Receptor-mediated tobacco toxicity: acceleration of sequential expression of alpha5 and alpha7 nicotinic receptor subunits in oral keratinocytes exposed to cigarette smoke

Cell signaling and epigenetic regulation of nicotine-induced carcinogenesis

Nicotine, a naturally occurring tobacco alkaloid responsible for tobacco addiction, has long been considered non-carcinogenic. However, emerging evidence suggests that nicotine may possess carcinogenic properties in mice and could be a potential carcinogen in humans. This review aims to summarize the potential molecular mechanisms underlying nicotine-induced carcinogenesis, with a specific focus on epigenetic regulation and the activation of nicotinic acetylcholine receptors (nAChRs) in addition to genotoxicity and excess reactive oxygen species (ROS). Additionally, we explore a novel hypothesis regarding nicotine's carcinogenicity involving the downregulation of stem-loop binding protein (SLBP), a critical regulator of canonical histone mRNA, and the polyadenylation of canonical histone mRNA. By shedding light on these mechanisms, this review underscores the need for further research to elucidate the carcinogenic potential of nicotine and its implications for human health.

A Critical Interpretive Synthesis of the Role of Arecoline in Oral Carcinogenesis: Is the Local Cholinergic Axis a Missing Link in Disease Pathophysiology?

Arecoline is the primary active carcinogen found in areca nut and has been implicated in the pathogenesis of oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF). For this study, we conducted a stepwise review process by combining iterative scoping reviews with a post hoc search, with the aim of identifying the specific mechanisms by which arecoline initiates and promotes oral carcinogenesis. Our initial search allowed us to define the current trends and patterns in the pathophysiology of arecoline-induced OSF and OSCC, which include the induction of cell proliferation, facilitation of invasion, adhesion, and migration, increased collagen deposition and fibrosis, imbalance in immune and inflammatory mechanisms, and genotoxicity. Key molecular pathways comprise the activation of NOTCH1, MYC, PRDX2, WNT, CYR61, EGFR/Pl3K, DDR1 signaling, and cytokine upregulation. Despite providing a comprehensive overview of potential pathogenic mechanisms of OSF, the involvement of molecules functioning as areca alkaloid receptors, namely, the muscarinic and nicotinic acetylcholine receptors (AChRs), was not elucidated with this approach. Accordingly, our search strategy was refined to reflect these evidence gaps. The results of the second round of reviews with the post hoc search highlighted that arecoline binds preferentially to muscarinic AChRs, which have been implicated in cancer. Consistently, AChRs activate the signaling pathways that partially overlap with those described in the context of arecoline-induced carcinogenesis. In summary, we used a theory-driven interpretive review methodology to inform, extend, and supplement the conventional systematic literature assessment workflow. On the one hand, the results of this critical interpretive synthesis highlighted the prevailing trends and enabled the consolidation of data pertaining to the molecular mechanisms involved in arecoline-induced carcinogenesis, and, on the other, brought up knowledge gaps related to the role of the local cholinergic axis in oral carcinogenesis, thus suggesting areas for further investigation.

The expression of nicotinic acetylcholine receptor subunits and their associations with local immune cells and prognosis in oral squamous cell carcinoma

BACKGROUND

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that may be responsible for cancer cell proliferation, epithelial-mesenchymal transition (EMT), and immune regulation. However, little is known about the associations of different nAChR subunits with tumor microenvironment in oral squamous cell carcinoma (OSCC).

METHODS

We retrospectively reviewed pathology samples from 75 OSCC patients by immunohistochemistry. In addition, a cohort of 307 OSCC patients in The Cancer Genome Atlas was analyzed.

RESULTS

Subunit α1 was specific to peri-OSCC skeletal muscle. Increased α1 was associated with increased CD44 (cancer stem cells), increased CD3 and 8 (T cells), increased CD56 and 16 (natural killer cells), a decreased T stage, and an increased N stage. Increased α3 was associated with increased CD56 and 16. Increased α5 was associated with decreased CD3, 8, and 56, a decreased T stage, an increased N stage, worse survival, and decreased epithelial features. Increased α7 was associated with increased CD3, 8, 56, and 16, decreased tumor/peritumor ratios of CD3, 8, and 56 immune cells, and increased epithelial features. Increased local immune cells were associated with a better prognosis.

CONCLUSIONS

α5 is the only subunit associated with decreased local immune cells and worse survival, while α1, α3, and α7 are associated with increased local immune cells in OSCC. α5 and α7 are correlated with different EMT states to be mesenchymal-like and epithelial-like OSCC, respectively. Protein expression data of the nAChR subunits, complementary to gene expression data, could provide meaningful information regarding the EMT status of OSCC associated with immune responses and prognosis.

Nicotine Exerts Cytotoxic Effects in a Panel of Healthy Cell Lines and Strong Irritating Potential on Blood Vessels

The use of tobacco products is a major global public health issue, as it is the leading cause of preventable death worldwide. In addition, nicotine (NIC) is a key component of electronic and conventional cigarettes. Although nicotine's addictive potential is well known, its health effects are not entirely understood. Thus, the main objective of the present study was to evaluate its toxicological profile both in vitro, at the level of three healthy cell lines, and in ovo, at the level of the chorioallantoic membrane. Five different concentrations of nicotine were used in keratinocytes, cardiomyocytes, and hepatocytes for the purpose of evaluating cell viability, cell morphology, and its impact on nuclei. Additionally, the hen's egg test on the chorioallantoic membrane (HET-CAM) method was used to assess the biocompatibility and irritant potential of the chorioallantoic membrane. Across all cell lines studied, nicotine was proven to be significantly damaging to cell viability, with the highest concentration tested resulting in less than 2% viable cells. Moreover, the morphology of cells changed dramatically, with alterations in their shape and confluence. Nicotine-induced cell death appears to be apoptotic, based on its impact on the nucleus. In addition, nicotine was also found to have a very strong irritating effect on the chorioallantoic membrane. In conclusion, nicotine has an extremely strong toxicological profile, as demonstrated by the drastic reduction of cell viability and the induction of morphological changes and nuclear alterations associated with cellular apoptosis. Additionally, the HET-CAM method led to the observation of a strong irritating effect associated with nicotine.

SLURP-1 Controls Growth and Migration of Lung Adenocarcinoma Cells, Forming a Complex With α7-nAChR and PDGFR/EGFR Heterodimer

Secreted Ly6/uPAR-related protein 1 (SLURP-1) is a secreted Ly6/uPAR protein that negatively modulates the nicotinic acetylcholine receptor of α7 type (α7-nAChR), participating in control of cancer cell growth. Previously we showed, that a recombinant analogue of human SLURP-1 (rSLURP-1) diminishes the lung adenocarcinoma A549 cell proliferation and abolishes the nicotine-induced growth stimulation. Here, using multiplex immunoassay, we demonstrated a decrease in PTEN and mammalian target of rapamycin (mTOR) kinase phosphorylation in A549 cells upon the rSLURP-1 treatment pointing on down-regulation of the PI3K/AKT/mTOR signaling pathway. Decreased phosphorylation of the platelet-derived growth factor receptor type β (PDGFRβ) and arrest of the A549 cell cycle in the S and G2/M phases without apoptosis induction was also observed. Using a scratch migration assay, inhibition of A549 cell migration under the rSLURP-1 treatment was found. Affinity extraction demonstrated that rSLURP-1 in A549 cells forms a complex not only with α7-nAChR, but also with PDGFRα and epidermal growth factor receptor (EGFR), which are known to be involved in regulation of cancer cell growth and migration and are able to form a heterodimer. Knock-down of the genes encoding α7-nAChR, PDGFRα, and EGFR confirmed the involvement of these receptors in the anti-migration effect of SLURP-1. Thus, SLURP-1 can target the α7-nAChR complexes with PDGFRα and EGFR in the membrane of epithelial cells. Using chimeric proteins with grafted SLURP-1 loops we demonstrated that loop I is the principal active site responsible for the SLURP-1 interaction with α7-nAChR and its antiproliferative effect. Synthetic peptide mimicking the loop I cyclized by a disulfide bond inhibited ACh-evoked current at α7-nAChR, as well as A549 cell proliferation and migration. This synthetic peptide represents a promising prototype of new antitumor drug with the properties close to that of the native SLURP-1 protein.

