Dimethyl itaconate protects against fungal keratitis by activating the Nrf2/HO-1 signaling pathway

Multifunctional natamycin modified chondroitin sulfate eye drops with anti-inflammatory, antifungal and tissue repair functions possess therapeutic effects on fungal keratitis in mice

Fungal keratitis (FK) is recognized as a stubborn ocular condition, caused by intense fungal invasiveness and heightened immune reaction. The glycosaminoglycan chondroitin sulfate exhibits properties of immunomodulation and tissue regeneration. In prior investigations, oxidized chondroitin sulfate (OCS) ameliorated the prognosis of FK in murine models. To further improve the curative efficacy, we used the antifungal drug natamycin to functionalize OCS and prepared oxidized chondroitin sulfate-natamycin (ON) eye drops. The structure of ON was characterized by FTIR, UV-vis, and XPS, revealing that the amino group of natamycin combined with the aldehyde group in OCS through Schiff base reaction. Antifungal experiments revealed that ON inhibited fungal growth and disrupted the mycelium structure. ON exhibited exceptional biocompatibility and promoted the proliferation of corneal epithelial cells. Pharmacokinetic analysis indicated that ON enhanced drug utilization by extending the mean residence time in tears. In murine FK, ON treatment reduced the clinical score and corneal fungal load, restored corneal stroma conformation, and facilitated epithelial repair. ON effectively inhibited neutrophil infiltration and decreased the expression of TLR-4, LOX-1, IL-1β, and TNF-α. Our research demonstrated that ON eye drops achieved multifunctional treatment for FK, including inhibiting fungal growth, promoting corneal repair, enhancing drug bioavailability, and controlling inflammatory reactions.

Licochalcone A Ameliorates Aspergillus fumigatus Keratitis by Reducing Fungal Load and Activating the Nrf2/HO-1 Signaling Pathway

Fungal keratitis (FK) is a blinding corneal infectious disease. The prognosis is frequently unfavorable due to fungal invasion and an excessive host inflammatory response. Licochalcone A (Lico A) exhibits a broad spectrum of pharmacological activities, encompassing antifungal, anti-inflammatory, antioxidation, and antitumor properties. However, the role of Lico A has not yet been studied in FK. In this study, we discovered that Lico A could disrupt Aspergillus fumigatus (A. fumigatus) biofilms, inhibit fungal growth and adhesion to host cells, induce alterations of hyphal morphology, and impair the cell membrane and cell wall integrity and mitochondrial structure of A. fumigatus. Lico A can alleviate the severity of FK in mice, reduce neutrophil infiltration and fungal load, and significantly decrease the pro-inflammatory cytokines in mouse corneas infected with A. fumigatus. In vitro, we also demonstrated that Lico A increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) around the nucleus in human corneal epithelial cells (HCECs) stimulated with A. fumigatus. We verified that the anti-inflammatory effect of Lico A is associated with the activation of the Nrf2/HO-1 axis. These results indicated that Lico A could provide a protective role in A. fumigatus keratitis through its anti-inflammatory and antifungal activities.

The role and therapeutic potential of itaconate in lung disease

Lung diseases triggered by endogenous or exogenous factors have become a major concern, with high morbidity and mortality rates, especially after the coronavirus disease 2019 (COVID-19) pandemic. Inflammation and an over-activated immune system can lead to a cytokine cascade, resulting in lung dysfunction and injury. Itaconate, a metabolite produced by macrophages, has been reported as an effective anti-inflammatory and anti-oxidative stress agent with significant potential in regulating immunometabolism. As a naturally occurring metabolite in immune cells, itaconate has been identified as a potential therapeutic target in lung diseases through its role in regulating inflammation and immunometabolism. This review focuses on the origin, regulation, and function of itaconate in lung diseases, and briefly discusses its therapeutic potential.

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.

Progranulin Protects against Aspergillus fumigatus Keratitis by Attenuating the Inflammatory Response through Enhancing Autophagy

Fungal keratitis (FK) is a severe corneal condition caused by pathogenic fungi and is associated with the virulence of fungi and an excessive tissue inflammatory response. Progranulin (PGRN), functioning as a multifunctional growth factor, exerts a pivotal influence on the regulation of inflammation and autophagy. The aim of our research was to analyze the role of PGRN in Aspergillus fumigatus (A. fumigatus) keratitis. We found that PGRN expression was increased in the mouse cornea with A. fumigatus keratitis. In our experiments, corneas of mice with FK were treated with 100 ng/mL of PGRN. In vitro, RAW 264.7 cells were treated with 10 ng/mL of PGRN before A. fumigatus stimulation. The findings suggested that PGRN effectively alleviated corneal edema and decreased the expression of pro-inflammatory cytokines in mice. In stimulated RAW 264.7 cells, PGRN treatment suppressed the expression of pro-inflammatory cytokines IL-6 and TNF-α but promoted the expression of the anti-inflammatory cytokines IL-10. PGRN treatment significantly upregulated the expression of autophagy-related proteins LC3, Beclin-1, and Atg-7. 3-Methyladenine (3-MA, autophagy inhibitor) reversed the regulation of inflammatory cytokines by PGRN. In addition, our study demonstrated that PGRN also enhanced phagocytosis in RAW 264.7 cells. In summary, PGRN attenuated the inflammatory response of A. fumigatus keratitis by increasing autophagy and enhanced the phagocytic activity of RAW 264.7 cells. This showed that PGRN had a protective effect on A. fumigatus keratitis.

Rosmarinic acid alleviates fungal keratitis caused by Aspergillus fumigatus by inducing macrophage autophagy

Fungal keratitis (FK) is an infectious keratopathy can cause serious damage to vision. Its severity is related to the virulence of fungus and response of inflammatory. Rosmarinic acid (RA) extracted from Rosmarinus officinalis exhibits antioxidant, anti-inflammatory and anti-viral properties. The aim of this study was to investigate the effect of RA on macrophage autophagy and its therapeutic effect on FK. In this study, we demonstrated that RA reduced expression of proinflammatory cytokine, lessened the recruitment of inflammatory cells in FK. The relative contents of autophagy markers, such as LC3 and Beclin-1, were significantly up-regulated in RAW 264.7 cells and FK. In addition, RA restored mitochondrial membrane potential (MMP) of macrophage to normal level. RA not only reduced the production of intracellular reactive oxygen species (ROS) but also mitochondria ROS (mtROS) in macrophage. At the same time, RA induced macrophage to M2 phenotype and down-regulated the mRNA expression of IL-6, IL-1β, TNF-α. All the above effects could be offset by the autophagy inhibitor 3-Methyladenine (3-MA). Besides, RA promote phagocytosis of RAW 264.7 cells and inhibits spore germination, biofilm formation and conidial adherence, suggesting a potential therapeutic role for RA in FK.

Mesoporous zinc oxide-based drug delivery system offers an antifungal and immunoregulatory strategy for treating keratitis

Fungal keratitis is a refractory eye disease that is prone to causing blindness. Fungal virulence and inflammatory responses are two major factors that accelerate the course of fungal keratitis. However, the current antifungal drugs used for treatment usually possess transient residence time on the ocular surface and low bioavailability deficiencies, which limit their therapeutic efficacy. In this work, natamycin (NATA)-loaded mesoporous zinc oxide (Meso-ZnO) was synthesized for treating Aspergillus fumigatus keratitis with excellent drug-loading and sustained drug release capacities. In addition to being a carrier for drug delivery, Meso-ZnO could restrict fungal growth in a concentration-dependent manner, and the transcriptome analysis of fungal hyphae indicated that it inhibited the mycotoxin biosynthesis, oxidoreductase activity and fungal cell wall formation. Meso-ZnO also promoted cell migration and exhibited anti-inflammatory role during fungal infection by promoting the activation of autophagy. In mouse models of fungal keratitis, Meso-ZnO/NATA greatly reduced corneal fungal survival, alleviated tissue inflammatory damage, and reduced neutrophils accumulation and cytokines expression. This study suggests that Meso-ZnO/NATA can be a novel and effective treatment strategy for fungal keratitis.

Oxymatrine mitigates Aspergillus fumigatus keratitis by suppressing fungal activity and restricting pyroptosis

Fungal keratitis (FK) is a refractory keratitis caused by excessive inflammation and fungal damage. Excessive inflammation can lead to tissue damage and corneal opacity, resulting in a poor prognosis for FK. Oxymatrine (OMT) is a natural alkaloid, which has rich pharmacological effects, such as antioxidant and anti-inflammation. However, its antifungal activity and the mechanism of action in FK have not been elucidated. This study confirmed that OMT suppressed Aspergillus fumigatus growth, biofilm formation, the integrity of fungal cell and conidial adherence. OMT not only effectively reduced corneal fungal load but also inflammation responses. OMT lessened the recruitment of neutrophils and macrophages in FK. In addition, OMT up-regulated the expression of Nrf2 and down-regulated the expression of IL-18, IL-1β, caspase-1, NLRP3 and GSDMD. Pre-treatment with Nrf2 inhibitor up-regulated the expression of IL-1β, IL-18, caspase-1, NLRP3 and GSDMD supressed by OMT. In conclusion, OMT has efficient anti-inflammatory and antifungal effects by suppressing fungal activity and restricting pyroptosis via Nrf2 pathway. OMT is considered as a potential option for the treatment of FK.

