Formation of lysophospholipids from unsaturated phosphatidylcholines under the influence of hypochlorous acid

The formation of lysophosphatidylcholines from unsaturated phosphatidylcholines upon treatment with hypochlorous acid was evaluated by means of MALDI-TOF mass spectrometry and 31P NMR spectroscopy. With an increasing number of double bonds in a fatty acid residue, the yield of lysophosphatidylcholines with a saturated fatty acid residue increased considerably in comparison to the total amount of higher molecular weight products like chlorohydrins and glycols. High amounts of lysophosphatidylcholines were formed from phospholipids containing arachidonic or docosahexaenoic acid residues. In phospholipids with monounsaturated fatty acid residues, the position of the double bond did not influence the yield of lyso-products. Besides the exclusive formation of chlorohydrin and glycol, hypochlorous acid caused the cleavage of the unsaturated fatty acid residue independent of its location at the first or second position of the glycerol backbone. In contrast, strong alkaline conditions, i.e. saponification led also to a hydrolysis of the saturated fatty acid residue from phosphatidylcholines. It is concluded that both MALDI-TOF mass spectrometry and 31P NMR spectroscopy are able to detect the formation of lysophosphatidylcholines. We conclude also that the formation of lysophospholipids from unsaturated phosphatidylcholines by hypochlorous acid can be relevant in vivo under acute inflammatory conditions.     

Interaction of exogenous hypochlorite or hypochlorite produced by myeloperoxidase + H2O2 + Cl- system with unsaturated phosphatidylcholines

The interaction between unsaturated phosphatidylcholines and either exogenous or endogenous (produced by the enzyme system involving myeloperoxidase (MPO), H₂ O₂ ,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-oleoyl-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-oleoyl-sn-glycero-3-phosphocholine were lysophosphatidylcholine (1-stearoyl-2-oleoyl-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 +H₂ O₂ +Cl^–,at pH 6.0. In the absence of the enzyme or either of its substrates (H₂ O₂ 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.     

Structural changes in erythrocyte membranes in nephropathy

Spin probes were used to study alteration of red cell membranes in nephropathy of varying degree of gravity. Iminoxyl radicals of the lipid nature were applied as spin probes, in particular 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyl (probe I). It was shown that in nephropathy, the orderliness parameter increases and the hydrophoby of probe I localized in a red cell suspension of nephropathy patients diminishes as compared with analogous parameters in healthy pregnant women. This attests to both immobilization of the fatty acid chains of phospholipids and to an increase in the polarity of the lipid bilayer in the area of probe localization. It was established that diminution of probe I hydrophoby is in a satisfactory agreement with the disease gravity and the degree of edema in patients. It was noted that alterations discovered in red cell membranes in nephropathy are similar to those seen during activation of lipid peroxidation in membranes. The possibility of lipid peroxidation involvement into the pathogenesis of nephropathy is discussed.     

Complementation Analysis of Associative Bacteria Azospirillum brasilense Sp245 and S27 Defective for Motility and Flagellation

Three mutants of Azospirillum brasilense Sp245 incapable of both formation of the polar flagellum (Fla^–-phenotype) and swarming in semisolid media (Swa^–-phenotype) were characterized. These mutants were shown to have lost the 85-MDa plasmid and to carry the Tn5-Mob transposon and pSUP5011 vector in different regions of their genomes. With the use of A. brasilense Sp245 gene bank, the capacity for both polar flagellum formation and swarming was restored in the above mutants and in the previously generated transposon mutants A. brasilense Sp245 and S27. The transconjugants obtained were only slightly motile in the liquid culture. In the gene bank of Sp245, the recombinant plasmids carrying wild-type fla/swa loci were identified.     

Impact of Antimony Fluoride Compounds on Soil Microflora and Methods of Their Detoxification

Microbiology - Solutions of SbF3 and NaSbF4 (50 and 100 mg/L) were found to have a toxic effect on soil microflora. At the final concentration of 50 mg/L, bacteria and microscopic fungi were...     

Formation of pAS8-1213 cointegrate with one of the plasmids of Azospirillum brasilense Sp245

Inheritance of the plasmid vector pAS8-1213 in Azospirillum brasilense Sp245 cells has been studied. The plasmid pAS8-1213 is shown to be uncapable of autonomous replication in the new host but able to integrate into the genetic structures of Azospirillum with high frequency. 90-95% of KmR-transconjugants of A. brasilense harbor pAS8-1213 cointegrated with the smaller host plasmid pAbSP245c(85Md). The formed cointegrate can be transferred into Azospirillum spp. 75 and RecA- strains of E. coli (HB101 and DH1) and stably maintained in these cells. The IS21 element inherent of the plasmid pAS8-1213 is supposed to participate in pAS8-1213::pAbSP245c cointegrate formation.     

Free radical modification of lipoproteins and cholesterol accumulation in cells upon atherosclerosis.

An electron spin probe study was made of the effect of lipid peroxidation (LPO) on the structure of surface proteolipid layer of human serum low-density lipoproteins (LDL). The results obtained with a positively charged spin label and stearic acid spin probes with doxyl labels at positions 5, 12, and 16 revealed that LPO caused a decrease in phospholipid molecule mobility both in the region of polar heads and in the region of acyl chains till the depth of at least 1.7 mm from water-lipid interface. Under relatively high levels of oxidation (more than 6 mumol MDA/g LDL phospholipid) the polarity of lipid phase increased. The decrease in efficiency of tryptophan fluorescence quenching by nitroxide fragments incorporated in hydrophobic regions at the depth of approximately 2 nm from water-lipid interface indicated that lipid-protein interaction was disturbed as a result of oxidation of LDL lipids. In addition, the LPO-induced modification of apo-B, the main protein of LDL, was examined with maleimide spin label. LPO led to increase in mobility of strongly immobilized maleimide labels and in the number of weakly immobilized ones. Oxidized LDL revealed decreased ability to incorporate spin-labeled steroid (androstane) as compared to native ones. LPO-induced structural changes of LDL surface are supposed to be a reason of enhanced accumulation of cholesterol in human monocytes during their incubation with oxidized LDL. The cholesterol content in red cells was shown to be directly correlated to MDA content in apo-B containing lipoproteins but not in whole serum. Our findings suggest that free radical modification of serum lipoproteins but not solely an increased level of LPO products in blood is one important cause for cholesterol accumulation in cells and, apparently, for their transformation into foam cells during atherosclerosis.     

Interaction of the small heat shock protein with molecular mass 25 kDa (hsp25) with actin.

The interaction of heat shock protein with molecular mass 25 kDa (HSP25) and its point mutants S77D + S81D (2D mutant) and S15D + S77D + S81D (3D mutant) with intact and thermally denatured actin was analyzed by means of fluorescence spectroscopy and ultracentrifugation. Wild type HSP25 did not affect the polymerization of intact actin. The HSP25 3D mutant decreased the initial rate without affecting the maximal extent of intact actin polymerization. G-actin heated at 40-45 degrees C was partially denatured, but retained its ability to polymerize. The wild type HSP25 did not affect polymerization of this partially denatured actin. The 3D mutant of HSP25 increased the initial rate of polymerization of partially denatured actin. Heating at more than 55 degrees C induced complete denaturation of G-actin. Completely denatured G-actin cannot polymerize, but it aggregates at increased ionic strength. HSP25 and especially its 2D and 3D mutants effectively prevent salt-induced aggregation of completely denatured actin. It is concluded that the interaction of HSP25 with actin depends on the state of both actin and HSP25. HSP25 predominantly acts as a chaperone and preferentially interacts with thermally unfolded actin, preventing the formation of insoluble aggregates.