Comparison of the Anti-Inflammatory Effects of Artificial Tears in a Rat Model of Corneal Scraping

Review of clinical outcomes of a cationic emulsion tear substitute in patients with dry eye disease

First-line options for the treatment of dry eye disease (DED) rely on artificial tears (ATs), among which cationic emulsion (CE)-based ATs have been developed in order to mimic the healthy tear film for an improved restoration of the ocular surface homeostasis. In this review, we describe the outcomes reported in several studies, assessing the mode of action, ocular tolerance and clinical performance of a CE-based AT. Pilot studies have revealed that CE-based ATs can increase the volume and stability of the tear film while limiting its evaporation rate. Larger studies have demonstrated that CE-based ATs play a significant role in the improvement of both objective and subjective DED parameters, including superior efficacy on DED symptoms compared to several other available AT formulation types. Concomitantly, CE-based ATs have been shown to help patients to prevent or recover from corneal defects associated with refractive surgery. These positive outcomes on ocular surface epithelia are likely due to the combination of unique rheological behaviour and intrinsic anti-inflammatory properties. Based on all clinical findings, CE-based ATs represent a valuable treatment option for patients with various etiologies of DED including evaporative forms and would deserve evaluation of benefits in other surgical intervention types triggering DED.

Cationic nanoemulsion vs. 0.15% sodium hyaluronate artificial tears in the healing process following modern surface keratorefractive surgery

PURPOSE

The aim of this study was to investigate the influence of artificial tears containing either cationic nanoemulsion (CCN) or sodium hyaluronate artificial tears (SH) on early postoperative healing after modern surface refractive surgery.

MATERIALS AND METHODS

In this multicenter, prospective, double-masked, parallel-group (1:1), comparative study, 129 patients (n = 255 eyes) were randomized to receive CCN (n = 128) or SH (n = 127) as an adjuvant treatment after either transepithelial photorefractive keratectomy (transPRK) or Epi-Bowman keratectomy (EBK). The patients' perspectives were gathered using the Ocular Surface Disease Index (OSDI) questionnaire, and uncorrected (UCVA), and corrected (BCVA) visual acuity were assessed before and one week and one month after the procedure. In addition, corneal epithelization and subjective assessment of visual blur and eye irritation on drop instillation were assessed at one week postoperatively.

RESULTS

No statistically significant differences were found between two groups in age, spherical equivalent refractive error, UCVA, BCVA or OSDI scores before the procedure. There was also no difference between groups in UCVA one week and one month after the procedure. However, statistically significantly lower OSDI scores were found one week and one month after the procedure in the CCN group. Moreover, blurred vision after use of the eye drops was observed less frequently in the CCN group than in the SH group.

CONCLUSIONS

The CCN and SH groups had similar postoperative UCVA. However the significantly lower OSDI scores and less frequently blurred vision after application of the eye drops in the CCN group suggest better subjective outcomes in this group.

Use of a Cationic Emulsion of Latanoprost to Treat Glaucoma Patients with Ocular Surface Disease: A Preclinical Review

Prostaglandin analogue topical medications are one of the most effective therapeutic approaches for the chronic management of glaucoma and ocular hypertension, through the reduction of elevated intra ocular pressure (IOP). While many of the first generations of anti-glaucoma eye drops were preserved with benzalkonium chloride, their repeated use may induce chronic ocular surface toxicity that leads to ocular surface disease (OSD) signs and symptoms. As a result, soft-preservatives and preservative-free formulations have been developed with the goal to avoid the long-term iatrogenic toxicity of the preservative agents. In addition, it has been suggested that OSD and its associated inflammation may negatively impact the efficacy of the IOP-lowering medications, including treatment adherence and compliance. Hence, it may be particularly interesting that glaucoma medications can concomitantly protect and "heal" the ocular surface and its environment while lowering elevated IOP, for the greater benefit of glaucoma patients. The objective of the present review is to briefly present the preclinical data of the cationic oil-in-water emulsion of latanoprost (latanoprost-CE) to shed some light on its mechanisms of action. It overall supports the following hypothesis: the restoration of a healthy ocular surface environment and treatment of the OSD signs and symptoms will allow for an improved elevated IOP reduction and glaucoma management. This would be achieved with a once daily dosing regimen to preserve glaucoma patients' vision, ocular surface, and quality-of-life and wellness.

