Neurobehavioral toxicity of carbon nanotubes in mice: Focus on brain-derived neurotrophic factor mRNA and protein

Abstract

© The Author(s) 2016. Objectives: The aim of this study was to evaluate neurobehavioral toxicity of single-walled (SWNTs) and multiwalled carbon nanotubes (MWNTs) in mice. Methods: Male NMRI mice were randomized into 5 groups (n = 10 each): Normal control (NC) group was injected intraperitoneally (i.p.) with phosphate-buffered saline (PBS) solution (pH 7.8; ca. 1 mL), MW80 and MW800 groups were injected with either i.p. 80 or 800 mg kg -'1 MWNTs suspended in 1 mL of PBS and SW80 and SW800 groups were injected with either i.p. 80 or 800 mg kg -'1 SWNTs suspended in 1 mL of PBS. After 2 weeks, five mice from each group were evaluated for brain-derived neurotrophic factor (BDNF) messenger RNA expression and protein content of brain tissues. Locomotion, anxiety, learning and memory, and depression were measured by open field test (OFT), elevated plus-maze (EPM), object recognition test (ORT), and forced swimming test (FST), respectively. Results: Ambulation time and center arena time in the OFT did not change among groups. In the EPM paradigm, SWNTs (800 mg kg -'1 ) and MWNTs (80 and 800 mg kg -'1 ) showed an anxiogenic effect. In ORT, MWNTs (80 mg kg -'1 ) increased the discrimination ratio while in FST, MWNTs showed a depressant effect as compared to vehicle. The BDNF gene expression in mice treated with 80 and 800 mg kg -'1 SWNTs or 80 mg kg -'1 MWNTs decreased as compared to NC mice although BDNF gene expression increased in mice that were treated with 800 mg kg -'1 MWNTs. The whole brain BDNF protein content did not change among groups. Conclusion: Our study showed that i.p. exposure to carbon nanotubes (CNTs) ma y result in behavioral toxicity linked with expression of depression or anxiety that depends on the type of CNTs. In addition, exposure to CNTs changed BDNF gene expression.