Biomedical subjects

B Soreghan

Publications and source records attributed to B Soreghan.

8 recordsLinked to original sources

PubMed2001

MAPK (ERK2) kinase--a key target for NSAIDs-induced inhibition of gastric cancer cell proliferation and growth.

UNLABELLED: Limited clinical and experimental studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) may inhibit gastric cancer growth. However, the mechanisms involved are not completely understood and cannot be explained by COX-2 inhibition alone. MAPK signaling pathway is essential for cell proliferation, but the effect of NSAIDs on MAPK activity and phosphorylation in gastric cancer has never been studied. Since increased and unregulated cell proliferation and reduced cell apoptosis are important features of cancer growth, we studied whether NS-398, a selective COX-2 inhibitor and/ or indomethacin (IND), a non-selective NSAID: 1) inhibit gastric cancer cell proliferation, 2) whether this inhibition is mediated via MAPK (ERK2), and 3) whether NSAIDs enhance apoptosis in gastric cancer cells. Human gastric epithelial cells (MKN28) derived from gastric tubular adenocarcinoma were cultured and treated with either vehicle, IND (0.25-0.5mM) or NS-398 (50-100 microM) for 6, 16, 24 and 48h. STUDIES: 1) Cellular proliferation was determined by 3H-thymidine uptake. 2) MAPK activity was measured by incorporation of radiolabeled phosphate into myelin basic protein. 3) Apoptosis was evaluated using TUNEL assay. IND and NS-398 significantly inhibited the proliferation of MKN28 cells at 24h by 3.5 - 5 fold (p<0.002) and at 48h by 2.5 - 10 fold (p<0.02). Both NSAIDs also significantly inhibited ERK2 activity: IND >53% inhibition, NS-398, 100 microM >72% inhibition; all p<0.05. Both IND and NS-398 significantly increased apoptotic index. In conclusion, IND and NS-398 significantly inhibit proliferation and growth of human gastric cancer cell line MKN28. This effect is mediated by NSAID-induced inhibition of MAPK (ERK2) kinase signaling pathway, essential for cell proliferation. NSAIDs also increase apoptosis in MKN28 cells. In addition to inhibiting cyclooxygenase, NSAIDs inhibit phosphorylating enzymes--kinases essential for signaling cell proliferation.

Adenocarcinoma↗

PubMed1997

Complement activation by cross-linked truncated and chimeric full-length beta-amyloid.

The activation of complement by beta-amyloid (A beta) has been implicated in the local inflammatory response in Alzheimer's disease. To assess the structural parameters required for this activation, beta-sheet-containing fibrils of A beta1-28 were induced by low pH and then chemically cross-linked to constrain the beta-sheet conformation. Chimeric A beta peptides with a substituted C-terminal sequence derived from two different transmembrane proteins were also assessed for the ability to form fibrils rich in beta-sheet structure and to activate complement. Both the cross-linked A beta1-28 and the chimeric A beta peptides were strong activators of the classical complement pathway. These results suggest that the C-terminal residues (29-42) of A beta facilitate fibril assembly required for complement activation but do not contain the interaction sites required for complement activation, further supporting the hypothesis that C1q binds to the N-terminal hydrophilic domain of A beta, and that a fibrillar beta-sheet-rich conformation is required for effective binding and activation of C1.

Amino Acid Sequence↗

PubMed1994

Surfactant properties of Alzheimer's A beta peptides and the mechanism of amyloid aggregation.

The major proteinaceous component of amyloid deposits associated with Alzheimer's disease is a self-assembling 40-42-residue peptide, known as A beta, which is generated by the proteolytic processing of the amyloid precursor protein (Kang, J., Lemaire, H. G., Unterbeck, A., Salbaum, J. M., Masters, C. L., Grzeschik, K. H., Multhaup, G., Beyreuther, K., and Muller-Hill, B. (1987) Nature 325, 733-736; Haass, C., Hung, A. Y., Schlossmacher, M. G., Oltersdorf, T., Teplow, D. B., and Selkoe, D. J. (1993) Ann. N. Y. Acad. Sci. 695, 109-116; Estus, S., Golde, T. E., and Younkin S. G. (1992) Ann. N. Y. Acad. Sci. 674, 138-148) and is implicated as one of the causal factors in the pathology of the disease. A beta is now shown to display properties commonly associated with surfactants or detergents, which form micelles in solution. Increasing concentrations of A beta lower the surface tension of water up to a critical concentration, above which little further decrease in surface tension is observed. At concentrations above this critical concentration, increasing amounts of non-covalent aggregates of A beta are observed. A beta aggregation is also correlated with the formation of a hydrophobic environment that excludes water. The extent of this hydrophobic environment, as reflected by the partitioning of hydrophobic fluorescent probes, is much higher for the longer A beta 1-42 isoform, which may be more intimately associated with Alzheimer's disease pathology than A beta 1-40. Although the solution structure of A beta is not yet known, these results suggest that the structure of A beta has the same type of axial amphipathic organization as detergent molecules and that the same principles that govern micelle formation may also apply to A beta aggregation and amyloid fibril self-assembly.

