Intracellular Reactive Oxygen Species Mark and Influence the Megakaryocyte-Erythrocyte Progenitor Fate of Common Myeloid Progenitors

The Evaluation of Mass/DNA Copy Number of Mitochondria in Umbilical Cord Blood-derived Hematopoietic Stem Cells Cocultured with MSCs

Over recent decades, UCB has been widely used as an excellent alternative source of HSCs for treating many hematologic disorders. Recent studies suggest using mesenchymal stroma cell co-cultures to increase the number of HSCs prior to transplantation. Considering the critical role of mitochondria in the cell's fate and the importance of the self-renewal capacity of HSCs in HSCT, we decided to investigate the mass/DNA copy number of mitochondria in HSCs while co-cultured with MSCs and alone after seven days. UCB units were collected from full-term deliveries. MSCs and HSCs were isolated from UCB and the purity of cells was confirmed by flow cytometry. The mtDNA-Copy Number of HSCs was calculated using prob-based real-time PCR. Furthermore, Mito Tracker Green dye measured the mass of mitochondria of HSCs. HSCs from MSC co-culture group showed significantly fewer mtDNA-CN compared to HSCs alone after seven days (p < 0.001). Besides, by comparing the two groups on day seven to HSCs on day zero, we observed a mild increase in the mitochondrial mass of HSCs alone compared to the MSC-HSC co-culture group (p < 0.05). Concerning previous studies that have proved the association between lower mass/DNA-copy number of mitochondria in CD34 + HSCs and lower metabolic activity along with higher quiescence maintenance, and by considering the results of this experiment, it seems that the MSC-HSC co-cultures might be associated with a higher expansion of HSCs as well as stemness maintenance leading to the improvement in engraftment. Nevertheless, further investigations are required to clarify the exact connection between lower mass/DNA-copy number of mitochondria and stemness maintenance in HSCs.

Emerging role of glutathione peroxidase 4 in myeloid cell lineage development and acute myeloid leukemia

Phospholipid Hydroperoxide Gluthatione Peroxidase also called Glutathione Peroxidase 4 is one of the 25 described human selenoproteins. It plays an essential role in eliminating toxic lipid hydroxy peroxides, thus inhibiting ferroptosis and favoring cell survival. GPX4 is differentially expressed according to myeloid differentiation stage, exhibiting lower expression in hematopoietic stem cells and polymorphonuclear leucocytes, while harboring higher level of expression in common myeloid progenitors and monocytes. In addition, GPX4 is highly expressed in most of acute myeloid leukemia (AML) subtypes compared to normal hematopoietic stem cells. High GPX4 expression is consistently correlated to poor prognosis in patients suffering AML. However, the role of GPX4 in the development of the myeloid lineage and in the initiation and progression of myeloid leukemia remains poorly explored. Given its essential role in the detoxification of lipid hydroperoxides, and its overexpression in most of myeloid malignancies, GPX4 inhibition has emerged as a promising therapeutic strategy to specifically trigger ferroptosis and eradicate myeloid leukemia cells. In this review, we describe the most recent advances concerning the role of GPX4 and, more generally ferroptosis in the myeloid lineage and in the emergence of AML. We also discuss the therapeutic interest and limitations of GPX4 inhibition alone or in combination with other drugs as innovative therapies to treat AML patients.

Small-molecule α-lipoic acid targets ELK1 to balance human neutrophil and erythrocyte differentiation

BACKGROUND

Erythroid and myeloid differentiation disorders are commonly occurred in leukemia. Given that the relationship between erythroid and myeloid lineages is still unclear. To find the co-regulators in erythroid and myeloid differentiation might help to find new target for therapy of myeloid leukemia. In hematopoiesis, ALA (alpha lipoic acid) is reported to inhibit neutrophil lineage determination by targeting transcription factor ELK1 in granulocyte-monocyte progenitors via splicing factor SF3B1. However, further exploration is needed to determine whether ELK1 is a common regulatory factor for erythroid and myeloid differentiation.

METHODS

In vitro culture of isolated CD34+, CMPs (common myeloid progenitors) and CD34+ CD371- HSPCs (hematopoietic stem progenitor cells) were performed to assay the differentiation potential of monocytes, neutrophils, and erythrocytes. Overexpression lentivirus of long isoform (L-ELK1) or the short isoform (S-ELK1) of ELK1 transduced CD34+ HSPCs were transplanted into NSG mice to assay the human lymphocyte and myeloid differentiation differences 3 months after transplantation. Knocking down of SRSF11, which was high expressed in CD371+GMPs (granulocyte-monocyte progenitors), upregulated by ALA and binding to ELK1-RNA splicing site, was performed to analyze the function in erythroid differentiation derived from CD34+ CD123mid CD38+ CD371- HPCs (hematopoietic progenitor cells). RNA sequencing of L-ELK1 and S-ELK1 overexpressed CD34+ CD123mid CD38+ CD371- HPCs were performed to assay the signals changed by ELK1.

