Development of nanoparticles based on amphiphilic cyclodextrins for the delivery of active substances

Although amphiphilic cyclodextrin derivatives (ACDs) serve as valuable building blocks for nanomedicine formulations, their widespread production still encounters various challenges, limiting large-scale manufacturing. This work focuses on a robust alternative pathway using mineral base catalysis to transesterify β-cyclodextrin with long-chain vinyl esters, yielding ACD with modular and controlled hydrocarbon chain grafting. ACDs with a wide range of degrees of substitution (DS) were reliably synthesized, as indicated by extensive physicochemical characterization, including MALDI-TOF mass spectrometry. The influence of various factors, including the type of catalyst and the length of the hydrocarbon moiety of the vinyl ester, was studied in detail. ACDs were assessed for their ability to form colloidal suspensions by nanoprecipitation, with or without PEGylated phospholipid. Small-angle X-ray scattering and cryo-electron microscopy revealed the formation of nanoparticles with distinct ultrastructures depending on the DS: an onion-like structure for low and very high DS, and reversed hexagonal organization for DS between 4.5 and 6.1. We confirmed the furtivity of the PEGylated versions of the nanoparticles through complement activation experiments and that they were well tolerated in-vivo on a zebrafish larvae model after intravenous injection. Furthermore, a biodistribution experiment showed that the nanoparticles left the bloodstream within 10 h after injection and were phagocytosed by macrophages.

Targeted therapy in glomerular diseases

Targeted therapy has emerged as a more precise approach to treat glomerular diseases, focusing on specific molecular or cellular processes that contribute to disease development or progression. This approach complements or replaces traditional immunosuppressive therapy, optimizes supportive care, and provides a more personalized treatment strategy. In this review, we summarize the evolving understanding of pathogenic mechanisms in immune-mediated glomerular diseases and the developing targeted therapies based on these mechanisms. We begin by discussing pan-B-cell depletion, anti-CD20 rituximab, and targeting B-cell survival signaling through the BAFF/APRIL pathway. We also exam specific plasma cell depletion with anti-CD38 antibody. We then shift our focus to complement activation in glomerular diseases, which is involved in antibody-mediated glomerular diseases, such as IgA nephropathy, membranous nephropathy, ANCA-associated vasculitis, and lupus nephritis. Non-antibody-mediated complement activation occurs in glomerular diseases, including C3 glomerulopathy, complement-mediated atypical hemolytic uremic syndrome, and focal segmental glomerulosclerosis. We discuss specific inhibition of terminal, lectin, and alternative pathways in different glomerular diseases. Finally, we summarize current clinical trials targeting the final pathways of various glomerular diseases, including kidney fibrosis. We conclude that targeted therapy based on individualized pathogenesis should be the future of treating glomerular diseases.

Effects of PEG antibodies on in vivo performance of LNP-mRNA vaccines

Polyethylene glycol (PEG) plays important roles in stabilizing and lengthening circulation time of lipid nanoparticle (LNP) vaccines. Nowadays various levels of PEG antibodies have been detected in human blood, but the impact and mechanism of PEG antibodies on the in vivo performance of LNP vaccines has not been clarified thoroughly. By illustrating the distribution characteristics of PEG antibodies in human, the present study focused on the influence of PEG antibodies on the safety and efficacy of LNP-mRNA vaccine against COVID-19 in animal models. It was found that PEG antibodies led to shortened blood circulation duration, elevated accumulation and mRNA expression in liver and spleen, enhanced expression in macrophage and dendritic cells, while without affecting the production of anti-Spike protein antibodies of COVID-19 LNP vaccine. Noteworthily, PEG antibodies binding on the LNP vaccine increased probability of complement activation in animal as well as in human serum and led to lethal side effect in large dosage via intravenous injection of mice. Our data suggested that PEG antibodies in human was a risky factor of LNP-based vaccines for biosafety concerns but not efficacy.

Complement-pentraxins synergy: Navigating the immune battlefield and beyond

The complement is a crucial immune defense system that triggers rapid immune responses and offers efficient protection against foreign invaders and unwanted host elements, acting as a sentinel. Activation of the complement system occurs upon the recognition of pathogenic microorganisms or altered self-cells by pattern-recognition molecules (PRMs) such as C1q, collectins, ficolins, and pentraxins. Recent accumulating evidence shows that pentraxins establish a cooperative network with different classes of effector PRMs, resulting in synergistic effects in complement activation. This review describes the complex interaction of pentraxins with the complement system and the implications of this cooperative network for effective host defense during pathogen invasion.

Cardiometabolic disease in Black African and Caribbean populations: an ethnic divergence in pathophysiology?

In the UK, populations of Black African and Caribbean (BAC) ethnicity suffer higher rates of cardiometabolic disease than White Europeans (WE). Obesity, leading to increased visceral adipose tissue (VAT) and intrahepatic lipid (IHL), has long been associated with cardiometabolic risk, driving insulin resistance and defective fatty acid/lipoprotein metabolism. These defects are compounded by a state of chronic low-grade inflammation, driven by dysfunctional adipose tissue. Emerging evidence has highlighted associations between central complement system components and adipose tissue, fatty acid metabolism and inflammation; it may therefore sit at the intersection of various cardiometabolic disease risk factors. However, increasing evidence suggests an ethnic divergence in pathophysiology, whereby current theories fail to explain the high rates of cardiometabolic disease in BAC populations. Lower fasting and postprandial TAG has been reported in BAC, alongside lower VAT and IHL deposition, which are paradoxical to the high rates of cardiometabolic disease exhibited by this ethnic group. Furthermore, BAC have been shown to exhibit a more anti-inflammatory profile, with lower TNF-α and greater IL-10. In contrast, recent evidence has revealed greater complement activation in BAC compared to WE, suggesting its dysregulation may play a greater role in the high rates of cardiometabolic disease experienced by this population. This review outlines the current theories of how obesity is proposed to drive cardiometabolic disease, before discussing evidence for ethnic differences in disease pathophysiology between BAC and WE populations.

A shift of paradigm: From avoiding nanoparticular complement activation in the field of nanomedicines to its exploitation in the context of vaccine development

The complement system plays a central role in our innate immunity to fight pathogenic microorganisms, foreign and altered cells, or any modified molecule. Consequences of complement activation include cell lysis, release of histamines, and opsonization of foreign structures in preparation for phagocytosis. Because nanoparticles interact with the immune system in various ways and can massively activate the complement system due to their virus-mimetic size and foreign texture, detrimental side effects have been described after administration like pro-inflammatory responses, inflammation, mild to severe anaphylactic crisis and potentially complement activated-related pseudoallergy (CARPA). Therefore, application of nanotherapeutics has sometimes been observed with restraint, and avoiding or even suppressing complement activation has been of utmost priority. In contrast, in the field of vaccine development, particularly protein-based immunogens that are attached to the surface of nanoparticles, may profit from complement activation regarding breadth and potency of immune response. Improved transport to the regional lymph nodes, enhanced antigen uptake and presentation, as well as beneficial effects on immune cells like B-, T- and follicular dendritic cells may be exploited by strategic nanoparticle design aimed to activate the complement system. However, a shift of paradigm regarding complement activation by nanoparticular vaccines can only be achieved if these beneficial effects are accurately elicited and overshooting effects avoided.

Ginsenoside Rg3 endows liposomes with prolonged blood circulation and reduced accelerated blood clearance

PEGylated cholesterol-containing liposomes (Chol-PEG-lipo) have been widely used as a drug carrier for their good stealth property in blood circulation where cholesterol maintains the stability of the liposomal lipid bilayer and PEGylation endows liposomes with long circulation capability. However, cholesterol-related disadvantages and the accelerated blood clearance (ABC) phenomenon caused by PEGylation greatly limit the application of conventional stealth liposomes in clinic. Herein, ginsenoside Rg3 was selected to substitute cholesterol and PEG for liposomes preparation (Rg3-lipo). Rg3 was proved with similar liposomal membrane regulation ability to cholesterol and comparable long circulation effect to PEG. In addition, repeated administrations of Chol-PEG-lipo and Rg3-lipo were performed. The circulation time of the second dose of Chol-PEG-lipo was substantially reduced accompanied by a greatly increased accumulation in the liver due to the induction of anti-PEG IgM and the subsequent activated complement system. In contrast, no significantly increased level of relative plasma cells, IgM secretion and the complement activation in blood circulation was observed after the second injection of Rg3-lipo. As a result, Rg3-lipo showed great stealth property without ABC phenomenon. Therefore, developing liposomes utilizing Rg3 instead of PEG and cholesterol presents a promising strategy to prolong the blood circulation time of liposomes without triggering the ABC phenomenon and activated immune responses.

Anti-complement factor H (CFH) autoantibodies could delay pristane-induced lupus nephritis

PURPOSE

Anti-complement factor H (CFH) autoantibodies could be detected in lupus and its significance remained to be elucidated. Herein, we aimed to explore the roles of anti-CFH autoantibodies based on pristane-induced lupus mice.

METHODS

Twenty-four female Balb/c mice were randomly divided into four groups, with one group injected with pristane (pristane group), one group with pristane and then human CFH (hCFH) (pristane-CFH group) 3 times, and the other two as vertical controls, PBS group and PBS-CFH group. Histopathological analysis was performed six months after pristane administration. Levels of hCFH, anti-CFH autoantibodies and anti-dsDNA antibody were detected. Murine IgG (mIgG) were purified and cross-reactivity, epitopes, subclasses and functional analysis were further evaluated in vitro.

RESULTS

Immunization with hCFH and subsequent development of anti-CFH autoantibodies significantly attenuated nephritis of pristane-induced lupus, including lower levels of urinary protein and serum creatinine, decreased levels of serum anti-dsDNA antibody, greatly ameliorated renal histopathologic damage, decreased IgG, complements (C1q, C3) deposits and lower inflammatory factor (IL-6) expression in glomerulus. Furthermore, the purified mIgG (contained anti-CFH autoantibodies) could recognize both hCFH and murine CFH, and the epitopes were predominantly located in hCFH short consensus repeats (SCRs) 1-4, 7 and 11-14. The IgG subclasses were predominant IgG1. The autoantibodies could enhance the binding between hCFH and C3b, and increase factor I mediated-C3b lysis in vitro.

CONCLUSION

Our results suggested that anti-CFH autoantibodies could attenuate pristane-induced lupus nephritis by increasing bio-functions of CFH on regulating complement activation and controlling inflammation.

Immunothrombosis and Complement Activation Contribute to Disease Severity and Adverse Outcome in COVID-19

Severe COVID-19 is characterized by systemic inflammation and multiple organ dysfunction syndrome (MODS). Arterial and venous thrombosis are involved in the pathogenesis of MODS and fatality in COVID-19. There is evidence that complement and neutrophil activation in the form of neutrophil extracellular traps are main drivers for development of microvascular complications in COVID-19. Plasma and serum samples were collected from 83 patients infected by SARS-CoV-2 during the two first waves of COVID-19, before the availability of SARS-CoV-2 vaccination. Samples were collected at enrollment, day 11, and day 28; and patients had differing severity of disease. In this comprehensive study, we measured cell-free DNA, neutrophil activation, deoxyribonuclease I activity, complement activation, and D-dimers in longitudinal samples of COVID-19 patients. We show that all the above markers, except deoxyribonuclease I activity, increased with disease severity. Moreover, we provide evidence that in severe disease there is continued neutrophil and complement activation, as well as D-dimer formation and nucleosome release, whereas in mild and moderate disease all these markers decrease over time. These findings suggest that neutrophil and complement activation are important drivers of microvascular complications and that they reflect immunothrombosis in these patients. Neutrophil activation, complement activation, cell-free DNA, and D-dimer levels have the potential to serve as reliable biomarkers for disease severity and fatality in COVID-19. They might also serve as suitable markers with which to monitor the efficacy of therapeutic interventions in COVID-19.

Ocrelizumab and ofatumumab, but not rituximab, trigger complement induction in vitro

The clinical and adverse effects of the therapeutic monoclonal antibodies (mAb) ocrelizumab, ofatumumab and rituximab in multiple sclerosis (MS) are presently subject to extensive study. While the two former are approved for MS, the older and less costly rituximab is used off label, and adverse effect profiles are important in their evaluation. The three mAbs all induce B cell depletion, with complement-dependent cytotoxicity (CDC) as one of several mechanisms of action. Complement activation is also postulated to underlie adverse reactions related to infusion/injection. Such administration-related reactions are associated with all three mAbs, but comparisons have so far been indirect, resting on incidence reports from separate clinical trials. The objective of this study was to perform head-to-head comparison of complement activation by ofatumumab, ocrelizumab and rituximab. In vitro experiments were performed in whole blood from healthy donors. The complement-activating potential of the three mAbs was analyzed after 30 min of exposure to 0.3 mg/mL or 0.9 mg/mL of each drug, and compared with those of the well-known TNF inhibitory mAbs adalimumab and infliximab, the latter with recognized potential for infusion reactions. Ofatumumab, ocrelizumab, and infliximab, but not rituximab and adalimumab, triggered statistically significant complement activation measured as increased levels of terminal C5b-9 complement complex (TCC), a sensitive marker of such activation. While results demand careful interpretation, they provide an indication of distinct complement-inducing potential among anti-CD20 mAbs currently used to treat MS.

Eculizumab suppresses zymosan-induced release of inflammatory cytokines IL-1α, IL-1β, IFN-γ and IL-2 in autologous serum-substituted PBMC cultures: Relevance to cytokine storm in Covid-19

BACKGROUND AND OBJECTIVE

Cytokine storm (CS) is a major contributor to the fatal outcome of severe infectious diseases, including Covid-19. Treatment with the complement (C) C5 inhibitor eculizumab was beneficial in end-stage Covid-19, however, the mechanism of this effect is unknown. To clarify this, we analyzed the relationship between C activation and production of pro-inflammatory cytokines in a PBMC model.

METHODS

Human PBMC with or without 20 % autologous serum was incubated with C3a, C5a, zymosan or zymosan-pre-activated serum (ZAS) for 24 h with or without eculizumab or the C5a receptor antagonist, DF2593A. C activation (sC5b-9) and 9 inflammatory cytokines were measured by ELISA.

RESULTS

In serum-free unstimulated PBMC only IL-8 release could be measured during incubation. Addition of C5a increased IL-8 secretion only, ZAS induced both IL-2 and IL-8, while zymosan led to significant production of all cytokines, most abundantly IL-8. In the presence of serum the above effects were greatly enhanced, and the zymosan-induced rises of IL-1α, IL-1β IFN-γ and IL-2 were significantly attenuated by eculizumab but not by DF2593a.

CONCLUSIONS

These data highlight the complexity of interrelationships between C activation and cytokine secretion under different experimental conditions. The clinically relevant findings include the abundant formation of the chemokine IL-8, which was stimulated by C5a, and the suppression of numerous inflammatory cytokines by eculizumab, which explains its therapeutic efficacy in severe Covid-19. These data strengthen the clinical relevance of the applied PBMC model for drug screening against CS, enabling the separation of complex innate immune cross-talks.

Cholesterol crystal formation is a unifying pathogenic mechanism in the development of diabetic retinopathy

AIMS/HYPOTHESIS

Hyper-reflective crystalline deposits found in retinal lesions have been suggested to predict the progression of diabetic retinopathy, but the nature of these structures remains unknown.

METHODS

Scanning electron microscopy and immunohistochemistry were used to identify cholesterol crystals (CCs) in human donor, pig and mouse tissue. The effects of CCs were analysed in bovine retinal endothelial cells in vitro and in db/db mice in vivo using quantitative RT-PCR, bulk RNA sequencing, and cell death and permeability assays. Cholesterol homeostasis was determined using 2H2O and 2H7-cholesterol.

RESULTS

We identified hyper-reflective crystalline deposits in human diabetic retina as CCs. Similarly, CCs were found in the retina of a diabetic mouse model and a high-cholesterol diet-fed pig model. Cell culture studies demonstrated that treatment of retinal cells with CCs can recapitulate all major pathogenic mechanisms leading to diabetic retinopathy, including inflammation, cell death and breakdown of the blood-retinal barrier. Fibrates, statins and α-cyclodextrin effectively dissolved CCs present in in vitro models of diabetic retinopathy, and prevented CC-induced endothelial pathology. Treatment of a diabetic mouse model with α-cyclodextrin reduced cholesterol levels and CC formation in the retina, and prevented diabetic retinopathy.

CONCLUSIONS/INTERPRETATION

We established that cholesterol accumulation and CC formation are a unifying pathogenic mechanism in the development of diabetic retinopathy.

