Role and function of macrophages in the metabolic syndrome

Macrophages are key innate immune effector cells best known for their role as professional phagocytes, which also include neutrophils and dendritic cells. Recent evidence indicates that macrophages are also key players in metabolic homoeostasis. Macrophages can be found in many tissues, where they respond to metabolic cues and produce pro- and/or anti-inflammatory mediators to modulate metabolite programmes. Certain metabolites, such as fatty acids, ceramides and cholesterol crystals, elicit inflammatory responses through pathogen-sensing signalling pathways, implicating a maladaptation of macrophages and the innate immune system to elevated metabolic stress associated with overnutrition in modern societies. The outcome of this maladaptation is a feedforward inflammatory response leading to a state of unresolved inflammation and a collection of metabolic pathologies, including insulin resistance, fatty liver, atherosclerosis and dyslipidaemia. The present review summarizes what is known about the contributions of macrophages to metabolic diseases and the signalling pathways that are involved in metabolic stress-induced macrophage activation. Understanding the role of macrophages in these processes will help us to develop therapies against detrimental effects of the metabolic syndrome.     

Adenosine reduces reactive oxygen species and interleukin-8 production by <Emphasis Type="Italic">Trichomonas vaginalis-</Emphasis>stimulated neutrophils

Trichomonas vaginalis is a flagellated protozoan that affects the human urogenital tract causing 276.4 million new infections a year. The parasite elicits a vaginal mucosal infiltration of immune cells, especially neutrophils which are considered to be primarily responsible for cytological change observed at the infection site as well as the major contributor in the inflammatory response against the parasite. Extracellular nucleotides and their nucleosides are signaling compounds involved in several biological processes, including inflammation and immune responses. Once in the extracellular space, the nucleotides and nucleosides can directly activate the purinergic receptors. Herein, we investigated the involvement of purinergic signaling on the production of reactive oxygen species (ROS) and cytokines by T. vaginalis-stimulated neutrophils. Parasites were able to induce an increase in ROS and IL-8 levels while they did not promote IL-6 secretion or neutrophil elastase activity. Adenine and guanine nucleotides or nucleosides were not able to modulate ROS and cytokine production; however, when T. vaginalis-stimulated neutrophils were incubated with adenosine and adenosine deaminase inhibitor, the levels of ROS and IL-8 were significantly reduced. These immunosuppressive effects were probably a response to the higher bioavailability of adenosine found in the supernatant as result of inhibition of enzyme activity. The involvement of P1 receptors was investigated by immunofluorescence and A1 receptor was the most abundant. Our data show that the influence of purinergic signaling, specifically those effects associated with adenosine accumulation, on the modulation of production of proinflammatory mediators by T. vaginalis-stimulated neutrophils contribute to the understanding of immunological aspects of trichomoniasis.     

Ginsenoside Rg1, a novel glucocorticoid receptor agonist of plant origin, maintains glucocorticoid efficacy with reduced side effects

Glucocorticoids (GCs) are widely used to treat inflammatory diseases. However, they cause debilitating side effects, which limit the use of these compounds. In the past decade, many researchers have attempted to find so-called dissociated GCs that have separate distinct transactivation and transrepression activities. Anti-inflammation of GCs is a result of glucocorticoid receptor (GR)-mediated transactivation and transrepression in some tissues, similar to their side effects; therefore, the goal to discover a compound that has anti-inflammatory properties, but lacks the negative side effects seen with GCs, has yet to be achieved. In the present study, we introduce a plant-derived compound, ginsenoside Rg1, which possesses GC and estrogen-like activities. In this study, we show that Rg1 downmodulates LPS-induced proinflammatory cytokine release and inhibits NF-κB nuclear translocation and DNA binding activity. The negative effects on NF-κB activation are due to a decrease in IκB phosphorylation and protein stabilization. Furthermore, the inhibitory effect of Rg1 on NF-κB is GR-dependent, as small interfering RNA knockdown of GR abrogated this function. Rg1 also displayed profound inhibitory effects on LPS-induced MAPK activation. Importantly, Rg1 did not impair proliferation or differentiation of mouse osteoblasts. Finally, we show that Rg1 can effectively inhibit acute and chronic inflammation in vivo, but it does not cause hyperglycemia or osteoporosis as seen with dexamethasone. These results suggest that ginsenoside Rg1 may serve as a novel anti-inflammatory agent and may exhibit a potential profile for therapeutic intervention in inflammatory diseases.     

