Exposure to paraquat associated with periodontal disease causes motor damage and neurochemical changes in rats

Abstract

Exposure to paraquat is possibly involved with the development of several conditions, including neurodegenerative diseases, such as Parkinson’s disease (PD). This condition is mainly characterized by the loss of dopaminergic neurons in the nigrostriatal pathway and the development of classical motor symptoms. Etiology includes exposure to environmental factors, such as the paraquat exposure, and inflammatory diseases may exacerbate paraquat neurotoxicity. The aim of the study was to investigate whether the exposure to paraquat associated with the presence of periodontal disease is able to induce motor and biochemical changes in rats similar to that observed in PD. Adult male Wistar rats were sent to ligature. After 48 h, they were sent to daily treatment paraquat (1 mg/kg/day; 2 mL/kg; intragastric) or vehicle for 4 weeks. Twenty-four hours after the last administration, the open field test was performed. The rats were euthanized and the left hemimandibles and striatum were dissected for the analysis of dopaminergic and inflammatory markers. Only the combination of periodontal disease model plus paraquat exposure induced motor impairments. Remarkably, the paraquat exposure increased the ligature-induced alveolar bone loss in hemimandibles. Moreover, only the combination of periodontal disease and paraquat exposure induced the loss of dopaminergic neurons and astrocyte activation in the striatum.

Impacts of Pesticides on Oral Cavity Health and Ecosystems: A Review

“…In all cases, it was reported that paraquat increased the release of ROS due to mitochondrial damage, which induced oxidation of lipids, proteins, and nucleic acids, in addition to increase inflammatory responses, and in some cases, apoptosis, which led to the development of ulcers of the oral mucosa and bleeding [ 61 , 62 , 63 , 64 , 65 ]. The increases in oxidative stress and inflammation are responses that were also observed in a murine model exposed to paraquat, and they are very similar to those seen in the pathology of periodontitis with loss of the alveolar bone [ 52 ].…”

“…In patients with periodontal disease, there are increase in the well-known red, orange, and yellow complexes ( Table 2 ). The first two complexes are associated with severe and moderate periodontal disease, while the yellow complex is associated with lower virulence [ 1 , 35 , 41 , 43 , 51 , 52 ].…”

“…Previous reports indicate that exposure to pesticides activates an immune response that enhances inflammation and tissue damage [ 27 , 30 , 48 ]. The increase in inflammation may be associated with the etiologies of gingivitis, periodontitis, and oral cancer [ 30 , 51 , 52 ].…”

“…Contact of the oral tissue with pesticides triggers an immune response and increased oxidative stress due to increased levels of reactive oxygen species (ROS). Oxidative stress damages the epithelium, alters cell function, and favors the development of caries, periodontitis, oral cancer, and a higher degree of bacterial infections [ 4 , 51 , 52 , 57 ].…”

“…Exposure to paraquat (B) enhanced the development of periodontal disease by limiting the proliferation of the epithelium of the oral cavity, thereby enhancing its thinning [ 52 ]. It should be noted that one protective mechanism that limits the colonization of pathogens is the continuous turnover of cells from the surface of the oral mucosa [ 30 ].…”