Nicotine promotes colon tumor growth and angiogenesis through β-adrenergic activation

Cigarette smoking is a putative environmental risk factor for colon cancer. Nicotine, an active alkaloid in tobacco, has been implicated in carcinogenesis. In the present study, we demonstrated that oral nicotine administration (50 or 200 μg/ml) for 25 days stimulated growth of human colon cancer xenograft in nude mice. It also increased vascularization in the tumors and elevated cotinine and adrenaline plasma levels. β-Adrenoceptors, cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and vascular endothelial growth factor (VEGF) in tumor tissues were also increased by nicotine. I.p. injection of β1-selective antagonist (atenolol, 5 or 10 mg/kg) or β2-selective antagonist (ICI 118,551, 5, or 10 mg/kg) blocked the nicotine-stimulated tumor growth dose dependently, in which β2-selective antagonist produced a more prominent effect. β-Adrenoceptors blockade also abrogated the stimulatory action of nicotine on microvessel densities as well as cell expression of COX-2, PGE2, and VEGF, in which β2-selective antagonist produced a significant effect. These findings provide a direct evidence that nicotine can enhance colon tumor growth mediated partly by stimulation of β-adrenoceptors, preferentially the β2-adrenoceptors. Activation of β-adrenoceptors and the subsequent stimulation of COX-2, PGE2, and VEGF expression is perhaps an important mechanism in the tumorigenic action of nicotine on colon tumor growth. These data suggest that β-adrenoceptors play a modulatory role in the development of colon cancer and partly elucidate the carcinogenic action of cigarette smoke. © The Author 2007. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.link_to_subscribed_fulltex

A new role for cathelicidin in ulcerative colitis in mice

Cathelicidin, an antimicrobial peptide of the innate immune system, modulates microbial growth, wound healing, and inflammation. However, its association with inflammatory bowel diseases (IBDs) is unknown. Our objective was to determine whether cathelicidin would exert a modulatory effect on the progression of IBD and, if so, investigate the mechanism of action through which this effect occurred. We evaluated the potential for a synthetic cathelicidin, the mouse cathelin-related antimicrobial peptide (mCRAMP), to prevent the initiation and promote the healing of lesions from inflammatory colitis that was experimentally induced in mice with dextran sulfate sodium (DSS). During the experiment, mCRAMP was given: (i) as a parallel treatment starting together with 3% DSS feeding, and (ii) as a posttreatment starting 7 days after 3% DSS feeding. The body weight, fecal microflora populations, clinical symptoms, and histologic findings of colonic tissues were measured. Relative gene expression of mucins (MUC1, MUC2, MUC3, and MUC4) in colonic tissues was determined by real-time polymerase chain reaction. Intrarectal administration of mCRAMP ameliorated DSS-induced colitis with negligible effects on mucosal healing. The peptide also significantly reduced the increased number of fecal microflora in colitis animals. It reversed the decline of colonic mucus thickness during colitis through upregulation of the expression of mucin genes. Treatment with mCRAMP also prevented colitis development by suppressing the induction of apoptosis by DSS. The current study demonstrates for the first time that intrarectal administration of cathelicidin may be a novel therapeutic option for IBDs. Copyright © 2007 by the Society for Experimental Biology and Medicine.link_to_subscribed_fulltex

Nicotine promotes cell proliferation via α7-nicotinic acetylcholine receptor and catecholamine-synthesizing enzymes-mediated pathway in human colon adenocarcinoma HT-29 cells

Cigarette smoking has been implicated in colon cancer. Nicotine is a major alkaloid in cigarette smoke. In the present study, we showed that nicotine stimulated HT-29 cell proliferation and adrenaline production in a dose-dependent manner. The stimulatory action of nicotine was reversed by atenolol and ICI 118,551, a β1- and β2-selective antagonist, respectively, suggesting the role of β-adrenoceptors in mediating the action. Nicotine also significantly upregulated the expression of the catecholamine-synthesizing enzymes [tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DβH) and phenylethanolamine N-methyltransferase]. Inhibitor of TH, a rate-limiting enzyme in the catecholamine-biosynthesis pathway, reduced the actions of nicotine on cell proliferation and adrenaline production. Expression of α7-nicotinic acetylcholine receptor (α7-nAChR) was demonstrated in HT-29 cells. Methyllycaconitine, an α7-nAChR antagonist, reversed the stimulatory actions of nicotine on cell proliferation, TH and DβH expression as well as adrenaline production. Taken together, through the action on α7-nAChR nicotine stimulates HT-29 cell proliferation via the upregulation of the catecholamine-synthesis pathway and ultimately adrenaline production and β-adrenergic activation. These data reveal the contributory role α7-nAChR and β-adrenoceptors in the tumorigenesis of colon cancer cells and partly elucidate the carcinogenic action of cigarette smoke on colon cancer. © 2007 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

Effects of cigarette smoking and restraint stress on human colon tumor growth in mice

