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

Mystery Solved: Why Smoke Extract Worsens Disease in Smokers with Crohn's Disease and Not Ulcerative Colitis? Gut MAP!

Cigarette smoke (CS) exacerbates symptoms in Crohn’s disease (CD) patients while protecting those with ulcerative colitis (UC). CD has been associated with immuno-dysregulation, mucosal dysfunction, and infection. Among the CD-debated pathogens are Mycobacterium avium subsp. paratuberculosis (MAP), adherent invasive Escherichia coli (AIEC), and Klebsiella pneumoniae. The mechanism of how CS modulates nicotinic acetylcholine receptor-α7 (α7nAChR) and elicits inflammatory response in CD-like macrophages is unknown. Here, we investigated the effect of CS/nicotine on macrophages infected with CD-associated pathogens. We measured apoptosis, bacterial viability, macrophage polarization, and gene expression/cytokine levels involved in macrophage response to nicotine/CS extracts from Havana-Leave extract (HLE-nicotine rich) and germplasm line of Maryland tobacco (LAMD-nicotine less). Nicotine (4 µg/mL) and HLE extracts (0.18%) significantly favored anti-inflammatory response in macrophages (increased CD-206 (M2) and IL-10, and decreased M1/M2 ratio; p < 0.05). While macrophages infected with MAP or treated with LPS promoted pro-inflammatory response. Further treatment of these macrophages with nicotine or HLE extracts caused higher inflammatory response (increased iNOS (M1), TNF-α, IL-6, and M1/M2 ratio, p < 0.05), increased MAP burden, and decreased apoptosis. Pre-conditioning macrophages with nicotine ahead of infection resulted in lower pro-inflammatory response. Blocking α7nAChR with an antagonist voided the effect of nicotine on macrophages. Overall, the study provides an insight toward understanding the contradictory effect of nicotine on Inflammatory Bowel Disease patients and about the mechanistic role of α7nAChR in modulation of macrophages in tobacco smokers.

Nicotine attenuates concanavalin A-induced liver injury in mice by regulating the α7-nicotinic acetylcholine receptor in Kupffer cells

Nicotine, a potent parasympathomimetic alkaloid, manifests anti-inflammatory properties by activating nicotinic acetylcholine receptors (nAChRs). In this study, we evaluated the effects of nicotine on concanavalin A (ConA)-induced autoimmune hepatitis. Nicotine (0.5 and 1 mg/kg) was intraperitoneally administered to BALB/c mice and mice were intravenously injected with ConA (15 mg/kg) to induce hepatitis. The results showed that nicotine treatment ameliorated pathological lesions in livers and significantly suppressed the expression of pro-inflammatory cytokines in the livers. Such effects were mediated by inhibiting the nuclear factor-kappa B (NF-κB) signaling in livers. Interestingly, nicotine inhibited the ConA-induced inflammatory response in primary cultured Kupffer cells (KCs) but did not alter the proliferation of splenocytes. The protective effects of nicotine against ConA-induced hepatitis were abolished in KC-depleted mice, indicating the requirement of KCs in this process. Additionally, the expression of α7-nAChR on KCs was dramatically increased by nicotine treatment, and the protective effects of nicotine on ConA-induced liver injury were significantly suppressed by treatment with methyllycaconitine (MLA), a specific α7-nAChR antagonist. Consistently, in primary cultured KCs, the activation of NF-κB signaling was also regulated by nicotine treatment. This study suggests that nicotine increases α7-nAChR-mediated cholinergic activity in KCs resulting in decrease of ConA-induced autoimmune hepatitis through inhibiting NF-κB signaling.

Nicotine Impairs Macrophage Control of Mycobacterium tuberculosis

Pure nicotine impairs macrophage killing of Mycobacterium tuberculosis (MTB), but it is not known whether the nicotine component in cigarette smoke (CS) plays a role. Moreover, the mechanisms by which nicotine impairs macrophage immunity against MTB have not been explored. To neutralize the effects of nicotine in CS extract, we used a competitive inhibitor to the nicotinic acetylcholine receptor (nAChR)-mecamylamine-as well as macrophages derived from mice with genetic disruption of specific subunits of nAChR. We also determined whether nicotine impaired macrophage autophagy and whether nicotine-exposed T regulatory cells (Tregs) could subvert macrophage anti-MTB immunity. Mecamylamine reduced the CS extract increase in MTB burden by 43%. CS extract increase in MTB was also significantly attenuated in macrophages from mice with genetic disruption of either the α7, β2, or β4 subunit of nAChR. Nicotine inhibited autophagosome formation in MTB-infected THP-1 cells and primary murine alveolar macrophages, as well as increased the intracellular MTB burden. Nicotine increased migration of THP-1 cells, consistent with the increased number of macrophages found in the lungs of smokers. Nicotine induced Tregs to produce transforming growth factor-β. Naive mouse macrophages co-cultured with nicotine-exposed Tregs had significantly greater numbers of viable MTB recovered with increased IL-10 production and urea production, but no difference in secreted nitric oxide as compared with macrophages cocultured with unexposed Tregs. We conclude that nicotine in CS plays an important role in subverting macrophage control of MTB infection.

Chlorisondamine, a sympathetic ganglionic blocker, moderates the effects of whole-body irradiation (WBI) on early host defense to a live bacterial challenge

There is a growing consensus that long-term deficits in the brain are due to dynamic interactions between multiple neural and immune cell types. Specifically, radiation induces an inflammatory response, including changes in neuromodulatory pro- and anti-inflammatory cytokine secretion. The purpose of this study was to establish that there is sympathetic involvement in radiation-induced decrements early in in vivo immune function host defense. Female, 8-9 week-old C57BL/6J mice were exposed to whole-body irradiation (WBI). There were 8 groups with radiation (0 vs. 3 Gy protons), immune challenge (Escherichia coli) and exposure to the sympathetic ganglionic blocker, chlorisondamine (1 mg/kg weight, i.p.), as independent variables. Ten days post-irradiation, mice were inoculated with E. coli intraperitoneally and sacrificed 90-120 min later. The data suggest that radiation-induced changes in immune function may in part be mediated by the sympathetic nervous system. Briefly, we found that radiation augments the bacteria-induced inflammatory cytokine response, particularly those cytokines involved in innate immunity. However, this augmentation can be reduced by the ganglionic blockade.

Tobacco exposure and susceptibility to tuberculosis: is there a smoking gun?

In many regions of the world, there is a great overlap between the prevalence of cigarette smoke exposure and tuberculosis. Despite the large body of epidemiologic evidence that tobacco smoke exposure is associated with increased tuberculosis infection, active disease, severity of disease, and mortality from tuberculosis, these studies cannot distinguish whether the mechanism is principally through direct impairment of anti-tuberculosis immunity by cigarette smoke or due to potential confounders that increase risk for tuberculosis and are commonly associated with smoking--such as poverty, malnutrition, and crowded living conditions. While there are several in vivo murine and in vitro macrophage studies showing cigarette smoke impairs control of tuberculous infection, little is known of the molecular and cellular mechanisms by which this impairment occurs. Herein, we highlight the key findings of these studies. Additionally, we review key immune cells that play critical roles in host-defense or pathogenesis of tuberculosis and generate a hypothesis-driven discussion of the possible mechanisms by which cigarette smoke impairs or enhances their functions, respectively, ultimately resulting in compromised immunity against tuberculosis.

