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Biomedical subjects

E G Seidman

Publications and source records attributed to E G Seidman.

At least 19 recordsLinked to original sources
PubMed2003

Modulation of cytokine release from colonic explants by bacterial antigens in inflammatory bowel disease.

The intestinal flora play an important role in experimental colitis and inflammatory bowel disease (IBD). Using colonic explant cultures from 132 IBD and control subjects, we examined tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 and interleukin-1 receptor antagonist (IL-1RA) production in vitro in response to bacterial activators. Unstimulated TNF-alpha release was increased significantly in rectal biopsies from involved IBD tissue, correlating with inflammation severity. Whereas lipopolysaccharide (LPS) only moderately stimulated TNF-alpha production from inflamed tissue, pokeweed mitogen (PWM) induced its release in all groups, with a stronger response in involved IBD tissue. Superantigen staphylococcal enterotoxin A (SEA) had a similar, but weaker effect. SEB was observed to be the strongest inducer of TNF-alpha for all groups, again with a more marked response in inflamed tissue. Stimulated release of IL-1 was considerably less than for TNF-alpha. The superantigens' superior potency over LPS was not as marked for IL-1 as it was for TNF-alpha. In addition to IL-1, IL-1RA release was also triggered by the bacterial products. The net effect of activation on the IL-1RA/IL-1 ratio was relatively modest. Release of the proinflammatory cytokines TNF-alpha and IL-1, as well as that of the anti-inflammatory cytokine IL-1RA was increased by incubation of colonic tissue with bacterial factors. TNF-alpha production and release was increased significantly in involved colonic explants from IBD. SEB was even capable of inducing TNF-alpha release from uninvolved colonic tissue.

Adolescent↗
PubMed2003

Mannan-binding lectin in children with Escherichia coli O157:H7 haemmorrhagic colitis and haemolytic uraemic syndrome.

Mannan-binding lectin (MBL) triggers complement activation upon binding to microbial surfaces. MBL deficiency has been associated with increased susceptibility to severe bacterial infections. We hypothesized that MBL deficiency may predispose children to Shiga toxin-producing Escherichia coli (STEC) O157:H7 infections and the associated haemolytic uraemic syndrome (HUS). We compared circulating levels of MBL among children with uncomplicated O157:H7 haemorrhagic colitis (HC), patients with O157:H7 HUS, normal and diseases control groups. Circulating MBL concentrations on admission were as follows: 3.22 +/- 2.43 micro g/ml among normal controls (n = 23); 2.90 +/- 2.44 micro g/ml in patients with rotavirus enteritis (n = 10); 2.78 +/- 1.65 micro g/ml in children with HC due to non-STEC bacterial pathogen (n = 15); 2.67 +/- 2.44 micro g/ml in patients with uncomplicated O157:H7 HC (n = 27); 2.80 +/- 2.97 micro g/ml in children with O157:H7 HUS (n = 15); 6.70 +/- 4.49 micro g/ml in patients with chronic renal failure unrelated to O157:H7 infection (n = 6). Higher MBL levels were found in patients with chronic renal failure compared to O157:H7 HC (P < 0.047). However, MBL concentrations <0.5 micro g/ml, which have been associated with MBL deficiency in relation to increased susceptibility to infections, were noted at comparable rates between the different groups (P = NS). Our data does not support that MBL deficiency may predispose to O157:H7 infections nor than the development of diarrhoea associated HUS.

Case-Control Studies↗
PubMed2003

Butyrate induced Caco-2 cell apoptosis is mediated via the mitochondrial pathway.

