Participation of beta-adrenergic receptors on macrophages in modulation of LPS-induced cytokine release

Inflammation in the pathogenesis of depression: a disorder of neuroimmune origin

There are several hypotheses concerning the underlying pathophysiological mechanisms of major depression, which centre largely around adaptive changes in neuronal transmission and plasticity, neurogenesis, and circuit and regional connectivity. The immune and endocrine systems are commonly implicated in driving these changes. An intricate interaction of stress hormones, innate immune cells and the actions of soluble mediators of immunity within the nervous system is described as being associated with the symptoms of depression. Bridging endocrine and immune processes to neurotransmission and signalling within key cortical and limbic brain circuits are critical to understanding depression as a disorder of neuroimmune origins. Emergent areas of research include a growing recognition of the adaptive immune system, advances in neuroimaging techniques and mechanistic insights gained from transgenic animals. Elucidation of glial-neuronal interactions is providing additional avenues into promising areas of research, the development of clinically relevant disease models and the discovery of novel therapies. This narrative review focuses on molecular and cellular mechanisms that are influenced by inflammation and stress. The aim of this review is to provide an overview of our current understanding of depression as a disorder of neuroimmune origin, focusing on neuroendocrine and neuroimmune dysregulation in depression pathophysiology. Advances in current understanding lie in pursuit of relevant biomarkers, as the potential of biomarker signatures to improve clinical outcomes is yet to be fully realised. Further investigations to expand biomarker panels including integration with neuroimaging, utilising individual symptoms to stratify patients into more homogenous subpopulations and targeting the immune system for new treatment approaches will help to address current unmet clinical need.

Induction of tetraspanin 13 contributes to the synergistic anti-inflammatory effects of parasympathetic and sympathetic stimulation in macrophages

The autonomic nervous system plays an important role in the regulation of peripheral inflammation. Sympathetic nervous activation stimulates inflammatory gene expression and cytokines, whereas parasympathetic nervous activation suppresses the production of inflammatory cytokines by immune cells. However, most studies on the relationship between the autonomic nervous system and immune processes have analyzed a single branch of the autonomic nerves in isolation. Therefore, this study aimed to examine the effects of sympathetic and parasympathetic stimulation on macrophages, which are controlled by autonomic regulation. Macrophages were stimulated with lipopolysaccharide (LPS) to induce TNF-α. Then, the effects of β2 adrenergic receptor and α7 nicotinic acetylcholine receptor activation on TNF-α production were assessed using concentration-dependent assays. RNA-seq data were also used to identify genes whose expression was enhanced by parasympathetic and sympathetic stimulation. The simultaneous activation of β2 adrenergic receptors and α7 nicotinic acetylcholine receptors suppressed LPS-induced TNF-α production in a concentration-dependent manner. Moreover, simultaneous activation of these receptors had synergistic anti-inflammatory effects and induced Tspan13 expression, thereby contributing to anti-inflammatory mechanisms in macrophages. Our study revealed the synergistic anti-inflammatory effects of the parasympathetic and sympathetic stimulation of macrophages. Our results suggest that targeting both sympathetic and parasympathetic signaling is a promising therapeutic approach for inflammatory diseases.

Thermoneutral housing shapes hepatic inflammation and damage in mouse models of non-alcoholic fatty liver disease

Introduction

Inflammation is a common unifying factor in experimental models of non-alcoholic fatty liver disease (NAFLD) progression. Recent evidence suggests that housing temperature-driven alterations in hepatic inflammation correlate with exacerbated hepatic steatosis, development of hepatic fibrosis, and hepatocellular damage in a model of high fat diet-driven NAFLD. However, the congruency of these findings across other, frequently employed, experimental mouse models of NAFLD has not been studied.

Methods

Here, we examine the impact of housing temperature on steatosis, hepatocellular damage, hepatic inflammation, and fibrosis in NASH diet, methionine and choline deficient diet, and western diet + carbon tetrachloride experimental models of NAFLD in C57BL/6 mice.

Results

We show that differences relevant to NAFLD pathology uncovered by thermoneutral housing include: (i) augmented NASH diet-driven hepatic immune cell accrual, exacerbated serum alanine transaminase levels and increased liver tissue damage as determined by NAFLD activity score; (ii) augmented methionine choline deficient diet-driven hepatic immune cell accrual and increased liver tissue damage as indicated by amplified hepatocellular ballooning, lobular inflammation, fibrosis and overall NAFLD activity score; and (iii) dampened western diet + carbon tetrachloride driven hepatic immune cell accrual and serum alanine aminotransferase levels but similar NAFLD activity score.

Discussion

Collectively, our findings demonstrate that thermoneutral housing has broad but divergent effects on hepatic immune cell inflammation and hepatocellular damage across existing experimental NAFLD models in mice. These insights may serve as a foundation for future mechanistic interrogations focused on immune cell function in shaping NAFLD progression.

Effect of Thiazolidin-4-one Against Lipopolysaccharide-Induced Oxidative Damage, and Alterations in Adenine Nucleotide Hydrolysis and Acetylcholinesterase Activity in Cultured Astrocytes

Astrocytes play multiple important roles in brain physiology. However, depending on the stimuli, astrocytes may exacerbate inflammatory reactions, contributing to the development and progression of neurological diseases. Therefore, therapies targeting astrocytes represent a promising area for the development of new brain drugs. Thiazolidinones are heterocyclic compounds that have a sulfur and nitrogen atom and a carbonyl group in the ring and represent a class of compounds of great scientific interest due to their pharmacological properties. The aim of this study was to investigate the effect of 3-(3-(diethylamino)propyl)-2-(4-(methylthio)phenyl)thiazolidin-4-one (DS27) on cell proliferation and morphology, oxidative stress parameters, activity of the enzymes ectonucleotidases and acetylcholinesterase (AChE) and interleukin 6 (IL-6) levels in primary astrocyte cultures treated with lipopolysaccharide (LPS), to model neuroinflammation. The astrocyte culture was exposed to LPS (10 μg/ml) for 3 h and subsequently treated with compound DS27 for 24 and 48 h (concentrations ranging to 10-100 μM). LPS induced an increase in astrocyte proliferation, AChE activity, IL-6 levels, oxidative damage, ATP and ADP and a reduction in AMP hydrolysis in rat primary astrocyte cultures. DS27 treatment was effective in reversing these alterations induced by LPS. Our findings demonstrated that DS27 is able to modulate cholinergic and purinergic signaling, redox status, and the levels of pro-inflammatory cytokines in LPS-induced astrocyte damage. These glioprotective effects of DS27 may be very important for improving neuroinflammation, which is associated with many brain diseases.

Adrenergic Signaling Regulation Of Macrophage Function: Do We Understand It Yet?

Macrophages are immune cells that are widespread throughout the body and critical for maintaining tissue homeostasis. Their remarkable plasticity allows them to acquire different phenotypes, becoming able either to fight infection (M1-like, classically activated macrophages) or to promote tissue remodeling and repair (M2-like, alternatively activated macrophages). These phenotypes are induced by different cues present in the microenvironment. Among the factors that might regulate macrophage activation are mediators produced by different branches of the nervous system. The regulation exerted by the sympathetic nervous system (SNS) on macrophages (and the immune system in general) is becoming a subject of increasing interest, indeed a great number of articles have been published lately. Catecholamines (noradrenaline and adrenaline) activate α and β adrenergic receptors expressed by macrophages and shape the effector functions of these cells in contexts as diverse as the small intestine, the lung, or the adipose tissue. Activation of different subsets of receptors seems to produce antagonistic effects, with α adrenergic receptors generally associated with pro-inflammatory functions and β adrenergic receptors (particularly β2) related to the resolution of inflammation and tissue remodeling. However, exceptions to this paradigm have been reported, and the factors contributing to these apparently contradictory observations are still far from being completely understood. Additionally, macrophages per se seem to be sources of catecholamines, which is also a subject of some debate. In this review, we discuss how activation of adrenergic receptors modulates macrophage effector functions and its implications for inflammatory responses and tissue homeostasis.

