Glucose Homeostasis Is Important for Immune Cell Viability during Candida Challenge and Host Survival of Systemic Fungal Infection

STING contributes to the inflammation and proliferation of Staphylococcus aureus via mitochondrial reactive oxygen species-hypoxic inducible factor 1α axis in epithelial cells

Staphylococcus aureus infection poses a serious threat to the dairy industry and public health safety. The stimulator of interferon gene (STING) signaling pathway has been well established as effective in defending against viral infections. However, the role of STING is controversial during bacterial infections. Herein, we provide an insight into the role of STING during S. aureus infection. Our data revealed that the STING signaling pathway was activated in S. aureus-infected cells. In vitro investigations demonstrated that inhibiting STING reduced inflammation, hypoxia-inducible factor-1 alpha (HIF1α) expression, and mitochondrial reactive oxygen species (mROS) production. Interestingly, blocking HIF1α eliminated the escalation of inflammation associated with STING. Additionally, suppressing mROS production significantly reduced HIF1α expression and inflammation levels, while elevating mROS had the opposite effect. These results indicate that STING promoted inflammation through the mROS-HIF1α pathway. Given that glycolysis is driven by HIF1α, we investigated the role of glycolysis during infection. As expected, STING-elevated inflammation was linked with HIF1α-driven glycolysis. In terms of pathogenesis, STING contributed to S. aureus proliferation within cells and mouse mammary glands. Collectively, our findings demonstrate that STING facilitates infection via the mROS-HIF1α-glycolysis axis, highlighting its potential as a promising anti-inflammatory target.

Lipid droplets restrict phagosome formation in antifungal immunity

Lipid droplets (LDs) are intracellular organelles that can be induced and interact with phagosomes during the process of pathogen phagocytosis in macrophages. However, the function of LDs in phagocytosis remains elusive. Here, we unveil the role of LDs in modulating phagosome formation via a fungal infection model. Specifically, LD accumulation restricted the degree of phagosome formation and protected macrophages from death. Mechanistically, LD formation competitively consumed the intracellular endoplasmic reticulum membrane and altered RAC1 translocation and GTPase activity, which resulted in limited phagosome formation in macrophages during fungal engulfment. Mice with Hilpda-deficient macrophages were more susceptible to the lethal sequelae of systemic infection with C. albicans. Notably, administration of the ATGL inhibitor atglistatin improved host outcomes in disseminated fungal infections. Taken together, our study elucidates the mechanism by which LDs control phagosome formation to prevent immune cell death and offers a potential drug target for the treatment of C. albicans infections.

Influence of cell bioenergetics on host-pathogen interaction in the lung

Pulmonary diseases, arising from infections caused by bacteria, fungi, and viruses, or stemming from underlying genetic factors are one of the leading causes of mortality in humans, accounting for millions of deaths every year. At the onset of pulmonary diseases, crucial roles are played by phagocytic immune cells, particularly tissue-resident macrophages, in regulating the immune response at the mucosal barrier. Recent strides have illuminated the pivotal role of host bioenergetics modulated by metabolites derived from both pathogens and hosts in influencing the pathophysiology of major organs. Their influence extends to processes such as the infiltration of immune cells, activation of macrophages, and the polarization phenomenon. Furthermore, host-derived metabolites, such as itaconate, contribute to the promotion of anti-inflammatory responses, thereby preventing immunopathology and facilitating the preservation of mucosal niches to thrive for the long-term. This review explores recent advancements in the field of immunometabolism, with a particular emphasis on the intricacies of disease progression in pulmonary infections caused by bacteria such as P. aeruginosa, M. tuberculosis and S. aureus and fungi like C. albicans.

Exploring the female genital tract mycobiome in young South African women using metaproteomics

BACKGROUND

Female genital tract (FGT) diseases such as bacterial vaginosis (BV) and sexually transmitted infections are prevalent in South Africa, with young women being at an increased risk. Since imbalances in the FGT microbiome are associated with FGT diseases, it is vital to investigate the factors that influence FGT health. The mycobiome plays an important role in regulating mucosal health, especially when the bacterial component is disturbed. However, we have a limited understanding of the FGT mycobiome since many studies have focused on bacterial communities and have neglected low-abundance taxonomic groups, such as fungi. To reduce this knowledge deficit, we present the first large-scale metaproteomic study to define the taxonomic composition and potential functional processes of the FGT mycobiome in South African reproductive-age women.

RESULTS

We examined FGT fungal communities present in 123 women by collecting lateral vaginal wall swabs for liquid chromatography-tandem mass spectrometry. From this, 39 different fungal genera were identified, with Candida dominating the mycobiome (53.2% relative abundance). We observed changes in relative abundance at the protein, genus, and functional (gene ontology biological processes) level between BV states. In women with BV, Malassezia and Conidiobolus proteins were more abundant, while Candida proteins were less abundant compared to BV-negative women. Correspondingly, Nugent scores were negatively associated with total fungal protein abundance. The clinical variables, Nugent score, pro-inflammatory cytokines, chemokines, vaginal pH, Chlamydia trachomatis, and the presence of clue cells were associated with fungal community composition.

CONCLUSIONS

The results of this study revealed the diversity of FGT fungal communities, setting the groundwork for understanding the FGT mycobiome. Video Abstract.

Immunometabolic reprogramming in macrophages infected with active and dormant Cryptococcus neoformans: differential modulation of respiration, glycolysis, and fatty acid utilization

Dormancy is an adaptation in which cells reduce their metabolism, transcription, and translation to stay alive under stressful conditions, preserving the capacity to reactivate once the environment reverts to favorable conditions. Dormancy and reactivation of Cryptococcus neoformans (Cn) are closely linked to intracellular residency within macrophages. Our previous work showed that in vitro murine macrophages rely on the viable but not cultivable (VBNC-a dormancy phenotype) fungus from active Cn, with striking differences in immunometabolic gene expression. Here, we analyzed the influence of VBNC and active Cn on the immunometabolism of infected macrophages, combining metabolic gene expression, mitochondrial membrane potential (ΔΨm), oxygen consumption analysis, and uptake of glucose and fatty acids. The active fungus induced mitochondrial depolarization, and increased glycolysis and mitochondrial oxygen consumption. VBNC infection in bone marrow-derived macrophage (BMDM) caused an attenuated modification in mitochondrial metabolism. However, we found differences in BMDM infected with VBNC vs those infected with active fungus, where VBNC induced an increment in fatty acid uptake in M0 and M1 BMDM, measured by incorporation of BODIPY-palmitate, accompanied by an increase in expression of fatty acid transporters Fabp1 and Fabp4. Overall, distinct fatty acid-related responses induced by VBNC and active Cn suggest different immunomodulatory reactions, depending on the microbial growth stage. We posit that, for VBNC, some of these macrophage metabolic responses reflect the establishment of prolonged microbial intracellular residency and possibly initial stages of granuloma formation.

Triglyceride glucose-waist circumference as a predictor of mortality and subtypes of cardiovascular disease: a systematic review and meta-analysis

BACKGROUND

The significant burden of cardiovascular diseases underscores the necessity for identifying novel predictive markers that can forecast both cardiovascular diseases and mortality. In recent years, TyG-obesity-related parameters have gained special attention in this regard. This study aimed to assess the association between TyG-waist circumference (TyG-WC) and cardiovascular diseases and mortality.

METHODS

A comprehensive search was performed in databases including PubMed, Scopus, and Web of Science from their inception until October 6, 2024. The key outcomes of interest included all-cause mortality, cardiovascular mortality, cardiovascular diseases, myocardial infarction, stroke, coronary artery diseases, peripheral artery diseases, and heart failure. The pooled risk ratio (RR) with corresponding 95% confidence intervals (CI) was calculated. Meta-analysis was carried out using StataMP 14.0.

