5-Hydroxytryptamine Modulates Migration, Cytokine and Chemokine Release and T-Cell Priming Capacity of Dendritic Cells In Vitro and In Vivo

Beside its well described role in the central and peripheral nervous system 5-hydroxytryptamine (5-HT), commonly known as serotonin, is also a potent immuno-modulator. Serotoninergic receptors (5-HTR) are expressed by a broad range of inflammatory cell types, including dendritic cells (DCs). In this study, we aimed to further characterize the immuno-biological properties of serotoninergic receptors on human monocyte-derived DCs. 5-HT was able to induce oriented migration in immature but not in LPS-matured DCs via activation of 5-HTR1 and 5-HTR2 receptor subtypes. Accordingly, 5-HT also increased migration of pulmonary DCs to draining lymph nodes in vivo. By binding to 5-HTR3, 5-HTR4 and 5-HTR7 receptors, 5-HT up-regulated production of the pro-inflammatory cytokine IL-6. Additionally, 5-HT influenced chemokine release by human monocyte-derived DCs: production of the potent Th1 chemoattractant IP-10/CXCL10 was inhibited in mature DCs, whereas CCL22/MDC secretion was up-regulated in both immature and mature DCs. Furthermore, DCs matured in the presence of 5-HT switched to a high IL-10 and low IL-12p70 secreting phenotype. Consistently, 5-HT favoured the outcome of a Th2 immune response both in vitro and in vivo. In summary, our study shows that 5-HT is a potent regulator of human dendritic cell function, and that targeting serotoninergic receptors might be a promising approach for the treatment of inflammatory disorders

Serotonin and GI Disorders: An Update on Clinical and Experimental Studies

The gastrointestinal (GI) tract is the largest producer of serotonin (5-hydroxytryptamine (5-HT)) in the body, and as such it is intimately connected with GI function and physiology. 5-HT produced by enterochromaffin (EC) cells is an important enteric mucosal signaling molecule and has been implicated in a number of GI diseases, including inflammatory bowel disease and functional disorders such as irritable bowel syndrome. This review will focus on what is known of basic 5-HT physiology and also on the emerging evidence for its novel role in activation of immune response and inflammation in the gut. Utilizing pubmed.gov, search terms such as “5-HT,” “EC cell,” and “colitis,” as well as pertinent reviews, were used to develop a brief overview of EC cell biology and the association between 5-HT and various GI disorders. It is the aim of this review to provide the readers with an update on EC cell biology and current understanding on the role of 5-HT in GI disorders specifically in inflammatory conditions

An overlooked connection: serotonergic mediation of estrogen-related physiology and pathology

BACKGROUND: In humans, serotonin has typically been investigated as a neurotransmitter. However, serotonin also functions as a hormone across animal phyla, including those lacking an organized central nervous system. This hormonal action allows serotonin to have physiological consequences in systems outside the central nervous system. Fluctuations in estrogen levels over the lifespan and during ovarian cycles cause predictable changes in serotonin systems in female mammals. DISCUSSION: We hypothesize that some of the physiological effects attributed to estrogen may be a consequence of estrogen-related changes in serotonin efficacy and receptor distribution. Here, we integrate data from endocrinology, molecular biology, neuroscience, and epidemiology to propose that serotonin may mediate the effects of estrogen. In the central nervous system, estrogen influences pain transmission, headache, dizziness, nausea, and depression, all of which are known to be a consequence of serotonergic signaling. Outside of the central nervous system, estrogen produces changes in bone density, vascular function, and immune cell self-recognition and activation that are consistent with serotonin's effects. For breast cancer risk, our hypothesis predicts heretofore unexplained observations of the opposing effects of obesity pre- and post-menopause and the increase following treatment with hormone replacement therapy using medroxyprogesterone. SUMMARY: Serotonergic mediation of estrogen has important clinical implications and warrants further evaluation

Serotonin decreases HIV-1 replication in primary cultures of human macrophages through 5-HT1A receptors

Background and purpose: 5-HT (serotonin) is known to be involved in neuroinflammation and immunoregulation. The human immunodeficiency virus (HIV) targets cells such as monocytes/macrophages, which colocalize with 5-HT-releasing cell types, mostly platelets. In this study, we investigated the effects of 5-HT on HIV-1-infected macrophages in vitro

Alpha7-nicotinic receptors modulate nicotine-induced reinforcement and extracellular dopamine outflow in the mesolimbic system in mice.