Beta2-adrenoreceptor agonist clenbuterol produces transient decreases in alpha-synuclein mRNA but no long-term reduction in protein

β2-adrenoreceptor (β2AR) agonists have been associated with a decreased risk of developing Parkinson's disease (PD) and are hypothesized to decrease expression of both alpha-synuclein mRNA (Snca) and protein (α-syn). Effects of β2AR agonist clenbuterol on the levels of Snca mRNA and α-syn protein were evaluated in vivo (rats and mice) and in rat primary cortical neurons by two independent laboratories. A modest decrease in Snca mRNA in the substantia nigra was observed after a single acute dose of clenbuterol in rats, however, this decrease was not maintained after multiple doses. In contrast, α-syn protein levels remained unchanged in both single and multiple dosing paradigms. Furthermore, clenbuterol did not decrease Snca in cultured rat primary cortical neurons, or decrease Snca or α-syn in mice. Additionally, compared to the single-dose paradigm, repeat dosing resulted in substantially lower levels of clenbuterol in plasma and brain tissue in rodents. Based on our observations of a transient decrease in Snca and no effect on α-syn protein in this preclinical study, these data support the conclusion that clenbuterol is not likely a viable disease-modifying strategy for PD.

Blockade of beta adrenergic receptors protects the blood brain barrier and reduces systemic pathology caused by HIV-1 Nef protein

Combination antiretroviral therapy (cART) targets viral replication, but early viral protein production by astrocytes may still occur and contribute to the progression of HIV-1 associated neurocognitive disorders and secondary complications seen in patients receiving cART. In prior work with our model, astrocytic HIV-1 Nef expression exhibits neurotoxic effects leading to neurological damage, learning impairment, and immune upregulation that induces inflammation in the lungs and small intestine (SI). In this follow-up study, we focus on the sympathetic nervous system (SNS) as the important branch for peripheral inflammation resulting from astrocytic Nef expression. Male and female Sprague Dawley rats were infused with transfected astrocytes to produce Nef. The rats were divided in four groups: Nef, Nef + propranolol, propranolol and naïve. The beta-adrenergic blocker, propranolol, was administered for 3 consecutive days, starting one day prior to surgery. Two days after the surgery, the rats were sacrificed, and then blood, brain, small intestine (SI), and lung tissues were collected. Levels of IL-1β were higher in both male and female rats, and treatment with propranolol restored IL-1β to basal levels. We observed that Nef expression decreased staining of the tight junction protein claudin-5 in brain tissue while animals co-treated with propranolol restored claudin-5 expression. Lungs and SI of rats in the Nef group showed histological signs of damage including larger Peyer's Patches, increased tissue thickness, and infiltration of immune cells; these findings were abrogated by propranolol co-treatment. Results suggest that interruption of the beta adrenergic signaling reduces the peripheral organ inflammation caused after Nef expression in astrocytes of the brain.

β2-Adrenergic Receptor Enhances the Alternatively Activated Macrophages and Promotes Biliary Injuries Caused by Helminth Infection

The autonomic nervous system has been studied for its involvement in the control of macrophages; however, the mechanisms underlying the interaction between the adrenergic receptors and alternatively activated macrophages (M2) remain obscure. Using FVB wild-type and beta 2 adrenergic receptors knockout, we found that β2-AR deficiency alleviates hepatobiliary damage in mice infected with C. sinensis. Moreover, β2-AR-deficient mice decrease the activation and infiltration of M2 macrophages and decrease the production of type 2 cytokines, which are associated with a significant decrease in liver fibrosis in infected mice. Our in vitro results on bone marrow-derived macrophages revealed that macrophages from Adrb2-/- mice significantly decrease M2 markers and the phosphorylation of ERK/mTORC1 induced by IL-4 compared to that observed in M2 macrophages from Adrb2+/+ . This study provides a better understanding of the mechanisms by which the β2-AR enhances type 2 immune response through the ERK/mTORC1 signaling pathway in macrophages and their role in liver fibrosis.

Immune cell β2-adrenergic receptors contribute to the development of heart failure

β-Adrenergic receptors (βARs) regulate normal and pathophysiological heart function through their impact on contractility. βARs are also regulators of immune function where they play a unique role depending on the disease condition and immune cell type. Emerging evidence suggests an important role for the β2AR subtype in regulating remodeling in the pathological heart; however, the importance of these responses has never been examined. In heart failure, catecholamines are elevated, leading to chronic βAR activation and contributing to the detrimental effects in the heart. We hypothesized that immune cell β2AR plays a critical role in the development of heart failure in response to chronic catecholamine elevations through their regulation of immune cell infiltration. To test this, chimeric mice were generated by performing bone marrow transplant (BMT) experiments using wild-type (WT) or β2AR knockout (KO) donors. WT and β2ARKO BMT mice were chronically administered the βAR agonist isoproterenol. Immune cell recruitment to the heart was examined by histology and flow cytometry. Numerous changes in immune cell recruitment were observed with isoproterenol administration in WT BMT mice including proinflammatory myeloid populations and lymphocytes with macrophages made up the majority of immune cells in the heart and which were absent in β2ARKO BMT animal. β2ARKO BMT mice had decreased cardiomyocyte death, hypertrophy, and interstitial fibrosis following isoproterenol treatment, culminating in improved function. These findings demonstrate an important role for immune cell β2AR expression in the heart's response to chronically elevated catecholamines.NEW & NOTEWORTHY Immune cell β2-adrenergic receptors (β2ARs) are important for proinflammatory macrophage infiltration to the heart in a chronic isoproterenol administration model of heart failure. Mice lacking immune cell β2AR have decreased immune cell infiltration to their heart, primarily proinflammatory macrophage populations. This decrease culminated to decreased cardiac injury with lessened cardiomyocyte death, decreased interstitial fibrosis and hypertrophy, and improved function demonstrating that β2AR regulation of immune responses plays an important role in the heart's response to persistent βAR stimulation.

Shedding Light on the Role of Neurotransmitters in the Microenvironment of Pancreatic Cancer

Pancreatic cancer (PC) is a highly lethal malignancy with a 5-year survival rate of less than 8%. The fate of PC is determined not only by the malignant behavior of the cancer cells, but also by the surrounding tumor microenvironment (TME), consisting of various cellular (cancer cells, immune cells, stromal cells, endothelial cells, and neurons) and non-cellular (cytokines, neurotransmitters, and extracellular matrix) components. The pancreatic TME has the unique characteristic of exhibiting increased neural density and altered microenvironmental concentration of neurotransmitters. The neurotransmitters, produced by both neuron and non-neuronal cells, can directly regulate the biological behavior of PC cells via binding to their corresponding receptors on tumor cells and activating the intracellular downstream signals. On the other hand, the neurotransmitters can also communicate with other cellular components such as the immune cells in the TME to promote cancer growth. In this review, we will summarize the pleiotropic effects of neurotransmitters on the initiation and progression of PC, and particularly discuss the emerging mechanisms of how neurotransmitters influence the innate and adaptive immune responses in the TME in an autocrine or paracrine manner. A better understanding of the interplay between neurotransmitters and the immune cells in the TME might facilitate the development of new effective therapies for PC.

β-Adrenoceptor regulation of metabolism in U937 derived macrophages

Macrophages have important roles in the immune system including clearing pathogens and wound healing. Metabolic phenotypes in macrophages have been associated with functional phenotypes, where pro-inflammatory macrophages have an increased rate of glycolysis and anti-inflammatory macrophages primarily use oxidative phosphorylation. β-adrenoceptor (βAR) signalling in macrophages has been implicated in disease states such as cancer, atherosclerosis and rheumatoid arthritis. The impact of βAR signalling on macrophage metabolism has not been defined. Using metabolomics and proteomics, we describe the impact of βAR signalling on macrophages treated with isoprenaline. We found that βAR signalling alters proteins involved in cytoskeletal rearrangement and redox homeostasis of the cell. We showed that βAR signalling in macrophages shifts glucose metabolism from glycolysis towards the tricarboxylic acid cycle and pentose phosphate pathways. We also show that βAR signalling perturbs purine metabolism by accumulating adenylate and guanylate pools. Taken together, these results indicate that βAR signalling shifts metabolism to support redox processes and upregulates proteins involved in cytoskeletal changes, which may contribute to βAR effects on macrophage function.

