Galectins as inflammatory mediators

Over the last decade a vast amount of reports have shown that galectin-1 and galectin-3 are important mediators of inflammation. In this review we describe how the galectins may be involved in several parts of the inflammatory process, including the recruitment of neutrophils into an infected tissue and the recognition and killing of bacteria by activation of the tissue destructive phagocytic respiratory burst. During bacterial infection or aseptic inflammatory processes, galectins are produced and released by e.g. infected epithelium, activated tissue-resident macrophages and endothelial cells. These extracellular galectins may facilitate binding of neutrophils to the endothelium by cross-linking carbohydrates on the respective cells. Further the galectins improve binding of the neutrophil to the extracellular matrix proteins laminin and fibronectin, and are potential chemotactic factors, inducing migration through the extracellular matrix towards the inflammatory focus. When the cells encounter bacteria, galectin-3 could function as an opsonin, cross-linking bacterial lipopolysaccharide or other carbohydrate-containing surface structures to phagocyte surface glycoconjugates. Both galectin-1 and galectin-3 have the capacity to induce a respiratory burst in neutrophils, provided that the cells have been primed by degranulation and receptor upregulation. The reactive oxygen species produced may be destructive to the invading micro-organisms as well as to the surrounding host tissue, pointing out the possible role of galectins, not only in defence toward infection, but also in inflammatory-induced tissue destruction. Published in 2004.     

B cells as under-appreciated mediators of non-auto-immune inflammatory disease

B lymphocytes play roles in many auto-immune diseases characterized by unresolved inflammation, and B cell ablation is proving to be a relatively safe, effective treatment for such diseases. B cells function, in part, as important sources of regulatory cytokines in auto-immune disease, but B cell cytokines also play roles in other non-auto-immune inflammatory diseases. B cell ablation may therefore benefit inflammatory disease patients in addition to its demonstrated efficacy in auto-immune disease. Current ablation drugs clear both pro- and anti-inflammatory B cell subsets, which may unexpectedly exacerbate some pathologies. This possibility argues that a more thorough understanding of B cell function in human inflammatory disease is required to safely harness the clinical promise of B cell ablation. Type 2 diabetes (T2D) and periodontal disease (PD) are two inflammatory diseases characterized by little autoimmunity. These diseases are linked by coincident presentation and alterations in toll-like receptor (TLR)-dependent B cell cytokine production, which may identify B cell ablation as a new therapy for co-affected individuals. Further analysis of the role B cells and B cell cytokines play in T2D, PD and other inflammatory diseases is required to justify testing B cell depletion therapies on a broader range of patients.     

Galectins as modulators of cell adhesion

The galectins are a family of carbohydrate-binding proteins that are distributed widely in metazoan organisms. Each galectin exhibits a specific pattern of expression in various cells and tissues, and expression is often closely regulated during development. Although these proteins are found mainly in the cell cytoplasm, some are secreted from cells and interact with appropriately glycosylated proteins at the cell surface or within the extracellular matrix. These receptors include cell-adhesion molecules such as integrins, and matrix glycoproteins such as laminin and fibronectin isoforms. Recent studies have increased understanding of the roles of the galectins in regulating cell-cell and cell-matrix adhesion. These interactions are critically involved in modulation of normal cellular motility and polarity and during tissue formation, and loss of adhesive function is implicated in several disease states including tumour progression, inflammation and cystic development in branching epithelia such as kidney tubules. This review discusses recent progress in defining the specificities and mechanisms of action of secreted galectins as multifunctional cell regulators.     

The evolution of inflammatory mediators

Invertebrates do not display the level of sophistication in immune reactivity characteristic of mammals and other 'higher' vertebrates. Their great number and diversity of forms, however, reflect their evolutionary success and hence they must have effective mechanisms of defence to deal with parasites and pathogens and altered self tissues. Inflammation appears to be an important first line defence in all invertebrates and vertebrates. This brief review deals with the inflammatory responses of invertebrates and fish concentrating on the cell types involved and the mediators of inflammation, in particular, eicosanoids, cytokines and adhesion molecules.     

Chemokines: inflammatory mediators of atherosclerosis

Atherosclerosis as the underlying mechanisms of myocardial infarction, stroke and peripheral artery disease remains the major cause of morbidity and mortality in developed countries. Recent developments in vascular biology have indicated that atherosclerosis can be best characterized as a chronic inflammatory disease of the vessel wall that promotes lesion development and progression. Chemokines regulate and control these processes by orchestrating adhesive interactions of circulating blood cells with the arterial wall and their subsequent extravasation. Exhibiting a high degree of specialization and cooperation, different chemokines mediate distinct steps during the atherogenic recruitment of monocytes and T cells. This diversity of chemokine expression and function might lead to the identification of selective therapeutic targets for the prevention and treatment of atherosclerosis.     

