Diversity of mRNA expression for muscarinic acetylcholine receptor subtypes and neuronal nicotinic acetylcholine receptor subunits in human mononuclear leukocytes and leukemic cell lines

Cholinergic stimulation attenuates the IL-4 induced expression of E-selectin and vascular endothelial growth factor by equine pulmonary artery endothelial cells

The endothelium plays a critical role in regulating leukocyte recruitment and migration during inflammation. Recent studies provide evidence that acetylcholine (ACh) and other cholinergic mediators block endothelial cells activation and leukocyte recruitment during inflammation. We thus postulated that the non-neuronal cholinergic system might modulate the recruitment of neutrophils during allergic pulmonary inflammation. In the present study, we examined the effects of cholinergic stimulation on the expression of neutrophil chemokines and adhesion molecules by endothelial cells stimulated by recombinant equine (re) IL-4. Using primary equine pulmonary artery endothelial cells culture and real-time RT-PCR method, we observed that ACh, nicotine, and muscarine inhibit the expression of E-selectin and vascular endothelial growth factor by endothelial cells stimulated by reIL-4. The expression of CXCL-8, a potent neutrophil chemotactic cytokine, remained unaffected however. These findings suggest that the cholinergic anti-inflammatory pathway may modulate pulmonary allergic inflammation and remodeling by the inhibition of selected adhesion molecules and growth factors.

Role of non-neuronal nicotinic acetylcholine receptors in angiogenesis

Angiogenesis is a critical physiological process for cell survival and development. Endothelial cells, necessary for the course of angiogenesis, express several non-neuronal nicotinic acetylcholine receptors (AChRs). The most important functional non-neuronal AChRs are homomeric alpha7 AChRs and several heteromeric AChRs formed by a combination of alpha3, alpha5, beta2, and beta4 subunits, including alpha3beta4-containing AChRs. In endothelial cells, alpha7 AChR stimulation indirectly triggers the activation of the integrin alphavbeta3 receptor and an intracellular MAP kinase (ERK) pathway that mediates angiogenesis. Non-selective cholinergic agonists such as nicotine have been shown to induce angiogenesis, enhancing tumor progression. Moreover, alpha7 AChR selective antagonists such as alpha-bungarotoxin and methyllycaconitine as well as the non-specific antagonist mecamylamine have been shown to inhibit endothelial cell proliferation and ultimately blood vessel formation. Exploitation of such pharmacologic properties can lead to the discovery of new specific cholinergic antagonists as anti-cancer therapies. Conversely, the pro-angiogenic effect elicited by specific agonists can be used to treat diseases that respond to revascularization such as diabetic ischemia and atherosclerosis, as well as to accelerate wound healing. In this mini-review we discuss the pharmacological evidence supporting the importance of non-neuronal AChRs in angiogenesis. We also explore potential intracellular mechanisms by which alpha7 AChR activation mediates this vital cellular process.

Differentiating nicotine- versus schizophrenia-associated decreases of the alpha7 nicotinic acetylcholine receptor transcript, CHRFAM7A, in peripheral blood lymphocytes

Nicotine addiction is prevalent in individuals with schizophrenia. Nicotine activation of nicotinic receptors (nAChRs) is time- and dose-dependent, but gene expression analyses often rely on qualitative self- or family-reported measures of smoking. We sought lymphocyte surrogates for cerebral alpha7-nAChR activity and tested if receptor transcription correlated with concurrently measured serum biomarkers for smoking [cotinine, C-reactive protein (CRP)]. PCR surveys to detect lymphocytic alpha7-related isoforms identified CHRFAM7A as the only consistently amplifiable transcript. In 20 smoking-matched people (n = 10 schizophrenia, n = 10 controls), we found significantly lower CHRFAM7A in cotinine and self-reported smokers versus nonsmokers (p <or= 0.001-0.03) and an inverse correlation of cotinine with CHRFAM7A (p <or= 0.04) in regression models. CHRFAM7A was not associated with diagnosis or CRP in any bi- or multi-variate analysis. Smoking-related CRP elevations only occurred in cotinine-based comparisons (p <or= 0.03), and not when smoking was self-reported. Including biochemical indicators of serum nicotine can help differentiate smoking- versus disease-associated changes in nAChR expression.

Blood plasma proteins modulate the broncholytic effects of a muscarinic receptor antagonist

Blood plasma proteins modulated the effects of muscarinic receptor antagonist methacin. Administration of methacin in combination with albumin or C-reactive protein (but not with IgG) abolished the broncholytic effect of methacin. It was probably associated with allosteric antagonism to M2, cholinergic receptors on non-nervous cells, which increased antibody production and mediator response. The concentration of serotonin in mesenteric lymph nodes was high during shock.

Does nicotine influence cytokine profile and subsequent cell cycling/apoptotic responses in inflammatory bowel disease?

BACKGROUND

Smoking differentially influences susceptibility to the inflammatory bowel diseases (IBDs) Crohn's disease (CD) and ulcerative colitis (UC). We investigated the effects of nicotine on cytokine, cell cycle, and apoptotic responses in peripheral blood mononuclear cells (PBMCs) from IBD patients and healthy controls (HCs).

METHODS

PBMCs from IBD patients and HC were stimulated with lipopolysaccharide (LPS; 1 microg/mL) or phytohemagglutinin (PHA, 5 or 0.5 microg/mL), +/- nicotine (1, 10, 100 microg/mL). Cytokines (IL1beta, IL2, IL10, IL12/IL23p40, TGFbeta, TNFalpha) were measured in supernatants at 24 hours. After 72 hours cells were analyzed by flow cytometry for cell cycle and apoptosis. Statistical modeling was used to identify interactions between cytokines and cell cycle / apoptosis and minimize confounding effects.

RESULTS

Stimulation by LPS and PHA (5 microg/mL) increased IL12/IL23p40 production from CD and UC versus HC (P < 0.05); PHA (0.5 microg/mL) increased IL1beta in UC and decreased TGFbeta from CD and UC (P < 0.01). In all groups, nicotine reduced LPS- and PHA (0.5 microg/mL)-stimulated production of IL1beta, IL10, TGFbeta, and TNFalpha (P < 0.001). Cell cycle analysis showed that PHA, but not LPS, induced proliferation and decreased G(0)/G(1) resting cells in CD and UC versus HC (P < 0.001). Nicotine decreased PHA-stimulated S-phase proliferation and increased G(0)/G(1) resting cells (P < 0.01). Modeling showed independent associations between IL12/IL23p40 and apoptosis (P = 0.01), IL1beta and resting cells (P = 0.006), TNFalpha and proliferating cells (P < 0.001). Disease activity and smoking habit had no effect.

CONCLUSIONS

Dysregulated cytokine profiles in UC and CD are associated with specific alterations in cell cycle responses; these effects may be modified by nicotine, and potentially by anticytokine therapies.

