Exposure to tungsten particles via inhalation triggers early toxicity marker expression in the rat brain.

Objective: Our work is focused on tungsten, considered as an emerging contaminant. Its environmental dispersion is partly due to mining and military activities. Exposure scenario can also be occupational, in areas such as the hard metal industry and specific nuclear facilities. Our study investigated the cerebral effects induced by the inhalation of tungsten particles.

Methods: Inhalation exposure campaigns were carried out at two different concentrations (5 and 80 mg/m³) in single and repeated modes (4 consecutive days) in adult rats within a nose-only inhalation chamber. Processes involved in brain toxicity were investigated 24 h after exposure.

Results and discussion: Site-specific effects in terms of neuroanatomy and concentration-dependent changes in specific cellular actors were observed. Results obtained in the olfactory bulb suggest a potential early effect on the survival of microglial cells. Depending on the mode of exposure, these cells showed a decrease in density accompanied by an increase in an apoptotic marker. An abnormal phenotype of the nuclei of mature neurons, suggesting neuronal suffering, was also observed in the frontal cortex, and can be linked to the involvement of oxidative stress. The differential effects observed according to exposure patterns could involve two components: local (brain-specific) and/or systemic. Indeed, tungsten, in addition to being found in the lungs and kidneys, was present in the brain of animals exposed to the high concentration.

Conclusion: Our data question the perceived innocuity of tungsten relative to other metals and raise hypotheses regarding possible adaptive or neurotoxic mechanisms that could ultimately alter neuronal integrity.