CiteULike: jyuh's Yamagishi

Pericyte biology and diseases.

S Yamagishi — 2008-04-22T09:53:35-00:00

International journal of tissue reactions, Vol. 27, No. 3. (2005), pp. 125-135.

Microvessels are composed of two types of cells: endothelial cells and pericytes. Pericytes are elongated cells of mesodermal origin that partially surround the endothelial cells of small vessels. As pericytes contain contractile muscle filaments on their endothelial cell side, they have long been regarded as just microvascular counterparts of smooth muscle cells, thus being implicated in the regulation of capillary tone. However recent understanding of pericyte biology suggests that pericytes play an important role in the maintenance of microvascular homeostasis. Indeed, loss or dysfunction of pericytes has been considered to play an active part in the pathogenesis of various types of disorders. In this study, we review the biology of pericytes and the pathological role of pericyte loss or dysfunction in various devastating disorders such as diabetic retinopathy, atherosclerosis and tumor angiogenesis

Troglitazone improves endothelial function and augments renal klotho mRNA expression in Otsuka Long-Evans Tokushima Fatty (OLETF) rats with multiple atherogenic risk factors.

T Yamagishi — 2008-01-28T04:04:01-00:00

Hypertens Res, Vol. 24, No. 6. (November 2001), pp. 705-709.

Targeted disruption of the klotho gene induces multiple phenotypes characteristic of human aging, including arteriosclerosis, pulmonary emphysema and osteoporosis. Moreover, we previously observed that insufficient klotho expression in mice leads to endothelial dysfunction. In the present study, we used Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which exhibit hypertension, obesity, severe hyperglycemia and hypertriglyceridemia, and are thus considered an animal model of atherogenic disease, to test the effects of oral administration of troglitazone (200 mg/kg) on renal klotho mRNA expression and endothelial function. Systolic blood pressure, body weight, plasma glucose and triglyceride levels were all significantly higher in 30-week-old OLETF rats than in controls (LETO; Long-Evans Tokushima Otsuka) (p<0.05, n=7). In addition, endothelium-dependent relaxation of the aorta in response to 10(-5) M acetylcholine was significantly attenuated in OLETF rats (p<0.05, n=7), as was renal expression of klotho mRNA. Administration of troglitazone for 10 weeks significantly reduced systolic blood pressure, plasma glucose and triglyceride levels in OLETF rats, while augmenting endothelium-dependent aortic relaxation and renal klotho mRNA expression. These findings suggest that troglitazone protects the vascular endothelium against damage caused by the presence of multiple atherogenic factors.

Asymmetric dimethylarginine may be a missing link between cardiovascular disease and chronic kidney disease (Review Article)

Seiji Ueda — 2007-11-06T08:43:52-00:00

Nephrology, Vol. 12, No. 6. (December 2007), pp. 582-590.

Olmesartan blocks advanced glycation end products (AGEs)-induced angiogenesis in vitro by suppressing receptor for AGEs (RAGE) expression.

S Yamagishi — 2008-01-16T02:06:09-00:00

Microvasc Res, Vol. 75, No. 1. (January 2008), pp. 130-134.

We have previously shown that advanced glycation end products (AGEs)-their receptor (RAGE) interaction elicits angiogenesis through autocrine production of vascular endothelial growth factor (VEGF), thus suggesting the active involvement of the AGEs-RAGE system in proliferative diabetic retinopathy (PDR). Since the crosstalk between the AGEs-RAGE and the renin-angiotensin system has also been proposed in the pathogenesis of PDR, we investigated here whether olmesartan, an angiotensin II type 1 receptor blocker, inhibited the AGEs-elicited angiogenesis in vitro by suppressing the NF-kappaB-mediated RAGE expression. Olmesartan significantly inhibited the AGEs-induced NF-kappaB promoter activity and RAGE gene expression in cultured microvascular endothelial cells (ECs). Further, olmesartan was found to block the AGEs-induced up-regulation of VEGF mRNA levels and consequent increase in DNA synthesis in ECs. These results demonstrated for the first time that olmesartan inhibited the AGEs signaling to angiogenesis by suppressing RAGE expression in ECs. Our present study suggests that blockade of the renin-angiotensin system by olmesartan may play a protective role against PDR by attenuating the deleterious effects of AGEs via down-regulation of RAGE.

