-
Journal of Neuroinflammation Nov 2023Emerging evidence has shown that myeloid cells that infiltrate into the peri-infarct region may influence the progression of ischemic stroke by interacting with...
BACKGROUND
Emerging evidence has shown that myeloid cells that infiltrate into the peri-infarct region may influence the progression of ischemic stroke by interacting with microglia. Properdin, which is typically secreted by immune cells such as neutrophils, monocytes, and T cells, has been found to possess damage-associated molecular patterns (DAMPs) properties and can perform functions unrelated to the complement pathway. However, the role of properdin in modulating microglia-mediated post-stroke neuroinflammation remains unclear.
METHODS
Global and conditional (myeloid-specific) properdin-knockout mice were subjected to transient middle cerebral artery occlusion (tMCAO). Histopathological and behavioral tests were performed to assess ischemic brain injury in mice. Single-cell RNA sequencing and immunofluorescence staining were applied to explore the source and the expression level of properdin. The transcriptomic profile of properdin-activated primary microglia was depicted by transcriptome sequencing. Lentivirus was used for macrophage-inducible C-type lectin (Mincle) silencing in microglia. Conditioned medium from primary microglia was administered to primary cortex neurons to determine the neurotoxicity of microglia. A series of cellular and molecular biological techniques were used to evaluate the proinflammatory response, neuronal death, protein-protein interactions, and related signaling pathways, etc. RESULTS: The level of properdin was significantly increased, and brain-infiltrating neutrophils and macrophages were the main sources of properdin in the ischemic brain. Global and conditional myeloid knockout of properdin attenuated microglial overactivation and inflammatory responses at the acute stage of tMCAO in mice. Accordingly, treatment with recombinant properdin enhanced the production of proinflammatory cytokines and augmented microglia-potentiated neuronal death in primary culture. Mechanistically, recombinant properdin served as a novel ligand that activated Mincle receptors on microglia and downstream pathways to drive primary microglia-induced inflammatory responses. Intriguingly, properdin can directly bind to the microglial Mincle receptor to exert the above effects, while Mincle knockdown limits properdin-mediated microglial inflammation.
CONCLUSION
Properdin is a new medium by which infiltrating peripheral myeloid cells communicate with microglia, further activate microglia, and exacerbate brain injury in the ischemic brain, suggesting that targeted disruption of the interaction between properdin and Mincle on microglia or inhibition of their downstream signaling may improve the prognosis of ischemic stroke.
Topics: Mice; Animals; Microglia; Ischemic Stroke; Properdin; Neuroinflammatory Diseases; Macrophages; Infarction, Middle Cerebral Artery; Brain Injuries; Brain Ischemia; Mice, Inbred C57BL
PubMed: 37951917
DOI: 10.1186/s12974-023-02946-z -
Clinical and Experimental Immunology Aug 2020Properdin is the only positive regulator of the complement system. In this study, we characterize the prevalence, functional consequences and disease associations of...
Properdin is the only positive regulator of the complement system. In this study, we characterize the prevalence, functional consequences and disease associations of autoantibodies against properdin in a cohort of patients with autoimmune disease systemic lupus erythematosus (SLE) suffering from lupus nephritis (LN). We detected autoantibodies against properdin in plasma of 22·5% of the LN patients (16 of 71) by enzyme-linked immunosorbent assay (ELISA). The binding of these autoantibodies to properdin was dose-dependent and was validated by surface plasmon resonance. Higher levels of anti-properdin were related to high levels of anti-dsDNA and anti-nuclear antibodies and low concentrations of C3 and C4 in patients, and also with histological signs of LN activity and chronicity. The high negative predictive value (NPV) of anti-properdin and anti-dsDNA combination suggested that patients who are negative for both anti-properdin and anti-dsDNA will not have severe nephritis. Immunoglobulin G from anti-properdin-positive patients' plasma increased the C3b deposition on late apoptotic cells by flow cytometry. Nevertheless, these IgGs did not modify substantially the binding of properdin to C3b, the C3 convertase C3bBb and the pro-convertase C3bB, evaluated by surface plasmon resonance. In conclusion, anti-properdin autoantibodies exist in LN patients. They have weak but relevant functional consequences, which could have pathological significance.
Topics: Adult; Antibodies, Antinuclear; Antigen-Antibody Complex; Autoantibodies; Cohort Studies; Complement C3; Complement C4; Disease Progression; Humans; Immunoglobulin G; Kidney; Lupus Erythematosus, Systemic; Lupus Nephritis; Predictive Value of Tests; Properdin
PubMed: 32306375
DOI: 10.1111/cei.13443 -
The American Journal of Pathology Jul 1974From a series of 470 specimens of renal tissue examined by immunofluorescence microscopy, 20 specimens were identified and studied in detail from patients without...
