Nicotine-induced Ca2+ signaling and down-regulation of nicotinic acetylcholine receptor subunit expression in the CEM human leukemic T-cell line

Expression and Function of Nicotinic Acetylcholine Receptors in Induced Regulatory T Cells

A contribution of the cholinergic system to immune cell function has been suggested, though the role of nicotine and its receptors in T cells, especially regulatory T (Treg) cells, is unclear. We herein investigated the expression and function of nicotinic acetylcholine receptors (nAChRs) in murine-induced Treg (iTreg) cells. Upon differentiation of naive BALB/c T cells into iTreg cells and other T-cell subsets, the effect of nicotine on cytokine production and proliferation of iTreg cells was examined. The expression of nAChRs and its regulatory mechanisms were comparatively analyzed among T-cell subsets. Stimulation-induced transforming growth factor-β1 (TGF-β1) production of iTreg cells was suppressed by nicotine, whereas interleukin (IL)-10 production and proliferation was not affected. α2-, α5-, α9-, and β2-nAChRs were differentially expressed in naive, Th1, Th2, Th9, Th17, and iTreg cells. Among these cell types, the α9-nAChR was particularly upregulated in iTreg cells via its gene promoter, but not through tri-methylation at the 4th lysine residue of the histone H3-dependent mechanisms. We conclude that the immunoregulatory role of Treg cells is modified by the cholinergic system, probably through the characteristic expression of nAChRs.

New insights into neuropeptides regulation of immune system and hemopoiesis: effects on hematologic malignancies

Several neurotransmitters and neuropeptides were reported to join to or to cooperate with different cells of the immune system, bone marrow, and peripheral cells and numerous data support that neuroactive molecules might control immune system activity and hemopoiesis operating on lymphoid organs, and the primary hematopoietic unit, the hematopoietic niche. Furthermore, many compounds seem to be able to take part to the leukemogenesis and lymphomagenesis process, and in the onset of multiple myeloma. In this review, we will assess the possibility that neurotransmitters and neuropeptides may have a role in the onset of haematological neoplasms, may affect the response to treatment or may represent a useful starting point for a new therapeutic approach. More in vivo investigations are needed to evaluate neuropeptide's role in haematological malignancies and the possible utilization as an antitumor therapeutic target. Comprehending the effect of the pharmacological administration of neuropeptide modulators on hematologic malignancies opens up new possibilities in curing clonal hematologic diseases to achieve more satisfactory outcomes.

Regulation of Immune Functions by Non-Neuronal Acetylcholine (ACh) via Muscarinic and Nicotinic ACh Receptors

Acetylcholine (ACh) is the classical neurotransmitter in the cholinergic nervous system. However, ACh is now known to regulate various immune cell functions. In fact, T cells, B cells, and macrophages all express components of the cholinergic system, including ACh, muscarinic, and nicotinic ACh receptors (mAChRs and nAChRs), choline acetyltransferase, acetylcholinesterase, and choline transporters. In this review, we will discuss the actions of ACh in the immune system. We will first briefly describe the mechanisms by which ACh is stored in and released from immune cells. We will then address Ca²⁺ signaling pathways activated via mAChRs and nAChRs on T cells and B cells, highlighting the importance of ACh for the function of T cells, B cells, and macrophages, as well as its impact on innate and acquired (cellular and humoral) immunity. Lastly, we will discuss the effects of two peptide ligands, secreted lymphocyte antigen-6/urokinase-type plasminogen activator receptor-related peptide-1 (SLURP-1) and hippocampal cholinergic neurostimulating peptide (HCNP), on cholinergic activity in T cells. Overall, we stress the fact that ACh does not function only as a neurotransmitter; it impacts immunity by exerting diverse effects on immune cells via mAChRs and nAChRs.

α-Conotoxins and α-Cobratoxin Promote, while Lipoxygenase and Cyclooxygenase Inhibitors Suppress the Proliferation of Glioma C6 Cells

Among the brain tumors, glioma is the most common. In general, different biochemical mechanisms, involving nicotinic acetylcholine receptors (nAChRs) and the arachidonic acid cascade are involved in oncogenesis. Although the engagement of the latter in survival and proliferation of rat C6 glioma has been shown, there are practically no data about the presence and the role of nAChRs in C6 cells. In this work we studied the effects of nAChR antagonists, marine snail α-conotoxins and snake α-cobratoxin, on the survival and proliferation of C6 glioma cells. The effects of the lipoxygenase and cyclooxygenase inhibitors either alone or together with α-conotoxins and α-cobratoxin were studied in parallel. It was found that α-conotoxins and α-cobratoxin promoted the proliferation of C6 glioma cells, while nicotine had practically no effect at concentrations below 1 µL/mL. Nordihydroguaiaretic acid, a nonspecific lipoxygenase inhibitor, and baicalein, a 12-lipoxygenase inhibitor, exerted antiproliferative and cytotoxic effects on C6 cells. nAChR inhibitors weaken this effect after 24 h cultivation but produced no effects at longer times. Quantitative real-time polymerase chain reaction showed that mRNA for α4, α7, β2 and β4 subunits of nAChR were expressed in C6 glioma cells. This is the first indication for involvement of nAChRs in mechanisms of glioma cell proliferation.

Cholinergic modulation of the immune system - A novel therapeutic target for myocardial inflammation

The immune system and the nervous system depend on each other for their fine tuning and working, thus cooperating to maintain physiological homeostasis and prevent infections. The cholinergic system regulates the mobilization, differentiation, secretion, and antigen presentation of adaptive and innate immune cells mainly through α7 nicotinic acetylcholine receptors (α7nAChRs). The neuro-immune interactions are established and maintained by the following mechanisms: colocalization of immune and neuronal cells at defined anatomical sites, expression of the non-neuronal cholinergic system by immune cells, and the acetylcholine receptor-mediated activation of intracellular signaling pathways. Based on these immunological mechanisms, the protective effects of cholinergic system in animal models of diseases were summarized in this paper, such as myocardial infarction/ischemia-reperfusion, viral myocarditis, and endotoxin-induced myocardial damage. In addition to maintaining hemodynamic stability and improving the energy metabolism of the heart, both non-neuronal acetylcholine and neuronal acetylcholine in the heart can alleviate myocardial inflammation and remodeling to exert a significant cardioprotective effect. The new findings on the role of cholinergic agonists and vagus nerve stimulation in immune regulation are updated, so as to develop improved approaches to treat inflammatory heart disease.

Immunological Dysfunction in Tourette Syndrome and Related Disorders

Chronic tic disorder and Tourette syndrome are common childhood-onset neurological diseases. However, the pathophysiology underlying these disorders is unclear, and most studies have focused on the disinhibition of the corticostriatal–thalamocortical circuit. An autoimmune dysfunction has been proposed in the pathogenetic mechanism of Tourette syndrome and related neuropsychiatric disorders such as obsessive–compulsive disorder, autism, and attention-deficit/hyperactivity disorder. This is based on evidence from animal model studies and clinical findings. Herein, we review and give an update on the clinical characteristics, clinical evidence, and genetic studies in vitro as well as animal studies regarding immune dysfunction in Tourette syndrome.

The Role of α7nAChR-Mediated Cholinergic Anti-inflammatory Pathway in Immune Cells

Alpha 7 nicotinic acetylcholine receptor (α7nAChR) is widely distributed in the nervous and non-cholinergic immune systems. It is necessary for the cholinergic transmitter to participate in the regulation of inflammatory response and is the key element of cholinergic anti-inflammatory pathway (CAP). Because of the profound impact of CAP on the immune system, α7nAChR is considered as a potential therapeutic target for the treatment of inflammatory diseases. Available evidences confirmed that manipulation of CAP by activating α7nAChR with either endogenous acetylcholine (ACh) or cholinergic agonists can substantially alleviate inflammatory responses both in vivo and in vitro. However, the mechanism through which CAP curbs the excessive pro-inflammatory responses and maintains immune homeostasis is not fully understood. Obtained clues suggest that the crosstalk between CAP and classical inflammatory pathways is the key to elucidate the anti-inflammatory mechanism, and the impacts of CAP activation in α7nAChR-expressing immune cells are the foundation of the immunoregulatory property. In this article, we review and update the knowledge concerning the progresses of α7nAChR-based CAP, including α7nAChR properties, signal transductions, interactions with classic immune pathways, and immunoregulatory functions in different immune cells. Certain critical issues to be addressed are also highlighted. By providing a panoramic view of α7nAChR, the summarized evidences will pave the way for the development of novel anti-inflammatory reagents and strategy and inspire further researches.

Acetylcholine suppresses phagocytosis via binding to muscarinic- and nicotinic-acetylcholine receptors and subsequently interfering Ca2+- and NFκB-signaling pathways in blood clam

Though immunomodulation via cholinergic neurotransmitter acetylcholine (ACh), an important part of neuroendocrine-immune (NEI) regulatory network, has been well established in vertebrate species, the mechanisms remain poorly understood in invertebrates. In the present study, the immunomodulatory effect of ACh on haemocyte phagocytosis was investigated in an invertebrate bivalve species, Tegillarca granosa. Data obtained showed that in vitro ACh incubation suppressed phagocytic activity of haemocytes along with a significant elevation in intracellular Ca²⁺. In addition, the expressions of genes from Ca²⁺ signaling pathway were significantly induced whereas those from NF-κB signaling pathway were significantly down-regulated by ACh incubation. Furthermore, these adverse impacts of ACh were significantly relieved by the blocking of muscarinic acetylcholine receptors (mAChRs) or nicotinic acetylcholine receptors (nAChRs) using corresponding antagonists. Our study suggests that ACh suppresses phagocytosis via binding to both mAChRs and nAChRs, which disrupts intracellular Ca²⁺ homeostasis and subsequently interferes with downstream Ca²⁺ and NF-κB signaling pathways.

