MAPK/AP-1 signal pathway in tobacco smoke-induced cell proliferation and squamous metaplasia in the lungs of rats

Nicotine-induced survival signaling in lung cancer cells is dependent on their p53 status while its down-regulation by curcumin is independent

Background

Lung cancer is the most lethal cancer and almost 90% of lung cancer is due to cigarette smoking. Even though nicotine, one of the major ingredients of cigarette smoke and the causative agent for addiction, is not a carcinogen by itself, several investigators have shown that nicotine can induce cell proliferation and angiogenesis. We observed that the proliferative index of nicotine is different in the lung cancer cell lines H1299 (p53-/-) and A549 (p53+/+) which indicates that the mode of up-regulation of survival signals by nicotine might be different in cells with and without p53.

Results

While low concentrations of nicotine induced activation of NF-κB, Akt, Bcl2, MAPKs, AP1 and IAPs in H1299, it failed to induce NF-κB in A549, and compared to H1299, almost 100 times higher concentration of nicotine was required to induce all other survival signals in A549. Transfection of WT-p53 and DN-p53 in H1299 and A549 respectively, reversed the mode of activation of survival signals. Curcumin down-regulated all the survival signals induced by nicotine in both the cells, irrespective of their p53 status. The hypothesis was confirmed when lower concentrations of nicotine induced NF-κB in two more lung cancer cells, Hop-92 and NCI-H522 with mutant p53 status. Silencing of p53 in A549 using siRNA made the cells susceptible to nicotine-induced NF-κB nuclear translocation as in A549 DN-p53 cells.

Conclusions

The present study reveals a detrimental role of nicotine especially in lung cancer patients with impaired p53 status and identifies curcumin as a potential chemopreventive.

Lung injury and cancer: Mechanistic insights into ceramide and EGFR signaling under cigarette smoke

Cigarette smoke has been connected to an array of chronic lung diseases and is a major source of morbidity and mortality. Active smoking is responsible for approximately 90% of lung cancer cases. In addition, cigarette smoke is associated with other chronic pulmonary diseases such as pulmonary edema, chronic bronchitis, and pulmonary emphysema, the last two also termed chronic obstructive pulmonary disease (COPD). Lung cancer and COPD are developed very frequently in chronic cigarette smokers. It has been known for some time that lung cancer incidence increases in patients with COPD. Even the existence of some low-grade emphysema without noticeable airflow obstruction is associated with significantly elevated risk of lung cancer. These recent clinical insights demand new thinking and exploration of novel mechanistic studies to fully understand these observations. Lung injury and repair involve cell death and hyperplasia of airway epithelial cells and infiltration of inflammatory cells. All of these occur simultaneously. The mechanisms of cell death and hyperplasia in the lung constitute two sides of the coin of lung injury and repair. However, most molecular studies in airway epithelial cells center on the mechanism(s) of either cell growth and proliferation or cell death and the ceramide-generating machinery that drives aberrant induction of apoptotic cell death. Very few address both sides of the coin as an outcome of cigarette smoke exposure, which is the focus of this review.

A label-free differential proteomic analysis of mouse bronchoalveolar lavage fluid exposed to ultrafine carbon black

Ultrafine carbon black (ufCB) is a potential hazard to the lung. It causes changes in protein expression and it increases alveolar-capillary permeability in the lung. Label-free quantitative proteomic methods allow a sensitive and accurate analytical method for identifying and quantifying proteins in a protein mixture without chemically modifying the proteins. We used a label-free quantitative proteomic approach that combined and aligned LC-MS and LC-MS/MS spectra to analyze mouse bronchoalveolar lavage fluid (BALF) protein changes associated with exposure to ufCB. We developed a simple normalization method for quantification without spiking the internal standard. The intensities of unchanged peptides were used as normalization factors based on a statistical method to avoid the influence of peptides changed because of ufCB. LC-MS/MS spectra and then database searching were used to identify proteins. The relative abundances of the aligned peptides of identified proteins were determined using LC-MS spectra. We identified 132 proteins, of which 77 are reported for the first time. In addition, the expression of 15 inflammatory proteins and surfactant-associated proteins was regulated (i.e., 7 upregulated and 8 downregulated) compared with the controls. Several proteins not previously reported provide complementary information on the proteins present in mouse BALF, and they are potential biomarkers for the understanding of mechanisms involved in ufCB-induced lung disorders hypothesize that using the label-free quantitative proteomic approach introduced here is well suited for more rigorous, large-scale quantitative analysis of biological samples. We hypothesize that this label-free quantitative proteomic approach will be suited for a large-scale quantitative analysis of biological samples.

