Nucleoside transporter proteins (NTs) encoded by members of the SLC28 and SLC29 gene families contribute to nucleoside and nucleobase recycling but also modulate extracellular adenosine levels and thus adenosine-regulated metabolic targets.
Methods
We have examined the expression pattern of NT-encoding genes in human adipose tissue and we have further analysed whether the mRNA related to these genes show changes in their amounts associated with either HIV-1 infection, highly active antiretroviral therapy (HAART) or development of HIV-1-associated lipodystrophy syndrome (HALS).
Results
Human adipocytes express SLC28A1, SLC28A2 and SLC28A3 (encoding hCNT1, hCNT2 and hCNT3, respectively) and SLC29A1 and SLC29A2 (encoding hENT1 and hENT2, respectively). HIV-1 infection, prior to HAART and HALS development, is associated with the upregulation of the mRNA levels of the genes encoding hCNT1, hCNT3 and hENT2. The increase in the mRNA amounts for the former two genes may be due to the action of tumour necrosis factor-α (TNF-α), a cytokine with enhanced expression in adipose tissue following HIV-1 infection, as the effect is also observed in human adipocytes in culture after treatment with TNF-α. HAART and HALS development are associated with the upregulation of the mRNA levels encoding hCNT2 and hENT1, and further enhancement of hCNT1, hCNT3 and hENT2 gene expression.
Conclusions
These data suggest that selected genes of the SLC28 and SLC29 families are not only targets of HIV-1 infection, but might also contribute to the development of adipose tissue alterations leading to lipodystrophy.
References
1.
CarrA., SamarasK., ThorisdottirA.Diagnosis, prediction, and natural course of HIV-1 protease-inhibitor-associated lipodystrophy, hyperlipidaemia, and diabetes mellitus: a cohort study.Lancet1999; 353: 2093–2099.
2.
ChenD., MisraA., GargA.Clinical review 153: Lipodystrophy in human immunodeficiency virus-infected patients.J Clin Endocrinol Metab2002; 87: 4845–4856.
3.
MillerJ., CarrA., EmeryS.HIV lipodystrophy: prevalence, severity and correlates of risk in Australia.HIV Med2003; 4: 293–301.
4.
NolanD., JohnM., MallalS.Antiretoviral therapy and the lipodystrophy syndrome, part 2: concepts in aetiopathogenesis.Antivir Ther2001; 6: 145–160.
5.
GiraltM., DomingoP., GuallarJ.P.HIV-1 infection alters gene expression in adipose tissue, which contributes to HIV-1/HAART-associated lipodystrophy.Antivir Ther2006; 11: 729–740.
6.
VillarroyaF., DomingoP., GiraltM.Lipodystrophy associated with highly active anti-retroviral therapy for HIV infection: the adipocyte as a target of anti-retroviral-induced mitochondrial toxicity.Trends Pharmacol Sci2005; 26: 88–93.
7.
BrinkmanK., SmeitinkJ.A., RomijnJ.A., ReissP.Mitochondrial toxicity induced by nucleoside-analogue reverse-transcriptase inhibitors is a key factor in the pathogenesis of antiretroviral-therapy-related lipodystrophy.Lancet1999; 354: 1112–1115.
8.
CaronM., AuclairM., LagathuC.The HIV-1 nucleoside reverse transcriptase inhibitors stavudine and zidovudine alter adipocyte functions in vitro.AIDS2004; 18: 2127–2136.
9.
Rodriguez de la ConcepcionM.L., YuberoP., DomingoJ.C.Reverse transcriptase inhibitors alter uncoupling protein-1 and mitochondrial biogenesis in brown adipocytes.Antivir Ther2005; 10: 515–526.
10.
WalkerU.A., AuclairM., LebetchD., KornprobstM., CapeauJ., CaronM.Uridine abrogates the adverse effects of antiretroviral pyrimidine analogues on adipose cell functions.Antivir Ther2006; 11: 25–34.
Pastor-AngladaM., CasadoF.J.Nucleoside transport into cells: the role of nucleoside transporters SLC28 and SLC29 in cancer chemotherapy. In Deoxynucleoside analogs in cancer therapy. Edited by PetersG.J.. Totowa, NJ: Humana Press2006; pp. 1–28.
LaiY., TseC.M., UnadkatJ.D.Mitochondrial expression of the human equilibrative nucleoside transporter 1 (hENT1) results in enhanced mitochondrial toxicity of antiviral drugs.J Biol Chem2004; 279: 4490–4497.
15.
AymerichI., DuflotS., Fernandez-VeledoS.The concentrative nucleoside transporter family (SLC28): new roles beyond salvage?Biochem Soc Trans2005; 33: 216–219.
16.
Cano-SoldadoP., LorrayozI.M., Molina-ArcasM.Interaction of nucleoside inhibitors of HIV-1 reverse transcriptase with the concentrative nucleoside transporter-1 (SLC28A1).Antivir Ther2004; 9: 993–1002.
17.
Pastor-AngladaM., Cano-SoldadoP., Molina-ArcasM.Cell entry and export of nucleoside analogues.Virus Res2005; 107: 151–164.
18.
PurcetS., MinuesaG., Molina-Arcas3’-Azido-2’,3’-dideoxythymidine (zidovudine) uptake mechanisms in T lymphocytes.Antivir Ther2006; 11: 803–811.
19.
RitzelM.W., NgA.M., YaoS.Y.Molecular identification and characterization of novel human and mouse concentrative Na+-nucleoside cotransporter proteins (hCNT3 and mCNT3) broadly selective for purine and pyrimidine nucleosides (system cib).J Biol Chem2001; 276: 2914–2927.
