Flavonoid,morin inhibits oxidative stress,inflammation and enhances neurotrophic support in the brain of streptozotocin-induced diabetic rats

Diabetes-induced damages in brain are known as diabetic encephalopathy, which is well characterized by cellular, molecular and functional changes in the brain of diabetic subjects and rodents. However, little is known about the mechanism of damages and the therapeutic strategies in ameliorating those damages in the diabetic brain. In this study, we utilized a flavonoid, morin which is emerging as a potent drug against a wide range of free radical-mediated as well as neurodegenerative diseases. Morin (15 and 30 mg/kg body weight/day) was orally administered to two different groups of rats after 1 week of diabetes induction, and continued for five consecutive weeks. Two other untreated groups of diabetic and non-diabetic rats were used to compare with drug-treated groups. After drug treatments, cerebral cortex of the brain harvested and analyzed for different factors. Morin supplementation especially at high dose increased the levels of insulin, reduced glutathione, superoxide dismutase and catalase activities, and decreased fasting glucose and thiobarbituric acid reactive substances in the diabetic brain compared to untreated diabetic rats (P < 0.05). Morin also significantly decreased the level of inflammatory markers (TNFα, IL1β, IL-6) in the diabetic brain compared to untreated diabetic rats. Furthermore, the drug influenced an increase in the level of neurotrophic factors (BDNF, NGF and IGF-1) in the diabetic brain compared to untreated diabetic rats (P < 0.05). Thus, our results indicate a beneficial effect of morin by decreasing oxidative stress, inflammation and increasing the neurotrophic support in the diabetic brain, which may ameliorate diabetic encephalopathy.     

缬沙坦对糖尿病大鼠脑组织氧化应激的影响

目的探讨缬沙坦对糖尿病大鼠脑组织氧化应激的影响。方法Wistar大鼠24只,随机分为正常对照组(NC组)、糖尿病组(DM1组)、糖尿病缬沙坦治疗组(DM2组),每组8只。用链脲佐菌素诱发糖尿病大鼠模型制模成功后,DM2组予以缬沙坦40mg/(kg.d)灌胃,共12周。12周后测定各组质量、血糖,Morris水迷宫试验观察大鼠认知功能,比色法测定脑组织中羟自由基(OH-)、丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性,荧光实时定量反转录-聚合酶链反应检测尼克酰胺腺嘌呤二核苷酸磷酸(NADPH)氧化酶p47phoxmRNA表达。结果(1)第12周未DM1组和DM2组质量明显轻于NC组(均P<0.01),血糖明显高于NC组(均P<0.01);DM1组与DM2组间差异无统计学意义。(2)DM1组、DM2组逃避潜伏期较NC组明显延长(P<0.01,P<0.05),DM2组较DM1组明显缩短(P<0.01)。(3)DM1组OH-、MDA水平显著高于DM2组和NC组(均P<0.01),而SOD活性显著低于DM2组和NC组(均P<0.01)。(4)NADPH氧化酶p47phox mRNA的表达量DM1组是NC组的4.89倍,DM2组是NC组的2.67倍,DM2组是DM1组的54.5%;各组间差异有统计学意义(均P<0.01)。结论缬沙坦能提高SOD的活性,降低OH-、MDA的活性和NADPH的表达,抑制机体的氧化应激水平,改善认知功能。     

Oxidative damage is ameliorated by curcumin treatment in brain and sciatic nerve of diabetic rats

To date, there have not been enough studies about the effects of curcumin against oxidative stress on sciatic nerves caused by streptozotocin (STZ) in diabetic rats. Therefore, this study was undertaken to determine whether curcumin, by virtue of its antioxidant properties, could affect the oxidant/antioxidant balance in the sciatic nerve and brain tissues of streptozotocin (STZ)-induced diabetic rats. A total of 28 rats were randomly divided into four groups of seven rats each: normal controls, only curcumin treated, diabetic controls, and diabetics treated with curcumin. Biomarkers-malondialdehyde (MDA), total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), and NO levels-for oxidative stress in the brain and sciatic nerve tissues of the rats were measured. We found a significant increase in MDA, NO, TOS, and OSI, along with a reduction in TAS levels in the brains and sciatic nerves of the STZ-induced diabetic rats (for both parameters p < 0.05). The MDA, TOS, OSI, and NO levels in these tissues were significantly reduced in the curcumin-treated diabetic group compared to the untreated diabetic group. In conclusion, the results of this study suggested that curcumin exhibits neuroprotective effects against oxidative damage in the brain and sciatic tissues of diabetic rats.     

