Endogenous Arteriolar Fibrinolysis Requires Urokinase Plasminogen Activator and Leukocyte Urokinase Plasminogen Activator Receptor-1.
Bibliographic record
Abstract
Abstract Background: In venous thrombi, urokinase associated with leukocytes activates plasminogen to initiate endogenous fibrinolysis. Leukocytes also interact with arteriolar thrombi. Objectives: We hypothesized that urokinase plasminogen activator (uPA) activity would also be delivered to arteriolar thrombi by leukocytes. Methods: Using established techniques of high-speed intravital fluorescence microscopy to observe the cremaster muscle of mice, we measured platelet and fibrin accumulation in thrombi generated by a laser injury to arterioles. The accumulation of platelets in a thrombus is quantitated by measuring the fluorescence from anti-CD41 antibody tagged with a fluorescent secondary antibody and the presence of fibrin is detected using a fluorescence-tagged anti-fibrin antibody (T2G1). Results: In C57BL/6 wild type mice, fibrin increased to a maximum at about three minutes after thrombus formation and then decreased, such that by eight minutes after thrombus formation fibrin is present at 34% of its maximal value. When wild type mice are pretreated with epsilon-aminocaproic acid (16 mg/kg IV), the decrease in thrombus fibrin content was less (to 54% of maximal 8 minutes after thrombus formation), implying that the fibrin loss is at least partially the result of plasmin activity. Thrombus fibrin accumulation in tissue-plasminogen activator deficient mice (Plat) was greater, peaking at 229% the amount found in wild type mice, but the amount of fibrin present at eight minutes after thrombus formation was not dissimilar from wild type mice (45% ± 5% v. 34% ± 3%, P=0.09). In uPA-deficient mice (Plau) and uPA-receptor-1-deficient mice (Plaur), the amount of maximal thrombus fibrin was 189% and 273% that of fibrin content in wild type mice. Also, although thrombus fibrin did decrease over time in Plau and Plaur mice, it decreased to only 51% and 48% of maximal (each were P < 0.005 v. wild type) at eight minutes after thrombus formation. When wild type leukocytes, isolated from blood by differential centrifugation and sucrose density gradient, were transfused into Plaur mice, thrombus fibrin loss was restored to wild type levels (38% of maximal at 8 minutes after thrombus formation, P=0.36 vs. wild type, P=0.016 vs. Plaur), implying that transfused wild type leukocytes, which express uPA-receptor-1, can rescue fibrinolysis in uPA-receptor-1-deficient mice. Conclusions: These results confirm that endogenous fibrinolytic activity in vivo occurs soon after arteriolar thrombus formation. The plasminogen activators that are required for this fibrinolysis to occur are uPA, and the uPA-receptor-1 on leukocytes. These findings are compatible with the hypothesis that leukocytes can deliver plasminogen activator activity to arteriolar thrombi to initiate endogenous fibrinolysis.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".