Nicotine-induced vascular endothelial growth factor release via the EGFR-ERK pathway in rat vascular smooth muscle cells

The potential role of nicotine in breast cancer initiation, development, angiogenesis, invasion, metastasis, and resistance to therapy

A large body of research studying the relationship between tobacco and cancer has led to the knowledge that smoking cigarettes adversely affects cancer treatment while contributing to the development of various tobacco-related cancers. Nicotine is the main addictive component of tobacco smoke and promotes angiogenesis, proliferation, and epithelial-mesenchymal transition (EMT) while promoting growth and metastasis of tumors. Nicotine generally acts through the induction of the nicotinic acetylcholine receptors (nAChRs), although the contribution of other receptor subunits has also been reported. Nicotine contributes to the pathogenesis of a wide range of cancers including breast cancer through its carcinogens such as (4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN). Current study aims to review the mechanistic function of nicotine in the initiation, development, angiogenesis, invasion, metastasis, and apoptosis of breast cancer with the main focus on nicotine acetylcholine receptors (nAChRs) and nAChR-mediated signaling pathways as well as on its potential for the development of an effective treatment against breast cancer. Moreover, we will try to demonstrate how nicotine leads to poor treatment response in breast cancer by enhancing the population, proliferation, and self-renewal of cancer stem cells (CSCs) through the activation of α7-nAChR receptors.

Receptor tyrosine kinases as a therapeutic target by natural compounds in cancer treatment

Background

Receptor tyrosine kinases (RTKs) are single-pass transmembrane proteins that play significant roles in regulating cellular processes, including cell division and growth. Overexpression and mutations of RTKs have been found in clinical manifestations of different forms of cancer. Therefore, RTKs have received considerable interest as a therapeutic biomarker in the treatment of cancer cells.

Main body of the abstract

Comprehensive data on RTKs, pharmacological and biological properties of natural compounds were systematically searched up to 2021 using relevant keywords from various databases, such as Google Scholar, PubMed, Web of Science, and Scopus. The scientific search by various standard electronic resources and databases unveils the effectiveness of medicinal plants in the treatment of various cancers. In vitro and in vivo studies suggested that bioactive compounds such as flavonoids, phenols, alkaloids, and many others can be used pharmacologically as RTKs inhibitors (RTKI) either by competing with ATP at the ATP binding site of the tyrosine kinase domain or competing for the receptor extracellular domain. Additionally, studies conducted on animal models indicated that inhibition of RTKs catalytic activity by natural compounds is one of the most effective ways to block the activation of RTKs signaling cascades, thereby hampering the proliferation of cancer cells. Furthermore, various pharmacological experiments, transcriptomic, and proteomic data also reported that cancer cells treated with different plants extracts or isolated phytochemicals exhibited better anticancer properties with minimal side effects than synthetic drugs. Clinically, natural compounds have demonstrated significant anti-proliferative effect via induction of cell apoptosis in cancer cell lines.

Short conclusion

An in-depth knowledge of the mechanism of inhibition and structural characterization of RTKs is important to the design of novel and selective RTKIs. This review focuses on the molecular mechanisms and structures of natural compounds RTKI targeting vascular endothelial growth factor, epidermal growth factor receptor, insulin receptor, and platelet-derived growth factor while also giving future directions to ameliorate the scientific burden of cancer.

Graphic abstract

Smoking and the Pathophysiology of Peripheral Artery Disease

Smoking is one of the most important preventable factors causing peripheral artery disease (PAD). The purpose of this review is to comprehensively analyze and summarize the pathogenesis and clinical characteristics of smoking in PAD based on existing clinical, in vivo, and in vitro studies. Extensive searches and literature reviews have shown that a large amount of data exists on the pathological process underlying the effects of cigarette smoke and its components on PAD through various mechanisms. Cigarette smoke extracts (CSE) induce endothelial cell dysfunction, smooth muscle cell remodeling and macrophage phenotypic transformation through multiple molecular mechanisms. These pathological changes are the molecular basis for the occurrence and development of peripheral vascular diseases. With few discussions on the topic, we will summarize recent insights into the effect of smoking on regulating PAD through multiple pathways and its possible pathogenic mechanism.

Nicotine: Regulatory roles and mechanisms in atherosclerosis progression

Smoking is an independent risk factor for atherosclerosis. The smoke produced by tobacco burning contains more than 7000 chemicals, among which nicotine is closely related to the occurrence and development of atherosclerosis. Nicotine, a selective cholinergic agonist, accelerates the formation of atherosclerosis by stimulating nicotinic acetylcholine receptors (nAChRs) located in neuronal and non-neuronal tissues. This review introduces the pathogenesis of atherosclerosis and the mechanisms involving nicotine and its receptors. Herein, we focus on the various roles of nicotine in atherosclerosis, such as upregulation of growth factors, inflammation, and the dysfunction of endothelial cells, vascular smooth muscle cells (VSMC) as well as macrophages. In addition, nicotine can stimulate the generation of reactive oxygen species, cause abnormal lipid metabolism, and activate immune cells leading to the onset and progression of atherosclerosis. Exosomes, are currently a research hotspot, due to their important connections with macrophages and the VSMC, and may represent a novel application into future preventive treatment to promote the prevention of smoking-related atherosclerosis. In this review, we will elaborate on the regulatory mechanism of nicotine on atherosclerosis, as well as the effects of interference with nicotine receptors and the use of exosomes to prevent atherosclerosis development.

Ion-Selective Carbon Nanotube Field-Effect Transistors for Monitoring Drug Effects on Nicotinic Acetylcholine Receptor Activation in Live Cells

We developed ion-selective field-effect transistor (FET) sensors with floating electrodes for the monitoring of the potassium ion release by the stimulation of nicotinic acetylcholine receptors (nAChRs) on PC12 cells. Here, ion-selective valinomycin-polyvinyl chloride (PVC) membranes were coated on the floating electrode-based carbon nanotube (CNT) FETs to build the sensors. The sensors could selectively measure potassium ions with a minimum detection limit of 1 nM. We utilized the sensor for the real-time monitoring of the potassium ion released from a live cell stimulated by nicotine. Notably, this method also allowed us to quantitatively monitor the cell responses by agonists and antagonists of nAChRs. These results suggest that our ion-selective CNT-FET sensor has potential uses in biological and medical researches such as the monitoring of ion-channel activity and the screening of drugs.

Nicotine in Senescence and Atherosclerosis

Cigarette smoke is a known exacerbator of age-related pathologies, such as cardiovascular disease (CVD), atherosclerosis, and cellular aging (senescence). However, the role of nicotine and its major metabolite cotinine is yet to be elucidated. Considering the growing amount of nicotine-containing aerosol use in recent years, the role of nicotine is a relevant public health concern. A number of recent studies and health education sites have focused on nicotine aerosol-induced adverse lung function, and neglected cardiovascular (CV) impairments and diseases. A critical review of the present scientific literature leads to the hypothesis that nicotine mediates the effects of cigarette smoke in the CV system by increasing MAPK signaling, inflammation, and oxidative stress through NADPH oxidase 1 (Nox1), to induce vascular smooth muscle cell (VSMC) senescence. The accumulation of senescent VSMCs in the lesion cap is detrimental as it increases the pathogenesis of atherosclerosis by promoting an unstable plaque phenotype. Therefore, nicotine, and most likely its metabolite cotinine, adversely influence atherosclerosis.