Aspergillus fumigatus-Derived Extracellular Vesicles Mitigate Fungal Keratitis by Modulating the Immune Cell Function

Fungal keratitis (FK) is a refractory global disease characterized by a high incidence of blindness and a lack of effective therapeutic options, and Aspergillus fumigatus (A. fumigatus, AF) is one of the most common causative fungi. This study aimed to investigate the role of extracellular vesicles (EVs) from A. fumigatus in the immune cell function and their protective role in A. fumigatus keratitis in order to explore their therapeutic potential. First, we isolated and characterized the EVs (AF-derived EVs). In vitro, we stimulated RAW264.7 cells and polymorphonuclear cells with AF-derived EVs. The expression levels of inflammatory factors increased in both immune cells along with an M1 polarization variation of RAW264.7 cells. After being incubated with AF-derived EVs, both immune cells exhibited an increased conidia-phagocytic index and a decreased conidia survival rate. In vivo, we injected EVs subconjunctivally on mice resulting in a heightened production of secretory immunoglobulin A (sIgA) in tear fluid. By the injection of EVs on mice in advance, a significant reduction in severity of A. fumigatus FK was witnessed by lower clinical scores, inflammatory appearances, and mitigated fungal load. Collectively, these results positioned AF-derived EVs as a promising and innovative immune therapy for combating FK, while also providing a platform for further investigation into developing an optimal formulation for modulating inflammation in the context of FK.

Thymoquinone attenuates inflammation in C. Albicans keratitis by activating Nrf2/HO-1 signaling pathway and reducing fungal load

PURPOSE

This study aims to investigate the anti-inflammatory and antifungal properties of thymoquinone (TQ) and elucidate its mechanism of action in the context of C. albicans keratitis.

METHODS

Various methods were employed to identify a safe and effective concentration of TQ with antifungal properties, including the determination of the minimum inhibitory concentration (MIC), the cell counting kit-8 (CCK-8) test, and the Draize experiment. The severity of fungal keratitis (FK) was assessed through clinical ratings and slit-lamp imaging. Fungus burden was determined using plate counting and periodic acid Schiff (PAS) staining. Neutrophil infiltration and activity were investigated through immunofluorescence staining (IFS), myeloperoxidase (MPO) analysis, and hematoxylin and eosin (HE) staining. To explore the anti-inflammatory effects of TQ and its mechanism of action, we employed RT-PCR, ELISA, and western blot techniques.

RESULTS

TQ effectively controlled fungal growth at a concentration of 50 µg/mL while preserving the integrity of mouse corneas. Human corneal epithelial cells (HCECs) remained unaffected by TQ at concentrations ≤ 3.75 µg/mL. Treatment with TQ led to significant improvements in clinical scores, fungal burden, neutrophil infiltration, and the expression of inflammatory factors compared to the DMSO group. Moreover, TQ demonstrated the ability to reduce the levels of inflammatory factors in HCECs stimulated by C. albicans. Additionally, TQ enhanced the expressions of Nrf2 and HO-1 in mouse corneas. The downregulation of cytokines induced by TQ was reversed upon pretreatment with inhibitors of Nrf2 or HO-1.

CONCLUSION

TQ exhibits a protective effect in the context of C. albicans keratitis through multiple mechanisms, including inhibition of C. albicans growth, reduction of neutrophil recruitment, activation of the Nrf2/HO-1 pathway, and limitation of the expression of pro-inflammatory factors.

Itaconate: A promising precursor for treatment of neuroinflammation associated depression

Neuroinflammation triggers the production of inflammatory factors, influences neuron generation and synaptic plasticity, thus playing an important role in the pathogenesis of depression and becoming an important direction of depression prevention and treatment. Itaconate is a metabolite secreted by macrophages in immunomodulatory responses, that has potent immunomodulatory effects and has been proven to exert anti-inflammatory effects in a variety of diseases. Microglia are mononuclear macrophages that reside in the central nervous system (CNS), and may be the source of endogenous itaconate in the brain. Itaconate can directly inhibit succinate dehydrogenase (SDH), reduce the production of NOD-like receptor thermal protein domain associated protein 3 (NLRP3), activate nuclear factor erythroid-2 related factor 2 (Nrf2), and block glycolysis, and thereby improving the depressive symptoms associated with the above mechanisms. Notably, itaconate also indirectly ameliorates the depressive symptoms associated with some inflammatory diseases. With the optimization of the structure and the development of new delivery systems, the application value and therapeutic potential of itaconate have been significantly improved. Dimethyl itaconate (DI) and 4-octyl itaconate (4-OI), cell-permeable derivatives of itaconate, are more suitable for crossing the blood-brain barrier (BBB), exhibiting therapeutic effects in the research of multiple diseases. This article provides an overview of the immunomodulatory effects of itaconate and its potential therapeutic efficacy in inflammatory depression, focusing on the promising application of itaconate as a precursor of antidepressants.

Dimethyl itaconate selectively targets inflammatory and metabolic pathways in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) co-evolves with its own microenvironment where inflammatory stimuli including toll-like receptors (TLR) signaling can protect CLL cells from spontaneous and drug-induced apoptosis by upregulating IκBζ, an atypical co-transcription factor. To dissect IκBζ-centered signaling pathways, we performed a gene expression profile of primary leukemic cells expressing either high or low levels of IκBζ after stimulation, highlighting that IκBζ is not only an inflammatory gene but it may control metabolic rewiring of malignant cells thus pointing to a novel potential opportunity for therapy. We exploited the capacity of the dimethyl itaconate (DI), an anti-inflammatory electrophilic synthetic derivative of the metabolite Itaconate, to target IκBζ. CLL cells, murine leukemic splenocytes, and leukocytes from healthy donors were treated in vitro with DI that abolished metabolic activation and reduced cell viability of leukemic cells only, even in the presence of robust TLR prestimulation. RNA sequencing highlighted that in addition to the expected electrophilic stress signature observed after DI treatment, novel pathways emerged including the downregulation of distinct MHC class II complex genes. In conclusion, DI not only abrogated the proinflammatory effects of TLR stimulation but also targeted a specific metabolic vulnerability in CLL cells.

Pseudolaric Acid B Ameliorates Fungal Keratitis Progression by Suppressing Inflammation and Reducing Fungal Load

This study aimed to determine the mechanisms of antifungal and anti-inflammation effects of pseudolaric acid B (PAB) on Aspergillus fumigatus (A. fumigatus) keratitis. In vitro MIC assay and crystal violet staining were conducted to evaluate the efficacy of PAB against A. fumigatus. PAB inhibited A. fumigatus growth and inhibited the formation of fungal biofilms in a dose-dependent manner. Molecular docking analysis revealed that PAB possesses strong binding properties with Rho1 of A. fumigatus, which is devoted to encoding (1,3)-β-d-glucan of A. fumigatus. RT-PCR results also showed that Rho1 was inhibited by PAB. In vivo, PAB treatment reduced clinical scores, fungal load, and macrophage infiltration, which were increased by A. fumigatus in mice corneas. In addition, PAB treatment suppressed the expression of Mincle, p-Syk, and cytokines (TNF-α, MIP2, iNOS, and CCL2) in infected corneas and in RAW264.7 cells, which were tested by RT-PCR, Western blot, and enzyme-linked Immunosorbent Assay. Notably, trehalose-6,6-dibehenate, an agonist of Mincle, pretreatment reversed the regulatory function of PAB in RAW 264.7 cells. Moreover, flow cytometry showed that PAB upregulated the ratio of M2/M1 macrophages in A. fumigatus-infected corneas and RAW264.7 cells. In conclusion, PAB produced antifungal activities against A. fumigatus and decreased the inflammatory response in mouse A. fumigatus keratitis.

Itaconate family-based host-directed therapeutics for infections

Itaconate is a crucial anti-infective and anti-inflammatory immunometabolite that accumulates upon disruption of the Krebs cycle in effector macrophages undergoing inflammatory stress. Esterified derivatives of itaconate (4-octyl itaconate and dimethyl itaconate) and its isomers (mesaconate and citraconate) are promising candidate drugs for inflammation and infection. Several itaconate family members participate in host defense, immune and metabolic modulation, and amelioration of infection, although opposite effects have also been reported. However, the precise mechanisms by which itaconate and its family members exert its effects are not fully understood. In addition, contradictory results in different experimental settings and a lack of clinical data make it difficult to draw definitive conclusions about the therapeutic potential of itaconate. Here we review how the immune response gene 1-itaconate pathway is activated during infection and its role in host defense and pathogenesis in a context-dependent manner. Certain pathogens can use itaconate to establish infections. Finally, we briefly discuss the major mechanisms by which itaconate family members exert antimicrobial effects. To thoroughly comprehend how itaconate exerts its anti-inflammatory and antimicrobial effects, additional research on the actual mechanism of action is necessary. This review examines the current state of itaconate research in infection and identifies the key challenges and opportunities for future research in this field.