RESULTS

Here, we presented new evidence that ALA promoted erythroid differentiation by targeting the transcription factor ELK1 in CD34+ CD371- hematopoietic stem progenitor cells (HSPCs). Overexpression of either the long isoform (L-ELK1) or the short isoform (S-ELK1) of ELK1 inhibited erythroid-cell differentiation, but knockdown of ELK1 did not affect erythroid-cell differentiation. RNAseq analysis of CD34+ CD123mid CD38+ CD371- HPCs showed that L-ELK1 upregulated the expression of genes related to neutrophil activity, phosphorylation, and hypoxia signals, while S-ELK1 mainly regulated hypoxia-related signals. However, most of the genes that were upregulated by L-ELK1 were only moderately upregulated by S-ELK1, which might be due to a lack of serum response factor interaction and regulation domains in S-ELK1 compared to L-ELK1. In summary, the differentiation of neutrophils and erythrocytes might need to rely on the dose of L-ELK1 and S-ELK1 to achieve precise regulation via RNA splicing signals at early lineage commitment.

CONCLUSIONS

ALA and ELK1 are found to regulate both human granulopoiesis and erythropoiesis via RNA spliceosome, and ALA-ELK1 signal might be the target of human leukemia therapy.

Environmental Chemical-Induced Reactive Oxygen Species Generation and Immunotoxicity: A Comprehensive Review

Significance: Reactive oxygen species (ROS), the reactive oxygen-carrying chemicals moieties, act as pleiotropic signal transducers to maintain various biological processes/functions, including immune response. Increased ROS production leads to oxidative stress, which is implicated in xenobiotic-induced adverse effects. Understanding the immunoregulatory mechanisms and immunotoxicity is of interest to developing therapeutics against xenobiotic insults. Recent Advances: While developmental studies have established the essential roles of ROS in the establishment and proper functioning of the immune system, toxicological studies have demonstrated high ROS generation as one of the potential mechanisms of immunotoxicity induced by environmental chemicals, including heavy metals, pesticides, aromatic hydrocarbons (benzene and derivatives), plastics, and nanoparticles. Mitochondrial electron transport and various signaling components, including NADH oxidase, toll-like receptors (TLRs), NF-κB, JNK, NRF2, p53, and STAT3, are involved in xenobiotic-induced ROS generation and immunotoxicity. Critical Issues: With many studies demonstrating the role of ROS and oxidative stress in xenobiotic-induced immunotoxicity, rigorous and orthogonal approaches are needed to achieve in-depth and precise understanding. The association of xenobiotic-induced immunotoxicity with disease susceptibility and progression needs more data acquisition. Furthermore, the general methodology needs to be possibly replaced with high-throughput precise techniques. Future Directions: The progression of xenobiotic-induced immunotoxicity into disease manifestation is not well documented. Immunotoxicological studies about the combination of xenobiotics, age-related sensitivity, and their involvement in human disease incidence and pathogenesis are warranted. Antioxid. Redox Signal. 40, 691-714.

Reactive oxygen species and its role in pathogenesis and resistance to therapy in acute myeloid leukemia

Relapse following a short clinical response to therapy is the major challenge for the management of acute myeloid leukemia (AML) patients. Leukemic stem cells (LSC), as the source of relapse, have been investigated for their metabolic preferences and their alterations at the time of relapse. As LSC rely on oxidative phosphorylation (OXPHOS) for energy requirement, reactive oxygen species (ROS), as by-products of OXPHOS, have been investigated for their role in the effectiveness of the standard AML therapy. Increased levels of non-mitochondrial ROS, generated by nicotinamide adenine dinucleotide phosphate oxidase, in a subgroup of AML patients add to the complexity of studying ROS. Although there are various studies presenting the contribution of ROS to AML pathogenesis, resistance, and its inhibition or activation as a target, a model that can clearly explain its role in AML has not been conceptualized. This is due to the heterogeneity of AML, the dynamics of ROS production, which is influenced by factors such as the type of treatment, cell differentiation state, mitochondrial activity, and also the heterogeneous generation of non-mitochondrial ROS and limited available data on their interaction with the microenvironment. This review summarizes these challenges and the recent progress in this field.

Hematopoietic Stem Cell Factors: Their Functional Role in Self-Renewal and Clinical Aspects

Hematopoietic stem cells (HSCs) possess two important properties such as self-renewal and differentiation. These properties of HSCs are maintained through hematopoiesis. This process gives rise to two subpopulations, long-term and short-term HSCs, which have become a popular convention for treating various hematological disorders. The clinical application of HSCs is bone marrow transplant in patients with aplastic anemia, congenital neutropenia, sickle cell anemia, thalassemia, or replacement of damaged bone marrow in case of chemotherapy. The self-renewal attribute of HSCs ensures long-term hematopoiesis post-transplantation. However, HSCs need to be infused in large numbers to reach their target site and meet the demands since they lose their self-renewal capacity after a few passages. Therefore, a more in-depth understanding of ex vivo HSCs expansion needs to be developed to delineate ways to enhance the self-renewability of isolated HSCs. The multifaceted self-renewal process is regulated by factors, including transcription factors, miRNAs, and the bone marrow niche. A developed classical hierarchical model that outlines the hematopoiesis in a lineage-specific manner through in vivo fate mapping, barcoding, and determination of self-renewal regulatory factors are still to be explored in more detail. Thus, an in-depth study of the self-renewal property of HSCs is essentially required to be utilized for ex vivo expansion. This review primarily focuses on the Hematopoietic stem cell self-renewal pathway and evaluates the regulatory molecular factors involved in considering a targeted clinical approach in numerous malignancies and outlining gaps in the current knowledge.