Nicotine increased VEGF and MMP2 levels in the rat eye and kidney

Chronic cigarette smoking affects many tissues negatively. Nicotine in tobacco has negative effects on tissues, kidneys, and eyes especially, where microcirculation is vitally important for the survival and functioning. It is known that appropriate vascular endothelial growth factor (VEGF) and (matrix metalloproteinase 2) MMP2 levels are required for suitable vascularity and enough microcirculation. The aim of this study was to investigate the effect of nicotine on VEGF and MMP2 levels in kidney and eyes, where microcirculation is very important for their function. The nicotine was given into drinking water, to male and female rats for 6 weeks. During the first 2 weeks, the nicotine concentration was 10 mg/L, then was given at a fixed dose of 20 mg/L until the end of the experiment. The VEGF and MMP2 levels were increased in kidney tissue of both genders as a result of given nicotine. MMP2 levels were also increased in the eye tissue for both genders similarly. However, VEGF levels increased in the eye tissue with nicotine in males, whereas it did not change in females. The use of nicotine made VEGF and MMP2 levels increase in kidney tissue in both genders of rats. This increase in VEGF was observed only in male eye tissue, not in females. According to our findings, it can be suggested that nicotine has negative effects on microvascular circulation by increasing VEGF and MMP2 levels. In addition, it should be pointed out that estrogen might have protective effects on female eye tissue. Further studies are necessary to understand the complex relationship between the role of nicotine and estrogen on eye and kidney tissues.

Disruption of retinal pigment epithelial cell properties under the exposure of cotinine

Cigarette smoking is a major risk factor for age-related macular degeneration (AMD), in which progressive retinal pigment epithelial (RPE) cell degeneration is a major pathological change. Nicotine is a major biologically active component in cigarette smoke. It is continuously catabolized into cotinine, which has longer half-life and higher concentration in tissue cells and fluids. Here we hypothesized that continuous exposure of cotinine has more potent effects on human RPE cell properties than nicotine. Human RPE cell line (ARPE-19) was treated continuously with 1-2 µM of nicotine and/or cotinine for 7 days. RPE cells treated with 2 μM cotinine and nicotine-cotinine mixture has lower MTT signals without significant changes in cell apoptosis or integrity. Moreover, RPE cell migration was retarded under cotinine treatments, but not nicotine. Both nicotine and cotinine treatments attenuated the phagocytotic activity of RPE cells. In addition, cotinine and nicotine-cotinine mixture suppressed VEGF and IL-8 expression and upregulated TIMP-2 expression. Expressions of autophagy genes were upregulated by the cotinine treatment, whereas expressions of epithelial-to-mesenchymal transition markers were downregulated. In conclusion, our study, for the first time, demonstrated that cotinine, rather than nicotine, affects the properties of RPE cells in vitro, which could explain the smoking-induced RPE pathology.

Potential of α7 nicotinic acetylcholine receptor PET imaging in atherosclerosis

Atherosclerotic events are usually acute and often strike otherwise asymptomatic patients. Although multiple clinical risk factors have been associated with atherosclerosis, as of yet no further individual prediction can be made as to who will suffer from its consequences based on biomarker analysis or traditional imaging methods like CT, MRI or angiography. Previously, non-invasive imaging with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET was shown to potentially fill this niche as it offers high sensitive detection of metabolic processes associated with inflammatory changes in atherosclerotic plaques. However, ¹⁸F-FDG PET imaging of arterial vessels suffers from non-specificity and has still to be proven to reliably identify vulnerable plaques, carrying a high risk of rupture. Therefore, it may be regarded only as a secondary marker for monitoring treatment effects and it does not offer alternative treatment options or direct insight in treatment mechanisms. In this review, an overview is given of the current status and the potential of PET imaging of inflammation and angiogenesis in atherosclerosis in general and special emphasis is given to imaging of α7 nicotinic acetylcholine receptors (α7 nAChRs). Due to the gaps that still exist in our understanding of atherogenesis and the limitations of the available PET tracers, the search continues for a more specific radioligand, able to differentiate between stable atherosclerosis and plaques prone to rupture. The potential role of the α7 nAChR as imaging marker for plaque vulnerability is explored. Today, strong evidence exists that nAChRs are involved in the atherosclerotic disease process. They are suggested to mediate the deleterious effects of the major tobacco component, nicotine, a nAChR agonist. Mainly based on in vitro data, α7 nAChR stimulation might increase plaque burden via increased neovascularization. However, in animal studies, α7 nAChR manipulation appears to reduce plaque size due to its inhibitory effects on inflammatory cells. Thus, reliable identification of α7 nAChRs by in vivo imaging is crucial to investigate the exact role of α7 nAChR in atherosclerosis before any therapeutic approach in the human setting can be justified. In this review, we discuss the first experience with α7 nAChR PET tracers and developmental considerations regarding the "optimal" PET tracer to image vascular nAChRs.

Nicotine facilitates VSMC dysfunction through a miR-200b/RhoGDIA/cytoskeleton module

Nicotine can induce the abnormal migration and proliferation of vascular smooth muscle cells (VSMCs). We have previously shown that cytoskeletal proteins and RhoGDIA, a negative regulator of the Rho GTPase pathway, are involved in the nicotine-induced dysfunction of VSMCs. Here, we found that nicotine can activate the Rho GTPase pathway and induce the synthesis of the cytoskeletal proteins in VSMCs through the activation of intracellular downstream signaling pathways, including targets such as MYPT1, PAK1 and PI3K/AKT. Upon nicotine treatment, the mRNA level of RhoGDIA is increased but protein level is decreased both in vitro and in vivo, which suggested a mechanism of post-translational regulation. By the dual luciferase reporter assay, we identified the microRNA-200b (miR-200b) as a modulator of the behavioural changes of VSMCs in response to nicotine through targeting RhoGDIA directly. Introducing miR-200b inhibitors into cultured VSMCs significantly attenuated cell proliferation and migration. Additionally, we found that hypomethylation in the CpG island shore region of miR-200b was responsible for the nicotine-induced miR-200b up-regulation in VSMCs. The study demonstrates that nicotine facilitates VSMC dysfunction through a miR-200b/RhoGDIA/cytoskeleton module through the hypomethylation of miR-200b promoter and suggests that epigenetic modifications may play an important role in the pathological progression.

PET Imaging of the Human Nicotinic Cholinergic Pathway in Atherosclerosis

During the past years, non-neuronal vascular nicotinic acetylcholine receptors (nAChRs) increasingly have gained interest in cardiovascular research, as they are known to mediate the deleterious effects of nicotine and nitrosamines, components of tobacco smoke, on the vasculature. Because smoking is a major risk factor for the development of atherosclerosis, it is obvious that understanding the pathophysiologic role of nAChRs in the atherosclerotic disease process, as well as in the development of new diagnostic and therapeutic nAChR-related options, has become more important. Accordingly, we briefly summarize the pathophysiologic role of vascular nAChRs in the atherosclerotic disease process. We also provide an overview of currently available nAChR positron emission tomography (PET) tracers and their performance in the noninvasive imaging of vascular nAChRs, as well as potential nAChR PET tracers that might be an option for vascular nAChR PET imaging in the future.

