Quantification of PPAR-gamma protein in monocyte/macrophages from healthy smokers and non-smokers: a possible direct effect of nicotine.
Previous observations demonstrated that Peroxisome Proliferator-Activated Receptor-gamma (PPAR-gamma), a key regulator of adipocyte differentiation, is expressed in a large variety of cells, including cells of the monocyte/macrophage lineage. This study was aimed to quantify both the constitutive and ligand-induced PPAR-gamma expression in monocytes and monocyte-derived macrophages (MDM) isolated from healthy smokers and non-smokers, and to evaluate the possible direct effect of nicotine. PPAR-gamma protein was detected by Western blot and quantification was performed by calculating the ratio between PPAR-gamma and beta-actin protein expression. Cytokine release was measured with enzyme-linked immunoassay kits. Constitutive PPAR-gamma protein was detected in human monocytes and its expression was up-regulated along with differentiation to MDM. The endogenous ligand 15-deoxy-delta(12,14)-prostaglandin J(2) and the synthetic agonist ciglitazone enhanced PPAR-gamma expression, the former being effective also at low micromolar concentrations. Both agonists significantly inhibited the basal secretion of pro-inflammatory cytokines (e.g., TNF-alpha, IL-6), ciglitazone being more potent. Monocytes and MDM from healthy smokers presented a significantly enhanced (4-fold and 2.5-fold, respectively) constitutive PPAR-gamma expression, as compared to those from healthy non-smokers. However, ligand-induced PPAR-gamma expression and inhibition of cytokine secretion were similar in healthy smokers and non-smokers. Nicotine dose-dependently enhanced PPAR-gamma expression with a maximum at 10 muM, and inhibited release of pro-inflammatory cytokines; these effects were reversed by alpha-bungarotoxin. Nicotine and PPAR-gamma agonists did not exert synergistic effects. In conclusion, monocytes and MDM from healthy smokers present a constitutively enhanced PPAR-gamma expression; this effect is reproduced, to some extent, by nicotine in vitro.
Amoruso
Angela
A
Department of Medical Sciences, School of Medicine, University of Piemonte Orientale A. Avogadro, Via Solaroli, 17 - 28100 Novara, Italy.
Bardelli
Claudio
C
Gunella
Gabriele
G
Fresu
Luigia Grazia
LG
Ferrero
Valeria
V
Brunelleschi
Sandra
S
D000199:Actins / Q000378:metabolism; D000328:Adult; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D009538:Nicotine / Q000009:adverse effects / Q000494:pharmacology*; D047495:PPAR gamma / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism; D012907:Smoking; D045162:Thiazolidinediones / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation; D064569:alpha7 Nicotinic Acetylcholine Receptor
D000199:Actins; C579167:Chrna7 protein, human; D015850:Interleukin-6; D047495:PPAR gamma; D011978:Receptors, Nicotinic; D045162:Thiazolidinediones; D014409:Tumor Necrosis Factor-alpha; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; C039671:ciglitazone