Heme oxygenase-1 deficiency alters erythroblastic Island formation, steady-state erythropoiesis and red blood cell lifespan in mice

Heme oxygenase-1 is critical for iron recycling during red blood cell turnover, whereas its impact on steady-state erythropoiesis and red blood cell lifespan is not known. We show here that in 8- to 14-week old mice, heme oxygenase- 1 deficiency adversely affects steady-state erythropoiesis in the bone marrow. This is manifested by a decrease in Ter-119+-erythroid cells, abnormal adhesion molecule expression on macrophages and erythroid cells, and a greatly diminished ability to form erythroblastic islands. Compared with wild-type animals, red blood cell size and hemoglobin content are decreased, while the number of circulating red blood cells is increased in heme oxygenase-1 deficient mice, overall leading to microcytic anemia. Heme oxygenase-1 deficiency increases oxidative stress in circulating red blood cells and greatly decreases the frequency of macrophages expressing the phosphatidylserine receptor Tim4 in bone marrow, spleen and liver. Heme oxygenase-1 deficiency increases spleen weight and Ter119+-erythroid cells in the spleen, although α4β1-integrin expression by these cells and splenic macrophages positive for vascular cell adhesion molecule 1 are both decreased. Red blood cell lifespan is prolonged in heme oxygenase-1 deficient mice compared with wild-type mice. Our findings suggest that while macrophages and relevant receptors required for red blood cell formation and removal are substantially depleted in heme oxygenase- 1 deficient mice, the extent of anemia in these mice may be ameliorated by the prolonged lifespan of their oxidatively stressed erythrocytes

A Study of the Apoptotic Effects of Detergent Sclerosants on Vascular and Circulating Blood Cells

The in vitro effects of detergent sclerosants, sodium tetradecylsulphate (STS) andpolidocanol (POL) on cell activation, cytokine release, apoptosis and oncosis wereinvestigated. The general hypothesis of this thesis was that detergent sclerosants at lowconcentrations induce the release of proinflammatory and proangiogenic cytokines.Leukocytes, platelets, and endothelial cells (ECs) were incubated with varying concentrations(0%, 0.075%, 0.15%, 0.30%, 0.60% and 1.2%) of sclerosants. ELISA was used to detect therelease of proinflammatory and proangiogenic cytokines. Interferon-g and tumour necrosisfactor-a were released from STS-stimulated polymorphonuclear cells (PMNC). Bothsclerosants induced the release of vascular endothelial growth factor (VEGF).Morphological changes were analysed using fluorescence microscopy. Nuclear andcytoplasmic changes consistent with cell activation, apoptosis, oncosis and senescencewere found with both STS and POL at low concentrations (< 0.3%).Leukocyte and EC apoptosis was assessed using confocal microscopy and flow cytometry.Lactadherin and PI were used to stage apoptosis and Caspase-3, -8, -9 and Bax to assessapoptotic pathways. Porimin was used to assess oncosis. STS induced activation ofcaspase-3, -8, -9 and increase in Bax expression. POL only induced activation of Caspase-3, -9 and Bax. Active Caspase 3, 8 and 9 but not Bax were increased in EC stimulated withlow concentrations of both STS and POL. Both agents increased the activation of poriminat all concentrations.In Conclusion, detergent sclerosants induce cell activation and the release of proinflammatoryand proangiogenic cytokines. Sclerosants at low concentrations are also capable of inducingcell apoptosis and cell oncosis in leukocytes and EC