Dysregulation of FOXO1 (Forkhead Box O1 Protein) Drives Calcification in Arterial Calcification due to Deficiency of CD73 and Is Present in Peripheral Artery Disease

Objective: The recessive disease arterial calcification due to deficiency of CD73 (ACDC) presents with extensive nonatherosclerotic medial layer calcification in lower extremity arteries. Lack of CD73 induces a concomitant increase in TNAP (tissue nonspecific alkaline phosphatase;ALPL), a key enzyme in ectopic mineralization. Our aim was to investigate how loss of CD73 activity leads to increasedALPLexpression and calcification in CD73-deficient patients and assess whether this mechanism may apply to peripheral artery disease calcification. Approach and Results: We previously developed a patient-specific disease model using ACDC primary dermal fibroblasts that recapitulates the calcification phenotype in vitro. We found that lack of CD73-mediated adenosine signaling reduced cAMP production and resulted in increased activation of AKT. The AKT/mTOR (mammalian target of rapamycin) axis blocks autophagy and inducing autophagy prevented calcification; however, we did not observe autophagy defects in ACDC cells. In silico analysis identified a putative FOXO1 (forkhead box O1 protein) binding site in the humanALPLpromoter. Exogenous AMP induced FOXO1 nuclear localization in ACDC but not in control cells, and this was prevented with a cAMP analogue or activation of A2a/2b adenosine receptors. Inhibiting FOXO1 reducedALPLexpression and TNAP activity and prevented calcification. Mutating the FOXO1 binding site reducedALPLpromoter activation. Importantly, we provide evidence that non-ACDC calcified femoropopliteal arteries exhibit decreased CD73 and increased FOXO1 levels compared with control arteries. Conclusions: These data show that lack of CD73-mediated cAMP signaling promotes expression of the humanALPLgene via a FOXO1-dependent mechanism. Decreased CD73 and increased FOXO1 was also observed in more common peripheral artery disease calcification.