Effects of MAPK inhibitors on H2O2-induced IL-8 production and cell death in primary cultures of human bronchial epithelial cells

The airway epithelium is continuously exposed to inhaled oxidants, including airborne pollutants and cigarette smoke, which can exert harmful proinflammatory and cytotoxic actions. Therefore, the aim of our study was to investigate, in primary cultures of human bronchial epithelial cells (HBEC), the effects of hydrogen peroxide (H2O2) on cell viability and interleukin-8 (IL-8) production. HBEC were exposed to increasing concentrations of H2O2 (0.25, 0.5 and 1 mM), in the presence or absence of a 12 h pretreatment with specific inhibitors of mitogen-activated protein kinases (MAPK). After H2O2 removal, cell death was detected by propidium iodide staining and, moreover, IL-8 release into cell culture supernatants was assayed by ELISA. Our results show that H2O2 elicited a concentration-dependent increase in MAPK phosphorylation, which was paralleled by a significant induction of IL-8 synthesis and a dramatically enhanced cell death. Pretreatment with MAPK inhibitors was able to significantly inhibit the effects of H2O2 on IL-8 secretion (p<0.01), and to completely prevent HBEC death. Therefore, these findings suggest that MAPK play a key role as molecular transducers of the airway epithelial injury triggered by oxidative stress, as well as potential pharmacologic targets for indirect antioxidant intervention.