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B N Setty

Publications and source records attributed to B N Setty.

31 records · Page 2Linked to original sources
PubMed1988

Changes in oxygen tension and effects on cyclooxygenase metabolites: III. Decrease of retinal prostacyclin in kittens exposed to hyperoxia.

The acute phase of oxygen-induced retinopathy is associated with vasoconstriction and occlusion of the retinal vessels. Because this acute vasoobliterative phase could be due to the inhibition in retinal vessels of the production of the potent vasodilator and antithrombotic metabolite prostacyclin, animal experiments were performed to assess this possibility. Eight litters of 27 kittens (four to six days of age) were used. Control kittens were left in room air; hyperoxic kittens were placed in 80% oxygen for 48 hours; recovery kittens were returned to room air for 24 hours following hyperoxic exposure. Following treatments, the animals were killed, retinas isolated, and prostaglandin formation assessed. Retinal tissues produced 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha, prostaglandin E2, and thromboxane B2 from exogenous arachidonate. A significant (approximately 33%) reduction in retinal 6-keto-prostaglandin F1 alpha (the end product of prostacyclin) was observed both in the hyperoxic and recovery litter mates when compared with controls. Both of the experimental groups also demonstrated a reduction in total retinal prostanoids that paralleled the changes observed in prostacyclin, suggesting that the biochemical effect of hyperoxia on retinal vascular arachidonic acid metabolism occurred at the level of cyclooxygenase. A decrease in the local production of prostacyclin during hyperoxia is consistent with the histologic retinal changes observed during the acute phase of oxygen-induced retinopathy.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

The mitogenic effect of 15- and 12-hydroxyeicosatetraenoic acid on endothelial cells may be mediated via diacylglycerol kinase inhibition.

15-Hydroxyeicosatetraenoic acid (15-HETE), a major lipoxygenase metabolite of arachidonic acid in fetal bovine aortic endothelial cells, was a mitogen for these cells, stimulating both cell proliferation and DNA synthesis in the presence of serum and serum-deprived cells. In [14C]arachidonic acid-labeled confluent endothelial cell monolayers, 15-HETE (30 microM) caused an elevation of [14C]diacylglycerol (DAG) with a concomitant decrease in cellular [14C]phosphatidylinositol (PI) in both unstimulated and stimulated cells. 1-Oleoyl-2-acetylglycerol, a synthetic DAG analog, stimulated endothelial cell DNA synthesis in a concentration-dependent manner. In [3H]inositol-labeled cells, 15-HETE also caused a decrease in cellular PI content under both basal and stimulated conditions. 15-HETE, however, had no effect on either isolated phospholipase C activity or phosphoinositide turnover in lithium chloride-treated cells. In intact cells, 15-HETE (30 microM) inhibited the synthesis of [3H]PI from [3H]inositol (80% inhibition, p less than 0.001). In human red cell membranes, the production of phosphatidic acid from endogenous DAG was inhibited by 15-HETE in a concentration-dependent manner with an IC50 of 41 microM. Although 12-HETE had effects similar to those of 15-HETE, the parent compound arachidonic acid did not affect DNA synthesis or DAG kinase activity. Our study thus demonstrates that the mitogenic activity of 15- and 12-HETE on endothelial cells may be mediated via DAG kinase inhibition with the concomitant accumulation of cellular DAG.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

13-Hydroxyoctadecadienoic acid (13-HODE) stimulates prostacyclin production by endothelial cells.

The effect of 13-hydroxyoctadecadienoic acid (13-HODE), an endogenous lipoxygenase metabolite of linoleic acid, on prostacyclin production by fetal bovine aortic endothelial cells was evaluated. Time-dependent release of radioimmunoassayable 6KPGF1 alpha in the presence of 13-HODE (10 uM) was stimulated by 39%, 27%, and 34% at 10, 30 and 120 min respectively. 13-HODE (10 uM) had no effect on the conversion of exogenous [14C] arachidonic acid (AA) to prostacyclin. When the effect on AA release was evaluated in [14C] AA prelabeled cells, 13-HODE (10nM) stimulated the release of AA from membrane phospholipids. Analysis of cellular phospholipids revealed a significant decrease in phosphatidylethanolamine. Our results demonstrate that 13-HODE stimulates prostacyclin production by enhancing AA release from phospholipids.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Endothelial cell proliferation may be mediated via the production of endogenous lipoxygenase metabolites.

