Syk-dependent glycolytic reprogramming in dendritic cells regulates IL-1β production to β-glucan ligands in a TLR-independent manner

Glucans and applications in drug delivery

Glucan is a natural polysaccharide widely distributed in cereals and microorganisms that has various biological activities, including immunomodulatory, anti-infective, anti-inflammatory, and antitumor activities. In addition to wide applications in the broad fields of food, healthcare, and biomedicines, glucans hold promising potential as drug delivery carrier materials or ligands. Specifically, glucan microparticles or yeast cell wall particles are naturally enclosed vehicles with an interior cavity that can be exploited to carry and deliver drug payloads. The biological activities and targeting capacities of glucans depend largely on the recognition of glucan moieties by receptors such as dectin-1 and complement receptor 3, which are widely expressed on the cell membranes of mononuclear phagocytes, dendritic cells, neutrophils, and some lymphocytes. This review summarizes the chemical structures, sources, fundamental properties, extraction methods, and applications of these materials, with an emphasis on drug delivery. Glucans are utilized mainly as vaccine adjuvants, targeting ligands and as carrier materials for various drug entities. It is believed that glucans and glucan microparticles may be useful for the delivery of both small-molecule and macromolecular drugs, especially for potential treatment of immune-related diseases.

Immunometabolic Signature during Respiratory Viral Infection: A Potential Target for Host-Directed Therapies

RNA viruses are known to induce a wide variety of respiratory tract illnesses, from simple colds to the latest coronavirus pandemic, causing effects on public health and the economy worldwide. Influenza virus (IV), parainfluenza virus (PIV), metapneumovirus (MPV), respiratory syncytial virus (RSV), rhinovirus (RhV), and coronavirus (CoV) are some of the most notable RNA viruses. Despite efforts, due to the high mutation rate, there are still no effective and scalable treatments that accompany the rapid emergence of new diseases associated with respiratory RNA viruses. Host-directed therapies have been applied to combat RNA virus infections by interfering with host cell factors that enhance the ability of immune cells to respond against those pathogens. The reprogramming of immune cell metabolism has recently emerged as a central mechanism in orchestrated immunity against respiratory viruses. Therefore, understanding the metabolic signature of immune cells during virus infection may be a promising tool for developing host-directed therapies. In this review, we revisit recent findings on the immunometabolic modulation in response to infection and discuss how these metabolic pathways may be used as targets for new therapies to combat illnesses caused by respiratory RNA viruses.

Rapid glycolytic activation accompanying innate immune responses: mechanisms and function

Innate immune responses to pathogens, mediated by activation of pattern recognition receptors and downstream signal transduction cascades, trigger rapid transcriptional and epigenetic changes to support increased expression of pro-inflammatory cytokines and other effector molecules. Innate immune cells also rapidly rewire their metabolism. The most prominent metabolic alteration following innate immune activation is rapid up-regulation of glycolysis. In this mini-review, we summarize recent advances regarding the mechanisms of rapid glycolytic activation in innate immune cells, highlighting the relevant signaling components. We also discuss the impact of glycolytic activation on inflammatory responses, including the recently elucidated links of metabolism and epigenetics. Finally, we highlight unresolved mechanistic details of glycolytic activation and possible avenues of future research in this area.

HDM induces distinct immunometabolic phenotype in macrophages in TLR4-dependent manner

Asthma is one of the most common chronic diseases. In many cases it is preceded by the development of an immune response to allergens such as animal fur, dust, pollens and etc. In human population this disease is heterogeneous, and no selective drugs are available at the moment for some endotypes of asthma. The role of the adaptive immune system in the pathogenesis of asthma was extensively studied, while the role of innate immune cells, in particular myeloid cells, was not sufficiently addressed. Myeloid cells, such as macrophages and dendritic cells, are characterized by high plasticity, heterogenicity and ability to undergo polarization in response to various pathogenic stimuli, including those engaging innate immune receptors. Recently, special attention was drawn to the link between polarization of macrophages and cell metabolism. We hypothesized that immunometabolic reprogramming of myeloid cells, in particular, of macrophages and dendritic cells during sensitization with an allergen may affect further immune response and asthma development. To test this hypothesis, we generated distinct types of myeloid cells in vitro from murine bone marrow and analyzed their immunometabolic profiles upon activation with house dust mite extract (HDM) and its key active components. We found that the combination of lipopolysaccharide (LPS) and beta-glucan is sufficient to upregulate proinflammatory cytokine production as well as respiratory and glycolytic capacity of myeloid cells, comparably to HDM. This specific immunometabolic phenotype was associated with altered mitochondrial morphology and possibly with increased ROS production in macrophages. Moreover, we found that both TNF production and metabolic remodeling of macrophages in response to HDM are TLR4-dependent processes. Altogether, these results expand our understanding of molecular mechanisms underlying asthma induction and pathogenesis and may potentially lead to new therapeutic strategies for the treatment of this disease.

