A 68-year-old man is brought to the emergency department 50 minutes after sudden onset of right-sided weakness and difficulty speaking. He has a history of hypertension, hyperlipidemia, and tobacco use. On examination, he has expressive aphasia and right facial droop with right arm and leg weakness. Noncontrast CT of the head shows no hemorrhage. MRI performed shortly afterward shows restricted diffusion in the left middle cerebral artery territory. Which of the following cellular mechanisms most directly explains the early development of the cerebral edema in the affected region?