Galectins and cancer

The galectins are a family of proteins that are distributed widely in all living organisms. All of them share galactose-specificity. At present, 14 members of the family are characterized in mammals. The galectins have been implicated in many essential functions including development, differentiation, cell-cell adhesion, cell-matrix interaction, growth regulation, apoptosis, RNA splicing, and tumor metastasis. Although efforts have mostly focused on the possible function of galectins in tumor development and invasiveness, their precise role in this field is still debated. This review discusses the recent way in which the expression of galectins and galectin-binding sites may affect the behavior of a variety of human neoplastic tissues.     

Galectins and urological cancer

Galectins are a family of proteins defined by their affinity for beta-galactoside and by their conserved sequence. Each galectins exhibits a specific expression pattern in various tissues and their expression is regulated during development. Their expression is altered in many types of cancers and non-cancerous disorders. They interact with glycoproteins in both extracellular and intracellular milieu and regulate various biological phenomenon including cell growth, cell differentiation, cell adhesion, and apoptosis. A series of experimental and clinical evidences have been reported to support correlation between galectin expressions and neoplastic transformation. The recent findings show that expressions of galectins are elevated with neoplastic progression in certain malignancies, and therefore, galectins are expected to serve as reliable tumor markers. In this review, we describe the expression and role of galectins in urological cancers and their clinical applications for diagnostic and therapeutic use.     

Galectins in kidney development

Galectins are a family of proteins with overlapping but distinct carbohydrate-binding specificities. They differ in cell-type and tissue distribution, and have various functions. Extracellularly several galectins can modulate cellular adhesive interactions and signalling pathways, effects that may be important in the establishment and maintenance of tissue organization during normal development. This review will summarise recent progress in defining the roles of galectins that are expressed in the kidney in normal development, and discuss the evidence linking aberrant expression of galectins with kidney disease.     

Galectins in kidney development

Galectins are a family of proteins with overlapping but distinct carbohydrate-binding specificities. They differ in cell-type and tissue distribution, and have various functions. Extracellularly several galectins can modulate cellular adhesive interactions and signalling pathways, effects that may be important in the establishment and maintenance of tissue organization during normal development. This review will summarise recent progress in defining the roles of galectins that are expressed in the kidney in normal development, and discuss the evidence linking aberrant expression of galectins with kidney disease. Published in 2004.     

HCl-induced inflammatory mediators in cat esophageal mucosa and inflammatory mediators in esophageal circular muscle in an in vitro model of esophagitis

Platelet-activating factor (PAF) and interleukin-6 (IL-6) are produced in the esophagus in response to HCl and affect ACh release, causing changes in esophageal motor function similar to esophagitis (Cheng L, Cao W, Fiocchi C, Behar J, Biancani P, and Harnett KM. Am J Physiol Gastrointest Liver Physiol 289: G418-G428, 2005). We therefore examined HCl-activated mechanisms for production of PAF and IL-6 in cat esophageal mucosa and circular muscle. A segment of normal mucosa was tied at both ends, forming a mucosal sac (Cheng L, Cao W, Fiocchi C, Behar J, Biancani P, and Harnett KM. Am J Physiol Gastrointest Liver Physiol 289: G860-G869, 2005) that was filled with acidic Krebs buffer (pH 5.8) or normal Krebs buffer (pH 7.0) as control and kept in oxygenated Krebs buffer for 3 h. The supernatant of the acidic sac (MS-HCl) abolished contraction of normal muscle strips in response to electric field stimulation. The inhibition was reversed by the PAF antagonist CV3988 and by IL-6 antibodies. PAF and IL-6 levels in MS-HCl and mucosa were significantly elevated over control. IL-6 levels in mucosa and supernatant were reduced by CV3988, suggesting that formation of IL-6 depends on PAF. PAF-receptor mRNA levels were not detected by RT-PCR in normal mucosa, but were significantly elevated after exposure to HCl, indicating that HCl causes production of PAF and expression of PAF receptors in esophageal mucosa and that PAF causes production of IL-6. PAF and IL-6, produced in the mucosa, are released to affect the circular muscle layer. In the circular muscle, PAF causes production of additional IL-6 that activates NADPH oxidase to induce production of H(2)O(2). H(2)O(2) causes formation of IL-1beta that may induce production of PAF in the muscle, possibly closing a self-sustaining cycle of production of inflammatory mediators.     

