Regulation of cytosolic phospholipase A2 activation and cyclooxygenase 2 expression in macrophages by the beta-glucan receptor

Fatty acid desaturation and lipoxygenase pathways support trained immunity

Infections and vaccines can induce enhanced long-term responses in innate immune cells, establishing an innate immunological memory termed trained immunity. Here, we show that monocytes with a trained immunity phenotype, due to exposure to the Bacillus Calmette-Guérin (BCG) vaccine, are characterized by an increased biosynthesis of different lipid mediators (LM) derived from long-chain polyunsaturated fatty acids (PUFA). Pharmacological and genetic approaches show that long-chain PUFA synthesis and lipoxygenase-derived LM are essential for the BCG-induced trained immunity responses of human monocytes. Furthermore, products of 12-lipoxygenase activity increase in monocytes of healthy individuals after BCG vaccination. Grasping the underscoring lipid metabolic pathways contributes to our understanding of trained immunity and may help to identify therapeutic tools and targets for the modulation of innate immune responses.

Dynamics of Docosahexaenoic Acid Utilization by Mouse Peritoneal Macrophages

In this work, the incorporation of docosahexaenoic acid (DHA) in mouse resident peritoneal macrophages and its redistribution within the various phospholipid classes were investigated. Choline glycerophospholipids (PC) behaved as the major initial acceptors of DHA. Prolonged incubation with the fatty acid resulted in the transfer of DHA from PC to ethanolamine glycerophospholipids (PE), reflecting phospholipid remodeling. This process resulted in the cells containing similar amounts of DHA in PC and PE in the resting state. Mass spectrometry-based lipidomic analyses of phospholipid molecular species indicated a marked abundance of DHA in ether phospholipids. Stimulation of the macrophages with yeast-derived zymosan resulted in significant decreases in the levels of all DHA-containing PC and PI species; however, no PE or PS molecular species were found to decrease. In contrast, the levels of an unusual DHA-containing species, namely PI(20:4/22:6), which was barely present in resting cells, were found to markedly increase under zymosan stimulation. The levels of this phospholipid also significantly increased when the calcium-ionophore A23187 or platelet-activating factor were used instead of zymosan to stimulate the macrophages. The study of the route involved in the synthesis of PI(20:4/22:6) suggested that this species is produced through deacylation/reacylation reactions. These results define the increases in PI(20:4/22:6) as a novel lipid metabolic marker of mouse macrophage activation, and provide novel information to understand the regulation of phospholipid fatty acid turnover in activated macrophages.

Metabolic pathways altered by air pollutant exposure in association with lipid profiles in young adults

Mounting evidence suggests that air pollution influences lipid metabolism and dyslipidemia. However, the metabolic mechanisms linking air pollutant exposure and altered lipid metabolism is not established. In year 2014-2018, we conducted a cross-sectional study on 136 young adults in southern California, and assessed lipid profiles (triglycerides, total cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, very-low-density lipoprotein (VLDL)-cholesterol), and untargeted serum metabolomics using liquid chromatography-high-resolution mass spectrometry, and one-month and one-year averaged exposures to NO2, O3, PM2.5 and PM10 air pollutants at residential addresses. A metabolome-wide association analysis was conducted to identify metabolomic features associated with each air pollutant. Mummichog pathway enrichment analysis was used to assess altered metabolic pathways. Principal component analysis (PCA) was further conducted to summarize 35 metabolites with confirmed chemical identity. Lastly, linear regression models were used to analyze the associations of metabolomic PC scores with each air pollutant exposure and lipid profile outcome. In total, 9309 metabolomic features were extracted, with 3275 features significantly associated with exposure to one-month or one-year averaged NO2, O3, PM2.5 and PM10 (p < 0.05). Metabolic pathways associated with air pollutants included fatty acid, steroid hormone biosynthesis, tryptophan, and tyrosine metabolism. PCA of 35 metabolites identified three main PCs which together explained 44.4% of the variance, representing free fatty acids and oxidative byproducts, amino acids and organic acids. Linear regression indicated that the free fatty acids and oxidative byproducts-related PC score was associated with air pollutant exposure and outcomes of total cholesterol and LDL-cholesterol (p < 0.05). This study suggests that exposure to NO2, O3, PM2.5 and PM10 contributes to increased level of circulating free fatty acids, likely through increased adipose lipolysis, stress hormone and response to oxidative stress pathways. These alterations were associated with dysregulation of lipid profiles and potentially could contribute to dyslipidemia and other cardiometabolic disorders.

Immunomodulatory Effect and Biological Significance of β-Glucans

β-glucan, one of the homopolysaccharides composed of D-glucose, exists widely in cereals and microorganisms and possesses various biological activities, including anti-inflammatory, antioxidant, and anti-tumor properties. More recently, there has been mounting proof that β-glucan functions as a physiologically active "biological response modulator (BRM)", promoting dendritic cell maturation, cytokine secretion, and regulating adaptive immune responses-all of which are directly connected with β-glucan-regulated glucan receptors. This review focuses on the sources, structures, immune regulation, and receptor recognition mechanisms of β-glucan.

Extracellular Vesicles from Candida haemulonii var. vulnera Modulate Macrophage Oxidative Burst

Members of the Candida haemulonii species complex are multidrug-resistant emergent yeast pathogens able to cause superficial and invasive infections in risk populations. Fungal extracellular vesicles (EVs) play a critical role in the pathogenicity and virulence of several species and may perform essential functions during infections, such as carrying virulence factors that behave in two-way communications with the host, affecting survival and fungal resistance. Our study aimed to describe EV production from Candida haemulonii var. vulnera and evaluate whether murine macrophage RAW 264.7 cells respond to their stimuli by generating an oxidative response after 24 h. For this purpose, reactive oxygen species detection assays demonstrated that high concentrations of yeast and EVs (10¹⁰ particles/mL) of Candida haemulonii did not change macrophage viability. However, the macrophages recognized these EVs and triggered an oxidative response through the classical NOX-2 pathway, increasing O₂^•- and H₂O₂ levels. However, this stress did not cause lipid peroxidation in the RAW 264.7 cells and neither lead to the activation of the COX-2-PGE₂ pathway. Thus, our data suggest that low concentrations of C. haemulonii EVs are not recognized by the classical pathway of the oxidative burst generated by macrophages, which might be an advantage allowing the transport of virulence factors via EVs, not identified by the host immune system that could work as fine tube regulators during infections caused by C. haemulonii. In contrast, C. haemulonii var. vulnera and high EV concentrations activated microbicidal actions in macrophages. Therefore, we propose that EVs could participate in the virulence of the species and that these particles could be a source of antigens to be exploited as new therapeutic targets.

Blocking Dectin-1 prevents colorectal tumorigenesis by suppressing prostaglandin E2 production in myeloid-derived suppressor cells and enhancing IL-22 binding protein expression

Dectin-1 (gene Clec7a), a receptor for β-glucans, plays important roles in the host defense against fungi and immune homeostasis of the intestine. Although this molecule is also suggested to be involved in the regulation of tumorigenesis, the role in intestinal tumor development remains to be elucidated. In this study, we find that azoxymethane-dextran-sodium-sulfate-induced and Apc^Min-induced intestinal tumorigenesis are suppressed in Clec7a^-/- mice independently from commensal microbiota. Dectin-1 is preferentially expressed on myeloid-derived suppressor cells (MDSCs). In the Clec7a^-/- mouse colon, the proportion of MDSCs and MDSC-derived prostaglandin E₂ (PGE₂) levels are reduced, while the expression of IL-22 binding protein (IL-22BP; gene Il22ra2) is upregulated. Dectin-1 signaling induces PGE₂-synthesizing enzymes and PGE₂ suppresses Il22ra2 expression in vitro and in vivo. Administration of short chain β-glucan laminarin, an antagonist of Dectin-1, suppresses the development of mouse colorectal tumors. Furthermore, in patients with colorectal cancer (CRC), the expression of CLEC7A is also observed in MDSCs and correlated with the death rate and tumor severity. Dectin-1 signaling upregulates PGE₂-synthesizing enzyme expression and PGE₂ suppresses IL22RA2 expression in human CRC-infiltrating cells. These observations indicate a role of the Dectin-1-PGE₂-IL-22BP axis in regulating intestinal tumorigenesis, suggesting Dectin-1 as a potential target for CRC therapy.

