Covalent adduct formation between the plasmalogen-derived modification product 2-chlorohexadecanal and phloretin

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Üllen, Andreas ; Nusshold, Christoph ; Glasnov, Toma ; Saf, Robert ; Cantillo, David ; Eibinger, Gerald ; Reicher, Helga ; Fauler, Günter ; Bernhart, Eva ; Hallstrom, Seth ; Kogelnik, Nora ; Zangger, Klaus ; Oliver Kappe, C. ; Malle, Ernst ; Sattler, Wolfgang (2015)
  • Publisher: Elsevier BV
  • Journal: Biochemical Pharmacology, volume 93, issue 4, pages 470-481 (issn: 0006-2952, eissn: 1873-2968)
  • Related identifiers: pmc: PMC4321883, doi: 10.1016/j.bcp.2014.12.017
  • Subject: Chlorinated fatty aldehyde | Plasmalogens | Blood–brain barrier | Neuroinflammation | Biochemistry | Pharmacology | Myeloperoxidase | Article
    mesheuropmc: technology, industry, and agriculture

Hypochlorous acid added as reagent or generated by the myeloperoxidase (MPO)-H2O2-Cl− system oxidatively modifies brain ether-phospholipids (plasmalogens). This reaction generates a sn2-acyl-lysophospholipid and chlorinated fatty aldehydes. 2-Chlorohexadecanal (2-ClHDA), a prototypic member of chlorinated long-chain fatty aldehydes, has potent neurotoxic potential by inflicting blood–brain barrier (BBB) damage. During earlier studies we could show that the dihydrochalcone-type polyphenol phloretin attenuated 2-ClHDA-induced BBB dysfunction. To clarify the underlying mechanism(s) we now investigated the possibility of covalent adduct formation between 2-ClHDA and phloretin. Coincubation of 2-ClHDA and phloretin in phosphatidylcholine liposomes revealed a half-life of 2-ClHDA of approx. 120 min, decaying at a rate of 5.9 × 10−3 min−1. NMR studies and enthalpy calculations suggested that 2-ClHDA-phloretin adduct formation occurs via electrophilic aromatic substitution followed by hemiacetal formation on the A-ring of phloretin. Adduct characterization by high-resolution mass spectroscopy confirmed these results. In contrast to 2-ClHDA, the covalent 2-ClHDA-phloretin adduct was without adverse effects on MTT reduction (an indicator for metabolic activity), cellular adenine nucleotide content, and barrier function of brain microvascular endothelial cells (BMVEC). Of note, 2-ClHDA-phloretin adduct formation was also observed in BMVEC cultures. Intraperitoneal application and subsequent GC–MS analysis of brain lipid extracts revealed that phloretin is able to penetrate the BBB of C57BL/6J mice. Data of the present study indicate that phloretin scavenges 2-ClHDA, thereby attenuating 2-ClHDA-mediated brain endothelial cell dysfunction. We here identify a detoxification pathway for a prototypic chlorinated fatty aldehyde (generated via the MPO axis) that compromises BBB function in vitro and in vivo.
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