Inhibition of macrophage migration inhibitory factor ameliorates ocular Pseudomonas aeruginosa-induced keratitis

New Insight Into the Neuroimmune Interplay In Pseudomonas aeruginosa Keratitis

Purpose

The miR-183/96/182 cluster (miR-183C) is required for normal functions of sensory neurons (SN) and various immune cells, including myeloid cells (MC). This research aims to reveal the roles of miR-183C of SN in the interplay of corneal sensory nerves (CSN) and MC during Pseudomonas aeruginosa (PA) keratitis.

Methods

Double-tracing mice with SN-specific (SNS) conditional knockout of miR-183C (CKO) and age- and sex-matched wild type (WT) controls were used. Their CSN are labeled with Red Fluorescent Protein (RFP); MC with Enhanced Green (EG)FP. The left corneas were scarified and infected with ATCC19660 PA. Corneal flatmounts were prepared at 3, 6, and 12 hours post-infection (hpi) and 1, 3, and 5 days (d)pi for confocal microscopy. Myeloperoxidase (MPO) assay and plate count were performed at 1 dpi.

Results

In WT mice, CSN began to degenerate as early as 3 hpi, starting from the fine terminal CSN in the epithelial/subepithelial layers, most prominently in the central region. By 1 dpi, CSN in the epithelium/subepithelial layer were nearly completely destroyed, while stromal nerves persisted. From 3 dpi, CSN were obliterated in both layers. In CKO vs WT mice, CNS followed a slightly slower pace of degeneration. CSN density was decreased at 3 and 6 hpi. However, at 3 dpi, residual large-diameter stromal CSN were better preserved.MC were decreased in the central cornea at 3 and 6 hpi, but increased in the periphery. Both changes were more prominent in CKO vs WT mice. At 12 hpi, densely packed MC formed a ring-shaped band circling a "dark" zone nearly devoid of MC, colocalizing with CSN most degenerated zone in the central cornea. In CKO vs WT, the ring center was larger with fewer MC. At 1 dpi, the entire cornea was filled with MC; however, MC density was lower in CKO mice. An MPO assay showed decreased neutrophils in PA-infected cornea of CKO mice. This led to a decreased severity of PA keratitis at 3 dpi.

Conclusions

This double-tracing model reveals the interplay between CSN and MC during PA keratitis with greater clarity, providing new insights into PA keratitis. CSN-imposed modulation on innate immunity is most impressive within 24 hours after infection. Functionally, the miR-183C in CSN modulates CSN density and the dynamics of MC fluxes- a neuroimmune interaction in display.

Photothermal Iron-Based Riboflavin Microneedles for the Treatment of Bacterial Keratitis via Ion Therapy and Immunomodulation

Bacterial biofilm formation protects bacteria from antibiotics and the immune system, excessive inflammation further complicates treatment. Here, iron-based metal-organic framework (MIL-101)-loaded riboflavin nanoparticles are designed for the therapeutic challenge of biofilm infection and hyperinflammation in bacterial keratitis. Specifically, MIL-101 produces a thermal effect under exogenous near-infrared light irradiation, which synergizes with ferroptosis-like bacterial death induced by iron ions to exert an effective biofilm infection eradication effect. On the other hand, the disintegration of MIL-101 sustains the release of riboflavin, which inhibits the pro-inflammatory response of macrophage over-activation by modulating their phenotypic switch. In addition, to solve the problems of short residence time, poor permeability, and low bioavailability of corneal medication, the MR@MN microneedle patch is further prepared by loading nanoparticles into SilMA hydrogel, which ultimately achieves painless, transepithelial, and highly efficient drug delivery. In vivo and ex vivo experiments demonstrate the effectiveness of this approach in eliminating bacterial infection and promoting corneal healing. Therefore, the MRMN patch, acting as an ocular drug delivery system with the ability of rapid corneal healing, promises a cost-effective solution for the treatment of bacterial keratitis, which may also lead to a new approach for treating bacterial keratitis in clinics.

TLR2 Supports γδ T cell IL-17A Response to ocular surface commensals by Metabolic Reprogramming

The ocular surface is a mucosal barrier tissue colonized by commensal microbes, which tune local immunity by eliciting IL-17 from conjunctival γδ T cells to prevent pathogenic infection. The commensal Corynebacterium mastitidis (C. mast) elicits protective IL-17 responses from conjunctival Vγ4 T cells through a combination of γδ TCR ligation and IL-1 signaling. Here, we identify Vγ6 T cells as a major C. mast-responsive subset in the conjunctiva and uncover its unique activation requirements. We demonstrate that Vγ6 cells require not only extrinsic (via dendritic cells) but also intrinsic TLR2 stimulation for optimal IL-17A response. Mechanistically, intrinsic TLR2 signaling was associated with epigenetic changes and enhanced expression of genes responsible for metabolic shift to fatty acid oxidation to support Il17a transcription. We identify one key transcription factor, IκBζ, which is upregulated by TLR2 stimulation and is essential for this program. Our study highlights the importance of intrinsic TLR2 signaling in driving metabolic reprogramming and production of IL-17A in microbiome-specific mucosal γδ T cells.

The roles of macrophage migration inhibitory factor in retinal diseases

Macrophage migration inhibitory factor (MIF), a multifunctional cytokine, is secreted by various cells and participates in inflammatory reactions, including innate and adaptive immunity. There are some evidences that MIF is involved in many vitreoretinal diseases. For example, MIF can exacerbate many types of uveitis; measurements of MIF levels can be used to monitor the effectiveness of uveitis treatment. MIF also alleviates trauma-induced and glaucoma-induced optic nerve damage. Furthermore, MIF is critical for retinal/choroidal neovascularization, especially complex neovascularization. MIF exacerbates retinal degeneration; thus, anti-MIF therapy may help to mitigate retinal degeneration. MIF protects uveal melanoma from attacks by natural killer cells. The mechanism underlying the effects of MIF in these diseases has been demonstrated: it binds to cluster of differentiation 74, inhibits the c-Jun N-terminal kinase pathway, and triggers mitogen-activated protein kinases, extracellular signal-regulated kinase-1/2, and the phosphoinositide-3-kinase/Akt pathway. MIF also upregulates Toll-like receptor 4 and activates the nuclear factor kappa-B signaling pathway. This review focuses on the structure and function of MIF and its receptors, including the effects of MIF on uveal inflammation, retinal degeneration, optic neuropathy, retinal/choroidal neovascularization, and uveal melanoma.

Phosphorylation of MIF by PIP4K2a is necessary for cilia biogenesis

Primary cilia are microtubule-based organelles that play important roles in development and tissue homeostasis. Macrophage migration inhibitory factor (MIF) has long been recognized as a secreted cytokine in the pathogenesis of various human diseases, including cancer and autosomal dominant polycystic kidney disease (ADPKD). Unlike other cytokines, unique functional characteristics of intracellular MIF have emerged. In this study, we show that MIF is localized and formed a ring like structure at the proximal end of centrioles, where it regulates cilia biogenesis through affecting 1) the recruitment of TTBK2 to basal body and the removal of CP110 from mother centriole, 2) the accumulation of CEP290 at centriolar satellites, and 3) the trafficking of intraflagellar transport (IFT) related proteins. We also show that MIF functions as a novel transcriptional factor to regulate the expression of genes related to ciliogenesis via binding on the promotors of those genes. MIF also binds chromatin and regulates transcription of genes involved in diverse homeostatic signaling pathways. We identify phosphatidylinositol-5-phosphate 4-kinase type 2 alpha (PIP4K2a) as an upstream regulator of MIF, which interacts with and phosphorylates MIF at S91 to increase its interaction with 14-3-3ζ, resulting in its nuclear translocation and transcription regulation. This study suggests that MIF is a key player in cilia biogenesis and a novel transcriptional regulator in homeostasis, which forward our understanding of how MIF is able to carry out several nonoverlapping functions.