Inflammatory Hypoxia: Role of Hypoxia-Inducible Factor

Sites of inflammation are characterized by significant changes in metabolic activity. Shifts in energy supply and demand can result in diminished delivery and/or avai lability of oxygen, leading to inflammation-associated tissue hypoxia and metabolic acidosis. These shifts in tissue metabolism, as indicated by previous studies, are frequently associ ated with vasculitis and profound recruitment of inflammatory cell types, particularly myeloid cells such as neutrophils ( PMN) and monocytes.Here, we review recent work addressing the influence of hypoxia on development of inflammatory lesions, with particular emphasis on molecular pathways regulated by hypoxia-inducible factor (HIF).     

六种中药及其复方对鳗鲡致病性气单胞菌的体外抑制作用

针对病鳗内脏中分离的5 株致病性气单胞菌, 采用琼脂稀释法测定五倍子、石榴皮、大黄、虎杖、黄芩及黄连各味中药的最低抑菌浓度(MIC)和最低杀菌浓度(MBC); 再根据棋盘法设计15 种双联用药方和4 种三联用药方, 同样检测各组合配方的抑菌作用。实验结果表明, 6 味中药对养殖鳗鲡5 株致病性气单胞菌均有不同程度的抗菌效果, 其中五倍子的抑菌作用最强, 其次是大黄和石榴皮, 而黄连的抑菌效果最差; 15 种双联用药方较各味中药单用的抑菌活性绝大多数出现增强, 抑菌浓度至少减低39%, FICFIC≤0.5 表现显著增强抗菌活性的协同比例占23.3%; 4 种三联用药方对5 株致病性气单胞菌均具有显著的协同抑制效应, 复方中单味中药的抑菌浓度可以降低80%以上; 而双联用HC14 对4 株致病菌出现FIC≥2 的降低彼此抗菌活性的相互拮抗现象。由此说明合理运用不同中药的联用配伍, 不仅可提高单味中药的抗菌疗效, 而且大大减少了单一中药在实际养殖生产中的给药浓度, 降低药物在环境中的残留量, 防止残留药物造成环境污染, 并且降低用药成本, 提高水产养殖业的经济和社会效益。研究为中药复方防治细菌性鱼病提供科学理论参考。       

Ellagitannins modulate the inflammatory response of human neutrophils ex vivo

BackgroundTannin-rich plant materials are commonly used in the traditional medicine as external anti-inflammatory, antioxidant and antimicrobial agents. Plant extracts containing significant quantities of tannins are often used in the prevention and treatment of oral cavity diseases such as periodontosis or gingivitis. The contribution of pure ellagitannins to the observed anti-inflammatory activity of tannin-rich remedies is still not resolved.PurposeThe aim of the present study the study was to establish if ellagitannins and their precursor – pentagalloylglucose (1) can modulate the inflammatory response of ex-vivo stimulated neutrophils.MethodsHuman neutrophils were isolated from the buffy coats obtained from healthy volunteers. Neutrophils were cultivated with or without tested compounds. The influence of ellagitannins and 1 on the production and release of pro-inflammatory factors such as elastase, reactive oxygen species, interleukin-8, tumour necrosis factor alpha (TNF-α) and metalloproteinase-9 was evaluated using ELISA sets or chemical methods. The effect on surface expression of toll like receptor 4 (TLR-4) and apoptosis was also checked using flow cytometry.ResultsThe results showed that ellgitannins modulate the inflammatory response of human neutrophils by the inhibition of production and release of chosen cytokines and pro-inflammatory enzymes. By the induction of TNF-α ellagitannins enhance neutrophil apoptosis, which is of interest in the case of chronic inflammation within oral cavity. Ellagitannins also decrease the surface expression of TLR-4 in activated neutrophils.ConclusionThe results support the traditional use of tannin-rich products in the prevention and treatment of oral cavity diseases. The present study proves the substantial contribution of ellagitannins to the anti-inflammatory activity of tannin-rich medicinal plant materials.     

