Abstract
BackgroundPsychosocial stress is one of the risk factors for atherosclerosis. As occlusal disharmony induces psychological stress, we hypothesized that psychological stress by occlusal disharmony accelerates atherosclerosis. The aim of this study was to investigate the effects of occlusal disharmony on the initiation of atherosclerosis in apolipoprotein E (apoE) knockout rats.MethodsFourteen male apoE-knockout rats (age; 8 weeks) (Sprague–Dawley strain background) were divided into two groups of seven rats: the occlusal disharmony group and the no treatment (control) group. In the occlusal disharmony group, the maxillary molar cusps were cut off for the 8-week experimental period.ResultsIn the occlusal disharmony group, the percentages of the area of total aortic lumen occupied by plaques and lipid were significantly higher than those in the control group (p < 0.05, t-test). The occlusal disharmony group also showed significantly higher serum levels of very low-density lipoprotein-cholesterol (VLDL) and low-density lipoprotein-cholesterol (LDL), plasma levels of corticosterone (1.9, 1.3 and 1.3 times, respectively), higher aortic protein expression levels of vascular cell adhesion molecule-1 (VCAM1) and intercellular adhesion molecule-1 (ICAM1) (1.5 and 1.4 times, respectively), and higher aortic gene expression of levels of VCAM1 and Toll-like receptor 4 (TLR4) (1.9 and 4.3 times, respectively), as compared to the control group (p < 0.05). However, there were no significant differences in serum levels of oxidized LDL, reactive oxygen metabolites and C-reactive protein between the two groups.ConclusionIn apoE knockout rats, occlusal disharmony may induce VCAM1, ICAM1 and TLR4 expression and accelerate the initiation of atherosclerosis.
Highlights
Psychosocial stress is one of the risk factors for atherosclerosis
Experimental design Rats were randomly divided into two groups of seven rats each: a control group, which received no treatment for 8 weeks, and an occlusal disharmony group, in which all maxillary molar crowns were cut off at the gingival margin using a dental turbine for 8 weeks [26]
There were no significant differences in serum levels of oxidized low-density lipoprotein-cholesterol (LDL), reactive oxygen metabolites (ROM) and C-reactive protein (CRP) between the two groups (p > 0.05) (Table 1)
Summary
Psychosocial stress is one of the risk factors for atherosclerosis. Atherosclerosis is a chronic disease of the arterial wall that leads to death and loss of productive life years worldwide [1]. The initial step in the development of atherosclerotic plaques is mediated, in part, by the monolayer of endothelial cells lining the inner wall of the arterial vessel [2]. Numerous risk factors contribute to atherosclerosis, including smoking [6], diabetes mellitus [7], dyslipidemia [8], hypertension [9,10] and periodontitis [11,12]. The absence of such traditional risk factors does not completely protect from the disease, which indicates additional factors involved in the development of atherosclerosis [13]. Oxidative stress is an important manifestation of the inflammatory responses during the atherogenesis [16]
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