Treatment with recombinant tissue plasminogen activator (r-TPA) induces neutrophil degranulation in vitro via defined pathways

Thrombolysis is recommended for reperfusion following acute ischemic stroke (AIS), but its effects on stroke-associated injury remain to be clarified. Here, we investigated the effects of recombinant tissue plasminogen activator (r-tPA) on neutrophil pathophysiology in vitro and in a case-control study with AIS patients submitted (n=60) or not (n=30) to thrombolysis. Patients underwent radiological and clinical examination as well as blood sampling at admission and after 1, 7 and 90days. In vitro, 30-min incubation with 0.1-1 mg/ml r-tPA induced neutrophil degranulation in different substrate cultures. Pre-incubation with kinase inhibitors and Western blot documented that degranulation was associated with activation of PI3K/Akt and ERK1/2 pathways in Teflon dishes and PI3K/Akt in polystyrene. In thrombolysed patients, a peak of neutrophil degranulation products (matrix metalloproteinase [MMP]-9, MMP-8, neutrophil elastase and myeloperoxidase), was shown during the first hours from drug administration. This was accompanied by serum augmentation of protective tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2. An increased rate of haemorrhagic transformations on day 1 after AIS was shown in thrombolysed patients as compared to non-thrombolysed controls. In conclusion, r-tPA treatment was associated with in vitro neutrophil degranulation, indicating these cells as potential determinants in early haemorrhagic complications after thrombolysis in AIS patients.