PubMed Health⌕ Search

Biomedical subjects

B Samuelsson

Publications and source records attributed to B Samuelsson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cyclooxygenase-2 involved in stimulation of renal mechanosensitive neurons.

Stretching of the renal pelvic wall activates renal mechanosensitive neurons, resulting in an increase in afferent renal nerve activity (ARNA). Prostaglandin (PG)E(2) plays a crucial role in the activation of renal mechanosensitive neurons through facilitation of the release of substance P from the sensory neurons in the renal pelvic wall. Because wall stretch may induce cyclooxygenase-2 activity, we examined whether cyclooxygenase-2 was expressed in the renal pelvic wall and whether activation of cyclooxygenase-2 contributed to the ARNA response produced through increased renal pelvic pressure. In situ hybridization showed a strong cyclooxygenase-2 mRNA signal in the papilla and subepithelial layer of the renal pelvic wall from time control kidneys and from kidneys exposed to 15 minutes of increased renal pelvic pressure in anesthetized surgically operated rats. In anesthetized rats, an increase in renal pelvic pressure increased ARNA by 40+/-2% and increased renal pelvic release of PGE(2) from 289+/-46 to 1379+/-182 pg/min (P<0.01). Renal pelvic perfusion with the cyclooxygenase-2 inhibitor etodolac reduced the increases in ARNA and PGE(2) by 66+/-7% and 55+/-13%, respectively (P<0.01). Likewise, the cyclooxygenase-2 inhibitor 5, 5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone reduced the increases in ARNA and PGE(2) by 43+/-5% and 47+/-8%, respectively. We conclude that cyclooxygenase-2 is expressed in the renal pelvic wall and that the activation of cyclooxygenase-2 contributes to the stimulation of renal mechanosensitive neurons in the pelvic wall.

Animals↗
PubMed2000

Characterization of a set of HIV-1 protease inhibitors using binding kinetics data from a biosensor-based screen.

The interaction between 290 structurally diverse human immunodeficiency virus type 1 (HIV-1) protease inhibitors and the immobilized enzyme was analyzed with an optical biosensor. Although only a single concentration of inhibitor was used, information about the kinetics of the interaction could be obtained by extracting binding signals at discrete time points. The statistical correlation between the biosensor binding data, inhibition of enzyme activity (K(i)), and viral replication (EC(50)) revealed that the association and dissociation rates for the interaction could be resolved and that they were characteristic for the compounds. The most potent inhibitors, with respect to K(i) and EC(50) values, including the clinically used drugs, all exhibited fast association and slow dissociation rates. Selective or partially selective binders for HIV-1 protease could be distinguished from compounds that showed a general protein-binding tendency by using three reference target proteins. This biosensor-based direct binding assay revealed a capacity to efficiently provide high-resolution information on the interaction kinetics and specificity of the interaction of a set of compounds with several targets simultaneously.

Biosensing Techniques↗
PubMed1999

Inhibitors of the C(2)-symmetric HIV-1 protease: nonsymmetric binding of a symmetric cyclic sulfamide with ketoxime groups in the P2/P2' side chains.

Symmetric cyclic sulfamides, substituted in the P2/P2' position with functional groups foreseen to bind preferentially to the S2/S2' subsites of HIV-1 protease, have been prepared. Despite efforts to promote a symmetric binding, the sulfamides seemed prone to bind nonsymmetrically, as deduced from X-ray crystal structure analysis of one of the most potent inhibitors, possessing ketoxime groups in the P2/P2' side chains. Ab initio calculations suggested that the nonsymmetric conformation of the cyclic sulfamide scaffold had lower energy than the corresponding symmetric, cyclic urea-like conformation.

Crystallography, X-Ray↗
PubMed1999

Design and fast synthesis of C-terminal duplicated potent C(2)-symmetric P1/P1'-modified HIV-1 protease inhibitors.