RESULTS

A total of 17 studies were included in the analysis. The number of participants ranged between 2,224 and 95,342. The meta-analysis revealed that TyG-WC is significantly associated with an increased risk of all-cause mortality, cardiovascular mortality, cardiovascular diseases, myocardial infarction, stroke, coronary artery diseases, and peripheral artery diseases. However, only one study addressed the relationship between TyG-WC and heart failure with a positive correlation.

CONCLUSION

This study indicates that TyG-WC could serve as a promising predictor of cardiovascular diseases, along with cardiovascular and all-cause mortality. Given its accessibility, TyG-WC may be a practical tool for screening purposes.

T. pallidum achieves immune evasion by blocking autophagic flux in microglia through hexokinase 2

Increasing evidence suggests that immune cell clearance is closely linked to cellular metabolism. Neurosyphilis, a severe neurological disorder caused by Treponema pallidum (T. pallidum) infection, significantly impacts the brain. Microglia, the innate immune cells of the central nervous system, play a critical role in neuroinflammation and immune surveillance. However, the inability of the nervous system to fully eliminate T. pallidum points to a compromised clearance function of microglia. This study investigates how T. pallidum alters the immune clearance ability of microglia and explores the underlying metabolic mechanisms. RNA sequencing (RNA seq), LC-MS metabolomics, and XFe96 Seahorse assays were employed to assess metabolic activity in microglial cells. Western blotting, qPCR, and immunofluorescence imaging were utilized to evaluate autophagy flux and extent of T. pallidum infections. Transcriptomic analysis revealed that T. pallidum alters the transcription expression of key glycolytic enzymes, including hexokinase 1 (HK1), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), leading to significant metabolic dysregulation. Specifically, metabolomic analysis showed reduced levels of phosphoenolpyruvate and citrate, while lactate production was notably increased. Functional assays confirmed that T. pallidum impairs glycolytic activity in microglial, as evidenced by decreased glycolytic flux, glycolytic reserve capacity, and maximum glycolytic capacity. Moreover, our results indicate that HK2, a crucial glycolytic enzyme, is closely associated with the autophagy. T. pallidum infection inhibits HK2 expression, which in turn suppresses autophagic flux by reducing the formation of lysosome-associated membrane protein 2 (LAMP2) and disrupting autophagosome-lysosome fusion. These findings suggest that T. pallidum hijacks microglial metabolic pathways, specifically glycolysis, to evade immune clearance. By inhibiting the glycolytic enzyme HK2, T. pallidum modulates autophagy and enhances immune evasion, providing a novel insight into the pathogenesis of neurosyphilis. This study paves the way for further investigations into the role of metabolic reprogramming in the immune escape mechanisms of T. pallidum.

GATA1-deficient human pluripotent stem cells generate neutrophils with improved antifungal immunity that is mediated by the integrin CD18

Neutrophils are critical for host defense against fungi. However, the short life span and lack of genetic tractability of primary human neutrophils has limited in vitro analysis of neutrophil-fungal interactions. Human induced pluripotent stem cell (iPSC)-derived neutrophils (iNeutrophils) provide a genetically tractable system to study host defense responses of human neutrophils. Here, we show that deletion of the transcription factor GATA1 from human iPSCs results in iNeutrophils with improved antifungal activity against Aspergillus fumigatus. GATA1-knockout (KO) iNeutrophils have increased maturation, antifungal pattern recognition receptor expression and have improved neutrophil effector functions compared to wild-type iNeutrophils. iNeutrophils also show a shift in their metabolism following stimulation with fungal β-glucan to the pentose phosphate pathway (PPP), similar to primary human neutrophils. Furthermore, we show that deletion of the integrin CD18 attenuates the ability of GATA1-KO iNeutrophils to kill A. fumigatus but is not necessary for the metabolic shift. Collectively, these findings support iNeutrophils as a robust system to study human neutrophil antifungal immunity and has identified specific roles for CD18 in the defense response.

Circadian metabolic adaptations to infections

Circadian clocks are biological oscillators that evolved to coordinate rhythms in behaviour and physiology around the 24-hour day. In mammalian tissues, circadian rhythms and metabolism are highly intertwined. The clock machinery controls rhythmic levels of circulating hormones and metabolites, as well as rate-limiting enzymes catalysing biosynthesis or degradation of macromolecules in metabolic tissues, such control being exerted both at the transcriptional and post-transcriptional level. During infections, major metabolic adaptation occurs in mammalian hosts, at the level of both the single immune cell and the whole organism. Under these circumstances, the rhythmic metabolic needs of the host intersect with those of two other players: the pathogen and the microbiota. These three components cooperate or compete to meet their own metabolic demands across the 24 hours. Here, we review findings describing the circadian regulation of the host response to infection, the circadian metabolic adaptations occurring during host-microbiota-pathogen interactions and how such regulation can influence the immune response of the host and, ultimately, its own survival.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

Glycogenesis and glyconeogenesis from glutamine, lactate and glycerol support human macrophage functions

Macrophages fight infection and ensure tissue repair, often operating at nutrient-poor wound sites. We investigated the ability of human macrophages to metabolize glycogen. We observed that the cytokines GM-CSF and M-CSF plus IL-4 induced glycogenesis and the accumulation of glycogen by monocyte-derived macrophages. Glyconeogenesis occurs in cells cultured in the presence of the inflammatory cytokines GM-CSF and IFNγ (M1 cells), via phosphoenolpyruvate carboxykinase 2 (PCK2) and fructose-1,6-bisphosphatase 1 (FBP1). Enzyme inhibition with drugs or gene silencing techniques and 13C-tracing demonstrate that glutamine (metabolized by the TCA cycle), lactic acid, and glycerol were substrates of glyconeogenesis only in M1 cells. Tumor-associated macrophages (TAMs) also store glycogen and can perform glyconeogenesis. Finally, macrophage glycogenolysis and the pentose phosphate pathway (PPP) support cytokine secretion and phagocytosis regardless of the availability of extracellular glucose. Thus, glycogen metabolism supports the functions of human M1 and M2 cells, with inflammatory M1 cells displaying a possible dependence on glyconeogenesis.

Alpha1-antitrypsin impacts innate host-pathogen interactions with Candida albicans by stimulating fungal filamentation

Our immune system possesses sophisticated mechanisms to cope with invading microorganisms, while pathogens evolve strategies to deal with threats imposed by host immunity. Human plasma protein α1-antitrypsin (AAT) exhibits pleiotropic immune-modulating properties by both preventing immunopathology and improving antimicrobial host defence. Genetic associations suggested a role for AAT in candidemia, the most frequent fungal blood stream infection in intensive care units, yet little is known about how AAT influences interactions between Candida albicans and the immune system. Here, we show that AAT differentially impacts fungal killing by innate phagocytes. We observed that AAT induces fungal transcriptional reprogramming, associated with cell wall remodelling and downregulation of filamentation repressors. At low concentrations, the cell-wall remodelling induced by AAT increased immunogenic β-glucan exposure and consequently improved fungal clearance by monocytes. Contrastingly, higher AAT concentrations led to excessive C. albicans filamentation and thus promoted fungal immune escape from monocytes and macrophages. This underscores that fungal adaptations to the host protein AAT can differentially define the outcome of encounters with innate immune cells, either contributing to improved immune recognition or fungal immune escape.

Starvation and infection: The role of sickness-associated anorexia in metabolic adaptation during acute infection

Sickness-associated anorexia, the reduction in appetite seen during infection, is a widely conserved and well-recognized symptom of acute infection, yet there is very little understanding of its functional role in recovery. Anorexic sickness behaviours can be understood as an evolutionary strategy to increase tolerance to pathogen-mediated illness. In this review we explore the evidence for mechanisms and potential metabolic benefits of sickness-associated anorexia. Energy intake can impact on the immune response, control of inflammation and tissue stress, and on pathogen fitness. Fasting mediators including hormone-sensitive lipase, peroxisome proliferator-activated receptor-alpha (PPAR-α) and ketone bodies are potential facilitators of infection recovery through multiple pathways including suppression of inflammation, adaptation to lipid utilising pathways, and resistance to pathogen-induced cellular stress. However, the effect and benefit of calorie restriction is highly heterogeneous depending on both the infection and the metabolic status of the host, which has implications regarding clinical recommendations for feeding during different infections.

