Graded sensitiveness of the various retinal neuron populations on the glyoxal-mediated formation of advanced glycation end products and ways of protection

The accumulation of advanced glycation end products (AGEs) in retinal cells is known to be associated with the risk of diabetic retinopathy. To develop a model of AGE-related metabolic stress in retinal organ cultures, we investigated the accumulation of a typical glycoxidation product (N(epsilon)-[carboxymethyl] lysine [CML]) and its possible pro-apoptotic effects on different retinal cell populations. Retinal organ cultures (rat) were kept for 9 h in the Ames medium containing 0 (control), 5, 25, 50, 150, 300 and 800 micro M glyoxal. The expression of bax, active caspase-3, and the accumulation of CML were studied by using immunohistochemistry after the paraffin embedding of retinal explants. Apoptosis was studied using the terminal deoxynucleotidyl transferase-mediated dUTP digoxigenin nick end labeling (TUNEL) test and electron microscopy. Alpha lipoic acid (alpha-LA), sodium metavanadate (NaVO(3)), N-acetylcysteine (NAC), aminoguanidine (AG), and nicotinamide (NA) were used to influence glyoxal effects in organ cultures. In cultured normal non-diabetic retinae, small amounts of CML and the apoptosis-promoting factors bax and active caspase-3 were present. CML, bax and active caspase-3 increased after incubation with glyoxal. Incubation with glyoxal (