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Background/Aims: This study investigated the role of the microRNA miR-298 and its target Act1 in ischemic stroke. Methods: Cell viability was assessed with the 3-(4,5-dimethythiazol-2- yl)-2,5-diphenyl tetrazolium bromide assay. Apoptotic cells were detected by flow cytometry, and mRNA and protein expression were assessed by quantitative real-time PCR and western blotting, respectively. The regulatory relationship between miR-298 and Act1 was evaluated with the luciferase assay. To clarify the role of Act1 following ischemic stroke, the transcript was knocked down by short interfering RNA. The in vitro findings were validated in a mouse model of middle cerebral artery occlusion by administration of miR-298 mimic. Results: Act1 was upregulated whereas miR-298 was downregulated in ischemic stroke. miR-298 overexpression by transfection of a mimic suppressed Act1 protein levels in vitro and in vivo, and the luciferase assay showed that miR-298 directly binds to the 3’ untranslated region of the Act1 transcript. miR-298 overexpression enhanced cell apoptosis and autophagy and exacerbated ischemic infarction and neurological deficits, effects that were exerted via negative regulation of Act1/c-Jun N-terminal kinase (JNK)/nuclear factor (NF)-κB signaling and downstream autophagy pathways. Conclusions: Upregulation of miR-298 following ischemic stroke promotes brain injury in vitro and vivo by inhibiting the Act1/JNK/NF-κB signaling cascade and the downstream autophagy pathway. Therapeutic strategies that target miR-298 could be beneficial for the treatment of ischemic stroke. [ABSTRACT FROM AUTHOR]