Proinflammatory cytokine-induced and chemical mediator-induced IL-8 expression in human bronchial epithelial cells through p38 mitogen-activated protein kinase-dependent pathway.

The p38 mitogen-activated protein (MAP) kinase is activated in various cells by proinflammatory cytokines and environmental stresses. However, little is known about the role of p38 MAP kinase in proinflammatory cytokine- and chemical mediator-induced cytokine expression in human bronchial epithelial cells (BECs). In this study we examined the role of p38 MAP kinase in IL-8 expression in BECs to clarify the signal transduction pathway regulating IL-8 expression in BECs stimulated with tumor necrosis factor-alpha (TNF-alpha), IL-1alpha, and platelet-activating factor (PAF). We used TNF-alpha, IL-1alpha, and PAF as inducers for the analysis of the signal transduction pathway and determined IL-8 expression in BECs because TNF-alpha, IL-1alpha, and PAF are known to induce cytokine expression in BECs, and these proinflammatory cytokines and PAF are described to have a role in the production of allergic inflammation. The results showed that TNF-alpha, IL-1alpha, and PAF induced tyrosine phosphorylation of p38 MAP kinase in a dose- and time-dependent manner. The specific p38 MAP kinase inhibitor, SB 203580, completely inhibited TNF-alpha-, IL-1alpha-, or PAF-induced IL-8 protein and mRNA expression in BECs. These results indicated that p38 MAP kinase plays an important role in TNF-alpha-, IL-1alpha-, or PAF-activated signaling pathway, which regulates IL-8 expression in BECs. In addition, these results provide new evidence on a strategy for treatment of airway inflammation with the specific p38 MAP kinase inhibitor.