title: Covalent adduct formation between the plasmalogen-derived modification product 2-chlorohexadecanal and phloretin.
abstract: 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. 120min, 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.
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Üllen
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Nusshold
authors.affiliation: Christian Doppler Laboratory for Flow Chemistry, Institute of Chemistry, University of Graz, Graz, Austria.
authors.forename: Toma
authors.initials: T
authors.lastname: Glasnov
authors.affiliation: Institute of Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Saf
authors.affiliation: Institute of Chemistry, University of Graz, Graz, Austria.
authors.forename: David
authors.initials: D
authors.lastname: Cantillo
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Gerald
authors.initials: G
authors.lastname: Eibinger
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Helga
authors.initials: H
authors.lastname: Reicher
authors.affiliation: Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria.
authors.forename: Günter
authors.initials: G
authors.lastname: Fauler
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Bernhart
authors.affiliation: Institute of Physiological Chemistry, Medical University of Graz, Graz, Austria.
authors.forename: Seth
authors.initials: S
authors.lastname: Hallstrom
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Nora
authors.initials: N
authors.lastname: Kogelnik
authors.affiliation: Institute of Chemistry, University of Graz, Graz, Austria.
authors.forename: Klaus
authors.initials: K
authors.lastname: Zangger
authors.affiliation: Institute of Chemistry, University of Graz, Graz, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Oliver Kappe
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Ernst
authors.initials: E
authors.lastname: Malle
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria. Electronic address: wolfgang.sattler@medunigraz.at.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sattler
mesh_terms: D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010693:Phloretin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010955:Plasmalogens / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D012756:Sheep; D013552:Swine
chemical_list: C432398:2-chlorohexadecanal; D000447:Aldehydes; D010955:Plasmalogens; D010693:Phloretin
keywords: Blood–brain barrier; Chlorinated fatty aldehyde; Myeloperoxidase; Neuroinflammation; Plasmalogens