An analysis of the X-ray structure of a complex of HIV-1 protease with a linear C(2)-symmetric C-terminal duplicated inhibitor guided the selection of a series of diverse target compounds. These were synthesized with the objective to identify suitable P1/P1' substituents to provide inhibitors with improved antiviral activity. Groups with various physical properties were attached to the para-positions of the P1/P1' benzyloxy groups in the parent inhibitor. A p-bromobenzyloxy compound, prepared in only three steps from commercially available starting materials, was utilized as a common precursor in all reactions. The subsequent coupling reactions were completed within a few minutes and relied on palladium catalysis and flash heating with microwave irradiation. All of the compounds synthesized exhibited good inhibitory potency in the protease assay, with K(i) values ranging from 0.09 to 3.8 nM. A 30-fold improvement of the antiviral effect in cell culture, compared to the parent compound, was achieved with four of the inhibitors. The differences in K(i) values were not correlated to the differences in antiviral effect, efficiency against mutant virus, or reduced potency in the presence of human serum. The poorest enzyme inhibitors in fact belong to the group with the best antiviral effect. The binding features of two structurally related inhibitors, cocrystallized with HIV-1 protease, are discussed with special emphasis on the interaction at the enzyme/water phase.

Animals↗
PubMed1999

Identification of human prostaglandin E synthase: a microsomal, glutathione-dependent, inducible enzyme, constituting a potential novel drug target.

Human prostaglandin (PG) E synthase (EC 5.3.99.3) is a member of a recently recognized protein superfamily consisting of membrane associated proteins involved in eicosanoid and glutathione metabolism (the MAPEG family). Previous designations of the protein are PIG12 and MGST1-L1. PGE synthase was expressed in Escherichia coli, and both cytosolic and membrane fractions were prepared. Western blot analysis specifically detected a 15- to 16-kDa protein in the membrane fraction. Both fractions were incubated with prostaglandin H2 in the presence or absence of reduced glutathione. The membrane but not the cytosolic fraction was found to possess high glutathione-dependent PGE synthase activity (0.25 micromol/min/mg). The human tissue distribution was analyzed by Northern blot analysis. High expression of PGE synthase mRNA was detected in A549 and HeLa cancer cell lines. Intermediate level of expression was demonstrated in placenta, prostate, testis, mammary gland, and bladder whereas low mRNA expression was observed in several other tissues. A549 cells have been used as a model system to study cyclooxygenase-2 induction by IL-1beta. If A549 cells were grown in the presence of IL-1beta, a significant induction of the PGE synthase was observed by Western blot analysis. Also, Western blot analysis specifically detected a 16-kDa protein in sheep seminal vesicles. In summary, we have identified a human membrane bound PGE synthase. The enzyme activity is glutathione-dependent, and the protein expression is induced by the proinflammatory cytokine IL-1beta. PGE synthase is a potential novel target for drug development.

Amino Acid Sequence↗
PubMed1999

Interaction of 5-lipoxygenase with cellular proteins.

5-Lipoxygenase (5LO) plays a pivotal role in cellular leukotriene synthesis. To identify proteins interacting with human 5LO, we used a two-hybrid approach to screen a human lung cDNA library. From a total of 1.5 x 10(7) yeast transformants, nine independent clones representing three different proteins were isolated and found to specifically interact with 5LO. Four 1.7- to 1.8-kb clones represented a 16-kDa protein named coactosin-like protein for its significant homology with coactosin, a protein found to be associated with actin in Dictyostelium discoideum. Coactosin-like protein thus may provide a link between 5LO and the cytoskeleton. Two other yeast clones of 1.5 kb encoded transforming growth factor (TGF) type beta receptor-I-associated protein 1 partial cDNA. TGF type beta receptor-I-associated protein 1 recently has been reported to associate with the activated form of the TGF beta receptor I and may be involved in the TGF beta-induced up-regulation of 5LO expression and activity observed in HL-60 and Mono Mac 6 cells. Finally, three identical 2.1-kb clones contained the partial cDNA of a human protein with high homology to a hypothetical helicase K12H4. 8 from Caenorhabditis elegans and consequently was named DeltaK12H4. 8 homologue. Analysis of the predicted amino acid sequence revealed the presence of a RNase III motif and a double-stranded RNA binding domain, indicative of a protein of nuclear origin. The identification of these 5LO-interacting proteins provides additional approaches to studies of the cellular functions of 5LO.

Activin Receptors, Type I↗
PubMed1999

Intravenous synthetic alphaGal saccharides delay hyperacute rejection following pig-to-baboon heart transplantation.