From a series of 470 specimens of renal tissue examined by immunofluorescence microscopy, 20 specimens were identified and studied in detail from patients without evidence of systemic disease in which IgA was the predominant localizing immunoglobulin. All patients presented with hematuria which was recurrent or persistent, often being exacerbated by upper respiratory infection. Most of the group pursued a benign clinical course with little evidence of decline in renal function. Histopathologic changes in renal biopsy specimens of most of the group consisted of a proliferative glomerulonephritis of variable intensity. Characteristic alterations were seen by electron microscopy which included the presence of electron-dense deposits within the mesangium, the hilar regions of the glomerulus and the basement membrane of Bowman's capsule. Evidence for activation of complement by the alternate pathway at C3 was found with properdin localization in 14 of 15 specimens and with the absence of detectable Clq and C4 in 15 specimens studied for these early acting components. It is concluded that the combined clinical, morphologic and immunologic findings warrant consideration of IgA nephropathy as a distinct clinicopathologic entity.
Topics: Adolescent; Adult; Biopsy; Child; Chronic Disease; Complement Fixation Tests; Female; Fluorescent Antibody Technique; Glomerulonephritis; Hematuria; Humans; Immunoglobulin A; Immunoglobulins; Kidney; Kidney Glomerulus; Male; Microscopy, Electron; Nephrectomy; Properdin; Recurrence; Respiratory Tract Infections
PubMed: 4601708
DOI: No ID Found -
Frontiers in Immunology 2020The complement system is readily triggered by the presence of damage-associated molecular patterns on the surface of tumor cells. The complement alternative pathway...
The complement system is readily triggered by the presence of damage-associated molecular patterns on the surface of tumor cells. The complement alternative pathway provides rapid amplification of the molecular stress signal, leading to complement cascade activation to deal with pathogens or malignant cells. Properdin is the only known positive regulator of the alternative pathway. In addition, properdin promotes the phagocytic uptake of apoptotic T cells by macrophages and dendritic cells without activating the complement system, thus, establishing its ability to recognize "altered-self". Dysregulation of properdin has been implicated in substantial tissue damage in the host, and in some cases, chronic unresolved inflammation. A corollary of this may be the development of cancer. Hence, to establish a correlation between properdin presence/levels in normal and cancer tissues, we performed bioinformatics analysis, using Oncomine and UALCAN. Survival analyses were performed using UALCAN and PROGgeneV2 to assess if properdin can serve as a potential prognostic marker for human lung adenocarcinoma (LUAD), liver hepatocellular carcinoma (LIHC), cervical squamous cell carcinoma (CESC), and pancreatic adenocarcinoma (PAAD). We also analyzed levels of tumor-infiltrating immune cells using TIMER, a tool for characterizing immune cell composition in cancers. We found that in LUAD and LIHC, there was a lower expression of properdin in the tumors compared to normal tissues, while no significant difference was observed in CESC and PAAD. Survival analysis demonstrated a positive association between properdin mRNA expression and overall survival in all 4 types of cancers. TIMER analysis revealed that properdin expression correlated negatively with tumor purity and positively with levels of infiltrating B cells, cytotoxic CD8 T cells, CD4 helper T cells, macrophages, neutrophils and dendritic cells in LUAD, CESC and PAAD, and with levels of B cells, CD8 T cells and dendritic cells in LIHC. Immunohistochemical analysis revealed that infiltrating immune cells were the most likely source of properdin in the tumor microenvironment. Thus, complement protein properdin shows promise as a prognostic marker in cancer and warrants further study.
Topics: Complement Pathway, Alternative; Data Mining; Datasets as Topic; Dendritic Cells; Female; Humans; Lymphocyte Subsets; Lymphocytes, Tumor-Infiltrating; Macrophages; Male; Neoplasms; Neutrophils; Prognosis; Properdin; RNA, Messenger; RNA, Neoplasm; Transcriptome; Tumor Microenvironment
PubMed: 33542722
DOI: 10.3389/fimmu.2020.614980 -
Frontiers in Immunology 2020Properdin (P) is a positive regulatory protein that stabilizes the C3 convertase and C5 convertase of the complement alternative pathway (AP). Several studies have...
Properdin (P) is a positive regulatory protein that stabilizes the C3 convertase and C5 convertase of the complement alternative pathway (AP). Several studies have suggested that properdin can bind directly to the surface of certain pathogens regardless of the presence of C3bBb. Saprophytic are susceptible to complement-mediated killing, but the interaction of properdin with spp. has not been evaluated so far. In this work, we demonstrate that properdin present in normal human serum, purified properdin, as well as properdin oligomers P2, P3, and P4, interact with . Properdin can bind directly to the bacterial surface even in the absence of C3b. In line with our previous findings, AP activation was shown to be important for killing nonpathogenic , and properdin plays a key role in this process since this microorganism survives in P-depleted human serum and the addition of purified properdin to P-depleted human serum decreases the number of viable leptospires. A panel of pathogenic recombinant proteins was used to identify putative properdin targets. Lsa30, an outer membrane protein from , binds to unfractionated properdin and to a lesser extent to P2-P4 properdin oligomers. In conclusion, properdin plays an important role in limiting bacterial proliferation of non-pathogenic species. Once bound to the leptospiral surface, this positive complement regulatory protein of the AP contributes to the formation of the C3 convertase on the leptospire surface even in the absence of prior addition of C3b.
