Chinese Herbal Medicine: A Great Opportunity for Reducing Thrombolysis-mediated Hemorrhagic Transformation in Ischemic Stroke Treatment

Abstract

Tissue plasminogen activator (t-PA) remains the only FDA approved drug for acute ischemic stroke treatment, but with a limited time window of 4.5 hours. Treatment beyond this time window increased the risk of hemorrhagic transformation (HT). Understanding the molecular mechanisms of HT is essential for developing adjunct therapy to attenuate HT. By using our newly developed specific and sensitive probe HKYellow AM, we directly observed the increase of peroxynitrite, a representative reactive nitrogen species, in the ischemic brains with delayed t-PA treatment, which led to matrix metalloproteinase (MMPs) activation. Importantly, co-treatment of peroxynitrite decomposition catalyst FeTmPyP significantly inhibited MMPs activation, decreased the HT and improved neurological outcomes. We then screened natural compounds from Chinese herbal medicine and found that baicalin efficiently and directly reacted with peroxynitrite in vivo and in vitro. Baicalin co-treatment with delayed t-PA significantly reduced the peroxynitrite level in ischemic neurons and brain microvascular endothelial cells, subsequently inhibited the MMPs activation and cell apoptosis, protected tight junction proteins and reduced the blood-brain barrier (BBB) damage, brain edema and hemorrhagic transformation. Importantly, the combination of baicalin with t-PA reduced the mortality rate and improved the neurological outcomes of ischemic stroke. We stepped forward to test the therapeutic effects of Angong Niuhuang pill (ANP), a traditional Chinese Medicine formula used for ischemic stroke treatment, and found that ANP could protect ischemic brains, and reduce HT through targeting the peroxynitrite-mediated MMP-9 activation in the ischemic brains. Our study highlights a novel therapeutic target for alleviating hemorrhagic transformation and the potential drug candidates for combination therapy with t-PA for ischemic stroke treatment.