Complement and its role in innate and adaptive immune responses

No relationship between non-IgE-mediated mechanisms (complement activation or direct activation of mast cells and basophils) during diclofenac etalhyaluronate (SI-613/ONO-5704)-induced anaphylaxis

It was previously reported that half of the anaphylaxis cases occurring after intra-articular administration of diclofenac etalhyaluronate (DEH) - developed as SI-613/ONO-5704 and marketed as JOYCLU® - were induced by IgE-mediated mechanisms; mechanisms for the remaining cases remain unclear. In this study, we investigated the relationship of DEH-induced anaphylaxis to non-IgE-mediated mechanisms in vitro. Assays were carried out based on the production of downstream products of the complement cascade, calcium influx due to Mas-related G protein-coupled receptor-X2 (MRGPRX2) activation, mast cell degranulation, and expression of basophil activation markers. Human plasma, CHO-K1 cells stably expressing MRGPRX2, the human mast cell line LAD2, and the human basophil leukemia cell line KU812 were used for these evaluations. No effect of DEH treatment was found on complement activation, MRGPRX2 agonist activity, direct mast cell activation, or direct basophil activation. From this it could be concluded that DEH-induced anaphylaxis is unlikely to involve complement activation or direct activation of mast cells and basophils. However, the possibility remains that the anaphylaxis might be a non-immunological hypersensitivity reaction due to inhibition of cyclooxygenase-1 by non-steroidal anti-inflammatory drugs (NSAID). Further investigation into the relationship between the non-immunological hypersensitivity and anaphylaxis following DEH administration is warranted.

Probiotic-based immunization improves immune responses in Oreochromis mossambicus against Aeromonas hydrophila pathogen: Insights from Bacillus licheniformis (Dahb1)

The study was aimed to evaluate the immunization potential of different cellular components such as whole-cell protein (WCP), extracellular protein (ECP), and cell wall protein (CWP) of probiotic Bacillus licheniformis in Oreochromis mossambicus against Aeromonas hydrophila infection. At the end of 14th and 28th days, increased humoral and cellular immune parameters in CWP, WCP, and ECP cellular component treated groups of O. mossambicus were observed. This was attributed to the elevation of reactive oxygen species (ROS), superoxide & hydroxyl radical ions, which increased the immune parameter activity by activating macrophage, the complement system and the opsonization process in cellular components treated groups. After 28 days of administration, the aquaculture bacterial pathogen A. hydrophila (1 × 107 cells/mL), increased survival rate in experimental group fish which were immunized with probiotic cellular components CWP, WCP and ECP, compared with the control group were detected. Moreover, the isolated cellular components show great anti-bacterial and anti-biofilm activity against Aeromonas hydrophila. Overall results have shed light on probiotic B. licheniformis (Dahb1) cellular components especially CWP that effectively control bacterial disease under A. hydrophila burden conditions.

AAV-mediated inner ear gene delivery triggers mild host immune responses in the mammalian inner ear

Hearing loss is a common disability affecting the world's population. Currently, its treatment options are limited. Adeno-associated virus (AAV)-mediated inner ear gene therapy has shown great promise as a treatment for hereditary hearing loss. However, the host immune responses to AAV-mediated gene therapy in the mammalian inner ear is not well understood. In this study, two serotypes of AAV vectors were injected individually into the mouse inner ear to evaluate the host innate and adaptive immune responses up to 1 month after inner ear gene delivery. Our results suggest that the host innate and adaptive immune responses to AAV-mediated inner ear gene delivery are limited and mild, which is favorable for its clinical translation.

Emerging Thrombotic Disorders Associated with Virus-Based Innovative Therapies: From VITT to AAV Gene Therapy-Related Thrombotic Microangiopathy

Gene therapy is a promising therapeutic approach for treating life-threatening disorders. Despite the clinical improvements observed with gene therapy, immune responses either innate or adaptive against the vector used for gene delivery, can affect treatment efficacy and lead to adverse reactions. Thrombotic microangiopathy (TMA) is a thrombosis with thrombocytopenia syndrome (TTS) characterized by microangiopathic hemolytic anemia, thrombocytopenia, and small vessel occlusion known to be elicited by several drugs, that has been recently reported as an adverse event of adeno-associated virus (AAV)-based gene therapy. TMA encompasses a heterogenous group of disorders, its classification and underlining mechanisms are still uncertain, and still lacks validated biomarkers. The identification of predictors of TMA, such as vector dose and patient characteristics, is a pressing need to recognize patients at risk before and after AAV-based gene therapy administration. This review aims to explore the literature on TMA associated with AAV-based gene therapy in the larger context of TMA (i.e., hemolytic-uremic syndrome, thrombotic thrombocytopenic purpura, and other drug-related TMAs). Considering the wide attention recently gained by another TTS associated with a non-gene therapy viral platform (adenovirus, AV COVID-19 vaccine), namely vaccine-induced immune thrombocytopenia and thrombosis (VITT), AAV gene therapy-related TMA mechanisms will be discussed and differentiated from those of VITT to avoid recency bias and favor a correct positioning of these two recently emerged syndromes within the heterogenous group of drug-related TTS. Finally, the review will discuss strategies for enhancing the safety and optimize the management of AAV-based gene therapy that is emerging as an efficacious therapeutic option for disparate, severe, and often orphan conditions.

The structural characteristics and expression characteristics of C1S in response to GCRV infection in grass carp

The complement system, a critical component of innate immunity in fish, plays a pivotal role in the defense against Grass Carp Reovirus (GCRV) infection in grass carp. This study explores the structural characteristics of C1S, a crucial molecule in the classical pathway of the complement system, and its involvement in the response to GCRV infection. We found that the grass carp C1S gene comprises six domains similar to those in mammals: two CUB (Complement C1r/C1s, Uegf, Bmp1) domains, two CCP (Complement control protein) domains, one EGFCA (Calcium-binding epidermal growth factor) domain, and one Tryp_SPc (Trypsin-like serine protease) domain, albeit without chromosomal collinearity to humans. Comparative analysis revealed that the identity and similarity of this gene with those in other species range from 30.6 to 89.4 % and 30.7-89.7 %, respectively. Phylogenetic analysis positioned C1S in close relation with R. klamathensis and D. rerio. Tissue expression profiles in both healthy and GCRV-infected grass carp indicated primary expression of C1S in the liver, with expression peaks at day 7 post-infection in the liver and spleen, and at day 5 in the kidney. Functional assays demonstrated that C1S activates the complement system via cleavage of complement component 3 (C3) into C3b, further inhibiting GCRV replication and upregulating antiviral genes IFN1, IRF3, and IRF7. These findings elucidate the mechanism by which the complement system mediates resistance to GCRV infection in grass carp, offering a substantial theoretical foundation for further research.

Complement system is activated in acute inflammatory response to environmental particulates in the lungs

Short-term exposure (typically ranging from a few hours to 7 days) to particulate matter (PM) elicits acute inflammatory responses with significant activation of complement component C5. However, the relationship between PM-induced complement system activation, acute inflammation, and the contributing factors remains unclear. In this study, we aimed to investigate the intensity of acute inflammatory responses, as well as the activation levels of complement C5 and its related products, C5aR1 and C5b-9, following exposure to different types of PM. Acute inflammatory responses and complement activation were assessed in mice intratracheally administered four types of PM: titanium dioxide (TiO₂), diesel exhaust particles (DEP), Asian sand dust (ASD), and ambient PM with an aerodynamic diameter ≤ 2.5 μm (PM2.5). Complement system and inflammatory markers were evaluated by analyzing increased C5 protein levels, C5b-9 deposition, and C5aR1 expression. Additionally, dark-field microscopy and Raman microscopy were used to detect PM components adjacent to infiltrating neutrophils, and elemental composition was quantified using ICP-MS and EDXRF. ASD, DEP, and PM2.5 exposure significantly increased C5b-9 deposition in lung tissues. All PM-exposed groups exhibited substantial upregulation of C5aR1 expression, primarily in neutrophils. Raman spectroscopic analysis revealed Si, K, Mg, Al, and Fe adjacent to infiltrating neutrophils in ASD-exposed lungs. Furthermore, elemental analysis identified Si, Mg, Al, and K as the most potent contributors to complement activation and inflammatory responses. Of the four types of PM, ASD induced the most severe acute inflammatory response and complement system activation. Therefore, ASD-induced complement system activation, driven at least partly by its mineral components, may play a critical role in neutrophil activation and acute pulmonary inflammation. These findings highlight the differential impact of PM types on complement system activation and underscore the importance of PM composition in the evaluation of air pollution-related health risks, particularly acute pulmonary inflammation.

Insights into the Pathogenesis of Pyoderma Gangrenosum

Pyoderma gangrenosum (PG) is a neutrophilic dermatosis of unclear etiology. Numerous theories of its underlying pathogenesis have been proposed, including external triggers, neutrophilic dysfunction, complement activation, and autoimmunity, as well as a possible component of underlying genetic susceptibility. This review seeks to synthesize current understanding of the pathogenesis of PG and integrate interactions between the multitude of implicated host immune pathways to guide and inform future directions into the treatment of PG.

