Innervation of the guinea pig spleen studied by electron microscopy

The innervation of the guinea pig spleen was investigated by electron microscopy. Unmyelinated nerve fibers in the capsulotrabecular and arterial systems were found to contain large and small granular and small agranular synaptic vesicles in their terminals and are thought to be sympathetic adrenergic in nature. They influence the contraction of the smooth muscle cells by diffusion innervation in these systems. These nerve terminals were also scattered in both the red and the white pulp. Pulp nerves wrapped by Schwann cells were further enclosed by myofibroblastic reticular cells. This condition revealed that the pulp nerves pass through the connective-tissue spaces of the reticular fibers, which contain elastic fibers, collagenous fibrils, and lamina densa-like materials of the usual basement laminae. One of the target cells for the pulp nerves is considered to be the myofibroblastic reticular cell in the reticular meshwork. Neurotransmitter substances released from the naked adrenergic nerve terminals travel through the reticular fibers and may play a role, by both close association innervation and diffusion innervation, in the contraction of reticular cells to expose the reticular fibers. At the exposed sides, connective-tissue elements of the reticular fibers are bathed with blood plasma, and the included naked nerve terminals, devoid of Schwann cells but with basement laminae of these cells, face free cells at some distance or are in close association with free cells, especially lymphocytes, macrophages, and plasma cells. The close ultrastructural relationship between the naked adrenergic nerve terminals and immunocytes strongly suggests that there is an intimate relationship between the immune system and the sympathetic nervous system through both close association innervation and diffusion innervation. Thus splenic adrenergic nerves of the guinea pig may play a triple role in 1) contraction of smooth muscle cells to regulate blood flow in the organ, 2) induction of the exposure of reticular fibers by contraction of the reticular cells in order to form a close relationship of the nerve terminals with the immunocytes, and 3) subsequent neuroimmunomodulation of the immunocytes.     

Stimulation of nonshivering thermogenesis in the Syrian hamster by norepinephrine and β-selective adrenergic agents: A phenomenon of refractoriness

The ability of different adrenergic agents to stimulate nonshivering thermogenesis in Syrian hamsters was investigated. The hamsters were cold-acclimated to 6 °C and their thermogenic response was investigated in an open-circuit system at 24 °C. Both norepinephrine and the β₃-specific adrenergic agonist CGP-12177 induced a high rate of nonshivering thermogenesis. However, neither CGP-12177 nor other β₃-selective agonists (BRL-37344, ICI-D7114) could induce nonshivering thermogenesis fully to the extent induced by norepinephrine. It was further observed that an apparent “thermogenic refractoriness” was induced by certain adrenergic agents (isoprenaline, CGP-12177) but not by others (norepinephrine, BRL-37344, ICI-D7114). It is discussed whether the refractoriness could be secondary to effects of these agents on the vascular system. It is pointed out that the thermogenic response to adrenergic stimulation observed in the intact animal does not always fully correspond to what would be predicted from corresponding studies with isolated brown-fat cells.     

Endogenously produced catecholamines improve the regulatory function of TLR9-activated B cells

The sympathetic nervous system (SNS) contributes to immune balance by promoting anti-inflammatory B cells. However, whether B cells possess a self-regulating mechanism by which they modulate regulatory B cell (Breg) function is not well understood. In this study, we investigated the ability of B cells to synthesize their own catecholamines upon stimulation with different B cell activators and found that expression of the enzyme tyrosine hydroxylase (TH), required to generate catecholamines, is up-regulated by Toll-like receptor (TLR)9. This TLR9-dependent expression of TH correlated with up-regulation of adrenergic receptors (ADRs), enhanced interleukin (IL)-10 production, and overexpression of the co-inhibitory ligands programmed death ligand 1 (PD-L1) and Fas ligand (FasL). Moreover, concomitant stimulation of ß1-3-ADRs together with a B cell receptor (BCR)/TLR9 stimulus clearly enhances the anti-inflammatory potential of Bregs to suppress CD4 T cells, a crucial population in the pathogenesis of autoimmune diseases, like rheumatoid arthritis (RA). Furthermore, TH up-regulation was also demonstrated in B cells during the course of collagen-induced arthritis (CIA), a mouse model for the investigation of RA. In conclusion, our data show that B cells possess an autonomous mechanism to modulate their regulatory function in an autocrine and/or paracrine manner. These findings help to better understand the function of B cells in the regulation of autoimmune diseases and the interplay of SNS.

