OBJECTIVEEstablishing Caenorhabditis elegans as a model for glucose toxicity–mediated life span reduction.RESEARCH DESIGN AND METHODSC. elegans were maintained to achieve glucose concentrations resembling the hyperglycemic conditions in diabetic patients. The effects of high glucose on life span, glyoxalase-1 activity, advanced glycation end products (AGEs), and reactive oxygen species (ROS) formation and on mitochondrial function were studied.RESULTSHigh glucose conditions reduced mean life span from 18.5 ± 0.4 to 16.5 ± 0.6 days and maximum life span from 25.9 ± 0.4 to 23.2 ± 0.4 days, independent of glucose effects on cuticle or bacterial metabolization of glucose. The formation of methylglyoxal-modified mitochondrial proteins and ROS was significantly increased by high glucose conditions and reduced by mitochondrial uncoupling and complex IIIQo inhibition. Overexpression of the methylglyoxal–detoxifying enzyme glyoxalase-1 attenuated the life-shortening effect of glucose by reducing AGE accumulation (by 65%) and ROS formation (by 50%) and restored mean (16.5 ± 0.6 to 20.6 ± 0.4 days) and maximum life span (23.2 ± 0.4 to 27.7 ± 2.3 days). In contrast, inhibition of glyoxalase-1 by RNAi further reduced mean (16.5 ± 0.6 to 13.9 ± 0.7 days) and maximum life span (23.2 ± 0.4 to 20.3 ± 1.1 days). The life span reduction by glyoxalase-1 inhibition was independent from the insulin signaling pathway because high glucose conditions also affected daf-2 knockdown animals in a similar manner.CONCLUSIONSC. elegans is a suitable model organism to study glucose toxicity, in which high glucose conditions limit the life span by increasing ROS formation and AGE modification of mitochondrial proteins in a daf-2 independent manner. Most importantly, glucose toxicity can be prevented by improving glyoxalase-1–dependent methylglyoxal detoxification or preventing mitochondrial dysfunction.

SummaryStudies of mutations affecting lifespan in Caenorhabditis elegans show that mitochondrial generation of reactive oxygen species (ROS) plays a major causative role in organismal aging. Here, we describe a novel mechanism for regulating mitochondrial ROS production and lifespan in C . elegans : progressive mitochondrial protein modification by the glycolysis-derived dicarbonyl metabolite methylglyoxal (MG). We demonstrate that the activity of glyoxalase-1, an enzyme detoxifying MG, is markedly reduced with age despite unchanged levels of glyoxalase-1 mRNA. The decrease in enzymatic activity promotes accumulation of MG-derived adducts and oxidative stress markers, which cause further inhibition of glyoxalase-1 expression. Over-expression of the C . elegans glyoxalase-1 orthologue CeGly decreases MG modifications of mitochondrial proteins and mitochondrial ROS production, and prolongs C . elegans lifespan. In contrast, knock-down of CeGly increases MG modifications of mitochondrial proteins and mitochondrial ROS production, and decreases C . elegans lifespan.

Molecular events that result in loss of pain perception are poorly understood in diabetic neuropathy. Our results show that the receptor for advanced glycation end products (RAGE), a receptor associated with sustained NF-κB activation in the diabetic microenvironment, has a central role in sensory neuronal dysfunction. In sural nerve biopsies, ligands of RAGE, the receptor itself, activated NF-κBp65, and IL-6 colocalized in the microvasculature of patients with diabetic neuropathy. Activation of NF-κB and NF-κB-dependent gene expression was upregulated in peripheral nerves of diabetic mice, induced by advanced glycation end products, and prevented by RAGE blockade. NF-κB activation was blunted in RAGE-null (RAGE -/-) mice compared with robust enhancement in strain-matched controls, even 6 months after diabetes induction. Loss of pain perception, indicative of long-standing diabetic neuropathy, was reversed in WT mice treated with soluble RAGE. Most importantly, loss of pain perception was largely prevented in RAGE -/-mice, although they were not protected from diabetes-induced loss of PGP9.5-positive plantar nerve fibers. These data demonstrate, for the first time to our knowledge, that the RAGE-NF-κB axis operates in diabetic neuropathy, by mediating functional sensory deficits, and that its inhibition may provide new therapeutic approaches.

Previous studies have shown that renal function in type 2 diabetes correlates better with tubular changes than with glomerular pathology. Since advanced glycation end products (AGEs; AGE-albumin) and in particular carboxymethyllysine (CML) are known to play a central role in diabetic nephropathy, we studied the activation of nuclear factor B (NF-B) in tubular epithelial cells in vivo and in vitro by AGE-albumin and CML. Urine samples from healthy control subjects (n ‫؍‬ 50) and type 2 diabetic patients (n ‫؍‬ 100) were collected and tested for excretion of CML and the presence of proximal tubular epithelial cells (pTECs). CML excretion was significantly higher in diabetic patients than in healthy control subjects (P < 0.0001) and correlated with the degree of albuminuria (r ‫؍‬ 0.7, P < 0.0001), while there was no correlation between CML excretion and HbA 1c (r ‫؍‬ 0.03, P ‫؍‬ 0.76). Urine sediments from 20 of 100 patients contained pTECs, evidenced by cytokeratin 18 positivity, while healthy control subjects (n ‫؍‬ 50) showed none (P < 0.0001). Activated NF-B could be detected in the nuclear region of excreted pTECs in 8 of 20 patients with pTECs in the urine sediment (40%).

BackgroundCisplatin (CP) is known as a potent anti-cancer drug. The most therapeutic adverse effect of CP is induced hepatotoxicity. In the present study, the protective effect of thymoquinone (TQ) on CP-induced hepatotoxicity was studied.MethodsWistar rats were divided into three groups (15 rats each). Group 1 served as the control group. Group 2 rats were injected ip with a single dose of CP (12 mg/kg b.w, i.p.). Group 3 rats were orally pre-treated with TQ (500 mg. kg−1. day−1) for one month, then the animals were injected i.p with CP 12 mg.kg−1.ResultsThe beneficial effects of TQ with its antioxidant/anti-inflammatory effects were observed. Injection of rats with CP markedly affected the liver functions and histopathological changes. The antioxidant enzyme activities and reduced glutathione (GSH) contents were significantly decreased while the levels of malondialdehyde (MDA) significantly increased. The electromobility shift assay (EMSA) showed a significant activation of NF-κB-p65 in the rat liver injected with CP. Furthermore, the expression and concentrations of inflammatory tumor necrosis factor (TNF-α), nitric oxide synthetase (iNOS), and interleukin (IL-1β) were markedly elevated in the CP injected rats. The administration of TQ improved all the altered functions, histopathology of the liver and attenuated the activated NF-κB. The antioxidant enzyme activities (glutathione peroxidase and glutathione –S transferase) of the rat livers were markedly increased while MDA was reduced as a result of TQ administration. In addition, the expression of TNF-α, iNOS, and IL-1β were markedly reduced.ConclusionIt was concluded that, TQ has potential benefits in the prevention of the onset and progression of CP induced hepatotoxicity.