Activation of Toll-Like Receptor-Mediated NF-κβ by Zymosan-Derived Water-Soluble Fraction: Possible Contribution of Endotoxin-Like Substances

Yeast-based vaccines: New perspective in vaccine development and application

In presently licensed vaccines, killed or attenuated organisms act as a source of immunogens except for peptide-based vaccines. These conventional vaccines required a mass culture of associated or related organisms and long incubation periods. Special requirements during storage and transportation further adds to the cost of vaccine preparations. Availability of complete genome sequence, well-established genetic, inherent natural adjuvant and non-pathogenic nature of yeast species viz. Saccharomyces cerevisiae, Pichia pastoris makes them an ideal model system for the development of vaccines both for public health and for on-farm consumption. In this review, we compile the work in this emerging field during last two decades with major emphases on S. cerevisiae and P. pastoris which are routinely used worldwide for expression of heterologous proteins with therapeutic value against infectious diseases along with possible use in cancer therapy. We also pointed towards the developments in use of whole recombinant yeast, yeast surface display and virus-like particles as a novel strategy in the fight against infectious diseases and cancer along with other aspects including suitability of yeast in vaccines preparations, yeast cell wall component as an immune stimulator or modulator and present status of yeast-based vaccines in clinical trials.

Development of a Quantitative Assay for the Characterization of Human Collectin-11 (CL-11, CL-K1)

Collectin-11 (CL-11) is a pattern recognition molecule of the lectin pathway of complement with diverse functions spanning from host defense to embryonic development. CL-11 is found in the circulation in heterocomplexes with the homologous collectin-10 (CL-10). Abnormal CL-11 plasma levels are associated with the presence of disseminated intravascular coagulation, urinary schistosomiasis, and congenital disorders. Although there has been a marked development in the characterization of CL-11 there is still a scarcity of clinical tools for its analysis. Thus, we generated monoclonal antibodies and developed a quantitative ELISA to measure CL-11 in the circulation. The antibodies were screened against recombinant CL-11 and validated by ELISA and immunoprecipitation of serum and plasma. The best candidates were pairwise compared to develop a quantitative ELISA. The assay was validated regarding its sensitivity, reproducibility, and dilution linearity, demonstrating a satisfactory variability over a working range of 0.29–18.75 ng/ml. The mean plasma concentration of CL-11 in healthy controls was determined to be 289.4 ng/ml (range 143.2–459.4 ng/ml), highly correlated to the levels of CL/10/11 complexes (r = 0.729). Plasma CL-11 and CL-10/11 co-migrated in size exclusion chromatography as two major complexes of ~400 and >600 kDa. Furthermore, we observed a significant decrease at admission in CL-11 plasma levels in patients admitted to intensive care with systemic inflammatory response syndrome. By using the in-house antibodies and recombinant CL-11, we found that CL-11 can bind to zymosan independently of calcium by a separate site from the carbohydrate-binding region. Finally, we showed that CL-11/MASP-2 complexes trigger C4b deposition on zymosan. In conclusion, we have developed a specific and sensitive ELISA to investigate the ever-expanding roles of CL-11 in health and disease and shown a novel interaction between CL-11 and zymosan.

Zymosan A enhances humoral immune responses to soluble protein in chickens

Vaccination is the most effective method for controlling the infectious diseases that threaten the poultry industry worldwide. The use of adjuvants or immunostimulants is often necessary to improve vaccine efficacy, particularly for vaccines based on recombinant protein or inactivated pathogens. The adjuvant effects of zymosan A on antigen-specific antibody production were investigated in chickens. First, the optimal adjuvant dose of zymosan A was determined. Chicks were immunized with dinitrophenyl-keyhole limpet hemocyanin (DNP-KLH) at a dosage of 2 mg/kg body weight (BW) with or without zymosan A (at a dosage of 0.5 mg/kg BW) co-administration at 4, 5 and 6 weeks of age. Different routes of immunization (oral, intranasal (i.n.), intraocular (i.o.), subcutaneous (s.c.), intramuscular (i.m.) and intraperitoneal (i.p.) were tested. Anti-DNP IgY and IgA concentrations in serum samples from all chicks were measured by an enzyme-linked immunosorbent assay. The results revealed that co-administration of zymosan A with DNP-KLH significantly increased anti-DNP IgY concentrations in chicks immunized by the oral and s.c. routes of administration when compared with control groups. In addition, co-administration of zymosan A with DNP-KLH significantly increased anti-DNP IgA concentrations in chicks immunized by the oral, i.o. and s.c. routes compared with control groups. In conclusion, zymosan A is a useful immune-potentiator adjuvant in chickens, and its co-administration with vaccine antigens enhances humoral immune responses.

