sPLA2-IIa is an inflammatory mediator when the ocular surface is compromised

Targeted metabolomic analysis of serum free fatty acids: Lipidomics disturbance in patients with superior limbic keratoconjunctivitis

This study aimed to identify and quantify free fatty acids (FFAs), secretory phospholipase A2 group IIa (sPLA2-IIa) and cytosolic phospholipase A2 (cPLA2) in serum of superior limbic keratoconjunctivitis (SLK) patients and explored the association between FFAs, sPLA2-IIa and cPLA2 variations and SLK. Targeted metabolomic analysis of FFAs in serum was performed by gas chromatography tandem mass spectrometry (GC-MS/MS) analysis on 16 SLK patients (43.88 ± 7.88 years; female: 62.50%) and 25 healthy controls (43.12 ± 7.88 years; female: 64.00%). Qualitative and absolute quantitative results of FFAs were obtained and classified according to gender and thyroid tests. Differential lipid metabolites, metabolomic pathways and biomarkers were further evaluated. The serum sPLA2-IIa and cPLA2 were determined by enzyme linked immunosorbent assay (ELISA). Among 40 FFAs identified, 6 FFAs showed significant changes (P < 0.05) in SLK patients, including 4 decreased and 2 increased. They were mainly related to unsaturated fatty acid biosynthesis, α-linolenic acid and linoleic acid metabolism, and fatty acid biosynthesis. When dividing the data by gender or abnormal thyroid tests, some comparable FFAs alterations displayed in SLK patients. The ROC analysis revealed that the AUC values of linoleic acid, γ-linolenic acid, cis-8,11,14-eicosatrienoic acid, stearic acid, and palmitic acid, were all greater than 0.8. The serum concentrations of sPLA2-IIa and cPLA2 in patients with SLK were significantly higher than that in healthy controls. Lipidomics disturbance might be the potential mechanism of SLK. Serum FFA biomarkers associated with SLK have potential for the diagnosis and treatment of the disease.

Lipidomic analysis reveals altered lipid profiles of gingival tissues with periodontitis

AIM

The role of lipids in periodontitis has not been well studied. Thus, this study aimed to explore periodontitis-associated lipid profile changes and identify differentially expressed lipid metabolites in gingival tissues.

MATERIALS AND METHODS

Gingival tissues from 38 patients with periodontitis (periodontitis group) and 38 periodontally healthy individuals (control group) were collected. A UHPLC-QTOF-MS-based non-targeted metabolomics platform was used to identify and compare the lipid profiles of the two groups. The distribution and expression of related proteins were subsequently analyzed via immunohistochemistry to further validate the identified lipids.

RESULTS

Lipid profiles significantly differed between the two groups, and 20 differentially expressed lipid species were identified. Lysophosphatidylcholines (lysoPCs), diacylglycerols (DGs), and phosphatidylethanolamines (PEs) were significantly upregulated, while triacylglycerols (TGs) were downregulated in the periodontitis group. Moreover, the staining intensity of ABHD5/CGI-58, secretory phospholipase A2 (sPLA2), and sPLA2-IIA was significantly stronger in the gingival tissues of patients with periodontitis than in those of healthy controls.

CONCLUSIONS

LysoPCs, DGs, and PEs were significantly upregulated, whereas TGs were downregulated in gingival tissues of patients with periodontitis. Correspondingly, the immunohistochemical staining of ABHD5/CGI-58, sPLA2, and sPLA2-IIA in gingival tissues was consistent with the downstream production of lipid classes (lysoPCs, TGs, and DGs).

Combinatorial therapy with immunosuppressive, immunomodulatory and tear substitute eyedrops ("Triple Play") in Recalcitrant Immunological Ocular Surface Diseases

PURPOSE

The current paradigm for therapy of recalcitrant ocular surface diseases (OSD) consists of a sequential, step-up treatment approach. A combinatorial topical therapy (anti-inflammatory/immunosuppressive [steroid] with immunomodulatory [pooled human immune globulin] and tear substitute [serum]) that simultaneously targets several immunological pathways may be more efficacious. This report evaluates if the combinatorial therapy resulted in clinical benefit in patients with recalcitrant OSD.

METHODS

We performed a retrospective case study of patients receiving topical, preservative-free, compounded formulations of steroids, pooled human immune globulin, and serum tears. Outcome measures included visual acuity, ocular surface disease index (OSDI), ocular discomfort score, subjective global assessment (SGA), corneal staining, conjunctival redness, and slit lamp photographs.

RESULTS

Patients consisted of one male and 11 females ranging in age from 27 to 87 years old. Pathologies included ocular graft-versus-host disease (n = 4), Sjögren's syndrome (n = 3), ocular cicatricial pemphigoid (n = 1), pemphigus vulgaris (n = 1), peripheral ulcerative keratitis (n = 1), Stevens-Johnson syndrome (n = 1), and giant papillary conjunctivitis (n = 1). All patients were "improved" or "much improved" on SGA after combinatorial therapy. There was a clinically meaningful reduction in OSDI, ocular discomfort, corneal staining, and conjunctival injection. Additionally, three patients had improvement in their visual acuity (one from 20/400 to 20/20). Adverse effects included increased intraocular pressure in two patients, presumably due to topical steroid use.

CONCLUSIONS

Combinatorial therapy provides clinical benefit by reducing the symptoms and signs in recalcitrant OSD. Our study provides the rationale for performing prospective clinical trials to evaluate the efficacy of combinatorial therapy for treating recalcitrant OSD.

