Mechanism of erythropoietin regulation by angiotensin II.
Erythropoietin (EPO) is the primary regulator of red blood cell development. Although hypoxic regulation of EPO has been extensively studied, the mechanism(s) for basal regulation of EPO are not well understood. In vivo studies in healthy human volunteers and animal models indicated that angiotensin II (Ang II) and angiotensin converting enzyme inhibitors regulated blood EPO levels. In the current study, we found that Ang II induced EPO expression in situ in murine kidney slices and in 786-O kidney cells in culture as determined by reverse transcription polymerase chain reaction. We further investigated the signaling mechanism of Ang II regulation of EPO in 786-O cells. Pharmacological inhibitors of Ang II type 1 receptor (AT1R) and extracellular signal-regulated kinase 1/2 (ERK1/2) suppressed Ang II transcriptional activation of EPO. Inhibitors of AT2R or Src homology 2 domain-containing tyrosine phosphatase had no effect. Coimmunoprecipiation experiments demonstrated that p21Ras was constitutively bound to the AT1R; this association was increased by Ang II but was reduced by the AT1R inhibitor telmisartan. Transmembrane domain (TM) 2 of AT1R is important for G protein-dependent ERK1/2 activation, and mutant D74E in TM2 blocked Ang II activation of ERK1/2. Ang II signaling induced the nuclear translocation of the Egr-1 transcription factor, and overexpression of dominant-negative Egr-1 blocked EPO promoter activation by Ang II. These data identify a novel pathway for basal regulation of EPO via AT1R-mediated Egr-1 activation by p21Ras-mitogen-activated protein kinase/ERK kinase-ERK1/2. Our current data suggest that Ang II, in addition to regulating blood volume and pressure, may be a master regulator of erythropoiesis.
Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland (Y.-C.K., O.M., E.A.M., P.J.R., R.M.D.); and Department of Animal Biology, University of Pennsylvania, Philadelphia, Pennsylvania (D.K.Y.).
Yong-Chul
YC
Kim
Ognoon
O
Mungunsukh
Elizabeth A
EA
McCart
Peter J
PJ
Roehrich
Daniel K
DK
Yee
Regina M
RM
Day
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004789:Enzyme Activation; D004921:Erythropoietin / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000187:drug effects
D017931:DNA Primers; D004921:Erythropoietin; D000804:Angiotensin II