Host cell-type and pathogen-specific immunomodulatory functions of macrophage migration inhibitory factor (MIF) in infectious keratitis

Therapeutic management of inflammation in infectious keratitis (IK) requires new strategy and targets for selective immunomodulation. Targeting host cell-type specific inflammatory responses might be a viable strategy to curtail unnecessary inflammation and reduce tissue damage without affecting pathogen clearance. This study explores the possibility of pathogen and host cell-type dependent differences in the inflammatory pathways relevant in the pathogenesis of IK. Human corneal epithelial cell line (HCEC) and phorbol 12-myristate-13 acetate (PMA) differentiated THP-1 macrophage line were infected with either Aspergillus flavus conidia or Acanthamoeba castellanii trophozoites and the elicited inflammatory responses were studied in terms of gene expression and secretion of proinflammatory factors interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) and an upstream inflammatory regulator and mediator protein-the Macrophage Migration Inhibitory Factor (MIF). Given the pleotropic mode of MIF function in diverse cell types relevant in many human diseases, we tested if MIF driven responses to infection is different in HCECs and THP-1 macrophages by studying its expression, secretion and involvement in inflammation by siRNA mediated knockdown. We also examined IK patient tear samples for MIF levels. Infection with A. flavus or A. castellanii induced IL-8 and TNF-α responses in HCECs and THP-1 macrophages but to different levels. Our preliminary human data showed that the level of secreted MIF protein was elevated in IK patient tear, however, MIF secretion by the two cell types were strikingly different in-vitro, under both normal and infected conditions. We found that HCECs released MIF constitutively, which was significantly inhibited with infection, whereas THP-1 macrophages were stimulated to release MIF during infection. MIF gene expression remained largely unaffected by infection in both the cell lines. Although MIF in HCECs appeared to be intracellularly captured during infection, MIF knockdown in HCECs associated with a partial reduction of the IL-8 and TNF-α expression produced by either of the pathogens, suggesting a pro-inflammatory role for MIF in HCECs, independent of its canonical cytokine like function. In contrast, MIF knockdown in THP-1 macrophages accompanied a dramatic increase in IL-8 and TNF-α expression during A. castellanii infection, while the responses to A. flavus infection remained unchanged. These data imply a host cell-type and pathogen specific distinction in the MIF- related inflammatory signaling and MIF as a potential selective immunomodulatory target in infectious keratitis.

Targeting macrophage migration inhibitory factor (MIF): a promising therapy for inflammatory ocular diseases

Inflammatory ocular diseases are characterized by the presence of a persistent inflammatory response which cause tissue injury, decrease visual acuity and in severe cases, blindness. Several cytokines represent a therapeutic opportunity since they are key amplifiers of these pathologies, and thus neutralizing agents against them have been developed. Amongst others, macrophage migration inhibitory factor (MIF), an early produced inflammatory cytokine, has consistently been found elevated in patients with distinct ocular diseases (inflammatory and autoimmune). Here, we present and discuss evidence showing that preclinical trials using diverse strategies to neutralize MIF resulted in significant attenuation of disease signs and therefore MIF blockage might be a promising therapy for ocular diseases.

Clinicopathological Correlation of Microbial Keratitis and Ahead: Is There a Corneal Sepsis?

Microbial, infectious keratitis is a relevant indication for penetrating keratoplasty. The requirement for transplantation results in histopathological examination of the entire thickness of the cornea. Although the clinical diagnosis is not always possible to confirm, pathology can support diagnostic evidence of clinical presentation and pathogenesis. This is achieved with multiple methods from cytology, histochemistry, immunohistology, molecular pathology and in rare cases electron microscopy. These allow tissue-based detection of previous and parallel diseases and the responsible pathogens. The failure of satisfactory clinicopathological correlation raises the question whether a suspected pathogen was not ultimately responsible for destroyed corneal tissue. The pathogenesis of keratitis requiring transplantation is not yet completely understood, also on the experimental level. The development of such a keratitis can lead to a clinical symptomatology which can be described as "threatening organ dysfunction", a term used in sepsis research. Considering recent literature, possible correlations between sepsis and microbial keratitis and their relation to histopathology are discussed.

A Cross-Kingdom View on the Immunomodulatory Role of MIF/D-DT Proteins in Mammalian and Plant Pseudomonas Infections

Gram-negative Pseudomonas bacteria are largely harmless saprotrophs, but some species can be potent pathogens of both plants and mammals. Macrophage migration inhibitory factor (MIF) and its homolog D-dopachrome tautomerase (D-DT, also referred to as MIF-2) are multifunctional proteins that in addition to their intracellular functions also serve as extracellular signaling molecules (cytokines) in orchestrating mammalian immune responses. It recently emerged that plants also possess MIF-like proteins, termed MIF/D-DT-like (MDL) proteins. We here provide a comparative cross-kingdom view on the immunomodulatory role of MIF and MDL proteins during Pseudomonas infections in mammals and plants. Although in both kingdoms the lack of MIF/MDL proteins is associated with a reduction in bacterial load and disease symptoms, the underlying molecular principles seem to be different. We provide a perspective for future research activities to unravel additional commonalities and differences in the MIF/MDL-mediated adjustment of antibacterial immune activities.

Condensins are essential for Pseudomonas aeruginosa corneal virulence through their control of lifestyle and virulence programs

Pseudomonas aeruginosa is a significant opportunistic pathogen responsible for numerous human infections. Its high pathogenicity resides in a diverse array of virulence factors and an ability to adapt to hostile environments. We report that these factors are tied to the activity of condensins, SMC and MksBEF, which primarily function in structural chromosome maintenance. This study revealed that both proteins are required for P. aeruginosa virulence during corneal infection. The reduction in virulence was traced to broad changes in gene expression. Transcriptional signatures of smc and mksB mutants were largely dissimilar and non-additive, with the double mutant displaying a distinct gene expression profile. Affected regulons included those responsible for lifestyle control, primary metabolism, surface adhesion and biofilm growth, iron and sulfur assimilation, and numerous virulence factors, including type 3 and type 6 secretion systems. The in vitro phenotypes of condensin mutants mirrored their transcriptional profiles and included impaired production and secretion of multiple virulence factors, growth deficiencies under nutrient limiting conditions, and altered c-di-GMP signaling. Notably, c-di-GMP mediated some but not all transcriptional responses of the mutants. Thus, condensins are integrated into the control of multiple genetic programs related to epigenetic and virulent behavior of P. aeruginosa.

