Toxicological evaluation of preservative-containing and preservative-free topical prostaglandin analogues on a three-dimensional-reconstituted corneal epithelium system

Excipients of preservative-free latanoprost induced inflammatory response and cytotoxicity in immortalized human HCE-2 corneal epithelial cells

Various preservative-free eye drop formulations for glaucoma treatment have been marketed intending to decrease ocular surface side effects and improve tolerability. However, preservative-free eye drops including different solubilizers to dissolve the antiglaucoma drugs may induce detrimental effects in the eye. In this study, we exposed human corneal epithelial cells (HCE-2) for 1, 6, 12, 24 and 48 hours to the first preservative-free (PF) tafluprost (Taflotan^®), the recently-launched preservative-free (PF) latanoprost (Monoprost^®), preservative benzalkonium chloride (BAK) and the excipient macrogolglycerol hydroxystearate 40 (MGHS40) using dilutions 0.1%, 0.3%, 1.0%, 3.0% and 10.0% of the original products. The cells also were exposed to undiluted PF tafluprost and PF latanoprost once a day for 9 days. Cellular morphology was examined by light microscopy and cell proliferation by Ki-67 fluorescent staining with cell viability being determined by erythrosine staining and the release of lactate dehydrogenase (LDH). Mitochondrial metabolic activity was evaluated with the colorimetric MTT assay. The secretion of interleukin 6 (IL-6) was measured with ELISA. HCE-2 cells displayed no significant morphological changes after PF tafluprost treatment, but PF latanoprost caused clear cell loss. Moreover, PF latanoprost, BAK and MGHS40 evoked cellular damage and inflammation with increasing concentrations and time. Furthermore, undiluted daily PF latanoprost application significantly increased LDH release and IL-6 secretion as compared to PF tafluprost. MGHS40 was observed to be associated with the toxicity of PF latanoprost. Excipients in ocular drops should receive more attention in the future, since they seem to trigger similar detrimental effects in cells as preservatives.

Identification of cornifelin and early growth response-1 gene as novel biomarkers for in vitro eye irritation using a 3D reconstructed human cornea model MCTT HCE™

Evaluation of the eye irritation is essential in the development of new cosmetic products. Draize rabbit eye irritation test has been widely used in which chemicals are directly applied to rabbit eye, and the symptoms and signs of eyes are scored. However, due to the invasive procedure, it causes substantial pain and discomfort to animals. Recently, we reported in vitro eye irritation test method using a 3D human corneal epithelial model (MCTT HCE™) which is reconstructed from remaining human tissues after a corneal transplantation. This model exhibited an excellent predictive capacity for 25 reference chemicals (sensitivity 100%, specificity 77% and accuracy 88% vs. GHS). To improve the test performance, we explored new biomarkers for the eye irritation through transcriptomic approach. Three surfactants were selected as model eye irritants that include sodium lauryl sulfate, benzalkonium chloride and triton X-100. After test chemicals were treated, we investigated differentially expressed genes through a whole-gene microarray (Affymetrix GeneChip(®) Human Gene 2.0 ST Array, 48,000 probes). As a result, we identified that mRNAs of cornifelin (CNFN), a constituent of the insoluble cornified cell envelope of stratified squamous epithelia, and early growth response-1 (EGR1), a nuclear transcriptional regulator, were significantly up-regulated by all three irritants. Up-regulation of CNFN and EGR1 was further confirmed by Q-RT-PCR, and immunohistochemistry revealed increased level of CNFN in irritant-treated tissues, supporting the relevance of CNFN and EGR1 as new biomarkers for eye irritation.

Comparison of the ocular surface changes following the use of two different prostaglandin F2α analogues containing benzalkonium chloride or polyquad in rabbit eyes

OBJECTIVE

The aim of this study is to compare the effect of prostaglandin analogues preserved with either 0.015% or 0.001% benzalkoium chloride (BAK); or 0.001% polyquad (PQ) on the ocular surface of rabbit eyes.

