Differential subcellular redistribution of protein kinase C isozymes in the rat hippocampus induced by kainic acid

Protein kinase C (PKC) consists of a family of Ca2+/phospholipid-dependent isozymes that has been implicated in the delayed neurotoxic effects of glutamate in vitro. In the present study, we assessed the effect of the glutamate analogue kainic acid (KA) on the subcellular expression of PKC isozymes in the hippocampus (HPC) in the period preceding (0.5, 1.5, 12, and 24 h) and during (120 h) hippocampal necrosis using western blot analysis and PKC isozyme-specific antibodies. Before subcellular fractionation (cytosol + membrane), hippocampi were microdissected into "HPC" (fields CA1-CA3) and "dentate gyrus" (DG; granule cells + hilus) regions. Four general patterns of alterations in PKC isozyme expression/distribution were observed following KA treatment. The first pattern was a relative stability in expression following KA treatment and was most apparent for cytosol PKCalpha (HPC + DG) and membrane (HPC) and cytosol (DG) PKCbetaII. The second pattern, observed with PKCgamma and PKCepsilon, was characterized by an initial increase in expression in both membrane and cytosolic fractions before seizure activity (0.5 h) followed by a gradual decrease until significant reductions are observed by 120 h. The third pattern, exhibited by PKCdelta, involved an apparent translocation, increasing in the membrane and decreasing in the cytosol, followed by down-regulation in both fractions and subsequent recovery. The fourth pattern was observed with PKCzeta only and entailed a significant reduction in expression before and during limbic motor seizures followed by a dramatic fivefold increase in the membrane fraction during the period of hippocampal necrosis (120 h). Although these patterns did not segregate according to conventional PKC isozyme classifications, they do indicate dynamic isozyme-specific regulation by KA. The subcellular redistribution of PKC isozymes may contribute to the histopathological sequelae produced by KA in the hippocampus and may model the pathogenesis associated with diseases involving glutamate-induced neurotoxicity.     

Effect of thiamazole on kainic acid-induced seizures in mice

Kainic acid (KA) induced epileptic seizures in mice is a commonly used experimental model of epilepsy. Previous studies have suggested the roles of various neurotransmitters and oxidative stress in KA-induced seizures. An important role of hypothyroidism has also been suggested in epilepsy. Thiamazole (TZ) is an anti-hyperthyroid drug with antioxidant property. This study reports the effect of TZ on KA-induced epileptic seizures in mice, produced by intraperitoneal (IP) injection of KA (18 mg/kg). Prior to KA injection, the animals were treated with TZ (12.5, 25 and 50 mg/kg IP). Our results showed that in KA alone group, about half of the animals developed seizures. Pre-treatment of mice with TZ significantly increased the frequency of seizures in dose-dependent manner. Administration of TZ significantly reduced the latency time and aggravated the severity of seizures. TZ also increased the mortality in KA-treated mice. Striatal dopamine and serotonin levels were markedly increased in KA alone treated mice, which were not significantly affected by TZ treatment. Among the indices of oxidative stress, we observed a significant reduction in cerebral vitamin E whereas the levels of cerebral malondialdehyde and conjugated dienes were significantly increased in animals with high severity of seizures. In conclusion, TZ potentiated the frequency and severity of experimental seizure in mice. There is a possibility of altered metabolism of KA in presence of TZ that might have potentiated the toxicity of KA. These findings suggest a caution while administering anti-hyperthyroid drugs in epileptic seizures.     

Transmitter release in hippocampal slices from rats with limbic seizures produced by systemic administration of kainic acid

The systemic injection of kainic acid (KA) has been shown to destroy neurons in the hippocampus and to induce limbic-type seizure activity. However, little is known on the neurochemical events that are associated with this convulsant effect. In the present work we studied the spontaneous and the K⁺-stimulated release of labeled -aminobutyric acid (GABA), glutamate, serotonin and dopamine, in hippocampal slices of KA-treated rats, at the moment of clinical seizures (2 h) and 72 h later. At the onset of convulsions we found a 40–45% decrease in the K⁺-stimulated release of GABA. The release of the other neurotransmitters was not significantly affected by KA treatment. After 72 h GABA release was still reduced by 30–40%. It is concluded that the epileptogenic effect of KA in the hippocampus is probably related to a diminished inhibitory GABAergic neurotransmission.     

