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Biomedical subjects

J Arts

Publications and source records attributed to J Arts.

At least 19 recordsLinked to original sources
PubMed2006

Influence of intrapyloric botulinum toxin injection on gastric emptying and meal-related symptoms in gastroparesis patients.

BACKGROUND: Recent observations in limited numbers of patients suggest a potential benefit of intrapyloric injection of botulinum toxin in the treatment of gastroparesis. AIM: To characterize the effect of botulinum toxin on solid and liquid gastric emptying and on meal-related symptoms. METHODS: In 20 gastroparesis patients (17 women, mean age 37 +/- 3 years, three diabetic and 17 idiopathic), gastric emptying for solids and liquids was measured before and one month after intrapyloric botulinum toxin 4 x 25 units. Before the meal and at 15-min intervals up to 240 min postprandially, the patient graded the intensity of six gastroparesis symptoms, and a meal-related severity score was obtained by adding all intensities. Data (mean +/- S.E.M.) were compared using paired Student's t-test. RESULTS: Treatment with botulinum toxin significantly enhanced solid (t(1/2) 132 +/- 16 vs. 204 +/- 35 min, P < 0.05) but not liquid (92 +/- 10 vs. 104 +/- 11 min, N.S.) emptying. This was accompanied by a significant decrease in cumulative meal-related symptom score (73.5 +/- 16.3 vs. 103 +/- 17.1 baseline, P = 0.01) as well as individual severity scores for postprandial fullness, bloating, nausea and belching (all P < 0.001, two-way anova). CONCLUSIONS: Botulinum toxin improves solid but not liquid gastric emptying in gastroparesis, and this is accompanied by significant improvement of several meal-related symptoms.

Adult↗
PubMed2006

Determinants of symptom pattern in idiopathic severely delayed gastric emptying: gastric emptying rate or proximal stomach dysfunction?

BACKGROUND: Idiopathic gastroparesis is a syndrome characterised by severely delayed gastric emptying of solids without an obvious underlying organic cause. Although delayed gastric emptying is traditionally considered the mechanism underlying the symptoms in these patients, poor correlations with symptom severity have been reported. AIMS: To investigate proximal stomach function and to study the correlation of delayed gastric emptying and proximal stomach dysfunction with symptom pattern and severity in idiopathic gastroparesis. METHODS: 58 consecutive patients (19 men, mean (standard deviation) age 41 (2) years) with severely delayed solid gastric emptying (gastric half-emptying time (t(1/2))>109 min) without an organic cause were recruited. They filled out a symptom-severity questionnaire and underwent a gastric barostat study for assessment of gastric sensitivity and accommodation. Correlation of these mechanisms with symptom pattern and overall symptom severity (sum of individual symptoms) was analysed. RESULTS: At two different cut-off levels for gastric emptying (upper limit of normal t(1/2) up to 1.5 and 2 times), no significant change in symptom pattern occurred. 25 (43%) patients had impaired accommodation, and this was associated with higher prevalence of early satiety (p<0.005) and weight loss (p = 0.009). 17 (29%) patients had hypersensitivity to gastric distension, and this was associated with higher prevalences of epigastric pain (p = 0.005), early satiety (p = 0.04) and weight loss (p<0.005). Overall symptom severity was not correlated with gastric emptying or accommodation, but only with sensitivity to gastric distension (R = -0.3898, p = 0.003) and body weight (R = -0.4233, p = 0.001). CONCLUSIONS: In patients with idiopathic gastroparesis, the symptom pattern is determined by proximal stomach dysfunction rather than by the severity of delayed emptying.

Adult↗
PubMed2006

Effect of an hdm-2 antagonist peptide inhibitor on cell cycle progression in p53-deficient H1299 human lung carcinoma cells.

