CD11b/CD18-dependent interactions of neutrophils with intestinal epithelium are mediated by fucosylated proteoglycans

Mechanism of TLR4-Mediated Anti-Inflammatory Response Induced by Exopolysaccharide from the Probiotic Bacillus subtilis

Intestinal inflammatory diseases affect millions of people worldwide, and one class of drugs showing promise toward treatment of several inflammatory diseases is probiotics. Numerous studies have been performed using probiotics to prevent and treat intestinal inflammatory diseases. Most of these studies used intact bacteria, and neither the active molecule nor the molecular mechanisms by which they affect immune responses are known. We have shown that the probiotic Bacillus subtilis is anti-inflammatory and can protect mice from acute colitis induced by the enteric pathogen Citrobacter rodentium. We identified and purified the active molecule, exopolysaccharide (EPS), and showed that it protects mice from C. rodentium-induced colitis by inducing anti-inflammatory M2 macrophages or inhibitory dendritic cells (DCs), both of which inhibit excessive T cell responses. We showed previously that EPS affects macrophages and DCs in a TLR4-dependent manner, and in the current study we asked how EPS induces these anti-inflammatory cells and how they function to inhibit T cells. By investigating the signaling downstream of TLR4 that leads to acquisition of inhibitory properties of macrophages and DCs, we found that EPS induces expression of the inhibitory molecule IDO in bone marrow-derived DCs, and that inhibition of T cell proliferation by IDO-expressing bone marrow-derived DCs utilizes the kynurenine/aryl hydrocarbon receptor circuit. Furthermore, unlike LPS, EPS does not induce inflammatory cytokines upon injection in vivo, directly demonstrating different outcomes induced by two different TLR4 agonists.

Fucosylated TLR4 mediates communication between mutualist fucotrophic microbiota and mammalian gut mucosa

Objective

The glycans on the mucosa of suckling mice are predominantly sialylated; upon weaning, fucosylated glycans preponderate. This manifestation of mutualism between fucotrophic bacteria and the mature host utilizes a sentinel receptor in the intestinal mucosa; this receptor was isolated to distinguish its structural and functional features.

Design

Provisional identification of the sentinel gut receptor as fuc-TLR4 was through colonization of germ-free mutant mice. Conventional mice whose microbiota was depleted with a cocktail of antibiotics were used to further define the nature and functions of fuc-TLR4 sentinel, and to define the role of the fucotrophic microbiota in gut homeostasis and recovery from insult. The nature of the sentinel was confirmed in cultured human HEL cells.

Results

Fuc-TLR4 activity is distinct from that of TLR4. Activated mucosal fuc-TLR4 induces a fuc-TLR4 dependent non-inflammatory (ERK and JNK dependent, NF-κB independent) signaling cascade, initiating induction of fucosyltransferase 2 (secretor) gene transcription. In vitro, either defucosylation or TLR4 knockdown abrogates FUT2 induction, indicating that fuc-TLR4 activity requires both the peptide and glycan moieties. In vivo, fucose-utilizing bacteria and fucose-binding ligands induce mucosal fucosylation. Activation of this pathway is essential for recovery from chemically induced mucosal injury in vivo.

Conclusion

In mature mice, fucosyl-TLR4 mediated gut fucosylation creates a niche that supports the healthy fucose-dependent mutualism between the mammalian gut and its fucotrophic microbes. Such microbiota-induced Fuc-TLR4 signaling supports initial colonization of the secretor gut, recovery from dysbiosis, and restoration or preservation of intestinal homeostasis.

Sialylation regulates neutrophil transepithelial migration, CD11b/CD18 activation, and intestinal mucosal inflammatory function

Polymorphonuclear neutrophils (PMNs) play a critical role in clearing invading microbes and promoting tissue repair following infection/injury. However, dysregulated PMN trafficking and associated tissue damage is pathognomonic of numerous inflammatory mucosal diseases. The final step in PMN influx into mucosal lined organs (including the lungs, kidneys, skin, and gut) involves transepithelial migration (TEpM). The β2-integrin CD11b/CD18 plays an important role in mediating PMN intestinal trafficking, with recent studies highlighting that terminal fucose and GlcNAc glycans on CD11b/CD18 can be targeted to reduce TEpM. However, the role of the most abundant terminal glycan, sialic acid (Sia), in regulating PMN epithelial influx and mucosal inflammatory function is not well understood. Here we demonstrate that inhibiting sialidase-mediated removal of α2-3-linked Sia from CD11b/CD18 inhibits PMN migration across intestinal epithelium in vitro and in vivo. Sialylation was also found to regulate critical PMN inflammatory effector functions, including degranulation and superoxide release. Finally, we demonstrate that sialidase inhibition reduces bacterial peptide-mediated CD11b/CD18 activation in PMN and blocks downstream intracellular signaling mediated by spleen tyrosine kinase (Syk) and p38 MAPK. These findings suggest that sialylated glycans on CD11b/CD18 represent potentially novel targets for ameliorating PMN-mediated tissue destruction in inflammatory mucosal diseases.

Contact-dependent, polarized acidification response during neutrophil-epithelial interactions

Neutrophil (PMN) infiltration during active inflammation imprints changes in the local tissue environment. Such responses are often accompanied by significant extracellular acidosis that result in predictable transcriptional responses. In this study, we explore the mechanisms involved in inflammatory acidification as a result of PMN-intestinal epithelial cell (IEC) interactions. Using recently developed tools, we revealed that PMN transepithelial migration (TEM)-associated inflammatory acidosis is dependent on the total number of PMNs present during TEM and is polarized toward the apical surface. Extending these studies, we demonstrate that physical separation of the PMNs and IECs prevented acidification, whereas inhibition of PMN TEM using neutralizing antibodies enhanced extracellular acidification. Utilizing pharmaceutical inhibitors, we demonstrate that the acidification response is independent of myeloperoxidase and dependent on reactive oxygen species generated during PMN TEM. In conclusion, inflammatory acidosis represents a polarized PMN-IEC-dependent response by an as yet to be fully determined mechanism.

Neutrophil-Epithelial Crosstalk During Intestinal Inflammation

Neutrophils are the most abundant leukocyte population in the human circulatory system and are rapidly recruited to sites of inflammation. Neutrophils play a multifaceted role in intestinal inflammation, as they contribute to the elimination of invading pathogens. Recently, their role in epithelial restitution has been widely recognized; however, they are also associated with bystander tissue damage. The intestinal epithelium provides a physical barrier to prevent direct contact of luminal contents with subepithelial tissues, which is extremely important for the maintenance of intestinal homeostasis. Numerous studies have demonstrated that transepithelial migration of neutrophils is closely related to disease symptoms and disruption of crypt architecture in inflammatory bowel disease and experimental colitis. There has been growing interest in how neutrophils interact with the epithelium under inflammatory conditions. Most studies focus on the effects of neutrophils on intestinal epithelial cells; however, the effects of intestinal epithelial cells on neutrophils during intestinal inflammation need to be well-established. Based on these data, we have summarized recent articles on the role of neutrophil-epithelial interactions in intestinal inflammation, particularly highlighting the epithelium-derived molecular regulators that mediate neutrophil recruitment, transepithelial migration, and detachment from the epithelium, as well as the functional consequences of their crosstalk. A better understanding of these molecular events may help develop novel therapeutic targets for mitigating the deleterious effects of neutrophils in inflammatory bowel disease.