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.

Role of muscarinic receptors in the regulation of immune and inflammatory responses

Leukocytes contain both nicotinic and muscarinic receptors, and while activation of nicotinic receptors suppresses immune/inflammatory responses, the role of muscarinic receptors in immunity is unclear. We examined the effects of a muscarinic receptor antagonist (atropine) and agonist (oxotremorine), administered chronically through miniosmotic pumps, on immune/inflammatory responses in the rat. Results show that while oxotremorine stimulated, atropine inhibited the antibody and T-cell proliferative responses. Moreover, atropine also suppressed the turpentine-induced leukocytic infiltration and tissue injury, and inhibited chemotaxis of leukocytes toward neutrophil and monocyte/lymphocyte chemoattractants. Thus, activation of nicotinic and muscarinic receptors has opposite effects on the immune/inflammatory responses.

Chronic nicotine stimulation modulates the immune response of mucosal T cells to Th1-dominant pattern via nAChR by upregulation of Th1-specific transcriptional factor

Inflammatory bowel disease (IBD) consists of Crohn's disease (CD) and ulcerative colitis (UC). The etiology has not been clarified yet, but immune disorder is thought to be involved in the pathogenic physiology. Recently, general consensus has been reached that CD and UC are distinct, especially in respect of the immune response. Interestingly, smoking has diverse effects on CD, Th1-type enteritis, and on UC, Th2-type. However, the mechanisms remain obscure. Therefore, we hypothesized that nicotine altered the distinct immune responses in each form of IBD to affect their pathophysiology. In this study, we first demonstrated by RT-PCR analysis that human lamina propria T (LPT) cells had nicotinic acetylcholine receptor (nAChR), and express alpha7 nAChR subunit universally. In addition, the expression of T-bet mRNA in human LPT cells was significantly upregulated after the culture with 10(-7)M and 10(-5)M nicotine for 9 days, while chronic nicotine stimulation showed negligible effect on the expression of GATA-3 mRNA by real-time PCR. The effect of nicotine was inhibited by mecamylamine (MEC). These results suggested that nicotine could modulate the immune balance to Th1-dominant via nAChR in the intestine, to improve Th2-type enteritis. This may provide the experimental evidence for the fact that nicotine has a beneficial influence on UC, and exacerbates CD. Furthermore, it is of great interest that nicotine acts oppositely on CD and UC by modulation of the mucosal immune balance via the neurotransmitter receptor.

Immmunohistochemical study of the blood and lymphatic vasculature and the innervation of mouse gut and gut-associated lymphoid tissue

The blood and lymphatic vascular system of the gut plays an important role in tissue fluid homeostasis, nutrient absorption and immune surveillance. To obtain a better understanding of the anatomic basis of these functions, the blood and lymphatic vasculature of the lower segment of mouse gut and several constituents of gut-associated lymphoid tissue (GALT) including Peyer's patch, specialized lymphoid nodules in the caecum, small lymphoid aggregates and lymphoid nodules in the colon were studied by using confocal microscopy. Additionally, the innervation and nerve/immune cell interactions in the gut and Peyer's patch were investigated by using cell surface marker PGP9.5 and Glial fibrillary acidic protein (GFAP). In the gut and Peyer's patch, the nerves have contact with B cell, T cell and B220CD3 double-positive cells. Dendritic cells, the most important antigen-presenting cells, were closely apposed to some nerves. Some dendritic cells formed membrane-membrane contact with nerve terminals and neuron cell body. Many fine nerve fibres, which are indirectly detected by GFAP, have contact with dendritic cells and other immune cells in the Peyer's patch. Furthermore, the expression of Muscarinic Acetylcholine receptor (subtype M2) was characterized on dendritic cells and other cell population. These findings are expected to provide a route to understand the anatomic basis of neuron-immune regulation/cross-talk and probably neuroinvasion of prion pathogens in the gut and GALT.

Cholinergic modulation of anaphylactic shock: plasma proteins influence

Cholinergic drugs can modulate anaphylactic shock and change lymphocyte functions. Plasma proteins modulate effects of muscarinic antagonists during anaphylactic shock. The present investigation was carried out to study the antianaphylactic activity of methacine (antagonist at muscarinic receptors) in combination with neostigmine (anticholinesterase drug). However, it is not known whether plasma proteins-albumin, C-reactive protein (CRP) and immunoglobulin G (IgG) - modify the effects of cholinergic drugs like methacine, serotonin (5-HT) level in the lymphoid organs and quantity of antibody-forming cells (AFC) in the spleen of guinea pigs during experimental anaphylactic shock. It was shown that administration of methacine with neostigmine (40 min and 15 min prior to shock induction, accordingly) at the pathochemical stage revokes shock development. By blocking cholinesterase endogenous acetylcholine is increased and methacine blocks muscarinic receptors and therewith unwanted side effects in the airways (bronchoconstriction) and heart (bradycardia). Administration of the combination of methacine with neostigmine at the immunological stage (guinea pig sensitization) does not affect the course of anaphylactic shock. Administration of methacine with IgG at the pathochemical stage of shock significantly decreases shock intensity, while administration of methacine with CRP or albumin has no influence on the shock. Administration of IgG or CRP (not albumin) at the immunological stage of shock and albumin or IgG (not CRP) at the pathochemical stage leads to reduction of the anaphylactic reaction. Application of methacine with neostigmine or IgG (effective combinations of drugs) results in normalization of antibody response in the spleen and 5-HT level in the lymphoid organs. Administration of methacine with CRP or albumin (ineffective combinations of drugs) leads to increase of antibody response in the spleen and 5-HT level in the lymphoid organs. Administration of hexamethonium or aceclidine aggravated anaphylactic shock reaction. Thus, the combination of methacine with neostigmine can regulate the pathochemical stage of shock and the 5-HT release. At the pathochemical stage of shock IgG increases the antianaphylactic activity of methacine, but albumin and CRP abolish it.

The alpha7 nicotinic acetylcholine receptor as a pharmacological target for inflammation

The physiological regulation of the immune system encompasses comprehensive anti-inflammatory mechanisms that can be harnessed for the treatment of infectious and inflammatory disorders. Recent studies indicate that the vagal nerve, involved in control of heart rate, hormone secretion and gastrointestinal motility, is also an immunomodulator. In experimental models of inflammatory diseases, vagal nerve stimulation attenuates the production of proinflammatory cytokines and inhibits the inflammatory process. Acetylcholine, the principal neurotransmitter of the vagal nerve, controls immune cell functions via the alpha7 nicotinic acetylcholine receptor (alpha7nAChR). From a pharmacological perspective, nicotinic agonists are more efficient than acetylcholine at inhibiting the inflammatory signaling and the production of proinflammatory cytokines. This 'nicotinic anti-inflammatory pathway' may have clinical implications as treatment with nicotinic agonists can modulate the production of proinflammatory cytokines from immune cells. Nicotine has been tested in clinical trials as a treatment for inflammatory diseases such as ulcerative colitis, but the therapeutic potential of this mechanism is limited by the collateral toxicity of nicotine. Here, we review the recent advances that support the design of more specific receptor-selective nicotinic agonists that have anti-inflammatory effects while eluding its collateral toxicity.