Chronic Tear Deficiency Sensitizes Transient Receptor Potential Vanilloid 1-Mediated Responses in Corneal Sensory Nerves

Chronic tear deficiency enhances the excitability of corneal cold-sensitive nerves that detect ocular dryness, which can lead to discomfort in patients with dry eye disease (DED). However, changes in corneal nerve excitations through the polymodal nociceptor “transient receptor potential vanilloid 1” (TRPV1) and the potential link between this receptor and symptoms of DED remain unclear. In this study, we examined the firing properties of corneal cold-sensitive nerves expressing TRPV1 and possible contributions of chronic tear deficiency to corneal nerve excitability by TRPV1 activation. The bilateral excision of lacrimal glands in guinea pigs decreased the tear volume and increased the frequency of spontaneous eyeblinks 1–4 weeks after surgery. An analysis of the firing properties of the cold-sensitive nerves was performed by single-unit recordings of corneal preparations 4 weeks after surgery in both the sham-operated and gland-excised groups. Perfusion of the TRPV1 agonist, capsaicin (1 μM), transiently increased the firing frequency in approximately 46–48% of the cold-sensitive nerves characterized by low-background activity and high threshold (LB-HT) cold thermoreceptors in both groups. Gland excision significantly decreased the latency of capsaicin-induced firing in cold-sensitive nerves; however, its magnitude was unchanged. Calcium imaging of cultured trigeminal ganglion neurons from both groups showed that intracellular calcium elevation of corneal neurons induced by a low concentration of capsaicin (0.03 μM) was significantly larger in the gland excision group, regardless of responsiveness to cold. An immunohistochemical study of the trigeminal ganglion revealed that gland excision significantly increased the proportion of corneal neurons enclosed by glial fibrillary acidic protein (GFAP)-immunopositive satellite glial cells. Topical application of the TRPV1 antagonist, A784168 (30 μM), on the ocular surface attenuated eye-blink frequency after gland excision. Furthermore, gland excision enhanced blink behavior induced by a low concentration of capsaicin (0.1 μM). These results suggest that chronic tear deficiency sensitizes the TRPV1-mediated response in the corneal LB-HT cold thermoreceptors and cold-insensitive polymodal nociceptors, which may be linked to dry eye discomfort and hyperalgesia resulting from nociceptive stimuli in aqueous-deficient dry eyes.

sPLA2-IIa participates in ocular surface inflammation in humans with dry eye disease

PURPOSE

To determine the roles of secretory phospholipase A2-IIa (sPLA₂-IIa) in the inflammatory responses of the compromised ocular surface.

METHODS

Conjunctival impression cytology (IC) samples and tears were collected from patients with mild to severe non-Sjogren's dry eye disease (DED) and normal controls. The IC samples were analyzed for transcription of sPLA₂-IIa and inflammatory cytokine/chemokine genes using quantitative real-time RT-PCR (qRT²-PCR) and pathway-focus PCR-array. The tear samples were analyzed for 13 inflammatory cytokines and chemokines with Millipore 13-Plex kit. Finally, sPLA2-IIa-treated human conjunctival epithelial cell (HCjE) cultures were analyzed with a pathway-focused PCR array.

RESULTS

Transcription of sPLA2-IIa was significantly increased in severe DED patients as compared to those of mild DED patients and normal controls. The transcription of inflammatory cytokines (IL-1β, IL-4, IL-6, IL-17, TNF-α, IFN-γ), chemokines (IL-8, CXCL10, CXCL11, CXCL-14, CCR6, LTB) and matrix metalloproteinase 9 (MMP9) were simultaneously increased in the same IC samples of DED. Concentrations of IL-6 and IL-8 in tears were significantly higher in DED patients than those of the controls and positively correlated to DED severity scores. On the other hand, IL-2, IL-4, IL-10, IL-12 and IFN-γ were significantly lower in DED patients than those in the controls and inversely correlated to DEWS scores. Single treatment of sPLA2-IIa, IL-1β or TNF-α of HCjE cells induced minimal to no PGE2 production. When sPLA2-IIa was added to HCjE cells that were pre-treated with pro-inflammatory cytokines (TNF-α or IL-1β), significant stimulation of PGE2 production was observed, concurrent with the extensive transcriptional changes of many inflammatory cytokines/chemokines and their receptors.

CONCLUSION

sPLA₂-IIa activity was elevated and not only associated with inflammatory changes in DED patient samples, but was also found to cooperate with TNF- α and IL-1β to induce inflammatory response in human conjunctival epithelial cells. Understanding the roles of sPLA₂-IIa in ocular surface inflammation may lead to better strategies for the treatment of chronic inflammation associated with DED and other ocular inflammatory conditions.

High sPLA2-IIA level is associated with eicosanoid metabolism in patients with bacterial sepsis syndrome

The aim of this study was to determine the association between secretory phospholipase A2 group IIA (sPLA2-IIA) and eicosanoid pathway metabolites in patients with bacterial sepsis syndrome (BSS). Levels of sPLA2-IIA, eicosanoids prostaglandin (PG)E2, PGD synthase were quantified in the sera from patients confirmed to have bacterial sepsis (BS; N = 45), bacterial severe sepsis/septic shock (BSS/SS; N = 35) and healthy subjects (N = 45). Cyclooxygenase (COX)-1 and COX-2 activities were analyzed from cell lysate. Serum levels of sPLA2-IIA, PGE2, and PGDS increased significantly in patients with BS and BSS/SS compared to healthy subjects (p<0.05). COX-2 activity was significantly increased in patients with BS compared to healthy subjects (p<0.05), but not COX-1 activity. Binary logistic regression analysis showed that sPLA2-IIA and PGE2 were independent factors predicting BSS severity. In conclusion, high level of sPLA2-IIA is associated with eicosanoid metabolism in patients with BSS.

Changes in Human Tear Proteome Following Topical Treatment of Dry Eye Disease: Cyclosporine A Versus Diquafosol Tetrasodium

Purpose

To compare the changes in human tear proteome and clinical effects following topical cyclosporine A (CsA) 0.05% or diquafosol tetrasodium (DQS) 3% treatment of dry eye disease (DED), and to identify biomarkers for determining disease severity and treatment effectiveness in DED.

Methods

A total of 18 patients were diagnosed with non-Sjögren DED. Nine patients in each group were treated with topical CsA 0.05% or DQS 3% for 4 weeks. Tear samples were collected after evaluation of tear breakup time, corneal and conjunctival erosion staining, and results of Schirmer's test 1 before and after treatment. Proteomes were characterized using liquid chromatography mass spectrometry, and proteins exhibiting a fold change >1.5 or <0.67 (P < 0.05) were considered differentially expressed (DEP).

