The effect of interleukin-1 on cytokine gene expression by human corneal epithelial cells

What is the impact of microbiota on dry eye: a literature review of the gut-eye axis

BACKGROUND

Dry eye is a chronic and multifactorial ocular surface disease caused by tear film instability or imbalance in the microenvironment of the ocular surface. It can lead to various discomforts such as inflammation of the ocular surface and visual issues. However, the mechanism of dry eye is not clear, which results in dry eye being only relieved but not cured in clinical practice. Finding multiple environmental pathways for dry eye and exploring the pathogenesis of dry eye have become the focus of research. Studies have found that changes in microbiota may be related to the occurrence and development of dry eye disease.

METHODS

Entered the keywords "Dry eye", "Microbiota", "Bacteria" through PUBMED, summarised the articles that meet the inclusion criteria and then filtered them while the publication time range of the literature was defined in the past 5 years, with a deadline of 2023.A total of 13 clinical and 1 animal-related research articles were screened out and included in the summary.

RESULTS

Study found that different components of bacteria can induce ocular immune responses through different receptors present on the ocular surface, thereby leading to an imbalance in the ocular surface microenvironment. Changes in the ocular surface microbiota and gut microbiota were also found when dry eye syndrome occurs, including changes in diversity, an increase in pro-inflammatory bacteria, and a decrease in short-chain fatty acid-related bacterial genera that produce anti-inflammatory effects. Fecal microbiota transplantation or probiotic intervention can alleviate signs of inflammation on the ocular surface of dry eye animal models.

CONCLUSIONS

By summarizing the changes in the ocular surface and intestinal microbiota when dry eye occurs, it is speculated and concluded that the intestine may affect the occurrence of eye diseases such as dry eye through several pathways and mechanisms, such as the occurrence of abnormal immune responses, microbiota metabolites- intervention of short-chain fatty acids, imbalance of pro-inflammatory and anti-inflammatory factors, and release of neurotransmitters, etc. Analyzing the correlation between the intestinal tract and the eyes from the perspective of microbiota can provide a theoretical basis and a new idea for relieving dry eyes in multiple ways in the future.

Nano Self-Assemblies of Caffeic Acid-Fibronectin Mimic a Peptide Conjugate for the Treatment of Corneal Epithelial Injury

Rapid corneal re-epithelialization is important for corneal wound healing. Corneal epithelial cell motility and oxidative stress are important targets for therapeutic intervention. In this study, we covalently conjugated the antioxidant caffeic acid (CA) with a bioactive peptide sequence (PHSRN) to generate a CA-PHSRN amphiphile, which was formulated into nanoparticular eye drops with an average size of 43.21 ± 16 nm. CA-PHSRN caused minimal cytotoxicity against human corneal epithelial cells (HCECs) and RAW264.7 cells, exhibited an excellent free radical scavenging ability, and remarkably attenuated reactive oxygen species (ROS) levels in H2O2-stimulated HCECs. The antioxidant and anti-inflammatory activities of CA-PHSRN were assessed in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The results show that CA-PHSRN treatment effectively prevented LPS-induced DNA damage and significantly reduced the levels of LPS-induced pro-inflammatory cytochemokines (i.e., iNOS, NO, TNF-α, IL-6, and COX-2) in a dose-dependent manner. Moreover, using a rabbit corneal epithelial ex vivo migration assay, we demonstrated that the proposed CA-PHSRN accelerated corneal epithelial cell migration and exhibited high ocular tolerance and ocular bioavailability after topical instillation. Taken together, the proposed CA-PHSRN nanoparticular eye drops are a promising therapeutic formulation for the treatment of corneal epithelial injury.

Pulmonary health effects of wintertime particulate matter from California and China following repeated exposure and cessation

Epidemiological studies show strong associations between fine particulate matter (PM2.5) air pollution and adverse pulmonary effects. In the present study, wintertime PM2.5 samples were collected from three geographically similar regions-Sacramento, California, USA; Jinan, Shandong, China; and Taiyuan, Shanxi, China-and extracted to form PMCA, PMSD, and PMSX, respectively, for comparison in a BALB/c mouse model. Each of four groups was oropharyngeally administered Milli-Q water vehicle control (50 μL) or one type of PM extract (20 μg/50 μL) five times over two weeks. Mice were necropsied on post-exposure days 1, 2, and 4 and examined using bronchoalveolar lavage (BAL), histopathology, and assessments of cytokine/chemokine mRNA and protein expression. Chemical analysis demonstrated all three extracts contained black carbon, but PMSX contained more sulfates and polycyclic aromatic hydrocarbons (PAHs) associated with significantly greater neutrophil numbers and greater alveolar/bronchiolar inflammation on post-exposure days 1 and 4. On day 4, PMSX-exposed mice also exhibited significant increases in interleukin-1 beta, tumor necrosis factor-alpha, and chemokine C-X-C motif ligands-3 and -5 mRNA, and monocyte chemoattractant protein-1 protein. These combined findings suggest greater sulfate and PAH content contributed to a more intense and progressive inflammatory response with repeated PMSX compared to PMCA or PMSD exposure.

