Development of an in vitro model for the detection of airway irritants

UKEMS 2025 -- Environmental exposure to airway irritants can result in several acute respiratory symptoms, including pain, cough, dyspnea and bronchospasm. In addition, several chronic disorders can result such as chronic obstructive pulmonary disorder (COPD), asthma and airway hyper-responsiveness. Current assays used to measure irritancy include in vitro skin and eye corrosion assays. However, test systems for measuring respiratory irritation are limited to the in vivo sensory irritation test that measures the 50% reduction in respiration rate, or RD50. Although the in vivo RD50 assay (OECD TG-413) demonstrates correlation with human irritancy for certain compounds, disadvantages include the inability to predict human mechanistic responses and lack of high-throughput screening. Furthermore, limitations are reflected in epidemiological data with cleaning occupations demonstrating increased incidence of irritant-induced asthma associated with irritant exposure levels below established occupational exposure limits (OELs). Mode-of-action and mechanistic testing, such as use of adverse outcome pathways (AOPs) has been proposed as an alternative method for setting OELs. The recently described AOP-196 describes the activation of TRPA1 and TRPV1 channels as the main initiating event of airway irritation. In this study, the human alveolar cell line, A549, was used to screen a panel of known airway irritants. Following confirmation of TRPA1 and TRPV1 presence in A549 cells by qPCR and flow cytometry, activation was confirmed using a flow cytometric-based Ca2+-influx assay using known agonists and antagonists. Finally, the ability of the developed model to detect known airway irritants was examined.