Candida Albicans Cell Wall Research Articles

The effect of Candida cell wall beta-glucan on treatment-resistant LL/2 cancer cell line: in vitro evaluation.

Candida albicans (C. albicans) cell wall beta-glucan has been considered as a potential agent in the treatment of cancers due to its anti-tumor properties. Therefore, in the present study, we investigated the anti-cancer effects of Candida cell wall beta-glucan on Lewis lung carcinoma cell line (LL/2) cells. Beta-glucan of C. albicans cell wall was extracted. LL/2 cell line was cultured, then sphere cells and parental cells were exposed to the different concentrations of beta-glucan extracted from C. albicans (10-6000μg/ml), for 24, 48 and 72h. Cytotoxicity of beta-glucan was assayed by MTT test, then RNA extracted from cells population (treated and untreated cells), cDNA synthetized and expression level of Sox2, Oct4, C-myc, Nanog genes were also investigated using Real-time methods. At optimal concentrations of 800 and 1000μg/ml, the extracted beta-glucan showed a significant cytotoxic effect on both parental and sphere cell populations (p < 0.05). Real-time PCR analysis revealed a decreased expression of Oct4 and Sox2 genes in treatment of cells with beta-glucan compared with control group. Since the extracted beta-glucan showed an inhibitory effect on the expression of Oct4 and Sox2 genes involved in LL/2 metastasis, therefore, beta-glucan can be considered as an anti-tumor agent because of its anti-metastatic properties, however, more in vitro and in vivo studies are needed to provide further evidence on this topic in the future.

Fluconazole and Lipopeptide Surfactin Interplay During Candida albicans Plasma Membrane and Cell Wall Remodeling Increases Fungal Immune System Exposure.

Recognizing the β-glucan component of the Candida albicans cell wall is a necessary step involved in host immune system recognition. Compounds that result in exposed β-glucan recognizable to the immune system could be valuable antifungal drugs. Antifungal development is especially important because fungi are becoming increasingly drug resistant. This study demonstrates that lipopeptide, surfactin, unmasks β-glucan when the C. albicans cells lack ergosterol. This observation also holds when ergosterol is depleted by fluconazole. Surfactin does not enhance the effects of local chitin accumulation in the presence of fluconazole. Expression of the CHS3 gene, encoding a gene product resulting in 80% of cellular chitin, is downregulated. C. albicans exposure to fluconazole changes the composition and structure of the fungal plasma membrane. At the same time, the fungal cell wall is altered and remodeled in a way that makes the fungi susceptible to surfactin. In silico studies show that surfactin can form a complex with β-glucan. Surfactin forms a less stable complex with chitin, which in combination with lowering chitin synthesis, could be a second anti-fungal mechanism of action of this lipopeptide.

RHOA-mediated mechanical force generation through Dectin-1.

Dendritic cell-associated C-type lectin 1 (Dectin-1, also known as CLEC7A) is an innate immune pattern recognition receptor that recognizes β-glucan on the Candida albicans cell wall. Recognition of β-glucan by immune cells leads to phagocytosis, oxidative burst, cytokine and chemokine production. We looked for specific mechanisms that coordinate phagocytosis downstream of Dectin-1 leading to actin reorganization and internalization of fungus. We found that stimulation of Dectin-1 by soluble β-glucan leads to mechanical force generation and areal contraction in Dectin-1-transfected HEK-293 cells and M1 macrophages. With inhibitor studies, we found this force generation is a spleen tyrosine kinase (SYK)-independent, but SRC family kinase (SFK)-dependent process mediated through the RHOA-ROCK-myosin light chain (MLC) pathway. We confirmed activation of RHOA downstream of Dectin-1 using activity assays and stress fiber formation. Through phagocytosis assays, we found direct evidence for the importance of RHOA-ROCK-MLC signaling in the process of phagocytosis of C. albicans.

Pathways That Synthesize Phosphatidylethanolamine Impact Candida albicans Hyphal Length and Cell Wall Composition through Transcriptional and Posttranscriptional Mechanisms.

