Investigating Microtubule-Associated Protein 2 in the Study of Postoperative Delirium

Background This study explored potential associations between microtubule-associated protein 2 (MAP2), as a marker of neuronal stress, and postoperative delirium. Methods Custom single-molecule immunoassays were used to measure MAP2 in serum collected from two small cohorts of older adults undergoing major cardiac surgery. An in vitro study of differentiated SH-SY5Y cells derived from a neuroblastoma cell line was performed to assess MAP2 secretion following exposure to acute glutamate stimulation. Results Patients who experienced postoperative delirium within 3 days of surgery had increased MAP2 serum levels on postoperative day 1. Perioperative blood sampling revealed an increase in circulating MAP2 at the end of cardiopulmonary bypass that was sustained up to postoperative day 3 in patients who developed delirium. Differentiated SH-SY5Y cells exposed to high-dose glutamate showed increased MAP2 in conditioned media independent of changes in total cytosolic protein levels suggesting that extracellular stimuli may promote acute secretion of MAP2 without inducing cell rupture. Conclusion Further studies exploring the MAP family as biomarkers of cognitive changes following surgery are warranted.