Cholinergic innervation of human mesenteric lymphatic vessels

The Sympathetic Nervous System Promotes Hepatic Lymphangiogenesis, which Is Protective Against Liver Fibrosis

Liver is the largest lymph-producing organ. In cirrhotic patients, lymph production significantly increases concomitant with lymphangiogenesis. The aim of this study was to determine the mechanism of lymphangiogenesis in liver and its implication in liver fibrosis. Liver biopsies from portal hypertensive patients with portal-sinusoidal vascular disease (n = 22) and liver cirrhosis (n = 5) were evaluated for lymphangiogenesis and compared with controls (n = 9 and n = 6, respectively). For mechanistic studies, rats with partial portal vein ligation (PPVL) and bile duct ligation (BDL) were used. A gene profile data set (GSE77627), including 14 histologically normal liver, 18 idiopathic noncirrhotic portal hypertension, and 22 cirrhotic patients, was analyzed. Lymphangiogenesis was significantly increased in livers from patients with portal-sinusoidal vascular disease, cirrhotic patients, as well as PPVL and BDL rats. Importantly, Schwann cells of sympathetic nerves highly expressed vascular endothelial growth factor-C in PPVL rats. Vascular endothelial growth factor-C neutralizing antibody or sympathetic denervation significantly decreased lymphangiogenesis in livers of PPVL and BDL rats, which resulted in progression of liver fibrosis. Liver specimens from cirrhotic patients showed a positive correlation between sympathetic nerve/Schwann cell-positive areas and lymphatic vessel numbers, which was supported by gene set analysis from patients with noncirrhotic portal hypertension and cirrhotic patients. Sympathetic nerves promote hepatic lymphangiogenesis in noncirrhotic and cirrhotic livers. Increased hepatic lymphangiogenesis can be protective against liver fibrosis.

Positive chronotropic action of HCN channel antagonism in human collecting lymphatic vessels

Spontaneous action potentials precede phasic contractile activity in human collecting lymphatic vessels. In this study, we investigated the expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in human collecting lymphatics and by pharmacological inhibition ex vivo tested their potential role in controlling contractile function. Spontaneous and agonist-evoked tension changes of isolated thoracic duct and mesenteric lymphatic vessels-obtained from surgical patients with informed consent-were investigated by isometric myography, and ivabradine, ZD7288 or cesium were used to inhibit HCN. Analysis of HCN isoforms by RT-PCR and immunofluorescence revealed HCN2 to be the predominantly expressed mRNA isoform in human thoracic duct and mesenteric lymphatic vessels and HCN2-immunoreactivity confirmed protein expression in both vessel types. However, in functional experiments ex vivo the HCN inhibitors ivabradine, ZD7288, and cesium failed to lower contraction frequency: conversely, all three antagonists induced a positive chronotropic effect with concurrent negative inotropic action, though these effects first occurred at concentrations regarded as supramaximal for HCN inhibition. Based on these results, we conclude that human collecting vessels express HCN channel proteins but under the ex vivo experimental conditions described here HCN channels have little involvement in regulating contraction frequency in human collecting lymphatic vessels. Furthermore, HCN antagonists can produce concentration-dependent positive chronotropic and negative inotropic effects, which are apparently unrelated to HCN antagonism.

Immunohistochemical and ultrastructural study of the immune cell system and epithelial surfaces of the respiratory organs in the bimodally-breathing African sharptooth catfish (Clarias gariepinus Burchell, 1822)

Ach, represents the old neurotransmitter in central and peripheral nervous system. Its muscarinic and nicotinic receptors (mAChRs and nAChRs) constitute an independent cholinergic system that is found in immune cells and playsa key role in regulation of the immune function and cytokine production. Gas exchanging surfaces of the gills and air-breathing organs (ABOs) of the sharptooth catfish Clarias gariepinus were investigated using ultrastructural and confocal immunofluorescence techniques. This study was predominantly focused on the structure of the immune cell types, the expression of their neurotransmitters, including the antimicrobial peptide piscidin 1, and the functional significance of respiratory gas exchange epithelia. A network of immune cells (monocytes, eosinophils, and mast cells) was observed in the gill and theABO epithelia. Eosinophils containing 5HT immunoreactivity were seen in close association with mast cells expressing acetylcholine (Ach), 5HT, nNOS and piscidin 1. A rich and dense cholinergic innervation dispersing across the islet capillaries of the gas exchange barrier, and the localization of Ach in the squamous pavement cells covering the capillaries, were evidenced byVAChT antibodies.We report for the first time that piscidin 1(Pis 1) positive mast cells interact with Pis 1 positive nerves found in the epithelia of the respiratory organs.Pis 1 immunoreactivity was also observed in the covering respiratory epithelium of the ABOs and associated with a role in local mucosal immune defense . The above results anticipate future studies on the neuro-immune interactions at mucosal barrier surfaces, like the gill and the skin of fish, areas densely populated by different immune cells and sensory nerves that constantly sense and adapt to tissue-specific environmental challenges. This article is protected by copyright. All rights reserved.

Adipose Tissue and Biological Factors. Possible Link between Lymphatic System Dysfunction and Obesity

The World Health Organization (WHO) has recognised obesity as one of the top ten threats to human health. Obesity is not only a state of abnormally increased adipose tissue in the body, but also of an increased release of biologically active metabolites. Moreover, obesity predisposes the development of metabolic syndrome and increases the incidence of type 2 diabetes (T2DM), increases the risk of developing insulin resistance, atherosclerosis, ischemic heart disease, polycystic ovary syndrome, hypertension and cancer. The lymphatic system is a one-directional network of thin-walled capillaries and larger vessels covered by a continuous layer of endothelial cells that provides a unidirectional conduit to return filtered arterial and tissue metabolites towards the venous circulation. Recent studies have shown that obesity can markedly impair lymphatic function. Conversely, dysfunction in the lymphatic system may also be involved in the pathogenesis of obesity. This review highlights the important findings regarding obesity related to lymphatic system dysfunction, including clinical implications and experimental studies. Moreover, we present the role of biological factors in the pathophysiology of the lymphatic system and we propose the possibility of a therapy supporting the function of the lymphatic system in the course of obesity.