Fungal-mediated lung allergic airway disease: The critical role of macrophages and dendritic cells

Fungi are abundant in the environment, causing our lungs to be constantly exposed to a diverse range of species. While the majority of these are cleared effectively in healthy individuals, constant exposure to spores (especially Aspergillus spp.) can lead to the development of allergic inflammation that underpins and worsen diseases such as asthma. Despite this, the precise mechanisms that underpin the development of fungal allergic disease are poorly understood. Innate immune cells, such as macrophages (MΦs) and dendritic cells (DCs), have been shown to be critical for mediating allergic inflammation to a range of different allergens. This review will focus on the crucial role of MΦ and DCs in mediating antifungal immunity, evaluating how these immune cells mediate allergic inflammation within the context of the lung environment. Ultimately, we aim to highlight important future research questions that will lead to novel therapeutic strategies for fungal allergic diseases.

Enhanced Therapeutic Efficacy of Combining Losartan and Chemo-Immunotherapy for Triple Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a particularly aggressive subtype of breast cancer, which is relatively resistant to anti-programmed cell death-1 (α-PD1) therapy, characterized as non-immunogenic, dense stroma and accumulation of M2 tumor-associated macrophages (TAMs). Despite progress in strategies to deplete extracellular matrix (ECM) and enhance tumor-cell immunogenicity, the combinatorial anti-cancer effects with α-PD1 need to be explored. Here, we applied doxorubicin hydrochloride liposome (Dox-L) as immunogenic cell death (ICD)-inducing nano-chemotherapy and used losartan as stroma-depleting agent to improve α-PD1 efficacy (Losartan + Dox-L + α-PD1). The results showed that losartan could cause ECM reduction, facilitating enhanced delivery of Dox-L and further dendritic cell (DC) maturation. Additionally, losartan could also alleviate hypoxia for TNBC, thus reprogramming pro-cancer M2 TAMs to anti-cancer M1 TAMs, successfully overcoming immune-suppressive microenvironment. These modifications led to a significant increase in T cells’ infiltration and augmented anti-tumor immunity as exemplified by the notable reduction in tumor size and lung metastases. In summary, our findings support that combined treatment of losartan with Dox-L normalizes immunological-cold microenvironment, improves immuno-stimulation and optimizes the efficacy of TNBC immunotherapy. A novel combinational strategy with FDA-approved compounds proposed by the study may potentially be useful in TNBC clinical treatment.

Fungal Patterns Induce Cytokine Expression through Fluxes of Metabolic Intermediates That Support Glycolysis and Oxidative Phosphorylation

Cytokine expression is fine-tuned by metabolic intermediates, which makes research on immunometabolism suitable to yield drugs with a wider prospect of application than the biological therapies that block proinflammatory cytokines. Switch from oxidative phosphorylation (OXPHOS) to glycolysis has been considered a characteristic feature of activated immune cells. However, some stimuli might enhance both routes concomitantly. The connection between the tricarboxylic acid cycle and cytokine expression was scrutinized in human monocyte-derived dendritic cells stimulated with the fungal surrogate zymosan. Results showed that nucleocytosolic citrate and ATP-citrate lyase activity drove IL1B, IL10, and IL23A expression by yielding acetyl-CoA and oxaloacetate, with the latter one supporting glycolysis and OXPHOS by maintaining cytosolic NAD⁺ and mitochondrial NADH levels through mitochondrial shuttles. Succinate dehydrogenase showed a subunit-specific ability to modulate IL23A and IL10 expression. Succinate dehydrogenase A subunit activity supported cytokine expression through the control of the 2-oxoglutarate/succinate ratio, whereas C and D subunits underpinned cytokine expression by conveying electron flux from complex II to complex III of the electron transport chain. Fatty acids may also fuel the tricarboxylic acid cycle and influence cytokine expression. Overall, these results show that fungal patterns support cytokine expression through a strong boost of glycolysis and OXPHOS supported by the use of pyruvate, citrate, and succinate, along with the compartmentalized NAD(H) redox state maintained by mitochondrial shuttles.

