Multiple roles of nicotine on cell proliferation and inhibition of apoptosis: implications on lung carcinogenesis

Synthesis and Structure of Novel Phenothiazine Derivatives, and Compound Prioritization via In Silico Target Search and Screening for Cytotoxic and Cholinesterase Modulatory Activities in Liver Cancer Cells and In Vivo in Zebrafish

Phenothiazines (PTZ) are antipsychotics known to modulate a variety of neurotransmitter activities that include dopaminergic and cholinergic signaling and have been identified as potential anticancer agents in vitro. However, it is important to also test whether a highly cytotoxic, repurposed, or novel PTZ has low toxicity and neuromodulatory activity in vivo using vertebrate model organisms, such as zebrafish. In this study, we synthesized novel phenothiazines and screened them in vitro in liver cancer and in vivo in zebrafish embryos/larvae. The syntheses of several intermediate PTZ 10-yl acyl chlorides were followed by elemental analysis and determination of 1H NMR and 13C NMR mass (ESI+) spectra of a large number of novel PTZ 10-carboxamides. Cytotoxicities of 28 PTZ derivatives (1-28) screened against Hep3B and SkHep1 liver cancer cell lines revealed five intermediate and five novel leads along with trifluoperazine (TFP), prochlorperazine (PCP), and perphenazine, which are relatively more cytotoxic than the basic PTZ core. Overall, the derivatives were more cytotoxic to Hep3B than SkHep1 cells. Moreover, in silico target screening identified cholinesterases as some of the commonest targets of the screened phenothiazines. Interestingly, molecular docking studies with acetylcholinesterase (AChE) and butyrylcholinesterase proteins showed that the most cytotoxic compounds 1, 3, PCP, and TFP behaved similar to Huprin W in their amino acid interactions with the AChE protein. The highly cytotoxic intermediate PTZ derivative 1 exhibited a relatively lower toxicity profile than those of 2 and 3 during the zebrafish development. It also modulated in vivo the cholinesterase activity in a dose-dependent manner while significantly increasing the total cholinesterase activity and/or ACHE mRNA levels, independent of the liver cancer cell type. Our screen also identified novel phenothiazines, i.e., 8 and 10, with significant cytotoxic and cholinesterase modulatory effects in liver cancer cells; yet both compounds had low levels of toxicity in zebrafish. Moreover, they modulated the cholinesterase activity or expression of ACHE in a cancer cell line-specific manner, and compound 10 significantly inhibited the cholinesterase activity in zebrafish. Accordingly, using a successful combination of in silico, in vitro, and in vivo approaches, we identified several lead anticancer and cholinesterase modulatory PTZ derivatives for future research.

Low levels of nicotine and cotinine but not benzo[a]pyrene induce human trophoblast cell proliferation

E-cigarettes use constitutes a source of thirdhand nicotine exposure. The increasing use of electronic cigarettes in homes and public places increases the risk of exposure of pregnant women to thirdhand nicotine. The effects of exposure of pregnant women to very low levels of nicotine have not been studied in humans but detrimental in experimental animals. The objective of this study is to investigate the effect of nanomolar concentrations of nicotine and its metabolite cotinine on the proliferation of JEG-3, a human trophoblast cell line. We also studied the proliferative effect of nanomolar concentrations of benzo[a]pyrene (B[a]P), a polycyclic hydrocarbon in tobacco smoke, for comparison. We treated JEG-3 cells in culture with nanomolar concentrations of nicotine, cotinine, and B[a]P. Their effect on cell proliferation was determined, relative to untreated cells, by MTT assay. Western blotting was used to assess the mitogenic signaling pathways affected by nicotine and cotinine. In contrast to the inhibitory effects reported with higher concentrations, we showed that nanomolar concentrations of nicotine and cotinine resulted in significant JEG-3 cell proliferation and a rapid but transient increase in levels of phosphorylated ERK and AKT, but not STAT3. Biphasic, non-monotonic effect on cell growth is characteristic of endocrine disruptive chemicals like nicotine. The mitogenic effects of nicotine and cotinine potentially contribute to increased villous epithelial thickness, seen in placentas of some smoking mothers. This increases the diffusion distance for oxygen and nutrients between mother and fetus, contributing to intrauterine growth restriction in infants of smoking mothers.

Why Female Smokers Have Poorer Long-Term Health Outcomes than Male Smokers: The Role of Cigarette Smoking During Pregnancy

Objectives: Women's health status is better than men but the opposite is true for female smokers who usually have poorer long-health outcomes than male smokers. The objectives of this study were to thoroughly reviewed and analyzed relevant literature and to propose a hypothesis that may explain this paradox phenomenon. Methods: We conducted a search of literature from three English databases (EMBASE, MEDLINE, and Google Scholar) from inception to 13 November 2023. A combination of key words and/or subject headings in English was applied, including relevant terms for cigarette smoking, sex/gender, pregnancy, and health indicators. We then performed analysis of the searched literature. Results: Based on this review/analysis of literature, we proposed a hypothesis that may explain this paradox phenomenon: female smokers have worse long-term health outcomes than male smokers because some of them smoke during pregnancy, and the adverse effects of cigarette smoking during pregnancy is much stronger than cigarette smoking during non-pregnancy periods. Conclusion: Approval of our pregnancy-amplification theory could provide additional evidence on the adverse effect on women's long-term health outcomes for cigarette smoking during pregnancy.

The role of α7-nAChR-mediated PI3K/AKT pathway in lung cancer induced by nicotine

Nicotine enters the environment mainly through human activity, as well as natural sources. This review article examines the increasing evidence implicating nicotine in the initiation and progression of lung cancer. Moreover, it primarily focuses on elucidating the activation mechanism of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, also known as AKT) signaling pathway, regulated by α7 subtype nicotinic acetylcholine receptor (α7-nAChR), in relation to the proliferation, invasion, and metastasis of lung cancer cells induced by nicotine, as well as nicotine-mediated anti-apoptotic effects. This process involves PI3K/AKT phosphorylated-B-cell lymphoma-2 (Bcl-2) family proteins, PI3K/AKT/mammalian target of rapamycin (mTOR), PI3K/AKT/nuclear factor-κB (NF-κB), hepatocyte growth factor (HGF)/cellular-mesenchymal epithelial transition factor (c-Met)-induced PI3K/AKT and PI3K/AKT activated-hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathways. In addition, we also deliberated on the related challenges and upcoming prospects within this field. These lay the foundation for further study on nicotine, lung tumorigenesis, and PI3K/AKT related molecular mechanisms. This work has the potential to significantly contribute to the treatment and prognosis of gastric cancer in smokers. Besides, the crucial significance of PI3K/AKT signaling pathway in multiple molecular pathways also suggests that its target antagonists may inhibit the development and progression of lung cancer, providing a possible new perspective for solving the problem of nicotine-promoted lung cancer. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the environmental assessment of tobacco and other nicotine-containing products.

A review on the effect of COX-2-mediated mechanisms on development and progression of gastric cancer induced by nicotine

Smoking is a documented risk factor for cancer, e.g., gastric cancer. Nicotine, the principal tobacco alkaloid, would exert its role of contribution to gastric cancer development and progression through nicotinic acetylcholine receptors (nAChRs) and β-adrenergic receptors (β-ARs), which then promote cancer cell proliferation, migration and invasion. As a key isoenzyme in conversion of arachidonic acid to prostaglandins, cyclooxygenase-2 (COX-2) has been demonstrated to have a wide range of effects in carcinogenesis and tumor development. At present, many studies have reported the effect of nicotine on gastric cancer by binding to nAChR, as well as indirectly stimulating β-AR to mediate COX-2-related pathways. This review summarizes these studies, and also proposes more potential COX-2-mediated mechanisms. These events might contribute to the growth and progression of gastric cancer exposed to nicotine through tobacco smoke or cigarette substitutes. Also, this review article has therefore the potential not only to make a significant contribution to the treatment and prognosis of gastric cancer for smokers but also to the clinical application of COX-2 antagonists. In addition, this work also discusses the considerable challenges of this field with special reference to the future perspective of COX-2-mediated mechanisms in development and progression of gastric cancer induced by nicotine.