Candida albicans is a leading cause of systemic bloodstream infections, and synthesis of the phospholipid phosphatidylethanolamine (PE) is required for virulence. The psd1Δ/Δ psd2Δ/Δ mutant, which cannot synthesize PE by the cytidine diphosphate diacylglycerol (CDP-DAG) pathway, is avirulent in the mouse model of systemic candidiasis. Similarly, an ept1Δ/Δ mutant, which cannot produce PE by the Kennedy pathway, exhibits decreased kidney fungal burden in systemically infected mice. Conversely, overexpression of EPT1 results in a hypervirulent phenotype in this model. Thus, mutations that increase PE synthesis increase virulence, and mutations that decrease PE synthesis decrease virulence. However, the mechanism by which virulence is regulated by PE synthesis is only partially understood. RNA sequencing was performed on strains with deficient or excessive PE biosynthesis to elucidate the mechanism. Decreased PE synthesis from loss of EPT1 or PSD1 and PSD2 leads to downregulation of genes that impact mitochondrial function. Losses of PSD1 and PSD2, but not EPT1, cause significant increases in transcription of glycosylation genes, which may reflect the substantial cell wall defects in the psd1Δ/Δ psd2Δ/Δ mutant. These accumulated defects could contribute to the decreased virulence observed for mutants with deficient PE synthesis. In contrast to mutants with decreased PE synthesis, there were no transcriptional differences between the EPT1 overexpression strain and the wild type, indicating that the hypervirulent phenotype is a consequence of posttranscriptional changes. It was found that overexpression of EPT1 causes increased chitin content and increased hyphal length. These phenotypes may help to explain the previously observed hypervirulence in the EPT1 overexpressor.

Modification of Candida albicans cell wall by commensal gut bacteria

The human gut is populated with a vast community of microbes, the microbiota. Fungi comprise 0.1% of the total gut microbiota. Some of these fungi exist as benign members, however others such Candida albicans can undergo a pathogenic switch causing disease. The fungal cell wall is the first target for immune system recognition. Recent studies have suggested that Candida is decorated with different cell wall epitopes within different physiological niches, due to the impact of carbon source and oxygen availability on cell wall remodelling. Here we hypothesize that resident gut bacteria also play a major role in fungal cell wall remodelling and immune recognition. Data from our lab has shown that a common bacterium from the gut, Bacteroides thetaiotaomicron (Bt), produces an extensive repertoire of degradative enzymes to breakdown the Candida cell wall. Recently, we have identified novel enzymes in Bt from the glycoside hydrolase family 130 (GH130), which specifically target β1,2-linked mannan, a unique feature of Candida mannan. We have deleted multiple fungal mannan specific loci in Bt and examined the ability of deletion strains to utilise Candida mannan as a carbon source. These data suggest that Bt contains multiple pathways to degrade the Candida cell wall. Now we are systematically dissecting the impact of mannan degradation on the physiology of the fungus. This will provide insights into how two prominent members of the gut microbiota interact with each other, how the Candida cell wall is modified in the anaerobic environment of the gut, and the importance of this in promoting immune homeostasis.

Candida albicans cell wall integrity transcription factors regulate polymicrobial biofilm formation with Streptococcus gordonii.

Polymicrobial biofilms play important roles in oral and systemic infections. The oral plaque bacterium Streptococcus gordonii is known to attach to the hyphal cell wall of the fungus Candida albicans to form corn-cob like structures in biofilms. However, the role of C. albicans in formation of polymicrobial biofilms is not completely understood. The objective of this study was to determine the role of C. albicans transcription factors in regulation of polymicrobial biofilms and antibiotic tolerance of S. gordonii. The proteins secreted by C. albicans and S. gordonii in mixed planktonic cultures were determined using mass spectrometry. Antibiotic tolerance of S. gordonii to ampicillin and erythromycin was determined in mixed cultures and mixed biofilms with C. albicans. Additionally, biofilm formation of S. gordonii with C. albicans knock-out mutants of 45 transcription factors that affect cell wall integrity, filamentous growth and biofilm formation was determined. Furthermore, these mutants were also screened for antibiotic tolerance in mixed biofilms with S. gordonii. Analysis of secreted proteomes resulted in the identification of proteins being secreted exclusively in mixed cultures. Antibiotic testing showed that S. gordonii had significantly increased survival in mixed planktonic cultures with antibiotics as compared to single cultures. C. albicans mutants of transcription factors Sfl2, Brg1, Leu3, Cas5, Cta4, Tec1, Tup1, Rim101 and Efg1 were significantly affected in mixed biofilm formation. Also mixed biofilms of S. gordonii with mutants of C. albicans transcription factors, Tec1 and Sfl2, had significantly reduced antibiotic tolerance as compared to control cultures. Our data indicates that C. albicans may have an important role in mixed biofilm formation as well as antibiotic tolerance of S. gordonii in polymicrobial biofilms. C. albicans may play a facilitating role than being just an innocent bystander in oral biofilms and infections.

