Tim Marczylo

Slow lung clearance and limited translocation of four sizes of inhaled iridium nanoparticles

BackgroundConcerns have been expressed that inhaled nanoparticles may behave differently to larger particles in terms of lung clearance and translocation, with potential implications for their toxicity. Studies undertaken to investigate this have typically involved limited post-exposure periods. There is a shortage of information on longer-term clearance and translocation patterns and their dependence on particle size, which this study aimed to address.MethodsRats were exposed (<3xa0h) nose-only to aerosols of spark-generated radioactive iridium-192 nanoparticles of four sizes: 10xa0nm, 15xa0nm, 35xa0nm and 75xa0nm (count median diameter) (aerosol mass concentrations 17, 140, 430, and 690xa0μg/m3, respectively). The content of iridium-192 in the whole animal, organs, tissues, and excreta was measured at various times post-exposure tou2009≥u20091xa0month. Limited toxicological investigations were undertaken for the 10xa0nm aerosol using bronchoalveolar lavage fluid. Elemental maps of tissue samples were produced using laser ablation inductively coupled plasma mass spectrometry and synchrotron micro-focus x-ray fluorescence. The chemical speciation of the iridium was explored using synchrotron micro focus x-ray near-edge absorption spectroscopy.ResultsLong-term lung retention half-times of several hundred days were found, which were not dependent on particle size. There was significant variation between individual animals. Analysis of bronchoalveolar lavage fluid for the 10xa0nm aerosol indicated a limited inflammatory response resolving within the first 7xa0days. Low levels of, particle size dependent, translocation to the kidney and liver were found (maximum 0.4% of the lung content). Any translocation to the brain was below the limits of detection (i.e. < 0.01% of the lung content). The kidney content increased to approximately 30xa0days and then remained broadly constant or decreased, whereas the content in the liver increased throughout the study. Laser ablation inductively coupled plasma mass spectrometry analysis indicated homogeneous iridium distribution in the liver and within the cortex in the kidney.ConclusionsSlow lung clearance and a pattern of temporally increasing concentrations in key secondary target organs has been demonstrated for inhaled iridium aerosol particlesu2009<u2009100xa0nm, which may have implications for long-term toxicity, especially in the context of chronic exposures.

A global initiative to refine acute inhalation studies through the use of 'evident toxicity' as an endpoint: Towards adoption of the fixed concentration procedure.

Acute inhalation studies are conducted in animals as part of chemical hazard identification and characterisation, including for classification and labelling purposes. Current accepted methods use death as an endpoint (OECD TG403 and TG436), whereas the fixed concentration procedure (FCP) (draft OECD TG433) uses fewer animals and replaces lethality as an endpoint with evident toxicity. Evident toxicity is defined as clear signs of toxicity that predict exposure to the next highest concentration will cause severe toxicity or death in most animals. A global initiative including 20 organisations, led by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) has shared data on the clinical signs recorded during acute inhalation studies for 172 substances (primarily dusts or mists) with the aim of making evident toxicity more objective and transferable between laboratories. Pairs of studies (5 male or 5 female rats) with at least a two-fold change in concentration were analysed to determine if there are any signs at the lower dose that could have predicted severe toxicity or death at the higher concentration. The results show that signs such as body weight loss (>10% pre-dosing weight), irregular respiration, tremors and hypoactivity, seen at least once in at least one animal after the day of dosing are highly predictive (positive predictive value > 90%) of severe toxicity or death at the next highest concentration. The working group has used these data to propose changes to TG433 that incorporate a clear indication of the clinical signs that define evident toxicity.