Differential Analysis of Core Complement Components Expression and Localization Across Rodent, Non-Human Primate, and Human Ocular Tissues

Age-related macular degeneration (AMD) is a leading cause of blindness. Genetic and pathophysiological studies have implicated that complement pathway dysfunction is a key contributor to progressive vision loss in AMD. Though the association between complement and AMD is recognized, numerous anti-complement therapeutics that had been tested in rodent model systems had limited success in clinical trials. Understanding complement factor production and site of action in ocular pathophysiology is critical for the development of efficacious therapeutics. However, our limited understanding of how these aspects of complement biology vary across species restricts our ability to predict clinical outcomes from studies using animal models. Here, we integrated transcriptomic and immunohistochemical assays to understand the expression and localization of core complement components (complement factor H (FH), complement 3 (C3), and complement 5 (C5)) between ocular tissues of rodent, non-human primate, and human species. We found that complement distribution varied significantly across the studied species, with the most striking differences observed in the FH. While rodents expressed Cfh, an alternative pathway inhibitor, mainly in the RPE, CFH expression in primate eyes was primarily confined to the choroid. These differences were consistent at the protein level, with rodent FH localized in the RPE and primate FH within the choriocapillaris, choroid and sclera. Regarding C5, a terminal complement pathway component, we observed minimal ocular mRNA levels in all three species. However, we observed detectable protein levels in the RPE in rodents and the choroid in humans. Next, C3 mRNA transcripts and C3 protein exhibited similar distribution in the choroid in both rodent and primate eyes. Together, our findings highlight key differences and similarities between rodent and primate complement biology that may offer insights into the translatability of animal models and inform the design of effective therapeutics.

Diverse cell types establish a pathogenic immune environment in peripheral neuropathy

Neuroinflammation plays a complex and context-dependent role in many neurodegenerative diseases. We identified a key pathogenic function of macrophages in a mouse model of a rare human congenital neuropathy in which SARM1, the central executioner of axon degeneration, is activated by hypomorphic mutations in the axon survival factor NMNAT2. Macrophage depletion blocked and reversed neuropathic phenotypes in this sarmopathy model, revealing SARM1-dependent neuroimmune mechanisms as key drivers of disease pathogenesis. In this study, we investigated the impact of chronic subacute SARM1 activation on the peripheral nerve milieu using single cell/nucleus RNA-sequencing (sc/snRNA-seq). Our analyses reveal an expansion of immune cells (macrophages and T lymphocytes) and repair Schwann cells, as well as significant transcriptional alterations to a wide range of nerve-resident cell types. Notably, endoneurial fibroblasts show increased expression of chemokines (Ccl9, Cxcl5) and complement components (C3, C4b, C6) in response to chronic SARM1 activation, indicating enhanced immune cell recruitment and immune response regulation by non-immune nerve-resident cells. Analysis of CD45+ immune cells in sciatic nerves revealed an expansion of an Il1b+ macrophage subpopulation with increased expression of markers associated with phagocytosis and T cell activation/proliferation. We also found a significant increase in T cells in sarmopathic nerves. Remarkably, T cell depletion rescued motor phenotypes in the sarmopathy model. These findings delineate the significant changes chronic SARM1 activation induces in peripheral nerves and highlights the potential of immunomodulatory therapies for SARM1-dependent peripheral neurodegenerative disease.

Boosting Immunity Through Nutrition and Gut Health: A Narrative Review on Managing Allergies and Multimorbidity

The increasing global burden of allergic diseases and multimorbidity underscores the urgent need for innovative strategies to strengthen immune health. This review explores the complex relationships among nutrition, gut microbiota, immune regulation, allergic diseases, and multimorbidity. It highlights how targeted nutritional and microbial interventions may influence disease outcomes. Dietary components and microbial metabolites dynamically modulated immune function, highlighting the critical role of the gut-immune-metabolism axis in disease pathogenesis and management. Personalized nutrition, guided by advances in diagnostics such as component-resolved diagnostics, basophil activation tests, and epigenetic biomarkers, allows for precise dietary interventions tailored to individual allergy phenotypes and multimorbidity profiles. The Mediterranean diet, breastfeeding, and microbiota-targeted therapies have emerged as effective strategies to enhance immune resilience, reduce inflammation, and manage allergic reactions. Technological advancements, including artificial intelligence-driven dietary assessments, wearable devices, and mobile applications, have further revolutionized personalized dietary management, enabling real-time, precise nutritional monitoring and intervention. Despite these advances, challenges in implementing personalized nutrition persist, including variability in dietary patterns, cultural and socioeconomic factors, and accessibility concerns. Future research should focus on long-term interventional and longitudinal studies to validate precision nutrition strategies and enhance clinical applicability. This integrative approach, combining nutrition, microbiome science, technology, and personalized healthcare, holds substantial promises for sustainable disease prevention and enhanced immune resilience across diverse populations.

Quercetin-doped sol-gel coatings on titanium implants: a promising approach for enhanced immune response and cell adhesion

Quercetin (QUE), a natural flavonoid found in various fruits and vegetables, has diverse biological functions, including anti-inflammatory effects, regulation of cell adhesion and oxidative stress mitigation. In this study, sol-gel materials with increasing concentrations of quercetin (0.5, 1 and 2 wt%) were synthesised and applied onto titanium (Ti) surfaces as coatings. The materials were characterised physiochemically, and in vitro responses were examined using HOb osteoblastic cells and THP-1 macrophages. Human serum protein adsorption was evaluated using nLC-MS/MS. The incorporation of quercetin did not affect the sol-gel network cross-linking, and a controlled release of quercetin was achieved. The materials exhibited no cytotoxicity at any concentration. The HOb cells cultured on quercetin-doped materials were more elongated than those grown on QUE-free coatings, with protruding lamellipodia and increased cell surface. QUE-doped surfaces enhanced the expression of BMP-2, RANKL, and cell adhesion-related genes CTNNB1 and β-actin. In the THP-1 cells, pro-inflammatory gene expression (IL-1β, MCP-1 and iNOS) was down-regulated on 0.5QUE material, while it increased on 2QUE, as did the cytokine liberation. These changes correlated with altered protein adsorption patterns. The 2QUE coatings enhanced the adsorption of acute-phase proteins (SAA1, SAA2 and SAA4), indicating an inflammatory response; this behaviour was not seen on 0.5QUE. Moreover, cell adhesion (COF1, PROF1) and oxidative stress proteins (GPX3, SEPP1, AMBP) were preferentially adsorbed onto QUE-doped coatings. These results highlight the significance of optimising quercetin concentration in sol-gel coatings to modulate the immune response and enhance cell adhesion effectively.

At The Interface: Small-Molecule Inhibitors of Soluble Cytokines

Cytokines are crucial regulators of the immune system that orchestrate interactions between cells and, when dysregulated, contribute to the progression of chronic inflammation, cancer, and autoimmunity. Numerous biologic-based clinical agents, mostly monoclonal antibodies, have validated cytokines as important clinical targets and are now part of the standard of care for a number of diseases. These agents, while impactful, still suffer from limitations including a lack of oral bioavailability, high cost of production, and immunogenicity. Small-molecule cytokine inhibitors are attractive alternatives that can address these limitations. Although targeting cytokine-cytokine receptor complexes with small molecules has been a challenging research endeavor, multiple small-molecule inhibitors have now been identified, with a number of them undergoing clinical evaluation. In this review, we highlight the recent advancements in the discovery and development of small-molecule inhibitors targeting soluble cytokines. The strategies for identifying these novel ligands as well as the structural and mechanistic insights into their activity represent important milestones in tackling these challenging and clinically important protein-protein interactions.

HRS-5965, a small-molecule factor B inhibitor, in healthy participants and participants with renal insufficiency: A first-in-human, phase 1 trial

BACKGROUND

HRS-5965 is an oral selective small-molecule inhibitor of complement factor B, a key component of the alternative pathway. This study assessed the safety, tolerability, pharmacokinetics, and pharmacodynamics of HRS-5965 in healthy participants and participants with renal insufficiency.

METHODS

The first-in-human, phase 1 study consisted of 3 parts (ClinicalTrials.gov: NCT05505955). Part 1 was a single-ascending-dose, randomized, double-blind study with 5 dose groups preset, including a food effect evaluation. Part 2 was a multiple-ascending-dose, randomized, double-blind study with 9 dose groups preset. Part 3 was an open-label, single-dose study on severe renal insufficiency. The primary endpoints were safety and tolerability.

FINDINGS

A total of 82 participants were enrolled and received either HRS-5965 or placebo (26 in part 1, 40 in part 2, and 16 in part 3). HRS-5965 was well tolerated. Treatment-emergent adverse events were comparable between the HRS-5965 groups and placebo groups in part 1 (17/20 [85.0%] vs. 6/6 [100.0%]) and part 2 (27/30 [90.0%] vs. 10/10 [100.0%]). No deaths were reported. HRS-5965 was absorbed rapidly, with a median time to reach peak concentration (Tmax) ranging from 0.75 to 1.50 h in fasted states and 2.00 h in fed states. Pharmacokinetics was nonlinear, and food delayed the absorption of HRS-5965 but did not impact the exposure. Alternative pathway activity was inhibited by over 80% with HRS-5965, compared to less than 20% with placebo.

