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1.
Int J Mol Sci ; 23(20)2022 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-36293087

RESUMO

Complement pathway proteins are reported to be increased in polycystic ovary syndrome (PCOS) and may be affected by obesity and insulin resistance. To investigate this, a proteomic analysis of the complement system was undertaken, including inhibitory proteins. In this cohort study, plasma was collected from 234 women (137 with PCOS and 97 controls). SOMALogic proteomic analysis 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). The alternative pathway of the complement system was primarily overexpressed in PCOS, with increased C3 (p < 0.05), properdin and factor B (p < 0.01). In addition, inhibition of this pathway was also seen in PCOS, with an increase in CFHR5, factor H and factor I (p < 0.01). Downstream complement factors iC3b and C3d, associated with an enhanced B cell response, and C5a, associated with an inflammatory cytokine release, were increased (p < 0.01). Hyperandrogenemia correlated positively with properdin and iC3b, whilst insulin resistance (HOMA-IR) correlated with iC3b and factor H (p < 0.05) in PCOS. BMI correlated positively with C3d, factor B, factor D, factor I, CFHR5 and C5a (p < 0.05). This comprehensive evaluation of the complement system in PCOS revealed the upregulation of components of the complement system, which appears to be offset by the concurrent upregulation of its inhibitors, with these changes accounted for in part by BMI, hyperandrogenemia and insulin resistance.


Assuntos
Resistência à Insulina , Lectina de Ligação a Manose , Síndrome do Ovário Policístico , Feminino , Humanos , Properdina/metabolismo , Fator H do Complemento , Fator B do Complemento/metabolismo , Antígenos CD55 , Fator D do Complemento , Estudos de Coortes , Proteômica , Complemento C1q , Complemento C3b , Fibrinogênio , Citocinas
2.
Front Immunol ; 13: 953674, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36211440

RESUMO

Hidradenitis suppurativa (HS) is a chronic auto-inflammatory skin disease with a complex and multifactorial pathogenesis involving both the innate and adaptive immune system. Despite limited evidence for local complement activation, conflicting results have been published on the role of systemic complement activation in HS. It was hypothesized that complement was consumed in highly inflamed HS skin, trapping complement from the circulation. Therefore, the aim of this study was to evaluate this local complement deposition in HS skin lesions using routine and commonly used complement antibodies.Direct immunofluorescence for C1q, C3c, C4d, C5b-9, and properdin was performed on frozen tissue sections of 19 HS patients and 6 controls. C5a receptor 1 (C5aR1) was visualized using immunohistochemistry. Overall, we found no significant local complement deposition in HS patients versus controls regarding C1q, C3c, C4d, C5b-9, or properdin on either vessels or immune cells. C5aR1 expression was exclusively found on immune cells, predominantly neutrophilic granulocytes, but not significantly different relatively to the total infiltrate in HS lesions compared with controls. In conclusion, despite not being able to confirm local complement depositions of C1q, C3c, C4d, or properdin using highly sensitive and widely accepted techniques, the increased presence of C5aR1 positive immune cells in HS suggests the importance of complement in the pathogenesis of HS and supports emerging therapies targeting this pathway.


Assuntos
Hidradenite Supurativa , Ativação do Complemento , Complemento C1q , Complexo de Ataque à Membrana do Sistema Complemento , Humanos , Inflamação , Properdina , Receptor da Anafilatoxina C5a
3.
Protein Sci ; 31(10): e4432, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36173177

RESUMO

Structure determination of macromolecular complexes is challenging if subunits can dissociate during crystallization or preparation of electron microscopy grids. We present an approach where a labile complex is stabilized by linking subunits though introduction of a peptide tag in one subunit that is recognized by a nanobody tethered to a second subunit. This allowed crystal structure determination at 3.9 Å resolution of the highly non-globular 320 kDa proconvertase formed by complement components C3b, factor B, and properdin. Whereas the binding mode of properdin to C3b is preserved, an internal rearrangement occurs in the zymogen factor B von Willebrand domain type A domain compared to the proconvertase not bound to properdin. The structure emphasizes the role of two noncanonical loops in thrombospondin repeats 5 and 6 of properdin in augmenting the activity of the C3 convertase. We suggest that linking of subunits through peptide specific tethered nanobodies represents a simple alternative to approaches like affinity maturation and chemical cross-linking for the stabilization of large macromolecular complexes. Besides applications for structural biology, nanobody bridging may become a new tool for biochemical analysis of unstable macromolecular complexes and in vitro selection of highly specific binders for such complexes.


