Biochemistry of the lipoxygenase pathways in neutrophils

1989 ◽  
Vol 67 (8) ◽  
pp. 936-942 ◽  
Author(s):  
Pierre Borgeat
Keyword(s):  
Arachidonic Acid ◽  
Ring Opening ◽  
Arachidonic Acid Metabolism ◽  
Biologically Active ◽  
Eicosatetraenoic Acid ◽  
Major Pathway ◽  
Inflammatory Reactions ◽  
Conjugated Triene ◽  
Hydroxyeicosatetraenoic Acids ◽  
Active Substances

Three mammalian lipoxygenases have been reported to date. They catalyze the insertion of oxygen at positions 5, 12, and 15 of various 20-carbon polyunsaturated fatty acids. In the case of arachidonic acid, the immediate products are hydroperoxyeicosatetraenoic acids (HPETEs). HPETEs can undergo different transformations. One reaction is a reduction of the hydroperoxy group yielding the corresponding hydroxyeicosatetraenoic acids (HETEs). In the neutrophils, the major pathway of arachidonic acid metabolism is the 5-lipoxygenase. In these cells the 5-HPETE undergoes a cyclization reaction leading to a 5(6)-epoxy(oxido)eicosatetraenoic acid or leukotriene A4. The 5(6)-epoxy fatty acid can undergo three additional transformations: (a) a nonenzymatic hydrolysis to epimeric dihydroxyeicosatetraenoic acids (diHETEs); (b) stereospecific enzymatic hydrolysis to a specific diHETE, leukotriene B4; or (c) ring opening by reduced glutathione (GSH) to yield a peptidolipid, named leukotriene C4, in which GSH is attached via a sulfoether linkage. The leukotrienes constitute a group of biologically active substances probably involved in allergic and inflammatory reactions. The 5(6)-epoxy-eicosatetraenoic acid and the products derived from it contain a conjugated triene unit; the term leukotriene also denotes the cells (leukocytes) recognized to form these products, mainly the neutrophils, eosinophils, basophils, monocytes, mast cells, and macrophages. In the present article various aspects of the biochemistry of the lipoxygenase pathways of neutrophils are reviewed.Key words: arachidonic acid, leukotrienes, leukocytes, lipoxygenase, inflammation.

The interaction Between Arachidonic Acid Metabolism and Homocysteine

2020 ◽  
Vol 20 ◽  
Author(s):  
Elisa Domi ◽  
Malvina Hoxha ◽  
Bianka Hoxha ◽  
Bruno Zappacosta
Keyword(s):  
Cardiovascular Disease ◽  
Arachidonic Acid ◽  
Acid Metabolism ◽  
Neurological Diseases ◽  
Arachidonic Acid Metabolism ◽  
Epoxyeicosatrienoic Acids ◽  
Pathological Conditions ◽  
Literature Searches ◽  
Hydroxyeicosatetraenoic Acids ◽  
Improve Health

Purpose: Hyperhomocysteinemia (HHcy) has been considered a risk factor for different diseases including cardiovascular disease (CVD), inflammation, neurological diseases, cancer and many other pathological conditions. Likewise, arachidonic acid (AA) metabolism is implicated in both vascular homeostasis and inflammation as shown by the development of CVD following the imbalance of its metabolites. Aim of The Review: This review summarizes how homocysteine (Hcy) can influence the metabolism of AA. Methods: In silico literature searches were performed on PubMed and Scopus as main sources. Results: Several studies have shown that altered levels of Hcy, through AA release and metabolism, can influence the synthesis and the activity of prostaglandins (PGs), prostacyclin (PGI₂), thromboxane (TXA), epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs). Conclusions: We believe that by targeting Hcy in AA pathways, novel compounds with better pharmacological and pharmacodynamics benefits may be obtained and that this information is valuable for dietician to manipulate diets to improve health.

