Deoxyribonuclease
Deoxyribonuclease
Deoxyribonuclease (pronounced "dee-oxy-rybo-noo-clee-ase"), or recombinant human deoxyribonuclease 1 (rhDNase or DNase), is an experimental drug used to treat cystic fibrosis (CF), an inherited lung disease. People with CF experience chronic (constant) and increasingly worse symptoms throughout their lives. CF patients often die in their late twenties. CF treatment has usually meant antibiotics and chest therapy (a physical pounding on the chest to loosen accumulated fluids).
DNase
Scientists discovered that the mucus (slimy secretion) of CF patients is full of DNA, which spills out of white blood cells as they die. DNase is an enzyme (a protein-like substance) that cuts the DNA present in the mucus. At first DNase was made from cows, but many patients had allergic reactions to it. Then a company separated the gene for human deoxyribonuclease, which chops up the protein but does not cause allergic reactions.
DNase is delivered to the patient in aerosol form, and it improves lung function by breaking up the thick mucus in the lungs. The patient is then able to clear the lungs by coughing. Considered among the ten most important advances of 1993—the year the drug was approved by the Food and Drug Administration (FDA)—it is also being considered for the treatment of chronic bronchitis.
[See also Antihistamine ; Enzyme ; Gene ; Gene therapy ]
Cystic Fibrosis
An inherited (genetic) disease that affects about 1 out of every 2,000 Caucasians of European descent, cystic fibrosis (CF) is the leading fatal genetic disease in the United States. CF occurs less frequently in African Americans and very rarely in Asians and Native Americans.
The disease causes a thick mucus to accumulate in the lungs, pancreas, and intestine. If the mucus blocks the lungs, the patient can die. Pneumonia, caused by bacterial infections, is a common problem for CF sufferers. People with CF suffer with abdominal (stomach) cramps, malnutrition, growth retardation, and coughing.
Other serious complications common in people with cystic fibrosis include respiratory (breathing) failure, diabetes, enlarged heart, liver cirrhosis (a disease in which liver cells are destroyed), intestinal blockage (bowel obstruction), pancreatic dysfunction (blocked ducts of the pancreas, preventing digestive enzymes from leaving the pancreas), sterility (inability to have children), and sodium (salt) deficiency. The increased saltiness of sweat is a highly useful test to diagnose CF, since predicting when any of these symptoms will appear or how severe they will be is a difficult task. Cystic fibrosis used to be fatal to nearly all children who developed it, but now more than 50 percent of CF patients live longer than 20 years.
Antihistamines and decongestants aid breathing by helping to open air passages. Antibiotics treat the pneumonia that often results from repeated lung infections. Physical therapy and surgery play roles in managing CF. Cough suppressants are avoided since coughing helps to loosen the mucus in the trachea and lungs. Newer treatments, such as DNase and gene therapy, have given mixed results.