To study the biological function of the N-glycosylation modification of prion proteins (PrP), various eukaryotic expression vectors for the mutants with N-glycosylation modification of human PrP had been constructed and expressed. With site-direct mutation technique, human PRNP gene was mutated and the obtained mutants were subcloned into eukaryotic expressing plasmid pcDNA3.1 and transiently expressed in Hela cervical adenocarcinoma cell. The expression products of the mutated PrP were identified with Western blotting assay and the PNGase digestion assay. Several mutants with specific glycosylation modification were identified from the expressed products by Western blot, including two mutants with one glycosylation site mutated and one without any mutation at glycosylation sites. The expressed products were digested with PNGase F. The wild type proteins and those with one of glycosylation sites mutated were digested, resulting in their molecular weights reduced, while the molecular weights of products with mutations at both glycosylation sites were not changed. The mutant of wild type human PRNP gene at N-glycosylation modification sites and six modified mutants with mono- or non-N-glycosylation had been obtained successfully in the study. Moreover, the modified PrP with mono- and non-N-glycosylation were able to be expressed transitantly in Hela cells, which could be a useful means for studying prions.
Escherichia coli ; genetics ; metabolism ; Glycation End Products, Advanced ; biosynthesis ; genetics ; Glycosylation ; HeLa Cells ; Humans ; Mutagenesis, Site-Directed ; Mutant Proteins ; biosynthesis ; genetics ; Prions ; biosynthesis ; genetics ; Transfection

Diabetes mellitus (DM) is a complex disease with various systemic and oral complications including periodontitis. Periodontitis is a disease that leads to destruction of the soft and hard tissues of periodontium, which can result in periodontal bone loss and tooth loss. Although the etiology for periodontitis is bacterial plaque, the host immune response also mediates the destruction of periodontal tissues. DM is related to the development, progression and severity of periodontitis. There are several factors potentially contributing to the development of periodontitis in DM patients: 1) altered immune function, 2) hyperglycemia and advanced glycation end products, and 3) altered lipid metabolism. With limited number of studies, the potential mechanisms involved in the development of DM in periodontitis have also been suggested. DM clearly increases the risk of periodontitis and biological mechanisms have been illucidated. Less clear is the impact of periodontitis on the development of DM. It is possible that periodontitis may serve as initiators or propagators of insulin resistance in a way similar to obesity, thereby aggravating glycemic control.
Alveolar Bone Loss ; Diabetes Mellitus ; Glycosylation End Products, Advanced ; Humans ; Hyperglycemia ; Insulin Resistance ; Lipid Metabolism ; Obesity ; Periodontal Diseases* ; Periodontitis ; Periodontium ; Tooth Loss

An early feature of diabetic nephropathy is the alteration of the glomerular basement membrane (GBM), which may result in microalbuminuria, subsequent macroproteinuria, and eventual chronic renal failure. Although type IV collagen is the main component of thickened GBM in diabetic nephropathy, cellular metabolism of each alpha chains of type IV collagen has not been well studied. To investigate the regulation of alpha(IV) chains in diabetic conditions, we examined whether glucose and advanced glycosylation endproduct (AGE) regulate the metabolism of each alpha(IV) chains in the diabetic tissue and glomerular epithelial cells (GEpC). Glomerular collagen alpha3(IV) and alpha5(IV) chains protein were higher and more intense in immunofluorescence staining according to diabetic durations compared to controls. In vitro, mainly high glucose and partly AGE usually increased total collagen protein of GEpC by [3H]-proline incorporation assay and each alpha(IV) chain proteins including alpha1(IV), alpha3(IV), and alpha5(IV) in time-dependent and subchain-specific manners. However, the changes of each alpha(IV) chains mRNA expression was not well correlated to the those of each chain proteins. The present findings suggest that the metabolism of individual alpha(IV) chains of GBM is differentially regulated in diabetic conditions and those changes might be induced not only by transcriptional level but also by post-translational modifications.
Animals ; Cells, Cultured ; Collagen Type IV/genetics/*metabolism/physiology ; Diabetic Nephropathies/*metabolism ; Epithelial Cells/*metabolism ; Glomerular Basement Membrane/metabolism ; Glucose/metabolism ; Glycosylation End Products, Advanced/metabolism ; Male ; Podocytes/*metabolism ; RNA, Messenger/metabolism ; Rats ; Rats, Sprague-Dawley

