Nicotine-induced phosphorylation of Akt through epidermal growth factor receptor and Src in PC12h cells

Prognostic significance of tetraspanin CD9 and oncogenic epidermal growth factor receptor in tongue squamous cell carcinoma survival

The most prevalent locations for head and neck cancer is the tongue. The surviving patients who are receiving therapy have considerably compromised speech, taste, chewing, and swallowing. CD9 is a cell surface protein that has contradictory role in cancer progression. The objective of the study is to analyze the Cluster of Differentiation 9(CD9), Epidermal Growth Factor Receptor (EGFR) and Phosphorylated Akt (p-Akt) expression in tongue cancer specimens and its clinical significance.50 tongue cancer sections were used to analyze the expression of CD9,EGFR and p-Akt by immunohistochemistry. Data regarding the histological grade of the tumor, age, sex, and habits were recorded, and relation with CD9,EGFR and p-Akt expression was assessed. Data were expressed as mean ± SEM. Categorical data was analyzed by Chi-square test. Student t-test was used to check the significance of data between two groups.A significant increase in the CD9,EGFR and p-Akt expression (1.8 ± 0.11, 2.06 ± 0.18 and 2.3 ± 0.15 respectively) was seen in the tongue cancer specimens. CD9 and p-Akt expression had a significant association with the histological grade (p < 0.004 and p < 0.006 respectively). CD9 expression was higher in patients with the combination of addiction/habit compared to patients with single addictions(1.08 ± 0.11 and 0.75 ± 0.47). Overall a poor rate of survival was observed in CD9 positive patients(p < 0.039). EGFR and p-Akt expression increased with increasing expression of CD9, suggesting its use as a biomarker to track the development of TSCC.

Reducing Chemotherapy-Induced DNA Damage via nAChR-Mediated Redox Reprograming-A New Mechanism for SCLC Chemoresistance Boosted by Nicotine

Up to 60% of patients with small cell lung cancer (SCLC) continue to smoke, which is associated with worse clinical outcomes. Platinum-based chemotherapies, in combination with topoisomerase inhibitors, are first-line therapies for SCLC, with rapid chemoresistance as a major barrier. We provided evidence in this study that nicotine and its major metabolite, cotinine, at physiologically relevant concentrations, reduced the efficacy of platinum-based chemotherapies and facilitated chemoresistance in SCLC cells. Mechanistically, nicotine or cotinine reduced chemotherapy-induced DNA damage by modulating cellular redox processes, with nAChRs as the upstream targets. Surprisingly, cisplatin treatment alone also increased the levels of nAChRs in SCLC cells, which served as a self-defense mechanism against platinum-based therapies. These discoveries were confirmed in long-term in vitro and in vivo studies. Collectively, our results depicted a novel and clinically important mechanism of chemoresistance in SCLC treatment: nicotine exposure significantly compromises the efficacy of platinum-based chemotherapies in SCLC treatment by reducing therapy-induced DNA damage and accelerating chemoresistance acquisition. The results also emphasized the urgent need for tobacco cessation and the control of NRT use for SCLC management.

A Synthetic Small RNA Homologous to the D-Loop Transcript of mtDNA Enhances Mitochondrial Bioenergetics

Mitochondrial malfunction is a hallmark of many diseases, including neurodegenerative disorders, cardiovascular and lung diseases, and cancers. We previously found that alveolar progenitor cells, which are more resistant to cigarette smoke-induced injury than the other cells of the lung parenchyma, upregulate the mtDNA-encoded small non-coding RNA mito-ncR-805 after exposure to smoke. The mito-ncR-805 acts as a retrograde signal between the mitochondria and the nucleus. Here, we identified a region of mito-ncR-805 that is conserved in the mammalian mitochondrial genomes and generated shorter versions of mouse and human transcripts (mmu-CR805 and hsa-LDL1, respectively), which differ in a few nucleotides and which we refer to as the "functional bit". Overexpression of mouse and human functional bits in either the mouse or the human lung epithelial cells led to an increase in the activity of the Krebs cycle and oxidative phosphorylation, stabilized the mitochondrial potential, conferred faster cell division, and lowered the levels of proapoptotic pseudokinase, TRIB3. Both oligos, mmu-CR805 and hsa-LDL1 conferred cross-species beneficial effects. Our data indicate a high degree of evolutionary conservation of retrograde signaling via a functional bit of the D-loop transcript, mito-ncR-805, in the mammals. This emphasizes the importance of the pathway and suggests a potential to develop this functional bit into a therapeutic agent that enhances mitochondrial bioenergetics.

Repurposing calcium channel blockers: may be sensible combination with erlotinib for non-small cell lung cancer

Erlotinib is a tyrosine kinase inhibitor that inhibits epidermal growth factor receptor. It is being used for metastatic non-small cell lung cancer patients (NSCLC). Repurposing noncancer drugs for cancer treatment is a current issue and it has many advantages. We planned to reveal the effects of noncancer drugs [calcium channel blockers (CCBs) and others] on erlotinib. We scanned the files of NSCLC patients retrospectively who were applied to Karadeniz Technical University between January 2013 and April 2019 and used erlotinib. There were 63 patients, 9 of them were taking CCB simultaneously for arterial hypertension. We analyzed some parameters of these patients and their effects on overall survival (OS) and progression-free survival (PFS). A χ2 or Fisher's exact test, Kaplan-Meier and Cox regressions were used in the statistical analysis. 12-month OS rates of CCB user and nonuser were 78.3 and 39.7%, respectively, [odds ratio (OR),0.14; 95% confidence interval (CI), 0.27-0.75; P = 0.023]. 24-month PFS rates of CCB user and nonuser were 44.4 and 8.3%, respectively (OR,0.11; 95% CI, 0.02-0.60; P = 0.016). There was 12-month OS and 24-month PFS advantage with simultaneously taking CCBs and erlotinib, they have an additive effect for NSCLC. This study will be inspiring future prospective studies.

Retrograde signaling by a mtDNA-encoded non-coding RNA preserves mitochondrial bioenergetics

Alveolar epithelial type II (AETII) cells are important for lung epithelium maintenance and function. We demonstrate that AETII cells from mouse lungs exposed to cigarette smoke (CS) increase the levels of the mitochondria-encoded non-coding RNA, mito-RNA-805, generated by the control region of the mitochondrial genome. The protective effects of mito-ncR-805 are associated with positive regulation of mitochondrial energy metabolism, and respiration. Levels of mito-ncR-805 do not relate to steady-state transcription or replication of the mitochondrial genome. Instead, CS-exposure causes the redistribution of mito-ncR-805 from mitochondria to the nucleus, which correlated with the increased expression of nuclear-encoded genes involved in mitochondrial function. These studies reveal an unrecognized mitochondria stress associated retrograde signaling, and put forward the idea that mito-ncRNA-805 represents a subtype of small non coding RNAs that are regulated in a tissue- or cell-type specific manner to protect cells under physiological stress.

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.

An Integrated Genomic Strategy to Identify CHRNB4 as a Diagnostic/Prognostic Biomarker for Targeted Therapy in Head and Neck Cancer

Although many studies have shown the association between smoking and the increased incidence and adverse prognosis of head and neck squamous cell carcinoma (HNSCC), the mechanisms and pharmaceutical targets involved remain unclear. Here, we integrated gene expression signatures, genetic alterations, and survival analyses to identify prognostic indicators and therapeutic targets for smoking HNSCC patients, and we discovered that the FDA-approved drug varenicline inhibits the target for cancer cell migration/invasion. We first identified 18 smoking-related and prognostic genes for HNSCC by using RNA-Seq and clinical follow-up data. One of these genes, CHRNB4 (neuronal acetylcholine receptor subunit beta-4), increased the risk of death by approximately threefold in CHRNB4-high expression smokers compared to CHRNB4-low expression smokers (log rank, p = 0.00042; hazard ratio, 2.82; 95% CI, 1.55–5.14), former smokers, and non-smokers. Furthermore, we examined the functional enrichment of co-regulated genes of CHRNB4 and its 246 frequently occurring copy number alterations (CNAs). We found that these genes were involved in promoting angiogenesis, resisting cell death, and sustaining proliferation, and contributed to much worse outcomes for CHRNB4-high patients. Finally, we performed CHRNB4 gene editing and drug inhibition assays, and the results validate these observations. In summary, our study suggests that CHRNB4 is a prognostic indicator for smoking HNSCC patients and provides a potential new therapeutic drug to prevent recurrence or distant metastasis.

