Inflammatory cytokine of basal and reflex tears analysed by multicytokine assay

Tear Biomarkers and Alzheimer's Disease

Alzheimer's disease (AD) is an age-related progressive neurodegenerative brain disorder that represents the most common type of dementia. It poses a significant diagnostic challenge that requires timely recognition and treatment. Currently, there is no effective therapy for AD; however, certain medications may slow down its progression. The discovery of AD biomarkers, namely, magnetic resonance imaging, positron emission tomography and cerebrospinal fluid molecules (amyloid-β and tau) has advanced our understanding of this disease and has been crucial for identifying early neuropathologic changes prior to clinical changes and cognitive decline. The close interrelationship between the eye and the brain suggests that tears could be an interesting source of biomarkers for AD; however, studies in this area are limited. The identification of biomarkers in tears will enable the development of cost-effective, non-invasive methods of screening, diagnosis and disease monitoring. In order to use tears as a standard method for early and non-invasive diagnosis of AD, future studies need to be conducted on a larger scale.

Association of Tear Cytokine Concentrations with Symptoms and Signs of Dry Eye Disease: Baseline Data from the Dry Eye Assessment and Management (DREAM) Study

PURPOSE

To describe tear concentrations of IL-1β, Il-6, IL-8, IL-10, IL-17A, IFNγ and TNFα in tears, collected by microcapillaries, and their correlation with symptoms and signs in subjects with dry eye disease (DED) in the DREAM Study.

METHODS

Cytokine levels of patients with moderate to severe DED were determined using a magnetic bead assay. Scores for Ocular Surface Disease Index, corneal and conjunctival staining, tear break-up time (TBUT), and Schirmer's test were obtained using standardized procedures. Associations of cytokines with each other and signs/symptoms were assessed with Spearman correlation coefficients (r).

RESULTS

Assay results from 131 patient samples from 10 sites with tear volumes ≥ 4 ul were analyzed. Cytokine concentrations did not correlate with each other in a generally acknowledged pro-inflammatory/anti-inflammatory pattern, such as proinflammatory IL-17A and IFNγ were not inversely correlated to anti-inflammatory cytokine IL-10, and cytokines did not correlate with DED symptoms. Lower corneal staining was correlated with higher concentrations of IL-17A (r= -0.24, p = 0.006), IL-10 (r= -0.25, p = 0.005) and IFNγ (r= -0.33, p = 0.0001). Higher concentrations of IFNγ were associated with lower conjunctival staining (r= -0.18, p = 0.03). Higher concentrations of IL-17A were associated with higher TBUT scores (r = 0.19 p = 0.02).

CONCLUSIONS

Cytokines IL-10, IL-17A and IFNγ were highly correlated with each other but weakly correlated with some DED signs. No key cytokines or definitive expression patterns were identified in this study of moderate to severe DED patients. Further studies addressing various biases, including methodological and sampling biases, and standardization of methodology for inter-laboratory consistency are needed to confirm and establish pathological and clinical relevance of tear cytokines in DED.

Tear Biomarkers in Alzheimer's and Parkinson's Diseases, and Multiple Sclerosis: Implications for Diagnosis (Systematic Review)

Biological material is one of the most important aspects that allow for the correct diagnosis of the disease, and tears are an interesting subject of research because of the simplicity of collection, as the well as the relation to the components similar to other body fluids. In this review, biomarkers for Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS) in tears are investigated and analyzed. Records were obtained from the PubMed and Google Scholar databases in a timeline of 2015-2022. The keywords were: tear film/tear biochemistry/tear biomarkers + diseases (AD, PD, or MS). The recent original studies were analyzed, discussed, and biomarkers present in tears that can be used for the diagnosis and management of AD, PD, and MS diseases were shown. α-synTotal and α-synOligo, lactoferrin, norepinephrine, adrenaline, epinephrine, dopamine, α-2-macroglobulin, proteins involved in immune response, lipid metabolism and oxidative stress, apolipoprotein superfamily, and others were shown to be biomarkers in PD. For AD as potential biomarkers, there are: lipocalin-1, lysozyme-C, and lacritin, amyloid proteins, t-Tau, p-Tau; for MS there are: oligoclonal bands, lipids containing choline, free carnitine, acylcarnitines, and some amino acids. Information systematized in this review provides interesting data and new insight to help improve clinical outcomes for patients with neurodegenerative disorders.

Change in Ocular Surface Staining during Eyelid Warming Is Related to Tear Cytokine Levels

Purpose

To investigate the changes in the tear cytokine profile of patients with meibomian gland dysfunction (MGD) treated with eyelid warming and to correlate these changes with clinical parameters for dry eye disease (DED).

