteins are now emerging as subjects of intense research and drug development, since dysregulation of the complement system plays a critical role in several diseases and disorders, such as paroxysmal nocturnal hemoglobinuria (PNH) and geographic atrophy (GA). Within the complement cascade, complement C3 is the central component, situated at the convergence of all complement activation pathways, rendering it an attractive target for complement-related diseases. However, due to the complicated structure-activity relationship (SAR) of C3, elucidating the mechanisms of C3 inhibition on diverse epitopes is the basis for the rational design of C3-targeted therapeutics. Here, we have developed a set of comprehensive biochemical assays that are tailored to the specific steps within the complement cascade, allowing for a thorough understanding of the pharmacological consequences of different C3 inhibitors at each stage. Utilizing three model inhibitors (MIs) with different epitopes, we found that inhibition of MG4/MG5 domains has potent inhibition efficacy across all the complement activation pathways by interrupting C3-C3 convertase interaction, while inhibition of C345C domain displays a bias over the Alternative pathway (AP) inhibition by impairing AP C3 proconvertase formation. This study elucidates the intricate impact of C3 inhibition by targeting different epitopes, offering valuable insights into understanding the mechanism and facilitating the rational design of C3-targeted therapeutics.

Identification of multiple novel procoagulant plasma ligands for stabilin-2

BACKGROUND

Damaging STAB2 gene variants are associated with increased venous thromboembolic risk. STAB2 encodes stabilin-2, a clearance receptor, expressed by the liver and spleen. Given its function, it is likely that the prothrombotic state associated with stabilin-2 deficiency is due to reduced procoagulant protein clearance, but the identity of these ligands is unknown.

OBJECTIVES

To identify plasma stabilin-2 ligands using proximity biotinylation proteomics.

METHODS

Cells stably expressing stabilin-2-TurboID were incubated with human plasma and biotin to initiate TurboID labeling of plasma ligands in endocytic vesicles. Biotinylated proteins were purified and identified using mass spectrometry. Candidate plasma ligands with roles in hemostasis were fluorescently labeled and incubated with stabilin-2 expressing and control cells. Flow cytometry assessed ligand surface binding and confocal microcopy assessed colocalization with stabilin-2 and lysosomes. Furthermore, plasma levels of ligands were measured in Stab2-deficient mice and littermate controls.

RESULTS

Twenty-eight stabilin-2 specific ligands were identified. Interactions with von Willebrand factor, fibrinogen, pro(thrombin), heparin cofactor II, high molecular weight kininogen, plasminogen, and C4b-binding protein were probed. Heparin cofactor II, high molecular weight kininogen, plasminogen, and fibrinogen showed binding to stabilin-2 using flow cytometry (>2-fold higher than controls). Confocal microscopy demonstrated stabilin-2 dependent colocalization of all ligands with lysosomes. In Stab2-deficient mice, ligand levels were not significantly increased, suggesting in mice stabilin-2 is not their main clearance receptor.

CONCLUSION

These results confirm the value of proximity labeling proteomics in identifying receptor ligands and suggest damaging STAB2 variants may increase venous thromboembolic risk potentially through altered hemostatic protein clearance.

Factor B as a therapeutic target for the treatment of complement-mediated diseases

The complement system, consisting of three initiating pathways-classical, lectin and alternative, is an important part of innate immunity. Dysregulation of the complement system is implicated in the pathogenesis of several autoimmune and inflammatory diseases. Therapeutic inhibition of the complement system has been recognized as a viable approach to drug development and has been successful with the approval of a small number of complement inhibitors for diseases such as paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, neuromyelitis optica, myasthenia gravis and geographic atrophy. More recently, therapies selectively targeting the alternative pathway (AP), which drives the amplification of the complement responses, are being evaluated for these complement-mediated diseases. Complement Factor B, a serine protease, is a unique component of the AP that is essential for the catalytic activity of AP C3 convertase and AP C5 convertase. Inhibition of Factor B blocks the activity of the alternative pathway and the amplification loop, and subsequent generation of the membrane attack complex downstream; however, it has no effect on the initial activation mediated by the classical and lectin complement pathways. Therefore, Factor B is an attractive target for diseases in which the AP is overactivated. In this review, we provide an overview of Factor B and its critical role in the AP, discuss the benefit-risk of Factor B inhibition as a targeted therapeutic strategy, and describe the various Factor B inhibitors that are approved and/or in clinical development.

Diagnosis and Staging of Metabolic Dysfunction-Associated Steatotic Liver Disease Using Biomarker-Directed Aptamer Panels

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects one-third of adults globally. Despite efforts to develop non-invasive diagnostic tools, liver biopsy remains the gold standard for diagnosing metabolic dysfunction-associated steatohepatitis (MASH) and assessing fibrosis. This study investigated RNA aptamer panels, selected using APTASHAPE technology, for non-invasive MASLD diagnosis and fibrosis stratification. Aptamer panels were selected in a cohort of individuals with MASLD (development cohort, n = 77) and tested in separate cohorts: one with MASLD (test cohort, n = 57) and one assessed for bariatric surgery (bariatric cohort, n = 62). A panel distinguishing MASLD without steatohepatitis from MASH accurately stratified individuals in the developmentcohort (AUC = 0.83) but failed in the test and bariatric cohorts. It did, however, distinguish healthy controls from individuals with MASLD, achieving an AUC of 0.72 in the test cohort. A panel for fibrosis stratification differentiated F0 from F3-4 fibrosis in the development cohort (AUC = 0.68) but not in other cohorts. Mass spectrometry identified five plasma proteins as potential targets of the discriminative aptamers, with complement factor H suggested as a novel MASLD biomarker. In conclusion, APTASHAPE shows promise as a non-invasive tool for diagnosing and staging MASLD and identifying associated plasma biomarkers.

Determining Ligand Binding and Specificity Within the β2-Integrin Family with a Novel Assay Platform

The family of the β2-integrin receptors is critically involved in host defense and homeostasis, by mediating immune cell adhesion, migration, and phagocytosis. Due to their key roles in immune surveillance and inflammation, their modulation has been recognized as an attractive drug target. However, the development of therapeutics has been limited, partly due to the high promiscuity of endogenous ligands, their functional responses, and gaps in our understanding of their disease-related molecular mechanisms. The delineation of the molecular role of β2 integrins and their ligands has been hampered by a shortage of validated assay systems. To facilitate molecular and functional studies on the β2-integrin family, and to enable screening of modulators, this study provides a uniform and validated assay platform. For this purpose, the major ligand-binding domains (αI) of all four β2 integrins were recombinantly expressed in both low- and high-affinity states. By optimizing the expression parameters and selecting appropriate purification tags, all αI-domain variants could be produced with high yield and purity. Direct binding studies using surface plasmon resonance (SPR) confirmed the expected activity and selectivity profiles of the recombinant αI domains towards their reported ligands, validating our approach. In addition, the SPR studies provided additional insights into ligand binding, especially for the scarcely described family member CD11d. Alongside characterizing endogenous ligands, the platform can be employed to test pharmacologically active compounds, such as the reported β2-integrin antagonist simvastatin. In addition, we established a bead-based adhesion assay using the recombinant αI domains, and a cell-based adhesion assay underlining most findings generated with the isolated αI domains. Interestingly, the binding of ligands to the recombinant αDI is not dependent on divalent cation, in contrast to the full integrin CD11d/CD18, suggesting a binding mode distinct of the metal ion-dependent adhesion site (MIDAS). The setup highlights the applicability of recombinant αI domains for first screenings and direct or competitive interaction studies, while the full integrin is needed to validate those findings.

