The phosphodiesterase inhibitor, pentoxifylline, alters rat intestinal epithelial cell proliferation via changes in the expression of transforming growth factors.
BACKGROUND
Phosphodiesterase (PDE) inhibitors, among which pentoxifylline (PTX), are candidate molecules for the treatment of TNF-alpha-dependent inflammatory diseases. Based on the controversial effects of PTX observed in experimentally-induced colitis, the aim of this work was to analyse its influence on intestinal epithelial cell proliferation and growth factor expression using the well-established IEC18 cell line.


METHODS
The effects of PTX, and of an activation (addition of dibutyryl-cAMP, db-cAMP) or inhibition (by a specific cAMP-protein kinase inhibitor, PKI) of the cAMP pathway, were examined after 3 days of culture. The IEC18 cell proliferation and [3H] thymidine incorporation, as well as the expression of TGF-alpha, TGF-beta1 and -beta2 mRNAs, were analysed in basal culture conditions and in the presence of the pro-inflammatory cytokine, TNF-alpha.


RESULTS
PTX, like exogenous db-cAMP, inhibited in a dose-dependent manner the basal and TNF-alpha-modulated IEC18 cell proliferation; this effect was partly prevented by PKI. We confirmed that PTX induced a dose-related increase in intracellular cAMP. Concomitantly, the expression of TGF-alpha mRNA dropped and that of TGF-beta2 increased. Addition of db-cAMP instead of PTX also decreased TGF-alpha mRNA, but did not change TGF-beta2 transcripts. The decrease in the expression of TGF-alpha mRNA caused by PTX and db-cAMP was completely abolished by PKI; in contrast, TGF-beta2 remained unaltered. Yet, anti-TGF-beta2 antibodies partially restored the PTX-inhibited cell proliferation.


CONCLUSIONS
The phosphodiesterase inhibitor, PTX, inhibits IEC18 cell proliferation via a differential modulation of TGF-alpha and TGF-beta2 expression. The drop in TGF-alpha mRNA is related to increasing intracellular cAMP, whereas the effect upon TGF-beta2 appears cAMP-independent.
Diab-Assef
M
M
INSERM U381, Strasbourg, France.
Reimund
J M
JM
Ezenfis
J
J
Duclos
B
B
Kedinger
M
M
Foltzer-Jourdainne
C
C
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology*; D007413:Intestinal Mucosa / Q000166:cytology; D010431:Pentoxifylline / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger; D051381:Rats; D015291:Transforming Growth Factors / Q000096:biosynthesis*
D010726:Phosphodiesterase Inhibitors; D012333:RNA, Messenger; D003994:Bucladesine; D015291:Transforming Growth Factors; D000242:Cyclic AMP; D010431:Pentoxifylline