Temporal regulation by adrenergic receptor stimulation of macrophage (M phi)-derived tumor necrosis factor (TNF) production post-LPS challenge

Sympathetic innervation induces exosomal miR-125 transfer from osteoarthritic chondrocytes, disrupting subchondral bone homeostasis and aggravating cartilage damage in aging mice

INTRODUCTION

Osteoarthritis (OA) is a progressive disease that poses a significant threat to human health, particularly in aging individuals: Although sympathetic activation has been implicated in bone metabolism, its role in the development of OA related to aging remains poorly understood. Therefore, this study aimed to investigate how sympathetic regulation impacts aging-related OA through experiments conducted both in vivo and in vitro.

METHODS

To analyze the effect of sympathetic regulation on aging-related OA, we conducted experiments using various mouse models. These models included a natural aging model, a medial meniscus instability model, and a load-induced model, which were used to examine the involvement of sympathetic nerves. In order to evaluate the expression levels of β1-adrenergic receptor (Adrβ1) and sirtuin-6 (Sirt6) in chondrocytes of naturally aging OA mouse models, we performed assessments. Additionally, we investigated the influence of β1-adrenergic receptor knockout or treatment with a β1-adrenergic receptor blocker on the progression of OA in aging mice and detected exosome release and detected downstream signaling expression by inhibiting exosome release. Furthermore, we explored the impact of sympathetic depletion through tyrosine hydroxylase (TH) on OA progression in aging mice. Moreover, we studied the effects of norepinephrine(NE)-induced activation of the β1-adrenergic receptor signaling pathway on the release of exosomes and miR-125 from chondrocytes, subsequently affecting osteoblast differentiation in subchondral bone.

RESULTS

Our findings demonstrated a significant increase in sympathetic activity, such as NE levels, in various mouse models of OA including natural aging, medial meniscus instability, and load-induced models. Notably, we observed alterations in the expression levels of β1-adrenergic receptor and Sirt6 in chondrocytes in OA mouse models associated with natural aging, leading to an improvement in the progression of OA. Critically, we found that the knockout of β1-adrenergic receptor or treatment with a β1-adrenergic receptor blocker attenuated OA progression in aging mice and the degraded cartilage explants produced more exosome than the nondegraded ones, Moreover, sympathetic depletion through TH was shown to ameliorate OA progression in aging mice. Additionally, we discovered that NE-induced activation of the β1-adrenergic receptor signaling pathway facilitated the release of exosomes and miR-125 from chondrocytes, promoting osteoblast differentiation in subchondral bone.

CONCLUSION

In conclusion, our study highlights the role of sympathetic innervation in facilitating the transfer of exosomal miR-125 from osteoarthritic chondrocytes, ultimately disrupting subchondral bone homeostasis and exacerbating cartilage damage in aging mice. These findings provide valuable insights into the potential contribution of sympathetic regulation to the pathogenesis of aging-related OA.

Neural control of the spleen as an effector of immune responses to inflammation: mechanisms and treatments

Immune system responses are a vital defense mechanism against pathogens. Inflammatory mediators finely regulate complex inflammatory responses from initiation to resolution. However, in certain conditions, the inflammation is initiated and amplified, but not resolved. Understanding the biological mechanisms underlying the regulation of the immune response is critical for developing therapeutic alternatives, including pharmaceuticals and bioelectronic tools. The spleen is an important immune effector organ since it orchestrates innate and adaptive immune responses such as pathogen clearance, cytokine production, and differentiation of cells, therefore playing a modulatory role that balances pro- and anti-inflammatory responses. However, modulation of splenic immune activity is a largely unexplored potential therapeutic tool that could be used for the treatment of inflammatory and life-threatening conditions. This review discusses some of the mechanisms controlling neuroimmune communication and the brain-spleen axis.

The Interplay between Autonomic Nervous System and Inflammation across Systemic Autoimmune Diseases

The autonomic nervous system (ANS) and the immune system are deeply interrelated. The ANS regulates both innate and adaptive immunity through the sympathetic and parasympathetic branches, and an imbalance in this system can determine an altered inflammatory response as typically observed in chronic conditions such as systemic autoimmune diseases. Rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis all show a dysfunction of the ANS that is mutually related to the increase in inflammation and cardiovascular risk. Moreover, an interaction between ANS and the gut microbiota has direct effects on inflammation homeostasis. Recently vagal stimulation techniques have emerged as an unprecedented possibility to reduce ANS dysfunction, especially in chronic diseases characterized by pain and a decreased quality of life as well as in chronic inflammation.

Metabolic stress drives sympathetic neuropathy within the liver

The nervous system instructs the body's metabolism, including that in the liver. However, the neural anatomy of the liver under either normal or metabolically stressed conditions remains to be unequivocally assessed. Here, we examined neural distributions in the mouse, nonhuman primate, and human livers with advanced 3D imaging. We observed that neural innervations within the liver are predominantly sympathetic, but not parasympathetic, inputs. Moreover, we discovered the profound and reversible loss of such sympathetic innervations during metabolic challenges. This hepatic sympathetic neuropathy was caused by TNFα derived from CD11b⁺ F4/80⁺ immune cells under high-fat-diet (HFD) condition. We further demonstrated that the Sarm1 deletion mitigated the hepatic sympathetic neuropathy and improved metabolic parameters in HFD-challenged mice. Mechanistically, the sympathetic neurotransmitter norepinephrine attenuated the immune-cell inflammation that would otherwise trigger the insulin insensitivity of hepatocytes. These results together reveal the previously unrecognized neuropathic event in the liver with metabolic relevance.

The intestinal neuro-immune axis: crosstalk between neurons, immune cells, and microbes

The gastrointestinal tract is densely innervated by a complex network of neurons that coordinate critical physiological functions. Here, we summarize recent studies investigating the crosstalk between gut-innervating neurons, resident immune cells, and epithelial cells at homeostasis and during infection, food allergy, and inflammatory bowel disease. We introduce the neuroanatomy of the gastrointestinal tract, detailing gut-extrinsic neuron populations from the spinal cord and brain stem, and neurons of the intrinsic enteric nervous system. We highlight the roles these neurons play in regulating the functions of innate immune cells, adaptive immune cells, and intestinal epithelial cells. We discuss the consequences of such signaling for mucosal immunity. Finally, we discuss how the intestinal microbiota is integrated into the neuro-immune axis by tuning neuronal and immune interactions. Understanding the molecular events governing the intestinal neuro-immune signaling axes will enhance our knowledge of physiology and may provide novel therapeutic targets to treat inflammatory diseases.

