CD73-TNAP crosstalk regulates the hypertrophic response and cardiomyocyte calcification due to α1 adrenoceptor activation

Abstract

Cluster of differentiation 73 (CD73) is an ecto-5' nucleotidase which catalyzes the conversion of AMP to adenosine. One of the many functions of adenosine is to suppress the activity of tissue nonspecific alkaline phosphatase (TNAP), an enzyme important in regulating intracellular calcification. Since myocardial calcification is associated with various cardiac disease states, we studied the individual roles and crosstalk between CD73 and TNAP in regulating myocyte responses to the α1 adrenoceptor agonist phenylephrine in terms of calcification and hypertrophy. Cultured neonatal rat cardiomyocytes were treated with 10 µM phenylephrine for 24 h in the absence or presence of the stable adenosine analog 2-chloro-adenosine, the TNAP inhibitor tetramisole or the CD73 inhibitor α,β-methylene ADP. Phenylephrine produced marked hypertrophy as evidenced by significant increases in myocyte surface area and ANP gene expression, as well as calcification determined by Alizarin Red S staining. These responses were associated with reduced CD73 gene and protein expression and CD73 activity. Conversely, TNAP expression and activity were significantly increased although both were suppressed by 2-chloro-adenosine. CD73 inhibition alone significantly reduced myocyte-derived adenosine levels by >50 %, and directly induced hypertrophy and calcification in the absence of phenylephrine. These responses and those to phenylephrine were abrogated by TNAP inhibition. We conclude that TNAP contributes to the hypertrophic effect of phenylephrine, as well as its ability to produce cardiomyocyte calcification. These responses are minimized by CD73-dependent endogenously produced adenosine.

TNAP limits TGF-β-dependent cardiac and skeletal muscle fibrosis by inactivating SMAD2/3 transcription factors

“…Here we analysed two different models of fibrosis: rapid-onset cardiac fibrosis induced by the hypertensive molecule Ang II, and chronic skeletal muscle fibrosis in the Sgca null mice. We confirm earlier evidence showing that TNAP is upregulated in tissue fibrosis (Herencia et al, 2015) (Gan et al, 2014), but also show here that the number of cells expressing TNAP increases in both heart and skeletal muscle. Furthermore, as the abrogation of TGF-β signaling in TNAP positive cells dramatically reduces vascular and interstitial fibrosis, we can conclude that TNAP is actively expressed in cells driving tissue fibrosis.…”

The role of ecto-5′-nucleotidase in endothelial dysfunction and vascular pathologies

“…These effects are abolished by TNAP inhibition. This proves that the CD73 activity, and thus CD73-derived adenosine may act as endogenous negative regulators of hypertrophy and also calcification -possibly via inhibiting of TNAP [45].…”

“…There are also data on individual roles of CD73 and TNAP, as well as on the link between them, in the regulation of myocyte response to the a 1 -adrenoreceptor agonist-phenylephrine in the context of calcification and hypertrophy [45]. These studies clearly shows that cardiomyocyte hypertrophy in the response to phenylephrine is associated with TNAP stimulation and at the same time -CD73 inhibition, both in terms of expression and enzyme activity.…”

Calcification of joints and arteries: second report with novel NT5E mutations and expansion of the phenotype

“…9 One of the many functions of adenosine is to suppress the activity of tissue nonspecific alkaline phosphatase, an enzyme important in regulating extracellular matrix calcification. 17 p.Arg463X is a nonsense mutation, so it will cause a truncated, and often nonfunctional protein product. By protein structural modeling, we showed that p.Gly454Arg in our family may influence the folding of β-pleated sheet and make the protein unstable, thus leading to an impaired CD73 enzymatic activity.…”