Upregulation of the ligand-RAGE pathway via the angiotensin II type I receptor is essential in the pathogenesis of diabetic atherosclerosis.

Y Ihara — 2008-01-16T02:06:38-00:00

J Mol Cell Cardiol, Vol. 43, No. 4. (October 2007), pp. 455-464.

The receptor for advanced glycation end products (RAGE) and the angiotensin II type I receptor (AT1R) have been separately linked to the pathogenesis of diabetic atherosclerosis. However, no prior study has addressed a linkage between RAGE and AT1R in diabetic atherogenesis. Therefore, we tested the hypothesis that upregulation of the ligand-RAGE axis via AT1R is an essential process underlying the disease. Diabetes was induced in apolipoprotein E-deficient (ApoE(-/-)) mice by streptozotocin, and diabetic mice were treated with AT1 receptor blocker (ARB) for 6 weeks. Diabetic ApoE(-/-) mice that were AT1R-deficient (ApoE(-/-)AT1aR(-/-)) were also investigated. In diabetic ApoE(-/-) mice, AT1R was found to increase within 1 week of diabetes induction, before ligand-RAGE pathway activation and other inflammatory changes were observed. Both ARB treatment and AT1aR deficiency suppressed diabetic atherosclerosis, ligand-RAGE expression and inflammatory changes. In contrast, upregulation of the ligand-RAGE pathway was noted in atherosclerotic plaques from non-diabetic ApoE(-/-) mice infused with angiotensin II. In cultured vascular smooth muscle cells, angiotensin II increased RAGE protein levels via AT1R stimulation. Upregulation of the ligand-RAGE pathway via AT1R is an essential mechanism in diabetic atherosclerosis, implying that ARB might decrease diabetic atherogenesis by inhibiting ligand-RAGE signals.

Oral administration of AST-120 (Kremezin) is a promising therapeutic strategy for advanced glycation end product (AGE)-related disorders.

S Yamagishi — 2008-01-14T12:00:04-00:00

Med Hypotheses, Vol. 69, No. 3. (2007), pp. 666-668.

The pathological role of the non-enzymatic modification of proteins by reducing sugars has become increasingly evident in various disorders. It is now well established that early glycation products undergo progressive modification over time in vivo to the formation of irreversible cross-links, after which these molecules are termed "AGEs (advanced glycation end products)". AGEs have been implicated in the development of many of the pathological sequelae of diabetes and aging, such as diabetic microangiopathy, ischemic heart disease and neurodegenerative diseases. Recently, digested food-derived AGEs are also found to play an important role in the pathogenesis of AGE-related disorders. Diet is a major environmental source of pro-inflammatory AGEs. Indeed, restriction of dietary glycotoxins decreases excessive AGE levels and subsequently reduces the inflammatory responses in patients with diabetes. These observations suggest that inhibition of absorption of dietary AGEs may be a novel target for therapeutic intervention in the above-mentioned AGE-related disorders. AST-120 (Kremezin) is an oral adsorbent that attenuates the progression of chronic renal failure (CRF) by removing uremic toxins. We have recently found that AST-120 binds to carboxymethyllysine (CML), one of the well-characterized, digested food-derived AGEs in vitro and that administration of AST-120 decreases serum levels of AGEs in non-diabetic CRF patients. These findings suggest that digested food-derived AGEs such as CML may be a novel molecular target for oral adsorbent AST-120 and that AST-120 could exert beneficial effects on CRF patients by adsorbing diet-derived AGEs and subsequently decreasing serum AGE levels. If our speculation is correct, AST-120 may have therapeutic potentials for the treatment of patients with various AGE-related disorders as well. In this paper, we would like to propose the possible ways of testing our hypotheses. Does the long-term treatment of AST-120 decrease serum and tissue levels of AGEs in diabetic patients? Does this treatment also reduce the risk for the development and progression of diabetic vascular complications such as diabetic retinopathy or ischemic heart disease? If the answers are yes, do the serum and/or tissue levels of AGEs after AST-120 treatment predict its beneficial effects on diabetic vascular complications? How about the effects of AST-120 on Alzheimer's disease, another AGE-related neurodegenerative disorder? Does the treatment of AST-120 reduce the risk for Alzheimer's disease and/or improve the cognitive impairment of patients with this disorder? These prospective studies will provide further valuable information whether the inhibition of absorption of dietary AGEs by AST-120 could be clinically relevant.