Toxicological interaction between tobacco smoke toxicants cadmium and nicotine: An in-vitro investigation

Cigarettes and other tobacco products are used to obtain nicotine that is responsible for their stimulating effects. However, a lot of other organic and inorganic chemicals are also released along with nicotine. Cadmium (Cd) is one of the several heavy metals that are health hazards and is one of the inorganic elements released in tobacco smoke. The in-vitro investigation focused on exploring the effects of nicotine hydrogen tartrate (NHT) and cadmium (Cd) and their toxic interactions in the A549 cell line. In cell viability assay NHT exhibited its IC50 at 11.71 mM concentration, and the IC50 of Cd was found to be 83 µM after a 24 h exposure. Toxic effects of NHT (5 mM and 10 mM), Cd (50 µM and 100 µM), and their combination were also investigated by flowcytometry. The investigation included apoptotic and necrotic events, the effect on different cell cycle phases, and generation of reactive oxygen species by NHT, Cd, and their combination of different concentrations. Data reveal evident toxic effects of NHT, Cd, and NHT + Cd. It also indicates that the toxic interaction of NHT and Cd is not additive and appears to be minimal when compared with NHT or Cd exposures alone.

Low-Dose Nicotine Activates EGFR Signaling via α5-nAChR and Promotes Lung Adenocarcinoma Progression

Nicotine in tobacco smoke is considered carcinogenic in several malignancies including lung cancer. The high incidence of lung adenocarcinoma (LAC) in non-smokers, however, remains unexplained. Although LAC has long been less associated with smoking behavior based on previous epidemiological correlation studies, the effect of environmental smoke contributing to low-dose nicotine exposure in non-smoking population could be underestimated. Here we provide experimental evidence of how low-dose nicotine promotes LAC growth in vitro and in vivo. Screening of nicotinic acetylcholine receptor subunits in lung cancer cell lines demonstrated a particularly high expression level of nicotinic acetylcholine receptor subunit α5 (α 5-nAChR) in LAC cell lines. Clinical specimen analysis revealed up-regulation of α 5-nAChR in LAC tumor tissues compared to non-tumor counterparts. In LAC cell lines α 5-nAChR interacts with epidermal growth factor receptor (EGFR), positively regulates EGFR pathway, enhances the expression of epithelial-mesenchymal transition markers, and is essential for low-dose nicotine-induced EGFR phosphorylation. Functionally, low-dose nicotine requires α 5-nAChR to enhance cell migration, invasion, and proliferation. Knockdown of α 5-nAChR inhibits the xenograft tumor growth of LAC. Clinical analysis indicated that high level of tumor α 5-nAChR is correlated with poor survival rates of LAC patients, particularly in those expressing wild-type EGFR. Our data identified α 5-nAChR as an essential mediator for low-dose nicotine-dependent LAC progression possibly through signaling crosstalk with EGFR, supporting the involvement of environmental smoke in tumor progression in LAC patients.

Drug Discovery on Natural Products: From Ion Channels to nAChRs, from Nature to Libraries, from Analytics to Assays

Natural extracts are complex mixtures that may be rich in useful bioactive compounds and therefore are attractive sources for new leads in drug discovery. This review describes drug discovery from natural products and in explaining this process puts the focus on ion-channel drug discovery. In particular, the identification of bioactives from natural products targeting nicotinic acetylcholine receptors (nAChRs) and serotonin type 3 receptors (5-HT3Rs) is discussed. The review is divided into three parts: "Targets," "Sources," and "Approaches." The "Targets" part will discuss the importance of ion-channel drug targets in general, and the α7-nAChR and 5-HT3Rs in particular. The "Sources" part will discuss the relevance for drug discovery of finding bioactive compounds from various natural sources such as venoms and plant extracts. The "Approaches" part will give an overview of classical and new analytical approaches that are used for the identification of new bioactive compounds with the focus on targeting ion channels. In addition, a selected overview is given of traditional venom-based drug discovery approaches and of diverse hyphenated analytical systems used for screening complex bioactive mixtures including venoms.

Nicotine suppresses apoptosis by regulating α7nAChR/Prx1 axis in oral precancerous lesions

Nicotine, a tumor promoter in tobacco, can increase Peroxiredoxin (Prx1) and nicotinic acetylcholine receptors (nAChRs) in oral squamous cell carcinoma (OSCC). In the present study, we investigate the effects of nicotine in oral precancerous lesions focusing on apoptosis and nAChR/Prx1 signaling. We detected expression of Prx1, α3nAChR, α7nAChR, phosphorylation of mitogen-activated protein kinases (MAPK) and apoptosis in dysplastic oral keratinocyte (DOK) cells as well as in 4-nitroquinoline 1-oxide (4NQO) or 4NQO + nicotine – induced oral precancerous lesions in Prx1 wild-type (Prx1^+/+) and Prx1 knockdown (Prx1^+/-) mice. In DOK cells, Prx1 knockdown and blocking α7nAChR activated apoptosis, and nicotine increased the expression of Prx1, α3nAChR and α7nAChR, and inhibited MAPK activation. Moreover, nicotine suppressed apoptosis depending on Prx1 and α7nAChR in DOK cells. In animal bioassay, nicotine and Prx1 promoted growth of 4NQO-induced precancerous lesions in mouse tongue. 4NQO plus nicotine suppressed MAPK activation in Prx1 wild-type mice but not in Prx1 knockdown mice. Our data demonstrate that nicotine inhibits cell apoptosis and promotes the growth of oral precancerous lesions via regulating α7nAChR/Prx1 during carcinogenesis of OSCC.

The effect of nicotine on the expressions of the α7 nicotinic receptor gene and Bax and Bcl-2 proteins in the mammary gland epithelial-7 breast cancer cell line and its relationship to drug resistance

The binding of nicotine with nicotinic acetylcholine receptors (nAChRs) stimulates cell division and increases drug resistance in cancer. Experiments with specific inhibitors such as RNAi, hexamethonium, and α-bungarotoxin showed that α7 nicotinic receptor plays a key role in the pro-proliferation activity of nicotine. However, the mechanism of nicotine in the progress of breast cancer, the commonest malignancy in women, remains unknown. This study focuses on the effect of nicotine on the expressions of the α7 nicotinic receptor gene and Bax and Bcl-2 proteins in mammary gland epithelial-7 (MCF-7) breast cancer cells and its relationship to drug resistance. To evaluate the effect on drug resistance, human mammary gland epithelial adenocarcinomas from the MCF-7 line were exposed to 100 μl of nicotine at a concentration of 9.2 mg/ml for varying periods of time. Then, the cells were treated with 1, 2, 3 or 5 μl/ml of doxorubicin, either with or without the continued presence of nicotine. Cell viability was determined using the MTT assay. The biochemical parameters of apoptosis, including the expressions of Bax, Bcl-2 and α7 nicotinic receptor proteins were determined via western blotting, and the α7 nicotinic receptor gene expression level was assessed via real-time qPCR using the 2(-ΔΔCt) method. Differences in the target gene expression levels were evaluated with ANOVA with p ≤ 0.05 considered significant. We found a novel and effective signaling pathway of nicotine in the MCF-7 breast cancer cell line. The levels of α7 nicotinic receptor and Bcl-2 protein increased but the Bax protein levels decreased, while the α7 nicotinic receptor gene expression level was not significantly different compared with the control.

Nicotinic cholinergic and dopaminergic receptor mRNA expression in male and female rats with high or low preference for nicotine

BACKGROUND

Nicotine exerts its central actions through nicotinic acetylcholine receptors (nAChRs), which in turn regulate major neurotransmitter systems including dopamine. Nicotinic and dopaminergic systems play significant roles in physiological functions, neuropsychiatric disorders, and addiction.

OBJECTIVES

To evaluate possible differences in the expression of nAChR subunit and dopamine receptor (DR) mRNAs following voluntary nicotine intake.

