Branching out: a molecular fingerprint of endothelial differentiation into tube-like structures generated by Affymetrix oligonucleotide arrays

The process of endothelial differentiation into a network of tube-like structures with patent lumens requires an integrated program of gene expression. To identify genes upregulated in endothelial cells during the process of tube formation, RNA was prepared from several different time points (0, 4, 8, 24, 40, and 48 hours) and from three different experimental models of human endothelial tube formation: in collagen gels and fibrin gels driven by the combination of PMA (80), bFGF (40 ng/ml) and bFGF (40 ng/ml) or in collagen gels driven by the combination of HGF (40 ng/ml) and VEGF (40 ng/ml). Gene expression was evaluated using Affymetrix Gene Chip oligonucleotide arrays. Over 1000 common genes were upregulated greater than twofold over baseline at one or more time points in the three different models. In the present study, we discuss the identified genes that could be assigned to major functional classes: apoptosis, cytoskeleton, proteases, matrix, and matrix turnover, pumps and transporters, membrane lipid turnover, and junctional molecules or adhesion proteins.     

Red cell glucose-6-phosphate dehydrogenase status and pyruvate kinase activity in a Nigerian population

Glucose-6-phosphate dehydrogenase A- (G6PD A-) deficiency is a common enzymopathy in Africa that sporadically leads to manifest haemolytic anaemia. It is not exactly known how far the haematological status of individuals with either homozygous or heterozygous G6PD A- deficiency differs from that of individuals with normal G6PD activity. In a field study in Nigeria, we determined G6PD gene variants, the corresponding G6PD and pyruvate kinase (PK) activities, and basic haematological parameters in clinically healthy individuals, who were, in part, asymptomatically infected by malaria parasites. Red blood cell counts and haemoglobin levels were lower in G6PD A- deficient than in G6PD normal subjects. PK activities were higher in G6PD deficients, indicating a younger red cell population in these individuals. These findings suggest that G6PD A- deficiency is accompanied by chronic subclinical haemolysis. As a consequence, the reduced life span of red cells leads to an impaired diagnosis of G6PD heterozygosity when applying routine biochemical methods.     

TNF-α induces dyscohesion of epithelial cells. Association with disassembly of actin filaments

TNF-α induced, in a time and dose-dependent fashion, cell-cell dissociation (dyscohesion) of endometrial epithelial cells. Within the time frame that dyscohesion was induced, TNF-α, in a dose-dependent fashion, reduced filamentous (F) actin and resulted in the loss of F-actin from the intercellular boundaries. Loss of F-actin mediated by TNF-α was not due to a reduction in the overall amount of actin or its β-isoform. Two proteins, Rho and Rho guanine nucleotide dissociation inhibitor (Rho-GDI), have been implicated in the regulation of organization of actin cytoskeleton. The reduced level of F-actin was not associated with altered expression of Rho protein, however, it was associated with an increase in the amount of Rho available for ribosylationin vitro by the C3 exoenzyme of Clostridium botulinum. The amount of Rho-GDI protein did not change after treatment with TNF-α suggesting that elevated expression of this protein is not responsible for the disassembly of actin filaments. These findings show that TNF-α induces dyscohesion. Dyscohesion induced by this cytokine is associated with perturbation of the actin cytoskeleton which may be due to the regulatory role of TNF-α on Rho.     

The role of protein kinase C in insulin biosynthesis

Activation of protein kinase C (PKC) by the phorbol ester 4-phorbol myristate acetate (4-PMA) stimulated (pro)insulin biosynthesis in collagenase-isolated rat islets of Langerhans, as assessed by measuring the incorporation of [³⁵S]cysteine into proinsulin and insulin after fractionation by high performance liquid chromatography. The stimulatory effects of 4-PMA were observed at a substimulatory concentration of glucose (2 mM) but were not additive to the stimulatory effects of 20 mM glucose on insulin biosynthesis. Prolonged exposure to 4-PMA caused a marked down-regulation of PKC activity in islets. PKC-depleted islets showed a much reduced biosynthetic response to 20 mM glucose, but this was caused, at least in part, by an enhanced basal rate of (pro)insulin synthesis. These elevations in the basal rate of insulin synthesis were not secondary to an inerease in the amount of preproinsulin mRNA in PKC-depleted islets since Northern blot analysis showed that prolonged exposure to 4-PMA, and the subsequent loss of PKC activity, did not detectably alter basal levels of preproinsulin mRNA. These results suggest that the activation of PKC stimulates (pro)insulin synthesis in rat islets by enhancing translation of existing preproinsulin mRNA, and that this may play some part in the biosynthetic responses of -cells to glucose.     