Results

A total of 794 proteins were identified, with no significant difference observed between pretreatment and posttreatment conditions. Proteomic analysis identified 54 and 106 DEPs between treatment groups (CsA and DQS, respectively), with gene ontology analysis indicating that both treatments enhanced innate and adaptive immune responses and cellular detoxification. Protein-network analysis showed that inflammation associated with the immune response was primarily responsible for the therapeutic process in both groups.

Conclusions

These results provide insight into the broad scope of changes at the ocular surface in DED and indicated that although both drugs improved the clinical parameters, the activated tear-specific biomarkers differed significantly between treatments. Our findings suggest that the DEPs identified here and those correlated with the clinical parameters might represent candidate biomarkers for DED.

Wide-Range Effects of 1,25(OH)2D3 on Group 4A Phospholipases Is Related to Nuclear Factor κ-B and Phospholipase-A2 Activating Protein Activity in Mast Cells

INTRODUCTION

Phospholipases are enzymes that occur in many types of human cells, including mast cells, and play an important role in the molecular background of asthma pathogenesis, and the development of inflammation NF-κB activities that affect numerous biological processes has been reported in many inflammatory diseases including asthma. Vitamin D is a widely studied factor that affects many diseases, including asthma. The aim of this study is to assess the influence of 1,25-(OH)2D3 on regulation of chosen phospholipase-A2 (PLA2) expression-selected inflammation mediators.

METHODS

LUVA mast cells were stimulated with 1,25(OH)2D3, and inhibitors of NF-κB p65 and ubiquitination. Expression analysis of phospholipases (PLA2G5, PLA2G10, PLA2G12, PLA2G15, PLA2G4A, PLA2G4B, PLA2G4C, PLAA, NF-κB p65, and UBC) was done utilizing real-time PCR and Western blot. Eicosanoid (LTC4, LXA4, 15[S]-HETE, and PGE2) levels and sPLA2 were also measured.

RESULTS

We found that 1,25(OH)2D3 decreased the expression of PLA2G5, PLA2G15, PLA2G5,UBC, and NF-κB p65 but increased expression of PLAA and PLA2G4C (p < 0.05). Moreover, the expression of PLA2G5 and PLA2G15 decreased after inhibition of NF-κB p65 and UBC. Increased levels of released LXA4 and 15(S)-HETE, decreased levels of LTC4, and sPLA2s enzymatic activity in response to 1,25(OH)2D3 were also observed. Additionally, NF-κB p65 inhibition led to an increase in the LXA4 concentration.

CONCLUSION

Future investigations will be needed to further clarify the role of 1,25(OH)2D3 in the context of asthma and the inflammatory process; however, these results confirm a variety of effects which can be caused by this vitamin. 1,25(OH)2D3-mediated action may result in the development of new therapeutic strategies for asthma treatment.

The Role of SKQ1 (Visomitin) in Inflammation and Wound Healing of the Ocular Surface

Introduction

SkQ1 (Visomitin) is a novel mitochondrial-targeted antioxidant that holds promise in the treatment of inflammation associated with ocular surface diseases such as dry eye disease (DED) and corneal wounds. However, the specific role of SkQ1 in ocular surface epithelial tissue has yet to be explicated. The goal of this study is to identify roles of SkQ1 in conjunctival inflammation and corneal wound healing.

Methods

To determine the role of SkQ1 in inflammation, human conjunctival epithelial (HCjE) cell cultures were sensitized with pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) followed by treatments with SkQ1. The production of inflammatory biomarker prostaglandin E2 (PGE2) and cell viability were quantitatively evaluated. To determine the role of SkQ1 in wound healing, human corneal limbus epithelial (HCLE) cell cultures were streaked to create wounds. The wound closure times, ability to support single HCLE cell proliferation and changes of cell migration in the presence of SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK), were further compared.

Results

The HCjE and HCLE cultures showed no apparent cytotoxicity to SkQ1 in concentrations up to 250 nM (HCjE) or 2500 nM (HCLE). The HCLE cultures showed no toxicity to SkQ1 at all the SkQ1 concentrations tested. SkQ1 significantly suppressed PGE2 production of HCjE at concentrations < 300 nM (24 h) and 50 nM (48 h), apparently being SkQ1 dose and treatment time dependent. The wound closure rates were increased by 4% in 4 h and by 9% after 8–12 h in the presence of 50 nM SkQ1. Furthermore, as little as 25 nM of SkQ1 significantly stimulated HCLE single-cell proliferation. Lastly, the SkQ1-stimulated wound healing was completely abolished by SB203580.

Conclusion

Results of the current study demonstrate that SkQ1 exhibits an anti-inflammatory role and can be safely applied to ocular surface epithelium up to a concentration of 300 nM (181 ng/ml) for 24 h. SkQ1 also significantly enhances corneal epithelial wound healing, likely through enhancement of cell proliferation and migration. The data provide solid support for SkQ1 as a promising new therapeutic strategy for treatment of conjunctival inflammation as well as corneal wounds.

Funding

This study was sponsored by Mitotech SA Pharmaceuticals.

Electronic supplementary material

The online version of this article (10.1007/s40123-018-0158-2) contains supplementary material, which is available to authorized users.

Proteomic analysis of human lacrimal and tear fluid in dry eye disease

To understand the pathophysiology of dry eye disease (DED), it is necessary to characterize proteins in the ocular surface fluids, including tear fluid (TF) and lacrimal fluid (LF). There have been several reports of TF proteomes, but few proteomic studies have examined LF secreted from the lacrimal gland (LG). Therefore, we characterized the proteins constituting TF and LF by liquid chromatography mass spectrometry. TF and LF were collected from patients with non-Sjögren syndrome DED and from healthy subjects. Through protein profiling and label-free quantification, 1165 proteins from TF and 1448 from LF were identified. In total, 849 proteins were present in both TF and LF. Next, candidate biomarkers were verified using the multiple reaction monitoring assay in both TF and LF of 17 DED patients and 17 healthy controls. As a result, 16 marker proteins were identified (fold-change > 1.5, p-value < 0.05), of which 3 were upregulated in TF and 8 up- and 5 down-regulated in LF. In conclusion, this study revealed novel DED markers originating from the LG and tears by in-depth proteomic analysis and comparison of TF and LF proteins.

