The fixation of complement protein pairs to CR2 isoforms

Reviewing old protocols, it was found that Raji, a CR2-posistive cell line, binds both endogenous (e-C3) and exogenous C3 (i-C3). The processing of i-C3 to an i-C3b-like protein and their fixation to CR2 isoforms resulted in the formation of heterodimers whose units might be linked via thioester by low m.w. molecule(s). In an attempt to study the origin of the low m.w. molecules, it was found that they were detected following I12⁵-C3d treatment with NHS or hi-S. Indirect evidence would suggest that the products of C3 fragment fixation could have a short half-life and that the aromatic residues present in C3d might have different physico-chemical characteristics than those present in C3c. The surface hydrophobicity expressed by these aromatic residues could be required for the fixation of C3 or CR2 fragments to cell surface proteins.

The effect of complement C3 or C5 inhibition on geographic atrophy secondary to age-related macular degeneration: A living systematic review and meta-analysis

With the introduction of therapies to treat geographic atrophy (GA), GA management in clinical practice is now possible. A living systematic review can provide access to timely and robust evidence synthesis. This review found that complement factor 3 and 5 (C3 and C5) inhibition compared to sham likely reduces change in square root GA area at 12 months and untransformed GA area at 24 months. There is likely little to no difference in the rate of systemic treatment-emergent adverse events compared to sham. C3 and C5 inhibition, however, likely does not improve best-corrected visual acuity (BCVA) at 12 months, and the evidence is uncertain regarding change in BCVA at 24 months. Higher rates of ocular treatment emergent adverse effects with complement inhibition occur at 12 months and likely at 24 months. Complement inhibition likely results in new onset neovascular age-related macular degeneration at 12 months. This living meta-analysis will continuously incorporate new evidence.

Validation of dot blot immunoassay for measurement of complement opsonization of nanoparticles

Complement plays a critical role in the immune response toward nanomaterials. The complement attack on a foreign surface results in the deposition of C3, assembly of C3 convertases, the release of anaphylatoxins C3a and C5a, and finally, the formation of membrane attack complex C5b-9. Various technologies can measure complement activation markers in the fluid phase, but measurements of surface C3 deposition are less common. Previously, we developed an ultracentrifugation-based dot blot immunoassay (DBI) to measure the deposition of C3 and other protein corona components on nanoparticles. Here, we validate the repeatability of the DBI and its correlation with pathway-specific and common fluid phase markers. Moreover, we discuss the advantages of DBI, such as cost-effectiveness and versatility, while addressing potential limitations. This study provides insights into complement activation at the nanosurface level, offering a valuable tool for nanomedicine researchers in the field.

Molecular mechanism of complement inhibition by the trypanosome receptor ISG65

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

Mannose Binding Lectin and C3 Serum Levels in Coronary Artery Disease: A Cross-Sectional Study

BACKGROUND

The process of tissue injury in coronary artery disease (CAD) has been associated with activation of the complement system, partly due to the action of mannose-binding lectin (MBL) and C3, which are expressed in atherosclerotic lesions.

OBJECTIVE

The aim of this study was to evaluate the serum levels of MBL and C3 in patients with CAD and to compare them with healthy controls. Additionally, we aim to assess the correlation between MBL and C3 levels and cardiometabolic parameters.

METHODS

MBL and C3 serum concentration were determined by ELISA and immunoturbidimetry, respectively, in up to 119 patients undergoing coronary angiography for CAD evaluation, comprising 48 individuals diagnosed with acute myocardial infarction (MI) and 71 without MI. A total of 93 paired healthy controls were included in the study.

RESULTS

Individuals with CAD had MBL serum concentration higher than controls (p = .002), regardless of the presence of MI (p = .006). In addition, high concentration of MBL (>2000 ng/mL) was more frequent in patients with CAD (p = .007; OR = 2.6; 95% CI = 1.3-5.1). C3 levels were not significantly associated with any of the patient groups but were positively correlated with cardiometabolic parameters such as body mass index (BMI) and triglycerides levels.

CONCLUSIONS

Higher concentrations of MBL were found to be associated with CAD, whereas C3 levels were found to be associated with cardiovascular risk factors.

Recurrent C3 glomerulopathy after kidney transplantation

The complement system is part of innate immunity and is pivotal in protecting the body against pathogens and maintaining host homeostasis. Activation of the complement system is triggered through multiple pathways, including antibody deposition, a mannan-binding lectin, or activated complement deposition. C3 glomerulopathy (C3G) is a rare glomerular disease driven by complement dysregulation with high post-transplantation recurrence rates. Its treatment is mainly based on immunosuppressive therapies, specifically mycophenolate mofetil and glucocorticoids. Recent years have seen significant progress in understanding complement biology and its role in C3G pathophysiology. New complement-tergeting treatments have been developed and initial trials have shown promising results. However, challenges persist in C3G, with recurrent post-transplantation cases leading to suboptimal outcomes. This review discusses the pathophysiology and management of C3G, with a focus on its recurrence after kidney transplantation.

Prenatal air pollution exposure is associated with inflammatory, cardiovascular, and metabolic biomarkers in mothers and newborns

BACKGROUND

Prenatal air pollution exposure has been associated with individual inflammatory, cardiovascular, and metabolic biomarkers in mothers and neonates. However, studies of air pollution and a comprehensive panel of biomarkers across maternal and cord blood samples remain limited. Few studies used data-driven methods to identify biomarker groupings that converge biomarkers from multiple biological pathways. This study aims to investigate the impacts of prenatal air pollution on groups of biomarkers in maternal and cord blood samples.

METHODS

In the Maternal And Developmental Risks from Environmental and Social Stressors (MADRES) cohort, 87 biomarkers were quantified from 45 trimester 1 maternal blood and 55 cord blood samples. Pregnancy and trimester 1-averaged concentrations of particulate matter ≤2.5 μm and ≤10 μm in diameter (PM2.5 and PM10), nitrogen dioxide (NO2), and ozone (O3) were estimated, using inverse distance squared weighted spatial interpolation from regulatory air monitoring stations. Traffic-related NOx was assessed using California Line Source Dispersion Model: freeway/highway roads, non-freeway major roads, non-freeway minor roads, and their sum as total NOx. Elastic Net (EN) regression within the rexposome R package was used to group biomarkers and assess their associations with air pollution.

RESULTS

In maternal samples, trimester 1-averaged PM10 was associated with elevated inflammation biomarkers and lowered cardiovascular biomarkers. NO2 exhibited positive associations with cardiovascular and inflammation markers. O3 was inversely associated with inflammation, metabolic, and cardiovascular biomarkers. In cord blood, pregnancy-averaged PM2.5 was associated with higher cardiovascular biomarkers and lower metabolic biomarkers. PM10 was associated with lower inflammation and higher cardiovascular biomarkers. Total and major road NOx was associated with lower cardiovascular biomarkers.

CONCLUSION

Prenatal air pollution exposure was associated with changes in biomarkers related to inflammation, cardiovascular, metabolic, cancer, and neurological function in both mothers and neonates. This study shed light on mechanisms by which air pollution can influence biological function during pregnancy.

Mechanism of scutellarin inhibition of astrocyte activation to type A1 after ischemic stroke

OBJECTIVE

The aim of this study was to investigate the effects of scutellarin on the activation of astrocytes into the A1 type following cerebral ischemia and to explore the underlying mechanism.

METHODS

In vivo, a mouse middle cerebral artery wire embolism model was established to observe the regulation of astrocyte activation to A1 type by scutellarin, and the effects on neurological function and brain infarct volume. In vitro, primary astrocytes were cultured to establish an oxygen-glucose deprivation model, and the mRNA and protein expression of C3, a specific marker of A1-type astrocytes pretreated with scutellarin, were examined. The neurons were cultured in vitro to detect the toxic effects of ischemia-hypoxia-activated A1 astrocyte secretion products on neurons, and to observe whether scutellarin could reduce the neurotoxicity of A1 astrocytes. To validate the signaling pathway-related proteins regulated by scutellarin on C3 expression in astrocytes.

RESULTS

The results showed that scutellarin treatment reduced the volume of cerebral infarcts and attenuated neurological deficits in mice caused by middle cerebral artery embolism. Immunofluorescence and Western blot showed that treatment with scutellarin down-regulated middle cerebral artery embolism and OGD/R up-regulated A1-type astrocyte marker C3. The secretory products of ischemia-hypoxia-activated A1-type astrocytes were toxic to neurons and induced an increase in neuronal apoptosis, and astrocytes treated with scutellarin reduced the toxic effects on neurons. Further study revealed that scutellarin inhibited the activation of NF-κB signaling pathway and thus inhibited the activation of astrocytes to A1 type.