In Vitro Anti-Orthohantavirus Activity of the High-and Low-Molecular-Weight Fractions of Fucoidan from the Brown Alga Fucus evanescens

The Hantaan orthohantavirus (genovariant Amur-AMRV) is a rodent-borne zoonotic virus; it is the causative agent of haemorrhagic fever with renal syndrome in humans. The currently limited therapeutic options require the development of effective anti-orthohantavirus drugs. The ability of native fucoidan from Fucus evanescens (FeF) and its enzymatically prepared high-molecular-weight (FeHMP) and low-molecular-weight (FeLMP) fractions to inhibit different stages of AMRV infection in Vero cells was studied. The structures of derivatives obtained were determined using nuclear magnetic resonance (NMR) spectroscopy. We found that fucoidan and its derivatives exhibited significant antiviral activity by affecting the early stages of the AMRV lifecycle, notably virus attachment and penetration. The FeHMP and FeLMP fractions showed the highest anti-adsorption activity by inhibiting AMRV focus formation, with a selective index (SI) > 110; FeF had an SI of ~70. The FeLMP fraction showed a greater virucidal effect compared with FeF and the FeHMP fraction. It was shown by molecular docking that 2O-sulphated fucotetrasaccharide, a main component of the FeLMP fraction, is able to bind with the AMRV envelope glycoproteins Gn/Gc and with integrin β3 to prevent virus-cell interactions. The relatively small size of these sites of interactions explains the higher anti-AMRV activity of the FeLMP fraction.

The Promiscuous Profile of Complement Receptor 3 in Ligand Binding, Immune Modulation, and Pathophysiology

The β2-integrin receptor family has a broad spectrum of physiological functions ranging from leukocyte adhesion, cell migration, activation, and communication to the phagocytic uptake of cells and particles. Among the members of this family, complement receptor 3 (CR3; CD11b/CD18, Mac-1, αMβ2) is particularly promiscuous in its functional profile and ligand selectivity. There are close to 100 reported structurally unrelated ligands for CR3, and while many ligands appear to cluster at the αMI domain, molecular details about binding modes remain largely elusive. The versatility of CR3 is reflected in its functional portfolio, which includes prominent roles in the removal of invaders and cell debris, induction of tolerance and synaptic pruning, and involvement in the pathogenesis of numerous autoimmune and chronic inflammatory pathologies. While CR3 is an interesting therapeutic target for immune modulation due to these known pathophysiological associations, drug development efforts are limited by concerns of potential interference with host defense functions and, most importantly, an insufficient molecular understanding of the interplay between ligand binding and functional impact. Here, we provide a systematic summary of the various interaction partners of CR3 with a focus on binding mechanisms and functional implications. We also discuss the roles of CR3 as an immune receptor in health and disease, as an activation marker in research and diagnostics, and as a therapeutic target.

Regulatory mechanisms of neutrophil migration from the circulation to the airspace

The neutrophil, a short-lived effector leukocyte of the innate immune system best known for its proteases and other degradative cargo, has unique, reciprocal physiological interactions with the lung. During health, large numbers of ‘marginated’ neutrophils reside within the pulmonary vasculature, where they patrol the endothelial surface for pathogens and complete their life cycle. Upon respiratory infection, rapid and sustained recruitment of neutrophils through the endothelial barrier, across the extravascular pulmonary interstitium, and again through the respiratory epithelium into the airspace lumen, is required for pathogen killing. Overexuberant neutrophil trafficking to the lung, however, causes bystander tissue injury and underlies several acute and chronic lung diseases. Due in part to the unique architecture of the lung’s capillary network, the neutrophil follows a microanatomic passage into the distal airspace unlike that observed in other end-organs that it infiltrates. Several of the regulatory mechanisms underlying the stepwise recruitment of circulating neutrophils to the infected lung have been defined over the past few decades; however, fundamental questions remain. In this article, we provide an updated review and perspective on emerging roles for the neutrophil in lung biology, on the molecular mechanisms that control the trafficking of neutrophils to the lung, and on past and ongoing efforts to design therapeutics to intervene upon pulmonary neutrophilia in lung disease.

Getting Your Neutrophil: Neutrophil Transepithelial Migration in the Lung

Neutrophil transepithelial migration is a fundamental process that facilitates the rapid trafficking of neutrophils to inflammatory foci and occurs across a diverse range of tissues. For decades there has been widespread interest in understanding the mechanisms that drive this migratory process in response to different pathogens and organ systems. This has led to the successful integration of key findings on neutrophil transepithelial migration from the intestines, lungs, liver, genitourinary tract, and other tissues into a single, cohesive model. However, recent studies have identified organ specific differences in neutrophil transepithelial migration. These findings support a model where the tissue in concert with the pro-inflammatory stimuli dictate a unique collection of signals that drive neutrophil trafficking. This review focuses on the mechanisms that drive neutrophil transepithelial migration in response to microbial infection of a single organ, the lung. Herein we provide a detailed analysis of the adhesion molecules and chemoattractants that contribute to the recruitment of neutrophil into the airways. We also highlight important advances in experimental models for studying neutrophil transepithelial migration in the lung over the last decade.

Anti-neoplastic Potential of Flavonoids and Polysaccharide Phytochemicals in Glioblastoma

Clinically, gliomas are classified into four grades, with grade IV glioblastoma multiforme being the most malignant and deadly, which accounts for 50% of all gliomas. Characteristically, glioblastoma involves the aggressive proliferation of cells and invasion of normal brain tissue, outcomes as poor patient prognosis. With the current standard therapy of glioblastoma; surgical resection and radiotherapy followed by adjuvant chemotherapy with temozolomide, it remains fatal, because of the development of drug resistance, tumor recurrence, and metastasis. Therefore, the need for the effective therapeutic option for glioblastoma remains elusive. Previous studies have demonstrated the chemopreventive role of naturally occurring pharmacological agents through preventing or reversing the initiation phase of carcinogenesis or arresting the cancer progression phase. In this review, we discuss the role of natural phytochemicals in the amelioration of glioblastoma, with the aim to improve therapeutic outcomes, and minimize the adverse side effects to improve patient's prognosis and enhancing their quality of life.

Targeting the tumor immune microenvironment with "nutraceuticals": From bench to clinical trials

The occurrence of immune effector cells in the tissue microenvironment during neoplastic progression is critical in determining tumor growth outcomes. On the other hand, tumors may also avoid immune system-mediated elimination by recruiting immunosuppressive leukocytes and soluble factors, which coordinate a tumor microenvironment that counteracts the efficiency of the antitumor immune response. Checkpoint inhibitor therapy results have indicated a way forward via activation of the immune system against cancer. Widespread evidence has shown that different compounds in foods, when administered as purified substances, can act as immunomodulators in humans and animals. Although there is no universally accepted definition of nutraceuticals, the term identifies a wide category of natural compounds that may impact health and disease statuses and includes purified substances from natural sources, plant extracts, dietary supplements, vitamins, phytonutrients, and various products with combinations of functional ingredients. In this review, we summarize the current knowledge on the immunomodulatory effects of nutraceuticals with a special focus on the cancer microenvironment, highlighting the conceptual benefits or drawbacks and subtle cell-specific effects of nutraceuticals for envisioning future therapies employing nutraceuticals as chemoadjuvants.

Effect of vitamin E on stroke-associated pneumonia

OBJECTIVE

To study the role of vitamin E in stroke-associated pneumonia.

