Nicotine primarily suppresses lung Th2 but not goblet cell and muscle cell responses to allergens

Tobacco smoking: patterns, health consequences for adults, and the long-term health of the offspring

Tobacco use started several centuries ago and increased markedly after the invention of the cigarette making machine. Once people start smoking they find it difficult to quit the habit. This is due to the addictive effect of nicotine in tobacco smoke. Various epidemiologic and laboratory studies clearly showed that smoking is associated with various diseases such as heart diseases, asthma and emphysema and the associated increase in morbidity and mortality of smokers. Several studies implicate nicotine as the causative factor in tobacco smoke. Apart from nicotine, various carcinogens also occur in tobacco smoke resulting in an increase in the incidence of cancer in smokers. While the smoking habit is decreasing in developed countries, tobacco use increases in the developing countries. Smoking prevalence is also highest in poor communities and amongst those with low education levels. It is important to note that, although ther is a decline in the number of smokers in the developed countries, there is a three to four decades lag between the peak in smoking prevalence and the subsequent peak in smoking related mortality. It has been shown that maternal smoking induces respiratory diseases in the offspring. There is also evidence that parental smoking may program the offspring to develop certain diseases later in life. Various studies showed that maternal nicotine exposure during pregnancy and lactation via tobacco smoke of nicotine replacement therapy (NRT), program the offspring to develop compromised lung structure later in life with the consequent compromised lung function. This implies that NRT is not an option to assist pregnant or lactating smokers to quit the habit. Even paternal smoking may have an adverse effect on the health of the offspring since it has been shown that 2nd and 3rd hand smoking have adverse health consequences for those exposed to it.

Role of nicotinic receptors and acetylcholine in mucous cell metaplasia, hyperplasia, and airway mucus formation in vitro and in vivo

BACKGROUND

Airway mucus hypersecretion is a key pathophysiologic feature in a number of lung diseases. Cigarette smoke/nicotine and allergens are strong stimulators of airway mucus; however, the mechanism of mucus modulation is unclear.

OBJECTIVES

We sought to characterize the pathway by which cigarette smoke/nicotine regulates airway mucus and identify agents that decrease airway mucus.

METHODS

IL-13 and γ-aminobutyric acid type A receptors (GABA(A)Rs) are implicated in airway mucus. We examined the role of IL-13 and GABA(A)Rs in nicotine-induced mucus formation in normal human bronchial epithelial (NHBE) and A549 cells and secondhand cigarette smoke-induced, ovalbumin-induced, or both mucus formation in vivo.

RESULTS

Nicotine promotes mucus formation in NHBE cells; however, the nicotine-induced mucus formation is independent of IL-13 but sensitive to the GABA(A)R antagonist picrotoxin. Airway epithelial cells express α7-, α9-, and α10-nicotinic acetylcholine receptors (nAChRs), and specific inhibition or knockdown of α7- but not α9/α10-nAChRs abrogates mucus formation in response to nicotine and IL-13. Moreover, addition of acetylcholine or inhibition of its degradation increases mucus in NHBE cells. Nicotinic but not muscarinic receptor antagonists block allergen- or nicotine/cigarette smoke-induced airway mucus formation in NHBE cells, murine airways, or both.

CONCLUSIONS

Nicotine-induced airway mucus formation is independent of IL-13, and α7-nAChRs are critical in airway mucous cell metaplasia/hyperplasia and mucus production in response to various promucoid agents, including IL-13. In the absence of nicotine, acetylcholine might be the biological ligand for α7-nAChRs to trigger airway mucus formation. α7-nAChRs are downstream of IL-13 but upstream of GABA(A)Rα2 in the MUC5AC pathway. Acetylcholine and α7-nAChRs might serve as therapeutic targets to control airway mucus.

Chronic aspiration shifts the immune response from adaptive immunity to innate immunity in a murine model of asthma

OBJECTIVE AND DESIGN

The hypothesis that aspiration of gastric fluid drives the anti-ovalbumin response toward a Th2 reaction even in animals not prone to Th2 responses was evaluated.

SUBJECTS

Forty-eight male C57BL/6 mice were used.

METHODS

Mice were sensitized and challenged with ovalbumin starting 5 weeks prior to the initiation of weekly aspirations of either gastric fluid or normal saline as a control. Weekly aspiration continued during the course of exposure to ovalbumin.

TREATMENT

Aspiration consisted of 50 μl of gastric fluid with 50 μl of 0.9 % normal saline used as a control. Antigen exposure consisted of sensitization to ovalbumin via intraperitoneal injection on days 0 and 14 and challenge on day 21 with aerosolized antigen for 30 min.

RESULTS

No evidence of a shift toward a Th2 response as a result of gastric fluid aspiration was seen in the Th1-prone strain utilized, although a profound down-regulation of a broad array of T cell-associated cytokines and chemokines and up-regulation of macrophage-associated markers was observed as a result of aspiration.

