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Alternative Complement Pathway

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Gregory L. Stahl – One of the best experts on this subject based on the ideXlab platform.

  • The Alternative Complement Pathway regulates pathological angiogenesis in the retina
    FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2014
    Co-Authors: J. Harry Sweigard, Ryoji Yanai, Philipp Gaissert, Magali Saint-geniez, Keiko Kataoka, Aristomenis Thanos, Gregory L. Stahl, John D. Lambris, Kip M. Connor
    Abstract:

    A defining feature in proliferative retinopathies is the formation of pathological neovessels. In these diseases, the balance between neovessel formation and regression determines blindness, making the modulation of neovessel growth highly desirable. The role of the immune system in these retinopathies is of increasing interest, but it is not completely understood. We investigated the role of the Alternative Complement Pathway during the formation and resolution of aberrant neovascularization. We used Alternative Complement Pathway-deficient (Fb(-/-)) mice and age- and strain-matched control mice to assess neovessel development and regression in an oxygen-induced retinopathy (OIR) mouse model. In the control mice, we found increased transcription of Fb after OIR treatment. In the Fb(-/-) mice, we prepared retinal flatmounts and identified an increased number of neovessels, peaking at postnatal day 17 (P17; P=0.001). Subjecting human umbilical vein endothelial cells (HUVECs) to low oxygen, mimicking a characteristic of neovessels, decreased the expression of the Complement inhibitor Cd55. Finally, using laser capture microdissection (LCM) to isolate the neovessels after OIR, we found decreased expression of Cd55 (P=0.005). Together, our data implicate the Alternative Complement Pathway in facilitating neovessel clearance by down-regulating the Complement inhibitor Cd55 specifically on neovessels, allowing for their targeted removal while leaving the established vasculature intact.-Sweigard, J. H., Yanai, R., Gaissert, P., Saint-Geniez, M., Kataoka, K., Thanos, A., Stahl, G. L., Lambris, J. D., Connor, K. M. The Alternative Complement Pathway regulates pathological angiogenesis in the retina.

  • The Alternative Complement Pathway Propagates Inflammation and Injury in Murine Ischemic Stroke
    Journal of immunology (Baltimore Md. : 1950), 2012
    Co-Authors: Andrew Elvington, Gregory L. Stahl, Carl Atkinson, Hong Zhu, Kazue Takahashi, Mark S. Kindy, Stephen Tomlinson
    Abstract:

    There is mounting evidence indicating an important role for Complement in the pathogenesis of cerebral ischemia-reperfusion injury, or ischemic stroke. The role of the Alternative Complement Pathway in ischemic stroke has not been investigated, and there is conflictingdataon the roleof the terminal Pathway. Inthisstudy,we show that comparedwith wild-typemice, mice deficient in the Alternative Pathway protein factor B or mice treated with the Alternative Pathway inhibitor CR2-fH have improved outcomes after 60-min middle cerebral arteartery occlusion and 24-h reperfusion. Factor B-deficient or CR2-fH‐treated mice were protected in terms of improved neurologic function and reduced cerebral infarct, demyelination, P-selectin expression, neutrophil infiltration, and microthrombi formation. Mice deficient in both the classical and lectin Pathways (C1q/MBL deficient) were also protected from cerebral ischemia-reperfusion injury, and there was no detectable C3d deposition in the ipsilateral brain of these mice. These data demonstrate that the Alternative Pathway is not alone sufficient to initiate Complement activation and indicate that the Alternative Pathway propagates cerebral injury via amplification of the cascade. Deficiency of C6, a component of the terminal cytolytic membrane attack complex, had no effect on outcome after ischemic stroke, indicating that the membrane attack complex is not involved in mediating injury in this model. We additionally show that the protective effect of factor B deficiency and CR2-fH treatment is sustained in the subacute stage of infarct development, adding to the clinical relevance of these findings. The Journal of Immunology, 2012, 189: 4640‐4647.

