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

Circulating extracellular choline acetyltransferase regulates inflammation

BACKGROUND

Choline acetyltransferase (ChAT) is required for the biosynthesis of acetylcholine, the molecular mediator that inhibits cytokine production in the cholinergic anti-inflammatory pathway of the vagus nerve inflammatory reflex. Abundant work has established the biology of cytoplasmic ChAT in neurons, but much less is known about the potential presence and function of ChAT in the extracellular milieu.

OBJECTIVES

We evaluated the hypothesis that extracellular ChAT activity responds to inflammation and serves to inhibit cytokine release and attenuate inflammation.

METHODS

After developing novel methods for quantification of ChAT activity in plasma, we determined whether ChAT activity changes in response to inflammatory challenges.

RESULTS

Active ChAT circulates within the plasma compartment of mice and responds to immunological perturbations. Following the administration of bacterial endotoxin, plasma ChAT activity increases for 12-48 h, a time period that coincides with declining tumor necrosis factor (TNF) levels. Further, a direct activation of the cholinergic anti-inflammatory pathway by vagus nerve stimulation significantly increases plasma ChAT activity, whereas the administration of bioactive recombinant ChAT (r-ChAT) inhibits endotoxin-stimulated TNF production and anti-ChAT antibodies exacerbate endotoxin-induced TNF levels, results of which suggest that ChAT activity regulates endogenous TNF production. Administration of r-ChAT significantly attenuates pro-inflammatory cytokine production and disease activity in the dextran sodium sulfate preclinical model of inflammatory bowel disease. Finally, plasma ChAT levels are also elevated in humans with sepsis, with the highest levels observed in a patient who succumbed to infection.

CONCLUSION

As a group, these results support further investigation of ChAT as a counter-regulator of inflammation and potential therapeutic agent.

Sinomenine inhibits macrophage M1 polarization by downregulating α7nAChR via a feedback pathway of α7nAChR/ERK/Egr-1

BACKGROUND

Sinomenine (SIN) is an anti-inflammatory drug that has been used for decades in China to treat arthritis. In a previous study, SIN acted on α7 nicotinic acetylcholine receptor (α7nAChR) to inhibit inflammatory responses in macrophages, which indicates a new anti-inflammatory mechanism of SIN. However, the level of α7nAChR was increased in the inflammatory responses and was downregulated by SIN in vitro, so the underlying mechanisms of SIN acting on α7nAChR remain unclear.

PURPOSE

To analyze the role of α7nAChR in inflammation and the effect and mechanism of SIN regulation of α7nAChR.

METHODS

The effects of SIN on α7nAChR in endotoxemic mice and LPS-stimulated macrophages were observed. Nicotine (Nic) was used as a positive control, and berberine (Ber) was used as a negative control targeting α7nAChR. The antagonists of α7nAChR, α-bungarotoxin (BTX) and mecamylamine (Me), were used to block α7nAChR. In RAW264.7 macrophage cells in vitro, α7nAChR short hairpin RNA (shRNA) was used to knock down α7nAChR. Macrophage polarization was analyzed by the detection of TNF-α, IL-6, iNOS, IL-10, Arg-1, and Fizz1. U0126 was used to block ERK phosphorylation. The cytokines α7nAChR, ERK1/2, p-ERK1/2 and Egr-1 were detected.

RESULTS

SIN decreased the levels of TNF-α, IL-6 and the expression of α7nAChR increased by LPS in endotoxemic mice. The above effects of SIN were attenuated by BTX. In the α7nAChR shRNA transfected RAW264.7 cells, compared with the control, α7nAChR was knocked down, and M1 phenotype markers (including TNF-α, IL-6, and iNOS) were significantly downregulated, whereas M2 phenotype markers (including IL-10, Arg-1, and Fizz1) were significantly upregulated when stimulated by LPS. SIN inhibited the expression of p-ERK1/2 and the transcription factor Egr-1 induced by LPS in RAW264.7 cells, and the above effects of SIN were attenuated by BTX. The expression of α7nAChR was suppressed by U0126, which lessened the expression of p-ERK1/2 and Egr-1.

CONCLUSIONS

SIN acts on α7nAChR to inhibit inflammatory responses and downregulates high expression of α7nAChR in vivo and in vitro. The increase of α7nAChR expression is correlated with inflammatory responses and participates in macrophage M1 polarization. SIN downregulates α7nAChR via a feedback pathway of α7nAChR/ERK/Egr-1, which contributes to inhibiting macrophage M1 polarization and inflammatory responses.

Cross-Talk of Cholinergic and β-Adrenergic Receptor Signalling in Chronic Myeloid Leukemia K562 Cells

In many studies on breast, skin, and intestinal cancers, beta-adrenergic receptor antagonists have been shown to inhibit cell proliferation and angiogenesis and increase apoptosis in cancers. Carbachol inhibits chronic myeloid leukemia K562 cell proliferation. Beta-blockers are known to inhibit cell progression. The aim of this study, explain the mechanism of action of beta-adrenergic receptors agonists and antagonists on apoptosis in chronic myeloid leukemia cells. We tried to determine the effect of combined treatment of beta-adrenergic and cholinergic drugs on Adrenergic β1 and β2 gene expression, cell proliferation and apoptosis in chronic myeloid leukemia K562 cells. Cell proliferation was evaluated by the BrdU incorporation kit. Caspase 3, 8, 9 activities were measured by the caspase-assay kit. Protein expression level detected by western blotting. We found that exposure to propranolol either by combination with carbachol facilitates additive effects on inhibition of caspase 3 and 8 expression in chronic myeloid leukemia K562 cells. But caspase 9 expression level was increased by propranolol alone or with propranolol and Carbachol combination. The combined therapy of cholinergic and adrenergic receptor drugs will decrease cell proliferation in K562 cells. This decrease in cell proliferation may be mediated by the mitochondrial dependent intrinsic apoptosis pathway.

Roles of Simvastatin and Sildenafil in Modulation of Cranial Irradiation-Induced Bystander Multiple Organs Injury in Rats

In radiobiology and radiation oncology fields, the observation of a phenomenon called radiation-induced bystander effect (RIBE) has introduced the prospect of remotely located tissues' affection. This phenomenon has been broadly developed to involve the concept of RIBE, which are relevant to the radiation-induced response of a distant tissue other than the irradiated one. The current study aimed at investigating each of the RIBE of cranial irradiation on oxidative and inflammatory status in different organs such as liver, kidney, heart, lung, and spleen. Being a vital target of the cholinergic anti-inflammatory response to an inflammatory stimulus, the splenic α-7-nicotinic acetylcholine receptor (α-7nAchR) was evaluated and the hepatic contents of thioredoxin, peroxisome proliferator-activated receptor-alpha and paraoxinase-1 (Trx/PPAR-α/PON) were also assessed as indicators for the liver oxidative stress and inflammatory responses. Being reported to act as antioxidant and anti-inflammatory agents, simvastatin (SV) and/or sildenafil (SD) were investigated for their effects against RIBE on these organs. These objectives were achieved via the biochemical assessments and the histopathological tissues examinations. Five experimental groups, one sham irradiated and four irradiated groups, were exposed to cranial irradiation at dose level of 25 Gy using an experimental irradiator with a Cobalt (Co60) source, RIBE, RIBE + SV (20 mg.(kg.bw)-1 day-1), RIBE + SD (75 mg.(kg.bw)-1 day-1), and RIBE + SV + SD. Cranial irradiation induced structural, biochemical, and functional dys-regulations in non-targeted organs. RIBE-induced organs' injuries have been significantly corrected by the administration of SV and/or SD. Our results suggest the possibility of a potentiated interaction between SV and SD in the modulation of the RIBE associated with head and neck radiotherapy.

