Effects of nicotine on the immune response. I. Chronic exposure to nicotine impairs antigen receptor-mediated signal transduction in lymphocytes

Early postnatal exposure to cigarette smoke impairs the antigen-specific T-cell responses in the spleen

Annually, approximately two million babies are exposed to cigarette smoke in utero and postnatally through cigarette smoking of their mothers. Exposure to mainstream cigarette smoke is known to impair both innate and adaptive immunities, and it has been hypothesized that the effects of in utero exposure to cigarette smoke on children's health might primarily stem from the adverse effects of cigarette smoke on the immune system. To simulate the environment that babies from smoking mothers encounter, we examined the effects of prenatal mainstream and postnatal sidestream cigarette smoke on spleen cell responses. Results show that postnatal exposure of newborn Balb/c mouse pups to sidestream cigarette smoke through the first 6 weeks of life strongly suppresses the antibody response of spleen cells to the T-cell-dependent antigen, sheep red blood cells. The reduction in the antibody response seen within 6 weeks of postnatal smoke exposure is much quicker than the published data on the time 25 weeks) required to establish reproducible immunosuppression in adult rats and mice. Moreover, the immunosuppression is not associated with significant changes in T-cell numbers or subset distribution. While the postnatal exposure to cigarette smoke did not affect the mitogenic response of T and B cells, the exposure inhibited the T cell receptor-mediated rise in the intracellular calcium concentration. These results suggest that the early postnatal period is highly sensitive to the immunosuppressive effects of environmental tobacco smoke, and the effects are causally associated with impaired antigen-mediated signaling in T cells.

Cigarette smoke extract modulates respiratory defence mechanisms through effects on T-cells and airway epithelial cells

Chronic obstructive pulmonary disease (COPD) is a disease primarily caused by cigarette smoking, which in turn has been shown to affect the susceptibility to and progression of airway infections. The question addressed in this study was how components from cigarette smoke could affect the defence mechanisms of T-cells and epithelial cells, and thereby contribute to the development of the COPD pathology. T-cells and monocytes were isolated from buffycoats from healthy donors and T-cell responses studied in response to cigarette smoke extract (CSE). Activation level (CD25 expression), proliferation (BrdU incorporation) and intracellular expression of the cytotoxic markers granzyme-b and TIA-1 were determined using flowcytometry. Normal human bronchial epithelial cells were obtained from Cambrex and differentiated in air-liquid interface cultures. After exposure to CSE barrier function (trans-epithelial electric resistance, TEER), MUC5AC and interleukin-8 production were measured. T-cell activation, proliferation and expression of the cytotoxic proteins granzyme-b and TIA-1 were significantly reduced in response to 0.5-1% of CSE. The epithelial cells were more resistant to CSE and responded at doses 20 times higher than T-cells. The expression of interleukin-8 and MUC5AC was significantly increased after exposure to 15% and 30% CSE and TEER was largely unaffected at 30% CSE but clearly reduced at 40% CSE. This study shows that mechanisms, in both T-cells and airway epithelial cells, involved in the defence against infectious agents are modulated by CSE.

The role of nicotinic acetylcholine receptors in lymphocyte development

The sizes of lymphocyte populations in lymphoid organs of nicotinic acetylcholine receptor knockout and chimera (knockout/wild-type) mice were studied by flow cytometry. The absence of beta2 subunit decreased, while nicotine treatment increased B lymphocyte numbers in the bone marrow. In chimera mice, either beta2 or alpha7 subunits influenced lymphocyte populations in primary lymphoid organs, while in the spleen, only alpha7 receptors were critical. More annexin V-positive B cells were found in the bone marrow of knockout than wild-type animals. We conclude that nicotinic receptors are involved in regulating lymphocyte development and control the B lymphocyte survival.

Active immunisation against nicotine blocks the reward facilitating effects of nicotine and partially prevents nicotine withdrawal in the rat as measured by dopamine output in the nucleus accumbens, brain reward thresholds and somatic signs

We recently showed that active immunisation with the nicotine immunoconjugate IP18-KLH reduces the nicotine-induced increase in dopamine (DA) output in the nucleus accumbens (NAC) and prevents reinstatement of nicotine-seeking behaviour in rats. These effects are mediated by altered distribution of nicotine, resulting in reduced amounts of nicotine reaching the brain, thereby interfering with the rewarding properties of the drug. The present study was designed to explore the effect of immunisation against nicotine on mecamylamine-precipitated nicotine withdrawal as assessed by the reduction in DA output in the NAC in rats. Measuring brain reward thresholds and somatic signs of nicotine withdrawal, the effects of immunisation were also tested during chronic nicotine treatment and after its withdrawal. Finally, we examined the effect of immunisation on challenge injections of nicotine on brain reward thresholds after the increases in somatic signs and reward thresholds associated with nicotine withdrawal had dissipated. The results show that immunisation with IP18-KLH prevented the decrease in DA output in the NAC associated with mecamylamine-precipitated nicotine withdrawal. Moreover, immunisation against nicotine did not precipitate a withdrawal syndrome, as measured by brain reward thresholds and somatic signs, in rats chronically exposed to nicotine. Furthermore, the withdrawal syndrome elicited after cessation of chronic nicotine administration was attenuated in immunised rats compared to that of mock-immunised rats. Finally, the lowering in reward thresholds after nicotine challenge injections was attenuated in both naïve and previously nicotine-exposed immunised rats. In conclusion, the present results show that immunisation with IP18-KLH did not precipitate nicotine withdrawal in rats. Thus, immunisation with IP18-KLH may not elicit nicotine withdrawal in smokers either. Furthermore, since the withdrawal syndrome in rats was attenuated by immunisation, the nicotine withdrawal in smokers should not be worsened but may even be ameliorated during a quit attempt.

Mechanisms of Disease: nicotine—a review of its actions in the context of gastrointestinal disease

Smoking tobacco is associated with a number of gastrointestinal disorders. In some, such as Crohn's disease and peptic ulcer disease, it increases the risk of disease and has a detrimental effect on their course. In others, such as ulcerative colitis, it decreases the risk of disease and can have a favorable effect on disease course and severity. In the eighteenth and nineteenth centuries, nicotine was used as a 'panacea' for various ailments, including abdominal symptoms--it is now under investigation to elucidate its role in gastrointestinal diseases that are associated with smoking. The actions of nicotine are complex; it is likely that its effects on the central nervous system, gastrointestinal tract and immune system interact with other risk factors, such as genetic susceptibility, to influence disease outcomes. This review focuses on the mechanisms of action of nicotine that might be relevant in gastrointestinal disease.

Second-hand smoke increases nitric oxide and alters the IgE response in a murine model of allergic aspergillosis

This study was performed to determine the effects of environmental tobacco smoke (ETS) on nitric oxide (NO) and immunoglobulin (Ig) production in a murine model of allergic bronchopulmonary aspergillosis (ABPA). Adult BALB/c mice were exposed to aged and diluted sidestream cigarette smoke from day 0 through day 43 to simulate “second-hand smoke”. During exposure, mice were sensitized to soluble Aspergillus fumigatus (Af) antigen intranasally between day 14 and 24. All Af sensitized mice in ambient air (Af + AIR) made elevated levels of IgE, IgG1, IgM, IgG2a and IgA. Af sensitized mice housed in ETS (Af + ETS) made similar levels of immunoglobulins except for IgE that was significantly reduced in the serum and bronchoalveolar lavage (BAL). However, immunohistochemical evaluation of the lung revealed a marked accumulation of IgE positive cells in the lung parenchyma of these Af + ETS mice. LPS stimulation of BAL cells revealed elevated levels of NO in the Af + AIR group, which was further enhanced in the Af+ETS group. In vitro restimulation of the BAL cells on day 45 showed a TH0 response with elevated levels of IL3, 4, 5, 10 and IFN-γ. However, by day 28 the response shifted such that TH2 cytokines increased while IFN-γ decreased. The Af + ETS group showed markedly reduced levels in all cytokines tested, including the inflammatory cytokine IL6, when compared to the Af+AIR group. These results demonstrate that ETS affects ABPA by further enhancing the NO production and reduces the TH2 and the inflammatory cytokines while altering the pattern of IgE responses.