Eph signaling is regulated by miRNA-210: Implications for corneal epithelial repair

A distinct boundary exists between the progenitor cells in the basal limbal epithelium and the more differentiated corneal epithelial basal cells. We have shown that reciprocal expression patterns of EphA2 and Ephrin-A1 are likely to contribute to normal limbal-corneal epithelial compartmentalization as well as play a role in response to injury. How this signaling axis is regulated remains unclear. We have demonstrated that microRNAs (miRNAs) play critical roles in corneal epithelial wound healing and several miRNAs (e.g. miR-210) have been predicted to target ephrins. Previous expression profiling experiments demonstrated that miR-210 is prominently expressed in corneal epithelial cells. RNA-seq data acquired from miR-210-depleted HCECs showed up-regulation of genes involved in cellular migration. In addition, miR-210 is decreased after corneal injury while EphA2 is increased. Moreover, antago-210-treated HCECs markedly enhanced wound closure in a scratch wound assay. Antago-210 treatment resulted in increased EphA2 protein levels as well as pS897-EphA2, the pro-migratory form of EphA2. As expected, Ephrin-A1 levels were reduced, while levels of a well-known target of miR-210, Ephrin-A3, were increased by antago-210 treatment. The increase in migration with antago-210 could be inhibited by Ephrin-A1 overexpression, Ephrin-A1-Fc treatment or siRNA depletion of EphA2. However, depletion of Ephrin-A3 did not have effects on the antago-210-induced increase in migration. In addition, Ephrin-A1 overexpression and siEphA2 dampened EGFR signaling, which is increased by antago-210. Our data clearly demonstrate a link between miR-210 and EphA2/Ephrin-A1 signaling that regulates, in part, corneal epithelial migration. This interaction might potentially control the limbal-corneal epithelial boundary.

Biomolecular evaluation of cryopreserved amniotic membranes for ophthalmological use by ELISA and RT-PCR at one and eighteen months

PURPOSE

To study the presence of certain proteins - EGF (epidermal growth factor), KGF (keratinocyte growth factor), IL-10 (interleukin 10), HGF (hepatocyte growth factor), Alpha2-macroglobulin and IL-1RA (interleukin 1 receptor antagonist) in cryopreserved amniotic membranes at 1 and 18 months and, as a secondary objective, to detect mRNA corresponding to KGF, IL-1Ra, Alpha2-macroglobulin, Fas Ligand, TGF beta (transforming growth factor beta) and Lumican by RT-PCR in membranes preserved at 1 and 18 months.

MATERIAL AND METHODS

Four samples of amniotic membrane were divided into 2 groups: the first group (N=2) cryopreserved for 1 month and the second group (N=2) cryopreserved for 18 months, in order to be studied by RT-PCR and ELISA.

RESULTS

RT-PCR detected KGF, IL-1Ra, Alpha2-macroglobulin, Fas Ligand, and Lumican. Of these, FAS Ligand mRNA was found in samples preserved for 1and 18 months. KGF, Lumican, and alpha2-microglobulin mRNA were found only at 1 month, and IL-1Ra mRNA was absent in both sample groups. RT-PCR for TGF-beta was inconclusive. ELISA was performed for detection and quantification of 6 proteins (EGF, KGF, IL-10, HGF, Alpha2-macroglobulin and IL-1Ra) in both amniotic membrane groups. All 6 proteins were found in all samples, with a lower concentration at 18 months compared to 1 month of preservation.

CONCLUSION

This study shows that membranes cryopreserved in 50% glycerol for 18 months do retain the proteins necessary for regeneration of the corneal surface, giving these membranes their biochemical properties.

Corneal epithelial biology: Lessons stemming from old to new

The anterior surface of the eye functions as a barrier to the external environment and protects the delicate underlying tissues from injury. Central to this protection are the corneal, limbal and conjunctival epithelia. The corneal epithelium is a self-renewing stratified squamous epithelium that protects the underlying delicate structures of the eye, supports a tear film and maintains transparency so that light can be transmitted to the interior of the eye (Basu et al., 2014; Cotsarelis et al., 1989; Funderburgh et al., 2016; Lehrer et al., 1998; Pajoohesh-Ganji and Stepp, 2005; Parfitt et al., 2015; Peng et al., 2012b; Stepp and Zieske, 2005). In this review, dedicated to James Funderburgh and his contributions to visual science, in particular the limbal niche, corneal stroma and corneal stromal stem cells, we will focus on recent data on the identification of novel regulators in corneal epithelial cell biology, their roles in stem cell homeostasis, wound healing, limbal/corneal boundary maintenance and the utility of single cell RNA sequencing (scRNA-seq) in vision biology studies.

Kinetics of Tear Fluid Proteins after Endothelial Keratoplasty and Predictive Factors for Recovery from Corneal Haze

Endothelial keratoplasty (EK) is less invasive with faster recovery as compared to conventional penetrating keratoplasty, however, it relies on the clarity of the host corneal stroma. Corneal transplantation involves the induction of immune tolerance for allogeneic tissues as well as the corneal wound healing process, in which coordinated interactions between cytokines and growth factors are critical. In this study, we profiled the expression of 51 soluble factors in the tear fluid over the course of EK and have provided evidence of dynamic changes in cytokine expression in the ipsilateral and contralateral eyes. Cluster analyses classified the cytokine expression kinetics into five groups. Group 1 proteins included TGF-b1, IL-1b, and innate proinflammatory cytokines, which bilaterally increased after surgery, despite the use of topical corticosteroid in the transplanted eyes. Local corticosteroids suppressed cytokines involved in adaptive immunity in the transplanted eyes but not in the contralateral eyes. We found tear protein expression at baseline and one week post-surgery to be a potential predictive biomarker of delayed recovery after EK in terms of the corneal haze and visual acuity. Furthermore, Group 1 tear proteins were most associated with persistent corneal haze pre-surgery as well as visual acuity at one month-post transplant.