Nicotinic Agonist Inhibits Cardiomyocyte Apoptosis in CVB3-Induced Myocarditis via α3β4-nAChR/PI3K/Akt-Dependent Survivin Upregulation

Background

Cardiomyocyte apoptosis is critical for the development of coxsackievirus B3- (CVB3-) induced myocarditis, which is a common cardiac disease that may result in heart failure or even sudden death. Previous studies have associated CVB3-induced apoptosis with the downregulation of antiapoptotic proteins. Here, attempts were made to examine whether nicotinic acetylcholine receptors (nAChRs), especially α3β4-nAChRs, were a novel therapeutic antiapoptotic target via the activation of survivin, a strong antiapoptotic protein, in viral myocarditis (VMC).

Methods and Results

In the present study, we demonstrated that nAChRs, α3β4-nAChR subunits in particular, were present and upregulated in CVB3-infected neonatal rat cardiomyocytes (NRC) and H9c2 cells by RT-qPCR. The function of α3β4-nAChRs was next examined using its specific blocker α-CTX AuIB in vitro. The results of the TUNEL assay and western blot experiments showed that the block of α3β4-nAChRs abrogated nicotine-mediated protection of NRC from CVB3-induced apoptosis, and this effect displayed a substantial correlation with the protein expressions of pAkt, survivin, and Cleaved Caspase-3. Hence, the involvement of the PI3K/Akt pathway was further verified by LY294002, a selective inhibitor of PI3K. As a result, nicotine-mediated induction of pAkt and survivin was abolished by LY294002; meanwhile, apoptotic NRC were increased accompanied by an increase of Cleaved Caspase-3 expression. Regarding CVB3-infected BALB/c mice, the α-CTX AuIB- and LY294002-treated groups had a lower survival rate, deteriorative ventricular systolic function, and more severe inflammation than the nicotine-treated group and the modulation of pAkt, survivin, and Cleaved Caspase-3 protein expressions was similar to that in CVB3-infected NRC. In addition, we found that a nicotinic agonist reduced CVB3 replication in a dose-dependent manner in vitro, which indicates that nAChR activation may serve as a possible protection mechanism of CVB3-induced myocarditis.

Conclusions

Our study demonstrated that α3β4-nAChR subunits are essential in the nicotine-mediated antiapoptotic effect of protecting cardiomyocytes from CVB3-induced apoptosis in vivo and in vitro. This protection correlated with the PI3K/Akt pathway and the inducement of the antiapoptotic protein survivin. A combination of these mechanisms serves as a novel protective response to treat viral myocarditis.

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.

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.

Molecular Mechanism: ERK Signaling, Drug Addiction, and Behavioral Effects

Addiction to psychostimulants has been considered as a chronic psychiatric disorder characterized by craving and compulsive drug seeking and use. Over the past two decades, accumulating evidence has demonstrated that repeated drug exposure causes long-lasting neurochemical and cellular changes that result in enduring neuroadaptation in brain circuitry and underlie compulsive drug consumption and relapse. Through intercellular signaling cascades, drugs of abuse induce remodeling in the rewarding circuitry that contributes to the neuroplasticity of learning and memory associated with addiction. Here, we review the role of the extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase, and its related intracellular signaling pathways in drug-induced neuroadaptive changes that are associated with drug-mediated psychomotor activity, rewarding properties and relapse of drug seeking behaviors. We also discuss the neurobiological and behavioral effects of pharmacological and genetic interferences with ERK-associated molecular cascades in response to abused substances. Understanding the dynamic modulation of ERK signaling in response to drugs may provide novel molecular targets for therapeutic strategies to drug addiction.

Prefrontal microRNA-221 Mediates Environmental Enrichment-Induced Increase of Locomotor Sensitivity to Nicotine

BACKGROUND

Environmental enrichment alters susceptibility in developing drug addiction. We have demonstrated that rats raised in an enriched condition are more sensitive than rats raised in an impoverished condition to nicotine-induced locomotor activity, and this is associated with alterations of phosphorylated extracellular signal-regulated kinase 1/2 within the prefrontal cortex. This study determined the impact of microRNA-221 in the prefrontal cortex on phosphorylated extracellular signal-regulated kinase 1/2 and the enriched environment-dependent behavioral changes in response to nicotine.

METHODS

A microRNA array was conducted to profile microRNA expression in the prefrontal cortex of enriched condition and impoverished condition rats in response to repeated nicotine (0.35 mg/kg, s.c.) administration. microRNA-221 in the prefrontal cortex, nucleus accumbens, and striatum was further verified by quantitative real-time PCR. Lentiviral-mediated overexpression of microRNA-221 in PC12 cells and the medial prefrontal cortex was performed to determine the effects of microRNA-221 on nicotine-mediated phosphorylated extracellular signal-regulated kinase 1/2, phosphorylated cAMP-response element-binding protein, and locomotor activity.

RESULTS

microRNA-221 was profoundly upregulated in the prefrontal cortex but not in nucleus accumbens and striatum of enriched condition rats relative to impoverished condition rats following repeated administration of nicotine. Overexpression of lentiviral-microRNA-221 attenuated nicotine-induced increase in phosphorylated extracellular signal-regulated kinase 1/2 in PC12 cells. Lentiviral-microRNA-221 overexpression in the medial prefrontal cortex further increased locomotor activity in impoverished condition but not in enriched condition rats in response to repeated nicotine administration. Accordingly, lentiviral-microRNA-221 attenuated nicotine-induced increases in phosphorylated extracellular signal-regulated kinase 1/2 and phosphorylated cAMP-response element-binding protein in the medial prefrontal cortex of impoverished condition but not enriched condition rats.

CONCLUSION

These findings suggest that environmental enrichment, via upregulation of prefrontal microRNA-221 expression, suppresses the nicotine-induced activation of extracellular signal-regulated kinase and cAMP-response element-binding protein, which provides a potential mechanism underlying enhanced locomotor sensitivity to nicotine.

Nicotinic acetylcholine receptors in glucose homeostasis: the acute hyperglycemic and chronic insulin-sensitive effects of nicotine suggest dual opposing roles of the receptors in male mice

Cigarette smoking causes insulin resistance. However, nicotine induces anti-inflammation and improves glucose tolerance in insulin-resistant animal models. Here, we determined the effects of nicotine on glucose metabolism in insulin-sensitive C57BL/J6 mice. Acute nicotine administration (30 min) caused fasting hyperglycemia and lowered insulin sensitivity acutely, which depended on the activation of nicotinic-acetylcholine receptors (nAChRs) and correlated with increased catecholamine secretion, nitric oxide (NO) production, and glycogenolysis. Chlorisondamine, an inhibitor of nAChRs, reduced acute nicotine-induced hyperglycemia. qRT-PCR analysis revealed that the liver and muscle express predominantly β4 > α10 > α3 > α7 and β4 > α10 > β1 > α1 mRNA for nAChR subunits respectively, whereas the adrenal gland expresses β4 > α3 > α7 > α10 mRNA. Chronic nicotine treatment significantly suppressed expression of α3-nAChR (predominant peripheral α-subunit) in liver. Whereas acute nicotine treatment raised plasma norepinephrine (NE) and epinephrine (Epi) levels, chronic nicotine exposure raised only Epi. Acute nicotine treatment raised both basal and glucose-stimulated insulin secretion (GSIS). After chronic nicotine treatment, basal insulin level was elevated, but GSIS after acute saline or nicotine treatment was blunted. Chronic nicotine exposure caused an increased buildup of NO in plasma and liver, leading to decreased glycogen storage, along with a concomitant suppression of Pepck and G6Pase mRNA, thus preventing hyperglycemia. The insulin-sensitizing effect of chronic nicotine was independent of weight loss. Chronic nicotine treatment enhanced PI-3-kinase activities and increased Akt and glycogen synthase kinase (GSK)-3β phosphorylation in an nAChR-dependent manner coupled with decreased cAMP response element-binding protein (CREB) phosphorylation. The latter effects caused suppression of Pepck and G6Pase gene expression. Thus, nicotine causes both insulin resistance and insulin sensitivity depending on the duration of the treatment.