In vitro effects of epinephrine, norepinephrine, and dobutamine on lipopolysaccharide-stimulated production of tumor necrosis factor-α, interleukin-6, and interleukin-10 in blood from healthy dogs

OBJECTIVE

To determine the in vitro effects of epinephrine, norepinephrine, and dobutamine on lipopolysaccharide (LPS)-stimulated production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) in blood from healthy dogs.

SAMPLES

Blood samples from 9 healthy dogs.

PROCEDURES

Blood samples were incubated with LPS from Escherichia coli O127:B8 or PBSS (control) for 1 hour. Afterward, the samples were incubated with 10μM epinephrine, norepinephrine, or dobutamine or with saline (0.9% NaCl) solution (control) for 23 hours. Leukocyte viability was assessed by use of trypan-blue exclusion in blood from 2 dogs to ensure cell viability was not altered by the catecholamines. Tumor necrosis factor-α, IL-6, and IL-10 concentrations were measured in the supernatant in duplicate with a canine-specific multiplex bead-based assay. Blood samples from 2 dogs were used to create dose-response curves to evaluate whether the observed cytokine modulation was dependent on catecholamine concentration.

RESULTS

Incubation of blood with epinephrine and norepinephrine significantly increased LPS-stimulated production of IL-10, compared with the control. Epinephrine and norepinephrine significantly decreased LPS-stimulated production of TNF-α, compared with the control. Epinephrine and norepinephrine did not significantly alter LPS-stimulated production of IL-6. Dobutamine did not alter catecholamine production.

CONCLUSIONS AND CLINICAL RELEVANCE

Epinephrine and norepinephrine, but not dobutamine, had immunomodulatory effects on LPS-stimulated TNF-α and IL-10 production in blood from healthy dogs in this in vitro model of sepsis. Data suggested that dobutamine may have immune system-sparing effects in dogs with sepsis.

Systemic administration of a β2-adrenergic receptor agonist reduces mechanical allodynia and suppresses the immune response to surgery in a rat model of persistent post-incisional hypersensitivity

Beta 2 adrenergic receptor (β2 AR) activation in the central and peripheral nervous system has been implicated in nociceptive processing in acute and chronic pain settings with anti-inflammatory and anti-allodynic effects of β2-AR mimetics reported in several pain states. In the current study, we examined the therapeutic efficacy of the β2-AR agonist clenbuterol in a rat model of persistent postsurgical hypersensitivity induced by disruption of descending noradrenergic signaling in rats with plantar incision. We used growth curve modeling of ipsilateral mechanical paw withdrawal thresholds following incision to examine effects of treatment on postoperative trajectories. Depletion of spinal noradrenergic neurons delayed recovery of hypersensitivity following incision evident as a flattened slope compared to non-depleted rats (-1.8 g/day with 95% CI -2.4 to -1.085, p < 0.0001). Chronic administration of clenbuterol reduced mechanical hypersensitivity evident as a greater initial intercept in noradrenergic depleted (6.2 g with 95% CI 1.6 to 10.8, p = 0.013) and non-depleted rats (5.4 g with 95% CI 1.2 to 9.6, p = 0.018) with plantar incision compared to vehicle treated rats. Despite a persistent reduction in mechanical hypersensitivity, clenbuterol did not alter the slope of recovery when modeled over several days (p = 0.053) or five weeks in depleted rats (p = 0.64). Systemic clenbuterol suppressed the enhanced microglial activation in depleted rats and reduced the density of macrophage at the site of incision. Direct spinal infusion of clenbuterol failed to reduce mechanical hypersensitivity in depleted rats with incision suggesting that beneficial effects of β2-AR stimulation in this model are largely peripherally mediated. Lastly, we examined β2-AR distribution in the spinal cord and skin using in-situ hybridization and IHC. These data add to our understanding of the role of β2-ARs in the nervous system on hypersensitivity after surgical incision and extend previously observed anti-inflammatory actions of β2-AR agonists to models of surgical injury.

β2-Adrenergic Receptors Increase Cardiac Fibroblast Proliferation Through the Gαs/ERK1/2-Dependent Secretion of Interleukin-6

Fibroblasts are an important resident cell population in the heart involved in maintaining homeostasis and structure during normal conditions. They are also crucial in disease states for sensing signals and initiating the appropriate repair responses to maintain the structural integrity of the heart. This sentinel role of cardiac fibroblasts occurs, in part, through their ability to secrete cytokines. β-adrenergic receptors (βAR) are also critical regulators of cardiac function in the normal and diseased state and a major therapeutic target clinically. βAR are known to influence cytokine secretion in various cell types and they have been shown to be involved in cytokine production in the heart, but their role in regulating cytokine production in cardiac fibroblasts is not well understood. Thus, we hypothesized that βAR activation on cardiac fibroblasts modulates cytokine production to influence fibroblast function. Using primary fibroblast cultures from neonatal rats and adult mice, increased interleukin (IL)-6 expression and secretion occurred following β2AR activation. The use of pharmacological inhibitors and genetic manipulations showed that IL-6 elevations occurred through the Gαs-mediated activation of ERK1/2 and resulted in increased fibroblast proliferation. In vivo, a lack of β2AR resulted in increased infarct size following myocardial infarction and impaired wound closure in a murine dermal wound healing assay. These findings identify an important role for β2AR in regulating fibroblast proliferation through Gαs/ERK1/2-dependent alterations in IL-6 and may lead to the development of improved heart failure therapies through targeting fibrotic function of β2AR.

Isoproterenol-Dependent Activation of TRPM7 Protects Against Neurotoxin-Induced Loss of Neuroblastoma Cells

Neuronal function and their survival depend on the activation of ion channels. Loss of ion channel function is known to induce neurodegenerative diseases such as Parkinson’s that exhibit loss of dopaminergic neurons; however, mechanisms that could limit neuronal loss are not yet fully identified. Our data suggest that neurotoxin-mediated loss of neuroblastoma SH-SY5Y cells is inhibited by the addition of β-adrenergic receptor (β-AR) agonist isoproterenol. The addition of isoproterenol to SHSY-5Y cells showed increased Mg²⁺ influx and cell survival in the presence of neurotoxin especially at higher concentration of isoproterenol. Importantly, isoproterenol potentiated transient receptor potential melastatin-7 (TRPM7) channel activation that leads to an increase in intracellular Mg²⁺ levels. The addition of 2APB, which is a known TRPM7 channel blocker, significantly decreased the TRPM7 function and inhibited isoproterenol-mediated protection against neurotoxins. Moreover, neurotoxins inhibited TRPM7 expression and function, but the restoration of TRPM7 expression increased neuroblastoma cell survival. In contrast, TRPM7 silencing increased cell loss, decreased Mg²⁺ homeostasis, and inhibited mitochondrial function. Moreover, isoproterenol treatment prevented neurotoxin-mediated loss of TRPM7 expression and inhibited Bax expression that induces cell survival. These effects were dependent on the neurotoxin-induced increase in oxidative stress, which inhibits TRPM7 expression and function. Together, our results suggest a positive role for β-AR in activating TRPM7 channels that regulate Mg²⁺ homeostasis and are essential for the survival of SH-SY5Y cells from neurotoxin.

Transportation and Routine Veterinary Interventions Alter Immune Function in the Dog

Rapid activation of the hypothalamic pituitary adrenal axis and the sympathetic nervous system are hallmarks of the acute stress response and these systems interact with the immune system by signaling though glucocorticoid and adrenergic receptors on immune cells. There is limited information about the effect of these physiologic responses on immunologic parameters of pet dogs enrolled in clinical studies. The objective of this study was to evaluate how travel, instrumentation, and hospitalization alter immunologic parameters in pet dogs. Blood was collected from healthy dogs in a home environment and from healthy dogs at the time of presentation to the hospital and after instrumentation and 24 hours of hospitalization. We found that lipopolysaccharide (LPS)-induced downregulation of toll like receptor 4 (TLR4) was blunted in dogs exposed to stress. Neutrophil and monocyte major histocompatibility complex class II (MHCII) expression increased after transportation to the veterinary hospital but then became similar to that of the control dogs at the end of hospitalization. Peripheral blood mononuclear cell cytotoxicity function was blunted in dogs exposed to the stress of transportation as well as hospitalization. Neutrophil apoptosis was greater in dogs exposed to stress compared to controls although this effect significantly decreased after hospitalization stress. Conversely, stress did not alter induced or spontaneous cytokine production from leukocytes, neutrophil or monocyte expression of TLR4, LPS-induced downregulation of monocyte TLR4, LPS-induced neutrophil and monocyte expression of MHCII or peripheral blood lymphocyte phenotype. Transportation and instrumentation/hospitalization stress should be considered when interpreting immunologic studies in pet dogs.

