Symptoms 3 to 8 Hours After Exposure
New research led by scientists from Imperial College London explains
why nearly half of people with asthma experience a late phase of symptoms
several hours after exposure to allergens.
The findings have been published in the journal Thorax, and could lead to
several hours after exposure to allergens.
The findings have been published in the journal Thorax, and could lead to
better treatments for the disease.
An estimated 300 million people suffer
from asthma, and the prevalence of the
disease is rising. Symptoms are commonly triggered by allergens in the environment, such as pollen and dust mites.
These stimuli can cause the airways to tighten within minutes, causing breathing difficulties which range from mild to severe. Many sufferers also experience a late asthmatic response three to eight hours after exposure to allergens, causing breathing difficulties which
can last up to 24 hours.
from asthma, and the prevalence of the
disease is rising. Symptoms are commonly triggered by allergens in the environment, such as pollen and dust mites.
These stimuli can cause the airways to tighten within minutes, causing breathing difficulties which range from mild to severe. Many sufferers also experience a late asthmatic response three to eight hours after exposure to allergens, causing breathing difficulties which
can last up to 24 hours.
In the early asthmatic response, the allergen is recognised by mast cells, which release chemical signals that cause the airways to narrow.
The Imperial College research team have discovered that the late
asthmatic response happens because the allergen triggers sensory
nerves in the airways. These nerves activate reflexes which trigger
other nerves that release the neurotransmitter acetylcholine, which
causes the airways to narrow. If the findings translate to humans, it
would mean that drugs that block acetylcholine (anti-cholinergics)
could be used to treat asthma patients that experience late phase responses following exposure to allergens.
asthmatic response happens because the allergen triggers sensory
nerves in the airways. These nerves activate reflexes which trigger
other nerves that release the neurotransmitter acetylcholine, which
causes the airways to narrow. If the findings translate to humans, it
would mean that drugs that block acetylcholine (anti-cholinergics)
could be used to treat asthma patients that experience late phase responses following exposure to allergens.
Steroids are the main treatments for asthma prescribed now, but
they are not effective for all patients. A recent clinical trial involving
asthma patients found that the anticholinergic drug Tiotropium
improved symptoms when added to a steroid inhaler.
they are not effective for all patients. A recent clinical trial involving
asthma patients found that the anticholinergic drug Tiotropium
improved symptoms when added to a steroid inhaler.
"Many asthmatics have symptoms at night after exposure to allergens during the day, but until now we haven't understood how this late
response is brought about," said scientists from the National Heart
and Lung Institute at Imperial College London, who conducted the
research.
"Our study in animals suggests that anticholinergic drugs
might help to alleviate these symptoms, and this is supported by the
recent clinical data. We are seeking funding to see if these findings
are reproduced in proof of concept clinical studies in asthmatics."
response is brought about," said scientists from the National Heart
and Lung Institute at Imperial College London, who conducted the
research.
"Our study in animals suggests that anticholinergic drugs
might help to alleviate these symptoms, and this is supported by the
recent clinical data. We are seeking funding to see if these findings
are reproduced in proof of concept clinical studies in asthmatics."
The researchers hypothesised that sensory nerves were involved after observing that anaesthesia prevented the late asthmatic response in laboratory subjects. They succeeded in blocking the late asthmatic response using drugs that block different aspects of sensory nerve cell function, adding further evidence for this idea.
After establishing that sensory nerves detect the allergen, the researchers tested the effect of Tiotropium, an anticholinergic drug that is used to treat chronic obstructive pulmonary disease. Tiotropium blocks the receptor for acetylcholine, which is released by nerves in the parasympathetic nervous system. Tiotropium also blocked the late asthmatic response, suggesting that parasympathetic nerves cause the airways to constrict.
The study was funded by the Medical Research Council (MRC) and reported: "Unravelling the complex biology of asthma is vitally important,
as it is an extremely dangerous condition which exerts lifelong damaging effects. The Medical Research Council is committed to research that
opens doors to improving disease resilience, particularly in conditions which attack our body over the long-term."
as it is an extremely dangerous condition which exerts lifelong damaging effects. The Medical Research Council is committed to research that
opens doors to improving disease resilience, particularly in conditions which attack our body over the long-term."
Story Source: Imperial College London,
Journal Reference: A role for sensory nerves in the late asthmatic response. Thorax, 2011
Imperial College London (2011, August 12) Study sheds light on late
phase of asthma attacks.
phase of asthma attacks.
This article is for informational and educational purposes only, and is not intended to provide medical advice, diagnosis or treatment. Contact your doctor or healthcare professional for medical and nutritional consultation.
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