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.

Role of the α7 Nicotinic Acetylcholine Receptor in the Pathophysiology of Atherosclerosis

Atherosclerosis constitutes a major risk factor for cardiovascular diseases, the leading cause of morbidity and mortality worldwide. This slowly progressing, chronic inflammatory disorder of large- and medium-sized arteries involves complex recruitment of immune cells, lipid accumulation, and vascular structural remodeling. The α7 nicotinic acetylcholine receptor (α7nAChR) is expressed in several cell types involved in the genesis and progression of atherosclerosis, including macrophages, dendritic cells, T and B cells, vascular endothelial and smooth muscle cells (VSMCs). Recently, the α7nAChR has been described as an essential regulator of inflammation as this receptor mediates the inhibition of cytokine synthesis through the cholinergic anti-inflammatory pathway, a mechanism involved in the attenuation of atherosclerotic disease. Aside from the neuronal cholinergic control of inflammation, the non-neuronal cholinergic system similarly regulates the immune function. Acetylcholine released from T cells acts in an autocrine/paracrine fashion at the α7nAChR of various immune cells to modulate immune function. This mechanism additionally has potential implications in reducing atherosclerotic plaque formation. In contrast, the activation of α7nAChR is linked to the induction of angiogenesis and VSMC proliferation, which may contribute to the progression of atherosclerosis. Therefore, both atheroprotective and pro-atherogenic roles are attributed to the stimulation of α7nAChRs, and their role in the genesis and progression of atheromatous plaque is still under debate. This minireview highlights the current knowledge on the involvement of the α7nAChR in the pathophysiology of atherosclerosis.

Acetylcholine Regulates Pulmonary Pathology During Viral Infection and Recovery

Introduction

This study was designed to explore the role of acetylcholine (ACh) in pulmonary viral infection and recovery. Inflammatory control is critical to recovery from respiratory viral infection. ACh secreted from non-neuronal sources, including lymphocytes, plays an important, albeit underappreciated, role in regulating immune-mediated inflammation.

Methods

ACh and lymphocyte cholinergic status in the lungs were measured over the course of influenza infection and recovery. The role of ACh was examined by inhibiting ACh synthesis in vivo. Pulmonary inflammation was monitored by Iba1 immunofluorescence, using a novel automated algorithm. Tissue repair was monitored histologically.

Results

Pulmonary ACh remained constant through the early stage of infection and increased during the peak of the acquired immune response. As the concentration of ACh increased, cholinergic lymphocytes appeared in the BAL and lungs. Cholinergic capacity was found primarily in CD4 T cells, but also in B cells and CD8 T cells. The cholinergic CD4⁺ T cells bound to influenza-specific tetramers and were retained in the resident memory regions of the lung up to 2 months after infection. Histologically, cholinergic lymphocytes were found in direct physical contact with activated macrophages throughout the lung. Inflammation was monitored by ionized calcium-binding adapter molecule 1 (Iba1) immunofluorescence, using a novel automated algorithm. When ACh production was inhibited, mice exhibited increased tissue inflammation and delayed recovery. Histologic examination revealed abnormal tissue repair when ACh was limited.

Conclusion

These findings point to a previously unrecognized role for ACh in the transition from active immunity to recovery and pulmonary repair following respiratory viral infection.

The retrotrapezoid nucleus and the neuromodulation of breathing

Breathing is regulated by a host of arousal and sleep-wake state-dependent neuromodulators to maintain respiratory homeostasis. Modulators such as acetylcholine, norepinephrine, histamine, serotonin (5-HT), adenosine triphosphate (ATP), substance P, somatostatin, bombesin, orexin, and leptin can serve complementary or off-setting functions depending on the target cell type and signaling mechanisms engaged. Abnormalities in any of these modulatory mechanisms can destabilize breathing, suggesting that modulatory mechanisms are not overly redundant but rather work in concert to maintain stable respiratory output. The present review focuses on the modulation of a specific cluster of neurons located in the ventral medullary surface, named retrotrapezoid nucleus, that are activated by changes in tissue CO₂/H⁺ and regulate several aspects of breathing, including inspiration and active expiration.

Effects mediated by the α7 nicotinic acetylcholine receptor on cell proliferation and migration in rat adipose-derived stem cells

Adipose-derived stem cells (ASCs) are an attractive source for regenerative medicine as they can be easily isolated, rapidly expandable in culture and show excellent in vitro differentiation potential. Acetylcholine (ACh), one of the main neurotransmitters in central and peripheral nervous systems, plays key roles in the control of several physiological processes also in non-neural tissues. As demonstrated in our previous studies, ACh can contribute to the rat ASCs physiology, negatively modulating ASCs proliferation and migration via M2 muscarinic receptor (mAChR) activation. In the present work we show that rat ASCs also express α7 nicotinic receptors (nAChRs). In particular, we have investigated the effects mediated by the selective activation of α7 nAChRs, which causes a reduction of ASC proliferation without affecting cell survival and morphology, and significantly promotes cell migration via upregulation of the CXCR4 expression. Interestingly, the activation of the α7 nAChR also upregulates the expression of M2 mAChR protein, indicating a cooperation between muscarinic and nicotinic receptors in the inhibition of ASC proliferation.

Attenuation in Nicotinic Acetylcholine Receptor α9 and α10 Subunit Double Knock-Out Mice of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is attenuated in nicotinic acetylcholine receptor (nAChR) α9 subunit knock-out (α9 KO) mice. However, protection is incomplete, raising questions about roles for related, nAChR α10 subunits in ionotropic or recently-revealed metabotropic contributions to effects. Here, we demonstrate reduced EAE severity and delayed onset of disease signs in nAChR α9/α10 subunit double knock-out (DKO) animals relative to effects in wild-type (WT) control mice. These effects are indistinguishable from contemporaneously-observed effects in nicotine-treated WT or in α9 KO mice. Immune cell infiltration into the spinal cord and brain, reactive oxygen species levels in vivo, and demyelination, mostly in the spinal cord, are reduced in DKO mice. Disease severity is not altered relative to WT controls in mice harboring a gain-of-function mutation in α9 subunits. These findings minimize the likelihood that additional deletion of nAChR α10 subunits impacts disease differently than α9 KO alone, whether through ionotropic, metabotropic, or alternative mechanisms. Moreover, our results provide further evidence of disease-exacerbating roles for nAChR containing α9 subunits (α9*-nAChR) in EAE inflammatory and autoimmune responses. This supports our hypothesis that α9*-nAChR or their downstream mediators are attractive targets for attenuation of inflammation and autoimmunity.

A Novel Immunomodulatory Mechanism Dependent on Acetylcholine Secreted by Human Bone Marrow-derived Mesenchymal Stem Cells

Background and Objectives

Mesenchymal stem cells (MSCs) are used to treat autoimmune or inflammatory diseases. Our aim was to determine the immunomodulatory mechanisms elicited by MSCs during inflammation.

Methods and Results

We cocultured MSCs with peripheral blood mononuclear cells for a mixed lymphocyte reaction or stimulated them by phytohemagglutinin. Morphological changes of MSCs and secretion of acetylcholine (ACh) from MSCs were measured. The effects of an ACh antagonist and ACh agonist on lymphocyte proliferation and proinflammatory-cytokine production were determined. The inflammatory milieu created by immune-cell activation caused MSCs to adopt a neuronlike phenotype and induced them to release ACh. Additionally, nicotinic acetylcholine receptors (nAChRs) were upregulated in activated peripheral blood mononuclear cells. We observed that ACh bound to nAChR on activated immune cells and led to the inhibition of lymphocyte proliferation and of proinflammatory-cytokine production. MSC-mediated immunosuppression through ACh activity was reversed by an ACh antagonist called α-bungarotoxin, and lymphocyte proliferation was inhibited by an ACh agonist, ACh chloride.