METHODS

We selected 183 patients with stroke-related pneumonia who were divided into different nutrition groups according to the Mini Nutritional Assessment score. Patients were then administered different doses of vitamin E.

RESULTS

CD55 and CD47 levels in patients taking vitamin E across different nutrition score groups were better than those in patients who did not use vitamin E. The levels of CD55 and CD47 and the duration of hospitalization were better in the high-dose vitamin E group than in the low-dose vitamin E group.

CONCLUSION

Vitamin E may have an auxiliary therapeutic effect in patients with stroke-associated pneumonia.

Molecular Targets and Related Biologic Activities of Fucoidan: A Review

Fucoidan-a marine natural active polysaccharide derived from brown algae with a variety of medicinal activities and low toxicity-has been used as clinical drug for renal diseases for nearly 20 years. The pharmacological mechanism of fucoidan has been well-investigated, based on target molecules and downstream signaling pathways. This review summarizes some important molecular targets of fucoidan and its related biologic activities, including scavenger receptor (SR), Toll-like receptors (TLRs), C-type lectin (CLEC) and some newly found target molecules, which may be beneficial for further understanding the pharmacological mechanism of fucoidan and discovering its new functions, as well as developing related clinical or adjuvant drugs and functional preparations.

Extracts and Marine Algae Polysaccharides in Therapy and Prevention of Inflammatory Diseases of the Intestine

Inflammatory bowel disease (IBD) is a serious public health problem worldwide. Current therapeutic strategies that use anti-inflammatory drugs, immunosuppressants, and biological treatments are often ineffective and have adverse health effects. In this regard, the use of natural compounds aimed at key pathogenic therapeutic targets in IBD attracts universal attention. Seaweed is a valuable source of structurally diverse biologically active compounds. The materials presented in the review indicate that seaweed extracts and polysaccharides are effective candidates for the development of drugs, biological food additives, and functional nutrition products for the treatment and prevention of IBD. The structural features of algal polysaccharides provide the possibility of exposure to therapeutic targets of IBD, including proinflammatory cytokines, chemokines, adhesion molecules, nuclear factor NF-kB, intestinal epithelial cells, reactive oxygen and nitrogen. Further study of the relationship between the effect of polysaccharides from different types of algae, with different structure and molecular weights on immune and epithelial cells, intestinal microorganisms will contribute to a deeper understanding of their mechanisms and will help in the development of drugs, dietary supplements, functional foods for the treatment of patients with IBD.

Carboxymethylated Sulfated Heteroexopolysaccharide from a Haloarchaeal Strain as Potential Biomolecule for Harmless Adjuvant Therapy in Cancer Treatment

This study explored the possible use of a microbial carboxymethylated sulfated heteroexopolysaccharide (CS-hEPS) as a potential anticancer agent. The investigation was carried out through antioxidant, antifatigue, and antiproliferative activities. Antioxidant potential including scavenging DPPH and hydroxyl radical activities and reducing power was evaluated. Antifatigue activity was determined by assessing the endurance of mice using the forced swimming test. Following 30 days of CS-hEPS oral treatment at different doses, biochemical parameters related to fatigue such as lactic dehydrogenase (LDH), serum urea nitrogen (SUN), and hepatic glycogen (HG) contents were measured. Antitumor activities were investigated against human cancer liver and myelogenous leukemia cells. Results showed that CS-hEPS possesses notable antioxidant, antifatigue, and antitumor effects. CS-hEPS significantly inhibited the proliferation of leukemia (86.6 ± 0.32%) and cancer liver (58.6 ± 0.43%) cells. CS-hEPS are promising natural antioxidant, antifatigue, and antitumor harmless adjuvant materials that could be applied in human cancer therapy.

Regulation of neutrophil function by selective targeting of glycan epitopes expressed on the integrin CD11b/CD18

Polymorphonuclear neutrophils (PMNs) play a critical role in the innate immune response to invading pathogens. However, dysregulated mucosal trafficking of PMNs and associated epithelial tissue damage is a pathological hallmark of numerous inflammatory conditions including inflammatory bowel disease. The glycoprotein CD11b/CD18 plays a well-described role in regulating PMN transepithelial migration and PMN inflammatory functions. Previous studies have demonstrated that targeting of the N-linked glycan Lewis X on CD11b blocks PMN transepithelial migration (TEpM). Given evidence of glycosylation-dependent regulation of CD11b/CD18 function, we performed MALDI TOF Mass Spectrometry (MS) analyses on CD11b/CD18 purified from human PMNs. Unusual glycan epitopes identified on CD11b/CD18 included high Mannose oligosaccharides recognized by the Galanthus Nivalis lectin and biantennary galactosylated N-glycans recognized by the Phaseolus Vulgaris erythroagglutinin lectin. Importantly, we show that selective targeting of glycans on CD11b with such lectins results in altered intracellular signaling events that inhibit TEpM and differentially affect key PMN inflammatory functions including phagocytosis, superoxide release and apoptosis. Taken together, these data demonstrate that discrete glycan motifs expressed on CD11b/CD18 such as biantennary galactose could represent novel targets for selective manipulation of CD11b function and reduction of PMN-associated tissue damage in chronic inflammatory diseases.

Chemical modifications of polysaccharides and their anti-tumor activities

With the rising trend of incidence of cancers, effective therapies are urgently needed to control human malignancies. However, the chemotherapy drugs currently on the market cause serious side effects. Polysaccharides belong to a class of biomacromolecules, which have drawn considerable research interest over the years as it possess anti-cancer activities or can increase the efficacy of conventional chemotherapy drugs with fewer side effects. The antitumor activity of many polysaccharides was significantly increased after modification. Based on these encouraging observations, a great deal of effort has been focused on discovering anti-cancer polysaccharides and modified derivatives for the development of effective therapeutics for various human cancers. This review highlights recent advances on the major chemical modification methods of polysaccharides, and discusses the effect of molecular modification on the physicochemical properties and anti-tumor activities of polysaccharides. Meanwhile, the underlying anti-tumor mechanisms of polysaccharide and its modified derivatives were also discussed.

Analysis of leukocyte transepithelial migration using an in vivo murine colonic loop model

Molecular mechanisms that control leukocyte migration across the vascular endothelium (transendothelial migration; TEndoM) have been extensively characterized in vivo, but details of leukocyte transepithelial migration (TEpM) and its dysregulation (a pathologic feature of many mucosal diseases) are missing due to the lack of suitable animal models. Here, we describe a murine model that utilizes a vascularized proximal colonic segment (pcLoop) and enables quantitative studies of leukocyte trafficking across colonic epithelium. Consistent with previous in vitro studies, intraluminal injection of antibodies against integrin CD11b/CD18 reduced recruitment of polymorphonuclear neutrophils (PMN) into the lumen of pcLoops, and it increased subepithelial accumulation of PMN. We extended studies using the pcLoop to determine contributions of Junctional Adhesion Molecule-A (JAM-A, or F11R) in PMN TEpM and confirmed that mice with total loss of JAM-A or mice with intestinal epithelial selective loss of JAM-A had increased colonic permeability. Furthermore, there was reduced PMN migration into the colonic lumen that paralleled subepithelial accumulation of PMN in global-KO mice, as well as in intestinal epithelial-targeted JAM-A-deficient mice. These findings highlight a potentially novel role for JAM-A in regulating PMN TEpM in vivo and demonstrate utility of this model for identifying receptors that may be targeted in vivo to reduce pathologic intestinal inflammation.

