Corneal UV Protective Effects of a Topical Antioxidant Formulation: A Pilot Study on In Vivo Rabbits

Abstract

This study aimed to evaluate the protective effect of a topical antioxidant and ultraviolet (UV) shielding action formulation containing riboflavin and D-α-tocopherol polyethylene glycol succinate (TPGS) vitamin E against corneal UV-induced damage in vivo rabbit eyes. In vivo experiments were performed using male albino rabbits, which were divided into four groups. The control group (CG) did not receive any UV irradiation; the first group (IG) was irradiated with a UV-B−UV-A lamp for 30 min; the second (G30) and third (G60) groups received UV irradiation for 30 and 60 min, respectively, and were topically treated with one drop of the antioxidant and shielding formulation every 15 min, starting one hour before irradiation, until the end of UV exposure. The cornea of the IG group showed irregular thickening, detachment of residual fragments of the Descemet membrane, stromal fluid swelling with consequent collagen fiber disorganization and disruption, and inflammation. The cornea of the G30 group showed edema, a mild thickening of the Descemet membrane without fibrillar collagen disruption and focal discoloration, or inflammation. In the G60 group, the cornea showed a more severe thickening, a more abundant fluid accumulation underneath the Descemet membrane with focal detachment, and no signs of severe tissue alterations, as were recorded in the IG group. Our results demonstrate that topical application of eye drops containing riboflavin and TPGS vitamin E counteracts UV corneal injury in exposed rabbits.

Comparative antioxidant activity of various ophthalmic product types for artificial tears under different experimental conditions

“…The sample drop in maximum inhibition-free radicals was of a polynomial type. This means a higher and more rapid rate of deterioration of the activity with and without exposure to UVC at a 254 nm wavelength (50)(51)(52).…”

Nerve Growth Factor (NGF) as Partaker in the Modulation of UV-Response in Cultured Human Conjunctival Fibroblasts

“…Furthermore, the low KEAP1 and high NRF2 expressions detected in UV/NGF-exposed FBs might imply the activation of NRF2/KEAP1 axis with modulatory roles on tissue remodeling and fibrosis [ 23 , 49 ]. All of these biomolecular aspects are of great importance, as epigenetic modifications are reversible and, therefore, suitable “prime targets” for therapeutic intervention [ 50 , 51 ].…”

“…Noteworthily, the ocular surface unit needs to be protected from any kind of insult to maintain the corneal functionality [ 54 ]. Recently, increased UV exposure due to ozone thinning has been associated with “dry eyes of environmental origin”, “urban syndrome”, exacerbations of preexisting ocular fibrosis (conjunctival pterygium, photokeratitis, climatic droplet keratopathy), and cataract-genesis, and the current generation is more greatly exposed to UV radiation than earlier ones, due to the increase in unshielded UV rays reaching the Earth’s surface [ 32 , 33 , 34 , 43 , 51 , 54 , 55 , 56 , 57 , 58 ]. This aspect appears of great importance, as the corneo-conjunctival limbus is also populated by mast cells with gatekeeper functions that might react to photo-exposure influencing the local microenvironment [ 57 , 58 ].…”

“…Herein, the interest was double, as most of the chronic exposures to solar UV rays are associated with exacerbation of existing ocular fibrosis (pterygium, pinguecula, squamous metaplasia, or carcinoma) or with some environment-associated dry eye forms [ 32 , 33 , 53 ]. NGF eye drop substitute might represent, in the near future, an alternative for protecting the ocular surface from UV lights [ 3 , 15 , 51 , 58 , 61 ]. Further in vitro studies on UV-exposed conjunctival epithelial and fibroblast co-cultures (3D) are underway to better clarify the potential contribution of NGF in sub-cytotoxic UV exposure herein prospected.…”

“…Briefly, cells were grown on round-glass placed on 24-well plates in the presence of complete DMEM (10% FBS, glutamine and antibiotics), and 24 h serum-starved monolayers were exposed to UVA/B with a medical/cosmetic vertical UV source lamp (KN-4003A/BL2; Kernel, Xuzhou, China) equipped with UV bulbs (9 W PL-S 2P/01; Philips, Amsterdam, the Netherlands) providing an emission spectrum ranging between 300 and 400 nm (peak 368 ± 3 nm for UVA and 311 ± 3 nm for UVB). Irradiation was performed placing the UV source apparatus on a home-made scaffold placed under the tissue culture hood to fix the distance, avoiding any movement (working distance: 3 cm ± 0.5 cm; exposure time: 15 min; irradiance for: UVB, 0.047 W/m 2 and UVA, 0.230 W/m 2 ; total irradiance: 0.277 W/m 2 ) [ 30 , 31 , 51 ]. Briefly, DMEM (0.05% FBS) alone or supplemented with NGF (1–10–100 ng/mL) was added to monolayers before UV exposure.…”