CONCLUSION

HRS-5965 demonstrated favorable safety and robust inhibition of alternative pathway activity, supporting further clinical development.

FUNDING

The study was funded by Jiangsu Hengrui Pharmaceuticals Co., Ltd.

Complement 3 (C3) within the hypothalamic arcuate nucleus is a potential key mediator of the effect of enhanced nutrition on reproductive development in young bull calves

BACKGROUND

Reproductive development may be advanced in bull calves through enhanced dietary intake during the early life period. This effect between enhanced nutrition with subsequent earlier reproductive development is orchestrated through signalling within the hypothalamic-pituitary-testicular axis. Within the hypothalamus, the arcuate nucleus (ARC) is crucial for the integration of peripheral metabolic status with subsequent gonadotropin releasing hormone (GnRH) signalling; however, the precise molecular control regulating this effect is not fully known. The aim of this study was to evaluate the global transcriptomic and proteomic responses to varied plane of nutrition during early calf-hood in young dairy bull calves. Additionally, we sought to integrate these 'omics' datasets to determine key genes and proteins contributing to earlier reproductive development. Between 2-12 weeks of age, 30 Holstein-Friesian bull calves (mean age: 17.5 days; mean bodyweight 48.8 kg), were offered either a high or moderate plane of nutrition with 15 calves in each group. At 12 weeks of age, all calves were euthanised and the ARC tissue isolated from each calf. The ARC tissue was then used for global transcriptomic (miRNAseq and mRNAseq) and proteomic analyses.

RESULTS

Bioinformatic analyses were undertaken to determine differentially expressed transcripts (FDR < 0.1; fold change > 1.5) between the dietary treatment groups, resulting in the identification of 1 differentially expressed miRNA (miR-2419-3p) and 83 differentially expressed mRNA in the ARC region. mRNA target gene prediction identified Complement 3 (C3) as a target of miR-2419-3p, suggesting a relationship between the two transcripts. Furthermore, through a co-regulatory network analysis conducted on the proteomics dataset, C3 was revealed as a hub protein. Additionally, through the proteomic network analysis, C3 was interacting with proteins involved in both insulin and GnRH signalling, highlighting a potential role for C3 in mediated the effect of enhanced nutritional status with earlier reproductive development within the ARC.

CONCLUSION

This study highlights an effect of altered plane of nutrition in early life on the molecular control of the hypothalamic ARC. Additionally, results generated suggest a potential role for the C3 gene in mediating the interaction between enhanced metabolic status with reproductive development within the ARC, regulated by miR-2419-3p.

Characterization of anti-neutrophil extracellular traps (NET) antibodies according to systemic lupus erythematosus clinical phenotypes

Anti-neutrophil extracellular traps (NETs) antibodies have been observed in patients with lupus nephritis and may contribute to the pathogenic role of NETs in patients with systemic lupus erythematosus (SLE). However, the prevalence of anti-NETs antibodies and their relationship with clinical features of patients with SLE have not been thoroughly studied, which is the aim of this study. Eighty-seven patients who fulfilled the 2019 EULAR/ACR Classification criteria for SLE were included. Plasmatic neutrophil elastase-DNA complexes as NETs remnants and the IgG anti-NETs antibodies were quantified by ELISA in the same sample. Thirty-one (35.6%) patients had positive anti-NETs antibodies. Patients with anti-NETs antibodies were younger at the time of recruitment (28.7 years (23.8-33.2) vs. 35.58 (27.88-45.77), p = 0.003) and had more prominent serological disease activity, with a higher prevalence of positive anti-double stranded (ds)-DNA antibodies (29 (93.5%) vs. 41 (73.2%), p = 0.022), higher titers (148.2 mg/dL vs. 35.6 mg/dL, p = 0.015), and lower levels of C3 and C4 (58 (37-85.5) vs. 77 (54-127), p = 0.017) and C4 (8 (8-12.5) vs. 20 (9-27), p < 0.001). From all clinical manifestations present at the time of recruitment, serositis showed a trend towards anti-NETs positivity (p 0.06). The global SLEDAI-2 K score was higher in the patient's IgG anti-NETs antibodies positive (13 (6.5-18) vs. 6 (4-15), p = 0.042). Anti-NETs antibodies were positively correlated with the systemic lupus erythematosus disease activity index (SLEDAI-2 K) score as well as with the titers of anti-dsDNA antibodies. IgG anti-NET antibodies were found in one-third of SLE patients. This is the first description of the association between IgG anti-NET and clinical features of SLE. Their characterization might allow us to address their role as potential novel biomarkers.

Relationship between complement and macrophage markers with kidney survival in patients with diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is the leading cause of end-stage kidney disease (ESKD) worldwide. Macrophages and the complement system have interrelated roles in DN. We aimed to determine associations between macrophage and complement markers with the progression of DN.

METHODS

This retrospective cohort study included patients diagnosed with sole DN by kidney biopsy. Using immunohistochemistry, CD68+ and CD163+ cells and complement markers were counted in glomerular and tubulointerstitial areas. The primary outcome was evolution to ESKD and/or doubling serum creatinine (SCr).

RESULTS

Forty-six patients were included. The median SCr at baseline was 2.7 (1.41-3.1) mg/dL. During the median follow-up of 32 months (range 6-54), 50% of patients reached the primary outcome. Most of the clinical and histological findings were comparable between progressors and non-progressors, while progressors had a higher median number of glomerular CD68+ cells and a higher percentage of glomerulosclerosis. After adjustments for age, sex, and SCr, the median glomerular CD68+ cell number was the sole independent predictor of progression. Glomerular C4d was associated with nephrotic-range proteinuria but not with the progression of kidney failure.

CONCLUSIONS

Glomerular CD68+ cell count may serve as a promising predictor of kidney disease progression among patients with DN. Glomerular C4d was associated with nephrotic-range proteinuria but not with the progression of kidney failure.

Transfer of SARS-CoV-2 nucleocapsid protein to uninfected epithelial cells induces antibody-mediated complement deposition

SARS-CoV-2 infection triggers a strong antibody response toward nucleocapsid protein (NP), suggesting its extracellular presence beyond intravirion RNA binding. Our co-culture experiments show NP decorates infected and proximal uninfected cell surfaces. We propose a mechanism whereby extracellular NP on uninfected cells contributes to COVID-19 pathogenicity. We show that NP binds to cell-surface sulfated glycosaminoglycans using its RNA-binding sites, facilitated by the flexible, positively charged linker. Coating uninfected lung-derived cells with NP attracted anti-NP IgG from lung fluids and sera of COVID-19 patients. Immune recognition was significantly higher in moderate versus mild COVID-19. Binding of anti-NP IgG in sera generated clusters, triggering C3b deposition via the classical complement pathway on SARS-CoV-2 non-susceptible cells co-cultured with infected cells. The heparin analog enoxaparin outcompeted NP binding, rescuing cells from anti-NP IgG-mediated complement deposition. Our findings reveal how extracellular NP may exacerbate COVID-19 damage and suggest preventative therapy avenues.

Evaluation of Ficolin-3 deficiency as a risk factor in the development of rheumatic heart disease

OBJECTIVE

Ficolin-3 is a crucial protein for the activation of the complement system. Previous work has indicated this protein may play a role in the pathogenesis of rheumatic heart disease (RHD), and it has been hypothesised that ficolin-3 has potential as a biomarker for early identification of patients with suspected RHD. This study investigated FCN3 gene polymorphisms rs532781899 (c.349del) and rs4494157 (c.658 + 250 C > A) and ficolin-3 serum concentrations in an ethnically diverse cohort of 53 RHD cases and 45 healthy controls from across Africa.

RESULTS

Ficolin-3 was found to be increased by 16% in RHD patients (p = 0.03) compared to controls, but polymorphisms did not associate with the risk of developing RHD nor with ficolin-3 concentrations. Carriers of the c.349del haploinsufficiency locus had normal levels of ficolin-3, while the previously described c.658 + 250 C > A RHD susceptibility locus was found equally in cases and controls. The higher serum ficolin-3 in RHD supports the potential role of this protein in RHD pathogenesis. However, these results suggest that rs532781899 and rs4494157 are not risk factors for the development of RHD in patients from sub-Saharan Africa and would not be reliable as early-stage markers of RHD susceptibility.

Cerebrospinal fluid proteome of patients with persistent pain and/or postpartum depression after elective cesarean delivery: An exploratory prospective cohort study

BACKGROUND

Persistent pain (>2 months) after cesarean delivery (CD) can affect up to 20 % of patients, and is associated with increased risk for postpartum depression (PPD). Preoperative identification of patients at risk for persistent pain and PPD remains a challenge due to poorly understood underlying mechanisms. To better understand these potential mechanisms, here, we examined the preoperative cerebrospinal (CSF) proteome for changes associated with persistent pain or PPD at 3 months post-CD.