Itaconate: A Potent Macrophage Immunomodulator

With advances in immunometabolic studies, more and more evidence has shown that metabolic changes profoundly affect the immune function of macrophages. The tricarboxylic acid cycle is a central metabolic pathway of cells. Itaconate, a byproduct of the tricarboxylic acid cycle, is an emerging metabolic small molecule that regulates macrophage inflammation and has received much attention for its potent anti-inflammatory effects in recent years. Itaconate regulates macrophage function through multiple mechanisms and has demonstrated promising therapeutic potential in a variety of immune and inflammatory diseases. New progress in the mechanism of itaconate continues to be made, but it also implies complexity in its action and a need for a more comprehensive understanding of its role in macrophages. In this article, we review the primary mechanisms and current research progress of itaconate in regulating macrophage immune metabolism, hoping to provide new insights and directions for future research and disease treatment.

Pentoxifylline treats Aspergillus fumigatus keratitis by reducing fungal burden and suppressing corneal inflammation

Fungal keratitis (FK) is a blinding ocular disease, which mainly results from fungal damage and excessive inflammation. Pentoxifylline, a kind of methylxanthine, has been discovered to have anti-inflammatory properties in various infectious diseases, hinting a potential therapeutic effect on treating corneal fungal infection. Whereas, the therapeutic impact of pentoxifylline on fungal keratitis is still uncertain. This study investigated the antifungal capability against Aspergillus fumigatus and the anti-inflammatory role of pentoxifylline by activating nuclear factor, erythroid 2 like 2 (Nrf2)/heme oxygenase1 (HO1) pathway in the process of FK. In our research, we demonstrated that pentoxifylline could effectively inhibit fungal growth and inflammatory reaction. Pentoxifylline reduced the production of pro-inflammatory factors by stimulating the Nrf2/HO1 pathway. Although there was no statistical difference between the curative efficacy of pentoxifylline and natamycin application to FK, pentoxifylline could promote corneal epithelial repair and was less toxicity to the ocular surface than natamycin. In conclusion, pentoxifylline performs antifungal and anti-inflammatory effects by lessening the fungus burden and activating the Nrf2/HO1 pathway, hinting that it has the potential to be a new therapeutic medication for Aspergillus fumigatus keratitis.

Modern Technologies in Diagnosis of Fungal Keratitis (Review)

Traumas and infectious diseases of the eye play a leading role in the development of corneal blindness responsible for 1.5-2 million cases of vision loss per year. To date, the issue of reducing the incidence of fungal keratitis is acute and needs to be solved worldwide. Trauma as a risk factor for corneal fungal disease is thought to be prevalent in developing countries due to agricultural involvement, while in developed countries the onset of the disease is predisposed by medical advances such as contact vision correction and modern ophthalmic surgery. Thorough analysis of the pathogenesis gives the possibility to describe the action of fungal enzymes, biofilm formation, and the resistance mechanism, which on the one hand explains the aggressive course of the disease and difficulties in its diagnosis, and on the other hand, it encourages searching for new methods of diagnosis and treatment. The non-specific clinical picture of fungal keratitis, the variety and availability of antibiotics nowadays become an obstacle for rapid detection of this pathology. Low public awareness and late visit to an ophthalmologist are also a barrier to successful combating the increasing incidence of fungal keratitis. Belated diagnosis, increasing resistance of fungi to antibiotics, and lack of registered antifungal ophthalmic drugs justify poor treatment efficacy resulting in decreased visual acuity or vision loss. Existing diagnostic methods need systematization and detailed comparison, identifying the advantages and disadvantages of each. This review considers causative agents and their influence on pathogenesis of the disease, describes difficulties of fungal keratitis diagnosis and possible ways of overcoming these problems using new developments, and also outlines further prospects of research in this direction.

Dimethyl itaconate is effective in host-directed antimicrobial responses against mycobacterial infections through multifaceted innate immune pathways

BACKGROUND

Itaconate, a crucial immunometabolite, plays a critical role in linking immune and metabolic functions to influence host defense and inflammation. Due to its polar structure, the esterified cell-permeable derivatives of itaconate are being developed to provide therapeutic opportunities in infectious and inflammatory diseases. Yet, it remains largely uncharacterized whether itaconate derivatives have potentials in promoting host-directed therapeutics (HDT) against mycobacterial infections. Here, we report dimethyl itaconate (DMI) as the promising candidate for HDT against both Mycobacterium tuberculosis (Mtb) and nontuberculous mycobacteria by orchestrating multiple innate immune programs.

RESULTS

DMI per se has low bactericidal activity against Mtb, M. bovis Bacillus Calmette-Guérin (BCG), and M. avium (Mav). However, DMI robustly activated intracellular elimination of multiple mycobacterial strains (Mtb, BCG, Mav, and even to multidrug-resistant Mtb) in macrophages and in vivo. DMI significantly suppressed the production of interleukin-6 and -10, whereas it enhanced autophagy and phagosomal maturation, during Mtb infection. DMI-mediated autophagy partly contributed to antimicrobial host defenses in macrophages. Moreover, DMI significantly downregulated the activation of signal transducer and activator of transcription 3 signaling during infection with Mtb, BCG, and Mav.

CONCLUSION

Together, DMI has potent anti-mycobacterial activities in macrophages and in vivo through promoting multifaceted ways for innate host defenses. DMI may bring light to new candidate for HDT against Mtb and nontuberculous mycobacteria, both of which infections are often intractable with antibiotic resistance.

Dimethyl itaconate ameliorates cognitive impairment induced by a high-fat diet via the gut-brain axis in mice

BACKGROUND

Gut homeostasis, including intestinal immunity and microbiome, is essential for cognitive function via the gut-brain axis. This axis is altered in high-fat diet (HFD)-induced cognitive impairment and is closely associated with neurodegenerative diseases. Dimethyl itaconate (DI) is an itaconate derivative and has recently attracted extensive interest due to its anti-inflammatory effect. This study investigated whether intraperitoneal administration of DI improves the gut-brain axis and prevents cognitive deficits in HF diet-fed mice.

RESULTS

DI effectively attenuated HFD-induced cognitive decline in behavioral tests of object location, novel object recognition, and nesting building, concurrent with the improvement of hippocampal RNA transcription profiles of genes associated with cognition and synaptic plasticity. In agreement, DI reduced the damage of synaptic ultrastructure and deficit of proteins (BDNF, SYN, and PSD95), the microglial activation, and neuroinflammation in the HFD-fed mice. In the colon, DI significantly lowered macrophage infiltration and the expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in mice on the HF diet, while upregulating the expression of immune homeostasis-related cytokines (IL-22, IL-23) and antimicrobial peptide Reg3γ. Moreover, DI alleviated HFD-induced gut barrier impairments, including elevation of colonic mucus thickness and expression of tight junction proteins (zonula occludens-1, occludin). Notably, HFD-induced microbiome alteration was improved by DI supplementation, characterized by the increase of propionate- and butyrate-producing bacteria. Correspondingly, DI increased the levels of propionate and butyrate in the serum of HFD mice. Intriguingly, fecal microbiome transplantation from DI-treated HF mice facilitated cognitive variables compared with HF mice, including higher cognitive indexes in behavior tests and optimization of hippocampal synaptic ultrastructure. These results highlight the gut microbiota is necessary for the effects of DI in improving cognitive impairment.

CONCLUSIONS

The present study provides the first evidence that DI improves cognition and brain function with significant beneficial effects via the gut-brain axis, suggesting that DI may serve as a novel drug for treating obesity-associated neurodegenerative diseases. Video Abstract.

Dimethyl fumarate ameliorates fungal keratitis by limiting fungal growth and inhibiting pyroptosis

PURPOSE

We aimed to investigate the therapeutic role of dimethyl fumarate (DMF) in fungal keratitis.

METHODS

Human corneal epithelial cells (HCECs) and mouse models of fungal keratitis were used in this study. The antifungal effect of DMF on Aspergillus fumigatus (A. fumigatus) was confirmed by examining the minimum inhibitory concentration (MIC), biofilm formation, conidial adherence and corneal fungal loads. Slit-lamp photography, haematoxylin and eosin staining and immunostaining were used to assess the severity of corneal impairment. RT-PCR, western blot, ELISA, immunohistochemistry and immunostaining were performed to examine the effects of DMF on the expression of the inflammatory mediators during fungal infection.

