LOX-1 and TLR4 affect each other and regulate the generation of ROS in A. fumigatus keratitis

Immune Mechanisms of Filamentous Fungal Keratitis

Filamentous fungal keratitis is a particularly serious eye infection that often results in ulceration, corneal perforation, and blindness. The cornea acts as a natural barrier against harmful agents due to the close connection of its epithelial cells. In addition, on its surface, there is a large number of substances with anti-inflammatory and bactericidal properties, such as secretory IgA and mucin glycoproteins, and antimicrobial peptides (AMPs), such as human β-defensin 2 (HBD-2) and LL-37, which are especially increased in filamentous fungal keratitis. The interaction between pathogenic fungi and the host's immune mechanisms is a complex process: pathogen-associated molecular pattern (PAMP) molecules (chitin, β-glucan, and mannan) found in the fungal cell wall are recognized by pattern recognition receptors (PRRs) (toll-like receptors {TLRs}, C-type lectin receptors {CLRs}, nucleotide-binding oligomerization domain-like receptors {NLRs}, and scavenger receptors {SR}) found in host defense cells, triggering the secretion of various types of cytokines, such as interleukins (IL), tumor necrosis factors (TNFs), and chemokines, which recruit macrophages and neutrophils to migrate to the site of infection and activate inflammatory responses. In addition, the interaction of hyphae and corneal epithelial cells can activate cluster of differentiation (CD) 4+ T cells, CD8+ T cells, and B cells and induce secretion of T-helper (Th)-type cytokines 2 (IL-4 and IL-13) and IgG.

Plumbagin inhibits fungal growth, HMGB1/LOX-1 pathway and inflammatory factors in A. fumigatus keratitis

To investigate the anti-inflammatory and antifungal effects of plumbagin (PL) in Aspergillus fumigatus (A. fumigatus) keratitis, the minimum inhibitory concentration (MIC), time-killing curve, spore adhesion, crystal violet staining, calcium fluoride white staining, and Propidium Iodide (PI) staining were employed to assess the antifungal activity of PL in vitro against A. fumigatus. The cytotoxicity of PL was assessed using the Cell Counting Kit-8 (CCK8). The impact of PL on the expression of HMGB1, LOX-1, TNF-α, IL-1β, IL-6, IL-10 and ROS in A. fumigatus keratitis was investigated using RT-PCR, ELISA, Western blot, and Reactive oxygen species (ROS) assay. The therapeutic efficacy of PL against A. fumigatus keratitis was assessed through clinical scoring, plate counting, Immunofluorescence and Hematoxylin-Eosin (HE) staining. Finally, we found that PL inhibited the growth, spore adhesion, and biofilm formation of A. fumigatus and disrupted the integrity of its cell membrane and cell wall. PL decreased IL-6, TNF-α, and IL-1β levels while increasing IL-10 expression in fungi-infected mice corneas and peritoneal macrophages. Additionally, PL significantly attenuated the HMGB1/LOX-1 pathway while reversing the promoting effect of Boxb (an HMGB1 agonist) on HMGB1/LOX-1. Moreover, PL decreased the level of ROS. In vivo, clinical scores, neutrophil recruitment, and fungal burden were all significantly reduced in infected corneas treated with PL. In summary, the inflammatory process can be inhibited by PL through the regulation of the HMGB-1/LOX-1 pathway. Simultaneously, PL can exert antifungal effects by limiting fungal spore adhesion and biofilm formation, as well as causing destruction of cell membranes and walls.

Schaftoside reduces inflammation in Aspergillus fumigatus keratitis through the inhibition of the TLR4/MyD88 pathway

PURPOSE

The purpose of this research study was to investigate the impact of schaftoside on Aspergillus fumigatus (A. fumigatus) keratitis and elucidate its underlying mechanisms.

METHODS

In order to establish safe experimental concentrations of schaftoside in human corneal epithelial cells (HCECs), RAW264.7 cells, and mouse models, various techniques were employed including cytotoxicity assay (CCK-8) assay, cell scratch assay, and Draize test. The therapeutic effect of schaftoside was assessed using slit-lamp biomicroscopy, clinical scores, as well as determination of neutrophil infiltration through hematoxylin and eosin (HE) staining, immunofluorescence (IF) staining, and myeloperoxidase (MPO) assay. The levels of Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), pro-inflammatory mediators interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 were determined using quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and IF techniques.

RESULTS

Schaftoside at a concentration of 160 μM displayed no harmful side effects on HCECs, RAW cells, and mouse corneas, rendering it suitable for further experiments. In a murine fungal keratitis model, schaftoside mitigated the severity of fungal keratitis by inhibiting neutrophil infiltration and reducing MPO activity. Both in vitro and in vivo experiments demonstrated that schaftoside treatment suppressed the upregulation of IL-1β, TNF-α, and IL-6 expression, while also downregulating the expressions of TLR4 as well as MyD88 at both mRNA and protein levels.

CONCLUSIONS

Schaftoside demonstrated a protective effect against A. fumigatus keratitis by reducing corneal damage through inhibition of neutrophil recruitment and downstream inflammatory cytokines. The anti-inflammatory properties of schaftoside in A. fumigatus keratitis may involve modulation of the TLR4/MyD88 pathway.

Multifunctional Polymer Vesicles for Synergistic Antibiotic-Antioxidant Treatment of Bacterial Keratitis

As an acute ophthalmic infection, bacterial keratitis (BK) can lead to severe visual morbidity, such as corneal perforation, intraocular infection, and permanent corneal opacity, if rapid and effective treatments are not available. In addition to eradicating pathogenic bacteria, protecting corneal tissue from oxidative damage and promoting wound healing by relieving inflammation are equally critical for the efficient treatment of BK. Besides, it is very necessary to improve the bioavailability of drugs by enhancing the ocular surface adhesion and corneal permeability. In this investigation, therefore, a synergistic antibiotic-antioxidant treatment of BK was achieved based on multifunctional block copolymer vesicles, within which ciprofloxacin (CIP) was simultaneously encapsulated during the self-assembly. Due to the phenylboronic acid residues in the corona layer, these vesicles exhibited enhanced muco-adhesion, deep corneal epithelial penetration, and bacteria-targeting, which facilitated the drug delivery to corneal bacterial infection sites. Additionally, the abundant thioether moieties in the hydrophobic membrane enabled the vesicles to both have ROS-scavenging capacity and accelerated CIP release at the inflammatory corneal tissue. In vivo experiments on a mice model demonstrated that the multifunctional polymer vesicles achieved efficient treatment of BK, owing to the enhanced corneal adhesion and penetration, bacteria targeting, ROS-triggered CIP release, and the combined antioxidant-antibiotic therapy. This synergistic strategy holds great potential in the treatment of BK and other diseases associated with bacterial infections.

