Acute-phase response and sickle crisis

Apolipoprotein A-I and serum amyloid A plasma levels are biomarkers of acute painful episodes in patients with sickle cell disease

BACKGROUND

Acute painful episodes are the clinical hallmark of sickle cell disease and have been linked to morbidity and mortality in the sickle cell population.

DESIGN AND METHODS

We undertook exploratory proteomic studies on paired plasma samples collected from a cohort of 26 adult sickle cell patients during steady state and on the first day of an acute painful episode. We screened for changes in abundance of specific protein peaks via surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF MS), and confirmed the identify of candidate protein peaks by specific immunoassays.

RESULTS

The levels of hemoglobin, hematocrit, total protein, and albumin were lower and the levels of lactate dehydrogenase and absolute reticulocytes higher during acute painful episodes than during the steady state. Surface-enhanced laser desorption/ionization time of flight mass spectrometry spectral analysis consistently showed a mass-to-charge peak at 11.7 kDa with elevated intensities during acute painful episodes, which correlated significantly with the serum amyloid A immunoassay. Serum amyloid A levels were significantly elevated during acute painful episodes, especially in four patients with marked end-organ complications of such episodes. A second, recurring peak, less abundant during acute painful episodes, was present at 28.1 kDa; this peak was correlated significantly with immunoassay measurements of apolipoprotein A1.

CONCLUSIONS

On the average, plasma serum amyloid A rises and apolipoprotein AI falls during acute painful episodes. The serum amyloid A/apolipoprotein AI ratio increased in 81% of the patients during acute painful episodes, potentially making it a useful objective marker of such episodes. We propose that these protein alterations, known to contribute to endothelial dysfunction in other settings, might do likewise acutely in acute painful episodes and present a new target for therapeutic intervention in sickle cell disease. (ClincalTrials.gov Identifier: NCT00081523).

Vitamin A status, hospitalizations, and other outcomes in young children with sickle cell disease

OBJECTIVE

To determine the relation of serum vitamin A status to growth, nutritional and hematologic status, and to the number of hospitalizations in children with sickle cell disease-SS (homozygous for the S allele, SCD-SS).

STUDY DESIGN

Children (2-9.9 years of age) with SCD-SS were assessed for serum retinol, hemoglobin, hematocrit, reticulocyte count, height, weight, body mass index, and recalled dietary intake. Vitamin A status was defined on the basis of serum retinol concentration as suboptimal (<30 microg/dL) and normal (> or =30 microg/dL). Hospitalizations were determined for 1 year after vitamin A assessment.

RESULTS

Mean serum retinol was 26.7 +/- 6.8 microg/dL in 66 subjects (39 girls) and was suboptimal in 66% of children. Compared with those with normal status, children with suboptimal vitamin A had significantly lower body mass index z score (-0.7 +/- 1.0 vs -0.1 +/- 0.6) and hemoglobin (7.9 +/- 1.1 vs 8.5 +/- 1.1), and hematocrit (23.3 +/- 3.0 vs 25.1 +/- 3.8) and significantly more hospitalizations (2.8 +/- 2.0 vs 0.7 +/- 0.8). After adjusting for age and sex, suboptimal vitamin A status was associated with a 10-fold increased risk for hospitalization (OR, 10.5; 95% CI, 2.3, 48.6) and with increased pain (OR,5.3; 95% CI, 1.3, 21.6) and fever episodes (OR, 6.4; 95% CI, 1.7, 24.9) requiring hospitalization.

CONCLUSIONS

Suboptimal vitamin A status was prevalent in US children with SCD-SS and was associated with increased hospitalizations and poor growth and hematologic status.

Assessment of painful episode frequency in sickle-cell disease

Frequency of painful episodes in sickle-cell disease is considered to be related to clinical severity and possibly to other aspects of the disease. Measurements of frequency often include only hospital-related or more severe, longer-lasting episodes. Since painful episodes, however, may regularly occur in nonhospital settings or be shorter-lasting with possible different pathologic effects, we measured all painful episodes in 10 adults with sickle-cell disease for 1.0-3.8 years, using a daily questionnaire. The results were related to other indices of disease severity and to possible precipitating factors, such as cold weather and menses. Sixty-one percent (on average) of the total number of episodes (243) were nonhospital-related, and 33% (on average) were shorter-lasting. Episode frequencies, whether determined as total, hospital-related, nonhospital-related, or shorter-lasting, were not related to each other or to other indicators of disease severity. The highest incidence of episode frequency occurred in the winter. The association of episodes with menses was moderately close in individual patients. The findings suggest that nonhospital-related painful episodes and shorter-lasting episodes may contribute significantly to episode frequency. Measurement of frequency of all painful episodes would require consideration when evaluating episode frequency and its relationship to disease severity, to possible precipitating factors of episodes, and to treatment of the disease, and for study of the natural course of the disease.

New concepts in the immunology of sickle cell disease

OBJECTIVE

Our objective is to review the role of adhesion molecules, cytokines, and inflammation in the abnormal adherence of sickle red blood cells to vascular endothelia in the pathogenesis of vascular complication in patients with sickle cell anemia.

DATA SOURCES

The MEDLINE database was used to review the hematologic, immunologic, and allergy literature in English with respect to the adhesion molecules involved in sickle hematopoiesis and vascular complications.

STUDY SELECTION

Studies selected for review were those that identified the adhesion molecules involved in reticulocyte-endothelial adhesion and the influence that cytokines, infections, and atopy have upon the expression of these molecules.

RESULTS

In sickle cell disease, a constant low level of inflammation caused by abnormal adhesion of sickle erythrocytes to endothelial cells in the microvasculature produces low-level tissue ischemia. Allergic and infectious inflammations are likely to lead to increased sickle erythrocyte trapping in the microvascular endothelia which progresses to vessel obstruction, end organ ischemic damage, and dysfunction.

CONCLUSION

The identification of underlying immune defects that predispose patients to infections and inflammation needs to be emphasized. Anti-inflammatory medications, anti-adhesion molecule monoclonal antibodies, and adhesion molecule binding-site analogs may have a future in the treatment of the acute vascular complications of sickle cell disease.