Cellular cytotoxicity of antiglaucoma drugs in cultured corneal endothelial cells

Different concentrations of betaxolol switch cell fate between necroptosis, apoptosis, and senescence in human corneal stromal cells

Betaxolol is commonly used to manage glaucoma in clinical practice. However, its long-term use may damage the cornea. Thus, the cytotoxicity and mechanisms of betaxolol in human corneal stromal cells (HCSCs) warrant further study. In this study, we used in vitro HCSCs and in vivo rabbit corneal models to investigate betaxolol cytotoxic effects and mechanism of action. At near-clinical concentrations (0.28% and 0.14%), betaxolol inhibited caspase-8 activity, activated receptor-interacting protein kinase (RIPK)1, RIPK3, and mixed-spectrum kinase-like domain (MLKL), and phosphorylated MLKL to induce necroptosis in HCSCs. Similarly, moderate concentrations of betaxolol (0.07%-0.0175%) activated caspase-8 to trigger the exogenous apoptotic pathway. Through the intrinsic apoptotic pathway, betaxolol upregulated the expression of Bcl-2 family apoptotic proteins Bax and Bad and downregulated that of anti-apoptotic proteins Bcl-2 and Bcl-xL. This subsequently disrupted the mitochondrial membrane potential and cytoplasmic transfer of cytochrome c and apoptosis-inducing factor, activated caspase-9, and induced apoptosis in HCSCs. Furthermore, continuous treatment with low betaxolol concentrations (0.00875%) for three generations of HCSCs prevented apoptosis by promoting the expression of Bcl-xL and suppressing that of Bax. However, its toxic effects initiated cellular senescence by increasing reactive oxygen species, leading to the disruption of energy metabolism and DNA damage. Finally, clinical concentrations of betaxolol had a pro-apoptotic effect on rabbit corneal stromal cells in vivo. These results suggest that betaxolol induces cytotoxicity in a concentration-dependent manner in HCSCs, and that caspase-8 and Bcl-2 family proteins may be critical switches in the conversion of different HCSC death mechanisms.

The Multifarious Effects of Various Glaucoma Pharmacotherapy on Corneal Endothelium: A Narrative Review

Corneal endothelium is a single cell layer that is mainly responsible for maintaining corneal clarity. Endothelial damage secondary to toxicity, stress, or genetic predisposition are common and in conjunction with the low regenerative ability of the cells, making their preservation critical for maintaining visual acuity. Patients with glaucoma, who are estimated to be close to 80 million worldwide, have a plethora of reasons for developing endothelial damage, being exposed to a spectrum that extends from various medical and surgical interventions to the disease itself. The wide spectrum of glaucoma pharmacotherapy that has been recently extended by addition of newer classes of medications has been the focus of extensive research on its effects on corneal endothelium. Both basic and clinical research have attempted to shine a light on the complex mechanisms associated with the effects of glaucoma medication on corneal endothelium and to answer the important question as to whether these findings are clinically significant. The aim of this review is to summarize and present current literature of the various findings, both from in vivo and in vitro studies that have focused on the complex relationship between different classes of glaucoma medication and their effect on corneal endothelium.

Cytotoxic, Apoptotic, and Oxidative Effects of Preserved and Preservative-Free Brimonidine in a Corneal Epithelial Cell Line

Purpose: This study aims to compare the cytotoxic, apoptotic, and oxidative effects of preserved and preservative-free forms of brimonidine 0.15% on the human corneal epithelial cell (HCEC) line. Methods: Time-dependent cytotoxicity studies were performed with the Alamar Blue method. For apoptotic studies, PE Annexin V and 7-amino-actinomycin (7-AAD) staining and flow cytometry were performed. Messenger RNA (mRNA) expressions of Bax, Bcl-2, and caspase-3, -9, -12, and protein expressions of Bax and Bcl-2 were evaluated by quantitative real-time polymerase chain reaction and Western blot method, respectively. Results: Cell viability was 76.4% with the preserved solution and 36.05% with the preservative-free solution at the fifth minute. No significant difference was observed with either solution at the 15-min mark, whereas cell viability did not change significantly after 1 h. In the apoptosis evaluation, it was observed that the preservative-free solution increased the early apoptotic activity to a greater degree (P < 0.05). Preservative-free solution also induced gene expression of proapoptotic Bax, caspase-9 and -12, and protein expression of Bax while reducing the protein expression of anti-apoptotic Bcl-2 (P < 0.0001). Preserved solution induced only the gene expression of caspase-12, and reduced the protein expression of Bcl-2 (P < 0.0001). No significant difference was observed in the reactive oxygen species (ROS) levels of either solution compared with the control group (P > 0.05). Conclusion: It was demonstrated that the preserved solution is less cytotoxic to the HCEC line in the early period, has less early apoptotic activity, and does not significantly increase ROS levels.

Corneal Endothelial Cell Density in Normal Tension Glaucoma Compared to Healthy Controls

The purpose of this study was to investigate corneal endothelial cell density (ECD) and morphology between normal tension glaucoma (NTG) and controls. A cross-sectional, single center study of 24 NTG and 26 age-matched healthy eyes were included. ECD, mean cell size (MCA) and coefficient of variance (CV) were analyzed, controlling for age and number and duration of concurrent glaucoma medications. NTG subjects had significantly lower ECD (2307 ± 514.7 vs. 2558 ± 278.5, p = 0.044) and larger MCA (458.3 ± 94.8 vs. 386.7 ± 57.3, p = 0.004), but no difference in CV compared to healthy subjects. NTG subjects stratified by number of glaucoma medications showed significant differences in ECD (p = 0.024) and MCA (p = 0.021), but no difference in CV. There were no significant differences in ECD, MCA or CV between subjects stratified by duration of glaucoma medication usage. After age-adjusting, there was no dose-dependent relationship between mean ECD or MCA and number of glaucoma medications. Post hoc analysis demonstrated only NTG subjects on three or more glaucoma medications had statistically significant differences in ECD (p = 0.032) and MCA (p = 0.037) compared to NTG subjects on two glaucoma medications. This study suggests that NTG is associated with lower corneal endothelial cell density and mean cell size.

Factors affecting the corneal endothelium after selective laser trabeculoplasty in primary open angle and angle closure glaucoma

Purpose

To study the factors affecting the corneal endothelium after selective laser trabeculoplasty (SLT) in primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG).

Method

This prospective interventional study included 56 patients (56 eyes) with POAG and 55 patients (55 eyes) with PACG. All participants received a standard SLT session. Patients with PACG were pretreated with laser peripheral iridotomy for at least 2 months before SLT. Corneal endothelium cell count (ECC), pleomorphism and polymegathism were measured before SLT, as well as at the increments of 1 hour, 1 day, 1 week, 1 month, 3 months and 6 months following SLT using confocal microscopy. A multiple regression analysis was applied to detect the factors affecting the ECC in the long-term post-SLT period.

Results

In both groups, the mean ECC significantly decreased from the baseline after SLT. While in POAG, corneal endothelium recovered within 1 month, in PACG, its damage persisted throughout the whole follow-up period.

According to the multiple analysis, baseline ECC (β=0.891, p=0.000 in POAG and β=0.706, p=0.000 in PACG) and age (β=−0.227, p=0.000 in POAG and β=−0.196, p=0.000 in PACG) were the common risk factors affecting ECC in both glaucoma forms, while the initial anterior chamber depth (β=0.254, p=0.000), only in PACG. The duration of glaucoma treatment (β=−0.317, p=0.043 in POAG and β=−0.302, p=0.047 in PACG) and pigmented deposits on the corneal endothelium in PACG (β=−0.326, p=0.019) were the risk factors determined in the univariate analysis.

Conclusion

Age and the baseline ECC are the risk factors for corneal endothelium damage after SLT in POAG and PACG. Shallow anterior chamber may affect corneal endothelium in PACG. These data should be considered when choosing an algorithm for glaucoma treatment.