Reduced arachidonate metabolism in ATP-depleted myocardial cells occurs early in cell injury

1990 ◽  
Vol 259 (2) ◽  
pp. H582-H591 ◽  
Author(s):  
G. E. Revtyak ◽  
L. M. Buja ◽  
K. R. Chien ◽  
W. B. Campbell
Keyword(s):  
Arachidonic Acid ◽  
Acid Metabolism ◽  
Cell Injury ◽  
Arachidonic Acid Metabolism ◽  
Atp Depletion ◽  
Neonatal Rat ◽  
Eicosatetraenoic Acid ◽  
Metabolic Inhibitors ◽  
Early Event ◽  
Myocardial Cells

Exposure of cultured neonatal rat myocardial cells to metabolic inhibitors results in cellular ATP depletion. If prolonged, arachidonic acid is released from membrane phospholipid and irreversible cell injury may ensue. The present study was undertaken to identify the major products of arachidonic acid formed when myocardial cells are depleted of ATP by the metabolic inhibitors 2-deoxy-D-glucose (2-DG) and oligomycin (OG). Under basal conditions, myocardial cells metabolize [3H]arachidonic acid to 6-keto-[3H]prostaglandin (PG)F1 alpha, [3H]PGE2, [3H]PGF2 alpha, 12-[3H]hydroxy-6,8,11,14-eicosatetraenoic acid (12-[3H]HETE) and 11-[3H]HETE, indicating that these cells contain both cyclooxygenase and lipoxygenase pathways. After exposure of myocardial cells to 10 mM 2-DG and 0.1 micrograms/ml OG for 4 h, the basal release of 6-keto-PGF1 alpha and PGE2 is reduced by 3.4-fold and 2-fold, respectively. Supernatants obtained from cells prelabeled with [3H]arachidonic acid and treated with 2-DG and OG for 4 or 12 h did not contain detectable [3H]prostaglandins or [3H]HETEs, but only [3H]arachidonic acid when compared with untreated cells. After 4 and 12 h of treatment with 2-DG and OG, there was a 3.4- and 4.4-fold net release of endogenous arachidonic acid from treated compared with untreated cells. When stimulated with bradykinin, melittin (a phospholipase activator), or arachidonic acid, the synthesis of 6-keto-PGF1 alpha increased to a similar extent in both 2-DG- and OG-treated and -untreated cells. Hence, ATP-depleted myocardial cells do not convert arachidonic acid to oxygenated metabolites under basal conditions. The reduced arachidonic acid metabolism during ATP depletion is not due to direct inactivation of cyclooxygenase or membrane phospholipase. This impairment in arachidonic acid metabolism may represent an early event in myocardial cell injury.

scholarly journals Incorporation of platelet and leukocyte lipoxygenase metabolites by cultured vascular cells

Blood ◽  
1986 ◽  
Vol 67 (2) ◽  
pp. 373-378 ◽  
Author(s):  
AI Schafer ◽  
H Takayama ◽  
S Farrell ◽  
MA Jr Gimbrone
Keyword(s):  
Endothelial Cells ◽  
Arachidonic Acid ◽  
Smooth Muscle ◽  
Fatty Acid ◽  
Smooth Muscle Cells ◽  
Vascular Function ◽  
Muscle Cells ◽  
Arachidonic Acid Metabolism ◽  
Eicosatetraenoic Acid

Abstract When arachidonic acid metabolism is studied during platelet-endothelial interactions in vitro, the predominant cyclooxygenase end products of each cell type (thromboxane B2 and 6-keto-prostaglandin-F1 alpha, respectively) are essentially completely recovered in the cell-free supernatants of these reactions. In contrast, 50% of 12-hydroxy- 5,8,10,14-eicosatetraenoic acid (12-HETE), the major lipoxygenase metabolite from platelets, is released into the cell-free supernatant. In investigating the basis of this observation, we have found that platelet lipoxygenase metabolites were generated to the same extent during these coincubations but became rapidly incorporated into the endothelial cells. The endothelial cell-associated 12-HETE was present not only as free fatty acid, but was also incorporated into cellular phospholipids and triglycerides. When purified 3H-12-HETE, 3H-5-HETE (the major hydroxy acid lipoxygenase product of leukocytes), and 3H- arachidonic acid (the common precursor of these metabolites) were individually incubated with suspensions of cultured bovine aortic endothelial cells or smooth muscle cells, different patterns of intracellular lipid distribution were found. In endothelial cells, 12- HETE was incorporated equally into phospholipids and triglycerides, whereas 5-HETE was incorporated preferentially into triglycerides, and arachidonic acid was incorporated into phospholipids. In smooth muscle cells, both 12-HETE and 5-HETE showed more extensive incorporation into triglycerides. The rapid and characteristic incorporation and esterification of platelet and leukocyte monohydroxy fatty acid lipoxygenase products by endothelial and smooth muscle cells suggests a possible physiologic role for these processes in regulating vascular function.

