Comprehensive Evaluation of Ocular Toxicity of Topical Levofloxacin in Rabbit and Primate Models

Levofloxacin, the L-isomer of ofloxacin and a potent quinolone with a broad spectrum of antibacterial activity, was evaluated in a series of toxicology studies including acute and chronic dosing in rabbits and primates with intact and injured eyes. No evidence of ocular toxicity was observed in rabbits with intact eyes that were topically instilled with levofloxacin ophthalmic solutions under various treatment regimens, including multiple dosing (four to six times daily) for up to 26 weeks at levofloxacin concentrations from 0.3% to 3%. When rabbits were repetitively instilled (10 times at 30 minute intervals) with 0.3%, 1%, or 3% levofloxacin ophthalmic solutions over a single day, they exhibited no increase in ocular irritation scores, whereas dosing with 10% and 25% levofloxacin produced dose-dependent increases in ocular discharge, conjunctival injection and edema, corneal edema fluorescein staining, iridic congestion, and behavioral abnormalities. Healing of 7.5 mm diameter epithelial wounds in rabbit eyes was not delayed by dosing four times daily (QID) with 0.5% or 1.5% levofloxacin in four different vehicles, with complete healing after 48 hours. The QID dosing with 3% or 6% levofloxacin retarded healing at 24 hours, but healing was complete in eyes treated with 3% levofloxacin by 72 hours after injury, and nearly complete in eyes treated with 6% levofloxacin by 96 hours. Using a similar model in primates, QID treatment with 1.5% levofloxacin produced no delay in healing of epithelial wounds or increased corneal thickness compared to glycerin vehicle, while QID treatment with 3% levofloxacin delayed healing at 24 and 48 hours after injury and increased corneal thickness for 11 days. Histological evaluation of the eyes confirmed that there was no detrimental effect to the corneal endothelium as a result of treatment with 1.5% levofloxacin. In conclusion, the results of these studies support the ocular safety of concentrations of levofloxacin up to 1.5% when administered topically to the intact or wounded eye

Effects of substance P and IGF-1 in corneal epithelial barrier function and wound healing in a rat model of neurotrophic keratopathy.

PURPOSE. To establish a rat model of neurotrophic keratopathy and to examine the effects of the combination of substance P (SP) and insulin-like growth factor (IGF)-1 on corneal epithelial barrier function and wound healing in this model. METHODS. Corneal denervation was achieved by thermocoagulation of the ophthalmic branch of the trigeminal nerve. A modified Schirmer test was performed without topical anesthesia. Corneal epithelial barrier function was assessed by measurement of fluorescein permeability with an anterior fluorophotometer. Epithelial wound healing was evaluated by measurement of the area of the defect at various times after removal of the entire epithelium. Eye drops containing both 1 mM SP and IGF-1 (1 g/mL) were administered six times daily. RESULTS. The Schirmer test result in eyes subjected to trigeminal denervation was lower than that in control eyes. The fluorescein permeability of the corneal epithelium of denervated eyes was increased relative to that of control eyes. Furthermore, trigeminal denervation induced a delay in corneal epithelial wound healing. Application of eye drops containing SP and IGF-1 to denervated corneas restored the fluorescein permeability of the corneal epithelium to control levels and abolished the delay in epithelial wound healing. T he cornea is the most heavily innervated tissue in the body. Corneal innervation is thought to be important for maintenance of a healthy corneal epithelium. Loss of corneal sensation as a result of damage to the trigeminal nerve often leads to neurotrophic keratopathy, which is associated with various types of corneal disorders, including superficial punctate keratitis, persistent epithelial defects, and stromal melting. Prompt and appropriate treatment for such disorders is important in individuals with neurotrophic keratopathy, to prevent serious complications such as corneal ulceration, perforation, and infection. However, no specific standard treatment regimen for neurotrophic keratopathy based on the pathobiology of this condition has been established. Rather, attempts have been made to manage the epithelial disorders with ocular lubricants, soft contact lenses, or tarsorrhaphy. Although corneal denervation due to trigeminal nerve injury has been shown to result in abnormalities in the physiology of the corneal epithelium, including increased permeability, 1 decreased cell proliferation, 2 phenotypic changes, 1,3,4 and delayed wound healing 5 Growth factors, such as epidermal growth factor 6 -10 and basic fibroblast growth factor, 11,12 as well as interleukin- The purpose of the present study was therefore to establish an animal model of neurotrophic keratopathy and then to use this model to examine the effects of eye drops containing both SP and IGF-1 on the barrier properties of and wound healing in the corneal epithelium. For development of the animal model, we modified a technique described by Sigelman and Friedenwald 2 to achieve trigeminal denervation in the rat. METHODS Animals Male Brown Norway rats with body masses of 230 to 345 g were obtained from Japan Charles River (Yokohama, Japan). The study was performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Trigeminal Denervation A schematic representation of the thermocoagulation track for trigeminal denervation of the right eye is shown in From th

TNF-α is crucial for the development of autoimmune arthritis in IL-1 receptor antagonist–deficient mice

IL-1 receptor antagonist–deficient (IL-1Ra(–/–)) mice spontaneously develop autoimmune arthritis. We demonstrate here that T cells are required for the induction of arthritis; T cell–deficient IL-1Ra(–/–) mice did not develop arthritis, and transfer of IL-1Ra(–/–) T cells induced arthritis in nu/nu mice. Development of arthritis was also markedly suppressed by TNF-α deficiency. We found that TNF-α induced OX40 expression on T cells and blocking the interaction between either CD40 and its ligand or OX40 and its ligand suppressed development of arthritis. These findings suggest that IL-1 receptor antagonist deficiency in T cells disrupts homeostasis of the immune system and that TNF-α plays an important role in activating T cells through induction of OX40