CONCLUSIONS

These data provide support for the hypothesis that the clinical association between asthma and gastroesophageal reflux disease (GERD) does not involve an exacerbation of asthma by GERD-associated aspiration of gastric fluid, but may cause immune reactions unrelated to the asthma pathology.

The prevalence of rhinitis and its association with smoking and obesity in a nationwide survey of Japanese adults

BACKGROUND

Rhinitis is a common disease, and its prevalence is increasing worldwide. Several studies have provided evidence of a strong association between asthma and rhinitis. Although smoking and obesity have been extensively analyzed as risk factors of asthma, associations with rhinitis are less clear.

OBJECTIVE

The aims of our study were (i) to evaluate the prevalence of rhinitis using the European Community Respiratory Health Survey (ECRHS) questionnaire in Japanese adults and (ii) to evaluate the associations of smoking and body mass index (BMI) with rhinitis.

METHODS

Following our study conducted in 2006-2007 to determine the prevalence of asthma using the ECRHS questionnaire, our present analysis evaluates the prevalence of rhinitis and its association with smoking and BMI in Japanese adults 20-79 years of age (N = 22819). We classified the subjects (20-44 or 45-79 years) into four groups as having (i) neither rhinitis nor asthma; (ii) rhinitis without asthma; (iii) asthma without rhinitis; or (iv) rhinitis with asthma. We then evaluated associations with smoking and BMI in each group.

RESULTS

The overall age-adjusted prevalence of rhinitis was 35.1% in men and 39.3% in women. A higher prevalence was observed in the younger population than in the older population. Active smoking and obesity were positively associated with asthma without rhinitis. In contrast, particularly in the 20- to 44-year age-group, active smoking and obesity were negatively associated with rhinitis without asthma.

CONCLUSION

The results of the present study suggest that smoking and obesity may have different effects on the development of rhinitis and asthma.

Molecular changes in smoking-related lung cancer

To elucidate the effect of cigarette smoke on developing lung cancer among individuals, numerous genetic and epigenetic factors related to cigarette smoke-induced lung cancers have been widely investigated and a various genes, loci and pathways have been identified as candidates to date. However, the importance of these molecular alterations in the initiation and progression of lung cancer still remains imprecise and different molecules altered in lung cancer are being used for stratification of patients for targeted therapy. There are a number of molecular pathways involved in the development of lung cancer, and environmental factors related to these alterations are still unclear. Furthermore, various genetic alterations determined by candidate gene approach have not been re-evaluated for their functional significance together with epigenetic alterations in the same population. Accumulated evidence suggested that lung cancer in ever smokers and never smokers follow distinct molecular pathways and may therefore respond to distinct therapy. Therefore, additional studies will be essential to re-evaluate the individual risk of developing lung cancer based on the combination of genetic and epigenetic alterations and to set up a guideline to assess the individual risk for lung cancer and for its prevention.

Inhalation of sulfur mustard causes long-term T cell-dependent inflammation: possible role of Th17 cells in chronic lung pathology

Sulfur mustard (SM) is a highly toxic chemical warfare agent that remains a threat to human health. The immediate symptoms of pulmonary distress may develop into chronic lung injury characterized by progressive lung fibrosis, the major cause of morbidity among the surviving SM victims. Although SM has been intensely investigated, little is known about the mechanism(s) by which SM induces chronic lung pathology. Increasing evidence suggests that IL-17(+) cells are critical in fibrosis, including lung fibrotic diseases. In this study we exposed F344 rats and cynomolgus monkeys to SM via inhalation and determined the molecular and cellular milieu in their lungs at various times after SM exposure. In rats, SM induced a burst of pro-inflammatory cytokines/chemokines within 72 h, including IL-1β, TNF-α, IL-2, IL-6, CCL2, CCL3, CCL11, and CXCL1 that was associated with neutrophilic infiltration into the lung. At 2 wks and beyond (chronic phase), lymphocytic infiltration and continued elevated expression of cytokines/chemokines were sustained. TGF-β, which was undetectable in the acute phase, was strongly upregulated in the chronic phase; these conditions persisted until the animals were sacrificed. The chronic phase was also associated with myofibroblast proliferation, collagen deposition, and presence of IL-17(+) cells. At ≥30 days, SM inhalation promoted the accumulation of IL-17(+) cells in the inflamed areas of monkey lungs. Thus, SM inhalation causes acute and chronic inflammatory responses; the latter is characterized by the presence of TGF-β, fibrosis, and IL-17(+) cells in the lung. IL-17(+) cells likely play an important role in the pathogenesis of SM-induced lung injury.