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.

Innate Immune System Activation, Inflammation and Corneal Wound Healing

Corneal wounds resulting from injury, surgeries, or other intrusions not only cause pain, but also can predispose an individual to infection. While some inflammation may be beneficial to protect against microbial infection of wounds, the inflammatory process, if excessive, may delay corneal wound healing. An examination of the literature on the effect of inflammation on corneal wound healing suggests that manipulations that result in reductions in severe or chronic inflammation lead to better outcomes in terms of corneal clarity, thickness, and healing. However, some acute inflammation is necessary to allow efficient bacterial and fungal clearance and prevent corneal infection. This inflammation can be triggered by microbial components that activate the innate immune system through toll-like receptor (TLR) pathways. In particular, TLR2 and TLR4 activation leads to pro-inflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activation. Similarly, endogenous molecules released from disrupted cells, known as damage-associated molecular patterns (DAMPs), can also activate TLR2, TLR4 and NFκB, with the resultant inflammation worsening the outcome of corneal wound healing. In sterile keratitis without infection, inflammation can occur though TLRs to impact corneal wound healing and reduce corneal transparency. This review demonstrates the need for acute inflammation to prevent pathogenic infiltration, while supporting the idea that a reduction in chronic and/or excessive inflammation will allow for improved wound healing.

Roles of pattern recognition receptors in response to fungal keratitis

Fungal keratitis is one of the leading causes of blindness worldwide, which has become an increasingly serious threat to public ocular health, but no effective treatment strategies are available now. Pattern recognition receptors (PRRs) of the innate immune system are the first line of host defense against fungal infections. They could recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and trigger an array of inflammatory responses. Over the last decades, research has resulted in significant progress regarding the roles of PRRs in fungal keratitis. This review will highlight the importance of several pattern recognition receptors (C-type lectin-like receptors, Toll-like receptors, and NOD-like receptors) in regulating the innate immunity under fungal keratitis and describe the crosstalk and collaboration in PRRs contributing to disease pathology. Meanwhile, some potential therapy-based PRRs against corneal fungal infections are discussed.

TLR4-Dependent DUOX2 Activation Triggered Oxidative Stress and Promoted HMGB1 Release in Dry Eye

Dry eye disease (DED) is one of the most common ocular surface diseases worldwide. DED has been characterized by excessive accumulation of reactive oxygen species (ROS), following significant corneal epithelial cell death and ocular surface inflammation. However, the key regulatory factor remains unclear. In this study, we tended to explore whether DUOX2 contributed to DED development and the underlying mechanism. Human corneal epithelial (HCE) cells were treated with hyperosmolarity, C57BL/6 mice were injected of subcutaneous scopolamine to imitate DED. Expression of mRNA was investigated by RNA sequencing (RNA-seq) and quantitative real-time PCR (qPCR). Protein changes and distribution of DUOX2, high mobility group box 1 (HMGB1), Toll-like receptor 4 (TLR4), and 4-hydroxynonenal (4-HNE) were evaluated by western blot assays and immunofluorescence. Cell death was assessed by Cell Counting Kit-8 (CCK8), lactate dehydrogenase (LDH) release, and propidium iodide (PI) staining. Cellular ROS levels and mitochondrial membrane potential (MMP) were analyzed by flow cytometry. RNA-seq and western blot assay indicated a significant increase of DUOX2 dependent of TLR4 activation in DED both in vitro and in vivo. Immunofluorescence revealed significant translocation of HMGB1 within corneal epithelial cells under hyperosmolar stress. Interestingly, after ablated DUOX2 expression by siRNA, we found a remarkable decrease of ROS level and recovered MMP in HCE cells. Moreover, knockdown of DUOX2 greatly inhibited HMGB1 release, protected cell viability and abolished inflammatory activation. Taken together, our data here suggest that upregulation of DUOX2 plays a crucial role in ROS production, thereafter, induce HMGB1 release and cell death, which triggers ocular surface inflammation in DED.

The role of Glabridin in antifungal and anti-inflammation effects in Aspergillus fumigatus keratitis

PURPOSE

To investigate the effect of Glabridin (GLD) in Aspergillus fumigatus keratitis and its associated mechanisms.

METHODS

Aspergillus fumigatus (A. fumigatus) conidia was inoculated in 96-well plate, and minimal inhibitory concentration (MIC) and biofilm formation ability were evaluated after GLD treatment. Spore adhesion ability was evaluated in conidia infected human corneal epithelial cells (HCECs). Keratitis mouse model was created by corneal intrastromal injection with A. fumigatus conidia, and GLD treatment started at the day after infection. The number of fungal colonies was calculated by plate count, and degree of corneal inflammation was assessed by clinical score. Flow cytometry, myeloperoxidase (MPO), and immunofluorescence staining (IFS) experiments were used to assess neutrophil infiltrations. PCR, ELISA and Western blot were conducted to determine levels of TLR4, Dectin-1 as well as downstream inflammatory factors.

RESULTS

GLD treatment suppressed the proliferation, biofilm formation abilities and adhesive capability of A. fumigatus. In mice upon A. fumigatus infection, treatment of GLD showed significantly decreased severity of corneal inflammation, reduced number of A. fumigatus in cornea, and suppressed neutrophil infiltration in cornea. GLD treatment obviously inhibited mRNA and protein levels of Dectin-1, TLR4 and proinflammatory mediators such as IL-1β, HMGB1, and TNF-α in mice corneas compared to the control group.

CONCLUSION

GLD has antifungal and anti-inflammatory effects in fungal keratitis through suppressing A. fumigatus proliferation and alleviating neutrophil infiltration, and repressing the expression of TLR4, Dectin-1 and proinflammatory mediators.

Stabilin-1 plays a protective role against Listeria monocytogenes infection through the regulation of cytokine and chemokine production and immune cell recruitment

Scavenger receptors are part of a complex surveillance system expressed by host cells to efficiently orchestrate innate immune response against bacterial infections. Stabilin-1 (STAB-1) is a scavenger receptor involved in cell trafficking, inflammation, and cancer; however, its role in infection remains to be elucidated. Listeria monocytogenes (Lm) is a major intracellular human food-borne pathogen causing severe infections in susceptible hosts. Using a mouse model of infection, we demonstrate here that STAB-1 controls Lm-induced cytokine and chemokine production and immune cell accumulation in Lm-infected organs. We show that STAB-1 also regulates the recruitment of myeloid cells in response to Lm infection and contributes to clear circulating bacteria. In addition, whereas STAB-1 appears to promote bacterial uptake by macrophages, infection by pathogenic Listeria induces the down regulation of STAB-1 expression and its delocalization from the host cell membrane.