Resveratrol increases tear production and ocular pain after corneal abrasion in male, but not female, rats using a photorefractive keratectomy model

Photorefractive keratectomy (PRK) is an alternative to LASIK and can cause intense acute pain that is often not relieved by standard treatments. To assess potential therapeutics for this type of acute pain, appropriate preclinical models are needed. We describe a preclinical corneal abrasion rat model that simulates the initial stages of PRK surgery and demonstrates similar pain and tear dysfunction as seen clinically. We used both behavioral and homeostatic assays to determine the therapeutic potential of resveratrol on pain and tear production. Studies were conducted in male and female Sprague-Dawley rats. Heptanol was applied to one eye and the superficial corneal epithelium was removed, mimicking the abrasion used in PRK. Spontaneous pain was assessed with orbital tightening (OT) scores for 7 days. Topical resveratrol increased OT scores sex-specifically in abraded males, but not females, at 72 h and 1 week after abrasion. Resveratrol increased tear production in abraded males, with no effect in abraded females. There was no correlation between OT score at 1 week and tear production measurements, demonstrating no relationship between spontaneous ocular pain and tear dysfunction in this model. These findings demonstrate the usefulness of our corneal abrasion preclinical PRK model for the assessment of ocular pain therapeutics and indicate that topical resveratrol may not be useful for managing PRK-induced pain.

Development of a Novel In Vitro Immuno-Competent Model of Dry Eye Disease and Its Use to Evaluate the Efficacy of an Ocular Surface Modulator

PURPOSE

To develop an in vitro model of severe immunocompetent-dry eye disease (ic-DED) and to investigate the mechanism of action of a T-lysial ocular surface modulator.

MATERIALS AND METHODS

The reconstructed human corneal epithelium (HCE) was exposed to dryness stimuli. THP-1 cell infiltration into HCE was monitored at 4 h and 24 h from T-lysial application by immunohistochemistry (CD14, CD86, AQP3) and molecular biology (AQP3, TLR4 and TNF-α).

RESULTS

A reduction of CD14, CD86 and AQP3 was observed after T-lysial treatment at 24 h. TLR4 was overexpressed in ic-DED model and downregulated by T-Lysial after 24 h. TNF-α expression was not modified.

CONCLUSION

The ic-DED model can be used to monitor the migration and differentiation of THP-1 into HCE. T-lysial was found to exert anti-inflammatory activity. This experimental model is a promising tool to study the crosstalk between epithelial and immune cells, providing new insights on the mechanisms of DED onset.

Thermogels containing sulfated hyaluronan as novel topical therapeutics for treatment of ocular surface inflammation

The development of long lasting therapeutic agents is critically important for efficient treatment of chronic diseases. We herein report a rational strategy to develop a therapeutic thermogel featured with prolonged anti-inflammatory and corneal-protective effects. Specifically, a hyaluronic acid with different sulfation degrees and an amine-terminated poly(N-isopropylacrylamide) are conjugated to achieve the thermogels. In vitro studies reveal that the thermogels are highly biocompatible to statens seruminstitut rabbit cornea cells and their anti-inflammatory properties are strongly dependent on the sulfation degree. In a rabbit model of ocular inflammation, single-dose topical administration of a thermogel formulation could repair defects in corneal epithelium (∼99% thickness restored), prevent corneal cell apoptosis (∼68.3% cells recovered), and suppress ocular surface inflammation (∼4-fold decrease) for a follow-up period of 7 days. This high treatment efficacy of the thermogel can be attributed to its potent inhibition in selectin-mediated leukocyte infiltration as well as effective corneal protection. These findings show a great promise for topical treatment of ocular inflammation and advancement of ophthalmic formulations using the bioactive thermogel as a therapeutic component that is not rapidly cleared from the eye and thus considerably reduces administration times.

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Sulfated hyaluronan thermogels served as intrinsic therapeutic agents.

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Thermogels exert inhibitory effects on selectin-mediated leukocyte infiltration.

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Sulfation degree is a key to achieve superior therapeutic thermogels.

