Formation of leukotriene B4-coenzyme A ester by rat liver microsomes

Effects of carnitine and its congeners on eicosanoid discharge from rat cells: implications for release of TNFalpha

THE acyl carrier coenzyme A (CoA) is involved in fatty acid metabolism. The carnitine/CoA ratio is of particular importance in regulating the transport of long-chain fatty acids into mitochondria for oxidation. Also CoA has a role in the formation and breakdown of products from both the cyclooxygenase and lipoxygenase pathways of the precursor arachidonic acid. In the present study the effect of 4 days feeding of 300 mg/kg/day of L-carnitine, acetyl Lcarnitine and propionyl L-carnitine on the basal and calcium ionophore (A23187) stimulated release of arachidonic acid metabolites from rat carrageenin elicited peritoneal cells was investigated. There were two series of experiments carried out. In the first, the harvested peritoneal cell population consisted of less than 90% macrophages and additional polymorphonuclear (PMN) leucocytes. The basal release of prostaglandin E₂ (PGE₂), 6-ketoprostaglandin F_1α (6-keto-PGF_1α) and leukotriene B₄ (LTB₄) was stimulated by all treatments. The A23187 stimulated release of 6-keto-PGF_1α and LTB₄ was increased by all three compounds. The 6-keto-PGF_1α:TxB₂ and 6-keto-PGF_1α:LTB₄ ratios were increased by carnitine treatment. These results suggested that carnitine could modify the macrophage component of an inflammatory site in vivo. In the second series of experiments the harvested cell population was highly purified (>95% macrophages) and none of the compounds fed to the rats caused a change of either eicosanoid or TNFα formation. Moreover the 6-keto-PGF_1α:TxB₂ and 6-keto-PGF_1α:LTB₄ ratios were not enhanced by any of the compounds tested. It is conceivable that in the first series the increased ratios 6-keto-PGF_1α:TxB₂ and 6-keto-PGF_1α:LTB₄ reflected the effect of carnitine or its congeners on PMN leucocytes rather than on macrophages.

Effects of short- and long-term feeding of L-carnitine and congeners on the production of eicosanoids from rat peritoneal leucocytes

The effect of short- and long-term feeding with L-carnitine, L-acetyl carnitine and L-propionyl carnitine on the production of eicosanoids from in vitro stimulated carrageenan-induced rat peritoneal macrophages was investigated. Both young (4 weeks) and old (18 months) rats were used. A lower number of cells was isolated from the peritonea of treated than control young rats after 4 d feeding, but after 60 d no differences were observed. A similar reduction in cell number was found when old animals were given L-acetyl carnitine or L-propionyl carnitine (acutely) or L-acetyl carnitine or L-carnitine (chronically). Plasma carnitine levels were higher in young rats given carnitine both chronically and acutely. Carnitine derivatives were without effect. In contrast, levels of total carnitine in the plasma of old rats given L-carnitine and L-acetyl carnitine for 4 d and 60 d were higher than in controls. There was no correlation between total plasma carnitine level and effects on prostaglandin, thromboxane and leukotriene B4 (LTB4) production. In young rats the most important changes were observed in relation to the production of prostacyclin (PGI2), measured as 6 keto-prostaglandin F1 alpha. Prostacyclin production was higher in the groups given carnitine or its derivatives. The net result of the changes in PGI2 was that the 6 keto-prostaglandin F1 alpha: thromboxane B2 and the 6-keto-prostaglandin F1 alpha: LTB4 ratios tended to be higher in cells from young animals following short-term feeding with L-carnitine.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of long-chain fatty acyl coenzyme a thioesters by negative ion fast-atom bombardment mass spectrometry and tandem mass spectrometry

Long-chain acyl Coenzyme A (CoA) is essentially composed of three major chemical groups, fatty acyl-, phosphopantetheino-, and 3', 5',-adenosine diphospho-moieties. The negative ion fast-atom bombardment mass spectrometry spectra of long-chain acyl CoA thioesters were characterized by the formation of abundant [M - H](-) and two distinct classes of fragment ions, one class which retained the acyl group and another class which is related to CoA that contains the phosphopantethene and adenine. The ions which retained the acyl group in the spectrum of palmitoyl CoA appeared at m/z 675, 657, 595, and 577 and were found to decompose by loss of alkylketene observed at m/z 357 and 339. Those ions which retained the adenine group were observed at m/z 426 and 408. In contrast to these ions observed following fast-atom bombardment ionization, tandem mass spectrometry of the [M - H](-), from palmitoyl CoA (m/z 1004), yielded the adenine-containing ions as major products and the acyl-containing ions were of low abundance or not detected. These results suggested that the formation of many characteristic ions observed in direct FAB analysis occurred during the desorption process. The unique relationship between ions which involved the transition from acyl-containing ions to only CoA-containing ions by the loss of alkylketene allowed the development of tandem mass spectrometry protocols for the analysis of acyl CoA mixtures. Precursor scans of either m/z 357 or 339 yielded the identification of each species in a complex mixture. Identification of specific species was obtained with a neutral loss scan of the mass for a specific alkylketene.

Novel 3-hydroxylated leukotriene b4 metabolites from ethanol-treated rat hepatocytes

Coincubations of radiolabeled leukotriene B4 (LTB4) and ethanol with isolated rat hepatocytes led to formation of one dihydroxylated and two novel β-oxidized metabolites of LTB4. The major radioactive peaks from reverse-phase-high performance liquid chromatography (RP-HPLC) eluted with material absorbing UV light maximally at 270 nm, with shoulders at 260 and 280 nm, indicating retention of the conjugated triene structure of the parent molecule in each metabolite structure. Following purification, catalytic reduction, and derivatization, mass spectrometric analysis revealed that all three metabolites were hydroxylated at the C-3 carbon atom based on characteristic ions at m/z 201 and 175 in the electron ionization mass spectra of the metabolites. Negative-ion electron capture mass spectrometry of the metabolites as pentafluorobenzyl (PFB) ester, trimethylsilyl ether derivatives aided structural characterizations while revealing interesting fragmentations. A ketene-containing ion appeared to result from the loss of both PFB groups (one as PFB alcohol), while a lactone alkoxide ion appeared to result following loss of PFB and bis (trimethylsilyl) ether. From these data three novel LTB4 metabolites were suggested to be 3,20-dihydroxy-LTB4 (3,20-diOH-LTB4), 3-hydroxy-18-carboxy-LTB4 (3-OH-18-COOH-LTB4), and 3-hydroxy-16-carboxy-LTB3 (3-OH-16-COOH-LTB3). The significance of the almost exclusive formation of these 3-hydroxylated LTB4 metabolites in the presence of ethanol is currently unknown, but may result from interrupted β-oxidation from the C-1 carboxyl moiety.