Conjunctival Neuropathic and Inflammatory Pain-Related Gene Expression with Contact Lens Wear and Discomfort

Purpose: To identify alterations in neuropathic and inflammatory pain gene expression associated with contact lens (CL) wear and CL discomfort (CLD).Methods: Eight non-wearers, eight asymptomatic CL wearers (CLWs) and eight symptomatic CLWs were included. Conjunctival cells were collected by impression cytology and the mRNA expression levels of 85 genes were analyzed. Differentially expressed genes between non-wearers and CLWs and between asymptomatic and symptomatic CLWs were analyzed. An enrichment analysis was also performed.Results: Twelve genes were upregulated (including IL10, PDYN and PENK) and 28 downregulated (CCL2, IL1A, IL1B, IL2 and NGF) in CLWs (p ≤ 0.050). Eleven genes were upregulated (CCL2, IL1A, IL1B, IL2 and NGF) and nine downregulated (PDYN and PENK) in symptomatic CLWs (p ≤ 0.035). Enriched overrepresented terms were related to pain, neuronal transmission and inflammation.Conclusion: Contact lens wear might produce a desensitization-like mechanism responsible for comfortable CL wear. A malfunction of this mechanism might contribute to CLD.

Evaluation of Long-Term Silicone Hydrogel Use on Ocular Surface Inflammation and Tear Function in Patients With and Without Meibomian Gland Dysfunction

OBJECTIVES

To determine whether silicone hydrogel (SH) contact lens (CL) use, with or without meibomian gland dysfunction (MGD), promotes ocular surface inflammation.

METHODS

Subjects wearing SH-CL for at least 6 months who also had coexisting MGD (group 1, n=20), SH-CL users who did not have MGD (group 2, n=20), patients who had MGD but did not use CL (group 3, n=20), and healthy CL-naive individuals with no known systemic or ocular diseases (group 4, n=20) were included in this cross-sectional, single-center study. All subjects underwent tear function tests consisting of tear break-up time (tBUT), ocular surface staining, Schirmer test, and the Ocular Surface Disease Index (OSDI) questionnaire, as well as determination of tear IL-1RA, IL-1β, IL-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, IFN-α, IFN-γ, TNF-α, granulocyte-macrophage colony-stimulating factor, IP-10, monokine induced by gamma interferon, RANTES, eotaxin, MIP-1α, MIP-1β, and MCP-1 levels using Luminex multicytokine immunobead assay. Intergroup comparisons were made using one-way analysis of variance or Kruskal-Wallis test.

RESULTS

The tBUT was lower (P=0.048) and ocular surface staining (P=0.032) as well as OSDI scores (P=0.001) were higher in group 1 but not in groups 2 or 3 when compared with those in the control group. Tear cytokine levels were similar across all groups. None of the tear cytokine levels were elevated in CL wearers (groups 1 and 2) or those with MGD (groups 1 and 3) as compared to those in control subjects.

CONCLUSION

Silicone hydrogel contact lens use with concomitant MGD is not associated with cytokine-driven ocular surface inflammation but may impact tear function leading to dry eye symptoms.

Current and emerging therapies for corneal neovascularization

The cornea is unique because of its complete avascularity. Corneal neovascularization (CNV) can result from a variety of etiologies including contact lens wear; corneal infections; and ocular surface diseases due to inflammation, chemical injury, and limbal stem cell deficiency. Management is focused primarily on the etiology and pathophysiology causing the CNV and involves medical and surgical options. Because inflammation is a key factor in the pathophysiology of CNV, corticosteroids and other anti-inflammatory medications remain the mainstay of treatment. Anti-VEGF therapies are gaining popularity to prevent CNV in a number of etiologies. Surgical options including vessel occlusion and ocular surface reconstruction are other options depending on etiology and response to medical therapy. Future therapies should provide more effective treatment options for the management of CNV.

Contributions of MyD88-dependent receptors and CD11c-positive cells to corneal epithelial barrier function against Pseudomonas aeruginosa

Previously we reported that corneal epithelial barrier function against Pseudomonas aeruginosa was MyD88-dependent. Here, we explored contributions of MyD88-dependent receptors using vital mouse eyes and confocal imaging. Uninjured IL-1R (−/−) or TLR4 (−/−) corneas, but not TLR2 (−/−), TLR5 (−/−), TLR7 (−/−), or TLR9 (−/−), were more susceptible to P. aeruginosa adhesion than wild-type (3.8-fold, 3.6-fold respectively). Bacteria adherent to the corneas of IL-1R (−/−) or TLR5 (−/−) mice penetrated beyond the epithelial surface only if the cornea was superficially-injured. Bone marrow chimeras showed that bone marrow-derived cells contributed to IL-1R-dependent barrier function. In vivo, but not ex vivo, stromal CD11c+ cells responded to bacterial challenge even when corneas were uninjured. These cells extended processes toward the epithelial surface, and co-localized with adherent bacteria in superficially-injured corneas. While CD11c+ cell depletion reduced IL-6, IL-1β, CXCL1, CXCL2 and CXCL10 transcriptional responses to bacteria, and increased susceptibility to bacterial adhesion (>3-fold), the epithelium remained resistant to bacterial penetration. IL-1R (−/−) corneas also showed down-regulation of IL-6 and CXCL1 genes with and without bacterial challenge. These data show complex roles for TLR4, TLR5, IL-1R and CD11c+ cells in constitutive epithelial barrier function against P. aeruginosa, with details dependent upon in vivo conditions.