Environmental Tobacco Smoke and Risk of Adult Leukemia

BACKGROUND

The role of environmental tobacco smoke (ETS) in the causation of lung and breast cancer has been repeatedly evaluated over recent years. In contrast, its impact on the risk of adult leukemia has received little attention.

METHODS

We used the lifetime residential and occupational ETS exposure histories from a population-based sample of 1068 incident and histologically confirmed adult leukemia cases and 5039 population controls age 20 to 74 years to evaluate the relationship between ETS exposure and adult leukemia risk among nonsmokers in Canada. The duration of exposure and smoker-years index were used as indices of ETS exposure. We restricted our analysis to the 266 case and 1326 control subjects who reported being lifetime nonsmokers and provided residential ETS exposure history for at least 75% of their lifetime.

RESULTS

No association was found for most leukemia subtypes, and in particular for acute myeloid leukemia. In contrast, the risk for chronic lymphocytic leukemia was clearly associated with ETS exposure, with an adjusted odds ratio of 2.3 (95% confidence interval = 1.2-4.5) for more than 83 smoker-years of residential exposure and 2.4 (1.3-4.3) for more than 72 smoker-years of occupational exposure. There was a dose-response relationship for chronic lymphocytic leukemia with both indices of exposure. Risk was not higher with recent exposure, using time-window-exposure analyses.

CONCLUSIONS

Regular long-term ETS exposure may be a risk factor for chronic lymphocytic leukemia.

IgE-mediated sensitisation, rhinitis and asthma from occupational exposures. Smoking as a model for airborne adjuvants?

OBJECTIVE

Airborne pollutants with adjuvant effect, called airborne adjuvants, may promote IgE-sensitisation and development of allergic airway diseases. Smoking and occupational allergen exposures were reviewed to establish a general and verified framework for hazard identification and risk assessment of adjuvant effects of airborne pollutions.

METHODS

The relative risks and the attributable risks of adjuvant effect of smoking were determined for co-exposures with green coffee and castor beans, ispaghula, senna, psyllium, flour and grain dust, latex, laboratory animals, seafood, enzymes, platinum salts, organic anhydrides, or reactive dyes.

RESULTS

Adjuvant effects of smoking depended on the types of allergen, but not on whether sensitisation or allergy was promoted by atopy-the hereditarily increased ability to increase IgE formation.

CONCLUSION

Promotion of IgE sensitisation in humans and in animals may serve for hazard identification of adjuvant effects. Risk assessment has been based mainly on epidemiological studies, which are sensitive to confounding factors. This highlights the need to develop appropriate animal models for risk assessment.

Cigarette Smoke Extract Suppresses Human Dendritic Cell Function Leading to Preferential Induction of Th-2 Priming

Dendritic cells (DC) are key regulators of immune responses. In the current study, we hypothesized that cigarette smoke-induced aberrance in DC function is an important mechanism by which smokers develop cancer, infection, and allergy--diseases common in smokers. We demonstrate that cigarette smoke extract (CSE) inhibits DC-mediated priming of T cells, specifically inhibiting the secretion of IFN-gamma whereas enhancing the production of IL-4 in the MLR. Conditioning with CSE did not effect cytokine (IL-10, IL-6, or IL-12) production from immature DCs, but significantly inhibited IL-12p70 release by LPS-matured DCs. In contrast, IL-10 secretion by LPS-activated CSE-conditioned DCs was enhanced when compared with control DCs. CSE also induced cyclooxygenase-2 protein levels in maturing DCs and significantly augmented endogenous PGE2 release. Conditioning of DCs with CSE also suppressed LPS-mediated induction of CD40, CD80, and CD86, and suppressed maturation-associated CCR7 expression. Although CSE has been reported to induce apoptosis of fibroblasts and epithelial cells, the immunomodulatory effects observed with CSE were not due to diminished DC viability. The effects of CSE on DC function were not exclusively mediated by nicotine, because equivalent, or even higher concentrations of nicotine than those found in CSE, failed to suppress DC-induced T cell priming. These data provide evidence that soluble components extracted from cigarette smoke suppress key DC functions and favor the development of Th-2 immunity.

Effect of Cigarette Smoke on Autoimmunity in Murine and Human Systemic Lupus Erythematosus

Several studies have found that smoking cigarettes is a risk factor for systemic lupus erythematosus (SLE). To examine this issue in a mouse model, we subjected pre-autoimmune MRL-lpr/lpr mice for 4 weeks to cigarette smoke to provide standardized smoke effluents equivalent to moderate or to heavy smoking habits for people. The spontaneous production of IgG anti-chromatin but not IgM anti-chromatin, anti-denatured DNA, or rheumatoid factor antibodies was lower in mice exposed to 250 mg/m3 particulates from mainstream smoke, and this suppression of autoimmunity was sustained for 8 weeks (p < 0.02). In contrast to control mice anti-chromatin activity in smoke-exposed mice began to increase in 16-week-old mice, reaching levels at 6 months that were two- to three-fold higher than controls for IgG (p < 0.03) and 10-fold higher for IgM (p < 0.001). There was no significant effect on total IgG or IgM. In newly diagnosed SLE patients, smoking was negatively correlated with IgG anti-DNA antibodies (p < 0.03). However, of nine patients who discontinued smoking prior to diagnosis, eight had elevated IgG anti-DNA compared to 29/79 never smokers and 9/31 smokers (p < 0.01 compared to former smokers). Inhaled cigarette smoke appears to have a long-lasting immunosuppressive effect on T-cell-dependent autoimmune responses, although autoantibodies increase to supra-elevated levels after the suppressive effect has abated.

Nicotinic receptors regulate B lymphocyte activation and immune response

The presence of nicotinic acetylcholine receptors (nicotinic receptors) composed of either alpha7 or alpha4 and beta2 subunits is revealed in B lymphocytes by means of radioligand binding assay and Cell ELISA. Mouse B lymphocytes contained 12,200+/-3200 of epibatidine-binding sites and 3130+/-750 of alpha-Bungarotoxin-binding sites per cell. Mice lacking nicotinic receptor subunits alpha4, beta2 or alpha7 had less serum IgG and IgG-producing cells in the spleen, but showed stronger immune response to both protein antigen in vivo and CD40-specific antibody in vitro than wild-type mice. Anti-CD40-stimulated proliferation of B lymphocytes from beta2 knockout, but not wild-type mice was inhibited with nicotine. Our results indicate that signalling through nicotinic receptors affects both the pre-immune state and activation of B lymphocytes in the immune response, possibly via CD40-dependent pathway. This could contribute to immune depression found in tobacco smokers.

Proteomic changes in rat serum, polymorphonuclear and mononuclear leukocytes after chronic nicotine administration

In order to gain information about the effect triggered at the molecular level by nicotine, its neuroimmunomodulatory properties and its impact on the pathogenesis of inflammatory diseases, peripheral blood serum and leukocytes of rat submitted to passive nicotine administration were subjected to proteomic investigation. Serum, polymorphonuclear (PMN) and mononuclear (MN) leukocytes from chronically treated animals and from control animals were analysed by a two-dimensional (2-D) gel electrophoresis/mass spectrometry approach to detect differentially expressed proteins. The nicotine regimen selected is known to have a stimulatory effect on locomotor activity and to produce a sensitisation of the mesolimbic dopamine system mechanism involved in addiction development. After 2-D gel analysis and matching, 36 spots in serum, seven in PMN and five in MN were found to display a statistical difference in their expression and were subjected to matrix-assisted laser desorption/ionization-time of flight-mass spectrometry peptide fingerprinting for protein identification. Fifteen different proteins were identified. The results indicate an overall impact of nicotine on proteins involved in a variety of cellular and metabolic pathways, including acute phase response (suggesting the effect on inflammatory cascades and more in general on the immune system), oxidative stress metabolism and assembly and regulation of cytoskeleton. In particular, the observed changes imply a general reduction in the inflammatory response with a concomitant increased unbalance of the oxidative stress metabolism in the periphery and point to a number of potential noninvasive markers for the central nervous system (CNS) and non-CNS mediated activities of nicotine.