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Highly sulfated agent reveals potent anti-inflammatory/corneal-protective effects.

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Single dose reduces corneal inflammation by 4-folds at 7 days post-instillation.

Nanoemulsions as Ophthalmic Drug Delivery Systems

Nanoemulsions are liquid-in-liquid dispersion with a droplet size of about 100 nm. They have a transparent appearance, high rate of bioavailability, and increased shelf life. Nanoemulsions mainly consist of oil, water, surfactant, and cosurfactant and can be prepared by high- and low-energy methods. Diluted nanoemulsions are utilized for the delivery of ophthalmic drugs due to their capability to penetrate the deep layers of the ocular structure, provide a sustained release effect, and reduce the frequency of administration and side effects. These nanoemulsions are subjected to certain tests, such as safety, stability, pH profile, rheological studies, and so on. Cationic nanoemulsions are prepared for topical ophthalmic delivery of active ingredients from cationic agents to increase the drug residence time on the ocular surface, reducing their clearance from the ocular surface and improving drug bioavailability. This review article summarizes the main characteristics of nanoemulsions, ophthalmic nanoemulsions, and cationic nanoemulsions and their components, methods of preparation, and the evaluation parameters for ophthalmic nanoemulsions.

Dry eye: why artificial tears are not always the answer

Dry eye disease (DED) is a multifactorial disease that manifests in patients with a variety of symptoms and signs such as ocular pain, visual issues, rapid tear evaporation and/or decreased tear production. It is a global health problem and is the leading cause of optometry and ophthalmology clinic visits. The mainstay therapy for DED is artificial tears (ATs), which mimics tears and improves tear stability and properties. ATs have been found to improve symptoms and signs of disease in all DED subtypes, including aqueous deficient DED and evaporative DED. However, given the heterogeneity of DED, it is not surprising that ATs are not effective in all patients. When AT fails to relieve symptoms and/or signs of DED, it is critical to identify the underlying contributors to disease and escalate therapy appropriately. This includes underlying systemic diseases, meibomian gland dysfunction, anatomical abnormalities and neuropathic dysfunction. Thus, this review will discuss the benefits and limitations of ATs and review conditions when escalation of therapy should be considered in DED.

Ocular surface response of two preservative-free cylcosporine A emulsion eye drops in a mouse model of dry eye

PURPOSE/AIM

Dry eye (DE) disease is a multifactorial disease in which uncontrolled inflammation can lead to corneal epithelium lesions and symptoms of discomfort. The aim of the present study was to evaluate the efficacy of two cyclosporine emulsions in a mouse model of DE with corneal epithelium lesions.

MATERIALS AND METHODS

Six- to 9-week-old female C57BL/6 N mice were housed in a controlled-environment room to induce DE. Following DE development, mice were instilled with: QD 0.1%CsA cationic emulsion (CaEm), BID 0.05%CsA anionic emulsion (AEm), or left untreated. Aqueous tear production and corneal epithelium lesions were assessed throughout the experiment. At the end of the treatment period, left eyes were sampled, fixed, and stained for histology, while the cornea, conjunctiva, and lacrimal gland of right eyes were sampled for transcriptomic analysis.

RESULTS

Corneal lesion scores were reduced by 10.4%, 18.4%, and 10.9% at day 6, 10, and 14, respectively, with CaEm (QD), and by 2.6%, 3.0%, and 5.5% at day 6, 10, and 14, respectively, with AEm (BID). Histology demonstrated that 7 out of 10 DE mice presented moderate to severe ocular lesions, while only 2 and 5 out of 10 mice presented slight to moderate ocular lesions when treated with the CaEm (QD) and AEm (BID), respectively. The transcriptomic profile analysis suggests that a different set of inflammatory genes are modulated in the cornea, conjunctiva, and lacrimal gland upon DE development. In addition, the two emulsions distinctively modulate the gene expression profile.

CONCLUSIONS

This study demonstrates that both emulsions were effective at reducing corneal lesions, with the CaEm (QD) being slightly better than the AEm (BID). Interestingly, this study suggests that ocular tissues may not respond similarly to a dry environment and that a different set of genes is modulated by the two formulations in the ocular tissues.