Several oligosaccharides containing the terminal structure Gal(alpha)1-3Gal (alphaGal) and different side chains were tested in vitro for their ability to block natural anti(alpha)Gal antibodies. A di-and a trisaccharide (di(alpha)Gal and tri(alpha)Gal) were selected. A blood group B baboon, having IgG and IgM natural antipig titers of 1:256 and 1:1024 and a hemolytic titer (to pig red blood cells, RBCs) of 1:8, was chosen to measure pharmacokinetic parameters of the saccharides and to assess the extent of in vivo neutralization of the antibodies. Three grams each of the di(alpha)Gal and the tri(alpha)Gal dissolved in saline were administered by bolus intravenous (i.v.) injection. Blood samples were collected at various times and urine was collected at 8 and 24 h. Plasma and urine concentrations of the alphaGal saccharides were estimated by an ELISA specially developed for this study. A fast distribution phase followed by equilibrium and excretion phases were observed, indicating a T1/2 in the order of 1 h. Fifty-eight per cent of the saccharides were recovered in the urine within 24 h. Determination of antipig antibody binding by FACS analysis and of serum cytotoxicity titers for pig endothelial cells demonstrated that a 70% reduction in binding and cytotoxicity could be achieved with plasma saccharide levels of 300-400 microg/ml. Six months later, a pig heart was transplanted heterotopically into the baboon. A 3-g bolus of the saccharide mixture (1.5 g of each saccharide) was given i.v. before allowing blood reperfusion of the transplanted heart, followed by an i.v. infusion of 1 g/hr for 1 hr and 0.5 g/hr for the 3 succeeding hours. Blood concentrations of the saccharides, CH50, hematology and cytotoxicity for PK15 cells were estimated in blood samples taken at various times. Heart function was observed to be satisfactory for 8 h, but was found to have ceased at 18 h. Myocardial biopsies taken at 3 and 5 h showed congestion only, suggestive of minimal vascular rejection, but by 18 h demonstrated severe vascular rejection. In conclusion, alphaGal saccharide therapy given for a period of 4 h delayed, but did not totally prevent, the development of vascular rejection in the pig-to-baboon heart transplant model. alphaGal saccharide therapy may be one of several useful approaches for the prevention of hyperacute rejection in pig-to-primate organ transplantation.

Acute Disease↗
PubMed1998

Design and synthesis of new potent C2-symmetric HIV-1 protease inhibitors. Use of L-mannaric acid as a peptidomimetic scaffold.

A study on the use of derivatized carbohydrates as C2-symmetric HIV-1 protease inhibitors has been undertaken. L-Mannaric acid (6) was bis-O-benzylated at C-2 and C-5 and subsequently coupled with amino acids and amines to give C2-symmetric products based on C-terminal duplication. Potent HIV protease inhibitors, 28 Ki = 0.4 nM and 43 Ki = 0.2 nM, have been discovered, and two synthetic methodologies have been developed, one whereby these inhibitors can be prepared in just three chemical steps from commercially available materials. A remarkable increase in potency going from IC50 = 5000 nM (23) to IC50 = 15 nM (28) was observed upon exchanging -COOMe for -CONHMe in the inhibitor, resulting in the net addition of one hydrogen bond interaction between each of the two -NH- groups and the HIV protease backbone (Gly 48/148). The X-ray crystal structures of 43 and of 48 have been determined (Figures 5 and 6), revealing the binding mode of these inhibitors which will aid further design.

Adipates↗
PubMed1998

Calcitriol and transforming growth factor-beta upregulate 5-lipoxygenase mRNA expression by increasing gene transcription and mRNA maturation.

Differentiation of the human monocytic cell line Mono Mac 6 with calcitriol plus transforming growth factor-beta (TGFbeta) strongly induces 5-lipoxygenase (5-LO) mRNA and protein expression. The mechanism of 5-LO mRNA induction by these agents was investigated. Analysis of mature 5-LO mRNA by reverse-transcriptase-PCR gave a 42-fold induction which was not due to alterations in 5-LO half life and which was only in part due to an induction of gene transcription. There was an up to fivefold increase in 5-LO primary transcripts by TGFbeta and calcitriol, which could be inhibited by cycloheximide. No significant effects on 5-LO transcription were observed with TGFbeta or calcitriol alone. However, treatment of the cells with either calcitriol or TGFbeta and addition of the corresponding second inducer lead to an about fourfold induction of primary transcript levels. Addition of cycloheximide together with the second inducer inhibited only the TGFbeta but not the calcitriol effects, which indicated that there is a direct stimulation of 5-LO transcription by calcitriol in the presence of TGFbeta-induced proteins. In order to investigate the effects of TGFbeta/calcitriol on 5-LO transcript, elongation and maturation, the relative changes in immature and mature 5-LO RNA species were analyzed by reverse-transcription-PCR. Analysis of exons 1-5 indicated an about threefold induction of 5-LO transcripts by calcitriol/TGFbeta, respectively. However, when exons 6-14 were determined, more pronounced increments were found (3.6-12-fold). Selective analysis of polyadenylated and spliced 5-LO mRNA species gave a 42-fold induction. The effects of both TGFbeta and calcitriol on transcript elongation and maturation were inhibited by cycloheximide. Our results show that induction of 5-LO mRNA by calcitriol and TGFbeta is due to a modest increase in 5-LO gene transcription and to the stimulation of transcript elongation and maturation.

