HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Metzen, E. Articles by Jelkmann, W. Search for Related Content PubMed PubMed Citation Articles by Metzen, E. Articles by Jelkmann, W.

Evidence against a major role for Ca²⁺ in hypoxia-induced gene expression in human hepatoma cells (Hep3B)

Eric Metzen, Joachim Fandrey and Wolfgang Jelkmann

The human hepatoma cell line Hep3B is a widely used model for studies of hypoxia-related gene expression. Cytosolic free calcium concentration ([Ca²⁺]_i) has been implicated in cellular oxygen-sensing processes. We investigated whether calcium ions have a significant impact on the production of erythropoietin (EPO) and vascular endothelial growth factor (VEGF).

We found that the calcium ionophore ionomycin induced a rapid and sustained increase of [Ca²⁺]_i while thapsigargin, an inhibitor of endoplasmic reticulum calcium ATPase, only caused a 20 % elevation of [Ca²⁺]_i within 10 min after application. However, the calcium content of intracellular stores was considerably reduced by thapsigargin after an incubation period of 24 h.

Variations in [Ca²⁺]_o did not result in altered EPO or VEGF secretion rates. Ionomycin decreased EPO production while the lowering of VEGF production was not statistically significant. In the presence of extracellular Ca²⁺ the membrane permeant calcium chelator BAPTA-AM stimulated the production of EPO (P < 0·05) but not of VEGF while EGTA-AM, a closely related agent, affected neither EPO nor VEGF formation under these conditions. Incubation with thapsigargin resulted in decreased EPO synthesis (P < 0·05) but stimulated VEGF secretion (P < 0·05).
In the absence of extracellular calcium, EGTA-AM led to an accumulation of hypoxia-inducible factor-1 (HIF-1). This treatment significantly stimulated VEGF synthesis but also decreased EPO secretion (P < 0·05).
Our data suggest that the calcium transient and the cytosolic Ca²⁺ concentration do not play a key role in hypoxia-induced EPO and VEGF production in Hep3B cells.

This article has been cited by other articles:

				Q. Liu, U. Moller, D. Flugel, and T. Kietzmann Induction of plasminogen activator inhibitor I gene expression by intracellular calcium via hypoxia-inducible factor-1 Blood, December 15, 2004; 104(13): 3993 - 4001. [Abstract] [Full Text] [PDF]

				U. Berchner-Pfannschmidt, F. Petrat, K. Doege, B. Trinidad, P. Freitag, E. Metzen, H. de Groot, and J. Fandrey Chelation of Cellular Calcium Modulates Hypoxia-inducible Gene Expression through Activation of Hypoxia-inducible Factor-1{alpha} J. Biol. Chem., October 22, 2004; 279(43): 44976 - 44986. [Abstract] [Full Text] [PDF]

				S. F. Abcouwer, P. L. Marjon, R. K. Loper, and D. L. Vander Jagt Response of VEGF Expression to Amino Acid Deprivation and Inducers of Endoplasmic Reticulum Stress Invest. Ophthalmol. Vis. Sci., August 1, 2002; 43(8): 2791 - 2798. [Abstract] [Full Text] [PDF]

				X. Ren, K. L. Dorrington, P. H. Maxwell, and P. A. Robbins Effects of desferrioxamine on serum erythropoietin and ventilatory sensitivity to hypoxia in humans J Appl Physiol, August 1, 2000; 89(2): 680 - 686. [Abstract] [Full Text] [PDF]