Objective: To observe the pulmonary toxicity of multi-walled carbon nanotubes (MWCNTs) in high-fat diet SD rats.
Methods: One hundred forty male SD rats were randomly divided into 6 groups. The normal control group, high-fat diet model group, vehicle group, and group treated with low dose of MWCNTs consisted of 30 rats, respectively, which were divided in 3 subgroups (10 rats each subgroup), respectively. The groups treated with medium and high loses of MWCNTs consisted of 10 rats, respectively. All the animals were exposed to high-fat-diet except for the control group which was given with normal diet. Before intravenous exposure, the high-fat diet model group, vehicle group, and three MWCNTs treated groups were gavaged with 700 thousand U/kg Vit D3 for three days, then given with high-fat-diet. The vehicle group was exposed to normal saline containing 1% Tween 80 and the low exposure group was exposed to MWCNTs at the dose of 50 µg/kg by tail vein injection twice a week for 8, 12 or 16 weeks. Other tow exposure groups were exposed to MWCNTs at the doses of 100, and 200 µg/kg by tail vein injection twice a week, respectively for 16 weeks. The lungs were from the executed rats, the lung indexes were calculated, the pathological changes of lungs were examined under light microscope after HE staining. qRT-PCR assay was utilized to detect the expression levels of pro-inflammation cytokines IL-1β (IL-1β) and TNF-α mRNA in the lungs.
Results: As compared with the vehicle group, the lung indexes in groups exposed to 100 and 200 µg/kg MWCNTs increased significantly (P < 0.05). It was found under light microscope that the MWCNTs were accumulated in lungs of three exposure groups in 16 weeks after exposure, including pneumorrhagia, alveolar walls thicken, fibrosis, and granulomas. As compared with the vehicle group, the levels of IL-1β mRNA in group exposed to 50 µg/kg MWCNTs for 12 weeks and the groups exposed to 50, 100 and 200 µg/kg MWCNTs for 16 weeks decreased significantly (P < 0.05). As compared with the vehicle group, the levels of TNF-α mRNA in the groups exposed to 50 µg/kg MWCNTs for 8 and 16 weeks increased significantly (P < 0.05), the level of TNF-α mRNA in the groups exposed to 50 µg/kg MWCNTs for 12 weeks decreased significantly (P < 0.05). As compared with the vehicle group, the level of TNF-α mRNA in the groups exposed to 200 µg/kg MWCNTs for 16 weeks reduced significantly (P < 0.05).
Conclusion: The MWCNTs accumulation and chronic inflammatory changes were found in the lungs of rats exposed to MWCNTs by tail vein injection.