Assuntos
Properdina , Anticorpos de Domínio Único , Convertases de Complemento C3-C5/química , Convertases de Complemento C3-C5/metabolismo , Fator B do Complemento/química , Fator B do Complemento/metabolismo , Precursores Enzimáticos , Substâncias Macromoleculares , Properdina/química , Properdina/metabolismo , Trombospondinas
4.
Front Immunol ; 13: 910993, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36091001

RESUMO

Objectives: The goal of this exploratory study is to determine if urine:serum fractional excretion ratios can outperform the corresponding urinary biomarker proteins in identifying active renal disease in systemic lupus erythematosus (SLE). Methods: Thirty-six adult SLE patients and twelve healthy controls were examined for serum and urine levels of 8 protein markers, namely ALCAM, calpastatin, hemopexin, peroxiredoxin 6 (PRDX6), platelet factor 4 (PF4), properdin, TFPI and VCAM-1, by ELISA. Fractional excretion of analyzed biomarkers was calculated after normalizing both the urine and serum biomarker levels against creatinine. A further validation cohort of fifty SLE patients was included to validate the initial findings. Results: The FE ratios of all 8 proteins interrogated outperformed conventional disease activity markers such as anti-dsDNA, C3 and C4 in identifying renal disease activity. All but VCAM-1FE were superior to the corresponding urine biomarkers levels in differentiating LN activity, exhibiting positive correlation with renal SLEDAI. ALCAMFE, PF4FE and properdinFE ratios exhibited the highest accuracy (AUC>0.9) in distinguishing active LN from inactive SLE. Four of the FE ratios exhibited perfect sensitivity (calpastatin, PRDX6, PF4 and properdin), while ALCAMFE, PF4FE and properdinFE exhibited the highest specificity values for active LN. In addition, several of these novel biomarkers were associated with higher renal pathology activity indices. In the validation cohort ALCAMFE, PF4FE and properdinFE once again exhibited higher accuracy metrics, surpassing corresponding urine and serum biomarkers levels, with ALCAMFE exhibiting 95% accuracy in distinguishing active LN from inactive SLE. Conclusions: With most of the tested proteins, urine:serum fractional excretion ratios outperformed corresponding urine and serum protein measurements in identifying active renal involvement in SLE. Hence, this novel class of biomarkers in SLE ought to be systemically evaluated in larger independent cohorts for their diagnostic utility in LN assessment.


Assuntos
Lúpus Eritematoso Sistêmico , Nefrite Lúpica , Molécula de Adesão de Leucócito Ativado , Adulto , Biomarcadores , Humanos , Lúpus Eritematoso Sistêmico/diagnóstico , Nefrite Lúpica/diagnóstico , Fator Plaquetário 4 , Properdina , Molécula 1 de Adesão de Célula Vascular
5.
Immunobiology ; 227(4): 152246, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35843030

RESUMO

The complement system does not only play an important role in the defence against microorganism and pathogens, but also contributes to the regulation of innate and adaptive immunity. Especially activation fragments C3a and C5a and complement activation at the interface of antigen presenting cell (APC) and T cell, were shown to have a role in T cell activation and proliferation. Whereas most complement factors are produced by the liver, properdin, a positive regulator of the C3 convertase, is mainly produced by myeloid cells. Here we show that properdin can be detected in myeloid cell infiltrate during human renal allograft rejection. In vitro, properdin is produced and secreted by human immature dendritic cells (iDCs), which is further increased by CD40-L-matured DCs (mDCs). Transfection with a specific properdin siRNA reduced properdin secretion by iDCs and mDCs, without affecting the expression of co-stimulatory markers CD80 and CD86. Co-culture of properdin siRNA-transfected iDCs and mDCs with human allogeneic T cells resulted in reduced T cell proliferation, especially under lower DC-T cell ratio's (1:30 and 1:90 ratio). In addition, T cell cytokines were altered, including a reduced TNF-α and IL-17 secretion by T cells co-cultured with properdin siRNA-transfected iDCs. Taken together, these results indicate a local role for properdin during the interaction of DCs and allogeneic T cells, contributing to the shaping of T cell proliferation and activation.