Conclusions

Our findings point to a novel immunomodulatory mechanism in which ACh secreted by MSCs under inflammatory conditions might modulate immune cells. This study may provide a novel method for the treatment of autoimmune diseases by means of MSCs.

Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease

The nervous and immune systems both serve as essential assessors and regulators of physiological function. Recently, there has been a great interest in how the nervous and immune systems interact to modulate both physiological and pathological states. In particular, the autonomic nervous system has a direct line of communication with immune cells anatomically, and moreover, immune cells possess receptors for autonomic neurotransmitters. This circumstantial evidence is suggestive of a functional interplay between the two systems, and extensive research over the past few decades has demonstrated neurotransmitters such as the catecholamines (i.e. dopamine, norepinephrine, and epinephrine) and acetylcholine have potent immunomodulating properties. Furthermore, immune cells, particularly T-lymphocytes, have now been found to express the cellular machinery for both the synthesis and degradation of neurotransmitters, which suggests the ability for both autocrine and paracrine signaling from these cells independent of the nervous system. The details underlying the functional interplay of this complex network of neuroimmune communication are still unclear, but this crosstalk is suggestive of significant implications on the pathogenesis of a number of autonomic-dysregulated and inflammation-mediated diseases. In particular, it is widely accepted that numerous forms of cardiovascular diseases possess imbalanced autonomic tone as well as altered T-lymphocyte function, but a paucity of literature exists discussing the direct role of neurotransmitters in shaping the inflammatory microenvironment during the progression or therapeutic management of these diseases. This review seeks to provide a fundamental framework for this autonomic neuroimmune interaction within T-lymphocytes, as well as the implications this may have in cardiovascular diseases.

Toxins for decoding interface selectivity in nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels that play crucial roles in neurotransmission and regulate complex processes in brain functions, including anxiety, learning and memory, food intake, drug addiction, cognition and nociception. To perform these and other functions, a diverse array of nAChR subtypes are generated by homomeric or heteromeric assembly of 17 homologous nAChR subunits. Agonists, acetylcholine and nicotine, bind to the interface formed between two α subunits and between α and non-α subunits to activate the nAChR and allow cation influx. The diversity of subunit interfaces determines the channel properties, the responses to different agonists/antagonists, desensitization and downstream signaling and thus, define specialized properties and functions. Over the last several decades, snake venom neurotoxins have contributed to the purification, localization and characterization of molecular details of various nAChRs. Utkin et al. have described the purification and characterization of αδ-bungarotoxins, a novel class of neurotoxins in a recent paper published in the Biochemical Journal [Biochem. J. (2019) 476, 1285-1302]. These toxins from Bungarus candidus venom preferably bind to α-δ site with two orders of magnitude higher affinity compared with α-γ or α-ε sites. The subtle changes in the structure of αδ-bungarotoxins led to variation in interface selectivity. Such new classes of antagonists will offer us great opportunity to delineate the pharmacophores and design new highly selective antagonists. Thus, their findings provide new impetus to re-evaluate molecular details of pharmacological properties of α-neurotoxins with careful consideration towards subtype-, interface- and species-selectivity.

Activation of Dendritic Cells in Dry Eye Mouse Model

Purpose

The immune system plays a major role in the pathogenesis of dry eye diseases (DED), and dendritic cells (DCs) are known to be important initiators of acquired immunity. Thus, the purpose of this study was to determine the contribution of DCs to the development of DED.

Methods

Mouse dry eye model was induced by subcutaneous injections of scopolamine and was euthanized at the baseline, and 2, 4, and 7 days postinjection. The activation of the DCs was determined by the mixed leukocyte reaction (MLR), and the number of activated CD86+ DCs in the lymph nodes was determined by flow cytometry. Upregulation of cytokines in the culture supernatant of MLR was determined by ELISA.

Results

Significantly increased superficial corneal punctate lesions and decreased number of goblet cells in the conjunctiva were observed in scopolamine-injected mice. The number of activated CD86+ DCs was significantly increased in the cervical lymph nodes but not in the inguinal lymph nodes of the dry eye mice. The stimulatory activity of the DCs derived from the cervical lymph nodes of dry eye mice was significantly higher than that of control mice, and upregulations of IL-17, IL-2, and IL-4 were observed in the culture supernatant of MLR. These results indicate that the DCs of the cervical lymph nodes were activated by the scopolamine injections.

Conclusions

Our results indicate that DCs in our dry eye model were sufficiently activated to stimulate the T cells that participate in the onset and progression of DED.

Neuroimmune Interactions: From the Brain to the Immune System and Vice Versa

Because of the compartmentalization of disciplines that shaped the academic landscape of biology and biomedical sciences in the past, physiological systems have long been studied in isolation from each other. This has particularly been the case for the immune system. As a consequence of its ties with pathology and microbiology, immunology as a discipline has largely grown independently of physiology. Accordingly, it has taken a long time for immunologists to accept the concept that the immune system is not self-regulated but functions in close association with the nervous system. These associations are present at different levels of organization. At the local level, there is clear evidence for the production and use of immune factors by the central nervous system and for the production and use of neuroendocrine mediators by the immune system. Short-range interactions between immune cells and peripheral nerve endings innervating immune organs allow the immune system to recruit local neuronal elements for fine tuning of the immune response. Reciprocally, immune cells and mediators play a regulatory role in the nervous system and participate in the elimination and plasticity of synapses during development as well as in synaptic plasticity at adulthood. At the whole organism level, long-range interactions between immune cells and the central nervous system allow the immune system to engage the rest of the body in the fight against infection from pathogenic microorganisms and permit the nervous system to regulate immune functioning. Alterations in communication pathways between the immune system and the nervous system can account for many pathological conditions that were initially attributed to strict organ dysfunction. This applies in particular to psychiatric disorders and several immune-mediated diseases. This review will show how our understanding of this balance between long-range and short-range interactions between the immune system and the central nervous system has evolved over time, since the first demonstrations of immune influences on brain functions. The necessary complementarity of these two modes of communication will then be discussed. Finally, a few examples will illustrate how dysfunction in these communication pathways results in what was formerly considered in psychiatry and immunology to be strict organ pathologies.

Distinctive Roles for α7*- and α9*-Nicotinic Acetylcholine Receptors in Inflammatory and Autoimmune Responses in the Murine Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis

Previous studies have demonstrated immunosuppressive and anti-inflammatory effects of nicotine, including in the experimental autoimmune encephalomyelitis (EAE) model in mice of some forms of multiple sclerosis (MS). Other studies using knock-out (KO) mice have implicated nicotinic acetylcholine (ACh) receptors containing α7, α9, or β2 subunits (α7*-, α9*- or β2*-nAChR) in different, disease-exacerbating or disease-ameliorating processes. These outcomes are in harmony with gene expression analyses showing nAChR subunit mRNA in many classes of immune system cell types. Consistent with influences on disease status, predictable effects of nAChR subunit (and subtype) KO, or of nicotine exposure, are seen on immune cell numbers and distribution and on cytokine levels or other markers of immunity, inflammation, demyelination, and axonal degradation. Providing support for our hypotheses about distinctive roles for nAChR subtypes in EAE, here we have used direct and adoptive EAE induction and a nAChR subunit gene double knock-out (DKO) strategy. Immune cell expression of nAChR α9 subunits as protein is demonstrated by immunostaining of isolated CD4⁺, CD8⁺, CD11b⁺ and CD11c⁺ cells from wild-type (WT) mice, but not in cells from nAChR α9 subunit KO animals. Nicotine exposure is protective against directly-induced EAE in WT or α7/α9 DKO animals relative to effects seen in WT/vehicle-treated mice, but, remarkably, EAE is exacerbated in vehicle-treated α7/α9 DKO mice. Brain lesion volume and intra-cranial inflammatory activity similarly are higher in DKO/vehicle than in WT/vehicle-treated animals, although nicotine’s protective effects are seen in each instance. By contrast, in adoptive transfer studies, disease severity is attenuated and disease onset is delayed in recipients of splenocytes from WT animals treated with nicotine rather than with vehicle. Moreover, protection as seen in nicotine-treated WT animals is the same in recipients of splenocytes from nAChR α7/α9 DKO mice irrespective of their exposure to nicotine or vehicle. When combined with previous observations, these findings are consistent with disease exacerbation (or even induction) being mediated at least in part via α9*-nAChR in peripheral immune cells. They also suggest protective roles of central nervous system (CNS) α7*-nAChR. The results suggest that both α7*- and α9*-nAChR are potential targets of therapeutic ligands to modulate inflammation and autoimmunity.

Granulocytes as models for human protein marker identification following nicotine exposure

Nicotinic acetylcholine receptors (nAChRs) are pentameric cation channels expressed in the mammalian CNS, in the peripheral nervous system, and in skeletal muscle. Neuronal-type nAChRs are also found in several non-neuronal cell types, including leukocytes. Granulocytes are a subtype of leukocytes that include basophils, eosinophils, and neutrophils. Granulocytes, also known as polymorphonuclear leukocytes, are characterized by their ability to produce, store, and release compounds from intracellular granules. Granulocytes are the most abundant type of leukocyte circulating in the peripheral blood. Granulocyte abundance, nAChR expression, and nAChR upregulation following chronic nicotine administration makes granulocytes interesting models for identifying protein markers of nicotine exposure. Nicotinic receptor subunits and several non-nAChR proteins have been identified as protein markers of granulocyte nicotine exposure. We review methods to isolate granulocytes from human tissue, summarize present data about the expression of nAChRs in the three granulocyte cell types (basophils, eosinophils, and neutrophils), describe current knowledge of the effects of nicotine exposure on human granulocyte protein expression, and highlight areas of interest for future investigation. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.

Cholinergic modulation of the immune system presents new approaches for treating inflammation

The nervous system and immune system have broad and overlapping distributions in the body, and interactions of these ubiquitous systems are central to the field of neuroimmunology. Over the past two decades, there has been explosive growth in our understanding of neuroanatomical, cellular, and molecular mechanisms that mediate central modulation of immune functions through the autonomic nervous system. A major catalyst for growth in this field was the discovery that vagal nerve stimulation (VNS) caused a prominent attenuation of the systemic inflammatory response evoked by endotoxin in experimental animals. This effect was mediated by acetylcholine (ACh) stimulation of nicotinic receptors on splenic macrophages. Hence, the circuit was dubbed the "cholinergic anti-inflammatory pathway". Subsequent work identified the α7 nicotinic ACh receptor (α7nAChR) as the crucial target for attenuation of pro-inflammatory cytokine release from macrophages and dendritic cells. Further investigation made the important discovery that cholinergic T cells within the spleen and not cholinergic nerve cells were the source of ACh that stimulated α7 receptors on splenic macrophages. Given the important role that inflammation plays in numerous disease processes, cholinergic anti-inflammatory mechanisms are under intensive investigation from a basic science perspective and in translational studies of animal models of diseases such as inflammatory bowel disease and rheumatoid arthritis. This basic work has already fostered several clinical trials examining the efficacy of VNS and cholinergic therapeutics in human inflammatory diseases. This review provides an overview of basic and translational aspects of the cholinergic anti-inflammatory response and relevant pharmacology of drugs acting at the α7nAChR.

The cholinergic anti-inflammatory pathway: An innovative treatment strategy for neurological diseases

Acetylcholine (ACh), as a classical neurotransmitter, regulates the neuronal network in response to internal and external stimuli. In recent decades, the biology of ACh has been endowed with unparalleled new insights, especially with respect to cholinergic anti-inflammatory properties in non-neuronal cells. In fact, a mechanism frequently referred to as the "cholinergic anti-inflammatory pathway" has been termed to describe interactions between the central nervous system (CNS) and the immune system via vagus nerve. As well documented, immune cells express choline acetyltransferase, a direct synthetase for ACh, and other corresponding cholinergic components. Alternatively, the ACh released from immune cells or cholinergic neurons modulates immune function in an autocrine/paracrine manner by acting on its receptors. Moreover, muscarinic or nicotinic ACh receptors on various immune cells and CNS glial cells administer the work of their respective agonists, causing functional and biochemical changes. In this review, we focus on the anti-inflammatory benefits of non-neuronal and neuronal ACh as a means of providing new insights into treating inflammation-related neurological diseases, as exemplified by those described herein.

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.

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.

Reduced expression of VAChT increases renal fibrosis

Chronic kidney disease (CKD) is associated with several other long-lasting conditions such as diabetes and cardiovascular diseases and it is a significant contributor to mortality worldwide. Obstructive kidney disease is one of the leading causes of CKD in children and may result from a wide variety of pathologic processes. Recent studies have shown that α7 nicotinic acetylcholine receptor (α7 nAChR) activation in the cholinergic anti-inflammatory pathway reduces production of inflammatory mediators and consequently prevents tissue injury and death. Here, we examined the role of endogenous release of acetylcholine on the development of fibrosis in renal tissue using a model of unilateral ureter obstruction (UUO)-induced CKD, in which obstruction promotes inflammation-mediated kidney damages. To interfere with acetylcholine secretion, we used mice in which the vesicular acetylcholine transporter is genetically reduced (VAChT KD(hom) mice). We observed a higher renal damage in VAChT mutant mice when compared to wild type controls, exemplified by higher proteinuria and increased amount of type 1 collagen in the kidney tissue, indicating accentuated fibrogenesis. These results were accompanied by enhanced localized kidney inflammation, with increased TH1/TH17 profile response. Administration of PNU-282987, a selective agonist of α7 nAChR, significantly attenuated kidney injury after UUO in VAChT KD(hom) mice, indicating that the lack of acetylcholine release decrease the action of the cholinergic anti-inflammatory pathway, promoting an up-regulation of pro-inflammatory and pro-fibrotic pathways. These results suggest that physiological activation of the cholinergic anti-inflammatory pathway regulates inflammatory responses in the kidney suggesting a new therapeutic approach for kidney disease.

Potential association of reduced cholinesterase activity with Trypanosoma evansi pathogenesis in buffaloes

The present study aimed to investigate the association of cholinesterase activity with trypanosomosis in buffaloes. Thirty-three clinical cases of trypanosomosis in water buffaloes, found positive for trypomastigotes of T. evansi on blood smear examination, were divided into two groups based on clinical manifestations. Twenty diseased buffaloes revealing only common clinical signs were allocated to Group I, while the remaining 13 buffaloes showing common clinical manifestations along with neurological disturbances were allocated to Group II. Twelve clinically healthy buffaloes, free from any haemoprotozoa infection, were kept as healthy control (Group III). Blood samples were collected from buffaloes of all three groups to determine serum cholinesterase activity. Compared to buffaloes of healthy control group, cholinesterase activity in T. evansi-infected buffaloes of Group I and II was significantly (P<0.001) lower. However, no significant difference was observed in cholinesterase activity between the T. evansi-infected buffaloes exhibiting neurological disorders and no neurological disorders. Summing up, reduced cholinesterase activity seems to be associated with the pathogenesis of natural T. evansi infection and its clinical manifestations in buffaloes possibly by evading immune response. Further studies are warranted on association of cholinesterase activity in T. evansi-infected buffaloes with neurological disorders.