Optimizing Tumor Microenvironment for Cancer Immunotherapy: β-Glucan-Based Nanoparticles

Immunotherapy is revolutionizing cancer treatment. Recent clinical success with immune checkpoint inhibitors, chimeric antigen receptor T-cell therapy, and adoptive immune cellular therapies has generated excitement and new hopes for patients and investigators. However, clinically efficacious responses to cancer immunotherapy occur only in a minority of patients. One reason is the tumor microenvironment (TME), which potently inhibits the generation and delivery of optimal antitumor immune responses. As our understanding of TME continues to grow, strategies are being developed to change the TME toward one that augments the emergence of strong antitumor immunity. These strategies include eliminating tumor bulk to provoke the release of tumor antigens, using adjuvants to enhance antigen-presenting cell function, and employ agents that enhance immune cell effector activity. This article reviews the development of β-glucan and β-glucan-based nanoparticles as immune modulators of TME, as well as their potential benefit and future therapeutic applications. Cell-wall β-glucans from natural sources including plant, fungi, and bacteria are molecules that adopt pathogen-associated molecular pattern (PAMP) known to target specific receptors on immune cell subsets. Emerging data suggest that the TME can be actively manipulated by β-glucans and their related nanoparticles. In this review, we discuss the mechanisms of conditioning TME using β-glucan and β-glucan-based nanoparticles, and how this strategy enables future design of optimal combination cancer immunotherapies.

Laminarin counteracts diet-induced obesity associated with glucagon-like peptide-1 secretion

Laminarin, a type of β-glucan isolated from brown seaweeds, exhibits verity of physiological activities, which include immunology modulation and antitumor function. To investigate the effect of laminarin on energy homeostasis, mice were orally administrated with laminarin to test food intake, fat deposition, and glucose homeostasis. Chronically, laminarin treatment significantly decreases high-fat-diet-induced body weight gain and fat deposition and reduces blood glucose level and glucose tolerance. Acutely, laminarin enhances serum glucagon-like peptide-1 (GLP-1) content and the mRNA expression level of proglucagon and prohormone convertase 1 in ileum. Subsequently, laminarin suppresses the food intake of mice, the hypothalamic AgRP neuron activity, and AgRP expression but activates pancreatic function. Furthermore, laminarin-induced appetite reduction was totally blocked by Exendin (9-39), a specific competitive inhibitor of GLP-1 receptor. Then, STC-1 cells were adopted to address the underlying mechanism, by which laminarin promoted GLP-1 secretion in vitro. Results showed that laminarin dose-dependently promoted GLP-1 secretion and c-Fos protein expression in STC-1 cells, which were independent of Dectin-1 and CD18. Interestingly, BAPTA-AM, a calcium-chelating agent, potently attenuated laminarin-induced [Ca²⁺]_i elevation, c-Fos expression, and GLP-1 secretion. In summary, our data support that laminarin counteracts diet-induced obesity and stimulates GLP-1 secretion via [Ca²⁺]_i; this finding provides an experimental basis for laminarin application to treat obesity and maintain glucose homeostasis.

Pathobiology of neutrophil-epithelial interactions

Polymorphonuclear neutrophils (PMNs) are innate immune system cells that play an essential role in eradicating invading pathogens. PMN migration to sites of infection/inflammation requires exiting the microcirculation and subsequent crossing of epithelial barriers in mucosa-lined organs such as the lungs and intestines. Although these processes usually occur without significant damage to surrounding host tissues, dysregulated/excessive PMN transmigration and resultant bystander-tissue damage are characteristic of numerous mucosal inflammatory disorders. Mechanisms controlling PMN extravasation have been well characterized, but the molecular details regarding regulation of PMN migration across mucosal epithelia are poorly understood. Given that PMN migration across mucosal epithelia is strongly correlated with disease symptoms in many inflammatory mucosal disorders, enhanced understanding of the mechanisms regulating PMN transepithelial migration should provide insights into clinically relevant tissue-targeted therapies aimed at ameliorating PMN-mediated bystander-tissue damage. This review will highlight current understanding of the molecular interactions between PMNs and mucosal epithelia and the associated functional consequences.

Deep insight into neutrophil trafficking in various organs

Neutrophils are professional phagocytes that constitute the first line of defense in humans. The primary function of neutrophils is to eliminate invading pathogens through oxidative and nonoxidative mechanisms. Because neutrophils rapidly migrate into inflammatory foci via diapedesis and chemotaxis, neutrophil recruitment has long been considered a hallmark of inflammation. Recent advances in intravital microscopic technologies using animal model systems have enabled researchers to directly visualize neutrophil trafficking. Consequently, the specific mechanisms of neutrophil transmigration have been identified, and even the reverse migration of neutrophils can be verified visually. Moreover, the detailed phenomena of neutrophil infiltration into various organs, such as the liver, lymphoid organs, and CNS have been identified. This progress in the study of neutrophil migration from the blood vessels to organs results in a deeper understanding of these immune cells' motility and morphology, which are closely related to the spatiotemporal regulation of the overall immune response. In this review, we discuss our current understanding of neutrophil trafficking in various organs.

Prospects for the therapeutic application of sulfated polysaccharides of brown algae in diseases of the cardiovascular system: review

CONTEXT

Fucoidans are water-soluble, highly sulfated, branched homo- and hetero-polysaccharides derived from the fibrillar cell walls and intercellular spaces of brown seaweeds of the class Phaeophyceae. Fucoidans possess mimetic properties of the natural ligands of protein receptors and regulate functions of biological systems via key signaling molecules.

OBJECTIVES

The aim of this review was to collect and combine all available scientific literature about the potential use of the fucoidans for diseases of cardiovascular system.

MATERIALS AND METHODS

The review has been compiled using references from major databases such as Web of Science, PubMed, Scopus, Elsevier, Springer and Google Scholar (up to September 2015). After obtaining all reports from database (a total number is about 580), the papers were carefully analyzed in order to find data related to the topic of this review (129 references).

RESULTS

An exhaustive survey of literature revealed that fucoidans possess a broad spectrum of biological activity, including anti-coagulant, hypolipidemic, anti-thrombotic, anti-inflammatory, immunomodulatory, anti-tumor, anti-adhesive and anti-hypertensive properties. Numerous investigations of fucoidans in diseases of the cardiovascular system mainly focus on pleiotropic anti-inflammatory effects. Fucoidans also possess pro-angiogenic and pro-vasculogenic properties.

CONCLUSION

A great number of investigations in the past years have demonstrated that fucoidans has great potential for in-depth investigation of their effects on cardiovascular system. Through this review, the authors hope to attract the attention of researchers to use fucoidan as mimetic of natural ligand receptor protein with the view of developing new formulations with an improved therapeutic value.

