Does angiotensin II directly stimulate erythropoietin production in HepG2 cells?
Angiotensin II does not directly stimulate EPO production in HepG2 cells, suggesting that in vivo increases in EPO from angiotensin II are likely due to hemodynamic effects rather than direct receptor stimulation.
BACKGROUND: In humans, infusion of angiotensin II increases erythropoietin (EPO) serum levels in a dose-dependent manner. However, it is not known whether angiotensin II stimulates EPO-producing renal fibroblasts directly via a receptor or by alteration of renal hemodynamics with a consecutive decrease of renal blood flow. The purpose of this study was to investigate EPO secretion and gene expression under direct angiotensin II stimulation in a cell model thereby excluding hemodynamic effects. METHODS: In an established EPO-secreting cell line (HepG2), EPO concentrations were measured under various conditions (normoxia and hypoxia) and different angiotensin II concentrations. mRNA levels of EPO were analyzed by LightCycler quantitative PCR after reverse transcription normalized to the housekeeping gene cyclophilin. RESULTS: Angiotensin II did not affect EPO production in any concentration (1 nM or 100 microM) under conditions of normoxia. Reduced oxygen tension (1% O2) led to the expected increase of EPO and EPO gene expression. EPO secretion stimulated by hypoxia is not significantly changed by any concentration of angiotensin II. CONCLUSION: In summary, this study shows that angiotensin II does not alter EPO production in HepG2 cell culture under normoxic or hypoxic conditions. This might point towards the hypothesis that in vivo renal cortical blood flow and consecutively the decrease of oxygen tension may lead to an increase of EPO secretion.
Benöhr et al. (Wed,) studied this question.
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