Iron chelation abrogates excessive formation of hydroxyl radicals and lipid peroxidation products in monocytes of patients with Eales' disease: Direct evidence using electron spin resonance spectroscopy

Abstract

Purpose. Eales' disease (ED) is an idiopathic retinal vasculitis condition, which affects the retina of young adult males. Retinal changes include perivasculitis, non-perfusion and neovascularization. Disruption of blood-retinal barrier (BRB) is the common feature in intra-ocular inflammatory diseases. Disruption of BRB results in vascular hyper permeability and infiltration of circulating leukocytes into the retinal parenchyma. Monocyte (MC) activation results in oxidant thrust and subsequent tissue damage. This has been reported in various intra-ocular inflammatory diseases such as uveitis and Behcet's disease. However, there are no such reports available in ED. Hence in the present study we have investigated the role of MC activation and hydroxyl radicals (•OH) production and its possible involvement in promoting the development of retinal vasculitis in patients with ED. Methods. Twelve patients with ED and twelve healthy volunteers were recruited for the study. MC was separated from their peripheral blood. MC from patients with ED and control subjects was stimulated with phorbol-12-myristate - acetate (PMA) and •OH generated was analyzed using an electron spin resonance spectrometer (ESR). Superoxide dismutase (SOD), thiobarbituric acid reactive substances (TBARS), and iron content was determined in MC to assess the oxidant thrust and antioxidant defense. Results. •OH generation was elevated in MC from patients with ED, which coincided with diminished SOD activity and elevated levels of iron and TBARS, when compared with healthy control subjects. •OH generation was abrogated when MC from ED were co-incubated with PMA and iron chelators such as diethylenetriaminepentacetic acid (DTPA) and desferrioxamine. Iron chelation also inhibited TBARS accumulation restored SOD activity in MC of patients with ED. Conclusions. For the first time we have demonstrated the production of •OH generation in MC of patients with ED using ESR. Further we have shown the beneficial effect of iron chelation in mitigating free radical mediated changes in cellular metabolism. Based on our findings, we provide further evidence for the role of oxidant thrust in promoting retinal tissue damage in patients with ED.