METHODS

Forty white rabbits were randomized to receive four-times daily instillation of either 0.0015% tafluprost (TF) preserved with 0.001% BAK (TF-BAK); 0.004% travoprost (TR) with 0.015% BAK (TR-BAK) or 0.001% PQ (TR-PQ); or preservative-free artificial tears in one eye for a 4-week period. Tear samples collected from the 40 rabbits were analyzed by enzyme-linked immunosorbent assays (ELISA) to identify the presence of inflammatory cytokines: interleukin (IL)-1β and IL-6 on day 14. Subsequently, harvested cornea and bulbar conjunctiva were evaluated using light and transmission electron microscopy (TEM).

RESULTS

IL-6 was significantly increased in TF-BAK and TR-BAK groups compared to controls and TR-PQ group (p = 0.005); however, IL-1β level was not significantly different among four groups (p = 0.360). Rabbits treated with TR-BAK showed decreased goblet cell density of bulbar conjunctiva and increased pyknotic change and vacuolization of corneal epithelial cells on light microscopy; similar change occurred but was less severe in TF-BAK group. The TR-PQ group showed similar results as the controls. The destruction of the microvillar architecture of bulbar conjunctiva and cornea was most prominent in the TR-BAK group.

CONCLUSIONS

Preservatives included in the anti-glaucoma eye-drops showed different ocular surface changes according to the concentration and type in the rabbits. Prostaglandin analogues preserved with higher level of BAK may cause more harmful effects on the ocular surface than PQ-preserved medications.

In vitro effects of preserved and unpreserved anti-allergic drugs on human corneal epithelial cells

PURPOSE

Treatment with topical eye drops for long-standing ocular diseases like allergy can induce detrimental side effects. The purpose of this study was to investigate in vitro cytotoxicity of commercially preserved and unpreserved anti-allergic eye drops on the viability and barrier function of monolayer and stratified human corneal-limbal epithelial cells.

METHODS

Cells were treated with unpreserved ketotifen solution, benzalkonium chloride (BAC)-containing anti-allergic drugs (ketotifen, olopatadine, levocabastine) as well as BAC alone. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to determine cell viability. Effects of compounds on barrier function were analyzed measuring transepithelial electrical resistance (TEER) to determine paracellular permeability and rose bengal assays to evaluate transcellular barrier formation.

RESULTS

The BAC-preserved anti-allergic formulations and BAC alone significantly reduced cell viability, monolayer cultures being more sensitive to damage by these solutions. Unpreserved ketotifen induced the least diminution in cell viability. The extent of decrease of cell viability was clearly dependent of BAC presence, but it was also affected by the different types of drugs when the concentration of BAC was low and the short time of exposure. Treatment with BAC-containing anti-allergic drugs and BAC alone resulted in increased paracellular permeability and loss of transcellular barrier function as indicated by TEER measurement and rose bengal assays.

CONCLUSIONS

The presence of the preservative BAC in anti-allergic eye drop formulations contributes importantly to the cytotoxic effects induced by these compounds. Stratified cell cultures seem to be a more relevant model for toxicity evaluation induced on the ocular surface epithelia than monolayer cultures.

Development of a curved, stratified, in vitro model to assess ocular biocompatibility

PURPOSE

To further improve in vitro models of the cornea, this study focused on the creation of a three-dimensional, stratified, curved epithelium; and the subsequent characterization and evaluation of its suitability as a model for biocompatibility testing.

METHODS

Immortalized human corneal epithelial cells were grown to confluency on curved cellulose filters for seven days, and were then differentiated and stratified using an air-liquid interface for seven days before testing. Varying concentrations of a commercial ophthalmic solution containing benzalkonium chloride (BAK), a known cytotoxic agent, and two relevant ocular surfactants were tested on the model. A whole balafilcon A lens soaked in phosphate buffered saline (BA PBS) was also used to assess biocompatibility and verify the validity of the model. Viability assays as well as flow cytometry were performed on the cells to investigate changes in cell death and integrin expression.