IBU-octyl-cytisine, a novel bifunctional compound eliciting anti-inflammatory and cholinergic activity, ameliorates CNS inflammation by inhibition of T-cell activity

Experimental autoimmune encephalomyelitis (EAE) is a central nervous system (CNS) inflammatory model in which MOG-specific T-cells initiate an autoimmune attack leading to demyelinization and consequently, neurological damage and morbidity. As EAE pathogenesis results from the involvement of immune cells, CNS resident-cells and inflammatory mediators, our treatment strategy was to use a bifunctional compound with dual anti-inflammatory properties: a non-steroidal anti-inflammatory moiety and a nicotinic agonist moiety, intended to interact with the alpha7 nicotinic receptor present on immune cells. We used IBU-Octyl-Cytisine, with an ibuprofen (IBU) moiety and Cytisine, as the nicotinic agonist. The two moieties are attached by an eight carbon (octyl) spacer. Treatment of EAE with IBU-Octyl-Cytisine (2.5 mg/kg/day, i.p.) reduced significantly (by 70%) disease severity and inflammatory infiltrates in the spinal cord. An equivalent dose of IBU was ineffective, whereas Cytisine was significantly toxic. Treatment with IBU-Octyl-Cytisine inhibited the T-cell response toward the encephalitogenic epitope of myelin oligodendrocyte glycoprotein (MOG). In addition, expression of CCR5 by CD4(+)T-cells was lower, indicating a reduced migratory capacity following treatment. IBU-Octyl-Cytisine reduced Th(1) but not Th(2) cytokine production. This reduction was accompanied by a drop in the level of T-bet mRNA, a transcription factor pivotal to Th(1) lineage differentiation. Thus, IBU-Octyl-Cytisine is an effective treatment for EAE, influencing T-cell responses in several stages of disease pathogenesis. This bifunctional compound was more efficient than IBU or Cytisine separately, as well as than both moieties unconjugated. Thus, it seems that this strategy may be applicable in wider context.

Impact of chronic nicotine on sciatic nerve injury in the rat

Chronic nicotine exposure and the immune response to peripheral nerve injury has not been investigated thoroughly. Rats were exposed to chronic nicotine or saline followed by chronic constriction injury (CCI) of the sciatic nerve. Mechanical sensitivity was measured at various time points and the immune response was investigated at 21 days post-CCI. Chronic nicotine increased mechanical hypersensitivity, microglia activation, and the production of IL-1beta, but not the number of immune cells at the site of injury. These results suggest that chronic nicotine increases mechanical hypersensitivity following peripheral nerve injury through a mechanism that may involve an increased production and release of central and peripheral cytokines.

Expression and function of genes encoding cholinergic components in murine immune cells

It is now evident that acetylcholine (ACh) synthesized by choline acetyltransferase (ChAT) and released from T cells during antigen presentation binds to muscarinic and nicotinic ACh receptors (mAChRs and nAChRs, respectively) on T and B cells or dendritic cells, leading to modulation of their function. In the present study, we used reverse transcription-polymerase chain reaction (RT-PCR) to investigate whether mononuclear leukocytes (MNLs), bone marrow-derived dendritic cells (DCs) and macrophages from C57BL/6J mice express components of the cholinergic system. Expression of ChAT mRNA was detected in MNLs activated with ConA and DCs stimulated with LPS, but not in resting MNLs and DCs or in resting and stimulated macrophages. MNLs, DCs and macrophages all expressed mRNAs encoding the five mAChR subtypes (M(1)-M(5)) and the nAChR alpha2, alpha5, alpha6, alpha7, alpha10 and beta2 subunits. Expression of VIP mRNA was detected in MNLs and macrophages, but not in DCs. MNLs, DCs and macrophages all expressed VIP receptor-1 (VPAC1) and -2 (VPAC2) mRNAs, as well as mRNAs encoding secreted mammalian Ly-6/urokinase-type plasminogen activator receptor-related protein (SLURP)-1 and SLURP-2, two endogenous nAChR ligands. These results suggest that the lymphocytic cholinergic system is activated by ACh via mAChR- and nAChR-mediated pathways during antigen presentation between T cells and DCs or macrophages, leading to modulation of immune cell function. Moreover, VIP released from both postganglionic cholinergic neurons and immune cells may play a role in the cholinergic anti-inflammatory reflex, acting via VPAC1 and VPAC2 on immune cells.

Analysis of CD8+ T cell-mediated anti-viral responses in mice with targeted deletions of the M1 or M5 muscarinic cholinergic receptors

A number of studies have demonstrated that non-neuronal acetylcholine can play a role in the regulation of T cell function. Recently, we reported that CD8(+) T cells, from mice with a targeted deletion of the M(1) muscarinic receptor, had a defect in differentiating into cytolytic T lymphocytes when stimulated in vitro. In the current report, we analyze the in vivo function of CD8(+) T cells from mice with targeted deletions of either M(1) or M(5) muscarinic receptors. M(1) or M(5) knockout mice were infected with either lymphocytic choriomeningitis virus or vesicular stomatitis virus. Expansion of anti-viral CD8(+) T cells was monitored by staining with tetramer reagents specific for the immunodominant peptides of the viruses. No defect in expansion of CD8(+) T cells was observed in either M(1) or M(5) knockout mice. The extent to which one can draw a generalized conclusion that M(1) and M(5) are not involved in anti-viral immunity depends upon issues of antigen strength, genetic background, induction of redundant receptors, and the potential for qualitative defects in the expanded CD8(+) T cells.

Bilateral vagotomy or atropine pre-treatment reduces experimental diesel-soot induced lung inflammation

To investigate the role of the vagus nerve in acute inflammatory and cardiorespiratory responses to diesel particulate (DP) in the rat airway, we measured changes in respiration, blood pressure and neutrophils in lungs of urethane anesthetized Wistar rats 6-h post-instillation of DP (500 microg) and studied the effect of mid-cervical vagotomy or atropine (1 mg kg(-1)) pre-treatment. In conscious rats, we investigated DP, with and without atropine pre-treatment. DP increased neutrophil level in BAL (bronchoalveolar lavage) fluid from intact anesthetized rats to 2.5+/-0.7x10(6) cells (n=8), compared with saline instillation (0.3+/-0.1x10(6), n=7; P<0.05). Vagotomy reduced DP neutrophilia to 0.8+/-0.2x10(6) cells (n=8; P<0.05 vs. intact); atropine reduced DP-induced neutrophilia to 0.3+/-0.2x10(6) (n=4; P<0.05). In conscious rats, DP neutrophilia of 8.5+/-1.8x10(6), n=4, was reduced by pre-treatment with atropine to 2.2+/-1.2x10(6) cells, n=3. Hyperventilation occurred 6 h after DP in anesthetized rats with intact vagi, but not in bilaterally vagotomized or atropine pre-treated animals and was abolished by vagotomy (P<0.05, paired test). There were no significant differences in the other variables (mean blood pressure, heart rate and heart rate variability) measured before and 360 min after DP. In conclusion, DP activates a pro-inflammatory vago-vagal reflex which is reduced by atropine. Muscarinic ACh receptors in the rat lung are involved in DP-induced neutrophilia, and hence muscarinic antagonists may reduce airway and/or cardiovascular inflammation evoked by inhaled atmospheric DP in susceptible individuals.

