Biomedical subjects

B N Setty

Publications and source records attributed to B N Setty.

At least 19 recordsLinked to original sources

PubMed2001

Thrombophilia in sickle cell disease: the red cell connection.

Complex pertubations of hemostasis occur in sickle cell disease (SCD). Although the procoagulant property of sickle erythrocytes in vitro is tied to exposure of phosphatidylserine (PS), no study has directly linked this PS positivity to in vivo thrombin generation. This study was designed to determine if thrombin generation in SCD correlates with erythrocyte PS, or whether platelets play a significant role. PS was quantified on erythrocytes and platelets from 40 patients with SCD (SS genotype = 25; SC genotype = 15) and 11 controls. Markers of thrombin generation (prothrombin fragment F1.2; thrombin-antithrombin or TAT complexes) and fibrin dissolution (D-dimer; plasmin-antiplasmin or PAP complexes) were also evaluated. Thrombin generation and activation of fibrinolysis occurred with elevations in F1.2, TAT, and D-dimer. Although numbers of both PS-positive erythrocytes and platelets were elevated, there was no correlation between PS-positive platelets and any hemostatic markers. In contrast, correlations were noted between PS-positive erythrocytes and F1.2 (P <.0002), D-dimer (P <.000002), and PAP (P <.01). Correlations between F1.2 and D-dimer (P <.0001) demonstrated that fibrinolysis was secondary to thrombin generation. In patients with the SC genotype, abnormalities in coagulation, although present, were of a lesser magnitude than in SS disease. This study suggests that the sickle erythrocyte is the cell responsible for the thrombophilic state in SCD because associations between erythrocyte PS and thrombin generation were observed. No such relationship with platelet PS was noted. The use of erythrocyte PS as a surrogate marker in trials testing new therapeutic modalities may provide insights into the vascular complications of SCD.

Adolescent↗

PubMed2001

Fetal hemoglobin in sickle cell anemia: relationship to erythrocyte adhesion markers and adhesion.

To assess whether fetal hemoglobin (HbF) modulates the adhesion of sickle erythrocytes to endothelium, children with homozygous sickle cell anemia (SS disease) were studied, using this physiologically crucial period to evaluate the relationships between HbF and the major erythrocyte adhesion markers. The mean level of CD36(+) erythrocytes was 2.59% +/- 2.15% (+/- SD, n = 40) with an inverse relationship between CD36 positivity and F cells (R = -0.76, P < .000 00 002). In univariate analyses, significant correlations with various hematologic parameters and age were noted. Multiple regression analyses, however, revealed a relationship solely with F cells. Minimal levels of very late activation antigen-4(+) (VLA4(+)) erythrocytes (0.31% +/- 0.45%, n = 40) with relationships similar to those noted for CD36(+) cells were also observed. The subpopulation of strongly adhesive stress reticulocytes was further assessed, using CD71 as their marker. The mean level of CD71(+) erythrocytes was 5.81% +/- 4.21%, with statistical correlates in univariate and multivariate analyses similar to those discussed above. When adhesion ratios were evaluated, inverse correlations were noted between basal and plasma-induced adhesion and F-cell numbers (R = -0.54, P < .0005; R = -0.53, P < .0006, n = 39). In addition, in analyses where basal or plasma-induced adhesion was the dependent variable and the independent variables included F cells and the various adhesion-related parameters, significant relationships solely with F cells were noted. The results demonstrate that SS patients with higher levels of F cells have concomitant decreases in the numbers of CD36(+), VLA4(+), and CD71(+) erythrocytes and that these findings translate into less adherent erythrocytes. These findings extend knowledge regarding the protective effects of HbF in the pathophysiology of sickle cell disease.

Adolescent↗

PubMed2001

Acute chest syndrome of sickle cell disease: new light on an old problem.

The pulmonary findings of acute chest syndrome of sickle cell disease have been well characterized in numerous studies. Whereas a third of patients have a documented infection associated with this syndrome, and fat embolism from necrotic marrow is the etiologic factor in another approximately 10%, no cause is discovered in the majority of patients. In most patients, however, the underlying pathophysiology is the presence of a hypoxia-driven, adhesion-related occlusive event in the pulmonary microcirculation. This may be accompanied by a decrease in the levels of normal cytoprotective and anti-adhesive mediators such as nitric oxide. In the patient with sickle cell disease, the lung is also a uniquely vulnerable target organ because its vasculature constricts with hypoxia in contrast to other vascular beds. This review will establish the links between known etiologic agents and the pathophysiology of this syndrome. An additional section of this review will deal with experimental therapies. The use of inhaled nitric oxide will be explored in depth because advances in this area are current and uniquely relevant to acute chest syndrome.

