Safe dose of intravitreal imatinib and its effect on laser-induced choroidal neovascularization: a rat-model experiment

Retinal toxicities of systemic anticancer drugs

Newer anticancer drugs have revolutionized cancer treatment in the last decade, but conventional chemotherapy still occupies a central position in many cancers, with combination therapy and newer methods of delivery increasing their efficacy while minimizing toxicities. We discuss the retinal toxicities of anticancer drugs with an emphasis on the mechanism of toxicity. Uveitis is seen with the use of v-raf murine sarcoma viral oncogene homolog B editing anticancer inhibitors as well as immunotherapy. Most of the cases are mild with only anterior uveitis, but severe cases of posterior uveitis, panuveitis, and Vogt-Koyanagi-Harada-like disease may also occur. In the retina, a transient neurosensory detachment is observed in almost all patients on mitogen-activated protein kinase kinase (MEK) inhibitors. Microvasculopathy is often seen with interferon α, but vascular occlusion is a more serious toxicity caused by interferon α and MEK inhibitors. Crystalline retinopathy with or without macular edema may occur with tamoxifen; however, even asymptomatic patients may develop cavitatory spaces seen on optical coherence tomography. A unique macular edema with angiographic silence is characteristic of taxanes. Delayed dark adaptation has been observed with fenretinide. Interestingly, this drug is finding potential application in Stargardt disease and age-related macular degeneration.

Beneficial Effects of Melatonin and Atorvastatin on Retinopathy in Streptozocin-induced Diabetic Rats

Objective:

The present study was designed to evaluate the effects of Atorvastatin (ATO) plus Melatonin (MEL) on streptozocin-induced Diabetic Retinopathy (DR) in rats.

Methods:

Diabetes was induced in Wistar rats with an intraperitoneal injection of streptozocin (50 mg/kg). Animals were randomly assigned to one of the following groups (8 rats/group): Control group, Diabetic group, Diabetic + MEL group (20 mg/kg/day), Diabetic + ATO group (10 mg/kg/day), Diabetic + MEL + ATO group (as above). Treatments were started one week after induction of diabetes and continued for 7 weeks. At the end of the experiment, angiography was performed and the rats were killed and retinas were harvested for pathological and molecular examinations.

Results:

Administration of MEL reduced the fluorescein leakage, MDA and ROS levels compared to diabetic group. Treatment with ATO only reduced ROS levels compared to diabetic group. In addition, administration of ATO plus MEL decreased these indices compared to the diabetic and ATO groups. Histologically, retinal vascular congestion was not observed in the combined ATO and MEL group as compared to the diabetic, ATO, and MEL groups.

Conclusion:

These data provide evidence for the therapeutic value of MEL in combination with ATO in clinical practice for prevention of DR.

Retina transduction by rAAV2 after intravitreal injection: comparison between mouse and rat

Adeno-associated virus vectors (rAAV) are currently the most common vehicle used in clinical trials of retinal gene therapy, usually delivered through subretinal injections to target cells of the outer retina. However, targeting the inner retina requires intravitreal injections, a simple and safe procedure, which is effective for transducing the rodent retina, but still of low efficiency in the eyes of primates. We investigated whether adjuvant pharmacological agents may enhance rAAV transduction of the retinas of mouse and rat after intravitreal delivery. Tyrosine kinase inhibitors were highly efficient in mice, especially imatinib and genistein, and promoted transduction even of the outer retina. In rats, however, we report that they were not effective. Even with direct proteasomal inhibition in rats, the effects upon transduction were only minimal and restricted to the inner retina. Even tyrosine capsid mutant rAAVs in rats had a transduction profile similar to wtAAV. Thus, the differences between mouse and rat, in both eye size and the inner limiting membrane, compromise the efficiency of AAV vectors penetration from the vitreous into the retina, and impact the efficacy of strategies developed to enhance intravitreal retinal rAAV transduction. Further improvement of strategies, then are required.

Protective effect of melatonin in the diabetic rat retina

Diabetic retinopathy (DR) is one of the most common and serious microvascular complications of diabetes. The aim of this study was to evaluate the effects of melatonin (MEL) on retinal injury in diabetic rats. In this study, 21 rats were randomly divided into three groups: control, diabetic, and diabetic + MEL. Streptozotocin was used to induce diabetes at a dose of 50 mg/kg, i.p., and blood glucose was measured to choose the diabetic rats for the study. MEL (20 mg/kg) was given orally for 7 weeks in diabetic rats starting 1 week after induction of diabetes. After 8 weeks, the groups were compared in terms of mean scores of fluorescein leakage, using fluorescein angiography. Reactive oxygen species (ROS) and malondialdehyde (MDA) levels were estimated in retina using commercially available assays. Structural changes in retinas were evaluated by light microscopy. Results showed that diabetes significantly increased the mean scores of fluorescein leakage, and MDA and ROS levels compared to control group. Treatment of the diabetic rats with MEL for 7 weeks prevented the alterations induced by diabetes in comparison with the diabetic control group.Based on these findings, it can be concluded that MEL might have beneficial effects in prevention of DR.