The disclosure provides methods and pharmaceutical compositions that include a microRNA (miR) or a mimic thereof and a pharmaceutically acceptable carrier for treating brain injuries (e.g., traumatic brain injury (TBI)), preventing or reducing neuronal death, preventing or reducing leukocyte infiltration, and/or preventing or reducing blood-brain barrier (BBB) disruption after brain injuries (e.g., TBI) in a subject. The miR may be selected from the group consisting of miR-125b-5p, miR-122-5p, and a combination thereof. In some embodiments, the methods include administering to the subject the miR or the mimic thereof to decrease the expression level of one or more genes (e.g., Mknk2, Alpk3, and Neu1).