Non-invasive objective and contemporary methods for measuring ocular surface inflammation in soft contact lens wearers - A review

Contact lens wear is one of the primary risk factors for the development of ocular surface inflammatory events. The purpose of this review is to examine and summarize existing knowledge on the mechanisms of contact lens related ocular surface inflammation and the evidence for the effectiveness of current objective methods to measure ocular surface inflammation. Contact lens wear is postulated to trigger an inflammatory response on the ocular surface due to mechanical, chemical, hypoxic stress, or by the introduction of microbes and their toxins. Apart from the traditional signs of inflammation, such as swelling, oedema, redness and heat, on the ocular surface, other methods to measure ocular surface inflammation in sub-clinical levels include tear inflammatory mediator concentrations, conjunctival cell morphology, and corneal epithelial dendritic cell density and morphology. Tear inflammatory mediator concentrations are up- or down-regulated during contact lens wear, with or without the presence of associated inflammatory events. There is higher conjunctival cell metaplasia observed with contact lens wear, but changes in goblet cell density are inconclusive. Dendritic cell density is seen to increase soon after initiating soft contact lens wear. The long term effects of contact lens wear on dendritic cell migration in the cornea and conjunctiva, including the lid wiper area, require further investigation. Currently patient factors, such as age, smoking, systemic diseases and genetic profile are being studied. A better understanding of these mechanisms may facilitate the development of new management options and strategies to minimize ocular surface inflammation related to contact lens wear.

Changes in Tear Cytokine Concentrations Following Discontinuation of Soft Contact Lenses-A Pilot Study

PURPOSE

This study investigated changes in selected tear cytokine concentrations (IL-1β, IL-1Ra, IL-6, IL-10, IL-12 (p70), and TNF-α) after a 1-week washout from soft contact lens wear (CLW), and the repeatability of cytokine measurements using custom multiplex assays.

METHODS

A total of 10 subjects completed this 6-visit (immediately following contact lens removal, and after 1, 2, 3, 4, and 7 [±1] days without CLW) pilot study. Approximately 20 to 30 μL of pooled basal tears were collected from both eyes at each visit. Two custom multiplex assays were used by two operators to quantify the concentration of tear cytokines. Tear samples from subjects 1 to 6 were analyzed using the first kit by operator 1. Tear samples from subject 7 to 10 plus additional tear samples from subjects 1 to 5, which were used to determine the between-kit per operator repeatability, were analyzed using the second kit by operator 2. Linear mixed models were used to determine changes in tear cytokine concentrations over time. Between-kit per operator and within-kit per operator repeatabilities were assessed using the Bland and Altman analysis.

RESULTS

There were no significant changes in tear cytokine concentrations over a 1-week washout of CLW. More than 99% of the tear samples had detectable levels of cytokines using custom multiplex assays. Within-kit per operator repeatability was good, but between-kit per operator repeatability was poor; likely due to protein degradation, differences in operator experience, and operating procedures.

CONCLUSION

A washout period may not be necessary when evaluating changes in tear cytokines with new contact lenses or lens care products. A well-trained operator using standardized operating procedures can produce repeatable measurements using custom multiplex assays.

A distinct cytokines profile in tear film of dry eye disease (DED) patients with HIV infection

PURPOSE

To investigate the tear cytokine profile in HIV patients with dry eye disease (DED) and study the association between the severity of ocular inflammatory complications and tear cytokines levels. We postulate that HIV-mediated inflammation may be the underlying pathogenic mechanism for HIV-associated DED.

METHODS

The current prospective case-control study compared tear film cytokine profiles in DED patients with HIV infection (n=34) and age/gender-matched DED patients without HIV infection [controls (n=32)]. Participants were recruited from tertiary referral eye care centre and communicable disease clinics, Singapore. Ocular surface health was documented using tear film, Schirmer's test, corneal staining, and conjunctival injection measurements. Tear samples were collected using Schirmer's strips and analysed for the levels of 41 cytokines using Luminex bead assay. Logistic regression models were performed to determine correlation and significance.

RESULTS

Among the 41 cytokines analysed, statistically significant differences were observed in the mean values of epithelial growth factor (EGF), growth related oncogene (GRO) and interferon gamma-induced protein 10 (IP-10). EGF and IP-10 levels were higher and GRO levels were lower in the tears of DED patients with HIV infection compared to DED patients without HIV infection. No significant association was found between varying levels of ocular surface parameters and cytokine concentrations in HIV patients with DED (p>0.05).

CONCLUSIONS

EGF and IP-10 were significantly elevated and GRO levels were lower in the tear profile of HIV patients with DED compared to immunocompetent patients with DED. This study suggests a novel cytokine driven paradigm for ocular inflammatory complications of HIV infection. Additional studies in large organised cohorts can validate the results.