Intracellular C3 protects β-cells from IL-1β-driven cytotoxicity via interaction with Fyn-related kinase

One of the hallmarks of type 1 but also type 2 diabetes is pancreatic islet inflammation, associated with altered pancreatic islet function and structure, if unresolved. IL-1β is a proinflammatory cytokine which detrimentally affects β-cell function. In the course of diabetes, complement components, including the central complement protein C3, are deregulated. Previously, we reported high C3 expression in human pancreatic islets, with upregulation after IL-1β treatment. In the current investigation, using primary human and rodent material and CRISPR/Cas9 gene-edited β-cells deficient in C3, or producing only cytosolic C3 from a noncanonical in-frame start codon, we report a protective effect of C3 against IL-1β-induced β-cell death, that is attributed to the cytosolic fraction of C3. Further investigation revealed that intracellular C3 alleviates IL-1β-induced β-cell death, by interaction with and inhibition of Fyn-related kinase (FRK), which is involved in the response of β-cells to cytokines. Furthermore, these data were supported by increased β-cell death in vivo in a β-cell-specific C3 knockout mouse. Our data indicate that a functional, cytoprotective association exists between FRK and cytosolic C3.

Complement tunes glutamate release and supports synaptic impairments in an animal model of multiple sclerosis

BACKGROUND AND PURPOSE

To deepen our knowledge of the role of complement in synaptic impairment in experimental autoimmune encephalomyelitis (EAE) mice, we investigated the distribution of C1q and C3 proteins and the role of complement as a promoter of glutamate release in purified nerve endings (synaptosomes) and astrocytic processes (gliosomes) isolated from the cortex of EAE mice at the acute stage of the disease (21 ± 1 day post-immunization).

EXPERIMENTAL APPROACH

EAE cortical synaptosomes and gliosomes were analysed for glutamate release efficiency (measured as release of preloaded [3 H]D-aspartate ([3 H]D-ASP)), C1q and C3 protein density, and for viability and ongoing apoptosis.

KEY RESULTS

In healthy mice, complement releases [3 H]D-ASP from gliosomes more efficiently than from synaptosomes. The releasing activity occurs in a dilution-dependent manner and involves the reversal of the excitatory amino acid transporters (EAATs). In EAE mice, the complement-induced releasing activity is significantly reduced in cortical synaptosomes but amplified in cortical gliosomes. These adaptations are paralleled by decreased density of the EAAT2 protein in synaptosomes and increased EAAT1 staining in gliosomes. Concomitantly, PSD95, GFAP, and CD11b, but not SNAP25, proteins are overexpressed in the cortex of the EAE mice. Similarly, C1q and C3 protein immunostaining is increased in EAE cortical synaptosomes and gliosomes, although signs of ongoing apoptosis or altered viability are not detectable.

CONCLUSION AND IMPLICATIONS

Our results unveil a new noncanonical role of complement in the CNS of EAE mice relevant to disease progression and central synaptopathy that suggests new therapeutic targets for the management of MS.

Assessment of Interleukin 17 in Egyptian Systemic Lupus Erythematosus Patients as a Biomarker in Disease Activity

INTRODUCTION

Systemic lupus erythematosus (SLE) is a chronic idiopathic systemic autoimmune disorder with dysregulation of adaptive and innate immune systems. Interleukin (IL)-17 is the prototypical pro-inflammatory cytokine of T helper 17 (Th17) cells. Therefore, it contributes to the pathogenesis of human SLE.

AIM

The aim of the research paper was the evaluation of IL-17 level as a biomarker in the SLE cohort and its relation to disease activity and analysis of IL-17 concentration in patients with lupus nephritis and non-lupus nephritis.

METHODS

The research enrolled 45 SLE patients according to Systemic Lupus International Collaborating Clinics Classification Criteria (SLICC), and age and sex-matched. The patients underwent full history, clinical examination, laboratory investigation, and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) calculation.

RESULTS

The mean age ± SD of the participants equaled 32 ± 11 years, and serum IL-17 in SLE cases was statistically significantly high (p < 0.001). No statistically significant correlations were reported between disease activity according to SLEDAI and IL-17. In addition, a statistically significant positive correlation was reported between IL-17 and ESR, and a high statistically significant negative correlation was reported between IL-17 and C3 and C4 (P < 0.001). A statistically significant positive correlation was reported between IL-17 and 24-hour urinary proteins with a Pvalue of 0.01.

CONCLUSION

SLE cases demonstrated higher levels of serum IL-17, contributing to SLE pathogenesis. However, no statistically significant difference was reported between IL-17 and Lupus nephritis. IL-17 and SLE activity (SLEDAI) did not correlate. A statistically significant positive relation was reported between IL-17 and 24-hour urinary proteins. Additionally, a high statistically significant negative correlation was reported between IL-17 and C3 and C4.

Complement component C3 is associated with body composition parameters and sarcopenia in community-dwelling older adults: a cross-sectional study in Japan

BACKGROUND

Chronic inflammation is a factor in the pathogenesis of sarcopenia, which is characterized by low muscle mass and reduced strength. Complement C3 is important in the management of the immune network system. This study seeks to determine the relationship between serum C3 levels and body composition and sarcopenia-related status in community-dwelling older adults.

METHODS

Study participants were 269 older adults living in rural Japan. A bioelectrical impedance analysis device was used to measure body composition parameters including body mass index (BMI), body fat percentage, waist-hip-ratio, and appendicular skeletal muscle mass index (SMI). Muscle function was measured by handgrip strength and 6-m walking speed. The correlation coefficients for C3 level and measurements were calculated using Pearson correlation analysis. Participants were categorized into normal, pre-sarcopenia, dynapenia, or sarcopenia groups. Sarcopenia was defined according to 2019 Asian Working Group for Sarcopenia definition, dynapenia was defined as low muscle function without low muscle mass, and pre-sarcopenia was defined as the presence of low muscle mass only. The C3 threshold score for sarcopenia status was evaluated by receiver operating characteristic curve (ROC) analysis.

RESULTS

Significant positive correlations were found between C3 and BMI, body fat percentage, and waist-hip ratio in both sexes, and further positive correlations with SMI were found in women. The relationship with body fat percentage was particularly strong. Body composition measurements (BMI, body fat percentage, and waist- hip ratio) and C3 levels were lowest in the sarcopenia group compared with the others. ROC analysis showed that the significant threshold of C3 for discriminating between the normal and sarcopenia groups was 105 mg/dL. Multiple logistic regression analysis showed that participants with C3 < 105 mg/dL had an odds ratio of 3.27 (95% confidence interval, 1.49-7.18) for sarcopenia adjusted by sex, age and body fat percentage.

CONCLUSION

C3 levels are suggested to be related to body composition and pathophysiological functions of sarcopenia. C3 is expected to become a useful biomarker for sarcopenia, for predicting the onset of the disease and for predicting the effectiveness of interventions.

Using Carbon Stable Isotopes to Study C3 and C4 Photosynthesis: Models and Calculations

Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13C photosynthetic discrimination. Beginning in the twenty-first century, laser absorption spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available. This has allowed collection of large data sets at lower cost and with unprecedented temporal resolution. More data and accompanying knowledge have permitted refinement of 13C discrimination model equations, but often at the expense of increased model complexity and difficult parametrization. This chapter describes instantaneous online measurements of 13C photosynthetic discrimination, provides recommendations for experimental setup, and presents a thorough compilation of equations available to researchers. We update our previous 2018 version of this chapter by including recently improved descriptions of (photo)respiratory processes and associated fractionations. We discuss the capabilities and limitations of the diverse 13C discrimination model equations and provide guidance for selecting the model complexity needed for different applications.

Quantifying preferences for urea cycle disorder treatments using a discrete choice experiment

AIMS

Urea cycle disorders (UCDs) can cause ammonia accumulation and central nervous system toxicity. Nitrogen-binding medications can be efficacious, but certain attributes may negatively impact adherence. This study sought to quantify the administration-related attributes influencing overall prescription selection and patient adherence.

METHODS

A web-based, quantitative survey including discrete choice experiment (DCE) methodology captured responses from health care providers for patients with UCDs. A series of hypothetical treatment profile sets with attributes such as route of administration, taste/odor, preparation instructions, packaging, dose measurement, and weight use restrictions were presented. From 16 sets of 3 hypothetical product profiles, respondents evaluated attributes most preferred for prescription selection or patient adherence. Attributes assumed a higher overall preference if relative importance (RI) scores were >16.67% (the value if all attributes were of equal importance). Preference weight scores were assessed. A nine-point Likert scale assessed respondent attitudes, such as satisfaction.

RESULTS

A total of 51 respondents completed the survey. Respondents reported dissatisfaction with current treatments (mean [SD] = 5.4 [1.7]). For prescription selection, four attributes achieved RI >16.67%: taste/odor (24%), weight restrictions (21%), preparation instructions (18%), and route of administration (17%). For adherence, three attributes related to administration achieved RI >16.67%: taste/odor (28%), preparation instructions (21%), and route of administration (17%). Preference weights for "taste/odor masked" were higher than "not taste/odor masked" for prescription selection (mean [SD]; 1.52 [1.10] vs -1.52 [1.10]) and treatment adherence (73.8 [55.2] vs -73.8 [55.2]).

LIMITATIONS

This study contained a relatively small sample size. Survey respondent selection, the use of hypothetical product profiles, and exclusion of non-pharmacologic treatment options could have contributed to potential biases.

CONCLUSIONS

Among attributes tested, taste/odor was the most important attribute influencing overall preference for both prescribing and patient adherence, with taste/odor masking preferred. Optimizing nitrogen-binding medications through masking taste/odor may support improved patient adherence and outcomes in UCDs.

Sex differences in the association between tau PET and cognitive performance in a non-Hispanic White cohort with preclinical AD

INTRODUCTION

We investigated how the associations between tau and cognitive measures differ by sex in the preclinical Alzheimer's disease (AD) stage.

METHODS

A total of 343 cognitively unimpaired, amyloid-positive individuals (205 women, 138 men) who self-identified as non-Hispanic White from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's (A4) Study were included. We assessed sex-stratified associations between 18 F-flortaucipir positron emission tomography (PET) standardized uptake value ratio (SUVR) in the meta-temporal region and Preclinical Alzheimer's Cognitive Composite (PACC) and Computerized Cognitive Composite (C3) components.

RESULTS

We observed that higher tau level was significantly associated with worse cognitive performance only in women: PACC and its components except for Mini-Mental State Examination (MMSE) and C3 components: First Letter Name Recall (FNLT) and One-Card Learning Reaction Time (OCL RT). These associations except for FNLT were apolipoprotein E (APOE) ε4 independent.

DISCUSSION

Women show stronger associations between tau PET and cognitive outcomes in preclinical AD. These findings have important implications for sex-specific tau-targeted preventive AD clinical trials.

HIGHLIGHTS

The tau positron emission tomography (PET) signal in the meta-temporal region was associated with poor cognitive performance in preclinical Alzheimer's disease (AD). After sex stratification, the associations between regional tau PET and cognitive outcomes were observed only in women. The associations between tau PET and some cognitive outcomes were independent of apolipoprotein E (APOE) ε4.

Silencing HE4 alleviates the renal fibrosis in lupus nephritis mice by regulating the C3/MMPs/prss axis

To explore the regulatory effect of human epididymis protein 4 (HE4) on renal fibrosis in mice with lupus nephritis (LN) and the underlying mechanism. Ten-week old MRL/LPR mice were injected with HE4 shRNA adenovirus vector through the renal pelvis for 5 days. Renal tissues were extracted for HE and Masson staining to evaluate pathological changes and fibrosis in lupus nephritis mice. The level of urine protein was measured using a biochemical analyzer, while the expression level of HE4 and p-NF-κB p65 in renal tissues was visualized using an immunofluorescence assay. The level of β2-microglobulin (β2-MG), neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule 1 (Kim-1) was determined by the immunohistochemical assay. Western blotting was used to determine the levels of C3, HE4, matrix metalloproteinase-2 (MMP2), MMP9, p-p65, prss23, and prss35 in renal tissues. Compared to wild-type C57BL/6 mice, MRL/LPR mice showed a marked increase in the number of glomeruli, hyperplasic basement membrane, severe infiltration of inflammatory cells in renal tubules and glomeruli, obvious necrosis in glomeruli, elevated fibrosis levels, and increased levels of urine protein, β2-MG, NGAL, Kim-1, C3, HE4, MMP2, MMP9, and p-p65; and decreased levels of prss23 and prss35 were observed in MRL/LPR mice. After the administration of the HE4 shRNA adenovirus vector, the repaired structure of renal tubules and glomeruli improved infiltration of inflammatory cells, reduced collagen fiber and urine protein, suppressed levels of C3, HE4, MMP2, MMP9, and p-P65, and facilitated the expression of prss23 and prss35 which were observed. Silencing HE4 improved renal fibrosis and inhibited inflammation in mice with lupus nephritis, which may play a role in inhibiting C3/MMPs and promoting prss-related protein expression.

The correlates of neonatal complement component 3 and 4 protein concentrations with a focus on psychiatric and autoimmune disorders

Complement components have been linked to schizophrenia and autoimmune disorders. We examined the association between neonatal circulating C3 and C4 protein concentrations in 68,768 neonates and the risk of six mental disorders. We completed genome-wide association studies (GWASs) for C3 and C4 and applied the summary statistics in Mendelian randomization and phenome-wide association studies related to mental and autoimmune disorders. The GWASs for C3 and C4 protein concentrations identified 15 and 36 independent loci, respectively. We found no associations between neonatal C3 and C4 concentrations and mental disorders in the total sample (both sexes combined); however, post-hoc analyses found that a higher C3 concentration was associated with a reduced risk of schizophrenia in females. Mendelian randomization based on C4 summary statistics found an altered risk of five types of autoimmune disorders. Our study adds to our understanding of the associations between C3 and C4 concentrations and subsequent mental and autoimmune disorders.

Comparative analysis of immunological biomarkers in COVID-19 and bacterial pneumonia

Coronavirus disease 2019 (COVID-19) is a severe and infectious respiratory condition caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This case-control study aimed to evaluate serum levels of various immunological markers in patients with COVID-19 compared to those with bacterial pneumonia and a healthy control group. Serum samples were collected from adult participants across various COVID-19 isolation centers, including Kassala State and Ahmed Gasim Hospital, between April and June 2021. The study included 70 patients diagnosed with COVID-19, 30 with bacterial pneumonia, and 50 healthy controls. Serum levels of C-reactive protein (CRP), complement components C3 and C4, and cytokines IL-8, IL-10, IL-12, TNF-α, and IFN-γ were measured using standard reagent kits. Serum level of CRP was significantly elevated in both bacterial pneumonia and COVID-19 but significantly higher among patients with bacterial pneumonia. C3 and C4 were also increased in both patient groups, with C3 significantly higher in bacterial pneumonia. IL-8, IL-10, IL-12, TNF-α, and IFN-γ were significantly increased in bacterial pneumonia and SARS-Cov-2 compared to healthy controls. However, IFN-γ was significantly increased among patients with COVID-19 than patients with bacterial pneumonia. This study highlights the potential significant impact of COVID-19 on the immunological biomarkers investigated.

Is the central complement component C3 altered in the synergy of HIV infection and preeclampsia?

Objective

In light of complement activation in preeclampsia and HIV infection, this study evaluates the concentration of complement component 3 (C3) in HIV-associated preeclampsia.

Method

The study population (n = 76) was equally stratified by pregnancy type (normotensive pregnant and preeclampsia) and by HIV status (HIV positive and HIV negative). The plasma concentration of C3 was determined using a Bioplex immunoassay procedure.

Results

We report a significant increase in C3 concentration in the HIV-negative versus the HIV-positive groups (p < 0.05), regardless of pregnancy type. However, based on pregnancy type and irrespective of HIV status, C3 concentration was similar between normotensive versus preeclampsia. Concentration of C3 was significantly increased in the HIV-positive preeclamptic compared HIV-negative preeclamptic groups (p = 0.04). The correlation of C3 with all study groups was non-significant.

Conclusion

This study demonstrates that C3 was upregulated in HIV-associated PE compared to HIV- associated normotensive pregnancies. The dysregulation of C3 expression by HIV infection may be attributed to antiretroviral therapy.

Effects of heat shock protein 90 on complement activation in myocardial ischemia/reperfusion injury after pioglitazone preconditioning

BACKGROUND

Heat shock protein 90 (HSP90) appears to have a pivotal function in ischemic preconditioning. Pioglitazone preconditioning (PioC) attenuates myocardial ischemia/reperfusion (I/R) injuries.

OBJECTIVES

The current study aims to investigate the role of HSP90, complement C3 and C5a, and nuclear factor kappa-B (NF-κB) in PioC-induced cardioprotection.

MATERIAL AND METHODS

A total of 80 rats were randomly categorized into 4 groups, as follows: sham, I/R, PioC, and PioC+HSP90 inhibitor geldanamycin (PioC+GA). The sham group rats had a thoracotomy, in which the ligature was passed by the heart with no ligation (150 min). The other 3 groups were exposed to ischemia (30 min) followed by reperfusion (2 h). In the PioC group, pioglitazone (3 mg/kg) was administered intravenously 24 h before ischemia. In the PioC+GA group, after being pretreated with pioglitazone, GA was administered (intraperitoneally, 1 mg/kg) 30 min before ischemia. Myocardial infarct sizes (ISs), apoptosis rates, creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and cardiac troponin I (cTnI) serum levels were determined. The HSP90, C3, NF-κB, C5a, B-cell lymphoma-2 (Bcl-2), and Bax expression levels, as well as interleukin (IL)-1β, IL-6, intercellular cell adhesion molecule-1 (ICAM-1), and tumor necrosis factor alpha (TNF-α) mRNA levels were measured.