Methods

Seventy patients with MGD were included and treated with the warming of eyelids. Of these, 61 still used the treatment three months after baseline, while 48 completed the whole treatment period of six months. The concentrations of 39 cytokines in the tear fluid were measured at baseline and after three and six months of treatment. All participants were examined with tests for DED, including tear film break-up time (TBUT), ocular surface staining (OSS), and the self-reporting Ocular Surface Disease Index (OSDI). Changes in cytokine concentrations were assessed from baseline to three months, from three to six months, and from baseline to six months. Correlation analyses were performed between changes in the cytokine concentrations and changes in TBUT, OSS, and OSDI during the same time intervals.

Results

No significant changes were found in the concentrations of the 39 cytokines during any of the three treatment intervals. However, several correlations were detected between changes in the level of cytokines and OSS from baseline to three months of treatment. Decreasing concentrations of granulocyte chemotactic protein 2 (GCP-2/CXCL6, mean effect 2.36, p=0.042), interleukin 10 (IL-10, mean effect 1.04, p=0.045), and IL-16 (mean effect 1.36, p=0.035) were associated with decreasing OSS. Decreasing concentrations of granulocyte macrophage colony-stimulating factor (GM-CSF, mean effect −2.98, p=0.024), IL-8 (IL-8/CXCL8, mean effect −1.35, p=0.026), and macrophage migration inhibitory factor (MIF, mean effect −2.44, p=0.033) were related to increasing OSS.

Conclusions

Warming of eyelids did not change the concentration of cytokines in the tear fluid of patients with MGD significantly. However, alterations in the level of several cytokines were associated with changes in the OSS. This finding indicates a close connection between tear cytokines and OSS in MGD patients treated with eyelid warming.

A review of meibomian gland structure, function, and contact lens wear

PURPOSE

To provide a balanced literature review of the studies that have evaluated the effect of contact lenses on meibomian gland (MG) health.

METHODS

A PubMed.gov literature search was conducted on or before May 15, 2021. No other time constraints were applied. Search terms included the following: "meibomian gland(s)" plus "contact lens(es)" or "meibography" plus "contact lens(es)". Only full text articles written in English were considered. The reference lists of recovered papers were used to identify articles missed during the primary search. Included articles were required to discuss the impact of contact lenses on MG morphology or function and were graded according to the level of evidence presented.

RESULTS

The literature indicates that contact lenses impact MG function; however, the data are equivocal regarding contact lenses inducing MG structural changes. The literature likewise indicates that the mechanism(s) by which contact lenses impact the MGs are likely multifactorial. Recent data suggests that MGs may have some plasticity. Detected differences between studies likely stem from varied populations evaluated, study designs, and the duration of the evaluation periods.

CONCLUSIONS

With this literature review finding conflicting relationships between MG health and contact lens use, future longitudinal studies with standardized clinical MG assessments are needed to determine the true impact of contact lenses on MG health. Until these data are obtained, contact lens wearers should undergo a full MG evaluation, especially because recent data suggest that MG treatments may restore MG structure and function.

Profiling ocular surface responses to preserved and non-preserved topical glaucoma medications: A 2-year randomized evaluation study

BACKGROUND

Use of topical glaucoma medications has been reported to cause ocular surface (OS) discomfort and inflammation. This study explores the profile of inflammatory cytokines and OS symptoms induced in response to preserved and non-preserved drops.

METHODS

Prospective, randomized evaluation on 36 treatment-naïve patients over 24 months of three differently preserved glaucoma drop preparations: Preservative-free (PF), polyquad (PQ) and benzalkonium chloride (BAK). Study participants were evaluated at baseline and then at 1, 3, 6, 12 and 24 months while on medication. At each visit, participants completed the OS disease index (OSDI) questionnaire, had basal tear sampling and impression cytology (IC) of the conjunctival epithelium. Quantitative polymerase chain reaction was performed to measure the gene expression of inflammatory cytokines [interleukin (IL)-6, IL-8, IL-10, IL-12A, IL-12B, IL-17A, IL-1β and tumour necrosis factor-α] in the IC samples. Corresponding protein expression of cytokines in tear samples was assessed by the Becton-Dickinson cytometric bead arrays.

RESULTS

Compared to PF and PQ groups, mRNA and protein expression of IL-6, IL-8 and IL-1β increased in samples from the BAK group in a time-dependent fashion, whereas all other cytokines showed a non-significant increase. In the BAK group, there was a strong correlation between OSDI and the levels of IC/IL-1β (r = .832, R² = .692 and P = .040); IC/IL-10 (r = .925, R² = .856 and P = .008) and tear/IL-1β (r = .899, R² = .808 and P = .014).

CONCLUSIONS

BAK-preserved topical drops stimulate a sterile inflammatory response on the OS within 3 months which is maintained thereafter, whereas PF-drops and PQ-preserved drops showed no significant OS inflammation.