Dynamic change in natural killer cell type in the human ocular mucosa in situ as means of immune evasion by adenovirus infection

The most severe form of virus-induced inflammation at the ocular surface is epidemic keratoconjunctivitis (EKC), often caused by group D human adenoviruses (HAdVs). We investigated the dynamics and mechanisms of changes in natural killer (NK) cell types in the human ocular mucosal surface in situ over the course of infection. In the acute phase of infection, the mature CD56(dim)NK cells that comprise a major subpopulation in the normal human conjunctiva are replaced by CD56(bright)NK cells recruited to the ocular surface by chemokines produced by the infected epithelium, and NKG2A-expressing CD56(dim) and CD56(bright) NK cells become the major subpopulations in severe inflammation. These NK cells attracted to the mucosal surface are however incapable of mounting a strong antiviral response because of upregulation of the inhibitory ligand human leukocyte antigen-E (HLA-E) on infected epithelium. Furthermore, group D HAdVs downregulate ligands for activating NK cell receptors, thus rendering even the mature NKG2A(-)NK cells unresponsive, an immune-escape mechanism distinct from other adenoviruses. Our findings imply that the EKC-causing group D HAdVs utilize these multiple pathways to inhibit antiviral NK cell responses in the initial stages of the infection.

Experimental study on cryotherapy for fungal corneal ulcer

Background

Fungal corneal ulcer is one of the major causes of visual impairment worldwide. Treatment of fungal corneal ulcer mainly depends on anti-fungal agents. In the current study, we developed an integrated combination therapy of cryotherapy and anti-fungal agents to facilitate effective treatment of fungal corneal ulcer.

Methods

Rabbit models of cornea infection were established using a combined method of intrastromal injection and keratoplasty. After treatment with cryotherapy and anti-fungal agents, scanning electron microscopy, transmission electron microscopy, and confocal microscopy were conducted to observe changes in microstructure in the rabbits. Periodic acid Schiff A and hematoxylin and eosin staining were used for detection of histological changes.

Results

Continuous scanning electron microscopy and transmission electron microscopy observations showed that cryothermal treatment inhibited growth of fungal mycelium by destroying fungal cellular structures. Typical cryotherapy was effective in curing fungal corneal ulcer. Different fungi showed different susceptibilities to treatment. The curative effect of Candida albicans was the best, while that of Aspergillus fumigates was the worst.

Conclusions

Our study provides a novel method of a combination of cryotherapy and anti-fungal agents for treatment of fungal corneal ulcer. This treatment could help facilitate the practice of fungal keratitis treatment in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-015-0011-5) contains supplementary material, which is available to authorized users.

Herpes simplex virus-1 infection or Simian virus 40-mediated immortalization of corneal cells causes permanent translocation of NLRP3 to the nuclei

AIM

To investigate into the potential involvement of pyrin containing 3 gene (NLRP3), a member of the nucleotide-binding oligomerization domain-like receptors with cytosolic pattern recognition, in the host defense of corneas against viruses.

METHODS

The herpes viral keratitis model was utilized in BALB/c mice with inoculation of herpes simplex virus-1 (HSV-1). Corneal tissues removed during therapy of patients with viral keratitis as well as a Simian vacuolating virus 40 (SV40)-immortalized human corneal epithelial cell line were also examined. Immunohistochemistry was used to detect NLRP3 in these subjects, focusing on their distribution in tissue or cells. Western blot was used to measure the level of NLRP3 and another two related molecules in NLPR3 inflammasome, namely caspase-1 and IL-1β.

RESULTS

The NLRP3 activation induced by HSV-1 infection in corneas was accompanied with redistribution of NLRP3 from the cytoplasm to the nucleus in both murine and human corneal epithelial cells. Furthermore, in the SV40-immortalized human corneal epithelial cells, NLRP3 was exclusively located in the nucleus, and treatment of the cells with high concentration of extracellular potassium (known as an inhibitor of NLRP3 activation) effectively drove NLRP3 back to the cytoplasm as reflected by both immunohistochemistry and Western blot.

CONCLUSION

It is proposed that herpes virus infection activates and causes redistribution of NLRP3 to nuclei. Whether this NLRP3 translocation occurs with other viral infections and in other cell types merit further study.

Acanthamoeba-cytopathic protein induces apoptosis and proinflammatory cytokines in human corneal epithelial cells by cPLA2α activation

PURPOSE

We have shown that Acanthamoeba interacts with a mannosylated protein on corneal epithelial cells and stimulates trophozoites to secrete a mannose-induced 133 kDa protease (MIP-133), which facilitates corneal invasion and induces apoptosis. The mechanism of MIP-133-induced apoptosis is unknown. The aim of this study was to determine if MIP-133 induces apoptosis and proinflammatory cytokines/chemokines in human corneal epithelial (HCE) cells via the cytosolic phospholipase A(2α) (cPLA(2α)) pathway.

METHODS

HCE cells were incubated with or without MIP-133 at doses of 7.5, 15, and 50 μg/mL for 6, 12, and 24 hours. The effects of cPLA(2α) inhibitors on cPLA(2α), arachidonic acid (AA) release, and apoptosis were tested in vitro. Inhibition of cPLA(2α) involved preincubating HCE cells for 1 hour with cPLA(2α) inhibitors (10 μM methyl-arachidonyl fluorophosphonate [MAFP] or 20 μM arachidonyl trifluoromethyl ketone [AACOCF3]) with or without MIP-133 for 24 hours. Expression of cPLA(2α) mRNA and enzyme was examined by RT-PCR and cPLA(2) activity assays, respectively. Apoptosis of corneal epithelial cells was determined by caspase-3 and DNA fragmentation assays. Expression of IL-8, IL-6, IL-1β, and IFN-γ was examined by RT-PCR and ELISA.

