Increasing Intracellular Levels of Iron with Ferric Ammonium Citrate Leads to Reduced P-glycoprotein Expression in Human Immortalised Brain Microvascular Endothelial Cells

Pharmaceutical Research - P-glycoprotein (P-gp) at the blood-brain barrier (BBB) precludes the brain penetration of many xenobiotics and mediates brain-to-blood clearance of β-amyloid, which...     

The Changes of P-glycoprotein Activity by Interferon-γ and Tumor Necrosis Factor-α in Primary and Immortalized Human Brain Microvascular Endothelial Cells

The purpose of this study was to investigate the modification of expression and functionality of the drug transporter P-glycoprotein (P-gp) by tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) at the blood-brain barrier (BBB). We used immortalized human brain microvessel endothelial cells (iHBMEC) and primary human brain microvessel endothelial cells (pHBMEC) as in vitro BBB model. To investigate the change of p-gp expression, we carried out real time PCR analysis and Western blotting. To test the change of p-gp activity, we performed rhodamin123 (Rh123) accumulation study in the cells. In results of real time PCR analysis, the P-gp mRNA expression was increased by TNF-α or IFN-γ treatment for 24 hr in both cell types. However, 48 hr treatment of TNF-α or IFN-γ did not affect P-gp mRNA expression. In addition, co-treatment of TNF-α and IFN-γ markedly increased the P-gp mRNA expression in both cells. TNF-α or IFN-γ did not influence P-gp protein expression whatever the concentration of cytokines or duration of treatment in both cells. However, P-gp expression was increased after treatments of both cytokines together in iHBMEC cells only compared with untreated control. Furthermore, in both cell lines, TNF-α or IFN-γ induced significant decrease of P-gp activity for 24 hr treatment. And, both cytokines combination treatment also decreased significantly P-gp activity. These results suggest that P-gp expression and function at the BBB is modulated by TNF-α or/and IFN-γ. Therefore, the distribution of P-gp depending drugs in the central nervous system can be modulated by neurological inflammatory diseases.     

The Effects of Clioquinol on P-glycoprotein Expression and Biometal Distribution in the Mouse Brain Microvasculature

Previous studies have demonstrated that the ionophore clioquinol (CQ), in conjunction with the biometals copper and zinc, increases the expression of P-glycoprotein (P-gp) in human cerebral microvascular endothelial (hCMEC/D3) cells. As P-gp expression and function at the blood-brain barrier (BBB) is of great interest regarding CNS drug access and endogenous toxin trafficking (e.g., amyloid beta), the present study assessed the in vivo translation of these previous in vitro findings. Swiss outbred mice received an 11-day treatment of CQ (30 mg/kg) by oral gavage, after which brain microvessel-enriched fractions (MEFs) and surrounding interfaces (subcortical brain tissue and plasma) were extracted. P-gp expression was quantified in the MEF, and biometal concentrations in all 3 compartments were assessed via inductively coupled plasma mass spectrometry. CQ treatment did not modify the expression of P-gp, nor copper or zinc concentrations in the brain MEF under this treatment regime. Metallomic analysis revealed, however, that CQ reduced potassium and magnesium levels in the brain MEF and also lowered brain iron levels. This study has shown that under this dosing regimen, CQ does not increase BBB P-gp expression in Swiss outbred mice, but that CQ facilitates redistribution of certain metal ions within the brain MEF, plasma, and brain parenchyma.     

