Retinoic acid increases hypoxia-inducible factor-1α through intracrine prostaglandin E(2) signaling in human renal proximal tubular cells HK-2.
We have previously shown in HK-2 cells that ATRA (all-trans-retinoic acid) up-regulates HIF-1α (hypoxia-inducible factor-1α) in normoxia, which results in increased production of renal protector VEGF-A (vascular endothelial growth factor-A). Here we investigated the role of COXs (cyclooxygenases) in these effects and we found that, i) ATRA increased the expression of COX-1 and COX-2 mRNA and protein and the intracellular levels (but not the extracellular ones) of PGE(2). Furthermore, inhibitors of COX isoenzymes blocked ATRA-induced increase in intracellular PGE(2), HIF-1α up-regulation and increased VEGF-A production. Immunofluorescence analysis found intracellular staining for EP1-4 receptors (PGE(2) receptors). These results indicated that COX activity is critical for ATRA-induced HIF-1α up-regulation and suggested that intracellular PGE(2) could mediate the effects of ATRA; ii) Treatment with PGE(2) analog 16,16-dimethyl-PGE(2) resulted in up-regulation of HIF-1α and antagonists of EP1-4 receptors inhibited 16,16-dimethyl-PGE(2)- and ATRA-induced HIF-1α up-regulation. These results confirmed that PGE(2) mediates the effects of ATRA on HIF-1α expression; iii) Prostaglandin uptake transporter inhibitor bromocresol green blocked the increase in HIF-1α expression induced by PGE(2) or by PGE(2)-increasing cytokine interleukin-1β, but not by ATRA. Therefore only intracellular PGE(2) is able to increase HIF-1α expression. In conclusion, intracellular PGE(2) increases HIF-1α expression and mediates ATRA-induced HIF-1α up-regulation.
Departamento de Fisiología, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain. anab.fernandez@uah.es
Ana B
AB
Fernández-Martínez
María I
MI
Arenas Jiménez
Francisco J
FJ
Lucio Cazaña
D015153:Blotting, Western; D015687:Cell Hypoxia; D002460:Cell Line; D045744:Cell Line, Tumor; D051545:Cyclooxygenase 1 / Q000235:genetics / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D053583:Interleukin-1beta / Q000494:pharmacology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D016861:Cyclooxygenase Inhibitors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053583:Interleukin-1beta; D011720:Pyrazoles; C115461:SC 560; D013449:Sulfonamides; D042461:Vascular Endothelial Growth Factor A; D014212:Tretinoin; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D015232:Dinoprostone; C012655:nimesulide