Gladiolin produced by pathogenic Burkholderia synergizes with amphotericin B through membrane lipid rearrangements

Amphotericin B (AmpB) is an effective but toxic antifungal drug. Thus, improving its activity/toxicity relationship is of interest. AmpB disrupts fungal membranes by two proposed mechanisms: ergosterol sequestration from the membrane and pore formation. Whether these two mechanisms operate in conjunction and how they could be potentiated remains to be fully understood. Here, we report that gladiolin, a polyketide antibiotic produced by Burkholderia gladioli, is a strong potentiator of AmpB and acts synergistically against Cryptococcus and Candida species, including drug-resistant C. auris. Gladiolin also synergizes with AmpB against drug-resistant fungal biofilms, while exerting no mammalian cytotoxicity. To explain the mechanism of synergy, we show that gladiolin interacts with membranes via a previously unreported binding mode for polyketides. Moreover, gladiolin modulates lipid binding by AmpB and, in combination, causes faster and more pronounced lipid rearrangements relative to AmpB alone which include membrane thinning consistent with ergosterol extraction, areas of thickening, pore formation, and increased membrane destruction. These biophysical data provide evidence of a functional interaction between gladiolin and AmpB at the membrane interface. The data further indicate that the two proposed AmpB mechanisms (ergosterol sequestration and pore formation) act in conjunction to disrupt membranes, and that gladiolin synergizes by enhancing both mechanisms. Collectively, our findings shed light on AmpB's mechanism of action and characterize gladiolin as an AmpB potentiator, showing an antifungal mechanism distinct from its proposed antibiotic activity. We shed light on the synergistic mechanism at the membrane, and provide insights into potentiation strategies to improve AmpB's activity/toxicity relationship.

IMPORTANCE

Amphotericin B (AmpB) is one of the oldest antifungal drugs in clinical use. It is an effective therapeutic, but it comes with toxicity issues due to the similarities between its fungal target (the membrane lipid ergosterol) and its mammalian counterpart (cholesterol). One strategy to improve its activity/toxicity relationship is by combinatorial therapy with potentiators, which would enable a lower therapeutic dose of AmpB. Here, we report on the discovery of the antibiotic gladiolin as a potentiator of AmpB against several priority human fungal pathogens and fungal biofilms, with no increased toxicity against mammalian cells. We show that gladiolin potentiates AmpB by increasing and accelerating membrane damage. Our findings also provide insights into the on-going debate about the mechanism of action of AmpB by indicating that both proposed mechanisms, extraction of ergosterol from membranes and pore formation, are potentiated by gladiolin.

Phenotypic Heterogeneity in Pathogens

Pathogen diversity within an infected organism has traditionally been explored through the lens of genetic heterogeneity. Hallmark studies have characterized how genetic diversity within pathogen subpopulations contributes to treatment escape and infectious disease progression. However, recent studies have begun to reveal the mechanisms by which phenotypic heterogeneity is established within genetically identical populations of invading pathogens. Furthermore, exciting new work highlights how these phenotypically heterogeneous subpopulations contribute to a pathogen population better equipped to handle the complex and fluctuating environment of a host organism. In this review, we focus on how bacterial pathogens, including Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa, and Mycobacterium tuberculosis, establish and maintain phenotypic heterogeneity, and we explore recent work demonstrating causative links between this heterogeneity and infection outcome.

Bacteria-derived short-chain fatty acids as potential regulators of fungal commensalism and pathogenesis

The human gastrointestinal microbiome encompasses bacteria, fungi, and viruses forming complex bionetworks which, for organismal health, must be in a state of homeostasis. An important homeostatic mechanism derives from microbial competition, which maintains the relative abundance of microbial species in a healthy balance. Microbes compete for nutrients and secrete metabolites that inhibit other microbes. Short-chain fatty acids (SCFAs) are one such class of metabolites made by gut bacteria to very high levels. SCFAs are metabolised by microbes and host cells and have multiple roles in regulating cell physiology. Here, we review the mechanisms by which SCFAs regulate the fungal gut commensal Candida albicans. We discuss SCFA's ability to inhibit fungal growth, limit invasive behaviours and modulate cell surface antigens recognised by immune cells. We review the mechanisms underlying these roles: regulation of gene expression, metabolism, signalling and SCFA-driven post-translational protein modifications by acylation, which contribute to changes in acylome dynamics of C. albicans with potentially large consequences for cell physiology. Given that the gut mycobiome is a reservoir for systemic disease and has also been implicated in inflammatory bowel disease, understanding the mechanisms by which bacterial metabolites, such as SCFAs, control the mycobiome might provide therapeutic avenues.

GATA1-deficient human pluripotent stem cells generate neutrophils with improved antifungal immunity that is mediated by the integrin CD18

Neutrophils are critical for host defense against fungi. However, the short life span and lack of genetic tractability of primary human neutrophils has limited in vitro analysis of neutrophil-fungal interactions. Human induced pluripotent stem cell (iPSC)-derived neutrophils (iNeutrophils) are a genetically tractable alternative to primary human neutrophils. Here, we show that deletion of the transcription factor GATA1 from human iPSCs results in iNeutrophils with improved antifungal activity against Aspergillus fumigatus. GATA1 knockout (KO) iNeutrophils have increased maturation, antifungal pattern recognition receptor expression and more readily execute neutrophil effector functions compared to wild-type iNeutrophils. iNeutrophils also show a shift in their metabolism following stimulation with fungal β-glucan, including an upregulation of the pentose phosphate pathway (PPP), similar to primary human neutrophils in vitro. Furthermore, we show that deletion of the integrin CD18 attenuates the ability of GATA1-KO iNeutrophils to kill A. fumigatus but is not necessary for the upregulation of PPP. Collectively, these findings support iNeutrophils as a robust system to study human neutrophil antifungal immunity and has identified specific roles for CD18 in the defense response.

Temporal transcriptional response of Candida glabrata during macrophage infection reveals a multifaceted transcriptional regulator CgXbp1 important for macrophage response and fluconazole resistance

Candida glabrata can thrive inside macrophages and tolerate high levels of azole antifungals. These innate abilities render infections by this human pathogen a clinical challenge. How C. glabrata reacts inside macrophages and what is the molecular basis of its drug tolerance are not well understood. Here, we mapped genome-wide RNA polymerase II (RNAPII) occupancy in C. glabrata to delineate its transcriptional responses during macrophage infection in high temporal resolution. RNAPII profiles revealed dynamic C. glabrata responses to macrophages with genes of specialized pathways activated chronologically at different times of infection. We identified an uncharacterized transcription factor (CgXbp1) important for the chronological macrophage response, survival in macrophages, and virulence. Genome-wide mapping of CgXbp1 direct targets further revealed its multi-faceted functions, regulating not only virulence-related genes but also genes associated with drug resistance. Finally, we showed that CgXbp1 indeed also affects fluconazole resistance. Overall, this work presents a powerful approach for examining host-pathogen interaction and uncovers a novel transcription factor important for C. glabrata's survival in macrophages and drug tolerance.