We propose STAB-1 as a new SR involved in the control of Lm infection through the regulation of host defense mechanisms, a process that would be targeted by bacterial virulence factors to promote infection.

LOX-1 Regulates Neutrophil Apoptosis and Fungal Load in A. Fumigatus Keratitis

PURPOSE

To determine whether LOX-1 regulates neutrophil apoptosis and fungal load in A. fumigatus keratitis.

METHODS

Fas, FasL, CASP3, CASP8, CASP9 and BCL2 were tested in normal and infected corneas of C57BL/6 mice. Mice corneas were infected with A. fumigatus with or without pretreatment of LOX-1 neutralizing antibody or inhibitor (Poly I). Clinical score was recored and HE staining was tested. Fungal load in mice corneas was observed by plate counting. Poly morphonuclear neutrophilic leukocytes (PMNs) were stimulated with 75% ethanol-killed A. fumigatus with or without pretreatment of LOX-1 neutralizing antibody or Poly I. PCR, western blot and immunostaining tested expression of Fas, FasL, CASP3, CASP8, CASP9, BCL2 and cleaved caspase-3. PMNs infiltration and TUNEL-positive cells were assessed by immunofluorescent staining. Flow cytometry assay tested the percentage of apoptosis neutrophils.

RESULTS

Fas, Fas ligand, caspase-8, caspase-9 and caspase-3 mRNA levels were significantly higher in C57BL/6 mice corneas infected with A. fumigatus than normal corneas. Poly I treatment alleviated the severity and decreased clinical score at 3, 5 and 7 days post infecrion (p.i.). HE staining showed less infiltration in corneal tissue after LOX-1 inhibition. Plate counting experiment showed that number of viable fungus in corneas of Poly I treated group was significantly less than control group. LOX-1 neutralizing antibody or Poly I treatment significantly decreased neutrophil infiltration, the quantity of TUNEL-positive cells, the expression of Fas, Fas ligand, caspase-8, caspase-9, caspase-3, cleaved caspase-3 and the percentage of apoptosis neutrophils compared with control corneas. LOX-1 neutralizing antibody treatment significantly decreased Fas, FasL, CASP3, CASP8, CASP9 and cleaved caspase-3 expression in neutrophils.

CONCLUSION

LOX-1 inhibition decrease neutrophil apoptosis and fungal load in A. fumigatus keratitis.

Immunologic mechanism of fungal keratitis

Fungal keratitis (FK) is a refractory disease that poses a serious threat to vision, with common risk factors like eye trauma, contact lens wearing, topical corticosteroids and antibiotic abuse. Nowadays, topical and systemic anti-fungal drugs and ocular surgeries are still the main therapeutic modalities. However, the pathogenesis of FK, especially the immunologic mechanism within it, has not yet been deeply clarified. A better understanding of the pathogenesis of FK is imperative for more effective therapies and prognosis. Meanwhile, the immune protection strategies are also urgently required to manage FK. This review highlights recent advances in the immunologic mechanism in the pathogenesis of FK, in hope of providing valuable reference information for more effective anti-fungal treatment.

Inhibition of miR-665-3p Enhances Autophagy and Alleviates Inflammation in Fusarium solani-Induced Keratitis

Purpose

Accumulated evidence has shown that microRNAs (miRNAs) are closely related with the regulation of autophagy, which plays vital roles in fungal keratitis (FK). Microarray data showed elevated expression of miR-665-3p in mouse corneal tissues after infection with Fusarium solani (F. solani). Here, we investigated the effect of miR-665-3p in regulating autophagy in experimental F. solani keratitis and determined the potential molecular mechanisms involved.

Methods

In this article, we established an in vivo mouse model of FK and an in vitro model of corneal stromal cells by inoculating with F. solani. We divided them into the following six groups: control, chloroquine (CQ), rapamycin (Rapa), miR-665-3p antagomir (ant-665), miR-665-3p agomir (miR-665), and the negative control group (miR-NC). The levels of autophagy were detected by electron microscopy, Western blotting, and immunofluorescence. Then, we used a dual-luciferase reporter assay to determine the binding of miR-665-3p to the autophagy-related gene (ATG)5 3'UTR. Detection of IL-1β protein levels and hematoxylin and eosin (H&E) staining of corneal tissues were used to observe the effect of miR-665-3p on inflammation in FK.

Results

Here, we showed that inhibition of miR-665-3p expression in FK upregulated autophagy and alleviated inflammation. Nevertheless, the opposite results were found by overexpressing miR-665-3p. Additionally, ATG5 was a direct target gene for miR-665-3p.

Conclusions

Together, our data demonstrated that miR-665-3p might be involved in F. solani keratitis of mice by regulating autophagic pathways and inflammation.

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.

The cornea IV immunology, infection, neovascularization, and surgery chapter 1: Corneal immunology

PURPOSE

of Review: This review offers an informed and up-to-date insight on the immune profile of the cornea and the factors that govern the regulation of such a unique immune environment.

SUMMARY

The cornea is a unique tissue that performs the specialized task of allowing light to penetrate for visual interpretation. To accomplish this, the ocular surface requires a distinct immune environment that is achieved through unique structural, cellular and molecular factors. Not only must the cornea be able to fend off invasive infectious agents but also control the inflammatory response as to avoid collateral, and potentially blinding damage; particularly of post-mitotic cells such as the corneal endothelium. To combat infections, both innate and adaptive arms of the inflammatory immune response are at play in the cornea. Dendritic cells play a critical role in coordinating both these responses in order to fend off infections. On the other side of the spectrum, the ocular surface is also endowed with a variety of anatomic and physiologic components that aid in regulating the immune response to prevent excessive, potentially damaging, inflammation. This attenuation of the immune response is termed immune privilege. The balance between pro and anti-inflammatory reactions is key for preservation of the functional integrity of the cornea.

RECENT FINDINGS

The understanding of the molecular and cellular factors governing corneal immunology and its response to antigens is a growing field. Dendritic cells in the normal cornea play a crucial role in combating infections and coordinating the inflammatory arms of the immune response, particularly through coordination with T-helper cells. The role of neuropeptides is recently becoming more highlighted with different factors working on both sides of the inflammatory balance.