METHODS

Male and female rats (n = 67) were exposed to long-term free-choice oral nicotine (24 hours/day, 6 weeks); rats with maximum and minimum nicotine preference/intake were selected. The mRNA levels of genes encoding α4,β2,α5, and α7 nAChR subunits and DR Drd1and Drd2 subtypes were evaluated in the striatum (STR), prefrontal cortex (PFC), and hippocampus using quantitative real-time polymerase chain reaction in selected rats (n = 30) and their control groups (n = 15).

RESULTS

In addition to baseline differences, expression changes were observed in the mRNA levels of evaluated genes in rats exposed to voluntary oral nicotine in a brain region-, sex-, and preference-related manner. Nicotine intake is correlated negatively with Chrnb2, Chrna7 and positively with Drd1 expression. In the cholinergic system, regional differences in Chnrb2 and Chrna5, sex differences in Chrna4 and Chrna5, and nicotine preference effects in the expression of all subunits except α4 were observed. Chrna5 was lower in maximum than in minimum preferring, and in male than female rats, supporting the inhibitory role of the α5 subunit in nicotine dependence. Nicotine increased Drd2 mRNA expression only in minimum preferring female rats in STR and PFC.

CONCLUSION

Modulation of nAChR and DR gene expression by nicotine may have clinical implications and aid drug development. Pharmaceuticals targeting the nicotinic cholinergic and dopaminergic systems might be expected to have differential efficacy that varies with the patient's sex or smoking status.

Nicotinic modulation of hippocampal cell signaling and associated effects on learning and memory

The hippocampus is a key brain structure involved in synaptic plasticity associated with long-term declarative memory formation. Importantly, nicotine and activation of nicotinic acetylcholine receptors (nAChRs) can alter hippocampal plasticity and these changes may occur through modulation of hippocampal kinases and transcription factors. Hippocampal kinases such as cAMP-dependent protein kinase (PKA), calcium/calmodulin-dependent protein kinases (CAMKs), extracellular signal-regulated kinases 1 and 2 (ERK1/2), and c-jun N-terminal kinase 1 (JNK1), and the transcription factor cAMP-response element-binding protein (CREB) that are activated either directly or indirectly by nicotine may modulate hippocampal plasticity and in parallel hippocampus-dependent learning and memory. Evidence suggests that nicotine may alter hippocampus-dependent learning by changing the time and magnitude of activation of kinases and transcription factors normally involved in learning and by recruiting additional cell signaling molecules. Understanding how nicotine alters learning and memory will advance basic understanding of the neural substrates of learning and aid in understanding mental disorders that involve cognitive and learning deficits.

Nicotine-Mediated Ca(2+)-Influx Induces IL-8 Secretion in Oral Squamous Cell Carcinoma Cell

Cigarette smoking is one of the most important risk factors for the development of various diseases. Nicotine is the most extensively investigated component of cigarette smoke, and a comprehensive analysis of the genes induced by nicotine stimulation revealed that interleukin-8 (IL-8) was induced in oral squamous cell carcinoma cell (OSCC). Based on this background, the signaling mechanisms of nicotine-mediated IL-8 induction in OSCC was investigated. Augmented IL-8 secretion by Ca9-22 cells was blocked by the NF-κB inhibitor L-1-4'-tosylamino-phenylethyl-chloromethyl ketone (TPCK) and the nicotinic acetylcholine receptor (nAChR)-specific inhibitor α-bungarotoxin (αBtx). The downstream signaling pathway was further examined by pre-incubating the cells with inhibitors against mitogen-activated protein kinase (MEK), protein kinase C (PKC), and Ca(2+)/calmodulin-dependent kinase II (CaMK II). Only the CaMK II inhibitor was found to exert an inhibitory effect on nicotine-mediated IL-8 secretion. Pre-treatment of the Ca9-22 cells with the Ca(2+) chelator BAPTA-AM drastically inhibited IL-8 secretion. Although nicotine stimulation induced the phosphorylation of the NF-κB p65 subunit, pre-treatment with BAPTA-AM was found to inhibit this activity significantly. CaMK II-dependent p65 phosphorylation was confirmed by pre-incubation of the cells with CaMK II inhibitor. The results from this study indicate that the binding of nicotine to nAChR induces Ca(2+) influx, which results in the activation and phosphorylation of CaMK II and NF-κB p65, respectively. Nicotine-mediated IL-8 induction should be a trigger for the initiation of various diseases.

Response to Transdermal Selegiline Smoking Cessation Therapy and Markers in the 15q24 Chromosomal Region

INTRODUCTION

Current treatments for smoking cessation have limited efficacy. A potential pharmaceutical treatment for smoking cessation is selegiline, a selective and irreversible monoamine oxidase B inhibitor. A few clinical trials have been carried out using selegiline but the results have been mixed. We sought to determine if genetic markers in cholinergic loci in the 15q24 chromosomal region predict response to smoking cessation therapy with selegiline.

METHODS

We performed an 8-week double-blind, placebo-controlled clinical trial of the selegiline transdermal system in heavy smokers, with follow-up at weeks 25 and 52. Eight single nucleotide polymorphisms (SNPs) in the 15q24 region, which contains the genes for the nicotinic acetylcholine receptor subunits CHRNA5, CHRNA3, and CHRNB4, were investigated for association with treatment response.

RESULTS

The CHRNB4 promoter SNP rs3813567 was associated with both point prevalence abstinence and post-quit craving. Carriers of the minor C allele treated with selegiline showed lower rates of abstinence and higher levels of craving than selegiline-treated non-carriers, indicating that the rs3813567 C allele adversely affects abstinence in selegiline-treated smokers. This effect was not present among placebo-treated smokers. Selegiline-treated smokers with the CHRNA5 rs680244 GG genotype had lower post-quit craving, and unlike placebo-treated GG-carrying smokers, did not experience a post-quit increase in depressive symptoms.

CONCLUSIONS

Variants in genes encoding cholinergic receptors affect abstinence, craving and mood in selegiline-treated smokers. Selegiline primarily affects dopamine levels in the brain, but cholinergic input affects nicotine-induced dopaminergic activity. These markers may have value in identifying those likely to respond to selegiline for smoking cessation.

Differential Gene Expression in Colon Tissue Associated With Diet, Lifestyle, and Related Oxidative Stress

Several diet and lifestyle factors may impact health by influencing oxidative stress levels. We hypothesize that level of cigarette smoking, alcohol, anti-inflammatory drugs, and diet alter gene expression. We analyzed RNA-seq data from 144 colon cancer patients who had information on recent cigarette smoking, recent alcohol consumption, diet, and recent aspirin/non-steroidal anti-inflammatory use. Using a false discovery rate of 0.1, we evaluated gene differential expression between high and low levels of exposure using DESeq2. Ingenuity Pathway Analysis (IPA) was used to determine networks associated with de-regulated genes in our data. We identified 46 deregulated genes associated with recent cigarette use; these genes enriched causal networks regulated by TEK and MAP2K3. Different differentially expressed genes were associated with type of alcohol intake; five genes were associated with total alcohol, six were associated with beer intake, six were associated with wine intake, and four were associated with liquor consumption. Recent use of aspirin and/or ibuprofen was associated with differential expression of TMC06, ST8SIA4, and STEAP3 while a summary oxidative balance score (OBS) was associated with SYCP3, HDX, and NRG4 (all up-regulated with greater oxidative balance). Of the dietary antioxidants and carotenoids evaluated only intake of beta carotene (1 gene), Lutein/Zeaxanthine (5 genes), and Vitamin E (4 genes) were associated with differential gene expression. There were similarities in biological function of de-regulated genes associated with various dietary and lifestyle factors. Our data support the hypothesis that diet and lifestyle factors associated with oxidative stress can alter gene expression. However genes altered were unique to type of alcohol and type of antioxidant. Because of potential differences in associations observed between platforms these findings need replication in other populations.