Mid-Term Evaluation of iStent Inject® Trabecular Micro-Bypass Stent Implantation with or without Phacoemulsification: A Retrospective Study

Introduction

This study evaluated the 6-month performance and safety of micro-invasive glaucoma surgery (MIGS) with iStent inject either with or without cataract surgery.

Material and Methods

Longitudinal retrospective study of 86 surgeries in 49 patients with inadequately controlled open-angle glaucoma (OAG) or ocular hypertension who underwent iStent inject trabecular micro-bypass implantation either alone (isolated group) or combined with cataract surgery (combined group). The two primary outcomes included an intraocular pressure (IOP) drop of ≥20% versus preoperative values (adequate drop) and IOP maintenance between 6 and 18 mmHg (adequate Range). For both outcomes, we determined “complete” and “qualified” success if patients did not require or did require glaucoma medications, respectively, at the end of follow-up. Safety outcomes included best-corrected visual acuity, adverse events, and secondary surgeries.

Results

In the adequate drop analysis, 30.2% achieved “complete success,” and 37.2% achieved “qualified success.” For adequate range, 40.7% achieved “complete success” and 39.5% achieved “qualified success.” There was no difference in medication decrease (p=0.77) nor IOP reduction (p=0.46) between the isolated and combined groups. Safety was generally favorable and similar between groups, with mild transient adverse events that resulted in no sequelae.

Discussion/Conclusion

iStent inject implantation either with or without cataract surgery was able to safely decrease IOP and medication requirements through 6 months after surgery.

Corneal Parameters after Tube-Shunt Implantation through the Ciliary Sulcus

PURPOSE

To monitor bilateral corneal parameters after unilateral Baerveldt 350 tube-shunt implantation (Advanced Medical Optics, Santa Ana, CA) through the ciliary sulcus.

DESIGN

Retrospective, interventional case series.

PARTICIPANTS

Patients from 1 private glaucoma practice with severe uncontrolled glaucoma treated with sulcus tube-shunt implantation in 1 pseudophakic eye.

METHODS

Specular microscopy data were collected before and after unilateral sulcus tube-shunt implantation from the surgical and the glaucomatous fellow eyes.

MAIN OUTCOME MEASURES

Central corneal endothelial cell density (CECD), coefficient of variation (CV), percent of hexagonal cells, central corneal thickness (CCT), intraocular pressure (IOP), IOP-lowering medications, visual acuity, and complications.

RESULTS

Forty-six patients (mean age, 69.9 years; standard deviation [SD], 4.6 years; range, 20-88 years; male gender, 41.3%) were identified. After surgery, IOP and the number of IOP-lowering medications decreased significantly by 42.3% (P < 0.0001) and 32.1% (P < 0.0001), respectively, in the surgical eye group. Preoperative CECD measured 1807 cells/mm² (SD, 172 cells/mm²) and 1825 cells/mm² (SD, 172 cells/mm²) in the surgical and fellow eyes, respectively (P = 0.92), and compared with baseline, it decreased by 8.6% (P = 0.17) and 3.1% (P = 0.65), respectively, by 24 months. Preoperative CV, percent of hexagonal cells, and CCT were similar in both groups and remained stable. All corneal parameters remained unchanged in a subgroup of 15 patients with low preoperative CECD (1273 cells/mm²; SD, 99 cells/mm²). Best-corrected visual acuity remained stable in both groups. Hyphema occurred in 23.9% of the surgical eyes and resolved with no intervention. We found no sight-threatening complications or corneal failures during follow-up.

CONCLUSIONS

Tube-shunt implantation through the ciliary sulcus in pseudophakic eyes appears relatively safe to the corneal endothelium, demonstrating a small and nonsignificant decline in central CECD compared with baseline and with glaucomatous fellow eyes. No significant disruption to corneal endothelial cell morphologic features, increased corneal thickness, or corneal failures were found during the 24-month follow-up period. A prospective head-to-head comparison to assess the effects of the various methods of tube-shunt implantation on the corneal endothelium is needed.