RESULTS

The reconstructed curved corneal epithelium was composed of 3-5 layers of cells. Increasing concentrations of BAK showed dose-dependent decreased cell viability and increased integrin expression and cell death. No significant change in viability was observed in the presence of the surfactants. As expected, the BA PBS combination appeared to be very biocompatible with no adverse change in cell viability or integrin expression.

CONCLUSIONS

The stratified, curved, epithelial model proved to be sensitive to distinct changes in cytotoxicity and is suitable for continued assessment for biocompatibility testing of contact lenses. Our results showed that flow cytometry can provide a quantitative measure of the cell response to biomaterials or cytotoxic compounds for both the supernatant and adherent cell populations. As a specifically designed in vitro model of the corneal epithelium, this quantitative model for biocompatibility at the ocular surface may help improve our understanding of cell-material interactions and reduce the use of animal testing.

Corneal alterations induced by topical application of commercial latanoprost, travoprost and bimatoprost in rabbit

Prostaglandin (PG) analogs, including latanoprost, travoprost, and bimatoprost, are currently the most commonly used topical ocular hypotensive medications. The purpose of this study was to investigate the corneal alterations in rabbits following exposure to commercial solution of latanoprost, travoprost and bimatoprost. A total of 64 New Zealand albino rabbits were used and four groups of treatments were constituted. Commercial latanoprost, travoprost, bimatoprost or 0.02% benzalkonium chloride (BAK) was applied once daily to one eye each of rabbits for 30 days. The contralateral untreated eyes used as controls. Schirmer test, tear break-up time (BUT), rose Bengal and fluorescein staining were performed on days 5, 10, 20, and 30. Central corneal changes were analyzed by in vivo confocal microscopy, and the corneal barrier function was evaluated by measurement of corneal transepithelial electrical resistance on day 5. Whole mount corneas were analyzed by using fluorescence confocal microscopy for the presence of tight-junction (ZO-1, occludin) and adherens-junction (E-cadherin, β-catenin) proteins, actin cytoskeleton, proliferative marker Ki67 and cell apoptosis in the epithelium. Topical application of commercial PG analogs resulted in significant corneal epithelial and stromal defects while no significant changes in aqueous tear production, BUT, rose bengal and fluorescein staining scores on day 5. Commercial PG analogs induced dislocation of ZO-1 and occludin from their normal locus, disorganization of cortical actin cytoskeleton at the superficial layer, and disruption of epithelial barrier function. The eyes treated with 0.02% BAK and latanoprost exhibited significantly reduced Schirmer scores, BUT, and increased fluorescein staining scores on days 10 and 30, respectively. Topical application of commercial PG analogs can quickly impair the corneal epithelium and stroma without tear deficiency. Commercial PG analogs break down the barrier integrity of corneal epithelium, concomitant with the disruption of cell junction and actin cytoskeleton between superficial cells in the corneal epithelium in vivo.

Ocular surface cytotoxicity and safety evaluation of tafluprost, a recently developed anti-glaucoma prostaglandin analog

In vitro cytotoxicity of tafluprost, which is the most recently developed anti-glaucoma prostaglandin (PG) analog, in ocular surface cells is addressed in comparison with other PG analogs. Irrespective of cell lines and models, the cytotoxicity of anti-glaucoma PG eyedrops was primarily related to the concentration of benzalkonium chloride (BAK) contained in the eyedrops as a preservative. Accordingly, preservative-free tafluprost was apparently less cytotoxic than BAK-preserved PG analogs. Furthermore, our study for cytotoxicity assays on ocular cells, conducted by comprehensive investigations covering a variety of concentrations and treatment times, which is termed the cell viability score (CVS) system, demonstrated that 0.001% BAK-preserved tafluprost was not cytotoxic, and suggested that tafluprost may even reduce the cytotoxic effect of BAK. It has been reported that adverse reactions associated with tafluprost in healthy human volunteers and patients with glaucoma include conjunctival hyperemia, eyelid pigmentation, eyelash bristles, and deepening of upper eyelid sulcus. Nonetheless, most clinical studies have demonstrated that not only preservative-free tafluprost but also BAK-preserved tafluprost is well tolerated and safe in patients with glaucoma and ocular hypertension.

Changes in the morphological and functional patterns of the ocular surface in patients treated with prostaglandin analogues after the use of TSP 0.5%® preservative-free eyedrops: a prospective, multicenter study

AIM

To investigate and compare the effects of topical benzalkonium chloride-preserved prostaglandins (PGAs) on the ocular surface in patients with primary open-angle glaucoma before and after 3 months of treatment with additional 0.5% preservative-free tamarind seed polysaccharide single-dose eyedrops (TSP®, Oftagen, Pisa, Italy).

METHODS

This was a prospective, longitudinal, multicenter study. From 5 different Italian glaucoma centers, 10 glaucomatous patients were recruited in each center. All the patients were treated with a PGA with preservative for at least 1 year. Preservative-free artificial tears 3 times per day were prescribed. The participants were subjected to clinical and instrumental evaluation at baseline, after 1 month and after 3 months of treatment. All patients were examined with a digital corneal confocal laser scanning microscope (HRT II Rostock Cornea Module).

RESULTS

After 3 months of TSP 0.5% treatment, an improvement of some ocular signs and symptoms was found. The percentage of conjunctival hyperemia decreased from 67 to 13%. Schirmer's test and breakup time significantly changed from the baseline after 3 months. Confocal microscopy showed a significant increase in conjunctival goblet cells.

CONCLUSION

Artificial substitutes, in particular TSP 0.5%, might protect the ocular surface hence giving higher compliance, adherence and quality of life to the patients.

Ocular toxicity of benzalkonium chloride homologs compared with their mixtures

This study was performed to assess the in vivo ocular toxicity of benzalkonium chloride (BAK) homologs compared with commercially available BAK (BAK mixture) and to assess the ocular toxicity of BAK homolog after repeated ocular application. Rabbit eyes were examined by ophthalmology and scanning electron microscopy (SEM) after 10 applications of BAK homologs with C12 (C12-BAK) and C14 (C14-BAK) alkyl chain lengths and a BAK mixture at concentrations of 0.001% (w/v), 0.003% (w/v), 0.005% (w/v), 0.01% (w/v) and 0.03% (w/v). The ocular toxicity of C12-BAK to rabbit eyes was examined by ophthalmology and histopathology after repeated ocular application for 39 weeks. In addition, the antimicrobial activities of C12-BAK and C14-BAK against A. niger, S. aureus and P. aeruginosa were assessed. Ocular toxicity of C12-BAK was less than those of the BAK mixture and C14-BAK. No ocular toxicity was noted after ocular application of 0.01% C12-BAK to rabbits for 39 weeks. C12-BAK showed antimicrobial activities at a concentration of 0.003%. These results suggest that the use of C12-BAK to replace BAK mixture as a preservative in ophthalmic solutions should be considered in order to reduce the incidence of the corneal epithelial cell injury induced clinically by BAK.

[The effects of ocular hypotensive drugs on the cornea: an in vivo analysis with confocal microscopy]

PURPOSE

To evaluate the effects of anti-glaucoma treatments containing benzalconium chloride (BAC) on the human cornea.

METHODS

A prospective single masked cohort study was conducted on the 50 eyes of 50 patients. The inclusion criteria were: recently diagnosed glaucoma or ocular hypertension with previous treatment, or ophthalmologist-prescribed anti-glaucoma therapy, and oral consent to participate in the study. The patients were not randomised, as the ophthalmologist decided the best therapy according to clinical criteria. The patients were divided in 2 cohorts: one exposed to BAC (23 patients), and not exposed (27 patients). The mean follow-up period was 22 weeks (range 18-30). The change in cell density before and after therapy was measured in: basal layer epithelium, basal layer of limbal epithelium and endothelium. The change in stromal reflectivity and the number of nerve branches in sub-basal nerve plexus was also measured. BAC exposure was blinded to the main researcher.