The interplay between PEGylated nanoparticles and blood immune system

During the last two decades, an increasing number of reports have pointed out that the immunogenicity of polyethylene glycol (PEG) may trigger accelerated blood clearance (ABC) and hypersensitivity reaction (HSR) to PEGylated nanoparticles, which could make PEG modification counterproductive. These phenomena would be detrimental to the efficacy of the load and even life-threatening to patients. Consequently, further elucidation of the interplay between PEGylated nanoparticles and the blood immune system will be beneficial to developing and applying related formulations. Many groups have worked to unveil the relevance of structural factors, dosing schedule, and other factors to the ABC phenomenon and hypersensitivity reaction. Interestingly, the results of some reports seem to be difficult to interpret or contradict with other reports. In this review, we summarize the physiological mechanisms of PEG-specific immune response. Moreover, we speculate on the potential relationship between the induction phase and the effectuation phase to explain the divergent results in published reports. In addition, the role of nanoparticle-associated factors is discussed based on the classification of the action phase. This review may help researchers to develop PEGylated nanoparticles to avoid unfavorable immune responses based on the underlying mechanism.

Exploration of complement split products in plasma and urine as biomarkers of kidney graft rejection

INTRODUCTION

The complement system, consisting of more than thirty different soluble and cell-bound proteins, exerts essential functions both in the innate and adaptive immune systems and is believed to be an important contributor to allograft injury in kidney transplantation. The anaphylatoxins C3a and C5a are powerful chemoattractants, recruiting immune effector cells toward the site of complement activation and enhance T-cell response, while C3dg binding to CR2 on B-cells, enhances B-cell immunity at several stages of the B-cell differentiation. Complement split products in plasma and urine could reflect ongoing inflammation and tissue injury. We, therefore, investigated if complement split products increase in plasma and urine in kidney transplant recipients with rejection.

METHOD

In this case-control feasibility study, complement factors C3a, C3dg, C4a, and C5a were measured in plasma and C3dg and sC5b-9 associated C9 neoantigen in urine in 15 kidney transplant recipients with rejection (cases) and 15 kidney transplant recipients without (controls). The groups were matched on the type of transplantation and the time from transplantation to sampling. The complement split products were compared (i) between cases and controls and (ii) within the rejection group over time, comparing the measurements at rejection with measurements where the kidney transplant recipients were clinically stable. Possible moderators were explored, and results adjusted accordingly. P values < 0.05 were considered significant. Plasma C3dg was analyzed by immune-electrophoresis, plasma C3a, plasma C4a, and plasma C5a by flow cytometry, and urine C3dg and urine C9neo by ELISA.

RESULTS

In plasma, there were no significant differences between the rejection and the control group. However, steroids and pretransplant C3dg levels significantly influenced C3dg. Within the rejection group, plasma C3a and C3dg were significantly higher at the time of rejection compared to the stable phase (p < 0.01). In urine, C3dg/creatinine and C9 neoantigen/creatinine ratios were not different between the rejection and the control group. Urine C3dg/creatinine and urine C9 neoantigen/creatinine ratios correlated to urine albumin and significantly increased after the transplantation (p < 0.001).

CONCLUSION

This study shows increased plasma C3a and C3dg in kidney transplant recipients, primarily with T cell mediated rejection. This finding suggests that consecutive measurements of C3a and C3dg in plasma could be applicable to monitor alloreactivity in kidney transplant recipients. Urine complement split products are unsuitable as rejection biomarkers since the permeability of the glomerular filtration barrier strongly influences them. Prospective longitudinal studies on plasma C3a and C3dg dynamics will be needed to validate present findings.

Complement and complement regulatory proteins are upregulated in lungs of COVID-19 patients

We explored the pathological changes and the activation of local complement system in COVID-19 pneumonia. Lung paraffin sections of COVID-19 infected patients were analyzed by HE (hematoxylin-eosin) staining. The deposition of complement C3, the deposition of C3b/iC3b/C3d and C5b-9, and the expression of complement regulatory proteins, CD59, CD46 and CD55 were detected by immunohistochemistry. In COVID-19 patients' lung tissues, fibrin exudation, mixed with erythrocyte, alveolar macrophage and shed pneumocyte are usually observed in the alveoli. The formation of an "alveolar emboli" structure may contribute to thrombosis and consolidation in lung tissue. In addition, we also found that compared to normal tissue, the lung tissues of COVID-19 patients displayed the hyper-activation of complement that is represented by extensive deposition of C3, C3b/iC3b/C3d and C5b-9, and the increased expression level of complement regulatory proteins CD55, and especially CD59 but not CD46. The thrombosis and consolidation in lung tissues may contribute to the pathogenesis of COVID-19. The increased expression of CD55 and CD59 may reflect a feedback of self-protection on the complement hyper-activation. Further, the increased C3 deposition and the strongly activated complement system in lung tissues may suggest the rationale of complement-targeted therapeutics in conquering COVID-19.

Bupleurum chinense exerts a mild antipyretic effect on LPS-induced pyrexia rats involving inhibition of peripheral TNF-α production

ETHNOPHARMACOLOGICAL RELEVANCE

Bupleuri Radix, the dried roots of Bupleurum chinense DC. (BC) or Bupleurum scorzonerifolium Willd., is one of the most frequently used traditional Chinese medicines. As the species in Xiao-Chai-Hu decoction, BC has been used as an antipyretic medicine with a long history. However, its antipyretic characteristics and underlying mechanism(s) remain unclear.

AIM OF THE STUDY

To elucidate the antipyretic characteristics and mechanism(s) of BC used in its traditional way.

METHODS

The water extract of BC (BCE) was prepared according to the traditional decocting mode. Murine fever and endotoxemia models were induced by intravenous injection of lipopolysaccharide (LPS). In vitro complement activation assay and the levels of TNF-α, IL-6, IL-1β, and C5a were determined by ELISA.

RESULTS

BCE exerted a confirmed but mild antipyretic effect on LPS-induced fever of rat. In vitro, it significantly lowered LPS-elevated TNF-α in the supernatant of rat complete blood cells and THP-1 cells, but failed to decrease IL-6 and IL-1β. In murine endotoxemia models, BCE markedly decreased serum TNF-α, but had no impact on IL-6 and IL-1β. BCE also restricted complement activation in vitro and in vivo. Nevertheless, the mixture of saikosaponin A and D could not suppress supernatant TNF-α of monocytes and serum TNF-α of endotoxemia mice.

CONCLUSIONS

The present study dissects the peripheral mechanism for the antipyretic effect of BC used in the traditional way. Our findings indicate that BCE directly suppresses monocyte-produced TNF-α, thus decreasing circulating TNF-α, which may be responsible for its mild but confirmed antipyretic action.

Measurement of Complement Activation via Plasma-Soluble C5b-9 Comparison with Terminal Complement Complex Staining in a Series of Kidney Biopsies

INTRODUCTION

With the emergence of therapeutic complement inhibitors, there is a need to identify patients with complement-driven inflammation. C5b-9 is the terminal product of the three complement pathways and therefore a marker of total complement activation. We present a pilot study which aims to assess whether plasma soluble C5b-9 (sC5b-9) correlates with terminal complement complex (TCC) staining in kidney tissue. The secondary aim was to assess the utility of plasma sC5b-9 as part of routine workup in kidney patients undergoing kidney biopsy.

METHODS

Thirty-seven patients undergoing kidney biopsy had plasma sC5b-9 and TCC staining on kidney tissue performed. Additional blood markers including creatinine, haemoglobin, CRP, factor H, factor I, and midkine levels were also taken. These parameters were correlated with the histological diagnoses. Patients were divided into a diseased group (n = 31) and a control group (n = 6) consisting of transplanted kidneys with minor or no changes. Of the biopsies in the control group, 50% were performed as per protocol, and the other 50% were performed due to clinical need.

RESULTS

There was no correlation found between plasma sC5b-9 and TCC kidney staining. Elevated sC5b-9 levels were found in a heterogeneous group of patients but were associated with higher CRP and lower haemoglobin levels. Overall, there was more TCC kidney staining in the diseased group compared with the control group, and a trend was observed of diabetic, primary membranous nephropathy, and amyloidosis patients having more intense glomerular and peritubular/interstitial staining.

CONCLUSION

Plasma sC5b-9 as a marker of total complement activation does not correlate with TCC kidney staining. This discordance suggests that plasma sC5b-9 and TCC staining are distinct markers of disease. TCC staining reflects chronicity and tissue deposition of complement over time. Conversely, plasma sC5b-9 concentrations change rapidly and reflect systemic complement activation. Complement activation was present in a heterogeneous group of kidney disease, indicating the underlying role of complement in many disorders.

