How "good" cholesterol protects arteries.

• Position: Circulatory System - Brief Article

Scientists at The University of Texas Southwestern Medical Center at Dallas have discovered that high-density lipoprotein (HDL)--the "good cholesterol"--triggers a process that keeps arteries clean and flexible. This, researchers believe, could lead to new strategies to prevent or treat vascular diseases such as atherosclerosis, commonly known as hardening of the arteries.

"What we have found is that HDL is a robust stimulator of nitric oxide production in endothelial cells, which are the thin layer of cells lining the arterial wall," explains Philip W. Shaul, professor of pediatrics. Nitric oxide, he says, is a potent signaling molecule that keeps arteries clean and flexible, thereby preventing them from clogging and constricting, processes that restrict blood flow and lead to high blood pressure, strokes, and heart attacks. The study found that:

* One of the major protein components of HDL, apolipoprotein A-I, which is protective against atherosclerosis in humans, is crucial to stimulating nitric oxide production.

* Another protein, known as scavenger receptor-BI, which enables the HDL particle to bind to the cell surface, is...