Conjugation Chemistry Markedly Impacts Toxicity and Biodistribution of Targeted Nanoparticles, Mediated by Complement Activation

Conjugation chemistries are a major enabling technology for the development of drug delivery systems, from antibody-drug conjugates to antibody-targeted lipid nanoparticles inspired by the success of the COVID-19 vaccine. However, here it is shown that for antibody-targeted nanoparticles, the most popular conjugation chemistries directly participate in the activation of the complement cascade of plasma proteins. Their activation of complement leads to large changes in the biodistribution of nanoparticles (up to 140-fold increased uptake into phagocytes of the lungs) and multiple toxicities, including a 50% drop in platelet count. It is founded that the mechanism of complement activation varies dramatically between different conjugation chemistries. Dibenzocyclooctyne, a commonly used click-chemistry, caused aggregation of conjugated antibodies, but only on the surface of nanoparticles (not in bulk solution). By contrast, thiol-maleimide chemistry do not activate complement via its effects on antibodies, but rather because free maleimide bonded to albumin in plasma, and clustered albumin is then attacked by complement. Using these mechanistic insights, solutions are engineered that reduced the activation of complement for each class of conjugation chemistry. These results highlight that while conjugation chemistry is essential for the future of nanomedicine, it is not innocuous and must be designed with opsonins like complement in mind.

Differences in physicochemical properties and proteomics analysis of spray- and freeze-dried milk powders from bovine, goat, and horse sources

Milk powder, a nutrient-rich dairy product, lacks comprehensive information summarizing its specific properties when produced by spray- and freeze-dried technologies from different sources. Therefore, this study investigated the differences in physicochemical properties, microstructure, and proteome of spray- and freeze-dried milk powders from bovine, goat, and horse sources. The results revealed that spray-dried milk powder exhibited a smaller particle size, lower air content within the powder particles, inferior reconstitution properties, and lower lactose crystallinity compared with freeze-dried milk powder. Additionally, among the studied varieties, horse milk powder showed the lowest flowability but the most effective reconstitution properties. Proteomic analysis indicated that freeze-dried milk powder exhibited higher levels of immune-related proteins, including complement C3, C7, and complement factor B, and antimicrobial enzymes such as lysozyme and lactoperoxidase compared with spray-dried milk powder. Furthermore, specific milk powders contained more immune-related proteins such as serum amyloid A, myeloid antimicrobial peptide-28, polymeric immunoglobulin receptor, and mucin-1 compared with bovine milk powder. These findings contribute to a deeper understanding of the differences in the physicochemical properties and potential biological functions of spray- and freeze-dried milk powders from various sources, which may help in further optimizing specific milk powder processing technologies.

Complement Component 3 Promotes Regeneration of Olfactory Receptor Neurons

Olfactory receptor neurons (ORNs) in the olfactory epithelium are characterized by high regenerative capacity even after birth, but the molecular mechanisms involved in ORN regeneration remain unclear. Complement component 3 (C3) has been shown to promote tissue regeneration, so we hypothesized that C3 activates innate immunity and also promotes the regeneration of ORNs. In this study, we investigate the role of C3 in ORN regeneration. We used C3 knockout (KO) and wild-type C57BL/6J mice in this study to examine the olfactory regeneration process for 42 days after methimazole-induced olfactory disorder. To compare the regeneration process after ORN damage between C3 KO and wild-type mice, we conducted olfactory behavioral tests and immunohistologic analysis and examined growth factors and inflammatory cell induction. C3 KO mice showed delayed olfactory recovery with lower olfactory epithelial thickness. In C3 KO mice, ORN maturation was delayed in association with increased accumulation of immature ORNs. In the normal ORN regeneration process, undesirable immature ORNs are produced and eliminated by apoptosis. C3 deficiency reduced neutrophils induced during ORN regeneration, suggesting the involvement of C3 in ORN regeneration through neutrophil-dependent elimination of undesired ORNs. C3 is therefore suggested to have promoted ORN regeneration by preventing the accumulation of immature ORNs. In addition, C3 may assist ORN maturation by participating in ORN axon selection such as synaptic pruning. Our results indicate that C3, which is activated during pathogen infection, also promotes recovery from ORN damage. These findings may lead to new therapeutic strategies for olfactory disorder.

Peptide Backbone Cleavage and Transamidation via Thioester-to-Imide Acyl Transfer

Cysteine thioesters are involved in a myriad of central biological transformations due to their unique reactivity. Despite their well-studied properties, we discovered an unexpected transamidation reaction of cysteine thioesters that leads to peptide backbone cleavage. S-Acylcysteine-containing peptides were found to spontaneously fragment by cleavage of the amide bond in the i-1 position to the acylated cysteine residue at pH 8-10. We present compelling evidence of a mechanism involving a central reversible thioester-to-imide acyl transfer step. The discovered transamidation reaction was found to be highly sequence dependent and to occur in peptides containing post-translational modifications (PTMs) such as cysteine S-acetylation and S-palmitoylation as well as in peptide-peptide branched thioesters, mimicking class I intein splicing. Thus, the inherent reactivity of peptide backbones containing S-acylcysteine residues should represent a starting point for investigation of endogenous protein behavior and may serve as a foundation for the discovery of mild new peptide and protein transformations.

Characterization of the colostrum proteome of primiparous Holstein cows and its association with colostrum immunoglobulin G concentrations

BACKGROUND

The objective was to characterize the colostrum proteome of primiparous Holstein cows in association with immunoglobulin G (IgG) content. Immediately after calving, colostrum samples were collected from 18 cows to measure IgG concentration. Based on colostrum IgG content, samples were classified through cluster analysis and were identified as poor, average, and excellent quality. The proteome was assessed with quantitative shotgun proteomics; abundance data were compared among the colostrum types; enrichment analysis of metabolic processes and proteins classes was performed as well. We also tested correlations between this proteome and blood globulin level of cows and passive immunity level of calves.

RESULTS

On average, 428 proteins were identified per sample, which belonged mainly to cellular process, biological regulation, response to stimulus, metabolic process, and immune system process. Most abundant proteins were complement C3 (Q2UVX4), alpha-S1-casein (P02662), Ig-like domain-containing protein (A0A3Q1M032), albumin (A0A140T897), polymeric immunoglobulin receptor (P81265), lactotransferrrin (P24627), and IGHG1*01 (X16701_4). Colostrum of excellent quality had greater (P < 0.05) abundance of serpin A3-7 (A2I7N3), complement factor I (A0A3Q1MIF4), lipocalin/cytosolic fatty-acid binding domain-containing protein (A0A3Q1MRQ2), complement C3 (E1B805), complement component 4 binding protein alpha (A0AAF6ZHP5), and complement component C6 (F1MM86). However, colostrum of excellent quality had lower (P < 0.05) abundance of HGF activator (E1BCW0), alpha-S1-casein (P02662), and xanthine dehydrogenase/oxidase (P80457). This resulted in enrichment of the biological processes predominantly for complement activation alternative pathway, complement activation, complement activation classical pathway, humoral immune response, leukocyte mediated immunity, and negative regulation of endopeptidase activity in excellent-quality colostrum. Additionally, some colostrum proteins were found to be correlated with the blood globulin level of cows and with the passive immunity level of calves (P < 0.05; r ≥ 0.57).

CONCLUSIONS

This study provides new insights into the bovine colostrum proteome, demonstrating associations between IgG levels and the abundance of other proteins, as well as the enrichment of metabolic processes related to innate immune response. Thus, results suggest that the colostrum proteomic profile is associated with the content of IgG. Future research should deeply explore the association of these findings with pre-calving nutrition status and blood composition of the cow, and with passive immunity transfer to the calf.