Expression and subcellular localization of thymosin beta15 following kainic acid treatment in rat brain

Thymosin β15 (Tβ15) is a pleiotropic factor which exerts multiple roles in the development of nervous system and brain diseases. In this study, we found that the expressions of Tβ15 mRNA and protein were substantially increased in several brain regions including hippocampal formation and cerebral cortex, following kainic acid (KA)-evoked seizures in rat. Interestingly, a subset of cortex neurons exhibited nuclear Tβ15 immunoreactivity upon KA treatment. Furthermore, translocation of Tβ15 from cytosol to nuclei was observed in cultured neurons or HeLa cells during staurosporine (STS)-induced apoptosis, which was also verified by time-lapse imaging of YFP-tagged Tβ15. It appeared that localization of Tβ15 is restricted to the cytosol in normal condition by its G-actin-interacting domain, because site-directed mutagenesis of this region resulted in the nuclear localization of Tβ15 in the absence of STS treatment. To explore the role of nuclear Tβ15, we enforced Tβ15 to localize in the nuclei by fusion of Tβ15 with nuclear localization signal (NLS-Tβ15). However, overexpression of NLS-Tβ15 did not alter the viability of cells in response to STS treatment. Collectively, these results suggest that nuclear localization of Tβ15 is a controlled process during KA or STS stimulation, although its functional significance is yet to be clarified.     

Recent developments in analytical methodology for 8-hydroxy-2'-deoxyguanosine and related compounds

When biomolecules such as proteins, lipids, and DNA are subjected to oxidative attack by free radicals or other reactive species, a number of measurable biomarkers may be produced. The study of oxidative DNA damage is valuable in research concerning cancer and aging. The current review includes methodology involving various separation science techniques for the analysis of DNA oxidation biomarkers, mainly 8-hydroxy-2'-deoxyguanosine. This review will present recent analytical developments with respect to sample preparation and instrumental considerations, noting key outcomes and biological relevance where appropriate.     

Effect of α-MSH upon cyclic AMP levels induced by the glutamatergic agonists NMDA, quisqualic acid, and kainic acid

This study was carried out to investigate possible interactions between some glutamatergic agonists and the peptide α-MSH upon the cyclic AMP levels. We used an in vitro tissue slice preparation incubated in the presence of different glutamatergic agonists such as N-methyl- -aspartic acid (NMDA), quisqualic acid (QUIS), kainic acid (KA), and the peptide α-MSH together with each agonist. Slices containing caudate putamen and accumbens were chosen according to neurochemical data indicating that the striatum contains a moderate amount of MSH binding sites and also receives glutamatergic innervation. Exposure of these slices to either MSH or to the agonists NMDA or QUIS resulted in an increase in the cAMP levels in relation to controls. Nevertheless, incubation with KA resulted in no changes in the nucleotide levels. The combination of MSH/NMDA induced a reduction of cAMP levels in relation to those obtained with NMDA alone. The combinations of QUIS/MSH or KA/MSH also induced variations in the values of nucleotide in relation to the those obtained with the peptide alone or with the corresponding agonist; these changes were related to the dose of agonist used in each case. The results obtained in these experiments suggest the existence of some interaction between the peptide and the agonist used.     