Bone marrow-derived cells in ocular neovascularization: contribution and mechanisms

Ocular neovascularization often leads to severe vision loss. The role of bone marrow-derived cells (BMCs) in the development of ocular neovascularization, and its significance, is increasingly being recognized. In this review, we discuss their contribution and the potential mechanisms that mediate the effect of BMCs on the progression of ocular neovascularization. The sequence of events by which BMCs participate in ocular neovascularization can be roughly divided into four phases, i.e., mobilization, migration, adhesion and differentiation. This process is delicately regulated and liable to be affected by multiple factors. Cytokines such as vascular endothelial growth factor, granulocyte colony-stimulating factor and erythropoietin are involved in the mobilization of BMCs. Studies have also demonstrated a key role of cytokines such as stromal cell-derived factor-1, tumor necrosis factor-α, as well as vascular endothelial growth factor, in regulating the migration of BMCs. The adhesion of BMCs is mainly regulated by vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and vascular endothelial cadherin. However, the mechanisms regulating the differentiation of BMCs are largely unknown at present. In addition, BMCs secrete cytokines that interact with the microenvironment of ocular neovascularization; their contribution to ocular neovascularization, especially choroidal neovascularization, can be aggravated by several risk factors. An extensive regulatory network is thought to modulate the role of BMCs in the development of ocular neovascularization. A comprehensive understanding of the involved mechanisms will help in the development of novel therapeutic strategies related to BMCs. In this review, we have limited the discussion to the recent progress in this field, especially the research conducted at our laboratory.

Nicotine induces mitochondrial fission through mitofusin degradation in human multipotent embryonic carcinoma cells

Nicotine is considered to contribute to the health risks associated with cigarette smoking. Nicotine exerts its cellular functions by acting on nicotinic acetylcholine receptors (nAChRs), and adversely affects normal embryonic development. However, nicotine toxicity has not been elucidated in human embryonic stage. In the present study, we examined the cytotoxic effects of nicotine in human multipotent embryonal carcinoma cell line NT2/D1. We found that exposure to 10 μM nicotine decreased intracellular ATP levels and inhibited proliferation of NT2/D1 cells. Because nicotine suppressed energy production, which is a critical mitochondrial function, we further assessed the effects of nicotine on mitochondrial dynamics. Staining with MitoTracker revealed that 10 μM nicotine induced mitochondrial fragmentation. The levels of the mitochondrial fusion proteins, mitofusins 1 and 2, were also reduced in cells exposed to nicotine. These nicotine effects were blocked by treatment with mecamylamine, a nonselective nAChR antagonist. These data suggest that nicotine degrades mitofusin in NT2/D1 cells and thus induces mitochondrial dysfunction and cell growth inhibition in a nAChR-dependent manner. Thus, mitochondrial function in embryonic cells could be used to assess the developmental toxicity of chemicals.

Nornicotine and Nicotine Induced Neovascularization via Increased VEGF/PEDF Ratio

PURPOSE

The purpose of the current study was to evaluate the influences of nornicotine and nicotine (NT) in cigarette smoke on the expression of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in retinal pigment epithelium cells and human umbilical vein endothelial cells (HUVECs). Furthermore, the angiogenic behaviors of endothelial cells under nornicotine and NT treatment were assessed by using in vitro methods.

METHODS

ARPE-19 cells and HUVECs were treated with different concentrations of either nornicotine or NT for different periods of time. The cell proliferative effect was investigated by using the method of MTT analysis. HUVEC migration and tube formation were assessed by using the scratch assay and Matrigel models. The expressions of VEGF and PEDF gene and protein in both types of cells were examined by real-time RT-PCR and Western blot.

RESULTS

There was no proliferation of ARPE-19 cells following treatment with various concentrations of nornicotine or NT. In contrast, nornicotine or NT significantly stimulated HUVEC proliferation, migration and tube formation. Nornicotine and NT upregulated the expression of VEGF but suppressed the expression of PEDF at both mRNA and protein levels in a dose- and time-dependent manner in ARPE-19 cells and HUVECs.

CONCLUSIONS

Our results demonstrate that nornicotine and NT promoted endothelial cellular proliferation, migration and tube formation of HUVECs in vitro. These effects might be partly due to simultaneous modulation of VEGF/PEDF signaling in ARPE-19 cells and HUVECs.

Predictive value of vascular endothelial growth factor polymorphisms on the risk of renal cell carcinomas: a case-control study

We conducted this case-control study to assess the role of vascular endothelial growth factor (VEGF) -2578C/A, +460T/C, +1612G/A, +936C/T, and -634G/C polymorphisms in the development of renal cell carcinoma (RCC), and analyzed the association of gene polymorphisms with demographic and clinical characteristics of RCC. This study included 412 consecutive primary RCC patients and 824 controls. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to detect VEGF -2578C/A, +460T/C, +1612G/A, +936C/T, and -634G/C polymorphisms. Compared with the control subjects, the RCC cancer cases were more likely to have a habit of cigarette smoking, and suffered from hypertension and diabetes. Conditional logistic regression analysis showed that individuals carrying the AA genotype of -2578C/A were more likely to greatly increase risk of RCC, and the CC genotype of +460T/C revealed a significant association with increased risk of RCC. The CA + AA genotype of -2578C/A had a significantly increased risk of RCC in ever cigarette smokers, and individuals who suffered from hypertension and diabetes. TC + CC genotype of +460T/C was significantly associated with the elevated risk of RCC in those suffered from hypertension and diabetes. Our study suggests that -2578C/A and +460T/C polymorphisms of VEGF modulate the risk of developing RCC in Chinese population.

Cigarette smoke adversely affects functions and cell membrane integrity in c-kit+ cardiac stem cells

Cigarette smoking is a major risk factor for numerous diseases including cardiovascular diseases. Exposure to cigarette smoke (CS) leads to increased cardiovascular risk, myocardial injury, and mortality. Stem cell therapy is one of the promising therapeutic options available to treat myocardial injuries. Understanding the impact of cigarette smoke extract (CSE) on stem cell function would be valuable in determining the risk passed on during transplant. In this study, the impact of CSE on cardiac stem cell (CSC) functions was investigated using c-kit+ rat cardiac stem cells as the experimental model. Here, we hypothesized that CSE attenuates CSC membrane integrity, causes cytotoxicity, and affects many CSC functions via multiple mechanisms including modulation of extracellular stress-regulated kinase (ERK) (44/42) signaling and oxidative stress. The effects of CSE on CSCs were examined in vitro. Based on a published method, CSE was prepared. CSE-induced ERK signaling was detected by western blotting. CSE-induced modulation of catalase activity was also measured. Functional modulations due to CSE were examined via several methods including Apostain, BrdU, and LDH assays. In agreement with the CSE-induced activation of ERK, CSE-induced reduction in viability, migration, and increase in both cytotoxicity and para-cellular permeability were observed in CSCs. These results suggest that CSE impaired CSC responses that contribute to decreased ability of CSC to respond to stress or injury leading to exacerbation of the damage. Our findings will contribute to the understanding of the discipline and might contribute to the development of stem cell therapy approaches in the future.