Acute Disease↗

PubMed2000

Fetal hemoglobin in sickle cell disease: relationship to erythrocyte phosphatidylserine exposure and coagulation activation.

In sickle cell disease (SCD), loss of erythrocyte membrane phospholipid asymmetry occurs with the exposure of phosphatidylserine (PS), which provides a docking site for coagulation proteins. In vivo sickling/desickling, with resulting red cell membrane changes and microvesicle formation, appears to be one of the factors responsible for PS exposure. We evaluated children with SCD homozygous for sickle hemoglobin (SS disease) and controls (n = 65) and demonstrate that high levels of fetal hemoglobin (assessed as F cells) are associated with decreased microvesicle formation, PS exposure, and thrombin generation. F cells correlated inversely with both microvesicles and PS positivity (P <.000001) in SS disease. Multiple regression analyses using various hematologic parameters as independent variables, and either microvesicles or PS positivity as the dependent variable, showed a strong relationship only with F cells. Additionally, plasma prothrombin fragment F1.2 levels (a marker for thrombin generation) correlated with both PS positivity (P <.001) and F cells (P <.01). An F-cell level of approximately 70% was associated with normal levels of prothrombin fragment F1.2 and with microvesicle formation indistinguishable from control values. We suggest that the use of such surrogate biologic markers in conjunction with F-cell numbers may provide valuable insights into the biology and consequences of in vivo sickling.

Adolescent↗

PubMed1999

Sickle cell acute chest syndrome: pathogenesis and rationale for treatment.

Acute chest syndrome (ACS) is a leading cause of death in sickle cell disease (SCD). Our previous work showed that hypoxia enhances the ability of sickle erythrocytes to adhere to human microvessel endothelium via interaction between very late activation antigen-4 (VLA4) expressed on sickle erythrocytes and the endothelial adhesion molecule vascular cell adhesion molecule-1 (VCAM-1). Additionally, hypoxia has been shown to decrease the production of nitric oxide (NO) which inhibits VCAM-1 upregulation. Based on these observations, we hypothesize that during ACS, the rapidly progressive clinical course that can occur is caused by initial hypoxia-induced pulmonary endothelial VCAM-1 upregulation that is not counterbalanced by production of cytoprotective mediators, including NO, resulting in intrapulmonary adhesion. We assessed plasma NO metabolites and soluble VCAM-1 in 36 patients with SCD and 23 age-matched controls. Patients with SCD were evaluated at baseline (n = 36), in vaso-occlusive crisis (VOC; n = 12), and during ACS (n = 7). We observed marked upregulation of VCAM-1 during ACS (1,290 +/- 451 ng per mL; mean +/- 1 SD) with values significantly higher than controls (P <.0001) or patients either in steady state or VOC (P <. 01). NO metabolites were concomitantly decreased during ACS (9.2 +/- 1.5 nmol/mL) with values lower than controls (22.2 +/- 5.5), patients during steady state (21.4 +/- 5.5), or VOC (14.2 +/- 1.2) (P <.0001). Additionally, the ratio of soluble VCAM-1 to NO metabolites during ACS (132.9 +/- 46.5) was significantly higher when compared with controls (P <.0001) or patients either in steady state or VOC (P <.0001). Although hypoxia enhanced in vitro sickle erythrocyte-pulmonary microvessel adhesion, NO donors inhibited this process with concomitant inhibition of VCAM-1. We suggest that in ACS there is pathologic over expression of endothelial VCAM-1. Our investigations also provide a rationale for the therapeutic use in ACS of cytoprotective modulators including NO and dexamethasone, which potentially exert their efficacy by an inhibitory effect on VCAM-1 and concomitant inhibition of sickle erythrocyte-endothelial adhesion.

Adolescent↗

PubMed1999

Measurement of hemoglobin saturation by oxygen in children and adolescents with sickle cell disease.

