Researchers at the University of Rochester Medical Center in New York said removing the gene that makes the protein cyclophilin A protected mice genetically predisposed to developing aneurysms.

Reporting in the journal Nature Medicine, the researchers said they were looking for drugs that might block this same protein in humans, offering a new way to protect people from abdominal aortic aneurysms, which kill 15,000 people a year in the United States.

Abdominal aortic aneurysms occur when the aorta - the body's main blood vessel - develops a weak spot and begins to bulge. They are often undetected, and when they rupture, they are fatal in 90 percent of cases.

Dr Bradford Berk, who led the study, said the cyclophilin A protein may offer a highly targeted way of preventing this process.

Prior studies of abdominal aneurysms have suggested that angiotensin II, a hormone for controlling blood pressure, brings about the vessel damage. Dr Berk thinks angiotensin II unlocks cyclophilin A, which causes a lot of the damage.

He said cyclophilin A encourages the production of harmful compounds known as reactive oxygen species, which trigger cells to self-destruct.

It also increases inflammation and degrades structural components in the vessel wall, weakening blood vessels. -- REUTERS

'ABSOLUTE PROTECTION'

To understand what role cyclophilin A plays, Dr Bradford Berk and colleagues used mice bred to be predisposed to high cholesterol and high blood pressure.

From this group, they bred mice that lacked cyclophilin A.

All were treated with angiotensin II, which is known to raise blood pressure and accelerate the development of aneurysms.

While 78 per cent of mice with normal amounts of the cyclophilin A developed aortic aneurysms, none of the mice who lacked the protein did.

Dr Berk said the same protein was found in abundance inside human aneurysms that were surgically removed.

Dr Berk said certain drugs, including cholesterol-lowering statins and ACE inhibitors, already have some effect on preventing aneurysms. He thinks a drug specifically targeting the cyclophilin A protein would have a stronger effect, especially when used in combination with these drugs. -- REUTERS