APP and Alzheimer disease: In addition, elevated thromboxane A2 (TxA2) level activated microglia and showed an association with high concentrations of amyloid precursor protein (APP) in the brains of 5X5AD transgenic mice [77], whereas abnormally high levels of prostacyclin I2 (PGI2) were linked to the accumulation of Aβ in brain tissues and hastened AD development [78].