Pulse oximetry is a noninvasive method of measuring oxyhemoglobin saturation. The validity of pulse oximetry in sickle cell disease (SCD) has been questioned. We evaluated pulse oximetry, arterial blood gas analysis, and co-oximetry in patients with SCD, and we assessed the effect of dyshemoglobin and altered blood-oxygen affinity on their accuracy. Sixteen patients with SCD aged 7-21 years had arterial and venous blood drawn and transcutaneous pulse oximetry performed. Oxyhemoglobin dissociation curves were plotted from the venous blood of 15 patients. Oxyhemoglobin saturation estimated by arterial blood gas analysis (SaO(2)) and measured by pulse oximetry (SpO(2)) were both higher than the saturation by co-oximetry (FO(2)Hb) (mean +/- SD = 96.3 +/- 1.6%, 94 +/- 3.1%, and 89.1 +/- 3.8%, respectively). There was a significant, positive correlation between SpO(2) and FO(2)Hb (r = 0.7, P = 0.002). The patients had elevated levels of methemoglobin (MetHb) and carboxyhemoglobin (COHb) (2.3 +/- 1.4% and 4.7 +/- 1.3%, respectively). The oxyhemoglobin dissociation curves were frequently shifted to the right with oxygen tensions elevated when hemoglobin was 50% saturated with oxygen (P(50)) (32.5 +/- 4.5 mm Hg). There was a strong correlation between the amounts of dyshemoglobin (MetHb + COHb) and the difference between SaO(2) and FO(2)Hb (r = 0.7, P = 0.002). There was no correlation between the difference between SaO(2) and FO(2)Hb and the P(50) (r = 0.27, P = 0.33) There was also a strong positive correlation between SaO(2)-SpO(2) and dyshemoglobin fraction (r = 0.77, P = 0.001). We conclude that pulse oximetry and arterial blood gas analysis overestimate oxygen saturation when compared to co-oximetry, but that SpO(2) is consistently closer than SaO(2) to FO(2)Hb. SpO(2) is partially affected by MetHb and COHb. The discrepancy between SaO(2) and FO(2)Hb is due to the presence of dyshemoglobin and a shifted oxyhemoglobin dissociation curve, but the effect from dyshemoglobin predominates.

Adolescent↗

PubMed1998

Eicosanoids in sickle cell disease: potential relevance of 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid to the pathophysiology of vaso-occlusion.

The monohydroxyeicosanoid 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), which is derived from oxygenation of arachidonic acid by 12-lipoxygenase, is one of the major metabolites in platelets. In a recent study, we have showed that this eicosanoid stimulated basal sickle-red-cell-endothelial-cell adhesion. To understand the pathophysiologic significance of 12-HETE, we measured the levels of this eicosanoid in plasma and urine from children with sickle cell disease. We found that as compared with controls, plasma 12-HETE levels are increased in patients with sickle-cell disease in the steady state, and are increased further during vaso-occlusive crises. Urinary 12-HETE levels were also increased during the steady state. We also assessed plasma levels of soluble P-selectin (another potential marker for platelet activation), and found changes in the levels of this marker similar to those seen with plasma 12-HETE. In additional studies, we found that 12-HETE enhanced hypoxia-induced sickle-red-cell-endothelial adherence, and that this effect was mediated by potentiation of agonist-induced upregulation of the expression of the mRNA for vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells. Because 12-HETE appears to enhance both basal and agonist-induced sickle-red-cell adhesion, this metabolite could potentially play a role in the pathogenesis of the vaso-occlusive crisis (VOC) in sickle-cell disease.

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

PubMed1996

Vascular cell adhesion molecule-1 is involved in mediating hypoxia-induced sickle red blood cell adherence to endothelium: potential role in sickle cell disease.

We investigated the effects of hypoxia on red blood cell (RBC)-endothelial cell (EC) adherence and the potential mechanism(s) involved in mediating this effect. We report that hypoxia significantly increased sickle RBC adherence to aortic EC when compared with the normoxia controls. However, hypoxia had no effect on the adherence of normal RBCs. In additional studies, we found that the least dense sickle RBCs containing CD36+ and VLA-4+ reticulocytes were involved in hypoxia-induced adherence. We next evaluated the effects of hypoxia on the expression of EC surface receptors involved in RBC adherence to macrovascular ECs, including vascular cell adhesion molecule-1 (VCAM-1), intracellular adhesion molecule-1 (ICAM-1), and the vitronectin receptor (VnR). Hypoxia upregulated the expression of both VCAM-1 and ICAM-1, whereas no effect on VnR was noted. Potential involvement of VCAM-1 and ICAM-1 in mediating hypoxia-induced sickle RBC-EC adhesion was next investigated using monoclonal antibodies against these receptors. Whereas anti-VCAM-1 had no effect on basal adherence, it inhibited hypoxia-induced sickle RBC adherence in a concentration-dependent manner, with 50% to 75% inhibition noted at 10 to 60 micrograms/mL antibody (n = 6, P < .05 to P < .01). Anti-ICAM-1 (10 to 60 micrograms/mL, n = 8) had no effect on either basal or hypoxia-induced adherence. As noted in the bovine aortic ECs, hypoxia stimulated the adherence of sickle RBCs to human retinal capillary ECs, and this response appeared to be mediated via mechanisms similar to those observed with macro-endothelium, ie, via the adhesive receptor combination VCAM-1-VLA-4. Our studies show that hypoxia enhances sickle RBC adhesion to both macrovascular and human microvascular ECs via the adhesive receptor VCAM-1. Our findings are of interest because hypoxia is an integral part of the pathophysiology of the vaso-occlusive phenomenon in sickle cell anemia.