Endothelial cell pyroptosis plays an important role in Kawasaki disease via HMGB1/RAGE/cathespin B signaling pathway and NLRP3 inflammasome activation

Kawasaki disease (KD) is the most common cause of pediatric cardiac disease in developed countries, and can lead to permanent coronary artery damage and long term sequelae such as coronary artery aneurysms. Given the prevalence and severity of KD, further research is warranted on its pathophysiology. It is known that endothelial cell damage and inflammation are two essential processes resulting in the coronary endothelial dysfunction in KD. However, detailed mechanisms are largely unknown. In this study, we investigated the role of pyroptosis in the setting of KD, and hypothesized that pyroptosis may play a central role in its pathophysiology. In vivo experiments of patients with KD demonstrated that serum levels of pyroptosis-related proteins, including ASC, caspase-1, IL-1β, IL-18, GSDMD and lactic dehydrogenase (LDH), were significantly increased in KD compared with healthy controls (HCs). Moreover, western blot analysis showed that the expression of GSDMD and mature IL-1β was notably elevated in KD sera. In vitro, exposure of human umbilical vein endothelial cells (HUVECs) to KD sera-treated THP1 cells resulted in the activation of NLRP3 inflammasome and subsequent pyroptosis induction, as evidenced by elevated expression of caspase-1, GSDMD, cleaved p30 form of GSDMD, IL-1β and IL-18, and increased LDH release and TUNEL and propidium iodide (PI)-positive cells. Furthermore, our results showed that NLRP3-dependent endothelial cell pyroptosis was activated by HMGB1/RAGE/cathepsin B signaling. These findings were also recapitulated in a mouse model of KD induced by Candida albicans cell wall extracts (CAWS). Together, our findings suggest that endothelial cell pyroptosis may play a significant role in coronary endothelial damage in KD, providing novel evidence that further elucidates its pathophysiology.

Cell wall mannoprotein of Candida albicans polarizes macrophages and affects proliferation and apoptosis through activation of the Akt signal pathway

Candida albicans is a commensal fungus that associates with human hosts. Under normal circumstances this interaction does not produce any severe life-threatening disease, as macrophages of the innate immune system will result in its clearance. However, disorders may arise in immunosuppressed individuals. To understand the bioactivity of Candida albicans cell wall polysaccharides, which represent an important component of its function, mannoprotein from this fungus was extracted, purified and analyzed. Mannoprotein with α-(1,2) and α-(1,6) linkages was investigated with use of HPLC and NMR. Co-incubation of mannoprotein with macrophages resulted in a mannoprotein with the potential to polarize macrophages to M1 and promote phagocytosis/microbial killing ability thus increasing the clearance of pathogens through Akt2. Moreover, mannoprotein within the cell wall promoted cell proliferation and inhibited apoptosis by activation of the Akt signaling pathway. Collectively, α-(1,6)(1,2)-mannoprotein, one of the five polysaccharides extracted from the cell wall of Candida albicans, demonstrates immune-enhancing effects by activation of the Akt signaling pathway. These findings provide important new insights into the biological effects of polysaccharides on macrophages. Such information can then serve as the foundation for the development of novel anti-fungal medications.

