Advanced glycosylation end products increase diacylglycerol levels in cultured human umbilical vein endothelial cells

To study whether the diacylglycerol (Dia) signaling pathway is stimulated by advanced glycosylation end products (AGEP) and to test the effect of vitamin E and aminoguanidine (AG) on the elevation of Dia induced by AGEP in cultured human umbilical vein endothelial cells (HUVECs) Methods The effects of AGEP on Dia levels in cultured HUVEC were studied with radio enzymatic assay Quantitative measurements of 32 P phosphatidic acid were achieved by thin layer chromatography and autoradiography Results The Dia levels in HUVECs were increased by AGEP modified bovine serum albumin (AGEP BSA) in a dose dependent, biphasic manner The early phase was rapid and transient, peaking at 15?s; the late phase reached the maximal level at 10?min and then decayed slowly Dia levels in HUVEC exposed to different concentrations (50, 100 and 200?mg/L) of AGEP BSA (341±14, 678±16, and 873±18?pmol/L, respectively vs control 225±10?pmol/L) and AGEP BSA samples with various glycosylation times (4, 8 and 12 weeks) were significantly increased (270±12, 394±16, and 556±19?pmol/L) as compared with the controls 50 and 100?mmol/L of vitamin E can reduce AGEP BSA induced Dia levels from 873±18?pmol/L to 764±29 and 441±21?pmol/L in HUVEC, respectively In AG treated (100?mmol/L) groups, the same concentration (100 and 200?mg/L) of AGEP BSA induced elevation of Dia was decreased to 312±8 and 351±13?pmol/L, respectively Glycosylated low density lipoprotein (LDL) did not affect Dia levels Conclusion AGEP causes a robust stimulation of the Dia/protein kinase C pathway in HUVEC Vitamin E can attenuate the AGEP BSA induced elevation of Dia levels AG can suppress the ability of AGEP BSA to increase Dia levels in HUVEC

Expression of platelet-endothelial cell adhesion molecule-1 in human umbilical vein endothelial cells by exposure to advanced glycosylation end products and inflammatory mediators

Objective To determine whether advanced glycosylation end products modified bovine serum albumin (AGEs-BSA) affects endothelial cell lateral junction protein, platelet-endothelial cell adhesion molecule-1 (PECAM-1) in the presence or absence of inflammatory mediators.Methods Cultured human umbilical vein endothelial cells (HUVECs) were exposed to AGEs-BSA for 6, 12, 24, and 36 hours, and exposed to AGEs-BSA glycosylated with different concentrations of glucose, tumor necrosis factord-α (TNF-α), interferon (IFN-γ), TNF-α + IFN-y and AGEs-BSA + TNF-α for 24 hours, respectively. Expression of PECAM-1 mRNA was measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) with β-actin as an internal standard, and sequencing of RT-PCR products was performed to confirm the specificity of amplification for PECAM-1 gene. The endothelial cell surface expression of PECAM-1 was determined by flow cytometry (FCM).Results There were no significant changes in the expression of PECAM-1 mRNA and protein when the cells were exposed to AGEs-BSA with different concentrations or periods ( P>0. 05). However, PECAM-1 expression was reduced in the cells treated with TNF-α, IFN-y, TNF-α + IFN-γ and AGEs-BSA + TNF-α. The level of PECAM-1 treated with AGEs-BSA + TNF-α was lower than that of TNF-α treated alone (P<0. 01).Conclusions AGEs-BSA had no effect on the expression of PECAM-1 mRNA and protein in cultured HUVEC. With the presence of inflammatory mediator TNF-α, AGEs-BSA decreased the level of PECAM-1, which might reduce the adhesion interaction between adjacent endothelial cells, enhance the permeability of endothelial cells, and might be implicated in the endothelial dysfunction and pathogenesis of atherosclerosis in patients with diabetes mellitus. The significance of this phenomenon in intracellular signal transduction remains to be determined.