Exposure to nicotine adversely affects the dendritic cell system and compromises host response to vaccination

The magnitude of Th1 cells response to vaccination is a critical factor in determining protection from clinical disease. Our previous in vitro studies suggested that exposure to the nicotine component of cigarette smoke skews the differentiation of both human and mouse dendritic cell (DC) precursors into atypical DCs (DCs differentiated ex vivo in the presence of nicotine) lacking parameters essential for the development of Th1-mediated immunity. In this study, we determined the causal relationship between nicotine-induced DC alterations and host response to vaccines. We show that animals exposed to nicotine failed to develop and maintain Ag-specific effector memory Th1 cells and Ab production to protein-based vaccine formulated with Th1 adjuvants. Accordingly, both prophylactic and therapeutic vaccines failed to protect and cure the nicotine-exposed mice from disease. More importantly, we demonstrate the nicotine-induced defects in the biological activities of in vivo DCs as an underlying mechanism. Indeed, i.v. administration of DCs differentiated in the presence of nicotine preferentially promoted the development of Ag-specific IL-4-producing effector cells in the challenged mice. In addition, DC subsets isolated from mice exposed to nicotine produced significantly less cytokines in response to Th1 adjuvants and inadequately supported the development of Ag-specific Th1 cells. Collectively, our studies suggest that nicotine-induced defects in the DC system compromises vaccine efficacy in smokers.

Cholinergic regulation of airway inflammation and remodelling

Acetylcholine is the predominant parasympathetic neurotransmitter in the airways that regulates bronchoconstriction and mucus secretion. Recent findings suggest that acetylcholine regulates additional functions in the airways, including inflammation and remodelling during inflammatory airway diseases. Moreover, it has become apparent that acetylcholine is synthesized by nonneuronal cells and tissues, including inflammatory cells and structural cells. In this paper, we will discuss the regulatory role of acetylcholine in inflammation and remodelling in which we will focus on the role of the airway smooth muscle cell as a target cell for acetylcholine that modulates inflammation and remodelling during respiratory diseases such as asthma and COPD.

Nicotine exerts an anti-inflammatory effect in a murine model of acute lung injury

Activation of the cholinergic anti-inflammatory pathway through direct activation of nicotinic acetylcholine receptors on immune cells can inhibit pro-inflammatory chemokine and cytokine release and thereby protect in a variety of inflammatory diseases. The aim of this study was to investigate whether nicotine treatment protected against acute lung inflammation. Mice challenged with intratracheal lipopolysaccharide (LPS, 50 μg) were treated with nicotine (0.2 or 0.4 mg/kg, sc). After 24 h, bronchoalveolar lavage fluid (BALF) was obtained to measure leukocyte infiltration, lung edema, and pro-inflammatory chemokine (MIP-1α, MIP-2, and eotaxin) and cytokine (IL-1, IL-6, and TNF-α) levels. Nicotine treatment reduced the LPS-mediated infiltration of leukocytes and edema as evidenced by decreased BALF inflammatory cells, myeloperoxidase, and protein. Nicotine also downregulated lung production of pro-inflammatory chemokines and cytokines. These data support the proposal that activation of the cholinergic anti-inflammatory pathway may represent a useful addition to the therapy of acute respiratory distress syndrome.

Effective treatment of experimental ragweed-induced asthma with STAT-6-IP, a topically delivered cell-penetrating peptide

BACKGROUND

Treatment of allergic airways disease including asthma remains primarily local immunosuppression with topical corticosteroid and symptomatic management with antihistamines and anti-leucotrienes. We have developed a novel topical therapy designed to specifically inhibit the events associated with Th2 cell activation.

OBJECTIVE

We assessed the efficacy of our cell-penetrating STAT-6 inhibitory peptide (STAT-6-IP), a novel treatment for allergic airways disease, in a model of chronic ragweed-induced asthma.

METHODS

Six- to eight-week-old mice were sensitized over 5 weeks with intranasal (IN) exposures to whole ragweed allergen without adjuvant. Mice were then IN challenged with Amba 1 with and without treatment IN with STAT-6-IP and allergic responses assessed. Two weeks later, some animals were rechallenged with Amba 1 with or without STAT-6-IP.

RESULTS

Animals exposed to IN ragweed developed significant airway hyperresponsiveness and airways inflammation upon challenge. Cell cultures showed increases in Th2 cytokines IL-4 and IL-13. Topical STAT-6-IP treatment reduced production of Th2 cytokines, demonstrated increased expression of IL-10 and reduced frequency of cultured IL-4 positive CD4+ T cells derived from treated mice, suggesting that STAT-6-IP treatment may be immunomodulatory. Airway responsiveness to methacholine challenge in the treatment group was similarly reduced to that of the non-allergic PBS-exposed animals. Importantly, STAT-6-IP-treated mice remained hyporesponsive following second ragweed challenge 2 weeks after treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

These data suggest that topical application of the STAT-6-IP is sufficient to inhibit allergic airways responses in animals chronically sensitized and challenged with ragweed. Data show that a single topical treatment course is sufficient to block signs of allergic responses to ragweed in the airways for at least 2 weeks. STAT-6-IP is a novel potential treatment for chronic allergic asthma.

