Hormone Behind Heart Failure Tests May Also Fuel Blood Clots

Heart Failure Hormone BNP Sped Clotting in Mice, Study Finds

For years, a high result on a heart failure blood test has worked like a warning light: the heart is straining, and that is all it says. A new study in the journal Blood hints that light may be doing more than warning. The hormone behind the test, called BNP, may also push blood toward clotting, the kind that can block an artery and cause a heart attack or stroke.

Doctors check BNP, short for B-type natriuretic peptide, to help diagnose heart failure and gauge a patient’s risk. High levels also go hand in hand with heart attacks, strokes, and clots in people with heart disease and atrial fibrillation, an irregular heartbeat. Whether the hormone simply reflects that danger or adds to it has been an open question.

Researchers at Texas A&M University found that BNP latches onto a receptor on platelets, the tiny blood cells that form clots, and makes them quicker to clump. In mice, a small dose sped up clotting, and more of the mice given BNP died after a clot-triggering lung test. Nearly all of this comes from animals and lab dishes, so it is not yet known whether BNP triggers clots in patients.

BNP Makes Platelets Quicker to Clump in Lab Tests

Experiments began in dishes, with platelets from mice and from healthy adult volunteers. BNP alone did not make them stick together. Added to weak clotting triggers, though, it made platelets far more reactive: they clumped more, released more of their stored chemicals, spread out further, and pulled clots tighter. That happened at BNP levels like those found in people with heart failure or a sudden heart emergency. Platelets act like the body’s emergency patch crew, rushing to plug a cut, so a hormone that makes them jumpier could, in theory, tip a helpful response into a harmful one.

Next, researchers looked for how BNP pulled this off. Platelets carry a receptor called NPRA, the same docking site BNP uses elsewhere in the body to relax blood vessels. Human and mouse platelets both had it. Once BNP docked, platelets became more willing to clot. In platelets from mice bred without NPRA, BNP did nothing, and a drug that blocks the receptor reversed BNP’s boost in human platelets. Platelets lacking the receptor were also sluggish even without added BNP, and BNP turned up inside platelets, which can take it in from the blood.

BNP Sped Up Blood Clots in Mice That Had the Receptor

Live animals came next. Young adult mice, male and female, got either a tiny BNP injection, enough to raise blood levels within minutes, or plain saltwater. Researchers then injured a neck artery with a chemical, a standard way to trigger a clot. Across groups of 13 to 14 mice, those given BNP formed blocking clots significantly faster. A second test mimicked a dangerous lung clot, using a substance injected into the bloodstream that sets off clotting. Without BNP, clots in large lung vessels only partly blocked flow. With BNP, they blocked it completely, and lung tissue showed heavier clot damage.

Mice lacking NPRA behaved differently from the start. Their tails bled longer after a cut and artery clots took longer to form (17 to 27 mice per group), hinting that the receptor also helps the body stop bleeding. Given BNP, these mice clotted no faster in the artery test, and clots in large lung vessels did not worsen. Only a slight rise in small-vessel clots appeared. They were also spared the extra deaths seen in normal mice.

Patients With Higher BNP Tended to Have Stickier Platelets

Then came patients. Blood from 21 patients with atrial fibrillation, a rhythm disorder tied to higher stroke risk, was collected at the University of Kentucky with written consent. Patients with higher BNP tended to have platelets that clumped more in response to a weak clotting trigger. Earlier research had tied high BNP in atrial fibrillation to clot-related strokes. In this group, the platelet link was modest, and the sample was small.

Aspirin, one of the most common clot-preventing drugs, still slowed platelet clumping in lab tests when BNP was present. The authors add that BNP’s route may not be directly targeted by aspirin or similar drugs, so the hormone may be pushing platelets down a path those medications miss, an idea still untested.

Blocking BNP’s Receptor Could Carry Risks, Authors Caution

Any treatment aimed at NPRA would need care, since the receptor is common in heart and blood vessel tissue and helps control blood pressure and heart function. The authors say future work must show whether blocking it in platelets can help without causing side effects elsewhere in the body.

For now, a high BNP reading is still a warning sign, and nothing here changes how doctors use it. But the mouse results give researchers a clear reason to test whether the hormone is also adding to the clotting risk it flags.

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Disclaimer: This article summarizes a scientific study for general information only and is not medical advice. Findings from mouse and laboratory research may not apply to people. Anyone with questions about heart health, BNP test results, or medication should talk with a qualified healthcare professional.

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