Transport Characteristics of 6-Mercaptopurine in Brain Microvascular Endothelial Cells Derived From Human Induced Pluripotent Stem Cells

The likelihood of reoccurrence of acute lymphoblastic leukemia is influenced by the cerebral concentration of the therapeutic agent 6-mercaptopurine (6-MP) during treatment. Therefore, it is important to understand the blood-brain barrier (BBB) transport mechanism of 6-MP. The purpose of this study was to characterize this mechanism using human induced pluripotent stem cell-derived microvascular endothelial cells (hiPS-BMECs). The permeability coefficient of 6-MP across hiPS-BMECs monolayer in the basal-to-apical direction (B-to-A) was significantly greater than that in the opposite direction (A-to-B). The inhibition profiles of 6-MP transport in the A-to-B direction were different from those in the B-to-A direction. Transport in the A-to-B direction was mainly inhibited by adenine (an inhibitor of equilibrative nucleobase transporter 1; ENBT1), while transport in the B-to-A direction was significantly reduced by inhibitors of multidrug resistance-associated proteins (MRPs), especially zaprinast (an MRP5 inhibitor). Immunocytochemical analyses demonstrated the expression of ENBT1 and MRP5 proteins in hiPS-BMECs. We confirmed that the cellular uptake of 6-MP is decreased by ENBT1 inhibitors in hiPS-BMECs and by knockdown of ENBT1 in hCMEC/D3 cells. These results suggest that ENBT1 and MRP5 make substantial contributions to the transport of 6-MP in hiPS-BMECs and hCMEC/D3 cells.     

氟西汀对丙酮醛诱导的人脑微血管内皮细胞损伤的保护作用

目的 研究氟西汀对丙酮醛诱导的人脑微血管内皮细胞（HBMEC）损伤的保护作用。方法 在培养的HBMEC上,利用丙酮醛诱导的细胞损伤,通过MTT检测细胞活力,SOD、MDA试剂盒检测细胞的氧化活性,casepase 3活性试剂盒和流式细胞仪检测细胞凋亡,观察氟西汀的作用和机制。结果 氟西汀呈浓度依赖地保护丙酮醛（MGO）诱导的细胞损伤,在10^-5 mol·L^-1时呈最大保护作用。MGO能降低细胞上清SOD活性而升高MDA含量,而氟西汀（10^-5 mol·L^-1）能逆转这种作用,并能抑制MGO诱导的caspase-3活性上升和凋亡。结论 氟西汀对丙酮醛诱导的HBMEC的损伤具有保护作用,这可能与其抗自由基和抗凋亡作用有关。     

Characterization and Modulation of the Transferrin Receptor on Brain Capillary Endothelial Cells

PURPOSE: The expression level of the transferrin receptor (TfR) on brain capillary endothelial cells (BCECs) and the endocytosis of 125I-transferrin (125I-Tf) by this receptor was investigated. Furthermore, the influence of iron, the iron scavenger deferoxamine mesylate (DFO), astrocytic factors, a GTP-ase inhibitor (tyrphostin-A8, T8), lipopolysaccharide (LPS), and the radical scavenger N-acetyl-L-cysteine (NAC) on the TfR expression was studied to gain insight in the use and optimization of the TfR for drug targeting to the brain. METHODS: Experiments were performed with primary cultured bovine BCECs that were incubated with 125I-Tf at 4 degrees C (to determine binding) or at 37 degrees C (to determine endocytosis) in the absence or presence of the modulators. For full saturation curves in the absence or presence of iron or DFO, analysis was performed with a population approach using NONMEM, allowing us to estimate a single value for affinity (Kd, concentration of 50% receptor occupancy) and separate values for maximum receptor occupancy (B(max). RESULTS: On BCECs, the TfR is expressed extracellularly (B(max) of 0.13 fmol/microg cell protein), but also has a large intracellular pool (total B(max) of 1.37 fmol/microg cell protein), and is actively endocytosing Tf via clathrin-coated vesicles. At 4 degrees C, a Kd of 2.38 microg/ml was found, whereas the Kd at 37 degrees C was 5.03 microg/ml. Furthermore, DFO is able to increase both the extracellular as well as the total binding capacity to 0.63 and 3.67 fmol/microg cell protein, respectively, whereas it had no influence on Kd. B(max) at 37 degrees C after DFO preincubation was also increased from 0.90 to 2.31 fmol/microg cell protein. Other modulators had no significant influence on the TfR expression levels, though LPS increased cellular protein concentrations after 2-h preincubation. CONCLUSIONS: The TfR is expressed on BCECs and actively endocytoses Tf, making it a suitable target for drug delivery to the bloodbrain barrier and the CNS. DFO up-regulates the TfR expression level, which may influence targeting efficiency.     

