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Biomedical subjects

R Bucala

Publications and source records attributed to R Bucala.

At least 181 records · Page 10Linked to original sources
PubMed1992

Advanced glycosylation endproducts block the antiproliferative effect of nitric oxide. Role in the vascular and renal complications of diabetes mellitus.

Advanced glycosylation endproducts (AGEs) accumulate on long-lived tissue proteins such as basement membrane collagen and have been implicated in many of the long-term complications of diabetes mellitus. These products originate from glucose-derived Schiff base and Amadori products but undergo a series of complex rearrangement reactions to form ultimately protein-bound, fluorescent heterocycles. AGEs can react with and chemically inactivate nitric oxide (NO), a potent endothelial cell-derived vasodilator and antiproliferative factor. Since mesenchymal cell proliferation is an early and characteristic lesion of diabetic vasculopathy and glomerulopathy, we investigated the possibility that collagen-bound AGEs functionally inactivate the antiproliferative effect of NO. In model cell culture systems, AGEs were found to block the cytostatic effect of NO on aortic smooth muscle and renal mesangial cells. The inactivation of endothelial cell-derived NO by basement membrane AGEs may represent a common pathway in the development of the accelerated vascular and renal disease that accompany long-term diabetes mellitus.

Animals↗
PubMed1992

Polyclonal activation of B lymphocytes by lipopolysaccharide requires macrophage-derived interleukin-1.

Lipopolysaccharide (LPS) is a potent murine polyclonal B-cell activator which induces cellular proliferation and IgM secretion. The precise role of activated macrophages in the induction of LPS-dependent, B-cell responses has been unclear. Although early reports concluded that the LPS effect occurs independently of other cell types, other studies have suggested that adherent macrophages exert either potentiating or inhibitory effects. In the present study, B-cell mitogenesis and IgM production were measured in primary spleen cell cultures after removing adherent cells by a variety of experimental procedures. B-cell activation by LPS was found to be strictly dependent on the presence of adherent macrophages. Antibody neutralization and cytokine reconstitution studies demonstrated that macrophage-derived interleukin- (IL-1) is a necessary co-factor for LPS-induced polyclonal activation.

Animals↗
PubMed1991

Constitutive production of inflammatory and mitogenic cytokines by rheumatoid synovial fibroblasts.

Conditioned media obtained from fibroblasts cultured from rheumatoid and certain other inflammatory synovia were observed to stimulate [3H]thymidine incorporation in an indicator murine fibroblast line. Synovial fibroblasts derived from the joints of patients with osteoarthritis did not display this property. This effect persisted in culture for many weeks and occurred in the absence of co-stimulatory immune cells. Antibody neutralization studies implicated a role for basic fibroblast growth factor (bFGF), transforming growth factor beta (TGF-beta), granulocyte/macrophage colony-stimulating factor (GM-CSF), and interleukin 1 beta (IL-1 beta) in the increased proliferative activity of synovial fibroblast-conditioned media. Synovial cell synthesis of bFGF, TGF beta 1, GM-CSF, IL-1 beta, and IL-6 was confirmed by 35S-methionine labeling and immunoprecipitation. The constitutive production of inflammatory and mitogenic cytokines by synovial fibroblasts may represent the result of long-term, phenotypic changes that occurred in vivo. Persistent cytokine production by synovial fibroblasts may play an important role in the continued recruitment and activation of inflammatory cells in chronic arthritis and in the formation of rheumatoid pannus.

Animals↗
PubMed1991

Advanced glycosylation products quench nitric oxide and mediate defective endothelium-dependent vasodilatation in experimental diabetes.

Nitric oxide (an endothelium-derived relaxing factor) induces smooth muscle relaxation and is an important mediator in the regulation of vascular tone. Advanced glycosylation end products, the glucose-derived moieties that form nonenzymatically and accumulate on long-lived tissue proteins, have been implicated in many of the complications of diabetes and normal aging. We demonstrate that advanced glycosylation products quench nitric oxide activity in vitro and in vivo. Acceleration of the advanced glycosylation process in vivo results in a time-dependent impairment in endothelium-dependent relaxation. Inhibition of advanced glycosylation with aminoguanidine prevents nitric oxide quenching, and ameliorates the vasodilatory impairment. These results implicate advanced glycosylation products as important modulators of nitric oxide activity and endothelium-dependent relaxation.

Animals↗
PubMed1987

Anti-oestrogen antibodies in users of oral contraceptives and in patients with systemic lupus erythematosus.