Choline Acetyltransferase Mutations Causing Congenital Myasthenic Syndrome: Molecular Findings and Genotype-Phenotype Correlations

Choline acetyltransferase catalyzes the synthesis of acetylcholine at cholinergic nerves. Mutations in human CHAT cause a congenital myasthenic syndrome due to impaired synthesis of ACh; this severe variant of the disease is frequently associated with unexpected episodes of potentially fatal apnea. The severity of this condition varies remarkably, and the molecular factors determining this variability are poorly understood. Furthermore, genotype-phenotype correlations have been difficult to establish in patients with biallelic mutations. We analyzed the protein expression of phosphorylated ChAT of seven CHAT mutations, p.Val136Met, p.Arg207His, p.Arg186Trp, p.Val194Leu, p.Pro211Ala, p.Arg566Cys, and p.Ser694Cys, in HEK-293 cells to phosphorylated ChAT, determined their enzyme kinetics and thermal stability, and examined their structural changes. Three mutations, p.Arg207His, p.Arg186Trp, and p.Arg566Cys, are novel, and p.Val136Met and p.Arg207His are homozygous in three families and associated with severe disease. The characterization of mutants showed a decrease in the overall catalytic efficiency of ChAT; in particular, those located near the active-site tunnel produced the most seriously disruptive phenotypic effects. On the other hand, p.Val136Met, which is located far from both active and substrate-binding sites, produced the most drastic reduction of ChAT expression. Overall, CHAT mutations producing low enzyme expression and severe kinetic effects are associated with the most severe phenotypes.

Role of Lynx1 and related Ly6 proteins as modulators of cholinergic signaling in normal and neoplastic bronchial epithelium

The ly-6 proteins are a large family of proteins that resemble the snake three finger alpha toxins such as α-bungarotoxin and are defined by their multiple cysteine residues. Multiple members of the ly-6 protein family can modulate nicotinic signaling including lynx1, lynx2, slurp-1, slurp-2 and prostate stem cell antigen (PSCA). Consistent with the expression of multiple nicotinic receptors in bronchial epithelium, multiple members of the nicotinic-modulatory ly-6 proteins are expressed in lung including lynx1 and lynx2. We studied the role of lynx1 as an exemplar of the role of ly-6 proteins in lung. Our data demonstrates that lynx1 acts as a negative modulator of nicotinic signaling in normal and neoplastic lung. In normal lung lynx1 serves to limit the ability of chronic nicotine exposure to increase levels of nicotinic receptors and also serves to limit the ability of nicotine to upregulate levels of GABAA receptors in lung. In turn this allows lynx1 to limit the ability of nicotine to upregulate levels of mucin which is mediated by GABAergic signaling. This suggests that lynx1-mimetics may have potential for treatment of asthma and COPD. In that most lung cancer cells also express nicotinic receptor and lynx1 we examined the role of lynx-1 in lung cancer. Lynx1 levels are decreased in lung cancers compared to adjacent normal lung. Knockdown of lynx1 by siRNAs increased growth of lung cancer cells while expression of lynx1 in lung cancer cell decreased cell proliferation. This suggests that lynx1 is an endogenous regulator of lung cancer growth. Given that multiple small molecule negative and positive allosteric modulators of nicotinic receptors have already been developed, this suggests that lynx1 is a highly druggable target both for development of drugs that may limit lung cancer growth as well as for drugs that may be effective for asthma or COPD treatment.

Mechanisms of tumor-promoting activities of nicotine in lung cancer: synergistic effects of cell membrane and mitochondrial nicotinic acetylcholine receptors

Background

One of the major controversies of contemporary medicine is created by an increased consumption of nicotine and growing evidence of its connection to cancer, which urges elucidation of the molecular mechanisms of oncogenic effects of inhaled nicotine. Current research indicates that nicotinergic regulation of cell survival and death is more complex than originally thought, because it involves signals emanating from both cell membrane (cm)- and mitochondrial (mt)-nicotinic acetylcholine receptors (nAChRs). In this study, we elaborated on the novel concept linking cm-nAChRs to growth promotion of lung cancer cells through cooperation with the growth factor signaling, and mt-nAChRs — to inhibition of intrinsic apoptosis through prevention of opening of mitochondrial permeability transition pore (mPTP).

Methods

Experiments were performed with normal human lobar bronchial epithelial cells, the lung squamous cell carcinoma line SW900, and intact and NNK-transformed immortalized human bronchial cell line BEP2D.

Results

We demonstrated that the growth-promoting effect of nicotine mediated by activation of α7 cm-nAChR synergizes mainly with that of epidermal growth factor (EGF), α3 — vascular endothelial growth factor (VEGF), α4 — insulin-like growth factor I (IGF-I) and VEGF, whereas α9 with EGF, IGF-I and VEGF. We also established the ligand-binding abilities of mt-nAChRs and demonstrated that quantity of the mt-nAChRs coupled to inhibition of mPTP opening increases upon malignant transformation.

Conclusions

These results indicated that the biological sum of simultaneous activation of cm- and mt-nAChRs produces a combination of growth-promoting and anti-apoptotic signals that implement the tumor-promoting action of nicotine on lung cells. Therefore, nAChRs may be a promising molecular target to arrest lung cancer progression and re-open mitochondrial apoptotic pathways.

Connections of nicotine to cancer

This Opinion article discusses emerging evidence of direct contributions of nicotine to cancer onset and growth. The list of cancers reportedly connected to nicotine is expanding and presently includes small-cell and non-small-cell lung carcinomas, as well as head and neck, gastric, pancreatic, gallbladder, liver, colon, breast, cervical, urinary bladder and kidney cancers. The mutagenic and tumour-promoting activities of nicotine may result from its ability to damage the genome, disrupt cellular metabolic processes, and facilitate growth and spreading of transformed cells. The nicotinic acetylcholine receptors (nAChRs), which are activated by nicotine, can activate several signalling pathways that can have tumorigenic effects, and these receptors might be able to be targeted for cancer therapy or prevention. There is also growing evidence that the unique genetic makeup of an individual, such as polymorphisms in genes encoding nAChR subunits, might influence the susceptibility of that individual to the pathobiological effects of nicotine. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the evaluation of regulations on nicotine product manufacturing, distribution and marketing.

COOH-terminal collagen Q (COLQ) mutants causing human deficiency of endplate acetylcholinesterase impair the interaction of ColQ with proteins of the basal lamina

Collagen Q (ColQ) is a key multidomain functional protein of the neuromuscular junction (NMJ), crucial for anchoring acetylcholinesterase (AChE) to the basal lamina (BL) and accumulating AChE at the NMJ. The attachment of AChE to the BL is primarily accomplished by the binding of the ColQ collagen domain to the heparan sulfate proteoglycan perlecan and the COOH-terminus to the muscle-specific receptor tyrosine kinase (MuSK), which in turn plays a fundamental role in the development and maintenance of the NMJ. Yet, the precise mechanism by which ColQ anchors AChE at the NMJ remains unknown. We identified five novel mutations at the COOH-terminus of ColQ in seven patients from five families affected with endplate (EP) AChE deficiency. We found that the mutations do not affect the assembly of ColQ with AChE to form asymmetric forms of AChE or impair the interaction of ColQ with perlecan. By contrast, all mutations impair in varied degree the interaction of ColQ with MuSK as well as basement membrane extract (BME) that have no detectable MuSK. Our data confirm that the interaction of ColQ to perlecan and MuSK is crucial for anchoring AChE to the NMJ. In addition, the identified COOH-terminal mutants not only reduce the interaction of ColQ with MuSK, but also diminish the interaction of ColQ with BME. These findings suggest that the impaired attachment of COOH-terminal mutants causing EP AChE deficiency is in part independent of MuSK, and that the COOH-terminus of ColQ may interact with other proteins at the BL.

