Absence of equilibrative nucleoside transporter 1 in ENT1 knockout mice leads to altered nucleoside levels following hypoxic challenge

Jennifer B. Rose, Zlatina Naydenova, Andrew Bang, Azza Ramadan, Jost Klawitter, Kristin Schram, Gary Sweeney, Almut Grenz, Holger Eltzschig, James Hammond, Doo Sup Choi, Imogen R. Coe

Research output: Contribution to journalArticle

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Abstract

Aims: Equilibrative nucleoside transporters (ENT) modulate the flux of adenosine. The ENT1-null (KO) mouse heart is endogenously cardioprotected but the cellular basis of this phenotype is unknown. Therefore, we investigated the cellular mechanisms underlying ENT1-mediated cardioprotection. Main methods: Circulating adenosine levels were measured in WT and KO mice. Cellular levels of nucleosides and nucleotides were investigated in isolated adult cardiomyocytes from WT and KO mice using HPLC following hypoxic challenge (30 min, 2% O 2). Changes in hypoxic gene expression were analyzed by PCR arrays and cAMP levels were measured to investigate contributions from adenosine receptors. Key findings: Circulating adenosine levels were significantly higher in KO (416 ± 42 nmol/l, n = 12) compared to WT animals (208 ± 21, n = 13, p < 0.001). Absence of ENT1 led to an elevated expression of genes involved in cardioprotective pathways compared to WT cardiomyocytes. Following hypoxic challenge, extracellular adenosine levels were significantly elevated in KO (4360 ± 1840 pmol/mg protein) versus WT cardiomyocytes (3035 ± 730 pmol/mg protein, n ≥ 12, p < 0.05). This effect was enhanced in the presence of dipyridamole (30 μM), which inhibits ENT1 and ENT2. Enhanced extracellular adenosine levels in ENT1-null cardiomyocytes appeared to come from a pool of extracellular nucleotides including IMP, AMP and ADP. Adenosine receptor (AR) activation mimicked increases in cAMP levels due to hypoxic challenge suggesting that ENT1 modulates AR-dependent signaling. Significance: ENT1 contributes to modulation of extracellular adenosine levels and subsequent purinergic signaling via ARs. ENT1-null mice possess elevated circulating adenosine levels and reduced cellular uptake resulting in a perpetually cardioprotected phenotype.

Original languageEnglish (US)
Pages (from-to)621-630
Number of pages10
JournalLife Sciences
Volume89
Issue number17-18
DOIs
StatePublished - Oct 24 2011

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Equilibrative Nucleoside Transporter 1
Nucleosides
Knockout Mice
Adenosine
Cardiac Myocytes
Purinergic P1 Receptors
Nucleotides
Nucleoside Transport Proteins
Phenotype
Gene Expression
Inosine Monophosphate
Dipyridamole
Adenosine Monophosphate
Gene expression
Adenosine Diphosphate
Animals
Proteins
Genes
Chemical activation
High Pressure Liquid Chromatography

Keywords

  • Adenosine
  • ADP
  • AMP
  • ATP
  • Cardiomyocytes
  • ENT1
  • IMP
  • Inosine
  • Nucleoside transporters

ASJC Scopus subject areas

  • Pharmacology, Toxicology and Pharmaceutics(all)
  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

Absence of equilibrative nucleoside transporter 1 in ENT1 knockout mice leads to altered nucleoside levels following hypoxic challenge. / Rose, Jennifer B.; Naydenova, Zlatina; Bang, Andrew; Ramadan, Azza; Klawitter, Jost; Schram, Kristin; Sweeney, Gary; Grenz, Almut; Eltzschig, Holger; Hammond, James; Choi, Doo Sup; Coe, Imogen R.

In: Life Sciences, Vol. 89, No. 17-18, 24.10.2011, p. 621-630.

Research output: Contribution to journalArticle

Rose, JB, Naydenova, Z, Bang, A, Ramadan, A, Klawitter, J, Schram, K, Sweeney, G, Grenz, A, Eltzschig, H, Hammond, J, Choi, DS & Coe, IR 2011, 'Absence of equilibrative nucleoside transporter 1 in ENT1 knockout mice leads to altered nucleoside levels following hypoxic challenge', Life Sciences, vol. 89, no. 17-18, pp. 621-630. https://doi.org/10.1016/j.lfs.2011.08.007
Rose, Jennifer B. ; Naydenova, Zlatina ; Bang, Andrew ; Ramadan, Azza ; Klawitter, Jost ; Schram, Kristin ; Sweeney, Gary ; Grenz, Almut ; Eltzschig, Holger ; Hammond, James ; Choi, Doo Sup ; Coe, Imogen R. / Absence of equilibrative nucleoside transporter 1 in ENT1 knockout mice leads to altered nucleoside levels following hypoxic challenge. In: Life Sciences. 2011 ; Vol. 89, No. 17-18. pp. 621-630.
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AU - Ramadan, Azza

AU - Klawitter, Jost

AU - Schram, Kristin

AU - Sweeney, Gary

AU - Grenz, Almut

AU - Eltzschig, Holger

AU - Hammond, James

AU - Choi, Doo Sup

AU - Coe, Imogen R.

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KW - Inosine

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