Endoglin modulates cellular responses to TGF-beta 1

Endoglin is a homodimeric membrane glycoprotein which can bind the beta 1 and beta 3 isoforms of transforming growth factor-beta (TGF-beta). We reported previously that endoglin is upregulated during monocyte differentiation. We have now observed that TGF-beta itself can stimulate the expression of endoglin in cultured human monocytes and in the U-937 monocytic line. To study the functional role of endoglin, stable transfectants of U-937 cells were generated which overexpress L- or S- endoglin isoforms, differing in their cytoplasmic domain. Inhibition of cellular proliferation and downregulation of c-myc mRNA which are normally induced by TGF-beta 1 in U-937 cells were totally abrogated in L-endoglin transfectants and much reduced in the S-endoglin transfectants. Inhibition of proliferation by TGF-beta 2 was not altered in the transfectants, in agreement with the isoform specificity of endoglin. Additional responses of U-937 cells to TGF-beta 1, including stimulation of fibronectin synthesis, cellular adhesion, platelet/endothelial cell adhesion molecule 1 (PECAM-1) phosphorylation, and homotypic aggregation were also inhibited in the endoglin transfectants. However, modulation of integrin and PECAM-1 levels and stimulation of mRNA levels for TGF-beta 1 and its receptors R-I, R-II, and betaglycan occurred normally in the endoglin transfectants. No changes in total ligand binding were observed in L-endoglin transfectants relative to mock, while a 1.5-fold increase was seen in S-endoglin transfectants. The degradation rate of the ligand was the same in all transfectants. Elucidating the mechanism by which endoglin modulates several cellular responses to TGF-beta 1 without interfering with ligand binding or degradation should increase our understanding of the complex pathways which mediate the effects of this factor.

Endoglin, a component of the TGF-beta receptor system, is a differentiation marker of human choriocarcinoma cells

Endoglin is an integral membrane glycoprotein that binds transforming growth factor-beta1 (TGF-beta1) with high affinity and it is strongly expressed on syncytiotrophoblasts throughout pregnancy. Here, we describe the expression of endoglin by the choriocarcinoma cell line JAR as evidenced by flow cytometry, immunoprecipitation, Western blot and reverse transcriptase polymerase chain reaction analyses. Cross-linking experiments of [125I]-labeled TGF-beta1 to JAR cells indicated that endoglin expressed at the surface of these cells binds TGF-beta. Furthermore, staining of human choriocarcinoma tissue sections with a polyclonal antibody to endoglin demonstrated a high expression of endoglin in syncytiotrophoblast-like areas, as opposed to a negative staining of cytotrophoblast-like cells. This pattern of endoglin expression was confirmed by experiments with methotrexate, an inducer of giant, multinucleated, non-proliferative cells, morphologically indistinguishable from the naturally occurring syncytiotrophoblasts. Thus, treatment of the JAR and JEG-3 choriocarcinoma cell lines with methotrexate led to an increase in endoglin expression, as demonstrated by Western and Northern blot analyses. Taken together, our results suggest that endoglin, in addition to being involved in placental development, may also be a cellular differentiation marker.

Identification of a functional NF-kappa B site in the platelet endothelial cell adhesion molecule-1 promoter

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a type I transmembrane adhesion protein of 130 kDa that belongs to a subgroup of the Ig gene superfamily, characterized by the presence of immunoreceptor tyrosine-based inhibitory motifs. PECAM-1 is expressed in circulating platelets, monocytes, neutrophils, a selective subgroup of T cells, and in endothelial cells, where it is preferentially located at intercellular junctions and participates in leukocyte transmigratory processes. The identification of two consensus NF-kappa B sites within the PECAM-1 promoter led us to analyze their possible involvement in the PECAM-1 expression regulated by inflammatory stimuli. We found that surface expression and promoter activity of PECAM-1 in myeloid cells are regulated by modulators of NF-kappa B, including TNF-alpha, PMA, and pyrrolidine dithiocarbamate. Mobility shifts assays identified a specific NF-kappa B-binding element at +110/+120, whose mutation abolished the basal promoter activity of PECAM-1 and decreased NF-kappa B-dependent responses of the PECAM-1 gene promoter. Furthermore, cotransfection experiments with an expression vector encoding the p65 subunit of NF-kappa B showed transactivation of the PECAM-1 promoter. These results demonstrate that NF-kappa B can regulate the transcriptional activity of PECAM-1.

