title: Occlusal disharmony increases amyloid-β in the rat hippocampus.
abstract: Amyloid-β plays a causative role in Alzheimer's disease. Occlusal disharmony causes chronic psychological stress, and psychological stress increases amyloid-β accumulation. The purpose of the present study was to investigate whether occlusal disharmony-induced psychological stress affects the accumulation of amyloid-β and its related gene expressions in the rat hippocampus. Eight-week-old male Wistar rats (n = 18) were divided into three groups of six rats each: (1) a control group that received no treatment for 8 weeks; (2) an occlusal disharmony group that underwent cutoff maxillary molar cusps for 8 weeks; and (3) a recovered group that underwent cutoff maxillary molar cusps for 4 weeks followed by recovery for 4 weeks. Occlusal disharmony increased plasma corticosterone levels in a time-dependent manner. Levels of amyloid-β 40 and 42, glucocorticoid receptor (Gr) protein, and cleaved caspase 3 (Casp3) as well as gene expressions of amyloid precursor protein, beta-secretase, Casp3, and Gr in the hippocampus in the occlusal disharmony group were significantly higher than those in the control group (P < 0.016). These findings were significantly improved by recovery of occlusion (P < 0.016). These results indicate that psychological stress induced by occlusal disharmony reversibly induces amyloid-β 40 and 42 in the rat hippocampus through the glucocorticoid signal.
authors.affiliation: Department of Preventive Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama, 700-8558, Japan. dekuni7@md.okayama-u.ac.jp
authors.forename: D
authors.initials: D
authors.lastname: Ekuni
authors.forename: T
authors.initials: T
authors.lastname: Tomofuji
authors.forename: K
authors.initials: K
authors.lastname: Irie
authors.forename: T
authors.initials: T
authors.lastname: Azuma
authors.forename: Y
authors.initials: Y
authors.lastname: Endo
authors.forename: K
authors.initials: K
authors.lastname: Kasuyama
authors.forename: M
authors.initials: M
authors.lastname: Morita
mesh_terms: D000544:Alzheimer Disease / Q000209:etiology* / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D003345:Corticosterone / Q000097:blood; D003766:Dental Occlusion; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008310:Malocclusion / Q000150:complications*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D013315:Stress, Psychological / Q000150:complications* / Q000209:etiology*
chemical_list: D016229:Amyloid beta-Peptides; D011965:Receptors, Glucocorticoid; D053148:Caspase 3; D003345:Corticosterone