Dexpanthenol exhibits antiapoptotic and anti-inflammatory effects against nicotine-induced liver damage by modulating Bax/Bcl-xL, Caspase-3/9, and Akt/NF-κB pathways

Chronic tobacco use can lead to liver damage and inflammation due to the accumulation of various toxins in the body. This study aimed to investigate the correlation between the molecular mechanisms of nicotine-induced liver injury, the caspase cascade, and the Akt/NF-κB signaling pathway, as well as the protective effects of dexpanthenol (DEX). Male rats were subjected to intraperitoneal injections of nicotine at a concentration of 0.5 mg/kg/day and/or DEX at a concentration of 500 mg/kg/day for 8 weeks. After the treatment period, liver function tests were conducted on serum samples, and tissue samples were analyzed for protein levels of Akt, NF-κB, Bax, Bcl-xL, Caspase-3, and Caspase-9, along with histopathological changes. Additionally, assessments of oxidative stress markers and proinflammatory cytokines were carried out. Nicotine administration led to elevated levels of IL-6, IL-1β, MDA, TOS, and oxidative stress index, accompanied by decreased TAS levels. Moreover, nicotine exposure reduced the p-Akt/Akt ratio, increased NF-κB, Bax, Caspase-3, and Caspase-9 protein levels, and decreased the antiapoptotic protein Bcl-xL levels. DEX treatment significantly mitigated these effects, restoring the parameters to levels comparable to those of the control group. Nicotine-induced liver injury resulted in oxidative stress, inflammation, and apoptosis, mediated by Bax/Bcl-xL, Caspase-3, Caspase-9, and Akt/NF-κB pathways. Conversely, DEX effectively attenuated nicotine-induced liver injury by modulating apoptosis through NF-κB, Caspase-3, Caspase-9, Bax inhibition, and Bcl-xL activation.

Terahertz label-free detection of nicotine-induced neural cell changes and the underlying mechanisms

Nicotine exposure can lead to neurological impairments and brain tumors, and a label-free and nondestructive detection technique is urgently required by the scientific community to assess the effects of nicotine on neural cells. Herein, a terahertz (THz) time-domain attenuated total reflection (TD-ATR) spectroscopy approach is reported, by which the effects of nicotine on normal and cancerous neural cells, i.e., HEB and U87 cells, are successfully investigated in a label/stain-free and nondestructive manner. The obtained THz absorption coefficients of HEB cells exposed to low-dose nicotine and high-dose nicotine are smaller and larger, respectively, than the untreated cells. In contrast, the THz absorption coefficients of U87 cells treated by nicotine are always smaller than the untreated cells. The THz absorption coefficients can be well related to the proliferation properties (cell number and compositional changes) and morphological changes of neural cells, by which different types of neural cells are differentiated and the viabilities of neural cells treated by nicotine are reliably assessed. Collectively, this work sheds new insights on the effects of nicotine on neural cells, and provides a useful tool (THz TD-ATR spectroscopy) for the study of chemical-cell interactions.

Nicotine: From Discovery to Biological Effects

Nicotine, the primary psychoactive agent in tobacco leaves, has led to the widespread use of tobacco, with over one billion smokers globally. This article provides a historical overview of tobacco and discusses tobacco dependence, as well as the biological effects induced by nicotine on mammalian cells. Nicotine induces various biological effects, such as neoangiogenesis, cell division, and proliferation, and it affects neural and non-neural cells through specific pathways downstream of nicotinic receptors (nAChRs). Specific effects mediated by α7 nAChRs are highlighted. Nicotine is highly addictive and hazardous. Public health initiatives should prioritize combating smoking and its associated risks. Understanding nicotine's complex biological effects is essential for comprehensive research and informed health policies. While potential links between nicotine and COVID-19 severity warrant further investigation, smoking remains a significant cause of morbidity and mortality globally. Effective public health strategies are vital to promote healthier lifestyles.

α7nAChR activation in AT2 cells promotes alveolar regeneration through WNT7B signaling in acute lung injury

Reducing inflammatory damage and improving alveolar epithelium regeneration are two key approaches to promoting lung repair in acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Stimulation of cholinergic α7 nicotinic acetylcholine receptor (α7nAChR, coded by Chrna7) signaling could dampen lung inflammatory injury. However, whether activation of α7nAChR in alveolar type II (AT2) cells promotes alveolar epithelial injury repair and underlying mechanisms is elusive. Here, we found that α7nAChR was expressed on AT2 cells and was upregulated in response to LPS-induced ALI. Meanwhile, deletion of Chrna7 in AT2 cells impeded lung repair process and worsened lung inflammation in ALI. Using in vivo AT2 lineage-labeled mice and ex vivo AT2 cell-derived alveolar organoids, we demonstrated that activation of α7nAChR expressed on AT2 cells improved alveolar regeneration by promoting AT2 cells to proliferate and subsequently differentiate toward alveolar type I cells. Then, we screened out the WNT7B signaling pathway by the RNA-Seq analysis of in vivo AT2 lineage-labeled cells and further confirmed its indispensability for α7nAChR activation-mediated alveolar epithelial proliferation and differentiation. Thus, we have identified a potentially unrecognized pathway in which cholinergic α7nAChR signaling determines alveolar regeneration and repair, which might provide us a novel therapeutic target for combating ALI.

Molluscicidal activity of Nicotiana tabacum extracts on the invasive snail Pomacea canaliculata

Botanical molluscicides for controlling the invasive snail Pomacea canaliculata have attracted worldwide attention because of their cost and environmental friendliness. Aqueous extracts from discarded tobacco leaf (Nicotiana tobacum) were evaluated for molluscicidal activity against different-sized P. canaliculata under laboratory conditions. The results showed that over 90% of the snails died in 1 g/L tobacco extract within 4 days, and the survival of P. canaliculata was inversely proportional to the snail size, tobacco extract concentration and length of exposure time. Adult males were more susceptible to tobacco extract than females. The snails had few chances to feed or mate in 0.5 g/L tobacco extract, and reproduction was greatly limited in 0.2 g/L. The growth of juvenile snails was inhibited in 0.2 g/L tobacco extract, but adults were unaffected. The antioxidant capacity of P. canaliculata in response to tobacco extract can be size- and sex-dependent, and the activities of superoxide dismutase, catalase, and acetylcholinesterase and the contents of glutathione and malondialdehyde were increased in adult males. These results suggest that discarded tobacco leaves can be useful as a molluscicide for controlling the invasive snail P. canaliculata based on its effects on survival, behaviour, food intake, growth performance and antioxidant capacity.

Nicotine activates HIF-1α and regulates acid extruders through the nicotinic acetylcholine receptor to promote the Warburg effect in non-small cell lung cancer cells

Cigarette smoking is the greatest risk factor for lung cancer, accounting for approximately 90% of all lung cancer-related deaths. Moreover, nicotine is associated with lung cancer onset and progression. Hypoxia-inducible factor 1α (HIF-1α) is involved in the metabolic reprogramming of cancer cells and accelerates cancer progression via regulation of pH and acid-base homeostasis. Previous studies have reported that nicotine upregulates HIF-1α expression. Therefore, we hypothesized that nicotine-mediated activation of HIF-1α regulates metabolic reprogramming and pH homeostasis in non-small cell lung cancer A549 cells and could potentially play a role in the progression of lung cancer. We examined the effects of nicotine on metabolic reprogramming and intracellular pH (pH_i) homeostasis, which are critical for cancer progression. A549 cells were exposed to nicotine in the absence and presence of the nicotinic acetylcholine receptor antagonist, mecamylamine (MEC). We then analyzed glycolytic stress and the activity and expression of acid-extruder proteins, including the Na⁺-H⁺ exchanger 1 (NHE1) and monocarboxylate cotransporters 1 & 4 (MCT1 and MCT4, respectively). Nicotine promoted the Warburg effect, which is associated with accelerated migration of A549 cells through the activation of nicotinic acetylcholine receptors. Furthermore, nicotine upregulated the activities and expression of acid-extruder proteins, namely NHE1 and MCT4, and facilitated glycolysis. To the best of our knowledge, this is the first study to demonstrate that nicotine plays a pivotal regulatory role in metabolic reprogramming as well as regulation of pH_i homeostasis in A549 cells via activation of nicotinic acetylcholine receptors and can therefore aggravate lung cancer progression.