Metabolic homeostasis in fungal infections from the perspective of pathogens, immune cells, and whole-body systems

SUMMARYThe ability to overcome metabolic stress is a major determinant of outcomes during infections. Pathogens face nutrient and oxygen deprivation in host niches and during their encounter with immune cells. Immune cells require metabolic adaptations for producing antimicrobial compounds and mounting antifungal inflammation. Infection also triggers systemic changes in organ metabolism and energy expenditure that range from an enhanced metabolism to produce energy for a robust immune response to reduced metabolism as infection progresses, which coincides with immune and organ dysfunction. Competition for energy and nutrients between hosts and pathogens means that successful survival and recovery from an infection require a balance between elimination of the pathogen by the immune systems (resistance), and doing so with minimal damage to host tissues and organs (tolerance). Here, we discuss our current knowledge of pathogen, immune cell and systemic metabolism in fungal infections, and the impact of metabolic disorders, such as obesity and diabetes. We put forward the idea that, while our knowledge of the use of metabolic regulation for fungal proliferation and antifungal immune responses (i.e., resistance) has been growing over the years, we also need to study the metabolic mechanisms that control tolerance of fungal pathogens. A comprehensive understanding of how to balance resistance and tolerance by metabolic interventions may provide insights into therapeutic strategies that could be used adjunctly with antifungal drugs to improve patient outcomes.

Disruption of glucose homeostasis by bacterial infection orchestrates host innate immunity through NAD+/NADH balance

Metabolic reprogramming is crucial for activating innate immunity in macrophages, and the accumulation of immunometabolites is essential for effective defense against infection. The NAD+/NADH (ratio of nicotinamide adenine dinucleotide and its reduced counterpart) redox couple serves as a critical node that integrates metabolic pathways and signaling events, but how this metabolite couple engages macrophage activation remains unclear. Here, we show that the NAD+/NADH ratio serves as a molecular signal that regulates proinflammatory responses and type I interferon (IFN) responses divergently. Salmonella Typhimurium infection leads to a decreased NAD+/NADH ratio by inducing the accumulation of NADH. Further investigation shows that an increased NAD+/NADH ratio correlates with attenuated proinflammatory responses and enhanced type I IFN responses. Conversely, a decreased NAD+/NADH ratio is linked to intensified proinflammatory responses and restrained type I IFN responses. These results show that the NAD+/NADH ratio is an essential cell-intrinsic factor that orchestrates innate immunity, which enhances our understanding of how metabolites fine-tune innate immunity.

Synergistic cross-kingdom host cell damage between Candida albicans and Enterococcus faecalis

The fungus Candida albicans and the Gram-positive bacterium Enterococcus faecalis share mucosal niches in the human body. As opportunistic pathogens, both are found to expand population size during dysbiosis, and can cause severe systemic infections in susceptible individuals. Here, we show that the presence of C. albicans results in increased host cell damage by E. faecalis . Furthermore, E. faecalis aggravates oropharyngeal candidiasis in mice. Increased damage is mediated by enterococcal cytolysin, and involves both physical interaction and altered glucose availability. Physical interaction promotes accumulation of bacteria on host cells, facilitating contact of cytolysin with host cells. Glucose depletion by the metabolic activity of the fungus sensitized host cells to cytolysin. This work illustrates how a complex interplay between fungi and bacteria can result in detrimental consequences for the host.

Metabolic regulation of the host-fungus interaction: from biological principles to therapeutic opportunities

Fungal infections present a significant global public health concern, impacting over 1 billion individuals worldwide and resulting in more than 3 million deaths annually. Despite considerable progress in recent years, the management of fungal infections remains challenging. The limited development of novel diagnostic and therapeutic approaches is largely attributed to our incomplete understanding of the pathogenetic mechanisms involved in these diseases. Recent research has highlighted the pivotal role of cellular metabolism in regulating the interaction between fungi and their hosts. In response to fungal infection, immune cells undergo complex metabolic adjustments to meet the energy demands necessary for an effective immune response. A comprehensive understanding of the metabolic circuits governing antifungal immunity, combined with the integration of individual host traits, holds the potential to inform novel medical interventions for fungal infections. This review explores recent insights into the immunometabolic regulation of host-fungal interactions and the infection outcome and discusses how the metabolic repurposing of immune cell function could be exploited in innovative and personalized therapeutic approaches.

The immunology of sickness metabolism

Everyone knows that an infection can make you feel sick. Although we perceive infection-induced changes in metabolism as a pathology, they are a part of a carefully regulated process that depends on tissue-specific interactions between the immune system and organs involved in the regulation of systemic homeostasis. Immune-mediated changes in homeostatic parameters lead to altered production and uptake of nutrients in circulation, which modifies the metabolic rate of key organs. This is what we experience as being sick. The purpose of sickness metabolism is to generate a metabolic environment in which the body is optimally able to fight infection while denying vital nutrients for the replication of pathogens. Sickness metabolism depends on tissue-specific immune cells, which mediate responses tailored to the nature and magnitude of the threat. As an infection increases in severity, so do the number and type of immune cells involved and the level to which organs are affected, which dictates the degree to which we feel sick. Interestingly, many alterations associated with metabolic disease appear to overlap with immune-mediated changes observed following infection. Targeting processes involving tissue-specific interactions between activated immune cells and metabolic organs therefore holds great potential for treating both people with severe infection and those with metabolic disease. In this review, we will discuss how the immune system communicates in situ with organs involved in the regulation of homeostasis and how this communication is impacted by infection.

Yersinia infection induces glucose depletion and AMPK-dependent inhibition of pyroptosis in mice

Nutritional status and pyroptosis are important for host defence against infections. However, the molecular link that integrates nutrient sensing into pyroptosis during microbial infection is unclear. Here, using metabolic profiling, we found that Yersinia pseudotuberculosis infection results in a significant decrease in intracellular glucose levels in macrophages. This leads to activation of the glucose and energy sensor AMPK, which phosphorylates the essential kinase RIPK1 at S321 during caspase-8-mediated pyroptosis. This phosphorylation inhibits RIPK1 activation and thereby restrains pyroptosis. Boosting the AMPK-RIPK1 cascade by glucose deprivation, AMPK agonists, or RIPK1-S321E knockin suppresses pyroptosis, leading to increased susceptibility to Y. pseudotuberculosis infection in mice. Ablation of AMPK in macrophages or glucose supplementation in mice is protective against infection. Thus, we reveal a molecular link between glucose sensing and pyroptosis, and unveil a mechanism by which Y. pseudotuberculosis reduces glucose levels to impact host AMPK activation and limit host pyroptosis to facilitate infection.

Including glutamine in a resource allocation model of energy metabolism in cancer and yeast cells

Energy metabolism is crucial for all living cells, especially during fast growth or stress scenarios. Many cancer and activated immune cells (Warburg effect) or yeasts (Crabtree effect) mostly rely on aerobic glucose fermentation leading to lactate or ethanol, respectively, to generate ATP. In recent years, several mathematical models have been proposed to explain the Warburg effect on theoretical grounds. Besides glucose, glutamine is a very important substrate for eukaryotic cells-not only for biosynthesis, but also for energy metabolism. Here, we present a minimal constraint-based stoichiometric model for explaining both the classical Warburg effect and the experimentally observed respirofermentation of glutamine (WarburQ effect). We consider glucose and glutamine respiration as well as the respective fermentation pathways. Our resource allocation model calculates the ATP production rate, taking into account enzyme masses and, therefore, pathway costs. While our calculation predicts glucose fermentation to be a superior energy-generating pathway in human cells, different enzyme characteristics in yeasts reduce this advantage, in some cases to such an extent that glucose respiration is preferred. The latter is observed for the fungal pathogen Candida albicans, which is a known Crabtree-negative yeast. Further, optimization results show that glutamine is a valuable energy source and important substrate under glucose limitation, in addition to its role as a carbon and nitrogen source of biomass in eukaryotic cells. In conclusion, our model provides insights that glutamine is an underestimated fuel for eukaryotic cells during fast growth and infection scenarios and explains well the observed parallel respirofermentation of glucose and glutamine in several cell types.