Methamphetamine exacerbates the toxic effect of kainic acid in the adult rat retina

The recreational use of the psychoactive drug, methamphetamine has increased markedly over the last three decades. It has long been known that this drug has detrimental effects upon the mammalian brain monoaminergic system, but the long- or short-term effects on the retina, a neurological extension of the central nervous system, have received little attention. The aim of this study was, therefore, to determine whether intraocular injection of methamphetamine (MA) is toxic to the healthy adult rat retina and to analyse its effects on the compromised retina after an injection of the ionotropic glutamate receptor agonist, kainate, which is known to cause retinal neuropathology. The equivalent of 1 mM (in the vitreous humour) MA and/or kainate (40 μM) were injected intravitreally. Flash electroretinograms (ERGs) were recorded before and 2 and 4 days after treatment. Five days after treatment, animals were killed and the retinas analysed either for the immunohistochemical localisation of various antigens or for electrophoresis/Western blotting. Some animals were kept for 19 days after treatment and the retinas analysed for tyrosine hydroxylase immunoreactivity. No differences could be found between vehicle- and MA-treated retinas with respect to the nature or localisation of either tyrosine hydroxylase immunoreactivity after 5 or 19 days or other antigens after 5 days. Moreover, the normal ERG and GFAP and calretinin protein antigens were unaffected by MA. Kainate treatment, however, caused a change in the ERGs after 2 and 4 days, an alteration in every antigen localised by immunohistochemistry and an increase in the retinal levels of calretinin and GFAP proteins. Significantly, the changes seen in the b-wave amplitude and implicit time of the ERG after 4 days and the increased level of GFAP protein after 5 days following kainate treatment were enhanced when MA was co-injected. Intravitreal injection of methamphetamine had no detectable detrimental effect on the normal adult rat retina but exacerbated the damaging effects of kainic acid. Such data suggest that a neurotoxic effect of MA may be more obviously illustrated when the tissue is already compromised as occurs in, for example, ischemia.     

Suppression of 8-oxo-2'-deoxyguanosine formation and carcinogenesis induced by N-nitrosobis (2-oxopropyl)amine in hamsters by esculetin and esculin

Effects of esculetin (6,7-dihydroxycoumarin) and its glycoside, esculin, on 8-oxo-2'-deoxyguanosine (8-oxodG) formation and carcinogenesis induced by a chemical carcinogen, N-nitrosobis(2-oxopropyl)amine (BOP), were examined in the pancreas of female Syrian golden hamsters. Animals were administered esculetin by gastric intubation into the stomach 30 min before BOP administration or ingestion of a diet containing esculin for 7 days before BOP administration, and killed 1 or 4 h after BOP treatment, and the contents of thiobarbituric acid-reacting substrates (TBARS) and 8-oxodG in the pancreas were determined. Both compounds suppressed significantly the BOP-induced increases in 8-oxodG and TBARS contents in hamster pancreas. We further investigated the effect of esculin on pancreatic carcinogenesis by the rapid production model induced by augmentation pressure with a choline-deficient diet, ethionine, methionine and BOP. Esculin was given ad libitum as a 0.05% aqueous solution in either the initiation or promotion phases. The incidence of invasive tumors in animals given esculin during the initiation phase was significantly smaller than in the control group, while esculin given during the promotion phase showed no apparent effects. These results suggest that the intake of esculin has an inhibitory effect on BOP-induced oxidative DNA damage and carcinogenesis in hamster pancreas.     

Involvement of caspase-3-like protease in the mechanism of cell death following focally evoked limbic seizures

The cysteine protease caspase-3 may be involved in the mechanism of cell death following seizures. Using a rat model of focally evoked limbic epilepsy with continuous electroencephalography monitoring, we investigated seizure-induced changes in caspase-3 protein expression and processing, enzyme activity, and the in vivo effect of caspase-3 inhibition. Seizures were induced by intraamygdaloid injection of kainic acid (0.1 microg) and were terminated after 45 min by diazepam (30 mg/kg) administration. Animals were killed 0-72 h following diazepam administration. Levels of the 32-kDa proenzyme form of caspase-3 were unaffected by seizures. Levels of the 17-kDa cleaved (active) fragment of caspase-3 were almost undetectable in control brain, but were increased significantly at 4 and 24 h within ipsilateral hippocampus and cortex in seizure animals. Caspase-3-like protease activity was increased within the ipsilateral hippocampus at 8 and 24 h following seizures. Caspase-3 immunoreactivity was increased within the vulnerable ipsilateral CA3/CA4 subfield at 24 and 72 h following seizures and was associated predominantly, but not exclusively, with neurons exhibiting DNA fragmentation. The putatively selective caspase-3 inhibitor N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone significantly improved neuronal survival bilaterally within the hippocampal CA3/CA4 subfields following seizures. Collectively, these data suggest that caspase-3 may play a significant role in the mechanism by which neurons die following seizures.     

