Active α-macroglobulin is a reservoir for urokinase after fibrinolytic therapy in rabbits with tetracycline-induced pleural injury and in human pleural fluids

• Published in: American journal of physiology. Lung cellular and molecular physiology 2013-11, Vol.305 (10), p.L682-L692
• Main Authors: Komissarov, Andrey A, Florova, Galina, Azghani, Ali, Karandashova, Sophia, Kurdowska, Anna K, Idell, Steven
• Format: Article
• Language: English
• Subjects: alpha-Macroglobulins - metabolism; Animals; Blotting, Western; Cell Proliferation; Female; Fibrinolysis - drug effects; Fibrinolytic Agents - pharmacology; Humans; Immunoenzyme Techniques; Immunoprecipitation; Plasminogen Activator Inhibitor 1 - metabolism; Pleura - drug effects; Pleura - injuries; Pleura - metabolism; Rabbits; Receptors, Urokinase Plasminogen Activator - metabolism; Recombinant Proteins - metabolism; Tetracyclines - pharmacology; Thrombolytic Therapy; Urokinase-Type Plasminogen Activator - metabolism
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00102.2013

Intrapleural processing of prourokinase (scuPA) in tetracycline (TCN)-induced pleural injury in rabbits was evaluated to better understand the mechanisms governing successful scuPA-based intrapleural fibrinolytic therapy (IPFT), capable of clearing pleural adhesions in this model. Pleural fluid (PF) was withdrawn 0-80 min and 24 h after IPFT with scuPA (0-0.5 mg/kg), and activities of free urokinase (uPA), plasminogen activator inhibitor-1 (PAI-1), and uPA complexed with α-macroglobulin (αM) were assessed. Similar analyses were performed using PFs from patients with empyema, parapneumonic, and malignant pleural effusions. The peak of uPA activity (5-40 min) reciprocally correlated with the dose of intrapleural scuPA. Endogenous active PAI-1 (10-20 nM) decreased the rate of intrapleural scuPA activation. The slow step of intrapleural inactivation of free uPA (t1/2(β) = 40 ± 10 min) was dose independent and 6.7-fold slower than in blood. Up to 260 ± 70 nM of αM/uPA formed in vivo [second order association rate (kass) = 580 ± 60 M(-1)·s(-1)]. αM/uPA and products of its degradation contributed to durable intrapleural plasminogen activation up to 24 h after IPFT. Active PAI-1, active α2M, and α2M/uPA found in empyema, pneumonia, and malignant PFs demonstrate the capacity to support similar mechanisms in humans. Intrapleural scuPA processing differs from that in the bloodstream and includes 1) dose-dependent control of scuPA activation by endogenous active PAI-1; 2) two-step inactivation of free uPA with simultaneous formation of αM/uPA; and 3) slow intrapleural degradation of αM/uPA releasing active free uPA. This mechanism offers potential clinically relevant advantages that may enhance the bioavailability of intrapleural scuPA and may mitigate the risk of bleeding complications.