Dose- and Time-Dependent Cytotoxicity of Carteolol in Corneal Endothelial Cells and the Underlying Mechanisms

Carteolol is a non-selective β-adrenoceptor antagonist used for the treatment of glaucoma, and its abuse might be cytotoxic to the cornea. However, its cytotoxicity and underlying mechanisms need to be elucidated. Herein, we used an in vivo model of feline corneas and an in vitro model of human corneal endothelial cells (HCECs), respectively. In vivo results displayed that 2% carteolol (clinical dosage) could induce monolayer density decline and breaking away of feline corneal endothelial (FCE) cells. An in vitro model of HCECs that were treated dose-dependently (0.015625–2%) with carteolol for 2–28 h, resulted in morphological abnormalities, declining in cell viability and elevating plasma membrane (PM) permeability in a dose- and time- dependent manner. High-dose (0.5–2%) carteolol treatment induced necrotic characteristics with uneven distribution of chromatin, marginalization and dispersed DNA degradation, inactivated caspase-2/-8, and increased RIPK1, RIPK3, MLKL, and pMLKL expression. The results suggested that high-dose carteolol could induce necroptosis via the RIPK/MLKL pathway. While low-dose (0.015625–0.25%) carteolol induced apoptotic characteristics with chromatin condensation, typical intranucleosomal DNA laddering patterns, G₁ cell-cycle arrest, phosphatidylserine (PS) externalization, and apoptotic body formation in HCECs. Meanwhile, 0.25% carteolol treatment resulted in activated caspase-2, -3, -8, and -9, downregulation of Bcl-2 and Bcl-xL, upregulation of Bax and Bad, ΔΨm disruption, and release of cytoplasmic cytochrome c (Cyt.c) and AIF into the cytoplasm. These observations suggested that low-dose carteolol could induce apoptosis via a caspase activated and mitochondrial-dependent pathway. These results suggested that carteolol should be used carefully, as low as 0.015625% cartelol caused apoptotic cell death in HCECs in vitro.

Glaucoma-associated corneal endothelial cell damage: A review

The corneal endothelium is critical in maintaining a healthy and clear cornea. Corneal endothelial cells have a significant reserve function, but preservation of these cells is paramount as they have limited regenerative capacity. Glaucoma is a prevalent disease, and damage to the corneal endothelium may be caused by the disease process itself as well as by its treatment. The mechanisms involved in glaucoma-associated damage to the corneal endothelium need further investigation. Understanding how glaucoma and glaucoma surgery impact the endothelium is important for protecting corneal clarity and visual acuity in all glaucoma patients, including those undergoing corneal transplant. We will discuss a range of identified factors that may impact corneal endothelial cell health in glaucoma, including intraocular pressure, glaucoma medications, surgical glaucoma management, mechanical forces, and alterations in the aqueous environment.

Effects of Brinzolamide, a Topical Carbonic Anhydrase Inhibitor, on Corneal Endothelial Cells

INTRODUCTION

This clinical study aimed to investigate the effect of brinzolamide, a topical carbonic anhydrase inhibitor, on corneal endothelial cells (CECs) in patients with glaucoma using a follow-up clinical study design.

METHODS

Patients with primary open-angle glaucoma or ocular hypertension were administrated an ophthalmic solution of either latanoprost alone (LT) as a control (n = 18) or latanoprost plus brinzolamide (LT + BR; n = 16). CECs were examined at baseline and at 4, 12, 24, and 48 weeks in 18 and 16 eyes of the LT and LT + BR groups, respectively, using a non-contact specular microscope. CECs were evaluated by parameters, including cell density (CD), coefficient of variation (CV) in cell size, and percentage hexagonality (Hex).

RESULTS

Compared with the baseline intraocular pressure (IOP), the mean IOP in the LT group was significantly reduced at 12 and 24 weeks, whereas that in the LT + BR group was significantly reduced at all time points (P < 0.01). The mean CD, CV, and Hex at baseline were not significantly different between the two groups. No significant time-course changes in CD, CV, or Hex were observed in either group. At 48 weeks, there was no significant difference in the mean CD, CV, or Hex between the two groups.

CONCLUSION

Patients treated with LT + BR showed significant IOP reduction. However, the use of brinzolamide in addition to latanoprost had no influence on CECs during the one-year follow-up period.