Neuroendocrine immunoregulation in multiple sclerosis

Currently, it is generally accepted that multiple sclerosis (MS) is a complex multifactorial disease involving genetic and environmental factors affecting the autoreactive immune responses that lead to damage of myelin. In this respect, intrinsic or extrinsic factors such as emotional, psychological, traumatic, or inflammatory stress as well as a variety of other lifestyle interventions can influence the neuroendocrine system. On its turn, it has been demonstrated that the neuroendocrine system has immunomodulatory potential. Moreover, the neuroendocrine and immune systems communicate bidirectionally via shared receptors and shared messenger molecules, variously called hormones, neurotransmitters, or cytokines. Discrepancies at any level can therefore lead to changes in susceptibility and to severity of several autoimmune and inflammatory diseases. Here we provide an overview of the complex system of crosstalk between the neuroendocrine and immune system as well as reported dysfunctions involved in the pathogenesis of autoimmunity, including MS. Finally, possible strategies to intervene with the neuroendocrine-immune system for MS patient management will be discussed. Ultimately, a better understanding of the interactions between the neuroendocrine system and the immune system can open up new therapeutic approaches for the treatment of MS as well as other autoimmune diseases.

Age-related effects of sodium arsenite on splenocyte proliferation and Th1/Th2 cytokine production

Aging is associated with immune dysfunction and conditions such as inflamm-aging and immunosuppression. Arsenic, an environmental contaminant distributed worldwide, affects the immune system. This study tested the hypothesis that arsenic has distinct effects on T cell proliferation and the production of cytokines by activated T cells. Murine splenocytes from young (2 months) and aged (24-26 months) C57BL/6 mice were exposed to arsenite (As(3+)), the most toxic form of inorganic arsenic, and stimulated with concanavalin A (Con A) or anti-CD3 antibody. T cell proliferation decreased significantly in response to Con A and anti-CD3 at subtoxic doses of arsenite in splenocytes from both young and aged mice. Arsenite, added concurrently with Con A or anti-CD3, significantly inhibited the production of interleukin-2 (IL-2), interferon-γ (IFN-γ), and interleukin-4 (IL-4) by splenocytes from young mice and significantly reduced the production of IL-10 by splenocytes from aged mice. In contrast, the production of IL-2 and IL-4 by splenocytes from aged mice was only slightly affected by arsenite. The results show that arsenic exposure reduces the immune response in splenocytes. Moreover, this effect may be influenced by aging.

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.

Cytokine-induced alterations of α7 nicotinic receptor in colonic CD4 T cells mediate dichotomous response to nicotine in murine models of Th1/Th17- versus Th2-mediated colitis

Ulcerative colitis (UC) and Crohn's disease (CD) are two forms of chronic inflammatory bowel disease. CD4 T cells play a central role in the pathogenesis of both diseases. Smoking affects both UC and CD but with opposite effects, ameliorating UC and worsening CD. We hypothesized that the severity of gut inflammation could be modulated through T cell nicotinic acetylcholine receptors (nAChRs) and that the exact clinical outcome would depend on the repertoire of nAChRs on CD4 T cells mediating each form of colitis. We measured clinical and immunologic outcomes of treating BALB/c mice with oxazolone- and trinitrobenzene sulfonic acid (TNBS)-induced colitides by nicotine. Nicotine attenuated oxazolone colitis, which was associated with an increased percentage of colonic regulatory T cells and a reduction of Th17 cells. TCR stimulation of naive CD4(+)CD62L(+) T cells in the presence of nicotine upregulated expression of Foxp3. In marked contrast, nicotine worsened TNBS colitis, and this was associated with increased Th17 cells among colonic CD4 T cells. Nicotine upregulated IL-10 and inhibited IL-17 production, which could be abolished by exogenous IL-12 that also abolished the nicotine-dependent upregulation of regulatory T cells. The dichotomous action of nicotine resulted from the up- and downregulation of anti-inflammatory α7 nAChR on colonic CD4 T cells induced by cytokines characteristic of the inflammatory milieu in oxazolone (IL-4) and TNBS (IL-12) colitis, respectively. These findings help explain the dichotomous effect of smoking in patients with UC and CD, and they underscore the potential for nicotinergic drugs in regulating colonic inflammation.

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

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

Nicotine 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.