Inflammation and the Intestinal Barrier: Leukocyte-Epithelial Cell Interactions, Cell Junction Remodeling, and Mucosal Repair

The intestinal tract is lined by a single layer of columnar epithelial cells that forms a dynamic, permeable barrier allowing for selective absorption of nutrients, while restricting access to pathogens and food-borne antigens. Precise regulation of epithelial barrier function is therefore required for maintaining mucosal homeostasis and depends, in part, on barrier-forming elements within the epithelium and a balance between pro- and anti-inflammatory factors in the mucosa. Pathologic states, such as inflammatory bowel disease, are associated with a leaky epithelial barrier, resulting in excessive exposure to microbial antigens, recruitment of leukocytes, release of soluble mediators, and ultimately mucosal damage. An inflammatory microenvironment affects epithelial barrier properties and mucosal homeostasis by altering the structure and function of epithelial intercellular junctions through direct and indirect mechanisms. We review our current understanding of complex interactions between the intestinal epithelium and immune cells, with a focus on pathologic mucosal inflammation and mechanisms of epithelial repair. We discuss leukocyte-epithelial interactions, as well as inflammatory mediators that affect the epithelial barrier and mucosal repair. Increased knowledge of communication networks between the epithelium and immune system will lead to tissue-specific strategies for treating pathologic intestinal inflammation.

Immunotoxicity of skin acid secretion produced by the sea slug Berthellina citrina in mice spleen: Histological and Immunohistochemical study

Acid secretion containing sulfuric and hydrochloric acids is a fascinating defensive phenomenon within many groups of marine organisms. This study aimed to investigate the mice spleen histology and immunotoxicity using skin acid secretion (SAS) of the sea slug Berthellina citrina after oral administration. The spleen showed atrophy in the white pulp, decrease in the splenocytes density, megakaryocytes cytoplasmic degeneration as well as inflammatory cells infiltrations. The white and red pulp splenocytes number decreased time-dependently in the treated spleens. Additionally, the size of the megakaryocytes increased as compared with the control. The administration with SAS increased the number of the IgA(+) cells aggregation in the splenic red pulp. Furthermore, after 7days of the administration, large number of dispersed IgA(+) cells were distributed in splenic parenchyma. The IgA(+) cells numbers increased time-dependently as compared with those in the control. The aggregation sizes and number of the F4/80(+) cell in the splenic red pulp were increased. Furthermore the F4/80(+) cells numbers increased time-dependently as compared with those in the control. The UEAI(+) cells were found as free cells but not in aggregations in the control splenic red pulp. Contradictory to the number of IgA(+) cells and F4/80(+) cells the number of the UEAI(+) cells decreased time-dependently after administration with SAS. Hematologically, abnormal numbers of WBCs different cells were observed after administration with SAS. This study provides new insight about the toxicity of a marine extract may be used in natural products industry or medical applications.

Neutrophil-Epithelial Interactions: A Double-Edged Sword

In recent years, it has become clear that innate immune cells termed neutrophils act as double-edged swords by playing essential roles in clearing infection but also causing tissue damage, yet being critical for wound healing. Neutrophil recruitment to sites of injured tissue or infection has been well studied, and many of the molecular events that regulate passage of leukocytes out of the microcirculation are now understood. However, after exiting the circulation, the molecular details that regulate neutrophil passage to end targets, such mucosal surfaces, are just beginning to be appreciated. Given that migration of neutrophils across mucosal epithelia is associated with disease symptoms and disruption of critical barrier function in disorders such as inflammatory bowel disease, there has been long-standing interest in understanding the molecular basis and functional consequences of neutrophil-epithelial interactions. It is a great honor that my work was recognized by the Rous-Whipple Award this past year, giving me the opportunity to summarize what we have learned during the past few decades about leukocyte interactions with epithelial cells.

Cellular Barriers after Extravasation: Leukocyte Interactions with Polarized Epithelia in the Inflamed Tissue

During the inflammatory response, immune cells egress from the circulation and follow a chemotactic and haptotactic gradient within the tissue, interacting with matrix components in the stroma and with parenchymal cells, which guide them towards the sites of inflammation. Polarized epithelial cells compartmentalize tissue cavities and are often exposed to inflammatory challenges such as toxics or infections in non-lymphoid tissues. Apicobasal polarity is critical to the specialized functions of these epithelia. Indeed, a common feature of epithelial dysfunction is the loss of polarity. Here we review evidence showing that apicobasal polarity regulates the inflammatory response: various polarized epithelia asymmetrically secrete chemotactic mediators and polarize adhesion receptors that dictate the route of leukocyte migration within the parenchyma. We also discuss recent findings showing that the loss of apicobasal polarity increases leukocyte adhesion to epithelial cells and the consequences that this could have for the inflammatory response towards damaged, infected or transformed epithelial cells.

Lectin histochemistry shows the comparative biosynthesis and cellular biodistribution of alpha L-fucose residues in some tissues of tetrapoda representatives

Fucose is a monosaccharide that plays several immunological roles. This study investigated the comparative biosynthesis and cellular biodistribution of fucose residues in some tissues of tetrapoda representatives using lectin histochemistry. In this study, the mouse was used as a representative for mammalian, pigeon for avian, lizard for reptilian, and toad for amphibians. The localization of the fucose residues was seen in several cell types of mice ileum, such as villi microfold (M) cells, goblet cells, some of intestinal crypts cells, and lamina propria cells. In other tetrapoda representatives, fucose was only seen in M cells of lizard ileum and some cells of villi lamina propria of pigeon, lizard, and toad. It was also observed in the pancreatic acinar cells of the mouse and some cell aggregations of pancreatic parenchyma of the lizard. Contrarily, it was not seen either in pigeon or in toad pancreases parenchyma. Spleen of all animals showed the fucose residues in some splenic cells in the red pulp only, barring the white pulp. The liver parenchyma of all tetrapoda representatives hadn't fucose residues. The fucose cellular biodistribution in some cells of tetrapoda representatives differed based on the cell type. In the mouse, it was highly seen in the apical cytoplasm of the villi M cells as well as in the cup-like part of goblet cells. In addition, it was seen as "rings" in the granule membranes of the Ulex europeaus agglutinin I (UEAI(+)) cells in the intestinal crypts cells. Furthermore, the UEAI(+) cells in the lamina propria showed fucose granules in their cytoplasm. There is no clear evidence about the relation between the cellular biosynthesis of fucose residues and mucosal immune cells. The role of fucose residues in the pancreatic acinar cells are not well understood and need further investigations. In this study, fucose residues were synthesized in several types of cells in the mouse ileum, spleen and pancreas as compared with other tetrapoda. The data obtained from this study can help us to get more information about the cellular biodistribution and synthesis of fucose residues in several animal species rather than mammalians.

Targeting of Neutrophil Lewis X Blocks Transepithelial Migration and Increases Phagocytosis and Degranulation

Polymorphonuclear leukocytes (PMNs) are innate immune cells whose principal function is to migrate from the blood to sites of inflammation, where they exert crucial anti-infectious and immunomodulatory effects. However, dysregulated migration of PMNs into mucosal epithelial tissues is characteristic of chronic inflammatory disorders, including inflammatory bowel disease. Carbohydrate-mediated binding interactions between PMN Lewis glycans and endothelial glycan-binding proteins are critical for initial migration of PMN out of the vasculature. However, the role of Lewis glycans during transepithelial migration (TEM) has not been well characterized. Herein, we show that antibody blockade of Lewis X (Le(x)) displayed as terminal glycan residues on the PMN surface blocks chemotaxis and TEM while enhancing PMN-adhesive interactions with intestinal epithelia. Unexpectedly, targeting of subterminal Le(x) residues within glycan chains had no effect on PMN migration or adhesive interactions. There was increased surface expression of Le(x) on PMN after TEM, and blockade of terminal Le(x) regulated post-migratory PMN functions, increasing PMN phagocytosis and the surface mobilization of azurophilic (CD63, myeloperoxidase, and neutrophil elastase) and specific (CD66b and lactoferrin) granule markers. These findings suggest that terminal Le(x) represents a potential target for regulating PMN trafficking and function in inflamed mucosa. Furthermore, given its abundant expression on migrating PMN, Le(x) may be a rational target for modulating inflammation in diseases where dysregulated PMN influx is associated with host tissue damage.