Recent studies have demonstrated that many patients with SLE have elevated plasma levels of the minor oestrogen metabolite 16 alpha-hydroxyestrone (16 alpha OHE). This oestrogen is unique in its ability to react with lysine residues and form stable, covalent Heyns products with proteins. Increased levels of 16 alpha OHE-modified proteins have been found to occur on the membranes of red cells and lymphocytes in patients with SLE. In the present study, patient and control sera were analysed for the presence of circulating immunoglobulins which react with an oestrogen hapten. Anti-oestrogen antibodies were detected in 26% (9/34) of male and female SLE patients, and were found to correlate both with levels of plasma 16 alpha OHE (P less than 0.001) and with the presence of active disease (P less than 0.005). Surprisingly, this antibody activity was also observed in 25% (13/52) of normal, disease-free women who had a history of oral contraceptive use. No detectable activity was observed in normal men, women who had not taken oral contraceptives, or patients with a variety of other immunological diseases. The possible role of anti-oestrogen antibodies in both the hormonal exacerbation of SLE and in the long-term sequelae of oral contraceptive usage is discussed.

Adult↗
PubMed1986

Structure of lysine adducts with 16 alpha-hydroxyestrone and cortisol.

Recent studies indicate that steroids containing a vicinal hydroxyketone moiety can react with proteins both in vitro and in vivo to form covalent addition products. This reaction is non-enzymatic and occurs via the Heyns rearrangement of an initial Schiff base adduct between the steroid carbonyl and the epsilon-amino group of lysine residues. The present study describes the synthesis, isolation, and structural analysis of model adducts prepared by the incubation of 16 alpha-hydroxyesterone or cortisol with NaCNBH3 and lysine derivatives blocked in the N alpha-position. The product formed from the reaction of 16 alpha-hydroxyesterone and lysine was found to have the structure predicted for a reduced Schiff base between these molecules. A stable, cortisol-lysine adduct was similarly synthesized and isolated. This conjugate was found not to be the expected reduced Schiff base but rather a C-20 cyano amine. This compound most likely was formed by the nucleophilic addition of cyanide during the course of the incubation. The observation that the cortisol-lysine Schiff base is not reducible with NaCNBH3 accounts for the observation that the incorporation rate of glucocorticoids into proteins is not increased by the presence of NaCNBH3.

Estrone↗
PubMed1985

Detection of an advanced glycosylation product bound to protein in situ.

Protein amino groups can react with glucose without the aid of enzymes to form stable Amadori products containing 1-amino-1-deoxyketose residues. These adducts can undergo subsequent rearrangements and dehydrations to form various brown and fluorescent pigments. Recently, a chromophore, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), was isolated from acid hydrolysates of bovine serum albumin (BSA) and poly-L-lysine which had been incubated with glucose. To confirm the presence of FFI in situ, a radioimmunoassay was developed. A derivative of FFI, 4-furanyl-2-furoyl-1H-imidazole-1-hexanoic acid, was coupled to BSA and used to immunize rabbits. A radioactive FFI derivative was synthesized by reaction of 2-furyl-glyoxal with gamma-amino-[2,3-3H]butyric acid to form FFI-[3H]butyric acid. The resultant antiserum showed binding affinity to FFI and cross-reactivity for related compounds. FFI bound to proteins was liberated by acid hydrolysis or digestion by proteinase K prior to measurement. A linear relationship was seen between the amount of FFI equivalent detected and the amount of acid hydrolysate or enzymatic digest assayed. Poly-L-lysine and BSA incubated with glucose showed a time-dependent increase in the amounts of fluorescence and FFI equivalence. The detection of a time-related increase in the amount of FFI or a closely related structure in enzymatically digested proteins implicates it as an in situ product on proteins which have undergone the Maillard reaction with glucose. Of physiological significance is that FFI could also be detected in human globin and serum albumin from normal individuals. Thus, proteins exposed to glucose in vitro and in vivo form FFI as an in situ glycosylation product.

Fluorescent Dyes↗
PubMed1985

Determination of 16 alpha-hydroxyestrone by radioimmunoassay in systemic lupus erythematosus.

A radioimmunoassay for the feminizing metabolite 16 alpha-hydroxyestrone was applied to a variety of sera from healthy volunteers, patients with active or inactive systemic lupus erythematosus (SLE), and patients with other rheumatic diseases. A significant increase in this metabolite was detected in patients with SLE, especially those with active disease, compared with normal controls (P less than 0.001). SLE patients were categorized as having either active or inactive disease by clinical and laboratory criteria. Many patients who had clinically and serologically active disease were found to have normal levels of this estrogenic metabolite, and several explanations for these differences are explored in this report. Despite a poor correlation of hormone levels with age, antibody levels, or complement levels in patients with SLE, those patients with the highest levels of hormone were among those whose disease was clinically most active.