Angiotensin II-induced relaxation of fowl aorta

1988 ◽  
Vol 255 (4) ◽  
pp. R591-R599 ◽  
Author(s):  
K. Yamaguchi ◽  
H. Nishimura
Keyword(s):  
Arachidonic Acid ◽  
Angiotensin Ii ◽  
Arachidonic Acid Metabolism ◽  
Isometric Tension ◽  
Eicosatetraenoic Acid ◽  
Ang Ii ◽  
Acid Metabolites ◽  
Relaxation Responses ◽  
Underlying Mechanisms ◽  
Dose Dependent

Angiotensin II (ANG II) decreases blood pressure of fowl. To characterize the vasodilating action of ANG II and its underlying mechanisms, we examined the effect of [Asp1, Val5]ANG II (fowl ANG II) on isometric tension of fowl aortic rings. [Val5]ANG II (10(-8) to 10(-5) M) produced rapid, reversible, dose-dependent relaxation of aortas precontracted with phenylephrine. [Sar1,Ile8]ANG II blocked ANG II-induced relaxation; propranolol, atropine, methysergid, pyrilamine, and cimetidine did not. Endothelium removal abolished relaxation responses to ANG II and acetylcholine but not to isoproterenol or sodium nitroprusside. Inhibitors of phospholipase or arachidonic acid metabolism (quinacrine, indomethacin, 5,8,11,14-eicosatetraenoic acid, hydroquinone, metyrapone, SKF 525A) and a calcium channel blocker (verapamil) did not inhibit ANG II-induced relaxation, whereas indomethacin nearly completely blocked arachidonic acid-induced dilation of aortas with or without endothelia. Guanosine 3',5'-cyclic monophosphate (cGMP) levels in the aorta increased 15 s after ANG II application. Aortic relaxation was caused by 8-bromo-cGMP with or without intact endothelium. These results suggest that ANG II-induced relaxation of fowl aortas involves 1) an endothelium-dependent mechanism and 2) cGMP but not arachidonic acid metabolites.

scholarly journals A New Pathway for Arachidonic Acid Metabolism in Human Platelets

1977 ◽  
Author(s):  
S. Rittenhouse-Simmons ◽  
F. A. Russell ◽  
D. Deykin
Keyword(s):  
Arachidonic Acid ◽  
Acid Metabolism ◽  
De Novo ◽  
Platelet Rich Plasma ◽  
Gel Filtration ◽  
Kinetic Studies ◽  
Arachidonic Acid Metabolism ◽  
Biologically Active ◽  
Resting Cells ◽  
Active Metabolites

We are reporting a novel pathway of arachidonic acid metabolism in the phosphatides of thrombin-activated platelets. For kinetic studies of arachidonic acid turnover, platelet phosphatides were labeled by incubation of platelet rich plasma with (3H)-arachidonic acid for 15 min. Unincorporated isotope was removed during subsequent gel-filtration. Platelet phosphatides were resolved and quantitated following two-dimensional silica paper chromatography of chloroform/methanol extracts of incubated platelets. Plasmalogen phosphatidylethanolamine (PPE) was examined on paper chromatograms after its breakdown to lysoPPE with HgCl2. In other experiments, gel-filtered platelets were incubated with (14C)-glycerol to monitor de novo phosphatide synthesis. (3H)-Arachidonic acid was released from phosphatidylcholine and phosphatidylinositol of pre-labeled platelets exposed to thrombin and appeared increasingly in PPE in acyl linkage at glycerol-C-2. (3H)-Arachidonic acid was not found in PPE of resting cells. Maximum transfer occurred with 5 U/ml of thrombin and 15 min, of incubation, with t½ of 2½ min., and was Ca+2 dependent. The presence of aspirin, indomethacin, or eicosatetraynoic acid did not prevent the thrombin-activated transfer of (3H)-arachidonic acid to PPE. The stimulated incorporation of (3H)-arachidonic acid into PPE was not accompanied by a stimulation of (14C)-glycerol uptake into this phosphatide. We suggest that perturbation of the platelet may activate a phospholipase A2 leading to turnover of arachidonic acid in PPE, which is rich in this fatty acid. Such turnover may provide substrate for conversion by cyclo-oxygenase and lipoxydase to biologically active metabolites, and therefore, may offer a locus for regulation of prostaglandin synthesis in the human platelet.

