AQP4 and brain edema: AQP4 expression is also sharply increased in ischemic brain edema (De Castro Ribeiro et al., 2006; Hirt et al., 2009), and AQP4-ko or inhibitor administration has been shown to be effective in reducing cellular edema (Manley et al., 2000; Igarashi et al., 2011; Akdemir et al., 2014; Yao et al., 2015).