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Major histocompatibility class II transactivator expression in smooth muscle cells from A2b adenosine receptor knock-out mice: cross-talk between the adenosine and interferon-gamma signaling.

ABSTRACT: Atherosclerosis characterized by sustained inflammation and aberrant extracellular matrix alterations. Our previous investigation has defined major histocompatibility class II transactivator (CIITA) as a key factor in mediating these two processes in smooth muscle cells. Here, we demonstrate that CIITA and major histocompatibility class II expression are elevated in interferon-gamma (IFN-gamma)-treated smooth muscle cells from A2b adenosine receptor (A2bAR(-/-)) knock-out mice, as compared with wild type cells. An A2-type adenosine receptor agonist suppresses these effects of IFN-gamma in wild type cells, which can be blocked by an A2bAR-specific antagonist. We further identify that increased cellular cAMP levels are responsible for the down-regulation of CIITA expression and, hence, reduced IFN-gamma response as evidenced by the following data: 1) direct activation of adenylyl cyclase activity is both necessary and sufficient to suppress the IFN-gamma response; 2) inhibition of phosphodiesterase activity attenuates IFN-gamma induced transcription events; and 3) direct treatment with cAMP analog abrogates CIITA activation and IFN-gamma response. Therefore, our data establish possible cross-talk between the adenosine signaling through cAMP and IFN-gamma during regulation of CIITA expression.

SUBMITTER: Xu Y

PROVIDER: S-EPMC2386913 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Interferon-gamma induces major histocompatibility class II transactivator (CIITA), which mediates collagen repression and major histocompatibility class II activation by human aortic smooth muscle cells.

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