A Review of the Mechanism of Action of Cyclosporine A: The Role of Cyclosporine A in Dry Eye Disease and Recent Formulation Developments

Dry eye disease (DED) is a multifactorial disease of the ocular surface and tear film that has gained awareness as a public health problem. Characteristics of DED include tear film instability, hyperosmolarity, and ocular surface inflammation, which can occur independently or may be a sequela of numerous ocular diseases, ocular surgery or contact lens wear. Much has been learned about the impact of the disease to help affected individuals who report symptoms of poor vision, pain, and tearing. Recently, new research highlights the importance of the role of ocular surface inflammation and damage in DED-leading to a vicious cycle of inflammation as well as loss of tear film homeostasis. DED immunopathophysiology is characterized by four stages: initiation, amplification, recruitment, and re-initiation. Cyclosporine is proven to be a valuable ophthalmic therapeutic for DED through its immunomodulatory actions and regulation of the adaptive immune response. Cyclosporine mechanism of action is well described in the published literature and the myriad of benefits in all four stages lend a broad-based immunomodulatory function particularly suitable for addressing DED. Furthermore, cyclosporine has unique goblet cell density improvement capabilities as well as anti-apoptotic properties. Topical formulations of cyclosporine are centered around addressing the highly lipophilic nature of the molecule. The poor aqueous solubility of cyclosporine traditionally presented technical challenges in drug delivery to the ocular surface. Newer formulations such as cationic emulsions and nanomicellar aqueous solutions address formulation, tissue concentration, and drug delivery challenges.

High-Frequency Application of Cationic Agents Containing Lubricant Eye Drops Causes Cumulative Corneal Toxicity in an Ex Vivo Eye Irritation Test Model

Purpose: High-frequency applied cetalkonium chloride (CAC) and benzalkonium chloride (BAC) 0.02% did not hamper corneal healing in a living rabbit model of induced corneal erosion. In contrast, the ex vivo eye irritation test (EVEIT) shows inhibition of healing for these substances. In a systematic ex vivo reproduction of the in vivo experiments, we discuss the background of these differences. Methods: Excised rabbit corneas (n = 5 per group) were cultured in artificial anterior chambers (EVEIT). Four erosions were induced for each cornea before starting regular 21 installations/day over 3 days of (1) CAC containing eye drops (Cationorm^®), (2) 0.02% BAC. Corneal fluorescein staining, quantification of glucose-/lactate consumption, and histology were performed. Results: BAC 0.02% treated corneas showed increased epithelial lesions from 10.13 ± 0.65 mm² to 10 ± 0.8 mm² on day 0, to 86.82 ± 5.18 mm² (P < 0.0001) by day 3. After a trend toward smaller lesions for CAC on day 1, erosion sizes increased significantly by day 3 from 9.82 ± 0.30 mm² to 29.51 ± 16.87 mm² (P < 0.05). For 1 cornea, corneal erosions nearly disappeared on day 3 (0.89 mm²). Corneal lactate increased significantly for BAC and CAC, whereas glucose concentrations were unchanged. Histology revealed disintegration of the corneal structures for both compounds. Conclusions: The data underline the EVEIT as a predictive toxicity test to show side effects in a time-compressed manner. The consistency of these predictions was previously demonstrated by the EVEIT for BAC, phosphate buffer, and others. The EVEIT is suited for a chronic application prediction of tolerability and toxic side effects of eye drops in particular, and other chemicals in general.

Therapeutic nanoemulsions in ophthalmic drug administration: Concept in formulations and characterization techniques for ocular drug delivery

