Read-across, RDT, REACH, respiratory disease, NAM


The alpha-diketone diacetyl (2,3- butadiene) is known to induce the so-called “popcorn lung” condition. This disease was frequently observed among microwave popcorn manufacturing employees who inhaled the butter flavour vapour of diacetyl. This condition represents an obstructive pulmonary disease in which the airway epithelium is the initial target of injury. The disease is called bronchiolitis obliterans and is characterized by fibroproliferative airway lesions.
In this case study, the effects of alpha-diketone have been investigated together with two structurally similar groups (β and γ diketone) which seem to have a different mode of action based on available information.
This approach can show how far selected NAMs are also able to differentiate the α, β, and γ diketone specific toxicity in the selected in vitro test systems. The three groups of structurally related compounds are sufficiently data-rich to allow the exploration of NAMs to adequately perform chemical hazard identification and herewith replacing the regulatorily required animal study. EU-ToxRisk tools were applied to predict toxicokinetics properties of the target compounds (e.g. PBPK and metabolism). Furthermore, we explored to which extent chemical similarity can be enriched by biological data, e.g. derived from omics investigations or cellular readouts.

Testing Strategy

All case study compounds were evaluated in fluorescent cell stress reporter assay high-throughput screens. Alpha diketones are known to have a high electron affinity and can transfer electrons and, thus, can induce ROS and oxidative stress. Αlpha-diketones as well as the beta-diketone 2,4-pentanedione were shown to induce activation of oxidative stress and DNA damage response pathways. The air-liquid interface (ALI) exposure setup for diacetyl and analogues was preferred in further experiments since dose control is ensured by online measurements of volatile test atmosphere employing FT-IR spectroscopy. Cultures of primary airway epithelial cells (PBECs) as well as human precision cut lung slices (PCLuS) were set up for ALI exposures. Additionally, transcriptomics as well as cytokine data are currently being analysed. Kinetic studies with diacetyl aiming at the determination of diacetyl uptake and intracellular concentrations are ongoing.


ITEM,  UL,  UKN, DC, SimCyp, LUMC, Mario Negri IRCCS