Linked Life Data

9680174

Source:http://linkedlifedata.com/resource/pubmed/id/9680174

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1998-10-13
pubmed:abstractText
Mono-thiols can act either as pro- or anti-oxidants during metal-catalyzed low density lipoprotein (LDL) peroxidation, however investigation of the role of vicinal thiols has been neglected. Therefore dihydrolipoic acid (DHLA), a vicinal dithiol, and lipoic acid, its oxidized form, were used to investigate Cu2+-mediated LDL peroxidation. We demonstrate here that DHLA inhibited Cu2+-dependent LDL peroxidation by chelating copper. DHLA (0-20 microM) increased lag-times of conjugated diene formation in LDL (100 microg/ml) oxidized with 5 microM Cu2+ in a concentration dependent manner, and this effect was saturated after 5 microM DHLA; enough to chelate all of the added Cu2+. In a similar fashion DHLA prevented LDL-mediated reduction of Cu2+ to Cu+. Lipoic acid had no effect in these systems. DHLA alone also reduced Cu2+, however this was inhibited when DHLA was in excess of the copper concentration. Hence there is complex formation between the two species. Copper:DHLA complex formation was further investigated and found to be dependent upon pH and the presence of oxygen. At low pH (<6), or in the absence of oxygen, the complex is stable, presumably due to vicinal thiol chelation. As the pH is increased, the carboxylate group also participates in copper chelation, this results in a less stable complex which is susceptible to oxidation, and copper is eventually released. Electron spin resonance studies demonstrate the formation of hydroxyl, but not superoxide, radicals during Cu2+-catalyzed DHLA oxidation. Thus in our LDL experiments at physiological pH, DHLA is able to either reductively inactivate Cu2+ when Cu2+ is in excess, or effectively chelate Cu2+ when DHLA is in excess. The Cu2+:DHLA complex eventually undergoes copper-catalyzed oxidation, copper is released and LDL peroxidation proceeds. DHLA, thus, has both pro- and antioxidant properties depending upon the ratio of Cu2+:DHLA and the pH. These results provide an additional mechanism of thiol-mediated formation of radicals and metal chelation.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0891-5849
pubmed:author
pubmed:issnType
Print
pubmed:volume
25
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
287-97
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Thiol chelation of Cu2+ by dihydrolipoic acid prevents human low density lipoprotein peroxidation.
pubmed:affiliation
Department of Molecular and Cell Biology, University of California at Berkeley, 94720-3200, USA. johnkl@socrates.berkeley.edu
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't