RESULTS

A greater increase in basal layer epithelium cell density was observed in BAC exposed cohort (P<.05). No significant differences were detected in the endothelium, limbal cell density, stromal reflectivity, or sub-basal nerve plexus. Age, sex, IOP, active ingredient or BAC concentration did not affect the direction or magnitude of the ocular surface alterations found.

CONCLUSION

Chronic anti-glaucoma therapy induces changes in the corneal epithelium. Preservative free drops showed less disruption of the ocular surface by confocal microscopy analysis. Further studies should be conducted to evaluate the clinical impact of these histological findings.

Local toxicity of benzalkonium chloride in ophthalmic solutions following repeated applications

We performed repeated toxicity studies of benzalkonium chloride (BAK)-containing vehicles of ophthalmic solutions in monkeys and rabbits to assess the local toxicity of BAK after repeated applications on the ocular surface. Local toxicity of BAK was evaluated by toxicity studies in which a 0.01% BAK-containing vehicle was applied twice/day for 52 weeks, 4 times/day for 39 weeks, or 6 times/day for 13 weeks, or in which a 0.005% BAK-containing vehicle was applied 6 times/day for 52 weeks or twice/day for 4 weeks in monkeys. Local toxicity of BAK was also evaluated where a 0.01% BAK-containing vehicle was applied 6 times/day for 6 weeks, or a 0.005% BAK-containing vehicle was applied twice/day for 39 weeks or 8 times/day for 4 weeks in rabbits. These doses were chosen because BAK is generally used at concentrations up to 0.01% in ophthalmic solutions. The BAK-containing vehicle did not cause ophthalmological changes suggestive of irritation, allergy, or corneal damage. We also did not observe any histopathological changes in the eyeball, eyelid, lacrimal gland, and nasal cavity, with repeated applications of BAK for up to 52 weeks, up to 8 times/day, or at concentrations up to 0.01%, in monkeys and rabbits. Our results suggest that BAK in concentrations up to 0.01% in ophthalmic solution is non-toxic to the eyeball, its accessory organs, and the nasal cavity after long repeated applications.

Ocular pharmacokinetics of bimatoprost formulated in DuraSite compared to bimatoprost 0.03% ophthalmic solution in pigmented rabbit eyes

PURPOSE

To compare the aqueous humor (AH) and iris-ciliary body (ICB) concentration of bimatoprost in rabbit eyes treated with ISV-215 (0.03% bimatoprost formulated in DuraSite) with the marketed product bimatoprost 0.03% ophthalmic solution.

METHODS

The left eye of rabbits received a single topical instillation of either ISV-215 (n = 32 eyes) or bimatoprost 0.03% (n = 32 eyes). At predetermined time points, levels of bimatoprost and bimatoprost acid in the AH and the ICB were quantified by HPLC-MS/MS.

RESULTS

Both bimatoprost and bimatoprost acid were detected in the AH and the ICB within 15 minutes of dosing. Bimatoprost acid concentrations in both compartments were markedly higher than bimatoprost. There was a statistically significant (P < 0.01) increase in the concentration of the prodrug in the AH and its acid form in the ICB in animals treated with ISV-215 compared to bimatoprost 0.03%. In the ISV-215-treated rabbit eyes, the highest concentrations of bimatoprost and bimatoprost acid were in the ICB and AH, respectively, while in the bimatoprost 0.03%-treated eyes, no differences in the drug content of the selected ocular tissues were observed.

CONCLUSIONS

Bimatoprost 0.03% formulated in DuraSite has superior ocular distribution and area under the curve compared to bimatoprost 0.03% in rabbit eyes. This improvement in the pharmacokinetic parameters of ISV-215 may provide us with a better platform to optimize a bimatoprost formulation that offers the same degree of efficacy in lowering intraocular pressure and improved therapeutic index in glaucomatous patients by lessening the ocular side effects associated with long-term use of topical prostaglandin F2α analogs.

