RESPONSE OF THE PERIODONTAL TISSUES TO β-ADRENERGIC STIMULATION

Abstract

Objectives Stress is a risk factor for periodontitis, and β-adrenergic receptor (βAR) stimulation increases angiogenesis on long bones. Enhanced periodontal vascularization could act as a potential host susceptibility factor. The aim was to investigate the mandibular angiogenic response to βAR stimulation. Study Design Twenty C57BL6 female mice received daily intraperitoneal injections of isoproterenol (ISO) or phosphate-buffered saline (PBS) for 6 weeks. Hemimandibles and tibias were collected for immunolocalization of endomucin, tyrosine hydroxylase, neuropeptide Y, and norepinephrine transporter (NET). Vascular Endothelial Growth Factor A, IL-1β, IL-6, Adrb2, and Rankl mRNA expression were assessed 2 hours after PBS or ISO treatment. Results Despite similar sympathetic innervation and Adrb2 expression in mandibular tissues and tibias, ISO treatment did not increase endomucin+ vessel area or the total number of endomucin+ vessels in the mandible. Moreover, the expression of VEGFa, IL-6, IL-1β, and Rankl in the molar region did not change following ISO administration. We also detected high expression of NET by immunofluorescence in mandibular alveolar osteoblasts, osteocytes, and periodontal ligament fibroblasts, which was confirmed by quantitative polymerase chain reaction, compared to the tibia from the same animals. Conclusions Stress and sympathetic nervous system activation increase the risk of periodontitis via mechanisms other than change in microvascular density and possibly requiring inflammatory cells. Stress is a risk factor for periodontitis, and β-adrenergic receptor (βAR) stimulation increases angiogenesis on long bones. Enhanced periodontal vascularization could act as a potential host susceptibility factor. The aim was to investigate the mandibular angiogenic response to βAR stimulation. Twenty C57BL6 female mice received daily intraperitoneal injections of isoproterenol (ISO) or phosphate-buffered saline (PBS) for 6 weeks. Hemimandibles and tibias were collected for immunolocalization of endomucin, tyrosine hydroxylase, neuropeptide Y, and norepinephrine transporter (NET). Vascular Endothelial Growth Factor A, IL-1β, IL-6, Adrb2, and Rankl mRNA expression were assessed 2 hours after PBS or ISO treatment. Despite similar sympathetic innervation and Adrb2 expression in mandibular tissues and tibias, ISO treatment did not increase endomucin+ vessel area or the total number of endomucin+ vessels in the mandible. Moreover, the expression of VEGFa, IL-6, IL-1β, and Rankl in the molar region did not change following ISO administration. We also detected high expression of NET by immunofluorescence in mandibular alveolar osteoblasts, osteocytes, and periodontal ligament fibroblasts, which was confirmed by quantitative polymerase chain reaction, compared to the tibia from the same animals. Stress and sympathetic nervous system activation increase the risk of periodontitis via mechanisms other than change in microvascular density and possibly requiring inflammatory cells.