The sympathetic nervous system produces neurotransmitters such as catecholamines which contribute to immune balance by promoting anti-inflammatory B cells. This study shows that mouse B cells can themselves synthesize, sense, and transport catecholamines, which in turn modulate regulatory B cell function in an autocrine and/or paracrine manner to suppress T cell proliferation.     

Norepinephrine inhibits energy metabolism of human peripheral blood mononuclear cells via adrenergic receptors

Previous studies demonstrated that the adaptive response to stressors and inflammatory signals involves the activation of the automotic nervous system. Catecholamines have been shown to modulate the activity of various immune effector cells directly via membrane adrenergic receptors. Here, we investigated immediate effects of norepinephrine on energy metabolism of immune cells. Norepinephrine inhibits oxygen consumption of human peripheral blood mononuclear cells at concentrations that are relevant to its physiological range. The -adrenoreceptor antagonist propranolol, but not the -adrenoreceptor antagonist phentolamine reversed the norepinephrine induced inhibition in quiescent cells. Conversely, phentolamine but not propranolol is capable of blocking norepinephrine mediated effects in mitogen activated human peripheral blood mononuclear cells. Our data indicate that the sensitization of - and -adrenoreceptors on immune cells is differentially regulated, and that these processes depend on the activation state of these cells. These findings have important implications for the understanding of stress-induced suppression of immune function and may contribute to the elucidation of the pathogenesis of immunologically mediated diseases.     

Catecholamines inhibit the antigen-presenting capability of epidermal Langerhans cells

The sympathetic nervous system modulates immune function at a number of levels. Within the epidermis, APCs (Langerhans cells (LC)) are frequently anatomically associated with peripheral nerves. Furthermore, some neuropeptides have been shown to regulate LC Ag-presenting function. We explored the expression of adrenergic receptors (AR) in murine LC and assessed their functional role on Ag presentation and modulation of cutaneous immune responses. Both purified LC and the LC-like cell lines XS52-4D and XS106 expressed mRNA for the ARs alpha(1A) and beta(2). XS106 cells and purified LC also expressed beta(1)-AR mRNA. Treatment of murine epidermal cell preparations with epinephrine (EPI) or norepinephrine inhibited Ag presentation in vitro. Furthermore, pretreatment of epidermal cells with EPI or norepinephrine in vitro suppressed the ability of these cells to present Ag for elicitation of delayed-type hypersensitivity in previously immunized mice. This effect was blocked by use of the beta(2)-adrenergic antagonist ICI 118,551 but not by the alpha-antagonist phentolamine. Local intradermal injection of EPI inhibited the induction of contact hypersensitivity to epicutaneously administered haptens. Surprisingly, injection of EPI at a distant site also suppressed induction of contact hypersensitivity. Thus, catecholamines may have both local and systemic effects. We conclude that specific ARs are expressed on LC and that signaling through these receptors can decrease epidermal immune reactions.     

Adrenergic control of luminescence and cellular metabolism in Porichthys isolated luminous organs

1. Isolated photophores from the luminous fish Porichthys produce light in response to adrenaline and the metabolic inhibitors iodoacetic acid (IAA) or potassium cyanide (KCN).2. We attempted to analyse the interactions of cellular metabolism and adrenergic stimulation of the photogenic cells.3. Photophores were treated with IAA in the presence of pyruvate. In these conditions, IAA does inhibit glycolysis without inducing any luminescent activity of the cells.4. Similarly, other photophores were incubated with KCN in the presence of glucose, in order to inhibit cellular respiration while keeping the luminous system inactive.5. We observed that adrenergic stimulation of these photophores remained effective and induced a light emission, demonstrating that glycolytic and oxidative metabolism are not absolutely essential to the mechanism underlying adrenergic activation of the luminous system.6. The comparison of these luminescences with adrenergic responses of control photophores showed that the light emission to adrenaline was markedly inhibited by glycolysis blockade but potentiated by an inhibition of cellular respiration.7. As the inhibitory effect of IAA does not result from a direct action of IAA on the luminous system, these results suggest that adrenaline activation of adrenergic receptors might interact with glycolysis in photogenic cells.8. Glyceraldehyde 3-phosphate, or some derivatives, could be implicated in the glycolytic control of luminescence in the photophores.     