Guillen-GomezE., CalbetM., CasadoJ.Distribution of CNT2 and ENT1 transcripts in rat brain: selective decrease of CNT2 mRNA in the cerebral cortex of sleep-deprived rats.J Neurochem2004; 90: 883–893.
22.
DuflotS., RieraB., Fernandez-VeledoS.ATP-sensitive K+ channels regulate the concentrative adenosine transporter CNT2 following activation by A(1) adenosine receptors.Mol Cell Biol2004; 24: 2710–2719.
23.
FariasM., San MartinR., PueblaC.Nitric oxide reduces adenosine transporter ENT1 gene (SLC29A1) promoter activity in human fetal endothelium from gestational diabetes.J Cell Physiol2006; 208: 451–460.
24.
Pinto-DuarteA., CoelhoJ.E., CunhaR.A., RibeiroJ.A., SebastiaoA.M.Adenosine A2A receptors control the extracellular levels of adenosine through modulation of nucleoside transporters activity in the rat hippocampus.J Neurochem2005; 93: 595–604.
25.
FruhbeckG., Gomez-AmbrosiJ., SalvadorJ.Leptin-induced lipolysis opposes the tonic inhibition of endogenous adenosine in white adipocytes.Faseb J2001; 15: 333–340.
FarréX., Guillén-GómezE., SánchezL.Expression of the nucleoside-derived drug transporters hCNT1, hENT1 and hENT2 in gynecologic tumors.Int J Cancer2004; 112: 959–966.
29.
MataJ.F., García-ManteigaJ.M., LostaoM.P.Role of the human concentrative nucleoside transporter (hCNT1) in the cytotoxic action of 5’-deoxy-5-fluorouridine, an active intermediate metabolite of capecitabine, a novel oral anticancer drug.Mol Pharmacol2001; 59: 1542–1548.
30.
SolerC., ValdesR., Garcia-ManteigaJ.Lipopolysaccharide-induced apoptosis of macrophages determines the up-regulation of concentrative nucleoside transporters Cnt1 and Cnt2 through tumor necrosis factor-alpha-dependent and -independent mechanisms.J Biol Chem2001; 276: 30043–30049.
31.
Fernandez-VeledoS., ValdesR., WalleniusV., CasadoF.J., Pastor-AngladaM.Up-regulation of the high-affinity pyrimidine-preferring nucleoside transporter concentrative nucleoside transporter 1 by tumor necrosis factor-alpha and interleukin-6 in liver parenchymal cells.J Hepatol2004; 41: 538–544.
32.
SolerC., Garcia-ManteigaJ., ValdesR.Macrophages require different nucleoside transport systems for proliferation and activation.Faseb J2001; 15: 1979–1988.
33.
ValdesR., OrtegaM.A., CasadoF.J.Nutritional regulation of nucleoside transporter expression in rat small intestine.Gastroenterology2000; 119: 1623–1630.
34.
MangraviteL.M., LipschutzJ.H., MostovK.E., GiacominiK.M.Localization of GFP-tagged concentrative nucleoside transporters in a renal polarized epithelial cell line.Am J Physiol Renal Physiol2001; 280: F879–F885.
35.
MangraviteL.M., BadagnaniI., GiacominiK.M.Nucleoside transporters in the disposition and targeting of nucleoside analogs in the kidney.Eur J Pharmacol2003; 479: 269–281.
36.
HamiltonS.R., YaoS.Y., IngramJ.C.Subcellular distribution and membrane topology of the mammalian concentrative Na+-nucleoside cotransporter rCNT1.J Biol Chem2001; 276: 27981–27988.
KatherH.Purine accumulation in human fat cell suspensions. Evidence that human adipocytes release inosine and hypoxanthine rather than adenosine.J Biol Chem1988; 263: 8803–8809.
39.
RitzelM.W., YaoS.Y., NgA.M., MackeyJ.R., CassC.E., YoungJ.D.Molecular cloning, functional expression and chromosomal localization of a cDNA encoding a human Na+/nucleoside cotransporter (hCNT2) selective for purine nucleosides and uridine.Mol Membr Biol1998; 15: 203–211.
40.
GriffithsM., YaoS.Y., AbidiF.Molecular cloning and characterization of a nitrobenzylthioinosine-insensitive (ei) equilibrative nucleoside transporter from human placenta.Biochem J1997; 328 Pt 3: 739–743.
41.
CrawfordC.R., PatelD.H., NaeveC., BeltJ.A.Cloning of the human equilibrative, nitrobenzylmercaptopurine riboside (NBMPR)-insensitive nucleoside transporter ei by functional expression in a transport-deficient cell line.J Biol Chem1998; 273: 5288–5293.
42.
AlankoL., StenbergD., Porkka-HeiskanenT.Nitrobenzylthioinosine (NBMPR) binding and nucleoside transporter ENT1 mRNA expression after prolonged wakefulness and recovery sleep in the cortex and basal forebrain of rat.J Sleep Res2003; 12: 299–304.
43.
LopezS., GarrabouG., MartinezE.Mitochondrial studies in adipose tissue of HIV-infected patients without fat redistribution.Antivir Ther2004; 9: L20.
ValdesR., Fernandez-VeledoS., AymerichI., CasadoF.J., Pastor-AngladaM.TGF-beta transcriptionally activates the gene encoding the high-affinity adenosine transporter CNT2 in rat liver parenchymal cells.Cell Mol Life Sci2006; 63: 2527–2537.