Treatment With the CSF1R Antagonist GW2580, Sensitizes Microglia to Reactive Oxygen Species

Microglia activation and proliferation are hallmarks of many neurodegenerative disorders and may contribute to disease pathogenesis. Neurons actively regulate microglia survival and function, in part by secreting the microglia mitogen interleukin (IL)-34. Both IL-34 and colony stimulating factor (CSF)-1 bind colony stimulating factor receptor (CSFR)1 expressed on microglia. Systemic treatment with central nervous system (CNS) penetrant, CSFR1 antagonists, results in microglia death in a dose dependent matter, while others, such as GW2580, suppress activation during disease states without altering viability. However, it is not known how treatment with non-penetrant CSF1R antagonists, such as GW2580, affect the normal physiology of microglia. To determine how GW2580 affects microglia function, C57BL/6J mice were orally gavaged with vehicle or GW2580 (80mg/kg/d) for 8 days. Body weights and burrowing behavior were measured throughout the experiment. The effects of GW2580 on circulating leukocyte populations, brain microglia morphology, and the transcriptome of magnetically isolated adult brain microglia were determined. Body weights, burrowing behavior, and circulating leukocytes were not affected by treatment. Analysis of Iba-1 stained brain microglia indicated that GW2580 treatment altered morphology, but not cell number. Analysis of RNA-sequencing data indicated that genes related to reactive oxygen species (ROS) regulation and survival were suppressed by treatment. Treatment of primary microglia cultures with GW2580 resulted in a dose-dependent reduction in viability only when the cells were concurrently treated with LPS, an inducer of ROS. Pre-treatment with the ROS inhibitor, YCG063, blocked treatment induced reductions in viability. Finally, GW2580 sensitized microglia to hydrogen peroxide induced cell death. Together, these data suggest that partial CSF1R antagonism may render microglia more susceptible to reactive oxygen and nitrogen species.

Mitochondria Turnover and Lysosomal Function in Hematopoietic Stem Cell Metabolism

Hematopoietic stem cells (HSCs) reside in a hypoxic microenvironment that enables glycolysis-fueled metabolism and reduces oxidative stress. Nonetheless, metabolic regulation in organelles such as the mitochondria and lysosomes as well as autophagic processes have been implicated as essential for the determination of HSC cell fate. This review encompasses the current understanding of anaerobic metabolism in HSCs as well as the emerging roles of mitochondrial metabolism and lysosomal regulation for hematopoietic homeostasis.

β3-Adrenoreceptors as ROS Balancer in Hematopoietic Stem Cell Transplantation

In the last decades, the therapeutic potential of hematopoietic stem cell transplantation (HSCT) has acquired a primary role in the management of a broad spectrum of diseases including cancer, hematologic conditions, immune system dysregulations, and inborn errors of metabolism. The different types of HSCT, autologous and allogeneic, include risks of severe complications including acute and chronic graft-versus-host disease (GvHD) complications, hepatic veno-occlusive disease, lung injury, and infections. Despite being a dangerous procedure, it improved patient survival. Hence, its use was extended to treat autoimmune diseases, metabolic disorders, malignant infantile disorders, and hereditary skeletal dysplasia. HSCT is performed to restore or treat various congenital conditions in which immunologic functions are compromised, for instance, by chemo- and radiotherapy, and involves the administration of hematopoietic stem cells (HSCs) in patients with depleted or dysfunctional bone marrow (BM). Since HSCs biology is tightly regulated by oxidative stress (OS), the control of reactive oxygen species (ROS) levels is important to maintain their self-renewal capacity. In quiescent HSCs, low ROS levels are essential for stemness maintenance; however, physiological ROS levels promote HSC proliferation and differentiation. High ROS levels are mainly involved in short-term repopulation, whereas low ROS levels are associated with long-term repopulating ability. In this review, we aim summarize the current state of knowledge about the role of β3-adrenoreceptors (β3-ARs) in regulating HSCs redox homeostasis. β3-ARs play a major role in regulating stromal cell differentiation, and the antagonist SR59230A promotes differentiation of different progenitor cells in hematopoietic tumors, suggesting that β3-ARs agonism and antagonism could be exploited for clinical benefit.

Involvement of GPx-3 in the Reciprocal Control of Redox Metabolism in the Leukemic Niche

The bone marrow (BM) microenvironment plays a crucial role in the development and progression of leukemia (AML). Intracellular reactive oxygen species (ROS) are involved in the regulation of the biology of leukemia-initiating cells, where the antioxidant enzyme GPx-3 could be involved as a determinant of cellular self-renewal. Little is known however about the role of the microenvironment in the control of the oxidative metabolism of AML cells. In the present study, a coculture model of BM mesenchymal stromal cells (MSCs) and AML cells (KG1a cell-line and primary BM blasts) was used to explore this metabolic pathway. MSC-contact, rather than culture with MSC-conditioned medium, decreases ROS levels and inhibits the Nrf-2 pathway through overexpression of GPx3 in AML cells. The decrease of ROS levels also inactivates p38MAPK and reduces the proliferation of AML cells. Conversely, contact with AML cells modifies MSCs in that they display an increased oxidative stress and Nrf-2 activation, together with a concomitant lowered expression of GPx-3. Altogether, these experiments suggest that a reciprocal control of oxidative metabolism is initiated by direct cell–cell contact between MSCs and AML cells. GPx-3 expression appears to play a crucial role in this cross-talk and could be involved in the regulation of leukemogenesis.

