Cytokine-induced apoptosis of beta-thalassemia/hemoglobin E erythroid progenitor cells via nitric oxide-mediated process in vitro.

BACKGROUND/AIM β-Thalassemia/hemoglobin E (β-thal/HbE) is a common hereditary anemia in Thailand. Ineffective erythropoiesis due to apoptosis and decreased lifespan of circulating thalassemic red blood cells are the major causes of anemia. Changes to bone marrow microenvironment could contribute to apoptotic events. This study examined the effects of cytokines interleukin-1β, tumor necrosis factor-α and interferon-γ on apoptosis of β-thal/HbE erythroid progenitor cells in vitro, including nitric oxide-mediated apoptotic processes. METHODS Percent apoptosis of erythroid progenitor cells from 5 β-thal/HbE patients and 5 normal control subjects was examined using flow cytometry. In addition, the inducible nitric oxide synthase (iNOS) mRNA level and nitrite production were measured using quantitative PCR and the Griess method, respectively. RESULTS Upon cytokine treatment, a higher percent apoptosis was obtained with β-thal/HbE erythroid progenitor cells compared with control, and the maximum effect was observed using 20 ng/ml interferon-γ on day 14 of culture. There was an increase in iNOS mRNA level and a concomitant elevation of nitrite concentration in culture medium. Apoptosis and nitrite level were abrogated when β-thal/HbE and control cells were treated with S-methylisothiourea sulfate, an iNOS inhibitor. CONCLUSION The marked sensitivity of erythroid progenitor cells from β-thal/HbE patients to cytokine-induced apoptosis via an NO-mediated process reflects a proapoptotic status of such thalassemic red blood cells.