Silica-induced TNF-alpha and TGF-beta1 expression in RAW264.7 cells are dependent on Src-ERK/AP-1 pathways

The cytokines secreted by lung macrophages have been shown to play a critical role in the pathogenesis of silicosis, tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta1 (TGF-beta1) are prominent cytokines in silicosis, but the underlying mechanism remains to be determined. The aim of the present study was to investigate the roles of Src-mitogen-activated protein kinase (MAPKs)/activator protein-1 (AP-1) signaling pathways in silica-induced TNF-alpha and TGF-beta1 expression in macrophage cells (RAW264.7). It was found that silica activated Src, p38 kinase, and extracellular signal-regulated kinase (ERK) in RAW264.7 cells. The induction of TNF-alpha and TGF-beta1 by silica was suppressed by Src inhibitor (PP1), ERK inhibitor (PD98059), but not by p38 kinase inhibitor (SB203580). Dominant negative mutant c-Jun (TAM67) inhibited silica-induced AP-1 DNA binding activity and downregulated the TNF-alpha and TGF-beta1 expression. In addition, PD98059 but not SB203580 inhibited the AP-1 DNA binding activity induced by silica. Based on these findings, it was conclude that Src-ERK/AP-1 signaling pathways are involved in the TNF-alpha and TGF-beta1 expression induced by silica in macrophages.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Effects of short-term cigarette smoke exposure on Fischer 344 rats and on selected lung proteins

A short-term 5-day cigarette smoke exposure study was conducted in Fischer 344 rats to identify smoke-induced lung protein changes. Groups of 10 male and 10 female rats at 5 weeks of age were randomly assigned to one of four exposure groups. Animals received filtered air (control) or 75, 200, or 400 mg total particulate matter (TPM)/m(3) of diluted Kentucky reference 3R4F cigarette smoke. Nose-only exposures were conducted for 3 hours/day for 5 consecutive days. Mean body weights were significantly reduced only in male rats exposed to 400 mg TPM/m(3). Body weight gains were significantly reduced in 200- and 400-mg TPM/m(3)-exposed males and in all smoke-exposed females compared with controls. Alveolar histiocytosis increased slightly in all smoke exposed-females and 200- and 400-mg TPM/m(3)-exposed males. Cyclooxygenase-2 staining increased at 400 mg TPM/m(3). Matrix metalloproteinase-12 staining of alveolar macrophages and bronchiolar epithelia increased in smoke-exposed animals, especially 400-mg TPM/m(3)-exposed females. Protein kinase C-alpha staining increased in macrophages at 200- and 400-mg TPM/m(3) doses. c-Jun NH(2)-terminal kinases staining decreased in smoke-exposed tissues. The identified changed proteins play roles in inflammation, transformation, proliferation, stress activation, and apoptosis.

Employing a Mechanistic Model for the MAPK Pathway to Examine the Impact of Cellular all or None Behavior on Overall Tissue Response

The mitogen activated protein kinase (MAPK) cascade is a three-tiered phosphorylation cascade that is ubiquitously expressed among eukaryotic cells. Its primary function is to propagate signals from cell surface receptors to various cytosolic and nuclear targets. Recent studies have demonstrated that the MAPK cascade exhibits an all-or-none response to graded stimuli. This study quantitatively investigates MAPK activation in Xenopus oocytes using both empirical and biologically-based mechanistic models. Empirical models can represent overall tissue MAPK activation in the oocytes. However, these models lack description of key biological processes and therefore give no insight into whether the cellular response occurs in a graded or all-or-none fashion. To examine the propagation of cellular MAPK all-or-none activation to overall tissue response, mechanistic models in conjunction with Monte Carlo simulations are employed. An adequate description of the dose response relationship of MAPK activation in Xenopus oocytes is achieved. Furthermore, application of these mechanistic models revealed that the initial receptor-ligand binding rate contributes to the cells' ability to exhibit an all-or-none MAPK activation response, while downstream activation parameters contribute more to the magnitude of activation. These mechanistic models enable us to identify key biological events which quantitatively impact the shape of the dose response curve, especially at low environmentally relevant doses.

