Lipid oxidation and environmental pollutants are major sources of α,β-unsaturated aldehydes such as acrolein and 4-hydroxynonenal. Acrolein (2-propenal), a major product of organic combustion such as tobacco smoke, represents the most reactive α,β-unsaturated aldehyde, with high reactivity toward nucleophilic targets such as sulfhydryl groups. To investigate how acrolein affects respiratory tract cell activation, we exposed either primary (NHBE) or immortalized human bronchial epithelial cells (HBE1) to 0-25 μM acrolein, and determined effects on basal and tumor necrosis factor-α (TNFα)-induced production of the chemokine interleukin (IL)-8. Cell exposure to acrolein dose-dependently suppressed IL-8 mRNA levels in HBE1 cells (26, 40, and 79% at 5, 10, and 25 μM acrolein concentrations, respectively) and resulted in corresponding decreases in IL-8 production. Studies of nuclear factor-κB (NFκB) activation, an essential event in IL-8 production, showed decreased TNFα-induced NFκB activation by acrolein, illustrated by inhibition of nuclear translocation of NFκB and reduced IκBα degradation. Immunochemical analysis of IκB kinase (IKK), a redox-sensitive regulator of NFκB activation, indicated direct modification of the IKK β-subunit by acrolein, suggesting that acrolein may act directly on IKK. In summary, our results demonstrate that acrolein can suppress inflammatory processes in the airways by inhibiting epithelial IL-8 production through direct or indirect inhibitory effects on NFκB activation.
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