Anemia, Sickle Cell↗

PubMed1996

Sickle red blood cells stimulate endothelial cell production of eicosanoids and diacylglycerol.

The effects of sickle red cell-endothelial cell interaction on endothelial cell arachidonic: acid (AA) mobilization, eicosanoid release, and diacylglycerol (DAG) production were evaluated by using bovine aortic endothelial cells. We have shown that coincubation of washed red blood cells (RBCs) from patients with sickle cell disease with endothelial cells stimulate AA release (90% increase as compared with buffer controls, n = 8, p < 0.002). Released AA was mobilized from membrane phosphatidylcholine and phosphatidylserine and was converted to eicosanoids via the cyclooxygenase and lipoxygenase pathways in increased amounts in the presence of sickle erythrocytes. The production of prostacyclin and 15-hydroxyeicosatetraenoic acid (15-HETE) were increased by 78% (p < 0.01) and 103% (p < 0.025), respectively, as shown by both chromatographic and immunoassay procedures. Sickle erythrocytes also stimulated the hydrolysis of endothelial cell phosphoinositides, including phosphatidylinositol-mono-phosphate (p < 0.03) and phosphatidylinositol-bis-phosphate (p < 0.006). This response was accompanied by a significant increase in the production of DAG (50% increase as compared with buffer control, n = 8, p < 0.025). In contrast, coincubation of washed erythrocytes from normal healthy donors with endothelial cells had no significant effect on endothelial cell phospholipid turnover. When the sickle RBC-induced biochemical changes in endothelial cells were contrasted with those observed with normal RBCs, the ability of sickle RBCs to induce AA mobilization and the production of mono-HETEs and DAG was markedly increased (p = 0.05 to p < 0.025). Because 15-HETE is a pro-adhesinogenic eicosanoid and DAG is an endogamous activator of protein kinase C, an enzyme involved in modulating cell surface adhesive properties, both 15-HETE and DAG could potentially play a role in the vascular pathophysiology of sickle cell disease.

Anemia, Sickle Cell↗

PubMed1996

Impaired mobilization of intracellular calcium in neonatal platelets.

Abnormalities in platelet functions including aggregation and the release reaction have long been recognized to be present in neonatal platelets. Because calcium is an important mediator of many platelet functions, we have investigated the mobilization of calcium in neonatal platelets. All umbilical cord blood samples were obtained from healthy, full term gestations. Changes in cytoplasmic calcium levels were monitored using Fura-2 as a fluorescent probe. Fura-2-loaded washed platelets were stimulated with the agonists collagen (2 micrograms/mL) or thrombin (1.0 U/mL). When compared with adult controls, intracellular calcium release in the platelets of the neonate was significantly impaired in response to these agonists. Mean levels for calcium release in adults versus neonates in response to collagen were 168 +/- 120 nM (+/-SD, n = 10), and 61 +/- 69 nM (n = 7, p < 0.05). A decrease in response to thrombin was also observed [1296 +/- 503 nM (n = 8) in adults versus 603 +/- 482 nM (n = 7) in neonates, p < 0.025]. Results similar to those observed with unpaired neonatal and adult platelets were also obtained when neonatal platelets (n = 5) were compared with their paired maternal controls. In further studies, we have documented that the calcium content of the dense tubular system was normal in the neonatal platelet, indicating that the observed impairment in calcium mobilization in the neonate was not due to a decrease in calcium stores. The previously documented abnormalities in neonatal platelet function appear to be due to the impaired mobilization of this important intracellular mediator.

