脂多糖对小胶质细胞血管内皮生长因子表达的影响

摘要： 目的 探讨脂多糖（LPS）是否能够通过低氧诱导因子-1α（HIF-1α）调节小胶质细胞血管内皮生长因子（VEGF） 的表达。方法 培养 BV2 小胶质细胞系, 分为 4 组： 对照组、 LPS （100 µg/L） 刺激组、 LRS 干预组 （LPS 100 µg/L及脂多糖拮抗剂 200 µg/L）, HIF-1α抑制剂干预组 （LPS 100 µg/L 及 FM19G11 10 mmol/L）。分别采用免疫荧光、 Western blot、 ELISA 检测 VEGF 和 HIF-1α 的表达情况。结果 与对照组比较, LPS 可显著增加 BV2 细胞 VEGF 表达, 脂多糖拮抗剂可明显抑制 LPS 的这一作用。HIF-1α的表达在 LPS 刺激 8 h 后明显增加。HIF-1α抑制剂 FM19G11 可减少 LPS 引起的 BV2 细胞 VEGF 表达增加。结论 LPS 促进小胶质细胞 VEGF 的表达, HIF-1α参与这一调节过程。     

铁含量对小胶质细胞释放促炎因子的影响

目的探索小胶质细胞（MI）内铁含量对MI释放促炎因子的影响。方法使用3,5,5-三甲基乙酰铁（3。5,5-trime~ylhexanoyl,TMHF）或去铁胺（deferoxamine,DFO）改变大鼠离体脑MI内铁离子含量,使用EusA检测上清液中白介素lB（IL-1B）、肿瘤坏死因子仅（TNF—n）表达水平及细胞核因子KB（NF—KB）表达数量在MI使用LPS激活前后的变化。结果与对照组相比,LPS激活后MI释放促炎因子增多,并且在铁超载组进一步增多,反之,在铁剥夺组增多程度下降;NF—KB表达在MI被LPS激活后增加,但铁超载MI表达量没有进一步增加。结论激活后M-I释放促炎因子量明显受细胞内铁含量影响,但机制可能与NF—KB无关。     

鹅去氧胆酸抗脂多糖诱导的BV2小胶质细胞炎症反应作用及机制

目的研究鹅去氧胆酸(CDCA)抗脂多糖(LPS)诱导的BV2小胶质细胞炎症反应的作用及其机制。方法 BV2细胞与CDCA 25～100μmol·L~(-1)预孵育2 h,加LPS 200 mg·L~(-1)继续培养22 h,采用Griess试剂法检测一氧化氮(NO)含量;Western印迹法检测细胞内环氧合酶2(COX-2)和诱导型一氧化氮合酶(iNOS)蛋白表达水平;RT-PCR法检测细胞肿瘤坏死因子α(TNF-α)、白细胞介素6(IL-6)、IL~(-1)β和G蛋白偶联受体5(TGR5)mRNA表达水平。BV2细胞与CDCA 25～100μmol·L~(-1)预孵育2 h,加入LPS 200 mg·L~(-1)继续培养1 h,Western印迹法检测NF-κB、NF-κB抑制蛋白α(IκBα)和丝氨酸/苏氨酸蛋白激酶(Akt)磷酸化水平;细胞免疫荧光法观察NF-κB入核情况。结果与正常对照组相比,模型组培养基中NO含量显著增加(P<0.01);COX-2和iNOS蛋白表达水平升高(P<0.05,P<0.01);TNF-α,IL-6和IL~(-1)βmRNA表达显著上调(P<0.01);TGR5 mRNA表达显著下调(P<0.01);并且NF-κB,IκBα和AKT磷酸化水平显著增加(P<0.05,P<0.01),NF-κB入核增多。与模型组相比,CDCA显著减少培养基中NO含量(P<0.01),降低COX-2和iNOS蛋白表达水平(P<0.05,P<0.01);显著下调TNF-α,IL-6和IL~(-1)βmRNA表达(P<0.01);显著上调TGR5 mRNA表达(P<0.01)。与模型组相比,CDCA显著降低NF-κB,IκBα和AKT磷酸化水平(P<0.05,P<0.01),并观察到NF-κB核转位减少现象。结论 CDCA可显著抑制LPS诱导BV2细胞炎症反应,其作用机制可能与激活TGR5、抑制Akt/NF-κB信号通路相关。     

