Cannabinol-mediated inhibition of nuclear factor-kappaB, cAMP response element-binding protein, and interleukin-2 secretion by activated thymocytes.
Cannabinol (CBN), an immunosuppressive cannabinoid and ligand for the peripheral cannabinoid receptor CB2, inhibits the cAMP signaling cascade in forskolin-stimulated thymocytes. The objective of the present studies was to further characterize the mechanism of CBN immune modulation by investigating its effects on interleukin-2 (IL-2) secretion, cAMP response element (CRE), and kappaB DNA binding activity in phorbol ester (phorbol-12-myristate-13-acetate, PMA) plus calcium ionophore (PMA/Io)-activated thymocytes. PMA/Io treatment induced CRE and kappaB DNA binding activity that was attenuated in the presence of CBN. A concomitant and concentration-related inhibition of IL-2 also was produced by CBN in PMA/Io-activated thymocytes. PMA/Io induced two CRE DNA binding complexes, a major complex consisting of a cAMP response element-binding protein (CREB)-1 homodimer, and a minor CREB-1/activating transcription factor (ATF)-2 complex. Both CRE complexes were inhibited by CBN. Conversely, two kappaB DNA binding complexes were observed, but only one was PMA/Io-inducible. However, the DNA binding activity of both complexes was diminished in the presence of CBN. The PMA/Io-inducible kappaB complex was a p65/c-Rel heterodimer. Analysis of up-stream regulation revealed a decrease in phosphorylated CREB/ATF nuclear proteins in PMA/Io-activated thymocytes after CBN treatment. Similarly, CBN prevented the phosphorylation-dependent degradation of the nuclear factor-kappaB inhibitory protein IkappaB-alpha. These results provide a potential link between the CBN-mediated inhibition of thymocyte function, including IL-2 production, and the inhibition of two critical transcription factor families, CREB/ATF and NF-kappaB/Rel.
Herring
A C
AC
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, USA.
Kaminski
N E
NE
D051697:Activating Transcription Factor 1; D000818:Animals; D015153:Blotting, Western; D002187:Cannabinol / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004268:DNA-Binding Proteins; D003720:Densitometry; D003864:Depression, Chemical; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007376:Interleukin-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism
D051697:Activating Transcription Factor 1; C497100:Atf1 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D007376:Interleukin-2; D016328:NF-kappa B; D014157:Transcription Factors; D002187:Cannabinol; D013755:Tetradecanoylphorbol Acetate