Adult↗

PubMed1995

Intravenous morphine pharmacokinetics in pediatric patients with sickle cell disease.

To examine the pharmacokinetics of parenteral opioids, such as morphine, in patients with sickle cell disease, we determined the plasma morphine clearances in 18 patients (aged 6 to 19 years) who were receiving continuous intravenous infusions, and the pharmacokinetics of morphine in an additional six patients after single intravenous doses. Plasma morphine clearances ranged from 6.2 to 59.1 ml min-1 kg-1 (35.5 +/- 12.4, mean +/- SD) during steady-state infusions. There was a negative correlation between clearance values and age over the age range studied (p = 0.013). A significant difference (p = 0.042) was also observed in clearance values between patients who had serious adverse symptoms (23.4 +/- 10.7 ml min-1 kg-1) and those who had less serious symptoms (36.3 +/- 6.4 ml min-1 kg-1) when morphine was given at high dosage rates (> or = 0.15 mg kg-1 hr-1). Pharmacokinetic modeling of plasma morphine concentrations adequately fit a two-compartment model with a short initial distribution phase (mean half-life = 4.5 minutes) and a rapid terminal elimination half-life (77.6 +/- 19.2 minutes). These findings suggest that considerable individualization of morphine dosing may be necessary to achieve optimal analgesia and minimal adverse effects in these patients.

Adolescent↗

PubMed1995

Sickle cell vaso-occlusive crisis is associated with abnormalities in the ratio of vasoconstrictor to vasodilator prostanoids.

Plasma levels of 6-keto-prostaglandin F1 alpha (6kPGF1 alpha) and thromboxane (Tx) B2 have been assessed in sickle cell disease (SCD) with discrepant results. Inasmuch as direct measurement of plasma prostanoids is fraught with the problem of interfering substances, we assessed plasma 6kPGF1 alpha and TxB2 levels in patients with SCD by RIA after extraction of eicosanoids and separation by HPLC. We demonstrate that the 6kPGF1 alpha and TxB2 levels in children with SCD in steady state as well as in vaso-occlusive crisis (VOC) are significantly lower when compared with those from age-matched controls. The VOC plasma 6kPGF1 alpha and TxB2 levels were, however, significantly elevated when compared with those from children in steady state. Changes similar to those noted with unpaired plasma samples were also observed when paired steady state and VOC plasmas from the same patients were assessed. The ratio of TxB2 to 6kPGF1 alpha was, however, significantly elevated in patients with SCD in crisis when compared with eicosanoid ratios obtained during steady state. In an attempt to understand whether the abnormality in 6kPGF1 alpha was due to an impairment in endothelial cell prostacyclin-regenerating ability, we compared the ability of plasma from controls and children with SCD to activate arachidonic acid (AA) release and prostacyclin production by [14C]AA-prelabeled bovine aortic endothelial cells. Our results suggest that the decreased 6kPGF1 alpha levels in plasma from children with SCD was not due to an effect on substrate AA release but rather a modulatory effect of sickle plasma components on endothelial cell cyclooxygenase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1995

Arachidonic acid metabolites are involved in mediating red blood cell adherence to endothelium.

