Biomedical subjects

H Vlassara

Publications and source records attributed to H Vlassara.

At least 73 records · Page 4Linked to original sources

PubMed1993

Advanced glycosylation end products in continuous ambulatory peritoneal dialysis patients.

Low molecular weight advanced glycosylation end products (AGEs) were evaluated for by an enzyme-linked immunosorbent assay in 30 patients on continuous ambulatory peritoneal dialysis (29 patients) and continuous cyclic peritoneal dialysis (one patient). Thirteen patients were diabetic and 17 patients were nondiabetic. All patients underwent peritoneal equilibration tests and, in addition to routine chemistries, serum and dialysate were evaluated for AGEs. Serum creatinine levels were similar in the diabetic and nondiabetic patients, but serum AGE levels were significantly higher in the diabetic patients (16.2 +/- 5.3 v 8.2 +/- 2.3 U/mL; P < 0.0001). Overall, the dialysate to plasma ratio at 4 hours was 0.69 +/- 0.08 for creatinine and 0.18 +/- 0.06 for AGEs. The mass transfer area coefficient for all patients was 12.4 +/- 3.12 mL/min for creatinine and 2.03 +/- 0.93 mL/min for AGEs. The peritoneal transport of AGEs as measured by dialysate to plasma ratios at 4 hours and by mass transfer area coefficients was significantly less (P < 0.001) than that for creatinine. No significant difference in dialysate to plasma ratios or mass transfer area coefficient for creatinine or AGEs was noted between diabetic and nondiabetic patients. The peritoneal transport of AGEs is poor and leads to elevated serum levels, especially in patients with diabetes mellitus. The accumulation of AGEs may contribute to the increased cardiovascular mortality seen in patients with end stage renal disease. This is most marked in patients with diabetes mellitus.

Adult↗

PubMed1993

Immunohistochemical localization of advanced glycosylation end products in coronary atheroma and cardiac tissue in diabetes mellitus.

Advanced glycosylation end products (AGEs) accumulate on long-lived extracellular matrix proteins and have been implicated in the micro- and macrovascular complications of diabetes mellitus. Within the arterial wall, AGE-modified proteins increase vascular permeability, inactivate nitric oxide activity, and induce the release of growth-promoting cytokines. Recently developed anti-AGE antibodies were used in an immunohistochemical analysis of coronary arteries obtained from type II diabetic and nondiabetic patients. High levels of AGE reactivity were observed within the atherosclerotic plaque present in vessels from selected patients with diabetes. Considered together with the pathological effects of AGEs on vascular wall homeostasis, these data support the role of advanced glycosylation in the rapidly progressive atherosclerosis associated with diabetes mellitus.

Aged↗

PubMed1992

Exogenous advanced glycosylation end products induce complex vascular dysfunction in normal animals: a model for diabetic and aging complications.

Advanced glycosylation end products (AGEs) have been implicated in many of the complications of diabetes and normal aging. Markedly elevated vascular tissue and circulating AGEs were linked recently to the accelerated vasculopathy of end-stage diabetic renal disease. To determine the pathogenic role of AGEs in vivo, AGE-modified albumin was administered to healthy nondiabetic rats and rabbits alone or in combination with the AGE-crosslink inhibitor aminoguanidine. Within 2-4 weeks of AGE treatment, the AGE content of aortic tissue samples rose to six times the amount found in controls (P < 0.001). Cotreatment with aminoguanidine limited tissue AGE accumulation to levels two times that of control. AGE administration was associated with a significant increase in vascular permeability, as assessed by 125I label tracer methods. This alteration was absent in animals that received aminoguanidine in addition to AGE. Significant mononuclear cell migratory activity was observed in subendothelial and periarteriolar spaces in various tissues from AGE-treated rats compared to normal cellularity noted in tissues from animals treated with aminoguanidine. Blood pressure studies of AGE-treated rats and rabbits revealed markedly defective vasodilatory responses to acetylcholine and nitroglycerin compared to controls (P < 0.001), consistent with marked NO. inactivation; aminoguanidine treatment significantly prevented this defect. These in vivo data demonstrate directly that AGEs, independent of metabolic or genetic factors, can induce complex vascular alterations resembling those seen in diabetes or aging. AGE administration represents an animal model system for the study of diabetic and aging complications as well as for assessing the efficacy of newly emerging therapies aimed at inhibiting advanced glycosylation.