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.

Insight into the Role of Psychological Factors in Oral Mucosa Diseases

With the development of psychology and medicine, more and more diseases have found their psychological origins and associations, especially ulceration and other mucosal injuries, within the digestive system. However, the association of psychological factors with lesions of the oral mucosa, including oral squamous cell carcinoma (OSCC), burning mouth syndrome (BMS), and recurrent aphthous stomatitis (RAS), have not been fully characterized. In this review, after introducing the association between psychological and nervous factors and diseases, we provide detailed descriptions of the psychology and nerve fibers involved in the pathology of OSCC, BMS, and RAS, pointing out the underlying mechanisms and suggesting the clinical indications.

Neurological repercussions of neonatal nicotine exposure: A review

Smoking during pregnancy is hazardous to both the mother and the foetus, according to a substantial amount of recorded data. Exposure to nicotine and other compounds in cigarette smoke increases the risk of sudden infant death syndrome (SIDS) by two to five times during pregnancy. Serotonergic abnormalities have been discovered in SIDS infants in the zone of the medulla oblongata, which is known to control cardio-respiratory function. SIDS establishes a connection between depression, learning difficulties and behavioural disorders. Prenatal nicotine intake during the second trimester affects the dopaminergic neurological system, making the foetal brain more susceptible to nicotine and developing ADHD symptoms not just in a foetus but in adolescents also. Prenatal nicotine exposure alters the neurological route of neurotransmitters, acetylcholine and dopamine. Nicotine enhances neuronal activity in adults but desensitizes these processes in babies and young children exposed prenatally. The impact of a neurotoxin like nicotine is determined by the amount and duration of exposure. Continued exposure throughout pregnancy will influence a wide range of activities in the neurodevelopment, whereas exposure confined to a single stage of pregnancy may only affect the processes that are forming at that stage. To decrease the effect of nicotine on neonates due to maternal smoking strategies like nicotine replacement therapy (NRT), folic acid treatment and other behavioural treatments have been studied. Hence, this review focuses on the impact of exposure to nicotine on neonates, which results in various neurological consequences and smoking cessation therapies.

Nicotine-related misperceptions among faculty and students at a Midwestern dental school

PURPOSE/OBJECTIVES

To determine the perceptions about the ill-effects of nicotine in students and faculty at a Midwestern dental school. This information will help inform the school and improve teaching on this subject during a time when electronic nicotine delivery systems are increasingly popular.

METHODS

An online survey of dental students and faculty of a Midwestern dental school was deployed in November, 2020 to determine their level of misperception about the ill effects of nicotine. An online Qualtrics survey was administered to approximately 212 predoctoral students at a dental institution and approximately 100 part- and full-time faculty at the same school.

RESULTS

The response rate for faculty was 55.1% and that for students was 37.5%. The majority of faculty and students "agreed" or "strongly agreed" that nicotine causes cancer, birth defects, cardiovascular disease, oral inflammation, and Chronic Obstructive Pulmonary Disease.

CONCLUSIONS

Dental school faculty and students linked the risks of smoking tobacco to nicotine. Based on the results of this study, we feel our institution's curriculum should consider including information specific to nicotine in addition to tobacco in general.

The relationship between CHRNA5/A3/B4 gene cluster polymorphisms and lung cancer risk: An updated meta-analysis and systematic review

BACKGROUND

Genetic polymorphisms in the 15q25 region have been associated with the risk of lung cancer (LC). However, studies have yielded conflicting results.

METHODS

Searches were conducted in databases, including PubMed, EMbase, Web of Science, CNKI, and Wanfang, for case-control studies up to August 1, 2019. After retrieving eligible studies and data extraction, we calculated pooled odds ratios with 95% confidence intervals. In the meta-analysis, we included 32 publications with a total of 52,795 patients with LC and 97,493 control cases to evaluate the polymorphisms in the CHRNA5/A3/B4 gene cluster in the 15q25 region.

RESULTS

Data of the meta-analysis showed a significantly increased risk of LC in the presence of genetic polymorphisms (rs1051730, rs16969968, rs8034191). In the smoking subgroup, the CHRNA3 rs1051730 polymorphism was found to contribute to LC risk using following 5 models: the allelic model, the homozygous model, the heterozygous model, the dominant model, and the recessive model. Thus, the rs1051730 polymorphism may modify LC susceptibility under the condition of smoking. Stratification studies for CHRNA5-rs8034191 showed that Caucasian groups with the wild-type genotype (C/C) may be susceptible to LC in all 5 models. No significant relationship between CHRNA3 rs6495309 or rs3743073 and LC susceptibility was found. However, Asians with the rs3743037 B-allele showed an obviously higher risk of LC susceptibility than the Caucasian population, observed via allelic, heterozygous, and dominant models.

CONCLUSIONS

The 3 polymorphisms of rs1051730, rs16969968 and rs8034191 in the CHRNA5/A3/B4 gene cluster in the 15q25 region were associated with LC risk, which might be influenced by ethnicity and smoking status.

Nicotine Changes Airway Epithelial Phenotype and May Increase the SARS-COV-2 Infection Severity

(1) Background: Nicotine is implicated in the SARS-COV-2 infection through activation of the α7-nAChR and over-expression of ACE2. Our objective was to clarify the role of nicotine in SARS-CoV-2 infection exploring its molecular and cellular activity. (2) Methods: HBEpC or si-mRNA-α7-HBEpC were treated for 1 h, 48 h or continuously with 10-7 M nicotine, a concentration mimicking human exposure to a cigarette. Cell viability and proliferation were evaluated by trypan blue dye exclusion and cell counting, migration by cell migration assay, senescence by SA-β-Gal activity, and anchorage-independent growth by cloning in soft agar. Expression of Ki67, p53/phospho-p53, VEGF, EGFR/pEGFR, phospho-p38, intracellular Ca2+, ATP and EMT were evaluated by ELISA and/or Western blotting. (3) Results: nicotine induced through α7-nAChR (i) increase in cell viability, (ii) cell proliferation, (iii) Ki67 over-expression, (iv) phospho-p38 up-regulation, (v) EGFR/pEGFR over-expression, (vi) increase in basal Ca2+ concentration, (vii) reduction of ATP production, (viii) decreased level of p53/phospho-p53, (ix) delayed senescence, (x) VEGF increase, (xi) EMT and consequent (xii) enhanced migration, and (xiii) ability to grow independently of the substrate. (4) Conclusions: Based on our results and on evidence showing that nicotine potentiates viral infection, it is likely that nicotine is involved in SARS-CoV-2 infection and severity.

Functional Characterization of Cholinergic Receptors in Melanoma Cells

In the last two decades, the scientific community has come to terms with the importance of non-neural acetylcholine in light of its multiple biological and pathological functions within and outside the nervous system. Apart from its well-known physiological role both in the central and peripheral nervous systems, in the autonomic nervous system, and in the neuromuscular junction, the expression of the acetylcholine receptors has been detected in different peripheral organs. This evidence has contributed to highlight new roles for acetylcholine in various biological processes, (e.g., cell viability, proliferation, differentiation, migration, secretion). In addition, growing evidence in recent years has also demonstrated new roles for acetylcholine and its receptors in cancer, where they are involved in the modulation of cell proliferation, apoptosis, angiogenesis, and epithelial mesenchymal transition. In this review, we describe the functional characterization of acetylcholine receptors in different tumor types, placing attention on melanoma. The latest set of data accessible through literature, albeit limited, highlights how cholinergic receptors both of muscarinic and nicotinic type can play a relevant role in the migratory processes of melanoma cells, suggesting their possible involvement in invasion and metastasis.