Emerging Roles of Sympathetic Nerves and Inflammation in Perivascular Adipose Tissue

Perivascular adipose tissue (PVAT) is no longer recognised as simply a structural support for the vasculature, and we now know that PVAT releases vasoactive factors which modulate vascular function. Since the discovery of this function in 1991, PVAT research is rapidly growing and the importance of PVAT function in disease is becoming increasingly clear. Obesity is associated with a plethora of vascular conditions; therefore, the study of adipocytes and their effects on the vasculature is vital. PVAT contains an adrenergic system including nerves, adrenoceptors and transporters. In obesity, the autonomic nervous system is dysfunctional; therefore, sympathetic innervation of PVAT may be the key mechanistic link between increased adiposity and vascular disease. In addition, not all obese people develop vascular disease, but a common feature amongst those that do appears to be the inflammatory cell population in PVAT. This review will discuss what is known about sympathetic innervation of PVAT, and the links between nerve activation and inflammation in obesity. In addition, we will examine the therapeutic potential of exercise in sympathetic stimulation of adipose tissue.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.

Dipeptidyl peptidase-4 inhibitors and aerobic exercise synergistically protect against liver injury in ovariectomized rats

Menopause increases the risk of non-alcoholic fatty liver disease (NAFLD). We investigated the effect of incretin and/ or exercise on the hepatic fat accumulation in ovariectomized rats. Rats were divided into five groups: Group 1: Control rats, Group 2: Ovariectomized rats, Group 3: Ovariectomized rats + Dipeptidyl peptidase-4 inhibitor (DPPi) (30 mg/kg/day, orally), Group 4: Ovariectomized rats + swimming, and Group 5: Ovariectomized rats + swimming + DPPi. After 6 weeks, Alanine aminotransferase (ALT), glucose, insulin, HOMA IR (Homeostatic Model Assessment for Insulin Resistance), FFA (free fatty acids), Tumor necrosis factor alpha (TNF α), IL6, IL1B levels were measured in blood. The livers were collected for Hematoxylin and eosin (H&E) examination and evaluation of hepatic gene expression of SREBP (sterol regulatory element-binding protein1c), PPAR α (peroxisome proliferator-activated receptor alpha), ACC 1 (acetyl-CoA carboxylase), LC3 (microtubule-associated protein 1 light chain 3), SIRT (sirtuin), hepatic triglycerides, IL6, IL10, caspase 3 and AMPK (adenosine monophosphate-activated protein kinase). A significant increase in ALT level and area of liver tissue defects with a significant increase in glucose HOMA IR, serum FFA, IL6, IL1B, TNF α, liver TGs (triglycerides), inflammation, apoptosis, SREBP1c, ACC1 were found in ovariectomized rats as compared to control group with a significant decrease in PPAR α, LC3, AMPK and SIRT1. DPPi treated rats with and without exercise showed a significant improvement in ALT and area of liver tissue defects, inflammation and apoptosis and serum IL6, IL1B, TNF α, FFA, liver LC3, SIRT1, AMPK, TGs, PPAR α, ACC1 and SREBP1c as compared to the ovariectomized group. Findings from the study confirm the derangement of fat metabolism in the ovariectomized rats and showed that incretin-based therapy and exercise synergistically improved liver fat metabolism, achieved significant beneficial metabolic effects and offer full protection against NAFLD.

sp2-Iminosugar glycolipids as inhibitors of lipopolysaccharide-mediated human dendritic cell activation in vitro and of acute inflammation in mice in vivo

Glycolipid mimetics consisting of a bicyclic polyhydroxypiperidine-cyclic carbamate core and a pseudoanomeric hydrophobic tail, termed sp²-iminosugar glycolipids (sp²-IGLs), target microglia during neuroinflammatory processes. Here we have synthesized and investigated new variants of sp²-IGLs for their ability to suppress the activation of human monocyte-derived dendritic cells (DCs) by lipopolysaccharide (LPS) signaling through Toll-like receptor 4. We report that the best lead was (1R)-1-dodecylsulfonyl-5N,6O-oxomethylidenenojirimycin (DSO₂-ONJ), able to inhibit LPS-induced TNFα production and maturation of DCs. Immunovisualization experiments, using a mannoside glycolipid conjugate (MGC) that also suppress LPS-mediated DC activation as control, evidenced a distinct mode of action for the sp²-IGLs: unlike MGCs, DSO₂-ONJ did not elicit internalization of the LPS co-receptor CD14 or induce its co-localization with the Toll-like receptor 4. In a mouse model of LPS-induced acute inflammation, DSO₂-ONJ demonstrated anti-inflammatory activity by inhibiting the production of the pro-inflammatory interleukin-6. The ensemble of the data highlights sp²-IGLs as a promising new class of molecules against inflammation by interfering in Toll-like receptor intracellular signaling.

The spleen as a neuroimmune interface after spinal cord injury

Traumatic spinal cord injury (SCI) causes widespread damage to neurons, glia and endothelia located throughout the spinal parenchyma. In response to the injury, resident and blood-derived leukocytes orchestrate an intraspinal inflammatory response that propagates secondary neuropathology and also promotes tissue repair. SCI also negatively affects autonomic control over peripheral immune organs, notably the spleen. The spleen is the largest secondary lymphoid organ in mammals, with major roles in blood filtration and host defense. Splenic function is carefully regulated by neuroendocrine mechanisms that ensure that the immune responses to infection or injury are proportionate to the initiating stimulus, and can be terminated when the stimulus is cleared. After SCI, control over the viscera, including endocrine and lymphoid tissues is lost due to damage to spinal autonomic (sympathetic) circuitry. This review begins by examining the normal structure and function of the spleen including patterns of innervation and the role played by the nervous system in regulating spleen function. We then describe how after SCI, loss of proper neural control over splenic function leads to systems-wide neuropathology, immune suppression and autoimmunity. We conclude by discussing opportunities for targeting the spleen to restore immune homeostasis, reduce morbidity and mortality, and improve functional recovery after SCI.

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.

Aerobic exercise improves quality of life, psychological well-being and systemic inflammation in subjects with Alzheimer's disease

BACKGROUND

Alzheimer's disease has a destructive drawbacks on the patient and his/her entire family as this disease badly af fects the behavior, cognition and abilities to do activities of daily living (ADL). The physical and mental benefits of exercise are widely known but seldom available to persons suffering from Alzheimer's disease.

OBJECTIVE

The aim of this study was to measure quality of life, systemic inflammation and psychological well-being response to aerobic exercises in Alzheimer's.

METHODS

Forty Alzheimer elderly subjects were enrolled in two groups; the first group received treadmill aerobic exercise, while the second group was considered as a control group and received no training intervention for two months. Assessment of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), Rosenberg Self-Esteem Scale (RSES),Beck Depression Inventory (BDI), Profile of Mood States(POMS) and SF-36 health quality of life (SF-36 HRQL) were taken before and at the end of the study.

