title: Increased expression of leukotriene C4 synthase and predominant formation of cysteinyl-leukotrienes in human abdominal aortic aneurysm.
abstract: Leukotrienes (LTs) are arachidonic acid-derived lipid mediators involved in the pathogenesis and progression of diverse inflammatory disorders. The cysteinyl-leukotrienes LTC(4), LTD(4), and LTE(4) are important mediators of asthma, and LTB(4) 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 LTC(4) synthase (LTC(4)S), are significantly increased in the wall of human abdominal aortic aneurysms (AAAs). In contrast, mRNA levels of LTA(4) hydrolase, the enzyme responsible for the biosynthesis of LTB(4), are not increased. Immunohistochemical staining of AAA wall revealed focal expression of 5-LO, FLAP, and LTC(4)S 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 LTA(4) into significant amounts of cysteinyl-leukotrienes and to a lesser extent LTB(4). Furthermore, challenge of AAA wall tissue with exogenous LTD(4) 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 LTC(4)S, 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.
authors.affiliation: Division of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden.
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Gennaro
authors.forename: Dick
authors.initials: D
authors.lastname: Wågsäter
authors.forename: Mikko I
authors.initials: MI
authors.lastname: Mäyränpää
authors.forename: Anders
authors.initials: A
authors.lastname: Gabrielsen
authors.forename: Jesper
authors.initials: J
authors.lastname: Swedenborg
authors.forename: Anders
authors.initials: A
authors.lastname: Hamsten
authors.forename: Bengt
authors.initials: B
authors.lastname: Samuelsson
authors.forename: Per
authors.initials: P
authors.lastname: Eriksson
authors.forename: Jesper Z
authors.initials: JZ
authors.lastname: Haeggström
mesh_terms: D058927:5-Lipoxygenase-Activating Proteins / Q000032:analysis / Q000235:genetics; D017544:Aortic Aneurysm, Abdominal / Q000201:enzymology / Q000378:metabolism*; D001094:Arachidonate 5-Lipoxygenase / Q000032:analysis / Q000235:genetics; D050197:Atherosclerosis; D003545:Cysteine / Q000096:biosynthesis*; D005982:Glutathione Transferase / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D015289:Leukotrienes / Q000096:biosynthesis*; D020782:Matrix Metalloproteinases / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis
chemical_list: D058927:5-Lipoxygenase-Activating Proteins; D015289:Leukotrienes; D012333:RNA, Messenger; C112381:cysteinyl-leukotriene; D001094:Arachidonate 5-Lipoxygenase; D005982:Glutathione Transferase; D020782:Matrix Metalloproteinases; D053504:Matrix Metalloproteinases, Membrane-Associated; C041116:leukotriene-C4 synthase; D003545:Cysteine