TFOS DEWS II Tear Film Report

The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.

ω-3 Tear Film Lipids Correlate With Clinical Measures of Dry Eye

PURPOSE

ω-3 and ω-6 polyunsaturated fatty acids modulate inflammatory processes throughout the body through distinct classes of lipid mediators that possess both proinflammatory and proresolving properties. The purpose of this cross-sectional study was to explore the relationship between lipid profiles in human tears and dry eye (DE) symptoms and signs.

METHODS

Forty-one patients with normal eyelid and corneal anatomy were prospectively recruited from a Veterans Administration Hospital over 18 months. Symptoms and signs of DE were assessed, and tear samples was analyzed by mass spectrometry-based lipidomics. Statistical analyses comparing the relationship between tear film lipids and DE included Pearson/Spearman correlations and t-tests.

RESULTS

Arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) were present in more than 90% of tear film samples. The ratio of ω-6 (AA) to ω-3 (DHA+EPA) fatty acids was correlated with multiple measures of tear film dysfunction (tear breakup time, Schirmer 2 scores, and corneal staining; all P < 0.05). Arachidonic acid-derived prostaglandin E2 was detected in the majority of samples and correlated with low tear osmolarity, meibomian gland plugging, and corneal staining.

CONCLUSIONS

Both ω-3 and ω-6 lipid circuits are activated in the human tear film. The ratio of ω-6:ω-3 tear lipids is elevated in DE patients in proportion to the degree of tear film dysfunction and corneal staining. Metabolic deficiency of ω-3 tear film lipids may be a driver of chronic ocular surface inflammation in DE.

The Growing Need for Validated Biomarkers and Endpoints for Dry Eye Clinical Research

Purpose

Biomarkers with minimally invasive and reproducible objective metrics provide the key to future paradigm shifts in understanding of the underlying causes of dry eye disease (DED) and approaches to treatment of DED. We review biomarkers and their validity in providing objective metrics for DED clinical research and patient care.

Methods

The English-language literature in PubMed primarily over the last decade was surveyed for studies related to identification of biomarkers of DED: (1) inflammation, (2) point-of-care, (3) ocular imaging, and (4) genetics. Relevant studies in each group were individually evaluated for (1) methodological and analytical details, (2) data and concordance with other similar studies, and (3) potential to serve as validated biomarkers with objective metrics.

Results

Significant work has been done to identify biomarkers for DED clinical trials and for patient care. Interstudy variation among studies dealing with the same biomarker type was high. This could be attributed to biologic variations and/or differences in processing, and data analysis. Correlation with other signs and symptoms of DED was not always clear or present.

Conclusions

Many of the biomarkers reviewed show the potential to serve as validated and objective metrics for clinical research and patient care in DED. Interstudy variation for a given biomarker emphasizes the need for detailed reporting of study methodology, including information on subject characteristics, quality control, processing, and analysis methods to optimize development of nonsubjective metrics. Biomarker development offers a rich opportunity to significantly move forward clinical research and patient care in DED.

Overview

DED is an unmet medical need - a chronic pain syndrome associated with variable vision that affects quality of life, is common with advancing age, interferes with the comfortable use of contact lenses, and can diminish results of eye surgeries, such as cataract extraction, LASIK, and glaucoma procedures. It is a worldwide medical challenge with a prevalence rate ranging from 8% to 50%. Many clinicians and researchers across the globe are searching for better answers to understand the mechanisms related to the development and chronicity of DED. Though there have been many clinical trials for DED, few new treatments have emerged over the last decade. Biomarkers may provide the needed breakthrough to propel our understanding of DED to the next level and the potential to realize our goal of truly personalized medicine based on scientific evidence. Clinical trials and research on DED have suffered from the lack of validated biomarkers and less than objective and reproducible endpoints. Current work on biomarkers has provided the groundwork to move forward. This review highlights primarily ocular biomarkers that have been investigated for use in DED, discusses the methodologic outcomes in providing objective metrics for clinical research, and suggests recommendations for further work.

Contact Lens-Induced Discomfort and Inflammatory Mediator Changes in Tears

PURPOSE

Studies indicate that contact lens (CL) discontinuation mostly occurs because of dryness and discomfort symptoms. This study aimed to investigate relationships between changes in the concentration of tear inflammatory mediators with subjective comfort ratings with CL wear and no contact lens wear between morning and evening.

METHOD

Forty-five subjects collected tears twice daily in the morning and in the evening with or without lenses. Comfort was rated subjectively on a scale from 1 to 100 (where 100 was extremely comfortable) just before each tear collection. Tear samples were assayed for complement components (C3 and C3a), leukotriene B4 (LTB4), secretory phospholipase A2 (sPLA2), secretory immunoglobulin A (sIgA), and bradykinin using commercially available immuno-based assay kits.

RESULTS

Comfort ratings showed a statistically significant decline from morning to evening both with CL (89.0±10.1 AM vs. 76.7±15.2 PM; P<0.001) and without CL (89.1±10.2 AM vs. 84.2±12.6 PM; P<0.005) wear. The decline was steeper with lens wear (P<0.001). Bradykinin and sPLA2 levels did not change between morning and evening or with CL wear (P>0.05). Leukotriene B4 levels were slightly higher in CL (CL 43.4±12.6 pg/ml vs. No CL 39.4±13.4 pg/mL; P=0.034), whereas the concentration of LTB4, C3, C3a, and sIgA dropped by the end of the day in the presence or absence of lens wear (P<0.001). For most mediators, tear levels were not correlated with comfort ratings in any of the conditions. Leukotriene B4 had a higher concentration in the evening, and when measured as a ratio to sIgA, there was a trend for increased concentration of this mediator during CL wear.