METHODS

Eighty patients undergoing elective CD under neuraxial anesthesia were recruited. We collected baseline demographics, obstetric data, and Edinburgh Postnatal Depression Scale (EPDS) scores. EPDS and pain scores were also obtained at 3 months post-CD. CSF was collected before spinal anesthetic placement. Liquid chromatography coupled with tandem mass spectrometry was used to study the CSF proteome.

RESULTS

63 patients completed clinical follow-up, however only 61 of the patients had adequate preoperative CSF sample for analysis. Of these 61 patients, 21 developed pain or PPD at 3 months post-CD (14 had persistent pain alone and 7 had PPD alone). Over 1600 proteins were quantified in each CSF sample. Forty-three of these proteins were nominally differentially expressed in patients with persistent pain and/or PPD vs those with neither disorder. Pathway analysis showed a downregulation of the complement and coagulation cascades in the preoperative CSF of patients who later developed persistent pain or PPD 3 months after CD.

CONCLUSIONS

These results suggest that the CSF complement and coagulation cascades may play a role in patients who develop postpartum pain or PPD 3 months later.

Role of Angiotensin II in Venezuelan Equine Encephalitis: Narrative Review

Venezuelan equine encephalitis virus (VEEV) is an alphavirus in the family Togaviridae, transmitted by a mosquito bite and is highly infectious in aerosol form. Inflammation plays a role of antiviral response as well as development of lethal encephalitis. Infection through a mosquito bite is biphasic, beginning with an inflammatory process and viral replication in different organs with subsequent infiltration to the central nervous system (CNS), inducing encephalitis. The direct route is through inhalation of aerosols containing the virus with direct brain infection through the olfactory nerve. Significant damage is due to exacerbated inflammation in the host. Angiotensin II (Ang II) is a molecule with high pro-inflammatory capacity, which has been found to be upregulated in the brain of VEEV-infected rats, suggesting its role in the pathogenesis of this disease. Limited information regarding the association of Ang II expression with VEEV brain infection has been reported. The aim of this review is to highlight published reports indicating a possible association between Ang II expression and VEEV-induced encephalitis. Several studies reflect a possible expression and function of Ang II during VEEV infection. Factors such as the relationship of Ang II with proteins involved in viral replication and entry into the cell (furin, Rab5, Rab7), activation of protein kinase C (necessary for the phosphorylation of VEEV), presence of microRNAs related to viral biology, increased permeability of the blood-brain barrier, and use of transcription pathways common to Ang II and VEEV, may conceivable an association of Ang II with the pathogenesis of VEEV encephalitis.

Complement and Coagulation Cascade Activation Regulates the Early Inflammatory Mechanism of Resistance of Suckling Lambs Against Haemonchus contortus

Haemonchus contortus is a highly pathogenic blood-sucking nematode from the abomasum of small ruminants. To develop effective control strategies, it is essential to understand the initial mechanisms involved in host resistance to this parasite. In this study, we used computational tools to analyze the complement and coagulation pathways generated from RNA sequencing of abomasal tissue from resistant (Santa Ines) and susceptible (Ile de France) young sheep artificially infected with H. contortus. Thirty-two differentially expressed genes annotated to the ovine genome were associated with the complement and coagulation cascades, of which 29 of them were overexpressed in Santa Ines. Our data identified potential markers for resistance trait selection in sheep, such as C3 (complement C3), F3 (tissue factor), F5 (coagulation factor V), CFB (complement factor B), and CFI (complement factor I). Santa Ines may have a more robust coagulation system, being activated by extrinsic pathways associated with tissue damage. The complement may act as a mediator of the innate immunity, and its activation in Santa Ines is associated with the classical, the lectin, and the alternative pathway. Finally, resistant Santa Ines lambs had a polygenic overexpressed architecture controlling both complement and coagulation cascades, which probably contributed to the early-onset protection against H. contortus.

Endothelial damage and complement dysregulation in fetuses from pregnancies complicated by preeclampsia

INTRODUCTION

Our objective was to evaluate the endothelial function profile and complement system in fetuses from preeclamptic pregnancies using ex vivo and in vitro approaches.

MATERIAL AND METHODS

A total of 66 singleton pregnancies were prospectively recruited comprising 34 cases of preeclampsia and 32 normotensive pregnancies matched for baseline characteristics. In the ex vivo approach, soluble tumor necrosis factor-a receptor 1 (sTNFR1), vascular cell adhesion molecule-1 (sVCAM-1), intercellular adhesion molecule-1 (sICAM-1), Von Willebrand factor (sVWF), terminal complement complex (sC5b-9), Factor H, complement component C3a and Factor Bb were analyzed in fetal cord blood samples. In the in vitro model, vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), Von Willebrand factor (VWF), vascular endothelial cadherin (VE-Cadherin), endothelial nitric oxide synthase (eNOS), reactive oxygen species (ROS) and C5b-9 deposits were evaluated on endothelial cells in culture exposed to fetal sera or plasma.

RESULTS

Increased sVCAM-1, sICAM- l and decreased Factor H and Factor Bb concentrations were detected in preeclampsia fetuses as compared to fetuses from normotensive mothers (509.4 ± 28 vs. 378.4 ± 34.3 ng/mL, 161.1 ± 11.9 vs. 114.8 ± 6.8, 199.6 ± 18.3 vs. 267.1 ± 15.4 ng/mL and 6.6 ± 0.7 vs. 10.3 ± 1.4 μg/mL respectively, p < 0.05) with similar results in sTNFR1, sVWF, sC5b-9 and C3a. Endothelial cells exposed to fetal sera from preeclampsia showed incremented expression of VCAM-1(38.1 ± 1.4% vs. 28.3 ± 1.6%, p < 0.01), ICAM-1 (12 ± 0.9% vs. 8.6 ± 0.6%, p < 0.05), VWF (43.5 ± 2.9% vs. 3.7 ± 0.3%, p < 0.05), and ROS (5 × 1013 ± 1 × 1012 vs. 3.5 × 1013 ± 1.4 × 1012, p < 0.01) with similar expression of VE-Cadherin and eNOS as compared to those exposed to control fetuses. While soluble C5b-9 was similar between the study groups (851.4 ± 177.5 vs. 751.4 ± 132.81 ng/mL, p > 0.05), significantly less C5b-9 deposits on endothelial cells were induced by fetal plasma from preeclamptic compared to normotensive mothers (fold change 0.08 ± 0.02 vs. 0.48 ± 0.13, p < 0.01).

CONCLUSIONS

High levels of endothelial adhesion molecules and oxidative stress products suggest endothelial damage and reduced in vitro deposition of C5b-9 indicates complement dysregulation in preeclampsia fetuses. More research is necessary to study the impact of preeclampsia on fetal vascular health and innate immunity.

Non-canonical extracellular complement pathways and the complosome paradigm in cancer: a scoping review

The Complement System (CS) comprises three catalytic pathways that can be activated by specific immune triggers. However, within the tumor microenvironment (TME), CS intracellular components, recently named as complosome, play roles that extend beyond the activation and regulation of its pathways. The interaction between TME elements and tumor cells alters the local immune response, leading to inflammation, cell proliferation, and tumor invasion. Our focus is on understanding the significance of complosome and non-canonical pathways in cancer. In this scoping review, we analyzed 45 articles that discussed the various roles of CS components in carcinogenesis. Many CS components, including C1q, C3a-C3aR, C5a-C5aR, factor H, and properdin, some of them at the intracellular level, may play a dual role in tumor progression, demonstrating either anti-tumor or pro-tumor activity independent of complement pathway activation. The specific function of each component can influence both the type and stage of tumor cells. There is a notable lack of studies on the role of the lectin pathway in tumor development, and this knowledge gap must be addressed to fully understand the role of complosome in cancer. Nevertheless, the activation of CS and the roles of its components in complosome pathways are crucial steps in tumor development.

Colon-targeted complement C5a1 receptor inhibition using pH-sensitive nanoparticles ameliorates experimental colitis

BACKGROUND AND PURPOSE

The complement system is associated with inflammatory bowel disease (IBD) pathology. Complement activation induces C5a production, which signals through the C5a1 receptor (C5aR1) to drive inflammatory responses that may underlie IBD.

EXPERIMENTAL APPROACH

We examined mucosal biopsies from ulcerative colitis patients and identified C5a1 receptor up-regulated in active lesions, supporting the C5a1 receptor as a target for therapeutic intervention. Cyclic peptide C5a1 receptor antagonists such as PMX205 are orally efficacious in preclinical colitis models; however, their clinical application may be limited by rapid metabolism. We therefore encapsulated PMX205 within pH-sensitive polymers to target drug for colon delivery following oral administration.

KEY RESULTS

PMX205 nanoparticles were non-toxic and released bioactive PMX205 in simulated colon fluid. In vivo imaging of Cy5-labelled nanoparticles demonstrated rapid entry and persistence in the mouse colon for up to 48 h. Next, we utilised the dextran sodium sulphate-induced colitis model to examine efficacy of the C5a1 receptor-antagonist formulation. We show that oral administration of PMX205 nanoparticles every 2 days from symptom onset significantly mitigated weight loss, clinical illness, colon length reduction and epithelial damage to a similar degree as C5a1 receptor-/- mice. Notably, unformulated PMX205 was markedly less effective in this dosing regimen.