Differential Mobilization of the Phospholipid and Triacylglycerol Pools of Arachidonic Acid in Murine Macrophages

Innate immune cells such as monocytes and macrophages contain high levels of arachidonic acid (AA), part of which can be mobilized during cellular activation for the formation of a vast array of bioactive oxygenated metabolites. Monocytes and macrophages present in inflammatory foci typically incorporate large amounts of AA, not only in membrane phospholipids, but also in neutral lipids such as triacylglycerol. Thus, it was of interest to investigate the metabolic fate of these two AA pools in macrophages. Utilizing a variety of radiolabeling techniques to distinguish the phospholipid and triacylglycerol pools, we show in this paper that during an acute stimulation of the macrophages with yeast-derived zymosan, the membrane phospholipid AA pool acts as the major, if not the only, source of releasable AA. On the contrary, the AA pool in triacylglycerol appears to be used at a later stage, when the zymosan-stimulated response has declined, as a source to replenish the phospholipid pools that were consumed during the activation process. Thus, phospholipids and triacylglycerol play different in roles AA metabolism and dynamics during macrophage activation.

The role of PAF in immunopathology: From immediate hypersensitivity reactions to fungal defense

Platelet-activating factor (PAF, 1-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) was discovered when the mechanisms involved in the deposition of immune complex in tissues were being scrutinized in the experimental model of rabbit serum sickness. The initial adscription of PAF to IgE-dependent anaphylaxis was soon extended after disclosing its release from phagocytes stimulated by calcium mobilizing agents, formylated peptides, and phagocytosable particles. This explains why ongoing research in the field turned to the analysis of immune cell types and stimuli involved in PAF production with the purpose of establishing its role in pathology. This was spurred by the identification of the chemical structure of PAF and the enzymic mechanisms involved in its biosynthesis and degradation, which showed commonalities with those involved in eicosanoid production and the Lands' cycle of phospholipid fatty acid remodeling. The reassignment of PAF function in immunopathology is explained by the finding that the most robust mechanisms leading to PAF production are associated with opsonic and non-opsonic phagocytosis, depending on the cell type. While polymorphonuclear leukocytes exhibit opsonic phagocytosis, monocyte-derived dendritic cells show a marked preference for non-opsonic phagocytosis associated with C-type lectin receptors. This is particularly relevant to the defense against fungal invasion and explains why PAF exerts an autocrine feed-forwarding mechanism required for the selective expression of some cytokines.

A proof of principle study investigating the effects of supplemental concentrated brewer's yeast on markers of gut permeability, inflammation, and fecal metabolites in healthy non-challenged adult sled dogs

Yeast-derived β-glucans impact immunity, though their effects on gut permeability and inflammation are less understood. Most research has investigated other components of the yeast cell wall, such as the prebiotic mannan- and fructo-oligosaccharides. The objective of this study was to assess the effects of feeding a concentrated yeast product on markers of inflammation (serum amyloid A [SAA] and haptoglobin [Hp]) and oxidative status (malondialdehyde [MDA]), fecal products of fermentation, and gut permeability. Nineteen privately owned domestic Siberian huskies, and one Alaskan husky (9 females: 5 intact, 4 spayed; 11 males: 3 intact, 8 neutered), with an average age of 4.8 ± 2.6 yr and body weight (BW) of 25.6 ± 4.1 kg, were used in this study. Dogs were blocked and randomly allocated to one of two diet groups. Ten dogs received a dry extruded diet. The other 10 received the same diet top dressed with yeast for a daily β-glucan dose of 7 mg/kg BW for 10 wk. Fecal collection, for evaluation of fecal metabolites, and scoring occurred weekly. Gut permeability was assessed using the chromium-labeled ethylenediamine tetra-acetic acid (Cr-EDTA) and iohexol markers prior to the initiation of dietary treatment and after 10 wk of treatment. Blood samples were collected premarker administration and 0.5, 1, 2, 3, 4, 5, and 6 h postadministration. Fasting concentrations of SAA, Hp, and MDA were measured on weeks -1, 2, 4, and 8. Incremental area under the curve (I-AUC) was calculated for serum iohexol and Cr-EDTA concentrations. All data were analyzed using PROC GLIMMIX of SAS with dog as random effect, and week as fixed effect and repeated measure. Dogs receiving treatment tended to have decreased I-AUC of Iohexol (P = 0.10) and Cr-EDTA (P = 0.06) between baseline and cessation of treatment compared to the change over time in I-AUC for control (Ctl) dogs. Treatment dogs had lower Hp concentrations (P ≤ 0.05) than Ctl. There were no differences between treatments for SAA and MDA concentrations (P > 0.05). Fecal arabinose concentrations were greater in treatment (Trt) dogs (P ≤ 0.05) compared to Ctl, though no other fecal metabolites were affected by treatment. There was no difference in the relative frequency of defecations scored at any fecal score between Trt and Ctl dogs, and mean score did not differ between groups (P > 0.10). These data suggest that concentrated brewer's yeast may have the potential to reduce gut permeability without impacting inflammatory status and markers of health in adult dogs.

Mitofusin 2 Deficiency Causes Pro-Inflammatory Effects in Human Primary Macrophages

Mitofusin 2 (MFN2) is a mitochondrial outer membrane GTPase, which modulates mitochondrial fusion and affects the interaction between endoplasmic reticulum and mitochondria. Here, we explored how MFN2 influences mitochondrial functions and inflammatory responses towards zymosan in primary human macrophages. A knockdown of MFN2 by small interfering RNA decreased mitochondrial respiration without attenuating mitochondrial membrane potential and reduced interactions between endoplasmic reticulum and mitochondria. A MFN2 deficiency potentiated zymosan-elicited inflammatory responses of human primary macrophages, such as expression and secretion of pro-inflammatory cytokines interleukin-1β, -6, -8 and tumor necrosis factor α, as well as induction of cyclooxygenase 2 and prostaglandin E₂ synthesis. MFN2 silencing also increased zymosan-induced nuclear factor kappa-light-chain-enhancer of activated B cells and mitogen-activated protein kinases inflammatory signal transduction, without affecting mitochondrial reactive oxygen species production. Mechanistic studies revealed that MFN2 deficiency enhanced the toll-like receptor 2-dependent branch of zymosan-triggered responses upstream of inhibitor of κB kinase. This was associated with elevated, cytosolic expression of interleukin-1 receptor-associated kinase 4 in MFN2-deficient cells. Our data suggest pro-inflammatory effects of MFN2 deficiency in human macrophages.

Beta-glucans is a potential inhibitor of ovarian cancer: based on molecular and biological aspects

Ovarian cancer is a lethal type of cancer which is initiated in the ovaries and affects 1 out of every 75 women. Due to the high number of deaths (almost 152,000) related to this cancer, it seems that novel effiecient therapeutic methods are required in this field. Beta-glucans are a type of glucose linear polymers which have proven to have a lot of advantageous activities. Recently, investigations have declared that these polysaccharides have the potential to be used as anti-cancer drugs. These agents are able to affect several mechanisms such as inflammation and apoptosis and that is how cancers are prone to be affected by them. In this review, we attempt to investigate the role of beta-glucans on ovarian cancer. We hope that this paper might give novel insights in the field of ovarian cancer treatment.

Divergent Roles for Macrophage C-type Lectin Receptors, Dectin-1 and Mannose Receptors, in the Intestinal Inflammatory Response

Colonic macrophages are considered to be major effectors of inflammatory bowel diseases (IBDs) and the control of gut inflammation through C-type lectin receptors is an emerging concept. We show that during colitis, the loss of dectin-1 on myeloid cells prevents intestinal inflammation, while the lack of mannose receptor (MR) exacerbates it. A marked increase in dectin-1 expression in dextran sulfate sodium (DSS)-exposed MR-deficient mice supports the critical contribution of dectin-1 to colitis outcome. Dectin-1 is crucial for Ly6C^highCCR2^high monocyte population enrichment in the blood and their recruitment to inflamed colon as precursors of inflammatory macrophages. Dectin-1 also promotes inflammasome-dependent interleukin-1β (IL-1β) secretion through leukotriene B4 production. Interestingly, colonic inflammation is associated with a concomitant overexpression of dectin-1/CCL2/LTA4H and downregulation of MR on macrophages from IBD patients. Thus, MR and dectin-1 on macrophages are important mucosal inflammatory regulators that contribute to the intestinal inflammation.

Serum 1,3-beta-D-glucan as a noninvasive test to predict histologic activity in patients with inflammatory bowel disease

BACKGROUND

1,3-beta-D-glucan (BG) is a ubiquitous cell wall component of gut micro-organisms. We hypothesized that the serum levels of BG could reflect active intestinal inflammation in patients with inflammatory bowel disease.

AIM

To determine whether the serum BG concentrations correlate with intestinal inflammation.

METHODS

A prospective observational study was performed in a tertiary referral center, from 2016 to 2019, in which serum BG was determined in 115 patients with Crohn’s disease (CD), 51 with ulcerative colitis (UC), and 82 controls using a photometric detection kit. Inflammatory activity was determined by ileocolonoscopy, histopathology, magnetic resonance enterography, and biomarkers, including fecal calprotectin (FC), C-reactive protein, and a panel of cytokines. The ability of BG to detect active vs inactive disease was assessed using the area under the receiver operating characteristic curve. In subgroup analysis, serial BG was used to assess the response to therapeutic interventions.