Aging-related hyperinflammation in endotoxemia is mediated by the α2A-adrenoceptor and CD14/TLR4 pathways

AimsSepsis is a major cause of morbidity and mortality in the elderly population. In prior studies, we have shown that in vivo, the inflammatory response in aged animals is exaggerated as compared to young animals and that this response likely accounts for the increased morbidity and mortality. Part of this uncontrolled inflammatory response in sepsis is due to the innate immune response. However, recent studies have shown that the pathogenesis of sepsis is much more complex. The adrenergic autonomic nervous system is now thought to play a key role in modulating the inflammatory response in sepsis. In this study, we hypothesize that not only is the innate immune response enhanced in response to lipopolysaccharide (LPS) in aged animals, but that the adrenergic nervous system also plays a role in the release of excess inflammatory cytokines.Main methodsMale Fischer-344 rats (young: 3 months; aged: 24 months) were used. Endotoxemia was induced by intravenous injection of lipopolysaccharide (LPS, 15 mg/kg BW). Splenic tissues were harvested and mRNA and protein were extracted. The protein expression of CD14 and TLR4, key mediators of LPS in the innate response, as well as alpha-2A adrenergic receptor (α_2A-AR) and phosphodiesterase 4D (PDE4D), as the means by which the autonomic nervous system exerts its effects were analyzed.Key findingsSplenic tissue concentrations of α_2A-AR, PDE4D, CD14, and TLR4 were significantly increased in septic aged rats as compared to aged sham rats and septic young rats. The increased expression of α_2A-AR in septic aged rats was further confirmed by immunohistochemical staining of splenic tissues.SignificanceThese data support the hypothesis that not only is the innate immune response increased in aged animals during sepsis, but that there is also an upregulated response of the adrenergic autonomic nervous system that contributes to excess proinflammatory cytokine release.     

Norepinephrine and serotonin content of the murine spleen: its relationship to lymphocyte beta-adrenergic receptor density and the humoral immune response in vivo and in vitro

Numerous reports in the literature describe the effects of beta-adrenergic agonists and/or their second messenger cyclic AMP on in vitro and in vivo immune responses. The fact that the murine spleen receives rich adrenergic innervation and that the pharmacologic disruption of this innervation leads to altered immune responsiveness has led some investigators to postulate that the immune system may be modulated in vivo by the sympathetic nervous system. In this report HPLC is used to quantitate the norepinephrine (NE) and serotonin (5-HT) found in the B6C3F1 spleen. These transmitters were found to be distributed nonhomogeneously among the cell, supernatant, and capsule fractions of the spleen. The majority of NE was found in the capsule while most 5-HT was found associated with the cell pellet. During an immune response to sheep red blood cells the concentration of NE in the spleen was found to be decreased. However, the total amount of splenic NE was unaltered and thus the decreased concentration may be attributed to the increased weight of immunized spleens. Simultaneously, the total amount of the dopamine metabolite 3,4-dihydroxyphenylacetic acid found in the spleen was found to be increased, a difference not explained by increased spleen size. These results suggest an antigen-induced increase in sympathetic activity in the spleen. Splenic NE could be rapidly depleted using 6-hydroxydopamine. Lymphocytes from the NE-depleted animals were found to have upregulated the number of beta-adrenergic receptors on their surfaces and demonstrated a reduced ability to respond to sheep red blood cells in vitro.     