  • Essential Role of Factor B of the Alternative Complement Pathway in Complement Activation and Opsonophagocytosis during Acute Pneumococcal Otitis Media in Mice
    Infection and immunity, 2011
    Co-Authors: Gregory L. Stahl, Joshua M. Thurman, H. H. Tong
    Abstract:

    We recently reported that the Complement system plays a pivotal role in innate immune defense against Streptococcus pneumoniae during acute otitis media (OM) in mice. The current study was designed to determine which of the Complement Pathways are activated during acute pneumococcal OM and whether components of Complement are expressed in the middle ear epithelium. Gene expression was determined by quantitative PCR, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining. We found that S. pneumoniae induced increased gene expression of factor B of the Alternative Complement Pathway and C3 in mouse middle ear epithelium. Activation of factor B and C3 in the middle ear lavage fluids was significantly greater than in simultaneously obtained serum samples as determined by Western blotting. Using mice deficient in Complement C1qa, factor B, and factor B/C2, we found that Complement C3 activation and opsonophagocytosis of S. pneumoniae were greatly attenuated in factor B- and factor B/C2-deficient mice. These findings support the concept that local Complement activation is an important host innate immune response and that activation of the Alternative Complement Pathway represents one of the innate immune defense mechanisms against pneumococcal infection during the early stage of acute OM.

Hui Zhao – One of the best experts on this subject based on the ideXlab platform.

  • role for the Alternative Complement Pathway in ischemia reperfusion injury
    American Journal of Pathology, 2003
    Co-Authors: Gregory L. Stahl, Liming Hao, Mendy Miller, Jon A. Buras, Michael Fung, Hui Zhao
    Abstract:

    The terminal Complement components play an important role in mediating tissue injury after ischemia and reperfusion (I/R) injury in rats and mice. However, the specific Complement Pathways involved in I/R injury are unknown. The role of the Alternative Pathway in I/R injury may be particularly important, as it amplifies Complement activation and deposition. In this study, the role of the Alternative Pathway in I/R injury was evaluated using factor D-deficient (−/−) and heterozygote (+/−) mice. Gastrointestinal ischemia (GI) was induced by clamping the mesenteric artery for 20 minutes and then reperfused for 3 hours. Sham-operated control mice (+/− versus −/−) had similar baseline intestinal lactate dehydrogenase activity (P = ns). Intestinal lactate dehydrogenase activity was greater in −/− mice compared to +/− mice after GI/R (P = 0.02) thus demonstrating protection in the −/− mice. Intestinal myeloperoxidase activity in +/− mice was significantly greater than −/− mice after GI/R (P < 0.001). Pulmonary myeloperoxidase activity after GI/R was significantly higher in +/− than −/− mice (P = 0.03). Addition of human factor D to −/− animals restored GI/R injury and was prevented by a functionally inhibitory antibody against human factor D. These data suggest that the Alternative Complement Pathway plays an important role in local and remote tissue injury after GI/R. Inhibition of factor D may represent an effective therapeutic approach for GI/R injury.

  • Role for the Alternative Complement Pathway in ischemia/reperfusion injury.
    The American journal of pathology, 2003
    Co-Authors: Gregory L. Stahl, Liming Hao, Mendy Miller, Jon A. Buras, Michael Fung, Hui Zhao
    Abstract:

    The terminal Complement components play an important role in mediating tissue injury after ischemia and reperfusion (I/R) injury in rats and mice. However, the specific Complement Pathways involved in I/R injury are unknown. The role of the Alternative Pathway in I/R injury may be particularly important, as it amplifies Complement activation and deposition. In this study, the role of the Alternative Pathway in I/R injury was evaluated using factor D-deficient (−/−) and heterozygote (+/−) mice. Gastrointestinal ischemia (GI) was induced by clamping the mesenteric artery for 20 minutes and then reperfused for 3 hours. Sham-operated control mice (+/− versus −/−) had similar baseline intestinal lactate dehydrogenase activity (P = ns). Intestinal lactate dehydrogenase activity was greater in −/− mice compared to +/− mice after GI/R (P = 0.02) thus demonstrating protection in the −/− mice. Intestinal myeloperoxidase activity in +/− mice was significantly greater than −/− mice after GI/R (P < 0.001). Pulmonary myeloperoxidase activity after GI/R was significantly higher in +/− than −/− mice (P = 0.03). Addition of human factor D to −/− animals restored GI/R injury and was prevented by a functionally inhibitory antibody against human factor D. These data suggest that the Alternative Complement Pathway plays an important role in local and remote tissue injury after GI/R. Inhibition of factor D may represent an effective therapeutic approach for GI/R injury.