Differential gene expression analysis of HNSCC tumors deciphered tobacco dependent and independent molecular signatures

Head and neck cancer is the sixth most common cancer worldwide, with tobacco as the leading cause. However, it is increasing in non-tobacco users also, hence limiting our understanding of its underlying molecular mechanisms. RNA-seq analysis of cancers has proven as effective tool in understanding disease etiology. In the present study, RNA-Seq of 86 matched Tumor/Normal pairs, of tobacco smoking (TOB) and non-smokers (N-TOB) HNSCC samples analyzed, followed by validation on 375 similar datasets. Total 2194 and 2073 differentially expressed genes were identified in TOB and N-TOB tumors, respectively. GO analysis found muscle contraction as the most enriched biological process in both TOB and N-TOB tumors. Pathway analysis identified muscle contraction and salivary secretion pathways enriched in both categories, whereas calcium signaling and neuroactive ligand-receptor pathway was more enriched in TOB and N-TOB tumors respectively. Network analysis identified muscle development related genes as hub node i. e. ACTN2, MYL2 and TTN in both TOB and N-TOB tumors, whereas EGFR and MYH6, depicts specific role in TOB and N-TOB tumors. Additionally, we found enriched gene networks possibly be regulated by tumor suppressor miRNAs such as hsa-miR-29/a/b/c, hsa-miR-26b-5p etc., suggestive to be key riboswitches in regulatory cascade of HNSCC. Interestingly, three genes PKLR, CST1 and C17orf77 found to show opposite regulation in each category, hence suggested to be key genes in separating TOB from N-TOB tumors. Our investigation identified key genes involved in important pathways implicated in tobacco dependent and independent carcinogenesis hence may help in designing precise HNSCC diagnostics and therapeutics strategies.

Cholinesterase's activities of infected mice by Brucella ovis

The role of cholinesterase in inflammatory reactions has been described in several infectious diseases. However, in Brucella spp. this has not yet been studied. Therefore, the objective of this study was to evaluate whether experimental infection by Brucella ovis alters the cholinergic activity in pro- or anti-inflammatory responses to the disease. For the study 48 mice were used, 24 infected by B. ovis and 24 non-infected. We collected samples of whole blood on days 7, 15, 30 and 60 post-infection (PI) by B. ovis. Acetylcholinesterase (AChE) activity in the blood increased on days 15 and 60 PI (P < 0.05). Butyrylcholinesterase (BChE) activity in serum increased on days 7 and 60 PI (P < 0.05). An increase in serum free radical levels occurred on days 7, 15 and 60 PI (P < 0.05), and consequently superoxide dismutase activity increased on day 15 PI (P < 0.05). A reduction in catalase activity occurred when the infection became chronic (60 PI). The increase in AChE and BChE characterized a pro-inflammatory response, since these enzymes regulate levels of acetylcholine (ACh) and butyrylcholine (BuSCh), molecules with anti-inflammatory properties. Therefore, with the increase of cholinesterase activity, there was an extracellular reduction of ACh, an inhibitor of several inflammatory mediators. This proinflammatory response of B. ovis infection leads to oxidative stress, and consequently to cellular damage.

The sarco(endo)plasmic reticulum calcium ATPase SCA-1 regulates the Caenorhabditis elegans nicotinic acetylcholine receptor ACR-16

Nicotinic acetylcholine receptors (nAChR) are present in many excitable tissues and are found both pre and post-synaptically. Through their non-specific cationic permeability, these nAChRs have excitatory roles in neurotransmission, neuromodulation, synaptic plasticity, and neuroprotection. Thus, nAChR mislocalization or functional deficits are associated with many neurological disease states. Therefore identifying the mechanisms that regulate nAChR expression and function will inform our understanding of normal as well as pathological physiological conditions and offer avenues for potential therapeutic advances. Taking advantage of the genetic tractability of the soil nematode Caenorhabditis elegans, a forward genetic screen was performed to isolate regulators of the vertebrate α7 nAChR homologue ACR-16. From this screen a novel regulator of the ACR-16 receptor was identified, the sarco(endo)plasmic reticulum calcium ATPase sca-1. The sca-1 mutant affects ACR-16 receptor level at the NMJ, receptor functionality, and synaptic transmission. Responses to pressure-ejected nicotine in sca-1 mutants are indistinguishable from wild type, which implies the ACR-16 receptors are mislocalized at the NMJ. Changes in cytosolic baseline calcium levels in sca-1 and other mutants indicates a calcium-driven regulation mechanism of the α7-like NAChR ACR-16.