An IFNγ-dependent immune-endocrine circuit lowers blood glucose to potentiate the innate antiviral immune response

Viral infection makes us feel sick as the immune system alters systemic metabolism to better fight the pathogen. The extent of these changes is relative to the severity of disease. Whether blood glucose is subject to infection-induced modulation is mostly unknown. Here we show that strong, nonlethal infection restricts systemic glucose availability, which promotes the antiviral type I interferon (IFN-I) response. Following viral infection, we find that IFNγ produced by γδ T cells stimulates pancreatic β cells to increase glucose-induced insulin release. Subsequently, hyperinsulinemia lessens hepatic glucose output. Glucose restriction enhances IFN-I production by curtailing lactate-mediated inhibition of IRF3 and NF-κB signaling. Induced hyperglycemia constrained IFN-I production and increased mortality upon infection. Our findings identify glucose restriction as a physiological mechanism to bring the body into a heightened state of responsiveness to viral pathogens. This immune-endocrine circuit is disrupted in hyperglycemia, possibly explaining why patients with diabetes are more susceptible to viral infection.

Correlation of TyG-BMI and TyG-WC with severity and short-term outcome in new-onset acute ischemic stroke

Objectives

To research the connection between the indexes of the indexes of triglyceride-glucose (TyG) combined with obesity indices and the initial neurological severity and short-term outcome of new-onset acute ischemic stroke.

Methods

Data of patients with acute ischemic stroke admitted to the Stroke Ward of the Affiliated Hospital of Beihua University from November 2021 to October 2023, were collected. The two indexes were calculated by combining TyG and obesity indices: TyG-body mass index (TyG-BMI) and TyG-waist circumference (TyG-WC). The National Institute of Health Stroke Scale (NIHSS) was used to assess and group patients with neurological deficits within 24 hours of admission: mild stroke (NIHSS ≤5) and moderate-severe stroke (NIHSS >5). Short-term prognosis was evaluated using the modified Rankin Scale (mRS) at discharge or 14 days after onset of the disease and grouped: good outcome (mRS ≤2) and poor outcome (mRS >2). According to the quartiles of TyG-BMI and TyG-WC, the patients were placed into four groups: Q1, Q2, Q3 and Q4. Multi-factor logistic regression analysis was utilized to evaluate the correlation of TyG-BMI and TyG-WC with the severity and short-term outcome.

Results

The study included 456 patients. After adjusting for multiple variables, the results showed that compared with the quartile 1, patients in quartile 4 of TyG-BMI had a reduced risk of moderate-severe stroke [Q4: OR: 0.407, 95%CI (0.185-0.894), P = 0.025]; Patients in quartiles 2, 3 and 4 of TyG-BMI had sequentially lower risk of short-term adverse outcomes [Q2: OR: 0.394, 95%CI (0.215-0.722), P = 0.003; Q3: OR: 0.324, 95%CI (0.163-0.642), P = 0.001; Q4: OR: 0.158, 95%CI (0.027-0.349), P <0.001]; Patients in quartiles 3 and 4 of TyG-WC had sequentially lower risk of moderate-severe stroke [Q3: OR: 0.355, 95%CI (0.173-0.728), P = 0.005; Q4: OR: 0.140, 95%CI (0.056-0.351), P <0.001]; Patients in quartiles 3 and 4 of TyG-WC had sequentially lower risk of short-term adverse outcomes [Q3: OR: 0.350, 95%CI (0.175-0.700), P = 0.003; Q4: OR: 0.178, 95%CI (0.071-0.451), P <0.001].

Conclusions

TyG-WC and TyG-BMI were correlated with the severity and short-term outcome of new-onset acute ischemic stroke. As TyG-WC and TyG-BMI increased, stroke severity decreased and short-term outcome was better.

Hyphal Als proteins act as CR3 ligands to promote immune responses against Candida albicans

Patients with decreased levels of CD18 (β2 integrins) suffer from life-threatening bacterial and fungal infections. CD11b, the α subunit of integrin CR3 (CD11b/CD18, αMβ2), is essential for mice to fight against systemic Candida albicans infections. Live elongating C. albicans activates CR3 in immune cells. However, the hyphal ligands that activate CR3 are not well defined. Here, we discovered that the C. albicans Als family proteins are recognized by the I domain of CD11b in macrophages. This recognition synergizes with the β-glucan-bound lectin-like domain to activate CR3, thereby promoting Syk signaling and inflammasome activation. Dectin-2 activation serves as the "outside-in signaling" for CR3 activation at the entry site of incompletely sealed phagosomes, where a thick cuff of F-actin forms to strengthen the local interaction. In vitro, CD18 partially contributes to IL-1β release from dendritic cells induced by purified hyphal Als3. In vivo, Als3 is vital for C. albicans clearance in mouse kidneys. These findings uncover a novel family of ligands for the CR3 I domain that promotes fungal clearance.

Quantitative Assessment of Fungal Biomarkers in Clinical Samples via an Interface-Modulated Optical Fiber Biosensor

Invasive fungal infections pose a significant public health threat. The lack of precise and timely diagnosis is a primary factor contributing to the significant increase in patient mortality rates. Here, an interface-modulated biosensor utilizing an optical fiber for quantitative analysis of fungal biomarkers at the early stage of point-of-care testing (POCT), is reported. By integrating surface refractive index (RI) modulation and plasmon enhancement, the sensor to achieve high sensitivity in a directional response to the target analytes, is successfully optimized. As a result, a compact fiber-optic sensor with rapid response time, cost-effectiveness, exceptional sensitivity, stability, and specificity, is developed. This sensor can successfully identify the biomarkers of specific pathogens from blood or other tissue specimens in animal models. It quantifies clinical blood samples with precision and effectively discriminates between negative and positive cases, thereby providing timely alerts to potential patients. It significantly reduces the detection time of fungal infection to only 30 min. Additionally, this approach exhibits remarkable stability and achieves a limit of detection (LOD) three orders of magnitude lower than existing methods. It overcomes the limitations of existing detection methods, including a high rate of misdiagnosis, prolonged detection time, elevated costs, and the requirement for stringent laboratory conditions.

Candida albicans increases the aerobic glycolysis and activates MAPK-dependent inflammatory response of liver sinusoidal endothelial cells

The liver, and more specifically, the liver sinusoidal endothelial cells, constitute the beginning of one of the most important responses for the elimination of hematogenously disseminated Candida albicans. Therefore, we aimed to study the mechanisms involved in the interaction between these cells and C. albicans. Transcriptomics-based analysis showed an increase in the expression of genes related to the immune response (including receptors, cytokines, and adhesion molecules), as well as to aerobic glycolysis. Further in vitro analyses showed that IL-6 production in response to C. albicans is controlled by MyD88- and SYK-pathways, suggesting an involvement of Toll-like and C-type lectin receptors and the subsequent activation of the MAP-kinases and c-Fos/AP-1 transcription factor. In addition, liver sinusoidal endothelial cells undergo metabolic reprogramming towards aerobic glycolysis induced by C. albicans, as confirmed by the increased Extracellular Acidification Rate and the overexpression of enolase (Eno2), hexonikase (Hk2) and glucose transporter 1 (Slc2a1). In conclusion, these results indicate that the hepatic endothelium responds to C. albicans by increasing aerobic glycolysis and promoting an inflammatory environment.