Effect of advanced glycosylation end products on activity of protein kinase C in human peripheral blood mononuclear cells

To investigate the effect of advanced glycosylation end products (AGEs) on the activity of protein kinase C (PKC) in human peripheral blood mononuclear cells (PBMC) and to observe whether aminoguanidine (AG) can influence the effect of AGEs Methods After PBMC were isolated from human peripheral blood and incubated with different concentrations of AGEs BSA for various periods, total PKC activity in PBMC was determined by measuring the incorporation of 32 P from [γ 32 P] ATP into a special substrate using Promega PKC assay kit Results AGEs BSA increased the total PKC activity in PBMC from 83 43±6 57?pmol/min/mg protein to 116 8±13 82?pmol/min/mg protein with a peak at 15?min AGEs BSA also increased the total PKC activity in a concentration dependent manner from 83 1±6 4?pmol/min/mg protein (control) to 119 1±13 3?pmol/min/mg protein (control vs AGEs BSA 400?mg/L, P <0 01) Furthermore, AGEs BSA induced an elevation of PKC activity in a glycosylating time related manner, from 80 9±8 2 (control) to 118 3±11 5?pmol/min/mg protein (glycosylation for 12 wk, P <0 01) The total PKC activity stimulated by AGEs BSA pretreated with AG (100, 200?mg/L) was markedly lower than that of AGEs BSA group not pretreated with AG ( P <0 05, P <0 01) Conclusions AGEs BSA increased the total PKC activity in PBMC in a concentration and incubation time dependent manner The ability of AGEs BSA to stimulate PKC activity was markedly decreased by pretreatment of AGEs BSA with AG

Effects of advanced glycosylation end products and rosiglitazone on the expression and secretion of galectin-3 in human renal mesangial cells

Background Galectin-3 is the most recently identified advanced glycosylation end products （AGEs） binding protein. This study aimed to investigate the effects of AGEs and rosiglitazone on the expression and secretion of galectin-3 in cultured human renal mesangial cells （HRMCs）. Methods HRMCs were incubated with different concentrations of AGE-bovine serum albumin （BSA） （0, 50, 100, 200, and 400 mg/L） for different time （0, 24, 36, 48, and 72 hours）, and exposed to AGE-BSA in the presence of different concentrations of rosiglitazone （1, 10, and 100 μmol/L）. The mRNA and protein expression of galectin-3 in HRMCs were analyzed by reverse transcription polymerase chain reaction （RT-PCR） and Western blotting. The culture medium of HRMCs was collected and concentrated, and the content of galectin-3 in the medium was detected by Western blotting. Results Both RT-PCR and Western blotting revealed that AGE-BSA up-regulated the expression of galectin-3 in HRMCs in a concentration- （P 〈0.05） and time-dependent （P 〈0.05） manner compared with the control. Compared with the control, AGE-BSA elevated the content of galectin-3 in the culture medium of HRMCs time- and concentrationdependently （P 〈0.05, respectively）. Both protein and mRNA expression of galectin-3, and its content in the medium of HRMCs exposed to different concentrations of rosiglitazone in the presence of AGE-BSA were increased compared with those of cells exposed to AGE-BSA alone （P 〈0.05）. Rosiglitazone increased the expression and secretion of galectin-3 in a dose-dependent manner （P 〈0.05）. Conclusions AGEs up-regulates the expression and secretion of galectin-3 in HRMCs. Rosiglitazone further enhances the upregulation of galectin-3 in HRMCs induced by AGEs, which suggests that rosiglitazone may play a role of reno-protection via up-regulation of galectin-3.

Advanced glycosylation end products, protein kinase C and renal alterations in diabetic rats

To study the relationship between advanced glycosylation end products (AGE) and protein kinase C (PKC), and their effects on renal alteration in diabetic rats Methods Insulin or aminoguanidine was administered to diabetic rats Blood glucose, hemoglobin A 1C (HbA 1C ), glomerular tissue extracts AGE (GTE AGE), PKC, glomerular basement membrane thickness (GBMT) and urine protein/creatinine (Pr/Cr) ratio in diabetic rats were measured and analysed Results Levels of blood glucose, HbA 1C and AGE, PKC activity, the Pr/Cr ratio and GBMT were all significantly increased ( P values all less than 0 01) in diabetic rats Insulin could decrease the formation of HbA 1C and AGE, and improve PKC activity Aminoguanidine had no influence on PKC activity ( P >0 05) although it decreased the formation of AGE Both drugs could delay the increase of urine Pr/Cr ratio and GBMT ( P <0 05 or P <0 01) Conclusions Chronic hyperglycemia may lead to an increase of PKC activity HbA 1C and AGE may not directly contribute to alterations of PKC activity, but the increase of PKC activity could promote the action of AGE on GBM thickening It is important to inhibit the formation of AGE and reduce the PKC activity so as to prevent or delay the development of diabetic nephropathy