Acetylcholine↗

PubMed1992

Hemoglobin-AGE: a circulating marker of advanced glycosylation.

Advanced glycosylation end products (AGEs) form spontaneously from glucose-derived Amadori products and accumulate on long-lived tissue proteins. AGEs have been implicated in the pathogenesis of several of the complications of aging and diabetes, including atherosclerosis and renal disease. With the use of recently developed AGE-specific antibodies, an AGE-modified form of human hemoglobin has been identified. Termed hemoglobin-AGE (Hb-AGE), this modified species accounts for 0.42 percent of circulating hemoglobin in normal individuals but increases to 0.75 percent in patients with diabetes-induced hyperglycemia. In a group of diabetic patients treated with the advanced glycosylation inhibitor aminoguanidine, Hb-AGE levels decreased significantly over a 1-month period. Hemoglobin-AGE measurements may provide an index of long-term tissue modification by AGEs and prove useful in assessing the contribution of advanced glycosylation to a variety of diabetic and age-related complications.

Adult↗

PubMed1992

Receptor-specific increase in extracellular matrix production in mouse mesangial cells by advanced glycosylation end products is mediated via platelet-derived growth factor.

Renal disease is one of the most common and severe complications of diabetes mellitus. The hallmark of the disease, glomerulosclerosis, is characterized by an accumulation of extracellular matrix in the mesangial areas, leading to progressive obliteration of the vascular spaces. The role of the metabolic derangements of diabetes mellitus in the development of these lesions is incompletely understood. One of the consequences of hyperglycemia is the formation of advanced glycosylation end products (AGEs), which result from a series of rearrangements secondary to nonenzymatic reaction of glucose with proteins. Specific receptors for proteins modified by AGEs, present in several cell types, were recently described in human and rat mesangial cells. Furthermore, exposure of mesangial cells to AGEs was followed by an increase in fibronectin production. In the present study we show evidence that mouse mesangial cells exhibit an increase in collagen type IV mRNA and peptide synthesis after exposure to AGEs. Antibodies to AGE receptors prevent this increase, indicating that the response is AGE-receptor-mediated. In addition, anti-platelet-derived growth factor abrogates the AGE response, suggesting that platelet-derived growth factor acts as an intermediate factor. Transcription assay reveals that the elevated mRNA levels are due to an increase in the transcription rate, rather than to an increase in the stability of the message. Finally, the mRNAs coding for laminin and heparan sulfate proteoglycan are also increased after exposure to AGE, whereas glyceraldehyde 3-phosphate dehydrogenase mRNA levels remain constant. The increase in extracellular matrix mRNAs seen in the current study suggests that AGE formation in vivo may be one of the metabolic events leading to the development of diabetic glomerulosclerosis.

Animals↗

PubMed1992

Immunochemical detection of advanced glycosylation end products in vivo.

