Nicotine stimulates PPARbeta/delta expression in human lung carcinoma cells through activation of PI3K/mTOR and suppression of AP-2alpha.
We previously showed that nicotine stimulates non-small cell lung carcinoma (NSCLC) cell proliferation through nicotinic acetylcholine receptor (nAChR)-mediated signals. Activation of peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) has also been shown to induce NSCLC cell growth. Here, we explore the potential link between nicotine and PPARbeta/delta and report that nicotine increases the expression of PPARbeta/delta protein; this effect was blocked by an alpha7 nAChR antagonist (alpha-bungarotoxin), by alpha7 nAChR short interfering RNA, and by inhibitors of phosphatidylinositol 3-kinase (PI3K; wortmannin and LY294002) and mammalian target of rapamycin (mTOR; rapamycin). In contrast, this effect was enhanced by PUN282987, an alpha7 nAChR agonist. Silencing of PPARbeta/delta attenuated the stimulatory effect of nicotine on cell growth, which was overcome by transfection of an exogenous PPARbeta/delta expression vector. Of note, nicotine induced complex formation between alpha7 nAChR and PPARbeta/delta protein and increased PPARbeta/delta gene promoter activity through inhibition of AP-2alpha as shown by reduced AP-2alpha binding using electrophoretic gel mobility shift and chromatin immunoprecipitation assays. In addition, silencing of Sp1 attenuated the effect of nicotine on PPARbeta/delta. Collectively, our results show that nicotine increases PPARbeta/delta gene expression through alpha7 nAChR-mediated activation of PI3K/mTOR signals that inhibit AP-2alpha protein expression and DNA binding activity to the PPARbeta/delta gene promoter. Sp1 seems to modulate this process. This study unveils a novel mechanism by which nicotine promotes human lung carcinoma cell growth.
Sun
XiaoJuan
X
Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
Ritzenthaler
Jeffrey D
JD
Zhong
XiaoRong
X
Zheng
Ying
Y
Roman
Jesse
J
Han
ShouWei
S
D002038:Bungarotoxins / Q000494:pharmacology; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D018679:Cholinergic Agonists / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009538:Nicotine / Q000494:pharmacology*; D047494:PPAR delta / Q000235:genetics / Q000378:metabolism*; D048068:PPAR-beta / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism* / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism* / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology; D058570:TOR Serine-Threonine Kinases; D050656:Transcription Factor AP-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002038:Bungarotoxins; D018679:Cholinergic Agonists; D009538:Nicotine; D047494:PPAR delta; D048068:PPAR-beta; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D011978:Receptors, Nicotinic; D058570:TOR Serine-Threonine Kinases; D050656:Transcription Factor AP-2; D064569:alpha7 Nicotinic Acetylcholine Receptor; C579167:Chrna7 protein, human; C546842:MTOR protein, human