Eric A Pierce – One of the best experts on this subject based on the ideXlab platform.

  • changes in extracellular matrix cause rpe cells to make basal deposits and activate the Alternative Complement Pathway
    Human Molecular Genetics, 2018
    Co-Authors: Rosario Fernandezgodino, Eric A Pierce, Kinga M Bujakowska
    Abstract:

    The design of efficient therapies for age-related macular degeneration (AMD) is limited by our understanding of the pathogenesis of basal deposits, which form between retinal pigment epithelium (RPE) and Bruch’s membrane (BrM) early in disease, and involve activation of the Complement system. To investigate the roles of BrM, RPE and Complement in an AMD, we generated abnormal extracellular matrix (ECM) using CRISPR-edited ARPE-19 cells. We introduced to these cells the p.R345W mutation in EFEMP1, which causes early-onset macular degeneration. The abnormal ECM binds active Complement C3 and causes the formation of basal deposits by normal human fetal (hf)RPE cells. Human fetal RPE (hfRPE) cells grown on abnormal ECM or BrM explants from AMD donors show chronic activation of the Alternative Complement Pathway by excessive deposition of C3b. This process is exacerbated by impaired ECM turnover via increased matrix metalloproteinase-2 activity. The local cleavage of C3 via convertase-independent mechanisms can be a new therapeutic target for early AMD.

  • changes in extracellular matrix cause rpe cells to make basal deposits and activate the Alternative Complement Pathway
    bioRxiv, 2017
    Co-Authors: Rosario Fernandezgodino, Kinga M Bujakowska, Eric A Pierce
    Abstract:

    The design of efficient therapies for age-related macular degeneration (AMD) is limited by our understanding of the pathogenesis of basal deposits, which form between retinal pigment epithelium (RPE) and Bruch membrane (BrM) early in disease, and involve activation of the Complement system. To investigate the roles of BrM, RPE and Complement in AMD, we generated ARPE-19 cells with the p.R345W mutation in EFEMP1, which causes early-onset macular degeneration. The ARPE-19-EFEMP1R345W/R345W cells make abnormal extracellular matrix (ECM) that binds active Complement C3 and causes the formation of basal deposits by normal human fetal (hf)RPE cells. hfRPE cells grown on abnormal ECM or BrM explants from AMD donors show chronic activation of the Alternative Complement Pathway by excessive deposition of C3b. This process is exacerbated by impaired ECM turnover via increased matrix metalloproteinase-2 (MMP-2) activity. Therapies that target ECM synthesis and turnover and activation of C3 could be effective for early AMD.

Joel L. Moake – One of the best experts on this subject based on the ideXlab platform.

  • Regulatory Components of the Alternative Complement Pathway in Endothelial Cell Cytoplasm, Factor H and Factor I, Are Not Packaged in Weibel-Palade Bodies
    PloS one, 2015
    Co-Authors: Nancy A. Turner, Sarah E. Sartain, Shiu-ki Rocky Hui, Joel L. Moake
    Abstract:

    It was recently reported that factor H, a regulatory component of the Alternative Complement Pathway, is stored with von Willebrand factor (VWF) in the Weibel-Palade bodies of endothelial cells. If this were to be the case, it would have therapeutic importance for patients with the atypical hemolytic-uremic syndrome that can be caused either by a heterozygous defect in the factor H gene or by the presence of an autoantibody against factor H. The in vivo Weibel-Palade body secretagogue, des-amino-D-arginine vasovasopressin (DDAVP), would be expected to increase transiently the circulating factor H levels, in addition to increasing the circulating levels of VWF. We describe experiments demonstrating that factor H is released from endothelial cell cytoplasm without a secondary storage site. These experiments showed that factor H is not stored with VWF in endothelial cell Weibel-Palade bodies, and is not secreted in response in vitro in response to the Weibel-Palade body secretagogue, histamine. Furthermore, the in vivo Weibel-Palade body secretagogue, DDAVP does not increase the circulating factor H levels concomitantly with DDAVP-induced increased VWF. Factor I, a regulatory component of the Alternative Complement Pathway that is functionally related to factor H, is also located in endothelial cell cytoplasm, and is also not present in endothelial cell Weibel-Palade bodies. Our data demonstrate that the factor H and factor I regulatory proteins of the Alternative Complement Pathway are not stored in Weibel-Palade bodies. DDAVP induces the secretion into human plasma of VWF —- but not factor H.

