IDO1 and Alzheimer disease: On the other hand, using AD mouse models [APOE knockout and APPswe/PSEN1dE9 double-transgenic (APP/PS1)], Duan Z. et al. demonstrated that proinflammatory cytokines and KP enzymes (IDO1, KYNU, KMO, and HAOO) were upregulated in the mouse hippocampus [85].