Undernutrition affects metabolism and immune response in subcutaneous adipose tissue of pregnant ewes

Pregnant ewes mobilize body fat to increase energy supply for fetal growth and development upon undernutrition, which disrupts the metabolic homeostasis of the body. However, the comprehensive metabolic changes in subcutaneous adipose tissue upon undernutrition are poorly understood. In this study, an undernutrition sheep model was established to investigate the effects of undernutrition on metabolic changes, immune response, and inflammation in subcutaneous fat through transcriptome, RT-qPCR, and metabolome analysis. Results showed that undernutrition changed the total transcriptional and metabolic profiles of adipose tissue. Compared to the controls, differentially expressed genes (DEGs) involved in fatty acid synthesis, triglyceride genesis, and lipid transport were downregulated in undernourished ewes, while DEGs related to fatty acid and triglyceride degradation were upregulated. Almost all lipid-related differential metabolites (DMs) were downregulated. DEGs and DMs involved in glucose metabolism and glycogen degradation were downregulated, while glycogen synthesis and carbohydrate transport were upregulated. DEGs linked to amino acid degradation were upregulated and some amino acids and derivatives were downregulated. KEGG pathway analysis showed complement and coagulation cascades were enriched significantly by DEGs, and DEGs related to coagulation, macrophage, and inflammation were upregulated while DEGs associated with the complement system were downregulated. Undernutrition during late gestation disrupted the metabolism of lipids, carbohydrates, and amino acids in adipose tissue, which weakened the complement system and immune response and may have ultimately led to inflammation.

Complement in Kidney Transplantation

Transplantation is the treatment of choice in most patients with kidney failure. The complement system plays a vital role in transplantation. The complement system forms a major part of innate immunity and acts as a bridge between innate and acquired immunity. Many diseases, particularly concerning the kidneys, result from complement system dysregulation, like atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy (C3GN), systemic lupus erythematosus (SLE and some other immune complex diseases. The complement system activation is a very important part of post-transplant events like ischemia-reperfusion injury (IRI), delayed graft function (DGF), antibody-mediated rejection (ABMR) and thrombotic microangiopathy (TMA). A better understanding of the complement cascade can help to plan strategies to prevent and manage complement-related problems before and after kidney transplantation. Many newer molecules are either being developed or in the pipeline, which target the complement system at various stages. These novel therapeutics are now considered additional measures to improve graft survival. This review summarises the complement cascade, its role in kidney diseases and kidney transplantation, and possible areas of target and novel therapeutics.

Sex-based difference in immune responses and efficacy of the pneumococcal conjugate vaccine

Vaccine-mediated protection and susceptibility to Streptococcus pneumoniae (pneumococcus) infections are influenced by biological sex. The incidence of invasive pneumococcal disease remains higher in males compared to females even after the introduction of the pneumococcal conjugate vaccine. However, sex-based differences in the immune response to this conjugate vaccine remain unexplored. To investigate those differences, we vaccinated adult male and female mice with pneumococcal conjugate vaccine and assessed cellular and humoral immune responses. Compared to females, male mice displayed lower levels of T follicular helper cells, germinal center B cells, and plasmablasts, which are all required for antibody production following vaccination. This was linked to lower IgG and IgM levels against pneumococci and lower isotype switching to IgG3 in vaccinated males. Due to lower antibody levels, sera of vaccinated male mice had lower efficacy in several anti-pneumococcal functions, including neutralization of bacterial binding to pulmonary epithelial cells as well as direct cytotoxicity against S. pneumoniae. Importantly, while the vaccine was highly protective in females, vaccinated males succumbed to infection more readily and were more susceptible to both lung-localized infection and systemic spread following S. pneumoniae challenge. These findings identify sex-based differences in immune responses to pneumococcal conjugate vaccine that can inform future vaccine strategies.

Decoding burn trauma: biomarkers for early diagnosis of burn-induced pathologies

Burn injuries represent a significant global challenge due to their multifaceted nature, characterized by a complex cascade of metabolic and immune dysfunction that can result in severe complications. If not identified and managed promptly, these complications can escalate, often leading to fatal outcomes. This underscores the critical importance of timely and precise diagnosis. Fortunately, biomarkers for burn-induced pathologies and outcomes have emerged as powerful diagnostic and prognostic tools. These biomarkers enable early diagnosis and intervention, facilitate risk assessment, support patient-specific treatment, monitoring of disease progression, and therapeutic efficacy, ultimately contributing to improved patient outcomes. However, while previous studies have provided valuable biomarkers for the detection of burn-induced pathologies, many of these were constrained by the techniques and sample sizes available at the time, which can limit the generalizability of the findings. This review highlights numerous biomarkers studied in the literature to date, underscoring the need to replicate these findings in more diverse and representative populations. It also emphasizes the importance of advancing research efforts to develop more efficient, accurate, and cost-effective approaches for integrating biomarkers into clinical practice.

The relationship between serum CTRP-5, C3a/desArg, and complement-C3 levels and hypothyroidism in women with polycystic ovary syndrome

INTRODUCTION

Many patients with polycystic ovary syndrome (PCOS) also experience thyroid disorders. There is a notable similarity in energy metabolism among PCOS, C1q/tumor necrosis factor (TNF)-related proteins (CTRP-5)deficiency, C3a/desArg (also known as acylation-stimulating protein (ASP)) deficiency, and hypothyroidism. This study aimed to investigate the relationship between serum levels of these factors and hypothyroidism in patients with PCOS. Improved clarity and vocabulary, corrected minor grammatical issues, and enhanced readability.

METHODS

This case-control study involved three groups: healthy women (control group), women with PCOS and hypothyroidism, and women with PCOS without hypothyroidism. Serum levels of FBS, total cholesterol, triglycerides, and HDL-C were measured using enzymatic and colorimetric methods. TSH, T4, T3, and anti-thyroid peroxidase (Anti-TPO) levels were determined by ELISA to screen for hypothyroidism in women with PCOS. Additionally, serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), CTRP-5, ASP, and complement C3 were assessed using the ELISA method.

RESULTS

The results indicated that reduced blood levels of CTRP-5, along with elevated levels of ASP (C3a/desArg) and complement C3 in patients with PCOS, may be linked to dysregulation of the thyroid gland. Furthermore, the study observed that changes in these parameters, in conjunction with thyroid dysfunction, are associated with pathological alterations in lipid profiles and blood glucose levels.

CONCLUSION

While changes in CTRP-5, ASP, and complement C3 can influence energy expenditure and storage in PCOS and thyroid function, the complex nature of PCOS requires further research to investigate the prevalence of hypothyroidism in individuals with PCOS.

CLINICAL TRIAL NUMBER

Not applicable.

