Differential contribution of hypertonic electrolytes to corneal epithelial dysfunction

Quality of vision and tear film osmolarity

SIGNIFICANCE

We evaluate the relationship between tear film osmolarity measurements and quality of vision in patients presenting for routine eye clinic appointments. We found that the hyperosmolar group (>316 mOsm/L) had a worse quality-of-vision score than the normal osmolarity group, with glare being the most problematic symptom.

PURPOSE

Quality of vision is a perception and measure of real-world vision, which is not measured routinely in a clinical setting. This study aimed to evaluate the relationship between tear film osmolarity measurements and quality of vision in patients presenting for routine eye clinic appointments.

METHODS

This was an observational nonrandomized study. The participants were placed in groups based on tear film osmolarity (normal, ≤316 mOsm/L; hyperosmolar, >316 mOsm/L; or a difference of >8 mOsm/L between each eye). Thirty-three participants were enrolled in the study, of whom 22 were deemed to have a hyperosmolar tear film. A 30-item questionnaire including 10 symptoms rated on scales of frequency, severity, and bothersomeness was administered to participants in both groups. The quality-of-vision score ranged from 25 to 100 points, with lower scores indicating better quality of vision.

RESULTS

The hyperosmolar group had a significantly worse quality-of-vision score than the normal osmolarity group across all three scales; mean differences for frequency, severity, and bothersomeness were 12.66 ± 9.75 (p=0.003), 9.44 ± 7.45 (p=0.003), and 11.90 ± 11.14 (p=0.008), respectively. Of the 10 symptoms that were included in the questionnaire, glare was the most problematic in the hyperosmolar group.

CONCLUSIONS

In this study, we demonstrated a significant relationship between tear film hyperosmolarity and quality of vision, as patients with hyperosmolar tear films had worse quality of vision.

The relationship between corneal calcareous degeneration and various ophthalmic diseases in dogs: A retrospective study

OBJECTIVE

To investigate ocular factors that influence the development of corneal calcareous degeneration (CCD) in dogs.

ANIMALS AND PROCEDURES

The medical records of 96 eyes of dogs with CCD and 288 eyes without CCD were retrospectively reviewed. Dogs with evidence of causative systemic illness associated with CCD were excluded from the study. Logistic regression analysis was used to identify the ocular factors associated with the development of CCD. To identify the effect of phosphate-containing eyedrops on CCD, the application periods of phosphate-containing antiglaucoma eyedrops were compared between the glaucomatous eyes in the CCD and non-CCD groups.

RESULTS

Increased age, brachycephalic breed, keratoconjunctivitis sicca, advanced cataract, history of phacoemulsification, and topical corticosteroid application were significantly associated with CCD development. Glaucoma was significantly overrepresented in the non-CCD group, and the application period of phosphate-containing antiglaucoma eyedrops was significantly longer in eyes with CCD than in those without CCD.

CONCLUSIONS

Ophthalmic diseases requiring long-term management of ocular inflammation and long-term application of phosphate-containing eyedrops may contribute to the development of CCD. Glaucoma is overrepresented in dogs without CCD, which is thought to be due to the differences in predisposed age and breeds between dogs with glaucoma and CCD.

The Potential Role of Regulated Cell Death in Dry Eye Diseases and Ocular Surface Dysfunction

The research on new treatments for dry eye diseases (DED) has exponentially grown over the past decades. The increased prevalence of dry eye conditions, particularly in the younger population, has received much attention. Therefore, it is of utmost importance to identify novel therapeutical targets. Regulated cell death (RCD) is an essential process to control the biological homeostasis of tissues and organisms. The identification of different mechanisms of RCD stimulated the research on their involvement in different human pathologies. Whereas apoptosis has been widely studied in DED and included in the DED vicious cycle, the role of RCD still needs to be completely elucidated. In this review, we will explore the potential roles of different types of RCD in DED and ocular surface dysfunction. Starting from the evidence of oxidative stress and inflammation in dry eye pathology, we will analyse the potential therapeutic applications of the following principal RCD mechanisms: ferroptosis, necroptosis, and pyroptosis.

Human tear fluid modulates the Pseudomonas aeruginosa transcriptome to alter antibiotic susceptibility

PURPOSE

Previously, we showed that tear fluid protects corneal epithelial cells against Pseudomonas aeruginosa without suppressing bacterial viability. Here, we studied how tear fluid affects bacterial gene expression.

