Airway lipoxin A4 generation and lipoxin A4 receptor expression are decreased in severe asthma.
BACKGROUND
Airway inflammation is common in severe asthma despite antiinflammatory therapy with corticosteroids. Lipoxin A(4) (LXA(4)) is an arachidonic acid-derived mediator that serves as an agonist for resolution of inflammation.


OBJECTIVE
Airway levels of LXA(4), as well as the expression of lipoxin biosynthetic genes and receptors, in severe asthma.


METHODS
Samples of bronchoalveolar lavage fluid were obtained from subjects with asthma and levels of LXA(4) and related eicosanoids were measured. Expression of lipoxin biosynthetic genes was determined in whole blood, bronchoalveolar lavage cells, and endobronchial biopsies by quantitative polymerase chain reaction, and leukocyte LXA(4) receptors were monitored by flow cytometry.


RESULTS
Individuals with severe asthma had significantly less LXA(4) in bronchoalveolar lavage fluids (11.2 +/- 2.1 pg/ml) than did subjects with nonsevere asthma (150.1 +/- 38.5 pg/ml; P < 0.05). In contrast, levels of cysteinyl leukotrienes were increased in both asthma cohorts compared with healthy individuals. In severe asthma, 15-lipoxygenase-1 mean expression was decreased fivefold in bronchoalveolar lavage cells. In contrast, 15-lipoxgenase-1 was increased threefold in endobronchial biopsies, but expression of both 5-lipoxygenase and 15-lipoxygenase-2 in these samples was decreased. Cyclooxygenase-2 expression was decreased in all anatomic compartments sampled in severe asthma. Moreover, LXA(4) receptor gene and protein expression were significantly decreased in severe asthma peripheral blood granulocytes.


CONCLUSIONS
Mechanisms underlying pathological airway responses in severe asthma include lipoxin underproduction with decreased expression of lipoxin biosynthetic enzymes and receptors. Together, these results indicate that severe asthma is characterized, in part, by defective lipoxin counterregulatory signaling circuits.
Planagumà
Anna
A
Pulmonary and Critical Care Medicine Division, Department of Internal Medicine, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA.
Kazani
Shamsah
S
Marigowda
Gautham
G
Haworth
Oliver
O
Mariani
Thomas J
TJ
Israel
Elliot
E
Bleecker
Eugene R
ER
Curran-Everett
Douglas
D
Erzurum
Serpil C
SC
Calhoun
William J
WJ
Castro
Mario
M
Chung
Kian Fan
KF
Gaston
Benjamin
B
Jarjour
Nizar N
NN
Busse
William W
WW
Wenzel
Sally E
SE
Levy
Bruce D
BD
D000328:Adult; D001249:Asthma / Q000097:blood / Q000378:metabolism*; D001980:Bronchi / Q000378:metabolism*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000097:blood; D044045:Lipoxins / Q000096:biosynthesis* / Q000097:blood; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D044042:Receptors, Formyl Peptide / Q000378:metabolism*; D044067:Receptors, Lipoxin / Q000378:metabolism*
C105101:FPR2 protein, human; D006893:Hydroxyeicosatetraenoic Acids; D044045:Lipoxins; D044042:Receptors, Formyl Peptide; D044067:Receptors, Lipoxin; C040527:lipoxin A4; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid