Biomedical subjects

Marie J Stuart

Publications and source records attributed to Marie J Stuart.

4 recordsLinked to original sources

PubMed2003

Hypoxaemia in sickle cell disease: biomarker modulation and relevance to pathophysiology.

BACKGROUND: Nocturnal oxyhaemoglobin desaturation might have a role in CNS complications related to sickle cell disease, and rates of painful crises. We attempted to examine the biological relations, and describe the haematological risk factors for oxyhaemoglobin desaturation. METHODS: The study population included children with sickle cell disease and controls. Cellular activation was assessed by measurement of soluble vascular cell adhesion molecule 1, P-selectin, L-selectin, and leukotriene B4. Erythrocyte-endothelial adhesion and routine haematological variables were assessed. Oxygen saturation (SaO2) was measured by pulse oximetry while children were awake and asleep. Children with a mean sleeping SaO2 of < or =93% were identified as hypoxaemic. Children were divided into four groups: controls (ten children), HbSC (nine, all normoxic), HbSS normoxic (13), and HbSS hypoxaemic (15). FINDINGS: Among haematological variables, sleeping SaO2 correlated only with packed-cell volume (r=0.7; p<0.0001). Inverse relations were noted between sleeping SaO2 and adhesion (-0.45; p<0.01), and markers of white-cell (-0.51; p<0.01), platelet (-0.61; p<0.001), and endothelial activation (-0.46; p<0.01). In the HbSS group who had sleeping hypoxaemia, waking SaO2 measurements showed continuing hypoxaemia, with similar correlation between SaO2 and cell activation markers. INTERPRETATION: Our adhesion-related findings suggest a potential mechanism for the increased occurrence of clinical vaso-occlusive crises in individuals with sickle cell disease who have oxyhaemoglobin desaturation. Release of cellular mediators in hypoxaemia, and the relation between anaemia and oxyhaemoglobin desaturation, suggest that risk factors for stroke, including anaemia, might have a role in CNS-vasculopathy through hypoxia-mediated pathways. Further more, hypoxaemia in the older child also occurs during the day; such mild untreated hypoxia could lead to an increased risk of vaso-occlusive episodes.

Adolescent↗

PubMed2002

Role of erythrocyte phosphatidylserine in sickle red cell-endothelial adhesion.

Phosphatidlyserine (PS) exposure on the erythrocyte surface endows the cell with the propensity of adhering to vascular endothelium. Because individuals with sickle cell disease (SCD) manifest loss of erythrocyte membrane asymmetry with PS exposure, we have assessed the contribution of this marker to the process of sickle erythrocyte-microendothelial adhesion. Assays for plasma-induced adhesion were conducted on unactivated endothelium, in the absence of immobilized ligands, such that PS was compared to the erythrocyte adhesion receptor CD36. Blocking studies with erythrocytes pretreated with annexin V (to cloak PS) or anti-CD36 or both revealed an inhibitory effect on adhesion of 36% +/- 10% and 23% +/- 8% with blocking of both sites suggestive of an additive effect. We next evaluated 87 blood samples from patients with SCD and grouped them into 4 categories based on adhesion marker (CD36 and PS) levels. Results revealed a striking correlation between erythrocyte PS positivity and adhesion. Analyses of the individual patient data demonstrated a positive correlation between PS and adhesion (R = 0.52, P <.000 001), whereas none was noted between adhesion and CD36 (R = 0.2, P >.07). The effect of PS on adhesion appears to be related to the quantitative differences in erythrocyte markers in SCD, with PS the predominant marker when compared to CD36 both in the total erythrocyte population, and when the adherence-prone erythrocyte, the CD71(+) stress reticulocyte, was evaluated. Our study signals the entrance of an important new contributor to the field of sickle erythrocyte-endothelial adhesion. The implications of erythrocyte PS exposure in relation to the vascular pathology of SCD need to be assessed.

Adolescent↗

PubMed2002

Eicosanoids in sickle cell disease: potential relevance of neutrophil leukotriene B4 to disease pathophysiology.

Neutrophil activation with the release of intracellular granule contents has been observed in sickle cell disease (SCD). Because leukotriene B(4) (LTB(4)), a 5-lipoxygenase metabolite of arachidonic acid in neutrophils, is a chemoattractant and enhances neutrophil adhesion to endothelium, we assessed plasma levels of this metabolite in controls (n = 9) and individuals with SCD, SS genotype, both in basal "steady state" (n = 37) and during episodes of vaso-occlusion (n = 10) and acute chest syndrome (n = 5). Thirteen patients with SCD, SC genotype, in steady state were also studied. Although no significant differences were noted between the control (136 +/- 32 fmol/mL) and SC genotype (177 +/- 83 fmol/mL, P >.15), LTB(4) levels were markedly increased in patients with SS genotype in basal steady state (207 +/- 64 fmol/mL, P <.003) compared with those in controls. Values were further increased during vaso-occlusion (264 +/- 94 fmol/mL) and acute chest syndrome (363 +/- 124 fmol/mL). These levels were significantly different from measurements taken during steady state (P <.04 and P <.0001, respectively). No correlation was noted between LTB(4) level and total white cell or neutrophil count. Additionally, the significant correlation noted in SCD between increased levels of plasma LTB(4) and soluble L-selectin (P <.03) reflects neutrophil activation. We also observed an effect of LTB(4) on red cell-endothelial adhesion at concentrations that appear clinically relevant (1-10 pmol/mL) with concomitant up-regulation of mRNA for the endothelial vitronectin receptor. These properties of LTB(4) are relevant to disease pathophysiology, providing further evidence of the contribution of the neutrophil to the proinflammatory and proadhesive phenotype in SCD.

Adolescent↗

PubMedDate not supplied

Sickle-cell disease.

With the global scope of sickle-cell disease, knowledge of the countless clinical presentations and treatment of this disorder need to be familiar to generalists, haematologists, internists, and paediatricians alike. Additionally, an underlying grasp of sickle-cell pathophysiology, which has rapidly accrued new knowledge in areas related to erythrocyte and extra-erythrocyte events, is crucial to an understanding of the complexity of this molecular disease with protean manifestations. We highlight studies from past decades related to such translational research as the use of hydroxyurea in treatment, as well as the therapeutic promise of red-cell ion-channel blockers, and antiadhesion and anti-inflammatory therapy. The novel role of nitric oxide in sickle-cell pathophysiology and the range of its potential use in treatment are also reviewed. Understanding of disease as the result of a continuing interaction between basic scientists and clinical researchers is best exemplified by this entity.

Acute Disease↗