Glomerular Filtration and Autoregulation

A 68-year-old man with decompensated heart failure (ejection fraction 25%) and mild baseline renal impairment (creatinine 1.8 mg/dL) presents to the emergency department. His wife reports he has been taking ibuprofen 400 mg three times daily for chronic knee pain for the past 2 weeks. On examination, he is orthostatic and clinically volume-depleted. His serum creatinine has risen to 3.2 mg/dL, and urinalysis shows no proteinuria or casts. The structure marked **A** in the diagram is the site of action of a critical autoregulatory mechanism that has been disrupted in this patient. Which of the following best explains the acute kidney injury in this clinical scenario?