Lithium, Inflammation and Neuroinflammation with Emphasis on Bipolar Disorder-A Narrative Review

This narrative review examines lithium's effects on immune function, inflammation and cell survival, particularly in bipolar disorder (BD) in in vitro studies, animal models and clinical studies. In vitro studies show that high lithium concentrations (5 mM, beyond the therapeutic window) reduce interleukin (IL)-1β production in monocytes and enhance T-lymphocyte resistance, suggesting a protective role against cell death. Lithium modulates oxidative stress in lipopolysaccharide (LPS)-activated macrophages by inhibiting nuclear factor (NF)-ƙB activity and reducing nitric oxide production. At therapeutically relevant levels, lithium increased both pro-inflammatory [interferon (INF)-γ, IL-8 and tumor necrosis factor (TNF)-α)] and anti-inflammatory (IL-10) cytokines on whole blood supernatant culture in healthy volunteers, influencing the balance of pro- and anti-inflammatory responses. Animal models reveal lithium's potential to alleviate inflammatory diseases by reducing pro-inflammatory cytokines and enhancing anti-inflammatory responses. It also induces selective macrophage death in atherosclerotic plaques without harming other cells. In primary rat cerebellum cultures (ex vivo), lithium prevents neuronal loss and inhibits astroglial growth, impacting astrocytes and microglia. Clinical studies show that lithium alters cytokine profiles and reduces neuroinflammatory markers in BD patients. Chronic treatment decreases IL-2, IL-6, IL-10 and IFN-γ secretion from peripheral blood leukocytes. Lithium response correlates with TNF-α levels, with poor responders showing higher TNF-α. Overall, these findings elucidate lithium's diverse mechanisms in modulating immune responses, reducing inflammation and promoting cell survival, with significant implications for managing BD and other inflammation-related conditions. Yet, to better understand the drug's impact in BD and other inflammatory/neuroinflammatory conditions, further research is warranted to appreciate lithium's therapeutic potential and its role in immune regulation.

A 2-year calorie restriction intervention reduces glycomic biological age biomarkers

Background/Objective

In a subset of participants from the CALERIE™ Phase 2 study we evaluated the effects of 2y of ~25% Calorie Restriction (CR) diet on IgG N-glycosylation (GlycAge), plasma and complement C3 N-glycome as markers of aging and inflammaging.

Methods

Plasma samples from 26 participants in the CR group who completed the CALERIE2 trial and were deemed adherent to the intervention (~>10 % CR at 12 mo) were obtained from the NIA AgingResearchBiobank. Glycomic investigations using UPLC or LC-MS analyses were conducted on samples from baseline (BL), mid-intervention (12 mo) and post-intervention (24 mo), and changes resulting from the 2y CR intervention were examined. In addition, anthropometric, clinical, metabolic, DNA methylation (epigenetic) and skeletal muscle transcriptomic data were analyzed to identify aging-related changes that occurred in tandem with the N-glycome changes.

Results

Following the 2y CR intervention, IgG galactosylation was higher at 24mo compared to BL (p = 0.051), digalactosylation and GlycAge (the IgG-based surrogate for biological age) were not different between BL and 12mo or BL and 24mo, but increased between 12mo and 24mo (p = 0.016, 0.027 respectively). GlycAge was also positively associated with TNF-α and ICAM-1 (p=0.030, p=0.017 respectively). Plasma highly branched glycans were decreased by the 2y intervention (BL vs 24 mo: p=0.013), but both plasma and IgG bisecting GlcNAcs were increased (BL vs 24mo: p<0.001, p = 0.01 respectively). Furthermore, total complement C3 protein concentrations were reduced (BL vs 24mo: p <0.001), as were Man9 glycoforms (BL vs 24mo: p<0.001), and Man10 (which is glucosylated) C3 glycoforms (BL vs 24mo: p = 0.046).

Conclusions

24-mos of CR was associated with several favorable, anti-aging, anti-inflammatory changes in the glycome: increased galactosylation, reduced branching glycans, and reduced GlycAge. These promising CR effects were accompanied by an increase in bisecting GlcNAc, a known pro-inflammatory biomarker. These intriguing findings linking CR, clinical, and glycomic changes may be anti-aging and inflammatory, and merit additional investigation.

Complement-targeted therapeutics: Are we there yet, or just getting started?

Therapeutic interventions in the complement system, a key immune-inflammatory mediator and contributor to a broad range of clinical conditions, have long been considered important yet challenging or even unfeasible to achieve. Almost 20 years ago, a spark was lit demonstrating the clinical and commercial viability of complement-targeted therapies. Since then, the field has experienced an impressive expansion of targeted indications and available treatment modalities. Currently, a dozen distinct complement-specific therapeutics covering several intervention points are available in the clinic, benefiting patients suffering from eight disorders, not counting numerous clinical trials and off-label uses. Observing this rapid rise of complement-targeted therapy from obscurity to mainstream with amazement, one might ask whether the peak of this development has now been reached or whether the field will continue marching on to new heights. This review looks at the milestones of complement drug discovery and development achieved so far, surveys the currently approved drug entities and indications, and ventures a glimpse into the future advancements yet to come.

HylS', a fragment of truncated hyaluronidase of Streptococcus suis, contributes to immune evasion by interaction with host complement factor C3b

Pathogenic bacteria have evolved many strategies to evade surveillance and attack by complements. Streptococcus suis is an important zoonotic pathogen that infects humans and pigs. Hyaluronidase (HylA) has been reported to be a potential virulence factor of S. suis. However, in this study, it was discovered that the genomic region encoding HylA of the virulent S. suis strain SC19 and other ST1 strains was truncated into four fragments when aligned with a strain containing intact HylA and possessing hyaluronidase activity. As a result, SC19 had no hyaluronidase activity, but one truncated HylA fragment, designated as HylS,' directly interacted with complement C3b, as confirmed by western ligand blotting, pull-down, and ELISA assays. The deposition of C3b and membrane attack complex (MAC) formation on the surface of a HylS'-deleted mutant (ΔhylS') was significantly increased compared to wild-type SC19. In human sera and whole blood, ΔhylS' survival was significantly reduced compared to that in SC19. The resistance of ΔhylS' to macrophages and human polymorphonuclear neutrophil PMNs also decreased. In a mouse infection model, ΔhylS' showed reduced lethality and lower bacterial load in the organs compared to that of SC19. We conclude that the truncated hyaluronidase HylS' fragment contributes to complement evasion and the pathogenesis of S. suis.

Unveiling the impact of Leptospira TolC efflux protein on host tissue adherence, complement evasion, and diagnostic potential

The TolC family protein of Leptospira is a type I outer membrane efflux protein. Phylogenetic analysis revealed significant sequence conservation among pathogenic Leptospira species (83%-98% identity) compared with intermediate and saprophytic species. Structural modeling indicated a composition of six β-strands and 10 α-helices arranged in two repeats, resembling bacterial outer membrane efflux proteins. Recombinant TolC (rTolC), expressed in a heterologous host and purified via Ni-NTA chromatography, maintained its secondary structural integrity, as verified by circular dichroism spectroscopy. Polyclonal antibodies against rTolC detected native TolC expression in pathogenic Leptospira but not in nonpathogenic ones. Immunoassays and detergent fractionation assays indicated surface localization of TolC. The rTolC's recognition by sera from leptospirosis-infected hosts across species suggests its utility as a diagnostic marker. Notably, rTolC demonstrated binding affinity for various extracellular matrix components, including collagen and chondroitin sulfate A, as well as plasma proteins such as factor H, C3b, and plasminogen, indicating potential roles in tissue adhesion and immune evasion. Functional assays demonstrated that rTolC-bound FH retained cofactor activity for C3b cleavage, highlighting TolC's role in complement regulation. The rTolC protein inhibited both the alternative and the classical pathway-mediated membrane attack complex (MAC) deposition in vitro. Blocking surface-expressed TolC on leptospires using specific antibodies reduced FH acquisition by Leptospira and increased MAC deposition on the spirochete. These findings indicate that TolC contributes to leptospiral virulence by promoting host tissue colonization and evading the immune response, presenting it as a potential target for diagnostic and therapeutic strategies.

