NOS3 and Alzheimer disease: Of note, while in APP23 mice it has been shown that BBB opening is required to clear Aβ [43], USonly applied in another AD mouse model (using a transducer at a higher (1.875 MHz) frequency) activated endothelial nitric oxide synthase (eNOS), an enzyme with a role in angiogenesis and vasodilation, stimulated microglia and removed Aβ [44].