Biomedical subjects

Keith T Oldham

Publications and source records attributed to Keith T Oldham.

23 records · Page 2Linked to original sources

PubMed2003

L-4F, an apolipoprotein A-1 mimetic, restores nitric oxide and superoxide anion balance in low-density lipoprotein-treated endothelial cells.

BACKGROUND: Low-density lipoprotein (LDL) impairs endothelial cell function by uncoupling endothelial nitric oxide synthase (eNOS) activity, which allows superoxide anion (O2*-)) to be generated rather than nitric oxide (*NO). Recent reports indicate that apolipoprotein (apo) A-1 mimetics inhibit the development of atherosclerotic lesions in LDL receptor-null mice. Here we hypothesize that L-4F, an apoA-1 mimetic that inhibits atherosclerosis induced by hypercholesterolemia, protects endothelial cell function by preventing LDL from uncoupling eNOS activity. METHODS AND RESULTS: Bovine aortic endothelial cells were incubated with LDL+/-L-4F, and changes in A23187-stimulated.NO and O2*- generation were determined by ozone chemiluminescence and superoxide dismutase-inhibitable ferricytochrome c reduction, respectively. Western analysis of eNOS immunoprecipitates was used to determine effects of LDL and L-4F on heat shock protein 90 (hsp90) interactions with eNOS. LDL decreased.NO production and increased eNOS-dependent O2*- generation. Pretreatment of LDL with L-4F increased.NO and decreased O2*- generation. By itself, L-4F had no effect on O2*- but did increase *NO generation. Stimulation of endothelial cells incubated with LDL decreased the association of hsp90 with eNOS. Pretreatment of LDL with L-4F prevented a decrease in hsp90 association with eNOS and often enhanced association on stimulation. CONCLUSIONS: These data demonstrate that L-4F protects endothelial cell function by preventing LDL from uncoupling eNOS activity. L-4F allows endothelial cell to maintain coupled eNOS activity to generate.NO even in the face of atherogenic concentrations of LDL.

Animals↗

PubMed2003

Angiostatin: a negative regulator of endothelial-dependent vasodilation.

BACKGROUND: Angiostatin is known to inhibit certain aspects of endothelial function, eg, angiogenesis. Here we investigated the effects of angiostatin on another aspect of endothelial function, vasodilation, and examined mechanisms of inhibition--namely, association of heat-shock protein 90 (hsp90) with endothelial nitric oxide synthase (eNOS) and endothelial generation of nitric oxide (*NO) and superoxide anion (O2-). This avenue of investigation was based on recent reports suggesting that hsp90 modulates NOS production of *NO and O2-. METHODS AND RESULTS: Effects of angiostatin on vasodilation were determined in arterioles with the use of videomicroscopy in response to endothelium- and *NO-dependent vasodilators, acetylcholine (ACh) and vascular endothelial growth factor (VEGF), and an endothelium-independent agonist, papaverine. Association of hsp90 with eNOS was determined in rat aortas and bovine aortic endothelial cells (BAECs). Effects of angiostatin on *NO and O2- generation by BAECs were determined by ozone chemiluminescence and superoxide dismutase (SOD)--inhibitable ferricytochrome c reduction, respectively. Angiostatin impaired vasodilation mediated by ACh and VEGF but not papaverine. Pretreating arterioles with polyethylene glycolated--SOD (PEG-SOD) improved vasodilation to ACh and VEGF. Angiostatin decreased the association of hsp90 with eNOS in aortas and BAEC cultures and increased O2- generation in stimulated BAECs by an Lgamma-nitroargininemethylester (L-NAME)--inhibitable mechanism. CONCLUSIONS: These data indicate angiostatin alters endothelial function by allowing eNOS to generate O2- on activation. Such changes in enzyme function begin to explain, in part, why angiostatin is antiangiogenic and impairs endothelium-dependent vasodilation.

Angiostatins↗

PubMed2003

Inhibition of heat shock protein 90 (hsp90) in proliferating endothelial cells uncouples endothelial nitric oxide synthase activity.