Arachidonate 5-Lipoxygenase↗
PubMed1998

5-Lipoxygenase expression in Langerhans cells of normal human epidermis.

We studied expression of the 5-lipoxygenase (5-LO) pathway in normal human skin. In situ hybridization revealed a 5-LO mRNA-containing epidermal cell (EC) population that was predominantly located in the midportion of the spinous layer, in outer hair root sheaths, and in the epithelial compartment of sebaceous glands. Examination of skin specimens by immunohistochemistry and of primary ECs by flow cytometry mapped the 5-LO protein exclusively to Langerhans cells (LCs). The LC 5-LO protein was largely found in the nuclear matrix, in nuclear envelopes, and perinuclear regions as indicated by in situ confocal laser scan microscopy. Reverse transcription-PCR and immunoblot analyses of purified primary EC populations further indicated that LCs are major 5-LO expressing cells. Enriched primary LCs were also found to contain 5-LO activating protein (FLAP), leukotriene (LT) C4 synthase, and LTA4 hydrolase. By contrast, 5-LO, FLAP, and LTC4 synthase were undetectable or largely reduced, but LTA4 hydrolase transcripts and protein were identified in ECs depleted of LCs. These data show that naive LCs are major, and possibly the sole, 5-LO pathway expressing cells in the normal human epidermis.

Arachidonate 5-Lipoxygenase↗
PubMed1998

Egr-1 and Sp1 interact functionally with the 5-lipoxygenase promoter and its naturally occurring mutants.

5-Lipoxygenase (5-LO), an enzyme essential for the formation of leukotrienes, is functionally modulated by a number of mechanisms, including transcriptional controls. The 5-LO promoter has a unique G+C-rich sequence, located between 176 and 147 base pairs upstream of the ATG translation start site, which contains five tandem Sp1 (a zinc-finger transcription factor) consensus binding sites overlapping five tandem early growth response protein 1 (Egr-1), a zinc-finger transcription factor, consensus binding sites. A family of naturally occurring mutations has been identified that consists of additions or deletions of these binding sites. The role of these overlapping Sp1/Egr-1 sites in the regulation of 5-LO transcription and the effects of these mutations on transcriptional regulatory mechanisms are unknown. We now show that Sp1 and Egr-1 bind specifically to the G+C-rich promoter sequence using in vitro deoxyribonuclease I footprinting. Both Sp1 and Egr-1 activate 5-LO promoter-reporter constructs in a minimally active drosophila SL2 cotransfection system, and the G+C-rich sequence is involved in this process. Moreover, studies comparing mutant promoter function indicate that both Sp1 and Egr-1 trans-activation are proportional to the number of Sp1/Egr-1 consensus binding sites within the G+C-rich sequence. It is possible that basal and inducible 5-LO gene transcriptions are mediated by an interplay of Sp1, Egr-1, and other transcription factors within the G+C-rich promoter region, and the naturally occurring mutations alter transcription by modifying their trans-activation potential.

Animals↗
PubMed1997

Increased levels of cyclooxygenase-2 mRNA in the rat spinal cord after peripheral inflammation: an in situ hybridization study.

Cyclooxygenase-2 (COX-2) is considered to play a major role in inflammation processes by catalyzing the production of prostaglandins (PGs). Using in situ hybridization histochemistry we studied the localization of COS-1 and COX-2 mRNA in the spinal cord and dorsal root ganglia (DRGs) after peripheral inflammation or after axotomy in the rat. No COX-2 mRNA signals were detected in the spinal cord under normal conditions, but strong expression was seen bilaterally in non-neuronal cells within the grey and white matter and along the leptomeninges and blood vessels 6 h after unilateral carrageenan injection into the hind paw, but not after peripheral nerve injury. The results suggest that COX-2 expressed in non-neuronal cells contributes to PG production in and around the spinal cord under peripheral inflammatory processes.

Animals↗