Antioxidant alpha-keto-carboxylate pyruvate protects low-density lipoprotein and atherogenic macrophages.
Oxidative modification of low-density lipoprotein (oxLDL) plays a pathogenic role in atherogenesis. Classical antioxidants such as L-ascorbic acid can inhibit formation of oxLDL. Alpha-Keto-carboxylates such as pyruvate and congeners also display antioxidant properties in some cell-free and intact cell systems. We tested the hypothesis that pyruvate or alpha-keto-glutarate may function as antioxidants with respect to LDL incubated with 5 or 10 microM Cu2+ alone or in combination with THP-1-derived macrophages. alpha-Hydroxy-carboxylates (L-lactate), linear aliphatic monocarboxylates (acetate/caprylate) and L-ascorbic acid served as controls. The oxLDL formation was ascertained by electrophoretic mobility and oxLDL cytotoxicity was judged by macrophage viability and thiobarbituric acid reactive substances (TBARS) formation. Cu2+ alone was not cytotoxic but increased electrophoretic mobility of cell-free LDL, stimulating TBARS. Millimolar pyruvate, alpha-ketoglutarate, or micromolar L-ascorbic acid partially inhibited oxLDL formation, while alpha-hydroxy-carboxylate or the aliphatic mono-carboxylates had no measurable antioxidant properties in cell-free LDL. Co-culture of LDL with macrophages and Cu2+ augmented TBARS release and resulted in 95% macrophage death. Pyruvate improved macrophage viability with 5 microM Cu2+ up to 60%. L-Ascorbic acid (> or = 100 microM) protected macrophages up to 80%. When > or = 100 microM L-ascorbic acid was combined with pyruvate, oxLDL formation and macrophage death were fully prevented. Thus, alpha-keto-carboxylates, but not physiological alpha-hydroxy-carboxylates or aliphatic monocarboxylates qualify as antioxidants in LDL systems. Since alpha-keto-carboxylates enhanced the antioxidant power of L-ascorbic acid, our findings may have implications for strategies attenuating atherosclerosis.
Kang
Young-Hee
YH
Division of Life Sciences and Institute of Environment and Life Science, Hallym University, Chuncheon, Kangwon-do, South Korea. yhkang@hallym.ac.kr
Park
Sung-Hee
SH
Lee
Yong-Jin
YJ
Kang
Jung-Sook
JS
Kang
Il-Jun
IJ
Shin
Hyun-Kyung
HK
Park
Jung Han Yoon
JH
Bünger
Rolf
R
D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology; D001808:Blood Vessels / Q000378:metabolism* / Q000502:physiology; D002264:Carboxylic Acids / Q000494:pharmacology*; D002470:Cell Survival; D002474:Cell-Free System; D018920:Coculture Techniques; D003300:Copper / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007659:Ketones / Q000494:pharmacology*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology; D019289:Pyruvic Acid / Q000494:pharmacology*; D017392:Thiobarbituric Acid Reactive Substances / Q000494:pharmacology
D000975:Antioxidants; D002264:Carboxylic Acids; D007659:Ketones; D008077:Lipoproteins, LDL; D017392:Thiobarbituric Acid Reactive Substances; D003300:Copper; D019289:Pyruvic Acid; D001205:Ascorbic Acid