Nicotine induces the up-regulation of the α7-nicotinic receptor (α7-nAChR) in human squamous cell lung cancer cells via the Sp1/GATA protein pathway

Nicotine, the addictive component of cigarettes, promotes lung cancer proliferation via the α7-nicotinic acetylcholine receptor (α7-nAChR) subtype. The present manuscript explores the effect of nicotine exposure on α7-nAChR levels in squamous cell carcinoma of the lung (SCC-L) in vitro and in vivo. Nicotine (at concentrations present in the plasma of average smokers) increased α7-nAChR levels in human SCC-L cell lines. Nicotine-induced up-regulation of α7-nAChR was confirmed in vivo by chicken chorioallantoic membrane models. We also observed that the levels of α7-nAChR in human SCC-L tumors (isolated from patients who are active smokers) correlated with their smoking history. Nicotine increased the levels of α7-nAChR mRNA and α7-nAChR transcription in human SCC-L cell lines and SCC-L tumors. Nicotine-induced up-regulation of α7-nAChR required GATA4 and GATA6. ChIP assays showed that nicotine induced the binding of GATA4 or GATA6 to Sp1 on the α7-nAChR promoter, thereby inducing its transcription and increasing its levels in human SCC-L. Our data are clinically relevant because SCC-L patients smoked for decades before being diagnosed with cancer. It may be envisaged that continuous exposure to nicotine (in such SCC-L patients) causes up-regulation of α7-nAChRs, which facilitates tumor growth and progression. Our results will also be relevant to many SCC-L patients exposed to nicotine via second-hand smoke, electronic cigarettes, and patches or gums to quit smoking.

In-cell Western™ detection of organic cation transporters in bronchial epithelial cell layers cultured at an air-liquid interface on Transwell(®) inserts

INTRODUCTION

Organic cation transporters (OCT) have been shown to mediate the transport of inhaled drugs in bronchial epithelial cells and might have important physiological functions in the airway epithelium. However, a quantitative method to evaluate OCT protein expression in physiologically relevant airway epithelial cell culture models is currently lacking. In-cell Western™ (ICW) techniques might fill that gap but to date, have only been performed on cells grown on 96 or 384-well microplates.

METHODS

An ICW assay was designed for measuring levels of the different OCT subtypes in intact layers of the human bronchial epithelial Calu-3 cell line cultured at an air-liquid interface on Transwell(®) inserts. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as the internal standard for normalisation of cell number between the layers. The protocol was subsequently validated by exposing cell layers to compounds known to cause variations in OCT expression.

RESULTS

Antibody signals above the background fluorescence were detected for OCT1, OCT3, OCTN1 and OCTN2 but not for OCT2 in 21day old Calu-3 layers, in agreement with previous studies which had reported OCT2 was absent in the Calu-3 cell line. Furthermore, increases in the fluorescence signal associated with OCT1, OCTN1 and OCTN2 were obtained following treatment of the layers with, respectively, the nitric oxide inducer sodium nitroprusside, the peroxisome proliferator activated receptor α (PPARα) agonist fenofibrate or the PPARγ agonist rosiglitazone, confirming the reliability of the ICW method developed. However, a suitable positive control for OCT3 could not be identified.

DISCUSSION

This novel ICW assay can be exploited to quantify basal OCT protein expression as well as changes in transporter levels following external stimuli in various in vitro models. It can also be easily adapted to probe any protein in epithelial layers maintained on permeable filters.

Development of novel approach to diagnostic imaging of lung cancer with 18F-Nifene PET/CT using A/J mice treated with NNK

Development of novel methods of early diagnosis of lung cancer is one of the major tasks of contemporary clinical and experimental oncology. In this study, we utilized the tobacco nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung cancer in A/J mice as an animal model for development of a new imaging technique for early diagnosis of lung cancer. Lung cancer cells in A/J mice overexpress nicotinic acetylcholine receptors. Longitudinal CT scans were carried out over a period of 8 months after NNK treatment, followed by PET/CT scans with 18F-Nifene that binds to α4-made nicotinic receptors with high affinity. PET/CT scans of lungs were also obtained ex vivo. CT revealed the presence of lung nodules in 8-month NNK-treated mice, while control mice had no tumors. Imaging of live animals prior to necropsy allowed correlation of results of tumor load via PET/CT and histopathological findings. Significant amount of 18F-Nifene was seen in the lungs of NNK-treated mice, whereas lungs of control mice showed only minor uptake of 18F-Nifene. Quantitative analysis of the extent and amount of 18F-Nifene binding in lung in vivo and ex vivo demonstrated a higher tumor/nontumor ratio due to selective labeling of tumor nodules expressing abundant α4 nicotinic receptor subunits. For comparison, we performed PET/CT studies with 18F-FDG, which is used for the imaging diagnosis of lung cancer. The tumor/nontumor ratios for 18F-FDG were lower than for 18F-Nifene. Thus, we have developed a novel diagnostic imaging approach to early diagnosis of lung cancer using 18F-Nifene PET/CT. This technique allows quantitative assessment of lung tumors in live mice, which is critical for establishing tumor size and location, and also has salient clinical implications.

The guggulsterone derivative GG-52 inhibits NF-κB signaling in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice

Gastric mucosal inflammation can develop after challenge with noxious stimuli such as alcohol. Specially, alcohol stimulates the release of inflammatory cytokines but does not increase gastric acid secretion, leading to gastric mucosal damage. The plant sterol guggulsterone and its novel derivative GG-52 have been reported to inhibit nuclear factor-κB (NF-κB) signaling in intestinal epithelial cells and experimental colitis. In the present study, we investigated the anti-inflammatory effects of GG-52 on gastric epithelial cells and on ethanol-induced gastric mucosal inflammation in mice. GG-52 inhibited the expression of interleukin-8 (IL-8) in gastric epithelial AGS and MKN-45 cell lines stimulated with tumor necrosis factor (TNF)-α in a dose-dependent manner. Pretreatment with GG-52 suppressed TNF-α-induced activation of IκB kinase (IKK) and NF-κB signaling in MKN-45 cells. In contrast, the inactive analog GG-46 did not produce significant changes in IL-8 expression or NF-κB activation. In a model of ethanol-induced murine gastritis, administration of GG-52 significantly reduced the severity of gastritis, as assessed by macroscopic and histological evaluation of gastric mucosal damage. In addition, the ethanol-induced upregulation of chemokine KC, a mouse homolog of IL-8, and phosphorylated p65 NF-κB signals were significantly inhibited in murine gastric mucosa pretreated with GG-52. These results indicate that GG-52 suppresses NF-κB activation in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice, suggesting that GG-52 may be a potential gastroprotective agent.

The role of Src kinase in macrophage-mediated inflammatory responses

Src kinase (Src) is a tyrosine protein kinase that regulates cellular metabolism, survival, and proliferation. Many studies have shown that Src plays multiple roles in macrophage-mediated innate immunity, such as phagocytosis, the production of inflammatory cytokines/mediators, and the induction of cellular migration, which strongly implies that Src plays a pivotal role in the functional activation of macrophages. Macrophages are involved in a variety of immune responses and in inflammatory diseases including rheumatoid arthritis, atherosclerosis, diabetes, obesity, cancer, and osteoporosis. Previous studies have suggested roles for Src in macrophage-mediated inflammatory responses; however, recently, new functions for Src have been reported, implying that Src functions in macrophage-mediated inflammatory responses that have not been described. In this paper, we discuss recent studies regarding a number of these newly defined functions of Src in macrophage-mediated inflammatory responses. Moreover, we discuss the feasibility of Src as a target for the development of new pharmaceutical drugs to treat macrophage-mediated inflammatory diseases. We provide insights into recent reports regarding new functions for Src that are related to macrophage-related inflammatory responses and the development of novel Src inhibitors with strong immunosuppressive and anti-inflammatory properties, which could be applied to various macrophage-mediated inflammatory diseases.

The ly-6 protein, lynx1, is an endogenous inhibitor of nicotinic signaling in airway epithelium

Our laboratory has previously reported that bronchial epithelial cells (BEC) express a regulatory cascade of classic neurotransmitters and receptors that communicate in an almost neuronal-like manner to achieve physiological regulation. In this paper we show that the similarity between neurotransmitter signaling in neurons and BEC extends to the level of transmitter receptor allosteric modulators. Lynx1 is a member of the ly-6/three-finger superfamily of proteins, many of which modulate receptor signaling activity. Lynx1 specifically has been shown to modulate nicotinic acetylcholine receptor (nAChR) function in neurons by altering receptor sensitivity and desensitization. We now report that lynx1 forms a complex with α7 nAChR in BEC and serves to negatively regulate α7 downstream signaling events. Treatment of primary cultures of BEC with nicotine increased levels of nAChR subunits and that increase was potentiated by lynx1 knockdown. Lynx1 knockdown also potentiated the nicotine-induced increase in GABA(A) receptors (GABA(A)R) and MUC5AC mRNA expression, and that effect was blocked by α7 antagonists and α7 knockdown. In parallel with the increases in nAChR, GABA(A)R, and mucin mRNA levels, lynx1 knockdown also increased levels of p-Src. Consistent with this, inhibition of Src signaling blocked the ability of the lynx1 knockdown to increase basal and nicotine-stimulated GABA(A)R and mucin mRNA expression. Thus lynx1 appears to act as a negative modulator of α7 nAChR-induced events by inhibiting Src activation. This suggests that lynx1 agonists or mimetics are a potentially important therapeutic target to develop new therapies for smoking-related diseases characterized by increased mucin expression.

