Hyperosmolar Saline Is a Proinflammatory Stress on the Mouse Ocular Surface

Cleavage of functional IL-2 receptor alpha chain (CD25) from murine corneal and conjunctival epithelia by MMP-9

BACKGROUND

IL-2 has classically been considered a cytokine that regulates T cell proliferation and differentiation, signaling through its heterotrimeric receptor (IL-2R) consisting of alpha (CD25), beta (CD122), gamma chains (CD132). Expression of IL-2R has also been detected in mucosal epithelial cells. Soluble IL-2Ralpha (CD25) has been reported as an inflammatory marker. We evaluated the expression of CD25 and CD122 in the ocular surface epithelium and investigated the mechanism of proteolytic cleavage of CD25 from these cells.

METHODS

Desiccating stress (DS) was used as an inducer of matrix metalloproteinase 9 (MMP-9). DS was created by subjecting C57BL/6 and MMP-9 knockout (BKO) mice and their wild-type littermates (WT) mice to a low humidity and drafty environment for 5 days (DS5). A separate group of C57BL/6 mice was subjected to DS5 and treatment with topical 0.025% doxycycline, a MMP inhibitor, administered QID. The expression of CD25 and CD122 was evaluated in cryosections by dual-label laser scanning confocal microscopy. Western blot was used to measure relative levels of CD25 in epithelial lysates. Gelatinase activity was evaluated by in situ zymography. Soluble CD25 in tear fluid was measured by an immunobead assay.

RESULTS

CD25 and CD122 were abundantly expressed in cornea (all layers) and conjunctiva epithelia (apical and subapical layers) in nonstressed control mice. After desiccating stress, we found that immunoreactivity to CD25, but not CD122, decreased by the ocular surface epithelia and concentration of soluble CD25 in tears increased as MMP-9 staining increased. CD25 was preserved in C57BL/6 mice topically treated with an MMP-9 inhibitor and in MMP-9 knock-out mice. MMP-9 treatment of human cultured corneal epithelial cells decreased levels of CD25 protein in a concentration dependent fashion.

CONCLUSION

Our results indicate that functional IL-2R is produced by the ocular surface epithelia and that CD25 is proteolytic cleaved to its soluble form by MMP-9, which increases in desiccating stress. These findings provide new insight into IL-2 signaling in mucosal epithelia.

Management of dysfunctional tear syndrome: a Canadian consensus

Dry eye complaints are common, have a diverse etiology, and result from disruption of the normal tear film; hence, the term "dysfunctional tear syndrome." Recent research has shown that ocular surface disorders have an inflammatory origin, that inflammation of the ocular surface does not always manifest as "red eye," and that a patient does not have to have a systemic autoimmune disease to experience a local, ocular autoimmune event. A panel of Canadian cornea and external disease subspecialists met and developed a questionnaire and treatment algorithm to aid the comprehensive ophthalmologist. Management of ocular surface disorders begins with a review of the patient's medical history, with particular attention to medication use, and a thorough ophthalmological examination. Use of a simple questionnaire can aid in the diagnosis. A variety of treatment modalities are available, the most effective of which are those that target the underlying inflammatory process with the goal of restoring the normal tear film. A treatment algorithm is presented that matches the severity of symptoms with the intensity of treatment. Lifestyle modifications, regular hygiene, and tear supplements may be sufficient in patients with mild symptoms. Anti-inflammatory medications (topical cyclosporin A, short courses of topical steroids, and [or] oral tetracyclines) and physical measures (punctal plugs, moisture-retaining eye wear) are implemented for those with moderate-to-severe symptoms. Autologous serum tears, scleral contact lenses, and surgery are reserved for patients with severe symptoms who have an unsatisfactory response to anti-inflammatory medications. Patients with lid disease or rosacea and those with allergic conditions should be identified during the initial encounter and should receive specific therapy to relieve their symptoms.

Evaluation of a new tear osmometer for repeatability and accuracy, using 0.5-microL (500-Nanoliter) samples

PURPOSE

To evaluate the repeatability and accuracy of a new tear osmometer that measures the osmolality of 0.5-microL (500-nanoliter) samples.

METHODS

Four standardized solutions were tested with 0.5-microL (500-nanoliter) samples for repeatability of measurements and comparability to standardized technique. Two known standard salt solutions (290 mOsm/kg H2O, 304 mOsm/kg H2O), a normal artificial tear matrix sample (306 mOsm/kg H2O), and an abnormal artificial tear matrix sample (336 mOsm/kg H2O) were repeatedly tested (n = 20 each) for osmolality with use of the Advanced Instruments Model 3100 Tear Osmometer (0.5-microL [500-nanoliter] sample size) and the FDA-approved Advanced Instruments Model 3D2 Clinical Osmometer (250-microL sample size).