A possible role of classical complement pathway activation in the pathogenesis of immunoglobulin G nephropathy: a case report

Immunoglobulin G (IgG) nephropathy refers to a rare group of diseases characterized by deposits of IgG in the mesangial region. However, IgG nephropathy is controversial as a single disease entity, and its pathogenesis remains to be elucidated. In the present report, we discuss a case of IgG nephropathy in which we observed activation of the classical complement pathway.A 47-year-old woman was admitted to our hospital with nephrotic syndrome. Light-microscopic examination revealed neither proliferative nor sclerotic lesions in the glomeruli. However, unusual and large deposits were observed in the paramesangial area. An immunofluorescence study revealed predominant IgG and C1q and slight C3 deposits in the paramesangial area, suggesting immune-complex-type glomerular disease. An electron microscopic study also revealed different sizes of non-organized electron-dense deposits with a similar pattern of distribution, which were accompanied by foot process effacement. Clinically, there was no evidence of systemic diseases, such as infectious or autoimmune diseases (including systemic lupus erythematosus). Based on these findings, she was diagnosed with IgG nephropathy and treated with prednisolone. Steroid therapy was effective, and complete remission was maintained.Additional immunological examination revealed that IgG deposits were polyclonal and consisted mainly of the IgG1 and IgG3 subclasses. Furthermore, staining was positive for C4d and C5b-9. The present findings indicate that the pathogenesis of IgG nephropathy in our patient may have involved activation of the classical complement pathway.

Accommodation in allogeneic and xenogeneic organ transplantation: Prevalence, impact, and implications for monitoring and for therapeutics

Accommodation refers to acquired resistance of organs or tissues to immune or inflammatory reactions that might otherwise cause severe injury or rejection. As first observed in ABO-incompatible kidney transplants and heterotopic cardiac xenografts, accommodation was identified when organ transplants continued to function despite the presence of anti-graft antibodies and/or other reactants in the blood of recipients. Recent evidence suggests many and perhaps most organ transplants have accommodation, as most recipients mount B cell responses specific for the graft. Wide interest in the impact of graft-specific antibodies on the outcomes of transplants prompts questions about which mechanisms confer protection against such antibodies, how accommodation might be detected and whether and how rejection could be superimposed on accommodation. Xenotransplantation offers a unique opportunity to address these questions because immune responses to xenografts are easily detected and the pathogenic impact of immune responses is so severe. Xenotransplantation also provides a compelling need to apply these and other insights to decrease the intensity and toxicity of immunosuppression that otherwise could limit clinical application.

Overview on the role of complement-specific autoantibodies in diseases

The complement system is recognized as a major pathogenic or contributing factor in an ever-growing number of diseases. In addition to inherited factors, autoantibodies to complement proteins have been detected in various systemic and organ-specific disorders. These include antibodies directed against complement components, regulators and receptors, but also protein complexes such as autoantibodies against complement convertases. In some cases, the autoantibodies are relatively well characterized and a pathogenic role is incurred and their detection has diagnostic value. In other cases, the relevance of the autoantibodies is rather unclear. This review summarizes what we know of complement specific autoantibodies in diseases and identifies unresolved questions regarding their functional effect and relevance.

Elastin turnover in ocular diseases: A special focus on age-related macular degeneration

The extracellular matrix (ECM) and its turnover play a crucial role in the pathogenesis of several inflammatory diseases, including age-related macular degeneration (AMD). Elastin, a critical protein component of the ECM, not only provides structural and mechanical support to tissues, but also mediates several intracellular and extracellular molecular signaling pathways. Abnormal turnover of elastin has pathological implications. In the eye elastin is a major structural component of Bruch's membrane (BrM), a critical ECM structure separating the retinal pigment epithelium (RPE) from the choriocapillaris. Reduced integrity of macular BrM elastin, increased serum levels of elastin-derived peptides (EDPs), and elevated elastin antibodies have been reported in AMD. Existing reports suggest that elastases, the elastin-degrading enzymes secreted by RPE, infiltrating macrophages or neutrophils could be involved in BrM elastin degradation, thus contributing to AMD pathogenesis. EDPs derived from elastin degradation can increase inflammatory and angiogenic responses in tissues, and the elastin antibodies are shown to play roles in immune cell activity and complement activation. This review summarizes our current understanding on the elastases/elastin fragments-mediated mechanisms of AMD pathogenesis.

Immunosuppression participated in complement activation-mediated inflammatory injury caused by 4-octylphenol via TLR7/IκBα/NF-κB pathway in common carp (Cyprinus carpio) gills

4-octylphenol (4-OP), a toxic estrogenic environmental pollutant, can threaten aquatic animal and human health. However, toxic effect of 4-OP on fish has not been reported. To investigate molecular mechanism of gill poisoning caused by 4-OP exposure, a carp 4-OP poisoning model was established, and then blood and gills were collected on day 60. The results demonstrated that gill was a target organ attacked by 4-OP, and exposure to 4-OP caused carp gill inflammatory injury. There were 1605 differentially expressed genes (DEGs, including 898 up-regulated DEGs and 707 down-regulated DEGs). KEGG and GO were used to further analyze obtained 1605 DEGs, indicating that complement activation, immune response, and inflammatory response participated in the mechanism of 4-OP-caused carp gill inflammatory injury. Our data at transcription level further revealed that 4-OP caused complement activation through triggering complement component 3a/complement component 3a receptor (C3a/C3aR) axis and complement component 5a/complement component 5a receptor 1 (C5a/C5aR1) axis, induced immunosuppression through the imbalances of T helper (Th) 1/Th2 cells and regulatory T (Treg)/Th17 cells, as well as caused inflammatory injury via toll like receptor 7/inhibitor kappa B alpha/nuclear factor-kappa B (TLR7/IκBα/NF-κB) pathway. Taken together, immunosuppression participated in complement activation-mediated inflammatory damage in carp gills after 4-OP treatment. The findings of this study will provide pioneering information and theoretical support for the mechanism of 4-OP poisoning, and will provide reference for the assessment of estrogenic environmental pollution risk.

Pathophysiology and system biology of rat c-BSA induced immune complex glomerulonephritis and pathway comparison with human gene sequencing data

Immune-complex glomerulonephritis (ICGN) is a major cause of nephrotic syndrome in adults and children. Cationic BSA (c-BSA) intravenous injection could produce significant albuminuria within a short time, and is a suitable in vivo experimental animal model to investigate the pathophysiology of ICGN and for drug screening, but lack of thorough study to clarify its dynamic pathophysiological alteration so far, as well as detailed changes in mRNA and LncRNA levels. The purpose of this study is to investigate the dynamic alteration in renal function, lipid metabolism and histopathology during the progress of c-BSA induced ICGN. RNA sequencing was used to identified differentially expressed mRNA and LncRNA in kidney cortex of ICGN. Results demonstrated that c-BSA induced ICGN model could completely exhibit clinical features of immune-mediated nephrotic syndrome with gradual declining renal function, and increased albuminuria and deteriorated histopathological injuries. The correlation analysis suggested that complement activation was the most key element in mediating of ICGN. RNA sequencing using rat kidney tissues combined with Gene Expression Omnibus (GEO) data of human glomerulonephritis showed the most enriched KEGG pathways in ICGN were Toll-like receptor signaling pathway, B cell receptor and Focal adhesion. The differential lncRNAs in ICGN rats were also screened, and the lncRNA-mRNA co-expression network was constructed to clarify lncRNA role in molecular mechanism of ICGN progression. Their human homogenous lncRNAs were also identified, such as ST3GAL5-AS1 and DIO3OS, which provide the potential lncRNA targets to treat ICGN. All the differential LncRNAs in ICGN kidneys caused by MMF were also identified and provided another possible pharmacological mechanism of MMF through lncRNA regulation. In summary, the current study firstly described the dynamic physiological changes of c-BSA induced ICGN, identified most key KEGG pathways, and provided lncRNA-mRNA regulatory network in ICGN.

Sustained ICP Elevation Is a Driver of Spatial Memory Deficits After Intraventricular Hemorrhage and Leads to Activation of Distinct Microglial Signaling Pathways

The mechanisms of cognitive decline after intraventricular hemorrhage (IVH) in some patients continue to be poorly understood. Multiple rodent models of intraventricular or subarachnoid hemorrhage have only shown mild or even no cognitive impairment on subsequent behavioral testing. In this study, we show that intraventricular hemorrhage only leads to a significant spatial memory deficit in the Morris water maze if it occurs in the setting of an elevated intracranial pressure (ICP). Histopathological analysis of these IVH + ICP animals did not show evidence of neuronal degeneration in the hippocampal formation after 2 weeks but instead showed significant microglial activation measured by lacunarity and fractal dimensions. RNA sequencing of the hippocampus showed distinct enrichment of genes in the IVH + ICP group but not in IVH alone having activated microglial signaling pathways. The most significantly activated signaling pathway was the classical complement pathway, which is used by microglia to remove synapses, followed by activation of the Fc receptor and DAP12 pathways. Thus, our study lays the groundwork for identifying signaling pathways that could be targeted to ameliorate behavioral deficits after IVH.