Assuntos
Transplante de Rim , Properdina , Células Cultivadas , Células Dendríticas , Humanos , Properdina/genética , Properdina/metabolismo , RNA Interferente Pequeno , Linfócitos T
6.
Sci Rep ; 12(1): 5818, 2022 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-35388026

RESUMO

Sialic acids as the terminal caps of the cellular glycocalyx play an essential role in self-recognition and were shown to modulate complement processes via interaction between α2,3-linked sialic acids and complement factor H. Previously, it was suggested that low molecular weight α2,8-linked polysialic acid (polySia avDP20) interferes with complement activation, but the exact molecular mechanism is still unclear. Here, we show that soluble polySia avDP20 (molecular weight of ~ 6 kDa) reduced the binding of serum-derived alternative pathway complement activator properdin to the cell surface of lesioned Hepa-1c1c7 and PC-12 neuroblastoma cells. Furthermore, polySia avDP20 added to human serum blocked the alternative complement pathway triggered by plate-bound lipopolysaccharides. Interestingly, no inhibitory effect was observed with monosialic acid or oligosialic acid with a chain length of DP3 and DP5. In addition, polySia avDP20 directly bound properdin, but not complement factor H. These data show that soluble polySia avDP20 binds properdin and reduces the alternative complement pathway activity. Results strengthen the previously described concept of self-recognition of sialylation as check-point control of complement activation in innate immunity.


Assuntos
Via Alternativa do Complemento , Properdina , Humanos , Peso Molecular , Properdina/metabolismo , Ácidos Siálicos/metabolismo
7.
Adv Immunol ; 153: 1-90, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35469595

RESUMO

The complement system consists of three pathways (alternative, classical, and lectin) that play a fundamental role in immunity and homeostasis. The multifunctional role of the complement system includes direct lysis of pathogens, tagging pathogens for phagocytosis, promotion of inflammatory responses to control infection, regulation of adaptive cellular immune responses, and removal of apoptotic/dead cells and immune complexes from circulation. A tight regulation of the complement system is essential to avoid unwanted complement-mediated damage to the host. This regulation is ensured by a set of proteins called complement regulatory proteins. Deficiencies or malfunction of these regulatory proteins may lead to pro-thrombotic hematological diseases, renal and ocular diseases, and autoimmune diseases, among others. This review focuses on the importance of two complement regulatory proteins of the alternative pathway, Factor H and properdin, and their role in human diseases with an emphasis on: (a) characterizing the main mechanism of action of Factor H and properdin in regulating the complement system and protecting the host from complement-mediated attack, (b) describing the dysregulation of the alternative pathway as a result of deficiencies, or mutations, in Factor H and properdin, (c) outlining the clinical findings, management and treatment of diseases associated with mutations and deficiencies in Factor H, and (d) defining the unwanted and inadequate functioning of properdin in disease, through a discussion of various experimental research findings utilizing in vitro, mouse and human models.


Assuntos
Doenças Autoimunes , Properdina , Animais , Doenças Autoimunes/genética , Fator H do Complemento/genética , Humanos , Camundongos , Fagocitose , Properdina/genética , Properdina/metabolismo
8.
Nat Commun ; 13(1): 317, 2022 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-35031611

RESUMO

Activation of the serum-resident complement system begins a cascade that leads to activation of membrane-resident complement receptors on immune cells, thus coordinating serum and cellular immune responses. Whilst many molecules act to control inappropriate activation, Properdin is the only known positive regulator of the human complement system. By stabilising the alternative pathway C3 convertase it promotes complement self-amplification and persistent activation boosting the magnitude of the serum complement response by all triggers. In this work, we identify a family of tick-derived alternative pathway complement inhibitors, hereafter termed CirpA. Functional and structural characterisation reveals that members of the CirpA family directly bind to properdin, inhibiting its ability to promote complement activation, and leading to potent inhibition of the complement response in a species specific manner. We provide a full functional and structural characterisation of a properdin inhibitor, opening avenues for future therapeutic approaches.


