Co-exposure to Toluene and Noise Made Synergistic and Antagonistic Effects on Some Neurotoxic Parameters in New Zealand White Rabbits

Abstract

Introduction: Numerous physical and chemical agents can induce destructive effects on the brain tissue. Noise and toluene, which are some of these harmful agents, have significant adverse effects on the brain tissue. This work aims to investigate the neurotoxic changes induced by co-exposure to toluene and noise. Methods: Totally, 24 male white New Zealand rabbits were randomly segregated into 4 groups including toluene exposure, noise exposure, co-exposure to noise and toluene, and control. This in-vivo study tested the neurotoxic effects of exposure to 1000 ppm toluene and 100 dB noise during two weeks (8 h/day). The serum levels of brain-derived neurotrophic factor-α (BDNF-α) and malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase levels in the brain tissue were measured. Moreover, hematoxylin and eosin staining was utilized for brain pathological analysis. Results: Exposure to noise increased TAC level in the cerebral cortex. Co- exposure to toluene and noise increased the serum level of BDNF-α. Nevertheless, exposure to noise decreased the level of BDNF-α in serum. On the other hand, hispathological examinations using hematoxylin-eosin (H&E) exhibited that different signs of inflammation such as lymphocyte infiltration, pyknosis, vacuolization, and chromatolysis were induced by exposure to noise and toluene in the cerebellum, hippocampus, and frontal section in the brain tissue. In addition, simultaneous exposure to toluene and noise induced antagonistic and synergistic changes on some neurotoxic parameters. Conclusion: Exposure to noise and toluene, which caused inflammation in the brain tissue cells, could be a noticeable risk factor for neurological system.