Nicotine enhancement of lipopolysaccharide/interferon-γ-induced cytotoxicity with elevating nitric oxide production

Effect of Nicotine on STAT1 Pathway and Oxidative Stress in Rat Lungs

Background

Tobacco use is responsible for millions of preventable deaths due to cancer. Nicotine, an alkaloid chemical found in tobacco was proved to cause chronic inflammation and oxidative stress. The transcription factor STAT1 induces the expression of many proinflammatory genes and has been suggested to be a target for anti-inflammatory therapeutics. The following study investigated the effect of Nicotine on STAT1 pathway and oxidative stress in rat lung tissue.

Methods

Thirty rats were divided into 3 groups; group I considered as control, group II; its rats were daily injected with Nicotine at a dose of 0.4 mg/100 gm body for 8 successive weeks and group III; its rats were daily injected with Nicotine as group II, but the injection was stopped for another 4 weeks. STAT1α protein was assessed by immunohistochemistry, COX-2 and iNOS genes expression were evaluated by real time PCR and thiobarbituric acid reactive substances (TBARS) and total thiols were measured using spectrophotometric methods in the lung tissues of the rats.

Results

The results of the study revealed that group II rats had the highest expression of STAT1α protein and COX-2 and iNOS genes and oxidative stress in their lung tissues. Nicotine cessation for 4 weeks caused a marked reduction in the expression of STAT1α protein, COX-2 and iNOS genes and oxidative stress.

Conclusion

Induction of STAT1 pathway and the increase in oxidative stress may be the mechanisms through which Nicotine may induce its harmful effects.

Use of electronic cigarettes (e-cigarettes) impairs indoor air quality and increases FeNO levels of e-cigarette consumers

Despite the recent popularity of e-cigarettes, to date only limited data is available on their safety for both users and secondhand smokers. The present study reports a comprehensive inner and outer exposure assessment of e-cigarette emissions in terms of particulate matter (PM), particle number concentrations (PNC), volatile organic compounds (VOC), polycyclic aromatic hydrocarbons (PAH), carbonyls, and metals. In six vaping sessions nine volunteers consumed e-cigarettes with and without nicotine in a thoroughly ventilated room for two hours. We analyzed the levels of e-cigarette pollutants in indoor air and monitored effects on FeNO release and urinary metabolite profile of the subjects. For comparison, the components of the e-cigarette solutions (liquids) were additionally analyzed. During the vaping sessions substantial amounts of 1,2-propanediol, glycerine and nicotine were found in the gas-phase, as well as high concentrations of PM2.5 (mean 197 μg/m(3)). The concentration of putative carcinogenic PAH in indoor air increased by 20% to 147 ng/m(3), and aluminum showed a 2.4-fold increase. PNC ranged from 48,620 to 88,386 particles/cm(3) (median), with peaks at diameters 24-36 nm. FeNO increased in 7 of 9 individuals. The nicotine content of the liquids varied and was 1.2-fold higher than claimed by the manufacturer. Our data confirm that e-cigarettes are not emission-free and their pollutants could be of health concern for users and secondhand smokers. In particular, ultrafine particles formed from supersaturated 1,2-propanediol vapor can be deposited in the lung, and aerosolized nicotine seems capable of increasing the release of the inflammatory signaling molecule NO upon inhalation. In view of consumer safety, e-cigarettes and nicotine liquids should be officially regulated and labeled with appropriate warnings of potential health effects, particularly of toxicity risk in children.

Chronic nicotine exposure attenuates proangiogenic activity on human umbilical vein endothelial cells

The pathogenic mechanism of nicotine, a major product of smoking, on vascular endothelial cells is not well defined yet. The purpose of this study was to determine whether chronic exposure to nicotine alters angiogenic activity in human umbilical vein endothelial cells and to identify a potential role for endothelial nitric oxide synthase (eNOS) expression. Our study demonstrated that acute nicotine treatment enhanced nitric oxide release, eNOS activation, and proangiogenic activity. However, chronic nicotine exposure impaired proangiogenic function (decreased cell migration and tubular structure formation) in human umbilical vein endothelial cells compared with acute exposure, but sustained the antiapoptotic effect. These findings seem to be related to eNOS gene expression and nitric oxide production, which may be involved in the pathophysiology of chronic nicotine addicts.

Heme oxygenase-1 mediates nicotine- and lipopolysaccharide-induced expression of cyclooxygenase-2 and inducible nitric oxide synthase in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Although heme oxygenase-1 (HO-1) plays a key role in inflammation, its anti-inflammatory effects and mechanism of action in periodontitis are still unknown. This study aimed to identify the effects of HO-1 on the proinflammatory mediators activated by nicotine and lipopolysaccharide (LPS) stimulation in human periodontal ligament (PDL) cells.

MATERIAL AND METHODS

The production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) was evaluated using Griess reagent and an enzyme immunoassay, respectively. The expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and HO-1 proteins was evaluated by Western blot analysis.