Alzheimer Disease↗

PubMed1992

Intracellular accumulation and resistance to degradation of the Alzheimer amyloid A4/beta protein.

The A4 or beta protein is a peptide that constitutes the major protein component of senile plaques in Alzheimer disease. The A4/beta protein is derived from a larger, transmembrane amyloid precursor protein (APP). The putative abnormal processing events leading to amyloid accumulation are largely unknown. Here we report that a 42-residue synthetic peptide, beta 1-42, corresponding to one of the longer forms of the A4/beta protein, accumulates in cultured human skin fibroblasts and is stable for at least 3 days. The peptide appears to accumulate intracellularly, since it does not accumulate under conditions that prevent endocytosis and accumulation is correlated with the acquisition of resistance to removal by trypsin digestion. This intracellular accumulation is also correlated with the ability of the peptide to aggregate as determined by SDS/polyacrylamide gel electrophoresis. At low concentrations of the beta 1-42 peptide, which favor the nonaggregated state, no accumulation is observed. Shorter peptide analogs (28 or 39 residues) that are truncated at the C terminus, which lack the ability to aggregate in SDS gels, fail to accumulate. The accumulated intracellular beta 1-42 peptide is in an aggregated state and is contained in a dense organellar compartment that overlaps the distribution of late endosomes or secondary lysosomes. Immunofluorescence of the internalized peptide in permeabilized cells reveals that it is contained in granular deposits, consistent with localization in late endosomes or secondary lysosomes. Sequence analysis indicates that some of the internalized peptide is subject to N-terminal trimming. These results suggest that the aggregated A4/beta protein may be resistant to degradation and suggest that the A4/beta protein may arise, at least in part, by endosomal or lysosomal processing of APP. Our results also suggest that relatively nonspecific proteolysis may be sufficient to generate the A4/beta protein if this part of APP is selectively resistant to proteolysis.

Amino Acid Sequence↗

PubMed1992

Assembly and aggregation properties of synthetic Alzheimer's A4/beta amyloid peptide analogs.

The amyloid A4 or beta peptide is a major component of extracellular amyloid deposits that are a characteristic feature of Alzheimer's disease. We synthesized a series of peptide analogs of the A4/beta peptide which are progressively longer at their carboxyl termini, including 42- and 39-residue peptides which represent the major forms of the A4/beta peptide in senile plaque and the hereditary cerebral hemorrhage with amyloidosis form, respectively. All peptides tested, beta 1-28 through beta 1-42, formed amyloid-like fibrils and previously unreported thin sheet-like structures which stained with thioflavin T and Congo Red. The solubility of beta 1-42 and shorter peptides was pH and concentration dependent, with a broad insolubility profile in the pH range of 3.5-6.5 and at concentrations above 0.75 mg/ml. Only peptides of 42 residues or longer were significantly insoluble at pH 7.4. beta 1-47 and beta 1-52 peptides are highly insoluble in aqueous media but are soluble at 40 mg/ml in the alpha helix-promoting solvent, 1,1,1,3,3,3-hexafluoro-2-propanol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the beta 1-42 peptide migrates as a series of higher molecular mass aggregates whereas shorter peptides migrate as monomers. Aggregation is also dependent on pH, peptide concentration, and time of incubation in aqueous medium. These results indicate that the length of the hydrophobic carboxyl terminus of the A4/beta peptide is important in determining the solubility and aggregation properties of the A4/beta peptide and that acid pH environment, high peptide concentration, and long incubation time would be predicted to be important factors in promoting amyloid deposition.

Alzheimer Disease↗

PubMed1990

Organization of the beta-galactoside alpha 2,6-sialyltransferase gene. Evidence for the transcriptional regulation of terminal glycosylation.