Kinetic profile of the rat CYP4A isoforms: arachidonic acid metabolism and isoform-specific inhibitors

1999 ◽  
Vol 276 (6) ◽  
pp. R1691-R1700 ◽  
Author(s):  
Xuandai Nguyen ◽  
Mong-Heng Wang ◽  
Komandla M. Reddy ◽  
John R. Falck ◽  
Michal Laniado Schwartzman
Keyword(s):  
Arachidonic Acid ◽  
Biological Effects ◽  
Catalytic Efficiency ◽  
Arachidonic Acid Metabolism ◽  
Biologically Active ◽  
Epoxyeicosatrienoic Acid ◽  
Active Metabolites ◽  
Extrahepatic Tissues ◽  
Renal Tubular ◽  
Biologically Active Metabolites

20-Hydroxyeicosatetraenoic acid (HETE), the cytochrome P-450 (CYP) 4A ω-hydroxylation product of arachidonic acid, has potent biological effects on renal tubular and vascular functions and on the control of arterial pressure. We have expressed high levels of the rat CYP4A1, -4A2, -4A3, and -4A8 cDNAs, using baculovirus and Sf 9 insect cells. Arachidonic acid ω- and ω-1-hydroxylations were catalyzed by three of the CYP4A isoforms; the highest catalytic efficiency of 947 nM−1 ⋅ min−1for CYP4A1 was followed by 72 and 22 nM−1 ⋅ min−1for CYP4A2 and CYP4A3, respectively. CYP4A2 and CYP4A3 exhibited an additional arachidonate 11,12-epoxidation activity, whereas CYP4A1 operated solely as an ω-hydroxylase. CYP4A8 did not catalyze arachidonic or linoleic acid but did have a detectable lauric acid ω-hydroxylation activity. The inhibitory activity of various acetylenic and olefinic fatty acid analogs revealed differences and indicated isoform-specific inhibition. These studies suggest that CYP4A1, despite its low expression in extrahepatic tissues, may constitute the major source of 20-HETE synthesis. Moreover, the ability of CYP4A2 and -4A3 to catalyze the formation of two opposing biologically active metabolites, 20-HETE and 11,12-epoxyeicosatrienoic acid, may be of great significance to the regulation of vascular tone.

Arachidonic Acid Metabolism in the Neonatal Platelet

PEDIATRICS ◽  
1982 ◽  
Vol 69 (6) ◽  
pp. 714-718
Author(s):  
Marie J. Stuart ◽  
Judith B. Allen
Keyword(s):  
Arachidonic Acid ◽  
Acid Metabolism ◽  
Arachidonic Acid Metabolism ◽  
Thromboxane B2 ◽  
Eicosatetraenoic Acid ◽  
Lipoxygenase Product ◽  
Adult Control ◽  
Control Subjects