Induction of differentiation of the acute myeloid leukemia cell line (HL-60) by a securinine dimer

Differentiation therapy has been successfully applied clinically in cases of acute promyelocytic leukemia (APL), but few differentiation-induction agents other than all-trans retinoic acid (ATRA) have been discovered clinically. Based on our previously reported neuritogenic differentiation activity of synthetic dimeric derivatives of securinine, we explored the leukemia differentiation-induction activity of such as compound, SN3-L6. It was found that SN3-L6 induces transdifferentiation of both acute myeloid leukemia (AML) and chronic myelogenous leukemia (CML) cells but unexpectedly, a new transdifferentiation pathway from APL cells to morphologically and immunologically normal megakaryocytes and platelets were discovered. SN3-L6 fails to induce transdifferentiation of ATRA–produced mature granulocytes into megakaryocytes, indicating its selectivity between mature and immature cells. SN3-L6 induces CML K562 cells to transdifferentiate into apoptotic megakaryocytes but without platelet formation, indicating a desirable selectivity between different leukemia cells. Our data illuminate a differentiation gap between AML cells and platelets, and promises applications in leukemia differentiation therapy strategy.

Biochemical characterization of biliverdins IXβ/δ generated by a selective heme oxygenase

The pro-oxidant effect of free heme (Fe2+-protoporphyrin IX) is neutralized by phylogenetically-conserved heme oxygenases (HMOX) that generate carbon monoxide, free ferrous iron, and biliverdin (BV) tetrapyrrole(s), with downstream BV reduction by non-redundant NADPH-dependent BV reductases (BLVRA and BLVRB) that retain isomer-restricted functional activity for bilirubin (BR) generation. Regioselectivity for the heme α-meso carbon resulting in predominant BV IXα generation is a defining characteristic of canonical HMOXs, thereby limiting generation and availability of BVs IXβ, IXδ, and IXγ as BLVRB substrates. We have now exploited the unique capacity of the Pseudomonas aeruginosa (P. aeruginosa) hemO/pigA gene for focused generation of isomeric BVs (IXβ and IXδ). A scalable system followed by isomeric separation yielded highly pure samples with predicted hydrogen-bonded structure(s) as documented by 1H NMR spectroscopy. Detailed kinetic studies established near-identical activity of BV IXβ and BV IXδ as BLVRB-selective substrates, with confirmation of an ordered sequential mechanism of BR/NADP+ dissociation. Halogenated xanthene-based compounds previously identified as BLVRB-targeted flavin reductase inhibitors displayed comparable inhibition parameters using BV IXβ as substrate, documenting common structural features of the cofactor/substrate-binding pocket. These data provide further insights into structure/activity mechanisms of isomeric BVs as BLVRB substrates, with potential applicability to further dissect redox-regulated functions in cytoprotection and hematopoiesis.

Genetic aberrations in iPSCs are introduced by a transient G1/S cell cycle checkpoint deficiency

A number of point mutations have been identified in reprogrammed pluripotent stem cells such as iPSCs and ntESCs. The molecular basis for these mutations has remained elusive however, which is a considerable impediment to their potential medical application. Here we report a specific stage at which iPSC generation is not reduced in response to ionizing radiation, i.e. radio-resistance. Quite intriguingly, a G1/S cell cycle checkpoint deficiency occurs in a transient fashion at the initial stage of the genome reprogramming process. These cancer-like phenomena, i.e. a cell cycle checkpoint deficiency resulting in the accumulation of point mutations, suggest a common developmental pathway between iPSC generation and tumorigenesis. This notion is supported by the identification of specific cancer mutational signatures in these cells. We describe efficient generation of human integration-free iPSCs using erythroblast cells, which have only a small number of point mutations and INDELs, none of which are in coding regions.

Point mutations have been found in induced pluripotent stem cells (iPSCs) but when they arise is unclear. Here, the authors show that a G1/S cell cycle checkpoint deficiency transiently occurs early in genome reprogramming, suggesting a common developmental pathway between iPSC and tumorigenesis, and generate genetic burden-free human iPSCs.

Reactive Oxygen Species and Nrf2: Functional and Transcriptional Regulators of Hematopoiesis

Hematopoietic stem cells (HSCs) are characterized by self-renewal and multilineage differentiation potentials. Although they play a central role in hematopoietic homeostasis and bone marrow (BM) transplantation, they are affected by multiple environmental factors in the BM. Here, we review the effects of reactive oxygen species (ROS) and Nrf2 on HSC function and BM transplantation. HSCs reside in the hypoxic microenvironment of BM, and ROS play an important role in HSPC regulation. Recently, an extraphysiologic oxygen shock/stress phenomenon was identified in human cord blood HSCs collected under ambient air conditions. Moreover, Nrf2 has been recently recognized as a master transcriptional factor that regulates multiple antioxidant enzymes. Since several years, the role of Nrf2 in hematopoiesis has been extensively studied, which has functional similarities of cellular oxygen sensor hypoxia-inducible factor-1 as transcriptional factors. Increasing evidence has revealed that abnormally elevated ROS production due to factors such as genetic defects, aging, and ionizing radiation unexceptionally resulted in lethal impairment of HSC function and hematopoiesis. Both experimental and clinical studies have identified elevated ROS levels as a major culprit of ineffective BM transplantation. Lastly, we discuss the possibility of using small molecule antioxidants, such as N-acetyl cysteine, resveratrol, and curcumin, to augment HSC function and improve the therapeutic efficacy of BM transplantation. Further research on the function of ROS levels and improving the efficacy of BM transplantation may have a great potential for broad clinical applications of HSCs.

