%0 Generic
%A Buck, Isabelle
%D 2008
%F heidok:8752
%K Tumor necrosis factor alpha , inflammation , cancer , anemia , transcription factors
%R 10.11588/heidok.00008752
%T Molecular mechanisms leading to the inhibition of erythroid differentiation by the proinflammatory cytokine tumor necrosis factor alpha
%U https://archiv.ub.uni-heidelberg.de/volltextserver/8752/
%X Erythropoiesis is considered as a multistep and tightly regulated process under the control of a series of cytokines including erythropoietin (Epo). Epo activates specific signaling pathways and key transcription factors such as GATA-1, in order to ensure erythroid differentiation. Dysregulation leads to a decreased number of red blood cells, a hemoglobin deficiency, thus a limited oxygen-carrying capacity in the blood.Anemia represents a frequent complication in various diseases such as cancer or inflammation related disease. Tumor necrosis factor alpha (TNFalpha) was described to be involved in the pathogenesis of inflammation and cancer related anemia, which reduces both quality of life and prognosis in patients. Blood transfusions and erythroid stimulating agents (ESAs) including human recombinant Epo (rhuEpo) are currently used as efficient treatments. However, the recently described conflicting effects of ESAs in distinct studies require further investigations on the molecular mechanisms involved in TNFalpha-caused anemia. The aim of this study was to reveal the molecular mechanisms linked to the inhibition of erythroid differentiation by the proinflammatory cytokine TNFalpha. In order to achieve this goal, we used three different hematopoietic cell lines (K562, HEL, and TF-1) as well as purified CD34+ hematopoietic progenitor cells from umbilical cord blood. For K562 and HEL cells, distinct chemical compounds such as Aclacynomicin (Acla), Doxorubicin (Dox), or Hemin (He) were used to induce erythroid differentiation, whereas TF-1 and CD34+ cells were treated with Epo.  Results showed an inhibitory effect of TNFalpha on hemoglobin synthesis in the different cellular models, independently of the inducer used. This effect was correlated with a decrease of the major erythroid transcription factor GATA-1 and its coactivator Friend of GATA-1 (FOG-1). We further demonstrated that the reduction of the GATA-1/FOG-1 complex was partly due to a proteasome-dependent degradation of the interaction partners. Moreover, an unsettling of the complementary expression profiles of GATA-1 and GATA-2 in the three cell lines tested was observed, which is in disfavor of final erythroid differentiation. The observed abolishment of the acetylation status of GATA-1 by TNFalpha in He-induced K562 cells even suggested an impact of the cytokine on GATA-1 transcriptional activity. As assessed by transfection experiments, TNFalpha had also an inhibitory effect on GATA-1 transactivation activity, independently of the inducer used. Then we analyzed the expression of specific marker genes partly known as GATA-1 target genes. Results revealed a decrease in Epo receptor (EpoR), alpha- and gamma-globin, erythroid-associated factor (ERAF), hydroxymethylbilane synthetase (HMBS), and glycophorin A (GPA) expressions after TNFalpha treatment. Furthermore, we showed that p38 is involved in the TNFalpha-mediated inhibition of Epo-triggered erythroid differentiation, as the p38 inhibitor SB203580 reverses the inhibition of hemoglobin production, gamma-globin gene and GATA-1 expression. These data contribute to a better understanding of the molecular mechanisms involved in cytokine-dependent anemia both by revealing modulations of key erythroid transcription factors as well as potential diagnostic markers. Overall this study gives first hints of the key players involved in TNFalpha-mediated inhibition of erythroid differentiation, which can be seen as foundation for future investigations.