METHODS

RNA-sequencing was used to study the P. aeruginosa transcriptome after tear fluid exposure (5 h, 37 ^oC). Outcomes were further investigated by biochemical and physiological perturbations to tear fluid and tear-like fluid (TLF) and assessment of bacterial viability following tear/TLF pretreatment and antibiotic exposure.

RESULTS

Tear fluid deregulated ~180 P. aeruginosa genes ≥8 fold versus PBS including downregulating lasI, rhlI, qscR (quorum sensing/virulence), oprH, phoP, phoQ (antimicrobial resistance) and arnBCADTEF (polymyxin B resistance). Upregulated genes included algF (biofilm formation) and hemO (iron acquisition). qPCR confirmed tear down-regulation of oprH, phoP and phoQ. Tear fluid pre-treatment increased P. aeruginosa resistance to meropenem ~5-fold (4 μg/ml), but enhanced polymyxin B susceptibility ~180-fold (1 μg/ml), the latter activity reduced by dilution in PBS. Media containing a subset of tear components (TLF) also sensitized bacteria to polymyxin B, but only ~22.5-fold, correlating with TLF/tear fluid Ca²⁺ and Mg²⁺ concentrations. Accordingly, phoQ mutants were not sensitized by TLF or tear fluid. Superior activity of tear fluid versus TLF against wild-type P. aeruginosa was heat resistant but proteinase K sensitive.

CONCLUSION

P. aeruginosa responds to human tear fluid by upregulating genes associated with bacterial survival and adaptation. Meanwhile, tear fluid down-regulates multiple virulence-associated genes. Tears also utilize divalent cations and heat resistant/proteinase K sensitive component(s) to enhance P. aeruginosa sensitivity to polymyxin B.

Ions, the Movement of Water and the Apoptotic Volume Decrease

The movement of water across the cell membrane is a natural biological process that occurs during growth, cell division, and cell death. Many cells are known to regulate changes in their cell volume through inherent compensatory regulatory mechanisms. Cells can sense an increase or decrease in their cell volume, and compensate through mechanisms known as a regulatory volume increase (RVI) or decrease (RVD) response, respectively. The transport of sodium, potassium along with other ions and osmolytes allows the movement of water in and out of the cell. These compensatory volume regulatory mechanisms maintain a cell at near constant volume. A hallmark of the physiological cell death process known as apoptosis is the loss of cell volume or cell shrinkage. This loss of cell volume is in stark contrast to what occurs during the accidental cell death process known as necrosis. During necrosis, cells swell or gain water, eventually resulting in cell lysis. Thus, whether a cell gains or loses water after injury is a defining feature of the specific mode of cell death. Cell shrinkage or the loss of cell volume during apoptosis has been termed apoptotic volume decrease or AVD. Over the years, this distinguishing feature of apoptosis has been largely ignored and thought to be a passive occurrence or simply a consequence of the cell death process. However, studies on AVD have defined an underlying movement of ions that result in not only the loss of cell volume, but also the activation and execution of the apoptotic process. This review explores the role ions play in controlling not only the movement of water, but the regulation of apoptosis. We will focus on what is known about specific ion channels and transporters identified to be involved in AVD, and how the movement of ions and water change the intracellular environment leading to stages of cell shrinkage and associated apoptotic characteristics. Finally, we will discuss these concepts as they apply to different cell types such as neurons, cardiomyocytes, and corneal epithelial cells.

Electrolyte composition of tears in normal dogs and its comparison to serum and plasma

PURPOSE

The dog is an important animal model for tear dysfunction diseases, however to-date the electrolyte composition of the dog's tears is unknown. The aim of this study was to analyze the electrolyte content of canine tears and compare it to serum and plasma.

METHODS

Tear samples were collected from 18 eyes of 9 dogs. Blood for serum was collected in tubes with no anticoagulants; plasma was obtained by using two different anticoagulants: Citrate-Phosphate-Dextrose (CPD) and heparin. The electrolytes were measured in all samples, analyzed, and compared.

RESULTS

Most of the electrolyte values in tears were statistically different (P < 0.05) from electrolyte values in serum and plasma. Potassium and chloride values were significantly higher in tears compared to serum and plasma, while calcium and phosphate values were significantly lower. Sodium values in tears were higher than in serum and heparinized-plasma, but lower than CPD-plasma. Bicarbonate values were lower in tears compared to serum and heparinized plasma, but was not statistically different than CPD-plasma. While magnesium values were lower in tears compared to serum and heparinized-plasma, the difference was not statistically different.

