Physiologic variations in blood plasminogen levels affect outcomes after acute cerebral thromboembolism in mice: a pathophysiologic role for microvascular thrombosis

Singh, Satish; Houng, Aiilyan K.; Wang, Dong; Reed, Guy L.

doi:10.1111/jth.13390

Cited by 14 publications

(17 citation statements)

References 43 publications

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“…the overall mortality from MCAo by 24 h after successful surgeries was 5.9% (1/17) in C57BL/6J mice [10% (1/10) for vehicle- and 0 (0/7) for t-PA-treated animals] and 31.25% (5/16) in plg −/− mice [28.6% (2/7) for vehicle- and 33.3% (3/9) for t-PA-treated animals]. The higher mortality rates of plg −/− compared to wild-type mice were expected due to increased cerebral microthrombosis in the plg deficient mice, resulting from the absence of plasmin-driven fibrinolysis (13).…”

Section: Methodsmentioning

confidence: 99%

t-PA Suppresses the Immune Response and Aggravates Neurological Deficit in a Murine Model of Ischemic Stroke

Draxler

Lee

et al. 2019

Front. Immunol.

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Introduction: Acute ischemic stroke (AIS) is a potent trigger of immunosuppression, resulting in increased infection risk. While thrombolytic therapy with tissue-type plasminogen activator (t-PA) is still the only pharmacological treatment for AIS, plasmin, the effector protease, has been reported to suppress dendritic cells (DCs), known for their potent antigen-presenting capacity. Accordingly, in the major group of thrombolyzed AIS patients who fail to reanalyze (>60%), t-PA might trigger unintended and potentially harmful immunosuppressive consequences instead of beneficial reperfusion. To test this hypothesis, we performed an exploratory study to investigate the immunomodulatory properties of t-PA treatment in a mouse model of ischemic stroke. Methods: C57Bl/6J wild-type mice and plasminogen-deficient (plg −/− ) mice were subjected to middle cerebral artery occlusion (MCAo) for 60 min followed by mouse t-PA treatment (0.9 mg/kg) at reperfusion. Behavioral testing was performed 23 h after occlusion, pursued by determination of blood counts and plasma cytokines at 24 h. Spleens and cervical lymph nodes (cLN) were also harvested and characterized by flow cytometry. Results: MCAo resulted in profound attenuation of immune activation, as anticipated. t-PA treatment not only worsened neurological deficit, but further reduced lymphocyte and monocyte counts in blood, enhanced plasma levels of both IL-10 and TNFα and decreased various conventional DC subsets in the spleen and cLN, consistent with enhanced immunosuppression and systemic inflammation after stroke. Many of these effects were abolished in plg −/− mice, suggesting plasmin as a key mediator of t-PA-induced immunosuppression. Conclusion: t-PA, via plasmin generation, may weaken the immune response post-stroke, potentially enhancing infection risk and impairing neurological recovery. Due to the large number of comparisons performed in this study, additional pre-clinical work is required to confirm these significant possibilities. Future studies will also need to ascertain the functional implications of t-PA-mediated immunosuppression for thrombolyzed AIS patients, particularly for those with failed recanalization.

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Section: Methodsmentioning

confidence: 99%

t-PA Suppresses the Immune Response and Aggravates Neurological Deficit in a Murine Model of Ischemic Stroke

Draxler

Lee

et al. 2019

Front. Immunol.

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“…Adult male and female MMP-9 +/+ and MMP-9 −/− mice on a C57Black/6J background (Jackson Labs, Bar Harbor, ME) of 9-15 weeks of age were used in a series of randomized and blinded experiments in which the operator and data analyst were blinded to the agent under study. Thromboembolic stroke was induced by injecting plasma clots made with pooled fresh frozen normal mouse plasma (with traces of I 125 -fibrinogen~ 5000 cpm) at the origin of left middle cerebral artery (MCA) essentially as we have described (Houng et al, 2014; Singh et al, 2016). Embolization was confirmed by ≥ 80% drop in hemispheric blood flow measured by a laser Doppler flow (LDF, ADInstruments, Oxford Optronics, UK) probe mounted on the skull.…”

Section: Methodsmentioning

confidence: 99%

“…Following whole body saline perfusion, the whole brain tissue was harvested and residual I 125 -fibrinogen radioactivity was immediately recorded in a gamma counter to calculate percent thrombus dissolution as we have previously described (Houng et al, 2014). The brain tissue was sectioned (2 mm) coronally to calculate the percent brain swelling, hemorrhage and infarction as we have described (Houng et al, 2014; Singh et al, 2016). Brain slices were immediately photographed digitally on both sides through a microscope before and after triphenyl tetrazolium chloride (TTC, 2%) staining.…”