CONCLUSION

Although specific mediators showed changes from morning to evening with and without lens wear, most of these were not correlated with subjective comfort ratings in lens wear. The only mediator that showed an increase in concentration during the day and during lens wear was LTB4, and further studies on this mediator are warranted.

The core mechanism of dry eye disease is inflammation

PURPOSE

The purpose of this article is to review the evidence for the hypothesis that the core mechanism of dry eye disease (DED) is inflammation, including evidence from recent basic, clinical, and translational research involving human patients, animal models, and cell cultures.

METHODS

Using the key words "dry eye + inflammation," the authors conducted a comprehensive search of the PubMed and Web of Science databases for scientific articles published in English between January 1, 1900 and August 30, 2013 on the role of inflammation in DED in cell cultures, animal models, and humans. The resulting articles were then categorized and reviewed.

RESULTS

The literature search revealed a total of 458 publications, almost all published after 1992. The percentages of original studies and review articles are 77.29% (354) and 22.71% (104), respectively. Among the original studies, the number of reports on human DED is 200 (43.7%), on animal models is 115 (25.1%), and cell cultures is 39 (8.5%). A yearly distributing plot revealed that 76% were published from 2003 to 2011, 53% from 2008 to 2012, and 11% during the first 9 months of 2013. This distribution signifies a rapidly growing awareness of the importance of inflammation in DED pathogenesis.

CONCLUSIONS

Inflammation plays a key role in the pathogenesis of DED as evidenced by research using tissue culture, animal models, and subjects with DED. Developing biomarkers for inflammation of the ocular surface will provide improved understanding of the mechanisms leading to DED, classification of the severity of DED, and objective metrics for outcome measures of treatment. The chronicity of the disease suggests that dysregulation of immune mechanisms leads to a cycle of continued inflammation, accompanied by alterations in both innate and adaptive immune responses. Given the underlying mechanism for DED, developing effective and safe anti-inflammatory treatments is likely to be beneficial for patients with DED.

Efficacy of bromfenac sodium ophthalmic solution for treatment of dry eye disease

PURPOSE

To evaluate the efficacy of bromfenac sodium ophthalmic solution (BF) in patients with dry eye disease (DED) inadequately controlled by monotherapy with artificial tears (ATs).

DESIGN

An investigator-oriented trial with a single-arm, nonrandomized, open-label design.

METHODS

Twenty-six patients, who showed no symptomatic improvement of DED after 1 month of AT treatment, were enrolled. Bromfenac sodium ophthalmic solution was administered adjunctively with AT for 1 month. The BF treatment was then discontinued, and AT treatment alone was continued for 3 months. The signs and symptoms were evaluated at the beginning of BF treatment (Pre), at the end of the combined BF and AT treatment (BF1M), and at 1 and 3 months after discontinuation of BF treatment (Po1M and Po3M, respectively).

RESULTS

The dryness scores at BF1M were significantly improved compared with Pre (P < 0.001) and significantly superior to Po3M (P < 0.001). No significant changes in the Schirmer scores were observed throughout the treatment period. The tear film breakup time was significantly improved at BF1M (4.4 ± 2.3 seconds) compared with Pre (2.8 ± 1.8 seconds; P < 0.001). Superficial punctate keratopathy showed significant improvements in the total score of area and density at BF1M compared with Pre (P < 0.001). However, these parameters had significantly worsened at Po3M compared with BF1M. No adverse events were observed.

CONCLUSIONS

Bromfenac sodium ophthalmic solution has improved the dryness of the eye and signs of DED through its anti-inflammatory effects. Nonsteroidal anti-inflammatory drugs were suitable as anti-inflammatory ophthalmic solutions for patients with DED.

Oleanolic acid controls allergic and inflammatory responses in experimental allergic conjunctivitis

Pollen is the most common aeroallergen to cause seasonal conjunctivitis. The result of allergen exposure is a strong Th2-mediated response along with conjunctival mast cell degranulation and eosinophilic infiltration. Oleanolic acid (OA) is natural a triterpene that displays strong anti-inflammatory and immunomodulatory properties being an active anti-allergic molecule on hypersensitivity reaction models. However, its effect on inflammatory ocular disorders including conjunctivitis, has not yet been addressed. Hence, using a Ragweed pollen (RWP)-specific allergic conjunctivitis (EAC) mouse model we study here whether OA could modify responses associated to allergic processes. We found that OA treatment restricted mast cell degranulation and infiltration of eosinophils in conjunctival tissue and decreased allergen-specific Igs levels in EAC mice. Th2-type cytokines, secreted phospholipase A2 type-IIA (sPLA2-IIA), and chemokines levels were also significantly diminished in the conjunctiva and serum of OA-treated EAC mice. Moreover, OA treatment also suppressed RWP-specific T-cell proliferation. In vitro studies, on relevant cells of the allergic process, revealed that OA reduced the proliferative and migratory response, as well as the synthesis of proinflammatory mediators on EoL-1 eosinophils and RBL-2H3 mast cells exposed to allergic and/or crucial inflammatory stimuli such as RWP, sPLA2-IIA or eotaxin. Taken together, these findings demonstrate the beneficial activity of OA in ocular allergic processes and may provide a new intervention strategy and potential therapy for allergic diseases.

Tear cytokine profile as a noninvasive biomarker of inflammation for ocular surface diseases: standard operating procedures

PURPOSE

To provide standard operating procedures (SOPs) for measuring tear inflammatory cytokine concentrations and to validate the resulting profile as a minimally invasive objective metric and biomarker of ocular surface inflammation for use in multicenter clinical trials on dry eye disease (DED).

METHODS

Standard operating procedures were established and then validated with cytokine standards, quality controls, and masked tear samples collected from local and distant clinical sites. The concentrations of the inflammatory cytokines in tears were quantified using a high-sensitivity human cytokine multiplex kit.