Background: Cigarette smoking is a risk factor for colon cancer. Studies suggest that stress increases the incidence and promotes the development of cancers. Cigarette smoking and stress are closely associated, as people often smoke under stressful conditions and both of them can activate the adrenergic nervous system. Aims: To investigate the effects of cigarette smoking and restraint stress on colon cancer growth and the possible underlying mechanisms in these pathological processes. Methods: Nude mice bearing a HT-29 human colon cancer xenograft were either exposed to cigarette smoke and/or restraint stress. Cotinine and epinephrine levels in plasma of nude mice were measured by enzyme immunoassays. Expression of cyclooxygenase-2 (COX-2) and B-cell lymphoma-2 (Bcl-2) in tumor tissues were detected by Western blot. Prostaglandin E 2 (PGE2) concentrations were determined by enzyme immunoassay. Results: 4% cigarette smoking together with restraint stress 1 h daily for 33 days promoted tumor growth in nude mice. This was accompanied by the increase of plasma levels of cotinine and epinephrine in these animals. They also enhanced the COX-2, Bcl-2 expressions and PGE2 levels in tumor tissues. Conclusion: These findings are important in understanding the pathogenesis of colon cancer, particularly related to cigarette smoking and stress. © 2009 S. Karger AG, Basel.link_to_subscribed_fulltex

Erratum: Shift of homeostasis from parenchymal regeneration to fibroblast proliferation induced by lipopolysaccharide-activated macrophages in gastric mucosal healing in vitro (Wound Repair and Regeneration (March/April 2007) 15, 2, (221))

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The cationic host defense peptide rCRAMP promotes gastric ulcer healing in rats

Cathelicidin, a cationic host defense peptide, has been shown to promote cutaneous wound repair and reaches high levels in the gastric mucosa during infection and inflammation. Therefore, we investigated whether this peptide contributes to gastric ulcer healing in rats. Ulcer induction increased the expression of rat cathelicidin rCRAMP in the gastric mucosa. Further increase in expression of rCRAMP by local injection of rCRAMP-encoding plasmid promoted ulcer healing by enhancing cell proliferation and angiogenesis. rCRAMP directly stimulated proliferation of cultured rat gastric epithelial cells (RGM-1), which was abolished by inhibitors of matrix metalloproteinase (MMP), epidermal growth factor receptors (EGFR) tyrosine kinase, or mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase. rCRAMP also increased EGFR and ERK1/2 phosphorylation via an MMP-dependent mechanism. Knockdown of transforming growth factor α (TGFα), which is a ligand of EGFR, by small interfering RNA completely nullified the mitogenic signals evoked by rCRAMP in RGM-1 cells. These findings suggest that rCRAMP exhibits prohealing activity in stomachs through TGFα-dependent transactivation of EGFR and its related signaling pathway to induce proliferation of gastric epithelial cells. Copyright © 2006 by The American Society for Pharmacology and Experimental Therapeutics.link_to_subscribed_fulltex

Nicotine induces cyclooxygenase-2 and vascular endothelial growth factor receptor-2 in association with tumor-associated invasion and angiogenesis in gastric cancer

Blockade of angiogenesis is a promising strategy to suppress tumor growth, invasion, and metastasis. Vascular endothelial growth factor (VEGF), which binds to tyrosine kinase receptors [VEGF receptors (VEGFR) 1 and 2], is the mediator of angiogenesis and mitogen for endothelial cells. Cyclooxygenase-2 (COX-2) plays an important role in the promoting action of nicotine on gastric cancer growth. However, the action of nicotine and the relationship between COX-2 and VEGF/VEGFR system in tumorigenesis remain undefined. In this study, the effects of nicotine in tumor angiogenesis, invasiveness, and metastasis were studied with sponge implantation and Matrigel membrane models. Nicotine (200 μg/mL) stimulated gastric cancer cell proliferation, which was blocked by SC-236 (a highly selective COX-2 inhibitor) and CBO-P11 (a VEGFR inhibitor). This was associated with decreased VEGF levels as well as VEGFR-2 but not VEGFR-1 expression. Topical injection of nicotine enhanced tumor-associated vascularization, with a concomitant increase in VEGF levels in sponge implants. Again, application of SC-236 (2 mg/kg) and CBO-P11 (0.4 mg/kg) partially attenuated vascularization by ∼30%. Furthermore, nicotine enhanced tumor cell invasion through the Matrigel membrane by 4-fold and promoted migration of human umbilical vein endothelial cells in a cocultured system with gastric cancer cells. The activity of matrix metalloproteinases 2 and 9 and protein expressions of plasminogen activators (urokinase-type plasminogen activator and its receptor), which are the indicators of invasion and migration processes, were increased by nicotine but blocked by COX-2 and VEGFR inhibitors. Taken together, our results reveal that the promoting action of nicotine on angiogenesis, tumor invasion, and metastasis is COX-2/VEGF/VEGFR dependent. Copyright © 2005 American Association for Cancer Research.link_to_subscribed_fulltex