Differential redox-regulation and mitochondrial dynamics in normal and leukemic hematopoietic stem cells: A potential window for leukemia therapy

The prognosis for many patients with acute myeloid leukemia (AML) is poor, mainly due to disease relapse driven by leukemia stem cells (LSCs). Recent studies have highlighted the unique metabolic properties of LSCs, which might represent opportunities for LSC-selective targeting. LSCs characteristically have low levels of reactive oxygen species (ROS), which apparently result from a combination of low mitochondrial activity and high activity of ROS-removing pathways such as autophagy. Due to this low activity, LSCs are highly dependent on mitochondrial regulatory mechanisms. These include the anti-apoptotic protein BCL-2, which also has crucial roles in regulating the mitochondrial membrane potential, and proteins involved in mitophagy. Here we review the different pathways that impact mitochondrial activity and redox-regulation, and highlight their relevance for the functionality of both HSCs and LSCs. Additionally, novel AML therapy strategies that are based on interference with those pathways, including the promising BCL-2 inhibitor Venetoclax, are summarized.

Putative Role of Nuclear Factor-Kappa B But Not Hypoxia-Inducible Factor-1α in Hypoxia-Dependent Regulation of Oxidative Stress in Hematopoietic Stem and Progenitor Cells

Aims: Adaptation to low oxygen of hematopoietic stem cells (HSCs) in the bone marrow has been demonstrated to depend on the activation of hypoxia-inducible factor (HIF)-1α as well as the limited production of reactive oxygen species (ROS). In this study, we aimed at determining whether HIF-1α is involved in protecting HSCs from ROS. Results: Oxidative stress was induced by DL-buthionine-(S,R)-sulfoximine (BSO)-treatment, which increases the mitochondrial ROS level. Hypoxia rescued Lineage-Sca-1+c-kit+ (LSK) cells from BSO-induced apoptosis, whereas cells succumbed to apoptosis in normoxia. Apoptosis in normoxia was inhibited with the antioxidant N-acetyl-L-cysteine or by overexpression of anti-apoptotic BCL-2. Moreover, stabilized expression of oxygen-insensitive HIFs could not protect LSK cells from oxidative stress-induced apoptosis at normoxia, neither could short hairpin RNA to Hif-1α inhibit the protective effects by hypoxia in LSK cells. Likewise, BSO treatment of LSK cells from Hif-1α knockout mice did not suppress the effects seen in hypoxia. Microarray analysis identified the nuclear factor-kappa B (NF-κB) pathway as a pathway induced by hypoxia. By using NF-κB lentiviral construct and DNA-binding assay, we found increased NF-κB activity in cells cultured in hypoxia compared with normoxia. Using an inhibitor against NF-κB activation, we could confirm the involvement of NF-κB signaling as BSO-mediated cell death was significantly increased in hypoxia after adding the inhibitor. Innovation: HIF-1α is not involved in protecting HSCs and progenitors to elevated levels of ROS on glutathione depletion during hypoxic conditions. Conclusion: The study proposes a putative role of NF-κB signaling as a hypoxia-induced regulator in early hematopoietic cells.

Vascular Regenerative Cell Exhaustion in Diabetes: Translational Opportunities to Mitigate Cardiometabolic Risk

Ischemic cardiovascular complications remain a major cause of mortality in people with type 2 diabetes (T2D). Individuals with T2D may have a reduced ability to revascularize ischemic tissues due to abnormal production of circulating provascular progenitor cells. This 'regenerative cell exhaustion' process is intensified by increasing oxidative stress and inflammation and during T2D progression. Chronic exhaustion may be mediated by changes in the bone marrow microenvironment that dysregulate the wingless related integration site network, a central pathway maintaining the progenitor cell pool. Restoration of vascular regenerative cell production by reducing glucotoxicity with contemporary antihyperglycemic agents, by reducing systemic inflammation postbariatric surgery, or by modulating progenitor cell provascular functions using exosomal manipulation, may provide unique approaches for mitigating ischemic disease.

Circulating Pro-Vascular Progenitor Cell Depletion During Type 2 Diabetes: Translational Insights Into the Prevention of Ischemic Complications in Diabetes

•

This study combined ALDH activity with cell surface marker expression to develop a multiparametric flow cytometry assay to assess proangiogenic progenitor and proinflammatory cell content in the peripheral blood of patients with T2D compared with age-matched control subjects.

•

Patients with T2D exhibited an increased frequency of proinflammatory ALDH^hi cells with granulocyte side scatter properties and a decreased frequency of circulating monocytes with an M2 phenotype that is associated with proangiogenic and anti-inflammatory functions.