Neuroprotective effects of lactation against kainic acid treatment in the dorsal hippocampus of the rat

Marked hippocampal changes in response to excitatory amino acid agonists occur during pregnancy (e.g. decreased frequency in spontaneous recurrent seizures in rats with KA lesions of the hippocampus) and lactation (e.g. reduced c-Fos expression in response to N-methyl-d,l-aspartic acid but not to kainic acid). In this study, the possibility that lactation protects against the excitotoxic damage induced by KA in hippocampal areas was explored. We compared cell damage induced 24 h after a single systemic administration of KA (5 or 7.5 mg/kg bw) in regions CA1, CA3, and CA4 of the dorsal hippocampus of rats in the final week of lactation to that in diestrus phase. To determine cellular damage in a rostro-caudal segment of the dorsal hippocampus, we used NISSL and Fluorojade staining, immunohistochemistry for active caspase-3 and TUNEL, and we observed that the KA treatment provoked a significant loss of neurons in diestrus rats, principally in the pyramidal cells of CA1 region. In contrast, in lactating rats, pyramidal neurons from CA1, CA3, and CA4 in the dorsal hippocampus were significantly protected against KA-induced neuronal damage, indicating that lactation may be a natural model of neuroprotection.     

Up-regulation of base excision repair activity for 8-hydroxy-2'-deoxyguanosine in the mouse brain after forebrain ischemia-reperfusion

The repair enzyme 8-oxoguanine glycosylase/ apyrimidinic/apurinic lyase (OGG) removes 8-hydroxy-2'deoxyguanosine (oh8dG) in human cells. Our goal was to examine oh8dG-removing activity in the cell nuclei of male C57BL/6 mouse brains treated with either forebrain ischemia-reperfusion (FblR) or sham operations. We found that the OGG activity in nuclear extracts, under the condition in which other nucleases did not destroy the oligodeoxynucleotide duplex, excised oh8dG with the greatest efficiency on the oligodeoxynucleotide duplex containing oh8dG/dC and with less efficiency on the heteroduplex containing oh8dG/dT, oh8dG/dG, or oh8dG/dA. This specificity was the same as for the recombinant type 1 OGG (OGG1) of humans. We observed that the OGG1 peptide and its activity in the mouse brain were significantly increased after 90 min of ischemia and 20-30 min of reperfusion. The increase in the protein level and in the activity of brain OGG1 correlated positively with the elevation of FblR-induced DNA lesions in an indicator gene (the c-fos gene) of the brain. The data suggest a possibility that the OGG1 protein may excise oh8dG in the mouse brain and that the activity of OGG1 may have a functional role in reducing oxidative gene damage in the brain after FblR.     

The role of the glutathione system in seizures induced by diphenyl diselenide in rat pups