Propranolol Attenuates Proangiogenic Activity of Mononuclear Phagocytes: Implication in Choroidal Neovascularization

Purpose

Targeting β-adrenergic receptor signaling with propranolol has emerged as a potential candidate to counteract choroidal neovascularization (CNV). Little is known of its effect on macrophages, which play a critical role in CNV. We investigated the effect of propranolol on angiogenic response of mononuclear phagocytes (MPs).

Methods

The angiogenic effect of propranolol was evaluated in laser-induced CNV model. Mice received intraperitoneal injections of propranolol (6 mg/kg/d) or vehicle. CNV area and inflammatory cells were determined respectively by using lectin staining and an anti-IBA-1 antibody on RPE/choroid flat mounts. Inflammatory gene expression was evaluated by quantitative (q) PCR analysis. Mechanisms of propranolol was studied in MP cell lines J774 and RAW264.7 and in primary peritoneal macrophages. Expression of pro- and antiangiogenic mediators was studied. In addition, effects of propranolol treatment of MPs was assessed on choroidal explant.

Results

CNV was attenuated by propranolol and concomitantly associated with decreased inflammatory mediators IL-6 and TNFα, albeit with accumulation of (β-adrenoceptor harboring) MPs in the CNV area. Conditioned media from MPs preincubated with propranolol exerted antiangiogenic effects. Treatment of J774 confirmed the attenuation of inflammatory response to propranolol and increased cleaved caspase-3 on choroidal explant. We found that propranolol increased pigment epithelium-derived factor (PEDF) expression in MPs. Trapping of PEDF with an antibody abrogated antiangiogenic effects of propranolol. PEDF was also detected in CNV-associated MPs.

Conclusions

We hereby show that propranolol confers on MPs antiangiogenic properties by increasing PEDF expression, which complements its effects on vascular tissue resulting in inhibition of choroidal vasoproliferation in inflammatory conditions. The study supports possible use of propranolol as a therapeutic modality for CNV.

Phenomenon of atypical vascular effects of epinephrine and an increase of photodynamic response by nitroglycerin in rats with colon adenocarcinoma: adrenergic and nitrergic mechanisms and novel applied aspects

Using an original model of stress-induced colon adenocarcinoma, we uncover atypical vasorelaxation effects of a mucosa injection of epinephrine assessed by laser speckle contrast imaging and a significant increase of fluorescent intensity of 5-ALA/PpIX from malignant colon tissues by a mucosa injection of nitroglycerine. We clearly demonstrate a high activity of adrenergic and nitrergic mechanisms underlying this phenomenon and discuss their application in improving of optical approaches for effective diagnosis of gastrointestinal cancer.

Stress hormone signaling through β-adrenergic receptors regulates macrophage mechanotype and function

Critical functions of immune cells require them to rapidly change their shape and generate forces in response to cues from their surrounding environment. However, little is known about how soluble factors that may be present in the microenvironment modulate key aspects of cellular mechanobiology-such as immune cell deformability and force generation-to impact functions such as phagocytosis and migration. Here we show that signaling by soluble stress hormones through β-adrenoceptors (β-AR) reduces the deformability of macrophages; this is dependent on changes in the organization of the actin cytoskeleton and is associated with functional changes in phagocytosis and migration. Pharmacologic interventions reveal that the impact of β-AR signaling on macrophage deformability is dependent on actin-related proteins 2/3, indicating that stress hormone signaling through β-AR shifts actin organization to favor branched structures rather than linear unbranched actin filaments. These findings show that through remodeling of the actin cytoskeleton, β-AR-mediated stress hormone signaling modulates macrophage mechanotype to impact functions that play a critical role in immune response.-Kim, T.-H., Ly, C., Christodoulides, A., Nowell, C. J., Gunning, P. W., Sloan, E. K., Rowat, A. C. Stress hormone signaling through β-adrenergic receptors regulates macrophage mechanotype and function.

Effect of betamethasone, indomethacin and fenoterol on neonatal and maternal mononuclear cells stimulated with Escherichia coli

Despite considerable progress in the field of perinatal care, infectious diseases, especially when caused by gram negative bacteria, remain a major reason for neonatal morbidity and mortality. Notably infants born prematurely and those with very low birth weight are at risk due to their immature and deficient immune system and their prolonged hospitalization which promotes nosocomial infections. In case of impending preterm birth, betamethasone is given to induce lung maturation and tocolytic agents like indomethacin or fenoterol are administered to suppress premature labor. The aim of this study was to analyze the effects of these drugs on the immune system of mothers and neonates. Therefore, mononuclear cells from cord blood and peripheral maternal blood were stimulated with Escherichia coli and incubated with betamethasone, indomethacin and fenoterol. Subsequently the effect of the treatment on cytokine production was determined. Betamethasone alone and in combination with tocolytic agents inhibited the production of pro- and anti-inflammatory cytokines. Not only does betamethasone dampen the immune response by reducing the production of cytokines, it also has a variety of other detrimental short- and long-term effects on the neonate. In conclusion we would recommend using biological markers to determine if premature labor actually leads to preterm birth and subsequently administer betamethasone only to mothers giving birth prematurely.

Noradrenaline through β-adrenoceptor contributes to sexual dimorphism in primary CD4+ T-cell response in DA rat EAE model?

Males exhibit stronger sympathetic nervous system (SNS) activity, but weaker primary CD4+ T-cell (auto)immune responses. To test the role of catecholamines, major end-point SNS mediators, in this dimorphism, influence of propranolol (β-adrenoceptor blocker) on mitogen/neuroantigen-stimulated CD4+ T cells from female and male EAE rat draining lymph node (dLN) cell cultures was examined. Male rat dLNs exhibited higher noradrenaline concentration and frequency of β₂-adrenoceptor-expressing CD4+ T lymphocytes and antigen presenting cells. Propranolol, irrespective of exogenous noradrenaline presence, more prominently augmented IL-2 production and proliferation of CD4+ lymphocytes in male than female rat dLN cell cultures. In neuroantigen-stimulated dLN cells of both sexes propranolol increased IL-1β and IL-23/p19 expression and IL-17+ CD4+ cell frequency, but enhanced IL-17 production only in male rat CD4+ lymphocytes, thereby abrogating sexual dimorphism in IL-17 concentration observed in propranolol-free cultures. Thus, β-adrenoceptor-mediated signalling may contribute to sex bias in rat IL-17-producing cell secretory capacity.

The role of catecholamines in HIV neuropathogenesis

The success of anti-retroviral therapy has improved the quality of life and lifespan of HIV + individuals, transforming HIV infection into a chronic condition. These improvements have come with a cost, as chronic HIV infection and long-term therapy have resulted in the emergence of a number of new pathologies. This includes a variety of the neuropathological and neurocognitive effects collectively known as HIVassociated neurocognitive disorders (HAND) or NeuroHIV. These effects persist even in the absence of viral replication, suggesting that they are mediated the long-term changes in the CNS induced by HIV infection rather than by active replication. Among these effects are significant changes in catecholaminergic neurotransmission, especially in dopaminergic brain regions. In HIV-infected individuals not treated with ARV show prominent neuropathology is common in dopamine-rich brain regions and altered autonomic nervous system activity. Even infected individuals on therapy, there is significant dopaminergic neuropathology, and elevated stress and norepinephrine levels correlate with a decreased effectiveness of antiretroviral drugs. As catecholamines function as immunomodulatory factors, the resultant dysregulation of catecholaminergic tone could substantially alter the development of HIVassociated neuroinflammation and neuropathology. In this review, we discuss the role of catecholamines in the etiology of HIV neuropathogenesis. Providing a comprehensive examination of what is known about these molecules in the context of HIV-associated disease demonstrates the importance of further studies in this area, and may open the door to new therapeutic strategies that specifically ameliorate the effects of catecholaminergic dysregulation on NeuroHIV.