Simvastatin regulates non-neuronal cholinergic activity in T lymphocytes via CD11a-mediated pathways

Lymphocyte function associated antigen-1 (LFA-1; CD11a/CD18) is an important mediator of leukocyte migration and T cell activation. We previously showed that antithymocyte globulin stimulates an independent, non-neuronal cholinergic system in T cells via LFA-1-mediated pathways, as evidenced by increases in acetylcholine (ACh) synthesis and choline acetyltransferase (ChAT) mRNA expression. The cholesterol-lowering drug simvastatin inhibits LFA-1 signaling by binding to an allosteric site on CD11a (LFA-1 alpha chain), which leads to immunomodulation. In the present study, we investigated whether simvastatin modulates lymphocytic cholinergic activity in T cells. We found that anti-CD11a monoclonal antibody (mAb) increased ChAT activity, ACh synthesis and release, and expression of ChAT and M5 muscarinic ACh receptor mRNA in MOLT-3 cells, a human leukemic T cell line. Simvastatin abolished these anti-CD11a mAb-induced increases in lymphocytic cholinergic activity in a manner independent of its cholesterol-lowering activity. These results indicate that LFA-1 contributes to the regulation of lymphocytic cholinergic activity via CD11a-mediated pathways, and suggest that simvastatin exerts its immunosuppressive effects in part via modification of lymphocytic cholinergic activity.

Cholinergic regulation of epithelial ion transport in the mammalian intestine

Acetylcholine (ACh) is critical in controlling epithelial ion transport and hence water movements for gut hydration. Here we review the mechanism of cholinergic control of epithelial ion transport across the mammalian intestine. The cholinergic nervous system affects basal ion flux and can evoke increased active ion transport events. Most studies rely on measuring increases in short-circuit current (ISC = active ion transport) evoked by adding ACh or cholinomimetics to intestinal tissue mounted in Ussing chambers. Despite subtle species and gut regional differences, most data indicate that, under normal circumstances, the effect of ACh on intestinal ion transport is mainly an increase in Cl- secretion due to interaction with epithelial M3 muscarinic ACh receptors (mAChRs) and, to a lesser extent, neuronal M1 mAChRs; however, AChR pharmacology has been plagued by a lack of good receptor subtype-selective compounds. Mice lacking M3 mAChRs display intact cholinergically-mediated intestinal ion transport, suggesting a possible compensatory mechanism. Inflamed tissues often display perturbations in the enteric cholinergic system and reduced intestinal ion transport responses to cholinomimetics. The mechanism(s) underlying this hyporesponsiveness are not fully defined. Inflammation-evoked loss of mAChR-mediated control of epithelial ion transport in the mouse reveals a role for neuronal nicotinic AChRs, representing a hitherto unappreciated braking system to limit ACh-evoked Cl- secretion. We suggest that: i) pharmacological analyses should be supported by the use of more selective compounds and supplemented with molecular biology techniques targeting specific ACh receptors and signalling molecules, and ii) assessment of ion transport in normal tissue must be complemented with investigations of tissues from patients or animals with intestinal disease to reveal control mechanisms that may go undetected by focusing on healthy tissue only.

Adrenergic and Cholinergic Control in the Biology of Epidermis: Physiological and Clinical Significance

The presence of an autocrine adrenergic and cholinergic intra/intercellular signal transduction network in the human epidermis contributes significantly to homeostatic and compensatory responses regulating vital functions in keratinocytes and melanocytes. The ligands produced control autocrine and paracrine loops to initiate responses through cognate receptors expressed within the same or adjacent cells. The epidermal adrenergic signal controls calcium homeostasis, cell growth, differentiation, motility, and pigmentation via the beta2 and alpha1 adrenoceptors. The cholinergic system is highly complex comprising both nicotinic and muscarinic receptors with multiple subtypes and this system plays an important role in keratinocyte cell cycle progression, differentiation, directional migration, adhesion, and apoptotic secretion. Moreover, lymphocytes also express adrenergic and cholinergic receptors. Both types of signal transduction receptors are coupled to classical intracellular second messenger pathways, including cAMP-, cGMP-, and calcium-mediated downstream responses. To date, it has been recognized that several dermatoses such as psoriasis, atopic dermatitis, Mal de Meleda, vitiligo, palmoplantar pustulosis, and pemphigus may be mediated, in part, by the non-neuronal adrenergic/cholinergic systems. A detailed understanding of the physiology and pathophysiology of the adrenergic/cholinergic network in the skin could offer the development of specific drugs for novel treatment modalities.

Low levels of alpha7-nicotinic acetylcholine receptor mRNA on peripheral blood lymphocytes in schizophrenia and its association with illness severity

BACKGROUND

There is evidence that the nicotinic alpha7-acetylcholine receptor (alpha7-AChR) is involved in the pathophysiology of schizophrenia. Several neurotransmitter receptors, including alpha7-AChR, have been demonstrated on peripheral blood lymphocytes (PBL) and it has been suggested that these peripheral receptors may reflect corresponding brain receptors.

OBJECTIVE

In this study we compare alpha7 mRNA expression in PBL between schizophrenia patients and control individuals in order to determine whether any correlation exists between alpha7 mRNA expression in PBL and severity of schizophrenia. In addition, the isoforms of alpha7-AChR expressed are identified.

METHOD

Peripheral venous blood samples were collected from individuals with schizophrenia (n = 44) and from healthy subjects (n = 16). Symptomatology and illness severity were assessed using standard clinical psychiatric evaluation scales. RNA was prepared from isolated lymphocytes and alpha7 mRNA was measured by RT-PCR.

RESULTS

We observed a significantly lower level of alpha7 mRNA on PBLs of schizophrenia patients in comparison with healthy controls (p < 0.00). A tendency to a negative correlation was noted between the CGI score, reflecting illness severity, and the alpha7-subunit gene expression.