RESULTS

In vitro, DMF limited A. fumigatus growth, biofilm formation, and conidial adherence and reduced the mRNA levels of AldA, GlkA, GAPDH, HxkA, PgkA, Sdh2, GelA and ChsF in A. fumigatus. In vivo, DMF effectively decreased corneal fungal loads. DMF attenuated corneal inflammatory impairment by suppressing inflammatory cell accumulation and downregulating cytokine expression. DMF notably downregulated the high expression of NLRP3, cleaved GSDMD, cleaved caspase-1, mature IL-1β and mature IL-18 induced by fungi. The production of Nrf2 and HO-1 could be further increased by DMF in infected HCECs. Nrf2 siRNA pretreatment counteracted DMF-mediated downregulation of the expression of the active forms of IL-18, IL-1β, caspase-1 and GSDMD.

CONCLUSION

DMF limits fungal growth by suppressing biofilm formation, conidial adherence and respiratory metabolism. It also exerts an anti-inflammatory effect on fungal keratitis by inhibiting pyroptosis, which could be regulated by Nrf2. Our results suggest that DMF plays a therapeutic role in fungal keratitis.

Protective effects of dietary dimethyl itaconate supplementation on oxidative stress, inflammation, and apoptosis in broilers under chronic heat stress

This study was conducted to evaluate the effects of dietary dimethyl itaconate (DI) supplementation on oxidative stress, inflammation, and apoptosis in broilers under chronic heat stress (HS). Twenty-one-day-old male Ross 308 broilers (n = 120) were randomly allocated to 5 groups: a control group, HS group, HS + 50 mg/kg DI group, HS + 150 mg/kg DI group, and HS + 200 mg/kg DI group. The birds in the control group received the basal diets and were maintained at 21 ± 1 °C for 24 h daily. The birds in the HS group and HS + DI groups were raised at 32 ± 1 °C for 8 h daily and received basal diets containing DI at the indicated dose (0, 50, 150, or 200 mg/kg). The results showed that the contents of alanine aminotransferase, aspartate aminotransferase, and malondialdehyde (MDA) in serum were markedly elevated by exposure to chronic HS (P < 0.01), and this elevation was alleviated by 150 and 200 mg/kg DI supplementation (P < 0.05). Chronic HS-induced declines (P < 0.05) in total antioxidant capacity (T-AOC) and activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in serum were markedly attenuated after 200 mg/kg DI treatment in broilers (P < 0.05). Moreover, broilers subjected to chronic HS exhibited higher contents of MDA, protein carbonyl, and hydrogen peroxide (P < 0.01), but lower T-AOC and activities of antioxidant enzymes (P < 0.05), as well as reduced inhibition of superoxide and hydroxyl free radicals (P < 0.01) in the liver compared to the control group; these changes were effectively mitigated by treatment with 200 mg/kg DI in broilers (P < 0.05). In addition, 50-200 mg/kg DI effectively ameliorated chronic HS-stimulated upregulation of the mRNA levels of pro-inflammatory mediators in the livers of broilers (P < 0.01). Dietary supplementation with 150 and 200 mg/kg DI significantly alleviated chronic HS challenge-induced upregulation of the mRNA levels of Bcl-2-associated X, caspase 3, and caspase 9 (P < 0.01), but downregulation of Bcl-2 mRNA levels (P < 0.01) in broilers (P < 0.05). Importantly, chronic HS-induced downregulation of the mRNA or protein levels of nuclear factor (erythroid-derived 2)-like 2 (NRF-2), NADPH quinone acceptor oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), SOD2, or glutathione-S-transferases (GST) (P < 0.01) was markedly improved by 150 and 200 mg/kg DI (P < 0.05). The above results indicated that DI can ameliorate oxidative stress, inflammation, and apoptosis in broilers under chronic HS.

A metabolite attenuates neuroinflammation, synaptic loss and cognitive deficits induced by chronic infection of Toxoplasma gondii

Background

Neurodegenerative diseases including AD is currently one of intractable problems globally due to the insufficiency of intervention strategies. Long-term infection of Toxoplasma gondii (T. gondii) can induce cognitive impairment in hosts, which is closely implicated in the pathogenesis of neurodegenerative diseases. Aconitate decarboxylase 1 (Acod1) and its produced metabolite itaconate (termed Acod1/itaconate axis), have recently attracted extensive interests due to its anti-inflammatory role in macrophages. However, whether the axis can influence cognitive function remains unknown.

Methods

A chronic T. gondii-infected mice (C57BL/6J) model was established via administration of cysts by gavage. Novel location (NL), novel object recognition (NOR), Y-maze spatial memory and nest building tests were used to evaluate the behavior performance. Transmission electron microscopy, immunofluorescence, RT-PCR, western-blotting and RNA sequencing were utilized to determine the pathological changes, neuroinflammation and transcription profile in hippocampus tissues post infection, respectively. Moreover, the protective effect of Acod1/itaconate axis in T. gondii-induced cognitive deficits was evaluated.

Results

We found that the latent infection of the parasite impaired the cognitive function, which was assessed behaviorally by novel location (NL), novel object recognition (NOR), Y-maze spatial memory and nest building tests. RNA sequencing of hippocampus showed that the infection downregulated the expression of genes related to synaptic plasticity, transmission and cognitive behavior. To our attention, the infection robustly upregulated the expression of genes associated with pro-inflammatory responses, which was characterized by microglia activation and disorder of Acod1/itaconate axis. Interestingly, administration of dimethyl itaconate (DI, an itaconate derivative with cell membrane permeability) could significantly ameliorate the cognitive deficits induced by T. gondii, which was proved by improvement of behavior performance and synaptic ultrastructure impairment, and lower accumulation of pro-inflammatory microglia. Notably, DI administration had a potential therapeutic effect on the cognitive deficits and synaptic impairment induced by the parasitic infection.

Conclusions

Overall, these findings provide a novel insight for the pathogenesis of T. gondii-related cognitive deficits in hosts, and also provide a novel clue for the potential therapeutic strategies.

Flavopiridol Protects against Fungal Keratitis due to Aspergillus fumigatus by Alleviating Inflammation through the Promotion of Autophagy

Fungal keratitis is a serious infectious keratopathy related to fungal virulence and excessive inflammatory responses. Autophagy exhibits a potent ability to resolve inflammation during fungal infection. This study aimed to investigate the protective function of flavopiridol in Aspergillus fumigatus keratitis and explore its effects on autophagy. In our study, the corneas of the fungal keratitis mouse model were treated with 5 μM flavopiridol. In vitro, RAW 264.7 cells were pretreated with 200 nM flavopiridol before fungal stimulation. A. fumigatus was incubated with flavopiridol, and the antifungal activity of flavopiridol was detected. Our results indicated that flavopiridol treatment notably reduced clinical scores as well as cytokines expression of infected corneas. In infected RAW 264.7 cells, flavopiridol treatment inhibited IL-1β, IL-6, and TNF-α expression but promoted IL-10 expression. Transmission electron microscopy (TEM) images showed that more autolysosomes were present in infected corneas and RAW 264.7 cells after flavopiridol treatment. Flavopiridol treatment notably upregulated the protein expression of LC3, Beclin-1, and Atg-7. 3-Methyladenine (3-MA, an inhibitor of autophagy) pretreatment counteracted the cytokine regulation induced by flavopiridol. Moreover, flavopiridol promoted the phagocytosis of RAW 264.7 cells. Flavopiridol also exhibited antifungal activity by restricting fungal growth and limiting fungal biofilm formation and conidial adhesion. In conclusion, flavopiridol significantly alleviated the inflammation of fungal keratitis by activating autophagy. In addition, flavopiridol promoted the phagocytosis of RAW 264.7 cells and exhibited antifungal function, indicating the potential therapeutic role of flavopiridol in fungal keratitis.

