K. Berhane et al., Characterization of rabbit SP-B promoter region responsive to downregulation by tumor necrosis factor-alpha, AM J P-LUNG, 279(5), 2000, pp. L806-L814
Citations number
42
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY
Surfactant protein B (SP-B) is essential for the maintenance of biophysical
properties and physiological function of pulmonary surfactant. Tumor necro
sis factor-alpha (TNF-alpha), an important mediator of lung inflammation, i
nhibits surfactant phospholipid and surfactant protein synthesis in the lun
g. In the present study, we investigated the TNF-alpha inhibition of rabbit
SP-B promoter activity in a human lung adenocarcinoma cell line (NCI-H441)
. Deletion experiments indicated that the TNF-alpha response elements are l
ocated within -236 bp of SP-B 5'-flanking DNA. The TNF-alpha response regio
n contained binding sites for nuclear factor-kappaB (NF-kappaB), Sp1/Sp3, t
hyroid transcription factor (TTF)-1, and hepatocyte nuclear factor (HNF)-3
transcription factors. Inhibitors of NF-kappaB activation such as dexametha
sone and N-tosyl-L-phenylalanine chloromethyl ketone and mutation of the NF
-kappaB element did not reverse TNF-alpha inhibition of SP-B promoter, indi
cating that TNF-alpha inhibition of SP-B promoter activity occurs independe
ntly of NF-kappaB activation. TNF-alpha treatment decreased the binding act
ivities of TTF-1 and HNF-3 elements without altering the nuclear levels of
TTF-1 and HNF-3 alpha proteins. Pretreatment of cells with okadaic acid rev
ersed TNF-alpha inhibition of SP-B promoter activity. Taken together these
data indicated that in NCI-H441 cells 1) TNF-alpha inhibition of SP-B promo
ter activity may be caused by decreased binding activities of TTF-1 and HNF
-3 elements, 2) the decreased binding activities of TTF-1 and HNF-3 alpha a
re not due to decreased nuclear levels of the proteins, and 3) okadaic acid
-sensitive phosphatases may be involved in mediating TNF-alpha inhibition o
f SP-B promoter activity.