RESULTS

The serum BG levels were higher in CD patients than in controls (P = 0.0001). The BG levels paralleled the endoscopic activity in CD patients and histologic activity and combined endoscopic and histologic activity in both CD and UC patients. The area under the curve (AUC) in receiver operating characteristic analysis to predict endoscopic activity was 0.694 [95% confidence interval (CI): 0.60-0.79; P = 0.001] in CD, and 0.662 (95%CI: 0.51-0.81; P = 0.066) in UC patients. The AUC in receiver operating characteristic analysis to predict histologic activity was 0.860 (95%CI: 0.77-0.95; P < 0.001) in CD, and 0.786 (95%CI: 0.57-0.99; P = 0.015) in UC patients. The cut-off values of BG for both endoscopic and histologic activity were 60 µg/mL in CD, and 40 µg/mL in UC patients. Performance analysis showed that the results based on BG of 40 and 60 µg/mL were more specific for predicting endoscopic activity (71.8% and 87.2% for CD; and 87.5% and 87.5% for UC, respectively) than FC (53.3% and 66.7% for CD; and 20% and 80% for UC, respectively); and also histologic activity (60.5% and 76.3% for CD; and 90.0% and 95.0% for UC, respectively) than FC (41.7% and 50.0% for CD; and 25% and 50% for UC, respectively). Regarding the clinical, endoscopic, and histologic activities, the BG levels were reduced following therapeutic intervention in patients with CD (P < 0.0001) and UC (P = 0.003). Compared with endoscopic (AUC: 0.693; P = 0.002) and histologic (AUC: 0.868; P < 0.001) activity, no significant correlation was found between serum BG and transmural healing based on magnetic resonance enterography (AUC: 0.576; P = 0.192). Positive correlations were detected between BG and IL-17 in the CD (r: 0.737; P = 0.001) and the UC group (r: 0.574; P = 0.005), and between BG and interferon-gamma in the CD group (r: 0.597; P = 0.015).

CONCLUSION

Serum BG may represent an important novel noninvasive approach for detecting mucosal inflammation and therapeutically monitoring inflammatory bowel diseases, particularly in CD.

Recognition of Candida albicans and Role of Innate Type 17 Immunity in Oral Candidiasis

Candida albicans is an opportunistic pathogenic fungus considered to be a common member of the human microflora. Similar to some other opportunistic microbes, C. albicans can invade and benefit from its host when the immune status of that host is weakened. Most often this happens to immunocompromised individuals, leading to the infection of oral and vaginal mucosae or the systemic spread of the pathogen throughout the entire body. Oropharyngeal candidiasis (OPC) occurs in up to 90 percent of patients with acquired immunodeficiency syndrome (AIDS), making it the most frequent opportunistic infection for this group. Upon first signs of fungal invasion, a range of host signaling activates in order to eliminate the threat. Epithelial and myeloid type cells detect C. albicans mainly through receptor tyrosine kinases and pattern-recognition receptors. This review provides an overview of downstream signaling resulting in an adequate immune response through the activation of various transcription factors. The study discusses recent advances in research of the interleukin-17 (IL-17) producing innate cells, including natural T helper 17 (nTh17) cells, γδ T cells, invariant natural killer T (iNKT) cells and type 3 innate lymphoid cells (ILC3) that are involved in response to oral C. albicans infections.

Phospholipid Arachidonic Acid Remodeling During Phagocytosis in Mouse Peritoneal Macrophages

Macrophages contain large amounts of arachidonic acid (AA), which distributes differentially across membrane phospholipids. This is largely due to the action of coenzyme A-independent transacylase (CoA-IT), which transfers the AA primarily from diacyl choline-containing phospholipids to ethanolamine-containing phospholipids. In this work we have comparatively analyzed glycerophospholipid changes leading to AA mobilization in mouse peritoneal macrophages responding to either zymosan or serum-opsonized zymosan (OpZ). These two phagocytic stimuli promote the cytosolic phospholipase A₂-dependent mobilization of AA by activating distinct surface receptors. Application of mass spectrometry-based lipid profiling to identify changes in AA-containing phospholipids during macrophage exposure to both stimuli revealed significant decreases in the levels of all major choline phospholipid molecular species and a major phosphatidylinositol species. Importantly, while no changes in ethanolamine phospholipid species were detected on stimulation with zymosan, significant decreases in these species were observed when OpZ was used. Analyses of CoA-IT-mediated AA remodeling revealed that the process occurred faster in the zymosan-stimulated cells compared with OpZ-stimulated cells. Pharmacological inhibition of CoA-IT strongly blunted AA release in response to zymosan but had only a moderate effect on the OpZ-mediated response. These results suggest a hitherto undescribed receptor-dependent role for CoA-independent AA remodeling reactions in modulating the eicosanoid biosynthetic response of macrophages. Our data help define novel targets within the AA remodeling pathway with potential use to control lipid mediator formation.

The Contribution of Cytosolic Group IVA and Calcium-Independent Group VIA Phospholipase A2s to Adrenic Acid Mobilization in Murine Macrophages

Adrenic acid (AA), the 2-carbon elongation product of arachidonic acid, is present at significant levels in membrane phospholipids of mouse peritoneal macrophages. Despite its abundance and structural similarity to arachidonic acid, very little is known about the molecular mechanisms governing adrenic acid mobilization in cells of the innate immune system. This contrasts with the wide availability of data on arachidonic acid mobilization. In this work, we used mass-spectrometry-based lipidomic procedures to define the profiles of macrophage phospholipids that contain adrenic acid and their behavior during receptor activation. We identified the phospholipid sources from which adrenic acid is mobilized, and compared the data with arachidonic acid mobilization. Taking advantage of the use of selective inhibitors, we also showed that cytosolic group IVA phospholipase A₂ is involved in the release of both adrenic and arachidonic acids. Importantly, calcium independent group VIA phospholipase A₂ spared arachidonate-containing phospholipids and hydrolyzed only those that contain adrenic acid. These results identify separate mechanisms for regulating the utilization of adrenic and arachidonic acids, and suggest that the two fatty acids may serve non-redundant functions in cells.

Functional activities of beta-glucans in the prevention or treatment of cervical cancer

Cervical cancer is the fourth-ranked cancer in the world and is associated with a large number of deaths annually. Chemotherapy and radiotherapy are known as the common therapeutic approaches in the treatment of cervical cancer, but because of their side effects and toxicity, researchers are trying to discovery alternative therapies. Beta-glucans, a group of glucose polymers that are derived from the cell wall of fungi, bacteria, and etc. it has been showed that beta-glucans have some anti-cancer properties which due to their impacts on adaptive and innate immunity. Along to these impacts, these molecules could be used as drug carriers. In this regard, the application of beta-glucans is a promising therapeutic option for the cancer prevention and treatment especially for cervical cancer. Herein, we have summarized the therapeutic potential of beta-glucans alone or as adjuvant therapy in the treatment of cervical cancer. Moreover, we highlighted beta-glucans as drug carriers for preventive and therapeutic purposes.

Functional activities of beta-glucans in the prevention or treatment of cervical cancer

Cervical cancer is the fourth-ranked cancer in the world and is associated with a large number of deaths annually. Chemotherapy and radiotherapy are known as the common therapeutic approaches in the treatment of cervical cancer, but because of their side effects and toxicity, researchers are trying to discovery alternative therapies. Beta-glucans, a group of glucose polymers that are derived from the cell wall of fungi, bacteria, and etc. it has been showed that beta-glucans have some anti-cancer properties which due to their impacts on adaptive and innate immunity. Along to these impacts, these molecules could be used as drug carriers. In this regard, the application of beta-glucans is a promising therapeutic option for the cancer prevention and treatment especially for cervical cancer. Herein, we have summarized the therapeutic potential of beta-glucans alone or as adjuvant therapy in the treatment of cervical cancer. Moreover, we highlighted beta-glucans as drug carriers for preventive and therapeutic purposes.

