Astroglial N‐myc downstream‐regulated gene 2 protects the brain from cerebral edema induced by stroke

Brain edema is a grave complication of brain ischemia and is the main cause of herniation and death. Although astrocytic swelling is the main contributor to cytotoxic edema, the molecular mechanism involved in this process remains elusive. N‐myc downstream‐regulated gene 2 (NDRG2), a well‐studied tumor suppressor gene, is mainly expressed in astrocytes in mammalian brains. Here, we found that NDRG2 deficiency leads to worsened cerebral edema, imbalanced Na(+) transfer, and astrocyte swelling after ischemia. We also found that NDRG2 deletion in astrocytes dramatically changed the expression and distribution of aquaporin‐4 and Na(+)‐K(+)‐ATPase β1, which are strongly associated with cell polarity, in the ischemic brain. Brain edema and astrocyte swelling were significantly alleviated by rescuing the expression of astrocytic Na(+)‐K(+)‐ATPase β1 in NDRG2‐knockout mouse brains. In addition, the upregulation of astrocytic NDRG2 by lentiviral constructs notably attenuated brain edema, astrocytic swelling, and blood–brain barrier destruction. Our results indicate a particular role of NDRG2 in maintaining astrocytic polarization to facilitate Na(+) and water transfer balance and to protect the brain from ischemic edema. These findings provide insight into NDRG2 as a therapeutic target in cerebral edema.