The eye is the specialized part of the body and is comprised of numerous physiological ocular barriers that limit the drug absorption at the action site. Regardless of various efforts, efficient topical ophthalmic drug delivery remains unsolved, and thus, it is extremely necessary to advance the contemporary treatments of ocular disorders affecting the anterior and posterior cavities. Nowadays, the advent of nanotechnology-based multicomponent nanoemulsions for ophthalmic drug delivery has gained popularity due to the enhancement of ocular penetrability, improve bioavailability, increase solubility, and stability of lipophilic drugs. Nanoemulsions offer the sustained/controlled drug release and increase residence time which depend on viscosity, compositions, and stabilization process, etc.; hence, decrease the instillation frequency and improve patient compliance. Further, due to the nanosized of nanoemulsions, the sterilization process is easy as conventional solutions and cause no blur vision. The review aims to summarizes the various ocular barriers, manufacturing techniques, possible mechanisms to the retention and deep penetration into the eye, and appropriate excipients with their under-lying selection principles to prevent destabilization of nanoemulsions. This review also discusses the characterization parameters of ocular drug delivery to spike the interest of those contemplating a foray in this field. Here, in short, nanoemulsions are abridged with concepts to design clinically advantageous ocular drug delivery.

Cationic Emulsion-Based Artificial Tears as a Mimic of Functional Healthy Tear Film for Restoration of Ocular Surface Homeostasis in Dry Eye Disease

Dry eye disease (DED) is a complex multifactorial disease that affects an increasing number of patients worldwide. Close to 30% of the population has experienced dry eye (DE) symptoms and presented with some signs of the disease during their lifetime. The significant heterogeneity in the medical background of patients with DEs and in their sensitivity to symptoms renders a clear understanding of DED complicated. It has become evident over the past few years that DED results from an impairment of the ocular surface homeostasis. Hence, a holistic treatment approach that concomitantly addresses the different mechanisms that result in the destabilization of the tear film (TF) and the ocular surface would be appropriate. The goal of the present review is to compile the different types of scientific evidence (from in silico modeling to clinical trials) that help explain the mechanism of action of cationic emulsion (CE)-based eye drop technology for the treatment of both the signs and the symptoms of DED. These CE-based artificial tear (AT) eye drops designed to mimic, from a functional point of view, a healthy TF contribute to the restoration of a healthy ocular surface environment and TF that leads to a better management of DE patients. The CE-based AT eye drops help restore the ocular surface homeostasis in patients who have unstable TF or no tears.

An in situ hydrogel based on carboxymethyl chitosan and sodium alginate dialdehyde for corneal wound healing after alkali burn

There is currently no optimal scaffold for the transplantation of limbal stem cells (LSCs) to induce corneal reconstruction after corneal alkali burns. This study attempts to fabricate a novel in situ Alginate‐Chitosan hydrogel (ACH) for LSCs transplantation. Sodium alginate dialdehyde (SAD), a biological crosslinker, was prepared by periodate‐mediated sodium alginate oxidization. Carboxymethyl chitosan was rapidly crosslinked with SAD via Schiff's base formation between the available aldehyde and amino groups. The ACH is rapidly formed on the wound surface by self‐crosslinking without adding any chemical crosslinking component. Gelation time, transmittance, microscopic structure, equilibrium swelling, cytotoxicity, histocompatibility and degradability of the hydrogel were all examined. Rabbit primary LSCs were encapsulated in the hydrogel and transplanted to alkali burn wounds in vivo. Cornea reconstruction was evaluated by visual observation, slit lamp, histological analysis, and immunofluorescence staining. Results showed that the in situ hydrogel was highly transparent, gelated quickly, biocompatible, and had low cytotoxicity. LSCs cultured in vitro expressed the stem marker p63 but lacked the differentiated epithelial markers cytokeratin 3 and 12. Furthermore, the hydrogel encapsulating LSCs could be formed quickly on the alkali burn wound of the cornea and was shown to significantly improve epithelial reconstruction. Taken together, treatment with this novel in situ hydrogel‐mediated LSC transplantation system may serve as a rapid and effective method for corneal wound healing. © 2018 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 742–754, 2019.

Safety and Tolerability of Overdosed Artificial Tears by Abraded Rabbit Corneas

Purpose: Preservative-free cationic emulsion-based artificial tear (AT) is an innovative eye drop based on the Novasorb^® technology with cetalkonium chloride (CKC) as the cationic agent. The cationic emulsion Cationorm is designed for the management of mild-to-moderate dry eye disease (DED) patients that present cornea epithelium alterations. The aim of the present study was to evaluate the safety and tolerability of overdosed ATs by altered corneal epithelium in vivo and assess the usefulness of the ex vivo eye irritation test (EVEIT) as a predictive alternate toxicity test method.

