Objective – Endocannabinoids are important lipid mediators which excert a multitude of different functions in the body. In particular the endocannabinoid anadamide (AEA) is considered an important signalling molecule in the cardiovascular system. We set-out to determine the function of AEA in vascular smooth muscle cells.  

Results – RNA-Seq analysis of human aortic smooth muscle cells (HAoSMCs) treated with and without AEA revealed disparten effects on gene expression, suggesting that AEA induces pro-inflammatory gene expression but also has an important anti-inflammatory component. The anti-inflammatory effect of AEA was unique as it was not mediated by any other endocannabinoid nor by endocannabinoid receptors. To identify the potential receptor mediating this effect, the RNAseq data were reanalyzed: AEA massively induced the nuclear receptor family NR4A. Indeed, knockdown of NR4A blocked the AEA-mediated anti-inflammatory effect and prevented parts of the AEA-induced gene expression. Artificial NR4A agonists (CsnB, C-DIM12 and PGA1) mimic parts of the AEA response, albeit at much higher concentrations. Further experiments revealed, that binding of AEA to NR4A recruits the nuclear corepressor NCoR1 to mediate gene inhibition. To demonstrate direct interaction of NR4A with AEA, microscale thermophoresis was  performed, which indeed demonstrated a specific binding with exceedingly high efficacy.

Conclusions – By activating NR4A AEA elicits a novel and specific anti-inflammatory response in smooth muscle cells. AEA therefore represents a lead structure for a novel class of anti-inflammatory drugs.