脂多糖刺激体外大鼠小胶质细胞产生细胞肽和一氧化氮

AIM: To study the characterization of interleukin (IL)-1, IL-2, tumor necrosis factor-alpha (TNF-alpha), and nitric oxide (NO) production in microglia stimulated with lipopolysaccharides (LPS). METHODS: Primary cultured neonatal rat microglia were incubated with LPS (0-10 mg.L-1) for 0-72 h. The supernatants and lysates were collected. IL-1, IL-2, and TNF-alpha were assayed by mouse thymocyte proliferation, mouse spleen cell proliferation, and 1929 cytotoxity, respectively. NO was assayed by Griess reaction. RESULTS: Extracellular IL-1, TNF-alpha, and NO production reached peak levels at LPS 1 mg.L-1. Intracellular IL-1 production reached its peak level at LPS 100 micrograms.L-1. Intracellular TNF-alpha level was very low. IL-1, TNF-alpha, and NO activities were detected at 1, 4, and 8 h, after the cells were stimulated with LPS. IL-1 got to its peak value at 8 h, TNF-alpha, and NO reached the highest levels at 24 h. However, IL-2 activity was not detected after the microglia were stimulated with LPS 0-10 mg.L-1 during the incubation period. CONCLUSION: Rat microglia stimulated with LPS in vitro produced proinflammatory cytokines and NO.     

麻黄碱对脂多糖诱导的小胶质细胞功能损伤的修复作用及机制

目的 研究麻黄碱对脂多糖（LPS）诱导的小胶质细胞功能损伤的修复作用及机制。方法 以人小胶质细胞HMC3为研究对象,考察不同质量浓度麻黄碱（75、150、300、600μg/mL）对HMC3细胞活力和凋亡的影响。然后将HMC3细胞分为对照组（不受药物干预）、LPS组（1μg/mL）、麻黄碱组（1μg/mL LPS+300μg/mL麻黄碱）、BAY11-7082组[1μg/mL LPS+5μmol/L核因子κB(NF-κB)信号通路抑制剂BAY11-7082]、抑制剂组（1μg/mL LPS+300μg/mL麻黄碱+5μmol/L BAY11-7082）和激活剂组（1μg/mL LPS+300μg/mL麻黄碱+1μmol/L NF-κB信号通路激活剂Prostratin）,加入相应药物作用24 h后,检测细胞迁移能力和细胞中可溶性白细胞介素6(s IL-6)、白细胞介素10(IL-10)、超氧化物歧化酶（SOD）、丙二醛（MDA）水平以及NF-κB信号通路相关蛋白表达水平。结果 300μg/mL的麻黄碱可使HMC3细胞活力显著升高、凋亡率显著降低（P<0.05）。与对照组相比,LP...     

石菖蒲抑制脂多糖诱导的神经胶质细胞炎性反应及其机制

目的 观察石菖蒲对脂多糖(lipopolysaccharide,LPS)诱导的大鼠原代神经胶质细胞炎性反应的抑制作用并探讨其可能机制.方法 分离提取大鼠原代神经胶质细胞,用LPS刺激2h后分别加入不同浓度的石菖蒲含药血清,采用硝酸还原酶法检测石菖蒲对一氧化氮的影响,运用酶联免疫吸附法(ELISA)测定培养上清液中IL-1 β、IL-8、TNF-α水平,通过实时逆转录聚合酶链反应(RT-PCR)测定细胞中诱导型一氧化氮合酶(iNOS) mRNA表达.结果 LPS能够激活神经胶质细胞,不同浓度的石菖蒲含药大鼠血清在不影响细胞存活率的情况下,可以显著降低细胞培养上清液中NO、IL-1β、IL-8、TNF-α水平,抑制细胞内iNOS mRNA表达(P＜0.05).结论 石菖蒲的神经保护机制可能与抑制胶质细胞炎症反应有关.     