It has been demonstrated that inhibitors of advanced glycation end products (AGE), such as aminoguanidine, can suppress peritoneal AGE in rats on peritoneal dialysis (PD). However, it is unknown whether late administration of a putative crosslink breaker, alagebrium, could reverse peritoneal AGE. We therefore compared alagebrium with aminoguanidine in their ability to reverse peritoneal AGE in rats on PD. Male Sprague-Dawley rats were randomly divided into 3 groups: group I dialyzed with 4.25% glucose solution for all exchanges; group II dialyzed with 4.25% glucose solution containing aminoguanidine, and group III dialyzed with 4.25% glucose solution containing alagebrium for last 8 weeks of 12-week dialysis period. Dialysis exchanges were performed 2 times a day for 12 weeks. Immunohistochemistry was performed using a monoclonal anti-AGE antibody. One-hour PET was performed for comparison of transport characteristics. The immunolabelling of AGE in peritoneal membrane was markedly decreased in the alagebrium group. Consistent with this, the alagebrium group exhibited significantly higher D/Do glucose and lower D/P urea, suggesting low peritoneal membrane transport. But there were no significant differences between the control and the aminoguanidine group. These results suggest that the alagebrium may be the optimal therapeutic approach, compared with treatment with inhibitors of AGE formation, in rats on PD.
Animals ; Biological Transport ; Body Weight ; Cell Membrane/metabolism ; Glycosylation End Products, Advanced/*metabolism ; Guanidines/metabolism ; Immunohistochemistry/methods ; Male ; Peritoneal Dialysis/*methods ; Peritoneum/metabolism/*pathology ; *Permeability ; Rats ; Rats, Sprague-Dawley

The incidence of diastolic heart failure increases dramatically with age. We investigated the impact of long-term exercise training on age-related diastolic dysfunction. Old (25-month-old) male Fischer 344 rats were studied after 12 weeks of treadmill exercise training or sedentary cage life (N=7, in each group). We determined cardiac performance using a pressure-volume conductance catheter and magnetic resonance imaging. Collagen volume fraction (CVF) and myocardial collagen solubility by pepsin as an index of advanced glycation end products (AGEs) crosslinked collagen were measured. The maximal slope of systolic pressure increment (+dP/dt) and the slope of end-systolic pressure-volume relation were higher, and end diastolic volume (EDV), delta EDV (the percentage of the EDV increment-to-baseline EDV) and the slope of end-diastolic pressure-volume relation were lower in training group. The maximal slope of diastolic pressure decrement (-dP/dt) and time constant of LV pressure decay (tau) had no difference. AGEs cross-linked collagen, not CVF was reduced by exercise training. Long-term exercise training appears to attenuate age-related deterioration in cardiac systolic function and myocardial stiffness and could be reduce in pathologic AGEs cross-linked collagen in myocardium.
*Aging ; Animals ; Blood Pressure ; Collagen/*metabolism ; Glycosylation End Products, Advanced/metabolism ; Heart Failure, Diastolic/metabolism/*physiopathology ; Magnetic Resonance Imaging ; Male ; Myocardium/*metabolism ; Physical Conditioning, Animal ; Rats ; Rats, Inbred F344 ; Solubility ; Stroke Volume/physiology