RESULTS

There was a 25.2%, 19.4%, 23.5%, 21.3%, 17.7% , 11.7%, 12.5% and 10.1 % reduction in mean values of TNF-α, IL-6, BDI, POMS, health transition SF-36 subscale, bodily pain SF-36 subscale, role functioning: emotional SF-36 subscale and mental health SF-36 subscale respectively in addition to 15.7%, 13.1%, 12.6%, 11.1%, 13.2% and 11.2 % increase in mean values of RSES, physical functioning SF-36 subscale, role functioning:physical SF-36 subscale, general health SF-36 subscale, Vitality SF-36 subscale and Social functioning SF-36 subscale respectively in group (A) received aerobic exercise training, so that there was a significant reduction in the mean values of TNF-α, IL-6, BDI & POMS and increase in the mean values of SF-36 HRQL subscale scores, RSES in group (A) as a result of aerobic exercise training, while the results of group (B) who received no training intervention were not significant. Also, there were significant differences between mean levels of the investigated parameters in group (A) and group (B) at the end of the study (P<0.05).

CONCLUSION

Treadmill walking exercise training is an effective treatment policy to improve quality of life, systemic inflammation and psychological wellbeing in Alzheimer's.

The pituitary adenylate cyclase-activating polypeptide (PACAP) protects adrenal function in septic rats administered etomidate

BACKGROUND

Both hyperinflammation during sepsis and etomidate can suppress adrenal function. In this study, we explored whether treatment with pituitary adenylate cyclase-activating polypeptide (PACAP) relieves adrenal suppression in cecal ligation and puncture (CLP)-induced septic rats.

MATERIALS AND METHODS

Female Sprague-Dawley rats were randomly divided into five groups (n=7 per group), including the sham group, sepsis group (CLP group), sepsis and etomidate group (CLP+ETO group), PACAP group, and etomidate alone group (ETO group). Rats were sacrificed on the third day of sepsis, and blood and adrenal gland samples were obtained for further testing.

RESULTS

The PACAP reduced the apoptosis rate of adrenal cells and peripheral lymphocytes, improving adrenal function, inhibiting the secretion of interferon gamma (IFN-γ) from peripheral lymphocytes, and slightly relieving the suppression of the adrenal function induced by the injection of etomidate in sepsis.

CONCLUSION

In septic conditions, the PACAP protects the adrenal gland by regulating peripheral inflammation, which slightly relieves the toxic effects of etomidate on adrenal function.

Sex-, stress-, and sympathetic post-ganglionic-dependent changes in identity and proportions of immune cells in the dura

Aim of investigation Due to compelling evidence in support of links between sex, stress, sympathetic post-ganglionic innervation, dural immune cells, and migraine, our aim was to characterize the impacts of these factors on the type and proportion of immune cells in the dura. Methods Dural immune cells were obtained from naïve or stressed adult male and female Sprague Dawley rats for flow cytometry. Rats with surgical denervation of sympathetic post-ganglionic neurons of the dura were also studied. Results Immune cells comprise ∼17% of all cells in the dura. These included: macrophages/granulocytes ("Macs"; 63.2% of immune cells), dendritic cells (0.88%), T-cells (4.51%), natural killer T-cells (0.51%), natural killer cells (3.08%), and B-cells (20.0%). There were significantly more Macs and fewer B- and natural killer T-cells in the dura of females compared with males. Macs and dendritic cells were significantly increased by stress in males, but not females. In contrast, T-cells were significantly increased in females with a 24-hour delay following stress. Lastly, Macs, dendritic cells, and T-cells were significantly higher in sympathectomized-naïve males, but not females. Conclusions It may not only be possible, but necessary to use different strategies for the most effective treatment of migraine in men and women.

Sex-, Stress-, and Sympathetic Post-Ganglionic Neuron-Dependent Changes in the Expression of Pro- and Anti-Inflammatory Mediators in Rat Dural Immune Cells

BACKGROUND

Migraine attacks are associated with sterile inflammation of the dura. Immune cells are a primary source of inflammatory mediators, and we therefore sought to further explore the link between dural immune cells and migraine.

OBJECTIVE

Based on the observations that migraine is more common in women than in men, stress is the most common trigger for a migraine attack, and sympathetic post-ganglionic innervation of the dura enables local control of dural immune cells, we hypothesized that stress shifts the balance of inflammatory mediator expression in dural immune cells toward those that trigger a migraine attack, where these changes are larger in females and dependent, at least in part, on sympathetic post-ganglionic innervation of the dura. Our objective was to test this hypothesis.

METHODS

Dura were obtained from naïve or stressed, intact or surgically sympathectomized, adult male and female rats. Dura were assessed immediately or 24 hours after termination of 4 continuous days of unpredictable, mild stressors. Following enzymatic digestion of each dura, myeloid and lymphoid-derived dural immune cells were isolated by fluorescence-activated cell sorting for semi-quantitative polymerase chain reaction analysis.

RESULTS

In myeloid-derived dural immune cells, there was an increase in pro-inflammatory mediator mRNA following stress, particularly in females, which remained elevated with a 24-hour delay after stress. There was a stress-induced decrease in anti-inflammatory mediator mRNA immediately after stress in females, but not males. The stress-induced changes were attenuated in sympathectomized females. In lymphoid-derived dural immune cells, there was a persistent increase in pro-inflammatory mediator mRNA following stress, particularly in females. A stress-induced increase in anti-inflammatory mediator mRNA was also observed in both males and females, and was further attenuated in sympathectomized females.

CONCLUSIONS

Consistent with our hypothesis, there is a stress-induced shift in the balance of pro- and anti-inflammatory mediator expression in dural immune cells that is more pronounced in females, and is dependent, at least in part, on sympathetic post-ganglionic innervation in females. This shift in the balance of inflammatory mediator expression may not only play an important role in triggering migraine attacks, but also suggests it may be possible, if not necessary, to employ different strategies to most effectively treat migraine in men and women.

Catecholamines and acetylcholine are key regulators of the interaction between microbes and the immune system

Recent studies suggest that catecholamines (CAs) and acetylcholine (ACh) play essential roles in the crosstalk between microbes and the immune system. Host cholinergic afferent fibers sense pathogen-associated molecular patterns and trigger efferent cholinergic and catecholaminergic pathways that alter immune cell proliferation, differentiation, and cytokine production. On the other hand, microbes have the ability to produce and degrade ACh and also regulate autogenous functions in response to CAs. Understanding the role played by these neurotransmitters in host-microbe interactions may provide valuable information for the development of novel therapies.

