Sodium‐chloride‐induced effects on the expression profile of human periodontal ligament fibroblasts with focus on simulated orthodontic tooth movement

Abstract

Increased salt (NaCl) consumption triggers chronic diseases such as hypertension or osteopenia. Its impact on orthodontic tooth movement and periodontitis, however, has not been investigated, although both processes are related to the immune system, with periodontal ligament fibroblasts (PDLFs) playing a key mediating role. Here, we investigated the impact of NaCl on the expression pattern of PDLFs in a model of simulated compressive orthodontic strain. Periodontal ligament fibroblasts were preincubated for 24 h with additional 0 or 40 mM NaCl and concurrently treated for another 48 h with or without compressive strain of 2 g cm−2. We analyzed the expression of genes and proteins involved in orthodontic tooth movement by reverse transcription quantitative polymerase chain reaction (RT‐qPCR), ELISA, and immunoblot. Co‐culture experiments were performed to observe PDLF‐mediated osteoclastogenesis. A higher (40 mM) concentration of NaCl in the culture medium resulted in increased secretion of prostaglandin, expression of alkaline phosphatase, and expression of genes involved in extracellular matrix remodeling, but decreased compression‐induced expression of the interleukin‐6 (IL6) gene. The 40 mM concentration of NaCl also enhanced receptor activator of nuclear factor kappa‐B ligand (RANKL) but reduced that of osteoprotegerin (OPG), resulting in upregulated PDLF‐mediated osteoclastogenesis. A high NaCl concentration in the periodontal ligament, corresponding to a high‐salt diet in vivo, may influence orthodontic tooth movement and periodontitis through increased secretion of prostaglandins by PDLFs and upregulated PDLF‐mediated osteoclastogenesis, possibly accelerating orthodontic tooth movement and propagating periodontitis and periodontal bone loss.

Impact of salt and the osmoprotective transcription factor NFAT‐5 on macrophages during mechanical strain

“…PTGS‐2 is an important enzyme in the production pathway of PG‐E2 from arachidonic acid. It is known that this pathway plays a role in inflammation and tooth movement 5,6,19 . In vitro experiments revealed increased Ptgs‐2 expression following stimulation with proinflammatory cytokines such as IL‐1 and TNF in many cell types, including synoviocytes, endothelial cells and osteoblasts 35 .…”

“…Increased salt intake provokes and triggers chronic diseases such as hypertension or osteopenia 14,38 . A higher amount of NaCl in the culture medium of periodontal ligament fibroblasts has already been reported to result in an increased secretion of prostaglandins and expression of alkaline phosphatase and genes involved in extracellular matrix rearrangement, but decreased compression‐related expression of IL‐6 19 . NaCl also seems to impair the expression of proinflammatory factors via NFAT‐5.…”

“…Even electrolytes such as sodium and potassium are consumed in modern society to a high degree as a dietary supplement and can therefore be pharmacologically and immunologically effective in appropriate doses via the electrolyte balance and their local tissue concentration 14,18 . These phenomena also occur in tissues of the oral cavity, in particular the oral mucosa, the gingiva and the periodontal ligament as components of the periodontal ligament 19 . Salt (NaCl) exposure is known to promote osteoclast formation during pressure application in periodontal ligament fibroblasts, indicating a direct effect on tooth movement velocity 19 .…”

“…These phenomena also occur in tissues of the oral cavity, in particular the oral mucosa, the gingiva and the periodontal ligament as components of the periodontal ligament 19 . Salt (NaCl) exposure is known to promote osteoclast formation during pressure application in periodontal ligament fibroblasts, indicating a direct effect on tooth movement velocity 19 . Observed Na + accumulation, however, can also impact on the activity of immune cells such as macrophages 18 .…”

Pharmaka, Noxen und die Ernährung – welche anamnestische Relevanz haben sie für die kieferorthopädische Therapie?

“…Der Großteil der täglichen Aufnahme von Kochsalz erfolgt dabei über sogenannte "versteckte" Salze in Käse, Brot oder sonstigen Fertigmahlzeiten, die in der heutigen Gesellschaft oft verstärkt konsumiert werden. Erste zellbiologisch-tierexperimentelle eigene Studien zu diesem Thema zeigten eine geringere Knochendichte und verbesserte Osteoklastendifferenzierung bei einer Hochsalzdiät und weisen darauf hin, dass ein erhöhter Kochsalzkonsum auch im Parodont die Osteoklastendifferenzierung fördern und damit die kieferorthopädische Zahnbewegung beschleunigen könnte [24,25]. Analog zu Nikotin ist jedoch auch eine unkontrollierte Zunahme von parodontalen Knochenverlusten und Zahnwurzelresorptionen denkbar, was in weitergehenden Studien geklärt werden muss.…”