Researchers have found a link between common environmental bacteria and airway inflammation, suggesting that some cases of asthma may be caused by an allergic reaction to such bacteria. The researchers’ findings indicate that some strains of Pseudomonas aeruginosa cause white blood cells to produce very high levels of histamine, which in turn leads to inflammation, a hallmark symptom of asthma.
The findings appear in the Journal of Leukocyte Biology.
The researchers studied the effect of two strains of pseudomonas bacteria on isolated mouse white blood cells tasked with killing bacteria, called neutrophils. Results showed that one strain killed the neutrophils to increase their production of histamine significantly. To see if this discovery was applicable outside the test tube, the researchers then used the histamine-stimulating strain to infect mice to produce bronchitis and pneumonia. These mice experienced a significant increase of histamine in their airways and lungs. Additional work showed that the bacteria persuade neutrophils to produce histamine by causing them to make much more of the key enzyme in histamine synthesis (histidine decarboxylase) than neutrophils would otherwise do in the unstimulated state.
"Despite advances in diagnosing and treating the symptoms of asthma and allergy, our understanding of the underlying initiating events remains elusive," said John Wherry, PhD, deputy editor of the Journal of Leukocyte Biology. "This report helps shed light on how an ‘everyday organism’ might trigger asthma and allergy from an immune cell type not normally thought to be involved in allergic disease."
Source: Federation of American Societies for Experimental Biology