title: Ferric cycle activity and Alzheimer disease.
abstract: Elevated plasma homocysteine is an independent risk factor for the development of Alzheimer disease, however, the precise mechanisms underlying this are unclear. In this article, we expound on a novel hypothesis depicting the involvement of homocysteine in a vicious circle involving iron dysregulation and oxidative stress designated as the ferric cycle (Dwyer et al., 2004). Moreover, we suspect that the development of a critical heme deficiency in vulnerable neurons is an additional consequence of ferric cycle activity. Oxidative stress and heme deficiency are consistent with many pathological changes found in Alzheimer disease including mitochondrial abnormalities and impaired energy metabolism, cell cycle and cell signaling abnormalities, neuritic pathology, and other features of the disease involving alterations in iron homeostasis such as the abnormal expression of heme oxygenase-1 and iron response protein 2. Based on the ferric cycle concept, we have developed a model of Alzheimer disease development and progression, which offers an explanation for why sporadic Alzheimer disease is different than normal aging and why familial Alzheimer disease and sporadic Alzheimer disease could have different etiologies but a common end-stage.
authors.affiliation: Research Service, VA Medical and Regional Office Center, White River Junction, Vermont 05009, USA. barney.e.dwyer@dartmouth.edu
authors.forename: Barney E
authors.initials: BE
authors.lastname: Dwyer
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takeda
authors.forename: Xiongwei
authors.initials: X
authors.lastname: Zhu
authors.forename: George
authors.initials: G
authors.lastname: Perry
authors.forename: Mark A
authors.initials: MA
authors.lastname: Smith
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D000818:Animals; D001923:Brain Chemistry; D002453:Cell Cycle / Q000502:physiology; D006418:Heme / Q000172:deficiency; D006710:Homocysteine / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008954:Models, Biological; D018384:Oxidative Stress / Q000502:physiology
chemical_list: D006710:Homocysteine; D006418:Heme; D007501:Iron