Suppression of tumor necrosis factor alpha production by cAMP in human monocytes: dissociation with mRNA level and independent of interleukin-10.
BACKGROUND
Elevation of cellular cAMP inhibits lipopolysaccharide(LPS)-stimulated tumor necrosis factor alpha (TNF-alpha) production and increases the expression of interleukin (IL)-10 in mononuclear cells. TNF-alpha gene expression obligates activation of the transcription factor nuclear factor kappaB (NF-kappaB). Exogenous IL-10 inhibits NF-kappaB in monocytes and thus attenuates TNF-alpha production. We examined the role of endogenous IL-10 in the regulation of NF-kappaB activation and TNF-alpha production in human monocytes by cAMP.


METHODS
Human monocytes were stimulated with Escherichia coli LPS (100 ng/ml) with and without forskolin (FSK, 50 microM) or dibutyryl cyclic AMP (dbcAMP, 100 microM). Cytokine (TNF-alpha and IL-10) release was measured by immunoassay. TNF-alpha mRNA was measured by reverse transcription polymerase chain reaction, and NF-kappaB DNA binding activity was assessed by gel mobility shift assay.


RESULTS
cAMP-elevating agents inhibited LPS-stimulated TNF-alpha release (0.77 +/- 0.13 ng/10(6) cells in LPS + dbcAMP and 0.68 +/- 0.19 ng/10(6) cells in LPS + FSK, both P < 0.05 vs 1.61 +/- 0.34 ng/10(6) cells in LPS alone). Conversely, cAMP enhanced LPS-stimulated IL-10 release (100 +/- 21.5 pg/10(6) cells in LPS + dbcAMP and 110 +/- 25.2 pg/10(6) cells in LPS + FSK, both P < 0.05 vs 53.3 +/- 12.8 pg/10(6) cells in LPS alone). Neither TNF-alpha mRNA expression nor NF-kappaB activation stimulated by LPS was inhibited by the cAMP-elevating agents. Neutralization of IL-10 with a specific antibody did not attenuate the effect of cAMP-elevating agents on TNF-alpha production.


CONCLUSIONS
The results indicate that cAMP inhibits LPS-stimulated TNF-alpha production through a posttranscriptional mechanism that is independent of endogenous IL-10.
Shames
B D
BD
Department of Surgery, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Denver, CO 80262, USA.
McIntyre
R C
RC
Bensard
D D
DD
Pulido
E J
EJ
Selzman
C H
CH
Reznikov
L L
LL
Harken
A H
AH
Meng
X
X
D000906:Antibodies / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D006801:Humans; D016753:Interleukin-10 / Q000235:genetics* / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
D000906:Antibodies; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP