PSEN1 and Alzheimer disease: In another study, in the APP/PS1 model of AD, intraperitoneally injected triptolide was found to reduce astrocyte proliferation and microglial activation in the hippocampal region, which was also related to the formation of pathological plaques and neurofibrillary tangles (Li et al., 2016; Villegas-Llerena et al., 2016).