To See or Not to See: A Systematic Review of the Importance of Human Ocular Surface Cytokine Biosignatures in Ocular Allergy

Cytokines are key cell signalling proteins in a number of immune and homeostatic pathways of the human body. In particular, they mediate intracellular mechanisms of allergy on the ocular surface by triggering cellular responses that result in typical physiological ocular allergy symptoms, such as itchiness, watery eyes, irritation, and swelling. Given the recent research focus in optometry on the aetiology of corneal ectasia subtypes like keratoconus, there is an increasing need for the development of new clinical diagnostic methods. An increasing trend is evident among recent publications in cytokine studies, whereby the concentrations of cytokines in healthy and disease states are compared to derive a specific cytokine profile for that disease referred to as ‘biosignatures’. Biosignatures have diagnostic applications in ocular allergy as a cheap, non-invasive alternative to current techniques like IgE antibody testing and skin prick tests. Cytokine detection from tear samples collected via microcapillary flow can be analysed either by enzyme-linked immunosorbent assays (ELISA), multiplex magnetic bead assays, or immunoblot assays. Characterising patient hypersensitivities through diagnostic tests is the first step to managing exposure to triggers. Investigating cytokine biosignatures in ocular allergy and their links to physiology are imperative and will be the focus of this systematic review article.

The inflammation influence on corneal surface after frontalis suspension surgery

AIM

To study the influence of frontalis muscle flap suspension on ocular surface by analyzing the clinical features and inflammatory cytokines.

METHODS

A prospective, observational case series. Thirty-one eyes of 25 patients with severe congenital blepharoptosis who underwent frontalis muscle flap suspension surgery with at least 6mo of follow-up were included in the study. The main outcome measures were margin reflex distance 1 (MRD₁), degree of lagophthalmos, ocular surface disease index (OSDI), fluorescein staining (Fl), tear break-up time (BUT), Schirmer I test, and inflammatory cytokine assay.

RESULTS

The degrees of lagophthalmos significantly increased after surgery. The OSDI scores significantly increased 1wk postoperatively and then decreased 4wk after operation. The Fl scores reflected corneal epithelial defects in sixteen patients at early stage postoperatively. The BUT and Schirmer I test values remained stable and did not show change compared to those before surgery. The inflammatory cytokines in conjunctival epithelial cells (including IL-1β, IL-6, IL-8, TNF-α, and IL-17A) significantly increased 1wk after the surgery (P<0.001), then returned to the normal level at 24wk postoperatively. The levels of inflammatory cytokine IL-1β, IL-6, IL-8, TNF-α, and IL-17A elevated significantly and were positively correlated with OSDI and Fl scores.

CONCLUSION

Frontalis muscle flap suspension surgery results in lagophthalmos in early period of post-operation and relieved after months. The elevation of inflammatory cytokines level may participate in the occurrence of corneal epithelial defects at the early postoperative stage.

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.

Cytokines in tears during the secondary keratoconjunctival responses induced by allergic reaction in the nasal mucosa

BACKGROUND

Allergic keratoconjunctivitis (KC) can occur in a primary form due to an allergic reaction taking place in the conjunctivae or in a secondary form induced by nasal allergy.

OBJECTIVES

To search for the cytokine changes in tears accompanying the secondary keratoconjunctival response types (SKCR), caused by the nasal allergy.

METHODS

In 43 KC patients developing 15 immediate (SIKCR), 16 late (SLKCR) and 12 delayed (SDYKCR) responses to nasal provocation tests with allergens (NPT), the NPTs were repeated with subsequent recording of cytokine concentrations in tears up to 72 h.

RESULTS

The SIKCRs (p<0.001), occurring 10-120 min after the NPT, were accompanied by significant changes (p<0.05) of interleukin (IL)-4, IL-6, IL-10, IL-12p70 and granulocyte-macrophage colony-stimulating factor (GM-CSF). The SLKCRs (p<0.01), appearing 5-12 h after the NPT, were associated with significant changes (p<0.05) of IL-3, IL-4, IL-5, IL-8, IL-10, tumor necrosis factor (TNF)-α, GM-CSF and granulocyte colony-stimulating factor. The SDYKCRs (p<0.01), occurring 24-48 h after the NPT, were accompanied by significant changes (p<0.05) of IL-2, IL-8, IL-10, interferon-γ, transforming growth factor-β and TNF-α.

CONCLUSIONS

The particular SKCR types, induced by an allergic reaction in the nasal mucosa, were accompanied by different cytokine profiles in the tears, suggesting involvement of different hypersensitivity mechanisms. These results also stress the diagnostic usefulness of NPTs combined with monitoring of ocular features in KC patients who did not respond satisfactorily to the topical ophthalmological treatment.

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.

Cytokine profiles in tears accompanying the secondary conjunctival responses induced by nasal allergy

PURPOSE/AIM

Allergic conjunctivitis (AC) occurs either in a primary form, due to the allergic reaction localized in the conjunctivae or in a secondary form, induced by an allergic reaction initiated primarily in the nasal mucosa. The purpose of this study was to investigate the cytokine profiles in tears associated with the secondary conjunctival response (SCR) types.