Methods: The experimental procedure, treatment duration, and instillation frequency closely mimic in vivo the ex vivo protocol described by Pinheiro et al. and discussed in the Discussion and Conclusion section of this article. Two to 3-month-old female New Zealand white rabbits, n = 6 per group, were treated with ATs (21 instillations/day over 3 days) following corneal abrasion. Corneal fluorescein staining, in vivo confocal microscopy (IVCM), and slit lamp examinations were performed to assess corneal epithelium recovery and the ocular tolerability of the overdosed ATs.

Results: All abraded eyes experienced almost complete epithelium recovery within 3 days following treatments with Cationorm, Optive, Vismed, and Saline. Benzalkonium chloride (BAK, 0.02%) treatment resulted in 82.4% reepithelialization. IVCM data illustrated corneal epithelium normal recovery. Acute local tolerability of the overdosed ATs was confirmed using Draize and McDonald–Shadduck's test scales.

Conclusions: The different ATs were demonstrated to be well tolerated by abraded corneas in vivo, and the extreme overdosing regimen did not hamper the wound healing process of the rabbit eye in comparison to saline. These data did not confirm the ones obtained with the nonvalidated ex vivo eye irritation test.

Trehalose/hyaluronate eyedrop effects on ocular surface inflammatory markers and mucin expression in dry eye patients

Aim

To assess the ocular surface parameters, inflammatory marker level in tears, and mucin expression in conjunctival epithelium before and after treatment with trehalose/hyaluronate tear substitute in dry eye (DE) patients.

Patients and methods

Fifteen DE patients were evaluated in an open-label, pilot study at enrollment, after 2 days of washout (baseline) and after 1 and 2 months (endpoint) of treatment with a trehalose/hyaluronate tear substitute (one drop/eye/three times daily). Data for symptoms of discomfort (Ocular Surface Disease Index and Visual Analogue Scale pain score), tear film (Schirmer test I, tear film breakup time), ocular surface damage (corneal National Eye Institute) and conjunctival van Bijsterveld scores, impression cytology scored by Nelson’s grade and goblet cells (GCs) number/mm² analysis, and MUC4 immunostaining, and inflammation (interleukin [IL]-1β, IL-6, and IL-8 levels) were measured.

Results

Significant changes at endpoint as compared to baseline were found for Ocular Surface Disease Index score (respectively, mean±SD, 22.2±2.9 vs 38.7±12.7), Visual Analogue Scale score (3.4±1.3 vs 6.6±1.4), tear film breakup time (8.6±1.28 vs 6.17±1.9 seconds), corneal staining (National Eye Institute grade 1.23±0.64 vs 3.37±0.49), conjunctival staining (1.73±1.14 vs 4.17±0.91), impression cytology (Nelson grade 1.10±0.20 vs 1.63±0.54), and GC density (139.9±22.0 vs 107.8±16.2 GC/mm²). IL-1β, IL-6, and IL-8 tear levels showed a significant decrease at endpoint as compared to baseline (respectively, pg/mL tears: 12.3±6.9, 26.6±25.2, 743.5±477.7 vs 33.6±17.3, 112.0±24.3, 1,139.2±671.7).

Conclusions

A decrease in ocular discomfort symptoms, surface damage, and tear cytokine levels was shown after 2 months’ treatment with trehalose/hyaluronate tear substitute in DE patients, along with a significant GC density recovery. These results may be associated with the synergic action of both trehalose and hyaluronic acid in targeting different entries of the DE vicious loop.

Anti-inflammatory activity of CKC-containing cationic emulsion eye drop vehicles

PURPOSE

Preservative-free cationic emulsion-based artificial tears (ATs) or drug vehicles are innovative eye drop formulations with tear film stabilization and drug delivery properties, and valuable in vivo anti-inflammatory and wound healing properties. These ATs have recently reached the market as ATs for the management of dry eye disease (DED) symptoms (i.e., Cationorm) or as a drug vehicle for cyclosporine (Ikervis). The aim of the present study was to explore the mechanism of action underlying the intrinsic anti-inflammatory and wound-healing efficacies harbored by the cationic emulsions of cetalkonium chloride (CE-CKC).