Short-term effect of topical brinzolamide 1%-timolol 0.5% fixed combination on human central corneal thickness

PURPOSE

To evaluate the short-term effect of fixed combination of brinzolamide 1% and timolol 0.5% (FCBT) application on human central corneal thickness (CCT).

METHODS

This prospective clinical study included 97 patients having Nd:YAG laser posterior capsulotomy for posterior capsule opacification. Patients were randomized to receive apraclonidine hydrochloride 0.5% (APRA) (n=48) or FCBT (n=49) at 1 h before laser surgery. The baseline CCT was evaluated by ultrasonographic pachymetry from the central region ∼1 h before the laser procedure. CCT measurements were applied just before the laser application and then the first, second, and third hour, and the first, third, and seventh day after the Nd:YAG laser capsulotomy.

RESULTS

There was no statistically significant difference between the baseline intraocular pressures, CCTs, and demographic and clinical data (age, sex, surgery laser interval, total laser energy) of the APRA and the FCBT groups. The mean CCT values of the APRA group at the first, second, and third hour, and the first, third, and seventh day were 553.8±28.0, 551.4±35.3, 556.8±28.7, 552.6±27.5, 548.2±26.2, and 546.2±25.5 μm, respectively. The mean CCT values of the FCBT group at the first, second, and third hour, and the first, third, and seventh day were 544.21±34.4, 549.4±27.6, 555.94±33.1, 550.8±33.4, 547.2±33.6, and 544.9±33.4 μm, respectively. No statistically significant difference was detected between the 2 groups.

CONCLUSION

The difference in CCT increase between both groups was not statistically significant at any follow-up visits. FCBT application does not have a short-term effect on CCT.

Cytotoxic effects of betaxolol on healthy corneal endothelial cells both in vitro and in vivo

AIM

To demonstrate the cytotoxic effect of betaxolol and its underlying mechanism on human corneal endothelial cells (HCE cells) in vitro and cat corneal endothelial cells (CCE cells) in vivo, providing experimental basis for safety anti-glaucoma drug usage in clinic of ophthalmology.

METHODS

In vivo and in vitro experiments were conducted to explore whether and how betaxolol participates in corneal endothelial cell injury. The in vitro morphology, growth status, plasma membrane permeability, DNA fragmentation, and ultrastructure of HCE cells treated with 0.021875-0.28g/L betaxolol were examined by light microscope, 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay, acridine orange (AO)/ethidium bromide (EB) double-fluorescent staining, DNA agarose gel electrophoresis, and transmission electron microscope (TEM). The in vivo density, morphology, and ultrastructure of CCE cells, corneal thickness, and eye pressure of cat eyes treated with 0.28g/L betaxolol were investigated by specular microscopy, applanation tonometer, alizarin red staining, scanning electron microscope (SEM), and TEM.

RESULTS

Exposure to betaxolol at doses from 0.0875g/L to 2.8g/L induced morphological and ultrastructural changes of in vitro cultured HCE cells such as cytoplasmic vacuolation, cellular shrinkage, structural disorganization, chromatin condensation, and apoptotic body appearance. Simultaneously, betaxolol elevated plasma membrane permeability and induced DNA fragmentation of these cells in a dose-dependent manner in AO/EB staining. Furthermore, betaxolol at a dose of 2.8g/L also induced decrease of density of CCE cells in vivo, and non-hexagonal and shrunk apoptotic cells were also found in betaxolol-treated cat corneal endothelia.

CONCLUSION

Betaxolol has significant cytotoxicity on HCE cells in vitro by inducing apoptosis of these cells, and induced apoptosis of CCE cells in vivo as well. The findings help provide new insight into the apoptosis-inducing effect of anti-glaucoma drugs in eye clinic.

Apoptosis in the iris and trabecular meshwork of medically treated and untreated primary open angle glaucoma patients

AIM

To compare the trabecular meshwork (TM) and iris apoptosis of treated and untreated primary open angle glaucoma (POAG) patients.