Complement system component 3 deficiency modulates the phenotypic profile of murine macrophages

The Complement System is composed of more than 40 proteins that act in innate and adaptive immunity. C3 is the most abundant one and C3-deficient patients are more susceptible to recurrent and severe infections. Several studies have demonstrated the importance of C3 in controlling infections. However, its role in leukocyte biology is still poorly understood. This study aimed to evaluate several cellular parameters in macrophages from C3-deficient mice and compare them to similar cells from wild-type counterparts. We observed that in the absence of C3, the population of F4/80low macrophages in the peritoneal cavity of thioglycolate-treated mice is diminished, probably due to the lack of chemotactic factors like C3a and low levels of C5a. Using fluorescence microscopy analysis, we observed that macrophages from C3-deficient mice exhibited morphological alterations when compared to similar cells from wild-type mice. We observed a significant increase in the expression of CD11c, which is part of CR4 (CD11c/CD18), in macrophages from C3-deficient compared to cells from wild-type mice. Treatment with 12-o-tetradecanoylphorbol-13-acetate, stimulated ROS production and MAPK activation by macrophages. However, these parameters were lower in macrophages from C3-deficient mice when compared to wild-type counterparts. In addition, the phagocytosis of iC3b-opsonized Zymosan particles was diminished in macrophages from C3-deficient mice. Our results suggest that C3 deficiency in C57Black/6 mice may influence specific morphological and functional parameters of macrophages, cells of fundamental importance for both the innate and acquired immune responses.

Novel Antibody-Based Protection/Therapeutics in Staphylococcus aureus

Staphylococcus aureus is a commensal of the skin and nares of humans as well as the causative agent of infections associated with significant mortality. The acquisition of antibiotic resistance traits complicates the treatment of such infections and has prompted the development of monoclonal antibodies. The selection of protective antigens is typically guided by studying the natural antibody responses to a pathogen. What happens when the pathogen masks these antigens and subverts adaptive responses, or when the pathogen inhibits or alters the effector functions of antibodies? S. aureus is constantly exposed to its human host and has evolved all these strategies. Here, we review how anti-S. aureus targets have been selected and how antibodies have been engineered to overcome the formidable immune evasive activities of this pathogen. We discuss the prospects of antibody-based therapeutics in the context of disease severity, immune competence, and history of past infections.

Complement regulation in tumor immune evasion

The complement system plays crucial roles in both innate and adaptive immune responses, facilitating the elimination of pathogens such as microorganisms and damaged cells, including cancer cells. It is tightly regulated and integrated with cell-mediated immunity. In the tumor microenvironment, the complement system performs both immune and nonimmune functions in tumor and immune cells through pathways that depend on or are independent of complement activation, thereby promoting immune evasion and tumor progression.

A percolation-type criticality threshold controls immune protein coating of surfaces

When a material enters the body, it is immediately attacked by hundreds of proteins, organized into complex networks of binding interactions and reactions. How do such complex systems interact with a material, "deciding" whether to attack? We focus on the "complement" system of ∼40 blood proteins that bind microbes, nanoparticles, and medical devices, initiating inflammation. We show a sharp threshold for complement activation upon varying a fundamental material parameter, the surface density of potential complement attachment points. This sharp threshold manifests at scales spanning single nanoparticles to macroscale pathologies, shown here for diverse engineered and living materials. Computational models show these behaviors arise from a minimal subnetwork of complement, manifesting percolation-type critical transitions in the complement response. This criticality switch explains the "decision" of a complex signaling network to interact with a material, and elucidates the evolution and engineering of materials interacting with the body.

Genomic Validation in the UK Biobank Cohort Suggests a Role of C8B and MFG-E8 in the Pathogenesis of Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a severe facial pain disease of uncertain pathophysiology and unclear genetic background. Although recent research has reported a more important role of genetic factors in TN pathogenesis, few candidate genes have been proposed to date. The present study aimed to identify independent genetic variants in the protein-coding genes associated with TN. We focused on genes previously linked to TN based on the results of four proteomic studies conducted by our research team. The goal was to validate these findings on the genetic level to enhance our understanding of the role of genetics in TN. The study is based on the participants from UK Biobank cohort. Following quality control, 175 independent single nucleotide polymorphisms (SNPs) in 17 genes were selected. The study sample comprised of diagnosed TN cases (N = 555) and randomly matched controls (N = 6245) based on specific criteria. Two SNPs corresponding to C8B rs706484 [odds ratio (OR) (95% confidence interval (CI)): 1.357 (1.158-1.590); p: 0.00016] and MFG-E8 rs2015495 [OR (95% CI): 1.313 (1.134-1.521); p: 0.00028] showed significant positive association with TN, indicating a positive effect of the SNP alleles on gene expression and disease risk. Interestingly, both SNPs are Expression Quantitative Trait Loci (eQTLs), and are associated with changes in the expression activity of their corresponding gene. Our findings suggest novel genetic associations between C8B, a key component of the complement system, and MFG-E8, which plays a role in regulating neuroinflammation, in relation to TN. The identified genetic variations may help explain why some individuals develop TN while others do not, indicating a potential genetic predisposition to the condition.

Potential applications of dual haptoglobin expression in the reclassification and treatment of hepatocellular carcinoma

HCC is a malignancy characterized by high incidence and mortality rates. Traditional classifications of HCC primarily rely on tumor morphology, phenotype, and multicellular molecular levels, which may not accurately capture the cellular heterogeneity within the tumor. This study integrates scRNA-seq and bulk RNA-seq to spotlight HP as a critical gene within a subgroup of HCC malignant cells. HP is highly expressed in HCC malignant cells and lowly expressed in T cells. Within malignant cells, elevated HP expression interacts with C3, promoting Th1-type responses via the C3/C3AR1 axis. In T cells, down-regulating HP expression favors the expression of Th1 cell-associated marker genes, potentially enhancing Th1-type responses. Consequently, we developed a "HP-promoted Th1 response reclassification" gene set, correlating higher activity scores with improved survival rates in HCC patients. Additionally, four predictive models for neoadjuvant treatment based on HP and C3 expression were established: 1) Low HP and C3 expression with high Th2 cell infiltration; 2) High HP and low C3 expression with high Th2 cell infiltration; 3) High HP and C3 expression with high Th1 cell infiltration; 4) Low HP and high C3 expression with high Th1 cell infiltration. In conclusion, the HP gene selected from the HCC malignant cell subgroup (Malignant_Sub 6) might serve as a potential ally against the tumor by promoting Th1-type immune responses. The establishment of the "HP-promoted Th1 response reclassification" gene set offers predictive insights for HCC patient survival prognosis and neoadjuvant treatment efficacy, providing directions for clinical treatments.

Proteomic profiling of oleamide-mediated polarization in a primary human monocyte-derived tumor-associated macrophages (TAMs) model: a functional analysis

BACKGROUND

Tumor-associated macrophages (TAMs) play a critical function in the development of tumors and are associated with protumor M2 phenotypes. Shifting TAMs towards antitumor M1 phenotypes holds promise for tumor immunotherapy. Oleamide, a primary fatty acid amide, has emerged as a potent anticancer and immunomodulatory compound. However, the regulatory effects of oleamide on TAM phenotypes remain unclear.

METHODS

We used real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) techniques to study the influence of oleamide on primary human monocyte-derived TAM phenotypes, and we investigated the protein expression profiles based on mass spectrometry to analyze the effect of oleamide on macrophage polarization. Moreover, the advantageous binding scores between oleamide and these target candidate proteins are examined using molecular docking.