Endogenous regulators of endothelial cell proliferation have not been clearly defined. We investigated whether the cyclooxygenase and/or lipoxygenase metabolites are involved in this process, and report that lipoxygenase products can modulate endothelial cell growth. Nordihydroguaiaretic acid--a lipoxygenase inhibitor, inhibited endothelial cell proliferation as well as DNA synthesis. 5,8,11,14-Eicosatetraynoic acid--an inhibitor of both lipoxygenase and cyclooxygenase also inhibited endothelial cell DNA synthesis, while indomethacin--a selective cyclooxygenase inhibitor did not affect cell proliferation or DNA synthesis. While arachidonic acid stimulated DNA synthesis, this effect was completely abolished by nordihydroguaiaretic acid. These results demonstrate that products of the lipoxygenase pathway can affect endothelial cell proliferation.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1987

The platelet cyclooxygenase metabolite 12-L-hydroxy-5, 8, 10-hepta-decatrienoic acid (HHT) may modulate primary hemostasis by stimulating prostacyclin production.

Although HHT accounts for approximately one third of the arachidonic acid (AA) metabolites produced by stimulated platelets, no well defined function has been attributed to this product. We report that HHT stimulates prostacyclin production by endothelial cells, and have identified the mechanism for this effect. In human umbilical venous endothelial cells, HHT (0.5 and 1 microM) stimulated prostacyclin (RIA for 6KPGF1 alpha) by 32 +/- 22% (1SD) and 42 +/- 38% (P less than 0.05 and less than 0.01). Similar changes were observed when the effect of HHT on exogenous [1-14C] AA metabolism in fetal bovine aortic endothelial cells (FBAECs) was studied. Kinetic analyses revealed that HHT affected vascular cyclooxygenase. HHT (1 microM) increased Vmax in test microsomes (706 +/- 21 pmol/mg/min, mean +/- 1SE) when compared to controls (529 +/- 20; P less than 0.02). No concomitant effect on Km was observed. A further effect of HHT on AA release from endothelial cell membrane phospholipids was noted. Prelabeling experiments revealed that HHT (1 microM) increased the ionophore stimulated release of AA from FBAECs (20952 +/- 555 cpm/well control mean +/- 1SE vs 25848 +/- 557 for paired HHT treated cells; P less than 0.05). The effect of HHT on platelet AA metabolism was next studied. Preincubation of washed platelets with HHT (1 microM) did not enhance thrombin or arachidonic acid induced platelet TXB2 formation. In platelets prelabelled with [1-14C]AA, HHT (1 microM) had no effect on AA release post thrombin stimulation. Conversion to cyclooxygenase metabolites was also not enhanced. HHT stimulates vascular prostacyclin without a concomitant effect on platelet AA metabolism. HHT may thus be an important local modulator of platelet plug formation.

Animals↗
PubMed1986

Time-dependent inhibition of platelet cyclooxygenase by indomethacin is slowly reversible.

Indomethacin has been characterized in vitro as a time-dependent, irreversible inhibitor of cyclo-oxygenase, yet its effects on human platelets have been found to be reversible in vivo. To understand this apparent contradiction, we have investigated the kinetics of recovery of platelet thromboxane production after a single dose of indomethacin. The inhibition of platelet thromboxane production was greater than would be expected from the levels of indomethacin found in the plasma suggesting that the time-dependent inhibition occurs in vivo. Yet recovery of platelet thromboxane production was faster than expected for an irreversible inhibitor, with 50% of control values being regained within 24 hours after ingestion of the drug. When platelets were isolated and resuspended in homologous drug-free plasma, slow recovery of thromboxane production was seen to occur with 50% of control activity regained in 100 minutes. This recovery was much slower than that seen from a competitive inhibitor of cyclo-oxygenase, ibuprofen. Ibuprofen-treated platelets recovered nearly completely immediately on being resuspended in drug-free plasma. When microsomes were isolated from platelets, then treated with indomethacin, no time-dependent recovery of activity was seen. The recovery of cyclo-oxygenase after indomethacin inhibition appears to be limited to the unperturbed enzyme in its natural milieu.

Adult↗
PubMed1986

15-Hydroxy-5,8,11,13-eicosatetraenoic acid inhibits human vascular cyclooxygenase. Potential role in diabetic vascular disease.

