Scientists are rethinking a long-standing asthma theory after researchers identified “pseudo leukotrienes,” newly recognized molecules that may help drive the airway inflammation linked to asthma. These compounds appear to form through uncontrolled free-radical reactions rather than the enzyme-controlled pathway traditionally associated with leukotrienes, and their levels in urine rose alongside asthma severity in a study reported in the Journal of Allergy and Clinical Immunology.
For decades, leukotrienes have been widely described as key inflammatory molecules released by white blood cells when airways are irritated or exposed to allergens, and multiple asthma medicines were built to block their effects. The new findings suggest that look-alike molecules produced through a different chemistry may be major contributors to the same inflammatory signaling that constricts airways and makes breathing difficult.
What researchers discovered
The newly described molecules are called pseudo leukotrienes, and they are described as cysteinyl leukotriene (CysLT)-like biomolecules produced through radical-induced oxidation of arachidonate. Unlike classic leukotrienes, which are formed under enzyme control, pseudo leukotrienes are linked to a free-radical-driven lipid oxidation process described by the researchers as more chaotic and prone to running out of control.
In statements released with the research, Case Western Reserve University researcher Robert Salomon said the team found molecules similar in structure to leukotrienes but generated through a completely different chemical pathway, and he suggested these “pseudo leukotrienes” may be dominant players in the inflammatory cascade. The work was described as opening new avenues for treating asthma and potentially other inflammatory diseases, with the materials also noting possible relevance to neurological diseases such as Parkinson’s and Alzheimer’s diseases.
Evidence tied to asthma severity
In the study’s abstract, the researchers reported that mean urinary concentrations of two pseudo leukotrienes—øLTC and øLTD—were elevated four-fold to five-fold in severe asthma, with reported P values of 0.004 and 0.0015. The abstract also reported that combining øLTC and øLTD improved the statistical significance of differences between controls and moderate asthma (P=0.0004) or severe asthma (P=0.00008).
Separate write-ups of the research described urine testing that compared samples from people designated with mild or severe asthma against people without asthma, and reported that pseudo leukotrienes were detected at higher levels in asthma and tracked with severity. Those reports also stated that even mild asthma was associated with pseudo leukotriene levels four to five times higher than controls.
How pseudo leukotrienes may act in the airways
The study’s stated objective included testing whether pseudo leukotriene levels are elevated in asthma and whether the molecules induce CysLT receptor-dependent inflammatory signaling in bronchial epithelial cells. In reported results, pseudo leukotrienes induced phosphorylation of extracellular signal-regulated protein kinase (ERK) and protein kinase B (Akt) in bronchial epithelial cells, and this signaling was inhibited by CysLT receptor antagonists.
The abstract also reported that pulmonary pseudo leukotriene concentrations increased by 100% in mice after allergen exposure, with methods describing LC-MS/MS measurement in urine from humans and lung tissue from mice exposed to house dust mite extract. The conclusions section stated that pseudo leukotrienes provide a mechanistic link between radical-induced biochemistry, activation of the ERK/Akt pathway, and asthma, and said the discoveries require re-examining long-held paradigms about leukotrienes in asthma pathology.
What it could mean for treatment
Current leukotriene receptor-blocking medications were described as working by blocking the receptor that leukotrienes (and their mimics) bind to, preventing the downstream cascade that leads to airway constriction. In the materials accompanying the study, Salomon said the discovery raises the possibility of treating disease by preventing or moderating the free-radical process rather than blocking the receptor.
Those materials also emphasized that inflammation is not always harmful and noted roles in healing and in memory and development, while warning that blocking leukotrienes could interfere with beneficial effects. The study abstract similarly stated that inhibiting the biosynthesis of pseudo leukotrienes may provide new therapeutic strategies for preventing asthmatic inflammation.
Researchers also described pseudo leukotrienes as potential biomarkers that could help with non-invasive assessment of asthma severity and monitoring therapeutic efficacy. The related reports said the team plans to investigate whether pseudo leukotrienes are involved in other respiratory diseases, including RSV, bronchiolitis in babies, and chronic obstructive pulmonary disease.
