Jing-Shan Shi

Neuroprotective effect of resveratrol on 6-OHDA-induced Parkinson's disease in rats.

The present study was undertaken to investigate the neuroprotective effects of resveratrol on 6-hydroxydopamine (6-OHDA)-induced Parkinsons disease in rats. 6-OHDA-induced Parkinsons disease rat model involves chronic inflammation, mitochondrial dysfunction, and oxidative stress, and the loss of the dopaminergic neurons in the substantia nigra is the predominant lesion. Resveratrol has been shown to have anti-inflammatory actions, and thus was tested for its beneficial effects using 6-OHDA-induced Parkinsons disease rat model. Adult Sprague-Dawley (SD) rats were unilaterally injected with 6-OHDA (5 microg/2 microl) into the right striatum, and the striatum damage was assessed by rotational test, ultrahistopathology, and molecular alterations. Resveratrol (10, 20 and 40 mg/kg) was then given orally to Parkinsons disease rats, daily for 10 weeks to examine the protective effects. Rotational test (turns of rats) showed that resveratrol significantly attenuated apomorphine-induced turns of rats in 6-OHDA-injuried Parkinsons disease rat model as early as two weeks of administration. Ultrastructural analysis showed that resveratrol alleviated 6-OHDA-induced chromatin condensation, mitochondrial tumefaction and vacuolization of dopaminergic neurons in rat substantia nigra. Furthermore, resveratrol treatment also significantly decreased the levels of COX-2 and TNF-alpha mRNA in the substantia nigra as detected by real-time RT-PCR. COX-2 protein expression in the substantia nigra was also decreased as evidenced by Western blotting. These results demonstrate that resveratrol exerts a neuroprotective effect on 6-OHDA-induced Parkinsons disease rat model, and this protection is related to the reduced inflammatory reaction.

Anti-inflammatory activities of resveratrol in the brain: Role of resveratrol in microglial activation

Neuroinflammation is an important contributor to pathogenesis of neurological disorders, with microglial activation as a hallmark of neuroinflammation. Microglia serve the role of immune surveillance under normal conditions, but after brain damage or exposure to inflammation, microglia are activated and secrete pro-inflammatory and neurotoxic mediators. Sustained production of these factors contributes to neuronal damage. Therefore, inhibition of microglia-mediated neuroinflammation may become a promising therapeutic target for neurological disorders. Resveratrol, a non-flavonoid polyphenol rich in red wine and grapes, has beneficial health effects from its antioxidant, anticancer and anti-inflammatory properties. Recently, resveratrol has been shown to protect against various neurological disorders in experimental models, including brain ischemia, seizures, and neurodegenerative disease models. This minireview summarized the anti-inflammatory activities of resveratrol in the brain from both in vivo and in vitro studies, and highlighted the inhibition of activated microglia as a potential mechanism of neuroprotection. The release of various pro-inflammatory factors, the production of reactive oxygen species, and the activation of signal pathways leading to neuroinflammation were discussed in relation to microglial activation. Taken together, microglia are an important target for anti-inflammatory activities of resveratrol in the brain.

Resveratrol protects dopamine neurons against lipopolysaccharide-induced neurotoxicity through its anti-inflammatory actions.

Parkinsons disease (PD) is the second most common neurodegenerative disease characterized by a progressive loss of dopamine (DA) neurons in the substantia nigra. Accumulating evidence indicates that inhibition of microglia-mediated neuroinflammation may become a reliable protective strategy for PD. Resveratrol, a nonflavonoid polyphenol naturally found in red wine and grapes, has been known to possess antioxidant, anticancer, and anti-inflammatory properties. Although recent studies have shown that resveratrol provided neuroprotective effects against ischemia, seizure, and neurodegenerative disorders, the mechanisms underlying its beneficial effects on dopaminergic neurodegeneration are poorly defined. In this study, rat primary midbrain neuron-glia cultures were used to elucidate the molecular mechanisms underlying resveratrol-mediated neuroprotection. The results clearly demonstrated that resveratrol protected DA neurons against lipopolysaccharide (LPS)-induced neurotoxicity in concentration- and time-dependent manners through the inhibition of microglial activation and the subsequent reduction of proinflammatory factor release. Mechanistically, resveratrol-mediated neuroprotection was attributed to the inhibition of NADPH oxidase. This conclusion is supported by the following observations. First, resveratrol reduced NADPH oxidase-mediated generation of reactive oxygen species. Second, LPS-induced translocation of NADPH oxidase cytosolic subunit p47 to the cell membrane was significantly attenuated by resveratrol. Third and most importantly, resveratrol failed to exhibit neuroprotection in cultures from NADPH oxidase-deficient mice. Furthermore, this neuroprotection was also related to an attenuation of the activation of mitogen-activated protein kinases and nuclear factor-κB signaling pathways in microglia. These findings suggest that resveratrol exerts neuroprotection against LPS-induced dopaminergic neurodegeneration, and NADPH oxidase may be a major player in resveratrol-mediated neuroprotection.