Tobacco smoke exposure induces nicotine dependence in rats

RATIONALE

Tobacco smoke contains nicotine and many other compounds that act in concert on the brain reward system. Therefore, animal models are needed that allow the investigation of chronic exposure to the full spectrum of tobacco smoke constituents.

OBJECTIVES

The aim of these studies was to investigate if exposure to tobacco smoke leads to nicotine dependence in rats.

METHODS

The intracranial self-stimulation procedure was used to assess the negative affective aspects of nicotine withdrawal. Somatic signs were recorded from a checklist of nicotine abstinence signs. Nicotine self-administration sessions were conducted to investigate if tobacco smoke exposure affects the motivation to self-administer nicotine. Nicotinic receptor autoradiography was used to investigate if exposure to tobacco smoke affects central alpha7 nicotinic acetylcholine receptor (nAChR) and non-alpha7 nAChR levels (primarily alpha4beta2 nAChRs).

RESULTS

The nAChR antagonist mecamylamine dose-dependently elevated the brain reward thresholds of the rats exposed to tobacco smoke and did not affect the brain reward thresholds of the untreated control rats. Furthermore, mecamylamine induced more somatic withdrawal signs in the smoke-exposed rats than in the control rats. Nicotine self-administration was decreased 1 day after the last tobacco smoke exposure sessions and was returned to control levels 5 days later. Tobacco smoke exposure increased the alpha7 nAChR density in the CA2/3 area and the stratum oriens and increased the non-alpha7 nAChR density in the dentate gyrus.

CONCLUSION

Tobacco smoke exposure leads to nicotine dependence as indicated by precipitated affective and somatic withdrawal signs and induces an upregulation of nAChRs in the hippocampus.

Sulfur mustard analog induces oxidative stress and activates signaling cascades in the skin of SKH-1 hairless mice

A monofunctional analog of the chemical warfare agent sulfur mustard (HD), 2-chloroethyl ethyl sulfide (CEES), induces tissue damage similar to HD. Herein we studied the molecular mechanisms associated with CEES-induced skin inflammation and toxicity in SKH-1 hairless mice. Topical CEES exposure caused an increase in oxidative stress as observed by enhanced 4-hydroxynonenal and 5,5-dimethyl-2-(8-octanoic acid)-1-pyrroline N-oxide protein adduct formation and an increase in protein oxidation. The CEES-induced increase in the formation of 8-oxo-2-deoxyguanosine indicated DNA oxidation. CEES exposure instigated an increase in the phosphorylation of mitogen-activated protein kinases (MAPKs; ERK1/2, JNK, and p38). After CEES exposure, a significant increase in the phosphorylation of Akt at Ser473 and Thr308 was observed as well as upregulation of its upstream effector, PDK1, in mouse skin tissue. Subsequently, CEES exposure caused activation of AP-1 family proteins and the NF-kappaB pathway, including phosphorylation and degradation of IkappaBalpha in addition to phosphorylation of the NF-kappaB essential modulator. Collectively, our results indicate that CEES induces oxidative stress and the activation of the transcription factors AP-1 and NF-kappaB via upstream signaling pathways including MAPKs and Akt in SKH-1 hairless mouse skin. These novel molecular targets could be supportive in the development of prophylactic and therapeutic interventions against HD-related skin injury.

Characterisation of the proximal airway squamous metaplasia induced by chronic tobacco smoke exposure in spontaneously hypertensive rats

Background

Continuous exposure to tobacco smoke (TS) is a key cause of chronic obstructive pulmonary disease (COPD), a complex multifactorial disease that is difficult to model in rodents. The spontaneously hypertensive (SH) rat exhibits several COPD-associated co-morbidities such as hypertension and increased coagulation. We have investigated whether SH rats are a more appropriate animal paradigm of COPD.