Microsomal prostaglandin E synthase-1 gene deletion impairs neuro-immune circuitry of the cholinergic anti-inflammatory pathway in endotoxaemic mouse spleen

The cholinergic anti-inflammatory pathway (CAP) is an innate neural reflex where parasympathetic and sympathetic nerves work jointly to control inflammation. Activation of CAP by vagus nerve stimulation (VNS) has paved way for novel therapeutic strategies in treating inflammatory diseases. Recently, we discovered that VNS mediated splenic acetylcholine (ACh) release and subsequent immunosuppression in response to LPS associated inflammation is impaired in mice lacking microsomal prostaglandin E synthase-1 (mPGES-1) expression, a key enzyme responsible for prostaglandin E2 synthesis. Here, we have further investigated the consequences of mPGES-1 deficiency on various molecular/cellular events in the spleen which is critical for the optimal functioning of VNS in endotoxaemic mice. First, VNS induced splenic norepinephrine (NE) release in both mPGES-1 (+/+) and (-/-) mice. Compared to mPGES-1 (+/+), immunomodulatory effects of NE on cytokines were strongly compromised in mPGES-1 (-/-) splenocytes. Interestingly, while LPS increased choline acetyltransferase (ChAT) protein level in mPGES-1 (+/+) splenocytes, it failed to exert similar effects in mPGES-1 (-/-) splenocytes despite unaltered β₂ AR protein expression. In addition, nicotine inhibited TNFα release by LPS activated mPGES-1 (+/+) splenocytes in vitro. However, such immunosuppressive effects of nicotine were reversed both in mPGES-1 (-/-) mouse splenocytes and human PBMC treated with mPGES-1 inhibitor. In summary, our data implicate PGE2 as an important mediator of ACh synthesis and noradrenergic/cholinergic molecular events in the spleen that constitute a crucial part of the CAP immune regulation. Our results suggest a possible link between cholinergic and PG system of CAP that may be of clinical significance in VNS treatment.

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.

Vagal influences in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disease with a prevalence of 0.5-1% in Western populations. Conventionally, it is treated with therapeutic interventions that include corticosteroids, disease-modifying anti-rheumatic drugs, and biological agents. RA exerts a significant socio-economic burden and despite the use of existing treatments some patients end up with disabling symptoms. The autonomic nervous system (ANS) is a brain-body interface that serves to regulate homeostasis by integrating the external environment with the internal milieu. The main neural substrate of the parasympathetic branch of the ANS is the vagus nerve (VN). The discovery of the role of the ANS and the VN in mediating and dampening the inflammatory response has led to the proposal that modulation of neural circuits may serve as a valuable therapeutic tool. Recent studies have explored the role of the VN in this inflammatory reflex and have provided evidence that stimulation may represent a novel new therapeutic intervention. Accumulating evidence suggests that modulation of the parasympathetic tone results in a broad physiological multi-level response, including decreased pro-inflammatory cytokine response in terms of tumour necrosis factor-α, interleukin-1 (IL-1), and IL-6, and may result in an enhanced macrophage switch from M1 to M2 cells and potentially an increased level of the anti-inflammatory cytokine IL-10. Therefore, therapeutic electrical modulation of the VN may serve as an alternative, non-pharmacological, neuroimmunomodulatory intervention in RA in the future. This review gives a focused introduction to the mechanistic link between the ANS and the immune system.

Thermoneutral housing exacerbates nonalcoholic fatty liver disease in mice and allows for sex-independent disease modeling

Nonalcoholic fatty liver disease (NAFLD), a common prelude to cirrhosis and hepatocellular carcinoma, is the most common chronic liver disease worldwide. Defining the molecular mechanisms underlying the pathogenesis of NAFLD has been hampered by a lack of animal models that closely recapitulate the severe end of the disease spectrum in humans, including bridging hepatic fibrosis. Here we demonstrate that a novel experimental model employing thermoneutral housing, as opposed to standard housing, resulted in lower stress-driven production of corticosterone, augmented mouse proinflammatory immune responses and markedly exacerbated high-fat diet (HFD)-induced NAFLD pathogenesis. Disease exacerbation at thermoneutrality was conserved across multiple mouse strains and was associated with augmented intestinal permeability, an altered microbiome and activation of inflammatory pathways that are associated with the disease in humans. Depletion of Gram-negative microbiota, hematopoietic cell deletion of Toll-like receptor 4 (TLR4) and inactivation of the IL-17 axis resulted in altered immune responsiveness and protection from thermoneutral-housing-driven NAFLD amplification. Finally, female mice, typically resistant to HFD-induced obesity and NAFLD, develop full disease characteristics at thermoneutrality. Thus, thermoneutral housing provides a sex-independent model of exacerbated NAFLD in mice and represents a novel approach for interrogation of the cellular and molecular mechanisms underlying disease pathogenesis.

β-Adrenergic-stimulated macrophages: Comprehensive localization in the M1-M2 spectrum

β-Adrenergic signaling can regulate macrophage involvement in several diseases and often produces anti-inflammatory properties in macrophages, which are similar to M2 properties in a dichotomous M1 vs. M2 macrophage taxonomy. However, it is not clear that β-adrenergic-stimulated macrophages may be classified strictly as M2. In this in vitro study, we utilized recently published criteria and transcriptome-wide bioinformatics methods to map the relative polarity of murine β-adrenergic-stimulated macrophages within a wider M1-M2 spectrum. Results show that β-adrenergic-stimulated macrophages did not fit entirely into any one pre-defined category of the M1-M2 spectrum but did express genes that are representative of some M2 side categories. Moreover, transcript origin analysis of genome-wide transcriptional profiles located β-adrenergic-stimulated macrophages firmly on the M2 side of the M1-M2 spectrum and found active suppression of M1 side gene transcripts. The signal transduction pathways involved were mapped through blocking experiments and bioinformatics analysis of transcription factor binding motifs. M2-promoting effects were mediated specifically through β2-adrenergic receptors and were associated with CREB, C/EBPβ, and ATF transcription factor pathways but not with established M1-M2 STAT pathways. Thus, β-adrenergic-signaling induces a macrophage transcriptome that locates on the M2 side of the M1-M2 spectrum but likely accomplishes this effect through a signaling pathway that is atypical for M2-spectrum macrophages.

Adrenergic regulation of innate immunity: a review

The sympathetic nervous system has a major role in the brain-immune cross-talk, but few information exist on the sympathoadrenergic regulation of innate immune system. The aim of this review is to summarize available knowledge regarding the sympathetic modulation of the innate immune response, providing a rational background for the possible repurposing of adrenergic drugs as immunomodulating agents. The cells of immune system express adrenoceptors (AR), which represent the target for noradrenaline and adrenaline. In human neutrophils, adrenaline and noradrenaline inhibit migration, CD11b/CD18 expression, and oxidative metabolism, possibly through β-AR, although the role of α₁- and α₂-AR requires further investigation. Natural Killer express β-AR, which are usually inhibitory. Monocytes express β-AR and their activation is usually antiinflammatory. On murine Dentritic cells (DC), β-AR mediate sympathetic influence on DC-T cells interactions. In human DC β₂-AR may affect Th1/2 differentiation of CD4+ T cells. In microglia and in astrocytes, β₂-AR dysregulation may contribute to neuroinflammation in autoimmune and neurodegenerative disease. In conclusion, extensive evidence supports a critical role for adrenergic mechanisms in the regulation of innate immunity, in peripheral tissues as well as in the CNS. Sympathoadrenergic pathways in the innate immune system may represent novel antiinflammatory and immunomodulating targets with significant therapeutic potential.

Neural Regulation of Pancreatic Cancer: A Novel Target for Intervention

The tumor microenvironment is known to play a pivotal role in driving cancer progression and governing response to therapy. This is of significance in pancreatic cancer where the unique pancreatic tumor microenvironment, characterized by its pronounced desmoplasia and fibrosis, drives early stages of tumor progression and dissemination, and contributes to its associated low survival rates. Several molecular factors that regulate interactions between pancreatic tumors and their surrounding stroma are beginning to be identified. Yet broader physiological factors that influence these interactions remain unclear. Here, we discuss a series of preclinical and mechanistic studies that highlight the important role chronic stress plays as a physiological regulator of neural-tumor interactions in driving the progression of pancreatic cancer. These studies propose several approaches to target stress signaling via the β-adrenergic signaling pathway in order to slow pancreatic tumor growth and metastasis. They also provide evidence to support the use of β-blockers as a novel therapeutic intervention to complement current clinical strategies to improve cancer outcome in patients with pancreatic cancer.