An assessment of arachidonic acid metabolism in the platelet of the neonate was performed. The uptake of [14C]arachidonic acid into platelets of both the neonate and the adult were similar. Neonatal platelets, however, released a significantly greater amount (P < .001) of prelabeled arachidonic acid (24.7% ± 2.8%) in response to the physiologic agent thrombin when compared with platelets from adult control subjects (14.6% ± 0.8%). When the activities of the lipoxygenase (12-L-hydroxy-5,8,10,14-eicosatetraenoic acid) and cyclooxygenase pathways (12-L-hydroxy-5,8,10-heptadecatrienoic acid and thromboxane B2) were evaluated following incubation of platelets with [14C]arachidonic acid, significant differences were observed between adult and neonatal platelets. Platelets from the neonate produced less (P < .01) thromboxane B2 (11.1% ± 1.7%) when compared with platelets from adult control subjects (19% ± 1.7%). In contrast, the lipoxygenase product 12-L-hydroxy-5,8,l0,14-eicostatetraenoic acid was increased (P < .005) in the platelet from the neonate (41.5% ± 2%), when compared with the adult (31.2% ± 2.1%). The observation that the availability of substrate arachidonic acid is increased in the platelet of the neonate may have general implications in neonatal pathophysiologic processes.

Preferential increase in prostaglandin endoperoxide H synthase compared with lipoxygenase activity in sheep placenta and amnion at term pregnancy and after intrafetal glucocorticoid administration

1993 ◽  
Vol 139 (2) ◽  
pp. 195-204 ◽  
Author(s):  
D. A. Langlois ◽  
L. J. Fraher ◽  
M. W. Khalil ◽  
M. Fraser ◽  
J. R. G. Challis
Keyword(s):  
Arachidonic Acid ◽  
Late Pregnancy ◽  
Mean Value ◽  
Arachidonic Acid Metabolism ◽  
Arachidonic Acid Content ◽  
Lipoxygenase Products ◽  
Specific Increase ◽  
Endoperoxide H Synthase ◽  
Term Labour ◽  
Hydroxyeicosatetraenoic Acids

ABSTRACT Prostaglandins (PGs) have been implicated as stimulants to myometrial contractility at parturition in many species. To determine whether the increased production of PGs at parturition reflects a general increase in the metabolism of arachidonic acid or a specific increase in PG endoperoxide H synthase (PGHS) compared with lipoxygenase activities, and to determine intrauterine sites of these activities, we examined the metabolism of [3H]arachidonic acid by homogenates of placenta, amnion and chorion from sheep at days 78–80, 100–105, 135–140 of pregnancy and at term (day 145). Tissues were also obtained from fetuses at day 125; four of these were infused for 84 h with cortisol and four were used as saline-treated controls. The endogenous arachidonic acid content at the start of incubation was measured by capillary gas chromatography. Radioactive metabolites were separated and quantified by reverse-phase high-pressure liquid chromatography. At each gestational age arachidonic acid was converted to PGs, leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs). Conversion to PGs was greater in amnion than in chorion or placenta between days 78 and 140. The formation of PGs rose in placenta at term to a mean value twice that of amnion and ten times that of chorion. In amnion, the ratio of PG: LT rose significantly at term relative to 100–140 days of gestation. In placenta, the ratio of PG: LT produced from arachidonic acid and the ratio of total PGHS: lipoxygenase products rose significantly at term. In the day-125 fetuses treated with cortisol there was a significant increase in PG production relative to that in control fetuses infused with saline in placenta, amnion and chorion; the placenta and amnion being the major sites of PG production. Production of LTs and HETEs also rose significantly in the chorion and the placenta relative to controls. In both the placenta and the amnion there was a significant increase in the ratio of total PGHS to lipoxygenase products formed. We conclude that at term labour and in labour induced by intrafetal cortisol infusion, the placenta is the major site of arachidonic acid metabolism, and that there is a preferential increase in the formation of PGs over lipoxygenase products. These results are consistent with the suggestion that there is an increase in the expression or activity of PGHS in the placenta of sheep in late pregnancy. Journal of Endocrinology (1993) 139, 195–204

scholarly journals Leukotriene generation by eosinophils.