Targeting Inflammation Driven by HMGB1 in Bacterial Keratitis-A Review

Pseudomonas (P.) aeruginosa is a Gram-negative bacteria that causes human infectionsinfections. It can cause keratitis, a severe eye infection, that develops quickly and is a major cause of ulceration of the cornea and ocular complications globally. Contact lens wear is the greatest causative reason in developed countries, but in other countries, trauma and predominates. Use of non-human models of the disease are critical and may provide promising alternative argets for therapy to bolster a lack of new antibiotics and increasing antibiotic resistance. In this regard, we have shown promising data after inhibiting high mobility group box 1 (HMGB1), using small interfering RNA (siRNA). Success has also been obtained after other means to inhinit HMGB1 and include: use of HMGB1 Box A (one of three HMGB1 domains), anti-HMGB1 antibody blockage of HMGB1 and/or its receptors, Toll like receptor (TLR) 4, treatment with thrombomodulin (TM) or vasoactive intestinal peptide (VIP) and glycyrrhizin (GLY, a triterpenoid saponin) that directly binds to HMGB1. ReducingHMGB1 levels in P. aeruginosa keratitis appears a viable treatment alternative.

Foundational concepts in the biology of bacterial keratitis

Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.

Pseudomonas aeruginosa-induced nociceptor activation increases susceptibility to infection

We report a rapid reduction in blink reflexes during in vivo ocular Pseudomonas aeruginosa infection, which is commonly attributed and indicative of functional neuronal damage. Sensory neurons derived in vitro from trigeminal ganglia (TG) were able to directly respond to P. aeruginosa but reacted significantly less to strains of P. aeruginosa that lacked virulence factors such as pili, flagella, or a type III secretion system. These observations led us to explore the impact of neurons on the host's susceptibility to P. aeruginosa keratitis. Mice were treated with Resiniferatoxin (RTX), a potent activator of Transient Receptor Potential Vanilloid 1 (TRPV1) channels, which significantly ablated corneal sensory neurons, exhibited delayed disease progression that was exemplified with decreased bacterial corneal burdens and altered neutrophil trafficking. Sensitization to disease was due to the increased frequencies of CGRP-induced ICAM-1+ neutrophils in the infected corneas and reduced neutrophil bactericidal activities. These data showed that sensory neurons regulate corneal neutrophil responses in a tissue-specific matter affecting disease progression during P. aeruginosa keratitis. Hence, therapeutic modalities that control nociception could beneficially impact anti-infective therapy.

Aerosolized drug-loaded nanoparticles targeting migration inhibitory factors inhibit Pseudomonas aeruginosa-induced inflammation and biofilm formation

Aim: Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine, which has been shown to promote disease severity in cystic fibrosis. Methods: In this study, aerosolized drug-loaded nanoparticles containing SCD-19, an inhibitor of MIF's tautomerase enzymatic activity, were developed and characterized. Results: The aerosolized nanoparticles had an optimal droplet size distribution for deep lung deposition, with a high degree of biocompatibility and significant cellular uptake. Conclusion: For the first time, we have developed an aerosolized nano-formulation against MIF's enzymatic activity that achieved a significant reduction in the inflammatory response of macrophages, and inhibited Pseudomonas aeruginosa biofilm formation on airway epithelial cells. This represents a potential novel adjunctive therapy for the treatment of P. aeruginosa infection in cystic fibrosis.

Effects of Glycyrrhizin on Multi-Drug Resistant Pseudomonas aeruginosa

The effects of glycyrrhizin (GLY) on multi-drug resistant (MDR) systemic (MDR9) vs. ocular (B1045) Pseudomonas aeruginosa clinical isolates were determined. Proteomes of each isolate with/without GLY treatment were profiled using liquid chromatography mass spectrometry (LC-MS/MS). The effect of GLY on adherence of MDR isolates to immortalized human (HCET) and mouse (MCEC) corneal epithelial cells, and biofilm and dispersal was tested. Both isolates were treated with GLY (0.25 minimum inhibitory concentration (MIC), 10 mg/mL for MDR9 and 3.75 mg/mL for B1045) and subjected to proteomic analysis. MDR9 had a greater response to GLY (51% of identified proteins affected vs. <1% in B1045). In MDR9 vs. controls, GLY decreased the abundance of proteins for: antibiotic resistance, biofilm formation, and type III secretion. Further, antibiotic resistance and type III secretion proteins had higher control abundances in MDR9 vs. B1045. GLY (5 and 10 mg/mL) significantly reduced binding of both isolates to MCEC, and B1045 to HCET. MDR9 binding to HCET was only reduced at 10 mg/mL GLY. GLY (5 and 10 mg/mL) enhanced dispersal for both isolates, at early (6.5 h) but not later times (24–72 h). This study provides evidence that GLY has a greater effect on the proteome of MDR9 vs. B1045, yet it was equally effective at disrupting adherence and early biofilm dispersal.

Label-Free Quantitative Proteomics Distinguishes General and Site-Specific Host Responses to Pseudomonas aeruginosa Infection at the Ocular Surface

Mass spectrometry-based proteomics enables the unbiased and sensitive profiling of cellular proteomes and extracellular environments. Recent technological and bioinformatic advances permit identifying dual biological systems in a single experiment, supporting investigation of infection from both the host and pathogen perspectives. At the ocular surface, Pseudomonas aeruginosa is commonly associated with biofilm formation and inflammation of the ocular tissues, causing damage to the eye. The interaction between P. aeruginosa and the immune system at the site of infection describes limitations in clearance of infection and enhanced pathogenesis. Here, the extracellular environment (eye wash) of murine ocular surfaces infected with a clinical isolate of P. aeruginosa is profiled and neutrophil marker proteins are detected, indicating neutrophil recruitment to the site of infection. The first potential diagnostic markers of P. aeruginosa-associated keratitis are also identified. In addition, the deepest murine corneal proteome to date is defined and proteins, categories, and networks critical to the host response are detected. Moreover, the first identification of bacterial proteins attached to the ocular surface is reported. The findings are validated through in silico comparisons and enzymatic profiling. Overall, the work provides comprehensive profiling of the host-pathogen interface and uncovers differences between general and site-specific host responses to infection.

Glycyrrhizin Use for Multi-Drug Resistant Pseudomonas aeruginosa: In Vitro and In Vivo Studies

Purpose

Our purpose was to test glycyrrhizin (GLY) effects and ciprofloxacin interactions on multidrug resistant (MDR) isolates of Pseudomonas aeruginosa in vitro and in vivo in a mouse model of keratitis.

Methods

A Hardy-disk tested antibiotic sensitivity of isolates MDR9 (nonocular) and B1045 (ocular). GLY MIC (both isolates) and ciprofloxacin was determined spectrophotometrically. A live/dead assay using confocal microscopy and plate count, tested GLY effects on bacterial permeabilization/viability. Proteomics profiled bacterial efflux pumps (MDR9 vs. PAO1); RT-PCR comparatively tested GLY effects on their mRNA expression levels. The activity of efflux pumps was tested using ethidium bromide (EB); and scanning electron microscopy (SEM) visualized the effects of GLY treatment of bacteria. A combination of GLY and ciprofloxacin was tested in C57BL/6 mice (begun 18 hours after infection) and disease scored, photographed and MPO and plate counts done.

