Toxicity of Subretinal Ribozyme to the Proliferating Cell Nuclear Antigen and 5-Fluorouracil in Rat Eyes

Abstract

Purpose: To investigate the subretinal toxicity profile of the ribozyme to the proliferating cell nuclear antigen (PCNA-Rz) and 5-fluorouracil (5-FU), as well as the highest nontoxic subretinal dose of the mixture of the two agents in rat eyes. Methods: Brown-Norway rats received subretinal injections of 1 μ g, 10 μ g, and 100 μ g/μ l PCNA-Rz and 0.06 μ g/μ l, 0.3 μ g/μ l, and 1.5 μ g/μ l 5-FU in the right eyes, and the left eyes were injected with H-BSS as control. Each dose was tested on 5 eyes in a 5 μ l volume. In a second study, a combination of 5-FU (1.5 μ g/μ L) with varying 10–30–50 μ g/μ l doses of PCNA-Rz was tested in a regimen of four sequential subretinal injections. Toxicity was monitored by biomicroscopy, indirect ophthalmoscopy, electroretinography (ERG), and histology. Results: The highest nontoxic dose for subretinal PCNA-Rz was 10 μ g/μ l, whereas 100 μ g/μ l showed disturbance of pigmentation with corresponding histological changes of retinal photoreceptor loss and retinal pigment epithelium proliferation or irregularities. Subretinal injection of all three doses of 5-FU did not show any toxicity. Serial injections of a mixture of 1.5 μ g/μ l 5-FU with 10 μ g/μ l of PCNA-Rz was found to be safe in rat eyes. Conclusions: Subretinal injections of the combination of PCNA-Rz (10 μ g/μ l) and 5-FU (1.5 μ g/μ l) demonstrated to be safe in rat eyes during the course of this study, even with a multiple administration of four injections.

KEYWORDS:

• 5-FU
• PCNA-Rz
• subretinal injection
• toxicity