Loss of Cell Surface CD47 Clustering Formation and Binding Avidity to SIRPα Facilitate Apoptotic Cell Clearance by Macrophages

CD47, a self recognition marker expressed on tissue cells, interacts with immunoreceptor SIRPα expressed on the surface of macrophages to initiate inhibitory signaling that prevents macrophage phagocytosis of healthy host cells. Previous studies suggested that cells may lose surface CD47 during aging or apoptosis to enable phagocytic clearance. In the current study, we demonstrate that the level of cell surface CD47 is not decreased, but the distribution pattern of CD47 is altered, during apoptosis. On nonapoptotic cells, CD47 molecules are clustered in lipid rafts forming punctates on the surface, whereas on apoptotic cells, CD47 molecules are diffused on the cell surface following the disassembly of lipid rafts. We show that clustering of CD47 in lipid rafts provides a high binding avidity for cell surface CD47 to ligate macrophage SIRPα, which also presents as clusters, and elicits SIRPα-mediated inhibitory signaling that prevents phagocytosis. In contrast, dispersed CD47 on the apoptotic cell surface is associated with a significant reduction in the binding avidity to SIRPα and a failure to trigger SIRPα signal transduction. Disruption of plasma membrane lipid rafts with methyl-β-cyclodextrin diffuses CD47 clusters, leading to a decrease in the cell binding avidity to SIRPα and a concomitant increase in cells being engulfed by macrophages. Taken together, our study reveals that CD47 normally is clustered in lipid rafts on nonapoptotic cells but is diffused in the plasma membrane when apoptosis occurs; this transformation of CD47 greatly reduces the strength of CD47-SIRPα engagement, resulting in the phagocytosis of apoptotic cells.

In vivo immunological activity of carboxymethylated-sulfated (1→3)-β-D-glucan from sclerotium of Poria cocos

β-Glucans are one of the polysaccharides known as biological response modifiers extracted from the sclerotium of Poria cocos which has been used for several decades as Traditional Chinese Medicine. Due to its ability to activate immune system, it can be applied in chemotherapy after being chemically modified. In this study, sulfated (1→3)-β-D-glucan (S-P), carboxymethyl (1→3)-β-D-glucan (CMP), and carboxymethylated-sulfated (1→3)-β-D-glucan (S-CMP), which are (1→3)-β-D-glucan derivatives were synthesized. The current study was aimed to investigate in vivo potential immunological activity of S-CMP in mice. In addition, mice were separately treated with S-P, CMP and S-CMP to evaluate the relationship between single and multiple functional groups. Interestingly, S-CMP exhibited the best in vivo immunological activities and the highest inhibition rate against the implanted HepG2 tumor in BALB/c mice, with significant increase in serum hemolysin antibody titer, spleen antibody production as well as delayed type hypersensitivity compared with S-P and CMP. Furthermore, it was assumed that simultaneous introduction of carboxymethyl and sulfate groups also had great potential effect on antioxidant activity, as substantial decrease in malondialdehyde (MDA) content was remarked. Therefore, it may suggest that S-CMP has better immunological and anti-tumor effects on mice in vivo.

Epithelial adhesion molecules and the regulation of intestinal homeostasis during neutrophil transepithelial migration

Epithelial adhesion molecules play essential roles in regulating cellular function and maintaining mucosal tissue homeostasis. Some form epithelial junctional complexes to provide structural support for epithelial monolayers and act as a selectively permeable barrier separating luminal contents from the surrounding tissue. Others serve as docking structures for invading viruses and bacteria, while also regulating the immune response. They can either obstruct or serve as footholds for the immune cells recruited to mucosal surfaces. Currently, it is well appreciated that adhesion molecules collectively serve as environmental cue sensors and trigger signaling events to regulate epithelial function through their association with the cell cytoskeleton and various intracellular adapter proteins. Immune cells, particularly neutrophils (PMN) during transepithelial migration (TEM), can modulate adhesion molecule expression, conformation, and distribution, significantly impacting epithelial function and tissue homeostasis. This review discusses the roles of key intestinal epithelial adhesion molecules in regulating PMN trafficking and outlines the potential consequences on epithelial function.

The α-tocopherol form of vitamin E reverses age-associated susceptibility to streptococcus pneumoniae lung infection by modulating pulmonary neutrophil recruitment

Streptococcus pneumoniae infections are an important cause of morbidity and mortality in older patients. Uncontrolled neutrophil-driven pulmonary inflammation exacerbates this disease. To test whether the α-tocopherol (α-Toc) form of vitamin E, a regulator of immunity, can modulate neutrophil responses as a preventive strategy to mitigate the age-associated decline in resistance to S. pneumoniae, young (4 mo) and old (22-24 mo) C57BL/6 mice were fed a diet containing 30-PPM (control) or 500-PPM (supplemented) α-Toc for 4 wk and intratracheally infected with S. pneumoniae. Aged mice fed a control diet were exquisitely more susceptible to S. pneumoniae than young mice. At 2 d postinfection, aged mice suffered 1000-fold higher pulmonary bacterial burden, 2.2-fold higher levels of neutrophil recruitment to the lung, and a 2.25-fold higher rate of lethal septicemia. Strikingly, α-Toc supplementation of aged mice resulted in a 1000-fold lower bacterial lung burden and full control of infection. This α-Toc-induced resistance to pneumococcal challenge was associated with a 2-fold fewer pulmonary neutrophils, a level comparable to S. pneumoniae-challenged, conventionally fed young mice. α-Toc directly inhibited neutrophil egress across epithelial cell monolayers in vitro in response to pneumococci or hepoxilin-A3, an eicosanoid required for pneumococcus-elicited neutrophil trans-epithelial migration. α-Toc altered expression of multiple epithelial and neutrophil adhesion molecules involved in migration, including CD55, CD47, CD18/CD11b, and ICAM-1. These findings suggest that α-Toc enhances resistance of aged mice to bacterial pneumonia by modulating the innate immune response, a finding that has potential clinical significance in combating infection in aged individuals through nutritional intervention.

Transmigrated neutrophils in the intestinal lumen engage ICAM-1 to regulate the epithelial barrier and neutrophil recruitment

Neutrophil (PMN) transepithelial migration (TEM) and accumulation in luminal spaces is a hallmark of mucosal inflammation. TEM has been extensively modeled; however, the functional consequences and molecular basis of PMN interactions with luminal epithelial ligands are not clear. Here we report that cytokine-induced expression of a PMN ligand, intercellular adhesion molecule-1 (ICAM-1), exclusively on the luminal (apical) membrane of the intestinal epithelium results in accumulation and enhanced motility of transmigrated PMN on the apical epithelial surface. Using complementary in-vitro and in-vivo approaches, we demonstrate that ligation of epithelial ICAM-1 by PMN or with specific antibodies results in myosin light-chain kinase-dependent increases in epithelial permeability that are associated with enhanced PMN TEM. Effects of ICAM-1 ligation on epithelial permeability and PMN migration in vivo were blocked after intraluminal addition of peptides derived from the cytoplasmic domain of ICAM-1. These findings provide new evidence for functional interactions between PMN and epithelial cells after migration into the intestinal lumen. Although such interactions may aid in clearance of invading microorganisms by promoting PMN recruitment, engagement of ICAM-1 under pathologic conditions would increase accumulation of epithelial-associated PMN, thus contributing to mucosal injury as observed in conditions, including ulcerative colitis.