Nicotine effect on inflammatory and growth factor responses in murine cutaneous wound healing

The aim of the current study was to investigate the effect of nicotine in an experimental mouse model of cutaneous injury and healing responses, during the inflammatory phase of repair. Nicotine injection in full-thickness excisional skin wounds minimally affected inflammatory mediators like TNF, IL-6 and IL-12 while it induced a down-regulation in the expression of growth factors like VEGF, PDGF, TGF-β1 and TGF-β2, and the anti-inflammatory cytokine IL-10. Analysis of wound closure rate indicated no significant differences between nicotine and saline injected controls. In-vitro studies using bone marrow derived macrophages, resident peritoneal macrophages and RAW 264.7 macrophages, indicated that nicotine down-regulates TNF production. Moreover, nicotine was shown to down-regulate VEGF, PDGF and TGF-β1 in both bone marrow derived macrophages and RAW 264.7 cells. Using an NF-κB luciferase reporter RAW 264.7 cell line, we show that nicotine effects are minimally dependent on NF-κB inhibition. Moreover, nicotinic acetylcholine receptor (nAChR) subunit expression analyses indicated that while β2 nAChR subunit is expressed in mouse macrophages, α7 nAChR is not. In conclusion, while skin inflammatory parameters were not significantly affected by nicotine, a down-regulation of growth factor expression in both mouse skin and macrophages was observed. Reduced growth factor expression by nicotine might contribute, at least in part, to the overall detrimental effects of tobacco use in wound healing and skin diseases.

Four common vascular endothelial growth factor polymorphisms (-2578C>A, -460C>T, +936C>T, and +405G>C) in susceptibility to lung cancer: a meta-analysis

BACKGROUND AND OBJECTIVE

Vascular endothelial growth factor (VEGF) is one of the key initiators and regulators of angiogenesis and it plays a vital role in the onset and development of malignancy. The association between VEGF gene polymorphisms and lung cancer risk has been extensively studied in recent years, but currently available results remain controversial or ambiguous. The aim of this meta-analysis is to investigate the associations between four common VEGF polymorphisms (i.e., -2578C>A, -460C>T, +936C>T and +405C>G) and lung cancer risk.

METHODS

A comprehensive search was conducted to identify all eligible studies to estimate the association between VEGF polymorphisms and lung cancer risk. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of this association.

RESULTS

A total of 14 published case-control studies with 4,664 cases and 4,571 control subjects were identified. Our meta-analysis provides strong evidence that VEGF -2578C>A polymorphism is capable of increasing lung cancer susceptibility, especially among smokers and lung squamous cell carcinoma (SCC) patients. Additionally, for +936C>T polymorphism, increased lung cancer susceptibility was only observed among lung adenocarcinoma patients. In contrast, VEGF -460C>T polymorphism may be a protective factor among nonsmokers and SCC patients. Nevertheless, we did not find any association between +405C>G polymorphism and lung cancer risk, even when the groups were stratified by ethnicity, smoking status or histological type.

CONCLUSION

This meta-analysis recommends more investigations into the relationship between -2578C>A and -460C>T lung cancer risks. More detailed and well-designed studies should be conducted to identify the causal variants and the underlying mechanisms of the possible associations.

Silencing of periostin inhibits nicotine-mediated tumor cell growth and epithelial-mesenchymal transition in lung cancer cells

Nicotine has been found to induce the proliferation of lung cancer cells through tumor invasion and to confer resistance to apoptosis. Periostin is abnormally highly expressed in lung cancer and is correlated with angiogenesis, invasion and metastasis. Here, we investigated the roles of periostin in the lung cancer cell proliferation, drug resistance, invasion and epithelial-mesenchymal transition (EMT) induced by nicotine. The periostin gene was silenced using small interfering RNA (siRNA) in A549 non-small cell lung cancer (NSCLC) cells. The cells were transfected with control or periostin siRNA plasmids. Periostin mRNA was evaluated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Cell proliferation was detected using the MTT assay and cell apoptosis was detected by Annexin V-FITC and propidium iodide (PI) double staining. Tumor invasion was detected by the Boyden chamber invasion assay. Western blotting was performed to detect the expression of the EMT marker Snail. Our results revealed that stably periostin-silenced cells were acquired by G418 screening, and the periostin mRNA expression levels of which were decreased by nearly 80%. Periostin-silenced A549 cells exhibited reduced cell proliferation, elevated sensitivity to chemotherapy with cisplatin, decreased cell invasion and Snail expression (P<0.05). Nicotine upregulated the periostin protein levels in the A549 cells and this upregulation was not blocked by the generalized nicotinic acetylcholine receptor (nAChR) antagonist, hexamethonium. In conclusion, periostin is one of the targets regulated by nicotine in lung cancer cells and is involved in the cancer cell growth, drug resistance, invasion and EMT induced by nicotine.

Nicotinic acetylcholine receptor signaling in atherogenesis

Smoking is a major risk factor for the development of atherosclerosis, stroke and myocardial infarction. Cigarette smoke consists of a complex mixture of about 4000 compounds. Out of these, polycyclic hydrocarbons, tobacco-specific nitrosamines, oxidizing agents and carbon monoxide have been implicated in the development of atherosclerosis. Recent studies have shown that nicotine (the addictive component of cigarettes) binds to high affinity cell-surface receptors and accelerates the atherogenic process. These receptors are called nicotinic acetylcholine receptors (nAChRs) and are expressed ubiquitously in almost all cells existing in the blood vessels. The present review summarizes the pro-atherogenic effects of nAChR ligands such as nicotine and tobacco nitrosamines. The contribution of different nAChR subunits in plaque growth, progression and neovascularization are discussed in detail. The signaling pathways underlying the actions of the nAChRs ligands in blood vessels are also described. Finally, the feasibility of nAChR ligands as therapeutic targets for atherosclerosis is summarized. We believe that the information presented in this review is relevant for atherosclerosis patients who are active smokers, exposed to environmental tobacco smoke or use nicotine patches or gums for smoking cessation.

Nicotine enhances proliferation, migration, and radioresistance of human malignant glioma cells through EGFR activation

It has been suggested that continued tobacco use during radiation therapy contributes to maintenance of neoplastic growth despite treatment with radiation. Nicotine is a cigarette component that is an established risk factor for many diseases, neoplastic and otherwise. The hypothesis of this work is that nicotine promotes the proliferation, migration, and radioresistance of human malignant glioma cells. The effect of nicotine on cellular proliferation, migration, signaling, and radiation sensitivity were evaluated for malignant glioma U87 and GBM12 cells by use of the AlamarBlue, scratch healing, and clonogenic survival assays. Signal transduction was assessed by immunoblotting for activated EGFR, ERK, and AKT. At concentrations comparable with those found in chronic smokers, nicotine induced malignant glioma cell migration, growth, colony formation, and radioresistance. Nicotine increased phosphorylation of EGFR(tyr992), AKT(ser473), and ERK. These molecular effects were reduced by pharmacological inhibitors of EGFR, PI3K, and MEK. It was therefore concluded that nicotine stimulates the malignant behavior of glioma cells in vitro by activation of the EGFR and downstream AKT and ERK pathways.

