Effect of Retinol Palmitate Eye Drops on Experimental Keratoconjunctival Epithelial Damage Induced byn-Heptanol in Rabbit

Management Strategies of Ocular Chemical Burns: Current Perspectives

Ocular chemical burns are absolute ophthalmic emergencies and require immediate management to minimize devastating sequelae. Management of alkali and acid burns is started at the scene of the accident by copious irrigation. Treatment is directed at improving epithelial integrity and stromal stability, reduction of undue inflammation, and prevention or timely management of complications. To ascertain the best possible outcome, numerous biological medications and surgical interventions have been merged into conventional therapeutic regimens. These include autologous and umbilical cord serum preparations, platelet-rich plasma, amniotic membrane transplantation, limbal stem-cell transplantation, and anti-angiogenic agents.

Treatment of acute ocular chemical burns

Ocular chemical burns are an ophthalmic emergency and are responsible for 11.5%-22.1% of ocular injuries. Immediate copious irrigation is universally recommended in acute ocular burns to remove the offending agent and minimize damage. Conventional medical therapy consists of the use of agents that promote epithelialization, minimize inflammation, and prevent cicatricial complications. Biological fluids such as autologous serum, umbilical cord blood serum, platelet-rich plasma, and amniotic membrane suspension are a rich source of growth factors and promote healing when used as adjuncts to conventional therapy. Surgical treatment of acute ocular burns includes the debridement of the necrotic tissue, application of tissue adhesives, tenoplasty, and tectonic keratoplasty. Amniotic membrane transplantation is a novel surgical treatment that is increasingly being used as an adjunct to conventional treatment to promote epithelial healing, minimize pain, and restore visual acuity. Various experimental treatments that aim to promote wound healing and minimize inflammation are being evaluated such as human mesenchymal and adipose stem cells, beta-1,3 glucan, angiotensin-converting enzyme inhibitors, cultivated fibroblasts, zinc desferrioxamine, antifibrinolytic agents, antioxidants, collagen cross-linking, and inhibitors of corneal neovascularization.

Efficacy and safety of retinol palmitate ophthalmic solution in the treatment of dry eye: a Japanese Phase II clinical trial

Purpose

The purpose of this study was to investigate the efficacy and safety of the administration of retinol palmitate (VApal) ophthalmic solution (500 IU/mL) for the treatment of patients with dry eye.

Patients and methods

This study included 66 patients with dry eye. After a 2-week washout period, patients were randomized (1:1) into either a VApal ophthalmic solution or a placebo group, and a single drop of either solution was administered six times daily for 4 weeks. Efficacy measures were 12 subjective symptoms, rose bengal (RB) and fluorescein staining scores, tear film breakup time, and tear secretion. Safety measures included clinical blood and urine analyses and adverse event recordings.

Results

In comparisons of the two groups, the mean change in RB staining score from baseline was significantly lower in the VApal group at 2 and 4 weeks (P<0.05 and P<0.01, respectively). Furthermore, the fluorescein clearance rate (fluorescein staining score) was significantly higher in the VApal group at 4 weeks (P<0.05). The VApal group showed a significant improvement in blurred vision at 1 and 2 weeks (P<0.01 and P<0.05, respectively), and the mean change in the total score for subjective symptoms from baseline was significantly lower in the VApal group at 1 week (P<0.05). In before- and after-intervention comparisons, the fluorescein and RB staining scores showed improvement in both groups. Improvement was noted for 11 subjective symptoms in the VApal group and for seven symptoms in the placebo group. No significant differences in adverse events and reactions were found between the groups.

Conclusion

VApal ophthalmic solution (500 IU/mL) is safe and effective for the treatment of patients with dry eye.