Peripheral and central effects of repeated social defeat stress: monocyte trafficking, microglial activation, and anxiety

The development and exacerbation of depression and anxiety are associated with exposure to repeated psychosocial stress. Stress is known to affect the bidirectional communication between the nervous and immune systems leading to elevated levels of stress mediators including glucocorticoids (GCs) and catecholamines and increased trafficking of proinflammatory immune cells. Animal models, like the repeated social defeat (RSD) paradigm, were developed to explore this connection between stress and affective disorders. RSD induces activation of the sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA) axis activation, increases bone marrow production and egress of primed, GC-insensitive monocytes, and stimulates the trafficking of these cells to tissues including the spleen, lung, and brain. Recently, the observation that these monocytes have the ability to traffic to the brain perivascular spaces and parenchyma have provided mechanisms by which these peripheral cells may contribute to the prolonged anxiety-like behavior associated with RSD. The data that have been amassed from the RSD paradigm and others recapitulate many of the behavioral and immunological phenotypes associated with human anxiety disorders and may serve to elucidate potential avenues of treatment for these disorders. Here, we will discuss novel and key data that will present an overview of the neuroendocrine, immunological and behavioral responses to social stressors.

Effects of selective β1-adrenoceptor blockade on cardiovascular and renal function and circulating cytokines in ovine hyperdynamic sepsis

Introduction

Activation of the sympathetic nervous system has beneficial cardiovascular effects in sepsis, but there is also evidence that sympatholytics have beneficial actions in sepsis. We therefore determined the effect of selective β₁-adrenoceptor blockade on cardiac and renal function and cytokine release in ovine hyperdynamic sepsis.

Methods

Hyperdynamic sepsis was induced by infusion of live E. coli for 24 hours in nine conscious sheep instrumented with flow probes on the pulmonary and left renal artery. Cardiovascular and renal function and levels of plasma cytokines were determined in a control group and during selective β1-adrenoceptor blockade with atenolol (10 mg intravenous bolus then 0.125 mg/kg/h) from 8 to 24 hours of sepsis.

Results

Hyperdynamic sepsis was characterized by hypotension with increases in cardiac output (CO), heart rate (HR) and renal blood flow (RBF), and acute kidney injury. Atenolol caused sustained reductions in HR (P <0.001) and CO (P <0.001). Despite the lower CO the sepsis-induced fall in mean arterial pressure (MAP) was similar in both groups. The sepsis-induced increase in RBF, decrease in renal function and increase in arterial lactate were unaffected by atenolol. Sepsis increased plasma levels of tumour necrosis factor alpha (TNF-α), interleukin 6 (IL-6) and IL-10. Atenolol caused a further increase in IL-10, but did not affect levels of TNF-α or IL-6.

Conclusions

In sepsis, selective β₁-adrenoceptor blockade reduced CO, but not MAP. During sepsis, atenolol did not alter the development of acute kidney injury or the levels of pro-inflammatory cytokines, but enhanced the release of IL-10. Atenolol appears safe in sepsis, has no deleterious cardiovascular or renal effects, and has an anti-inflammatory effect.

Effect of intravenous infusion of dobutamine hydrochloride on the development of early postoperative cognitive dysfunction in elderly patients via inhibiting the release of tumor necrosis factor-α

To investigate the effects of dobutamine hydrochloride on early postoperative cognitive dysfunction (POCD) and plasma tumor necrosis factor (TNF)-α concentration in patients undergoing hip arthroplasty, 124 patients undergoing unilateral total hip arthroplasty, aged 70-92 years old, were randomly assigned to four groups (n=31) as follows: a control group of patients receiving only saline (intravenous infusion, i.v.); and groups receiving 2, 4, or 6μgkg(-1)min(-1) (i.v.) of dobutamine hydrochloride. Cognitive functions were assessed on the day before surgery (T1), and the 1st day (T2), 3rd day (T3), and 7th day (T4) postsurgery using the Mini Mental State Examination (MMSE). The plasma TNF-α protein level was determined 10min before anesthesia (Ta), and 10min (Tb), 30min (Tc), and 60min (Td) after anesthesia by an enzyme-linked immunosorbent assay. Cognitive disorder was observed within the first 3 days after hip arthroplastic surgery, and it had recovered 7 days after the operation in the control group of patients. Administration of 2 or 4μgkg(-1)min(-1) dobutamine hydrochloride was able to reverse the early POCD. Simultaneously, an increase of plasma TNF-α levels 30min after anesthesia was observed (41.34±9.61 vs. 27.75±5.45), which was significantly suppressed by the administration of low-dose dobutamine hydrochloride (29.23±7.32 vs. 41.34±9.61) but not by high-dose dobutamine hydrochloride (45.9±12.11 vs. 41.34±9.61). Together, our data indicated that the plasma concentration of TNFα was engaged in the effect of dobutamine hydrochloride on POCD.

Functional β-adrenoceptors are important for early muscle regeneration in mice through effects on myoblast proliferation and differentiation

Muscles can be injured in different ways and the trauma and subsequent loss of function and physical capacity can impact significantly on the lives of patients through physical impairments and compromised quality of life. The relative success of muscle repair after injury will largely determine the extent of functional recovery. Unfortunately, regenerative processes are often slow and incomplete, and so developing novel strategies to enhance muscle regeneration is important. While the capacity to enhance muscle repair by stimulating β₂-adrenoceptors (β-ARs) using β₂-AR agonists (β₂-agonists) has been demonstrated previously, the exact role β-ARs play in regulating the regenerative process remains unclear. To investigate β-AR-mediated signaling in muscle regeneration after myotoxic damage, we examined the regenerative capacity of tibialis anterior and extensor digitorum longus muscles from mice lacking either β₁-AR (β₁-KO) and/or β₂-ARs (β₂-KO), testing the hypothesis that muscles from mice lacking the β₂-AR would exhibit impaired functional regeneration after damage compared with muscles from β₁-KO or β₁/β₂-AR null (β₁/β₂-KO) KO mice. At 7 days post-injury, regenerating muscles from β₁/β₂-KO mice produced less force than those of controls but muscles from β₁-KO or β₂-KO mice did not exhibit any delay in functional restoration. Compared with controls, β₁/β₂-KO mice exhibited an enhanced inflammatory response to injury, which delayed early muscle regeneration, but an enhanced myoblast proliferation later during regeneration ensured a similar functional recovery (to controls) by 14 days post-injury. This apparent redundancy in the β-AR signaling pathway was unexpected and may have important implications for manipulating β-AR signaling to improve the rate, extent and efficacy of muscle regeneration to enhance functional recovery after injury.

Identification of host-targeted small molecules that restrict intracellular Mycobacterium tuberculosis growth

Mycobacterium tuberculosis remains a significant threat to global health. Macrophages are the host cell for M. tuberculosis infection, and although bacteria are able to replicate intracellularly under certain conditions, it is also clear that macrophages are capable of killing M. tuberculosis if appropriately activated. The outcome of infection is determined at least in part by the host-pathogen interaction within the macrophage; however, we lack a complete understanding of which host pathways are critical for bacterial survival and replication. To add to our understanding of the molecular processes involved in intracellular infection, we performed a chemical screen using a high-content microscopic assay to identify small molecules that restrict mycobacterial growth in macrophages by targeting host functions and pathways. The identified host-targeted inhibitors restrict bacterial growth exclusively in the context of macrophage infection and predominantly fall into five categories: G-protein coupled receptor modulators, ion channel inhibitors, membrane transport proteins, anti-inflammatories, and kinase modulators. We found that fluoxetine, a selective serotonin reuptake inhibitor, enhances secretion of pro-inflammatory cytokine TNF-α and induces autophagy in infected macrophages, and gefitinib, an inhibitor of the Epidermal Growth Factor Receptor (EGFR), also activates autophagy and restricts growth. We demonstrate that during infection signaling through EGFR activates a p38 MAPK signaling pathway that prevents macrophages from effectively responding to infection. Inhibition of this pathway using gefitinib during in vivo infection reduces growth of M. tuberculosis in the lungs of infected mice. Our results support the concept that screening for inhibitors using intracellular models results in the identification of tool compounds for probing pathways during in vivo infection and may also result in the identification of new anti-tuberculosis agents that work by modulating host pathways. Given the existing experience with some of our identified compounds for other therapeutic indications, further clinically-directed study of these compounds is merited.

