| Cerebral ischemia is a leading cause of neurological disability and death in the agingpopulation all over the world. However, we still lack knowledge about its complexpathological mechanisms. However, neuroprotective drugs for clinical treatment arehardly beneficial for the patients with cerebral ischemia to date. Therefore, it is importantto screen the effective neuroprotectants which can protect neurons against ischemic injury.Panax ginseng and Panax notoginseng are famous for their various biological andpharmacological activities throughout Chinese herb medicine history. Our previous studiesshowed that ginsenoside Rd (GSRd), a main active components extracted from ginseng,has multiple neuroprotective effects. We found that GSRd can attenuate the apoptosis ofcultured neurons, protect the injured neurons against glutamate-induced excitotoxicity andinhibit Ca2+influx. Moreover, our randomized, double-blind, placebo-controlled, phase IIand III multicenter trials showed that GSRd had efficacy and safety for the treatment ofacute ischemic stroke. More importantly, our lasted study revealed that late administration of GSRd (4h after ischemic stroke) still showed significant effectiveness. Sincemicroglia-mediated inflammatory response is a key pathological change during lateischemic process, we propose that GSRd may exert its neuroprotective effects againstischemic stroke by suppressing inflammation.Therefore, this thesis aims to explore whether GSRd can protect against cerebralischemic injury via an anti-inflammatory effect. In addition, considering the similarstructure and function of GSRd and corticosteroids, we also compared theanti-inflammatory effect and adverse reaction of GSRd with dexamethasone.Experiment1Ginsenoside Rd suppresses inflammatory response afterexperimental ischemic injuryObjective: To investigate the effects of GSRd on inflammation in experimentalischemic model.Methods: SD rats and cultured microglia were received the pretreatment of10mg/Kgor10μM GSRd,50mg/Kg minocycline,100ng/ml lipopolysaccharide,5mg/Kg or100nMDEX,10mg/Kg or1μM RU486. The rats were subjected to transient middle cerebralartery occlusion/reperfusion. Cultured microglia was stimulated by lipopolysaccharide andoxygen glucose deprivation.2,3,5-triphenyltetrazolium chloride (TTC) staining was usedto assess the infarct volume. Thiazolyl blue tetrazolium bromide (MTT) was used to detectcell viability. The mRNA and protein expression of cytokines were detected by real-timePCR and liquid chip, respectively.Results:(1) GSRd markedly reduced the size of infarction, increased the survival ofimpaired cultured neurons. However, DEX and RU486have no effects on the infarctvolume in brain damage.(2) GSRd, DEX and minocycline evidently attenuated themRNA and protein expression levels of kinds of cytokines. The inhibition of cytokines didnot differ statistically among the three groups.(3) RU486attenuated the inhibition effectof GSRd on cytokine expression. Conclusion: GSRd was capable of protecting against neuronal injury of ischemicmodels. These effects may account for its ability to suppress inflammatory and decreasethe expression of various cytokine.Experiment2Ginsenoside Rd protects against ischemic injury via aglucocorticoid-like anti-inflammatory effectObjective: To investigate the effects of GSRd on inflammation in experimentalischemic model.Methods: BV2microglia were received the pretreatment of10μM GSRd,100nMDEX, or1μM RU486. Cultured microglia were injured by oxygen glucose deprivation.The mRNA expression of NFκB was detected by real-time PCR. The protein expression ofp-IκBα, IκBα, NFκB p65, p-p38, p38, or GR was examined by Western blot.Results:(1) NFκB is a key transcription factor for regulating the expression ofpro-inflammatory cytokines. Our results showed that GSRd markedly reduced IκBαphosphorylation and inhibited NFκB transcription.(2) P38also involves in the regulationof pro-inflammatory cytokine expression. GSRd obviously lowered P38phosphorylationand consequently repressed its activity.(3) Glucocorticoid receptor activation is essentialfor NFκB and P38activities. We revealed that GSRd was able to increase glucocorticoidreceptor transcription, subseqently activating the glucocorticoid receptor, which can beblocked by glucocorticoid receptor agonist RU486.Conclusion: GSRd can suppress the activities of NFκB and P38, two key regulatorsfor inflammatory response. This effect may be due to its capability of inhibiting theactivation of glucocorticoid receptor.Experiment3A functional comparison of ginsenoside Rd withdexamethasone in anti-inflammatory and adverse effectsObjective: Glucocorticoids are known for its anti-inflammatory effect as well as sideeffects. Thus, we compare anti-inflammatory and adverse effects between GSRd and dexamethasone (DEX).Methods: The C57/B6mice were administrated respectively by saline,10mg/Kg GSRd,and2.5mg/Kg DEX for four weeks. Blood glucose, body weight, and weight of spleen andthymus were then examined. In a collagen-induced arthritis (CIA) model, theanti-inflammatory effects of GSRd were compared with that of DEX. In culturedMC-3T3-E1osteoblast-like cells, the effects of GSRd and DEX their proliferation anddifferentiation were studies.Results:(1) Compared with the normal mice, GSRd had no effects on body weight,blood glucose, weight and relative weight of spleen and thymus. However, theconcentrations of blood glucose were increased, and relative weight of spleen, thymus, andbody mass were decreased in DEX-treated mice.(2) In the CIA model, both GSRd andDEX decreased the number of inflammatory cells, but there was no significant differencebetween two groups.(3) GSRd had a similar promotive effect to DEX on proliferation anddifferentiation of MC-3T3-E1cells, but had a relative broad range of effective dosage(10nM-1M) as compared with DEX.Conclusion: Compare with DEX, GSRd has a similar effect on anti-inflammation andbone formation, but less affects blood glucose, immune organs, and body mass. Takentogether, GSRd maybe serve as a promising anti-inflammatory drug in the treatment ofischemic stroke. |
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