Functional role of the nicotinic arm of the acetylcholine regulatory axis in human B-cell lines

We studied the involvement of nicotinic acetylcholine receptors (nAChRs) in the inflammation-related activity of human B-cell lines. Activation of nAChRs in Daudi cells with epibatidine abolished the pansorbin-dependent upregulation of the pro-inflammatory marker Cox-2 both at the mRNA and protein levels, indicating that the nicotinergic signaling suppresses B-cell activation. While the anti-inflammatory action on B-cells was mediated predominantly through α7 nAChR, as could be judged from abolishing epibatidine effects with methyllycaconitine, both α7 and non-α7 nAChRs, such as α2-containing receptors, were involved in regulation of B-cell apoptosis. The net effect was antiapoptotic. To determine the role of nAChRs in regulating B-cell activation/plasmacytic differentiation, we measured changes in the CD38, CD138 and Bcl-6 gene expression. Epibatidine significantly (P < 0.05) upregulated CD38 at the transcriptional level and CD138 and Bcl-6 – at the translational levels. AR-R17779 significantly (P < 0.05) increased the protein levels of CD38 and CD138. In both cases, the effect of epibatidine was abolished with Mec, and that of AR-R17779 – by MLA, demonstrating a functional role of nAChRs in regulating Daudi cell differentiation. The obtained results revealed distinct contributions of α7 and non-α7 nAChRs to regulation of B-cell activation/differentiation, and suggested that signaling through the nicotinic arm of acetylcholine regulatory axis is important for B-cell involvement in inflammation.

Is environmental tobacco smoke exposure a risk factor for acute gastroenteritis in young children?

Because passive smoke exposure has not been previously linked to diarrhea diseases in children, it was hypothesized that very young children exposed to environmental tobacco smoke (ETS) exposure at home would also be more likely to develop infectious gastroenteritis (GE) than their unexposed counterparts. During 1-year period, 260 children 36 months and younger were prospectively followed up in a private pediatric practice in a southern community in the United States. Multiple logistic regression analysis showed that ETS was strongly predictive of acute GE in the univariate analysis (P = .003). Even after controlling for the various confounders, ETS exposure was still significantly associated with acute GE (relative risk = 2.55; 95% CI = 1.26-5.18). It is speculated that, similar to acute respiratory infections, the same mechanisms may explain why ETS may also be associated with acute infectious GE.

Nicotine and inflammatory neurological disorders

Cigarette smoke is a major health risk factor which significantly increases the incidence of diseases including lung cancer and respiratory infections. However, there is increasing evidence that smokers have a lower incidence of some inflammatory and neurodegenerative diseases. Nicotine is the main immunosuppressive constituent of cigarette smoke, which inhibits both the innate and adaptive immune responses. Unlike cigarette smoke, nicotine is not yet considered to be a carcinogen and may, in fact, have therapeutic potential as a neuroprotective and anti-inflammatory agent. This review provides a synopsis summarizing the effects of nicotine on the immune system and its (nicotine) influences on various neurological diseases.

Structure and function of the nicotinic arm of acetylcholine regulatory axis in human leukemic T cells

Although acetylcholine (ACh) is widely known as a neurotransmitter, it also functions as a local humoral factor translating environmental stimuli into alterations in T cell development and function. The cholinergic components present in neurons are expressed in T cells where they constitute an independent cholinergic system. Both non-immunologic and immunologic stimulations can alter expression and function of cholinergic elements in T cells. Recent studies have convincingly demonstrated regulation of immune system by auto/paracrine ACh, which provides a basis for development of new immunomodulatory therapies with nicotinic agonists. The purpose of our research is to integrate information about the structure and activity of the ACh regulatory axis with the phenotypic and functional alterations of T cells during their development and commitment. In this study, we used the Ach producing human leukemic T cell line CCRF-CEM (CEM) to investigate auto/paracrine mechanisms of T cell regulation through the nicotinic class of ACh receptors (nAChRs). The intact CEM expressed alpha3, alpha5, alpha6, alpha7, alpha 9, beta2 and beta4 nAChR subunits. Stimulation of CEM with 10 microg/ml of phytohemagglutinin (PHA) for 16 h upregulated expression of the alpha3, alpha5, alpha7, alpha9 and beta2 and downregulated that of alpha6 and beta4 subunits, indicating that TCR activation leads to overexpression of high Ca2+-permeable ACh-gated ion channels. Activation of alpha7- and alpha3 AChRs predominantly abrogated PHA-dependent upregulation of the pro-inflammatory cytokine TNF-alpha and IFN-gamma receptors, respectively, at the mRNA and protein levels. Signaling through alpha7 and alpha3 nAChRs also significantly (p<0.05) altered expression of the cell state regulators p21 and Bcl-2, respectively, suggesting that downregulation of inflammation via nAChRs includes effects on the T cell cycle progression and apoptosis. These findings indicate that constant stimulation of alpha7 and alpha3 nAChRs by endogenously released ACh controls T cell activation and that signaling downstream of distinct nAChR subtypes targets specific inflammatory and cell cycle genes. Learning the cholinergic pharmacology of inflammation should allow to regulate specific types of immune reactions by selectively activating or blocking the types of nAChRs expressed by the immune cells mediating specific immune reactions.

