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

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 aimed to investigate the neurotoxic changes induced by co-exposure to toluene and noise.

Methods: A total of 24 male white New Zealand rabbits were randomly segregated into four 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), malondialdehyde (MDA), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase and total antioxidant capacity (TAC) values in the brain tissue were measured. Moreover, hematoxylin and eosin (H&E) staining was utilized for brain pathological analysis.

Results: Exposure to noise increased TAC values in the cerebral cortex. Co-exposure to toluene and noise increased the serum levels of BDNF-α. Nevertheless, exposure to noise decreased the levels of BDNF-α in serum. On the other hand, histopathological examinations using H&E staining 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 in some neurotoxic parameters.

Conclusion: Exposure to noise and toluene, which caused inflammation in the brain tissue cells, could be a noticeable risk factor for the neurological system.

Highlights: Exposure to noise increased total antioxidant capacity.Exposure to toluene decreased brain-derived neurotrophic factor-α.Exposure to noise decreased brain-derived neurotrophic factor-α.Co-exposure to noise and toluene increased brain-derived neurotrophic factor-α.Noise and toluene induced some histopathological effects on the brain tissue.

Plain Language Summary: The brain tissue can be adversely affected by various agents, including noise and toluene. This study aimed to examine the effects of simultaneous exposure to noise and toluene on the nervous system. Twenty-four healthy male white New Zealand rabbits were randomly divided into four groups: control, noise, toluene, and simultaneous exposure to noise and toluene. The study involved a two-week in-vivo experiment, subjecting the rabbits to 100 dB noise and 1000 ppm toluene for eight hours per day. This study showed that exposure to noise and toluene changed different parameters relating to the neurological system. Furthermore, noise and toluene induced some adverse effects on the brain tissue. This study suggested that exposure to noise and toluene can lead to harmful effects on the brain tissue, posing a significant risk to the neurological system.