Pathogenesis of human enterovirulent bacteria: lessons from cultured, fully differentiated human colon cancer cell lines

Hosts are protected from attack by potentially harmful enteric microorganisms, viruses, and parasites by the polarized fully differentiated epithelial cells that make up the epithelium, providing a physical and functional barrier. Enterovirulent bacteria interact with the epithelial polarized cells lining the intestinal barrier, and some invade the cells. A better understanding of the cross talk between enterovirulent bacteria and the polarized intestinal cells has resulted in the identification of essential enterovirulent bacterial structures and virulence gene products playing pivotal roles in pathogenesis. Cultured animal cell lines and cultured human nonintestinal, undifferentiated epithelial cells have been extensively used for understanding the mechanisms by which some human enterovirulent bacteria induce intestinal disorders. Human colon carcinoma cell lines which are able to express in culture the functional and structural characteristics of mature enterocytes and goblet cells have been established, mimicking structurally and functionally an intestinal epithelial barrier. Moreover, Caco-2-derived M-like cells have been established, mimicking the bacterial capture property of M cells of Peyer's patches. This review intends to analyze the cellular and molecular mechanisms of pathogenesis of human enterovirulent bacteria observed in infected cultured human colon carcinoma enterocyte-like HT-29 subpopulations, enterocyte-like Caco-2 and clone cells, the colonic T84 cell line, HT-29 mucus-secreting cell subpopulations, and Caco-2-derived M-like cells, including cell association, cell entry, intracellular lifestyle, structural lesions at the brush border, functional lesions in enterocytes and goblet cells, functional and structural lesions at the junctional domain, and host cellular defense responses.

JAM-related proteins in mucosal homeostasis and inflammation

Mucosal surfaces are lined by epithelial cells that form a physical barrier protecting the body against external noxious substances and pathogens. At a molecular level, the mucosal barrier is regulated by tight junctions (TJs) that seal the paracellular space between adjacent epithelial cells. Transmembrane proteins within TJs include junctional adhesion molecules (JAMs) that belong to the cortical thymocyte marker for Xenopus family of proteins. JAM family encompasses three classical members (JAM-A, JAM-B, and JAM-C) and related molecules including JAM4, JAM-like protein, Coxsackie and adenovirus receptor (CAR), CAR-like membrane protein and endothelial cell-selective adhesion molecule. JAMs have multiple functions that include regulation of endothelial and epithelial paracellular permeability, leukocyte recruitment during inflammation, angiogenesis, cell migration, and proliferation. In this review, we summarize the current knowledge regarding the roles of the JAM family members in the regulation of mucosal homeostasis and leukocyte trafficking with a particular emphasis on barrier function and its perturbation during pathological inflammation.

Leukocyte-epithelial interactions and mucosal homeostasis

Many common inflammatory disorders are characterized by the infiltration of neutrophils across epithelial lined (mucosal) surfaces resulting in disruption of critical barrier function that protects from microbes and noxious agents. In such conditions, disease symptoms are complex but directly related to leukocyte effects on the barrier and epithelial cell function. It is now highly regarded that cellular factors such as cytokines and receptor-ligand interactions mediating adhesion of leukocytes to epithelial cells have potent effects on epithelial homeostasis, defined by coordinated proliferation, migration, differentiation, and regulated cell shedding. Certain cytokines, for example, not only alter leukocyte interactions with epithelia through changes in expression of adhesion molecules but also affect barrier function through alterations in the composition and dynamics of intercellular junctions. In particular, inflammation-induced loss of many tight junction molecules, in part, can account for dysregulated cellular proliferation, migration, survival, and barrier function. This review will highlight how neutrophils interact with epithelial cells with particular focus on adhesion molecules involved and signaling events that play roles in regulating mucosal homeostasis and pathobiology. A better understanding of these molecular events may provide new ideas for therapeutics directed at attenuating consequences of pathologic inflammation of mucosal surfaces.

The role of polymorphonuclear leukocyte trafficking in the perpetuation of inflammation during inflammatory bowel disease

The inflammatory bowel diseases (IBDs; Crohn's disease, and ulcerative colitis) are chronically relapsing inflammatory disorders of the intestine and/or colon. The precise etiology of IBD remains unclear, but it is thought that a complex interplay between various factors including genetic predisposition, the host immune system, and the host response to luminal microbes play a role in disease pathogenesis. Furthermore, numerous lines of evidence have implicated the accumulation of large numbers of polymorphonuclear leukocyte (PMN) in the mucosa and epithelial crypts of the intestine as a hallmark of the active disease phase of IBD. Massive infiltration of PMNs is thought to be instrumental in the pathophysiology of IBD with the degree of PMN migration into intestinal crypts correlating with patient symptoms and mucosal injury. Specifically, migrated PMN have been implicated in the impairment of epithelial barrier function, tissue destruction through oxidative and proteolytic damage, and the perpetuation of inflammation through the release of inflammatory mediators. This review highlights the multifactorial role of PMN egress into the intestinal mucosa in the pathogenesis of IBD because it represents an important area of research with therapeutic implications for the amelioration of the symptoms associated with IBD.

Effects of carboxymethylpachymaran on signal molecules in chicken immunocytes

The study was carried out to investigate the immunomodulation mechanism of carboxymethylpachymaran (CMP). Chicken splenic lymphocytes were cultured in medium alone or with CMP at the final concentration of 50mg/L, 100mg/L, 200mg/L or 400mg/L in vitro for 4h, 8h, 12h or 24h, respectively. The supernatants at different culture periods were analyzed for changes in levels of 6-keto-prostaglandin F1α (6-keto-PGF1α), thromboxane B2 (TXB2) and nitric oxide (NO). The cells were collected to determine contents of oxidized glutathione (GSSG), reduced glutathione (GSH), cyclic AMP (cAMP) and cyclic GMP (cGMP). The results showed that CMP increase the values of NO, 6-keto-PGF1α, TXB2, and the ratio of 6-keto-PGF1α to TXB2 in supernatants. The contents of intracellular GSH, cAMP, cGMP and the ratio of cAMP to cGMP were increased in the cells treated with CMP. The results suggested that CMP enhanced immune functions by increasing the contents of GSH and by regulating arachidonic acid signal transduction systems in chicken splenic lymphocytes. The signal pathway of NO-cGMP plays an important role in CMP-induced activation of chicken splenic lymphocytes.

The role of neutrophils during intestinal inflammation

Polymorphonuclear leukocytes or neutrophils play a critical role in the maintenance of intestinal homeostasis. They have elegant defense mechanisms to eliminate microbes that have translocated across a single layer of mucosal epithelial cells that form a critical barrier between the gut lumen and the underlying tissue. During the inflammatory response, neutrophils also contribute to the recruitment of other immune cells and facilitate mucosal healing by releasing mediators necessary for the resolution of inflammation. Although the above responses are clearly beneficial, excessive recruitment and accumulation of activated neutrophils in the intestine under pathological conditions such as inflammatory bowel disease is associated with mucosal injury and debilitating disease symptoms. Thus, depending on the circumstances, neutrophils can be viewed as either good or bad. In this article, we summarize the beneficial and deleterious roles of neutrophils in the intestine during health and disease and provide an overview of what is known about neutrophil function in the gut.

