Vibration activates the actin/NF-κB axis and upregulates IL-6 and IL-8 expression in human periodontal ligament cells.

We previously reported that mechanical vibration-induced proinflammatory cytokines, interleukin-6 (IL-6) and IL-8, expression in human periodontal ligament (hPDL) cells, however, the underlying mechanism remained unclear. Mechanical stimuli are able to activate cellular responses by inducing the activation of several signaling pathways including cytoskeletal changes and inflammation. The actin cytoskeleton is a highly dynamic network and plays many important roles in intracellular events. Here, we aimed to investigate the involvement of a pivotal mediator of inflammatory responses, nuclear factor-κB (NF-κB), and actin polymerization in vibration-induced upregulation of IL-6 and IL-8 expression in hPDL cells. hPDL cells were pretreated with the NF-κB inhibitor BAY 11-7082 or cytochalasin D, respectively, before exposure to vibration. IL-6 and IL-8 messenger RNA (mRNA) and protein expression were quantified by quantitative polymerase chain reaction and enzyme-linked immunosorbent assays, respectively. Subcellular localization of the NF-κB p65 subunit was visualized by immunofluorescent staining. We found an increase in NF-κB nuclear translocation in vibrated cells compared with control cells. Pretreatment with BAY 11-7082 significantly inhibited vibration-induced IL-6 and IL-8 mRNA and protein expression in hPDL cells. Moreover, pretreatment with cytochalasin D inhibited NF-κB nuclear translocation and attenuated upregulation of IL-6 and IL-8 mRNA and protein in vibrated cells. Therefore, modulation of actin cytoskeletal polymerization in response to vibration may activate the NF-κB signaling pathway and subsequently upregulate IL-6 and IL-8 expression in hPDL cells.

Vibration enhances PGE2 , IL-6, and IL-8 expression in compressed hPDL cells via cyclooxygenase pathway.

BACKGROUND: Although vibration combined with orthodontic force may accelerate orthodontic tooth movement, little is known about the mechanisms that regulate the associated cellular responses. The goal of this study was to investigate whether mechanical vibration combined with compressive force regulates cyclooxygenase (COX)-2/prostaglandin E2 (PGE2 ) and interleukin (IL)-6 and IL-8 messenger RNA (mRNA) and protein expression in human periodontal ligament (hPDL) cells via the COX pathway. METHODS: The primary cultured hPDL cells were exposed to mechanical vibration, compressive force or a combination of both mechanical vibration and compressive force at 24, 48, and 72 hours. The COX-2, IL-6, IL-8, receptor activator of nuclear factor kappa-Β ligand (RANKL), and osteoprotegrin (OPG) mRNA expressions were determined using quantitative real-time polymerase chain reaction (qPCR). The PGE2 , IL-6, and IL-8 protein expressions were quantified by enzyme-linked immunosorbent assay (ELISA). To demonstrate whether the expression of PGE2 , IL-6, and IL-8 was in the COX-dependent pathway, the hPDL cells were treated with indomethacin. To determine whether PGE2 stimulated the hPDL cells to express IL-6 and IL-8, exogenous PGE2 was added to the culture media. RESULTS: The combination of mechanical vibration and compressive force synergistically upregulated RANKL/OPG, COX-2/PGE2 , IL-6 and IL-8 mRNA, and protein expression. The indomethacin significantly attenuated the increases of PGE2 , IL-6, and IL-8 expression in cells stimulated with compressive force or mechanical vibration combined with compressive force. In addition, exogenous PGE2 increased IL-6 and IL-8 mRNA and protein expressions in hPDL cells. CONCLUSION: Mechanical vibration may enhance alveolar bone resorption at the compression side during orthodontic tooth movement via a mechanism involving the cyclooxygenase pathway.