Triiodothyronine (T3) Excess Inhibits Hemin-Induced Erythroid Differentiation of Human Erythroleukemia K562 Cells

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 414-436-HPT Axis Biology & Action
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-423
Mieno Shiraishi*1, Yoritsuna Yamamoto2, Yousuke Ono1, Nobutaka Hirooka1, Shoichi Tachibana2 and Yuji Tanaka1
1National Defense Medical College, Tokorozawa, Japan, 2National Defense Medical College Research Institute, Tokorozawa, Japan
Background: Thyroid hormone has been reported to stimulate hemato/erythropoietic differentiation. However, severe anemia is sometimes seen in patients with hyperthyroidism. Mechanism of the anemia in hyperthyroidism has not been explained by any of the known etiological factors, while the anemia responds well to treatment of hyperthyroidism.

Objective: Effect of triiodothyronine (T3) excess on erythroid differentiation of K562 human erythroleukemia cells was investigated to explore the mechanism of anemia in hyperthyroidism.

Methods: K562 cells were cultured in RPMI 1640 medium with 10% fetal bovine serum (FBS). Expression of thyroid hormone receptors (TRs; TR alpha, TR beta, and RXR) was confirmed by PCR. K562 cells were preincubated in the presence (treatment group) or absence (control group) of 10-100nM T3 for 4 days. Then, the cells in both group were exposed to 50μM hemin for 72 hours to induce erythroid differentiation. Hemin-induced erythroid differentiation was analyzed by benzidine staining and measuring hemoglobin content. Additionally, cell surface markers (CD71) were analyzed by flow cytometry.

Results: Steady expression of TRs was detected in K562 cells. Benzidine-positive rate before hemin exposure was approximately 7%. When 50μM hemin was added to the culture medium, K562 cells showed signs of differentiation and synthesized hemoglobin. In the control group, benzidine-positive rate increased approximately 70%. In the treatment group, T3 treatment inhibited the erythroid differentiation in a concentration-dependent manner, where maximum inhibitory effect of T3 occurred at the concentration of 100nM. Benzidine-positive rate in the treatment group decreased approximately 60%. T3 treatment also decreased hemoglobin content of hemin-induced K562 cells. Flow cytometry analysis revealed that the number of CD71 positive cells with mature differentiation was markedly lower in the treatment group.

Discussion: T3 is an essential hormone for erythropoiesis similar to erythropoietin. TRs were expressed in K562 human erythroleukemia cells. Excess of T3 induced a significant decrease of benzidine-positive rate and hemoglobin content after hemin-induced erythroid differentiation. In addition, T3 preincubation reduced CD71 positive cells with mature differentiation, suggesting the important role of T3 excess in erythropoiesis.

Conclusion: T3 excess inhibited hemin-induced erythroid differentiation of K562 cells.

Nothing to Disclose: MS, YY, YO, NH, ST, YT

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