Oxidized LDLs alter the activity of the ubiquitin‐proteasome pathway: potential role in oxidized LDL‐induced apoptosis

Abstract

Oxidized low-density lipoproteins (oxLDL) play a role in the genesis of atherosclerosis. OxLDL are able to induce apoptosis of vascular cells, which is potentially involved in the formation of the necrotic center of atherosclerotic lesions, plaque rupture, and subsequent thrombotic events. Because oxLDL may induce structural modifications of cell protein and altered proteins may impair cell viability, the present work aimed to evaluate the extent of protein alterations, the degradation of modified proteins through the ubiquitin-proteasome system (a major degradative pathway for altered and oxidatively modified proteins) and their role during apoptosis induced by oxLDL. This paper reports the following: 1) oxLDL induce derivatization of cell proteins by 4-hydroxynonenal (4-HNE) and ubiquitination. 2) Toxic concentrations of oxLDL elicit a biphasic effect on proteasome activity. An early and transient activation of endogenous proteolysis is followed rapidly by a subsequent decay (resulting probably from the 26S proteasome inhibition) and followed later by the inhibition of the 20S proteasome (as assessed by inhibition of sLLVY-MCA hydrolysis). 3) Specific inhibitors of proteasome (lactacystin and proteasome inhibitor I) potentiated considerably the toxicity of oxLDL (nontoxic doses of oxLDL became severely toxic). The defect of the ubiquitination pathway (in temperature-sensitive mutants) also potentiated the toxicity of oxLDL. This suggests that the ubiquitin-proteasome pathway plays a role in the cellular defenses against oxLDL-induced toxicity. 4) Dinitrophenylhydrazine (DNPH), an aldehyde reagent, prevented both the oxLDL-induced derivatization of cell proteins and subsequent cytotoxicity. Altogether, the reported data suggest that both derivatization of cell proteins (by 4-HNE and other oxidized lipids) and inhibition of the proteasome pathway are involved in the mechanism of oxLDL-induced apoptosis.

Phenolic antioxidants trolox and caffeic acid modulate the oxidized LDL‐induced EGF‐receptor activation

“…Cells were routinely grown in RPMI 1640 medium (Life Technologies-Gibco) containing 10% foetal calf serum (Biowhittaker, Gagny, France) as described (Suc et al, 1998;Vieira et al, 2000). The B82LK+ cells (transduced with wild type EGFR) (Wright et al, 1995), were a generous gift from Dr M. Weber (Charlottesville, VA, U.S.A.), and were grown in DMEM containing 10% foetal calf serum.…”

“…Ferrylmyoglobin mediated-LDL oxidation was carried out by incubation of LDL samples (2 mg apoB ml 71 , in PBS, pH 7.4) with 18 mM metmyoglobin/27 mM H 2 O 2 during 2 h at 378C, under the previously used conditions (Vieira et al, 2000). LDL oxidation was evaluated by the content in thiobarbituric acid reactive substances (TBARS) (Yagi, 1987) and lipid hydroperoxides (FOX-2 method of Wol , 1994), by the relative electrophoretic mobility (REM) on Hydragel (Sebia, Paris, France) and by the level of trinitrobenzene sulphonic acid (TNBS)-reactive amino groups (Steinbrecher et al, 1990).…”

“…We recently reported that oxLDL induce derivatization of various cell proteins by 4-hydroxynonenal (4-HNE) (Vieira et al, 2000) and other oxidized lipids (Chang et al, 1999). Among the cell proteins derivatized by 4-HNE, we have shown that EGFR is a target of 4-HNE from oxLDL which induce 4-HNE-adducts formation and activation of the EGFR (Suc et al, 1998).…”

CD4+/FOXP3+ Regulatory T Cells in End-Stage Kidney Disease: Molecular Pathways Trough Cell-Cycle Arrest and Apoptosis

“…On the other hand, oxLDL affect the anti-apoptotic protein Bcl-xL degradation by increasing its removal in parallel with the activation of the 20 S and 26 S proteasome in Phytohemagglutinin (PHA)-stimulated Tregs from healthy subjects treated with various concentrations of oxLDL or cultured with uremic serum from HD patients [15,69,70].…”

Signalisation apototique induite par les LDL oxydées Implication dans l’athérosclérose

“…La formation d'aldéhyde-adduits sur les protéines entraîne des dysfonctions enzymatiques, méta-boliques, et de signalisation, d'où une dysfonction cellulaire pouvant induire de l'apoptose [66]. Les LDL oxydées altèrent l'activité du système ubiquitine/proteasome, ce qui entraîne une accumulation de protéines modifiées et potentialise l'effet toxique des LDL, et induit une inhibition de NF-jB [67,68].…”