Induction of COX-2/PGE2/IL-6 is crucial for cigarette smoke extract-induced airway inflammation: Role of TLR4-dependent NADPH oxidase activation

Chih Chung Lin, I. Ta Lee, Ya Lin Yang, Chiang Wen Lee, Yu Ru Kou, Chuen Mao Yang

Research output: Contribution to journalArticlepeer-review

75 Citations (Scopus)

Abstract

Exposure to cigarette smoke extract (CSE) leads to airway and lung inflammation through an oxidant-antioxidant imbalance. Cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) have been shown to play critical roles in respiratory inflammation. Here, we show that COX-2/PGE2/IL-6 induction is dependent on Toll-like receptor 4 (TLR4)/NADPH oxidase signaling in human tracheal smooth muscle cells (HTSMCs). CSE induced COX-2 expression in vitro in HTSMCs and in vivo in the airways of mice. CSE also directly caused an increase in TLR4. Moreover, CSE-regulated COX-2, PGE2, and IL-6 generation was inhibited by pretreatment with TLR4 Ab; inhibitors of c-Src (PP1), NADPH oxidase (diphenylene iodonium chloride and apocynin), p38 MAPK (SB202190), MEK1/2 (U0126), JNK1/2 (SP600125), and NF-κB (helenalin); a ROS scavenger (N-acetyl-l-cysteine); and transfection with siRNA of TLR4, MyD88, TRAF6, Src, p47phox, p38, p42, JNK2, or p65. CSE-induced leukocyte numbers in BAL fluid were also reduced by pretreatment with these inhibitors. Furthermore, CSE induced p47phox translocation and TLR4/MyD88/TRAF6 and c-Src/p47phox complex formation. We found that PGE2 enhanced IL-6 production in HTSMCs and leukocyte count in BAL fluid. In addition, treatment with nicotine could induce COX-2, PGE2, and IL-6 generation in in vivo and in vitro studies. These results demonstrate that CSE-induced ROS generation was mediated through the TLR4/MyD88/TRAF6/c-Src/NADPH oxidase pathway, in turn initiated the activation of MAPKs and NF-κB, and ultimately induced COX-2/PGE2/IL-6-dependent airway inflammation.

Original languageEnglish
Pages (from-to)240-254
Number of pages15
JournalFree Radical Biology and Medicine
Volume48
Issue number2
DOIs
Publication statusPublished - Jan 15 2010
Externally publishedYes

Keywords

  • Cigarette smoke
  • Cyclooxygenase-2
  • Free radicals
  • Human tracheal smooth muscle cells
  • Oxidative stress
  • Prostaglandin E

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)

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