RESULTS

The myocardial ISs, serum CK-MB, cTnI and LDH levels, apoptosis rates, IL-1β, IL-6, TNF-α, ICAM-1 release, as well as Bax, C5a, C3, and NF-κB protein expression were considerably lower in the PioC group than in the I/R group (p < 0.05). The Bcl-2 and HSP90 expression was higher in the PioC group than in the I/R group (p < 0.05). Geldanamycin inhibited the effects of PioC. These data strongly demonstrate that the PioC-induced is dependent upon HSP90 activity.

CONCLUSIONS

The HSP90 is indispensable for PioC-mediated cardioprotection. The HSP90 attenuates I/R-induced ISs, apoptosis of cardiomyocytes and myocardial inflammation through C3, C5a and NF-κB activation inhibition.

A neuron-immune circuit regulates neurodegeneration in the hindbrain and spinal cord of Arf1-ablated mice

Neuroimmune connections have been revealed to play a central role in neurodegenerative diseases (NDs). However, the mechanisms that link the central nervous system (CNS) and peripheral immune cells are still mostly unknown. We recently found that specific ablation of the Arf1 gene in hindbrain and spinal cord neurons promoted NDs through activating the NLRP3 inflammasome in microglia via peroxided lipids and adenosine triphosphate (ATP) releasing. Here, we demonstrate that IL-1β with elevated chemokines in the neuronal Arf1-ablated mouse hindbrain and spinal cord recruited and activated γδ T cells in meninges. The activated γδ T cells then secreted IFN-γ that entered into parenchyma to activate the microglia-A1 astrocyte-C3-neuronal C3aR neurotoxic pathway. Remarkably, the neurodegenerative phenotypes of the neuronal Arf1-ablated mice were strongly ameliorated by IFN-γ or C3 knockout. Finally, we show that the Arf1-reduction-induced neuroimmune-IFN-γ-gliosis pathway exists in human NDs, particularly in amyotrophic lateral sclerosis and multiple sclerosis. Together, our results uncover a previously unknown mechanism that links the CNS and peripheral immune cells to promote neurodegeneration.

Mice deficient in complement C3 are protected against recognition memory deficits and astrogliosis induced by status epilepticus

Introduction

Status epilepticus (SE) can significantly increase the risk of temporal lobe epilepsy (TLE) and cognitive comorbidities. A potential candidate mechanism underlying memory defects in epilepsy may be the immune complement system. The complement cascade, part of the innate immune system, modulates inflammatory and phagocytosis signaling, and has been shown to contribute to learning and memory dysfunctions in neurodegenerative disorders. We previously reported that complement C3 is elevated in brain biopsies from human drug-resistant epilepsy and in experimental rodent models. We also found that SE-induced increases in hippocampal C3 levels paralleled the development of hippocampal-dependent spatial learning and memory deficits in rats. Thus, we hypothesized that SE-induced C3 activation contributes to this pathophysiology in a mouse model of SE and acquired TLE.

Methods

In this study C3 knockout (KO) and wild type (WT) mice were subjected to one hour of pilocarpine-induced SE or sham conditions (control; C). Following a latent period of two weeks, recognition memory was assessed utilizing the novel object recognition (NOR) test. Western blotting was utilized to determine the protein levels of C3 in hippocampal lysates. In addition, we assessed the protein levels and distribution of the astrocyte marker glial fibrillary acidic protein (GFAP).

Results

In the NOR test, control WT + C or C3 KO + C mice spent significantly more time exploring the novel object compared to the familiar object. In contrast, WT+SE mice did not show preference for either object, indicating a memory defect. This deficit was prevented in C3 KO + SE mice, which performed similarly to controls. In addition, we found that SE triggered significant increases in the protein levels of GFAP in hippocampi of WT mice but not in C3 KO mice.

Discussion

These findings suggest that ablation of C3 prevents SE-induced recognition memory deficits and that a C3-astrocyte interplay may play a role. Therefore, it is possible that enhanced C3 signaling contributes to SE-associated cognitive decline during epileptogenesis and may serve as a potential therapeutic target for treating cognitive comorbidities in acquired TLE.

Increased infiltration of CD4+ T cell in the complement deficient lymphedema model

BACKGROUND

Lymphedema is an intractable disease that can be caused by injury to lymphatic vessels, such as by surgical treatments for cancer. It can lead to impaired joint mobility in the extremities and reduced quality of life. Chronic inflammation due to infiltration of various immune cells in an area of lymphedema is thought to lead to local fibrosis, but the molecular pathogenesis of lymphedema remains unclear. Development of effective therapies requires elucidation of the immunological mechanisms involved in the progression of lymphedema. The complement system is part of the innate immune system which has a central role in the elimination of invading microbes and acts as a scavenger of altered host cells, such as apoptotic and necrotic cells and cellular debris. Complement-targeted therapies have recently been clinically applied to various diseases caused by complement overactivation. In this context, we aimed to determine whether complement activation is involved in the development of lymphedema.

RESULTS

Our mouse tail lymphedema models showed increased expression of C3, and that the classical or lectin pathway was locally activated. Complement activation was suggested to be involved in the progression of lymphedema. In comparison of the C3 knockout (KO) mouse lymphedema model and wild-type mice, there was no difference in the degree of edema at three weeks postoperatively, but the C3 KO mice had a significant increase of TUNEL+ necrotic cells and CD4+ T cells. Infiltration of macrophages and granulocytes was not significantly elevated in C3 KO or C5 KO mice compared with in wild-type mice. Impaired opsonization and decreased migration of macrophages and granulocytes due to C3 deficiency should therefore induce the accumulation of dead cells and may lead to increased infiltration of CD4+ T cells.

CONCLUSIONS

Vigilance for exacerbation of lymphedema is necessary when surgical treatments have the potential to injure lymphatic vessels in patients undergoing complement-targeted therapies or with complement deficiency. Future studies should aim to elucidate the molecular mechanism of CD4+ T cell infiltration by accumulated dead cells.

The correlation of anxiety and depression with C3 and C4 Levels and systemic lupus erythematosus activity

BACKGROUND

Anxiety and depression are psychosomatic disorders that are frequently observed in chronic conditions such as systemic lupus erythematosus (SLE). Anxiety and depression can be induced by immunological and neurotransmitter dysregulation, which is characterized by hypothalamic-pituitary-adrenal (HPA) axis dysfunction, production of proinflammatory cytokines, and activation of complement in the blood, such as C3 and C4. The causes of anxiety and depression in SLE are complex, ranging from neuropsychiatric involvement to drug adverse effects. Detecting anxiety and depression symptoms in SLE patients is critical to preventing disability from impacting quality of life.

OBJECTIVE

To assess the relationship between anxiety and depression symptomatology, SLE disease activity with levels of C3 and C4 in Cipto Mangunkusumo National Hospital.

METHODS

This study used a cross-sectional design. The study included 120 SLE patients from Cipto Mangunkusumo National Hospital, aged 18 to 60 years. All patients were requested to complete a Hospital Anxiety and Depression Scale (HADS) questionnaire to assess their anxiety and depression symptoms. Subjects with anxiety and depression were assessed for disease activity using the Mexican Systemic Lupus Erythematosus Systemic Disease Activity (Mex-SLEDAI), and blood samples were collected to test complement C3 and C4 levels. Spearman's correlation test was used to examine the relationship between HADS scores, Mex-SLEDAI, and C3 and C4 levels.

RESULTS

The results of the study showed a very weak statistically significant negative correlation between anxiety symptoms based on HADS and C3 levels (r = -0.189; p = 0.038) and a weak correlation between anxiety symptoms and C4 levels (r = -204; p = 0.026). Depressive symptoms based on HADS revealed a very poor connection and no statistical significance with levels of C3 (r = -0.056; p = 0.546) and C4 (r = -0.068; p = 0.461). Anxiety (r = 0.06; p = 0.173) and depression (r = 0.031; p = 0.753) symptoms have a weak and insignificant positive connection with SLE activity.

CONCLUSION

C3 and C4 serum levels appeared to decrease when the presence of anxious symptoms increased. There was no significant correlation in SLE disease activity between anxious and depressed patients.

