In a recent study pulsed C EBP expression

In a recent study, pulsed C/EBPα expression was shown to induce a GMP-like state according to gene expression and chromatin accessibility data. However, during prolonged exposure only a macrophage fate was consolidated (Di Stefano et al., 2016). Remarkably, the stable C/EBPβ B cell converts reported here resembled self-renewing bipotential GMP progenitors that were responsive to GM-CSF but not dependent on cytokine signaling, and stably retained G/M differentiation potential. In the absence of cytokines, expression of macrophage- and granulocyte-specific markers emerged in a mutually exclusive fashion. These data suggest the involvement of C/EBPβ in maintenance, commitment, or both at the GMP stage.
Experimental Procedures
Author Contributions B.C. conceived the methodology, performed the experiments, analyzed the data, and wrote the draft. V.B. provided Cebpaf/f;Cebpbf/f mouse resources and experimental advice. E.K.-L. generated CEBP-EGFP fusion construct resources, and J.S. and C.K. validated experiments. V.B., J.I., N.P., J.S., and E.K.-L. were involved in reviewing the manuscript. B.C. and A.L. conceptualized the work and wrote the manuscript. A.L. was responsible for supervision, project administration, and funding acquisition.
Acknowledgments
Introduction Cells undergoing oxidative respiration rid the cell of undesirable metabolites, such as reactive oxygen species (ROS), to avoid oxidative stress and cellular damage. Most ginsenoside rh2 have a specific cellular response when exposed to compounds (toxins, medicines, foods) that increase free radical production beyond what can be detoxified. Recent data suggest that the oxidative stress response can involve the TP53 pathway where TP53 can function both as a sensor of ROS and ROS-mediated DNA damage but may also be involved in the regulation of ROS levels (reviewed by Sharpless and DePinho, 2002). In some situations, TP53 can function as an antioxidant, given that when TP53 levels were reduced via small interfering RNA (siRNA) in a variety of cell lines, oxidative stress and ROS increased 2-fold (Sablina et al., 2005). Specific target genes implicated as part of the antioxidant pathway mediated by TP53 included SESN2, SESN1, GPX1, and CDKN1A (Budanov and Karin, 2008; Sablina et al., 2005). Alternatively, TP53 can stabilize the anti-apoptotic protein, BCLXL, at the mitochondrial outer membrane. In the absence of TP53, the mitochondrial outer membrane is destabilized and cytochrome c is released (Mihara et al., 2003). Cell death then occurs through the “mitochondrial pathway,” now recently termed necroptosis (Jouan-Lanhouet et al., 2014). Mature red cells are exposed to both extrinsic and intrinsic ROS, which can lead to impairment of membrane deformability, reduced red cell lifespan, and reduced oxygen delivery (Mohanty et al., 2014; Perrone et al., 2012). Very little is known about how erythroid progenitors process oxidative stress, although mechanisms are likely different, given that they retain both nuclei and mitochondria, which mediate metabolism distinct from their progeny. We have previously used the zebrafish to model oxidative stress in Gata1+ erythroid cells caused by glucose-6-phosphate dehydrogenase (G6PD) deficiency (Patrinostro et al., 2013). Gata1+ erythroid cells with reduced G6PD activity developed elevated levels of ROS and were very sensitive to cell lysis with pro-oxidant exposure. Specific mechanisms of how Gata1+ erythroid cells respond to oxidative stress remain unknown. The zebrafish is an excellent model of hemato- and erythropoiesis and has many of the conserved genetic regulators of hematopoiesis, including gata1, lck, and c-myb (Bahary and Zon, 1998; Davidson and Zon, 2004). There have been several models of human erythroid disorders created in the zebrafish, including Diamond-Blackfan anemia, porphyria, and hereditary spherocytosis (Dooley et al., 2008; Taylor et al., 2012). In this article, we describe the effects of pro-oxidant exposure on Gata1+ erythroid cells. Specifically, we found that Gata1+ erythroid cells are a significant source of total-body ROS after pro-oxidant exposure in zebrafish early in development. Furthermore, we determined that a specific program associated with tp53 activation drives the response to pro-oxidant exposure, and mutation in tp53 was associated with increased basal mitochondrial respiration to maximal levels. This created a situation of decreased mitochondrial respiratory capacity when encountering a pro-oxidant challenge and elevated ROS, resulting in increased cell death.