RESULTS

Four standard solutions were used, with osmolality values of 290, 304, 306, and 336 mOsm/kg H2O. The respective precision data, including the mean and standard deviation, were: 291.8 +/- 4.4, 305.6 +/- 2.4, 305.1 +/- 2.3, and 336.4 +/- 2.2 mOsm/kg H2O. The percent recoveries for the 290 mOsm/kg H2O standard solution, the 304 mOsm/kg H2O reference solution, the normal value-assigned 306 mOsm/kg H2O sample, and the abnormal value-assigned 336 mOsm/kg H2O sample were 100.3, 100.2, 99.8, and 100.3 mOsm/kg H2O, respectively.

CONCLUSIONS

The repeatability data are in accordance with data obtained on clinical osmometers with use of larger sample sizes. All 4 samples tested on the tear osmometer have osmolality values that correlate well to the clinical instrument method. The tear osmometer is a suitable instrument for testing the osmolality of microliter-sized samples, such as tears, and therefore may be useful in diagnosing, monitoring, and classifying tear abnormalities such as the severity of dry eye disease.

Acidic mammalian chitinase in dry eye conditions

PURPOSE

An acidic mammalian chitinase (AMCase) seems to be implicated in allergic asthma and allergic ocular pathologies. The aim of this work was to investigate the role of AMCase during Sjögren's Syndrome (SS) and Meibomian Gland Dysfunction (MGD) dry eye diseases.

METHODS

Six patients with MGD dry eye (20-58 years, median 40) and six patients with dry eye associated to SS (32-60 years, median 47) were enrolled in this study. AMCase activity was measured in tears and AMCase mRNA expression was evaluated by real-time polymerase chain reaction from RNA extracted from epithelial cells of the conjunctiva. Six healthy adult subjects of the same age (34-44 years, median 39) were also studied as the control group.

RESULTS

AMCase activity was significantly increased in patients affected by MGD dry eye (18.54 +/- 1.5 nmol/ml/h) and SS dry eye (8.94 +/- 1.0 nmol/ml/h) respectively, compared to healthy controls (1.6 +/- 0.2 nmol/ml/h). AMCase activity was higher in the tears of subjects with MGD dry eye (P < 0.001). AMCase mRNA was detected in conjunctival epithelial cells and the expression was significantly higher in MGD dry eye than SS dry eye. A significant correlation between AMCase activity in the tears and mRNA in conjunctival epithelial cells was found.

CONCLUSION

AMCase may be an important marker in the pathogenesis of dry eye, suggesting the potential role of AMCase as a therapeutic target in these frequent pathologies.

Predicted phenotypes of dry eye: proposed consequences of its natural history

This paper reviews current knowledge of the pathophysiology of dry eye and predicts that the clinical picture in late disease differs in both severity and quality from that in early disease. It is hypothesized that hybrid forms evolve, in which aqueous-deficient dry eye (ADDE) takes on features of evaporative dry eye (EDE) and vice versa. As a consequence, early and late forms may require different diagnostic criteria and respond to different therapeutic regimes. Tear hyperosmolarity plays a key role in the damage mechanism of dry eye, and ADDE is recognized to be a low-volume, hyperosmolar state. As ADDE advances, a progressive decrease in lacrimal secretion occurs, exacerbated by loss of the corneal reflex. This causes a decrease in tear volume, thinning of the aqueous tear film, and retarded spreading of the tear film lipid layer. The latter is hypothesized to cause an increase in evaporative water loss and an added evaporative component to the dry eye. Thus, in advanced disease, the hybrid state would be an organic ADDE, accompanied by a functional EDE in the absence of meibomian gland dysfunction. This functional EDE would respond to agents that expand the tear volume, restore corneal sensitivity, or provide an artificial tear film lipid layer.

Is inflammation a consequence of extracellular hyperosmolarity?

Background

There are several reports suggesting that hyperosmolarity induces inflammation. We recently showed that Dextran Sodium Sulfate causes inflammatory bowel disease due to hyperosmolarity. The aim of this study was to confirm the link between hyperosmolarity and inflammation by assessing osmolarity values in vivo during inflammation, compare the inflammatory potential of different osmotic agents and finally study the long-term consequences of hyperosmolarity on cell fate.