Methods

SH rats were exposed to TS for 6 hours/day, 3 days/week for 14 weeks, and the lung tissues examined by immunohistochemistry.

Results

TS induced a CK13-positive squamous metaplasia in proximal airways, which also stained for Ki67 and p63. We hypothesise that this lesion arises by basal cell proliferation, which differentiates to a squamous cell phenotype. Differences in staining profiles for the functional markers CC10 and surfactant D, but not phospho-p38, indicated loss of ability to function appropriately as secretory cells. Within the parenchyma, there were also differences in the staining profiles for CC10 and surfactant D, indicating a possible attempt to compensate for losses in proximal airways. In human COPD sections, areas of CK13-positive squamous metaplasia showed sporadic p63 staining, suggesting that unlike the rat, this is not a basal cell-driven lesion.

Conclusion

This study demonstrates that although proximal airway metaplasia in rat and human are both CK13+ and therefore squamous, they potentially arise by different mechanisms.

Effect of dietary selenium and cigarette smoke on pulmonary cell proliferation in mice

The objective of this study was to determine if dietary selenium could inhibit pulmonary cell proliferation in control and cigarette smoke-exposed female A/J mice. Selenium in the form of sodium selenite was supplemented to purified diets similar to the AIN-93M diet to yield 0.15, 0.5, or 2.0 mg selenium/kg diet. After 3 weeks, mice in each dietary group were divided into two subgroups; one used as control, whereas the other was exposed to cigarette smoke for five consecutive days. Mice from both groups were euthanized 3 days later. Mice were administered bromodeoxyuridine in the drinking water starting 5 days before the initiation of the smoke exposure and continuing until they were euthanized. After euthanasia, the left lung lobe was processed for histology and cell proliferation analysis. Cigarette smoke increased cell proliferation in the terminal bronchioles and large airways, but not in alveoli. High-selenium diets inhibited cell proliferation in the alveoli, terminal bronchioles and large airways areas in both control and smoke-exposed mice. Increasing the dietary selenium level led to increased selenium levels in the blood and lung, and increased glutathione peroxidase (GPx) activity in the lung. Cytochrome P-450 1A1 protein levels in the lung were increased by cigarette smoke but were not affected by dietary selenium. It is concluded that dietary selenium inhibits pulmonary cell proliferation in both control and cigarette smoke-exposed mice, indicating that selenium is inhibiting cell proliferation independently of smoke exposure, and that this inhibition may be related to selenium concentration and GPx activity in the lung.

Relationship of phospho-pRb (Ser-807/811) level to exposure to tobacco smoke in primary non-small cell lung cancer

This study was aimed at understanding the effect of smoking on pRb phosphorylation and the clinicopathological significance of phospho-pRb in non-small cell lung cancers (NSCLCs). Phospho-pRb (Ser-807/811) expression was not detected in 149 (39%) of 382 patients, and the mean phospho-pRb (Ser-807/811) level was 5.7%. Squamous cell carcinoma had higher phospho-pRb (Ser-807/811) levels than adenocarcinoma (7.1%+/-10.4% versus 4.7%+/-7.9%; P=0.003). The association between phospho-pRb (Ser-807/811) levels and exposure to tobacco smoke was different according to the statuses of cyclin D1 expression and p16 methylation, suggesting that their statuses might play a role as an effect modifier in the relationship between phospho-pRb (Ser-807/811) levels and exposure to tobacco smoke. In stratified multivariate analysis, phospho-pRb (Ser-807/811) levels were not associated with exposure to tobacco smoke in 38 patients with p16 hypermethylation and cyclin D1 expression >5%, after adjusting for confounding factors. However, in the remaining 344 patients, the mean phospho-pRb (Ser-807/811) levels in patients who had smoked >40 pack years increased by 4.65% (P<0.0001) on average than those who had never smoked. No association was found between the phospho-pRb (Ser-807/811) levels and overall survival. In conclusion, the present study suggests that exposure to tobacco smoke is associated with phosphorylation of pRb in NSCLC patients and its relationship depends on the p16 methylation status and cyclin D1 expression levels.