Cancer potencies and margin of exposure used for comparative risk assessment of heated tobacco products and electronic cigarettes aerosols with cigarette smoke

Health risk associated with the use of combustible cigarettes is well characterized and numerous epidemiological studies have been published for many years. Since more than a decade, innovative non-combusted tobacco products have emerged like heated tobacco products (HTP) or electronic cigarettes (EC). Long-term effects of these new products on health remain, however, unknown and there is a need to characterize associated potential health risks. The time dedicated to epidemiological data generation (at least 20 to 40 years for cancer endpoint), though, is not compatible with innovative development. Surrogates need, therefore, to be developed. In this work, non-cancer and cancer risks were estimated in a range of HTP and commercial combustible cigarettes based upon their harmful and potentially harmful constituent yields in aerosols and smoke, respectively. It appears that mean lifetime cancer risk values were decreased by more than one order of magnitude when comparing HTPs and commercial cigarettes, and significantly higher margin of exposure for non-cancer risk was observed for HTPs when compared to commercial cigarettes. The same approach was applied to two commercial ECs. Similar results were also found for this category of products. Despite uncertainties related to the factors used for the calculations and methodological limitations, this approach is valuable to estimate health risks associated to the use of innovative products. Moreover, it acts as predictive tool in absence of long-term epidemiological data. Furthermore, both cancer and non-cancer risks estimated for HTPs and ECs highlight the potential of reduced risk for non-combusted products when compared to cigarette smoking.

The Constitutive Lack of α7 Nicotinic Receptor Leads to Metabolic Disorders in Mouse

Objective: Type 2 diabetes (T2D) occurs by deterioration in pancreatic β-cell function and/or progressive loss of pancreatic β-cell mass under the context of insulin resistance. α7 nicotinic acetylcholine receptor (nAChR) may contribute to insulin sensitivity but its role in the pathogenesis of T2D remains undefined. We investigated whether the systemic lack of α7 nAChR was sufficient to impair glucose homeostasis. Methods: We used an α7 nAChR knock-out (α7^−/−) mouse model fed a standard chow diet. The effects of the lack of α7 nAChR on islet mass, insulin secretion, glucose and insulin tolerance, body composition, and food behaviour were assessed in vivo and ex vivo experiments. Results: Young α7^−/− mice display a chronic mild high glycemia combined with an impaired glucose tolerance and a marked deficit in β-cell mass. In addition to these metabolic disorders, old mice developed adipose tissue inflammation, elevated plasma free fatty acid concentrations and presented glycolytic muscle insulin resistance in old mice. Finally, α7^−/− mice, fed a chow diet, exhibited a late-onset excessive gain in body weight through increased fat mass associated with higher food intake. Conclusion: Our work highlights the important role of α7 nAChR in glucose homeostasis. The constitutive lack of α7 nAChR suggests a novel pathway influencing the pathogenesis of T2D.

Tobacco Smoking: Risk to Develop Addiction, Chronic Obstructive Pulmonary Disease, and Lung Cancer

BACKGROUND

The morbidity and mortality associated with tobacco smoking is well established. Nicotine is the addictive component of tobacco. Nicotine, through the non-neuronal α7nicotinic receptor, induces cell proliferation, neo-angiogenesis, epithelial to mesenchymal transition, and inhibits drug-induced apoptosis.

OBJECTIVE

To understand the genetic, molecular and cellular biology of addiction, chronic obstructive pulmonary disease and lung cancer.

METHODS

The search for papers to be included in the review was performed during the months of July- September 2018 in the following databases: PubMed (http://www.ncbi.nlm.nih.gov), Scopus (http://www.scopus.com), EMBASE (http://www.elsevier.com/online-tools/embase), and ISI Web of Knowledge (http://apps.webofknowledge.com/). The following searching terms: "nicotine", "nicotinic receptor", and "addiction" or "COPD" or "lung cancer" were used. Patents were retrieved in clinicaltrials.gov (https://clinicaltrials.gov/). All papers written in English were evaluated. The reference list of retrieved articles was also reviewed to identify other eligible studies that were not indexed by the above-mentioned databases. New experimental data on the ability of nicotine to promote transformation of human bronchial epithelial cells, exposed for one hour to Benzo[a]pyrene-7,8-diol-9-10-epoxide, are reported.

RESULTS

Nicotinic receptors variants and nicotinic receptors upregulation are involved in addiction, chronic obstructive pulmonary disease and/or lung cancer. Nicotine through α7nicotinic receptor upregulation induces complete bronchial epithelial cells transformation.

CONCLUSION

Genetic studies highlight the involvement of nicotinic receptors variants in addiction, chronic obstructive pulmonary disease and/or lung cancer. A future important step will be to translate these genetic findings to clinical practice. Interventions able to help smoking cessation in nicotine dependence subjects, under patent, are reported.

Alpha7 nicotinic acetylcholine receptors in lung inflammation and carcinogenesis: Friends or foes?

The lung tissue expresses the cholinergic system including nicotinic acetylcholine receptors (nAChRs) which included in many physiologic and pathologic processes. Mounting evidence revealed that these receptors have important roles in lung carcinogenesis via modulating either stimulatory or inhibitory signaling pathways. Among different members of nicotinic receptors family, alpha7-subtype of nAChR (α7nAChR) is a critical mediator involved in both inflammatory responses and cancers. Several studies have shown that this receptor is the most powerful regulator of responses that stimulate lung cancer processes such as proliferation, angiogenesis, metastasis, and inhibition of apoptosis. Moreover, aside from its roles in the regulation of cancer pathways, there is growing evidence indicating that α7nAChR has profound impacts on lung inflammation through the cholinergic anti-inflammatory pathway. Regarding such diverse effects as well as the critical roles of nicotine as an activator of α7nAChR on lung cancer pathogenesis, its modulation has emerged as a promising target for drug developments. In this review, we aim to highlight the detrimental as well as the possible beneficial influences of α7nAChR downstream signaling cascades in the control of lung inflammation and cancer-associated properties. Consequently, by considering the significant global burden of lung cancer, delineating the complex influences of α7 receptors would be of great interest in designing novel anticancer and anti-inflammatory strategies for the patients suffering from lung cancer.

The α7 nicotinic receptor silent agonist R-47 prevents and reverses paclitaxel-induced peripheral neuropathy in mice without tolerance or altering nicotine reward and withdrawal

Various antitumor drugs, including paclitaxel, frequently cause chemotherapy-induced peripheral neuropathy (CIPN) that can be sustained even after therapy has been completed. The current work was designed to evaluate R-47, an α7 nAChR silent agonist, in our mouse model of CIPN. R-47 was administered to male C57BL/6J mice prior to and during paclitaxel treatment. Additionally, we tested if R-47 would alter nicotine's reward and withdrawal effects. The H460 and A549 non-small cell lung cancer (NSCLC) cell lines were exposed to R-47 for 24-72 h, and tumor-bearing NSG mice received R-47 prior to and during paclitaxel treatment. R-47 prevents and reverses paclitaxel-induced mechanical hypersensitivity in mice in an α7 nAChR-dependent manner. No tolerance develops following repeated administration of R-47, and the drug lacks intrinsic rewarding effects. Additionally, R-47 neither changes the rewarding effect of nicotine in the Conditioned Place Preference test nor enhances mecamylamine-precipitated withdrawal. Furthermore, R-47 prevents paclitaxel-mediated loss of intraepidermal nerve fibers and morphological alterations of microglia in the spinal cord. Moreover, R-47 does not increase NSCLC cell viability, colony formation, or proliferation, and does not interfere with paclitaxel-induced growth arrest, DNA fragmentation, or apoptosis. Most importantly, R-47 does not increase the growth of A549 tumors or interfere with the antitumor activity of paclitaxel in tumor-bearing mice. These studies suggest that R-47 could be a viable and efficacious approach for the prevention and treatment of CIPN that would not interfere with the antitumor activity of paclitaxel or promote lung tumor growth.

A review of the effects of tobacco smoking on cancer treatment: smoking cessation intervention should be integrated into the cancer care continuum

Background:

The adverse health effects associated with smoking tobacco have been well investigated, and its detrimental effects on cancer treatment outcomes, efficacy and quality of life (QOL) for cancer patients have also been well documented. Tobacco smoke contains many thousands of chemicals, including a plethora of carcinogens, and the exposure of human cells to these carcinogens, and their metabolic activation, is the main mechanism by which smoking-related cancer is initiated.

