Differential inhibition of oxidized LDL-induced apoptosis in human endothelial cells treated with different flavonoids.
High plasma level of cholesterol is a well-known risk factor for atherosclerotic diseases. Oxidized LDL induces cellular and nuclear damage that leads to apoptotic cell death. We tested the hypothesis that flavonoids may function as antioxidants with regard to LDL incubated with 5 microm-Cu(2+) alone or in combination with human umbilical vein endothelial cells (HUVEC). Cytotoxicity and formation of thiobarbituric acid-reactive substances induced by Cu(2+)-oxidized LDL were examined in the presence of various subtypes of flavonoid. Flavanols, flavonols and flavanones at a non-toxic dose of 50 microm markedly inhibited LDL oxidation by inhibiting the formation of peroxidative products. In contrast, the flavones luteolin and apigenin had no such effect, with >30 % of cells killed after exposure to 0.1 mg LDL/ml. Protective flavonoids, especially (-)-epigallocatechin gallate, quercetin, rutin and hesperetin, inhibited HUVEC nuclear condensation and fragmentation induced by Cu(2+)-oxidized LDL. In addition, immunochemical staining and Western blot analysis revealed that anti-apoptotic Bcl-2 expression was enhanced following treatment with these protective flavonoids. However, Bax expression and caspase-3 cleavage stimulated by 18 h incubation with oxidized LDL were reduced following treatment with these protective flavonoids. The down-regulation of Bcl-2 and up-regulation of caspase-3 activation were reversed by the cytoprotective flavonoids, (-)-epigallocatechin gallate, quercetin and hesperetin, at >/=10 microm. These results suggest that flavonoids may differentially prevent Cu(2+)-oxidized LDL-induced apoptosis and promote cell survival as potent antioxidants. Survival potentials of certain flavonoids against cytotoxic oxidized LDL appeared to stem from their disparate chemical structure. Furthermore, dietary flavonoids may have therapeutic potential for protecting the endothelium from oxidative stress and oxidized LDL-triggered atherogenesis.
Jeong
Yu-Jin
YJ
Division of Life Sciences, Hallym University, Chuncheon, South Korea.
Choi
Yean-Jung
YJ
Kwon
Hyang-Mi
HM
Kang
Sang-Wook
SW
Park
Hyoung-Sook
HS
Lee
Myungsook
M
Kang
Young-Hee
YH
D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D003300:Copper / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D019254:Genes, bcl-2; D006569:Hesperidin / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011794:Quercetin / Q000494:pharmacology; D012431:Rutin / Q000494:pharmacology; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014471:Umbilical Veins; D051028:bcl-2-Associated X Protein
D000975:Antioxidants; C494826:BAX protein, human; D005419:Flavonoids; D008077:Lipoproteins, LDL; D019253:Proto-Oncogene Proteins c-bcl-2; D017392:Thiobarbituric Acid Reactive Substances; D051028:bcl-2-Associated X Protein; C099252:oxidized low density lipoprotein; D012431:Rutin; D003300:Copper; D002392:Catechin; D011794:Quercetin; C045651:epigallocatechin gallate; D006569:Hesperidin; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C013015:hesperetin