Targeting gene expression to endothelium in transgenic animals: a comparison of the human ICAM-2, PECAM-1 and endoglin promoters

It is highly likely that successful pig-to-human xenotransplantation of vascularized organs will require genetic modification of the donor pig, and in particular of donor vascular endothelium. Promoters are generally tested in transgenic mice before generating transgenic pigs. Several promoters have been used to drive endothelial cell-specific expression in mice but none have yet been tested in pigs. We compared the promoters of three human genes that are predominantly expressed in vascular endothelium: intercellular adhesion molecule 2 (ICAM-2), platelet endothelial cell adhesion molecule 1 (PECAM-1) and endoglin. Expression of human complement regulatory proteins (hCRPs), directed by each of the promoters in mice, was largely restricted to vascular endothelium and leukocyte subpopulations. However, expression from the PECAM-1 promoter was weak in liver and non-uniform in the small vessels of heart, kidney, and lung. Conversely, expression from the endoglin promoter was consistently strong in the small vessels of these organs but was absent in larger vessels. The ICAM-2 promoter, which produced strong and uniform endothelial expression in all organs examined, was therefore used to generate hCRP transgenic pigs. Leukocytes from 57 pigs containing at least one intact transgene were tested for transgene expression by flow cytometry. Forty-seven of these transgenic pigs were further analyzed by immunohistochemical staining of liver biopsies, and 18 by staining of heart and kidney sections. Only two of the pigs showed expression, which appeared to be restricted to vascular endothelium in heart and kidney but was markedly weaker than in transgenic mice produced with the same batch of DNA. Thus, in this case, promoter performance in mice and pigs was not equivalent. The weak expression driven by the human ICAM-2 promoter in pigs relative to mice suggests the need for additional regulatory elements to achieve species-specific gene expression in pigs.

L-Dopa release from mesoporous silica nanoparticles engineered through the concept of drug-structure-directing agents for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease, the 2nd most common after Alzheimer's disease, the main effect of which is the loss of dopaminergic neurons. Levodopa or l-Dopa is an amino acid used in the treatment of PD that acts as the immediate precursor to dopamine. However, over time the efficacy of the medication gradually decreases requiring modified delivery methods. One of the major challenges for the medication to work is to achieve a gradual continuous supply of l-Dopa to the brain to minimise symptoms. Herein, mesoporous silica nanoparticles (MSNs) were engineered through the concept of drug-structure-directing agents (DSDAs) with inherent therapeutic activity. The DSDA used was l-Dopa drug modified by amidation with fatty acids to build anionic surfactants that were able to form micelles as templates for the assembly of inorganic precursors to form the silica framework. This templating route produced MSNs with tunable sizes ranging from 100 nm to 1 μm and with different shapes: spherical, with either solid structures with radial mesopores and porous shells, or hollow-shells with inside large void cavities; and elongated, characterized by long hollows covered by mesoporous shells. The concept of using DSDAs to synthesize drug nanocarriers can be used to avoid the surfactant removal and subsequent drug loading steps involved in the synthesis of conventional MSNs. We hypothesized that the l-Dopa released from MSN materials is mediated by the size and solubility of the DSDAs, and the surface chemical interactions between the DSDAs and MSN hosts. Different pHs (acidic and neutral) simulating gastrointestinal tract conditions were tested, and the results showed hardly any release for gastric conditions at pH 1.2, avoiding the premature release in the stomach typical of conventional MSNs, while for intestinal conditions of pH 7.4, the release of l-Dopa occurred in a continuous and sustained manner, which is well suited to the drug's application and delivery route, and matches well with achieving a sustained l-Dopa delivery to relief symptoms. This could open up new uses for MSNs synthesized by this approach to treat PD.

Safety of balloon kyphoplasty in the treatment of osteoporotic vertebral compression fractures in Europe: a meta-analysis of randomized controlled trials

PURPOSE

The study aims to evaluate the safety of balloon kyphoplasty in the treatment of painful osteoporotic vertebral compression fractures in Europe.