Materials and Methods:

This paper reports on a narrative review of recent studies in the field of effects of tobacco smoking on cancer treatment, including the effects of carcinogens in smoke on carcinogenesis, cell mutations and the immune system. The health effects of smokeless tobacco, effects of tobacco smoking on cancer treatment, and its impact on surgery, radiation therapy and chemotherapy are reported. The potential risks of second primary cancers or recurrence from tobacco use, the effects of second-hand smoking and cancer treatment, the impact of smoking on the QOL after cancer treatment and the need to integrate smoking cessation programs into the cancer care continuum are also reported.

Conclusions:

Tobacco use has a direct impact on cellular function by inhibiting apoptosis, stimulating proliferation and decreasing the efficacy of cancer treatment; therefore, quitting its use has the potential to improve treatment response rates and survival, as well as reduces the risk of developing second cancers and potentially improves the QOL after treatment. Smoking cessation is one of the most important interventions to prevent cancer and is also essential after the diagnosis of cancer to improve clinical outcomes. Due to the numerous benefits of smoking cessation, it should become a critical component of the cancer care continuum in all oncology programs – from prevention of cancer through diagnosis, treatment, survivorship and palliative care. Evidence-based smoking cessation intervention should be sustainably integrated into any comprehensive cancer program, and the information should be targeted to the specific benefits of cessation in cancer patients.

Nicotine Induces Resistance to Erlotinib Therapy in Non-Small-Cell Lung Cancer Cells Treated with Serum from Human Patients

Previously, we reported that nicotine reduces erlotinib sensitivity in a xenograft model of PC9, an epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI)-sensitive non-small-cell lung cancer cell line. The present study examined whether smoking induces erlotinib resistance in vitro. We assessed resistance to EGFR-TKIs by treating cancer cell lines with erlotinib, afatinib, or osimertinib, and serum collected from smokers within 30 min of smoking and that from a non-smoker as a control. We also assessed erlotinib resistance by treating PC9 cells exposed to serum from a smoker or a non-smoker, or serum from an erlotinib user. Treatment of the cancer cell lines with serum from smokers induced significant erlotinib resistance, compared with the control (p < 0.05). Furthermore, serum samples with a high concentration of cotinine (a nicotine exposure indicator) demonstrated stronger erlotinib resistance than those with low concentrations. Similar to the observations with erlotinib treatment of cell lines, the analysis of serum from erlotinib users revealed that smokers demonstrated significantly reduced sensitivity to erlotinib (p < 0.001). In conclusion, our present results support the hypothesis that smoking contributes to resistance to erlotinib therapy in non-small-cell lung cancer.

Nicotine exposure induces the proliferation of oral cancer cells through the α7 subunit of the nicotinic acetylcholine receptor

Oral cancer and smoking are closely related, because the oral cavity, which is the route of ingestion of tobacco smoke, is in direct contact with the oral mucosa. Nicotine, one of the components of tobacco, can diffuse rapidly to the central nervous system and is responsible for tobacco addiction. Nicotine is present in high concentrations in the bloodstream of smokers; while the addictive effects of this alkaloid have extensively been studied, its effect on tumorigenesis is not clear yet. Therefore, in this study, we examined the effect of nicotine on cell proliferation and the signaling pathways it activates. The human oral squamous cell carcinoma cell line HSC-2 was used as a model system. We demonstrated the correlation between nicotine and epidermal growth factor receptor (EGFR) signaling. Nicotine treatment induced HSC-2 cell proliferation and migration and the phosphorylation of EGFR. Furthermore, nicotine treatment activated the EGFR downstream effectors phosphatidylinositol-3 kinase/AKT and p44/42 mitogen-activated protein kinases (ERK), which, in turn, promoted cell proliferation. Overall, our study suggests that nicotine promotes cell growth and migration through epidermal growth factor (EGF) signaling and plays an important role in oral cancer progression.

Biomarkers of Exposure to Secondhand and Thirdhand Tobacco Smoke: Recent Advances and Future Perspectives

Smoking is the leading preventable disease worldwide and passive smoking is estimated to be the cause of about 1.0% of worldwide mortality. The determination of tobacco smoke biomarkers in human biological matrices is key to assess the health effects related to the exposure to environmental tobacco smoke. The biomonitoring of cotinine, the main nicotine metabolite, in human biofluids-including urine, serum or saliva-has been extensively used to assess this exposure. However, the simultaneous determination of cotinine together with other tobacco biomarkers and the selection of alternative biological matrices, such as hair, skin or exhaled breath, would enable a better characterization of the kind and extent of tobacco exposure. This review aims to perform a critical analysis of the up-to-date literature focused on the simultaneous determination of multiple tobacco smoke biomarkers studied in different biological matrices, due to the exposure to secondhand smoke (SHS) and thirdhand smoke (THS). Target biomarkers included both tobacco-specific biomarkers-nicotine and tobacco specific nitrosamine biomarkers-and tobacco-related biomarkers, such as those from polycyclic aromatic hydrocarbons, volatile organic compounds, metals and carbon monoxide. To conclude, we discuss the suitability of determining multiple biomarkers through several relevant examples of SHS and THS exposure.

The Influence of Nicotine on Lung Tumor Growth, Cancer Chemotherapy, and Chemotherapy-Induced Peripheral Neuropathy

Studies in animal models have suggested that nicotine, an agonist of nicotinic acetylcholine receptors, may have the potential to prevent and/or reverse the peripheral neuropathy induced by cancer chemotherapeutic drugs, such as paclitaxel and oxaliplatin. However, a large body of evidence suggests that nicotine may also stimulate lung tumor growth and/or interfere with the effectiveness of cancer chemotherapy. Whereas the reported proliferative effects of nicotine are highly variable, the antagonism of antitumor drug efficacy is more consistent, although this latter effect has been demonstrated primarily in cell culture studies. In contrast, in vitro and in vivo studies from our own laboratory indicate that nicotine fails to enhance the growth of nonsmall cell lung cancer cells or attenuate the effects of chemotherapy (paclitaxel). Given the inconsistencies in the literature, coupled with our own findings, the weight of evidence suggests that caution may be warranted in proposing to use nicotine to mitigate chemotherapy-induced peripheral neuropathy in cancer patients receiving chemotherapy. Conversely, clinical trials could be performed in patients who have completed therapy and are considered to be disease-free to determine whether nicotine, in the form of commercially available patches or gum, is effective in alleviating peripheral neuropathy symptoms.

Duration-dependent effects of nicotine exposure on growth and AKT activation in human kidney epithelial cells

Exposure to nicotine is known to cause adverse effects in many target organs including kidney. Epidemiological studies suggest that nicotine-induced kidney diseases are prevalent worldwide. However, the impact of duration of exposure on the nicotine-induced adverse effects in normal kidney cells and the underlying molecular mechanism is still unclear. Hence, the objective of this study was to evaluate both acute and long-term effects of nicotine in normal human kidney epithelial cells (HK-2). Cells were treated with 1 and 10 µM nicotine for acute and long-term duration. The result of cell viability showed that the acute exposure to 1 µM nicotine has no significant effect on growth. However, the 10 µM nicotine caused significant decrease in the growth of HK-2 cells. The long-term exposure resulted in significantly increased cell growth in both 1 and 10 µM nicotine-treated groups. Analysis of cell cycle and expression of marker genes related to proliferation and apoptosis further confirmed the effects of nicotine. Additionally, the analysis of growth signaling pathway revealed the decreased level of pAKT in cells with acute exposure whereas the increased level of pAKT in long-term nicotine-exposed cells. This suggests that nicotine, through modulating the AKT pathway, controls the duration-dependent effects on the growth of HK-2 cells. In summary, this is the first report showing long-duration exposure to nicotine causes increased proliferation of human kidney epithelial cells through activation of AKT pathway.