CONCLUSION

Observations confirm that the alpha7 mRNA in PBL represents the duplicated alpha7-AChR gene rather than the classic alpha7-AChR gene. Our study observations further substantiate the involvement of alpha7-AChR in the pathophysiology of schizophrenia and, while preliminary, indicate that the alpha7-AChR may be expressed and be readily measured in the peripheral blood circulation.

The vagus nerve and nicotinic receptors modulate experimental pancreatitis severity in mice

BACKGROUND & AIMS

The nervous system, through the vagus nerve, controls inflammation by decreasing the release of tumor necrosis factor-alpha from endotoxin stimulated macrophages. This anti-inflammatory effect is mediated by an interaction of acetylcholine, the principal neurotransmitter of the vagus nerve, with macrophage cholinergic nicotinic receptors expressing the alpha7 subunit.

METHODS

To determine the role of this "nicotinic anti-inflammatory pathway" in experimental pancreatitis, we induced pancreatitis in mice by 12 hourly intraperitoneal injections of cerulein. Pancreatitis was preceded by unilateral left cervical vagotomy or pretreatment with the nicotinic receptor antagonist mecamylamine or by pretreatment with the selective alpha7 nicotinic receptor agonist 3-(2,4-dimethoxybenzylidene) anabaseine (GTS-21).

RESULTS

Vagotomy or pretreatment with mecamylamine resulted in an enhanced severity of pancreatitis, as reflected by histology, edema, plasma hydrolases, and interleukin-6 levels. Furthermore, the number of neutrophils migrated to the pancreas was increased in these mice, as shown by myeloperoxidase content and intrapancreatic staining of neutrophils. Conversely, GTS-21 pretreatment strongly decreased the severity of pancreatitis. Pancreatitis-associated pulmonary inflammation was independent of the integrity of the vagus nerve and nicotinic receptors.

CONCLUSIONS

This study provides the first evidence for a therapeutic potential of the vagus nerve and the "nicotinic anti-inflammatory pathway" in attenuating inflammation and injury during experimental pancreatitis.

The acetylcholinesterase inhibitor, Donepezil, regulates a Th2 bias in Alzheimer's disease patients

The increased pro-inflammatory cytokine production was previously observed in Alzheimer's disease (AD). We sought to explore whether acetylcholinesterase inhibitor (AChEI) therapy ameliorates clinical symptoms in AD through down-regulation of inflammation. Expression and release of monocyte chemotactic protein-1 (MCP-1), a positive regulator of Th2 differentiation, and interleukin (IL)-4, an anti-inflammatory cytokine from peripheral blood mononuclear cells (PBMC) in AD patients, were investigated. PBMC were purified from AD patients at time of enrollment (T0) and after 1 month of treatment with AChEI (T1) and from healthy controls (HC). Supernatants were analyzed for cytokine levels by ELISA methods. mRNA expression were determined by RT-PCR. Expression and production of MCP-1 and IL-4 were significantly increased in AD subjects under therapy with the AChEI Donepezil, compared to the same AD patients at time of enrollment (P < 0.001). Our data suggest another possible explanation for the ability of Donepezil [diethyl(3,5-di-ter-butyl-4-hydroxybenzyl)phosphonate] to delay the progression of AD; in fact, Donepezil may modulate MCP-1 and IL-4 production, which may reflect a general shift towards type Th0/Th2 cytokines which could be protective in AD disease. The different amounts of MCP-1 and IL-4 observed might reflect the different states of activation and/or responsiveness of PBMC, that in AD patients could be kept in an activated state by pro-inflammatory cytokines.

Expression and production of two selected beta-chemokines in peripheral blood mononuclear cells from patients with Alzheimer's disease

MCP-1 and RANTES are molecules that regulate monocyte and T-lymphocyte recruitment towards sites of inflammation. We sought to evaluate the role of these chemokines in Alzheimer's disease (AD), and the effect of acetylcholinesterase inhibitor (AchEI) therapy on their release from peripheral blood mononuclear cells (PBMC). MCP-1 and RANTES mRNA expressions were determined by RT-PCR and the amount of secreted chemokines was assayed using specific ELISA methods from purified PBMC from each AD patients (n = 40) at the time of enrolment (T0) and after 1 month of treatment with AchEI (T1) and from 20 healthy age and sex-matched subjects (HC). We found that expression and production of MCP-1 in AD patients was significantly lower than in HC subjects. After 1 month of therapy with AchEI (Donepezil), MCP-1 levels increased in each patient. However, higher levels were detected for RANTES in AD patients compared to control subjects and in AD patients treated with Donepezil. MCP-1 and RANTES have a compensatory role in balancing the impaired mechanisms involved in immune response during ageing. Our present findings suggest that these two chemokines are both involved in AD pathogenesis and might reflect different states of activation and/or responsiveness of PBMC from AD patients, contributing to the impaired of the peripheral immune system in these patients.

Control by cholinergic mechanisms

In the respiratory tract acetylcholine is neurotransmitter in ganglia and postganglionic parasympathetic nerves, but in addition is paracrine mediator released from various non-neuronal cells. Almost every cell type present in the respiratory tract expresses nicotinic and muscarinic receptors and therefore appears to be a target for acetylcholine. The present review describes the mechanisms of synthesis and release of acetylcholine from neuronal and non-neuronal cells and the differential control mechanisms. The different cholinoceptors, multiple nicotinic and muscarinic receptors and their signalling are outlined and their involvement in the modulation of the function of various target cells, smooth muscles, nerves, surface epithelial, secretory cells, fibroblasts and inflammatory cells is discussed in detail.

Anti-inflammatory properties of cholinergic up-regulation: A new role for acetylcholinesterase inhibitors

We investigated the anti-inflammatory effects of acetylcholinesterase inhibitors (AChEI) at the cellular and molecular levels. AChEI suppressed lymphocyte proliferation and pro-inflammatory cytokine production, as well as extracellular esterase activity. Anti-inflammatory activity was mediated by the alpha7 nicotinic acetylcholine receptor (neuronal); the muscarinic receptor had the opposite effect. Treatment of the central nervous system (CNS) inflammatory disease, experimental autoimmune encephalomyelitis (EAE), with EN101, an anti-sense oligodeoxynucleotide, targeted to AChE mRNA, reduced the clinical severity of the disease and CNS inflammation intensity. The results of our experiments suggest that AChEI increase the concentration of extracellular acetylcholine (ACh), rendering it available for interaction with a nicotinic receptor expressed on lymphocytes. Our findings point to a novel role for AChEI which may be relevant in CNS inflammatory diseases such as EAE and multiple sclerosis. They also emphasize the importance of cholinergic balance in neurological disorders, such as Alzheimer's disease and myasthenia gravis, in which these drugs are used.