RESULTS

MIP-133 induced significant cPLA(2α) (approximately two to four times) and AA release (approximately six times) from corneal cells while cPLA(2α) inhibitors significantly reduced cPLA(2α) (approximately two to four times) and AA release (approximately three times) (P < 0.05). cPLA(2α) inhibitors significantly inhibited MIP-133-induced DNA fragmentation approximately 7 to 12 times in HCE cells (P < 0.05). MIP-133 specifically activates cPLA(2α) enzyme activity in HCE cells, which is blocked by preincubation with anti-MIP-133 antibody. In addition, MIP-133 induced significant IL-8, IL-6, IL-1β, and IFN-γ production, approximately two to three times (P < 0.05).

CONCLUSIONS

MIP-133 interacts with phospholipids on plasma membrane of HCE cells and activates cPLA(2α). cPLA(2α) is involved in apoptosis, AA release, and activation of proinflammatory cytokines/chemokines from HCE cells. cPLA(2α) inhibitors may be a therapeutic target in Acanthamoeba keratitis.

EphA2/Ephrin-A1 signaling complexes restrict corneal epithelial cell migration

PURPOSE

Eph/ephrin signaling proteins are present in the corneal epithelium, where their function remains unknown. The authors examined the role of the EphA2 receptor and ephrin-A1 ligand in human corneal epithelial cell migration.

METHODS

Immunohistochemical analysis of EphA2 and ephrin-A1 in healthy and diabetic corneas was performed in concert with linear scratch wound healing studies in primary and telomerase-immortalized human corneal epithelial cells. Corneal epithelial cells were exposed to a soluble ephrin-A1-Fc peptide mimetic that targets EphA2 to trigger receptor phosphorylation and subsequent downregulation. Genetic modulation of EphA2 and ephrin-A1 levels was combined with manipulation of Erk1/2 or Akt signaling during wound healing.

RESULTS

EphA2 was immunolocalized to human corneal epithelial cells in vivo and in vitro. Ephrin-A1 ligand targeting of EphA2 restricted the ability of corneal epithelial cells to seal linear scratch wounds in a manner that was associated with a transient reduction in Erk1/2 and Akt activation state. Ephrin-A1-Fc treatment delayed wound healing independently of Mek-Erk1/2 signaling but was no longer capable of restricting migration after pharmacologic blockade of the PI3K-Akt pathway. Interestingly, ephrin-A1 immunoreactivity was increased in the corneal epithelia of diabetic individuals, mice maintained on a high-fat diet, or cultured corneal epithelial cells exposed to high glucose, which exhibit impaired Akt signaling and slower wound healing responses.

CONCLUSIONS

EphA2 attenuates corneal epithelial cell migration when stimulated by ephrin-A1 ligand in a manner that involves the suppression of Akt. Elevated levels of ephrin-A1 may contribute to diabetic keratopathies by persistently engaging EphA2 and prohibiting Akt-dependent corneal epithelial repair processes.

Matrix revolution: molecular mechanism for inflammatory corneal neovascularization and restoration of corneal avascularity by epithelial stem cell transplantation

Corneal neovascularization (CNV) associated with severe limbal stem cell (LSC) deficiency remains a challenging ocular surface disease in that corneal inflammation may persist and progress, and the condition will not improve without LSC transplantation. A prominent feature after successful LSC transplantation is the suppression of corneal inflammation and CNV, which is generally attributed to the endogenous anti-angiogenic/anti-inflammatory factors secreted by corneal epithelial cells. In addition, corneal epithelial basement membrane (EBM) plays a unique role in the regulation of angiogenesis; several potent anti-angiogenic factors are derived from the matrix component of EBM, such as endostatin (from collagen XVIII) and restin (from collagen XV). Also, angio-inhibitory thrombospondin and tissue inhibitor of metalloproteinase-3 are deposited in EBM. Moreover, the heparan sulphate proteoglycan in EBM can bind and sequester VEGF and FGF-2 from activation. Recently, cultivated corneal epithelial transplantation (CCET) and cultivated oral mucosal epithelial transplantation (COMET) have emerged as promising techniques for the treatment of LSC deficiency. When human limbo-corneal epithelial (HLE) cells are cultivated on cryopreserved amniotic membrane, production of endostatin, restin, and IL-1ra is enhanced. This highlights the significance of delicate epithelial-matrix interactions in the generation of anti-angiogenic/anti-inflammatory factors by HLE cells, and this may, in part, explain the rapid restoration of corneal avascularity following CCET. In addition, whether epithelial stem cells can persist after transplantation is the key for CCET and COMET. Emerging evidence of long-term survival of cultivated epithelial cells after transplantation suggest that epithelial stem cells can be isolated and cultivated in vitro, and can re-establish the epithelial phenotype in vivo. Taken together, the merits of enhanced anti-angiogenic activity and the preservation of corneal epithelial stem cells encourage further application of this tissue engineering technique for ocular surface reconstruction.

Cytokines and chemokines in immune-based ocular surface inflammation

Altered levels of several cytokines and chemokines have been found in different types of inflammatory ocular surface diseases, such as allergy or dry-eye syndrome. It has also been demonstrated that epithelial cells play a key role in the persistence and even initiation of chronic mucosal inflammation. The recent development of 'multiplex detection' technologies has facilitated the identification of specific patterns of expression of these molecules in some ocular immune-based inflammatory disorders. Analysis of these molecules in tissues, cells (in vivo and in vitro) and tears has revealed that not only inflammatory cells but also epithelial and fibroblast resident cells are sources of these molecules. The purpose of this review is to summarize recent studies in this field.