Diurnal decline in photosynthesis and stomatal conductance in several tropical species

Photosynthesis (A) and stomatal conductance (gs) change diurnally due to internal signals, but the effects of diurnal rhythms on dynamic photosynthetic behavior are understudied. We examined diurnal changes in A and gs in ten tropical species: across species, there was a tendency for A and gs to decline diurnally when these were repeatedly measured under either steady-state or fluctuating irradiance conditions. We then examined in more detail the irradiance-induced kinetics of gas exchange in a C3 and C4 crop species each, namely fig (Ficus carica) and sugarcane (Saccharum officinarum). During the day, fig showed significantly slower photosynthetic induction and lower gs, as well as a slower gs increase, in the afternoon than in the morning and noon. Sugarcane showed a reduction in steady-state A reached under high irradiance and slower gs increase as well as lower gs reached under high irradiance, but no changes in the rate of photosynthetic induction, in the afternoon, compared to morning and noon. These reductions in the afternoon were not reverted by a dark treatment in the middle of the day, suggesting that the decrease was not proportional to diurnal time-integrated carbon fixation. Repeated exposure to light- and shadeflecks (1000 and 50 μmol m-2 s-1, lasting 20 min each) revealed fundamental differences in stomatal regulation between species: in fig, stomata opened and closed slowly, and their opening became progressively slower under a series of lightflecks, whereas sugarcane showed much faster stomatal opening than closure that was unchanged during the course of the day. Our results highlight that steady-state rates and irradiance-induced kinetics of photosynthesis and stomatal movement change diurnally in most species studied, and that they do so differently in fig and sugarcane.

Revisiting the role of the complement system in intracerebral hemorrhage and therapeutic prospects

Intracerebral hemorrhage (ICH) is a stroke subtype characterized by non-traumatic rupture of blood vessels in the brain, resulting in blood pooling in the brain parenchyma. Despite its lower incidence than ischemic stroke, ICH remains a significant contributor to stroke-related mortality, and most survivors experience poor outcomes that significantly impact their quality of life. ICH has been accompanied by various complex pathological damage, including mechanical damage of brain tissue, hematoma mass effect, and then leads to inflammatory response, thrombin activation, erythrocyte lysis, excitatory amino acid toxicity, complement activation, and other pathological changes. Accumulating evidence has demonstrated that activation of complement cascade occurs in the early stage of brain injury, and the excessive complement activation after ICH will affect the occurrence of secondary brain injury (SBI) through multiple complex pathological processes, aggravating brain edema, and pathological brain injury. Therefore, the review summarized the pathological mechanisms of brain injury after ICH, specifically the complement role in ICH, and its related pathological mechanisms, to comprehensively understand the specific mechanism of different complements at different stages after ICH. Furthermore, we systematically reviewed the current state of complement-targeted therapies for ICH, providing a reference and basis for future clinical transformation of complement-targeted therapy for ICH.

Association of Serum Complement C3 Levels with Severity and Mortality in COVID 19

The severe acute respiratory distress syndrome-associated coronavirus-2 infection can activate innate and adaptive immune responses which may lead to harmful tissue damage, both locally and systemically. C3, a member of complement system of serum proteins, is a major component of innate immune and inflammatory responses. This study is aimed to assess serum C3 as a marker of COVID-19 severity and a predictor of disease progression. A total of 150 COVID-19 patients, confirmed by RT-PCR, and 50 healthy controls were recruited. Serum C3 levels were determined by using direct colorimetric method. Median levels of serum C3 in total cases and controls were 157.8 and 165.7 mg/dL respectively. Serum C3 although not significantly decreased, they were lower in cases when compared to controls. Similarly, significant differences were found between the groups, with severe group (140.6 mg/dL) having low levels of serum C3 protein when compared to mild (161.0 mg/dL) and moderate group (167.1 mg/dL). Interestingly, during hospitalization, significant difference between baseline (admission) and follow-up (discharge) was observed only in patients with moderate disease. Based on our results, lower levels of C3, with an increase in IL-6 and d-dimer levels, are associated with higher odds of mortality. Therefore, we would like to emphasize that measuring serum C3 levels along with other inflammatory markers might give an added advantage in early identification of patients who are prone to having a severe disease course and can help in a more effective follow-up of disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-023-01148-x.

Complement-mediated immune mechanisms in allergy

Allergic conditions are associated with canonical and noncanonical activation of the complement system leading to the release of several bioactive mediators with inflammatory and immunoregulatory properties that regulate the immune response in response to allergens during the sensitization and/or the effector phase of allergic diseases. Further, immune sensors of complement and regulator proteins of the cascade impact on the development of allergies. These bioactive mediators comprise the small and large cleavage fragments of C3 and C5. Here, we provide an update on the multiple roles of immune sensors, regulators, and bioactive mediators of complement in allergic airway diseases, food allergies, and anaphylaxis. A particular emphasis is on the anaphylatoxins C3a and C5a and their receptors, which are expressed on many of the effector cells in allergy such as mast cells, eosinophils, basophils, macrophages, and neutrophils. Also, we will discuss the multiple pathways, by which the anaphylatoxins initiate and control the development of maladaptive type 2 immunity including their impact on innate lymphoid cell recruitment and activation. Finally, we briefly comment on the potential to therapeutically target the complement system in different allergic conditions.

Modelling and analysis of the complement system signalling pathways: roles of C3, C5a and pro-inflammatory cytokines in SARS-CoV-2 infection

The complement system is an essential part of innate immunity. It is activated by invading pathogens causing inflammation, opsonization, and lysis via complement anaphylatoxins, complement opsonin's and membrane attack complex (MAC), respectively. However, in SARS-CoV-2 infection overactivation of complement system is causing cytokine storm leading to multiple organs damage. In this study, the René Thomas kinetic logic approach was used for the development of biological regulatory network (BRN) to model SARS-CoV-2 mediated complement system signalling pathways. Betweenness centrality analysis in cytoscape was adopted for the selection of the most biologically plausible states in state graph. Among the model results, in strongly connected components (SCCs) pro-inflammatory cytokines (PICyts) oscillatory behaviour between recurrent generation and downregulation was found as the main feature of SARS-CoV-2 infection. Diversion of trajectories from the SCCs leading toward hyper-inflammatory response was found in agreement with in vivo studies that overactive innate immunity response caused PICyts storm during SARS-CoV-2 infection. The complex of negative regulators FI, CR1 and DAF in the inhibition of complement peptide (C5a) and PICyts was found desirable to increase immune responses. In modelling role of MAC and PICyts in lowering of SARS-CoV-2 titre was found coherent with experimental studies. Intervention in upregulation of C5a and PICyts by C3 was found helpful in back-and-forth variation of signalling pattern linked with the levels of PICyts. Moreover, intervention in upregulation of PICyts by C5a was found productive in downregulation of all activating factors in the normal SCCs. However, the computational model predictions require experimental studies to be validated by exploring the activation role of C3 and C5a which could change levels of PICyts at various phases of SARS-CoV-2 infection.

Complement component C3 as a new target to lower albuminuria in hypertensive kidney disease

BACKGROUND AND PURPOSE

Complement activation may drive hypertension through its effects on immunity and tissue integrity.

EXPERIMENTAL APPROACH

We examined expression of C3, the central protein of the complement cascade, in hypertension.

KEY RESULTS

Increased C3 expression was found in kidney biopsies and micro-dissected glomeruli of patients with hypertensive nephropathy. Renal single cell RNA sequence data from normotensive and hypertensive patients confirmed expression of C3 in different cellular compartments of the kidney. In angiotensin II (Ang II) induced hypertension renal C3 expression was up-regulated. C3-/- mice revealed a significant lower albuminuria in the early phase of hypertension. However, no difference was found for blood pressure, renal injury (histology, glomerular filtration rate, inflammation) and cardiac injury (fibrosis, weight, gene expression) between C3-/- and wildtype mice after Ang II infusion. Also, in deoxycorticosterone acetate (DOCA) salt hypertension, a significantly lower albuminuria was found in the first weeks of hypertension in C3 deficient mice but no significant difference in renal and cardiac injury. Down-regulation of C3 by C3 targeting GalNAc (n-acetylgalactosamine) small interfering RNA (siRNA) conjugate decreased C3 in the liver by 96% and lowered albuminuria in the early phase but showed no effect on blood pressure and end-organ damage. Inhibition of complement C5 by siRNA showed no effect on albuminuria.

CONCLUSION AND IMPLICATIONS

Increased C3 expression is found in the kidneys of hypertensive mice and men. Genetic and therapeutic knockdown of C3 improved albuminuria in the early phase of hypertension but did not ameliorate arterial blood pressure nor renal and cardiac injury.