Synthesis and immunological studies of β-1,2-mannan-peptide conjugates as antifungal vaccines

Fungal cell surface carbohydrates and proteins are useful antigens for the development of antifungal vaccines. In this study, glycopeptides consisting of the β-1,2-mannan and N-terminal peptide epitopes of Candida albicans (C. albicans) cell wall phosphomannan complex and Als1p (rAls1p-N) protein, respectively, were synthesized and covalently conjugated with keyhole limpet hemocyanin (KLH) and human serum albumin (HSA) through homobifunctional disuccinimidyl glutarate. The resultant KLH-conjugates were immunologically evaluated using Balb/c mice to reveal that they induced high levels of IgG antibodies. Furthermore, these conjugates showed self-adjuvanting property, as they could promote robust antibody responses without the presence of an external adjuvant. More significantly, the obtained antisera could effectively recognize both the carbohydrate and the Als1 peptide epitopes and immunofluorescence and flow cytometry assays also demonstrated that the elicited antibodies could react with the cell surface of a number of fungi, including C. albicans, C. tropicalis, C. lustaniae and C. glabrata. These results suggested the great potential of these conjugates as antifungal vaccines.

Candida albicans cell wall mannoprotein synergizes with lipopolysaccharide to affect RAW264.7 proliferation, phagocytosis and apoptosis

With the widespread use of invasive surgery, immunosuppressive therapy and broad-spectrum antibiotics, there has resulted a corresponding increase in severe systemic infections as produced by Candida albicans (C.albicans), as it combines with bacterial infections. Such infections often result in high rates of mortality. In this report, we examined the effects of the C. albicans cell wall mannoprotein (MP) on macrophage immunity. The MTS assay was used to detect cell proliferation activity and neutral red staining to observe cell phagocytosis. The Griess method was used to detect NO secretion in culture supernatants and apoptosis of macrophages were determined with use of FITC-Annexin V and PI staining. mRNA and protein expressions of JAK2, STAT3, IL-1β, IL-6, TNF-α and iNOS in RAW264.7 cells were determined with use of RT-PCR and western blot. MP significantly promoted the proliferation of RAW264.7 cells, inhibited their phagocytic capacity, but exerted no significant effects on apoptosis of macrophages. In addition, MP not only up-regulated the expression of cytokines, but also the expressions of p-stat3 and p-jak2. Interestingly, when MP was combined with lipopolysaccharide (LPS) a markedly accentuated release of inflammatory cytokines was observed. MP promotes macrophage inflammation induced by LPS and participates in the inflammatory response. One of the potential mechanisms of this effect involves MP activation of the JAK2/STAT3 signaling pathway in RAW264.7 cells, which enables macrophages to transform from M0 to M1 and promote the occurrence of inflammation.

Effects of the binding of a Helianthus annuus lectin to Candida albicans cell wall on biofilm development and adhesion to host cells

BackgroundIn our previous study, we isolated and characterized a lectin called Helja from Helianthus annuus (sunflower) and then, in a further study, demonstrated its antifungal activity against Candida spp. Since Candida infections are a major health concern due to the increasing emergence of antifungal resistant strains, the search for new antifungal agents offers a promising opportunity for improving the treatment strategies against candidiasis. PurposeThe aim of this work was to get insights about the mechanism of action of Helja, an antifungal lectin of H. annuus, and to explore its ability to inhibit Candida albicans biofilm development and adherence to buccal epithelial cells (BEC). Study design/methodsYeast viability was evaluated by Evans Blue uptake and counting of colony forming units (CFU). The yeast cell integrity was assessed using Calcofluor White (CFW) as a cell wall perturbing agent and sorbitol as osmotic protectant. The induction of oxidative stress was evaluated using 3,3′-diaminobenzidine (DAB) for detection of hydrogen peroxide. The adherence was determined by counting the yeast cells attached to BEC after methylene blue staining. The biofilms were developed on polystyrene microplates, visualized by confocal laser scanning microscopy and the viable biomass was quantified by CFU counting. The binding lectin-Candida was assessed using Helja conjugated to fluorescein isothiocyanate (Helja-FITC) and simultaneous staining with CFW. The cellular surface hydrophobicity (CSH) was determined using a microbial adhesion to hydrocarbons method. ResultsC. albicans cells treated with 0.1 µg/µl of Helja showed a drastic decrease in yeast survival. The lectin affected the fungal cell integrity, induced the production of hydrogen peroxide and inhibited the morphological transition from yeast to filamentous forms. Helja caused a significant reduction of adherent cells and a decrease in biofilm biomass and coverage area. The treatment with the protein also reduced the surface hydrophobicity of fungal cells. We show the binding of Helja-FITC to yeast cells distributed as a thin outer layer to the CFW signal, and this interaction was displaced by mannose and Concanavalin A. ConclusionThe results demonstrate the interaction of Helja with the mannoproteins of C. albicans cell wall, the disruption of the cell integrity, the induction of oxidative stress, the inhibition of the morphological transition from yeast to filamentous forms and the fungal cell viability loss. The binding Helja-Candida also provides a possible explanation of the lectin effect on cell adherence, biofilm development and CSH, relevant features related to virulence of the pathogen.