Cerium dioxide nanoparticles exacerbate house dust mite induced type II airway inflammation

BackgroundNanomaterial inhalation represents a potential hazard for respiratory conditions such as asthma. Cerium dioxide nanoparticles (CeO2NPs) have the ability to modify disease outcome but have not been investigated for their effect on models of asthma and inflammatory lung disease. The aim of this study was to examine the impact of CeO2NPs in a house dust mite (HDM) induced murine model of asthma.ResultsRepeated intranasal instillation of CeO2NPs in the presence of HDM caused the induction of a type II inflammatory response, characterised by increased bronchoalveolar lavage eosinophils, mast cells, total plasma IgE and goblet cell metaplasia. This was accompanied by increases in IL-4, CCL11 and MCPT1 gene expression together with increases in the mucin and inflammatory regulators CLCA1 and SLC26A4. CLCA1 and SLC26A4 were also induced by CeO2NPsu2009+u2009HDM co-exposure in air liquid interface cultures of human primary bronchial epithelial cells. HDM induced airway hyperresponsiveness and airway remodelling in mice were not altered with CeO2NPs co-exposure. Repeated HMD instillations followed by a single exposure to CeO2NPs failed to produce changes in type II inflammatory endpoints but did result in alterations in the neutrophil marker CD177. Treatment of mice with CeO2NPs in the absence of HDM did not have any significant effects. RNA-SEQ was used to explore early effects 24xa0h after single treatment exposures. Changes in SAA3 expression paralleled increased neutrophil BAL levels, while no changes in eosinophil or lymphocyte levels were observed. HDM resulted in a strong induction of type I interferon and IRF3 dependent gene expression, which was inhibited with CeO2NPs co-exposure. Changes in the expression of genes including CCL20, CXCL10, NLRC5, IRF7 and CLEC10A suggest regulation of dendritic cells, macrophage functionality and IRF3 modulation as key early events in how CeO2NPs may guide pulmonary responses to HDM towards type II inflammation.ConclusionsCeO2NPs were observed to modulate the murine pulmonary response to house dust mite allergen exposure towards a type II inflammatory environment. As this type of response is present within asthmatic endotypes this finding may have implications for how occupational or incidental exposure to CeO2NPs should be considered for those susceptible to disease.

The small airway epithelium as a target for the adverse pulmonary effects of silver nanoparticle inhalation.

Abstract Experimental modeling to identify specific inhalation hazards for nanomaterials has in the main focused on in vivo approaches. However, these models suffer from uncertainties surrounding species-specific differences and cellular targets for biologic response. In terms of pulmonary exposure, approaches which combine ‘inhalation-like’ nanoparticulate aerosol deposition with relevant human cell and tissue air–liquid interface cultures are considered an important complement to in vivo work. In this study, we utilized such a model system to build on previous results from in vivo exposures, which highlighted the small airway epithelium as a target for silver nanoparticle (AgNP) deposition. RNA-SEQ was used to characterize alterations in mRNA and miRNA within the lung. Organotypic-reconstituted 3D human primary small airway epithelial cell cultures (SmallAir) were exposed to the same spark-generated AgNP and at the same dose used in vivo, in an aerosol-exposure air–liquid interface (AE-ALI) system. Adverse effects were characterized using lactate, LDH release and alterations in mRNA and miRNA. Modest toxicological effects were paralleled by significant regulation in gene expression, reflective mainly of specific inflammatory events. Importantly, there was a level of concordance between gene expression changes observed in vitro and in vivo. We also observed a significant correlation between AgNP and mass equivalent silver ion (Ag+) induced transcriptional changes in SmallAir cultures. In addition to key mechanistic information relevant for our understanding of the potential health risks associated with AgNP inhalation exposure, this work further highlights the small airway epithelium as an important target for adverse effects.