BACKGROUND: During the process of tumorigenesis most colon cancer cells acquire resistance to apoptosis. The short chain fatty acid butyrate is well established as an antitumour agent which selectively induces apoptosis in colon cancer cells but not in normal intestinal epithelial cells. AIMS: To analyse the signalling pathway of butyrate induced apoptosis. METHODS: Using Caco-2 cells we focused on the bcl family of proteins, mitochondrial pathway, and caspase signalling cascade involved in butyrate induced apoptosis. Techniques employed included western blots, immunofluorescence, as well as experiments with peptide inhibitors of specific caspases. RESULTS: Butyrate induced a clear shift of the mitochondrial bcl rheostat towards a proapoptotic constellation, as demonstrated by upregulation of proapoptotic bak accompanied by reduced antiapoptotic bcl-x(L) levels. This was associated with translocation of cytochrome-c from the mitochondria to the cytosol, resulting in activation of the caspase cascade via caspase-9. Key executioner enzymes were caspases-3 and -1. No effect of butyrate on regulatory proteins of the inhibitor of apoptosis family was observed. CONCLUSIONS: Butyrate induced Caco-2 cell apoptosis via the mitochondrial pathway. Upregulation of bak and translocation of cytochrome-c were upstream of the caspase cascade. Subsequently, this cascade was activated via the formation of an apoptosome.

Apoptosis↗
PubMed2002

The susceptibility to Fas-induced apoptosis in normal enterocytes is regulated on the level of cIAP1 and 2.

Various members of the tumor necrosis factor receptor superfamily are implicated in the regulation of enterocyte apoptosis. Previously, we observed that human intestinal epithelial cells are rather unsusceptible to Fas-induced apoptosis. In the present study we analyzed these protective mechanisms in the human intestinal epithelial cell line HIEC, focusing on antiapoptotic molecules of the IAP family which block apoptosis at the level of the caspase cascade. HIEC expressed all key molecules required to trigger Fas-induced apoptosis. However, no apoptosis occurred after activation of Fas, whereas an upregulation of antiapoptotic cIAP1 and 2 was observed. Suppression of this upregulation with the proteasome inhibitor MG132 or the protein synthesis inhibitor cycloheximide highly sensitized HIEC toward Fas-induced apoptosis. Western blot analyses revealed that both inhibitors potently suppressed endogenously produced cIAP1 and 2. No effect was observed on XIAP expression. These data indicate that enterocytes are particularly protected against Fas-induced apoptosis on the level of executionary caspases.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Lipopolysaccharide modulation of normal enterocyte turnover by toll-like receptors is mediated by endogenously produced tumour necrosis factor alpha.

BACKGROUND: Circulating levels of endotoxin (or lipopolysaccharide (LPS)) and anti-endotoxin antibodies are increased in patients with inflammatory bowel disease, supporting the hypothesis of a role for endogenous bacterial products in the pathogenesis of these disorders. AIM: The aim of this study was to analyse the direct effects of LPS on intestinal epithelial cell turnover. METHODS AND RESULTS: LPS significantly inhibited growth of the human non-transformed immature crypt cell line (HIEC), whereas IEC-6 cell proliferation was stimulated by LPS. As LPS is a physiological inducer of tumour necrosis factor alpha (TNFalpha) in various cell systems and this cytokine exerted similar anti-proliferative (HIEC) or growth stimulatory (IEC-6 cells) effects, the study thus tested the hypothesis that endogenously produced TNFalpha in response to LPS mediates this growth modulatory effect in an autoparacrine/paracrine way. Therefore, during LPS stimulation, the biological activity of TNFalpha was blocked using neutralising anti-TNFalpha antibodies, as well as inhibitory, antagonistic antibodies directed against the p55 TNF receptor, signalling the antimitotic TNFalpha effect in HIEC. Both experimental approaches completely abolished the growth modulatory effects of LPS in HIEC/IEC-6 cells. Production and secretion of TNFalpha by HIEC/IEC-6 cells in response to LPS was confirmed on mRNA and protein level by reverse transcription polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay. LPS signalling was independent of CD14 in HIEC, as these cells lack this receptor. However, HIEC expressed TLR4 and MD2 resulting in a fully functional signalling complex as demonstrated by RT-PCR, western blot, and immunofluorescence analyses. CONCLUSION: These results support the hypothesis that LPS induced changes of intestinal epithelial cell turnover may directly contribute to the pathogenesis of inflammatory epithelial cell lesions by endogenous TNFalpha production by enterocytes.