Assessing electronic cigarette emissions: linking physico-chemical properties to product brand, e-liquid flavoring additives, operational voltage and user puffing patterns

Users of electronic cigarettes (e-cigs) are exposed to particles and other gaseous pollutants. However, major knowledge gaps on the physico-chemical properties of such exposures and contradictory data in published literature prohibit health risk assessment. Here, the effects of product brand, type, e-liquid flavoring additives, operational voltage, and user puffing patterns on emissions were systematically assessed using a recently developed, versatile, e-cig exposure generation platform and state-of-the-art analytical methods. Parameters of interest in this systematic evaluation included two brands (A and B), three flavors (tobacco, menthol, and fruit), three types of e-cigs (disposable, pre-filled, and refillable tanks), two puffing protocols (4 and 2 s/puff), and four operational voltages (2.2-5.7 V). Particles were generated at a high number concentration (106-107 particles/cm3). The particle size distribution was bi-modal (∼200 nm and 1 µm). Furthermore, organic species (humectants propylene glycol and glycerin, nicotine) that were present in e-liquid and trace metals (potassium and sodium) that were present on e-cig heating coil were also released into the emission. In addition, combustion-related byproducts, such as benzene and toluene, were also detected in the range of 100-38,000 ppbv/puff. Parametric analyzes performed in this study show the importance of e-cig brand, type, flavor additives, user puffing pattern (duration and frequency), and voltage on physico-chemical properties of emissions. This observed influence is indicative of the complexity associated with the toxicological screening of emissions from e-cigs and needs to be taken into consideration.

E-Cigarettes and Smoking Cessation: A Primer for Oncology Clinicians

BACKGROUND

Electronic cigarettes 
(e-cigarettes) are a psychosocial phenomenon of the 21st century with serious implications to public and individual health. The significant increase of their popularity and use has raised concerns in the healthcare community regarding their potential benefits and harm, particularly their use as a smoking cessation methodology.

OBJECTIVES

Current knowledge is presented about e-cigarettes, including the clinical implications of their use, and associated controversies are analyzed. In addition, practice recommendations and communication guidance are provided.

METHODS

An integrative review was performed.

FINDINGS

The long-term effect of e-cigarettes on individual and public health is unknown. Evidence from short-term studies, although limited, shows that e-cigarette use is less harmful than smoking. However, the evidence does not support the use of e-cigarettes as a smoking cessation methodology. Such recommendation remains a judgment call for the clinician based on each individual case.

Tobacco nitrosamine NNK increases ALDH-positive cells via ROS-Wnt signaling pathway in A549 human lung cancer cells

Epidemiological studies suggest that lung cancer, which is a major cause of cancer death, has a critical association with cigarette smoking. Tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in cigarette smoke is a major risk factor for carcinogenesis. However, the mechanisms by which NNK promotes cancer development have not been fully elucidated. Growing evidence suggests that lung cancer originates from cancer stem cells (CSCs), which are a minor population of lung cancer cells. In the present study, we investigated the effects of NNK on the CSCs in A549 human lung cancer cells using flow cytometry with aldehyde dehydrogenase (ALDH), a functional marker of CSCs. We found that NNK increased the proportion of ALDH-positive cells in a dose-dependent manner. A Wnt inhibitor PNU74654 reduced NNK-induced expression levels of Wnt target gene Dkk1 and increase in ALDH-positive cells. We next examined the signaling pathway that mediates the NNK-induced increase in ALDH-positive cells via Wnt signaling. DCF assay revealed that NNK induced reactive oxygen species (ROS) production. The ROS scavenger N-acetylcysteine (NAC) inhibited the NNK-induced Wnt activation and increase in ALDH-positive cells. These data suggest that NNK-induced ROS activate the Wnt signaling pathway in A549 cells. These findings would provide new insights into the role of NNK in the lung CSCs.

β-Cryptoxanthin Reduced Lung Tumor Multiplicity and Inhibited Lung Cancer Cell Motility by Downregulating Nicotinic Acetylcholine Receptor α7 Signaling

Despite the consistent association between a higher intake of the provitamin A carotenoid β-cryptoxanthin (BCX) and a lower risk of lung cancer among smokers, potential mechanisms supporting BCX as a chemopreventive agent are needed. We first examined the effects of BCX on 4-[methyl nitrosamino]-1-[3-pyridyl]-1-butanone (NNK)-induced lung tumorigenesis in A/J mice. BCX supplementation was given daily to the mice starting 2 weeks prior to the injection of NNK and continued 16 weeks after NNK injection. BCX supplementation resulted in a dose-dependent increase of BCX concentration in both serum and lungs of the mice without a significant alteration of vitamin A (retinol and retinyl palmitate) concentration. BCX significantly reduced the multiplicity of the NNK-induced lung tumor by 52% to 63% compared with the NNK-treated mice without BCX supplementation. The protective effect of BCX in the lungs was associated with reductions of both mRNA and protein of the homopentameric neuronal nicotinic acetylcholine receptor α7 (α7-nAChR), which has been implicated in lung tumorigenesis. We then conducted an in vitro cell culture study and found that BCX treatment suppressed α7-nAChR expression and inhibited the migration and invasion of α7-nAChR-positive lung cancer cells but not in cells lacking α7-nAChR. The activities of BCX were significantly attenuated by activators of α7-nAChR/PI3K signaling or by overexpression of constitutively active PI3K. Collectively, the results suggest that BCX inhibits lung tumorigenesis and cancer cell motility through the downregulation of α7-nAChR/PI3K signaling, independent of its provitamin A activity. Therefore, BCX can be used as a chemopreventive agent or a chemotherapeutic compound against lung cancer. Cancer Prev Res; 9(11); 875-86. ©2016 AACR.

Nicotinic acetylcholine receptors and cancer

Nicotine, the primary addictive constituent of cigarettes, is believed to contribute to cancer promotion and progression through the activation of nicotinic acetylcholine receptors (nAChRs), which are membrane ligand-gated cation channels. nAChRs activation can be triggered by the neurotransmitter Ach, or certain other biological compounds, such as nicotine. In recent years, genome-wide association studies have indicated that allelic variation in the α5-α3-β4 nAChR cluster on chromosome 15q24-15q25.1 is associated with lung cancer risk. The role of nAChRs in other types of cancer has also been reported. The present review highlights the role of nAChRs in types of human cancer.

Perceptions about e-cigarette safety may lead to e-smoking during pregnancy

Electronic cigarettes (e-cigarettes) are nicotine-delivery devices that are increasingly used, especially by young people. Because e-cigarettes lack many of the substances found in regular tobacco, they are often perceived as a safer smoking alternative, especially in high-risk situations such as pregnancy. However, studies suggest that it is exposure to nicotine that is most detrimental to prenatal development. The authors studied perceptions of tobacco and e-cigarette health risks using a multiple-choice survey. To study the perceived safety of e-cigarettes versus tobacco cigarettes, 184 modified Global Health Youth Surveys (WHO, http://www.who.int/tobacco/surveillance/gyts/en/ ) were completed electronically or on paper. Age range, smoking status, and perceptions about tobacco cigarettes and e-cigarettes were studied. The results verified that younger people use e-cigarettes more than older people. Tobacco cigarettes were perceived as more harmful than e-cigarettes to health in general, including lung cancer and pregnancy. Although more research is necessary, the authors postulate that the perception that e-cigarettes are safer during pregnancy may induce pregnant women to use these devices more freely. Given that nicotine is known to cause fetal harm, pregnant mothers who smoke e-cigarettes could cause even greater harm to the fetus because e-cigarettes are perceived as being safer than tobacco cigarettes. Until more data about the effects of nicotine during pregnancy are available, the authors advocate for labeling of e-cigarettes as potentially harmful, at least during pregnancy.

Nicotine-induced cellular stresses and autophagy in human cancer colon cells: A supportive effect on cell homeostasis via up-regulation of Cox-2 and PGE(2) production

Nicotine, one of the active components in cigarette smoke, has been described to contribute to the protective effect of smoking in ulcerative colitis (UC) patients. Furthermore, the nicotinic acetylcholine receptor α7 subunit (α7nAChR) expressed on immune cells, is an essential regulator of inflammation. As intestinal epithelial cells also express α7nAChR, we investigated how nicotine could participate in the homeostasis of intestinal epithelial cells. First, using the human adenocarcinoma cell line HT-29, we revealed that nicotine, which triggers an influx of extracellular Ca(2+) following α7nAChR stimulation, induces mitochondrial reactive oxygen species (ROS) production associated with a disruption of the mitochondrial membrane potential and endoplasmic reticulum stress. This results in caspase-3 activation, which in turn induces apoptosis. Additionally, we have shown that nicotine induces a PI3-K dependent up-regulation of cyclooxygenase-2 (Cox-2) expression and prostaglandin E2 (PGE2) production. In this context, we suggest that this key mediator participates in the cytoprotective effects of nicotine against apoptosis by stimulating autophagy in colon cancer cells. Our results provide new insight into one potential mechanism by which nicotine could protect from UC and suggest an anti-inflammatory role for the cholinergic pathway at the epithelial cell level.