Methods

Osmotic pressures were measured in inflammatory liquids withdrawn from mice subjected to inflammation caused either by subcutaneous injection of Bacille Calmette-Guérin (BCG) or Freund adjuvant. Three epithelial cell lines (HT29, T24 and A549) were exposed up to 48 hours to increasing osmolarities (300, 600, 900 mOsm) of chemically inert molecules such as Mannitol, Propylene Glycol, and Glycerol and inflammatory response was assessed by Enzyme Linked ImmunoSorbent Assay (ELISA) and RNA Protection Assay (RPA). Finally, normal mouse macrophages were exposed to hyperosmotic conditions for long-term culture.

Results

The inflammation caused either by BCG or Freund adjuvant is correlated to hyperosmolarity in inflammatory liquids. The exposure of cells to the different compounds, whatever their molecular weight, has no effect on the secretion of cytokines as long as the osmolarity is below a threshold of 300 mOsm. Higher osmolarities result in the secretion of proinflammatory cytokines (Interleukin-8, Interleukin-6, Interleukin-1β and Tumor Necrosis factor-α). Long-term hyperosmotic culture extends normal macrophage half-life, from 44 days to 102 days, and alters the expression of p53, Bcl-2 and Bax.

Conclusion

The present study further suggests inflammation and hyperosmolarity are closely related phenomena if not synonymous.

Assessment and impact of the time of day on aqueous tear evaporation in normal subjects

OBJECTIVES

To determine the impact of the time of day on aqueous tear (AT) evaporation in normal subjects on two consecutive days.

METHODS

In a controlled laboratory setting, morning and afternoon AT evaporation was tested in 19 normal subjects, at the same time of day on two consecutive days. Evaporometry was used at two ranges of relative humidity (RH) 25% to 35% and 35% to 45%.

RESULTS

Mean AT evaporation rates were 0.069 +/- 0.024 for 25% to 35% RH and 0.049 +/- 0.018 for 35% to 45% (P = 0.001). There were significant differences for both RH between time of day (P < 0.05) on day 1, but not observed on day 2. Variation between days showed no difference for RH during the afternoon, but there was a difference during the morning (P = 0.042).

CONCLUSIONS

The data are remarkably consistent between study days, but there is more fluctuation during the morning than in the afternoon. Therefore, to further standardize AT evaporation study protocol, we recommend perform evaporometry measurements during the afternoon rather than the morning, because our results showed less variability during the afternoon test between days.

Ste20-related proline/alanine-rich kinase (SPAK) regulated transcriptionally by hyperosmolarity is involved in intestinal barrier function

The Ste20-related protein proline/alanine-rich kinase (SPAK) plays important roles in cellular functions such as cell differentiation and regulation of chloride transport, but its roles in pathogenesis of intestinal inflammation remain largely unknown. Here we report significantly increased SPAK expression levels in hyperosmotic environments, such as mucosal biopsy samples from patients with Crohn's disease, as well as colon tissues of C57BL/6 mice and Caco2-BBE cells treated with hyperosmotic medium. NF-kappaB and Sp1-binding sites in the SPAK TATA-less promoter are essential for SPAK mRNA transcription. Hyperosmolarity increases the ability of NF-kappaB and Sp1 to bind to their binding sites. Knock-down of either NF-kappaB or Sp1 by siRNA reduces the hyperosmolarity-induced SPAK expression levels. Furthermore, expression of NF-kappaB, but not Sp1, was upregulated by hyperosmolarity in vivo and in vitro. Nuclear run-on assays showed that hyperosmolarity increases SPAK expression levels at the transcriptional level, without affecting SPAK mRNA stability. Knockdown of SPAK expression by siRNA or overexpression of SPAK in cells and transgenic mice shows that SPAK is involved in intestinal permeability in vitro and in vivo. Together, our data suggest that SPAK, the transcription of which is regulated by hyperosmolarity, plays an important role in epithelial barrier function.

Epithelial-immune cell interaction in dry eye

Dry eye is a potent stimulus of both innate and adaptive immune systems. At the nexus of the dry eye inflammatory/immune response is the dynamic interplay between the ocular surface epithelia and the bone marrow-derived immune cells. On the one hand, ocular surface epithelial cells play a key initiating role in this inflammatory reaction. On the other hand, they are targets of cytokines produced by activated T cells that are recruited to the ocular surface in response to dry eye. This interaction between epithelial and immune cells in dry eye will be thoroughly reviewed.