Assuntos
Proteínas de Artrópodes/química , Proteínas de Artrópodes/imunologia , Inativadores do Complemento/química , Inativadores do Complemento/imunologia , Properdina/imunologia , Rhipicephalus/imunologia , Sequência de Aminoácidos , Animais , Proteínas de Artrópodes/genética , Ativação do Complemento , Complemento C3/química , Complemento C3/imunologia , Via Alternativa do Complemento , Humanos , Cinética , Properdina/química , Properdina/genética , Rhipicephalus/química , Rhipicephalus/genética , Alinhamento de Sequência
9.
Eur J Immunol ; 52(4): 597-608, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35092629

RESUMO

Properdin, the only known positive regulator of the complement system, stabilizes the C3 convertase, thereby increasing its half-life. In contrast to most other complement factors, properdin is mainly produced extrahepatically by myeloid cells. Recent data suggest a role for properdin as a pattern recognition molecule. Here, we confirmed previous findings of properdin binding to different necrotic cells including Jurkat T cells. Binding can occur independent of C3, as demonstrated by HAP-1 C3 KO cells, excluding a role for endogenous C3. In view of the cellular source of properdin, interaction with myeloid cells was examined. Properdin bound to the surface of viable monocyte-derived pro- and anti-inflammatory macrophages, but not to DCs. Binding was demonstrated for purified properdin as well as fractionated P2, P3, and P4 properdin oligomers. Binding contributed to local complement activation as determined by C3 and C5b-9 deposition on the cell surfaces and seems a prerequisite for alternative pathway activation. Interaction of properdin with cell surfaces could be inhibited with the tick protein Salp20 and by different polysaccharides, depending on sulfation and chain length. These data identify properdin as a factor interacting with different cell surfaces, being either dead or alive, contributing to the local stimulation of complement activation.


Assuntos
Convertases de Complemento C3-C5 , Properdina , Ativação do Complemento , Convertases de Complemento C3-C5/metabolismo , Complexo de Ataque à Membrana do Sistema Complemento , Via Alternativa do Complemento , Humanos , Necrose , Properdina/metabolismo
10.
J Allergy Clin Immunol ; 149(2): 550-556.e2, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34800432

RESUMO

BACKGROUND: Severe coronavirus disease 2019 (COVID-19) is characterized by impaired type I interferon activity and a state of hyperinflammation leading to acute respiratory distress syndrome. The complement system has recently emerged as a key player in triggering and maintaining the inflammatory state, but the role of this molecular cascade in severe COVID-19 is still poorly characterized. OBJECTIVE: We aimed at assessing the contribution of complement pathways at both the protein and transcriptomic levels. METHODS: To this end, we systematically assessed the RNA levels of 28 complement genes in the circulating whole blood of patients with COVID-19 and healthy controls, including genes of the alternative pathway, for which data remain scarce. RESULTS: We found differential expression of genes involved in the complement system, yet with various expression patterns: whereas patients displaying moderate disease had elevated expression of classical pathway genes, severe disease was associated with increased lectin and alternative pathway activation, which correlated with inflammation and coagulopathy markers. Additionally, properdin, a pivotal positive regulator of the alternative pathway, showed high RNA expression but was found at low protein concentrations in patients with a severe and critical disease, suggesting its deposition at the sites of complement activation. Notably, low properdin levels were significantly associated with the use of mechanical ventilation (area under the curve = 0.82; P = .002). CONCLUSION: This study sheds light on the role of the alternative pathway in severe COVID-19 and provides additional rationale for the testing of drugs inhibiting the alternative pathway of the complement system.


Assuntos
COVID-19/imunologia , Ativação do Complemento/genética , Via Alternativa do Complemento/genética , Proteínas do Sistema Complemento/genética , Coagulação Intravascular Disseminada/imunologia , SARS-CoV-2/patogenicidade , COVID-19/genética , COVID-19/terapia , COVID-19/virologia , Doenças Cardiovasculares/genética , Doenças Cardiovasculares/imunologia , Doenças Cardiovasculares/terapia , Doenças Cardiovasculares/virologia , Estudos de Casos e Controles , Comorbidade , Proteínas do Sistema Complemento/imunologia , Diabetes Mellitus/genética , Diabetes Mellitus/imunologia , Diabetes Mellitus/terapia , Diabetes Mellitus/virologia , Coagulação Intravascular Disseminada/genética , Coagulação Intravascular Disseminada/terapia , Coagulação Intravascular Disseminada/virologia , Feminino , Regulação da Expressão Gênica , Humanos , Hipertensão/genética , Hipertensão/imunologia , Hipertensão/terapia , Hipertensão/virologia , Lectinas/genética , Lectinas/imunologia , Masculino , Pessoa de Meia-Idade , Neoplasias/genética , Neoplasias/imunologia , Neoplasias/terapia , Neoplasias/virologia , Properdina/genética , Properdina/imunologia , Respiração Artificial , SARS-CoV-2/genética , SARS-CoV-2/imunologia , Índice de Gravidade de Doença
11.
Pediatr Nephrol ; 37(3): 601-612, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34476601