Co-opted JNK/SAPK signaling in Wnt/beta-catenin-induced tumorigenesis

Aberrant stimulation of the canonical Wnt pathway induces mammary tumorigenesis in mice. It has been well documented that two types of tumors, adenocarcinoma and adenocarcinoma with squamous metaplasia, develop in these mutants. However, the molecular mechanism underlying the induction of squamous transdifferentiation remains largely unknown. Here, we show that JNK/SAPK signaling plays an important role in Wnt-dependent mammary development and malignant transformation. The JNK/SAPK pathway is stimulated in pregnancy-mediated lobulo-alveolar morphogenesis, a process highly dependent on Wnt/beta-catenin signaling. Strong elevations of JNK/SAPK signaling are associated with squamous metaplasia of the Wnt-induced adenocarcinoma. Reconstitution of beta-catenin and JNK/SAPK signaling activities also promotes expression of the squamous cell marker in cultured epithelial cells. Furthermore, a synergistic activation of these two pathways can be identified in the malignant squamous cells of human endometrial and lung cancers. This is potentially a significant discovery in modern cancer therapy because of the effectiveness of an angiogenesis inhibitor, Avastin, for the treatment of adenocarcinoma, but not squamous cell carcinoma, in human lung cancers. Our finding may improve the usage of biomarkers to distinguish these two poorly differentiated tumor types, sharing similar histologic features.

NF-kappaB inhibition is involved in tobacco smoke-induced apoptosis in the lungs of rats

Apoptosis is a vital mechanism for the regulation of cell turnover and plays a critical role in tissue homeostasis and development of many disease processes. Previous studies have demonstrated the apoptotic effect of tobacco smoke; however, the molecular mechanisms by which tobacco smoke triggers apoptosis remain unclear. In the present study we investigated the effects of tobacco smoke on the induction of apoptosis in the lungs of rats and modulation of nuclear factor-kappa B (NF-kappaB) in this process. Exposure of rats to 80 mg/m(3) tobacco smoke significantly induced apoptosis in the lungs. Tobacco smoke resulted in inhibition of NF-kappaB activity, noted by suppression of inhibitor of kappaB (IkappaB) kinase (IKK), accumulation of IkappaBalpha, decrease of NF-kappaB DNA binding activity, and downregulation of NF-kappaB-dependent anti-apoptotic proteins, including Bcl-2, Bcl-xl, and inhibitors of apoptosis. Initiator caspases for the death receptor pathway (caspase 8) and the mitochondrial pathway (caspase 9) as well as effector caspase 3 were activated following tobacco smoke exposure. Tobacco smoke exposure did not alter the levels of p53 and Bax proteins. These findings suggest the role of NF-kappaB pathway in tobacco smoke-induced apoptosis.

Stat3 downstream genes serve as biomarkers in human lung carcinomas and chronic obstructive pulmonary disease

Smoking causes lung cancer and chronic obstructive pulmonary disease (COPD) that impose severe health problem to humans. Both diseases are related to each other and can be induced by chronic inflammation in the lung. To identify the molecular mechanism for lung cancer formation, a CCSP-rtTA/(teto)(7)Stat3C bitransgenic model was generated recently. In this model, persistent activation of the Stat3 signaling pathway induced pulmonary inflammation and adenocarcinoma formation in the lung. A group of Stat3 downstream genes were identified by Affymetrix GeneChip microarray analysis that can be used as biomarkers for lung cancer diagnosis and prognosis. To determine which human lung cancers are related to the Stat3 pathway, multiple Stat3 downstream genes were screened in human lung cancers (adenocarcinomas and squamous cell carcinomas) and lung tissue with COPD. In both cancer and COPD, the Stat3 gene was up-regulated. A panel of Stat3-up-regulated downstream genes in mice was up-regulated in human adenocarcinomas, but not in human squamous cell carcinomas. This panel of genes was also modestly up-regulated in lung tissue with COPD from patients with a history of smoking and not up-regulated in those without histories of smoking. Several Stat3-down-regulated downstream genes also showed differential expression patterns in carcinoma and COPD. These studies support a concept that Stat3 is a potent oncogenic molecule that plays a role in formation of lung adenocarcinomas in both mice and humans. The carcinogenesis of adenocarcinoma and squamous cell carcinoma is mediated by different molecular mechanisms and pathways in vivo. Stat3 and its downstream genes can serve as biomarkers for lung adenocarcinoma and COPD diagnosis and prognosis in mice and humans.