Analysis of inflammatory cytokines in the tears of dry eye patients

PURPOSE

To determine the levels of 8 important cytokines and 1 chemokine in tears of patients with dry eye disease.

METHODS

Tear samples were collected from 7 patients with dry eye disease and 7 healthy volunteers, and impression cytology samples were collected from 3 of the dry eye patients and 3 of the normal controls. Tears were analyzed for the presence of 8 cytokines [interleukin (IL)-2, IL-4, IL-5, IL-6, IL-10, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, IL-1beta] and 1 chemokine (IL-8). The cytokines and chemokine in each tear sample were measured using Invitrogen's Multiplex Bead Immunoassays. The impression cytology samples were analyzed for IL-1beta, IL-6, IL-8, and TNF-alpha mRNA expression using real-time reverse transcriptase polymerase chain reaction anlaysis.

RESULTS

All cytokines and the chemokine measured were significantly increased in the tears of dry eye patients as compared to normal controls. mRNA of all four markers was increased, and the fold increase correlated well with the fold increase of the cytokine concentration found in the tear samples.

CONCLUSION

Tears from dry eye patients contain significantly increased concentrations of cytokines that show correlation to severity of the disease. The upregulation of their respective genes in the conjunctiva suggests that the concentration increase is not the result of evaporative effects, but of overproduction. These findings suggest that cytokines may play an important role in dry eye disease and topical cytokine modulators may be explored as a therapeutic approach to dry eye disease.

Different inflammatory responses are associated with Ureaplasma parvum-induced UTI and urolith formation

Background

Epidemiologic studies show a strong association between Ureaplasmas and urogenital tract disease in humans. Since healthy humans can be colonized with Ureaplasmas, its role as a pathogen remains controversial. In order to begin to define the role of the host in disease, we developed a rodent model of urinary tract infection (UTI) using Fischer 344 (F344) rats. Animals were inoculated with sterile broth, 10¹, 10³, 10⁵, 10⁷, or 10⁹ log CFU of a rat-adapted strain of Ureaplasma parvum.

Results

Infected animals exhibited two distinct profiles, asymptomatic UTI and UTI complicated with struvite urolithiasis. Inoculum dose of U. parvum affected the incidence of UTI, and 50% to 57% of animals inoculated with ≥ 10⁷ CFU of U. parvum remained infected (p < 0.04). However, inoculum dose did not influence immune response to U. parvum. Asymptomatic UTI was characterized by a minimal immune response that was predominantly monocytic and lymphocytic, with limited lesions, and elevated urinary levels of IFN-γ, IL-18 and MCP-1 (P ≤ 0.02). UTI complicated with struvite formation was characterized by an exaggerated immune response that was mostly neutrophilic (P ≤ 0.0001), with lesions that showed extensive uroepithelial hyperplasia (P ≤ 0.0001), and a predominance of IL-1α, IL-1β, and GRO/KC in the urine (P ≤ 0.02). Animals with asymptomatic UTI also had a significantly high rate of kidney infection (P ≤ 0.0005).

Conclusion

Complications associated with U. parvum infection are primarily dependent upon host-specific factors rather than Ureaplasma microbial load. The immune response in F344 rats is similar to that which occurs in humans with ureaplasmal associated disease. Therefore, this model of infection is a useful tool for elucidating U. parvum-host interactions that confer UTI and disease.

Topical interleukin-1 receptor antagonist inhibits inflammatory cell infiltration into the cornea

Interleukin (IL)-1alpha and beta are important modulators of many functions of corneal epithelial and stromal cells that occur following injury to the cornea, including the influx of bone marrow-derived inflammatory cells into the stroma attracted by chemokines released from the stroma and epithelium. In this study, we examined the effect of topical soluble IL-1 receptor antagonist on bone marrow-derived cell influx following corneal epithelial scrape injury in a mouse model. C57BL/6 mice underwent corneal epithelial scrape followed by application of IL-1 receptor antagonist (Amgen, Thousand Oaks, CA) at a concentration of 20 mg/ml or vehicle for 24 h prior to immunocytochemical detection of marker CD11b-positive cells into the stroma. In two experiments, topical IL-1 receptor antagonist had a marked effect in blocking cell influx. For example, in experiment 1, topical IL-1 receptor antagonist markedly reduced detectible CD11b-positive cells into the corneal stroma at 24h after epithelial injury compared with the vehicle control (3.5+/-0.5 (standard error of the mean) cells/400x field and 13.9+/-1.2 cells/400x field, respectively, p<0.01). A second experiment with a different observer performing cell counting had the same result. Thus, the data demonstrate conclusively that topical IL-1 receptor antagonist markedly down-regulates CD-11b-positive monocytic cell appearance in the corneal stroma. Topical IL-1 receptor antagonist could be an effective adjuvant for clinical treatment of corneal conditions in which unwanted inflammation has a role in the pathophysiology of the disorder.

Pharmacological modulation of wound healing in experimental burns

Factors involved in wound healing and their interdependence are not yet fully understood; nevertheless, new prospects for therapy to favor speedy and optimal healing are emerging. Reports about wound healing modulation by local application of simple and natural agents abound even in the recent literature, however, most are anecdotal and lack solid scientific evidence. We describe the effect of silver sulfadiazine and moist exposed burn ointment (MEBO), a recently described burn ointment of herbal origin, on mast cells and several wound healing cytokines (bFGF, IL-1, TGF-beta, and NGF) in the rabbit experimental burn model. The results demonstrate that various inflammatory cells, growth factors and cytokines present in the wound bed may be modulated by application of local agents with drastic effects on their expression dynamics with characteristic temporal and spatial regulation and changes in the expression pattern. Such data are likely to be important for the development of novel strategies for wound healing since they shed some light on the potential formulations of temporally and combinatory optimized therapeutic regimens.

