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Particle_Fibre Toxicology 14_51 - SRiedle et al 081217.pdf (936.51 kB)

Pro-inflammatory adjuvant properties of pigment-grade titanium dioxide are augmented by a genotype that potentiates interleukin 1β processing

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posted on 2023-05-03, 14:50 authored by Sebastian Riedle, Laetitia Pele, Don Otter, Rachel Hewitt, Harjinder Singh, Nicole Roy, Jonathan Powell
Background: Pigment-grade titanium dioxide (TiO2) particles are an additive to some foods (E171 on ingredients lists), toothpastes, and pharma−/nutraceuticals and are absorbed, to some extent, in the human intestinal tract. TiO2 can act as a modest adjuvant in the secretion of the pro-inflammatory cytokine interleukin 1β (IL-1β) when triggered by common intestinal bacterial fragments, such as lipopolysaccharide (LPS) and/or peptidoglycan. Given the variance in human genotypes, which includes variance in genes related to IL-1β secretion, we investigated whether TiO2 particles might, in fact, be more potent pro-inflammatory adjuvants in cells that are genetically susceptible to IL-1β-related inflammation. Methods: We studied bone marrow-derived macrophages from mice with a mutation in the nucleotide-binding oligomerisation domain-containing 2 gene (Nod2m/m), which exhibit heightened secretion of IL-1β in response to the peptidoglycan fragment muramyl dipeptide (MDP). To ensure relevance to human exposure, TiO2 was food-grade anatase (119 ± 45 nm mean diameter ± standard deviation). We used a short ‘pulse and chase’ format: pulsing with LPS and chasing with TiO2 +/− MDP or peptidoglycan. Results: IL-1β secretion was not stimulated in LPS-pulsed bone marrow-derived macrophages, or by chasing with MDP, and only very modestly so by chasing with peptidoglycan. In all cases, however, IL-1β secretion was augmented by chasing with TiO2 in a dose-dependent fashion (5–100 μg/mL). When co-administered with MDP or peptidoglycan, IL-1β secretion was further enhanced for the Nod2m/m genotype. Tumour necrosis factor α was triggered by LPS priming, and more so for the Nod2m/m genotype. This was enhanced by chasing with TiO2, MDP, or peptidoglycan, but there was no additive effect between the bacterial fragments and TiO2. Conclusion: Here, the doses of TiO2 that augmented bacterial fragment-induced IL-1β secretion were relatively high. In vivo, however, selected intestinal cells appear to be loaded with TiO2, so such high concentrations may be ‘exposure-relevant’ for localised regions of the intestine where both TiO2 and bacterial fragment uptake occurs. Moreover, this effect is enhanced in cells from Nod2m/m mice indicating that genotype can dictate inflammatory signalling in response to (nano)particle exposure. In vivo studies are now merited.

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Rights statement

© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Language

  • English

Does this contain Māori information or data?

  • No

Publisher

Springer Nature

Journal title

Particle and Fibre Toxicology

ISSN

1743-8977

Citation

Riedle, S., Pele, L. C., Otter, D. E., Hewitt, R. E., Singh, H., Roy, N. C., & Powell, J. J. (2017). Pro-inflammatory adjuvant properties of pigment-grade titanium dioxide are augmented by a genotype that potentiates interleukin 1β processing. Particle and Fibre Toxicology, 14, 51. doi:10.1186/s12989-017-0232-2

Funder

Riddet Institute

Contract number

A23004

Job code

11354x03

Report number

FBP 78219

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