Chemical sympathectomy increases neutrophil-to-lymphocyte ratio in tumor-bearing rats but does not influence cancer progression

The sympathetic nervous system regulates many immune functions and modulates the anti-tumor immune defense response, too. Therefore, we studied the effect of 6-hydroxydopamine induced sympathectomy on selected hematological parameters and inflammatory markers in rats with Yoshida AH130 ascites hepatoma. We found that chemically sympathectomized tumor-bearing rats had significantly increased neutrophil-to-lymphocyte ratio, leukocyte-to-lymphocyte ratio, and plasma levels of tumor necrosis factor alpha. Although our findings showed that sympathetic denervation in tumor-bearing rats led to increased neutrophil-to-lymphocyte ratio, that is an indicator of the disease progression, we found no significant changes in tumor growth and survival of sympathectomized tumor-bearing rats.

Divergent neuroendocrine responses to localized and systemic inflammation

The sympathetic nervous system (SNS) is part of an integrative network that functions to restore homeostasis following injury and infection. The SNS can provide negative feedback control over inflammation through the secretion of catecholamines from postganglionic sympathetic neurons and adrenal chromaffin cells (ACCs). Central autonomic structures receive information regarding the inflammatory status of the body and reflexively modulate SNS activity. However, inflammation and infection can also directly regulate SNS function by peripheral actions on postganglionic cells. The present review discusses how inflammation activates autonomic reflex pathways and compares the effect of localized and systemic inflammation on ACCs and postganglionic sympathetic neurons. Systemic inflammation significantly enhanced catecholamine secretion through an increase in Ca(2+) release from the endoplasmic reticulum. In contrast, acute and chronic GI inflammation reduced voltage-gated Ca(2+) current. Thus it appears that the mechanisms underlying the effects of peripheral and systemic inflammation neuroendocrine function converge on the modulation of intracellular Ca(2+) signaling.

Neural regulation of gastrointestinal inflammation: role of the sympathetic nervous system

The sympathetic innervation of the gastrointestinal (GI) tract regulates motility, secretion and blood flow by inhibiting the activity of the enteric nervous system (ENS) and direct vasoconstrictor innervation of the gut microvasculature. In addition to these well-established roles, there is evidence that the sympathetic nervous system (SNS) can modulate GI inflammation. Postganglionic sympathetic neurons innervate lymphoid tissues and immune cells within the GI tract. Furthermore, innate and adaptive immune cells express receptors for sympathetic neurotransmitters. Activation of these receptors can affect a variety of important immune cell functions, including cytokine release and differentiation of helper T lymphocyte subsets. This review will consider the neuroanatomical evidence of GI immune cell innervation by sympathetic axons, the effects of blocking or enhancing SNS activity on GI inflammation, and the converse modulation of sympathetic neuroanatomy and function by GI inflammation.

Increased IgA responses to the LPS of commensal bacteria is associated with inflammation and activation of cell-mediated immunity in chronic fatigue syndrome

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is accompanied by a) systemic IgA/IgM responses against the lipopolysaccharides (LPS) of commensal bacteria; b) inflammation, e.g. increased plasma interleukin-(IL)1 and tumor necrosis factor (TNF)α; and c) activation of cell-mediated immunity (CMI), as demonstrated by increased neopterin.

METHODS

To study the relationships between the IgA/IgM responses to the LPS of microbiota, inflammation, CMI and the symptoms of ME/CFS we measured the IgA/IgM responses to the LPS of 6 different enterobacteria, serum IL-1, TNFα, neopterin, and elastase in 128 patients with ME/CFS and chronic fatigue (CF). Severity of symptoms was assessed by the Fibromyalgia and Chronic Fatigue Syndrome (FF) Rating Scale.

RESULTS

Serum IL-1, TNFα, neopterin and elastase are significantly higher in patients with ME/CFS than in CF patients. There are significant and positive associations between the IgA responses to LPS and serum IL-1, TNFα, neopterin and elastase. Patients with an abnormally high IgA response show increased serum IL-1, TNFα and neopterin levels, and higher ratings on irritable bowel syndrome (IBS) than subjects with a normal IgA response. Serum IL-1, TNFα and neopterin are significantly related to fatigue, a flu-like malaise, autonomic symptoms, neurocognitive disorders, sadness and irritability.

CONCLUSIONS

The findings show that increased IgA responses to commensal bacteria in ME/CFS are associated with inflammation and CMI activation, which are associated with symptom severity. It is concluded that increased translocation of commensal bacteria may be responsible for the disease activity in some ME/CFS patients.

Evidence for inflammation and activation of cell-mediated immunity in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): increased interleukin-1, tumor necrosis factor-α, PMN-elastase, lysozyme and neopterin

BACKGROUND

There is evidence that inflammatory pathways and cell-mediated immunity (CMI) play an important role in the pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Activation of inflammatory and CMI pathways, including increased levels of cytokines, is known to induce fatigue and somatic symptoms. Given the broad spectrum inflammatory state in ME/CFS, the aim of this study was to examine whether inflammatory and CMI biomarkers are increased in individuals with ME/CFS.

METHODS

In this study we therefore measured plasma interleukin-(IL)1, tumor necrosis factor (TNF)α, and PMN-elastase, and serum neopterin and lysozyme in 107 patients with ME/CFS, 37 patients with chronic fatigue (CF), and 20 normal controls. The severity of ME/CFS was measured with the Fibromyalgia and Chronic Fatigue Syndrome (FF) Rating Scale.

RESULTS

Serum IL-1, TNFα, neopterin and lysozyme are significantly higher in patients with ME/CFS than in controls and CF patients. Plasma PMN-elastase is significantly higher in patients with ME/CFS than in controls and CF patients and higher in the latter than in controls. Increased IL-1 and TNFα are significantly correlated with fatigue, sadness, autonomic symptoms, and a flu-like malaise; neopterin is correlated with fatigue, autonomic symptoms, and a flu-like malaise; and increased PMN-elastase is correlated with concentration difficulties, failing memory and a subjective experience of infection.

CONCLUSIONS

The findings show that ME/CFS is characterized by low-grade inflammation and activation of CMI. The results suggest that characteristic symptoms of ME/CFS, such as fatigue, autonomic symptoms and a flu-like malaise, may be caused by inflammatory mediators, e.g. IL-1 and TNFα.

Interferon-beta, but not tumor necrosis factor-alpha, production in response to poly I:C is maintained despite exhaustive exercise in mice

It remains unclear whether immune response to viral infection is inhibited by severe exercise. We determined whether exhaustive exercise inhibits interferon (IFN)-β and tumor necrosis factor (TNF)-α production after injection of synthetic double-stranded (ds) RNAs, a polyriboinosinic polyribocytidylic acid (poly I:C), as viral infection model. Male C3H/HeN mice, which were divided into exhaustive-exercised and non-exercised groups, were injected with poly I:C (5 mg/kg). Although TNF-α in response to poly I:C was significantly inhibited by exhaustive exercise, IFN-β was no different in both groups. In in-vitro experiments, catecholamines inhibited poly I:C-induced TNF-α, but not IFN-β, production in macrophages. These results suggest that anti-virus cytokine IFN-β in response to poly I:C might be maintained despite severe stressful exercise.