1982 ◽  
Vol 155 (2) ◽  
pp. 390-402 ◽  
Author(s):  
A Jörg ◽  
W R Henderson ◽  
R C Murphy ◽  
S J Klebanoff
Keyword(s):  
Arachidonic Acid ◽  
Calcium Ionophore ◽  
Leukotriene B4 ◽  
Arachidonic Acid Metabolism ◽  
Calcium Ionophore A23187 ◽  
Eicosatetraenoic Acid ◽  
Gas Chromatography Mass Spectrometry ◽  
Ionophore A23187 ◽  
Lipoxygenase Pathway ◽  
Leukotriene D4

Horse eosinophils purified to greater than 98% generated slow reacting substance (SRS) when incubated with the calcium ionophore A23187. On a per cell basis, eosinophils generated four to five times the SRS produced by similarly treated horse neutrophils. Eosinophil SRS production was inhibited by 5,8,11,14-eicosatetraynoic acid and augmented by indomethacin and arachidonic acid, suggesting that it was a product(s) of the lipoxygenase pathway of arachidonic acid metabolism. Compounds with SRS activity were purified by high-pressure liquid chromatography (HPLC) and identified by ultraviolet spectra, spectral shift on treatment with lipoxygenase, incorporation of [14C]arachidonic acid, gas chromatography-mass spectrometry, and comparison of retention times on HPLC to authentic standards. The eosinophil products characterized were 5-(S), 12-(R)-dihydroxy-6-cis-8, 10-trans-14-cis-eicosatetraenoic acid (leukotriene B4) and its 5-(S), 12-(R)-6-trans and 5-(S), 12-(S)-6-trans isomers, 5-(S)-hydroxy-6-(R)-S-glutathionyl-7,9-trans-11, 14-cis-eicosatetraenoic acid (leukotriene C4) and its 11-trans isomer, and 5-(S)-hydroxy-6-(R)-S-cysteinylglycine-7,9-trans-11,14-cis-eicosatetraenoic acid (leukotriene D4).

Cultured bovine coronary arterial endothelial cells synthesize HETEs and prostacyclin

1988 ◽  
Vol 254 (1) ◽  
pp. C8-C19 ◽  
Author(s):  
G. E. Revtyak ◽  
A. R. Johnson ◽  
W. B. Campbell
Keyword(s):  
Endothelial Cells ◽  
Arachidonic Acid ◽  
Cell Monolayer ◽  
Arachidonic Acid Metabolism ◽  
Biologically Active ◽  
Vasoactive Agent ◽  
Exogenous Arachidonic Acid ◽  
Coronary Endothelial Cells ◽  
Qualitative Pattern ◽  
Von Willebrand’S Factor

Arachidonic acid metabolism was examined in endothelial cells cultured from bovine coronary arteries. In culture, these cells exhibit specific characteristics of endothelial cells. They form a contact-inhibited monolayer with a cobblestone appearance, contain immunoreactive von Willebrand's factor antigen, and have angiotensin I converting enzyme activity. Prostacyclin was the major prostaglandin synthesized from exogenous and endogenous arachidonic acid in these cells. In addition, exogenous arachidonic acid was metabolized to small amounts of prostaglandin E2 (PGE2) and several relatively nonpolar metabolites including 12-, 15-, and 11-hydroxyeicosatetraenoic acids (12-, 15-, and 11-HETE). Histamine, bradykinin, and thrombin increased PGI2 synthesis in these bovine coronary endothelial cells. Of these agonists, bradykinin was the most potent, increasing basal PGI2 release by fourfold. More vigorous stimulation of the cells with mechanical disruption of the cell monolayer, melittin, or A23187 resulted in release of both PGI2 and PGE2. Pretreatment of cells with exogenous arachidonic acid (10(-5) M) abolished their responsiveness to subsequent stimulation by arachidonic acid or vasoactive agents, but not PGH2. Furthermore, treatment of cells with 15-HPETE (10(-7)-10(-4) M), but not 15-HETE, specifically inhibited basal as well as A23187-stimulated PGI2 release. PGE2 release was increased slightly after 15-HPETE treatment. These studies indicate that bovine coronary endothelial cells can metabolize arachidonic acid to several biologically active products and that PGI2 synthesis by these cells is specifically related to the type of vasoactive agent employed. Both the qualitative pattern and quantity of eicosanoids synthesized by bovine coronary endothelial cells differ substantially from endothelial cells isolated from noncardiac vascular beds.

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