A 54-year-old man with a long history of alcohol use disorder is brought to the emergency department for progressive confusion, asterixis, and slurred speech. His family reports he has been increasingly somnolent over the past 2 days. He has scleral icterus, ascites, and disorientation to time and place. Labs show: ammonia 142 μmol/L (elevated), AST 98 U/L, ALT 62 U/L, total bilirubin 4.1 mg/dL. CT head shows no acute intracranial abnormality. The patient’s neurologic symptoms are attributed to the effect of hyperammonemia on glial cell metabolism.

Which of the following cellular changes is most directly responsible for cerebral edema and impaired neurotransmission in this condition?