L. Ermert et al., In situ localization and regulation of thromboxane A(2) synthase in normaland LPS-primed lungs, AM J P-LUNG, 278(4), 2000, pp. L744-L753
Citations number
39
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY
Thromboxane (Tx) A(2) synthase catalyzes the conversion of prostaglandin H-
2 to the unstable metabolite TxA(2), which is a potent mediator of vasocons
triction and bronchoconstriction. The cellular localization of TxA(2) synth
ase was examined by immunohistochemistry and in situ hybridization in human
and rat lung tissues. Bronchial epithelial cells, bronchial smooth muscle
cells, peribronchial nerve fibers, single cells of bronchus-associated lymp
hoid tissue, single cells located in the alveolar septum, and alveolar macr
ophages exhibited positive immunostaining for TxA(2) synthase protein in lu
ng tissue of both species. In addition, vascular smooth muscle cells of mus
cular and partially muscular vessels displayed strong (rat) and moderate (h
uman) immunostaining for TxA(2) synthase. In situ hybridization performed i
n the rat lungs demonstrated TxA(2) synthase mRNA localization in accordanc
e with the immunostaining pattern. Perfusing isolated rat lungs with endoto
xin for 1 and 2 h resulted in a marked increase in TxA(2) synthase protein
staining intensity in most cell types as measured by quantitative image ana
lysis, whereas the in situ hybridization signal was unchanged. We conclude
that the pulmonary distribution of TxA(2) synthase displays close similarit
y between rat and human lung tissues and matches well with the previously d
escribed immunolocalization of cyclooxygenase-1 and cyclooxygenase-2 in thi
s tissue. Endotoxin challenge is suggested to cause a rapid upregulation of
TxA(2) synthase at the posttranscriptional level. These data provide a mor
phological basis for the understanding of the role of TxA(2) in the regulat
ion of lung bronchial and vascular tone and in immunologic events.