β-Glucan of Candida albicans Cell Wall Extract Inhibits Salmonella Typhimurium Colonization by Potentiating Cellular Immunity (CD8 + and CD4 + T Cells).

Antimicrobial resistance has been reported in the drugs used for the treatment of typhoid fever. The immunomodulatory substance β-glucan can be used as an alternative therapy as it potentiates host immunity. The aims of this study are to observe the effect of Candida albicans cell wall (CCW) extract towards host immunity (TCD8+ and TCD4+ cells in spleen, intestinal sIgA) and its capacity to kill Salmonella in the intestine and liver of typhoid fever mice models. Typhoid fever mice models were created by infecting mice with S. Typhimurium orally. Mice were divided into four groups: the Non-Infected, Infected, CCW (infected mice treated with 300 µg CCW extract/mouse once a day), and Ciprofloxacin groups (infected mice treated with 15 mg/kg BW ciprofloxacin twice a day). Secretory IgA (sIgA) concentrations of mice in the CCW group remained unchanged. However, their TCD4+ and TCD8+ cells increased substantially compared to those in the Non-Infected group. In the Ciprofloxacin group, sIgA concentrations increased markedly compared to those in the Non-Infected and CCW groups; TCD4+ and TCD8+ cells also increased significantly compared to those in the Infected Group, but not significant compared to those in the CCW group. Colonization of S. Typhimurium in the intestine and liver decreased significantly in the CCW and Ciprofloxacin groups compared to that in the Infected group, with the lowest reduction being found in the Ciprofloxacin group. The inhibition of S. Typhimurium colonization by CCW is associated with the increase in TCD4+ and TCD8+ cells.

Candida albicans β-Glucan Differentiates Human Monocytes Into a Specific Subset of Macrophages.

β-Glucan derived from cell walls of Candida albicans is a potent immune modulator. It has been shown to induce trained immunity in monocytes via epigenetic and metabolic reprogramming and to protect from lethal sepsis if applied prior to infection. Since β-glucan-trained monocytes have not been classified within the system of mononuclear phagocytes we analyzed these cells metabolically, phenotypically and functionally with a focus on monocyte-to-macrophage differentiation and compared them with naïve monocytes and other types of monocyte-derived cells such as classically (M1) or alternatively (M2) activated macrophages and monocyte-derived dendritic cells (moDCs). We show that β-glucan inhibits spontaneous apoptosis of monocytes independent from autocrine or paracrine M-CSF release and stimulates monocyte differentiation into macrophages. β-Glucan-differentiated macrophages exhibit increased cell size and granularity and enhanced metabolic activity when compared to naïve monocytes. Although β-glucan-primed cells expressed markers of alternative activation and secreted higher levels of IL-10 after lipopolysaccharide (LPS), their capability to release pro-inflammatory cytokines and to kill bacteria was unaffected. Our data demonstrate that β-glucan priming induces a population of immune competent long-lived monocyte-derived macrophages that may be involved in immunoregulatory processes.

Effect of cinnamaldehyde on 1, 3-β-D-glucans in cell wall of Candida albicans in immunosuppressed BALB/c mice

ObjectiveInvasive pulmonary candidiasis is a disease with high incidence, difficult treatment, poor prognosis, and high mortality. The present study analyzed the influence of cinnamaldehyde on 1,3-β-D-glucans in the cell wall of Candida albicans in order to provide a theoretical basis for the research of antifungal drugs. MethodsAn immunosuppressed BALB/c mouse model with invasive pulmonary candidiasis was established by nasal perfusion of 50 µL of C. albicans suspension (107 cfu/mL). 1,3-β-D-glucans examination and electron microscopy were carried out. Fluconazole was used as the control. ResultsCinnamaldehyde was administered at a dose of 240 mg/kg/d for 14 consecutive days, and the measured value of 1,3-β-D-glucans was (1160.62 ± 89.65) pg/mL, whereas that of fluconazole was (4285.87 ± 215.62) pg/mL. The difference between the two groups was statistically significant (P < 0.05). Electron microscopy observation indicated that the 2−3 layers outside the cell wall of C. albicans (1,3-β-D-glucans layer) were rough, deformed, and incomplete, although the cell membrane was clear and intact. ConclusionCinnamaldehyde demonstrated special efficacy on 1,3-β-D-glucans in the cell wall of C. albicans.