褪黑素对糖尿病周围神经病变大鼠氧化应激及周围神经功能和形态的作用

背景：课题组前期针对糖尿病肾病的实验显示，褪黑素可以显著提高糖尿病大鼠血浆和肾脏内抗氧化酶的活性，改善肾脏的形态学变化。 目的：在前期实验的基础上，进一步观察褪黑素对糖尿病周围神经病变大鼠氧化应激和周围神经功能和形态的作用。 设计、时间及地点：随机对照动物试验，于2005-04/11在解放军第二军医大学动物实验中心完成。 材料：2月龄健康雄性SD大鼠，单次腹腔注射链脲佐菌素60 mg/kg诱导建立糖尿病大鼠模型。 方法：将糖尿病模型大鼠维持饲养8周建立糖尿病周围神经病变大鼠模型，然后按体质量随机分为3组：模型组，褪黑素0.5，10 mg/(kg?d)组，以未造模、鼠龄及体质量相匹配的8只大鼠为正常对照组。褪黑素0.5，10 mg/(kg?d)组大鼠每日16:00灌胃给予相应剂量的褪黑素，其他2组大鼠予等量体积分数为0.02的乙醇溶液灌胃，持续8周。 主要观察指标：检测各组大鼠坐骨神经内超氧化物歧化酶、谷胱甘肽过氧物酶活性和脂质过氧化产物丙二醛含量的变化，大鼠摆尾阈值、坐骨神经神经传导速度和超微结构的变化。 结果：各组糖尿病大鼠坐骨神经传导速度显著低于正常对照组 (P < 0.01)，褪黑素0.5，10 mg/(kg?d)治疗后神经传导速度高于模型组(P < 0.05，0.01)。褪黑素0.5，10 mg/（kg?d）组丙二醛含量低于模型组(P < 0.01)，血清超氧化物歧化酶、谷胱甘肽过氧物酶活性高于模型组(P < 0.01)。模型组大鼠坐骨神经多数有髓纤维髓鞘板结构破坏严重，出现裂隙、空泡等现象，轴突严重被挤压，轴突变性、萎缩。褪黑素治疗后坐骨神经纤维的髓鞘仍不正常，但较模型组明显减轻，褪黑素10 mg/(kg?d)组改变要好于褪黑素0.5 mg/(kg?d)组。 结论：褪黑素能有效抑制糖尿病周围神经病变大鼠的氧化应激反应，改善神经功能和结构变化。糖尿病时自由基损伤和抗氧化能力的降低可能在糖尿病周围神经病变的发生发展中发挥重要作用。     

Cerebrolysin improves sciatic nerve dysfunction in a mouse model of diabetic peripheral neuropathy

To examine the effects of Cerebrolysin on the treatment of diabetic peripheral neuropathy, we first established a mouse model of type 2 diabetes mellitus by administering a high-glucose, high-fat diet and a single intraperitoneal injection of streptozotocin. Mice defined as diabetic in this model were then treated with 1.80, 5.39 or 8.98 mL/kg of Cerebrolysin via intraperitoneal injections for 10 consecutive days. Our results demonstrated that the number, diameter and area of myelinated nerve fibers increased in the sciatic nerves of these mice after administration of Cerebrolysin. The results of several behavioral tests showed that Cerebrolysin dose-dependently increased the slope angle in the inclined plane test (indicating an improved ability to maintain body position), prolonged tail-flick latency and foot-licking time (indicating enhanced sensitivity to thermal and chemical pain, respectively, and reduced pain thresholds), and increased an index of sciatic nerve function in diabetic mice compared with those behavioral results in untreated diabetic mice. Taken together, the anatomical and functional results suggest that Cerebrolysin ameliorated peripheral neuropathy in a mouse model of type 2 diabetes mellitus.     

