Ecto-5-nucleotidase (Nt5e/CD73)-mediated adenosine signaling attenuates TGF-2 induced elastin and cellular contraction

Arterial calcification due to deficiency of CD73 (ACDC) is a rare genetic disease caused by a loss-of-function mutation in the NT5E gene encoding the ecto-5'-nucleotidase (cluster of differentiation 73, CD73) enzyme. Patients with ACDC develop vessel arteriomegaly, tortuosity, and vascular calcification in their lower extremity arteries. Histological analysis shows that patients with ACDC vessels exhibit fragmented elastin fibers similar to that seen in aneurysmal-like pathologies. It is known that alterations in transforming growth factor beta (TGF beta) pathway signaling contribute to this elastin phenotype in several connective tissue diseases, as TGF beta regulates extracellular matrix (ECM) remodeling. Our study investigates whether CD73-derived adenosine modifies TGF beta signaling in vascular smooth muscle cells (SMCs). We show that Nt5e-/SMCs have elevated contractile markers and elastin gene expression compared with Nt5e(+/+) SMCs. Ecto-5'-nucleotidase (Nt5e)-deficient SMCs exhibit increased TGF beta-2 and activation of small mothers against decapentaplegic (SMAD) signaling, elevated elastin transcript and protein, and potentiate SMC contraction. These effects were diminished when the A2b adenosine receptor was activated. Our results identify a novel link between adenosine and TGF beta signaling, where adenosine signaling via the A2b adenosine receptor attenuates TGF beta signal-ing to regulate SMC homeostasis. We discuss how disruption in adenosine signaling is implicated in ACDC vessel tortuosity and could potentially contribute to other aneurysmal pathogenesis.