GSDMD, an executor of pyroptosis, is involved in IL-1β secretion in Aspergillus fumigatus keratitis

The protein GSDMD is an important performer of pyroptosis and a universal substrate for the inflammatory caspase. However, the role and regulatory mechanism of GSDMD in Aspergillus fumigatus keratitis is remains unknown. Here we detected GSDMD protein in the cornea of normal and fungal-infected C57BL/6 mice. Human corneal epithelial cell (HCECs) were preincubated with a hydrochloride solution (IFNR inhibitor), ruxolitinib (JAK/STAT inhibitor), belnacasan (caspase-1 inhibitor) before infection with A. fumigatus conidia. Mice corneas were infected with Aspergillus fumigatus after pretreatment of GSDMD siRNA via subconjunctival injection. After, samples were harvested at specific time points and the expression of GSDMD and IL-1β was assessed by PCR, Western blot and immunofluorescence staining. Compared with the control group, we observed that the expression of GSDMD in fungal-infected mice cornea was significantly increased. After pretreatment with IFNR, JAK/STAT and caspase-1 inhibitors before fungal infection, the expression of GSDMD was significantly inhibited compared to the DMSO control in HCECs. Moreover, the GSDMD siRNA treatment have significantly weaken corneal inflammatory response, decreasing the proinflammatory factor IL-1β secretion and reducing neutrophils and macrophages recruitment in mice infected corneas. In summary, the data here provided evidences that GSDMD, an executor of pyroptosis, is involved in the early immune response of A. fumigatus keratitis. Additionally, the inhibition of GSDMD expression can affect the secretion of IL-1β and the recruitment of neutrophil and macrophages by blocking IFNR, JAK/STAT and caspase-1 signaling pathway. The protein GSDMD may emerge as a potential therapeutic target for A. fumigatus keratitis.

Analysis of differentially expressed genes in bacterial and fungal keratitis

Purpose:

This study was aimed at identifying differentially expressed genes (DEGs) in bacterial and fungal keratitis. The candidate genes can be selected and quantified to distinguish between causative agents of infectious keratitis to improve therapeutic outcomes.

Methods:

The expression profile of bacterial or fungal infection, and normal corneal tissues were downloaded from the Gene Expression Omnibus. The limma package in R was used to screen DEGs in bacterial and fungal keratitis. The Co-Express tool was used to calculate correlation coefficients of co-expressed genes. The “Advanced network merge” function of Cytoscape tool was applied to obtain a fusional co-expression network based on bacterial and fungal keratitis DEGs. Finally, functional enrichment analysis by DAVID software and KEGG analysis by KOBAS of DEGs in fusion network were performed.

Results:

In total, 451 DEGs in bacterial keratitis and 353 DEGs in fungal keratitis were screened, among which 148 DEGs were found only in bacterial keratitis and 50 DEGs only in fungal keratitis. Besides, 117 co-expressed gene pairs were identified among bacterial keratitis DEGs and 87 pairs among fungal keratitis DEGs. In total, nine biological pathways and seven KEGG pathways were screened by analyzing DEGs in the fusional co-expression network.

Conclusion:

TLR4 is the representative DEG specific to bacterial keratitis, and SOD2 is the representative DEG specific to fungal keratitis, both of which are promising candidate genes to distinguish between bacterial and fungal keratitis.

Matrix Metalloproteinase 9 is Regulated by LOX-1 and erk1/2 Pathway in Dental Peri-Implantitis

BACKGROUND AND OBJECTIVE

Dental peri-implantitis, which can be caused by several different microbial factors, is characterized by inflammatory lesions of the surrounding hard and soft tissues of an oral implant. Matrix Metalloproteinase 9 (MMP9) is thought to be involved in the pathogenesis of peri-implantitis. However, the regulatory mechanism of MMP9 in peri-implantitis has not been fully elucidated. In this study, we tried to evaluate the regulatory mechanism of MMP9 in peri-implantitis.

METHODS

We collected Peri-Implant Crevicular Fluid (PICF) from ten healthy implants and ten periimplantitis patients and compared their expression level of MMP9. We also cultured macrophages from the peripheral blood of healthy volunteers infected by Porphyromonas gingivalis to reveal the regulatory mechanism of MMP9 in peri-implantitis. Western blot, immunofluorescence staining and quantitative Polymerase Chain Reaction (RT-PCR) were used to better characterize the mechanism of MMP9.

RESULTS

The expression of MMP9 was up-regulated in peri-implantitis patient PICF and P. gingivalis infected human macrophages. LOX-1, not dectin-1, was found to mediate MMP9 expression in human macrophages with P. gingivalis infection. Expression of Erk1/2 was responsible for infection-induced MMP9 expression. Finally, use of a broad-spectrum metalloproteinase inhibitor impaired LOX-1 expression in infected macrophages.

CONCLUSION

Our results demonstrate that MMP9 is involved in dental peri-implantitis and is regulated by LOX-1 and Erk1/2. This LOX-1/MMP9 signaling pathway may represent a potential drug target for peri-implantitis.

Bibliometric and visualized analysis of global research on fungal keratitis from 1959 to 2019

BACKGROUND

Fungal keratitis is one of the leading causes of ocular morbidity. The prognosis of fungal keratitis is poorer than many other forms of keratitis but the research of which relatively lags behind. We conducted a bibliometric and visualized analysis in order to characterize the overall status, general trends and current foci of keratomycosis research field.

METHODS

Literature database ranged from 1959 to 2019 was obtained from web of science core collection and analyzed by Citespace and VOSviewer software.

RESULTS

A total of 1906 papers of fungal keratitis were retrieved and derived a 27,917 references document set. The number of publications increased rapidly in past 30 years. Cornea was the journal published most papers of keratomycosis. The leading countries were United States of America (USA), India and Peoples Republic of China (PRC), from where came the most productive and most cited institutions and authors. Co-cited reference analysis revealed the most cited manuscripts were concerned about epidemiology or spectrum. Lens-associated Fusarium, amphotericin B, voriconazole, corneal cross-linking, predisposing factor are some of the high frequency topics in clustered co-cited reference analysis and co-occurrence keywords analysis. Burst detection analysis of keywords showed ocular drug delivery was the new research foci.

CONCLUSION

From this study, we received an overall view to the current status, trends and hot spots of fungal keratitis research field. Visualized bibliometric analysis is an efficient way for literature learning and useful for future researchers.

High-mobility group box1 as an amplifier of immune response and target for treatment in Aspergillus fumigatus keratitis

AIM

To determine the roles of high-mobility group box1 (HMGB1) in pro-inflammation, host immune response and its potential target for treatment in Aspergillus fumigatus (A.fumigatus) keratitis.

