Subcellular distribution of lipoxygenase products in rabbit reticulocyte membranes*

Abstract

Mitochondria1 membranes and plasma membranes of rabbit reticulocytes contain oxygenated polyenoic fatty acids such as (9Z,1 1E)-(l3S)-13-hydroxy-9,1l-octadecadienoic acid, 9 s and 9R isomers of (IOE,12Z)-9-hydroxy-10,12-octadecadienoic acid and their all-E isomers. Furthermore (5Z,8Z,112,13E)-(1 5S)-15-hydroxy-5,8,11,13-icosatetraenoic acid, 9-and 13-oxooctadecadienoic acid were detected as minor products. The chemical structure of these products has been identified by co-chromatography with authentic standards, by ultraviolet and infrared spectroscopy, and by gas chromatography/mass spectrometry of the native compounds and their hydrogenated derivatives. The oxygenated fatty acids originate most probably from the intracellular action of the erythroid arachidonate 15-lipoxygenase. In membranes of the mature erythrocyte only small amounts of hydroxy fatty acids were detected. Young peripheral reticulocytes contain more oxygenated polyenoic fatty acids in their membranes than older cells. In mixed cell populations, about 85% of the lipoxygenase products were found esterified to the membrane ester lipids, whereas 15% were associated as free hydroxy fatty acids with the membranes. The hydroxy fatty acid content of the mitochondrial membranes is more than threefold higher than that of the plasma membranes. The pattern of the products isolated from plasma membranes shows a high specificity with (92,llE)-(13S)-13-hydroxy-9,1 I-octadecadienoic acid as the main product. In contrast, the pattern found in the mitochondrial membranes was much more unspecific; a complex mixture of all positional and optical isomers was detected.The data presented indicate that the reticulocyte lipoxygenase in vivo acts on both plasma membranes and mitochondrial membranes. The results are discussed in the light of the involvement of the lipoxygenase in the breakdown of mitochondria and other organelles in reticulocytes during maturation.Reticulocytes of different species [l, 21 contain a lipoxygenase which is able to oxygenate polyenoic fatty acids esterified to membrane lipids [3]. This enzyme was proposed to play an important role in the breakdown of mitochondria during the maturation of red blood cells [4]. Free arachidonic acid was converted by the pure enzyme to a mixture of (52,8Z,lIZ,-13E)- (13S) In contrast to our knowledge of the properties of the isolated enzyme, little is known about the intracellular action of the lipoxygenase. Rabbit reticulocytes exhibit an antimycin-A-resistant oxygen uptake which was partly inhibited by various lipoxygenase inhibitors. This partial inhibition amounts to about 5% of the total oxygen uptake [9]. Recently the occurrence of oxygenated polyenoic fatty acids in the membranes of rabbit reticulocytes has been reported [lo], which indicates the intracelluIar action of the lipoxygenase on membrane lipids.In this study, we report the subcellular distribution of the oxygenated polyenoic fatty acids in various membrane fractions of rabbit reticulocytes and in reticulocytes at different stages of maturation.

Specific inflammatory cytokines regulate the expression of human monocyte 15-lipoxygenase.

“…In addition, these data document changes in membrane composition that occur due to 15-lipoxygenase. While the significance of the observed membrane remodeling is not entirely clear, it has been shown that exogenous 15-HETE can be reincorporated into the membrane (20,21) in such a way that it structurally alters the second messenger diacylglycerol, which is released during cell signaling (21). Alternatively, mammalian 15-lipoxygenases are capable of directly oxygenating phospholipids (22) and biomembranes (3). This oxygenation of membrane lipids is proposed to initiate the degradation of intracellular organelles during red-cell maturation (23,24).…”

“…Alternatively, mammalian 15-lipoxygenases are capable of directly oxygenating phospholipids (22) and biomembranes (3). This oxygenation of membrane lipids is proposed to initiate the degradation of intracellular organelles during red-cell maturation (23,24). Hence monocyte 15-lipoxygenase may be recruited to degrade intracellular organelles during differentiation or to digest extracellular particles during phagocytosis.…”

“…The 12-and 15-lipoxygenases are involved in the biosynthesis of other bioactive metabolites from free arachidonic acid, such as lipoxins (1). However, 15-lipoxygenase is unique among the human lipoxygenases in that it is capable of oxygenating polyenoic fatty acids esterified to membrane lipids (3) or lipoproteins (H.K., unpublished observation) and hence it may have biological roles distinct from its action on free arachidonic acid.…”

Accumulation of 9- and 13-KODEs in response to jasmonic acid treatment and pathogenic infection in rice

“…32) The presence of KODE in plant tissues was reported in Arabidopsis 33) and the soybean (Glycine max). 34) KODEs can be produced directly and efficiently by purified lipoxygenases, 35,36) but the enzymatic dehydroge- Fig.…”

Modulation of soybean lipoxygenase expression and membrane oxidation by water deficit

“…The free fatty aCIds were separated from the esterified fatty aCIds on octadecyl-SPE columns accordmg to Kiihn [21], then the absorbances of the fractions were recorded at 205 nm and 235 nm on a Hewlett Packard 8450A double-beam diode array spectrophotometer. The oxidative modification of the membrane lipid fractIOn was expressed by means of the oxidative mdex, I.e.…”