Lysyl oxidase-like 4 involvement in retinoic acid epithelial wound healing

Vitamin A and its active forms (retinoic acids/RAs) are known to have pro-healing properties, but their mechanisms of action are still poorly understood. This work aimed to identify the cellular and molecular processes by which atRA (all-trans RA) improves wound healing, using an in vivo model of mouse corneal alkali burns and an in vitro cellular human corneal epithelial injury model. Regulation by atRA has been studied on most of the cellular events that occur in wound healing. We investigated the direct influence of atRA on a specific target gene known to be involved in the extracellular matrix (ECM) dynamics, one of the pathways contributing to epithelial repair. Our results demonstrate that atRA promotes corneal epithelial wound healing by acting preferentially on migration. The induction of lysyl oxidase-like 4 (LOXL4) expression by atRA in the corneal epithelium environment was established as essential in the mechanism of atRA-dependent wound healing. Our study describes for the first time a direct link between a retinoic-induced gene and protein, LOXL4, and its general clinical pro-healing properties in ECM dynamics.

PEP-1-FK506BP inhibits alkali burn-induced corneal inflammation on the rat model of corneal alkali injury

FK506 binding protein 12 (FK506BP) is a small peptide with a single FK506BP domain that is involved in suppression of immune response and reactive oxygen species. FK506BP has emerged as a potential drug target for several inflammatory diseases. Here, we examined the protective effects of directly applied cell permeable FK506BP (PEP-1-FK506BP) on corneal alkali burn injury (CAI). In the cornea, there was a significant decrease in the number of cells expressing pro-inflammation, apoptotic, and angiogenic factors such as TNF-α, COX-2, and VEGF. Both corneal opacity and corneal neovascularization (CNV) were significantly decreased in the PEP-1-FK506BP treated group. Our results showed that PEP-1-FK506BP can significantly inhibit alkali burn-induced corneal inflammation in rats, possibly by accelerating corneal wound healing and by reducing the production of angiogenic factors and inflammatory cytokines. These results suggest that PEP-1-FK506BP may be a potential therapeutic agent for CAI. [BMB Reports 2015; 48(11): 618-623]

Structural analysis and adsorbability onto the corneal epithelial cells-model interface of vitamin nano-emulsions

O/W nano-emulsions can be used as effective drug carriers of hydrophobic active ingredients in an aqueous solution, because nano-emulsions are comparatively stable and their structure can be controlled by changing the compositions and the preparation methods. In this paper, we focused on vitamin A and its derivatives (VA), which are among the widely-used lipophilic active ingredients, and tried to develop the nano-emulsions, which can bring out the efficiency of VA for the healing of injured corneas, with the detailed structural analysis of them using the small-angle X-ray scattering (SAXS) method. As a result, we elucidated that the nano-emulsions bearing the hydrophobic oil/water interface can be prepared by decreasing the surfactant concentration against vitamins. Moreover, we clarified that the nano-emulsions composed of lower surfactant concentration tend to adsorb VA onto the corneal epithelial cells-model interface. Therefore it is necessary to prepare the nano-emulsions, which have the hydrophobic oil/water interface for improving the adsorbability onto cell membranes.

Efficacy of retinol palmitate eye drops for dry eye in rabbits with lacrimal gland resection

Purpose

We examined the efficacy of retinol palmitate (VApal) for dry eyes using dry eye model rabbits whose lacrimal glands were resected.

Materials and methods

After alkaline injury on keratoconjunctival epithelium, VApal eye drops were administered 6 times a day for 7 days. The efficacy of VApal was also compared with that of 0.1% hyaluronic acid eye drops.

Results

The fluorescein staining and rose bengal scores showed a significant decrease compared with the score in the vehicle group at 7 days (P < 0.05) in the 1000 IU/mL VApal group and at both 3 days (P < 0.05) and 7 days (P < 0.01) in the 1500 IU/mL VApal group. Histological examination revealed recovery of the corneal epithelium, and PAS staining disclosed the recovery of mucin-producing lower palpebral conjunctival goblet cells after 7 days in the 1500 IU/mL VApal group compared with the vehicle group. Results from impression cytology showed a significant increase in density of conjunctival goblet cells compared with that in the vehicle group after 7 days in the 1000 IU/mL VApal group and after 3 and 7 days in the 1500 IU/mL VApal group. There were no significant changes in tear flow in either group. Topical application of VApal at 1500 IU/mL showed greater improvement than 0.1% hyaluronic acid in both fluorescein and rose bengal score and in the density of conjunctival goblet cells.

Conclusion

It is suggested that VApal is effective for the improvement of keratoconjunctival epithelial damage associated with tear abnormalities, such as dry eyes.