The formation of advanced glycation end products (AGEs), in various tissues has been known to enhance immunoinflammatory reactions and local oxidant stresses in long standing diabetes. Recently, AGEs have been reported to play a role in neointimal formation in animal models of arterial injury. We attempted to determine whether the serum levels of AGEs are associated with coronary restenosis in diabetic patients. Blood samples were collected from diabetic patients with coronary artery disease undergoing stent implantation and the serum levels of AGEs were analyzed by the fluorescent intensity method. The development of in-stent restenosis (ISR) was evaluated by a 6-month follow-up coronary angiography. A total of 263 target lesions were evaluated, in 203 patients. The ISR rate in the high-AGE (> 170 U/ml) group (40.1%) was significantly higher than in the low-AGE group (< or =170 U/ml) (19.6%) (p < 0.001). Furthermore, multivariate analysis revealed that a high level of serum AGEs is an independent risk factor for the development of ISR (odds ratio, 2.659; 95% CI, 1.431-4.940; p=0.002). The serum levels of AGEs constitute an excellent predictive factor for ISR, and should be one of the guidelines for medical therapy and interventional strategy to prevent ISR in diabetic patients.
Aged ; Coronary Arteriosclerosis/epidemiology/*metabolism/*therapy ; Coronary Restenosis/epidemiology/*metabolism ; Diabetes Mellitus, Type 2/epidemiology/*metabolism ; Female ; Glycosylation End Products, Advanced/*blood ; Humans ; Male ; Middle Aged ; Research Support, Non-U.S. Gov't ; Risk Factors ; *Stents

PURPOSE: To investigate the effect of advanced glycation end products (AGE) on oxidative stress and cellular senescence in cultured human trabecular meshwork cells (HTMC). METHODS: Primarily cultured HTMC were exposed to 0, 10, 50, 100, 200 microg/mL of glycated bovine serum albumin (G-BSA) for 5 days. Also co-exposed were L-arginine, sepiapterin, and antioxidant N-acetylcysteine (NAC). Cellular survival and production of nitric oxide (NO), superoxide, and reactive oxygen species were assessed by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide assay, Griess assay, cytochrome c assay, and dichlorofluorescin diacetate assay, respectively. Senescence-associated beta-galactosidase staining was performed to quantify the degree of cellular senescence. RESULTS: G-BSA decreased cellular survival, NO production, and increased superoxide production significantly in a dose-dependent manner. The effects of G-BSA were abolished with co-exposure of L-arginine, sepiapterin, and NAC. G-BSA enhanced cellular senescence accompanied by increased production of reactive oxygen species. G-BSA-induced cellular senescence was suppressed by application of L-arginine, sepiapterin, and NAC. CONCLUSIONS: AGE enhances cellular senescence of HTMC accompanied with increased oxidative stress. AGE-induced oxidative stress and cellular senescence could be delayed by application of anti-oxidants.
Acetylcysteine/metabolism ; Apoptosis/drug effects/physiology ; Arginine/metabolism ; Cell Aging/drug effects/*physiology ; Cell Survival/drug effects/physiology ; Cells, Cultured ; Glycosylation End Products, Advanced/metabolism/*toxicity ; Humans ; Nitric Oxide/metabolism ; Oxidative Stress/*physiology ; Pterins/metabolism ; Reactive Oxygen Species/metabolism ; Serum Albumin, Bovine/metabolism/toxicity ; Trabecular Meshwork/drug effects/*metabolism/*pathology

Idiopathic pulmonary fibrosis (IPF) is a lethal parenchymal lung disease characterized by myofibroblast proliferation. Alveolar epithelial cells (AECs) are thought to produce myofibroblasts through the epithelial to mesenchymal transition (EMT). Receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface receptors whose activation is associated with renal fibrosis during diabetes and liver fibrosis. RAGE is expressed at low basal levels in most adult tissues except the lung. In this study, we evaluated the interaction of ligand advanced glycation end products (AGE) with RAGE during the epithelial to myofibroblast transition in rat AECs. Our results indicate that AGE inhibited the TGF-beta-dependent alveolar EMT by increasing Smad7 expression, and that the effect was abolished by RAGE siRNA treatment. Thus, the induction of Smad7 by the AGE-RAGE interaction limits the development of pulmonary fibrosis by inhibiting TGF-beta-dependent signaling in AECs.
Animals ; Epithelial Cells/cytology ; Epithelial-Mesenchymal Transition/*drug effects ; Glycosylation End Products, Advanced/genetics/*metabolism ; Idiopathic Pulmonary Fibrosis/metabolism ; Pulmonary Alveoli/cytology ; RNA, Small Interfering/genetics ; Rats ; Receptors, Immunologic/genetics/*metabolism ; Smad7 Protein/genetics/*metabolism ; Transforming Growth Factor beta/genetics/metabolism