Acute tobacco smoke-induced airways inflammation in spontaneously hypertensive rats

Common laboratory rats and mice fail to develop persistent, progressive pulmonary inflammation found in chronic obstructive pulmonary disease as a result of tobacco smoke exposure. We hypothesized that spontaneously hypertensive rats would be more susceptible than normal Wistar Kyoto rats to acute tobacco smoke-induced pulmonary inflammation due to impaired apoptosis. Spontaneously hypertensive rats display systemic oxidative stress, inflammation, hypercoagulation, and immunosupression, similar to humans with chronic obstructive pulmonary disease. Male spontaneously hypertensive rats and Wistar Kyoto rats were exposed whole-body to tobacco smoke (total particulate concentration 75-85 mg/m(3)) or filtered air for 6 h/day for 2 or 15 days (3 days/wk). Tobacco smoke caused an increase in bronchoalveolar lavage fluid neutrophils at both time points in each strain. Significantly more neutrophils were noted in spontaneously hypertensive rats at 15 days compared to Wistar Kyoto rats. There was a trend of increase for macrophages in spontaneously hypertensive rats at both time points (significant at 2 days). TUNEL assay detected apoptotic cells in bronchoalveolar lavage fluid and lung tissue sections. The number of apoptotic neutrophils in airway walls and bronchoalveolar lavage fluid increased at 2 days in both strains, but at 15 days the effect was much lower in spontaneously hypertensive rats than in Wistar Kyoto rats. Tobacco smoke induces a greater inflammatory response associated with lower apoptotic neutrophils in the lungs of spontaneously hypertensive rats compared to Wistar Kyoto rats. The spontaneously hypertensive rat may be a more relevant animal model of acute tobacco smoke-induced airway inflammation than other laboratory rats.

Air exposure induced squamous metaplasia of human limbal epithelium

PURPOSE

Squamous metaplasia is a pathologic process that frequently occurs in nonkeratinized stratified ocular surface epithelia. The mechanism for this occurrence is largely unknown except for vitamin A deficiency.

METHODS

Human limbal explants were cultured under airlift with or without p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 or in a submerged manner for different durations up to 2 weeks. Epithelial cell proliferation, differentiation, limbal stem cell maintenance, and expansion were studied using certain markers such as Ki67, p63, K10 and K12 keratins, filaggrin, Pax6, ABCG-2, and Musashi-1. Expression of phospho-p38 MAPK and its downstream transcription factors, C/EBPalpha and C/EBPbeta, were studied by immunohistochemistry. Epithelial cells harvested from explants after 2 weeks of culturing under different conditions were seeded onto 3T3 feeder layers and cultured for 12 days. The differentiation of clonal epithelial cells was investigated by double staining to K12 and K10 keratins.

RESULTS

The squamous metaplasia model was successfully created by culturing human limbal explants at an air-liquid interface (airlift) for 2 weeks. Increased stratification and hyperproliferation only happened in the limbal, but not the corneal, epithelium in airlift, but not submerged, cultures. Epithelial proliferation was associated with a transient increase of limbal epithelial stem cells. Abnormal epidermal differentiation-evidenced by positive expression of K10 keratin in suprabasal cells and filaggrin in superficial cells-ensued. Clones generated from epithelial cells harvested from airlift culture only expressed K12 keratin without K10. As early as 2 days in airlift cultures, p38 expression emerged in limbal basal epithelial cells and gradually extended to the cytoplasm and nuclei. Furthermore, addition of the p38 inhibitor SB203580 abolished abnormal epidermal differentiation without affecting limbal epithelial proliferation. Expression of C/EBPalpha and C/EBPbeta, downstream of the p38 MAPK signaling pathway, was strongly induced by airlift culture and partially was inhibited by SB203580.

CONCLUSIONS

Dryness resulting from exposure activates p38 MAPK signaling coupled with abnormal epidermal differentiation without intrinsic alteration of stem cells in the limbus. On the ocular surface, p38 inhibitors may have the potential to revert the pathologic process of squamous metaplasia induced by dryness.