Quantification of cytokines and inflammatory mediators in a three-dimensional model of inflammatory arthritis

Human recombinant IL-1beta and TNFalpha have been previously used to induce a cytokine response in canine chondrocytes. In order to establish this functional relation in a homologous system in vitro, we have developed both 2D and 3D models of inflammatory arthritis using canine recombinant cytokines in canine articular chondrocytes. IL-1beta and TNFalpha were cloned and subsequently expressed in Escherichia coli. The purified recombinant canine cytokines were used to simulate inflammation in vitro and the expression of typical inflammation markers such as proinflammatory cytokines (IL-1beta, IL-6, IL-8, GM-CSF and TNFalpha), enzyme mediators (MMP-3 MMP-13, iNOS, COX-2) and their catabolites (NO, PGE(2)) was measured. High expression of proinflammatory cytokines, enzyme mediators and their catabolites was only observed in IL-1beta/TNFalpha stimulated cells. We conclude that the canine IL-1beta and TNFalpha generated in this study are biologically active and equally effective in the canine cell culture systems. Inducing an inflammatory pathway by canine exogenous cytokines in canine chondrocytes provides a useful tool for the study of canine inflammatory arthritis.     

Modulation of monocyte chemotactic function in inflammatory lesions. Role of inflammatory mediators

Monocyte recruitment and accumulation in the synovial tissue is pivotal in the evolution of rheumatoid arthritis (RA). In the present study we examined the chemotactic potential of monocytes obtained from synovial fluid (SF) of patients with RA. Functionally, SF monocytes exhibited greatly diminished chemotactic activity to C5a compared with monocytes from the peripheral blood. In contrast, their chemotactic responsiveness to the synthetic peptide, FMLP, was nearly normal. To define a mechanism for this differential chemotactic dysfunction, cell-surface receptors for C5a (C5aR) and FMLP (FMLP-R) were evaluated. Whereas FMLP-R expression was similar on both blood and inflammatory monocytes, C5aR expression was markedly reduced on SF cells. Because decreased C5a binding in certain RA SF samples could not be attributed to free C5a, known or suspected components of inflammatory SF were evaluated for their ability to modulate chemotactic ligand receptors. Bacterial products including LPS and streptococcal cell walls, which are potent monocyte activators, down-regulated C5aR without affecting FMLP-R. Moreover, the cytokines IFN-gamma and granulocyte-macrophage-CSF selectively decreased C5aR in parallel with decreased in vitro chemotactic activity to C5a. Thus, these data indicate that 1) synovial effusions may contain C5a and/or inflammatory mediators that modulate phenotypic and functional changes in monocytes, 2) chemotactic ligand receptors are independently regulated in inflammatory lesions, and 3) decreased C5aR expression and chemotactic potential likely provide a mechanism whereby monocyte-macrophages persist within the inflamed synovium.     

Role of lung inflammatory mediators as a cause of exercise-induced arterial hypoxemia in young athletes.

We examined whether lung inflammatory mediators are increased during exercise and whether pharmacological blockade can prevent exercise-induced arterial hypoxemia (EIAH) in young athletes. Seventeen healthy athletes (9 men, 8 women; age 23 +/- 3 yr) with varying degrees of EIAH completed maximal incremental treadmill exercise tests after administration of fexofenadine, zileuton, and nedocromil sodium or placebo in a randomized double-blind crossover study. Lung function, arterial blood gases, and inflammatory metabolites in plasma, urine, and induced sputum were assessed. Drug administration did not improve EIAH or gas exchange during exercise. At maximal exercise, oxygen saturation fell to 91.4 +/- 2.6% (drug trial) and 91.9 +/- 2.1% (placebo trial) and alveolar-arterial oxygen difference widened to 28.1 +/- 6.3 Torr (drug trial) and 29.3 +/- 5.7 Torr (placebo trial). Oxygen consumption, ventilation, and other exercise variables were similarly unaffected by drug treatment. Although plasma histamine increased with exercise, values did not differ between trials, and urinary leukotriene E(4) and 11beta-prostaglandin F(2alpha) levels were unchanged after exercise. Postexercise sputum revealed no significant changes in markers of inflammation. These results demonstrate that EIAH in young athletes is not attenuated with acute administration of drugs targeting histamine and bioactive lipids. We conclude that airway inflammation is of insufficient magnitude to cause impairments in gas exchange and does not appear to be linked to EIAH in healthy young athletes.     