甘草黄酮抑制脂多糖诱导的小胶质细胞诱导型一氧化氮合酶表达

目的探究甘草黄酮(Gla)对脂多糖(LPS)诱导的BV-2小胶质细胞一氧化碳(NO)生成和诱导型一氧化氮合酶(i NOS)表达影响。方法将BV-2细胞分为对照组、LPS组和Gla处理组,并进行相应处理。采用NO试剂盒检测NO释放量;转录聚合酶链反应(RT-PCR)法检测i NOS m RNA表达量;免疫荧光染色显示i NOS蛋白在BV-2细胞表达情况。结果 LPS刺激可显著增加BV-2小胶质细胞NO释放量和i NOS mRNA生成量(P<0.01),造成大量i-NOS阳性细胞出现,细胞体积增大,突起变粗短。Gla处理则可显著降低BV-2细胞NO释放量和i NOS mRNA生成量(P<0.01),同时i NOS阳性细胞数明显减少,细胞体积缩小,突起变细长。结论 Gla可调节BV-2细胞i-NOS表达,抑制LPS诱导的小胶质细胞神经炎症。     

槲皮黄酮对Aβ诱导小神经胶质细胞损伤的保护机制研究

目的探讨槲皮黄酮对β-淀粉样蛋白(Aβ)诱导小神经胶质细胞(BV-2)损伤的保护作用及其作用机制。方法体外培养BV-2细胞,利用Aβ诱导BV-2细胞发生损伤;将低(10μg/m L)、中(20μg/m L)、高(40μg/m L)3种浓度槲皮黄酮对细胞进行处理,共24 h,采用CCK8实验对BV-2细胞的增殖情况进行评价,应用ELISA试剂盒对细胞培养基上清中炎症因子IL-6、TNF-α的表达水平进行分析,采用免疫印迹技术分析β-分泌酶(BACE)、早老素(PS1)、呆蛋白(NCT)蛋白表达水平,并对脑啡肽酶(NEP)、胰岛素降解酶(IDE)表达水平进行检测。结果采用Aβ诱导可较好地构建BV-2细胞损伤模型,经过低、中、高3种剂量的槲皮黄酮处理后,BV-2细胞的相对存活率较模型组显著增加(P<0.05);药物处理组细胞培养基上清中IL-6、TNF-α表达水平低于模型组(P<0.05);Western blot结果显示,槲皮黄酮组BACE、PS1、NCT蛋白表达水平较模型组降低(P<0.05);槲皮黄酮可以促进Aβ消化酶NEP、IDE的表达。结论槲皮黄酮对Aβ诱导的BV-2细胞损伤具有保护作用,其作用机制可能与抑制Aβ分泌酶表达和激活Aβ消化酶表达有关。     