Antibodies, Monoclonal↗
PubMed2001

An open-label pilot study using thioguanine as a therapeutic alternative in Crohn's disease patients resistant to 6-mercaptopurine therapy.

BACKGROUND AND AIMS: A substantial number of patients with inflammatory bowel disease (IBD) fail to achieve a complete clinical response with 6-mercaptopurine (6-MP) and azathioprine (AZA). Inability to achieve therapeutic 6-thioguanine nucleotide (6-TGN) levels due to the preferential overproduction of 6-methylmercaptopurine ribonucleotides (6-MMPR) upon dose escalation characterizes a newly described subgroup of IBD patients resistant to 6-MP/AZA therapy. Treatment with 6-thioguanine (6-TG), a related thiopurine, which forms 6-TGNs more directly may be beneficial in such patients. This pilot study evaluated the safety, tolerance, and efficacy of 6-TG in the subgroup of Crohn's disease (CD) patients failing to attain adequate disease control with traditional 6-MP/AZA therapy. METHODS: Ten CD patients with preferential 6-MMPR production upon 6-MP/AZA dose escalation were enrolled in an open-label pilot study. Seven of 10 patients had experienced dose-related 6-MP toxicities. RESULTS: Seventy percent of the patients (7 of 10) responded or were in remission at week 16. Clinical response was evident by week 4 in most. 6-TGN levels were nine-fold higher with 6-TG treatment than with 6-MP, whereas 6-MMPR levels were undetectable. No patient developed a recurrence of hepatic or hematological toxicity. CONCLUSIONS: 6-TG was a safer and more efficacious thiopurine in this subgroup of IBD patients resistant to 6-MP therapy. Larger controlled trials are warranted to further evaluate both the short- and long-term safety and efficacy in this subgroup of patients as well as a broader spectrum of IBD patients.

Adult↗
PubMed2001

Clinical utility of serodiagnostic testing in suspected pediatric inflammatory bowel disease.

OBJECTIVES: Confronted with nonspecific symptoms, accurate screening tests would be useful to clinicians to distinguish between functional childhood disorders and inflammatory bowel disease (IBD), thus avoiding invasive diagnostic testing. Traditional ulcerative colitis-specific perinuclear antineutrophil cytoplasmic antibody (pANCA) and Crohn's disease-specific anti-Saccharomyces cerevisiae antibody (ASCA) serodiagnostic assays have recently been modified, with ELISA cut-off values recalculated to maximize sensitivity. The aim of this study was to determine whether the combination of these serodiagnostic tests could maximize diagnostic accuracy and minimize invasive investigations in pediatric patients presenting with nonspecific symptoms suggestive of IBD. METHODS: With investigators blinded to clinical diagnoses, ASCA, ANCA, and pANCA profiles were obtained prospectively from 128 patients undergoing complete diagnostic evaluation for IBD. In phase I, diagnostic accuracy and predictive values of the modified and traditional assays were compared for the IBD (n = 54) and non-IBD groups (n = 74). In phase II, the overall accuracy of a novel sequential diagnostic testing strategy was determined. Additionally, the potential number of invasive investigations avoided with the hypothetical application of this strategy to the cohort was determined. RESULTS: For phase I, the modified serodiagnostic assay was more sensitive (81 vs 69%), whereas the traditional assay had a higher specificity (96 vs 72%) for IBD (p < 0.05) For phase II, false-positive diagnoses would have been reduced by 81%, yielding an overall sequential testing strategy accuracy of 84%. CONCLUSIONS: The incorporation of sequential noninvasive testing into a diagnostic strategy may avoid unnecessary and costly evaluations and facilitate clinical decision making when the diagnosis of IBD in children is initially uncertain.

Adolescent↗
PubMed2001

Immunolocalization, ontogeny, and regulation of microsomal triglyceride transfer protein in human fetal intestine.