Acetylcholinesterase is associated with a decrease in cell proliferation of hepatocellular carcinoma cells

Acetylcholinesterase (AChE), the enzyme that rapidly splits acetylcholine into acetate and choline, presents non-cholinergic functions through which may participate in the control of cell proliferation and apoptosis. These two features are relevant in cancer, particularly in hepatocellular carcinoma (HCC), a very aggressive liver tumor with high incidence and poor prognosis in advanced stages. Here we explored the relation between acetylcholinesterase and HCC growth by testing the influence of AChE on proliferation of Huh-7 and HepG2 cell lines, addressed in monolayer cultures, spheroid formation and human liver tumor samples. Results showed a clear relation in AChE expression and cell cycle progression, an effect which depended on cell confluence. Inhibition of AChE activity led to an increase in cell proliferation, which was associated with downregulation of p27 and cyclins. The fact that Huh-7 and HepG2 cell lines provided similar results lent weight to the relationship of AChE expression with cell cycle progression in hepatoma cell lines at least. Human liver tumor samples exhibited a decrease in AChE activity as compared with normal tissue. The evidence presented herein provides additional support for the proposed tumor suppressor role of AChE, which makes it a potential therapeutic target in therapies against hepatocellular carcinoma.

Onset of the lymphocytic infiltration and hyperplasia preceding the proliferation in F1 mouse lungs from the N-ethyl-N-nitrosourea exposed mothers: Prevention during the lactation period by inositol hexaphosphate

Maternal exposure to a carcinogen is associated with increased risk of different cancers in the offspring. The foetus is highly sensitive to carcinogens and this contributes to the foetal basis of the onset of disease. The better understanding of the molecular mechanisms involved in the early stage of lung tumourigenesis in the offspring is needed for the newer preventive strategies. We evaluated the effects of N-ethyl-N-nitrosourea (ENU) given on the 17th day of gestation and antitumour agent inositol hexaphosphate (IP6) to the mothers at the early stage of lung tumourigenesis in F1 mice. There was no treatment related effects on the litter size or body weight of the F1 mice at the PND12 or 24. Analysis of PCNA, NF-κB (p50), IL-6, COX-2, pSTAT3, STAT3, caspase-3, caspase-9, PARP, Akt signalling and downstream cyclin D1 along with miR-155, suggested the modulation of proliferation, inflammation and apoptosis at PND12 and 24. IP6 administration to the predisposed mothers prevented the proliferation, inflammation and enhanced apoptosis in F1 lung as showed by a reduction in PCNA, NF-κB (p50), IL-6, COX-2, pSTAT3, STAT3, miR-155 and increase in caspases, cleavage of poly (ADP-ribose) polymerase. IP6 administration also inhibited the activation of Akt and cyclin D1. Our study shows that tumourigenic changes take place in the lungs of the F1 generation from the carcinogen predisposed mothers even before the onset of tumours and the simultaneous intake of chemopreventive agent during the gestation or lactation period could prevent the lymphocytic infiltration and hyperplasia preceding the tumourigenesis.

CHRFAM7A: a human-specific α7-nicotinic acetylcholine receptor gene shows differential responsiveness of human intestinal epithelial cells to LPS

The human genome contains a unique, distinct, and human-specific α7-nicotinic acetylcholine receptor (α7nAChR) gene [CHRNA7 (gene-encoding α7-nicotinic acetylcholine receptor)] called CHRFAM7A (gene-encoding dup-α7-nicotinic acetylcholine receptor) on a locus of chromosome 15 associated with mental illness, including schizophrenia. Located 5' upstream from the "wild-type" CHRNA7 gene that is found in other vertebrates, we demonstrate CHRFAM7A expression in a broad range of epithelial cells and sequenced the CHRFAM7A transcript found in normal human fetal small intestine epithelial (FHs) cells to prove its identity. We then compared its expression to CHRNA7 in 11 gut epithelial cell lines, showed that there is a differential response to LPS when compared to CHRNA7, and characterized the CHRFAM7A promoter. We report that both CHRFAM7A and CHRNA7 gene expression are widely distributed in human epithelial cell lines but that the levels of CHRFAM7A gene expression vary up to 5000-fold between different gut epithelial cells. A 3-hour treatment of epithelial cells with 100 ng/ml LPS increased CHRFAM7A gene expression by almost 1000-fold but had little effect on CHRNA7 gene expression. Mapping the regulatory elements responsible for CHRFAM7A gene expression identifies a 1 kb sequence in the UTR of the CHRFAM7A gene that is modulated by LPS. Taken together, these data establish the presence, identity, and differential regulation of the human-specific CHRFAM7A gene in human gut epithelial cells. In light of the fact that CHRFAM7A expression is reported to modulate ligand binding to, and alter the activity of, the wild-type α7nAChR ligand-gated pentameric ion channel, the findings point to the existence of a species-specific α7nAChR response that might regulate gut epithelial function in a human-specific fashion.

Nicotine induces resistance to erlotinib via cross-talk between α 1 nAChR and EGFR in the non-small cell lung cancer xenograft model

OBJECTIVES

Given our previously published study, α 1 nicotinic acetylcholine receptor (nAChR) plays an essential role in nicotine-induced cell signaling and nicotine-induced resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) in non-small cell lung cancer (NSCLC) PC9 cells. The aim of this study was to investigate the potential mechanism between nAChR and EGFR for nicotine-induced resistance to EGFR-TKI erlotinib in the NSCLC xenograft model.

MATERIALS AND METHODS

We identified the role of nicotine to EGFR/AKT/ERK pathways and to erlotinib-resistance in NSCLC PC9 and HCC827 cells by MTS assay and western blot. Then, we established the PC9 xenograft model with nicotine exposure and treated mice with erlotinib combined with vehicle or nicotine.

RESULTS

We confirmed the effects of nicotine on EGFR/AKT/ERK pathways and determined nicotine's potential in preventing from the effect of erlotinib on NSCLC cells. Then, we showed that nicotine exposures can promote tumor growth and induce resistance to erlotinib in the PC9 xenograft model. Our results also indicated that chronic oral administration of nicotine can cause more significant erlotinib-resistance compared with acute i.v. injection of nicotine through activating α 1 nAChR and EGFR pathways.

CONCLUSIONS

These results suggest that nicotine contributes to the progression and erlotinib-resistance of the NSCLC xenograft model via the cooperation between nAChR and EGFR.

Electronic cigarettes: overview of chemical composition and exposure estimation

Background

Electronic cigarettes (e-cigarettes) are advertised to tobacco users as a tool to decrease cigarette consumption and to reduce toxic exposure associated with conventional tobacco smoking. Little is known about the compounds contained in such products, their exposure and long-term health effects.

Methods

NMR spectroscopy was used to ascertain the content of several constituents of e-cigarette liquids including nicotine, solvents and some bioactive flavour compounds. Risk assessment was based on probabilistic exposure estimation and comparison with toxicological thresholds using the margin of exposure (MOE) approach.

Results

In 54 samples of e-cigarette liquids, the average nicotine content was 11 mg/ml. Only 18 from 23 samples were confirmed as nicotine-free samples and in one e-cigarette liquid nicotine was not detected while being declared on the labelling. Major compounds of e-cigarette liquids include glycerol (average 37 g/100 g), propylene glycol (average 57 g/100 g) and ethylene glycol (average 10 g/100 g). Furthermore, 1,3-propanediol, thujone and ethyl vanillin were detected in some samples. The average exposure for daily users was estimated as 0.38 mg/kg bw/day for nicotine, 8.9 mg/kg bw/day for glycerol, 14.5 mg/kg bw/day for 1,2-propanediol, 2.1 mg/kg bw/day for ethylene glycol, and below 0.2 mg/kg bw/day for the other compounds. The MOE was below 0.1 for nicotine, but all other compounds did not reach MOE values below 100 except ethylene glycol and 1,2-propanediol.