Prenatal secondhand cigarette smoke promotes Th2 polarization and impairs goblet cell differentiation and airway mucus formation

Parental, particularly maternal, smoking increases the risk for childhood allergic asthma and infection. Similarly, in a murine allergic asthma model, prenatal plus early postnatal exposure to secondhand cigarette smoke (SS) exacerbates airways hyperreactivity and Th2 responses in the lung. However, the mechanism and contribution of prenatal versus early postnatal SS exposure on allergic asthma remain unresolved. To identify the effects of prenatal and/or early postnatal SS on allergic asthma, BALB/c dams and their offspring were exposed gestationally and/or 8-10 wk postbirth to filtered air or SS. Prenatal, but not postnatal, SS strongly increased methacholine and allergen (Aspergillus)-induced airway resistance, Th2 cytokine levels, and atopy and activated the Th2-polarizing pathway GATA3/Lck/ERK1/2/STAT6. Either prenatal and/or early postnatal SS downregulated the Th1-specific transcription factor T-bet and, surprisingly, despite high levels of IL-4/IL-13, dramatically blocked the allergen-induced mucous cell metaplasia, airway mucus formation, and the expression of mucus-related genes/proteins: Muc5ac, γ-aminobutyric acid A receptors, and SAM pointed domain-containing Ets-like factor. Given that SS/nicotine exposure of normal adult mice promotes mucus formation, the results suggested that fetal and neonatal lung are highly sensitive to cigarette smoke. Thus, although the gestational SS promotes Th2 polarization/allergic asthma, it may also impair and/or delay the development of fetal and neonatal lung, affecting mucociliary clearance and Th1 responses. Together, this may explain the increased susceptibility of children from smoking parents to allergic asthma and childhood respiratory infections.

Smoking and nonsmoking asthma: differences in clinical outcome and pathogenesis

Cigarette smoking in asthma is frequently present and is associated with worsening of symptoms, accelerated lung-function decline, a higher frequency of hospital admissions, a higher degree of asthma severity, poorer asthma control and reduced responsiveness to corticosteroids. Furthermore, it is associated with reduced numbers of eosinophils and higher numbers of mast cells in the submucosa of the airway wall. Airway remodeling is increased as evidenced by increased epithelial thickness and goblet cell hyperplasia in smoking asthmatics. The pathogenesis responsible for smoking-induced changes in airway inflammation and remodeling in asthma is complex and largely unknown. The underlying mechanism of reduced corticosteroid responsiveness is also unknown. This article discusses differences between smoking and nonsmoking asthmatics regarding the clinical expression of asthma, lung function, response to corticosteroids, airway inflammation and remodeling processes. Possible pathogenetic mechanisms that may explain the links between cigarette smoking and changes in the clinical expression of asthma will be discussed, as well as the beneficial effects of smoking cessation.

The role of IL-1β in nicotine-induced immunosuppression and neuroimmune communication

Although a number of inflammatory cytokines are increased during sepsis, the clinical trials aimed at down-regulating these mediators have not improved the outcome. These paradoxical results are attributed to loss of the "tolerance" phase that normally follows the proinflammatory response. Chronic nicotine (NT) suppresses both adaptive and innate immune responses, and the effects are partly mediated by the nicotinic acetylcholine receptors in the brain; however, the mechanism of neuroimmune communication is not clear. Here, we present evidence that, in rats and mice, NT initially increases IL-1β in the brain, but the expression is downregulated within 1-2 week of chronic exposure, and the animals become resistant to proinflammatory/pyrogenic stimuli. To examine the relationship between NT, IL-1β, and immunosuppression, we hypothesized that NT induces IL-1β in the brain, and its constant presence produces immunological "tolerance". Indeed, unlike wild-type C57BL/6 mice, chronic NT failed to induce immunosuppression or downregulation of IL-1β expression in IL-1β-receptor knockout mice. Moreover, while acute intracerebroventricular administration of IL-1β in Lewis (LEW) rats activated Fyn and protein tyrosine kinase activities in the spleen, chronic administration of low levels of IL-1β progressively diminished the pyrogenic and T cell proliferative responses of treated animals. Thus, IL-1β may play a critical role in the perception of inflammation by the CNS and the induction of an immunologic "tolerant" state. Moreover, the immunosuppressive effects of NT might be at least partly mediated through its effects on the brain IL-1β. This represents a novel mechanism for neuroimmune communication.

Effects of nicotine on apoptosis in human gingival fibroblasts

AIM

Cigarette smoke is a complex mixture of more than 4700 chemical compounds including free radicals and oxidants and it is a world widely known problem to health. Nicotine is the major compound of tobacco and known as the cause of gingivitis and periodontitis. It induces intracellular oxidative stress recognized as the important agent in the damage of biological molecules. The aim of this study is to clarify the cytotoxic pathway of nicotine in human gingival fibroblasts (HGFs).

