Experimental Periodontitis Worsens Dopaminergic Neuronal Degeneration

ABSTRACT Aim To investigate the hypothesis supporting the link between periodontitis and dopaminergic neuron degeneration. Materials and Methods Adult male Wistar rats were used to induce dopaminergic neuronal injury with 6‐hydroxydopamine (6‐OHDA) neurotoxin and experimental periodontitis via ligature placement. Motor function assessments were conducted before and after periodontitis induction in controls and 6‐OHDA‐injury‐induced rats. Tissue samples from the striatum, jaw and blood were collected for molecular analyses, encompassing immunohistochemistry of tyrosine hydroxylase, microglia and astrocyte, as well as micro‐computed tomography, to assess alveolar bone loss and for the analysis of striatal oxidative stress and plasma inflammatory markers. Results The results indicated motor impairment in 6‐OHDA‐injury‐induced rats exacerbated by periodontitis, worsening dopaminergic striatal degeneration. Periodontitis alone or in combination with 6‐OHDA‐induced lesion was able to increase striatal microglia, while astrocytes were increased by the combination only. Periodontitis increased striatal reactive oxygen species levels and plasma tumour necrosis factor‐alpha levels in rats with 6‐OHDA‐induced lesions and decreased the anti‐inflammatory interleukin‐10. Conclusions This study provides original insights into the association between periodontitis and a neurodegenerative condition. The increased inflammatory pathway associated with both 6‐OHDA‐induced dopaminergic neuron lesion and periodontal inflammatory processes corroborates that the periodontitis‐induced systemic inflammation may aggravate neuroinflammation in Parkinson's‐like disease, potentially hastening disease progression.