Inhibition of glutathione on vascular smooth muscle cell proliferation mediate by advanced glycation end products

Background To confirm the proliferation of vascular smooth muscle cell （VSMC） lead by advanced glycation end products （AGEs） and investigate weather the mechanism is work through MAPK pathway. To investigate weather the prolification of VSMC lead by AGEs can be inhibited by reduced glutathione（GSH） and what the mechanisam is. Methods VSMC of rats were isolated and cultivated, separated in 8 groups, each group contained 12 samples. Density of cell was 1×105 /mL in each sample, cultivated with AGEs at different concentrations and intervened with GSH at different concentrations. In order to determine the mechanism and interventional factors of VSMCs, sandwich ELISA method was used to test the concentration of P-P38 and MTT colorimetry was adopted to evaluate the amount of VSMC. Results 1.Effect of AGEs to the OD value of MTT in VSMC： with stimulation of AGEs, OD valued of P-P38 in VSMC increased simultaneously （P0.01）, their value were 0.43±0.15, 0.49±0.16, 0.48±0.19 [L/（g·cm）]. With the increase of the dose of AGEs, there were no difference between groups B, C of MTT OD value（P0.05）. 2.Effect of GSH to the OD value of MTT in VSMC stimulated by AGEs： OD value of MTT decreased with the increase of GSH concentration, their value were 0.347±0.102, 0.333±0.108, 0.285±0.080 [L/（g·cm）] respectively, decreased by 45%, 56%, 60%（P0.01）compared with value of AGEs control group. With the increasing of the dose of GSH, the MTT OD value had no difference between groups F, G and H （P0.05）. 3.Effect of AGEs to the OD value of P-P38 in VSMC： with stimulation of AGEs, OD valued of P-P38 in VSMC increased obviously （P0.01）, their value were 0.65±0.17, 0.85±0.26, 0.94±0.17 [L/（g·cm）]. With the increasing of the dose of AGEs, the P-P38 OD value increase simultaneously（P0.05）. 4.Effect of GSH on the OD value of P-P38 in VSMC stimulated by AGEs： OD value of P-P38 decreased with the increasing of GSH concentration, their value were 0.356±0.090, 0.281±0.070, 0.256±0.072 [L/（g·cm）] respectively, decreased by 45%, 56%, 60%（P0.01）compared with the value of control group. With the increasing of the dose of GSH, the P-P38 OD value between groups F, G and H were decreased gradually （P0.01）. Conclusions 1.AGEs has the function of inducing the proliferation of vascular SMC, the activation of the P-P38 MAPK signal pathway may be the mechanism of the proliferation of VSMC. 2.GSH can inhibit the proliferation of VSMC lead by AGEs, The P-P38-MAPK pathway is being blocked by GSH, which is the mechanism of inhibiting the proliferation of VSMC lead by AGEs.

Effect of icarisid II on diabetic rats with erectile dysfunction and its potential mechanism via assessment of AGEs, autophagy, roTOR and the NO-cGMP pathway