CONCLUSION AND IMPLICATIONS

This novel colon-targeted formulation therefore offers a potent therapeutic strategy for translating C5a1 receptor antagonists for IBD conditions such as ulcerative colitis.

Pharmacology and macrophage modulation of HPGDS inhibitor PK007 demonstrate reduced disease severity in DMD-affected muscles of the mdx mouse model

BACKGROUND

Duchenne Muscular Dystrophy (DMD) is an X-linked disease characterised by chronic inflammation, progressive muscle damage, and muscle loss. Typically, initial symptoms affect lower limb muscles, including the gastrocnemius (GA), tibialis anterior (TA), and extensor digitorum longus (EDL). During the acute phase of DMD, particularly in boys aged 2-8 years, muscle damage resulting in necrosis (myonecrosis) involves a complex immune-inflammatory response. Prostaglandin D2 (PGD2) is recognised for enhancing pro-inflammatory chemokine and interleukin signalling and recruiting infiltrating immune cells such as pro-inflammatory macrophages, exacerbating myonecrosis.

METHODS

To reduce levels of PGD2, a novel hematopoietic prostaglandin D2 synthase (HPGDS) inhibitor, PK007, was characterised (i) for potency and pharmacokinetic profiles and then tested in the mdx mouse model of DMD during the acute early onset of disease progression. Juvenile mdx and wild type (WT) C57Bl/10Scsn mice were orally treated with PK007 and control vehicle solution for 10 days, from postnatal day 18 to 28. This builds upon a previous study with PK007 with (ii) additional analyses of disease progression assessed for muscle grip strength, metabolic and locomotor activity, myonecrosis in a wide range of muscles (3 from hindlimb, diaphragm, heart, and tongue), macrophage infiltration and pro-inflammatory cytokines (TNF-α, IL-1β and iNOS).

RESULTS

PK007 exhibited high potency (17.23 ± 12 nM), a long half-life (3.0 ± 0.3 h), and good oral bioavailability (81%). Treatment with PK007 decreased serum PGD2 levels (33.36%) in mdx mice compared to control (vehicle-treated) mdx mice. In mdx mice (compared with controls), PK007 enhanced grip strength (69.05% increase) and improved locomotor activity (69.05% increase). Histological analysis revealed a significant reduction in the total myonecrotic area in PK007-treated GA (49.75%), TA (73.87%), EDL (60.31%), diaphragm (48.02%), and tongue (37.93%) muscles of mdx mice (compared with controls). Additionally, PK007 decreased macrophage cell area by 55.56% in GA and 47.83% in EDL muscles. Further expression of pro-inflammatory cytokines and enzymes such as TNF-α, IL-1β and iNOS were significantly reduced in PK007 treated mice. These results demonstrate that PK007 significantly reduces the inflammatory response, protects muscles from necrosis and increases strength in juvenile mdx mice.

CONCLUSION

This study lays a strong foundation for progressing the use of HPDGS inhibitors such as PK007, which specifically inhibit PGD2 and reduce inflammation, as a viable therapeutic approach for DMD. This approach protects dystrophic muscles from necrosis and reduces the severity of this debilitating disease, improving outcomes and quality of life.

The Role of Oxidative Stress and Inflammation in the Pathogenesis and Treatment of Vascular Dementia

Vascular dementia (VaD) is a heterogeneous group of brain disorders caused by cerebrovascular pathologies and the second most common cause of dementia, accounting for over 20% of cases and posing an important global health concern. VaD can be caused by cerebral infarction or injury in critical brain regions, including the speech area of the dominant hemisphere or arcuate fasciculus of the dominant hemisphere, leading to notable cognitive impairment. Although the exact causes of dementia remain multifactorial and complex, oxidative stress (reactive oxygen species), neuroinflammation (TNFα, IL-6, and IL-1β), and inflammasomes are considered central mechanisms in its pathology. These conditions contribute to neuronal damage, synaptic dysfunction, and cognitive decline. Thus, antioxidants and anti-inflammatory agents have emerged as potential therapeutic targets in dementia. Recent studies emphasize that cerebrovascular disease plays a dual role: first, as a primary cause of cognitive impairment and then as a contributor to the manifestation of dementia driven by other factors, such as Alzheimer's disease and other neurodegenerative conditions. This comprehensive review of VaD focuses on molecular mechanisms and their consequences. We provided up-to-date knowledge about epidemiology, pathophysiological mechanisms, and current therapeutic approaches for VaD.

Intestinal immunoglobulins under microbial dysbiosis: implications in opioid-induced microbial dysbiosis

Intestinal immunoglobulins (Igs) maintain homeostasis between the microbiome and host. IgA facilitates microbial balance through a variety of increasingly well-described mechanisms. However, IgM and IgG have less defined intestinal functions but have the potential to activate clearance mechanisms such as the complement system and receptor-mediated bacterial killing. Very little is known regarding the role of Igs under microbial dysbiosis. In this review, we explore how Igs sculpt the intestinal microbiome and respond to microbial dysbiosis. We discuss how IgM, IgA, IgG, and complement individually maintain harmony with the microbiome and consider how these mechanisms could work in synergy. Finally, we explore using an opioid-induced microbial dysbiosis as a model to elucidate immediate changes in Ig-bacterial interactions.

Mechanism and regulation of the complement activity in kidney xenotransplantation

Xenotransplantation is emerging as one of several potential solutions for addressing organ donor shortages, with significant progress bringing it closer to clinical application. However, challenges remain, particularly concerning complement system dysregulation caused by species differences, as well as xenoantigens and coagulopathy. Complement regulatory proteins expressed on endothelial cells of donor xenografts are less compatible with complement components in recipients. These difficulties contribute to hyperacute rejection, characterized by antibody-mediated complement activation that destroys the graft within 24 h. Moreover, because molecules are incompatible across different species, ischemia-reperfusion injury or infection can easily elicit complement activity via all three pathways, resulting in xenograft loss via complement-mediated vascular injury. Complement activity also stimulate innate and adaptive immune cells. To address this issue, genetic modifications in donor pigs and the development of novel medicines have been tested in preclinical models with promising results. Pigs modified to express human complement-regulating molecules such as CD46, CD55, and CD59 have shown longer kidney xenograft survivals over years in preclinical models with nonhuman primates, paving the way for clinical trials. Anti-complement component agents such as C1 esterase and C5 inhibitors have also been shown to increase xenograft survivals. This review examines the role of the complement system in kidney xenotransplantation, emphasizing new research and clinical trial advancements.

Multimodal sequencing of neoadjuvant nivolumab treatment in hepatocellular carcinoma reveals cellular and molecular immune landscape for drug response

A striking characteristic of liver cancer is its extensive heterogeneity, particularly with regard to its varied response to immunotherapy. In this study, we employed multimodal sequencing approaches to explore the various aspects of neoadjuvant nivolumab treatment in liver cancer patients. We used spatially-resolved transcriptomics, single- and bulk-cell transcriptomics, and TCR clonotype analyses to examine the spatiotemporal dynamics of the effects of nivolumab. We observed a significantly higher clonal expansion of T cells in the tumors of patients who responded to the treatment, while lipid accumulation was detected in those of non-responders, likely due to inherent differences in lipid metabolic processes. Furthermore, we found a preferential enrichment of T cells, which was associated with a better drug response. Our results also indicate a functional antagonism between tumor-associated macrophages (TAMs) and CD8 cells and their spatial separation. Notably, we identified a UBASH3B/NR1I2/CEACAM1/HAVCR2 signaling axis, highlighting the intense communication among TAMs, tumor cells, and T-cells that leads to pro-tumorigenic outcomes resulting in poorer nivolumab response. In summary, using integrative multimodal sequencing investigations, combined with the multi-faceted exploration of pre- and post-treatment samples of neoadjuvant nivolumab-treated HCC patients, we identified useful mechanistic determinants of therapeutic response. We also reconstructed the spatiotemporal model that recapitulates the physiological restoration of T cell cytotoxicity by anti-PD1 blockade. Our findings could provide important biomarkers and explain the mechanistic basis differentiating the responders and non-responders.

Expression of innate immunity genes in human hematopoietic stem/progenitor cells - single cell RNA-seq analysis

Background

The complement system expressed intracellularly and known as complosome has been indicated as a trigger in the regulation of lymphocyte functioning. The expression of its genes was confirmed also in several types of human bone marrow-derived stem cells: mononuclear cells (MNCs), very small embryonic-like stem cells (VSELs), hematopoietic stem/progenitor cells (HSPCs), endothelial progenitors (EPCs) and mesenchymal stem cells (MSCs). In our previous studies, we demonstrated the expression of complosome proteins including C3, C5, C3aR, and cathepsin L in purified HSPCs. However, there is still a lack of results showing the expression of complosome system elements and other immunity-related proteins in human HSPCs at the level of single cell resolution.