Acetylcholine released from T cells regulates intracellular Ca2+, IL-2 secretion and T cell proliferation through nicotinic acetylcholine receptor

AIMS

T lymphocytes synthesize acetylcholine (ACh) and express muscarinic and nicotinic ACh receptors (mAChR and nAChR, respectively) responsible for increases in the intracellular Ca²⁺ concentration ([Ca²⁺]_i). Our aim in the present study was to assess whether autocrine ACh released from T lymphocytes regulates their physiological functions.

MAIN METHODS

MOLT-3 human leukemic cell line and murine splenocytes were loaded with fura-2 to monitor [Ca²⁺]_i changes in the absence or presence of several AChR antagonists, including mecamylamine, methyllycaconitine and scopolamine. Real-time PCR and ELISA were performed to measure interleukin-2 (IL-2) mRNA and protein levels.

KEY FINDINGS

T lymphocytes constitutively produce sufficient amounts of ACh to elicit autocrine changes in [Ca²⁺]_i. These autocrine ACh-evoked [Ca²⁺]_i transients were mediated by nAChRs and then influx of extracellular Ca²⁺. Mecamylamine, a nAChR inhibitor, suppressed not only these [Ca²⁺]_i transients, but also IL-2 release and T cell proliferation.

SIGNIFICANCE

Here, we confirmed that T lymphocytes utilize ACh as a tool to interact with each other and that autocrine ACh-activated nAChRs are involved in cytokine release and cell proliferation. These findings suggest the possibility that nAChR agonists and antagonists and smoking are able to modulate immune function, which in turn suggests the therapeutic potential of immune activation or suppression using nAChR agonists or antagonists.

"Manganese-induced neurotoxicity: a review of its behavioral consequences and neuroprotective strategies"

Manganese (Mn) is an essential heavy metal. However, Mn’s nutritional aspects are paralleled by its role as a neurotoxicant upon excessive exposure. In this review, we covered recent advances in identifying mechanisms of Mn uptake and its molecular actions in the brain as well as promising neuroprotective strategies. The authors focused on reporting findings regarding Mn transport mechanisms, Mn effects on cholinergic system, behavioral alterations induced by Mn exposure and studies of neuroprotective strategies against Mn intoxication. We report that exposure to Mn may arise from environmental sources, occupational settings, food, total parenteral nutrition (TPN), methcathinone drug abuse or even genetic factors, such as mutation in the transporter SLC30A10. Accumulation of Mn occurs mainly in the basal ganglia and leads to a syndrome called manganism, whose symptoms of cognitive dysfunction and motor impairment resemble Parkinson’s disease (PD). Various neurotransmitter systems may be impaired due to Mn, especially dopaminergic, but also cholinergic and GABAergic. Several proteins have been identified to transport Mn, including divalent metal tranporter-1 (DMT-1), SLC30A10, transferrin and ferroportin and allow its accumulation in the central nervous system. Parallel to identification of Mn neurotoxic properties, neuroprotective strategies have been reported, and these include endogenous antioxidants (for instance, vitamin E), plant extracts (complex mixtures containing polyphenols and non-characterized components), iron chelating agents, precursors of glutathione (GSH), and synthetic compounds that can experimentally afford protection against Mn-induced neurotoxicity.

Cholinergic Machinery as Relevant Target in Acute Lymphoblastic T Leukemia

Various types of non-neuronal cells, including tumors, are able to produce acetylcholine (ACh), which acts as an autocrine/paracrine growth factor. T lymphocytes represent a key component of the non-neuronal cholinergic system. T cells-derived ACh is involved in a stimulation of their activation and proliferation, and acts as a regulator of immune response. The aim of the present work was to summarize the data about components of cholinergic machinery in T lymphocytes, with an emphasis on the comparison of healthy and leukemic T cells. Cell lines derived from acute lymphoblastic leukemias of T lineage (T-ALL) were found to produce a considerably higher amount of ACh than healthy T lymphocytes. Additionally, ACh produced by T-ALL is not efficiently hydrolyzed, because acetylcholinesterase (AChE) activity is drastically decreased in these cells. Up-regulation of muscarinic ACh receptors was also demonstrated at expression and functional level, whereas nicotinic ACh receptors seem to play a less important role and not form functional channels in cells derived from T-ALL. We hypothesized that ACh over-produced in T-ALL may act as an autocrine growth factor and play an important role in leukemic clonal expansion through shaping of intracellular Ca²⁺ signals. We suggest that cholinergic machinery may be attractive targets for new drugs against T-ALL. Specifically, testing of high affinity antagonists of muscarinic ACh receptors as well as antagomiRs, which interfere with miRNAs involved in the suppression of AChE expression, may be the first choice options.

