Lack of Amino Acid Spurs Deadly Sickle Cell Complication

    A molecule of the amino acid alanineA deficiency of the amino acid arginine may contribute to the development of
    pulmonary hypertension — a potentially deadly complication — in people with
    sickle cell anemia, a new study suggests.

    A process called hemolysis, in which red blood cells rupture, is what causes
    the arginine deficiency, researchers said.

    “Within the red blood cell, there is a high concentration of an
    arginine-consuming enzyme called arginase,” said the study’s lead author, Dr.
    Claudia Morris, the director of research for the pediatric emergency fellowship
    at Children’s Hospital and Research Center in Oakland, Calif.

    When arginase is released during hemolysis, explained Morris, that “triggers
    a cascade of events that lead to pulmonary hypertension.”

    The study findings appear in the July 6 issue of the Journal of the
    American Medical Association
    .

    Sickle cell anemia is a disease that causes red blood cells to become
    sickle-shaped. This abnormal shape makes blood clots more likely, and when a
    blood clot blocks a blood vessel it can cause extreme pain, according to the
    National Institutes of Health (NIH). These damaged blood cells are also more
    likely to break down prematurely in a process known as hemolysis. Sickle cell
    disease strikes African-Americans more frequently than other racial groups.

    An estimated one person of every three with sickle cell disease will
    eventually develop pulmonary hypertension — high blood pressure in the arteries
    of the lungs, Morris said. According to the NIH, pulmonary hypertension causes
    the heart to work harder and become enlarged. Eventually, it can lead to heart
    failure and death,

    “It’s a life-threatening condition, and it’s what many adult sickle cell
    patients die from,” she said.

    For this study, Morris and her colleagues compared 228 people with sickle
    cell anemia — ages 18 to 74 — to 36 healthy individuals.

    The researchers measured blood amino acid levels and arginase activity. They
    also tested all of the participants with sickle cell disease for pulmonary
    hypertension using Doppler echocardiography — ultrasound of the lungs.

    The researchers found that activity of the enzyme arginase was significantly
    higher in people with sickle cell anemia than in the healthy individuals, and
    those participants with pulmonary hypertension had the highest arginase
    levels.

    Arginase consumes an important amino acid, arginine, the researchers
    explained. They found that study participants with the lowest amounts of
    arginine were also 3.6 times more likely to die than those with the highest
    levels of bioavailable arginine.

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