Activation of the aryl hydrocarbon receptor increases pulmonary neutrophilia and diminishes host resistance to influenza A virus

Unlike their role in bacterial infection, less is known about the role of neutrophils during pulmonary viral infection. Exposure to pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) results in excess neutrophils in the lungs of mice infected with influenza A virus. TCDD is the most potent agonist for the aryl hydrocarbon receptor (AhR), and exposure to AhR ligands has been correlated with exacerbated inflammatory lung diseases. However, knowledge of the effects of AhR agonists on neutrophils is limited. Likewise, the factors regulating neutrophil responses during respiratory viral infections are not well characterized. To address these knowledge gaps, we determined the in vivo levels of KC, MIP-1alpha, MIP-2, LIX, IL-6, and C5a in infected mouse lungs. Our data show that these neutrophil chemoattractants are generally produced transiently in the lung within 12-24 h of infection. We also report that expression of CD11a, CD11b, CD49d, CD31, and CD38 is increased on pulmonary neutrophils in response to influenza virus. Using AhR-deficient mice, we demonstrate that excess neutrophilia in the lung is mediated by activation of the AhR and that this enhanced neutrophilia correlates directly with decreased survival in TCDD-exposed mice. Although AhR activation results in more neutrophils in the lungs, we show that this is not mediated by deregulation in levels of common neutrophil chemoattractants, expression of adhesion molecules on pulmonary neutrophils, or delayed death of neutrophils. Likewise, exposure to TCDD did not enhance pulmonary neutrophil function. This study provides an important first step in elucidating the mechanisms by which AhR agonists exacerbate pulmonary inflammatory responses.

Exposure to Nicotine during Gestation Interferes with the Colonization of Fetal Bone Marrow by Hematopoietic Stem/Progenitor Cells

Environmental factors, including cigarette smoke components, can cross the placental barrier and accumulate in amniotic fluid and fetal tissue, and, therefore, interfere with the normal course of ontogenesis. Although cigarette smoke contains numerous compounds, the most adverse effects on mammalian tissues have been associated with nicotine. The aim of this study was to investigate the effect of intrauterine exposure to nicotine on hematopoiesis during fetal development and postpartum. Intrauterine exposure of mice to nicotine resulted in a more than two-fold reduction of the delayed- type hypersensitivity (DTH) response and a 2.5-fold decrease in the number of plaque forming cell (PFC) in offspring after 1 month of postnatal life, and correlated with low counts of mature lymphocytes and lymphoid progenitors in hematopoietic tissues. Neonates exposed to nicotine during gestation showed a significant decrease in the number of bone marrow hematopoietic progenitors, as measured by colony-forming unit (CFU) and long-term culture initiating cell (LTC-IC) assays, and decreased concentration of interleukin-6 (IL-6) in their serum. Analysis of the fetal bone marrow (E15) obtained from nicotine-exposed fetuses demonstrated a lower number of hematopoietic progenitors, whereas their number in the fetal liver was not significantly changed. Our data provide evidence that by targeting the nicotinic acetylcholine receptor (nAChR) nicotine interferes with the fetal development of the hematopoietic system. Inferior colonization of the fetal bone marrow by hematopoietic stem/progenitor cells (HSPC) subsequently results in an imbalance of mature blood and immune cell production after birth.

Mechanisms of action of environmental factors--tobacco smoking

AIM

To review the potential biological mechanisms underlying the effects of tobacco smoking on periodontitis.

MAIN FINDINGS

Smoking has major effects on the host response, but there are also a number of studies that show some microbiological differences between smokers and non-smokers. Smoking has a long-term chronic effect on many important aspects of the inflammatory and immune responses. Histological studies have shown alterations in the vasculature of the periodontal tissues in smokers. Smoking induces a significant systemic neutrophilia, but neutrophil transmigration across the periodontal microvasculature is impeded. The suppression of neutrophil cell spreading, chemokinesis, chemotaxis and phagocytosis have been described. Protease release from neutrophils may be an important mechanism in tissue destruction. Tobacco smoke has been found to affect both cell-mediated immunity and humoral immunity. Research on gingival crevicular fluid has demonstrated that there are lower levels of cytokines, enzymes and possibly polymorphonuclear cells in smokers. In vitro studies have shown detrimental effects of nicotine and some other tobacco compounds on fibroblast function, including fibroblast proliferation, adhesion to root surfaces and cytotoxicity.

CONCLUSION

Tobacco smoking has widespread systemic effects, many of which may provide mechanisms for the increased susceptibility to periodontitis and the poorer response to treatment.

Nicotine activates nuclear factor of activated T cells c2 (NFATc2) and prevents cell cycle entry in T cells

We used primary peripheral blood T cells, a population that exists in G(0) and can be stimulated to enter the cell cycle synchronously, to define more precisely the effects of nicotine on pathways that control cell cycle entry and progression. Our data show that nicotine decreased the ability of T cells to transit through the G(0)/G(1) boundary (acquire competence) and respond to progression signals. These effects were due to nuclear factor of activated T cells c2 (NFATc2)-dependent repression of cyclin-dependent kinase 4 (CDK4) expression. Growth arrest at the G(0)/G(1) boundary was further enforced by inhibition of cyclin D2 expression and by increased expression and stabilization of p27Kip1. Intriguingly, T cells from habitual users of tobacco products and from NFATc2-deficient mice constitutively expressed CDK4 and were resistant to the antiproliferative effects of nicotine. These results indicate that nicotine impairs T cell cycle entry through NFATc2-dependent mechanisms and suggest that, in the face of chronic nicotine exposure, selection may favor cells that can evade these effects. We postulate that cross talk between nicotinic acetylcholine receptors and growth factor receptor-activated pathways offers a novel mechanism by which nicotine may directly impinge on cell cycle progression. This offers insight into possible reasons that underlie the unique effects of nicotine on distinct cell types and identifies new targets that may be useful control tobacco-related diseases.

Chronic nicotine inhibits inflammation and promotes influenza infection

Epidemiological data suggest an association between smoking, respiratory infections, and impaired wound healing. Inflammation is critical in the body's defense against pathogens and in the wound-healing process. Although nicotine is used to treat some inflammatory conditions, the mechanism of this action is largely unknown. To determine how nicotine affects inflammation, rats and mice were exposed to nicotine via miniosmotic pumps, and the inflammatory response to turpentine or influenza virus was assessed. Results showed that while nicotine suppressed the migration of leukocytes to the inflammation/infection site, it increased the influenza titer in the lung. The decreased inflammation correlated with lower chemotaxis/chemokinesis of peripheral blood mononuclear cells (PBMC) toward formyl-methionyl-leucyl-phenylalanine and monocyte chemoattractant protein-1 without affecting the density of their respective receptors. However, nicotine suppressed the chemokine-induced Ca(2+) response in PBMC, indicating impaired chemokine signaling. Thus, because nicotine suppresses leukocyte migration, it might contribute to the delayed wound healing and increased incidence of respiratory infections among smokers.

Plasma antibody levels in periodontitis patients and controls

BACKGROUND

A major aspect of the adaptive host response in periodontitis is the production of antibodies. Several risk and susceptibility factors for periodontitis, including smoking, age and composition of the subgingival microflora, have also been suggested to influence antibody production.

AIM

The present study was conducted to investigate plasma levels of immunoglobulin (Ig) G, A and M antibodies in periodontitis patients of Caucasian European heritage in relation to disease severity, smoking, diagnosis and prevalence of periodontopathogens.