The pro-proliferative effects of nicotine and its underlying mechanism on rat airway smooth muscle cells

Recent studies have shown that nicotine, a major component of cigarette smoke, can stimulate the proliferation of non-neuronal cells. Cigarette smoking can promote a variety of pulmonary and cardiovascular diseases, such as chronic obstructive pulmonary disease (COPD), atherosclerosis, and cancer. A predominant feature of COPD is airway remodeling, which includes increased airway smooth muscle (ASM) mass. The mechanisms underlying ASM remodeling in COPD have not yet been fully elucidated. Here, we show that nicotine induces a profound and time-dependent increase in DNA synthesis in rat airway smooth muscle cells (RASMCs) in vitro. Nicotine also significantly increased the number of RASMCs, which was associated with the increased expression of Cyclin D1, phosphorylation of the retinoblastoma protein (RB) and was dependent on the activation of Akt. The activation of Akt by nicotine occurred within minutes and depended upon the nicotinic acetylcholine receptors (nAchRs). Activated Akt increased the phosphorylation of downstream substrates such as GSK3β. Our data suggest that the binding of nicotine to the nAchRs on RASMCs can regulate cellular proliferation by activating the Akt pathway.

Nicotine increases the resistance of lung cancer cells to cisplatin through enhancing Bcl-2 stability

Background:

Nicotine is able to activate mitogenic signalling pathways, which promote cell growth or survival as well as increase chemoresistance of cancer cells. However, the underlying mechanisms are not fully understood.

Methods:

In this study, we used immunoblotting and immunoprecipitation methods to test the ubiquitination and degradation of Bcl-2 affected by nicotine in lung cancer cells. Apoptotic assay was also used to measure the antagonising effect of nicotine on cisplatin-mediated cytotoxicity.

Results:

We demonstrated that the addition of nicotine greatly attenuated Bcl-2 ubiquitination and degradation, which further desensitised lung cancer cells to cisplatin-induced cytotoxicity. In this process, Bcl-2 was persistently phosphorylated in the cells cotreated with nicotine and cisplatin. Furthermore, Akt was proven to be responsible for sustained activation of Bcl-2 by nicotine, which further antagonised cisplatin-mediated apoptotic signalling.

Conclusions:

Our study suggested that nicotine activates its downstream signalling to interfere with the ubiquitination process and prevent Bcl-2 from being degraded in lung cancer cells, resulting in the increase of chemoresistance.

Nicotine induces resistance to epidermal growth factor receptor tyrosine kinase inhibitor by α1 nicotinic acetylcholine receptor-mediated activation in PC9 cells

INTRODUCTION

Nicotine, the major component among the 4000 identified chemicals in cigarette smoke, binds to nicotinic acetylcholine receptors (nAChRs) on non-small-cell lung cancer (NSCLC) cells and regulates cellular proliferation by activating mitogen-activated protein kinases [AQ: MAPK has been expanded to mitogen-activated protein kinases. Please approve.]and PI3K/Akt pathways. In patients with smoking-related lung cancer who continue smoking, the anticancer effect of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) is weaker than that in nonsmokers; however, the precise reason for this difference remains unclear. We investigated the role of α1 nAChR subunit in this phenomenon.

METHODS

We screened for α1 nAChR mRNA in three NSCLC cell lines and analyzed the protein in resected primary NSCLC tissues. We used Western blot and RNA interference (siRNA) methodology to confirm the results.

RESULTS

We determined that α1 nAChR plays an essential role in nicotine-induced cell signaling and nicotine-induced resistance to EGFR-TKI. In addition, we showed that silencing of α1 nAChR subunit in NSCLC may suppress the nicotine-induced resistance to EGFR-TKI.

CONCLUSIONS

These results further implicate nicotine in lung carcinogenesis, and suggest that α1 nAChR may be a biomarker for EGFR-TKI treatment and also a personalizing target molecule for patients with smoking-related lung cancer.

Nitric oxide enhances increase in cytosolic Ca(2+) and promotes nicotine-triggered MAPK pathway in PC12 cells

The purpose of this study was to investigate the roles of neuronal nitric oxide synthase (nNOS), Ca(2+)/calmodulin (CaM)-dependent protein kinases (CaMKs), and protein kinase C (PKC) in nicotine-induced extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) activation. Treatment with nicotine stimulated ERK1/2 and p38 MAPK phosphorylation in the PC12 cells expressing nNOS (NPC12 cells) as compared with that in control PC12 cells. An inhibitor of L-type voltage-sensitive Ca(2+) channel suppressed the nicotine-induced phosphorylation of p38 MAPK. The inhibition of CaMK-kinase, the upstream activator of CaMKI and CaMKIV, did not inhibit the enhanced their phosphorylation. ERK1/2 phosphorylation was attenuated by inhibitors of p38 MAPK, PKC, and MAPK-kinase 1/2, indicating the involvement of these protein kinases upstream of ERK1/2. Furthermore, we found that nNOS expression enhances the nicotine-induced increase in the intracellular concentration of Ca(2+), using the Ca(2+)-sensitive fluorescent probe Fura2. These data suggest that NO promotes nicotine-triggered Ca(2+) transient in PC12 cells to activate possibly CaMKII, leading to sequential phosphorylation of p38 MAPK and ERK1/2.

Aberrantly activated EGFR contributes to enhanced IL-8 expression in COPD airways epithelial cells via regulation of nuclear FoxO3A

BACKGROUND

Decreased activity of forkhead transcription factor class O (FoxO)3A, a negative regulator of NF-κB-mediated chemokine expression, is implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Previously, we showed that quercetin reduces lung inflammation in a murine model of COPD. Here, we examined the mechanisms underlying decreased FoxO3A activation and its modulation by quercetin in COPD human airway epithelial cells and in a COPD mouse model.

METHODS

Primary COPD and normal human airway epithelial cells were treated with quercetin, LY294002 or erlotinib for 2 weeks. IL-8 was measured by ELISA. FoxO3A, Akt, and epidermal growth factor (EGF) receptor (EGFR) phosphorylation and nuclear FoxO3A levels were determined by Western blot analysis. Effects of quercetin on lung chemokine expression, nuclear FoxO3A levels and phosphorylation of EGFR and Akt were determined in COPD mouse model.

RESULTS

Compared with normal, COPD cells showed significantly increased IL-8, which negatively correlated with nuclear FoxO3A levels. COPD bronchial biopsies also showed reduced nuclear FoxO3A. Decreased FoxO3A in COPD cells was associated with increased phosphorylation of EGFR, Akt and FoxO3A and treatment with quercetin, LY294002 or erlotinib increased nuclear FoxO3A and decreased IL-8 and phosphorylation of Akt, EGFR and FoxO3A, Compared with control, elastase/LPS-exposed mice showed decreased nuclear FoxO3A, increased chemokines and phosphorylation of EGFR and Akt. Treatment with quercetin partially reversed these changes.

CONCLUSIONS

In COPD airways, aberrant EGFR activity increases PI 3-kinase/Akt-mediated phosphorylation of FoxO3A, thereby decreasing nuclear FoxO3A and increasing chemokine expression. Quercetin restores nuclear FoxO3A and reduces chemokine expression partly by modulating EGFR/PI 3-kinase/Akt activity.