The hdm-2 oncogene is overexpressed in several types of malignancies including osteosarcomas, soft tissue sarcomas and gliomas and hdm-2 has been associated with accelerated tumor formation in both hereditary and sporadic cancers. Among the other key binding partners, hdm-2 forms a complex with the tumor suppressor p53, resulting in a rapid proteasome-mediated degradation of the p53 protein. This positions the hdm-2-p53 complex as an attractive target for the development of anticancer therapy and recently the first small molecule hdm-2 antagonist has been reported. Development of hdm-2 antagonists is currently focused on malignancies containing a wild-type p53 genotype, which is the case in approximately half of human cancer indications. However, hdm-2 has also been implicated in oncogenesis in the absence of p53. We therefore studied the effect of hdm-2 antagonists in p53-deficient human H1299 lung carcinoma cells. The hdm-2 antagonistic peptide caused G1 cell cycle arrest, inhibited colony growth and induced expression of G1 checkpoint regulatory proteins, such as p21(waf1,cip1). These data demonstrate that hdm-2 regulates the G1 cell cycle checkpoint in a p53-independent manner, suggesting that hdm-2 antagonists represent a novel class of anticancer therapeutics with broad applicability towards tumors with different p53 genetic backgrounds.

Carcinoma↗
PubMed2005

Prevalence of acid reflux in functional dyspepsia and its association with symptom profile.

AIM: A subset of functional dyspepsia patients respond to acid suppressive therapy, but the prevalence of non-erosive reflux disease in functional dyspepsia and its relevance to symptoms have never been established. The aim of the present study was to study 24 hour pH monitoring in consecutive functional dyspepsia patients. METHODS: A total of 247 patients with dyspeptic symptoms (166 women, mean age 44 (SEM 1) year), with a negative upper gastrointestinal endoscopy and without dominant symptoms of heartburn participated in the study. In all patients, the severity of dyspeptic symptoms and the presence of heartburn was assessed by a questionnaire and a 24 hour oesophageal pH monitoring study was performed. All patients underwent a gastric emptying breath test and in 113 a gastric barostat study was performed. RESULTS: Abnormal pH monitoring (acid exposure >5% of time) was found in 58 patients (23%). Of 21 patients with a positive heartburn questionnaire, 76% had pathological pH monitoring, while this was the case in only 18.5% of patients with a negative heartburn questionnaire. Demographic characteristics and the prevalence of other pathophysiological mechanisms did not differ between heartburn negative patients with normal or abnormal acid exposure. Pathological acid exposure in heartburn negative patients was associated with the presence of epigastric pain (65 v 84%, p<0.005) and of moderate or severe pain (48 v 69%, p = 0.005). CONCLUSION: Pathological oesophageal acid exposure is only present in a subset of heartburn negative functional dyspepsia patients, which are characterised by a higher prevalence of epigastric pain.

Adult↗
PubMed2005

A one-year follow-up study of endoluminal gastroplication (Endocinch) in GERD patients refractory to proton pump inhibitor therapy.

In a subset of patients with gastroesophageal reflux disease (GERD), symptoms persist in spite of proton pump inhibitor (PPI) therapy. Endoscopic gastroplication (EG) was reported to provide a novel therapeutic option in GERD. To evaluate symptomatic and objective outcome of EG in PPI refractory GERD, consecutive GERD patients with persisting reflux symptoms during at least 2 months double dose PPI were recruited for EG (Endocinch). Exclusion criteria were high-grade esophagitis, Barrett's esophagus, and hiatal hernia > 3 cm. Symptoms and PPI use were evaluated before and 1, 3, and 12 months after the EG; 24-hr pH monitoring off PPI was performed before and after 3 and 12 months. All data are given as mean +/- SD and were analyzed by Student's t test. Twenty patients (10 females; mean age, 45 +/- 11 years) were recruited. Under conscious sedation with midazolam (6 +/- 2 mg) and pethidine (53 +/- 5 mg), a mean of 2.0 +/- 0.2 sutures was applied during a procedure time of 33 +/- 6 min. Throat ache and mild epigastric pain for up to 3 days after the procedure were the only adverse events. At 3 and 12 months symptom score (11.6 +/- 6 vs. 6.4 +/- 3.7 [P < 0.01] and 7.1 +/- 4.5 [P < 0.05]) as well as pH monitoring (% time pH < 4: 17.0 +/- 11.1 vs. 8.1 +/- 5.7% [P < 0.01] and 9.8 +/- 4.1% [P < 0.01]) significantly improved. Ph monitoring was normalized (< 4% of time) in seven patients after 3 months. PPIs could be stopped in 13 patients, with 2 patients still using H2-blockers and 1 using cisapride after 3 months. After 12 months only six patients were free of PPI use and pH monitoring was normalized in six patients. We conclude that EG provides short- and medium-term symptomatic and objective relief to a subset of GERD patients refractory to high-dose PPI.

