Toxicology 132 (1999) 19 – 32
Pb
2 +
promotes lipid oxidation and alterations in membrane
physical properties
V.N. Adonaylo, P.I. Oteiza *
Instituto de Quı ´mica y Fisicoquı ´mica Biolo ´gicas (UBA-CONICET), Uniersidad de Buenos Aires,
Facultad de Farmacia y Bioquı ´mica, Junı ´n 956, 1113 Buenos Aires, Argentina
Received 22 June 1998; accepted 4 October 1998
Abstract
Experimental evidence suggests that cellular damage mediated by oxidants could be involved in the pathology
associated with lead (Pb) toxicity. We investigated the effect of Pb
2 +
on lipid oxidation in liposomes using different
initiators. In the presence of Fe
2 +
, Pb
2 +
(12.5 – 200 M) stimulated lipid oxidation in phosphatidyl-
choline:phosphatidylserine-containing liposomes, measured as 2-thiobarbituric acid-reactive substances (TBARS) and
conjugated dienes. This stimulatory effect depended on the presence of membrane negative charges and on bilayer
integrity. Pb
2 +
did not stimulate TBARS formation in the presence of 25 mM 2,2-azo-bis (2,4 dimethylvaleronitrile
(AMVN) and 2,2 azobis (2-amidinopropane) (AAPH). Pb
2 +
significantly stimulated TBARS production and NADH
oxidation in the presence of photoactivated rose Bengal. The use of specific inhibitors indicated that several reactive
oxygen species were involved in the pro-oxidant action of Pb
2 +
. Pb
2 +
(12.5 – 200 M) caused membrane lateral phase
separation and this effect was positively correlated with its capacity to stimulate Fe
2 +
and rose Bengal-initiated
TBARS production. Pb
2 +
could bind to the membrane and act to stimulate lipid oxidation by causing changes in
membrane physical properties. Through this mechanism Pb
2 +
would favor the propagation of lipid oxidation. By
causing lateral phase separation and/or by increasing lipid oxidation rates, Pb
2 +
could be cytotoxic by altering
membrane-related processes. © 1999 Elsevier Science Ireland Ltd. All rights reserved.
Keywords: Lead; Lipid oxidation; Iron; Free radicals; Phase separation
Abbreiations: AMVN, 2,2-azo-bis (2,4 dimethylvaleronitrile); AAPH, 2,2 azobis (2-amidinopropane); PC, phosphatidylcholine;
PS, phosphatidylserine; TBARS, 2-thiobarbituric acid-reactive substances; C6-NBD-PC, 2-(6-(7nitrobenz-2-oxa-1,3-diazol-4-yl)
amino) dodecanoyl-1-hexadecanoyl-sn -glycero-3-phosphocholine.
* Corresponding author. Fax: +54-1-9625457; e-mail: oteiza@qb.ffyb.uba.ar.
0300-483X/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved.
PII:S0300-483X(98)00134-6