The activator protein-1 transcription factor in respiratory epithelium carcinogenesis

Respiratory epithelium cancers are the leading cause of cancer-related death worldwide. The multistep natural history of carcinogenesis can be considered as a gradual accumulation of genetic and epigenetic aberrations, resulting in the deregulation of cellular homeostasis. Growing evidence suggests that cross-talk between membrane and nuclear receptor signaling pathways along with the activator protein-1 (AP-1) cascade and its cofactor network represent a pivotal molecular circuitry participating directly or indirectly in respiratory epithelium carcinogenesis. The crucial role of AP-1 transcription factor renders it an appealing target of future nuclear-directed anticancer therapeutic and chemoprevention approaches. In the present review, we will summarize the current knowledge regarding the implication of AP-1 proteins in respiratory epithelium carcinogenesis, highlight the ongoing research, and consider the future perspectives of their potential therapeutic interest.

Gene expression profile of esophageal cancer in North East India by cDNA microarray analysis

AIM

To identify alterations in genes and molecular functional pathways in esophageal cancer in a high incidence region of India where there is a widespread use of tobacco and betel quid with fermented areca nuts.

METHODS

Total RNA was isolated from tumor and matched normal tissue of 16 patients with esophageal squamous cell carcinoma. Pooled tumor tissue RNA was labeled with Cy3-dUTP and pooled normal tissue RNA was labeled with Cy5-dUTP by direct labeling method. The labeled probes were hybridized with human 10K cDNA chip and expression profiles were analyzed by Genespring GX V 7.3 (Silicon Genetics).

RESULTS

Nine hundred twenty three genes were differentially expressed. Of these, 611 genes were upregulated and 312 genes were downregulated. Using stringent criteria (P < or = 0.05 and > or = 1.5 fold change), 127 differentially expressed genes (87 upregulated and 40 downregulated) were identified in tumor tissue. On the basis of Gene Ontology, four different molecular functional pathways (MAPK pathway, G-protein coupled receptor family, ion transport activity, and serine or threonine kinase activity) were most significantly upregulated and six different molecular functional pathways (structural constituent of ribosome, endopeptidase inhibitor activity, structural constituent of cytoskeleton, antioxidant activity, acyl group transferase activity, eukaryotic translation elongation factor activity) were most significantly downregulated.

CONCLUSION

Several genes that showed alterations in our study have also been reported from a high incidence area of esophageal cancer in China. This indicates that molecular profiles of esophageal cancer in these two different geographic locations are highly consistent.

Non-genomic effects of 17beta-estradiol in activation of the ERK1/ERK2 pathway induces cell proliferation through upregulation of cyclin D1 expression in bovine artery endothelial cells

OBJECTIVE

Growing evidence indicates that estrogen's non-genomic effects play important roles in cellular functions and backs up the hypothesis of the existence of a membrane estrogen receptor (mER) in a number of cell types, but little is known about the complementary effects between traditional genomic and novel non-genomic effects of estrogen. The aim of the present study was to explore the non-genomic activation of ERK1/2 mitogen-activated protein kinase (MAPK) by 17beta-estradiol (E(2)) through mER and its role in cell proliferation.

METHODS

On cultured bovine artery endothelial cells (BAECs) we used the [(3)H]thymidine incorporation assay to evaluate the influence of E(2) on cell proliferation and fluorescence microscopy to show the presence of mER on the cell membrane. Scatchard analysis was performed to identify and characterize the mER on a purified membrane fraction of BAECs.

RESULTS

E(2) upregulated cyclin D1 protein expression and enhanced cell proliferation. Inhibition of the MAPK cascade with PD98059 or of G protein with pertussis toxin (PTX) completely abolished the above effects, while the estrogen receptor antagonist tamoxifen attenuated E(2)-dependent upregulation of cyclin D1 and cell proliferation. Accordingly, E(2) rapidly led to ERK1/ERK2 activation, which was prevented by tamoxifen or PTX and was entirely reproduced by membrane-impermeable estradiol-bovine serum albumin conjugate (E(2)coBSA). Immunofluorescent staining with E(2)coBSA-fluorescein isothiocyanate resulted in a punctuate staining pattern of the plasma membrane and Scatchard analysis of the E(2)-binding protein in a purified membrane fraction of BAECs showed that E(2) binds to the membrane fraction with a dissociation constant of 0.2394 nmol/l.