Drug Resistance↗
PubMed2005

Influence of erythromycin on gastric emptying and meal related symptoms in functional dyspepsia with delayed gastric emptying.

BACKGROUND AND AIMS: Although delayed gastric emptying is considered a major pathophysiological mechanism in functional dyspepsia, the efficacy of prokinetic drugs has not been established. Recent studies using macrolide prokinetics were negative but receptor desensitisation may have played a role. The aim of the present study was to evaluate the influence on meal induced symptoms of acutely administered erythromycin in patients with gastroparesis. METHODS: In 20 patients with functional dyspepsia, gastric emptying was studied twice using the (14)C octanoic acid and (13)C glycin breath test to establish the reproducibility of the test. Breath samples were taken before the meal and at 15 minute intervals for a period of 240 minutes postprandially. At each breath sampling, the patient was asked to grade the intensity (0-3) of six dyspeptic symptoms. Twenty four patients (three men, mean age 43.5 (3) years) with dyspeptic symptoms and delayed gastric emptying were studied twice after pretreatment with saline or erythromycin intravenously. RESULTS: Meal related symptom severity scores were reproducible. Treatment with erythromycin significantly enhanced solid and liquid gastric emptying (t(1/2) 146 (27) v 72 (7) minutes, respectively (p<0.01), and 87 (6) v 63 (5) minutes (p<0.001)). Only the severity of bloating was significantly improved by erythromycin (23 (3.9) v 14.5 (2.7); p<0.01); all other symptoms and the cumulative meal related symptom score were not altered by erythromycin. CONCLUSIONS: In a setting where desensitisation played no role, erythromycin enhanced gastric emptying was not associated with a beneficial effect on meal related symptom severity.

Adolescent↗
PubMed2004

Assay development for high throughput screening of p21(Waf1/Cip1) protein expression in intact cells using fluorometric microvolume assay technology.

The p21(Waf1/Cip1) protein represents a broad-acting cyclin-dependent kinase inhibitor that plays a key role in cell cycle regulation. Furthermore, p21(Waf1/Cip1) protein has been described as a direct participant in regulating genes involved in growth arrest, senescence and aging. In response to genotoxic insults (e.g., following chemotherapeutic treatment), p21(Waf1/Cip1) protein accumulates mainly through p53-mediated transcriptional activation and is also regulated at the post-transcriptional level. In tumor cells, p53 is frequently mutated leading to reduced p21(Waf1/Cip1) protein induction that may contribute to resistance to treatment by DNA-damaging agents. In order to identify compounds capable of restoring p21(Waf1/Cip1) protein level, we have developed a 96-multi-well plate-based high throughput screening assay in intact cells using the Applied Biosystems Fluorometric Microvolume Assay Technology (FMAT) macro-confocal system. Briefly, following incubation with test compounds, human MCF7 breast carcinoma cells were fixed and p21(Waf1/Cip1) protein was detected using anti-p21(Waf1/Cip1) monoclonal antibody and anti-mouse IgG conjugated to the red fluorescent dye Alexafluor 633. FMAT provides a set of raw images at a high magnification, in which fluorescence concentrated in a cell is detected as a specific signal. The mean fluorescence of a population of cells is calculated independently of the number of cells as with a classical FACS analysis. This is of particular interest for screening anticancer drugs that may affect cell number and therefore may impact on the readout. This assay was validated using reference compounds such as camptothecin and actinomycin D, known inducers of p21(Waf1/Cip1) protein.

Belgium↗
PubMed1999

Estradiol formation by human osteoblasts via multiple pathways: relation with osteoblast function.

