Modification of platelet proteins by malondialdehyde: prevention by dicarbonyl scavengers

Abstract

This article is available online at http://www.jlr.org to prostaglandin H 2 (PGH 2 ). In platelets, the thromboxane synthase enzyme catalyzes conversion of PGH 2 to both thromboxane A 2 and malondialdehyde (MDA) in approximately equimolar amounts ( 1 ) (supplementary Fig. 1).MDA is an electrophile that reacts with amino groups, including the -amine of protein lysines. Reaction of MDA with lysine in vitro leads to formation of adducts with several structures ( 2, 3 ), including one that results from the reaction of this dicarbonyl with two lysines to produce intra-and intermolecular cross-links of macromolecules. Such cross-links have been demonstrated when MDA is added to purifi ed apoA-1 in vitro ( 2 ).This evidence that MDA is a major product of the thromboxane synthase and can modify protein structure in vitro suggests a hypothesis that platelet activation could lead to modifi cation of platelet proteins by MDA. However, there previously has been no evidence that this occurs.The investigations reported here demonstrate that activation of platelets ex vivo leads to thromboxane synthasedependent MDA modifi cation of platelet proteins. A stable isotope dilution method for analysis for the dilysyl-MDA cross-link utilizing LC/MS/MS has been developed, making it possible to demonstrate increased levels of MDA adducts of platelet proteins in diseases that are associated with increased platelet activation. Activation of platelets signals cytosolic phospholipase A 2 ␣ activation and an explosive release of arachidonic acid, which is metabolized by cyclooxygenase (COX

Scavenging of reactive dicarbonyls with 2-hydroxybenzylamine reduces atherosclerosis in hypercholesterolemic Ldlr−/− mice

“…Samples (around 1 mg of protein) were digested with proteases for lysyl-lactam adducts 69 . Five nanograms of 13 C 6 -dilysyl-MDA crosslink standard were added to each cell sample and dilysyl-MDA crosslinks were purified 70 . The dilysyl-MDA crosslink was quantified by isotopic dilution by LC–ESI/MS/MS 70 .…”

Malondialdehyde Assay in the Evaluation of Aspirin Antiplatelet Effects

“…MDA is a side product of COX-1 mediated TX formation and is synthesized in equimolar concentrations [11,38]. MDA plays a major role in oxidative stress and is an important biomarker, especially of lipid peroxidation [39].…”

“…It can be measured by fluoroscopy [10] and by spectroscopy [7]. MDA and TXB2 are both products of platelet TX synthase and occur in equimolar accounts [9,11]. Therefore, plasma MDA levels reflect cyclooxygenase (COX)-1 activity [12] and quantify the effect of COX inhibitors [13].…”

Effect of Compound Sbt-828, a New Indole Derivative Exhibiting Antiaggregant Activity, on the Prostacyclin—Thromboxane A2 Balance

“…Increased TXA 2 synthesis in platelets was confirmed by high MDA level [15]. The baseline MDA level in platelets of intact rats was 1.68 rel.…”