•

Patients with T2D exhibited significant depletion of circulating provascular ALDH^hiCD34+ progenitor cells with primitive, migratory, endothelial, and pericyte phenotypes.

•

Subgroup analyses that stratified patients with T2D according to age, duration of T2D, insulin requirement, and glycosylated hemoglobin levels revealed that only the duration of T2D correlated with vascular progenitor cell depletion.

•

Flow cytometric assessment of circulating ALDH^hi cell subsets represents a promising translational approach for identifying patients with T2D at increased risk for cardiovascular comorbidities.

Detection of vascular regenerative cell exhaustion is required to combat ischemic complications during type 2 diabetes mellitus (T2D). We used high aldehyde dehydrogenase (ALDH) activity and surface marker co-expression to develop a high-throughput flow cytometry–based assay to quantify circulating proangiogenic and proinflammatory cell content in the peripheral blood of individuals with T2D. Circulating proangiogenic monocytes expressing anti-inflammatory M2 markers were decreased in patients with T2D. Individuals with longer duration of T2D exhibited reduced frequencies of circulating proangiogenic ALDH^hiCD34+ progenitor cells with primitive (CD133) and migratory (CXCR4) phenotypes. This approach consistently detected increased inflammatory cell burden and decreased provascular progenitor content in individuals with T2D.

Pharmacological Regulation of Oxidative Stress in Stem Cells

Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and antioxidant defense mechanisms. The regulation of stem cell self-renewal and differentiation is crucial for early development and tissue homeostasis. Recent reports have suggested that the balance between self-renewal and differentiation is regulated by the cellular oxidation-reduction (redox) state; therefore, the study of ROS regulation in regenerative medicine has emerged to develop protocols for regulating appropriate stem cell differentiation and maintenance for clinical applications. In this review, we introduce the defined roles of oxidative stress in pluripotent stem cells (PSCs) and hematopoietic stem cells (HSCs) and discuss the potential applications of pharmacological approaches for regulating oxidative stress in regenerative medicine.

Expression of Intracellular Reactive Oxygen Species in Hematopoietic Stem Cells Correlates with Time to Neutrophil and Platelet Engraftment in Patients Undergoing Autologous Bone Marrow Transplantation

Reactive oxygen species (ROS) play important roles in hematopoiesis and regulate the self-renewal, migration, and myeloid differentiation of hematopoietic stem cells (HSCs). This study was conducted to determine whether ROS levels in donor HSCs correlate with neutrophil and platelet engraftment in patients after bone marrow transplantation. Cryopreserved HSC samples from 51 patients who underwent autologous transplantation were studied. Levels of intracellular ROS were assessed by flow cytometry using 2',7'-dichlorodihydrofluorescein diacetate (H₂DCFDA) in the CD45⁺/CD34⁺ HSC population. Colony forming unit assays were performed on HSCs isolated from the ROS^high and ROS^low populations to assess the differentiation potential of these 2 cell subsets. Distinct populations of ROS^high and ROS^low cells were evident in all patient samples. The median percentage of ROS^high expressing HSCs in the study cohort was 75.8% (range, 2% to 95.2%). A significant correlation was identified between the percentage of ROS^high stem cells present in the hematopoietic progenitor cells collected by apheresis product infused and the time to neutrophil engraftment (P < .001, r = -.54), as well as time to plt20, plt50, and plt100 (P < 0.001; r = -.55, -.59, and -.56 respectively). The dose of CD34⁺/ROS^high/kg infused also inversely correlated with a shorter time to neutrophil engraftment; time to engraftment for patients receiving > or ≤3 × 10⁶ cells/kg was 11.5 days (range, 9 to 23) versus 14 days (range, 10 to 28), respectively (P = .02). The dose of ROS^high HSCs delivered did not correlate with platelet engraftment. Collectively, these data suggest that the dose of ROS^high stem cells delivered to patients may predict time to neutrophil engraftment after autologous transplantation.

Oxidative stress in normal hematopoietic stem cells and leukemia

Leukemia is developed following the abnormal proliferation of immature hematopoietic cells in the blood when hematopoietic stem cells lose the ability to turn into mature cells at different stages of maturation and differentiation. Leukemia initiating cells are specifically dependent upon the suppression of oxidative stress in the hypoglycemic bone marrow (BM) environment to be able to start their activities. Relevant literature was identified by a PubMed search (2000-2017) of English-language literature using the terms 'oxidative stress,' 'reactive oxygen species,' 'hematopoietic stem cell,' and 'leukemia.' The generation and degradation of free radicals is a main component of the metabolism in aerobic organisms. A certain level of ROS is required for proper cellular function, but values outside this range will result in oxidative stress (OS). Long-term overactivity of reactive oxygen species (ROS) has harmful effects on the function of cells and their vital macromolecules, including the transformation of proteins into autoantigens and increased degradation of protein/DNA, which eventually leads to the change in pathways involved in the development of cancer and several other disorders. According to the metabolic disorders of cancer, the relationship between OS changes, the viability of cancer cells, and their response to chemotherapeutic agents affecting this pathway are undeniable. Recently, studies have been conducted to determine the effect of herbal agents and cancer chemotherapy drugs on oxidative stress pathways. By emphasizing the role of oxidative stress on stem cells in the incidence of leukemia, this paper attempts to state and summarize this subject.