Cigarette Smoke Disturbs the Survival of CD8+ Tc/Tregs Partially through Muscarinic Receptors-Dependent Mechanisms in Chronic Obstructive Pulmonary Disease

BACKGROUND

CD8+ T cells (Cytotoxic T cells, Tc) are known to play a critical role in the pathogenesis of smoking related airway inflammation including chronic obstructive pulmonary disease (COPD). However, how cigarette smoke directly impacts systematic CD8+ T cell and regulatory T cell (Treg) subsets, especially by modulating muscarinic acetylcholine receptors (MRs), has yet to be well elucidated.

METHODS

Circulating CD8+ Tc/Tregs in healthy nonsmokers (n = 15), healthy smokers (n = 15) and COPD patients (n = 18) were evaluated by flow cytometry after incubating with anti-CD3, anti-CD8, anti-CD25, anti-Foxp3 antibodies. Peripheral blood T cells (PBT cells) from healthy nonsmokers were cultured in the presence of cigarette smoke extract (CSE) alone or combined with MRs agonist/antagonist for 5 days. Proliferation and apoptosis were evaluated by flow cytometry using Ki-67/Annexin-V antibodies to measure the effects of CSE on the survival of CD8+ Tc/Tregs.

RESULTS

While COPD patients have elevated circulating percentage of CD8+ T cells, healthy smokers have higher frequency of CD8+ Tregs. Elevated percentages of CD8+ T cells correlated inversely with declined FEV1 in COPD. CSE promoted the proliferation and inhibited the apoptosis of CD8+ T cells, while facilitated both the proliferation and apoptosis of CD8+ Tregs. Notably, the effects of CSE on CD8+ Tc/Tregs can be mostly simulated or attenuated by muscarine and atropine, the MR agonist and antagonist, respectively. However, neither muscarine nor atropine influenced the apoptosis of CD8+ Tregs.

CONCLUSION

The results imply that cigarette smoking likely facilitates a proinflammatory state in smokers, which is partially mediated by MR dysfunction. The MR antagonist may be a beneficial drug candidate for cigarette smoke-induced chronic airway inflammation.

A Distinct Functional Site in Ω-Neurotoxins: Novel Antagonists of Nicotinic Acetylcholine Receptors from Snake Venom

Snake venom α-neurotoxins from the three-finger toxin (3FTx) family are competitive antagonists with nanomolar affinity and high selectivity for nicotinic acetylcholine receptors (nAChR). Here, we report the characterization of a new group of competitive nAChR antagonists: Ω-neurotoxins. Although they belong to the 3FTx family, the characteristic functional residues of α-neurotoxins are not conserved. We evaluated the subtype specificity and structure-function relationships of Oh9-1, an Ω-neurotoxin from Ophiophagus hannah venom. Recombinant Oh9-1 showed reversible postsynaptic neurotoxicity in the micromolar range. Experiments with different nAChR subtypes expressed in Xenopus oocytes indicated Oh9-1 is selective for rat muscle type α1β1εδ (adult) and α1β1γδ (fetal) and rat neuronal α3β2 subtypes. However, Oh9-1 showed low or no affinity for other human and rat neuronal subtypes. Twelve individual alanine-scan mutants encompassing all three loops of Oh9-1 were evaluated for binding to α1β1εδ and α3β2 subtypes. Oh9-1's loop-II residues (M25, F27) were the most critical for interactions and formed the common binding core. Mutations at T23 and F26 caused a significant loss in activity at α1β1εδ receptors but had no effect on the interaction with the α3β2 subtype. Similarly, mutations at loop-II (H7, K22, H30) and -III (K45) of Oh9-1 had a distinctly different impact on its activity with these subtypes. Thus, Oh9-1 interacts with these nAChRs via distinct residues. Unlike α-neurotoxins, the tip of loop-II is not involved. We reveal a novel mode of interaction, where both sides of the β-strand of Oh9-1's loop-II interact with α1β1εδ, but only one side interacts with α3β2. Phylogenetic analysis revealed functional organization of the Ω-neurotoxins independent of α-neurotoxins. Thus, Ω-neurotoxin: Oh9-1 may be a new, structurally distinct class of 3FTxs that, like α-neurotoxins, antagonize nAChRs. However, Oh9-1 binds to the ACh binding pocket via a different set of functional residues.

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.

Placing ion channels into a signaling network of T cells: from maturing thymocytes to healthy T lymphocytes or leukemic T lymphoblasts

T leukemogenesis is a multistep process, where the genetic errors during T cell maturation cause the healthy progenitor to convert into the leukemic precursor that lost its ability to differentiate but possesses high potential for proliferation, self-renewal, and migration. A new misdirecting "leukemogenic" signaling network appears, composed by three types of participants which are encoded by (1) genes implicated in determined stages of T cell development but deregulated by translocations or mutations, (2) genes which normally do not participate in T cell development but are upregulated, and (3) nondifferentially expressed genes which become highly interconnected with genes expressed differentially. It appears that each of three groups may contain genes coding ion channels. In T cells, ion channels are implicated in regulation of cell cycle progression, differentiation, activation, migration, and cell death. In the present review we are going to reveal a relationship between different genetic defects, which drive the T cell neoplasias, with calcium signaling and ion channels. We suggest that changes in regulation of various ion channels in different types of the T leukemias may provide the intracellular ion microenvironment favorable to maintain self-renewal capacity, arrest differentiation, induce proliferation, and enhance motility.

Cigarette smoking promotes inflammation in patients with COPD by affecting the polarization and survival of Th/Tregs through up-regulation of muscarinic receptor 3 and 5 expression

Background

CD4⁺ T cells in the lung are involved in the pathogenesis of chronic obstructive pulmonary disease (COPD), although CD4⁺ T cell subsets and the direct effect of smoking on these cells, especially the expression of MRs, have not been comprehensively examined.

Methods

First, circulating CD4⁺ T cell subsets in healthy nonsmokers, patients with SCOPD and patients with AECOPD were evaluated by flow cytometry. Then, differentiation experiments were carried out using RT-PCR, and Ki-67/Annexin V antibodies were used to measure proliferation and apoptosis. We also explored the impact of CSE on the differentiation and survival of CD4⁺Th/Tregs and examined the expression of MRs in healthy nonsmokers and patients with SCOPD.

Results

We found the percentages of circulating Th1 and Th17 cells were increased in patients with AECOPD, while the percentage of Th2 cells was decreased in patients with SCOPD. The percentages of Th10 cells were decreased in both patients with SCOPD and patients with AECOPD, while the percentages of Tregs were increased. In addition, the percentages of CD4⁺α-7⁺ T cells were decreased in patients with SCOPD and patients with AECOPD. However, only the decrease observed in patients with AECOPD was significant. In vitro studies also revealed MR expression affected the polarization of T cells, with different CD4⁺ T cell subtypes acquiring different MR expression profiles. The addition of CSE facilitated CD4⁺ T cell polarization towards pro-inflammatory subsets (Th1 and Th17) and affected the survival of CD4⁺ T cells and Treg cells by up-regulating the expression of MR3 and 5, resulting in an imbalance of CD4⁺ T cell subsets.