International audienceNicotine is the main addictive component of tobacco and modifies brain function via its action on neuronal acetylcholine nicotinic receptors (nAChRs). The mesolimbic dopamine (DA) system, where neurons of the ventral tegmental area (VTA) project to the nucleus accumbens (ACb), is considered a core site for the processing of nicotine's reinforcing properties. However, the precise subtypes of nAChRs that mediate the rewarding properties of nicotine and that contribute to the development of addiction remain to be identified.OBJECTIVES : We investigated the role of the nAChRs containing the α7 nicotinic subunit (α7 nAChRs) in the reinforcing properties of nicotine within the VTA and in the nicotine-induced changes in ACb DA outflow in vivo.METHODS : We performed intra-VTA self-administration and microdialysis experiments in genetically modified mice lacking the α7 nicotinic subunit or after pharmacological blockade of α7 nAChRs in wild-type mice.RESULTS : We show that the reinforcing properties of nicotine within the VTA are lower in the absence or after pharmacological blockade of α7 nAChRs. We also report that nicotine-induced increases in ACb DA extracellular levels last longer in the absence of these receptors, suggesting that α7 nAChRs regulate the action of nicotine on DA levels over time.CONCLUSIONS : The present results reveal new insights for the role of α7 nAChRs in modulating the action of nicotine within the mesolimbic circuit. These receptors appear to potentiate the reinforcing action of nicotine administered into the VTA while regulating its action over time on DA outflow in the ACb

Contribution of 7 nicotinic receptor to airway epithelium dysfunction under nicotine exposure

International audienceLoss or dysfunction of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) leads to impairment of airway mucus transport and to chronic lung diseases resulting in progressive respiratory failure. Nicotinic acetylcholine receptors (nAChRs) bind nicotine and nicotine-derived nitrosamines and thus mediate many of the tobacco-related deleterious effects in the lung. Here we identify α7 nAChR as a key regulator of CFTR in the airways. The airway epithelium in α7 knockout mice is characterized by a higher transepithelial potential difference, an increase of amiloride-sensitive apical Na(+) absorption, a defective cAMP-dependent Cl(-) conductance, higher concentrations of Na(+), Cl(-), K(+), and Ca(2+) in secretions, and a decreased mucus transport, all relevant to a deficient CFTR activity. Moreover, prolonged nicotine exposure mimics the absence of α7 nAChR in mice or its inactivation in vitro in human airway epithelial cell cultures. The functional coupling of α7 nAChR to CFTR occurs through Ca(2+) entry and activation of adenylyl cyclases, protein kinase A, and PKC. α7 nAChR, CFTR, and adenylyl cyclase-1 are physically and functionally associated in a macromolecular complex within lipid rafts at the apical membrane of surface and glandular airway epithelium. This study establishes the potential role of α7 nAChR in the regulation of CFTR function and in the pathogenesis of smoking-related chronic lung diseases

5-HT moduline: an endogenous inhibitor of 5-HT(1B/1D)-mediated contraction in pulmonary arteries

1. 5-HT moduline (5-HTm) is tetrapeptide (Leu-Ser-Ala-Leu) previously shown to act as a specific endogenous antagonist to central 5-HT(1B/1D) receptors. Its effects were investigated in rat and rabbit pulmonary arteries (PAs). 2. In rabbit PAs, contractile responses to the 5-HT(1B/1D) receptor agonist 5-carboxamidotryptamine (5-CT) were inhibited by 1 and 10 μM 5-HTm in a non-competitive fashion with the maximum contractile response (E(max), per cent of response to 50 mM KCl) being reduced from 65.6±7% (n=6) to 39.7±6.5% (n=6) and 25.2±7.9 (n=4), respectively. The ability of 5-HTm to inhibit responses to 5-CT was increased by the aminopeptidase inhibitor bestatin (10 μM). 3. In the rabbit PAs, the nitric oxide synthase inhibitor, N(ω)-nitro-L-arginine methylester (L-NAME) potentiated responses to 5-CT (E(max): 106±22.5 (n=4)) and this response was also inhibited by 10 μM 5-HTm (E(max): 38±13% (n=8)). 4. 5-HTm (10 μM) inhibited responses to 5-CT in rat PAs, the E(max) being reduced from 24.8±4.1% (n=7) to 15.5±3.7% (n=9). 5-HTm induced relaxation of 5-CT-pre-constricted rat PAs with a pIC(50) of 9.0±0.6 (n=9). 5. In PAs from chronic hypoxic, pulmonary hypertensive rats, the maximum response to 5-CT was increased to 80±8.5% (n=11). 5-HTm reduced this response to 34.4±6.3% (n=12). L-NAME markedly inhibited the ability of 5-HTm to inhibit responses to 5-CT (E(max) before 5-HTm: 100.5±16% (n=5), E(max) after 5-HTm: 107±11.3% (n=4)). 6. In conclusion we show here for the first time that 5-HTm is a non-competitive inhibitor of 5-HT(1B/1D) receptor-mediated constriction in PAs. In rat PAs, L-NAME can inhibit this effect of 5-HTm