cDNA cloning and characterization of a secreted luciferase from the luminous Japanese ostracod, Cypridina noctiluca.

Y Nakajima — 2007-10-31T16:26:15-00:00

Biosci Biotechnol Biochem, Vol. 68, No. 3. (March 2004), pp. 565-570.

A secreted luciferase from the marine ostracod, Vargula hilgendorfii, is a useful tool for gene expression assays in living mammalian cells. We have cloned the cDNA of a new secreted luciferase from the ostracod Cypridina noctiluca, which inhabits the coast of Japan. C. noctiluca luciferase consists of 553 amino acid residues with a molecular mass of 61,415 Da, as deduced from the nucleotide sequence. The homologies of nucleotide and amino acid sequences with V. hilgendorfii luciferase are 79.2% and 83.1%, respectively. C. noctiluca luciferase can expressed in and secreted from cultured mammalian cells. The characteristic properties of expressed C. noctiluca luciferase are similar to those of V. hilgendorfii luciferase. However, the activity of C. noctiluca luciferase in culture medium is much higher than that of V. hilgendorfii luciferase, suggesting that C. noctiluca luciferase is a highly potent reporter enzyme for real-time and continuous monitoring of gene expression in living cells.

Perfusion-culture-based secreted bioluminescence reporter assay in living cells.

K Yamagishi — 2007-10-31T16:25:57-00:00

Anal Biochem, Vol. 354, No. 1. (1 July 2006), pp. 15-21.

Bioluminescence reporter proteins have been widely used in the development of tools for monitoring biological events in living cells. In this study, we describe the development of a reporter system with secreted Cypridina noctiluca luciferase (CLuc) for a pharmacological assay that is based on targeted promoter activity. A model cell line was established with Rat-1 fibroblasts expressing CLuc driven by the promoter of a circadian clock gene, Bmal1. To accurately assay for temporally secreted CLuc activity, a perfusion culture in which the promoter activity was sequentially monitored by the reporter activity in the perfusate was adopted. By pulsing with dexamethasone (DEX), a glucocorticoid (GC) analog, the profile of the reporter activity successfully showed diurnal fluctuation, which is a canonical expression pattern of the Bmal1 gene. Trial studies illustrated that the DEX-pulsed circadian oscillation was reasonably attenuated by RU486, a GC receptor antagonist. Moreover, SP600125, a c-Jun N-terminal kinase inhibitor, caused phase shifting of the rhythmicity. We conclude that the CLuc reporter assay in combination with perfusion culture is a suitable pharmacological tool for drug discovery.

Telmisartan inhibits AGE-induced C-reactive protein production through downregulation of the receptor for AGE via peroxisome proliferator-activated receptor-gamma activation.

T Yoshida — 2007-10-23T09:08:36-00:00

Diabetologia, Vol. 49, No. 12. (December 2006), pp. 3094-3099.