METHODS

Human gingival fibroblasts stimulated by nicotine were used as an in vitro model. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to detect cell viability and reactive oxygen species (ROS) generation was assessed with 2,7-dichlorofluoroscein diacetate (DCF-DA). Morphological change was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labelling (TUNEL) assay, stained with 4,6-diamidino-2-phenylindole (DAPI). To delineate the roles of extracellular signal-regulated kinase (ERK), P38 and c-Jun N-terminal kinase (JNK), Western blot and caspase-3 (CASP3) activity assay were performed.

RESULTS

Exposure of the human gingival fibroblasts to nicotine reduced cell viability by time and dose dependent and increased the generation of ROS. It also showed morphological evidence of increased apoptosis, resulted in transient activation of JNK and ERK concomitant with activation of P38, and stimulated apoptosis as evidenced by CASP3 activation and Poly ADP ribose polymerase (PARP) cleavage.

CONCLUSION

These results suggest that nicotine induces apoptosis through the ROS generation and CASP3 dependent pathways in HGFs.

Life-long programming implications of exposure to tobacco smoking and nicotine before and soon after birth: evidence for altered lung development

Tobacco smoking during pregnancy remains common, especially in indigenous communities, and likely contributes to respiratory illness in exposed offspring. It is now well established that components of tobacco smoke, notably nicotine, can affect multiple organs in the fetus and newborn, potentially with life-long consequences. Recent studies have shown that nicotine can permanently affect the developing lung such that its final structure and function are adversely affected; these changes can increase the risk of respiratory illness and accelerate the decline in lung function with age. In this review we discuss the impact of maternal smoking on the lungs and consider the evidence that smoking can have life-long, programming consequences for exposed offspring. Exposure to maternal tobacco smoking and nicotine intake during pregnancy and lactation changes the genetic program that controls the development and aging of the lungs of the offspring. Changes in the conducting airways and alveoli reduce lung function in exposed offspring, rendering the lungs more susceptible to obstructive lung disease and accelerating lung aging. Although it is generally accepted that prevention of maternal smoking during pregnancy and lactation is essential, current knowledge of the effects of nicotine on lung development does not support the use of nicotine replacement therapy in this group.

Polymorphisms in NF-κB, PXR, LXR, PPARγ and risk of inflammatory bowel disease

AIM: To investigate the contribution of polymorphisms in nuclear receptors to risk of inflammatory bowel disease (IBD).

METHODS: Genotypes of nuclear factor (NF)-κB (NFKB1) NFκB -94ins/del (rs28362491); peroxisome proliferator-activated receptor (PPAR)-γ (PPARγ) PPARγ Pro12Ala (rs 1801282) and C1431T (rs 3856806); pregnane X receptor (PXR) (NR1I2) PXR A-24381C (rs1523127), C8055T (2276707), and A7635G (rs 6785049); and liver X receptor (LXR) (NR1H2) LXR T-rs1405655-C and T-rs2695121-C were assessed in a Danish case-control study of 327 Crohn’s disease patients, 495 ulcerative colitis (UC) patients, and 779 healthy controls. Odds ratio (OR) and 95% CI were estimated by logistic regression models.

RESULTS: The PXR A7635G variant, the PPARγ Pro12Ala and LXR T-rs2695121-C homozygous variant genotypes were associated with risk of UC (OR: 1.31, 95% CI: 1.03-1.66, P = 0.03, OR: 2.30, 95% CI: 1.04-5.08, P = 0.04, and OR: 1.41, 95% CI: 1.00-1.98, P = 0.05, respectively) compared to the corresponding homozygous wild-type genotypes. Among never smokers, PXR A7635G and the LXR T-rs1405655-C and T-rs2695121-C variant genotypes were associated with risk of IBD (OR: 1.41, 95% CI: 1.05-1.91, P = 0.02, OR: 1.63, 95% CI: 1.21-2.20, P = 0.001, and OR: 2.02, 95% CI: 1.36-2.99, P = 0.0005, respectively) compared to the respective homozygous variant genotypes. PXR A7635G (rs6785049) variant genotype was associated with a higher risk of UC diagnosis before the age of 40 years and with a higher risk of extensive disease (OR: 1.34, 95% CI: 1.03-1.75 and OR: 2.49, 95% CI: 1.24-5.03, respectively).

CONCLUSION: Common PXR and LXR polymorphisms may contribute to risk of IBD, especially among never smokers.