丹皮酚对脂多糖诱导的星形胶质细胞炎性因子分泌的影响

目的观察丹皮酚对体外培养的星形胶质细胞炎性因子分泌的影响,并探讨其作用机制。方法采用神经胶质原纤维酸性蛋白(GFAP)免疫荧光染色法鉴定星形胶质细胞;实验分为对照组,模型组和2.5、5、10μmol·L-1丹皮酚组,0.5 mg·L-1脂多糖(LPS)诱导炎症反应。采用ELISA法测定培养液中白细胞介素-1β(IL-1β)、白细胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)水平;采用Western blot检测细胞IκBα蛋白表达和磷酸化水平及胞核NF-κB(p65)蛋白表达水平。结果与对照组相比,模型组星形胶质细胞上清液中IL-1β、IL-6和TNF-α水平显著增加(P<0.01),胞浆IκBα蛋白表达受抑(P<0.01),IκBα蛋白磷酸化和胞核NF-κB(p65)蛋白表达水平上调(P<0.01);5、10μmol·L-1丹皮酚能减少LPS活化的星形胶质细胞上清液中IL-1β、IL-6和TNF-α水平(P<0.05或P<0.01),增加胞浆IκBα蛋白表达(P<0.05或P<0.01),抑制LPS上调的IκBα蛋白磷酸化和胞核NF-κB(p65)蛋白表达水平(P<0.05或P<0.01)。结论丹皮酚能抑制LPS诱导的星形胶质细胞炎性因子IL-1β、IL-6和TNF-α的分泌,IκBα/NF-κB信号通路可能参与了丹皮酚对星形胶质细胞炎症反应的抑制作用。     

金钗石斛多糖对脂多糖作用大鼠皮层胶质细胞-神经元体系的保护作用

目的观察金钗石斛多糖(NDP)对脂多糖(LPS)作用的新生大鼠大脑皮层胶质细胞-神经元混合培养体系的保护作用。方法原代制备新生大鼠大脑皮层胶质细胞-神经元混合培养体系,NDP作用于LPS刺激的胶质细胞-神经元混合培养体系,观察细胞生长情况,并采用Real time PCR法检测体系中炎症相关因子IL-1β、TNF-α、COX-2的基因表达。结果 NDP作用于LPS刺激的大鼠皮层胶质细胞-神经元混合培养体系后,胶质细胞激活减少、神经元损伤减轻,较单用LPS作用的模型组相比,炎症相关因子IL-1β、TNF-α、COX-2的基因表达明显降低。结论 NDP能抑制LPS对小胶质细胞和星形胶质细胞的激活,减少炎性因子的生成。     

Inhibitory effects of diallyl disulfide on the production of inflammatory mediators and cytokines in lipopolysaccharide-activated BV2 microglia

Diallyl disulfide (DADS), a main organosulfur component responsible for the diverse biological effects of garlic, displays a wide variety of internal biological activities. However, the cellular and molecular mechanisms underlying DADS' anti-inflammatory activity remain poorly understood. In this study, therefore, the anti-inflammatory effects of DADS were studied to investigate its potential therapeutic effects in lipopolysaccharide (LPS)-stimulated BV2 microglia. We found that pretreatment with DADS prior to treatment with LPS significantly inhibited excessive production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) in a dose-dependent manner. The inhibition was associated with down-regulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. DADS also attenuated the production of pro-inflammatory cytokines and chemokines, including interleukin-1β (IL-1β), tumor necrosis factor (TNF)-α, and monocyte chemoattractant protein-1 (MCP-1) by suppressing the expression of mRNAs for these proteins. The mechanism underlying this protective effect might be related to the inhibition of nuclear factor-kappaB, Akt and mitogen-activated protein kinase signaling pathway activation in LPS-stimulated microglial cells. These findings indicated that DADS is potentially a novel therapeutic candidate for the treatment of various neurodegenerative diseases.     

The effects of paeoniflorin on LPS-induced liver inflammatory reactions

Paeoniflorin (PF), a monoterpene glucoside, is a primary bioactive component of paeony, the root extract of Paeonia lactiflora. We tested the antioxidant effects of PF and its ability to prevent lipopolysaccharide (LPS)-induced oxidative stress. We intraperitoneally administered PF (2.5, 5, or 10 mg/kg) to rats for 20 days. On day 21, we injected the rats with LPS 4 h before sacrifice and measured serum levels of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase as well as the levels of malondialdehyde, superoxide dismutase, catalase, and glutathione peroxidase in liver whole-cell homogenates and mitochondrial fractions. LPS treatment increased levels of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase, and malondialdehyde, but PF treatment blocked these increases. LPS treatment also decreased antioxidant levels of superoxide dismutase, catalase, and glutathione peroxidase, but PF blocked these decreases. PF also protected liver tissue, as shown by histopathology. These results suggest that PF can protect against LPS-induced liver inflammation.     

