Effects of particle exposure and particle-elicited inflammatory cells on mutation in rat alveolar epithelial cells

Abstract

To investigate mechanisms underlying development of lung adenomas and carcinomas in rats exposed to poorly soluble particles the relationships between particle exposure, inflammation and mutagenesis in rat alveolar type II cells were characterized. Rats were exposed to saline or saline suspensions of 10 and 100 mg/kg of alpha-quartz, carbon black or titanium dioxide by intratracheal instillation. Fifteen months after exposure, bronchoalveolar lavage (BAL) cells were characterized as to number and type and lung histopathology performed. The alveolar type II cells were isolated and cultured in 6 thioguanine (6TG) containing media to select for mutation in the hprt gene. The potential contribution of lung inflammatory cells to in vivo mutagenic responses, were evaluated by co-culturing BAL cells with the rat alveolar epithelial cell line, RLE-6TN for 24 h and the RLE-6TN cells selected for 6TG resistance. Neutrophilic inflammation was detected in all rats exposed to 10 and 100 mg/kg of alpha-quartz and carbon black and 100 mg/kg titanium dioxide; epithelial hyperplasia was observed in rats exposed to 10 and 100 mg/kg of alpha-quartz and 100 mg/kg carbon black. Hprt mutation frequency was increased in alveolar type II cells from rats exposed to 10 and 100 mg/kg of alpha-quartz, 100 mg/kg carbon black and 100 mg/kg titanium dioxide. In vitro exposure of RLE-6TN cells to BAL cells from rats treated with 10 and 100 mg/kg of alpha-quartz or 100 mg/kg carbon black increased hprt mutant frequency. Both macrophage and neutrophil enriched BAL cell populations were mutagenic to RLE-6TN cells, however, the mutagenic activity appeared greatest for neutrophils. Addition of catalase to BAL cell:RLE-6TN co-cultures inhibited the increase in hprt mutation frequency. These studies demonstrate exposure of rats to doses of particles producing significant neutrophilic inflammation is associated with increased mutation in rat alveolar type II cells. The ability of particle-elicited macrophages and neutrophils to exert a mutagenic effect on epithelial cells in vitro supports a role for these inflammatory cells in the in vivo mutagenic effects of particle exposure. The inhibition of BAL cell-induced mutations by catalase implies a role for cell-derived oxidants in this response.

Titanium dioxide (respirable fraction) [MAK Value Documentation, 2009]

“…The data confirm findings according to which BAL cells of exposed rats (exposure to carbon black or titanium dioxide) caused mutations in the Hprt gene after in vitro incubation together with alveolar type II rat cells (cell strain: RLE-6TN) (Driscoll et al 1997). Like α-quartz, carbon black and titanium dioxide induced epithelial hyperplasia in the rat lung.…”

“…DNA damage and mutations follow. Mutations, induced by the oxidants released by inflammatory cells, have been identified in both co-cultivated bacteria and mammalian cells (Driscoll et al 1997;Evans et al 2004;Jackson et al 1989;Weitzman and Stossel 1981). By incubating polymorphonuclear leukocytes of humans together with alveolar type II epithelial cells of rats, it was possible to demonstrate that the reactive oxygen species released by leukocytes reach the genome of the epithelial cells, where they induce premutagenic 8-oxo-2'-desoxyguanine adducts (Knaapen et al 1999).…”

Role of Carnosine and Melatonin in Ameliorating Cardiotoxicity of Titanium Dioxide Nanoparticles in the Rats

“…The exposure of peripheral human lymphocytes to TiO 2 NPs can lead to the activation of DNA damage check points and accumulation of tumour suppressor protein p53 (Kang et al 2008). In vitro and in vivo studies of different experimental models showed that nanoTiO 2 could cause genotoxic effects through indirect mechanisms like oxidative stress and inflammation (Driscoll et al 1997;Xu et al 2008;Trouiller et al 2009;Petković et al 2011). ROS are important signalling molecules that can affect cell proliferation, inflammation and cell death (Sha et al 2013).…”

Selective mutation of K-ras by N-ethylnitrosourea shifts from codon 12 to codon 61 during fetal mouse lung maturation

“…Ozone caused lung tumors in mice, with a high frequency of K-ras mutations including G to T transversion in codon 12 (Sills et al, 1995). Alveolar type II cells in rat lungs exposed intratracheally to inorganic particles, resulting in neutrophil and macrophage in®ltration, showed a large increase in HPRT mutations (Driscoll et al, 1997).…”