Nicotine suppresses inflammatory factors in HBE16 airway epithelial cells after exposure to cigarette smoke extract and lipopolysaccharide

Cigarette smoke is a major cause of chronic inflammatory pulmonary disease, leading to inflammation, mucin (MUC) production, tissue damage, and remodeling. It is also well known that the major addictive component of cigarette smoke is nicotine. This study focused on the role of nicotine in the development of inflammatory pulmonary disease induced by cigarette smoke. HBE16 human airway epithelial cells were treated with serial dilutions of cigarette smoke chloroform extract (CE), lipopolysaccharide (LPS), and nicotine. The release of MUC5AC, tumor necrosis factor (TNF)-α, interleukin (IL)-8, and IL-6 protein were assayed by enzyme-linked immunosorbent assay. The MUC5AC protein also was observed by immunofluorescence. The expression of MUC5AC, TNF-α, IL-8, and IL-6 mRNA were detected by real-time polymerase chain reaction. We found that the mRNA of the proinflammatory mediators TNF-α, IL-8, and IL-6, as well as MUC5AC was highly expressed after CE and LPS stimulation. Nicotine did not cause an excessive expression of TNF-α, IL-8, and IL-6, nor did it affect protein production from the MUC5AC gene. Nicotine not only failed to stimulate production of TNF-α, IL-8, and IL-6, but its presence was shown to suppress the activation resulting from exposure to CE and LPS (P < 0.05). Preincubation with nicotine also would reduce the level of MUC5AC protein in culture supernatants of CE- and LPS-treated cells. However, mRNA expression of MUC5AC showed no significant change in nicotine-treated cells when compared with normal control cells. This distinctive pattern implies that nicotine may have potential to suppress airway inflammation and maintain the mucus over retention in airway secretory cells to some extent, thus forming a balance between mucus hyperproduction and hypersecretion in airways exposed to smoking and LPS.

Down-regulation of secreted lymphocyte antigen-6/urokinase-type plasminogen activator receptor-related peptide-1 (SLURP-1), an endogenous allosteric alpha7 nicotinic acetylcholine receptor modulator, in murine and human asthmatic conditions

Whereas acetylcholine (ACh) acts as a bronchoconstrictor and stimulator of mucus secretion from bronchial epithelium, it acts via alpha7 nicotinic Ach receptors (nAChRs) on macrophages in the airways to exert anti-inflammatory effects by reducing synthesis of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha). Moreover, the effects of ACh are modified by secreted ly-6/urokinase-type plasminogen activator receptor-related peptide-1 (SLURP-1), a positive allosteric modulator of alpha7 nAChR signaling. Our aim was to explore the roles played by SLURP-1 in the pathophysiology of asthma by assessing SLURP-1 expression in the OVA-sensitized murine asthma model and in cultured human bronchial epithelial cells. Using real-time PCR we found that expression of SLURP-1 mRNA is down-regulated in the lungs of asthmatic model mice, as compared to healthy mice. In addition, immunohistochemical studies confirmed the diminished expression of SLURP-1 in the bronchioles of asthmatic mice, and showed it was due to extensive metaplasia of mucus-secreting cells and the concomitant loss of ciliated epithelial cells. Expression of SLURP-1 mRNA and protein was also significantly down-regulated in human epithelial cells stimulated with the pro-inflammatory cytokine interleukin-13 (IL-13), which is related to asthmatic condition. Thus SLURP-1 appears to be down-regulated in both an animal model of asthma and human epithelial cells treated with an inflammatory cytokine related to asthma. Those findings suggest that diminished expression of SLURP-1 in asthma attenuates its negative regulation of airway inflammation, and that perhaps changes in SLURP-1 expression could serve as a marker of airway damage in asthma.

Challenges of treating asthma in people who smoke

Cigarette smoking is common in asthma and is associated with poor symptom control and a reduced therapeutic response to inhaled and oral corticosteroids as compared with nonsmokers with asthma. This review examines the range of adverse health effects of smoking in asthma, the inflammatory mechanisms that may influence the efficacy of current drugs and discusses potential future therapeutic directions.

Nicotine inhibits Fc epsilon RI-induced cysteinyl leukotrienes and cytokine production without affecting mast cell degranulation through alpha 7/alpha 9/alpha 10-nicotinic receptors

Smokers are less likely to develop some inflammatory and allergic diseases. In Brown-Norway rats, nicotine inhibits several parameters of allergic asthma, including the production of Th2 cytokines and the cysteinyl leukotriene LTC(4). Cysteinyl leukotrienes are primarily produced by mast cells, and these cells play a central role in allergic asthma. Mast cells express a high-affinity receptor for IgE (FcepsilonRI). Following its cross-linking, cells degranulate and release preformed inflammatory mediators (early phase) and synthesize and secrete cytokines/chemokines and leukotrienes (late phase). The mechanism by which nicotine modulates mast cell activation is unclear. Using alpha-bungarotoxin binding and quantitative PCR and PCR product sequencing, we showed that the rat mast/basophil cell line RBL-2H3 expresses nicotinic acetylcholine receptors (nAChRs) alpha7, alpha9, and alpha10; exposure to exceedingly low concentrations of nicotine (nanomolar), but not the biologically inactive metabolite cotinine, for > or = 8 h suppressed the late phase (leukotriene/cytokine production) but not degranulation (histamine and hexosaminidase release). These effects were unrelated to those of nicotine on intracellular free calcium concentration but were causally associated with the inhibition of cytosolic phospholipase A(2) activity and the PI3K/ERK/NF-kappaB pathway, including phosphorylation of Akt and ERK and nuclear translocation of NF-kappaB. The suppressive effect of nicotine on the late-phase response was blocked by the alpha7/alpha9-nAChR antagonists methyllycaconitine and alpha-bungarotoxin, as well as by small interfering RNA knockdown of alpha7-, alpha9-, or alpha10-nAChRs, suggesting a functional interaction between alpha7-, alpha9-, and alpha10-nAChRs that might explain the response of RBL cells to nanomolar concentrations of nicotine. This "hybrid" receptor might serve as a target for novel antiallergic/antiasthmatic therapies.