Fluoxetine protects neurons against microglial activation-mediated neurotoxicity

Neuroinflammation is closely associated with the pathogenesis of Parkinsons disease (PD) and other neurological disorders. Increasing evidence suggests that inhibition of microglia-mediated neuroinflammation might represent a promising therapeutic potential for PD and related disorders. Fluoxetine, a selective serotonin reuptake inhibitor, is commonly used for the treatment of major depression due to its tolerability and safety profiles. Recent studies have shown that fluoxetine affords robust neuroprotection in a series of neurological disease models. However, the mechanism underlying fluoxetine-mediated neuroprotection remains unclear. Here, by using rat primary midbrain neuronglia cultures, we report that both R and S enantiomers of fluoxetine attenuated chronic neurodegeneration induced by a common inflammogen lipopolysaccharide (LPS) and a neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)). Reconstituted cell culture studies further revealed that microglia were required for fluoxetine-mediated neuroprotection. Fluoxetine significantly inhibited LPS-induced activation of microglia and subsequent release of multiple pro-inflammatory and cytotoxic factors including tumor necrosis factor-α, interleukin-1β, nitric oxide, and reactive oxygen species. Furthermore, inhibition of microglial NF-κB signaling pathway participated in fluoxetine-mediated neuroprotection. Collectively, fluoxetine exerted neuroprotection against microglia-mediated neurotoxicity. Thus, fluoxetine might hold a potential to retard inflammation-mediated chronic neurodegenerative process of PD.

Inhibition of IκB Kinase-β Protects Dopamine Neurons Against Lipopolysaccharide-Induced Neurotoxicity

Parkinsons disease (PD) is a progressive neurological disorder characterized by a selective loss of dopamine (DA) neurons in the substantia nigra (SN). Although current therapy can control symptoms of this disorder, there is no effective therapy available to halt its progression. Recently, neuroinflammation has been recognized as an important contributor to the pathogenesis of PD, and nuclear factor-κB (NF-κB) plays a key role in regulating neuroinflammation. Hence, the modulation of NF-κB pathway may have therapeutic potential for PD. Activation of NF-κB depends on the phosphorylation of its inhibitor, IκB, by the specific IκB kinase (IKK) subunit IKK-β. Compound A (7-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-5-[(3S)-3-piperidinyl]-1, 4-dihydro-2H-pyrido[2,3-d][1,3]oxazin-2-one hydrochloride), a potent and selective inhibitor of IKK-β, has recently been reported to provide cardioprotection through specific suppression of NF-κB signaling. The present study, for the first time, elucidates neuroprotective effects of compound A. Daily subcutaneous injection of compound A (1 mg/kg) for 7 days inhibited the activation of microglia induced by nigral stereotaxic injection of lipopolysaccharide (LPS) and significantly attenuated LPS-induced loss of DA neurons in the SN. In vitro mechanistic studies revealed that neuroprotective effects of compound A were mediated by 1) suppressing the activity of microglial NADPH oxidase and decreasing the production of reactive oxygen species, and 2) inhibiting NF-κB-mediated gene transcription of various proinflammatory mediators in microglia via IKK-β suppression. These findings indicate that compound A afforded potent neuroprotection against LPS-induced neurodegeneration through selective inhibition of NF-κB activation and may be of potential benefit in the treatment of PD.

Icariin isolated from Epimedium brevicornum Maxim attenuates learning and memory deficits induced by d-galactose in rats.

The effects of icariin (ICA), a major constituent of flavonoids from the Chinese medical herb Epimedium brevicornum Maxim, on spatial memory performances and expressions of hippocampus brain-derived neurotrophic factor (BDNF) and tyrosine kinase TrkB (tropomyosin receptor kinase B) were investigated in d-galactose (d-gal)-treated rats. Subcutaneous injection of d-gal (500mg/kg/d) for four months caused memory loss as detected by the Morris water maze, morphologic abnormalities of neurons in hippocampus region and the reduced expression of BDNF and TrkB were observed. ICA (60mg/kg/d) given orally 1h after subcutaneous injection of d-gal daily for 4months markedly attenuated d-gal-induced rats behavioral dysfunction and neurodegeneration, as evidenced by shortened escape latency and searching distance and rescued morphologic abnormalities, and also elevated the mRNA levels and the protein expressions of BDNF and TrkB in hippocampus, as evidenced by quantitative real-time RT-PCR and Western blotting analysis. But ICA had no significant influence on normal rats which were not injected d-gal. These results clearly demonstrated that d-gal produced learning and memory deficits after chronic administration, and ICA can protect neuron from d-gal insults and improve the memory loss.

Protective effects of icariin against learning and memory deficits induced by aluminium in rats.