The C-terminal protein interaction domain of the chromatin reader Yaf9 is critical for pathogenesis of Candida albicans

Fungal infections cause a large health burden but are treated by only a handful of antifungal drug classes. Chromatin factors have emerged as possible targets for new antifungals. These targets include the reader proteins, which interact with posttranslationally modified histones to influence DNA transcription and repair. The YEATS domain is one such reader recognizing both crotonylated and acetylated histones. Here, we performed a detailed structure/function analysis of the Candida albicans YEATS domain reader Yaf9, a subunit of the NuA4 histone acetyltransferase and the SWR1 chromatin remodeling complex. We have previously demonstrated that the homozygous deletion mutant yaf9Δ/Δ displays growth defects and is avirulent in mice. Here we show that a YEATS domain mutant expected to inactivate Yaf9's chromatin binding does not display strong phenotypes in vitro, nor during infection of immune cells or in a mouse systemic infection model, with only a minor virulence reduction in vivo. In contrast to the YEATS domain mutation, deletion of the C-terminal domain of Yaf9, a protein-protein interaction module necessary for its interactions with SWR1 and NuA4, phenocopies the null mutant. This shows that the C-terminal domain is essential for Yaf9 roles in vitro and in vivo, including C. albicans virulence. Our study informs on the strategies for therapeutic targeting of Yaf9, showing that approaches taken for the mammalian YEATS domains by disrupting their chromatin binding might not be effective in C. albicans, and provides a foundation for studying YEATS proteins in human fungal pathogens.IMPORTANCEThe scarcity of available antifungal drugs and rising resistance demand the development of therapies with new modes of action. In this context, chromatin regulation may be a target for novel antifungal therapeutics. To realize this potential, we must better understand the roles of chromatin regulators in fungal pathogens. Toward this goal, here, we studied the YEATS domain chromatin reader Yaf9 in Candida albicans. Yaf9 uses the YEATS domain for chromatin binding and a C-terminal domain to interact with chromatin remodeling complexes. By constructing mutants in these domains and characterizing their phenotypes, our data indicate that the Yaf9 YEATS domain might not be a suitable therapeutic drug target. Instead, the Yaf9 C-terminal domain is critical for C. albicans virulence. Collectively, our study informs how a class of chromatin regulators performs their cellular and pathogenesis roles in C. albicans and reveals strategies to inhibit them.

"We've got to get out"-Strategies of human pathogenic fungi to escape from phagocytes

Human fungal pathogens are a deadly and underappreciated risk to global health that most severely affect immunocompromised individuals. A virulence attribute shared by some of the most clinically relevant fungal species is their ability to survive inside macrophages and escape from these immune cells. In this review, we discuss the mechanisms behind intracellular survival and elaborate how escape is mediated by lytic and non-lytic pathways as well as strategies to induce programmed host cell death. We also discuss persistence as an alternative to rapid host cell exit. In the end, we address the consequences of fungal escape for the host immune response and provide future perspectives for research and development of targeted therapies.

PFKFB3-Meditated Glycolysis via the Reactive Oxygen Species-Hypoxic Inducible Factor 1α Axis Contributes to Inflammation and Proliferation of Staphylococcus aureus in Epithelial Cells

Mastitis caused by antibiotic-resistant strains of Staphylococcus aureus is a significant concern in the livestock industry due to the economic losses it incurs. Regulating immunometabolism has emerged as a promising approach for preventing bacterial inflammation. To investigate the possibility of alleviating inflammation caused by S aureus infection by regulating host glycolysis, we subjected the murine mammary epithelial cell line (EpH4-Ev) to S aureus challenge. Our study revealed that S aureus can colonize EpH4-Ev cells and promote inflammation through hypoxic inducible factor 1α (HIF1α)-driven glycolysis. Notably, the activation of HIF1α was found to be dependent on the production of reactive oxygen species (ROS). By inhibiting PFKFB3, a key regulator in the host glycolytic pathway, we successfully modulated HIF1α-triggered metabolic reprogramming by reducing ROS production in S aureus-induced mastitis. Our findings suggest that there is a high potential for the development of novel anti-inflammatory therapies that safely inhibit the glycolytic rate-limiting enzyme PFKFB3.

Macrophage pyroptosis induced by Candida albicans

Candida albicans (C. albicans) is a prevalent opportunistic pathogen that causes mucocutaneous and systemic infections, particularly in immunocompromised individuals. Macrophages play a crucial role in eliminating C. albicans in local and bloodstream contexts, while also regulating antifungal immune responses. However, C. albicans can induce macrophage lysis through pyroptosis, a type of regulated cell death. This process can enable C. albicans to escape from immune cells and trigger the release of IL-1β and IL-18, which can impact both the host and the pathogen. Nevertheless, the mechanisms by which C. albicans triggers pyroptosis in macrophages and the key factors involved in this process remain unclear. In this review, we will explore various factors that may influence or trigger pyroptosis in macrophages induced by C. albicans, such as hypha, ergosterol, cell wall remodeling, and other virulence factors. We will also examine the possible immune response following macrophage pyroptosis.

Immunometabolism in the pathogenesis of asthma

Bronchial asthma is a heterogeneous disease characterised by chronic airway inflammation. A variety of immune cells such as eosinophils, mast cells, T lymphocytes, neutrophils and airway epithelial cells are involved in the airway inflammation and airway hyperresponsiveness in asthma pathogenesis, resulting in extensive and variable reversible expiratory airflow limitation. However, the precise molecular mechanisms underlying the allergic immune responses, particularly immunometabolism, remains unclear. Studies have detected enhanced oxidative stress, and abnormal metabolic progresses of glycolysis, fatty acid and amino acid in various immune cells, inducing dysregulation of innate and adaptive immune responses in asthma pathogenesis. Immunometabolism mechanisms contain multiple signalling pathways, providing novel therapy targets for asthma. This review summarises the current knowledge on immunometabolism reprogramming in asthma pathogenesis, as well as potential therapy strategies.

Gut microbiota regulates host melatonin production through epithelial cell MyD88

Melatonin has various physiological effects, such as the maintenance of circadian rhythms, anti-inflammatory functions, and regulation of intestinal barriers. The regulatory functions of melatonin in gut microbiota remodeling have also been well clarified; however, the role of gut microbiota in regulating host melatonin production remains poorly understood. To address this, we studied the contribution of gut microbiota to host melatonin production using gut microbiota-perturbed models. We demonstrated that antibiotic-treated and germ-free mice possessed diminished melatonin levels in the serum and elevated melatonin levels in the colon. The influence of the intestinal microbiota on host melatonin production was further confirmed by fecal microbiota transplantation. Notably, Lactobacillus reuteri (L. R) and Escherichia coli (E. coli) recapitulated the effects of gut microbiota on host melatonin production. Mechanistically, L. R and E. coli activated the TLR2/4/MyD88/NF-κB signaling pathway to promote expression of arylalkylamine N-acetyltransferase (AANAT, a rate-limiting enzyme for melatonin production), and MyD88 deficiency in colonic epithelial cells abolished the influence of intestinal microbiota on colonic melatonin production. Collectively, we revealed a specific underlying mechanism of gut microbiota to modulate host melatonin production, which might provide novel therapeutic ideas for melatonin-related diseases.

The short-chain fatty acid crotonate reduces invasive growth and immune escape of Candida albicans by regulating hyphal gene expression

IMPORTANCE

Macrophages curtail the proliferation of the pathogen Candida albicans within human body niches. Within macrophages, C. albicans adapts its metabolism and switches to invasive hyphal morphology. These adaptations enable fungal growth and immune escape by triggering macrophage lysis. Transcriptional programs regulate these metabolic and morphogenetic adaptations. Here we studied the roles of chromatin in these processes and implicate lysine crotonylation, a histone mark regulated by metabolism, in hyphal morphogenesis and macrophage interactions by C. albicans. We show that the short-chain fatty acid crotonate increases histone crotonylation, reduces hyphal formation within macrophages, and slows macrophage lysis and immune escape of C. albicans. Crotonate represses hyphal gene expression, and we propose that C. albicans uses diverse acylation marks to regulate its cell morphology in host environments. Hyphal formation is a virulence property of C. albicans. Therefore, a further importance of our study stems from identifying crotonate as a hyphal inhibitor.