Nicotine and pathological angiogenesis

This paper describes the role of endothelial nicotinic acetylcholine receptors (nAChR) in diseases where pathological angiogenesis plays a role. An extensive review of the literature was performed, focusing on studies that investigated the effect of nicotine upon angiogenesis. Nicotine induces pathological angiogenesis at clinically relevant concentrations (i.e. at tissue and plasma concentrations similar to those of a light to moderate smoker). Nicotine promotes endothelial cell migration, proliferation, survival, tube formation and nitric oxide (NO) production in vitro, mimicking the effect of other angiogenic growth factors. These in vitro findings indicate that there may be an angiogenic component to the pathophysiology of major tobacco related diseases such as carcinoma, atherosclerosis, and age-related macular degeneration. Indeed, nicotine stimulates pathological angiogenesis in pre-clinical models of these disorders. Subsequently, it has been demonstrated that nicotine stimulates nAChRs on the endothelium to induce angiogenic processes, that these nAChRs are largely of the α7 homomeric type, and that there are synergistic interactions between the nAChRs and angiogenic growth factor receptors at the phosphoproteomic and genomic levels. These findings are of potential clinical relevance, and provide mechanistic insights into tobacco-related disease. Furthermore, these findings may lead to novel therapies for diseases characterized by insufficient or inappropriate angiogenesis.

Effects of chronic nicotine on the autocrine regulation of pancreatic cancer cells and pancreatic duct epithelial cells by stimulatory and inhibitory neurotransmitters

Pancreatic ductal adenocarcinoma (PDAC) has a mortality rate near 100%. Smoking is a documented risk factor. However, the mechanisms of smoking-associated pancreatic carcinogenesis are poorly understood. We have shown that binding of nicotine to nicotinic acetylcholine receptors (nAChRs) expressing subunits α7, α3 and α5 in PDAC and pancreatic duct epithelial cells in vitro triggered the production of the neurotransmitters noradrenaline and adrenaline by these cells. In turn, this autocrine catecholamine loop significantly stimulated cell proliferation via cyclic adenosine 3',5'-monophosphate-dependent signaling downstream of beta-adrenergic receptors. However, the observed responses only represent acute cellular reactions to single doses of nicotine whereas nicotine exposure in smokers is chronic. Using the PDAC cell lines BxPC-3 and Panc-1 and immortalized pancreatic duct epithelial cell line HPDE6-C7, our current experiments reveal a significant sensitization of the nAChR-driven autocrine catecholamine regulatory loop in cells pre-exposed to nicotine for 7 days. The resulting increase in catecholamine production was associated with significant inductions in the phosphorylation of signaling proteins ERK, CREB, Src and AKT, upregulated protein expression of nAChR subunits α3, α4, α5 and α7 and increased responsiveness to nicotine in 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide and cell migration assays. All three cell lines produced the inhibitory neurotransmitter γ-aminobutyric acid, an activity inhibited by gene knockdown of the α4β2nAChR and suppressed by chronic nicotine via receptor desensitization. All of the observed adverse effects of chronic nicotine were reversed by treatment of the cells with γ-aminobutyric acid, suggesting the potential usefulness of this agent for the improvement of PDAC intervention strategies in smokers.

Acetylcholine and the alpha 7 nicotinic receptor: a potential therapeutic target for the treatment of periodontal disease?

OBJECTIVES

The aim of this review is to examine the evidence for a functional cholinergic system operating within the periodontium and determine the evidence for its role in periodontal immunity.

INTRODUCTION

Acetylcholine can influence the immune system via the 'cholinergic anti-inflammatory pathway'. This pathway is mediated by the vagus nerve which releases acetylcholine to interact with the α7 subunit of the nicotinic acetylcholine receptor (α7nAChR) on proximate immuno-regulatory cells. Activation of the α7nAChR on these cells leads to down-regulated expression of pro-inflammatory mediators and thus regulates localised inflammatory responses. The role of the vagus nerve in periodontal pathophysiology is currently unknown. However, non-neuronal cells can also release acetylcholine and express the α7nAChR; these include keratinocytes, fibroblasts, T cells, B cells and macrophages. Therefore, by both autocrine and paracrine methods non-neuronal acetylcholine can also be hypothesised to modulate the localised immune response.

METHODS

A Pubmed database search was performed for studies providing evidence for a functional cholinergic system operating in the periodontium. In addition, literature on the role of the 'cholinergic anti-inflammatory pathway' in modulating the immune response was extrapolated to hypothesise that similar mechanisms of immune regulation occur within the periodontium.

CONCLUSION

The evidence suggests a functional non-neuronal 'cholinergic anti-inflammatory pathway' may operate in the periodontium and that this may be targeted therapeutically to treat periodontal disease.

LG2 agrin mutation causing severe congenital myasthenic syndrome mimics functional characteristics of non-neural (z-) agrin

We describe a severe form of congenital myasthenic syndrome (CMS) caused by two heteroallelic mutations: a nonsense and a missense mutation in the gene encoding agrin (AGRN). The identified mutations, Q353X and V1727F, are located at the N-terminal and at the second laminin G-like (LG2) domain of agrin, respectively. A motor-point muscle biopsy demonstrated severe disruption of the architecture of the neuromuscular junction (NMJ), including: dispersion and fragmentation of endplate areas with normal expression of acetylcholinesterase; simplification of postsynaptic membranes; pronounced reduction of the axon terminal size; widening of the primary synaptic cleft; and, collection of membranous debris material in the primary synaptic cleft and in the subsynaptic cytoplasm. Expression studies in heterologous cells revealed that the Q353X mutation abolished expression of full-length agrin. Moreover, the V1727F mutation decreased agrin-induced clustering of the acetylcholine receptor (AChR) in cultured C2 muscle cells by >100-fold, and phosphorylation of the MuSK receptor and AChR beta subunit by ~tenfold. Surprisingly, the V1727F mutant also displayed increased binding to α-dystroglycan but decreased binding to a neural (z+) agrin-specific antibody. Our findings demonstrate that agrin mutations can associate with a severe form of CMS and cause profound distortion of the architecture and function of the NMJ. The impaired ability of V1727F agrin to activate MuSK and cluster AChRs, together with its increased affinity to α-dystroglycan, mimics non-neural (z-) agrin and are important determinants of the pathogenesis of the disease.

Nicotinic acetylcholine receptor α7 and β4 subunits contribute nicotine-induced apoptosis in periodontal ligament stem cells

Nicotine, a major component of cigarette smoking, is the important risk factor for the development of periodontal disease. However, the mechanisms that underlie the cytotoxicity of nicotine in human periodontal ligament stem cells (PDLSCs) are largely unknown. Thus, the purpose of this study was to determine the cytotoxic effect of nicotine by means of nicotinic acetylcholine receptor (nAChR) activation in PDLSCs. We first detected α7 and β4 nAChRs in PDLSCs. The gene expressions of α7 and β4 nAChR were increased by nicotine administration. Nicotine significantly decreased cell viability at a concentration higher than 10(-5) M. DNA fragmentation was also detected at high doses of nicotine treatment. Moreover, the detection of sub G1 phase and TUNEL assay demonstrated that nicotine significantly induced apoptotic cell death at 10(-2) M concentration. Western blot analysis confirmed that p53 proteins were phosphorylated by nicotine. Under various doses of nicotine, a decrease in the anti-apoptotic protein Bcl-2, but an increase in p53 and cleaved caspase-3 protein levels, was detected in a dose-dependent manner. However, the apoptotic effect of nicotine was inhibited by the pretreatment of α-bungarotoxin, a selective α7 nAChR antagonist or mecamylamine, a non-selective nAChR antagonist. Finally, increases in the subG1 phase and DNA fragmentation by nicotine was attenuated by each nAChR antagonist. Collectively, the presence of α7 and β4 nAChRs in PDLSCs supports a key role of nAChRs in the modulation of nicotine-induced apoptosis.