Oxidized chondroitin sulfate eye drops ameliorate the prognosis of fungal keratitis with anti-inflammatory and antifungal effects

Fungal keratitis (FK) is a refractory ophthalmic disease that can result in vision impairment and even blindness due to the severe fungal invasiveness and excessive inflammatory response. Therefore, antifungal treatment combined with local immunosuppressive therapy is regarded as the most effective strategy to improve the clinical outcome of FK. Oxidized polysaccharides with aldehyde groups possess obvious inhibitory activity towards microorganisms. Herein, we use chondroitin sulfate (CS), a recognized anti-inflammatory biopolysaccharide, to prepare oxidized chondroitin sulfate (OCS) via sodium periodate (NaIO₄) oxidation for the treatment of FK. The chemical structure of OCS was characterized by FTIR, ¹H NMR, and XPS, revealing that the O-dihydroxy in the D-glucuronic acid unit of CS was selectively broken by NaIO₄, forming active aldehyde groups. The introduction of aldehydes not only retains the anti-inflammatory activity but also confers OCS with antifungal property. In vitro antifungal experiments showed that OCS inhibits the growth, represses the biofilm formation and alters the membrane integrity of A. fumigatus. The toxicity of OCS was evaluated by cytotoxicity tests (CCK-8) and the Draize eye test in vitro and in vivo. qRT-PCR confirmed that OCS had similar anti-inflammatory activity as CS. In mice with A. fumigatus keratitis, OCS versus CS or PBS showed an excellent therapeutic effect, characterized by a lower corneal inflammation score, less fungal load, reduced neutrophil recruitment, and the downregulated expression of pro-inflammatory factors. Our findings demonstrate that OCS improves the prognosis of A. fumigatus keratitis in mice by inhibiting the growth of fungi, reducing the recruitment of neutrophils and inhibiting the inflammatory response. It provides innovative ideas for the development and application of OCS in medicine and biomaterials fields.

Aconitate decarboxylase 1 regulates glucose homeostasis and obesity in mice

OBJECTIVE

The intersection between immunology and metabolism contributes to the pathogenesis of obesity-associated metabolic diseases as well as molecular control of inflammatory responses. The metabolite itaconate and the cell-permeable derivatives have robust anti-inflammatory effects; therefore, it is hypothesized that cis-aconitate decarboxylase (Acod1)-produced itaconate has a protective, anti-inflammatory effect during diet-induced obesity and metabolic disease.

METHODS

Wild-type and Acod1-/- mice were subjected to diet-induced obesity. Glucose metabolism was analyzed by glucose tolerance tests, insulin tolerance tests, and indirect calorimetry. Gene expression and transcriptome analysis was performed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and RNA sequencing.

RESULTS

Wild-type and Acod1-/- mice on high-fat diet had equivalent weight gain, but Acod1-/- mice had impaired glucose metabolism. Insulin tolerance tests and glucose tolerance tests after 12 weeks on high-fat diet revealed significantly higher blood glucose levels in Acod1-/- mice. This was associated with significant enrichment of inflammatory gene sets and a reduction in genes related to adipogenesis and fatty acid metabolism. Analysis of naive Acod1-/- mice showed a significant increase in fat deposition at 3 and 6 months of age and obesity and insulin resistance by 12 months.

CONCLUSIONS

The data show that Acod1 has an important role in the regulation of glucose homeostasis and obesity under normal and high-fat diet conditions.

Mechanism of antifungal activity and therapeutic action of β-ionone on Aspergillus fumigatus keratitis via suppressing LOX1 and JNK/p38 MAPK activation

PURPOSE

To investigate the anti-inflammatory and antifungal role of β-ionone (BI) in fungal keratitis (FK).

METHODS

In vitro antifungal activity of BI against Aspergillus fumigatus (A. fumigatus) was evaluated by using minimum inhibitory concentration (MIC), crystal violet staining, biofilm biomass measurement, propidium iodide uptake test, and adherence assay. And RT-PCR was carried out to measure the levels of RodA, RodB, Rho, FKs, CshA-D, RlmA, Cyp51A-B and Cdr1B. Network pharmacology analysis was applied to predict the relationship between BI and FK. Cell Count Kit-8 (CCK8) assay was utilized to detect the cytotoxicity of BI to RAW264.7 and immortalized human corneal epithelial cells (HCECs). The underlying mechanism of BI at regulating the level of inflammatory factors in FK was assessed by RT-PCR, ELISA and Western blot in vitro and in vivo. The therapeutic effect of BI has investigated in A. fumigatus keratitis by employing the clinical score, pathological examination, plate count, immunofluorescence and myeloperoxidase (MPO) assay. We also used the slit-lamp microscopy, clinical scores, and HE staining to assess the effect of natamycin compared with BI treatment in vivo.

RESULTS

BI suppressed the growth of A. fumigatus and had a significant effect on A. fumigatus biofilms and membrane permeability. RT-PCR demonstrated that exposure of A. fumigatus to BI inhibited the expression of genes that function in hydrophobin (RodA, RodB), cell wall integrity (Rho, FKs, CshA-D, RlmA), azole susceptibility (Cyp51A-B, Cdr1B). Network pharmacology showed that the effects of BI in FK implicate with C-type lectin receptor signaling pathway. In vivo, after A. fumigatus infection, BI treatment markedly reduced the severity of FK by decreasing clinical score, neutrophil recruitment, and fungal load. And BI treatment also obviously reduced the expression of inflammatory cytokines, Lectin-like oxidized LDL receptor (LOX-1), phosphorylation of p38MAPK and p-JNK versus the DMSO-treated group. BI and natamycin both significantly increased corneal transparency and decreased inflammatory cell recruitment in the FK in the mice model.

CONCLUSION

These results indicated that BI had fungicidal activities against A. fumigatus. It also ameliorated FK in mice by reducing inflammation, which was regulated by LOX-1, p-p38MAPK and p-JNK.

A comparison study between dimethyl itaconate and dimethyl fumarate in electrophilicity, Nrf2 activation, and anti-inflammation in vitro

Dimethyl itaconate (DMI) is an analog of dimethyl fumarate (DMF), an approved NF-E2-related Factor 2 (Nrf2) activator for multiple sclerosis. This study evaluated the potential of DMI as an anti-inflammatory agent by comparing DMI with DMF in electrophilicity, Nrf2 activation, and anti-inflammation in vitro. The results showed that DMI was less electrophilic but better at inducing a durable activation of Nrf2 when compared with DMF. However, DMI demonstrated poor anti-inflammatory effects in Jurkat cells, bone marrow-derived dendritic cells, and RAW264.7 cells. Our study suggested that DMI was a potent electrophilic Nrf2 activator but was probably not a promising anti-inflammatory agent.

Drug-loaded mesoporous carbon with sustained drug release capacity and enhanced antifungal activity to treat fungal keratitis

Fungal keratitis is a severe infectious corneal disease with a high rate of incidence and blindness. Since traditional treatments natamycin (NATA) eye drops, exhibit poor dissolution and bioavailability, and the efficacy of current therapeutic approaches remains limited. In this study, we innovatively utilized mesoporous carbon (Meso-C) and microporous carbon (Micro-C) as nanocarriers loaded with the antifungal drug NATA and silver nanoparticles (Ag-NPs). Porous carbon loaded with NATA and Ag-NPs has not previously been studied in fungal keratitis. Due to the mesoporous structure, high surface area and larger pore volume of Meso-C, it displayed greater superiority in sustained drug release and drug dispersity than Micro-C. Moreover, Meso-C could adsorb inflammatory cytokines during fungal infection. In vitro, Meso-C/NATA/Ag showed excellent antifungal effects. In vivo, compared with pure NATA treatment, Meso-C/NATA/Ag exhibited significantly improved therapeutic effects and reduced dosing frequency when treating fungal keratitis. Our study is the first to report the sustained drug release and improved drug dispersity of Meso-C/NATA and demonstrates that NATA and Ag-NPs-loaded Meso-C has therapeutic effects against fungal keratitis.

Resolvin D1 protects against Aspergillus fumigatus keratitis in diabetes by blocking the MAPK-NF-κB pathway

Fungal keratitis (FK) is one of the main causes of blindness in China. People with diabetes are susceptible to corneal epithelial disease, even fungal keratitis. At present, there are few studies on this disease. Resolvins (Rv) has been reported as a mediators that exert crucial anti-inflammatory and immune regulation roles in serval diseases. In order to investigate the roles and underlying mechanism of Resolvins D1 (RvD1) on the Aspergillus fumigatus (A. fumigatus) keratitis in diabetes, we established in vivo and in vitro models of A. fumigatus keratitis, which were then exposed to high glucose. The expression levels of RvD1, 5-lipoxygenase (5-LOX), and 15-lipoxygenase (15-LOX) in A. fumigatus keratitis patients with diabetes were determined through Enzyme Linked Immunosorbent Assay (ELISA), Western blot and immunohistochemistry. Reactive Oxygen Species (ROS) production, ELISA, flow cytometry, Hematoxylin-Eosin (HE) staining and fungal loading determination were conducted to evaluate the severity of A. fumigatus infection. Lymphangiogenesis and angiogenesis were examined by immunofluorescence assay. Western blot was applied to detect the proteins of the MAPK-NF-κB pathway. The results showed that RvD1 diminished the high glucose-induced oxidative stress and inflammatory response, as evidenced by the reduction of ROS production, Interleukin-6 (IL-6), Interleukin-8 (IL-8), Heme Oxygenase-1 (HMOX-1), and the elevation of Cyclooxygenase-2 (COX2), Superoxide Dismutase (SOD-1), and Glutathione Peroxidase-2 (GPX2) levels in A. fumigatus-infected Human Corneal Endothelial Cells (HCECs). Additionally, lymphangiogenesis and angiogenesis prominently decreased after intervention with RvD1. Furthermore, RvD1 significantly reduced the levels of p-MEK1/2 and p-ERK1/2, and restrained the NF-κB and GPR32 activation. The above results showed that RvD1 protects against A. fumigatus keratitis in diabetes by suppressing oxidative stress, inflammatory response, fungal growth, and immunoreaction via modulating MAPK-NF-κB pathway. RvD1 provides clues for the therapeutic targets of Fungal keratitis complicated with diabetes.

