Abstract
Tissue plasminogen activator (t-PA) has a restrictive therapeutic window within 4.5 h after ischemic stroke with the risk of hemorrhagic transformation (HT) and neurotoxicity when it is used beyond the time window. In the present study, we tested the hypothesis that baicalin, an active compound of medicinal plant, could attenuate HT in cerebral ischemia stroke with delayed t-PA treatment. Male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) for 4.5 h and then continuously received t-PA infusion (10 mg/kg) for 0.5 h and followed by 19-h reperfusion. Baicalin (50, 100, 150 mg/kg) was administrated via femoral vein at 4.5 h after MCAO cerebral ischemia. Delayed t-PA infusion significantly increased the mortality rate, induced HT, blood-brain barrier (BBB) damage, and apoptotic cell death in the ischemic brains and exacerbated neurological outcomes in cerebral ischemia-reperfusion rats at 24 h after MCAO cerebral ischemia. Co-treatment of baicalin significantly reduced the mortality rates, ameliorated the t-PA-mediated BBB disruption and HT. Furthermore, baicalin showed to directly scavenge peroxynitrite and inhibit MMP-9 expression and activity in the ischemic brains with the delayed t-PA treatment. Baicalin had no effect on the t-PA fibrinolytic function indicated by t-PA activity assay. Taken together, baicalin could attenuate t-PA-mediated HT and improve the outcomes of ischemic stroke treatment possibly via inhibiting peroxynitrite-mediated MMP-9 activation.
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Acknowledgements
We thank Mr. Chong Gao and Ms. Jinghan Feng, Dr. Lei Zhao and Dr. Hao Wu for assistance in the immunofluorescence study and animal study.
Funding
This work was supported by Hong Kong General Research Fund (GRF No. 17102915, GRF No. 17118717), Research Grant Council, Hong Kong SAR; Health and Medical Research Fund, Hong Kong SAR (No. 13142901); AoE/P-705/16 Areas of Excellence Scheme, RGC, Hong Kong SAR; SIRI/04/04/2015/06 Shenzhen Basic Research Plan Project; National Natural Science Foundation of China (No. 81671164); and Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No. 13KJA310005).
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Animal experimental protocols were conducted in accordance with the national and institutional guidelines on ethics and biosafety, which were approved and regulated by the Committee on the Use of Live Animals in Teaching and Research (CULATR), HKU.
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Supplementary Figure 1
Baicalin inhibited AQP4 expression in ischemic brains with delayed t-PA treatment. A, representative immunoblotting of AQP4 in ischemic brains; B, statistical analysis of AQP4 expression; * or & p < 0.05, ** or ## p < 0.01, n = 4. (JPEG 45 kb)
Supplementary Figure 2
baicalin scavenged peroxynitrite in human neuroblastoma SHSY-5Y cells treated with oxygen and glucose deprivation (OGD) plus tissue plasminogen activator (t-PA), or treated with peroxynitrite donor SIN-1. A, SHSY-5Y cells were subjected to OGD 6 h plus reoxygenation 2 h, with or without t-PA treatment. t-PA was dissolved in DMEM medium and treated at a dosage of 20 μg/ml. Baicalin was given at a concentration of 10 uM; B, Normal SHSY-5Y cells was incubated with peroxynitrite donor SIN-1 (500 uM) at 37 °C for 4 h, with or without baicalin (10 uM). Peroxynitrite was detected with specific probe HK-Yellow AM with red fluorescence. (JPEG 40 kb)
Supplementary Figure 3
Baicalin protected brain microvascular endothelial b.End3 cells viability against oxygen and glucose deprivation (OGD) injury. b.End3 was subjected to OGD 5 h plus reoxygenation 19 h. Baicalin was given during reperfusion at 10 uM. Cell viability was determined by MTT assay. **** p < 0.0001, ## p < 0.01, &&& p < 0.001, n = 3. (JPEG 32 kb)
Supplementary Figure 4
baicalin did not induce cell death at 100 uM in brain microvascular endothelial b.End3 cells and neuroblastoma SH-SY5Y cells. b. End3 or SH-SY5Y cells were incubated with baicalin at 10 uM or 100 uM for 24 h. Cell viability was determined after treated for 24 h via MTT assay. (JPEG 34 kb)
Supplementary Figure 5
baicalin did not induce cell shrinkage at 100 uM in brain microvascular endothelial b.End3 cells and neuroblastoma SH-SY5Y cells. b.End3 or SH-SY5Y cells were incubated with baicalin at 10 uM or 100 uM for 24 h. Cell morphology was observed by optical microscope. (JPEG 250 kb)
Supplementary Figure 6
baicalin inhibited the 3-NT signaling in ischemic brains with delayed t-PA treatment, which partially co-localized with neuron marker MAP2. Co-staining of 3-NT and MAP2 was performed in ischemic brain tissues to observe the 3-NT production in the neurons. Green signal stands for MAP2 positive; Pink signal stands for 3-NT positive; blue signal represents nucleus (DAPI positive); white color stands for overlap of MAPs2 and 3-NT signal. n = 3 (JPEG 135 kb)
Supplementary Figure 7
3-NT did not co-localize with astrocyte marker GFAP in ischemic brains with delayed t-PA treatment. Ischemic brain tissues were stained with GFAP antibody and 3-NT antibody, and results revealed no significant overlap of these two signal. Green signal stands for GFAP positive, pink signal stands for 3-NT positive, the blue signal represents nucleus (DAPI positive). n = 3 (JPEG 69 kb)
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Chen, H., Guan, B., Chen, X. et al. Baicalin Attenuates Blood-Brain Barrier Disruption and Hemorrhagic Transformation and Improves Neurological Outcome in Ischemic Stroke Rats with Delayed t-PA Treatment: Involvement of ONOO−-MMP-9 Pathway. Transl. Stroke Res. 9, 515–529 (2018). https://doi.org/10.1007/s12975-017-0598-3
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DOI: https://doi.org/10.1007/s12975-017-0598-3