Involvement of nicotinic acetylcholine receptor in the proliferation of mouse induced pluripotent stem cells

AIMS

As the clinical use of induced pluripotent stem (iPS) cells may have the potential to overcome current obstacles in stem cell-based therapy, the molecular mechanisms that regulate the proliferation of iPS cells are of great interest. However, to our knowledge, no previous studies have examined whether stimulation with nicotinic acetylcholine receptor (nAchR) enhances the growth of iPS cells. In the present study, we examined the involvement of nAchR in the proliferation of mouse iPS cells.

MAIN METHODS

We performed immunofluorescence staining to determine whether mouse iPS cells could express nAchRs. Mouse iPS cells were treated with nicotine for 24h under feeder-free conditions in the presence of leukemia inhibitory factor (LIF). The DNA synthesis was examined by the BrdU incorporation assay. Intracellular calcium levels were measured using Fluo-4-acetoxymethyl (a cell-permeable calcium indicator). In addition, we examined the involvement of the CaMKП pathway in nicotine-enhanced proliferation of mouse iPS cells.

KEY FINDINGS

The fluorescence images revealed that α(4)-nAchR and α(7)-nAchR are expressed on mouse iPS cells. Treatment of the cells with 300nM nicotine significantly increases DNA synthesis. This is significantly inhibited by pretreatment with antagonists of α(4)-nAchR and α(7)-nAchR or a CaMKП inhibitor. In addition, treatment with nicotine increases the intracellular Ca(2+) level dose-dependently in mouse iPS cells. Treatment with nicotine significantly enhances CaMKП phosphorylation.

SIGNIFICANCE

The present study indicates that stimulation of α(4)-nAchR and α(7)-nAchR may lead to a significant increase in the rate of mouse iPS cell proliferation through enhancement of the CaMKП signaling pathway.

Pathogenesis of abdominal aortic aneurysms: role of nicotine and nicotinic acetylcholine receptors

Inflammation, proteolysis, smooth muscle cell apoptosis, and angiogenesis have been implicated in the pathogenesis of abdominal aortic aneurysms (AAAs), although the well-defined initiating mechanism is not fully understood. Matrix metalloproteinases (MMPs) such as MMP-2 and -9 and other proteinases degrading elastin and extracellular matrix are the critical pathogenesis of AAAs. Among the risk factors of AAAs, cigarette smoking is an irrefutable one. Cigarette smoke is practically involved in various aspects of the AAA pathogenesis. Nicotine, a major alkaloid in tobacco leaves and a primary component in cigarette smoke, can stimulate the MMPs expression by vascular SMCs, endothelial cells, and inflammatory cells in vascular wall and induce angiogenesis in the aneurysmal tissues. However, for the inflammatory and apoptotic processes in the pathogenesis of AAAs, nicotine seems to be moving in just the opposite direction. Additionally, the effects of nicotine are probably dose dependent or associated with the exposure duration and may be partly exerted by its receptors—nicotinic acetylcholine receptors (nAChRs). In this paper, we will mainly discuss the pathogenesis of AAAs involving inflammation, proteolysis, smooth muscle cell apoptosis and angiogenesis, and the roles of nicotine and nAChRs.

Influence of nicotine on the biological activity of rabbit osteoblasts

OBJECTIVES

To assess the influence of nicotine on the proliferation and gene expression of osteogenic and angiogenic mediators of osteoblasts.

MATERIAL AND METHODS

Rabbit primary osteoblasts were exposed to various concentrations of nicotine (0.001, 0.1 and 10 μmol/l). The cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The gene expression of transforming growth factor (TGF)-β(1), bone morphogenetic protein (BMP)-2, platelet-derived growth factor (PDGF)-AA and vascular endothelial growth factor (VEGF) was evaluated using real-time reverse transcription - polymerase chain reaction.

RESULTS

The osteoblast proliferation was inhibited by nicotine at the concentration of 0.001-10 μM at 48 and 72 h of culture, but with no significant effect at 24 h. The expression of TGF-β(1), BMP-2, PDGF-AA and VEGF was inhibited by nicotine at the concentrations of 0.1 and 10 μM, but with no significant difference at the low concentration of 0.001 μM.

CONCLUSIONS

Nicotine suppresses osteoblast proliferation and inhibits the expression of some key osteogenic and angiogenic mediators in the in vitro experimental model. These inhibitory effects of nicotine on the osteoblast activity may reflect, to a certain degree, the overall detrimental effects of tobacco use on the survival rate of dental implants.

Cigarette smoke and α,β-unsaturated aldehydes elicit VEGF release through the p38 MAPK pathway in human airway smooth muscle cells and lung fibroblasts

BACKGROUND AND PURPOSE

Vascular endothelial growth factor (VEGF) is an angiogenic factor known to be elevated in the sputum of asymptomatic smokers as well as smokers with bronchitis type of chronic obstructive pulmonary disease. The aim of this study was to investigate whether acute exposure to cigarette smoke extract altered VEGF production in lung parenchymal cells.

EXPERIMENTAL APPROACH

We exposed human airway smooth muscle cells (ASMC), normal human lung fibroblasts (NHLF) and small airways epithelial cells (SAEC) to aqueous cigarette smoke extract (CSE) in order to investigate the effect of cigarette smoke on VEGF expression and release.

KEY RESULTS

Vascular endothelial growth factor release was elevated by sub-toxic concentrations of CSE in both ASMC and NHLF, but not in SAEC. CSE-evoked VEGF release was mimicked by its component acrolein at concentrations (10-100 µM) found in CSE, and prevented by the antioxidant and α,β-unsaturated aldehyde scavenger, N-acetylcysteine (NAC). Both CSE and acrolein (30 µM) induced VEGF mRNA expression in ASMC cultures, suggesting an effect at transcriptional level. Crotonaldehyde and 4-hydroxy-2-nonenal, an endogenous α,β-unsaturated aldehyde, stimulated VEGF release, as did H(2)O(2). CSE-evoked VEGF release was accompanied by rapid and lasting phosphorylation of p38 MAPK (mitogen-activated protein kinase), which was abolished by NAC and mimicked by acrolein. Both CSE- and acrolein-evoked VEGF release were blocked by selective inhibition of p38 MAPK signalling.

CONCLUSIONS AND IMPLICATIONS

α,β-Unsaturated aldehydes and possibly reactive oxygen species contained in cigarette smoke stimulate VEGF expression and release from pulmonary cells through p38 MAPK signalling.

Nicotine increases the VEGF/PEDF ratio in retinal pigment epithelium: a possible mechanism for CNV in passive smokers with AMD

PURPOSE

Cigarette smoking is the strongest environmental risk factor for wet age-related macular degeneration (AMD). Inappropriate expression of proangiogenic vascular endothelial growth factor (VEGF) and antiangiogenic pigment epithelium derived factor (PEDF) may cause choroidal neovascularization (CNV), a key event in wet AMD, resulting in vision loss. Nicotine (NT), a potent angiogenic agent abundant in second-hand smoke, may play a major role in the pathogenesis of wet AMD. The purpose of this study was to evaluate the expression of nicotinic acetylcholine receptors (nAchR) in retinal pigment epithelium (RPE) and determine the effects of NT on RPE-derived VEGF and PEDF expression in the context of passive smoking.

