The cellular response to Viagra may be harnessed to help create new anticoagulant therapies, according to an article released on August 26, 2008 in the Proceedings of the National Academy of Sciences (PNAS.)

The enzyme PDE5 is known to modulate platelet activity. Normally, platelets exist in the blood and have an integral role in blood clotting. However, when patient have certain biomedical devices implanted, such as stents, which are installed in the arteries to maintain blood flow through them, the foreign materials of the devices , are recognized by the body and platelets often clot to them. If too many clot, this can block blood flow, potentially inducing a stroke or heart attack.

While Viagra is most famous for its use in treatment of erectile dysfunction, it was initially targeted as a drug for the cardiovascular system as a whole and is also used to treat pulmonary hypertension in some patients. Drugs like Viagra have been previously shown to inhibit PDE5, but further research was necessary to understand where or how this was occurring.

This study, led by Prof. Donald Maurice of Queen’s College focused on the relationship between Viagra and the levels of PDE5 inhibition in cells. They showed that, within each cell, several pools of the PDE5 enzyme may exist. However, only one of these pools might regulate platelet activation. By targeting each pool, it may be possible to revamp Viagra’s use to regulate clotting in the blood, helping prevent heart attacks and strokes. “Understanding how the cell works should allow us to affect the activity of enzymes in one neighborhood — and leave alone their ‘identical twins’ in a different neighborhood in that cell,” says Ms. Wilson, lead author on the study.

The authors note the potential that arises from these developments, both in basic and clinical science. “As scientists, we’re excited about this discovery because it’s a fundamentally new approach to regulating what enzymes do in cells,” states Dr. Maurice. “The fact that it also offers a potentially novel use of a drug already widely in use for other applications is an unexpected bonus.” Ms. Wilson continues, hopeful for the potential application of this new knowledge: “The idea is to use a PDE5 inhibitor such as Viagra selectively to inhibit platelet function. We now know that not all the enzymes in the cell are doing the same job. Just like in real estate, it’s all about the location!”

Tuesday August 26, 2008
Proceedings of the National Academy of Sciences
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Written by Anna Sophia McKenney