As an initial investigation into the possible role of endothelial cell (EC) lipoxygenase and cyclooxygenase metabolites in the adherence of red blood cells (RBCs) to ECs, we evaluated the effect of nordihydroguaiaretic acid, (NDGA; 10 mumols/L, BW755c (30 mumols/L), aspirin (100 mumols/L), and indomethacin (10 mumols/L) on RBC-EC adherence using a static incubation system and 51Cr-labeled RBCs. NDGA and 3-amino-L-[3'-(trifluoromethyl)phenyl]-2-pyrazoline inhibitors of both the lipoxygenase and cyclooxygenase pathways, significantly decreased basal adhesion of RBCs to fetal bovine aortic ECs, whereas aspirin and indomethacin, selective inhibitors of the cyclooxygenase pathway, stimulated the adherence process. The inhibitor effect appeared to be mediated via an effect on EC functions, since preincubation of ECs with NDGA, in contrast to RBC-NDGA preincubation, inhibited the adherence process. Because bovine aortic ECs generate mainly prostacyclin and 15-HETE from arachidonic acid (AA) via the cyclooxygenase and the lipoxygenase pathways respectively, the role of these products (100 pmol/L to 1 mumol/L) on the adhesive process was further assessed. 15-HETE potentiated basal adhesion of RBCs to bovine aortic ECs in a concentration-dependent manner, with maximal responses of approximately 50% to 150% over baseline noted at concentrations between 1 and 100 nmol/L 12-HETE, a structural isomer of 15-HETE and the major platelet lipoxygenase product, also stimulated RBC adherence. In contrast, prostacyclin (assessed using carbacyclin, a stable synthetic analog of prostacyclin with similar biologic properties) had no significant effect on this process. In further studies, we demonstrated that the 12-HETE-induced adherence of sickle RBCs was mediated via an up-regulation of the vitronectin receptor on bovine aortic endothelium. Because microvascular capillary endothelium is the surface most likely to encounter erythrocytes in vivo, we extended our studies to human retinal capillary ECs to assess the involvement of eicosanoids in sickle RBC-microvessel adhesion. As with bovine aortic ECs, aspirin stimulated and NDGA decreased the adherence of sickle RBCs to human retinal capillary endothelium. These microvascular ECs generated prostacyclin, HHT, 15-HETE, and 15-HPETE from endogenous AA. Although carbacyclin and HHT had no effect on the adherence process, both 15-HETE and 15-HPETE (10 pmol/L to 100 nmol/L) stimulated RBC adhesion to capillary endothelium. Our studies document a role for the lipoxygenase metabolites in modulating basal adhesion of RBCs to both macrovascular and microvascular endothelium; the major cyclooxygenase metabolites appear to play no role in this process.

Animals↗

PubMed1992

15-Hydroxyeicosatetraenoic acid-mediated potentiation of thrombin-induced platelet functions occurs via enhanced production of phosphoinositide-derived second messengers--sn-1,2-diacylglycerol and inositol-1,4,5-trisphosphate.

We investigated whether biologically relevant concentrations of the mono-hydroxyeicosatetraenoic acids (mono-HETEs) modulate platelet functions. We report that 15-HETE, an eicosanoid produced by endothelial cells, granulocytes, and lymphocytes, potentiated platelet aggregation, nucleotide release, and elevation in intracellular calcium levels induced by a threshold concentration of thrombin (0.025 U/mL). Significant potentiation effects on these responses were observed at concentrations between 1 and 100 nmol/L. 15-HETE at these concentrations enhanced thrombin-induced platelet aggregation by 32% to 57%, nucleotide release by 40% to 65%, and elevation of intracellular calcium by 31% to 52% (P < .05 to .01). Both 12-HETE and 5-HETE, the structural isomers of 15-HETE, also potentiated thrombin-induced platelet aggregation and nucleotide release. While 12-HETE showed a small but significant effect at 100 pmol/L, 5-HETE had effects similar to those of 15-HETE at micromolar concentrations. To understand the mechanism of the HETE modulation of platelet functions, we studied the effect of 10 and 100 nmol/L 15-HETE on the production of sn-1,2-diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (1,4,5-IP3). 15-HETE enhanced thrombin-induced production of DAG and 1,4,5-IP3 in a time- and concentration-dependent manner. 15-HETE also potentiated agonist-induced phosphorylation of the 47-Kd platelet protein. These studies demonstrate an important modulatory role for 15-HETE on platelet functions. Since this eicosanoid is elevated in pathologic states associated with platelet hyperfunction, including diabetes mellitus and atherosclerosis, an elucidation of its mechanism(s) of action appears relevant to our understanding of the genesis of atherothrombotic vascular disease.

Adenosine Triphosphate↗

PubMed1992

1-Deamino-8 D-arginine vasopressin decreases the production of 13-hydroxyoctadecadienoic acid by endothelial cells.