METHODS

Expression of HMGB1 was tested in C57BL/6 normal and infected corneas. Dual immunostaining tested co-expression of HMGB1 with TLR4 or LOX-1. C57BL/6 mice were pretreated with Box A or PBS and then infected. Clinical scores, polymerase chain reaction, ELISA, and MPO assay were used to assess the disease response. Flow cytometry were used to test the effect of Box A on reactive oxygen species (ROS) expression after A.fumigatus stimulation in polymorphonuclear neutrophilic leukocytes (PMN). C57BL/6 peritoneal macrophages were pretreated with Box B before A.fumigatus stimulation, and MIP-2, IL-1β, TNF-α, HMGB1 and LOX-1 were measured. Macrophages were pretreated with Box B or Box B combined with Poly(I) (an inhibitor of LOX-1) before stimulating with A.fumigatus, and MIP-2, IL-1β, TNF-α, LOX-1, p38-MAPK, p-p38-MAPK were measured.

RESULTS

HMGB1 levels were elevated in C57BL/6 mice after infection. HMGB1 co-expressed with TLR4, and LOX-1 in infiltrated cells. Box A vs PBS treated C57BL/6 mice had lower clinical scores and down-regulated corneal HMGB1, MIP-2, IL-1β expression and neutrophil influx. Box B treatment amplified expression of MIP-2, IL-1β, TNF-α, HMGB1 and LOX-1 that induced by A.fumigatus in macrophage. Compared to the treatment of Box B only, the protein expression of IL-1β, TNF-α showed inhibition of Box B combined with Poly(I), which also reduced the A.fumigatus-evoked protein level of LOX-1 and phosphorylation level of p38-MAPK. The production of A.fumigatus-stimulated ROS was significantly declined after Box A pretreatment in PMN.

CONCLUSION

Blocking HMGB1 reduces the disease response in C57BL/6 mice. HMGB1 can amplify the host immune response through p38-MAPK, and is a target for treatment of A.fumigatus keratitis.

Paeonol ameliorates murine alcohol liver disease via mycobiota-mediated Dectin-1/IL-1β signaling pathway

Alcoholic liver disease (ALD) is caused by long-term consumption of alcohol and has become an important social and medical problem. Intestinal fungal flora (mycobiota) play an important role in ALD, so we used the mycobiota as an entry point to explore the mechanism of action of Paeonol against ALD. Here, we found that Paeonol is effective against ALD inflammatory lesions and relieves liver fat lesions. Furthermore, we found that after the treatment of Paeonol, the fungal dysbiosis is improved, and the fungal abundance is reduced, and the translocation of β-glucan to the liver and its mediated Dectin-1/IL-1β signaling pathway is blocked. Our study shows that paeonol ameliorated acute ALD-related inflammatory injury to the liver by alleviating intestinal fungal dysbiosis and inhibiting the mycobiota-mediated Dectin-1/IL-1β signaling pathway.

Inhibition of LOX-1 prevents inflammation and photoreceptor cell death in retinal degeneration

PURPOSE

To explore the expression and role of lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) in retinal degeneration.

METHODS

The retinal degeneration of BALB/c mice was induced by light exposure. BV2 cells were activated by LPS stimulation. Retinas or BV2 cells were pretreated with LOX-1 neutralizing antibody or Polyinosinic acid (PolyI) (the inhibitor of LOX-1) before light damage (LD) or LPS stimulation. LOX-1, TNF-α, IL-1β, CCL2 and NF-κB expression were detected in retinas or BV2 cells by real-time RT-PCR, western blot or ELISA. Histological analyses of retinas were performed. Photoreceptor cell death was assessed by TUNEL assay in retinas or by flow cytometry in 661W cells cultured in microglia-conditioned medium.

RESULTS

Photoreceptor cell death and elevated expression of LOX-1 were induced by LD in retinas of BALB/c mice. LOX-1 neutralizing antibody or PolyI pretreatment significantly reduced the elevated expression of LOX-1, TNF-α, IL-1β, CCL2 and p-NF-κB caused by LD in retinas. Inhibition of LOX-1 by LOX-1 neutralizing antibody or PolyI significantly reduced photoreceptor cell death induced by LD in retinas. Elevated levels of TNF-α, IL-1β and CCL2 caused by LPS were down-regulated by inhibition of LOX-1 in BV2 cells. Inhibition of LOX-1 reduces microglial neurotoxicity on photoreceptors.

CONCLUSIONS

LOX-1 expression is increased in light induced retinal degeneration, what's more, inhibition of LOX-1 prevents inflammation and photoreceptor cell death in retinal degeneration and reduces microglial neurotoxicity on photoreceptors. Therefore, LOX-1 can be used as a potential therapeutic target for such retinal degeneration diseases.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

C-type Lectins in Immunity to Lung Pathogens

The respiratory tract is tasked with responding to a constant and vast influx of foreign agents. It acts as an important first line of defense in the innate immune system and as such plays a crucial role in preventing the entry of invading pathogens. While physical barriers like the mucociliary escalator exert their effects through the clearance of these pathogens, diverse and dynamic cellular mechanisms exist for the activation of the innate immune response through the recognition of pathogen-associated molecular patterns (PAMPs). These PAMPs are recognized by pattern recognition receptors (PRRs) that are expressed on a number of myeloid cells such as dendritic cells, macrophages, and neutrophils found in the respiratory tract. C-type lectin receptors (CLRs) are PRRs that play a pivotal role in the innate immune response and its regulation to a variety of respiratory pathogens such as viruses, bacteria, and fungi. This chapter will describe the function of both activating and inhibiting myeloid CLRs in the recognition of a number of important respiratory pathogens as well as the signaling events initiated by these receptors.

PAMPs of the Fungal Cell Wall and Mammalian PRRs

Fungi are opportunistic pathogens that infect immunocompromised patients and are responsible for an estimated 1.5 million deaths every year. The antifungal innate immune response is mediated through the recognition of pathogen-associated molecular patterns (PAMPs) by the host's pattern recognition receptors (PRRs). PRRs are immune receptors that ensure the internalisation and the killing of fungal pathogens. They also mount the inflammatory response, which contributes to initiate and polarise the adaptive response, controlled by lymphocytes. Both the innate and adaptive immune responses are required to control fungal infections. The immune recognition of fungal pathogen primarily occurs at the interface between the membrane of innate immune cells and the fungal cell wall, which contains a number of PAMPs. This chapter will focus on describing the main mammalian PRRs that have been shown to bind to PAMPs from the fungal cell wall of the four main fungal pathogens: Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Pneumocystis jirovecii. We will describe these receptors, their functions and ligands to provide the reader with an overview of how the immune system recognises fungal pathogens and responds to them.

