Leukocytosis in tobacco smokers has been well recognized; however, the exact cause has not been elucidated. To test the hypothesis that tobacco nicotine stimulates neutrophils in the respiratory tract to produce IL-8, which causes neutrophilia in vivo, we examined whether nicotine induces neutrophil-IL-8 production in vitro; the causative role of NF-kappaB in its production, in association with the possible production of reactive oxygen intermediates that activate NF-kappaB; and the nicotinic acetylcholine receptors (nAChRs) involved in IL-8 production. Nicotine stimulated neutrophils to produce IL-8 in both time- and concentration-dependent manners with a 50% effective concentration of 1.89 mM. A degradation of IkappaB-alpha/beta proteins and an activity of NF-kappaB p65 and p50 were enhanced following nicotine treatment. The synthesis of superoxide and the oxidation of dihydrorhodamine 123 (DHR) were also enhanced. The NOS inhibitor, nomega-Nitro-l-arginine methyl ester, prevented nicotine-induced IL-8 production, with an entire abrogation of DHR oxidation, IkappaB degradation, and NF-kappaB activity. Neutrophils spontaneously produced NO whose production was not increased, but rather decreased by nicotine stimulation, suggesting that superoxide, produced by nicotine, generates peroxynitrite by reacting with preformed NO, which enhances the NF-kappaB activity, thereby producing IL-8. The nAChRs seemed to be involved in IL-8 production. In smokers, blood IL-8 levels were significantly higher than those in nonsmokers. In conclusion, nicotine stimulates neutrophil-IL-8 production via nAChR by generating peroxynitrite and subsequent NF-kappaB activation, and the IL-8 appears to contribute to leukocytosis in tobacco smokers.

CpG DNA induces plasmacytoid dendritic cells (pDC) to produce type I IFN and chemokines. However, it has not been fully elucidated how the TLR9 signaling pathway is linked to these gene expressions. We examined the mechanisms involving the TLR9 and type I IFN signaling pathways, in relation to CpG DNA-induced IFN-α, IFN regulatory factor (IRF)-7, and chemokines CXCL10 and CCL3 in human pDC. In pDC, NF-κB subunits p65 and p50 were constitutively activated. pDC also constitutively expressed IRF-7 and CCL3, and the gene expressions seemed to be regulated by NF-κB. CpG DNA enhanced the NF-κB p65/p50 activity, which collaborated with p38 MAPK to up-regulate the expressions of IRF-7, CXCL10, and CCL3 in a manner independent of type I IFN signaling. We then examined the pathway through which IFN-α is expressed. Type I IFN induced the expression of IRF-7, but not of IFN-α, in a NF-κB-independent way. CpG DNA enabled the type I IFN-treated pDC to express IFN-α in the presence of NF-κB/p38 MAPK inhibitor, and chloroquine abrogated this effect. With CpG DNA, IRF-7, both constitutively and newly expressed, moved to the nuclei independently of NF-κB/p38 MAPK. These findings suggest that, in CpG DNA-stimulated human pDC, the induction of IRF-7, CXCL10, and CCL3 is mediated by the NF-κB/p38 MAPK pathway, and that IRF-7 is activated upstream of the activation of NF-κB/p38 MAPK in chloroquine-sensitive regulatory machinery, thereby leading to the expression of IFN-α.

No abstract

Thrombocytosis is occasionally seen in patients with carcinomas and has been assumed to be attributable to interleukin-6 or granulocyte-macrophage colony-stimulating factor produced by carcinoma cells. In this study, we clarified whether thrombopoietin (TPO) is involved in carcinoma-associated thrombocytosis. Expression of TPO mRNA was observed in the majority of 27 carcinoma cell lines as determined by reverse transcriptase-polymerase chain reaction (RT-PCR). There were 6 PCR products differing in size; sequence analysis showed the full-length TPO mRNA (TPO-1), 12- and 116-bp deleted variants (TPO-2 and TPO-3, respectively), and 3 novel isoforms (197- and 128-bp deleted forms and a 60-bp insert form of TPO-3; named TPO-4, TPO-5, and TPO-6, respectively). Of 27 lines, 24 expressed TPO-1 mRNA with various other isoforms. Culture supernatants of COS-1 cells transfected with TPO-5 or TPO-6 cDNA did not promote the proliferation of TPO-responsive cells, whereas Western blot analysis on the cell lysates demonstrated TPO-5 but not TPO-6 protein, suggesting poor extracellular secretion (TPO-5) or poor protein synthesis (TPO-6). TPO protein was detected in 10-fold concentrated culture supernatants of cells of these carcinoma lines, with a median concentration of 0.38 fmol/mL as evaluated by enzyme-linked immunosorbent assay. High blood TPO levels were observed with a median value of 3.46 fmol/mL (range, 0.34 to 8.67 fmol/mL) in patients with advanced carcinomas associated with thrombocytosis. These results indicate that thrombocytosis in patients with carcinomas might be caused, at least in part, by TPO produced by carcinoma cells.