Enhancement of gastric mucosal integrity by Lactobacillus rhamnosus GG

The gastric mucosa is frequently exposed to different exogenous and endogenous ulcerative agents. Alcoholism is one of the risk factors for the development of mucosal damage in the stomach. This study aimed to assess if a probiotic strain Lactobacillus rhamnosus GG (LGG) is capable of protecting the gastric mucosa from acute damage induced by intragastric administration of ethanol. Pre-treatment of rats with LGG at 109 cfu/ml twice daily for three consecutive days markedly reduced ethanol-induced mucosal lesion area by 45%. LGG pre-treatment also significantly increased the basal mucosal prostaglandin E2 (PGE2) level. In addition, LGG attenuated the suppressive actions of ethanol on mucus-secreting layer and transmucosal resistance and reduced cellular apoptosis in the gastric mucosa. It is suggested that the protective action of LGG on ethanol-induced gastric mucosal lesions is likely attributed to the up-regulation of PGE2, which could stimulate the mucus secretion and increase the transmucosal resistance in the gastric mucosa. All these would protect mucosal cells from apoptosis in the stomach. © 2007 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

Functional role of β-adrenergic receptors in the mitogenic action of nicotine on gastric cancer cells

We previously reported that nicotine promoted gastric cancer cell growth via upregulation of cyclooxygenase 2 (COX-2). In the present study, we further investigated whether β-adrenoceptors, protein kinase C (PKC), and extracellular signal-regulated kinase-1/2 (ERK1/2) were involved in the modulation of COX-2 expression and cell proliferation by nicotine in AGS, a human gastric adenocarcinoma cell line. Results showed that nicotine dose dependently increased the phosphorylation of EKR1/2 and the expression of AP-1 subunits c-fos and c-jun. In this connection, the ERK1/2 inhibitor U0126 abrogated the upregulation of AP-1 and COX-2 as well as cell proliferation induced by nicotine. Moreover, nicotine induced the translocation of PKC-βI from cytosol to membrane and increased the total levels of PKC expression. Inhibition of PKC by staurosporine attenuated nicotine-induced ERK1/2 phosphorylation and COX-2 expression. Furthermore, atenolol and ICI 118,551, a β1- and β2-adrenoceptor antagonist, respectively, reversed the stimulatory action of nicotine on the expression of PKC, ERK1/2 phosphorylation, and COX-2 together with cell proliferation. Collectively, these results suggest that nicotine stimulates gastric cancer cell growth through the activation of β-adrenoceptors and the downstream PKC-βI/ERK1/2/COX-2 pathway. © 2007 Oxford University Press.link_to_subscribed_fulltex

E series of prostaglandin receptor 2-mediated activation of extracellular signal-regulated kinase/activator protein-1 signaling is required for the mitogenic action of prostaglandin E2 in esophageal squamous-cell carcinoma

The use of nonsteroidal anti-inflammatory drugs is associated with a lower risk for esophageal squamous cell carcinoma, in which overexpression of cyclooxygenase-2 (COX-2) is frequently reported. Prostaglandin E2 (PGE2), a COX-2-derived eicosanoid, is implicated in the promotion of cancer growth. However, the precise role of PGE2 in the disease development of esophageal squamous cell carcinoma remains elusive. In this study, we investigated the effect of PGE2 on the proliferation of cultured esophageal squamous cell carcinoma cells (HKESC-1). Results showed that HKESC-1 cells expressed all four series of prostaglandin (EP) receptors, namely, EP1 to EP4 receptors. In this regard, PGE2 and the EP2 receptor agonist (±)-15-deoxy-16S-hydroxy-17-cyclobutyl PGE1 methyl ester (butaprost) markedly increased HKESC-1 cell proliferation. Moreover, the mitogenic effect of PGE2 was significantly attenuated by RNA interference-mediated knockdown of the EP2 receptor, indicating that this receptor mediated the mitogenic effect of PGE2. In this connection, PGE2 and butaprost induced phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2), whose down-regulation by RNA interference significantly attenuated PGE2-induced cell proliferation. In addition, PGE2 and butaprost increased c-Fos expression and activator protein 1 (AP-1) transcriptional activity, which were abolished by the mitogen-activated protein kinase/Erk kinase inhibitor 1,4-diamino-2,3-dicyano-1, 4-bis(o-aminophenylmercapto)-butadiene ethanolate (U0126). AP-1-binding inhibitor curcumin also partially reversed the mitogenic effect of PGE 2. Taken together, these data demonstrate for the first time that the EP2 receptor mediates the mitogenic effect of PGE2 in esophageal squamous cell carcinoma via activation of the Erk/AP-1 pathway. This study supports the growth-promoting action of PGE2 in esophageal squamous cell carcinoma and the potential application of EP2 receptor antagonists in the treatment of this disease. Copyright © 2008 by The American Society for Pharmacology and Experimental Therapeutics.link_to_subscribed_fulltex