Carbon black nanoparticle instillation induces sustained inflammation and genotoxicity in mouse lung and liver

Julie A Bourdon,Keld A Jensen,Jacob S Lamson,Håkan Wallin,Carole L Yauk,Steffen Loft,Nicklas R Jacobsen,Peter Møller,Anne T Saber,Ulla B Vogel,Anne M Madsen

doi:10.1186/1743-8977-9-5

Abstract

BackgroundWidespread occupational exposure to carbon black nanoparticles (CBNPs) raises concerns over their safety. CBNPs are genotoxic in vitro but less is known about their genotoxicity in various organs in vivo.MethodsWe investigated inflammatory and acute phase responses, DNA strand breaks (SB) and oxidatively damaged DNA in C57BL/6 mice 1, 3 and 28 days after a single instillation of 0.018, 0.054 or 0.162 mg Printex 90 CBNPs, alongside sham controls. Bronchoalveolar lavage (BAL) fluid was analyzed for cellular composition. SB in BAL cells, whole lung and liver were assessed using the alkaline comet assay. Formamidopyrimidine DNA glycosylase (FPG) sensitive sites were assessed as an indicator of oxidatively damaged DNA. Pulmonary and hepatic acute phase response was evaluated by Saa3 mRNA real-time quantitative PCR.ResultsInflammation was strongest 1 and 3 days post-exposure, and remained elevated for the two highest doses (i.e., 0.054 and 0.162 mg) 28 days post-exposure (P < 0.001). SB were detected in lung at all doses on post-exposure day 1 (P < 0.001) and remained elevated at the two highest doses until day 28 (P < 0.05). BAL cell DNA SB were elevated relative to controls at least at the highest dose on all post-exposure days (P < 0.05). The level of FPG sensitive sites in lung was increased throughout with significant increases occurring on post-exposure days 1 and 3, in comparison to controls (P < 0.001-0.05). SB in liver were detected on post-exposure days 1 (P < 0.001) and 28 (P < 0.001). Polymorphonuclear (PMN) cell counts in BAL correlated strongly with FPG sensitive sites in lung (r = 0.88, P < 0.001), whereas no such correlation was observed with SB (r = 0.52, P = 0.08). CBNP increased the expression of Saa3 mRNA in lung tissue on day 1 (all doses), 3 (all doses) and 28 (0.054 and 0.162 mg), but not in liver.ConclusionsDeposition of CBNPs in lung induces inflammatory and genotoxic effects in mouse lung that persist considerably after the initial exposure. Our results demonstrate that CBNPs may cause genotoxicity both in the primary exposed tissue, lung and BAL cells, and in a secondary tissue, the liver.

Highlights

Widespread occupational exposure to carbon black nanoparticles (CBNPs) raises concerns over their safety
We report that instillation of CBNPs leads to prolonged generation of DNA damage in Bronchoalveolar lavage (BAL) cells, lung and liver of exposed mice as well as persistent pulmonary inflammation, acute phase response and oxidatively damaged DNA
Particle characterization Printex 90 CBNPs were a gift from Evonik/Degussa (Frankfurt, Germany)

Summary

Introduction

Widespread occupational exposure to carbon black nanoparticles (CBNPs) raises concerns over their safety. CBNPs are genotoxic in vitro, as shown by increases in DNA base oxidation [26], mutation frequency [26,27], strand breaks [28,29] and micronucleus frequency in lung epithelial cells [30] as well as increases in strand breaks in fibroblasts [31]. A few studies in rats have demonstrated CBNP-induced DNA base oxidation [32] and increased mutation frequency [20]. Studies in mice have demonstrated DNA strand breaks in BAL cells [21,33] and one study has established CBNP-induced lung DNA strand breaks, but this was found using a high dose (i.e., 0.2 mg) immediately (3 hours) post instillation [30]

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