Expression of calmodulin in germ cells is associated with fenvalerate-induced male reproductive toxicity

Exposure to fenvalerate was demonstrated to be toxic to the male reproductive system. Our previous data revealed that intracellular calcium plays an important role in regulating the above toxicity, through actions on both T-type calcium channels and endoplasmic reticulum calcium signals. The present study explored the effects of fenvalerate on the expression of calmodulin in mouse testis and GC-2spd(ts) cells, and its association with fenvalerate-induced male reproductive toxicity. Male mice were subjected to different doses (3.71, 18.56, 37.12, 92.81 mg/kg bw) of fenvalerate or vehicle control for 4 weeks. Expression of calmodulin was determined by real-time polymerase chain reaction (PCR) and Western blot analysis in mouse testis. Similar approaches were utilized in GC-2spd(ts) cells cultured with 5 μM fenvalerate at different time points. In the in vivo study, all mice survived through the entire 4 weeks. Administration of fenvalerate resulted in a dose-dependent reduction in testis weight/body weight, sperm motility, and increased head abnormality rate. By histological staining, mice treated with fenvalerate at higher doses showed dilated seminiferous tubules and disturbed arrangement of spermatogenic cells. Meanwhile, both mRNA and protein expression of calmodulin were significantly increased in the testes of mice exposed to fenvalerate compared to control mice. Moreover, in the in vitro study, 5 μM fenvalerate significantly increased the expression of calmodulin at the mRNA and protein levels in GC-2spd(ts) cells after 8 h of incubation and sustained these levels for at least 24 h. Collectively, these data suggested that enhanced expression of calmodulin correlates with male reproductive damage induced by fenvalerate.

Sensitization of epithelial growth factor receptors by nicotine exposure to promote breast cancer cell growth

Introduction

Tobacco smoke is known to be the main cause of lung, head and neck tumors. Recently, evidence for an increasing breast cancer risk associated with tobacco smoke exposure has been emerging. We and other groups have shown that nicotine, as a non-conventional carcinogen, has the potential to facilitate cancer genesis and progression. However, the underlying mechanisms by which the smoke affects the breast, rather than the lung, remain unclear. Here, we examine possible downstream signaling pathways of the nicotinic acetylcholine receptor (nAChR) and their role in breast cancer promotion.

Methods

Using human benign MCF10A and malignant MDA-MB-231 breast cells and specific inhibitors of possible downstream kinases, we identified nAChR effectors that were activated by treatment with nicotine. We further tested the effects of these effector pathways on the regulation of E2F1 activation, cell cycle progression and on Bcl-2 expression and long-term cell survival.

Results

In this study, we demonstrated a novel signaling mechanism by which nicotine exposure activated Src to sensitize epidermal growth factor receptor (EGFR)-mediated pathways for breast cancer cell growth promotion. After the ligation of nAChR with nicotine, EGFR was shown to be activated and then internalized in both MCF10A and MDA-MB-231 breast cancer cells. Subsequently, Src, Akt and ERK1/2 were phosphorylated at different time points following nicotine treatment. We further demonstrated that through Src, the ligation of nicotine with nAChR stimulated the EGFR/ERK1/2 pathway for the activation of E2F1 and further cell progression. Our data also showed that Akt functioned directly downstream of Src and was responsible for the increase of Bcl-2 expression and long-term cell survival.

Conclusions

Our study reveals the existence of a potential, regulatory network governed by the interaction of nicotine and nAChR that integrates the conventional, mitogenic Src and EGFR signals for breast cancer development.

Chaperoning α7 neuronal nicotinic acetylcholine receptors

The α7 subtype of nicotinic acetylcholine receptors (AChRs) is one of the most abundant members of the Cys-loop family of receptors present in the central nervous system. It participates in various physiological processes and has received much attention as a potential therapeutic target for a variety of pathologies. The importance of understanding the mechanisms controlling AChR assembly and cell-surface delivery lies in the fact that these two processes are key to determining the functional pool of receptors actively engaged in synaptic transmission. Here we review recent studies showing that RIC-3, a protein originally identified in the worm Caenorhabditis elegans, modulates the expression of α7 AChRs in a subtype-specific manner. Potentiation of AChR expression by post-transcriptional events is also critically assessed.

Effects of cigarette smoke residues from textiles on fibroblasts, neurocytes and zebrafish embryos and nicotine permeation through human skin

Toxic substances from cigarette smoke can attach to carpets, curtains, clothes or other surfaces and thus may pose risks to affected persons. The phenomenon itself and the potential hazards are discussed controversially, but scientific data are rare. The objective of this study was to examine the potential of textile-bound nicotine for permeation through human skin and to assess the effects of cigarette smoke extracts from clothes on fibroblasts, neurocytes and zebrafish embryos. Tritiated nicotine from contaminated cotton textiles penetrated through adult human full-thickness skin as well as through a 3D in vitro skin model in diffusion chambers. We also observed a significant concentration-dependent cytotoxicity of textile smoke extracts on fibroblast viability and structure as well as on neurocytes. Early larval tests with zebrafish embryos were used as a valid assay for testing acute vertebrate toxicity. Zebrafish development was delayed and most of the embryos died when exposed to smoke extracts from textiles. Our data show that textiles contaminated with cigarette smoke represent a potential source of nicotine uptake and can provoke adverse health effects.

Chronic exposure to cigarette smoke increases matrix metalloproteinases and Filaggrin mRNA expression in oral keratinocytes: role of nicotine stimulation

The vegetal alkaloid nicotine has been proved to modify the expression of many keratinocyte markers. In this study, the basal expression of MMP-2, MMP-9, MMP-28, and Filaggrin has been evaluated in oral keratinocytes, in order to collect information about the ability of cigarette smoke to modify the basal expression pattern of these key enzymes in the absence of evident clinical signs in the oral epithelium. MMP-2, MMP-9, MMP-28, and Filaggrin basal expression was investigated by RT-PCR in oral keratinocytes derived from smokers (n=11), non-smokers (n=11), and ex-smokers (n=6) healthy volunteers. Moreover keratinocytes from non-smokers volunteers were stimulated in vitro by a single dose administration of nicotine (10 μM) in order to estimate the effect of nicotinic receptors activation on the basal expression of the studied markers. RT-PCR analysis showed that all the markers studied were overexpressed in keratinocytes from smoker donors compared to control keratinocytes, while a single dose of nicotine was able to induce only Filaggrin expression in keratinocytes from non-smoking donors. Markers expression in ex-smoker donors was similar to that observed in normal non-smoker donors. These data indicate for the first time that cigarette smoking affects basal expression of some important markers in oral mucosa keratinocytes in vivo in the absence of clinical signs and that smoke quitting restores basal expression levels of these markers.

From smoking to cancers: novel targets to neuronal nicotinic acetylcholine receptors

Cigarette smoking bears a strong etiological association with many neovascularization-related diseases, including cancer, cardiovascular disease, and age-related macular degeneration. Cigarette smoke is a complex mixture of many compounds, including nicotine, which is the major active and addictive component of tobacco. Nicotine and its specific metabolized carcinogens directly bind to nicotinic acetylcholine receptors (nAChRs) on cell membranes and trigger the nAChR signal cascade. The nAChRs were originally thought to be ligand-gated ion channels that modulate physiological processes ranging from neurotransmission to cancer signaling. For several decades, the nAChRs served as a prototypic molecule for neurotransmitter receptors; however, they are now important therapeutic targets for various diseases, including Alzheimer's and Parkinson's diseases, schizophrenia, and even cancer. This paper describes recent advances in our understanding of the assembly, activity, and biological functions of nicotinic receptors, as well as developments in the therapeutic application of nicotinic receptor ligands.