Conclusions

NMR spectroscopy is a useful and rapid method to simultaneously detect several ingredients in e-cigarette liquids. From all compounds tested, only nicotine may reach exposures that fall into a high risk category with MOE <1. Therefore, e-cigarette liquid products should be subjected to regulatory control to ensure consistent nicotine delivery. Solvents with more favourable toxicological profiles should be used instead of ethylene glycol and 1,2-propanediol, which may fall into a risk category with MOE < 100.

Early events in the pathogenesis of chronic obstructive pulmonary disease. Smoking-induced reprogramming of airway epithelial basal progenitor cells

The airway epithelium is the primary site of the earliest pathologic changes induced by smoking, contributing to the development of chronic obstructive pulmonary disease (COPD). The normal human airway epithelium is composed of several major cell types, including differentiated ciliated and secretory cells, intermediate undifferentiated cells, and basal cells (BC). BC contain the stem/progenitor cell population responsible for maintenance of the normally differentiated airway epithelium. Although inflammatory and immune processes play a significant role in the pathogenesis of COPD, the earliest lesions include hyperplasia of the BC population, suggesting that the disease may start with this cell type. Apart from BC hyperplasia, smoking induces a number of COPD-relevant airway epithelial remodeling phenotypes that are likely initiated in the BC population, including mucous cell hyperplasia, squamous cell metaplasia, epithelial-mesenchymal transition, altered ciliated and nonmucous secretory cell differentiation, and suppression of junctional barrier integrity. Significant progress has been recently made in understanding the biology of human airway BC, including gene expression features, stem/progenitor, and other functions, including interaction with other airway cell types. Accumulating evidence suggests that human airway BC function as both sensors and cellular sources of various cytokines and growth factors relevant to smoking-associated airway injury, as well as the origin of various molecular and histological phenotypes relevant to the pathogenesis of COPD. In the context of these considerations, we suggest that early BC-specific smoking-induced molecular changes are critical to the pathogenesis of COPD, and these represent a candidate target for novel therapeutic approaches to prevent COPD progression in susceptible individuals.

A systematic review of health effects of electronic cigarettes

OBJECTIVE

To provide a systematic review of the existing literature on health consequences of vaporing of electronic cigarettes (ECs).

METHODS

Search in: PubMed, EMBASE and CINAHL.

INCLUSION CRITERIA

Original publications describing a health-related topic, published before 14 August 2014. PRISMA recommendations were followed. We identified 1101 studies; 271 relevant after screening; 94 eligible.

RESULTS

We included 76 studies investigating content of fluid/vapor of ECs, reports on adverse events and human and animal experimental studies. Serious methodological problems were identified. In 34% of the articles the authors had a conflict of interest. Studies found fine/ultrafine particles, harmful metals, carcinogenic tobacco-specific nitrosamines, volatile organic compounds, carcinogenic carbonyls (some in high but most in low/trace concentrations), cytotoxicity and changed gene expression. Of special concern are compounds not found in conventional cigarettes, e.g. propylene glycol. Experimental studies found increased airway resistance after short-term exposure. Reports on short-term adverse events were often flawed by selection bias.

CONCLUSIONS

Due to many methodological problems, severe conflicts of interest, the relatively few and often small studies, the inconsistencies and contradictions in results, and the lack of long-term follow-up no firm conclusions can be drawn on the safety of ECs. However, they can hardly be considered harmless.

Acetylcholine receptor pathway in lung cancer: New twists to an old story

Genome-wide association studies revealed that allelic variation in the α5-α3-β4 nicotine acetylcholine receptor (nAChR) cluster on chromosome 15q24-15q25.1 was associated with lung cancer risk. nAChRs are membrane ligand-gated cation channels whose activation is triggered by the binding of the endogenous neurotransmitter acetylcholine (ACh) or other biologic compounds including nicotine. nAChRs have been found on lung cancer cells, underscoring the idea that the non-neuronal nAChR pathway has important implications for lung cancer. Several studies focusing on the treatment with nAChR antagonists with improved selectivity might trigger novel strategies for the intervention and prevention of lung cancer. Here we review the genetic risk factors for lung cancer in the nAChR gene cluster, the roles of nicotine receptors, and the molecular mechanisms of acetylcholine receptor pathways to lead to more opportunities for intervention and prevention of lung cancer.

Identification of nuclear phosphoproteins as novel tobacco markers in mouse lung tissue following short-term exposure to tobacco smoke

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We analyzed nuclear phosphoprotein expression activated by tobacco smoke exposure.

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253 phosphoproteins were identified in 1-day and 7-day exposure groups.

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Of these, 33 were significantly differentially expressed in control and exposed groups.

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Identified proteins were related to inflammation, response to stress and nicotine.

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OSF3 and spectrin β chain were identified as candidate tobacco smoke markers.

Smoking is a risk factor for lung diseases, including chronic obstructive pulmonary disease and lung cancer. However, the molecular mechanisms mediating the progression of these diseases remain unclear. Therefore, we sought to identify signaling pathways activated by tobacco-smoke exposure, by analyzing nuclear phosphoprotein expression using phosphoproteomic analysis of lung tissue from mice exposed to tobacco smoke. Sixteen mice were exposed to tobacco smoke for 1 or 7 days, and the expression of phosphorylated peptides was analyzed by mass spectrometry. A total of 253 phosphoproteins were identified, including FACT complex subunit SPT16 in the 1-day exposure group, keratin type 1 cytoskeletal 18 (K18), and adipocyte fatty acid-binding protein, in the 7-day exposure group, and peroxiredoxin-1 (OSF3) and spectrin β chain brain 1 (SPTBN1), in both groups. Semi-quantitative analysis of the identified phosphoproteins revealed that 33 proteins were significantly differentially expressed between the control and exposed groups. The identified phosphoproteins were classified according to their biological functions. We found that the identified proteins were related to inflammation, regeneration, repair, proliferation, differentiation, morphogenesis, and response to stress and nicotine. In conclusion, we identified proteins, including OSF3 and SPTBN1, as candidate tobacco smoke-exposure markers; our results provide insights into the mechanisms of tobacco smoke-induced diseases.

Unmethylation of the CHRNB4 gene is an unfavorable prognostic factor in non-small cell lung cancer

OBJECTIVES

Lung cancer is the leading cause of cancer-related deaths and is currently a major health problem owing to difficulties in diagnosis at the early stage of the disease. Changes in DNA methylation status have now been identified as a critical component in the initiation of lung cancer, and the detection of DNA methylation is expected to be an important method for the early diagnosis of lung cancer. Nicotine, the principal tobacco alkaloid, directly contributes to lung carcinogenesis through the activation of nicotinic acetylcholine receptors (nAchRs).

MATERIALS AND METHODS

To investigate the role of the CHRNB4 gene, which encodes the nAchR β4 subunit that is ubiquitously expressed on lung epithelial cells, we analyzed its methylation status in 266 patients with non-small cell lung cancer (NSCLC) by using methylation-specific polymerase chain reaction and compared it with clinicopathological parameters.

RESULTS AND CONCLUSION

The frequency of CHRNB4 unmethylation was 13.5% and 8.3% in malignant and nonmalignant tissues, respectively. CHRNB4 demethylation was associated with upregulation of its mRNA expression and was more frequent in squamous cell carcinoma and pathological stages II-IIIA disease than in adenocarcinoma and pathological stage I disease, respectively (P=0.003 and P=0.01, respectively). Univariate and multivariate analyses showed that CHRNB4 unmethylation was significantly associated with unfavorable overall survival in the entire patient group as well as in men and ever-smokers. These results suggest that epigenetic regulation of CHRNB4 may affect tumor progression and survival in patients with NSCLC. Further investigation into the molecular basis of the role of CHRNB4 in the progression of NSCLC is warranted.