Natural killer cells and single nucleotide polymorphisms of specific ion channels and receptor genes in myalgic encephalomyelitis/chronic fatigue syndrome

AIM

The aim of this paper was to determine natural killer (NK) cytotoxic activity and if single nucleotide polymorphisms (SNPs) and genotypes in transient receptor potential (TRP) ion channels and acetylcholine receptors (AChRs) were present in isolated NK cells from previously identified myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) patients.

SUBJECTS AND METHODS

A total of 39 ME/CFS patients (51.69±2 years old) and 30 unfatigued controls (47.60±2.39 years old) were included in this study. Patients were defined according to the 1994 Centers for Disease Control and Prevention criteria. Flow cytometry protocols were used to examine NK cytotoxic activity. A total of 678 SNPs from isolated NK cells were examined for 21 mammalian TRP ion channel genes and for nine mammalian AChR genes via the Agena Bioscience iPlex Gold assay. SNP association and genotype was determined using analysis of variance and Plink software.

RESULTS

ME/CFS patients had a significant reduction in NK percentage lysis of target cells (17%±4.68%) compared with the unfatigued control group (31%±6.78%). Of the 678 SNPs examined, eleven SNPs for TRP ion channel genes (TRPC4, TRPC2, TRPM3, and TRPM8) were identified in the ME/CFS group. Five of these SNPs were associated with TRPM3, while the remainder were associated with TRPM8, TRPC2, and TRPC4 (P<0.05). Fourteen SNPs were associated with nicotinic and muscarinic AChR genes: six with CHRNA3, while the remainder were associated with CHRNA2, CHRNB4, CHRNA5, and CHRNE (P<0.05). There were sixteen genotypes identified from SNPs in TRP ion channels and AChRs for TRPM3 (n=5), TRPM8 (n=2), TRPC4 (n=3), TRPC2 (n=1), CHRNE (n=1), CHRNA2 (n=2), CHRNA3 (n=1), and CHRNB4 (n=1) (P<0.05).

CONCLUSION

We identified a number of SNPs and genotypes for TRP ion channels and AChRs from isolated NK cells in patients with ME/CFS, suggesting these SNPs and genotypes may be involved in changes in NK cell function and the development of ME/CFS pathology. These anomalies suggest a role for dysregulation of Ca(2+) in AChR and TRP ion channel signaling in the pathomechanism of ME/CFS.

The Role of nAChR and Calcium Signaling in Pancreatic Cancer Initiation and Progression

Pancreatic cancer shows a strong correlation with smoking and the current therapeutic strategies have been relatively ineffective in improving the survival of patients. Efforts have been made over the past many years to understand the molecular events that drive the initiation and progression of pancreatic cancer, especially in the context of smoking. It has become clear that components of tobacco smoke not only initiate these cancers, especially pancreatic ductal adenocarcinomas (PDACs) through their mutagenic properties, but can also promote the growth and metastasis of these tumors by stimulating cell proliferation, angiogenesis, invasion and epithelial-mesenchymal transition. Studies in cell culture systems, animal models and human samples have shown that nicotinic acetylcholine receptor (nAChR) activation enhances these tumor-promoting events by channeling signaling through multiple pathways. In this context, signaling through calcium channels appear to facilitate pancreatic cancer growth by itself or downstream of nAChRs. This review article highlights the role of nAChR downstream signaling events and calcium signaling in the growth, metastasis as well as drug resistance of pancreatic cancer.

Non-neuronal cholinergic system in regulation of immune function with a focus on α7 nAChRs

In 1929, Dale and Dudley described the first reported natural occurrence of acetylcholine (ACh) in an animal's body. They identified this ACh in the spleens of horses and oxen, which we now know suggests possible involvement of ACh in the regulation of lymphocyte activity and immune function. However, the source and function of splenic ACh were left unexplored for several decades. Recent studies on the source of ACh in the blood revealed ACh synthesis catalyzed by choline acetyltransferase (ChAT) in CD4(+) T cells. T and B cells, macrophages and dendritic cells (DCs) all express all five muscarinic ACh receptor subtypes (mAChRs) and several subtypes of nicotinic AChRs (nAChRs), including α7 nAChRs. Stimulation of these mAChRs and nAChRs by their respective agonists causes functional and biochemical changes in the cells. Using AChR knockout mice, we found that M(1)/M(5) mAChR signaling up-regulates IgG(1) and pro-inflammatory cytokine production, while α7 nAChR signaling has the opposite effect. These findings suggest that ACh synthesized by T cells acts in an autocrine/paracrine fashion at AChRs on various immune cells to modulate immune function. In addition, an endogenous allosteric and/or orthosteric α7 nAChR ligand, SLURP-1, facilitates functional development of T cells and increases ACh synthesis via up-regulation of ChAT mRNA expression. SLURP-1 is expressed in CD205(+) DCs residing in the tonsil in close proximity to T cells, macrophages and B cells. Collectively, these findings suggest that ACh released from T cells along with SLURP-1 regulates cytokine production by activating α7 nAChRs on various immune cells, thereby facilitating T cell development and/or differentiation, leading to immune modulation.