Reducing sugars react with protein amino groups to form a diverse group of protein-bound moieties with fluorescent and cross-linking properties. These compounds, called advanced glycosylation end products (AGEs), have been implicated in the structural and functional alterations of proteins that occur during aging and long-term diabetes. Although several AGEs have been identified on the basis of de novo synthesis and tissue isolation procedures, the measurement of AGE compounds in vivo has remained difficult. As an approach to the study of AGE formation in vivo, we prepared polyclonal antiserum to an AGE epitope(s) which forms in vitro after incubation of glucose with ribonuclease (RNase). This antiserum proved suitable for the detection of AGEs which form in vivo. Both diabetic tissue and serum known to contain elevated levels of AGEs readily competed for antibody binding. Cross-reactivity studies revealed the presence of a common AGE epitope(s) which forms after the incubation of diverse proteins with glucose. Cross-reactive epitopes also formed with glucose 6-phosphate or fructose. These data suggest that tissue AGEs which form in vivo appear to contain a common immunological epitope which cross-reacts with AGEs prepared in vitro, supporting the concept that immunologically similar AGE structures form from the incubation of sugars with different proteins (Horiuchi, S., Araki, N., and Morino, Y. (1991) J. Biol. Chem. 266, 7329-7332). None of the known AGEs, such as 4-furanyl-2-furoyl-1H-imidazole, 1-alkyl-2-formyl-3,4-diglycosylpyrrole, pyrraline, carboxymethyllysine, or pentosidine, were found to compete for binding to anti-AGE antibody. These data further suggest that the dominant AGE epitope which forms from the reaction of glucose with proteins under native conditions is immunologically distinct from the structurally defined AGEs described to date.

Adolescent↗

PubMed1992

Receptor-specific induction of insulin-like growth factor I in human monocytes by advanced glycosylation end product-modified proteins.

Normal tissue homeostasis requires a finely balanced interaction between phagocytic scavenger cells (such as monocytes and macrophages) that degrade senescent material and mesenchymal cells (such as fibroblasts and smooth muscle cells), which proliferate and lay down new extracellular matrix. Macrophages and monocytes express specific surface receptors for advanced glycosylation end products (AGEs), which are covalently attached adducts resulting from a series of spontaneous nonenzymatic reactions of glucose with tissue proteins. Receptor-mediated uptake of AGE-modified proteins induces human monocytes to synthesize and release cytokines (TNF and IL-1), which are thought to contribute to normal tissue remodeling by mechanisms not entirely understood. We now report that AGEs also induce human monocytes to generate the potent progression growth factor insulin-like growth factor I (IGF-I), known to stimulate proliferation of mesenchymal cells. After in vitro stimulation with AGE-modified proteins, normal human blood monocytes express IGF-IA mRNA leading to the secretion of IGF-IA prohormone. The signal for IGF-IA mRNA induction seems to be initiated via the monocyte AGE-receptor, and to be propagated in an autocrine fashion via either IL-1 beta or PDGF. These data introduce a novel regulatory system for IGF-I, with broad in vivo relevance, and provide an essential link to the chain of events leading from the spontaneously formed tissue AGEs, hypothesized to act as markers of protein senescence, to their replacement and to tissue remodeling by the locally controlled induction of growth factors.

Gene Expression↗

PubMed1992

Receptor-mediated interactions of advanced glycosylation end products with cellular components within diabetic tissues.

AGEs are nonenzymatically glycosylated adducts of proteins that accumulate in vascular tissues with aging and at an accelerated rate in people with diabetes; AGEs are closely linked to tissue damage due to their high reactivity in protein cross-linking. A macrophage-monocyte receptor system for AGE moieties is shown to mediate the uptake of AGE-modified proteins by a process that also induces cachectin-TNF, IL-1, IGF-I, and PDGF secretion. Thus, in addition to removing senescent glucose-modified proteins and cells, AGE-mediated release of growth-promoting factors may represent a mechanism by which macrophages signal mesenchymal cells the need for replacement of senescent proteins. The age of the macrophage correlates inversely with the binding and removal capacity of the AGE receptor, possibly preventing the clearance of cross-linked proteins and the compounding aging-related tissue damage. In addition to monocyte and macrophages, other cells express similar receptors for AGE-proteins, including endothelial cells, fibroblasts, and mesangial cells. Endothelial cell AGE-receptors mediate transcytosis of AGEs to the subendothelium, induce increased permeability, and enhance endothelium-dependent procoagulant activity. Renal mesangial AGE receptors mediate PDGF-dependent extracellular matrix protein production. Fibroblast AGE receptors may influence cellular proliferation by EGF and EGF-receptor regulation. These findings, in connection with the known abundance of AGEs in aged and diabetic tissues, indicate that AGE-ligand-receptor interactions are crucial for the development of age- and diabetes-related vascular tissue and renal pathology.