Thyroid Hormone Regulates the Expression and Function of P-glycoprotein in Caco-2 Cells

Purpose In patients with thyroid disorders, abnormalities in the pharmacokinetics of various drugs including digoxin, a substrate of P-glycoprotein (Pgp) which plays a crucial role in drug absorption and disposition, have been reported. In this study, we examined the effect of 3,5,3′-l-triiodothyronine (T₃) on the function and expression of Pgp using the human intestinal epithelial cell line Caco-2. Materials and Methods The effect of T₃ on the expression of Pgp and MDR1 mRNA was assessed by Western blotting and competitive polymerase chain reaction, respectively. Digoxin uptake and transport by Pgp was assessed using Caco-2 cell monolayers. Results The expression of MDR1 mRNA was increased by T₃ treatment in a concentration-dependent manner. Pgp expression was also increased by 100 nM T₃, whereas it decreased on depletion of T₃. The amount of [³H]digoxin accumulated in Caco-2 cell monolayers treated with T₃ was diminished significantly compared with that in control cells. In addition, the basal-to-apical transcellular transport of [³H]digoxin was accelerated by T₃ treatment. Conclusions These results indicate that T₃ regulates the expression and function of Pgp. It is possible that changes in Pgp expression alter the pharmacokinetics of Pgp substrates in patients with thyroid disorders.     

Modulation of the Cellular Junction Protein E-Cadherin in Bovine Brain Microvessel Endothelial Cells by Cadherin Peptides

Cadherins are calcium-dependent glycoproteins involved in homophilic cell-cell adhesion of tight intercellular junctions. The ability of cadherin peptides to inhibit cadherin-mediated cell-cell adhesion of bovine brain microvessel endothelial cells (BBMECs) was investigated. This was accomplished by using two cadherin function assays, the inhibition of calcium-dependent reaggrega-tion and the dissociation of BBMECs. Peptides that exhibit inhibitory and dissociating properties are presumably bound to cadherins on the surface of BBMECs, inhibiting cadherin-cadherin interactions. We have found six peptides from the EC-1 domain of E-and N-cadherins that inhibit cell-cell adhesion of BBMECs. A very significant inhibitory activity was displayed by a 24-mer peptide (3) derived from the human-E-cadherin sequence. One hexapeptide (7) derived from the E-cadherin sequence can effectively inhibit aggregation of BBMECs. These results will improve our ability to design peptides that can modulate cell-cell adhesion in the intercellular tight junctions.     

VEGF MVD在子宫腺肌病中的表达

目的 探讨子宫腺肌病异位内膜组织中血管内皮生长因子(VEGF)和微血管密度(MVD)的表达.方法 采用免疫组织化学方法检测子宫腺肌病异位内膜与正常子宫内膜中VEGF和MVD的表达.结果 子宫腺肌病异位内膜组织中VEGF和MVD在增生期和分泌期的表达均明显高于正常内膜(P＜0.05).结论 异位内膜组织中VEGF和MVD的高表达可能对子宫腺肌病的发生发展起重要作用.     