Dual increases in nitric oxide ((*)NO) and superoxide anion (O(2)(*-)) production are one of the hallmarks of endothelial cell proliferation. Increased expression of endothelial nitric oxide synthase (eNOS) has been shown to play an important role in maintaining high levels of (*)NO generation to offset the increase in O(2)(*-) that occurs during proliferation. Although recent reports indicate that heat shock protein 90 (hsp90) associates with eNOS to increase (*)NO generation, the role of hsp90 association with eNOS during endothelial cell proliferation remains unknown. In this report, we examine the effects of endothelial cell proliferation on eNOS expression, hsp90 association with eNOS, and the mechanisms governing eNOS generation of (*)NO and O(2)(*-). Western analysis revealed that endothelial cells not only increased eNOS expression during proliferation but also hsp90 interactions with the enzyme. Pretreatment of cultures with radicicol (RAD, 20 microM), a specific inhibitor that does not redox cycle, decreased A23187-stimulated (*)NO production and increased L(omega)-nitroargininemethylester (L-NAME)-inhibitable O(2)(*-) generation. In contrast, A23187 stimulation of controls in the presence of L-NAME increased O(2)(*-) generation, confirming that during proliferation eNOS generates (*)NO. Our findings demonstrate that hsp90 plays an important role in maintaining (*)NO generation during proliferation. Inhibition of hsp90 in vascular endothelium provides a convenient mechanism for uncoupling eNOS activity to inhibit (*)NO production. This study provides new understanding of the mechanisms by which ansamycin antibiotics inhibit endothelial cell proliferation. Such information may be useful in the development and design of new antineoplastic agents in the future.

Animals↗

PubMed2003

Clinical and hematologic benefits of partial splenectomy for congenital hemolytic anemias in children.

OBJECTIVE: To assess the role of partial splenectomy for symptomatic children with various congenital hemolytic anemias. SUMMARY BACKGROUND DATA: The use of total splenectomy for symptomatic children with congenital hemolytic anemias is restricted by concern of postsplenectomy sepsis. A partial splenectomy is an alternative procedure, although its utility remains incompletely defined. METHODS: This longitudinal cohort study followed 25 symptomatic children with various congenital anemias who underwent partial splenectomy. Sixteen children had hereditary spherocytosis (HS), and nine children had other erythrocyte disorders. Outcome measures were clinical and laboratory hemolysis, splenic phagocytic and immune function, and splenic regrowth as measured by ultrasonography. Discrete parameters were compared using the Student test. RESULTS: Partial splenectomy was successful in all 25 children, with minimal morbidity. Follow-up ranged from 7 months to 6 years (mean 2.3 +/- 1.5 years). Following surgery, children with HS had increased hemoglobin values, decreased reticulocyte and bilirubin levels, and preserved splenic function. Most children without HS had decreased symptoms of hypersplenism and splenic sequestration. Over time, variable rates of splenic regrowth were noted, although regrowth did not necessarily correlate with recurrent hemolysis. CONCLUSIONS: In children with hereditary spherocytosis, a partial splenectomy appears to control hemolysis while retaining splenic function. In children with other congenital hemolytic anemias, a partial splenectomy appears to control symptoms of hypersplenism and splenic sequestration.

Adolescent↗

PubMedDate not supplied

Rosiglitazone antagonizes vascular endothelial growth factor signaling and nuclear factor of activated T cells activation in cardiac valve endothelium.

Nuclear factor of activated T cells, Cytoplasmic 1 (NFATc1) is required for heart valve formation. Vascular endothelial growth factor (VEGF) signaling, mediated by NFATc1 activation, positively regulates growth of valvular endothelial cells. However, regulators of VEGF/NFATc1 signaling in valve endothelium are poorly understood. Peroxisome proliferator-activated receptor gamma (PPARgamma) inhibits NFATc1 activity in T cells and cardiomyocytes, but it is not known if PPARgamma controls NFATc1 function in endothelial cells. The authors hypothesize PPARgamma antagonizes VEGF signaling in valve endothelium by inhibiting NFATc1. Endothelial cells isolated from human valve leaflet tissue were shown by immunocytochemistry to express the endothelial-specific markers von Willebrand factor (vWF) and platelet endothelial cell adhesion molecule (PECAM)-1. VEGF-induced proliferation and migration of human pulmonary valve endothelial cells (HPVECs) were inhibited by rosiglitazone (ROSI), a specific ligand of PPARgamma activation, suggesting that PPARgamma disrupts VEGF signaling in the valve endothelium. ROSI also antagonized VEGF-mediated NFATc1 nuclear translocation in HPVECs, suggesting that PPARgamma inhibits VEGF signaling of NFATc1 activation in the valve. The effect of ROSI on nonvalve human umbilical vein endothelial cells (HUVECs) was tested in parallel and a similar inhibition of NFATc1 activation was observed. These data provide the first demonstration that ROSI negatively regulates VEGF signaling in the valve endothelium by a mechanism involving NFATc1 activation and nuclear translocation.

Active Transport, Cell Nucleus↗