Sickle Cell Anemia

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What is sickle cell anemia?

Sickle cell anemia is an inherited disorder that affects hemoglobin, a protein that enables red blood cells to carry oxygen to all parts of the body. The disorder produces abnormal hemoglobin, which causes the red blood cells to sickle or become crescent-shaped.

Sickle cell anemia is characterized by a low number of red blood cells (anemia), infection, and periodic episodes of pain, usually beginning in early childhood. Symptoms vary from person to person; some people have mild symptoms, while others are frequently hospitalized.

With this disorder, sickle-shaped red blood cells are destroyed rapidly, causing anemia. Anemia can lead to shortness of breath, fatigue, and delayed growth and development in children. The rapid breakdown of red blood cells may also cause yellowing of the eyes and skin, which are signs of jaundice. Other symptoms of sickle cell anemia occur when the stiff, inflexible sickled red blood cells get stuck in small blood vessels, depriving organs and tissues of oxygen-rich blood. A serious complication of sickle cell anemia is high blood pressure in the blood vessels that supply the lungs (pulmonary hypertension). Pulmonary hypertension occurs in about one-third of adults with sickle cell disease and can lead to heart failure.

How common is sickle cell anemia?

Sickle cell anemia affects millions of people worldwide. It is particularly common among people whose ancestors come from Africa, Mediterranean countries (such as Greece, Turkey, and Italy), the Arabian peninsula, India, and Spanish-speaking regions (South America, Central America, and parts of the Caribbean).

Sickle cell anemia is the most common inherited blood disorder in the United States, affecting 70,000 to 80,000 Americans. The disease occurs in approximately 1 in 500 African-American newborns and 1 in 1,000 to 1,400 Hispanic-American births.

What genes are related to sickle cell anemia?

Mutations in the HBB gene cause sickle cell anemia.

The HBB gene produces one of the subunits of hemoglobin, called beta hemoglobin or the beta chain. A mutation in the HBB gene produces an abnormal version of beta hemoglobin known as hemoglobin S (HbS). Hemoglobin S can distort red blood cells into a sickle or crescent shape. The sickle-shaped red blood cells die prematurely, which can lead to anemia. Sometimes the inflexible, sickle-shaped cells get stuck in small blood vessels and can cause serious medical complications.

How do people inherit sickle cell anemia?

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder.

Source: National Institutes of Health

Research on sickle cell anemia published by scientists at State University of Campinas

"Neutrophils from SCD individuals showed an inhibition of spontaneous apoptosis when cultured in vitro, in the presence of autologous serum for 20 h. Intracellular cyclic adenosine monophosphate (cAMP) levels were approximately twofold increased in SCD neutrophils; possible cAMP-upregulating factors present in SCD serum include interleukin-8, granulocyte-macrophage colony-stimulating factor and prostaglandin. Accordingly, co-incubation of SCD neutrophils with KT5720, a cAMP-dependent protein kinase (PKA) inhibitor, abrogated increased SCD neutrophil survival. Caspase-3 activity was also significantly diminished in SCD neutrophils cultured for 16 h and this activity was restored when cells were co-incubated with KT5720. BIRC2 (encoding cellular inhibitor of apoptosis protein 1, cIAP(1)), MCL1 and BAX expression were unaltered in SCD neutrophils; however, BIRC3 (encoding the caspase inhibitor, cIAP(2)), was expressed at significantly higher levels. Thus, we report an inhibition of spontaneous SCD neutrophil apoptosis that appears to be mediated by upregulated cAMP-PKA signalling and decreased caspase activity," wrote N. Conran and colleagues, State University of Campinas.

The researchers concluded: "Increased neutrophil survival may have significant consequences in SCD; contributing to leucocytosis, tissue damage and exacerbation of the chronic inflammatory state."

Conran and colleagues published the results of their research in British Journal of Haematology (Inhibition of caspase-dependent spontaneous apoptosis via a cAMP-protein kinase A dependent pathway in neutrophils from sickle cell disease patients. British Journal of Haematology, 2007;139(1):148-58).

For additional information, contact N. Conran, State University of Campinas - UNICAMP, The Haematology and Haemotherapy Centre, Campinas, SP, Brazil.

The publisher of the British Journal of Haematology can be contacted at: Blackwell Publishing Ltd., 9600 Garsington Rd., Oxford OX4 2DG, Oxon, England.

Keywords: Brazil, Campinas, Apoptosis, Caspase, Cell Biology, Enzyme Research, Hematology, Kinase, Sickle Cell Anemia, Sickle Cell Disease.

This article was prepared by Hematology Week editors from staff and other reports. Copyright 2007, Hematology Week via NewsRx.com.