TREM2 receptor protects against complement-mediated synaptic loss by binding to complement C1q during neurodegeneration

Triggering receptor expressed on myeloid cells 2 (TREM2) is strongly linked to Alzheimer's disease (AD) risk, but its functions are not fully understood. Here, we found that TREM2 specifically attenuated the activation of classical complement cascade via high-affinity binding to its initiator C1q. In the human AD brains, the formation of TREM2-C1q complexes was detected, and the increased density of the complexes was associated with lower deposition of C3 but higher amounts of synaptic proteins. In mice expressing mutant human tau, Trem2 haploinsufficiency increased complement-mediated microglial engulfment of synapses and accelerated synaptic loss. Administration of a 41-amino-acid TREM2 peptide, which we identified to be responsible for TREM2 binding to C1q, rescued synaptic impairments in AD mouse models. We thus demonstrate a critical role for microglial TREM2 in restricting complement-mediated synaptic elimination during neurodegeneration, providing mechanistic insights into the protective roles of TREM2 against AD pathogenesis.

Complement Inhibitors for Advanced Dry Age-Related Macular Degeneration (Geographic Atrophy): Some Light at the End of the Tunnel?

Geographic atrophy (GA) affects around 5 million individuals worldwide. Genome-wide, histopathologic, in vitro and animal studies have implicated the activation of the complement system and chronic local inflammation in the pathogenesis of GA. Recently, clinical trials have demonstrated that an intravitreal injection of pegcetacoplan, a C3 inhibitor, and avacincaptad pegol, a C5 inhibitor, both statistically significantly reduce the growth of GA up to 20% in a dose-dependent fashion. Furthermore, the protective effect of both pegcetacoplan and avacincaptad appear to increase with time. However, despite these anatomic outcomes, visual function has not improved as these drugs appear to only slow down the degenerative process. Unexpected adverse events included conversion to exudative NV-AMD with both drugs. Occlusive retinal vasculitis and anterior ischemic optic neuropathy have been reported in pegcetacoplan-treated eyes.

Complement Dysregulation in Obese Versus Nonobese Polycystic Ovary Syndrome Patients

INTRODUCTION

Upregulation of complement system factors are reported to be increased in polycystic ovary syndrome (PCOS) and may be due to obesity and insulin resistance rather than inherently due to PCOS. We directly compared complement factors from an obese, insulin-resistant PCOS population to a nonobese, non-insulin-resistant PCOS population in a proteomic analysis to investigate this.

METHODS

Plasma was collected from 234 women (137 with PCOS and 97 controls) from a biobank cohort and compared to a nonobese, non-insulin-resistant population (24 with PCOS and 24 controls). Slow off-rate modified aptamer (SOMA) scan plasma protein measurement was undertaken for the following complement system proteins: C1q, C1r, C2, C3, C3a, iC3b, C3b, C3d, C3adesArg, C4, C4a, C4b, C5, C5a, C5b-6 complex, C8, properdin, factor B, factor D, factor H, factor I, Mannose-binding protein C (MBL), complement decay-accelerating factor (DAF) and complement factor H-related protein 5 (CFHR5).

RESULTS

The alternative pathway of the complement system was overexpressed in both obese and nonobese PCOS, with increased C3 (p < 0.05) and properdin (p < 0.01); additionally, factor B increased in obese PCOS (p < 0.01). For inhibitors of this pathway, factor I was increased (p < 0.01) in both slim and obese PCOS, with an increase in CFHR5 and factor H in obese PCOS (p < 0.01). Complement factors iC3b, C3d and C5a, associated with an enhanced B cell response and inflammatory cytokine release, were increased in both slim and obese PCOS (p < 0.05). C3a and its product, C3adesArg, were both significantly elevated in nonobese PCOS (<0.01) but not altered in obese PCOS. Hyperandrogenemia correlated positively with properdin and iC3b in obese PCOS (p < 0.05) but not in nonobese PCOS. There was no association with insulin resistance. BMI correlated positively in both groups with factor B, factor H and C5a. Additionally, in obese PCOS, BMI correlated with C3d, factor D, factor I, CFHR5 and C5a (p < 0.05), and in nonobese PCOS, BMI correlated with properdin, iC3b, C3, C3adesArg, C3a, C4, C5, C5a and C1q. In obese controls, BMI correlated with C3, C3desArg, C3a, C3d, C4, factor I, factor B, C5a and C5, whilst in nonobese controls, BMI only correlated negatively with C1q. Comparison of nonobese and obese PCOS showed that properdin, C3b, iC3b, C4A, factor D, factor H and MBL differed.

CONCLUSION

The upregulation of the alternative complement pathway was seen in nonobese PCOS and was further exacerbated in obese PCOS, indicating that this is an inherent feature of the pathophysiology of PCOS that is worsened by obesity and is reflected in the differences between the nonobese and obese PCOS phenotypes. However, the increase in the complement proteins associated with activation was counterbalanced by upregulation of complement inhibitors; this was evident in both PCOS groups, suggesting that insults, such as a cardiovascular event or infection, that cause activation of complement pathways may be amplified in PCOS.

Does Ending a Posterior Construct Proximally at C2 Versus C3 Impact Patient Reported Outcomes in Degenerative Cervical Myelopathy Patients up to 24 months After the Surgery?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The primary objective was to evaluate the impact of the upper instrumented level (UIV) being at C2 vs C3 in posterior cervical construct on patient reported outcomes (PROs) up to 24 months after surgery for cervical degenerative myelopathy (DCM). Secondary objectives were to compare operative time, intra-operative blood loss (IOBL), length of stay (LOS), adverse events (AEs) and re-operation.

METHODOLOGY

Patients who underwent a posterior cervical instrumented fusion (3 and + levels) with a C2 or C3 UIV, with 24 months follow-up were analyzed. PROs (NDI, EQ5D, SF-12 PCS/MCS, NRS arm/neck pain) were compared using ANCOVA. Operative duration, IOBL, AEs, and re-operation were compared. Subgroup analysis was performed on patient presenting with pre-operative malalignment (cervical sagittal vertical axis ≥40 mm and/or T1slope- cervical lordosis >15°).

RESULTS

173 patients were included, of which 41 (24%) had a C2 UIV and 132 (76%) a C3 UIV. There was no statistically significant difference between the groups for the changes in PROs up to 24 months. Subgroup analysis of patients with pre-operative malalignment showed a trend towards greater improvement in the NDI at 12 months with a C2 UIV (P = .054). Operative time, IOBL and peri-operative AEs were more in C2 group (P < .05). There was no significant difference in LOS and re-operation (P > .05).

CONCLUSION

In this observational study, up to 24 months after surgery for posterior cervical fusion in DCM greater than 3 levels, PROs appear to evolve similarly.

Integrated glycomics and genetics analyses reveal a potential role for N-glycosylation of plasma proteins and IgGs, as well as the complement system, in the development of type 1 diabetes

AIMS/HYPOTHESIS

We previously demonstrated that N-glycosylation of plasma proteins and IgGs is different in children with recent-onset type 1 diabetes compared with their healthy siblings. To search for genetic variants contributing to these changes, we undertook a genetic association study of the plasma protein and IgG N-glycome in type 1 diabetes.

METHODS

A total of 1105 recent-onset type 1 diabetes patients from the Danish Registry of Childhood and Adolescent Diabetes were genotyped at 183,546 genetic markers, testing these for genetic association with variable levels of 24 IgG and 39 plasma protein N-glycan traits. In the follow-up study, significant associations were validated in 455 samples.

RESULTS

This study confirmed previously known plasma protein and/or IgG N-glycosylation loci (candidate genes MGAT3, MGAT5 and ST6GAL1, encoding beta-1,4-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase, alpha-1,6-mannosylglycoprotein 6-beta-N-acetylglucosaminyltransferase and ST6 beta-galactoside alpha-2,6-sialyltransferase 1 gene, respectively) and identified novel associations that were not previously reported for the general European population. First, novel genetic associations of IgG-bound glycans were found with SNPs on chromosome 22 residing in two genomic intervals close to candidate gene MGAT3; these include core fucosylated digalactosylated disialylated IgG N-glycan with bisecting N-acetylglucosamine (GlcNAc) (p_discovery=7.65 × 10^-12, p_replication=8.33 × 10^-6 for the top associated SNP rs5757680) and core fucosylated digalactosylated glycan with bisecting GlcNAc (p_discovery=2.88 × 10^-10, p_replication=3.03 × 10^-3 for the top associated SNP rs137702). The most significant genetic associations of IgG-bound glycans were those with MGAT3. Second, two SNPs in high linkage disequilibrium (missense rs1047286 and synonymous rs2230203) located on chromosome 19 within the protein coding region of the complement C3 gene (C3) showed association with the oligomannose plasma protein N-glycan (p_discovery=2.43 × 10^-11, p_replication=8.66 × 10^-4 for the top associated SNP rs1047286).

CONCLUSIONS/INTERPRETATION

This study identified novel genetic associations driving the distinct N-glycosylation of plasma proteins and IgGs identified previously at type 1 diabetes onset. Our results highlight the importance of further exploring the potential role of N-glycosylation and its influence on complement activation and type 1 diabetes susceptibility.