Mechanism of Enhanced Hematopoietic Response by Soluble β-Glucan SCG in Cyclophosphamide-Treated Mice

SCG is a major 6-branched 1,3-beta-D-glucan in Sparassis crispa Fr. SCG shows antitumor activity and also enhances the hematopoietic response in cyclophosphamide (CY)-treated mice. In the present study, the molecular mechanism of the enhancement of the hematopoietic response was investigated. The levels of interferon-(IFN-)gamma, tumor necrosis factor-(TNF-)alpha, granulocyte-macrophage-colony stimulating factor (GM-CSF), interleukin-(IL-) 6 and IL-12p70 were significantly increased by SCG in CY-treated mice. GM-CSF production in the splenocytes from the CY-treated mice was higher than that in normal mice regardless of SCG stimulation. Neutralizing GM-CSF significantly inhibited the induction of IFN-gamma, TNF-alpha and IL-12p70 by SCG. The level of cytokine induction by SCG was regulated by the amount of endogenous GM-CSF produced in response to CY treatment in a dose-dependent manner. The expression of beta-glucan receptors, such as CR3 and dectin-1, was up-regulated by CY treatment. Blocking dectin-1 significantly inhibited the induction of TNF-alpha and IL-12p70 production by SCG. Taken together, these results suggest that the key factors in the cytokine induction in CY-treated mice were the enhanced levels of both endogenous GM-CSF production and dectin-1 expression.

β-Glucan Derived from Zymosan Acts as an Adjuvant for Collagen-Induced Arthritis

Collagen-induced arthritis (CIA) is an experimental model of rheumatoid arthritis (RA) and has helped researchers to analyze the pathogenesis of inflammatory joint disease. In classical CIA, Freund's complete adjuvant (FCA), which contains heat-killed Mycobacterium tuberculosis, is used as an adjuvant. In our previous study, we reported that particles of beta-glucan, OX-CA, derived from Candida albicans, acted as a proper adjuvant in the CIA model. In this study, to establish pure beta-glucan as an adjuvant for CIA, we tested a commercially available preparation of Zymosan A (ZYM) and modified its products. beta-Glucan fractions of ZYM were prepared by oxidation with various concentrations of NaClO. The oxidized ZYM (OX-ZYM) was mainly composed of beta-glucan. In this study, we examined its effect as an adjuvant for CIA. DBA/1 mice injected with CII and OX-CA developed arthritis 7-10 days after receiving booster injections; the OX-ZYM fractions induced arthritis with the same time course. 0.01% OX-ZYM (oxidized with a 0.01% NaClO solution) caused arthritis faster than 0.1% OX-ZYM or 0.5% OX-ZYM. In conclusion, beta-glucan derived from ZYM by brief oxidation with NaClO is a suitable adjuvant for a CIA model with anti-CII antibody production.

Toll Like Receptors Signaling Pathways as a Target for Therapeutic Interventions

This review summarizes the key role of Toll-Like Receptor (TLRs) molecules for igniting the immune system. Activated by a broad spectrum of pathogens, cytokines or other specific molecules, TLRs trigger innate immune responses. Published data demonstrate that the targeting and suppression of TLRs and TLR-related proteins with particular inhibitors may provide pivotal treatments for patients with cancer, asthma, sepsis, Crohn's disease and thrombosis. Many drugs that target cytokines act in the late phases of the activated pathways, after the final peptides, proteins or glycoproteins are formed in the cell environment. TLR activity occurs in the early activation of cellular pathways; consequently inhibiting them might be most beneficial in the treatment of human diseases.

Induction of IFN-γ by a highly branched 1,3-β-d-glucan from Aureobasidium pullulans in mouse-derived splenocytes via dectin-1-independent pathways

We have previously elucidated the precise structure of a unique type of 1,3-β-D-glucan, AP-FBG (Aureobasidium pullulans-fermented β-D-glucan), from the fungus A. pullulans and found that AP-FBG strongly induced the production of various cytokines in DBA/2 mouse-derived splenocytes in vitro. However, the mechanism(s) of action of AP-FBG on in vitro mouse primary cells have not been characterized in detail. Herein, we report that the production of IFN-γ in DBA/2 mouse-derived splenocytes by AP-FBG was not inhibited following treatment with an anti-dectin-1 neutralizing antibody. In addition, AP-FBG not only failed to activate dectin-1-mediated signaling pathways, examined by a reporter gene assay but also failed to bind to dectin-1, a pivotal receptor for 1,3-β-D-glucan. Taken together, AP-FBG induced cell activation via dectin-1-independent pathways.