Lower serum cytokine levels in smokers than nonsmokers with chronic schizophrenia on long-term treatment with antipsychotics

OBJECTIVE

Schizophrenia is associated with various abnormalities in the immune system. Suppression of inflammatory cytokines by cigarette smoke is well-established. The purpose of this study was to determine any differences in cytokine profiles in smokers and nonsmokers with schizophrenia and whether there were any relationships among altered cytokine profiles and psychopathological symptoms.

MATERIALS AND METHODS

Serum interleukin (IL)-2, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha levels were measured in 96 male inpatients with DSM-IV schizophrenia: 66 smokers and 30 nonsmokers. Symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS).

RESULTS

The positive PANSS symptoms were lower in smokers than nonsmokers, while the negative symptoms were lower in those who smoked more cigarettes. Cytokine levels were positively correlated: IL-2 level with IL-6 and IL-6 with both IL-8 and TNF-alpha. Both IL-2 and IL-6, but not IL-8 or TNF-alpha, were significantly lower in smokers than nonsmokers (p < 0.002; p < 0.01). Lower IL-2 levels correlated with fewer negative symptoms and with smoking more cigarettes.

CONCLUSIONS

The fewer positive symptoms in smokers and fewer negative symptoms in those who smoked more cigarettes may be associated with nicotine-induced suppression of some inflammatory cytokines.

Basic and clinical aspects of non-neuronal acetylcholine: expression of an independent, non-neuronal cholinergic system in lymphocytes and its clinical significance in immunotherapy

Lymphocytes possess all the components required to constitute an independent, non-neuronal cholinergic system. These include acetylcholine (ACh); choline acetyltransferase (ChAT), its synthesizing enzyme; and both muscarinic and nicotinic ACh receptors (mAChRs and nAChRs, respectively). ACh modifies T and B cell function via both mAChR- and nAChR-mediated pathways. Stimulation of lymphocytes with the T cell activator phytohemagglutinin, protein kinase C activator phorbol ester, or cell surface molecules enhances the synthesis and release of ACh and up-regulates ChAT and/or M(5) mAChR gene expression. Furthermore, animal models of immune disorders exhibit abnormal lymphocytic cholinergic activity. The cholesterol-lowering drug simvastatin attenuates the lymphocytic cholinergic activity of T cells by inhibiting LFA-1 signaling in a manner independent of its cholesterol-lowering activity. This suggests that simvastatin exerts its immunosuppressive effects in part by modifying lymphocytic cholinergic activity. Nicotine, an active ingredient of tobacco, ameliorates ulcerative colitis but exacerbates Crohn's disease. Expression of mRNAs encoding the nAChR alpha7 and alpha5 subunits are significantly diminished in peripheral mononuclear leukocytes from smokers, as compared with those from nonsmokers. In addition, long-term exposure of lymphocytes to nicotine reduces intracellular Ca(2+) signaling via alpha7 nAChR-mediated pathways. In fact, studies of humoral antibody production in M(1)/M(5) mAChR-deficient and alpha7 nAChR-deficient animals revealed the role of lymphocytic cholinergic activity in the regulation of immune function. These results provide clues to understanding the mechanisms underlying immune system regulation and could serve as the basis for the development of new immunomodulatory drugs.