The present study investigated the role of the glutathione system in seizures induced by diphenyl diselenide (PhSe)₂ (50 mg/kg) in rat pups (post natal day, 12–14). Reduced glutathione (GSH) (300 nmol/site; i.c.v.), administered 20 min before (PhSe)₂, abolished the appearance of seizures, protected against the inhibition of catalase and δ-aminolevulinic dehydratase (δ-ALA-D) activities and increased glutathione peroxidase (GPx) activity induced by (PhSe)₂. Administration of l-buthionine sulfoximine (BSO, a GSH-depleting compound) (3.2 μmol/site; i.c.v.) 24 h before (PhSe)₂ increased the percentage (42–100%) of rat pups which had seizure episodes, reduced the onset for the first convulsive episode. In addition, BSO increased thiobarbituric acid reactive species (TBARS) levels and decreased GSH content, catalase, δ-ALA-D and Na⁺, K⁺-ATPase activities. Treatment with sub effective doses of GSH (10 nmol/site) and d-2-amino-7-phosphonoheptanoic acid (AP-7, an antagonist of the glutamate site at the NMDA receptor; 5 mg/kg, i.p.) abolished the appearance of seizures induced by (PhSe)₂ in rat pups. Sub effective doses of GSH and kynurenic acid (an antagonist of strychnine-insensitive glycine site at the NMDA receptor; 40 mg/kg, i.p.) were also able in abolishing the appearance of seizures induced by (PhSe)₂. In conclusion, administration of GSH protected against seizure episodes induced by (PhSe)₂ in rat pups by reducing oxidative stress and, at least in part, by acting as an antagonist of glutamate and glycine modulatory sites in the NMDA receptor.     

Effects of boric acid feeding on the oxidative stress parameters in testes,sperm parameters and DNA damage in mice

This study was aimed to determine the effects of boric acid on oxidative stress, testicular tissue and spermatozoon DNA. Experiments were performed with Swiss Albino mice divided equally into two groups based on the tratment period: one for 4 and the other for 6-week duration. These groups were further divided into subgroups as Control and those administered daily at oral doses of 115 mg/kg, 250 mg/kg and 450 mg/kg of boric acid. Then, testicular tissue were examined postmortem and analyzed using ex-vivo biochemical tools for oxidative stress, spermatozoon membrane integrity, sperm motility and live cell rate (%). In both 4 and 6-week groups, v. seminalis weight, membrane integrity, motility, live cells and GSH levels exhibited a decreasing trent compared to the controls. In addition, 6-week group had a decrease in SOD level. MDA level was higher in controls in both 4 and 6-week groups. Spermatozoon DNA was intact in the 4-week group, but damaged in the 6-week group, and the degree of the damage dependent on the administered dose. Boric acid induces oxidative stress in testicular tissue, and its long-term application (only 6 weeks) caused damage in spermatozoon DNA.     

Caffeic acid phenethyl ester (CAPE) protects brain against oxidative stress and inflammation induced by diabetes in rats

Diabetic patients reveal significant disorders, such as nephropathy, cardiomyopathy, and neuropathy. As oxidative stress and inflammation seem to be implicated in the pathogenesis of diabetic brain, we aimed to investigate the effects of caffeic acid phenethyl ester (CAPE) on oxidative stress and inflammation in diabetic rat brain. Diabetes was induced by a single dose of streptozotocin (45 mg kg⁻¹, i.p.) injection into rats. Two days after streptozotocin treatment 10 μM kg⁻¹ day⁻¹ CAPE was administrated and continued for 60 days. Here, we demonstrate that CAPE significantly decreased the levels of nitric oxide and malondialdehyde induced by diabetes, and the activities of catalase, glutathione peroxidase, and xanthine oxidase in the brain. However, glutathione levels were increased by CAPE. The mRNA expressions of tumor necrosis factor (TNF)-α and interferon (IFN)-γ, and inducible nitric oxide synthase (iNOS) were remarkably enhanced in brain by diabetes. CAPE treatments significantly suppressed these inflammatory cytokines (about 70% for TNF-α, 26% for IFN-γ) and NOS (completely). Anti-inflammatory cytokine IL-10 mRNA expression was not affected by either diabetes or CAPE treatments. In conclusion, diabetes induces oxidative stress and inflammation in the brain, and these may be contributory mechanisms involved in this disorder. CAPE treatment may reverse the diabetic-induced oxidative stress in rat brains. Moreover, CAPE reduces the mRNA expressions of TNF-α and IFN-γ in diabetic brain; suggesting CAPE suppresses inflammation as well as oxidative stress occurred in the brain of diabetic patients.     