RESULTS

Lipopolysaccharide and nicotine synergistically induced the production of NO and PGE(2) and increased the protein expression of iNOS, COX-2 and HO-1. Treatment with an HO-1 inhibitor and HO-1 small interfering RNAs blocked the LPS- and nicotine-stimulated NO and PGE(2) release as well as the expression of iNOS and COX-2.

CONCLUSION

Our data suggest that the nicotine- and LPS-induced inflammatory effects on PDL cells may act through a novel mechanism involving the action of HO-1. Thus, HO-1 may provide a potential therapeutic target for the treatment of periodontal disease associated with smoking and dental plaque.

Effects of exogenous selenium on nicotine-induced oxidative stress in rats

The effect of two different doses of selenium [1 and 50 microg selenium/100 g body weight (wt)] on nicotine-induced oxidative damage in liver was investigated in experimental rats. Male albino rats were maintained for 60 days as follows: (1) control group (normal diet), (2) nicotine group (0.6 mg/kg body wt)/day, (3) high-dose selenium (50 microg/100 g body wt)/day, (4) high-dose selenium (50 microg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day, (5) low-dose selenium (1 microg/100 g body wt)/day, and (6) low-dose selenium (1 microg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day. Nicotine administration caused a decrease in the activity of antioxidant enzymes, an increase in the concentration of lipid peroxidation products and protein carbonyls and an increase in the activity of nitric oxide synthase compared to the control group. Coadministration of nicotine and selenium reduced the concentration of lipid peroxidation products and increased the activity of antioxidant enzymes compared to the nicotine group. Selenium also enhanced the metabolism of nicotine. The antioxidant effect was more significant in the group administered a low dose of selenium.

Nicotine enhances migration and invasion of human esophageal squamous carcinoma cells which is inhibited by nimesulide

AIM: To study the effect of nicotine on the migration and invasion of human esophageal squamous carcinoma cells and to investigate whether nimesulide can inhibit the effect of nicotine.

METHODS: The esophageal squamous carcinoma cell line (TE-13) was treated with different concentrations of nicotine (100 &mgr;g/mL and 200 &mgr;g/mL) or 200 &mgr;g/mL nicotine plus 100 &mgr;mol/L nimesulide. Cell migration and invasion were measured using migration and invasion chamber systems. COX-2 expression was determined by Western blotting. Matrix metalloproteinase-2 (MMP-2) was analyzed by zymography and ELISA.

RESULTS: Nicotine (100 &mgr;g/mL, 200 &mgr;g/mL) enhanced TE-13 cells migration and invasion, and increased the protein expression of COX-2 and the activity of MMP-2. Nicotine (200 &mgr;g/mL) stimulated TE-13 cells migration and invasion which were partly blocked by nimesulide. This was associated with decreased protein expression of COX-2 and decreased activity and protein expression of MMP-2.

CONCLUSION: Nicotine enhances the migration and invasion of the esophageal squamous carcinoma cell line, and nimesulide partly blocks the effect of nicotine-enhanced esophageal squamous carcinoma cell migration and invasion.

The vagus nerve as a modulator of intestinal inflammation

The cholinergic nervous system attenuates the production of pro-inflammatory cytokines and inhibits inflammatory processes. Hence, in animal models of intestinal inflammation, such as postoperative ileus and dextran sulfate sodium-induced colitis, vagus nerve stimulation ameliorates disease activity. On the other hand, in infectious models of microbial peritonitis, vagus nerve activation seemingly acts counteractive; it impairs bacterial clearance and increases mortality. It is originally indicated that the key mediator of the cholinergic anti-inflammatory pathway, acetylcholine (ACh), inhibits cytokine release directly via the alpha7 nicotinic ACh receptor (nAChR) expressed on macrophages. However, more recent data also point towards the vagus nerve as an indirect modulator of innate inflammatory processes, exerting its anti-inflammatory effects via postganglionic modulation of immune cells in primary immune organs. This review discusses advances in the possible mechanisms by which the vagus nerve can mediate the immune response, and the role of nAChR activation and signalling on macrophages and other immune cells.

Cigarette smoking and erectile dysfunction: focus on NO bioavailability and ROS generation

INTRODUCTION

Thirty million men in the United States suffer from erectile dysfunction (ED) and this number is expected to double by 2025. Considered a major public health problem, which seriously affects the quality of life of patients and their partners, ED becomes increasingly prevalent with age and chronic smoking is a major risk factor in the development of ED.

AIM

To review available evidence concerning the effects of cigarette smoking on vascular changes associated with decreased nitric oxide (NO) bioavailability and increased reactive oxygen species (ROS) generation.

METHODS

We examined epidemiological and clinical data linking cigarette smoking and ED, and the effects of smoking on vascular NO bioavailability and ROS generation.

MAIN OUTCOME MEASURES

There are strong parallels between smoking and ED and considerable evidence supporting the concept that smoking-related ED is associated with reduced bioavailability of NO because of increased ROS.