RESULTS

A panel of inflammatory cytokines was initially investigated, from which four key inflammatory cytokines (IL-1β, IL-6, INF-γ, and TNF-α) were chosen. Results with cytokine standards statistically satisfied the manufacturer's quality control criteria. Results with pooled tear samples were highly reproducible and reliable with tear volumes ranging from 4 to 10 μL. Incorporation of the SOPs into clinical trials was subsequently validated. Tear samples were collected at a distant clinical site, stored, and shipped to our Biomarker Laboratory, where a masked analysis of the four tear cytokines was successfully performed. Tear samples were also collected from a feasibility study on DED. Inflammatory cytokine concentrations were decreased in tears of subjects who received anti-inflammatory treatment.

CONCLUSIONS

Standard operating procedures for human tear cytokine assessment suitable for multicenter clinical trials were established. Tear cytokine profiling using these SOPs may provide objective metrics useful for diagnosing, classifying, and analyzing treatment efficacy in inflammatory conditions of the ocular surface, which may further elucidate the mechanisms involved in the pathogenesis of ocular surface disease.

Surfactant protein D contributes to ocular defense against Pseudomonas aeruginosa in a murine model of dry eye disease

Dry eye disease can cause ocular surface inflammation that disrupts the corneal epithelial barrier. While dry eye patients are known to have an increased risk of corneal infection, it is not known whether there is a direct causal relationship between these two conditions. Here, we tested the hypothesis that experimentally-induced dry eye (EDE) increases susceptibility to corneal infection using a mouse model. In doing so, we also examined the role of surfactant protein D (SP-D), which we have previously shown is involved in corneal defense against infection. Scopolamine injections and fan-driven air were used to cause EDE in C57BL/6 or Black Swiss mice (wild-type and SP-D gene-knockout). Controls received PBS injections and were housed normally. After 5 or 10 days, otherwise uninjured corneas were inoculated with 10(9) cfu of Pseudomonas aeruginosa strain PAO1. Anesthesia was maintained for 3 h post-inoculation. Viable bacteria were quantified in ocular surface washes and corneal homogenates 6 h post-inoculation. SP-D was measured by Western immunoblot, and corneal pathology assessed from 6 h to 4 days. EDE mice showed reduced tear volumes after 5 and 10 days (each by ∼75%, p<0.001) and showed fluorescein staining (i.e. epithelial disruption). Surprisingly, there was no significant difference in corneal pathology between EDE mice and controls (∼10-14% incidence). Before bacterial inoculation, EDE mice showed elevated SP-D in ocular washes. After inoculation, fewer bacteria were recovered from ocular washes of EDE mice (<2% of controls, p = 0.0004). Furthermore, SP-D knockout mice showed a significant increase in P. aeruginosa corneal colonization under EDE conditions. Taken together, these data suggest that SP-D contributes to corneal defense against P. aeruginosa colonization and infection in EDE despite the loss of barrier function to fluorescein.

Dry eye disease and microbial keratitis: is there a connection?

Dry eye is a common ocular surface disease of multifactorial etiology characterized by elevated tear osmolality and inflammation leading to a disrupted ocular surface. The latter is a risk factor for ocular surface infection, yet overt infection is not commonly seen clinically in the typical dry eye patient. This suggests that important innate mechanisms operate to protect the dry eye from invading pathogens. This article reviews the current literature on epidemiology of ocular surface infection in dry eye patients and laboratory-based studies on innate immune mechanisms operating at the ocular surface and their alterations in human dry eye and animal models. The review highlights current understanding of innate immunity in dry eye and identifies gaps in our knowledge to help direct future studies to further unravel the complexities of dry eye disease and its sequelae.

Secretory phospholipase A2 in dromedary tears: a host defense against staphylococci and other gram-positive bacteria

The best known physiologic function of secreted phospholipase A2 (sPLA2) group IIA (sPLA2-IIA) is defense against bacterial infection through hydrolytic degradation of bacterial membrane phospholipids. In fact, sPLA2-IIA effectively kills Gram-positive bacteria and to a lesser extent Gram-negative bacteria and is considered a major component of the eye's innate immune defense system. The antibacterial properties of sPLA2 have been demonstrated in rabbit and human tears. In this report, we have analyzed the bactericidal activity of dromedary tears and the subsequently purified sPLA2 on several Gram-positive bacteria. Our results showed that the sPLA2 displays a potent bactericidal activity against all the tested bacteria particularly against the Staphylococcus strains when tested in the ionic environment of tears. There is a synergic action of the sPLA2 with lysozyme when added to the bacteria culture prior to sPLA2. Interestingly, lysozyme purified from dromedary tears showed a significant bactericidal activity against Listeria monocytogene and Staphylococcus epidermidis, whereas the one purified from human tears displayed no activity against these two strains. We have also demonstrated that Ca(2+) is crucial for the activity of dromedary tear sPLA2 and to a less extent Mg(2+) ions. Given the presence of sPLA2 in tears and intestinal secretions, this enzyme may play a substantial role in innate mucosal and systemic bactericidal defenses against Gram-positive bacteria.

Molecular and cellular biomarkers in dry eye disease and ocular allergy

PURPOSE OF REVIEW

To summarize recent studies in biomarkers in dry eye disease (DED) and ocular allergy in the last 18 months.

RECENT FINDINGS

New significant correlations with clinical symptoms and signs have been described for some tear molecules (proteins, cytokines/chemokines, metalloproteinases, mucins and lipids). Correlation with disease severity has been shown for some of them. New proposed DED biomarkers include some proteins, such as S100A8, S100A9, lipocalin-1, secretory phospholipase A2 and some cytokines and chemokines; mucin-1 mRNA conjunctival expression levels are shown to be a very sensitive and specific DED diagnosis biomarker; metalloproteinase-9 tear level is confirmed as a good DED biomarker; cell parameters such as conjunctival cell viability and proliferative capacity have been also proposed as DED biomarkers. In ocular allergy, protein activated receptor-2, heat shock protein-70, eosinophil cationic protein and hemopexin have been pointed as potential biomarkers. Characterization of neuromediators tear levels confirmed the involvement of these molecules in both DED and ocular allergy.

SUMMARY

Biomarkers are essential to monitor health status. Several studies have proposed different molecules and/or cellular parameters as potential biomarkers for DED and ocular allergy. The knowledge presented in these studies will further add support to the discovery and development of new drugs and the establishment of personalized medicine.

