Annexin A2 Combined with Low-Dose tPA Improves Thrombolytic Therapy in a Rat Model of Focal Embolic Stroke

Abstract

Recent studies showed that soluble annexin A2 dramatically increases tissue plasminogen activator (tPA)-mediated plasmin generation in vitro, and reduces thrombus formation in vivo. Here, we hypothesize that combining annexin A2 with tPA can significantly enhance thrombolysis efficacy, so that lower doses of tPA can be applied in ischemic stroke to avoid neurotoxic and hemorrhagic complications. In vitro activity assays confirmed tPA-specific amplification of plasmin generation by recombinant annexin A2. In a rat focal embolic stroke model, combination therapy with tPA and recombinant annexin A2 protein at 2 h post-ischemia decreased the effective dose required for tPA by four-fold and reduced brain infarction. Combining annexin A2 with tPA also lengthened the time window for thrombolysis. Compared with tPA (10 mg/kg) alone, the combination of annexin A2 (5 mg/kg) plus low-dose tPA (2.5 mg/kg) significantly enhanced fibrinolysis, attenuated mortality, brain infarction, and hemorrhagic transformation, even when administered at 4 h post-ischemia. Combination with recombinant annexin A2, the effective thrombolytic dose of tPA can be decreased. As a result, brain hemorrhage and infarction are reduced, and the time window for stroke reperfusion prolonged. Our present findings provide a promising new approach for enhancing tPA-based thrombolytic stroke therapy.

High-density Lipoprotein–based Therapy Reduces the Hemorrhagic Complications Associated With Tissue Plasminogen Activator Treatment in Experimental Stroke

“…In fact, late administration of tPA (4 hours) has been shown to have no effect on infarct volume of focal IS in rodents. 31 The percentage of hematoma and death differed significantly between the 2 models probably because of the difference in MCA occlusion time. As we have shown in a duplex sonography study, in a similar embolic stroke model, 29% of rats with confirmed MCAO occlusion had undergone recanalization between 1 and 4 hours after stroke onset, 32 whereas MCA occlusion induced by a filament lasted exactly 4 hours.…”

Recombinant tissue plasminogen activator promotes, and progesterone attenuates, microglia/macrophage M1 polarization and recruitment of microglia after MCAO stroke in rats

“…Previous studies have shown 8 mg/kg to be the optimally effective PROG dose in a stroke model (Ishrat et al, 2009(Ishrat et al, , 2010. Physiologic saline with tPA (Genentech, San Francisco, CA, USA) was administered (10% bolus, 90% continuous infusion within 30 min) to the rats via femoral vein beginning 10 min before reperfusion at 5 mg/kg, a dose shown to have optimal fibrinolytic activity with lower mortality (Saver et al, 2013;Zhu et al, 2010) (see Table 1). …”

Progesterone Attenuates Hemorrhagic Transformation after Delayed tPA Treatment in an Experimental Model of Stroke in Rats: Involvement of the VEGF–MMP Pathway

“…Physiologic saline with tPA (Genentech, San Francisco, CA, USA) was administered (10% bolus, 90% continuous infusion within 30 minutes) to the rats via femoral vein beginning 10 minutes before reperfusion at 5 mg/kg, a dose shown to have optimal fibrinolytic activity with lower mortality. 16 Measurement of Brain Swelling Brain swelling was estimated 24 hours post-occlusion by measuring the hemispheric areas of 2-mm thick brain slices using ImageJ software (NIH, Bethesda, MD, USA). The extent of swelling was calculated using the following equation: extent of brain swelling ¼ (volume of ipsilateral hemisphere-volume of contralateral hemisphere)/volume of contralateral hemisphere.…”