Cys-leukotrienes mediate lung dysfunction but not histopathologies in an IL-5/Eotaxin-2 double transgenic mouse model of severe asthma (163.13)

Abstract Products of the 5-lipoxygenase (5-LO) pathway (i.e., cys-leukotrienes and LTB4), are contributors to lung inflammation, airway remodeling, and hyperresponsiveness associated with allergic respiratory inflammation. Eosinophils are capable of leukotriene synthesis/secretion and chemotactically respond to these compounds. However, the in vivo role of eosinophils in leukotriene mediated events during asthmatic airway inflammation is not defined. To study the link between eosinophils and leukotrienes we used the I5/E2 double transgenic mouse model of severe asthma, over-expressing IL-5 systemically and eotaxin-2 in airways, in which lung pathologies are entirely dependent on the presence of eosinophils. We show that airway levels of cysteinyl leukotrienes and LTB4 are significantly elevated in I5/E2 mice. Crosses of I5E2 mice with 5-LO knockout animals abolished AHR in the I5/E2 parental model without significant effects on lung histopathology. Administration of a cys-leukotriene receptor antagonist (Montelukast®) to I5/E2 mice replicates the effects of the total leukotriene loss in I5/E2/5-LO-/- animals. In contrast, I5/E2 mice crossed with BLT-1-/- mice which are deficient of the LTB4 receptor fail to display effects on the pulmonary pathologies occurring in the I5/E2 parental model. These data demonstrate a unique role for cys-leukotrienes in the development of AHR independent of lung remodeling events occurring in this transgenic model of severe asthma.