RESUMO

BACKGROUND: C3 glomerulopathy (C3G) is a rare kidney disorder characterized by predominant glomerular depositions of complement C3. C3G can be subdivided into dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). This study describes the long-term follow-up with extensive complement analysis of 29 Dutch children with C3G. METHODS: Twenty-nine C3G patients (19 DDD, 10 C3GN) diagnosed between 1992 and 2014 were included. Clinical and laboratory findings were collected at presentation and during follow-up. Specialized assays were used to detect rare variants in complement genes and measure complement-directed autoantibodies and biomarkers in blood. RESULTS: DDD patients presented with lower estimated glomerular filtration rate (eGFR). C3 nephritic factors (C3NeFs) were detected in 20 patients and remained detectable over time despite immunosuppressive treatment. At presentation, low serum C3 levels were detected in 84% of all patients. During follow-up, in about 50% of patients, all of them C3NeF-positive, C3 levels remained low. Linear mixed model analysis showed that C3GN patients had higher soluble C5b-9 (sC5b-9) and lower properdin levels compared to DDD patients. With a median follow-up of 52 months, an overall benign outcome was observed with only six patients with eGFR below 90 ml/min/1.73 m2 at last follow-up. CONCLUSIONS: We extensively described clinical and laboratory findings including complement features of an exclusively pediatric C3G cohort. Outcome was relatively benign, persistent low C3 correlated with C3NeF presence, and C3GN was associated with higher sC5b-9 and lower properdin levels. Prospective studies are needed to further elucidate the pathogenic mechanisms underlying C3G and guide personalized medicine with complement therapeutics.


Assuntos
Glomerulonefrite Membranoproliferativa , Glomerulonefrite , Nefropatias , Criança , Complemento C3 , Fator Nefrítico do Complemento 3 , Via Alternativa do Complemento , Feminino , Seguimentos , Glomerulonefrite Membranoproliferativa/patologia , Humanos , Masculino , Properdina
12.
Hypertens Pregnancy ; 41(1): 9-14, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34781830

RESUMO

OBJECTIVES: This study seeks to discover how the concentration of complement proteins, factors B and P are affected in HIV-associated PE. METHODS: This study included 72 pregnant women: 36 preeclamptic and 36 normotensive. Serum concentrations of factors B and P were measured using a Bioplex immunoassay. RESULTS: A significant decrease of factor B in the HIV+ compared to the HIV- group was noted. No significant difference across all groups for both analytes was observed. CONCLUSION: Our results suggest the alternative pathway (AP) is inhibited by HIV evading immune detection. The AP is not excessively activated in PE during the third trimester.


Assuntos
Infecções por HIV , Pré-Eclâmpsia , Fator B do Complemento , Feminino , Infecções por HIV/complicações , Humanos , Gravidez , Terceiro Trimestre da Gravidez , Properdina
13.
Front Immunol ; 12: 747654, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34956182

RESUMO

The complement system is designed to recognise and eliminate invading pathogens via activation of classical, alternative and lectin pathways. Human properdin stabilises the alternative pathway C3 convertase, resulting in an amplification loop that leads to the formation of C5 convertase, thereby acting as a positive regulator of the alternative pathway. It has been noted that human properdin on its own can operate as a pattern recognition receptor and exert immune functions outside its involvement in complement activation. Properdin can bind directly to microbial targets via DNA, sulfatides and glycosaminoglycans, apoptotic cells, nanoparticles, and well-known viral virulence factors. This study was aimed at investigating the complement-independent role of properdin against Influenza A virus infection. As one of the first immune cells to arrive at the site of IAV infection, we show here that IAV challenged neutrophils released properdin in a time-dependent manner. Properdin was found to directly interact with haemagglutinin, neuraminidase and matrix 1 protein Influenza A virus proteins in ELISA and western blot. Furthermore, modelling studies revealed that properdin could bind HA and NA of the H1N1 subtype with higher affinity compared to that of H3N2 due to the presence of an HA cleavage site in H1N1. In an infection assay using A549 cells, properdin suppressed viral replication in pH1N1 subtype while promoting replication of H3N2 subtype, as revealed by qPCR analysis of M1 transcripts. Properdin treatment triggered an anti-inflammatory response in H1N1-challenged A549 cells and a pro-inflammatory response in H3N2-infected cells, as evident from differential mRNA expression of TNF-α, NF-κB, IFN-α, IFN-ß, IL-6, IL-12 and RANTES. Properdin treatment also reduced luciferase reporter activity in MDCK cells transduced with H1N1 pseudotyped lentiviral particles; however, it was increased in the case of pseudotyped H3N2 particles. Collectively, we conclude that infiltrating neutrophils at the site of IAV infection can release properdin, which then acts as an entry inhibitor for pandemic H1N1 subtype while suppressing viral replication and inducing an anti-inflammatory response. H3N2 subtype can escape this immune restriction due to altered haemagglutinin and neuraminindase, leading to enhanced viral entry, replication and pro-inflammatory response. Thus, depending on the subtype, properdin can either limit or aggravate IAV infection in the host.