To examine the multiple stages of lipoprotein packaging during development, we studied localization, ontogeny, and regulation of microsomal transfer protein (MTP), a crucial protein for lipid transport. With the use of immunofluorescence, MTP was identified in villus and crypt epithelial cells in different regions of human fetal intestine, including colon. Staining was detected as early as the 13th wk of gestation in all gut segments and was almost entirely confined to the columnar epithelial cells of the jejunum and colon. Unlike immunofluorescence, which provides qualitative but not quantitative information on MTP signal, enzymatic assays revealed a decreasing gradient from proximal small intestine to distal, as confirmed by immunoblot. Activity of MTP in small intestinal explants cultured for different incubation periods (0, 4, 8, and 24 h) peaked at 4 h but remained insensitive to different concentrations of oleic acid. Also, a trend toward increasing MTP activity was observed at 20-22 wk of gestation. Finally, in strong contrast to jejunal efficiency, colonic explants displayed impaired lipid production, apolipoprotein biogenesis, and lipoprotein assembly, in association with poor expression of MTP. These findings provide the first evidence that human fetal gut is able to express MTP and emphasize the distinct regional distribution, regulation by oleic acid, and ontogeny of MTP.

Adult↗
PubMed2001

Pathogenesis of Shiga toxin-associated hemolytic uremic syndrome.

The aim of this review is to examine recent advances in experimental and clinical research relevant to the pathogenesis of diarrhea-associated hemolytic uremic syndrome with special reference to histopathologic findings, virulence factors of Shiga toxin-producing Escherichia coli, the host response, and the prothrombotic state. Despite significant advances during the past decade, the exact mechanism by which Shiga toxin-producing E. coli leads to hemolytic uremic syndrome remains unclear. Factors such as Shiga toxin, lipopolysaccharide, the adhesins intimin and E. coli-secreted proteins A, B, and D, the 60-MD plasmid, and enterohemolysin likely contribute to the pathogenesis. Data on the inflammatory response of the host, including leukocytes and inflammatory mediators, are updated. The pathogenesis of the prothrombotic state leading to thrombocytopenia secondary to endothelial cell damage and platelet activation is also discussed. A hypothetical sequence of events from ingestion of the bacteria to the development of full-blown hemolytic uremic syndrome is proposed.

Adhesins, Bacterial↗
PubMed2001

Role of endoscopy in inflammatory bowel disease.

Since its introduction into clinical use, flexible fiberoptic endoscopy progressively has become an indispensable tool to diagnose and treat gastrointestinal disorders. Few innovations have had a greater impact on the clinical practice of gastroenterology. In effect, diagnostic endoscopy has become an extension of physical diagnosis. This article reviews the expanding use of endoscopy in inflammatory bowel disease in the pediatric age group.

Adolescent↗
PubMed2000

Inhibition by deacetylase inhibitors of IL-1-dependent induction of haptoglobin involves CCAAT/Enhancer-binding protein isoforms in intestinal epithelial cells.

Intestinal epithelial cells participate in an acute phase response (APR) by responding to cytokines and by expressing acute phase protein genes. We hypothesized that butyrate, a fermentation product of the bacterial intestinal flora with deacetylase activity, affects the APR in intestinal epithelial cells. Sodium butyrate (NaBu) and Trichostatin A (TSA) induced alkaline phosphatase activity and histone H4 acetylation in IEC-6 rat intestinal epithelial cells treated with or without interleukin-1beta (IL-1). In contrast, both NaBu and TSA attenuated the IL-1-dependent induction of the acute phase protein gene haptoglobin, as well as C/EBPbeta and C/EBPdelta transcription factors mRNAs. Gel shift and supershift assays showed a strong decrease in the IL-1-induced C/EBPbeta and C/EBPdelta containing complexes binding to the HaptoA C/EBP DNA-binding site of the haptoglobin promoter, by NaBu and TSA. Furthermore, site-specific mutation of the HaptoA site abolished the NaBu- and TSA-dependent inhibition of haptoglobin, as determined by transient transfection assays. These results suggest that deacetylase inhibitors may regulate the IL-1 dependent induction of haptoglobin by down-regulating C/EBP isoforms, and that C/EBPs represent a target for the action of butyrate in the control of the APR of intestinal epithelial cells.