Psoriasin, a novel anti-Candida albicans adhesin

Candida albicans belongs to the normal microbial flora on epithelial surfaces of humans. However, under certain, still not fully understood conditions, it can become pathogenic and cause a spectrum of diseases, from local infections to life-threatening septicemia. We investigated a panel of antimicrobial proteins and peptides (AMPs), potentially involved in mucosal immunity against this pathogen. Out of six studied AMPs, psoriasin was most up-regulated during a mucosal infection, an acute episode of recurrent Candida vulvovaginitis, although candidacidal activity has not been demonstrated. We here show that psoriasin binds to β-glucan, a basic component of the C. albicans cell wall, and thereby inhibits adhesion of the pathogen to surfaces and increases IL-8 production by mucosal epithelial cells. In conclusion, we show a novel mechanism of action of psoriasin. By inhibiting C. albicans adhesion and by enhancing cytokine production, psoriasin contributes to the immune response against C. albicans.Key messagesThe antimicrobial peptide psoriasin is highly up-regulated during a local mucosal infection, Candida albicans vulvovaginitis.Psoriasin binds to β-glucan in the Candida albicans cell wall and thereby inhibits adhesion of the pathogen.Binding of psoriasin to Candida albicans induces an immune response by mucosal epithelial cells.

Proteomic analysis of a Candida albicans pga1 Null Strain

We previously characterized Pga1, a Candida albicans (C. albicans) cell wall protein necessary for proper virulence, adhesion, and resistance to oxidative stress. By utilizing tandem mass spectrometry coupled with bioinformatics to investigate cell wall proteome expression in a pga1 null fourteen and 36 proteins were identified in the wild type grown under filamentous and non-filamentous conditions respectively, but were not detected in the mutant, including members of the PGA GPI anchored family. Virulence and adhesion proteins such as Hsp 90, Sap10, Cdc11, Int 3 and members of the lipase family were also identified exclusively in the wild type.

Mannan Molecular Sub-structures Control Nanoscale Glucan Exposure in Candida

N-linked mannans (N-mannans) in the cell wall of Candida albicans are thought to mask β-(1,3)-glucan from recognition by Dectin-1, contributing to innate immune evasion. Lateral cell wall exposures of glucan on C. albicans are predominantly single receptor-ligand interaction sites and are restricted to nanoscale geometries. Candida species exhibit a range of basal glucan exposures and their mannans also vary in size and complexity at the molecular level. We used super resolution fluorescence imaging and a series of protein mannosylation mutants in C. albicans and C. glabrata to investigate the role of specific N-mannan features in regulating the nanoscale geometry of glucan exposure. Decreasing acid labile mannan abundance and α-(1,6)-mannan backbone length correlated most strongly with increased density and nanoscopic size of glucan exposures in C. albicans and C. glabrata, respectively. Additionally, a C. albicans clinical isolate with high glucan exposure produced similarly perturbed N-mannan structures and exhibited similar changes to nanoscopic glucan exposure geometry. We conclude that acid labile N-mannan controls glucan exposure geometry at the nanoscale. Furthermore, variations in glucan nanoexposure characteristics are clinically relevant and are likely to impact the nature of the pathogenic surface presented to innate immunocytes at dimensions relevant to receptor engagement, aggregation and signaling.