Topics: Bacterial Outer Membrane Proteins; Cell Growth Processes; Complement C3b; Complement Factor B; Complement Pathway, Alternative; Cytotoxicity, Immunologic; Humans; Leptospira; Leptospira interrogans; Leptospirosis; Properdin; Protein Binding; Virulence
PubMed: 33240263
DOI: 10.3389/fimmu.2020.572562 -
Immunobiology Jul 2022The 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...
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.
Topics: Cells, Cultured; Dendritic Cells; Humans; Kidney Transplantation; Properdin; RNA, Small Interfering; T-Lymphocytes
PubMed: 35843030
DOI: 10.1016/j.imbio.2022.152246 -
Frontiers in Immunology 2021Properdin, a positive regulator of complement alternative pathway, participates in renal ischemia-reperfusion (IR) injury and also acts as a pattern-recognition molecule...
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 (P) 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 P and positively correlated with injury and repair markers. Properdin in WT kidneys was also upregulated by IR, while HO-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 bioparticles, was promoted by HO but inhibited by P. These results were confirmed by counting phagocytosed HO-induced apoptotic TECs by end labeling fragmented DNAs but not affected by additional serum with/without properdin. Taken together, P 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.
Topics: Animals; Apoptosis; Disease Models, Animal; Epithelial Cells; Kidney; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Biological; Phagocytosis; Properdin; Reperfusion Injury
PubMed: 34552582
DOI: 10.3389/fimmu.2021.697760 -
Cells Aug 2023Upregulation 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...
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 ( < 0.05) and properdin ( < 0.01); additionally, factor B increased in obese PCOS ( < 0.01). For inhibitors of this pathway, factor I was increased ( < 0.01) in both slim and obese PCOS, with an increase in CFHR5 and factor H in obese PCOS ( < 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 ( < 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 ( < 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 ( < 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.
PubMed: 37566081
DOI: 10.3390/cells12152002 -
Frontiers in Immunology 2022The goal of this exploratory study is to determine if urine:serum fractional excretion ratios can outperform the corresponding urinary biomarker proteins in identifying...
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-1 were superior to the corresponding urine biomarkers levels in differentiating LN activity, exhibiting positive correlation with renal SLEDAI. ALCAM, PF4 and properdin 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 ALCAM, PF4 and properdin 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 ALCAM, PF4 and properdin once again exhibited higher accuracy metrics, surpassing corresponding urine and serum biomarkers levels, with ALCAM 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.
Topics: Activated-Leukocyte Cell Adhesion Molecule; Adult; Biomarkers; Humans; Lupus Erythematosus, Systemic; Lupus Nephritis; Platelet Factor 4; Properdin; Vascular Cell Adhesion Molecule-1
PubMed: 36091001
DOI: 10.3389/fimmu.2022.910993 -
Frontiers in Immunology 2019C3 glomerulopathy (C3G) is an umbrella classification for severe renal diseases characterized by predominant staining for complement component C3 in the glomeruli. The...
C3 glomerulopathy (C3G) is an umbrella classification for severe renal diseases characterized by predominant staining for complement component C3 in the glomeruli. The disease is caused by a dysregulation of the alternative pathway (AP) of the complement system. In more than half of C3G patients C3 nephritic factors (C3NeFs) are found. These autoantibodies bind to the AP C3 convertase, prolonging its activity. C3NeFs can be dependent or independent of the complement regulator properdin for their convertase-stabilizing function. However, studies to determine the properdin-dependency of C3NeFs are rare and not part of routine patient workup. Until recently, only supportive treatments for C3G were available. Complement-directed therapies are now being investigated. We hypothesized that patients with properdin-dependent C3NeFs may benefit from properdin-inhibiting therapy to normalize convertase activity. Therefore, in this study we validated two methods to distinguish between properdin-dependent and properdin-independent C3NeFs. These methods are hemolytic assays for measuring convertase activity and stability in absence of properdin. The first assay assesses convertase stabilization by patient immunoglobulins in properdin-depleted serum. The second assay measures convertase stabilization directly in patient serum supplemented with the properdin-blocking agent Salp20. Blood samples from 13 C3NeF-positive C3G patients were tested. Three patients were found to have properdin-dependent C3NeFs, whereas the C3NeF activity of the other ten patients was independent of properdin. The convertase-stabilizing activity in the samples of the patients with properdin-dependent C3NeFs disappeared in absence of properdin. These data indicate that inhibition of properdin in patients with properdin-dependent C3NeFs can normalize convertase activity and could represent a novel therapy for normalizing AP hyperactivity. Our assays provide a tool for identifying C3G patients who may benefit from properdin-inhibiting therapy and can be incorporated into standard C3G laboratory investigations.
Topics: Adolescent; Animals; Autoantibodies; Cells, Cultured; Child; Child, Preschool; Complement C3; Complement C3 Nephritic Factor; Complement Pathway, Alternative; Diagnosis, Differential; Female; Glomerulonephritis, Membranous; Hemolysis; Humans; Kidney; Male; Nephritis; Properdin
PubMed: 31263464
DOI: 10.3389/fimmu.2019.01350