Plasma C4 level was associated with mortality, cardiovascular and cerebrovascular complications in hemodialysis patients

BACKGROUND

Patients on maintenance hemodialysis (HD) exhibit a high risk of death, cardiovascular and cerebrovascular diseases (CCDs). Previous studies indicated complement activation associated with the increased risk of cardiovascular diseases in HD patients. This study aimed to explore whether the critical complement factors were associated with the adverse outcomes in HD patients.

METHODS

A total of 108 HD patients were included and followed up for 52 months. The baseline clinical characteristics and plasma C3c, C1q, CFH, CFB, C4, MAC, C5a, C3a and MBL were measured. The three endpoints were death, cardiovascular and cerebrovascular events (CCEs) and the composition of them. Univariate and multivariate Cox regression identified factors associated with the three endpoints respectively. X-tile analyses determined the optimal cut-off values for high risks. Restricted cubic spline plots illustrated the dose-response relationships. Correlations between the complement factors and risk factors for CCDs were analyzed.

RESULTS

Baseline plasma C4 was finally selected by univariate and multivariate Cox regression analyses for three endpoints, including all-cause mortality, CCEs and the composition of them. When baseline plasma C4 exceeded 0.47 (P = 0.001) or 0.44 (P = 0.018) g/L respectively, the risks for death or achieving the composite endpoint enhanced significantly. The relationships of C4 and HR for the three endpoints showed a positive linear trend. Plasma C4 had prominent correlations with blood TG (r = 0.62, P < 0.001) and HDL (r = -0.38, P < 0.001).

CONCLUSIONS

A higher baseline plasma C4 level was significantly associated with the future incidence of decease, CCEs and either of them. Plasma C4 level correlated with blood TG and HDL.

Glaucocalyxin a protect liver function via inhibiting platelet over-activation during sepsis

BACKGROUND

Rabdosia japonica (Burm. f.) var. glaucocalyx (Maxim.) is a perennial herb, and is traditionally used as folk medicine for treating inflammatory diseases and cancer. Gaucocalyxin A (GLA) is an ent‑kaurane diterpenoid that is isolated from the aerial parts of R. japonica (Burm. f.) var. glaucocalyx (Maxim.). In a recent study, we found that GLA protects against acute liver dysfunction induced by Escherichia coli, which is likely related to its anti-inflammatory effects. However, the mechanism by which GLA protects liver injury during sepsis is unknown.

AIM

To evaluate the anti-inflammatory function of GLA and its regulatory effect on platelet function.

METHOD

An in vivo model of sepsis was established by inoculating mice with E. coli. Live function and platelet activation were evaluated through standard assays. The levels of pro-inflammatory factors were measured through ELISA and qRT-PCR.

RESULTS

GLA alleviated liver dysfunction in the mouse model of sepsis. GLA-treated mice displayed lower complement activation and liver dysfunction after E. coli infection. GLA alleviated the decrease in peripheral platelet counts by inhibiting their clearance by Kupffer cells in liver. Furthermore, GLA inhibited platelet activation through the RIP1/RIP3/AKT pathway and downregulated C3aR expression on the platelets, thereby inhibiting liver injury and dysfunction due to excessive complement activation.

CONCLUSION

GLA can inhibit platelet activation by reducing surface expression of C3aR, which protect the liver from injury induced by excessive complement activation. GLA is a novel therapeutic agent for controlling sepsis-related liver dysfunction.

Esculetin alleviates murine lupus nephritis by inhibiting complement activation and enhancing Nrf2 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Esculetin is a bioactive compound of medicinal herb Hydrangea paniculata, and has showed anti-oxidation and anti-inflammation bioactivities. Renal local oxidative stress and inflammation are import contributors for progression of lupus nephritis (LN).

AIM OF THE STUDY

In the present study, the renal protective effect of esculetin against LN was evaluated using MRL/lpr mice.

MATERIALS AND METHODS

MRL/lpr mice were orally administrated with esculetin (20 mg/kg and 40 mg/kg) from 10 to 20 weeks and then renal function and kidney pathology were analyzed.

RESULTS

Esculetin significantly attenuated renal impairment in MRL/lpr mice by reducing blood urea nitrogen (BUN), serum creatinine (Scr) and albuminuria, and ameliorated the glomerular hypertrophy, tubular interstitial fibrosis and mononuclear cell infiltration into interstitium. mRNA microarray suggested that esculetin could significantly down-regulate complement cascade, inflammation and fibrosis pathway, and up-regulate Nrf2-related anti-oxidation genes. Most surprising finding in the current study was that esculetin could inhibit the complement activation both in classical and alternative pathway using in vitro hemolysis assay, further enzyme assay suggested that esculetin blocked the C3 convertase (C4b2a) to exert this inhibitory capability. Molecular docking predicted that esculetin had four conventional hydrogen bonds interacting with C4b2a, and CDOCKER energy is relatively lower. Luciferase reporter gene demonstrated that esculetin could activate Nrf2 signaling pathway, and further flow cytometry confirmed that anti-oxidation bioactivity of esculetin was dependent on Nrf2 activation. On the other hand, esculetin could inhibit NFκB nuclear translocation and TGFβ-smad3 profibrosis pathway.

CONCLUSION

Esculetin shows beneficial effect on LN progression, and it may be a good natural leading compound for design of chemical compounds to treat LN.

COVID-19 microthrombosis: unusually large VWF multimers are a platform for activation of the alternative complement pathway under cytokine storm

ADAMTS13, a metalloproteinase, specifically cleaves unusually large multimers of von Willebrand factor (VWF), newly released from vascular endothelial cells. The ratio of ADAMTS13 activity to VWF antigen (ADAMTS13/VWF) and indicators of the alternative complement pathway (C3a and sC5b-9) are both related to the severity of COVID-19. The ADAMTS13/VWF ratio is generally moderately decreased (0.18–0.35) in patients with severe COVID-19. When these patients experience cytokine storms, both interleukin-8 and TNFα stimulate VWF release from vascular endothelial cells, while interleukin-6 inhibits both production of ADAMTS13 and its interaction with VWF, resulting in localized severe deficiency of ADAMTS13 activity. Platelet factor 4 and thrombospondin-1, both released upon platelet activation, bind to the VWF-A2 domain and enhance the blockade of ADAMTS13 function. Thus, the released unusually-large VWF multimers remain associated with the vascular endothelial cell surface, via anchoring with syndecan-1 in the glycocalyx. Unfolding of the VWF-A2 domain, which has high sequence homology with complement factor B, allows the domain to bind to activated complement C3b, providing a platform for complement activation of the alternative pathway. The resultant C3a and C5a generate tissue factor-rich neutrophil extracellular traps (NETs), which induce the mixed immunothrombosis, fibrin clots and platelet aggregates typically seen in patients with severe COVID-19.

Increased cell stiffness contributes to complement-mediated injury of choroidal endothelial cells in a monkey model of early age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in the aging population. Yet, no therapies exist for approximately 85% of all AMD patients who have the dry form that is marked by degeneration of the retinal pigmented epithelium (RPE) and underlying choroidal vasculature. As the choroidal vessels are crucial for RPE development and maintenance, understanding how they degenerate may lead to effective therapies for dry AMD. One likely causative factor for choroidal vascular loss is the cytolytic membrane attack complex (MAC) of the complement pathway that is abundant on choroidal vessels of humans with early dry AMD. To examine this possibility, we studied the effect of complement activation on choroidal endothelial cells (ECs) isolated from a rhesus monkey model of early AMD that, we report, exhibits MAC deposition and choriocapillaris endothelial loss similar to that seen in human early AMD. Treatment of choroidal ECs from AMD eyes with complement-competent normal human serum caused extensive actin cytoskeletal injury that was significantly less pronounced in choroidal ECs from young normal monkey eyes. We further show that ECs from AMD eyes are significantly stiffer than their younger counterparts and exhibit peripheral actin organization that is distinct from the longitudinal stress fibers in young ECs. Finally, these differences in complement susceptibility and mechanostructural properties were found to be regulated by the differential activity of the small GTPases Rac and Rho, because Rac inhibition in AMD cells led to simultaneous reduction in stiffness and complement susceptibility while Rho inhibition in young cells exacerbated complement injury. Thus, by identifying cell stiffness and cytoskeletal regulators Rac and Rho as important determinants of complement susceptibility, the current findings offer a new mechanistic insight into choroidal vascular loss in early AMD that warrants further investigation for assessment of translational potential. This article is protected by copyright. All rights reserved.

