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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Antifibrinolytic Agents, Blood Coagulation Disorders, Carboxypeptidase B2, Cecum, Cells, Cultured, Complement C3a, Complement C5a, Disease Models, Animal, Enzyme Activation, Fibrin, Inflammation Mediators, Leukopenia, Ligation, Liver, Macrophage Activation, Macrophages, Peritoneal, Male, Mice, Inbred C57BL, Mice, Knockout, Peritonitis, Protective Factors, Punctures, Risk Factors, Sepsis, Thrombin, Thrombomodulin, Time Factors.
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Does carboxypeptidase B2 deficiency reveal opposite effects of complement C3a and C5a in a murine polymicrobial sepsis model? Context: Carboxypeptidase B2 (CPB2) is a basic carboxypeptidase with fibrin and complement C3a and C5a as physiological substrates. We hypothesized that in polymicrobial sepsis, CPB2-deficient mice would have sustained C5a activity, leading to disease exacerbation. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP). Contrary to our hypothesis, Cpb2(-/-) mice had significantly improved survival, with reduced lung edema, less liver and kidney damage, and less disseminated intravascular coagulation. Hepatic pro-CPB2 was induced by CLP, leading to increased pro-CPB2 levels. Thrombomodulin present on mesothelium supported thrombin activation of pro-CPB2. Both wild-type and Cpb2(-/-) animals treated with a C5a receptor antagonist had improved survival, demonstrating that C5a was detrimental in this model. Treatment with a fibrinolysis inhibitor, tranexamic acid, caused a decrease in survival in both genotypes; however, the Cpb2(-/-) animals retained their survival advantage. Administration of a C3a receptor antagonist exacerbated the disease in both wild-type and Cpb2(-/-) mice and eliminated the survival advantage of Cpb2(-/-) mice. C5a receptor is expressed in both peritoneal macrophages and neutrophils; in contrast, C3a receptor expression is restricted to peritoneal macrophages, and C3a induced signaling in macrophages but not neutrophils.
assistant
While C5a exacerbates the peritonitis, resulting in a deleterious generalized inflammatory state, C3a activation of peritoneal macrophages may limit the initial infection following CLP, thereby playing a diametrically opposing protective role in this polymicrobial sepsis model. Final Decision: yes