AIMS/HYPOTHESIS: C-reactive protein (CRP), an acute-phase reactant produced mainly by the liver, is elevated in diabetes, thus contributing to the development and progression of atherosclerosis. However, the molecular mechanism underlying the elevation of CRP in diabetes is not fully understood. Since a crosstalk between AGE and angiotensin II (Ang II) has been proposed in the pathogenesis of accelerated atherosclerosis in diabetes, we examined here whether and how telmisartan, a unique Ang II type 1 receptor blocker (ARB) with peroxisome proliferator-activated receptor-gamma (PPAR-gamma)-modulating activity, could inhibit AGE-induced CRP expression in a human hepatoma cell line, Hep3B cells. METHODS: Protein levels of the receptor for AGE (RAGE) were analysed by western blots. Gene expression was analysed by quantitative real-time RT-PCR. CRP released into the medium was measured with ELISA. Intracellular formation of reactive oxygen species (ROS) was measured using the fluorescent probe CM-H(2)DCFDA. RESULTS: Telmisartan, but not candesartan, another ARB, downregulated RAGE mRNA levels in a dose-dependent manner. Telmisartan decreased basal as well as AGE-induced RAGE protein expression in Hep3B cells. Furthermore, telmisartan dose-dependently inhibited AGE-induced ROS generation and subsequent CRP gene and protein induction in Hep3B cells. GW9662, an inhibitor of PPAR-gamma, blocked the inhibitory effects of telmisartan on RAGE expression and its downstream signalling in Hep3B cells. CONCLUSIONS/INTERPRETATION: Our present study indicates a unique beneficial aspect of telmisartan: it may work as an anti-inflammatory agent against AGE by suppressing RAGE expression via PPAR-gamma activation in the liver and may play a protective role in vascular injury in diabetes.

Nifedipine inhibits gene expression of receptor for advanced glycation end products (RAGE) in endothelial cells by suppressing reactive oxygen species generation.

S Yamagishi — 2007-10-23T09:09:32-00:00

Drugs Exp Clin Res, Vol. 30, No. 4. (2004), pp. 169-175.

Advanced glycation end products (AGEs), the senescent macroprotein derivatives that form in increased amounts in diabetes, have been implicated in the pathogenesis of diabetic vascular complications. Indeed, AGEs elicit oxidative stress generation in vascular wall cells through an interaction with their receptor (RAGE), thus playing an important role in vascular inflammation and altered gene expression of growth factors and cytokines. We have previously shown that nifedipine, one of the most popular dihydropyridine-based calcium antagonists, blocked tumor necrosis factor-alpha-induced monocyte chemoattractant protein-1 expression in endothelial cells (ECs) through its antioxidative properties. However, the effects of nifedipine on AGE-exposed ECs remain to be elucidated. In this study we investigated whether nifedipine could inhibit the AGE-induced reactive oxygen species (ROS) generation and subsequent RAGE gene expression in human umbilical vein endothelial cells (HUVEC). Nifedipine completely inhibited AGE-induced ROS generation in HUVEC. Furthermore, nifedipine was found to prevent up-regulation of RAGE mRNA levels in AGE-exposed HUVEC. These results demonstrate that nifedipine can inhibit RAGE overexpression in AGE-exposed ECs by suppressing ROS generation. Our present study suggests that nifedipine may have therapeutic potential in the treatment of patients with AGE-related disorders such as diabetic vascular complications.

Telmisartan inhibits expression of a receptor for advanced glycation end products (RAGE) in angiotensin-II-exposed endothelial cells and decreases serum levels of soluble RAGE in patients with essential hypertension.

K Nakamura — 2007-10-23T09:08:47-00:00

Microvasc Res, Vol. 70, No. 3. (November 2005), pp. 137-141.

There is a growing body of evidence that the advanced glycation end product (AGE)-their receptor (RAGE) system plays a central role in the pathogenesis of diabetic vascular complication. The renin-angiotensin system (RAS) contributes to the development and progression of diabetic angiopathy as well. However, the cross-talk between the AGE-RAGE system and the RAS is not fully understood. In this study, we examined the role of angiotensin II (Ang II) type 1 receptor system for RAGE expression in cultured endothelial cells (ECs) and in patients with essential hypertension. Ang II up-regulated RAGE mRNA levels of microvascular ECs and subsequently increased the soluble form of RAGE (sRAGE) expression in the medium of ECs, both of which were completely blocked by telmisartan, a commercially available Ang II type 1 receptor antagonist. Furthermore, telmisartan was found to decrease serum levels of sRAGE in patients with essential hypertension. These results demonstrate that sRAGE is released from the cell surface of Ang-II-exposed ECs. Our present study indicates that a cross-talk exists between the AGE-RAGE system and the RAS and suggests that serum levels of sRAGE may reflect endothelial RAGE expression.

