Effect of smoking on MAP kinase-induced modulation of IL‐8 in human alveolar macrophages

Inflammatory cytokine production by alveolar macrophages (AMs) is regulated by transcriptional activation and may be increased by cigarette smoking. The smoking-induced regulation of interleukin (IL)‐8 by extracellular signal-regulated kinase (ERK)‐1 and ‐2, p38 mitogen-activated protein kinase (MAPK) and the transcription factor nuclear factor‐κB (NF‐κB) in lipopolysaccharide-stimulated AMs was assessed in nine smokers compared with nine healthy nonsmokers. IL‐8 production was dependent on phosphorylation of ERK‐1 and ‐2 and p38 MAPK, as examined by PD 098059 (10 µM), an inhibitor of the upstream activator of MAPK kinase (MKK)‐1, and SB 203580 (10 µM), an inhibitor of p38 MAPK. IL‐8 release and the inhibitory effect of PD 098059 were increased in AMs from smokers. Moreover, ERK‐2 messenger ribonucleic acid expression, as examined by reverse transcriptase polymerase chain reaction and phosphorylation of ERK‐2 using Western blots, were increased in AMs from smokers, indicating a smoking-induced modulatory role of ERK‐1 and ‐2. Lipopolysaccharide-induced IL‐8 production was dependent on activation of NF‐κB, as examined by SN 50 (100 µM), an inhibitor of NF‐κB translocation, and the specific NF‐κB inhibitor kinase‐2 inhibitor, AS 602868 (10 µM), with no differences in AMs from smokers and nonsmokers. SN 50 but not PD 098059 and SB 203580 blocked NF‐κB deoxyribonucleic acid-binding, and this occurred to the same extent in AMs from smokers and nonsmokers, as examined by electromobility shift assay. It is concluded that cigarette smoking enhances mitogen-activated protein kinase activation more than nuclear factor‐κB activation to increase lipopolysaccharide-induced interleukin‐8 production in alveolar macrophages.