CONCLUSION

Our findings showed that E(2) induces cell proliferation through upregulation of cyclin D1 via non-genomic activation of the ERK1/ERK2 pathway mediated by mER and G protein.

c-Jun N-terminal kinase is activated in non-small-cell lung cancer and promotes neoplastic transformation in human bronchial epithelial cells

c-Jun N-terminal kinase (JNK) has been reported to either potentiate or inhibit oncogenesis, depending upon the cellular context, but its role in lung neoplasia is unclear. Here we sought to define the role of JNK in lung neoplasia by examining evidence of JNK phosphorylation in non-small-cell lung cancer (NSCLC) biopsy samples and by using genetic and pharmacologic approaches to modulate JNK expression and activity in cultured cells. Immunohistochemical staining for JNK phosphorylation was detected in 114 (45%) of 252 NSCLC biopsy samples and was predominantly nuclear, providing evidence of JNK activation in a subset of NSCLC cases. Introduction of a doxycycline-inducible, constitutively active, mutant mitogen-activated protein kinase kinase 4 (MKK4) into the human bronchial epithelial cell lines BEAS-2B and HB56B increased the cells' proliferation, migration, invasion and clonogenicity. Depletion of JNK in MKK4 mutant-transformed BEAS-2B cells by introduction of JNK1/2 short hairpin RNA reversed the transformed phenotype, indicating that JNK activation is oncogenic and MKK4 confers neoplastic properties in these cells. The proliferation of NSCLC cell lines HCC827 and H2009, in which JNK and its substrate c-Jun are constitutively phosphorylated, was inhibited by SP600125, a JNK kinase inhibitor. We conclude that JNK is activated in a subset of NSCLC biopsy samples and promotes oncogenesis in the bronchial epithelium, suggesting that strategies to inhibit the JNK pathway should be considered for the prevention and treatment of NSCLC.

Green tea polyphenol EGCG suppresses cigarette smoke condensate-induced NF-kappaB activation in normal human bronchial epithelial cells

Cigarette smoke is a powerful inducer of inflammatory responses resulting in disruption of major cellular pathways with transcriptional and genomic alterations driving the cells towards carcinogenesis. Cell culture and animal model studies indicate that (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol present in green tea, possesses potent anti-inflammatory and antiproliferative activity capable of selectively inhibiting cell growth and inducing apoptosis in cancer cells without adversely affecting normal cells. Here, we demonstrate that EGCG pretreatment (20-80 microM) of normal human bronchial epithelial cells (NHBE) resulted in significant inhibition of cigarette smoke condensate (CSC)-induced cell proliferation. Nuclear factor-kappaB (NF-kappaB) controls the transcription of genes involved in immune and inflammatory responses. In most cells, NF-kappaB prevents apoptosis by mediating cell survival signals. Pretreatment of NHBE cells with EGCG suppressed CSC-induced phosphorylation of IkappaBalpha, and activation and nuclear translocation of NF-kappaB/p65. NHBE cells transfected with a luciferase reporter plasmid containing an NF-kappaB-inducible promoter sequence showed an increased reporter activity after CSC exposure that was specifically inhibited by EGCG pretreatment. Immunoblot analysis showed that pretreatment of NHBE cells with EGCG resulted in a significant downregulation of NF-kappaB-regulated proteins cyclin D1, MMP-9, IL-8 and iNOS. EGCG pretreatment further inhibited CSC-induced phosphorylation of ERK1/2, JNK and p38 MAPKs and resulted in a decreased expression of PI3K, AKT and mTOR signaling molecules. Taken together, our data indicate that EGCG can suppress NF-kappaB activation as well as other pro-survival pathways such as PI3K/AKT/mTOR and MAPKs in NHBE cells, which may contribute to its ability to suppress inflammation, proliferation and angiogenesis induced by cigarette smoke.