Involvement of the Dectin-1 Receptor upon the Effector Mechanisms of Human Phagocytic Cells against Paracoccidioides brasiliensis

Paracoccidioidomycosis (PCM), a systemic mycosis endemic in Latin America, occurs after inhalation of mycelial components of Paracoccidioides spp. When the fungus reaches the lungs and interacts with the alveolar macrophages and other cells, phagocytic cells such as neutrophils and monocytes are immediately recruited to the injured site. The interaction between surface molecules of pathogens and homologous receptors, present on the surface membrane of phagocytes, modulates the innate immune cell activation. Studies have shown the importance of fungal recognition by the Dectin-1 receptor, which can induce a series of cellular protective responses against fungi. The objective of the present study was to evaluate Dectin-1 receptor expression and the effector mechanisms of human monocytes and neutrophils activated or not with different cytokines, such as IFN-γ, TNF-α, and GM-CSF, followed by the challenge with Paracoccidioides brasiliensis (P. brasiliensis or Pb265). Therefore, analysis of Dectin-1 receptor expression was done by flow cytometry whereas the effector mechanisms were evaluated by fungal recovery by colony-forming unit (CFU) counting and hydrogen peroxide (H₂O₂) production. Our results showed that, after treatment with IFN-γ, TNF-α, and GM-CSF and challenge with Pb265, cells, especially monocytes, demonstrated an increase in Dectin-1 expression. Both types of cells treated with the cytokines exhibited a decreased fungal recovery and, conversely, an increased production of H₂O₂. However, when cultures were treated with an anti-Dectin-1 monoclonal antibody, to block the P. brasiliensis binding, a decrease in H₂O₂ production and an increase in fungal recovery were detected. This effect was observed in all cultures treated with the specific monoclonal antibody. These results show the involvement of the Dectin-1 receptor in fungal recognition and its consequent participation in the induction of the killing mechanisms against P. brasiliensis.

Eicosanoid production by Candida parapsilosis and other pathogenic yeasts

Eicosanoids are bioactive lipid mediators generated in almost all mammalian cells from the oxidation of arachidonic acid and other related twenty-carbon polyunsaturated fatty acids (PUFA). Eicosanoids regulate various physiological functions, including cellular homoeostasis and modulation of inflammatory responses in mammals. The mode of action of these lipid mediators depend on their binding to different G-protein coupled receptors. The three main enzymatic pathways associated with their production are the COX pathway, LOX pathway and cytochrome P450 pathway. Interestingly, investigations have also revealed that several human pathogenic fungi are capable of producing these bioactive lipid mediators; however, the exact biosynthetic pathways and their function in pathogenicity are not yet extensively characterized. The aim of the current review is to summarize the recent discoveries pertaining to eicosanoid production by human pathogenic yeasts with a special focus on the opportunistic human fungal pathogen Candida parapsilosis.

Eicosanoid biosynthesis influences the virulence of Candida parapsilosis

Lipid mediators, derived from arachidonic acid metabolism, play an important role in immune regulation. The functions of bioactive eicosanoids range from modulating cytokine signaling and inflammasome formation to anti-inflammatory and pro-resolving activities. Human pathogenic fungi such as Candida albicans, Candida parapsilosis, Cryptococcus neoformans and Aspergillus fumigatus have been shown to produce such lipid mediators, associated with their virulence. To date, investigations into the molecular mechanisms of fungal eicosanoid biosynthesis in different species have revealed that several genes are associated with prostaglandin production. However, these routes remain uncharacterized in C. parapsilosis with early results suggesting it uses pathways distinct from those found in C. albicans. Therefore, we aimed to identify and characterize C. parapsilosis genes involved in eicosanoid biosynthesis. Following arachidonic acid treatment of C. parapsilosis cells, we identified several genes interfering with prostaglandin production. Out of the identified genes, homologues of a multi copper oxidase (FET3), an Acyl-CoA thiolase (POT1) and an Acyl-CoA oxidase (POX1-3) were found to play a significant role in prostaglandin synthesis. Furthermore, all three genes were confirmed to enhance C. parapsilosis pathogenicity, as the corresponding deletion mutants were cleared more efficiently by human macrophages and induced higher levels of pro-inflammatory cytokines. In addition, the mutants were less virulent than the wild-type strain in a mouse model of systemic infection. Taken together, we identified three genes that regulate eicosanoid biosynthesis in C. parapsilosis and impact the fungus’ virulence.

Gamma-tocotrienol attenuates the aberrant lipid mediator production in NLRP3 inflammasome-stimulated macrophages

The activation of NLRP3 inflammasome in innate immune cells is associated with enhanced production of pro-inflammatory lipid mediator eicosanoids that play a crucial role in propagating inflammation. Gamma-tocotrienol (γT3) is an unsaturated vitamin E that has been demonstrated to attenuate NLRP3-inflammasome. However, the role of γT3 in regulating eicosanoid formation is unknown. We hypothesized that γT3 abolishes the eicosanoid production by modulating the macrophage lipidome. LPS-primed bone marrow-derived macrophages (BMDM) were stimulated with saturated fatty acids (SFA) along with γT3, and the effects of γT3 in modulating macrophage lipidome were quantified by using mass spectrometry based-shotgun lipidomic approaches. The SFA-mediated inflammasome activation induced robust changes in lipid species of glycerolipids (GL), glycerophospholipids (GPL), and sphingolipids in BMDM, which were distinctly different in the γT3-treated BMDM. The γT3 treatment caused substantial decreases of lysophospholipids (LysoPL), diacylglycerol (DAG), and free arachidonic acid (AA, C20:4), indicating that γT3 limits the availability of AA, the precursor for eicosanoids. This was confirmed by the pulse-chase experiment using [³H]-AA, and by diminished prostaglandin E₂ (PGE₂) secretion by ELISA. Concurrently, γT3 inhibited LPS-induced cyclooxygenases 2 (COX2) induction, further suppressing prostaglandin synthesis. In addition, γT3 attenuated ceramide synthesis by transcriptional downregulation of key enzymes for de novo synthesis. The altered lipid metabolism during inflammation is linked to reduced ATP production, which was partly rescued by γT3. Taken together, our work revealed that γT3 induces distinct modification of the macrophage lipidome to reduce AA release and corresponding lipid mediator synthesis, leading to attenuated cellular lipotoxicity.

Dectin-1/2-induced autocrine PGE2 signaling licenses dendritic cells to prime Th2 responses

The molecular mechanisms through which dendritic cells (DCs) prime T helper 2 (Th2) responses, including those elicited by parasitic helminths, remain incompletely understood. Here, we report that soluble egg antigen (SEA) from Schistosoma mansoni, which is well known to drive potent Th2 responses, triggers DCs to produce prostaglandin E2 (PGE₂), which subsequently—in an autocrine manner—induces OX40 ligand (OX40L) expression to license these DCs to drive Th2 responses. Mechanistically, SEA was found to promote PGE₂ synthesis through Dectin-1 and Dectin-2, and via a downstream signaling cascade involving spleen tyrosine kinase (Syk), extracellular signal-regulated kinase (ERK), cytosolic phospholipase A₂ (cPLA₂), and cyclooxygenase 1 and 2 (COX-1 and COX-2). In addition, this pathway was activated independently of the actions of omega-1 (ω-1), a previously described Th2-priming glycoprotein present in SEA. These findings were supported by in vivo murine data showing that ω-1–independent Th2 priming by SEA was mediated by Dectin-2 and Syk signaling in DCs. Finally, we found that Dectin-2^−/−, and to a lesser extent Dectin-1^−/− mice, displayed impaired Th2 responses and reduced egg-driven granuloma formation following S. mansoni infection, highlighting the physiological importance of this pathway in Th2 polarization during a helminth infection. In summary, we identified a novel pathway in DCs involving Dectin-1/2-Syk-PGE₂-OX40L through which Th2 immune responses are induced.

T helper 2 (Th2) responses, which are initiated by dendritic cells (DCs), can cause allergic diseases, but they can also provide protection against metabolic disorders and parasitic helminth infections. As such, there is great interest in better understanding how their activity is induced and regulated by DCs. Parasitic helminths can potently induce Th2 responses. However, how helminths condition DCs for priming of Th2 responses remains incompletely understood. Here, we find that egg antigens from the parasitic helminth Schistosoma mansoni bind to pattern-recognition receptors (PRRs) Dectin-1 and Dectin-2 on DCs. This binding triggers a signaling cascade in DCs that results in synthesis of eicosanoid prostaglandin E2 (PGE₂). PGE₂ is sensed by the DCs themselves, resulting in expression of OX40 ligand (OX40L), which subsequently enables the DCs to promote Th2 differentiation. We show that this pathway is activated independently of omega-1 (ω-1), which is a glycoprotein secreted by the eggs and previously shown to condition DCs for priming of Th2 responses. Moreover, we demonstrate that this ω-1–independent pathway is crucial for Th2 induction and egg-driven immunopathology following S. mansoni infection in vivo. In summary, we identified a novel pathway in DCs involving Dectin-1/2–induced autocrine PGE₂ signaling through which Th2 responses are induced.