Methods

We employed scRNA-seq to investigate comprehensively the expression of genes connected with immunity, in two populations of human HSPCs: CD34+Lin-CD45+ and CD133+Lin-CD45+, with the division to subpopulations. We focused on genes coding complosome elements, selected cytokines, and genes related to antigen presentation as well as related to immune regulation.

Results

We observed the differences in the expression of several genes e.g. C3AR1 and C5AR1 between two populations of HSPCs: CD34+LinCD45+ and CD133+Lin-CD45+ resulting from their heterogeneous nature. However, in both kinds of HSPCs, we observed similar cell subpopulations expressing genes (e.g. NLRP3 and IL-1β) at the same level, which suggests the presence of cells performing similar functions connected with the activation of inflammatory processes contributing to the body's defense against infections.

Discussion

To our best knowledge, it is the first time that expression of complosome elements was studied in HSPCs at the single cell resolution with the use of single cell sequencing. Thus, our data sheds new light on complosome as a novel regulator of hematopoiesis that involves intracrine activation of the C5a-C5aR-Nlrp3 inflammasome axis.

Inhibition of C3/C3aR Pathway Alleviates Visual and Optic Nerve Impairments in a Rat Model of Neuromyelitis Optica Spectrum Disorder

Accumulating evidence suggests that the complement C3/C3a receptor (C3aR) pathway plays a pivotal role in the pathogenesis of neurodegenerative and autoimmune disorders, particularly neuromyelitis optica spectrum disorders (NMOSDs). Despite this, the specific pathogenic effect and mechanism of C3/C3aR pathway in NMOSD remains elusive. In this study, we demonstrated for the first time that the expression of C3aR and its upstream ligand C3 is significantly upregulated in the optic nerve of a rat model of NMOSD-related optic neuritis (NMOSD-ON). Our findings reveal that this upregulation leads to blood-brain barrier (BBB) disruption, demyelination and neuronal damage. Through the use of a novel C3aR inhibitor, JR14a, we demonstrate its effectiveness in reducing C3aR expression and mitigating pathological damage in the optic nerve. Furthermore, our transcriptome sequencing analysis of NMOSD optic nerve tissues reveals extensive enrichment of inflammation- and immune response-related pathways, with particular emphasis on the complement and coagulation cascades pathway. This study not only elucidated the crucial role of the C3-C3aR pathway in NMOSD-ON pathogenesis but also provided a new promising therapeutic target for NMOSD through C3aR pathway inhibition.

Astrocyte-derived complement C3 facilitated microglial phagocytosis of synapses in Staphylococcus aureus-associated neurocognitive deficits

The presence of pathogens is a significant challenge in causing brain infections and tissue damage. There is growing evidence that pathogen infections are commonly associated with cognitive dysfunction and mental health problems, but the underlying mechanisms are not yet fully understood. Here, we found microglia and astrocyte activation, neuronal damage, synapse loss, and cognitive impairment in a Staphylococcus aureus (S. aureus) induced mouse model. An unbiased transcription profile of isolated microglia derived from S. aureus-infected mice identified the involvement of microglial phagosome and regulation of neurogenesis. Our findings indicate that the complement C1q and C3 are upregulated, and astroglial release of C3 activates microglia to phagocytose synapses. Blocking the C3-C3aR axis can improve microglial phagocytosis, thus rescuing synapse loss and cognitive impairment in infected mice. These results indicate that S. aureus induces synapse elimination and cognitive impairment by activating microglia and astrocytes through C3-C3aR signaling. This suggests a mechanism of complement signaling bridged crosstalk between astrocyte and microglia in the S. aureus-associated post-infectious synapse loss and cognitive dysfunction, and provide potential therapeutic targets for managing pathogen-associated brain infections.

Aortic aneurysm and dissection: complement and precision medicine in aortic disease

Aortic disease encompasses life-threatening conditions such as aortic aneurysm and dissection, which are associated with high prevalence, morbidity, and mortality. The complement system, a key component of innate immunity, not only defends against pathogens but also maintains tissue homeostasis. Recent discoveries have expanded its role beyond immunity, linking complement dysregulation to numerous diseases and positioning it as a target for pharmacotherapy. Complement-based treatments for precision medicine are emerging, with several pharmaceuticals either already approved or under investigation. In aortic disease, complement activation and dysregulation have unveiled novel mechanisms and clinical implications. Human and experimental studies suggest that all three complement pathways contribute to disease pathophysiology. The complement system induces direct cellular damage via the membrane attack complex, as well as matrix-metalloproteinase (MMP)-associated tissue damage by promoting MMP-2 and MMP-9 expression. The anaphylatoxins C3a and C5a exacerbate disease by recruiting immune cells and triggering proinflammatory responses. Examples include neutrophil extracellular trap formation and cytokine release by polymorphonuclear neutrophils. These findings highlight the complement system as a promising novel diagnostic and therapeutic target in aortic disease with potential for individualized treatment. However, gaps remain, emphasizing the need for standardized multisite preclinical studies to improve reproducibility and translation. Biomarker studies must also be validated across diverse patient cohorts for clinical applicability. This review examines current knowledge regarding complement in aortic disease, aiming to evaluate its potential for innovative diagnostic and personalized treatment strategies.

Complement is primarily activated in the lung in a mouse model of severe COVID-19

In vitro studies and observational human disease data suggest the complement system contributes to SARS-CoV-2 pathogenesis, although how complement dysregulation develops in severe COVID-19 is unknown. Here, using a mouse-adapted SARS-CoV-2 virus (SARS2-N501YMA30) and a mouse model of COVID-19, we identify significant serologic and pulmonary complement activation post-infection. We observed C3 activation in airway and alveolar epithelia, and pulmonary vascular endothelia. Our evidence suggests the alternative pathway is the primary route of complement activation, however, components of both the alternative and classical pathways are produced locally by respiratory epithelial cells following infection, and increased in primary cultures of human airway epithelia following cytokine and SARS-CoV-2 exposure. This tissue-specific complement response appears to precede lung injury and inflammation. Our results suggest that complement activation is a defining feature of severe COVID-19 in mice, agreeing with previous publications, and provide the basis for further investigation into the role of complement in COVID-19.

Neutrophil-derived vesicles control complement activation to facilitate inflammation resolution

Although subsets with immunosuppressive properties exist, neutrophils are typically known for their pro-inflammatory role and pathogen clearance capabilities. Here, we reveal that neutrophils can paradoxically aid in resolving inflammation by actively producing anti-inflammatory extracellular vesicles. These large aging-neutrophil-derived vesicles (LAND-Vs) do not fit into classical vesicle categorizations due to their specific size, structure, or biogenesis pathway. They are protected from efferocytotic clearance by phagocytes due to surface "do not eat me" signals and accumulate in the resolution phase of inflammation. CD55 on LAND-Vs exerts a robust, sustained anti-inflammatory effect by inhibiting complement 3 convertase, thereby reducing neutrophil recruitment and tissue damage. CD55+ LAND-Vs originate in ordered lipid raft domains, where CD55 accumulates asymmetrically during neutrophil aging, and are subsequently formed through RhoA-dependent budding. Collectively, LAND-V emerges as a pivotal physiological immunomodulator and showcases functions that transcend the limited lifespan of neutrophils, offering a therapeutic target for inflammatory and infectious diseases.

Post-Secretion Processes and Modification of Extracellular Vesicles

Extracellular vesicles (EVs) are an important mediator of intercellular communication and the regulation of processes occurring in cells and tissues. The processes of EVs secretion by cells into the extracellular space (ECS) leads to their interaction with its participants. The ECS is a dynamic structure that also takes direct part in many processes of intercellular communication and regulation. Changes in the ECS can also be associated with pathological processes, such as increased acidity during the development of solid tumors, changes in the composition and nature of the organization of the extracellular matrix (ECM) during fibroblast activation, an increase in the content of soluble molecules during necrosis, and other processes. The interaction of these two systems, the EVs and the ESC, leads to structural and functional alteration in both participants. In the current review, we will focus on these alterations in the EVs which we termed post-secretory modification and processes (PSMPs) of EVs. PSPMs can have a significant effect on the immediate cellular environment and on the spread of the pathological process in the body as a whole. Thus, it can be assumed that PSPMs are one of the important stages in the regulation of intercellular communication, which has significant differences in the norm and in pathology.

