Interaction of Exogenous Hypochlorite or Hypochlorite Produced by Myeloperoxidase + H₂O₂ + Cl^- System with Unsaturated Phosphatidylcholines

O. M. Panasenko^1*, A. N. Osipov², J. Schiller³, and J. Arnhold³

¹Research Institute of Physico-Chemical Medicine, ul. Malaya Pirogovskaya 1a, Moscow, 119828 Russia; fax: (095) 246-4490; E-mail: oleg-panasenko@newmail.ru

²Russian State Medical University, ul. Ostrovityanova 1, Moscow, 117513 Russia; E-mail: an-osipov@mail.ru

³Institute of Medical Physics and Biophysics, University of Leipzig, Liebigstrasse 27, Leipzig, 04103, Germany; fax: (49-341) 971-5709; E-mail: arnj@server3.medizin.uni-leipzig.de

^* To whom correspondence should be addressed.

Received May 4, 2001; Revision received June 9, 2001

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The interaction between unsaturated phosphatidylcholines and either exogenous or endogenous (produced by the enzyme system involving myeloperoxidase (MPO), H₂O₂, and Cl^-) hypochlorite was studied in multilayer liposomes containing oleic, linoleic, and arachidonic acid residues using MALDI-TOF mass spectrometry. At pH 7.4, hypochlorite reacts with the double bond of the oleic acid residue in 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine producing oleic acid chlorohydrin as the main product. Minor amounts of glycols and epoxides were also detected. The main products of the reaction of hypochlorite with 1-stearoyl-2-linoleyl-sn-glycero-3-phosphocholine were mono- and di-chlorohydrins of linoleic acid. The signals of monoglycol, epoxide, and glycol- or epoxide-containing monochlorohydrin derivatives were also present in the mass spectrum. The main products of the reaction of hypochlorite with 1-stearoyl-2-arachidonyl-sn-glycero-3-phosphocholine were lysophosphatidylcholine (1-stearoyl-sn-glycero-3-phosphocholine) and mono-, di-, and trichlorohydrin. Monoglycol and its derivatives containing one or two chlorohydrin groups were also detected. Along with those, carbonyl compounds (aldehyde and acid) formed as a result of double bond breakage in fifth position of arachidonate were detected. Monochlorohydrin was also found when liposomes comprising 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine were incubated in the presence of enzymatic mixture, MPO + H₂O₂ + Cl^-, at pH 6.0. In the absence of the enzyme or either of its substrates (H₂O₂ or Cl^-) or in the presence of the MPO inhibitor (sodium azide) or hypochlorite scavengers (taurine or methionine), monochlorohydrin formation was not observed. These data confirm the suggestion that just the hypochlorite generated in MPO-catalysis provides for chlorohydrin formation. Thus, the use of MALDI-TOF mass spectrometry has shown, along with chlorohydrins, glycols and epoxides as the products of hypochlorite interaction with unsaturated phosphatidylcholines at physiological pH. It was first determined that hypochlorite breaks double bonds in polyunsaturated phosphatidylcholine and also causes lysophosphatidylcholine formation.

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KEY WORDS: hypochlorite, myeloperoxidase, phosphatidylcholine, unsaturated lipids, chlorohydrin, glycol, epoxide, lysophosphatidylcholine, MALDI-TOF (matrix assisted laser desorption/ionization time-of-flight) mass spectrometry

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