Translesion synthesis of 7,8-dihydro-8-oxo-2'-deoxyguanosine by DNA polymerase eta in vivo

7,8-Dihydro-8-oxo-2′-deoxyguanosine (8-oxo-dG) is one of the most common DNA lesions induced by oxidative stress. This lesion can be bypassed by DNA polymerase eta (Pol η) using in vitro translesion synthesis (TLS) reactions. However, the role that Pol η plays in vivo contributing to 8-oxo-dG mutagenesis remains unclear. To clarify the role of Pol η in 8-oxo-dG mutagenesis, we have used an siRNA knockdown approach in combination with a supF shuttle vector (pSP189) which replicates in mammalian cells. The pSP189 plasmid was treated with methylene blue plus light (MBL), which produces predominantly 8-oxo-dG in DNA, and was then replicated in GM637 cells in presence of siRNA that knocks down the expression of Pol η, or in XP-V cells, which lack functional Pol η. The mutant frequencies were increased in the Pol η siRNA knockdown cells and in XP-V cells relative to control, meaning that Pol η plays an important role in preventing 8-oxo-dG mutagenesis. In the same system, knockdown of OGG1 also led to an increase in mutagenesis. Neither the type of mutations nor their distribution along the supF gene were significantly different between control and target specific siRNA-transfected cells (or XP-V cells) and were predominantly G to T transversions. These results show that Pol η has an important role in error-free 8-oxo-dG lesion bypass and avoidance of oxidative stress-induced mutagenesis in vivo.     

杏仁核注射红藻氨酸诱导大鼠边缘叶癫痫发作时海马中Smac和XIAP蛋白的表达

应用红藻氨酸(kainic acid,KA)诱导的大鼠边缘叶癫痫发作模型,检测第二个线粒体源的半胱天冬蛋白酶激活物,直接与凋亡抑制蛋白结合的低等电点蛋白(second mitochondrial activator of caspases／direct inhibitor of apoptosis protein-binding protein of low isoelectric point[PI],Smac／DIABLO)和X染色体连锁的凋亡抑制蛋白(X-chromosome-linked inhibitor of apoptosis protein,XIAP)在癫痫大鼠海马神经元表达。单侧杏仁核内注射KA诱导癫痫发作,1h后用安定终止发作,然后分别用TUNEL染色和cresyl violet染色观察海马神经元存活和凋亡的变化,用免疫荧光和Western blot检测海马Smac／DIABLO、XIAP和半胱天冬蛋白酶-9(caspase-9)的表达。结果表明,发作终止2h时KA注射同侧海马CA3区细胞浆内Smac／DIABLO蛋白表达增加,4h时caspase-9出现裂解片断,8h时出现TUNEL阳性细胞,24h时达高峰。脑室内注射caspase-9抑制剂z-LEHD-fluoromethyl ketone(z-LEHD-fmk)可减少TUNEL阳性细胞,增加存活神经元。发作后KA注射同侧海马CA3区神经元caspase-9免疫反应性增强,Smac／DIABLO和XIAP弥散于整个神经元内。对侧海马未检测到TUNEL阳性细胞及Smac／DIABLO和XIAP蛋白的上述变化。以上结果提示,癫痫发作可诱导Smac／DIABLO蛋白从线粒体向细胞浆的移位、XIAP亚细胞分布改变和caspase-9的激活,Smac／DIABLO、XIAP和caspase-9可能参与了癫痫神经元损伤的病理生理机制,caspase-9可能是潜在的治疗靶点。     

Ameliorative effect of supplementation with l-glutamine on oxidative stress,DNA damage,cell viability and hepatotoxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat hepatocyte cultures