Beta 2-adrenergic agonist regulation of immune aggregate- and platelet-activating factor-stimulated hepatic metabolism

Vasoconstriction and subsequent glycogenolysis stimulated by immune complex infusion into perfused rat livers was inhibited by prior infusion of isoproterenol. Similarly, isoproterenol inhibited the biosynthesis of bioactive lipid autacoids such as platelet-activating factor, prostaglandin E2, and thromboxane B2 which was stimulated by immune aggregates. The adrenergic receptor specificity of these effects was determined through the use of specific adrenergic subtype-specific agonists and antagonists to be mediated by beta 2-adrenergic receptors. Indirect evidence for the differential expression of hepatic sinusoidal and parenchymal beta-adrenergic receptors in the male rat during ontogeny suggested that inhibition of immune aggregate-stimulated autacoid biosynthesis, vasoconstriction, and glycogenolysis by isoproterenol occurs at a sinusoidal locus, most likely Kupffer cells. In contrast with the ability of beta 2-adrenergic agonists to inhibit immune aggregate- and platelet-activating factor-stimulated hepatic metabolism, dibutyryl cyclic AMP did not mimic these sinusoidal beta 2-adrenergic effects, despite stimulating hepatic parenchymal cell glycogenolysis as effectively as isoproterenol. These observations suggest a role for cyclic AMP-independent mechanisms in the regulation of heterologous stimulus-response coupling by hepatic sinusoidal beta 2-adrenergic receptors.     

Norepinephrine Modulates the Motility of Resting and Activated Microglia via Different Adrenergic Receptors

Microglia, the resident immune cells of the central nervous system (CNS), monitor the brain for disturbances of tissue homeostasis by constantly moving their fine processes. Microglia respond to tissue damage through activation of ATP/ADP receptors followed by directional process extension to the damaged area. A common feature of several neurodegenerative diseases is the loss of norepinephrine, which might contribute to the associated neuroinflammation. We carried out a high resolution analysis of the effects of norepinephrine (NE) on microglial process dynamics in acute brain slices from mice that exhibit microglia-specific enhanced green fluorescent protein expression. Bath application of NE to the slices resulted in significant process retraction in microglia. Analysis of adrenergic receptor expression with quantitative PCR indicated that resting microglia primarily express β₂ receptors but switch expression to α_2A receptors under proinflammatory conditions modeled by LPS treatment. Despite the differential receptor expression, NE caused process retraction in both resting and LPS-activated microglia cultured in the gelatinous substrate Matrigel in vitro. The use of subtype-selective receptor agonists and antagonists confirmed the involvement of β₂ receptors in mediating microglial process dynamics in resting cells and α_2A receptors in activated cells. Co-application of NE with ATP to resting microglia blocked the ATP-induced process extension and migration in isolated microglia, and β₂ receptor antagonists prolonged ATP effects in brain slice tissues, suggesting the presence of cross-talk between adrenergic and purinergic signaling in microglia. These data show that the neurotransmitter NE can modulate microglial motility, which could affect microglial functions in pathogenic situations of either elevated or reduced NE levels.     

The immunomodulatory effects of tachykinins and their receptors

Tachykinins (TKs) are a family of neuropeptides mainly expressed by neuronal and non-neuronal cell types, especially immune cells. Expression of TKs receptors on immune cell surfaces, their involvement in immune-related disorders, and therefore, understanding their immunomodulatory roles have become of particular interest to researchers. In fact, the precise understanding of TKs intervention in the immune system would help to design novel therapeutic approaches for patients suffering from immune disorders. The present review summarizes studies on TKs function as modulators of the immune system by reviewing their roles in generation, activation, development, and migration of immune cells. Also, it discusses TKs involvement in three main cellular mechanisms including inflammation, apoptosis, and proliferation.     