Amyloid-β activates NLRP3 inflammasomes by affecting microglial immunometabolism through the Syk-AMPK pathway

Neuroinflammation is considered one of major factors in the pathogenesis of Alzheimer's disease (AD). In particular, inflammasome activation, including NLRP3 inflammasome in microglia, is regarded as fundamental for the pro-inflammatory response of immune cells. However, the precise molecular mechanism through which the NLRP3 inflammasome is associated with AD pathologies remains unclear. Here, we show that amyloid-β activates the NLRP3 inflammasome in microglia by activating Syk and inhibiting AMPK. Deactivated AMPK induces metabolic dysregulation, mitochondrial fragmentation, and reactive oxygen species formation, leading to the activation of the NLRP3 inflammasome. In addition, flufenamic acid (FA), a member of non-steroidal anti-inflammatory drugs, was found to effectively inhibit activation of the microglial NLRP3 inflammasome by regulating Syk and AMPK. Importantly, FA has marked therapeutic effects on major AD pathologies and memory function in vivo in microglia-dependent way. All together, these findings demonstrate the molecular mechanism of microglial NLRP3 inflammasome activation by amyloid-β, which acts as an important mediator of neuroinflammation. Also, we suggest that repurposing of FA for inhibiting microglial activation of the NLRP3 inflammasome is a potential treatment for AD.

Metabolic programming in dendritic cells tailors immune responses and homeostasis

It is being increasingly acknowledged that immune cells depend on certain metabolic traits to perform their functions and that the extracellular environment can influence cell metabolism and vice versa. Dendritic cell (DC) subsets traffic through highly diverse environments from the bone marrow, where they develop, to the various peripheral tissues, where they differentiate and capture antigens, before they migrate to the lymph node to present antigens and prime T cells. It is plausible that DC subsets modulate their stimulatory abilities in response to unique metabolic programming. The metabolic requirements of DCs are just recently being discovered, and subset- and context-specific metabolic phenotypes in DCs are highly intertwined with DC functions. In this review, we present the current knowledge on the intrinsic and extrinsic determinants of DC metabolism, how they regulate DC function with examples from tumor biology and in interaction with the microbiota, and discuss how this can be applied therapeutically.

Disulfiram inhibits IL-1β secretion and inflammatory cells recruitment in Aspergillus fumigatus keratitis

PURPOSE

Disulfiram, an inhibitor of gasdermin D-induced pore formation, is known to suppress interleukin (IL)-1β secretion and pyroptosis. However, its effects on fungal keratitis remain unknown. Therefore, we investigated the role of disulfiram in Aspergillus fumigatus keratitis.

METHODS

In vitro, Cell Count Kit-8 (CCK8) assay and cell scratch test were performed to determine optimal concentration. In vivo and in vitro experiments were conducted in a mouse model, human neutrophils, and mouse peritoneal macrophages. We pre-treated the mice or cells with disulfiram and infected them with A. fumigatus at specific times. We subsequently evaluated the development of fungal keratitis lesions, the recruitment of inflammatory cells, and the production of inflammatory cytokines using slit lamp microscopy, clinical evaluation, quantitative reverse transcription polymerase chain reaction, immunofluorescence staining, enzyme-linked immunosorbent assay, and western blotting. We also used slit lamp microscopy and clinical evaluation to assess the effect of natamycin with or without disulfiram.

RESULTS

Disulfiram at 20 μM has no significant cytotoxic effect and does not affect cell migration. In the mouse model, disulfiram significantly suppressed inflammatory responses, reduced neutrophil and macrophage recruitment, and down-regulated myeloperoxidase and nitric oxide synthase levels at earlier stages of infection. Disulfiram had no effect on IL-1β production and maturation, but it inhibited IL-1β secretion in macrophages. Disulfiram combined with natamycin significantly increased corneal transparency in the mice model.

CONCLUSION

Overall, disulfiram reduced the host immune response in fungal keratitis by attenuating neutrophil and macrophage recruitment and inhibiting IL-1β secretion in macrophages. Disulfiram in combination with antifungal agents may serve as a novel therapeutic method for reducing corneal opacity in fungal keratitis.