CONCLUSIONS

Herein, we report for the first time the electrolyte composition of the canine tears and its comparison to serum and plasma.

Genistein-Calcitriol Mitigates Hyperosmotic Stress-Induced TonEBP, CFTR Dysfunction, VDR Degradation and Inflammation in Dry Eye Disease

Dry eye disease (DED) signs and symptoms are causally associated with increased ocular surface (OS) inflammation. Modulation of key regulators of aberrant OS inflammation is of interest for clinical management. We investigated the status and the potential to harness key endogenous protective factors, such as cystic fibrosis transmembrane conductance regulator (CFTR) and vitamin D receptor (VDR) in hyperosmotic stress‐associated inflammation in patients with DED and in vitro. Conjunctival impression cytology samples from control subjects (n = 11) and patients with DED (n = 15) were used to determine the status of hyperosmotic stress (TonEBP/NFAT5), inflammation (IL‐6, IL‐8, IL‐17A/F, TNFα, MMP9, and MCP1), VDR, and intracellular chloride ion (GLRX5) by quantitative polymerase chain reaction and/or immunofluorescence. Human corneal epithelial cells (HCECs) were used to study the effect of CFTR activator (genistein) and vitamin D (calcitriol) in hyperosmotic stress (HOs)‐induced response in vitro. Western blotting was used to determine the expression of these proteins, along with p‐p38. Significantly, higher expression of inflammatory factors, TonEBP, GLRX5, and reduced VDR were observed in patients with DED and in HOs‐induced HCECs in vitro. Expression of TonEBP positively correlated with expression of inflammatory genes in DED. Increased TonEBP and GLRX5 provides confirmation of osmotic stress and chloride ion imbalance in OS epithelium in DED. These along with reduced VDR suggests dysregulated OS homeostasis in DED. Combination of genistein and calcitriol reduced HOs‐induced TonEBP, inflammatory gene expression, and p‐p38, and abated VDR degradation in HCECs. Henceforth, this combination should be further explored for its relevance in the management of DED.

Ocular Findings Associated with Hypoparathyroidism

Purpose: To determine the corneal and retinal changes associated with serum calcium, phosphorus and parathyroid hormone (PTH) levels in patients with hypoparathyroidism.Methods: Patients who were under follow-up for hypoparathyroidism in the endocrinology department were included in the study. All participants underwent a complete ophthalmological examination. Moreover, central corneal thickness (CCT), anterior chamber depth (ACD), retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL) thickness were recorded. Serum biochemical parameters were recorded.Results: In a total of 75 patients (35 in the hypoparathyroidism group and 40 in the healthy control group) were included in this study. Central corneal thickness (519.95 ± 33.21 vs. 539.10 ± 32.96, p: 0.001) and RNFL (105.10 ± 11.89 vs. 113.56 ± 9.54, p: 0.005) were significantly thinner and ACD was significantly deeper in the hypoparathyroidism group.Conclusion: We determined thinner CCT and RNFL values in patients with hypoparathyroidism related to serum calcium levels together with a significant deepness in ACD.

Tear electrolyte assessment of diabetic patients in Southern Nigeria

Background

Tears are a critical body extracellular fluid coating the surface epithelial cells of the cornea and conjunctiva, and providing the optically smooth surface necessary for refraction of light onto the retina. The biological and chemical properties of tears change in response to systemic disease.

Objectives

This study assessed the concentration of calcium, magnesium and phosphate levels in tears of diabetics.

Methods

A comparative cross-sectional study involving twenty diabetics visiting Department for Health Services, University of Benin and forty non-diabetics within the University between 35 to 65 years participated in the study. Calcium, magnesium and phosphorous were analysed in tears sample collected with 75mm glass capillary tubes.

Results

The fasting blood sugar (FBS) and age of diabetic patients was 7.48±1.88mmol/l and 56.75±5.82years and non-diabetics was 4.83±0.52mmol/l and 53.58±6.16years respectively. Magnesium showed no differences (P<0.05) between diabetics (0.76±0.45mmol/l) and non-diabetics (0.93±0.59mmol/l). Calcium was elevated (P=0.041) and phosphate (P=0.044) was decreased in diabetics (3.14±1.65mmol/l and 0.074±0.058mmol/l) than non-diabetics (2.41±1.05mmol/l and 0.11±0.081mmol/l).

