Ž.
Biochimica et Biophysica Acta 1403 1998 47–56
Regulation of the cellular expression of secretory and cytosolic
phospholipases A , and cyclooxygenase-2 by peptide growth factors
2
Waldemar Pruzanski
a,)
, Eva Stefanski
a
, Peter Vadas
a
, Brian P. Kennedy
b
,
Henk van den Bosch
c
a
Inflammation Research Group, The Wellesley Central Hospital, UniÕersity of Toronto, Toronto, Canada
b
Department of Molecular Biology, Merck Frosst Center for Therapeutic Research, Montreal, Canada
c
Centre for Biomembranes and Lipid Enzymology, Utrecht UniÕersity, Utrecht, Netherlands
Received 5 January 1998; revised 9 March 1998; accepted 19 March 1998
Abstract
Ž. Ž. Ž.
Secretory group II sPLA and cytosolic cPLA phospholipases A and cyclooxygenase-2 Cox-2 play a pivotal role
222
in release of proinflammatory eicosanoids. Excessive activity of sPLA per se can also propagate inflammation.
2
Endogenous control of the above enzymes has not been completely elucidated. We investigated the combined impact of
promoting cytokines and inhibitory peptide growth factors on the expression of mRNA of the above enzymes, on protein
Ž.
content and extracellular release of sPLA and on PGE production in osteoblasts FRCO . The synthesis and release of
22
sPLA were enhanced by about 20-fold by 0.5 ngrml IL-1
b
or by 50 ngrml of TNF
a
. Coaddition of both cytokines
2
resulted in synergistic 150-fold increase in the release of sPLA implying the existence of two paths of induction. IL-1
b
2
and TNF
a
markedly enhanced the transcription of sPLA mRNA. Kinetic study showed that IL-1rTNF initiated sPLA
2 2
release after 12 h, reaching maximum at 48 h. IL-1
a
was a weak stimulator of sPLA release, whereas IL-6, IL-8, IGF,
2
IFN-
g
, growth hormone, insulin and GM-CSF were not stimulatory. Peptide growth hormones TGF
b
, PDGF-BB, EGF and
bFGF markedly inhibited the extracellular release of sPLA . TGF
b
and PDGF-BB significantly reduced the level of sPLA
2 2
mRNA, thus acting upon transcription whereas EGF and bFGF were not inhibitory, acting rather upon the translational or
posttranslational steps. IL-1rTNF and growth factors had no significant effect on cPLA mRNA expression. Cox-2 mRNA
2
expression was markedly enhanced by IL-1rTNF and suppressed by all growth factors tested. Cytokines enhanced the
extracellular release of PGE and further enhancement was induced by growth factors with the exception of TGF
b
.
2
Cycloheximide abolished completely the release of sPLA and markedly reduced the release of PGE from cytokine-
22
stimulated FRCO, regardless of whether growth factors were present or not. NS-398, a specific inhibitor of Cox-2 abolished
almost completely the release of PGE from cytokine-stimulated cells, regardless of the presence of growth factors. Thus,
2
different signalling mechanisms are involved in the impact of growth factors on mRNA expression of sPLA , cPLA and
22
Abbreviations: sPLA , secretory phospholipase A ; cPLA , cytosolic phospholipase A ; Cox, 2-cyclooxygenase-2; PGE , prosta-
2222 2
glandin E ; IL-1, interleukin 1; TNF, tumor necrosis factor; FRCO, fetal rat calvaria osteoblasts
2
)
Corresponding author. The Wellesley Central Hospital, 104 Jones Building, 160 Wellesley Street East, Toronto, Ontario, Canada
M4Y 1J3. Fax: q1-416-966-5046.
0167-4889r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.
Ž.
PII S0167-4889 98 00029-9