Abstract
S-Adenosylmethionine (SAM) treatment has anti-inflammatory, cytoprotective effects against endotoxin-induced organ injury. An important component of the anti-inflammatory action of SAM involves down-regulation of the lipopolysaccharide (LPS)-induced transcriptional induction of tumor necrosis factor-α (TNF) expression by monocytes/macrophages. We examined the effect of SAM on expression and activity of LPS-induced up-regulation of phosphodiesterase 4 (PDE4), which regulates cellular cAMP levels and TNF expression. LPS treatment of RAW 264.7, a mouse macrophage cell line, led to the induction of Pde4b2 mRNA expression with no effect on Pde4a or Pde4d. SAM pretreatment led to a significant decrease in LPS-induced up-regulation of Pde4b2 expression in both RAW 264.7 cells and primary human CD14+ monocytes. Of note, the decreased Pde4b2 mRNA expression correlated with the SAM-dependent increase in the transcriptionally repressive histone H3 lysine 9 trimethylation on the Pde4b2 intronic promoter region. The SAM-mediated decrease in LPS-inducible Pde4b2 up-regulation resulted in an increase in cellular cAMP levels and activation of cAMP-dependent protein kinase A (PKA), which plays an inhibitory role in LPS-induced TNF production. In addition, SAM did not affect LPS-inducible inhibitor of nuclear factor-κB degradation or nuclear factor-κB (NF-κB)-p65 translocation into the nucleus but rather inhibited NF-κB transcriptional activity. These results demonstrate for the first time that inhibition of LPS-induced PDE4B2 up-regulation and increased cAMP-dependent PKA activation are significant mechanisms contributing to the anti-TNF effect of SAM. Moreover, these data also suggest that SAM may be used as an effective PDE4B inhibitor in the treatment of chronic inflammatory disorders in which TNF expression plays a significant pathogenic role.
Footnotes
This work was supported by the National Institutes of Health National Institute on Alcohol Abuse and Alcoholism [Grants R01-AA014371, R01-AA10762, 1R01-AA018869] (to S.B., C.J.M., and C.J.M., respectively).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.174268.
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- LPS
- lipopolysaccharide
- TNF
- tumor necrosis factor-α
- SAM
- S-adenosylmethionine
- PDE
- phosphodiesterase
- TLR
- Toll-like receptor
- PKA
- cAMP-dependent protein kinase A
- NF-κB
- nuclear factor κB
- CREB
- cAMP response element-binding protein
- ELISA
- enzyme-linked immunosorbent assay
- H-89
- N-[2-p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide
- IκB
- inhibitor of κB
- UT
- untreated
- ChIP
- chromatin immunoprecipitation
- bp
- base pairs
- PCR
- polymerase chain reaction
- H3K9
- histone H3 lysine 9
- H3K9Me3
- histone H3 lysine trimethylation.
- Received August 24, 2010.
- Accepted January 24, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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