Anti-inflammatory effects of dimemorfan on inflammatory cells and LPS-induced endotoxin shock in mice

BACKGROUND AND PURPOSE: Dimemorfan (a sigma1 receptor agonist) showed neuroprotective properties in animal models of inflammation-mediated neurodegenerative conditions, but its effects on inflammatory cells and systemic inflammation remain unclear. EXPERIMENTAL APPROACH: The effects of dimemorfan on phorbol-12-myristate-13-acetate (PMA)- and N-formyl-methionyl-leucyl-phenylalanine (fMLP)- induced neutrophils and lipopolysaccharide (LPS)-activated microglial cells, as well as LPS-induced endotoxin shock in mice were elucidated. KEY RESULTS :Dimemorfan decreased PMA- and fMLP-induced production of reactive oxygen species (ROS) and CD11b expression in neutrophils, through mechanisms independent of sigma1 receptors, possibly by blocking ROS production and G-protein-mediated intracellular calcium increase. Dimemorfan also inhibited LPS-induced ROS and nitric oxide (NO) production, as well as that of monocyte chemoattractant protein-1 and tumour necrosis factor-alpha (TNF-alpha), by inhibition of NADPH oxidase (NOX) activity and suppression of iNOS up-regulation through interfering with nuclear factor kappa-B (NF-kappaB) signalling in microglial cells. Treatment in vivo with dimemorfan (1 and 5 mg kg(-1), i.p., at three successive times after LPS) decreased plasma TNF-alpha, and neutrophil infiltration and oxidative stress in the lung and liver. CONCLUSIONS AND IMPLICATIONS: Our results suggest that dimemorfan acts via sigma1 receptor-independent mechanisms to modulate intracellular calcium increase, NOX activity, and NF-kappaB signalling, resulting in inhibition of iNOS expression and NO production, and production of pro-inflammatory cytokines. These effects may contribute its anti-inflammatory action and protective effects against endotoxin shock in mice.     

胆红素对内毒素致大鼠急性肺损伤的保护作用

目的探讨胆红素对内毒素致急性肺损伤(ALI)的保护作用及其可能机制。方法将雄性Wis-tar大鼠30只随机分为正常对照组、ALI模型组和胆红素干预组。检测肺系数(LI)、支气管肺泡灌洗液(BALF)中白细胞(WBC)计数和中性粒细胞(PMN)百分比、蛋白质含量(Pr)、肺泡通透指数(LPI);采用原位杂交技术半定量法和免疫组织化学染色测定肺血管内皮细胞间黏附分子1(ICAM-1)mRNA、核因子κB(NF-κB)和其抑制蛋白I-κBα的表达。结果①ALI模型组LI、BALF中WBC计数、PMN百分比和Pr及LPI均显著高于正常对照组(P均<0.01);胆红素干预组LI、BALF中WBC计数和LPI均显著低于ALI模型组(P均<0.01),PMN百分比和Pr也明显低于ALI模型组(P均<0.05),且与正常对照组差异无统计学意义(P>0.05)。②ALI模型组肺血管内皮ICAM-1 mRNA表达和胞核NF-κB含量与正常对照组比较显著升高(P均<0.01),胞质I-κBα水平却明显降低(P<0.01);胆红素干预组ICAM-1 mRNA表达和胞核NF-κB与模型组相比明显减低(P<0.01),胞质I-κBα含量显著升高(P<0.01),但与正常对照组比较差异有统计学意义(分别P<0.05、P<0.01)。结论胆红素通过抑制NF-κB和ICAM-1 mRNA的表达而减少中性粒细胞肺内浸润来对抗大鼠急性肺损伤。     