Altered adrenal chromaffin cell function during experimental colitis

The sympathetic nervous system regulates visceral function through the release of catecholamines and cotransmitters from postganglionic sympathetic neurons and adrenal chromaffin cells (ACCs). Previous studies have shown that norepinephrine secretion is decreased during experimental colitis due to the inhibition of voltage-gated Ca(2+) current (I(Ca)) in postganglionic sympathetic neurons. The present study examined whether colonic inflammation causes a similar impairment in depolarization-induced Ca(2+) influx in ACCs using the dextran sulfate sodium (DSS) model of acute colitis in mice. Alterations in ACC function during colitis were assessed using fura 2-acetoxymethyl ester Ca(2+) imaging techniques and perforated patch-clamp electrophysiology. In ACCs isolated from mice with DSS-induced acute colitis, the high-K(+)-stimulated increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) was significantly reduced to 74% of the response of ACCs from control mice. Acute colitis caused a 10-mV hyperpolarization of ACC resting membrane potential, without a significant effect on cellular excitability. Delayed-rectifier K(+) and voltage-gated Na(+) current densities were significantly enhanced in ACCs from mice with DSS-induced acute colitis, with peak current densities of 154 and 144% that of controls, respectively. Importantly, acute colitis significantly inhibited I(Ca) in ACCs between -25 and +20 mV. Peak I(Ca) density in ACCs from mice with DSS-induced acute colitis was 61% that of controls. High-K(+)-induced increases in [Ca(2+)](i) were also reduced in ACCs from mice with 2,4,6-trinitrobenzene sulfonic acid-induced acute colitis and DSS-induced chronic colitis to 68 and 78% of the control responses, respectively. Our results suggest that, during colitis, voltage-dependent Ca(2+) influx is impaired in ACCs. Given the importance of Ca(2+) signaling in exocytosis, these alterations may decrease systemic catecholamine levels, which could play an important role in inflammatory bowel disease. This is the first demonstration of aberrant ACC function during experimental colitis.

Thy-1 mRNA destabilization by norepinephrine a 3' UTR cAMP responsive decay element and involves RNA binding proteins

Thy-1 is a cell surface protein important in immunologic and neurologic processes, including T cell activation and proliferation, and neuronal outgrowth. In murine thymocytes, Thy-1 is downregulated in response to norepinephrine (NE) through posttranscriptional destabilization of its mRNA mediated by βAR/AC/cAMP/PKA signaling. In this study we investigated factors involved in NE/cAMP-mediated Thy-1 mRNA destabilization in S49 thymoma cells, and identified a region containing two copies of the AUUUA regulatory element (ARE), a motif commonly associated with mRNA decay, in the Thy-1 mRNA 3' UTR. Insertion of the Thy-1 ARE region into a reporter gene, resulted in cAMP induced destabilization of the reporter gene mRNA. RNA-protein binding studies revealed multiple Thy-1 ARE binding proteins, including AUF1, HuR, and TIAR. RNA silencing of HuR enhanced cAMP-mediated downregulation of Thy-1 mRNA, in contrast, silencing AUF1 had no effect. Immunoblotting revealed multiple proteins phosphorylated by PKA as a result of NE or cAMP signaling. These results reveal that the machinery of NE/cAMP modulation of Thy-1 mRNA decay involves a cAMP responsive ARE in its 3' UTR and multiple site specific ARE binding proteins. These findings add to our knowledge of Thy-1 mRNA regulation and provide insight into the regulation of ARE containing mRNAs, which impacts stress-related immunosuppression.

Exhaustive exercise reduces TNF-α and IFN-α production in response to R-848 via toll-like receptor 7 in mice

Stressful exercise results in temporary immune depression. However, the impact of exercise on the immune responses via toll-like receptor (TLR) 7, which recognizes the common viral genomic feature, single-stranded RNA, remains unclear. To clarify the effect of stressful exercise on immune function in response to viral infection, we measured the changes in the plasma concentration of tumor necrosis factor (TNF)-α and interferon (IFN)-α, which are induced downstream from the TLR–ligand interaction, in exhaustive-exercised mice immediately after treatment with the imidazoquinoline R-848, which can bind to and activate TLR7. Both exhaustive-exercised (EX) and non-exercised (N-EX) male C3H/HeN mice were injected with R-848 (5 mg kg⁻¹), and blood samples were collected. In addition, RAW264 cells, which are mouse macrophage cells, were cultured 30 min after epinephrine (10 μM) or norepinephrine (10 μM) treatments, and were then stimulated with R-848 (10 μg ml⁻¹). In addition, the effect of propranolol (10 mg kg⁻¹) as blockade of β-adrenergic receptors on R-848-induced TNF-α and IFN-α production in the exercised mice was examined. Both the TNF-α and IFN-α concentrations in the plasma of EX were significantly lower than those in the plasma of N-EX after R-848 injection (P < 0.05 and P < 0.01, respectively), although the R-848 treatment increased the plasma TNF-α and IFN-α concentrations in both groups (P < 0.01, respectively). The R-848-induced TNF-α production in RAW264 cells was significantly inhibited by epinephrine and norepinephrine pre-treatment, although IFN-α was not detected. The propranolol treatment completely inhibited exercise-induced TNF-α and IFN-α suppression in response to R-848 in the mice. These data suggest that EX induces a reduction in TNF-α and IFN-α production in response to R-848, and that these phenomena might be regulated by an exercise-induced elevation of the systemic catecholamines.

The role of stress mediators in modulation of cytokine production by ethanol

Acute ethanol exposure in humans and in animal models activates the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS); the resultant increases in concentration of neuroendocrine mediators contribute to some of the immunosuppressive effects of ethanol. However, the role of these mediators in the ethanol-induced inhibition of inflammatory responses is not clear. This is complicated by the fact that most inflammatory stimuli also activate the HPA axis and SNS, and it has not been determined if ethanol plus an inflammatory stimulus increases these stress responses. Addressing this issue is the major focus of the study described herein. Complementary approaches were used, including quantitative assessment of the stress response in mice treated with polyinosinic-polycytidylic acid (poly I:C, as an inflammatory stimulus) and inhibition of the production or action of key HPA axis and SNS mediators. Treatment of mice with ethanol shortly before treatment with poly I:C yielded a significant increase in the corticosterone response as compared to the response to poly I:C alone, but the increase was small and not likely sufficient to account for the anti-inflammatory effects of ethanol. Inhibition of catecholamine and glucocorticoid production by adrenalectomy, and inhibition of catecholamine action with a sustained release antagonist (nadalol) supported this conclusion and revealed that "excess" stress responses associated with ethanol treatment is not the mechanism of suppression of pro-inflammatory cytokine production, but stress-induced corticosterone does regulate production of several of these cytokines, which has not previously been reported.