Modulation and Apoptosis of Neutrophil Granulocytes by Extracorporeal Photopheresis in the Treatment of Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (cGVHD) is a common side effect of allogeneic stem cell transplantation and a major cause of morbidity and mortality in affected patients. Especially skin, eyes and oral mucosa are affected. This can lead to pain and functional impairment. Extracorporeal photopheresis (ECP) is an effective immunomodulatory therapy with minimal side effects but its mode of action is still largely unknown. The objective of the present study was to examine the effects of ECP on neutrophil granulocytes in patients with cGVHD. Analysis of leukocytes from cGVHD patients obtained from the ECP device during treatment showed that neutrophil granulocytes account for the majority of cells treated during ECP. Neutrophils from healthy donors treated in vitro with 8-methoxypsoralen and UVA light as well as neutrophils from buffy coats of patients with cGVHD treated by ECP showed increased apoptosis and decreased half-life. In remaining non-apoptotic cells chemoirradiation resulted in loss of activation markers and reduced effector functions. This was accompanied by an increase in extracellular arginase-1 activity. Additional comparison of neutrophils isolated from blood of cGVHD patients before and 24h after ECP revealed a decreased half-life and reduction of effector functions of post-ECP neutrophils ex vivo. These observations strongly suggest that ECP induces both apoptosis and physiological changes in neutrophils and that these changes also take place in vivo. This study is the first to show that ECP modulates apoptosis and inflammatory activity in neutrophil granulocytes, indicating that neutrophils may significantly contribute to the overall immunomodulatory effects attributed to this treatment.     

Synthesis of novel steroidal agonists,partial agonists,and antagonists for the glucocorticoid receptor

Adverse effects of glucocorticoids could be limited by developing new compounds that selectively modulate anti-inflammatory activity of the glucocorticoid receptor (GR). We have synthesized a novel series of steroidal GR ligands, including potent agonists, partial agonists and antagonists with a wide range of effects on inhibiting secretion of interleukin-6. Some of these new ligands were designed to directly impact conformational stability of helix-12, in the GR ligand-binding domain (LBD). These compounds modulated GR activity and glucocorticoid-induced gene expression in a manner that was inversely correlated to the degree of inflammatory response. In contrast, compounds designed to directly modulate LBD epitopes outside helix-12, led to dissociated levels of GR-mediated gene expression and inflammatory response. Therefore, these new series of compounds and their derivatives will be useful to dissect the ligand-dependent features of GR signaling specificity.     

Immune effects of glycolysis or oxidative phosphorylation metabolic pathway in protecting against bacterial infection

The metabolism of immune cells reprograms inflammatory responses to protect against infection by pathogenic microorganisms, but the immune effects of glycolysis and the oxidative phosphorylation (OXPHOS) metabolic pathway remain unclear. Herein, the effects of glycolysis or OXPHOS on the neutrophils and T cells were investigated using a pharmacological approach in mice. 2-Deoxy-d -glucose (2-DG), which blocks the key enzyme hexokinase of glycolysis, and dimethyl malonate (DMM), which blocks the key element succinate of OXPHOS, both efficiently expanded the population of neutrophils, but significantly inhibited tumor necrosis factor a secretion and reactive oxygen species (ROS) production. These compounds also effectively inhibited the differentiation of type 1 T helper cells (Th1) but had no effects on the differentiation of type 2 T helper cells (Th2) and regulatory T cells. A study of the underlying mechanism showed that hypoxia-inducible factor 1-alpha (HIF1α) was an upstream signal in the regulation of glycolysis, but not OXPHOS. In thioglycolate broth-induced neutrophil peritonitis, blockade of glycolysis or OXPHOS efficiently expanded the population of neutrophils, but diminished their abilities to secrete proinflammatory factors, produce ROS, and phagocytose bacteria. In Listeria monocytogenes bacteria-infected mice, 2-DG or DMM treatment consistently inhibited antibacterial activity and Th1 function. Thus, our results provide a basis for comprehensively understanding the role of glycolysis and OXPHOS in anti-infectious immunity.     

Oxidation of n-formyl methionyl chemotactic peptide by human neutrophils

Human neutrophils during phagocytosis oxidized the synthetic chemotactic peptide, n-formyl methionyl-leucyl-phenylalanine (n-FMLP), to its sulfoxide derivative (n-FMsLP). The oxidation of n-FMLP by phagocytosing neutrophils was inhibited by methionine, but not by methionine sulfoxide, leucine, or phenylalanine, confirming that it was the methionine moiety of n-FMLP that was oxidized. The oxidation of n-FMLP was also inhibited by myeloperoxidase inhibitors or catalase, but not by SOD or mannitol, suggesting the involvement of the myeloperoxidase system. Since n-FMsLP does not have chemotactic activity, the oxidation of n-FMLP by phagocytosing neutrophils may be one mechanism by which neutrophils modulate the inflammatory process.     