Characterization of LRRFIP1

LRRFIP1 has been identified as a regulator of toll-like receptor (TLR) pathway signaling; however, little is known about its own regulation and function. This study was undertaken to characterize the biochemical properties and its regulation. Over-expression of full length LRRFIP1 led to enhanced responses to lipopolysaccharide (LPS). We examined its expression in monocytic cell lines because they express a broad range of TLRs. We found that its level of expression was not altered by LPS or phorbol myristate acetate (PMA) but that it was up-regulated by nicotine, influenza infection, and serum starvation. Phosphorylation was examined because of the bioinformatically predicted serine phosphorylation sites. Serine phosphorylation was detected and was altered by both poly I:C and nicotine. Finally, we examined the regulation of intracellular localization in response to dsRNA and found that LRRFIP1 colocalized with labeled dsRNA in monocyte lysosomal structures but not with lysosomes lacking dsRNA. These data suggest that LRRFIP1 is phosphorylated in response to immunologic stimuli and it is directed to lysosomal structures.

Nicotine inhibits cisplatin-induced apoptosis in NCI-H446 cells

Nicotine is not only a major component in tobacco but is also a survival agonist that inhibits apoptosis induced by certain agents including chemotherapeutic drugs. Here, we first showed that nicotine inhibits cisplatin-induced apoptosis in NCI-H446 cells. An MTT assay, Annexin V-FITC staining, RT-PCR, and Western blot were applied to identify the viability of cells, stages of apoptosis, mRNA and signaling proteins expression, respectively. First, we observed that nicotine induced no significant apoptosis when used alone and promoted cell proliferation at a low concentration or for a short time, but the opposite was observed at a high concentration or for a long time. In addition, an increase in XIAP and Survivin mRNA or protein was observed. Next, when combined with cisplatin, growth inhibition rates were concentration dependent, decreased to the lowest level at first, but later climbed to the highest point. Furthermore, nicotine inhibited apoptosis induced by cisplatin and caused a concentration-dependent increase in both XIAP and Survivin mRNA or protein. Moreover, the apoptotic effect of the combination group was obviously higher than that of nicotine used alone at the same nicotine concentration and lower than that of cisplatin used alone at the same cisplatin concentration. These studies suggest that exposure to nicotine might negatively impact the apoptotic potential of chemotherapeutics.

Neuroprotection by donepezil against glutamate excitotoxicity involves stimulation of alpha7 nicotinic receptors and internalization of NMDA receptors

BACKGROUND AND PURPOSE

Glutamate excitotoxicity may be involved in ischaemic injury to the CNS and some neurodegenerative diseases, such as Alzheimer's disease. Donepezil, an acetylcholinesterase (AChE) inhibitor, exerts neuroprotective effects. Here we demonstrated a novel mechanism underlying the neuroprotection induced by donepezil.

EXPERIMENTAL APPROACH

Cell damage in primary rat neuron cultures was quantified by lactate dehydrogenase release. Morphological changes associated with neuroprotective effects of nicotine and AChE inhibitors were assessed by immunostaining. Cell surface levels of the glutamate receptor sub-units, NR1 and NR2A, were analyzed using biotinylation. Immunoblot was used to measure protein levels of cleaved caspase-3, total NR1, total NR2A and phosphorylated NR1. Immunoprecipitation was used to measure association of NR1 with the post-synaptic protein, PSD-95. Intracellular Ca(2+) concentrations were measured with fura 2-acetoxymethylester. Caspase 3-like activity was measured using enzyme substrate, 7-amino-4-methylcoumarin (AMC)-DEVD.

KEY RESULTS

Levels of NR1, a core subunit of the NMDA receptor, on the cell surface were significantly reduced by donepezil. In addition, glutamate-mediated Ca(2+) entry was significantly attenuated by donepezil. Methyllycaconitine, an inhibitor of alpha7 nicotinic acetylcholine receptors (nAChR), inhibited the donepezil-induced attenuation of glutamate-mediated Ca(2+) entry. LY294002, a phosphatidyl inositol 3-kinase (PI3K) inhibitor, had no effect on attenuation of glutamate-mediated Ca(2+) entry induced by donepezil.

CONCLUSIONS AND IMPLICATIONS

Decreased glutamate toxicity through down-regulation of NMDA receptors, following stimulation of alpha7 nAChRs, could be another mechanism underlying neuroprotection by donepezil, in addition to up-regulating the PI3K-Akt cascade or defensive system.

Glycogen synthase kinase 3 beta: can it be a target for oral cancer

Despite progress in treatment approaches for oral cancer, there has been only modest improvement in patient outcomes in the past three decades. The frequent treatment failure is due to the failure to control tumor recurrence and metastasis. These failures suggest that new targets should be identified to reverse oral epithelial dysplastic lesions. Recent developments suggest an active role of glycogen synthase kinase 3 beta (GSK3 β) in various human cancers either as a tumor suppressor or as a tumor promoter. GSK3β is a Ser/Thr protein kinase, and there is emerging evidence that it is a tumor suppressor in oral cancer. The evidence suggests a link between key players in oral cancer that control transcription, accelerated cell cycle progression, activation of invasion/metastasis and anti-apoptosis, and regulation of these factors by GSK3β. Moreover, the major upstream kinases of GSK3β and their oncogenic activation by several etiological agents of oral cancer support this hypothesis. In spite of all this evidence, a detailed analysis of the role of GSK3β in oral cancer and of its therapeutic potential has yet to be conducted by the scientific community. The focus of this review is to discuss the multitude of roles of GSK3β, its possible role in controlling different oncogenic events and how it can be targeted in oral cancer.

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

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

Nicotine, through upregulating pro-survival signaling, cooperates with NNK to promote transformation

Cigarette smoking is a mixture of thousands of compounds, many of which are carcinogens, such as NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone]. Nicotine, as an addictive substance in cigarette, has been shown to promote growth of non-neuronal cells. It is unclear how nicotine cooperates with tobacco-related carcinogens during tumorigenesis. Here, by concurrent treatment of nicotine and NNK, we investigate the effect of the cooperation of these two compounds on cell growth and apoptosis in various different lung epithelial (RLE) or cancer (LKR) cells. We demonstrated that short-term nicotine exposure moderately activated mitogenic signaling pathways (such as PKC, ERK, and Akt) and a mediocre protection against cisplatin-mediated apoptosis. In contrast, NNK strongly stimulated mitogenic signaling and rendered the cells a high resistance to cisplatin. The pre-ligation of nAChR by nicotine interfered with NNK-mediated mitogenic signaling and resistance to cisplatin, the magnitude of which was similar as that exposed to nicotine alone. Interestingly, a week after the exposure to nicotine or nicotine plus NNK, Bcl-2 expression was augmented, accompanied with the increased resistance to cisplatin-induced apoptosis. In comparison, long-term NNK treatment provided very little protection of the cells from cisplatin. We also showed that the combination treatment promoted more cells to grow in an anchorage-independent fashion than NNK exposure alone. Thus, the data suggest that through occupying nAChR, nicotine appears to modulate NNK-mediated signaling and persistently sustain pro-survival activities to promote transformation.

Pharmacology of alpha7 nicotinic acetylcholine receptor mediated extracellular signal-regulated kinase signalling in PC12 cells

BACKGROUND AND PURPOSE

Neuronal nicotinic acetylcholine receptors (nAChR) can modulate cell survival and memory processing. The involvement of specific nAChR subtypes in downstream signalling events has been ill defined thus far, because of a lack of subtype-selective ligands. In this study, we investigated activation and modulation of alpha7 nAChR-mediated phosphorylation of extracellular signal-regulated kinases (ERK1/2) in PC12 cells, using selective agonists and positive allosteric modulators.

