Effect of proinflammatory cytokines on interleukin-8 mRNA expression and protein production by isolated human alveolar epithelial cells type II in primary culture

Alveolar epithelial cells type II (AEC-LT) are ideally situated to regulate the recruitment and activation of different types of cells through the pro duction of chemokines in response to inflammatory stimulation from the alve olar space. We hypothesized that these cells are important producers of int erleukin-8 (IL-8) in the lung. This lead us to investigate the capacity of isolated human AEC-II cells to release IL-8 and whether this IL-8 release i s regulated by proinflammatory cytokines, i.e. IL-1 beta, TNF-alpha and IFN -gamma. We isolated AEC-II from tumor-free sections of human lungs obtained by pneumectomy and purified the cells by magnetic activated cell sorting. For control experiments the AEC-II-like cell line A549 was used. IL-8 conce ntration was measured by ELISA in supernatants of unstimulated and LPS-, IL -1 beta-, TNF-alpha- and IFN-gamma- stimulated cells, IL-8 mRNA expression was evaluated by RT-PCR, Spontaneous IL-8 mRNA expression and protein secre tion by AEC-II mere significantly higher in comparison with A549 cells. TNF -alpha increased both IL-8 mRNA expression and protein production, whereas IL-1 beta slightly increased IL-8 release but did not change mRNA expressio n in AEC-II. LPS and IFN-gamma did not influence IL-8 expression in AEC-II and A549 cells. These results show considerable differences between A549 ce ll and AEC-II, The latter are capable of producing IL-8 under the control o f proinflammatory cytokines, Our findings demonstrate that the modulation o f IL-8 release in AEC-II may have an important impact on the immunoreactivi ty of these cells during pulmonary inflammation in vivo.