Activation of ECs and induction of tissue factor by AGE albumin in ECs is dependent on RAGE.

Depletion of cellular antioxidant defense mechanisms and the generation of oxygen free radicals by advanced glycation end products (AGEs) have been proposed to play a major role in the pathogenesis of diabetic vascular complications. Here we demonstrate that incubation of cultured bovine aortic endothelial cells (BAECs) with AGE albumin (500 nmol/l) resulted in the impairment of reduced glutathione (GSH) and ascorbic acid levels. As a consequence, increased cellular oxidative stress led to the activation of the transcription factor NF-kappaB and thus promoted the upregulation of various NF-kappaB-controlled genes, including endothelial tissue factor. Supplementation of the cellular antioxidative defense with the natural occurring antioxidant alpha-lipoic acid before AGE albumin induction completely prevented the AGE albumin-dependent depletion of reduced glutathione and ascorbic acid. Electrophoretic mobility shift assays (EMSAs) revealed that AGE albumin-mediated NF-kappaB activation was also reduced in a time- and dose-dependent manner as long as alpha-lipoic acid was added at least 30 min before AGE albumin stimulation. Inhibition was not due to physical interactions with protein DNA binding, since alpha-lipoic acid, directly included into the binding reaction, did not prevent binding activity of recombinant NF-kappaB. Western blots further demonstrated that alpha-lipoic acid inhibited the release and translocation of NF-kappaB from the cytoplasm into the nucleus. As a consequence, alpha-lipoic acid reduced AGE albumin-induced NF-kappaB mediated transcription and expression of endothelial genes relevant in diabetes, such as tissue factor and endothelin-1. Thus, supplementation of cellular antioxidative defense mechanisms by extracellularly administered alpha-lipoic acid reduces AGE albumin-induced endothelial dysfunction in vitro.

Increased oxidative stress generated by hyperglycaemia, hyperlipidaemia or the presence of advanced glycation endproducts (AGEs) or both is regarded as an important mediator of late diabetic complications [1]. A clear relation between the quality of glycaemic control and the presence of free radicals has been shown thereby relating the appearance of oxidative stress to the underlying metabolic disorder rather than to the complication itself [2]. The presence of oxygen free radicals and the simultaneous decline of antioxidative defence mechanisms observed in diabetic patients could therefore promote the development of late diabetic complications [1, 3±5].Oxidative stress has been proposed as a major cause of diabetic nephropathy [6±9]. Animal models implicate that oxidative stress accompanying the early onset of diabetes increases the kidney's susceptibility to develop diabetic nephropathy [10]. One possible mechanism for this is the activation of the oxidative stress sensitive transcription factor NF-kB [6, 11±13]. Translocation of activated NF-kB into the nucleus results in gene expression of NF-kB controlled Diabetologia (1999) 42: 222±232 Peripheral blood mononuclear cells isolated from patients with diabetic nephropathy show increased activation of the oxidative-stress sensitive transcription factor NF-kB

Hyperglycemia induces activation of the transcription factor NF-kappa B in ex vivo-isolated PBMCs of patients with type 1 diabetes. NF-kappa B activation is at least partially dependent on oxidative stress, since the antioxidant thioctic acid significantly lowered the extent of NF-kappa B binding activity.

This exploratory analysis suggests that the use of gabapentin, lamotrigine, oxcarbazepine, and tiagabine, compared with the use of topiramate, may be associated with an increased risk of suicidal acts or violent deaths.