Jab1/COPS5 as a Novel Biomarker for Diagnosis, Prognosis, Therapy Prediction and Therapeutic Tools for Human Cancer

C-Jun activation domain-binding protein-1 (Jab1) involves in controlling cellular proliferation, cell cycle, apoptosis, affecting a series of pathways, as well as regulating genomic instability and DNA damage response (DDR). Jab1/COPS5 dysregulation contributes to oncogenesis by deactivating several tumor suppressors and activating oncogenes. Jab1 overexpression was found in many tumor types, illuminating its important role in cancer initiation, progression, and prognosis. Jab1/COPS5 has spurred a strong research interest in developing inhibitors of oncogenes/oncoproteins for cancer therapy. In this paper, we present evidences demonstrating the importance of Jab1/COPS5 overexpression in several cancer types and recent advances in dissecting the Jab1/COPS5 upstream and downstream signaling pathways. By conducting ingenuity pathway analysis (IPA) based on the Ingenuity Knowledge Base, we investigated signaling network that interacts with Jab1/COPS5. The data confirmed the important role of Jab1/COPS5 in tumorigenesis, demonstrating the potential of Jab1/COPS5 to be used as a biomarker for cancer patients, and further support that Jab1/COPS5 may serve as a potential therapeutic target in different cancers.

Jab1/Csn5-Thioredoxin Signaling in Relapsed Acute Monocytic Leukemia under Oxidative Stress

Purpose: High levels of ROS and ineffective antioxidant systems contribute to oxidative stress, which affects the function of hematopoietic cells in acute myeloid leukemia (AML); however, the mechanisms by which ROS lead to malignant transformation in relapsed AML-M5 are not completely understood. We hypothesized that alterations in intracellular ROS would trigger AML-M5 relapse by activating the intrinsic pathway.Experimental Design: We studied ROS levels and conducted c-Jun activation domain-binding protein-1 (JAB1/COPS5) and thioredoxin (TRX) gene expression analyses with blood samples obtained from 60 matched AML-M5 patients at diagnosis and relapse and conducted mechanism studies of Jab1's regulation of Trx in leukemia cell lines.Results: Our data showed that increased production of ROS and a low capacity of antioxidant enzymes were characteristics of AML-M5, both at diagnosis and at relapse. Consistently, increased gene expression levels of TRX and JAB1/COPS5 were associated with low overall survival rates in patients with AML-M5. In addition, stimulating AML-M5 cells with low concentrations of hydrogen peroxide led to increased Jab1 and Trx expression. Consistently, transfection of ectopic Jab1 into leukemia cells increased Trx expression, whereas silencing of Jab1 in leukemia cells reduced Trx expression. Mechanistically, Jab1 interacted with Trx and stabilized Trx protein. Moreover, Jab1 transcriptionally regulated Trx. Furthermore, depletion of Jab1 inhibited leukemia cell growth both in vitro and in vivoConclusions: We identified a novel Jab1-Trx axis that is a key cellular process in the pathobiologic characteristics of AML-M5. Targeting the ROS/Jab1/Trx pathway could be beneficial in the treatment of AML-M5. Clin Cancer Res; 23(15); 4450-61. ©2017 AACR.

Impaired haematopoietic stem cell differentiation and enhanced skewing towards myeloid progenitors in aged caspase-2-deficient mice

The apoptotic cysteine protease caspase-2 has been shown to suppress tumourigenesis in mice and its reduced expression correlates with poor prognosis in some human malignancies. Caspase-2-deficient mice develop normally but show ageing-related traits and, when challenged by oncogenic stimuli or certain stress, show enhanced tumour development, often accompanied by extensive aneuploidy. As stem cells are susceptible to acquiring age-related functional defects because of their self-renewal and proliferative capacity, we examined whether loss of caspase-2 promotes such defects with age. Using young and aged Casp2^−/− mice, we demonstrate that deficiency of caspase-2 results in enhanced aneuploidy and DNA damage in bone marrow (BM) cells with ageing. Furthermore, we demonstrate for the first time that caspase-2 loss results in significant increase in immunophenotypically defined short-term haematopoietic stem cells (HSCs) and multipotent progenitors fractions in BM with a skewed differentiation towards myeloid progenitors with ageing. Caspase-2 deficiency leads to enhanced granulocyte macrophage and erythroid progenitors in aged mice. Colony-forming assays and long-term culture-initiating assay further recapitulated these results. Our results provide the first evidence of caspase-2 in regulating HSC and progenitor differentiation, as well as aneuploidy, in vivo.

Normal Hematopoietic Progenitor Subsets Have Distinct Reactive Oxygen Species, BCL2 and Cell-Cycle Profiles That Are Decoupled from Maturation in Acute Myeloid Leukemia