RESULTS

Cigarette smoking-induced ED in human and animal models is associated with impaired arterial flow to the penis or acute vasospasm of the penile arteries. Long-term smoking produces detrimental effects on the vascular endothelium and peripheral nerves and also causes ultrastructural damage to the corporal tissue, all considered to play a role in chronic smoking-induced ED. Clinical and basic science studies provide strong indirect evidence that smoking may affect penile erection by the impairment of endothelium-dependent smooth muscle relaxation or more specifically by affecting NO production via increased ROS generation. Whether nicotine or other products of cigarette smoke mediate all effects related to vascular damage is still unknown.

CONCLUSIONS

Smoking prevention represents an important approach for reducing the risk of ED. The characterization of the components of cigarette smoke leading to ED and the mechanisms by which these components alter signaling pathways activated in erectile responses are necessary for a complete comprehension of cigarette smoking-associated ED.

Nicotine inhibits the production of proinflammatory mediators in human monocytes by suppression of I-kappaB phosphorylation and nuclear factor-kappaB transcriptional activity through nicotinic acetylcholine receptor alpha7

Macrophages/monocytes and the proinflammatory mediators, such as tumour necrosis factor (TNF)-alpha, prostaglandin E(2) (PGE(2)), macrophage inflammatory protein (MIP)-1alpha and MIP-1alpha, play a critical role in the progression of immunological disorders including rheumatoid arthritis, Behçet's disease and Crohn's disease. In addition, the nicotinic acetylcholine receptor-alpha7 (alpha7nAChR) subunit is an essential regulator of inflammation. In this study, we evaluated the expression of the alpha7nAChR subunit on human peripheral monocytes and the effect of nicotine on the production of these proinflammatory mediators by activated monocytes. Fluorescein isothiocyanate (FITC)-labelled alpha-bungarotoxin demonstrated the cell surface expression of the alpha7nAchR subunit. Pretreatment with low-dose nicotine caused inhibition of TNF-alpha, PGE(2), MIP-1alpha and MIP-1alpha production, and mRNA expression of TNF-alpha, MIP-1alpha and MIP-1alpha and COX-2 in lipopolysaccharide (LPS)-activated monocytes. These suppressive effects of nicotine were caused at the transcriptional level and were mediated through alpha7nAChR. Nicotine suppressed the phosphorylation of I-kappaB, and then inhibited the transcriptional activity of nuclear factor-kappaB. These immunosuppressive effects of nicotine may contribute to the regulation of some immune diseases.

Nicotine and serotonin in immune regulation and inflammatory processes: a perspective

Nicotine and serotonin modulate the innate and adaptive immune responses and the inflammatory states. Several nicotinic cholinergic and serotonergic receptor subtypes have been characterized in B and T lymphocytes, monocytes, macrophages, and dendritic cells. The use of knockout mice has allowed a better characterization of nicotinic receptors and their role in anti-inflammatory processes in these cells. Cytokines play a crucial role in controlling inflammatory reactions. Nicotine and serotonin have been reported to regulate cytokine release. Cholinergic mechanisms also play an important role in inflammation through endogenous acetylcholine. Nicotine mimics this effect by activating the cholinergic anti-inflammatory pathways. New concepts of reciprocal interactions between nicotine and serotonin are emerging. The role of nicotine as an anti-inflammatory agent has been established, whereas that of serotonin remains more controversial.

Genotoxicity of nicotine in mini-organ cultures of human upper aerodigestive tract epithelia

The direct role of nicotine in tobacco carcinogenesis is still controversial. Recently, DNA damage by nicotine has been demonstrated in isolated human tonsillar tissue cells. Presently, these effects were investigated using mini-organ cultures (MOC) of human nasal epithelia. Intact MOC were repeatedly exposed to 2 and 4 mM nicotine for 1 h on culture days 7, 9, and 11. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) served as a positive control. DNA damage was examined by Comet assay either directly after exposure or following a 24-h recovery period. Cell viability was not reduced by any treatment. On day 7, 1 h exposure to 2 and 4 mM nicotine caused a significant dose-dependent 3.3- and 5.6-fold increase in DNA damage compared to solvent controls. Although there was no evidence of significant repair within 24 h recovery, DNA damage was not further increased by nicotine on days 9 and 11. After double and triple exposure to 4 mM nicotine a significant reduction in DNA damage following 24 h recovery was observed. In contrast, treatment with MNNG resulted in a highly significant and cumulative increase in DNA migration up to 110-fold compared to controls. During recovery periods, MNNG-induced DNA damage was significantly repaired, leading to a 1.5- to 1.8-fold reduction in DNA migration within 24 h. These results confirm genotoxic effects of nicotine on human nasal epithelia. Further studies are needed to explain the lack of cumulative DNA-damaging effects of nicotine and the absence of significant DNA repair. These studies should include a battery of assays with multiple end points.