Myoglobin and creatine kinase rates of release during acute myocardial infarction

The release of cardiac enzymes as an index of infarct size (IS) development was studied in patients with acute myocardial infarction (AMI) treated at a coronary care unit. Serial determinations of serum myoglobin (MG) and creatine kinase (CK) were made on 34 consecutive patients with duration of symptoms less than 6 h at admission and with initial CK values below the upper reference limit. Computer-calculated CK-IS was determined on the basis of the log-normal algorithm. This was compared to discretely calculated CK and MG release. The correlation between computer- and discretely calculated cumulated CK release was 0.995 with a regression close to the line of equivalence. Computer-calculated CK rates of release showed a one-peak development, while, when discretely calculated, mostly three or four peaks were observed, as found also for MG rates of release. The occurrence of MG and CK peaks was related as indicated by a correlation coefficient of 0.75. The initial CK rate of release was slower when computer-calculated. In the group studied, CK release began about 3 h post onset of symptoms, at which time 56% had an MG value above the upper reference limit. The CK and MG releases were finished about 31 and 36 h post onset of symptoms, respectively, with MG peaks at 6, 11, 19, and 22 h with corresponding CK peaks delayed 2, 3, 3, and 9 h. The first MG and CK peaks represented between 30 and 40% of the total release while the following three peaks represented between 20 and 30% each. Cumulative MG release was correlated to the time of AMI development. No such correlation was found for CK. The results indicate that the development of AMI is a wavelike process not sufficiently described by the log-normal algorithm, on the basis of which, however, an index of total release might be obtained.     

Sites of proteolytic processing and noncovalent association of the distal C-terminal domain of CaV1.1 channels in skeletal muscle

In skeletal muscle cells, voltage-dependent potentiation of Ca2+ channel activity requires phosphorylation by cAMP-dependent protein kinase (PKA) anchored via an A-kinase anchoring protein (AKAP15), and the most rapid sites of phosphorylation are located in the C-terminal domain. Surprisingly, the site of interaction of the complex of PKA and AKAP15 with the alpha1-subunit of Ca(V)1.1 channels lies in the distal C terminus, which is cleaved from the remainder of the channel by in vivo proteolytic processing. Here we report that the distal C terminus is noncovalently associated with the remainder of the channel via an interaction with a site in the proximal C-terminal domain when expressed as a separate protein in mammalian nonmuscle cells. Deletion mapping of the C terminus of the alpha1-subunit using the yeast two-hybrid assay revealed that a distal C-terminal peptide containing amino acids 1802-1841 specifically interacts with a region in the proximal C terminus containing amino acid residues 1556-1612. Analysis of the purified alpha1-subunit of Ca(V)1.1 channels from skeletal muscle by saturation sequencing of the intracellular peptides by tandem mass spectrometry identified the site of proteolytic processing as alanine 1664. Our results support the conclusion that a noncovalently associated complex of the alpha1-subunit truncated at A1664 with the proteolytically cleaved distal C-terminal domain, AKAP15, and PKA is the primary physiological form of Ca(V)1.1 channels in skeletal muscle cells.     

厄贝沙坦和咪达普利对高血压大鼠心肌细胞外信号调节激酶的影响

目的　探讨血管紧张素Ⅱ受体阻滞剂厄贝沙坦和血管紧张素转换酶抑制剂 (ACEI)咪达普利对高血压大鼠心肌细胞外信号调节激酶 (ERK)和丝裂原活化蛋白激酶磷酸酶 1(MKP 1)的影响。方法　将 2 1只雄性自发性高血压大鼠 (SHR)随机分成 3组 ,每组 7只。其中 2组分别灌喂厄贝沙坦 5 0mg·kg-1·d-1和咪达普利 3mg·kg-1·d-1;对照组给正常饮水 ,并与雄性同周龄WistarKyoto大鼠 (WKY) 6只比较。共 13周 ,用Western blot方法检测大鼠心肌ERK 1和MKP 1。结果　高血压对照组心肌ERK 1明显高于其他三组 (P <0 0 1) ,厄贝沙坦组高于咪达普利组 (P <0 0 5 ) ,与WKY组接近 ;高血压对照组心肌MKP 1也明显高于其他三组 (P <0 0 1) ,厄贝沙坦组高于咪达普利组 (P <0 0 1) ;SHR对照组的心肌ERK 1/MKP 1值仍然明显高于其他三组 ,厄贝沙坦组低于咪达普利组 (P <0 0 5 ) ,两药物干预组的心肌ERK 1/MKP 1与WKY组无显著性差异。结论　血管紧张素Ⅱ受体阻滞剂和ACEI均能通过抑制MAPK途径而抑制左室肥厚 ,厄贝沙坦和咪达普利均能显著抑制心肌的ERK 1和MKP 1,但是抑制ERK 1和MKP 1的强度并不平行 ;厄贝沙坦对MKP的影响较小 ,其对MAPK的总体抑制效应优于咪达普利 ,这种现象可能与刺激血管紧张素Ⅱ受体对MKP 1具有诱导作用有关     