METHODS

In this study, 29 patients with severe periodontitis, 51 with moderate periodontitis and 55 controls without periodontal destruction were enrolled. From the total of 80 patients, 18 were diagnosed with aggressive periodontitis and 62 with chronic periodontitis. Total IgG, IgA and IgM as well as IgG isotypes were analyzed in plasma samples.

RESULTS

Levels of total IgG, IgA and IgM were not different between patients and controls; however, in periodontitis, higher levels of IgG1 and IgG2 were observed. Smoking appeared to be significantly and inversely related to antibody levels in periodontitis, in particular for total IgG and IgG2. The absence of an elevated total IgG and IgG2 in smoking patients was irrespective of severity, prevalence of periodontal pathogens and diagnosis. The elevation of total IgG and IgG1 and IgG2 in non-smoker periodontitis patients was observed in patients with moderate periodontitis and even greater in patients with severe periodontitis, but was independent whether patients were infected with Actinobacillus actinomycetemcomitans or Porphyromonas gingivalis and independent of diagnosis. Clinically, it was observed that patients who smoked had more periodontal bone loss; the current findings on antibody levels may be one of several mechanisms related to more extensive periodontal breakdown in smoker patients.

CONCLUSION

The current study shows that non-smoker periodontitis patients have higher levels of total IgG and IgG2 than smoker periodontitis patients.

Immunosuppressive and anti-inflammatory effects of nicotine administered by patch in an animal model

To study the immunological effects of nicotine, there are several rodent models for chronic nicotine administration. These models include subcutaneously implanted miniosmotic pumps, nicotine-spiked drinking water, and self-administration via jugular cannulae. Administration of nicotine via these routes affects the immune system. Smokers frequently use nicotine patches to quit smoking, and the immunological effects of nicotine patches are largely unknown. To determine whether the nicotine patch affects the immune system, nicotine patches were affixed daily onto the backs of Lewis rats for 3 to 4 weeks. The patches efficiently raised the levels of nicotine and cotinine in serum and strongly inhibited the antibody-forming cell response of spleen cells to sheep red blood cells. The nicotine patch also suppressed the concanavalin A-induced T-cell proliferation and mobilization of intracellular Ca(2+) by spleen cells, as well as the fever response of animals to subcutaneous administration of turpentine. Moreover, immunosuppression was associated with chronic activation of protein tyrosine kinase and phospholipase C-gamma1 activities. Thus, in this animal model of nicotine administration, the nicotine patch efficiently raises the levels of nicotine and cotinine in serum and impairs both the immune and inflammatory responses.

Central but not the peripheral action of cholinergic compounds suppresses the immune system

Cholinergic compounds modulate the immune system; however, the mechanism of cholinergic immunotoxicity is largely unknown. Lewis rats were exposed chronically to cholinergic compounds via subcutaneous or intracerebroventricular routes. Compounds that crossed the blood-brain barrier (BBB) inhibited the antibody response when given by either route, however, poorly permeable compounds, unless given in high doses, inhibited the antibody response only by intracerebroventricular administration. Intracerebroventricular administration of cholinergic agents also reduced serum corticosterone levels, which along with the antibody response was attenuated by pretreatment with the ganglionic blocker chlorisondamine. Thus, cholinergic agents affect the neuroimmune communication and inhibit glucocorticoid production; the latter may be a biomarker for cholinergic toxicity.

Smokeless tobacco or nicotine replacement therapy has no effect on serum immunoglobulin levels

BACKGROUND

Tobacco smokers have lower serum levels of immunoglobulin (Ig)G, mainly due to lower levels of IgG2, than non-smokers. The component(s) in tobacco smoke responsible for this effect is unknown, but animal studies have implicated nicotine as a major contributor to the immunologic effects of smoking. Does nicotine exposure due to use of smokeless tobacco (oral moist snuff) or nicotine replacement therapy influence serum Ig levels in humans?

METHODS

Serum content of Ig classes and IgG subclasses was analysed in 77 non-smoking nicotine consumers, including 48 users of oral moist snuff (smokeless tobacco users) and 29 ex-smokers on nicotine replacement therapy, and compared with 44 healthy controls. Former smokers in any group had quit smoking at least 6 months prior to study entry. Ig class and IgG subclass levels were determined by radial immunodiffusion. Systemic nicotine exposure was excluded and confirmed by measuring urine content of cotinine using a quantitative radioimmunoassay.

RESULTS

Ig class and IgG subclass levels did not differ significantly between the groups, with the sole exception of IgG4, which was significantly lower in nicotine consumers than in healthy subjects (0.4 +/- 0.3 vs. 0.6 +/- 0.4 g/l, mean +/- SD, 95% confidence interval [-0.3;-0.05]). There was no correlation between any Ig variable and cotinine concentration.

CONCLUSIONS

The decreased levels of IgG and IgG2 seen in tobacco smokers do not seem to be an effect of systemic exposure to nicotine.

The lymphocytic cholinergic system and its contribution to the regulation of immune activity

Lymphocytes express most of the cholinergic components found in the nervous system, including acetylcholine (ACh), choline acetyltransferase (ChAT), high affinity choline transporter, muscarinic and nicotinic ACh receptors (mAChRs and nAChRs, respectively), and acetylcholinesterase. Stimulation of T and B cells with ACh or another mAChR agonist elicits intracellular Ca2+ signaling, up-regulation of c-fos expression, increased nitric oxide synthesis and IL-2-induced signal transduction, probably via M3 and M5 mAChR-mediated pathways. Acute stimulation of nAChRs with ACh or nicotine causes rapid and transient Ca2+ signaling in T and B cells, probably via alpha7 nAChR subunit-mediated pathways. Chronic nicotine stimulation, by contrast, down-regulates nAChR expression and suppresses T cell activity. Activation of T cells with phytohemagglutinin or antibodies against cell surface molecules enhances lymphocytic cholinergic transmission by activating expression of ChAT and M5 mAChR, which is suggestive of local cholinergic regulation of immune system activity. This idea is supported by the facts that lymphocytic cholinergic activity reflects well the changes in immune system function seen in animal models of immune deficiency and immune acceleration. Collectively, these data provide a compelling picture in which lymphocytes constitute a cholinergic system that is independent of cholinergic nerves, and which is involved in the regulation of immune function.

Evidence for the immunosuppressive role of nicotine on human dendritic cell functions

Nicotine alters a wide range of immunological functions, including innate and adaptive immune responses. To date, no studies have been reported showing the immunoregulatory effects of nicotine on dendritic cells (DCs), which are critical cells for initiation of cell-mediated immunity against infection and neoplastic diseases. In this work, we report that, in a nicotinic environment, monocyte-derived DCs manifest lower endocytic and phagocytic activities. Interestingly, although immature DCs undergo maturation in response to bacterial antigen lipopolysaccharide, they produce decreased levels of pro-inflammatory cytokines, notably interleukin-12, and reveal a reduced ability to stimulate antigen-presenting cell-dependent T-cell responses. Importantly, the reduction in T-cell responses is associated with a diminished ability of DCs to induce differentiation and expansion of type 1 T cells, as evidenced by a decreased frequency of interferon-gamma-producing effector cells. These results strongly suggest that nicotine can exert its immunosuppressive effects on immune surveillance through functional impairment of the DC system.

Microbial infections, immunomodulation, and drugs of abuse

The use of recreational drugs of abuse has generated serious health concerns. There is a long-recognized relationship between addictive drugs and increased levels of infections. Studies of the mechanisms of actions of these drugs became more urgent with the advent of AIDS and its correlation with abused substances. The nature and mechanisms of immunomodulation by marijuana, opiates, cocaine, nicotine, and alcohol are described in this review. Recent studies of the effects of opiates or marijuana on the immune system have demonstrated that they are receptor mediated, occurring both directly via specific receptors on immune cells and indirectly through similar receptors on cells of the nervous system. Findings are also discussed that demonstrate that cocaine and nicotine have similar immunomodulatory effects, which are also apparently receptor mediated. Finally, the nature and mechanisms of immunomodulation by alcohol are described. Although no specific alcohol receptors have been identified, it is widely recognized that alcohol enhances susceptibility to opportunistic microbes. The review covers recent studies of the effects of these drugs on immunity and on increased susceptibility to infectious diseases, including AIDS.