1 The present study examined the protective effects of icariin against the learning and memory deficits in aluminium‐treated rats and its potential mechanisms of action. 2 Qualified rats were treated with 1600 p.p.m. AlCl3 in drinking water for 8 months and the ability of spatial learning and memory was tested by the Morris water maze. In the place navigation test, aluminium administration significantly increased the mean escape latency and searching distance. In space probing test, aluminium markedly decreased the searching time and searching distance in the quadrant where the platform was originally located. All tests indicated deficits in rat spatial learning and memory induced by aluminium. Icariin treatment (60 and 120 mg/kg, by gavage for 3 months) dose‐dependently protected against the development of aluminium‐induced spatial learning and memory deficits. 3 To examine the mechanisms responsible for the protection afforded by icariin, the superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in the hippocampus were assayed biochemically and the level of Aβ1−40 in the hippocampus was determined immunohistochemically. Icariin treatment significantly increased SOD activity and decreased MDA and Aβ1−40 content in the hippocampus of aluminium‐intoxicated rats. 4 In conclusion, the present study demonstrates that icariin is effective in improving the spatial learning and memory of aluminium‐intoxicated rats. The mechanisms responsible appear to be due, at least in part, to an increased anti‐oxidant capacity and decreased lipid peroxidation and Aβ1−40 levels in the rat hippocampus.

Protective effects of icariin on brain dysfunction induced by lipopolysaccharide in rats

In this study we examined the protective effects of icariin, a flavonol isolated from Herba epimedii, on learning and memory in a rat model with brain inflammation induced by lipopolysaccharide (LPS). Injecting LPS into the lateral ventricle caused rat brain dysfunction, as evidenced by deficits of spatial learning and memory in the Morris water maze. With administration of icariin (30, 60, 120mg/kg body wt./day) for 17 consecutive days, spatial learning and memory abilities were markedly altered. Escape latency and searching distance decreased, and the expressions of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) of brain were significantly reduced as observed by real-time RT-PCR and immunohistochemistry. This study used ibuprofen (40mg/kg body wt./day) as positive control. In conclusion, this study suggested that icariin can improve spatial learning and memory abilities in rats with brain dysfunction induced by LPS, an effect which may be due to decreased expressions of TNF-α, IL-1β and COX-2 in the hippocampus.

Icariin inhibits beta-amyloid peptide segment 25–35 induced expression of β-secretase in rat hippocampus

The present study was undertaken to investigate the protective effects of icariin on the learning and memory abilities in Alzheimers disease model rats and explore its protection mechanisms. Beta-amyloid peptide (Abeta) is a key etiology in Alzheimers disease and targeting on Abeta production and assembly is a new therapeutic strategy. Six-month (400-600 g) Wistar rats were unilaterally injected with amyloid beta-protein fragment 25-35 (Abeta(25-35)) 10 microg (5 g/l, 2 microl) into the right hippocampus. The day following Abeta injection, icariin 30, 60 or 120 mg/kg was administered by gavage for 14 days. The ability of spatial learning and memory of the animals was tested by the Morris water maze. In place navigation test, icariin significantly decreased the mean escape latency and searching distance. In the space probing test, icariin increased remarkably the searching time and searching distance in the quadrant where the platform was originally located. All tests indicated icariin improved the ability of spatial learning and memory in Alzheimers disease model rats. Furthermore, immunohistochemistry and real time RT-PCR analysis showed that icariin significantly reduced the contents of Abeta(1-40) and the mRNA levels of beta-secretase in the hippocampus and increased the mRNA level of superoxide dismutase-2, but it had no apparent effects on the immunostain and mRNA level of amyloid protein precursor. These results demonstrate that icariin can improve the learning and memory abilities in Abeta(25-35)-induced Alzheimers disease rats. The mechanisms appear to be due to the decreased production of insoluble fragments of Abeta through suppression of beta-secretase expression.

Neuroprotective effects of Dendrobium alkaloids on rat cortical neurons injured by oxygen-glucose deprivation and reperfusion.

In this study we investigated the protective effects of alkaloids from Dendrobium spez. on cortical neurons injured by oxygen-glucose deprivation/reperfusion (OGD/RP) in vitro. Rat primary cultured cerebral cortical neurons were investigated at different time points of OGD/RP. The MTT assay and the lactate dehydrogenase (LDH) release were used to determine cell viability. The concentration of intracellular free calcium [Ca(2+)](i) and mitochondrial membrane potential (MMP) were determined to evaluate the degree of neuron damage. Morphologic changes of neurons following OGD/RP were examined by electron microscope. To evaluate neuron apoptosis, flow cytometry was performed and the expressions of caspase-3 and caspase-12 mRNA were examined by real-time quantitative PCR during OGD 2h/RP 12h. Treatment with Dendrobium alkaloids (0.025 approximately 2.5mg/l) significantly attenuated neuronal damage, with evidence of increased cell viability, decreased cell apoptosis, and decreased cell morphologic impairment. Furthermore, Dendrobium alkaloids inhibited [Ca(2+)](i) elevation, increased MMP and decreased the expressions of caspase-3 and caspase-12 in a concentration-dependent manner at OGD 2h/RP 12h. Dendrobium alkaloids have significantly protective effects on OGD/RP-induced neuronal damages in rat primary neuron cultures. The protection against OGD/RP-induced apoptosis appears to be mediated through blocking the decrease in MMP and increase in [Ca(2+)](i), as well as by down-regulating mRNA expression of caspase-3 and caspase-12.