Aliphatic β-nitroalcohols for therapeutic corneoscleral cross-linking: corneal permeability considerations

PURPOSE

Our recent tissue cross-linking studies have raised the possibility of using aliphatic β-nitroalcohols (BNAs) for pharmacologic, therapeutic corneal cross-linking. The present study was performed to determine the permeability of BNAs and to explore the use of permeability-enhancing agents.

METHODS

Ex vivo rabbit corneas were mounted in a typical Franz diffusion chamber. BNA permeability was determined by assaying the recipient chamber over time using a modification of the Griess nitrite colorimetric assay. The apparent permeability coefficient (Ptot) was determined for 2 mono-nitroalcohols [2-nitroethanol (2ne) and 2-nitro-1-propanol (2nprop)], a nitrodiol [2-methyl-2-nitro-1,3-propanediol (MNPD)], and a nitrotriol [2-hydroxymethyl-2-nitro-1,3-propanediol (HNPD)]. Permeability-enhancing effects using benzalkonium chloride (BAC) (0.01% and 0.02%), ethylenediaminetetraacetic acid (0.05%), and a combination of 0.01% BAC + 0.5% tetracaine were also studied.

RESULTS

The Ptot (±SE) values (in centimeters per second) were as follows: 4.33 × 10 (±9.82 × 10) for 2ne [molecular weight (MW) = 91 Da], 9.34 × 10 (±2.16 × 10) for 2nprop (MW = 105 Da), 4.37 × 10 (±1.86 × 10) for MNPD (MW = 135 Da), and 8.95 × 10 (±1.93 × 10) for HNPD (MW = 151 Da). Using the nitrodiol, permeability increased approximately 2-fold using 0.01% BAC, 5-fold using 0.02% BAC, and 5-fold using the combination of 0.01% BAC + 0.5% tetracaine. No effect was observed using 0.05% ethylenediaminetetraacetic acid.

CONCLUSIONS

The results indicate that the corneal epithelium is permeable to BNAs, with the apparent permeability corresponding to MW. The findings are consistent with previous literature indicating that the small size of these compounds (<10Å) favors their passage through the corneal epithelium via the paracellular route. This information will help to guide dosing regimens for in vivo topical cross-linking studies.

Glaucoma therapy and ocular surface disease: current literature and recommendations

PURPOSE OF REVIEW

To provide an update on clinical and experimental literature for ocular surface effects of glaucoma therapy and to provide practical guidelines for ophthalmologists treating glaucoma patients with ocular surface disease (OSD).

RECENT FINDINGS

Preservatives, notably benzalkonium chloride (BAK), continue to contribute to OSD and demonstrate a variety of toxic ocular effects both in-vitro, and in animal/human studies. Recent literature frequently compares BAK with Polyquad, SofZia, and preservative-free therapies. Some clinical benefit has been demonstrated with newer BAK-free alternatives.

SUMMARY

BAK-free and preservative-free therapies are becoming available but are not always a feasible alternative. It is important to recognize different clinical manifestations of allergy and chronic inflammation and to discuss options for patients experiencing OSD.

Cell viability score (CVS) as a good indicator of critical concentration of benzalkonium chloride for toxicity in cultured ocular surface cell lines

Cytotoxicity of benzalkonium chloride (BAK) is a major factor affecting drug cytotoxicity. This study aimed to determine the critical concentration of BAK for cultured ocular cells, using SIRC (rabbit corneal epithelium), BCE C/D-1b (bovine corneal epithelial cells), RC-1 (rabbit corneal epithelium), and Chang (human conjunctival cells). Cell viability was determined following the exposure of cells to 11 concentrations of BAK for 10, 30, or 60 min using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and neutral red assays, and the cell viability score (CVS) was used to evaluate comprehensively the toxicity of BAK. The CVS system consists of two values. The CVS50 was determined by the number of measurements for viability ≥50% of control. The CVS40/80 was calculated as follows: CVS40/80=(number of measurements for viability values >80%)-(number of measurements for viability values <40%). Both %CVS50 and %CVS40/80 decreased with concentrations of BAK. When BAK concentrations were 0.01% or higher, %CVS50 and %CVS40/80 became 0 and less than -90, respectively. Meanwhile, when BAK concentrations were 0.001% or lower, %CVS50 became 100. In the case of %CVS40/80, when the BAK concentrations were 0.002% or lower, the values reached 75 or more, and when 0.0005% or lower, the %CVS40/80 value reached 100. Accordingly, BAK induced very low cytotoxicity in the cultured ocular cell lines at concentrations of 0.002% or lower. The concentration-dependency confirmed that the CVS score is useful for expressing drug cytotoxicity in a simple and comprehensive manner.