Autonomic innervation and regulation of the immune system (1987-2007)

Since 1987, only a few neuroanatomical studies have been conducted to identify the origin of innervation for the immune system. These studies demonstrated that all primary and secondary immune organs receive a substantial sympathetic innervation from sympathetic postganglionic neurons. Neither the thymus nor spleen receive any sensory neural innervation; however, there is evidence that lymph nodes and bone marrow may be innervated by sensory neurons located in dorsal root ganglia. There is no neuroanatomical evidence for a parasympathetic or vagal nerve supply to any immune organ. Thus, the primary pathway for the neural regulation of immune function is provided by the sympathetic nervous system (SNS) and its main neurotransmitter, norepinephrine (NE). Activation of the SNS primarily inhibits the activity of cells associated with the innate immune system, while it either enhances or inhibits the activity of cells associated with the acquired/adaptive immune system. Innate immune cells express both alpha and beta-adrenergic receptor subtypes, while T and B lymphocytes express adrenergic receptors of the beta2 subtype exclusively, except for murine Th2 cells that lack expression of any subtype. Via these adrenergic receptors, NE is able to regulate the level of immune cell activity by initiating a change in the level of cellular activity, which often involves a change in the level of gene expression for cytokines and antibodies.

Neuroimmunomodulation during exercise: role of catecholamines as 'stress mediator' and/or 'danger signal' for the innate immune response

Exercise-induced neuroimmunomodulation is clearly accepted today. The present article reviews the main literature concerning the immunomodulatory capacity of catecholamines on the innate immune response during physical exercise, and presents our laboratory's latest results on this topic. It is well known that the effects of exercise on the immune system are mediated by the 'stress hormones and mediators'. Although catecholamines have usually been regarded as immunosuppressors, they may stimulate innate immune response mechanisms (such as phagocytic function) during exercise-induced stress, even without previous antigenic stimulation. The exercise-induced stimulation of the phagocytic response in particular and the innate responses in general have been considered as a prevention strategy of the athlete's organism in order to prevent the entry and/or maintenance of antigens in a situation where the adaptive immune response seems to be depressed, and thus it has been suggested that catecholamines participate as a 'stress mediator' of these effects. Given this hypothesis, it is also suggested here that catecholamines may be the first 'danger signal' to the immune system during exercise-induced stress.

In vitro adrenergic modulation of cellular immune functions in experimental autoimmune encephalomyelitis

OBJECTIVE

To analyze the effects in vitro of alpha- and beta-adrenoceptor agonists on splenocyte proliferation and on proinflammatory cytokine production in splenocytes and peritoneal macrophages (MF) in different stages of EAE.

METHODS

Splenocytes and peritoneal macrophages were harvested in the acute phase of EAE and in remission, and from controls. The beta-agonist terbutaline, the alpha(1)-agonist methoxamine, and the alpha(2)-agonist UK-14304 were added with ConA or lipopolysaccharide (LPS). TNF-alpha and IFN-gamma contents in supernatant and splenocyte proliferation were determined.

RESULTS

Terbutaline and UK-14304 significantly suppressed TNF-alpha production by MF. However, EAE acute phase rats were resistant to the suppressive effect of UK-14304. Terbutaline significantly suppressed IFN-gamma and TNF-alpha production by splenocytes. EAE acute phase and remission animals showed reduced terbutaline-induced inhibition of IFN-gamma production.

CONCLUSIONS

Disturbed sympathetic-immune communication in EAE is characterized by alterations in adrenergic sensitivity via both alpha- and beta-adrenergic pathways.

Sympathetic blockade in a canine model of gram-negative bacterial peritonitis

We investigated, in a well-established canine model of human sepsis, the effects of two different techniques of sympathetic blockade during bacterial peritonitis on pain relief, hemodynamics, and survival rate. Twenty-two purpose-bred beagles (12-28 months old, weighing 10-12 kg) were studied. Fourteen animals received an epidural infusion of bupivicaine and morphine, and the other eight received either a celiac plexus block (n = 4) or a sham block (n = 4). Eighteen of the 22 animals received an intraperitoneal challenge of Escherichia coli (1-10 x 10(9) CFU kg(-1) body weight). At comparable doses of intraperitoneal-implanted E. coli (2.5-5 x 10(9) CFU kg(-1) body weight), the addition of sympathetic blockade produced a synergistic decrease in survival times (P = 0.002) and mean left ventricular ejection fraction (P = 0.008), and increase in creatinine levels (P = 0.02). There was also a significant increase in tumor necrosis factor (TNF) levels (P = 0.004) and decrease in blood endotoxin clearance (P = 0.006) associated with sympathetic blockade during sepsis. The celiac plexus-blocked animals had no improvement in pain scores, and subjectively looked clinically worse than animals with sepsis without a celiac plexus block. In contrast, the epidural block was effective in blocking the pain and discomfort associated with low lethality doses of intraperitoneal bacteria reflected by no increase in pain scores compared with animals not receiving bacterial challenge. This study shows that during severe bacterial peritonitis, maintenance of sympathetic tone irrespective of pain relief provided is necessary for clearance of bacterial toxins, control of proinflammatory mediator release, hemodynamic stability, and survival.

The relation of aggression, hostility, and anger to lipopolysaccharide-stimulated tumor necrosis factor (TNF)-alpha by blood monocytes from normal men

Aggression, hostility, and anger significantly predict morbidity and mortality from atherosclerotic cardiovascular disease (ACVD). ACVD is believed to be an inflammatory disease characterized by increased expression of a number of proinflammatory cytokines, such as tumor necrosis factor (TNF)-alpha. This study examined the relation of aggression, hostility, and anger to monocyte-associated TNF-alpha expression following lipopolysaccharide (LPS) stimulation. Participants were 62 healthy, non-smoking men (aged 18-45 years). Hostility, anger, verbal, and physical aggression were assessed using the Buss-Perry aggression questionnaire (BPAQ). LPS-stimulated TNF-alpha expression was determined using dual-color flow cytometry gating for CD14(+) cells. After controlling for age, race, education, and alcohol use, scores on the hostility (p=.013), physical aggression (p=.010), and verbal aggression (p=.034) subscales, and the total score (p=.007) on the BPAQ were positively associated with LPS-stimulated TNF-alpha expression. The results suggest that hostility and aggression are associated with an increased expression of TNF-alpha, a cytokine implicated in ACVD.