METHODS

The anti-inflammatory activity of two CE-CKC (0.002% and 0.005% CKC) emulsions was evaluated by assessing the expression of proinflammatory genes and the secretion of various markers in the following human cell types stressed by different agents: peripheral blood mononuclear cells (PBMCs; stimulation with anti-CD3/anti-CD28 or lipopolysaccharide (LPS)), CD4⁺ T lymphocytes (TCD4; stimulation with anti-CD3/anti-CD28), and a human corneal epithelial cell line (HCE-2; stimulation with LPS). The cells were incubated for 30 min with a 10% dilution of CE-CKC emulsions and then cultured without the emulsions for 24 h or 72 h in the presence of the various challenging agents. The supernatant was collected, and the secreted markers quantitated with flow cytometry or an enzyme-linked immunosorbent assay (ELISA). Gene expression of inflammatory markers was evaluated only in the PBMCs and HCE-2 cells stimulated with LPS. The in vitro protein kinase C (PKC) binding assay for IC₅₀ determination was performed using standard procedures.

RESULTS

The CE-CKC emulsions decreased inflammatory gene expression in LPS-stimulated PBMCs (IFN-γ, IL-17A, CXCL-9, and TNFα) and LPS-stimulated HCE-2 cells (THBS1 and CCL2). Both CE-CKC emulsions inhibited the secretion of IL-17 (from anti-CD3/anti-CD28-stimulated TCD4), TNFα, IFN-γ, and IL-2 (from anti-CD3-/anti-CD28-stimulated PBMCs), and IL-6 and IL-8 (from LPS-stimulated HCE-2). The in vitro PKC binding assay revealed that CKC, the cationic agent, is a specific PKCα inhibitor. In addition, tyloxapol, another excipient, showed some anti-inflammatory activity on IL-6 and IL-8 in the LPS-stimulated HCE-2 cells.

CONCLUSIONS

This study indicates that the CE-CKC emulsions are able to directly modulate the secretion and expression of proinflammatory cytokines and chemokines. The results also suggest that CKC and tyloxapol are pharmacologically active excipients with potentially beneficial effects in vivo. These data shed new light on the efficacy observed on the DED signs of these CE-CKC emulsions in clinical trials.

Impact of Hyaluronic Acid-Containing Artificial Tear Products on Reepithelialization in an In Vivo Corneal Wound Model

PURPOSE

To evaluate the effect of 6 commercially available hyaluronic acid (HA)-containing topical artificial tear products on corneal reepithelialization following injury, in an in vivo mouse model.

METHODS

Ninety-six C57Bl/6 mice (16 per treatment group; male to female ratio, 1:1 per group) were anesthetized. Epithelial debridement was performed on 1 cornea per animal, and the debrided eye was imaged. A 30 μL masked test solution containing 1 of 6 artificial tear products was instilled, immediately on debridement, and subsequently, every 2 h, for a total of 4 administrations. At 24 h post debridement, corneas were stained with fluorescein and imaged to calculate corneal healing rate (number of fluorescein-negative corneas).

RESULTS

All 6 artificial tear products used in this study permitted the initial process of corneal wound healing. However, the corneal reepithelialization rate after 24 h was higher with Hydroxypropyl guar (HPG)/HA (53.33%) compared with other HA-containing artificial tear products [HA1 (12.5%), HA2 (26.67%), HA3 (31.25%), HA4 (6.25%), and HA5 (43.75%)]. The average area and percentage area of reepithelialization after 24 h were also higher with HPG/HA compared with other treatment groups.

CONCLUSIONS

Percentage of eyes with complete corneal reepithelialization 24 h post debridement was highest with HPG/HA compared with other HA-containing artificial tear products tested. The results of this study provide additional evidence on the potential benefits of HPG/HA in the management of dry eye and its role in the rapid restoration of a healthy ocular epithelium. However, further studies are required to confirm the effects on human corneal wounds.

The Effect of Optive and Optive Advanced Artificial Tears on the Healthy Tear Film

PURPOSE

To evaluate the impact of Optive (Allergan, Irvine, CA) and Optive Advanced (Allergan, Irvine, CA) on tear film stability and quality during a one-hour observation period when compared to saline (Pfizer, Perth, WA).