The importance of estrogens in bone metabolism is illustrated by the accelerated bone loss and increase in osteoporotic fractures associated with postmenopausal estrogen deficiency. In this study, the expression and activity of the enzymes involved in estrogen metabolism in human osteoblastic cells were investigated in relation to differentiation of these cells. PCR reactions using mRNA from an in vitro differentiating human cell line (SV-HFO) were performed to assess mRNA expression of the enzymes aromatase, different subtypes of 17beta-hydroxysteroid dehydrogenase (17beta-HSD), and steroid sulfatase. Aromatase, sulfatase, and 17beta-HSD type 2 and 4 were found to be expressed throughout differentiation. Expression of 17beta-HSD type 3, however, was relatively weak, except for early time points in differentiation. Type 1 17beta-HSD expression was not detected. Aromatase activity decreased during differentiation, as was demonstrated by the conversion of androstenedione (A) and testosterone (T) into estrone (E(1)) and estradiol (E(2)), respectively. The 17beta-HSD isozymes catalysing a reductive reaction convert androstenedione and estrone into testosterone and estradiol, respectively. Their activity declined with differentiation. Analysis of 17beta-HSD activity indicated both oxidative (E(2) to E(1); T to A) and reductive (E(1) to E(2); A to T) metabolism at all stages of osteoblast differentiation. Both activities declined as cells moved toward a differentiating mineralizing phenotype. However, the oxidative reaction was increasingly in favor of the reductive reaction at all times during differentiation. Sulfatase activity, as demonstrated by the conversion of estrone-sulfate into estrone, was constant during differentiation. In conclusion, we have demonstrated that all enzymes necessary for estrogen metabolism are expressed and biologically active in differentiating human osteoblasts. The activity of aromatase and 17beta-HSD was found to be dependent on the stage of cell differentiation. In addition, human osteoblasts effectively convert estradiol into estrone. The efficacy of osteoblasts to synthesize estradiol may determine the ultimate change in rate of bone turnover after menopause, as well as the development of osteoporosis. Moreover, the enzymes involved in the metabolism of estradiol may form a target for intervention.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

On the role of c-Jun in the induction of PAI-1 gene expression by phorbol ester, serum, and IL-1alpha in HepG2 cells.

We have characterized the regulation of plasminogen activator inhibitor-1 (PAI-1) gene expression by phorbol 12-myristate 13-acetate (PMA), serum, and interleukin-1alpha (IL-1alpha) in the human hepatoma cell line HepG2. PMA, serum, and IL-1alpha induced a rapid and transient 28-fold (PMA), 9-fold (serum), and 23-fold (IL-1alpha) increase in PAI-1 mRNA, peaking after approximately 4 hours. These inductions of PAI-1 mRNA accumulation were reduced by pretreatment of the HepG2 cells with the protein tyrosine kinase inhibitor genistein. Conversely, stimulation of tyrosine phosphorylation by sodium orthovanadate, an inhibitor of protein tyrosine phosphatases, caused an increase in PAI-1 mRNA levels. The effects of PMA, serum, and IL-1alpha on PAI-1 mRNA expression have been compared with their ability to modulate the expression of a chloramphenicol acetyltransferase (CAT) reporter plasmid, which was under control of the -489 to +75 region of the PAI-1 promoter, and stably transfected into HepG2 cells. This region of the PAI-1 promoter was previously found to contain a tetradecanoyl phorbol acetate-response element (TRE; between -58 and -50) necessary for PMA responsiveness and with a high affinity for c-Jun homodimers. Whereas incubation of these transfected HepG2 cells with PMA and serum showed an induction profile of CAT mRNA similar to that of PAI-1 mRNA, hardly any induction of CAT mRNA was found with IL-1alpha. In line with these findings, IL-1alpha poorly induced c-Jun homodimer binding to the PAI-1 TRE in gel mobility-shift assays. Pretreatment of HepG2 cells with the protein kinase C inhibitor Ro 31-8220 or the mitogen-activated protein kinase kinase (MAPKK)1,2 activity blocker PD98059 selectively suppressed the induction of PAI-1 (and CAT) expression by PMA, but not that by IL-1alpha. In contrast, the protein tyrosine kinase inhibitor herbimycin A blocked PAI-1 mRNA induction by IL-1 alpha only. We propose 2 separate PAI-1 inductory pathways for PMA and IL-1alpha in HepG2, both involving protein tyrosine kinase activation; the serum-induced signaling pathway may (partially) overlap with the PMA-activated protein kinase C/mitogen-activated protein kinase kinase pathway, leading to c-Jun homodimer binding to the PAI-1 TRE.