Muscarinic receptors, leukotriene B4 production and neutrophilic inflammation in COPD patients

BACKGROUND

Acetylcholine (ACh) plays an important role in smooth muscle contraction and in the development of airway narrowing; preliminary evidences led us to hypothesize that ACh might also play a role in the development of airways inflammation in chronic obstructive pulmonary disease (COPD).

METHODS

We evaluated the concentrations of leukotriene B4 (LTB4) in induced sputum, and the expression of Ach M1, M2, and M3 receptors in sputum cells (SC) obtained from 16 patients with COPD, 11 smokers, and 14 control subjects. The SC were also treated with ACh and the production of LTB4 assessed in the presence or absence of a muscarinic antagonist (oxitropium). In blood monocytes, we evaluated LTB4 release and activation of the extracellular signal-regulated kinases (ERK) pathway after treatment with Ach.

RESULTS

The LTB4 concentrations were higher in COPD than in controls (P < 0.01) and correlated with the number of neutrophil (P < 0.01). The M3 receptors expression was increased in COPD subjects when compared to smokers and control (P < 0.05 and 0.0001, respectively), while M2 expression resulted decreased (P < 0.05 and 0.01). The ACh-induced LTB(4) production was observed in peripheral blood monocytes, and was sensitive to ERK inhibition. Similarly, ACh significantly increased neutrophil chemotactic activity and LTB4 released from SC of COPD patients only, and these effects were blocked by pretreatment with the inhibitor of ERK pathway PD98059.

CONCLUSIONS

The results obtained show that muscarinic receptors may be involved in airway inflammation in COPD subjects through ACh-induced, ERK1/2-dependent LTB4 release. Muscarinic antagonism may contribute to reduce neutrophil infiltration and activation in COPD.

A Novel α-Conotoxin, PeIA, Cloned from Conus pergrandis, Discriminates between Rat α9α10 and α7 Nicotinic Cholinergic Receptors

The alpha9 and alpha10 nicotinic cholinergic subunits assemble to form the receptor believed to mediate synaptic transmission between efferent olivocochlear fibers and hair cells of the cochlea, one of the few examples of postsynaptic function for a non-muscle nicotinic acetylcholine receptor (nAChR). However, it has been suggested that the expression profile of alpha9 and alpha10 overlaps with that of alpha7 in the cochlea and in sites such as dorsal root ganglion neurons, peripheral blood lymphocytes, developing thymocytes, and skin. We now report the cloning, total synthesis, and characterization of a novel toxin alpha-conotoxin PeIA that discriminates between alpha9alpha10 and alpha7 nAChRs. This is the first toxin to be identified from Conus pergrandis, a species found in deep waters of the Western Pacific. Alpha-conotoxin PeIA displayed a 260-fold higher selectivity for alpha-bungarotoxin-sensitive alpha9alpha10 nAChRs compared with alpha-bungarotoxin-sensitive alpha7 receptors. The IC50 of the toxin was 6.9 +/- 0.5 nM and 4.4 +/- 0.5 nM for recombinant alpha9alpha10 and wild-type hair cell nAChRs, respectively. Alpha-conotoxin PeIA bears high resemblance to alpha-conotoxins MII and GIC isolated from Conus magus and Conus geographus, respectively. However, neither alpha-conotoxin MII nor alpha-conotoxin GIC at concentrations of 10 microM blocked acetylcholine responses elicited in Xenopus oocytes injected with the alpha9 and alpha10 subunits. Among neuronal non-alpha-bungarotoxin-sensitive receptors, alpha-conotoxin PeIA was also active at alpha3beta2 receptors and chimeric alpha6/alpha3beta2beta3 receptors. Alpha-conotoxin PeIA represents a novel probe to differentiate responses mediated either through alpha9alpha10 or alpha7 nAChRs in those tissues where both receptors are expressed.

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.

Lymphocyte muscarinic receptors and platelet monoamine oxidase-B as biomarkers of CNS function: effects of age and gender in healthy humans

Lymphocyte cholinergic muscarinic receptors (MRs) and platelet monoamine oxidase-B (MAO-B) activity are considered surrogate markers of the same parameters in the central nervous system. Lymphocyte MR binding and platelet MAO-B activity were measured in a consistent number of healthy human adults and analysed according to gender and age. The mean value±S.D. of MR binding neither differed between males (12.2±10.0fmol/10(6)cells, range: 0.5-37.9, n=86) and females (10.7±9.7fmol/10(6)cells, range: 0.5-39.7, n=69) nor among age groups. MAO-B activity was significantly higher in women (geometric mean: 11.3nmol/mgprotein/h, with 65% of values from 7.3 to 17.6; n=43), than in men (7.7nmol/mgprotein/h, with 65% of values from 4.5 to 13; n=95). Males aged 56-66 years displayed a higher, though not statistically significant, basal enzyme activity than younger subjects. Altogether these data indicate gender-related differences in MAO activity, but not in MR binding, and inter-individual differences in the basal values of both peripheral blood markers in healthy subjects.

Relationship between α7 nAChR and apoptosis in human lymphocytes

The presence of nicotinic receptors (nAChRs) in blood cells has been demonstrated. However, little is known about their functional roles. We have detected mRNA of alpha7 nAChR in peripheral human lymphocytes and determined that its expression is highly variable among individuals and within the same individual at different times. Upregulation of alpha7 is systematically observed after incubation of lymphocytes with nicotine or alpha-bungarotoxin. In addition, the incubation with these drugs decreases the percentage of apoptotic cells induced by the exposure to cortisol. Our results suggest that alpha7 nAChRs are involved in the modulation of cortisol-induced apoptosis.

The immune system as the sixth sense

One of the truly remarkable discoveries in modern biology is the finding that the nervous system and immune system use a common chemical language for intra- and inter-system communication. This review will discuss some of the pivotal results that deciphered this chemical language. Specifically the nervous and immune systems produce a common set of peptide and nonpeptide neurotransmitters and cytokines that act on a common repertoire of receptors in the two systems. The paper will also review more recent studies that have delineated hardwired and humoral pathways for such bidirectional communication. This is discussed in the context of the idea that the sharing of ligands and receptors allows the immune system to serve as the sixth sense that notifies the nervous system of the presence of entities, such as viruses and bacteria, that are imperceptible to the classic senses. Lastly, this review will suggest ways to apply the newfound knowledge of the sixth sense to understand a placebo effect and to treat human disease.