Suppressive effects of azithromycin on zymosan-induced production of proinflammatory mediators by human corneal epithelial cells

PURPOSE

In addition to its antibiotic effects, azithromycin has been noted to have anti-inflammatory activity, particularly in the context of microbial infections. This study was conducted to explore the suppressive effects of azithromycin on the production of proinflammatory mediators by human corneal epithelial cells (HCECs) stimulated by a fungal component, zymosan.

METHODS

Primary HCECs were cultured from donor corneal limbal explants and grown to subconfluence. The cells were treated with toll-like receptor (TLR) 2 agonist zymosan (1-50 μg/mL) for 4 to 48 hours, with or without preincubation with azithromycin (1-50 μg/mL), TLR2 antibody, or NF-κB activation inhibitor quinazoline (NF-κB-I). The cells were subjected to total RNA extraction, reverse transcription (RT), and real-time PCR using gene expression assays. Cells treated for 48 hours were used for immunofluorescence staining and Western blot analysis, and their medium supernatants were collected for protein quantitation by immunobead assays.

RESULTS

The mRNA expression and protein production of proinflammatory cytokines (TNF-α and IL-1β), chemokines (IL-8 and RANTES), and matrix metalloproteinases (MMP-1, -3, and -9) by HCECs were stimulated by zymosan in a concentration-dependent manner, with peak levels noted at 4 hours. These stimulated levels of proinflammatory mediators by zymosan were significantly inhibited by TLR2 antibody, NF-κB-I, or azithromycin, which blocked zymosan-induced NF-κB activation as determined by p65 protein nuclear translocation.

CONCLUSIONS

These findings demonstrated that the fungal component zymosan induces proinflammatory responses through TLR2 and NF-κB signaling pathways, whereas azithromycin suppresses its stimulation by blocking NF-κB activation in HCECs, suggesting the potential efficacy of this antibiotic for treating ocular surface inflammatory disorders.

Auxiliary role for D-alanylated wall teichoic acid in Toll-like receptor 2-mediated survival of Staphylococcus aureus in macrophages

We previously reported that Staphylococcus aureus avoids killing within macrophages by exploiting the action of Toll-like receptor 2 (TLR2), which leads to the c-Jun N-terminal kinase (JNK)-mediated inhibition of superoxide production. To search for bacterial components responsible for this event, a series of S. aureus mutants, in which the synthesis of the cell wall was interrupted, were screened for the level of JNK activation in macrophages. In addition to a mutant lacking the lipoproteins that have been suggested to act as a TLR2 ligand, two mutant strains were found to activate the phosphorylation of JNK to a lesser extent than the parental strain, and this defect was recovered by acquisition of the corresponding wild-type genes. Macrophages that had phagocytosed the mutant strains produced more superoxide than those engulfing the parental strain, and the mutant bacteria were more efficiently killed in macrophages than the parent. The genes mutated, dltA and tagO, encoded proteins involved in the synthesis of D-alanylated wall teichoic acid. Unlike a cell wall fraction rich in lipoproteins, D-alanine-bound wall teichoic acid purified from the parent strain by itself did not activate JNK phosphorylation in macrophages. These results suggest that the d-alanylated wall teichoic acid of S. aureus modulates the cell wall milieu for lipoproteins so that they effectively serve as a ligand for TLR2.

Toll-like receptor 2 is upregulated by hog confinement dust in an IL-6-dependent manner in the airway epithelium

Hog confinement workers are at high risk to develop chronic bronchitis as a result of their exposure to organic dust. Chronic bronchitis is characterized by inflammatory changes of the airway epithelium. A key mediator in inflammation is Toll-like receptor 2 (TLR2). We investigated the role of TLR2 in pulmonary inflammation induced by hog confinement dust. Normal human bronchial epithelial cells (NHBE) were grown in culture and exposed to hog confinement dust extract. Hog confinement dust upregulated airway epithelial cell TLR2 mRNA in a concentration- and time-dependent manner using real-time PCR. There was a similar increase in TLR2 protein at 48 h as shown by Western blot. TLR2 was upregulated on the surface of airway epithelial cells as shown by flow cytometry. A similar upregulation of pulmonary TLR2 mRNA and protein was shown in a murine model of hog confinement dust exposure. Hog confinement dust is known to stimulate epithelial cells to produce IL-6. To determine whether TLR2 expression was being regulated by IL-6, the production of IL-6 was blocked using an IL-6-neutralizing antibody. This resulted in attenuation of the dust-induced upregulation of TLR2. To further demonstrate the importance of IL-6 in the regulation of TLR2, NHBE were directly stimulated with recombinant human IL-6. IL-6 alone was able to upregulate TLR2 in airway epithelial cells. Hog confinement dust upregulates TLR2 in the airway epithelium through an IL-6-dependent mechanism.