METHODS

Eight treatment-naive, newly diagnosed (group 1) and 11 medicaly treated (group 2) patients with POAG were included in the study. Each patient underwent a limbus-based trabeculectomy. The TM and peripheral iris specimens were dissected out and were snap-frozen in liquid nitrogen and stored at -80°C until they were assayed. Apoptosis in each group was assesed by TUNEL method.

RESULTS

The mean patient age was 60.6±5.8 years (53-68 years) vs 58.9±8.9 years (47-70 years) in group 1 and group 2 (P=0.859). The mean treatment time in group 2 was 22.2±7.3 months (12-34 months). Apoptotic indexes in TM and iris were significantly higher in POAG patients using medication (group 2) compared to treatment-naive POAG patients (group 1) (P=0.004, 0.015; respectively).

CONCLUSION

Long term administration of topical antiglaucoma medications causes additional toxic effects on TM.

Preservative use in topical glaucoma medications

Benzalkonium chloride (BAK) is the principal preservative employed in topical ocular hypotensive medications, although alternative compounds recently have begun to be employed or examined. Individual clinical trials have shown that exposure to BAK concentrations contained in ophthalmic solutions does not produce adverse sequelae in the majority of glaucoma patients, but concerns continue with regard to its long-term use. These concerns have resulted from an extensive research effort, including preclinical studies with in vitro and in vivo models, as well as recent clinical investigations dedicated specifically to this issue. The aim of this systematic literature review of both preclinical and clinical data was to determine the relevance of these findings to clinical practice. Most preclinical studies reported negative effects of BAK exposure, but with few exceptions, BAK concentrations and exposure times greatly exceeded those likely to be experienced by patients, given the normal physiological dilution by the tear film. In addition, consistent evidence of BAK-related toxicity did not emerge from our review of dedicated clinical investigations. Thus, taken together, current evidence supports the safety of BAK for most glaucoma patients, although subpopulations with abnormal tearing may benefit from alternative preservative compounds or preservative-free formulations. Further studies to identify these populations are needed.

Changes in corneal parameters at confocal microscopy in treated glaucoma patients

Background:

The purpose of this study was to evaluate corneal parameters in treated glaucoma patients, nontreated glaucoma patients, and normal subjects using confocal microscopy.

Methods:

Forty patients with primary open-angle glaucoma and 22 untreated controls underwent confocal microscopy of the cornea using the Heidelberg retinal tomograph cornea module. The glaucoma group was divided into two subgroups, ie, patients on medical treatment for at least two years before inclusion (with beta-blockers or prostaglandin analogs) and nontreated glaucoma patients. The following corneal parameters were evaluated: endothelial cell density and number, reflectivity, and tortuosity of sub-basal nerves. For reflectivity and tortuosity, a dedicated grading scale ranging from 0 to 4 was used. Differences between treatments were also evaluated in the treated glaucoma group.

Results:

Number of fibers and reflectivity of the sub-basal plexus were significantly lower in glaucoma patients as compared with controls (2.5 ± 0.7 versus 2.9 ± 0.9, P = 0.006, and 2.3 ± 0.8 versus 2.7 ± 0.9, P = 0.04, respectively), whereas tortuosity was significantly higher (2.6 ± 1 versus 2.0 ± 0.8, P = 0.007). Endothelial cell density (measured as cells per mm²) was lower in the glaucoma group comparing treated patients with nontreated patients (2826 ± 285 versus 3124 ± 272, P = 0.0003). Comparing treated patients with nontreated patients, relevant differences were found in number (2.3 ± 0.7 versus 2.8 ± 0.8, P = 0.004), tortuosity (2.8 ± 1 versus 2.2 ± 0.8, P = 0.004), and reflectivity (2.2 ± 0.8 versus 2.6 ± 0.8, P = 0.04). No differences in corneal parameters were found between beta-blockers and prostaglandin analogs.

Conclusion:

This study shows that differences in corneal parameters between glaucoma patients and controls may be due to the medical treatments used for glaucoma. These data should be taken into consideration in long-standing medical glaucoma treatment and in potential candidates for surgery.

