Iron overload may increase asthma severity, finds study

Australia: Asthma is a chronic, or long-term, a condition that intermittently inflames and narrows the airways in the lungs. The inflammation makes the airways swell. Asthma causes periods of wheezing, chest tightness, shortness of breath, and coughing. People who have asthma may experience symptoms that range from mild to severe and that may happen rarely or every day. When symptoms get worse, it is called an asthma attack. Asthma affects people of all ages and often starts during childhood.

Iron build-up in the lung tissues can worsen asthma symptoms and lower lung function, according to new research conducted by the researchers from the University of Newcastle and Hunter Medical Research Institute, Australia. 

The study which was published in the European Respiratory Journal showed that increasing the lung cell iron levels causes inflammatory cell responses such as increased mucus secretion and scarring in the airways, which leads to worsening of asthma. 

There is evidence that irregular iron absorption and abnormal iron levels are linked to lung disease. Both high and low iron levels are reported in asthma, but it is not clear whether iron build-up in the lungs contributes to disease development. To sort this out the researchers tried investigating the link between iron and asthma, to better understand whether increased or decreased iron levels in the lung cells make the disease worse.

Researchers at the University of Newcastle, Australia, collected airway cell samples from participants using a biopsy, and using a bronchoscope 'wash', where a thin tube is inserted into the mouth or nose to pass a small amount of salty water into a certain part of the lung. The liquid is sucked back out through the tube and then tested. These samples were collected from 39 severe and 29 mild-to-moderate asthmatics and 29 healthy people as part of the wider data collection for the Europe-wide U-BIOPRED project.

The researchers found that iron levels outside of the lung cells were lower in asthma patients compared with healthy people; iron levels were also significantly lower in severe asthmatics compared with mild-to-moderate asthmatics. In contrast, iron levels within the lung cells were markedly higher in the bronchoscope 'wash' samples of mild-to-moderate and severe asthmatics compared with healthy people. The difference in lung cell iron levels between severe asthmatics compared with mild-to-moderate asthmatics was not significant, but the analyses showed that having high levels of iron in the lung cells and less iron outside of cells was associated with more severe airflow obstruction.

Overall the results show that lower iron levels outside of cells and higher iron levels within cells were both associated with lower lung function and worsen asthma.

Next, the researchers carried out lab tests using two different mouse models to investigate the effects of increasing lung cell iron levels on asthma severity.

a)In one of the experimental models conducted over an eight-week period, one group of mice was exposed to iron overload through diet and another group were fed a normal low-iron diet.

b)After eight weeks, liver and lung tissues were collected from the mice for further analysis and airway inflammation was measured.

c)In a separate genetic model, the researchers triggered iron overloading in the lung cells of mice that were fed a normal iron diet, to assess the effects on the lungs.

d)The analysis showed that increasing the lung cell iron levels caused inflammatory cell responses such as increased mucus secretion and scarring in the airways, which the researchers say leads to worsening of asthma.

 "In humans, mucous secretion and lung scarring narrow the airways, causing airflow obstruction and breathing difficulties. These symptoms are common in asthma and other chronic lung diseases, and our data shows that increasing iron in the lung cells and tissues led to an increase in these effects. explained Professor Horvat.

The research team is now investigating ways to modify the iron storage process in lung cells, and whether it is possible to alter the number of the cells that are responsible for iron absorption into the lung cells.

For further reading click on the following link,

https://erj.ersjournals.com/content/early/2020/01/24/13993003.01340-2019