Preparation of a Nanobody Specific to Dectin 1 and Its Anti-inflammatory Effects on Fungal Keratitis

Objective

To prepare a nanobody specific to dectin 1 and verify its specificity and anti-inflammatory effects on Aspergillus fumigatus keratitis.

Methods

The nanobody was selected from a high-quality shark-antibody library constructed with phage-display technology. The nanobody was developed in the expression systems of Escherichia coli. Indirect ELISA was used to determine the specificity of the nanobody to recombinant dectin 1 protein. The potential of the nanobody to be recognized and expressed on the surfaces of cells and corneas was detected by immunofluorescence, and its anti-inflammatory effect on A. fumigatus keratitis was further verified. After infection with A. fumigatus, eyes of C57B L/6 mice were treated with nanobodies. Human corneal epithelial cells (HCECs) were pretreated with nanobodies and then incubated with A. fumigatus. Clinical scores and slit-lamp photography were used to assess disease response in mouse corneas. RT-PCR and ELISA were used to evaluate mRNA and protein expression of IL1β and IL6 in both mouse corneas and HCECs.

Results

The nanobody was successfully expressed through microbial system and showed specific high-affinity binding to recombinant dectin 1. Furthermore, it exhibited specific binding to dectin 1 expressed on the surfaces of cells and recognized dectin 1 in mouse corneas. Importantly, it reduced clinical scores of A. fumigatus keratitis in mice compared with a PBS-treatment group. In addition, it decreased mRNA and protein expression of IL1β and IL6 in infected corneas and HCECs stimulated with A. fumigatus.

Conclusion

These results suggest that this nanobody can bring about anti-inflammatory effects. This highlights the potential of these nanobodies as innovative therapeutic agents in A. fumigatus.

Itaconate and derivatives reduce interferon responses and inflammation in influenza A virus infection

Excessive inflammation is a major cause of morbidity and mortality in many viral infections including influenza. Therefore, there is a need for therapeutic interventions that dampen and redirect inflammatory responses and, ideally, exert antiviral effects. Itaconate is an immunomodulatory metabolite which also reprograms cell metabolism and inflammatory responses when applied exogenously. We evaluated effects of endogenous itaconate and exogenous application of itaconate and its variants dimethyl- and 4-octyl-itaconate (DI, 4OI) on host responses to influenza A virus (IAV). Infection induced expression of ACOD1, the enzyme catalyzing itaconate synthesis, in monocytes and macrophages, which correlated with viral replication and was abrogated by DI and 4OI treatment. In IAV-infected mice, pulmonary inflammation and weight loss were greater in Acod1^-/- than in wild-type mice, and DI treatment reduced pulmonary inflammation and mortality. The compounds reversed infection-triggered interferon responses and modulated inflammation in human cells supporting non-productive and productive infection, in peripheral blood mononuclear cells, and in human lung tissue. All three itaconates reduced ROS levels and STAT1 phosphorylation, whereas AKT phosphorylation was reduced by 4OI and DI but increased by itaconate. Single-cell RNA sequencing identified monocytes as the main target of infection and the exclusive source of ACOD1 mRNA in peripheral blood. DI treatment silenced IFN-responses predominantly in monocytes, but also in lymphocytes and natural killer cells. Ectopic synthesis of itaconate in A549 cells, which do not physiologically express ACOD1, reduced infection-driven inflammation, and DI reduced IAV- and IFNγ-induced CXCL10 expression in murine macrophages independent of the presence of endogenous ACOD1. The compounds differed greatly in their effects on cellular gene homeostasis and released cytokines/chemokines, but all three markedly reduced release of the pro-inflammatory chemokines CXCL10 (IP-10) and CCL2 (MCP-1). Viral replication did not increase under treatment despite the dramatically repressed IFN responses. In fact, 4OI strongly inhibited viral transcription in peripheral blood mononuclear cells, and the compounds reduced viral titers (4OI>Ita>DI) in A549 cells whereas viral transcription was unaffected. Taken together, these results reveal itaconates as immunomodulatory and antiviral interventions for influenza virus infection.

Interferon responses are part of the primary host defenses against infections. However, excessive inflammation is often a major factor in severe disease or even death in respiratory infections such as influenza, as it can lead to acute respiratory distress syndrome and sepsis-like multiorgan involvement. We applied itaconate and chemically modified versions of it (which enter cells more efficiently and can be applied at lower doses) to influenza A virus-infected human cells and lung tissue and found that these compounds markedly repress interferon responses and some pro-inflammatory processes without increasing viral replication. In fact, 4-octyl itaconate greatly decreased viral RNA replication in peripheral blood, and itaconate and 4-octyl itaconate reduced production of infectious virus in a human lung cell line. By analyzing gene expression patterns of single mononuclear cells in peripheral blood, we found that the virus infects predominantly monocytes and that these cells are the only source of ACOD1, the enzyme that synthesizes itaconate in humans. In a mouse model of influenza A virus infection, dimethyl-itaconate prevented lung inflammation and improved survival. Thus, our results suggest that novel medications based on itaconate promise to be effective treatments for influenza because they reduce deleterious inflammation and potentially also limit viral spread in the patient.

Dimethyl itaconate alleviates the pyroptosis of macrophages through oxidative stress

Macrophages are involved in the pathophysiology of many diseases as critical cells of the innate immune system. Pyroptosis is a form of macrophage death that induces cytokinesis of phagocytic substances in the macrophages, thereby defending against infection. Dimethyl itaconate (DI) is an analog of itaconic acid with anti-inflammatory effects. However, the effect of dimethyl itaconate on macrophage pyroptosis has not been elucidated clearly. Thus, the present study aimed to analyze the effect of DI treatment on a macrophage pyroptosis model (Lipopolysaccharide, LPS + Adenosine Triphosphate, ATP). The results showed that 0.25 mM DI ameliorated macrophage pyroptosis and downregulated interleukin (IL)-1β expression. Then, real-time quantitative polymerase chain reaction (RT-qPCR) was used to confirm the result of RNA-sequencing of the upregulated oxidative stress-related genes (Gclc and Gss) and downregulated inflammation-related genes (IL-12β and IL-1β). In addition, Gene Ontology (GO) enrichment analysis showed that differential genes were associated with transcript levels and DNA replication. Kyoto encyclopedia of genes and genomes (KEGG) enrichment showed that signaling pathways, such as tumor necrosis factor (TNF), Jak, Toll-like receptor and IL-17, were altered after DI treatment. N-acetyl-L-cysteine (NAC) reversed the DI effect on the LPS + ATP-induced macrophage pyroptosis and upregulated the IL-1β expression. Oxidative stress-related protein Nrf2 is involved in the DI regulation of macrophage pyroptosis. Taken together, these findings suggested that DI alleviates the pyroptosis of macrophages through oxidative stress.

Antitumor effect of dimethyl itaconate on thymic carcinoma by targeting LDHA-mTOR axis

AIMS

Thymic carcinoma is a rare type of cancer without an established standard pharmaceutical treatment. This study investigated the antitumor effect of dimethyl itaconate (DI), a cell-permeable derivative of itaconate, on human thymic carcinoma cell line.

MAIN METHODS

Human thymic carcinoma cell line Ty82 was used to evaluate the effect of DI on cell viability. Western blotting and immunohistochemistry were performed to determine the molecular mechanism of antitumor effects of DI on Ty82.

KEY FINDINGS

DI suppressed cell growth and promoted apoptosis of Ty82. The suppressive effect of DI on Ty82 was mediated by the downregulation of lactate dehydrogenase A (LDHA), and the subsequent decrease in the activity of mechanistic target of rapamycin (mTOR). DI exhibited synergistic antitumor effects with a specific inhibitor of large neutral amino acid transporter 1 (LAT1), an amino acid transporter currently being investigated as a novel target for cancer therapy.

SIGNIFICANCE

Our findings demonstrate that DI is a novel potential strategy for thymic carcinoma treatment.

The Role of SREC-Ⅰ in Innate Immunity to Aspergillus fumigatus Keratitis

Purpose

To determine the role of scavenger receptor expressed by endothelial cell-1 (SREC-Ⅰ) in vitro and in a mouse model of Aspergillus fumigatus keratitis.

