Receptor-mediated endothelial cell dysfunction in diabetic vasculopathy. Soluble receptor for advanced glycation end products blocks hyperpermeability in diabetic rats

Dysfunctional endothelium is associated with and, likely, predates clinical complications of diabetes mellitus, by promoting increased vascular permeability and thrombogenicity. Irreversible advanced glycation end products (AGEs), resulting from nonenzymatic glycation and oxidation of proteins or lipids, are found in plasma, vessel wall, and tissues and have been linked to the development of diabetic complications. The principal means through which AGEs exert their cellular effects is via specific cellular receptors, one of which, receptor for AGE (RAGE), is expressed by endothelium. We report that blockade of RAGE inhibits AGE-induced impairment of endothelial barrier function, and reverse, in large part, the early vascular hyperpermeability observed in diabetic rats. Inhibition of AGE- and diabetes-mediated hyperpermeability by antioxidants, both in vitro and in vivo, suggested the central role of AGE-RAGE-induced oxidant stress in the development of hyperpermeability. Taken together, these data support the concept that ligation of AGEs by endothelial RAGE induces cellular dysfunction, at least in part by an oxidant-sensitive mechanism, contributing to vascular hyperpermeability in diabetes, and that RAGE is central to this pathologic process.

The receptor for advanced glycation end products (RAGE) is a cellular binding site for amphoterin. Mediation of neurite outgrowth and co-expression of rage and amphoterin in the developing nervous system

The receptor for advanced glycation end products (RAGE), a newly-identified member of the immunoglobulin superfamily, mediates interactions of advanced glycation end product (AGE)-modified proteins with endothelium and other cell types. Survey of normal tissues demonstrated RAGE expression in situations in which accumulation of AGEs would be unexpected, leading to the hypothesis that under physiologic circumstances, RAGE might mediate interaction with ligands distinct from AGEs. Sequential chromatography of bovine lung extract identified polypeptides with M(r) values of approximately 12,000 (p12) and approximately 23,000 (p23) which bound RAGE. NH2-terminal and internal protein sequence data for p23 matched that reported previously for amphoterin. Amphoterin purified from rat brain or recombinant rat amphoterin bound to purified sRAGE in a saturable and dose-dependent manner, blocked by anti-RAGE IgG or a soluble form of RAGE (sRAGE). Cultured embryonic rat neurons, which express RAGE, displayed dose-dependent binding of 125I-amphoterin which was prevented by blockade of RAGE using antibody to the receptor or excess soluble receptor (sRAGE). A functional correlate of RAGE-amphoterin interaction was inhibition by anti-RAGE F(ab')2 and sRAGE of neurite formation by cortical neurons specifically on amphoterin-coated substrates. Consistent with a potential role for RAGE-amphoterin interaction in development, amphoterin and RAGE mRNA/antigen were co-localized in developing rat brain. These data indicate that RAGE has physiologically relevant ligands distinct from AGEs which are likely, via their interaction with the receptor, to participate in physiologic processes outside of the context of diabetes and accumulation of AGEs.

Advanced glycation endproducts interacting with their endothelial receptor induce expression of vascular cell adhesion molecule-1 (VCAM-1) in cultured human endothelial cells and in mice. A potential mechanism for the accelerated vasculopathy of diabetes

Vascular cell adhesion molecule-1 (VCAM-1), an inducible cell-cell recognition protein on the endothelial cell surface (EC), has been associated with early stages of atherosclerosis. In view of the accelerated vascular disease observed in patients with diabetes, and the enhanced expression of VCAM-1 in diabetic rabbits, we examined whether irreversible advanced glycation endproducts (AGEs), could mediate VCAM-1 expression by interacting with their endothelial cell receptor (receptor for AGE, RAGE). Exposure of cultured human ECs to AGEs induced expression of VCAM-1, increased adhesivity of the monolayer for Molt-4 cells, and was associated with increased levels of VCAM-1 transcripts. The inhibitory effect of anti-RAGE IgG, a truncated form of the receptor (soluble RAGE) or N-acetylcysteine on VCAM-1 expression indicated that AGE-RAGE-induced oxidant stress was central to VCAM-1 induction. Electrophoretic mobility shift assays on nuclear extracts from AGE-treated ECs showed induction of specific DNA binding activity for NF-kB in the VCAM-1 promoter, which was blocked by anti-RAGE IgG or N-acetylcysteine. Soluble VCAM-1 antigen was elevated in human diabetic plasma. These data are consistent with the hypothesis that AGE-RAGE interaction induces expression of VCAM-1 which can prime diabetic vasculature for enhanced interaction with circulating monocytes.

[Mortality study of cancer among Anshan iron and steel workers]

Cancer mortality in the period between 1971 and 1988 was surveyed among 71,803 male workers at thirty two major plants in Anshan Iron and Steel Corporation. A total of 5,896 deaths was registered. Cancer deaths occurred in 1,830, accounting for 31.04% of all deaths. The five leading cancers were that of lung, liver, stomach, esophagus and intestine. Cancer death rate increased with age and with calender year. The SMR for all cancers and for the cancer of lung, stomach and esophagus indicated significant excess (P < 0.01). 77.49% of all cancer deaths, and 82.82% of deaths with lung cancer occurred in smokers. The findings show that the mortality of cancer amongiron and steel workers in Anshan was the leading cause of death, and the death rate was higher than that of local and large city population such as in Beijing, Shanghai, etc. The excess cancer rate, especially that of lung cancer, may be related to carcinogenic agents in the working environment and smoking habit.

