— An angiogenesis-regulating protein has been identified by a team led by UCSD researchers. Called AIBP, the protein may provide a new tool to identify drugs to retard blood vessel growth in tumors or promote it when new blood vessels are desired, such as in the hearts of heart attack patients.

AIBP helps remove cholesterol from endothelial cells, which line blood vessels. Cholesterol is necessary for normal cell function, but excess leads to inflammation and other disease processes. AIPB prevents excessive growth of blood vessels, such as that seen in tumors.

The study was published Wednesday in Nature. The first author is Longhou Fang, senior author is Yury I. Miller. The team studied the protein's effect in zebrafish, a common model organism, in addition to examining the protein's role in cholesterol removal from human umbilical vein endothelial cells, or HUVECs.

The study noted that AIBP is evolutionarily conserved between Drosophila, zebrafish, mouse and human.

Disorganized blood vessels shown in AIBP knockdown zebrafish: Green, endothelial cells; red, fluorescent dextran were injected to visualize the blood vessel lumen.
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Researchers have been pursuing anti-angiogenic drugs such as Genentech's Avastin for decades to control cancers and other diseases in which blood vessel growth plays a role, such as wet macular degeneration.

Conversely, promoting new blood vessel growth is desirable in heart attack patients. So the protein may be of use in both indications, depending on whether production is suppressed or enhanced.

While the role of cholesterol-removal mechanisms in preventing atherosclerosis is known, the paper said the study is the first to demonstrate the role AIBP plays in this process.

As part of the research, HUVECS were grown with AIBP and HDL3, a subfraction of HDL which efficiently binds to cholesterol. The cells were then given vascular endothelial growth factor, or VEGF, which is known to stimulate blood vessel growth.

"AIBP and HDL3 added separately did not affect endothelial cell tube formation, but together they significantly reduced angiogenesis," the paper stated.