Conclusion

This study concluded that being diabetic can affect the levels of some tear electrolytes in the tear fluid which may lead to an increased risk of diabetic ocular complications.

Importance of tear film instability in dry eye disease in office workers using visual display terminals: the Osaka study

PURPOSE

To evaluate the relationship between subjective symptoms and clinical signs in dry eye disease (DED) in office workers using visual display terminals (VDTs).

DESIGN

Cross-sectional study.

METHODS

This study involved 672 Japanese young and middle-aged office workers who use VDTs. The subjects completed questionnaires designed to detect subjective symptoms and risk factors for DED. Dry eye tests, including tear film break-up time (TBUT), corneal-conjunctival staining with fluorescein and lissamine green, and the Schirmer test, were performed. Based on the Japanese diagnostic criteria for DED, the subjects were classified into 3 groups: definite DED, probable DED, and non-DED. Between each group, subjective symptoms and clinical signs were compared.

RESULTS

Of the 672 subjects, 561 (374 male, 187 female) completed the questionnaire (response rate: 83.5%). Definite DED was diagnosed in 65 subjects (11.6%), probable DED in 303 subjects (54.0%), and non-DED in 193 subjects (34.4%). The mean subjective symptom score was significantly less in subjects with probable DED (2.05 ± 0.42) and non-DED (1.63 ± 0.38) than in those with definite DED (2.19 ± 0.40) (P < .05 and P < .01, respectively). In the subjects with probable DED, a subgroup with positive subjective symptoms and abnormal TBUT (≤5 seconds) was categorized as short TBUT-type DED, and it was found that they had a higher subjective symptom score (2.09 ± 0.40), equivalent to that of those with definite DED (P = .269).

CONCLUSIONS

Despite no or minor epithelial damage, the severity of subjective symptoms was greater in short TBUT-type DED, most likely attributable to tear film instability. Thus, it might prove important to evaluate TBUT to successfully treat those patients.

Hyperosmolar tears enhance cooling sensitivity of the corneal nerves in rats: possible neural basis for cold-induced dry eye pain

PURPOSE

Tear hyperosmolarity is a ubiquitous feature of dry-eye disease. Although dry-eye patients' sensitivity to cooling is well known, the effects of tear hyperosmolarity on a small amount of cooling in the corneal nerves have not been quantitatively examined. Recently reported corneal afferents, high-threshold cold sensitive plus dry-sensitive (HT-CS + DS) neurons, in rats is normally excited by strong (>4°C) cooling of the cornea, which, when applied to healthy humans, evokes the sensation of discomfort. However, corneal cooling measured between blinks does not exceed 2°C normally. Thus, we sought to determine if these nociceptors could be sensitized by hyperosmolar tears such that they are now activated by small cooling of the ocular surface.

METHODS

Trigeminal ganglion neurons innervating the cornea were extracellularly recorded in isoflurane-anesthetized rats. The responses of single corneal neurons to cooling stimuli presented in the presence of hyperosmolar (350-800 mOsm NaCl) tears were examined.

RESULTS

The HT-CS + DS neurons with thresholds averaging 4°C cooling responded to cooling stimuli presented after 15 minutes of hyperosmolar tears with thresholds of less than 1°C. The response magnitudes also were enhanced so that the responses to small (2°C) cooling emerged, where none was observed before.

CONCLUSIONS

These results demonstrate that after exposure to hyperosmolar tears, these nociceptive corneal neurons now begin to respond to the slight cooling normally encountered between blinks, enabling the painful information to be carried to the brain, which could explain the cooling-evoked discomfort in dry eye patients.

Substituted E-3-(3-indolylmethylene)1,3-dihydroindol-2-ones with antiproliferative activity. Study of the effects on HL-60 leukemia cells

The synthesis of new substituted E-3-(3-indolylmethylene)1,3-dihydroindol-2-ones is reported. The antiproliferative activity was evaluated according to protocols available at the National Cancer Institute (NCI), Bethesda, MD. The action of the most active compound 10 was further investigated in HL-60 leukemia cells. Results obtained show that it causes a block in cell cycle progression, with cell arrest in the G2/M phase, associated with activation of apoptosis accompanied with increased oxidative stress and deregulation of the homeostasis of divalent cations, with significant increase in the cellular concentrations of free Ca(2+) and Mg(2+).