8-hydroxy-2--deoxyguanosine and Diabetic-Neuropathies

Spinal cord neurons located in laminae I-III respond to nociceptive stimuli and participate in the transmission of painful information to the brain. In the present study we evaluated if nociceptive laminae I-III neurons are affected by oxidative stress damage in a model of diabetic neuropathic pain (DNP), the streptozotocin-induced diabetic rat (STZ rat). Additionally, we evaluated the effects of a preventive antioxidant treatment with epigallocatechin-gallate (EGCG) in nociceptive neuronal activation and behavioural signs of DNP. Three days after diabetes induction, a treatment protocol of STZ rats with an aqueous solution of EGCG in the drinking water was initiated. Ten weeks after the onset of treatment, the spinal cords were immunoreacted against validated markers of oxidative stress damage (8-hydroxy-2'-deoxyguanosine; 8-OHdG) and of nociceptive neuronal activation (Fos). Mechanical hypersensitivity was assessed before and after EGCG treatment. Untreated STZ rats presented increased levels of 8-OHdG immunoreaction, higher numbers of Fos-immunoreacted neurons and high levels of co-localization of 8-OHdG and Fos in laminae I-III. Treatment with EGCG normalized the increase of the above mentioned parameters and ameliorated mechanical hypersensitivity. The present study shows that nociceptive neurons in spinal cord laminae I-III exhibit oxidative stress damage during diabetic neuropathy, which probably affects ascending pain transmission during DNP. The neurobiological mechanisms and translational perspectives of the beneficial effects of a preventive and sustained EGCG treatment in DNP need to be evaluated in the future.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Catechin; Deoxyguanosine; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Hyperalgesia; Immunohistochemistry; Male; Neuralgia; Neuroprotective Agents; Nociceptors; Oxidative Stress; Proto-Oncogene Proteins c-fos; Rats, Wistar; Spinal Cord; Touch

Neural vascular insufficiency plays an important role in diabetic peripheral neuropathy (DPN). Peroxisome proliferative-activated receptor (PPAR)α has an endothelial protective effect related to activation of PPARγ coactivator (PGC)-1α and vascular endothelial growth factor (VEGF), but its role in DPN is unknown. We investigated whether fenofibrate would improve DPN associated with endothelial survival through AMPK-PGC-1α-eNOS pathway. Fenofibrate was given to db/db mice in combination with anti-flt-1 hexamer and anti-flk-1 heptamer (VEGFR inhibition) for 12 weeks. The db/db mice displayed sensory-motor impairment, nerve fibrosis and inflammation, increased apoptotic cells, disorganized myelin with axonal shrinkage and degeneration, fewer unmyelinated fibers, and endoneural vascular rarefaction in the sciatic nerve compared to db/m mice. These findings were exacerbated with VEGFR inhibition in db/db mice. Increased apoptotic cell death and endothelial dysfunction via inactivation of the PPARα-AMPK-PGC-1α pathway and their downstream PI3K-Akt-eNOS-NO pathway were noted in db/db mice, human umbilical vein endothelial cells (HUVECs) and human Schwann cells (HSCs) in high-glucose media. The effects were more prominent in response to VEGFR inhibition. In contrast, fenofibrate treatment ameliorated neural and endothelial damage by activating the PPARα-AMPK-PGC-1α-eNOS pathway in db/db mice, HUVECs and HSCs. Fenofibrate could be a promising therapy to prevent DPN by protecting endothelial cells through VEGF-independent activation of the PPARα-AMPK-PGC-1α-eNOS-NO pathway.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adenosine Monophosphate; AMP-Activated Protein Kinases; Animals; Blood Glucose; Body Weight; Cell Survival; Deoxyguanosine; Diabetic Neuropathies; Disease Models, Animal; Endothelial Cells; Fenofibrate; Fibrosis; Glycated Hemoglobin; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Lipids; Mice; Neural Conduction; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Platelet Endothelial Cell Adhesion Molecule-1; PPAR alpha; Receptors, Vascular Endothelial Growth Factor; Schwann Cells; Sciatic Nerve; Sciatic Neuropathy; Transcription Factors; Transforming Growth Factor beta1

Fidarestat, an aldose reductase inhibitor (ARI), has been reported to improve clinical symptoms and nerve conduction deficits in human diabetic neuropathy. We evaluated the dose-dependency and some of the mechanisms of the drug action in experimental diabetic neuropathy (EDN).. Control rats and rats with EDN were fed on normal pellets or pellets containing 0.00066% (1 mg/kg) or 0.00263% (4 mg/kg) fidarestat for 10 weeks. We evaluated the effect of fidarestat on nerve blood flow (NBF), electrophysiology, and sorbitol and fructose content in sciatic nerve in control and diabetic rats. For detection of oxidative stress in peripheral nerve, we measured sciatic nerve reduced glutathione (GSH) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunolabelling of dorsal root ganglion (DRG) neurons.. NBF, compound muscle action potential and amplitude of C-potential were significantly improved in diabetic rats fed on the diet supplemented with fidarestat. Fidarestat suppressed the increase in sorbitol and fructose, normalised GSH in sciatic nerve, and reduced the number of 8-OHdG-positive cells in DRG.. Fidarestat improves neuropathy, presumably via an improvement in oxidative stress. This study supports a role for fidarestat in the treatment of diabetic neuropathy.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aldehyde Reductase; Animals; Blood Flow Velocity; Deoxyguanosine; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Ganglia, Spinal; Glutathione; Imidazolidines; Male; Mice; Neurons; Rats; Rats, Sprague-Dawley; Sciatic Nerve