Norepinephrine-induced hepatocellular dysfunction in early sepsis is mediated by activation of alpha2-adrenoceptors

Gut-derived norepinephrine (NE) has been shown to play a critical role in producing hepatocellular dysfunction in early sepsis, but it is not known whether alpha2-adrenoceptor activation mediates this dysfunction. We infused normal male adult rats with NE, NE plus the specific alpha2-adrenergic antagonist rauwolscine (RW), or vehicle (normal saline) for 2 h. Hepatocellular function was determined by in vivo indocyanine green (ICG) clearance. An isolated perfused liver preparation was also used to assess hepatocellular function by in vitro ICG clearance; NE alone or with RW was added to the perfusate. Rats were subjected to sepsis by cecal ligation and puncture (CLP). At 1 h after CLP, RW was infused for 15 min. At 5 h after CLP, we measured hepatocellular function and serum tumor necrosis factor-alpha (TNF-alpha) levels. Intraportal NE infusion in normal rats produced hepatocellular dysfunction, which was prevented by RW and NE infusion. This is confirmed by findings with the isolated perfused liver preparation. RW administration in early sepsis maintained hepatocellular function and downregulated TNF-alpha production at 5 h after CLP. These results suggest that NE-induced hepatocellular dysfunction in early sepsis is mediated by alpha2-adrenoceptor activation, which appears to upregulate TNF-alpha production. Modulation of hepatic responsiveness to NE by alpha2-adrenergic antagonists should provide a novel approach for maintaining cell and organ functions during sepsis.

Clonidine suppresses plasma and cerebrospinal fluid concentrations of TNF-alpha during the perioperative period

The analgesic properties of alpha(2)-agonists are well known. In experimental models, tumor necrosis factor (TNF)-alpha regulates adrenergic responses in the brain. Constitutive TNF-alpha, in brain regions involved in pain perception, is decreased after the administration of clonidine. We investigated patients undergoing lower-extremity revascularization. Seven patients were treated with clonidine 0.2 mg per os (low), and three patients received 0.4 mg per os clonidine (high) before surgery. Eight patients received placebo and served as controls. Continuous spinal anesthesia was provided by insertion of a pliable catheter into the subarachnoid space. Baseline plasma and cerebrospinal fluid (CSF) samples were obtained before injection of local anesthetic. Samples were analyzed for TNF-alpha using a biologic assay. Systemic and central release of catecholamines were assessed by high-pressure liquid chromatography measurement of norepinephrine in plasma and CSF, vanillylmandelic acid and methoxy hydroxyl phenyl glycol in 24-h urinary excretion, respectively. Clonidine 0.2 mg pretreatment decreased TNF-alpha concentrations both in plasma and CSF. Patients receiving clonidine had lower pain visual analog scale scores and required less morphine compared with the Placebo group (P < 0.01). Preoperative administration of clonidine decreased catecholamine release in the periphery, as well as in the central nervous system. A smaller norepinephrine concentration in plasma and CSF, and less secretion of vanillylmandelic acid (P < 0.01) and methoxy hydroxyl phenyl glycol in the urine, were observed. Larger dose clonidine (0.4 mg) resulted in no detectable TNF-alpha in CSF. These results suggest that an interaction between TNF-alpha and the function of adrenergic neurons in the central nervous system may contribute to the sedative and analgesic effects of adrenergic agonists.

IMPLICATIONS

Preoperative administration of clonidine decreases both plasma and cerebrospinal fluid concentrations of inflammatory cytokines, resulting in perioperative analgesia and decreased sympathetic tone.

Clonidine suppresses plasma and cerebrospinal fluid concentrations of TNF-alpha during the perioperative period

The analgesic properties of alpha(2)-agonists are well known. In experimental models, tumor necrosis factor (TNF)-alpha regulates adrenergic responses in the brain. Constitutive TNF-alpha, in brain regions involved in pain perception, is decreased after the administration of clonidine. We investigated patients undergoing lower-extremity revascularization. Seven patients were treated with clonidine 0.2 mg per os (low), and three patients received 0.4 mg per os clonidine (high) before surgery. Eight patients received placebo and served as controls. Continuous spinal anesthesia was provided by insertion of a pliable catheter into the subarachnoid space. Baseline plasma and cerebrospinal fluid (CSF) samples were obtained before injection of local anesthetic. Samples were analyzed for TNF-alpha using a biologic assay. Systemic and central release of catecholamines were assessed by high-pressure liquid chromatography measurement of norepinephrine in plasma and CSF, vanillylmandelic acid and methoxy hydroxyl phenyl glycol in 24-h urinary excretion, respectively. Clonidine 0.2 mg pretreatment decreased TNF-alpha concentrations both in plasma and CSF. Patients receiving clonidine had lower pain visual analog scale scores and required less morphine compared with the Placebo group (P < 0.01). Preoperative administration of clonidine decreased catecholamine release in the periphery, as well as in the central nervous system. A smaller norepinephrine concentration in plasma and CSF, and less secretion of vanillylmandelic acid (P < 0.01) and methoxy hydroxyl phenyl glycol in the urine, were observed. Larger dose clonidine (0.4 mg) resulted in no detectable TNF-alpha in CSF. These results suggest that an interaction between TNF-alpha and the function of adrenergic neurons in the central nervous system may contribute to the sedative and analgesic effects of adrenergic agonists.

IMPLICATIONS

Preoperative administration of clonidine decreases both plasma and cerebrospinal fluid concentrations of inflammatory cytokines, resulting in perioperative analgesia and decreased sympathetic tone.

Noradrenaline induces phosphorylation of ERK-2 in human peripheral blood mononuclear cells after induction of alpha(1)-adrenergic receptors

alpha(1)-Adrenergic receptors (ARs) are not expressed by peripheral blood mononuclear cells (PBMCs) of healthy human individuals. However, in the present study we show that alpha(1)-ARs can be induced in lymphocytes after culturing with either the mitogen PHA or the glucocorticoid dexamethasone. Moreover, incubation of these activated PBMCs with noradrenaline (NA) results in enhanced phosphorylation of ERK-2, a kinase involved in the activation of many immune functions. Similar induction of alpha(1)-AR mRNA with concomitant NA-induced activation of ERK-2 occurs in monocytes after culture with LPS. Our results demonstrate that functional alpha(1)-ARs can be induced on PBMCs and that these alpha(1)-ARs mediate NA-induced activation of ERK-2.