Telmisartan, an angiotensin II type 1 receptor blocker, inhibits advanced glycation end-product (AGE)-induced monocyte chemoattractant protein-1 expression in mesangial cells through downregulation of receptor for AGEs via peroxisome proliferator-activated receptor-gamma activation.

T Matsui — 2007-10-23T08:05:47-00:00

J Int Med Res, Vol. 35, No. 4. (g 2007), pp. 482-489.

Interaction between advanced glycation end-products (AGEs) and their receptor (RAGE) plays a central role in diabetic nephropathy pathogenesis. Pathophysiological crosstalk between the AGEs-RAGE system and angiotensin II (Ang II) is also involved in this disease. This study investigated the role of proliferator-activated receptor-gamma (PPAR-gamma)-modulating activity on inhibition of monocyte chemoattractant protein (MCP-1) expression. Telmisartan, an Ang II type 1 receptor blocker, downregulated RAGE mRNA and inhibited superoxide generation and MCP-1 gene expression in mesangial cells; these processes were blocked by GW9662, a PPAR-gamma inhibitor. Candesartan, an Ang II type 1 receptor blocker, did not suppress AGEs-induced superoxide generation. Telmisartan and the antioxidant, N-acetylcysteine, completely inhibited AGEs-induced MCP-1 overproduction by mesangial cells. These results suggest that telmisartan inhibits AGEs-signalling to MCP-1 expression in mesangial cells by downregulating RAGE gene expression and subsequent oxidative stress generation via PPAR-gamma activation. This study has demonstrated a unique benefit of telmisartan in that it may function as an anti-inflammatory agent against AGEs via PPAR-gamma activation and may play a protective role in diabetic nephropathy.

Advanced glycation end product-induced apoptosis and overexpression of vascular endothelial growth factor and monocyte chemoattractant protein-1 in human-cultured mesangial cells.

S Yamagishi — 2007-10-23T02:19:52-00:00

J Biol Chem, Vol. 277, No. 23. (7 June 2002), pp. 20309-20315.

Advanced glycation end products (AGE) have been implicated in the pathogenesis of glomerulosclerosis in diabetes. However, their involvement in the development of the early phase of diabetic nephropathy has not been fully elucidated. We investigated the effects of AGE on growth and on vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1) expression in human cultured mesangial cells. We prepared three immunochemically distinct AGE by incubating bovine serum albumin (BSA) with glucose, glyceraldehyde, or glycolaldehyde. When human mesangial cells were cultured with various types of AGE-BSA, viable cell numbers as well as DNA syntheses were significantly decreased. All of the AGE-BSA were found to significantly increase p53 and Bax protein accumulations and subsequently induce apoptotic cell death in mesangial cells. An antioxidant, N-acetylcysteine, significantly prevented the AGE-induced apoptotic cell death in mesangial cells. Human mesangial cells stimulated prostacyclin production by co-cultured glomerular endothelial cells. Furthermore, various types of AGE-BSA were found to up-regulate the levels of mRNAs for VEGF and stimulate the secretion of VEGF and MCP-1 proteins in mesangial cells. The results suggest that AGE disturbed glomerular homeostasis by inducing apoptotic cell death in mesangial cells and elicited hyperfiltration and microalbuminuria by stimulating the secretion of VEGF and MCP-1 proteins, thereby being involved in the pathogenesis of the early phase of diabetic nephropathy.

The relationships of proteinuria, serum creatinine, glomerular filtration rate with cardiovascular disease mortality in Japanese general population.

F Irie — 2007-10-02T03:05:30-00:00

Kidney Int, Vol. 69, No. 7. (April 2006), pp. 1264-1271.