EXPERIMENTAL APPROACH

We used undifferentiated PC12 cells endogenously expressing alpha7 nAChR for both biochemical and functional studies. ERK phosphorylation changes were measured by using a novel In-Cell Western procedure. alpha7 nAChR-mediated Ca(2+) signalling was determined by using the fluorometric imaging plate reader assay.

KEY RESULTS

Robust induction of ERK phosphorylation followed exposure of PC12 cells to the selective agonist PNU-282987 in the presence of the alpha7 nAChR modulator PNU-120596. ERK phosphorylation was transient and was attenuated by the selective antagonist methyllycaconitine. Consistent with allosteric modulation of alpha7 nAChRs, PNU-120596 enhanced both the agonist potency and efficacy in activating ERK. Moreover, alpha7 nAChR agonists could be quantitatively differentiated based on their potency in activating ERK signalling. The rank order of potencies correlated fairly well with the corresponding binding K(i) values of these alpha7 nAChR agonists.

CONCLUSIONS AND IMPLICATIONS

The present work extends previous observations demonstrating the involvement of alpha7 nAChRs in ERK1/2 phosphorylation in PC12 cells. The In-Cell Western procedure allowed a detailed investigation of alpha7 nAChR function and downstream ERK signalling in response to agonist and allosteric modulators.

Nicotine promotes mammary tumor migration via a signaling cascade involving protein kinase C and CDC42

Nicotine, one of the major components in tobacco, is at high concentrations in the bloodstream of cigarette smokers. However, the mechanisms of how nicotine affects tumor development and whether nicotine is a potential carcinogen for malignancies induced by secondhand smoking are not fully understood yet. Here, we investigate the signaling pathways by which nicotine potentiates tumorigenesis in human mammary epithelial-like MCF10A or cancerous MCF7 cells. We show that human MCF10A and MCF7 cells both express four subunits of nicotine acetylcholine receptor (nAChR). The treatment of these cells with nicotine enhances the activity of protein kinase C (PKC) alpha without altering the expression level of this kinase. Nicotine also stimulates [(3)H]thymidine incorporation into the genome of these cells as well as forces serum-starved cells to enter S phase of the cell cycle, resulting in growth promotion. Importantly, on nicotine treatment, the mobility of MCF10A and MCF7 cells is enhanced, which can be blocked by the addition of nAChR or PKC inhibitor. Experiments using small interfering RNA knockdown or ectopic expression of cdc42 showed that cdc42 functions as a downstream effector of PKC and is crucial in the regulation of nicotine-mediated migratory activity in the cells. Together, our findings suggest that nicotine, through interacting with its receptor, initiates a signaling cascade that involves PKC and cdc42 and consequently promotes migration in mammary epithelial or tumor cells.

Activated cholinergic signaling provides a target in squamous cell lung carcinoma

The binding of exogenous nicotine to nicotinic acetylcholine (ACh) receptors (nAChR) and the binding of endogenous ACh to both nAChR and muscarinic ACh receptors (mAChR) stimulate growth of both small cell and non-small cell lung carcinomas. Understanding how cholinergic signaling is up-regulated in lung cancer may suggest new therapeutic approaches. Analysis of 28 squamous cell lung carcinomas (SCC) showed increased levels of alpha5 and beta3 nAChR mRNA and increased levels of ACh associated with increased levels of choline acetyltransferase mRNA and decreased cholinesterase mRNAs. Lynx1, an allosteric inhibitor of nAChR activity, was also decreased in SCC. Thus, cholinergic signaling is broadly increased in SCC caused by increased levels of receptors, increased levels of ligands, and decreased levels of receptor inhibitors. Partially explaining the cholinergic up-regulation seen in SCC, incubation of the H520 SCC cell line with nicotine increased levels of ACh secretion, increased expression of nAChR, and, as measured by electrophysiologic recording, increased activity of the expressed nAChR. Consistent with these effects, nicotine stimulated proliferation of H520 cells. One approach to blocking proliferative effects of nicotine and ACh on growth of lung cancers may be through M3 mAChR antagonists, which can limit the activation of mitogen-activated protein kinase that is caused by both nicotinic and muscarinic signaling. This was tested with the M3-selective muscarinic antagonist darifenacin. Darifenacin blocked nicotine-stimulated H520 growth in vitro and also blocked H520 growth in nude mice in vivo. Thus, cholinergic signaling is broadly up-regulated in SCC and blocking cholinergic signaling can limit basal and nicotine-stimulated growth of SCC.

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

Tobacco products and nicotine alter the cell cycle and lead to squamatization of oral keratinocytes (KCs) and squamous cell carcinoma. Activation of nicotinic acetylcholine receptors (nAChRs) elicits Ca(2+) influx that varies in magnitude between different nAChR subtypes. Normal differentiation of KCs is associated with sequential expression of the nAChR subtypes with increasing Ca(2+) permeability, such as alpha5-containing alpha3 nAChR and alpha7 nAChR. Exposure to environmental tobacco smoke (ETS) or an equivalent concentration of nicotine accelerated by severalfold the alpha5 and alpha7 expression in KCs, which could be abolished by mecamylamine and alpha-bungarotoxin with different efficacies, suggesting the following sequence of autoregulation of the expression of nAChR subtypes: alpha3(beta2/beta4) > alpha3(beta2/beta4)alpha5 > alpha7 > alpha7. This conjecture was corroborated by results of quantitative assays of subunit mRNA and protein levels, using nAChR-specific pharmacologic antagonists and small interfering RNAs. The genomic effects of ETS and nicotine involved the transcription factor GATA-2 that showed a multifold increase in quantity and activity in exposed KCs. Using protein kinase inhibitors and dominant negative and constitutively active constructs, we characterized the principal signaling cascades mediating a switch in the nAChR subtype. Cumulative results indicated that the alpha3(beta2/beta4) to alpha3(beta2/beta4)alpha5 nAChR transition predominantly involved protein kinase C, alpha3(beta2/beta4)alpha5 to alpha7 nAChR transition-Ca(2+)/calmodulin-dependent protein kinase II and p38 MAPK, and alpha7 self-up-regulation-the p38 MAPK/Akt pathway, and JAK-2. These results provide a mechanistic insight into the genomic effects of ETS and nicotine on KCs and characterize signaling pathways mediating autoregulation of stepwise overexpression of nAChR subtypes with increasing Ca(2+) permeability in exposed cells. These observations have salient clinical implications, because a switch in the nAChR subunit composition can bring about a corresponding switch in receptor function, leading to profound pathobiologic effects observed in KCs exposed to tobacco products.

Nicotine suppresses tunicamycin-induced, but not thapsigargin-induced, expression of GRP78 during ER stress-mediated apoptosis in PC12 cells

We previously reported that nicotine protected against tunicamycin (Tm)-induced ER stress-mediated apoptosis, but not thapsigargin (Tg)-induced apoptosis in PC12 cells. In the present study, we report that the expression of glucose-regulated protein 78 (GRP78) was suppressed by nicotine in Tm-treated PC12 cells. Interestingly, the GRP78 expression was not changed by nicotine in Tg-treated cells. Moreover, nicotine reduced the activation of caspase-12 in Tm-treated cells, but not in Tg-treated cells. These results suggest that nicotine prevented Tm-induced ER stress-mediated apoptosis by attenuating an early stage of Tm-induced ER stress. It was possible that the suppression of GRP78 expression by nicotine was achieved through the suppression of the Ire1-XBP1 and/or ATF6 pathways. We observed that nicotine suppressed the Tm-induced, but not Tg-induced, splicing of XBP1 mRNA, and also suppressed the Tm-induced, but not Tg-induced, production of cleaved ATF6 in PC12 cells. These results indicate that the suppression of Ire1-XBP1 and ATF6 pathways contributes to the suppression of GRP78 expression by nicotine in Tm-treated PC12 cells, suggesting that nicotine suppresses a common step upstream of both the Ire1-XBP1 and ATF6 pathways which are required for the expression of GRP78 during Tm-induced ER stress.