Change in prostaglandin expression levels and synthesizing activities in dry eye disease

OBJECTIVE

To investigate the expression level of prostaglandins (PGs) and their de novo synthesis in dry eye (DE) disease.

DESIGN

Cross-sectional case-control study and in vivo mouse experimental study.

PARTICIPANTS

Forty-six eyes from 23 DE patients and 33 eyes from 17 age- and sex-matched controls were studied. Also, DE-induced murine eyes were compared with control eyes.

METHODS

Patients completed a symptom questionnaire using a 100-mm visual analog scale (VAS). Nano-liquid chromatography tandem mass spectrometry was used for the quantification of PGE2 and PGD2. A DE disease environmental chamber was used to induce DE in mice. One week after induction, enzyme expressions of cyclooxygenase-1, cyclooxygenase-2 (COX-2), PG E synthase (PGES), and PG D synthase (PGDS) in the lacrimal glands, meibomian glands, and corneas were examined using immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR).

MAIN OUTCOME MEASURES

The mean PGE2 and PGD2 levels in the tears of DE patients were measured and compared with symptom severity scores. Immunohistochemistry staining patterns and qRT-PCR data of DE mice were quantified.

RESULTS

The mean PGE2 level in the tears of DE patients (2.72 ±3 .42 ng/ml) was significantly higher than that in the control group (0.88 ± 0.83 ng/ml; P = 0.003). However, the mean PGD2 level in the tears of DE patients (0.11 ± 0.22 ng/ml) was significantly lower (0.91 ± 3.28 ng/ml; P = 0.028). The mean PGE2-to-PGD2 ratio correlated strongly with VAS scoring (P = 0.008). In DE mice, COX-2 mRNA was significantly higher in ocular surface tissue and lacrimal glands. Furthermore, PGES mRNA was significantly higher in ocular surface tissue, whereas PGDS mRNA was decreased. Immunohistochemistry staining showed elevated COX-2 expression in the lacrimal glands, meibomian glands, corneas, and conjunctivas. Furthermore, PGES expression was found in periductal infiltrated cells of the lacrimal glands and conjunctival epithelium. Also, PGDS expression was decreased in meibomian glands and increased focally in the conjunctival epithelium.

CONCLUSIONS

A reciprocal change in PGE2 and PGD2 levels was found in the tears of DE patients, which correlated with patients' symptom scores. These clinical results were supported by increased COX-2 and PGES expression levels found in tear-producing tissues of DE mice.

Topical steroid and non-steroidal anti-inflammatory drugs inhibit inflammatory cytokine expression on the ocular surface in the botulinum toxin B-induced murine dry eye model

PURPOSE

To evaluate the effect of the topical steroid, fluorometholone, and the non-steroidal anti-inflammatory drugs (NSAIDs), nepafenac and ketorolac, on inflammatory cytokine expression of the ocular surface in the botulium toxin B-induced murine dry eye model.

METHODS

Topical artificial tears (0.5% carboxymethylcellulose sodium), 0.1% fluorometholone, 0.1% nepafenac, and 0.4% ketorolac were applied 3 times per day in a dry eye mouse model 1 week after intralacrimal botulium toxin B (BTX-B) or saline (sham) injection. Tear production and corneal fluorescein staining were evaluated in all groups before injection at baseline and at 3 time points up to 4 weeks after injection. The pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were evaluated by immunohistochemistry.

RESULTS

BTX-B-injected mice showed significantly decreased aqueous tear production and increased corneal fluorescein staining at the 1 and 2 week time points compared with normal control and saline-injected mice. In the BTX-B-injected mice, immunofluorescent staining for TNF-α and IL-1β in corneal and conjunctival epithelial cells increased significantly at the 2 and 4 week time points compared to that of normal and saline-injected mice, and returned to normal levels at the 4 week time point. Topical fluorometholone significantly improved corneal surface staining in the BTX-B-injected mice after 1 week of treatment, and increased the tear production within 2 weeks, but without statistical significant difference. Topical fluorometholone significantly decreased the staining of TNF-α and IL-1β in corneal and conjunctival epithelia after 1-week treatment. Topical artificial tears, 0.1% nepafenac, and 0.4% ketorolac did not show obvious effects on tear production, corneal surface staining, and levels of IL-1β and TNF-α expression in normal, and BTX-B-injected dry eye mice.

CONCLUSIONS

Topical fluorometholone caused suppression of inflammatory cytokine expression on the ocular surface in the Botulium toxin B-induced murine dry eye model, while topical NSAIDs demonstrated no clearly beneficial effects.

Comparison of mucin levels at the ocular surface of postmenopausal women with and without a history of dry eye

PURPOSE

To determine if levels of the glycocalyx membrane mucins, MUC1 and MUC16, and the secreted goblet cell mucin MUC5AC are altered in conjunctival cells and tears of postmenopausal women presenting with a history of non-Sjögren dry eye and if mucin levels correlate with dry eye clinical diagnostic data.

METHODS

Eighty-four postmenopausal women with a history of non-Sjögren dry eye and 30 normal subjects were recruited for this study. Impression cytology samples were collected for mucin messenger RNA (mRNA) and protein analysis. Tears were collected for mucin protein assay. Quantitative polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay were used to quantitate MUC1, MUC16, and MUC5AC levels.

RESULTS

Postmenopausal women with a history of dry eye displayed significantly increased MUC1 mRNA expression and cellular protein compared with normal subjects (P < 0.001 and P < 0.01, respectively). Similarly, cellular MUC16 protein levels were significantly higher (P < 0.001). Mucin levels were found to be correlated with the clinical characterization of the subjects, including staining and symptoms. Although cellular MUC5AC protein levels were increased in symptomatic subjects, the increase did not reach statistical significance.