Infection with the bacterial pathogen Mycobacterium tuberculosis causes the disease tuberculosis (TB) that imposes significant worldwide morbidity and mortality. Approximately 2 billion people are infected with M. tuberculosis, and almost 1.5 million people die annually from TB. With increasing drug resistance and few novel drug candidates, our inability to effectively treat all infected individuals necessitates a deeper understanding of the host-pathogen interface to facilitate new approaches to treatment. In addition, the current anti-tuberculosis regimen requires months of strict compliance to clear infection; targeting host immune function could play a strategic role in reducing the duration and complexity of treatment while effectively treating drug-resistant strains. Here we use a microscopy-based screen to identify molecules that target host pathways and inhibit the growth of M. tuberculosis in macrophages. We identified several host pathways not previously implicated in tuberculosis. The identified inhibitors prevent growth either by blocking host pathways exploited by M. tuberculosis for virulence, or by activating immune responses that target intracellular bacteria. Fluoxetine, used clinically for treating depression, induces autophagy and enhances production of TNF-α. Similarly, gefitinib, used clinically for treating cancer, inhibits M. tuberculosis growth in macrophages. Importantly, gefitinib treatment reduces bacterial replication in the lungs of M. tuberculosis-infected mice.

The cholinergic anti-inflammatory pathway: a critical review

From a critical review of the evidence on the cholinergic anti-inflammatory pathway and its mode of action, the following conclusions were reached. (1) Both local and systemic inflammation may be suppressed by electrical stimulation of the peripheral cut end of either vagus. (2) The spleen mediates most of the systemic inflammatory response (measured by TNF-α production) to systemic endotoxin and is also the site where that response is suppressed by vagal stimulation. (3) The anti-inflammatory effect of vagal stimulation depends on the presence of noradrenaline-containing nerve terminals in the spleen. (4) There is no disynaptic connection from the vagus to the spleen via the splenic sympathetic nerve: vagal stimulation does not drive action potentials in the splenic nerve. (5) Acetylcholine-synthesizing T lymphocytes provide an essential non-neural link in the anti-inflammatory pathway from vagus to spleen. (6) Alpha-7 subunit-containing nicotinic receptors are essential for the vagal anti-inflammatory action: their critical location is uncertain, but is suggested here to be on splenic sympathetic nerve terminals. (7) The vagal anti-inflammatory pathway can be activated electrically or pharmacologically, but it is not the efferent arm of the inflammatory reflex response to endotoxemia.

Adrenal hormone deprivation affects macrophage catecholamine metabolism and β2-adrenoceptor density, but not propranolol stimulation of tumour necrosis factor-α production

Catecholamines modulate the production of inflammatory mediators by macrophages in an autocrine/paracrine manner. They also tune β2-adrenoceptor expression. Glucocorticoids influence catecholamine metabolism and adrenoceptor expression in many cell types. We hypothesized that adrenal hormones affect the production of tumour necrosis factor-α (TNF-α) and NO by macrophages by altering the modulatory influence of catecholamines. To prove the hypothesis, peritoneal exudate macrophages from propranolol-treated non-operated and adrenalectomized rats and from corticosterone-supplemented adrenalectomized rats were examined for lipopolysaccharide-stimulated NO and TNF-α production in vitro and for expression of β2-adrenoceptors and major catecholamine-metabolizing enzymes. Glucocorticoid deprivation increased NO production by macrophages, whereas 4 days of propranolol treatment was ineffective in this respect. However, propranolol treatment, via β2-adrenoceptor blockade, increased production of TNF-α by macrophages in both non-operated and adrenalectomized rats (showing dramatically enhanced TNF-α production due to a lack of circulating glucocorticoids) for the same value. The expression of β2-adrenoceptor was increased in peritoneal macrophages that were freshly isolated from non-operated, propranolol-treated and adrenalectomized rats (due to adrenal catecholamine deficiency). Propranolol did not affect macrophage β2-adrenoceptor expression in adrenalectomized rats. Given that propranolol increased the density of macrophage tyrosine hydroxylase expression only in non-operated rats and affected the mRNA expression of monoamine oxidase-A in neither non-operated nor adrenalectomized animals, a significant influence of propranolol on peritoneal exudate cell noradrenaline content was found only in non-operated rats. A lack of circulating adrenal hormones also affected noradrenaline metabolism and content in peritoneal exudate cells including macrophages. Collectively, despite differences in the abundance of macrophage catecholamine-β2-adrenoceptor system components and in the TNF-α response to lipopolysaccharide between adrenalectomized and non-operated rats, propranolol increased TNF-α production by the same amount in macrophages from these two groups of animals.

β2AR antagonists and β2AR gene deletion both promote skin wound repair processes

Skin wound healing is a complex process requiring the coordinated, temporal orchestration of numerous cell types and biological processes to regenerate damaged tissue. Previous work has demonstrated that a functional β-adrenergic receptor autocrine/paracrine network exists in skin, but the role of β2-adrenergic receptor (β2AR) in wound healing is unknown. A range of in vitro (single-cell migration, immunoblotting, ELISA, enzyme immunoassay), ex vivo (rat aortic ring assay), and in vivo (chick chorioallantoic membrane assay, zebrafish, murine wild-type, and β2AR knockout excisional skin wound models) models were used to demonstrate that blockade or loss of β2AR gene deletion promoted wound repair, a finding that is, to our knowledge, previously unreported. Compared with vehicle-only controls, β2AR antagonism increased angiogenesis, dermal fibroblast function, and re-epithelialization, but had no effect on wound inflammation in vivo. Skin wounds in β2AR knockout mice contracted and re-epithelialized faster in the first few days of wound repair in vivo. β2AR antagonism enhanced cell motility through distinct intracellular signalling mechanisms and increased vascular endothelial growth factor secretion from keratinocytes. β2AR antagonism promoted wound repair processes in the early stages of wound repair, revealing a possible new avenue for therapeutic intervention.

Loss of surface beta-2 adrenoceptors accounts for the insensitivity of cultured human monocytes to beta-2 adrenoceptor agonists

The short-acting beta-2 adrenoceptor agonists (β(2)-agonists), such as salbutamol, are effective bronchodilators used to treat asthma. They lack significant anti-inflammatory effect in vivo as well as on isolated alveolar macrophages even though they exhibit this effect on freshly isolated monocytes. The purpose of this study was to determine if this observation is related to a change in the expression and/or function of surface β(2)-receptors during the differentiation of these cells to macrophages. Purified monocytes, cultured for 1-48 h were pre-treated with the β(2)-agonists (salbutamol or procaterol) or PGE(2) before being stimulated with bacterial lipopolysaccharide (LPS). Subsequently, the amount of TNF-α (a typical inflammatory mediator) released over 24 h, as well as agonist-stimulated cAMP, were determined by enzyme immunoassays. Western blotting techniques were used to study the expression of the membrane β(2)-receptor protein. Results showed that in freshly isolated human monocytes, both the β(2)-agonists and PGE(2) significantly inhibited LPS-induced TNF-α release as well as increased intracellular cAMP. After culturing adherent monocytes for 24-48 h, the ability of the β(2)-agonists to produce both effects was completely lost, whereas that of PGE(2) was essentially intact. Western blotting data showed a near complete loss of surface expression of β(2)-receptors in cells cultured for ≥24 h. These results show that as human monocytes adhere to surfaces to begin differentiation into macrophages, they selectively lose their surface β(2)-receptors and hence become insensitive to the anti-inflammatory effect of β(2)-agonists. This may explain why β(2)-agonists lack significant anti-inflammatory effect on alveolar macrophages or in clinical asthma.