Regional blood flow in resting and stimulated sciatic nerve of diabetic rats

The role of ischemia in the pathogenesis of diabetic peripheral neuropathy remains uncertain. We used the distribution of [14C]butanol to measure resting regional sciatic nerve blood flow in normal, anesthetized rats and in rats with acute experimental diabetes from streptozotocin administration. Regional flows in hind limb biceps femoris muscle and skin were simultaneously measured. In additional diabetic rats, these blood flows were compared in both limbs after proximal electrical stimulation of one sciatic trunk (10 shocks/s) for 15 min. One month after streptozotocin administration, 8 of 11 test rats were hyperglycemic. Resting nerve blood flow in the hyperglycemic rats--5.6 +/- 3.07 ml.min-1.100 g-1--was significantly less than that in the controls (9.4 +/- 3.9 ml.min-1.100 g-1, P = 0.002). Muscle blood flow was normal and skin blood flow decreased in these rats. Calculated tissue vascular resistances were elevated in all three tissues. Stimulation of one sciatic trunk in five other diabetic rats resulted in a stimulated nerve blood flow of 15.7 +/- 7.7 ml.min-1.100 g-1, and nerve blood flow in the resting control limb was 7.7 +/- 4.3 ml.min-1.100 g-1 (P = 0.009). Muscle blood flow increased approximately fourfold on the stimulated side but skin blood flow did not increase. Resting sciatic nerve blood flow is modestly decreased in acute streptozotocin-induced diabetes, but the neural blood vessels are still responsive to the increase in nerve metabolic activity associated with nerve stimulation.     

Erythropoietin attenuates hyperoxia-induced oxidative stress in the developing rat brain

Oxygen toxicity contributes to the pathogenesis of adverse neurological outcome in survivors of preterm birth in clinical studies. In infant rodent brains, hyperoxia triggers widespread apoptotic neurodegeneration, induces pro-inflammatory cytokines and inhibits growth factor signaling cascades. Since a tissue-protective effect has been observed for recombinant erythropoietin (rEpo), we hypothesized that rEpo would influence hyperoxia-induced oxidative stress in the developing rat brain. The aim of this study was to investigate the level of glutathione (reduced and oxidized), lipid peroxidation and the expression of heme oxygenase-1 (HO-1) and acetylcholinesterase (AChE) after hyperoxia and rEpo treatment. Six-day-old Wistar rats were exposed to 80% oxygen for 2–48 h and received 20,000 IU/kg rEpo intraperitoneally (i.p.). Sex-matched littermates kept under room air and injected with normal saline or rEpo served as controls. Treatment with rEpo significantly reduced hyperoxia-induced upregulation of oxidized glutathione (GSSG) and malondialdehyde, a product of lipid breakdown, whereas reduced glutathione (GSH) was upregulated by rEpo. In parallel, hyperoxia-treated immature rat brains revealed rEpo-suppressible upregulation of synaptic AChE-S as well as of the stress-inducible AChE-R variant, together predicting rEpo-protected cholinergic signaling and restrained inflammatory reactions. Furthermore, treatment with rEpo induced upregulation of HO-1 on mRNA, protein and activity level in the developing rat brain. Our results suggest that rEpo generates its protective effect against oxygen toxicity by a reduction of diverse oxidative stress parameters and by limiting the stressor-inducible changes in both HO-1 and cholinergic functions.     

Effect of cadmium on sciatic nerve in diabetic rats: an ultrastructural study

The present study demonstrated the ultrastructural effects of diabetes and cadmium on the peripheral nervous system. In this study we used 52 healthy Swiss male albino rats. They were divided into four groups: control (C), diabetic (D), cadmium (Cd), and diabetic and cadmium (D + Cd). The diabetic condition was induced by intravenous injection of 5 mg alloxan/100 g body weight, via the caudal vein. Cd and D + Cd groups were injected with CdCl2 intraperitoneally (2 mg/Kg/week) for two months. At the end of the experimental period, animals were sacrificed and their sciatic nerves were dissected. The tissue samples were investigated by using light and electron microscopic techniques. Upon investigation, it was seen that myelinated axons in sciatic nerve of diabetic and Cd treatment groups had onion-bulb type myelin destruction, melting, and protrusion. Basal lamina of capillary endothelia of D, Cd, and D + Cd groups were thickened and the endothelial apical membrane was rough. In conclusion, Cd toxicity exacerbated the destructive effect of diabetes on the peripheral nervous system.     