Adult↗
PubMed1985

Glucocorticoid-lens protein adducts in experimentally induced steroid cataracts.

The injection of glucocorticoids into the vitreous chamber of the rabbit eye results in the development of posterior subcapsular opacities. These lesions appear to be similar in morphology to human steroid-induced cataracts. Electron microscopic analysis revealed fiber cell separation, vacuolization, and changes within the matrix of the crystallins. Opacification could only be produced by glucocorticoids possessing a reactive C-20,21 hydroxylcarbonyl function, supporting the hypothesis that glucocorticoid addition products are involved in the induction of these lesions. The occurrence of glucocorticoid-lens proteins adducts was confirmed by tritium incorporation and by radioimmunoassay of protein hydrolysates obtained from these lenses.

17-alpha-Hydroxyprogesterone↗
PubMed1985

Nonenzymatic modification of lens crystallins by prednisolone induces sulfhydryl oxidation and aggregate formation: in vitro and in vivo studies.

Steroid-induced cataracts occur as a consequence of prolonged, therapeutic levels of glucocorticoids. Previous studies have shown that these lens opacities are associated with the occurrence of covalent glucocorticoid-lens protein adducts. In vitro, the glucocorticoid prednisolone nonenzymatically modifies the lysine residues of lens crystallins. This modification increases the reactivity of protein thiols and leads to the formation of high-molecular-weight, disulfide-linked aggregates. Prednisolone-induced aggregates result in an opalescence in the crystallins solution which is reversed by the addition of dithiothreitol. The acetylation of lens proteins prior to incubation inhibits both the incorporation of prednisolone and the development of opalescence. Gel filtration chromatography of the prednisolone lens protein incubations shows that the majority of the protein-incorporated prednisolone is associated with the disulfide-linked complexes. Similar analysis of proteins obtained from a human steroid-induced cataract demonstrates that prednisolone adducts which form in vivo are also present in reducible, high-molecular-weight complexes. These results implicate the nonenzymatic modification of lens crystallins in the cataractogenic effect of glucocorticoids and suggest possible pharmacological strategies in preventing this toxic manifestation of steroid therapy.

Acetylation↗
PubMed1985

Modification of DNA by glucose 6-phosphate induces DNA rearrangements in an Escherichia coli plasmid.

Reducing sugars such as glucose or glucose 6-phosphate (Glc-6-P) have been shown previously to modify the amino groups of nucleotides and single-stranded DNA. We have examined the mutagenic effect of Glc-6-P-induced lesions in the double-stranded DNA plasmid pBR322. Seventeen mutants of the Ampr Tets phenotype were isolated from plasmid preparations whose transforming capacity had been decreased by incubation with Glc-6-P. A number of the mutant plasmids were found to have undergone gross DNA alterations, including insertions and deletions, as well as the development of multiple species originating from a single cell. The ability of an endogenous reducing sugar to induce extensive DNA rearrangements suggests that these lesions may be significant contributors to cellular mutation.

Chromosome Deletion↗
PubMed1985

Increased levels of 16 alpha-hydroxyestrone-modified proteins in pregnancy and in systemic lupus erythematosus.

The ketolic estrogen 16 alpha-hydroxyestrone (16 alpha OHE) reacts with lysine residues, forming stable covalent adducts with proteins. To determine the extent of protein modification by 16 alpha OHE in vivo, we measured the level of 16 alpha OHE-lysine present within proteins of varying half-lives obtained from normal subjects, patients with systemic lupus erythematosus (SLE), and pregnant women. The latter groups have higher than normal levels of plasma 16 alpha OHE. The proteins analyzed were membrane proteins of the red cell and the lymphocyte and basement membrane proteins of the glomerulus. We report that elevated levels of plasma 16 alpha OHE led to increased formation of 16 alpha OHE-protein adducts and that the level of these adducts increases with the half-life of the protein. In the case of erythrocyte membrane proteins, pregnant women and women with SLE had significantly higher mean levels of 16 alpha OHE-lysine than normal women (normal, 5.2 pmol 16 alpha OHE-lysine/mmol leucine; SLE, 15.7; pregnant, 24.9). A similar elevation in the modification of lymphocyte proteins in women was found (normal, 15.6; SLE, 40.5). Since the degree of protein modification also was dependent on the ambient level of free 16 alpha OHE, these measurements provide a useful indicator of the long term 16 alpha OHE status of an individual. The modification of proteins by 16 alpha OHE may be a link in the relationship between female hormones, pregnancy, and systemic lupus erythematosus.