丝裂原激活蛋白激酶磷酸酶-1和p38在内膜损伤后血管平滑肌细胞表型转化过程中的表达变化

目的:观察动脉内膜损伤后血管平滑肌细胞(VSMC)表型转化和p38MAPK及丝裂原激活蛋白激酶磷酸酶-1(MKP-1)表达的动态变化。方法:分别用免疫组化、免疫印迹(Westernblot)和逆转录-聚合酶链反应方法检测假损伤组(S组)和损伤组损伤后不同时间点血管壁中增殖细胞核抗原(PCNA)、平滑肌α肌动蛋白(SMα-actin)、p38蛋白和MKP-1mRNA及蛋白表达的变化。结果:①S组中膜VSMC及内皮细胞PCNA为阴性表达;中膜于损伤后1~14d,新生内膜(NI)于5~14d阳性细胞率逐渐增加,28d后开始逐渐减少,NI阳性率高于中膜。②S组中膜SMα-actin表达为阳性,内皮为阴性;中膜阳性表达于损伤后1d开始减少,3d最为明显,5d后开始逐渐增加,NI阳性表达弱于中膜。③S组中膜p38呈阴性或弱阳性;损伤后1~35d呈持续高表达,NI阳性表达强于中膜。p38与PCNA表达变化呈正相关。④S组中膜MKP-1呈弱阳性或阳性表达;损伤后1d即开始下降,14~28d稍有回升,至35d仍未回到S组水平,NI阳性表达稍弱于中膜。MKP-1与PCNA表达变化呈负相关。结论:VSMC增殖能力与其表型转化密切相关,p38MAPK和MKP-1参与了损伤后VSMC表型转化的信号转导及其调节。     

槲皮素抑制血小板活化因子受体结合作用的研究

目的 :观察槲皮素对氚标记的血小板活化因子与血小板膜上受体结合的影响 ,试图证明该药为一新型血小板激活因子 (PAF)受体拮抗剂。方法 :以放射配基结合试验观察 [3H]PAF与兔血小板受体特异性结合的作用 ;以分光光度法测定PAF诱发血小板黏附的强度。结果 :槲皮素可浓度依赖地抑制2 5 ,5 0 ,10 0nmol·L- 1 [3H]PAF与兔血小板受体的特异性结合 ;该药可明显抑制PAF诱发的血小板黏附 ,具明显的量效关系 ,其IC50 为 39 8μmol·L- 1 。结论 :槲皮素具抗PAF作用 ,为一新的PAF受体拮抗剂。     

Integrin and extracellular matrix interactions regulate engraftment of transplanted hepatocytes in the rat liver

BACKGROUND & AIMS: Recognition and circumvention of the hepatic endothelial barrier is critical in the engraftment of transplanted cells. We examined whether interactions between integrin and extracellular matrix component receptors could be manipulated for improving transplanted cell engraftment and liver repopulation. METHODS: Fischer 344 rat hepatocytes were transplanted into syngeneic dipeptidyl peptidase IV-deficient rats. Coating of cells or of liver sinusoids with natural collagen, natural laminin, or an engineered fibronectin-like polymer was studied with analysis of cell engraftment and liver repopulation using histologic and molecular assays. Focal adhesion complexes were identified by vinculin immunostaining. The role of integrin receptors in cell engraftment was analyzed with RGD peptide inhibition assays. RESULTS: Coating of cells with extracellular matrix components before transplantation did not enhance cell engraftment. In contrast, intraportal infusion of collagen or fibronectin-like polymer in recipients prior to cell transplantation increased cell engraftment. Adherence of transplanted cells to the hepatic endothelium resulted in rapid activation of vinculin-containing focal adhesion complexes. Superior cell engraftment in animals treated with fibronectin-like polymer was RGD sensitive, verifying the integrin-dependent nature of this process. Moreover, studies in the retrorsine-partial hepatectomy rat model showed that intraportal infusion of the fibronectin-like polymer before cell transplantation significantly accelerated liver repopulation. CONCLUSIONS: Integrin-extracellular matrix component interactions can be manipulated for enhancing cell engraftment in the liver. Such mechanisms will be relevant for engraftment of other cell types and for strategies concerning liver-directed cell therapy.