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Sickle Cell Anemia

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Red blood cells contain hemoglobin which carries oxygen from the lungs to the rest of the body. Hemoglobin is an iron-rich protein therefore cells have a red colour. Normal red blood cells are disc-shaped and that helps them move easily through blood vessels. By contrast, sickle cells contain abnormal hemoglobin that causes the cells to have a sickle or crescent shape which complicates their movement through blood vessels. In addition, sickle cells are sticky and stiff therefore they constantly form clumps and get stuck blocking other cell movement.  This can cause pain, serious infections and organ damage due to a lack of oxygen supply to these parts.

Sickle cell anemia is an inherited, lifelong disease. People who have the disease inherit two copies of the sickle cell gene—one from each parent. Sickle cell anemia is one type of anemia – a condition in which blood has either a lower than normal number of red blood cells or cells do not contain enough hemoglobin. In sickle cell anemia, the number of red blood cells is low because sickle cells do not last long. They usually die after 10 to 12 days, whereas normal red blood cells live for about 120 days.
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People who inherit a sickle cell gene from one parent and a normal gene from the other parent have a condition called sickle cell trait which is different than sickle cell anemia. However, like people who have sickle cell anemia, people who have sickle cell trait can pass the sickle cell gene on to their children.


Nitric Oxide – a Key Link in Oxygen Supply

Research into Sickle Cell as recently as 2005 suggests that an inability of red blood cells to relax blood vessels through the release of nitric oxide is a major factor behind the disease’s primary symptoms — including oxygen deprivation and blocked vessels that can lead to pain, clots and stroke. Thus, therapies that restore nitric oxide to blood cells might serve as a useful method for treating the disease, said HHMI researcher Jonathan Stamler, M.D., professor of pulmonary medicine and cardiology at Duke University Medical Center.

The symptoms of sickle cell disease have generally been attributed to the physical obstruction of blood vessels by distorted, or “sickled,” and rigid red cells, Stamler said. The new findings, for the first time, implicate abnormal vessel dilation by the red cells themselves in oxygen deficiency. That oxygen deficiency, in turn, may result in sickling and, ultimately, the irreversible obstruction of blood vessels.

Nitric Oxide and Hemoglobin production

Patients with sickle cell disease have an abnormal form of hemoglobin – it has an incorrectly folded protein. In the late 1990s, Stamler’s team discovered that, in addition to its role in oxygen delivery, hemoglobin acts a biosensor, adjusting blood flow according to the oxygen demand of tissues and organs, by distributing nitric oxide.

Reports in 2001 and 2002 further detailed nitric oxide’s role in the red blood cell membrane, confirming it as the third major blood gas, along with oxygen and carbon dioxide. Those findings suggested that nitric oxide defects might play a role in the cardiovascular side effects of many disorders, including diabetes, heart attacks, septic shock and sickle cell disease. 

In the current study, the researchers found that hemoglobin in the red cells of patients with sickle cell disease fails to process nitric oxide properly. As a result, they reported, the membranes of sickle red blood cells are deficient for the form of nitric oxide normally released by the cells. The blood cells therefore fail to open blood vessels normally.


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