Real-time mechanisms of exacerbated synaptic remodeling by microglia in acute models of systemic inflammation and tauopathy

Remodeling of synapses by microglia is essential for synaptic plasticity in the brain. However, during neuroinflammation and neurodegenerative diseases, microglia can induce excessive synaptic loss, although the precise underlying mechanisms are unknown. To directly observe microglia-synapse interactions under inflammatory conditions, we performed in vivo two-photon time-lapse imaging of microglia-synapse interactions after bacterial lipopolysaccharide administration to model systemic inflammation, or after inoculation of Alzheimer's disease (AD) brain extracts to model disease-associated neuroinflammatory microglial response. Both treatments prolonged microglia-neuron contacts, decreased basal surveillance of synapses and promoted synaptic remodeling in response to synaptic stress induced by focal single-synapse photodamage. Spine elimination correlated with the expression of microglial complement system/phagocytic proteins and the occurrence of synaptic filopodia. Microglia were observed contacting spines, then stretching and phagocytosing spine head filopodia. Thus, in response to inflammatory stimuli microglia exacerbated spine remodeling through prolonged microglial contact and elimination of spines 'tagged' by synaptic filopodia.

C3aR in astrocytes mediates post-thoracotomy pain by inducing A1 astrocytes in male rats

BACKGROUND

Astrocyte activation, which is polarized into classical neurotoxic A1, neuroprotective A2, A-pan, etc., is thought to be involved in the transition from acute to chronic post-thoracotomy pain. The C3aR receptor associated with astrocyte-neuron and -microglia interactions is necessary for A1 astrocytes polarization. This study aimed to determine whether C3aR in astrocytes mediates post-thoracotomy pain by inducing A1 expression in a rat thoracotomy pain model.

METHODS

A rat thoracotomy pain model was employed. The mechanical withdraw threshold was measured to evaluate pain behavior. Lipopolysaccharide (LPS) was injected intraperitoneally to induce A1. Intrathecal injection of AAV2/9-rC3ar1 shRNA-GFAP was used to knock down in vivo C3aR expression in astrocytes. The expression of associated phenotypic markers before and after intervention was assessed by RT-PCR, western blot, co-immunofluorescence, and single-cell RNA sequencing.

RESULTS

C3aR downregulation was found to inhibit LPS-induced A1 astrocytes activation, decrease the expression of C3aR, C3, and GFAP, which were activated from acute to chronic pain, and alleviate the mechanical withdrawal threshold and chronic pain incidence. In addition, more A2 astrocytes were activated in the model group that did not develop chronic pain. C3aR downregulation increased the number of A2 astrocytes upon LPS exposure. Knockdown of C3aR also decreased the activation of M1 microglia induced by LPS or thoracotomy.

CONCLUSIONS

Our study confirmed that C3aR-induced A1 polarization contributes to chronic post-thoracotomy pain. Inhibition of A1 activation via C3aR downregulation increases anti-inflammatory A2 and decreases pro-inflammatory M1 activation, which may also be involved in the mechanism of chronic post-thoracotomy pain.

Targeted genotyping of COVID-19 patients reveals a signature of complement C3 and factor B coding SNPs associated with severe infection

We have attempted to explore further the involvement of complement components in the host COVID-19 (Coronavirus disease-19) immune responses by targeted genotyping of COVID-19 adult patients and analysis for missense coding Single Nucleotide Polymorphisms (coding SNPs) of genes encoding Alternative pathway (AP) components. We have identified a small group of common coding SNPs in Survivors and Deceased individuals, present in either relatively similar frequencies (CFH and CFI SNPs) or with stark differences in their relative abundance (C3 and CFB SNPs). In addition, we have identified several sporadic, potentially protective, coding SNPs of C3, CFB, CFD, CFH, CFHR1 and CFI in Survivors. No coding SNPs were detected for CD46 and CD55. Our demographic analysis indicated that the C3 rs1047286 or rs2230199 coding SNPs were present in 60 % of all the Deceased patients (n = 25) (the rs2230199 in 67 % of all Deceased Males) and in 31 % of all the Survivors (n = 105, p = 0.012) (the rs2230199 in 25 % of all Survivor Males). When we analysed these two major study groups using the presence of the C3 rs1047286 or rs2230199 SNPs as potential biomarkers, we noticed the complete absence of the protective CFB rs12614 and rs641153 coding SNPs from Deceased Males compared to Females (p = 0.0023). We propose that in these individuals, C3 carrying the R102G and CFB lacking the R32W or the R32Q amino acid substitutions, may contribute to enhanced association dynamics of the C3bBb AP pre-convertase complex assembly, thus enabling the exploitation of the activation of the Complement Alternative pathway (AP) by SARS-CoV-2.

Microglia PKM2 Mediates Neuroinflammation and Neuron Loss in Mice Epilepsy through the Astrocyte C3-Neuron C3R Signaling Pathway

Epilepsy is a neurological disease and approximately 30% of patients have failed to respond to current anti-epilepsy drugs. The neuroinflammation mechanism has raised increasing concerns and been regarded as the novel treatment strategy in epilepsy, but the target molecules require further research. Pyruvate kinase isoform 2 (PKM2) is well studied in peripheral inflammation, but its role in epilepsy neuroinflammation remains unclear. We knocked down microglia PKM2 in the hippocampus using a stereotaxic adeno-associated virus (AAV) microinjection and established a pilocarpine-induced status epilepticus (PISE) model. Racine score was used to evaluate the seizure grade. Next, we used WB, Multiplex tyramide signal amplification (TSA) staining and other methods to determine neuroinflammation and the complement component 3 (C3)-C3aR interaction in primary microglia. Results showed that microglia PKM2 knockdown reduced epilepsy grade and rescued neuron loss. Mechanistically, PKM2 knockdown inhibited microglia activation and inflammation factor secretion through suppressing p65 expression and phosphorylation. The reduced microglia C1q, TNF-α, and IL-1α were responsible for the decreased astrocyte C3 expression and the following neuron damage caused by the C3-C3aR interaction. Our data suggest that microglia PKM2 inhibition ameliorates neuroinflammation and neuron loss through C3-C3aR interaction in epilepsy, which provides an attractive target for the intervention of damaged neuron-glia crosstalk in epilepsy.

The primitive complement system in molluscs

The complement system is an important immune defense mechanism that plays essential roles in both innate and adaptive immunity of vertebrates. Since complement components are identified in deuterostome and even primitive protostome species, the origin and evolution of complement system in invertebrates have been of great interest. Recently, research on the complement system in mollusc immunity has been increasing due to their importance in worldwide aquaculture, and their phylogenetic position. Complement components including C3, C1q domain containing protein (C1qDCP), C-type lectin (CTL), ficolin-like, mannose-binding lectin (MBL)-associated serine proteases like (MASPL), and factor B have been identified, suggesting the existence of complement system in molluscs. The lectin pathway has been outlined in molluscs, which is initiated by CTL with CCP domain and MASPL protein to generate C3 cleavage fragments. The molluscan C1qDCP exhibits the capability to bind human IgG, indicating the existence of possible C1qDCP-mediated activation pathway in molluscs. The activation of C3 regulates the expressions of immune effectors (cytokines and antibacterial peptides), mediates the haemocyte phagocytosis, and inhibits the bacterial growth. Some MACPF domain containing proteins may replace the missing terminal pathway in molluscs. This article provides a review of complement system in molluscs, including its components, activation mechanisms and functions in the immune response of molluscs.

The evolution and expression of stomatal regulators in C3 and C4 crops: Implications on the divergent drought tolerance

Drought stress is a major environmental hazard. Stomatal development is highly responsive to abiotic stress and has been used as a cellular marker for drought-tolerant crop selection. C3 and C4 crops have evolved into different photosynthetic systems and physiological responses to water deficits. The genome sequences of maize, sorghum, and sugarcane make it possible to explore the association of the stomatal response to drought stress with the evolution of the key stomatal regulators. In this study, phylogenic analysis, gene expression analysis and stomatal assay under drought stress were used to investigate the drought tolerance of C3 and C4 plants. Our data shows that C3 and C4 plants exhibit different drought responses at the cellular level. Drought represses the growth and stomatal development of C3 crops but has little effect on that of C4 plants. In addition, stomatal development is unresponsive to drought in drought-tolerant C3 crops but is repressed in drought-tolerant C4 plants. The different developmental responses to drought in C3 and C4 plants might be associated with the divergent expression of their SPEECHLESS genes. In particular, C4 crops have evolved to generate multiple SPEECHLESS homologs with different genetic structure and expression levels. Our research provides not only molecular evidence that supports the evolutionary history of C4 from C3 plants but also a possible molecular model that controls the cellular response to abiotic stress in C3 and C4 crops.