Increased on oxidative brain injury in the diabetic rats following sepsis

Diabetes has been the subject of recent research by increase susceptibility to infections, thus the aim of this study was to evaluate in animal model of diabetes induced by alloxan (ALX) and subjected to sepsis the parameters of oxidative stress on the brain. Diabetes was induced in Wistar rats by ALX (150 mg/kg), and 15 days after, sepsis was induced by cecal ligation and puncture (CLP). The myeloperoxidase activity (MPO), nitrite/nitrate, oxidative damage parameters, and the activity of superoxide dismutase (SOD) and catalase (CAT) were measured in the cerebellum, hippocampus, striatum, prefrontal, and cortex in 6, 12, and 24 h after CLP. The results showed the potentiation of diabetes with sepsis. We verified these potentiation on MPO levels in the cerebellum, hippocampus, and prefrontal and an increase of the nitrite/nitrate concentration in the hippocampus, striatum, prefrontal, and cortex in 24 h after sepsis surgery. To oxidative damage, we verified in 6 h an increase on lipid and protein damage parameters in the striatum and hippocampus in 24 h. When we associate sepsis and diabetes, the SOD and CAT activity not were altered. Thus, diabetes associated with sepsis exacerbates brain damage resulting from inflammation and oxidative stress in brain. Synapse, 2014 . © 2014 Wiley Periodicals, Inc.     

Resveratrol improves cognition and reduces oxidative stress in rats with vascular dementia

Resveratrol possesses beneficial biological effects,which include anti-oxidant,anti-inflammatory and anti-carcinogenic properties.Recently,resveratrol has been shown to exhibit neuroprotective effects in models of Parkinson’s disease,cerebral ischemia and Alzheimer’s disease.However,its effects on vascular dementia remain unclear.The present study established a rat model of vascular dementia using permanent bilateral common carotid artery occlusion.At 8-12 weeks after model induction,rats were intragastrically administered 25 mg/kg resveratrol daily.Our results found that resveratrol shortened the escape latency and escape distances in the Morris water maze,and prolonged the time spent percentage and swimming distance percentage in the target quadrant during the probe test,indicating that resveratrol improved learning and memory ability in vascular dementia rats.Further experiments found that resveratrol decreased malonyldialdehyde levels,and increased superoxide dismutase activity and glutathione levels in the hippocampus and cerebral cortex of vascular dementia rats.These results confirmed that the neuroprotective effects of resveratrol on vascular dementia were associated with its anti-oxidant properties.     

Quinolinic acid induces oxidative stress in rat brain synaptosomes

The oxidative action of quinolinic acid (QUIN), and the protective effects of glutathione (GSH), and 2-amino-5-phosphonovaleric acid (APV), were tested in rat brain synaptosomes, Reactive oxygen species (ROS) formation was quantified after the exposure of synaptosomes to increasing concentrations of QUIN (25-500 microM). The potency of QUIN to induce lipid peroxidation (LP) was tested as a regional index of thiobarbituric acid-reactive substances (TBARS) production, and the antioxidant actions of both GSH (50 microM) and APV (250 microM) on QUIN-induced LP were evaluated in synaptosomes prepared from different brain regions. QUIN induced concentration-dependent increases in ROS formation and TBARS in all regions analyzed, but increased production of fluorescent peroxidized lipids only in the striatum and the hippocampus, whereas both GSH and APV decreased this index. These results suggest that the excitotoxic action of QUIN involves regional selectivity in the oxidative status of brain synaptosomes, and may be prevented by substances exhibiting antagonism at the NMDA receptor.     

