Scientist discovers natural molecule indirectly prevents stable clot formation

Feb 01, 2011

A scientist from The Scripps Research Institute has identified a new role for a natural signaling molecule in preventing blood clot formation. The molecule could become a target for the development of novel and cost-effective treatments for blood clotting diseases such as Hemophilia A.

The findings, from a study by Scripps Research Assistant Professor Laurent O. Mosnier, were published in a recent edition of .

The study focused on Platelet Factor 4 – a small (intracellular signaling molecule) released during platelet aggregation.

Based on Platelet Factor 4 effects on another coagulation protein, it was thought that Platelet Factor 4 could potentially stimulate activation of thrombin-activatable fibrinolysis inhibitor (TAFI) – an enzyme (soluble protein) that protects clot longevity, making clots last longer and preventing excess bleeding; TAFI is like a hardener that is added to the mortar used between the bricks in a brick wall, without which the mortar would never completely solidify, and the wall would never be solid.

The new study, however, found exactly the opposite role for Platelet Factor 4—inhibition of TAFI activation.

For Mosnier, this finding led to a radical idea—sequestering Platelet Factor 4 using such as heparin derivatives could improve clot stability. Heparin - a highly sulfated or negatively charged glucoseaminoglycan (polysaccharide or sugar derivative) – is a commonly used anticoagulant. Mosnier, however, was able to modify the compound to have the reverse effect and aid in blood clotting in laboratory tests.

"The idea of using heparin to prevent bleeding in kids [who have bleeding tendencies] would be outrageous because that would just greatly accelerate bleeding," said Mosnier, "Our trick, however, was to modulate heparin's anticoagulant properties. This opens up new possibilities."

Converting Heparin from an Anticoagulant into a Non-Anticoagulant

Heparin's anticoagulant activity is derived from a specific pattern of nitrogen- and oxygen-linked sulfation (or simply negative charges) that is recognized by anti-thrombin – the inactivator of coagulation. However, in addition to binding to anti-thrombin heparin also binds to Platelet Factor 4, which is glittered with positive charge, and they attract one another like magnets.

Mosnier found heparin's anticoagulant activity could be prevented, and its Platelet Factor 4 binding selected for, by selectively removing the N-linked sulfations (and further acetylation). This effectively prevented heparin from being recognized by anti-thrombin and allowed it to instead take the Factor 4 out of the equation. This resulted in prevention of clot breakdown (fibrinolysis), by allowing TAFI to do its job.

To test the effectiveness of the modified heparin derivatives in enhancing clot stability, Mosnier employed a functional assay called a "clot lysis assay." Using a light scattering technique, plasma was used to generate a clot, which was degraded. Further modulation of the conditions allowed measurement of clot stability via TAFI activation. Mosnier found that, indeed, the modified-version heparin promoted clot stability.

Toward a Cheaper, Cost-Effective Treatment for Hemophilia A

An optimistic Mosnier admits his new discovery is in its infancy, but hopes it may one day provide an alternative treatment for bleeding conditions such as A.

Hemophilia A, which affects 1 in 5,000 males, is an X-linked genetic bleeding disorder whereby there is a reduced amount or activity of factor VIII. This results in the unstable clots, lacking fibrin – a fibrous clot-forming protein. Currently, the treatment for Hemophilia A is prophylactically taking factor VIII as a medicine to improve clotting. Unfortunately, immunity against factor VIII is a significant side effect.

Mosnier hopes that modification of heparin – which is cheaper than factor VIII and already used clinically – could one day stabilize clots in these patients.

"The next step is to see if the modified compound will improve bleeding complications in the Hemophilia mouse," said Mosnier. "We are still a long way from claiming anything clinically."

His optimism is contagious, however, and it is an exciting time for science in the Mosnier lab.

Explore further: Chemical biologists find new halogenation enzyme

More information: Professor Laurent O. Mosnier of the Scripps Research Institute was sole author of the study, "Platelet Factor 4 Inhibits Thrombomodulin-dependent Activation of Thrombin-activatable Fibrinolysis Inhibitor (TAFI) by Thrombin." For more information, see www.jbc.org/content/286/1/502.… 9a-b999-0eb4d69e474a

Related Stories

New animal model for hemophilia A developed

Sep 03, 2010

(PhysOrg.com) -- Researchers at Yale School of Medicine have developed a new animal model for studying hemophilia A, with the goal of eventually treating people with the disorder. Hemophilia A, a hereditary defect that prevents ...

Blood clotting finding may lead to new treatments

Feb 10, 2010

A key protein that causes the blood to clot is produced by blood vessels in the lungs and not just the liver, according to new research published today in the journal PLoS One, led by scientists at Imperial College London ...

Key found to breakthrough drug for clot victims

Mar 10, 2008

A team of researchers at Oregon Health & Science University and Washington University in St. Louis have described for the first time the mechanism that gives a mutant enzyme molecule that they have engineered – and patented ...

Researchers create new synthetic heparin

Sep 21, 2007

Researchers at the University of North Carolina at Chapel Hill have patented a synthetic version of the drug heparin, called Recomparin, that is less complex chemically and should be easier to produce than previous forms.

Redesigned protein accelerates blood clotting

Dec 22, 2008

Researchers have made several, subtle changes in the structure of a key protein, dramatically increasing its ability to drive blood clotting, according to a study published in a December edition of the Journal of Thrombosis an ...

Recommended for you

Chemical biologists find new halogenation enzyme

15 hours ago

Molecules containing carbon-halogen bonds are produced naturally across all kingdoms of life and constitute a large family of natural products with a broad range of biological activities. The presence of halogen substituents ...

Protein secrets of Ebola virus

20 hours ago

The current Ebola virus outbreak in West Africa, which has claimed more than 2000 lives, has highlighted the need for a deeper understanding of the molecular biology of the virus that could be critical in ...

Protein courtship revealed through chemist's lens

20 hours ago

Staying clear of diseases requires that the proteins in our cells cooperate with one another. But, it has been a well-guarded secret how tens of thousands of different proteins find the correct dancing partners ...

Decoding 'sweet codes' that determine protein fates

22 hours ago

We often experience difficulties in identifying the accurate shape of dynamic and fluctuating objects. This is especially the case in the nanoscale world of biomolecules. The research group lead by Professor Koichi Kato of ...

Conjecture on the lateral growth of Type I collagen fibrils

Sep 12, 2014

Whatever the origin and condition of extraction of type I collagen fibrils, in vitro as well as in vivo, the radii of their circular circular cross sections stay distributed in a range going from 50 to 100 nm for the most ...

User comments : 0