Assuntos
Vírus da Influenza A Subtipo H1N1/imunologia , Vírus da Influenza A Subtipo H3N2/imunologia , Influenza Humana/imunologia , Neutrófilos/imunologia , Properdina/imunologia , Animais , Cães , Humanos , Células Madin Darby de Rim Canino/imunologia , Células Madin Darby de Rim Canino/virologia
14.
J Immunol ; 207(10): 2465-2472, 2021 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-34635587

RESUMO

The complement system is an important part of innate immunity. Complement activation leads to formation of convertase enzymes, switch of their specificity from C3 to C5 cleavage, and generation of lytic membrane attack complexes (C5b-9) on surfaces of pathogens. Most C5 cleavage occurs via the complement alternative pathway (AP). The regulator properdin promotes generation and stabilization of AP convertases. However, its role in C5 activation is not yet understood. In this work, we showed that serum properdin is essential for LPS- and zymosan-induced C5b-9 generation and C5b-9-mediated lysis of rabbit erythrocytes. Furthermore, we demonstrated its essential role in C5 cleavage by AP convertases. To this end, we developed a hemolytic assay in which AP convertases were generated on rabbit erythrocytes by using properdin-depleted serum in the presence of C5 inhibitor (step 1), followed by washing and addition of purified C5-C9 components to allow C5b-9 formation (step 2). In this assay, addition of purified properdin to properdin-depleted serum during convertase formation (step 1) was required to restore C5 cleavage and C5b-9-mediated hemolysis. Importantly, C5 convertase activity was also fully restored when properdin was added together with C5b-9 components (step 2), thus after convertase formation. Moreover, with C3-depleted serum, not capable of forming new convertases but containing properdin, in step 2 of the assay, again full C5b-9 formation was observed and blocked by addition of properdin inhibitor Salp20. Thus, properdin is essential for the convertase specificity switch toward C5, and this function is independent of properdin's role in new convertase formation.


Assuntos
Ativação do Complemento/fisiologia , Convertases de Complemento C3-C5/metabolismo , Complexo de Ataque à Membrana do Sistema Complemento/metabolismo , Via Alternativa do Complemento/fisiologia , Properdina/metabolismo , Animais , Coelhos
15.
Front Immunol ; 12: 697760, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34552582

RESUMO

Properdin, a positive regulator of complement alternative pathway, participates in renal ischemia-reperfusion (IR) injury and also acts as a pattern-recognition molecule affecting apoptotic T-cell clearance. However, the role of properdin in tubular epithelial cells (TECs) at the repair phase post IR injury is not well defined. This study revealed that properdin knockout (PKO) mice exhibited greater injury in renal function and histology than wild-type (WT) mice post 72-h IR, with more apoptotic cells and macrophages in tubular lumina, increased active caspase-3 and HMGB1, but better histological structure at 24 h. Raised erythropoietin receptor by IR was furthered by PKO and positively correlated with injury and repair markers. Properdin in WT kidneys was also upregulated by IR, while H2O2-increased properdin in TECs was reduced by its small-interfering RNA (siRNA), with raised HMGB1 and apoptosis. Moreover, the phagocytic ability of WT TECs, analyzed by pHrodo Escherichia coli bioparticles, was promoted by H2O2 but inhibited by PKO. These results were confirmed by counting phagocytosed H2O2-induced apoptotic TECs by in situ end labeling fragmented DNAs but not affected by additional serum with/without properdin. Taken together, PKO results in impaired phagocytosis at the repair phase post renal IR injury. Properdin locally produced by TECs plays crucial roles in optimizing damaged cells and regulating phagocytic ability of TECs to effectively clear apoptotic cells and reduce inflammation.