Integrated Spheroid-to-Population Framework for Evaluating PFHpA-Associated Metabolic Dysfunction and Steatotic Liver Disease

The rising prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD), particularly among pediatric populations, requires identification of modifiable risk factors to control disease progression. Per- and polyfluoroalkyl substances (PFAS) have emerged as potential contributors to liver damage; however, their role in the etiology of MASLD remains underexplored. This study aimed to bridge the gap between human epidemiological data and in vitro experimental findings to elucidate the effect of perfluoroheptanoic acid (PFHpA), a short chain, unregulated PFAS congener on MASLD development. Our analysis of the Teen-LABS cohort, a national multi-site study on obese adolescents undergoing bariatric surgery, revealed that doubling of PFHpA plasma levels was associated with an 80% increase in MASLD risk (OR, 1.8; 95% CI: 1.3-2.5) based on liver biospies. To further investigate the underlying mechanisms, we used 3D human liver spheroids and single-cell transcriptomics to assess the effect of PFHpA on hepatic metabolism. Integrative analysis identified dysregulation of common pathways in both human and spheroid models, particularly those involved in innate immunity, inflammation, and lipid metabolism. We applied the latent unknown clustering with integrated data (LUCID) model to assess associations between PFHpA exposure, multiomic signatures, and MASLD risk. Our results identified a proteome profile with significantly higher odds of MASLD (OR = 7.1), whereas a distinct metabolome profile was associated with lower odds (OR = 0.51), highlighting the critical role of protein dysregulation in disease pathogenesis. A translational framework was applied to uncover the molecular mechanisms of PFAS-induced MASLD in a cohort of obese adolescents. Identifying key molecular mechanisms for PFAS-induced MASLD can guide the development of targeted prevention and treatment.

Assay of cardiopulmonary bypass system for porcine alveolar macrophages removing GFP-E. coli from erythrocyte surfaces

While it is established that complement receptor molecules on the surface of erythrocytes are crucial for the clearance of immune complexes in the body, the molecular mechanisms underlying the interaction between macrophages and erythrocytes in pigs remain inadequately understood. Consequently, we built a detection system with a closed-circulation flow chamber and a constant flow pump. Additionally, we optimized parameters including system flow velocity and fluid shear force. In the circulatory system, our study measured the fluorescence intensity of erythrocyte and pulmonary alveolar macrophages (PAMs) surfaces before and after the blockade of complement receptor 1 (CR1)-like receptors and Fc receptors. The results indicated that porcine erythrocytes and PAMs exhibited a diminished rate of change in fluorescence intensity under the blocked condition. Through transmission electron microscopy, it was observed that PAMs effectively removed sensitized GFP-E. coli adhering immunologically to porcine erythrocytes. The findings indicate that PAMs effectively removed sensitized GFP-E. coli from the surface immunoadhesion of porcine erythrocytes, facilitated by the mediation of surface CR1-like receptors and Fc receptors.

Enhancing AAV-microdystrophin gene therapy after repeat dosing by blocking phagocytosis

Background

Inefficient transduction is a major limitation in achieving therapeutic levels of AAV-delivered microdystrophin capable of improving muscle function in patients with Duchenne muscular dystrophy. Additionally, some patients experience acute complications due to activation of innate immune pathways, such as complement. We propose that inhibiting complement receptor 1/2/3 (CR 1/2/3)-mediated phagocytosis and endosomal TLR 7/8/9 signaling pathways may decrease immune and inflammatory responses while simultaneously increasing the availability of AAV virus for muscle transduction.

Methods

Mdx mice were randomly assigned to the following three experimental conditions (n=8-9/group): Group 1, mdx untreated; Group 2, mdx + rAAV9-microdystrophin; Group 3, mdx + rAAV9-microdystrophin + semiweekly dosing of TLR 7/8/9 antagonist + complement receptor antibodies (combination therapy). The rAAV9-microdystrophin was administered twice to 6- and 12-week-old mice. A separate group of 6-week-old mice received a single rAAV9-microdystrophin dose and no other treatment (Group 4). We assessed several immune and inflammatory responses and dystrophin expression in the muscle.

Results

Viral load was significantly increased by 77-fold in white blood cells after two rAAV9-microdystrophin doses compared to mice receiving a single dose. Repeated gene therapy resulted in a lower viral load and microdystrophin expression in muscle compared to a single rAAV dose. 63% of mice treated with two rAAV9-microdystrophin doses produced antibodies to dystrophin, which was less in mice treated with two rAAV9-microdystrophin doses and combination therapy (25%). Likewise, AAV capsid specific antibody levels were reduced in mice receiving combination therapy. Microdystrophin expression in skeletal muscle evaluated by mass spectrometry, immunofluorescence, and western blotting showed significantly higher levels in combination-treated mice compared to rAAV9-microdystrophin alone.

Conclusions

Our results demonstrate that combination treatment with complement receptor 1/2/3 antibodies and a TLR 7/8/9 antagonist enhances rAAV9-microdystrophin gene therapy in mdx mice by partially reducing inflammatory and immune responses and increasing microdystrophin expression in skeletal muscle. Furthermore, repeated gene therapy is associated with greater uptake by white blood cells and less microdystrophin expression in the skeletal muscle. This suggests that blocking complement receptors and/or TLR 7/8/9 pathways would be a promising strategy to enhance AAV-microdystrophin therapy.

The role of the complement system in the response to cytotoxic therapy

The complement system is increasingly recognised as a key player in tumour progression and response to cancer treatment. Cytotoxic therapies, including chemo- and radiotherapy are standard-of-care for the majority of cancer patients. Cytotoxics have been found to alter the expression of complement system proteins and activation of components. Many recent reports highlight the role of local dysregulation of complement proteins in the tumour microenvironment and how targeting such dysregulation can have either anti- or pro-tumoricidal effects depending on several factors including treatment scheduling, the tumour type and its microenvironment characteristics. This review will explore the complex effects of cytotoxic therapy on complement regulation and what lessons can be learnt to identify the most effective way to therapeutically modulate complement system proteins for cancer therapy.

Reduction reactions dominate the interactions between Mg alloys and cells: Understanding the mechanisms

Magnesium (Mg) alloys are popular biodegradable metals studied for orthopedic and cardiovascular applications, mainly because Mg ions are essential trace elements known to promote angiogenesis and osteogenesis. However, Mg corrosion consists of oxidation and reduction reactions that produce by-products, such as hydrogen gas, reactive oxygen species, and hydroxides. It is still unclear how all these by-products and Mg ions concomitantly alter the microenvironment and cell behaviors spatially and temporally. This study shows that Mg corrosion can enhance cell proliferation by reducing intracellular ROS. However, Mg cannot decrease ROS and promote cell proliferation in simulated inflammatory conditions, meaning the microenvironment is critical. Furthermore, cells may respond to Mg ions differently in chronic or acute alkaline pH or oxidative stress. Depending on the corrosion rate, Mg modulates HIF1α and many signaling pathways like PI3K/AKT/mTOR, mitophagy, cell cycle, and oxidative phosphorylation. Therefore, this study provides a fundamental insight into the importance of reduction reactions in Mg alloys.

Microglial cell proliferation is regulated, in part, by reactive astrocyte ETBR signaling after ischemic stroke

Reciprocal communication between reactive astrocytes and microglial cells provides local, coordinated control over critical processes such as neuroinflammation, neuroprotection, and scar formation after CNS injury, but is poorly understood. The vasoactive peptide hormone endothelin (ET) is released and/or secreted by endothelial cells, microglial cells and astrocytes early after ischemic stroke and other forms of brain injury. To better understand glial cell communication after stroke, we sought to identify paracrine effectors produced and secreted downstream of astroglial endothelin receptor B (ETBR) signaling. Using a genetic loss-of-function screen, we identified angiopoietin-2 (Ang-2) as a factor produced by reactive astrocytes in response to ET. In experiments with primary adult astrocytes stimulated by IRL1620, a specific ETBR agonist, we found that ERK1/2 and NFkB mediated the effects of ET on Ang-2 production. To determine astroglial Ang-2 levels in vivo, reactive astrocytes expressing the high affinity glutamate transporter (GLAST, EAAT1) were isolated by magnetic-activated cell sorting 3 days after stroke. Astrocytes obtained from the ipsilateral hemisphere expressed significantly more Ang-2 compared with astrocytes isolated from the contralateral hemisphere, or from cortices of sham-operated (control) mice. Notably, analysis of microglia sorted from CX3CR1-eGFP mice demonstrated increased cell surface expression of Tie-2, the Ang-2 receptor, on cells obtained from ipsilateral versus contralateral tissue. Addition of recombinant Ang-2 to astrocyte-conditioned medium significantly increased the number of SIM-A9 murine microglial cells cultured under hypoxic conditions (1 % oxygen for 48 h). In transgenic GFAP-CreER™-EDNRB-fl/fl mice with stroke, conditional knockout of astroglial ETBR significantly decreased the number of proliferating cells in the peri-infarct area with a microglial phenotype (Ki67+/CD11b+). Our results indicate that Ang-2, and possibly other paracrine effectors functioning downstream of astroglial ETBR signaling, are important mediators of microglial cell dynamics after stroke.

Beyond the Norm: The emerging interplay of complement system and extracellular matrix in the tumor microenvironment

Ground-breaking awareness has been reached about the intricate and dynamic connection between developing tumors and the host immune system. Being a powerful arm of innate immunity and a functional bridge with adaptive immunity, the complement system (C) has also emerged as a pivotal player in the tumor microenvironment (TME). Its "double-edged sword" role in cancer can find an explanation in the controversial relationship between C capability to mediate tumor cell cytolysis or, conversely, to sustain chronic inflammation and tumor progression by enhancing cell invasion, angiogenesis, and metastasis to distant organs. However, comprehensive knowledge about the actual role of C in cancer progression is impaired by several limitations of the currently available studies. In the current review, we aim to bring a fresh eye to the controversial role of C in cancer by analyzing the interplay between C and extracellular matrix (ECM) components as potential orchestrators of the TME. The interaction of C components with specific ECM components can determine C activation or inhibition and promote specific non-canonical functions, which can, in the tumor context, favor or limit progression based on the cancer setting. An in-depth and tumor-specific characterization of TME composition in terms of C components and ECM proteins could be essential to determine their potential interactions and become a key element for improving drug development, prognosis, and therapy response prediction in solid tumors.

