HMOX1 and early-onset autosomal dominant Alzheimer disease: However, more than 53 studies have revealed the cytotoxic effect of HO-1 in Alzheimer's disease, such as abnormal iron deposition in astrocytes [27], nerve damage [28], and the uptake of excitotoxic neurotransmitters from the synaptic cleft [29], leading to cognitive decline, olfactory impairment, and neuronal endocrine disorders.