Contributions of evaporation and other mechanisms to tear film thinning and break-up

PURPOSE

To evaluate the contribution of three mechanisms-evaporation of the tear film, inward flow of water into the corneal epithelium or contact lens, and "tangential flow" along the surface of epithelium or contact lens-to the thinning of the tear film between blinks and to tear film break-up. In addition to a discussion of relevant studies, some previously unpublished images are presented illustrating aspects of tear film break-up. CONTRIBUTIONS OF THREE MECHANISMS TO TEAR FILM BREAK-UP: Inward flow of water into the epithelium or contact lens is probably unimportant, and a small flow in the opposite direction may actually occur. Tangential flow is probably important in certain special cases of tear film break-up-at the black line near the tear meniscus, over surface elevations, after partial blinks, and from small thick lipid spots in the tear film. In all these special cases it is argued that tangential flow is important initially, but evaporation may be needed for final thinning to break-up. It is argued that most of the observed tear film thinning between blinks is due to evaporation, rather than tangential flow, and that large "pool" break-up regions are the result of evaporation over an extended area.

CONCLUSION

Evaporation in our "free-air" conditions may be four to five times faster than the average of the values reported in the literature when air currents are prevented by preocular chambers. However, recent evaporation measurements using "ventilated chambers" give higher values, which may correspond better to free-air conditions. Thus evaporation may be fast enough to explain many cases of tear film break-up, and to give rise to considerable increases in the local osmolarity of the tear film between blinks.

Effects of osmoprotectants on hyperosmolar stress in cultured human corneal epithelial cells

PURPOSE

Increased tear osmolarity in dry eye disease has been found to stimulate production of inflammatory cytokines and matrix metalloproteinases by ocular surface epithelial cells. Prokaryotic and mammalian organ system cells maintain normal function under hypertonic conditions by the synthesis or accumulation of osmoprotectant compounds. This study assessed the effect of osmoprotectant compounds on the activation state of mitogen-activated protein (MAP) kinases in human corneal epithelial cells incubated in hyperosmolar conditions.

METHODS

Human corneal epithelial cells were incubated in media of isotonic, physiological osmolarity (300 mOsm) and in hyperosmolar media (400 mOsm), in the presence and absence of osmoprotectants, including several amino acids (L-carnitine and betaine), glycerol, and the polyol erythritol. The phosphorylation (activation) states of c-Jun N-terminal kinases (JNK) and p38 MAP kinases were monitored by Western blot and bead-based immunoassays.

RESULTS

Hyperosmolar conditions achieved by addition of sodium chloride or sucrose increased ratios of phosphorylated JNK and p38 to total JNK and p38. Compared with controls, 10 mM L-carnitine or 40 mM erythritol significantly lowered levels of activated MAP kinases in response to hyperosmolar stress. They also lowered ratios of phosphorylated to total kinases to barely detectable levels in cells cultured in isotonic media.

CONCLUSIONS

The osmoprotectants L-carnitine and erythritol, alone or in combination, were found to protect against stress activation of corneal epithelial cells cultured in hyperosmolar media.

Pharmacological management of dry eye in the elderly patient

Dry eye disease is a common and increasingly prevalent condition particularly associated with advancing age and postmenopausal women. Epidemiological studies identify prevalence rates ranging from 7% in the US to 33% in the Asian population. Research increasingly identifies risk factors of increasing age, female sex, smoking, use of video display terminals and use of certain medications as well as environmental stresses as aggravating factors for the disease. Basic and clinical investigations provide cumulative evidence of hyperosmolarity of the tear film and ocular surface/lacrimal gland inflammation as pathogenic features of dry eye disease. A decline in systemic and local levels of sex hormones is associated with advancing age and advancing disease. Pharmacological therapeutic interventions include enhanced lubricants and anti-inflammatory drugs such as topical corticosteroids and ciclosporin (cyclosporine A). Secretagogues and hormonal supplementation are potential future therapies. The increased understanding of the contributing and pathogenetic factors responsible for dry eye provides a rationale for multiple therapeutic options for this multi-factorial disease. In the elderly patient it is important to recognize the physical and cognitive limitations that will influence the selection of appropriate topical medication.

Hyperosmolarity-induced cornification of human corneal epithelial cells is regulated by JNK MAPK

PURPOSE

To evaluate the effects of hyperosmolar stress on expression of cornified envelope (CE) precursors and transglutaminases (TGs) by primary cultured human corneal epithelial (PCHCE) cells and the regulatory effects of JNK MAPK on this process.

METHODS

Expression of CE precursors and TGs were evaluated in PCHCE cells exposed to media of increasing osmolarity (350-450 mOsM) for 24, 48, and 72 hours. JNK1 and -2 MAPKs were inhibited by addition of short interfering (si)RNA. Relative levels of mRNA transcripts and proteins were evaluated. TG activity, cell viability, and apoptosis were detected in PCHCE cells, with or without siRNA-JNKs.

