effect of chloroquine on the retina of adult male albino rat and the possible protective role of Ginkgo biloba extract. A histological and immunohistochemical study

ABSTRACT

Chloroquine is an antimalarial drug and is widely used for the treatment of various rheumatic diseases. Unfortunately, its use has been associated with the development of toxic retinopathy. Because treatment with chloroquine is sometimes inevitable, interventions that abolish or at least attenuate retinal affection are of great importance. Several studies indicated that antioxidants may be beneficial for those at risk of developing retinal diseases. Of these, Ginkgo biloba extract [EGb 761] is a recently used agent for its known oxygenated radical scavenging properties. For demonstration of the effect of chloroquine on retinal structure and the possible protective role of EGb 761, forty adult male albino rats were used. They were divided into four equal groups; control group, EGb 761-treated group [100 mg/Kg body weight], chloroquine-treated group [28 mg/Kg body weight] and the fourth group was concomitantly treated with both EGb 761 and chloroquine. The animals were treated orally daily for 4 weeks and retinal specimens were examined by light and electron microscopy. Moreover, immunohistochemical study was performed to explore immunoreactivity for caspase-3 as an apoptotic marker. Light microscopic examination revealed structural changes in the retina of chloroquine-treated animals such as vacuolation of retinal pigment epithelial cells and photoreceptors, displacement of some cells of the outer and inner nuclear layers, pyknotic and fragmented nuclei in the inner nuclear layer as well as vascular congestion. Many caspase-3 positive cells were also observed in the inner nuclear and ganglion cell layers. Electron microscopy showed marked disorganization of photoreceptors and accumulation of lysosomes in retinal pigment epithelial cells. Condensation of nuclear chromatin was also observed in many nerve cells in inner nuclear and ganglion cell layers. Many Muller cells and microglia were detected inbetween the nerve cells. On the contrary, retinal structure was more preserved in EGb 761-treated rats. These findings suggested that EGb 761 could reduce the severity of chloroquine-induced retinopathy