Characterization of NADPH Oxidase Expression and Activity in Acute Myeloid Leukemia Cell Lines: A Correlation with the Differentiation Status.

In acute myeloid leukemia (AML), a low level of reactive oxygen species (ROS) is associated with leukemic stem cell (LSC) quiescence, whereas a high level promotes blast proliferation. ROS homeostasis relies on a tightly-regulated balance between the antioxidant and oxidant systems. Among the oxidants, NADPH oxidases (NOX) generate ROS as a physiological function. Although it has been reported in AML initiation and development, the contribution of NOX to the ROS production in AML remains to be clarified. The aim of this study was to investigate the NOX expression and function in AML, and to examine the role of NOX in blast proliferation and differentiation. First, we interrogated the NOX expression in primary cells from public datasets, and investigated their association with prognostic markers. Next, we explored the NOX expression and activity in AML cell lines, and studied the impact of NOX knockdown on cell proliferation and differentiation. We found that NOX2 is ubiquitously expressed in AML blasts, and particularly in cells from the myelomonocytic (M4) and monocytic (M5) stages; however, it is less expressed in LSCs and in relapsed AML. This is consistent with an increased expression throughout normal hematopoietic differentiation, and is reflected in AML cell lines. Nevertheless, no endogenous NOX activity could be detected in the absence of PMA stimulation. Furthermore, CYBB knockdown, although hampering induced NOX2 activity, did not affect the proliferation and differentiation of THP-1 and HL-60 cells. In summary, our data suggest that NOX2 is a marker of AML blast differentiation, while AML cell lines lack any NOX2 endogenous activity.

Hemin decreases cardiac oxidative stress and fibrosis in a rat model of systemic hypertension via PI3K/Akt signalling.

AIMS: Angiotensin II induces cardiac myocyte apoptosis and hypertrophy, which contribute to heart failure, possibly through enhanced oxidative stress. The aim of this work was to assess the impact of hemin (heme oxygenase-1 inducer) on NADPH oxidase activation, cardiac oxidative stress, and development of fibrosis in a rat model of renovascular hypertensive cardiomyopathy in comparison to an anti-hypertensive reference treatment with losartan. METHODS AND RESULTS: A 3 week hemin treatment was tested in an angiotensin II-dependent hypertensive rat model and a cellular model of neonatal rat cardiomyocytes stimulated by angiotensin II. Our findings demonstrate that hemin prevented development of intercellular fibrosis, expression of collagen I, and disorganization of intracellular fibres. Oxidative stress and apoptosis evaluated in hypertensive myocardial tissue were decreased by hemin. The reference treatment with the angiotensin II receptor (AT(1)) antagonist (losartan) was less effective than hemin in prevention of fibrosis and oxidative stress, although it was more effective in reducing hypertension. Rac-1 activation and, subsequently, NADPH oxidase activity were further decreased with hemin than with losartan. Hemin enhanced the expression of phosphoinositide 3-kinase (PI3K) p85 regulatory subunit, in contrast to losartan. The PI3K/Akt signalling pathway activation by hemin was related to heme oxygenase-1 activation and an increase in biliverdin reductase, and its inhibition by LY294002 reversed the effects of hemin on collagen I and caspase-3 expression. Finally, hemin increased Akt activation, and concomitantly decreased RhoA and p38 mitogen-activated protein kinase activation. CONCLUSION: We confirmed a positive effect of hemin on oxidative cardiac damage, apoptosis, and fibrosis induced by hypertension by modulating the NADPH oxidase activation through enhanced expression of the PI3K p85 regulatory subunit.

Regeneration of three layers vascular wall by using BMP2-treated MSC involving HIF-1α and Id1 expressions through JAK/STAT pathways.

Engineering living, multilayered blood vessels to form in vivo arteries is a promising alternative to peripheral artery bypass using acellular grafts restricted by thrombosis and occlusion at long term. Bone Morphogenetic Protein 2 (BMP2) is a growth factor determining in the early vascular embryonic development. The aim of the present study was evaluate the collaborative effect of recombinant human--BMP2 and Bone marrow--Mesenchymal stem cells (BM-MSCs) seeded on vascular patch to regenerate a vascular arterial wall in a rat model. BM-MSCs expressing green fluorescent protein (GFP) seeded on vascular patch were cultured in presence of recombinant human-BMP2 [100 ng/mL] during 1 week before their implantation on the abdominal aorta of Wistar rats. We observed after 2 weeks under physiological arterial flow a regeneration of a three layers adult-like arterial wall with a middle layer expressing smooth muscle proteins and a border layer expressing endothelial marker. In vitro study, using Matrigel assay and co-culture of BM-MSCs with endothelial cells demonstrated that rh-BMP2 promoted tube-like formation even at long term (90 days) allowing the organization of thick rails. We demonstrated using inhibitors and siRNAs that rh-BMP2 enhanced the expression of HIF-1α and Id1 through, at least in part, the stimulation of JAK2/STAT3/STAT5 signaling pathways. Rh-BMP2 by mimicking embryological conditions allowed vascular BM-MSCs differentiation.