METHODS

Human RPE cells were treated with NT (10(-8) M), with or without the nAchR-nonspecific antagonist hexamethonium (HXM) (10(-5) M) for 72 hours. RPE sheets were microdissected from rats exposed to NT in drinking water (100 μg/mL), with or without HXM (40 mg/kg/d, intraperitoneally), for 72 hours. Cell death was determined by cell count and proliferation by Western blot for proliferating cell nuclear antigen (PCNA). nAchR expression was examined by real-time PCR and Western blot. ERK activation was evaluated by Western blot analysis. VEGF and PEDF expression was assessed by ELISA, Western blot, and real-time PCR.

RESULTS

Cultured RPE cells constitutively expressed the nAchR α3, α10, and β1 subunits, with β1 being the most prevalent. The nAchR α4, α5, α7, and β2 subunits were detected in RPE sheets from rats, among which α4 is the predominant subtype. NT, which did not result in either cell death or proliferation, induced β1 nAchR, upregulated VEGF, and downregulated PEDF expression through nAChR in ARPE-19 cells. Transcriptional activation of the nAchR α4 subunit and nAChR-mediated upregulation of VEGF and PEDF were observed in RPE from rats exposed to NT.

CONCLUSIONS

NT increased the VEGF-to-PEDF ratio in the RPE through nAchR in vitro and in vivo. This alteration in the ratio may play a key role in the progression to wet AMD in passive smokers.

Epigenetic effects and molecular mechanisms of tumorigenesis induced by cigarette smoke: an overview

Cigarette smoking is one of the major causes of carcinogenesis. Direct genotoxicity induced by cigarette smoke leads to initiation of carcinogenesis. Nongenotoxic (epigenetic) effects of cigarette smoke also act as modulators altering cellular functions. These two effects underlie the mechanisms of tumor promotion and progression. While there is no lack of general reviews on the genotoxic and carcinogenic potentials of cigarette smoke in lung carcinogenesis, updated review on the epigenetic effects and molecular mechanisms of cigarette smoke and carcinogenesis, not limited to lung, is lacking. We are presenting a comprehensive review of recent investigations on cigarette smoke, with special attentions to nicotine, NNK, and PAHs. The current understanding on their molecular mechanisms include (1) receptors, (2) cell cycle regulators, (3) signaling pathways, (4) apoptosis mediators, (5) angiogenic factors, and (6) invasive and metastasis mediators. This review highlighted the complexity biological responses to cigarette smoke components and their involvements in tumorigenesis.

Effect of cigarette smoke components on vascular smooth muscle cell migration toward platelet-derived growth factor BB

Cigarette smoking is one of the factors causing accumulation of vascular smooth muscle cells (VSMCs) in atherosclerotic plaques. Changes in cell migration toward platelet-derived growth factor BB were investigated using a Boyden chamber after 48-h preincubation of GBaSM-4 VSMCs with nicotine or nicotine-free cigarette smoke extract (CSE). A nicotine concentration of 0.1 µM maximally promoted cell migration; 0.1% CSE also promoted cell migration, while high CSE concentrations damaged GBaSM-4 cells. Fetal bovine serum (FBS) long-depletion induced decrease in migration of GBaSM-4 cells. Our results suggest that nicotine and some CSE components can induce GBaSM-4 cell migration.

Gestational nicotine treatment modulates cell death/survival-related pathways in the brains of adolescent female rats

Gestational exposure to nicotine affects brain development, leading to numerous behavioural and physiological deficits in the offspring during adolescence. To analyse the molecular mechanisms underlying these effects, a pathway-focused oligonucleotide microarray was used to determine gene expression profiles in five brain regions (i.e. amygdala, prefrontal cortex, nucleus accumbens, periventricular nucleus of the hypothalamus, and caudate putamen CPu) of adolescent rats that received nicotine or saline during gestation. Following appropriate statistical and Gene Set Enrichment Analyses, 24 cell death/survival-related pathways were found to be significantly modulated by gestational nicotine. On the basis of their biological functions, these pathways can be classified into three categories: growth factor, death receptor, and kinase cascade. We employed a quantitative real-time PCR array to verify the findings by measuring the expression of 29 genes involved in cell death/survival-related pathways. Together, our findings indicate that gestational nicotine exposure has significant effects on gene expression in cell death/survival-related pathways in the brains of adolescent offspring. Such effects appear to be brain region-specific and are realized through regulation of the expression of growth factors and receptors, caspases, kinases, and transcription factors. On the basis of these findings, we offer a hypothetical model to explain how gestational nicotine exposure may affect cell death and survival in the brains of adolescent offspring by regulating the balance between growth-factor and death-receptor pathways.

Effects of continued tobacco use during treatment of lung cancer

Lung carcinoma is one of the most common cancers diagnosed in the USA. A significant portion of these patients have a history of tobacco use and many are smoking at the time of diagnosis. Despite smoking cessation interventions, many patients continue to smoke even after their diagnosis. Those who are able to quit smoking after their diagnosis still have a high rate of relapse of smoking within the first year. Continued smoking has been found to have multiple negative consequences for these patients including increased toxicity from treatment and decreased effectiveness of therapy. Overall, patients who continue to smoke after their diagnosis have poorer outcomes than those patients who are successfully able to quit and abstain from smoking. Knowing this, physicians should encourage smoking cessation in this patient population. Future studies are needed to help define the best approach for encouraging smoking cessation, taking into account patient characteristics and the stress associated with the lung cancer diagnosis.

In vivo knockdown of nicotinic acetylcholine receptor α1 diminishes aortic atherosclerosis

OBJECTIVE

Nicotinic acetylcholine receptor α1 (nAChRα1) was recently identified as a functional cell receptor for urokinase, a potent atherogenic molecule. Here, we test the hypothesis that nAChRα1 plays a role in the pathogenesis of atherosclerosis.

METHODS

Apolipoprotein E-deficient mice were initially fed a Western diet for 8 wks. Plasmid DNA encoding scramble RNA (pscr) or siRNA (psir2) for nAChRα1 was injected into the mice (n=16) using an aortic hydrodynamic gene transfer protocol. Four mice from each group were sacrificed 7 days after the DNA injection to confirm the nAChRα1 gene silencing. The remaining mice continued on a Western diet for an additional 16 wks.

RESULTS

The nAChRα1 was up-regulated in aortic atherosclerotic lesions. A 78% knockdown of the nAChRα1 gene resulted in remarkably less severe aortic plaque growth and neovascularization at 16 wks (both P<0.05). In addition, significantly fewer macrophages (60% less) and myofibroblasts (80% less) presented in the atherosclerotic lesion of the psir2-treated mice. The protective mechanisms of the nAChRα1 knockdown may involve up-regulating interferon-γ/Y box protein-1 activity and down-regulating transforming growth factor-β expression.

CONCLUSIONS

The nAChRα1 gene plays a significant role at the artery wall, and reducing its expression decreases aortic plaque development.

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

Is nicotine a key player or spectator in the induction and progression of cardiovascular disorders?