METHODS

Systematic review of the literature, until September 2013, and meta-analysis of randomized controlled trials performed in Europe assessing the safety of balloon kyphoplasty in patients with symptomatic osteoporotic vertebral fractures. Outcomes sought include cement leaks, serious clinical complications and new vertebral fractures.

RESULTS

Six randomized controlled trials fulfilled the inclusion criteria. These studies included data on 525 treated levels in 424 patients. Cement leakages were detected in 18.3 % (95 % CI 11.6, 23.0) of fractures intervened. In about 0.5 % (95 % CI 0.1, 1.1) of fractures leakages proved to be symptomatic. Serious clinical complications were recorded in 11.5 % (95 % CI 1.1, 21.7) of patients treated with balloon kyphoplasty with several of these cases requiring intensive treatment or postoperative surgery. New vertebral fractures were detected in 20.7 % (95 % CI 0.4, 40.9) of patients treated but rates showed an upward pattern when the follow-up period increased. In 54 % of such cases, the fractures were located in regions adjacent to the treated level.

CONCLUSIONS

The safety profile and associated complications of balloon kyphoplasty shown in this analysis, based on the evidence provided by existing randomized controlled trials, can be of help to the practicing clinician who must contrast them with the potential benefits of the technique. These data represent an important step towards a balanced evaluation of the intervention though, a better reporting and more reliable data on long-term assessment of potential sequelae are needed.

Effectiveness and safety of glimepiride and iDPP4, associated with metformin in second line pharmacotherapy of type 2 diabetes mellitus: systematic review and meta-analysis

OBJECTIVE

Our review analyses the studies that have specifically compared the association iDPP4/metformin with glimepiride/metformin, both in second line pharmacotherapy of type 2 diabetes mellitus (DM2).

METHODS

Systematic literature review with a meta-analysis of clinical trials comparing glimepiride with any iDPP4, both used together with metformin as a second line treatment of DM2. The effectiveness variables used were as follows: %HbA1c variation, fasting plasma glucose variation, patients achieving the therapeutic objective of HbA1c <7%, treatment dropouts due to lack of effectiveness and rescue treatments needed. The safety variables included were as follows: weight variation at the end of treatment; presentation of any type of adverse event; presentation of serious adverse events; patients who experienced any type of hypoglycaemia; patients who experienced severe hypoglycaemia; treatments suspended due to adverse effects; and deaths for any reason.

RESULTS

Four studies met the inclusion criteria. The group treated with glimepiride showed better results in all effectiveness variables. Regarding safety variables, the main differences observed were in the greater number of cases with hypoglycaemia in the group treated with glimepiride, and the serious adverse events or treatment discontinuations due to these which occurred in slightly over 2% more cases in this group compared to the iDPP4 group. The remaining adverse events, including mortality, did not show any differences between both groups. The variation in the weight difference between groups (2.1 kg) is not considered clinically relevant.

CONCLUSIONS

A greater effectiveness is seen in the glimepiride/metformin association, which should not be diminished by slight differences in adverse effects, with absence of severe hypoglycaemia in over 98% of patients under treatment. The association of glimepiride/metformin, both due to cost as well as effectiveness and safety, may be the preferential treatment for most DM2 patients, and it offers a potential advantage in refractory hyperglycemic populations, tolerant to treatment.

Cloning of the human platelet endothelial cell adhesion molecule-1 promoter and its tissue-specific expression. Structural and functional characterization