Age-associated remodeling of neural and nonneural thymic catecholaminergic network affects thymopoietic productivity

Ageing is associated with a progressive decline in thymic cytoarchitecture followed by a less efficient T cell development and decreased emigration of naïve T cells to the periphery. These thymic changes are linked to increased morbidity and mortality from infectious, malignant and autoimmune diseases in old age. Therefore, it is of paramount importance to understand the thymic homeostatic processes across the life span, as well as to identify factors and elucidate mechanisms driving or contributing to the thymic involution. Catecholamines (CAs) derived from sympathetic nerves and produced locally by thymic cells represent an important component of the thymic microenvironment. In young rats, they provide a subtle tonic suppressive influence on T cell development acting via β(2)- and α(1)-adrenoceptors (ARs) expressed on thymic nonlymphoid cells and thymocytes. In the face of thymic involution, a progressive increase in the thymic noradrenaline level, reflecting a rise in the density of noradrenergic nerve fibers and CA-synthesizing cells, occurs. In addition, the density of β(2)- and α(1)-AR-expressing thymic nonlymphoid cells and the α(1)-AR thymocyte surface density also exhibit a pronounced increase with age. The data obtained from studies investigating effects of AR blockade on T cell development indicated that age-related changes in CA-mediated thymic communications, certainly those involving α(1)-ARs, may contribute to diminished thymopoietic efficiency in the elderly. Having in mind thymic plasticity in the course of ageing, and broadening possibilities for pharmacological modulation of CA signaling, we here present and discuss the progress in research related to a role of CAs in thymic homeostasis and age-related decay in the thymic naïve T cell output.

Auto/paracrine control of inflammatory cytokines by acetylcholine in macrophage-like U937 cells through nicotinic receptors

Although acetylcholine (ACh) is well known for its neurotransmitter function, recent studies have indicated that it also functions as an immune cytokine that prevents macrophage activation through a 'cholinergic (nicotinic) anti-inflammatory pathway'. In this study, we used the macrophage-like U937 cells to elucidate the mechanisms of the physiologic control of cytokine production by auto/paracrine ACh through the nicotinic class of ACh receptors (nAChRs) expressed in these cells. Stimulation of cells with lipopolysaccharide up-regulated expression of alpha1, alpha4, alpha5, alpha7, alpha10, beta1 and beta3 subunits, down-regulated alpha6 and beta2 subunits, and did not alter the relative quantity of alpha9 and beta4 mRNAs. Distinct nAChR subtypes showed differential regulation of the production of pro- and anti-inflammatory cytokines. While inhibition of the expression of the TNF-alpha gene was mediated predominantly by the alpha-bungarotoxin sensitive nAChRs, that of the IL-6 and IL-18 genes-by the mecamylamine-sensitive nAChRs. Both the Mec- and alphaBtx-sensitive nAChRs regulated expression of the IL-1beta gene equally efficiently. Upregulation of IL-10 production by auto/paracrine ACh was mediated predominantly through alpha7 nAChR. These findings offer a new insight on how nicotinic agonists control inflammation, thus laying a groundwork for the development of novel immunomodulatory therapies based on the nAChR subtype selectivity of nicotinic agonists.

Chronic propranolol treatment affects expression of adrenoceptors on peritoneal macrophages and their ability to produce hydrogen peroxide and nitric oxide

Using both immunocytochemical and flow cytometric analyses of rat peritoneal exudate cells constitutive expression of tyrosine hydroxylase and both beta(2)- and alpha(1)- adrenoceptors on macrophages was revealed. Furthermore, according to the characteristic assemblage of tyrosine hydroxylase and adrenoceptor subtype expression different macrophage subsets were identified. In vitro treatment of macrophages with the non-selective alpha,beta-adrenoceptor agonist arterenol and/or the beta-adrenoceptor antagonist propranolol indicated that beta-adrenoceptors potentiated nitric oxide (NO) production and suggested alpha-adrenoceptor-mediated suppression of hydrogen peroxide (H(2)O(2)) production. An increase in H(2)O(2) production in the presence of the alpha(1)-adrenoceptor antagonist ebrantil provided support for this. Chronic propranolol treatment in vivo led to increased NO and H(2)O(2) production by peritoneal macrophages. Furthermore, this treatment resulted in opposing effects on the expression of beta(2)- and alpha(1)-adrenoceptors on peritoneal macrophages (a stimulatory effect on beta(2)-adrenoceptors and a suppressive effect on alpha(1)-adrenoceptors). In conclusion, a subset of resident peritoneal macrophages synthesizes catecholamines, which may exert differential effects on H(2)O(2) and NO production via distinct adrenoceptors. Finally, chronic propranolol treatment affected adrenoceptor expression on peritoneal macrophages and altered their capacity to generate NO and H(2)O(2).

Phosphodiesterase 4 inhibition but not beta-adrenergic stimulation suppresses tumor necrosis factor-alpha release in peripheral blood mononuclear cells in septic shock

Introduction

Stimulation of beta₂-adrenergic receptors (β₂-ARs) inhibits tumor necrosis factor-alpha (TNF-α) release in monocytes. In septic shock, endogenous catecholamines induce β₂-AR downregulation, leading to an increased TNF-α release. The aims of this study were to analyze the molecular mechanisms of β-adrenergic downregulation and to explore therapeutic interventions with maintained anti-inflammatory efficacy in septic shock using the inhibition of phosphodiesterase 4 (PDE4).

Methods

We conducted in vitro stimulation of peripheral blood mononuclear cells of healthy volunteers (n = 20) and patients with septic shock (n = 20) with lipopolysaccharide (LPS) or Staphylococcus aureus enterotoxin B (SEB) without or with isoprenaline, forskolin (an activator of adenylate cyclase), or ropipram (an inhibitor of PDE4). We also conducted flow cytometric analysis of Toll-like receptor (TLR) 4 and TLR2 surface expression and intracellular TNF-α production of untreated and stimulated CD14⁺ monocytes. Protein expression of β-ARs, of G proteins, of adenylate cyclase, and of TLRs was measured by Western blotting.

Results

Investigations were done by LPS (100 ng/mL) or SEB (10 ng/mL) when TLR4 and TLR2 were maximally expressed. LPS- or SEB-treated CD14⁺ monocytes of healthy volunteers were able to produce TNF-α. This effect was attenuated by isoprenaline, forskolin, or rolipram in a concentration-dependent manner. In CD14⁺ monocytes of patients with septic shock, the anti-inflammatory effect of isoprenaline was completely blunted whereas efficacy of forskolin and rolipram was maintained. CD14⁺ monocytes of healthy volunteers were compared with patients with septic shock: protein expression of β₂-ARs was reduced and inhibitory G protein was increased, whereas no changes in adenylate cyclase and stimulatory G protein were found.

Conclusions

In septic shock, the anti-inflammatory effects of catecholamines are blunted by downregulation of β₂-ARs and upregulation of the inhibitory G protein in CD14⁺ monocytes. Beta-adrenergic downregulation is overcome by inhibitors of PDE4. These results provide a mechanistic rationale for the therapeutic use of selective PDE4 inhibitors in the treatment of septic shock.

Multiple G-protein-coupling specificity of beta-adrenoceptor in macrophages

Adrenergic signalling of the immune system is one of the important modulator pathways of the inflammatory immune response realized via G protein-mediated pathways. The resulted signal depends on the type of the receptor-coupled G-protein (GPCR) that, according to the classical paradigm in the case of beta-adrenergic receptor (beta-AR), is Gs-type. Recently, alternate and/or multiple G protein coupling specificity of GPCRs have been demonstrated including a switch from Gs to Gi binding. The possibility of a Gs/Gi switch and its role in the immune response of macrophages has not been investigated yet. In this study, we demonstrate that beta-adrenergic stimulation itself is able to induce a transient mitogen-activated protein kinase phosphorylation in murine peritoneal macrophages in a pertussis toxin-sensitive manner, suggesting that the Gs/Gi switch also occurs in the immune system. Although this process is very rapid, it can influence different signalling pathways and can reprogramme effector functions suggesting that sympathetic modulation of the defence mechanism of the innate immune system has an additional, Gs/Gi switch-dependent component.