RESULTS

Our study revealed that oleamide effectively suppressed the M2-like TAM phenotype by reducing interleukin (IL)-10 production and downregulating M2-like markers, including vascular endothelial growth factor A (VEGFA), MYC proto-oncogene, bHLH transcription factor (c-Myc), and mannose receptor C-type 1 (CD206). Moreover, the conditioned medium derived from oleamide-treated TAMs induces apoptosis of MDA-MB-231 breast cancer cells. Proteomic analysis identified 20 candidate up- and down-regulation proteins targeted by oleamide, showing modulation activity associated with the promotion of the M1-like phenotype. Furthermore, molecular docking demonstrated favorable binding scores between oleamide and these candidate proteins. Collectively, our findings suggest that oleamide exerts a potent antitumor effect by promoting the antitumor M1-like TAM phenotype. These novel insights provide valuable resources for further investigations into oleamide and macrophage polarization which inhibit the progression of breast cancer, which may provide insight into immunotherapeutic approaches for cancer.

Hypoxia-induced complement component 3 promotes aggressive tumor growth in the glioblastoma microenvironment

Glioblastoma (GBM) is the most aggressive form of glioma with a high rate of relapse despite intensive treatment. Tumor recurrence is tightly linked to radio-resistance, which in turn is associated with hypoxia. Here, we discovered a strong link between hypoxia and local complement signaling using publicly available bulk, single-cell, and spatially resolved transcriptomic data from patients with GBM. Complement component 3 (C3) and the receptor C3AR1 were both associated with aggressive disease and shorter survival in human glioma. In a genetically engineered mouse model of GBM, we found C3 specifically in hypoxic tumor areas. In vitro, we found an oxygen level-dependent increase in C3 and C3AR1 expression in response to hypoxia in several GBM and stromal cell types. C3a induced M2 polarization of cultured microglia and macrophages in a C3aR-dependent fashion. Targeting C3aR using the antagonist SB290157 prolonged survival of glioma-bearing mice both alone and in combination with radiotherapy while reducing the number of M2-polarized macrophages. Our findings establish a strong link between hypoxia and complement pathways in GBM and support a role of hypoxia-induced C3a/C3aR signaling as a contributor to glioma aggressiveness by regulating macrophage polarization.

Intracellular complement and immunometabolism: The advantages of compartmentalization

The complement system is a proteolytic cascade triggered by pathogen and danger-associated molecular patterns, with resultant outcomes of inflammation, cellular activation, and opsonization of material for removal by phagocytosis. While first discovered as an activity in serum, it is now recognized that complement components play important roles at local and individual cell-intrinsic levels. In particular, apart from the extracellular serum activities of complement, it is now believed that complement also acts intracellularly, as part of a cellular signal transduction cascade that can stimulate cellular survival and activation, and individual immune cell phenotypes, via effects on cellular metabolism. This review will describe what is currently known about how complement functions in intracellular signal transduction, and outline the functional advantages of a compartmentalized and intracellular complement system.

Synthesis and characterization of new hexahydroquinoline derivatives and evaluation of their cytotoxicity, intracellular ROS production, and inhibitory effects on inflammatory mediators

Inflammation is a response to injury and infection in an organism. It can be categorized as acute or chronic. Chronic inflammation is the underlying cause of many diseases such as Alzheimer disease, diabetes, rheumatoid arthritis, atherosclerosis, and cardiovascular diseases. Recent studies have proven the antiinflammatory properties of 1,4-dihydropyridines (1,4-DHPs) and their derivatives, which have many biological activities including the blocking of calcium channels. In this study, 15 compounds that are condensed derivatives of 1,4-DHPs, with the general structure of hexahydroquinoline-3-carboxylate, were synthesized. These compounds, expected to show inhibitory activity against inflammatory mediators, were obtained by the reaction of 4-(difluoromethoxy)benzaldehyde, substituted/nonsubstituted 1,3-cyclohexanedione derivatives, and appropriate alkyl acetoacetate compounds in the presence of ammonium acetate as a nitrogen source according to the Hantzsch synthesis method. The structures of the synthesized compounds were elucidated by IR, 1H NMR, 13C NMR, and HRMS methods. The cytotoxic properties of the compounds were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method in the 3T3 cell line. Among the 15 compounds, the three compounds with the lowest levels of cytotoxic effects were selected for further experiments. Inflammation was induced by lipoxygenase and the effects of the selected compounds on the levels of reactive oxygen species, cytokines, and complement C3 and C9 regulatory proteins were investigated. It was found that the three selected compounds decreased the levels of transforming growth factor-beta 1 (TGF-β1). Among these compounds, compound 3e provided the most significant decrease in this cytokine. Moreover, 3e increased both C3 and C9 levels. Molecular modeling studies also showed that 3e had better affinity for TGF-β1. When the binding modes of these compounds in the active site of TGF-β1 were analyzed, it was found that compound 3e had hydrophobic interactions with amino acids Leu142, Tyr84, and Ile13; halogen bond interactions with Asp92; and hydrogen bond interactions with Ser89, Gly88, and Gly14 in the active binding site. Further in vitro and in vivo studies are needed to show the possible mechanism of action of compound 3e.

Genetic Insights into Age-Related Macular Degeneration

One of the major causes of vision impairment among elderly people in developed nations is age-related macular degeneration (AMD). The distinctive features of AMD are the accumulation of extracellular deposits called drusen and the gradual deterioration of photoreceptors and nearby tissues in the macula. AMD is a complex and multifaceted disease influenced by several factors such as aging, environmental risk factors, and a person's genetic susceptibility to the condition. The interaction among these factors leads to the initiation and advancement of AMD, where genetic predisposition plays a crucial role. With the advent of high-throughput genotyping technologies, many novel genetic loci associated with AMD have been identified, enhancing our knowledge of its genetic architecture. The common genetic variants linked to AMD are found on chromosome 1q32 (in the complement factor H gene) and 10q26 (age-related maculopathy susceptibility 2 and high-temperature requirement A serine peptidase 1 genes) loci, along with several other risk variants. This review summarizes the common genetic variants of complement pathways, lipid metabolism, and extracellular matrix proteins associated with AMD risk, highlighting the intricate pathways contributing to AMD pathogenesis. Knowledge of the genetic underpinnings of AMD will allow for the future development of personalized diagnostics and targeted therapeutic interventions, paving the way for more effective management of AMD and improved outcomes for affected individuals.

Complement System Response to Adeno-Associated Virus Vector Gene Therapy

Adeno-associated virus (AAV) vectors represent a novel tool for the delivery of genetic therapeutics and enable the treatment of a wide range of diseases. Success of this new modality is challenged, however, by cases of immune-related toxicities that complicate the clinical management of patients and potentially limit the therapeutic efficacy of AAV gene therapy. While significant progress has been made to manage immune-related liver enzyme elevations following systemic AAV delivery in humans, recent clinical trials utilizing high vector doses have highlighted a new challenge to AAV gene transfer-activation of the complement system. While current in vitro models implicate AAV-specific antibodies in the initiation of the classical complement pathway, evidence from in vivo pre-clinical and clinical studies suggests that the alternative pathway also contributes to complement activation. A convergence of AAV-specific, environmental, and patient-specific factors shaping complement responses likely contributes to differential outcomes seen in clinical trials, from priming of the adaptive immune system to serious adverse events such as hepatotoxicity and thrombotic microangiopathy. Research focused on the interplay of patient-specific and AAV-related factors driving complement activation is needed to understand and identify critical components in the complement cascade to target and devise strategies to mitigate vector-related immune responses.

