Organic cation transporters (OCTs/OCTNs) in human primary alveolar epithelial cells

Alveolar epithelium, besides exerting a key role in gas exchange and surfactant production, plays important functions in host defense and inflammation. Pathological conditions associated to alveolar dysfunction include Acute Respiratory Distress Syndrome (ARDS), asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). The use of predictive in vitro models of human alveolar epithelium is nowadays required for the study of disease mechanisms, as well as of pharmacokinetic parameters of pulmonary drugs delivery. Here, we employed a novel 3D model of human alveoli, namely EpiAlveolar™, consisting of primary alveolar epithelial cells, pulmonary endothelial cells and fibroblasts, that reflects properly the in vivo-like conditions. In EpiAlveolar™ we performed a characterization of Organic Cation Transporters (OCTs and OCTNs) expression and activity and we found that OCTN2, OCT1 and OCT3 are expressed on the basolateral membrane; instead, ATB0,+ transporter for cationic and neutral amino acids, which shares with OCTN2 the affinity for carnitine as substrate, is readily detectable and functional at the apical side. We also show that these transporters differentially interact with anticholinergic drugs. Overall, our findings reveal close similarities of EpiAlveolar™ with the tracheal/bronchial epithelium (EpiAirway™ model) and entrust this alveolar tissue as a potential tool for the screening of biopharmaceuticals molecules.