Expression of phosphorylated Akt in oral carcinogenesis and its induction by nicotine and alkaline stimulation

BACKGROUND

In Taiwan, it is well documented that cigarette smoking and areca nut chewing contribute to the risk of oral squamous cell carcinoma (OSCC). The role of phosphorylated Akt (p-Akt) in oral carcinogenesis induced by nicotine and alkaline environments was investigated.

METHOD

Immunohistochemistry (IHC) was used to detect p-Akt expression in cancerous (n = 30) precancerous (n = 30), and normal mucosa tissues (n = 10). Western blotting was used to detect time-dependent induction of p-Akt by 100 microM nicotine in normal human bronchial epithelial cell (NHBE), normal human oral keratinocytes (NHOK), immortalized human epithelial cells (HaCaT) and OEC-M1 cells, dose-dependent induction of p-Akt in OEC-M1 and HaCaT cells and pH effect of p-Akt in OEC-M1. The unpaired t-test and the Fisher's exact test were used to analyze the p-Akt immunoreactivity in various groups and its association with clinicopathological parameters.

RESULTS

Higher p-Akt expression in cancerous group than in normal mucosa (P = 0.0002) and precancerous (P = 0.0049) groups was observed. A time-dependent increase in p-Akt in the NHBE, NHOK, HaCaT and OEC-M1 cell lines was observed with 100 microM nicotine treatment. The dose-dependent increase in p-Akt by nicotine treatment in HaCaT and OEC-M1 cells was obviously observed. Higher p-Akt expression in more alkaline environment (pH 8.0) was observed than at pH 7.4 in OEC-M1 cells.

CONCLUSION

A potential role for increased p-Akt may relate to the dose and time of nicotine use. The potential role of an alkaline environment to enhance nicotine-related oral carcinogenesis may exist.

Akt in the pathogenesis of COPD

In this review we consider the therapeutic potential of targeting Akt for the treatment of COPD. Akt is a serine/threonine protein kinase that functions as a signaling intermediate linked to multiple signaling programs involved in survival, inflammation, and growth. Akt is closely associated with key membrane-bound receptors and represents a convergent integration point for multiple stimuli implicated in COPD pathogenesis. Persistent activation of Akt secondary to somatic mutations in regulatory oncogenes, such as PTEN, may explain why inflammation in COPD does not resolve when smoking is ceased. Akt is also implicated in the systemic manifestations of COPD such as skeletal muscle wasting and metabolic disturbances. Furthermore, targeting Akt may provide a useful means of limiting the severity and duration of disease exacerbations in COPD. As such, Akt represents a particularly attractive therapeutic target for the treatment of COPD. Interestingly, current knowledge suggests that both inhibitors and activators of Akt may be useful for treating different clinical subpopulations of COPD patients.

Expression of nicotinic acetylcholine receptor subunit genes in non-small-cell lung cancer reveals differences between smokers and nonsmokers

Nicotine and its derivatives, by binding to nicotinic acetylcholine receptors (nAChR) on bronchial epithelial cells, can regulate cellular proliferation and apoptosis via activating the Akt pathway. Delineation of nAChR subtypes in non-small-cell lung cancers (NSCLC) may provide information for prevention or therapeutic targeting. Expression of nAChR subunit genes in 66 resected primary NSCLCs, 7 histologically non-involved lung tissues, 13 NSCLC cell lines, and 6 human bronchial epithelial cell lines (HBEC) was analyzed with quantitative PCR and microarray analysis. Five nonmalignant HBECs were exposed to nicotine in vitro to study the variation of nAChR subunit gene expression with nicotine exposure and removal. NSCLCs from nonsmokers showed higher expression of nAChR alpha6 (P < 0.001) and beta3 (P = 0.007) subunit genes than those from smokers, adjusted for gender. In addition, nAChR alpha4 (P < 0.001) and beta4 (P = 0.029) subunit gene expression showed significant difference between NSCLCs and normal lung. Using Affymetrix GeneChip U133 Sets, 65 differentially expressed genes associated with NSCLC nonsmoking nAChR alpha6beta3 phenotype were identified, which gave high sensitivity and specificity of prediction. nAChR alpha1, alpha5, and alpha7 showed significant reversible changes in expression levels in HBECs upon nicotine exposure. We conclude that between NSCLCs from smokers and nonsmokers, different nAChR subunit gene expression patterns were found, and a 65-gene expression signature was associated with nonsmoking nAChR alpha6beta3 expression. Finally, nicotine exposure in HBECs resulted in reversible differences in nAChR subunit gene expression. These results further implicate nicotine in bronchial carcinogenesis and suggest targeting nAChRs for prevention and therapy in lung cancer.

Nicotine-induced proliferation of isolated rat pancreatic acinar cells: effect on cell signalling and function

OBJECTIVES

The aim of the current study was to investigate whether nicotine treatment would induce the proliferation of isolated rat primary pancreatic acinar cells in culture by activating mitogen-activated protein kinase (MAPK) signalling and exocrine secretion.

MATERIALS AND METHODS

A nicotine dose- and time-response curve was initially developed to determine the optimal dose and time used for all subsequent studies. Proliferation studies were conducted by cell counting and confirmed further by bromodeoxyuridine (BrdU) incorporation and flow cytometry assays. MAPK signalling studies were conducted by Western blot analysis. Localization of ERK1/2 signals, with or without nicotine and the MAPK inhibitor, was visualized by immunofluorescence.

RESULTS

Nicotine treatment caused dose-dependent activation of extracellular signal-regulated kinases (ERK1/2), the maxima occurring at 100 micro m and at 3 min after treatment; the response was suppressed by the ERK1/2 inhibitor. Maximal nicotine-induced cell proliferation occurred at 24 h, and UO126-treatment significantly reduced this response. Exposure of cells to 100 microm nicotine for 6 min significantly enhanced both baseline and cholecystokinin-stimulated cell function, and these effects were not affected by treatment with the inhibitor of ERK1/2 but were suppressed by mecamylamine, a nicotinic receptor antagonist.

CONCLUSIONS

Our results suggest that nicotine treatment induced cell proliferation of isolated pancreatic acinar cells and that this is coupled with the activation of MAPK signalling with no effect on its function. Hence, in primary cells, the mechanism of induction and regulation of these two processes, cell proliferation and cell function, by nicotine treatment are independent of each other.

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

Cigarette smoke has been firmly established as an independent risk factor for atherosclerosis and other vascular diseases. The proliferation and migration of vascular smooth muscle cells (VSMC) induced by growth factors have been proposed to play an important role in the progression of atherosclerosis. In the present study, we investigated the effects of nicotine, which is one of the important constituents of cigarette smoke, on vascular endothelial growth factor (VEGF) release, in rat VSMC. The stimulation of cells with nicotine resulted in a time- and concentration-dependent release of VEGF. Hexamethonium, an antagonist of nicotinic acetylcholine receptor (nAChR), inhibited nicotine-induced VEGF release. We next investigated the mechanisms by which nicotine induces VEGF release in the cells. The nicotine-induced VEGF release was inhibited by treatment with U0126, a selective inhibitor of MEK, which attenuated the nicotine-induced ERK phosphorylation. Nicotine induced a transient phosphorylation of ERK. Furthermore, AG1478, a selective inhibitor of epidermal growth factor receptor (EGFR) kinase, inhibited nicotine-induced ERK phosphorylation and VEGF release. These data suggest that nicotine releases VEGF through nAChR in VSMC. Moreover, VEGF release induced by nicotine is mediated by an EGFR-ERK pathway in VSMC. VEGF may contribute to the risk of cardiovascular diseases in cigarette smokers.

Nicotine as a mitogenic stimulus for pancreatic acinar cell proliferation

Cell proliferation is an important process in life for growth of normal and cancer cells. The signal transduction pathways activated during this process are strictly regulated. This editorial focuses on the role of nicotine, a mitogen, in the induction of signaling pathways resulting in proliferation of pancreatic tumor cells and compares these events with those in normal acinar cells isolated from the rat pancreas. The data shows striking similarities between these two cellular systems. In addition, the editorial reviews very recent literature of the contribution of MAPK signaling in cell lines associated with human diseases. A prospective cellular model of nicotine induced activation of MAPK cascade is presented.

