A 52-year-old man with long-standing alcohol use disorder is brought to the ED for progressive confusion and somnolence. Family reports he has been more forgetful for 2 days and now is difficult to arouse. Exam shows asterixis and disorientation. Laboratory testing shows: ammonia 165 µmol/L (elevated), AST/ALT mildly elevated, total bilirubin elevated, INR elevated. Head CT shows no acute hemorrhage or mass effect. The patient is diagnosed with hepatic encephalopathy. Which CNS cell type is most directly responsible for the cytotoxic brain edema seen in this condition due to altered handling of nitrogen and neurotransmitters?