Differential Effects Of Pharmacological Leukotriene Pathway Modulators In A Human Lung Tissue Explant Model

Leukotrienes are potent mediators involved in chronic inflammatory diseases, and the leukotriene pathway is clinically validated in asthma. Still, it is unclear how different pathway modulators, including leukotriene synthesis inhibitors, receptor antagonists and glucocorticoids are differentiated in terms of downstream biological effects and scope for clinical efficacy. Here we describe a human ex vivo lung tissue explant model allowing interactions between leukotriene producing cells, e.g. mast cells, and responding cells, including structural cells and immune cells. Explants were prepared from normal areas of resected lung tissue from patients with suspected lung cancer and stimulated with fMLP or calcium ionophore (A23187) after pre-incubation with different leukotriene pathway modulators. Medium was collected at 60 min and analysed for LTB4 and LTE4 by ELISA, and after 6 h, RNA was extracted from the tissue and processed for RNA sequencing. Leukotriene production in unstimulated explants was low, whereas stimulation with fMLP or A23187 induced robust production of LTB4 and LTE4. The fMLP-induced LTB4-production was effectively blocked by the FLAP inhibitors AZ13581258 (IC50=39 nM) and GSK2190915 (18 nM), whereas the CysLTR1 antagonist montelukast had no effect on leukotriene production. The glucocorticoid receptor agonist budesonide also had no effect, indicating the leukotriene pathway is largely insensitive to treatment by steroids. Pathway analysis based on gene expression profiles is ongoing. The ex vivo lung explant model shows promise as a translational model system enabling differentiation between leukotriene pathway modulators.