Dendritic Cells: Versatile Players in Renal Transplantation

Dendritic cells (DCs) induce and regulate adaptive immunity through migrating and maturing in the kidney. In this procedure, they can adopt different phenotypes—rejection-associated DCs promote acute or chronic injury renal grafts while tolerogenic DCs suppress the overwhelmed inflammation preventing damage to renal functionality. All the subsets interact with effector T cells and regulatory T cells (Tregs) stimulated by the ischemia–reperfusion procedure, although the classification corresponding to different effects remains controversial. Thus, in this review, we discuss the origin, maturation, and pathological effects of DCs in the kidney. Then we summarize the roles of divergent DCs in renal transplantation: taking both positive and negative stages in ischemia–reperfusion injury (IRI), switching phenotypes to induce acute or chronic rejection, and orchestrating surface markers for allograft tolerance via alterations in metabolism. In conclusion, we prospect that multidimensional transcriptomic analysis will revolute researches on renal transplantation by addressing the elusive mononuclear phagocyte classification and providing a holistic view of DC ontogeny and subpopulations.

Biological Effects of β-Glucans on Osteoclastogenesis

Although the anti-tumor and anti-infective properties of β-glucans have been well-discussed, their role in bone metabolism has not been reviewed so far. This review discusses the biological effects of β-glucans on bone metabolisms, especially on bone-resorbing osteoclasts, which are differentiated from hematopoietic precursors. Multiple immunoreceptors that can recognize β-glucans were reported to be expressed in osteoclast precursors. Coordinated co-stimulatory signals mediated by these immunoreceptors are important for the regulation of osteoclastogenesis and bone remodeling. Curdlan from the bacterium Alcaligenes faecalis negatively regulates osteoclast differentiation in vitro by affecting both the osteoclast precursors and osteoclast-supporting cells. We also showed that laminarin, lichenan, and glucan from baker’s yeast, as well as β-1,3-glucan from Euglema gracilisas, inhibit the osteoclast formation in bone marrow cells. Consistent with these findings, systemic and local administration of β-glucan derived from Aureobasidium pullulans and Saccharomyces cerevisiae suppressed bone resorption in vivo. However, zymosan derived from S. cerevisiae stimulated the bone resorption activity and is widely used to induce arthritis in animal models. Additional research concerning the relationship between the molecular structure of β-glucan and its effect on osteoclastic bone resorption will be beneficial for the development of novel treatment strategies for bone-related diseases.

Dendritic cell metabolism: moving beyond in vitro-culture-generated paradigms

Dendritic cells (DCs) are key orchestrators of immunity and tolerance. It has become evident that DC function can be influenced by cellular metabolic programs. However, conclusions from early metabolic studies using in vitro GM-CSF DC cultures fail to correlate with bona fide DC populations. Here, we discuss the existing paradigms in the DC metabolism field, focusing on the limitations of the models utilized. Furthermore, we introduce alternative models to generate DCs in vitro that better emulate DCs found in vivo. Finally, we highlight new techniques to evaluate DC metabolism at the single-cell level. The combination of these two strategies could help advance the DC metabolism field towards a more physiological understanding, which is crucial for the development of effective DC-based therapies.

Role of NLRP3 Inflammasome Activation in Obesity-Mediated Metabolic Disorders

NLRP3 inflammasome is one of the multimeric protein complexes of the nucleotide-binding domain, leucine-rich repeat (NLR)-containing pyrin and HIN domain family (PYHIN). When activated, NLRP3 inflammasome triggers the release of pro-inflammatory interleukins (IL)-1β and IL-18, an essential step in innate immune response; however, defective checkpoints in inflammasome activation may lead to autoimmune, autoinflammatory, and metabolic disorders. Among the consequences of NLRP3 inflammasome activation is systemic chronic low-grade inflammation, a cardinal feature of obesity and insulin resistance. Understanding the mechanisms involved in the regulation of NLRP3 inflammasome in adipose tissue may help in the development of specific inhibitors for the treatment and prevention of obesity-mediated metabolic diseases. In this narrative review, the current understanding of NLRP3 inflammasome activation and regulation is highlighted, including its putative roles in adipose tissue dysfunction and insulin resistance. Specific inhibitors of NLRP3 inflammasome activation which can potentially be used to treat metabolic disorders are also discussed.

