Increased expression of leukotriene C4 synthase and predominant formation of cysteinyl-leukotrienes in human abdominal aortic aneurysm

A Di Gennaro, D Wågsäter… - Proceedings of the …, 2010 - National Acad Sciences
A Di Gennaro, D Wågsäter, MI Mäyränpää, A Gabrielsen, J Swedenborg, A Hamsten…
Proceedings of the National Academy of Sciences, 2010National Acad Sciences
Leukotrienes (LTs) are arachidonic acid-derived lipid mediators involved in the
pathogenesis and progression of diverse inflammatory disorders. The cysteinyl-leukotrienes
LTC4, LTD4, and LTE4 are important mediators of asthma, and LTB4 has recently been
implicated in atherosclerosis. Here we report that mRNA levels for the three key
enzymes/proteins in the biosynthesis of cysteinyl-leukotrienes, 5-lipoxygenase (5-LO), 5-LO-
activating protein (FLAP), and LTC4 synthase (LTC4S), are significantly increased in the …
Leukotrienes (LTs) are arachidonic acid-derived lipid mediators involved in the pathogenesis and progression of diverse inflammatory disorders. The cysteinyl-leukotrienes LTC4, LTD4, and LTE4 are important mediators of asthma, and LTB4 has recently been implicated in atherosclerosis. Here we report that mRNA levels for the three key enzymes/proteins in the biosynthesis of cysteinyl-leukotrienes, 5-lipoxygenase (5-LO), 5-LO-activating protein (FLAP), and LTC4 synthase (LTC4S), are significantly increased in the wall of human abdominal aortic aneurysms (AAAs). In contrast, mRNA levels of LTA4 hydrolase, the enzyme responsible for the biosynthesis of LTB4, are not increased. Immunohistochemical staining of AAA wall revealed focal expression of 5-LO, FLAP, and LTC4S proteins in the media and adventitia, localized in areas rich in inflammatory cells, including macrophages, neutrophils, and mast cells. Human AAA wall tissue converts arachidonic acid and the unstable epoxide LTA4 into significant amounts of cysteinyl-leukotrienes and to a lesser extent LTB4. Furthermore, challenge of AAA wall tissue with exogenous LTD4 increases the release of matrix metalloproteinase (MMP) 2 and 9, and selective inhibition of the CysLT1 receptor by montelukast blocks this effect. The increased expression of LTC4S, together with the predominant formation of cysteinyl-leukotrienes and effects on MMPs production, suggests a mechanism by which LTs may promote matrix degradation in the AAA wall and identify the components of the cysteinyl-leukotriene pathway as potential targets for prevention and treatment of AAA.
National Acad Sciences