Neutrophil-derived Oxidants and Proteinases as Immunomodulatory Mediators in Inflammation

Neutrophils generate potent microbicidal molecules via the oxygen-dependent pathway, leading to the generation of reactive oxygen intermediates (ROI), and via the non-oxygen dependent pathway, consisting in the release of serine proteinases and metalloproteinases stored in granules. Over the past years, the concept has emerged that both ROI and proteinases can be viewed as mediators able to modulate neutrophil responses as well as the whole inflammatory process. This is well illustrated by the oxidative regulation of proteinase activity showing that oxidants and proteinases acts is concert to optimize the microbicidal activity and to damage host tissues. ROI and proteinases can modify the activity of several proteins involved in the control of inflammatory process. Among them, tumour necrosis factor-alpha and interleukin-8, are elective targets for such a modulation. Moreover, ROI and proteinases are also able to modulate the adhesion process of neutrophils to endothelial cells, which is a critical step in the inflammatory process.     

Glycogen accumulation in polymorphonuclear leukocytes, and other intracellular alterations that occur during inflammation

Neutrophils isolated from the blood were compared to those from inflammatory exudates in the peritoneal cavity of guinea pigs. Inflammatory neutrophils were shown to have 10-fold more glycogen than blood neutrophils. This was also reflected in the morphology of these cells. The large accumulations of glycogen in inflammatory neutrophils exists in ordered arrays of beta-granules. Other morphological changes including accumulations of lipid droplets and a decrease in the number of lysosomal granules also accompany the change from blood neutrophils to inflammatory neutrophils. These results show that there are major metabolic differences in the two types of neutrophils.     

Crosstalk between Adipocytes and Immune Cells in Adipose Tissue Inflammation and Metabolic Dysregulation in Obesity

Recent findings, notably on adipokines and adipose tissue inflammation, have revised the concept of adipose tissues being a mere storage depot for body energy. Instead, adipose tissues are emerging as endocrine and immunologically active organs with multiple effects on the regulation of systemic energy homeostasis. Notably, compared with other metabolic organs such as liver and muscle, various inflammatory responses are dynamically regulated in adipose tissues and most of the immune cells in adipose tissues are involved in obesity-mediated metabolic complications, including insulin resistance. Here, we summarize recent findings on the key roles of innate (neutrophils, macrophages, mast cells, eosinophils) and adaptive (regulatory T cells, type 1 helper T cells, CD8 T cells, B cells) immune cells in adipose tissue inflammation and metabolic dysregulation in obesity. In particular, the roles of natural killer T cells, one type of innate lymphocyte, in adipose tissue inflammation will be discussed. Finally, a new role of adipocytes as antigen presenting cells to modulate T cell activity and subsequent adipose tissue inflammation will be proposed.     

Lipid emulsions for parenteral nutrition in critical illness

Critical illness is a life-threatening multisystem process that can result in significant morbidity and mortality. In most patients, critical illness is preceded by a physiological deterioration, characterized by a catabolic state and intense metabolic changes, resulting in malnutrition and impaired immune functions. In this context, parenteral lipid emulsions may modulate inflammatory and immune reactions, depending on their fatty acid composition. These effects appear to be based on complex modifications in the composition and structure of cell membranes, through eicosanoid and cytokine synthesis and by modulation of gene expression. The pathophysiological mechanisms underlying these fatty acid-induced immune function alterations in critical ill patients are however complex and partially understood. Indeed, despite a very abundant literature, experimental and clinical data remain contradictory. The optimization of lipid emulsion composition thus represents a major challenge for clinical medicine, to adequately modulate the inflammatory pathways. In the present review, we first address the metabolic response to aggression, the effects of parenteral lipid emulsions on inflammation and immunity, and finally the controversial place of these lipid emulsions during critical illness. The analysis furthermore highlights the pathophysiological mechanisms underlying the differential effects of lipid emulsions and their potential for improving the handling of critically ill patients.     

Adipocytes under assault: Environmental disruption of adipose physiology

The burgeoning obesity epidemic has placed enormous strains on individual and societal health mandating a careful search for pathogenic factors, including the contributions made by endocrine disrupting chemicals (EDCs). In addition to evidence that some exogenous chemicals have the capacity to modulate classical hormonal signaling axes, there is mounting evidence that several EDCs can also disrupt metabolic pathways and alter energy homeostasis. Adipose tissue appears to be a particularly important target of these metabolic disruptions. A diverse array of compounds has been shown to alter adipocyte differentiation, and several EDCs have been shown to modulate adipocyte physiology, including adipocytic insulin action and adipokine secretion. This rapidly emerging evidence demonstrating that environmental contaminants alter adipocyte function emphasizes the potential role that disruption of adipose physiology by EDCs may play in the global epidemic of metabolic disease. Further work is required to better characterize the molecular targets responsible for mediating the effects of EDCs on adipose tissue. Improved understanding of the precise signaling pathways altered by exposure to environmental contaminants will enhance our understanding of which chemicals pose a threat to metabolic health and how those compounds synergize with lifestyle factors to promote obesity and its associated complications. This knowledge may also improve our capacity to predict which synthetic compounds may alter energy homeostasis before they are released into the environment while also providing critical evidentiary support for efforts to restrict the production and use of chemicals that pose the greatest threat to human metabolic health. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.     