Results

MDR9 was resistant to 6/12 and B1045 to 7/12 antibiotics (both to ciprofloxacin). MIC GLY for MDR9 was 40 mg/mL and 15 mg/mL for B1045. Ciprofloxacin MIC (32 μg/mL) was reduced 2-fold to 16 μg/mL when ciprofloxacin and GLY were combined. GLY altered bacterial membrane permeability and reduced viability. Proteomics revealed increased efflux pumps in MDR9 versus PAO1; GLY reduced their mRNA expression levels and EB suggested decreased activity. In C57BL/6 mice, treatment with GLY and ciprofloxacin versus ciprofloxacin, significantly reduced clinical scores, plate count, and MPO.

Conclusions

GLY decreases MDR by: altering bacterial parameters, including viability and efflux pump activity. In vivo, it increases the effectiveness of ciprofloxacin, reducing ocular disease, plate count, and MPO activity.

Repair Process Impairment by Pseudomonas aeruginosa in Epithelial Tissues: Major Features and Potential Therapeutic Avenues

Epithelial tissues protecting organs from the environment are the first-line of defense against pathogens. Therefore, efficient repair mechanisms after injury are crucial to maintain epithelial integrity. However, these healing processes can be insufficient to restore epithelial integrity, notably in infectious conditions. Pseudomonas aeruginosa infections in cutaneous, corneal, and respiratory tract epithelia are of particular concern because they are the leading causes of hospitalizations, disabilities, and deaths worldwide. Pseudomonas aeruginosa has been shown to alter repair processes, leading to chronic wounds and infections. Because of the current increase in the incidence of multi-drug resistant isolates of P. aeruginosa, complementary approaches to decrease the negative impact of these bacteria on epithelia are urgently needed. Here, we review the recent advances in the understanding of the impact of P. aeruginosa infections on the integrity and repair mechanisms of alveolar, airway, cutaneous and corneal epithelia. Potential therapeutic avenues aimed at counteracting this deleterious impact of infection are also discussed.

Expression of macrophage migration inhibitory factor in Aspergillus fumigatus keratitis

AIM

To investigate the expression of macrophage migration inhibitory factor (MIF) and detect its role in the innate immune response of fungal keratitis (FK).

METHODS

We collected the paraffin-embedded cornea tissues from 10 FK and 6 ocular trauma patients to explore the MIF expression by immunohistochemistry. Then we cultured telomease-immortalized human corneal epithelial cells (THCEs), stimulated by the hyphae suspension of Aspergillus fumigatus (A. fumigatus) to detect the change of MIF with or without the pretreatment of MIF inhibitor [4-Iodo-6-phenylpyrimidine (4-IPP)] by real-time polymerase chain reaction (PCR). The protein level of MIF was also tested by immunohistochemistry, and the level of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) mRNA were compared between normal, hyphae stimulated and 4-IPP pretreated groups by real-time PCR to study the influence of MIF on the expression of TNF-α and IL-6. Corneal severity of rats' FK models was documented by clinical scores, and real-time PCR. Western blot and immunohistochemistry were used to test the expression of MIF, TNF-α and IL-6 in rats' corneas.

RESULTS

In the corneas of FK patients, there was much stronger expression of MIF than that in the normal group showed by immunohistochemistry. In cultured THCEs stimulated by A. fumigatus, the expression of MIF became stronger in both immunohistochemistry and PCR at 16, 24, 32 and 48h post infection (p.i.; P<0.01, P<0.01, P<0.01, P<0.05). After pretreated with 4-IPP, the expression of MIF reduced at 4, 8, 16h p.i. (P<0.05, P<0.05, P<0.05) and the downstream TNF-α and IL-6 decreased obviously (P<0.05, P<0.01). In rats with A. fumigatus keratitis, the relative mRNA and protein level of MIF increased than those in the normal group by PCR (at 1d: P<0.01, 3d: P<0.01, 5d: P<0.01), Western blot and immunohistochemistry. After blocked MIF with 4-IPP, the clinical outcomes of rat keratitis showed markedly reduced inflammatory response (P<0.01), with TNF-α and IL-6 decreased in accordance with those in THCEs by PCR (P<0.05, P<0.01).

CONCLUSION

The expression of MIF increased significantly in FK patients, THCEs and rats stimulated by A. fumigatus. After blocked with 4-IPP, the expression of MIF reduced, and so did its downstream cytokines: TNF-α and IL-6. The inflammation reaction of the rats' corneas lightened after pretreated with 4-IPP. MIF may play a role in the innate immune response of the corneal resistance against A. fumigatus.

MicroRNAs in the cornea: Role and implications for treatment of corneal neovascularization

With no safe and efficient approved therapy available for treating corneal neovascularization, the search for alternative and effective treatments is of great importance. Since the discovery of miRNAs as key regulators of gene expression, knowledge of their function in the eye has expanded continuously, facilitated by high throughput genomic tools such as microarrays and RNA sequencing. Recently, reports have emerged implicating miRNAs in pathological and developmental angiogenesis. This has led to the idea of targeting these regulatory molecules as a therapeutic approach for treating corneal neovascularization. With the growing volume of data generated from high throughput tools applied to study corneal neovascularization, we provide here a focused review of the known miRNAs related to corneal neovascularization, while presenting new experimental data and insights for future research and therapy development.

Macrophage migration inhibitory factor enhances Pseudomonas aeruginosa biofilm formation, potentially contributing to cystic fibrosis pathogenesis

Macrophage migration inhibitory factor (MIF) is a key proinflammatory mediator that we have previously shown to be associated with an aggressive clinical phenotype in cystic fibrosis. It possesses unique tautomerase enzymatic activity. However, to date, no human-derived substrate has been identified that has the capacity to interact with this cytokine's unique tautomerase activity. This led us to hypothesize that MIF may have the capacity to interact with external substrates. We describe for the first time how Pseudomonas aeruginosa can utilize human recombinant MIF (rMIF) to significantly (P < 0.01) enhance its endogenous biofilm formation. Our in vivo studies demonstrate that utilizing a small-molecular-weight inhibitor targeting MIF's tautomerase activity (SCD-19) significantly reduces the inflammatory response in a murine pulmonary chronic P. aeruginosa model. In addition, we show that in in vitro experiments, pretreatment of P. aeruginosa with rMIF is associated with reduced bacterial killing by tobramycin. Our novel findings support the concept of an anti-MIF strategy that targets this enzymatic activity as a potential future antibacterial therapeutic approach.-Tynan, A., Mawhinney, L., Armstrong, M. E., O'Reilly, C., Kennedy, S., Caraher, E., Jülicher, K., O'Dwyer, D., Maher, L., Schaffer, K., Fabre, A., McKone, E. F., Leng, L., Bucala, R., Bernhagen, J., Cooke, G., Donnelly, S. C. Macrophage migration inhibitory factor enhances Pseudomonas aeruginosa biofilm formation, potentially contributing to cystic fibrosis pathogenesis.

An Ocular Commensal Protects against Corneal Infection by Driving an Interleukin-17 Response from Mucosal γδ T Cells

Mucosal sites such as the intestine, oral cavity, nasopharynx, and vagina all have associated commensal flora. The surface of the eye is also a mucosal site, but proof of a living, resident ocular microbiome remains elusive. Here, we used a mouse model of ocular surface disease to reveal that commensals were present in the ocular mucosa and had functional immunological consequences. We isolated one such candidate commensal, Corynebacterium mastitidis, and showed that this organism elicited a commensal-specific interleukin-17 response from γδ T cells in the ocular mucosa that was central to local immunity. The commensal-specific response drove neutrophil recruitment and the release of antimicrobials into the tears and protected the eye from pathogenic Candida albicans or Pseudomonas aeruginosa infection. Our findings provide direct evidence that a resident commensal microbiome exists on the ocular surface and identify the cellular mechanisms underlying its effects on ocular immune homeostasis and host defense.