Autonomic neural regulation of immunity

The 'cytokine theory of disease' states that an overproduction of cytokines can cause the clinical manifestations of disease. Much effort has been expended to determine how cytokines are regulated in normal health. Transcriptional, translational and other molecular control mechanisms protect the host from excessive cytokine production. A recent discovery revealed an unexpected pathway that inhibits macrophage cytokine production. The inflammatory reflex is a physiological pathway in which the autonomic nervous system detects the presence of inflammatory stimuli and modulates cytokine production. Afferent signals to the brain are transmitted via the vagus nerve, which activates a reflex response that culminates in efferent vagus nerve signalling. Termed the 'cholinergic anti-inflammatory pathway', efferent activity in the vagus nerve releases acetylcholine (ACh) in the vicinity of macrophages within the reticuloendothelial system. ACh can interact specifically with macrophage alpha7 subunits of nicotinic ACh receptors, leading to cellular deactivation and inhibition of cytokine release. This 'hard-wired' connection between the nervous and immune systems can be harnessed therapeutically in animal models of inflammatory disease, via direct electrical stimulation of the vagus nerve, or through the use of cholinergic agonists that specifically activate the macrophage alpha7 subunit of the ACh receptor. Autonomic dysfunction has been associated with human inflammatory diseases including rheumatoid arthritis, diabetes and sepsis; whether this dysfunction results from the inflammatory component of these diseases, or is actually an underlying cause, is now less clear. The description of the cholinergic anti-inflammatory now brings to the fore several new therapeutic strategies for inflammatory disease, and suggests that many of these diseases may actually be diseases of autonomic dysfunction.

Ethanol stimulates the expression of fibronectin in lung fibroblasts via kinase-dependent signals that activate CREB

Ethanol renders the lung susceptible to acute lung injury in the setting of insults such as sepsis. The mechanisms mediating this effect are unknown, but activation of tissue remodeling is considered key to this process. We found that chronic ethanol ingestion in rats increased the expression of fibronectin, a matrix glycoprotein implicated in acute lung injury. In cultured NIH/3T3 cells and in primary rat and mouse lung fibroblasts, ethanol induced fibronectin mRNA and protein expression in a dose- and time-dependent fashion. The effect of ethanol was prevented by inhibitors of protein kinase C and mitogen-activated protein kinases and was associated with the phosphorylation and increased DNA binding of the transcription factor cAMP response element binding protein, followed by increased transcription of the fibronectin gene. Fibroblasts were found to express alpha(7) nicotinic acetylcholine receptor (nAChR), and ethanol induction of fibronectin was abolished by alpha-bungarotoxin and methyllcaconitine, inhibitors of alpha(7) nAChRs. However, ethanol was able to induce fibronectin mRNA and protein in primary lung fibroblasts isolated from alpha(7) nAChR knockout mice. The ethanol-induced fibronectin response was dependent on ethanol metabolism since 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, abolished the effect and acetaldehyde induced it. These observations suggest that ethanol or ethanol metabolites stimulate lung fibroblasts to produce fibronectin by inducing specific signals transmitted via nAChRs independent of the alpha(7-)subunit, and this might represent a mechanism by which ethanol renders the lung susceptible to acute lung injury.

The role of anticholinergics in chronic obstructive pulmonary disease

Anticholinergics are the bronchodilators of choice in the management of chronic obstructive pulmonary disease (COPD). They work by blocking muscarinic receptors in airway smooth muscle. Cholinergic tone appears to be the only reversible component of COPD. With the discovery of different muscarinic receptor subtypes, the development of more selective anticholinergics is possible. A major advance in this therapeutic area has been the discovery of tiotropium bromide, which has kinetic selectivity for M3 receptors as well as a duration of action of >24 hours. Once-daily administration of tiotropium is well tolerated and has shown significant advantages over ipratropium bromide, given 4 times daily, in the control of COPD.

The airway cholinergic system: physiology and pharmacology

The present review summarizes the current knowledge of the cholinergic systems in the airways with special emphasis on the role of acetylcholine both as neurotransmitter in ganglia and postganglionic parasympathetic nerves and as non-neuronal paracrine mediator. The different cholinoceptors, various nicotinic and muscarinic receptors, as well as their signalling mechanisms are presented. The complex ganglionic and prejunctional mechanisms controlling the release of acetylcholine are explained, and it is discussed whether changes in transmitter release could be involved in airway dysfunctions. The effects of acetylcholine on different target cells, smooth muscles, nerves, surface epithelial and secretory cells as well as mast cells are described in detail, including the receptor subtypes involved in signal transmission.

An in vitro investigation of the effects of the nerve agent pretreatment pyridostigmine bromide on human peripheral blood T-cell function

The current pretreatment against nerve agent poisoning deployed by the UK and US armed forces is the acetylcholinesterase (EC 3.1.1.7) inhibitor pyridostigmine bromide (PB). At higher doses, PB is also used to treat the autoimmune disease myasthenia gravis. In both cases, the therapeutic effect is mediated by inhibition of acetylcholinesterase (AChE) at cholinergic synapses. However, the location of AChE is not restricted to these sites. AChE, acetylcholine (ACh) receptors and choline acetyltransferase have been reported to be expressed by T cells, suggesting that cholinergic signalling may exert some modulatory influence on T-cell function and consequently on the immune system. The aim of this study was to investigate the role of the T-cell cholinergic system in the immunological activation process and to examine whether inhibitors of AChE such as PB affect immune function. To investigate this, human peripheral blood mononuclear cells (PBMC) were stimulated using either mitogen, cross-linking of the T-cell receptor and co-receptors with antibodies (anti-CD3/CD28) or by antigen presentation in the presence of various AChE inhibitors and ACh receptor agonists or antagonist. Several indices were used to assess T-cell activation, including the secretion of IL-2, cell proliferation and expression of CD69. Treatment with PB had no significant effect on the immunological assays selected. Physostigmine (PHY), a carbamate compound similar to PB, consistently showed inhibition of T-cell activation, but only at concentrations in excess of those required to inhibit AChE. No evidence was found to support previously published findings showing muscarinic enhancement of cell proliferation or IL-2 secretion.

Long-Term Exposure to Nicotine Modulates the Level and Activity of Acetylcholine Receptors in White Blood Cells of Smokers and Model Mice

Long-term consumption of tobacco by smokers causes addiction and increases the level of neuronal nicotinic acetylcholine receptors (nAChRs) in the brain, a phenomenon known as up-regulation. Here, we show that up-regulation of specific nAChR subunits takes place in white blood cells (WBCs) of smokers and mice subjected to long-term administration of nicotine. The basal level of alpha-bungarotoxin binding site, which corresponds to the homomeric alpha7 nAChR subtype, was not affected in WBCs of both smokers and mice administered nicotine. In contrast, epibatidine (EB) binding sites, which correspond to heteromeric nAChR subtypes, were detected in WBCs of smokers but not in WBCs of nonsmokers. The number of EB binding sites significantly decreased after incubation of the smokers' WBCs for 3 days in nicotine-free culture medium. In WBCs of wild-type mice, basal level of EB binding sites was detected before nicotine administration. This basal level is reduced by approximately 60% in knockout mice lacking the genes encoding either the beta2 or the alpha4 receptor subunits. Additional analysis of knockout mice revealed that the remaining approximately 40% do not undergo up-regulation, indicating that the alpha4/beta2 subunits comprise the up-regulated nAChRs. We further found that upregulation in mouse WBCs is accompanied by a significant decrease in the capacity of the up-regulated receptor channels to convey calcium ions. The phenomenon of nAChR up-regulation in WBCs provides a simple tool to evaluate and study tobacco addiction.

