APOE and Alzheimer disease: The presence of Aβ plaques and elevated RAGE expression enhanced MMP secretion from the brain capillaries in an animal model of AD.[129] Also Aβ1‐42 (as oligo) increased the levels of MMP‐2 and MMP‐9 in the brain ECs.[130] Furthermore, MMP‐9 is also accumulated in pericytes of AD ApoE4 carrier patients.[125] These enzymes further affect the BBB integrity and make it more permeable.