The immune system and hypertension

A powerful interaction between the autonomic and the immune systems plays a prominent role in the initiation and maintenance of hypertension and significantly contributes to cardiovascular pathology, end-organ damage and mortality. Studies have shown consistent association between hypertension, proinflammatory cytokines and the cells of the innate and adaptive immune systems. The sympathetic nervous system, a major determinant of hypertension, innervates the bone marrow, spleen and peripheral lymphatic system and is proinflammatory, whereas the parasympathetic nerve activity dampens the inflammatory response through α7-nicotinic acetylcholine receptors. The neuro-immune synapse is bidirectional as cytokines may enhance the sympathetic activity through their central nervous system action that in turn increases the mobilization, migration and infiltration of immune cells in the end organs. Kidneys may be infiltrated by immune cells and mesangial cells that may originate in the bone marrow and release inflammatory cytokines that cause renal damage. Hypertension is also accompanied by infiltration of the adventitia and perivascular adipose tissue by inflammatory immune cells including macrophages. Increased cytokine production induces myogenic and structural changes in the resistance vessels, causing elevated blood pressure. Cardiac hypertrophy in hypertension may result from the mechanical afterload and the inflammatory response to resident or migratory immune cells. Toll-like receptors on innate immune cells function as sterile injury detectors and initiate the inflammatory pathway. Finally, abnormalities of innate immune cells and the molecular determinants of their activation that include toll-like receptor, adrenergic, cholinergic and AT1 receptors can define the severity of inflammation in hypertension. These receptors are putative therapeutic targets.

Influence of Toxoplasma gondii acute infection on cholinesterase activities of Wistar rats

Several studies have shown the mechanisms and importance of immune responses against Toxoplasma gondii infection and the notable role of cholinesterases in inflammatory reactions. However, the association between those factors has not yet been investigated. Therefore, the aim of this study was to evaluate the acetylcholinesterase (AChE) activity in blood and lymphocytes and the activity of butyrylcholinesterase (BChE) in serum of rats experimentally infected with T. gondii during the acute phase of infection. For that, an in vivo study was performed with evaluations of AChE and BChE activities on days 5 and 10 post-infection (PI). The activity of AChE in blood was increased on day 5 PI, while in lymphocytes its activity was enhanced on days 5 and 10 PI (P<0.05). No significant difference was observed between groups regarding to the activity of BChE in serum. A positive (P<0.01) correlation was observed between AChE activity and number of lymphocytes. The role of AChE as an inflammatory marker is well known in different pathologies; thus, our results lead to the hypothesis that AChE has an important role in modulation of early immune responses against T. gondii infection.

Reconciling neuronally and nonneuronally derived acetylcholine in the regulation of immune function

Immune cells, including lymphocytes, express muscarinic and nicotinic acetylcholine (ACh) receptors (mAChRs and nAChRs, respectively), and agonist stimulation of these AChRs causes functional and biochemical changes in the cells. The origin of the ACh that acts on immune cell AChRs has remained unclear until recently, however. In 1995, we identified choline acetyltransferase mRNA and protein in human T cells, and found that immunological T cell activation potentiated lymphocytic cholinergic transmission by increasing ACh synthesis and AChR expression. We also found that M(1) /M(5) mAChR signaling upregulates IgG(1) and proinflammatory cytokine production, whereas α7 nAChR signaling has the opposite effect. These findings suggest that ACh synthesized by T cells acts as an autocrine and/or paracrine factor via AChRs on immune cells to modulate immune function. In addition, a recently discovered endogenous allosteric α7 nAChR ligand, SLURP-1, also appears to be involved in modulating normal T cell function.

Biochemistry detection of acetylcholinesterase activity in Trypanosoma evansi and possible functional correlations

Several chemical and immunohistochemical techniques can be used for the detection of acetylcholinesterase (AChE) activity. In this experiment we aimed to detect AChE activity in Trypanosoma evansi. For this, the parasites were isolated from the blood of experimentally infected rats using a DEA-cellulose column. Enzymatic activity was determined in trypomastigote forms at 0, 0.2, 0.4, 0.8 and 1.2 mg/mL of protein concentrations by a standard biochemical protocol. At all concentrations tested, the study showed that T. evansi expresses the enzyme AChE and its activity was proportional to the concentration of protein, ranging between 0.64 and 2.70 μmol of AcSCh/h. Therefore, we concluded that it is possible to biochemically detect AChE in T. evansi, an enzyme that may be associated with vital functions of the parasite and also can be related to chemotherapy treatments, as further discussed in this article.