Aging↗

PubMed1991

Differential regulation of transforming growth factor beta and interleukin 2 genes in human T cells: demonstration by usage of novel competitor DNA constructs in the quantitative polymerase chain reaction.

The regulation of mRNA encoding transforming growth factor beta (TGF-beta) and interleukin 2 (IL-2) in normal human T cells was explored using novel competitor DNA constructs in the quantitative polymerase chain reaction and accessory cell-independent T cell activation models. Our experimental design revealed the following: (a) TGF-beta mRNA and IL-2 mRNA are regulated differentially in normal human T cells, quiescent or signaled with the synergistic combinations of: sn-1,2-dioctanoylglycerol and ionomycin or anti-CD3 monoclonal antibody (mAb) and anti-CD2 mAb; (b) the steady-state level of TGF-beta mRNA in the stimulated T cells, in contrast to that of IL-2 mRNA, is increased by the immunosuppressant cyclosporine (CsA); and (c) the paradoxical effect of CsA on TGF-beta mRNA levels is also appreciable at the level of production of functionally active TGF-beta protein. Our findings, in addition to demonstrating the utility of the competitor DNA constructs for the precise quantification of immunoregulatory cytokines, suggest a novel and unifying mechanistic basis for the immunosuppression and some of the complications (e.g., renal fibrosis) associated with CsA usage.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1991

Human and rat mesangial cell receptors for glucose-modified proteins: potential role in kidney tissue remodelling and diabetic nephropathy.

Advanced glycosylation endproducts (AGEs) are derived from the nonenzymatic addition of glucose to proteins. AGEs have been found to accumulate on tissue proteins in patients with diabetes, and their accumulation is thought to play a role in the development of diabetic complications. The finding that macrophages and endothelial cells contain AGE-specific receptors led us to examine whether mesangial cells (MCs) also possess a mechanism for recognizing and processing AGEs. Membrane extracts isolated from rat and human MCs were found to bind AGE-bovine serum albumin (BSA) in a saturable fashion, with a binding affinity of 2.0 +/- 0.4 x 10(6) M-1 (500 nM). The binding was specific for the AGE adduct, since AGE-modified collagen I and ribonuclease both competitively inhibited 125I-AGE-BSA binding to MC membranes, while the unmodified proteins did not compete. Binding of AGE proteins was followed by slow internalization and degradation of the ligand. Ligand blotting of MC membrane extracts demonstrated three distinct AGE-binding membrane proteins of 50, 40, and 30 kD. Growth of MCs on various AGE-modified matrix proteins resulted in alterations in MC function, as demonstrated by enhanced production of fibronectin and decreased proliferation. These results point to the potential role that the interaction of AGE-modified proteins with MCs may play in vivo in promoting diabetic kidney disease.

Adult↗

PubMed1991

Advanced glycosylation end products in patients with diabetic nephropathy.