Animals↗
PubMed2000

Modulation of endoplasmic reticulum-bound cholesterol regulatory enzymes by iron/ascorbate-mediated lipid peroxidation.

Mammalian sterol regulatory enzymes are integral membrane proteins of the endoplasmic reticulum. They play a critical role in liver cholesterol homeostasis and the maintenance of overall cholesterol balance in different species. Because lipid peroxidation has been implicated in hepatic dysfunction and atherosclerosis, we hypothesized that its occurrence could alter the composition and properties of the bilayer lipid environment, and thereby affect the functions of these membrane proteins. Preincubation of rat liver microsomes with iron (Fe)/ascorbate (50 microM/200 microM), known to induce peroxidation, resulted in a significant inhibition of (i) the rate-limiting enzyme in cholesterol biosynthesis, HMG-CoA reductase (46%, p < .01), (ii) the crucial enzyme controlling the conversion of cholesterol in bile acids, cholesterol 7alpha-hydroxylase (48%, p < .001), and (iii) the central enzyme for cholesterol esterification: Acyl-CoA:cholesterol acyltransferase (ACAT, 80%, p < .0001). The disturbances of these key enzymes took place concomitantly with the high production of malondialdehyde (350%, p < .007) and the loss of polyunsaturated fatty acids (36.19 +/- 1.06% vs. 44.24 +/- 0.41 in controls, p < .0008). While alpha-tocopherol simultaneously neutralized lipid peroxidation, preserved microsomal fatty acid status, and restored ACAT activity, it was not effective in preventing Fe/ascorbate-induced inactivation of both HMG-CoA reductase (44%, p < .01) and cholesterol 7alpha-hydroxylase (71%, p < .0001). These results indicate that Fe/ascorbate alters the activity of the rate-determining steps in liver cholesterol metabolism, either directly or via lipid peroxidation, capable of modifying their membrane environment. The present data also suggest that the three regulatory enzymes respond differently when exposed to Fe/ascorbate or antioxidants, which may be due to dissimilar mechanisms.

Animals↗
PubMed2000

Recent advances in the diagnosis and treatment of pediatric inflammatory bowel disease.

The diagnosis and management of inflammatory bowel disease (IBD) in children and adolescents is a challenge to patients, their families, and to the healthcare team. This review highlights recent advances in the epidemiology, diagnosis, and management of pediatric IBD. Among the most prominent advances are the new diagnostic serologic assays that can help screen for IBD in the absence of physical signs of disease and help discriminate between ulcerative and Crohn's colitis. Other tests have been identified as potential noninvasive markers of disease activity, including color Doppler abdominal ultrasound and sugar permeability tests. Recent advances in pharmacogenetics afford clinicians the ability to optimize and individualize therapy using azathioprine or 6-mercaptopurine. Finally, bone health has come forth as a major issue in the complete management of pediatric IBD.

Adolescent↗
PubMed2000

Pharmacogenomics and metabolite measurement for 6-mercaptopurine therapy in inflammatory bowel disease.

BACKGROUND & AIMS: The effects of 6-mercaptopurine (6-MP) are mediated via its intracellular conversion to 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) nucleotide metabolites, the latter genetically controlled by thiopurine methyltransferase (TPMT). We sought to determine optimal therapeutic 6-MP metabolite levels and their correlation with medication-induced toxicity and TPMT genotype. METHODS: Therapeutic response was determined in 92 pediatric patients with inflammatory bowel disease coincidentally with hematologic, pancreatic, and hepatic laboratory parameters, and compared with erythrocyte metabolite levels and TPMT genotype. RESULTS: Clinical response was highly correlated with 6-TG levels (P < 0.0001) but not with any other variable, including 6-MMP levels, drug dose, gender, and concurrent medications. The frequency of therapeutic response increased at 6-TG levels > 235 pmol/8 x 10(8) erythrocytes (P < 0.001). Hepatotoxicity correlated with elevated 6-MMP levels (>5700 pmol/8 x 10(8) erythrocytes; P < 0.05). Although leukopenia was associated with higher 6-TG levels (P < 0.03), it was observed in only 8% of responders. Patients heterozygous for TPMT (8/92) had higher 6-TG levels (P < 0.0001), and all responded to therapy. CONCLUSIONS: 6-MP metabolite levels and TPMT genotyping may assist clinicians in optimizing therapeutic response to 6-MP and identifying individuals at increased risk for drug-induced toxicity.