RESULTS

Exposure of PCHCE cells to hyperosmolar medium increased TG activity at 3 hours, levels of the CE precursors SPRR1b and -2a and membrane-associated TG1 mRNA at 6 hours, and tissue-type TG2 mRNA at 24 hours. Osmotic stress decreased corneal epithelial cell viability, which was due in part to stimulation of apoptosis and cornification death. Inhibiting JNK2 production by siRNA in osmotically stressed PCHCE cells prevented the stimulation of SPRR and membrane-associated TG1 production and TG activity, and improved cell viability, whereas inhibition of JNK1 prevented early apoptosis.

CONCLUSIONS

Osmotic stress promotes production of certain CE proteins and cross-linking membrane-associated TG1 and decreases cell viability via JNK MAPK-mediated pathways. Strategies that inhibit JNK production downregulate the cornification response of PCHCE cells to osmotic stress. These findings have potential therapeutic implications for preventing cornification of the corneal epithelium in response to the hyperosmolar tear film in dry eye disease.

Boston scleral lens prosthetic device for treatment of severe dry eye in chronic graft-versus-host disease

PURPOSE

To determine if the Boston Scleral Lens Prosthetic Device (BSLPD) reduces symptoms and improves quality of life in patients with severe dry eye from chronic graft-versus-host disease (cGvHD).

METHODS

This is a noncomparative interventional case series reporting 33 consecutive patients with severe dry eye from cGvHD, unresponsive to conventional therapy, who were fitted with the BSLPD. A patient survey was undertaken after lenses were dispensed and worn regarding the effect of scleral lens wear on their symptoms, quality of life, and activities of daily living. The patient population was characterized from a retrospective chart review. Survey data were tabulated.

RESULTS

BSLPD wear resulted in improvement in pain, photophobia, and general quality of life in nearly all patients, with more than half reporting the highest improvement level for pain (52%) and photophobia (63%), and more than two thirds (73%) reporting the highest improvement level for quality of life. There was improvement in reading and driving in >90% of those who reported previous compromise, with >60% reporting the highest improvement level for each of these activities.

CONCLUSIONS

The BSLPD mitigates symptoms and improves quality of life in patients with severe dry eye from cGHvD.

[Osmoprotection as a new therapeutic principle]

Dry eye syndrome is one of the most common disorders encountered in daily ophthalmological practice. New pathophysiological concepts have been developed over the last few years. Hyperosmolarity of the tear film is one of the key pathogenetic factors in the development of a - commonly subclinical - inflammation of the ocular surface, the lacrimal gland and the tear film in dry eye syndrome. Osmoprotective agents act through compatible solutes to prevent - at least in theory -a hyperosmolar tear film from damaging the ocular surface.

Matrix metalloproteinases in corneal inflammation

Matrix metalloproteinases (MMPs) are a family of calcium-dependent, zinc-containing endoproteinases capable of degrading the extracellular matrix and basement membrane. Many inflammatory stimuli, such as wound healing, ultraviolet, hyperosmolarity, and stress, can stimulate production of inflammatory cytokines and a variety of MMPs, including gelatinases, collagenases, and stromelysins. Pro-inflammatory cytokines and growth factors can further promote the production of MMPs. Thus, MMPs participate in and promote the inflammation process. MMP-9 may be a most important amplifying factor for corneal inflammation. Mitogen activated protein kinases are involved in MMPs amplified inflammation. These pathway studies provide new therapeutic potential to block MMP mediated inflammation.

Stress-activated protein kinase signaling pathways in dry eye and ocular surface disease

Inflammation is recognized as a key component in the pathogenesis of dry eye and a variety of ocular surface diseases. Stress-activated protein kinases have been identified as pathways signaling ocular surface stresses, such as increased tear film osmolarity and ultraviolet light exposure. Activation of these stress pathways results in transcription of stress related genes, including inflammatory cytokines (e.g. interleukin-1 and tumor necrosis factor (TNF)-alpha and matrix metalloproteinases (MMPs), such as MMP-9. Treatment of osmo-stressed cultured corneal epithelia with inhibitors of the stress associated kinase c-jun N-terminal kinases was found to decrease production of MMPs by these cells. These findings suggest that SAPKs may be key therapeutic targets for dry eye and ocular surface diseases.

Strain-related cytokine profiles on the murine ocular surface in response to desiccating stress

PURPOSE

To evaluate the effects of desiccating ocular surface stress on levels of inflammatory cytokines in the corneal epithelium, conjunctiva, and tear fluid of BALB/c and C57BL/6 mice.