Conclusions

Our findings suggest an imbalance of circulating CD4⁺ T cell subsets is involved in COPD pathogenesis in smokers. Cigarette smoking may contribute to this imbalance by affecting the polarization and survival of Th/Tregs through the up-regulation of MR3 and MR5.

Regulation of gene expression by tobacco product preparations in cultured human dermal fibroblasts

Skin fibroblasts comprise the first barrier of defense against wounds, and tobacco products directly contact the oral cavity. Cultured human dermal fibroblasts were exposed to smokeless tobacco extract (STE), total particulate matter (TPM) from tobacco smoke, or nicotine at concentrations comparable to those found in these extracts for 1h or 5h. Differences were identified in pathway-specific genes between treatments and vehicle using qRT-PCR. At 1h, IL1α was suppressed significantly by TPM and less significantly by STE. Neither FOS nor JUN was suppressed at 1h by tobacco products. IL8, TNFα, VCAM1, and NFκB1 were suppressed after 5h with STE, whereas only TNFα and NFκB1 were suppressed by TPM. At 1h with TPM, secreted levels of IL10 and TNFα were increased. Potentially confounding effects of nicotine were exemplified by genes such as ATF3 (5h), which was increased by nicotine but suppressed by other components of STE. Within 2h, TPM stimulated nitric oxide production, and both STE and TPM increased reactive oxygen species. The biological significance of these findings and utilization of the gene expression changes reported herein regarding effects of the tobacco product preparations on dermal fibroblasts will require additional research.

Increased levels of Th17 cells are associated with non-neuronal acetylcholine in COPD patients

T-lymphocytes, including Th17-cells and T-cells expressing acetylcholine (ACh), are key components of systemic inflammation in chronic obstructive pulmonary disease (COPD). We investigated whether ACh promotes Th17 cells in COPD. ACh, IL-17A, IL-22, RORγt, FOXP3 expression and AChIL-17A, AChIL-22, AChRORγt coexpression was evaluated in peripheral blood mononuclear cells (PBMC) from COPD patients (n=16), healthy smokers (HS) (n=12) and healthy control subjects (HC) (n=13) (cultured for 48 h with PMA) by flow cytometry. Furthermore, we studied the effect of Tiotropium (Spiriva®) (100 nM) and Olodaterol (1nM) alone or in combination, and of hemicholinium-3 (50 μM) on AChIL-17A, AChIL-22, AChRORγt, and FOXP3 expression in CD3+PBT-cells of PBMC from COPD patients (n=6) cultured for 48 h with PMA. CD3+PBT-cells expressing ACh, IL-17A, IL-22 and RORγt together with CD3+PBT-cells co-expressing AChIL-17A, AChIL-22 and AChRORγt were significantly increased in COPD patients compared to HC and HS subjects with higher levels in HS than in HC without a significant difference. CD3+FOXP3+PBT-cells were increased in HS than in HC and COPD. Tiotropium and Olodaterol reduced the percentage of CD3+PBT-cells co-expressing AChIL-17A, AChIL-22, and AChRORγt while increased the CD3+FOXP3+PBT-cells in PBMC from COPD patients, cultured in vitro for 48 h, with an additive effect when used in combination. Hemicholnium-3 reduced the percentage of ACh+IL-17A+, ACh+IL-22+, and ACh+RORγt+ while it did not affect FOXP3+ expression in CD3+PBT-cells from cultured PBMC from COPD patients. We concluded that ACh might promote the increased levels of Th17-cells in systemic inflammation of COPD. Long-acting β2-agonists and anticholinergic drugs might contribute to control this event.

Alterations in the cholinesterase and adenosine deaminase activities and inflammation biomarker levels in patients with multiple sclerosis

Multiple sclerosis (MS) is one of the main chronic inflammatory diseases of the CNS that cause functional disability in young adults. It has unknown etiology characterized by the infiltration of lymphocytes and macrophages into the brain. The aim of this study was to evaluate the acetylcholinesterase (AChE) activity in lymphocytes and whole blood, as well as butyrylcholinesterase (BChE) and adenosine deaminase (ADA) activities in serum. We also checked the levels of nucleotides, nucleosides, biomarkers of inflammation such as cytokines (interleukin (IL)-1, IL-6, interferon (IFN)-γ, tumor necrosis factor-alpha (TNF-α) and IL-10) and C-reactive protein (CRP) in serum from 29 patients with the relapsing-remitting form of MS (RRMS) and 29 healthy subjects as the control group. Results showed that AChE in lymphocytes and whole blood as well as BChE, and ADA activities in serum were significantly increased in RRMS patients when compared to the control group (P<0.05). In addition, we observed a decrease in ATP levels and a significant increase in the levels of ADP, AMP, adenosine and inosine in serum from RRMS patients in relation to the healthy subjects (P<0.05). Results also demonstrated an increase in the IFN-γ, TNF-α, IL-1, IL-6 and CRP (P<0.05) and a significant decrease in the IL-10 (P<0.0001) in RRMS patients when compared to control. Our results suggest that alterations in the biomarkers of inflammation and hydrolysis of nucleotides and nucleosides may contribute to the understanding of the neurological dysfunction of RRMS patients.

Neuronal and nonneuronal cholinergic structures in the mouse gastrointestinal tract and spleen

Accumulating evidence demonstrates that acetylcholine can directly modulate immune function in peripheral tissues including the spleen and gastrointestinal tract. However, the anatomical relationships between the peripheral cholinergic system and immune cells located in these lymphoid tissues remain unclear due to inherent technical difficulties with currently available neuroanatomical methods. In this study, mice with specific expression of the tdTomato fluorescent protein in choline acetyltransferase (ChAT)-expressing cells were used to label preganglionic and postganglionic cholinergic neurons and their projections to lymphoid tissues. Notably, our anatomical observations revealed an abundant innervation in the intestinal lamina propria of the entire gastrointestinal tract principally originating from cholinergic enteric neurons. The aforementioned innervation frequently approached macrophages, plasma cells, and lymphocytes located in the lamina propria and, to a lesser extent, lymphocytes in the interfollicular areas of Peyer's patches. In addition to the above innervation, we observed labeled epithelial cells in the gallbladder and lower intestines, as well as Microfold cells and T-cells within Peyer's patches. In contrast, we found only a sparse innervation in the spleen consisting of neuronal fibers of spinal origin present around arterioles and in lymphocyte-containing areas of the white pulp. Lastly, a small population of ChAT-expressing lymphocytes was identified in the spleen including both T- and B-cells. In summary, this study describes the variety of cholinergic neuronal and nonneuronal cells in a position to modulate gastrointestinal and splenic immunity in the mouse.

Tiotropium bromide inhibits relapsing allergic asthma in BALB/c mice

Recurrent relapses of allergic lung inflammation in asthmatics may lead to airway remodeling and lung damage. We tested the efficacy of tiotropium bromide, a selective long-acting, muscarinic receptor antagonist as an adjunct therapy in relapses of allergic asthma in mice. We compared the effectiveness of local intranasal administration of tiotropium and dexamethasone in acute and relapsing allergic asthma in BALB/c mice. Although tiotropium at low doses is a potent bronchodilator, we tested higher doses to determine effectiveness on inflammation and mucus hypersecretion. A 5-day course of twice daily intranasal tiotropium or dexamethasone (1 mg/kg (b.w.)) suppressed airway eosinophils by over 87% during disease initiation and 88% at relapse compared to vehicle alone. Both drugs were comparable in their capacity to suppress airway and parenchymal inflammation and mucus hypersecretion, though tiotropium was better than dexamethasone at reducing mucus secretion during disease relapse. Despite treatment with either drug, serum antigen-specific IgE or IgG1 antibody titres remained unchanged. Our study indicates that tiotropium at higher doses than required for bronchodilation, effectively suppresses inflammation and mucus hypersecretion in the lungs and airways of mice during the initiation and relapse of asthma. Tiotropium is currently not approved for use in asthma. Clinical studies have to demonstrate the efficacy of tiotropium in this respiratory disease.