BACKGROUND: Glucose reacts nonenzymatically with proteins in vivo, chemically forming covalently attached glucose-addition products and cross-links between proteins. The excessive accumulation of rearranged late-glucose-addition products, or advanced glycosylation end products (AGEs), is believed to contribute to the chronic complications of diabetes mellitus. METHODS: To elucidate the relation of AGEs to diabetic complications, we used a radioreceptor assay to measure serum and tissue AGEs in diabetic (Types I and Type II) and nondiabetic patients with different levels of renal function. Serum AGEs were measured as a low-molecular-weight (less than or equal to 10 kd) peptide fraction and a high-molecular-weight (greater than 10 kd) protein fraction. RESULTS: The mean (+/- SD) AGE content of samples of arterial-wall collagen from 9 diabetic patients was significantly higher than that of samples from 18 nondiabetic patients (14.5 +/- 5.2 vs. 3.6 +/- 1.5 AGE units per milligram, P less than 0.001). Moreover, diabetic patients with end-stage renal disease had almost twice as much AGE in tissue as diabetic patients without renal disease (21.3 +/- 2.8 vs. 11.5 +/- 1.9 AGE units per milligram, P less than 0.001). The AGE levels in both serum fractions were elevated in the patients with diabetes, and the levels of AGE peptides correlated directly with serum creatinine (P less than 0.001) and inversely with creatinine clearance (P less than 0.005), suggesting that levels of AGE peptides increased with the severity of diabetic nephropathy. In six patients with diabetes who required hemodialysis, the levels of AGE peptides were five times higher than in eight normal subjects (82.8 +/- 9.4 vs. 15.6 +/- 3.4 AGE units per milliliter, P less than 0.001). In another group of diabetic patients the mean serum creatinine level, which decreased by 75 percent during a session of hemodialysis, whereas the level of AGE peptides decreased by only 24 percent. Serum levels of AGE peptides were normal in two patients with normal serum creatinine levels after renal transplantation. CONCLUSIONS: AGEs accumulate at a faster-than-normal rate in arteries and the circulation of patients with diabetes; the increase in circulating AGE peptides parallels the severity of renal functional impairment in diabetic nephropathy.

Adult↗

PubMed1991

Two novel rat liver membrane proteins that bind advanced glycosylation endproducts: relationship to macrophage receptor for glucose-modified proteins.

Advanced glycosylation endproducts (AGEs), the glucose-derived adducts that form nonenzymatically and accumulate on tissue proteins, are implicated in many chronic complications associated with diabetes and aging. We have previously described a monocyte/macrophage surface receptor system thought to coordinate AGE protein removal and tissue remodeling, and purified a corresponding 90-kD AGE-binding protein from the murine RAW 264.7 cell line. To identify AGE-binding proteins in normal animals, the tissue distribution of 125I-AGE rat serum albumin taken up from the blood was determined in rats in vivo. These uptake studies demonstrated that the liver was a major site of AGE protein sequestration. Using a solid-phase assay system involving the immobilization of solubilized membrane proteins onto nitrocellulose to monitor binding activity, and several purification steps including affinity chromatography over an AGE bovine serum albumin matrix, two rat liver membrane proteins were isolated that specifically bound AGEs, one migrating at 60 kD (p60) and the other at 90 kD (p90) on SDS-PAGE. NH2-terminal sequence analysis revealed no significant homology between these two proteins nor to any molecules available in sequence databases. Flow cytometric analyses using avian antibodies to purified rat p60 and p90 demonstrated that both proteins are present on rat monocytes and macrophages. Competition studies revealed no crossreactivity between the two antisera; anti-p60 and anti-p90 antisera prevented AGE-protein binding to rat macrophages when added alone or in combination. These results indicate that rat liver contains at least two novel and distinct proteins that recognize AGE-modified macromolecules, although p90 may be related to the previously described 90-kD AGE receptor isolated from RAW 264.7 cells. The constitutive expression of AGE-binding proteins on rat monocytes and macrophages, and the sequestration of circulating AGE-modified proteins by the liver, provides further evidence in support of a role for these molecules in the normal removal of proteins marked as senescent by accumulated glucose-derived covalent addition products, or AGEs.

Aging↗

PubMed1991

Radioreceptor assay for advanced glycosylation end products.