Fungal keratitis: Pathogenesis, diagnosis and prevention

As a kind of serious, potentially sight-threatening corneal infections with poor prognosis, fungal keratitis can bring a heavy economic burden to patients and seriously affect the quality of life, especially those in developing countries where fungal keratitis is more prevalent. Typical clinical features include immune rings, satellite lesions, pseudopods, hypha moss, hypopyon and endothelial plaques. The ideal therapeutic effects could not be achieved by current treatments for many reasons. Therefore, under the current status, understanding the pathogenesis, early diagnosis and prevention strategies might be of great importance. Here, in this review, we discuss the recent progresses that may advance our understanding of pathogenesis, early diagnosis and prevention of fungal keratitis.

Wnt5a is involved in LOX-1 and TLR4 induced host inflammatory response in peri-implantitis

BACKGROUND AND OBJECTIVE

Peri-implantitis is a plaque-associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri-implant mucosa and subsequent progressive loss of supporting bone. Wnt5a is the activating ligand of the non-canonical Wnt signaling pathways and plays important roles in leukocyte infiltration and cytokine/ chemokine production in inflammatory disorders. Previous studies showed that Wnt5a was significantly up-regulated in gingival tissues of chronic and aggressive periodontitis. However, the roles and the regulatory mechanisms of Wnt5a in peri-implantitis are not well known.

METHODS

The expression of Wnt5a in gingival tissues collected from 8 healthy implant patients and 8 peri-implantitis patients was analyzed by Western blotting and immunofluorescence. Porphyromonas gingivalis infected macrophages isolated from the peripheral blood of healthy volunteers were used as an in vitro cellular model of peri-implantitis. Using neutralizing antibodies, inhibitors and siRNA, the production and roles of Wnt5a in peri-implantitis were assessed by immunofluorescence, quantitative polymerase chain reaction (RT-PCR) and Western blotting. Unpaired two-tailed Student's t test was used to compare qRT-PCR and Western blotting results. P ≤ .05 was considered statistically significant.

RESULTS

Wnt5a was highly expressed in the gingival tissues of peri-implantitis patients. Compared to controls, Wnt5a increased in P gingivalis infected macrophages. Wnt5a production in response to P gingivalis infection was dependent on LOX-1 and TLR4. Compared to controls, Wnt5a knockdown impaired IL-1β, MCP-1, and MMP2 production induced by P gingivalis infection.

CONCLUSION

Our results indicate that Wnt5a is involved in LOX-1 and TLR4 induced inflammatory signature via inflammatory cytokines production in response to P gingivalis infection. These findings demonstrate that Wnt5a maybe an important component of the host immune response in peri-implantitis.

Inhibition of LOX-1 alleviates the proinflammatory effects of high-mobility group box 1 in Aspergillus fumigatus keratitis

AIM

To investigate the inflammatory amplification effect of high-mobility group box 1 (HMGB1) in Aspergillus fumigatus (A. fumigatus) keratitis and the relationship between lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) and HMGB1 in keratitis immune responses.

METHODS

Phosphate buffer saline (PBS), and Boxb were injected into BALB/c mice subconjunctivally before the corneas were infected with A. fumigatus. RAW264.7 macrophages and neutrophils were pretreated with PBS and Boxb to determine the HMGB1 inflammatory amplification effects. Abdominal cavity extracted macrophages were pretreated with Boxb and Poly (I) (a LOX-1 inhibitor) before A. fumigatus hyphae stimulation to prove the the relationship between the two molecules. LOX-1, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-2 (MIP-2) and IL-10 were assessed by polymerase chain reaction and Western blot.

RESULTS

Pretreatment with Boxb exacerbated corneal inflammation. In macrophages and neutrophils, A. fumigatus induced LOX-1, IL-1β, TNF-α and MIP-2 expression in Boxb group was higher than those in PBS group. Poly (I) treatments before infection alleviated the proinflammatory effects of Boxb in abdominal cavity extracted macrophages. Pretreatment with Boxb did not influence Dectin-1 mRNA levels in macrophages and neutrophils.

CONCLUSION

In fungal keratitis, HMGB1 is a proinflammatory factor in the first line of immune response. HMGB1 mainly stimulates neutrophils and macrophages to produce inflammatory cytokines and chemokines during the immune response. LOX-1 participates in HMGB1 induced inflammatory exacerbation in A. fumigatus keratitis.

S-ethyl ethanethiosulfinate, a derivative of allicin, induces metacaspase-dependent apoptosis through ROS generation in Penicillium chrysogenum

Allicin can be used as fumigant to protect food and cultural relics from fungal contamination because of its strong antifungal activity and the characteristics of high volatility and no residues. However, the obvious disadvantages such as high minimal inhibitory concentration and instability prevent it from wide application. In this study, a stable derivative of allicin, S-ethyl ethanethiosulfinate (ALE), was synthesized. We further explored its antifungal activity and apoptosis-inducing effect, as well as the underlying mechanism. ALE had an excellent capability of inhibiting spore germination and mycelial growth of Penicillium chrysogenum observed by inverted microscope and scanning electron microscopy. XTT colorimetric assay indicated ALE could reduce the cell viability obviously and IC₅₀ was 0.92 μg/ml, only 1/42 of allicin (38.68 μg/ml). DHR 123 ROS Assay Kit, flow cytometry assay and confocal immunofluorescence revealed intercellular ROS generation and metacaspase-dependent apoptosis triggered by ALE, while antioxidant tocopherol could reverse ALE-induced cytotoxicity effect and metacaspase activation. These results indicate that ALE induces metacaspase-dependent apoptosis through ROS generation, thus possesses an effective antifungal activity. This new derivative of allicin might be developed as a high efficient alternative to the conventional fungicides for food storage and cultural relic protection.

ATF4 Involvement in TLR4 and LOX-1-Induced Host Inflammatory Response to Aspergillus fumigatus Keratitis

Purpose

Activating transcription factor 4 (ATF4) is induced by various stressors. Here, we investigated the expression of ATF4 in the host inflammatory response to Aspergillus fumigatus (A. fumigatus) keratitis.

Methods

A. fumigatus keratitis mouse models developed by intrastromal injection as well as corneal epithelium scratching were examined daily with a slit lamp microscope for corneal opacification and ulceration. Subsequent in vitro experimentation was carried out in human corneal epithelial cells (HCECs) as well as THP-1 macrophages infected with A. fumigatus. Inhibitors, including CLI-095, Poly (I), SCH772984, and SP600125, were used to assess the role of proteins like toll-like receptor 4 (TLR4), lectin-type oxidized LDL receptor 1 (LOX-1), extracellular signal-regulated kinases (ERK1/2), and c-Jun N-terminal kinase (JNK) in ATF4 expression as a response to A. fumigatus infection. This assessment was made in both mouse models and HCECs using western blot.