Platelet endothelial cell adhesion molecule-1 (PECAM-1; CD31) is a cell adhesion molecule involved in transendothelial migration and expressed by hemopoietic and endothelial cells. To understand the mechanisms underlying its regulated expression, a genomic clone containing 1555 bp of the 5'-flanking region and the first exon of the human PECAM-1 gene has been isolated. The 5'-flanking region of the PECAM-1 gene lacks a consensus TATA box, but contains consensus motifs for Sp1, EGR1, ets, helix-loop-helix (HLH) box, GATA, AP-2, C/EBP, YY1, CCACC, LyF-1, imperfect octamer, heptamer, high mobility group proteins (HMG) box, and nuclear factor-kappaB, as well as shear stress-, retinoic acid-, glucocorticoid-, and acute phase-responsive elements, and an Alu sequence. Successive 5' to 3' or 3' to 5' deletions revealed tissue-specific promoter activity within the two contiguous 0.22-kb NheI/BglII and 0.44-kb BglII/PstI fragments. The transcriptional activity displayed by the 0.22-kb NheI/BglII fragment was specific for the myeloid lineage, whereas the promoter activity of the 0.44-kb BglII/PstI fragment was apparently restricted to endothelial cells. The transcriptional activity of the 0.22-kb NheI/BglII fragment was confirmed by 5' RACE (rapid amplification of 5' cDNA ends) and S1 nuclease protection experiments that revealed previously unidentified transcription start sites. The 0.22-kb NheI/BglII promoter exhibited PMA inducibility in myeloid cells and contained a PMA-responsive element recognized by Sp1 and EGR-1 transcription factors. Isolation and characterization of the human PECAM-1 promoter represent an initial step in elucidating the controlled expression of the PECAM-1 gene.

Cloning of the promoter region of human endoglin, the target gene for hereditary hemorrhagic telangiectasia type 1

Endoglin (CD105) is a cell surface component of the transforming growth factor-beta (TGF-beta) receptor complex highly expressed by endothelial cells. Mutations in the endoglin gene are responsible for the hereditary hemorrhagic telangiectasia type 1 (HHT1), also known as Osler-Weber-Rendu syndrome (OMIM 187300). This is an autosomal dominant vascular disorder probably caused by a haploinsufficiency mechanism displaying low levels of the normal protein. To understand the mechanisms underlying the regulated expression of endoglin, a genomic DNA clone containing 3.3 kb of the 5'-flanking sequence of the human endoglin gene has been isolated. The 5'-flanking region of the endoglin gene lacks consensus TATA and CAAT boxes, but contains two GC-rich regions and consensus motifs for Sp1, ets, GATA, AP-2, NFkappaB, and Mad, as well as TGF-beta-, glucocorticoid-, vitamin D-, and estrogen-responsive elements. As determined by primer extension and 5' RACE experiments, a cluster of transcriptional start sites was found to be located 350 bp upstream from the translation initiation codon. To analyze the endoglin promoter activity, the upstream -400/+341 fragment was fused to the luciferase gene and transient transfections were conducted in several cell types. This construct displayed a tissue-specific activity in human and bovine endothelial cells. Analysis of various deletion constructs showed the existence of a basal promoter region within the -81/+350 fragment as well as major transcriptional regulatory elements within the -400/-141 fragment. Electrophoretic mobility shift assays demonstrated the specific interaction of a member of the ets family with a consensus motif located at position -68. A promoter construct mutated at this ets sequence showed a much reduced activity as compared with the wild-type construct, supporting the involvement of this ets motif in the basal activity of the promoter. The endoglin promoter exhibited inducibility in the presence of TGF-beta1, suggesting possible therapeutic treatments in HHT1 patients, in which the expression level of the normal endoglin allele might not reach the threshold required for its function. Isolation and characterization of the human endoglin promoter represents an initial step in elucidating the controlled expression of the endoglin gene.

Cloning of the human platelet endothelial cell adhesion molecule-1 promoter and its tissue-specific expression. Structural and functional characterization