A sex-specific association between a 15q25 variant and upper aerodigestive tract cancers

BACKGROUND

Sequence variants located at 15q25 have been associated with lung cancer and propensity to smoke. We recently reported an association between rs16969968 and risk of upper aerodigestive tract (UADT) cancers (oral cavity, oropharynx, hypopharynx, larynx, and esophagus) in women (OR = 1.24, P = 0.003) with little effect in men (OR = 1.04, P = 0.35).

METHODS

In a coordinated genotyping study within the International Head and Neck Cancer Epidemiology (INHANCE) consortium, we have sought to replicate these findings in an additional 4,604 cases and 6,239 controls from 10 independent UADT cancer case-control studies.

RESULTS

rs16969968 was again associated with UADT cancers in women (OR = 1.21, 95% CI = 1.08-1.36, P = 0.001) and a similar lack of observed effect in men [OR = 1.02, 95% CI = 0.95-1.09, P = 0.66; P-heterogeneity (P(het)) = 0.01]. In a pooled analysis of the original and current studies, totaling 8,572 UADT cancer cases and 11,558 controls, the association was observed among females (OR = 1.22, 95% CI = 1.12-1.34, P = 7 × 10(-6)) but not males (OR = 1.02, 95% CI = 0.97-1.08, P = 0.35; P(het) = 6 × 10(-4)). There was little evidence for a sex difference in the association between this variant and cigarettes smoked per day, with male and female rs16969968 variant carriers smoking approximately the same amount more in the 11,991 ever smokers in the pooled analysis of the 14 studies (P(het) = 0.86).

CONCLUSIONS

This study has confirmed a sex difference in the association between the 15q25 variant rs16969968 and UADT cancers.

IMPACT

Further research is warranted to elucidate the mechanisms underlying these observations.

Markers in the 15q24 nicotinic receptor subunit gene cluster (CHRNA5-A3-B4) predict severity of nicotine addiction and response to smoking cessation therapy

Stopping smoking is difficult even with treatment. Many patients prescribed pharmacologic treatments for smoking cessation experience side effects or lack of efficacy. We performed a pharmacogenetic study of the efficacy and tolerability of bupropion and transdermal nicotine (TN), two treatments for smoking cessation. Samples were drawn from two studies. In the first study (Maintenance 1, MT1), 301 smokers received bupropion plus TN for 11 weeks, followed by 14 weeks of placebo or bupropion. In the second study (MT2), 276 smokers received bupropion and TN for 8 weeks. We focused on eight SNPs in the 15q24 region, which contains the genes for the nicotinic cholinergic receptor subunits CHRNA5, CHRNA3, and CHRNB4, and has previously been implicated in nicotine addiction and smoking cessation. Analyses of baseline smoking quantity (SQ) identified an association between SQ and both the functional CHRNA5 SNP rs16969968 (D398N) and the CHRNA3 SNP rs1051730 (Y215Y) in a combined cohort containing MT1 and MT2. An association between SQ and ethnicity was also identified in the combined cohort. Pharmacogenetic analysis showed a significant association between rs8192475 (R37H) in CHRNA3 and both higher craving after quitting and increased withdrawal symptoms over time in MT2. Two markers for point prevalence abstinence, CHRNA5 SNP rs680244 and CHRNB4 SNP rs12914008, were also identified in MT2, with the strongest findings at week 52. These results provide further support for the role of the CHRNA5/A3/B4 subunits in determining number of cigarettes smoked and response to smoking cessation therapy.

Nicotinic acetylcholine receptor signaling in tumor growth and metastasis

Cigarette smoking is highly correlated with the onset of a variety of human cancers, and continued smoking is known to abrogate the beneficial effects of cancer therapy. While tobacco smoke contains hundreds of molecules that are known carcinogens, nicotine, the main addictive component of tobacco smoke, is not carcinogenic. At the same time, nicotine has been shown to promote cell proliferation, angiogenesis, and epithelial-mesenchymal transition, leading to enhanced tumor growth and metastasis. These effects of nicotine are mediated through the nicotinic acetylcholine receptors that are expressed on a variety of neuronal and nonneuronal cells. Specific signal transduction cascades that emanate from different nAChR subunits or subunit combinations facilitate the proliferative and prosurvival functions of nicotine. Nicotinic acetylcholine receptors appear to stimulate many downstream signaling cascades induced by growth factors and mitogens. It has been suggested that antagonists of nAChR signaling might have antitumor effects and might open new avenues for combating tobacco-related cancer. This paper examines the historical data connecting nicotine tumor progression and the recent efforts to target the nicotinic acetylcholine receptors to combat cancer.

Plasticity of the murine spleen T-cell cholinergic receptors and their role in in vitro differentiation of naïve CD4 T cells toward the Th1, Th2 and Th17 lineages

Acetylcholine (ACh) regulates vital functions of T cells by acting on the nicotinic and muscarinic classes of cholinergic receptors, nAChR and mAChRs, respectively. This study was performed in murine splenic T cells. In freshly isolated CD4 and CD8 T cells, we detected mRNAs encoding α5, α9, α10, β1, β2, β4 nAChR subunits and M₁, M₃, M₄ and M₅ mAChR subtypes, whereas α2 was detected only in CD8 T cells. In vitro activation of CD4 T cells through T-cell receptor (TCR)/CD3 cross-linking was associated with the appearance of α4 and α7, upregulation of α5, α10, β4, M₁ and M₅ and downregulation of α9 and β2, whereas in vitro activation of CD8 T cells also featured the appearance of α4 and α7, as well as upregulation of α2, α5, β4, M₁ and M₄, and downregulation of α10, β1, β2 and M₃. In vitro polarization toward T helper (Th) 1 lineage was associated with a decrease of β2, β4 and M₃ expression; that toward Th2 cells with downregulation of α9 and M₃, and upregulation of M₁ and M₅; and that toward Th17 phenotype with downregulation of α9, α10, β2 and M₃ mAChR. Polarized T cells also expressed α4, but not α1, α2, α3, α6, β3 or M₂. To determine the role of cholinergic receptors in mediating the immunoregulatory action of autocrine/paracrine ACh, we analyzed the effects of nicotinic and muscarinic agonists±antagonists on cytokine production in the CD4+CD62L+ T cells co-stimulated via TCR/CD3 cross-linking. The nicotinergic stimulation upregulated interferon-γ (IFN-γ) and downregulated interleukin (IL)-17 secretion, whereas the muscarinic stimulation enhanced IL-10 and IL-17 and inhibited INF-γ secretion. These results demonstrated plasticity of the T-cell cholinergic system.

Nicotine induces upregulated expression of beta defensin-2 via the p38MAPK pathway in the HaCaT human keratinocyte cell line

Human beta-defensins (hBDs), a group of antimicrobial peptides, are involved in the protective barrier of the oral epithelium. Nicotine induces periodontal and oral epithelial diseases. The purpose of the present study was to investigate the effect of nicotine on the expression pattern of hBD-2 in keratinocytes. HaCaT cells, a keratinocyte cell line, were incubated with 8, 15, 30, or 80 μM nicotine for 24 h. Expression of hBD-2 was observed by RT-PCR, qRTPCR, and ELISA assay. The cells were treated with inhibitors for intracellular pathways (p38MAP kinase, NF-κB, JNK, MAPK-ERK) and with nicotinic acetylcholine receptor (nAChR) inhibitors in a series of experiments. Data were analyzed using Student's t test. qRT-PCR revealed that the expression level of hBD-2 mRNA was significantly higher at 30 and 80 μM nicotine than the control without nicotine (P < 0.05). The 80 μM cell extraction contained significantly higher hBD-2 peptide levels than the control (P < 0.05). The p38MAP kinase inhibitor abolished the upregulated expression of hBD-2 by nicotine. Both nAChR inhibitors also abolished the upregulation of hBD-2 by nicotine. The present study demonstrated that nicotine causes upregulated expression of hBD-2 via the p38MAP kinase pathway in keratinocytes.