Cellular Physiology and Biochemistry (Nov 2015)

Extracellular Adenosine Diphosphate Ribose Mobilizes Intracellular Ca2+ via Purinergic-Dependent Ca2+ Pathways in Rat Pulmonary Artery Smooth Muscle Cells

  • Chun Huang,
  • Jinxing Hu,
  • Krishna P. Subedi,
  • Amanda H.Y. Lin,
  • Omkar Paudel,
  • Pixin Ran,
  • James S.K. Sham

DOI
https://doi.org/10.1159/000438564
Journal volume & issue
Vol. 37, no. 5
pp. 2043 – 2059

Abstract

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Background/Aims: Adenosine diphosphate ribose (ADPR), a product of β-NAD+ metabolism generated by the multifunctional enzyme CD38, is recognized as a novel signaling molecule. The catalytic site of CD38 orients extracellularly or intracellularly, capable of generating ADPR outside and inside the cells. CD38-dependent pathways have been characterized in pulmonary artery smooth muscle cells (PASMCs); however the physiological function of extracellular ADPR is unclear. Methods: Ca2+ mobilizing and proliferative effects of extracellular ADPR were characterized and compared with the ATP-induced responses in rat PASMCs; and the expression of purinergic receptor (P2X and P2Y) subtypes were examined in pulmonary arteries. Results: ADPR elicited concentration-dependent increase in [Ca2+]i with a fast transient and a sustained phase in PASMCs. The sustained phase was abolished by Ca2+ removal and inhibited by the non-selective cation channel blocker SKF-96365, but was unaffected by TRPM2 antagonists or nifedipine. The purinergic receptor (P2X) antagonist pyridoxal-phosphate-6-azophenyl-2', 4'-disulfonate inhibited partially the transient and the sustained Ca2+ response, while the P2(XY) inhibitor suramin and the phospholipase C inhibitor U73122 abolished the sustained Ca2+ influx. The P2Y1 antagonist MRS2179 had no effect on the response. By contrast, ATP and ADP activated Ca2+ response exhibited a high and a low affinity component, and the pharmacological profile of ATP-induced Ca2+ response was distinctive from that of ADPR. BrdU incorporation assay showed that ADPR caused significant inhibition whereas ATP caused slight stimulation of PASMC proliferation. RT-PCR analysis found that almost all P2X and P2Y subtypes are expressed in PAs. Conclusion: ADPR and ATP activate Ca2+ responses through different combinations of multiple purinergic receptor subtypes; and extracellular ADPR may exert an autocrine/paracrine action via purinergic receptors on PASMCs.

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