Adolescent↗
PubMed2000

The effect of inflammation severity and of treatment on the production and release of TNFalpha by colonic explants in inflammatory bowel disease.

BACKGROUND: Despite its pivotal role in mucosal inflammation, data on TNFalpha levels in inflammatory bowel diseases have been contradictory. AIM: To examine TNFalpha production in relation to the type and severity of inflammation and therapy, using colonic explant cultures. MATERIALS AND METHODS: Rectal mucosal biopsies from 271 paediatric patients (178 inflammatory bowel disease, 27 inflammatory controls, 66 normal) were cultured for 4 or 18 h. Basal TNFalpha tissue content and release into the medium were measured by ELISA and compared to histological severity and clinical parameters. RESULTS: TNFalpha release as well as tissue-associated TNFalpha levels were significantly increased in rectal biopsies from involved inflammatory bowel disease tissue. The amount of TNFalpha correlated with inflammation severity scores. TNFalpha levels were higher at 18 compared to 4 h in all groups, whether inflamed or not. TNFalpha released from rectal biopsies was lower among treated patients at 18 h. The presence of proximal colonic involvement was associated with higher TNFalpha release by uninvolved Crohn's disease rectal biopsies compared to patients with ileitis alone. CONCLUSIONS: TNFalpha production and release is increased in involved rectal explants from inflammatory bowel disease. Anti-inflammatory treatment diminishes this response.

Adolescent↗
PubMed2000

Soluble Fas and soluble Fas-ligand in children with Escherichia coli O157:H7-associated hemolytic uremic syndrome.

We measured soluble Fas-ligand (sFas-L) and soluble Fas (sFas) levels by sandwich enzyme-linked immunosorbeny assay and compared them among (1) healthy controls (n = 11), (2) children with hemorrhagic colitis (HC) caused by a non-verotoxin-producing pathogen (n = 23), (3) patients with uncomplicated Escherichia coli O157:H7 HC (n = 14), and (4) children with O157:H7-associated hemolytic uremic syndrome (HUS) (n = 24). Children with uncomplicated E coli O157:H7 HC and HUS were matched for duration of enteric prodrome before blood sample collection. We also compared sFas-L and sFas levels among patients with HUS according to severity of renal dysfunction; abnormally increased sFas-L levels were noted in only 4% of the children (n = 3). Abnormally high concentrations of sFas were noted in 9% of the children with HC caused by a non-verotoxin-producing pathogen, 29% of the patients with uncomplicated E coli O157:H7 HC, and 69% of the children with O157:H7-associated HUS. Compared with healthy controls, patients with HUS had twofold greater concentrations of sFas (P: < 0.0001). Levels of sFas were not statistically different between 14 patients with uncomplicated O157:H7 HC and 14 children with HUS (8.2 +/- 4.7 versus 11.0 +/- 4.6 U/mL, respectively; P: < 0.07) when matched for time after onset of enteritis (7.0 +/- 3.7 versus 7.3 +/- 3.8 days, respectively). Greater concentrations of sFas were noted in patients with HUS who developed oligoanuria (n = 10; P: < 0.007), required peritoneal dialysis (n = 10; P: < 0.007), or had a decreased glomerular filtration rate (n = 5; P: < 0.002) 1 year later. Our data show that plasma concentrations of sFas but not sFas-L are abnormally increased in children with O157:H7 infections. Levels of sFas are associated with severity of renal dysfunction during HUS. Further studies are needed to clearly determine the role and origin of circulating sFas among children with infections caused by E coli O157:H7.

Adolescent↗