While the exact mechanisms of ischemia/reperfusion injury remain unclear, our laboratory and others have shown that inhibition of complement activation (e.g., sCR1 or C1 esterase inhibitor), depletion of complement components (e.g., cobra venom factor) and complement component (e.g., C3 and C4) deficient mice reveal an important role of complement in ischemia/reperfusion injury. In the last funding cycle, we showed that inhibition of mannose binding lectin (MBL) protected the ischemic gastrointestinal system from the primary ischemic event. In contrast, the pulmonary system, which takes a second hit from the primary ischemic gastrointestinal tract, was not protected. Complement activation in the lung was observed in C1qa- or MBL-deficient mice, but not in C2/factor B deficient (KO) mice. Addition of C2 restored the complement activation and tissue inflammation/injury in the C2/fB KO mice following gastrointestinal ischemia/reperfusion (GI/R). These data suggest that a C2 dependent, but C1q or MBL independent, process is responsible for the complement activation, inflammation and injury following GI/R. Preliminary data suggest that another lectin, ficolin-A is the initiating molecule responsible for complement activation in the lungs following GI/R. Recent publications also showed a C2/C4 bypass mechanism involving MBL may be responsible for complement activation via the alternative pathway. Preliminary studies demonstrate biological evidence of this bypass mechanism in vitro and several potential molecular mechanisms involving the MBL complex and the coagulation system. Studies by others show several different interactions with the coagulation system and complement. Using the FeCl3 model of arterial thrombogenesis, we observed that thrombogenesis was absent in MBL null mice, yet present in C2/fB null mice. We show that trauma patients demonstrate a link between complement activation and coagulopathy with a significant decrease in MBL levels observed early on. At least one of these interacting links involves the direct activation of the alternative pathway by the MBL complex, bypassing the need for C2 or C4. Our preliminary data demonstrate multiple interactions of lectin complexes with coagulation proteins and may explain why inhibition of complement has proven unsuccessful in clinical studies for CABG and CAD, warranting a better understanding of the complex interactions of complement with the coagulation system. In this competitive renewal, we will continue to investigate the molecular mechanisms involved in complement activation during oxidative stress of endothelial cells in vitro and in vivo and its interactions with the coagulation cascade. The general aim of this application is to characterize the molecular mechanisms governing lectin induced activation of coagulation following endothelial oxidative stress. Studies in this renewal will investigate the molecular mechanism of complement activation and interactions of complement with coagulation proteins. We will also be characterizing the potential use of a novel complement inhibitor that was recently discovered, cloned and expressed since our last submission, and is part of the lectin complex.

Public Health Relevance

Clinical inhibition of complement has failed for ischemia and reperfusion diseases (e.g., CAD and CABG), despite basic science studies showing protection in animal models. This grant will characterize the role of a novel lectin, ficolin-A, in the pulmonary injury observed following gastrointestinal ischemia, while also investigating the connections between the lectin complexes'ability to activate the coagulation system. The data demonstrate the importance of selecting the appropriate complement inhibitor for human disease because of the connectivity observed in these two cascade systems: complement and coagulation.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Surgery, Anesthesiology and Trauma Study Section (SAT)
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Schwartz, Lisa
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Brigham and Women's Hospital
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Ozaki, Masayuki; Kang, Yulin; Tan, Ying Siow et al. (2016) Human mannose-binding lectin inhibitor prevents Shiga toxin-induced renal injury. Kidney Int 90:774-82
Pavlov, Vasile I; Tan, Ying S; McClure, Erin E et al. (2015) Human mannose-binding lectin inhibitor prevents myocardial injury and arterial thrombogenesis in a novel animal model. Am J Pathol 185:347-55
Tong, Hua Hua; Lambert, Garrett; Li, Yong Xing et al. (2014) Deletion of the complement C5a receptor alleviates the severity of acute pneumococcal otitis media following influenza A virus infection in mice. PLoS One 9:e95160
Harboe, Morten; Garred, Peter; Lindstad, Julie K et al. (2012) The role of properdin in zymosan- and Escherichia coli-induced complement activation. J Immunol 189:2606-13
Zou, Chenhui; La Bonte, Laura R; Pavlov, Vasile I et al. (2012) Murine hyperglycemic vasculopathy and cardiomyopathy: whole-genome gene expression analysis predicts cellular targets and regulatory networks influenced by mannose binding lectin. Front Immunol 3:
Li, Qian; Li, Yong Xing; Douthitt, Kelsey et al. (2012) Role of the alternative and classical complement activation pathway in complement mediated killing against Streptococcus pneumoniae colony opacity variants during acute pneumococcal otitis media in mice. Microbes Infect 14:1308-18
Orsini, Franca; Villa, Pia; Parrella, Sara et al. (2012) Targeting mannose-binding lectin confers long-lasting protection with a surprisingly wide therapeutic window in cerebral ischemia. Circulation 126:1484-94
Stahl, Gregory L; Shernan, Stanton K; Smith, Peter K et al. (2012) Complement activation and cardiac surgery: a novel target for improving outcomes. Anesth Analg 115:759-71
La Bonte, Laura R; Pavlov, Vasile I; Tan, Ying S et al. (2012) Mannose-binding lectin-associated serine protease-1 is a significant contributor to coagulation in a murine model of occlusive thrombosis. J Immunol 188:885-91
Pavlov, Vasile I; Skjoedt, Mikkel-Ole; Siow Tan, Ying et al. (2012) Endogenous and natural complement inhibitor attenuates myocardial injury and arterial thrombogenesis. Circulation 126:2227-35

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