Respiration supports intraphagosomal filamentation and escape of Candida albicans from macrophages

IMPORTANCE

Candida albicans is a leading human fungal pathogen that often causes life-threatening infections in immunocompromised individuals. The ability of C. albicans to transition between yeast and filamentous forms is key to its virulence, and this occurs in response to many host-relevant cues, including engulfment by host macrophages. While previous efforts identified C. albicans genes required for filamentation in other conditions, the genes important for this morphological transition upon internalization by macrophages remained largely enigmatic. Here, we employed a functional genomic approach to identify genes that enable C. albicans filamentation within macrophages and uncovered a role for the mitochondrial ribosome, respiration, and the SNF1 AMP-activated kinase complex. Additionally, we showed that glucose uptake and glycolysis by macrophages support C. albicans filamentation. This work provides insights into the metabolic dueling that occurs during the interaction of C. albicans with macrophages and identifies vulnerabilities in C. albicans that could serve as promising therapeutic targets.

Quantitative live-cell imaging of Candida albicans escape from immune phagocytes

Population-level dynamics of host-pathogen interactions can be characterized using quantitative live-cell imaging. Here, we present a protocol for infecting macrophages with the fungal pathogen Candida albicans in vitro and quantitative live-cell imaging of immune and pathogen responses. We describe steps for detailed image analysis and provide resources for quantification of phagocytosis and pathogen escape, as well as macrophage membrane permeabilization and viability. This protocol is modifiable for applications with a range of pathogens, immune cell types, and host-pathogen mechanisms. For complete details on the use and execution of this protocol, please refer to Olivier et al.1.

The F1Fo-ATP synthase α subunit of Candida albicans induces inflammatory responses by controlling amino acid catabolism

Sepsis is a leading cause of fatality in invasive candidiasis. The magnitude of the inflammatory response is a determinant of sepsis outcomes, and inflammatory cytokine imbalances are central to the pathophysiological processes. We previously demonstrated that a Candida albicans F1Fo-ATP synthase α subunit deletion mutant was nonlethal to mice. Here, the potential effects of the F1Fo-ATP synthase α subunit on host inflammatory responses and the mechanism were studied. Compared with wild-type strain, the F1Fo-ATP synthase α subunit deletion mutant failed to induce inflammatory responses in Galleria mellonella and murine systemic candidiasis models and significantly decreased the mRNA levels of the proinflammatory cytokines IL-1β, IL-6 and increased those of the anti-inflammatory cytokine IL-4 in the kidney. During C. albicans-macrophage co-culture, the F1Fo-ATP synthase α subunit deletion mutant was trapped inside macrophages in yeast form, and its filamentation, a key factor in inducing inflammatory responses, was inhibited. In the macrophage-mimicking microenvironment, the F1Fo-ATP synthase α subunit deletion mutant blocked the cAMP/PKA pathway, the core filamentation-regulating pathway, because it failed to alkalinize environment by catabolizing amino acids, an important alternative carbon source inside macrophages. The mutant downregulated Put1 and Put2, two essential amino acid catabolic enzymes, possibly due to severely impaired oxidative phosphorylation. Our findings reveal that the C. albicans F1Fo-ATP synthase α subunit induces host inflammatory responses by controlling its own amino acid catabolism and it is significant to find drugs that inhibit F1Fo-ATP synthase α subunit activity to control the induction of host inflammatory responses.

Proteomic analysis reveals changes in the proteome of human THP-1 macrophages infected with Paracoccidioides brasiliensis

Paracoccidioides spp. is the etiologic agent of Paracoccidioidomycosis (PCM), a systemic disease with wide distribution in Latin America. Macrophages are very important cells during the response to infection by P. brasiliensis. In this study, we performed a proteomic analysis to evaluate the consequences of P. brasiliensis yeast cells on the human THP-1 macrophage proteome. We have identified 443 and 2247 upregulated or downregulated proteins, respectively, in macrophages co-cultured with yeast cells of P. brasiliensis in comparison to control macrophages unexposed to the fungus. Proteomic analysis revealed that interaction with P. brasiliensis caused metabolic changes in macrophages that drastically affected energy production pathways. In addition, these macrophages presented regulated many factors related to epigenetic modifications and gene transcription as well as a decrease of many proteins associated to the immune system activity. This is the first human macrophage proteome derived from interactions with P. brasiliensis, which contributes to elucidating the changes that occur during the host response to this fungus. Furthermore, it highlights proteins that may be targets for the development of new therapeutic approaches to PCM.

Leveraging the MMV Pathogen Box to Engineer an Antifungal Compound with Improved Efficacy and Selectivity against Candida auris

Fungal infections pose a significant and increasing threat to human health, but the current arsenal of antifungal drugs is inadequate. We screened the Medicines for Malaria Venture (MMV) Pathogen Box for new antifungal agents against three of the most critical Candida species (Candida albicans, Candida auris, and Candida glabrata). Of the 14 identified hit compounds, most were active against C. albicans and C. auris. We selected the pyrazolo-pyrimidine MMV022478 for chemical modifications to build structure-activity relationships and study their antifungal properties. Two analogues, 7a and 8g, with distinct fluorine substitutions, greatly improved the efficacy against C. auris and inhibited fungal replication inside immune cells. Additionally, analogue 7a had improved selectivity toward fungal killing compared to mammalian cytotoxicity. Evolution experiments generating MMV022478-resistant isolates revealed a change in morphology from oblong to round cells. Most notably, the resistant isolates blocked the uptake of the fluorescent dye rhodamine 6G and showed reduced susceptibility toward fluconazole, indicative of structural changes in the yeast cell surface. In summary, our study identified a promising antifungal compound with activity against high-priority fungal pathogens. Additionally, we demonstrated how structure-activity relationship studies of known and publicly available compounds can expand the repertoire of molecules with antifungal efficacy and reduced cytotoxicity to drive the development of novel therapeutics.

The effect of Staphylococcus aureus on innate and adaptive immunity and potential immunotherapy for S. aureus-induced osteomyelitis

Osteomyelitis is a chronic inflammatory bone disease caused by infection of open fractures or post-operative implants. Particularly in patients with open fractures, the risk of osteomyelitis is greatly increased as the soft tissue damage and bacterial infection are often more severe. Staphylococcus aureus, one of the most common pathogens of osteomyelitis, disrupts the immune response through multiple mechanisms, such as biofilm formation, virulence factor secretion, and metabolic pattern alteration, which attenuates the effectiveness of antibiotics and surgical debridement toward osteomyelitis. In osteomyelitis, immune cells such as neutrophils, macrophages and T cells are activated in response to pathogenic bacteria invasion with excessive inflammatory factor secretion, immune checkpoint overexpression, and downregulation of immune pathway transcription factors, which enhances osteoclastogenesis and results in bone destruction. Therefore, the study of the mechanisms of abnormal immunity will be a new breakthrough in the treatment of osteomyelitis.

Metabolic and oxidative stress response of sea cucumber Apostichopus japonicus exposed to acute high concentration of bisphenol AF

Bisphenols are known as endocrine disruptor that affect the development, and growth of marine creatures, including human. There were plenty of manuscripts evaluated the toxicology of bisphenol A (BPA) and its analogues such as bisphenol F (BPF), bisphenol AF (BPAF), and bisphenol S (BPS), but limits of them studied the effects of bisphenol analogues on echinoderms. In this study, we used metabolomics to investigate the metabolic response of sea cucumber (Apostichopus japonicus) exposed to BPAF, and the activities of glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) were determined. The results demonstrated alterations in lipid metabolism, glycerophospholipid metabolism, and biosynthesis of amino acids following BPAF treatment. Sea cucumbers upregulated the glycerophospholipid metabolism to repair the destruction of intestine cellular homeostasis. Six metabolites were selected as the potential biomarkers for the exposure of BPAF. This study revealed the metabolic response and oxidative response of sea cucumber arising from BPAF exposure, and provided theoretical support for the risk assessment of bisphenol analogues on economically important echinoderms, such as A. japonicus.

