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Macrophages: A potential new target for reducing hypertension?

HYPERTENSION is a global health problem with a number of modifiable risk factors; stress, diet, and activity levels are all known to play a part in the development of this condition, but new research has uncovered the potential role of macrophages in increasing blood pressure. Using mouse models to test the theory, researchers found that, alongside consumption of foreign bodies and cellular debris, macrophages also digest molecules of endothelin, a vasoconstricting hormone, thus indicating their role in the narrowing and relaxing of blood vessels.

In light of this discovery, the team set out to test whether reducing the level of macrophages in the blood would have a direct impact on blood pressure by administering a high-salt diet to mice with low blood macrophage levels. The result was an increase in blood pressure in the mice, which returned to normal after the macrophage levels were corrected. Genetically modified mice who had a poor endothelin system demonstrated the same effect.

To discover whether the results translated in humans, the study group assessed patients who were on medication for antineutrophil cytoplasmic antibody vasculitis, which damages blood vessels as well as impacting a person’s immune system. The drugs that these patients were taking, for example cyclophosphamide, reduced their macrophage levels and were associated with raised blood pressure in patients.

The findings of the study could prove invaluable for helping doctors to recognise those patients who are at an increased risk of high blood pressure; however, the researchers note that further studies are warranted before they can be adopted into day-to-day clinical use. Prof Matthew Bailey, University of Edinburgh, Edinburgh, UK, explained: “Our discovery sheds light on risk factors and, crucially, opens routes to investigate new drugs that could help patients.”