Role of the lectin pathway of complement in hematopoietic stem cell transplantation-associated endothelial injury and thrombotic microangiopathy

Hematopoietic stem cell transplantation-associated thrombotic microangiopathy (HSCT-TMA) is a life-threatening syndrome that occurs in adult and pediatric patients after hematopoietic stem cell transplantation. Nonspecific symptoms, heterogeneity within study populations, and variability among current diagnostic criteria contribute to misdiagnosis and underdiagnosis of this syndrome. Hematopoietic stem cell transplantation and associated risk factors precipitate endothelial injury, leading to HSCT-TMA and other endothelial injury syndromes such as hepatic veno-occlusive disease/sinusoidal obstruction syndrome, idiopathic pneumonia syndrome, diffuse alveolar hemorrhage, capillary leak syndrome, and graft-versus-host disease. Endothelial injury can trigger activation of the complement system, promoting inflammation and the development of endothelial injury syndromes, ultimately leading to organ damage and failure. In particular, the lectin pathway of complement is activated by damage-associated molecular patterns (DAMPs) on the surface of injured endothelial cells. Pattern-recognition molecules such as mannose-binding lectin (MBL), collectins, and ficolins—collectively termed lectins—bind to DAMPs on injured host cells, forming activation complexes with MBL-associated serine proteases 1, 2, and 3 (MASP-1, MASP-2, and MASP-3). Activation of the lectin pathway may also trigger the coagulation cascade via MASP-2 cleavage of prothrombin to thrombin. Together, activation of complement and the coagulation cascade lead to a procoagulant state that may result in development of HSCT-TMA. Several complement inhibitors targeting various complement pathways are in clinical trials for the treatment of HSCT-TMA. In this article, we review the role of the complement system in HSCT-TMA pathogenesis, with a focus on the lectin pathway.

Clinical relevance of glomerular IgM deposition in patients with lupus nephritis

BACKGROUND

The aim of the study was to investigate the clinical relevance of IgM deposition in patients with lupus nephritis (LN) in a large cohort.

RESULTS

217 patients with renal biopsy-proven active LN were enrolled. The associations between glomerular IgM deposition and clinicopathological parameters were further analyzed. IgM deposition was positively correlated with glomerular C1q and C3 deposition moderately (r = 0.436, P < 0.001; r = 0.408, P < 0.001, respectively), and inversely correlated with plasma levels of C3 and CFH mildly (r =  - 0.138, P = 0.043; r =  - 0.147, P = 0.037, respectively). By multivariate analysis, we found that glomerular IgM deposition independently contributed to glomerular C3 deposition in patients with LN (OR = 2.002, 95% CI 1.295-3.094, P = 0.002). In addition, we also found that patients with IgM 0-2+ had similar plasma CFH levels, but in patients with IgM3+-4+, plasma CFH levels were significantly lower (300.4 ± 155.8 μg/mL vs. 429.9 ± 187.5 μg/mL, P < 0.001). Furthermore, patients with high density of glomerular IgM and low levels of CFH had heavier proteinuria, higher serum creatinine and lower plasma C3 levels (5.7 ± 3.1 g/d vs. 4.7 ± 3.5 g/d, P = 0.037; 150.1 ± 121.0 μmol/L vs. 105.6 ± 97.1 μmol/L, P = 0.005; 0.3 ± 0.2 μg/L vs. 0.4 ± 0.2 μg/L, P = 0.04, respectively), comparing with those with low density of glomerular IgM and low levels of CFH.

CONCLUSIONS

Our results suggested the involvement of glomerular deposited IgM in complement activation and renal injury in LN.

COVID-19 adenovirus vaccine triggers antibodies against PF4 complexes to activate complement and platelets

BACKGROUND

Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare coagulation disorder reported after administration of COVID-19 adenovirus-vectored vaccines. VITT is mediated by anti-platelet factor 4 (PF4) antibodies activating platelets through the Fcγ-receptor II (FcγRII), and it is associated with strong fibrin turnover. The complement system is involved in several other immunothrombotic entities, but its impact on VITT is not established.

OBJECTIVE

To assess antibodies in interaction with the activation of platelets and complement triggered by VITT.

METHODS

Antibodies against adenovirus type 2 hexon protein, ChAdOx1 adenoviral vector-specific IgG and PF4 were analyzed by enzyme immunoassays from VITT patients (n = 5). The EDTA plasma samples of the patients and controls were used to measure both terminal complement complexes (TCC) by ELISA and aggregation of healthy donor platelets. We studied the effects of human immunoglobulin (IVIG) and glycoprotein IIb/IIIa inhibitor (GPIIb/IIIa) on spontaneous and collagen-induced platelet aggregation supplemented with VITT plasma.

RESULTS

None of the patients had experienced a COVID-19 infection. Antibody analyses confirmed the immunogenicity of the adenovirus-vectored ChAdOx1 vaccine. Moreover, VITT plasma had anti-PF4 antibodies and elevated TCC levels as a sign of complement activation. In isolated healthy donor platelets, VITT patient plasma caused marked, spontaneous aggregation of platelets, which was abolished by eptifibatide and high-dose therapeutic IVIG.

CONCLUSIONS

Our findings suggest that VITT is triggered by antibodies against adenovirus vector and PF4-polyanion complexes which strongly co-activate complement and platelets. The spontaneous platelet aggregation was suppressed by IVIG or eptifibatide, indicating that besides FcγRII, also GPIIb/IIIa receptor exerts platelet procoagulant role in VITT.

RNA sequencing reveals induction of specific renal inflammatory pathways in a rat model of malignant hypertension

In malignant hypertension, far more severe kidney injury occurs than in the "benign" form of the disease. The role of high blood pressure and the renin-angiotensin-aldosterone system is well recognized, but the pathogenesis of the renal injury of malignant hypertension (MH) remains incompletely understood. Using the rat model of two-kidney, one-clip renovascular hypertension in which some but not all animals develop MH, we performed a transcriptomic analysis of gene expression by RNA sequencing to identify transcriptional changes in the kidney cortex specific for MH. Differential gene expression was assessed in three groups: MH, non-malignant hypertension (NMH), and normotensive, sham-operated controls. To distinguish MH from NMH, we considered two factors: weight loss and typical renovascular lesions. Mean blood pressure measured intraarterially was elevated in MH (220 ± 6.5 mmHg) as well as in NMH (192 ± 6.4 mmHg), compared to controls (119 ± 1.7 mmHg, p < 0.05). Eight hundred eighty-six genes were exclusively regulated in MH only. Principal component analysis revealed a separated clustering of the three groups. The data pointed to an upregulation of many inflammatory mechanisms in MH including pathways which previously attracted relatively little attention in the setting of hypertensive kidney injury: Transcripts from all three complement activation pathways were upregulated in MH compared to NMH but not in NMH compared with controls; immunohistochemistry confirmed complement deposition in MH exclusively. The expression of chemokines attracting neutrophil granulocytes (CXCL6) and infiltration of myeloperoxidase-positive cells were increased only in MH rats. The data suggest that these pathways, especially complement deposition, may contribute to kidney injury under MH. KEY MESSAGES: The most severe hypertension-induced kidney injury occurs in malignant hypertension. In a rat model of malignant hypertension, we assessed transcriptional responses in the kidney exposed to high blood pressure. A broad stimulation of inflammatory mechanisms was observed, but a few specific pathways were activated only in the malignant form of the disease, notably activation of the complement cascades. Complement inhibitors may alleviate the thrombotic microangiopathy of malignant hypertension even in the absence of primary complement abnormalities.

Complement activation and increased expression of Syk, mucin-1 and CaMK4 in kidneys of patients with COVID-19

Acute and chronic kidney failure is common in hospitalized patients with COVID-19, yet the mechanism of injury and predisposing factors remain poorly understood. We investigated the role of complement activation by determining the levels of deposited complement components (C1q, C3, FH, C5b-9) and immunoglobulin along with the expression levels of the injury-associated molecules spleen tyrosine kinase (Syk), mucin-1 (MUC1) and calcium/calmodulin-dependent protein kinase IV (CaMK4) in the kidney tissues of people who succumbed to COVID-19. We report increased deposition of C1q, C3, C5b-9, total immunoglobulin, and high expression levels of Syk, MUC1 and CaMK4 in the kidneys of COVID-19 patients. Our study provides strong rationale for the expansion of trials involving the use of inhibitors of these molecules, in particular C1q, C3, Syk, MUC1 and CaMK4 to treat patients with COVID-19.

Complement activation and blockade in massive post-partum haemorrhage, thrombotic microangiopathy and acute kidney injury: a case report

Background

Thrombotic microangiopathy (TMA)-mediated acute kidney injury (AKI) following massive haemorrhage is a rare but severe complication of the post-partum period. It is associated with a poor renal prognosis and a high risk of end-stage kidney disease. Complement activation may occur in this picture. However, whether complement activation, and thus complement blockade, may be critically relevant in this setting is unknown.