1-Deamino-8 D-arginine vasopressin (DDAVP) has been used effectively to normalize the bleeding time in various hemostatic disorders. In von Willebrand disease the reduction in bleeding time is due to the preferential release of large multimers of von Willebrand factor from endothelial cells. However, since the bleeding time correction in patients with uremia and liver disease is independent of the release of von Willebrand antigen and activity, other mechanisms of action of DDAVP need to be considered. Endothelial cells generate several thromborepellant factors including 13-hydroxyoctadecadienoic acid (13-HODE), an inhibitor of platelet adhesion to subendothelium. Using cultured fetal bovine aortic endothelial cells (FBAECs), we have investigated whether DDAVP modulates the production of 13-HODE. We have demonstrated that 14C-linoleic acid labeled FBAECs release several oxygenated derivatives of linoleic acid following a 120 min incubation in the presence of serum. One of these products was identified by chromatographic procedures as 13-HODE. The production of 13-HODE was decreased significantly by DDAVP (1-100 ng/ml) with maximal reduction (approx. 25%) seen at 1 ng/ml of DDAVP. While vehicle treated control FBAECs generated 6780 +/- 690 cpm of 13-HODE per 10(6) cells (mean +/- SE, n = 8), DDAVP treated FBAECs produced 4950 +/- 310 (P < 0.01), 5390 +/- 390 (P < 0.01), and 5720 +/- 410 cpm (P < 0.05) of 13-HODE at 1, 10, and 100 ng/ml DDAVP respectively. Our findings of a decrease in 13-HODE would explain the previously observed morphologic changes of increased platelet adhesion to subendothelium following DDAVP infusion and contributes to our understanding of the mode of action of this therapeutic agent in hemostatic disorders.

Animals↗

PubMed1991

Identification of prostaglandins and hydroxyeicosatetraenoic acids in kitten retina: comparison with other species.

Conversion of arachidonic acid to eicosanoids by kitten retinae was investigated to evaluate whether the pattern of kitten retinal eicosanoids simulates that found in the human and other animal species. Freshly isolated kitten retinae were incubated with 20 microM radiolabeled arachidonic acid, and the metabolites were analysed by reverse phase-high pressure liquid chromatography, thin-layer chromatography and gas chromatography-mass spectroscopy. Kitten retinal tissues converted arachidonic acid into prostaglandins (PGs), thromboxane (Tx) and hydroxyeicosatetraenoic acids (HETEs). The major eicosanoid identified was 6kPGF1 alpha--the stable non-enzymatic hydrolysis product of prostacyclin. Other eicosanoids identified included TxB2, PGE2, PGF2 alpha, 12-hydroxy-heptadecatrienoic acid, 12-HETE, and 15-HETE. The spectrum of kitten retinal cyclooxygenase metabolites is similar to those obtained from bovine retina and human retinal vascular endothelium with prostacyclin being the major cyclooxygenase metabolite produced.

6-Ketoprostaglandin F1 alpha↗

PubMed1990

15-Hydroxyeicosatetraenoic acid stimulates migration of human retinal microvessel endothelium in vitro and neovascularization in vivo.

We evaluated 15-hydroxyeicosatetraenoic acid (15-HETE), a major arachidonic acid product of vascular endothelium and leukocytes, for its effect on neovascularization. In a modified Boyden chamber assay, 15-HETE (10-7 M) stimulated human retinal microvessel endothelial cell migration by 42 +/- 10% (mean +/- S.E.M., p less than 0.01). 12-HETE, a major arachidonic acid metabolite of platelets, had no such effect. Further studies in the rabbit corneal pocket assay revealed that 15-HETE stimulated neovascularization in vivo. Concentrations at which the in vivo effects were observed are within the range generated by several cell types and are achievable in human serum. 15-HETE stimulation of human endothelial cell migration in vitro and neovascularization in vivo suggests that it may play a role in vasoproliferative disorders.

Animals↗

PubMed1990

Effects of changes in oxygen tension on lipoxygenase metabolites. Serum 15-HETE is increased in kittens exposed to hyperoxia.

The chronic phase of O2-induced retinopathy is characterized by retinal neovascularization. We have previously demonstrated that 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE), a product of white cells, is proangiogenic. In this study, kittens exposed to in vivo hyperoxia produced increased amounts of 15-HETE. Nine litters of 30 kittens (aged 6-8 days) were used. Control kittens were left in room air; hyperoxic kittens were placed in 80% oxygen for 48 h; recovery kittens were returned to room air for 24 h following hyperoxic exposure. Following treatments, the animals were sacrified, and blood was evaluated for 15-HETE. Stimulated serum 15-HETE levels were assayed by high-performance liquid chromatography and GC-selected ion monitoring. While controls produced 0.48 +/- 0.16 (SE) nmol/ml of 15-HETE, values in the hyperoxic and recovery animals were increased at 0.7 +/0 0.2 and 0.68 +/- 0.15 nmol/ml (p less than 0.05 and p = 0.05, respectively). Increased production of this proangiogenic metabolite by WBCs (which can migrate out of blood vessels to set up extravascular angiogenic foci) may play a role in the genesis of the neovascularization process that occurs in response to oxygen-induced injury.

Animals↗