Proteinuria, high serum creatinine, and reduced glomerular filtration rate (GFR) have been associated with increased mortality from cardiovascular disease (CVD) and all causes. However, the combined effect of proteinuria with serum creatinine and GFR on CVD or all-cause mortality has not been well investigated. We conducted a 10-year prospective cohort study of 30,764 men and 60,668 women aged 40-79 years who participated in annual health checkups in 1993. The Cox proportional hazards model was used to estimate the relative risk (RR) after adjusting for age, smoking, and other cardiovascular risk factors. The multivariable RR (95% confidence interval (CI)) of CVD death for positive vs negative proteinuria was 1.38 (1.05-1.79) among men and 2.15 (1.64-2.81) among women. The respective RR for the highest vs lowest creatinine groups (> or = 1.3 vs < or = 0.8 mg/dl for men and > or = 1.1 vs < or = 0.6 mg/dl for women) was 1.56 (1.19-2.04) among men and 2.15 (1.58-2.93) among women. The respective RR for GFR < 60 vs > r = 100 ml/min/1.73 m2 was 1.65 (1.25-2.18) among men and 1.81 (1.39-2.36) among women. For individuals with proteinuria combined by hypercreatininemia or reduced GFR, the risk of CVD death was two-fold higher in men and 4-6-fold higher in women compared to those without proteinuria and with normal creatinine level or GFR. Similar associations were observed for stroke, coronary heart disease, and all-cause mortality. Proteinuria, and hypercreatininemia or reduced GFR and their combination were significant predictors of CVD and all-cause mortality.

Circulating advanced glycation end products (AGEs) and soluble form of receptor for AGEs (sRAGE) are independent determinants of serum monocyte chemoattractant protein-1 (MCP-1) levels in patients with type 2 diabetes.

Kazuo Nakamura — 2007-09-14T02:03:10-00:00

Diabetes Metab Res Rev (10 August 2007)

BACKGROUND: Atherosclerosis is an inflammatory disease. Monocyte chemoattractant protein-1 (MCP-1) is an essential chemokine responsible for the recruitment of monocytes to inflammatory lesions in the vasculature, an initial step of atherosclerosis. Since serum levels of MCP-1 are higher in patients with type 2 diabetes, inhibition of MCP-1 may be a novel therapeutic target for prevention of accelerated atherosclerosis in diabetes. However, little is known about the regulation and determinants of serum MCP-1 levels in patients with diabetes. In this study, we examined the determinants of serum MCP-1 levels in type 2 diabetic patients. METHODS: Eighty-six consecutive outpatients with type 2 diabetes (36 male and 50 female; mean age 68.4 +/- 9.6) underwent a complete history and physical examination, determination of blood chemistries, MCP-1, tumour necrosis factor-alpha, adiponectin, advanced glycation end products (AGEs), and soluble form of receptor for AGEs (sRAGE). We examined the association between MCP-1 levels and those in anthropometric, metabolic and inflammatory variables in these subjects. RESULTS: Univariate regression analysis showed that serum levels of MCP-1 were positively associated with AGEs (r = 0.386, p < 0.001) and sRAGE (r = 0.315, p < 0.001). After adjusting for age and sex, AGEs (p < 0.001) and sRAGE (p < 0.05) still remained significant. CONCLUSION: The results demonstrate for the first time that circulating levels of AGEs and sRAGE are independent determinants of serum MCP-1 levels in patients with type 2 diabetes. Our present observations suggest the AGEs-RAGE system may be mainly involved in the elevation of MCP-1 in type 2 diabetic patients. Copyright (c) 2007 John Wiley & Sons, Ltd.

Elevation of soluble form of receptor for advanced glycation end products (sRAGE) in diabetic subjects with coronary artery disease.

K Nakamura — 2007-09-14T02:03:31-00:00

Diabetes Metab Res Rev, Vol. 23, No. 5. (July 2007), pp. 368-371.