Platelet endothelial cell adhesion molecule-1 (PECAM-1; CD31) is a cell adhesion molecule involved in transendothelial migration and expressed by hemopoietic and endothelial cells. To understand the mechanisms underlying its regulated expression, a genomic clone containing 1555 bp of the 5'-flanking region and the first exon of the human PECAM-1 gene has been isolated. The 5'-flanking region of the PECAM-1 gene lacks a consensus TATA box, but contains consensus motifs for Sp1, EGR1, ets, helix-loop-helix (HLH) box, GATA, AP-2, C/EBP, YY1, CCACC, LyF-1, imperfect octamer, heptamer, high mobility group proteins (HMG) box, and nuclear factor-kappaB, as well as shear stress-, retinoic acid-, glucocorticoid-, and acute phase-responsive elements, and an Alu sequence. Successive 5' to 3' or 3' to 5' deletions revealed tissue-specific promoter activity within the two contiguous 0.22-kb NheI/BglII and 0.44-kb BglII/PstI fragments. The transcriptional activity displayed by the 0.22-kb NheI/BglII fragment was specific for the myeloid lineage, whereas the promoter activity of the 0.44-kb BglII/PstI fragment was apparently restricted to endothelial cells. The transcriptional activity of the 0.22-kb NheI/BglII fragment was confirmed by 5' RACE (rapid amplification of 5' cDNA ends) and S1 nuclease protection experiments that revealed previously unidentified transcription start sites. The 0.22-kb NheI/BglII promoter exhibited PMA inducibility in myeloid cells and contained a PMA-responsive element recognized by Sp1 and EGR-1 transcription factors. Isolation and characterization of the human PECAM-1 promoter represent an initial step in elucidating the controlled expression of the PECAM-1 gene.

Functional regulation of platelet/endothelial cell adhesion molecule-1 by TGF-beta 1 in promonocytic U-937 cells

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a widely distributed cell adhesion molecule present on monocytes, macrophages, and monocytic cell lines. Treatment of the promonocytic cell line U-937 with TGF-beta 1 induces homotypic cellular aggregations, simultaneous with an increase in surface expression and specific transcripts of PECAM-1. The TGF-beta-induced cell adhesion phenomena are not dependent on LFA-1, intercellular adhesion molecule-1 (ICAM-1), very late Ag-4 (VLA-4), or very late Ag-5 (VLA-5). However, the phenomena seem to be directly mediated by PECAM-1 because 1) it is inhibited by the addition of Abs or an antisense oligonucleotide specific for PECAM-1; and 2) TGF-beta 1-treated U-937 cells bind to PECAM-1-expressing mouse transfectant fibroblasts, but not to mock transfectants. In addition, this aggregation phenomena are divalent cation-dependent and requires the integrity of the cytoskeleton. Analysis of the intracellular signaling pathways indicates that TGF-beta 1 induces protein kinase C activity, as well as PECAM-1 phosphorylation and association with cytoskeletal components. Furthermore, in this model, an autocrine mechanism for releasing the bioactive form of TGF-beta 1 operates, allowing PECAM-1 activation. These results provide evidence that TGF-beta 1 regulates PECAM-1 function by increasing the expression and activating the adhesion of PECAM-1 in monocytic cells. These two mechanisms seem to be necessary for adhesion because independent inhibition of either expression or activation of PECAM-1 leads to abrogation of cellular aggregation.

Functional regulation of platelet/endothelial cell adhesion molecule-1 by TGF-beta 1 in promonocytic U-937 cells

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a widely distributed cell adhesion molecule present on monocytes, macrophages, and monocytic cell lines. Treatment of the promonocytic cell line U-937 with TGF-beta 1 induces homotypic cellular aggregations, simultaneous with an increase in surface expression and specific transcripts of PECAM-1. The TGF-beta-induced cell adhesion phenomena are not dependent on LFA-1, intercellular adhesion molecule-1 (ICAM-1), very late Ag-4 (VLA-4), or very late Ag-5 (VLA-5). However, the phenomena seem to be directly mediated by PECAM-1 because 1) it is inhibited by the addition of Abs or an antisense oligonucleotide specific for PECAM-1; and 2) TGF-beta 1-treated U-937 cells bind to PECAM-1-expressing mouse transfectant fibroblasts, but not to mock transfectants. In addition, this aggregation phenomena are divalent cation-dependent and requires the integrity of the cytoskeleton. Analysis of the intracellular signaling pathways indicates that TGF-beta 1 induces protein kinase C activity, as well as PECAM-1 phosphorylation and association with cytoskeletal components. Furthermore, in this model, an autocrine mechanism for releasing the bioactive form of TGF-beta 1 operates, allowing PECAM-1 activation. These results provide evidence that TGF-beta 1 regulates PECAM-1 function by increasing the expression and activating the adhesion of PECAM-1 in monocytic cells. These two mechanisms seem to be necessary for adhesion because independent inhibition of either expression or activation of PECAM-1 leads to abrogation of cellular aggregation.