Results

Compared to the controls, ATF4 was increased in corneas from two kinds of A. fumigatus keratitis models at 3 days after infection. ATF4 expression was upregulated with A. fumigatus conidia both in HCECs and THP-1 macrophages 16 hours after stimulation. Furthermore, ATF4 expression in response to A. fumigatus infection was shown to be dependent on TLR4 and LOX-1 expression, and ERK1/2 and JNK contributed to the expression of ATF4 in response to A. fumigatus.

Conclusion

Our results clearly indicate that ATF4 was involved in the host antifungal immune response to A. fumigatus keratitis; expression was found to be dependent on TLR4, LOX-1 expression, and MAPKs pathway.

Fenretinide Inhibits Neutrophil Recruitment and IL-1β Production in Aspergillus fumigatus Keratitis

Purpose:

Fungal keratitis is a major cause of corneal ulcers, resulting in significant visual impairment and blindness. Fenretinide, a derivative of vitamin A, has been shown to suppress inflammation in a multitude of diseases. In this study, we aimed to characterize the effect of fenretinide in Aspergillus fumigatus keratitis of the eye in a mouse model.

Methods:

In vivo and in vitro experiments were performed in mouse models and THP-1 macrophage cell cultures infected with A. fumigatus, respectively. Experimental subjects were first pretreated with fenretinide, and then the effect of the compound was assessed with clinical evaluation, neutrophil staining, myeloperoxidase assay, quantitative polymerase chain reaction (qRT-PCR), and western blot.

Results:

We confirmed that fenretinide contributed to protection of corneal transparency during early mouse A. fumigatus keratitis by reducing neutrophil recruitment, decreasing myeloperoxidase (MPO) levels and increasing apoptosis. Compared with controls, fenretinide impaired proinflammatory cytokine interleukin 1 beta (IL-1β) production in response to A. fumigatus exposure with contributions by lectin-type oxidized LDL receptor 1 (LOX-1) and c-Jun N-terminal kinase (JNK).

Conclusions:

Together, these findings demonstrate that fenretinide may suppress inflammation through reduced neutrophil recruitment and inflammatory cytokine production in A. fumigatus keratitis.

Scavenger Receptors: Promiscuous Players during Microbial Pathogenesis

Innate immunity is the most broadly effective host defense, being essential to clear the majority of microbial infections. Scavenger Receptors comprise a family of sensors expressed in a multitude of host cells, whose dual role during microbial pathogenesis gained importance over recent years. SRs regulate the recruitment of immune cells and control both host inflammatory response and bacterial load. In turn, pathogens have evolved different strategies to overcome immune response, avoid recognition by SRs and exploit them to favor infection. Here, we discuss the most relevant findings regarding the interplay between SRs and pathogens, discussing how these multifunctional proteins recognize a panoply of ligands and act as bacterial phagocytic receptors.

Wnt5a contributes to dectin-1 and LOX-1 induced host inflammatory response signature in Aspergillus fumigatus keratitis

Fungal keratitis causes devastating corneal ulcers which can result in significant visual impairment and even blindness. As a ligand that activates the non-canonical Wnt signaling pathways, Wnt5a triggers the production of important inflammatory chemokines and the chemotactic migration of neutrophils. In this study we aimed to characterize the role of Wnt5a production, in situ, in vivo and in vitro in response to fungal keratitis. Wnt5a expression in corneas of Aspergillus fumigatus (A. fumigatus) keratitis patients was determined by quantitative polymerase chain reaction (qRT-PCR) and immunofluorescence. In vivo and in vitro experiments were then performed in mouse models and THP-1 macrophages cell cultures infected with A. fumigatus, respectively. C57BL/6 mice were pretreated with siRNAs or neutralizing antibodies for dectin-1, LOX-1 and Wnt5a, or inhibitors of erk1/2 and JNK. Changes in Wnt5a expression were assessed by clinical evaluation, qRT-PCR, immunofluorescence, western blot and bioluminescence imaging system image acquisition. We confirmed that corneal Wnt5a expression increased with A. fumigatus keratitis in patients and a murine model. Wnt5a production was dependent on dectin-1 and LOX-1 expression with contributions by Erk1/2 and JNK pathways. Additionally, Wnt5a knockdown revealed decreased levels of MPO, lower neutrophil recruitment, and a higher fungal load in mouse models. Compared with controls, Wnt5a knockdown impaired pro-inflammatory cytokine IL-1β production in response to A. fumigatus exposure. Wnt5a also produces dectin-1 and LOX-1 induced inflammatory signature via effective neutrophil recruitment and inflammatory cytokine production in response to A. fumigatus keratitis. These findings demonstrate that Wnt5a is a critical component of the antifungal immune response.

Regulation of lipoxygenase-1 and Dectin-1 on interleukin-10 in mouse Aspergillus fumigatus keratitis

AIM

To investigate the regulation of lipoxygenase (LOX)-1 and Dectin-1 on interleukin-10 (IL-10) production in mice with Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The corneas of C57BL/6 mice were pretreated with LOX-1 inhibitor Poly(I) or Dectin-1 siRNA separately before the infection of A. fumigatus. Polymerase chain reaction (PCR) and Western blot were used to detect the expression of IL-10.

RESULTS

The mRNA and protein expressions of IL-10 were significantly increased in mice with A. fumigatus keratitis. Compared with the group pretreated with sterile water before infection, Poly(I) pretreatment suppressed IL-10 expression significantly. Compared with the group pretreated with scrambled siRNA before infection, Dectin-1 siRNA pretreatment significantly reduced IL-10 expression in response to A. fumigatus infection.

CONCLUSION

LOX-1 and Dectin-1 regulate IL-10 production in mouse A. fumigatus keratitis.

The Interaction of Human Pathogenic Fungi With C-Type Lectin Receptors

Fungi, usually present as commensals, are a major cause of opportunistic infections in immunocompromised patients. Such infections, if not diagnosed or treated properly, can prove fatal. However, in most cases healthy individuals are able to avert the fungal attacks by mounting proper antifungal immune responses. Among the pattern recognition receptors (PRRs), C-type lectin receptors (CLRs) are the major players in antifungal immunity. CLRs can recognize carbohydrate ligands, such as β-glucans and mannans, which are mainly found on fungal cell surfaces. They induce proinflammatory immune reactions, including phagocytosis, oxidative burst, cytokine, and chemokine production from innate effector cells, as well as activation of adaptive immunity via Th17 responses. CLRs such as Dectin-1, Dectin-2, Mincle, mannose receptor (MR), and DC-SIGN can recognize many disease-causing fungi and also collaborate with each other as well as other PRRs in mounting a fungi-specific immune response. Mutations in these receptors affect the host response and have been linked to a higher risk in contracting fungal infections. This review focuses on how CLRs on various immune cells orchestrate the antifungal response and on the contribution of single nucleotide polymorphisms in these receptors toward the risk of developing such infections.

