- Mechanism of Impaired Endothelium-dependent Vasodilation in Otsuka Long-Evans Tokushima Fatty (OLETF) Rats .
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Kook Jin Chun, Seok Man Son, In Ju Kim, Chi Dae Kim, Seok Dong Yoo, Yong Ki Kim
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Korean Diabetes J. 2002;26(1):47-57. Published online February 1, 2002
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 Abstract
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- BACKGROUND
Impaired vascular endothelium-dependent relaxation and augmented contractile responses have been reported in several long-term animals hyperglycemia models and human diabetic patients. Since oxidative stress has been implicated as a contributor to impaired vascular function, the mechanism of an impaired endothelium-dependent vasodilation in Otsuka Long-Evans Tokushima Fatty (OLETF) rats was investigated. METHODS: This present study was undertaken to characterize both the vascular production and the enzymatic source of the superoxide anion in the type 2 diabetic rats. RESULTS: In the thoracic aortas of OLETF rats, endothelium-dependent relaxation was markedly attenuated compared to that of the control rats (LETO, Long-Evans Tokushima Otsuka) in association with a significant increase in superoxide production (2421.39+/-07.01 nmol/min/mg). There was no difference in eNOS expression between the OLETF rats and LETO rats. The increased production of superoxide anion was significantly attenuated by diphenyleneiodonium (DPI, 10 mol/L), NAD (P)H oxidase inhibitor. In line with these results, studies using various enzyme inhibitors such as DPI, allopurinol, rotenone and L-NMMA suggest that the main source of superoxide anions in the aorta is NAD (P)H oxidase. CONCLUSION: These results suggest that enhanced NAD(P)H oxidase activity and reduced nitric oxide (NO) availability through an interaction between NO and superoxide anion contribute to the impaired endothelium-dependent vasodilation in OLETF rats.
- Effect of Glucose on Adherence of Neutrophils to Endothelial Cells.
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Seok Man Son, Seok Dong Yoo, In Ju Kim, Yong Ki Kim, Hee Bag Park, Chi Dae Kim, Ki Whan Hong
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Korean Diabetes J. 1997;21(3):262-270. Published online January 1, 2001
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Abstract
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- BACKGROUND
Accelerated atherosclerotic vascular disease is the leading cause of mortality in patients with diabetes mellitus. To clarify the mechanisms that cause macrovascular dysfunction in diabetes, we examined the effect of high glucose on the adhesion of neutrophils to the endothelial cells and release of TNF-a from cultured rabbit aortic endotheIial cells. METHODS: Rabbit aortic endothelial cells in primary culture were prepared by the collagenase digestion method. Cells were incubated for various time upto 24 hours to evaluate TNF-a response to different glucose concentrations(0, 5.5, 11, 22mmol/L). Isolated rabbit neutrophils were incubated with monolayers of rabbit aortic endothelial cells under different glucose condition. RESULTS: After 24 hrs incubation with various concentrations of glucose, neutrophil adherence to high concentration of glucose(11 and 22mM)-treated endothelium was significantly increased(46+/-7 and 64 +/-6%, respectively) compared with adhesion to low concentration of glucose(0 or 5.5mM)-treated endothelium(3l +/-5 and 30+/-3%, respectively), In addition, when TNF-a imrnunoreactivity in the culture medium was measured by enzyme-linked immunoassay after 24 hours of incubation with various concentration of glucose, the secretion of TNF-a from endothelial cells was significantly increased in a concentration-dependent manner upon exposure to high concentration of glucose, CONCLUSION: The results of this study ciemonstrate tht high concentration of glucose stimulates neutrophil adhesion to endothelial cells in association with increased production of TNF-a from endothelial cells. These results suggest that glucose directly causes increased interaction between neutrophil and endothelial cell through a TNF-a-dependent mechaniasm,
- Effect of high glucose on function of cultured rabbit vascular endothelial cells.
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Seok Man Son, In Ju Kim, Yong Ki Kim, Chi Dae Kim, Ki Whan Hong
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Korean Diabetes J. 1997;21(2):156-167. Published online January 1, 2001
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Abstract
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- BACKGROUND
Vascular disease accounts for the majority of the clinical complications of diabetes mellitus. Changes in local control of vascular tone such as imbalanced production of relaxing and contracting factors by endothelium may be related to the initiation and maintenance of abnormal vascular reactivity characteristically seen in diabetic vascular complications. Cytokines and growth factors released from injured endothelial cells, T-cells, and macro-phages enhance atherogenesis. In this study, we examined NO and TNF-a released from cultured rabbit aortic endothelial cells(RAECs) under different glucose concentration to investigate the relationship between high glucose and endothelial cell dysfunction. METHODS: The thoracic and abdominal aortae of rabbit(23kg) were isolated and periadventitial connective tissue was carefully removed. Rabbit aortic endothelial cells in primary culture were prepared by the m.ethod of Schwartz with modification. RAECs were grown to confluence in 25 cm2 flask in DMEM supplemented with 20% FBS, 150pg/mL endothelial cell growth supplernent, 90pg/mL heparin, 100 U/mL penicillin and 100pg/mL streptomycin at 37'C in humidified 5% carbon dioxide in air. For experiments, confluent cells were replaced in 1 1 mm, 48 well plate containing same medium composition. Cells were then incubated in the presence or absence of FBS for various times up to 48 hours(time course) to eveluate the NO and TNF-a response to different glucose concentrations(0, 5.5, 11, 22, and 44 mmol/ L). Cells were also incubated with various concentration of ACH and ADP(10, 10', 10 and 10' mol/L) and 10' mol/L of ACH or ADP with different glucose concentrations for 24 hours to evaluate stimulated effect of ACH and ADP on NO release. RESULTS: 1) Total NO release from RAECs was significantly in a time-dependent. After 48 hours incubation, the total secretion of NO was significantly higher in culture medium with FRS than without FBS. 2) Glucose concentration resembling severe hyper-glycemic conditions(22 and 44 mmol/L) significantly inhibited NO release from RAECs, 3) Acetylcholine and ADP induced a clear dose-dependent NO release in RAECs. 4) Stimulation of acetylcholine and ADP on NO release according to different glucose concentration was not significantly higher than NO release in culture medium with glucose alone. 5) The increment in TNF-a levels was associated with a significant increase at higher glucose concentration, 6) There was a negative correlation between NO and TNF-a release in culture medium with FBS but not in culture medium without FBS. CONCLUSION: Our data show that decreased NO release and increased TNF-a release from RAECs were noted under high glucose concentration. Such interaction could play a significant role in the development of diabetic vascular complication in hyperglycernic conditions.
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