Effects of nicotine exposure on T cell development in fetal thymus organ culture: arrest of T cell maturation

There is evidence for both physiological functions of the natural neurotransmitter, acetylcholine, and pharmacological actions of the plant alkaloid, nicotine, on the development and function of the immune system. The effects of continuous exposure to nicotine over a 12-day course of fetal thymus organ culture (FTOC) were studied, and thymocytes were analyzed by flow cytometry. In the presence of very low concentrations of nicotine many more immature T cells (defined by low or negative TCR expression) and fewer mature T cells (intermediate or high expression of TCR) were produced. In addition, the numbers of cells expressing CD69 and, to a lesser extent, CD95 (Fas) were increased. These effects took place when fetal thymus lobes from younger (13-14 days gestation) pups were used for FTOC. If FTOC were set up using tissue from older (15-16 days gestation pups), nicotine had little effect, suggesting that it may act only on immature T cell precursors. Consistent with an increase in immature cells, the expression of recombinase-activating genes was found to be elevated. Nicotine effects were partially blocked by the simultaneous addition of the nicotinic antagonist d-tubocurarine. Furthermore, d-tubocurarine alone blocked the development of both immature and mature murine thymocytes, suggesting the presence of an endogenous ligand that may engage nicotinic acetylcholine receptors on developing thymocytes and influence the course of normal thymic ontogeny.

Chronic self-administration of nicotine in rats impairs T cell responsiveness

Chronic exposure of rodents to nicotine via subcutaneously or intracerebroventricularly implanted miniosmotic pumps affects T cell function. However, this method of continuous nicotine administration does not replicate the self-motivated administration of nicotine in human smokers. To determine whether nicotine impairs the immune system under conditions pertinent to human smokers, we investigated the T cell responsiveness of male Lewis rats self-administering (SA) nicotine (0.03 mg/kg of body weight per injection) 40 to 50 times/day for 5 weeks, using a model of virtually unlimited access to nicotine. Compared with sham control animals, the concanavalin A-induced proliferation of spleen cells from SA rats was significantly decreased. Moreover, the ability of spleen cells to mobilize intracellular Ca(2+) after ligation of the T cell antigen receptor (TCR) with an anti-alphabeta TCR antibody was significantly less in SA than in control rats. In addition, inositol 1,4,5-trisphosphate (IP(3))-sensitive intracellular Ca(2+) stores were markedly depleted in spleen cells from SA animals. These results suggest that chronic nicotine self-administration suppresses T cell responsiveness, and this suppression may result from an impaired TCR-mediated signaling that stems from the depletion of IP(3)-sensitive intracellular Ca(2+) stores.

Differential expression of nicotinic acetylcholine receptor subunits in fetal and neonatal mouse thymus

Studies were initiated to identify nicotinic acetylcholine receptor (nAChR) subunits and subtypes expressed in the developing immune system and cell types on which nAChR are expressed. Reported here are reverse transcription-polymerase chain reactions (RT-PCR) studies of nAChR alpha2-alpha7 and beta2-beta4 subunit gene expression using fetal or neonatal regular or scid/scid C57BL/6 mouse thymus. Findings are augmented with studies of murine fetal thymic organ cultures (FOTC) and of human peripheral lymphocytes. Novel partial cDNA sequences were derived for mouse nAChR alpha2, alpha3, beta3 and beta4 subunits, polymorphisms were identified in mouse nAChR alpha4, alpha7 and beta2 subunits, and recently derived sequences for mouse nAChR alpha5 and alpha6 subunits were confirmed. Thymic stromal cells appear to express nAChR alpha2, alpha3, alpha4, alpha7 and beta4 subunits, perhaps in addition to alpha5 and beta2 subunits, in a pattern reminiscent of expression in the developing brain. Immature T cells appear to express alpha3, alpha5, alpha7, beta2 and beta4 subunits, just as do neural crest-derived cells targeted by cholinergic innervation. Peripheral T cells seem to express an unusual profile of alpha2, alpha5 and alpha7 subunits, perhaps indicating that their nAChR express yet-to-be-identified assembly partners or that T cell nicotinic responsiveness occurs through homomeric nAChR composed of alpha7 subunits. Our findings are consistent with published work but show a much wider array of nAChR subunit gene expression in mouse thymic stromal and/or lymphoid cells and evidence for developmental regulation of nAChR subunit expression. These studies suggest important roles for nAChR in immune system development and function and in the neuroimmune network.

Involvement of human heat shock protein 90 alpha in nicotine-induced apoptosis

There have been conflicting reports of the apoptotic effects of nicotine on human cells and those studies reporting nicotine-induced apoptosis have not unequivocally clarified the molecular mechanisms underlying the effect. However, we found here that human RSa cells, established from embryonic fibroblastic cells doubly infected with Rous sarcoma virus and Simian virus 40, underwent apoptosis when cultured with medium containing 0.06-0.6 microM nicotine. The apoptosis was assessed by cellular DNA fragmentation and caspase-3 protease activation. Viability of RSa cells was reduced by nicotine treatment, as analyzed by MTT assay and the reduction was lessened by combination treatment with a caspase-3 inhibitor, acetyl-L-aspartyl-L-glutamyl-L-valyl-L-aspart-1-al (Ac-DEVD-CHO). Levels of expression of heat shock protein 90 alpha (Hsp90 alpha) were found to be increased 20 min after the nicotine treatment, as analyzed by polymerase chain reaction-based mRNA differential display after Northern blotting analysis of mRNA amounts. Cellular contents of Hsp90 alpha were furthermore increased in the nicotine-treated RSa cells, as quantitated by Western immunoblot analysis. By contrast, in RSa cells treated with nicotine in combination with geldanamycin (GA), an inhibitor of Hsp90 alpha function, DNA fragmentation was not detected and caspase-3 protease activity levels were the same as those of mock-treated cells. Nicotine-induced caspase-3 activation and Hsp90 alpha expression, as well as suppression of the induction by GA, were also observed in a xeroderma pigmentosum patient-derived cell line, XP2OS cells. Thus, it was suggested that nicotine induces apoptosis, possibly via Hsp90 alpha expression, in human cells tested.

Side-stream cigarette smoke accentuates immunomodulation during murine AIDS

Side-stream cigarette smoke has become a hotly debated social, political, and scientific health and safety issue for nonsmokers. The harmful influences of side-stream cigarette smoke on human health are its adverse effects on the immune system, especially when already compromised by other agents. Acquired immune deficiency syndrome (AIDS) is a clinical disorder caused by human immunodeficiency virus (HIV). To facilitate studies, murine AIDS was induced in C57BL/6 mice by LP-BM5 murine leukemia virus infection, which mimics human AIDS. After 2 weeks of retroviral infection, the mice were exposed to side-stream cigarette smoke for 30 min, 5 days/week for 12 weeks using a side-stream cigarette smoke exposure system. Murine retrovirus infection reduced the in vitro proliferation of T lymphocytes stimulated by concanavalin A, increased the release of pro-inflammatory cytokine interleukin-6 (IL-6) tumor necrosis factor-alpha (TNF-alpha), increased the hepatic lipid peroxidation and decreased the alpha-tocopherol levels in liver, lung and heart. Concomitant side-stream cigarette smoke exposure for 12 weeks further inhibited the proliferation of T cells, increased the release of TNF-alpha, IL-6 cytokines and enhanced the hepatic lipid peroxidation from retrovirus infected mice. The loss of alpha-tocopherol was also further enhanced by side-stream cigarette smoke exposure during retrovirus infection. Our conclusions are that side-stream cigarette smoke induced increasing oxidative stress, reducing nutrient concentrations and suppressing immune function could make mice with murine AIDS more susceptible to opportunistic infections, potentially accelerating murine AIDS progression. Thus, the reduction of side-stream cigarette smoke exposure is an important health issue in AIDS patients to improve the quality and quantity of their lives.