Combined use of insoluble β-glucan from the cell wall of Candida albicans and cyclophosphamide: Validation in S180 tumor-bearing mice

BackgroundCyclophosphamide (CTX) is a widely used antitumor drug that can suppress the immune system. The effects of regulating immune response and antitumor of β-glucan from the cell wall of Candida albicans (CAIBG) have been confirmed. However, the effects of the combined use of CAIBG and CTX remain unclear and warrant further investigation. MethodsS180 tumor-bearing models were developed for CAIBG (100 mg/10 mL/kg) and CTX (30 mg/10 mL/kg) intervention. The weights of the body, tumor spleen, and Thymus were recorded to calculate the index of the spleen and Thymus. The spleen and Thymus were observed by hematoxylin and eosin staining, whereas the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β was determined by Western blot. The survival times of mice were followed and recorded for analysis. ResultsCAIBG, CTX, and combined use of CAIBG and CTX could down-regulate the tumor growth and prolong the survival time. The spleen and Thymus index significantly increased in the CAIBG + CTX group than in the CTX group, but it was lower than that in the CAIBG group. Moreover, the Thymus index was significantly lower in the CAIBG + CTX group than in the CAIBG group. The lymphocytes of the spleen and Thymus decreased significantly in the CTX group but improved significantly in the CAIBG and CAIBG + CTX groups. The expression level of TNF-α and IL-1β in the CTX+CAIBG group increased significantly compared with that in the CTX group. The survival time of the CAIBG group and CAIBG + CTX group was significantly higher than that of the CTX group. ConclusionsCAIBG has strong treatment potential in combating tumor growth and prolonging survival time of S180 tumor-bearing mice. Combined use of CAIBG and CTX can compensate the CTX-induced immunosuppression and provide antitumor effects. Future studies are necessary to elucidate the underlying mechanism.

MiR-146a negatively regulates dectin-1-induced inflammatory responses.

Dectin-1 is the critical sensor for β-glucan from Candida which is the most common human fungal pathogen and cause superficial and system infection. MicroRNAs (miRNAs) play crucial roles in regulating innate immunity. However, the functional role of miRNAs in inflammatory response dependent on the activation of dectin-1 pathway has not been defined. In the present study, we found insoluble β-glucan from the cell wall of Candida albicans (CaIG) was able to increase the production of of IL-6 and TNFα through Dectin-1-Syk-NF-κB and p38MAPK pathway. MiRNAs profiles combined with real-time PCR validation revealed that miR-146a, miR-30-5p, miR-210-3p expression level were increased in THP-1 cells treated with CaIG. The interaction between Dectin-1 and CaIG resulted in an long lasting increase of miR-146a expression dependent on Dectin-1-Syk-NF-κB, p38MAPK, contrasting with a rapid and transient increase of IL-6 and TNFα. Overexpression of miR-146a significantly suppressed the production of IL-6 and TNFα. MiR-146a mimics inhibited CaIG-induced activity of p-IκBα and translocation of NF-κB p65. Luciferase reporter assays showed miR-146a inhibited NF-κB promoter-binding activity. Together, our data suggest miR-146a may play the potent negative feedback regulator in inflammatory response following Dectin-1 stimulation.

Evaluation of trained immunity by β-1, 3 (d)-glucan on murine monocytes in vitro and duration of response in vivo.

The β-1, 3 (d)-glucan (β-glucan) present in the cell wall of Candida albicans induces epigenetic changes in human monocytes resulting in primed macrophages exhibiting increased cytokine responsiveness to reinfection. This phenomenon is referred to as trained immunity or innate immune memory. However, whether β-glucan can reprogramme murine monocytes in vitro or induce lasting effects in vivo has yet to be elucidated. Thus, purified murine spleen-derived monocytes were primed with β-glucan in vitro and assessed for markers of differentiation and survival. Important macrophage cell markers during monocyte-to-macrophage differentiation were downregulated and survival enhanced due to partial inhibition of apoptosis. Increased survival and not the β-glucan training effect explained the elevated production of tumour necrosis factor-α (TNFα) and interleukin-6 (IL-6) induced by subsequent lipopolysaccharide (LPS) challenge. In vivo, 4 days after systemic administration of β-glucan, mice were more responsive to LPS challenge as shown by the increased serum levels of TNFα, IL-6 and IL-10, an effect shown to be short lived as enhanced cytokine production was lost by day 20. Here, we have characterised murine macrophages derived from β-glucan-primed monocytes based on their surface marker expression and for the first time provide evidence that the training effect of β-glucan in vivo declines within a 3-week period.