丙丁酚对脑微血管内皮细胞损伤的保护作用研究

目的:观察同型半胱氨酸(Hcy)对大鼠脑微血管内皮细胞(RCMEC)损伤的保护作用。方法:将RCMEC分为损伤组和正常对照组,观察Hcy对RCMEC的影响;另将RCMEC分为正常对照组、损伤组和丙丁酚不同剂量组,观察各组细胞乳酸脱氢酶(LDH)释放率及细胞生长曲线。结果:与正常对照组比较,损伤组RCMEC生长受抑且细胞LDH释放率明显增加;丙丁酚浓度在10~50μmol/L范围内细胞LDH释放率依次减少。结论:Hcy对RCMEC有毒性损伤作用,丙丁酚呈剂量依赖性拮抗Hcy所致RCMEC损伤。     

Paraquat‐Induced Membrane Dysfunction in Pulmonary Microvascular Endothelial Cells

Membrane dysfunction monitored by lactate dehydrogenase release from cultured pulmonary microvascular endothelial cells of pigs, which were exposed to paraquat at different concentrations (0.1–2 mM), was examined. Paraquat caused a time‐dependent increase in lactate dehydrogenase release. Lactate dehydrogenase releases after 72 hr, 32, 58, and 84% by 0.1, 0.5, and 2 mM paraquat, respectively, were well correlated with cell viability measured by cell adherence. In contrast, reductions of two tetrazolium compounds were depleted profoundly by 72 hr after exposure to 0.5 mM paraquat, suggesting depletion of intracellular reductive substances. Extracellular hydrogen peroxide began to significantly increase 56 hr or 32 hr after exposure to 0.5 mM or 1.5 mM paraquat, respectively, preceding the initial increase of lactate dehydrogenase release (64 hr by 0.5 mM or 48 hr by 1.5 mM). Lactate dehydrogenase release 72 hr after exposure to 0.5 mM paraquat was prevented strongly by catalase (1000 units/ml), but weakly by superoxide dismutase (1000 units/ml). These enzymes failed to restore the reduced acid phosphatase activity. Also, 0.1 mM desferal or α,α′‐dipyridyl protected lactate dehydrogenase release. Similarly, 1 mM thiourea or dimethylthiourea, and 0.5 mM α‐tocopherol or trolox, were effective, but diethylenetriaminepentaacetic acid (0.1 mM) and probucol (5 or 10 μM) were ineffective. Exposure of 0.5 or 1.5 mM paraquat suppressed levels of lipid peroxidation. These results indicate that membrane dysfunction by paraquat is ascribed to an iron‐catalyzed reaction of extracellularly increased hydrogen peroxide. A deleterious species for the membrane dysfunction is discussed.     

Antioxidant Activity of Plicatin B on Cultured Human Microvascular Endothelial Cells Exposed to H2O2

Oxidative stress plays a crucial role in the pathogenesis of atherosclerosis by promoting endothelial dysfunction and impairing vascular relaxation. Flavonoids are largely investigated for their biological properties and particularly for their scavenging and antioxidant properties. In the current study, we evaluated the clastogenicity of the chalcone plicatin B in peripheral human lymphocytes (whole blood and pure lymphocytes) as well as its antioxidant activity and its ability to contrast dysfunction on human microvascular endothelial cells (HMEC-1) exposed to hydrogen peroxide. We measured in the cell culture medium the levels of 8-isoprostane, NO_x, ET-1, and ICAM-1, as well as the expression of e-NOS, prepro-ET-1, and ICAM-1. In conclusion, our results demonstrate that the chalcone plicatin B (1–10 μM) may represent a good candidate for the prevention of atherosclerosis, as it consistently reduces the oxidative/inflammatory process and is not genotoxic to human lymphocytes.     

Epigallocatechin-3-gallate Regulates NADPH Oxidase Expression in Human Umbilical Vein Endothelial Cells

Vascular NADPH oxidase plays a pivotal role in producing superoxide in endothelial cells and thus acts in the initiation and development of inflammatory cardiovascular diseases such as atherosclerosis. Epigallocatechin-3-gallate (EGCG), the major catechin derived from green tea, has multiple beneficial effects for treating cardiovascular disease but the effect of EGCG on the expression of vascular NADPH oxidase remains unknown. In this study, we investigated the mechanism(s) by which EGCG might inhibit the expression of subunits of NADPH oxidase, namely p47^phox, p67^phox and p22^phox, induced by angiotensin II (Ang II) in human umbilical vein endothelial cells. Ang II increased the expression levels of p47^phox, p67^phox, and p22^phox, but EGCG counteracted this effect on p47^phox. Moreover, EGCG did not affect the production of reactive oxygen species induced by Ang II. These data suggest a novel mechanism whereby EGCG might provide direct vascular benefits for treating inflammatory cardiovascular diseases.     