Random phage-epitope library based identification of a peptide antagonist of Mac-1 β2 integrin ligand binding

The leukocyte β2 integrin Mac-1 (CD11b/CD18) plays a pivotal role in inflammation and host defense. To develop peptide antagonists selectively inhibiting the function of Mac-1, we used a random constrained 6-mer (cys-6aa-cys) peptide library to map the structural features of CD11b, by determining the epitope of neutralizing monoclonal antibody mAb 44a (anti-CD11b). We have used a stringent phage display strategy, which resulted in the identification of one disulfide C-RLKEKH-C constrained peptide by direct biopanning of library on decreasing amounts of purified mAb 44a. The selected peptide mimics a discontinuous epitope, a peculiar shape on the CD11b-I-domain surface. Competitive ELISA experiments with different Mac-1 ligands showed that C-RLKEKH-C is able to bind to fibrinogen, iC3b, and C1q. Furthermore, the monomeric circular peptide C-RLKEKH-C, was effective in blocking the interaction between (125)I-fibrinogen and Mac-1 (IC(50)=3.35±0.1×10(-6)M), and inhibited the adhesion of human neutrophils to fibrinogen and iC3b. These data provide information about the relative location of amino acids on the I-domain surface using mAb 44a imprint of the CD11b protein. The derived mimotope may help in the design of future anti-inflammatory therapeutic agents that can act as specific therapeutic agents targeting PMNs mediated inflammation.

Fucoidan enhances the survival and sustains the number of splenic dendritic cells in mouse endotoxemia

Fucoidan is a sulfated polysaccharide derived from brown algae that has been reported to perform multiple biological activities, including immunostimulation. In this study, we investigated whether fucoidan has beneficial effects on endotoxemia induced by LPS, a septic model in mice. The focus of this study was on survival rates and spleen function of the mice upon treatment. We found that fucoidan had prophylactic effects on the survival rate of mice with endotoxemia. Flow cytometric analysis using antibodies for subset-specific markers revealed that fucoidan profoundly reversed the depleted population of dendritic cells in mice with endotoxemia. According to Western blot analysis, the spleen cells of LPS/fucoidan-treated mice showed a higher expression of anti-apoptotic molecules compared to those of LPS-treated mice. Also, fucoidan-treated spleen cells were more responsive to mitogens. Taken together, these results demonstrate that fucoidan pre-treatment has beneficial effects on the survival rate and function of the spleen in mice with endotoxemia. This study may broaden the use of fucoidan in clinical fields, especially endotoxemia.

Cleavage of the CD11b extracellular domain by the leukocyte serprocidins is critical for neutrophil detachment during chemotaxis

The β(2)-integrin CD11b/CD18 mediates the firm adhesion of neutrophils (PMNs) to epithelial monolayers, a key step in PMN transepithelial migration. To complete the transmigration process, adherent PMNs must detach from epithelial monolayer surfaces to move forward. The mechanism that governs the detachment of adherent PMNs, however, is not clear. Here, we present evidence that cleavage of the CD11b extracellular domain containing the ligand-binding I-domain by 3 structural and functional related serine proteases (elastase, proteinase-3 and cathepsin G) serves as a novel mechanism for PMN detachment after the initial cell adhesion. Kinetic studies showed that the cleavage of CD11b is positively correlated with PMN detachment and subsequent transmigration. Moreover, the results demonstrated that elastase, proteinase-3 and cathepsin G all cleaved the purified, functionally active form of CD11b in a pattern similar to the CD11b shedding that occurs during PMN transmigration. Their cleavage sites on purified CD11b were located at (761)Thr-Ala(762) (elastase/proteinase-3) and (760)Phe-Thr(761) (cathepsin G), respectively. CD11b cleavage and PMN detachment and chemotaxis, were impaired in elastase/cathepsin G-deficient Beige mice; this defect could be restored by the addition of extracellular elastase. By illustrating CD11b shedding by elastase, proteinase-3 and cathepsin G as a novel mechanism for PMN detachment, our study provides novel therapeutic targets for controlling inflammation.

Immunopotentiation and anti-tumor activity of carboxymethylated-sulfated beta-(1-->3)-d-glucan from Poria cocos

A carboxymethylated-sulfated derivative of (1-->3)-beta-d-glucan (PCS3-II) extracted from Poria cocos was synthesized and coded as CS-PCS3-II. Results of infrared (IR) and Carbon-13 nuclear magnetic resonance spectroscopy ((13)C NMR) indicated that CS-PCS3-II contained carboxymethyl and sulfate groups with a degree of substitution (DS) of 1.05 and 0.36 respectively. By using size exclusion chromatography (SEC) combined with laser light scatting (LLS), the dependence of radius of gyration (<S(2)>(z)(1/2)) on the molecular weight (M(w)) for CS-PCS3-II was established as <S(2)>(z)(1/2) = 6.92 x 10(-2)M(w)(0.59) in 0.15M NaCl solution at 25 degrees C, suggesting that CS-PCS3-II existed as an extended flexible chain. CS-PCS3-II exhibited significantly higher inhibition ratio to Sarcoma 180 tumor in BALB/c mice than PCS3-II. Histological examination of tumor cells treated with CS-PCS3-II had signs of necrosis and apoptosis. It is postulated that introduction of the carboxymethyl and sulfate groups to PCS3-II increased its possible contact with the receptors of immune cells through hydrogen binding and electrostatic attraction, leading to a stronger immunological responses that resulted in inhibition of tumor cell proliferation. Moreover, there were significant increases in phagocyte and thymus indexes, spleen index, hemolytic activity as well as spleen antibody production and delayed type hypersensitivity (DTH), suggesting that CS-PCS3-II could significantly enhance immunpotentiation in mice.

Fucoidan increases TNF-alpha-induced MMP-9 secretion in monocytic cell line U937

OBJECTIVE

To investigate the effect of fucoidan on the expression of matrix metalloproteinase-9 (MMP-9) from monocytes.

METHODS

Human monocytic cell line U937 was purchased from ATCC. During the experiment, FBS-free 1640 was used and U937 was cultivated with 20 ng/ml TNF-alpha and/or different concentrations of fucoidan for 24 h. RT-PCR experiments were used to determine the MMP-9 mRNA expression. ELISA and gelatin zymography detected MMP-9 amounts and activity in the supernatant. The intracellular level of MMP-9 was assayed by Western blot, and the level of CD44 on the surface was assayed by FACS.

RESULTS

In this study, we showed that pro-inflammatory cytokine TNF-alpha up-regulated U937 MMP-9 mRNA and protein levels (P < 0.05). Fucoidan can increase the TNF-alpha-induced MMP-9 secretion from U937 (P < 0.05), but no significant difference was observed in MMP-9 mRNA. The intracellular level of MMP-9 treated with TNF-alpha and fucoidan was lower (P < 0.05) than that treated with TNF-alpha alone. In addition, we demonstrated that fucoidan downregulated the surface level of CD44, the main molecule to which MMP-9 attaches.

CONCLUSIONS

We demonstrated that fucoidan post-translationally regulated MMP-9 secretion from U937. Reduced intracellular level and decreased membrane attachment may contribute to the increase in MMP-9 secretion.