Section: Methodsmentioning

confidence: 99%

Matrix Metalloproteinase-9 Mediates the Deleterious Effects of α2-Antiplasmin on Blood–Brain Barrier Breakdown and Ischemic Brain Injury in Experimental Stroke

2018

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During acute brain ischemia, α2-antiplasmin markedly enhances brain injury, blood brain barrier breakdown and matrix metalloproteinase-9 (MMP-9) expression. Although α2-antiplasmin inhibits fibrin thrombus-degradation, and MMP-9 is a collagen-degrading enzyme altering blood brain barrier, both have similar deleterious effects on the ischemic brain. We examined the hypothesis that MMP-9 is an essential downstream mediator of α2-antiplasmin’s deleterious effects during brain ischemia. Middle cerebral artery thromboembolic stroke was induced in a randomized, blinded fashion in mice with increased blood levels of α2-antiplasmin. There was a robust increase in MMP-9 expression (immunofluorescence) in the ischemic vs. the non-ischemic hemisphere of MMP-9+/+ but not MMP-9−/− mice, 24 h after stroke. Brain swelling and hemorrhage were significantly increased in the ischemic vs. the non-ischemic hemisphere of MMP-9+/+ mice. By comparison to MMP-9+/+ mice, the ischemic hemispheres of MMP-9−/− mice showed a ~6-fold reduction in brain swelling (p<0.001) and a ~9-fold reduction in brain hemorrhage. Brain infarction (p<0.0001) and TUNEL-positive cell death (p<0.001) were significantly diminished in the ischemic hemisphere of MMP-9−/− mice vs. MMP-9+/+ mice. Ischemic breakdown of the blood brain barrier and fibrin deposition were also significantly reduced in MMP-9−/− mice vs. MMP-9+/+ mice (p<0.05), as measured by quantitative immunofluorescence. We conclude that MMP-9 deficiency ablates many of the deleterious effects of high α2-antiplasmin levels, significantly reducing blood brain barrier breakdown, TUNEL-positive cell death, brain hemorrhage, swelling and infarction. This suggests that the two molecules may be in a shared pathway in which MMP-9 is essential downstream for the deleterious effects of α2-antiplasmin in ischemic stroke.

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“…69 Consistent with this observation, plasminogen deficiency enhances, and high plasminogen levels reduce microvascular thrombosis in experimental ischemic stroke. 70 The extent of microvascular thrombosis was more strongly associated with the sequelae of severe ischemic brain injury than the magnitude of dissolution of the middle cerebral thrombus. Although r-tPA therapy more efficiently dissolved the MCA thrombus than a2AP-I, the a2AP-I induced a greater reduction in microvascular thrombosis, which was associated with larger decrease in ischemic brain injury.…”

Section: Effects Of α 2 -Antiplasmin On the Ischemic Brain Microvascumentioning

confidence: 98%

α2-Antiplasmin: New Insights and Opportunities for Ischemic Stroke

Reed

Houng

Singh

et al. 2016

Semin Thromb Hemost

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Thrombotic vascular occlusion is the leading cause of ischemic stroke. High blood levels of α2-antiplasmin, an ultrafast, covalent inhibitor of plasmin, have been linked in humans to increased risk of ischemic stroke and failure of tissue plasminogen activator therapy. Consistent with these observations, α2-antiplasmin neutralizes the therapeutic benefit of tissue plasminogen activator therapy in experimental stroke. In addition, α2-antiplasmin has deleterious, dose-related effects on ischemic brain injury in the absence of therapy. Experimental therapeutic inactivation of α2-antiplasmin markedly reduces microvascular thrombosis, ischemic brain injury, brain swelling, brain hemorrhage and death after thromboembolic stroke. These data provide new insights into the critical importance of α2-antiplasmin in the pathogenesis of ischemic brain injury and suggest that transiently inactivating α2-antiplasmin may have therapeutic value in ischemic stroke.

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Physiologic variations in blood plasminogen levels affect outcomes after acute cerebral thromboembolism in mice: a pathophysiologic role for microvascular thrombosis

Cited by 14 publications

References 43 publications

t-PA Suppresses the Immune Response and Aggravates Neurological Deficit in a Murine Model of Ischemic Stroke

t-PA Suppresses the Immune Response and Aggravates Neurological Deficit in a Murine Model of Ischemic Stroke

Matrix Metalloproteinase-9 Mediates the Deleterious Effects of α2-Antiplasmin on Blood–Brain Barrier Breakdown and Ischemic Brain Injury in Experimental Stroke

α2-Antiplasmin: New Insights and Opportunities for Ischemic Stroke

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