Multi-disciplinary investigation identifies increased potency of ethyl-parathion inhaled within a soil-dust matrix to cause acetylcholinesterase-dependent molecular impacts

Neurotoxicity investigations of inhaled organophosphorus pesticide (OP), ethyl-parathion (EP), were conducted in Sprague Dawley rats comparing exposures to EP volatilized at 0, 1, 10, and 20 mg/m3 versus EP incorporated into soil dust (5 mg/m3) at 0, 0.0095, 0.09, and 0.185 mg/mg3. All exposures were sublethal, caused no respiratory effects, and no effects on balance and coordination behavior. Both volatilized and dust-incorporated EP exposures significantly decreased acetylcholinesterase (AChE) activity in plasma and hippocampus tissue. Correspondingly, plasma and hippocampal dopamine levels spiked in these exposures suggesting compensatory cholinergic / dopaminergic signal balancing. The EP exposures significantly increased expression of pro-inflammatory genes, including MAPK-14, IL6, IL1β, and TNF-α, while global RNA-seq results identified significant enrichment of inflammation, oxidative stress, and apoptosis pathways. Remarkably, dust-incorporated EP impacted similar molecular endpoints as volatilized EP but at concentrations two orders of magnitude lower highlighting potentially increased potency of EP incorporated into soil dust.

Potential mechanisms implied in tick infection by arboviruses and their transmission to vertebrate hosts

Ticks can transmit many pathogens, including arboviruses, to their vertebrate hosts. Arboviruses must overcome or evade defense mechanisms during their passage from the tick gut to the hemolymph, salivary glands, and the feeding site in the host skin. This review summarizes current knowledge of defense mechanisms in specific tick tissues and at the feeding site in the host skin. We discuss the possible roles of these defense mechanisms in viral infection and transmission. The responses of tick salivary proteins to arbovirus infection are also discussed. This review provides information that may help accelerate research on virus-tick interactions.

Complement regulators as novel targets for anti-cancer therapy: A comprehensive review

Cancer remains a formidable global health challenge requiring the continued exploration of innovative therapeutic approaches. While traditional treatment strategies including surgery, chemotherapy, and radiation therapy have had some success, primarily in early-stage disease, the quest for more targeted, personalized, safer, and effective therapies remains an ongoing pursuit. Over the past decade, significant advances in the field of tumor immunology have dramatically shifted a focus towards immunotherapy, although the ability to harness and coopt the immune system to treat cancer is still just beginning to be realized. One important area that has yet to be fully explored is the complement system, an integral part of innate immunity that has gathered attention recently as a source of potential targets for anti-cancer therapy. The complement system has a complex and context dependent role in cancer biology in that it not only contributes to immune surveillance but also may promote tumor progression. Complement regulators, including CD46, CD55, CD59, and complement factor H, exercise defined control over complement activation, and have also been acknowledged for their role in the tumor microenvironment. This review explores the intricate role of complement regulators in cancer development and progression, examining their potential as therapeutic targets, current strategies, challenges, and the evolving landscape of clinical research.

Overview of Oxidative Stress in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that is frequently diagnosed in female patients, caused by multiple interacting factors. It has a complex pathogenesis which can affect almost any organ, from the kidneys to the cardiovascular, pulmonary, neurological, osteoarticular, and hematological systems. The present narrative review seeks to elucidate the role of reactive oxygen species (ROS) in the pathogenesis of SLE. The central question guiding this study is to what extent these serum protein modifications correlate with disease activity and organ damage in SLE. It is characterized by the decreased apoptosis and increased necrosis of T cells and the NETosis of granulocytes. Given the impact of an SLE diagnosis on one's life, this narrative review aims to evaluate the intricacies of oxidative stress and its relevance to the pathogenesis and treatment of the disease. Topics such as understanding processes of oxidative stress, their damaging pathways, oxidative stress biomarkers, and their role in the future assistance of clinical decisions will be discussed in the article. The accurate determination of biomarkers is taught to improve both the diagnosis and the management of the disease, while antioxidant therapy may open a new door for the treatment.

Statins as an Adjunctive Antithrombotic Agent in Thrombotic Antiphospholipid Syndrome: Mechanisms and Clinical Implications

The thrombotic physiopathology of antiphospholipid syndrome (APS) is complex, heterogeneous, and dynamic. While venous thromboembolism (VTE) is the most common initial presentation, arterial thrombotic events (ATE) become more frequent in advanced stages and are associated with high morbidity and mortality. Despite the use of oral anticoagulants (OACs), thrombotic APS remains associated with a high risk of recurrent thrombosis. Given their potential antithrombotic effects capable of reducing the risk of both VTE and ATE, statins have been proposed as an adjunctive therapy to OACs for patients with APS and recurrent thrombosis. However, this recommendation is primarily based on studies not specifically conducted in APS populations, with only preclinical data or evidence from retrospective observational studies available from APS patients cohorts. For these reasons, this narrative review aims to synthesise the studies evaluating the potential antithrombotic effects of statins in patients with APS, highlighting the progress made and identifying areas for future research.

Mitochondrial injury and complement dysregulation are drivers of pathological inflammation in viral myocarditis

Enteroviruses cause nearly 1 billion global infections annually and are associated with a diverse array of human illnesses. Among these, myocarditis and the resulting chronic inflammation have been recognized as major contributing factors to virus-induced heart failure. Despite our growing understanding, very limited therapeutic strategies have been developed to address the pathological consequences of virus-induced chronic innate immune activation. Coxsackievirus B3 (CVB3) was used as a model cardiotropic enterovirus. We leveraged in vitro cell-based studies to investigate cardiomyocyte and macrophage interaction during CVB3 infection, as well as animal studies and unique human cardio specimens to evaluate mechanisms of viral heart injury. We present evidence that viral myocarditis is in part exacerbated by pathological activation of the complement pathway in cells, mice, and human cardiac tissues. We demonstrate unique cell type-specific responses to viral infection that are exacerbated by mitochondrial injury in cardiomyocytes and NFκB-dependent pro-inflammatory response in macrophages. Macrophages are robustly activated by damage-associated mitochondrial components, including mitochondrial proteins and lipid extracts. Mechanistically, we identify complement protective factors CD59/protectin and CD55/DAF as novel targets of viral proteinase that acts to release the brakes on complement-mediated autoinjury. Collectively, our study highlights a novel mechanism that can act as a potential contributor to CVB3 pathogenesis through mitochondrial injury-mediated autoimmunity.

IMPORTANCE

This study sheds light on how enteroviruses, specifically coxsackievirus B3, may contribute to heart failure by triggering harmful immune responses in the heart. We discovered that viral infections in heart cells cause mitochondrial damage, which in turn activates a destructive immune response involving the complement system. This immune activation is one of the significant contributors that lead to further injury of heart tissues, worsening the damage caused by the virus. Additionally, we identified key protective molecules that are targeted and disrupted by the virus, allowing the immune system to attack the heart even more aggressively. Understanding these mechanisms may provide additional insights into how viral infections can lead to chronic heart conditions and suggests potential therapeutic targets to prevent or reduce heart damage in patients affected by viral myocarditis.

Retina-Targeted 17β-Estradiol by the DHED Prodrug Rescues Visual Function and Actuates Neuroprotective Protein Networks After Optic Nerve Crush in a Rat Model of Surgical Menopause

The association between 17β-estradiol (E2) deprivation, seen in menopause, and a risk for developing glaucoma has been shown. Thus, exogenous supplementation of E2 may protect against retinal ganglion cell (RGC) degradation and vision loss. Here, we investigated the utility of topical 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), a prodrug of E2 that selectively produces the neuroprotective hormone in the retina, on visual function after optic nerve crush (ONC) and ovariectomy (OVX). We used female Brown Norway rats that underwent either Sham or OVX surgeries. After ONC, OVX animals received DHED or vehicle eye drops for 12 weeks. Visual function, via the optomotor reflex, and retinal thickness, via optical coherence tomography, were followed longitudinally. Afterward, we performed mass spectrometry-based label-free retina proteomics to survey retinal protein interaction networks in our selected animal model and to identify E2-responsive proteins after OVX on neurodegeneration. We found that ONC with OVX caused a significant decline in visual functions that were ameliorated by DHED treatments. Discovery-driven retina proteomics identified numerous proteins associated with neurodegenerative processes due to ONC that were remediated by DHED eye drops. Altogether, our three-pronged phenotypic preclinical evaluation of the topical DHED in the OVX + ONC model of glaucoma reveals the therapeutic potential of the prodrug to prevent visual deficits after glaucomatous retinal injury.