METHODS

Experimental dry eye (EDE) was created in BALB/c and C57BL/6 mice by cholinergic blockade and exposure to a desiccating environment. Real-time polymerase chain reaction was performed to measure levels of cytokine transcripts. A multiplex immunobead assay was used to measure concentrations of these cytokines in tears.

RESULTS

Experimental dryness significantly increased the expression of interleukin (IL)-1alpha, IL-6, and tumor necrosis factor (TNF)-alpha transcripts in the corneal epithelium and conjunctiva of C57BL/6 mice. Strain-specific changes in tear cytokine profiles were observed. C57BL/6 mice had significantly greater tear concentrations of IL-1alpha and TNF-alpha and the Th-1 cytokines IL-2, IL-12, and interferon-gamma in response to desiccating stress than BALB/c mice. The Th-2 cytokines IL-4 and IL-10 were significantly greater in BALB/c tears.

CONCLUSIONS

This study indicates that desiccating stress increases levels of certain cytokines in the corneal epithelium and conjunctiva in a strain-dependent fashion and that C57BL/6 mice had greater levels of Th-1 cytokines in their tears, whereas BALB/c mice had a greater increase in Th-2 cytokines.

The Correlation Between the Tear Film Lipid Layer and Dry Eye Disease

Dry eye, also known as keratoconjunctivitis sicca, can be due either to insufficient tear production or excessive tear evaporation, both resulting in tear hyperosmolarity that leads to symptoms of discomfort and ocular damage. Additionally, the severity of dry eye symptoms appears to be correlated to lipid layer thickness. It is now generally recognized that increased evaporation due to a compromised lipid layer is one of the most common etiologies for hyperosmolarity of the tear film. Thus, therapies targeted at replenishing or stabilizing the lipid layer are key to the treatment of dry eye, either as monotherapy or in conjunction with therapies designed to enhance aqueous production.

Effects of topical anti-inflammatory agents in a botulinum toxin B-induced mouse model of keratoconjunctivitis sicca

PURPOSE

The aim of this study was to compare the effects of topical nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroid, doxycycline, and artificial tears for the treatment of ocular surface damage in the Botulinum toxin B (BTX-B)-induced mouse model of dry eye.

METHODS

CBA/J mice were randomized into 2 experimental groups of 35 animals each. The control group received a transconjunctival injection of 0.05 mL of saline into the left lacrimal gland, and another group was injected with 0.05 mL of 20 milliunits BTX-B solution (SPSS, Inc., Chicago, IL). Three (3) days after intralacrimal gland injections, each group was equally randomized into 7 subgroups (n=5 each) to receive treatment unilaterally into their left eyes with topical artificial tears (0.5% carboxymethylcellulose sodium), 0.1% fluorometholone, 0.1% nepafenac, 0.4% ketorolac, 0.09% bromfenac, 0.1% diclofenac, or 0.025% doxycycline. Tear volume, ocular surface changes, and spontaneous blink rate were evaluated in each of the 14 experimental subgroups.

RESULTS

Topical fluorometholone, nepafenac, and doxycycline significantly improved corneal surface staining in the BTX-B-injected mice within 2 weeks of treatment. Topical ketorolac, diclofenac, and bromfenac, applied twice-daily, partially reduce corneal staining, and did so more slowly by the 4-week time point. In comparison, topical artificial tear-treated mice did not demonstrate significant improvement of the corneal surface at any time point. Aqueous tear production in the BTX-B-injected fluorometholone-treated group started to return to baseline level within 2 weeks, although not significantly. Meanwhile, BTX-B-injected mice treated with artificial tears, topical NSAIDs, and doxycycline still exhibited a reduction in tear production up to 4 weeks. No significant differences in blink rate between the control and study groups undergoing the various treatments were noted at all time points.

CONCLUSIONS

This study suggests the potential usefulness of topical NSAIDs, corticosteroid, and doxycycline for the clinical treatment of ocular surface epithelial disorders associated with dry eye.

Hyperosmolarity-induced apoptosis in human corneal epithelial cells is mediated by cytochrome c and MAPK pathways

PURPOSE

To study whether hyperosmolarity induces apoptosis in human corneal epithelial cells through cytochrome c-mediated death pathways and by activation of mitogen-activated protein kinases (MAPKs).