Cigarette smoking is common in societies worldwide and a growing body of evidence suggests that chronic cigarette smoking may affect the structure and function of cardiovascular system. The chronic exposure to high levels of nicotine, a major component of cigarette smoking, has been observed to play a pathogenic role in the induction and progression of cardiovascular disorders including cardiomyopathy and peripheral vascular disease. Nicotine alters the function of vascular endothelium, initiates the adhesion cascade and stimulates the vascular inflammatory events to induce atherosclerosis and hypertension. Moreover, nicotine has been noted to induce direct coronary spasm and ischemia, which develop coronary artery disease and myocardial infarction. In addition, nicotine stimulates the excessive release of impulses from sinoatrial node that may account for the induction of cardiac arrhythmia. The present review critically discussed the possible detrimental role of chronic nicotine exposure in cardiac and vascular endothelial dysfunction. Moreover, the signaling mechanisms involved in the pathogenesis of nicotine exposure-induced cardiovascular dysfunction have been discussed. In addition, the pharmacological interventions to ameliorate chronic nicotine exposure-induced cardiovascular abnormalities have been delineated.

Nicotinic acetylcholine receptor signalling: roles in Alzheimer's disease and amyloid neuroprotection

Alzheimer's disease (AD), the major contributor to dementia in the elderly, involves accumulation in the brain of extracellular plaques containing the beta-amyloid protein (Abeta) and intracellular neurofibrillary tangles of hyperphosphorylated tau protein. AD is also characterized by a loss of neurons, particularly those expressing nicotinic acetylcholine receptors (nAChRs), thereby leading to a reduction in nAChR numbers. The Abeta(1-42) protein, which is toxic to neurons, is critical to the onset and progression of AD. The discovery of new drug therapies for AD is likely to be accelerated by an improved understanding of the mechanisms whereby Abeta causes neuronal death. We examine the evidence for a role in Abeta(1-42) toxicity of nAChRs; paradoxically, nAChRs can also protect neurons when activated by nicotinic ligands. Abeta peptides and nicotine differentially activate several intracellular signaling pathways, including the phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene homolog pathway, the extracellular signal-regulated kinase/mitogen-activated protein kinase, and JAK-2/STAT-3 pathways. These pathways control cell death or survival and the secretion of Abeta peptides. We propose that understanding the differential activation of these pathways by nicotine and/or Abeta(1-42) may offer the prospect of new routes to therapy for AD.

Angiogenic activity of nicotinic acetylcholine receptors: implications in tobacco-related vascular diseases

Cigarette smoking bears a strong etiological association with many neovascularization-related diseases like cancer, cardiovascular disease and macular degeneration. Although cigarette smoke is a complex mixture of many compounds, nicotine is the major active and addictive component of tobacco. Recent studies have shown that nicotine can enhance angiogenesis and arteriogenesis in several experimental systems and animal models. The pro-angiogenic activity of nicotine is mediated by nicotinic acetylcholine receptors, which have been found to be expressed on several types of cells in the vasculature like endothelial cells, smooth muscle cells and immune cells. The present review summarizes the pro-angiogenic activity of nicotine in neoplastic and non-neoplastic disease. The present article focuses on the role of nAChRs, particularly alpha7-nAChR in mediating the pro-angiogenic effects of nicotine. The expression patterns of nAChRs on various components of the vasculature are discussed. The complex signaling pathways underlying the angiogenic effect of nAChRs are described. The review also takes a look at the therapeutic potential of nAChR agonists and antagonists in angiogenesis-related diseases. More basic research as well as patient-oriented clinical studies is needed to firmly establish the clinical potential of nAChR ligands in angiogenesis-based therapies. Also the side effects of targeting nAChRs remain to be established in patients. The development of selective nAChR agonists and antagonists with improved specificity may represent novel therapeutic regimens in the treatment of angiogenesis-related diseases.

Nicotine induces cell proliferation, invasion and epithelial-mesenchymal transition in a variety of human cancer cell lines

Cigarette smoking is strongly correlated with the onset of nonsmall cell lung cancer (NSCLC). Nicotine, an active component of cigarettes, has been found to induce proliferation of lung cancer cell lines. In addition, nicotine can induce angiogenesis and confer resistance to apoptosis. All these events are mediated through the nicotinic acetylcholine receptors (nAChRs) on lung cancer cells. In this study, we demonstrate that nicotine can promote anchorage-independent growth in NSCLCs. In addition, nicotine also induces morphological changes characteristic of a migratory, invasive phenotype in NSCLCs on collagen gel. These morphological changes were similar to those induced by the promigratory growth factor VEGF. The proinvasive effects of nicotine were mediated by alpha7-nAChRs on NSCLCs. RT-PCR analysis showed that the alpha7-nAChRs were also expressed on human breast cancer and pancreatic cancer cell lines. Nicotine was found to promote proliferation and invasion in human breast cancer. The proinvasive effects of nicotine were mediated via a nAChR, Src and calcium-dependent signaling pathway in breast cancer cells. In a similar fashion, nicotine could also induce proliferation and invasion of Aspc1 pancreatic cancer cells. Most importantly, nicotine could induce changes in gene expression consistent with epithelial to mesenchymal transition (EMT), characterized by reduction of epithelial markers like E-cadherin expression, ZO-1 staining and concomitant increase in levels of mesenchymal proteins like vimentin and fibronectin in human breast and lung cancer cells. Therefore, it is probable that the ability of nicotine to induce invasion and EMT may contribute to the progression of breast and lung cancers.

Nicotine potentiates vascular endothelial growth factor expression in balloon-injured rabbit aortas

Both nicotine and vascular endothelial growth factor (VEGF) have been proposed to play an important role in the development and progression of atherosclerosis. In vitro and ex vivo studies have demonstrated that nicotine significantly stimulates VEGF expression in several cell types. This study examined the effects and the mechanisms of nicotine on the expression of VEGF in a rabbit model of balloon-injured aortas. Forty-eight male New Zealand white rabbits were randomly divided into sham, control, nicotine, and nicotine plus hexamethonium (nicotine-hex) groups. Balloon catheter denuding injury iliac artery was performed in control, nicotine, and nicotine-hex animals fed with a high-cholesterol diet beginning 2 weeks before operation. Twenty-four hours after surgery, nicotine (0.05 microg/kg) or nicotine (0.05 microg/kg) and hexamethonium (6 mg/kg) was administered daily by intramuscular injection for 3 weeks in nicotine and nicotine-hex groups, respectively. Sham and control rabbits received an identical volume of phosphate-buffered saline injection, but without nicotine or hexamethonium. VEGF protein expression and intimal cell proliferation in balloon-injured aortas were determined by enzyme-link immunosorbent assay, immunohistochemistry, and Western blot analysis. Six rabbits died during the experiment. The remaining 42 rabbits were included in the study. VEGF protein expression in nicotine group was significantly higher than that in control group (P < 0.01). VEGF positive staining was seen in vascular endothelial cells, vascular smooth muscle cells, and infiltrative inflammatory cells. The number of the proliferative cells in intima was also significantly higher in nicotine group than in control group (P < 0.01). Hexamethonium, a nonselective antagonist of nicotinic acetylcholine receptors (nAChRs), significantly inhibited nicotine-induced VEGF protein expression (P < 0.01). The present study shows that intramuscular administration of nicotine markedly potentiates the expression of VEGF protein in balloon-injured rabbit aortas, which appears to be mediated through nAChRs.

