Induction of COX-2/PGE(2)/IL-6 is crucial for cigarette smoke extract-induced airway inflammation: Role of TLR4-dependent NADPH oxidase activation.
Exposure to cigarette smoke extract (CSE) leads to airway and lung inflammation through an oxidant-antioxidant imbalance. Cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)) have been shown to play critical roles in respiratory inflammation. Here, we show that COX-2/PGE(2)/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, PGE(2), 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-kappaB (helenalin); a ROS scavenger (N-acetyl-l-cysteine); and transfection with siRNA of TLR4, MyD88, TRAF6, Src, p47(phox), p38, p42, JNK2, or p65. CSE-induced leukocyte numbers in BAL fluid were also reduced by pretreatment with these inhibitors. Furthermore, CSE induced p47(phox) translocation and TLR4/MyD88/TRAF6 and c-Src/p47(phox) complex formation. We found that PGE(2) enhanced IL-6 production in HTSMCs and leukocyte count in BAL fluid. In addition, treatment with nicotine could induce COX-2, PGE(2), 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-kappaB, and ultimately induced COX-2/PGE(2)/IL-6-dependent airway inflammation.
Lin
Chih-Chung
CC
Department of Anesthetics, Chang Gung Memorial Hospital, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan.
Lee
I-Ta
IT
Yang
Ya-Lin
YL
Lee
Chiang-Wen
CW
Kou
Yu Ru
YR
Yang
Chuen-Mao
CM
D000818:Animals; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology; D011014:Pneumonia / Q000209:etiology / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012907:Smoking / Q000009:adverse effects; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
D015850:Interleukin-6; D034741:RNA, Small Interfering; D051197:Toll-Like Receptor 4; D009538:Nicotine; D051546:Cyclooxygenase 2; D019255:NADPH Oxidases; D015232:Dinoprostone