Fluoride-induced IL-8 release in human epithelial lung cells: relationship to EGF-receptor-, SRC- and MAP-kinase activation

Toxicol Appl Pharmacol. 2008 Feb 15;227(1):56-67. doi: 10.1016/j.taap.2007.09.022. Epub 2007 Oct 3.

Abstract

Exposure of human epithelial lung cells to fluorides is known to induce a marked increase in the release of interleukin (IL)-8, a chemokine involved in neutrophil recruitment. In the present study, the involvement of mitogen-activating protein kinases (MAPKs), the role of upstream activation of Src family kinases (SFKs), epidermal growth factor receptor (EGFR) activation and the interrelationships between these pathways in fluoride-induced IL-8 were examined in a human epithelial lung cell line (A549). Sodium fluoride strongly activated MAPK, in particular JNK1/2 and p38. The ERK1/2-inhibitor PD98059, the p38-inhibitor SB202190 and the JNK1/2-inhibitor SP600125 partially inhibited the fluoride-induced IL-8 response. Combinations of these inhibitors reduced the responses nearly to basal levels. Treatment with siRNA against JNK2 also reduced the IL-8 response to fluoride. Furthermore, fluoride activated SFKs, which was abolished by the SFK-inhibitor PP2. PP2 substantially inhibited the increased levels of IL-8, and partially reduced the fluoride-induced activation of ERK1/2, p38 and JNK1/2. Fluoride exposure also led to a phosphorylation of the EGFR, that was partially inhibited by PP2. AG1478, an EGFR-inhibitor, partially reduced the fluoride-induced IL-8 response and the phosphorylation of JNK1/2 and ERK1/2, but less the phosphorylation of p38. The effects of AG1478 were less than that of PP2. In conclusion, our findings suggest that the fluoride-induced IL-8 release involves the combined activation of ERK1/2, JNK1/2 and p38, and that the phosphorylation of these kinases, and in particular JNK1/2 and ERK1/2, partly, is mediated via a SFK-dependent EGFR-linked pathway. SFK-dependent, but EGFR-independent mechanisms seem important, and especially for phosphorylation of p38.

MeSH terms

  • Cell Line
  • Enzyme Activation
  • Epidermal Growth Factor / metabolism*
  • Epithelial Cells / drug effects
  • Epithelial Cells / enzymology
  • Epithelial Cells / metabolism
  • ErbB Receptors / metabolism
  • Fluorides / pharmacology*
  • Humans
  • Interleukin-8 / metabolism*
  • Lung / cytology
  • Lung / drug effects*
  • Lung / enzymology
  • Lung / metabolism
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / metabolism*
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology

Substances

  • Interleukin-8
  • Protein Kinase Inhibitors
  • Epidermal Growth Factor
  • ErbB Receptors
  • Mitogen-Activated Protein Kinases
  • Fluorides