Immunological actions of Sophy beta-glucan (beta-1,3-1,6 glucan), currently available commercially as a health food supplement

We examined the immunological actions of Sophy beta-glucan(Ikewaki N., et al. United States Patent 6956120 and Japan Patent 2004-329077), a type of beta-1,3-1,6 glucan produced by the black yeast Aureobasidium pullulans (A. pullulans) strain AFO-202, currently available commercially as a health food supplement, using different human in vitro experimental systems. Sophy beta-glucan significantly (P<0.01) stimulated the (3)H-thymidine incorporation rates (marker of DNA synthesis) in human peripheral blood mononuclear cells (PBMCs) obtained from normal adult donors, in vitro. Enzyme-linked immunoassays (EIAs) revealed that Sophy beta-glucan stimulated the production of interleukin-8 (IL-8) or soluble Fas (sFas), but not that of IL-1beta, IL-2, IL-6, IL-12 (p70+40), interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) or soluble Fas ligand (sFasL), in either cultured PBMCs or cells of the human monocyte-like cell line, U937. The induction by Sophy beta-glucan of DNA synthesis in PBMCs was completely blocked by the addition of monoclonal antibodies (mAbs) to CD11a, CD54, human leukocyte antigen-class II (HLA-class II), Toll-like receptor-2 (TLR-2), and Toll-like receptor-4 (TLR-4). In these blocking experiments using the mAbs, the main differences in the results between PBMCs and U937 cells were that the mAbs against TLR-2 and TLR-4 did not block the Sophy beta-glucan-induced production of IL-8 in the U937 cells. Furthermore, a mAb to the beta-glucan receptor, Dectin-1, significantly (P<0.05) blocked the Sophy beta-glucan induced DNA synthesis in the PBMCs, and Sophy beta-glucan-induced production of IL-8 in the U937 cells. The Sophy beta-glucan-induced production of IL-8 in the U937 cells was significantly (P<0.01) blocked by the conventional protein kinase C (PKC) inhibitor Go6976, the novel PKC inhibitor Rottlerin, the protein kinase A (PKA) inhibitor H-89, and the protein tyrosine kinase (PTK) inhibitor herbimycin A. Among these, the blocking effect of the novel PKC (PKC delta isoenzyme) inhibitor Rottlerin was the most pronounced. Studies employing reverse transcriptase-polymerase chain reaction (RT-PCR) showed that Sophy beta-glucan stimulated the expression of IL-8 mRNA in the U937 cells, and that this induction was inhibited by Rottlerin. Sophy beta-glucan also blocked the stimulator cell induction of DNA synthesis and IFN-gamma production in the responder cells in a one-way mixed lymphocyte reaction (MLR) using allogenic PBMCs. Interestingly, immunoglobulin G (IgG), but not IgM to Sophy beta-glucan was detected in the sera derived from normal adult donors and from the umbilical cord blood of neonates. Taken together, these findings strongly suggest that the Sophy beta-glucan may have unique immune regulatory or enhancing properties that could be exploited by the health food, medical and pharmaceutical industries.

Dissociation of Toll-like receptor 2-mediated innate immune response to Zymosan by organic solvent-treatment without loss of Dectin-1 reactivity

