COMMON blood-pressure drugs might help protect us against a flu pandemic by preventing the development of a lethal lung condition.
The condition, called acute respiratory distress syndrome (ARDS), can be triggered by noxious gases or infections that damage the lung. One such infection was SARS, the virus that emerged in China in 2003.
ARDS is the result of a runaway response of the host鈥檚 own immune system, and once it starts there is almost nothing doctors can do. Around half of patients who develop ARDS die, and most of those killed by SARS had ARDS.
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Now researchers have shown that the SARS virus unleashes the runaway immune response by boosting levels of a signalling chemical called angiotensin II in the lung. The same molecule has long been known to increase blood pressure through its actions elsewhere in the body. Crucially, this and other work by the group shows that some other infections and injuries which cause ARDS work the same way, suggesting this might also be how some flu viruses trigger the syndrome.
Josef Peninger and colleagues in Vienna and Beijing have found that the SARS virus binds to and blocks an enzyme called ACE2, which degrades angiotensin. The result is too much angiotensin.
The team also showed that giving mice extra doses of ACE2 prevented them developing ARDS after their lungs were damaged by acid or by a molecule that triggers bacterial sepsis. Even better, drugs such as losartan, which block one kind of angiotensin receptor and are widely used to control high blood pressure, also prevented ARDS, whether it was caused by SARS or by injury (Nature Medicine, DOI: 10.1038/nm1267).
鈥淚t might have shown us a way to prevent death in patients with acute lung failure, including in the feared epidemic of bird flu鈥�
鈥淲e now need to make human ACE2 protein to test in patients,鈥� says Peninger. 鈥淏ut if we are right SARS might have been a good thing to happen to us, since it might have shown us a way to prevent death in many patients with acute lung failure, including in the feared epidemic of bird flu.鈥�
Malik Peiris of Hong Kong University, who discovered the SARS virus, suggests that ARDS might well be the real killer in any future flu pandemic, as it was in 1918. If ARDS is always triggered by raised levels of angiotensin, then angiotensin-blocking drugs, or an even older class of blood pressure drugs that prevents angiotensin from being made in the first place, might save many lives, as vaccines and anti-flu drugs will likely be unavailable or in short supply.