Biliverdin protects against polymicrobial sepsis by modulating inflammatory mediators

Highly inducible heme oxygenase (HO)-1 is protective against acute and chronic inflammation. HO-1 generates carbon monoxide (CO), ferrous iron, and biliverdin. The aim of this study was to investigate the protective effects of biliverdin against sepsis-induced inflammation and intestinal dysmotility. Cecal ligation and puncture (CLP) was performed on Sprague-Dawley rats under isoflurane anesthesia with and without intraperitoneal biliverdin injections, which were done before, at the time of CLP, and after CLP. In vivo gastrointestinal transit was carried out with fluorescein-labeled dextran. Jejunal circular muscle contractility was quantified in vitro using organ bath-generated bethanechol dose-response curves. Neutrophilic infiltration into the muscularis externa was quantified. The jejunal muscularis was studied for cytokine mRNA expressions [interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1, inducible nitric oxide synthase, cyclooxygenase-2, biliverdin, IL-10, and HO-1] using real-time RT-PCR. Biliverdin treatment prevented the sepsis-induced suppression of gastrointestinal muscle contractility in vivo and in vitro and significantly decreased neutrophilic infiltration into the jejunal muscularis. Inflammatory mRNA expressions for small bowel IL-6 and MCP-1 were significantly reduced after biliverdin treatment in CLP-induced septic animals compared with untreated septic animals. The anti-inflammatory mediator expression of small bowel IL-10 was significantly augmented after CLP at 3 h compared with untreated septic animals. These findings demonstrate that biliverdin attenuates sepsis-induced morbidity to the intestine by selectively modulating the inflammatory cascade and its subsequent sequelae on intestinal muscularis function.     

Eupatilin inhibits lipopolysaccharide-induced expression of inflammatory mediators in macrophages

AimsEupatilin (5,7-dihydroxy-3,4,6-trimethoxyflavone) is a pharmacologically active ingredients in Stillen^TM, a drug for the gastric mucosal ulcers. Eupatilin has been known to possess anti-peptic, anti-cancer, and anti-allergy activity. In this report, we defined the effect of eupatilin on the endotoxin-induced inflammation in lipopolysaccharide (LPS)-stimulated macrophages.Main methodsMouse J774A.1 cell line and mouse peritoneal macrophages were used. Gene expression and production of inflammatory mediators were determined by real-time PCR and Western blot.Key findingsEupatilin dose-dependently suppressed LPS-induced expression of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO). Eupatilin decreased LPS-induced expression of inflammatory mediators and pro-inflammatory cytokines such as cyclooxygenase-2, monocyte chemoattractant protein-1, tumor necrosis factor-α, interleukin (IL)-1β and IL-6. In addition, this suppression of inflammatory mediators was nuclear factor (NF)-κB dependent.SignificanceOur findings imply that eupatilin suppresses inflammatory responses by the inhibition of NF-κB signaling pathway, and downstream inflammatory mediators in endotoxin-stimulated macrophages.     

Galectins as modulators of receptor tyrosine kinases signaling in health and disease

Receptor tyrosine kinases (RTKs) constitute a large group of cell surface proteins that mediate communication of cells with extracellular environment. RTKs recognize external signals and transfer information to the cell interior, modulating key cellular activities, like metabolism, proliferation, motility, or death. To ensure balanced stream of signals the activity of RTKs is tightly regulated by numerous mechanisms, including receptor expression and degradation, ligand specificity and availability, engagement of co-receptors, cellular trafficking of the receptors or their post-translational modifications. One of the most widespread post-translational modifications of RTKs is glycosylation of their extracellular domains. The sugar chains attached to RTKs form a new layer of information, so called glyco-code that is read by galectins, carbohydrate binding proteins. Galectins are family of fifteen lectins implicated in immune response, inflammation, cell division, motility and death. The versatility of cellular activities attributed to galectins is a result of their high abundance and diversity of their cellular targets. A various sugar specificity of galectins and the differential ability of galectin family members to form oligomers affect the spatial distribution and the function of their cellular targets. Importantly, galectins and RTKs are tightly linked to the development, progression and metastasis of various cancers. A growing number of studies points on the close cooperation between RTKs and galectins in eliciting specific cellular responses. This review focuses on the identified complexes between galectins and RTK members and discusses their relevance for the cell physiology both in healthy tissues and in cancer.