Alveolar macrophage plasminogen activator

Host-directed therapies targeting the tuberculosis granuloma stroma

Mycobacteria have co-evolved with their hosts resulting in pathogens adept at intracellular survival. Pathogenic mycobacteria actively manipulate infected macrophages to drive granuloma formation while subverting host cell processes to create a permissive niche. Granuloma residency confers phenotypic antimicrobial resistance by physically excluding or neutralising antibiotics. Host-directed therapies (HDTs) combat infection by restoring protective immunity and reducing immunopathology independent of pathogen antimicrobial resistance status. This review covers innovative research that has discovered ‘secondary’ symptoms of infection in the granuloma stroma are actually primary drivers of infection and that relieving these stromal pathologies with HDTs benefits the host. Advances in our understanding of the relationship between tuberculosis and the host vasculature, haemostatic system and extracellular matrix reorganisation are discussed. Preclinical and clinical use of HDTs against these stromal targets are summarised.

Production of protease inhibitors by postsurgical macrophages

The deposition and lysis of fibrin are important processes in normal peritoneal healing. Since macrophages secrete a neutral plasminogen activator, we studied the production of plasminogen-dependent, fibrinolytic activity by postsurgical macrophages. Peritoneal exudate macrophages were collected from rabbits after resection and reanastomosis of their ileum. Intracellular plasminogen activator (PA) activity of resident (nonsurgical) macrophages was 8.4 +/- 1.8 milli-Plough units (mPU)/10(6) cells. Postsurgical Day 1 macrophages had significantly less activity (0.33 +/- 0.056 mPU/10(6) cells) compared to resident cells. Thereafter, the PA activity gradually increased and reached control levels by Postsurgical Day 7. The PA activity secreted by postsurgical macrophages into serum-free medium after 48 hr of culture was also determined. Conditioned medium from macrophages collected on Postoperative Days 1-5 exhibited less PA activity than buffer controls. PA activity was detected after acid treatment of the conditioned medium to remove acid-labile inhibitors. The activities of PA in acid-treated conditioned medium increased gradually and reached nonsurgical levels by Postsurgical Day 7. In spent medium from macrophages collected on Postsurgical Days 1-3, high levels of urokinase inhibitory activities were secreted; production gradually decreased during the later postoperative period. This inhibitory activity of macrophage-conditioned medium on urokinase-like PA activity was partially diminished by acidification of the media. These results support the hypothesis that macrophages in the postsurgical exudate may play an important role in the fibrinolytic process during peritoneal wound healing, perhaps through production and secretion of plasminogen activator as well as acid-labile and resistant protease inhibitors.

The role of proteases in 4-ipomeanol-induced enhancement of Sendai viral pneumonia in mice

The ability of reconstituted, concentrated lyophilized lavage fluid to activate noninfectious Sendai virus (NISV) in vitro was examined. Lavage fluid was obtained from 4-ipomeanol (4-IP)-injured lungs at 1, 3, 5, 7, 9, and 13 days after treatment, and 1, 7, and 13 days after sham treatment (controls). Significantly higher viral titers were obtained using lavage fluid collected 1 day after 4-IP treatment. Higher protein concentrations were present in lavage fluid obtained at day 1 and 3 after 4-IP treatment. It is concluded that local viral-activating protease concentrations resulting from 4-IP-induced pulmonary injury is a likely microenvironmental modulator of paramyxoviral replication and can play an important role in paramyxoviral-induced lung injury.

Differential secretion of plasminogen activator activity by postsurgical activated macrophages

Macrophage functions during postsurgical tissue repair include secretion of neutral proteases like plasminogen activator. Accordingly, we studied the differential secretion of plasminogen activator by postsurgical macrophages. Rabbits underwent resection and reanastomosis of their small bowel (three rabbits/time group). Postoperatively (up to 28 days), they underwent a second laparotomy for collection of ascites cells by lavage. Cells were incubated with culture medium containing 10% acid-treated fetal calf serum. After 2 days, the medium was removed (1-2 days media, M1) and replaced for 2 more days (3-4 days media, M2). Plasminogen activator activity of the medium (M1 and M2) was determined using a modified indirect solid-phase radioassay. The specific plasminogen activator activity (plasminogen-dependent-plasminogen-independent activator activity) in M1 was 43 mPU/10(6) cells in nonsurgical control rabbits. Exudative cells on Day 1 had less activity than control, and by Day 5, the activity significantly increased to 290% of control levels, reaching peak value on Day 14 (360%). The specific plasminogen activator activity in M2 was 310 mPU/10(6) cells in nonsurgical control media. Exudative cells on Day 1 had less activity than control, while, on Days 3-7, they were the same as control. By day 10, specific activity significantly increased to peak levels 188% of control and then gradually decreased. Since a marked increase in the number of macrophages parallels the increase in these metabolic activities through postsurgical Day 10, postsurgical activated macrophages appear to play an important role in peritoneal healing.