MATERIALS AND METHODS

In 47 AC patients developing 16 immediate (SICR; p < 0.01), 20 late (SLCR; p < 0.001) and 11 delayed (SDYCR; p < 0.05) responses to nasal provocation tests (NPTs) with allergens, the NPTs were repeated and combined with recording of cytokine concentrations in the tears.

RESULTS

The SCRs were associated with significant concentration changes of particular cytokines in tears (p < 0.05) as follows: (1): SICRs: interleukin (IL)-3, IL-4, IL-10 and granulocyte macrophage colony-stimulating factor (GM-CSF); (2) SLCRs: IL-3, IL-4, IL-5, IL-8, IL-10, IL-12p40, GM-CSF and granulocyte colony-stimulating factor (G-CSF); and (3) SDYCRs: IL-2, IL-8, IL-10, interferon gamma, G-CSF and tumor necrosis factor alpha. No significant cytokine changes were recorded in tears during the phosphate-buffered saline controls or negative SCRs.

CONCLUSIONS

Different cytokine profiles in the tears accompanying the immediate, late and delayed types of SCR, induced by nasal allergy, would indicate involvement of different hypersensitivity mechanisms in the particular SCR types. The low cytokine concentrations in tears recorded during the SCRs may suggest their origin from the nasal mucosa. These results emphasize the diagnostic value of NPTs with allergens combined with monitoring of various ocular features in patients suffering from the secondary form of AC. These results may also have an impact on the therapeutical approach to this clinical entity.

Comparison of IgA, TNF-α and surface tension of the tear film in two different times of the day

PURPOSE

The main goal was to study the biochemical composition of the tear film in two different times of the day.

METHODS

Tear samples were collected from 10 individuals, non contact lenses wearers, from the university population without pathologies. To assess daily variations in the tear film, samples were collected twice in the day, one early in the morning and another in the evening using capillary tubes. Tear protein profile was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), tumor necrosis factor α (TNF-α) and immunoglobulin A (IgA) were quantified by Enzyme-Linked ImmunoSorbent Assay (ELISA). Tear film stability was obtained through measurements of Non-Invasive Break Up Time and tear surface tension was measured by obtaining the Langmuir isotherms.

RESULTS

The stability of the tear film was higher in the morning than in the afternoon; corresponding to a higher value of surface tension in the afternoon. Protein electrophoresis tear profile is variable during the day as IgA concentration decreased from morning to afternoon (p<0.05). TNF-α concentration also decreased, but there were not significant statistical differences (p=0.089).

CONCLUSION

We concluded that there are daily variations in the composition and properties of the tear film, indicating that changes occur without being caused by contact lenses wear or by the presence of ocular and systemic pathologies. Presence of TNF-α is not a direct indication of inflammatory pathology, since this cytokine was identified in relatively high amounts in subjects without inflammatory pathology.

Human tears reveal insights into corneal neovascularization

Corneal neovascularization results from the encroachment of blood vessels from the surrounding conjunctiva onto the normally avascular cornea. The aim of this study is to identify factors in human tears that are involved in development and/or maintenance of corneal neovascularization in humans. This could allow development of diagnostic tools for monitoring corneal neovascularization and combination monoclonal antibody therapies for its treatment. In an observational case-control study we enrolled a total of 12 patients with corneal neovascularization and 10 healthy volunteers. Basal tears along with reflex tears from the inferior fornix, superior fornix and using a corneal bath were collected along with blood serum samples. From all patients, ocular surface photographs were taken. Concentrations of the pro-angiogenic cytokines interleukin (IL)-6, IL-8, Vascular Endothelial Growth Factor (VEGF), Monocyte Chemoattractant Protein 1 (MCP-1) and Fas Ligand (FasL) were determined in blood and tear samples using a flow cytometric multiplex assay. Our results show that the concentration of pro-angiogenic cytokines in human tears are significantly higher compared to their concentrations in serum, with highest levels found in basal tears. Interestingly, we could detect a significantly higher concentration of IL- 6, IL-8 and VEGF in localized corneal tears of patients with neovascularized corneas when compared to the control group. This is the first study of its kind demonstrating a significant difference of defined factors in tears from patients with neovascularized corneas as compared to healthy controls. These results provide the basis for future research using animal models to further substantiate the role of these cytokines in the establishment and maintenance of corneal neovascularization.