Case presentation

A 50 year-old woman presented with massive delayed post-partum haemorrhage (PPH). Despite bleeding control and normalization of coagulation parameters, she rapidly developed AKI stage 3 associated with dysmorphic microhematuria and proteinuria up to 2 g/day with the need of renal replacement therapy. Blood tests showed signs of TMA associated with markedly increased sC5b-9 and factor Bb plasma levels, respectively markers of terminal and alternative complement pathway over-activation. This clinical picture prompted us to initiate anti-C5 therapy. sC5b-9 normalized within 12 h after the first dose of eculizumab, factor Bb and C3 after seven days, platelet count after nine days and haptoglobin after 3 weeks. The clinical picture improved rapidly with blood pressure control within 48 h. Diuresis resumed after three days, kidney function rapidly improved and haemodialysis could be discontinued after the sixth and last dose. Serum creatinine returned to normal two years after presentation.

Conclusions

We suggest that massive PPH induced major activation of complement pathways, which ultimately lead to TMA-induced AKI. Various causes, such as oocyte-donation, the potential retention of placental material and the use of tranexamic acid may have contributed to complement activation due to PPH. The prompt administration of anti-C5 therapy may have rapidly restored kidney microcirculation patency, thus reversing signs of TMA and AKI. We propose that complement activation may represent a major pathophysiological player of this complication and may provide a novel therapeutic avenue to improve renal prognosis in TMA-induced AKI following massive PPH.

Biomarkers of complement and platelet activation are not correlated with the one or twenty-four hours corrected count increments in prophylactically platelet transfused hematological patients: a prospective cohort study

Platelet transfusion refractoriness is a serious clinical concern that complicates the management of thrombocytopenic patients. Previous studies have suggested a potential role for both complement and platelet activation based on in vitro analyses of platelet concentrates. In this study, the post-transfusion platelet response, as indicated by the corrected count increment at 1 and 24 h after prophylactic platelet transfusions, respectively, was correlated with the 1 h post-transfusion Δconcentration (1 h post-transfusion - pretransfusion) of complement and platelet activation biomarkers. The study was registered as a clinical trial at ClinicalTrials.gov (identifier: NCT02601131) and patients were recruited during inpatient care in the hematological department. Soluble terminal complement complexes, soluble P-selectin and soluble CD40 ligand were analyzed. Confirmed alloimmunized patients were excluded. Included subjects were either given platelet transfusions (n = 43) and categorized into four clinical study groups or included in a non-transfused control group (n = 10). In total, 54 transfusions were included. No transfusion-mediated complement activation was observed. The transfusions were associated with a significant increase in the concentration of soluble P-selectin (p < .001), primarily corresponding to the passive infusion of soluble P-selectin-containing plasma residuals. The Δconcentration of soluble P-selectin was, however, not significantly correlated with the corrected count increments. Thus, significant correlations between biomarkers of complement and platelet activation and the post-transfusion platelet response could not be demonstrated in this study.

Complement as driver of systemic inflammation and organ failure in trauma, burn, and sepsis

Complement is one of the most ancient defense systems. It gets strongly activated immediately after acute injuries like trauma, burn, or sepsis and helps to initiate regeneration. However, uncontrolled complement activation contributes to disease progression instead of supporting healing. Such effects are perceptible not only at the site of injury but also systemically, leading to systemic activation of other intravascular cascade systems eventually causing dysfunction of several vital organs. Understanding the complement pathomechanism and its interplay with other systems is a strict requirement for exploring novel therapeutic intervention routes. Ex vivo models exploring the cross-talk with other systems are rather limited, which complicates the determination of the exact pathophysiological roles that complement has in trauma, burn, and sepsis. Literature reporting on these three conditions is often controversial regarding the importance, distribution, and temporal occurrence of complement activation products further hampering the deduction of defined pathophysiological pathways driven by complement. Nevertheless, many in vitro experiments and animal models have shown beneficial effects of complement inhibition at different levels of the cascade. In the future, not only inhibition but also a complement reconstitution therapy should be considered in prospective studies to expedite how meaningful complement-targeted interventions need to be tailored to prevent complement augmented multi-organ failure after trauma, burn, and sepsis.

This review summarizes clinically relevant studies investigating the role of complement in the acute diseases trauma, burn, and sepsis with important implications for clinical translation.

Upregulation of Nrf2 Attenuates Oxidative Stress-Induced, Complement Activation-Associated Endothelial Injury and Apoptosis in Transplant-Associated Thrombotic Microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) is a serious and life-threatening complication after hematopoietic stem cell transplantation. Studies have reported that the main pathological manifestation of the disease is an endothelial injury associated with complement activation, but its molecular biological mechanisms remain unclear. Our previous studies have shown that oxidative stress may induce complement activation in TA-TMA. Nuclear factor erythroid 2-related factor 2 (Nrf2), a molecule that regulates oxidative stress, can inhibit endothelial stimulation by reactive oxygen species (ROS). We assessed Nrf2 expression in peripheral blood mononuclear cells (PBMCs) from patients with TA-TMA compared with healthy donors. Nrf2 expression, ROS accumulation, complement activation, and apoptosis were then assessed in human umbilical vein endothelial cells (HUVECs) incubated with TA-TMA plasma to identify whether complement-associated endothelial damage induced by oxidative stress occurs in TA-TMA. The protective effect of Nrf2 pathway activation on TA-TMA-induced endothelial injury was also investigated to explore a new avenue for TA-TMA prevention and treatment. In this study, peripheral blood was collected from six patients with TA-TMA, and healthy donors served as negative controls. We determined the expression of Nrf2 through in vitro and in vivo experiments and measured the level of apoptosis. We found increased expression of Nrf2 in PBMCs from patients with TA-TMA. HUVECs were then incubated with plasma from patients with TA-TMA or with plasma from healthy donors, and we found that complement 3 (C3) levels were increased in HUVECs treated with TA-TMA plasma. In contrast, total Nrf2 levels were decreased, and ROS production and apoptosis levels were increased. To determine whether complement activation and apoptosis were caused by oxidative stress, we added N-acetyl-L-cysteine to HUVECs incubated with TA-TMA plasma. As a result, ROS production, complement activation, and apoptosis levels were reduced. Finally, we upregulated Nrf2 in HUVECs by rescue experiments, and we found that activation of Nrf2 attenuated endothelial cell apoptosis and ROS production and reduced C3 and C5b-9 levels. These results suggest that oxidative stress-induced, complement activation-associated endothelial injury occurs in TA-TMA and that upregulation of Nrf2 protects endothelial cells from damage. Activation of the Nrf2 pathway may be a potential target for the treatment of complement activation-associated endothelial injury in TA-TMA.

C3dg Quantification by PEG Precipitation and or TRIFMA

Detection of complement activation products can be carried out in a number of ways, and different methods are used in different laboratories. No international standard for measuring complement activation in the clinical setting has been agreed upon.Here we describe a modified assay for measuring C3dg. The assay is simple, inexpensive and stable. The estimation of C3dg directly reflects complement turnover independently of activation pathway.

Quantification of Porcine Complement Activation Fragment C3a by a Neoepitope-Based Enzyme-Linked Immunosorbent Assay

Enzyme-linked immunosorbent assay (ELISA) enables fast and simple quantification of analytes in the pico- to nanogram range in complex samples. Here, we describe an ELISA for the detection of porcine C3a as a marker for complement activation. Antibody specificity is critical for a robust assay. This assay is based on a pair of antibodies specific for the porcine C3a molecule and thus does not react with native C3.

The Benefits of Complement Measurements for the Clinical Practice

The complement cascade is an evolutionary ancient innate immune defense system, playing a major role in the defense against infections. Its function in maintaining host homeostasis on activated cells has been emphasized by the crucial role of its overactivation in ever growing number of diseases, such as atypical hemolytic uremic syndrome (aHUS), autoimmune diseases as systemic lupus erythematosus (SLE), C3 glomerulopathies (C3GN), age-related macular degeneration (AMD), graft rejection, Alzheimer disease, and cancer, to name just a few. The last decade of research on complement has extended its implication in many pathological processes, offering new insights to potential therapeutic targets and asserting the necessity of reliable, sensitive, specific, accurate, and reproducible biomarkers to decipher complement role in pathology. We need to evaluate accurately which pathway or role should be targeted pharmacologically, and optimize treatment efficacy versus toxicity. This chapter is an introduction to the role of complement in human diseases and the use of complement-related biomarkers in the clinical practice. It is a part of a book intending to give reliable and standardized methods to evaluate complement according to nowadays needs and knowledge.