BACKGROUND: Advanced glycation end products (AGEs)-receptor (RAGE) axis is implicated in diabetic vascular complication. Since a soluble form of RAGE (sRAGE) could be generated from the cleavage of cell surface RAGE in endothelial cells (ECs), serum sRAGE levels may be elevated in diabetes consequent to EC damage. In this study, we examined whether sRAGE levels were elevated in type 2 diabetic patients compared with non-diabetic healthy subjects. METHODS: Serum sRAGE levels were examined in 75 Japanese type 2 diabetic patients (29 men and 46 women; mean age 66 +/- 11 years) and 75 age- and sex-matched non-diabetic healthy control subjects. We explored the association between sRAGE levels and coronary artery disease (CAD) in diabetic patients. RESULTS: Serum sRAGE levels were significantly higher in diabetic patients than in non-diabetic subjects (965.3 +/- 544.2 vs 415 +/- 150.4 pg/mL, p < 0.001). In the univariate analysis, diastolic blood pressure (inversely), LDL cholesterol, triglycerides, HDL cholesterol, hemoglobin A(1c), and creatinine were significantly associated with sRAGE. After performing multivariate analyses, the presence of diabetes (p < 0.0001) was a sole independent determinant of sRAGE. Furthermore, there was a significant difference in sRAGE levels between diabetic patients with CAD and those without CAD (1680.6 +/- 891.1 vs 855.2 +/- 372.1 pg/mL, p < 0.001). Multiple stepwise regression analysis revealed that sRAGE and creatinine levels were independent determinants of CAD. CONCLUSIONS: The present study demonstrated that serum sRAGE levels were significantly higher in type 2 diabetic patients than in non-diabetic subjects and positively associated with the presence of CAD.

Serum levels of sRAGE, the soluble form of receptor for advanced glycation end products, are associated with inflammatory markers in patients with type 2 diabetes.

K Nakamura — 2007-09-14T02:04:19-00:00

Mol Med, Vol. 13, No. 3-4. (r 2007), pp. 185-189.

Advanced glycation end products (AGEs) and their receptor (RAGE) play an important role in accelerated atherosclerosis in diabetes. We have recently found that the soluble form of RAGE (sRAGE) levels are significantly higher in type 2 diabetic patients than in nondiabetic subjects and positively associated with the presence of coronary artery disease in diabetes. In this study, we examined whether serum levels of sRAGE correlated with inflammatory biomarkers in patients with type 2 diabetes. Eighty-six Japanese type 2 diabetic patients (36 men and 50 women, mean age 68.4+/-9.6 years) underwent a complete history and physical examination, determination of blood chemistries, sRAGE, monocyte chemotactic protein-1 (MCP-1), adiponectin, tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6). Univariate regression analysis showed that serum levels of sRAGE positively correlated with alanine aminotransferase (ALT) (r=0.437, P=0.0001), MCP-1 (r=0.359, P=0.001), TNF-alpha (r=0.291, P=0.006), and hyperlipidemia medication (r=0.218, P=0.044). After multiple regression analyses, ALT (P<0.0001), MCP-1 (P=0.007), and TNF-alpha (P=0.023) remained significant. The present study demonstrates for the first time that serum levels of sRAGE are positively associated with MCP-1 and TNF-alpha levels in type 2 diabetic patients. These observations suggest the possibility that sRAGE level may become a novel biomarker of vascular inflammation in type 2 diabetic patients.

Advanced glycation end products inhibit de novo protein synthesis and induce TGF-beta overexpression in proximal tubular cells.

S Yamagishi — 2007-07-25T01:13:50-00:00

Kidney Int, Vol. 63, No. 2. (February 2003), pp. 464-473.