Adrenergic neurons in teleost retina

Summary The adrenergic retinal neurons of perch and trout were studied with the fluorescence microscopical method of Falck and Hillarp. Pilot studies were also performed on pike, plaice, cod, eel, goldfish, cunner, black moor, cichlid and carp. Only minor differences were noted between the species.Adrenergic varicose terminals occur in three sublayers of the inner plexiform layer. The layer adjacent to the ganglion cells is the most elaborate. Adrenergic perikarya occur in the innermost cell rows of the inner nuclear layer, sending branches to all sublayers of the inner plexiform layer. Adrenergic perikarya also occur among the ganglion cells, sending their branches to the innermost sublayer of adrenergic fibres in the inner plexiform layer. Weakly fluorescent adrenergic fibres can be seen running through the entire depth of the inner nuclear layer. They originate from the adrenergic perikarya of the inner nuclear layer, and they end in an elaborate plexus of adrenergic terminals among the horizontal cells. Either of the horizontal cell types can be in contact with adrenergic terminals, but the middle horizontal cells have the greatest density about them, being surrounded by baskets of adrenergic terminals of presumably synaptic character. It cannot be excluded that some horizontal cells contain a catecholamine.Microspectrofluometry revealed dopamine in the perch and trout retinal neurons.The research reported in this document has been sponsored by USPHS Grant No. 06092 and by a Research Professorship from Research to Prevent Blindness, Inc. to A.M.L. and by the Swedish Medical Research Council (B69-14X-712-04C and B68-14X-2321-01).     

An Analysis of the Effects of Retinoic Acid and Other Retinoids on the Development of Adrenergic Cells from the Avian Neural Crest

In the present work, we have investigated the role of all-trans-retinoic acid (all-transRA), and several other natural and synthetic retinoids, in the development of adrenergic cells in quail neural crest cultures. Dose response studies using all-transRA and 13-cisRA revealed a dose-dependent increase in the number of adrenergic cells in neural crest cultures. Similar dose response studies using RA isomers and other natural retinoids did not result in the same increases. In order to determine the receptor mediating the effects of all-transRA in the neural crest, we tested several synthetic analogs which specifically bind to a particular RA receptor (RAR) subtype. We found that the compound AM 580, which activates the RAR-α, produced an increase in adrenergic cells similar to that seen with all-transRA. The compound TTNPB, which activates all RAR subtypes, also resulted in an increase in adrenergic cells. We conclude that the increase in adrenergic cells seen with all-transRA is mediated by RAR-α and possibly RAR-β. To further define the actions of all-transRA on the neural crest we incubated cultures with 5-bromo-2′-deoxyuridine (BrdU) to determine whether all-transRA could affect the rate of proliferation. The results show that while all-transRA did not increase the fraction of cells incorporating BrdU into their nuclei at early time points (24 h), it did increase BrdU incorporation by tyrosine hydroxylase (TH) positive cells at 5 days in culture. These findings demonstrate that the increase in adrenergic cells seen with all-transRA in neural crest cultures is likely due to an increase in the proliferation of cells already expressing TH.     

Confocal immunohistochemistry of the dermal glands and evolutionary considerations in the caecilian,Typhlonectes natans (Amphibia: Gymnophiona)

An immunohistochemical study of the cutaneous glands of the caecilian Typhlonectes natans was conducted. Analyses of nerve fibres revealed that adrenergic and galanin‐positive axons innervate the MECs and mediate their contraction. These glands may represent one of the main targets of the adrenergic ganglion cells and reflect the prominent preganglionic cell columns of the species studied. But neurochemical features of the sympathetic ganglia and retrograde tract‐tracing studies are necessary to study the morphology and organization of the sympathetic nervous system of studied species.     

Origin,production and molecular determinants of macrophages for their therapeutic targeting

Macrophages, the most heterogeneous cells of the hematopoietic system and the giant eaters of the immune system that present either as tissue-resident cells or infiltrated immune cells, eliminate foreign pathogens and microbes and also play different physiological roles to maintain the body's immune response. In this review, we basically provide a broad overview of macrophages from their origin, functional diversity to M1-M2 polarization, specialized markers, and their role as important therapeutic targets in different diseases based on the current research and evidence. Apart from this, we have precisely discussed about tumor-associated macrophages (TAMs) and their role in tumor progression and newly discovered lesser-known markers of TAMs that could be used as potential therapeutic targets to treat life-threatening diseases. It is really very important to understand the diversity of macrophages to develop TAM-modulating strategies to activate our own immune system against diseases and to overcome immune resistance.     

