The LSD1 inhibitor RN-1 induces fetal hemoglobin synthesis and reduces disease pathology in sickle cell mice.

Inhibition of lysine-specific demethylase 1 (LSD1) has been shown to induce fetal hemoglobin (HbF) levels in cultured human erythroid cells in vitro. Here we report the in vivo effects of LSD1 inactivation by a selective and more potent inhibitor, RN-1, in a sickle cell disease (SCD) mouse model. Compared with untreated animals, RN-1 administration leads to induced HbF synthesis and to increased frequencies of HbF-positive cells and mature erythrocytes, as well as fewer reticulocytes and sickle cells, in the peripheral blood of treated SCD mice. In keeping with these observations, histologic analyses of the liver and spleen of treated SCD mice verified that they do not exhibit the necrotic lesions that are usually associated with SCD. These data indicate that RN-1 can effectively induce HbF levels in red blood cells and reduce disease pathology in SCD mice, and may therefore offer new therapeutic possibilities for treating SCD.

mTOR Inhibition improves anaemia and reduces organ damage in a murine model of sickle cell disease.

Mechanistic target of rapamycin (mTOR) has been shown to play an important role in red blood cell physiology, with inhibition of mTOR signalling leading to alterations in erythropoiesis. To determine if mTOR inhibition would improve anaemia in sickle cell disease (SCD), mice with SCD were treated with the dual mTORC1/2 inhibitor, INK128. One week after daily oral drug treatment, erythrocyte count, haemoglobin, and haematocrit were all significantly increased while reticulocyte counts were reduced. These parameters remained stable during 3 weeks of treatment. Similar effects were observed following oral treatment with the mTORC1 inhibitor, sirolimus. Sirolimus treatment prolonged the lifespan of sickle cell erythrocytes in circulation, reduced spleen size, and reduced renal and hepatic iron accumulation in SCD mice. Following middle cerebral artery occlusion, stroke size was reduced in SCD mice treated with sirolimus. In conclusion, mTOR inhibition is protective against anaemia and organ damage in a murine model of SCD.

Forced TR2/TR4 expression in sickle cell disease mice confers enhanced fetal hemoglobin synthesis and alleviated disease phenotypes.

Sickle cell disease (SCD) is a hematologic disorder caused by a missense mutation in the adult ß-globin gene. Higher fetal hemoglobin (HbF) levels in red blood cells of SCD patients have been shown to improve morbidity and mortality. We previously found that nuclear receptors TR2 and TR4 repress expression of the human embryonic ε-globin and fetal γ-globin genes in definitive erythroid cells. Because forced expression of TR2/TR4 in murine adult erythroid cells paradoxically enhanced fetal γ-globin gene expression in transgenic mice, we wished to determine if forced TR2/TR4 expression in a SCD model mouse would result in elevated HbF synthesis and thereby alleviate the disease phenotype. In a "humanized" sickle cell model mouse, forced TR2/TR4 expression increased HbF abundance from 7.6% of total hemoglobin to 18.6%, accompanied by increased hematocrit from 23% to 34% and reticulocyte reduction from 61% to 18%, indicating a significant reduction in hemolysis. Moreover, forced TR2/TR4 expression reduced hepatosplenomegaly and liver parenchymal necrosis and inflammation in SCD mice, indicating alleviation of usual pathophysiological characteristics. This article shows that genetic manipulation of nonglobin proteins, or transcription factors regulating globin gene expression, can ameliorate the disease phenotype in a SCD model animal. This proof-of-concept study demonstrates that modulating TR2/TR4 activity in SCD patients may be a promising therapeutic approach to induce persistent HbF accumulation and for treatment of the disease.

Effect of Diabetes Mellitus on Sickle Hemoglobin Quantitation in Sickle Cell Trait.

OBJECTIVES: We evaluated the effect of diabetes on sickle hemoglobin (HbS) measurement on two common clinical hemoglobin separation platforms. METHODS: We performed a method comparison between the Bio-Rad Variant II high-performance liquid chromatography (HPLC) and Sebia Capillarys 2 Flex Piercing capillary electrophoresis (CE) using clinical specimens from 38 patients without hemoglobin variants and 57 patients with sickle cell trait (AS) (HbA1c%, 4.1%-15.4%). We investigated the effect of intermethod Hb% differences on result interpretation by a panel of expert clinical observers. RESULTS: In diabetic specimens, HPLC undermeasured HbS% up to 7.4% vs CE, due to S1c eluting closely with A0 in HPLC. This increased concern for underlying α-thalassemia in diabetic patients with AS based on HPLC results. HPLC P2% was linearly related to HbA1c% and can be a screen for diabetic AS samples. CONCLUSIONS: Glycosylation can interfere with HbS% measurement by HPLC. Susceptible specimens should be identified and preferentially analyzed via CE.

Melanoma tumor growth is accelerated in a mouse model of sickle cell disease.

BACKGROUND: The effect of sickle cell disease (SCD) on tumor growth is unknown. Sickled red blood cells may form aggregates within the microvasculature of hypoxic tumors and reduce blood flow leading to impairment of tumor growth. However, there is a paucity of data related to tumor growth in SCD. METHODS: To investigate the effect of SCD on tumor growth in a melanoma model, we generated SCD and control mice using bone marrow transplantation and inoculated the chest wall with B16-F10 melanoma cells. Tumor growth was monitored and angiogenesis was studied in vivo and in vitro. RESULTS: From day 1 to 21, tumor growth rate was nearly identical between SCD and WT mice, however from day 22 to day 29 tumor growth was accelerated in SCD mice compared to WT mice. Disparity in tumor size was confirmed at autopsy with an approximate 2-fold increase in tumor weights from SCD mice. Tumors from SCD mice showed increased vascularity and elevated levels of heme oxygenase-1 (HO-1). HO-1 inhibition with zinc protoporphyrin (ZnPP) blocked the angiogenic and tumor growth response to SCD in vivo and the response to hemin in vitro. CONCLUSIONS: Growth of melanoma tumors is potentiated in a mouse model of SCD. Therapies targeting angiogenesis or HO-1 may be useful in SCD patients with malignant tumors.