Alcohol and nicotine consumption exacerbates choroidal neovascularization by modulating the regulation of complement system

The objective of the present study was to investigate the effect of alcohol and nicotine consumption on the pathogenesis of choroidal neovascularization (CNV) in rats after laser-photocoagulation. Confocal microscopic analysis demonstrated an increase in CNV complex size in rats fed with alcohol (2.3-fold), nicotine (1.9-fold), and the combination of alcohol and nicotine (2.7-fold) compared with the control groups. Immunohistochemical analysis revealed that alcohol and nicotine consumption increased MAC deposition and VEGF expression in laser spots. Expression of CD59 by RT-PCR and Western blot was drastically reduced in the animals that were fed with alcohol, nicotine and alcohol and nicotine compared to those fed with water alone and this was associated with exacerbation of CNV.

Genetic polymorphisms of VEGF, interactions with cigarette smoking exposure and esophageal adenocarcinoma risk

Vascular endothelial growth factor (VEGF) is a major regulator of angiogenesis in the process of tumor growth and metastasis in esophageal adenocarcinoma (EA). Polymorphisms in the VEGF gene have been associated with altered VEGF expression and plasma VEGF levels. We hypothesized that polymorphisms of VEGF may contribute to EA risk. Functional polymorphisms in the VEGF gene (-460C/T, +405C/G and +936C/T) were determined in 308 patients with EA and 546 healthy controls. Logistic regression analysis was employed to assess the associations between genotypes, haplotypes of VEGF and EA risk, adjusting for multiple confounding factors. Compared with the +936CC genotype, the combined +936CT+TT genotypes were significantly associated with increased risk of developing EA, with adjusted odds ratio (OR) = 1.49 [95% confidence interval (CI), 1.05-2.12; P = 0.027]. The -460CT+CC were associated with increased risk of EA in smokers (adjusted OR = 1.57; 95% CI, 1.07-2.30; P = 0.021), whereas the -460CT/CC were associated with decreased risk of EA (adjusted OR = 0.47; 95% CI, 0.25-0.91; P = 0.025) in non-smokers. Compared with non-smokers with the +460TT, smokers with the +460CT+CC had significantly higher risk of EA (adjusted OR = 3.32; 95% CI, 1.56-7.10; P = 0.002). No overall or interacting association with EA risk was found for the +405C/G polymorphism. Haplotype CGT (-460C/+405G/+936T) was significantly associated with higher risk of EA (adjusted OR = 1.70; 95% CI, 1.04-2.73; P = 0.034). These results suggested that cigarette smoking modifies the association between VEGF polymorphisms and EA risk among Caucasians.

Recurrent exposure to nicotine differentiates human bronchial epithelial cells via epidermal growth factor receptor activation

Cigarette smoking is the major preventable cause of lung cancer in developed countries. Nicotine (3-(1-methyl-2-pyrrolidinyl)-pyridine) is one of the major alkaloids present in tobacco. Besides its addictive properties, its effects have been described in panoply of cell types. In fact, recent studies have shown that nicotine behaves as a tumor promoter in transformed epithelial cells. This research focuses on the effects of acute repetitive nicotine exposure on normal human bronchial epithelial cells (NHBE cells). Here we show that treatment of NHBE cells with recurrent doses of nicotine up to 500 muM triggered cell differentiation towards a neuronal-like phenotype: cells emitted filopodia and expressed neuronal markers such as neuronal cell adhesion molecule, neurofilament-M and the transcription factors neuronal N and Pax-3. We also demonstrate that nicotine treatment induced NF-kB translocation to the nucleus, phosphorylation of the epidermal growth factor receptor (EGFR), and accumulation of heparin binding-EGF in the extracellular medium. Moreover, addition of AG1478, an inhibitor of EGFR tyrosine phosphorylation, or cetuximab, a monoclonal antibody that precludes ligand binding to the same receptor, prevented cell differentiation by nicotine. Lastly, we show that differentiated cells increased their adhesion to the extracellular matrix and their protease activity. Given that several lung pathologies are strongly related to tobacco consumption, these results may help to better understand the damaging consequences of nicotine exposure.

Transforming growth factor-beta1 enhanced vascular endothelial growth factor synthesis in mesenchymal stem cells

Angiogenesis is essential for transplantation of mesenchymal stem cells (MSCs). Vascular endothelial growth factor (VEGF) is one of the most potent angiogenic factors identified to date. Elevated VEGF levels in MSCs correlate with the potential of MSCs transplantation. As an indirect angiogenic agent, transforming growth factor-beta1 (TGF-beta1) plays a pivotal role in the regulation of vasculogenesis and angiogenesis. However, the effect of TGF-beta1 on VEGF synthesis in MSCs is still unknown. Besides, the intracellular signaling mechanism by which TGF-beta1 stimulates this process remains poorly understood. In this article, we demonstrated that exposure of MSCs to TGF-beta1 stimulated the synthesis of VEGF. Meanwhile, TGF-beta1 stimulated the phosphorylation of Akt and extracellular signal-regulated kinase 1/2 (ERK1/2). Moreover, Ly 294002, a specific inhibitor of phosphatidylinositol-3-kinase (PI3K)/Akt significantly attenuated the VEGF synthesis stimulated by TGF-beta1. Additionally, U0126, a specific inhibitor of ERK1/2, also significantly attenuated the TGF-beta1-stimulated VEGF synthesis. These results indicated that TGF-beta1 enhanced VEGF synthesis in MSCs, and the Akt and ERK1/2 activation were involved in this process.

NF1 regulates a Ras-dependent vascular smooth muscle proliferative injury response

BACKGROUND

Neurofibromatosis type I (NF1) is a common autosomal dominant disorder with a broad array of clinical manifestations, including benign and malignant tumors, osseous dysplasias, and characteristic cutaneous findings. In addition, NF1 patients have an increased incidence of cardiovascular diseases, including obstructive vascular disorders. In animal models, endothelial expression of the disease gene, NF1, is critical for normal heart development. However, the pathogeneses of the more common vascular disorders are not well characterized.

METHODS AND RESULTS

To examine the role of NF1 in vascular smooth muscle, we generated mice with homozygous loss of the murine homolog Nf1 in smooth muscle (Nf1smKO). These mice develop and breed normally. However, in response to vascular injury, they display a marked intimal hyperproliferation and abnormal activation of mitogen-activated protein kinase, a downstream effector of Ras. Vascular smooth muscle cells cultured from these mice also display enhanced proliferation and mitogen-activated protein kinase activity. Smooth muscle expression of the NF1 Ras-regulatory domain (GTPase activating protein-related domain) rescues intimal hyperplasia in Nf1smKO mice and normalizes vascular smooth muscle cell Ras effector activity and proliferation in vitro, similar to blockade of downstream effectors of Ras.

CONCLUSIONS

In this in vivo model of NF1 obstructive vascular disease, we have shown that Nf1 regulation of Ras plays a critical role in vascular smooth muscle proliferation after injury. These results suggest opportunities for targeted therapeutics in the prevention and treatment of NF1-related vascular disease and in the treatment of neointimal proliferation in other settings.