Apigenin attenuates oxidative stress and neuronal apoptosis in early brain injury following subarachnoid hemorrhage

Apigenin (API) is a naturally occurring plant flavone that exhibits powerful antioxidant and antiapoptosis. Oxidative stress plays an important role in the pathogenesis of early brain injury (EBI) following subarachnoid hemorrhage (SAH). The potential anti-oxidative and anti-apoptosis effects of API on EBI following SAH, however, have not been elucidated. The aim of this study was to assess whether API alleviates EBI after SAH via its anti-oxidative and anti-apoptotic effects. The endovascular puncture model was used to induce SAH and all the rats were subsequently sacrificed at 24 h after SAH. Our data demonstrated that administration of API could significantly alleviate EBI (including neurological deficiency, brain edema, blood–brain barrier permeability, and cortical cell apoptosis) after SAH in rats. Meanwhile, API treatment reduced the reactive oxygen species (ROS) level and the concentration of malondialdehyde (MDA) and myeloperoxidase (MPO), elevated the ratio of glutathione (GSH) and oxidized glutathione (GSSG), and increased the amount of super-oxide dismutase (SOD) and hydrogen peroxide in brain cortex at 24 h following SAH. Moreover, API treatment inhibited SAH-induced the expression of Bax and caspase-3, significantly reduced neuronal apoptosis. Collectively, API exerts its neuroprotective effect likely through the dual activities of anti-oxidation and anti-apoptosis, at least partly. These data provide a basic platform to consider API may be safely used as a potential drug for treatment of SAH.     

Naringenin neutralises oxidative stress and nerve growth factor discrepancy in experimental diabetic neuropathy

Abstract

Objectives:

Present study aims to investigate the ameliorative effects of naringenin (NG) on experimentally induced diabetic neuropathy (DN) in rats.

Methods:

Diabetes was induced by single intraperitoneal injection of streptozotocin (STZ, 60?mg/kg). Naringenin (25 and 50?mg/kg/day) treatment was started 2?weeks after the diabetes induction and continued for five consecutive weeks. Pain threshold behaviour tests were performed at the end of the treatment. Serum levels of glucose, insulin and pro-inflammatory cytokines were assessed. In sciatic tissues, markers oxidative stress, cytokines and neurotrophic factors were measured.

Results:

NG treatments showed significant decrease in paw-withdrawal (P?<?0.01) and tail-flick latency (P?<?0.01). The drug attenuated the diabetic-induced changes in serum glucose, insulin and pro-inflammatory cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6). In sciatic nerve, the diabetic-induced alterations in interleukins and oxidative stress biomarkers were significantly attenuated by NG. Decreased sciatic expressions of insulin growth factor (IGF) and nerve growth factor (NGF) in diabetic rats were also ameliorated by NG. Diabetes-induced dysregulated levels of nitric oxide (NO), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were ameliorated by NG. Histological analysis showed that NG corrected the altered sciatic changes in diabetic animals.

Discussion:

We suggest that neuro-protective effect of NG molecules in sciatic nerve of diabetic rats, through its anti-diabetic as well as antioxidant and anti-inflammatory properties.     

Injury-induced activation of ERK 1/2 in the sciatic nerve of healthy and diabetic rats

Phosphorylation of extracellular-signal-regulated kinase 1/2 (p-ERK 1/2) was investigated by immunohistochemistry at 30 min, 1 h, and 48 h after nerve transection in the sciatic nerve of healthy and diabetic [streptozotocin (STZ)-induced diabetes mellitus and BioBreeding (BB; i.e. DR.lyp/lyp or BBDP)] rats. Transection injury increased the intensity of p-ERK 1/2 in nerve stumps at all time points. Staining was confined to Schwann cells with occasional faint staining in single axons. In diabetic rats, a lower intensity of p-ERK 1/2 was found at 1 and 48 h in the distal and proximal nerve stumps compared with healthy rats. STZ-induced diabetic rats were not different from BB rats. p-ERK 1/2 is activated differentially in Schwann cells after nerve injury in diabetic rats, whereas activation in STZ-induced diabetic rats did not differ from BB rats.     

Temporal course of streptozotocin-induced diabetic polyneuropathy in rats

The temporal course of diabetic polyneuropathy in a rat model plays a critical role in studies on diabetic polyneuropathy treatment. In this study, the temporal course of neuropathic symptoms was investigated in diabetic rats induced by streptozotocin and evaluated by nerve conduction velocity and behavioral assays, including the von Frey test for mechanical allodynia and the hot plate test for hyperalgesia. The results revealed that both mechanical allodynia and heat hyperalgesia started on the 2nd week, while nerve conduction velocity significantly decreased from the 1st week. In addition, the severity of allodynia did not change after the 3rd week. Hyperalgesia and nerve conduction velocity progressively aggravated even to the 8th week. Transmission electron microscopy showed that loss of unmyelinated axons, loosening of the myelin structure, and thickening of the perineurium layer were visible from the 4th week and worsened on the 8th week. Differences in the temporal course of neuropathic symptoms are discussed.     