Cholinergic activation of hematopoietic stem cells: role in tobacco-related disease?

Tobacco use is associated with an increase in the white blood cell (WBC) count. This association has been attributed to bronchopulmonary inflammation and/or infection. It is not known if nicotine itself may play a role. The objective of this study was to determine whether nicotine itself could affect the WBC count, and to determine whether this was due to a direct effect on hematopoietic stem cells (HSC). C57Bl6J mice received nicotine orally, and measurements of the WBC count, bone marrow and spleen cellularity, and HSC count were made. To determine the functionality of HSCs, irradiated animals received bone marrow transplants from vehicle or nicotine-treated mice. Nicotine increased leukocytes in the peripheral blood, bone marrow and spleen. The peripheral red cell and platelet count were unaffected. Nicotine increased the frequency of HSC in the bone marrow. Isolated long-term HSCs from nicotine-treated mice transplanted into irradiated mice regenerated all hematopoietic cell lineages, demonstrating the functional competence of those HSCs. HSCs expressed nicotinic acetylcholine receptors (nAChRs), as documented by FITC-conjugated alpha-bungarotoxin binding. Nicotine increased soluble Kit ligand, consistent with stem cell activation. In conclusion, the data suggest a new mechanism for the increased WBC associated with tobacco use. The effect of nicotine to activate hematopoiesis may contribute to tobacco-related diseases.

GABA- and acetylcholine-related gene expression in blood correlate with tic severity and microarray evidence for alternative splicing in Tourette syndrome: a pilot study

Tourette syndrome (TS) is a complex childhood neurodevelopmental disorder characterized by motor and vocal tics. Recently, altered numbers of GABAergic-parvalbumin (PV) and cholinergic interneurons were observed in the basal ganglia of individuals with TS. Thus, we postulated that gamma-amino butyric acid (GABA)- and acetylcholine (ACh)-related genes might be associated with the pathophysiology of TS. Total RNA isolated from whole blood of 26 un-medicated TS subjects and 23 healthy controls (HC) was processed on Affymetrix Human Exon 1.0 ST arrays. Data were analyzed to identify genes whose expression correlated with tic severity in TS, and to identify genes differentially spliced in TS compared to HC subjects. Many genes (3627) correlated with tic severity in TS (p < 0.05) among which GABA- (p = 2.1 × 10⁻³) and ACh- (p = 4.25 × 10⁻⁸) related genes were significantly over-represented. Moreover, several GABA and ACh-related genes were predicted to be alternatively spliced in TS compared to HC including GABA receptors GABRA4 and GABRG1, the nicotinic ACh receptor CHRNA4 and cholinergic differentiation factor (CDF). This pilot study suggests that at least some of these GABA- and ACh-related genes observed in blood that correlate with tics or are alternatively spliced are involved in the pathophysiology of TS and tics.

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.

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.

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.

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.

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.

T cells express alpha7-nicotinic acetylcholine receptor subunits that require a functional TCR and leukocyte-specific protein tyrosine kinase for nicotine-induced Ca2+ response

Acute and chronic effects of nicotine on the immune system are usually opposite; acute treatment stimulates while chronic nicotine suppresses immune and inflammatory responses. Nicotine acutely raises intracellular calcium ([Ca(2+)](i)) in T cells, but the mechanism of this response is unclear. Nicotinic acetylcholine receptors (nAChRs) are present on neuronal and non-neuronal cells, but while in neurons, nAChRs are cation channels that participate in neurotransmission; their structure and function in nonexcitable cells are not well-defined. In this communication, we present evidence that T cells express alpha7-nAChRs that are critical in increasing [Ca(2+)](i) in response to nicotine. Cloning and sequencing of the receptor from human T cells showed a full-length transcript essentially identical to the neuronal alpha7-nAChR subunit (>99.6% homology). These receptors are up-regulated and tyrosine phosphorylated by treatment with nicotine, anti-TCR Abs, or Con A. Furthermore, knockdown of the alpha7-nAChR subunit mRNA by RNA interference reduced the nicotine-induced Ca(2+) response, but unlike the neuronal receptor, alpha-bungarotoxin and methyllycaconitine not only failed to block, but also actually raised [Ca(2+)](i) in T cells. The nicotine-induced release of Ca(2+) from intracellular stores in T cells did not require extracellular Ca(2+), but, similar to the TCR-mediated Ca(2+) response, required activation of protein tyrosine kinases, a functional TCR/CD3 complex, and leukocyte-specific tyrosine kinase. Moreover, CD3zeta and alpha7-nAChR co-immunoprecipitated with anti-CD3zeta or anti-alpha7-nAChR Abs. These results suggest that in T cells, alpha7-nAChR, despite its close sequence homology with neuronal alpha7-nAChR, fails to form a ligand-gated Ca(2+) channel, and that the nicotine-induced rise in [Ca(2+)](i) in T cells requires functional TCR/CD3 and leukocyte-specific tyrosine kinase.