Electronic cigarettes: adolescent health and wellbeing – Authors' reply

474 www.thelancet.com Vol 392 August 11, 2018 3 Reid JL, Hammond D, Rynard VL, Madill CL, Burkhalter R. Tobacco use in Canada: patterns and trends, 2017 edition. Waterloo, ON: Propel Centre for Population Health Impact, 2017. 4 Centers for Disease Control and Prevention. Youth and tobacco use. March 26, 2018. https://www.cdc.gov/tobacco/data_statistics/ fact_sheets/youth_data/tobacco_use/index. htm (accessed May 30, 2018). 5 Barrington-Trimis JL, Urman R, Leventhal AM, et al. E-cigarettes, cigarettes, and the prevalence of adolescent tobacco use. Pediatrics 2016; published online July 11. DOI:10.1542/peds.2015-3983. 6 Hammond D, Reid JL, Cole AG, Leatherdale ST. Electronic cigarette use and smoking initiation among youth: a longitudinal cohort study. CMAJ 2017; 189: e1328–36. the National Academy of Sciences, Engineering, and Medicine report. We stand by our comment that the two reports broadly agree on most of the questions addressed—for example, on relative harm compared with smoking and on the role of ECs in smoking cessation. One area of substantial disagreement is on youth uptake. The National Academy of Sciences, Engineering, and Medicine relies heavily on studies that exclude youths who have already smoked, such as the study quoted by Bandara and Mehrnoush. Most regular use of ECs by young people is, however, in established smokers who were excluded from these studies. Furthermore, the apparent association between the use of ECs in young nonsmokers and subsequent smoking does not, by any means, show causation. Matthew J Peters unfairly accuses the authors of the Public Health England review of selective use of evidence including unpublished sources. Policy should be informed by the latest data, and the authors were asked to include the most recent data available, including survey data not yet in print. Unpublished data and research that had not been peer-reviewed were clearly highlighted. As we mentioned in our Comment, the evidence on ECs is incomplete and needs careful and ongoing review. However, on the questions we discussed, we are clear that particular messages are emerging, the international consensus is building, and policy makers should take note.

An evaluation of the fixed concentration procedure for assessment of acute inhalation toxicity

ABSTRACT Acute inhalation studies are conducted in animals as part of chemical hazard identification and for classification and labelling. Current methods employ death as an endpoint (Organisation for Economic Co‐operation and Development (OECD) test guideline (TG) 403 and TG436) while the recently approved fixed concentration procedure (FCP) (OECD TG433) uses fewer animals and replaces lethality as an endpoint with evident toxicity. Evident toxicity is the presence of clinical signs that predict that exposure to the next highest concentration will cause severe toxicity or death in most animals. Approval of TG433 was the result of an international initiative, led by the National Centre for the Replacement, Refinement & Reduction of Animals in Research (NC3Rs), which collected data from six laboratories on clinical signs recorded for inhalation studies on 172 substances. This paper summarises previously published data and describes the additional analyses of the dataset that were essential for approval of the TG. HighlightsThe FCP for acute inhalation toxicity has been accepted by OECD as TG433.TG433 uses evident toxicity while other approved methods use lethality.A sighting study with 1 M and 1 F animal reliably identifies the more sensitive sex.The three methods (LC50, ATC, FCP) showed good agreement in a retrospective analysis. Abbreviations: ATC: acute toxic class; CI: confidence interval; FCP: fixed concentration procedure; GHS: globally harmonised system; LC50: concentration causing death in 50% of animals tested; MTD: maximum tolerated dose; NC3Rs: National Centre for the Replacement, Refinement & Reduction of Animals in Research; OECD: Organisation for Economic Co‐operation and Development; PPV: positive predictive value; TC50: concentration causing toxicity in 50% of animals tested; TG: test guideline.

Chemical warfare agent simulants for human volunteer trials of emergency decontamination: A systematic review

Incidents involving the release of chemical agents can pose significant risks to public health. In such an event, emergency decontamination of affected casualties may need to be undertaken to reduce injury and possible loss of life. To ensure these methods are effective, human volunteer trials (HVTs) of decontamination protocols, using simulant contaminants, have been conducted. Simulants must be used to mimic the physicochemical properties of more harmful chemicals, while remaining non‐toxic at the dose applied. This review focuses on studies that employed chemical warfare agent simulants in decontamination contexts, to identify those simulants most suitable for use in HVTs of emergency decontamination. Twenty‐two simulants were identified, of which 17 were determined unsuitable for use in HVTs. The remaining simulants (n = 5) were further scrutinized for potential suitability according to toxicity, physicochemical properties and similarities to their equivalent toxic counterparts. Three suitable simulants, for use in HVTs were identified; methyl salicylate (simulant for sulphur mustard), diethyl malonate (simulant for soman) and malathion (simulant for VX or toxic industrial chemicals). All have been safely used in previous HVTs, and have a range of physicochemical properties that would allow useful inference to more toxic chemicals when employed in future studies of emergency decontamination systems.