Molecular mechanisms involved in pulmonary barrier damage induced by selected heavy metal compounds

The respiratory system is a primary interface between the organism and its environment and, therefore, is a major target for toxicity of inhaled compounds. Epidemiological studies have clearly shown an increase in morbidity and mortality associated with respiratory diseases due to the inhalation of toxic compounds in the ambient air such as gases, and airborne particles. Currently, the assessment of the toxicity of inhalable compounds for regulatory purposes is exclusively performed using animal experiments. Therefore, there is an urgent need for the development and optimisation of in vitro models that adequately simulate the respiratory system in vivo. In parallel, there is a need to identify reliable biomarkers for the assessment of the toxic effect. The aim of this study was to characterise and evaluate the usefulness of Calu-3 cells grown at the air interface as an in vitro model for the airway epithelium to assess pulmonary toxicity of heavy metals. Since the airways epithelium lining forms the first line of defence and provides a barrier against the entry of toxic compounds, we focused in elucidating the mechanisms underlying the pulmonary barrier damage induced by the selected heavy metals compounds, cadmium (Cd) and nickel (Ni). The model selected for our studies was Calu-3, a well differentiated human bronchial cell line that retained the main characteristics of the airway epithelium in vivo with the formation of tight junctions (TJs) and the presence of mucous when grown at the air interface. In conclusion, exposure to different heavy metal compounds (CdCl2, NiCl2, Ni particles) provoked disruption of the airway epithelial barrier function, and induction of oxidative stress. The alterations in TEER and gene expression (MT1X, HSP70, HMOX-1, ¿GCS) at sub-cytotoxic concentrations demonstrate the usefulness of these endpoints to evaluate heavy metals-induced toxic effects on the airway epithelium. Finally, our results indicate a significant potential of Calu- 3 cells grown at the air-interface as an in vitro model for the toxicity assessment of inhaled compounds and for elucidation of the pathways involved in pulmonary toxicity and adverse health effects in humans.

FORTI Efrat; 

2010-02-22

JRC56988