Assuntos
Rim/lesões , Rim/patologia , Fagocitose/fisiologia , Properdina/deficiência , Traumatismo por Reperfusão/patologia , Animais , Apoptose/imunologia , Apoptose/fisiologia , Modelos Animais de Doenças , Células Epiteliais/imunologia , Células Epiteliais/patologia , Células Epiteliais/fisiologia , Rim/irrigação sanguínea , Macrófagos/imunologia , Macrófagos/patologia , Macrófagos/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Biológicos , Fagocitose/imunologia , Properdina/genética , Properdina/imunologia , Traumatismo por Reperfusão/imunologia , Traumatismo por Reperfusão/fisiopatologia
16.
Front Immunol ; 12: 649882, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33868287

RESUMO

Intestinal ischemia reperfusion (IR)-induced tissue injury represents an acute inflammatory response with significant morbidity and mortality. The mechanism of IR-induced injury is not fully elucidated, but recent studies suggest a critical role for complement activation and for differences between sexes. To test the hypothesis that complement initiation differs by sex in intestinal IR, we performed intestinal IR on male and female WT C57B6L/, C1q-/-, MBL-/-, or properdin (P)-/- mice. Intestinal injury, C3b and C5a production and ex vivo secretions were analyzed. Initial studies demonstrated a difference in complement mRNA and protein in male and female WT mice. In response to IR, male C1q-, MBL- and P-deficient mice sustained less injury than male WT mice. In contrast, only female MBL-/- mice sustained significantly less injury than female wildtype mice. Importantly, wildtype, C1q-/- and P-/- female mice sustained significant less injury than the corresponding male mice. In addition, both C1q and MBL expression and deposition increased in WT male mice, while only elevated MBL expression and deposition occurred in WT female mice. These data suggested that males use both C1q and MBL pathways, while females tend to depend on lectin pathway during intestinal IR. Females produced significantly less serum C5a in MBL-/- and P-/- mice. Our findings suggested that complement activation plays a critical role in intestinal IR in a sex-dependent manner.


Assuntos
Complemento C1q/metabolismo , Via Clássica do Complemento/fisiologia , Lectina de Ligação a Manose da Via do Complemento/fisiologia , Lectina de Ligação a Manose/metabolismo , Traumatismo por Reperfusão/imunologia , Animais , Complemento C1q/genética , Modelos Animais de Doenças , Feminino , Humanos , Intestinos/irrigação sanguínea , Intestinos/imunologia , Intestinos/patologia , Masculino , Lectina de Ligação a Manose/genética , Camundongos , Camundongos Knockout , Properdina/genética , Properdina/metabolismo , Traumatismo por Reperfusão/patologia , Fatores Sexuais
17.
Front Immunol ; 12: 615620, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33664746

RESUMO

The homeostasis of tissues in a chronic disease is an essential function of the alternative pathway (AP) of the complement system (CS). However, if not controlled, it may also be detrimental to healthy cells with a consequent aggravation of symptoms. The protoporphyria (PP) is a rare chronic disease that causes phototoxicity in visible light with local skin pain and general malaise. In order to establish if there is a systemic involvement of the CS during sun exposure, we designed a non-invasive method with a serum collection in winter and summer from 19 PP and 13 controls to detect the levels of CS protein: Properdin, Factor H (FH), and C5. Moreover, the global radiation data were collected from the regional agency of environmental protection (ARPA). The results show growing values for every protein in patients with PP, compared to control, in both seasons, in particular in summer compared to winter. To reinforce the evidence, we have estimated the personal exposure of patients based on the global radiation data. The main factors of the AP increased over the season, confirming the involvement of the AP in relation to light exposure. The systemic response could justify the general malaise of patients after long light exposure and can be exploited to elucidate new therapeutic approaches.