A Mouse Model for Ocular Surface Staphylococcus aureus Infection

Creation of an appropriate animal model that accurately reflects the disease and host immune response to bacterial infection in humans is a major challenge in ocular-surface infection research. For decades, mice have been the ideal small animal model for ocular-surface infection research because of the availability and relatively low cost of various genetic backgrounds, targeted defects, and immunologic reagents. By employing different combinations of mouse and bacterial strains, murine infection models can be used to explore a complete picture of bacterial infection and innate immunity of the ocular surface. A murine model of Staphylococcus aureus infection under normal ocular circumstances is presented here as a convenient and tractable model system in which to study mammalian host responses to pathogens. © 2017 by John Wiley & Sons, Inc.

Label-free electrical sensing of bacteria in eye wash samples: A step towards point-of-care detection of pathogens in patients with infectious keratitis

The diagnosis of keratitis is based on visual exam, tissue cytology, and standard microbial culturing to determine the type of the infectious pathogen. To prescribe appropriate therapy, it is important to distinguish between bacterial, fungal, and viral keratitis, as the treatments are quite different. Diagnosis of the causative organism has a substantial prognostic importance. Further, timely knowledge of the nature of the pathogen is also critical to adapt therapy in patients unresponsive to empiric treatment options, which occurs in 10% of all cases. Currently, the identification of the nature of the pathogen that causes keratitis is achieved via microbial culture screening, which is laboratory-based, expensive, and time-consuming. The most frequent pathogens that cause the corneal ulcers are P. aeruginosa and S. aureus. Here, we report a microchip for rapid (<1h) detection of P. aeruginosa (6294), S. aureus(LAC), through on-chip electrical sensing of bacterial lysate. We evaluated the microchip with spiked samples of PBS with bacteria concentration between 10¹ to 10⁸ CFU/mL. The least diluted bacteria concentration in bacteria-spiked samples with statistically significant impedance change was 10 CFU/mL. We further validated our assay by comparing our microchip results with the standard culture-based methods using eye washes obtained from 13 infected mice.

MIF inhibition reverts the gene expression profile of human melanoma cell line-induced MDSCs to normal monocytes

Myeloid-derived suppressor cells (MDSCs) are potently immunosuppressive innate immune cells that accumulate in advanced cancer patients and actively inhibit anti-tumor T lymphocyte responses [1]. Increased numbers of circulating MDSCs directly correlate with melanoma patient morbidity and reduced anti-tumor immune responses [2], [3]. Previous studies have revealed that monocyte-derived macrophage migration inhibitory factor (MIF) is necessary for the immune suppressive function of MDSCs in mouse models of melanoma [4], [5]. To investigate whether MIF participates in human melanoma-induced MDSC differentiation and/or suppressive function, we have established an in vitro MDSC induction model using primary, normal human monocytes co-cultured with human melanoma cell lines in the presence or absence of the MIF antagonist—4-IPP [4], [6], [7], [8], [9]. To identify potential mechanistic effectors, we have performed transcriptome analyses on cultured monocytes and on melanoma-induced MDSCs obtained from either untreated or 4-IPP-treated A375:monocyte co-cultures. Here, we present a detailed protocol, which can facilitate easy reproduction of the microarray results (NCBI GEO accession number GSE73333) published by Yaddanapudi et al. (2015) in Cancer Immunology Research [10].

MIF Is Necessary for Late-Stage Melanoma Patient MDSC Immune Suppression and Differentiation

Highly aggressive cancers "entrain" innate and adaptive immune cells to suppress antitumor lymphocyte responses. Circulating myeloid-derived suppressor cells (MDSC) constitute the bulk of monocytic immunosuppressive activity in late-stage melanoma patients. Previous studies revealed that monocyte-derived macrophage migration inhibitory factor (MIF) is necessary for the immunosuppressive function of tumor-associated macrophages and MDSCs in mouse models of melanoma. In the current study, we sought to determine whether MIF contributes to human melanoma MDSC induction and T-cell immunosuppression using melanoma patient-derived MDSCs and an ex vivo coculture model of human melanoma-induced MDSC. We now report that circulating MDSCs isolated from late-stage melanoma patients are reliant upon MIF for suppression of antigen-independent T-cell activation and that MIF is necessary for maximal reactive oxygen species generation in these cells. Moreover, inhibition of MIF results in a functional reversion from immunosuppressive MDSC to an immunostimulatory dendritic cell (DC)-like phenotype that is at least partly due to reductions in MDSC prostaglandin E(2) (PGE(2)). These findings indicate that monocyte-derived MIF is centrally involved in human monocytic MDSC induction/immunosuppressive function and that therapeutic targeting of MIF may provide a novel means of inducing antitumor DC responses in late-stage melanoma patients.

TSP-1 Deficiency Alters Ocular Microbiota: Implications for Sjögren's Syndrome Pathogenesis

PURPOSE

The potential role of commensals as triggering factors that promote inflammation in dry eye disease has not been explored. The objective of this study was to evaluate whether ocular microbiota changes with the onset of dry eye disease in thrombospondin-1-deficient (TSP-1(-/-)) mice, a strain that develops Sjögren's syndrome-like disease.

METHODS

Conjunctival swabs were collected from TSP-1(-/-) and C57BL/6 mice and analyzed for bacterial presence. Opsonophagocytosis of the bacterial conjunctival isolates derived from the aged TSP-1(-/-) mice by neutrophils derived from either TSP-1(-/-) or C57BL/6 bone marrow was evaluated. The bactericidal activities of TSP-1-derived peptide were examined.

RESULTS

We found that in TSP-1(-/-) mice, the conjunctival colonization with Staphylococcus aureus and coagulase negative staphylococci sp (CNS) species was significantly increased with aging and preceded that of the wild-type C57BL/6 control mice. This correlated with increased neutrophil infiltration into the conjunctiva of the TSP-1(-/-) mice, suggesting that TSP-1 plays a significant role in regulating immunity to commensals. Accordingly, the TSP-1(-/-) PMNs opsonophagocytozed the ocular commensals less efficiently than the TSP-1-sufficient neutrophils. Furthermore, a TSP-1-derived peptide, 4N1K, exhibited significant antimicrobial activity when compared to a control peptide against commensal sp.

CONCLUSION

These studies illustrate that alterations in the commensal frequency occur in the early stages of development of Sjögren's-like pathology and suggest that interventions that limit commensal outgrowth such as the use of TSP-1-derived peptides could be used for treatment during the early stages of the disease to reduce the commensal burden and ensuing inflammation.