Zymosan activates phagocytes through the innate immune system and causes inflammatory responses in animals. Because of the complexity of the active substances included in Zymosan preparations, simplifying the active moiety actually responsible for innate immune recognition is needed. One way to remove possible active substances from commercially available Zymosan preparations is to wash then with pyrogen-free water to obtain a ZWIS (Zymosan water insoluble fraction), ethanol insoluble (EtIS), or chloroform/methanol insoluble (CMIS) preparation. The effects of various washed Zymosan preparations on nuclear factor (NF)-kappaB activation and binding to beta-glucan recognition protein were examined. Significant NF-kappaB activation by Toll-like receptor (TLR) 2-expressing HEK293 cells and enhanced NF-kappaB activity via the co-expression of TLR2 and Dectin-1, a functional beta-glucan receptor, was only observed in response to ZWIS. However, the ability of Zymosan preparations to bind Dectin-1 protein was not altered even after treatment with the organic solvents by which the TLR2-mediated NF-kappaB activity was abolished. Another NF-kappaB activation pathway involving CARD9/Bcl10 was triggered by these Zymosan preparations in the presence of Dectin-1. The results suggest that the beta-glucan-dependent characteristics of Zymosan were not affected by the washing with chloroform/methanol or ethanol, and that TLR2-mediated activity was easily eliminated with these organic solvents. This treatment might be useful for distinguishing natural ligands for TLR2 and beta-glucan receptors when studying the innate immune response to fungal macromolecules.

Contribution of dectin-1 and granulocyte macrophage-colony stimulating factor (GM-CSF) to immunomodulating actions of beta-glucan

beta-Glucans are major cell wall structural components in fungi. As they are not found in animals, these carbohydrates are considered to be classic pathogen-associated molecular patterns (PAMPs), and are recognized by the innate immune system. Although their immunomodulating activities have been shown to be associated with the recognition of some fungi, and with their medicinal properties in the field of cancer immunotherapy, it is still unclear how beta-glucans mediate their effects. Recent studies have started to shed some light on their cellular receptors, such as dectin-1, and their molecular mechanisms of action. We have extensively investigated the response of leukocytes to beta-glucan, focusing on cytokine induction by SCG, which is a major 6-branched 1,3-beta-d-glucan in Sparassis crispa Fr. There is a strain difference in the reactivity of mice to SCG, and DBA/1 and DBA/2 mice are highly sensitive strains. In the process of research on cytokine induction by SCG in DBA/2 mice, we found that GM-CSF plays a key biological role in this activity. Cytokine induction by SCG was completely abolished in dendritic cells from dectin-1 knockout mice. On the other hand, controlling the level of endogenous GM-CSF production and/or dectin-1 expression could regulate the reactivity to beta-glucan. These results indicate that the key factors in the responsiveness to beta-glucan are GM-CSF production and dectin-1 expression. In this review, we describe how the key molecules related to the expression of the immunomodulating activities of beta-glucan were identified, and how the response to beta-glucan is controlled.

Distinct roles of Ca2+ mobilization and G protein usage on regulation of Toll-like receptor function in human and murine mast cells

Toll-like receptors (TLRs) expressed in mast cells play important roles in orchestrating host defence against bacterial pathogens. Previous studies demonstrated that TLR2 agonist tripalmitoyl-S-glycero-Cys-(Lys)4 (Pam3Cys) stimulates both degranulation and cytokine production in human mast cells but only induces cytokine production in murine mast cells. To determine the molecular basis for this difference, we utilized a human mast cell line LAD 2, murine lung and bone marrow-derived mast cells (MLMC and BMMC). We found that Pam3Cys caused a sustained Ca2+ mobilization and degranulation in LAD 2 mast cells but not in MLMC or BMMC. Despite these differences, Pam3Cys stimulated equivalent chemokine CCL2 generation in all mast cell types tested. Cyclosporin A (CsA), an inhibitor of Ca2+/calcineurin-mediated nuclear factor of activated T cells (NFAT) activation, blocked chemokine production in LAD 2 but not in MLMC or BMMC. In contrast, inhibitors of nuclear factor kappa B (NF-kappaB) completely blocked CCL2 production in MLMC and BMMC but not in LAD 2 mast cells. Pertussis toxin and U0126, which, respectively, inhibit Galphai, extracellular signal-regulated kinase (ERK) phosphorylation substantially inhibited Pam3Cys-induced CCL2 generation in LAD 2 mast cells but had little or no effect on chemokine generation in MLMC and BMMC. These findings suggest that TLR2 activation in human LAD 2 mast cells and MLMC/BMMC promotes the release of different classes of mediators via distinct signalling pathways that depend on Ca2+ mobilization and G protein usage.