The influence of tobacco smoking on adhesion molecule profiles

Sequential interactions between several adhesion molecules and their ligands regulate lymphocyte circulation and leukocyte recruitment to inflammatory foci. Adhesion molecules are, therefore, central and critical components of the immune and inflammatory system. We review the evidence that tobacco smoking dysregulates specific components of the adhesion cascade, which may be a common factor in several smoking-induced diseases. Smoking causes inappropriate leukocyte activation, leukocyte-endothelial adhesion, and neutrophil entrapment in the microvasculature, which may help initiate local tissue destruction. Appropriate inflammatory reactions may thus be compromised. In addition to smoke-induced alterations to membrane bound endothelial and leukocyte adhesion molecule expression, which may help explain the above phenomena, smoking has a profound influence on circulating adhesion molecule profiles, most notably sICAM-1 and specific sCD44 variants. Elevated concentrations of soluble adhesion molecules may simply reflect ongoing inflammatory processes. However, increasing evidence suggests that specific soluble adhesion molecules are immunomodulatory, and that alterations to soluble adhesion molecule profiles may represent a significant risk factor for several diverse diseases. This evidence is discussed herein.

Molecular cloning and mapping of the human nicotinic acetylcholine receptor alpha10 (CHRNA10)

We report the isolation and initial characterization of a new member of the human nicotinic acetylcholine receptor (nAChR) subunit family, alpha10 (CHRNA10), from both inner-ear neuroepithelium and lymphoid tissue. The cDNA is 1959 nucleotides in length, with a coding region predicting a protein of 451 amino acids that is 90% identical to rat alpha10. The alpha10 gene was localized to chromosome 11p15.5. Human alpha10 was detected in human inner-ear tissue, tonsil, immortalized B-cells, cultured T-cells and peripheral blood lymphocytes using reverse transcriptase-polymerase chain reaction, Northern blot hybridization, and immunohistochemistry. We also detected the expression of the human nAChR alpha9 (CHRNA9) mRNA in these same tissues using RT-PCR and Northern blot hybridization.

The miseries of passive smoking

Passive smoking is defined as an involuntary exposure to a combined but diluted cigarette sidestream smoke (SS, gas and particle phases that are evolved from the smoldering end of a cigarette while the smoker is not puffing) and the exhaled smoke from smokers. SS contains numerous cytotoxic substances such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, nitrosamines, heavy metals, poisonous gases, pesticide residues, and radioactive elements in quantities much higher than those found from the cigarette mainstream smoke (MS) which is puffed by smokers. Passive smoking is found to be the cause of death from cancers and cardiac disease. Furthermore, it damagingly involves reproductive organs, the nervous system, genetic materials, and is particularly hazardous to mother and child during pregnancy and to those with a history of asthma, chronic infections, induced or earned immune deficiency, or predisposed susceptibility.

Plasma 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) levels and immune response

For determination of whether plasma 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) pesticide levels (< or =1-32 ppb) are associated with immune suppression or DNA damage in lymphocytes, 302 individuals residing in Moore County, North Carolina, in 1994-1996 provided a blood specimen, underwent a skin test, and answered a questionnaire concerning factors affecting plasma organochlorine pesticide levels and the immune system. The blood specimens were analyzed for levels of plasma DDE (a metabolite of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), numbers and types of blood cells, immunoglobulin levels, mitogen-induced lymphoproliferative activity, and lymphocyte micronuclei. When DDE levels were categorized as 1 or less, more than 1 to 2, more than 2 to 4.3, more than 4.3 to 7.6, and more than 7.6 ppb, individuals with higher plasma DDE levels had lowered mitogen-induced lymphoproliferative activity (concanavalin A, range: 74,218 dropping to 55,880 counts per minute, p = 0.03) and modestly increased total lymphocytes (range: 2.0-2.3 x 10(3)/microl, p = 0.05) and immunoglobulin A levels (range: 210-252 mg/dl, p = 0.04). There were no consistent differences in response to the skin tests by plasma DDE levels. Plasma DDE levels were not associated with a higher frequency of micronuclei. The authors conclude that relatively low levels of plasma DDE are associated with statistically significant changes in immune markers, although the magnitude of the effects are of uncertain clinical importance.

Effects on the immune system associated with living near a pesticide dump site

In this paper, we report results of the second phase of a larger study designed to evaluate the effects on the immune system of living near a Superfund site containing organochlorine pesticides, volatile organic compounds, and metals. Phase II was conducted to determine whether living near the site, consisting of six locations in Aberdeen, North Carolina, is associated with higher plasma organochlorine levels, immune suppression, or DNA damage. Each of 302 residents of Aberdeen and neighboring communities provided a blood specimen, underwent a skin test, and answered a questionnaire. Blood specimens were analyzed for organochlorine pesticides, immune markers, and micronuclei. Of 20 organochlorines tested, only DDE was detected in the blood of participants (except for one individual). Age-adjusted mean plasma DDE levels were 4.05 ppb for Aberdeen residents and 2.95 ppb (p = 0.01) for residents of neighboring communities. Residents of 40-59 years of age who lived within a mile of any site, but particularly the Farm Chemicals site, had higher plasma DDE levels than residents who lived farther away. Residents who lived near the Farm Chemicals site before versus after 1985 also had higher plasma DDE levels. Overall, there were few differences in immune markers between residents of Aberdeen and the neighboring communities. However, residents who lived closer to the dump sites had statistically significantly lower mitogen-induced lymphoproliferative activity than residents who lived farther away (p < 0.05). Residential location was not consistently associated with frequency of micronuclei or skin test responses. Although some statistically significant differences in immune markers were noted in association with residential location, the magnitude of effects are of uncertain clinical importance.

Differential effects of nicotine and aging on splenocyte proliferation and the production of Th1- versus Th2-type cytokines

Nicotine has a multitude of biological actions in the central and peripheral nervous systems where nicotinic acetylcholine receptors are found. Nicotinic acetylcholine receptors have also been identified on immune cells, but the effects of nicotine on immune responses are not well characterized. These studies tested the hypotheses that nicotine has an effect on both T-lymphocyte proliferation and the production of cytokines by activated T cells, processes that are necessary for effective T-cell-mediated immune responses. In addition, the effects of nicotine on these immune responses in aging animals and the effects of nicotine exposure prior to immunostimulation were investigated. Murine splenocytes were exposed to nicotine and stimulated with concanavalin A (ConA). The highest concentration of nicotine (128 microg/ml) significantly depressed proliferation of T cells both when nicotine and ConA were added concurrently and when nicotine was added 3 hr prior to ConA. Nicotine, added concurrently with ConA at concentrations between 0. 25 and 64 microg/ml, significantly inhibited the production of IL-10 by splenocytes from young adult mice, whereas the inhibition of production of IL-10 by splenocytes from old mice was significantly inhibited, but the response was more variable, depending on the nicotine concentration. In contrast, the production of IFN-gamma by splenocytes from either young adult or old mice was not affected when nicotine (0.016-64 microg/ml) was added concurrently with ConA. Pre-exposure to 1 microg/ml of nicotine for 3 hr significantly enhanced the production of IFN-gamma by splenocytes from young adult mice, whereas pre-exposure to 0.016 microg/ml of nicotine tended to but did not significantly enhance IFN-gamma production. Nicotine is now being used as an over-the-counter drug by people who differ in age and general immunocompetence. Therefore, the effects of nicotine on immune responses, independent from the effects of the other chemicals found in tobacco, need to be investigated.