Effects of tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) on the activation of ERK1/2 MAP kinases and the proliferation of human mammary epithelial cells

Cigarette smoking is a risk factor in the developing of various cancers including breast tumors. There are more than 60 chemical carcinogens in the cigarette smoke; 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) being one of the strongest tobacco-specific carcinogens. In this study, we demonstrated that NNK rapidly activated ERK1 and ERK2 MAP kinases and stimulated proliferation in human normal mammary epithelial cells. MEK1/2 specific inhibitor UO126 completely blocked NNK-induced ERK1/2 activation and cell proliferation, whereas nicotinic receptor nAchR antagonist mecamylamine partially and the selective α(7)-nAchR antagonist α-bungarotoxin essentially inhibited the NNK-induced ERK1/2 activation and cell proliferation. Surprisingly, receptor tyrosine kinase inhibitor genistein, the selective β(1)-adrenergic antagonist atenolol, and the selective β(2)-adrenergic antagonist ICI118.551 had a strong inhibitory effect on ERK1/2 activation and cell proliferation induced by NNK. These results suggest that there are at least two different routes in activating ERK1/2 by NNK. One is through nicotinic receptor α(7)-nAchR to MEK1/2; the other is from β(1)/β(2)-adrenergic transactivation of tyrosine kinase containing receptor(s) to MEK1/2. In human cancer mammary epithelial cell lines, we found that ERK MAPK signaling pathway was deregulated: (1) ERK1/2 was constitutively activated at various levels; (2) ERK1/2 was further significantly activated in response to NNK induction; (3) UO126 partially or totally failed to inhibit ERK1/2 activation induced by NNK; (4) The expression levels of ERK1/2 in the cancer cell lines were much higher than those in the normal mammary epithelial cells. The tobacco-specific carcinogen NNK showed a strong proliferative effect on human normal and cancer mammary epithelial cells; the proliferation multitudes of these cells are well correlated with the activation levels of ERK1/2 MAP kinases.

Nicotinic modulation of gene expression in SH-SY5Y neuroblastoma cells

Exposure to nicotine has a broad range of physiological and psychological effects that can be long lasting and contribute to nicotine dependence. On a time course longer than that needed to activate nicotinic acetylcholine receptor (nAChR) function, nicotine exposure induces functional inactivation of nAChR, upregulation of nAChR radioligand binding sites, and other alterations of cellular functions. To identify possible mechanisms underlying nicotine-induced changes in nAChR numbers and function, we defined changes in gene expression in neuron-like, SH-SY5Y human neuroblastoma cells following 24 h of continuous exposure to 1 mM nicotine. This treatment condition produces both functional inactivation and upregulation of nAChR. Repeat and cross-controlled microarray ( approximately 5000 genes queried) analyses revealed 163 genes whose expression was consistently altered at the p<0.01 level following nicotine treatment. Quantitative, real-time, reverse transcription-polymerase chain reaction analyses confirmed altered expression of thirteen out of fourteen of these genes chosen for further study, including contactin 1, myozenin 2, and ubiquitin-conjugating enzymes E2C and E2S. Inhibition or reversal of these effects by the general nAChR antagonist, d-tubocurarine, indicated that gene expression changes are dependent on nAChR activation. Studies using other nAChR subtype-selective antagonists identified gene expression changes that required activation of both alpha7- and alpha3*-nAChR, alpha7-nAChR alone, or either alpha7- or alpha3beta4*-nAChR, suggesting some convergent and some divergent pathways of gene activation coupled to these nAChR subtypes. These results suggest that longer-term physiological and psychological effects of nicotine exposure and changes in nAChR expression may be due in part to effects on gene expression initiated by interactions with nAChR.

SRC-family tyrosine kinases in wound- and ligand-induced epidermal growth factor receptor activation in human corneal epithelial cells

PURPOSE

The authors have previously demonstrated that wounding of human corneal epithelial cells (HCECs) transactivates epidermal growth factor (EGF) receptor (EGFR) and its downstream signaling pathways and that this EGFR signaling is required for epithelial wound healing. In this study, the authors sought to identify the underlying mechanisms for EGFR transactivation in response to wounding in HCECs.

METHODS

SV40-immortalized HCEC (THCE) monolayer was wounded and allowed to heal in the presence or absence of a selective inhibitor of the Src family kinases PP2 and EGFR ligand heparin-binding EGF-like growth factor (HB-EGF). Wound closure was monitored by photographing of the injury immediately or 24 hours after wounding. Activation of EGFR in THCE cells and in primary HCECs was analyzed by immunoprecipitation of EGFR, followed by Western blotting with phosphotyrosine antibody. Phosphorylation of extracellular signal-regulated kinase (ERK), AKT (a major substrate of phosphatidylinositol 3'-kinase [PI3K]), Src at tyrosine Y416, and EGFR at Y845 was analyzed by Western blotting with antibodies specific to phosphorylated proteins. Effects of PP2 on THCE cell migration were determined by Boyden chamber migration assay.

RESULTS

Among several inhibitors tested, PP2 blocked wound-induced EGFR phosphorylation in THCE cells. PP2 at 12.5 microM effectively inhibited EGFR transactivation in response to wounding and to the phosphorylation of ERK and AKT in THCE cells and primary HCECs. Consistent with the inhibition of EGFR transactivation, PP2 also attenuated epithelial migration and wound closure with or without exogenously added HB-EGF. PP2 at a concentration as high as 50 microM exhibited no effects on HB-EGF induced ERK phosphorylation. On the other hand, AKT phosphorylation was much more sensitive to PP2 than ERK or EGFR phosphorylation because 3.13 microM PP2 effectively inhibited wound- or HB-EGF-induced AKT phosphorylation.

CONCLUSIONS

These results suggest that Src kinase mediates wound-induced EGFR transactivation and participates in a pathway to activate the PI3K-AKT pathway downstream of EGFR in HCECs.

Nicotine prevents the apoptosis induced by menadione in human lung cancer cells

Approximately 50% of long-term cigarette smokers die prematurely from the adverse effects of smoking, including on lung cancer and other illnesses. Nicotine is a main component in tobacco and has been implicated as a potential factor in the pathogenesis of human lung cancer. However, the mechanism of nicotine action in the development of lung cancer remains largely unknown. In the present study, we designed a nicotine-apoptosis system, by pre-treatment of nicotine making lung cancer cell A549 to be in a physiological nicotine environment, and observed that nicotine promoted cell proliferation and prevented the menadione-induced apoptosis, and exerts its role of anti-apoptosis by shift of apoptotic stage induced by menadione from late apoptotic stage to early apoptotic stage, in which NF-kappaB was up-regulated. Interference analysis of NF-kappaB in A549 cells showed that knock down of NF-kappaB resulted in apoptosis promotion and counteracted the protective effect of nicotine. The findings suggest that nicotine has potential effect in lung cancer genesis, especially in patients with undetectable early tumor development and development of specific NF-kappaB inhibitors would represent a potentially exciting new pharmacotherapy for tobacco-related lung cancer.