Exposure to nanopollutants (nZnO) enhances the negative effects of hypoxia and delays recovery of the mussels' immune system

Aquatic environments face escalating challenges from multiple stressors like hypoxia and nanoparticle exposure, with impact of these combined stressors on mussel immunity being poorly understood. We investigated the individual and combined effects of short-term and long-term hypoxia and exposure to zinc oxide nanoparticles (nZnO) on immune system of the mussels (Mytilus edulis). Hemocyte functional traits (mortality, adhesion capacity, phagocytosis, lysosomal abundance, and oxidative burst), and transcript levels of immune-related genes involved in pathogen recognition (the Toll-like receptors, the complement system components, and the adaptor proteins MyD88) were assessed. Short-term hypoxia minimally affected hemocyte parameters, while prolonged exposure led to immunosuppression, impacting hemocyte abundance, viability, phagocytosis, and defensin gene expression. Under normoxia, nZnO stimulated immune responses of mussel hemocytes. However, combined nZnO and hypoxia induced more pronounced and rapid immunosuppression than hypoxia alone, indicating a synergistic interaction. nZnO exposure hindered immune parameter recovery during post-hypoxic reoxygenation, suggesting persistent impact. Opposing trends were observed in pathogen-sensing and pathogen-elimination mechanisms, with a positive correlation between pathogen-recognition system activation and hemocyte mortality. These findings underscore a complex relationship and potential conflict between pathogen-recognition ability, immune function, and cell survival in mussel hemocytes under hypoxia and nanopollutant stress, and emphasize the importance of considering multiple stressors in assessing the vulnerability and adaptability of mussel immune system under complex environmental conditions of anthropogenically modified coastal ecosystems.

Is the Complement System Dysregulated in Preeclampsia Comorbid with HIV Infection?

South Africa is the epicentre of the global HIV pandemic, with 13.9% of its population infected. Preeclampsia (PE), a hypertensive disorder of pregnancy, is often comorbid with HIV infection, leading to multi-organ dysfunction and convulsions. The exact pathophysiology of preeclampsia is triggered by an altered maternal immune response or defective development of maternal tolerance to the semi-allogenic foetus via the complement system. The complement system plays a vital role in the innate immune system, generating inflammation, mediating the clearance of microbes and injured tissue materials, and a mediator of adaptive immunity. Moreover, the complement system has a dual effect, of protecting the host against HIV infection and enhancing HIV infectivity. An upregulation of regulatory proteins has been implicated as an adaptive phenomenon in response to elevated complement-mediated cell lysis in HIV infection, further aggravated by preeclamptic complement activation. In light of the high prevalence of HIV infection and preeclampsia in South Africa, this review discusses the association of complement proteins and their role in the synergy of HIV infection and preeclampsia in South Africa. It aims to identify women at elevated risk, leading to early diagnosis and better management with targeted drug therapy, thereby improving the understanding of immunological dysregulation.

Immunological landscape of solid cancer: Interplay between tumor and autoimmunity

The immune system, a central player in maintaining homeostasis, emerges as a pivotal factor in the pathogenesis and progression of two seemingly disparate yet interconnected categories of diseases: autoimmunity and cancer. This chapter delves into the intricate and multifaceted role of the immune system, particularly T cells, in orchestrating responses that govern the delicate balance between immune surveillance and self-tolerance. T cells, pivotal immune system components, play a central role in both diseases. In autoimmunity, aberrant T cell activation drives damaging immune responses against normal tissues, while in cancer, T cells exhibit suppressed responses, allowing the growth of malignant tumors. Immune checkpoint receptors, example, initially explored in autoimmunity, now revolutionize cancer treatment via immune checkpoint blockade (ICB). Though effective in various tumors, ICB poses risks of immune-related adverse events (irAEs) akin to autoimmunity. This chapter underscores the importance of understanding tumor-associated antigens and their role in autoimmunity, immune checkpoint regulation, and their implications for both diseases. It also explores autoimmunity resulting from cancer immunotherapy and shared molecular pathways in solid tumors and autoimmune diseases, highlighting their interconnectedness at the molecular level. Additionally, it sheds light on common pathways and epigenetic features shared by autoimmunity and cancer, and the potential of repurposing drugs for therapeutic interventions. Delving deeper into these insights could unlock therapeutic strategies for both autoimmunity and cancer.

Association of complement components with risk of colorectal cancer: A systematic review and meta-analysis

BACKGROUND

Complement components could contribute to the tumor microenvironment and the systemic immune response. Nevertheless, their role in colorectal cancer (CRC) remains a contentious subject.

AIM

To elucidate the relationship between complement components and CRC risk and clinical characteristics.

METHODS

Searches were conducted in PubMed, the Cochrane Library, and the China National Knowledge Infrastructure database until June 1, 2023. We included cohort studies encompassing participants aged ≥ 18 years, investigating the association between complement components and CRC. The studies were of moderate quality or above, as determined by the Agency for Healthcare Research and Quality. The meta-analysis employed fixed-effects or random-effects models based on the I² test, utilizing risk ratio (RR) and their corresponding 95% confidence interval (CI) for outcomes. Sensitivity and subgroup analyses were performed to validate the robustness of the collective estimates and identify the source of heterogeneity.

RESULTS

Data from 15 studies, comprising 1631 participants that met the inclusion criteria, were included in the meta-analysis. Our findings indicated that protein levels of cluster of differentiation 46 (CD46) (RR = 3.66, 95%CI: 1.75-7.64, P < 0.001), CD59 (RR = 2.86, 95%CI: 1.36-6.01, P = 0.005), and component 1 (C1) (RR = 5.88, 95%CI: 1.75-19.73, P = 0.004) and serum levels of C3 (standardized mean difference = 1.82, 95%CI: 0.06-3.58, P = 0.040) were significantly elevated in patients with CRC compared to healthy controls. Strong expression of CD55 or CD59 was associated with a higher incidence of lymph node metastasis, whereas strong CD46 expression correlated with a higher incidence of tumor differentiation compared to low CD46 expression (P < 0.05 for all). Although specific pooled results demonstrated notable heterogeneity, subgroup analyses pointed to regional differences as the primary source of inconsistency among the studies.

CONCLUSION

Our analysis underscores that increased levels of specific complement components are associated with a heightened risk of CRC, emphasizing the potential significance of monitoring elevated complement component levels.

Effects of hibernation on two important contractile tissues in tibetan frogs, Nanorana parkeri: a perspective from transcriptomics and metabolomics approaches

BACKGROUND

In response to seasonal cold and food shortage, the Xizang plateau frogs, Nanorana parkeri (Anura: Dicroglossidae), enter a reversible hypometabolic state where heart rate and oxygen consumption in skeletal muscle are strongly suppressed. However, the effect of winter hibernation on gene expression and metabolic profiling in these two tissues remains unknown. In the present study, we conducted transcriptomic and metabolomic analyses of heart and skeletal muscle from summer- and winter-collected N. parkeri to explore mechanisms involved in seasonal hibernation.

RESULTS

We identified 2407 differentially expressed genes (DEGs) in heart and 2938 DEGs in skeletal muscle. Enrichment analysis showed that shared DEGs in both tissues were enriched mainly in translation and metabolic processes. Of these, the expression of genes functionally categorized as "response to stress", "defense mechanisms", or "muscle contraction" were particularly associated with hibernation. Metabolomic analysis identified 24 and 22 differentially expressed metabolites (DEMs) in myocardium and skeletal muscle, respectively. In particular, pathway analysis showed that DEMs in myocardium were involved in the pentose phosphate pathway, glycerolipid metabolism, pyruvate metabolism, citrate cycle (TCA cycle), and glycolysis/gluconeogenesis. By contrast, DEMs in skeletal muscle were mainly involved in amino acid metabolism.

CONCLUSIONS

In summary, natural adaptations of myocardium and skeletal muscle in hibernating N. parkeri involved transcriptional alterations in translation, stress response, protective mechanisms, and muscle contraction processes as well as metabolic remodeling. This study provides new insights into the transcriptional and metabolic adjustments that aid winter survival of high-altitude frogs N. parkeri.

