CLEVELAND — A Cleveland-led team from University Hospitals, Case Western Reserve University and the Louis Stokes VA has identified a protein that appears to act as a gatekeeper for brain aging, offering a potential new target to slow age-related memory and thinking problems. The research, published in the journal PNAS, focuses on the blood-brain barrier, the tightly regulated “shield” of blood vessel cells that keeps toxins out, clears waste and directs blood flow to busy areas of the brain.