Dextran sodium sulfate-induced colitis reveals nicotinic modulation of ion transport via iNOS-derived NO

In normal colon, ACh elicits a luminally directed Cl- efflux from enterocytes via activation of muscarinic receptors. In contrast, in the murine model of dextran sodium sulfate (DSS)-induced colitis, an inhibitory cholinergic ion transport event due to nicotinic receptor activation has been identified. The absence of nicotinic receptors on enteric epithelia and the ability of nitric oxide (NO) to modulate ion transport led us to hypothesize that NO mediated the cholinergic nicotinic receptor-induced changes in ion transport. Midportions of colon from control and DSS-treated mice were examined for inducible NO synthase (iNOS) expression by RT-PCR and immunofluorescence or mounted in Ussing chambers for assessment of cholinergic-evoked changes in ion transport (i.e., short-circuit current) with or without pretreatment with pharmacological inhibitors of NO production. iNOS mRNA and protein levels were increased throughout the tissue from DSS-treated mice and, notably, in the myenteric plexus, where the majority of iNOS immunoreactivity colocalized with the enteric glial cell marker glial fibrillary acidic protein. The drop in short-circuit current evoked by the cholinomimetic carbachol in tissue from DSS-treated mice was prevented by selective inhibitors of iNOS activity [N6-(1-iminoethyl)-lysine HCl and N-[3-(aminomethyl)benzyl]acetamidine] or an NO scavenger [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] or by removal of the myenteric plexus. Thus, in this model of colitis, a "switch" occurs from muscarinic to nicotinic receptor-dominated control of cholinergic ion transport. The data indicate a novel pathway involving activation of nicotinic receptors on myenteric neurons, resulting in release of NO from neurons or enteric glia and, ultimately, a dampening of stimulated epithelial Cl- secretion that would reduce secretory diarrhea.

Potential clozapine target sites on peripheral hematopoietic cells and stromal cells of the bone marrow

The antipsychotic drug clozapine, acts via interaction with selective neurotransmitter receptor systems. Its use however, is associated with life-threatening agranulocytosis. The mechanism by which this occurs and its possible relationship with the drug's atypicality remain unclear. As a first step in identifying mechanistic pathways involved, profiling of neurotransmitter receptors on human neutrophils, mononuclear and bone marrow stromal cells as putative targets for clozapine-mediated toxicity was undertaken. Expression of mRNA encoding dopaminergic d2, d3, d4; serotonergic 5ht2a, 5ht2c, 5ht3, 5ht6, 5ht7; adrenergic alpha1a, alpha2; histaminergic h1 and muscarinic m1, m2, m3, m4, m5 receptors was analyzed by reverse transcription-polymerase chain reaction methods. While 5ht2c, 5ht6, m1 and m2 mRNA were undetected, the presence of the other receptors indicates sites at which clozapine could bind and induce toxicity of neutrophils and stromal components which regulate granulopoiesis. The functional significance of differential receptor expression while unknown, may argue for neural regulation of hematopoiesis.

The endogenous, immunologically active peptide apelin inhibits lymphocytic cholinergic activity during immunological responses

We investigated the effects of apelin, an immunologically active peptide ligand for orphan receptor APJ, on acetylcholine (ACh) synthesis in MOLT-3 human leukemic T cells. We initially confirmed expression of APJ mRNA in several human T- and B-cell lines by reverse transcription-polymerase chain reaction (RT-PCR). We also found that in phytohemagglutinin (PHA)-stimulated MOLT-3 cells, an active apelin fragment, apelin-13, down-regulates expression of choline acetyltransferase (ChAT) mRNA and significantly reduces ChAT activity and cellular ACh content and release. It thus appears that apelin inhibits lymphocytic cholinergic activity via APJ during immunological responses.

[An independent, non-neuronal cholinergic system in lymphocytes and its roles in regulation of immune function]

Acetylcholine (ACh) is classically thought of as a neurotransmitter in mammalian species. However, lymphocytes express most of the cholinergic components found in the nervous system, including ACh, choline acetyltransferase (ChAT), high-affinity choline transporter, and acetylcholinesterase as well as both muscarinic and nicotinic ACh receptors (mAChRs and nAChRs, respectively). Activation of T cells via the T cell receptor/CD3 complex, contact of T cells with antigen presenting cells, or activation of the adenylyl cyclase pathway in T cells modulates cholinergic activity, as evidenced by up-regulation of ChAT and M(5) mAChR mRNA expression. Stimulation of mAChRs on T and B cells with ACh or another mAChR agonists elicits intracellular Ca(2+) signaling, up-regulation of c-fos expression, increased nitric oxide synthesis and interleukin-2-induced signal transduction via M(3) and M(5) mAChR-mediated pathways. Acute stimulation of nAChRs with ACh or nicotine causes rapid and transient Ca(2+) signaling in T and B cells, probably via alpha7 nAChRs subunit-mediated pathways. Chronic nicotine stimulation, by contrast, down-regulates nAChR expression and suppresses T cell activity. Abnormalities in lymphocytic cholinergic system have been seen in animal models of immune deficiency and immune acceleration. Collectively, these data provided a compelling picture in which immune function is, at least partly, under the control of an independent, non-neuronal cholinergic system in lymphocytes.

Up-regulation of lymphocytic cholinergic activity by ONO-4819, a selective prostaglandin EP4 receptor agonist, in MOLT-3 human leukemic T cells

We used a selective EP4 receptor agonist, ONO-4819, and a human leukemic T cell line MOLT-3 cells, which express all four prostaglandin E2 (PGE2) receptors (EP1-EP4), to investigate whether the EP4 PGE2 receptor subtype is involved in regulating lymphocytic cholinergic activity. Phytohemagglutinin (PHA), a T cell activator, significantly enhanced the expression of EP4 receptor mRNA during the first 3-6 h of exposure, after which, expression gradually declined. Furthermore, PHA stimulation slightly but significantly up-regulated the expression of EP2 mRNA after 12 h and of EP3 mRNA after 6 h. By contrast, expression level of EP1 receptor mRNA was not affected by PHA. ONO-4819 (1 microM), which was added to cultures after 3 h of PHA stimulation, significantly increased cellular ACh content and release, and up-regulated ChAT mRNA expression and activity but inhibited MOLT-3 cell proliferation. These findings suggest that the activation of T lymphocytes up-regulates EP4 receptor mRNA expression and, to a lesser extent, EP2 and EP3 receptors and that PGE2 enhances nonneuronal lymphocytic cholinergic transmission in activated T cells, at least in part, via EP4 receptor-mediated pathways.