We examined the ability of a pyridoxal-aminoguanidine adduct with both antiglycation and antioxidant activities in vitro to protect against neuropathy and cataract in streptozotocin-diabetic rats and compared the result with that of aminoguanidine. In vivo antiglycation and antioxidant activities were also compared between the adduct and aminoguanidine. Diabetic rats were given either of the compounds in their drinking water (9 mM) for 7 weeks. Neither compound affected body weight, blood glucose level or urine volume. The adduct, but not aminoguanidine, significantly improved motor nerve conduction velocity. The time to develop cataract was longer in adduct-treated rats than in untreated and aminoguanidine-treated rats. The increase in opacification of lenses in culture medium containing high glucose levels (55.5 mM) was more efficiently attenuated by the adduct than by aminoguanidine. Adduct and aminoguanidine similarly lowered glycated hemoglobin levels. The level of urinary 8-hydroxy-2'-deoxyguanosine, a marker of oxidative DNA damage, and the level of liver malondialdehyde plus 4-hydroxy-2-alkenals, a marker of tissue lipid peroxidation, both of which were elevated by diabetes, were significantly reduced by the adduct but not by aminoguanidine. These findings indicate that the pyridoxal-aminoguanidine adduct is superior to aminoguanidine in preventing diabetic neuropathy and cataracts, and we suggest that this may be at least partly due to the higher antioxidant activity of the former.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Cataract; Deoxyguanosine; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Dose-Response Relationship, Drug; Glucose; Glycated Hemoglobin; Guanidines; In Vitro Techniques; Lens, Crystalline; Lipid Peroxidation; Liver; Male; Motor Neurons; Neural Conduction; Pyridoxal; Rats; Rats, Wistar; Time Factors

We evaluated the effects of chronic hyperglycemia on L5 dorsal root ganglion (DRG) neurons using immunohistochemical and electrophysiologic techniques for evidence of oxidative injury. Experimental diabetic neuropathy was induced by streptozotocin. To evaluate the pathogenesis of the neuropathy, we studied peripheral nerve after 1, 3, and 12 months of diabetes. Electrophysiologic abnormalities were present from the first month and persisted over 12 months. 8-Hydroxy-2'-deoxyguanosine labeling was significantly increased at all time points in DRG neurons, indicating oxidative injury. Caspase-3 labeling was significantly increased at all three time points, indicating commitment to the efferent limb of the apoptotic pathway. Apoptosis was confirmed by a significant increase in the percentage of neurons undergoing apoptosis at 1 month (8%), 3 months (7%), and 12 months (11%). These findings support the concept that oxidative stress leads to oxidative injury of DRG neurons, with mitochondrium as a specific target, leading to impaired mitochondrial function and apoptosis, manifested clinically as a predominantly sensory neuropathy.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoptosis; Caspase 3; Caspases; Chronic Disease; Deoxyguanosine; Diabetic Neuropathies; Electrophysiology; Ganglia, Spinal; Histocytochemistry; In Situ Nick-End Labeling; Male; Neurons; Oxidative Stress; Rats; Rats, Sprague-Dawley

Recently, much attention has focused on the role of oxidative stress in the various forms of tissue damage in patients with diabetes. The aim of this study was to examine the involvement of oxidative stress in the progression of kidney dysfunction and neuropathy in diabetes and to evaluate the potential usefulness of glutathione (GSH) in diabetes. We examined the effect that treatment of streptozotocin (STZ)-induced diabetic rats with GSH has on the renal and neural functions. Diabetic rats were treated with 1 g/100 g GSH as a dietary supplement. GSH significantly suppressed the diabetes-induced increase in urinary 8-hydroxy-2'-deoxyguanosine, one of the markers of oxidative stress. It also prevented the diabetes-induced increases in albumin and creatinine in urine. The diabetes-induced increase in the tail flick reaction time to thermal stimuli also was normalized by treatment with dietary GSH. In conclusion, GSH treatment can beneficially affect STZ-induced diabetic rats, with preservation of in vivo renal and neural function. This suggests a potential usefulness of dietary GSH treatment to reduce diabetic complications.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Albuminuria; Animals; Blood Glucose; Creatinine; Deoxyguanosine; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Diabetic Neuropathies; Dietary Supplements; Disease Models, Animal; Glutathione; Hot Temperature; Male; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Wistar; Streptozocin