Erectile dysfunction （ED） is a major complication of diabetes mellitus. Icariin has been shown to enhance erectile function through its bioactive form, icarisid Ih This study investigates the effects of icarisid Ⅱ on diabetic rats with ED and its potential mechanism viathe assessment of advanced glycosylation end products （AGEs）, autophagy, mTOR and the NO-cGMP pathway. Icarisid Ⅱ was extracted from icariin by an enzymatic method. In the control and diabetic ED groups, rats were administered normal saline; in the icarisid Ⅱ group, rats were administered icarisid Ⅱ intragastrically. Erectile function was evaluated by measuring intracavernosal pressure/mean arterial pressure （ICP/MAP）. AGE concentrations, nitric oxide synthase （NOS） activity and cGMP concentration were assessed by enzyme immunoassay. Cell proliferation was analysed using methyl thiazolyl tetrazolium assay and flow cytometry. Autophagosomes were observed by transmission electron microscopy, monodansylcadaverine staining and GFP-LC3 Iocalisation. The expression of NOS isoforms and key proteins in autophagy were examined by western blot. Our results have shown that Icarisid Ⅱ increased ICP/MAP values, the smooth muscle cell （SMC） growth curve, S phase and SMC/collagen fibril （SMC/CF） proportions and decreased Beclin 1 （P〈0.05）. Icarisid Ⅱ significantly increased the proliferative index and p-p70S6K（Thr389） levels and decreased the numbers of autophagosomes and the levels of LC3-11 （P〈0.01）. Icarisid Ⅱ decreased AGE concentrations and increased cGMP concentration, NOS activity （P〈0.05） and cNOS levels （P〈0.01） in the diabetic ED group. Therefore, Icarisid Ⅱ constitutes a promising compound for diabetic ED and might be involved in the upregulation of SMC proliferation and the NO-cGMP pathway and the downregulation of AGEs, autophagy and the mTOR pathway.

Glycyrrhizic Acid Attenuates Balloon-Induced Vascular Injury Through Inactivation of RAGE Signaling Pathways

Percutaneous coronary intervention is a well-established technique used to treat coronary artery disease,but the risk of coronary artery in-stent restenosis following percutaneous coronary intervention is still high.Previous studies revealed that high mobility group protein B1(HMGB1)plays a critical role in neointima formation.In this study,we aimed to investigate the role of glycyrrhizic acid(GA),an HMGB1 inhibitor,in the process of neointima formation and the potential mechanisms.We investigated the role of GA in neointima formation through an iliac artery balloon injury model in rabbits.Proliferation,migration,and phenotype transformation of human vascular smooth muscle cells(VSMCs)were observed.Besides,infl ammation and receptor for advanced glycosylation end products(RAGE)signaling pathways were studied.The results indicate that GA attenuated neointima formation and downregulated HMGB1 expression in injured artery in rabbits.HMGB1 promoted proliferation,migration,and phenotype transformation through the activation of RAGE signaling pathways in VSMCs,and blockade of HMGB1 by GA(1,10,and 100μM)could attenuate those processes and reduce proliferation of human VSMCs.In conclusion,the HMGB1 inhibitor GA might be useful to treat proliferative vascular diseases by downregulating RAGE signaling pathways.Our results indicate a new and promising therapeutic agent for restenosis.

Antiglycation and antioxidation properties of juglans regia and calendula officinalis:possible role in reducing diabetic complications and slowing down ageing

OBJECTIVE:Accumulation of advanced glycation end products(AGEs) in the body due to the non-enzymatic glycation of proteins and oxidation is associated with aging and diabetes mellitus.In this study we wanted to investigate the antiglycation and antioxidation potential of two medicinal plants:Juglans regia and Calendula officinalis.METHODS:In-vitro investigation was carried out to discover the antiglycation and antioxidation potential of J.regia and C.officinalis.Using an Ultraviolet Double-beam Spectrophotometer,we evaluated the antiglycation property of the crude methanolic extracts of J.regia and C.officinalis by assessing their ability to inhibit the Maillard reaction.Employing the same instrument we also measured the antioxidation potential of these plant extracts using the nitric oxide(NO) free radical-scavenging assay.RESULTS:J.regia had greater antiglycation ability,with a minimum inhibitory concentration(MIC 50) of 28 μg/mL as compared with that of C.officinalis(270 μg/mL).C.officinalis had greater antioxidation potential(26.10,22.07 and 16.06% at 0.5 mg,0.25 mg and 0.125 mg,respectively,as compared with 18.15,16.50 and 16.06% of J.regia,respectively).CONCLUSION:J.regia and C.officinalis inhibited the Maillard reaction and prevented oxidation in-vitro.Hence,the extracts of these plants could have therapeutic uses in curbing chronic diabetic complications and slowing down aging.