Correlates of CD4+ and CD8+ lymphocyte counts in high-risk immunodeficiency virus (HIV)-seronegative women enrolled in the women's interagency HIV study (WIHS)

Studies of human immunodeficiency virus (HIV) infection often compare values from HIV-uninfected controls, including CD4 and CD8 lymphocyte counts. Nonetheless, little is known regarding factors associated with CD4 and CD8 cell numbers in HIV-uninfected individuals. To ascertain potential factors associated with differences in CD4 and CD8 cells among HIV negative women, we studied these cells in a group of 953 women, enrolled as HIV-negative comparators in the Women's Interagency HIV Study. Using standard techniques, we measured CD4 and CD8 cells obtained during study-related visits every six months through visit 20 (maximum of 9.5 years). Results were correlated with demographic and behavioral factors, and data were analyzed using a multiple linear regression approach with generalized estimating equations. At baseline, the median age was 32.4 years, body mass index (BMI) was 26.4 kg/m(2), CD4 cell count was 1010 (range 214-2705)/microL, and CD8 cell count was 542 (range 72-2448)/microL. African-Americans comprised 54%, 24% were Hispanic, and 19% were Caucasian. In multivariate analysis, increasing age (p = 0.0006), increasing BMI (p = 0.001), and current smoking status (p = 0.03) were independent predictors of higher CD4 counts. Multivariate analyses of CD8 cells revealed that lower age (p = 0.001), higher BMI (p = 0.03), Hispanic race/ethnicity (p = 0.01); current smoking (p = 0.006), injection drug use (p = 0.02), and Hepatitis C infection (p = 0.01) were independent predictors of higher CD8 cell counts. Multiple demographic and behavioral factors may influence CD4 and CD8 counts in HIV negative women. These factors must be considered in future analyses comparing lymphocyte subsets in HIV positive and negative women.

Disruption in Th1/Th2 immune response in young adult smokers

Interferon (IFN)-gamma and IL-10 cytokines, measures of Th1 and Th2 immunity, were examined in 20 healthy nonsmokers (12 males, 8 females) and 19 smokers (11 males, 8 females), aged 19-41 years (23.46+/-0.82 years). Nonsmokers came to the laboratory once; smokers came to the laboratory after ad lib smoking and following 24-h smoking abstinence. Salivary cotinine and expired CO confirmed smoking status. Plasma was collected at the end of each lab session and assayed for peripheral IFN-gamma and IL-10 levels. Among smokers, peripheral IFN-gamma, IL-10, or IFN-gamma/IL-10 ratio levels did not change in response to 24-h smoking abstinence. IFN-gamma levels and IFN-gamma/IL-10 ratios were higher among female smokers while smoking and following 24-h abstinence compared to male smokers in both conditions and compared to male and female nonsmokers. There was no sex or smoking status difference in IL-10 levels. Results suggest that cigarette smoking may have at least short-term damaging effects on the body's normal immune balance, particularly for women.

Nicotine and serotonin in immune regulation and inflammatory processes: a perspective

Nicotine and serotonin modulate the innate and adaptive immune responses and the inflammatory states. Several nicotinic cholinergic and serotonergic receptor subtypes have been characterized in B and T lymphocytes, monocytes, macrophages, and dendritic cells. The use of knockout mice has allowed a better characterization of nicotinic receptors and their role in anti-inflammatory processes in these cells. Cytokines play a crucial role in controlling inflammatory reactions. Nicotine and serotonin have been reported to regulate cytokine release. Cholinergic mechanisms also play an important role in inflammation through endogenous acetylcholine. Nicotine mimics this effect by activating the cholinergic anti-inflammatory pathways. New concepts of reciprocal interactions between nicotine and serotonin are emerging. The role of nicotine as an anti-inflammatory agent has been established, whereas that of serotonin remains more controversial.

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.