Previous assays for nonenzymatic advanced glycosylation end products (AGEs) formed in tissues and/or circulating in blood are unsatisfactory. Based on our earlier identification of AGE-specific receptors on the macrophagelike tumor cell line RAW 264.7, a new assay system for AGEs has been devised. RAW 264.7 cells were used in competitive radioreceptor assays (RRA) after a 3-day culture in 96-well plates with 1 mu CI/ml [3H]glycine. Bovine serum albumin (BSA), modified extensively by incubation with glucose-6-phosphate in vitro to form AGE-BSA, was labeled with 125I and was used as a model ligand at a concn of 10 micrograms/ml. One unit of AGE was defined as the amount of test protein required to inhibit 50% of the specific binding of [125I]-labeled AGE-BSA to the AGE-receptors of intact RAW 264.7 cells. Nonlabeled AGE-BSA was used as a specific competitor to construct standard curves. The reproducibility of the assay was assessed at AGE levels equivalent to mean, maximum, and minimum levels of sensitivity for assays run on a single day and over an extended period, and the RRA had a reproducibility (coefficient of variation) between 5.9 and 14.7%. Protease hydrolysis of in vitro glycosylated proteins before assay increases the competitive ability of these proteins in proportion to their glycosylation. Little or no AGE cross-reactivity was detected in native BSA, Amadori-BSA, maleylated BSA, formaldehyde-treated BSA, palmitic acid-BSA, and acetylated low-density lipoproteins (acetyl-LDL). Polyanions such as heparin or fucoidan strongly interfere with this receptor binding assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

A novel addition to the T cell repertory. Cell surface expression of tumor necrosis factor/cachectin by activated normal human T cells.

Expression of the pluripotent molecule TNF in a focused and antigen-restricted fashion might provide an advantage to the host organism. Given the central role of T cells in antigen-specific immunity, we examined whether activated T cells express TNF on their cell surface. FACS analysis of highly purified normal human T cells labeled with an anti-TNF mAb revealed that T cells express cell surface TNF when signaled with the synergistic combination of a calcium ionophore, ionomycin, and a protein kinase C activator, 12-o-tetradecanoyl phorbol acetate. Cell surface radioiodination studies of stimulated T cells demonstrated the presence of 26-kD transmembrane protein, a size predicted by TNF cDNA and different from that of the 17-kD secreted TNF molecule. The induced cell surface expression of TNF could be blocked with cyclosporine and/or methylprednisolone, and Northern analysis for TNF-specific transcripts revealed that this inhibitory effect occurs pretranslationally. Our demonstration for the first time that stimulated normal human T cells display cell surface TNF provides a mechanistic basis for the realization of effects of TNF in an antigen-specific fashion.

Cyclosporins↗

PubMed1990

Advanced protein glycosylation induces transendothelial human monocyte chemotaxis and secretion of platelet-derived growth factor: role in vascular disease of diabetes and aging.

Diabetes and aging are commonly accompanied by arterio- and atherosclerosis. Infiltration of the arterial subendothelial intima by macrophages/monocytes is an important early event preceding the development of atheromatous lesions; these macrophages are known to produce mitogenic factors in early atherosclerotic lesions. It has been previously shown that, over time, vascular matrix accumulates proteins nonenzymatically modified by advanced glycosylation end products (AGEs). In view of the fact that macrophages/monocytes have AGE-specific receptors associated with the expression of several growth factors, we investigated the possibility that AGEs mediate initial monocyte-vessel wall interactions that occur before overt formation of vascular lesions. This study demonstrates that (i) in vitro- and in vivo-formed AGEs are chemotactic for human blood monocytes, (ii) sub-endothelial AGEs can selectively induce monocyte migration across an intact endothelial cell monolayer, and (iii) subsequent monocyte interaction with AGE-containing matrix results in the expression of platelet-derived growth factor. These results support the existing hypothesis that in vivo-forming glucose-derived protein adducts can act as signals for the normal turnover of senescent tissue protein by means of the AGE-specific receptor system. Time-dependent glucose-induced deposition of AGEs on matrix proteins may promote monocyte infiltration into the subendothelium. Subsequent AGE-triggered macrophage activation and consequent elaboration of proliferative factors may normally coordinate remodeling but may also lead to the diverse pathogenic changes typical of arterio- and atherosclerosis in diabetic or aging populations.