Little is currently known about the mechanisms by which the cellular glycosylation machinery is regulated to produce cell type-specific glycosylation sequences on glycoprotein and glycolipid sugar chains. Previously, we have shown that one enzyme involved in terminal glycosylation, beta-galactoside alpha 2,6-sialyltransferase, is expressed in a tissue-specific fashion, with the highest enzyme activity as well as mRNA levels being found in the liver. In addition, the liver mRNA was found to be 4.3 kilobases (kb) in size as compared to a larger message of 4.7 kb in other tissues. To understand the cellular regulation of expression of this sialyltransferase, we have cloned the rat gene encoding the 4.3-kb liver mRNA and found that it spans 40 kb of genomic DNA and contains 6 exons. The gene was found to be very similar in size and exon organization to the murine beta 1,4-galactosyltransferase gene, even though this enzyme has no sequence homology to alpha 2,6-sialyltransferase. The promoter responsible for the production of the liver alpha 2,6-sialyltransferase mRNA is approximately 50-fold more active in a hepatoma cell line known to express this enzyme (HepG2) than in a cell line shown not to express this enzyme (Chinese hamster ovary) and contains consensus binding sites for the liver restricted transcription factors HNF-1 and DBP as well as the transcription factors AP-1 and AP-2. These observations are in accord with the restricted expression of the 4.3-kb mRNA, and provides evidence for the cellular regulation of glycosylation at the level of transcription.

Animals↗

PubMedDate not supplied

Regeneration of gastric mucosa during ulcer healing is triggered by growth factors and signal transduction pathways.

An ulcer is a deep necrotic lesion penetrating through the entire thickness of the gastrointestinal mucosa and muscularis mucosae. Ulcer healing is a complex and tightly regulated process of filling the mucosal defect with proliferating and migrating epithelial and connective tissue cells. This process includes the re-establishment of the continuous surface epithelial layer, glandular epithelial structures, microvessels and connective tissue within the scar. Epithelial cells in the mucosa of the ulcer margin proliferate and migrate onto the granulation tissue to re-epithelialize the ulcer. Growth factors, such as epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), trefoil peptides (TP), platelet derived growth factor (PDGF) and other cytokines produced locally by regenerating cells, control re-epithelialization and the reconstruction of glandular structures. These growth factors, most notably EGF, trigger epithelial cell proliferation via signal transduction pathways involving EGF-R- MAP (Erk1/Erk2) kinases. Granulation tissue, which develops at the ulcer base, consists of fibroblasts, macrophages and proliferating endothelial cells, which form microvessels under the control of angiogenic growth factors. These growth factors [bFGF, vascular endothelial growth factor (VEGF) and angiopoietins] promote angiogenesis--capillary vessel formation--thereby allowing for the reconstruction of microvasculature in the mucosal scar, which is essential for delivery of oxygen and nutrients to the healing site. The primary trigger to activate expression of angiogenic growth factors and their receptors appears to be hypoxia. During ulcer healing expression of growth factor genes is tightly regulated in a temporally and spatially ordered manner.

Animals↗

PubMedDate not supplied

NSAIDs inhibit the activation of egr-1 gene in microvascular endothelial cells. A key to inhibition of angiogenesis?

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin (IND), ibuprofen and newer cyclooxygenase-2 selective NSAIDs (e.g. celecoxib) delay gastric ulcer healing partly through the inhibition of angiogenesis, but the molecular mechanisms involved are not fully elucidated. Effective angiogenesis is required for ulcer healing to supply oxygen and nutrients to the healing site. The early growth response factor (Egr-1) is a transcription factor, which is rapidly activated by a variety of extracellular signals or tissue injury and is important for angiogenesis to occur. This study aimed to determine whether indomethacin (IND) and/or the selective COX-2 inhibitor, NS-398, interfere with egr-1 gene expression in human microvascular endothelial cells (HMVEC) in response to vascular endothelial growth factor (VEGF) stimulation. HMVEC were treated with 0.5 mM IND or 100 microM NS-398 for 16 h, and then VEGF (10 ng/ml) or vehicle was added. Egr-1 mRNA and protein expression levels were determined by RT-PCR and Western-blotting, respectively. VEGF treatment caused a significant elevation of Egr-1 mRNA (261+/-21%, P<0.001) and protein expression (174+/-15%, P<0.01) vs. vehicle. IND pre-treatment significantly inhibited VEGF-induced Egr-1 mRNA expression by 29+/-4% (P<0.01) and protein expression by 41+/-8% (P<0.05). NS-398 inhibited VEGF-induced Egr-1 mRNA and protein expression by 23+/-3% and 35+/-4%, respectively (both P<0.01). Since transcriptional activation of egr-1 is responsible for expression of proteins involved in proliferation of endothelial cells essential for angiogenesis, these results provide a new mechanism for NSAIDs' interference with angiogenesis.

Anti-Inflammatory Agents, Non-Steroidal↗