Advanced glycation endproducts (AGEs) have been reported to play a role in neointimal formation and increase the rate of in-stent restenosis (ISR) in the diabetic coronary artery disease patients treated with stents, but the potential pathogenic mechanisms of AGEs in vascular smooth muscle cell proliferation remain unclear. We sought to determine the AGEs related pathobiological mechanism of diabetic vasculopathy. Rat aortic smooth muscle cell (RAoSMC) culture was done with different concentrations of AGEs and proliferation was assessed. Immunohistochemistry for receptor of AGEs (RAGE) was performed with human carotid atheroma. Western blotting was performed to assess the activation of MAP kinase system in the cultured RAoSMC. AGEs increased RAoSMC proliferation and were associated with increased phosphorylation of ERK and p38 kinase by time and dose dependent manner. The MAP kinase activity was decreased by RNA interference for RAGE. AGEs stimulation increased reactive oxygen species (ROS) generation in cultured RAoSMC. From this study it is concluded that AGEs played a key role in RAoSMC proliferation via MAP kinase dependent pathways. Activation of vascular smooth muscle cell (VSMC) proliferation by MAP kinase system and increased formation of ROS may be the possible mechanisms of AGEs induced diabetic vasculopathy.
Animals ; Carotid Artery Diseases/metabolism/pathology ; Cell Proliferation/drug effects ; Cells, Cultured ; Diabetic Angiopathies/*etiology/metabolism/pathology ; Extracellular Signal-Regulated MAP Kinases/metabolism ; Glycosylation End Products, Advanced/adverse ; Humans ; MAP Kinase Signaling System/drug effects/*physiology ; Phosphorylation/drug effects ; RNA, Small Interfering/pharmacology ; Rats ; Rats, Sprague-Dawley ; Reactive Oxygen Species/metabolism ; Receptors, Immunologic/antagonists & inhibitors/metabolism

Early diabetic nephropathy is characterized by glomerular hyperpermeability as a result of impaired glomerular filtration structure caused by hyperglycemia, glycated proteins or irreversible advanced glycosylation endproducts (AGE). To investigate the effect of ginseng total saponin (GTS) on the pathologic changes of podocyte ZO (zonula occludens)-1 protein and podocyte permeability induced by diabetic conditions, we cultured mouse podocytes under: 1) normal glucose (5 mM, = control); 2) high glucose (HG, 30 mM); 3) AGE-added; or 4) HG plus AGE-added conditions and treated with GTS. HG and AGE increased the dextran filtration of monolayered podocytes at early stage (2-8 hr) in permeability assay. In confocal imaging, ZO-1 colocalized with actin filaments and beta-catenin at cell contact areas, forming intercellular filtration gaps. However, these diabetic conditions suppressed ZO-1 immunostainings and disrupted the linearity of ZO-1. In Western blotting, diabetic conditions also decreased cellular ZO-1 protein levels at 6 hr and 24 hr. GTS improved such quantitative and qualitative changes. These findings imply that HG and AGE have an influence on the redistribution and amount of ZO-1 protein of podocytes thereby causing hyperpermeability at early stage, which can be reversed by GTS.
Actin Cytoskeleton/metabolism ; Animals ; Cell Line ; Diabetic Nephropathies/physiopathology ; Glomerular Filtration Rate ; Glucose/*pharmacology ; Glycosylation End Products, Advanced/*pharmacology ; Hyperglycemia/physiopathology ; Membrane Proteins/*metabolism ; Mice ; *Panax ; Permeability/drug effects ; Phosphoproteins/*metabolism ; Plant Preparations/*pharmacology ; Podocytes/drug effects/pathology/physiology ; Saponins/*pharmacology ; beta Catenin/metabolism