A Distinct Role of the Autonomic Nervous System in Modulating the Function of Lymphatic Vessels under Physiological and Tumor-Draining Conditions

Lymphatic vessels (LVs) are important in the regulation of tissue fluid homeostasis and the pathogenesis of tumor progression. We investigated the innervation of LVs and the response to agonists and antagonists of the autonomic nervous system in vivo. While skin-draining collecting LVs express muscarinic, α₁- and β₂-adrenergic receptors on lymphatic endothelial cells and smooth muscle cells, intestinal lacteals express only β-adrenergic receptors and muscarinic receptors on their smooth muscle cells. Quantitative in vivo near-infrared imaging of the exposed flank-collecting LV revealed that muscarinic and α₁-adrenergic agonists increased LV contractility, whereas activation of β₂-adrenergic receptors inhibited contractility and initiated nitric oxide (NO)-dependent vasodilation. Tumor-draining LVs were expanded and showed a higher innervation density and contractility that was reduced by treatment with atropine, phentolamine, and, most potently, isoproterenol. These findings likely have clinical implications given the impact of lymphatic fluid drainage on intratumoral fluid pressure and thus drug delivery.

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Murine lymphatic vessels are innervated in an organ-specific manner

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α₁-adrenergic and muscarinic agents enhance lymphatic contractility in vivo

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β₂-adrenergic agents reduce lymphatic contractility

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Tumor-draining lymphatic vessels have increased innervation and contractility

The nervous system component of the mesentery of the sea cucumber Holothuria glaberrima in normal and regenerating animals

The mesenterial tissues play important roles in the interactions between the viscera and the rest of the organism. Among these roles, they serve as the physical substrate for nerves connecting the visceral nervous components to the central nervous system. Although the mesenterial nervous system component has been described in vertebrates, particularly in mammals, a description in other deuterostomes is lacking. Using immunohistochemistry in tissue sections and whole mounts, we describe here the nervous component of the intestinal mesentery in the sea cucumber Holothuria glaberrima. This echinoderm has the ability to regenerate its internal organs in a process that depends on the mesentery. Therefore, we have also explored changes in the mesenterial nervous component during intestinal regeneration. Extensive fiber bundles with associated neurons are found in the mesothelial layer, extending from the body wall to the intestine. Neuron-like cells are also found within a plexus in the connective tissue layer. We also show that most of the cells and nerve fibers within the mesentery remain during the regenerative process, with only minor changes: a general disorganization of the fiber bundles and a retraction of nerve fibers near the tip of the mesentery during the first days of regeneration. Our results provide a basic description of mesenterial nervous component that can be of importance for comparative studies as well as for the analyses of visceral regeneration.

Interaction of neurotransmitters and neurochemicals with lymphocytes

Neurotransmitters and neurochemicals can act on lymphocytes by binding to receptors expressed by lymphocytes. This review describes lymphocyte expression of receptors for a selection of neurotransmitters and neurochemicals, the anatomical locations where lymphocytes can interact with neurotransmitters, and the effects of the neurotransmitters on lymphocyte function. Implications for health and disease are also discussed.

Immunofluorescent characterization of non-myelinating Schwann cells and their interactions with immune cells in mouse mesenteric lymph node

The central nervous system (CNS) influences the immune system in a general fashion by regulating the systemic concentration of humoral substances, whereas the autonomic nervous system communicates specifically with the immune system according to local interactions. Data concerning the mechanisms of this bidirectional crosstalk of the peripheral nervous system (PNS) and immune system remain limited. To gain a better understanding of local interactions of the PNS and immune system, we have used immunofluorescent staining of glial fibrillary acidic protein (GFAP), coupled with confocal microscopy, to investigate the non-myelinating Schwann cell (NMSC)-immune cell interactions in mouse mesenteric lymph nodes. Our results demonstrate i) the presence of extensive NMSC processes and even of cell bodies in each compartment of the mouse mesenteric lymph node; ii) close associations/interactions of NMSC processes with blood vessels (including high endothelial venules) and the lymphatic vessel/sinus; iii) close contacts/associations of NMSC processes with various subsets of dendritic cells (such as CD4+CD11c+, CD8+CD11c+ dendritic cells), macrophages (F4/80+ and CD11b+ macrophages), and lymphocytes. Our novel findings concerning the distribution of NMSCs and NMSC-immune cell interactions inside the mouse lymph node should help to elucidate the mechanisms through which the PNS affects cellular- and humoral-mediated immune responses or vice versa in health and disease.

Semaphorins in cardiovascular medicine

During organogenesis, patterning is primarily achieved by the combined actions of morphogens. Among these, semaphorins represent a general system for establishing the appropriate wiring architecture of biological nets. Originally discovered as evolutionarily conserved steering molecules for developing axons, subsequent studies on semaphorins expanded their functions to the cardiovascular and immune systems. Semaphorins participate in cardiac organogenesis and control physiological vasculogenesis and angiogenesis, which result from a balance between pro- and anti-angiogenic signals. These signals are altered in several diseases. In this review, we discuss the role of semaphorins in vascular biology, emphasizing the mechanisms by which these molecules control vascular patterning and lymphangiogenesis, as well as in genetically inherited and degenerative vascular diseases.