Adolescent↗
PubMed1984

The reaction of 16 alpha-hydroxyestrone with erythrocytes in vitro and in vivo.

16 alpha-Hydroxyestrone (16 alpha OHE ) has been shown previously to react with albumin, forming stable covalent adducts with lysine residues. The incubation of [3H]16 alpha OHE with whole blood also results in the incorporation of tritium into cells, with the rate of incorporation paralleling that of 16 alpha OHE -protein adduct formation. 32% of erythrocyte acid-precipitable radioactivity was found to be present within membrane proteins and electrophoresis demonstrated that several of these proteins are modified by [3H]16 alpha OHE . Membrane proteins from the red cells of ten individuals were reduced with sodium borohydride, acid hydrolyzed, and the 16 alpha OHE -lysine adducts purified by hydrophobic chromatography and reverse-phase high-pressure liquid chromatography. The amount of these adducts was quantitated by radioimmunoassay and found to be five times higher than the plasma levels of free 16 alpha OHE . This reflects most likely the accumulation of 16 alpha OHE -protein adducts during the course of the red cell life. Quantitation of 16 alpha OHE -protein adducts with other cellular proteins may contribute to our understanding of systemic lupus erythematosus, an autoimmune disease in which elevated levels of 16 alpha OHE occur.

Blood Proteins↗
PubMed1984

Modification of DNA by reducing sugars: a possible mechanism for nucleic acid aging and age-related dysfunction in gene expression.

Reducing sugars react nonenzymatically with protein amino groups to initiate a process called nonenzymatic browning. Long-lived proteins, such as collagen and the lens crystallins, accumulate sufficient modification in vivo that they acquire many of the chemical properties characteristic of aged proteins. We have obtained evidence that nucleic acids also can undergo nonenzymatic modification by sugars. Incubation of DNA or nucleotides with glucose 6-phosphate (Glc-6-P) produces spectral changes similar to those described for nonenzymatic browning proteins. The occurrence of chemical modification was verified by measuring the transfection efficiency of viral DNA after incubation with glucose and Glc-6-P. A loss of transfection potential occurred that was first order with respect to time and sugar concentration. The rate of inactivation by Glc-6-P was 25 times that of glucose; 8 days of incubation with 150 mM Glc-6-P decreased transfection by 4 orders of magnitude. Glc-6-P also produced strand scission in a time- and concentration-dependent manner. We conclude that glucose, Glc-6-P, and possibly other sugars can react with DNA to produce significant structural and biological alterations. Since nucleic acids are long-lived molecules in the resting cell, the accumulation of these addition products might be a mechanism for the decreased genetic viability characteristic of the aged organism.

Aging↗
PubMed1984

Nonenzymatic addition of glucocorticoids to lens proteins in steroid-induced cataracts.

A frequent manifestation of long-term glucocorticoid administration is the occurrence of posterior subcapsular cataracts. The molecular basis for this effect has not yet been elucidated. The addition of prednisolone to the rat lens in culture results in a time- and concentration-dependent lens opacification that correlates with the formation of covalent prednisolone-lens protein adducts. Prednisolone adduct formation was analyzed by [3H]prednisolone incorporation and by immunoprecipitation with antiserum specific for proteins modified by the nonenzymatic addition of prednisolone. In the rat lens, these adducts were localized in both the water-soluble and urea-soluble lens protein fractions. Gel electrophoresis and fluorography revealed that the most extensively modified proteins were two crystallins subunits. Lens proteins from 33 normal and cataractous human lenses were fractionated and analyzed for the presence of prednisolone-protein adducts by competitive radioimmunoassay. Adducts were detected only in those samples derived from glucocorticoid-induced cataractous lenses. We conclude that elevated glucocorticoid levels lead to the formation of glucocorticoid-lens protein adducts both in vitro and in vivo. Lens protein modification by glucocorticoids may lead to sufficient biochemical or structural alterations so as to result in cataract formation. The ability of glucocorticoids to form adducts with proteins in vivo also may play a role in some of the other toxic manifestations of long-term glucocorticoid therapy.

Animals↗
PubMed1983

Cytotoxicity of a perfluorocarbon blood substitute to macrophages in vitro.

Murine macrophage and macrophage-depleted splenocyte cultures were incubated under ambient oxygen with a commercially available perfluorocarbon blood substitute. The perfluorocarbon preparation was found to be selectively cytotoxic to macrophages. This finding may be significant in view of the preliminary therapeutic usage of these preparations. In addition, perfluorocarbons may be useful as a means of selectively removing macrophages from tissue and organ cultures.

Animals↗