Involvement of oxidative stress and mitochondrial dysfunction in the osmotic swelling of retinal glial cells from diabetic rats

Osmotic swelling of retinal glial (Muller) cells may contribute to the development of edema in diabetic retinopathy. Here, we tested whether oxidative stress and mitochondrial dysfunction are pathogenic factors involved in the osmotic swelling of Muller cells in retinal slices from control and streptozotocin-injected hyperglycemic rats. Hypotonic challenge did not change the size of Muller cell somata from control animals but induced soma swelling in Muller cells of diabetic animals. Administration of a reducing agent blocked the osmotic swelling of Muller cell somata. In retinal tissues from control animals, administration of the reducing agent blocked also the swelling-inducing effects of antagonists of P2Y(1) and adenosine A(1) receptors. In tissues from diabetic animals, inhibition of xanthine oxidase decreased the soma swelling by approximately 50% while inhibition of NADPH oxidase and nitric oxide synthase had no effects. Blockade of mitochondrial oxidative stress by perindopril, as well as of mitochondrial permeability transition by cyclosporin A or minocycline, attenuated the swelling. In addition, activation of mitochondrial K-ATP channels by pinacidil fully prevented the swelling. The data suggest that oxidative stress produced by xanthine oxidase, as well as the mitochondria, are implicated in the induction of osmotic swelling of Muller cells from diabetic rats. (C) 2010 Elsevier Ltd. All rights reserved.