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Occlusal Disharmony Increases Amyloid-β in the Rat Hippocampus

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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.

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Acknowledgments

This study was supported by grants-in-aid for a scholarship supporting Japanese national dental schools to promote dental research for patient’s QOL improvement awarded to Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences (2009) and for Scientific Research (23792512) from the Ministry of Education, Culture, Sports, Science and Technology, Tokyo, Japan.

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The authors have no conflicts of interest to declare.

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Authors and Affiliations

  1. 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

    D. Ekuni, T. Tomofuji, K. Irie, T. Azuma, Y. Endo, K. Kasuyama & M. Morita

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  1. D. Ekuni
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Correspondence to D. Ekuni.

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Ekuni, D., Tomofuji, T., Irie, K. et al. Occlusal Disharmony Increases Amyloid-β in the Rat Hippocampus. Neuromol Med 13, 197–203 (2011). https://doi.org/10.1007/s12017-011-8151-0

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