Effect of lipoic acid on expression of angiogenic factors in diabetic rat retina

Background: This study evaluated the effect of a lipoic acid on reactive oxygen species formation and the simultaneous changes of several angiogenic factors in an experimental diabetic rat retina. Methods: Diabetes was induced chemically by intraperitoneal injection of streptozotocin in 30 Sprague-Dawley rats. After inducing diabetes, lipoic acid (10 mg/kg) was administered to 10 rats orally. The rats were divided into normal, diabetes mellitus, and lipoic acid-treated groups (each group n = 10). The eyeballs were harvested 8 weeks after inducing diabetes. The expression of vascular endothelial growth factor, erythropoietin, angiopoietin 1 and 2 and NADPH oxidase was examined in the rat retina using reverse transcription-polymerase chain reaction and Western blot. Superoxide formation was examined using dihydroethidium stain. Results: Dihydroethidium analyses showed increased superoxide formation in the retina of the diabetic group. The superoxide formation was suppressed with lipoic acid treatment. Western blot analysis showed that NADPH oxidase was decreased in the diabetic group and returned to normal level in the lipoic acid-treated group. Treatment with lipoic acid blocked hyperglycaemia induced increases of vascular endothelial growth factor, angiopoietin 2 and erythropoietin shown by reverse transcription-polymerase chain reaction and Western blot analysis. Conclusions: Lipoic acid treatment suppressed expression of vascular endothelial growth factor, angiopoietin 2 and erythropoietin via blockade of superoxide formation. Antioxidant treatment is suspected to have an antiangiogenic effect.