Mechanism And Effects Of Captopril On Endothelium Damage Induced By Homocysteine Thiolactone

Partâ… . Protective Effects of Captopril on Endothelial Dysfunction Induced by homocysteine thiolactone in Rat Isolated AortaObjective: To explore the effects of captopril, an angiotensin-conver- ting enzyme inhibitor with sulfhydryl(-SH)group, on endothelial dysfunction induced by homocysteine thiolactone in rat isolated aorta.METHODS: A 90min incubation of rat isolated aortic rings with homocysteine thiolactone (30mmol/L). Endothelium-dependent (EDR) and non-dependent relaxation of thoracic aortic rings in rats induced by acetylcholine (Ach) or sodium nitroprusside (SNP) and biochemical parameters including malondialdehyde (MDA), and nitric oxide (NO) were measured in rat isolated aorta.RESULTS: (1) Exposure of aortic rings to HTL (3～30mmool/L) for 90 minutes induced a significant inhibition of EDR induced by Ach, but had no effects on endothelium-independent relaxation. (2) HTL (30mmol/L) decreased contents of NO, and increased MDA concentration in aortic tissue. (3) After incubation of aortic rings with captopril (0.003～0.03mmol/L) attenuated the inhibition of EDR and significantly resisted the decrease of NO content, elevation of MDA concentration caused by HTL(30mmol/L) in aortic tissues. Following pretreatment with not only the nitric oxide synthase inhibitor Nomega-nitro-1-arginine methyl ester (L-NAME, 0.01mmol/L) but also the free sulfhydryl group blocking agent phydroxymer- curybenzoate (PHMB, 0.05mmol/L) could completely or partly abolished the protection of captopril and N-acetylcysteine respectively. Captopril was more effect than enalaprilat and losartan in attenuation of the inhibition of EDR by HTL in the same concentration. Similarly protective effect was observed when the aortic rings incubation with N-acetylcysteine (0.05mmol/L) which is an antioxidant with sulfhydryl group, superoxide dismutase (SOD, 200U/ml) which is a scavenger of superoxide anions and apocynin(0.03mmol/L) which is an inhibitor of NADPH oxidase, could reduced HTL (30mmol/L)-induced inhibition of EDR and significantly resisted the decrease of NO content, elevation of MDA concentration.CONCLUSION: These results suggested that mechanisms of endothelial dysfunction induced by HTL may include the decrease of NO and the generation of oxygen free radicals, captopril can restore the inhibition of endothelium-dependent relaxation induced by homocysteine thiolactone in isolated rat aorta, which may be related to scavenging oxygen free radicals and maybe sulfhydryl -dependent.Partâ…¡. Protective Effects of Captopril on Vascular Endothelial Dysfunction Induced by homocysteine thiolactone in Rat in vivoObjective: To investigate the effects of captopril on vascular endothelial dysfunction induced by homocysteine thiolactone in rat in vivo.METHODS: The model of hyperhomocysteinemia (HHcy) in rats was induced by intragastric gavaged HTL, and the intervention groups were intragastric gavaged captopril (10, 20, 40mg/kg/day ) in water. Aider treatment of 8 weeks, endothelium-dependent relaxation (EDR) and endothelium-independent relaxation of aortic rings were examined. Activity of paraoxonasel (PON1), SOD and angiotensin-converting enzyme(ACE), level of malondialdehyde (MDA), nitric oxide (NO), angiotensinâ…¡(Angâ…¡), 6-keto-PG-F_1α, a metabolic product of PGI₂, in serum were analyzed. The positive cell ratio of NF-κB P₆₅ were detected by immunohistochemistry in vascular of rats.RESULTS: (1) HTL significantly inhibited EDR induced by ACh, but had no effects on endothelium-independent relaxation; and induced the activation of NF-κB P₆₅ of vascular endothelium cell in rats; decreased the level of NO and 6-keto-PG-F_1α, increased the content of MDA, degraded the activity of PON1 and SOD in serum; down-regulated the PON1mRNA in the liver; but had no effects on the angiotensinâ…¡content. (2) Captopril could improve the EDR response and maintain serum NO, MDA content and the activity of PON1 and SOD; stimulated the releasing of PGI₂; up-regulated the PON1mRNA in the liver in dose-dependent manner. Captopril simultaneously inhibited the activation of NF-κBP₆₅ of vascular endothelium cell in rats. But captopril had no effects on the angiotensinâ…¡content.CONCLUSION: Captopril could protect vascular endothelial function induced by homocysteine thiolactone in rats. Partâ…¢Effects of Captopril on Homocysteine thiolactone-Induced damage in Cultured Endothelial Cells.Objective: To approach the effects of captopril on homocysteine thiolactone-induced damage in endothelial cells.METHODS: Human umbilicus vein endothelial cells (HUVECs) were incubated with HTL and the concentrations of soluble intercellular adhesion molecule (sICAM-1) (by ELISA), TNF-α(by ELISA) in the conditioned medium, the activity of NF-κB and the level of ROS were determined by fluorescence microscopy. Cell viability, lactate dehydrogenase (LDH) and NO content in the medium were measured.RESULTS: (1) Exposure of HUVEC to HTL (1mmol/L) for 3h potentiated the activity of NF-κB and increased the levels of ROS (2) Incubation of HUECV with HTL (1mmol/L) for 24h markedly decreased cell viability and NO content, and increased the level of LDH, ICAM-1 and TNF-αin the culture medium. (3) Pretreatment with captopril (0.003, 0.01, 0.03mmol/L) markedly inhibited activity of NF-κB increased by HTL and decreased the levels of ROS, TNF-α, sICAM-1, NO and LDH by HTL in a dose-dependent manner, and these effects were partly blocked by the sulfhydryl group blocking agent(PHMB). Similarly protective effect was observed when pretreatment with NAC, apocynin, PDTC. (4) Captopril was more effect than enalaprilat in attenuation of the damage to HUECV by HTL in the same concentration.CONCLUSION: Captopril could directly prevent from the damage to endothelial cell in vitro induced by homocysteine thiolactone.