Dehydrocostus lactone inhibits Candida albicans growth and biofilm formation

Candida albicans infections are threatening public health but there are only several antifungal drugs available. This study was to assess the effects of dehydrocostus lactone (DL) on the Candida albicans growth and biofilms Microdilution assays revealed that DL inhibits a panel of standard Candida species, including C. albicans, as well as 9 C. albicans clinical isolates. The morphological transition of C. albicans in RPMI-1640 medium and the adhesion to polystyrene surfaces can also be decreased by DL treatment, as evidenced by microscopic, metabolic activity and colony forming unit (CFU) counting assays. The XTT assay and microscopy inspection demonstrated that DL can inhibit the biofilms of C. albicans. Confocal microscopy following propidium iodide (PI) staining and DCFH-DA staining after DL treatment revealed that DL can increase the membrane permeability and intracellular reactive oxygen species (ROS) production. N-acetyl-cysteine could mitigate the inhibitory effects of DL on growth, morphological transition and biofilm formation, further confirming that ROS production induced by DL contributes to its antifungal and antibiofilm effects. This study showed that DL demonstrated antifungal and antibiofilm activity against C. albicans. The antifungal mechanisms may involve membrane damage and ROS overproduction. This study shows the potential of DL to fight Candida infections.

Candida auris uses metabolic strategies to escape and kill macrophages while avoiding robust activation of the NLRP3 inflammasome response

Metabolic adaptations regulate the response of macrophages to infection. The contributions of metabolism to macrophage interactions with the emerging fungal pathogen Candida auris are poorly understood. Here, we show that C. auris-infected macrophages undergo immunometabolic reprogramming and increase glycolysis but fail to activate a strong interleukin (IL)-1β cytokine response or curb C. auris growth. Further analysis shows that C. auris relies on its own metabolic capacity to escape from macrophages and proliferate in vivo. Furthermore, C. auris kills macrophages by triggering host metabolic stress through glucose starvation. However, despite causing macrophage cell death, C. auris does not trigger robust activation of the NLRP3 inflammasome. Consequently, inflammasome-dependent responses remain low throughout infection. Collectively, our findings show that C. auris uses metabolic regulation to eliminate macrophages while remaining immunologically silent to ensure its own survival. Thus, our data suggest that host and pathogen metabolism could represent therapeutic targets for C. auris infections.

"Under Pressure" - How fungi evade, exploit, and modulate cells of the innate immune system

The human immune system uses an arsenal of effector mechanisms to prevent and counteract infections. Yet, some fungal species are extremely successful as human pathogens, which can be attributed to a wide variety of strategies by which these fungi evade, exploit, and modulate the immune system. These fungal pathogens normally are either harmless commensals or environmental fungi. In this review we discuss how commensalism, but also life in an environmental niche without human contact, can drive the evolution of diverse and specialized immune evasion mechanisms. Correspondingly, we discuss the mechanisms contributing to the ability of these fungi to cause superficial to life-threatening infections.

The adaptive response to alternative carbon sources in the pathogen Candida albicans involves a remodeling of thiol- and glutathione-dependent redox status

Candida albicans is an opportunist pathogen responsible for a large spectrum of infections, from superficial mycosis to systemic diseases known as candidiasis. During infection in vivo, Candida albicans must adapt to host microenvironments and this adaptive response is crucial for the survival of this organism, as it facilitates the effective assimilation of alternative carbon sources others than glucose. We performed a global proteomic analysis on the global changes in protein abundance in response to changes in micronutrient levels, and, in parallel, explored changes in the intracellular redox and metabolic status of the cells. We show here that each of the carbon sources considered - glucose, acetate and lactate - induces a unique pattern of response in C. albicans cells, and that some conditions trigger an original and specific adaptive response involving the adaptation of metabolic pathways, but also a complete remodeling of thiol-dependent antioxidant defenses. Protein S-thiolation and the overproduction of reduced glutathione are two components of the response to high glucose concentration. In the presence of acetate, glutathione-dependent oxidative stress occurs, reduced thiol groups bind to proteins, and glutathione is exported out of the cells, these changes probably being triggered by an increase in glutathione-S-transferases. Overall, our results suggest that the role of cellular redox status regulation and defenses against oxidative stress, including the thiol- and glutathione-dependent response, in the adaptive response of C. albicans to alternative carbon sources should be reconsidered.

Glutamine Metabolism Supports the Functional Activity of Immune Cells against Aspergillus fumigatus

The reprogramming of cellular metabolism of immune cells is an essential process in the regulation of antifungal immune responses. In particular, glucose metabolism has been shown to be required for protective immunity against infection with Aspergillus fumigatus. However, given the intricate cross talk between multiple metabolic networks and signals, it is likely that cellular metabolic pathways other than glycolysis are also relevant during fungal infection. In this study, we demonstrate that glutamine metabolism is required for the activation of macrophage effector functions against A. fumigatus. Glutamine metabolism was found to be upregulated early after fungal infection and glutamine depletion or the pharmacological inhibition of enzymes involved in its metabolism impaired phagocytosis and the production of both proinflammatory and T-cell-derived cytokines. In an in vivo model, inhibition of glutaminase increased susceptibility to experimental aspergillosis, as revealed by the increased fungal burden and inflammatory pathology, and the defective cytokine production in the lungs. Moreover, genetic variants in glutamine metabolism genes were found to regulate cytokine production in response to A. fumigatus stimulation. Taken together, our results demonstrate that glutamine metabolism represents an important component of the immunometabolic response of macrophages against A. fumigatus both in vitro and in vivo. IMPORTANCE The fungal pathogen Aspergillus fumigatus can cause severe and life-threatening forms of infection in immunocompromised patients. The reprogramming of cellular metabolism is essential for innate immune cells to mount effective antifungal responses. In this study, we report the pivotal contribution of glutaminolysis to the host defense against A. fumigatus. Glutamine metabolism was essential both in vitro as well as in in vivo models of infection, and genetic variants in human glutamine metabolism genes regulated cytokine production in response to fungal stimulation. This work highlights the relevance of glutaminolysis to the pathogenesis of aspergillosis and supports a role for interindividual genetic variation influencing glutamine metabolism in susceptibility to infection.

Aeromonas hydrophila induction method in adult zebrafish (Danio rerio) as animal infection models

Background and Aim: Zebrafish are frequently used as model organisms in scientific research as their genes mirror those of humans. Aeromonas hydrophila bacteria can infect humans and animals, mainly fish. This study aimed to identify the concentration and route of A. hydrophila infection in adult zebrafish. Zebrafish had been used as a challenge test by analyzing their hematological profiles, blood glucose levels, and survival rates. Materials and Methods: Induction of cell supernatant free (CSF) from A. hydrophila bacteria in adult zebrafish was carried out via bath immersion (BI), intraperitoneal injection (IPI), intramuscular injection (IMI), and healthy zebrafish as a control (C). The bacterial concentrations were 107, 109, and 1011 colony-forming units (CFU)/mL. At 24 h post-infection, the outcomes of infection were evaluated based on survival rates, hematological profiles, and blood glucose levels. A one-way analysis of variance with a confidence level of 95% was employed to examine the data. Results: In the BI, IPI, and IMI treatment groups, the survival rate of the fish reached a peak of 100%, 22%–100%, and 16%–63%, respectively, compared with the injection technique. In the IMI2 group, a 109 CFU/mL bacterial concentration was determined to correspond to the lethal dosage 50. All infection groups had lower erythrocyte and hemoglobin counts but higher leukocyte counts than the control group. The blood sugar levels of the healthy and infected groups were not significantly different. Conclusion: The route of A. hydrophila infection through Intramuscular injection with a concentration of 109 CFU/mL indicated a high performance compared to other techniques. This method could be developed as a reproducible challenge test.