The most potent of the dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is a persistent and ubiquitous environmental contaminant. And the health impact of exposure to TCDD is of great concern to the general public. Recent data indicate that l-glutamine (Gln) has antioxidant properties and may influence hepatotoxicity. The objective of the present study was undertaken to explore the effectiveness of Gln in alleviating the hepatotoxicity of TCDD on primary cultured rat hepatocytes. Gln (0.5, 1 and 2 mM) was added to cultures alone or simultaneously with TCDD (0.005 and 0.01 mM). The hepatocytes were treated with TCDD and Gln for 48 h. Then cell viability was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC), total glutathione (TGSH) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by liver micronucleus assay (MN) and 8-oxo-2-deoxyguanosine (8-OH-dG). The results of MTT and LDH assays showed that TCDD decreased cell viability but not l-glutamine. TCDD also increased TOS level in rat hepatocytes and significantly decreased TAC and TGSH levels. On the basis of increasing doses, the dioxin in a dose-dependent manner caused significant increases of micronucleated hepatocytes (MNHEPs) and 8-OH-dG as compared to control culture. Whereas, in cultures exposured with Gln alone, TOS levels were not changed and TAC and TGSH together were significantly increased in dose-dependent fashion. The presence of Gln with TCDD modulated the hepatotoxic effects of TCDD on primary hepatocytes cultures. Noteworthy, Gln has a protective effect against TCDD-mediated DNA damages. As conclusion, we reported here an increased potential therapeutic significance of l-glutamine in TCDD-mediated hepatic injury for the first time.     

Effects of resveratrol on nerve functions, oxidative stress and DNA fragmentation in experimental diabetic neuropathy

Oxidative stress has been implicated in pathophysiology of diabetic neuropathy. All the pathways responsible for development of diabetic neuropathy are linked to oxidative stress in one way or the other. In the present study, we have targeted oxidative stress in diabetic neuropathy using resveratrol, a potent antioxidant. Eight weeks streptozotocin-diabetic rats developed neuropathy which was evident from significant reduction in motor nerve conduction velocity (MNCV), nerve blood flow (NBF) and increased thermal hyperalgesia. The 2-week treatment with resveratrol (10 and 20 mg/kg, i.p.) started 6 weeks after diabetes induction significantly ameliorated the alterations in MNCV, NBF, and hyperalgesia. Resveratrol also attenuated enhanced levels of malondialdehyde (MDA), peroxynitrite and produced increase in catalase levels in diabetic rats. There was marked reduction in DNA fragmentation observed after resveratrol treatment in diabetic rats as evident from decrease in Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells in sciatic nerve sections. Results of the present study suggest the potential of resveratrol in treatment of diabetic neuropathy and its protective effect may be mediated through reduction in oxidative stress and DNA fragmentation.     

Melatonin reduces oxidative stress induced by ochratoxin A in rat liver and kidney

Melatonin (MEL) displays antioxidant and free radical scavenger properties. In the present study, the effect of MEL on the oxidative stress induced by ochratoxin A (OTA) administration in rats was investigated. Four groups of 15 rats each were used: controls, MEL-treated rats (5 mg/kg body mass), OTA-treated rats (250 μg/kg) and MEL+OTA-treated rats. After 4 weeks of treatment, the levels of malondialdehyde (MDA), a lipid peroxidation product (LPO) were measured in serum and homogenates of liver and kidney. Also, the levels of glutathione (GSH), and activities of glutathione reductase (GR), glutathione peroxidase (GSPx), superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) in liver and kidney were determined. In OTA-treated rats, the levels of LPO in serum and in both liver and kidney were significantly increased compared to levels in controls. Concomitantly, the levels of GSH and enzyme activities of SOD, CAT, GSPx and GR in both liver and kidney were significantly decreased in comparison with controls. In rats received MEL+OTA, the changes in the levels of LPO in serum and in liver and kidney were not statistically significant compared to controls. Concomitantly, the levels of GSPx, GR and GST activities in both liver and kidney tissues were significantly increased in comparison with controls. Similar increases in GSPx, GR and GST activities were also observed in MEL-treated rats when compared with controls. In conclusion, the oxidative stress may be a major mechanism for the toxicity of OTA. MEL has a protective effect against OTA toxicity through an inhibition of the oxidative damage and stimulation of GST activities. Thus, clinical application of melatonin as therapy should be considered in cases of ochratoxicosis.