Formation of Immunodeficiency in Newborn Mice Exposed to Nicotine during Intrauterine Development

Exposure to nicotine during intrauterine development leads to immunodeficiency manifested in inhibition of delayed-type hypersensitivity reaction and reduced number of antibody-producing cells forming in response to sheep erythrocytes in newborn mice. The number of splenic CFU in the bone marrow of newborn mice exposed to nicotine in utero is decreased compared to the control. By contrast, nicotine induced an increase in splenic CFU count in fetal liver. We concluded that nicotine modifying the hemopoietic microenvironment delayed the release of primitive precursors from fetal liver, which impaired colonization of fetal bone marrow and led to imbalance in the production of mature blood cell, including immune system cells.

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.

Involvement of nicotinic acetylcholine receptors in suppression of antimicrobial activity and cytokine responses of alveolar macrophages to Legionella pneumophila infection by nicotine

Although nicotine is thought to be one of the major immunomodulatory components of cigarette smoking, how nicotine alters the host defense of the lung and, in particular, immune responses of alveolar macrophages, which are critical effector cells in the lung defense to infection, is poorly understood. Nicotinic acetylcholine receptors (nAChRs) are the receptor for nicotine and may be involved in the modulation of macrophage function by nicotine. In this study, therefore, nicotine-induced suppression of antimicrobial activity and cytokine responses of alveolar macrophages mediated by nAChRs to Legionella pneumophila, a causative agent for pneumonia, were examined. The murine MH-S alveolar macrophage cell line cells expressed the messages for alpha4 and beta2 subunits of nAChRs, but not alpha7 subunits, determined by RT-PCR. The nicotine treatment of MH-S alveolar macrophages after infection with L. pneumophila significantly enhanced the replication of bacteria in the macrophages and selectively down-regulated the production of IL-6, IL-12, and TNF-alpha, but not IL-10, induced by infection. These effects were completely blocked by a nonselective antagonist, d-tubocurarine, for nAChRs, but not by a selective antagonist, alpha-bungarotoxin, for alpha7-nAChRs. Furthermore, the stimulation of nAChRs with another agonist, 1,1-dimethyl-4-phenylpiperazinium iodide, showed the same effects, which were blocked by the antagonist d-tubocurarine, on the bacterial replication and cytokine regulation with that of nicotine. Thus, the results revealed that nAChRs, the major exogenous ligands of which are nicotine, are involved in the regulation of macrophage immune function by nicotine and may contribute to the cigarette-induced risk factors for respiratory infections in smokers.

The determination of draining lymph node cell cytokine mRNA levels in BALB/c mice following dermal sodium lauryl sulfate, dinitrofluorobenzene, and toluene diisocyanate exposure

Differential modulation has been demonstrated in interleukin-4 (IL-4), IL-10, and interferon gamma (IFN-gamma) mRNA and protein secretion patterns of cells isolated from the draining lymph nodes of mice following exposure to T cell and respiratory sensitizers. Using a multiprobe ribonuclease protection assay, the following investigation examined the mRNA expression patterns of multiple cytokines associated with respiratory sensitization for modulation following exposure to chemicals known primarily to induce irritation (sodium lauryl sulfate), respiratory sensitization (toluene diisocyanate), or T cell-mediated hypersensitivity (dinitrofluorobenzene) responses. On days 0 and +5 female BALB/c mice were exposed to either test article or vehicle on the shaven dorsal lumbar region; on days +10 through +12 the mice received test article on the dorsal aspect of each ear. On day +13 animals were euthanized, draining lymph nodes were excised, and mRNA was isolated immediately or following 24 or 48 h of culture in the presence or absence of concanavalin (Con) A. Differential expression of cytokine mRNA was most notable following 24 h incubation with Con A. Modulation of IL-4, -10, and IFN-gamma following chemical exposure was consistent with previous studies. In addition, IL-9, -13, and -15 were significantly elevated only following toluene diisocyanate exposure. Further investigations of these cytokines may provide additional insight into the mechanisms of chemically induced respiratory sensitization and provide endpoints for the detection of a chemical's ability to elicit IgE-mediated hypersensitivity responses.