MUC1/A and MUC1/B splice variants differentially regulate inflammatory cytokine expression

The frequency of a splice variant of mucin 1 (MUC1), MUC1/A was lower in dry eye disease patients compared to normal controls, suggesting a link between the absence of MUC1/A and the development of dry eye disease which is characterized by chronic inflammation. The objectives of the present study were to clone and characterize the phenotype of cells expressing solely MUC1/A versus MUC1/B or a variant lacking the extracellular domain (ΔEX) and to determine whether MUC1/A and MUC1/B differentially modulate inflammatory responses in transfected cells. The additional 27 bp and SNP present in the N-terminus of MUC1/A were cloned into a FLAG-MUC1/B expression vector. Transient transfection of MUC1/A and MUC1/B plasmids into MUC1-null COS-7 cells resulted in similar protein expression and plasma membrane localization. MUC1/B and MUC1/A differed in their ability to modulate tumor necrosis α (TNFα)-induced transcription of IL-1β and IL-8. MUC1/B and MUC1/A inhibited IL-8 induction by TNFα at 4 h. However with 24 h TNFα, MUC1/A increased IL-1β and IL-8 whereas MUC1/B had no effect on cytokine expression. MUC1/B inhibited TNFα-induced luciferase activity from an NF-κB reporter whereas MUC1/A either inhibited or increased this luciferase activity depending on the time of TNFα treatment. MUC1/A, but not MUC1/B, increased the basal TGFβ expression. Both MUC1/B and MUC1/A blocked TNFα-induced miR-21 expression. These data demonstrate that MUC1/A and MUC1/B have different inflammatory activities and support the hypothesis that MUC1 genotypic differences may affect susceptibility to ocular surface damage in dry eye disease.

The effects of 2 week senofilcon-A silicone hydrogel contact lens daily wear on tear functions and ocular surface health status

PURPOSE

To prospectively investigate the effects of 2 week senofilcon A contact lens (CL) daily wear on the functional visual acuity (VA), ocular surface and tear film.

METHODS

Seventeen right eyes of 17 senofilcon A CL wearers without any ocular or systemic diseases were examined before and 2 weeks after lens wear. Visual acuity measurements, tear evaporation rate, ELISA for tear cytokines, strip meniscometry, tear lipid layer interferometry, tear film break-up time (BUT), in vivo confocal microscopy, corneal sensitivity, ocular surface vital staining, Schirmer I test and brush cytology for MUC5AC mRNA expression were performed before and after CL wear.

RESULTS

The best corrected Landolt VA, functional VA parameters, the mean lipid layer interferometry grades, tear evaporation rates, Schirmer test values, vital staining scores and in vivo confocal microscopy parameters did not show any significant differences after 2 weeks of CL wear. The tear film BUT showed a significant decrease together with a significant down regulation of MUC5 AC mRNA expression after CL wear. A statistically significant elevation in the mean tear interleukin (IL)-6 concentration was also observed after 2 weeks of CL wear.

CONCLUSIONS

Two week senofilcon A daily CL wear seems to be associated with tear instability, a decrease in MUC5AC expression, and elevation of IL-6 in tears without significant alterations in epithelial damage scores or in the morphology or density of in vivo keratoconjunctival cells and nerves. Alterations associated with long term wear and patients with dry eye disease need to be studied in future trials.

Evaluation of lipid oxidative stress status and inflammation in atopic ocular surface disease

BACKGROUND

Although the oxidative stress status in atopic skin disease has been reported to be elevated, there are still no studies related to the status of oxidative stress in atopic ocular surface disease. The purpose of this study was to evaluate the ocular surface lipid oxidative stress status and inflammation in atopic keratoconjunctivitis (AKC) patients and normal subjects.

METHODS

Twenty eight eyes of 14 patients (9 males, 5 females) with AKC and 18 eyes of 9 age and sex matched (4 males and 5 females) normal healthy controls were examined in this prospective study. The severity of atopic dermatitis (AD) was scored by the SCORing Atopic Dermatitis (SCORAD) index. All subjects underwent Schirmer test, tear film break up time (BUT), fluorescein/Rose Bengal stainings, tear collection, and brush cytology from the upper palpebral conjunctiva. The brush cytology samples were stained with Diff-Quik for differentiation of inflammatory cells and immunohistochemistry (IHC) staining with HEL (hexanoyl-lysine) and 4-HNE (4-hydroxy-2-nonenal) to study lipid oxidation. HEL and cytokine (interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ)) levels were measured by enzyme-linked immunosorbent assay (ELISA) from tear samples of AKC patients and control subjects. Toluidine Blue and IHC staining with HEL, 4-HNE and cluster of differentiation 45 (CD45) were performed on papillary samples of AKC patients. This study was conducted in compliance with the "Declaration of Helsinki."

RESULTS

The tear stability and vital staining scores were significantly worse in eyes of AKC patients (p<0.05) compared to the controls. Inflammatory cells and positively stained conjunctival epithelial cells for HEL and 4-HNE showed a significant elevation in brush cytology samples of AKC patients. Significantly higher levels of HEL and cytokines were detected in tears of AKC patients compared to controls. Papillary specimens also revealed many CD45 inflammatory cells as well as many cells positively stained with HEL and 4-HNE in IHC. A strong significant linear positive correlation between conjunctival inflammation and epithelial lipid oxidative stress status was observed. Conjunctival lipid oxidative stress also correlated strongly with tear HEL levels and epithelial damage scores.