In acute myeloid leukemia (AML) quiescence and low oxidative state, linked to BCL2 mitochondrial regulation, endow leukemic stem cells (LSC) with treatment-resistance. LSC in CD34+ and more mature CD34- AML have heterogeneous immunophenotypes overlapping with normal stem/progenitor cells (SPC) but may be differentiated by functional markers. We therefore investigated the oxidative/reactive oxygen species (ROS) profile, its relationship with cell-cycle/BCL2 for normal SPC, and whether altered in AML and myelodysplasia (MDS). In control BM (n = 24), ROS levels were highest in granulocyte-macrophage progenitors (GMP) and CD34- myeloid precursors but megakaryocyte-erythroid progenitors had equivalent levels to CD34+CD38low immature-SPC although they were ki67high. BCL2 upregulation was specific to GMPs. This profile was also observed for CD34+SPC in MDS-without-excess-blasts (MDS-noEB, n = 12). Erythroid CD34- precursors were, however, abnormally ROS-high in MDS-noEB, potentially linking oxidative stress to cell loss. In pre-treatment AML (n = 93) and MDS-with-excess-blasts (MDS-RAEB) (n = 14), immunophenotypic mature-SPC had similar ROS levels to co-existing immature-SPC. However ROS levels varied between AMLs; Flt3ITD+/NPM1wild-type CD34+SPC had higher ROS than NPM1mutated CD34+ or CD34- SPC. An aberrant ki67lowBCL2high immunophenotype was observed in CD34+AML (most prominent in Flt3ITD AMLs) but also in CD34- AMLs and MDS-RAEB, suggesting a shared redox/pro-survival adaptation. Some patients had BCL2 overexpression in CD34+ ROS-high as well as ROS-low fractions which may be indicative of poor early response to standard chemotherapy. Thus normal SPC subsets have distinct ROS, cell-cycle, BCL2 profiles that in AML /MDS-RAEB are decoupled from maturation. The combined profile of these functional properties in AML subpopulations may be relevant to differential treatment resistance.

Oxidative stress and hypoxia in normal and leukemic stem cells

The main hematopoietic stem cell (HSC) functions, self-renewal and differentiation, are finely regulated by both intrinsic mechanisms such as transcriptional and epigenetic regulators and extrinsic signals originating in the bone marrow microenvironment (HSC niche) or in the body (humoral mediators). The interaction between regulatory signals and cellular metabolism is an emerging area. Several metabolic pathways function differently in HSCs compared with progenitors and differentiated cells. Hypoxia, acting through hypoxia-inducing factors, has emerged as a key regulator of stem cell biology and acts by maintaining HSC quiescence and a condition of metabolic dormancy based on anaerobic glycolytic energetic metabolism, with consequent low production reactive oxygen species (ROS) and high antioxidant defense. Hematopoietic cell differentiation is accompanied by changes in oxidative metabolism (decrease of anaerobic glycolysis and increase of oxidative phosphorylation) and increased levels of ROS. Leukemic stem cells, defined as the cells that initiate and maintain the leukemic process, show peculiar metabolic properties in that they are more dependent on oxidative respiration than on glycolysis and are more sensitive to oxidative stress than normal HSCs. Several mitochondrial abnormalities have been described in acute myeloid leukemia (AML) cells, explaining the shift to aerobic glycolysis observed in these cells and offering the unique opportunity for therapeutic metabolic targeting. Finally, frequent mutations of the mitochondrial isocitrate dehydrogenase-2 (IDH2) enzyme are observed in AML cells, in which the mutated enzyme acts as an oncogenic driver and can be targeted using specific inhibitors under clinical evaluation with promising results.

Xenograft models for normal and malignant stem cells

The model systems available for studying human hematopoiesis, malignant hematopoiesis, and hematopoietic stem cell (HSC) function in vivo have improved dramatically over the last decade, primarily due to improvements in xenograft mouse strains. Several recent reviews have focused on the historic development of immunodeficient mice over the last 2 decades, as well as their use in understanding human HSC and leukemia stem cell (LSC) biology and function in the context of a humanized mouse. However, in the intervening time since these reviews, a number of new mouse models, technical approaches, and scientific advances have been made. In this review, we update the reader on the newest and best models and approaches available for studying human malignant and normal HSCs in immunodeficient mice, including newly developed mice for use in chemotherapy testing and improved techniques for humanizing mice without laborious purification of HSC. We also review some relevant scientific findings from xenograft studies and highlight the continued limitations that confront researchers working with human HSC and LSC in vivo.

Opposing regulation of megakaryopoiesis by LPA receptors 2 and 3 in K562 human erythroleukemia cells

Erythrocytes and megakaryocytes (MK) are derived from a common progenitor that undergoes lineage specification. Lysophosphatidic acid (LPA), a lipid growth factor was previously shown to be a regulator for erythropoietic process through activating LPA receptor 3 (LPA3). However, whether LPA affects megakaryopoiesis remains unclear. In this study, we used K562 leukemia cell line as a model to investigate the roles of LPA in MK differentiation. We demonstrated that K562 cells express both LPA2 and LPA3, and the expression levels of LPA2 are higher than LPA3. Treatment with phorbol 12-myristate 13-acetate, a commonly used inducer of megakaryopoiesis, reciprocally regulates the expressions of LPA2 and LPA3. By pharmacological blockers and knockdown experiments, we showed that activation of LPA2 suppresses whereas, LPA3 promotes megakaryocytic differentiation in K562. The LPA2-mediated inhibition is dependent on β-catenin translocation, whereas reactive oxygen species (ROS) generation is a downstream signal for activation of LPA3. Furthermore, the hematopoietic transcriptional factors GATA-1 and FLI-1, appear to be involved in these regulatory mechanisms. Taken together, our results suggested that LPA2 and LPA3 may function as a molecular switch and play opposing roles during megakaryopoiesis of K562 cells.