Imaging microstructural damage and alveolar bone loss in rats systemically exposed to methylmercury: first experimental evidence

This work was supported by the Brazilian National Council for Scientific and Technological Development (CNPq), Fundação de Amparo a Pesquisa do Estado do Pará (FAPESPA), and Pró-Reitoria de Pesquisa e Pós-Graduação da UFPA (PROPESP, UFPA, Brazil).Federal University of Pará. Institute of Biological Sciences. Laboratory of Functional and Structural Biology. Belém, PA, Brazil.Federal University of Pará. Institute of Biological Sciences. Laboratory of Functional and Structural Biology. Belém, PA, Brazil.Federal University of Pará. Institute of Biological Sciences. Laboratory of Functional and Structural Biology. Belém, PA, Brazil.Federal University of Pará. Institute of Biological Sciences. Laboratory of Functional and Structural Biology. Belém, PA, Brazil.Federal University of Pará. Institute of Health Sciences. School of Dentistry. Belém, PA, Brazil.Laboratory of Clinical Immunology and Oxidative Stress, Pharmacy Faculty, Institute of Health Sciences, Federal University of Pará, Belém, BrazilLaboratory of Clinical Immunology and Oxidative Stress, Pharmacy Faculty, Institute of Health Sciences, Federal University of Pará, Belém, BrazilCytogenetics and Tissue Culture Laboratory, Evandro Chagas Institute, Ananindeua, Brazil Exact and Natural Sciences Institute, Federal University of Pará, Belém, BrazilLaboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Pará, Augusto Corrêa Street N. 01, Guamá, Belém, Pará, 66075-110, BrazilLaboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Pará, Augusto Corrêa Street N. 01, Guamá, Belém, Pará, 66075-110, BrazilThe alveolar bone is an important mineralized structure of the periodontal support apparatus, and information about the methylmercury (MeHg) effects on the structural integrity is scarce. Therefore, this study aimed to investigate whether systemic, chronic, and low-dose exposure to MeHg can change the alveolar bone microstructure of rats. Adult Wistar rats (n = 30) were exposed to 0.04 mg/kg/day of MeHg or vehicle through intragastric gavage. The animals were euthanized after 60 days, and blood samples were collected for trolox equivalent antioxidant capacity (TEAC), glutathione (GSH), lipid peroxidation (LPO), and comet assays. The mandible of each animal was collected and separated into hemimandibles that were used to determine the total Hg level in the bone and to analyze microstructural damage and alveolar bone loss in terms of trabecular number (Tb.N), trabecular thickness (Tb.Th), bone volume fraction (BV/TV), and exposed root area of the second molars. MeHg exposure triggered oxidative stress in blood represented by lower levels of GSH and TEAC and the increase in LPO and DNA damage of the blood cells. High total Hg levels were found in the alveolar bone, and the microstructural analyses showed a reduction in Tb.N, Tb.Th, and BV/TV, which resulted in an increase in the exposed root area and a decrease in bone height. Long-term MeHg exposure promotes a systemic redox imbalance associated with microstructural changes and alveolar bone loss and may indicate a potential risk indicator for periodontal diseases