Role of Dectin-1 receptor on cytokine production by human monocytes challenged with Paracoccidioides brasiliensis

Fungal recognition by Dectin-1 receptor triggers a series of cellular mechanisms involved in a protective activation of the immune system. In this study, we aimed to evaluate the participation of Dectin-1 receptor in the induction of IL-8, TNF-α, IL-12, IL-10 and IL-17A secretion by human monocytes activated with different cytokines, and challenged in vitro with Paracoccidioides brasiliensis (P. brasiliensis). Our results show that monocytes challenged with P. brasiliensis (Pb265) are able to produce IL-12, IL-8, IL-17, IL-10 and TNF-α. Dectin-1 receptor blockage decreased the IL-12, IL-17, IL-10 and TNF-α levels indicating the participation of such receptor in the induction of these cytokines. Only IL-8 production was not affected by the blockage. Cells activation with different cytokines showed that GM-CSF was able to induce secretion of all cytokines and the receptor blockage prior to the challenge also decreased the cytokine secretion, except IL-8. Monocytes activated with TNF-α promoted IL-8, IL-10 and TNF-α production, whereas stimulation with IFN-γ promoted mainly IL-12 and TNF-α. Thus, these findings bring new and important knowledge about Dectin-1 participation in cytokines production by monocytes challenged with Pb265.

Immune-regulation and -functions of eicosanoid lipid mediators

Bioactive lipids regulate most physiological processes, from digestion to blood flow and from hemostasis to labor. Lipid mediators are also involved in multiple pathologies including cancer, autoimmunity or asthma. The pathological roles of lipid mediators are based on their intricate involvement in the immune system, which comprises source and target cells of these mediators. Based on their biosynthetic origin, bioactive lipids can be grouped into different classes [e.g. sphingolipids, formed from sphingosine or eicosanoids, formed from arachidonic acid (AA)]. Owing to the complexity of different mediator classes and the prominent immunological roles of eicosanoids, this review will focus solely on the immune-regulation of eicosanoids. Eicosanoids do not only control key immune responses (e.g. chemotaxis, antigen presentation, phagocytosis), but they are also subject to reciprocal control by the immune system. Particularly, key immunoregulatory cytokines such as IL-4 and IFN-γ shape the cellular eicosanoid profile, thus providing efficient feedback regulation between cytokine and eicosanoid networks. For the purpose of this review, I will first provide a short overview of the most important immunological functions of eicosanoids with a focus on prostaglandins (PGs) and leukotrienes (LTs). Second, I will summarize the current knowledge on immunological factors that regulate eicosanoid production during infection and inflammation.

Beta-glucans and cancer: The influence of inflammation and gut peptide

Dietary β-glucans are soluble fibers with potentially health-promoting effects. Gut peptides are important signals in the regulation of energy and glucose homeostasis. This article reviews the effects of different enriched β-glucan food consumption on immune responses, inflammation, gut hormone and cancer. Gut hormones are influenced by enriched β-glucan food consumption and levels of such peptide as YY, ghrelin, glucagon-like peptide 1 and 2 in humans influence serum glucose concentration as well as innate and adaptive immunity. Cancer cell development is also regulated by obesity and glucose dishomeostasy that are influenced by β-glucan food consumption that in turn regulated gut hormones.

Potential Antifungal Targets against a Candida Biofilm Based on an Enzyme in the Arachidonic Acid Cascade-A Review

Candida is an important opportunistic fungal pathogen, especially in biofilm associated infections. The formation of a Candida biofilm can decrease Candida sensitivity to antifungal drugs and cause drug resistance. Although many effective antifungal drugs are available, their applications are limited due to their high toxicity and cost. Seeking new antifungal agents that are effective against biofilm-associated infection is an urgent need. Many research efforts are underway, and some progress has been made in this field. It has been shown that the arachidonic acid cascade plays an important role in fungal morphogenesis and pathogenicity. Notably, prostaglandin E2 (PGE₂) can promote the formation of a Candida biofilm. Recently, the inhibition of PGE₂ has received much attention. Studies have shown that cyclooxygenase (COX) inhibitors, such as aspirin, ibuprofen, and indomethacin, combined with fluconazole can significantly reduce Candida adhesion and biofilm development and increase fluconazole susceptibility; the MIC of fluconazole can be decrease from 64 to 2 μg/ml when used in combination with ibuprofen. In addition, in vivo studies have also confirmed the antifungal activities of these inhibitors. In this article, we mainly review the relationship between PGE₂ and Candida biofilm, summarize the antifungal activities of COX inhibitors and analyze the possible antifungal activity of microsomal prostaglandin E synthase-1 (MPGES-1) inhibitors; additionally, other factors that influence PGE₂ production are also discussed. Hopefully this review can disclose potential antifungal targets based on the arachidonic acid cascade and provide a prevailing strategy to alleviate Candida albicans biofilm formation.

Identification of a novel platelet antagonist that binds to CLEC-2 and suppresses podoplanin-induced platelet aggregation and cancer metastasis

Podoplanin (PDPN) enhances tumor metastases by eliciting tumor cell-induced platelet aggregation (TCIPA) through activation of platelet C-type lectin-like receptor 2 (CLEC-2). A novel and non-cytotoxic 5-nitrobenzoate compound 2CP was synthesized that specifically inhibited the PDPN/CLEC-2 interaction and TCIPA with no effect on platelet aggregation stimulated by other platelet agonists. 2CP possessed anti-cancer metastatic activity in vivo and augmented the therapeutic efficacy of cisplatin in the experimental animal model without causing a bleeding risk. Analysis of the molecular action of 2CP further revealed that Akt1/PDK1 and PKCμ were two alternative CLEC-2 signaling pathways mediating PDPN-induced platelet activation. 2CP directly bound to CLEC-2 and, by competing with the same binding pocket of PDPN in CLEC-2, inhibited PDPN-mediated platelet activation. This study provides evidence that 2CP is the first defined platelet antagonist with CLEC-2 binding activity. The augmentation in the therapeutic efficacy of cisplatin by 2CP suggests that a combination of a chemotherapeutic agent and a drug with anti-TCIPA activity such as 2CP may prove clinically effective.

Cytosolic phospholipase A2 contributes to innate immune defense against Candida albicans lung infection

BACKGROUND

The lung is exposed to airborne fungal spores, and fungi that colonize the oral cavity such as Candida albicans, but does not develop disease to opportunistic fungal pathogens unless the immune system is compromised. The Group IVA cytosolic phospholipase A2 (cPLA2α) is activated in response to Candida albicans infection resulting in the release of arachidonic acid for eicosanoid production. Although eicosanoids such as prostaglandins and leukotrienes modulate inflammation and immune responses, the role of cPLA2α and eicosanoids in regulating C. albicans lung infection is not understood.

METHODS

The responses of cPLA2α(+/+) and cPLA2α(-/-) Balb/c mice to intratracheal instillation of C. albicans were compared. After challenge, we evaluated weight loss, organ fungal burden, and the recruitment of cells and the levels of cytokines and eicosanoids in bronchoalveolar lavage fluid. The ability of macrophages and neutrophils from cPLA2α(+/+) and cPLA2α(-/-) mice to recognize and kill C. albicans was also compared.

RESULTS

After C. albicans instillation, cPLA2α(+/+) mice recovered a modest weight loss by 48 h and completely cleared fungi from the lung by 12 h with no dissemination to the kidneys. In cPLA2α(-/-) mice, weight loss continued for 72 h, C. albicans was not completely cleared from the lung and disseminated to the kidneys. cPLA2α(-/-) mice exhibited greater signs of inflammation including higher neutrophil influx, and elevated levels of albumin and pro-inflammatory cytokines/chemokines (IL1α, IL1β, TNFα, IL6, CSF2, CXCL1, CCL20) in bronchoalveolar lavage fluid. The amounts of cysteinyl leukotrienes, thromboxane B2 and prostaglandin E2 were significantly lower in bronchoalveolar lavage fluid from C. albicans-infected cPLA2α(-/-) mice compared to cPLA2α(+/+) mice. Alveolar macrophages and neutrophils from uninfected cPLA2α(-/-) mice exhibited less killing of C. albicans in vitro than cells from cPLA2α(+/+) mice. In addition alveolar macrophages from cPLA2α(-/-) mice isolated 6 h after instillation of GFP-C. albicans contained fewer internalized fungi than cPLA2α(+/+) macrophages.

CONCLUSIONS

The results demonstrate that cPLA2α contributes to immune surveillance and host defense in the lung to prevent infection by the commensal fungus C. albicans and to dampen inflammation.