Aging↗

PubMed1990

Advanced nonenzymatic tissue glycosylation: cell-mediated interactions implicated in the complications associated with diabetes and aging.

Tissue and cell surface proteins modified nonenzymatically by glucose are shown to be highly active in protein cross-linking and have been implicated in tissue damage. The production of such protein-glucose interactions called advanced glycosylation endproducts (AGE) are recently shown to be processed by macrophages through a recently characterized high-affinity receptor. Coupling of AGE proteins to their AGE receptor results in TNF and IL-1 synthesis and secretion. This suggests that AGE may act as a signal for growth-promoting factor secretion in a coordinated replacement process during tissue remodeling. A disturbance of this balance may lead to pathologic proliferative response such as in the vasculopathy of diabetes and aging. Since peritoneal surface proteins can be modified by AGE after exposure to high-glucose, a similar pathogenetic process may be involved in the peritoneal fibrosis associated with chronic peritoneal dialysis.

Aging↗

PubMed1990

Isolation of surface binding protein specific for advanced glycosylation end products from mouse macrophage-derived cell line RAW 264.7.

Macrophages internalize and degrade proteins modified by advanced glycosylation end products (AGEs) via a specific receptor (AGE-R). Chemical cross-linking studies with AGE-bovine serum albumin have demonstrated that the molecular weight of this receptor is approximately 90,000. We previously established that the binding constant (Ka) of this receptor site for the chemically synthesized model AGE, 2-(2-furoyl)-4(5)-(2-furanyl)-1H- imidazole-butyric acid (FFI-BA), on cells of the mouse macrophagelike cell line RAW 264.7 is identical to that for AGE proteins. Therefore, FFI was used as an affinity matrix in the first purification step of the AGE-R. The membranes of RAW 264.7 cells were solubilized in octyl-beta-glucoside and subjected to affinity chromatography on FFI-sepharose and gel permeation on Superose 6 fast protein liquid chromatography. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis analysis of this material revealed a high enrichment of a 90,000-Mr protein that had AGE binding activity. Approximately 25% of the protein at this step was the 90,000-Mr protein. The 90,000-Mr membrane protein was purified to homogeneity by rechromatographing the material on Superose 12 in the presence of SDS before and after reduction with 2-mercaptoethanol. After these harsh conditions, the 90,000-Mr protein lost AGE binding activity. Additional cross-linking studies on human peripheral monocytes revealed an AGE-R protein of identical size to that on RAW 264.7 cells, suggesting the relatively highly conserved nature of this molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Chronic diabetic complications and tissue glycosylation. Relevant concern for diabetes-prone black population.

A significant segment of the Black population is affected by chronic diabetes, and most of them are subjected to severe cardiovascular, renal, and neurological complications that shorten survival and diminish quality of life. One of the important pathogenetic mechanisms under intensive investigation is advanced tissue glycosylation. Tissue and cell surface proteins modified nonenzymatically by glucose are shown to be highly active in protein cross-linking and have been implicated in tissue damage. Such protein-glucose interactions, called advanced glycosylation end products (AGEs), are processed by macrophages through a high-affinity receptor. Coupling of AGE proteins to their AGE receptors results in their degradation and removal and, simultaneously, in synthesis and secretion of pluripotential cytokines such as tumor necrosis factor and interleukin 1. This suggests that AGE may act normally as a signal for growth-promoting factor secretion in a coordinated replacement process during tissue remodeling. In chronic diabetes, however, where accelerated accumulation of tissue AGE occurs, a disturbance of this balance may lead to several pathological, lytic, and/or proliferative responses like those in the vasculopathy of diabetes. Progress has been made with the discovery of aminoguanidine HCl, an AGE inhibitor, which has prevented significant pathology in short-term diabetic animal studies.

Black People↗