知母皂苷对脂多糖引起的大鼠学习记忆障碍和炎症反应的影响

目的观察知母皂苷(SAaB)是否对脂多糖(LPS)引起的大鼠学习记忆障碍和炎症反应有改善作用。方法大鼠随机分为对照组、LPS损伤组、LPS+SAaB(20、40mg·kg-1)组。对照组和LPS损伤组大鼠灌胃给予0.2%的二甲基亚砜,SAaB组大鼠灌胃给予SAaB。连续给药7d后,左侧脑室内单次注射LPS30μg/只大鼠,注射量为5μl,正常对照组大鼠注射等量的生理盐水。脑室注射后d2进行大鼠Morris水迷宫实验,连续6d,训练期间继续给药。水迷宫实验结束后,Nissl染色观察海马CA1区锥体神经元改变;白细胞介素-1β(IL-1β)分别与integrinαM和胶质原纤维酸性蛋白(GFAP)双重免疫荧光染色观察IL-1β表达部位;Westernblot检测海马IL-1β、诱导型一氧化氮合酶(iNOS)的表达水平。结果 SAaB(40mg·kg-1·d-1)能明显改善LPS所致大鼠学习记忆能力损伤,表现在明显缩短大鼠的逃避潜伏期,增加大鼠在原平台象限的游泳时间占总游泳时间的百分比;海马CA1区锥体神经元损伤较LPS组明显减轻,对抗LPS引起的IL-1β及iNOS的蛋白表达水平增加;激光共聚焦实验结果显示IL-1β主要在小胶质细胞表达,少量在星形胶质细胞表达。结论 SAaB能改善LPS引起的大鼠学习记忆障碍,抑制其海马的炎症反应。     

吡格列酮对脂多糖引起的大鼠学习记忆障碍及海马炎症反应的影响

目的研究吡格列酮(pioglitazone,Pio)能否对抗脂多糖(lipopolysaccharide,LPS)所致的大鼠学习记忆障碍及海马炎症反应。方法取SD大鼠40只,随机分为4组:生理盐水对照组,LPS损伤组,LPS+Pio 40和80 mg.kg-1组。灌胃给予Pio 2 d后,脑室注射LPS 5μl(1.0 mmol·L-1),生理盐水对照组注射等量生理盐水。脑室注射后d 2进行Morris定位航行实验,连续5 d,在d 6进行空间探索实验,训练期间继续给药。d 7,快速取海马CA1区,Western blot方法观察白介素-1β(Interleukin-1β,IL-1β),诱导型一氧化氮合酶(Inducible Nitric Oxide Synthase,iNOS),半胱氨酸天冬氨酸蛋白酶(caspase)3,caspase-9及多聚ADP-核糖聚合酶(PARP)蛋白表达水平的变化。RT-PCR检测IL-1β和iNOS的mRNA表达水平。结果脑室内注射LPS,大鼠出现明显的空间学习记忆障碍,表现为逃避潜伏期较生理盐水对照组明显延长(P<0.05),在原平台象限游泳时间占总游泳时间的百分比明显降低(P<0.01)。Western蛋白印迹及RT-PCR结果显示注射LPS后,与对照组相比海马CA1区IL-1β、iNOS蛋白及mRNA表达水平明显增加(P<0.01),活化的caspase-3,caspase-9蛋白表达水平明显增高,分子质量116 ku PARP表达明显减少,而分子质量89 ku劈切PARP表达明显增加(P<0.01)。Pio(40和80 mg.kg-1)能改善大鼠学习记忆功能,对抗LPS引起的海马CA1区IL-1β、iN-OS、活化的caspase-3、活化的caspase-9表达增加,也可明显抑制LPS所致的PARP表达的改变(P<0.01)。结论吡格列酮能够改善大鼠学习记忆功能,抑制LPS引起的海马炎症反应。     