Leukotriene E4 elicits respiratory epithelial cell mucin release through the G-protein-coupled receptor, GPR99

Cysteinyl leukotrienes (cysLTs), leukotriene C4 (LTC4), LTD4, and LTE4 are proinflammatory lipid mediators with pathobiologic function in asthma. LTE4, the stable cysLT, is a weak agonist for the type 1 and type 2 cysLT receptors (CysLTRs), which constrict airway smooth muscle, but elicits airflow obstruction and pulmonary inflammation in patients with asthma. We recently identified GPR99 as a high-affinity receptor for LTE4 that mediates cutaneous vascular permeability. Here we demonstrate that a single intranasal exposure to extract from the respiratory pathogen Alternaria alternata elicits profound epithelial cell (EpC) mucin release and submucosal swelling in the nasal mucosa of mice that depends on cysLTs, as it is absent in mice deficient in the terminal enzyme for cysLT biosynthesis, LTC4 synthase (LTC4S). These mucosal changes are associated with mast cell (MC) activation and absent in MC-deficient mice, suggesting a role for MCs in control of EpC function. Of the three CysLTRs, only GPR99-deficient mice are fully protected from EpC mucin release and swelling elicited by Alternaria or by intranasal LTE4 GPR99 expression is detected on lung and nasal EpCs, which release mucin to doses of LTE4 one log lower than that required to elicit submucosal swelling. Finally, mice deficient in MCs, LTC4S, or GPR99 have reduced baseline numbers of goblet cells, indicating an additional function in regulating EpC homeostasis. These results demonstrate a novel role for GPR99 among CysLTRs in control of respiratory EpC function and suggest that inhibition of LTE4 and of GPR99 may have therapeutic benefits in asthma.

Prostaglandins from Cytosolic Phospholipase A2α/Cyclooxygenase-1 Pathway and Mitogen-activated Protein Kinases Regulate Gene Expression in Candida albicans-infected Macrophages

In Candida albicans-infected resident peritoneal macrophages, activation of group IVA cytosolic phospholipase A2(cPLA2α) by calcium- and mitogen-activated protein kinases triggers the rapid production of prostaglandins I2 and E2 through cyclooxygenase (COX)-1 and regulates gene expression by increasing cAMP. InC. albicans-infected cPLA2α(-/-)or COX-1(-/-)macrophages, expression ofI l10,Nr4a2, and Ptgs2 was lower, and expression ofTnfα was higher, than in wild type macrophages. Expression was reconstituted with 8-bromo-cAMP, the PKA activator 6-benzoyl-cAMP, and agonists for prostaglandin receptors IP, EP2, and EP4 in infected but not uninfected cPLA2α(-/-)or COX-1(-/-)macrophages. InC. albicans-infected cPLA2α(+/+)macrophages, COX-2 expression was blocked by IP, EP2, and EP4 receptor antagonists, indicating a role for both prostaglandin I2 and E2 Activation of ERKs and p38, but not JNKs, by C. albicansacted synergistically with prostaglandins to induce expression of Il10,Nr4a2, and Ptgs2. Tnfα expression required activation of ERKs and p38 but was suppressed by cAMP. Results using cAMP analogues that activate PKA or Epacs suggested that cAMP regulates gene expression through PKA. However, phosphorylation of cAMP-response element-binding protein (CREB), the cAMP-regulated transcription factor involved inIl10,Nr4a2,Ptgs2, andTnfα expression, was not mediated by cAMP/PKA because it was similar inC. albicans-infected wild type and cPLA2α(-/-)or COX-1(-/-)macrophages. CREB phosphorylation was blocked by p38 inhibitors and induced by the p38 activator anisomycin but not by the PKA activator 6-benzoyl-cAMP. Therefore, MAPK activation inC. albicans-infected macrophages plays a dual role by promoting the cPLA2α/prostaglandin/cAMP/PKA pathway and CREB phosphorylation that coordinately regulate immediate early gene expression.

Pharmacological inhibition of eicosanoids and platelet-activating factor signaling impairs zymosan-induced release of IL-23 by dendritic cells

The engagement of the receptors for fungal patterns induces the expression of cytokines, the release of arachidonic acid, and the production of PGE2 in human dendritic cells (DC), but few data are available about other lipid mediators that may modulate DC function. The combined antagonism of leukotriene (LT) B4, cysteinyl-LT, and platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) inhibited IL23A mRNA expression in response to the fungal surrogate zymosan and to a lower extent TNFA (tumor necrosis factor-α) and CSF2 (granulocyte macrophage colony-stimulating factor) mRNA. The combination of lipid mediators and the lipid extract of zymosan-conditioned medium increased the induction of IL23A by LPS (bacterial lipopolysaccharide), thus suggesting that unlike LPS, zymosan elicits the production of mediators at a concentration enough for optimal response. Zymosan induced the release of LTB4, LTE4, 12-hydroxyeicosatetraenoic acid (12-HETE), and PAF C16:0. DC showed a high expression and detectable Ser663 phosphorylation of 5-lipoxygenase in response to zymosan, and a high expression and activity of LPCAT1/2 (lysophosphatidylcholine acyltransferase 1 and 2), the enzymes that incorporate acetate from acetyl-CoA into choline-containing lysophospholipids to produce PAF. Pharmacological modulation of the arachidonic acid cascade and the PAF receptor inhibited the binding of P-71Thr-ATF2 (activating transcription factor 2) to the IL23A promoter, thus mirroring their effects on the expression of IL23A mRNA and IL-23 protein. These results indicate that LTB4, cysteinyl-LT, and PAF, acting through their cognate G protein-coupled receptors, contribute to the phosphorylation of ATF2 and play a central role in IL23A promoter trans-activation and the cytokine signature induced by fungal patterns.

Serum Levels of Lipopolysaccharide and 1,3-β-D-Glucan Refer to the Severity in Patients with Crohn's Disease

Objectives. Interactions between the host and gut microbial community contribute to the pathogenesis of Crohn's disease (CD). In this study, we aimed to detect lipopolysaccharide (LPS) and 1,3-β-D-glucan (BG) in the sera of CD patients and clarify the potential role in the diagnosis and therapeutic approaches. Materials and Methods. Serum samples were collected from 46 patients with active CD (A-CD), 22 CD patients at remission stage (R-CD), and 20 healthy controls, and the levels of LPS, BG, and TNF in sera were determined by ELISA. Moreover, sixteen patients with A-CD received anti-TNF monoclonal antibody therapy (infliximab, IFX) at a dose of 5 mg/kg body weight at weeks 0, 2, and 6, and the levels of LPS and BG were also tested at week 12 after the first intravenous infusion. Results. Serum levels of LPS and BG were found to be markedly increased in A-CD patients compared with R-CD patients and healthy controls (P < 0.05). They were also observed to be positively correlated with CDAI, ESR, and SES-CD, respectively (P < 0.05). Furthermore, the levels of TNF in sera had a significant correlation with LPS and BG, respectively. The concentrations of LPS and BG were demonstrated to be significantly downregulated in the sera of A-CD patients 12 weeks after IFX treatment (P < 0.05), suggesting that blockade of TNF could inhibit bacterial endotoxin absorption, partially through improving intestinal mucosal barrier. Conclusions. Serum levels of LPS and BG are significantly increased in A-CD patients and positively correlated with the severity of the disease. Blockade of intestinal mucosal inflammation with IFX could reduce the levels of LPS and BG in sera. Therefore, this study has shed some light on measurement of serum LPS and BG in the diagnosis and treatment of CD patients.

β-glucans and eicosapolyenoic acids as MAMPs in plant-oomycete interactions: past and present

Branched β-1,3-glucans and the eicosapolyenoic acids (EP) are among the best characterized oomycete elicitors that trigger innate immune responses in plants. These elicitors were identified over three decades ago, and they were useful in the study of the sequence of physiological, biochemical and molecular events that induce resistance in plants. However, in spite of the cross-kingdom parallels where these molecules are well-characterized as immune system modulators in animals, their perception and modes of action in plants remains obscure. Oomycetes are among the most important plant pathogens, responsible for diseases that devastate crops, ornamentals, and tree species worldwide. With the recent interest and advances in our understanding of innate immunity in plants, and the redefining of many of the classical elicitors as microbe-associated molecular patterns (MAMPs), it seems timely and important to reexamine β-glucans and EP using contemporary approaches. In this review, we highlight early studies of β-glucans and EP, discuss their roles as evolutionarily conserved signals, and consider their action in relation to current models of MAMP-triggered immunity.

