Background and Purpose Atherosclerosis is associated with reduced vascular hydrogen sulfide (H2S) biosynthesis. GYY4137 is a novel slow‐releasing H2S compound that may effectively mimic the time course of H2S release in vivo. However, it is not known whether GYY4137 affects atherosclerosis. Experimental Approach RAW 264.7 cells and human blood monocyte‐derived macrophages were incubated with oxidized low density lipoprotein (ox‐LDL) with/without GYY4137. ApoE−/− mice were fed a high‐fat diet for 4 weeks and administered GYY4137 for 30 days. Lipid and atherosclerotic lesions were measured by oil red O staining. Endothelium‐dependent relaxation was assessed in response to acetylcholine. Superoxide production was detected by dihydroethidium staining. Expression of mRNA and protein were evaluated by quantitative real‐time PCR and Western blot. Key Results GYY4137 inhibited ox‐LDL‐induced foam cell formation and cholesterol esterification in cultured cells. GYY4137 decreased the expression of lectin‐like ox‐LDL receptor‐1, iNOS, phosphorylated IκBα, NF‐κB, ICAM‐1, VCAM‐1 and chemokines, including CXCL2, CXCR4, CXCL10 and CCL17, but increased the scavenger protein CD36, in ox‐LDL‐treated RAW 264.7 cells. In vivo, GYY4137 decreased aortic atherosclerotic plaque formation and partially restored aortic endothelium‐dependent relaxation in apoE−/− mice. GYY4137 decreased ICAM‐1, TNF‐α and IL‐6 mRNA expression as well as superoxide (O2−) generation in aorta. In addition, GYY4137 increased aortic eNOS phosphorylation and expression of PI3K, enhanced Akt Ser473 phosphorylation and down‐regulated the expression of LOX‐1. Conclusion and Implications GYY4137 inhibits lipid accumulation induced by ox‐LDL in RAW 264.7 cells. In vivo, GYY4137 decreased vascular inflammation and oxidative stress, improved endothelial function and reduced atherosclerotic plaque formation in apoE−/− mice.
Previous studies indicated that estrogen could improve endothelial function. However, whether estrogen protects vascular complications of diabetes has yet to be clarified. The study was designed to investigate the action of 17ß-estradiol on vascular endothelium in streptozotocin (STZ)-induced diabetic rats. Ovariectomized female Sprague-Dawley rats were administered with streptozotocin to produce an ovariectomized-diabetic (OVS) model which manifested as dysfunction of aortic dilation and contraction ability. Meanwhile, OVS animals with 17ß-estradiol supplementation significantly improved aortic function. Accordingly, nitric oxide synthase-3 (NOS-3), Akt, PI3K and estrogen receptor α (ERα) protein expression in aorta declined in the OVS group. Such effects were partially restored by estrogen replacement. The presence of 17ß-estradiol similarly counteracted the reduction of cyclic guanosine monophosphate (cGMP), the enhanced expression of inducible NOS (NOS-2) and NO metabolites (nitrite and nitrate), as well as the increase of matrix metalloproteinase-9/tissue inhibitor of metalloproteinase-1 (MMP-9/TIMP-1), which is an index of arterial compliance. 17ß-estradiol could also decrease ROS production in vascular endothelium. In EA hy 926 cells we found that ER antagonist, wortmannin and Akt inhibitor could block improvement effects of 17ß-estradiol. These results strongly suggest that functional impairment of the ERα/NOS-3 signaling network in OVS animals was partially restored by 17ß-estradiol administration, which provides experimental support for estrogen recruitment to improve vascular outcomes in female diabetes after endogenous hormone depletion.
Aspirin acetylates NOS-3 acutely in platelets, and this causes an increase in its activity as well as a decrease in its phosphorylation. It is also possible that aspirin indirectly affects NOS-3 activity by acetylating other substrates within the platelet, but this remains to be determined.
BACKGROUND AND PURPOSEOne key mechanism for endothelial dysfunction is endothelial NOS (eNOS) uncoupling, whereby eNOS generates superoxide (O2•-) rather than NO. We explored the effect of pyridoxine on eNOS uncoupling induced by oxidized low-density lipoprotein (ox-LDL) in human umbilical vein endothelial cells (HUVECs) and the potential molecular mechanism. EXPERIMENTAL APPROACHHUVECs were incubated with ox-LDL with/without pyridoxine, N G -nitro-L-arginine methylester (L-NAME), chelerythrine chloride (CHCI) or apocynin. Endothelial O2•-was measured using lucigenin chemiluminescence, and O2•--sensitive fluorescent dye dihydroethidium (DHE). NO levels were measured by chemiluminescence, PepTag Assay for non-radioactive detection of PKC activity, depletion of PKCa and p47phox by siRNA silencing and the states of phospho-eNOS Thr495, total-eNOS, phospho-PKCa/bII, total PKC, phospho-PKCa, total PKCa and p47phox were measured by Western blot. KEY RESULTS Ox-LDL significantly increased O2•-production and reduced NO levels released from HUVECs; an effect reversed by eNOS inhibitor, L-NAME. Pyridoxine pretreatment significantly inhibited ox-LDL-induced O2•-generation and preserved NO levels. Pyridoxine also prevented the ox-LDL-induced reduction in phospho-eNOS Thr495 and PKC activity. These protective effects of pyridoxine were abolished by the PKC inhibitor, CHCI, or siRNA silencing of PKCa. However, depletion of p47phox or treatment with the NADPH oxidase inhibitor, apocynin, had no influence on these effects. Also, cytosol p47phox expression was unchanged by the different treatments. CONCLUSIONS AND IMPLICATIONSPyridoxine mitigated eNOS uncoupling induced by ox-LDL. This protectant effect was related to phosphorylation of eNOS Thr495 stimulated by PKCa, not via NADPH oxidase. These results provide support for the use of pyridoxine in ox-LDL-related vascular endothelial dysfunction. AbbreviationsCHCI, chelerythrine chloride; DHE, dihydroethidium; eNOS, endothelial NOS; HUVEC, human umbilical vein endothelial cell; L-NAME, N G -nitro-L-arginine methylester; O2•-, superoxide; ox-LDL, oxidized low-density lipoprotein
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