High-throughput screening for small-molecule adiponectin secretion modulators

Adiponectin is an adipokine secreted by adipocytes and plays a role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. Several studies have shown that upregulation of adiponectin has a number of therapeutic benefits. Although peroxisome proliferator-activated receptor γ (PPARγ) agonists are known to increase adiponectin secretion both in cultured adipocytes and humans, they have several side effects, such as weight gain, congestive heart failure, and edema. Therefore, adiponectin secretion modulators that do not possess PPARγ agonistic activity seem to promising for a number of conditions. Here, the authors report on the development of a reporter-based high-throughput screening (HTS) assay using insulin-resistant-mimic 3T3-L1 adipocytes for discovery of adiponectin secretion modulators. They screened a library of approximately 100 000 small-molecule compounds using this model, performed several follow-up screens, and identified six hit compounds that increase adiponectin secretion without having PPARγ agonistic activity. These compounds may be useful drug candidates for diabetes, obesity, atherosclerosis, and other metabolic syndromes. This HTS assay might be applicable to screening for other adipokine modulators that can be useful for the treatment of other conditions.     

The Endocannabinoid/Endovanilloid N-Arachidonoyl Dopamine (NADA) and Synthetic Cannabinoid WIN55,212-2 Abate the Inflammatory Activation of Human Endothelial Cells

Although cannabinoids, such as Δ⁹-tetrahydrocannabinol, have been studied extensively for their psychoactive effects, it has become apparent that certain cannabinoids possess immunomodulatory activity. Endothelial cells (ECs) are centrally involved in the pathogenesis of organ injury in acute inflammatory disorders, such as sepsis, because they express cytokines and chemokines, which facilitate the trafficking of leukocytes to organs, and they modulate vascular barrier function. In this study, we find that primary human ECs from multiple organs express the cannabinoid receptors CB₁R, GPR18, and GPR55, as well as the ion channel transient receptor potential cation channel vanilloid type 1. In contrast to leukocytes, CB₂R is only minimally expressed in some EC populations. Furthermore, we show that ECs express all of the known endocannabinoid (eCB) metabolic enzymes. Examining a panel of cannabinoids, we demonstrate that the synthetic cannabinoid WIN55,212-2 and the eCB N-arachidonoyl dopamine (NADA), but neither anandamide nor 2-arachidonoylglycerol, reduce EC inflammatory responses induced by bacterial lipopeptide, LPS, and TNFα. We find that endothelial CB₁R/CB₂R are necessary for the effects of NADA, but not those of WIN55,212-2. Furthermore, transient receptor potential cation channel vanilloid type 1 appears to counter the anti-inflammatory properties of WIN55,212-2 and NADA, but conversely, in the absence of these cannabinoids, its inhibition exacerbates the inflammatory response in ECs activated with LPS. These data indicate that the eCB system can modulate inflammatory activation of the endothelium and may have important implications for a variety of acute inflammatory disorders that are characterized by EC activation.     

Dual action of isoprenols from herbal medicines on both PPARgamma and PPARalpha in 3T3-L1 adipocytes and HepG2 hepatocytes

Several herbal medicines improve hyperlipidemia, diabetes and cardiovascular diseases. However, the molecular mechanism underlying this improvement has not yet been clarified. In this study, we found that several isoprenols, common components of herbal plants, activate human peroxisome proliferator-activated receptors (PPARs) as determined using the novel GAL4 ligand-binding domain chimera assay system with coactivator coexpression. Farnesol and geranylgeraniol that are typical isoprenols in herbs and fruits activated not only PPARgamma but also PPARalpha as determined using the chimera assay system. These compounds also activated full-length human PPARgamma and PPARalpha in CV1 cells. Moreover, these isoprenols upregulated the expression of some lipid metabolic target genes of PPARgamma and PPARalpha in 3T3-L1 adipocytes and HepG2 hepatocytes, respectively. These results suggest that herbal medicines containing isoprenols with dual action on both PPARgamma and PPARalpha can be of interest for the amelioration of lipid metabolic disorders associated with diabetes.