Production of interleukin-1β related to mammalian target of rapamycin/Toll-like receptor 4 signaling pathway during Aspergillus fumigatus infection of the mouse cornea

AIM

To elucidate the effect of rapamycin on regulating the production of interleukin (IL)-1β in Aspergillus fumigatus (A. fumigatus)-induced keratitis and to verify whether the expression of IL-1β in A. fumigatus keratitis is associated with the mammalian target of rapamycin (mTOR)/Toll-like receptor 4 (TLR4) signaling pathway.

METHODS

Fungal keratitis mouse models of susceptible C57BL/6 mice were established using A. fumigatus. The mice were subsequently treated with rapamycin. The protein levels of p-mTOR, TLR4, and IL-1β in normal and infected corneal tissue were measured by Western blot. The TLR4 and IL-1β mRNA levels were determined by real-time polymerase chain reaction (PCR).

RESULTS

In C57BL/6 mice, rapamycin treatment decreased the clinical scores and production of the pro-inflammatory cytokine, IL-1β. The expression of TLR4, stimulated by A. fumigatus, was reduced as well when the mTOR signaling pathway was suppressed by rapamycin.

CONCLUSION

Rapamycin is beneficial for the outcome of fungal keratitis and has an inhibitory effect expression of the inflammatory cytokine IL-1β. The inhibitory effect on IL-1β expression can be associated with the mTOR/TLR4 signaling pathway in A. fumigatus infection in mice.

Boxb mediate BALB/c mice corneal inflammation through a TLR4/MyD88-dependent signaling pathway in Aspergillus fumigatus keratitis

AIM

To investigate whether high-mobility group box 1 (HMGB1) Boxb exacerbates BALB/c mice corneal immune responses and inflammatory through the Toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)-dependent signaling pathway in Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The mice corneas were pretreated with phosphate buffer saline (PBS), Boxb before A. fumigatus infection. The abdominal cavity extracted macrophages were pretreated with PBS, Boxb, TLR4 inhibitor (CLI-095), Dimethyl sulfoxide (DMSO) separately before A. fumigatus hyphae stimulation. HMGB1 was detected in normal and infected mice corneas and macrophages by real-time reverse transcriptase polymerase chain reaction (RT-PCR), the TLR4, MyD88, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) were detected by Western blot and PCR.

RESULTS

In BALB/c mice corneas, the expressions of TLR4, HMGB1, IL-1β, TNF-α were increased after A. fumigatus infection. While pretreatment with Boxb significantly increased the expressions of TLR4, HMGB1, MyD88, IL-1β, TNF-α compared with PBS control after infection. In BALB/c mice abdominal cavity extracted macrophages, pretreatment with Boxb increased the expressions of TLR4, HMGB1, MyD88, IL-1β, TNF-α, while pretreatment with CLI-095 and Boxb significantly decreased the expressions of TLR4, HMGB1, MyD88, IL-1β, TNF-α.

CONCLUSION

In A. fumigatus keratitis, Boxb play a pro-inflammatory role in corneal anti-fungi immune response through the HMGB1-TLR4-MyD88 signal pathway.

Osteopontin contributes to effective neutrophil recruitment, IL-1β production and apoptosis in Aspergillus fumigatus keratitis

Fungal keratitis is a major cause of corneal ulcers, resulting in significant visual impairment and blindness. A phosphorylated glycoprotein secreted by immunocompetent cells, osteopontin (OPN) mediates cluster formation of the host fungal receptors and enhances the phagocytosis and clearance of pathogenic fungi. However, whether OPN production and function occurs in fungal keratitis is unknown. OPN expression in Aspergillus fumigatus keratitis patient corneas was assessed by quantitative polymerase chain reaction (qRT-PCR) and immunofluorescence. Human neutrophils, THP-1 macrophages and corneal epithelial cells (HCECs) stimulated with A. fumigatus were utilized for in vitro experiments. Mouse models of A. fumigatus keratitis were developed by intrastromal injection for in vivo experiments. Using siRNAs, neutralizing antibodies, recombinant proteins and inhibitors, the production and role of OPN in A. fumigatus infection was assessed by clinical evaluation, qRT-PCR, immunofluorescence, western blotting and bioluminescence image acquisition. We observed increased corneal OPN expression in A. fumigatus keratitis patients and mouse models compared to controls. OPN production in response to A. fumigatus infection was dependent on LOX-1 and Erk1/2. Compared to controls, OPN knockdown impaired proinflammatory cytokine IL-1β production, which was dependent on 4E-BP1. OPN knockdown decreased myeloperoxidase levels, and resulted in decreased neutrophil recruitment, higher fungal load and increased apoptosis in mouse A. fumigatus keratitis. Our results indicate that OPN is a critical component of the antifungal immune response and is essential for effective neutrophil recruitment, inflammatory cytokine production and apoptosis in A. fumigatus keratitis.

Dectin-1 is essential for IL-1β production through JNK activation and apoptosis in Aspergillus fumigatus keratitis

PURPOSE

To investigate the role of phosphorylated JNK in Dectin-1-induced IL-1β production and the role of Dectin-1 in apoptosis in mouse Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

Mice corneas were pretreated with Dectin-1 siRNA or SP600125 (the inhibitor of JNK) before A. fumigatus infection. THP-1 macrophages were preincubated with SP600125 before the stimulation of A. fumigatus conidia. Dectin-1, IL-1β, JNK, Bax, Bcl-2, cytochrome-c (cyt-c), caspase-9, caspase-8 and caspase-3 expressions were tested by PCR, Western blot, or Immunofluorescence staining.

RESULTS

Pretreatment with Dectin-1 siRNA significantly decreased A. fumigatus-induced IL-1β production and JNK phosphorylation compared with scrambled control in C57BL/6 mice corneas. SP600125 treatment before infection significantly inhibited IL-1β production compared with DMSO control both in mice corneas and THP-1 macrophages. Furthermore, Dectin-1 deficiency resulted in increased ratio of Bax/Bcl-2, release of cyt-c, activation of caspase-9 and caspase-3 in mouse A. fumigatus keratitis. However, Dectin-1 deficiency didn't affect the activation of caspase-8.

CONCLUSIONS

Being an important inflammatory PRR to mediate host inflammatory response, Dectin-1 induced IL-1β production is JNK dependent in mouse A. fumigatus keratitis, and suppressed apoptosis mediated anti-inflammatory response.