Receptor for advanced glycation end products (AGEs) has a central role in vessel wall interactions and gene activation in response to circulating AGE proteins

The extended interaction of aldoses with proteins or lipids results in nonenzymatic glycation and oxidation, ultimately forming AGEs, the presence of which in the plasma and vessel wall is associated with diabetic vascular complications. We show here that AGE albumin in the intravascular space interacts with the vessel wall via binding to an integral membrane protein, receptor for AGE (RAGE), a member of the immunoglobulin superfamily, resulting in clearance from the plasma and induction of interleukin 6 mRNA. Intravenously infused 125I-AGE albumin showed a rapid phase of plasma clearance with deposition in several organs. Rapid removal of 125I-AGE albumin from the plasma was prevented by administration of a soluble, truncated form of RAGE, which blocked binding of 125I-labeled AGE albumin to cultured endothelial cells and mononuclear phagocytes, as well as by pretreatment with anti-RAGE IgG. Ultrastructural studies with AGE albumin-colloidal gold conjugates perfused in situ showed that in murine coronary vasculature this probe was taken up by endothelial plasmalemmal vesicles followed by transport either to the abluminal surface or by accumulation in intracellular vesicular structures reminiscent of endosomes and lysosomes. Consequences of AGE-RAGE interaction included induction of interleukin 6 mRNA expression in mice. These data indicate that RAGE mediates the interaction of AGEs with the vessel wall, both for removal of these glycated proteins from the plasma and for changes in gene expression.

The endothelial cell binding site for advanced glycation end products consists of a complex: an integral membrane protein and a lactoferrin-like polypeptide

Advanced glycation end products (AGEs), formed as the result of the extended interaction of proteins with ketoses, modulate central properties of endothelial cells and mononuclear phagocytes by interacting with a cell surface binding site comprised of a novel integral membrane protein (receptor for AGE = RAGE) and a lactoferrin-like polypeptide (LF-L), the latter having sequence identity to lactoferrin (LF). To further understand this cellular binding site, the interaction of RAGE with LF-L and LF was characterized. By ligand blotting and a solid state competitive binding assay, 125I-LF-L and 125I-LF bound to RAGE immobilized on nitrocellulose membranes or polypropylene tubes in a time-dependent and reversible manner, demonstrating a high affinity component with Kd approximately 100 pM. The interaction of 125I-LF-L and 125I-LF with RAGE was independent of iron in LF and was competed by addition of an excess of unlabeled carboxyl-terminal portion of LF. Cross-linking studies with purified 125I-LF-L and RAGE, in the presence of disuccinimidyl suberate, showed a new, slowly migrating band, corresponding to a complex of RAGE and LF-L, and cross-linking on mouse aortic endothelial cells showed two new slowly migrating bands on immunoblotting visualized with both anti-RAGE IgG and anti-LF-L IgG. These data lead us to propose that the endothelial cell surface binding site for AGEs consists of LF-L bound noncovalently to RAGE anchored in the cell membrane.

Population genetics of three VNTR polymorphisms in two different Spanish populations

Two different Spanish populations, one from Galicia (NW Spain) and the other from the rest of Spain, have been analyzed at three different hypervariable loci (YNH24, MS43a and MS31) using the EDNAP electrophoretic protocol and HinfI as restriction enzyme. Although the "rest of Spain" population is a clearly stratified population using classical blood groups, no evidence of stratification for these loci has been found and the differences to the Galician population were not significant, which suggests that a common Spanish population data-base could be possible. A semiparametric model is proposed for estimating frequencies, using the smoothed cross-validation of Hall et al. (1992) to calculate the size of the window utilized.

[Re-discovery of yinzhou chaihu]

This paper deals with the distribution, original plant, course of rise and fall in drug market and quality of Yinzhou Chaihu, which was once regarded as a fine sort of Chinese drug Chaihu (Radix Bupleuri) in ancient times. Further research on this medicinal plant is suggested to facilitate its re-exploitation and utilization.

[Protective effect of prostaglandin E on hepatocytes and its value of early treatment of severe viral hepatitis]

An animal model of hepatocytic necrosis was established with injection of D-galactosamine into peritoneal cavity. Examination at regular intervals after injection showed that the level of increased serum TB, ALT and GST and the degree of histological changes in the liver were less marked in PGE-treated animals (n = 34) than those in PGE-untreated animals (n = 29), suggesting that PGE has definite protective effect for experimental hepatocytic necrosis. According to severity of the condition hepatic failure was divided into early stage, typical stage and late stage. A treatment group of 55 cases received PGE1 therapy and a control group basic support therapy only. The results showed that difference of the total effective rate was not significant between the two groups, but in the early stage of hepatic failure, the effective rate in the treatment group was markedly higher than that in the control group. In addition, incidence of hepato-renal syndrome was lower in the treatment group. We are of the opinion that division of severe viral hepatitis into three stages for evaluation of therapeutic effect is rational and useful and early use of PGE1 may show certain efficacy.