Evidence for two distinct pathways in TNFalpha-induced membrane and soluble forms of ICAM-1 in human osteoblast-like cells isolated from osteoarthritic patients

OBJECTIVE

The present study aimed to investigate the modulation of membrane-bound intercellular adhesion molecule-1 (mICAM-1) and soluble ICAM-1 (sICAM-1) expression by tumor necrosis factor-alpha (TNFalpha) in human osteoarthritic (OA) osteoblasts.

METHODS

Cultured human primary osteoblasts were stimulated with increasing concentrations of human recombinant TNFalpha. Expression of mICAM-1 and sICAM-1 was evaluated by immunocytochemistry, enzyme-linked immunosorbent assay and semi-quantitative reverse transcriptase-polymerase chain reaction. In addition, we investigated the molecular mechanisms underlying ICAM-1 induction by TNFalpha, focusing on the activation of the mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) pathways.

RESULTS

Our data showed that TNFalpha dose-dependently increased mICAM-1 and sICAM-1 expression at the protein and mRNA levels in OA osteoblasts. The inhibitor of de novo mRNA synthesis, actinomycin D, suppressed TNFalpha-induced mICAM-1 and sICAM-1 expression. Upon examination of the signaling components, we found that TNFalpha was a potent activator of p38, p44/42, p54/46 MAPK, and IkappaBalpha (IkappaBalpha). The chemical inhibitors of p38, p44/42 MAPK, and NF-kappaB blocked TNFalpha-induced mICAM-1 expression but not that of sICAM-1. Transfection experiments revealed that p38 MAPK or IkappaB kinase alpha (IKKalpha) overexpression enhanced TNFalpha-induced mICAM-1 production. Furthermore, osteoblasts treatment with a chemical inhibitor of metalloproteinase-9 (MMP-9) activity, a proteolytic enzyme involved in ICAM-1 cleavage, evoked a significant 25% decrease of TNFalpha-induced sICAM-1 release.

CONCLUSION

Taken together, these findings illustrate the central role played by TNFalpha in the regulation of ICAM-1. We suggest that TNFalpha differentially regulates sICAM-1 and mICAM-1 expression and that sICAM-1 release involves, in part, the proteolytic cleavage of mICAM-1 by MMP-9. The capacity of the MMP-9 inhibitor to prevent sICAM-1 production may be useful for the development of novel therapeutic approaches relevant to OA.

Transcriptional profiling of enriched populations of stem cells versus transient amplifying cells. A comparison of limbal and corneal epithelial basal cells

The basal layer of limbal and central corneal epithelium is enriched in stem cells and transient amplifying cells, respectively. This physical separation of stem and transient amplifying cells makes the limbal/corneal epithelium an exceptionally suitable system for isolating basal cells enriched in these two proliferative populations. Prior attempts to isolate epithelial stem cells used methods such as proteolytic tissue dissociation and cell sorting that could potentially alter their gene expression profile. Using laser capture microdissection, we were able to isolate resting limbal and corneal basal cells from frozen sections with minimal tissue processing, thereby improving the yield and quality of RNA. Analyses of RNA isolated from 300 limbal and corneal basal cells from eight mice revealed a set of approximately 100 genes that are differentially expressed in limbal cells versus corneal epithelial basal cells. Semiquantitative reverse transcription-PCR confirmed the up-regulation of three limbal and three corneal genes. LacZ identification of epiregulin from epiregulin-null mice and immunohistochemical staining of wild type mice confirmed that epiregulin, one of the limbal epithelium-enriched genes, was associated with the limbal epithelial basal cells. Within the limbal and corneal basal cells, we detected previously unknown genes that were differentially expressed in these two regions that contribute further to our understanding of the unique heterogeneity of these two closely related basal cell populations. Our findings indicate that we can obtain accurate gene expression profiles of the stem cell-enriched limbal basal cell population in their "natural" quiescent state.

IL-1β-Mediated Proinflammatory Responses Are Inhibited by Estradiol via Down-Regulation of IL-1 Receptor Type I in Uterine Epithelial Cells

The objective of this study was to examine the effects of sex hormones on IL-1beta-mediated responses by uterine epithelial cells. The mRNA expression and secretion of human beta-defensin-2 and CXCL8 by uterine epithelial cells was examined following stimulation with IL-1beta in the presence of estradiol or progesterone. Estradiol inhibited the IL-1beta-mediated mRNA expression and secretion of human beta-defensin-2 and CXCL8 by uterine epithelial cells while progesterone had no effect. Inhibition of the IL-1beta-mediated response by estradiol was dose dependent, with maximal inhibition observed using 10(-7) to 10(-10) M, and was shown to be mediated through the estrogen receptor because addition of a pure estrogen receptor antagonist abrogated this effect. The mechanism by which estradiol inhibits IL-1beta-mediated responses by uterine epithelial cells appears to be the down-modulation of the IL-1R type I, thereby reducing the uterine epithelial cell's ability to respond to IL-1beta. These results suggest that the inhibitory effect of estradiol on IL-1beta-mediated inflammatory responses by uterine epithelial cells indicates a link between the endocrine and immune systems and may be crucial for dampening proinflammatory responses during the time of ovulation or pregnancy.