Stress and periodontitis: evaluation of sympathetic innervation in the periodontium and the influence of adrenergic signaling on Porphyromonas gingivalis infection

Author(s)

Renata Mendonça Moraes

• Document type: Doctoral Thesis
• Press: São José dos Campos. 2022-03-18.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Ciência e Tecnologia. São José dos Campos
• Defense date: 2022-01-25
• Advisor: Ana Lia Anbinder

Abstract

Stress aggravates periodontitis, and one possible mechanism is the activation of sympathetic nervous system (SNS). The literature shows that stimulation of β-adrenergic receptors (β-AR) induces angiogenesis in long bones, and microvasculature amplification was linked to periodontitis severity. Moreover, catecholamines increase the virulence of some periodontopathogenic bacteria in vitro and influences the innate immunity. Thus, the aim of this study was (1) evaluate the presence and influence of the SNS in the stimulation of periodontal vasculature, and (2) the influence of the adrenergic system on Porphyromonas gingivalis (Pg) virulence and on the immunological response to this pathogen in vivo (Galleria mellonella larvae). For the first part, mice received isoproterenol (ISO, a non-selective β-AR agonist) or saline (PBS) for 1 month, for in situ analysis of tyrosine hydroxylase, neuropeptide Y, norepinephrine transporter (NET) and endomucin in the mandibles. Vegfa, Il-1β, Il-6, Adrb2 and Rankl mRNA expression was assessed 2 hours after PBS/ISO treatment for mandibles and tibia, that served as positive control. We observed that, differently from the tibia, the expression of these genes did not alter on the mandible. However, NET expression was detected in osteoblasts, osteocytes, and periodontal ligament fibroblasts, and were higher expressed when compared to the tibias from the same animals. Although the pattern of sympathetic innervation and Adrb2 expression were similar between tissues, ISO treatment did not increase the area or number of endomucin+ vessels. For the second part, we addressed the adrenergic signaling influence on G. mellonella immune system during Pg infection using norepinephrine (NE, α- and β-AR agonist), ISO and octopamine (insect’s endogenous hormone). Pg was also cultivated in the presence of ISO (PgISO) or NE to investigate the direct action of the ligands on bacterial virulence. Systemic administration of ISO protected the larvae from Pg infection by increasing hemocyte density accompanied by reduction of Pg load in hemolymph, in a β-AR manner. In contrast, NE increased mortality, with decreased hemocyte count and no influence on the other parameters. Only PgISO increased larvae death, despite of ISO and NE increased virulence in vitro. The concomitant injection of systemic ISO partially reversed the toxicity of the PgISO. The influence of stress on periodontitis involves different pathways, that alter the two pillars of disease’s pathogenesis (microbiota and immune system). However, the influence on the host’s inflammatory response seems to overcome the other players, since β-AR activation on healthy alveolar bone didn’t alter cytokines production or microvasculature. Besides, the modulation of innate immunity by adrenergic signaling in G. mellonella was more important for the disease’s outcome than it’s direct action on the bacteria. (AU)

• FAPESP's process: 17/26461-5 - Stress and periodontitis: evaluation of sympathetic innervation in the periodontium and the influence of noradrenaline on Porphyromonas gingivalis in Galleria mellonella
• Grantee: Renata Mendonça Moraes
• Support Opportunities: Scholarships in Brazil - Doctorate