title: Inhibition of beta-carotene and astaxanthin of NADPH-dependent microsomal phospholipid peroxidation.
abstract: To evaluate the antioxidant effects of beta-carotene and astaxanthin, rat liver microsomes were exposed to a mixture of chelated iron (Fe3+/ADP) and NADPH. The carotenoids (190 pmol/mg protein) were incorporated into some of these microsomal membranes, and phospholipid hydroperoxides (PLOOH), thiobarbituric acid reactive substances (TBARS) and endogenous alpha-tocopherol content were measured over time after the initiation of oxidant stress. In control microsomes, oxidant stress led to accumulation of 1,865 (+/- 371) pmol PLOOH/mg protein during the initial 10-min peroxidation reaction, followed by a more gradual decrease during the subsequent 20-min of reaction. PLOOH accumulation during the initial 10-min reaction period was reduced to 588 (+/- 169) pmol/mg protein with beta-carotene present and 800 (+/- 288) pmol/mg protein with astaxanthin present. During the following 20-min of incubation, PLOOH levels declined in the carotenoid-supplemented microsomes but continued to increase at a slower rate in control preparations. TBARS did not show such large accumulation as observed in PLOOH during the initial 10-min incubation in any microsomal sample. The presence of carotenoids in the microsomal membrane partially inhibited the loss of alpha-tocopherol, especially during the later phase of oxidant stress. When lipid peroxidation is generated by membrane-bound cyt-P450, the specific measurement of PLOOH clearly demonstrates that the presence of carotenoids provides antioxidant protection.
authors.affiliation: Department of Applied Biological Chemistry, Tohoku University, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakagawa
authors.forename: S D
authors.initials: SD
authors.lastname: Kang
authors.forename: D K
authors.initials: DK
authors.lastname: Park
authors.forename: G J
authors.initials: GJ
authors.lastname: Handelman
authors.forename: T
authors.initials: T
authors.lastname: Miyazawa
mesh_terms: D000818:Animals; D015227:Lipid Peroxidation / Q000187:drug effects*; D008054:Lipid Peroxides / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000378:metabolism; D009249:NADP / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014810:Vitamin E / Q000378:metabolism; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: D008054:Lipid Peroxides; D010743:Phospholipids; D017392:Thiobarbituric Acid Reactive Substances; D024341:Xanthophylls; D019207:beta Carotene; D014810:Vitamin E; D009249:NADP; C005948:astaxanthine