Differential impact of nicotine on cellular proliferation and cytokine production by LPS-stimulated murine splenocytes

The immunoregulatory effects of nicotine have not been fully clarified and the reported data are often conflicting. The present study investigated the role of nicotine as an immunomodulator of murine splenocytes stimulated by lipopolysaccharide (LPS), the endotoxin component of gram-negative bacteria. BALB/c female mice of two different ages, young (2-3 months) and old (18-22 months), were used. The cells were incubated with nicotine at two different time points, 3 h pre-incubation and concurrent incubation relevant to LPS stimulation, before further incubation for 48 or 72 h. Treatment of murine splenocytes with nicotine showed an impact on cellular proliferation as well as on the production of the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). The results indicated that nicotine significantly inhibited cellular proliferation of murine splenocytes in a concentration-related manner (32, 64 and 128 microg/ml). Timing of nicotine exposure prior to LPS stimulation was critical in terms of immunological impact on cytokine production. TNF-alpha and IL-6 production were significantly enhanced by 1 microg/ml of nicotine when cells were pre-incubated with nicotine for 3 h compared to concurrent incubation relative to LPS stimulation. The alteration in cytokine production varied with the age of the mouse. TNF-alpha production was significantly inhibited by nicotine in young mice, while IL-6 production was significantly inhibited by nicotine in old mice. Since any immunomodulation that alters the profile of these cytokines may cause an imbalance in the immune system impinging on health status, these findings may be important when dealing with the concept of nicotine as a therapeutic agent.

Acute and chronic nicotine exposures modulate the immune system through different pathways

We have previously shown that T cells from rats exposed chronically to cigarette smoke or nicotine (NT) exhibit T cell anergy and decreased proliferation to T cell mitogens. Effects of chronic NT on T cell function persist for at least 2 weeks after the termination of NT treatment. Moreover, these effects of NT are causally related to the decreased Ca(2+) response to T cell receptor (TCR) ligation and constitutive activation of protein tyrosine kinase (PTK) and phospholipase C (PLC)-gamma1 activities. Acute NT treatment also suppresses the Con A-induced T cell proliferation; however, it is not known whether the mechanism(s) by which acute and chronic NT treatments inhibit T cell proliferation are identical. To evaluate this question, LEW rats were acutely treated with NT (1 mg/kg body wt) for 1, 2, or 24 h by an ip injection or implanted with constant-release miniosmotic pumps containing saline or NT (1 mg/kg body wt/day) for a 3-week chronic exposure. Inhibition of Con A-induced proliferation of peripheral blood cells (PBC) by both acute and chronic treatments was reversed by the inhibitor of nicotinic acetylcholine receptors, mecamylamine (MEC), indicating that these receptors are required for T cell proliferation. However, the effect of acute NT on the Con A response was short lived (i.e., observed at 1 and 2 h but not at 24 h after NT administration) and was seen in PBC but not in spleen cells. Unlike the chronic treatment, acute NT administration neither suppressed significantly the TCR-mediated [Ca(2+)](i) response nor did it cause the constitutive activation of PTK and PLC-gamma1 activities in blood lymphocytes. Acute, but not chronic, NT administration increased the plasma corticosterone concentration, and this increase was also inhibited by MEC. Moreover, adrenalectomy abrogated the acute but not chronic NT effects on the Con A response. Thus, the acute and chronic effects of NT on T lymphocytes are mechanistically distinct phenomena. Whereas chronic administration of NT causes T cell anergy, acute effects are primarily mediated via the activation of the hypothalamus-pituitary-adrenal axis.

Acute effects of nicotine infusion on platelets in nicotine users with normal and impaired renal function

The role of platelets in cardiovascular disease associated with smoking is becoming more established, but the effects of nicotine on platelets are unclear. Nicotine therapy is used for smoking cessation in both health and disease. Consequently, the effects of nicotine on platelets are of particular significance in disorders such as renal disease, which is associated with defective platelet function, increased cardiovascular morbidity, and altered nicotine metabolism. Thus, the aim of the present study was to investigate the acute effects of nicotine infusion (NI) on platelets in seven healthy subjects (HS) and seven patients with renal failure (RF). All subjects were nicotine users and had refrained from using nicotine for 36 h before NI. Blood was collected before, immediately after, and 2 h after NI. The plasma concentrations of nicotine and its main metabolite cotinine were determined by gas chromatography. Platelet responsiveness was assessed by aggregometry and flow cytometry in whole blood (P-selectin surface expression, fibrinogen- and von Willebrand factor-binding), P-selectin expression in isolated platelets, and immunoassays of platelet release (beta-thromboglobulin, platelet factor 4, and soluble P-selectin) and nitric oxide (NO) products. The plasma levels of cotinine, but not nicotine, were significantly higher in RF compared to HS at all time points. In both groups, collagen-induced platelet aggregation was restrained immediately after NI, when the plasma concentration of nicotine was maximal, and was restored after 2 h. Two hours after NI, activation-dependent P-selectin surface expression in isolated platelets increased in both groups. This increased platelet responsiveness occurred simultaneously with a significant increase of plasma cotinine and a decrease of NO products. Thus, the present study suggests that nicotine, directly or through some secondary mechanism or metabolite, only slightly potentiates some of the platelet responses. Renal failure appears not to influence the effects of nicotine on platelets.

Infection with respiratory syncytial virus and water-soluble components of cigarette smoke alter production of tumour necrosis factor alpha and nitric oxide by human blood monocytes

Cigarette smoke and virus infections contribute to the pathogenesis and exacerbation of chronic obstructive pulmonary disease and asthma. The objective of this study was to examine the effects of a water-soluble cigarette smoke extract (CSE) and/or respiratory syncytial virus (RSV) infection on release from monocytes of the blood from donors of tumour necrosis factor alpha (TNF-alpha) and nitric oxide (NO). Both RSV infection and CSE stimulated TNF-alpha release from monocytes and there was an additive effect if both the agents were present. There was a decrease in NO release, but the effect was significant only with CSE or a combination of CSE and RSV infection. Interferon gamma significantly increased TNF-alpha release and cotinine significantly increased NO release. Nicotine decreased both TNF-alpha and NO responses. The general pattern observed for individual donors was increased TNF-alpha and decreased NO. The proportion of extreme responses with very high TNF-alpha and very low NO in the presence of both RSV and CSE increased to 20% compared with 5% observed with CSE or RSV alone. The results show that RSV infection and components of cigarette smoke elicit inflammatory responses that could contribute to damage to the respiratory tract and these individual factors could be more harmful in combination.

Central injection of nicotine increases hepatic and splenic interleukin 6 (IL-6) mRNA expression and plasma IL-6 levels in mice: involvement of the peripheral sympathetic nervous system

Accumulating evidence suggests that plasma levels of interleukin 6 (IL-6), a major cytokine stimulating the synthesis of acute-phase proteins, are intimately regulated by the central nervous system. Nicotine, one of the major drugs abused by humans, has been shown to affect immunological functions. In the present study, effects of intracerebroventricular (i.c.v.) injection of nicotine on plasma IL-6 levels were investigated in mice. Nicotine administered i.c.v. dose-dependently increased plasma IL-6 levels; the lowest effective dose was 0.3 ng/mouse and the maximal effect was attained with the dose of 105 ng/mouse. The nicotine (105 ng/mouse, i.c.v.)-induced plasma IL-6 levels peaked at 3 h and approached basal levels 6 h after injection. Mecamylamine, a nicotinic receptor antagonist, blocked nicotine-induced plasma IL-6 levels. Depletion of peripheral norepinephrine with 6-hydroxydopamine [100 mg/kg, intraperitoneal (i. p.)] inhibited the nicotine-induced plasma IL-6 levels by 57%, whereas central norepinephrine depletion with 6-hydroxydopamine (50 microgram/mouse, i.c.v.) had no effect. Pretreatment with prazosin (alpha1-adrenergic antagonist; 1 mg/kg, i.p.), yohimbine (alpha2-adrenergic antagonist; 1 mg/kg, i.p.), and ICI-118,551 (beta2-adrenergic antagonist; 2 mg/kg, i.p.), but not with betaxolol (beta1-adrenergic antagonist; 2 mg/kg, i.p.), inhibited nicotine-induced plasma IL-6 levels. Among the peripheral organs, including the pituitary, adrenals, heart, lung, liver, spleen, and lymph nodes, nicotine (105 ng/mouse, i.c.v.) increased IL-6 mRNA expression only in the liver and spleen, which was inhibited by peripheral norepinephrine depletion. These results suggest that stimulation of central nicotinic receptors induces plasma IL-6 levels and IL-6 mRNA expression in the liver and spleen via the peripheral sympathetic nervous system, alpha1-, alpha2-, and beta2-adrenoreceptors being involved.