泮托拉唑对急性肺损伤模型大鼠和人肺微血管内皮细胞损伤的作用及作用机制

目的 探讨泮托拉唑对急性肺损伤(ALI)模型大鼠和人肺微血管内皮细胞(HPMECs)损伤的作用及作用机制.方法 将48只SD大鼠随机分为正常对照组,脂多糖组,阳性对照组,泮托拉唑低、高剂量组和泮托拉唑高剂量+氯喹组,各8只.除正常对照组外,其余各组大鼠均腹腔注射5 mg/kg脂多糖复制ALI模型;阳性对照组大鼠腹腔注射...     

石杉碱甲保护人脑微血管内皮细胞损伤的体外实验研究

目的体外实验研究石杉碱甲对人脑微血管内皮细胞(human brain microvascular endothelial cells,HBMEC)损伤的保护作用和机制。方法在培养的HBMEC上,利用丙酮醛诱导细胞损伤,通过MTT检测细胞活力,LDH、SOD活性试剂盒及caspase-3活性试剂盒检测细胞损伤情况,观察石杉碱甲的作用和机制。结果石杉碱甲呈浓度依赖地保护MGO诱导的细胞损伤,在10-5mol·L-1时呈最大保护作用。丙酮醛能诱导HBMEC的SOD活性下降,而石杉碱甲(10-6,10-5mol·L-1)能逆转这种作用。进一步研究发现石杉碱甲能抑制丙酮醛诱导的caspase-3活性上升。结论石杉碱甲对丙酮醛诱导的HBMEC的损伤具有保护作用,这可能与其抗自由基和抗凋亡作用有关。     

Establishing a Method to Isolate Rat Brain Capillary Endothelial Cells by Magnetic Cell Sorting and Dominant mRNA Expression of Multidrug Resistance-associated Protein 1 and 4 in Highly Purified Rat Brain Capillary Endothelial Cells

Purpose To establish a method for isolating highly purified brain capillary endothelial cells (BCECs) from rat brain by using magnetic cell sorting, and clarify the expression levels of multidrug resistance-associated protein (Mrp) subtypes in these highly purified BCECs. Methods The cells were prepared from the capillary enriched-fraction by enzyme digestion, and reacted with anti-PECAM-1 antibody. The cell sorting was performed by autoMACS. The mRNA levels were measured by quantitative real-time PCR analysis. Results From five rats, 2.3 × 10⁶ cells were isolated in the PECAM-1(+) fraction and the percentage of labeled cells in this was 85.9%. PECAM-1, claudin-5 and Tie-2 mRNA were concentrated in the PECAM-1(+) fraction compared with rat brain. The contamination by neurons and astrocytes was markedly less than in the brain capillary fraction prepared by the glass bead column method. Mrp1 and 4 were predominantly expressed in the PECAM-1(+) fraction at similar levels to Mdr1a. The mRNA levels of Mrp5 and 3 were 10.6 and 7.60% of that of Mrp1, respectively. Conclusions This new purification method provides BCECs with less contamination by neural cells. In the isolated BCECs, Mrp1 and 4 are predominantly expressed, suggesting that they play an important role at the rat blood-brain barrier.     