Inflammasome activation in acute lung injury

Inflammasomes are multiprotein complexes tasked with sensing endogenous or exogenous inflammatory signals and integrating this signal into a downstream response. Inflammasome activation has been implicated in a variety of pulmonary diseases, including pulmonary hypertension, bacterial pneumonia, COPD, and asthma. Of increasing interest is the contribution of inflammasome activation in the context of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Inflammasome activation in both the lung parenchyma and resident immune cells generates intereukin-1β (IL-1β) and IL-18, both of which drive the cascade of lung inflammation forward. Blockade of these responses has been shown to be beneficial in animal models and is a focus of translational research in the field. In this review, we will discuss the assembly and regulation of inflammasomes during lung inflammation, highlighting therapeutically viable effector steps. We will examine the importance of IL-1β and IL-18, two key products of inflammasome activation, in ALI, as well as the contribution of the pulmonary endothelial cell to this process. Finally, we will explore translational research moving toward anti-inflammasome therapies for ALI/ARDS and speculate toward future directions for the field.

Revisiting Glycogen in Cancer: A Conspicuous and Targetable Enabler of Malignant Transformation

Once thought to be exclusively a storage hub for glucose, glycogen is now known to be essential in a range of physiological processes and pathological conditions. Glycogen lies at the nexus of diverse processes that promote malignancy, including proliferation, migration, invasion, and chemoresistance of cancer cells. It is also implicated in processes associated with the tumor microenvironment such as immune cell effector function and crosstalk with cancer-associated fibroblasts to promote metastasis. The enzymes of glycogen metabolism are dysregulated in a wide variety of malignancies, including cancers of the kidney, ovary, lung, bladder, liver, blood, and breast. Understanding and targeting glycogen metabolism in cancer presents a promising but under-explored therapeutic avenue. In this review, we summarize the current literature on the role of glycogen in cancer progression and discuss its potential as a therapeutic target for cancer treatment.

Tolerogenic Dendritic Cells: The Pearl of Immunotherapy in Organ Transplantation

Over a half century, organ transplantation has become an effective method for the treatment of end-stage visceral diseases. Although the application of immunosuppressants (IS) minimizes the rate of allograft rejection, the common use of IS bring many adverse effects to transplant patients. Moreover, true transplant tolerance is very rare in clinical practice. Dendritic cells (DCs) are thought to be the most potent antigen-presenting cells, which makes a bridge between innate and adaptive immunity. Among their subsets, a small portion of DCs with immunoregulatory function was known as tolerogenic DC (Tol-DC). Previous reports demonstrated the ability of adoptively transferred Tol-DC to approach transplant tolerance in animal models. In this study, we summarized the properties, ex vivo generation, metabolism, and clinical attempts of Tol-DC. Tol-DC is expected to become a substitute for IS to enable patients to achieve immune tolerance in the future.

The NLRP3 Inflammasome: Metabolic Regulation and Contribution to Inflammaging

In response to inflammatory stimuli, immune cells reconfigure their metabolism and bioenergetics to generate energy and substrates for cell survival and to launch immune effector functions. As a critical component of the innate immune system, the nucleotide-binding and oligomerization domain, leucine-rich repeat, and pyrin domain-containing 3 (NLRP3) inflammasome can be activated by various endogenous and exogenous danger signals. Activation of this cytosolic multiprotein complex triggers the release of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 and initiates pyroptosis, an inflammatory form of programmed cell death. The NLRP3 inflammasome fuels both chronic and acute inflammatory conditions and is critical in the emergence of inflammaging. Recent advances have highlighted that various metabolic pathways converge as potent regulators of the NLRP3 inflammasome. This review focuses on our current understanding of the metabolic regulation of the NLRP3 inflammasome activation, and the contribution of the NLRP3 inflammasome to inflammaging.

Can medicinal mushrooms have prophylactic or therapeutic effect against COVID-19 and its pneumonic superinfection and complicating inflammation?

Medicinal mushrooms have documented effects against different diseases, including infections and inflammatory disorders. The related Basidiomycota Agaricus blazei Murill (AbM), Hericium erinaceus (HE), and Grifola frondosa (GF) have been shown to exert antimicrobial activity against viral agents, Gram‐positive and Gram‐negative bacteria, and parasites in vitro and in vivo. Since the mechanism is immunomodulatory and not antibiotical, the mushrooms should be active against multi‐drug resistant microbes as well. Moreover, since these Basidiomycota also have anti‐inflammatory properties, they may be suited for treatment of the severe lung inflammation that often follows COVID‐19 infection. An AbM‐based mushroom extract (Andosan™), also containing HE and GF, has been shown to significantly reduce bacteraemia and increase survival in mice with pneumococcal sepsis, and to improve symptoms and quality of life in IBD patients via an anti‐inflammatory effect. Hence, such mushroom extracts could have prophylactic or therapeutic effect against the pneumonic superinfection and severe lung inflammation that often complicates COVID‐19 infection. Here, we review antimicrobial and anti‐inflammatory properties of AbM, HE and GF mushrooms, which could be used for the battle against COVID‐19.