Macrophage migration inhibitory factor promotes cyst growth in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by renal cyst formation, inflammation, and fibrosis. Macrophages infiltrate cystic kidneys, but the role of these and other inflammatory factors in disease progression are poorly understood. Here, we identified macrophage migration inhibitory factor (MIF) as an important regulator of cyst growth in ADPKD. MIF was upregulated in cyst-lining epithelial cells in polycystin-1-deficient murine kidneys and accumulated in cyst fluid of human ADPKD kidneys. MIF promoted cystic epithelial cell proliferation by activating ERK, mTOR, and Rb/E2F pathways and by increasing glucose uptake and ATP production, which inhibited AMP-activated protein kinase signaling. MIF also regulated cystic renal epithelial cell apoptosis through p53-dependent signaling. In polycystin-1-deficient mice, MIF was required for recruitment and retention of renal macrophages, which promoted cyst expansion, and Mif deletion or pharmacologic inhibition delayed cyst growth in multiple murine ADPKD models. MIF-dependent macrophage recruitment was associated with upregulation of monocyte chemotactic protein 1 (MCP-1) and inflammatory cytokine TNF-α. TNF-α induced MIF expression, and MIF subsequently exacerbated TNF-α expression in renal epithelial cells, suggesting a positive feedback loop between TNF-α and MIF during cyst development. Our study indicates MIF is a central and upstream regulator of ADPKD pathogenesis and provides a rationale for further exploration of MIF as a therapeutic target for ADPKD.

Targeting distinct tautomerase sites of D-DT and MIF with a single molecule for inhibition of neutrophil lung recruitment

We report a new inflammatory activity for extracellular d-dopachrome tautomerase (D-DT), the recruitment of neutrophils to the lung on D-DT intratracheal installation of C57BL/6J mice with an EC50 of 5.6 μg. We also find that D-DT and macrophage migration inhibitory factor (MIF) have additive effects in neutrophil recruitment. Although the tautomerase site of D-DT and its homologue MIF are biophysically very different, 4-iodo-6-phenylpyrimidine (4-IPP) forms a covalent bond with Pro-1 of both proteins, resulting in a 6-phenylpyrimidine (6-PP) adduct. Recruitment of neutrophils to the lung for the 6-PP adducts of D-DT and MIF are reduced by ∼ 50% relative to the apo proteins, demonstrating that an unmodified Pro-1 is important for this activity, but there is no cooperativity in inhibition of the proteins together. The differences in the binding mode of the 6-PP adduct for D-DT was determined by crystallographic studies at 1.13 Å resolution and compared to the structure of the MIF-6-PP complex. There are major differences in the location of the 6-PP adduct to the D-DT and MIF active sites that provide insight into the lack of cooperativity by 4-IPP and into tuning the properties of the covalent inhibitors of D-DT and MIF that are necessary for the development of therapeutic small molecules against neutrophil damage from lung infections such as Pseudomonas aeruginosa in cystic fibrosis and immunocompromised patients.

Increased endothelial and macrophage markers are associated with disease severity and mortality in scrub typhus

OBJECTIVES

Scrub typhus is endemic in the Asia-Pacific region. Mortality is high even with treatment, and further knowledge of the immune response during this infection is needed. This study was aimed at comparing plasma levels of monocyte/macrophage and endothelial related inflammatory markers in patients and controls in South India and to explore a possible correlation to disease severity and clinical outcome.

METHODS

Plasma levels of ALCAM, VCAM-1, sCD163, sCD14, YKL-40 and MIF were measured in scrub typhus patients (n = 129), healthy controls (n = 31) and in infectious disease controls (n = 31), both in the acute phase and after recovery, by enzyme immunoassays.

RESULTS

Patients had markedly elevated levels of all mediators in the acute phase, differing from both healthy and infectious disease controls. During follow-up levels of ALCAM, VCAM-1, sCD14 and YKL-40 remained elevated compared to levels in healthy controls. High plasma ALCAM, VCAM-1, sCD163, sCD14, and MIF, and in particular YKL-40 were all associated with disease severity and ALCAM, sCD163, MIF and especially YKL-40, were associated with mortality.

CONCLUSIONS

Our findings show that scrub typhus is characterized by elevated levels of monocyte/macrophage and endothelial related markers. These inflammatory markers, and in particular YKL-40, may contribute to disease severity and clinical outcome.

Pathogenic strains of Acanthamoeba are recognized by TLR4 and initiated inflammatory responses in the cornea

Free-living amoebae of the Acanthamoeba species are the causative agent of Acanthamoeba keratitis (AK), a sight-threatening corneal infection that causes severe pain and a characteristic ring-shaped corneal infiltrate. Innate immune responses play an important role in resistance against AK. The aim of this study is to determine if Toll-like receptors (TLRs) on corneal epithelial cells are activated by Acanthamoeba, leading to initiation of inflammatory responses in the cornea. Human corneal epithelial (HCE) cells constitutively expressed TLR1, TLR2, TLR3, TLR4, and TLR9 mRNA, and A. castellanii upregulated TLR4 transcription. Expression of TLR1, TLR2, TLR3, and TLR9 was unchanged when HCE cells were exposed to A. castellanii. IL-8 mRNA expression was upregulated in HCE cells exposed to A. castellanii. A. castellanii and lipopolysaccharide (LPS) induced significant IL-8 production by HCE cells as measured by ELISA. The percentage of total cells positive for TLR4 was higher in A. castellanii stimulated HCE cells compared to unstimulated HCE cells. A. castellanii induced upregulation of IL-8 in TLR4 expressing human embryonic kidney (HEK)-293 cells, but not TLR3 expressing HEK-293 cells. TLR4 neutralizing antibody inhibited A. castellanii-induced IL-8 by HCE and HEK-293 cells. Clinical strains but not soil strains of Acanthamoeba activated TLR4 expression in Chinese hamster corneas in vivo and in vitro. Clinical isolates but not soil isolates of Acanthamoeba induced significant (P< 0.05) CXCL2 production in Chinese hamster corneas 3 and 7 days after infection, which coincided with increased inflammatory cells in the corneas. Results suggest that pathogenic species of Acanthamoeba activate TLR4 and induce production of CXCL2 in the Chinese hamster model of AK. TLR4 may be a potential target in the development of novel treatment strategies in Acanthamoeba and other microbial infections that activate TLR4 in corneal cells.

Staphylococcus aureus corneal infections: effect of the Panton-Valentine leukocidin (PVL) and antibody to PVL on virulence and pathology

PURPOSE

Community-associated methicillin-resistant Staphylococcus aureus strains expressing Panton-Valentine leukocidin (PVL) are associated with severe skin and soft tissue infections, necrotizing pneumonia, and eye infections. We determined PVL's toxicity on infected mouse and cultured human corneal epithelial cells and the role of PVL and antibody to PVL in pathogenesis of murine keratitis.

METHODS

Cytotoxicity on corneas and corneal epithelial cells was evaluated by LDH assays. Scratched corneas of female A/J mice were inoculated with approximately 10⁷ CFU/eye of either WT S. aureus, isogenic ΔPVL, or strains overproducing PVL. Antibodies to PVL or control sera were topically applied to infected corneas 0, 24, and 32 hours postinfection, corneas scored for pathology and tissue levels of S. aureus were determined.

RESULTS

PVL expression augmented the cytotoxicity of S. aureus on infected mouse corneas and human cultured corneal epithelial cells. Variable effects on leukocyte recruitment, pathogenesis, and immunity were obtained in the in vivo studies. Inactivation of PVL in USA300 strains caused reduced pathology and bacterial counts. Results were variable when comparing WT and ΔPVL USA400 strains, while USA400 strains overproducing PVL caused increased bacterial burdens. Topical treatment with polyclonal antibody to PVL yielded significant reductions in corneal pathology and bacterial CFU in corneas infected with USA300 strains, whereas effects were inconsistent in eyes infected with USA400 strains.