C肽对高糖状态下人脐静脉内皮细胞体外表达eNOS的影响

目的 :探讨在高糖状态下C肽对人脐静脉内皮细胞 (HUVEC)体外表达内皮型一氧化氮合酶 (eNOS)的影响。方法 :将培养成功的HUVEC在不同浓度的C肽和葡萄糖环境下孵育72h ,提取细胞总RNA ,应用半定量逆转录聚合酶链反应 (SQ -RT -PCR)法 ,检测eNOSmRNA表达的情况。结果 :生理浓度葡萄糖 (5 5mmol/L)状态下 ,低浓度的C肽 (0 3nmol/L)使HUVECeNOSmRNA表达减弱(P<0.01) ,生理浓度 (3nmol/L)和高浓度(30nmol/L)的C肽可使eNOSmRNA的表达明显增强(P<0.01) ;高浓度葡萄糖(33.3mmol/L)状态使HU VECeNOSmRNA表达减弱(P<0.01) ,加入生理浓度或高浓度C肽后 ,eNOSmRNA表达增强(P<0.01)。结论 :HUVEC体外eNOSmRNA表达可受C肽浓度影响 ;高浓度或生理浓度C肽可缓解高糖对HUVECeNOS表达的抑制作用。提示C肽可能对防治糖尿病大血管病变具有重要作用     

白藜芦醇对纤维蛋白上调大鼠脑血管内皮细胞白介素6表达的影响

目的观察白藜芦醇（resveratrol,Res）对体外大鼠脑血管内皮细胞与纤维蛋白共培养高表达白介素6（interleukin 6,IL 6）转录及蛋白水平的影响。方法大鼠脑血管内皮细胞分离后培养,加入1.0 mg&#8226;mL 1纤维蛋白和不同浓度白藜芦醇,通过RT PCR检测脑血管内皮细胞中IL 6转录水平,应用酶联免疫方法（ELISA）定量检测培养基中的IL 6水平。结果加入不同浓度（0,1,5,10,25和50 μmol&#8226;L 1）的白藜芦醇24 h后,25和50 μmol&#8226;L 1白藜芦醇组培养基中IL 6水平显著降低（均P＜0.01）;RT PCR结果显示,25和50 μmol&#8226;L 1白藜芦醇组大鼠脑血管内皮细胞中IL 6 mRNA显著下调（均P＜0.01）。结论白藜芦醇可降低纤维蛋白导致的大鼠脑血管内皮细胞中IL 6的表达。     

Regulation of P-glycoprotein by miR-27a-3p at the Brain Endothelial Barrier

Multi-drug resistance P-glycoprotein (P-gp/MDR1) is one of the most clinically relevant ABC transporters, highly enriched at the blood-brain barrier (BBB) with a broad substrate spectrum including therapeutic drugs and metabolic waste products. Altered P-gp transport function has been implicated in multi-drug resistance and in the pathogenesis and progression of neurological diseases. Recent studies have shown that P-gp expression is modulated by micro-RNAs in peripheral organs. Particularly, miR-27a-3p has been shown to play a critical role in the regulation of P-gp in multi-drug resistant cancer cells. In brain disorders, altered levels of miR-27a-3p were reported in several diseases associated with alterations in P-gp expression at the BBB. However, effect of altered miR-27a-3p expression on P-gp expression at the BBB remains to be determined. In this study, we investigated the role of miR-27a-3p in the regulation of P-gp expression and activity at the brain endothelium. Levels of miR-27a-3p were modulated by mimic and inhibitor transfection in an in-vitro model of human brain endothelial hCMEC/D3 cells. Effect of miR-27a-3p modulation on P-gp expression and activity was examined and the underlying regulatory mechanisms explored. Our results showed that transfection of hCMEC/D3 cells with miR-27a-3p mimic induces expression and activity of P-gp while miR-27a-3p inhibition exerted opposite effects. Mechanistic studies revealed that miR-27a-3p regulates P-gp by mediating Glycogen Synthase Kinase 3 Beta (GSK3ß) inhibition and activating Wnt/ß-catenin signaling. These findings shed light on miR-27a-3p/GSK3ß/ß-catenin as a novel axis that could be exploited to modulate P-gp efflux activity at the brain endothelium and help improving CNS diseases treatment or brain protection.