CONCLUSIONS

The ocular surface disease in AKC was characterized by marked tear instability, ocular surface epithelial damage, increase in inflammatory infiltrates and presence of increased lipid oxidation.

Cytokine and chemokine levels in tears from healthy subjects

PURPOSE

There is growing evidence for the existence of an 'immune tone' in normal tears. The aim of this study was to determine the levels of a large panel of cytokines and chemokines in tears obtained from healthy subjects. These levels can then serve as baseline values for comparison with patients suffering from ocular surface diseases.

SUBJECTS AND METHODS

Nine healthy subjects participated in this study, and normal ocular surface health was documented by the results of a dry eye questionnaire, Schirmer strip wetting, and vital staining of the cornea. Four microliters of tears were collected from each eye and analysed separately with multiplex bead-based assays for the concentration of 30 cytokines and chemokines.

RESULTS

Twenty-five cytokines/chemokines were detected. CCL11/Eotaxin1, GM-CSF, G-CSF, IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-10, IL-13, IL-12p70, IL-15, CX3CL1/Fractalkine, TNF-α, epidermal growth factor, and CCL4/MIP-1β were present at 5-100 pg/ml. IL-1β, IL-6, IL-7A, CXCL8/IL-8, and CCL2/MCP-1 were present at 100-400 pg/ml. IL-1Ra, CXCL10/IP-10 and vascular endothelial growth factor were present at more than 1000 pg/ml.

CONCLUSION

Multiplex bead-based assays are convenient for cytokine/chemokine detection in tears. Fracktalkine has been detected in human healthy tears for the first time. The knowledge of cytokine/chemokine concentrations in tears from normal subjects is an important reference for further comparison with patients suffering from ocular surface diseases. Variability in their levels can reflect a phenomenon of potential importance for the understanding of the ocular surface cytokine pattern.

Mediators of neovascularization and the hypoxic cornea

The maintenance of corneal avascularity is essential to vision. The mechanisms by which the cornea becomes vascularized in response to inflammation or hypoxic stress are beginning to be elucidated. A detailed understanding of the molecular responses of the cornea to hypoxia is critical for prevention and development of novel treatments for neovascularization in a range of disease states. Here, we have examined the current literature on the major mediators of angiogenesis, which have previously been reported during hypoxia in the cornea in order to better understand the mechanisms by which corneal angiogenesis occurs in circumstances where the available oxygen is reduced. The normal cornea produces angiogenic factors that are regulated by the production of anti-angiogenic molecules. The various cell types of the cornea respond differentially to inflammatory and hypoxic stimuli. An understanding of the factors that may predispose patients to development of corneal blood vessels may provide an opportunity to develop novel prophylactic strategies. The difficulties with extrapolating data from other cell types and animal models to the cornea are also examined.

Cytokines, matrix metalloproteases, angiogenic and growth factors in tears of normal subjects and vernal keratoconjunctivitis patients

BACKGROUND

To detect the presence of multiple mediators and growth factors in tears of vernal keratoconjunctivitis (VKC) patients with active disease using stationary phase antibody arrays.

METHODS

Tears were collected from 12 normal subjects (CT) and 24 active VKC patients. Tears were centrifuged and successively probed using three microwell plate arrays specific for: (i) cytokines: interleukin (IL)-2, IL-4, IL-5, IL-8, IL-10, IL-12, IL-13, interferon-gamma and tumour necrosis factor-alpha; (ii) growth factors: basic fibroblast growth factor (bFGF), platelet-derived growth factor, thrombopoietin, angiopoietin-2, vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), keratocyte growth factor, tissue inhibitor of metalloprotease (TIMP)-1 and heparin-binding epithelial growth factor (HB-EGF) and (iii) matrix metalloprotease (MMP)-1, MMP-2, MMP-3, MMP-8, MMP-9, MMP-10, MMP-13, TIMP-1 and TIMP-2.

RESULTS

Interleukin-8 signals were detected in all CT and highly detected in all VKC samples. The Th2-type cytokines, IL-4, IL-5 and IL-10 were detected only in tears of VKC patients. Signals for bFGF, HB-EGF, VEGF and HGF were detected in 41-87% of VKC samples and in few CT samples. Only TIMP-1 and TIMP-2 were found in all normal and patient tear samples, whereas MMP-1, MMP-2, MMP-3, MMP-9 and MMP-10 were highly present in all VKC samples.

CONCLUSIONS

Stationary phase antibody array methodology was useful for the screening of various cytokines, growth factors and MMPs in tears. These analyses identified in tears of VKC patients previously unreported factors including MMP-3 and MMP-10 and multiple proteases, growth factors and cytokines, which may all play an important role in the pathogenesis of conjunctival inflammation.