Binding Sites↗
PubMed1997

Cell-type specific DNA-protein interactions at the tissue-type plasminogen activator promoter in human endothelial and HeLa cells in vivo and in vitro.

Tissue-type plasminogen activator (t-PA) gene expression in human endothelial cells and HeLa cells is stimulated by the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) at the level of transcription. To study the mechanism of transcriptional regulation, we have characterized a segment of the t-PA gene extending from -135 to +100 by in vivo footprinting analysis [dimethyl sulphate (DMS) method] and gel mobility shift assay. In vivo footprinting analysis revealed changes in cleavage pattern in five distinct promoter elements in both endothelial cells and HeLa cells, including a PMA-responsive element (TRE), a CTF/NF-1 binding site and three GC-boxes, and an altered cleavage pattern of the TRE and CTF/NF-1 element after PMA treatment of HeLa cells. Although endothelial cells and HeLa cells differed in the exact G residues protected by nuclear proteins,in vitro bandshift analysis showed that nuclear protein binding to the t-PA promoter was qualitatively and quantitatively very similar in both cell types, except for the TRE. Protein binding to the TRE under non- stimulated conditions was much higher in human endothelial cells than in HeLa cells, and this TRE-bound protein showed a lower dissociation rate in the endothelial cells than in HeLa cells. In endothelial cells, the proteins bound to the TRE consisted mainly of the AP-1 family members JunD and Fra-2, while in HeLa cells predominantly JunD, FosB and Fra-2 were bound. The proteins bound to the other protected promoter elements were identified as SP-1 (GC-box II and III) and CTF/NF-1 (CTF/NF-1 binding site). After PMA treatment of the cells, AP-1 and SP-1 binding was increased two-fold in endothelial cell nuclear extracts and >20-fold in HeLa nuclear extracts. In the endothelial cells, all Jun and Fos forms (c-Jun, JunB, JunD, c-Fos, FosB, Fra-1 and Fra-2) were part of the AP-1 complex after PMA induction. In HeLa cells, the complex consisted predominantly of c-Jun and the Fos family members FosB and Fra-2. In the light of previous studies involving mutational analysis of the human and murine t-PA promoter our results underline an important role of the five identified promoter regions in basal and PMA-stimulated t-PA gene expression in intact human endothelial cells and HeLa cells. The small differences in DMS protection pattern and differences in the individual AP-1 components bound in endothelial cells and HeLa cells point to subtle cell-type specific differences in t-PA gene regulation.

CCAAT-Enhancer-Binding Proteins↗
PubMed1997

Studies on the mechanism of fibrate-inhibited expression of plasminogen activator inhibitor-1 in cultured hepatocytes from cynomolgus monkey.

Fibrates are widely used drugs in hyperlipidemic disorders. In addition to lowering serum triglyceride levels, fibrates have also been shown to reduce elevated plasma plasminogen activator inhibitor-1 (PAI-1) levels in vivo. We demonstrate that fibrates suppress PAI-1 synthesis in cultured cynomolgus monkey hepatocytes in a concentration-dependent way (0.1 to 1.0 mmol/L) and independent of their lipid-lowering effect. Different fibrates showed different potency in suppressing PAI-1 production: gemfibrozil and clofibric acid, at a concentration of 1 mmol/L, reduced PAI-1 synthesis over 24 hours to 52 +/- 20% and 60 +/- 5%, while clofibrate and bezafibrate lowered PAI-1 synthesis to only 86 +/- 17% and 84 +/- 15% of control values, respectively. These changes in PAI-1 production by fibrates correlated with changes in PAI-1 mRNA levels and were also visible at the level of gene transcription. Fibrates did not lower basal PAI-1 synthesis but attenuated an acceleration of PAI-1 production during culture. The suppressing effect of fibrates on PAI-1 synthesis could not be mimicked with activators or inhibitors of protein kinase C (PKC). Furthermore, fibrates did not inhibit the increase in PAI-1 synthesis induced by epidermal growth factor or transforming growth factor-beta. These results make mechanisms involving PKC modulation or growth factor receptor inactivation as a mode of action of fibrates unlikely. The suppressing effect of fibrates on PAI-1 synthesis could involve the nuclear receptor peroxisome proliferator-activated receptor (PPAR) and its heterodimeric partner, the retinoid X receptor (RXR). The alpha forms of PPAR and RXR were both found to be expressed in cynomolgus monkey hepatocytes. the ligand for RXR alpha, 9-cis retinoic acid, suppressed PAI-1 synthesis to the same extent as gemfibrozil, while a combination of gemfibrozil and 9-cis retinoic acid had no more effect on PAI-1 synthesis than any of these compounds alone at optimal concentrations. In conclusion, fibrates downregulate an induced PAI-1 production in cynomolgus monkey hepatocytes independent of a decrease in triglyceride levels. A possible involvement of PPAR alpha/RXR alpha in this down-regulation is discussed.