BACKGROUND: We have shown previously that OPB-9195, a novel inhibitor of advanced glycation end products (AGE), significantly prevented renal tubular injury and tubulointerstitial fibrosis in spontaneous diabetic rats. However, the molecular mechanisms underlying this have not been fully elucidated. METHODS: Three immunochemically distinct AGE were prepared by incubating bovine serum albumin (BSA) with glucose, glyceraldehyde, or methylglyoxal. Then, the effects of AGE on human proximal tubular epithelial cells were examined. The intracellular formation of reactive oxygen species (ROS) was detected using the fluorescent probe CM-H2DCFDA. DNA synthesis was evaluated by thymidine uptake, and de novo protein synthesis was determined by [3H]leucine incorporation. Prostaglandin E2 (PGE2) and transforming growth factor-beta (TGF-beta) released into media were quantitatively analyzed in an enzyme-linked immunosorbent assay. TGF-beta gene expression was analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: When these AGE-BSA were administered to tubular cells, each of them increased generation of intracellular ROS. All of the AGE-BSA, but not non-glycated BSA, were found to induce statistically significant decreases in de novo protein synthesis and PGE2 secretion by tubular cells. Furthermore, AGE-BSA up-regulated the levels of mRNAs for TGF-beta in tubular cells. The structural epitope designated glucose-derived AGE was found to have the greatest cytopathic effects on tubular cells. These AGE-induced inhibition of protein synthesis and PGE2 secretion as well as the up-regulation of TGF-beta mRNA were found to be completely prevented by N-acetylcysteine. Furthermore, H2O2 was shown to inhibit protein synthesis and PGE2 secretion by proximal tubular cells in a dose-dependent manner. CONCLUSION: The results suggest that AGE inhibits de novo protein synthesis and stimulates TGF-beta mRNA expression in proximal tubular epithelial cells through overgeneration of intracellular ROS. Thus, AGE are involved in the pathogenesis of tubular injury in diabetic nephropathy.

AGEs activate mesangial TGF-beta-Smad signaling via an angiotensin II type I receptor interaction.

K Fukami — 2007-07-25T01:11:50-00:00

Kidney Int, Vol. 66, No. 6. (December 2004), pp. 2137-2147.

BACKGROUND: The renin-angiotensin system (RAS) and the accumulation of advanced glycation end products (AGEs) have been implicated in the pathogenesis of diabetic nephropathy. Whether there is a functional interaction between the RAS and AGEs in diabetic nephropathy is not known. In this study, we investigated whether AGEs could activate autocrine angiotensin II (Ang II) signaling and subsequently induce transforming growth factor-beta (TGF-beta)-Smad signaling in cultured rat mesangial cells. METHODS: The intracellular formation of reactive oxygen species (ROS) was detected using the fluorescent probe CM-H2DCFDA. Ang II was measured by radioimmunoassay. TGF-beta released into media was quantitatively analyzed in an enzyme-linked immunosorbent assay (ELISA). Smad2, p27(Kip1) (p27), fibronectin, and receptor for AGEs (RAGE) protein expression were determined by Western blot analysis. TGF-beta-inducible promoter activity was analyzed by a luciferase assay. DNA synthesis was evaluated by 5-bomo-2'-deoxyuridine (BrdU) incorporation and de novo protein synthesis was determined by [3H]leucine incorporation. RESULTS: AGEs increased intracellular ROS generation in mesangial cells, and this effect was significantly inhibited by an antiserum against RAGE. AGEs also were found to stimulate Ang II production in a time- and dose-dependent manner, which was completely prevented by an antioxidant, N-acetylcysteine (NAC). AGE-induced TGF-beta overproduction was completely blocked by candesartan, an Ang II type 1 receptor (AT1R) antagonist. Both candesartan and neutralizing antibody against TGF-beta completely prevented AGEs-induced Smad2 phosphorylation and TGF-beta-inducible promoter activity. Furthermore, AGEs were found to inhibit DNA synthesis and to stimulate de novo protein synthesis and fibronectin production in association with up-regulation of p27. All of these phenomena were completely prevented by candesartan or a polyclonal antibody against TGF-beta. CONCLUSION: The present study suggests that AGE-RAGE-mediated ROS generation activates TGF-beta-Smad signaling and subsequently induces mesangial cell hypertrophy and fibronectin synthesis by autocrine production of Ang II. This pathway may provide an important link between metabolic and haemodynamic factors in promoting the development and progression of diabetic nephropathy.