Deficiency of CFHR plasma proteins and autoantibody positive hemolytic uremic syndrome: treatment rationale, outcomes, and monitoring

Deficiency of Complement Factor H Related (CFHR) plasma proteins and Autoantibody Positive Hemolytic Uremic Syndrome (DEAP-HUS) is a subtype of atypical hemolytic uremic syndrome, known to be associated with significant morbidity. Its pathogenesis is linked to the production of IgG autoantibodies against complement factor H, a regulator of the alternative complement pathway. The binding of the autoantibodies to the C terminal of complement factor H interferes with its regulatory function, leading to increased activation of the alternative complement pathway and consequent endothelial cellular damage. Early diagnosis and initiation of appropriate therapy is reported to lead to favorable outcomes. Institution of plasma exchange therapy within 24 h of diagnosis has been shown to rapidly lower antibody levels, leading to clinical improvement. Adjunctive immunosuppression therapy suppresses antibody production and helps in maintaining long-term clinical remission of the disease. Available data advocates a treatment regimen that combines plasma therapy (preferably plasma exchange) and immunosuppression to halt disease process and sustain long-term disease remission.

A deep-sea pathogenic Bacillus subtilis isolate employs different strategies to escape the killing of teleost and murine complements

Bacillus subtilis subsp. subtilis G7 was isolated from a deep-sea hydrothermal vent and is pathogenic to pathogenic to fish (Japanese flounder) and mice. G7 is able to survive in host sera and phagocytes. In this study, we investigated the underlying mechanism of G7 serum resistance. We found that (i) the remaining complement activity was very low in G7-incubated flounder serum but high in G7-incubated mouse serum; (ii) cleaved C3 and C5 components were detected on flounder serum-incubated G7 but not on mouse serum-incubated G7; (iii) abundant uncleaved C5 was localized in G7-incubated mouse, but not flounder, serum; (iv) G7-incubated flounder, but not mouse, serum exhibited strong chemotactic activity; (v) pre-treatment with low-dose lysozyme abolished the serum resistance of G7. Hence, G7 activates flounder complement but is protected from complement-mediated destruction by its cell wall structure, while G7 prevents the activation of mouse complement. These results indicate that G7 employs different mechanisms to avoid the complement killing of different hosts.

Cold Agglutinin-Mediated Autoimmune Hemolytic Anemia in Association with Antiphospholipid Syndrome

Antiphospholipid syndrome and cold agglutinin-mediated autoimmune hemolytic anemia are 2 distinct immune-mediated hematologic disorders. While no clear association exists between these 2 entities, complement activation is known to occur in both of them. Herein, we report a unique case of cold agglutinin hemolytic anemia in a patient with a known primary antiphospholipid syndrome.

Activation of classical and alternative complement pathways in the pathogenesis of lung injury in COVID-19

Lung inflammation and damage is prominent in people infected with SARS-Cov-2 and a major determinant of morbidity and mortality. We report the deposition of complement components in the lungs of people who succumbed to COVID-19 consistent with the activation of the classical and the alternative pathways. Our study provides strong rationale for the expansion of trials involving the use of complement inhibitors to treat patients with COVID-19.

Thrombotic Microangiopathy in a Patient With COVID-19 Infection and Metastatic Cholangiocarcinoma

This is a case report of a 63-year-old African American female with a past medical history most significant for metastatic cholangiocarcinoma that presented for evaluation of persistent shortness of breath. Initial workup was remarkable for refractory anemia, moderate schistocytes on peripheral smear and lab work suggestive of a hemolytic anemia. Due to concern for thrombotic thrombocytopenic purpura (TTP), she subsequently underwent several rounds of plasma exchange without significant improvement. Secondary to progressive renal failure, patient eventually had a renal biopsy with findings remarkable for thrombotic microangiopathy (TMA). Simultaneously, patient was also diagnosed with coronavirus disease 2019 (COVID-19) infection. After a few weeks of supportive care, she was stable for discharge. Unfortunately, she did become dialysis dependent. Prior to hospital admission, she was being treated for metastatic cholangiocarcinoma and had received chemotherapy with gemcitabine. Her last chemotherapy session was approximately 3 weeks prior to her first hospitalization. Furthermore, although her hemolytic work did suggest TMA, it was not consistent with the diagnosis of TTP. She was transferred to a tertiary care center where hemolytic labs were trended, and supportive care was maximized. In light of the current COVID-19 pandemic, it is crucial to further investigate the pathophysiology of TMA in patients with active malignancies and COVID-19 infections. To our knowledge, this is the first case of TMA in a patient with both metastatic cholangiocarcinoma and COVID-19 infection.

Scleritis and sclerokeratitis associated with IgA vasculitis: A case series

Purpose

To describe a case series of scleritis associated with IgA vasculitis (IgAV) at a tertiary referral center.

Observations

Three men with scleritis associated with IgAV were identified: one with anterior scleritis alone, one with anterior scleritis and peripheral ulcerative keratitis (sclerokeratitis), and one with anterior and posterior scleritis. Visual acuity was preserved except from the patient who developed posterior scleritis. Ocular pain was the main symptom at presentation. All patients had a previous history of palpable purpura, but only one was aware of his underlying IgAV. Laboratory results revealed microhematuria and proteinuria with normal urinary β₂ microglobulin levels and negative serum ANCAs. Skin or kidney biopsy demonstrated leukocytoclastic vasculitis or glomerulonephritis with dominant IgA immune deposits.

Conclusions and Importance

Although uncommon, IgAV should be included in the differential diagnosis of anterior scleritis alone or associated with peripheral ulcerative keratitis or posterior scleritis, even in systemically asymptomatic patients. Urinalysis should not be underestimated in assessment of scleritis to detect early stages of glomerular disease. Scleritis may be the first manifestation whose study may lead to the diagnosis of IgAV. Multidisciplinary approach is necessary to prevent irreversible organ damage such as renal failure.

Complement activation by an angiogenic imbalance leads to systemic vascular endothelial dysfunction: A new proposal for the pathophysiology of preeclampsia

The underlying mechanism of preeclampsia by which an angiogenic imbalance results in systemic vascular endothelial dysfunction remains unclear. Complement activation directly induces endothelial dysfunction and is known to be involved in preeclampsia; nevertheless, the association between complement activation and angiogenic imbalance has not been established. This study aimed to evaluate whether angiogenic imbalance affects the expression and secretion of inhibitory complement factor H (CFH) in endothelial cells, resulting in complement activation and systemic vascular endothelial dysfunction. Viability of human umbilical vein endothelial cells (HUVECs) was assessed upon CFH knockdown by targeted-siRNA, and were incubated with complement factors. HUVECs were also treated with placental growth factor (PlGF) and/or soluble fms-like tyrosine kinase 1 (sFlt1), and CFH expression and secretion were measured. These cells were evaluated by cell viability assay and cell surface complement activation was quantified by immunocytochemical assessment of C5b-9 deposition. HUVECs transfected with CFH-siRNA had significantly lower viability than that of control cells. Moreover, the expression and secretion of CFH were significantly increased upon PlGF treatment compared with PlGF + sFlt1 combo. HUVECs treated with PlGF had less C5b-9 deposition and higher viability than HUVECs treated with PlGF + sFlt1. In summary, CFH was found to be essential for endothelial cell survival by inhibiting complement activation. An angiogenic imbalance, including decreased PlGF and increased sFlt1, suppresses CFH expression and secretion, resulting in complement activation on the surface of endothelial cells and systemic vascular endothelial dysfunction.

The dual role of complement in cancers, from destroying tumors to promoting tumor development

Complement is an important branch of innate immunity; however, its biological significance goes far beyond the scope of simple nonspecific defense and involves a variety of physiological functions, including the adaptive immune response. In this review, to unravel the complex relationship between complement and tumors, we reviewed the high diversity of complement components in cancer and the heterogeneity of their production and activation pathways. In the tumor microenvironment, complement plays a dual regulatory role in the occurrence and development of tumors, affecting the outcomes of the immune response. We explored the differential expression levels of various complement components in human cancers via the Oncomine database. The gene expression profiling interactive analysis (GEPIA) tool and Kaplan-Meier plotter (K-M plotter) confirmed the correlation between differentially expressed complement genes and tumor prognosis. The tumor immune estimation resource (TIMER) database was used to statistically analyze the effect of complement on tumor immune infiltration. Finally, with a view to the role of complement in regulating T cell metabolism, complement could be a potential target for immunotherapies. Targeting complement to regulate the antitumor immune response seems to have potential for future treatment strategies. However, there are still many complex problems, such as who will benefit from this therapy and how to select the right therapeutic target and determine the appropriate drug concentration. The solutions to these problems depend on a deeper understanding of complement generation, activation, and regulatory and control mechanisms.