Helicobacter pylori-derived outer membrane vesicles contribute to Alzheimer's disease pathogenesis via C3-C3aR signalling

The gut microbiota represents a diverse and dynamic population of microorganisms that can influence the health of the host. Increasing evidence supports the role of the gut microbiota as a key player in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). Unfortunately, the mechanisms behind the interplay between gut pathogens and AD are still elusive. It is known that bacteria-derived outer membrane vesicles (OMVs) act as natural carriers of virulence factors that are central players in the pathogenesis of the bacteria. Helicobacter pylori (H. pylori) is a common gastric pathogen and H. pylori infection has been associated with an increased risk to develop AD. Here, we are the first to shed light on the role of OMVs derived from H. pylori on the brain in healthy conditions and on disease pathology in the case of AD. Our results reveal that H. pylori OMVs can cross the biological barriers, eventually reaching the brain. Once in the brain, these OMVs are taken up by astrocytes, which induce activation of glial cells and neuronal dysfunction, ultimately leading to exacerbated amyloid-β pathology and cognitive decline. Mechanistically, we identified a critical role for the complement component 3 (C3)-C3a receptor (C3aR) signalling in mediating the interaction between astrocytes, microglia and neurons upon the presence of gut H. pylori OMVs. Taken together, our study reveals that H. pylori has a detrimental effect on brain functionality and accelerates AD development via OMVs and C3-C3aR signalling.

Complement, but Not Platelets, Plays a Pivotal Role in the Outcome of Mucormycosis In Vivo

BACKGROUND

Mucormycetes, a heterogeneous group of fungi, induce a life-threatening disease called mucormycosis. Immune deficiencies represent a major risk factor; hence, we wanted to illuminate the role of complement and platelets in the defense against mucormycetes.

METHODS

Rhizopus arrhizus (Ra), Rhizopus microsporus (Rm), Lichtheimia ramosa (Lr), Lichtheimia corymbifera (Lc), Rhizomucor pusillus (Rmp), and Mucor circinelloides (Mc) spores were opsonized with human and mouse serum, and C1q, C3c, and terminal complement complex (C5b-9) deposition was measured. Additionally, thrombocytopenic, C3-deficient, or C6-deficient mice were intravenously infected with selected isolates. Survival and immunological parameters were monitored, and fungal burden was determined and compared to that of immunocompetent and neutropenic mice.

RESULTS

In vitro experiments showed significant differences in complement deposition between mucormycetes. Mc isolates bound up to threefold more human C5b-9 than other mucormycetes. Lr, Lc, and Mc bound high levels of murine C3c, whereas human C3c deposition was reduced on Mc compared to Lr and Lc. Murine C3c deposition negatively correlated with virulence. Complement deficiencies and neutropenia, but not thrombocytopenia, were shown to be a risk factor for a lethal outcome.

CONCLUSION

Complement deposition varies between mucormycetes. Additionally, we demonstrated that complement and neutrophilic granulocytes, but not platelets, play an important role in a murine model of disseminated mucormycosis.

C3-Symmetric Ligands in Drug Design: When the Target Controls the Aesthetics of the Drug

A number of proteins are able to adopt a homotrimeric spatial conformation. Among these structures, this feature appears as crucial for biologic targets, since it facilitates the design of C3-symmetric ligands that are especially suitable for displaying optimized ligand-target interactions and therapeutic benefits. Additionally, DNA as a therapeutic target, even if its conformation into a superhelix does not correspond to a C3-symmetry, can also take advantage of these C3-symmetric ligands for better interactions and therapeutic effects. For the moment, this opportunity appears to be under-exploited, but should become more frequent with the discovery of new homotrimeric targets such as the SARS-CoV2 spike protein. Besides their potential therapeutic interest, the synthetic access to these C3-symmetric ligands often leads to chemical challenges, although drug candidates with an aesthetic structure are generally obtained.

Microglial heterogeneity and complement component 3 elimination within emerging multisensory midbrain compartments during an early critical period

The lateral cortex of the inferior colliculus (LCIC) is a midbrain shell region that receives multimodal inputs that target discrete zones of its compartmental (modular-matrix) framework. This arrangement emerges perinatally in mice (postnatal day, P0-P12) as somatosensory and auditory inputs segregate into their respective modular and matrix terminal patterns. Microglial cells (MGCs) perform a variety of critical functions in the developing brain, among them identifying areas of active circuit assembly and selectively pruning exuberant or underutilized connections. Recent evidence in other brain structures suggest considerable MGC heterogeneity across the lifespan, particularly during established developmental critical periods. The present study examines the potential involvement of classical complement cascade signaling (C3-CR3/CD11b) in refining early multisensory networks, and identifies several microglial subsets exhibiting distinct molecular signatures within the nascent LCIC. Immunostaining was performed in GAD67-green fluorescent protein (GFP) and CX3CR1-GFP mice throughout and after the defined LCIC critical period. GAD labeling highlights the emerging LCIC modularity, while CX3CR1 labeling depicts MGCs expressing the fractalkine receptor. C3 expression is widespread throughout the LCIC neuropil early on, prior to its conspicuous absence from modular zones at P8, and more global disappearance following critical period closure. CD11b-expressing microglia while homogeneously distributed at birth, are biased to modular fields at P8 and then the surrounding matrix by P12. Temporal and spatial matching of the disappearance of C3 by LCIC compartment (i.e., modules then matrix) with CD11b-positive MGC occupancy implicates complement signaling in the selective refinement of early LCIC connectivity. Multiple-labeling studies for a variety of established MGC markers (CD11b, CX3CR1, Iba1, TMEM119) indicate significant MGC heterogeneity in the LCIC as its compartments and segregated multisensory maps emerge. Marker colocalization was the exception rather than the rule, suggesting that unique MGC subpopulations exist in the LCIC and perhaps serve distinct developmental roles. Potential mechanisms whereby microglia sculpt early multisensory LCIC maps and how such activity/inactivity may underlie certain neurodevelopmental conditions, including autism spectrum disorder and schizophrenia, are discussed.

Grass species with smoke-released seed dormancy: A response to climate and fire regime but not photosynthetic pathway

Both C3 and C4 photosynthetic pathways and smoke-released seed dormancy occur among grasses. C4 species evolved from C3 species as seasonality and fire frequency increased and might therefore imply that their smoke sensitivity increased. I searched the worldwide literature for reports on germination responses among grasses, whose photosynthetic pathway was known, to treatment by smoke. Data were obtained for 217 species and 126 genera. While subfamilies tended to be C3 (Pooideae), C4 (Chloridoideae) or a mixture (Panicoideae), a beneficial smoke response was independent of their photosynthetic pathway. The only exceptions were Danthonioideae (C3, non-smoke responsive) and Triodia (C4, smoke responsive). One third of both C3 and C4 genera were smoke responsive. Even within genera, 90% of species showed contrasting smoke responses, confirming that smoke sensitivity is rarely taxonomically constrained. Data on photosynthetic pathway, climate, fire regime and vegetation were compiled for 15 regions that formed four distinct groups: 1) In warm climates with aseasonal rainfall, C4 grasses are moderately better represented, with crown fires and limited smoke responses. 2) In cool regions, most species are C3, with surface-crown fires and lack smoke responses. 3) In warm regions with summer rain (savannas), most species are C4, with surface fires and lack smoke responses. 4) In Mediterranean-climate regions with summer drought, most species are C3, with crown fires and smoke-released dormancy. Thus, even though C3 and C4 grasses are equally capable of expressing smoke sensitivity, their response depends on the region's climate and fire regime that also dictate which photosynthetic pathway dominates.

With complements: C3 inhibition in the clinic

C3 is a key complement protein, located at the nexus of all complement activation pathways. Extracellular, tissue, cell-derived, and intracellular C3 plays critical roles in the immune response that is dysregulated in many diseases, making it an attractive therapeutic target. However, challenges such as very high concentration in blood, increased acute expression, and the elevated risk of infections have historically posed significant challenges in the development of C3-targeted therapeutics. This is further complicated because C3 activation fragments and their receptors trigger a complex network of downstream effects; therefore, a clear understanding of these is needed to provide context for a better understanding of the mechanism of action (MoA) of C3 inhibitors, such as pegcetacoplan. Because of C3's differential upstream position to C5 in the complement cascade, there are mechanistic differences between pegcetacoplan and eculizumab that determine their efficacy in patients with paroxysmal nocturnal hemoglobinuria. In this review, we compare the MoA of pegcetacoplan and eculizumab in paroxysmal nocturnal hemoglobinuria and discuss the complement-mediated disease that might be amenable to C3 inhibition. We further discuss the current state and outlook for C3-targeted therapeutics and provide our perspective on which diseases might be the next success stories in the C3 therapeutics journey.