Elevation of CD5+ B lymphocytes in schizophrenia

BACKGROUND

A variety of immunologic alterations have been observed in patients with schizophrenia. These findings have lent support to theories that autoimmune mechanisms may be important in some patients with the illness. The CD5+ B lymphocyte, a B-cell subset associated with autoimmune disease, has been the subject of two previously published studies yielding disparate results.

METHODS

In this study, we used immunofluorescent flow cytometry to measure CD5+ B cells, total B and T cells, and CD4 and CD8 subsets in patients with schizophrenia and in normal control subjects.

RESULTS

A significantly higher percentage of patients with schizophrenia, relative to normal control subjects, exhibited an elevated level of CD5+ B cells (27.6% vs 6.7%). Antipsychotic withdrawal had no effect on CD5+ B-cell levels, suggesting that medication effects were not the cause of this difference. No other studied lymphocyte subsets differed between the two groups.

CONCLUSIONS

A subset of patients with schizophrenia have elevated levels of CD5+ B cells. This finding replicates an earlier study by another group and provides further evidence suggestive of autoimmune manifestations in schizophrenia.

Effects of cigarette smoking on Fas/Fas ligand expression of human lymphocytes

Cigarette smoking has been shown to affect human immune responses. We have studied Fas/Fas ligand (FasL) expression, which is involved in the cytotoxic activity, immune privilege, and self-tolerance, and other apoptosis-associated molecule expression of peripheral blood lymphocytes (PBL) in healthy subjects with/without cigarette smoking. We found that expression of FasL protein was detected marginally in the fresh PBL and was induced upon mitogen activation in normal individuals without smoking. In contrast, fresh PBL from those with chronic cigarette smoking exhibited enhanced expression of FasL protein without in vitro mitogen stimulation. Moreover, mitogen stimulation failed to augment FasL protein expression of their lymphocytes, suggesting dysregulation of FasL expression of PBL in individuals with cigarette smoking. In contrast, Fas, Bcl-2, and p53 expression were not significantly different between normal individuals with chronic cigarette smoking and those without smoking. In addition, we found that in vitro brief treatment with nicotine induces and/or enhances FasL mRNA and protein expression of lymphocytes from normal donors without smoking. These results suggest that aberrant FasL expression of lymphocytes is, at least in part, involved in the immune impairment in individuals with chronic cigarette smoking.

Pigeon fanciers' lung: effects of smoking on serum and salivary antibody responses to pigeon antigens

A reduced prevalence of pigeon fanciers' lung has been reported in pigeon breeders who smoke cigarettes. Serum and salivary antibodies to pigeon intestinal mucin and pigeon serum proteins were investigated in 227 pigeon fanciers, subdivided according to smoking habit and clinical status. Smokers had a lower incidence of precipitating antibodies to pigeon antigens and lower titres of serum IgG and IgA antibodies to mucin and to pigeon serum proteins in ELISA compared with non-smokers and ex-smokers. In contrast, IgG antibody titres to tetanus toxoid were similar in smoking and non-smoking groups. In contrast to serum antibodies, salivary IgA antibody titres to pigeon antigens were similar in smokers and non- or ex-smokers. Approximately one third of the smokers reported symptoms consistent with pigeon fanciers' lung but did not have precipitating antibodies. Only some individuals with precipitating antibodies had disease symptoms, and IgG antibody titres in these individuals were not significantly higher than in many asymptomatic individuals. Salivary IgA titres against pigeon mucin were significantly higher in asymptomatic individuals, consistent with a protective role for these antibodies. The results confirm that smoking is associated with a decreased serum antibody response to inhaled pigeon antigens, affecting IgG1, IgG2 and IgA responses, but this impairment does not extend to salivary IgA or to antibody responses to a parenterally administered protein antigen. The fact that responses to pigeon serum proteins and to pigeon intestinal mucin were similarly affected suggests that cigarette smoking depresses both T-independent and T-dependent responses to inhaled antigens.

Immunomodulatory effects of cigarette smoke

Cigarette smoke is a major health risk factor which significantly increases the incidence of diseases including lung cancer and respiratory infections. This increased susceptibility may result from cigarette smoke-induced impairment of the immune system. While the acute effects of cigarette smoke on the immune system are less clear, chronic exposure to cigarette smoke or nicotine causes T cell unresponsiveness. This apparent T cell anergy may account for or contribute to the immunosuppressive and anti-inflammatory properties of cigarette smoke/nicotine. Nicotine-induced immunosuppression may result from its direct effects on lymphocytes, indirectly through its effects on the neuroendocrine system, or both.

The effects of nicotine on the immune system

Although considerable work has been done on the potential health effects of smoking, little is known about the contribution of nicotine to those effects. This paper presents an overview of the immune system, and a discussion of the existing literature on the effects of tobacco smoke and nicotine on immunity. Treatment with nicotine has been shown to influence all aspects of the immune system, including alterations in humoral and cellular immunity. In addition, preliminary data suggest that gender and genetic factors impact on the immunological effects of nicotine. Finally, the possible mechanisms that might mediate the effects of nicotine are discussed.

Effect of nicotine on the immune system: possible regulation of immune responses by central and peripheral mechanisms

Nicotine (NT) treatment impairs T-cell receptor (TCR)-mediated signaling, leading to the arrest of T cells in the G1 phase of the cell cycle and inhibition of the antibody plaque-forming cell (AFC) response to sheep red blood cells (SRBC). This paper summarizes some of the previous findings related to cigarette smoke/NT and the immune response, and presents preliminary evidence suggesting that mice chronically treated with NT (0.5 mg/day/kg body weight) have a depressed inflammatory response in the turpentine-induced abscess model of inflammation. This ability of nicotine to attenuate an inflammatory response may also be the cause of reduced mortality of chronically nicotine-treated mice from acute influenza A pneumonitis. Moreover, in LEW rats, decreased anti-SRBC AFC responses were also observed after intracerebroventricular (i.c.v.) administration of relatively small concentrations of NT (28 micrograms/day/kg body weight) which, when given peripherally, did not affect the AFC response. In vitro the addition of NT to T cells increased protein tyrosine kinase (PTK) activity and intracellular Ca2+ concentration [Ca2+]i. These results support the hypothesis that NT alters immune responses by directly interacting with T cells, as well as indirectly through brain-immune interactions.

Expression of alpha subunit genes of nicotinic acetylcholine receptors in human lymphocytes

Using immunohistochemistry and in situ hybridisation, we have studied whether alpha-subunits of nicotinic acetylcholine receptors (nAChRs) are expressed in human lymphocytes. Cells were isolated by differential low speed gradient centrifugation from heparinised venous blood of 10 healthy volunteers. Receptor sites were visualised using the monoclonal antibody WF6 which specifically recognises alpha-isoforms from several species including man. For visualisation of transcripts, digoxigenin-labelled cRNA probes for alpha 4- and alpha 3-subunits were used. Immunostaining revealed specific binding of WF6 to isolated human lymphoid cells. The antibody was bound to most cells and concentrated preferentially in the perinuclear/surface region. The immunoreactivity resembled that observed after application of an antibody recognising CD4 surface proteins which was conducted for comparison. In situ-hybridisation revealed that the alpha 4-subunit genes of nAChRs was expressed in lymphocytes of all probands. The alpha 3-subunit was found, with lower intensity than alpha 4-transcripts, in eight of the 10 individuals. Control incubations with corresponding sense cRNAs were negative. It is concluded that human lymphocytes are able to express alpha-subunit genes of nAChRs.