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.

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.

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.

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.

Receptor-mediated tobacco toxicity: regulation of gene expression through alpha3beta2 nicotinic receptor in oral epithelial cells

Tobacco is a known cause of oral disease but the mechanism remains elusive. Nicotine (Nic) is a likely culprit of pathobiological effects because it displaces the local cytotransmitter acetylcholine from the nicotinic receptors (nAChRs) expressed by oral keratinocytes (KCs). To gain a mechanistic insight into tobacco-induced morbidity in the oral cavity, we studied effects of exposures to environmental tobacco smoke (ETS) versus equivalent concentration of pure Nic on human and murine KCs. Both ETS and Nic up-regulated expression of cell cycle and apoptosis regulators, differentiation marker filaggrin, and signal transduction factors at both the mRNA and protein levels. These changes could be abolished in cultured human oral KCs transfected with anti-alpha3 small interfering RNA or treated with the alpha3beta2-preferring antagonist alpha-conotoxin MII. Functional inactivation of alpha3-mediated signaling in alpha3-/- mutant KCs prevented most of the ETS/Nic-dependent changes in gene expression. To determine relevance of the in vitro findings to the in vivo situation, we studied gene expression in oral mucosa of neonatal alpha3+/+ and alpha3-/- littermates delivered by heterozygous mice soon after their exposures to ETS or equivalent concentration of pure Nic in drinking water. In addition to reverse transcriptase-polymerase chain reaction and Western blot, the ETS/Nic-dependent alterations in gene expression were also detected by semiquantitative immunofluorescence assay directly in KCs comprising murine oral mucosa. Only wild-type mice consistently developed significant (P < 0.05) changes in the gene expression. These results identified alpha3beta2 nAChR as a major receptor mediating effects of tobacco products on KC gene expression. Real-time polymerase chain reaction demonstrated that in all three model systems the common genes targeted by alpha3beta2-mediated ETS/Nic toxicity were p21, Bcl-2, NF-kappaB, and STAT-1. The expression of the nAChR subunits alpha5 and beta2 and the muscarinic receptor subtypes M(2) and M(3) was also altered. This novel mechanism offers innovative solutions to ameliorate the tobacco-related cell damage and intercede in disease pathways, and may shed light on general mechanisms regulating and driving tobacco-related morbidity in human cells.

Chronic nicotine and smoke treatment modulate dopaminergic activities in ventral tegmental area and nucleus accumbens and the ?-aminobutyric acid type B receptor expression of the rat prefrontal cortex

Dopaminergic afferents from the mesencephalic areas, such as ventral tegmental area (VTA), synapse with the gamma-aminobutyric acid (GABA)-ergic interneurons in the prefrontal cortex (PFC). Pharmacological and electrophysiological data show that the reinforcement, the dependence-producing properties, as well as the psychopharmacologic effects of nicotine depend to a great extent on activation of nicotinic receptors within the mesolimbocortical dopaminergic projection. To explore further the relationship between the mesencephalic dopaminergic neurons and PFC GABAergic neurons, we investigated the effects of nicotine and passive exposure to cigarette smoke on the regulation of tyrosine hydroxylase (TH) in VTA and substantia nigra (SNC) and dopamine (DA) D1 receptor levels in nucleus accumbens (NAc) and caudate-putamen (CPu). Also, the simultaneous changes in GABAB receptors mRNAs in the PFC were studied. The results showed that chronic nicotine and smoking treatment differentially changed the levels of TH protein in VTA and SNC and DA D1 receptor levels in Nac and CPu. GABAB1 and GABAB2 receptor mRNA levels also showed different change patterns. Ten and thirty minutes of smoke exposure increased GABAB1 receptor mRNA to a greater extent than that of GABAB2, whereas GABAB2 was greatly enhanced after 1 hr of smoke exposure. The TH levels in VTA were closely related to DA D1 receptor levels in NAc and with GABAB receptor mRNA changes in PFC. These results suggest that the mesolimbic pathway and GABAB receptor mRNA in PFC are modulated by nicotine and cigarette smoke, implying an important role in nicotine's psychopharmacological effects.

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.