Effect of secreted lymphocyte antigen-6/urokinase-type plasminogen activator receptor-related peptide-1 (SLURP-1) on airway epithelial cells

Acetylcholine (ACh) exerts various anti-inflammatory effects through α7 nicotinic ACh receptors (nAChRs). We have previously shown that secreted lymphocyte antigen-6/urokinase-type plasminogen activator receptor-related peptide-1 (SLURP-1), a positive allosteric modulator of α7 nAChR signaling, is down-regulated both in an animal model of asthma and in human epithelial cells treated with an inflammatory cytokine related to asthma. Our aim of this study was to explore the effect of SLURP-1, signal through α7 nAChR, in the pathophysiology of airway inflammation. Cytokine production was examined using human epithelial cells. Ciliary beat frequency of murine trachea was measured using a high speed camera. The IL-6 and TNF-α production by human epithelial cells was augmented by siRNA of SLURP-1 and α7 nicotinic ACh receptor. The cytokine production was also dose-dependently suppressed by human recombinant SLURP-1 (rSLURP-1). The ciliary beat frequency and amplitude of murine epithelial cells were augmented by PNU282987, a selective α7 nAChR agonist. Those findings suggested that SLURP-1 and stimulus through α7 nicotinic ACh receptors actively controlled asthmatic condition by stimulating ciliary beating and also by suppressing airway inflammation.

Regulated Extracellular Choline Acetyltransferase Activity- The Plausible Missing Link of the Distant Action of Acetylcholine in the Cholinergic Anti-Inflammatory Pathway

Acetylcholine (ACh), the classical neurotransmitter, also affects a variety of nonexcitable cells, such as endothelia, microglia, astrocytes and lymphocytes in both the nervous system and secondary lymphoid organs. Most of these cells are very distant from cholinergic synapses. The action of ACh on these distant cells is unlikely to occur through diffusion, given that ACh is very short-lived in the presence of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), two extremely efficient ACh-degrading enzymes abundantly present in extracellular fluids. In this study, we show compelling evidence for presence of a high concentration and activity of the ACh-synthesizing enzyme, choline-acetyltransferase (ChAT) in human cerebrospinal fluid (CSF) and plasma. We show that ChAT levels are physiologically balanced to the levels of its counteracting enzymes, AChE and BuChE in the human plasma and CSF. Equilibrium analyses show that soluble ChAT maintains a steady-state ACh level in the presence of physiological levels of fully active ACh-degrading enzymes. We show that ChAT is secreted by cultured human-brain astrocytes, and that activated spleen lymphocytes release ChAT itself rather than ACh. We further report differential CSF levels of ChAT in relation to Alzheimer's disease risk genotypes, as well as in patients with multiple sclerosis, a chronic neuroinflammatory disease, compared to controls. Interestingly, soluble CSF ChAT levels show strong correlation with soluble complement factor levels, supporting a role in inflammatory regulation. This study provides a plausible explanation for the long-distance action of ACh through continuous renewal of ACh in extracellular fluids by the soluble ChAT and thereby maintenance of steady-state equilibrium between hydrolysis and synthesis of this ubiquitous cholinergic signal substance in the brain and peripheral compartments. These findings may have important implications for the role of cholinergic signaling in states of inflammation in general and in neurodegenerative disease, such as Alzheimer's disease and multiple sclerosis in particular.

Nicotine induces chromatin remodelling through decreases in the methyltransferases GLP, G9a, Setdb1 and levels of H3K9me2

Studies examining the epigenetic effects of nicotine are limited, but indicate that nicotine can promote a transcriptionally permissive chromatin environment by increasing acetylation of histone H3 and H4. To further explore nicotine-induced histone modifications, we measured histone methyltransferase (HMT) mRNA expression as well as total and promoter-specific H3K9me2 levels. Following administration of nicotine, HMT mRNA and H3K9me2 levels were examined in mouse primary cortical neuronal culture and cortex extracted from mice injected intraperitoneally, as well as in human lymphocyte culture. Furthermore, Bdnf/BDNF mRNA levels were examined as an epigenetically regulated read-out of gene expression. There was a significant decrease of the HMT GLP, G9a and Setdb1 mRNA expression in the nicotine-treated tissue examined, with significant decreases seen in both total and promoter-specific H3K9me2 levels. Increasing doses of nicotine resulted in significant decreases in Bdnf/BDNF promoter specific H3K9me2 binding, leading to enhanced Bdnf/BDNF transcription. Taken together, our data suggest that nicotine reduces markers of a restrictive epigenomic state, thereby leading to a more permissive epigenomic environment.

Blood chromatin as a biosensor of the epigenetic milieu: a tool for studies in living psychiatric patients

This article constructs an argument for using blood chromatin (contained in nucleated blood cells) as a protein biosensor to integrate the ambient epigenetic influences in the internal milieu. An analogy is made to blood glycated hemoglobin (HbA1c) in diabetes as an integrated proxy for glucose levels and body-wide protein glycation. Genome-wide chromatin can serve as an organizing principle that bridges the central and peripheral compartments by entraining commensurable gene networks. Chromatin deposition along these networks will be imposed by the totality of epigenetic influences, which incorporates significant contributions from biochemicals that readily traverse the blood-brain barrier. In a clinical trial, these influences would be dominated by pharmaceuticals designed to override pathophysiological signals. In practice, mRNA readouts would be limited to nonsynaptic gene networks whose critical nodes are occupied by a site-specific chromatin modification. Finally, chromatin measurements in peripheral tissue will retain the influences of a patient's lifestyle and unique genomic background.

Effect of desiccating environmental stress versus systemic muscarinic AChR blockade on dry eye immunopathogenesis

PURPOSE

A majority of experimental data on dry eye disease (DED) immunopathogenesis have been derived from a murine model of DED that combines desiccating environmental stress with systemic muscarinic acetylcholine receptor (mAChR) inhibition. However, to our knowledge the effects of pharmacologic mAChR blockade on the pathogenesis of experimental DED have not been evaluated systemically. The purpose of our study was to investigate the differential effects of desiccating environmental stress and mAChR inhibition on the pathogenesis of DED.

METHODS

DED was induced in female C57BL/6 mice by exposure to a desiccating environment in the controlled-environment chamber or to systemic scopolamine, or by performing extraorbital lacrimal gland excision. Clinical disease was assessed using corneal fluorescein staining (CFS) and the cotton thread test (CTT). Corneal CD11b(+) and conjunctival CD3(+) T-cell infiltration were evaluated by flow cytometry. T-cells from draining cervical lymph nodes (CLN) and distant inguinal lymph nodes (ILN) were analyzed for Th1, Th2, Th17, and Treg responses by flow cytometry and ELISA.

RESULTS

Desiccating environmental stress and systemic mAChR blockade induced similar clinical signs of DED. However, desiccating environmental stress imparted higher conjunctival CD3(+) T-cell infiltration, and greater Th17-cell activity and Treg dysfunction than mAChR blockade, while mAChR blockade decreased tear secretion to a greater extent than desiccating environmental stress. Systemic mAChR blockade attenuated Th17 activity and enhanced Th2 and Treg responses without affecting Th1 activity.

CONCLUSIONS

In vivo inhibition of mAChRs variably affects CD4(+) T-cell subsets, and desiccating environmental stress and systemic mAChR blockade induce DED through different primary pathogenic mechanisms.