CONCLUSIONS

PVL enhanced the virulence of a subset of MRSA strains in a keratitis model. Coupled with a variable effect of antibody treatment, it appears that PVL plays an inconsistent role in pathogenesis and immunity to S. aureus corneal infection.

Homotrimeric macrophage migration inhibitory factor (MIF) drives inflammatory responses in the corneal epithelium by promoting caveolin-rich platform assembly in response to infection

Acute inflammation that arises during Pseudomonas aeruginosa-induced ocular infection can trigger tissue damage resulting in long term impairment of visual function, suggesting that the appropriate treatment strategy should include the use of anti-inflammatory agents in addition to antibiotics. We recently identified a potential target for modulation during ocular infection, macrophage migration inhibitory factor (MIF). MIF deficiency protected mice from inflammatory-mediated corneal damage resulting from acute bacterial keratitis. To gain a better understanding of the molecular mechanisms of MIF activity, we analyzed the oligomeric states and functional properties of MIF during infection. We found that in human primary corneal cells infected with P. aeruginosa, MIF is primarily in a homotrimeric state. Homotrimeric MIF levels correlated with the severity of infection in the corneas of infected mice, suggesting that the MIF homotrimers were the functionally active form of MIF. During infection, human primary corneal cells released more IL-8 when treated with recombinant, locked MIF trimers than when treated with lower MIF oligomers. MIF promoted P. aeruginosa-induced IL-8 responses via the formation of caveolin-1-rich "signaling hubs" in the corneal cells that led to elevated MAPK p42/p44 activation and sustained inflammatory signaling. These findings suggest that inhibiting homotrimerization of MIF or the functional activities of MIF homotrimers could have therapeutic benefits during ocular inflammation.

Macrophage migration inhibitory factor enzymatic activity, lung inflammation, and cystic fibrosis

RATIONALE

Macrophage migration inhibitory factor (MIF) is a proinflammatory mediator with unique tautomerase enzymatic activity; the precise function has not been clearly defined. We previously demonstrated that individual patients with cystic fibrosis (CF) who are genetically predisposed to be high MIF producers develop accelerated end-organ injury.

OBJECTIVES

To characterize the effects of the MIF-CATT polymorphism in patients with CF ex vivo. To investigate the role of MIF's tautomerase activity in a murine model of Pseudomonas aeruginosa infection.

METHODS

MIF and tumor necrosis factor (TNF)-α protein levels were assessed in plasma or peripheral blood mononuclear cell (PBMC) supernatants by ELISA. A murine pulmonary model of chronic Pseudomonas infection was used in MIF wild-type mice (mif(+/+)) and in tautomerase-null, MIF gene knockin mice (mif (P1G/P1G)).

MEASUREMENTS AND MAIN RESULTS

MIF protein was measured in plasma and PBMCs from 5- and 6-CATT patients with CF; LPS-induced TNF-α production from PBMCs was also assessed. The effect of a specific inhibitor of MIF-tautomerase activity, ISO-1, was investigated in PBMCs. In the murine infection model, total weight loss, differential cell counts, bacterial load, and intraacinar airspace/tissue volume were measured. MIF and TNF-α levels were increased in 6-CATT compared with 5-CATT patients with CF. LPS-induced TNF-α production from PBMCs was attenuated in the presence of ISO-1. In a murine model of Pseudomonas infection, significantly less pulmonary inflammation and bacterial load was observed in mif(P1G/P1G) compared with mif(+/+) mice.

CONCLUSIONS

MIF-tautomerase activity may provide a novel therapeutic target in patients with chronic inflammatory diseases such as CF, particularly those patients who are genetically predisposed to produce increased levels of this cytokine.

Chemically injured keratocytes induce cytokine release by human peripheral mononuclear cells

PURPOSE

To establish an in vitro model to study the role of keratocytes in corneal chemical burns and to investigate the interaction between chemically injured keratocytes and human peripheral blood mononuclear cells (PBMCs).

METHODS

Human keratocytes, epithelial cells, and PBMCs were cultured. The PBMC stimulation assay was then performed using cultured human keratocytes, epithelial cells, and NaOH-treated keratocytes. Matrix metalloprotease-9 (MMP-9), transforming growth factor-beta 1 (TGF-β1), and macrophage migration inhibitory factor (MIF) secretion profiles of activated PBMCs stimulated by NaOH-treated keratocytes were determined by ELISA.

RESULTS

Human keratocytes stimulated PBMC proliferation (p=0.016), and keratocytes treated with various concentrations of NaOH further stimulated PBMC proliferation compared to control cells in a dose-dependent manner (p=0.028 and 0.009). MMP-9 and MIF levels were higher than in the negative controls, while TGF-β1 levels did not differ from those of the negative controls.

CONCLUSION

Our results suggest that PBMCs are stimulated by chemically injured keratocytes, and produce inflammatory cytokines in response. This may be a major mechanism underlying the process causing corneal chemical burn injuries. This model can be used as an in vitro model for further studies on corneal chemical burns.

Combined treatment with antioxidants and immunosuppressants on cytokine release by human peripheral blood mononuclear cells - chemically injured keratocyte reaction

PURPOSE

To investigate the effect of antioxidants and immunosuppresants on mixed peripheral blood mononuclear cells (PBMC) - chemically injured keratocytes reaction (MLKR).

METHODS

The PBMC stimulation assay was performed using chemically injured keratocytes treated with 0.05 N NaOH for 90 s (MLKR). MLKR were treated with various drugs including rapamycin, dexamethasone, mycophenoleic acid (MPA), alpha lipoic acid (ALA), and N-acetyl cysteine (NAC). Matrix metalloprotease-9 (MMP-9), transforming growth factor-beta 1 (TGF-β1), interleukin-6 (IL-6), and macrophage migration inhibitory factor (MIF) secretion profiles of activated PBMCs stimulated by NaOH-treated keratocytes were determined by ELISA.

RESULTS

Anti-oxidants as well as immunosuppressants suppressed PBMC proliferation. MMP-9 levels were lower in antioxidants group. IL-6 levels decreased in dexamethasone group and anti-oxidants group. Combination of immunosuppressants and antioxidants suppressed more PBMC proliferation except for rapamycin + ALA group, suppressed MMP-9 production except for MPA + ALA group, decreased IL-6 levels and increased MIF levels except for rapamycin + ALA group. TGF-β1 levels were elevated in rapamycin group and rapamycin + ALA group.

CONCLUSIONS

Cytokine production was different depending on combination of drugs.Our results suggest that the different drugs should be selected for treatment according to the phases of corneal chemical burn.

