Magnetite Nanoparticles Induce Genotoxicity in the Lungs of Mice via Inflammatory Response

Abstract

Nanomaterials are useful for their characteristic properties and are commonly used in various fields. Nanosized-magnetite (MGT) is widely utilized in medicinal and industrial fields, whereas their toxicological properties are not well documented. A safety assessment is thus urgently required for MGT, and genotoxicity is one of the most serious concerns. In the present study, we examined genotoxic effects of MGT using mice and revealed that DNA damage analyzed by a comet assay in the lungs of imprinting control region (ICR) mice intratracheally instilled with a single dose of 0.05 or 0.2 mg/animal of MGT was approximately two- to three-fold higher than that of vehicle-control animals. Furthermore, in gpt delta transgenic mice, gpt mutant frequency (MF) in the lungs of the group exposed to four consecutive doses of 0.2 mg MGT was significantly higher than in the control group. Mutation spectrum analysis showed that base substitutions were predominantly induced by MGT, among which G:C to A:T transition and G:C to T:A transversion were the most significant. To clarify the mechanism of mutation caused by MGT, we analyzed the formation of DNA adducts in the lungs of mice exposed to MGT. DNA was extracted from lungs of mice 3, 24, 72 and 168 h after intratracheal instillation of 0.2 mg/body of MGT, and digested enzymatically. 8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and lipid peroxide-related DNA adducts were quantified by stable isotope dilution liquid chromatography-mass spectrometry (LC-MS/MS). Compared with vehicle control, these DNA adduct levels were significantly increased in the MGT-treated mice. In addition to oxidative stress- and inflammation related-DNA adduct formations, inflammatory cell infiltration and focal granulomatous formations were also observed in the lungs of MGT-treated mice. Based on these findings, it is suggested that inflammatory responses are probably involved in the genotoxicity induced by MGT in the lungs of mice.

Establishment of an in vivo simulating co‐culture assay platform for genotoxicity of multi‐walled carbon nanotubes

“…However, nitric oxide is produced by activated macrophages in inflamed organs in vivo. In the in vivo toxicity tests of ENM, macrophage phagocytosing test substances are frequently observed . Similarly, MWNT‐7 was phagocytosed by RAW264.7 in the present study.…”

“…However, recently, large and global efforts have been made to assess and manage the risks of ENM. It has been pointed out that ENM may come to possess their biological functions, including toxicity, by the different modes of action from overscaled counterparts, and that inflammatory response by virtue of immune cells, such as macrophages, and oxidative stress and signaling agents, such as cytokines, play major roles in the mechanism underlying effects of ENM on tissue resident cells . In Kato et al (2017) we revealed that the interaction between tissue resident cells and immune cells is important for the genotoxic mechanisms of nanomaterials.…”

“…Lambda EG10 phages were rescued using a Transpack Packaging Extract (Stratagene). The gpt mutagenesis assay was performed according to the previously described method . The mutation spectra of the gpt coding sequence were assessed by PCR and direct sequencing.…”

“…Engineered nanomaterials (ENM) are used in various fields of the human environment, and assessment of their safety is, therefore, urgently required. So far, we have examined the genotoxicity of various ENM by using in vitro and in vivo assays, which indicated that inflammatory response, induced by macrophages and other immune cells, is considered a key mechanism for the genotoxicity and other toxic properties of ENM . In general, a single culture of tissue resident cells has been used for in vitro assays to evaluate genotoxicity of ENM.…”

Are iron oxide nanoparticles safe? Current knowledge and future perspectives

“…An increase in MN frequency was also detected in bone marrow cells of mice intraperitoneally exposed to magnetite nanoparticles [104], or after intravenous administration of polyaspartic acid-coated ION (magnetite) [105]. Totsuka et al [115] examined genotoxic effects of magnetite nanoparticles in mice intratracheally instilled, obtaining significant increases in DNA adduct levels, oxidative stress and DNA breaks in treated animals as compared with controls. In addition, inflammatory cell infiltration and focal granulomatous formations were also observed in lungs of exposed mice, suggesting that an inflammatory response might be involved in genotoxicity induced by ION in mice lungs [116].…”