Genome-wide analysis of early vascular tunic repair and regeneration for Botrylloides digenesis reveals striking similarities to human wound healing

The early stages of regeneration after injury are similar to those of wound healing. The ascidian Botrylloides diegensis can regenerate an entire adult from a small fragment of vascular tunic following the removal of all zooids in an injury-induced regeneration model. We investigated the molecular and cellular changes following injury to determine the differences between the healing process and the initiation of whole-body regeneration (WBR). We conducted transcriptome analysis at specific time points during regeneration and wound healing to identify differentially expressed genes (DEGs) and the unique biological processes associated with each state. Our findings revealed 296 DEGs at 10 h post-injury (hpi), with 71 highly expressed in healed tissue and 225 expressed during the WBR process. These DEGs were predicted to play roles in tissue reorganization, integrin signaling, extracellular matrix organization, and the innate immune system. Pathway analysis of the upregulated genes in the healed tunic indicated functional enrichment related to tissue repair, as has been observed in other species. Additionally, we examined the cell types in the tunic and ampullae in both tissue states using histology and in situ hybridization for six genes identified by transcriptome analysis. We observed strong mRNA expression in cells within the WBR tunic, and in small RNA-positive granules near the tunic edge. We hypothesized that many of these genes function in the compaction of the ampullae tunic, which is a pivotal process for WBR and dormancy in B. diegensis, and in an immune response. These findings establish surprising similarities between ascidian regeneration and human wound healing, emphasizing the potential for future investigations into human regenerative and repair mechanisms. This study provides valuable insights into the gene sets specifically activated during regeneration compared to wound healing, shedding light on the divergent activities of these processes.

Molecular mechanism of complement inhibition by the trypanosome receptor ISG65

African trypanosomes replicate within infected mammals where they are exposed to the complement system. This system centres around complement C3, which is present in a soluble form in serum but becomes covalently deposited onto the surfaces of pathogens after proteolytic cleavage to C3b. Membrane-associated C3b triggers different complement-mediated effectors which promote pathogen clearance. To counter complement-mediated clearance, African trypanosomes have a cell surface receptor, ISG65, which binds to C3b and which decreases the rate of trypanosome clearance in an infection model. However, the mechanism by which ISG65 reduces C3b function has not been determined. We reveal through cryogenic electron microscopy that ISG65 has two distinct binding sites for C3b, only one of which is available in C3 and C3d. We show that ISG65 does not block the formation of C3b or the function of the C3 convertase which catalyses the surface deposition of C3b. However, we show that ISG65 forms a specific conjugate with C3b, perhaps acting as a decoy. ISG65 also occludes the binding sites for complement receptors 2 and 3, which may disrupt recruitment of immune cells, including B cells, phagocytes, and granulocytes. This suggests that ISG65 protects trypanosomes by combining multiple approaches to dampen the complement cascade.

Therapy-induced senescent cancer cells exhibit complement activation and increased complement regulatory protein expression

Therapy-induced senescence (TIS) is a primary response to chemotherapy, contributing to untoward treatment outcomes such as evasion of immunosurveillance. Despite the established role of the complement system in the immune response to cancer, the role of complement in mediating the immune response against senescent tumor cells remains poorly understood. To explore this relationship, we exposed lung adenocarcinoma (A549), breast adenocarcinoma (MCF7) and pancreatic carcinoma (Panc-1) cell lines to sublethal doses of either etoposide or doxorubicin to trigger TIS. Identification of TIS was based on morphological changes, upregulation of the senescence-associated β-galactosidase, p21Cip1 induction and lamin B1 downregulation. Using immunofluorescence microscopy, quantitative PCR, ELISA of conditioned media and in silico analysis, we investigated complement activation, complement protein expression, C3 levels in the conditioned media of senescent cells and secreted complement proteins as part of the senescence-associated secretory phenotype (SASP), respectively. In cell lines undergoing TIS, complement-related changes included (i) activation of the terminal pathway, evidenced by the deposition of C5b-9 on senescent cells; (ii) an increase in the expression of CD59 and complement factor H and (iii) in A549 cells, an elevation in the expression of C3 with its secretion into the medium. In addition, increased C3 expression was observed in breast cancer samples expressing TIS hallmarks following exposure to neoadjuvant chemotherapy. In conclusion, TIS led to the activation of complement, upregulation of complement regulatory proteins and increased C3 expression. Complement appears to play a role in shaping the cancer microenvironment upon senescence induction.

Immortalized Human Conjunctival Epithelial Cells Produce Functional Complement C3 and C4 Proteins

PURPOSE

The aim of this study was to assess whether complement proteins C3 and C4 are produced by immortalized human conjunctival epithelial (HCjE) cells.

METHODS

Supernatants and cell lysates from undifferentiated and differentiated HCjE cells were assayed for C3 and C4 by enzyme-linked immunosorbent assay. To measure complement protein function, supernatants and lysates were treated with heat-aggregated IgG, and soluble C5b-9 was measured.

RESULTS

C3 was upregulated in supernatants from differentiated HCjE cells compared with undifferentiated HCjE cells (556.55 ± 91.75 vs. 56.95 ± 12.09 ng/mL, P <0.001). C4 was also increased in supernatants but to a much lesser extent (0.599 ± 0.476 vs. 0.172 ± 0.0133 ng/mL, P = 0.03). From HCjE cell lysates, total C3 production was 9.03 times higher in differentiated HCjE cells ( P <0.001), whereas total C4 remained relatively unchanged. After activation with heat-aggregated IgG, sC5b-9 could be detected from both undifferentiated and differentiated HCjE cell lysates, but not in the HCjE supernatants.

CONCLUSIONS

HCjE cells produce C3 and C4 in sufficient quantities to support the formation of sC5b-9, confirming their biological activity and suggesting that HCjE cells likely produce all complement proteins C1 through C9.

Mechanisms by which Factor H protects Trypanosoma cruzi from the alternative pathway of complement

Chagas disease, a chronic disabling disease caused by the protozoan Trypanosoma cruzi, has no standardized treatment or preventative vaccine. The infective trypomastigote form of T. cruzi is highly resistant to killing by the complement immune system. Factor H (FH), a negative regulator of the alternative pathway (AP) of complement on cell surfaces and in blood, contains 20 short consensus repeat domains. The four N-terminal domains of FH inactivate the AP, while the other domains interact with C3b/d and glycan markers on cell surfaces. Various pathogens bind FH to inactivate the AP. T. cruzi uses its trans-sialidase enzyme to transfer host sialic acids to its own surface, which could be one of the approaches it uses to bind FH. Previous studies have shown that FH binds to complement-opsonized T. cruzi and parasite desialylation increases complement-mediated lysis of trypomastigotes. However, the molecular basis of FH binding to T. cruzi remain unknown. Only trypomastigotes, but not epimastigotes (non-infective, complement susceptible) bound FH directly, independent of C3 deposition, in a dose-dependent manner. Domain mapping experiments using 3-5 FH domain fragments showed that domains 5-8 competitively inhibited FH binding to the trypomastigotes by ~35% but did not decrease survival in complement. FH-Fc or mutant FH-Fc fusion proteins (3-11 contiguous FH domains fused to the IgG Fc) also did not kill trypomastigotes. FH-related protein-5, whose domains bear significant sequence identity to all known polyanion-binding FH domains (6-7, 10-14, 19-20), fully inhibited FH binding to trypomastigotes and reduced trypomastigote survival to < 24% in the presence of serum. In conclusion, we have elucidated the role of FH in complement resistance of trypomastigotes.