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 (10-6000 μg/ml), for 24, 48 and 72 h. 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 1000 μg/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.

Glycogen Metabolism Supports Early Glycolytic Reprogramming and Activation in Dendritic Cells in Response to Both TLR and Syk-Dependent CLR Agonists

Dendritic cells (DCs) increase their metabolic dependence on glucose and glycolysis to support their maturation, activation-associated cytokine production, and T-cell stimulatory capacity. We have previously shown that this increase in glucose metabolism can be initiated by both Toll-like receptor (TLR) and C-type lectin receptor (CLR) agonists. In addition, we have shown that the TLR-dependent demand for glucose is partially satisfied by intracellular glycogen stores. However, the role of glycogen metabolism in supporting CLR-dependent DC glycolytic demand has not been formally demonstrated. In this work, we have shown that DCs activated with fungal-associated β-glucan ligands exhibit acute glycolysis induction that is dependent on glycogen metabolism. Furthermore, glycogen metabolism supports DC maturation, inflammatory cytokine production, and priming of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome in response to both TLR- and CLR-mediated activation. These data support a model in which different classes of innate immune receptors functionally converge in their requirement for glycogen-dependent glycolysis to metabolically support early DC activation. These studies provide new insight into how DC immune effector function is metabolically regulated in response to diverse inflammatory stimuli.

Nerolidol inhibits the LOX-1 / IL-1β signaling to protect against the Aspergillus fumigatus keratitis inflammation damage to the cornea

PURPOSE

Nerolidol, a naturally occurring sesquiterpene has both anti-microbial and anti-inflammatory properties. The current study aims to investigate the antifungal and the anti-inflammatory effects of nerolidol against mouse Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The minimum inhibitory concentration (MIC) and cytotoxicity tests were used to study the antifungal ability. For in vivo and in vitro studies, the mouse corneas and the human corneal epithelial cells (HCECs) infected with A. fumigatus spores were intervented with nerolidol or phosphate buffer saline (PBS). Thereafter, the effect of the nerolidol on the response against inflammation was analyzed using the following parameters: recruitment of the neutrophils or macrophages and the expression of the lectin-type oxidized low density lipoprotein receptor-1 (LOX-1) and interleukin 1β (IL-1β). Techniques used were the slit lamp, immunofluorescence, myeloperoxidase (MPO) detection, quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

Nerolidol directly inhibits the growth of A. fumigatus. The administration of nerolidol reduced the severity of fungal keratitis with infiltration of fewer inflammatory cells and reduced levels of the LOX-1, as well the anti-inflammatory cytokines such as IL-1β were reduced compared with the PBS group. Additionally, in vitro studies showed that treatment with nerolidol inhibited the production of the LOX-1 / IL-1β levels in A. fumigatus stimulated HCECs.

CONCLUSION

Nerolidol attenuated the A. fumigatus keratitis inflammatory response by inhibiting the growth of A. fumigatus, reducing the recruitment of the neutrophils and the macrophages, and inhibiting the LOX-1/ IL-1β signaling.

Syk-dependent glycolytic reprogramming in dendritic cells regulates IL-1β production to β-glucan ligands in a TLR-independent manner

Dendritic cells (DCs) activated via TLR ligation experience metabolic reprogramming, in which the cells are heavily dependent on glucose and glycolysis for the synthesis of molecular building blocks essential for maturation, cytokine production, and the ability to stimulate T cells. Although the TLR-driven metabolic reprogramming events are well documented, fungal-mediated metabolic regulation via C-type lectin receptors such as Dectin-1 and Dectin-2 is not clearly understood. Here, we show that activation of DCs with fungal-associated β-glucan ligands induces acute glycolytic reprogramming that supports the production of IL-1β and its secretion subsequent to NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome activation. This acute glycolytic induction in response to β-glucan ligands requires spleen tyrosine kinase signaling in a TLR-independent manner, suggesting now that different classes of innate immune receptors functionally induce conserved metabolic responses to support immune cell activation. These studies provide new insight into the complexities of metabolic regulation of DCs immune effector function regarding cellular activation associated with protection against fungal microbes.