Animals↗
PubMed1997

Differential expression of estrogen receptors alpha and beta mRNA during differentiation of human osteoblast SV-HFO cells.

Estrogens have been shown to be essential for maintaining a sufficiently high bone mineral density and ER alpha expression has been demonstrated in bone cells. Recently, a novel estrogen receptor, estrogen receptor beta (ERbeta) has been identified. Here we demonstrate that also ERbeta is expressed in human osteoblasts, and that ER alpha and ERbeta are differentially expressed during human osteoblast differentiation. ERbeta mRNA expression increased gradually during osteoblast culture, resulting in an average increase of 9.9+/-5.3 fold (mean+/-S.D., n=3) at day 21 (mineralization phase) as compared to day 6 (proliferation phase). In contrast, ER alpha mRNA expression levels increased only slightly until day 10 (2.3+/-1.7 fold) and then remained constant. The observed differential regulation of ER alpha and beta is suggestive for an additional functional role of ERbeta to ER alpha in bone metabolism.

Cell Differentiation↗
PubMed1996

Role of c-Jun and proximal phorbol 12-myristate-13-acetate-(PMA)-responsive elements in the regulation of basal and PMA-stimulated plasminogen-activator inhibitor-1 gene expression in HepG2.

Experiments were designed to clarify the role of c-Jun/c-Fos and of putative phorbol 12-myristate-13-acetate-(PMA)-responsive elements (TREs) in the induction of plasminogen-activator inhibitor 1 (PAI-1) gene transcription in the human hepatoma cell line HepG2 by activators of protein kinase C (PKC). Treatment of HepG2 cells with the phorbol ester PMA or serum rapidly and transiently increased c-Jun and c-Fos mRNA and protein levels prior to PAI-1 induction. This induction of PAI-1 gene transcription was found to be dependent on ongoing protein synthesis. An essential role of c-Jun and c-Fos in basal and PMA-stimulated transcription of the PAI-1 gene is demonstrated by our finding that antisense c-jun and c-fos oligodeoxynucleotides both strongly reduced basal and PMA-stimulated PAI-1 synthesis. Since it has already been shown that two TREs between positions -58 and -50 and between -79 and -72 of the PAI-1 promoter are essential for basal and PMA-induced PAI-1 promoter activity ([16]), we examined binding of nuclear proteins to these elements. The protein-binding activity to the TRE between positions -79 and -72 shows very strong PMA induction of an unknown factor, which is not related to c-Jun or c-Fos. The TRE binding between positions -58 and -50 forms two complexes, both containing c-Jun protein. The faster migrating complex primarily contains c-Jun homodimers. The amount of the faster migrating complex is enhanced more than 30-fold in PMA-treated cells, due to a strongly increased binding of c-Jun homodimers and, to a minor extent, to binding of c-Jun/c-Fos heterodimers. Dissociation experiments suggest that the c-Jun/c-Fos heterodimers bind with much lower affinity compared to binding of c-Jun homodimers. Together with the finding that both antisense c-jun and antisense c-fos oligodeoxynucleotides reduced the amount of c-Jun homodimer, we conclude that binding of c-Jun homodimer to the TRE at positions -58 to -50 is important in the basal activity and PMA activation of the PAI-1 promoter in HepG2 cells.

Base Sequence↗
PubMed1995

Involvement of retinoic acid receptor alpha in the stimulation of tissue-type plasminogen-activator gene expression in human endothelial cells.