Human umbilical arteries converted arachidonic acid to three hydroxyeicosatetraenoic acids (HETEs) as well as prostaglandins. The mono-HETEs have been identified by reverse-phase high pressure liquid chromatography and gas chromatography-mass spectroscopy as 15-HETE and 11-HETE. 15-HETE in arterial segments appears to be derived mainly via the 15-lipoxygenase pathway, whereas 11-HETE, and the presumed di-HETE(s) were products of cyclooxygenase. Nordihydroguaiaretic acid, a lipoxygenase inhibitor, stimulated prostanoid production with a concomitant inhibition of 15-HETE formation. These results suggested that 15-HETE may function as an endogenous regulator of prostacyclin. In human umbilical arterial microsomes, 15-HETE was found to inhibit 6-keto-prostaglandin F1 alpha and total prostanoid production in a concentration-dependent manner (median inhibition constant [IC50] of 52 +/- 3 and 63 +/- 4 microM respectively). The relative distribution of prostaglandins, however, remained unaffected, indicating that the site of action was cyclooxygenase. Kinetic analysis revealed that 15-HETE was a competitive inhibitor of the enzyme. Although no changes in maximum velocity occurred, the apparent Km was significantly different (9.3 +/- 6.9 microM [1 SD] for control vs. 37.6 +/- 17.7 microM for the 15-HETE-treated enzyme). Furthermore, the inhibitory effect of 15-HETE on prostacyclin production was confirmed using cultured bovine endothelial cells. In this cell system, not only did 15-HETE inhibit endogenous prostacyclin production, but also the conversion of exogenous [1-14C]arachidonic acid to prostacyclin (IC50 of 40 +/- 17 microM). No effect on arachidonic acid release was noted. To investigate whether our in vitro finding that 15-HETE inhibited prostacyclin production could be relevant to the in vivo situation, our final studies were performed on vasculature obtained from the diabetic milieu. We found that the production of 15-HETE was significantly increased in vasculature obtained from the infant of the diabetic mother (1.14 +/- 0.26 pmol/mg) when compared to control neonates (0.77 +/- 0.22; P less than 0.01). A concomitant decrease in prostacyclin production was seen (51.6 +/- 12.6 pmol/mg in infants of diabetic mothers vs. 71 +/- 22.3 in controls). Moreover, an inverse correlation between these two eicosanoids was also noted. Our results suggest a potential in vivo regulatory role for 15-HETE on prostacyclin production.

Animals↗
PubMed1985

Abnormalities in vascular arachidonic acid metabolism in the infant of the diabetic mother.

The infant of the diabetic mother has an increased incidence of thromboses in utero and in the neonatal period. In the adult with diabetes a decrease in prostacyclin formation has been suggested as a cause for the atherothrombotic tendency. We therefore evaluated arachidonic acid metabolism in infants of diabetic mothers. Endogenous radioimmunoassayable 6-keto prostaglandin F1 alpha (PGF1 alpha) was normal in umbilical vessels obtained from the infants of diabetic mothers whose glucose homoeostasis was maintained when compared with control values. Nevertheless, a significant inhibition of vascular production of 6-keto PGF1 alpha was observed in infants born to mothers with raised HbA1C concentrations. A decrease in the concentration of plasma 6-keto PGF1 alpha was also seen in the infants of diabetic mothers when compared with control neonates. The correlation observed between plasma 6-keto PGF1 alpha concentrations and endogenous vascular prostacyclin formation in the infants of diabetic mothers indicates that the in vitro deficiency of prostacyclin formation reflects a concomitant in vivo abnormality.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Formation of 11-hydroxyeicosatetraenoic acid and 15-hydroxyeicosatetraenoic acid in human umbilical arteries is catalyzed by cyclooxygenase.