Assuntos
Via Alternativa do Complemento/imunologia , Via Alternativa do Complemento/efeitos da radiação , Proteínas do Sistema Complemento/imunologia , Suscetibilidade a Doenças , Protoporfiria Eritropoética/etiologia , Luz Solar/efeitos adversos , Adulto , Biomarcadores , Complemento C5/imunologia , Complemento C5/metabolismo , Fator H do Complemento/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Properdina/imunologia , Properdina/metabolismo , Protoporfiria Eritropoética/diagnóstico , Protoporfiria Eritropoética/metabolismo , Estações do Ano
18.
Int Immunopharmacol ; 93: 107429, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33571820

RESUMO

BACKGROUND: IgA nephropathy (IgAN) has become the most prevalent form of glomerulonephritis affecting almost 1.3% of the total population worldwide. It is an autoimmune disorder where the host autoantibody forms an immune complex with the defective galactose-deficient IgA1 and gets deposited at the mesangium and endocapillary region of glomeruli. IgA has the capability to activate alternative and lectin complement cascades which even aggravates the condition. Properdin is directly associated with IgAN by activating and stabilising the alternative complement pathway at the mesangium, thereby causing progressive renal damage. OBJECTIVE: The present review mainly focuses on correlating the influence of properdin in activating the complement cascade at glomeruli which is the major cause of disease exacerbation. Secondly, we have described the probable therapies and new targets that are under trials to check their efficacy in IgAN. METHODS: An in-depth research was carried out from different peer-reviewed articles till December 2020 from several renowned databases like PubMed, Frontier, and MEDLINE, and the information was analysed and written in a simplified manner. RESULTS: Co-deposition of properdin is observed along with IgA and C3 in 75%-100% of the patients. It is not yet fully understood whether properdin inhibition can attenuate IgAN, as many conflicting reports have revealed worsening of IgAN after impeding properdin. CONCLUSION: With no specific cure still available, the treatment strategies are of great concern to find a better target to restrict the disease progression. More research and clinical trials are required to find out a prominent target to combat IgAN.


Assuntos
Complemento C3/metabolismo , Glomerulonefrite por IGA/metabolismo , Imunoglobulina A/metabolismo , Rim/metabolismo , Properdina/metabolismo , Animais , Complexo Antígeno-Anticorpo/metabolismo , Autoanticorpos/metabolismo , Via Alternativa do Complemento , Glomerulonefrite por IGA/genética , Humanos , Imunoglobulina A/genética , Rim/patologia
19.
Elife ; 102021 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-33480354

RESUMO

Properdin stabilizes convertases formed upon activation of the complement cascade within the immune system. The biological activity of properdin depends on the oligomerization state, but whether properdin oligomers are rigid and how their structure links to function remains unknown. We show by combining electron microscopy and solution scattering, that properdin oligomers adopt extended rigid and well-defined conformations which are well approximated by single models of apparent n-fold rotational symmetry with dimensions of 230-360 Å. Properdin monomers are pretzel-shaped molecules with limited flexibility. In solution, properdin dimers are curved molecules, whereas trimers and tetramers are close to being planar molecules. Structural analysis indicates that simultaneous binding through all binding sites to surface-linked convertases is unlikely for properdin trimer and tetramers. We show that multivalency alone is insufficient for full activity in a cell lysis assay. Hence, the observed rigid extended oligomer structure is an integral component of properdin function.


Assuntos
Properdina/química , Sítios de Ligação , Células HEK293 , Humanos , Conformação Molecular
20.
Medicina (Kaunas) ; 57(2)2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33494138

RESUMO

Background and Objectives: Tumours are often low immunogenic. The role of complement, an innate immune defence system, in tumour control has begun to be elucidated, but findings are conflicting. A role for properdin, an amplifier of complement activation, in tumour control has recently been implicated. Materials and Methods: Properdin-deficient and congenic wildtype mice were injected subcutaneously with B16F10 melanoma cells. Tumour mass and chemokine profile were assessed. The frequencies of CD45+CD11b+ Gr-1+ cells were determined from tumours and spleens, and CD206+ F4/80+ cells were evaluated in spleens. Sera were analysed for C5a, sC5b-9, and CCL2. Results: Whilst there was no difference in tumour growth at study endpoint, properdin-deficient mice had significantly fewer myeloid-derived suppressor cells (MDSCs) in their tumours and spleens. Splenic M2 type macrophages and serum levels of C5a, sC5b-9, and CCL2 were decreased in properdin-deficient compared to wildtype mice. Conclusions: The presence of intact complement amplification sustains an environment that lessens potential anti-tumour responses.


Assuntos
Modelos Animais de Doenças , Melanoma , Properdina , Neoplasias Cutâneas , Animais , Macrófagos , Melanoma/genética , Camundongos , Camundongos Endogâmicos C57BL , Properdina/genética , Neoplasias Cutâneas/genética
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