Immunomodulation of RAW 264.7 murine macrophage functions and antioxidant activities of 11 plant extracts

A group of 11 medicinal plants, including Lavandula pubescens, Trigonella foenugricium, Salsola schweinforthi, Calligonum comosum, Silene succulenta, Silene villosa, Bogonvillea glabra, Cakile maritime, Gomphrene celesoids, Mirabilis jalaba, and Silene nocturna growing in Egypt, were extracted and examined for their immunomodulatory and antioxidant activities. RAW 264.7 cells were recruited to investigate the immunomodulatory effect through multiple parameters analysis. First, the proliferation index of macrophages cells was evaluated revealing that Trigonella foenugricium, Silene succulenta and Silene villosa have a significant cytotoxic effect on RAW cells. Interestingly, we observed enhancement of macrophages phagocytic function of by all extracts except Cakile maritime, Gomphrena celosioides and Silene nocturna. Afterwards, macrophages were challenged by incubation with LPS and the effect of various extracts on inflammatory responses was investigated; the generation of NO from activated macrophage was substantially suppressed by 7 extracts namely, Trigonella foenugricium, Calligonum comosum, Silene succulenta, Bougainvillea glabra, Mirabilis jalaba, Gomphrena celosioides and Silene nocturna. TNF-α was decreased by percentage range from 3.8 to 85.8% and Trigonella foenugricium extract showed the highest inhibition of TNF-α release. All extracts except Trigonella foenugricium, Salsola schweinforthi, Silene succulenta and Mirabilis jalaba significantly inhibited COX-2 production from stimulated macrophage. Moreover, evaluating the potential antioxidant activity of these extracts showed that Trigonella foenugricium, Salsola schweinforthi, Calligonum comosum, Bogonvillea glabra and Mirabilis jalaba exhibited some antioxidant activities. Taken together, our results suggest that some of these extracts may have a considerable antinflammatory and antioxidant effects and may be a potential therapeutic choice in the treatment of inflammatory diseases.

Antrodan, A β-glucan obtained from Antrodia cinnamomea mycelia, is beneficial to benign prostate hyperplasia

Benign prostatic hyperplasia (BPH), one of the most common disease usually occurring in men in their 50s, has now become an atypical direct cause of mortality.

Significance of arachidonic acid in ocular infections and inflammation

Innate immune responses in the cornea mainly play an important role to mobilize multiple interrelated pathways of corneal lipid, which involve in inflammatory corneal diseases. Signaling lipid mediators derived from arachidonic acid (AA) control cell proliferation, apoptosis, metabolism, and migration, are known as eicosanoids, phosphoinositides, sphingolipids, and fatty acids. Emerging evidences have highlighted the implication of lipid mediators in both injury and repair mechanisms in the cornea. Recently, the role of AA and its metabolites to induce proinflammatory mediators and inflammatory cell infiltration in the pathogen-infected cornea and to cause severe keratitis have been revealed. In this review, we focus on the novel roles of AA downstream signaling in the corneal inflammatory diseases and also the biological relevance of AA signaling in the therapeutic strategies for targeting sight-threatening diseases.

Subanesthetic isoflurane reduces zymosan-induced inflammation in murine Kupffer cells by inhibiting ROS-activated p38 MAPK/NF-κB signaling

Volatile anesthetic isoflurane (ISO) has immunomodulatory effects. The fungal component zymosan (ZY) induces inflammation through toll-like receptor 2 or dectin-1 signaling. We investigated the molecular actions of subanesthetic (0.7%) ISO against ZY-induced inflammatory activation in murine Kupffer cells (KCs), which are known as the resident macrophages within the liver. We observed that ISO reduced ZY-induced cyclooxygenase 2 upregulation and prostaglandin E₂ release, as determined by western blot and radioimmunoassay, respectively. ISO also reduced the production of tumor necrosis factor-α, interleukin-1β, IL-6, high-mobility group box-1, macrophage inflammatory protein-1α, macrophage inflammatory protein-2, and monocyte chemoattractant protein-1 as assessed by enzyme-linked immunosorbent assays. ISO blocked the ZY-induced nuclear translocation and DNA-binding activity of nuclear factor- (NF)-κB p65. Moreover, ISO attenuated ZY-induced p38 mitogen-activated protein kinase (MAPK) activation partly by scavenging reactive oxygen species (ROS); the interregulation that ROS activated p38 MAPK followed by NF-κB activation was crucial for the ZY-induced inflammatory responses in KCs. An in vivo study by peritoneal injection of ZY into BALB/C mice confirmed the anti-inflammatory properties of 0.7% ISO against ZY in KCs. These results suggest that ISO ameliorates ZY-induced inflammatory responses in murine KCs by inhibiting the interconnected ROS/p38 MAPK/NF-κB signaling pathways.

Characterization of inflamin, the first member of a new family of snake venom proteins that induces inflammation

Unlike other sea snakes, Aipysurus eydouxii feeds exclusively on fish eggs. This unusual feeding habit prompted us to search for unique transcripts in their venom glands. In the present study we expressed a novel cysteine-rich secretory protein containing 94 amino acid residues that was identified in its cDNA library. As it induced inflammation and writhing in animals, this protein was named inflamin. It induced two waves of prostanoid production. The first wave peaked at 10 min and 6-oxo PGF1α (prostaglandin F1α) (6-keto PGF1α) was the major product. The second wave, specifically of 6-oxo PGF1α and PGE2 (prostanglandin E2), started after 2 h. In RAW 264.7 cells, COX-1 (cyclo-oxygenase-1) activity showed a transient increase at 10 min and is responsible for the first wave, but its expression was unaffected. COX-2 was induced after 3 h and is responsible for the second wave. Using specific inhibitors, we showed that cPLA2 (calcium-dependent phospholipase A2), and not sPLA2 (secretory phospholipase A2), iPLA2 (calcium-independent phospholipase A2) or DAG (diacylglycerol) lipase, plays a key role in arachidonate release. The cPLA2 activity showed a transient increase of 62% at 10 min; this increase was due to its phosphorylation and not due to an increase in its expression. Thus inflamin, the first member of a new family of snake venom proteins, leads to an increase in the cPLA2 and COX-1 activity resulting in inflammation and pain.

Polarization of the innate immune response by prostaglandin E2: a puzzle of receptors and signals

Eicosanoids tailor the innate immune response by supporting local inflammation and exhibiting immunomodulatory properties. Prostaglandin (PG) E2 is the most abundant eicosanoid in the inflammatory milieu due to the robust production elicited by pathogen-associated molecular patterns on cells of the innate immune system. The different functions and cell distribution of E prostanoid receptors explain the difficulty encountered thus far to delineate the actual role of PGE2 in the immune response. The biosynthesis of eicosanoids includes as the first step the Ca(2+)- and kinase-dependent activation of the cytosolic phospholipase A2, which releases arachidonic acid from membrane phospholipids, and later events depending on the transcriptional regulation of the enzymes of the cyclooxygenase routes, where PGE2 is the most relevant product. Acting in an autocrine/paracrine manner in macrophages, PGE2 induces a regulatory phenotype including the expression of interleukin (IL)-10, sphingosine kinase 1, and the tumor necrosis factor family molecule LIGHT. PGE2 also stabilizes the suppressive function of myeloid-derived suppressor cells, inhibits the release of IL-12 p70 by macrophages and dendritic cells, and may enhance the production of IL-23. PGE2 is a central component of the inflammasome-dependent induction of the eicosanoid storm that leads to massive loss of intravascular fluid, increases the mortality rate associated with coinfection by Candida ssp. and bacteria, and inhibits fungal phagocytosis. These effects have important consequences for the outcome of infections and the polarization of the immune response into the T helper cell types 2 and 17 and can be a clue to develop pharmacological tools to address infectious, autoimmune, and autoinflammatory diseases.

Cytosolic phospholipase A(2)α and eicosanoids regulate expression of genes in macrophages involved in host defense and inflammation

The role of Group IVA cytosolic phospholipase A₂ (cPLA₂α) activation in regulating macrophage transcriptional responses to Candida albicans infection was investigated. cPLA₂α releases arachidonic acid for the production of eicosanoids. In mouse resident peritoneal macrophages, prostacyclin, prostaglandin E₂ and leukotriene C₄ were produced within minutes of C. albicans addition before cyclooxygenase 2 expression. The production of TNFα was lower in C. albicans-stimulated cPLA₂α^+/+ than cPLA₂α^-/- macrophages due to an autocrine effect of prostaglandins that increased cAMP to a greater extent in cPLA₂α^+/+ than cPLA₂α^-/- macrophages. For global insight, differential gene expression in C. albicans-stimulated cPLA₂α^+/+ and cPLA₂α^-/- macrophages (3 h) was compared by microarray. cPLA₂α^+/+ macrophages expressed 86 genes at lower levels and 181 genes at higher levels than cPLA₂α^-/- macrophages (≥2-fold, p<0.05). Several pro-inflammatory genes were expressed at lower levels (Tnfα, Cx3cl1, Cd40, Ccl5, Csf1, Edn1, CxCr7, Irf1, Irf4, Akna, Ifnγ, several IFNγ-inducible GTPases). Genes that dampen inflammation (Socs3, Il10, Crem, Stat3, Thbd, Thbs1, Abca1) and genes involved in host defense (Gja1, Csf3, Trem1, Hdc) were expressed at higher levels in cPLA₂α^+/+ macrophages. Representative genes expressed lower in cPLA₂α^+/+ macrophages (Tnfα, Csf1) were increased by treatment with a prostacyclin receptor antagonist and protein kinase A inhibitor, whereas genes expressed at higher levels (Crem, Nr4a2, Il10, Csf3) were suppressed. The results suggest that C. albicans stimulates an autocrine loop in macrophages involving cPLA₂α, cyclooxygenase 1-derived prostaglandins and increased cAMP that globally effects expression of genes involved in host defense and inflammation.