Methods

SREC-Ⅰ mRNA and protein expression were tested in both normal and A fumigatus stimulated human corneal epithelial cells (HCECs). Immunofluorescence was used to detect SREC-Ⅰ expression in human corneas with or without A fumigatus infection. HCECs were incubated with SREC-Ⅰ small interfering RNA, then the mRNA levels of LOX-1, IL-1β, and TNF-α were detected after A fumigatus stimulation. A mouse fungal keratitis (FK) model was established and SREC-Ⅰ mRNA and protein expression were detected by RT-PCR, Western blot and immunofluorescence. The severity of FK was evaluated by clinical score. CLCX1, LOX-1, IL-1β, and TNF-α mRNA expression levels were tested before and after anti-SREC-Ⅰ treatment.

Results

SREC-Ⅰ expressed in normal and A fumigatus treated HCECs and human corneal epithelium. In vitro experiment showed that SREC-Ⅰ mRNA and protein levels were significantly increased after A fumigatus stimulation. SREC-Ⅰ small interfering RNA treatment inhibited the expressions of LOX-1, IL-1β, and TNF-α in HCECs. The expressions of CLCX1, LOX-1, IL-1β, and TNF-α were elevated in mice with A fumigatus keratitis, which could be decreased by SREC-Ⅰ-neutralizing antibody treatment.

Conclusions

SREC-Ⅰ is a key mediator in inflammatory response induced by A fumigatus keratitis. SREC-Ⅰ blockade could be a potential therapeutic approach for FK.

Baicalein Protects Against Aspergillus fumigatus Keratitis by Reducing Fungal Load and Inhibiting TSLP-Induced Inflammatory Response

Purpose

To investigate the antifungal and anti-inflammatory effects of baicalein on Aspergillus fumigatus (A. fumigatus) keratitis and the underlying mechanisms.

Methods

The noncytotoxic antifungal concentration of baicalein was determined using CCK8, cell scratch assay, minimum inhibitory concentration, biofilm formation, scanning electron microscopy, propidium iodide uptake test and adherence assay in vitro and Draize test in vivo. In fungal keratitis (FK) mouse models, clinical score and plate count were used to evaluate FK severity, and myeloperoxidase assay and immunofluorescence staining were performed to examine neutrophil infiltration and activity. Real-time PCR, ELISA, and Western blot were performed to explore the anti-inflammatory activity of baicalein and the underlying mechanisms in vivo and in vitro.

Results

Baicalein at 0.25 mM (noncytotoxic) significantly inhibited A. fumigatus growth, biofilm formation, and adhesion in vitro. In A. fumigatus keratitis mice, baicalein mitigated FK severity, reduced fungal load, and inhibited neutrophil infiltration and activity. Baicalein not only suppressed mRNA and protein levels of proinflammatory factors IL-1β, IL-6, and TNF-α, but also inhibited the expression of thymic stromal lymphopoietin (TSLP) and TSLP receptor (TSLPR) in vivo and in vitro. In HCECs, mRNA and protein levels of IL-1β, IL-6, and TNF-α were significantly lower in the TSLP siRNA–treated group, while higher in the rTSLP-treated group than in the corresponding control. Baicalein treatment significantly inhibited rTSLP induced the expression of IL-1β, IL-6, and TNF-α.

Conclusions

Baicalein plays a protective role in mouse A. fumigatus keratitis by inhibiting fungal growth, biofilm formation, and adhesion, and suppressing inflammatory response via downregulation of the TSLP/TSLPR pathway.

Glucose-impaired Corneal Re-epithelialization Is Promoted by a Novel Derivate of Dimethyl Fumarate

Glucose induces corneal epithelial dysfunctions characterized by delayed wound repair. Nuclear erythroid 2-related factor 2 (Nrf2) mediates cell protection mechanisms even through the Heme oxygenase-1 (HO-1) up-regulation. Here, we synthesized new HO-1 inducers by modifying dimethyl fumarate (DMF) and used docking studies to select VP13/126 as a promising compound with the best binding energy to Kelch-like ECH-associated protein 1 (keap1), which is the the regulator of Nrf2 nuclear translocation. We verified if VP13/126 protects SIRC cells from hyperglycemia compared to DMF. SIRC were cultured in normal (5 mM) or high glucose (25 mM, HG) in presence of DMF (1–25 μM) or VP13/126 (0.1–5 μM) with or without ERK1/2 inhibitor PD98059 (15 μM). VP13/126 was more effective than DMF in the prevention of HG-induced reduction of cell viability and proliferation. Reduction of wound closure induced by HG was similarly counteracted by 1 μM VP13/126 and 10 μM DMF. VP13/126 strongly increased phospho/total ERK1/2 and restored HO-1 protein in HG-treated SIRC; these effects are completely counteracted by PD98059. Moreover, high-content screening analysis showed a higher rate of Nrf2 nuclear translocation induced by VP13/126 than DMF in HG-stimulated SIRC. These data indicate that VP13/126 exerts remarkable pro-survival properties in HG-stimulated SIRC, promoting the Nrf2/HO-1 axis.

Update on the management of fungal keratitis

PURPOSE

The aim of this article is to introduce the recent advance on the studies of fungal keratitis published over past 5 years.

METHODS

We performed literature review of articles published on PubMed, Google Scholar, CNKI and Web of Science relevant to the diagnosis, pathogenesis and novel treatment of fungal keratitis.

RESULTS

Excessive inflammation can lead to stromal damage and corneal opacification, hence the research on immune mechanism provides many potential therapeutic targets for fungal keratitis. Many researchers discussed the importance of earlier definitive diagnosis and were trying to find rapid and accurate diagnostic methods of pathogens. Develop new drug delivery systems and new routes of administration with better corneal penetration, prolonged ocular residence time, and better mucoadhesive properties is also one of the research hotspots. Additionally, many novel therapeutic agents and methods have been gradually applied in clinical ophthalmology.

CONCLUSION

The diagnosis and treatment of fungal keratitis are still a challenge for ophthalmologist, and many researches provide new methods to conquer these problems.

Establishment, Validation, and Initial Application of a Sensitive LC-MS/MS Assay for Quantification of the Naturally Occurring Isomers Itaconate, Mesaconate, and Citraconate

Itaconate is derived from the tricarboxylic acid (TCA) cycle intermediate cis-aconitate and links innate immunity and metabolism. Its synthesis is altered in inflammation-related disorders and it therefore has potential as clinical biomarker. Mesaconate and citraconate are naturally occurring isomers of itaconate that have been linked to metabolic disorders, but their functional relationships with itaconate are unknown. We aimed to establish a sensitive high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay for the quantification of itaconate, mesaconate, citraconate, the pro-drug 4-octyl-itaconate, and selected TCA intermediates. The assay was validated for itaconate, mesaconate, and citraconate for intra- and interday precision and accuracy, extended stability, recovery, freeze/thaw cycles, and carry-over. The lower limit of quantification was 0.098 µM for itaconate and mesaconate and 0.049 µM for citraconate in 50 µL samples. In spike-in experiments, itaconate remained stable in human plasma and whole blood for 24 and 8 h, respectively, whereas spiked-in citraconate and mesaconate concentrations changed during incubation. The type of anticoagulant in blood collection tubes affected measured levels of selected TCA intermediates. Human plasma may contain citraconate (0.4-0.6 µM, depending on the donor), but not itaconate or mesaconate, and lipopolysaccharide stimulation of whole blood induced only itaconate. Concentrations of the three isomers differed greatly among mouse organs: Itaconate and citraconate were most abundant in lymph nodes, mesaconate in kidneys, and only citraconate occurred in brain. This assay should prove useful to quantify itaconate isomers in biomarker and pharmacokinetic studies, while providing internal controls for their effects on metabolism by allowing quantification of TCA intermediates.

Itaconate ameliorates methicillin-resistant Staphylococcus aureus-induced acute lung injury through the Nrf2/ARE pathway

Background

Methicillin-resistant Staphylococcus aureus (MRSA) are a critical predisposing factor of sepsis in the clinic. As a product of human energy metabolism and immune response, itaconate can effectively reduce inflammation in the body. This research employed 4-octyl itaconate (4-OI) to illustrate that itaconate exerted anti-inflammatory effects to protect the body from acute lung injury (ALI) induced by MRSA.

Methods

HE staining and immunohistochemistry are used to evaluate the MRSA-induced ALI in mice. WB and qPCR were used to verify the effect of 4-OI on inflammation and oxidative stress caused by MRSA. Molecular docking was used to verify the binding sites of 4-OI and Keap1.

Results

We demonstrated that 4-OI treatment increased the survival ratio, attenuated the pathological damage, inhibited neutrophil infiltration, and reduced lung bacterial burden in the mouse MRSA pneumonia model. 4-OI decreased the expression of inflammatory factors by stimulating the Nrf2 in vivo and in vitro. Furthermore, 4-OI exerted its effect by promoting nuclear transport of Nrf2 in vitro. The results of molecular docking indicated that 4-OI bound to the pocket of Keap1 and exerted a stable interaction. Both Nrf2 inhibitors (ML385) and Nrf2^−/− mice abolished the protective effect of 4-OI on MRSA-induced inflammation both in vitro and in vivo.

