Targeting neutrophil extracellular traps enhanced tPA fibrinolysis for experimental intracerebral hemorrhage

The minimally invasive surgery plus fibrinolysis has been identified as a promising treatment for spontaneous intracerebral hemorrhage (ICH). However, the fibrinolytic efficacy is not satisfactory. Neutrophil extracellular traps (NETs) have been demonstrated to impair fibrinolysis in sepsis and acute ischemic stroke. Therefore, we decided to explore the presence and potential effect of NETs in ICH fibrinolysis. Intracerebral hemorrhage was induced by autologous arterial blood injection into the basal ganglia in rats. First, at 0.5 hour, 1 hour, and 1.5 hours after blood injection, the brains were collected for NETs detection by immune-staining. Second, ICH rats were given intrahematoma fibrinolysis: rats were randomized to receive the equal amount of saline, DNAse 1, tissue-plasminogen activator (tPA), and tPA + DNAse 1 at 1 hour after hematoma placement. On day 3, animals were sacrificed for terminal deoxynucleotidyl transferase-mediated dUTP Nick-end labeling staining following MRI and behavioral tests. Third, on day 3 after ICH, the hematoma within brain were collected for ex vivo fibrinolysis assay to further evaluate the effect of NETs in ICH fibrinolysis. Co-staining of DAPI, H3, and MPO confirmed the presence of NETs in ICH. Disintegration of NETs using DNAse 1 enhanced tPA-induced hematoma fibrinolysis, relieved brain swelling, reduced cell death, and improved the functional outcome in ICH rats. Therefore, we concluded that NETs impaired the efficacy of tPA for ICH fibrinolysis in rats. Targeting NETs may be a new alternative to improve the fibrinolytic therapy following ICH.