Functional recovery and vitamin E level following sciatic nerve crush injury in normal and diabetic rats

Extensive biochemical data document the involvement of oxygen derived free radicals (ODFR) in recovery following neurotrauma as well as diabetic neuropathy. Vitamin E is considered as one of the principle protective mechanism against oxidative damage in neuronal tissue. The present study was undertaken to determine the association between functional recovery and vitamin E levels following sciatic nerve crush injury in normal and diabetic rats. The sciatic nerve of normal and streptozotocin (STZ) induced diabetic rats was crushed using a haemostat. The walking track analysis and vitamin E levels were recorded on 10, 20 and 30th day. Maximum functional deficiency and depletion of vitamin E in sciatic nerve was observed on 10th day following crush injury in both normal and diabetic animals. A progressive motor recovery and repletion of vitamin E was observed on day 20 and 30 following injury in both diabetic and normal rats. The functional recovery was slower whereas vitamin E level was higher in diabetic animals as compared to normal injured rats during healing phase suggesting that vitamin E alone may not be an efficient indicator of oxidative stress during regeneration of axons following trauma in diabetic rats.     

人神经生长因子对DPN大鼠坐骨神经CGT的作用

目的　观察人神经生长因子 ( h NGF)对早期糖尿病多发性神经病 ( DPN)大鼠坐骨神经中半乳糖神经酰胺转移酶 m RNA( CGTm RNA)表达的影响。方法　用链脲佐菌素 ( STZ)一次性腹腔注射诱导糖尿病大鼠模型 ,在 DPN 4周 (造模后 4周 )腹腔注射 h NGF( 90 U .kg- 1 .d- 1 ) ,共 4周。用 RT- PCR和免疫组化方法观察坐骨神经CGTm RNA,NGFm RNA和蛋白表达。结果　 DPN 8周大鼠坐骨神经 CGTm RNA升高 ,NGFm RNA和蛋白表达减少。用 h NGF治疗的 DPN大鼠 CGTm RNA明显降低 ,NGFm RNA和蛋白表达增加。结论　 h NGF治疗能纠正早期DPN大鼠坐骨神经 CGTm RNA异常     

Protective effect of lutein supplementation on oxidative stress and inflammatory progression in cerebral cortex of streptozotocin-induced diabetes in rats

Oxidative stress and inflammation are deemed to play a vital role in diabetic cerebral and neurological dysfunction. The present study was designed to investigate the protective effect of the naturally occurring antioxidant, lutein, against oxidative injury and inflammation in cerebral cortex (CCT) of diabetic animals. Using single IP injection of streptozotocin (STZ, 65 mg/kg) diabetes was induced in rats. Lutein dietary supplement was provided to diabetic animals for 5 consecutive weeks in three different doses. The extent of lipid peroxidation and cellular damage were estimated in CCT. Endogenous antioxidants molecules such as non-protein sulfhydryl groups (NP-SH) and enzymes including superoxide dismutase (SOD) and catalase (CAT) were also estimated in CCT. Levels of neurotrophic factors such as brain derived nerve factor (BDNF), nerve growth factor (NGF) and insulin growth factor (IGF) and pro-inflammatory cytokines, as markers for neural inflammation, were assessed in CCT. Lutein dietary supplement, significantly inhibited the diabetes induced increased in CCT levels of thiobarbituric acid reactive substances (TBARS), caspase-3, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6. Diabetes caused inhibition in the levels of NP-SH, DNA and RNA was significantly increased following lutein dietary supplementation to diabetic group compared to normal diet fed animals in dose dependent manner. Diabetes induced down regulation of BDNF, NGF and IGF was also attenuated by lutein dietary supplementation to diabetic model for 5 weeks. These findings suggest that lutein has the potential to ameliorate diabetes-induced oxidative and inflammatory damage and neural degeneration in the CCT.     