Human umbilical arteries convert arachidonic acid into three hydroxy-eicosatetraenoic acids as well as 6-ketoprostaglandin F1 alpha, prostaglandins E2, F2 alpha and D2 and thromboxane B2. Two of these hydroxy derivatives of arachidonic acid were purified by reverse-phase HPLC and identified by GC-MS as 11-hydroxyeicosatetraenoic acid (11-HETE) and 15-hydroxyeicosatetraenoic acid (15-HETE) while a third, presumed dihydroxy derivative has not yet been identified. Both the cyclooxygenase and HETE synthesizing activities were found to be localized mainly in the microsomal fraction (100 000 X g pellet) (51 and 61% of total, respectively), and approx. 25% of both activities was found in the 10 000 X g pellet. The formation of these HETEs was inhibited by the cyclooxygenase inhibitors indomethacin and aspirin but not by the lipoxygenase inhibitor nordihydroguaiaretic acid. Production of immunoreactive 15-HETE as well as 6-ketoprostaglandin F1 alpha were also decreased significantly when arterial segments were incubated in the presence of either indomethacin or aspirin. Indomethacin inhibited the formation of both prostanoids and HETEs by microsomes in a concentration-dependent and time-dependent manner. The ID50 values for indomethacin against HETE synthesizing activity and against cyclooxygenase were 4.5 and 3.8 microM, respectively. The inactivation constants were found to be 0.09 and 0.08 min-1 for HETE synthesizing activity and cyclooxygenase, respectively. These two microsomal activities were solubilized in parallel with Tween-20. Incubation with three distinct monoclonal antibodies against different epitopes on cyclooxygenase precipitated both cyclooxygenase and HETE synthesizing activity. Each of these activities was recovered in the immune pellets. These studies demonstrate that in human umbilical arteries 11-HETE, 15-HETE and a presumed di-HETE are the products of cyclooxygenase.

Arachidonic Acid↗
PubMed1985

Effect of changes in oxygen tension on vascular and platelet hydroxyacid metabolites. II. Hypoxia increases 15-hydroxyeicosatetraenoic acid, a proangiogenic metabolite.

Current strict O2 management may be precipitating more severe retinopathy of prematurity than would occur with a more lenient approach. Hypoxemia in an animal model has also been found to worsen retinal neovascularization. It has recently been shown that the hydroxyeicosatetraenoic acids can modulate angiogenesis. 15-Hydroxyeicosatetraenoic acid is proangiogenic, whereas 12-hydroxyeicosatetraenoic acid is an antiangiogenic metabolite. In vitro exposure of paired human neonatal vessels (n = 7) to hypoxia enhanced the production of total vascular hydroxyacids (232 +/- 36 pmol/mg of protein [experimental group] nu 168 +/- 31 pmol [control group]; P less than .01). The increase in vascular 15-hydroxyeicosatetraenoic acid under hypoxic conditions was even more significant (P less than .001). However, platelet production of 12-hydroxyeicosatetraenoic acid was not significantly affected by hypoxia. These observations suggest a possible biochemical basis for the abnormal angiogenic process that occurs during the proliferation phase of the retinopathy of prematurity. The production of local hydroxyeicosatetraenoic acids in tissues manifesting abnormal neovascularization needs to be further evaluated.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1984

Effects of hydrogen peroxide on vascular arachidonic acid metabolism.

Hydrogen peroxide (H2O2) released by granulocytes during phagocytosis has previously been demonstrated to affect the function of other cellular elements including red cells and platelets. We have evaluated the effect of H2O2 on vascular arachidonic acid (AA) metabolism. Exposure of human vascular segments to H2O2 (25 to 200 microM) results in a concentration dependent inhibition in the ability of these vessels to produce PGI2 either from endogenous stores of AA, or from exogenously provided substrate. The inhibition of PGI2 production was present at 5 minutes post addition of H2O2, with maximal inhibitory effect occurring by 15 minutes. Production of 6 Keto PGF1 alpha from exogenously provided 14C AA was similarly inhibited in isolated microsomes from these vessels, as was the production of the other vascular cyclo-oxygenase metabolites PGE2 and PGF2 alpha. These results demonstrate that the major effect of H2O2 on vascular AA metabolism appears to occur at the cyclo-oxygenase level. Vascular inhibition of PGI2 formation caused by the local release of H2O2 from phagocytizing cellular elements may play a role in the pathophysiology of the inflammatory process.

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

Hemostatic alterations in sickle cell disease: relationships to disease pathophysiology.

The protean manifestations of sickle cell disease (SCD), especially, microvessel involvement in the vaso-occlusive process, is classically ascribed to the phenomena of erythrocyte sickling and enhanced red cell-endothelial adherence. Pertubations in various hemostatic systems occurs in SCD, both in steady state and during vaso-occlusion, with the intravascular generation of thrombin. The etiology(s) of thrombin generation in SCD will be described. Whether the activation of the cellular and plasmatic phases of hemostasis is causative or occurs as a result of vascular injury will be discussed.

Anemia, Sickle Cell↗