A 48-year-old woman from Mumbai with a 5-year history of epigastric pain presents with acute hematemesis and melena. She has been taking ibuprofen daily for chronic knee pain for the past 18 months. On examination, she is hypotensive (88/54 mmHg) and tachycardic (112/min). Hemoglobin is 7.8 g/dL. Upper endoscopy shows a 2 cm ulcer in the gastric antrum with a clot at the base and surrounding edema. Rapid urease test is negative. What is the primary pathological consequence of chronic NSAID use that led to this ulcer?