Cell viability score as an integrated indicator for cytotoxicity of benzalkonium chloride-containing antiglaucoma eyedrops

We evaluated the in vitro cytotoxicity of benzalkonium chloride (BAK)-containing antiglaucoma eyedrops. We prepared cell cultures of SIRC, BCE C/D-1b, RC-1, and Chang conjunctiva. The viability of cell cultures was determined using the MTT and neutral red assays. The cell viability score (CVS) was used to compare the toxicity of test solutions. %CVS50 and %CVS40/80 of each eyedrop solution were 71 and 26 for Lumigan(®) (0.002% bimatoprost with 0.005% BAK), 100 and 99 for Tapros(®) (0.0015% tafluprost, a new formula from 2010 with 0.001% BAK), 39 and -29 for 2% Trusopt(®) (2% dorzolamide with 0.0075% BAK), 28 and -43 for Xalacom(®) (latanoprost/0.5% timolol with 0.02% BAK), 88 and 66 for DuoTrav(®) (travoprost/0.5% timolol with no BAK), 36 and -35 for Cosopt(®) (2% dorzolamide/0.5% timolol with 0.0075% BAK) and 53 and -1 for Combigan(®) (0.15% brimonidin/0.5% timolol with 0.005% BAK). Only Xalacom(®) and Tapros(®) did not show an apparent decrease in %CVS as compared to the corresponding concentration of BAK. In conclusion, the cytotoxicity of tested eyedrops was dependent on BAK. Only the eyedrops containing latanoprost or tafluprost showed a reduction in the cytotoxicity of BAK.

Corneal epithelial cell viability following exposure to ophthalmic solutions containing preservatives and/or antihypertensive agents

INTRODUCTION

This in-vitro study compared the toxicity of bimatoprost 0.01% containing benzalkonium chloride (BAK) 0.02% with other commercial BAK-free or BAK-containing prostaglandin analogs.

METHODS

Six test solutions were evaluated: travoprost 0.004% with polyquaternium-1 0.001% (PQ), PQ, bimatoprost 0.01% with BAK 0.02%, latanoprost 0.005% with BAK 0.02%, tafluprost 0.0015% preservative free (PF), and BAK 0.02%. Phosphate-buffered saline (PBS) was the live control and 70% methanol was the dead control. Confluent human corneal epithelial cells were incubated with test solutions (diluted 1:5 or 1:10 with PBS) or control solutions for 10 or 25 min, after which cells were fluorescently labeled to distinguish live and dead cells. Data were expressed as a percentage of PBS live-cell fluorescence for automated readouts. Live and dead cells were manually counted for numeric analyses.

RESULTS

For 1:5 and 1:10 dilutions using automated readout, cells exposed to bimatoprost with BAK, latanoprost with BAK, and BAK alone demonstrated significant reductions in the live cell signal compared with PBS, travoprost with PQ, and PQ alone (all P < 0.001). They also demonstrated significantly greater toxicity than tafluprost PF for 1:5 dilutions (all P < 0.001) and 1:10 dilutions (P ≤ 0.02), except for 1:10-diluted bimatoprost with BAK (P = 0.41). For 1:5 dilutions using manual cell count, cells exposed to bimatoprost with BAK demonstrated significant reductions in the percentage of live cells compared with PBS (P = 0.02). For 1:10 dilutions using manual cell count, cells exposed to bimatoprost with BAK, latanoprost with BAK, and BAK alone demonstrated significantly greater toxicity than PBS, travoprost with PQ, PQ alone, and tafluprost PF (all P ≤ 0.03). No significant differences were observed among PBS, travoprost with PQ, and PQ alone under any test conditions (P ≤ 0.63).

