DNase I treatment reduces tPA-mediated BBB breakdown and cerebral hemorrhage after ischemic stroke. (A) Permeability coefficient (P) of human brain endothelial monolayers to 40 KDa of FITC-dextran at 0 to 6 hours after normoxia or OGD with or without NETs (1.5 μg/mL). (B) Representative immunoblots of H3Cit levels in the ischemic cortex at 24 hours after stroke in mice treated with vehicle, tPA, or tPA in combination with DNase I. (C) Quantification of the numbers of H3Cit⁺ neutrophils in the ischemic cortex (n = 6). (D) Representative images of the dorsal surface (upper panel) and a coronal section (bottom panel) show Evans blue extravasation 24 hours after stroke in mice treated with vehicle, tPA, tPA in combination with DNase I, or DNase I alone. (E) Quantification of Evans blue fluorescence intensity for each group (n = 8). (F-G) Representative immunoblots and quantification of immunoglobulin G (IgG) levels in capillary-depleted brain tissue at 24 hours after stroke (n = 5). (H) Representative immunoblots of the tight junction proteins zonula occludens-1 (ZO-1), claudin-5, and occludin and the adherens junction protein vascular endothelial–cadherin (VE-cadherin) in isolated brain microvessels. (I) Representative images of the dorsal surface (upper panel) and a coronal section (bottom panel) show cerebral hemorrhage 24 hours after stroke in mice treated with vehicle, tPA, tPA in combination with DNase I, or DNase I alone. (J) Quantification of cerebral hemorrhage by spectrophotometric hemoglobin assay (n = 8). (K-M) DNase I treatment improved neurological functions in forelimb force test and beam walking test (n = 10). Values are means ± standard deviation. *P < .05 vs control group (A), ^#P < .05 vs OGD group (A), *P < .05 (C,E,G,J-M).