红景天苷调控PI3K/Akt信号通路对LPS诱导的BV2小胶质细胞的抗炎作用

目的探讨红景天苷对脂多糖(LPS)诱导的BV2小胶质细胞的抗炎作用及其机制。方法建立LPS诱导BV2小胶质细胞损伤模型。经不同浓度的红景天苷作用后,q PCR法检测细胞因子IL-6、IL-1β、TNF-αmRNA的表达; Western blot法检测Akt、p-Akt、核蛋白NF-κB p50的蛋白表达。PI3K抑制剂LY294002作用30 min,再经红景天苷作用后,检测Akt、p-Akt、核蛋白NF-κB p50、IL-6、IL-1β、TNF-α等指标。结果与模型组比较,红景天苷能够抑制BV2小胶质细胞IL-6、IL-1β、TNF-αmRNA的表达,促进p-Akt蛋白表达,抑制核蛋白NF-κB p50;经LY294002作用后,红景天苷对pAkt、核蛋白NF-κB p50、IL-6、IL-1β等作用不明显。结论红景天苷能够抑制LPS诱导的BV2小胶质细胞炎症反应,主要是通过激活PI3K/Akt信号通路,促进Akt的磷酸化,抑制NF-κB p50核转录,进而抑制细胞因子。     

Pharmacokinetics of oral entacapone after frequent multiple dosing and effects on levodopa disposition

Objective: Entacapone is a peripherally acting catechol O-methyltransferase (COMT) inhibitor used as an adjunct to each daily levodopa/dopa decarboxylase (DDC) inhibitor dose in the treatment of Parkinson's disease. Parkinsonian patients with advanced disease and motor fluctuations take several doses of levodopa daily, due to the short action of levodopa in this patient population. The present study was conducted in order to evaluate the pharmacokinetics of entacapone after multiple dosing and the pattern of COMT inhibition in erythrocytes during the first day of dosing as well as during steady state. Furthermore, the disposition of plasma levodopa and carbidopa was studied after a single dose of levodopa/carbidopa during the same conditions. Methods: Twelve healthy male volunteers received 200 mg entacapone eight times daily during study day 1 and day 6 at 2-h intervals from 0800 hours to 2200 hours. During days 3, 4 and 5, 200 mg of entacapone was taken ten times daily, from 0800 hours to 0200 hours on the following day. One levodopa/carbidopa tablet (100/25 mg) was taken on study day 1 and day 6 at 1000 hours. Plasma entacapone concentrations and erythrocyte COMT activities were measured frequently on study days 1–2 and 6–7, and twice daily on study days 3–5. Pharmacokinetic parameters calculated from plasma drug concentrations on days 1–2 and 6–7 were compared with each other. Results: There were no differences in maximal plasma concentration (C_max), time to maximal drug concentration in plasma (t_max), elimination half-life (t_1/2) and area under the plasma concentration–time curve (AUC) of entacapone between day 1 and day 6. The mean t_1/2 values of entacapone were 1.3 h and 1.8 h during the first and sixth days, respectively; the difference was not significant. No signs of accumulation of entacapone were noted after the first day. Entacapone reduced erythrocyte COMT activity after the first dose, and this effect was quite stable during frequent dosing. There were no indications of accumulation of COMT inhibition during frequent dosing of entacapone. There were no between-day differences in C_max, t_1/2 (2.4 h on days 1–2 and 2.3 h on days 6–7) or AUC of levodopa, whereas t_max occurred at 0.8 h on day 1 and at 1.2 h on day 6 (P = 0.03). There were no between-day differences in the pharmacokinetic parameters (C_max, t_max and AUC) of carbidopa. Conclusion: Even when dosed frequently, there are neither indications of accumulation of entacapone nor of its COMT inhibiting activity. Received: 28 December 1998 / Accepted in revised form: 29 March 1999