Objective To find out whether dexamethasone induces an uncoupling of the endothelial nitric oxide synthase （eNOS）. Methods ＆ Results A major cause of eNOS uncoupling is a deficiency of its cofactor tetrahydrobiopte...Objective To find out whether dexamethasone induces an uncoupling of the endothelial nitric oxide synthase （eNOS）. Methods ＆ Results A major cause of eNOS uncoupling is a deficiency of its cofactor tetrahydrobiopterin （BH4）. Treatment of human EA.hy 926 endothelial cells with dexamethasone decreased mRNA and protein expression of both BH4-synthesizing enzymes： GTP cyclobydrolase I and dihydrofolate reductase. Consistently, a concentration- and time-dependent reduction of BH4, dihydrobiopterin （BH2） as well as BH4：BH2 ratio was observed in dexamethasone-treated cells. Surprisingly, no evidence for eNOS uncoupling was found. We then analyzed the expression and phosphorylation of the eNOS enzyme. Dexamethasone treatment led to a down-regulation of eNOS protein and a reduction of eNOS phosphorylation at serine 1177. A reduction of eNOS expression may lead to a relatively normal BH4： eNOS molar ratio in dexamethasone-treated cells. Because the BH4-eNOS stoichiometry rather than the absolute BH4 amount is the key determinant of eNOS functionality （i.e., coupled or uncoupled）, the down-regulation of eNOS may represent an explanation for the absence of eNOS uncoupling. Phosphorylation of eNOS at serine 1177 is needed for both the NO-producing activity of the coupled eNOS and the superoxide-producing activity of the uncoupled eNOS. Thus, a reduction of serine 1177 phosphorylation may render a potentially uncoupled eNOS hardly detectable. Conclusions Although dexamethasone reduces BH4 levels in endothelial cells, eNOS uncoupling is not evident. The reduction of NO production in dexamethasone-treated endothelial cells is mainly attributable to reduced eNOS expression and decreased eNOS phosphorylation at serine 1177.展开更多
Identifying a potential dietary non-pharmacological treatment to prevent cerebrovascular damage in Alzheimer's disease is crucial for alleviating cognitive decline in older adults and enhancing quality of life.Thi...Identifying a potential dietary non-pharmacological treatment to prevent cerebrovascular damage in Alzheimer's disease is crucial for alleviating cognitive decline in older adults and enhancing quality of life.This study featured the combined supplementation of soy lecithin(SL)and soy isoflavones(SIF),using in vivo animal models,in vitro vascular ring preparation,and cell studies to investigate the potential advantages and mechanisms of SL combined with SIF on cognitive function and cerebrovascular health from multiple perspectives.The results show that Aβcan significantly induce learning and memory impairment in rats,as well as pathological changes in brain blood vessels,exacerbating damage to cerebral vasodilation function and subsequently reducing cerebral blood flow in the brain.The above-mentioned phenomena induced by Aβcan be significantly improved by the combined intervention of SL and SIF.Further research has revealed that the combined intervention of SL and SIF can reverse the downregulation of the PI3K/PIP3/PDK-1/Akt/eNOS signaling pathway and phosphorylated protein expression induced by Aβin rat brain vascular tissues and bEND.3 cells.Silencing PDK-1 expression in bEND.3 cells showed that the upregulation effect of SL and SIF on Akt and eNOS disappeared.Here we find that prophylactically supplementation with SL in conjunction with SIF appears to effectively activate the PI3K/PIP3/PDK-1/Akt/e NOS pathway within cerebral vascular.This activation improves cerebrovascular vasodilation,offering potential protective effects for both cerebral vascular health and cognitive function.展开更多
文摘Objective To find out whether dexamethasone induces an uncoupling of the endothelial nitric oxide synthase （eNOS）. Methods ＆ Results A major cause of eNOS uncoupling is a deficiency of its cofactor tetrahydrobiopterin （BH4）. Treatment of human EA.hy 926 endothelial cells with dexamethasone decreased mRNA and protein expression of both BH4-synthesizing enzymes： GTP cyclobydrolase I and dihydrofolate reductase. Consistently, a concentration- and time-dependent reduction of BH4, dihydrobiopterin （BH2） as well as BH4：BH2 ratio was observed in dexamethasone-treated cells. Surprisingly, no evidence for eNOS uncoupling was found. We then analyzed the expression and phosphorylation of the eNOS enzyme. Dexamethasone treatment led to a down-regulation of eNOS protein and a reduction of eNOS phosphorylation at serine 1177. A reduction of eNOS expression may lead to a relatively normal BH4： eNOS molar ratio in dexamethasone-treated cells. Because the BH4-eNOS stoichiometry rather than the absolute BH4 amount is the key determinant of eNOS functionality （i.e., coupled or uncoupled）, the down-regulation of eNOS may represent an explanation for the absence of eNOS uncoupling. Phosphorylation of eNOS at serine 1177 is needed for both the NO-producing activity of the coupled eNOS and the superoxide-producing activity of the uncoupled eNOS. Thus, a reduction of serine 1177 phosphorylation may render a potentially uncoupled eNOS hardly detectable. Conclusions Although dexamethasone reduces BH4 levels in endothelial cells, eNOS uncoupling is not evident. The reduction of NO production in dexamethasone-treated endothelial cells is mainly attributable to reduced eNOS expression and decreased eNOS phosphorylation at serine 1177.
基金supported by the National Natural Science Foundation of China(82273620,81302427)。
文摘Identifying a potential dietary non-pharmacological treatment to prevent cerebrovascular damage in Alzheimer's disease is crucial for alleviating cognitive decline in older adults and enhancing quality of life.This study featured the combined supplementation of soy lecithin(SL)and soy isoflavones(SIF),using in vivo animal models,in vitro vascular ring preparation,and cell studies to investigate the potential advantages and mechanisms of SL combined with SIF on cognitive function and cerebrovascular health from multiple perspectives.The results show that Aβcan significantly induce learning and memory impairment in rats,as well as pathological changes in brain blood vessels,exacerbating damage to cerebral vasodilation function and subsequently reducing cerebral blood flow in the brain.The above-mentioned phenomena induced by Aβcan be significantly improved by the combined intervention of SL and SIF.Further research has revealed that the combined intervention of SL and SIF can reverse the downregulation of the PI3K/PIP3/PDK-1/Akt/eNOS signaling pathway and phosphorylated protein expression induced by Aβin rat brain vascular tissues and bEND.3 cells.Silencing PDK-1 expression in bEND.3 cells showed that the upregulation effect of SL and SIF on Akt and eNOS disappeared.Here we find that prophylactically supplementation with SL in conjunction with SIF appears to effectively activate the PI3K/PIP3/PDK-1/Akt/e NOS pathway within cerebral vascular.This activation improves cerebrovascular vasodilation,offering potential protective effects for both cerebral vascular health and cognitive function.