Interactions between the alpha(2)-adrenergic and the prostaglandin response in the regulation of macrophage-derived tumor necrosis factor

Mediators such as prostaglandin E(2) (PGE(2)) and norepinephrine (NE) regulate macrophage (M&phi;) responsiveness. Activation of alpha(2)-adrenergic receptors on M&phi; potentiates lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNFalpha) production. PGE(2) inhibits LPS-stimulated TNFalpha production and gene expression, a response that can be desensitized by pretreatment of M&phi; with PGE(2). We have determined that concomitant pretreatment of M&phi; with PGE(2) and the alpha(2)-adrenergic agonist UK-14304 (UK) can prevent the PGE(2)-induced desensitization. PGE(2) concentration-effect curves have been determined for the inhibition of LPS-stimulated TNFalpha production by murine peritoneal M&phi;. The addition of 10 nM UK to M&phi; in culture significantly shifts the PGE(2) concentration-effect curve to the right; pretreatment of M&phi; with UK significantly shifts the PGE(2) concentration-effect curve to the left; and pretreatment with the cyclooxygenase inhibitor, indomethacin, increases the maximum response of PGE(2). Preincubation of M&phi; with PGE(2) (0.5 h) followed by washing significantly shifts the subsequent PGE(2) concentration-effect curve to the right. Concomitant preincubation of M&phi; with PGE(2) and UK prevents this rightward shift, an effect that is blocked by the alpha(2)-adrenergic receptor antagonist yohimbine. Northern blot analysis demonstrates that UK increases LPS-induced TNFalpha mRNA accumulation, and this is blocked by yohimbine, while PGE(2) decreases TNFalpha mRNA accumulation. Preincubation of M&phi; with PGE(2) prevents PGE(2) regulation of TNFalpha mRNA, and concomitant preincubation of M&phi; with PGE(2) and UK reverses this effect. These investigations support the role of NE as a regulator of M&phi; TNFalpha production, a response that has functional interactions with M&phi; sensitivity to PGE(2).

Synergistic interaction of catecholamine hormones and Mycobacterium avium results in the induction of interleukin-10 mRNA expression by murine peritoneal macrophages

The results of this investigation provides evidence that catecholamine hormones interact with macrophages that are infected with Mycobacterium avium resulting in the induction of IL-10 mRNA and protein. The effect of catecholamine hormones was prevented by treating the cells with the beta-adrenergic receptor antagonist propranolol but not by alpha-adrenergic antagonist phentolamine. The effect of catecholamine stimulation was mimicked by the addition of beta-2 adrenergic agonists and by the addition of cAMP to the infected macrophage cultures. These observations suggest that sympathetic nervous system activation together with microbial infection results in a synergistic interaction that could result in the control of inflammatory processes.

Exogenous and endogenous catecholamines inhibit the production of macrophage inflammatory protein (MIP) 1 alpha via a beta adrenoceptor mediated mechanism

Noradrenaline (NA) and adrenaline (Ad) are modulators of cytokine production. Here we investigated the role of these neurotransmitters in the regulation of macrophage inflammatory protein (MIP)-1alpha expression. Pretreatment of RAW 264.7 macrophages with NA or Ad decreased, in a concentration-dependent manner (1 nM-100 microM), MIP-1alpha release induced by bacterial lipopolysaccharide (LPS 10 ng ml(-1) LPS). The effect of NA was reversed by the selective beta-adrenoceptor antagonist propranolol (10 microM), but not by the alpha-adrenoceptor antagonist phentolamine (10 microM). In the concentration range of 10 nM-10 microM, isoproterenol, a beta-adrenoceptor agonist, but not phenylephrine (a selective alpha1-adrenoceptor agonist) or UK-14304 (a selective alpha2-adrenoceptor agonist) mimicked the inhibitory effects of catecholamines on MIP-1alpha production. Increases in intracellular cyclic adenosine monophosphate, elicited either by the selective type IV phosphodiesterase inhibitor rolipram (0.1 - 10 microM), or by prostaglandin E2, (10 nM-10 microM) decreased MIP-1alpha release, suggesting that increased cyclic AMP may contribute to the suppression of MIP-1alpha release by beta-adrenoceptor stimulation. Northern blot analysis demonstrated that NA (100 nM-10 microM), Ad, isoproterenol, as well as rolipram (100 nM-10 microM) decreased LPS-induced MIP-1alpha mRNA accumulation. NA and Ad (1-100 microM) also decreased MIP-1alpha production in thioglycollate-elicited murine peritoneal macrophages. Pretreatment of mice with either isoproterenol (10 mg kg(-1), i.p.) or rolipram (25 mg kg(-1), i.p.) decreased LPS-induced plasma levels of MIP-1alpha, while propranolol (10 mg kg(-1), i.p.) augmented the production of this chemokine, confirming the role of a beta-adrenoceptor mediated endogenous catecholamine action in the regulation of MIP-1alpha production in vivo. Thus, based on our data we conclude that catecholamines are important endogenous regulators of MIP-1alpha expression in inflammation.

Changes in noradrenergic sensitivity to tumor necrosis factor-alpha in brains of rats administered clonidine

Tumor necrosis factor-alpha (TNF alpha) and the imidazoline clonidine modulate norepinephrine (NE) release from noradrenergic nerve terminals in the central nervous system. The present study demonstrates an intrinsic association between presynaptic alpha 2-adrenergic receptor sensitivity and TNF alpha responsiveness in governing this NE release. Superfusion and electrical field stimulation were applied to a series of rat hippocampal brain slices in order to study the regulation of [3H]-NE release. The alpha 2-adrenergic agonist clonidine and the cytokine TNF alpha concentration-dependently inhibit [3H]-NE release; whereas, the alpha 2-adrenergic antagonist idazoxan potentiates [3H]-NE release. The fractional release of [3H]-NE during field stimulation of control hippocampal slices was decreased by the addition of TNF alpha in a concentration-dependent manner, an effect which was potentiated by the alpha 2-adrenergic antagonist idazoxan; whereas, TNF alpha attenuated the concentration-dependent potentiating effect of idazoxan. Furthermore, constitutive TNF alpha, demonstrated to be present in several brain areas, was significantly decreased following administration of the alpha 2-adrenergic agonist clonidine (0.6 mg/kg, i.p., twice daily) to rats for either 1 or 14 days, without a change in TNF alpha mRNA accumulation. We next investigated whether the presynaptic sensitivity to TNF alpha was changed after clonidine administration to rats. TNF alpha enhanced, rather than inhibited, [3H]-NE release after 1 day of clonidine administration, while a suppressed sensitivity to TNF alpha was observed in the hippocampus after 14 days of clonidine administration. In addition, in the presence of idazoxan, TNF alpha potentiation of [3H]-NE release after 1 day clonidine administration was reversed to a decreased inhibition as compared to control slices exposed to idazoxan. Therefore, the temporary reversal in the presynaptic TNF alpha response after 1 day of clonidine administration illustrates a mechanism of action for its persistent antihypertensive effect, its transient sedative and antihyperpathic effects, and its acute ability to promote antidepressants. These results demonstrate a novel role for an immune mediator in the central nervous system, and demonstrates that presynaptic TNF alpha responsiveness is intimately associated with adrenergic receptor sensitivity.