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5'-O-Alkylpyridoxamines: Lipophilic Analogues of Pyridoxamine Are Potent Scavengers of 1,2-Dicarbonyls.

ABSTRACT: Pyridoxamine (PM) is a prospective drug for the treatment of diabetic complications. In order to make zwitterionic PM more lipophilic and improve its tissue distribution, PM derivatives containing medium length alkyl groups on the hydroxymethyl side chain were prepared. The synthesis of these alkylpyridoxamines (alkyl-PMs) starting from pyridoxine offers high yields and is amenable to bulk preparations. Interestingly, alkyl-PMs were found to react with methylglyoxal (MGO), a major toxic product of glucose metabolism and autoxidation, several orders of magnitude faster than PM. This suggests the formation of nonionic pyrido-1,3-oxazine as the key step in the reaction of PM with MGO. Since the primary target of MGO in proteins is the guanidine side chain of arginine, alkyl-PMs were shown to be more effective than PM in reducing the modification of N-?-benzoylarginine by MGO. Alkyl-PMs in the presence of MGO also protected the enzymatic activity of lysozyme that contains several arginine residues next to its active site. Alkyl-PMs can be expected to trap MGO and other toxic 1,2-carbonyl compounds more effectively than PM, especially in lipophilic tissue environments, thus protecting macromolecules from functional damage. This suggests potential therapeutic uses for alkyl-PMs in diabetes and other diseases characterized by the elevated levels of toxic dicarbonyl compounds.

SUBMITTER: Amarnath V

PROVIDER: S-EPMC4996123 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Project description:ObjectiveOxidative stress contributes to the development of insulin resistance (IR) and atherosclerosis. Peroxidation of lipids produces reactive dicarbonyls such as Isolevuglandins (IsoLG) and malondialdehyde (MDA) that covalently bind plasma/cellular proteins, phospholipids, and DNA leading to altered function and toxicity. We examined whether scavenging reactive dicarbonyls with 5'-O-pentyl-pyridoxamine (PPM) protects against the development of IR and atherosclerosis in Ldlr-/- mice.MethodsMale or female Ldlr-/- mice were fed a western diet (WD) for 16 weeks and treated with PPM versus vehicle alone. Plaque extent, dicarbonyl-lysyl adducts, efferocytosis, apoptosis, macrophage inflammation, and necrotic area were measured. Plasma MDA-LDL adducts and the in vivo and in vitro effects of PPM on the ability of HDL to reduce macrophage cholesterol were measured. Blood Ly6Chi monocytes and ex vivo 5-ethynyl-2'-deoxyuridine (EdU) incorporation into bone marrow CD11b+ monocytes and CD34+ hematopoietic stem and progenitor cells (HSPC) were also examined. IR was examined by measuring fasting glucose/insulin levels and tolerance to insulin/glucose challenge.ResultsPPM reduced the proximal aortic atherosclerosis by 48% and by 46% in female and male Ldlr-/- mice, respectively. PPM also decreased IR and hepatic fat and inflammation in male Ldlr-/- mice. Importantly, PPM decreased plasma MDA-LDL adducts and prevented the accumulation of plaque MDA- and IsoLG-lysyl adducts in Ldlr-/- mice. In addition, PPM increased the net cholesterol efflux capacity of HDL from Ldlr-/- mice and prevented both the in vitro impairment of HDL net cholesterol efflux capacity and apoAI crosslinking by MPO generated hypochlorous acid. Moreover, PPM decreased features of plaque instability including decreased proinflammatory M1-like macrophages, IL-1β expression, myeloperoxidase, apoptosis, and necrotic core. In contrast, PPM increased M2-like macrophages, Tregs, fibrous cap thickness, and efferocytosis. Furthermore, PPM reduced inflammatory monocytosis as evidenced by decreased blood Ly6Chi monocytes and proliferation of bone marrow monocytes and HSPC from Ldlr-/- mice.ConclusionsPPM has pleotropic atheroprotective effects in a murine model of familial hypercholesterolemia, supporting the therapeutic potential of reactive dicarbonyl scavenging in the treatment of IR and atherosclerotic cardiovascular disease.

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5'-O-Alkylpyridoxamines: Lipophilic Analogues of Pyridoxamine Are Potent Scavengers of 1,2-Dicarbonyls.

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