Conclusions

4-OI prevents lung damage caused by MRSA bacteremia via activating Nrf2/ARE pathway.

Irg1-itaconate axis protects against acute kidney injury via activation of Nrf2

Acute kidney injury (AKI) is a common clinical implication with increased tissue damage, uncontrolled immune responses, and risk of mortality, in which ischemia-reperfusion injury (IRI) is one of the leading causes. As critical role for metabolic remodeling in inflammation, Irg1-itaconate axis has received much attention for its immunomodulation in the control of the inflammation. However, its role in the AKI and IRI remains unknown. Here, we found that Irg1 expression was negatively correlated with the expression of inflammatory cytokines during ischemia-reperfusion injury. And Irg1 deficiency promotes renal inflammation and ischemia-reperfusion injury in vivo. Itaconate treatment promoted the survival of WT mice from lethal ischemia and protected against renal IRI and systemic inflammation. Mechanistically, dimethyl itaconate protected renal cells from oxidative stress and prevented macrophage activation by enhancing the translocation of Nrf2 into the nuclei. Our study highlighted the importance of the Irg1-itaconate axis in the protecting against ischemia-reperfusion injury and acute kidney injury, providing potential therapeutic targets to control AKI.

Isorhamnetin Ameliorates Aspergillus fumigatus Keratitis by Reducing Fungal Load, Inhibiting Pattern-Recognition Receptors and Inflammatory Cytokines

Purpose

Isorhamnetin is a natural flavonoid with both antimicrobial and anti-inflammatory properties, but its effect on fungal keratitis (FK) remains unknown. The current study aims to investigate the antifungal and anti-inflammatory effects of isorhamnetin against mouse Aspergillus fumigatus keratitis.

Methods

In vitro, the lowest effective concentration of isorhamnetin was assessed by minimum inhibitory concentration and cytotoxicity tests in human corneal epithelial cells (HCECs) and RAW264.7 cells. The antifungal property was investigated by scanning electron microscopy and propidium iodide uptake test. The anti-inflammatory effect of isorhamnetin in HCECs and RAW264.7 cells was observed by quantitative real-time polymerase chain reaction (qRT-PCR). In the eyes of mice with A. fumigatus keratitis, FK severity was evaluated using clinical score, plate counting, histological staining and periodic acid Schiff staining. In vivo, the anti-inflammatory effect of isorhamnetin was examined by immunofluorescence staining, myeloperoxidase assay, Western blot, enzyme-linked immunosorbent assay, and qRT-PCR.

Results

In HCECs and RAW264.7 cells, isorhamnetin significantly inhibited A. fumigatus conidia growth and hyphae viability at 80 µg/mL without affecting cell viability. In vitro, isorhamnetin altered A. fumigatus hyphal morphology and membrane integrity. In A. fumigatus keratitis mouse model, isorhamnetin treatment alleviated the severity of FK by reducing corneal fungal load and inhibiting neutrophil recruitment. In addition, the mRNA and protein expression levels of TLR-2, TLR-4, Dectin-1, IL-1β, and tumor necrosis factor-α were significantly decreased in isorhamnetin-treated groups in vivo and in vitro.

Conclusions

Isorhamnetin improves the prognosis of A. fumigatus keratitis in mice by inhibiting the growth of A. fumigatus, reducing the recruitment of neutrophils and downregulating inflammatory factors.

Itaconate Alters Succinate and Coenzyme A Metabolism via Inhibition of Mitochondrial Complex II and Methylmalonyl-CoA Mutase

Itaconate is a small molecule metabolite that is endogenously produced by cis-aconitate decarboxylase-1 (ACOD1) in mammalian cells and influences numerous cellular processes. The metabolic consequences of itaconate in cells are diverse and contribute to its regulatory function. Here, we have applied isotope tracing and mass spectrometry approaches to explore how itaconate impacts various metabolic pathways in cultured cells. Itaconate is a competitive and reversible inhibitor of Complex II/succinate dehydrogenase (SDH) that alters tricarboxylic acid (TCA) cycle metabolism leading to succinate accumulation. Upon activation with coenzyme A (CoA), itaconyl-CoA inhibits adenosylcobalamin-mediated methylmalonyl-CoA (MUT) activity and, thus, indirectly impacts branched-chain amino acid (BCAA) metabolism and fatty acid diversity. Itaconate, therefore, alters the balance of CoA species in mitochondria through its impacts on TCA, amino acid, vitamin B₁₂, and CoA metabolism. Our results highlight the diverse metabolic pathways regulated by itaconate and provide a roadmap to link these metabolites to potential downstream biological functions.

4-Octyl Itaconate Alleviates Lipopolysaccharide-Induced Acute Lung Injury in Mice by Inhibiting Oxidative Stress and Inflammation

Background

Acute lung injury (ALI) is a fatal disease in the absence of pharmacological treatment. Oxidative stress and inflammation are closely related to ALI. Innate immune cells are the main source of reactive oxygen species (ROS). Macrophages play an extremely important role in ALI through the activation of inflammation and oxidative stress. Itaconate, a metabolite of tricarboxylic acid, has been reported to have strong antioxidant and anti-inflammatory effects. However, the role of itaconate in ALI is unclear. Herein, we use 4-octyl itaconate (OI), the cellular permeable derivate of itaconate, to study the effects of itaconate in vivo and in vitro.

Methods

We used OI to pretreat C57BL/6 mice and LPS-induced ALI models to illustrate the role of itaconate in acute lung injury. The mice were randomly divided into four groups: control group, OI (100 mg/kg) group, ALI Group, ALI + OI (50 mg/kg) group, and ALI + OI (100 mg/kg) group. RAW264.7 cells were used to further prove the role and mechanism of itaconate in vitro.

Results

According to the H&E staining of the lung, OI was observed to significantly reduce lung inflammation. The active oxygen content of tissues was also significantly reduced (P<0.05). OI reduced the accumulation of neutrophils and secretion of inflammatory factors in LPS-induced ALI (P<0.05). At the cellular level, OI also reduced oxidative stress and inflammation. Intervention with OI was also observed to upregulate the expression of nuclear factor erythroid 2-related factor-2 (Nrf-2) and Nrf-2 target genes in the lung tissue and RAW264.7 cells.

Conclusion

OI alleviates LPS-induced ALI. Moreover, the antioxidant and anti-inflammatory effects of OI might depend on the activation of Nrf-2. Therefore, OI might have therapeutic potential for the treatment of ALI.

Exploring the evolutionary roots and physiological function of itaconate

New small molecules are continuing to emerge as metabolically derived regulators of cell function. Itaconate is a recent example where endogenous mammalian synthesis was demonstrated only seven years ago. Since then, interest in the biochemistry and therapeutic potential of itaconate has grown dramatically. Itaconate is an unsaturated dicarboxylic acid that has antimicrobial properties and modulates metabolic pathways throughout the cell. Naturally occurring mutations of enzymes involved in human itaconate synthesis and degradation pathways are associated with disease susceptibility and immunity. Here, we highlight recent discoveries on itaconate metabolism and discuss the relevance of its evolutionary origin to its function in mammals. We also consider the therapeutic relevance of itaconate metabolism and its derivatives for treating metabolic and inflammatory diseases.

Itaconate: A Metabolite Regulates Inflammation Response and Oxidative Stress

Metabolic products can lead to crucial biological function alterations. Itaconate is probably the best example of how a metabolic process can be diverted to generate an immunomodulator effect in macrophages. Through inflammatory stimuli, such as lipopolysaccharide, the immune response gene 1 is activated and promotes the production of itaconate from the tricarboxylic acid cycle by decarboxylating cis-aconitate. Itaconate has been reported to have multiple immunoregulatory and antioxidative effects. In addition, reports have described its antibacterial and protumor effects. The involved mechanism in these effects includes the activation of nuclear factor E2-related factor 2 by alkylation of Kelch-like ECH-associated protein 1, inhibition of aerobic glycolysis by targeting glyceraldehyde-3-phosphate dehydrogenase and fructose-bisphosphate aldolase A, inhibition of succinate dehydrogenase, and blockade of IκBζ translation. All of these discoveries elucidated the transformation of the pro- into anti-inflammatory status in macrophages, which is crucial in innate immunity and set the ground for the emerging therapeutic implications of itaconate. In this review, we point out that itaconate is a novel and pivotal metabolic determinant of the immunoregulatory response in macrophages and highlight studies that have improved our understanding of the connection between the immune response and metabolism. In addition, we shed light on the therapeutic potential of itaconate and its derivatives to treat inflammatory diseases.