Epigenetic Control of Immunity

Immunity relies on the heterogeneity of immune cells and their ability to respond to pathogen challenges. In the adaptive immune system, lymphocytes display a highly diverse antigen receptor repertoire that matches the vast diversity of pathogens. In the innate immune system, the cell''s heterogeneity and phenotypic plasticity enable flexible responses to changes in tissue homeostasis caused by infection or damage. The immune responses are calibrated by the graded activity of immune cells that can vary from yeast-like proliferation to lifetime dormancy. This article describes key epigenetic processes that contribute to the function of immune cells during health and disease.     

Characterization of Two Chromaffin Cell Populations Isolated from Bovine Adrenal Medulla

Cultures of chromaffin cells isolated from the bovine adrenal medulla have been extremely useful for investigating secretory mechanisms, but such cultures used up to the present time represent mixed populations of adrenergic and noradrenergic cells. This report describes how, with slight modifications to standard procedures, two separate chromaffin cell populations may be separated from bovine adrenal medullae. These two cell fractions have been characterized by biochemical, immunocytochemical, and morphological techniques as enriched populations of adrenergic or noradrenergic cells, respectively. The adrenergic cell-enriched fraction consists of greater than 90% adrenergic cells, whereas the noradrenergic cell-enriched fraction contains greater than 60% noradrenergic cells. We also demonstrate that these cells may be cultured with their secretory machinery intact: analysis of secreted catecholamines from nicotine- or high K+ concentration-stimulated cells cultured from each fraction confirms that adrenaline is the major catecholamine secreted by one fraction, whereas noradrenaline is mainly secreted by the other.     

Targeting of the Enhanced Green Fluorescent Protein Reporter to Adrenergic Cells in Mice

Adrenaline and noradrenaline are important neurotransmitter hormones that mediate physiological stress responses in adult mammals, and are essential for cardiovascular function during a critical period of embryonic/fetal development. In this study, we describe a novel mouse model system for identifying and characterizing adrenergic cells. Specifically, we generated a reporter mouse strain in which a nuclear-localized enhanced green fluorescent protein gene (nEGFP) was inserted into exon 1 of the gene encoding Phenylethanolamine n-methyltransferase (Pnmt), the enzyme responsible for production of adrenaline from noradrenaline. Our analysis demonstrates that this knock-in mutation effectively marks adrenergic cells in embryonic and adult mice. We see expression of nEGFP in Pnmt-expressing cells of the adrenal medulla in adult animals. We also note that nEGFP expression recapitulates the restricted expression of Pnmt in the embryonic heart. Finally, we show that nEGFP and Pnmt expressions are each induced in parallel during the in vitro differentiation of pluripotent mouse embryonic stem cells into beating cardiomyocytes. Thus, this new mouse genetic model should be useful for the identification and functional characterization of adrenergic cells in vitro and in vivo.     

Coexpression of somatostatin-like immunoreactivity and catecholaminergic properties in neural crest derivatives: comodulation of peptidergic and adrenergic differentiation in cultured neural crest

In the avian embryo, somatostatin-like immunoreactivity (SLI) and adrenergic characteristics appear virtually simultaneously in the developing sympathetic nervous system and adrenal medulla. We have used double-labeling techniques to show that both properties coexist in the same cells. In the quail, not only do all somatostatin-containing cells in the adrenosympathetic system exhibit tyrosine hydroxylase immunoreactivity and possess catecholamines (CA), but this coexistence of the peptidergic and adrenergic phenotypes is already present very early in ontogeny. However, not all adrenergic cells express SLI. The development of sympathoadrenal precursors can be followed in vitro. Adrenergic precursor cells, obtained from the migrating neural crest, differentiate in culture into neuron-like cells that contain SLI and CA. This coexpression can be regulated by the same factors. For instance, corticosterone and progesterone increase SLI content and CA production in the neural crest cell cultures. The ontogeny of the autonomic lineage is discussed in the light of these results.     

Intraepithelial gamma delta T cells exposed by functional genomics

Epithelial tissues house γδ T cells, which are important for the mucosal immune system and may be involved in controlling malignancies, infections and inflammation. Whole-genome gene-expression analysis provides a new way to study the signals required for the activation of γδ T cells, their mode of action and relationships among cells of the mucosal immune system.