Effects of afferent and efferent denervation of vagal nerve on endotoxin-induced oxidative stress in rats

This study investigated the role of vagal innervation in oxidative stress after systemic administration of lipopolysaccharide (LPS) endotoxin. Control rats and rats subjected to bilateral subdiaphragmatic vagotomy, perivagal capsaicin application (5 mg/ml) or cholinergic receptor blockade with subcutaneous atropine (1 mg/kg), were intraperitoneally injected with 300 μg/kg of LPS and euthanized 4 h later. Results indicated that; (1) surgical vagotomy and sensory denervation by perivagal capsaicin increased brain oxidative stress and decreased reduced glutathione in basal condition (saline-treated rats) and following endotoxin challenge; (2) oxidative stress decreased after cholinergic blockade with atropine in endotoxemic rats; (3) nitric oxide decreased by abdominal vagotomy, sensory deafferentation and cholinergic blockade after endotoxin injection; (4) liver lipid peroxidation decreased after surgical vagotomy and cholinergic blockade but increased after sensory deafferentation; (5) liver reduced glutathione decreased following vagotomy and sensory denervation in basal state and by cholinergic blockade in basal state and during endotoxemia; (6) nitric oxide increased by vagotomy in basal state and by sensory denervation and cholinergic blockade in basal state and during endotoxemia; (7) liver histological damage increased by subdiaphragmatic vagotomy, sensory denervation or cholinergic blockade. These findings suggest that: (1) sensory fibers (signals from the periphery) running in the vagus nerves are important in maintaining the redox status of the brain; (2) capsaicin vagal sensory nerves are likely to maintain nitric oxide tone in basal conditions; (3) the vagus nerve modulates liver redox status and nitric oxide release, (4) the vagus nerve mediates protective role in the liver with both cholinergic and capsaicin-sensitive mechanisms being involved.     

Taurine counteracts oxidative stress and nerve growth factor deficit in early experimental diabetic neuropathy

Oxidative stress has a key role in the pathogenesis of diabetic complications. We have previously reported that taurine (T), which is known to counteract oxidative stress in tissues (lens, kidney, retina) of diabetic rats, attenuates nerve blood flow and conduction deficits in early experimental diabetic neuropathy (EDN). The purpose of this study was to evaluate whether dietary T supplementation counteracts oxidative stress and the nerve growth factor (NGF) deficit in the diabetic peripheral nerve. The experiments were performed in control rats and streptozotocin‐diabetic rats fed standard or 1% T‐supplemented diets for 6 weeks. All measurements were performed in the sciatic nerve. Malondialdehyde (MDA) plus 4‐hydroxyalkenals (4‐HA) were quantified with N‐methyl‐2‐phenylindole. GSH, GSSG, dehydroascorbate (DHAA), and ascorbate (AA) were assayed spectrofluorometrically, T by reverse‐phase HPLC, and NGF by ELISA. MDA plus 4‐HA concentration (mean +/? SEM) was increased in diabetic rats (0.127 +/?0.006 vs 0.053 +/?0.003 mu mol/g in controls, P<0.01), and this increase was partially prevented by T (0.0960.004, P<0.01 vs untreated diabetic group). GSH levels were similarly decreased in diabetic rats treated with or without taurine vs controls. GSSG levels were similar in control and diabetic rats but were lower in diabetic rats treated with T (P<0.05 vs controls). AA levels were decreased in diabetic rats (0.133+0.015 vs 0.219 +/?0.023 mu mol/g in controls, P<0.05), and this deficit was prevented by T. DHAA/AA ratio was increased in diabetic rats vs controls (P<0.05), and this increase was prevented by T. T levels were decreased in diabetic rats (2.7 +/?0.16 vs 3.8 +/?0.1 mu mol/g in controls, P<0.05) and were repleted by T supplementation (4.20.3). NGF levels were decreased in diabetic rats (2.35 +/?0.20 vs 3.57 +/?0.20 ng/g in controls, P<0.01), and this decrease was attenuated by T treatment (3.160.28, P<0.05 vs diabetic group). In conclusion, T counteracts oxidative stress and the NGF deficit in early EDN. Antioxidant effects of T in peripheral nerve are, at least in part, mediated through the ascorbate system of antioxidative defense. The findings are consistent with the important role for oxidative stress in impaired neurotrophic support in EDN.