The activity of medicinal plants and secondary metabolites on eosinophilic inflammation

Eosinophils are leukocytes that are present in several body compartments and in the blood at relatively low numbers under normal conditions. However, an increase in the number of eosinophils, in the blood or in the tissues, is observed in allergic or parasitic disorders. Although some progress has been made in understanding the development of eosinophil-mediated inflammation in allergic and parasitic diseases, the discovery of new compounds to control eosinophilia has lagged behind other advances. Plant-derived secondary metabolites are the basis for many drugs currently used to treat pathologic conditions, including eosinophilic diseases. Several studies, including our own, have demonstrated that plant extracts and secondary metabolites can reduce eosinophilia and eosinophil recruitment in different experimental animal models. In this review, we summarize these studies and describe the anti-eosinophilic activity of various plant extracts, such as Ginkgo biloba, Allium cepa, and Lafoensia pacari, as well as those of secondary metabolites (compounds isolated from plant extracts), such as quercetin and ellagic acid. In addition, we highlight the medical potential of these plant-derived compounds for treating eosinophil-mediated inflammation, such as asthma and allergy.

Nicotine enhances murine airway contractile responses to kinin receptor agonists via activation of JNK- and PDE4-related intracellular pathways

Background

Nicotine plays an important role in cigarette-smoke-associated airway disease. The present study was designed to examine if nicotine could induce airway hyperresponsiveness through kinin receptors, and if so, explore the underlying mechanisms involved.

Methods

Murine tracheal segments were cultured for 1, 2 or 4 days in serum-free DMEM medium in presence of nicotine (1 and 10 μM) or vehicle (DMSO). Contractile responses induced by kinin B₁ receptor agonist, des-Arg⁹-bradykinin, and B₂ receptor agonist, bradykinin, were monitored with myographs. The B₁ and B₂ receptor mRNA expressions were semi-quantified using real-time PCR and their corresponding protein expressions assessed with confocal-microscopy-based immunohistochemistry. Various pharmacological inhibitors were used for studying intracellular signaling pathways.

Results

Four days of organ culture with nicotine concentration-dependently increased kinin B₁ and B₂ receptor-mediated airway contractions, without altering the kinin receptor-mediated relaxations. No such increase was seen at day 1 or day 2. The airway contractile responses to 5-HT, acetylcholine and endothelin receptor agonists remained unaffected by nicotine. Two different neuronal nicotinic receptor antagonists MG624 and hexamethonium blocked the nicotine-induced effects. The enhanced contractile responses were accompanied by increased mRNA and protein expression for both kinin receptors, suggesting the involvement of transcriptional mechanisms. Confocal-microscopy-based immunohistochemistry showed that 4 days of nicotine treatment induced activation (phosphorylation) of c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase 1 and 2 (ERK1/2) and p38. Inhibition of JNK with its specific inhibitor SP600125 abolished the nicotine-induced effects on kinin receptor-mediated contractions and reverted the enhanced receptor mRNA expression. Administration of phosphodiesterase inhibitors (YM976 and theophylline), glucocorticoid (dexamethasone) or adenylcyclase activator (forskolin) suppressed the nicotine-enhanced airway contractile response to des-Arg⁹-bradykinin and bradykinin.

Conclusions

Nicotine induces airway hyperresponsiveness via transcriptional up-regulation of airway kinin B₁ and B₂ receptors, an effect mediated via neuronal nicotinic receptors. The underlying molecular mechanisms involve activation of JNK- and PDE4-mediated intracellular inflammatory signal pathways. Our results might be relevant to active and passive smokers suffering from airway hyperresponsiveness, and suggest new therapeutic targets for the treatment of smoke-associated airway disease.