CD74 deficiency ameliorates Pseudomonas aeruginosa-induced ocular infection

Eye trauma and contact lens wear are the main factors that predispose to the development of infectious keratitis. The existing therapies fail to control the inflammation-driven tissue damage that occurs during Pseudomonas aeruginosa infection. Antibiotic treatment reduces bacterial burdens, but better interventions are needed to alleviate tissue damage resulting from local inflammation. We have previously documented that inhibition of macrophage migration inhibitory factor (MIF) reduces the bacterial levels and the inflammatory damage during keratitis. Here, we report that mice deficient for CD74, the putative MIF receptor, developed milder Pseudomonas aeruginosa-induced disease, characterized by decreased proinflammatory mediators and reduced bacterial presence in the cornea. However, topical inhibition of MIF using antibodies applied to the cornea further promoted recovery from disease, suggesting that in addition to MIF-dependent signaling events, MIF-triggered CD74-independent signaling pathways regulate sensitization to P. aeruginosa-induced infection.

MIF as a disease target: ISO-1 as a proof-of-concept therapeutic

Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine that has been implicated as playing a causative role in many disease states, including sepsis, pneumonia, diabetes, rheumatoid arthritis, inflammatory bowel disease, psoriasis and cancer. To inhibit the enzymatic and biologic activities of MIF, we and others have developed small-molecule MIF inhibitors. Most MIF inhibitors bind within the hydrophobic pocket that contains highly conserved amino acids known to be essential for MIF's proinflammatory activity. The best characterized of these small-molecule MIF inhibitors, (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) has been validated in scores of laboratories worldwide. Like neutralizing anti-MIF antibodies, ISO-1 significantly improves survival and reduces disease progression and/or severity in multiple murine models where MIF is implicated. This MIF inhibitor, its derivatives and other MIF-targeted compounds show great promise for future testing in disease states where increased MIF activity has been discovered.

Inactivation of tautomerase activity of macrophage migration inhibitory factor by sulforaphane: a potential biomarker for anti-inflammatory intervention

BACKGROUND

Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine with keto-enol tautomerase activity, rises rapidly in response to inflammation and is elevated in many chronic diseases. Isothiocyanates, such as sulforaphane from broccoli, are very potent inactivators of MIF tautomerase activity. A simple rapid method for determining this activity in tissues and body fluids may therefore be valuable for assessing severity of inflammation and efficacy of intervention.

METHODS

Existing spectrophotometric assays of MIF, based on conversion of methyl L-dopachrome to methyl 5,6-dihydroxyindole-2-carboxylate and associated loss of absorption at 475 nm, lack sensitivity. Assay sensitivity and efficiency were markedly improved by reducing the nonenzymatic rate, by lowering pH to 6.2, replacing phosphate (which catalyzes the reaction) with Bis-Tris buffer, and converting to a microtiter plate format.

RESULTS

A structure-potency study of MIF tautomerase inactivation by isothiocyanates showed that sulforaphane, benzyl, n-hexyl, and phenethyl isothiocyanates were especially potent. MIF tautomerase could be readily quantified in human urine concentrated by ultrafiltration. This activity comprised: (i) a heat-labile, sulforaphane-inactivated macromolecular fraction (presumably MIF) that was concentrated during ultrafiltration; (ii) a flow-through fraction, with constant activity during filtration, that was heat stable and insensitive to sulforaphane. Administration of the sulforaphane precursor glucoraphanin to human volunteers almost completely abolished urinary tautomerase activity, which recovered over many hours.

CONCLUSION

A simple, rapid, quantitative MIF tautomerase assay has been developed as a potential biomarker for assessing inflammatory severity and effectiveness of intervention.

IMPACT

An improved assay for measuring MIF tautomerase activity and its applications are described.

Animal models of bacterial keratitis

Bacterial keratitis is a disease of the cornea characterized by pain, redness, inflammation, and opacity. Common causes of this disease are Pseudomonas aeruginosa and Staphylococcus aureus. Animal models of keratitis have been used to elucidate both the bacterial factors and the host inflammatory response involved in the disease. Reviewed herein are animal models of bacterial keratitis and some of the key findings in the last several decades.

The role of macrophage migration inhibitory factor in ocular surface disease pathogenesis after chemical burn in the murine eye

PURPOSE

To evaluate the role of macrophage migration inhibitory factor (MIF) in the wound healing process following severe chemical burns to the ocular surface.

METHODS

Chemical burning of the ocular surface was induced in mice (C57BL/6) via the application of 0.1 M NaOH. Macrophage migration inhibitory factor (MIF), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) mRNA expression in the ocular surface and lacrimal gland was evaluated via real-time reverse transcription PCR on days 2, 7, and 30 after induction of the chemical burn. The expression of MIF protein in the ocular surface and lacrimal gland was evaluated via western blot analysis. Immunohistochemical staining was conducted to detect MIF and vasculoendothelial growth factor in the cornea during the wound healing process. The angiogenic role of MIF was further evaluated using an 8-0 polyglactin suture technique to induce corneal neovascularization.

RESULTS

MIF, TNF-α, and IL-1β mRNA expression were elevated significantly in the ocular surface up to day 30 after chemical burn induction. TNF-α alone was elevated in the lacrimal gland. MIF protein elevation was confirmed via western blot analysis, and the spatial similarity of MIF and VEGF expression in the cornea was noted during the wound healing process. 8-0 polyglactin sutures soaked in MIF induced significantly higher numbers of new vessels on the mouse cornea after 7 days (p=0.003, Mann-Whitney test).

CONCLUSIONS

These findings indicate that MIF performs a crucial role in wound healing on the ocular surface after the induction of chemical burns.

TLR4 and TLR5 on corneal macrophages regulate Pseudomonas aeruginosa keratitis by signaling through MyD88-dependent and -independent pathways

Pseudomonas aeruginosa is a major cause of blindness and visual impairment in the United States and worldwide. Using a murine model of keratitis in which abraded corneas are infected with P. aeruginosa parent and ΔfliC (aflagellar) strains 19660 and PAO1, we found that F4/80(+) macrophages were the predominant cell type in the cornea expressing TLR2, TLR4, and TLR5. Depletion of macrophages and dendritic cells using transgenic Mafia mice, in which Fas ligand is selectively activated in these cells, resulted in diminished cytokine production and cellular infiltration to the corneal stroma and unimpaired bacterial growth. TLR4(-/-) mice showed a similar phenotype postinfection with ΔfliC strains, whereas TLR4/5(-/-) mice were susceptible to corneal infection with parent strains. Bone marrow-derived macrophages stimulated with ΔfliC bacteria induced Toll/IL-1R intracellular domain (TIR)-containing adaptor inducing IFN-β (TRIF)-dependent phosphorylation of IFN regulatory factor 3 in addition to TIR-containing adaptor protein/MyD88-dependent phosphorylation of IκB and nuclear translocation of the p65 subunit of NFκB. Furthermore, TRIF(-/-) mice showed a similar phenotype as TLR4(-/-) mice in regulating only ΔfliC bacteria, whereas MyD88(-/-) mice were unable to clear parent or ΔfliC bacteria. Finally, IL-1R1(-/-) and IL-1α/β(-/-) mice were highly susceptible to infection. Taken together, these findings indicate that P. aeruginosa activates TLR4/5 on resident corneal macrophages, which signal through TRIF and TIR-containing adaptor protein/MyD88 pathways, leading to NF-κB translocation to the nucleus, transcription of CXCL1 and other CXC chemokines, recruitment of neutrophils to the corneal stroma, and subsequent bacterial killing and tissue damage. IL-1α and IL-1β are also produced, which activate an IL-1R1/MyD88-positive feedback loop in macrophages and IL-1R on other resident cells in the cornea.