CONCLUSION

This study demonstrated that BAKcontaining solutions, including bimatoprost 0.01% with BAK, were toxic to human corneal epithelial cells, whereas BAK-free solutions showed little to no evidence of toxicity.

Free radicals and the pH of topical glaucoma medications: a lifetime of ocular chemical injury?

INTRODUCTION

Preservatives in ophthalmic preparations are known to cause ocular surface damage. Excipients can also contribute to oxidative stress in the compromised ocular surface. We evaluated commonly used topical glaucoma medications to ascertain pH levels and the intrinsic presence of free radicals.

METHODS

Samples of 27 topical glaucoma preparations were analysed for total free radical presence using a Randox Kit for total antioxidant status. Analytical grade indicator paper was used to ascertain pH levels.

RESULTS

Free radical concentrations for these 27 glaucoma preparations ranged from 0 to 4.54 mmol/l, with a median value of 0.66 mmol/l (mean value of 0.662 mmol/l, SD 0.839). Levels of pH ranged from 4.0 to 7.4, with a median value of 6.5 (mean 6.252, SD 0.826). There was no evidence of a direct correlation between these two variables (r=0.232, P=0.275).

CONCLUSION

This study is the first to document the range of pH and concentrations of free radicals intrinsically present in commonly used glaucoma medications. Long-term exposure to preservatives, free radicals, and pH levels could all contribute to ocular surface damage. The effect of excipients could be responsible for patient intolerance when changing products in the compromised ocular surface.

Multiple endpoint analysis of BAC-preserved and unpreserved antiallergic eye drops on a 3D-reconstituted corneal epithelial model

PURPOSE

To compare the effects of benzalkonium chloride (BAC)-preserved and unpreserved antiallergic eye drops on the human 3D-reconstituted corneal epithelial model (3D-HCE).

METHODS

3D-HCE were treated for 24 h followed or not by a 24 h post-incubation recovery period (24 h+24 h) with phosphate-buffered saline (PBS), 0.01% BAC, unpreserved formulations of ketotifen, N Acetyl-Aspartyl Glutamic Acid (NAAGA), cromoglycate, or BAC-preserved commercial formulations of ketotifen, olopatadine, epinastine, and levocabastine. The 3D-HCE viability was evaluated using the 3-(4,5-Dimethylthiazol-2-yl) -2,5-Diphenyltetrazolium Bromide (MTT) test at 24 h and 24 h+24 h. At 24 h, the numbers of Cluster of Differentiation 54 (CD54)- and Ki67-immunopositive cells as well as the number of apoptotic deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells were evaluated on 3D-HCE frozen sections. The expression of the tight junction-associated protein occludin was also assessed using fluorescence confocal microscopy on flat-mounted 3D-HCE epithelia.

RESULTS

The MTT and the TUNEL tests revealed a significant decrease of cell viability and an increased apoptosis in the superficial layers of the 3D-HCE only when treated with BAC-containing formulations and in a BAC concentration-dependent manner. The expression of CD54 and Ki67 in the basal layers was also increased in this group. A concentration-dependent disorganization of occludin distribution in the epithelium treated with BAC-containing solutions was also observed. The unpreserved formulations induced effects comparable to the control.

CONCLUSIONS

BAC-preserved solutions decreased cell viability and induced apoptosis in a concentration-dependent manner. Moreover, they induced CD54 expression, proliferation in the basal layers, and changes in the distribution of occludin, which is consistent with a disorganization of the tight-junctions and suggests the loss of the epithelial barrier function. On the contrary, the unpreserved solutions did not impair cell structures and viability, suggesting a better tolerance for the ocular surface. As allergic patients often exhibit impaired and inflammatory ocular surface, BAC-free compounds should be the first choice when treating allergic conjunctivitis.