Activation of p-ERK1/2 by nicotine in pancreatic tumor cell line AR42J: effects on proliferation and secretion

The objectives of the present study were to determine the effect of nicotine on MAPK signaling and on the proliferation of AR42J cells as well as to assess the relationship between MAPK activation and exocrine secretion in these cells. AR42J cells were incubated with nicotine and analyzed for the activation of MAPK by Western blot analysis using their respective antibodies and confirmed by immunohistochemistry. The effect of nicotine on cell proliferation was determined by the spectrophotometric method, and cell function was assessed by cholecystokinin (CCK)-stimulated amylase release into the culture medium. Nicotine at a dose of 100 microM induced phospho-ERK1/2 activation maximally in 3 min compared with untreated cells. Furthermore, immunofluorescence study confirmed the nicotine-induced increase in translocation of phospho-ERK1/2 to the nucleus. Activation of phospho-ERK1/2 was inhibited by an ERK1/2 pathway inhibitor but not by a nicotine receptor antagonist. At the same dose, there was significantly enhanced proliferation of AR42J cells until 72 h without toxic effect, as the percentage of lactate dehydrogenase release remained unchanged. Other MAPKs, c-Jun NH2-terminal kinase 1/2 and p38 MAPK, were not affected by nicotine treatment. At a nicotine dose of 100 microM, the CCK-stimulated release of amylase was maximal at 6 min, and, although a nicotinic receptor antagonist inhibited this response, it was not inhibited by the ERK1/2 pathway inhibitor. We conclude that nicotine treatment induced activation of ERK1/2 and increased the proliferation of AR42J cells. The data further indicate that MAPK signaling by nicotine is independent of the secretory response.

Subtypes of neuronal nicotinic acetylcholine receptors involved in nicotine-induced phosphorylation of extracellular signal-regulated protein kinase in PC12h cells

Although many kinds of nicotinic acetylcholine receptor (nAChR) subtypes have been reported in the neuronal tissues, subtype differences in the nAChR-mediated intracellular signaling remains obscure. Using nAChR agonists and antagonists, the involvement of nAChRs in extracellular signal-regulated protein kinase (ERK) phosphorylation in PC12h cells was investigated. Cytisine and nicotine induced the phosphorylation of ERKs in a dose-dependent manner, whereas RJR-2403 had no effect. Cytisine, but not RJR-2403, also induced phosphorylation of CREB. Mecamylamine, dextromethorphan and 18-methoxycoronaridine inhibited nicotine-induced ERK phosphorylation with much higher affinity than dihydro-beta-erythroidine and alpha-conotoxin MII. These results suggest the involvement of alpha3beta4 nAChRs in ERK phosphorylation in PC12h cells.

Effect of N'-nitrosonornicotine (NNN) on murine palatal fusion in vitro

Maternal smoking has been linked to an increased risk for orofacial clefts. N'-nitrosonornicotine (NNN) is one of the tobacco-specific nitrosamines that has been shown to be linked to the deleterious effects of tobacco and could be linked to the formation of cleft palate birth defects. The effect of NNN on palatal fusion was examined using an in vitro organ culture model of palatal development. The organ cultures were exposed to NNN (0.01, 0.1, 1, 10 and 100 mM) and the effects on palatal development characterized at defined points. Palatal fusion was evaluated at embryonic day 13 (E13)+72 h by characterizing the remaining medial edge epithelium (MEE) and determining the extent of fusion compared to controls. The NNN-treated group (1 mM) had more MEE remaining in the palatal midline than the untreated group at E13+72 h (P<0.05). Changes in cell proliferation in the MEE resulting from NNN exposure were examined by BrdU incorporation in replicating DNA. Changes in the pattern of MEE cell death were examined by TUNEL. BrdU incorporation and TUNEL staining showed that the NNN (1 mM)-treated palates had more MEE cell proliferation and less apoptosis than the untreated-palates at E13+24 h (P<0.05). The mechanism altered by NNN was further evaluated by characterizations of extracellular signal-regulated kinase (ERK) 1/2, p38 and c-jun amino-terminal kinase (JNK). NNN at 1 mM induced ERK1/2 phosphorylation, but reduced p38 phosphorylation (P<0.05, P<0.01, respectively) in the MEE. The results suggest that NNN inhibited palatal fusion by effects on cell proliferation and MEE cell death.

Protective effect of nicotine on tunicamycin-induced apoptosis of PC12h cells

Nicotine has been reported to have neuroprotective effects. The present study deals with the neuroprotective effect of nicotine on the tunicamycin-induced apoptosis of PC12h cells. Treatment of PC12h cells with tunicamycin causes endoplasmic reticulum stress leading to apoptosis. Nicotine dose-dependently prevented the tunicamycin-induced apoptosis. Hoechst 33258 staining demonstrated the protective effect of nicotine against tunicamycin-induced apoptosis. Treatment with nicotinic acetylcholine receptor (nAChR) and L-type voltage-sensitive calcium channel (L-VSCC) antagonists prevented the nicotine-induced protective effect. A phosphatidylinositol 3-kinase (PI3-K) inhibitor had no influence on the nicotine-induced neuroprotective effect. These results show that the neuroprotective effect of nicotine occurs through nAChRs including the alpha 7 subtype and L-VSCC in PC12h cells and not through the PI3-K/Akt pathway.

Nicotinic Enhancement of Proliferation in Bovine and Porcine Cerebral Microvascular Endothelial Cells

Nicotinic acetylcholine receptors are found in microvascular endothelial cells. To reveal the functional role in cerebral angiogenic processes, we studied the nicotinic modulation of proliferation activity in cultured bovine and porcine cerebral microvascular endothelial cells. The proliferation activity was determined by an increase in the number of cells present in culture dishes. When the bovine cerebral endothelial cells at different passages were cultured in the presence of nicotine (10 nM), the proliferation activities were significantly increased in the cells at passage 1 and passage 3, but not at passage 4. Reverse transcriptase-polymerase chain reaction studies demonstrated that the expression of mRNAs coding for alpha3 nicotinic receptor subunit was significantly reduced in the bovine cerebral endothelial cells at passage 4, compared with that at passage 1. The proliferation of porcine cerebral endothelial cells (passage 1) was enhanced by acetylcholine (10 nM-100 microM) in the presence of atropine, a muscarinic antagonist, and this enhancing effect was inhibited by hexamethonium (100 microM, a nicotinic antagonist). The stimulation by acetylcholine (1 microM, with atropine) or nicotine (10 nM) induced the phosphorylation of a mitogen-activated protein (MAP) kinase (extracellular-signal regulated kinase: ERK) in the serum-starved endothelial cells. In the presence of PD98059 (2 microM, a MAP kinase kinase inhibitor) and atropine, acetylcholine (1 microM) failed to enhance the proliferation of porcine cerebral endothelial cells. These results demonstrate that nicotinic stimulation promotes the proliferation of bovine and porcine cerebral microvascular endothelial cells, at least in part, through the MAP kinase activation.

Nicotine promoted colon cancer growth via epidermal growth factor receptor, c-Src, and 5-lipoxygenase-mediated signal pathway

Nicotine [3-(1-methyl-2-pyrrolidinyl)-pyridine], a major alkaloid in tobacco, has been implicated as playing a role in carcinogenesis. Our previous study showed that passive cigarette smoking promoted inflammation-associated colonic adenoma formation in mice, and 5-lipoxygenase (5-LOX) plays an important role in this process. In the present study, we aimed to investigate whether nicotine could stimulate colon cancer cell proliferation and tumor growth in nude mice xenograft model and the possible mechanisms involved. Results showed that nicotine stimulated SW1116 colon cancer cell proliferation in a dose-dependent manner. Epidermal growth factor receptor (EGFR) and c-Src phosphorylation levels together with protein expression of 5-LOX were also significantly enhanced in this proliferation process. Inhibitors of EGFR and c-Src alleviated the actions of nicotine on cell proliferation and 5-LOX protein expression. Combination of both agents produced additive effect. In contrast, 5-LOX inhibitor had no direct effect on the phosphorylation levels of EGFR and c-Src and yet inhibited cell proliferation. In the colon cancer xenograft model, nicotine also significantly enhanced tumor growth. This acceleration of tumor growth corresponded well with increased vascularization and its proangiogenic factors. Inhibitors of EGFR, c-Src, and 5-LOX all significantly impeded the tumor growth induced by nicotine. Together, nicotine can promote colonic tumorigenesis both in vitro and in vivo. Activation of the phosphorylated form of EGFR and c-Src followed by an increased 5-LOX expression are the prime pathogenic mechanisms in the tumorigenic process in the colon.