METHODS

This was a double-masked, cross-over study. Twenty participants attended three visits, randomly receiving either Optive, Optive Advanced or saline. Oculus Keratograph 5M (Oculus, Arlington, WA, USA), non-invasive keratograph break-up time (NIKBUT), Lipiview (TearScience Inc, Morrisville, NC, USA), lipid layer thickness (LLT) and comfort were measured prior to and 5, 15 and 60 min after drop instillation.

RESULTS

Optive Advanced demonstrated a significant increase in LLT between baseline (57.5 ± 12.3 nm) and both 5 min (67.5 ± 18.8 nm, p = 0.04) and 15 min (68.9 ± 17.3 nm, p = 0.04) but not 60 min (61.6 ± 14.3 nm, p = 0.47). Optive and saline were not different between timepoints for LLT (p > 0.05). There was no difference between timepoints for any of the drops for NIKBUT (p = 0.75). Comfort was significantly better at 5 min compared to baseline for Optive (8.3 ± 1.2 and 7.3 ± 1.4, respectively, p = 0.03) but not different for Optive Advance or saline (p > 0.05).

CONCLUSIONS

Optive Advanced increased LLT for 15 min following instillation, returning to baseline within one hour. This did not however, translate into an improvement in tear film stability over this time period. Only Optive demonstrated an improvement in comfort.

Relevance of Lipid-Based Products in the Management of Dry Eye Disease

Components of the ocular surface synergistically contribute to maintaining and protecting a smooth refractive layer to facilitate the optimal transmission of light. At the air-water interface, the tear film lipid layer (TFLL), a mixture of lipids and proteins, plays a key role in tear surface tension and is important for the physiological hydration of the ocular surface and for ocular homeostasis. Alterations in tear fluid rheology, differences in lipid composition, or downregulation of specific tear proteins are found in most types of ocular surface disease, including dry eye disease (DED). Artificial tears have long been a first line of treatment in DED and aim to replace or supplement tears. More recently, lipid-containing eye drops have been developed to more closely mimic the combination of aqueous and lipid layers of the TFLL. Over the last 2 decades, our understanding of the nature and importance of lipids in the tear film in health and disease has increased substantially. The aim of this article is to provide a brief overview of our current understanding of tear film properties and review the effectiveness of lipid-based products in the treatment of DED. Liposome lid sprays, emulsion eye drops, and other lipid-containing formulations are discussed.

Cyclosporine A delivery to the eye: A comprehensive review of academic and industrial efforts

Local ocular delivery of cyclosporine A (CsA) is the preferred method for CsA delivery as a treatment for ocular inflammatory diseases such as uveitis, corneal healing, vernal keratoconjunctivitis and dry eye disease. However, due to the large molecular weight and hydrophobic nature of CsA and the natural protective mechanisms of the eye, achieving therapeutic levels of CsA in ocular tissues can be difficult. This review gives a comprehensive overview of the current products available to clinicians as well as emerging drug delivery solutions that have been developed at both the academic and industry levels.

Benefits of cetalkonium chloride cationic oil-in-water nanoemulsions for topical ophthalmic drug delivery

Objectives

Topical ocular administration is the most convenient route of administration of drugs for the treatment of eye diseases. However, the bioavailability of drugs following eye instillations of eye drops is very low. Over the past 20 years, extensive efforts have been put into research to improve drug bioavailability without compromising treatment compliance and patients' quality of life.

Key findings

One of the most efficient ways to improve drug bioavailability is to increase the precorneal residence time of the eye drop formulations. As a result, new eye drops, with bioadhesive properties, have been developed based on the cationic oil-in-water (o/w) nanoemulsion technology. These low viscosity eye drop nanoemulsions have improved precorneal residence time through the electrostatic interactions between the positively charged oil nanodroplets and the negatively charged ocular surface epithelium.

Summary

This review is the first to present the benefits of this new strategy used to improve ocular drug bioavailability. The roles of the cationic agent in the stabilization of a safe cationic o/w nanoemulsion have been discussed, as well as the unexpected benefits of the cationic o/w nanoemulsion for the protection and restoration of a healthy tear film and corneal epithelium.