Short-term effect of topical brimonidine tartrate on intrastromal corneal pressure in rabbits

PURPOSE

Because topical brimonidine tartrate has been reported to decrease flap adherence in the early postoperative period after LASIK, its effect on the intrastromal corneal pressure (ICP) was evaluated.

METHODS

An interventional, prospective, animal study was performed. Intrastromal corneal pressure was recorded for 45 minutes in eight eyes of rabbits treated with topical brimonidine tartrate three times daily for 3 consecutive days (study group); eight contralateral eyes were treated with artificial tears (control group). All measurements were performed by the same, masked investigator.

RESULTS

Mean ICP was -4.00 +/- 2.90 mmHg, -6.70 +/- 3.00 mmHg, and -9.00 +/- 4.50 mmHg at 15, 30, and 45 minutes, respectively, in the control group. In the study group (brimonidine-treated eyes), the ICP readings were +2.75 +/- 2.90 mmHg, -2.50 +/- 13.00 mmHg, and -8.50 +/- 5.00 mmHg at the same time points, respectively. The differences in the ICP between both groups were statistically significant at 15 minutes (P = .01), but no significant difference was found at 30 or 45 minutes (P = .20 and P = .80, respectively).

CONCLUSIONS

Topical treatment with brimonidine tartrate induces a significant decrease in ICP at 15 minutes. This effect on ICP may explain the decreased corneal flap adherence reported in eyes treated with this drug.

Effects of benzalkonium chloride- and polyquad-preserved combination glaucoma medications on cultured human ocular surface cells

INTRODUCTION

The aim of this study is to investigate potential adverse effects of fixed combination glaucoma medications preserved with either benzalkonium chloride (BAK) or Polyquad® (PQ; Alcon Research Ltd., Fort Worth, TX, USA) on cultured ocular epithelial cells.

METHODS

Confluent cultures of human cornea and conjunctival cell lines were exposed for 25 minutes to different glaucoma medications as well as a range of concentrations of BAK (0.001%-0.050%). Balanced salt solution was used as the "live" control and a solution containing 70% methanol and 0.2% saponin was used as a "dead" control. The number of dead and live cells were determined via ethidium homodimer (Eth-1) and calcein acetoxymethyl ester (AM) fluorescence, respectively.

RESULTS

The toxicity of the prostaglandin analog with beta-blocker timolol fixed-combination formulations preserved with BAK was different from that observed in the respective BAK concentrations. Travoprost plus timolol fixed combination with BAK performed better than its respective BAK concentration alone, while the latanoprost plus timolol fixed combination performed worse than its respective BAK concentration. Travoprost plus timolol fixed combination preserved with PQ had greater corneal and conjunctival cell survival than either the travoprost plus timolol fixed combination preserved with BAK or the latanoprost plus timolol fixed combination.

CONCLUSION

Ocular surface side effects have previously been demonstrated with chronic, long-term exposure to intraocular-pressure-lowering medications containing the common preservative BAK. BAK alone has significant in-vitro cytotoxicity to cultured ocular epithelial cells. Substitution of BAK with PQ resulted in significantly higher percentages of live conjunctival and corneal cells. Further studies are needed to understand the clinical implications of these findings.

Cytometric assessment of cytostatic and cytotoxic effects of topical glaucoma medications on human epithelial corneal line cells

BACKGROUND

The long-term-treatment of glaucoma with topical medications is associated with side effects involving cornea damage. We examined the effect of glaucoma topical medications (bimatoprost, travoprost, latanoprost, timolol, betaxolol, dorzolamide, brinzolamide, brimonidine) on growth of cells of three human epithelial corneal lines.

METHODS

The cells were cultured in 8-chamber slides, treated with different concentrations of the medications, and fixed at 24, 48, and 72 h. Cell number on slides to estimate viability and growth curves, frequency of apoptosis (FLICA and caspase-3 activation probes), and proliferation (BrdU incorporation assay) were measured by laser scanning cytometry (LSC).