Sulfur mustard induces immune sensitization in hairless guinea pigs

Sulfur mustard (SM, bis-(2-chloroethyl) sulfide) is a well known chemical warfare agent that may cause long-term debilitating injury. Because of the ease of production and storage, it has a strong potential for chemical terrorism; however, the mechanism by which SM causes chronic tissue damage is essentially unknown. SM is a potent protein alkylating agent, and we tested the possibility that SM modifies cellular antigens, leading to an immunological response to "altered self" and a potential long-term injury. To that end, in this communication, we show that dermal exposure of euthymic hairless guinea pigs induced infiltration of both CD4(+) and CD8(+) T cells into the SM-exposed skin and strong upregulated expression of proinflammatory cytokines and chemokines (TNF-alpha, IFN-gamma, and IL-8) in distal tissues such as the lung and the lymph nodes. Moreover, we present evidence for the first time that SM induces a specific delayed-type hypersensitivity response that is associated with splenomegaly, lymphadenopathy, and proliferation of cells in these tissues. These results clearly suggest that dermal exposure to SM leads to immune activation, infiltration of T cells into the SM-exposed skin, delayed-type hypersensitivity response, and molecular imprints of inflammation in tissues distal from the site of SM exposure. These immunological responses may contribute to the long-term sequelae of SM toxicity.

Maternal exposure to secondhand cigarette smoke primes the lung for induction of phosphodiesterase-4D5 isozyme and exacerbated Th2 responses: rolipram attenuates the airway hyperreactivity and muscarinic receptor expression but not lung inflammation and atopy

Airway hyperreactivity (AHR), lung inflammation, and atopy are clinical signs of allergic asthma. Gestational exposure to cigarette smoke (CS) markedly increases the risk for childhood allergic asthma. Muscarinic receptors regulate airway smooth muscle tone, and asthmatics exhibit increased AHR to muscarinic agonists. We have previously reported that in a murine model of bronchopulmonary aspergillosis, maternal exposure to mainstream CS increases AHR after acute intratracheal administration of Aspergillus fumigatus extract. However, the mechanism by which gestational CS induces allergic asthma is unclear. We now show for the first time that, compared with controls, mice exposed prenatally to secondhand CS exhibit increased lung inflammation (predominant infiltration by eosinophils and polymorphs), atopy, and airway resistance, and produce proinflammatory cytokines (IL-4, IL-5, IL-6, and IL-13, but not IL-2 or IFN-gamma). These changes, which occur only after an allergen (A. fumigatus extract) treatment, are correlated with marked up-regulated lung expression of M1, M2, and M3 muscarinic receptors and phosphodiesterase (PDE)4D5 isozyme. Interestingly, the PDE4-selective inhibitor rolipram attenuates the increase in AHR, muscarinic receptors, and PDE4D5, but fails to down-regulate lung inflammation, Th2 cytokines, or serum IgE levels. Thus, the fetus is extraordinarily sensitive to CS, inducing allergic asthma after postnatal exposure to allergens. Although the increased AHR might reflect increased PDE4D5 and muscarinic receptor expression, the mechanisms underlying atopy and lung inflammation are unrelated to the PDE4 activity. Thus, PDE4 inhibitors might ease AHR, but are unlikely to attenuate lung inflammation and atopy associated with childhood allergic asthma.

How cigarette smoke skews immune responses to promote infection, lung disease and cancer

A complex and multilayered immune defence system protects the host against harmful agents and maintains tissue homeostasis. Cigarette smoke exposure markedly impacts the immune system, compromising the host's ability to mount appropriate immune and inflammatory responses and contributing to smoking-related pathologies. These adverse effects on the immune system not only occur in active smokers, but also in those exposed to smoke passively in contaminated environments, and may persist for decades after exposure has ended.

Effect of perinatal secondhand tobacco smoke exposure on in vivo and intrinsic airway structure/function in non-human primates

Infants exposed to second hand smoke (SHS) experience more problems with wheezing. This study was designed to determine if perinatal SHS exposure increases intrinsic and/or in vivo airway responsiveness to methacholine and whether potential structural/cellular alterations in the airway might explain the change in responsiveness. Pregnant rhesus monkeys were exposed to filtered air (FA) or SHS (1 mg/m(3) total suspended particulates) for 6 h/day, 5 days/week starting at 50 days gestational age. The mother/infant pairs continued the SHS exposures postnatally. At 3 months of age each infant: 1) had in vivo lung function measurements in response to inhaled methacholine, or 2) the right accessory lobe filled with agarose, precision-cut to 600 mum slices, and bathed in increasing concentrations of methacholine. The lumenal area of the central airway was determined using videomicrometry followed by fixation and histology with morphometry. In vivo tests showed that perinatal SHS increases baseline respiratory rate and decreases responsiveness to methacholine. Perinatal SHS did not alter intrinsic airway responsiveness in the bronchi. However in respiratory bronchioles, SHS exposure increased airway responsiveness at lower methacholine concentrations but decreased it at higher concentrations. Perinatal SHS did not change eosinophil profiles, epithelial volume, smooth muscle volume, or mucin volume. However it did increase the number of alveolar attachments in bronchi and respiratory bronchioles. In general, as mucin increased, airway responsiveness decreased. We conclude that perinatal SHS exposure alters in vivo and intrinsic airway responsiveness, and alveolar attachments.