Neurotrophin Production by Respiratory Epithelial Cells in Allergic Airway Diseases: A Model of Neuro-Immune Interactions

Allergic bronchial asthma (BA) is a model of neuro-immune interactions diseases, and it is characterized by chronic airway inflammation, development of airway hyperactivity and recurrent reversible airway obstruction. Neurotrophins (NGF, BDNF, NT-3 and NT-4) are also important mediators in the immune system, and they might be the candidate molecules for orchestrating neuro-immune interaction during chronic airway inflammation. Animal studies showed that in allergic airway inflammation, neurotrophins production is upregulated. It was also shown that human pulmonary epithelial cancer cells (A549) can produce NGF. The aim of this study was to characterize the role of the respiratory epithelial cells in the regulation of neurotrophin expression in allergic airway diseases. In order to investigate the overall production of neurotrophins by primary cultured mouse tracheal epithelial cells, a protocol for culturing mouse tracheal epithelial cells under air liquid interface conditions was established. Tracheal epithelial cells from wild type mice were dissociated by using a specific dissociation medium containing Pronase and Dnase, and cultured over the semi permeable membrane of the cell culture insert in the presence of some growth factors. In order to evaluate the purity of those cells, cultured cells were stained with Pancytokeratin (epithelial cells marker) at different stages. The basal production of neurotrophins was measured at different time points (6, 12, 24, 48 and 72 hours). The effects of the cytokines IL-1ß, IL-13 and IL-4 on neurotrophin production by mouse tracheal epithelial cell were dose-dependently studied and measuerd by enzyme-linked immunosorbent assay (ELISA). The same procedures were done by using murine airway epithelial LA 4 cancer cell line. It was shown that more than 95% of the cultured cells were pancytokeratin positive and viable for more than forty days. By measuring the basal production of neurotrophins by those cells, it was found that NGF and BDNF production is upregulated in a time dependent manner, whereas there was no production for NT-3 and NT-4. Specific bands of mRNA encoding for NGF, BDNF were detectable in all samples by RT-PCR. In primary cultured mouse tracheal epithelial cells, it was reported that IL-1ß, IL-13 and IL-4 at different concentrations may have no effect on neurotrophins production, whereas these cytokines have positive effects on the neurotrophin production by cultured airway epithelial LA 4 cancer cell line. There was upregulation production of NGF and BDNF in dose-dependent manner after incubation IL-1ß, IL-13 and IL-4 with cultured airway epithelial LA 4 cancer cell line. In summary these results show, that primary cell culture of the murine tracheal epithalial cells could be done. These cells are functionally active and produce NGF as well as BDNF. The cytokines IL-1ß, IL-13 and IL-4 do not play a role in regulation of the Neurotrophin production