RESULTS

Depending on concentration all examined medications induced cell necrosis or apoptosis and suppressed proliferation. Significant variability in proliferation and apoptosis was observed within the same cultures depending on local cell density, with cells in high density areas being more resistant. The data indicate that commonly used topical medications exert cytostatic and cytotoxic effects in cultures of corneal cells and suggest that caution should be exercised in their use, particularly, when the corneal diseases are accompanied by cell proliferation and regeneration, in long-term-treatment.

CONCLUSIONS

The present approach of using LSC makes it possible to assess and compare cytostatic and cytotoxic effects of different topical medications on the respective target cells.

Effects of benzalkonium chloride-preserved, polyquad-preserved, and sofZia-preserved topical glaucoma medications on human ocular epithelial cells

INTRODUCTION|: To investigate potentially adverse effects of different topical glaucoma medications and preservatives on cultured ocular epithelial cells. METHODS|: Confluent cultures of human corneal (10.014 pRSV-T) and conjunctival cells (1-5c-4) were assayed with 100 μL of different glaucoma medications for 25 minutes at 37°C and 5% CO₂. We also tested the preservative sofZia® (Alcon Laboratories, Fort Worth, TX, USA), as well as a range of concentrations of the preservative benzalkonium chloride (BAK; 0.001% to 0.050%). Balanced salt solution was used as the "live" control and a solution containing 70% methanol and 0.2% saponin was used as a "dead" control. The LIVE/DEAD viability/cytotoxicity kit (Invitrogen, Carlsbad, CA, USA) was used to determine the percentage of dead and live cells via ethidium homodimer and calcein fluorescence, respectively. RESULTS|: The toxicity of the prostaglandin analogs latanoprost, tafluprost and travoprost preserved with BAK was similar to the toxicity observed in their respective BAK concentrations. The prostaglandin analog travoprost (0.004%) preserved with the oxidizing preservative sofZia had much greater corneal and conjunctival cell survival than travoprost preserved with BAK. Travoprost (0.004%) containing polyquad also performed statistically better than its BAK-preserved formulation. CONCLUSION|: Ocular surface side effects have previously been demonstrated with chronic, long-term exposure to intraocular pressure-lowering medications containing the common preservative BAK. BAK alone has significant in-vitro cytotoxicity to cultured ocular epithelial cells. Substitution of BAK with polyquad or sofZia resulted in significantly higher percentages of live conjunctival and corneal cells. Further studies are needed to understand the- clinical implications of these findings.

The effects of combination glaucoma medications on ocular surface epithelial cells

INTRODUCTION

The purpose of this study was to determine the effects of two commercially available combination topical ophthalmic medications on human ocular surface cells in vitro.

METHODS

Tissue culture plates (96-well) containing immortalized human corneal and conjunctival epithelial cells were divided into five groups. The test solutions examined were: timolol 0.5%+brimonidine 0.2%, containing 0.0050% benzalkonium chloride (BAK); timolol 0.5%+dorzolamide 2%, containing 0.0075% BAK; and preservative-free artificial tears. Balanced salt solution (BSS) was used as the live control, and a fixative solution containing 70% methanol and 0.2% saponin was used as the dead control. Cells were exposed to 100 microL of test or control solution for 25 minutes at 37 degrees C and 5% carbon dioxide (CO(2)). A live cell assay was used to measure the toxicity of combination treatments compared with BSS controls.

RESULTS

Exposure to timolol 0.5%+brimonidine 0.2% resulted in a significantly higher percentage of living conjunctival cells (48%+/-12%) as compared with timolol 0.5%+dorzolamide 2% (10%+/-5%, P<0.00001). In corneal cells, testing revealed 12%+/-3% live cells after timolol 0.5%+brimonidine 0.2% exposure compared with 2%+/-3% after timolol 0.5%+dorzolamide 2% (P<0.001).

CONCLUSIONS

Both combination medications demonstrated a significant reduction in the percentage of live corneal and conjunctival epithelial cells compared with control. However, cell cultures exposed to timolol 0.5%+dorzolamide 2% had significantly fewer live cells compared with cell cultures exposed to timolol 0.5%+brimonidine 0.2%. Further studies are needed to better understand the clinical significance of these findings in patients using these medications for chronic treatment of glaucoma and ocular hypertension.