Differential modulation of EAE by α9*- and β2*-nicotinic acetylcholine receptors

Nicotine is a potent inhibitor of the immune response and is protective against experimental autoimmune encephalomyelitis (EAE). Initial studies suggested that the cholinergic system modulates inflammation via the α7-nicotinic acetylcholine receptor (nAChR) subtype. We recently have shown that effector T cells and myeloid cells constitutively express mRNAs encoding nAChR α9 and β2 subunits and found evidence for immune system roles for non-α7-nAChRs. In the present study, we assessed the effects of nAChR α9 or β2 subunit gene deletion on EAE onset and severity, with or without nicotine treatment. We report again that disease onset is delayed and severity is attenuated in nicotine-treated, wild-type mice, an effect that also is observed in α9 subunit knock-out (KO) mice irrespective of nicotine treatment. On the other hand, β2 KO mice fail to recover from peak measures of disease severity regardless of nicotine treatment, despite retaining sensitivity to nicotine’s attenuation of disease severity. Prior to disease onset, we found significantly less reactive oxygen species production in the CNS of β2 KO mice, elevated proportions of CNS myeloid cells but decreased ratios of CNS macrophages/microglia in α9 or β2 KO mice, and some changes in iNOS, TNF-α and IL-1β mRNA levels in α9 KO and/or β2 KO mice. Our data thus suggest that β2*- and α9*-nAChRs, in addition to α7-nAChRs, play different roles in endogenous and nicotine-dependent modulation of immune functions and could be exploited as therapeutic targets to modulate inflammation and autoimmunity.

Heart-specific overexpression of choline acetyltransferase gene protects murine heart against ischemia through hypoxia-inducible factor-1α-related defense mechanisms

Background

Murine and human ventricular cardiomyocytes rich in acetylcholine (Ach) receptors are poorly innervated by the vagus, compared with whole ventricular innervation by the adrenergic nerve. However, vagal nerve stimulation produces a favorable outcome even in the murine heart, despite relatively low ventricular cholinergic nerve density. Such a mismatch and missing link suggest the existence of a nonneuronal cholinergic system in ventricular myocardium.

Methods and Results

To examine the role of the nonneuronal cardiac cholinergic system, we generated choline acetyltransferase (ChAT)–expressing cells and heart‐specific ChAT transgenic (ChAT‐tg) mice. Compared with cardiomyocytes of wild‐type (WT) mice, those of the ChAT‐tg mice had high levels of ACh and hypoxia‐inducible factor (HIF)‐1α protein and augmented glucose uptake. These phenotypes were also reproduced by ChAT‐overexpressing cells, which utilized oxygen less. Before myocardial infarction (MI), the WT and ChAT‐tg mice showed similar hemodynamics; after MI, however, the ChAT‐tg mice had better survival than did the WT mice. In the ChAT‐tg hearts, accelerated angiogenesis at the ischemic area, and accentuated glucose utilization prevented post‐MI remodeling. The ChAT‐tg heart was more resistant to ischemia–reperfusion injury than was the WT heart.

Conclusions

These results suggest that the activated cardiac ACh‐HIF‐1α cascade improves survival after MI. We conclude that de novo synthesis of ACh in cardiomyocytes is a pivotal mechanism for self‐defense against ischemia.

Autonomic dysfunction and inflammatory bowel disease

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a chronic immune-mediated intestinal disorder, and its etiology and pathogenesis are not well clarified. The pathogenesis of IBD is multifactorial, and the nerve system may participate in the development of IBD by modulating immune responses. Recently, autonomic dysfunction in IBD patients has been intensively studied. It has been reported that IBD patients suffer from autonomic dysfunction, and the severity of autonomic dysfunction correlates with disease activity of IBD, suggesting that autonomic dysfunction is a potential marker for IBD disease activity and also a potential target for IBD treatment. In this paper, we review the recent advances in understanding the relationship between autonomic dysfunction and IBD.

Nicotine-induced chondrogenic differentiation of human bone marrow stromal cells in vitro

PURPOSE

Nicotine has been reported that it has a dose-dependent effect on matrix mineralization by human bone marrow cells. However, there is no relevant research concerning on chondrogenic differentiation potential of bone marrow stromal stem cells (BMSCs) treated with nicotine in vitro. The aims of the study were to examine the effects of nicotine (0, 10(-7), 10(-6) and 10(-5) M) on the proliferation and chondrogenic differentiation of BMSCs from three healthy donors in vitro.

METHODS

BMSCs proliferation was analyzed by CCK8 assay and real-time polymerase chain reaction was used to assay the expression of type II collagen, aggrecan, type I collagen and type X collagen. The proteoglycan content was stained by Alcian blue, and the sulfated glycosaminoglycan (sGAG) content of BMSCs was quantified spectrofluorometrically using dimethylmethylene blue.

RESULTS

The cell viability was not significantly impaired until up to a concentration of 10(-5) M nicotine. Nicotine promoted the proliferation and enhanced the expression of type II collagen at the level up to 10(-6) M (P < 0.05). The expression of aggrecan was reduced at the concentration of 10(-5) M nicotine at day 14 (P < 0.05), and there was no significant difference in aggrecan gene expression at 10(-7) and 10(-6) M nicotine levels compared to control group (n.s.). Also the fibroblastic and hypertrophic gene expressions were down-regulated in the chondrogenic medium with 10(-7)-10(-5) M nicotine (P < 0.05).

CONCLUSION

It was implied that local application of nicotine at an appropriate concentration may be a promising approach for enhancing chondrogenic differentiation capacity of BMSCs in cell-based cartilage tissue engineering. Also these results indicate that nicotine maybe a potentially useful drug for the treatment of Osteoarthritis.

The antinociceptive effects of nicotinic receptors α7-positive allosteric modulators in murine acute and tonic pain models

The α7 nicotinic acetylcholine receptor (nAChR) subtype is abundantly expressed in the central nervous system and in the periphery. Recent evidence suggests that α7 nAChR subtypes, which can be activated by an endogenous cholinergic tone, comprising acetylcholine and the α7 nAChR agonist choline, play an important role in subchronic pain and inflammation. This study's objective was to test whether α7 nAChR positive allosteric modulators (PAMs) produce antinociception in in vivo mouse models of acute and persistent pain. Testing type I [N-(5-chloro-2-hydroxyphenyl)-N'-[2-chloro-5-(trifluoromethyl)phenyl] (NS1738)] and type II [1-(5-chloro-2,4-dimethoxy-phenyl)-3-(5-methyl-isoxazol-3-yl) (PNU-120596)] α7 nAChR PAMs in acute and persistent pain, we found that, although neither reduced acute thermal pain, only PNU-120596 dose-dependently attenuated paw-licking behavior in the formalin test. The long-acting effect of PNU-120596 in this test was in discordance with its pharmacokinetic profile in mice, which suggests the involvement of postreceptor signaling mechanisms. Our results with selective mitogen-activated protein kinase kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)butadiene monoethanolate (U0126) argues for an important role of extracellular signal-regulated kinase-1/2 pathways activation in PNU-120596's antinociceptive effects. The α7 antagonist MLA, administered intrathecally, reversed PNU-120596's effects, confirming PNU-120596's action, in part, through central α7 nAChRs. Importantly, tolerance to PNU-120596 was not developed after subchronic treatment of the drug. Surprisingly, PNU-120596's antinociceptive effects were blocked by NS1738. Our results indicate that type II α7 nAChR PAM PNU-120596, but not type I α7 nAChR PAM NS1738, shows significant antinociception effects in persistent pain models in mice.