METHODS

Primary human corneal epithelial cells cultured in normal osmolar media (312 mOsM) were switched to hyperosmolar media (450, 500, and 550 mOsM) by adding 70, 90, and 120 mM NaCl, respectively, with or without the c-jun N-terminal kinase (JNK) inhibitor SB202190 or the extracellular-regulated kinase (ERK) inhibitor PD98059. Apoptosis was assessed by the ApopTag In Situ Oligo Ligation (ISOL) assay. Confocal microscopy was used to detect cytochrome c and active caspase-3. Total RNA was extracted and subjected to reverse transcriptase-polymerase chain reaction for apoptosis-associated genes. Western blots were performed on cell extracts for the apoptogenic molecules cytochrome c and Smac/DIABLO, and phospho-JNK and ERK.

RESULTS

ISOL-positive apoptotic cells significantly increased from 3.3 +/- 1.6% in control medium to 11.4 +/- 5.8%, 18.9 +/- 4.8%, and 43.9 +/- 8.8% in 70, 90, and 120 mM NaCl added media, respectively. The 90 mM NaCl high saline medium notably increased release of cytochrome c and Smac/DIABLO from mitochondria; activated caspase-3, JNK and ERK; stimulated mRNA expression of interleukin-1-converting enzyme and Bax; and reduced Bcl2 expression. SB202190 and PD98059 significantly suppressed hyperosmolarity-induced JNK/ERK activation and ISOL-positive cells. In addition, PD98059 inhibited the release of cytochrome c and Smac/DIABLO from mitochondria.

CONCLUSIONS

These findings show that hyperosmolarity induces apoptosis of human corneal epithelial cells through a cytochrome c-mediated death pathway, which may be mediated by JNK and ERK MAPK signaling pathways.

The Definition and Classification of Dry Eye Disease: Report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007)

The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

Management and Therapy of Dry Eye Disease: Report of the Management and Therapy Subcommittee of the International Dry Eye WorkShop (2007)

The members of the Management and Therapy Subcommittee assessed current dry eye therapies. Each member wrote a succinct evidence-based review on an assigned aspect of the topic, and the final report was written after review by and with consensus of all subcommittee members and the entire Dry Eye WorkShop membership. In addition to its own review of the literature, the Subcommittee reviewed the Dry Eye Preferred Practice Patterns of the American Academy of Ophthalmology and the International Task Force (ITF) Delphi Panel on Dry Eye. The Subcommittee favored the approach taken by the ITF, whose recommended treatments were based on level of disease severity. the recommendations of the Subcommittee are based on a modification of the ITF severity grading scheme, and suggested treatments were chosen from a menu of therapies for which evidence of therapeutic effect had been presented.

Measurements of Solutions and Contact Lenses With a Vapor Pressure Osmometer

PURPOSE

To investigate the influence of sample volume and contact lens material on osmolality measurements made with a Wescor vapor pressure osmometer.

METHODS

Accuracy: Sample volumes of 0.8, 2.0, and 10.0 microL were tested with 290, 320, and 1000 mmol/kg after the osmometer was calibrated with the intended sample volume. Influence of sample volume: Sample volumes ranging from 0.5 to 1.1 microL (0.1 steps) were applied with solutions of 290, 320, 500, and 1000 mmol/kg after the osmometer was calibrated with 0.8 microl, independent of the intended sample volume. Influence of contact lens material: Lens discs of 3.4 millimeters were trephined from the center of Lotrafilcon B, Nelfilcon A, Balafilcon A and Etafilcon A lenses, and equilibrated in phosphate buffered saline with 290 mmol/kg after dehydration for 16 h. The osmometer was calibrated with 0.8 microl and lens discs were inserted into the small sample holder of the osmometer.

RESULTS

There were no significant differences between the nominal and measured osmolalities for each sample volume and solution combination (all p > 0.05). Influence of sample volume: Differences of more than 0.1 microl between the calibration and sample volume significantly affected osmolality readings, with sample volumes larger than calibration volume resulting in lower readings, and smaller volumes resulting in higher readings. Influence of contact lens material: Measured osmolalities of Lotrafilcon B (358.8 +/- 45.4 mmol/kg) and Balafilcon A (356.7 +/- 38.7 mmol/kg) were not significantly different to each other (p = 0.999) but were significantly higher than Etafilcon A (298.2 +/- 15.9 mmol/kg) and Nelfilcon A (281.2 +/- 12.2 mmol/kg, p < 0.05). There was no significant difference between Etafilcon A and Nelfilcon A lenses (p = 0.056). The main factors associated with measured osmolality were water content, sample volume and their interaction (r(2) = 0.716).

CONCLUSION

Osmolality readings varied with calibration and sample volume, and with different contact lens materials.

