AQP4 and brain edema: In addition, exposure of astrocytes to ammonia also induces astrocytic swelling, which can be exacerbated by cytokines/inflammatory mediators.14 Some experimental studies have also shown that increased plasma membrane aquaporin 4 levels contribute to the astrocytic swelling/brain edema in hepatic encephalopathy.10 We found no increased immunoreactivity for aquaporin 4 in AA II.