Whole recombinant yeast-based immunotherapy induces potent T cell responses targeting HCV NS3 and Core proteins

Control of primary infection with hepatitis C virus (HCV) is associated with robust and broad T cell immunity. In contrast, chronic infection is characterized by weak T cell responses suggesting that an approach that boosts these responses could be a therapeutic advance. Saccharomyces cerevisiae is an effective inducer of innate and adaptive cellular immunity and we have generated recombinant yeast cells (GI-5005) that produce an HCV NS3-Core fusion protein. Pre-clinical studies in mice showed that GI-5005 induced potent antigen-specific proliferative and cytotoxic T cell responses that were associated with Th1-type cytokine secretion. In studies in which GI-5005 was administered up to 13 times, no detectable vector neutralization or induction of tolerance was observed. Prophylactic as well as therapeutic administration of GI-5005 in mice led to eradication of tumor cells expressing HCV NS3 protein. Immunotherapy with GI-5005 is being evaluated in chronic HCV infected individuals in a Phase 1 clinical trial.

[Contribution of dectin-1 to the recognition of fungal cell wall products and the activation of innate immune response]

1,3-Beta-glucans is a major cell wall component in fungi. Receptor molecules relating to innate immunity may recognize such cell wall products, and affect host defense systems. A beta-glucan receptor, dectin-1, is a C-type lectin and may contribute to the innate immune responses. To examine the role of dectin-1 in recognition of 1,3-beta-glucans and subsequent activation of intracellular signaling, the molecular characteristics of a carbohydrate recognition domain (CRD) of dectin-1 were investigated. The binding ability to beta-glucans was abolished by mutating two amino acid residues, Trp221 and His223, on the CRD. Dectin-1 increased TLR2-mediated NF-kappaB activation in response to zymosan. However, dectin-1 alone could not affect the activation pathway for NF-kappaB, nor did co-expression of dectin-1 mutant and TLR2 increase the NF-kappaB activation. These results suggest that dectin-1 may have a co-stimulatory effect on leukocyte activation in response to fungal infection.

Contribution of N-linked oligosaccharides to the expression and functions of beta-glucan receptor, Dectin-1

Dectin-1 is a C-type lectin receptor that recognizes fungal beta-glucan, and mediates the production of reactive oxygen species and inflammatory cytokines. Thus Dectin-1 is thought to be essential for anti-fungal immune responses. Murine Dectin-1 mRNA is alternatively spliced and generates two isoforms (isoform A and B). Human Dectin-1 mRNA is also alternatively spliced and its functional isoforms (isoform A and B) are structurally similar to each of the mouse isoforms. One of the major differences among the four murine and human isoforms is the position and number of N-linked glycosylation motifs. But the significance of the glycosylation to the recognition of beta-glucan is not known. In this paper, using various glycosylation consensus sequence mutants, we demonstrated that the N-linked glycosylation of Dectin-1 affects the cell surface expression of the molecule. The expression levels on the cell surface influence the ligand-binding and the collaboration with TLR2 in the activation of NF-kappaB. These results suggest that N-linked glycosylation on Dectin-1 is essential for the recognition of fungal beta-glucan and subsequent activation of NF-kappaB.

Differential Effects of Selective Cyclooxygenase (COX)-1 and COX-2 Inhibitors on Anorexic Response and Prostaglandin Generation in Various Tissues Induced by Zymosan

We have shown that anorexic response is induced by intraperitoneal injection of zymosan in mice, although the role of prostaglandins in this response is relatively unknown as compared with lipopolysaccharide (LPS)-induced anorexic response. Indomethacin (0.5 and 2.0 mg/kg), a non-selective cyclooxygenase (COX) inhibitor, as well as meloxicam (0.5 mg/kg), a selective COX-2 inhibitor, but not FR122047 (2.0 mg/kg), a selective COX-1 inhibitor, attenuated zymosan-induced anorexia. Zymosan injection elevated COX-2 expression in brain and liver but not in small intestine and colon. Meloxicam (0.5 mg/kg) and FR122047 treatment (2.0 mg/kg) similarly suppressed the generation of brain prostaglandin E(2) (PGE(2)) and peritoneal prostacyclin (PGI(2)) upon zymosan injection. PGE(2) generation in liver upon zymosan injection was suppressed by meloxicam (0.5 mg/kg) but not by FR122047 treatment (2.0 mg/kg). Our observations suggest that COX-2 plays an important role in zymosan-induced anorexia, which is a similar feature in LPS-induced anorexic response. However, non-selective inhibition by selective COX-1 and COX-2 inhibitors of brain PGE(2) generation upon zymosan injection does not support the role of COX-2 expressed in brain in zymosan-induced anorexic response. PGE(2) generation in liver may account for peripheral role of COX-2 in zymosan-induced anorexic response.