The response of human macrophages to β-glucans depends on the inflammatory milieu

Background

β-glucans are fungal cell wall components that bind to the C-type lectin-like receptor dectin-1. Polymorphisms of dectin-1 gene are associated with susceptibility to invasive fungal infection and medically refractory ulcerative colitis. The purpose of this study has been addressing the response of human macrophages to β-glucans under different conditions mimicking the composition of the inflammatory milieu in view of the wide plasticity and large range of phenotypical changes showed by these cells, and the relevant role of dectin-1 in several pathophysiological conditions.

Principal Findings

Serum-differentiated macrophages stimulated with β-glucans showed a low production of TNFα and IL-1β, a high production of IL-6 and IL-23, and a delayed induction of cyclooxygenase-2 and PGE₂ biosynthesis that resembled the responses elicited by crystals and those produced when phagosomal degradation of the phagocytic cargo increases ligand access to intracellular pattern recognition receptors. Priming with a low concentration of LPS produced a rapid induction of cyclooxygenase-2 and a synergistic release of PGE₂. When the differentiation of the macrophages was carried out in the presence of M-CSF, an increased expression of dectin-1 B isoform was observed. In addition, this treatment made the cells capable to release arachidonic acid in response to β-glucan.

Conclusions

These results indicate that the macrophage response to fungal β-glucans is strongly influenced by cytokines and microbial-derived factors that are usual components of the inflammatory milieu. These responses can be sorted into three main patterns i) an elementary response dependent on phagosomal processing of pathogen-associated molecular patterns and/or receptor-independent, direct membrane binding linked to the immunoreceptor tyrosine-based activation motif-bearing transmembrane adaptor DNAX-activating protein 12, ii) a response primed by TLR4-dependent signals, and iii) a response dependent on M-CSF and dectin-1 B isoform expression that mainly signals through the dectin-1 B/spleen tyrosine kinase/cytosolic phospholipase A₂ route.

A phosphatidylinositol species acutely generated by activated macrophages regulates innate immune responses

Activation of macrophages with stimuli of the innate immune response results in the intense remodeling of arachidonate-containing phospholipids, leading to the mobilization of large quantities of this fatty acid for conversion into biologically active eicosanoids. As a consequence of this process, the arachidonate levels in membrane phospholipids markedly decrease. We have applied mass spectrometry-based lipid profiling to study the levels of arachidonate-containing phospholipids under inflammatory activation of macrophages. We identify an unusual inositol phospholipid molecule, PI(20:4/20:4), the levels of which do not decrease but actually increase by 300% after activation of the macrophages. PI(20:4/20:4) is formed and degraded rapidly, suggesting a role for this molecule in regulating cell signaling events. Using a metabolipidomic approach consisting in exposing the cells to deuterium-labeled arachidonate at the time they are exposed to stimuli, we show that PI(20:4/20:4) biosynthesis occurs via the sequential incorporation of arachidonate, first into the sn-2 position of a preformed phosphatidylinositol (PI) molecule, followed by the rapid introduction of a second arachidonate moiety into the sn-1 position. Generation requires the participation of cytosolic phospholipase A2α and CoA-dependent acyltransferases. PI(20:4/20:4) formation is also detected in vivo in murine peritonitis exudates. Elevating the intracellular concentration of PI(20:4/20:4) by introducing the lipid into the cells results in enhancement of the microbicidal capacity of macrophages, as measured by reactive oxygen metabolite production and lysozyme release. These findings suggest that PI(20:4/20:4) is a novel bioactive inositol phospholipid molecule that regulates innate immune responses in macrophages.

Phospholipase A2IVα regulates phagocytosis independent of its enzymatic activity

Group IVα phospholipase A(2) (PLA(2)IVα) is a lipolytic enzyme that catalyzes the hydrolysis of membrane phospholipids to generate precursors of potent inflammatory lipid mediators. Here, the role of PLA(2)IVα in Fc receptor (FcR)-mediated phagocytosis was investigated, demonstrating that PLA(2)IVα is selectively activated upon FcR-mediated phagocytosis in macrophages and that it rapidly translocates to the site of the nascent phagosome. Moreover, pharmacological inhibition of PLA(2)IVα by pyrrophenone reduces particle internalization by up to 50%. In parallel, fibroblasts from PLA(2)IVα knock-out mice overexpressing FcγRIIA and able to internalize IgG-opsonized beads show 50% lower phagocytosis, compared with wild-type cells, and transfection of PLA(2)IVα fully recovers this impaired function. Interestingly, transfection of the catalytically inactive deleted PLA(2)IVα mutant (PLA(2)IVα(1-525)) and point mutant (PLA(2)IVα-S228C) also promotes recovery of this impaired function. Finally, transfection of the PLA(2)IVα C2 domain (which is directly involved in PLA(2)IVα membrane binding), but not of PLA(2)IVα-D43N (which cannot bind to membranes), rescues FcR-mediated phagocytosis. These data unveil a new mechanism of action for PLA(2)IVα, which demonstrates that the membrane binding, and not the enzymatic activity, is required for PLA(2)IVα modulation of FcR-mediated phagocytosis.

PTEN directly activates the actin depolymerization factor cofilin-1 during PGE2-mediated inhibition of phagocytosis of fungi

Macrophage ingestion of the yeast Candida albicans requires its recognition by multiple receptors and the activation of diverse signaling programs. Synthesis of the lipid mediator prostaglandin E(2) (PGE(2)) and generation of cyclic adenosine monophosphate (cAMP) also accompany this process. Here, we characterized the mechanisms underlying PGE(2)-mediated inhibition of phagocytosis and filamentous actin (F-actin) polymerization in response to ingestion of C. albicans by alveolar macrophages. PGE(2) suppressed phagocytosis and F-actin formation through the PGE(2) receptors EP2 and EP4, cAMP, and activation of types I and II protein kinase A. Dephosphorylation and activation of the actin depolymerizing factor cofilin-1 were necessary for these inhibitory effects of PGE(2). PGE(2)-dependent activation of cofilin-1 was mediated by the protein phosphatase activity of PTEN (phosphatase and tensin homolog deleted on chromosome 10), with which it directly associated. Because enhanced production of PGE(2) accompanies many immunosuppressed states, the PTEN-dependent pathway described here may contribute to impaired antifungal defenses.

Scavenger receptors and β-glucan receptors participate in the recognition of yeasts by murine macrophages

Objectives

Numerous receptors have been implicated in recognition of pathogenic fungi by macrophages, including the β-glucan receptor dectin-1. The role of scavenger receptors (SRs) in anti-fungal immunity is not well characterized.

Methods

We studied uptake of unopsonized Saccharomycetes cerevisiae (zymosan) and live Candida albicans yeasts as well as zymosan-stimulated H₂O₂ production in J774 macrophage-like cells and peritoneal exudate macrophages (PEMs). The role of different receptors was assessed with the use of competitive ligands, transfected cells and receptor-deficient macrophages.

Results

The uptake of zymosan by untreated J774 cells was mediated approximately half by SRs and half by a β-glucan receptor which was distinct from dectin-1 and not linked to stimulation of H₂O₂ production. Ligands of β-glucan receptors and of SRs also inhibited uptake of C. albicans by macrophages (J774 cells and PEMs). In macrophages pretreated with a CpG motif-containing oligodeoxynucleotide (CpG-ODN) the relative contribution of SRs to yeast uptake increased and that of β-glucan receptors decreased. Whereas the class A SR MARCO participated in the uptake of both zymosan and C. albicans by CpG-ODN-pretreated, but not untreated macrophages, the related receptor SR-A/CD204 was involved in the uptake of zymosan, but not of C. albicans. The reduction of zymosan-stimulated H₂O₂ production observed in DS-pretreated J774 cells and in class A SRs-deficient PEMs suggest that class A SRs mediate part of this process.

Conclusions

Our results revealed that SRs belong to a redundant system of receptors for yeasts. Binding of yeasts to different receptors in resting versus CpG-ODN-pre-exposed macrophages may differentially affect polarization of adaptive immune responses.