CONCLUSIONS

Elevation in MUC1 and MUC16 mRNA and/or protein levels in postmenopausal women with non-Sjögren dry eye with a history of dry eye may be a compensatory response to irritation and inflammation associated with the disease. Understanding the pattern of mucin expression associated with the dry eye pathology may clarify factors involved in the progression of the disease and enhance the development of targeted therapies.

sPLA2-IIa amplifies ocular surface inflammation in the experimental dry eye (DE) BALB/c mouse model

PURPOSE

sPLA2-IIa is a biomarker for many inflammatory diseases in humans and is found at high levels in human tears. However, its role in ocular surface inflammation remains unclear. An experimentally induced BALB/c mouse dry eye (DE) model was used to elucidate the role of sPLA2-IIa in ocular surface inflammation.

METHODS

BALB/c mice were subcutaneously injected with scopolamine and placed in a daytime air-drying device for 5 to 10 days. Control mice received no treatment. DE status was evaluated with tear production with a phenol-red thread method. Tear inflammatory cytokines were quantified by multiplex immunoassays. Ocular surface inflammation and sPLA2-IIa expression were examined by immune-staining and quantitative (q)RT(2)-PCR. Conjunctiva (CNJ) of the mice was cultured for prostaglandin E2 production induced by sPLA2-IIa with various amount of sPLA2-IIa inhibitor, S-3319.

RESULTS

Treated mice produced fewer tears and heavier corneal (CN) fluorescein staining than the untreated controls (P < 0.001). They also revealed lower goblet cell density (P < 0.001) with greater inflammatory cell infiltration within the conjunctiva, and higher concentration of tear inflammatory cytokines than the controls. Moreover, treated mice showed heavier sPLA2-IIa immune staining than the controls in the CNJ epithelium, but not in the CN epithelium or the lacrimal gland. Treated mice exhibited upregulated sPLA2-IIa and cytokine gene transcription. Furthermore, CNJ cultures treated with sPLA2-IIa inhibitor showed significantly reduced sPLA2-IIa-induced inflammation.

CONCLUSIONS

This is the first report regarding sPLA2-IIa in the regulation of ocular surface inflammation. The findings may therefore lead to new therapeutic strategies for ocular surface inflammation, such as DE disease.

Dry eye disease as an inflammatory disorder

PURPOSE

Dry eye disease (DED) is a prevalent inflammatory disorder of the lacrimal functional unit of multifactorial origin leading to chronic ocular surface disease, impaired quality of vision, and a wide range of complications, eventually causing a reduction in quality of life. It still is a frustrating disease because of the present scarcity of therapies that can reverse, or at least stop, its progression.

METHODS

A comprehensive literature survey of English-written scientific publications on the role of inflammation in DED.

RESULTS

New investigations have demonstrated that a chronic inflammatory response plays a key role in the pathogenesis of human DED. Additionally, correlations between inflammatory molecules and clinical data suggest that inflammation can be responsible for some of the clinical symptoms and signs.

CONCLUSIONS

Research efforts to clarify its pathophysiology are leading to a better understanding of DED, demonstrating that inflammation, in addition to many other factors, plays a relevant role.

The neurobiology of lipid metabolism in autism spectrum disorders

Autism is a neurodevelopmental disorder characterized by impairments in communication and reciprocal social interaction, coupled with repetitive behavior, which typically manifests by 3 years of age. Multiple genes and early exposure to environmental factors are the etiological determinants of the disorder that contribute to variable expression of autism-related traits. Increasing evidence indicates that altered fatty acid metabolic pathways may affect proper function of the nervous system and contribute to autism spectrum disorders. This review provides an overview of the reported abnormalities associated with the synthesis of membrane fatty acids in individuals with autism as a result of insufficient dietary supplementation or genetic defects. Moreover, we discuss deficits associated with the release of arachidonic acid from the membrane phospholipids and its subsequent metabolism to bioactive prostaglandins via phospholipase A(2)-cyclooxygenase biosynthetic pathway in autism spectrum disorders. The existing evidence for the involvement of lipid neurobiology in the pathology of neurodevelopmental disorders such as autism is compelling and opens up an interesting possibility for further investigation of this metabolic pathway.

Quantification of tear proteins and sPLA2-IIa alteration in patients with allergic conjunctivitis

PURPOSE

Allergic conjunctivitis (AC) has been reported to induce the instability of the tear film. The tear protein and the lipid layer play important roles in maintaining the tear film. The aim of this study was to quantify the alteration of the major tear protein components and a lipid related protein secretory type IIa phospholipase A2 (sPLA2-IIa) in tears of seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC) patients.

METHODS

Twenty-one SAC and PAC patients and thirteen normal controls completed a symptom questionnaire and underwent regular ocular examination. SAC and PAC patients were diagnosed based on the clinical presentation and elevated serum IgE levels. Schirmer test paper was used to collect tear samples from SAC and PAC patients and normal controls. Soybean trypsin inhibitor (SBTI) was used as an internal standard to analyze tear samples in 15% SDS-PAGE gel. Total tear protein and its major components from the SAC and PAC patients and normal controls were quantified by band densitometry. The major tear protein bands were determined by MALDI-TOF/TOF spectrum analysis. Western blot was used to detect the content of sPLA2-IIa in tears of allergic conjunctivitis patients and normal controls.

RESULTS

Schirmer test scores were more than 10 mm in all the SAC and PAC patients and control subjects. The tear film breakup time of SAC and PAC patients was much shorter than that of the normal controls. We obtained 15 bands of tear protein by one dimensional SDS-PAGE, in which 14 bands were determined by mass-spectrum analysis. The band densitometry analysis revealed that the total tear protein concentration was much higher in SAC and PAC patients than in normal controls (p<0.05). The quantity of tear protein band 4 (serum albumin precursor), band 6 (Ig gamma-2), band 9 (leukocyte elastase inhibitor) were also significantly higher in AC patients (p<0.05). Content of sPLA2-IIa, as shown by western blot, was much higher in AC patients than in controls.

CONCLUSIONS

The total tear protein concentration and some of the major tear protein components was increased in tears of SAC and PAC patients. In addition, the content of sPLA2-IIa in tears of SAC and PAC patients was elevated. The tear protein changes in SAC and PAC patients may contribute to instability of tear film.