Multiple cytokine analysis in human tears: an optimized procedure for cytometric bead-based assay

PURPOSE

To compare instruments and reagents used for cytometric bead-based assay (CBA) of cytokines in human tears.

METHODS

Two CBA instruments and reagent kits from five vendors were compared in parallel. Vendor protocols were modified to accommodate tear volumes. Precision, recovery, dilution linearity, and stability were evaluated.

RESULTS

Luminextrade mark and Bio-Radtrade mark proved optimal for tear CBA. Good correlation for dilution linearity was observed (r > 0.80, p < 0.05) for 1-4-mu l sample volumes. Samples were stable for 30 min at 25 degrees C.

CONCLUSION

Many tear cytokines can be reliably measured by CBA using an optimized protocol. Concentrations remain stable during periods consistent with collection.

Investigation of the human tear film proteome using multiple proteomic approaches

PURPOSE

The purpose of this work was to examine the tear film proteome using a combination of one-dimensional (1D) and two dimensional (2D) gel electrophoresis and mass spectrometry-based techniques and to explore the effect of the tear collection methods on the tear proteome.

METHODS

Tear samples from eight normal non-contact lens wearing human subjects collected by Drummond glass microcapillary and Schirmer strips were subjected to 1D-sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), 2D-SDS-PAGE, and 2D LC-MS/MS (Multidimensional protein identification technology - MudPIT). Bands or cores from the 1D- and 2D-SDS-PAGE were cut, digested with trypsin, and analyzed by tandem mass spectrometry for identification by the generation of sequence tags.

RESULTS

In total (across sampling and proteomic methods), 97 unique proteins were observed, and a significant number of the spots/bands in the PAGE were from posttranslational modifications. Fifty-four unique proteins were identified from proteins extracted from the Schirmer strips in comparison to 13 unique proteins identified from capillary tubes, and 30 unique proteins were identified by both collection methods. Secreted (serum) proteins were predominantly observed from tears collected by capillary whereas a combination of cellular and serum proteins were identified from tear film collected by Schirmer strips.

CONCLUSIONS

Overall, these results suggest that the tear film collection and the proteomic method impacts the proteins present in the tear film and that care should be exercised in choosing a tear collection method to best correlate to the experiment being conducted or the hypothesis that is being tested.

The impact of nasal conjunctivochalasis on tear functions and ocular surface findings

PURPOSE

To investigate the effect of grade 3 nasal conjunctivochalasis (NCCh) on the tear film inflammation, ocular surface findings, and tear function findings.

DESIGN

Prospective, observational case series.

METHODS

Eleven eyes with Yokoi grade 3 NCCh in which the chalatic conjunctiva occluded the punctum and 18 eyes without NCCh but with central or temporal conjunctivochalasis, or both, and 16 eyes of healthy controls were recruited prospectively. Enzyme-linked immunosorbent assay for inflammatory tear cytokines, tear film break-up time (BUT), Schirmer I test measurements, and fluorescein and rose bengal vital stainings and impression cytologic and brush cytologic analysis for real-time reverse-transcriptase polymerase chain reaction analysis of MUC5AC messenger ribonucleic acid (mRNA) expression were performed.

RESULTS

Eyes with grade 3 NCCh had significantly delayed tear clearance. All inflammatory cytokines showed higher values in eyes with grade 3 NCCh compared with the eyes without nasal chalasis with a comparably significant elevation in interleukin-1b and tumor necrosis factor alpha levels. The mean rose bengal score in eyes with grade 3 NCCh was significantly higher compared with eyes without nasal chalasis and eyes of controls. The mean goblet cell density was significantly lower in eyes with grade 3 NCCh with downregulation of the relative MUC5AC mRNA expression.

CONCLUSIONS

Inflammation plays an important role in the pathogenesis of conjunctivochalasis and is more pronounced in eyes with nasal chalasis. Pooling of inflammatory cytokines in tears of patients with NCCh associated with delayed tear clearance induces distinct adverse effects that affect the ocular surface health.

Antibody array characterization of inflammatory mediators in allergic and normal tears in the open and closed eye environments