Corticosteroid and doxycycline suppress MMP-9 and inflammatory cytokine expression, MAPK activation in the corneal epithelium in experimental dry eye

We investigated the effects of corticosteroid and doxycycline on expression of matrix metalloproteinase (MMP)-9 and inflammatory cytokines and activation of mitogen-activated protein kinase (MAPK) signaling pathways, c-jun N-terminal kinases (JNK), extracellular-regulated kinases (ERK) and p38, in experimental murine dry eye. Experimental dry eye (EDE) was created in C57BL6 mice, with or without or topical treatment consisting of 1% methylprednisolone, 0.025% doxycycline or balanced salt solution four times per day. MMP-9 expression in the cornea epithelia was evaluated by laser scanning confocal microscopy. Gelatinase activity in the cornea was evaluated by in situ zymography and MMP-9 activity in tear washings was evaluated by gelatin zymography. Total and phosphorylated MAPKs (JNK1/2, ERK1/2, p38) were detected by Luminex immunobead assay. Levels of MMP-9, interleukin (IL)-1alpha, IL-1beta and tumor necrosis factor (TNF)-alpha RNA transcripts were evaluated by real-time PCR. MMP-9 immunoreactivity was localized to the apical corneal epithelial cell membranes in normal control eyes. Desiccating stress significantly increased production of MMP-9 by the corneal epithelium and increased its activity in the corneal epithelium and tear fluid. Dryness also increased expression of IL-1alpha, IL-1beta and TNF-alpha mRNA and stimulated phosphorylation of JNK1/2, ERK1/2 and p38 MAPKs in the corneal epithelium. Both methylprednisolone and doxycycline reduced expression and activity of MMP-9, decreased levels of inflammatory cytokines transcripts and reduced activation of MAPKs in the corneal epithelium in response to EDE. Desiccating stress stimulates expression of MMP-9, IL-1alpha, IL-1beta and TNF-alpha mRNA , as well as activates MAPK signaling pathways in the corneal epithelium. Both corticosteroid and doxycycline suppressed this molecular stress response.

JNK and ERK MAP kinases mediate induction of IL-1beta, TNF-alpha and IL-8 following hyperosmolar stress in human limbal epithelial cells

Hyperosmolarity has been recognized to be a pro-inflammatory stress to the corneal epithelium. The cell signalling pathways linking hyperosmolar stress and inflammation have not been well elucidated. This study investigated whether exposure of human limbal epithelial cells to hyperosmotic stress activates the mitogen-activated protein kinase (MAPK) pathways and induces production of pro-inflammatory cytokines, interleukin (IL) -1beta, tumor necrosis factor (TNF) alpha, and the C-X-C chemokine IL-8. Primary human limbal epithelial cultures in normal osmolar media (312 mOsM) were exposed to media with higher osmolarity (400-500 mOsM) by adding 50-90 mM NaCl, with or without SB202190, an inhibitor of c-Jun N-terminal kinases (JNK) pathway, PD 98059, an inhibitor of extracellular-regulated kinase (ERK) pathway, dexamethasone or doxycycline for different lengths of time. The conditioned media were collected after 24 hr of treatment for ELISA. Total RNA was extracted from cultures treated for 6 hr for semi-quantitative RT-PCR. Cells treated for 15-60 min were lysed in RIPA buffer and subjected to Western blot with phospho (p)-specific antibodies against p-JNK and p-ERK. The concentrations of IL-1beta, TNF-alpha and IL-8 proteins in 24 hr conditioned media of limbal epithelial cells progressively increased as the media osmolarity increased from 312 to 500 mOsM. Active p-JNK-1/p-JNK-2 and p-ERK-1/p-ERK-2 were detected by Western blot and peaked at 60 min in cells exposed to hyperosmolar media. The levels of p-JNK-1/p-JNK-2 and p-ERK1/p-ERK2 were positively correlated with the medium osmolarity. SB202190, PD98059 and doxycycline markedly suppressed the levels of p-JNK-1/p-JNK-2 and/or p-ERK1/p-ERK2, as well as IL-1beta, TNF-alpha and IL-8 mRNAs and proteins stimulated by hyperosmolar media. These findings provide direct evidence that hyperosmolarity induces inflammation in human limbal epithelial cells by increasing expression and production of pro-inflammatory cytokines and chemokines, a process that appears to be mediated through activation of the JNK and ERK MAPK signalling pathways. The efficacy of doxycycline in treating ocular surface diseases may be due to its ability to suppress JNK and ERK signalling activation and inflammatory mediator production in the limbal epithelium.