  • Thrombotic microangiopathies and the linkage between von Willebrand factor and the Alternative Complement Pathway.
    Seminars in thrombosis and hemostasis, 2014
    Co-Authors: Nancy A. Turner, Sarah E. Sartain, Leticia Nolasco, Jennifer Nolasco, Joel L. Moake
    Abstract:

    Molecular linkages between von Willebrand factor (VWF) and the Alternative Complement Pathway (AP) have recently been discovered. Endothelial cell (EC)-anchored ultra-large (UL) VWF multimeric strings function as an activating surface for the AP. C3 (in active C3b form) binds to the EC-anchored ULVWF strings, and promotes the assembly of C3bBb (C3 convertase) and C3bBbC3b (C5 convertase). These linkages may help to explain enigmatic clinical problems related to thrombotic microangiopathies, including some cases of refractory thrombotic thrombocytopenic purpura (TTP), TTP associated with only mild-modest deficiencies of ADAMTS-13, the provocation (or exacerbation) of acute episodes in patients with the atypical hemolytic uremic syndrome, and thrombosis in paroxysmal nocturnal hemoglobinuria. Recent experiments have also demonstrated that Complement factor H performs a dual role: participating in regulation of the AP by binding to EC-anchored ULVWF strings; and functioning as a reductase to decrease the size of soluble VWF multimers.

Rosario Fernandezgodino – One of the best experts on this subject based on the ideXlab platform.

  • changes in extracellular matrix cause rpe cells to make basal deposits and activate the Alternative Complement Pathway
    Human Molecular Genetics, 2018
    Co-Authors: Rosario Fernandezgodino, Eric A Pierce, Kinga M Bujakowska
    Abstract:

    The design of efficient therapies for age-related macular degeneration (AMD) is limited by our understanding of the pathogenesis of basal deposits, which form between retinal pigment epithelium (RPE) and Bruch’s membrane (BrM) early in disease, and involve activation of the Complement system. To investigate the roles of BrM, RPE and Complement in an AMD, we generated abnormal extracellular matrix (ECM) using CRISPR-edited ARPE-19 cells. We introduced to these cells the p.R345W mutation in EFEMP1, which causes early-onset macular degeneration. The abnormal ECM binds active Complement C3 and causes the formation of basal deposits by normal human fetal (hf)RPE cells. Human fetal RPE (hfRPE) cells grown on abnormal ECM or BrM explants from AMD donors show chronic activation of the Alternative Complement Pathway by excessive deposition of C3b. This process is exacerbated by impaired ECM turnover via increased matrix metalloproteinase-2 activity. The local cleavage of C3 via convertase-independent mechanisms can be a new therapeutic target for early AMD.

  • changes in extracellular matrix cause rpe cells to make basal deposits and activate the Alternative Complement Pathway
    bioRxiv, 2017
    Co-Authors: Rosario Fernandezgodino, Kinga M Bujakowska, Eric A Pierce
    Abstract:

    The design of efficient therapies for age-related macular degeneration (AMD) is limited by our understanding of the pathogenesis of basal deposits, which form between retinal pigment epithelium (RPE) and Bruch membrane (BrM) early in disease, and involve activation of the Complement system. To investigate the roles of BrM, RPE and Complement in AMD, we generated ARPE-19 cells with the p.R345W mutation in EFEMP1, which causes early-onset macular degeneration. The ARPE-19-EFEMP1R345W/R345W cells make abnormal extracellular matrix (ECM) that binds active Complement C3 and causes the formation of basal deposits by normal human fetal (hf)RPE cells. hfRPE cells grown on abnormal ECM or BrM explants from AMD donors show chronic activation of the Alternative Complement Pathway by excessive deposition of C3b. This process is exacerbated by impaired ECM turnover via increased matrix metalloproteinase-2 (MMP-2) activity. Therapies that target ECM synthesis and turnover and activation of C3 could be effective for early AMD.