To evaluate the use of stationary phase protein array technology for tear analysis and to characterize the distribution of inflammatory mediators in normal and allergic tears in the open and closed eye states. Microcapillary tube collected Open (OTF) and closed eye tear fluid (CTF) samples from normals (N), from individuals with various active chronic ocular and other allergies (CA), as well as from an individual subsequent to unilateral induction of an acute allergic conjunctivitis were assayed using membrane arrays that were optimized to allow the detection of GM-CSF, ILs-1 alpha, 1 beta, 2-10, 12-13, INF gamma, MCP-1 and TNFalpha in clinical size samples. The protocol of a micro-well plate array specific for ILs-2, 4, 5, 8, 10, 12, 13, TNFalpha and INF gamma was modified to minimize the impact of tear matrix effects. This was used to carry out parallel analysis on selected samples. By optimizing the protocol as well as the composition of a membrane array it proved possible to significantly increase the signal-to-noise ratio and sensitivity of assay allowing for the detection of some inflammatory mediators into the sub-picogram range. This provided sufficient sensitivity to allow the assay of clinically obtainable size samples. Analysis revealed that OTF from most Ns contained a high level of IL-8 and faint signals if any for the other probed proteins. In contrast, OTF samples from most CA individuals with and without ocular symptoms exhibited to varying degrees detectable levels of most of the other probed entities. The difference between normal and pathological tears and the levels of signals became far more pronounced in the CTF compared to the OTF samples. Use of the micro-well plate assay kit without modification revealed two tear matrix effects that profoundly impact the ability to obtain meaningful ELISA data. Modifying the assay protocol reduces but does not eliminate these artifacts making it possible to approximate the concentration of many of the probed entities. The obtained data is consistent using both methodologies revealing elevated levels of IL-8 and other cytokines in approximately 60% of the OTF samples from the CA population. Other than a modest increase in IL-8, no change could be observed in the profile of OTF after induction of an acute allergic reaction.

Inflammatory mediators of uveitis: cytokines and chemokines

PURPOSE OF REVIEW

The study of uveitis has been restricted by the difficulty in obtaining sufficient intraocular material from both human disease and experimental models. Recent developments in cytokine and chemokine detection have overcome many of these problems. This review presents a summary of the technologic advances in this area.

RECENT FINDINGS

Recent advances in cytokine analysis, in particular multiplexed bead immunoassays, have allowed the measurement of an extensive array of cytokines and chemokines from very small sample volumes. This has revolutionized uveitis research, enabling measurement of a large profile of cytokines and chemokines in intraocular fluid, such as aqueous humour. This allows us to recognize complex patterns of cytokines and chemokines from different forms of uveitis and to examine relationships between different molecules.

SUMMARY

The spectrum of proinflammatory cytokines and chemokines known to be implicated in uveitis has increased over recent years. Many of these molecules have also been found in experimental models of disease and may represent attractive therapeutic targets for the future. With recent advances in cytokine detection, an extension of these techniques with a more detailed analysis of different uveitis conditions may provide useful diagnostic and prognostic information for this potentially blinding group of diseases.

Bead-based multianalyte flow immunoassays: the cytometric bead array system

Analytical cytometry has significant potential beyond cellular analysis. The inherent capability of flow cytometers to efficiently discriminate between uniformly sized particles based on their intrinsic properties provides the foundation for multiplex bead assays. The technology can be exploited in designing immunoassays, Western blot-like antibody assays, and nucleic acid hybridization assays. This chapter focuses on immunoassay applications. The multiplex bead assays have recently evolved as a new and increasingly popular area for flow cytometry, becoming a good alternative to enzyme-linked immunosorbent assay for efficient evaluation of panels of analytes. This chapter provides detailed information about two bead platforms, the BD Cytometric Bead Array kits and the BD Cytometric Bead Array Flex Set Assays.

Multiple cytokines in human tear specimens in seasonal and chronic allergic eye disease and in conjunctival fibroblast cultures

BACKGROUND

Several cytokines are involved in the recruitment and activation of inflammatory cells in ocular allergic diseases. The purpose of the study was to assay multiple cytokines and chemokines in tears, to compare subgroups of allergic conjunctivitis (AC) with controls, and in culture supernatants to determine whether conjunctival fibroblasts produce some of these cytokines.

METHODS

Fifty to one hundred microlitre tears were obtained from patients with active seasonal allergic conjunctivitis (SAC; n=12), vernal keratoconjunctivitis (VKC; n=18), atopic keratoconjunctivitis (AKC; n=6) and non-atopic controls (n=14). Primary conjunctival fibroblasts grown in vitro were stimulated with IL-4, IL-13 or TNF-alpha for 24 h. Cell-free tear and culture supernatants were assayed for IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-13, IFN-gamma, TNF-alpha, eotaxin, MCP-1 and RANTES using multiplex bead analysis. Induction of chemokine gene expression was determined by PCR.

RESULTS

IL-1beta, IL-2, IL-5, IL-6, IL-12, IL-13, MCP-1 were increased in all tears groups compared with controls, with highly significant correlations between many of these molecules. In addition IL-4, IFN-gamma, and IL-10 were elevated in SAC and VKC, while eotaxin and TNF-alpha were only increased in VKC. IL-6, IL-8, MCP-1, RANTES and eotaxin were detected from fibroblasts cultures, and were all up-regulated by TNF-alpha. By PCR, fibroblasts expressed MCP-1 transcripts constitutively, whereas IP-10 and Mig were up-regulated by TNF-alpha.

CONCLUSIONS

Differential cytokine levels support tears as a useful indicator of immune mechanisms occurring during AC. The striking similarities in chemokine profiles between tears and fibroblasts suggest these cells as likely sources of chemokines in tears.