A previously unknown family of inflammatory biomolecules could reshape scientific understanding of severe asthma and open the door to new diagnostic and therapeutic tools. Researchers at Case Western Reserve University in Cleveland, Ohio, identified “pseudo‑leukotrienes” (øLTs) as potent, radical‑induced lipid byproducts that mimic the behavior of traditional cysteinyl leukotrienes (CysLTs). CysLTs are long considered key drivers of asthma‑related inflammation.
In their study, “Radical-Induced Lipid Oxidation Produces a Torrent of Leukotriene-Like Agonists in Severe Asthma,” researchers noted that leukotrienes are well‑established inflammatory mediators involved in airway constriction and asthma attacks. However, the newly identified øLTs appear to arise through radical‑induced oxidation of arachidonate, a lipid found in cell membranes, the authors wrote. These øLTs closely resemble conventional CysLTs in structure and biological behavior — enough to activate the same inflammatory receptors in bronchial epithelial cells, they said.
“We’ve found molecules that are alike in structure but generated through a completely different chemical pathway in the body,” lead researcher Robert Salomon, PhD, told Science Daily. Salomon is the university’s Charles Frederic Mabery professor of research in chemistry. “We think the molecules we’re calling ‘pseudo leukotrienes,’ may be the dominant players in the inflammatory cascade that causes disease.”
The research, which was published in The Journal of Allergy and Clinical Immunology, suggested that øLTs were “unknown unknowns,” silently influencing the disease while remaining undetected by standard testing methods. Using advanced liquid chromatography–tandem mass spectrometry (LC‑MS/MS), researchers measured øLTs in urine from asthma patients and in the lungs of allergen‑exposed mice.
Their findings revealed:
- Human subjects with severe asthma showed four‑ to five‑fold higher levels of øLTC and øLTD compared with healthy controls.
- Combining øLT measurements improved separation between moderate and severe asthma groups, suggesting strong potential as a noninvasive biomarker.
- In mice exposed to house dust mite extract — a common allergen, pulmonary øLT levels doubled, indicating the molecules actively rise during allergic airway inflammation.
According to the study, øLTs provoked inflammatory signaling in human bronchial epithelial cells by activating phosphorylation of ERK and Akt — key pathways involved in airway inflammation. Importantly, the response was blocked when cells were treated with CysLT receptor antagonists — drugs commonly prescribed for asthma.
The study suggests that øLTs may be far more abundant than traditional leukotrienes in some patients, possibly even the dominant driver of inflammation. The researchers said this could potentially explain why CysLT‑blocking medications work well in some individuals but poorly in others.
Researchers emphasized that the findings challenge several decades of assumptions about asthma biology and suggest that øLTs provide a missing mechanistic link between:
- Oxidative stress, which is elevated in severe asthma
- Depletion of antioxidants such as glutathione (GSH) in the airway
- Activation of leukotriene receptors that drive chronic inflammation
The inflammatory environment of severe asthma, which is rich in reactive oxygen species and poor in protective antioxidants, appears ideal for the generation of øLTs, they noted.
According to researchers, øLTs, which are easy to measure in urine, may soon serve as a simple, noninvasive biomarker for:
- Detecting early disease in genetically susceptible individuals
- Monitoring asthma severity
- Tracking response to treatment
- Identifying oxidative stress imbalances before symptoms worsen
Additionally, the study’s authors suggested the findings raise the possibility of new therapeutic strategies aimed not just at blocking leukotriene receptors but at preventing øLT formation altogether.