Retinoids stimulate tissue-type plasminogen-activator (t-PA) gene expression in human endothelial cells, and are likely to do so by binding to one or more nuclear retinoid receptors. The present study was initiated to identify the retinoid receptor(s) involved in this process. Expression and regulation of retinoic acid receptors (RARs) and retinoid X receptors (RXRs) were analyzed by Northern-blot analysis of total or poly(A)-rich RNA prepared from cultured human umbilical vein endothelial cells (HUVEC). Prior to any exposure to retinoids, HUVEC express two transcripts for RAR-alpha (3.6 kb and 2.8 kb), and low levels of transcripts for RAR-beta (3.4 kb and 3.2 kb) and RAR-gamma (3.3 kb and 3.1 kb). Two RXR subtypes were identified, RXR-alpha (4.8 kb) and, at a much lower concentration, RXR-beta (2.4 kb); no evidence for the presence of RXR-gamma was found. Furthermore, HUVEC express cellular retinol-binding protein I (CRBP-I) and cellular retinoic-acid-binding protein I (CRABP-I) mRNA. Exposure of HUVEC to 1 microM retinoic acid or the retinobenzoic acid, Ch55, led to the induction of the two RAR-beta mRNAs, RXR-alpha mRNA and CRBP-I mRNA, whereas the expression of the other receptor and CRABP-I transcripts did not change appreciably. Using retinoid analogues that bind preferentially to one of the RAR or RXR subtypes, we found evidence that RAR-alpha is involved in the retinoid-induced t-PA expression in HUVEC. This conclusion was strengthened by experiments in which blocking of RAR-alpha with a specific RAR-alpha antagonist, Ro 41-5253, was demonstrated to suppress the induction of t-PA by retinoids.

Benzoates↗
PubMed1995

Stimulation of tissue-type plasminogen activator gene expression by sodium butyrate and trichostatin A in human endothelial cells involves histone acetylation.

We have previously shown that the pleiotropic agent sodium butyrate strongly stimulates tissue-type plasminogen activator (t-PA) expression in human umbilical vein endothelial cells (HUVEC). Here we provide the following evidence that the butyrate-induced t-PA expression in HUVEC involves histone H4 acetylation. (1) t-PA induction by butyrate occurs at the transcriptional level and does not require new protein synthesis, indicating a direct effect. (2) t-PA induction by butyrate can be fully mimicked by a specific, structurally unrelated, histone deacetylase inhibitor, trichostatin A. (3) At optimally stimulatory conditions, a combination of butyrate and trichostatin A does not enhance t-PA production more than each of the compounds alone, indicating that both compounds act through a common regulatory mechanism. (4) Induction of t-PA transcription by butyrate and trichostatin A was found to be preceded by histone H4 acetylation; at suboptimal inducing concentrations of butyrate and trichostatin A, the degree of acetylation of histone H4 caused by each agent was similarly reduced. These results are consistent with a role for histone H4 acetylation in t-PA induction by butyrate in HUVEC.

Acetylation↗
PubMed1994

Regulation of endothelial cell t-PA synthesis and release.

The fibrinolytic activity of blood is to a large extent determined by the plasma level of tissue-type plasminogen activator (t-PA). Changes in the plasma level of t-PA are mainly achieved by the endothelium by two mechanisms: (a) a rapid, short-term release of t-PA, which occurs within minutes (acute release, regulated secretion) and (b) a long-term change in the rate of synthesis and constitutive secretion of t-PA. The rapid t-PA release response of the endothelium upon stimulation may play an important role in the dissolution of fibrin at the initial event of fibrin formation, and hence in the prevention of thrombus formation. The rate of constitutive t-PA secretion is an important determinant of the actual levels of t-PA under basal and stimulated conditions. Our insight into the regulation of the synthesis and release of t-PA has extended markedly in the last decade and still adapts by the continuous stream of new experimental data. In this review we summarize our present knowledge about the factors, including intracellular signalling pathways, promoter elements and transcription factors involved in the modulation of t-PA gene expression, with particular reference to the regulation in human endothelial cells. We also discuss the mechanisms underlying acute release of t-PA from the endothelium, and provide evidence that the regulated and constitutive secretion of t-PA are interrelated in several aspects.

Animals↗